Development Of Coded Aperture Spectral Imaging System In UV-VIS Band Based On DMD

As a new spectral imaging technology,coded aperture spectral imaging technology realizes certain pixel combination through ordered multi-channel coded aperture,which can simultaneously study and analyze two-dimensional spatial information and spectral information of the target.Compared with traditional spectral imaging,this technology can effectively improve the detection sensitivity,signal-to-noise ratio,spatial and spectral resolution of spectral imaging instruments and other indicators.Using coded aperture spectral imaging technology to explore the spatial distribution characteristics of various spectral light sources can directly and effectively reveal the mechanism of spectral light sources,so it is a research hotspot at present.In this paper,based on the theory of coded aperture imaging,a Digital Micromirror Device(DMD)based UV visible band coded aperture spectral imaging system is designed.In the range of190～800 nm,to realize hyperspectral imaging of spatial distribution of spectral source with a spatial resolution of no less than 70.16 μm,the application of 15-order S Hadamard transform imaging method compared with sequential scanning method can improve the signal-to-noise ratio of the system by about 2.16 times,providing a novel and effective detection method,which is conducive to promoting the development of spectral analysis instruments.The main work contents are as follows:(1)The simulation models of the pre-imaging optical path,the post-coupling optical path and the overall optical path of the DMD-based UV-VIS coded aperture spectral imaging system were designed by using Zemax optical design software,and the image quality was evaluated.According to the analysis results,the overall operating range of the optimized optical path is 190～800 nm.The modulation transfer function(MTF)values of the pre-imaging optical path model were all greater than 0.6 at the cutoff frequency(36.55 lp/ mm),and the point line radii of all bands in each field of view were within the radius of Alley spot(10.7 μm),indicating good imaging performance.(2)Based on the special DMD controller F2410 developed by the research group,the FPGA control and upper computer software of DMD are designed and developed.Based on VHDL language,the binary bitmap is generated directly by FPGA chip and output to DMD,overcoming the problem of slow image loading by upper computer or flash memory,and achieving 0.7 XGA DMD device ultimate turnover rate.At the same time,four coding modes,namely full pixel scanning,single pixel scanning,multi-pixel scanning and Hadamard coding,are developed,which meet the high-speed transmission requirements of complex spectral coding patterns in the coded aperture spectral imaging system in this paper.The network communication between upper computer and DMD controller is completed based on CH395 Q chip,and the corresponding upper computer software is developed(3)The integration,debugging and testing experiments of the whole coded aperture spectral imaging system are studied.First of all,on the basis of optical design,with Solidworks software for optical components fixed parts and prototype overall design;Secondly,laser and CMOS camera are used for system optical debugging and imaging detection,and LED lights,mercury(Hg)lights and USAF1951 resolution board are used for system resolution detection.Finally,the space distribution of mercury(Hg)and arsenic(As)lamps was tested and tested with the prototype of the coded spectral imaging system.The results show that the DMD-based UV-VIS coded aperture spectral imaging system can realize the hyperspectral imaging of the spatial distribution of detection targets in the range of 190～800 nm band with a spatial resolution of no less than 70.16 μm.Compared with the sequential scanning method,the signal to noise ratio of the system can be improved by about 2.16 times by the Hadamard transform method.