The high accuracy time interval measurement is a key technique to pulsed laser ranging. Therefore

a new high precision time interval measurement method is proposed. Field-Programmable Gate Arrays (FPGA) is used to implement the multi-level time interval measurement. The coarse time measurement is realized by the coarse counter to guarantee large dynamic range. The PLL unit in an FPGA is used to generate the N clock pulses with the same frequency and uniform distribution phase as counting clock. Based on the equal precision frequency measuring

the resolution of the time conversion is improved to Tclk/N. A chain of the latch flip-flops is used to measure the fine time interval. The problem of the traditional multi-phase sampling approach that the phase shift resolution is decreased as the increased frequency is solved. The fine resolution can be achieved with limited delay lines while no need to increase the counting clock. The test results show that the proposed method can realize wide dynamic range

small conversion time and high resolution.