Method for detecting velocity or displacement of an object over a surface by analyzing images of the surface
First Claim
1. A method for detecting relative displacement between an object and an illuminated surface comprising:
- providing an array of detecting elements each arranged to receive light from a portion of a field of view and to provide an output responsive thereto;
locating the array adjacent the surface during said displacement such that the field of view is moved across the surface by the displacement;
repeatedly acquiring the output signals of the detecting elements to generate a plurality of sequential signals each corresponding to a respective image of the surface with each successive image being displaced from the previous image by a distance proportional to an amount of said displacement;
selecting one of the sequential signals as a reference signal;
processing the sequential signals to effect a comparison of said reference signal with at least two subsequent sequential signals to generate for each subsequent sequential signal a value indicative of displacement between the image corresponding to the reference signal and the subsequent images corresponding to said at least two subsequent sequential signals;
and analyzing the values to determine a final value indicative of the displacement.
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Accused Products
Abstract
There is described a method for detecting relative displacement between an object such as a slow moving vehicle and an illuminated surface which is normally the ground surface illuminated by an infrared light source so as to provide an output indicating the displacement or a velocity calculated from the displacement. The method includes providing an array of CCD or similar elements each arranged to receive light from a portion of a field of view and to provide an output responsive thereto. The method involves selection of a reference image and repeatedly comparing the reference image of the surface with each successive image by calculating the convolution integral of the signals using a fast fourier transform to obtain a probable displacement value. The reference image is maintained as long as possible until a “Q” factor falls below an acceptable minimum, or until a predetermined time elapses or until a predetermined displacement is measured. The displacement values obtained from the comparisons can be filtered by discarding some values if they are outside an expected range of probable values.
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Citations
18 Claims
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1. A method for detecting relative displacement between an object and an illuminated surface comprising:
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providing an array of detecting elements each arranged to receive light from a portion of a field of view and to provide an output responsive thereto;
locating the array adjacent the surface during said displacement such that the field of view is moved across the surface by the displacement;
repeatedly acquiring the output signals of the detecting elements to generate a plurality of sequential signals each corresponding to a respective image of the surface with each successive image being displaced from the previous image by a distance proportional to an amount of said displacement;
selecting one of the sequential signals as a reference signal;
processing the sequential signals to effect a comparison of said reference signal with at least two subsequent sequential signals to generate for each subsequent sequential signal a value indicative of displacement between the image corresponding to the reference signal and the subsequent images corresponding to said at least two subsequent sequential signals;
and analyzing the values to determine a final value indicative of the displacement. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification