Miniaturized Scanning Laser Radar for Automotive Applications

Abstract

In the frame of an ESPRIT project called OLMO, CSEM has developed an innovative pre-industrial scanning range sensor based on laser radar techniques. OLMO is the acronym for “On-vehicle Laser Microsystem for Obstacle detection”, and the project was carried out in collaboration with Fiat Research Center (I), Magneti Marelli (I), Renault (F), CEA-LETI (F) and Jenoptik (D). Major results of this project are presented as well as further developments.

The key-features of the system are high compactness (less than a packet of cigarettes), low cost and high performance in adverse visibility. The system is based on the measurement of light time-of-flight by the means of an innovative signal processing algorithm and on a resonant, frictionless mechanical structure providing a sinusoidal horizontal scanning both of the emitted laser beam and of the detection optics. The signal processing technique, called Random-Modulation time-of-flight (RM-TOF), is inspired by the spread-spectrum techniques used in the field of telecom and GPS, and exploits the auto-correlation characteristic of pseudo-random sequences. Major advantages of this technique are robustness and the possibility of using a commercially available low power laser diode source (20 mW), thus reducing the costs. The scanning mechanical structure, which was inspired by mechanisms used in aerospace applications, consists of a resonant structure based on a Flextec pivot element composed of two cross-flexure elastic structures obtained by layering. Flexure structures are frictionless components in which kinematic joints are materialized by elastic thin beams. Major advantages of this concept are very high compactness, very long lifetime, low cost and low power consumption.