Abstract
FMCW (Frequency Modulated Continuous Wave) method has been used for long distance measurement. However, nonlinearity of optical frequency sweep of LD (Laser Diode) degrades the measurement accuracy. In this paper, first, the influence of nonlinearity of optical frequency sweep in distance measurement is defined by formulation. Second, the nonlinear sweep behavior is analyzed by using Hilbert transformation and the nonlinearity is reduced by making the LD current sweep nonlinear. The resultant performance of distance measurement is evaluated by comparing with a laser interferometer. The experimental result shows that it is possible to measure 1.8m distance with smaller than 10μm accuracy.
