Showing papers by "David P. Casasent published in 1978"
TL;DR: In this article, a hybrid field effect liquid crystal light valve (LCLV) is proposed for real-time coherent optical data processing, where the input image is directed onto the photo-conductor to reduce the impedance of the photoconductor, thereby switching the ac voltage that is impressed across the electrodes onto the liquid crystal to activate the device.
Abstract: This paper reviews the hybrid field-effect liquid crystal light valve (LCLV) and its application to real-time coherent optical data processing. The light valve is basically a high resolution optical-to-optical image converter. The device embodies a CdS photoconductor, a CdTe light-absorbing layer, a dielectric mirror, and a biphenyl liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The input image is directed onto the photo-conductor to reduce the impedance of the photoconductor, thereby switching the ac voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The ac operation ensures long operating life for the device. The liquid crystal is operated in a hybrid field-effect mode. It utilizes the twisted nematic effect to create a dark off-state (voltage off the liquid crystal) and optical birefringence to create the bright on-state. The liquid crystal modulates the phase of the coherent readout light. By an additional analyzer an intensity modulation is created.
201Â citations
TL;DR: The approach to be emphasized involves the development of space-variant optical pattern recognition systems that are invariant to various expected deformations that can arise between the input and reference functions to be correlated.
Abstract: Publisher Summary This chapter is concerned with optical pattern recognition applications. Specifically, it considers practical pattern recognition problems in which differences exist between the input and reference functions to be correlated. The approach to be emphasized involves the development of space-variant optical pattern recognition systems that are invariant to various expected deformations that can arise between the input and reference functions to be correlated. The specific type of space-variant optical processor is realized by applying a coordinate transformation preprocessing operation to the input and reference data. The vital approach to optical pattern recognition is needed if optical correlators are to see extensive use in real, practical applications and if they are to supplant sophisticated digital pattern recognition systems with their extensive algorithms but slow speed high cost.
44Â citations
Journal Article•
TL;DR: What do you do to start reading optical data processing applications ?
Abstract: What do you do to start reading optical data processing applications ? Searching the book that you love to read first or find an interesting book that will make you want to read? Everybody has difference with their reason of reading a book. Actuary, reading habit must be from earlier. Many people may be love to read, but not a book. It's not fault. Someone will be bored to open the thick book with small words to read. In more, this is the real condition. So do happen probably with this optical data processing applications .
24Â citations
TL;DR: The use of a polar camera to realize the coordinate transformation in real-time and the application of this system to real imagery rather than simple geometrical objects are presented for the first time.
Abstract: Optical pattern recognition invariant to a rotation between the input and reference opjects is described. This is achieved by a space-variant optical system using coordinate transformations. The use of a polar camera to realize the coordinate transformation in real-time and the application of this system to real imagery rather than simple geometrical objects are presented for the first time.
21Â citations
TL;DR: The goal is to determine the lens specifications needed to produce an optical Fourier transform of given accuracy rather than the design of the lens itself.
Abstract: The effects of amplitude nonuniformities and phase errors on the accuracy of the optical Fourier transform are considered for the case of a simple lens. A quadratic phase model is derived, analyzed, and compared to experimental and point-by-point optical path difference data. The goal is to determine the lens specifications needed to produce an optical Fourier transform of given accuracy rather than the design of the lens itself.
12Â citations
TL;DR: Several schemes for measuring those lens parameters that determine the performance of such simple lenses as Fourier transform elements in an optical computer are provided with emphasis on lens phase errors.
Abstract: The use of simple off-the-shelf lenses as Fourier transform elements in an optical computer is considered. Several schemes for measuring those lens parameters that determine the performance of such simple lenses as Fourier transform elements are provided with emphasis on lens phase errors. It is assumed that no lens design data are available for the lens under test.
11Â citations
TL;DR: A multichannel coherent optical processor for radar signals is described in which pulse compression is achieved by matched spatial filtering.
Abstract: A multichannel coherent optical processor for radar signals is described in which pulse compression is achieved by matched spatial filtering. The optical system can be used for phased array, linear frequency modulated pulse burst, or other radar systems. However, only its application to linear phased array signal processing is discussed in depth. From the output optical pattern, one can obtain data on the target's fine range and azimuth (for a phased array) or fine range and Doppler (for a pulse burst radar) etc.
9Â citations
TL;DR: In this article, a mathematical formulation of an optical processor that implements the inverse radon transform is described, which is of use in X-ray computed tomography, transaxial scanning and other image construction systems.
8Â citations
TL;DR: The principle of operation, structure, performance specifications, and numerous examples of the use of the electron-beam addressed potassium dideuterium phosphate (DKDP) light valve in optical processing are reviewed in this article.
Abstract: The principle of operation, structure, performance specifications, and numerous examples of the use of the electron-beam addressed potassium dideuterium phosphate (DKDP) light valve in optical processing are reviewed.
7Â citations
TL;DR: The structure, principles of operation, specifications, and numerous examples of the use of the optically addressed potassium dideuterium phosphate (photo DKDP) light valve in optical data processing are reviewed in this article.
Abstract: The structure, principles of operation, specifications, and numerous examples of the use of the optically addressed potassium dideuterium phosphate (photo DKDP) light valve in optical data processing are reviewed.
6Â citations
TL;DR: The optical section is the first Fourier transform taking stage of a joint transform correlator; its output is electronically processed by a modified spectrum analyzer, enabling increased flexibility and various processing operations beyond those normally possible in an optical system result.
Abstract: A correlator is described that combines optical and electronic processing. The optical section is the first Fourier transform taking stage of a joint transform correlator; its output is electronically processed by a modified spectrum analyzer. Increased flexibility and various processing operations beyond those normally possible in an optical system result.
TL;DR: In this article, the implementation of the inverse radon transformed by optical correlation is described, which does not require formation of the derivative of the projections and allows the use of a fixed mask that is both real and positive and is dependent only on the geometry of the recording system.
TL;DR: Applications of this scheme that are discussed include space variant processing, adaptive optics, data transmission, kinoforms, holography, and optical data processing.
Abstract: An electronic–optical method is described for obtaining the phase of an arbitrary complex 2-D wavefront. The method consists of intensity detection, limiting, pulse width normalization, differentiation, dc filtering, and integration. Theoretical analyses and experimental confirmation are included. Applications of this scheme that are discussed include space variant processing, adaptive optics, data transmission, kinoforms, holography, and optical data processing.
TL;DR: This once virgin discipline of optical computing is now maturing and emerging from the laboratory and research arena into deliverable and fielded systems, and one of the key technology items that continues to plague program managers and contractors is the real-time and reusable spatial light modulator.
Abstract: The real-time and parallel processing advantages of coherent optical processors are well known. The ease with which the Fourier transform and correlation operations (that are the hallmark of data processing and pattern recognition) can be performed optically has intrigued researchers for years. This once virgin discipline of optical computing is now maturing and emerging from the laboratory and research arena into deliverable and fielded systems. As this occurs, one of the key technology items that continues to plague program managers and contractors is the real-time and reusable spatial light modulator (SLM) used as the input (and often filter plane) transducer. Without such devices, the full speed advantages of optical processors cannot be realized.
TL;DR: An optical numerical processor using residue arithmetic is described and specific designs and experimental demonstrations of decimal-to-residue and residue- to-decimal converters using a coherent optical processor are presented.
31 Aug 1978
TL;DR: Coherent optical processing of multi-sensor imagery (with geometrical and intensity dis-tortions) for pattern recognition and registration is considered in this paper, where sensor-invariant high-information content image features are considered as well as the degree to which an aerialimage need be converted to its true radar image for frame registration and map matching applications.
Abstract: Coherent optical processing of multi- sensor imagery (with geometrical and intensity dis-tortions) for pattern recognition and registration are considered. Sensor -invariant highinformation content image features are considered as well as the degree to which an aerialimage need be converted to its true radar image for frame registration and map matchingapplications. Digital, electronic and optical edge enhancement, as well as the use ofspecial features of storage -mode real -time spatial light modulators and parameter controlin optical matched spatial filter synthesis are considered as adjuncts whereby the requiredfinal result can be achieved. The initial results of coherent optical correlations onactual multi- sensor imagery are reported. 1. IntroductionIn many practical pattern recognition and image processing applications, the referenceand input imagery originate from different sensors. In radar map matching [1], the classicproblem is to locate portions of an on -line radar image in a stored reference aerial photo-