| As the retain number of automobile has sharply increased recent years, road trafficsafety has been regarded as social problem. This dissertation is intended to design a laserranging system which can be used in automoblie active safety system. The system detectsthe road status in the distance using laser beam. It can assist the driver to estimate the risklevel and brake earlier in the dangerous situation.The design specification of automobile precrash system have been analysed in thisdissertaion. Then a detailed technical parameter of laser rangefinder which can be used inautomobile precrash system has been proposed. Related theory and critical problems oflaser rangefinder have been discussed. By weighing the pros and cons of kinds of rangingmethods, The technical scheme of miniaturized, high frenquency diode laser rangefinderhas been decided.The project adopts pulsed laser ranging in noncoherent detect mode, uses a 905nmpulsed laser diode as the laser source, detects object with a single APD, adopts ahigh-speed counter achieved in a programable logic device(CPLD) to measure theaccurate time-of-flight interval. A funtional prototype of rangefinder are manufacturedusing the scheduled technical scheme. Preliminary experiments are made using theprototype. |
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