This paper describes the determination and selection of tolerance values used by a tolerance based weighting program written by the authors. Equations for the amounts of low and medium order wavefront aberration permissible in an optical system are plotted as a series of wavefront and transverse ray aberration curves. This data provides the basis for a determination of individual tolerancing schemes for particular optical designs, based on their performance requirements. The maximum amount of wavefront aberration allowable in an optical system, where the required performance is limited by the maximum spatial frequency required to be passed, is also considered. These permissible wavefront aberrations in terms of reduced spatial frequency are presented as a series of curves for a range of reduced spatial frequencies s. For a tolerance-based weighting scheme it is necessary to assign a set of tolerances to each of the aberration sample sites involved in the merit function in such a way that they can be interpreted by the optimization program. The method presented in this paper is to translate the permissible wavefront aberration curves into transverse ray aberration data. In this form the data becomes accessible to transverse ray aberration based optimization algorithms.

A new version of the SCAN program for electro-optical systems design and simulation is presented. SCAN is integrated software package for synthesis, analysis and optimization of scanning electro-optical systems. The theoretical principles, primary possibilities and the current state of the user interface of the SCAN program are discussed. The use of SCAN modules in structure of the real equipment is considered. Integrated software package `SCAN is designed for Commercial', Military and Scientific application.

All instruments incorporating lenses are produced with the help of a range of Computer-Aided Design (CAD) programs. Standardization of the way optical data is specified by these programs will enable the combination of lens designs with mechanical, electrical or electronic designs to take place with less effort and greater accuracy. The STandard for the Exchange of Product model data (STEP), a universal interface for CAD programs, has been devised and is now accepted as an international standard (ISO 10303). The Neutral Optical Data Interface Format is proposed as an adjunct to STEP to deal with the optical interface and a working group ISO TC172/SC1/WG4 has been set up to define it. A statement of the Scope of this Working Group, a brief description of the Application Protocol and an example of an Application Activity Model will be presented in this paper and details of a proposed survey to determine the needs of users and industry will be given.

Three methods have been investigated for detecting linear dependence between variables during damped least squares optimization. They are the angle (delta) between column vectors calculated from the scalar product, the normalized standard deviation of the ratios of corresponding elements and the singular values computed from a singular value decomposition. Optimization runs were made on a test lens where attempts were made to eliminate the causes of ill- conditioning by removing variables which were close to linear dependence. Results showed an improvement in the final merit function for all techniques with the exception of singular values. There was also a difference in the final solution forms which indicated that attempting to improve the conditioning of the matrix equations at source was advantageous for the test lens examined with forms closer to the optimum for the two successful techniques used for detecting linear dependence.

This talk concerns applications of a ray-trace model to the computation of the effect of diffraction on beam propagation. It reports the use of the technique in the design of apertures for space-borne instruments having critical diffraction properties. The modeling technique used is that of gaussian beam decomposition, a numerical beam propagation technique incorporated in a commercially available ray-trace program. The result is the powerful capability to model the optical field at any point, in systems of any geometry, with any amount of aberration. The technique is particularly useful for design problems where `non-imaging' effects are important, and examples of its use will be given. Although the computation requirements for such detailed analysis may seem daunting, the continuing increase in readily available computing power is now overcoming this drawback. The application here is to certain `diffraction-critical' situations, where the design of correctly sized apertures is needed for the control of unwanted diffraction effects. Three recent design studies are illustrated: (1) Millimeter wave imaging with off-axis reflectors. Analysis of the effects of aberration on coherent detection efficiency. (2) Long-distance beam propagation in space-borne laser interferometry. This involves the analysis of coherent detection efficiency in the presence of aberrated gaussian beams. (3) Design of a Lyot stop system for an infra-red radiometer which is to view the Earth's limb from space. Here the critical (and unwanted) diffraction is that from the bright Earth disc, lying just outside of the instrument field of view. The analysis technique is explained, and examples given of diffracted energy patterns analyzed at progressive stages in the system. It is shown how these aid the design and analysis of the systems. The aim is to show the range problems in which this method is useful, and to hopefully learn from others at the conference about other cases where such techniques have been used or else might be useful.

This paper presents a method of automatically adjusting aberrational weighting factors in a damped least squares optimization program, based on tolerance data provided for each aberration site. The method which is based on previous work by the authors and that of Yao has been developed into a tolerance-based method for aberrational weight adjustment. This enhanced method allows the user to set and adjust weights by a new tolerance-based method. The use of a power index ((rho) ) in the tolerance-based method provides continuously variable control over the amount by which the aberrational weights are adjusted. The practical use of the tolerance-based method is demonstrated using simple and well understood test lenses to reveal the modifications that take place within the iterative design progress, that result from aberrational weight adjustment. Suggestions for suitable tolerance schemes have also been investigated as an integral part of this work, based on the work of Hopkins.

In the late seventies, a theory for the aberrations of optical systems that are not symmetric was developed. This particular approach had the advantage of building directly on an optical designer's insight into the conventional Seidel aberrations. In today's high performance computing environment, it is now possible to use aberration field visualization tools to optimize nonsymmetric systems, without a working knowledge of the underlying vector aberration theory. The application of these methods to current problems in astronomical instrumentation will be demonstrated.

Most imaging optical systems require a fixed and stable relationship between the object and the image. Tilting and decentering of optical components due to manufacturing tolerances or thermal expansion will cause the image to move or tilt about the desired position. A method of modeling imaging optical systems is presented which uses affine transformations based on the paraxial optical equations. The method uses matrix and vector equations which are easily input, usually exactly as they are written, into many of today's math software programs for personal computers. Structural influence coefficients, or sensitivities, are derived for several common optical components. The resulting sensitivities can be computed and used in optomechanical tolerance budgeting. The equations can also be used as stabilization equations in actively controlled optical systems.

For Seidel aberrations of thin radial gradient-index (GRIN) lenses, approximate expressions that have the same structure as the homogeneous thin-lens expressions but include also specific gradient effects depending on lens thickness have recently been obtained. In this paper it is shown that the approximate thin-lens formulas provide new insight into the possibilities and limitations of aberration correction with radial gradients. When lens parameters are varied, the change of the exact values of the Seidel coefficients is remarkably well described by the approximate expressions. As a simple example, aplanatic correction with a single radial GRIN lens is investigated. Features of several solutions that have been optimized with ray-tracing are explained with the thin lens approximation and exact Seidel correction.

The corrective features of diffractive optics, as well as their ability to reduce costs, weight, size of conventional optical systems, show the great potentiality of these optics. In this field, the main application carried out by SFIM ODS is the chromatic aberration correction for high quality imaging systems particularly in the infrared range. In section II, Basic properties of the surface relief Diffractive Optical Element are presented. Then, section III-IV discuss about hybrid optics, optical design and complementary analysis. Finally we present design and experimental results in sections V-VI.

A new technique has been developed to simultaneously and instantaneously discriminate the shapes of objects by using a Multiplexed Matched Spatial Filter (MMSF). In order to make a hologram automatically, rapidly and efficiently and to process the hologram on the initially setting place, the techniques processing a photoconductor-plastic plate by solvent vapor and cutting off tremor using optical system composed on a rail base have been developed by authors. The diffraction patterns generated from objects at the frontal focal plane of the convex lens in the parallel coherent laser beam are superimposed at the back focal plane of the lens and the information of these shapes are filtered by a hologram (MMSF). In a consequence of mention above, the grope of auto-correlation peaks discriminating the shapes of objects appear in each measuring field skew-symmetrically to the location of input objects. The spatial distributions of objects in each shape or size could be measured simultaneously and instantaneously using the technique.

Dual field of view sensors form the basis of many current IR systems. Emerging scenarios, however, are beginning to call for a wide range of field coverage, and are stretching the capabilities of dual field systems beyond the point where a comfortable balance of fields is obtainable. Provision of a 3rd field of view opens up an extended range of operational possibilities, and in many scenarios offers a sufficient level of functional availability when weighted against the cost of additional on-board FLIRs. The design evolution of a lightweight and compact triple field optical system is described. The system features a novel, optimum geometry carousel, which enables provision of 3 fields with a single mechanism. The design is modular and flexible, offering ratios up to 20:1 between the widest and narrowest field. Hybrid optical element assist in achieving performance with minimum element count, and a variant of the design featuring special materials (GaAs/KRS5) offers extended temperature capability and athermalization for specific applications. Configuration constraints are defined, limitations of alternative approaches explored, and characteristics of the preferred design are presented. Opto-mechanical design features are described which take advantage of the novel FOV change concept to produce a stable, balanced system which can offer advantages compared with a zoom in the operational environment. The modular nature of the configuration, which permits field of view and scanner interfacing to be readily tailored to suit any specific application while retaining commonality of main structural components and mechanisms, is also illustrated.

We describe a holographic system for recording particles suspended in water. The hologram plate is located in air, separated from the test tank by an air/glass/water boundary. The holographic emulsion is therefore unaffected by adverse aquatic conditions within the tank (i.e. surface contamination, non-uniform swelling). The design geometry is intended to minimize the aberrations that arise from recording subjects located in water and replaying their hologram image in air. Third order aberrations, most crucially spherical aberration and astigmatism, are suppressed to give an experimental resolution of 7 lp/mm using USAF 1951 target in water 600 mm from the boundary. Particles (plankton species) in the sub-millimeter to several millimeters size range are observed at planar sections within the recording volume by visual inspection of the hologram replayed in real image mode.

The two principal radii of curvature of toroidally curved Holographic Optical Elements offer two extra parameters in the design and optimization of HOE's. It appears to be possible to reduce to zero the second order astigmatism term in the series expansion of the wavefront aberration, that is expressed in the coordinates of a plane normal to the principal ray to the gaussian image point. Analytic expressions are derived for the optimal principal radii of curvature of the HOE to fulfill this condition. The wavefront aberration, elaborated to the fourth order and reordered in Zernike polynomials, together with an exact expression of the total wavefront aberration offer tools for further analysis of the aberrations. As an example, a HOE applicated as a diffraction-mirror in a infrared spectrograph is calculated for zero second-order astigmatism.

In the case of a single-element imaging system, aplanatic correction is of major importance. It can be achieved for single holographic lens, if recorded on a spherical surface. For this reason, however, a diffractive microstructure of high spatial frequency has to be recorded. From technological point of view, a combination of classic, glass lens giving most part of overall refractive power with a diffractive structure of relatively low spatial frequency acting as an aberration corrector seems to be more advantageous. In this paper the possibility of aplanatic correction if assuming that the object point is located in infinity and both refractive surfaces are spherical is analyzed.

Practical method for synthesis of optical systems with kinoforms is presented. But these glasses are very expensive and hard in manufacturing. Examples and comparison with classical schemes are given.

The optical design of a high performance short focal length lens system and several derivatives thereof which cover the Super 16 mm film format is described. Particular areas of discussion include the use of internal close focusing optics to eliminate the need for precision focusing mechanics and the use of multiple aspheric surfaces, as well as, internal filtration to reduce system size, weight and cost. Other areas, concerning optical `breathing', distortion and material choice, especially very high index glasses, are also addressed.

Optical devices for planetary spectral surveying and mapping, e.g. for Mars missions, require small-size lens systems of low mass. An optical system called `Apo- Orthometar 5.6/175' for such applications has been already manufactured and successfully tested. This system consists of conventional optical glasses. It uses a quartz glass plate in front and has an enlarged thickness of the mounting for shielding against cosmic radiation. A new camera lay-out for the Mars Surveyor 98 Orbiter requires the application of completely radiation resistant glasses and a further mass reduction. Investigations have shown that the Orthometer lens type is less suitable for the new requirement and for an application in the 440 nm to 1000 nm spectral region. More suitable lenses are of the extended triplet type at f- numbers of 8.

The latest advances in European IR Focal Plane Array Technology are being utilized in the development of two advanced thermal imaging demonstrator systems funded by EUCLID. The program, designed RTP 8.1, is part of EUCLID Common European Priority Area (CEPA) 8: Electro-Optics. The 5-year timescale (1993 - 1998) is designed to allow the advancement of core technologies as well as the development and assessment of the two sensors. Nine companies, under the consortium banner TOPAZ, and compromising the European leaders in electro-optics, are bringing together their wide experience and skills to design and build FLIRs based on the Medium Wave Infrared focal plane array technologies Platinum Silicide (PtSi) and Cadmium Mercury Telluride (CMT). In the laser case the detector technology itself is being developed within TOPAZ. The UK, Italy and the Netherlands are cooperating to build an IDCA with a focal plane geometry of 384 X 288 pixels on 20 micrometers pitch. For the PtSi sensor, the detector is being developed in Germany under government funding outwith EUCLID, the FPA compromising 640 X 480 pixels on 24 micrometers pitch. As well as providing system performance comparisons between CMT and PtSi, the demonstrators will be used as test beds for enabling IR technologies including microscan, diamond-turned diffractive optics, advanced coatings, and non-uniformity correction and image processing electronics.

A model of synthetic non-linear modulation is suggested to derive a fast and enhanced multi-probing recovering algorithm. The processing approach originally arises from minimizing non-linear errors caused by using optical modulators such as Pockels cells in an active vision system. The algorithm has been obtained in the case that the non- linear modulator and demodulator are identical. This paper will adapt the algorithm more flexible subject to a non- linear phase drifting due to non-identical or asymmetric modulators. The model of synthetic non-linear modulation reveals that a 3D color vision system can be realized in a compact and integral method. Various incoherent signals acting as color probes are synchronously modulated each with characterizing rf-signals. These signals are then incoherently superposed in the transmission medium. After being reflected from an object, the selectively attenuated signals are compactly demodulated by using one single broadband mixer. The colors are numerically filtered and evaluated rather than using optical filters. The rf- modulated 2D interferogram can be fast processed by the proposed algorithm to extract 3D and color properties. Considering the difficulty to obtain a broadband optical demodulator, a technique of `modulation matching' is also suggested in this paper thus improving the performance. It provides a prospect to recover 3D color properties with reduced optical elements and one black-white CCD camera at low cost and high resolution.

Telecentric image transmitting systems used in endoscopes and periscopes are mostly of symmetrical construction, and therefore, they are free of distortion. However, in order to improve the general barrel distortion of endoscopes and devices similar to endoscopes, it is desirable to have telecentric relay lens systems for unique magnification, which produce distortion, especially pincushion distortion. This paper describes the construction of a telecentric relay lens system for unique magnification which produces distortion and the imaging peculiarities of such systems. A practical embodiment of a 70-degree endoscope uses a chain of 5 image transmitting systems each producing only 1.5% distortion. As the result, the overall distortion of this endoscope is improved from -15% to -7%.

This paper describes a general approach to the analysis of thermal effects in optical systems. The lenses shape, refractive indices and spacings change with the temperature, changing also the focal length and shifting the image position. The temperature variation can be very critical in infrared systems, because the refractive index of infrared materials is more sensitive to the temperature than that of optical glasses, and there are only few materials allowing a thermal passive compensation. Therefore it is very important to consider the thermal defocusing in choosing the optical configurations. In this work the analysis of defocusing thermal effect is divided in two different parts. In the first part, suitable first order relationships are developed, in order to connect focus shift with temperature and to determine first order configurations, taking into account thermal defocusing. In the second part, a recursive algorithm, implemented in a suitable computer routine, is developed to include, during the raytracing, the thermal defocusing in the aberration set and to control it during the optimization process.

The correction of secondary spectrum has generally been achieved by the use of special optical materials having non- normal relative partial dispersions, such as fluorite. These optical materials are expensive, unobtainable in large pieces and difficult to work to a good polish. For these reasons the use of these special optical materials is not common in optical systems. In 1955, E.L. McCarthy discovered that an optical system may be substantially or completely freed of secondary spectrum by using standard glasses only. Later, in 1977, C.G. Wynne discussed that the classical theory of first-order chromatic aberrations, which neglects terms of paraxial order in aperture and powers higher than the first in glass dispersions, had led to the erroneous conclusion that in order to correct the secondary spectrum it was necessary to use special optical materials. And in 1978, C.G. Wynne extended the theory of first-order chromatic aberrations in order to consider those previously neglected terms. Up till now the extended-theory developed by C.G. Wynne has not been applied to the design of optical systems corrected of secondary spectrum by using normal glasses. It is the purpose of this paper to develop the algorithm for the evaluation of secondary spectrum contribution on each surface as well as to apply the algorithm to the design of optical systems. Some examples are given.

The availability of small detector arrays that operate in either the lower or the upper thermal infrared atmospheric windows has created the need for relatively simple low-mass optics. Crucial to the success of such an optic is the correct choice of optical materials. Infrared optical materials can be ranked in terms of their relative `lightness', but material choice also depends on other factors such as the correction of primary chromatic aberration, secondary spectrum and thermal effects. This paper provides details of the relative mass of materials when used in single element or achromatic doublet form, the limit set by secondary spectrum on the diameters of specific low-mass combinations, and the possible elimination of thermal defocus by the choice of lightweight combinations of materials. The use of surface relief holograms on candidate materials is included as part of the investigation.

The PRISM instrument is an imaging radiometer to be flown on a satellite in Earth orbit. The principle mission is to gather Earth radiance data from land areas, at a spatial resolution of approximately 50 m. It will have spectral resolution in the order of 10 nm in the visible to short- wave IR spectral band, and a few discrete spectral bands in the thermal IR. It will typically be operated to record multi-spectral images of selected areas about 50 km square. The field of view of the instrument must be capable of pointing control, in both across-track and along-track directions, to select specific targets in each orbit and to view selected targets in different directions. The instrument is in an early stage of concept development, in competitive studies carried out for the European Space Agency. The paper describes the principle conclusions of the initial study of the team led by Dornier Satellite Systems, with Sira and Matra Marconi Space as principle sub- contractors. Outline designs are presented for: pointing optics, imaging and relay optics, imaging spectrometer, channel separation and in-flight characterization. Brief notes are given on design trade-offs and rationales for baseline selections.

Reflective optical surfaces offer lower aberrations than the equivalent refractive optical components and they are also free of chromatic aberrations; so the use of reflective surfaces in zoom systems should lead to better performance than the equivalent refractive systems. This is clearly a naive view because it ignores the problem of central obstruction and also the very low level of complexity of a reflective zooming group (at least notionally a single surface). On this bases we have exploited the additional complexity that Mangin or back-reflective mirrors offer, showing how a high degree of correction over a modest zoom range may be achieved with remarkably compact constructions.

The two-group zoom lens is the simplest arrangement which is capable of achieving a modest useful zoom range and adequate aberration correction for practical implementation. The first order layout of these systems is straight-forward and the real battle that has to be fought is to balance the effects of vignetting and aberration stability. This paper reviews the `+-' type, the `-+' type and shows how the quality of the overall performance evolves with the redistribution of aberration correction between the two groups of the zoom system, finishing with the analysis of a practical system which uses a relatively complex construction to achieve high performance.

In optical systems with modest fields of view, pupil spherical aberration and pupil coma are the principal pupil aberrations of significance, but at extreme fields of view, astigmatic effects and field curvature and distortion effects of the pupil imagery play a part in understanding the subtleties of oblique object-image imagery. Biogon and fisheye wide angle lens systems have been investigated for their pupil aberration properties, along with the investigation of similar effects in a panoramic optical system.

Plots of the spectral shift of focus over the middle, 3 - 5 micrometers (MWIR), and far, 8 - 12 micrometers (LWIR), infrared wavelengths are presented for thin lenses using various combinations of optical material and employing a diffractive surface cut as a kinoform. Lens examples are given for small field of view aplanats, resolving a tenth of a milliradian and employing a minimal number of lens elements. Particular advantages of the use of the hologram are considered together with some potential problems.

The design, manufacture and testing of a high aperture and wide field of view optical system is reported. Under specified constraints, the design is discussed in terms of aperture, studying its effects on the performance, the barrel length, the weight and the costs of the system. Some design criteria are detailed, and mounting techniques are outlined in order to obtain optimum position and alignment of the lenses. A f/1.8 objective is described in particular, and system tolerances are given. Interferometric tests on prototype systems are required, comparing the results with the design data.

We have studied nonuniform transmission filters to improve resolution and/or Depth of Focus in lithography. To understand the transmission behavior of these filters for periodic structures we discuss the Apparent Transfer Function in dependence on the defocus. We use the Apparent Transfer Function that is defined by the contrast of the corresponding spatial frequencies, and we analyze the behavior of the system for coherent, incoherent and partially coherent illumination.

This article describes a technique employed in the development of anti-vignetting filters to be incorporated in wide angle lens systems. The technique requires no knowledge of the optical prescription, but would include lens parameters such as entrance pupil location, type of vignetting and intensity distribution across the image plane. Results are given for the application of this technique to an 85 degree camera objective.

Increasing demands in the areas of machine, computer and robot vision strongly motivate the renovation of optical sensing devices. Based on the physical effect of Frustrated Total Reflection (FTR), the essence of this paper deals with the new design of optical modulators used in 3D-vision systems. Optical modulators commercially available do not meet some extended requirements for 3D applications. However, the device presented in this paper permits the specifications of optical 3D-measurement techniques like accuracy, robustness, compactness as well as fastness to be realized with higher capabilities. For this purpose, we suggest two different types of optical 2D mixers. Both are intended to explore the FTR effect to modulate light in a large aperture with minimal image aberration. In one case an air gap between media of higher dense is modulated by an rf- voltage applied to a piezo crystal as an rf-controlled tuning medium. In the other case the variation of the gap or modulation is achieved by using a surface acoustic wave device which acts as a surface grating medium due to the effect of a travelling periodic corrugation. The integrated optical components play a substantial role for the optical modulation and imaging. Some simulation results of this optical devices show that the inherent non-linearity of the FTR modulator may be neglected in practical applications, thus yielding a high modulation depth. Furthermore, a 3D- image system adapting this modulation optics is also depicted in the paper.

A monolithic optical component able to focus a medium or high power laser beam in three different points on the same plane has been designed and constructed. The three-spot lens is constituted by an asymmetrical refractive lens. A face has been conventionally rounded in a convex shape, while the other face has a prismatic shape in order to split the laser beam in three parts. The optical characteristics of the three-spot lens (focal length, focal spot sizes, mutual distance between spots an spherical aberration) were evaluated in first approximation by extending the matrix optics method to misaligned systems. An experimental characterization of the lens has substantially confirmed the results of the theoretical analysis and it has shown that the lens can be conveniently used to design a device for simultaneous coupling of a number of large-diameter optical fibers to a medium or high power laser source (laser- multifiber coupler) or to a single launching fiber (fiber- multifiber coupler). The laser power can be uniformly coupled into the receiving fibers; it was verified that an asymmetrical power distribution between the fibers can be obtained as well.

An optical design concept is presented for a wide field of view camera, used to take pictures of a model board, which are displayed to the pilot of a simulated aircraft in real time. The concept achieves mapping functions and perspectives in three separate images that match the display system properties over 140 degrees field of view. This enables fast feedback of the model board images to the pilot by avoiding the need for computer correction of optical distortion. The geometry of the lens system also ensures good uniformity of brightness over the whole field of view. The provision of three axes of angular movement and computer optical design techniques are discussed. The general design and fabrication of a prototype is described.

The `Crusader' Helmet Display System utilizes advanced optical technology to produce a high performance, fast jet pilot's Head Mounted Display. In particular it includes non- conformal reflection holograms on a novel polycarbonate visor to combine the display with the outside scene. Also, the relay optics include tilted, decentered and aspherical optical elements and transmission holograms to correct chromatic aberration.

Five original designs of iris diaphragms to overlap coaxes round and annular apertures of the multichannel mirror or lens-mirror objectives are considered. Authors have proposed three novel configurations of the iris diaphragm lobes and also several diaphragm designs where referred lobes have been combined with ordinary ones. Horse-shoe shape lobe has been basic for all types of proposed iris diaphragm designs. Firstly this lobe is a main part of fan-diaphragm to intercept mirror objective annular aperture. Secondary that had been a prototype for both moon shape lobe and flat ring shape one. Thirdly usual iris diaphragm should be formed annular zone diaphragm in combination with fan-diaphragm. Proposed iris diaphragms has been designed to intercept both annular and round apertures of mirror and lens-mirror objectives simultaneously as well alternately. Formulas for calculation geometrical parameters of different kinds of the lobes and their disposition on the stationary mountings have been adduced. One attends that total light losses through screening should not be more than 18 - 20%. Technical realization most of proposed iris diaphragm designs have to be of interest for purposes of electro-optical test facility.

System for transformation of radiant flux as a delivery system with modification of the flux diameter was considered. That can be used with most efficiency in modelling radiators and simulators for electro-optical test facility where there is necessity of modulation of collimated radiant flux with considerable diameter D₁ and little angular convergence or divergence 2(alpha) . This system consists of consecutively installed coaxes reflecting concentrator with tapered angle 2(beta) and cylindrical hollow fiber of diameter D₂, at first; two mirror truncated cones formed in meridian section angular mirror with angular basis (beta) , at second. These two mirror cones carried out the recollimation of radiant flux for obtaining the starting angular convergence (divergence) 2(alpha) . Formulas for determining geometrical dimensions of this delivery system depending on concentration rate C both angles (alpha) and (beta) are adduced. One attends those energy losses for this transformation of radiant flux were not more than 2 - 3%. Focon-fiber configuration of proposed delivery system has been presented.

I give the results of a study for the optical design of wavefront sensors proposed for the Gemini 8-meter telescopes. The sensors are to provide information for wavefront profiles at various resolutions, including 20 X 20 points over the pupil and 4 X 4 points over the pupil. They include the tip-tilt (star tracking) system. Points discussed include: the use of off-axis sensors; following the curved focal surface in the telescope; methods for varying the resolution in the pupil; reproducibility injecting a point source of light for checking and calibration; methods of finding the positions of the sub- apertures in the whole aperture; and methods of switching to a wider or narrower field of view.

The mechanical reliability of 8 m class ULE^TM glass telescope mirror blanks is a key requirement for both the blank manufacturer and end-user. The massive monolithic blank experiences stresses during the various manufacturing steps including handling, grinding, sagging, and finishing. Likewise, it is subjected to vibrational loads and road shocks during transportation to end-user. And finally, it experiences transient stresses during installation and steady-state static stresses throughout its useful life in service. The large blank, which weighs nearly 35 tons, must have appropriate surface finish to sustain manufacturing, transportation, installation and service stresses with low probability of flaw initiation and propagation. This paper examines the critical stress/time histories the blanks experience during manufacturing and their ability to initiate slow crack growth from grinding flaws. Two different surface finishes, namely 120 grit and 270/325 grit, with and without acid etching are characterized with respect to strength, flaw, and fatigue behavior. These data show that the 270/325 grit finish with acid etching is appropriate for the sagging step which imposes a static stress of 750 psi in the center region of the mirror blank over a two-week sag period. Similarly, the 120 grit surface finish is adequate for grinding, packaging and transporting steps which impose a static stress of 435 psi in the support pad region for a three-month period. These predictions, based on Power law fatigue model, were verified by conducting static fatigue tests (at appropriate stress levels) on a large sample of 6' diameter ULE^TM discs (with appropriate surface finish) at 25 degree(s)C and 100% RH. Such a verification is imperative for selecting appropriate surface finishes for the mirror blanks to promote mechanical reliability during manufacturing and service.

High power diode lasers are anisotropic light emitters with high aperture angles in the plane perpendicular to the semiconductor plane. The collimation of this radiation with different cylindrical collimator types is discussed. Special attention is paid to the usable numerical aperture, the offense against Abbe's sine condition and production constraints.

Spherical mirrors with a variable radius of curvature are used inside laser resonators as well as in the beam path between the laser and the workpiece. Commercially-available systems use piezoelectric actuators, or the pressure of the coolant, to deform the mirror surface. In both cases, the actuator and the cooling system influence each other. This interaction is avoided through the integration of the cooling system with the flexible mirror membrane. A multi- channel design leads to an optimized cooling effect, which is necessary for high power applications. The contour of the variable metal mirror depends on the mounting between the membrane and the mirror body and on the distribution of forces. Four cases of deformation can be distinguished for a circular elastic membrane. The realization of an adaptive metal mirror requires a technical compromise to be made. A mechanical construction is presented which combines an elastic hinge with the inlet and outlet of the coolant. For the deformation of the mirror membranes two actuators with different character of deformation are used. The superposition of the two deformations results in smaller deviations from the spherical surface shape than can be achieved using a single actuator. DC proportional magnets have been introduced as cheap and rigid actuators. The use of this adaptive mirror, either in a low pressure atmosphere of a gas laser resonator, or in an extra-cavity beam path is made possible through the use of a ventilation system.

Aspheric surfaces provide a very necessary increase in the number of degrees of freedom needed to design wide-field eyepieces with large eye relief distance to focal length ratios. New economical diamond-turning lathes such as the Optoform 50 give a new flexibility to prototype manufacture with plastic materials which extends into medium-sized production quantities. This paper will explore the free use of aspherical surfaces in wide-field visual systems. The aspheric is now the general case and not a small modification of a spherical surface. The computing procedures used must provide the best balance between freedom and restraint.

This paper derives the light amplitude distribution expression of a laser resonator. Using a numerical analysis, the result shows that the laser output power is maximum when no dynamic aberrations are in the laser cavity. The power and mode distribution of the laser are obtained. The paper presents an adaptive correction theory of laser resonator phase aberrations by using a 3D model deformable mirror. The result of the computer simulation in the close loop system shows that the system can compensate the dynamic phase aberrations up to 90% for the phase disturbance within 0 - 10 Hz frequency range.

Numerical simulation on a computer is one of the main methods used for studying the possibilities of adaptive correction of turbulent distortions of imaging forming in the atmosphere. The problem of compensation for atmospheric distortions of a wave front has been studied sufficiently long. The first papers on this subject were published in the mid-1960's. At that time, however, the engineering base gives no way for designing the efficient devices for compensating for atmospheric distortions. In recent years much progress has been reached in developing wave front distortion meters and correctors and then fitting the optical facilities operating under atmospheric distortions with these devices. In this connection an increased interest of researchers is observed to the theoretical works concerning with selection of an optical design and configuration of the wave front corrections.

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is selected by ESA for the ENVISAT-mission, scheduled for launch in 1999. The instrument will measure the concentration of atmospheric trace gases in the earth atmosphere in a spectral region from 4.15 - 14.6 micrometers . MIPAS consists of scan mirrors, a telescope, a Michelson Interferometer, an optical reducer and a focal plane assembly. The optical reducer consists of a 2 concave and 1 convex mirror system. The focal plane assembly consists of a configuration of mirrors and dichroics, with which the spectral range is divided in 4 spectral bands. TNO Institute of Applied Physics has designed the optical/mechanical system and after manufacturing of the components has aligned the system with high accuracy. The design and alignment of this system is described.

Very high geometric and radiometric resolution requirements must be met by the digitization of photogrammetric aerial images or entire aerial films. Flat bed scanners scanning with CCD arrays are used in this field. The optical design will be discussed in detail. A scanner designed by Carl Zeiss will be used to illustrate alternative illumination and lens systems which project the aerial image onto a CCD array. An Offner catoptric system is shown to be superior to a conventional refractive lens.

An industrial 3D laser scanner is presented for measurement of solder paste screening quality in an automated PCB assembly line. The scanner provides telecentric illumination and imaging in a 305 mm (12') long scan line at a maximum rate of more than 1000 scans per second. Synchronized height measurement is performed using a double triangulation scheme at large angles and wide aperture. Pixel sizes range down to 18 micrometers , yielding more than 16,000 pixels in a scan line. Depth resolution is 10 micrometers over a 2.5 mm measuring range. Some practical details on scanner assembly will be discussed. Combined with accurate, fast processing and control electronics this 3D sensor enables 100% inspection at high production speeds.

As a fast two-axis deflection unit for laser beam positioning, an X/Y scanning head based on two galvanometric scanners with vertical crossed axes is a central component of different applications in industry, medicine and communications. Some of these are laser markers, stereolithography devices, scanning laser vibrometers, laser trimmers, laser cutting machines, infrared scanners, lead bonders, Q-switches, laser ophthalmoscope, robotic vision systems, range finders, image digitizers, and laser graphic projectors for entertainment. Velocity and accuracy of the X/Y scanning heads are very important for the performance of the devices in which they are used. Therefore the dynamic properties of the X/Y scanning head must be optimized. One important criterion is the mass moment of inertia of the second scanning mirror. It can be reduced by inclining the axis of the first galvanometric scanner. To solve these problems both computer tools for the optical and mechanical optimization, and measuring devices to minimize the wobble and jitter of galvanometric scanners were developed. The development of scanning heads for different apertures (laser beam diameters), scan angles and F-(Theta) -objectives was done for SCANLAB GmbH (Puchheim/Munchen, Germany), one of the three leading manufacturers for galvanometric scanners.

Our department at Eastman Kodak Company is responsible for substantial optical design and manufacturing projects. Software support for these efforts has included the development of special purpose optics codes which are considered to be strategic assets. Over time, these Fortran- based codes have become difficult to use and given their importance to our ongoing success, we have begun a large- scale effort to make them accessible to modern designers and engineers. In addition to making these legacy codes available on PCs, we realized the need for new methods to manage the quantities of data manipulated by our designers and engineers. We chose to center our development on Lens Documents, and the software framework we have constructed embodies this data-centric view. We will describe the process we went through to create this framework, with an emphasis on our design approach and the major decisions relating to hardware and software for development and deployment.

In scanning systems such as a Retinal Scanning Display, the pupil at the first scanning device is relayed onto a second scanning devices, which again is relayed onto the entrance pupil of the eye. The optics relaying the pupil not only must well image this pupil, but also the scanned beam must be imaged with good quality on the retina and the distortion must be low. We compared an Offner-type pupil relay with two more conventional systems. It appears that the Offner-type pupil relay has very good optical properties and can be especially useful as the first pupil relay in a Retinal Scanning Display.

A systematic approach to the design of scanning systems is presented, based on characteristics of the scan locus generated by rotating mirrors or polygons and their transformation by optical components. Examples include a simple 2D scanner, a high-efficiency line scanner and 2D scanner, a simple flat-field telecentric scanner and a line scanner with constant footprint.

The utilization of wide range spectrometers is a very important feature for the design of optical diagnostics. This paper describes an innovative approach, based on charged coupled device, which allows to analyze different spectral intervals with the same diffraction grating. The spectral interval is varied by changing the position of the entrance slit when the grating is stationary. The optical system can also include a spherical mirror. In this case the geometric position of the mirror is calculated aiming at compensating the first order astigmatism and the meridional coma of the grating. This device is planned to be used in Thomson scattering diagnostic of the TOKAMAK of Instituto Superior Tecnico, Lisbon (ISTTOK).

Since the introduction of CO₂ laser in surgery, various techniques such as laser pulsing, beam scanning and computer-assisted laser pulse generator have been applied for the purpose of reducing tissue carbonization (char) and thermal necrosis. Using a computer-assisted optical scanner, it is possible to sweep a focused CO₂ laser beam over a tissue area from several mm² to several cm², with a dwell time on each tissue point of less than 1 ms and a resolution of (2^N)² points, where N is the data bit number of the electronic servo drive. In this case, a quite simple optical scanner equipped with two galvanometric driven mirrors placed at 90 degree(s) in respect to XY scanning directions and an appropriate software to process the scanning data via a DA converter, enables a scanning operation with a linearity better than 1% for a maximum angular deviation of 20 degree(s). Because the scanning quality of the laser beam in surgical techniques is assured not only by the precise movement of the laser beam in the operating field, but also by beam characteristics in the focal point, laser beam cross distribution and dwell time, a special software was developed to provide the surgeon with an application-optimized surgical device.

Automatic high precision laser scanner has been manufactured. It consists of acousto-optic deflector (AOD), optics, drive power generator connected with computer and laser. Two modifications of laser scanner were developed. The first modification has two AODs manufactured from TeO₂ crystal with the following specification: the number of resolvable spots is 500*500, access time is 15 microsecond(s) ec, aperture dimensions equal to 10*10 mm², acoustic center frequency is 75 Mhz for visible and 34 Mhz for IR spectrum, input optical polarization is linear, maximum optical efficiency for one AOD is 90%, drive power is 1 W per one AOD. The second modification has one XY-dimensional AOD manufactured from KRS-5 crystal with the following specifications: spectral range - (0.6 - 1.1) (mu) , input optical polarization - any, active aperture - 6*6 mm², access time - 7 microsecond(s) , acoustic center frequency - 100 Mhz, RF input impedance - 50 ohms.

For cartography applications Frank Data R&D developed a new concept for taking measurements which consists in obtaining panoramic photographs, which are later scanned into a computer. The computer then processes consequent pictures from different locations and creates 3D images of the landscape. An extremely wide angle Fisheye Lens is part of this concept. Delft Instruments has designed and manufactured this lens. The specifications and design drivers are discussed. Under extreme sun illumination conditions ghost images may occur, which will be presented with photographs. Not all of these effects could be traced by experiments. The trace was then continued by computer simulation based on the ASAP software. A method of debugging such a lens is presented. A Fisheye Lens is characterized by a small entrance pupil, compared with the size of the first lens, at a field-depending position. Together with the number of 18 optical surfaces in this case and the large field of view, a tremendous amount of ray tracing was necessary to find out the surfaces and the conditions that lead to the ghost images. Although a powerful workstation was used, an efficient strategy was necessary to isolate the main contributing paths and to visualize them.

For the German `Institut fur Angewandte Geodasie (IfAG) a new state-of-the-art transportable satellite laser ranging (SLR)-system is under development. This SLR-system will be part of the TIGO project (Transportable Integrated Geodetic Observatory). The TNO Institute of Applied Physics (TNO-TPD) has overall system responsibility and also designs and manufactures major opto-mechanical subsystems (such as the telescope and the transmit/receive optical unit that interfaces with the pulse laser, the telescope and the detectors). The faculty of Geodetic Engineering of the Delft University of Technology develops the control electronics and software. The SLR-system will be capable of ranging to all cooperative satellites (upto and including geostationary orbits) at two wavelengths simultaneously (847 nm and 423.5 nm, generated by a Ti-Sapphire laser). A general overview on the opto-mechanical configuration of the SLR-system will be presented with emphasis on the telescope and the transmit/receive optical unit.

Tight tolerances of the elements are not enough to assure the required performance of high resolution wide field optical imaging systems. Two ways are possible to overcome this problem: Measurement of all element parameters and computer aided assembling (CAA)--or iteration cycles of system adjustment based on system performance measurements. But in some cases also each of these ways alone is not enough to fulfill all performance requirements. The authors developed a method to combine both opportunities. This method comprises new evaluation methods, CAA-software, high accuracy measurement equipment and new methods to control element positioning by adjustment.

The need to stabilize the line-of-sight of EO sensors and lasers on moving platforms has been satisfied by mechanical systems using the directional gyro technique. However such systems that use mirror or prism line-of-sight steering, stabilize in only 2-axes, have limited elevation steering range and require skilled fabrication. The use of the strapdown technique puts the functional control into software and offers improved functionality, e.g. 3-axis stabilization, absolute directional reference, simple mechanical design and low cost assembly. The main criticisms have been the extensive computation of space transformation algorithms and reliance on the precision of transducers. Until the present, the powerful real-time processing resources demanded by this technique for EO sensor applications have not been available in sufficiently compact and low cost form, although systems have been produced for radar antennae and direct view optics with inferior stability. Pilkington Optronics has studied various stabilization systems and has determined that with emerging technology, the strapdown technique is now feasible and desirable for many high performance applications. Accordingly, we have developed a 3-axis strapdown optical stabilization system, initially for a Submarine Optronics Mast, but readily applicable to vehicle sights and other moving platform applications. The system involves inertial sensing by fiber-optic gyros, processing by multiple digital signal processors and opto-mechanical steering by 2-axis gimballed prism plus optical de-rotator mechanism. The successful operation in terms of image stability has required the use of precise algorithms, advanced digital servo control and rigorous modellization of gyro's and resolvers.

Mechanical stability is an important consideration in the design of optical systems. Optical performance parameters will be affected by a combination of optical sensitivity to environmental effects and structural deformation. Traditional approaches have been constrained by limitations in design tools and in particular in structural design tools. An approach is presented here which takes advantage of recent improvements in computer aided engineering and which enables stability effects to be considered early in the design process. Key optical performance parameters are identified and typical results are presented.

The comparison of two widespread optical schemes for high precision electro-optical tracking or measuring devices may be realized with the help of the criterion which is determined by the correlation of detector noise equivalent powers and principal optical scheme parameters, such as the entrance and exit pupil sizes, objective lens and condenser (Fabry lens) focal lengths, condenser transmittance coefficient.

This paper describes the features of a new optimization method developed to facilitate the real time design of optical systems. Additionally we illustrate the method by describing its application to the design of an F/1.0 camera for use in a planned Astronomical spectrograph. This instrument is the High Resolution Optical Spectrograph, which is part of the international Gemini project to build twin 8 m aperture telescopes towards the end of the decade. The author describes the capabilities of the Global-Opt optical ray tracing program. This program allows the optical engineering to ray trace, in batch mode, up to 1 million optical systems. Once complete, the engineer can explore the results in real time in order to locate the merit function minima.

An imaging polarimeter has been designed and constructed at the Air Force Phillips Laboratories to measure the polarization properties of laser speckle patterns. An imaging polarimeter spatially measures the polarization state of light coming from an object, thereby producing a `polarization image'. The system describes was designed to image the pupil of an optical system containing speckle patterns created by illumination of diffuse objects with light from a pulsed 1315 nm laser. Difficulties encountered due to demanding specifications required for polarimeter components and for coherent imaging systems in general are described and their solutions are discussed. Diagnostic techniques developed to measure path length differences and to identify the source of interference fringes are described. System calibration and characterization tests are described and results are presented.

An overview of some aspects of the design of molded plastic lenses is presented. These include the characteristics of the material flow and freezing in the mold that need to be considered in the trade-offs between cost and performance. A brief example is given of the application of molded plastic lenses.

Binary gratings as holograms itself or as photographic masking tools for further fabrication steps can fulfill a lot of applications. The commonly used semiconductor technologies for direct writing of high resolution structures are often too expensive. On the other hand computer plots at a reasonable price with photographic reduction do not meet the needs of precision e.g. for interferometric inspection. The lack of cheap and reliable instruments for direct writing in an appropriate resolution is still a problem in fabricating synthetic holograms. Using off-the-shelf components a direct writing plotter for binary patterns can be built at moderate costs. Typical design rules as well as experimental results are given and the final setup is introduced.

The theory explaining how third-order aberrations depend on magnification has been discussed by Wynne and Welford. In this paper we show how the `conjugate-change equations' can be used to find out under what conditions a lens can be designed, with front-back symmetry, which is well-corrected, for a range of object distances.

An approach to color correction is described in which the ratio of the group velocity to the speed of light in vacuum (the group index of refraction) in glass is used, in conjunction with the more familiar phase index of refraction, to control longitudinal color in a system of thin lenses in contract. It is shown that at the wavelength of a turning point where the phase power of a lens is locally independent of wavelength, the phase power is equal to the group power. It is further shown that in a lens consisting of three or more elements, if the phase and group powers are equal and the group power has a turning point at the same wavelength, the second derivative of phase power with respect to wavelength is zero at that wavelength (the lens is confocal and achromatic in both phase and group power and the secondary spectrum is locally zero). The group index of refraction and the concept of group aberrations can equally by applied to exact raytracing for thick lens systems. In using easily calculated derivatives of the phase index of refraction the approach affords a computational simplicity that is well suited to computer-aided lens design.

Fixed legend light sources, manufactured using micro-mirror laterally emitting thin film electroluminescent (LETFEL) device technology, are suitable for avionic head-up display (HUD) systems. These devices utilize commercially accepted alternating current thin film electroluminescent device structures for internal light generation. However, light out-coupling occurs solely by the reflection of lateral light by micromirrors, whereas conventionally the emission occurs through transparent electrodes and substrates. The novel structure facilitates the use of black surface layers which maximize contrast ratio. LETFEL micro-fabrication processes, such as dry etching of Y₂O₃ and ZnS:Mn, define fixed legend symbology with feature sizes as small as 3 microns in width. Display contrast ratio is greater than 100:1, angular divergence is Lambertian and brightness can exceed 20,000 fL at 10 kHz sinusoidal excitation and 30 V above threshold. Extrapolated lifetimes of the structure exceed 10,000 hours with a reduction in brightness to 90% of initial readings. These ultra high resolution displays exceed specifications for avionic HUD systems operating in bright sunlight conditions.

A linear light pipe allowing the transformation of a quasi- point source into an extended lighting device has been developed. The control of the spatial light distribution is of special interest for the uniform illumination of extended surfaces. The distribution of the emitted light is achieved by the combination of scattering and reflective coatings on the light pipe faces. Paint has been used as scattering coating. Paint characterization and introduction of the measured parameters into the ray-tracing program are described. Several light pipe configurations have been simulated and manufactured. The performance of the different configurations are discussed and compared with experimental results.

Real-time optical processing is an area of increasing interest in several fields like pattern recognition and inspecting tasks. The development of Spatial Light Modulators (SLMs) capable to display a complex amplitude 2D- distribution in real-time has been very important to obtain real-time optical processors. One of the biggest challenges for improving these processors is to obtain SLMs with a pixel-by-pixel control, which could be easily implemented and fully controlled spatially and with grey-level addressing. Liquid Crystal Displays (LCDs) are inexpensive and suitable SLMs for recognition optical purposes. The LCD panels from the Epson VP100PS videoprojector have been deeply characterized and intensively used as SLMs in optical correlators for pattern recognition. The SLMs can be used in the filter plane as well as in the input plane. If the input image to analyze entails particular requirements in spatial resolution and grey level quantization the response features of the SLM used to display the input image can be critical. In this work we present a full pixel-by-pixel control of the matrix with a PC board. A Field Programmable Gate Array (FPGA) is designed to control a PC board as a prototype to implement a Very Large Scale Integration ASIC driver using the 2.5 microns technology available from the Centro National de Microelectronics (CNM-CSIC, Bellaterra, Spain). The project results in an inexpensive and easy- reconfigurable PC board with the FPGA prototype, and an easy migration to a fully integrated driver of the display.

An experimental realization of optical correlation for pattern recognition by using phase only filters as a reference in a real-time joint transform correlation is presented. The correlator operates with a liquid crystal television as the input and a photorefractive crystal at the recording plane. The use of photorefractive materials such as Bi₁₂SiO₂₀ as a dynamic holographic medium is becoming an interesting alternative to current liquid crystal based modulators in real-time optical image processing. In order to improve the performance of detection, the phase-only filter has been taken into account. Usually, this filter is used in the frequency domain, although it can be employed in the object space, becoming the reference in a joint transform correlator. As this filter requires negative values, holographic codification methods are required to encode it. Experimental results are presented and compared with those obtained with the classical matched filter.

In this communication, we calculate the reconstruction of a phase-only hologram corresponding to the linear combination of two phase functions. We multiplex two phase functions in a phase-only device and we study the performance of this hologram theoretically and experimentally. As a particular case, two Fresnel lenses are multiplexed and the performance characteristics are derived. We then study the effects of encoding the phase-only multiplexed hologram in a low resolution device. We show that the low resolution effects on the hologram performance are not negligible and the point spread function and the diffraction efficiency shows a strong dependence with the location and focal length. We study how to take these effects into account in order to obtain the desired performance.

The fabrication parameters of a Ti:LiNbO₃ waveguide determine the number and size of the modes supported by the waveguide. Optimization of the electro-optic-induced index change in the waveguide modulators requires both fabricating singlemode waveguides and controlling the mode size. We present a procedure of determining singlemode waveguide fabrication parameters from the needed mode size.

We propose a real-time optical pattern recognition system using an optical correlator. The system consists of two high speed spatial light modulators. To achieve high performance of pattern classification and to obtain bright correlation signals, the binary phase only modulation of both input patterns and correlation filters is applied. In order to suppress sidelobes in the correlation plane and to achieve the multiple-object pattern classification, optimized correlation filters are utilized. The experimental results shows that bright correlation peaks can be obtained without false peaks or large sidelobes.

Laser polarization nephelometer is used for measurement of light scattering matrix (LSM), known as Mueller matrix. The measurement method is based on the modulation of polarization state of incident and scattered light by rotation of some optical components. One can calculate the LSM elements via Fourier transformation of input signal by means of matrix of conversion C. Dimension of the matrix and values of it's elements depend on the ratio of rotation rates of the optical components. In the work nephelometer with rotating phase plates was considered. The scheme with motionless analyzer was taken into account as well as with the rotating one. This gives an opportunity to find several regimes, which allow to calculate the full LSM. For the regime 1:5 the dependence of condition number of matrix C versus the phase retardation of phase plates was investigated. Optimal parameters of devices were found by minimization. Dependencies of measurement errors versus the adjustment one were calculated by Monte-Carlo method for a set of matrices of different objects. The results allow to determine the error level for measurements of real objects.

The present paper is concerned with existing deformable bimorph mirrors, their advantages and disadvantages; an effective technology of their construction is proposed providing a significant increase of the mirrors sensitivity as well as their controllable aperture. In accordance with the technology described industrial one-channel bimorph mirrors have been developed and investigated intended for use in laser optics and as well as a 3.3-meter bimorph mirror for optical telescope. Results of the investigation strongly confirm the effectiveness of the proposed technology for improvement of characteristics of controllable bimorph mirrors which represent a perfect instrument for `small' adaptive optics being of great importance for laser techniques and astronomic telescopes even today.

Multiple lenslet array imagers (MLAIs) are compact optical systems made of several cascaded lenslet arrays. These systems can provide images that are many times larger than their total object to image distance. Here we describe a new variant of the MLAI that provides control over the optical transfer function (OTF) of the imaging process. This OTF synthesis capability makes it possible to control the resolution of MLAIs, as well as to use them as correlators or convolvers in optical information processing systems. Several variants of this new device, results from an experimental demonstration, and an analysis of its key performance issues, are presented.

The invention relates to a mirror system with two mirrors, comprising a concentrating reflector and a diffusion reflector fitted on the same optical axis, a image field and a detector. The diffusing reflector has a central drilling. A diaphragm is arranged in such a way that the point of intersection of the plane of the diaphragm and the optical axis forms the center of the curved image field of the mirror system. At the edge of the diffusing reflector there is a central diffuse light shutter. The concentrating reflector may optionally have a central drilling. The mirror system may be used as a telescope system. Prior art twin- mirror systems like the Ritchey-Chretien system do not correct astigmatism, image field curvature and distortion. According to the invention, spherical aberration, coma, astigmatism and distortion are corrected by double reflection from the concentrating reflector and the substantially hyperbolic shaping of both mirrors.

The invention relates to a mirror system with two mirrors and four reflections, comprising a concentrating reflector and a diffusion reflector fitted on the same optical axis, an image field and a detector. The concentrating reflector has a central drilling. The concentrating reflector reflects the light to the outer part of the diffusion reflector, from where the light is reflected on the concentrating reflector again, that reflects the light on the central part of the diffusion reflector, that in turn reflects the light through the central drilling to the image plane. Prior art twin- mirror systems like the Ritchey-Chretien system do not correct astigmatism, curvature of the image field and distortion. According to the invention spherical aberration, coma and astigmatism are corrected by double reflection at both mirrors, whereby the concentrating mirror and the outer part are hyperbolically shaped and whereby the inner part of the diffusion reflector is elliptical, spherical or ellipsoidal shaped. That depends from the axial radius of curvature of the diffusion mirror in relation to the distance between both mirrors. Hence--this shape depends from the overall focal length of the mirror system in relation to the paraxial focal length of the concentrating reflector.

The paper relates to different inventions, comprising three diffraction-limited catadioptric designs. All the systems use only spherical shaped surfaces and are designed from one kind of optical material only. In the examples the glass BK7 from the Schott-catalogue was used. The first example gives a three element design reaching equal performance as a Schmidt camera but with only 25 percent of its length. Additionally the field is flat and conveniently located behind the system. The second example is designed to reduce the central obstruction. It's somewhat based on the principle of the Houghton-camera. For a f-number 4 system with 1000 millimeters focal length it gives outstanding image quality at a 5 degree's field--even capable for diffraction-limited visual use. For reduced f-number 5,6 the image is diffraction-limited at the whole field. In terms of color correction it outperforms every Schmidt-Cassegrain or apochromatic triplet of even arbitrarily more reduced light gathering power. The third example is the equivalent for the so-called Wynne corrector triplet that corrects the aberrations of a parabolical mirror. But the invented corrector corrects additionally the spherical aberration of a spherical mirror. The corrector is able to correct all third order aberrations without introducing longitudinal and lateral color.

The Glasgow Lens Design Problem is ofcurrent interest in a special field of optics: Microlithography. This field is accompanied by high economic interests. Companies often do not allow their employees to publish their work. And the problem perhaps was too special: a lens consisting only ofinirrors was asked. This reasons (and probably additional ones) led to the situation, that only 6 solutions were received. Nevertheless, this few solutions show the range ofpossibilities given by this statement of the problem.