Abstract: The apparatus disclosed includes at least two optical measuring devices for forming independent images of the object in their respective focal planes. From these images a specific dimension of the object, for example its diameter where a circular object is concerned, may be obtained. To correct for inaccuracies due to product movement, the dimension of the product obtained from one of the measuring devices is compensated by a positional measurement obtained from the other camera and vice versa. By this means accurate determination of the size of a product, for example a cable moving in an extrusion run, is possible without contact being necessary within the product.

Abstract: A glass plate thickness measuring instrument wherein a beam of radiation is impinged on the glass to provide a pair of beams reflected from the front and back surfaces of the glass plate respectively. The two beams are made to fall on a radiation responsive device in the form of a charge coupled device, which provides pulsed image outputs of the beams in the form of staircase waveforms of a truncated Gaussian distribution. Electronic circuity, including a microprocessor, is employed to calculate the center of gravity of an area under both waveforms above a threshold value, and the distance between the respective centers of gravity calculated to provide a measure of the thickness of the material.