Aspherical surfaces are more and more used in some high precision optical systems of Thales Angenieux. They must conform to the same quality criteria of form and roughness as the other surfaces. However, their manufacturing is complex and cannot use the conventional methods of spherical or plano surfaces manufacturing. It is particularly difficult to meet simultaneously the form and roughness requirements even with the latest production techniques. Among the different possible aspherical surfaces manufacturing methods, Thales Angenieux chose to develop an industrial manufacturing process which combines two manufacturing methods: a microgrinding and a magnetorheological finishing. It was at first considered a manufacturing process with two stages of microgrinding and one stage of magnetorheological finishing. However, it was not possible to produce surfaces which meet the required criteria with these three stages despite an optimisation of microgrinding parameters. It proved to be necessary to insert a stage to insure the transition between a microgrinding stage and a magnetorheological finishing stage. This manufacturing process allows on the one hand to produce an aspherical surface with a form PV around 150 nm and a roughness Rms between 1 to 2 nm and, on the other hand, proves to be compatible with industrial manufacturing requirements.

A small distinction of some micron makes an awful difference between spheres and aspheres. It takes special technological equipment to manufacture and test aspheric optics. This equipment is clearly distinguished from that for classical optics manufacturing. This paper deals with equipment installed at JENOPTIK L.O.S. and give results based on serial manufacturing of aspheres.

Interferometric applications utilizing short coherence length sources, such as white light interferometry, require precise matching of optical path lengths for the two arms of the interferometer. If a cube beamsplitter element is utilized, the added dispersive material in the optical path could introduce undesirable optical path difference (OPD) effects and a consequent degradation in fringe visibility. For this reason a cube beamsplitter must be well matched for equal geometric path length in glass during the fabrication process. Two degrees of freedom must be controlled; the lateral position and relative rotation of the two prisms that comprise the beamsplitter. A method is described for efficiently assembling cubed beamsplitters utilizing a kinematic mount to adjust the relative position of the beamsplitter prisms with sub-micron precision for both degrees of freedom. The OPD is monitored simultaneously at three separate wavelengths during assembly by exploiting the color separation capabilities of a spatially congruent 3-CCD color camera. Once positioned to minimize the OPD, the prisms are bonded together with UV curing adhesive and any residual aberrations are quantified. The technique was proven by aligning prisms to 0.1μm accuracy and measuring the OPD error to 0.05μm accuracy.

Optical contacting is a very interesting technology to realise stable assemblies. We will describe the latest results that were achieved thanks to Silicate Bonding with different unusual materials as Silicon, Silicon Carbide and present some examples of complex assembly: 1. Double Fabry-Perot qualified for space application 2. Stabilised bench for ultra stables wavelength lock-up system.

As part of LMJ project (Laser Megajoule), CEA has built the LIL - Ligne d'Integration Laser - a LMJ prototype. This prototype uses full sized optics (400x400 mm²) with very tight specifications. SESO is one of the suppliers of optical components for this laser, among them filtering lenses - called L3 and L4 - used at 1053 nm (1ω), thin flat plates - continuous phase plates and debrishield - and thick windows, all used at 351 nm (3ω). All these optics are in fused silica and combine good wavefront specifications, very low roughness and no or few surface quality defects. Today, including spare parts, about 40 components have been produced. The purpose of this paper is to describe the facilities for grinding, polishing and finishing these optics. Computer Controlled Polishing robot for lenses Double side polishing machine for flat optics After a brief presentation of the specific metrology used, we give a detailed overview of the performances obtained on the produced components. This work is related to the LIL - LMJ project directed by CEA, France.

JSC "LZOS" manufactures astronomical mirrors from the stage of blanks to finished astronomical mirrors. During 1997-2002 JSC "LZOS" has fabricated a number of astronomical mirrors under the contracts with Carl Zeiss Jena, Germany, up to 2.6m in diameter and up to 100 μm asphericity. Concave surfaces are tested with lens and lens-mirror wavefront correctors of special design. The Hindle test set-up is used for convex hyperbolic surfaces. For high-aperture hyperbolic surface, we use two Hindle spheres to test one mirror. At the present time, we have developed the test procedures for high-aperture surfaces of primary (diameter 4100 mm, asphericity about 881 μm) and secondary (diameter 1240 mm, asphericity about 364 μm) mirrors for the VISTA Project as well as the Fizeau test set-up for the LAMOST M_B sub-mirrors.

Large optical elements are pivotal to the success of proposed Extremely Large Telescopes (ELTs) and are expected to constitute a significant proportion of the overall cost. It is expected that primary mirrors will be formed from several hundred to a few thousand 1 - 2 metre hexagonal segments. Existing manufacturing methods developed for producing large precision optics are characterised by long process times, significant measurement iterations and a high dependency on human skill. A previous low demand level for large optics has resulted in a correspondingly low attention to their production optimisation. Established manufacturing techniques for large optics in high volumes limit the range of optical shapes to spherical and flat forms. Methods for producing mirrors to aspheric shapes have been developed and used for astronomical telescopes but the cost and timescales involved in making large numbers of aspheric elements with such technology could be prohibitive. To enable reliable and cost effective manufacturing of such mirrors in volume a fresh perspective is necessary. A review has been made of both existing state-of-the-art and developing technologies which could improve the manufacturing efficiency of large optics processing. The suggested way forward is a manufacturing chain based on closely integrated machining and metrology operations. Capability of this integrated manufacturing route is oriented around “free form” aspheric surfaces but optimised to be cost competitive with established processes applicable to only spherical and flat surfaces.

This paper is intended to establish the second progress report of the manufacturing and testing of the Gran Telescopio Canarias optics, i.e. the segmented primary mirror and the lightweighted secondary mirror.

Modern optical systems must satisfy high demands in terms of functionality and performance. With complex optical elements the problems in manufacturing surfaces with sufficiently high quality require new approaches in manufacturing technology. Although the geometrical shape of such structures can be generated by different means, achieving a high surface quality is not always possible for complex surfaces. A concept for the manufacturing of high quality complex glass surfaces is presented within this publication. The idea is to develop a microwave assisted thermal polishing process supported by CO₂-laser radiation. This combination aims to the reduction of thermal gradients in the glass, by heating a definite glass volume during surface treatment using laser radiation. To realise the high surface quality it is absolutely necessary to control the process temperatures. With temperature measurement devices i.e. pyrometers, the average volume temperature is monitored as well as the temperature in the laser spot on the glass surface. By controlling the temperatures of the volume and the temperature on the optical glass surface, it is possible to implement a stress reduced thermal polishing process. The results of the software based process controlling will be shown by means of CO₂-laser polished samples. Additionally the method of process optimisation by analysing the control parameters will be explained and demonstrated. The use of such a system allows the processing of many temperature based laser process applications of amorphous materials. The request for quick polishing processes, independent from the 3D-shape of the surface will be reached by this innovative technique.

The manufacturing of optics is an important field of technology and will serve key-markets in the future. The research activities of the Transregional Collaborative Research Center ”Process Chains for the Replication of Complex Optical Elements” SFB/TR4 of the Universities of Aachen, Bremen and Stillwater (USA) have the objective to lay the scientific foundations for a deterministic and economic mass production of optical components with complex geometries, e.g. aspheric, non-rotational asymmetric or microstructured surfaces eventually superimposed on freeform geometries. The paper presents an approach for an integrated simulation and measurement interface for the analysis of manufacturing effects during the mold making as well as first results of its application on the basis of the manufacturing of mold inserts.

Germanium for many years has been the prevailing material in infrared equipmentis. The reduction in cost appeared recently in uncooled thermal imagers and peculiarly in uncooled detectors either bolometer or ferroelectric give to the cost of the Germanium optics an increased relative importance. Obviously it has been researched ways to reduce cost of the optics by limiting the number of lenses with aspherics or aspherodiffractive surfaces or by using faster manufactoring tools but it still remains the constraint of the cost per kg of Germanium and the fact that Germanium is not a moldable material. In Infrared some Chalchogenide Glass are known to be transparent and moldable and at least two of them (AMTIR and GASIR) have been developed and commercialized with technical characteristics enabling them to be used widely in IR equipmentis . Concerning the price as they are made of Ge As Se or Ge Sb Se with a percentage not exceeding 33% Ge and as their density is lower than Ge it allows to get blanks typically half price per volume. To get molded lenses specific process had to be developed to maintain the homogeneity of the material during the annealing , to achieve the right shape and roughness of the surface .In addition to that the molded surface should not be polluted to allow further efficient coatings (anti-refection or Diamond Like ) to be deposited . Nevertheless a minimum quantity of lenses is required to amortize the cost of the molding tools.

Umicore IR Glass is a company specialising in the production of chalcogenide glasses and moulded optics. The standard glass compositions are GASIR1 (Ge₂₂As₂₀Se₅₈) and GASIR2 (Ge₂₀Sb₁₅Se₆₅). These materials are transparent in the 3-5 μm and 8-12 μm bands. An industrial process has been developed to produce these two glasses with well controlled properties. The reproducibility of refractive index is for example better than 2.0 x 10^-4 at 10 μm. A unique and high precision moulding technology has been developed to produce low cost chalcogenide glass lenses with high performance levels. Spherical, aspherical and asphero-diffractive lenses are manufactured with very accurate surface precision. The form defect of the moulded surfaces can be less than 0.4 μm with a typical roughness of 10 nm. When depositing an antireflection coating onto the moulded lenses, the reflection losses are reduced, raising the transmission to 98%, compared to 70% for uncoated lenses. A durable coating has also been developed as a protection for exposed lenses. Coated asphero-diffractive GASIR optics, used in infrared cameras give good quality images. The performance is comparable to that of an optical system with aspherical germanium. GASIR offers a cost-effective alternative to germanium for thermal imaging, especially for medium to high volume applications, both commercial and military.

This paper presents the results of an experimental study on the influence of aging on the cutting mechanics of glassy polymers. Polystyrene (PS), a glassy polymer, typically behaves brittle when subjected to a stress, it can be made ductile by rejuvenation. It was expected that PS would show a different cutting behaviour when it would be aged or rejuvenated. To investigate this two different molecular weight PS grades were used. Both aged and (mechanically) rejuvenated samples were made from each grade and cut. Cutting forces, chip morphology and surface quality were investigated. Although the chips showed no differences in brittleness and ductility, the measured cutting forces indicated that there is a difference between aged and rejuvenated PS. Also an interesting difference in cutting forces between the two PS grades was found. Investigation of the surface quality of the PS samples showed that the aged samples have smoother surfaces than the rejuvenated samples. It can be concluded that aging does have effect on the cutting mechanics and the obtained surface roughness.

On the 3ω part of the LIL laser many optical components will have to sustain fluences above 10J/cm². Even if current progress in silica substrate technology decreases the number of defects/cm² which can induce a damage under such a laser flux, tens of damaged sites will appear on large surface optics. Knowing that these surface damaged sites grow exponentially with the number of laser shots, it is necessary to stop the growth of these defects before the use of the optical component is impaired. In this paper we use localized re-fusion of silica, induced by a continuous CO₂ laser, as a means to reshape the damaged site and circumvent the growth of laser-induced surface damages. In a first part we compare the 1 and 2D model of the interaction of a gaussian laser beam with an homogeneous material and deduce that the 1D model is convenient down to a laser beam radius waist of 100 μm in silica. We show that at atmospheric pressure total mitigation might not be achieved due to silica evaporation and peripheral redeposit in air. This risk cannot be managed with predetermined laser power and interaction time, because thermal conductivity of silica is not homogeneous. In order to keep the process “vacuum free”, a radiometry diagnostic has been mounted to monitor the surface temperature of silica. Real time retroaction on silica exposure to laser radiation enables us to control surface silica evaporation.

In the field of the development of LIL and LMJ fusion class high power lasers, CEA has made important efforts to understand and improve laser induced damage threshold of fused silica optics at the wavelength of 351 nm. Since several years, we have focused on optimizing the grinding, polishing and post polishing processes to overcome the existing performances with various industrials and academics partners. In this paper, we describe our understanding of the nature of the polished silica interface and our approach to rich our damage threshold goal. Our efforts were mainly put on reducing the cracks region extension and removing or optimizing the polishing top layer. We give also some details on the influences of each of the polishing process from rough material grinding to post processing. We demonstrate that some order of magnitude in laser damage initiation density can be gained by combining appropriate fabrication steps.

Unlike other drive fusion class laser, Megajoule laser (LMJ) and its first prototype, the Laser Integration Line (LIL) are equiped with specific diffractive optical components. All these optics are situated in the final optic assembly. An high efficiency diffraction focusing grating called 3w grating is used to focus the beam into the center of the target chamber instead of a classical focusing lens. Another large grating called 1w grating is used for optical path compensation purposes. Both gratings have a dimension of 420x470mm² and are working at an incidence of 25°. Gratings are plano transmission holographic gratings directly engraved into fused silica substrates. The 1w grating is working at the wavelength of 1.053μm, its grooves are straight and equispaced. The 3w grating, is a focusing grating working at the wavelength of 0.351μm. Its grooves are curved and non equispaced. Jobin Yvon was selected by CEA to manufacture these two types of diffraction graintgs. After processes developpements and facilitization, a complete batch of twelve 1w gratings and sixteen 3w gratings were delivered to CEA for integration. After a brief presentation of CEA's specification for this diffractive components, we give some details on the manufacturing processes. We also demonstrate good agreement between specified and manufactured component. We give an overview of the global production performances

French Megajoules laser (LMJ) and Ligne d'Integration Laser (LIL) are two high power lasers using large diffractive components for focal spot conditioning. Those components are a 420x470 mm² focusing grating and a 398x383 mm² continuous phase plate (CPP), both working at wavelength 0.351 μm. In order to control the tight specifications that have to meet those components, CEA and company Jobin-Yvon, in charge of their manufacturing, have developed specific setups. After a brief introduction describing specifications and requirements, we will present the different setups and analysis software used and finally discuss the different measurements that could be done.

The characterization of sub-micrometer period gratings by resolution of the inverse problem has become a real need in the area of the microelectronic. We present an optical scatteromettric method based on the use of a Neural Network (NN). This one permits to learn the relationship linking the diffracted efficiencies to the geometrical parameters. The great advantage of this method is to reject the limitations in resolution that occur with classical microscopic characterization. Theoretical results are demonstrated in this paper. The characterization can be achieved with accuracy close to 5 nm. We also study the index influence on the results and the importance of the choice of the assumed profile shape. Experimental results concerning a silicon 1-μm-period grating are also demonstrated. Finally, a comparison with results obtained by a microscopic characterization permits the validation of the presented method.

An ultra-high resolution measurement technique makes the assessment of the period uniformity in a long grating used as a phase mask for Fibre Bragg Gratings (FBG). It comprizes a pair of two identical displacement sensors placed close to each other at a strictly constant spacing flying over the grating under test at an essentially constant velocity. The phase difference between the two sensors is a simple function of the local spatial frequency of the grating. A proper solution of an inverse problem provides the period variation along the grating. The technique is used here to characterize phase masks fabricated by means of a MEBES 4500 electron beam pattern generator. The period does not deviate by more than 3 pm from the prescribed period over a length by more than 100 mm.

Many industrial and scientific applications require high power ultrashort laser pulses, so amplification of pulses is necessary. To avoid optical damage or nonlinear effects in the amplifier setup, the pulses are stretched before amplification and recompressed afterwards. One possibility for the efficient stretching and recompression is to apply highly efficient diffraction gratings, whereby dielectric gratings and especially dielectric transmission gratings feature a high damage threshold. If the incident pulses are not linear polarized, the polarization sensitive diffraction efficiency of the gratings mostly results in a significantly reduced pulse energy. To overcome this problem we developed highly efficient polarization independent gratings and present a theoretical and experimental study on the design and fabrication of highly dispersive transmission gratings in fused silica, that exhibit a high diffraction efficiency for TE and TM-polarized illumination as well. The dependence of the diffraction efficiency on the grating parameters is discussed for both polarization directions. One of the theoretical designs shows a diffraction efficiency exceeding 97% for unpolarized illumination. The fabrication of those gratings has been done by electron beam lithography and reactive ion beam etching, whereby the diffraction efficiency was maximized by a special trimming process. The theoretical considerations are confirmed by the fabricated samples.

In Astronomy field, grisms or transmission gratings replicated on a prism are widely used to transmit in line the spectrum. To work in the infrared range, classical grisms present important limitations: the epoxy layer, necessary for replication, absorbs IR light, and in addition this layer constitutes a problem when instrument is used at low temperature. Jobin-Yvon company, in collaboration with LAM in Marseille, France, designed and manufactured a transmission grating engraved directly into IR fused silica substrate. The transmission efficiency of the manufactured grating is 60% to 70% in natural light over the 1.5 to 2.5 microns wavelength range. The number of grooves was 400 g/mm. Other wavelength ranges are possible with similar efficiency, for example: 1.0 to 1.4 microns or 1.4 to 1.9 microns. This grating made only only of fused silica, will survive without problem at any low or very low temperature, or vacuum environment.

PLATIMO is a photonic devices micro-components integration unit set up by the CEA-LETI in the Optronics Department thanks to a contribution of the Rhone-Alpes region. The aim of PLATIMO is to propose to industrial and institutional designers a partnership with the knowledge, experience, and necessary automated equipment to speed up the prototyping process and to develop automated assembly solution. To illustrate the capabilities of PLATIMO, we present two very different realisations using the optobonder. The first realisation is a microchip laser assembling with pick-and-place components. The second realisation is an 8-channel V-groove assembling to a planar waveguide splitter by active alignment.

Grating coupled evanescent wave slab waveguide biosensors are now well established about twenty years after they were demonstrated. They usually rely upon mode excitation from the substrate side, providing a means to measure the bioreaction at the waveguide surface through the monitoring of the conditions of mode excitation. A new readout principle will be presented whereby the incident beam undergoes a sharp and high reflection while being trapped into the biomaterial loaded grating waveguide. The high index metal oxide waveguide and the grating are designed so that the evanescent wave sensitivity is maximum and the conditions for resonant reflection are fulfilled for both polarizations close to normal incidence. Under these conditions, the grating corrugation cannot be located on both sides of the waveguide, as usually preferred, since the grating strength of the TM polarization would be too low. The corrugation must therefore be at the analyte side of the metal oxide layer ; this calls for a specific grating fabrication technology. The option retained for low cost manufacturing is that of wet etching of Ta₂O₅. This is quite a challenging problem since there is no wet etchant of high density Ta₂O₅ which does not dissolve standard photoresist, and since the isotropy of wet etching is likely to smooth out the required short period corrugation by underetching. This paper describes the rationale of the design of the reflection interrogation scheme and brings the experimental evidence of the effect obtained on wet etched sensor platforms.

This paper presents a quantitative measurement of the effect of surface roughness of optical fiber end-faces on light coupling efficiency. Fibers tested included cleaved fibers and fibers with ground endfaces of varying degrees of surface roughness. The endfaces were ground on a specially built nano-grinding machine. The assessment was based on the Gaussian distribution of the intensity of light collected from both the cleaved and the ground endfaces of the fibers. Measurements of the total amount of light at the output end were also made. Results showed that light-coupling efficiency has improved dramatically with the improvement of surface finish. Surface roughness measurements were carried out using atomic force microscopy (AFM)

The latest development of sophisticated high-precision optical devices necessitates precision fabrication methodologies of freeform microlens having very tight, up to micron tolerance. Instead of adopting high-end multi-axis freeform machining approach, the proposed acrylic multi-surfaced microaspheric lens, with the axial diameter of 1.3mm, was cost-effectively prototyped and fabricated by single point diamond turning and micro-injection molding technology respectively. The micro-optical component was used as an opto-electronic module for high-speed data-transmission in fiber optics. Sequential fixturing technique was applied to facilitate the precise fabrication of the optical surfaces from different optical alignments. The aspherical accuracy and surface finish of the machined surfaces were evaluated, and end result was determined to be satisfactory. Further, the ultra precision tooling would be developed for micro-injection molding for carrying out mass production of the micro-optical component.

There are numerous methods for evanescently coupling energy into the modes of a sphere. In this paper, we provided a new methods, used long period fiber gratings (LPFG) coupling evanescent wave into microsphere resonator. We have illustrated this coupling mechanism in theoretical. As an potentially application, we describe a four-port passive Add/Drop device based on the microsphere-LPFG coupling mechanism.

In this letter, we designed and fabricated an all fiber-optic Add/Drop element based on Taper-Resonator-Taper (TRT) structure, assembling it with V-shaped grooves. We proposed a novel configuration composed of two microspheres and three taper fibers . We can cascade this kind of TRT structure, it will be potentially used as multi-wavelengths Optical Add/Drop Multiplexer and Wavelength Division Multiplexer/Demultiplexer.

In this paper we will present determination of refractive index profile of an ion exchanged planar waveguide using wedge technique. The sample preparation, data analysis and experimental results will be presented.

Problem of testing fine optics in industrial conditions with the highest accuracy is considered. Requirements to the quality of optical surfaces and wavefront errors referred to various kinds of optical systems are discussed. The disadvantages of the use of test parts with etalon surfaces in interferometric measurements are considered and the dead circle of the use of the unknown-shaped reference surfaces is revealed. The solution of this problem is proposed through application of the point diffraction interferometer (PDI). The advanced schematic of such an interferometer is presented; unlimited accuracy and industrial testing possibilities of the upgraded Linnik interferometer are discussed.

A complete absolute interferometric test of aspheres is presented. The method is based on a specially designed computer-generated hologram (CGH), which reconstructs an aspherical wave as well as auxiliary waves. The auxiliary waves are used for calibration. The aberrations of the auxiliary waves are measured absolutely by means of established absolute testing methods. The errors of the auxiliary waves can be transferred to those of the aspheric wave. Methods for absolute testing of aspheric surfaces using multiplex CGHs are described. Test procedures are explained and equations are derived. For axially symmetric aspheres, experimental results are presented and a comparison with the established N-position rotation test is given.

Interferometric testing of optical surfaces is problematic when strong asphericities are present. The spatial frequencies of the interference fringes exceed the detector resolution where the slope difference between test beam and reference beam is too large. CGHs are frequently used to avoid this effect but availability and flexibility is a problem. Alternatively we propose a new method to extend the dynamic range of interferometric measurements. For this purpose the reference beam in an interferometer is adapted. An active element containing a spatial light modulator (SLM) is used to vary the slope of the reference beam within a few degrees in both x- and y-directions. Hereby different areas of the interferogram become evaluable. Furthermore the active element can introduce phase shifts necessary for the phase shift interferometry algorithms. Several interferograms with different reference beam slopes are recorded and finally the phase functions are "stitched" together. By using an SLM for the reference beam tilt, no mechanical motion of any hardware which would limit the accuracy is necessary. A calibration of the tilts can be performed with interferometric accuracy.

Two experimental arrangements for measuring the local radii of curvature of an aspherical surface will be presented, together with a comparison between the experimental and theoretical values obtained. One of this experimental arrangement provides an average value of the radii of curvature in a subaperture with a ring shape. With the other method the measurements are done point by point over on a contour of the surfaces. The theoretical values for the local radii are calculate from the annular subapertures method testing an aspherical surface; also we be shown the advantage and limitations of these proposals.

A simple, ultra-compact, four wave achromatic interferometric technique is used to measure with high accuracy and high transverse resolution wavefront of polychromatic lightsource. The wave front to be measured is replicated by a diffraction grating into four copies interfering together leading to an interference pattern very similar to the intensity distribution obtained in the focal plane of a Shack-Hartmann microlens array. The grating is made of optical glass modulated in depth on top of which a chromium mask is printed. The amplitude mask acts like a Hartmann plate. Used in association with the phase mask, it allows suppression of the unwanted zero and second orders. A CCD detector located in the vicinity of the grating records the interference pattern. This new wavefront sensor is able to resolve wavefront spatial frequencies 3 to 4 times higher than a conventional Shack-Hartmann technique using an equivalent CCD detector. Its dynamic is also much higher.

A wavefront-generated simulator for Canada-France-Hawaii (CFH) 3.6-m telescope to test a novel wide-field IR camera (WIRCAM) of the telescope is presented. We investigate a Computer-Generated Hologram (CGH) wavefront generator to demonstrate off-axis aberrated wavefront generation with and with no rotational symmetry modes of Zernike polynomial as telescope wavefront simulator. A CGH simulator system to generate field optical performance of CFH telescope, while working on a F/3.8 prima focus with an field-of-view (FOV) of ±15 arcmin, is designed and computed for WIRCAM tests in optical labs for system performance evaluation. The CGH simulator is modeled as a diffractive surface defined by a phase function, and the optical phase function is specified by a Zernike polynomial phase equation. As the CGH simulator has to work in the first diffraction order, a carrier frequency must be added to the phase function in such a way to ensure the separation of the diffraction orders for eliminating unwanted light in the WIRCAM tests. Finally the nominal-design performance of the CGH simulator is compared with the tolerance analysis predictions as well as the system misalignment sensitivity.

Stitching Interferometry is a method of analysing large optical components using a standard "small" interferometer. This result is obtained by taking multiple overlapping images of the large component, and numerically "stitching" these sub-apertures together. We have already reported the industrial use our Stitching Interferometry systems (Previous SPIE symposia), but experimental results had been lacking because this technique is still new, and users needed to get accustomed to it before producing reliable measurements. We now have more results. We will report user comments and show new, unpublished results. We will discuss sources of error, and show how some of these can be reduced to arbitrarily small values. These will be discussed in some detail. We conclude with a few graphical examples of absolute measurements performed by us.

Zernike Polynomials are classically used to analyse optical wavefronts transmitted by optical systems, most of which have circular pupils. However, square (and rectangular) areas present a problem : Zernike polynomials are not orthogonal over theses shapes, and therefore care is required in their computation. A simple way around this is to use an ... orthogonal set ! One such set is readily obtained from the 1-dimensional Legendre set of polynomials, each 2-D polynomial resulting from the product of one "x" polynomial with " y" polynomial. However, this new set has a big drawback : It lacks desirable low order terms present in the Zernike set, most notably the essential "power" term ! One answer is to generate a set of polynomials, requiring them to adhere to the "Zernike format" as far as possible. As we show in this paper, this works very well, and generates terms such as the power term mentioned above. We will present the methods mentioned above, and show the new set which is being considered for inclusion in an ISO standard on interferometry, currently being drafted by an ISO Working Group. The author calls for comments on the usefulness of the new orthogonal set presented in this paper.

The coating deposition on large optical components (diameter 350 mm) has required the development of new metrology tools at 1064 nm. To give realistic values of the optical performances, the whole surface of the component needs to be scanned. Our scatterometer (commercial system) has been upgraded to support large and heavy samples. The other metrology tools are prototypes we have developed. We can mention the absorption (photothermal effect) and birefringence bench, a control interferometer equipped with an original stitching option, the optical profilometer (RMS roughness and small defect measurements). A detailed description of these metrology benches will be exposed. Their sensitivity, accuracy and capability to map the optical properties of substrates or mirrors will be discussed. We will describe the recent developments: the stitching option adapted to the Micromap profilometer to measure the RMS roughness on larger area (exploration of a new spatial frequency domain), the accurate bulk absorption calibration.

Since the wafer industry is using an increasing amount of double side polished wafers, the future of wafer metrology is very likely to shift from capacitance gauging techniques to optical measurement techniques. Participating in an international project the Technical University of Eindhoven is developing a self calibrating, traceable double side wafer flatness and thickness measurement device. By using proper measurement principles and advanced software a robust and traceable wafer thickness and flatness measurement instrument is created which combines high lateral resolution, nanometer accuracy, high speed and low cost.

Some of the techniques used for wavefront sensing that do not require coherent light sources are reviewed and a new arrangement developed by the authors is described. The latter ws produced as part of a study looking at absolute measurement of sphericity. It uses a measurement technique that basically determines the transverse ray-aberration (in effect the wavefront slope) associated with different parts of the pupil of the test piece and from this computes the wavefront distortion. The pixels of a CCD camera define the separate areas of the wavefront and in conjunction with scanning gratings, the signal from each pixel measures the associated wavefront slope. The wavefront distortion is computed from the slope values. The paper describes the results that have been obtained so far using the current breadboard arrangement as well as some of the advantages and disadvantages of the method compared to other techniques.

A new lens slope measurement system is developed and realized in the Philips CFT laboratory, which is named a transmission deflectometer. The slopes of two lenses are measured with this measurement system. A high measurement accuracy, 0.05 mrad, over a wide measurement range of ± 17° could be reached.

A novel optoelectronic set up based on a confocal extended field proprietary design has been developed for high resolution 3D surface sensing as well as for roughness and surface flaw characterization. The classical optical sectioning property of the basic confocal imaging design assumes that a monochromatic light beam is propagating forth and back from the elementary point source to the spatial filtering pinhole. When using a polychromatic light source, the residual chromatic aberration of the optical system reduces the optical sectioning global performance by enlarging the axial resolution (optical sectioning) by a quantity almost equal to the length of the axial chromatic aberration. When dealing with 3D surface sensing of the axial chromatic aberration can be considered as generating a highly accurate axial color coding, provided that an adequate color decoding of the backreflected light beam is realized. Consequently, it appears that it is possible to design customized confocal extended field point sensors with depths of field ranging from a few tens of microns (with subnanometric axial resolution) up to tens of millimeters (with micrometric axial resolution). Owing to the large Numerical Aperture of the confocal imaging set up perfectly specular optical surfaces can be easily captured with this type of instrument. Examples of Metrological 3D surface sensing of aspheric ophtalmic progressive lenses, small lens arrays and MOEMS will be presented and discussed.

A long-standing goal of optical metrology is testing aspherics without the need for part specific nulls lenses. The problem involves increasing the measurement dynamic range while preserving accuracy. The Shack-Hartmann wavefront sensor offers an interesting alternative to interferometry where the dynamic range is tied to the wavelength of light. Because the Shack-Hartmann wavefront sensor is a geometric test, the lenslet array can be designed in a way that trades sensitivity for dynamic range making it possible to test, without a null, aspheres that would otherwise require null optics. However, a system with this much dynamic range will have special calibration issues. Shack-Hartmann wavefront sensors are widely used in feedback control systems for adaptive optics. In that application, calibration is not a serious problem as the system drives the correction to a null; calibration errors slow the rate of convergence. For metrology applications, the calibration of the Shack-Hartmann wavefront sensor must be absolute. This presentation will discuss issues related to the design and calibration of a Shack-Hartmann metrology system including the design of an appropriate lenslet array, methods for dealing with induced aberrations, vignetting and spatial resolution limitations.

In this paper we describe an interferometric process using a polychromatic light source and a spectroscopic detection system. This method is used for surface metrology or for bulk optical components characterisation (dispersion for example). As classical monochromatic interferometry, it consists in comparing a reference wave front with one issued from the component to be tested. However this measurement is assumed by determination of the spectral dispersion induced upon the various frequencies of the light source spectrum. The aim of this work is both dispersion measurements and characterisation of aspherical surfaces

We present here a Z-scan based experimental setup and an adapted numerical simulation to perform absolute measurements of small nonlinear refractive indexes in the nanosecond regime, where bound electronic, as well as electrostriction and thermal effects, can occur. In order to have a reliable and stable experimental setup and a better sensitivity, a trimmed Airy beam has been used. An accurate study of the spatio-temporal parameters of the beam allows us to take into account the real nature of the beam in the nonlinear refractive index estimation. In these conditions, measurements have been performed in different types of fused silica at 1064nm and 532nm. A nonlinear refractive index of 5.2x10^-20m²/W has been found at 1064nm and 3.5x10^-20 m²/W at 532nm.

Focusing on small features for optical inspection or defect repair, shorter wavelengths are used to increase resolution and energy density. Objectives designed for 157 nm using calcium fluoride are optimized and evaluated interferometrically at the wavelength of use to include all actinic effects. An image evaluation set-up is presented using a custom illuminator to image 130nm features, enlarged 500 times, onto a back-thinned CCD camera in real time.

The functional lifetime of large aperture components used in high power lasers, like LIL and LMJ facilities, is mainly determined by laser damage measurements. Automatic damage test benches allow to obtain more data in less time than traditional tests. We present, first experimental procedures and statistical analysis made on small samples with mm-size beams, to determine damage densities and damage growth laws. The presented methods are the usual 1on1, Non1, Ron1 and Son1 tests and more specially the raster scan procedure. The tests and analysis are compared to other results obtained with larger beams (few cm²) on large optics. We show that the exact knowledge of each shot parameters (energy, surface and pulse duration) permits to determine the damage growth rate (and then to predict the lifetime of each optics), to precisely study self-focusing phenomenon and more to finely observe pre-damage-levels. In this way, the main parameters like fluence or intensity are associated to the observed phenomenon. Moreover laser beam diagnostics, many diagnostics used for the detection and the observation of damage occurrence are equally very important. It is also necessary to develop test procedures entirely computed which permit to scan all the surface of a component and to acquire in real time the beam parameters and the results of laser-matter interaction. Experimental results are reported to illustrate what could be achieved on an instrumented and automated facility.

A proper implementation of electro-optic materials in laser systems requires an accurate knowledge of their electro-optic coefficients, along with their temperature dependence which could be of importance at high power level. A new technique has been developed for this purpose, which takes advantage of the thermodynamic equivalence of two intensive parameters, namely the temperature and applied electric field. A suitably oriented parallelepipedic shaped sample is exposed to a laser beam and acts as a Fabry-Perot interferometer which is submitted to a linear ramp of temperature. The interference pattern is observed by reflection and the shift of interference fringes generated by the thermo-optic effect is detected through amplitude modulation of the light beam and recorded as a function of temperature. We then switch from amplitude- to phase- modulation by applying a suitable electric field to the crystal: the signal features now the derivative of the thickness fringes generated by the electro-optic effect. The thermo- and electro-optic coefficients are obtained from the fringe shift recorded respectively through amplitude- and phase- modulated operating modes. The study of both KTiOPO₄ and LiInS₂ single crystals is given as an example to illustrate the so-called Fabry-Perot Thermal Scanning Interferometric (FPTSI) method.

A group of European Research Institutes (Centre de Recherche Astronomique de Lyon (CRAL), Laboratoire d'Astrophysique de Marseille (LAM), University of Durham) and company (CYBERNETIX) have proposed to implement an Integral Field Unit (IFU) in NIRSpec instrument for the James Webb Space Telescope (JWST). After a brief presentation of the optical design of NIRSpec IFU, we will focus on the prototype of this module built by CRAL. This prototype is composed of two optical elements: a stack of eleven spherical tilted slices associated with a row of ten spherical tilted pupil mirrors. All the optical elements were manufactured by CYBERNETIX. We will introduce the fabrication procedures and an original method of assembling by molecular adhesion in order to comply with environment specifications. Afterwards, the image slicer is tested on the optical bench at CRAL. In fact, the first measure consists in placing a CCD camera in the pupil mirrors plane and determining the characteristics of the eleven images of the telescope pupil such as sizes, positions, photometric quality, diffraction effects and angular errors on slices and comparing these results with specifications. Then, the row of pupil mirrors is installed on the optical bench. In the slit mirrors plane, we observe a pseudo slit (ten images of the slices). We establish the same characteristics as in the first measure. Moreover, in the same plane, some Point Spread Function (PSF) measurements are made and we analyse the PSF in comparison with the simulation. The main results of the tests of the first image slicer prototype are presented. With the exploitation of the results, we validate and improve the image slicer systems for others instruments such as Multi Unit Spectroscopic Explorer (MUSE, study of a second generation instrument for the European Very Large Telescope (VLT)) and the European Space Agency (ESA) Integral Field Spectrograph (IFS) prototype.

Most optical systems are designed on the assumption that the optical component's performance is set soley by the functional specification i.e. that the shape, form, finish and refractive index of the component material. Lip service, at best, is paid to the fact that all materials have an absorption coefficient that dominates these parameters. Very little thought is given to the effect of the holder, that the absorption may not be spatially uniform or that the resulting temperature rise may be non-uniform, to birefringence, to changes in the refractive indices or to lowered damage thresholds, These effects in turn affect the beam propagation characteristics of the beam. All these effects have been observed in a variety of different laser systems. A series of examples are recorded to illustrate the theme and to illustrate the further contention that the performance of optical components needs to be tested in the systems in which they will be finally used. It will then follow that, in order to obtain agreement between optical component manufacturers and system manufacturers and users, standardised measurements have to be made.

The Infrared Atmospheric Sounding Interferometer (IASI), an instrument to be carried on METOP satellites, has been developed by Alcatel Space, for final use by CNES and EUMETSAT. The objective is an improvement of vertical resolution and accuracy of temperature and humidity atmospheric profiles measurement. This development created the need of an infrared collimator whose mission is to characterise Pixel Angular Response and to localise optical axis of the flight hardware. For this purpose, a collimator covering the spectral range 645 - 2760 cm^-1 has been designed, manufactured in collaboration with AMOS company and delivered to Alcatel Space. Infrared source uses a blackbody working from 310 to 1200 K followed by spectral filtering. Motorization allows angular orientation on two axes around the IASI instrument entrance pupil with a 10 μrad accuracy. The present contribution will provide the critical points, which have been identified and solved during manufacturing and testing inside CSL vacuum facilities.

The precise positioning of the individual optical elements is essential for attaining diffraction limited performance in high-numerical-aperture (high-NA) microscope objectives. Tolerances are in the micron range or lower for high-end objectives, e.g. for broad-band scanning confocal applications, metrology objectives in general, and especially for deep ultraviolet (DUV) applications. The ever increasing demands on imaging performance ask for the continuous development and improvement of specialized measurement equipment for the production line. Our award-winning 150x/0.90-DUV-AT-infinity/0 objective for wafer inspection and metrology at 248nm employs air spacings in its doublets because of the instability of optical cements against DUV radiation. This comes however at the cost of a higher number of surfaces and even higher precision demands on their geometry, orientation and positioning. We present several tools enabling us to meet these requirements. A Fourier transform fringe analysis scheme is adapted to high-NA Fizeau interferometry for surface characterization. A white light Mirau interferometer for dimensional measurements on lens groups with sub-μm resolution enables us to keep surface distance errors lower than 2 μm. Residual aberrations of the objective are compensated for by translating special correction elements under observation of the wave-front using a DUV-Twyman-Green interferometer, which also incorporates a 903nm branch for the parfocal adjustment of the infrared (IR) autofocus feature of the objective. To adjust the shifting element for the elimination of on-axis coma, we compute an artificial (real-time) star test from the interferogram, allowing interactive manipulations of the element while monitoring their influence on the point spread function (PSF).

Linear CCDs three-dimensional measurement system is constituted with three one dimensional imaging units (ODIUs) composed of charge-couple device (CCD) linear image sensor paired with equivalent cylindrical lens cells. The cylindrical lens is needed for optical transformation from object point to its realistic image line in the ODIU, and the imaging quality of equivalent cylindrical lens (width and distortion aberration of the image line) directly affected the reconstruction precision of three dimension coordinates. At present, the methods of how to design an equivalent cylindrical lens with both high precision and wide field of view were not reported in literatures. An improved Double Gauss structured lenses by replacing the first spherical lens in the traditional Double Gauss lenses with a cylindrical lens is introduced to realize the point to line optical transformation and aberration adjustment. The coma aberration and distortion can be automatically adjusted due to the structure symmetry of composite lenses, and the spherical aberration, astigmatism and curvature of field can also be largely adjusted by appropriately selecting material, luminous flux, curvature, thickness, and distance of lenses. Under the computer simulating by Zemax (an optical systems design software), the composite cylindrical lens was designed and fabricated. Finally, the three-dimensional positioning system made up of above-mentioned composite cylindrical lens and corresponding circuits is constructed, and the direct linear transformation (DLT) is adopted to three dimension coordinated reconstruction. The result of reconstruction error of X, Y, Z axis with in the view field of 700x760x500 mm less than 1mm are obtained.

The primary reflective surface of the Large Millimeter Telescope (LMT), it will be formed by a set of trapezoidal panels. Each panel has a paraboloid off-axis form and it is constructed with carbon fiber. The paraboloid off-axis surfaces is obtained copying by contact to a mold with the required form. One proposal in order to manufacture each mold, is made it of graphitizing steel fused. And after that, it lathing with a numerical control machine for obtain the paraboid off-axis section. But due to the dimensions of the sections, 5x3 meters for the biggest section; the mold of steel will be formed by two small segments. In consequence, it is necessary in the first place, alignment these segments in order to obtain a mold with a surface approximately continuous, with a minimum precision of 5mm. In this work we present a method in order to alignment these two molds' segments, as well as, the results of alignment obtained for the prototype mold.

Different applications of aspheric optics and their related fabrication methods are firstly summarized and then discussed using Carl Zeiss examples. This is done in order to highlight the potential and challenges of fabricating aspheric optics. The need to stimulate new ideas for extending manufacturing capabilities, process improvements and new fabrication technologies will also be outlined.