Light scanner with interlaced camera fields and parallel light beams

The object to be scanned is moved laterally through the scanner past a number of laser light sources and a number of photo-detector cameras spaced along the object. The coherent laser light beams are parallel to each other and to the lens axis centreline of the cameras for easier alignment and to prevent the laser light spot on the object from moving relative to such axis centreline for objects of different thickness. The cameras have a photo-detector target which may be a linear diode array CCD semiconductor device for producing scan data signals in response to reflected light beams which are processed by a computer system giving preference to the data produced by the beams in the outer portions of the camera viewing field to determine the thickness of the object at points spaced along the object.