Method and circuit arrangement for frequency-, distance-, and angle-independent surface measurement

US4643517A · kind A · utility

Assignee

• ELTRO GmbH · DE

Inventors

• James Ruger · Hoffenheim, DE
• Manfred Strauss · Heidelberg, DE
• Wolfgang Welz · Bammental, DE

Key dates

• Filing date: Apr 19, 1985
• Grant date: Feb 17, 1987
• Expiry date: Apr 19, 2005

Classification

• Technology area (CPC G): Physics
• CPC primary: G01C11/025
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A method and circuit arrangement for performing surface measurements to enable a beam source to be triggered such that changes in the oscillation frequency, maximum scanning angle, and distance from the measurement surface of the scanner are automatically compensated for. In one embodiment an alternating voltage proportional to the lateral displacement of the impinging beam from a reference point is generated and then compared with a stepped reference voltage. A trigger signal is produced when the alternating voltage equals the reference voltage, so that the beam impinges at equidistant intervals. The reference voltage is adjusted to compensate for changes in distance and maximum scanning angle. In another embodiment, a pulse sequence is generated such that the number of pulses occurring in the scanning cycle is constant. The pulses are counted and the count is compared with reference values corresponding to equiangular intervals. A trigger signal is output if the count equals the reference value.