Showing papers by "David P. Casasent published in 1979"
TL;DR: A numerical optical processor is described that performs operations in residue arithmetic that leads directly to novel residue adder and decimal/residue/decimal converter designs, which are described and experimentally demonstrated.
Abstract: A numerical optical processor is described that performs operations in residue arithmetic. The position coding used to represent decimal and residue numbers allows one to describe the various conversions and operations in a correlation formulation. This description of residue arithmetic leads directly to novel residue adder and decimal/residue/decimal converter designs, which are described and experimentally demonstrated. The accuracy, dynamic range and space bandwidth of an optical residue arithmetic processor are also discussed.
77 citations
TL;DR: A noncoherent optical vector-matrix multiplier using a linear LED source array and a linear P-I-N photodiode detector array has been combined with a 1-D adder in a feedback loop and its use in solving simultaneous linear equations is described.
Abstract: A noncoherent optical vector-matrix multiplier using a linear LED source array and a linear P-I-N photodiode detector array has been combined with a 1-D adder in a feedback loop. The resultant iterative optical processor and its use in solving simultaneous linear equations are described. Operation on complex data is provided by a novel color-multiplexing system.
53 citations
01 May 1979
TL;DR: The optical space-variant pattern-recognition systems described are examples of the growing repertoire of operations now achievable in optical computers.
Abstract: Pattern-recognition systems, techniques, and applications using coherent optical systems are reviewed. Many optical pattern-recognition system architectures exist that include time-domain optical correlators and the optical joint transform correlators and refinements in the original optical matched spatial filter synthesis processor. Advanced optical pattern-recognition systems are also described such as hybrid optical/digital processors and diffraction-pattern sampling systems using specially shaped Fourier plane detector arrays. The optical space-variant pattern-recognition systems described are examples of the growing repertoire of operations now achievable in optical computers.
45 citations
TL;DR: An experimental test procedure and associated theoretical formulations are described for the evaluation of spatial light modulators (SLMs) for coherent optical computing and their relationships to specific SLMs will be covered in separate papers.
Abstract: An experimental test procedure and associated theoretical formulations are described for the evaluation of spatial light modulators (SLMs) for coherent optical computing. The experimental data included were obtained by us on Hughes liquid crystal and photo DKDP SLMs among others. However, in this paper we address only the general procedures to be used to evaluate SLM performance. The detailed aspects of these tests and their relationships to specific SLMs will be covered in separate papers.
35 citations
TL;DR: Space variant optical processors using coordinate transformations and a new phase detection scheme are used to realize multiple invariant optical correlators that are invariance to more than one distortion parameter per axis of the processor.
Abstract: A multiple-invariant, space variant optical processor in which two functions described by any number of separate distortion parameters can be correlated with no loss in signal-to-noise ratio of the correlation. The unknown distortion parameters can also be determined in this scheme. Experimental confirmation of the key step, determination of the non-linear phase portion of a complex optical transform can be provided.
32 citations
TL;DR: The use of incoherent optical processors using carrier encoding to achieve bipolar operations in optical pattern recognition is described and experimental demonstrations of the use of this system are included.
Abstract: Recently reported incoherent optical processors using carrier encoding to achieve bipolar operations are discussed. In this paper we describe the use of these incoherent optical processors in optical pattern recognition. Experimental demonstrations of the use of this system are included.
20 citations
TL;DR: This poster presents a probabilistic simulation of the response of the immune system to EMT and shows clear patterns in response to EMMARM, including high levels of “good” and “bad” EMT.
Abstract: Reference EPFL-ARTICLE-158594doi:10.1364/AO.18.003203View record in Web of Science Record created on 2010-11-25, modified on 2017-07-31
16 citations
TL;DR: An optical image plane correlator is described which computes the ambiguity function for passive, wideband, complex, and basebanded signals.
Abstract: An optical image plane correlator is described which computes the ambiguity function for passive, wideband, complex, and basebanded signals. Quadrature input modulation, single-sideband filtering, and a modified image plane correlator requiring no moving parts are used to achieve the required complex correlations. The scenario, theory, and design are provided together with experimental verification on LFM and Barker-coded waveforms as well as synthetic data.
14 citations
04 Dec 1979
TL;DR: In this paper, a novel approach to coherent optical pattern recognition is described, where a 2D input function is described in terms of its absolute normalized invariant moments, and a parallel optical processor with a special mask is used to generate all moments for a 2-D scene in parallel.
Abstract: A novel approach to coherent optical pattern recognition is described. It does not utilize matched spatial filters and optical correlation methods. Rather, a 2-dimensional input function is described in terms of its absolute normalized invariant moments. Comparison of these moments enables one to determine the presence of a given object independent of geometrical distortions. A parallel optical processor with a special mask is used to generate all moments for a 2-D scene in parallel. A simple digital post processor calculates the actual absolute normalized invariant moments with the high dynamic range necessary. Our initial work reported upon here has concentrated on: the optical generation of individual moments, how the individual moments vary, the dynamic range requirements of the system and how they may best be met in a hybrid optical digital topology,and methods to generate all moments optically in parallel.© (1979) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
14 citations
TL;DR: Theoretical and experimental analyses are presented of the effects of phase errors in the components of an optical correlator and the empirically determined expression R = 1 - 0.5ø is found to describe the loss in intensity of the correlation peak in terms of the phase error ø in the first transform lens.
Abstract: Theoretical and experimental analyses are presented of the effects of phase errors in the components of an optical correlator. A position dependent treatment of the wavefront phase error of the optical system is needed to determine how these errors propagate through the system and their effect on the output correlation. The empirically determined expression R = 1 − 0.5 ϕ¯2 is found to describe the loss in intensity of the correlation peak in terms of the phase error ϕ in the first transform lens.
8 citations
TL;DR: Various real-time optical data processing experimentstusing the photo-DKDP spatial light modulator are described, including the performance of image subtraction and contrast reversal directly on the light valve and their application to practical pattern recognition situations in which the input and reference objects differ.
Abstract: Various real-time optical data processing experimentst using the photo-DKDP spatial light modulator are described. These include the performance of image subtraction and contrast reversal directly on the light valve and their application to practical pattern recognition situations in which the input and reference objects differ. Examples of real-time optical correlation on coded waveforms for signal processing are presented, and the accuracy of the optically produced ambiguity function outputs are compared to the theoretically expected ones. Real-time optical image pattern recognition experiments are also presented, together with comparative data obtained with off-line correlations performed using film.
TL;DR: It is shown that nonlinear transmitted coded signals must be used with a space-variant optical signal processor and that this results in novel waveform design and system approaches for radar and communications.
Abstract: The use of coded waveforms in space-variant optical signal processors using coordinate transformations is considered. It is shown that nonlinear transmitted coded signals must be used with such a processor and that this results in novel waveform design and system approaches for radar and communications.
17 Dec 1979
TL;DR: The problem of target identification and trackAssembly from successive image frames from a satellite based infrared mosaic detection is considered and the wide variety of digital and electronic algorithms for bulk filtering, target identification, and track assembly are described.
Abstract: The problem of target identification and track assembly from successive image frames from a satellite based infrared mosaic detection is considered. The wide variety of digital and electronic algorithms for bulk filtering, target identification, and track assembly are described. Optical pattern recognition techniques are also described.
TL;DR: The ambiguity function that results from the space-variant optical processing of nonlinear coded waveforms is analyzed and results in a Mellin transform-based Doppler-invariant signal processor.
Abstract: The ambiguity function that results from the space-variant optical processing of nonlinear coded waveforms is analyzed. The space-variant signal processor considered is realized by coordinate transformations. Specifically we consider x = lnt, which results in a Mellin transform-based Doppler-invariant signal processor. Ambiguity function data are provided for a nonlinearly coded 13-bit Barker code.
04 Dec 1979
TL;DR: In this article, a hyperspace description of the multiobject pattern recognition problem is presented, where average filters composed of linear sums of orthonormal basis functions are found to provide the necessary discriminant hypersurfaces.
Abstract: A hyperspace description of the multiclass (multiobject) pattern recognition problem is advanced. Average filters composed of linear sums of orthonormal basis functions are found to provide the necessary discriminant hypersurfaces. Optical correlation using weighted matched spatial filter synthesis is used to determine the basis functions and their linear weights. The average filters are then assembled on a digital computer and used in an optical frequency plane correlator. Initial problem formulation theory and simulation results are included for an infrared tank pattern recognition problem.© (1979) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
29 Oct 1979
TL;DR: A survey of optical Fourier transform techniques is presented for advanced focal plane Fourier spectroscopy in which multichannel Fourier analysis of long signals of modest band-width are required.
Abstract: A survey of optical Fourier transform techniques is presented. The specific application considered is advanced focal plane Fourier spectroscopy in which multichannel Fourier analysis of long signals of modest band-width are required.
TL;DR: Spatial sensitometry variations in a liquid crystal light valve are studied as well as signal induced noise and differences in global and local contrast ratio in this paper, where the device's off state is investigated and spatial variations in the thickness of the LC layer are used to quantify the results obtained.
Abstract: Spatial sensitometry variations in a liquid crystal light valve are studied as well as signal induced noise and differences in global and local contrast ratio The device's off state is investigated and spatial variations in the thickness of the LC layer are used to quantify the results obtained Operation with low frequency applied ac voltages appears preferable from noise considerations, whereas operation at high frequency appears preferable for improved uniformity
21 Sep 1979
TL;DR: A non-coherent vector-matrix multiplication system (using a linear LED input array, a covariance matrix mask and a linear photodiode detector array) is described, modified to perform complex multiplications and to be an iterative optical processor (I0P) to solve the adaptive phased array radar processing problem.
Abstract: A non-coherent vector-matrix multiplication system (using a linear LED input array, a covariance matrix mask and a linear photodiode detector array) is described. The system has been modified to perform complex multiplications and by feedback to be an iterative optical processor (I0P) to solve the adaptive phased array radar processing problem.
TL;DR: In this paper, a hybrid, a.c., field effect, liquid crystal light valve is analyzed and the control voltage and its frequency are shown to change the transmission threshold, sensitivity, linear dynamic range and the shape of the device's sensitometry curve.