Optical EngineeringLow-cost laser rangefinder with crystal-controlled accuracy
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We present a novel laser ranging system that offers improved accuracy and low-cost implementations for short to medium range target distance and velocity measurement. This is accomplished through the emission of an eye-safe amplitude modulated laser beam, whose echo return is processed with a phase-computing discrete Fourier transform (DFT). The data for the DFT are collected directly from the received signal through equivalent time sampling, and the automatic gain control (AGC) function is moved to that part of the system where its varying signal propagation time will not impact measurement accuracy. All emission and data collection signals are derived directly from a single crystal oscillator, which establishes the system's accuracy. The system is also capable of resolving the distance/velocity ambiguity problem inherent in conventional hetero/homodyne laser ranging systems, and, lastly, digital data can be transmitted and received concurrently with the distance measurement process.