Study of High Precision Measurement System in Pulsed Laser Ranging

To improve the accuracy of time interval measurement in pulsed laser ranging system, a method which combines clock counting and differential delay line based on Field Programmable Gate Array (FPGA) is used in time interval measurement. FPGA sets up two delay lines in its internal, one of them consists of several buffers; another consists of several D flip-flops. The time delay between them serves as the smallest unit of time interval measurement, which is the step length of measuring time interval within half a clock cycle. Compared with clock counting method, this method put time interval measurement accuracy up to ten times. The experiment results show that time interval of system measurement reach at +/- 300 ps, and 3 cm measuring distance precision is achieved, which means that the method can satisfy the requirements of high precision ranging.