A Triple Compensation Method for Correcting Temperature-Induced Distance Errors in SPAD-Based d-ToF LiDAR

This paper proposes a Triple Compensation Method to systematically eliminate thermal degradation and distance measurement errors induced by temperature variations in SPAD (Single-Photon Avalanche Diode)-based direct Time-of-Flight (d-ToF) LiDAR sensors. As temperature rises, the combined effects of reduced emission efficiency in the transmitter’s Laser Diode (LD) and an increase in the breakdown voltage (VBD) of the receiver’s SPAD element result in decreased peak intensity and pulse width distortion. These factors directly cause rising-edge timing distortions, introducing significant walk errors and thermal distance drift. The proposed triple compensation scheme comprises three distinct stages: 1. Track 1 (Dynamic Gain Control): Real-time monitoring of junction temperature dynamically adjusts the bias voltage (VBias) to maintain constant excess voltage (VEx), mitigating degradations in Photon Detection Efficiency (PDE) and gain. 2. Track 2 (Walk Error Compensation): Residual non-linear walk errors are corrected by real-time tracking of peak intensity using an empirically derived look-up table (LUT). 3. Track 3 (Unit-Specific LUT Compensation): Circuit delay drifts caused by manufacturing process variations are compensated by applying a unit-specific calibration curve, derived via 3-sigma filtering and second-order polynomial fitting (R2 = 0.991), stored in non-volatile memory (NVM). Experimental validation across a temperature range of −20 °C to 60 °C demonstrates that the proposed triple compensation reduces the peak-to-peak distance error from 1.11 m to 0.16 m (an 85.6% reduction) and decreases the standard deviation from 0.30 m to 0.035 m (an 88.3% reduction), achieving an 8.57-fold improvement in precision. This approach offers a highly practical and scalable solution for high-precision LiDAR operation without requiring costly physical cooling hardware.