Application Of Freeform Surface In Non-imaging And Imaging Optics

With the rapid development of global economy and human society, human are in the search of renewable energy as well as compacted, lightweight and energy conservatory instrument. Freeform surface can significantly simply the structure of the optical system, due to its flexible spatial layout and high degrees of design freedom. The freeform surface has good application prospects of lighting field, solar energy and imaging optics system.Based on the illumination application of freeform surface, we present a freeform reflector design composed of ellipsoid patches forming uniform illumination or arbitrary shaped irradiance distribution. A set of discrete data points of the freeform reflector surface are obtained by mathematically solving the geometry equation, and optimization algorithm is established. However, discrete spots distribution on the target plane is produced. A contour calculation method for the freeform reflector design is presented, aiming to achieve uniform illumination on the target plane. According to the energy conservation law and the law of reflection, the contour of freeform reflector is determined. Then, the Bisection method is used to computer the focal parameter until the ellipsoid patches satisfied the continuity condition. Since the prescribed distribution on the target plane can be obtained with point source, extended source will always lead to bad results. Optimization method has to be applied. This optimization method is integrated with two optimization steps. The first step is used to ensure a high irradiance uniformity of the discrete spots, ant the purpose of the second step is to achieve the continuity of irradiance distribution.Based on the principles of geometrical optics (the edge-ray principle, ray reversibility principle and Fermat’s principle), a Flyeye concentrator with improved irradiance distribution on the solar cell in a concentrator photovoltaic system is constructed without solving partial differential equations or using an optimization algorithm. Comparing our design Flyeye concentrator optical performance to those of the traditional concentrator, the Flyeye concentrator has higher CR, lower aspect ratio, and wider acceptance angle than the traditional concentrator.A novel hybrid Fresnel-based concentrator with improved uniformity irradiance distribution on the solar cell without using secondary optical element in concentrator photovoltaic system to overcome Fresnel loss. The improved uniformity on the solar cell is obtained using the prism displacement optimization method. The improved concentrator has outstanding optical performance and low cost.Finally, freeform surface has been taken to design optical system in imaging optics, which is remarkable different from the traditional design method. According to the partial differential equations, an initial freeform reflector is available. The freeform reflector is fitted using the odd polynomial surface. The on-axis and off-axis projector composed of refractive reflective hybrid system have been designed. The proposed projector has advantage of simple structure, which is developed to achieve large screen at ultra-short projection distance and a small optical distortion. The optical performance is analyzed for the refractive-reflective hybrid optical system. Results show that the optical performance of the proposed system have satisfied our requirement. Finally, based on the previous research, a traditional DLP projector is fabricated. The experiment results prove the practicality of the design method.