Computer-Controlled Laser Beams In Object Dimension Measurements

This paper describes some general features of a computer-controlled laser system for noncontact measurements of dimensions of objects. The laser beams are scanned over the object and a system of detectors mounted behind the object detects whether the beams are shadowed by the object or not. The detector signals are converted to digital values and transferred to a minicomputer, where they are processed. This may require special software to allow the dimensional data to be presented in real time. An ex-perimental system with a HeNe laser and controlled by an HP 21MX minicomputer has been built and tested. At a rate of 100 measurements per second the systematic error is in the order of 1 mm for absolute measurements and 0.1 mm for relative measurements. The imprecision is about 0.1 mm for both cases.