Automatic mask threshold
First Claim
1. A system for selecting an optimum mask threshold utilizing the correlation of two input signals associated with a live image and a reference image, the improvement comprising:
- means for defining the live image as a set of pixels, wherein each live image pixel has an intensity representation;
means for defining the reference image as a set of pixels, wherein each reference image pixel has an intensity representation;
means for defining an image threshold range;
means for processing a reference image signal from the reference image, said reference image signal including reference polarity bits for those pixels having an intensity outside of the threshold range and reference mask bits for those pixels having an intensity within the threshold range;
means for processing a live image signal from the live image, said live image signal including polarity bits for those pixels having an intensity outside of the threshold range and mask bits for those pixels having an intensity within the threshold range;
means connected to said means for processing a live image signal and said means for processing a reference image signal, for correlating said polarity bits of said reference and said live image signals to find a peak correlation, said means for correlating disregarding the mask bits; and
means connected to both said means for processing, for automatically adjusting said image threshold range to maximize said peak correlation and for identifying the magnitude of said image threshold range associated with said peak correlation, wherein the means for adjusting the image threshold range adjusts the image threshold range depending on a predetermined relationship between the peak correlation and the threshold range.
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Accused Products
Abstract
An improved method for finding the mask threshold for a maskable bilevel correlator operates on a series of frames of information. Beginning with an initial threshold, two rates are computed. The rate of change of the correlation peak magnitude P.sub.(T), a function of threshold T, with respect to the change in the value of the mask threshold T, or (dP.sub.(T) /dT), and the corresponding rate of change of correlation reference pixels with magnitude exceeding the mask threshold, U.sub.(T), a function of threshold T, with respect to the change in the value of the mask threshold T, or (dU.sub.(T) /dT), are measured. The correct, or best, value of the threshold occurs when |dP.sub.(T) /dT|≧0.5*|dU.sub.(T) /dT|.
18 Citations
19 Claims
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1. A system for selecting an optimum mask threshold utilizing the correlation of two input signals associated with a live image and a reference image, the improvement comprising:
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means for defining the live image as a set of pixels, wherein each live image pixel has an intensity representation; means for defining the reference image as a set of pixels, wherein each reference image pixel has an intensity representation; means for defining an image threshold range; means for processing a reference image signal from the reference image, said reference image signal including reference polarity bits for those pixels having an intensity outside of the threshold range and reference mask bits for those pixels having an intensity within the threshold range; means for processing a live image signal from the live image, said live image signal including polarity bits for those pixels having an intensity outside of the threshold range and mask bits for those pixels having an intensity within the threshold range; means connected to said means for processing a live image signal and said means for processing a reference image signal, for correlating said polarity bits of said reference and said live image signals to find a peak correlation, said means for correlating disregarding the mask bits; and means connected to both said means for processing, for automatically adjusting said image threshold range to maximize said peak correlation and for identifying the magnitude of said image threshold range associated with said peak correlation, wherein the means for adjusting the image threshold range adjusts the image threshold range depending on a predetermined relationship between the peak correlation and the threshold range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A process of correlating two input signals associated with a live image and a reference image, comprising the steps of:
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defining the live image as a set of pixels, wherein each live image pixel has an intensity representation; defining the reference image as a set of pixels, wherein each reference image pixel has an intensity representation; defining an image threshold range; establishing a reference image signal from the reference image, said reference image signal including reference polarity bits for those pixels having an intensity outside of the threshold range and mask bits for those pixels having an intensity within the threshold range; establishing a live image signal from the live image, said live image signal including live image polarity bits for those pixels having an intensity outside of the threshold range and mask bits for those pixels having an intensity within the threshold range; correlating said polarity bits of said reference image signal and said polarity bits of said live image signal to establish a peak correlation, said step of correlating disregarding the mask bits; adjusting said image threshold range to maximize said peak correlation depending on a predetermined relationship between the peak correlation and the threshold range; and
,identifying the magnitude of said image threshold range associated with said maximized peak correlation. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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Specification