Research On Optical System Of Infrared Scene Projector Based On Digital Mirror Device

IR scene projector is an economical, high efficient solution for analyzing IR seek-ers’ability of detection and guidance. It utilizes scene generators to generate infrared dynamic images, and simulates the detection process of the seeker for the infrared target and background with the projection structure of the simulation system. The Digital Mir-ror Device(DMD) chip has advantages of high resolution, high frame rate, high gray level and good uniformity, and has become one of the most widely used scene generator for target simulation system. This article demonstrates the research of infrared target simu-lation systems based on DMD chips, and completes the design of 4.3～4.8μm wavelength optical system.First of all, we have investigated the state of the art of the research done nationally and internationally on target simulation systems, analyzed the pros and cons of different scene generators, chose DMD as the target generator, and investigated on the structure and working principle of DMD, settled on the overall structure and the relationships of the sub-structures of the target simulator. By analyzing key structures and technologies, the overall concept and design objectives of the optical system were determined.Secondly, we analyzed and calculated the key structure of the optical illumination system. We elaborated on the function of the Total Internal Reflection(TIR) beam splitter in the subsystem coupling, by reverse raytracing we calculated the structural parameters of the TIR beam splitter, and chose zinc-sulfide(ZnS) for the structure design of the TIR beam splitter. We analyzed and settled on the external parameters of the illumination system and projection system, employed the critical illumination, and used Zemax to optimize the optical illumination system including the TIR beam splitter. Based on the current primary projection system, we inverse designed the projection system, by improving the primary system, we finished the tele-center structural design for the projection system. An optical projection system with system parameters and the image quality that satisfies the requirements has been obtained by the optimization of Zemax software.Moreover, this article has analyzed and evaluated the designed optical system. We have simulated the ’on’ state and ’off’ state of the optical illumination system with Zemax, to confirm the design results of the TIR beam splitter; we analyzed and calculated the homogeneity of the illumination of the DMD surface with the TracePro software, and evaluated the illumination system, and assessed the image quality of the projection system with MTF, spot diagram and distortion curve, and analyzed the tolerance of the projection system with Monte Carlo method, and evaluated the stability of the system with the actual MTF simulated.Finally, we analyzed the overall target simulator optical system by simulation. We have done research including the calculation of the radiation transmittance and working temperature of blackbody; analysis of the stray radiation, ghost and spontaneous radiation of the overall optical system simulation with TracePro software. In the analysis process, we have used function as Zemax Ghost、TracePro Reverse Raytrace to simplify the stray radiation model to improve analyzing efficiency. The finial results have demonstrated that the research done on the stray radiation of overall system is well controlled and satisfies the requirements for usage.