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Integral freeform illumination lens design of LED based pico-projector
Shuang Zhao1, Kai Wang, Fei Chen
1Division of MOEMS, Wuhan National Laboratory for Optoelectronics, School of Optoelectronics Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Abstract:
In this paper, an illumination lens design for a LED-based pico-projector is presented. Different from the traditional illumination systems composed by lens group, the integral illumination lens consists of a total internal reflector (TIR) and a freeform surface. TIR acts as collimation lens and its top surface formed by a freeform surface reshapes the nonuniform circular light pattern generated by TIR to be rectangular and uniform. Diameter and height of the lens are 16 and 10 mm, respectively. An optimization method to deal with the problem of extended light source is also presented in detail in this paper. According to the simulation results of the final optimized lens, 77% (neglecting the effect of polarization) of the power of light source is collected on liquid crystal on silicon panel with a 16∶9 ratio and illumination uniformity achieves 92%.
