Studies On Theoretical Analysis And Application Of The Optical Systems For Reflective Projection Displays

Projection display technology is an effective way to realize large screen display systems. As the most important component in projectors, optical system dominates system brightness, contrast, uniformity, resolution, and chromatic performance, and becomes the focus of the development of projection display technologies.The key objective of projection display optics is to improve system energy efficiency, uniformity and contrast. In this paper, the theory of non-imaging optics is introduced into the design of projection system and presents a new method for the evaluation of optical system performance based on the detailed research on current projection display technologies, especially the reflective spacial light modulators (SLM), light sources, and principles and design methods for all kinds of projection optics and key optical elements. Several issues, including the energy efficiency and polarization effect in reflective projection display systems, are studied in detail.The concept of Optical Extend (Etendue) is explained in the paper, and the transition of etendue in projection optical system is then discussed. According to the detailed analysis on lamp's etendue and the relationship between etendue and output lumens, it is found that the etendue and energy intensity distribution of light source should be considered together to form an optimized projection optical system. Then the design methods of Lens-Array (Fly-eye Lenses) and Light-Pipe illumination systems are presented, and mathematic models are established to get a clear impression of system etendue and energy efficiency.The research on polarization effect in LCoS (Liquid Crystal on Silicon) projection display systems is also an important work of this paper. A three dimensional mathematic model is built to trace the polarization state based on the theoretical analysis of all kinds of polarizing elements. The effects of wave plates and optical thin films are also analyzed here based on the theory of Jones Matrix and Vector Optics. With the theoretic calculation results of systems with/without wave plates, a new method of applying wave plates proper phase changes to LCoS projection display systems shows a great advantage of improvingsystem contrast.At the end of this paper, the detailed design of single-panel DLP rear-projection display optical engine and three-panel LCoS rear-projection display optical engine are presented, together with the discussion on the design method of all the key optical elements in these two systems and contrast and chromatic performance of DLP projector. Further more, the development trend of projection display technologies is also discussed.