This PDF file contains the editorial “The Key is People” for OE Vol. 50 Issue 03

We describe an all-fiber Mach-Zehnder interferometric configuration based on a suspended twin-core fiber. Because of the birefringence of the fiber cores, two interferometers are obtained by illuminating the fiber with polarized light. Applying strain, curvature, and temperature to the sensing head, different sensitivities are observed that permit the use of the matrix method to discriminate these three measurands.

Denoising is expected to improve the image quality and the performance of analysis. Combining the nonlocal-means filter and the mean-shift method, we derive a nonlocal weights estimator considering not only similarity of intensity but also the spatial relationship between image blocks. Filtering is performed in each image block and the center pixel is restored by an oriented filter. Experimental results show the performance of the proposed method in improving the signal-to-noise ratio and preserving local textures.

An all-optical diode (AOD) with structure (AB)^m(BA)ⁿ(BBAA)^k is proposed based on asymmetric light localization, and its optical bistability are numerically investigated by the nonlinear transfer matrix method. Research results show that the behavior of the AOD strongly depends on the period number m, n, and k, the transmission direction of the AOD is related to the values of m and n, while k affects the transmission contrast of the AOD. It is a significant reference for the design of all-optical signal processing devices.

In this paper, we propose using chalcogenide glasses for improved, large-angle, beam steering of infrared radiation, with minimal spectral dispersion and improved thermal performance over wavelength intervals covering the 2 to 12-μm range. For example, we evaluate that full-angle dispersion in the 2 to 5 μm region for LiF/As₂S₃ combination should be three times smaller than in the case of LiF/ZnS combination. We also evaluate that using the ZnSe/As₂Se₃ combination will provide twice as small thermal walk-off than a similar ZnS/Ge system in the 8 to 12-μm region.

Considering the problem of low and nonuniform resolution in omnidirectional imaging, a complementary catadioptric imaging method is proposed by using multiple mirrors. Due to the reflection of mirrors, each spatial object has two imaging positions, in the inner and outer of sampled omnidirectional images, respectively, which are generated from two different optical paths. For instance, a prototype of omnidirectional sensor based on complementary double imaging is designed, which contains two convex mirrors (cone and hyperboloid) in conjunction with a plane mirror. The design constraints and optical geometric model of imaging are analyzed in detail. By mathematical analysis, two improvements of resolution have been achieved: (1) more uniform distribution of resolution and (2) complementary resolution distribution in the radial and tangential directions between the inner and outer. To prove and demonstrate the remarkable complementarity, a simple fusion experiment based on wavelet decomposition and reconstruction is performed on a pair of cylindrical panoramic images unwrapped from an omnidirectional image.

An evaluation for objectively assessing the quality of visible and infrared color fusion image is proposed. On the basis of the consideration that human perception is most sensitive to color, sharpness, and contrast when assessing the quality of color image, we propose four objective metrics: image sharpness metric (ISM), image contrast metric (ICM), color colorfulness metric (CCM), and color naturalness metric (CNM). The ISM is evaluated by image gradient information. The ICM is defined based on both gray and color histogram characteristics. A color chroma metric, as well as a color variety metric based on a color difference gradient, is proposed, respectively, to define the CCM. The CNM is defined by measuring the color distribution's similarity between the fusion image and nature image, which are of the same scene. All the color attributions are computed in the CIELAB color space. Experimental results show that the proposed objective metrics are meaningful and effective on color fusion image evaluation because they correspond well to subjective evaluation.

We present a miniature snapshot multispectral imager based on using a monolithic filter array that operates in the short wavelength infrared spectral region and has a number of defense and commercial applications. The system is low-weight, portable with a miniature platform, and requires low power. The imager uses a 4×4 Fabry-Pérot filter array operating from 1487 to 1769 nm with a spectral bandpass ∼10 nm. The design of the filters is based on using a shadow mask technique to fabricate an array of Fabry-Pérot etalons with two multilayer dielectric mirrors. The filter array is installed in a commercial handheld InGaAs camera, replacing the imaging lens with a custom designed 4×4 microlens assembly with telecentric imaging performance in each of the 16 subimaging channels. We imaged several indoor and outdoor scenes. The microlens assembly and filter design is quite flexible and can be tailored for any wavelength region from the ultraviolet to the longwave infrared, and the spectral bandpass can also be customized to meet sensing requirements. In this paper we discuss the design and characterization of the filter array, the microlens optical assembly, and imager and present imaging results.

This paper presents a study of the lateral and axial resolutions of a transmission laser-scanning angle-deviation microscope (TADM) with different numerical aperture (NA) values. The TADM is based on geometric optics and surface plasmon resonance principles. The surface height is proportional to the phase difference between two marginal rays of the test beam, which is passed through the test medium. We used common-path heterodyne interferometry to measure the phase difference in real time, and used a personal computer to calculate and plot the surface profile. The experimental results showed that the best lateral and axial resolutions for NA = 0.41 were 0.5 μm and 3 nm, respectively, and the lateral resolution breaks through the diffraction limits.

Conventional close-up imaging uses lens arrays to form a continuous image of an extended object on a single focal plane sensor or photographic film. By imaging using microcamera arrays onto many separate sensors rather than a single large sensor, the subfields captured by individual sensors may be combined using image processing into a large synthetic image plane. This greatly increases the flexibility of the close-up imaging design because it is no longer required that the close up image be continuous. Using microcamera arrays, hundreds or thousands of megapixel sensors may be combined to form a synthetic gigapixel-scale sensor. This paper is an investigation into the design issues of microcamera arrays, and presents a simple design of a lens suitable for a megapixel class microcamera.

Analytical expressions for an instantaneous spectral point spread function (PSF) and an instantaneous spectral optical transfer function of a misaligned hypertelescope without delay lines, and containing circular and/or annular collecting mirrors, are presented. The formulas are deduced on the basis of the Fresnel approach to the Kirchhoff diffraction theory. Numerical results obtained for the system containing 60 identical annular mirrors, illustrate the pupil densification properties of the hypertelescope and the influence of random spatial and angular positioning errors of the optical elements on the average PSF (APSF), and on the average modulation transfer function (AMTF) calculated for the errors obeying specified probability distributions. The APSF and the AMTF give the opportunity to estimate the influence of the alignment errors on the resulting image quality in the hypertelescope image plane. This estimation can be used to produce the necessary requirements to the accuracy of the mirror control system and to the accuracy of the optical element alignment in dependence on the values of the exit pupil densification and the desirable resolution capability of the hypertelescope. The notion of the PSF and the modulation transfer function for off-axis beams can be useful for evaluation of a hypertelescope field of view.

In this paper, a new direct splicing method called push-pull welding is described. Direct coupling based on direct fusion splicing, which makes an optical fiber joining a multicomponent glass lens, gives not only a high optical performance but also high reliability and easy alignment.

Computer vision, despite all the recent progress, still cannot be employed technically in most hazardous and highly industrialized areas. Most of the alternative solutions to this modern issue are usually unavailable mainly due to the elevated cost of the overall visual inspection solution. The most suitable option is the use of an incoherent optical fiber bundle (IOFB), which clearly requires a calibration step prior to image transmission. This technique has been presented previously and has received national and international patents. We also contributed strongly to the improvement of this image transmission technique through IOFB. Thus, we summarize our chosen IOFB calibration method and associated essential steps that definitively improve the reconstructed image quality. Furthermore, by employing the new optimal steps combination that we introduce, we also drastically reduce the processing time needed to calibrate and reconstruct an IOFB-transmitted output image compared to previous proposals. Finally, we present a new full-resolution method, which also requires the previously described and optimized calibration methods, to achieve a higher image definition.

Fourier transform spectroscopy based on the theory of periodogram or maximum entropy spectral estimation may cause spurious peaks or frequency leakage, as well as distortion of the spectral intensity reconstruction. To solve these problems, spectral reconstruction is treated as an estimation of harmonic frequency and intensity in the interferogram, the super-resolution spectral reconstruction method, based on minimum variance spectral estimation and linear fitting (MVLF), is developed and discussed. MVLF is composed of two steps: frequency estimation with minimum variance frequency estimation and spectral intensity reconstruction with linear fitting. For MVLF, the spectral intensity reconstruction accuracy is only related to frequency estimation accuracy. Simulation results of both discrete and continuous spectral reconstruction show that, compared with traditional super-resolution spectral reconstruction methods, MVLF is able to constrain the frequency estimation error within 0.97% and the spectral intensity reconstruction error within 3%.

A position sensitive device (PSD) is frequently used in laser beam deviation measurement. However, it lacks the capability to retrieve the power distribution information of a laser beam. A charge-coupled device (CCD) gives much more information of a laser beam than a PSD. The requirement of a multifunctional sensor makes the replacement of a PSD with a CCD in measuring laser beam deviation to be a reasonable topic. In this paper a performance comparison between a PSD and a CCD combined with a centroid algorithm are discussed with special attention paid to the CCD-based system. According to the operating principle of the CCD-based system, several experiments were carried out to evaluate five factors of the CCD-based system: image window size, number of processed images, threshold, binning, and saturation. By applying the optimized parameters, several experiments were made to compare the CCD-based system with the state-of-the-art PSD-based system in terms of two performance indicators, namely resolution and speed. It is shown that, by applying the optimized parameters, the performance of a CCD-based system is comparable to that of a PSD-based system in measuring laser beam deviation.

We report the measurements of the nonlinear refractive index of a metal/porous silicon composite system as measured by the reflection Z-scan technique. The composite system is formed by using magnetron sputtering to deposit thin metallic films onto porous silicon anodized on p-type silicon. The experiment results indicate an enhancement over the nonlinear refractive index of the composite system, which suggests an opportunity to form new-type nonlinear-optical media consisting of porous silicon for nonlinear optical applications such as power limiting or optical switching.

We propose a new overdrive technology using third-order approximations. We can estimate overdrive (OD) values for all the transitions by linearly shifting a third-order base line. We investigate whether the proposed method is applicable to any liquid-crystal display (LCD) panels regardless of their characteristics. We examine the feasibility of the method using 11 LCD panels with different sizes, switching speed of liquid-crystal (LC) molecules, LC modes, and applications. After confirming the feasibility, we examine optimum position of the base line to minimize OD deviations from optimum OD values. We have four unknown coefficients of the third-order base line and a shifting parameter. We investigate if we can adjust only one coefficient with the three remaining coefficients fixed to create a base line optimized to each panel among the 11. We decide that we can adjust only one coefficient after analyzing experimental results. In addition, we look into fixing the shifting parameter. Finally, we conclude that we can accurately estimate OD values of all the transitions by adjusting only one value. Because of the extreme simplicity, we can implement our OD technology with an extremely simple circuit. We anticipate that common users can easily optimize the visual performance of their LCD system.

The technique under proposal for a precise spectrum analysis within an algorithm of the collinear wave heterodyning implies a two-stage integrated processing, namely, the wave heterodyning of a signal in a square-law nonlinear medium and then the optical processing in the same solid state cell. The technical advantage of this approach lies in providing a direct multichannel parallel processing of ultra-high-frequency radio-wave signals with essentially improved frequency resolution. This technique imposes specific requirements on the cell's material. We focus our attention on the solid solutions of thallium chalcogenides and take the TlBr-TlI (thallium bromine-thallium iodine) solution, which forms KRS-5 cubic-symmetry crystals with the mass-ratio 58% of TlBr to 42% of TlI. Analysis shows that the acousto-optical cell made of a KRS-5 crystal oriented along the [111]-axis and the corresponding longitudinal elastic mode for producing the dynamic diffractive grating can be exploited. With the acoustic velocity of about 1.92 × 10⁵ cm/s and attenuation of ∼10 dB/(cm GHz²), a similar cell is capable of providing an optical aperture of ∼5.0 cm and one of the highest figures of acousto-optical merit in solid states in the visible range. Such a cell is rather desirable for the application to direct 5000-channel parallel spectrum analysis with an improved up to 10−⁵ relative frequency resolution.

A volumetric display system based on a rotating light-emitting diode (LED) array panel can realize a three-dimensional (3-D) display truthfully in the space, but the drawback is missing the occlusion of a 3-D image. We propose an omnidirectional 3-D display with correct occlusion based on a direction-selective LED array panel, which is realized by setting a direction-convergent diaphragm array in front of the LED array. Every diaphragm restricts a light-emitting characteristic of every LED. By using direction-convergent diaphragm array, the observer around the display system can only see one image displayed by the LED array at the corresponding position. With the high-speed rotation of the LED panel, a series of views of a 3-D scene are displayed every angle patch in one circle. We set up an acquisition system to record 180 views of the 3-D scene with a rotating camera along a circle, and then the 180 images are displayed sequentially on the rotating direction-selective LED array to get a 360 deg 3-D display. This 3-D display technology has two main advantages: easy to get viewer-position-dependent correct occlusion and simplify the 3-D data preprocessing process which is helpful to real-time 3-D display.

Birefringent wave plates, often referred to as retarders, generally exhibit a strong wavelength dependence. However, there is a real need for achromatic retarders that exhibit identical characteristics over a broad wavelength range. In this paper, we have studied the design and characteristics of a cascaded system of birefringent plates in the near infrared region. Here we have studied a cascaded system of three birefringent plates using matrix analysis and designed a system which, by suitable reorientation of one of the plates, may perform both as an achromatic quarter-wave plate and half-wave plate, over the wavelength range of 1000 to 1800 nm. An inexpensive design for such an achromatic combination using crystalline quartz is described. The new arrangement of three birefringent plates proposed has the promise of producing achromatic combinations with fairly good accuracy.

Based on second-order nonlinearity, we present a tunable optical bandpass filter at c-band by introducing a back quasiphase-matching technique with a nanostructured named multiple resonator waveguide. Two injecting forward lights and one backward propagating light interact with difference frequency generation. At that juncture, the transmission of the forward signal can be modulated via changing the forward control power. As a result, a tunable optical bandpass filter with multiple flat-top transmit bands of the forward signal can be formed in the waveguide.

We developed a head-mounted display (HMD)-type multifocus display system using a laser-scanning method to provide an accommodation effect for viewers. This accomplishment indicates that providing a monocular depth cue is possible through this multifocus system. In the system, the optical path is changed by a scanning action. To provide an accurate accommodation effect for the viewer, the multifocus display system is designed and manufactured in accordance with the geometric analysis of the system's scanning action. Using a video camera as a substitute for the viewer, correct focus adjustment without the scanning action problem is demonstrated. By analyzing the scanning action and experimental results, we are able to illustrate the formation of a viewpoint in an HMD-type multifocus display system using a laser-scanning method. In addition, we demonstrate that the accommodation effect could be provided independent of the viewing condition of the viewer.

The single cavity all-dielectric thin film Fabry-Pérot filter (s-AFPF) has been investigated in this paper as a means of tuning the wavelength in an external cavity diode laser (ECDL), and the means of limiting longitudinal mode hopping has been also investigated. When a TE or TM plane wave irradiates an s-AFPF, a quasilinear relationship is found in a certain wavelength range between the optical intensity peak-transmittance wavelength of s-AFPF and the cosine value of plane wave incident angle at s-AFPF. Based on this feature, we proposed and investigated a configuration with an s-AFPF in an ECDL. By theoretical calculation, a mode-hop-free wavelength tuning range of about 8 nm around 1551.5 nm was achieved. Also, a method in further extending the width of the mode-hop-free wavelength region is proposed and discussed. The ECDL can be used in the application of environmental monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on.

In this paper, for the first time, we present a small signal circuit model of InGaAs/GaAs self-assembled quantum dot (QD) laser, based on the standard rate equations. By using the presented model, modulation response of QD laser is investigated. The simulation results show that retarded carrier relaxation due to phonon bottleneck degrades the modulation and impulse responses of a QD laser. It is shown that modulation bandwidth is increased with larger inhomogeneous broadening. Also, our model describes the effects of carrier recombinations inside and outside of a QD region, on the modulation response behavior.

In public security related applications, many suspicious samples may be a mixture of various chemical components that makes the usual spectral analysis difficult. In this paper, a terahertz spectroscopic statistical analysis method using a microgenetic algorithm (Micro-GA) has been proposed. Various chemical components in the mixture can be identified and the concentration of each component can be estimated based on the known spectral data of the pure chemical components. Five chemical mixtures have been tested using Micro-GA. The simulation results have shown agreement with other analytical methods. It is suggested that Micro-GA has potential applications for terahertz spectral identifications of chemical mixtures.

Surface plasmon resonance is particularly important due to the ability of biomolecules of interest to interact with a specific binding partner, and may therefore be more informative than generic measurement techniques. A growing number of robust and reproducible immobilized surfaces chips are available from Biacore, allowing us to analyze various biomolecular interactions. Here we describe a protocol by which the Biacore chips may be reused multiple times to analyze biomolecular interactions without interfering analysis from previously used surfaces or analytes. This procedure will not only help to extend the lifetime of these chips but at the same time render them to be more commercially affordable, especially in a resource-poor setting. The time range for the entire protocol is ∼1 day, including stripping off previously immobilized materials and re-functionalization of gold surface.

Although a sinusoidal bias method is introduced to avoid working in the death band for a majority of time, the mechanical dithered ring laser gyro (RLG) still encounters information loss when crossing the zero rate point. A novel lock-in error correction method is proposed which can pick up the lost information and remove the random walk error radically. The lost information at the zero rate crossing can be expressed by such parameters as the phase and phase acceleration of a beat frequency signal. These parameters are sampled every time the phase crosses the zero rate point, and two correction trains are formed. Using the minimum variance method, the correction trains are properly scaled to compensate the output of RLG. Experiment shows that even in a bad working condition, this method can achieve satisfactory results.

The process of preparing Er³⁺-doped barium borosilicate glass samples with different dopant concentrations using a high-temperature sintering technique is discussed. Under a 978-nm semiconductor laser excitation, the energy transfer from ²H11/2 to ⁴I15/2 and ⁴S3/2 to ⁴I15/2 caused by the transitions of Er³⁺ ions yields a 534- and a 549-nm green fluorescence. The relationship between the absolute temperature T and the fluorescence intensity ratio R of these two up-conversion photoluminescence spectra is discussed and fitted to the exponential function R = 1.782exp ( − 328/T) in the temperature range of 298 to 698 K. The sensitivity of the samples descends monotonously from 0.00219 to 0.00075 K−¹ with the temperature increase from 298 to 698 K. The data are of undoubted repeatability, and the proposed doped glass is suitable for sensitive, high-temperature measurement.

We present a prototype for optical single sideband (SSB) modulation with carrier (OSSB+C) by employing an overwritten fiber Bragg grating (FBG) is proposed and demonstrated. The grating is written using two different uniform phase masks of slight variation in the period. Then it is used in millimeter-wave SSB modulation scheme. Its operation principle can be concluded as the following two steps: (i) first, an intensity modulator double sideband (DSB) modulates the lightwave with millimeter-wave driving signals; (ii) then, the generated DSB modulation signals are reflected by the overwritten FBG. The overwritten FBG can reflect the carrier and the sideband simultaneously, resulting in two coherent subcarriers. Thus the conversion from DSB to OSSB+C can be easily achieved by using only one grating. Also, carrier-to-sideband ratio (CSR) can be optimized by using grating with different reflection depth. We demonstrate this scheme via simulation and successfully reduce signals' CSR from 14.44 to 1.25 dB.

An interesting security technique that uses the dark-bright soliton conversion control within the microring resonator is proposed. The obtained outputs for a dark-bright soliton dynamic state can be controlled and used to form the public key suppression for communication security application. However, a good design should be possible to be fabricated; therefore, by using the parameters based on the practical device parameters, the simulation results obtained have shown that the proposed system can indeed be achieved. The public key suppression and public key recovery can be used in a highly secure communication system and has potential applications in optical cryptography.

We present a novel upstream multiwavelength shared ethernet passive optical network architecture, based on a proposed self-seeding Fabry-Pérot laser diode (FP-LD) at the optical network unit. The performances of the wavelength and power stability, side-mode suppression ratio, and tuning range for the proposed tunable self-seeding laser module are experimentally investigated. The bit-error-rate measurement is performed with direct modulation on FP-LD of 1.25 Gbps upstream data. The performance benefits from the upstream wavelengths sharing are showed via simulations.

In this paper, we approximate the fundamental mode in single mode step and graded index optical fiber by a single parameter Lorentzian function within scalar variational framework. We show that it works in a low V region, a region important for evanescent wave coupling, more accurately in terms of propagation constant in comparison to single parameter Gaussian for linear and nonlinear fibers. Furthermore, we show that the low V variations of normalized propagation constant b(V), group delay d(V), and waveguide dispersion g(V) with V based on Lorentzian approximation match more accurately with the results for linear optical fiber in comparison to Gaussian approximation in the low V region.

Since a deep and long-term fading in optical intensity results in considerable burst errors in the data, a terrestrial free-space optical (FSO) system has to be designed with consideration of a frequency characteristic of optical scintillation to achieve high quality wireless services over the link. In designing a terrestrial FSO link, we had better design the system considering variations caused by some slow time-varying parameters. This paper proposes a Butterworth-type spectral model of optical scintillation to design a terrestrial FSO link, which enables us to estimate the power spectral density of optical scintillation in a current optical wireless channel when time zone and weather parameters, such as temperature and rainfall intensity, are given. The spectral parameters of optical scintillation, cut-off frequency, and spectral slope are estimated from the data obtained in the experiment, and then their dependencies on time zone, temperature, and rainfall intensity are examined.

This work presents a means of active actuation of the suspension structure with a holographic optical element (HOE) for the small-form-factor optical-disk drives. The proposed HOE module sensor is mounted on a swing arm swivel-drive mechanism with unique features, including a rotary actuator for tracking and a swing arm nutates along a pivot for focusing. The fabrication methodology for a cantilever-beam-like structure with HOE module sensor is investigated. Furthermore, the performances of optical module with swing arm-swivel actuation are experimentally evaluated to demonstrate the effectiveness of precise flying height positioning measurement method.

We propose a real-time pose estimation method that addresses the weaknesses of the numerical inverse kinematics method. Using conventional inverse kinematics based on the numerical method requires many iterations; moreover, a singularity in the Jacobian matrix as well as a local minimum problem can occur. To solve these problems, we propose an inverse kinematics method combined with an unscented Kalman filter (UKF) to recover intermediate joint information. Because the numerical inverse kinematics method optimizes a state, the solution can often converge to the local minimum and require many iterations. We use several sigma points for analysis to find the optimum state by using an unscented transform. The improved method using a UKF converges faster than the numerical inverse kinematics method for the global minimum of the existing inverse kinematics. We use 2-D image processes to extract body areas from the input images, and a 3-D reconstruction algorithm is used to estimate the 3-D positions of the extracted human body area. Using the improved method, we generate intermediate joints for each body part and the results show that the proposed method reduces the computational complexity and increases the accuracy of estimation compared to conventional numerical inverse kinematics.

We evaluate the performance of different key-point detectors and region descriptors when used for automatic classification of small sea targets in infrared video. In our earlier research performed on this subject as well as in other literature, many different region descriptors have been proposed. However, it is unclear which methods are most applicable to use on the type of infrared imagery as used onboard naval ships. The key-point detector should detect points of interest that can be used to effectively describe the objects in the imagery. On the basis of the detected key points, the descriptors should discriminate between different classes of small sea targets while being robust to differences in viewing conditions. We propose a similarity measure based on the distance between key-point location and the Euclidean distance between descriptors to quantify the similarity of images. For performance evaluation, we use the receiver operator characteristic as the criterion to rank the evaluated methods. We compare the Harris-, blob- and scale-invariant feature transform (SIFT) detectors and the square neighborhood, steerable filters, invariant moments, and SIFT descriptors. We conclude that the Harris detector combined with the square neighborhood of size 19×19 or the SIFT descriptor results in the best classification performance for our data set.

In this paper, we incorporate a set of sophisticated algorithms to implement a leaf segmentation and classification system. This system inherits the advantages of these algorithms while eliminating the difficulties each algorithm faced. Our system can segment leaves from images of live plants with arbitrary image conditions, and classify them against sketched leaf shapes or real leaves. This system can also estimate the three-dimensional (3-D) information of leaves which is not only useful for leaf segmentation but is also beneficial for further 3-D shape recovery. Although our system requires more than one image to reconstruct the 3-D structure of the scene, it has been designed so that only a few images with close viewpoints are sufficient to achieve the task, thus the system is still flexible and easy to use in image acquisition. For leaf classification, we adopt the normalized centroid-contour distance as our classification feature and employ a circular-shift comparing scheme to measure leaf similarity so that the system has the advantage of being invariant to leaf translation, rotation and scaling. We have conducted a series of experiments on many leaf images and the results are encouraging. The leaves can be well segmented and the classification results are also acceptable.

This paper proposes a polynomial-style region incremental multisecret image sharing (PBRIMSIS), for sharing multiple secrets in an image among n participants. The method enables the dealer to distribute the content of an image S to multiple regions, where each region is associated with a certain level of secrecy. In the proposed n-level PBRIMSIS scheme, input image S is encoded to n+1 shadow images that exhibit the following features: a. each shadow image cannot reveal any region in S, b. any t (2 ⩽ t ⩽ n + 1) shadow images can be used to reveal these regions associated with up to t - 1 secret levels, and c. S can be completely reconstructed when all of the n+1 shadow images are available. A discrete cosine transform-based PBRIMSIS with a smaller shadow image scheme is designed to improve the transmission and storage of the generated shadow images. The property of incremental disclosure to the region-based secrets in an image is applicable to image sharing in diverse applications that require the sharing of multiple secrets with different secrecy priorities, such as in cooperative working or in military secrets.

This paper illustrates a forward-flipping architecture for lifting-based discrete wavelet transform (DWT), in which the multiplication and addition operations are flipped to different computation paths in each lifting step through forward-flipping, and the critical path of each lifting step is shortened to one multiplication operation latency. Through case studies on the JPEG2000 default lossy (9,7) filter and the (6,10) filter, the efficiency of the proposed architecture has been demonstrated and confirmed. The comparison results have also shown that the proposed architecture is efficient in reducing the number of pipeline registers for the implementation of DWT under the given timing criteria.

Analyzing composite behaviors involving objects from multiple categories in surveillance videos is a challenging task due to the complicated relationships among human and objects. This paper presents a novel behavior analysis framework using a hierarchical dynamic Bayesian network (DBN) for video surveillance systems. The model is built for extracting objects' behaviors and their relationships by representing behaviors using spatial-temporal characteristics. The recognition of object behaviors is processed by the DBN at multiple levels: features of objects at low level, objects and their relationships at middle level, and event at high level, where event refers to behaviors of a single type object as well as behaviors consisting of several types of objects such as "a person getting in a car." Furthermore, to reduce the complexity, a simple model selection criterion is addressed, by which the appropriated model is picked out from a pool of candidate models. Experiments are shown to demonstrate that the proposed framework could efficiently recognize and semantically describe composite object and human activities in surveillance videos.

It has been demonstrated that multibiometrics can produce higher accuracy than single biometrics. This is mainly because the use of multiple biometric traits of the subject enables more information to be used for identification or verification. In this paper, we focus on bimodal biometrics and propose a novel representation and recognition approach to bimodal biometrics. This approach first denotes the biometric trait sample by a complex vector. Then, it represents the test sample through the training samples and classifies the test sample as follows: let the test sample be expressed as a linear combination of all the training samples each being a complex vector. The proposed approach obtains the solution by solving a linear system. After evaluating the effect, in representing the test sample of each class, the approach classifies the test sample into the class that makes the greatest effect. The approach proposed is not only novel but also simple and computationally efficient. A large number of experiments show that our method can obtain promising results.

A method is demonstrated for writing long grating phase masks, which can be used for patterning large-area (square meter size) submicron-period gratings. The method consist of illuminating a small area transmission grating phase mask by a continous wave transverse-electric-polarized collimated laser beam under the −1st order Littrow mounting to define a high-contrast interferogram composed of fringes. By sliding a long photoresist-coated substrate under this small area phase mask, gratings of arbitrary length may be written, with grating lines oriented in the scan direction. The patterning of uninterrupted gratings with lengths exceeding 300 mm is demonstrated.

A displacement measurement technology using phase-encoded target joint transform correlator (PETJTC) is analyzed in detail. A phase mask is generated electronically and applied to encode the target image. Input images include the phase-encoded target image and the reference image. The joint power spectrum of the input images are obtained and encoded by the same phase mask. Through another Fourier transform the brightest peak in relation to displacement between the reference and target image appears in the correlation plane. In contrast to the displacement measurement based on traditional joint transform correlator, PETJTC could efficiently use the space of the input plane such as spatial light modulator, disperse the autocorrelation item into system noises, and leave the cross-correlation items only, which is convenient for detection. The effects of phase mask with different sizes and different types of noises are analyzed. Results based on digital computation show that PETJTC has a higher performance if the phase mask is bigger and has strong robustness under severe noise. Different displacement measurement technologies are contrasted. PETJTC could accurately detect the displacement. Root mean square errors can remain within 0.1 pixel.

This paper is aimed to investigate the potentiality of describing and differentiating optical-anisotropic properties of biological liquid crystal net by statistic analysis of coordinate distributions of a new analytical parameter, a complex degree of mutual anisotropy.