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Digital Light Processing (DLP) is a trademark owned by Texas Instruments, representing a technology used in projectors and video projectors. It was originally developed in 1987 by Dr. Larry Hornbeck of Texas Instruments.
One application is DLP front projectors (small standalone projection units), another is DLP rear projection television.
DLP, along with LCD and LCoS, are the current display technologies behind rear-projection television, having supplanted CRT rear projectors.
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Encyclopedia
Digital Light Processing (DLP) is a trademark owned by Texas Instruments, representing a technology used in projectors and video projectors. It was originally developed in 1987 by Dr. Larry Hornbeck of Texas Instruments.
One application is DLP front projectors (small standalone projection units), another is DLP rear projection television.
DLP, along with LCD and LCoS, are the current display technologies behind rear-projection television, having supplanted CRT rear projectors. These rear-projection technologies compete against LCD and Plasma flat panel displays in the HDTV market.
DLP is also one of the leading technologies used in digital cinema projection.
In March 2008, TI announced the initial production of the DPP1500 Chipset, which are micro projectors to be used in mobile devices. Availability for final products would show up in the market early 2009.
Digital micromirror device
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 or more pixels in the projected image. The number of mirrors corresponds to the resolution of the projected image (often half as many mirrors as the advertised resolution due to wobulation). 800x600, 1024x768, 1280x720, and 1920x1080 (HDTV) 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).
Rapidly toggling the mirror between these two orientations (essentially on and off) produces grayscales, controlled by the ratio of on time to off time.
Color in DLP projection
There are two primary methods by which DLP projection systems create a color image, those utilized by single-chip DLP projectors, and those used by three-chip projectors. A third method, sequential illumination by three colored light emitting diodes, is being developed, and is currently used in televisions manufactured by Samsung.
Single-chip projectors
In a projector with a single DLP chip, colors are either produced by placing a color wheel between the lamp and the DLP chip or by using individual light sources to produce the primary colors, LEDs for example. The color wheel is divided into multiple sectors: the primary colors: red, green, and blue, and in many cases secondary colors including cyan, magenta, yellow and white. The use of the secondary colors is part of the new color performance system called BrilliantColor™ which processes the primary colors along with the secondary colors to create a broader spectrum of possible color combinations on the screen.
The DLP chip is synchronized with the rotating motion of the color wheel so that the green component is displayed on the DMD when the green section of the color wheel is in front of the lamp. The same is true for the red, blue and other sections. The colors are thus displayed sequentially at a sufficiently high rate that the observer sees a composite "full color" image. In early models, this was one rotation per frame. Now, most systems operate at up to 10x the frame rate.
Older DLP systems and the "rainbow effect"
DLP chips exhibit an anomaly known as the “rainbow effect”. While this has been improved with faster color wheels over the years (2x is standard in most business projectors), some people will still be able to notice this effect. This is best described as brief flashes of perceived red, blue, and 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 are a common example). Some people would perceive these rainbow artifacts frequently, while others may never see them at all. With the advent of increased color wheel speeds or projectors featuring LED illumination, the “rainbow effect” has been virtually eliminated.
Three-chip projectors
A three-chip DLP projector uses a prism to split light from the lamp, and each primary color of light is then routed to its own DLP chip, then recombined and routed out through the lens. Three chip systems are found in higher-end home theater projectors, large venue projectors and DLP Cinema® projection systems found in digital movie theaters.
According to DLP.com, the three-chip projectors used in movie theaters can produce 35 trillion colors, which many suggest is more than the human eye can detect. The human eye is suggested to be able to detect around 16 million colors, which is theoretically possible with the single chip solution. However, this high color precision does not mean that DLP projectors are capable of displaying the entire gamut of colors we can distinguish (this is fundamentally impossible with any system composing colors by adding three constant base colors).
Light source
The main light source used on DLP-based rear screen projection TVs is based on a replaceable mercury vapor arc lamp unit (containing a quartz arc tube, reflector, electrical connections, and sometimes a quartz/glass shield), while in some newer DLP projectors high-power LEDs are used as a source of illumination.
For mercury types, during start-up the lamp is "ignited" by a 5000V pulse from a current-regulating ballast to initiate an arc between two electrodes in the quartz tube. After warmup, the ballast's output voltage drops to approximately 60 volts while keeping the relative current high. As the lamp ages, the arc tube's electrodes wear out and light output declines somewhat; eventually, the required startup voltage will also rise to the point where ignition can no longer occur. In the rarest, most extreme situations, the quartz arc tube can crack and/or explode; however, practically all lamp housings contain heat-resistant barriers (in addition to those on the lamp unit itself) to prevent the red-hot quartz fragments from leaving the area. The mercury lamp's end of life is typically indicated via an LED on the unit, necessitating replacement of the lamp unit.
The first commercially-available LED-based DLP HDTV was the Samsung HL-S5679W in 2006, which also eliminated the use of color wheel. Besides long lifetime eliminating the need for lamp replacement and elimination of the color wheel, other advantages of LED illumination include instant-on operation and improved color, with increased color saturation and improved color gamut to over 140% of the NTSC color gamut. Samsung expanded the LED model line-up in 2007 with products available in 50", 56" and 61" screen sizes. For spring 2008, the third generation of Samsung LED DLP products are available in 61" (HL61A750) and 67" (HL67A750)screen sizes.
Ordinary LED technology does not produce the intensity and high lumen output characteristics required to replace arc lamps. The special patented LEDs used in all of the Samsung DLP TVs are PhlatLight LEDs, designed and manufactured by US based Luminus Devices. A single RGB PhlatLight LED chipset illuminates these projection TVs. The PhlatLight LEDs are also used in a new class of ultra-compact DLP front projector commonly referred to as a "pocket projector" and have been introduced in new models from LG Electronics (HS101)and Samsung electronics (SP-P400). Home Theater projectors will be the next category of DLP projectors that will use PhlatLight LED technology. At InfoComm, June 2008 Luminus and TI announced their collaboration on using their technology on home theater and business projectors and demonstrated a prototype PhlatLight LED based DLP home theater front projector. They also announced products will be available in the marketplace later in 2008 from Optoma and other companies to be named later in the year.
Digital Cinema
DLP is the current market-share leader in professional digital movie projection, largely because of its high contrast ratio and available resolution as compared to other digital front-projection technologies. As of December 2008, there are over 6,000 DLP-based Digital Cinema Systems installed worldwide.
DLP projectors are also used in Real D Cinema for 3-D films.
Manufacturers and market place
Texas Instruments remains the primary manufacturer of DLP technology, which is used by many licensees who market products based on T.I.'s chipsets. The Fraunhofer Institute of Dresden, Germany, also manufactures Digital Light Processors, termed Spatial Light Modulators, for use in specialized applications. For example, Micronic Laser Systems of Sweden utilizes Fraunhofer's SLMs to generate deep-ultraviolet imaging in its Sigma line of silicon mask lithography writers.
DLP technology has quickly gained marketshare in the front projection market and now holds roughly 50% of the worldwide share in front projection. Over 30 manufacturers use the DLP chipset to power their projectors.
Pros
- Smooth (at 1080p resolution), jitter-free images.
- Perfect geometry and excellent grayscale linearity achievable.
- Usually great ANSI contrast.
- No possibility of phosphor burn-in.
- Less "screen door effect" than with LCD projectors.
- DLP rear projection TVs generally have a smaller form factor than comparable CRT projectors.
- DLP rear projection TVs are considerably cheaper than LCD or plasma flat-panel displays and can still offer 1080p resolution.
- The use of a replaceable light source means a potentially longer life than CRTs and plasma displays (this may also be a con as listed below).
- The light source is more-easily replaceable than the backlights used with LCDs, and on DLPs is often user-replaceable.
- New LED DLP TVs and projectors eliminate the need for lamp replacement.
- Using two projectors, one can project full color stereoscopic images using polarized process (because beams can be polarized).
- Lighter weight than LCD and Plasma televisions.
- Unlike their LCD and Plasma counterparts, DLP screens do not rely on fluids as their projection medium and are therefore not limited in size by their inherent mirror mechanisms, making them ideal for increasingly larger high-definition theater and venue screens.
- DLP Projectors can process up to 7 separate colors giving them strong color performance
- DLP projectors do not suffer from “Color Decay” often seen with LCD projectors in which the image on the screen turns yellow after extended periods of usage.
Cons
- Some viewers are bothered by the "rainbow effect," explained above.
- Not as thin as LCD or plasma flat-panel displays (although approximately comparable in weight), although some models as of 2008 are becoming wall-mountable (while still being 10" to 14" thick)
- Replacement of the lamp / light bulb. The average life span of a TV light source averages 1-3 years (based upon how often the television is powered on and off and the duration of viewing) and the replacement cost for these range from $99 - $350, depending on the brand and model. After replacing the bulb a few times the cost can easily exceed the original purchase price of the television itself. Newer generations units use LED which effectively eliminates this issue, although a replacement bulb may be required over the extended lifespan of the television.
- Some devices may have fan noise.
- Dithering noise may be noticeable, especially in dark image areas. Newer (post ~2004) chip generations have less noise than older ones.
- Error-diffusion artifacts caused by averaging a shade over different pixels, since one pixel cannot render the shade exactly.
- Response time in video games may be affected by upscaling lag. While all HDTVs have some lag when upscaling lower resolution input to their native resolution, DLPs are commonly reported to have longer delays. Newer consoles such as the Xbox 360 and PlayStation 3 do not have this problem as long as they are connected with HD-capable cables.
- Lower viewing angle than direct-view technologies such as CRT, Plasma, and LCD.
DLP, LCD, and LCoS Rear Projection TV
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 (similar to a Liquid Crystal Display) to control how much light is reflected. DLP-based television systems are also arguably considered to be smaller in depth than traditional projection television.
See also
External links
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- Information about PhlatLight LEDs from Luminus Devices http://www.luminus.com
- LCoS, DLP, 3LCD comparison table http://www.pro-projectors.com/Lcoscompare.htm
- Projector.com DLP page http://www.projector.com/resources/dlpprojectortechnology.php
- BOXLIGHT Corp. DLP White Paper https://system.netsuite.com/core/media/media.nl?id=6485&c=492114&h=25551c21675d994130e9&_xt=.pdf
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