Patent ID: 6917415

Claim:
A method of electro-optical distance measurement, comprising the steps of: directing a laser beam onto an object to be measured; detecting a measurement beam reflected therefrom with a light detector; and determining a distance to be measured by measuring a light propagation time, wherein said laser beam is directed onto said object to be measured as an intensity modulated train of emitted light pulses, and a light component reflected or scattered from said object to be measured as a measurement light pulse train is detected by said light detector which generates, in response to said detection, a first photocurrent component, wherein a small portion of said intensity modulated train of emitted light pulses is branched out as a reference light pulse train that, after passing a known reference path, is detected by said light detector that generates, in response to said detection, a second photocurrent component, wherein said distance is determined by a propagation time difference between a propagation time of said reference light pulse train passing through said known reference path and a propagation time of said measurement light pulse train passing twice said distance—to be measured, and wherein said reference light pulse train and said measurement light pulse train are each subject to a signal mixing employing a mixing pulse train whose repetition frequency deviates slightly from a repetition frequency of said intensity modulated train of emitted light pulses, such that said reference light pulse train and said measurement light pulse train are converted into an intermediate frequency region having stretched time scales.