METHOD AND APPARATUS FOR SIGNAL PROCESSING IN A LASER RADAR RECEIVER

An apparatus for receiving signals from a photodetector in a photodetector array. The apparatus has a number of comparators (e.g. 5) connected to the photodetector. each photodetector in the array has a similar circuit connected. Each comparator compares the output of the photodetector with an adjustable threshold level. Each threshold level is controlled by a threshold controller. Each threshold level corresponds with a light intensity value. Outputs of the comparators are each connected to a shift register. Each shift register is triggered to sample the output of its associated comparator at a certain speed (e.g. 800 Mhz). In operation, the shift registers each store a bit sequence representative of the comparator output. The data acquired is used to adjust the threshold levels applied to the comparators. In this way, adjustable intensity resolution is provided at desired ranges of intensity. The present invention includes a method for combining data from multiple laser pulses and fitting the data to a best fit statistical distribution so that an intensity value is obtained for each voxel in a 3-D laser radar image. Also, the present invention includes embodiments where different photodetectors in the array have different set threshold levels.