Abstract

A narrow collimated light beam, such as a laser beam, is directed towards a mirror which is rotated to effect rotary planar scanning or sweeping of a lens constructed to convert the rotary scanning beam into a parallel scanning beam. An article to be measured is positioned in the path of the parallel scanning beam at generally the focal point of the lens, and interruptions of the parallel scanning beam, as produced by the article, are sensed by a photodetector. The photodetector controls transmission of pulses or signals to means for counting pulses produced by a high frequency generator so that the counted pulses correspond to the dimension of the article at the plane of the parallel scanning beam. In this invention a lens is positioned in the path of the light beam and changes a narrow substantially round light beam into an elongate or substantially flat light beam which is scanned across an object for measurement thereof. The greatest dimension of the light beam is substantially normal to the direction of scan movement. Thus, if there should be irregularities or small particles of foreign material upon the surface of the object or adjacent thereto, the entire light beam is not completely interrupted by such particles or by such irregularities. Thus, a light beam is received by the photodetector in accordance with the average dimension or contour of the object at the measured portion thereof. Thus, the dimension of the object is measured without consideration of small irregularities or small or minute particles of foreign material or the like which may be present upon or adjacent the object at the measured portion thereof.