An Optical Incoherent Correlator
TL;DR: In this paper, a technique for cross-correlating a one-dimensional input signal with a library of stored reference signals simultaneously is discussed, which involves the linear scanning of a temporally modulated image of a photographic reference mask across a temporal-integrating read-out device.
Abstract: This paper will discuss a technique for cross-correlating a one-dimensional input signal with a library of stored reference signals simultaneously The technique involves the linear scanning of a temporally-modulated image of a photographic reference mask across a temporally-integrating read-out device First, a physical feeling for the technique is given, followed by a mathematical analysis, a description of a breadboard system now in operation, a simple experiment to demonstrate the correlators features, and a mention of some alternate configurations desirable for specific applications
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01 Jan 1981
TL;DR: This process also illustrates the parallel nature of optical operations, and introduces a fundamental concept, the use of one-dimensional optical components configured for performing two-dimensional operations.
Abstract: Spectrum analysis is one of the most fundamental tools in science today. Its use in one form or another spans virtually every discipline. It was one of the first recognized applications of optical processing, and the usefulness of optical spectrum analysis has grown remarkably in the past decade. This is due to the fundamental simplicity, parallelism and intrinsic speed of optical spectrum analyzers, the maturity of the components now available, and the remarkable variety and versatility of the processing architectures that have been developed. This paper presents six selected topics on spectrum analysis using optics. The topics were selected because they represent practical techniques with broad applicability and illustrate different aspects of the technology. The topics are grouped by architecture as space integrating and time integrating. The space integrating sections cover radiometry for detecting low-level signals in wide-band noise, programmable filtering of electrical signals for interference rejection applications, and an optical technique that is equivalent to 105-106parallel filters for application where fast response, high resolution, and wide bandwidth of coverage are simultaneously required. The time integrating sections cover the versatile time integrating spectrum analyzer, and its extension to the calculation of ambiguity surfaces which have important application to radar processing problems requiring simultaneous measurement of a radar return's time of arrival and possible Doppler frequency shift. This process also illustrates the parallel nature of optical operations, and introduces a fundamental concept, the use of one-dimensional optical components configured for performing two-dimensional operations. The discussion of this concept continues into two-dimensional time integrating spectrum analyzers that use two time integrating spectrum analyzers, each capable of resolving N elements, and combines them to produce N2resolvable elements in real time.
136 citations
TL;DR: This paper describes an acoustooptic technique for achieving signal correlation with a time-bandwidth product of 10(6)-10(8), using existing devices and achieves the desired correlation function.
Abstract: This paper describes an acoustooptic technique for achieving signal correlation with a time-bandwidth product of 106–108, using existing devices. One signal is used to intensity modulate a light beam that illuminates an acoustic cell. The other signal appears in the cell as a traveling wave and is Schlieren imaged onto a detector array. The detected image intensity is integrated in time, achieving the desired correlation function. Since the correlation integration is performed in time rather than space, the time-bandwidth limitations of earlier acoustooptic correlators are greatly reduced. Experimental procedures for implementation of this technique are discussed and results shown.
83 citations
01 Jan 1977
TL;DR: A review of a variety of incoherent optical analog techniques for performing correlation and linear transform operations in scanning and nonscanning systems using spatial and/or temporal inputs are considered.
Abstract: The use of optical systems in signal processing applications can offer significant advantages over an equivalent electronic approach. These advantages stem chiefly from the high-speed analog multiply and parallel processing capability inherent in an optical system. This can be used to advantage in application areas requiring large quantities of data to be processed in near real time. Presented in this paper is a review of a variety of incoherent optical analog techniques for performing correlation and linear transform operations. Both scanning and nonscanning systems using spatial and/or temporal inputs are considered.
73 citations
TL;DR: The use of incoherent electrooptical analog methods for performing matrix-vector multiplication and a technique for encoding the matrix information on a two-dimensional binary optical transparency by means of an area modulation scheme are described.
Abstract: The use of incoherent electrooptical analog methods for performing matrix-vector multiplication has been investigated mathematically. A technique for encoding the matrix information on a two-dimensional binary optical transparency by means of an area modulation scheme is described. The one-dimensional discrete finite Fourier transform, viewed from the standpoint of matrix-vector multiplication, has been performed experimentally to demonstrate feasibility. Matrix and vector array sizes employed were 33 × 33 and 33 × 1, respectively. The average value of the correlation coefficients between theoretically derived and experimental data was found to be 0.95.
42 citations
TL;DR: In this paper, a 2D photodetector array and a single polarizing beam splitter are combined with two dynamic light valves operating in a reflection mode to perform matrix multiplication using incoherent light.
Abstract: Presented in this paper is one of several possible electrooptical engagement array architectures for performing matrix–matrix multiplication using incoherent light. Essential components of this new signal processing device include two dynamic light valves operating in a reflection mode, a 2-D photodetector array, and a single polarizing beam splitter.
40 citations
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TL;DR: In this article, a non-coherent optical correlation detector of the stored reference type is described, which makes use of real-time integration, thereby making it unnecessary to record received signals prior to correlation.
Abstract: A noncoherent optical‐correlation detector of the stored reference type is described. The correlator performs real‐time correlation of multiple delayed signals with the stored reference without a priori knowledge of the signal delays. The correlator makes use of real‐time integration, thereby making it unnecessary to record received signals prior to correlation. An experimental version of the correlator is described, its performance is analyzed, and the predicted performance is compared with the observed performance and found to agree to within 3 dB. A signal‐processing gain of 20 dB is obtained with the experimental version of the correlator.
10 citations
4 citations