实现均匀照明的自由曲面反射器

通过单个自由曲面反射器的反射,令光源发出的能量重新分布,在特定照明面上实现所需照明,从而简化了投影设备中的照明系统,使设备的进一步小型化成为可能。根据给出的光源辐射特性和所需实现的照明面上的能量分布,可得到一组偏微分方程,数值差分求解直接得到自由曲面反射器。光源采用发光面积1 mm×1 mm朗伯体发光的LED,视角为120°,照明面为4:3的均匀矩形光斑。设计了两种自由曲面反射器,并用软件对得到的曲面进行了照明模拟,模拟得到的照明均匀性接近90%。两种反射器在光轴方向上的投影尺寸均小于25 mm,垂直光轴方向上投影长度均小于22 mm,照明系统总长均小于40 mm,结构紧凑,适用于小型LED投影设备。

Freeform Reflector for Uniform Illumination

The energy from the source was rearranged through the reflection by a freeform reflector, and the desired illumination on a certain plane was got, which simplified the illumination system in the projectors and provided a choice to minimize the device further. A partial differential equations set was presented according to the character of the light source and the desired energy distribution on the illumination plane. The numerical results of the partial differential equations set were investigated to obtain a freeform reflector. LED with a Lambertian light emitting surface of 1 mm×1 mm and a viewing angle of 120° was applied as the light source, and the desired illumination on certain face was a 4∶3 rectangular. Two kinds of free reflectors were designed, and the simulated results showed a uniform illumination near to 90%. The projection lengths on the optical axis of both free form reflectors are less than 25 mm, and the projection lengths on the axis perpendicular to the optical axis are both less than 22 mm. The total lengths of the illumination system are both less than 40 mm, so this system is very compact and suitable for the portable LED projectors.