Walk Error Compensation of ToF LiDAR using Zero Crossing Discriminator with Auto Gain Control Amplifier

This paper proposes a walk error compensation method based on AGC (Auto Gain Control) amplifier and ZCD (Zero Crossing Discriminator). A walk error, often referred to as a time walk, is one of the errors that occurs in the distance measurement results of ToF LiDAR. Consistent thresholds cannot be used because the amplitude of the received signal varies depending on the distance from the target object or the optical characteristics such as the light reflectance of the target surface and the angle of incidence. This amplitude change creates an error at the time when the signal is recognized as an active signal. In this paper, to compensate for walk error, peak timing was detected by measuring peak amplitude of the input signal, calculating a suitable gain, and differentiating a variably amplified signal. The results were confirmed through simulation and actual experiment. In the range of APD output signal peak amplitude 1 uA to 40 uA, the standard deviation of walk error was reduced to about 4.2% compared to conventional leading edge discriminator methods, and the standard deviation was reduced to about 65% compared to ZCD without AGC amplifier.