Patent US 4,201,476

A laser gauge to measure a dimension of a workpiece is disclosed wherein a laser beam is directed through a beam splitter to a rotating mirror at the focal point of a parabolic mirror. This rotating mirror causes the laser beam to scan the parabolic mirror and establish a series of parallel laser beams emanating from the parabolic mirror and directed toward the workpiece which may be a hot forged bar or other such workpiece in a hostile environment. First and second laser beam paths lie immediately adjacent opposite sides of the workpiece and are reflected back to the parabolic mirror along the same beam paths by a retroreflective surface. The laser beams are reflected by the parabolic mirror and rotating mirror to the beam splitter whereby they are reflected to a photodetector. A microprocessor is programmed to determine the dimension of the workpiece in accordance with the positions of the rotating mirror which establish the first and second beam paths. The foregoing abstract is merely a resume of one general application, is not a complete discussion of all principles of operation or applications, and is not to be construed as a limitation on the scope of the claimed subject matter.