PDF《系统光学》

1 DMD 在投影光学系统中的使用概述

2 2 投影光学系统架构

2 2.1 平行光路架构

3 2.2 非平行光路架构

5 3 投影光学系统设计考虑因素

8 3.1 照明系统组件和设计参数

8 3.2 投影系统组件和设计参数

13 4 系统性能调优技巧与方法

15 4.1 对比度比

15 4.2 流明

19 4.3 优化光学成本

19 5 替代光源和系统

21 5.1 LED 光源

21 5.2 激光光源

24 5.3 非成像或非投影应用

25 插图清单

1 一个 12°微镜的简化光学功能

2 2 采用 TIR 棱镜的通用平行光路光学系统组件

3 3 针对因投影透镜偏移引起的最小封装高度的平行光路 TIR 棱镜设计布局

4 4 非平行光路光学系统组件

6 5 投影偏移对于照明角度的影响, 非平行光路设计, 侧视图

7 6 针对采用反射式和折射式照明元件之平面投影机的非平行光路光学系统布局 (等轴视图)7

7 积分前(左侧,在柱输入)及积分后(右侧,在柱输出)小型弧光灯在椭圆形反射器焦点处的空间辐 射照度分布

12 8 TIR 棱镜空气间隙中的受抑全内反射 (TIR) 应偏向照明路径

13 9 散射入射光束几何结构

16 10 散射光进入用于 Off 态微镜的投影光瞳,10° 器件

16 11 对比度和流明与照明角度的函数关系(针对 F/3 平行光路系统)17

12 0.9 XGA 的梯形失真(依据投射比和偏移)20 ZHCA631 - July

2010 0? -24? 24? 48? On State (+12 deg.) Off State (-12 deg.) Flat State F/2.4=24? Overview of DMD Use in Projection Optical Systems www.ti.com

1 Overview of DMD Use in Projection Optical Systems The DMD device is the heart of DLPTM projection systems. The device is a bistable spatial light modulator, consisting of an array of movable micromirrors functionally mounted over a CMOS memory cell. Each mirror is independently controlled by loading data into the memory cell below the mirror to steer reflected light, spatially mapping a pixel of video data to a pixel on a display. The data electrostatically controls the mirror'

s tilt angle in a binary fashion, where the mirror states are either +X degrees (on) or -X degrees (off). For current devices, X is typically

12 degrees (nominal). Light reflected by the on mirrors then is passed through a projection lens and onto a screen. Light is reflected off to create a dark field, and defines the black-level floor for the image. Images are created by gray-scale modulation between on and off levels at a rate fast enough to be integrated by the observer. Figure 1. Simplified Optical Function of a 12-Degree-Mirror-Tilt Device Flat state (zero) occurs when the mirrors are not energized. This is not an active state of the DMD mirrors (not tristable). The resting position of the mirrors nominally is zero degrees, but the mirrors are not controlled or actuated to this position and may vary from it slightly. Flat-state mirrors exist only when the device is turned off, or parked, and no image is being formed. This application report deals only with image effects and interactions between the device and the optical system. Therefore, it is more useful to think of flat state as the integrated energy falling in the area between on- and off-state pupils during transitions of the active mirror states, plus any fixed flat-surface contributions from the device package such as window reflectance, border metal, window-aperture reflectance, lenses or prisms, etc.

2 Projection Optical System Architectures Optical systems for single-panel projection applications can be grouped into two main architectures by describing the conditions at the device. Each type has unique advantages or disadvantages that determine suitability for a given application, depending on the most critical performance parameters for that application. Pros and cons of architectures, along with distinguishing performance characteristics for certain applications, are discussed in general terms. Because DMD devices are reflective, the illumination and projection paths to the device share the same space in front of the device. The architectures described below are typical ways to separate these paths in that space. Since the mirror hinges are along the diagonal of the mirror, the mirrors rotate about an axis