Patent ID: 6744049
Filing Date: 2004-06-01
Classification: H04N

Abstract:
A method of operating a pyroelectric array comprising a two dimensional array of detector elements onto which the image of a scene is focused by optical means, whereby events within the scene cause temperature changes at the detector elements to produce electrical signals, wherein during normal operation the image is stationary with respect to the array, the array is operated to detect dynamic events and only events within the scene cause the elements to produce electrical signals, and wherein during a reference mode the image of the scene is displaced with respect to the array to generate a set of detector element signals corresponding to a reference image indicating the position of static objects in the scene, a further set of detector element signals is generated by again displacing the image of the scene with respect to the array, and the further set of signals corresponding to a further image is compared to the set of signals corresponding to the reference image whereby to determine whether an object has moved during the time between the acguisition of the two sets of signals.