Novel time-of-flight (Tof) measurement, calibration, and errorcorrection methods for tof based lidars

Light detection and ranging (LiDAR) is an art of precise measurements of the time-of-flight (TOF) of light pulses, where even a 1-nanosecond error corresponds to 15 cm distance error, and 1 cm distance resolution requires 66 ps resolution approaching the state of art time measurement performance. In this thesis, firstly, a tapped delay line (TDL) based field programmable gate array (FPGA) time-to-digital converter (TDC) with 18 ps resolution and 35 ps single shot precision is developed. A wide dynamic range measurement from 10 ns to 1 ms is achieved without losing a notable precision with a worst value of 54 ps using only a low-cost FPGA board, and without using external complex circuitry. In addition, an online calibration method based on dynamic phase shifting (DPS) with 18 ps resolution, which is the best in the literature, is demonstrated. Since the TDL based FPGA TDCs are vulnerable to temperature variations, experiments are carried out to observe its performance from -30 °C to 105 °C, which is beyond the ranges commonly addressed. Then, a novel, low cost and low complexity FPGA based time-to-amplitude converter (TAC) is developed achieving a phase detection resolution better than 18 ps. In addition, temperature tests are performed in a wide range of temperature from 3 °C to 93 °C, and only 32 ps measurement deviation is observed. The presented FPGA TDC, and the novel FPGA based TAC are improved to compensate for the walk error. The improved FPGA TDC decreased a large walk error of 47 cm to 3 cm while the improved TAC decreased 42 cm walk error to 2 cm. A new FPGA TDC method with 32 channels is demonstrated based on DPS and high-speed counters achieving the performance of the state-of-the-art TDL based FPGA TDCs by reaching a 14.9 ps resolution and 13-16 ps precision with a resource utilization of only 10% of the low resources TDL based FPGA TDCs. A complete hardware to develop a single channel and 16-channel LiDAR is designed. While walk error compensation in the literature is typically demonstrated for a single channel using commercial TDCs or ASICs, this thesis presents compensation across all 16 channels using FPGA-based TDCs. Distance measurements on all 16 channels yielded maximum errors of 4.1 cm with and 43.6 cm without walk error compensation, confirming the method's effectiveness.