用Zernike自由曲面设计弯曲屏幕超薄投影系统

Design of ultra-thin projection system with curved screen based on Zernike free-form surfaces

基于非球面离轴反射式投影系统,提出了采用Zernike自由曲面取代非球面进一步优化系统结构的设计方法,并利用Zernike多项式与Seidel像差之间的关系,优化系统的成像性能.设计采用一片Zernike自由曲面取代四片非球面系统中的一片非球面,使投影系统的厚度从24 cm减为20 cm,边缘视场的调制传递函数(MTF)在50lp/mm时由45%提高到57%,中心视场及0.7视场的MTF由60%提高到了70%,两系统畸变均小于3%,且由于采用柱面弯曲屏幕设计,场曲均在18 mm以下.研究结果表明,应用Zernike自由曲面设计投影系统不仅可以提高光学系统的性能,而且可以实现更加超薄的系统结构.

Based on the aspheric off-axis reflection projection system, the Zernike free-form surface was adopted to replace the aspheric surface in order to further optimize the system structure. The relationship between Zernike polynomial and Seidel aberration was utilized to improve the system performance. One aspheric surface in four aspheric system was replaced by one Zernike free-form surface, thus the thickness of the projection system was reduced from 24 cm to 20 cm; the modulation transfer function （MTF） of ±1 field was improved from 45% to 57% at 50 1p/mm, and the MTFs of both center field and 0.7 field were improved from 60% to 70%; the distortions of both systems were less than 3%, and the field curvature was less than 18 mm because the screen was cylinder. The results show that the projection system with Zernike free-form surface can not only improve the performance of optical system but also realize more ultra-thin structures.