Multicycle synchronous digital phase measurement used to further improve phase-shift laser range finding

Multicycle synchronous digital phase measurement is proposed in this paper to further improve the phase measurement in phase-shift laser range finding. In the method, heterodyne processing is employed to convert the phase measurement of a high frequency signal into that of a low frequency signal, and by keeping phase measurement independent of the signal frequency to be measured and the gate signal synchronous with the measurement signal during multicycle phase measurement, errors caused by the frequency drift of a local oscillator during conventional auto-digital phase measurement are totally eliminated, and the time required to complete range measurement is shortened. Experimental results show that an uncertainty better than ?1.5 mm can be achieved at a data rate up to 20 Hz (t = 0.05 s) for a laser range finder using the method proposed with fe = 10.000 MHz.

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