Various radar systems have been proposed as collision avoidance sensors for automatic braking and warning applications. Practical use of laser radar systems is near with the introduction of high power, high reliability laser diodes.

Utilizing these new devices, a laser radar system has been adapted for measuring the distance to objects in its path. It was first shown that reflectors on the rear of the automobile possess high reflectivity and sharp directivity. Given these characteristics, a compact laser radar system was tested that employed 12W laser diodes and PIN photodiodes.

The maximum range of approximately 100 m was obtained. Furthermore, the ability to discriminate other vehicles from roadside objects was achieved by detecting discontinuity in measured distance data through a microprocessor. These results show that the performance of laser radar is comparable to that of microwave radar. Considering the cost and size of the radar systems, laser radar would appear to be the more practical of the two.