Investigation On Optical Engine Applied To Dual Field Angle Infrared Scene Projector Based On DMD

Due to the advantage of difficult to discover and strong anti-interference, people have paid more and more attention to infrared guided missile. With the development of infrared imaging guidance missile, infrared scene projector (IRSP) as the most effective method to evaluate the seeker’s performance has made great progress. Infrared optical engine is one of the most important parts of IRSP. The design of the IR optical engine directly affects the performance of the whole system, including illumination uniformity, contrast ratio, resolution and so on.In this dissertation, a duel field optical engine of IRSP is designed. Compared with the performance of numbers of IRSP technologies, DMD is chosen as the scene generator.This dissertation has analyzed the structure characteristic and design difficulties of optical engine based on DMD. In this dissertation, the component of telecentric structure used in DMD optical engine has been discussed. And the relationship between each component has also been analyzed. The optical engine of IRSP is an integration technology which associated with optic, mechanic, electron and compute. During the design of the optical engine, some problems need to be considered. First of all, the pupil of the illumination optical system should be matched with the light source. Secondly, the relationship of the incident angle and reflected angle for the chief ray of incident light bundle on each mirror of DMD should be considered. Thirdly, in order to ensure that all of the rays that transmitted by the illumination optical system should be guided to the pupil of the projection optical system when the mirrors of DMD is on state, and are prevented to enter the pupil when the mirrors is off state, the parameters of TIR prism requires precisely computation. Last but not the least; the IRSP should be matched with the seeker. Because of this, during the projection optical design, the seeker’s parameters should be considered. Meanwhile, the projection pupil should be matched with the illumination optical system.This dissertation has taken one duel-field seeker as an example, and designed one optical engine of IRSP for the seeker. Because of the structure chosen in this dissertation is telecentric structure, the light path of the projection and illumination optical system (for prism design) can be designed independently.First of all, the illumination optical system has been designed. By analysis of the light source, DMD and other technical parameters, the etendue was first calculated. Then we have analyzed the light source and the technical specifications of DMD and chosen critical illumination as the illumination mode. Finally the design specifications for the illumination optical systems have also been determined. In addition, in order to compute the parameters of TIR prism, some problems need to be considered. Based upon the characteristic of TIR prism used in illumination optical system, the relation between illumination angle and the mirror-tilt angle of DMD should be considered first. Secondly it is also necessary to make sure that the whole light of off state could not enter the projection optical system. After the analysis of all the technical parameters, the TIR prism system has been designed. The illumination uniformity of the illumination optical system is evaluated by Light Tools. The analysis results showed that the illumination system designed in this dissertation meets the design requirements. The illumination uniformity is good and the system could modulate the light reflection of DMD.One duel-field projection optical system has been designed. Because of the projection system should be matched with the duel-field seeker, the technical parameter of the seeker has been discussed before the design of the whole IRSP optical system. Meanwhile, in order to ensure that the illumination optical system is matched with the projection optical system, the projection optical system has been designed with the consideration that the Lagrange Invariant of the illumination and projection optical system should be equal. The MTF, spot radius and distortion have been analyzed to evaluate the projection optical system. The results have shown that the projection optical system met the design requirements. Finally, he tolerance of the projection optical system has been discussed. Analysis have shown that with relatively loose tolerances of tilt, decenter, thickness etc., this duel field projection optical system could still have a good imaging quality, which means that the optical design is fairly good.At the last part of the letter, the structure of the whole optical engine and its optical performances has been analyzed. The relation between simulating temperature and the working temperature of the illumination blackbody was also discussed. The energy loss coefficient of the whole optical engine has been computed. Finally, it has been shown that the optical engine of IRSP designed in this dissertation is designed rationally, and it is matched with the duel field seeker. It could achieve the function of duel field simulation.