A phase-shift laser scanner based on a time-counting method for high linearity performance

Abstract

In the phase-shift measurement method, the distance light travels can be obtained via the phase difference between the reference and the measured signals. In this paper, a multiple-step phase demodulation method with time counting is proposed for measuring the phase difference, with resulting robustness against electric noise. When the phase differences are close to 2n pi (n = 0, 1, 2, ...), 2 pi ambiguity problems commonly occur; here, a time-counting method using a 180 degrees-shifted reference signal is proposed in order to resolve this problem. (C) 2011 American Institute of Physics. [doi:10.1063/1.3600456]