Aiming at the problem of mismatching of the extreme points in extremum method for digital speckle images, a new algorithm named the whole pixel extremum displacement measurement for laser speckle images with multi-level crossing was proposed. The extremum method was used to figure out the extreme points of speckle images before and after displacement, constructed extremum value matrix and generated 3-D figure. Then the truncation points were got by multiple specified gray planes crossing 3-D figure. And relative displacement matrix of truncation points was analyzed to calculate displacement of object. The simulation results under the condition of no noise and noise prove that the improved algorithm under guaranteeing the accuracy of displacement measurement, decreases the number of extreme points of error matching and improves operation efficiency 103 times. The algorithm was applied to the laser mouse positioning and the experimental results show that the displacement of the mobile resolution reached 1 microns, and moving direction angle error was less than 2.72°. It is conclued proves that multi-level truncation extremum displacement method based on laser speckle image is a rapid, efficient and practical algorithm.
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2015, Vol. 35 
