Temperature calculation on retina irradiated by pulsed scanning LiDAR

In recent years, LiDARs as a type of vehicle sensors, have played a crucial role in the field of autonomous driving. LiDARs generally emit infrared pulsed laser and accomplish 3D reconstruction of the surrounding environment by detecting the received echo signal. LiDAR systems are often complex in architecture and scanning characteristics, which can be regarded as scanning pulsed laser source in normal operation, and their emitted laser pulses are separated temporally and spatially. As MPEs (Maximum Permissible Exposure) values in IEC 60825 standard are based on experimental threshold data from stationary laser source with certain pulse duration, there may be potential mismatch when applying the thresholds to scanning pulsed emission. For example, cooling may take into effect due to spatial pulses distribution. In this case, overly strict evaluation methods, which cannot reflect real biological damage mechanism for scanning systems, will be probably employed to limit emission level of the products, thus restricting their performance and even hindering the development of the industry in turn. The main problem is there is still a lack of experimental in-vivo data for scanning laser sources, experts in this area are calling for more research. Meanwhile, thermal simulation has been proved to be a reliable analysis method in previous studies, and it would be possible to conduct basic research to investigate damage mechanism for scanning pulsed laser. Therefore, in this paper, impacts of scanning parameters from LiDAR model, including beam divergence, beam repetitive pulse frequency, angular resolution, frame rate, on temperature rise and heat dissipation on the irradiated retina were discussed. The main goal of this work is to present basic findings and propose ideas to further investigate on retinal hazards of scanning pulsed emission using thermal simulation methods.