Study On The Design Method Of Uniform Illumination Based On Transmitted Free-form Surface Theory

Miniature and longer lifetime is the development trend of the micro-display projection system. In the recent years, the production of the high brightness LED provides possibility to develop longer lifetime and miniature micro-projection display. Compared to the traditional sources, the LED has the irreplaceable advantages of high efficiency, no infrared irradiation, small size, low power consumption and long lifetime. But the layout and the luminance distribution of the LED are so different from the traditional sources that the conventional illumination systems are not suitable for the LED especially for the miniature style. The free-form surface can simplify the structure of the system and increase the image quality with the flexible spatial layout and the degree of design freedom. Especially, the free-form optical surface can get the specific light distribution freely and control the physical quantity like angle of the ray and optical path difference in the optical design for illumination, so it has potential application prospects in the mini-type LED projectors. So it is meaningful and necessary to develop the research in this field.The dissertation introduces a new way to design free-form optical surface for uniform illumination, which is form optical surface using numerical solutions of differential equations. Given a specified light source with known intensity distribution, the light can be redirected from a source onto a target surface of given shape such as to produce a given desired irradiance distribution on the target though the refracting or reflecting by the free-form surface. The free-form optical surface can be getted by resolving a series of partial non-linear equations.In the beginning of the dissertation, typical kinds of the projection system are introduced including the background, category and the optical structures. In addition, the principles and optical technologies in the traditional illumination system are introduced such like the light pipe system and the refractive fly-eye system. Finally the recent development of the free-form optical surface and the advantages are presented.In the second chapter, the principle of the non-image theory is introduced, and then the design method of uniform illumination based on freeform theory is illustrated detailed.The third chapter introduces the basic theory of differential geometry then deduces the equation with this theory;get the scalar differential equation finally.In the forth chapter, the algorithm to solve the equations is presented. The shape of the free-form surface is calculateed using the method of numerical computing.In the fifth chap the ray tracing simulation was finally given by used the software ASAP. In addition, the uniformity and the efficiency are both satisfied.At the end of the dissertation, the conclusion and future research direction are given.