MAGNIFICATION OF PHASE-SHIFT FOR A LASER RANGEFINDER - INTRINSIC RESOLUTION AND IMPROVED CIRCUIT

A phase-shift expander has been designed for distance measurements wit h a low-frequency phase-shift laser rangefinder using two coherent ind irect frequency synthesizers. Using such a set-up, a theoretical analy sis shows that the resolution of the phase-shift measurements can be i mproved. The main error source due to the output voltage, which is a f requency-modulated signal, is then analysed. Other error sources, such as the output frequency stability and the cross talk between the two channels, are evaluated. The intrinsic resolution is estimated as a fu nction of the frequency drift of oscillators and an improved circuit i s proposed. Experimental results are presented for a 16 and 32 expansi on factor of the phase shift.