Note: Continuous-Wave Time-Of-Flight Laser Scanner Using Two Laser Diodes To Avoid 2 Pi Ambiguity

In the continuous-wave time-of-flight method, the distance traveled by light can be obtained by using the phase difference between the reference signal and the measured signal. However, when the phase difference exceeds 2 pi, the distance cannot be differentiated because the distance variation repeats every 2 pi period. In this paper, we propose a method in which low- and high-frequency signals are separately applied to two laser diodes simultaneously, and processed using two different signal processing circuits to solve the 2 pi ambiguity problem and achieve a high distance resolution for a longer distance measurement. (C) 2013 AIP Publishing LLC.