Research on absolute measurement of reflectance at small angles near LiDAR reflection conditions

Accurate traceability of LiDAR(Light Detection and Ranging) is still a difficult issue in the autonomous driving industry, as it serves as crucial 'eyes' for perception. To address this issue, a device was developed for absolute measurement of reflectance at small angles near θ/θ reflection condition of LiDAR. Through the fine design of the small angle optical path, the problem of mutual occlusion between the light source and the detector due to the actual size under this condition was optimized, the accurate value of the incident and reflected radiant flux were obtained, and the absolute measurements of the reflectance with the minimum angle better than 0.1°/-0.1° were realized. To verify the accuracy and reliability of the device, one 1 -inch diameter UV-enhanced aluminum film plane mirror and one 1-inch diameter silver film plane mirror were used. Absolute reflectance measurements were conducted at light source wavelengths of 532nm and 905nm, with reflection angles of 12°/-12°and 45°/-45°. The measured results were then compared with their calibrated values, achieving an optimal relative deviation of 0.4%, thereby providing preliminary validation of the device's measurement accuracy and reliability. Meanwhile, the light source and detection part of this device are planned to be extended to 1550 nm, providing better support for LiDAR reflection traceability in the autonomous driving industry.