Optical device for measuring the speed or the length of a moving surface using a measurement light beam emanating from a laser

摘要

The invention relates to an optical device for measuring the speed or length of a moving surface, a measuring beam emanating from a laser being directed towards the surface and the Doppler-shifted scattered light reflected from the surface and any other light, for example non-Doppler-shifted laser light or another Doppler-shifted laser light being heterodyned for achieving a beat, the frequency of which forms a measure of the speed of the surface and is received in an evaluating system in the form of continuously incident digital signals and is evaluated, particularly counted in a counting system. The signals corresponding to the input frequency Fein are distributed in part-frequencies Fteil = Fein x 1/n by means of a frequency divider to a number of n synchronous counters, the n counts of which can be continuously evaluated by means of an adder as output frequency Faus = SIGMA Fteil1 to n, which corresponds to the input frequency Fein. IMAGE