Verfahren zur Messung der Relativgeschwindigkeit einer Messvorrichtung parallel zu einer messtechnisch erfassbare Unregelmässigkeiten aufweisenden Fläche

An apparatus for a moving body and a method for measuring the velocity of that body over a surface arranged parallel thereto and which has local irregular features therein wherein two areas of the surface directly therebeneath are illuminated during movement of the body and optical reflection of the surface areas is received by two photo-electric converters, which are spaced from one another on the moving body and in the direction of motion of the moving body, and which produce two similar electrical signal sequences of the character of noise,but time delayed one with respect to the other. Both signals are sampled, the samples obtained from the leading surface area in the direction of motion is delayed by a controllable amount and thereafter multiplied by the samples obtained from the other surface area. A mean time value is produced from the result of this multiplication and the delay is regulated in such a manner that the delayed and the other signal coincide in time, and the velocity is ascertained as the quotient from the spacing of the two areas and the regulated delay.