LED Illumination System For CF-LCoS Based Pico-Projection Optical Engine

A review of the role of the optical surface slope angle in optical system was first carried out by recalling the refraction/reflection process in the traditional imaging and non-imaging optics. No matter in imaging or non-imaging optics, the optical surface slope angle plays an import role, with which the ray convergence, ray divergence, and light energy redistribution are directly applied. Compared with the surface profile control based optimization method used in the traditional non-imaging optical element design, the surface slope angle control based optimization method was proposed for the first time. With the proposed method, three problems which lied in the traditional surface profile control based optimization method can be effectively overcome. One non-imaging reflector design example for general illumination was run in this thesis to verify the advantages by applying the surface slope angle control based optimization method.The surface slope angle control based optimization method was applied in thesis to design for the illumination system of pico-projection optical engine. First one CF-LCoS based optical engine for emendation was designed with LED rays collimated by single collection lens. This optical engine has a simple structure, a low cost, and is very suitable for assembly and production. The optical engine can also provide efficient light output and uniform projection light distribution. Thus it is very suitable for mass application in mobile platforms like cell phone. Besides applying the surface slope angle control based optimization for the TIR lens to achieve high light efficiency and compact size, the surface slope angle control based optimization was also applied to optimize for the elliptical illumination, which was generated by the combination of the collection lens and the cylinder lens. Though the elliptical illumination based optical engine takes a larger volume, it can provide a flux improvement of over 10% compared with the single collection lens based system. The most important advantage kept by the elliptical illumination is that it can provide the same light collection efficiency for display panels with free aspect ratio.Another research in this thesis is the design for white LED powered stand-by CF-LCoS optical engine. The mathematical derivation was first carried out to analyze the common points and difference between fly-eyes and light pipe based traditional uniform illumination systems. Both two methods acquires uniform irradiance by dividing and integrating the output ray spreading angle, but the light pipe based system has its unique "mirror integration" process, with which the light pipe based system can have the same performance by applying both odd and even symmetrical sources. By discovering the disadvantages which lies in these two traditional uniform illumination systems, one LED illumination method was proposed based on the light pipe based uniform illumination, and magnification lens based light transfer. The proposed illumination system has simple structure, and is suitable for assembly and production. It can also provide the display panel with a rectangular light spot that has a high light efficiency and a uniform light distribution with the small ray incident angle. By the applying sample production and test process for the stand-by CF-LCoS based optical engine, the new proposed LED illumination method can be found to be effective.The novel ideas introduced by this thesis are listed as follow:(1) All the designs in this thesis were based on LED real ray file model instead of the perfect model. (2) A review of the role of the optical surface slope angle was carried out, and the optical surface slope angle control based optimization method for non-imaging optical element was proposed. (3) By successfully applying the surface slope angle control based optimization method, one LED powered CF-LCoS based optical engine was designed with LED ray collimated accomplished only by single collection lens, and this optical engine was very suitable for applications in mobile platforms like cell-phone. (4) The surface slope angle control based optimization method was also applied to optimize for the TIR lens based illumination system and the elliptical illumination system generated by the combination of both collection lens and cylinder lens, and both light efficiency improvements had been acquired. (5) The mathematical derivation method was applied to discover the common points and difference between the fly-eyes and light pipe based uniform illumination system, and one novel LED illumination method was proposed based on the light pipe based uniform illumination, and magnification lens based light transfer. (6) By applying the design, sample production, and sample test process of the LED powered stand-by CF-LCoS optical engine, the new proposed LED illumination method can be verified to be an effective method. The stand-by optical engine can provide an ANSI 9-point output flux of 401m, an irradiance uniformity of 94%, and a contrast ratio of over 180. The light efficiency of the sample optical engine is about 4.83%. This optical engine can satisfy the general need of the stand-by pico-projection.