Patent ID: 8270678
Filing Date: 2012-09-18
Classification: G06K,G06T

Abstract:
1. A computer implemented method to detect displacement of objects from a long range, the computer implemented method comprising the steps of: determining a cross-correlation between at least a portion of a first numerical function and a second numerical function by shifting a pixel at a time the portion of the first numerical function over the second numerical function to thereby determine the cross-correlation as a cross-correlation numerical value, the first numerical function derived from a first image of an identifier located on an object to be tracked when located at a first position, the second numerical function derived from a second image of the identifier located on the object to be tracked when located at a second position, the second image taken at a time temporally later than a time for the first image, the first image and the second image obtained by an optical device, the cross-correlation numerical value determined between the first image and the second image at a pixel produced by the optical device; repeating the step of determining the cross-correlation between the portion of the first numerical function and the second numerical function by shifting the portion of the first numerical function over the second numerical function by a pixel offset to thereby generate a plurality of cross correlation numerical values where each cross-correlation numerical value corresponds to a distinct pixel; comparing the plurality of cross-correlation numerical values to thereby determine a relative pixel location at which a peak cross-correlation value occurs; fitting a curve through the peak cross-correlation value by selecting two cross-correlation values adjacent and to either side of the peak cross-correlation value to refine the determined relative pixel location; determining a number of pixels the portion of the first numerical function moved that resulted in the peak cross-correlation value with the second numerical function, the peak cross-correlation corresponding to the refined relative pixel location; and determining a displacement of the object to be tracked by dividing the number of pixels that the portion of the first numerical function moved by a pixel per measurement unit, the displacement being perpendicular to a line of sight with respect to the optical device.