Real-time optical correlation system
First Claim
1. An optical correlation system for obtaining the correlation function of a first object by a second one, comprising means for illuminating the objects by means respectively of two coherent beams, first focusing means projecting in a first focal plane (PF) an illumination having an intensity substantially proportional to the algebraic sum of the Fourier transforms of the light amplitudes transmitted by the two objects respectively, a photosensitive support medium situated in the first focal plane (PF), recording this illumination in real time and formed from a continuously recyclable material in which the recording forms a three-dimensional grating of fringes, other means for illuminating the photosensitive support medium, second focusing means projecting in a second focal plane (P) an illumination having an intensity substantially proportional to the Fourier transform of the recorded illumination, and means for detecting correlation peaks situated in a zone of the second focal plane (P) and characterizing the correlation function, wherein said other means for illuminating said photosensitive support medium comprise angular sweep means ensuring optimum diffraction efficiency successively for the different points of the observed zone of said second focal plane (P).
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Abstract
A correlation system providing the correlation function of two objects illuminated with coherent light by using the principle of double diffraction.
The correlation system of the invention is essentially characterized in that it uses as recording medium a plate of recyclable material, i.e. inscribable and erasable at will, such as bismuth-silicon oxide. The recording provided in the plate by superimposition of the beams illuminating the objects is read by a beam undergoing angular sweeping so as to optimize the diffraction efficiency for all the correlation peaks in the observation plane.
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Citations
8 Claims
- 1. An optical correlation system for obtaining the correlation function of a first object by a second one, comprising means for illuminating the objects by means respectively of two coherent beams, first focusing means projecting in a first focal plane (PF) an illumination having an intensity substantially proportional to the algebraic sum of the Fourier transforms of the light amplitudes transmitted by the two objects respectively, a photosensitive support medium situated in the first focal plane (PF), recording this illumination in real time and formed from a continuously recyclable material in which the recording forms a three-dimensional grating of fringes, other means for illuminating the photosensitive support medium, second focusing means projecting in a second focal plane (P) an illumination having an intensity substantially proportional to the Fourier transform of the recorded illumination, and means for detecting correlation peaks situated in a zone of the second focal plane (P) and characterizing the correlation function, wherein said other means for illuminating said photosensitive support medium comprise angular sweep means ensuring optimum diffraction efficiency successively for the different points of the observed zone of said second focal plane (P).
Specification