Digital Image Processing Technology In The Projection Display Tri-color Convergence In Applied Research

Projection display has been growing up rapidly in the late 1990's. This display technology integrates microelectronics, precision optical instrumentation and precision mechanical technology, and is becoming the one of the main stream in the present display field. Due to its high outputting luminance, large screen and the high quality of the projective image, the projection display for large screen has been used in many fields, such as official business work, conferences, etc. Liquid Crystal Projection Display, for example, one of the most important micro-display techniques, has shown the tendency for substituting the CRT projection display in the conventional video display field.Large screen projection display presents high quality projected images, that should be sharp, vivid, and with high quality. The full color image is formed by superposition three primary colors image together. Normally, in current projection system, three array pixel type Spatial Light Modulator devices were used to form three primary colors image in the projection display. To achieve the high performance projected images, the three SLM devices must be adjusted precisely and superposed three primary colors images exactly one by one in space. It is means the correspondent pixels of the three colors' pixel devices must be overlapped exactly.In this dissertation, the auto-focusing and auto-alignment process of three primary colors images has been investigated. The theoretical model, controlling process and the auto-focusing and auto-alignment system in the projection full color display system has been presented in detail.First, digital image processing theory referred to this work has been introduced briefly.Then the imaging characteristic of the optical system has been analyzed. Based on the nature of the projection display, a mathematical model been developed to realize the accurate focusing and accurate alignment by using the digital image processing technology and the computer control technology. The model includesautomatic focusing and automatic alignment.Next, based on the adjusting model the automatic focusing and automatic alignment about the pixel devices is realized on the platform of the large screen rear projection display system. The key to the automatic focusing and alignment is to design an adequate evaluation function to judge the quality of the projected image. The focusing evaluation functions are tested in detail in this dissertation. The experiments indicated that using variance method could attain good stability, insensitivity to noise and good regulation effect. The gravity formula has been selected to calculate the center of a pixel in automatic alignment process. The automatic control algorithms are also studied deeply. The error operation is as low as possible and the adapting ability of the system is as good as possible by optimizing the design of the programs.At the end of the dissertation, the orientation to enhance the performance is also discussed briefly.