Patent ID: 6633367
Filing Date: 2003-10-14
Classification: G01C,G01S

Abstract:
A method for optoelectronic measuring the distance of a measurement object from an observation point, comprising the steps of:directing a main light beam intensity-modulated with a first modulation frequency and emitted by a main light emitter to a measurement object at a distance; receiving scattered light at the observation point at a main photoreceiver via reception optics, simultaneously directing a branched part of the main light beam to a reference photoreceiver via a first known reference distance (D1); simultaneously receiving at the reference photoreceiver via a second known reference distance (D2) a reference light beam intensity-modulated with a second modulation frequency different from said first modulation frequency and emitted by a reference light emitter; receiving part of the reference light beam at the main photoreceiver via a third reference distance (D3); subjecting the signals delivered by the main photoreceiver and the reference photoreceiver to a comparative signal evaluation for obtaining a corrected measurement signal converting signal mixtures supplied by the main photoreceiver and the reference photoreceiver to an intermediate frequency range containing two frequency components, wherein each of the signal mixtures contains a signal component with an intensity modulation frequency of the main light emitter and a signal component with an intensity modulation frequency of the reference photoreceiver and wherein one frequency component is formed by the signal of the reference light emitter and the other frequency component is formed by the signal of the main light emitter; basing separation of phase information contained in two simultaneously occurring intermediate frequency signals on different frequencies in the intermediate frequency range and the different modulation frequencies for the intensity modulation of the main light beam and reference light beam, for purposes of comparative signal evaluation; successively carrying out a plurality of measurement processes to achieve a definite distance measurement and to improve measurement results; exchanging the first and the second modulation frequencies for the intensity modulation of said main light beam one against the other, and equally changing the modulation frequencies for said two light beams according to a set pattern.