This PDF file contains the front matter associated with SPIE Proceedings Volume 7155, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

The visible trend in the implementation of new technologies and creation of new products is the continuous reduction of feature sizes. However, in the same way as the feature sizes are decreasing, the theoretical and practical constraints of making them and ensuring their quality are increasing. Consequently, modern production and inspection technologies are confronted with a bundle of challenges. An important barrier for optical imaging and sensing is the diffraction limited lateral resolution. The observation of this physical limitation is of increasing importance, not only for microscopic techniques but also for the application of 3D-measurement techniques on wafer scale level. A further challenge is the reliable detection of imperfections and material faults within the production chain. This means in-line metrology/defectoscopy is a must for future production systems. Only the real-time feedback of the inspection results into the production process can contribute to a consistent quality assurance in processes with high cost risk. Moreover the reliable measurement of free form surfaces, both technical and optical, the assurance of the traceability and the certified assessment of the uncertainty of the measurement results are ongoing challenges. The challenges and the physical limitations are addressed here by new approaches for testing semiconductor structures with enhanced resolution, the measurement of aspheric lenses with increased flexibility and the inspection of micro components with improved traceability.

Laser Metrology as a tool for 3D measurements is seeing increased use in industrial applications. With advances in computer processing power, there have been many publications on new algorithms to correct distortions, speckle and other problems affecting the errors in such systems. But there have also been many advances in the hardware tools, including specialty lenses, light sources, and feedback systems that offer many initial corrections than can be employed before any computer analysis is even attempted. This paper will discuss the tradeoff of hardware and software corrections, the primary sources of hardware based errors, and new methods to realize these corrections in the hardware.

Generalization of specific optical metrology and systematic testing of all delivered components has yield in the last decade to a significant improvement of the optical surfaces installed on synchrotron radiation (SR) beamlines around the world. Surface roughness is classically characterized by phase-shift interferential microscope, sometimes AFM. Long trace profiler (LTP)¹, which measures the local slope along a line profile, has been the choice instrument to measure figure errors of large size components. Present LTPs have accuracy around 0.2 μrad RMS, and a spatial resolution around 1 mm, but they cannot provide 2D measurement nor access the small radii that modern sagitally focusing SR optics calls for. Stiching interferometry or Shack-Hartmann methods are good candidate for 2D measurement of figure errors. With increasing quality of mirrors and increasing coherence of synchrotron sources the simple specification of surface figure by the RMS slope errors of low spatial frequencies and roughness by the standard deviation of the high frequency surface height fluctuation is becoming less and less relevant. In order to achieve given performances the properties of an optical surface are better specified by the power spectrum of the surface errors in different spatial frequency ranges, the definition of which depends on the actual use of the surface. Evaluating the quality of SR mirrors used to form micro or nano X-ray probes should be checked by modeling the point spread function. It requires an accurate measure of the surface shape in the low frequency range. The next step of SR optics improvement will come from local polishing techniques guided by metrology. The required level of accuracy is calling for a panel of measuring methods adapted to different spatial frequency that are still under development.

Vibration measurement by time-average methods of different full-field techniques like speckle interferometry, digital holography or analog, optical holography is a powerful technique, able to provide vibration amplitude maps of high spatial resolution. The essential characteristic of full-field techniques is the simultaneous acquisition of data for all object points. Quantitative data processing aiming to obtain the full-field amplitude map is affected by several difficulties. The most important are the weak contrast of Bessel-type fringes and the speckle noise. The greatest obstacle in achieving complete amplitude field estimation comes from the orthogonal components of time-averaged interferograms, where the multiplicative, high-frequency phase noise covers the deterministic, vibration-related phase. Several researchers studied these problems in relation with the double-exposure method. In the present paper, the author presents in a single, unifying approach, these methods, common to all full-field interferometric techniques. An important reduction of multiplicative high-frequency phase noise allows obtaining fringe-averaged patterns whose intensity noise is much lower than in classical methods. The analysis leads to lower noise of the fringe patterns and extended measurement range, and also to a method of vibration-related phase estimation based on the mathematical inversion of the Bessel function, which may include in some stages subpixel precision.

The inspection and characterisation of laser marks using digital holographic microscopy (DHM) is presented in this paper. A DHM system in transmission mode was designed and the reconstruction algorithm for this configuration was investigated. The software was developed to provide live reconstruction of holograms for real time numerical evaluation of amplitude and phase contrast images. A CO₂ laser-based marking system was employed to create marks on glass substrates. By analysing the quality, 3D profile measurement, and material distribution of the marked area, the parameters of the laser system could be optimised to achieve the desired mark. The phase contrast images provide quantitative refractive index analysis and 3D profile studies. The results were compared with those obtained using white light confocal microscopy. The capabilities and advantages of the DHM system for the analysis of laser marks are also presented.

It develops a digital micro-holographic optical system to record the magnified hologram (named post-magnification digital micro-holography in this paper), which can suppress the quadratic phase aberration introduced by micro-objective (MO) and the wave-front difference between the object wave and reference wave. In order to show its remarkable trait, post-magnification micro-holography is compared with the traditional digital micro-holography (DMH) (named pre-magnification DMH) from the view of digital processing and aberration eliminating. Their differences are also analyzed by the measurement results of a phase grating with period 30lines/mm and depth 0.3 μm. Fresnel approximation algorithm is used to reconstruct the phase-contrast one of this phase grating. The results show that the presented system is greatly helpful to restrain the quadratic phase error.

Digital holography extends the use of holography with the ability to provide quantitative values of both amplitude and phase information of object. As in traditional holography, a variety of setups are possible in reflection and transmission modes. Digital holography has shown to be applicable in a wide variety of applications from metrology to bio imaging. In transmission digital holography, quantitative phase information of the object can be related to the height variation of a transparent medium with constant refractive index to provide 3-D surface profile of the specimen. The Confocal microscope is an high resolution technique for optical metrology. By optical sectioning, out-of-focus blur is essentially absent from confocal imaging and high-resolution quantitative 3D images of specimen can be created. In this paper 3D profiles of micro-optical diffractive components are recorded with both a transmission digital holographic microscope (TDHM) and a confocal microscope to explore their capabilities and shortcomings. The principles and characteristics of TDHM and confocal microscope are discussed specifically towards surface-profiling of micro-optical diffractive components. For some components, 3-D imaging and profile measurements obtained with TDHM and the confocal microscope method provide close agreement while for others discrepancies between TDHM and the confocal microscope method are observed. The reasons for the differences in the 3-D imaging and profile measurement of these two methods are discussed and analyzed.

In order to avoid missing low-frequency information of three-dimensional (3D) object, pseudorandom phase is generally added to object planes in tomographic hologram calculation, but speckle noise is inevitably introduced. A novel method is proposed to improving the quality of image reconstructed from kinoform generated by computational tomographic holography. Multi-kinoforms of 3D object are calculated, and the images of these kinoforms are superposed to suppress the speckle noise of reconstructed image. An invariant pseudorandom phase is added to each object plane in calculating each kinoform, and the pseudorandom phase is generated randomly again in next kinoform calculating. Digital reconstruction results from single kinoform and multi-kinoforms are analyzed by considering the peak signal-to-noise ratio (PSNR) and correlation coefficient (CC) between reconstructed images and original object, which verifies that the speckle noise in reconstructed image can be suppressed by superposing enough images reconstructed from the kinoforms. Electro-optical reconstruction results also confirm that the method is available.

Microscopic TV holography is a reliable and versatile non-contact optical technique for whole-field deformation measurements with interferometric sensitivity for many micro-metrology applications. The technique is based on digital speckle interferometric subtraction correlation. Characterization of deformation and surface shape is an important parameter in quality testing of micro objects related to functionality, reliability and integrity of the components. Single wavelength TV holography is used widely for deformation analysis. However the single wavelength TV holographic configuration suffers from overcrowding of fringes for large deformation that sets in limitation due to speckle de-correlation for quantitative fringe analysis. In this paper, we describe a multiple wavelength microscopic TV holographic configuration that uses sequentially recorded phase shifted frames at three different wavelengths before and after deformation of the specimen for evaluation of relatively large deformation fields at effective wavelengths. Use of multiple wavelengths for deformation and shape evaluation is also discussed. The design of the system along with few experimental results on small scale rough specimens

Composite materials are used more and more in aircraft production. Main composite types are Carbon Fiber Reinforced Plastics (CFRP), Glass Fiber Reinforced Plastics (GFRP) and metal-aluminium laminates (e. g. Glass Fiber Aluminium Reinforced GLARE©). Typical parts made of CFRP material are flaps, vertical and horizontal tail planes, center wing boxes, rear pressure bulkheads, ribs and stringers. These composite parts require adequate nondestructive testing (NDT) methods. Flaws to be detected are delaminations and debondings, porosity and foreign body inclusion. Manual ultrasonic testing with single element transducers is still the most applied method for composite parts with small and medium size. The extension of the conventional ultrasound technique for nondestructive testing with the laser ultrasound method brings new possibilities into the production processes for example the inspection of complex CFRP-components and the possibilities of online observation under remote control. In this paper we describe the principle of laser ultrasound with respect to the demands of nondestructive testing especially of small complex CFRP and C/PPS parts. We report applications of laser-based ultrasound options with generated types of guided and bulk waves on modern aircraft materials.

Piezoelectric actuators are widely used active devices able to perform static and dynamic displacements in the micrometer and submicrometer range. Both the magnitudes and the directions of these displacements and forces applied to devices acted upon must be strictly controlled. Different actuators have been studied by using speckle interferometry. The results of the study show that some actuator designs lead to unexpected shapes of the deformed actuator. As a consequence, these actuators have an unsuitable behaviour, which may consist in uncontrolled directions of the forces applied, in unconveniant deformations of the structures acted upon, or in stress concentrations which are dangereous for the actuator itself. Several holographic and shearographic speckle interferometry techniques are used throughout the study, so as to allow separate measurement of orthogonal components of the displacement maps and an estimation of their spatial derivatives. Results of other experimental investigations show deformations which are convenient and may be used in the development of sensors and actuators.

This paper describes how a standard laser-Doppler vibrometer (LDV) system was modified and extended for long-term reliability measurements on micro-electromechanical (MEMS) devices. Since scanning LDV measurements are performed by successively pointing a laser beam at a predefined set of locations, it is of the utmost importance that no movement of the MEMS device relative to the laser source occurs during the extended lifetime testing period. In the proposed system, the inevitable drift is compensated in three dimensions. The Z-drift is compensated by a piezo-actuated lens and an autofocus algorithm. The in-plane drift is detected using an image correlation technique, and the coordinate system of the LDV tool is modified accordingly. In this manner the scan points of the LDV can track the drift of the MEMS device. During a 400-hour testing period, measurements were performed every 15 minutes. A total in-plane drift of about 30μm was observed. The tracking error was below the resolving power of the microscope.

Reliable inspection of large surfaces with low depth recovery error is needed in a wide variety of industrial applications, for example in external defect inspection in aeronautical surfaces. Active triangulation measurement systems with a rigid geometrical configuration are inappropriate for scanning large objects with low measuring tolerances due to the fixed ratio between the depth recovery error and the lateral extension. Therefore, with a rigid triangulation setup, if we are interested in defect inspection over extended surfaces then we have to assume errors proportional to the field of view that can preclude a precise local defect measurement. This problem can be solved by the use of multiresolution techniques. In this work we demonstrate the application of an active triangulation multiresolution method for defect inspection of large aeronautical panels. The technique is based on a standard camera-projector system used together with a second auxiliary camera that can move freely. The result is a global measurement with a superposed local measurement without any optimization, explicit registration or recalibration process. The presented results show that the depth recovery error of the local measurement permits the local defects measurement together with a wide-area inspection.

The rapid advancement of nanotechnology is increasingly demanding measurements carried out at nano-scale be more accurate, comparable and traceable to the international standards of units (the SI). The Atomic Force Microscope (AFM) is a very powerful tool for the measurement of surface texture and micro-/nano-structures, with wide applications in nanotechnology. However, the traceability and accuracy of quantitative measurements made by commercial AFMs are often questionable and large discrepancies among them have been reported. This paper describes a metrological AFM developed at the National Metrology Centre (NMC) which has a very large scanning range with nanometre uncertainty. In order to achieve direct traceability to the SI, the system was constructed by integrating an AFM probe with a 3-axis nano-translation stage furnished with high performance autocollimators and laser interferometers along its X, Y and Z axes on a metrological frame. The large scanning range (25 mm × 25 mm × 5 mm) enables the system to be used for surface inspection on much larger samples than those allowed in normal commercial AFMs. Details of the system design and operation will be described in the paper. The uncertainty evaluation was done using certified step height, 1D/2D lateral pitch gratings. The experimental results show that the system is capable of achieving an uncertainty in the order of a few nanometres, which demonstrates that the system is suitable for providing traceability to commercial scanning probe microscopes (SPMs) including AFMs through calibrated transfer artefacts.

Self-assembly is one of the few practical methods for fabricating nanostructures. Currently, the fabrication of a nanostructure is determined by the initial conditions such as temperature, concentration of the particle, pH balance, etc. In order to precisely fabricate nanostructure devices using self-assembly, it is necessary to use real-time controlling, which is based on in-situ evaluations. In this study, we have proposed an in-situ particle sizing system to visualize interactions between nanocomponents. The system uses two particle sizing methods to cover a range of particle diameters. In the first method (for diameters of 1-10 nm), particle sizes are evaluated from the rotational diffusion coefficient of Brownian motion using fluorescence polarization. In the second method (for diameters of 10-500 nm), particle sizes are evaluated from the diffusion coefficient of a particle tracking method. The system can be integrated into a fluorescence microscope with a particle tracking system. We constructed an optical system and a particle sizing system and evaluated their properties.

Micro-coordinate measuring machines (micro-CMMs) with small probes (φ300 μm or smaller), low probing force and high accuracy working stage have been developed in recent years for three-dimensional (3D) measurement of micro structures. In general, the performance of the micro-CMM depends on the accuracy of its working stage and the probing system. The accuracy of the working stage of a micro CMM can be assessed by laser interferometry to the order of a few tens of nanometers. However, the accuracy of its probing system is difficult to assess due to the small probe size and low probing force. The probing error of a micro-CMM (model F25 by Carl Zeiss) was investigated at our laboratory. The probes used in the system are based on silicon membrane and piezo-resistive elements. The stylus size of the probes ranges from φ120 μm to φ300 μm. The effect of various sources, including the stylus size, on the probing error of the system was evaluated by means of certified precision spheres with reference to ISO 10360-2:2001. Based on the results obtained, possible ways to reduce the probing error are discussed. This is illustrated by the uncertainty analysis of the diameter measurements of a ring gauge using the system.

We present a system of positioning a sample for various types of local probe microscopes with interferometric measurement of displacement. The positioning extends significantly the field of view of the local probe microscopy where not only the probe can be displaced over a small range by piezoelectric transducers but the sample can be positioned over a larger scale. The stage allows positioning with nanometer resolution in all three axes under a closed loop control with position detection via capacitive sensors. Interferometric system monitoring all six degrees of freedom of the stage ensures full metrological traceability of the positioning to the fundamental etalon of length and improves resolution and overall precision of the displacement monitoring.

This paper presents two distinct measurement systems that were custom-built for the parametric and functional yield inspection of MEMS devices on wafer-level. Throughput as well as accuracy was optimized by using automatic feature detection and data segmentation algorithms. Inaccuracies in stage positioning during scanning are compensated for by a grid detection algorithm. The analysis of the measurement data is performed in parallel with the ongoing measurements. The data analysis includes the detection, parameter extraction, analysis of failures or damage of a single device and the final stitching of the results in order to obtain a visual mapping of the measured arrays. The performance of both systems has been demonstrated using arrays of micromirrors as test vehicles.

A novel frequency-shifting method for phase retrieval from fringe patterns is proposed. It needs two fringe patterns. In the second fringe pattern, a low frequency carrier is introduced. The low carrier frequency is used to open only fringe patches near critical points rather than the whole fringe pattern. The windowed Fourier ridges algorithm is used to retrieve the phase, which is able to characterize the density of the fringe patterns so that critical points can be recognized. The method is verified by a simulation example.

Focusing is started with partial image characteristics and its region attained through Sampling Restraint Hough Transform. Both rough and fine focusing procedures are used to avoid partial interference caused by noise; the values of pixels in the 8-neighbouring area of each point are used in the improved gradient gray square function used as sharpness function; searching step is changed at real time in both rough and fine searching processes to enhance the focusing sensitivity; Field Programmable Gate Array is used to expedite the calculation of sharpness function. Experimental results indicate this way of focusing features fine singe peak, fast response, and good robustness; the caulcualtion of one frame image takes less than 20 ms, and auto-focusing is possible in a a range of 200μm with a uncertainty of less than 1μm.

A variety of defect types exist on steel strip surface, most of which will be seen best in the arrangement that camera and illumination are arranged in one plane and with the same angle on both sides of the orthogonal. But for surface directional texture defects like scratches due to the "turn around" effect for some rays of light meeting the violations. So the camera would not see the illumination in orthogonal direction. This paper presents the multi-sensor and image fusion method in the reasonable arrangement of camera and illumination which are in different angles and at different positions against the strip to obtain the surface defects information exhaustively. The approach will most probably avoid the situation of two types of defects in the same strip only one will become visible. On pixel level, image fusion based on spatial domain and wavelet decomposition is proposed. Test on defect images of inclusion and scratch collected at a different angle, crack and scratch collected in diffuse and directed light respectively. The experiment results show that directional texture defects can be sufficient inspected by the multi-sensor and image fusion method.

In recent years, many algorithms were proposed for fringe pattern analysis and phase unwrapping including median filter, Fourier transform, windowed Fourier transform and wavelet transforms. However most of them are computationally expensive, which may be a barrier for real-time analysis for fringe pattern. In this paper an FPGA-based system and optimization framework for fringe pattern processing is presented. Median filter and average filter are taken as examples to show the performance of FPGA system over normal PC in real-time fringe pattern processing. The algorithms have been implemented on Celoxica RC340 FPGA development board using Handel-C - a C-like language with inherent parallelism making the full use of FPGA hardware. Furthermore, evaluation and comparison for computation speed are given between FPGA-based system and normal PC to demonstrate high potential of our hardware system in fringe pattern analysis.

In-line digital holographic microscopy as a phase measurement tool for the inspection of micro-components is presented. Light diffracted by the micro-components interferes with the directly propagating beams to give the in-line digital hologram recorded by the CCD camera. The convolution method is used to calculate the diffractive propagation of the light in order to reconstruct the wavefront of the test specimen. A reference hologram without the test specimen is recorded for the phase reconstruction. Finally, the method is applied on a phase grating to test its refractive index of the coating material.

In the context of this article we demonstrate a novel Fizeau interferometric system that copes with the presence of vibrations. Besides the conventional high spatial, but low temporal resolution detector system (the CCD camera) used in phase shifting interferometry, an additional high temporal, but low spatial resolution detector system was integrated, in order to measure the random phase shifts that are induced under the influence of the vibrations. The additional sensor consists of three photodiodes. The acquired analog signals enable the measurement of the occurring phase shifts at three non-collinear locations on the test surface. Under the assumption of the rigid body shifts and tilts of the test object, the resulting phase shifts at the three individual locations enable the determination of the random phase shifts over the entire image aperture. While the random oscillations of the test object are continuously measured, the CCD camera acquires several interferograms. In consequence, a phase shifting algorithm for random phase shifts was applied. In order to prove the validity of the new interferometer, a test surface of known topography was measured. The results of the measurements in presence of vibrations show very good concordance with the surface data given by the supplier. The analysis of the root mean square (RMS) over ten different measurements shows a measurement repeatability of about 0.004 waves (approximately 2.5 nm for 632.8 nm laser wavelength).

Windowed Fourier Transform (WFT) filters, including Windowed Fourier Filtering (WFF) and Windowed Fourier Ridges (WFR), have recently been proven to be effective in analyzing fringes affected from speckle as well as various kinds of noise. These filters deliver high quality results since they process in the windowed Fourier domain which is more robust to noise than the spatial domain. However WFT is relatively slow because of convolution or Fourier transform needs to be executed for many times. In this paper, a revised version of WFT filters are proposed that reduces execution time yet offers almost the same result. Experiments are carried out to backup the theory.

Due to change in the plate constants/plate stiffness which is a function of elastic modulus, change in natural frequencies takes place. At each natural frequency, the plate has a unique mode shape of vibration which can be easily differentiated from mode shapes at other natural frequencies. In this paper, a technique for the evaluation of the elastic modulus is proposed which is based on the vibration analysis of the plate using digital speckle pattern interferometry (DSPI) and Rayleight's method. Large numbers of experiments were conducted on square aluminium plate for the boundary condition; one edge is fixed and other edges free. The experimental result reveals that a single observation of frequency at first torsional mode is sufficient to evaluate the elastic modulus for all practical purposes. The evaluated experimental error was found to be less than 1%. Ease in sample preparation, simplicity in evaluation, non destructive nature of the DSPI and speed of DSPI has good prospect to evaluate elastic modulus of a material.

Today, various types of high resolution dimensional metrology instrumentation are in use for a quantitative characterisation of micro- and nanostructures. Although sophisticated ultra high resolution microscopic techniques like SEM and AFM are available, optical methods like microscopy and scatterometry are still of interest and are important because they are non-destructive, fast and have a good in-line capability. At PTB different optical tools are used for high-resolution metrology. Our standard instrument for CD metrology is a special UV transmission microscope. A new 193nm microscope is currently under development which will meet future requirements at least for the 32nm node as specified in the ITRS roadmap. A special alternating grazing incidence dark field microscope is used to measure the width of single features down to 100nm. For grating structures, we developed an optical diffractometer for pitch calibrations with an uncertainty down to 10 pm. Recently we realised a DUV scatterometer and ellipsometer capable to measure accurately CD, edge profile, layer thickness, and optical parameters. A versatile EUV scatterometer can be used to characterise absorber structures e. g. on EUV photomasks. For accurate measurements a thorough modelling on the basis of rigorous diffraction calculation is essential, which accounts for both polarisation effects and the 3D geometry of the structures. We use the rigorous coupled wave analysis (RCWA) method and the finite elements (FEM) method. We present an overview of PTB's current and future activities in optical high-resolution metrology and how these systems compare to ultra-high resolution microscopy like SEM or AFM.

Scatterometry or optical CD metrology (OCD) has become one of the most common techniques in quantitative wafer metrology within the recent years. Different tool configurations are either available in commercial inspection tools or subject of recent and present research activities. Among these are normal incidence reflectometry, 2-θ scatterometry, spectroscopic ellipsometry and angle resolved Fourier scatterometry. The two latter techniques appear to be promising for future use in semiconductor fabs. Spectroscopic ellipsometry is well established, and Fourier scatterometry has become of increasing interest within the recent time. Line edge roughness, i.e. an edge position variation of printed lines in lithography, has been of less importance up to now, as its amplitude could largely be neglected with respect to the feature dimensions. This will, however, not be the case for future nodes, as on the one hand CDs are getting smaller and smaller, and on the other hand, even the absolute amplitude is expected to increase due to the higher complexity of lithography and etch processes. In this paper a comparison of scatterometric reconstructions in both spectroscopic and angle resolved techniques considering LER afflicted samples is presented. The validity and benefit of a simple effective medium model is investigated.

In metrology applications of laser interferometers like a scale calibration of capacitive or inductive sensors, strictly linear positioning of the measuring mirror of the interferometer is necessary. It is maintained usually by a stage, which is based on principle of linear guide ways with ball carrier bearings. But possible imperfection of guides of the travel stage can cause deviations of the mirror plane from the right angle to the axis of traveling. Mentioned angle deviations lead to distortion of interference fringes in the output of the interferometer and by other words it causes non-linearity of the interferometer scale. Because the phenomenon is very random for this type of the travel stage the uncertainty of calibration of sensors is higher. In the work we present a method, which eliminates this usual problem by two ways. The first of them utilizes a special configuration of the laser interferometer where possible angle deviation of the mirror plane is compensated by second pass of the laser beam in the measuring arm of the interferometer. The next way is based on continual monitoring of spatial position of laser beams in the interferometer when the measuring mirror is positioned. It works with condition that the mirror can be slightly tilted by piezoelectric actuators in servo-loop mode with respect to detected spatial position.

For future technology nodes, highly accurate dimensional metrology will become more and more important. At this stage, measuring layer thickness in planar test structures or geometrical dimensions in simplified proxy structures may be not sufficient for accurate control of highly sophisticated process steps. Model-based dimensional metrology has the potential to provide critical parameters of interest for process control in high volume manufacturing, while during process and technology development the constrained flexibility of models and the required model-building efforts may be a serious limitation. On the other hand, model-free dimensional metrology may provide sufficient flexibility for process development, while in some cases it may not be production-worthy in high volume manufacturing. This article details advantages and disadvantages of the different methods during the lifetime of a product starting from early development to high-volume production.

New lithography technologies, as for example Extreme Ultra Violet (EUV), require high flatness on the exposure surfaces as the depth of focus is impacted. It is essential for semiconductor manufacturing to measure and control flatness of wafer surfaces at nanometer scale. In-plane geometrical defects on wafer surfaces following Chemical Mechanical Planarization (CMP) processing in the lateral millimeter range and in vertical dimensions in the nanometer range are of increasing importance. They will become a severe yield limiting factor in the 32 nm generations and below. This paper shows the result from improvement and optimization of metrology using wavefront sensing methods according to Makyoh and Shack Hartmann. Magnification and increased density of measurement points were identified to improve the existing performance with respect to vertical resolution significantly below 100 nm. The achieved lateral resolution on the wafer surface was 750 μm. The accuracy of the measurement on patterned wafer surfaces was determined to be less than 15 nm. The accuracy was determined by repeating the topography measurement and filtering of the according data of the sensors using cross section analysis and spatial processing with double Gaussian filters. The samples were taken from different manufacturing steps, such as Shallow Trench Isolation (STI) and interconnect metallization. Wavefront sensing based on methods according to Makyoh and Shack Hartmann enabled instantaneous and non-destructive flatness measurement of surfaces.

This paper introduces the principle and execution of a new method for measuring of distributed minute birefringence based on simple polarimetry with phase-shifting method. The new method requires only three stepped photoelastic data although conventional phase-stepping methods require four or more. To evaluate the new method experimentally, two precise crystal wave plates having nominal retardation ± tolerance of 79.1±3.5 and 10.0±4.7 nanometers were used as specimens. The experimental averages of the distributed retardation in the specimens with standard deviations were found to be 80.2±15.0 and 18.8±7.06 nanometers. To estimate the measurement accuracy of the angular orientations of the distributed birefringence in the specimens, the angular positions of the rotation stage for the specimens were rotated intermittently 45 or 30 degrees at a time during the experiment. As a result, the averages of measured offsets of the angular orientations were found to be 30.1±8.14 for the specimen of 79.1 nanometers with standard deviations. It is concluded that the new method has potential of measuring for distributed minute birefringence.

The visible light polariscope has been developed to provide high-resolution, full field, stress visualization and analysis in transparent materials. The polariscope images are processed using a four-step phase shifting algorithm to provide qualitative information. The system is calibrated using a disk under compression and then applied to detect the laser induced damage. The capability of the system to locate laser induced damage induced by different power and scanning speed are explored and compared to that using conventional transmission imaging. From the thermal stress, the preliminary information of the laser power and the scanning speed can be obtained.

The infrared phase shift polariscope (IR-PSP) is a full-field optical technique for stress analysis in Silicon wafers. Phase shift polariscope is preferred to a conventional polariscope, as it can provide quantitative information of the normal stress difference and the shear stress in the specimen. The method is based on the principles of photoelasticity, in which stresses induces temporary birefringence in materials which can be quantitatively analyzed using a phase shift polariscope. Compared to other stress analysis techniques such as x-ray diffraction or laser scanning, infrared photoelastic stress analysis provides full-field information with high resolution and in near real time. As the semiconductor fabrication is advancing, larger wafers, thinner films and more compact packages are being manufactured. This results in a growing demand of process control. Residual stress exist in silicon during semiconductor fabrication and these stresses may make cell processing difficult or even cause the failure of the silicon. Reducing these stresses would improve manufacturability and reliability. Therefore stress analysis is essential to trace the root cause of the stresses. The polariscope images are processed using MATLAB and four-step phase shifting method to provide quantitative as well as qualitative information regarding the residual stress of the sample. The system is calibrated using four-point bend specimen and then the residual stress distribution in a MEMS sample is shown.

In this contribution a novel laser Doppler distance (LDD) sensor is presented, which allows simultaneous measurement of axial position and tangential velocity and, thus, determination of the shape of moving and especially rotating objects with one single sensor. Conventional laser Doppler velocimeters measure only velocities. A concurrent position measurement can be realized by generating two fan-shaped interference fringe systems with contrary fringe spacing gradients and evaluating the quotient of the two resulting Doppler frequencies. Alternatively, two tilted fringe systems in combination with phase evaluation can be employed. It will be shown that, in contrast to conventional distance sensors, high temporal resolution below 3 μs and high position resolution of about 1 μm can be achieved simultaneously, because the position uncertainty of the LDD sensor is in principle independent of the object velocity. This is advantageous especially for monitoring highly dynamic processes e.g. at turbo machines, where in-process measurements of tip clearance and rotor vibrations are reported for up to 600 m/s blade tip velocity.

This paper presents an endoscopic optical system to measure 3D shapes of inner cylindrical surfaces that combines photogrammetry and fringe projection. The device has two identical cameras aligned with the optical axis and facing each other, two conical lenses and one 360° helical fringe projector. The helical fringe pattern is projected in the inner surface to be measured, phase shifted and acquired by both cameras. The phase patterns are used to identify corresponding points and to reconstruct the surface in a regular cylindrical mesh using an alternative approach. A prototype was built, calibrated and tested. The paper presents the results and an application to inspect internal welding seams in 150 mm (6") diameter pipelines.

When wavefront is reflected by a surface, the information of the surface profile is carried by the reflected wavefront. Measure the wavefront can extract the profile information. There are different kinds of pre-defined surface profile with various dimensions. While the size of particular wavefront sensor is fixed, the measurement range is limited. The design of optical system to bridge the work piece and wavefront sensor is critical. This paper presents a platform for the guidance of optical system design. The parameters of commercial available optical components are input to the platforms and the propagation of reflected wavefront is simulated. The relationship of part profile and the measurement wavefront is provided. The discussion is focused on the 2f+2f system for surface flatness measurement. The measurement of aspherical surface is also presented. Shack-Hartmann wavefront sensor (SHWS) is selected due to its simple structure, insensitivity to vibration etc, which is suitable for in-line application. Optical system is designed with the guidance of simulation platform. The experimental results shows the 2f+2f system is compatible to misalignments, can be used to monitor the deformations of parts. The measurement of aspherical surface is also presented with the comparison of simulation results.

A complete procedure to reconstruct part shape using a 3-light photometric stereo technique is investigated and experimentally verified. The part reflectance parameters are initially estimated and then the photometric stereo technique is applied at selected illumination directions. Finally, the recovered surface normals are integrated to reconstruct the part shape. The light sources are placed at 120° azimuth angle spacing while the slant angle is optimized according to the range of slopes found in the part surface. For a free form surface with small radii of curvature, a 45° light source slant angle is found to give better results on the global scale, with relatively lower accuracy. For a near-flat surface, a light source slant angle of 25° may be used to attain more accurate results. For surfaces having slopes less than 40° the mean surface normal recovery error is experimentally found to be less than 5°.

The antenna which is used in space for satellite control command communication and data transmission is a key unit for a satellite to work properly and accomplish the task successfully. Accurately measuring the antenna reflector shape and the reflector distortion shortly after the antenna manufacturing or assembling on the satellite is very important to ensure that the antenna functions well. Considering the constraints during the measurement, an antenna reflector shape and distortion measuring system, which is based on the close-range photogrammetry, is proposed. The system configuration, measuring principles, calibration and measuring procedures, data processing, experiment configuration and results as well as error analysis are discussed in the paper. The system was constructed and tested in the laboratory environment. The experiment results show that the system has the ability of accurately measuring the shape of the reflector. The distortion of the reflector surface can then be gained from the shape data. The average accuracy of measurement about 240 points on a 600mm antenna reflector is less than 0.015 mm (1σ).

In recent years, optical interferometry has been applied to whole-field, non-contact measurement of vibrating or continuously-deforming objects. In optical dynamic measurement, an interferogram sequence is obtained by a highspeed camera. Retrieving dynamic phase values from this interferogram sequence leads to a precise measurement of different kinematic and deformation parameters of a continuously-deforming or vibrating object. In this paper, this interferogram sequence is classified into two types: (i) intensity variation; and (ii) exponential phase signal. Different temporal phase retrieving techniques, such as Hilbert transform, Fourier transform, windowed Fourier transform and wavelet transform are applied to extract the phase from a simulated signal. The advantage and drawback of each algorithm are discussed. In addition, a new method based on the combination of Fourier transform and windowed Fourier transform is proposed and the simulation shows it can eliminate the noise and evaluate the phase more accurately.

In the present work a polarisation sensitive trangular path interferometer is developed to analyse the photoelastic stress pattern. To increase the sensitivity of the proposed interferometer a birefringent lens is used as a longitudinal interferometer to generate background fringes. The stress-induced birefringence of the sample will modify the fringe pattern, which gives a method for measurement of stress distribution of the sample. The method has all the advantages of a common path interferometer.

A novel method of using two prisms to perform lateral-shear interferometry for wavefront analysis and collimation testing over a wide dynamic beam size range is presented. Two right-angled prisms are utilized to establish an adjustable air gap with a small wedge angle. A test beam directed into the air wedge will result in reflected beams that are laterally sheared and produce an interference pattern which can be analyzed in the conventional manner. The thickness of air gap can be adjusted to allow a wide range of beam sizes to be tested down to a few millimeters in diameter. By using rightangled prisms instead of shear plates, several advantages such as the elimination of unwanted beam reflections, increase in the amount of shear per unit separation, and the enhancement of intensity and contrast of the output beams. The gap separation and wedge angle can be varied to maintain high sensitivity over the wide beam size range. Theoretical and experimental investigation into the sensitivity achievable in collimation testing with the method will be reported.

A cube beam splitter (CBS), which is more often used in two beam interferometers to generate orthogonally directed light beams, can be used to construct a two beam interferometer by aligning its beam-splitting interface parallel to the direction of propagation of light. The monolithic design of the CBS interferometer renders sufficient immunity to ambient vibrations and is worth considering as a convenient arrangement for interferometric testing. The proposed set-up can be used to construct a phase shifting interferometer as well by suitably incorporationg a quarter-wave plate and two polarizers for polarization phase shifting. It is also shown that the CBS interferometer, in a slightly different testing configuration, is birefringence sensitive in the sense that the displacement of the fringes is solely dependent on the birefringence of the sample and not on its surface quality.

In the measurement of the infrared imager, noise is the primary parameter in evaluating the quality of the infrared imager. In the engineering application of the infrared imager, three-dimensional noise pattern is not applied widely in the hard technology of the infrared imager due to its pattern is complex, physical significance is not definite and visualized. Noise parameters include the temporal noise and the spatial noise. The temporal noise can be divided into high frequency temporal noise and low frequency temporal noise (namely 1/f noise), and the spatial noise can be divided into high frequency spatial noise (namely fixed pattern noise, FPN) and low frequency spatial noise (un-uniform noise). The strict definition about high frequency temporal noise and low frequency temporal noise is given in this paper. The algorithm and measuring methods for low frequency temporal noise equivalent temperature difference are proposed. The algorithms and measuring methods of high frequency noise equivalent temperature difference are given, ignoring low frequency temporal noise in short-time during measuring high frequency noise equivalent temperature difference or not. Moreover, the uncertainty of measurement results for high frequency temporal noise equivalent temperature difference is analyzed in the paper.

A new algorithm of data analysis is proposed for shape and deformation measurement of diffusely reflecting surfaces by digital holography. It derives the phase of the averaged conjugate product of complex amplitudes before and after wavelength change or object deformation, corresponding to the complex coherence factor and is consistent with a theory on fringe formation in holographic interferometry. By experiments and computer simulations it has been shown that the algorithm is much more immune to speckle noise in phase analysis and unwrapping than conventional methods.

High-resolution X-ray is now an essential tool for internal defect and structure inspection in electronics and advanced materials industry. However, it is always a challenge to use it for accurate dimensional measurement due to the nature of the fan-beam X-ray source, particularly for cylindrical objects. This paper presents a novel hybrid X-ray and microscopy method for the profile measurement of the internal hole of a cylinder-shaped steel component. The part to be measured has a beer bottle shape but is open at the bottom side. The objective is to measure the diametrical profile of the internal hole with an accuracy of about 10μm. Traditionally this is measured with using a microscope after cutting and polishing the specimen. This is not only a tedious work, but is also inaccurate due to the uncertainty in cutting and polishing. This report demonstrates that the two edge-profiles of the internal hole can be obtained with X-ray inspection by sequentially placing each of them at the central of the X-ray beam so that the fan-beam effect can be minimized. The resolution of the X-ray inspection is about 6µm under a 20x magnification. Subsequently, the diameter of the hole is measured at two positions through the open end using a microscope with a 20x and a 10x objectives respectively. The results obtained with the two methods are then combined to generate the whole diametrical profile of the internal hole.

A swept source system was realized in the wavelength range of 810-875 nm with the combination of a broad-band superluminescent diode (SLD) and an acousto-optic tunable filter (AOTF) as a frequency-tuning device. SLD has two spectral centers at 820 nm and 845 nm with spectral bandwidth (FWHM) of around 40 nm. Gaussian spectral shaping was performed onto the original SLD spectrum while reconstructing OCT images for various test samples such as onion slice and fingerprint impression taken on a glass substrate. As a pulse can be considered a Gaussian distribution of frequencies, spectral shaping yields sharper Fourier peaks. Application of Gaussian spectrum facilitates in precisely locating the reflective boundaries within the sample that results in improved OCT images.

To characterize the spherical surface of extreme ultraviolet (EUV), the fiber phase shifting point-diffraction interferometer (FPS/PDI) has recently been designed and implemented. The diffraction wavefront from an optical fiber acts as the perfect referenced spherical wave and new-style interferometer configuration is used. The laboratory apparatus has been put up to measure spherical surface in experiment. The main content of this paper is the key technique of FPS/PDI about the method of interference image processing and the precision analysis for the interferometer. In experiment apparatus, a concave spherical surface is measured and a piezoelectric ceramics (PZT) is used for phase shifting. The wrap phase distribution is got by five-step phase shifting method, and then the unweighted least-squares phase unwrapping algorithm is optimized and used to obtain the unwrapped phase distribution. The error of spherical figure is derived from the fitting method of Zernike polynomials. The data processing result is analyzed in comparison with the measurement result of ZYGO interferometer. The repeat precision of the FPS/PDI is evaluated by multimeasurement. Finally, the major error sources are discussed and some optimized methods for the system are proposed.The results show that the interferometer has achieved worthy measurement precision and has great development potential.

Coordinate Measuring Machine (CMM) is widely used as an accurate measuring instrument in manufacturing and design. Modern industry requires a CMM with higher accuracy and efficiency. The accuracy of CMM is influenced by many factors such as volumetric error and dynamic error. The volumetric error is the major component of CMM's errors in slowly probing while the dynamic error is not omitted during fast probing. Compensating the volumetric error is an effective approach to improve the precision of CMM. The volumetric error must be measured and the model in the working space of CMM must be set up while compensating. To measure the volumetric error, this paper proposes a new method for fast measuring 5 volumetric errors of a guide way at the same time. The error model is presented too. 3-beam laser interferometer method is used to measure the volumetric errors. The method can also be used in measuring the error in real-time dynamically. The research can be referred to design the super higher accuracy CMM and the precision CNC machine.

The determination of phase difference distributions is important in digital holographic interferometry. Many methods can be used to determine phase difference maps, such as Fourier transform, digital phase subtraction and phase-shifting. In recent years, some time-frequency analysis methods such as wavelet transform and short time Fourier transform (STFT) are developed to extract continuous phase maps without phase unwrapping in spatial and temporal domains. In this paper, STFT is investigated for the retrieval of phase difference in digital holographic interferometry. In addition, complex phasor (CP) method is employed in advance so as to make STFT available. An experiment is conducted to show the validity of the method based on STFT.

A setup for the simultaneous recording of axially-displaced intensity patterns of a volume speckle field to be used for phase retrieval is proposed. Beam splitters (BS) are cascaded directing the beams to different detectors, in turn, generating different sampling planes. The effective power, which is reflected in the speckle intensity measurements, is however compromised. The BS's transmission and reflection coefficients are evaluated according to the setup under the assumption that the only power loss induced is due to these optics. Simulations show a set of BS combination that delivers the same beam intensity of at least 6% to all the planes still results in successful phase retrieval. Other combinations of beam splitter transmission and reflection values are also explored. The single-shot operation of the proposed technique avoids the time-consuming sequential measurements of the speckle field. Possible future studies include application of the technique to measure a system's characteristic properties that are not temporally fixed like temperature and optical turbulence in the environment.

Crystallization is a widely used chemical process that finds applications in pharmaceutical industries. In an industrial crystallization process, it is not only important to produce pure crystals but also to control the shape and size of the crystals, as they affect the efficiency of downstream processes and the dissolution property of the drug. The effectiveness of control algorithms depend on the availability of on-line, real-time information about these critical properties. In this paper, we investigate the use of lens-less in-line digital holographic microscopy for size and shape measurements for crystallization processes. For this purpose, we use non-crystalline spherical microparticles and carbon fibers with known sizes present in a liquid suspension as test systems. We propose an algorithm to extract size and shape information for a population of microparticles from the experimentally recorded digital holograms. The measurements obtained from the proposed method show good agreement with the corresponding known size and shape of the particles.

The presence of speckle noise in the reconstruction process of digital hologram reduces the signal to noise ratio (SNR) in the reconstructed images. In this paper we present wavelet filtering to improve SNR in the reconstructed images. Experimental results are presented.

We demonstrate a fiber sensing system by using a fiber resonator which is formed by two fiber Bragg gratings. It is able to measure real time strain and stress directly by the variation of the intensity of the output power due to the modulation in the fiber resonator. It shows that recording of the strain variation can be achieved as high as 2K Hz. The frequency response, signal noise ratio, and maximum range of the sensing system are studied with various reflectivity of the FBG, and the coupling ratios of the couplers used in the system.

Digital Shearography and Infrared Thermography (IRT) techniques were employed to test non-destructively samples from aircraft structures of composite material nature. Background information on the techniques is presented and it is noted that much of the inspection work reviewed in the literature has focused on qualitative evaluation of the defects rather than quantitative. There is however, need to quantify the defects if the threshold rejection criterion of whether the component inspected is fit for service has to be established. In this paper an attempt to quantify induced defects on a helicopter main rotor blade and Unmanned Aerospace Vehicle (UAV) composite material is presented. The fringe patterns exhibited by Digital Shearography were used to quantify the defects by relating the number of fringes created to the depth of the defect or flaw. Qualitative evaluation of defects with IRT was achieved through a hot spot temperature indication above the flaw on the surface of the material. The results of the work indicate that the Shearographic technique proved to be more sensitive than the IRT technique. It should be mentioned that there is "no set standard procedure" tailored for testing of composites. Each composite material tested is more likely to respond differently to defect detection and this depends generally on the component geometry and a suitable selection of the loading system to suit a particular test. The experimental procedure that is reported in this paper can be used as a basis for designing a testing or calibration procedure for defects detection on any particular composite material component or structure.

Teeth have important roles in digestion of food, supporting the facial-structure, as well as in articulation of speech. Abnormality in teeth structure can be initiated by an erosion process due to diet or beverages consumption that lead to destruction which affect their functionality. Research to study the erosion processes that lead to teeth's abnormality is important in order to be used as a care and prevention purpose. Accurate measurement methods would be necessary as a research tool, in order to be capable for quantifying dental destruction's degree. In this work an inexpensive optical method as tool to study dental erosion process is developed. It is based on extraction the parameters from the 3D dental visual information. The 3D visual image is obtained from reconstruction of multiple lateral projection of 2D images that captured from many angles. Using a simple motor stepper and a pocket digital camera, sequence of multi-projection 2D images of premolar tooth is obtained. This images are then reconstructed to produce a 3D image, which is useful for quantifying related dental erosion parameters. The quantification process is obtained from the shrinkage of dental volume as well as surface properties due to erosion process. Results of quantification is correlated to the ones of dissolved calcium atom which released from the tooth using atomic absorption spectrometry. This proposed method would be useful as visualization tool in many engineering, dentistry, and medical research. It would be useful also for the educational purposes.

Coupled 1X2 Single Mode Fiber (SMF-28e"R") has been successfully fabricated using a slightly unstable torch flame at a temperature range of 800°C to 1350°C injecting hydrogen gas flowing at pressure of 1 bar. The coupling ratio and coupling coefficient can be examined from 1% until 75%. In this paper, we compare the experimental results by using a simple kinetic model of coupling coefficient where internal and external parametric functions are considered. This equation is time independent and is then integrated over the direction of the coupling ratio range for various separation fibers axis between two cores. The result shows that the separation between the cores significantly affects coupling coefficient exhibiting exponential behavior. In the experiment the coupling coefficient gradient is significantly changed towards the coupling ratio but in modeling it has a function of separation fiber axis and no power imposed. These phenomena will determine the effects of power losses at coupling region where fabrications of coupled fibers are demonstrated.

In the paper we present interferometric and photoelastic tomography methods applied for the 3D studies of refractive index (n) and birefringence (B) in photonics components such as optical fibres and microelements produced or replicated by a variety of novel technologies including deep proton writing (DPW) and hot embossing technology. The enhanced automated measurement and data analysis procedures are described and the experimental results obtained for microobjects working in transmission are given. Also the methodology to combine the tomographic data for full characterization of internal structure of 3D photonics elements is provided. The main samples under test are: microlens fabricated by DPW, Panda fibre and massive waveguide microinterferometer in the form of cuboids produced by hot embossing process.

A multipoint diffraction strain sensor (MDSS) in moire interferometer was developed earlier as direct approach for measuring strain of a macro-sized object. Recently a MDSS based on a micro-moire interferometer was proposed for measuring strain for a micro-sized object in wholefield with unique features, one of which is variable sensitivity and measurement range. The technique is now extended to measure both tilt and non-uniform strain of a material.

Continued advances in emerging technology of microelectromechanical systems (MEMS) and other microsystems of current interest require specialized design, analysis, fabrication, and characterization capabilities. Metrology is an inseparable part of the characterization. Recent advances in the field of optical holography make it particularly suitable for precision metrology of MEMS, especially as it relates to determination of operational characteristics of systems produced, to enable verification of their operation as well as refinement and optimization of the specific designs. This paper describes an optical metrology for measurement of MEMS and illustrates its use with representative examples of MEMS functioning at high frequencies while operating in demanding environments. This precision metrology facilitates characterization of dynamic and thermomechanical behavior of the individual components, their packages, and other complex material structures. Representative results presented herein indicate that the optical metrology is a viable tool for precision microscale measurements and, as such, it is particularly useful for development of MEMS, especially while considering MEMS reliability assessment.

For solving the problem of programming measurement path when inspecting Blade Profile, and improving the efficiency and precision, the self-adaptive dynamic path planning model of blade profile measurement is proposed, using Back Propagation Neutral Network, based on the blade measuring characteristic and non-contact measurement system of blade profile detecting in laser triangular principle. For the feature of blade profile measuring, with the factors affecting the Probe precision and efficiency (the range of depth of field, incident angle), we plan the probe position of next measurement point by selecting 3 layer BP networks of , using practically measured blade profile as Training Sample, and regarding probe coordinates of corresponding profile measuring point as networks input. This paper discusses and explains the factors affecting measurement path planning, the creating and training of the BP networks profile measurement path planning in details. Because of the use of Neural Network learning the ability of approximating nonlinear mapping in any precision and the application of regarding blade profile data as BP network training sample, measuring movement path can combine with the blade curvature variation closely. Then, practically measuring precision and efficiency are improved, and the Path Planning problem is solved, brought by curvature varying greatly of blade profile in large blade profile measurement. At last, a group of experimental data is given, and the results of experiment are analyzed in detail.

Extruded profiles are semi-finished products (made out of steel, brass, aluminum, synthetics...) which are appointed for wide applications in manufacturing of technical products. As yet used optical sensors in process control working to the shading technology detect the object's shadow orthographically to the axis of illumination. As a consequence they record it unattached by the profiles coat in measurement range at any point of the measured profile with high precision. As a matter of fact, concave zones cannot be captured. Alternatively the measurement of concave zones can be arranged by light-section systems. These do not comply with the required accuracy, are comparatively slow and moreover affected by dislocations of the section of the profile. A measurement system including a light-section and a shading system combines the advantages of both optical systems. It is to serve with a reliable conception for the assembly of a bi-sensorial measurement system consisting of both systems as well as suitable methods of analysis for the in-line inspection of concave profiles. As a result it contains conclusions concerning requirements of the light source, the arrangement of this source and the cameras, obtainable precision and sampling rate as well as the essential synchronization of both systems. After designing an appropriate prototype, the selected light-section system and the shading system will be synchronized and aligned. Therefore, the metered geometrical data will be merged for the evaluation of form deviation. So, developed and adapted software supports and contains proposals to the uncertainty after successful tests. The system and a calibration method will be proved in production where robustness will be a most critical despite of heat, dust and vibrations. The target uncertainty of less than 0.1 mm at every section of the profiles coat has to be met.

In the article, we propose a measurement method for a fluctuation of the air air-refractive refractive-index from the frequency measurement by combining a phase modulation homodyne interferometer (PMHI), an external cavity laser diode (ECLD) as the light source and a frequency stabilized laser (FSL) as the frequency reference. The PMHI, which is set in air environment, utilizes a Michelson interferometer and low low-thermal thermal-exp expansion ansion-glass (LTEG: the thermal expansion ratio: 2×10 10^-7 K^-1) for its main supporting structure. In the PMHI, a dark (or bright) interference fringe with a specific ) integer order N is converted to a null point by utilizing the phase modulation and the loc lock-in detection, and must be kept by use of the null null-method and the control on the ECLD frequency. Geometrical path change in the PMHI is neglected because of the ultra ultra-low low-thermal thermal-expansion condition. Therefore, at the null point for N-th order in the suff sufficient thermal icient condition, a fluctuation of the air air-refractive refractive-index can be measured by the ECLD frequency change, which is derived from a beat signal between the ECLD and the FSL. In the article, a measurement principle, instrumentation and experimental re results are discussed. sults

Optical profilometers for micrometer resolutions are getting increasingly popular for non-contact measurement of surface profiles. Confocal profilometer is one such optical technique which can pick up sub-micron height variations of the object surface. Though the system is a single point measurement scanning in the X-Y directions enables one to plot the 3-D profile of the surface. However, the Z-scanning range is limited to ±1mm. In this work we report a system which can adapt itself to widen the scanning range in the Z-direction. For increasing the scan range we have added another translation stage in the Z axis which adapts itself when the system profiles a surface with step heights more than its original range. The X-Y-Z translation stage is connected to the computer and is controlled using a LabVIEW program. The 3-D plot is obtained by plotting the Z-values from the confocal system to the corresponding X-Y position of the translation stage. When ever the system goes out of range the Z translation stage is increased or decreased thus adapting itself to plot a 3D profile of the specimen.

A method to measure the temperature by visualizing the laminar free convection flow of water is presented by using digital holography in lensless Fourier transform configuration. Temperature is measured within the boundary layer of the convective flow field. The deviation in temperature measured by this method and from that of obtained by thermocouple is within 2%.

We report here the micro-Raman and photoluminescence studies of acetate-capped colloidal ZnO nanoparticles synthesized by a low-cost hydrothermal synthesis method. The ZnO nanoparticles synthesized by this method exhibited a uniform particle size distribution, averaging from 3 to 5 nm in diameter. The visible Raman spectroscopy data show the presence of the wurtzite E₂ phonon mode around 438 cm^-1 and UV Raman spectra show longitudinal optical (LO) phonon modes up to the third order. Apart from the strong band-edge UV emission at around 3.28 eV in the photoluminescence spectra, a broad defect-induced emission at around 2.05 eV was also observed. However, the defectinduced emission was much weaker than the band-edge emission, suggesting that surface states of ZnO had been reduced by the adsorption of acetate molecules. Development of this synthesis method would not only be useful for improved device performance, but also for cost-saving measures in the optoelectronics industry.

We present the study of the output characteristics of a distributed Bragg grating fiber ring laser (DBGFL) with different coupling configuration with the fiber Bragg grating (FBG). The fiber ring laser was pumped by a 980 nm laser diode with pig tail fiber connection with a 980/1550 WDM, and the resonator is contained in a fiber Bragg grating loop. Two coupling configuration of the FBG have been used to study the effect to the output characteristics of the fiber ring laser. It shows about the same output efficiency between the fiber ring laser with only reflection coupling and with reflection /transmission coupling. In addition, a numerical model of calculating the multiple reflection/transmission feedback coupling of the FBG has been proposed, and explains reasonably the experimental results.

In this paper we present theoretical and experimental analysis on Nd:YAG laser microwelding for pigtailing laser diode transmitter through two ball lenses that are employed for effectively matching the elliptical mode field of the laser diode with the circular on of the single mode fiber. The fiber attachment and the fixing of various coupling components have been performed in what is so called active alignment process. The system continues measuring the coupled power during the processes of alignment and attachment of various coupling components as well as the working distance and misalignment tolerances optimizations. Results of theoretical modeling of laser weld penetration depth agree with the experimentally measured results in the low laser pulse energy range. Moreover the laser pulse parameters such as, duration, energy, number of pulse shoots as well as the focusing position over the workpiece and angle of laser pulse incidence are found to have very significant effects on the weld yields and greatly affect the laser weld depth to width ratio. Optimization of all the mentioned parameters found to be necessary for achieving strong laser microwelds with more penetration and less width in the attachments of the sensitive optical components inside the packaged photonic devices modules.

A sensitive single-beam technique for measuring the nonlinear absorption coefficient of ZnO nanoparticles is reported here. The transmittance T(z) of the sample is measured by open aperture Z-scan technique as the sample is moved along the propagation path(z) of a focused Gaussian laser beam. The ZnO nanoparticles synthesized by wet chemical method, by mixing zinc acetate dehydrate and NaOH in ethanol is a clear transparent colloidal solution. The average size of ZnO nanoparticles is 6nm as confirmed by TEM analysis. Two-photon absorption of colloidal solutions of ZnO nanoparticles in ethanol is investigated by the Z-scan method using the nanosecond pulses from the second harmonics of Nd:YAG laser (532nm). The value of β for ZnO dispersed in ethanol extracted from the Z-scan data are 2.1cm/GW. ZnO nanoparticles of various sizes were embedded in PVA matrix on glass substrate and size dependence on β value was analyzed. The high value of two photon absorption coefficient (β) demonstrate that ZnO nanoparticle is a potential material for optical limiting applications.

Frequency doubled Nd:YAG lasers are often the option with stabilization to the saturated absorption in molecular iodine featuring good signal-to-noise ratio at the 532 nm. Purity of iodine in the absorption cell is one of the most important factor how to achieve results in optical frequencies corresponding to theoretical values. We present results of measurement of purity of sets of iodine cells made at our institute. The purity was tested by improved method based on measurement of induced fluorescence and evaluation by the Stern-Volmer formula. Frequency-doubled Nd:YAG lasers stabilized with these cells were compared to evaluate their frequency shifts. The absolute frequencies of selected iodine hyperfine transitions were measured in direct laser frequency comparison with the reproducibility well below the kHz level. The results indicating the iodine cell purity are presented with relation to the absolute frequency shifts. This not only highlights the influence of iodine cell quality onto the stability and absolute frequency of lasers etalons but also shows the way towards improvements of the iodine cell manufacturing technology.

A theoretical and experimental study on the dynamics of pulsed laser generated Fe plasma is presented. The time resolved imaging of the plasma plume was done at two different Ar gas pressures of 2 and 20 mbar. Plasma ablation from the target was done using a pulsed Nd:YAG laser at 532 nm with a fluence of ~25 J/cm². The snow plow model is fitted to the experimental data of the plume front position, obtained by gated time resolved images, to estimate the ablation parameters. The simulation results are in good agreement with the experimental values.

Digital holography has been reported as an effective tool for particle analysis. Other image-based techniques have small depth of focus allowing only 2D analysis at microscopic level. On the other hand, digital holography offers the ability to study volume samples from a single recording as reconstructions at different depths can be obtained. This paper focuses on the processing of the digital hologram that follows its recording in order to obtain particle size. We present a stepwise processing procedure with discussion on aspects such as reconstruction, background correction, segmentation, focusing, magnification and particles' feature extraction. Solutions to common obstacles faced during particle analysis which include ways to obtain fixed size reconstructions, automatically determine the threshold value, calculate magnification, and locate particles' depth position using effective focusing metrics are highlighted. Real holograms of microparticles are used to illustrate and explain the different stages of the procedure. Experimental results show that the proposed algorithm can effectively extract particle size information from recorded digital holograms.

This paper presents a new configuration of a digital speckle pattern interferometer that uses a binary diffractive optical element (DOE) to achieve radial in-plane sensitivity. The use of the DOE ensures constant sensitivity to the interferometer since it only depends on the grating period and does not depend on the wavelength of the illumination source. The paper describes the principles as well as the concepts of a portable device that was integrated to a drilling module to apply the hole drilling method for residual stresses measurement. Comparative results showed that the combined system can measure residual stress fields with uncertainty comparable with the classical strain gage based hole drilling method, but at least four times faster. A practical application of residual stresses measurement outside the laboratory is briefly presented.

The spacecraft components viz., central cylinder, deck plates, solar panel substrates, antenna reflectors are made of aluminium/composite honeycomb sandwich construction. Detection of these defects spacecraft structural components is important to assess the integrity of the spacecraft structure. Electronic Speckle Interferometry (ESI) techniques identify the defects as anomalous regions in the interferometric fringe patterns of the specklegram while the component is suitably stressed to give rise to differential displacement/strain around the defective region. Calibration studies, different phase shifting methods associated with ESI and the development of a prototype Twin Head ESSI System (THESSIS) and its use for the NDE of a typical satellite structural component are presented.

We present a way to identify distortions of transparent micro-patterned substrates using a desktop document scanner and a set of image processing routines. The method requires neither expensive optical equipment nor precise positioning of the part. It is therefore ideally suited to rapid process monitoring. A 5000-dpi imagesetter is used to print a square reference grid of lines having a known pitch ~100 μm. This reference pattern is used to produce a hard stamp that is subsequently embossed into a sheet of thermoplastic polymer. The pattern transferred to the polymer may include distortions resulting from contraction of the sheet after separation from the stamp. To measure these distortions, the embossed polymeric part is placed on a document scanner. The reference grid is laid on top of the part and rotated by hand until moire fringes are seen. At least two scans are made, each with a different relative reference-part rotation. For each scan, the orientation of the part relative to the reference grid may be arbitrarily chosen within an allowable range of a few degrees. These orientations may be extracted from the captured images, and, together with the moire fringes' orientations and spacings, provide enough information to obtain the part's distortions. Estimates of part strains may be improved, at the expense of measurement time, by capturing more images. The approach can detect isotropic shrinkage of the part with a strain resolution ~10^-3.

The moire method has been extensively studied in the past and applied in various engineering applications. Several techniques are available for generating the moire fringes in these applications, which include moire interferometry, projection moire, shadow moire, moire deflectometry etc. Most of these methods use the superposition of linear gratings to generate the moire patterns. The use of non-linear gratings, such as circular, radial and elongated gratings has received less attention from the research community. The potential of non-linear gratings in engineering measurement has been realized in a limited number of applications, such as rotation measurement, measurement of linear displacement, measurement of expansion coefficients of materials and measurement of strain distribution. In this work, circular gratings of different pitch were applied to the sensing and measurement of crack displacement in concrete structures. Gratings of pitch 0.50 mm and 0.55 mm were generated using computer software and attached to two overlapping acrylic plates that were bonded to either side of the crack. The resulting moire patterns were captured using a standard digital camera and compared with a set of reference patterns generated using a precision positioning stage. Using several image pre-processing stages, such as filtering and morphological operations, and pattern matching the magnitude displacements along two orthogonal axes can be detected with a resolution of 0.05 mm.

Non-destructive optical techniques for 3D shape measuring are fundamental in science, engineering, medicine, and industry. Such 3D data offer advantages over 2D data: shape data are invariant against alteration of the illumination and object motion. One of the major and easy methods to obtain 3D shape is from its contours. There exist several optical techniques for contouring, but the easiest to put into operation is by using linear structured light projection. The present work focuses on the implementation of linear structured light projection techniques for static and dynamic 3D contouring at macro- and micro-levels. Linear structured light as a fringe pattern is projected on the surface to be contoured. White light and laser-illuminating Talbot image are used in order to project the fringe pattern. Projected fringe pattern is captured by a conventional or high-speed CCD camera for image digitalizing and further analysis. Fourier transform method is employed as a tool to obtain a contour-wrap optical phase map. The simple experimental arrangement is adapted for static or dynamic conditions of the surface to contour. Samples that are under harmonic vibration conditions, for example, their vibrating frequency is tuned with that of the capture CCD camera to obtain the mode shape. In the static case one can obtain the topographical comparison before and after the surface subject to a static load or simply its topography. Examples, at micro and macro levels, of static and dynamics surface conditions are shown.

Temporal Paul wavelet analysis for instantaneous phase extraction using shadow moire technique is proposed. Unlike the Morlet wavelet, the Paul wavelet has less restriction on the adjustment of wavelet parameters and can provide an optimal time and frequency resolution for a particular application by selecting the proper parameters. The Paul wavelet is a complex wavelet and is suitable for processing the temporal intensity data obtained from the shadow moire technique for the phase retrieval. The proposed method can extract the phase information related to the state of the dynamic object at every instant in temporal domain. The phase information is associated to the displacement, three-dimensional (3D) surface-profile and the instantaneous state of the dynamic object. In addition, the instantaneous frequency of vibrating object can be obtained using the scale of the wavelet ridge by direct integration without temporal and spatial phase unwrapping. Thus the phase unwrapping error can be avoided. An experiment is conducted on the central loaded beam to demonstrate the validity of the proposed technique.

In our previous paper, "Warpage of thin wafers using computer aided reflection moire method," the surface curvature and residual stresses were evaluated using the versatility of computer aided reflection grating method to manipulate and generate gratings in two orthogonal directions. A very good agreement between the theory and experimental results was established. The bending stresses of wafers due to the deposition of backside metallization were evaluated without the aid of reference grating. In this paper, some aspects of the work is extended. An optical flat with flatness λ/10 is used as a reference plate to extract the residual stress of the wafers with different backside metallization. By utilizing the phase information from the moiré pattern between deformed grating (wafer) and undeformed grating (optical flat), the surface deformation of the wafer and residual stresses are investigated quantitatively and numerically. This technique, with satisfactory sensitivity and accuracy, can be used to characterize the residual stress of wafer due to warpage that may lead to the crack issues in semiconductor manufacturing industry.

We demonstrate the pulse laser deposition (PLD) of zirconium tin titanium oxide (Zr0.8,Sn0.2)TiO4 (ZST) thin film on p-type Si (100)substrate by KrF excimer laser at room temperature, and the study of the effects of post-annealing to the optical and dielectric properties of the deposited ZST thin films. Deposition rate of ZST thin film at 0.3 Angstrom/pulse has been achieved with laser fluences of 1500 mJ/cm². Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) are used to study the effect of the crystalline properties of the deposited films on process parameters; such as laser fluence and annealing temperature. In addition, UV-Vis spectroscopy is used to characterize the optical properties of the deposited ZST films.

Vacuum ultraviolet spectroscopic reflectometry (VUV SR) is a non-destructive, thin film measurement technique extending traditional reflectance spectroscopy to complex, multi band-gap, films stacks. The VUV SR system is a high throughput, production worthy metrology tool, able to resolve ultra-thin, multi-layer films in a single, broad band (800nm down to 120nm) spectral measurement. The dispersion in the films at the smaller VUV wavelengths allows high resolution of disparate thickness, optical properties and composition within thin film systems, not possible with existing UV optical methods. Optical systems such as spectroscopic ellipsometers (SE) are unable to resolve wide band gap films such as the SiO₂-like interface layer between a Hf-based high-k layer and a Si substrate due to intrinsic hardware limitations of the low wavelength range (typically below 150nm). Absorption in the films begins to dominate at incident wavelengths below 190nm, resulting in enhanced reflectance resolution. The resolution of multiple band-gap films being used in sub-45nm semiconductor device manufacturing technology, includes individual films with absorption peaks in the broadband, and less than 190nm (190-150nm, 150-130nm and 130-120nm) wavelength ranges. Applying fitting models and optical properties to the reflectance data, the thicknesses of individual films and their composition can be determined.

The infrared absorption of a mono-atomic thin film of carbon, called graphene, in a magnetic field is studied. Its interpretation in terms of the square root of the product of the cyclotron frequency and the Fermi energy is examined. The interpretation in terms of the Dirac points which are at the centre of the positive and negative energies, is examined and found not to fit well. The spin properties are used to obtain the energy levels correctly. A set of fractional values are tabulated which give the correct Hall effect plateaus. The energy levels arising from the Landau levels are usually of the type of a harmonic oscillator. In the present problem, the harmonic oscillator type levels are just like the equally spaced spin levels in which the number of levels is not limited by 2S+1. The oscillator type series and the proper spin properties are sufficient to get the correct fractions. The flux quantization is needed to get the plateaus in the Hall effect. We are thus able to obtain the correct fractions without the use of relativistic effects. The theory presented is thus non-relativistic. The normal infrared absorption arises from the equally spaced energy levels so that there is only one line. The additional lines occur due to spin properties.

Two aspects of electroplated gold that are often inspected on are plating thickness, and verification of gold presence at desired regions. With the later, in-situ reporting is desired. In this work, 8 color spaces - RGB, rgb, I1I2I3, HSI, YUV, YIQ, XYZ, and L*a*b* - were investigated to differentiate between regions with and without electroplated gold. It was found that the r, b, I2, H, U, V, I, Q, Z, and b* color space components provided distinct two level differentiability; while the R, G, and S color space components permitted differentiation at non distinct two levels. It was also uncovered that grayscale imaging would not permit any form of differentiation. The findings here indicate feasibility in using machine vision in tandem with color space analysis for electroplated gold inspection.

As a crucial part of active three dimensional(3D) vision system based on fringe projection technique, correspondence search between two adjacent range images would directly influence on the accuracy of matching and fusion procedure of the depth data. The conventional sub-pixel matching method by means of phase correlation can achieve a high level of accuracy while it would also be associated with a time consuming procedure due to the requirement of capturing two orthogonal series of sinusoidal fringes. Another technique utilizing linear interpolation algorithm based on the fringe projection with single direction might cause accuracy declination as a result of the simplification in imaging model. A novel method under the framework of linear interpolation was proposed. This approach makes use of absolute phase values and parameters of epipolar line as two kinds of feature points for correspondence search, leading to a significant improvement on the measurement accuracy of the depth data. Theoretical analysis and experiment results demonstrate the validity of presented approach.

In the current study, we used the method of electronic speckle pattern interferometry (ESPI) to measure polymerization shrinkage of composite resins. Standardized cavities were prepared and placed into the ESPI apparatus before the cavities were filled with composites (n=2) .The ESPI apparatus was constructed to measure the out-of-plane displacement of the resins surface during the polymerization. Experiments demonstrated that the ESPI technique was a viable method to measure the deformation of composite resins. It was responsive and sensitive to dimensional changes. We found that cavity shape, size and C- factor influenced the date of resins shrinkage. And the tooth deformation in response to polymerization of resins was measured by the ESPI too. We concluded that ESPI was a feasible method for assessing resins deformation induced by its polymerization shrinkage when it was bonded in tooth cavities. And the results were greatly influenced by the dimensions of cavities , or interface adhesive and so on. It could also measure the tooth deformation induced by shrinkage of bonded composite resins. We found that resins polymerization shrinkage date may overestimate shrinkage-induced tooth deformation.

With the development of super precision machining technology, the requirement for the precision of super-smooth surfaces measurement has reached ever-higher levels. In this paper, we adopt the phase-shifting interferential microscope technology, and present a kind of algorithm called Geodesic Erosion which aims at eliminating noises in the wrapping phase image such as abrupt phase changes, holes, points with low modulation, etc. Experiments show that the system is effective to remove noises in the wrapping phase image and successful to achieve the unwrapping phase image. The accuracy of this system may attain nanometer magnitude, while can also meet the topography measurement requirement for the super-smooth surfaces perfectly.

In weapon-ammunition system, firing accuracy of projectile is major characteristic parameter weighing fire effect and capability of weapon-ammunition system for target. At present, firing accuracy of projectile is obtained by measuring the two-dimensional coordinates of projectile for target. In order to measure the parameters of two-dimensional coordinates of projectile for target, a new type of measurement system is proposed. The measurement system is composed of four high sensitivity light screens (known as target) with special geometrical frame. Light source of the screens is formed by special infrared LED array. The PIN infrared photodiodes array is used as the sensors. The longest effective distance between light source and sensors is 4m. It is impossible to achieve using traditional methods. Four light screens and high-precision timers are combined in order to acquire the value of time when the projectile flies across the position of four light screens. The real-time data acquirement and processing and display of two-dimensional coordinates and the projectile velocity can be realized. The principle of measurement system and the design of high sensitivity light screen are introduced emphatically. The measurement system was verified by using five kinds of small caliber pellets. As compared with the paper target sheet, the measurement system designed can meet the demand of check-up test of gun, bullet and ammunition. The firing testing in the target field has proved that the measurement system has the advantages of simple construction, easy operation and high precision and high sensitivity.

A measurement system for measuring effective focal length of a microlens is presented. The system consists of a microprocessor controlled 3-axis stage with an optical system which provides 500 times magnification for focal length and diameter measurement. The focal length testing is carried out by single pass (transmission) approach. A point source from halogen white light is used as the object for the measurement. A CCD camera displays the magnified image on a computer. Focusing is performed by moving the microlens along the principal axis by manual control of a stepper motor and observation of the image on the computer. Similarly, moving the microlens along its substrate plane and capturing three points on its circumference gives its diameter. The co-ordinates of the 3-axis stage and diameter are displayed separately on dot-matrix LCD panel. Anti-backlash mechanisms are employed on all axes, each with a positioning resolution of 1 μm.

In order to accurately position the nodes of a SAR(synthetic aperture radar), a special assemble workbench is designed and a laser tracker named LTS-1100 from the API is used to measure it. The two stations layout of laser tracker along the lengthways center line of the workbench are adopted. The six common points used when the laser tracker moving from one station to the other are selected based on the stability experiment under the working environment. The laser tracker measures the positions of all the points real time and directs their adjustments. The distance error of the points from the ideal on the workbench is less than ±0.105mm. The close range photogrammetric method is then used to measure the nodes position of the SAR antenna assembled on the workbench. The result indicates the coincidence with that obtained by the laser tracker.

Determining the location of the zero order fringes is one of the key aspects in scanning white-light interferometry. The measurement principle of the scanning white-light interferometry is introduced at first; then the location of the zero order fringes as calculated by four different algorithms; namely Weight-center, Phase-shift, Frequency Domain Analysis (FDA), and Coherent Correlation are compared. Finally, numerical simulations on random generated surfaces are done to reach conclusions by comparing and analyzing the results. The research is important in the understanding and development of white-light interferometry.

We describe in this paper an experimental arrangement for optical pumping of rubidium based on a high-power laser diode array. The emission spectrum of the array was narrowed by external injection locking technique by means of cw Ti:Sa resp. an extended cavity laser (ECL) based on a high-power laser diode. The array emission spectrum was reduced with the aim to achieve maximum efficiency of the Rb optical pumping process. By way of the external injection locking technique, the power spectral density at the desired wavelength 794.76 nm was increased about 9 times. The laser system was designed to be a crucial part of the HpXe (hyperpolarized xenon) production process.

The precision measurement on surperfinish surface scratch has been currently paid much attention to on electronic products. To meet these demands, a novel method has been proposed which is based on heterodyne interferometry that utilizes birefringent lens as beam splitter and cantilever tip as scanning probe to get the measurement values of sample topography. But the optical nonlinear errors affect the measurement precision of the system. In this paper, we adopt the Jones matrix to analyze the elliptic polarization caused by the three factors existing at the same time, which are polarization ellipticity of laser source, installation orientation error and phase retardation of birefringent lens. The measurement errors of frequency mixing about these elliptic polarization beams arriving at the photodiode detecter are studied by vector theory. The results show that the measurement errors are periodic errors, and they will change from 1.24nm to 3.94 nm when the magnitude of orientation error of birefringent lens changes from 1°to 5°. Also, the methods of reducing measurement errors according to the numerical results in the system are suggested. The measurement precision will be improved by reducing the orientation error or choosing high performance laser source.

Measurement errors in binocular stereo vision are analyzed. It is proved that multi-stage calibration can efficiently reduce systematic errors due to depth of field. Furthermore, for difficulty in carry-out of multi-stage calibration, the compensation methods of errors are presented in this paper. First, using standard plane template, system calibration is completed. Then, moving the cameras to different depths, multiple views are taken and 3d coordinates of special points on template are calculated. Finally, error compensation model in depth is established with least square fitting. Experiment based on CMM indicates the relative error of measurement is reduced by 5.1% with the proposed method in this paper. This is of practical value in expanding measurement range in depth and improving measurement accuracy.

Because absolute quantity thermal laser energy meter based on conical cavity has some features, for example, wavelength adaptation range is wide and laser damage threshold value is high. It is used for the standard of the high-energy laser energy meter and extensively in the domain of the high energy laser measurement. However, laser energy will lose because of the heat exchange and the back scattering of the conical absorption cavity. Therefore, only after compensating and amending the loss, the exact measurement of the laser energy can be achieved. Aimed to the energy loss compensation problem of the conical cavity high-energy laser energy meter, firstly, according to the heat transfer theory, this paper analyzes the heat energy loss of the conical cavity due to the heat emission, the heat convection and the heat exchange, and construct the mathematical model of the heat energy loss, based on which measuring result is curved fit using the least squares technique, and is compensated and amended utilizing the fitting curve, whose measurement repetitiveness is 0.7%, from which we can know that measuring repetitiveness is increased consumedly. Secondly, according to the optics principles of reciprocity of the conical cavity inner face and the incident laser and utilizing complexification Simpson numerical method, the mathematical model of conical cavity jaw opening optical power density distribution and back scattering gross power is established, based on which measuring result is compensated and amended, the back scattering energy loss is about 0.5% to 2.5%, high-energy laser energy measuring accuracy is improved availably.

The fiber point-diffraction interferometer is introduced for measuring spherical surface with high precision. The interferometer must use special laser source, the coherence length of which is no more than 10 cm. The laser source at present can not meet the demand and the research of laser source design is performed in this paper. The coherence length of laser source in experiment is inconsistent with that computed with general theory, which restrict the research progress. In this paper, Mutual Coherence Function is introduced to describe the coherence of optical field. Based on the spectral characteristic of laser source, the mode of Multi-Longitudinal Mode laser is built. Through numerical calculation, it is discussed that how coherence degree is related with Longitudinal Mode number, spectral half width and resonant cavity length. Some important conclusions are draw. For example, Multi-Longitudinal Mode laser source has periodic coherence degree no matter how many longitudinal modes it contains, and the period of laser coherence degree is always double resonant cavity length. The method for designing short coherence length laser is put forward based on the conclusions and its coherence is measured in experiment. The result shows that the coherence length reaches 5 cm and meets the need of the interferometer.

We present methods of improvement of wavelength stability and tuneability of semiconductor laser diodes in fiber laser interferometers by fiber Bragg gratings (FBGs). We developed simulation method to calculation of arbitrary fiber grating (apodized, chirp etc.) with high precision by combination of methods based on layered dielectric media (LDM) and transfer matrix. On the basis of our simulations and measurements of the commercially available fiber gratings we designed a special 100 mm long fiber Bragg grating with apodization. We expect the application of the FBG to improvement of the linewidth and mode-hop free tuning range of semiconductor lasers at the wavelength 760 nm to increase resolution of fiber laser interferometer based on these diodes. We built the absolute fiber laser interferometer with Vertical Cavity Surface Emitting Laser (VCSEL) to easy employ FBG to stabilize wavelength and control the tuning range. First set up is presented.

Dynamic cells scattering is one of the most efficient approaches exploring in measurements of cells size, morphology and growth states. This technique can be widely applied in real-time detection for pharmaceutical industry, food industry, liquor industry and other biological fields. A novel method named dynamic individual cells scattering measurement is designed in this paper, which can make cells pass through quartz glass measurement zone one by one with sheath flow driving force. During the experiments, an obvious phenomenon has been found which is called sheath flow dark zone phenomenon (SFDZ). Under the influence of SFDZ, sheath flow forming detection becomes very difficult. In this paper, the causes giving rise to SFDZ have been analyzed. And an improved method is put forward, in which the orifice inside the measurement zone is set as an optical system. Then the illuminating system is redesigned. In this way, almost all the illuminating light can enter orifice so that the total reflection energy decreases substantially. A comparison experiments have been done, which proves the efficiency of this redesigned optical system and its sound effects on SFDZ avoiding.

In the technology of aspherical surface measurement, the phase shifting aspherical surface interferometer have widely used, but the vibration error from the environment is the main factor that directly affects the measurement accuracy of the phase shifting interferometer. In this paper, based on the structure of lateral shearing aspherical surface interferometer, the resources and sorts of vibration error were introduced, and some methods to eliminate errors were mentioned. The vibration influence on measurement results was analyzed. In order to reduce error, a new error compensation algorithm was put forward. In this method, first, a vibration measurement theory was built. Then Based on optic-electrical detection technology and image acquisition system and image process technology, the vibration mode of lateral shearing interferometer was obtained. Finally the vibration error of fringe image can be compensated by image correction. The measurement results can be obtained by the four-step phase shifting interferogram. The theoretical analysis and simulative results demonstrate the feasibility of this approach to improve measurement accuracy.

In this study, a simple experimental setup was established and experiments were carried out to investigate light scattering for scratch detection. Many factors would affect the scratch line detection based on light scattering, such as the size and orientation of the scratches, state of the polarizer, light incident angle, detecting angle of light scattering, and light spot size. It is found that the scattered light intensity depends on the orientation of the scratch lines. The intensity power of scattered light would increase with increasing lines per millimeter on the test plate surface. The detection at the zerodegree detecting angle is more sensitive than that at other detecting angles. It is also found that the scratch detection based on light scattering may be performed using S polarization.

In this study, the interaction performance of three light sources, namely white light, laser diode and He-Ne laser, with two wave-front sensing systems was investigated experimentally using different sensing distances and sampling apertures (two hole-apertures for a Hartmann system and a spatial-light-modulator lenslet-array for a digital Shack-Hartmann system). It was found that the white light source was the best for the Hartmann system, while the He-Ne laser was the most suitable light source for the digital Shack-Hartmann system. Geometrical accuracy of a hole-array aperture and the sensing distance are important to generate stable wave fronts.

The giant magnetostrictive actuator has some unique characteristic, such as high displacement resolution, big output torque etc, so is suitable for the field of ultra precise measurement and fine machining. The principle of the giant magnetostrictive actuator is based on magnetostriction, and Tb_0.27Dy_0.73Fe_1.9 is drove by magnetic field. So the high resolution of the giant magnetostrictive actuator is relate to uniformity of magnetic field. Furthermore, the resolution of actuator is effect by output setup. Because of magnetic field asymmetry, the giant magnetostrictive actuator based on the principle of electromagnetism transforming can be easily causes of displacement nonlinearity. For this problem, the structure and principle of magnetic field is analyzed based on FEA. For improving the resolution farther, the flexible hinge is used to replace to the traditional output setup. At last, the principle of this type of actuator is validated through experiments.

The fiber phase shifting point-diffraction interferometer (FPS/PDI) has recently been designed to measure spherical surface with high precision. The wavefront shape emerging from the fiber, which acts as the referenced wave in FPS/PDI, must be controlled precisely in design. The rigorous theory model of fiber point diffraction is studied for instrument realization. To execute such high accurate (10^-4λ) simulation, vector diffraction method must be adopted because conventional scalar diffraction theory is unsuitable when the fiber core size is comparable to wavelength. Based on the model, the influence of fiber core diameter, end-face figure and so on is studied. Some important conclusions are inferred. Firstly, the residual aberration is reduced with decreasing of fiber core size, so that the available numerical aperture decreases. Secondly, when the end face of the optical fiber is ellipse, the effect of the ellipticity should be considered. Thirdly, the oblique fiber, like ordinary fibers cut with zero face angle, generates a high quality spherical wave, but the propagation direction changes with the oblique angle. Finally, the residual aberration of diffraction wavefront becomes larger when the surface error of the end-face figure increases. The result shows that the single mode fiber used in experiment is available for instrument design and its influence over systematic error is negligible within certain numerical aperture.

There are two main steps in the analysis of photoelastic fringe patterns: the isoclinics and isochromatics computation. For the isochromatic computation there exist several possibilities but one of the best, from the point of view of reliability and automatization, is the phase shift technique. However all phase shift isochromatic algorithms need a good estimation of the isoclinic direction angle that is a challenging task in presence of low birrefringence, isotropic points and monochromatic illumination. In this work we discuss the application of a novel isoclinic direction calculation method based in a phase shifting technique and a fast direction estimation regularized filter. Experimental results show that the proposed method together with a standard phase shifting isochromatic estimation is a good option for the automatic analysis of photoelastic fringe patterns under different illumination conditions, load levels and sample complexity, making possible further processing steps as full-field stress separation.

In this paper, the advantages of two recently proposed techniques to implement an automatic processing of multiple deflection measurements are presented. An experimental wavefront reconstruction of a progressive ophthalmic lens shown the accuracy and simplicity of these techniques used to process the deflection measurements.

As a new holographic display device, TFT-LCD (Thin Film Transistor Liquid Crystal Displays) is key technical component of holographic representation for easy controlled by computer. With the development of exquisite processing technology, that it instead of the traditional holographic plate become historical necessity and would be the development direction of holographic optics. Based on principles of holography and display character of LCD, the property which the LCD was used as a holographic plate was analyzed. The emphasis on discuss influence of LCD black matrix on holographic representation. First, analyzed on LCD pixel structure, the LCD pixel structure mathematical model was established. LCD was character representation by pixel structure parameters. Then, the influence of LCD pixels structure on holographic representation was analyzed by computer simulation. Meanwhile, the SONY LCX023 was chosen for holographic plate, the He-Ne laser which the wavelength is 0.6328um was holographic representation light source. The holographic representation system was established for test influence of LCD on holographic representation. Final, compared between computer simulations and optical experimental results, the mathematical model of LCD was proved to be true. When aperture ratio is 0.625, the holographic representation wouldn't be distinguished between representation images. At the same time, some useful results was acquired for improve application effects of LCD in holographic representation.

Digital holography technology, which adopt CCD digital camera to record holograph, can get amplitude and phase information of the sample tested respectively through processing the image. Re-focus of the sample image can be realized by calculating complex amplitude information obtained. However, digital holograph reproduction system can't offer any criterion which determine whether reproduction image achieve fixed-focus state when reproduction image stands in the optimum position. Digital holography reproduction process need add an exterior criterion function, which implement automatic focus as normal imaging system. Aimed to digital imaging automatic focusing problem of off-axis Fresnel holography, image gradient energy method, image Laplace energy method, image shade of gray variance method are compared from two points of theory and practice view, and present the advanced measurement method based on spectrum band-stop filter. Experiment shows that the algorithm has some adaptability, especially image Laplace energy method based on spectrum band-stop filter has non-skewness, monotonicity, unimodality, kurtosis and robust.

A measurement and imaging system has been developed for in-line continuous measurement of live, unmodified, human embryonic stem cells (hESC). The measurement will not affect cell growth, structure, sterility and suitability for clinical use. The stem cell imaging system (SCIS) can be used to support the optimization of automated stem cell growth for invitro study and for high-volume bio-manufacture. This paper present the experimental and analysis for the optimization of system parameters. A non-linear lighting is developed to obtain a clear images. The individual cluster can be traced from day one to day two. The whole system is calibrated with measurement microscope and haemacytometer. The measurement accuracy is better than 90%.

Digital shearography is an optical technique that allows direct measurement of strain in deforming samples and detection of surface and sub-surface defects. Because of its simple set-up and insensitivity to rigid body translations, the method has gained considerable importance in nondestructive testing in an industrial environment. Despite of its advantages, however, its application remains limited to highly scattering opaque samples due to its high dependence on the quality of speckles. This study demonstrates the suitability of digital shearography in the strain analysis of acrylic glass, a transparent sample, under sub-surface compaction loading. To generate the speckles, nominal roughness is induced at the front surface of the glass. As compared to the polariscope, digital shearography is shown to be able to resolve microscopic displacements that may not be evident as birefringence. Microscopic strain induced in the sample in the order of 60 microstrains is resolved using the shearographic set-up. For a more complete investigation of the deformation in the sample, the sub-surface displacements in the material are also mapped using Fourier digital holography to complement the shearographic results. The technique can be applied to fluid flow visualization and evaluation of polymers and other transparent materials.

PFM has the advantages of real color and anti-milled, widely be used in restoration of teeth destroyed, teeth incomplete and teeth beauty. However, due to the issue of brittleness of ceramics and its manufacturing technology, the case of lost ceramics, crack inside and interface separate often occurs in clinical. In this regard, it not only delay the restoration, but also greatly add the expense of restoration. Hence, a inspection method is required to develop, in order to judge whether there is flaw on the PFM teeth cover or inside or not both before and after restoration. This paper will adopt Scanning Acoustic Microscope and X-Ray Microscope Inspection to conduct the Nondestructive testing for PFM restoration. The results show that the above two methods are both feasible on flaw inspection. Especially, the combination of two methods could effectively inspect the flaw's depth and size on PFM cover or inside, this will provide widely application for clinical in the future.

With the rapid development of shape measurement technique, multi-resolution approach becomes one of valid way to enhance the accuracy. There are, however, still some key techniques such as simultaneous calibration and data fusion of several sensors being further studied. A multi-resolution system, which use light sectioning method, is developed and has been successful in many application areas for blade of aviation engine example. It can measure the shape of blade at high speed and high accuracy. The system is composed of four laser linear light sources, four or five cameras and three highprecision mechanical movement devices. Two cameras have relatively low amplifying ratios, and focus on the basin or back of blade where the radius of curvature is large. Other cameras have high amplifying ratios, and fix on the entering or ending edge of blade where the radius of curvature is small. So the system has 3600 measurement range and can carry out multi-resolution 3-D shape measurement with greatly different amplifying ratios of cameras. One measurement process has been finished when the blade mounted on mechanical movement device move up or down one time. Also the model building and principle of the measurement system, an algorithm of calibration and data fusion of several cameras are presented that calculate 3-D coordinates of one section of blade. The result shows that the accuracy of the system is about 0.05mm for the sectional circumradius approximately 50 mm measurement range, and also proves the system is feasible and efficient.

A novel multi-view connection method is proposed for whole field three-dimensional (3D) profile measurement. Firstly 3D profiles of tested object from different views can be measured by using the digital fringe projection profilometry, and then these profiles are transformed into the common coordinate by applying transform matrix. With the help of a new determination method for the revolution axis of rotary stage, the direction vector and one point of the axis are achieved. To improve the computability and feasibility of coordinate transformation, the quaternion method is also used to get the transform matrix. Considering the error movements between the views, an effective method based on multi-aperture overlap scanning technique (MAOST) is presented, which can determine the relationship between two adjacent views from their overlapping areas. The connection of adjacent views is performed accurately in 3D space. Both computer simulation and experimental results are presented to verify the feasibility of proposed method.

The correct monitoring of thin-film thickness is one of the main problems during the course of optical thin-film component manufacture, in recent years, the method which is spectrum intensity measurement of thin-film component for controlling thin-film thickness has been one of the most effective methods. When this method is used Chow spectrum intensity is real-time, correctly measured is critical. Compared with the conventional method which is mechanical scanning by stepper motor driving the grating of monochromator and receiving by photoelectrical multiplier tube, in structure, the author combines the grating spectrometer with the linear CCD, which makes the problem of spectrum intensity real-time measurement better solved, the result is satisfied. In this paper, the structure of system affecting the spectrum intensity measurement accuracy is analyzed, By experiment, the relative parameters are determined, the spectrum wavelength is calibrated, root-mean-square error is 0.234nm, which is up to the requirement of monitoring wavelength resolution in the course of thin-film deposition; The algorithm is used for the real-time compensation of spectrum intensity measurement data, which make the effect of CCD photoelectrical response non-uniformity and nonlinear less; By changing the integral time magnitude, the rate of signal to noise of the spectrum signal is improved, it satisfies the requirement of real-time thin film thickness control.

We have synthesized Zn/ZnO core-shell nanoparticles by pulsed laser ablation in liquid (PLAL) media using nanosecond pulsed Nd:YAG laser. The formation of crystalline core-shell nanoparticles of varying core and shell thickness with varying SDS concentration is confirmed by HRTEM images. The optical absorption shows distinct features corresponding to ZnO exciton and Zn surface plasmon. Raman spectrum from Zn/ZnO core-shell nanoparticles shows E2(high) phonon modes of the bulk which are insensitive to the size and modes unique to the core-shell structures. Moreover, the surface optical mode is dominant feature of the nonresonant spectrum. We have also examined the wavelength dependence of the phonon modes in Zn/ZnO core-shell structure.

In the present work, the temperature versus thermal deformation (strain) with respect to time, of different coating films were studied by a non-destructive technique (NDT) known as shearography. An organic coating, i.e., ACE Premium Enamel, on a metallic alloy, i.e., a carbon steel, was investigated at a temperature range simulating the severe weather temperatures in Kuwait especially between the daylight and the night time temperatures, 20-60 °C. The investigation focused on determining the in-plane displacement of the coating, which amounts to the thermal deformation (strain) with respect to the applied temperature range. Furthermore, the investigation focused on determining the thermal expansion coefficients of coatings, the slope of the plot of the thermal deformation (strain) versus the applied temperature range. In other words, one could determine, from the decreasing value of the thermal expansion coefficients of coatings, a critical (steady state) value of the thermal expansion coefficients of coatings, in which the integrity of the coatings can be assessed with respect to time. In fact, determination of critical (steady state) value of the thermal expansion coefficients of coatings could be accomplished independent of parameters, i.e., UV exposure, humidity, exposure to chemical species, and so on, normally are considered in conventional methods of the assessment of the integrity of coatings. In other words, with the technique of shearography, one would need only to determine the critical (steady state) value of the thermal expansion coefficients of coatings, regardless of the history of the coating, in order to assess the integrity of coatings. Furthermore, results of shearography indicate that the technique is very useful NDT method not only for determining the critical value of the thermal expansion coefficients of different coatings, but also the technique can be used as a 2D- microscope for monitoring the deformation of the coatings in real-time at a submicroscopic scale.