In his usual delightful fashion, Professor Richard Feynman recently recounted stories, insights, and observations from his life in science during a one hour interview on U.S. public television. All of what he said was enjoyable, but I think he erred in at least one judgment. He expressed disdain for organizations that form committees to determine who is worthy of an honor. With due deference to his insight, let me offer my own analysis in support of another view.

This special issue of Optical Engineering addresses a number of critical issues in the continuing development and characterization of spatial light modulators for optical processing and computing applications.

The November/December 1983 special issue of Optical Engineering (Spatial Light Modulators: Critical Issues) in which this call for papers appears inaugurates a series of special issues that seek to address significant advances in materials and devices for optical information processing systems.

A first-order analytical model which describes the imaging performance of the total internal reflection (TIR) linear array spatial light modulator is presented. Two modulator configurations are identified, each with a distinct imaging response. The modulator crystal orientation defines which image response model applies. Several optical readout techniques for converting the optical phase modulation into an intensity modulation are described.

A new two-dimensional, fast, analog, electrically addressable, silicon-based membrane spatial light modulator (SLM) has been developed for optical information processing applications. This SLM, the deformable mirror device (DMD), consists of a 128x128 array of deformable mirror elements addressed by an underlying array of metal-oxide-semiconductor (MOS) transistors. Coherent light reflected from the mirror elements is phase modulated producing an optical Fourier transform of an analog signal input to the device. The DMD architecture and operating parameters related to this application are presented. A model is developed that describes the optical Fourier transform properties of the DMD. The calculated peak first-order diffraction efficiency of 8.2% is in good agreement with the value of 8.4% obtained from experimental optical Fourier transform measurements.

The structure, operation, and performance of the silicon-based liquid crystal light valves--the photoactivated, CCD-addressed, and visible-to-IR converter--are described. The performance limitations of the readout structure, in particular those affecting resolution, sensitivity, contrast ratio, and speed, are discussed.

The physical principles of operation of the variable grating mode (VGM) liquid crystal device are described. The VGM device is capable of performing a two-dimensional intensity-to-spatial frequency conversion, which in turn allows the implementation of a wide range of nonlinear optical processing and computing functions. The device utilizes certain nematic liquid crystal mixtures that are observed to form variable frequency diffraction gratings under the influence of an applied bias voltage. Both fundamental and technological limitations to device performance characteristics are discussed.

The fundamental operating characteristics and materials limitations of the optically addressed microchannel spatial light modulator (MSLM) are discussed. The role of secondary electron emission in the operation of the device is stressed, and some of the write, cycling, and readout modes, and their limitations, are described. In addition, the limitations of the inherent space-domain image processing operations of the device are discussed.

The charge transport model of photorefractivity is used to evaluate four figures of merit that can be employed to characterize the performance of photorefractive materials. The figures of merit are the steady-state index change, the response time, the energy per area to write a grating with 1% diffraction efficiency, and the index change per absorbed energy per unit volume (photorefractive sensitivity). These indices are evaluated as a function of grating period and applied external electric field for Bi12Si020, a fast material with a relatively small electro-optic coefficient, and BaTiO3, a slower material with a much larger electro-optic coefficient. Methods for optimizing the mate-rials are discussed.

The wavelength of stimulated emission at 8175.25 A of GaAlAs broad-area, single-heterojunction laser diodes of the close-confinement type was experimentally found to increase as a function of emission angle. The shift was 0.42± 0.08 A/deg and approximately 0.01 A/deg in the lateral and transverse directions, respectively. The increase of wavelength is postulated to be due to momentum loss of the photons by inelastic reflections at the Fabry-Perot surfaces. An optical model was developed by which the changes in the following properties per photon per reflection were calculated for the optical cavity-air interface (no = 3.60, na = 1.00): wavelength, AX = 3.03 x 10-4 A; momentum, Ap = 3.00 x 10-30 erg.s/cm; momentum loss coefficient, n = 3.70 x 10-8; energy, DE = 2.50 x 10-20 erg; and increased angle of reflection, a = 2.04 x 10-4 deg. By determining the number of reflections per beam path in the cavity, the full width at half power for the lateral beam divergence was calculated to be 20.6°. The pressure and energy per pulse at the cavity surface of the diode were calculated from the momentum loss concept and are in reasonable agreement with the Knoop hardness and heat of fusion for the fracturing and melting of GaAs.

Partially coherent illumination significantly affects projection system performance. Our theoretical and experimental results cover a variety of test objects imaged with different projection system assemblies, including some nonuniform sources, and show that improved optical lithography performance can be realized.

The history and background of the Large Deployable Reflector (LDR) are reviewed. The results of the June 1982 Asilomar (California) workshop are incorporated into the LDR science objectives and telescope concept. The areas where the LDR may have the greatest scientific impact are in the study of star formation and planetary systems in our own and nearby galaxies and in cosmological studies of the structure and evolution of the early universe. The observational requirements for these and other scientific studies give rise to a set of telescope functional requirements. These, in turn, are satisfied by an LDR configuration which is a Cassegrain design with a 20 m diameter, actively controlled, segmented, primary reflector, diffraction limited at a wavelength of 30 to 50 um. Technical challenges in the LDR development include construction of high tolerance mirror segments, surface figure measurement, figure control, vibration control, pointing, cryogenics, and coherent detectors. Project status and future plans for the LDR are discussed.

This article describes the optical system for the visual locomotive simulator at the Canadian National Transportation Training Centre, Gimli, Manitoba. The projection system incorporates an aspheric reflector which expands the angular field of view presented to it from the projection lens by a factor of approximately 20 before the image is focused onto a spherical screen. The picture presented to the student has a horizontal and vertical field of view of 63° and 26° respectively. The large Petzval curvature and astigmatism introduced by the aspheric mirror is compensated for in the design of the projection lens.

The random nature of white light speckle is combined with newly developed video digital data acquisition procedures to experimentally determine parameters of interest for a rigid body dynamics problem. Digital correlation of subsequent images during a dynamic event is shown to yield displacements and velocities of discrete points in the rigid body and, therefore, the angular velocity and linear velocity of the rigid body.

Modulation transfer function (MTF) measurement of a thermal imaging system from the edge response function has been described. The measurement includes determination of the overall system modulation transfer function. The effects of different parameters have been analyzed.

An intercomparison of eleven independently owned and operated axially scattering spectrometer probes (ASSP), active scattering aerosol spectrometer probes (ASASP), and classical scattering aerosol spectrometer probes (CSASP) aerosol-size spectrometers manufactured by Particle Measuring Systems, Inc. (PMS) was conducted to assess their measurement reproducibility and usefulness for describing the effects of marine aerosols on atmospheric transmission. Comparison of the dN/dr curves versus radius shows the consistency among probes. Extinction coefficients were calculated from measured particle-size distributions and compared with transmissometer, interferometer, visioceilometer, polar nephelometer, and horizon contrast photometric measurements to assess their usefulness in describing the effects of the aerosols on atmospheric transmission. A brief summary of the intercomparison data is presented. The results demonstrated that for properly operated, factory calibrated ASSPs and ASASP-CSASP combinations a) measured aerosol-size distributions were found to agree within an order of magnitude for visibilities encountered between 12 and 51 km, and b) extinction coefficients computed from the PMS measured aerosol-size distributions agreed within a factor of two to three with the other extinction measuring devices previously listed.

Multilayer designs of antireflective (AR) coatings over high-index substrates are compared to double-layer coatings. Equireflectance contours are computed and presented for double-layer coatings of Si, Ge, CdTe, and ZnSe substrates. It is argued that the large theoretical improvement in the performance of AR coatings when going from double-layer to multilayer design is greatly reduced in practice due to fabrication errors. The contours given here for specific substrates can be used for the design and evaluation of double-layer AR coatings.

The atmospheric emissions photometric imaging (AEPI) experiment to be flown on Spacelab 1 is designed to study faint natural and artificial atmospheric emission phenomena. Atmospheric emissions in the spectral region 2000 A to 7500 A from two optical channels, wide angle and telephoto, are detected by an image-enhanced low-light-level TV system. A third, telephoto, optical channel images onto the photocathode of a microchannel plate photomultiplier tube having 100 discrete anodes. Photons are counted for each discrete anode, providing a direct measure of the luminosity of an object viewed by the TV telephoto lens, albeit with low spatial resolution. Detector pointing in the range ±40°x±80°exclusive of restrictions due to the proximity of other experiments is provided by a two-axis gimbal made from a surplus Apollo telescope mount (MAST). The pointing stability is 1 arc min with respect to the spacecraft coordinate system for an exposure of one s, and the tracking capability is 3.5 deg - s-1 with a stability of 1 arc min. The detector and pointing system are located on the Spacelab pallet and are controlled by stored programs resident in the dedicated experiment processor located in the Spacelab module.

The recent explosion of interest and activity in optical numerical processing has occurred despite the fact that calculations had to be carried out with integer or fixed point arithmetic. We show here that floating point optical matrix-vector multiplication is feasible.