<title>Correction of cyclic error in optical waveguide distance meter</title>

Abstract

Sinusoidal modulation method is utilized in optical distance meters. In this method, the phase delay of the returned beam is measured with high resolution. One of the dominant error factors in the phase measurement is cyclic error. We have already reported on a cyclic error compensation of an optical waveguide distance meter using a preliminary phase measurement with mechanical displacement. In this paper, a new technique of the cyclic error compensation is described, which is based on the modulation frequency scanning of the waveguide distance meter around 14 GHz. We have compared two types of cyclic error curves; one was obtained from the data during the displacement of the target and the other was obtained from the data during the scanning of the modulation frequency. The curve fitting technique was used to determine the amplitude and the phase of the cyclic error component for the two curves. We have obtained almost the same values for both parameters of the amplitude and the phase for the two cyclic error curves. Therefore, the cyclic error curve obtained from the data of frequency scanning can be utilized for the cyclic error compensation instead of the displacement of the target.