| 摘要 |
<p>A distance-measuring system (10) includes a light source (14) and modulator (18) for transmitting a modulated beam of light to a target, thereby generating a received beam. A calibration unit (40) periodically calibrates the system by positioning a calibration target (42) between the light source and the target so that the transmitted beam is interrupted, thereby generating a received calibration beam. A target sensor (30) receives the reflected target and provides a target signal (32) indicative of the reflected target beam. A reference sensor (36) receives light from the light source (14) and provides a reference signal (38) to processing circuitry (34). The processing circuitry receives the target signal (32) and the reference signal (38), adjusts the frequency of the transmitted beam until a zero phase difference exists between the target signal (32) and the reference signal (38), and calculates the distance to the target based upon frequency which produces a zero phase difference.</p> |
