| In recent years,with the development of unmanned driving technology and the widening of Li DAR application,high resolution Li DAR products have highlighted the broad prospects.At present,the mainstream products of high resolution Li DAR have gradually turned from mechanical Li DAR to miniaturized solid-state Li DAR,whose range resolution has exceeded cm level,but the intensity resolution is low.In order to improve the intensity resolution of miniaturized solid-state Li DAR,researchers mainly adopt the method of intensity image matching with the camera device to improve the intensity resolution,but the relatively high cost and complex assembly is not suitable for large-scale application of the product.In addition,the core detectors and highly integrated semiconductor products in the Li DAR system are in the state of international monopoly and technology blockade in China for a long time,which seriously affects the development of high resolution Li DAR technology in China.In order to improve the intensity resolution of the Li DAR system,this paper proposes a combination receiving method based on two-dimensional MEMS micromirror scanning and multi-unit APD detector,which strives to improve the intensity resolution of the Li DAR system from the perspective of constructing the Li DAR system in the absence of highly integrated photodetectors,and obtain the surface intensity image while obtaining threedimensional spatial location information.For this purpose,the following three studies were carried out:1 In order to realize the dynamic scanning of two-dimensional MEMS micromirror,the difficulties of application in the scanning based on two-dimensional MEMS micromirror were pointed out.The optical model of two-dimensional MEMS micromirror scanning was constructed,and the distortion problems existed in the scanning process of two-dimensional MEMS micromirror were analyzed.The distortion types were distinguished,and the distortion percentage was calculated and verified.A better micromirror scanning scheme is established from the optical point of view,so as to realize the accurate scanning of the target treated by MEMS micromirror.2 In order to realize the scanning and receiving of large FOV based on MEMS micromirror,the optical design methods of lidar optical system are analyzed and compared,and the biaxial design scheme is determined.The characteristics and application environment of various photodetectors are analyzed and APD is selected as the basic detector.Aiming at the limited photosensitive area of high sensitivity APD detector,a MEMS micromirror combined with defocus optical system and focusing lens was proposed to dynamically expand the FOV.The optical system of the receiving end is designed based on ZEMAX software,and the full FOV is expanded to 36 ×36.3 In order to improve the intensity resolution of Li DAR,a multi-cell APD receiving scheme is proposed.Without the photographic system and different scanning Settings,confirming the three-dimensional information of scanning target by the laser transmitter and ranging module,ranging accuracy of 1cm;Meanwhile,the intensity image is obtained and the intensity resolution is improved.In the single pixel test experiment,the number of APD intensity values obtained by single unit is 1/4 compare with the combined receiver.At a distance of two meters from the target,the MEMS micromirror can perform point scanning of 16×16 with angular resolution of 0.4 ×0.4,the 6×6 intensity image generated by the single detector is increased to the 12×12 intensity image generated by the combined receiver.Experiments show that the intensity resolution is four times that of the single detector.In the construction of the system,domestic photodetectors and industrial modules are used to greatly reduce the cost of the system.It also provides a new idea for the development of high resolution Li DAR technology to break foreign monopoly and technology blockade. |
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