Joubert C, Loiseaux B, Delboulbé A, Huignad J P
Appl Opt. 1997 Jul 10;36(20):4761-71. doi: 10.1364/ao.36.004761.
Projection systems based on liquid-crystal displays (LCD's) offer new opportunities to display high-definition and large-size TV images. There are two types of LCD projector architectures: the 3-LCD architecture uses one LCD for each primary color, red, green, and blue, whereas a single-LCD configuration employs only one LCD paved with color filters. The single-LCD projector is simple and compact but suffers from a poor luminous efficiency because of losses in the color filters: each filter transmits only ~1/3 of the flux emitted by the lamp. To increase this optical efficiency, we propose to introduce volume holographic elements in the architecture of a single-LCD projector. Innovative systems are presented in which volume holographic elements realize the spatiochromatic illumination of the LCD. This illumination consists of selectively directing all the light that corresponds to a primary color, red, green, or blue, in the pixel addressed with the corresponding video composite signal and exploits the spectral selectivity and dispersion properties of volume holographic gratings and lenses. The two main advantages of such illumination are the suppression of the color filters and the recovery of the light lost in a classical architecture by absorption of the color filters. A complete luminous efficiency analysis of spatiochromatic illumination with volume holographic elements is presented. The achieved performances are compared with classical single-LCD projectors.
基于液晶显示器（LCD）的投影系统为显示高清和大尺寸电视图像提供了新机遇。有两种类型的LCD投影仪架构：三LCD架构为红色、绿色和蓝色这三种原色分别使用一个LCD，而单LCD配置仅采用一个铺设了彩色滤光片的LCD。单LCD投影仪简单且紧凑，但由于彩色滤光片中的光损失，其发光效率较低：每个滤光片仅透射灯发出的约1/3的光通量。为提高这种光学效率，我们建议在单LCD投影仪架构中引入体全息元件。本文介绍了创新系统，其中体全息元件实现了LCD的空间色照明。这种照明包括用相应的视频复合信号有选择地将与原色（红色、绿色或蓝色）对应的所有光导向被寻址像素，并利用体全息光栅和透镜的光谱选择性和色散特性。这种照明的两个主要优点是消除了彩色滤光片，并通过吸收彩色滤光片来恢复传统架构中损失的光。本文给出了对使用体全息元件的空间色照明的完整发光效率分析。将所实现的性能与传统单LCD投影仪进行了比较。
