Electronic systems for distance ranging (measuring distance) include SONAR (SOund Navigation And Ranging), RADAR (RAdio Direction And Ranging) and LIDAR (LIght Detection And Ranging). Basically, these systems all use the same general principles to determine the distance to an object (the target). They all consist of an energy source and a method of detecting the reflected signal and examining it to determine various things about that object. One of the most common of these applications is determining the distance, or range, to a target.
This document describes a circuit for measuring the distance between vehicles using LIDAR. The vehicles may be moving or stationary. It is also possible to use the rate of change of distance to determine rate of closure. Adaptive speed control uses rate of closure and distance to determine whether the vehicular speed should be reduced.