投影式顯示器(Projection Display)

課程大綱

投影機基本概念

投影機種類✔ CRT投影機✔ LCD投影機

✗ High Temperature Polysilicon transmissive (HTP) Liquid Crystal Projector

✗ Liquid Crystal on Silicon (LCoS) reflective Projector

✔ Digital Light Processing (DLP)投影機✗ Digital Micromirror Device (DMD)

參考資料

[1]顧鴻壽﹑周本達﹑陳密﹑張德安﹑樊雨心﹑周宜衡 ..., 光電平面面板顯示器基本概論 , 高立圖書有限公司 , ISBN=986-412-001-8, 2004.[2]顧鴻壽 , 光電液晶平面顯示器技術基礎與應用 , 新文京開發出版有限公司 , ISBN=957-512-433-2, 2002. [3] http://www.projectorpoint.co.uk/projectorLCDvsDLP.htm[4]影像顯示科技種子師資培育計劃課程講義﹐2005。[5] http://www.dlp.com

投影機基本概念

投影機概念示意圖

CRT投影機

CRT投影機原理

LCD投影機

LCD投影機

➢High Temperature Polysilicon transmissive (HTP) Liquid Crystal Projector

➢Liquid Crystal on Silicon (LCoS) reflective Projector

HTP投影機概念示意圖

One Chip LCD Projection Display

Three Chips LCD Projection Display

LCD (liquid crystal display) projectors contain three separate LCD glass panels, one for red, green, and blue components of the image signal being transfered to the projector. As the light passes through the LCD panels, individual pixels can be opened to allow light to pass or closed to block the light. This activity modulates the light and produces the image that is projected onto the screen.

LCD光學結構

LCD光學結構圖

Dichroic Color Splitter

Color Recombination

Three Chips HTP Projector

# LCD is generally more 'light efficient' than DLP (ie. the same wattage lamp in both an LCD and DLP would produce a brighter image through the LCD).

# LCD tends to produce more saturated colors. However, the colors being more saturated makes people perceive the projector to be brighter overall, even though the DLP white may be brighter.

# Hence, with a data signal, if you put a 1000 lumen LCD next to a 1200 lumen DLP and showed a colour image people would probably prefer the LCD for brightness.

# LCD tends to produce a sharper image (ie. more precisely focused). This can actually be a bit of a disadvantage for video, where it makes the pixellation more obvious.

Advantages of LCD

Disadvantages of LCD

# Chicken wire effect causing the image to look more pixellated.

# Generally more bulky, as there are more internal components.

# 'Dead Pixels' - Pixels can become permanently on or permanently off, while this is barely noticeable with one dead pixel, if the projector develops multiple dead pixels it can be a irritation.

# LCD panels can fail, and are very expensive to replace. DLP chips can also fail but as there are fewer parts in a DLP projector this is relatively rare.

LCoS reflective Projector

LCoS reflective Projector

LCoS reflective Projector

On-Axis System Off-Axis System

DLP投影器

Digital Light Processing is the world's only all-digital display solution. DLP technology uses an ™optical semiconductor, known as the Digital Micromirror Device, or DMD chip to recreate source material. Please click on the icon below to launch a Flash demo to show you how it works.

DLP光學結構圖

DLP投影機工作原理

DLP投影機工作原理

DLP投影機工作原理

DLP投影機工作原理

Scrolling Color Recapture (SCR)

Less 'chicken wire' (or 'screen door') effect because pixels are much closer together. This doesn't make so much difference with data, but it produces smoother images for video.

A comparrison of an LCD and DLP projection to illustrate the 'screen door' or 'chicken wire effect on LCD projections.

LCD與DLP投影機比較

# Higher contrast achievable.

# DLP projectors are generally more poratable as fewer components are required.

# It has been claimed that DLP projectors last longer than LCD projectors.

Advantages of DLP

* Less colour saturation (more of a problem with data than video)* The 'rainbow' effect, appearing as a momentary flash of rainbow-like striping typically trailing the bright objects when looking from one side of the screen to the other, or when looking away from the projected image to an offscreen object. Only some people see this effect, or you can create it for yourself by moving your eyes very quickly across the screen. There are two types of DLP projector - the old ones had four segments on the color wheel, the new ones have six and spin faster, which means less rainbow effect and more saturated color.* The 'halo' effect (or 'light leakage'). It may bother some people using their projector for home cinema. Basically it's a grey band around the outside of the image, caused by stray light being bounced off the edges of the tiny mirrors on the DLP chip. It can be a distraction, but can be overcome by having a black border a few inches wide around the screen, so the halo falls on to the border. However the halo effect is less evident in the newer DLP chips such as the DDR chip* Generally, DLP is a better technology for home theater than LCD . Some of the more home theater-oriented projectors have virtually no halo effect.

Disadvantages of DLP

Digital Micromirror Device (DMD)

DMD

DMD 解析圖

DMD 機構解析圖

DMD Chip

LCD於DMD比較

掌上型DLP Projector

結論

結論