Absolute distance determination by coherent detection using a frequency-modulated laser diode

Abstract

An interferometric device for measuring absolute distance is described. A frequency-modulated laser diode is used as the light source. At the output of a Michelson interferometer a beat signal is detected-a process which may be recognized as coherent detection. The optical path difference is determined by numerical phase analysis. Experimental results are presented. The feasability of measuring absolute distance is shown with a submilimeter resolution over a two meter dynamic range.