Abstract: A distance-measuring system includes a light source for transmitting a beam of light to a target, thereby generating a received beam. A calibration unit periodically calibrates the system by positioning a calibration target between the light source and the target so that the transmitted beam is interrupted, thereby generating a received calibration beam. The calibration unit also generates a calibration signal which is indicative of when the calibration target is generating the received calibration beam. A target sensor receives the reflected target and calibration beams and provides a target signal indicative of the reflected target and calibration beams. A reference sensor receives light from the light source and provides a reference signal to the processing circuitry. Processing circuitry receives the calibration, target, and reference signals and calculates the distance to the target based upon the target and reference signals and/or calibrates the system based upon the calibration signal.