Research On Defocusing Detection Optical System Of Laser Rangefinder

As a non-contact measurement technology,laser ranging technology is one of the most widely used directions of laser technology.Photodetector is one of the core components of ranging system.When the positioning accuracy of photodetector is low,it seriously affects the performance and accuracy of laser rangefinder.Therefore,it is necessary to defocus the photodetector at the receiving end of laser rangefinder.The existing defocus detection methods are not suitable for on-line measurement of laser rangefinders which have been integrated and packaged as products.In this paper,the defocusing measurement of laser rangefinder receiver detector is studied and designed.Firstly,the structure and principle of split image mirror are introduced.Based on split image mirror,a defocusing detection method suitable for laser rangefinder is proposed.The measurement principle formula is deduced,the mathematical model is established,and the overall design scheme of the system is given.The appropriate optical elements are selected,and some parameters are designed according to the actual requirements.Then,based on the overall scheme described above,complete the design of the whole system.According to the measured system parameters,the preliminary design of subsystems is completed,and then they are combined together and optimized at the same time;ZEMAX software is used to evaluate the image quality and analyze the temperature of the optical system.The outcomes show that all the indicators satisfy the requirements within the temperature range,and the structure is convenient for the actual processing and adjustment;the results of the experiment suggest that the spot center positioning accuracy of the defocus detection system is about 0.002 mm.Finally,according to the composition and basic principle of the whole defocusing detection system,do in-depth calculation and analysis of measurement accuracy,and the detection of this measurement device prototype is completed through experiments.The experimental and analytical outcomes suggest that the focal length error of the measured system and the focal length error of the detection system make a great difference on the defocus detection accuracy,and the larger the top angle of the split image focusing screen is,the smaller the ratio of the measured system focal length to the detection system focal length is,the higher the defocus detection accuracy is;the actual error is close to the ideal value,and the smaller the defocus amount is,the higher the defocus detection accuracy is,which is in line with the habit of assembly and adjustment measurement.