- For political parties using this acronym, see Democratic Labour Party.
Digital Light Processing (initialised DLP) is a technology used in projectors and projection televisions. DLP was originally developed by Texas Instruments, and they remain the sole manufacturer of such technology, though many licensees market products based on their chipsets.
In DLP projectors, the image is created by microscopically small mirrors laid out in a matrix on a semiconductor chip, known as a Digital Micromirror Device (DMD). Each mirror represents one pixel in the projected image. The number of mirrors corresponds to the resolution of the projected image: 800x600, 1024x768, and 1280x720 matrices are some common DMD sizes. These mirrors can be repositioned rapidly to reflect light either through the lens or on to a heatsink (called a light dump in Barco terminology).
In a projector with a single DLP chip, colors are produced by placing a color wheel between the lamp and the DMD where it is reflected out through the optics. The color wheel is usually divided into 4 sectors: The primary colours: red, green and blue, and an additional clear section to boost brightness. Since the clear sector reduces color saturation, in some models it may be effectively disabled, and in others it is omitted altogether.
A 3-chip DLP projector uses a prism to split light from the lamp, and each primary colour of light is then routed to its own DLP chip, then recombined and routed out through the lens. Single-chip DLP systems are capable of displaying 16.7 million colours, whereas 3-chip DLP systems can display up to 35 trillion colours.
DLP is rapidly becoming a major player in the rear-projection TV market, having sold 2 million systems and achieved a 10% market share. Over 50 manufacturers will be offering models during the 2004 holidays, up from 18 the previous year. DLP chips currently constitute 5% of Texas Instrument's total sales. Small standalone projection units (also called front projectors) utilizing DLP technology have become very popular for office presentation and home theater duties.
- Pros: Smooth, jitter-free images; good color depth and contrast; no burn-in; DLP rear projection TVs are smaller, thinner and lighter than CRT-based models.
- Cons: In single chip designs, some people observe a "rainbow effect".
The DLP "Rainbow Effect"
This visual artifact is best described as brief flashes of perceived red/blue/green "shadows" observed most often when the projected content features bright/white objects on a mostly dark/black background (the scrolling end credits of many movies being a common example). Some people perceive these rainbow artifacts all of the time, while others say they only see them when they let their eyes pan across the image. Yet others do not notice the artifact at all. The effect is likely rooted in the concept of the flicker fusion threshold.
From a technical standpoint, these rainbow shadows are a side-effect of the spinning color wheel used in single-chip DLP projection systems. As such, three-chip DLP systems do not exhibit the rainbow effect. Newer single-chip systems have endeavored to minimize the effect by increasing the speed of the color wheel and hence the rate at which colours are cycled.
DLP and LCoS
The most similar competing system to DLP is known as LCoS (Liquid Crystal on Silicon), which creates images using a stationary mirror mounted on the surface of a chip, and uses a liquid crystal matrix to control how much light is reflected. Intel became a major backer when it very publicly announced plans to manufacture low cost LCoS chips that it hoped would commodify the projection television market. However in October 2004, following problems with the technology and changing market conditions, the project was cancelled.
- DLP Demo by Texas Instruments (Flash) (http://www.dlp.com/dlp_technology/includes/demo_flash.asp?bhcp=1)
- DLP Overview by Texas Instruments (http://www.dlp.com/dlp_technology/dlp_technology_overview.asp)
- "The Great Technology War: LCD vs. DLP" (projectorcentral.com) (http://www.projectorcentral.com/lcd_dlp_update.htm)
- What's so hot about LCOS technology?, a comparison of DLP and LCoS (http://www.projectorcentral.com/lcos.htm)