Phase-shift Laser Ranging System Design

Laser ranging is a kind of precision measuring technology that gradually developed with the generation of laser technology. It has been widely applied in the areas,such as topographic survey, tanks, planes, ships, field measurement, because of its its high directivity,fast speed of measurement, high monochromaticity, some penetrability, high brightness,strong anti-interference ability and other advantages. Aiming at the problem of low precision of measurement in china, a kind of medium and short range high precision phase type laser range finder system is designed.Starting from the basic principle of phase laser ranging, the paper established a general scheme of the differential frequency measurement of phase laser ranging system. The system is made up of programmable modulation signal source of the cascading double phase-locked loop architecture, laser transmitting and receiving, photoelectric control, automatic gain control, mixer and frequency selective network, data acquisition and process of digital phase.The system first configures each register of the low jitter clock source by upper computer,then output modulating signal and intrinsic signal, and filter them, then get the sine wave modulation signal. Infrared laser diode is drived by drive circuit, then the modulation signal emits modulation signal light. The detector accepts the signal light and at the same time, the reference signal and the measuring signal get two frequency signals through the signal processing circuit, such as the enlarge and automatic gain control of the exactly same photo-current. Frequency signal and intrinsic signal get the intermediate frequency signal which has the same phase information, through mixer circuit and frequency selection circuit.The system collects the data of two intermediate frequency signals by using multi-channel data acquisition system, and reads the collected data in matlab, and calculates the phase difference of the two channels signal by taking the vector inner product phase method, and then calculates the distance.The paper has completed the design of phase laser ranging system’s modulation signal source circuit, the design of laser emission circuit, signal conditioning circuit, the mixer and frequency selective circuit, and it also has completed the circuit board’s production and circuit debugging of PCB. The experimental results show that: the 30 meter ranging error is3 cm, and the ranging accuracy is not up to the expected requirements. In order to improve the accuracy of the measurement, the effect of the temperature of each module of the receiving circuit is analyzed by Pspice simulation, the optimization method is proposed, which can improve the measurement accuracy.