Real time image subtraction with a single liquid crystal light valve
First Claim
Patent Images
1. An image subtraction apparatus for subtracting a first and a second input image, comprising:
- a liquid crystal light valve having a write side and a readout side;
input means for projecting said first and second images onto the write side of said liquid crystal light valve;
a Ronchi grating positioned adjacent said write side of said liquid crystal light valve in the optical path of said input images and spaced apart from said liquid crystal light valve by a distance equal to or less than the Rayleigh length for the average spectral wavelength produced by said input images and having a spatial frequency approximately equal to or greater than twice the highest spectral frequency provided by said input images;
readout means for projecting a coherent optical beam on the readout side of said liquid crystal light valve where it is reflected toward an image plane where it is an output beam;
readout imaging means for focusing the reflected readout beam onto an output image plane;
optical filter means positioned in the optical path of said readout beam between said readout imaging means and said image plane for filtering all but one of the odd spectral orders for said output beam.
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Abstract
A technique for subtracting images in real time utilizing a single liquid crystal light valve (LCLV) is described. The two images are projected on the LCLV through a common grating in a well-determined geometry. The interrogating light beam is optically filtered, so that only different features in the two images are revealed.
31 Citations
5 Claims
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1. An image subtraction apparatus for subtracting a first and a second input image, comprising:
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a liquid crystal light valve having a write side and a readout side; input means for projecting said first and second images onto the write side of said liquid crystal light valve; a Ronchi grating positioned adjacent said write side of said liquid crystal light valve in the optical path of said input images and spaced apart from said liquid crystal light valve by a distance equal to or less than the Rayleigh length for the average spectral wavelength produced by said input images and having a spatial frequency approximately equal to or greater than twice the highest spectral frequency provided by said input images; readout means for projecting a coherent optical beam on the readout side of said liquid crystal light valve where it is reflected toward an image plane where it is an output beam; readout imaging means for focusing the reflected readout beam onto an output image plane; optical filter means positioned in the optical path of said readout beam between said readout imaging means and said image plane for filtering all but one of the odd spectral orders for said output beam. - View Dependent Claims (2, 3, 4, 5)
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Specification