对于近场大角度的匀光照明系统,透镜的一般设计方法是采用内表面为球形的自由曲面透镜设计,计算的自由曲面透镜只需考虑一次折射.但是当角度达到一定范围时,在透镜的内表面容易发生全反射,导致目标面照度不均匀.为了在近场照明系统中得到更大角度的配光,提出一种以合适的抛物面作为自由曲面透镜的内表面的设计方法,内抛物面先对光源的能量进行一次扩散,再计算自由曲面面型,通过模拟仿真,实现了在距离光源15 mm处形成半径40 mm的光斑,均匀度达到95%,能量利用率达到97.8%,相对于传统的直下式透镜,提高了照明的均匀度,同时减少了箱体的厚度.

In the system of near-field uniform lighting,lens design methods commonly use sphere as the inner surface,and the calculation of the free-form surface only considers primary reflection .But when the angle reaches a certain scope,total reflection on the free-form surface of the lens is easy to occur ,which will lead to the poor illumination performance.In order to get the larger light distribution in the near-field lighting system ,a free-form lens design method based on the modulation of the parabolic inner surface was proposed.The parabolic can diffuse the energy of the light source,and then calculate the free-form surface.Through simulation,the uniform light spot with 40 mm radius can be realized at 15 mm distance away from light source,while the uniformity reaches 95%,the efficiency reaches 97.8%.Comparing with traditional direct lens,the uniformity is enhanced and the height of backlight box is decreased by using the structure of this lens.