Kenneth G. Leib

Optical Matched Filter Correlator Memory Techniques And Storage Capacity

The techniques used for storing matched filters in image processing units of the optical matched filter image correlator (OMFIC) type determine to a large extent the capacity and discrimination of the complete system. Coherent and non-coherent addition of images for overlayed matched filter recording are investigated and reported upon. Results are related by performance in the areas of diffraction efficiency and signal-to-clutter measurements. Dichromated gelatins are used as matched filter recording media and the results compared with silver salt photographic materials. Finally, a formula is derived for matched filter capacity and the analysis extended to the case where the medium sets the resolution for matched filter recording.

The Formation and Optimization of Interferometric Fringes.

Expressions to describe fringe contours in the region of interference of two coherent beams are derived for three combinations of plane and spherical wave geometries. Equations for the fringe contours for these basic configurations are given in detail. The fringe contrast ratio is shown to be spatially variable whenever spherical wave fronts are involved and can be controlled by altering the reference‐ to signal‐beam irradiance ratio. These results are important for the fabrication of matched filters, holographic components, and optical interferometric testing.

Digital Analysis Of The Effects Of Terrain Clutter On The Performance Of Matched Filters For Target Identification And Location

A digital analysis of the effect of terrain-target interactions on the signal-to-clutter (S/C) ratio of the output of a matched filter is made. Three terrain types (wood-land, village, and roadside) were included in the investigation. A photographic image of an M-60 tank used as the target was digitized (512 x 512 pixels) and a matched filter constructed digitally, using a two-dimensional FFT algorithm. The matched filter was then used to obtain the correlation between the target and the various terrain types to obtain the signal-to-clutter ratio. Various high frequency versions of the matched filter were systematically investigated for possible optimization in the S/C ratio in an attempt to optimize the design which was eventually realized in analog optical form. The computational aspects of the problem, from the point of view of doing digital image analysis on a minicomputer with limited memory, is also discussed.

Holographic optical elements as laser irradiation sensor components

The use of holographic optical elements (HOEs) to discriminate between coherent irradiation and broadband, noncoherent light has been experimentally demonstrated under adverse scattering and attenuating conditions. As a passive sensor component in a laser irradiation detection system, an HOE can be used in several application areas, e.g., data transmission systems, aircraft warning system, underwater communications, and alignment systems, where wavelength and direction of arrival information can be used. The efficient concentration or focusing of laser light by an HOE onto a detector stage and, of equal importance, the ability to form bright, unique geometric patterns are characteristics that establish the HOEs use as a readily compatible irradiation sensor component. In addition, there is a considerable size and weight advantage over other functionally comparable optical components. Finally, as a passive element, an HOE can fmd use with CW or pulsed illumination. The properties and advantages, pros and cons, of the use of HOEs as sensor elements are discussed in the paper and illustrated in several laboratory experiments and a field test.

Analysis Of Complex Input Images For Matched Filter Construction

The storage capacity of a matched filter array can be increased by superposing a number of target diffraction patterns at each individual location in the corresponding multiple holographic lens array during matched filter fabrication. All required target orientations and scale size views can be accommodated in this manner. The Fourier transform properties of coherently added target diffraction patterns are described in this paper. The composite input image for coherent addition of Fourier patterns consists of rotated and translated target views. The Fourier transform of the composite input is derived, and several properties are described. When the target array has radial symmetry, matched filter optimization can be easily carried out.

Robotic Vision, Tray-Picking System Design Using Multiple, Optical Matched Filters

The optical correlator is applied to a robotic vision, tray-picking problem. Complex matched filters (MFs) are designed to provide sufficient optical memory for accepting any orientation of the desired part, and a multiple holographic lens (MHL) is used to increase the memory for continuous coverage. It is shown that with appropriate thresholding a small part can be selected using optical matched filters. A number of criteria are presented for optimizing the vision system. Two of the part-filled trays that Mendelsohn used are considered in this paper which is the analog (optical) expansion of his paper. Our view in this paper is that of the optical correlator as a cueing device for subsequent, finer vision techniques.

Application Of The Matched Filter Image Correlator To IR, SAR, And Visual Target Data

Optical matched filter image correlators (OMFICs) have usually been associated with visual sensors. This paper presents a discussion of OMFIC application to IR, SAR, and visual target data employing a validated digital simulation and/or laboratory experiments to detect, and in some cases track, targets using the three kinds of imagery. Extensive results are presented.

Aperture tapering in a coherent optical correlator.

Sharp edges located in an optical correlator input beam cause unwanted edge effects. A 1-D analysis is used to demonstrate this effect and how edge tapers can reduce this effect. Then an aperture made on film approximating the best taper is used to reduce the spurious signals in a matched filter correlator.

Validation Of A Digital Simulation Of An Optical Matched Filter Correlator Applied To Aerial Reconnaissance

Optical and digital approaches to 2-D image processors each have their unique advantages and limitations. Hybrid systems have been proposed to utilize the best of both. An equally important manner in which the two approaches can complement each other is through a digital simulation of the optical system. This paper reviews some of the problems of matched filter correlator applications and illustrates how valid models for simulations can be generated. Comparisons of the digital simulation to the analog approach are made for detection problems using specific targets and terrains. The relative merits of each technique as well as ways in which the digital simulation may be used to assist in the optimal design of the analog system are discussed.

Optical Matched Filtering Techniques For Automatic Interrogation Of Aerial Reconnaissance Film

The continuous need for aerial reconnaissance in its many forms has engendered support for studies to screen, process, and interpret the reconnaissance information. Some of these investigations deal with coherent optical signal processing approaches. In this paper, the authors describe the Grumman developed Optical Matched Filter Image Correlation (OMFIC) system. This automatic high speed system operates by processing photographic or other forms of imagery through multiple holographic memories of high density and effecting correlation between the input and stored imagery. The sensitivities of the matched filter to various target parameters were determined in this study, and they form, in general, the basis for establishing the memory. Three typical terrain models were processed for correlation and signal-to-clutter ratio. Estimates are given regarding processing speeds and their relationship to photointerpretation processing time.