The Design Of Phase-shift Laser Rangefinder And The Research Of It's Key Technologies

Laser rangefinder is one of the effective ways for distance measurement withwhich people don't have to set rulers. It could also make distance measurement to theplace where people can't reach much easier and safer.Semiconductor laser is characterized by low power consumption, small size andthe combination of light source and modulator, all which make it the best option fordistance measurement. With the development of electronic technology, themeasurement of phase difference could meet high accuracy, which makes phase-shiftrangefinder priority for distance measurement. By measuring phase differencebetween emitted modulated waves and receiving modulated waves which arereflected from the target, we could get the value of distance quite easily throughsimple calculation.Through the analysis of existing laser ranging technologies as well as thecomparison of the performance of different technologies, phase-shift laser rangingmethod is proposed. In light of the demerits of existing phase-shift laser rangingtechnology, many theoretical researches and experiments are conducted to improvethe performance of the device.DDS (Direct Digital Synthesis) technology, replacing PLL (Phase-Locked LoopSynthesis), is utilized to produce two frequencies used as signal source to modulatelaser diode. DDS features short frequency switching time, high frequency resolutionratio and low phase noise, all which meet the requirements of range and accuracy ofthe system. The variations in signal-to-noise ratio of input and output of each circuitare calculated and analyzed while realizing the hardware design of the whole system,which lays a solid foundation for error analysis. FFT technology is used to detectphase to improve the accuracy of the system.