When some optical processing systems firms proposed to the Defense Advanced Research Project Agency (DARPA) and the U.S. Navy some years ago that they could beat the ILLIAC-IV-that venerable supercomputer, which until recently was the world's largest by at least a factor of 100, it sounded too good to be true. But they were right, and they did not even have to try hard. The problem was a two-dimensional (2-D) processing task of generating ambiguity surfaces to test whether two received signals came from a common origin, with unknown time and Doppler shifts. The ILLIAC, going all out as an in-line processor for the Acoustic Research Center near San Francisco, California, could just make a handful of such surfaces per second; the optical processors made hundreds, literally sucking their digital inputs dry.

The concept of carrier-mean-frequency-selective convolution is introduced to solve the undersea problem of passive acoustic surveillance (PAS) and compared with the conventional notion of difference-frequency Doppler-corrected correlation. The former results in the cross-Wigner distribution function (WD), and the latter results in the cross-ambiguity function (AF). When the persistent time of a sound emitter is more important than the characteristic tone of the sound emitter, WD will be more useful than AF for PAS activity detection, and vice versa. Their mutual relationships with the instantaneous power spectrum (IPS) show the importance of the phase information that must be kept in any 2-D representation of a 1 -D signal. If a square-law detector is used, or an unsymmetric version of WD or AF is gener-ated, then one must produce the other 2-D representations directly, rather than transform one to the other.

An iterative optical matrix-vector processor that computes the adaptive weights for a phased array radar is described. Multidimensional adaptivity in both target angle and velocity is achieved by lexicographically ordering the antenna elements as they are fed to the optical processor. Complex weights are computed by spatial multiplexing of the vector and matrix inputs to the system. The error sources of the optical system and the convergence of the iterative algorithm are analyzed, and experimental demonstration of the accuracy and performance of the system is included. This novel processor is found to perform quite adequately and to be most appropriate for advanced multidimensional adaptive phased array radars.

A real-time optical synthetic aperture radar (SAR) processor is described. The processor utilizes an acousto-optic device as the input electronic-to-optical transducer and a CCD camera that serves as the optical detector and simultaneously performs the focusing of the SAR image in the azimuth direction.

Wavefront sensing by phase retrieval implies extraction of the Fourier transform of a complex signal based on observation of the modulus of the signal. Only the image intensity from a system's focal plane array is required to estimate the phase aberrations. These estimates are used to derive control signals to align (or to maintain alignment of) the optical system. The concept can be used in both a predetection and postdetection mode. In the former, the control system labors to keep the optics in a diffraction-limited mode all the time. In the latter, the control system induces a phase or wavelength diversity that allows successive images to be restored to nearly diffraction-limited quality by postprocessing of the image. This second mode is particularly interesting because it will reduce the design effort for both the optical system and the control system. How the phase or wavelength diversity is achieved is not clear at this time. If the method has utility, it provides an interesting challenge to designers of optical devices. In this paper we describe the mathematics of the technique and show some computer simulations which involve both point sources and extended objects.

A new architecture for performing systolic optical recognitiori of long codes is introduced. The resulting system is quite robust in that it is insensitive to time of arrival of the code word and to errors in recognizing parts of the code. The advantages, besides robustness, of this system are the use of simple, available components (independent of code word length), high speed, and the small number of components required.

The assembly of a pulsed laser spectroscopy laboratory is presented. The authors describe how they constructed pulsed lasers, fast photodetectors, a boxcar signal averager, and associated equipment. A molecular nitrogen laser operating up to 50 Hz with an ultraviolet (337.1 nm) 700 kW pulse was used to optically pump an organic dye laser. The resulting output could be tuned from 360.0 to 680.0 nm. This pulse was typically 30 kW and 8 nsec, which makes it ideally suited to selective excitation and fluorescence studies. By constructing this equipment, it is estimated that the investment was one-tenth the cost of commercial components.

The tone scale or gradation of a continuous tone picture is the most important factor related to the quality of an image. We have developed special purpose analog and digital circuitry that enables the real-time (30 updates per second) computation of a tone scale transformation which is then applied to a digitized picture being displayed on a television monitor. In our system the tone scale transformations are controlled by knobs that are labeled in terms meaningful to photographic artisans, rather than requiring an operator to specify points on a transfer characteristic, as is common with other systems. These knobs directly specify minimum and maximum densities, brightness, and shadow, highlight, and overall contrast. These control parameters may be selectively enabled by the operator. After the appropriate aesthetic modifications have been achieved on the television display, the operator may initiate the transformation of the complete stored image prior to subsequent computer processing or hard copy output.

Observational experiments on turbulent intensities and aerosol distributions in the marine boundary layer (MBL) have been performed over several years. Observations have been made with ship-mounted and airplane-mounted sensors. Objectives have been to relate optical properties to meteorological descriptions which utilize scaling laws for the MBL. The approach has been to incorporate* in the descriptions the surface fluxes of momentum, heat, and moisture, the processes at the inversion and the profiles within the intervening convectively mixed layer. We have found that the optical turbulence parameter Cn2 can be readily estimated using measured mean values of wind, temperature, and humidity with recent bulk formulas to derive the surface fluxes. These estimates appear to be more reliable than values obtained from direct (but difficult to perform) turbulence measurements. The model for obtain-ing the estimates was evaluated on the basis of optical Cn2 values with good agreement. Good comparisons have been observed between extinction values obtained from transmission measurements and those obtained from calculations on measured aerosol distributions. Existing empirical formulations which related the latter to wind speed and relative humidity appear to be inadequate except for climatological purposes. This is because other influences on equilibrium aerosol distribution are not included. Reformulation of these expressions is being performed to include the height of the inversion (mixing volume) and surface fluxes (aerosol generation and transport).

This paper is a preliminary report on investigations into the effects of data reduction on inverse synthetic aperture radar (ISAR) image quality and classifier performance. The case considered here is the effect of decimating the ISAR radar returns. Decimation of the type described induces image aliasing because of the signal processing involved in ISAR image formation. This familiar effect is used to model the degradation of object boundaries, which are used in classification. Constraints on subsampling will be derived as a function of target size, image signal-to-noise ratio, and classifier-required image quality. We will proceed in three main steps. The structure of a typical ISAR imaging and target classification system will be reviewed and the need for data reduction analyzed. We will then define a measure of image quality and its effect on classifier performance. The question will then be posed, and answered, as to the effect on image quality of decimation of the ISAR target spectral sequence (TSS). The technique used is to analyze the relationship between ISAR imaging and the two-dimensional Fourier transform, then to apply the sampling theorem from 2-D signal processing.

Quantitative methods for measurement of absolute (kinetic) surface temperatures of roof surfaces from aerial thermal data are discussed. Methods of accounting for atmospheric variation, background reflectance, path radiance, and roof emissivity effects are also discussed. The quantitative method has been tested in several research programs under the sponsorship of the New York State Energy Research and Development Authority and the U.S. Depart-ment of Energy. The results of these tests, which are presented here, represent a comparison of concurrent contact and aerial roof temperature measurements on a variety of roof surfaces. These tests indicate that kinetic roof surface temperatures can be measured from wholly airborne data with a standard error of 1.0°C. The implications of these results for airborne measurement of building heat loss are presented in this paper.

Recently a design was reported on a system of multiple moving mirrors which simulates an approaching or receding radiating source. Its particular features were a zoom capability of 30:1 and a total scaling range of 800:1. The mirror system operates with programmed stepper motors that provide the required mirror movements. In this paper, dynamics of the mirror system are analyzed from a different point of view which results in lower mirror velocities that are more compatible with commercially available motors and slides. Maximum velocities of the mirrors are then calculated, and the sensitivity of these maximum velocities to the simulated variables and the optical system parameters is also computed.

Jitter induced clutter in a staring sensor depends on the spatial gradients of background radiance, the detector footprint, and the line-of-sight jitter frequency characteristics. The clutter problem is most severe when there are sharp radiance gradients or edges in the scene; clutter models which describe the background by a spatial power spectrum lose the edge information. The model developed in this paper relates clutter directly to background radiance gradients and the sensor characteristics. The rms clutter is expressed in terms of structure function statistics of the background. The distribution of clutter amplitudes is not Gaussian (even for Gaussian jitter and spatially Gaussian backgrounds); extreme values occur much more often than predicted Gaussian analyses. These extreme values affect sensor threshold levels and the associated system data rates. An effective "jitter equivalent angle" is derived for the sensor which is independent of the background. Analysis of Skylab photos in the visible and near IR spectral regions indicates radiance gradients are approximately exponentially distributed and the rms jitter clutter is proportional to the footprint size raised to the 1.5 power.

In contrast to earlier work with nearly opaque photomasks, optical linewidth measurements on wafers encompass materials with a much wider variation in optical parameters and material profiles. Accurate optical edge detection requires corrections for both the relative reflectance and phase at the line edge because of the partial coherence present in optical microscopes. However, measurement systems which cannot provide the appropriate corrections and cannot detect edge location accurately can be calibrated. Since the correction curve is material dependent, calibrated standards are theoretically required for each step in the wafer fabrication process where linewidths are measured. In the proposed approach for thin layers (less than 200 nm), a small number of etched silicon-dioxide-on-silicon wafers can be used for calibration of a large class of wafer materials. Examples of wafer calibration data for filar, image-splitting, and image-scanning systems are given. The prob-lems associated with accurate linewidth measurement and calibration for thick layers are also discussed.

A linear diode array was used to scan a radiation field for pulsed high-energy x-ray imaging. With a signal of about 50 picocoulombs of charge from each diode for each beam pulse, the signal to noise ratio for an image of an open field was 119. An image of a porcine femur in a wax phantom was obtained by scanning the transmitted radiation. The resultant electronic image was superior in quality when compared to the standard radiotherapy port film. The simplicity of the detector system has demonstrated the feasibility of constructing an electronic portal imaging system for clinical use.

The operational range of low angle x-ray scattering was extended to particles and structures of about 1 to 2µm by using CKa radiation with a wavelength of 44.7 A . For particles of about 1µm in diameter, the central scattering was not observed accurately with characteristic x rays such as CuKa. The size, shape, and hydration of chloroplasts have been measured by using low angle soft x-ray scattering with CKa radia-tion, emitted from a high power x-ray tube and from synchrotron radiation. Chloroplasts were found to have a radius of gyration of 2.15 ± 0.5 um, corresponding to a particle diameter of 5.8 ± 0.2 µm. The volume was calculated from Porod's invariant and was found to be 41.0 ± 12.0 ttm3. Absolute measurements were performed directly, without weakening the primary beam, permitting the calculations of the mass of a chloroplast. The mass of the chloroplast was found to be 40.0 ± 0.07 pg, containing 0.45 pg H20/pg chloroplast. The maximum enlargement of the chloroplast particle was determined from the pair distribution function and was found to be 5.8 ± 0.2 Am. The central scattering for the chloroplast with a diameter of 6.0 um was observed within 20' of the scattering angle with CKa radiation. The origin of the difference from the nominal value in the Guinier region can be ascribed to the effect of interparticle interference when changing the density of the solvent to 10% glycerol. It should be pointed out that the use of this radiation and a synchrotron source enables us to obtain scattering of particles of Am size, almost free from the influence of the direct beam and parasitic scattering. Furthermore, by recording the intensity autocorrelation function, from which the weight average and number averaged radii of gyration, size, and size distribution can be obtained, we are enabled to study the relative dispersion from dilute particle dispersion within 0.01 arcsec and the physicochemical changes of whole cells and organelles with respect to aging, surface, and electr

A general purpose fringe pattern processing facility was developed in order to analyze moire photographs used for scoliosis diagnoses and interferometric patterns in optical shops. A TV camera reads a fringe profile to be analyzed, and peaks of the fringe are detected by a microcomputer. Fringe peak correction and fringe order determination are performed with the man-machine interactive software developed. A light pen facility and an image digitizer are employed for interaction. In the case of two-dimensional fringe analysis, we analyze independently analysis lines parallel to each other and a reference line perpendicular to the parallel analysis lines. Fringe orders of parallel analysis lines are uniquely determined by using the fringe order of the reference line. Some results of analysis of moire contourograms, interferometric testing of silicon wafers, and holographic measurement of thermal deformation are presented.

The diffraction pattern of a curved diamond-turned mirror is studied in terms of the surface autocorrelation function. These experimentally determined autocorrelation functions are used for calculation, and the results are analyzed to discriminate the parameters of the surfaces. Because of the limited range of information available, only gross features of the surfaces can be characterized. Our computation also suggests that the experimental diffraction pattern in the focal plane is more useful in describing the details of the surface.

Five optical disk recorder/readers were developed, each having an on-line user storage capacity of 101° user bits per disk side. The advantages of optical recording, as compared to magnetic-tape recording, are improved archival life, low cost media, and rapid random access capabilities. Recording at a 5 Mbit/s user data rate is done by laser machining of micron-sized holes in a thin tellurium alloy film allowing direct-read-after-write recording of information. Coding and error correction reduce the user error rate to 10-1°. The recorders have been interfaced to DEC PDP-11 minicomputers and for test purposes to a SEL 32/77 computer.

We report on the results of a collaboration between two independent research projects. In one, we have been developing a software system for the detection and display of surfaces of organs and organ systems from three-dimensional reconstructions; in the other, we have been developing hardware and software for the three-dimensional reconstruction of objects using nuclear magnetic resonance zeugmatographic imaging. The merging of these two modalities gives us a truly powerful tool for three-dimensional visualization. This is demonstrated by frames from movies illustrating the external and internal three-dimensional structure of organs, such as the brain and the heart, produced by applying the display programs to the nuclear magnetic resonance reconstructions.

Radiometry evolved over a long period of time around rather in-coherent sources of thermal nature. Only during the last few years have the effects of coherence begun to be taken into account in radiometric considerations of light sources. In this review article the fundamental concepts of conventional radiometry and of the theory of partial coherence will be first briefly recalled. The basic radiometric quantities, namely the radiance, the radiant emittance, and the radiant intensity, associated with a planar source of any state of coherence will then be introduced. It will be pointed out that the radiant intensity, representing the primary measurable quantity, obeys in all circumstances the usual postulates of conventional radiometry, whereas the radiance and the ra-diant emittance turn out to be much more elusive concepts. The radiometric characteristics of light from incoherent and coherent sources as well as from a certain type of partially coherent source, viz., the so-called quasihomogeneous source, will be analyzed. Quasihomogeneous sources are useful models for radiation sources that are usually found in nature. Lambertian sources will be discussed as examples.

Several radiometric properties of opaque fluorescent materials are measured with a 450/0 ° (illumination/viewing) spectroradiometer system interfaced to a desktop calculator. These measured values are then used to determine a sample's chromaticity coordinates and the fluorescent contribution to the radiance factor. To obtain these parameters, the calculator is used to optimize the design of an illuminant D65 simulator, accept instrument calibration data, calculate the sample's chromaticity coordinates, and graphically display the sample's nonfluorescent and total radiance factors. The performance requirements and chromaticity coordinates of a sample are displayed on a computer prepared plot to aid in evaluating a material's conformance to desired specifications.

A relatively inexpensive microprocessor-based charge coupled device (CCD) test console system has been built for the evaluation of CCD imaging arrays. The system consists of a commercially available microprocessor system (Commodore PET 2001) that controls test equipment used in CCD array testing. The test console is capable of measuring charge transfer efficiency (CTE) and noise for any size CCD array. The data collection is done by the computer interface to minimize operator error. The system is interactively controlled by an operator who runs the operation of the system from the keyboard of the microprocessor.

We describe the physics, construction, operational properties, and performance of Schottky mosaic sensors utilizing platinum silicide as the sensing layer. These devices are monolithic and are fabricated with standard integrated circuit grade silicon. Data are presented on quantum yield, transfer characteristic, uniformity and integration ele-ment size. The sensitivity and wide dynamic range of these devices are demonstrated by measurement and imagery. The construction and performance of a second generation, 32 x 64 element, area array is discussed. Several examples of thermal imagery are shown.

Synchrotron radiation is a source of continuum radiation ranging from the x-ray or soft x-ray region (depending on machine energy) to beyond the visible region. The amount of radiation emitted is a calculable function of machine operating parameters. This makes it possible to use synchrotron radiation from electron synchrotrons and electron storage rings as an absolute source particularly in the vacuum ultraviolet (VUV) and soft x-ray regions where other standards are difficult to find. At the National Bureau of Standards (NBS), an electron storage ring (SURF-II) has been used to calibrate spectrometers and photometers used in solar and aeronomy research and in fusion plasma diagnostics. A large chamber has recently been completed to facilitate such calibrations. The radiation incident on these spectrometers can be calculated to uncertainties of 3%. A technique to exactly determine the number of electrons orbiting in the ring is currently being developed to reduce this uncertainty. Detector calibrations between 5 to 55 nm (50 to 550 A) are routinely carried out at SURF-II, and transfer standard detec-tors with 6 to 10% uncertainties over the range of 5 to 254 nm (50 to 2540 A) are supplied. Special studies of "practical," high efficiency, and disposable photodiodes have been made by NBS in collaboration with other groups.

I recently corresponded with an author on the topic of originality. Optical Engineering seeks to publish "original papers." Over 90% of the paper submitted to us was taken verbatim from a prior paper by the same author (a discovery by a referee that was not volunteered by the author). The author says he thought he had exceeded some threshold of originality. This raises, in a somewhat exaggerated manner, a more general question of what constitutes your editor's definition of an original paper. Unfortunately, I can offer no clear definition. Thus I must ramble through some special cases hoping that my readers can sense the pattern and spirit of my decisions on this matter.