A laser radar based on a “impulse-like” laser diode transmitter and a 2D SPAD/TDC receiver

Abstract

A pulsed TOF laser radar has been implemented and its performance characterized. The transmitter applies a QW double-heterostructure laser diode producing 0.6 nJ/ 100 ps laser pulses at the central wavelength of ~ 817 nm. The detector is a single-chip IC, manufactured in the standard 0.35 µm HV CMOS process, including a 9x9 SPAD array and a 10-channel TDC circuit. Both the SPAD array and the TDC circuit support a time gating feature allowing photon detection only to occur within a predefined time window. The SPAD array also supports the sub-array selection feature in order to respond to the laser spot wandering effect due to paraxial optics. A sub-array is a 3x3 SPAD array freely chosen within a 9x9 SPAD array. The characteristic measurement results demonstrate the measurement range of tens of meters with a linearity precision +/-0.5 mm to the 11% target reflectivity and at pulsing frequency of 100 kHz. The distance dependent detection rate varies from 28% to 500%, thus providing a high measurement rate. The single-shot precision is ~ 20 mm. The deteriorating impact of high-level background radiation conditions on the SNR has been demonstrated as well as a scheme to improve it by detector time gating.