TIMING DISCRIMINATOR FOR PULSED TIME-OF-FLIGHT LASER RANGEFINDING MEASUREMENTS

A time-pickoff circuit based on the constant fraction discriminator (C FD) timing principle has been developed for pulsed time-of-fight laser rangefinding with pulse lengths of 5-10 ns. It is based on detection of the crossing point of the trailing edge of the original timing puls e and the leading edge of its delayed replica with a fast emitter coup led logic comparator. A simplified theory is presented here for its wa lk error. Three types of comparator were tested in the CFD. It is show n that the dominant source of walk error is that produced by the limit ed gain-bandwidth product of the comparator and that walk error can be reduced to +/-1 mm in a 1:10 dynamic range of input pulses by adding an external offset voltage between the input nodes of the comparator. (C) 1998 American Institute of Physics.