Research Of Semiconductor Pulse Laser Ranging System

The measuring precision and range are two important parameters for judging theperformance of the pulsed-laser ranging system. In order to achieve the higher precisionand the wider range of measurement, we theoretically analyze the emission unit, thedetection unit and the time-interval measurement unit respectively. According to theanalysis, the laser emitting circuit and the echo receiving circuit are designed, and then,the simulation testing of the time-interval measurement system is accomplished.By employing the technique of high speed nonlinear MOSFET switch and powercompression, and combining with push-pull driving circuit for the grid of MOSFET, wedesign the special driving circuit for the LD. Experimental results show that the peakpower of the emission laser could be about30W and the full width at half maximum(FWHM) could be about20ns.With respect to the echo detection system, for receiving the weak light signaleffectively, we choose the PIN optoelectronic diode with high-sensitivity and rightspectrum matching as a detector; and the high performance operational amplifier as apre-amplifier. The optoelectronic detector is connected with the pre-amplifier by theway of mutual impedance connection. As a result, the echo light signal is converted intoelectric signal through the detector and the pre-amplifier. Measured results havedemonstrated that the optoelectronic receiving circuit can achieve a response to lightsignal at microwatt magnitude at least. During the remote measuring, the convertedelectric signal is too weak, so it needs to be amplified. However, because the noise canbe amplified simultaneously with the signal, so a filter circuit is designed. After filtering,the pure electric signal is converted into TTL high level which is served as the start-stoptrigger signal for the timer.As regard to time-interval measurement, it is difficult to obtain high frequency andexcellent stability of the timing clock. In order to resolve these problems, a noveltime-interval measurement method is proposed, which is based on the multi-cycleself-triggering time interval measurement technique combining with the digitalphase-shift interpolation method. Theoretical analysis and simulation testing haveshowed that high measurement precision of less than100ps can be obtained by usingthis novel method.