Potential use of near, mid and far infrared laser diodes in automotive LIDAR applications

Laser infrared detection and ranging (LIDAR) may be used in on-board automotive applications for monitoring the distance to objects approaching the host vehicle and their relative velocities. The low total cost of equipping cars with LIDAR systems has motivated their development for the automotive market. We conducted an experimental study to assess the ability to detect painted car body panels and various reflectors with 850, 910, 1560, 5600 and 8100 nm LIDAR transceivers. Specular reflection from such targets was high at all wavelengths. However at 5.6 and 8.1 /spl mu/m, diffuse reflection was not detectable at meaningful distances due to (1) the high absorption of the clear paint coating of body panels and the plastic material used for making reflectors, and (2) the low detectivity achievable at such wavelengths. At 850 to 1560 nm, these targets behaved as in the visible range of the spectrum with high returns from reflectors and much weaker diffuse returns from painted panels. Nonetheless, the weak diffuse reflections were readily detectable at 850 to 1560 nm. As concern with eye safety favors wavelengths above 1.4 /spl mu/m, a 1.6 /spl mu/m LIDAR wavelength is suggested as optimum.