Patent ID: 6188480
Filing Date: 2001-02-13
Classification: G01B

Abstract:
A method for interferometrically measuring a position of a part, a position change of the part and a physical quantity of the part, the physical quantity being derived from the position and the position change, the part being tested using a heterodyne interferometry procedure, the method comprising the steps of:with a time-variable pulsating injection current, modulating a laser to change a frequency of a radiation which is emitted by the part for generating a heterodyne frequency;routing a first portion of the emitted radiation via an optical bypass to the part;routing a second portion of the emitted radiation without the optical bypass to the part;routing the second portion from the part to a measuring receiver, wherein a shape of a signal of the injection current has a rising edge, the edge being steeper as compared to a pulse length and a subsequent plateau of the signal;converting the signal in a photoelectric transducer of the measuring receiver; andevaluating the converted signal only after a predetermined time period following an occurrence of the edge of the injection current during the subsequent plateau of the signal.