AUTOMATIC BEAM RATIO CONTROL SYSTEM FOR HOLOGRAPHY
First Claim
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1. A system for producing holographic filters comprising:
- a coherent light beam source;
means for directing the beam from the source to illuminate an object for diffraction thereby in a signal beam;
means for focusing the light diffracted by the object so as to form the optical Fourier transform of the object at a transform plane;
means for directing a coherent reference light beam onto the transform plane at a non-normal angle of incidence;
means for separately measuring the intensity of the signal beam light forming said optical Fourier transform of the object at a multiplicity of distinct spatial frequencies;
means for measuring the intensity of the reference beam;
means for comparing the measured intensities of the signal and reference beams; and
means, responsive to the output of said means for comparing the measured intensities, for maintaining the beam intensities at a value such that the reference beam has an intensity substantially equal to the highest intensity measured for any spatial frequency in the signal beam other than the spatial frequencies near the zero spatial frequency.
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Abstract
This invention comprises apparatus for controlling the ratio of the signal and reference beams in a system for making holographic filters for use in matched filter pattern recognition apparatus. Means is provided for measuring the intensity of the spatial frequencies of a signal beam, and means is provided for measuring the intensity of a reference beam. The difference between the measured beam ratio and the optimum beam ratio controls an attenuator placed in either the reference beam path or the signal beam path. A shutter may also be controlled so that uniformity of exposure is maintained as the beam ratio is adjusted.
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1 Claim
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1. A system for producing holographic filters comprising:
- a coherent light beam source;
means for directing the beam from the source to illuminate an object for diffraction thereby in a signal beam;
means for focusing the light diffracted by the object so as to form the optical Fourier transform of the object at a transform plane;
means for directing a coherent reference light beam onto the transform plane at a non-normal angle of incidence;
means for separately measuring the intensity of the signal beam light forming said optical Fourier transform of the object at a multiplicity of distinct spatial frequencies;
means for measuring the intensity of the reference beam;
means for comparing the measured intensities of the signal and reference beams; and
means, responsive to the output of said means for comparing the measured intensities, for maintaining the beam intensities at a value such that the reference beam has an intensity substantially equal to the highest intensity measured for any spatial frequency in the signal beam other than the spatial frequencies near the zero spatial frequency.
- a coherent light beam source;
Specification
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Current AssigneeDonald C. Mead, James T. Thomasson, Niels Jensen
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Original AssigneeDonald C. Mead, James T. Thomasson, Niels Jensen
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InventorsJensen, Niels, Thomasson, James T., Mead, Donald C.
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Primary Examiner(s)Wibert, Ronald L.
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Assistant Examiner(s)Stern, Ronald J.
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Application NumberUS05/181,867Time in Patent Office582 DaysField of Search350/3.5,162SF 250/201,204,205 95/1R,1CT 356/16R,109US Class Current250/204CPC Class CodesG03H 1/00 Holographic processes or ap...Y10S 359/90 Methods
