Reflector difference electro-optical measurement - reducing difference of propagation times from max. likelihood estimate of reflected and time-shifted signals

摘要

The computer (1) generates a pseudo-random binary sequence of pulses, whose min. width is given by the reciprocal of the chip frequency, for conversion (2) to analogue form for modulation of an optical transmitter (3). The reflections from both objects (M1,M2) are detected (7), digitised (8) and stored (10). The computer (1) performs its approximation by summing time-shifted versions of the signal corresp. to reflection from a single object in order to obtain the propagation times of the pulses. ADVANTAGE - Precise and unambiguous measurements are achievable even when transmitted pulse sequence has large subsidiary correlation peaks.