This study investigates the effects of changing the flint glass of a Cooke triplet from the optimum glass type, in an attempt to determine how many different glass types are necessary. To this end, about 90 triplets were designed, each with a flint glass displaced from its optimum characteristics. Sixteen different combinations of field and aperture, and three different crown glass types were used. Variations of performance with flint changes are presented. An 'acceptable' variation of the flint glass V-value appears to be about plus or minus 2.

Hybrid optics -- diffractive structures on a refractive substrate -- have some specific applications in the lower of the two thermal infrared wavebands. These applications include optical systems where simplicity and/or low mass are major requisites. In many cases, however, the use of diffractive surfaces is limited to those substrate materials that can be diamond-machined successfully. The paper examines the optical merits of several substrate materials and gives design examples where hybrid optics have major advantages relative to conventional optics in terms of mass, thermal defocus, and complexity.

The generalized Coddington equations from caustic theory, the Abbe sine condition, and the constant optical path length condition have been used to design two-mirror microscope systems. These two-microscope systems are free of two of the three aberrations -- spherical aberration, coma, or astigmatism, depending on which two of the three design conditions are used. The optical performance of the resulting two-microscope systems has been compared to that of the Schwarzschild microscope and the Head microscope. The goal of this study is to identify design methods for reflective systems which will yield diffraction limited performance for large numerical apertures and fields of view. Also, these design methods are being extended to a three-mirror telescope.

Abnormal dispersive liquids have proven quite useful in the design of apochromatic optical systems for the visible and ultraviolet spectral regions. Furthermore, liquids with extended ultraviolet transmission can be very useful in the design of optical systems for use in the ultraviolet, whether or not they are abnormally dispersive. The results of investigations into optical properties of several liquids transparent in the ultraviolet are presented. Intense UV irradiation of the liquids was found to produce changes in both the UV transmission and refractive index. Methods of preventing these changes through the addition of a special chemical were investigated. The optical property measurements were made at the Vavilov State Optical Institute, St. Petersburg, Russia in collaboration with the Lockheed Palo Alto Research Laboratory, Palo Alto, California.

In any optical imaging system, tilting and decentering of optical components will cause the relationship between the object and image to change. Many precision imaging systems require the image to have a fixed relationship to the object within a certain tolerance. To obtain an object-to-image relationship within a specified tolerance, each of the possibly many components must in turn be positioned within certain tolerances. The allowable tilt and decenter of each component depends upon the sensitivity of the image position to that component's motion. This sensitivity is often referred to as a structural influence coefficient. A method is presented for the derivation and calculation of structural influence coefficients for finite conjugate optical imaging systems. A special differential rotation operator is introduced to model tilts of optical components. The method most easily results in numerical coefficients with the use of a personal computer and almost any common mathematical software package.

Current optical design software provides little support for the mundane human oriented tasks of personal project management. Project management tools from other domains are not readily applied to the optical design process. This paper discusses the salient issues and describes (via case studies) possible solutions to this problem.

In this article we have designed a new type of prismatic telescope which can be used to amplify the divergence of the laser beam. Theoretical analysis and computer analog indicate that the divergence multiplication factor is independent of the distance between the prismatic telescope and the waist of the laser beam, and the original divergence of the laser beam in 20 mrad, the laser beam as it passes through the prismatic telescope is still Gaussian beam. We have made and measured the prismatic telescope and found the result agrees with our theoretical analysis.

A spaceborne telescope has been designed and analyzed for a 2-micron solid state coherent lidar system operating on a satellite. The optical system consists of a large off-axis reflective telescope, a large-aperture diffractive scanner, an image derotator and a lag angle compensator. Due to the orbiting motion of the satellite and scanning, the boresight of the telescope shifts during the round trip travel time of the laser pulses to the target. In a coherent lidar system utilizing optical heterodyne detection, the relative alignment of the received signal with respect to the local oscillator beam is particularly critical. Two compensators have been designed to correct the boresight errors as well as the wavefront errors caused by beam wandering due to the boresight changes. Several design approaches for the compensators have been investigated. The optical and optomechanical design issues for such a system are discussed. The results of optical performance, modeling, and tolerance analysis for the telescope are also presented.

A description of the newly deployed ADONIS, daylight speckle-imaging camera, including optical design and layout, electronics, data acquisition system, and processing systems is given. Considerations of operating this system on a large telescope under daylight conditions are discussed, along with alignment to the telescope and system testing. Sample pre- and post- processed images are included.

The incorporation of abnormal dispersion liquids into an optical design can result in significant performance advantages. However, the large thermal coefficient of refractive index which is common to all liquids (dn/dT) can complicate the athermalization of these designs. One method is to use two different liquids to form both positive and negative liquid lens elements which balance each other thermally while maintaining color correction. The success of this approach is dependent on the proper selection of materials, and on a detailed knowledge of the wavelength dependence of the refractive index thermal coefficients. The thermal dependence of refractive index and dispersion in the visible spectral region for a number of liquids was investigated. A correlation between the refractive index thermal coefficient (dn/dT) and abnormal dispersion was found to exist in a majority of liquids. The optical property measurements were made at the Vavilov State Optical Institute, St. Petersburg, Russia in collaboration with the Lockheed Palo Alto Research Laboratory, Palo Alto, California.

The Cassini mission to Saturn will contain the CIRS instrument which is currently being developed and assembled at the Goddard Space Flight Center. The CIRS instrument contains two science interferometers that operate in the mid and far infrared regions of the spectrum and one reference interferometer which operates in the visible. The heart of each of the interferometers is a series of hollow glass retroreflectors (cube corners) and hollow dihedrals. The hollow retroreflectors are constructed of individual facets of zerodur glass which are bonded 90 degrees to each other to sub arc-second accuracies. They are then coated with a reflective overcoat to meet the wavelength requirements. The effort at Goddard resulted in the development of retroreflectors that not only performed well at ambient temperatures, but also retained a wavefront error of approximately 2 waves p-v with a maximum beam deviation of 15 arc seconds at a temperature of 170 degrees kelvin or below. Also developed at GSFC is a successful means of mounting the retroreflectors on a fixed zerodur mount to allow cooling them down to these temperatures without introducing any added stresses that are not already present in the unmounted retroreflectors.

A series of tests on a speckle imaging camera system using the Knox-Thompson image reconstruction algorithm was performed. For simulated and real point sources the speckle OTF remains above the noise level for spatial frequencies up to 0.8 of diffraction limit. Laboratory measurements of MTF curves using a resolution chart target were also made with and without simulated atmospheric phase aberrations. Even in the presence of aberrations the KT processed images have consistently higher MTF than those without phase aberrations. We also present a method for subtracting power spectra bias applicable to CCD focal planes with finite electronic noise.

Samples of PMMA [Poly-(Methyl-Meth-Acrylate)] were modified by ionizing radiation (especially UV-radiation) in order to generate regions of increased refractive index. These waveguiding structures were used to build optical power splitters and optical polarizers simply by varying the exposure time. The refractive index profile and the variation in thickness of the waveguides for different exposure times were observed. Also the cut-off- wavelength and the spectral absorption behavior for different exposure times were measured. The compaction at the surface was used to build up diffraction gratings with grating constants of 4 micrometer to 20 micrometer. By annealing the samples the diffraction efficiency was increased.

The purpose of this project is to investigate the feasibility of using composite materials to reduce the weight of high quality optical mirrors for space flight applications. The approach that is used to fabricate test optics uses the same optical quality glass material (Zerodur) as the mold used to form the composite. The mold is the actual material that is ground into the finished polished surface, and it is bonded onto the composite during the normal curing of the composite. No secondary bonding is necessary. The mold is now ground away leaving a thin layer of Zerodur that becomes the polished surface. The composite material used in this experiment is P75/ERL1962 laid up in a quasi-isotropic laminate. Its properties will be tailored such that its coefficient of thermal expansion is close to that of the mold in the plane of the laminate. One flat optic has been made and tested. A second flat optic is close to completion, but it has not been tested. The first optic was tested in a cryogenic vacuum chamber using a Zygo interferometer to measure the distortion of the surface of the optic while the chamber was cooled down to 200 K. The measured change in flatness was 0.4 lambda using a test wavelength of 633 nm. The average fiber volume was calculated to be 56.5% with a change in fiber volume from one side to the other of 2.5%.

Recently the laser microbeam instrument has been used for wider applications in biological science and medicine. A key problem of the laser microbeam instrument is designing the laser focusing system for getting a focal spot size of less than 1 micrometer. This paper presents a new laser focusing system which is composed of a spatial filter and an 80^X focusing objective lens. The 80^X focusing objective lens was designed as a double reflective sphere type. Using this focusing system, the laser microbeam instrument has gotten a focal spot size of less than 0.5 - 1 micrometer. The focal spot size depends on the pinhole diaphragm diameter of the spatial filter. Different pinhole diaphragm diameters could produce different focal spots that are given in the end of this paper.

We present a novel method for producing arbitrary valued, binary phase-only modulation from a commercially available ferroelectric liquid crystal spatial light modulator (FLCSLM) used in conjunction with simple polarization components. Three such stages can be cascaded together in an instrument capable of producing up to eight discrete, equally spaced levels of phase modulation. By using 128 by 128 pixel FLCSLMs a reconfigurable, pixellated, eight-level, optical phase modulator has been constructed which we refer to here as a programmable phase transformer (PPT). We report on the near diffraction limited performance of such an instrument when stopped down to 64 by 64 pixels in producing simple diffraction patterns and when used to generate asymmetric spot arrays in the Fourier plane of a lens. We also discuss the limitations of the current system and the projected improvements that will result from current and future developments in device technology and modulation schemes.

In this work, a method for evaluating the radiation losses of abrupt transitions in planar optical waveguides is presented. We analyze optical discontinuities due to geometrical changes and/or variations of the refractive index profile of the waveguides. The modal matching technique is used to evaluate the radiation, as well as the reflection and transmission coefficients. Both symmetrical and non-symmetrical planar waveguides are considered. Step and graded index profiles are taken into account. Results of radiation losses are given.

Although considered as low level processing, edge detection is a crucial step in object and image recognition. Such an operation can be implemented in real time by use of an appropriate transmittance in the Fourier plane of a so-called VanderLugt optical correlator. The performance of this scheme depends on both the contour enhancement operator chosen and the spatial filter design. For the latter point, great flexibility can be obtained by using computer generated holography techniques. In this framework, we propose to implement a particular contour extraction primitive, namely the summation of the partial derivatives of an input function, using a direct binary search (DBS) procedure for the design of the spatial filter. This first approach leads, however, to a non-detection of the contours oriented at 45 degrees to the abcissa axis. To solve this problem we propose a modified gradient holographic filter. A theoretical analysis and simulation results are presented.

We have developed a low transmission loss prism for optical switches suitable for optical fiber systems which monitor and control factory equipment. We have realized the low transmission loss prism by using the geometrical property of ellipsoids and a newly developed optical power evaluation computer program which facilitates estimating the coupling efficiency between two optical fibers considering total reflection phenomena, numerical aperture and far field pattern of the optical fiber for an aspherical optical system. The transmission loss of the present ellipsoidal prism is 5 dB for the plastic fiber with the core diameter of 1 mm, and 5.8 dB for polymer clad fiber with core diameter of 0.2 mm. The present ellipsoidal prism improves transmission loss by 4 dB as compared with the conventional spherical prism for the optical fibers usually adopted to the optical fiber systems. The calculated loss and experimental loss agreed well. This agreement confirms the usefulness of our computer program.

Nearly all light sources are partially polarized, photomultiplier tube, photocell detector, and grating all have a polarization sensitive effect. When we use natural light to do some study, the light from the light source must be depolarized. In order to reduce the polarization sensitive effect of the detector, we need a fixed depolarizer in front of the detector. Since Lyot times, there has been considerable attention paid to the study of the polychromatic light depolarizer, but there are only a very limited number of ways to depolarize monochromatic light. In this article we introduce single element structure monochromatic light depolarizers made by using birefringent crystal. They include a single wedge depolarizer, a single element double wedge depolarizer, a right angle prism depolarizer, and a plano-convex lens depolarizer. We study their structure character, working principle, and use specification in detail and also point out some errors in the calcite right angle depolarizer.

Beamsplitter is one kind of optical element which can change one light beam into two or more light beams. It has been widely used in optical technique. In this article we have introduced many kinds of beamsplitters made by using birefringent crystal. If the beamsplitter can change one light beam into two light beams, according to the two light beams property, the beamsplitter can be divided into two kinds: first kind, the two light beams both are polarized light; second kind, the two light beams both are nonpolarization light. The angle between two light beams out of the beamsplitter can be designed to be zero or not. According to two parallel light beams, the displacement between them can be fixed or adjusted. According to two nonparallel light beams, the angle between them can be fixed or adjusted also. Their structure character and working principle are discussed in detail in this article.

New developments in 2-D, wide-bandwidth HgCdTe (MCT) and GaAs quantum-well infrared photodetectors (QWIP) coupled with monolithic microwave integrated circuit (MMIC) technology are now making focal plane array coherent infrared (IR) cameras viable. Unlike conventional IR cameras which provide only thermal data about a scene or target, a coherent camera based on optical heterodyne interferometry will also provide spectral and range information. Each pixel of the camera, consisting of a single photo-sensitive heterodyne mixer followed by an intermediate frequency amplifier and illuminated by a separate local oscillator beam, constitutes a complete optical heterodyne receiver. Applications of coherent IR cameras are numerous and include target surveillance, range detection, chemical plume evolution, monitoring stack plume emissions, and wind shear detection.

Infrared 100% coldshielded systems have a fixed and inaccessible aperture stop location, with a long back focal length. Often, the back focal length of a wide field of view infrared lens is longer than its elementary focal length, like a wide angle 35 mm SLR lens. The long back focal length prevents the use of a field flattener lens near the image in order to correct for field curvature and astigmatism. A field lens is usually a key ingredient in wide field of view lenses. Some have designed long and complicated reimagers to create a second image plane for a virtual field flattener lens. An inverse telephoto lens has a long back focal length and allows for an inaccessible aperture stop. The inverse telephoto lens has at least two groups, a negative group and a positive group. The negative group increases the marginal ray height to create a longer back focal length. The positive group brings the marginal ray to focus. Using a single high index and low dispersion aspheric positive element will correct for spherical aberration and reduce axial color and the Petzval sum. A single low index and high dispersion aspheric negative element will correct for coma, axial color and Petzval sum. A low Petzval sum minimizes field curvature and astigmatism. A wide angle 010% coldshielded inverse telephoto lens can be designed with just two elements. Occasionaly in wider field of view systems or larger image plane formats a second negative aspheric is necessary to correct for distortion. Thus creating a third element. Also a diffractive element is sometimes needed to correct lateral color. The diffractive can be added to one of the single point diamond turned aspheres without adding a fourth element. For wider angle applications, a three element inverse telephoto lens will suffice.

The design of a large infrared refractive re-imager for use in the 3 - 5 micron waveband is described. Comparisons are made with designing for the longer 8 - 12 micron waveband. In particular, key design aspects of achromatization, athermalization, thermal gradients, and manufacturing sensitivity, have been emphasized.

Utilizing an athermal chart (the X_f(nu) -(nu) diagram), several different material combinations are identified which are suitable to form MWIR objectives that are athermal over a temperature range of -20 degree(s)C to +60 degree(s)C. Five of these combinations utilize a diffractive surface which effectively acts as a third material. Thin lens solutions are calculated, and the performance of optimized thick lenses is summarized.

The matrix approach and the flow graph approach are basic mathematical tools used for calculation of the transmission and the reflection of isotropic stratified planar structures. It is shown that both approaches give the same analytical expressions for both the transmission and the reflection of a substrate, and of a thin layer on a substrate, independently of the optical parameters and the angle of light incidence. The expressions for the transmission and the reflection are different in the two approaches for a structure of two substrates. T plus R equals 1 is valid in both approaches for all the cases investigated when the structures are transparent.

DEMOS software was developed in 1973 - 1975 for design of optical systems (OS) with conventional and holographic elements. It was constantly improved because of the necessity to solve a wide range of tasks dealing with display systems, lenses, multispectral systems for optical electronic units, and IR systems. A new version of DEMOS III was developed in 1994, and is an integrated dialogue system for simulation and design of a wide range of OS on personal computers compatible with IBM-PC. This article deals with the new possibilities of DEMOS-PC, version 3.

Combination of global optimization technique with 3-D order monochromatic and first order chromatic aberrations theory may be useful to search an initial system for optical design. Multivariant synthesis of an optical system consisting of thin components is discussed on the basis of Slusarev's theory of principal parameters.

In mid-1996, the Multiple Mirror Telescope (MMT) will be upgraded from its current configuration of six 1.8-meter primary mirrors to house a single 6.5-meter primary. To exploit the dramatic increase in collecting area and spatial resolution, as well as the high infrared quality of the observing site, we have designed a new spectrometer that will cover the thermal infrared (4 to 25 micrometer) at high spectral and spatial resolution. The design is based on the new generation of Si:As BIB detectors with 256 by 256 formats, which represent a substantial advance in array size at these wavelengths. The design consists entirely of reflecting optics, and is arranged to deliver diffraction-limited resolution longwards of 8 micrometers. A maximum spectral resolving power of R equals 15,000 is provided by an echelle grating. A lower resolution grating or a plane mirror for two-dimensional imaging may be substituted for the echelle.

Germanium (Ge) is the most widely used material in long wave infrared (LWIR) refractive telescopes due to its high index of refraction and very low dispersion characteristics. Unfortunately, germanium's absorption increases dramatically when operating in hot environments. Traditionally, the operating temperature of Ge is extended by doping to reduce the absorption coefficient's temperature dependence. However, depending upon the optical design form, transmission losses attributed to an operating temperature rise of 40 degrees, may still be as high as 5 to 15 percent. When such absorption losses are not tolerable, alternative materials such as ZnSe, Amtirl, and GaAs can be considered. In this paper a series of case studied is presented to compare the predicted performance of conventional Ge dominated designs with lenses composed almost entirely of these alternative materials. Fabrication and production cost issues are compared along with the utilization of hybrid refractive/diffractive optical elements.

Diffractive optical elements (DOEs) have found their acceptance in lens design as an additional tool to refractive and reflective elements. They are especially powerful for applications in the infrared spectrum, because many of the materials, suitable for transmission in this region, lend themselves exceptionally well to the correction of chromatic aberration. The phase profile of the grating superimposed onto the base surface of an IR lens is relatively coarse. This makes it economically advantageous to apply the single point diamond-turning process to the direct generation of such phase profiles. Different ways have been used to describe the profile of a DOE, which have in some cases led to costly misunderstandings. To provide some clarification and suggest a form of standardization for the specifications call-out in manufacturing documents is the primary purpose of this paper. Additional comments are being presented as guidelines and for better understanding of the advantages and limitations for applications of diffractive optical elements in general, and of diamond-turned elements in particular.