Experimental recognition using spatial filtering in a linear joint transform optical correlator

Santiago Vallmitjana; Arturo Carnicer; Estela Martin-Badosa; Ignacio Prades Juvells

doi:10.1117/12.196091

23 November 1994 Experimental recognition using spatial filtering in a linear joint transform optical correlator

Santiago Vallmitjana, Arturo Carnicer, Estela Martin-Badosa, Ignacio Prades Juvells

Proceedings Volume 2249, Automated 3D and 2D Vision; (1994) https://doi.org/10.1117/12.196091
Event: Optics for Productivity in Manufacturing, 1994, Frankfurt, Germany

Abstract

A method for the experimental realization of optical correlation for pattern recognition by using phase only filters as a reference in a real-time joint transform correlator is presented. The intensity of the interferences produced by the optical Fourier transform of both scene and reference is registered by means of a CCD camera and displayed through a liquid crystal device. A second Fourier transform accomplishes a real-time correlation. In our implementation we have used a videoprojector as a spatial light modulator. Non linear effects in the joint power spectrum have been shown as a technique for improving discrimination in a joint transform correlator. The design of spatial correlation filters is another technique to enhance discrimination. Usually, these filters are computed in the frequency domain, although they can be carried out in object space, by computing their inverse Fourier transform, becoming the reference in a joint transform correlator. In this case a codification is necessary because of the negative values. Another problem involved in the implementation is the filter normalization because usually the filters have a lower transmission than the scene. In this paper, the normalization factor has been chosen in order to optimize the optical efficiency of the process.

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Santiago Vallmitjana, Arturo Carnicer, Estela Martin-Badosa, and Ignacio Prades Juvells "Experimental recognition using spatial filtering in a linear joint transform optical correlator", Proc. SPIE 2249, Automated 3D and 2D Vision, (23 November 1994); https://doi.org/10.1117/12.196091

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KEYWORDS

Phase only filters

Fourier transforms

3D vision

Optical correlators

Joint transforms

Optical filters

Spatial filters

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