Application Of The Free Surface Of Thin Projection Display System Theory And Experimental Research

Projection display technology is an effective way to realize large screen display. The new directions of projection display are high brightness, high resolution, ultra-thin and large screen in order to meet the needs of display technology market. Ultra-thin structure of ultra-thin display system satisfied the market requirements of high quality display in narrow space, so ultra-thin technology has wide development scope.In order to research the design method of ultra-thin display system, light source, illumination system and imaging system of projectior were analyzed in this paper. The Etendue of light source with reflector was analyzed based on the theory of non-imaging optics, and the relationship between Etendue and collection efficiency was deduced. Especially, a new method for measuring the output intensity distribution of light source with reflector was put forward, and the collection efficiency vs. Etendue curves were measured by this method. This method can supply valuable reference for the subsequent design of illumination system. Because brightness and contrast of projection system are directly influenced by the matching degree between light source and illumination system, and the matching degree can be greatly improved by this method, the ultra-thin projection system can realize higher brightness and contrast.The free form surface was introduced in the design of illumination system. According to the luminescence properties of light source and the desired light distribution on illumination plane, the differential equations were deduced based on reflection law in order to acquire the data of free form surface. The illumination system realized simpler structure and higher performance by this method. Although the free form surface was expressed by discrete points and it can't be expressed by polynomial, it has a wide application prospect in illumination system design.In the design of imaging system, ultra-thin projection lens was designed to be off-axis form. The off-axis reflection system composed of four aspheric mirrors was designed, but the system structure was not so simple and the performance can also be improved, besides, manufacture and test for large aspheric mirrors are difficult; and then the spherical Fresnel mirror which is easier to be manufactured and tested was used to replace the aspheric mirror, the spherical Fresnel mirror has low cost of replication, but this design also can't be used in projection lens because it was only feasible in narrow wavebands; Furthermore, the design making use of catadioptric projection lens was accomplished, this design is greatly applied in rear projector because it has merits of both refraction and reflection. But it had difficulties in color aberration correction and had complex structure.In order to solve the problems in system of four aspheric mirrors, Fresnel mrirror and the catadioptric projection lens, the method that free form surfaces were used to design ultra-thin imageing system was put forward at last. Because the free form surface expressed by discret points has difficulties in aberration correction, manufacture and test, the Zernike polynomial was adopted to express the free form surface. The performance of this system was optimized on the basis of the relationship between Zernike polynomial and Seidel aberration. This method can be used in wide waveband and had no color aberration because the Zernike free form mirrors were adopted. Furthermore, because the free form has more design freedom, ultra-thin imaging system can be realized. Accordingly, ultra-thin imaging system composed of Zernike free form surfaces was designed by this method, this system had simpler structure and higher performance, and large screen display was realized in super short projection distance.In order to verify the performance of off-axis ultra-thin imaging system, an ultra-thin projector which can realize large screen display in super short projection distance was designed based on DLP illumination system. The experimental prototype was set up in consideration of cost and domestic machining levels, the prototype made contributions on transformation from research to mass production.