Improved performance in many optical instruments has been achieved by considering coherence effects in the design of the optical instrument. In this paper such improvements are reviewed by heuristically describing the fundamental principles of partial coherence which are required in the design of such instruments. Furthermore, these coherence effects, which arise from both coherent and incoherent sources of radiation, are illustrated by discussing a selected set of instruments in which improved performance has been achieved. These examples include high-resolution recording and analyzing instruments which use incoherent sources, as well as imaging and mensuration instruments which use coherent sources. A set of guidelines for determining when coherence effects influence system performance with respect to linearity, resolution, and noise is also presented.

This special issue is a double celebration: twenty-five years of SPIE and twenty years of Optical Engineering. The papers on photo-optical instrumentation engineering in this issue were invited by an anniversary committee comprised of Joseph B. Houston, Jr., Brian J. Thompson, William G. Hyzer, and the journal editor.

Recent advances in electro-optics have brought into use communication and information theory to analyze performance in coherent and incoherent optical information processing systems. An optical information processsing system can be analyzed with many of the same concepts of linear system theory (e.g., spatial impulse response, spatial frequency and spatial domain synthesis, etc.), and the photographic images to be processed can be regarded in the same manner as time signals (e.g., spatial frequency content, spatial amplitude and phase modulation, space-bandwidth product, etc.). Both coherent and incoherent optical processing systems can be treated as linear systems, and the processing operation can generally be carried out by communication theory concepts. Although coherent optical information processing operations have been used for performing complex amplitude operations, complex processing can also be performed with incoherent or white-light illumination. The importance of optical information processing operations, either coherent or incoherent, is due to the basic Fourier transform properties of lenses. In this paper, we will discuss mostly the incoherent systems because they are of more recent interest and possess certain advantages, we feel, over the traditional coherent optical processors. Experimental illustrations of the results are provided. In view of the broad area in optical processing of photographic images, we will confine ourselves to a few applications that we consider of general interest. We apologize for the omission of other techniques and applications, and for neglecting the inclusion of their references.

Digital image processing has been one of the more active fields at the interface between optics and computing. In particular, image displays have begun to assume many of the characteristics of general purpose computers, but with the full computational power of the system devoted to image manipulation. Where can the trends established in the past ten years be expected to take us in the coming years? We try to answer this question, after first reviewing and summarizing the current state of digital image processing.

Methods of enhancing underdeveloped, underexposed, or low optical density regions of properly exposed silver halide images using chemical treat ment techniques are reviewed and discussed. These procedures consist of modifying the transmission or emission characteristics of the original negative. Transmission methods increase the effective optical density of the original image by deposition of chemicals at or on the original silver grains and are therefore destructive. Emission methods such as autoradiography and fluores-cence provide a nondestructive enhancement alternative to the transmission approach.

The use of video equipment as instrumentation has been increasing steadily over the past decade. An indication of this trend can be found close to home: notice how rapidly the number of television (TV) displays has grown at our technical exhibits. It is this exhibited equipment and other equipment like it which form the subject of this summary. We will limit our discussions to readily available hardware (and a little software) and leave reports of the leading edge development work to other issues of this journal. We hope, in this manner, to present useful information to those who need to apply video to their instrumen-tation problems now. Along the way we will occasionally indicate what equipment might soon result from current research, but our clear emphasis will be on the state of the art of accessible instrumentation video.

Significant advances in high-speed camera technology are being made in the Union of Soviet Socialist Republics (USSR) and People's Republic of China (PRC), which were revealed to the author during recent visits to both of these countries. Past and present developments in high-speed cameras are described in this paper based on personal observations by the author and on private communications with other technical observers. Detailed specifications on individual instruments are presented in those specific cases where such information has been revealed and could be verified.

Over the years many photographic techniques have been developed' to aid the scientist and engineer in obtaining data of fast moving events. A variation of streak photography called ''synchro-ballistic- is one means of obtaining precise information about objects in linear motion. The purpose of this discussion is to review the principles of synchro-ballistic photography and to discuss recent improvements which simplify its application and increase its data yield.

The history of the tracking telescope used at missile ranges is traced as both a metric and surveillance instrument. The history begins with the Askanias in 1937 and ends with the Distant Object Attitude Measuring System (DOAMS) in 1981. The history and capabilities of the cinetheodolites are discussed, as are fixed metric systems and mobile tracking mounts. All are discussed from a historical perspective to the state-of-the-art. The direction in which we must head to really advance the overall capabilities of photo-optical range instrumentation is briefly addressed.

Exploitation of recent advances in acousto-optics can provide a significant improvement in data handling and analysis through the development of a new generation of instruments. These instruments exist in a variety of forms currently and are evolving rapidly into systems which are being fielded and used under adverse environmental conditions. The success ratio of these systems implies that a major effort will be supported during this decade to expand the number of applications and to explore the ultimate potential of acousto-optic devices and the collateral technologies. The feasibility of using equipment which has been augmented by or is based primarily on acousto-optic principles is described.

Boundary detection in conventional nuclear medicine scintigrams is often difficult for several reasons. First, scintigrams generally have a low signal-to-noise ratio. Second, edge structures are poorly defined because of the low resolution of gamma ray cameras; and finally, edge contrast is usually reduced by foreground and background activity. In this paper we report on heuristic approaches we have taken to solve these problems and to develop programs for the display of cardiac wall motion and for the automatic determination of left ventricular ejection fraction. Our approach to processing cardiac scintigrams entails several steps: smoothing, edge enhancement, and contour extraction. We discuss each of these steps in light of the goal of producing cardiac boundaries which are spatially and temporally smooth and continuous. Boundary detection results are presented for some selected clinical images.

Every improvement in infrared detector sensitivity afforded by modern technology amplifies apparent background "clutter," and complicates the task of designing target/background discrimination algorithms for autonomous surveillance systems. To the extent that background clutter rather than detector sensitivity limits over-all performance, the sensitivity inherent in the detector is not being fully exploited. In this paper we design adaptive threshold point target detectors that operate in the background-shot-noise-limited regime against structured backgrounds.

Expressions for the mean and variance of the images produced by Fourier multiaperture emission tomography are derived. Only quantum noise (counting statistics) is considered. The signal-to-noise ratio achieved by the system for a thin discshaped object is computed from these expressions. An example is used to demonstrate some significant features of this single photon emission tomographic imaging system.

The analysis and demonstration of a holographic coupler for single-mode optical fibers and cables is discussed. The holographic coupler is composed of two holographic windows. The holographic window is rigidly attached to the cable end. The coupling between windows proceeds by means of plane waves. The tolerances for some of the critical coupler parameters are relaxed, namely transverse alignment. Precision work is restricted to the factory produc-tion, but of simple implementation. The result is a coupler with relatively undemanding assembly operations in the field.

Experimental measurements of infrared transmittance are reported, which show that the computer code LOWTRAN-4 predicts too high a transmittance in the region 4.3 to 5.5 microns, and that the discrepancy is dependent on the water-vapor content. We have carried out experiments at various ranges up to 45 km in order to vary the precipitable water amount over a wide range, and, from the results, we have deduced that the anomalous transmittance results from an incorrect estimate of the continuum absorption, while the spectral component is substantially correct.

The exposure-control system described in this paper has been found extremely useful in the production of multicolor holograms, which require precise repetition of exposures at different laser wavelengths. It permits rapid measurements of the irradiances of the object and reference beams in the hologram plane for adjustments of the beam ratio, as well as summation of these irradiances and automatic determination of the exposure time for a desired radiant exposure. A separate detector continuously monitors the laser power and automatically adjusts the exposure time to compensate for varia-tions in laser output during the exposure. A simple interlock ensures the correct combination of settings of detector sensitivity and radiant exposure when changing from one wavelength to another.

A technique has been developed for producing transmission diffraction gratings suitable for use in the extreme ultraviolet. Thin self-supporting films of a transparent material are overlaid with several thousand opaque metallic strips per mm. Gratings with 2100, 2400, and 5675 1/mm have been produced and tested. Representative spectra over the wavelength range from 17.2 to 40.0 nm are given for a grating consisting of a 120 nm thick Al support layer overlaid with 2400, 34 nm thick, Ag strips/mm. The absolute transmittance is ~13% at 30 nm, and the efficiency in the first order is ~16%. The observed resolution of 0.2 nm is acceptable for many of the potential applications. These gratings have several advantages over the two presently available alternatives in the extreme ultraviolet (i.e., reflection gratings used at grazing incidence and free-standing metallic wire transmission gratings). Fabrication is relatively quick, simple, and cheap. The support layer can also serve as a filter and help conduct excessive heat away. Higher line densities and hence higher resolutions are possible, and when used at normal incidence the spectra are aberration free. Suitable materials, component thicknesses, and line densities can be chosen to produce a grating of optimum characteristics for a particular application.

A simple technique to generate holographic optical elements with diffraction-limited performance at a wavelength different from the construction wavelength has been developed. The method consists of specifying the desired grating performance at the operating wavelength, selecting one construction beam, and utilizing a ray-trace program to compute the aberrated construction beam required to create the hologram. A lens capable of focusing this aberrated beam to a point may then be designed using ACCOS-5. A point source used with this lens thus serves to generate the second required construction beam. A sample design which may be used to construct, with 0.4579 um light, a grating to operate at 2.8 uM is presented.

The dispersion of artificial aerosol plumes over sea surfaces was measured using a portable lidar system. The momentary distribution of aerosol concentrations could be derived from short-time measurements. Some effects of the aerosols and the sea surface on the plume dispersion were estimated.

This paper discusses a common reflective collimator approach to the alignment and testing of laser ranger/designators and thermal imaging systems mounted on common carriers. All test measurements are made at a common focal plane. A large aperture reflective common collimator is capable of testing multispectral systems independent of configuration as long as the total aperture of the system to be tested is less than the aperture of the collimator. An analysis of the test system capabilities with respect to measurement of imaging system performance, boresight of imaging system or laser receiver to laser transmitter, and measurement of laser transmitter parameters is outlined. A shearing plate technique for accurate focusing of the test collimator is discussed. The shearing plate technique is suitable for field use and can provide a focus accuracy on the order of tens of microradians.

Recent work in the area of rf pumped CO2 waveguide lasers has led to the development of high repetition rate pulsed rf devices. These lasers typically exhibit self-polarized, gain-switched outputs with remarkable amplitude and frequency stability. Peak output powers of nearly 800 watts have been observed at kilohertz repetition rates in 20 cm long devices. Minimal degradation in average power after 109 pulses has been observed during sealed-off operation in one such device.

Laboratory and flight radiometric performance testing of an experimental multispectral scanner system is described. High sensitivity performance is confirmed by test results using noise equivalent spectral radiance as the primary figure of merit. A performance comparison between the test-bed air-craft multispectral scanner (MAMS) and the Bendix modular multispectral scanner (MIS) is presented. Methods for achieving high sensitivity operation are discussed as well as some of the practical implications of such operation for flight remote sensing experiments.

The two techniques of backward-wave Raman pulse compression and pulse stacking are reviewed in the context of using KrF lasers as drivers in inertial confinement fusion. Experimental and theoretical results on Raman pulse compression in methane are presented including data on 70 to 75% pump energy extraction by the counterpropagating Stokes wave. Results from ongo-ing pulse stacker/Raman compressor experiments are also described, along with future investigations in this general area.

Using image restoration techniques, we report on an algorithm for determining the optimum correction of original masks, which are to be reduced by a given microphotographic system, in order to compensate for the system's distortion. The film is assumed highly nonlinear. As an example, we compute the profile of serifs that should be added to corners to compensate for distortion in a diffraction-limited imaging system.

A new method for measuring the resolution and contrast of calligraphic projection displays has been developed at NOSC (Naval Ocean Systems Center). The technique involves the use of a computer-controlled photometer and an X-Y plotter. The plotter is normally used to give hard copy records of the photometric data obtained from spectral or spatial scans and subsequently stored in the memory of the controlling computer. In this application the photo-metric sensor, a miniature integrating sphere with a slit aperture, is mounted on the X-Y plotter pen holder, which is in turn moved according to programmed instructions from the computer. With the X-Y plotter positioned vertically in front of a projection display, the projected brightness is measured and stored in the computer memory as a function of sensor position. The spatial displacement between measurements is under operator control and can be in increments as small as one-thousandth of an inch. After the data are stored in computer memory, they are made into hard copy with the X-Y plotter in one of several plotting modes. From this hard copy the display performance parameters of resolution and contrast can be extracted. The different plotting modes are used to enhance various differences when more scans than one are recorded on the same chart.

Absorption coefficients smaller than 0.001 cm-1 can, with more or less difficulty, be measured by several techniques. With diligence, all methods can be refined to permit measurement of absorption coefficients as small as 0.00001 cm-1. Spectral data are most readily obtained by transmission (spectrophotometric) methods, using multiple internal reflection to increase effective sample length. Emissivity measurements, requiring extreme care in the elimination of detector noise and stray light, nevertheless afford the most accessible spectral data in the 0.0001 to 0.00001 cm-1 range. Single-wavelength informa-tion is most readily obtained with modifications of laser calorimetry. Thermo-couple detection of energy absorbed from a laser beam is convenient, but involves dc amplification techniques and is susceptible to stray-light problems. Photoacoustic detection, using ac methods, tends to diminish errors of these types, but at some expense in experimental complexity. Laser calorimetry has been used for measurements of absorption coefficients as small as 0.000003 cm-1. Both transmission and calorimetric data, taken as functions of intensity, have been used for measurement of nonlinear absorption coefficients.

Recent emphasis placed upon real-time coherent radar signal processing has fostered competition between digital, charge-coupled device (CCD) and surface acoustic wave (SAW) technologists. In that this stimulates and encourages technological advances, this competition is a healthy one; to the extent that the complementary rather than competitive properties of the technologies are not effectively utilized, the competition is counterproductive. The application of the various technologies to ground radar signal processors is investigated. The emergent theme emphasizes the fact that all signal processor tasks must be considered to properly assess the applicability of the various technologies; it is insufficient to compare signal processor implementations on the basis of a filtering function alone. To illustrate this viewpoint, examples of digital, CCD, and SAW signal processors are given.

The use of a laser diode as a light source in schlieren flow visual-ization is discussed. A laser diode schlieren photograph and a white light schlieren photograph are presented for comparison.

The following are corrected Figs. 3(b). 6(b), 7, 9, and 14. These figures exhibited artifacts introduced bv the reproduction process, as seen on pages 487, 489, 489, 490, and 492, respectively.

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