Research On Techniques Related To Phase-shift Laser Range Finding

Laser range finding is chosen by virtue of its excellent performance in areassuch as aerospace technology, environment detection, precision manufacturing andso on. Phase-shift laser range finder becomes the preferred sensor in close range,high precision spatial position measurement, by virtue of merits such as highaccuracy, low power consumption, small volume, light weight and so on.On the background of phase-shift laser range finding, this thesis implements thesystem’s overall design scheme preliminarily. Aimed at key factors affectingranging accuracy such as phase difference measurement, temperature drift of thedetector and frequency source design, this subject begins research on improving thesystem’s accuracy of range finding.Firstly, choosing a proper phase discrimination method is the key to improvingthe accuracy of ranging. This thesis compares FFT and apFFT in phasediscrimination performance. Theoretical analysis and simulation experimentsindicate that FFT achieves higher accuracy than apFFT using the same length ofsampled data when system’s frequency deviation is small. Considering the actualsystem parameters, FFT is chosen as the phase discrimination method.Secondly, the multiplication factor of APD drifts with the change of temperature,which will result in ranging error. In order to restrict the influence of temperaturedrift, a bias voltage control circuit is designed according to the numericalrelationship between bias voltage of APD and temperature when APD’s gain isconstant. This circuit can automatically adjust the bias voltage of APD followingthe changing temperature in the range of-10oC~55oC with good linearity, thus themultiplication factor of APD remains constant during range measurement.At last, the design of the frequency source has an important influence on theranging accuracy. By comparing frequently-used frequency synthesis techniques,OCXO, DDS and PLL are chosen to implement the frequency synthesis circuitconsidering the system parameters. The fabrication of the circuit is completed.The research of this subject lays a foundation for the development ofphase-shift laser range finder, and also completed several design and fabricating tasks.