Target-distance and intensity information detecting with high precision in laser imaging system

In order to enhance the precision of target distance and intensity information in pulse laser 3D imaging system, the time-discriminating circuit and peak holding circuit were studied in detail. Based on analyzing the laser distance-detecting method and the selection of detector, the principle diagram of pulse laser 3D imaging system was given. In this system, pulse from laser was sent to transflective prism, and the reflected light triggered reference APD. Output signal from the reference APD was selected as starting signal for timing to enhance timing basic. Constant threshold discriminator and constant fraction discriminator were combined to form the timing discriminator. In this method, high precision of timing discriminator could be achieved while eliminating the effect of noise to the circuit. The transconductance circuit based on OPA861 was selected to hold the peak signal. The APD signal simulating system was constructed in laboratory, and performance of those circuits were tested. At last, testing result was given. Result shows that the precision of time discriminating circuit is better than 1 ns and the precision of peak holding circuit is better than 2.63% when the peak value of narrow pulse signal is less than 800 mV. The result can satisfy the requirement of latter experiment.