Optical and Mechanical Design of a Laser-Based Non-Intrusive Vehicle Delineation Detection System

Abstract

A field prototype of a laser-based non-intrusive vehicle detection system has been developed for measurement of delineations of moving vehicles on the highway. This prototype is based on our previous research on the principle of the measurement. The detection system uses two laser lines that are projected onto the ground as probes. The reflected light is collected and focused onto a photodiode array by an optical system. Vehicle presence is detected based on the absence of reflected laser light. By placing two identical laser/sensor pairs at a known distance apart, the speed of both the front and rear of a vehicle can be calculated based on the times when each sensor is triggered. The detector data are acquired and processed by a real-time system to obtain speed, acceleration, and length of a detected vehicle. The travel time of a vehicle can be acquired by detecting a vehicle at the beginning of a link and re-identifying the same vehicle at the end of link. Several tests have been done with the field prototype system on the highway. The testing results show that the system can obtain the accuracy of measurement necessary to distinguish between moving vehicles on the highway. This article describes the design and implementation of each functional component of an advanced version of the field prototype system.