Analysis And Design Of Optical Projection System For MEMS Grating Light Modulaotor Based On LED Light Source

With the development of digital technique, it has become a research focus in the area of projected display, which combines MEMS-technique with spatial light modulator to develop light modulators based on MEMS-technique; on the other hand, high-power LED has developed rapidly because of its notable virtue, and using high power LED as new light source for micro-projection display system is being researched actively. Nowadays, the major core technology of micro-projection display system in market is restricted by international patents, so it is quite necessary to develop a novel MEMS-based light modulator with independent intellectual property rights, taking advantages of LED to design corresponding light system for projection display, breaking up the monopoly of techniques of abroad products, and advancing the level and core-competitiveness in the area of display technique of our country.Based on a novel grating light modulator put forward by project's team, in this paper, an optical projection system is designed when LED is used as its light source, the system is analyzed and researched by simulations and experiments. On the basis of previous foundation of project's team, author analyzed the feasibility in detail when LED is used as the light source of grating light modulator, designed and evaluated the light condenser system and projection system with LED light source, built the experimental platform utilizing the result of design and proved the validity of theory and design. The main works of this paper are follows:①Based on the principle of grating light modulator, the optical model is optimized after the effects of the surface bending and the periodic structure of grating light modulator on the performance are analyzed, and an optimized precept for design and processing technique is brought forward.②The feasibility is analyzed by partial coherent light theory when LED is used as light source of the grating light modulator for projection display. The influences of the size, bandwidth and surface structure of LED on the modulating performance of the modulator are discussed. That are indicated by the light distribution on the spectrum and image plane and modulated contrast respectively. Two kinds of light information processing systems with LED light source are analyzed, the feasibility when LED is used as the light source of the grating light modulator for projection display is proved theoretically. That could direct the design of optical projection system. ③The colorimetric property of LED is analyzed with colorimetric theory, the influence of the ratio of the number of RGB light source and variety of bandwidth of light source on display quality are analyzed, and the optimal ratio of RGB light source is deduced with the irradiation of LED, and the high performance is illuminated further by color discrimination index when LED is used to projection display.④A TIR lens with free-form surface for light gather is designed by Tracepro and Codev software. The light field is uniformed by straight light pipe and terraced light pipe, which are compared and discussed in the matter of achieving light field uniform and improving angle of emergence light. A compact condensing lens is designed to realize high efficient converging of light, realize efficient gather of large angle of divergence of LED and uniform irradiation on modulator.⑤The type of projection objective lens is ascertained based on the theory of light modulation of the grating light modulator and the theory of optical imaging. Two different structures of projection objective lens are designed by Zeamx and Codev software, and the information processing and projection imaging of the grating light modulator are realized, the aberration valuation is used to compare the two types of projection imaging systems. The color of RGB LED is composed by X cube, and the simulation, modeling and estimate of compact optical projection system for grating light modulator with LED light source are realized, the theoretical principle of designing for optical engine system and solution for key technical matters are grasped.⑥Utilizing the manufactured grating light modulator based on MEMS technique, the influence of surface bending and periodic structure on the optical performance is testified by experiment, which indicated the validity of theoretical analysis. The experiment platform is built with the design philosophy, and utilizing a static MEMS grating light modulator, the diffractive light distribution and the projection image of modulator are got with LED light source, the color projection system of grating light modulator based on three primary colors of LED is built, and color projection display of LED light source is realized, which indicated the validity of the theoretical analysis and the reasonableness of the design. A truly original optical projection imaging system of grating light modulator based on MEMS technique combing with LED light source is first developed independently in China.