在脉冲激光测距系统中,设计实现了基于FPGA和TDC-GP21的高速精密时间间隔测量系统.采用TDC-GP21的高精度测量模式,配置TDC-GP21完成了时间间隔测量,通过校准测量对测量结果进行补偿修正,提高了系统的测量精度;设计了多级嵌套状态机实现高速SPI通信,减小了系统单次测量周期;分析了影响测量精度的因素,比较分析了3种时刻鉴别方法的漂移误差,设计了高通阻容时刻鉴别模块,减小了系统的非线性误差.实验分别进行了基于FPGA脉冲信号的时间间隔测量和激光测距试验,对比验证了系统的测量误差,分析了系统在测量区间的线性度.实验结果表明,系统可以实现高速稳定测量,线性度良好,重复测量频率达1 kHz,测量精度在±100 ps内.

A high speed and high precision time-interval measurement system based on FPGA and TDC-GP21 was introduced in this paper.The high precision module of TDC-GP21 was used and by configuring TDC-GP21,the time-interval measurement and calibration are finished to improve the precision,and a multi-level FSM were designed to realize the SPI communication and reduce the measurement period.According to the analysis of the factors which affected the precision of measure and the drift error of three discriminators,a discriminator was designed to reduce the nonlinearity error of the system.The signal of FPGA and the signal of laser echo were also used to realize time-interval measurement and laser ranging.The experiment results showed that the good linearity and the measurement repetition rate of 1 kHz and the measuring precision of ±100 ps can be achieved.