Research And Design On Short-Distance Laser Range Finding Sensor

Laser range finder is one of the effective ways for distance measurement with which people don't have to set rulers. It could also make distance measurement to the place where people can't reach much easier and safer. We can count the distance accurately by find the difference of phase which bring by modulated wave through the distance. With the development of space technology and cosmonautics industry, space distance measurement has become important research content of space technology field. Laser ranging technology covers many fields, such as laser, photon-detection and computer etc. For its characteristics of high ranging precision, wide range, high-reliability and so on, laser ranging technology meets the high-precision and wide-range requirements of distance measurement between two space objects, and it is widely used in space measurement field.Through the analysis of existing laser ranging technologies as well as the comparison of the performance of different technologies, phase-shift laser ranging method is proposed. This thesis researches some key technologies on phase-shift laser ranging for short-distance laser range finding sensor. The main work finished in the thesis is as follows:A modulation signal generating circuit is developed based on direct digital synthesizing integrated circuits. The frequency resolution of the sine wave generated is 0.02Hz and the short-term frequency stability is up to 10^-7. The frequency of modulation signal can be continuous and accurately adjusted, which is base of high-precision ranging, changing parameters frequently in the meanwhile it meets the requirements in the experiment system.A high -reliability LD inner modulation circuit is designed. Its constant current driving element and current-limiting element can not only accurately modulate LD but also effectively keep LD away from over-current breakdown.Aiming at the detection of feeble laser signal, the thesis designs a return light detection circuit based on high-sensitivity avalanche diode. The circuit has improved the sensitivity and measurement accuracy of the system and augmented action distance.DDS (Direct Digital Synthesis) technology, replacing PLL (Phase-Locked Loop Synthesis), is utilized to produce two frequencies used as signal source to modulate laser diode. DDS features short frequency switching time, high frequency resolution ratio and low phase noise, all which meet the requirements of range and accuracy of the system. The variations in signal-to-noise ratio of input and output of each circuit are calculated and analyzed while realizing the hardware design of the whole system, which lays a solid foundation for error analysis.