DLP TV Technology Buying Tips

Background Information:
Digital Light Processing (DLP) is a display technology developed by Texas Instruments. DLP imaging systems employ either one or three large (large for electronic chips, that is) devices called Digital Micromirror Devices, or DMDs. The micromirrors are mounted on the DMD chip and tilt in response to an electrical signal. The tilt directs light toward the screen, or into a "light trap" that eliminates unwanted light when reproducing blacks and shadows.

Who Invented DLP
DLP was invented in 1987 by Dr. Hornbeck of Texas Instruments Inc. He developed the Digital Micromirror Device, or DMD: an optical semiconductor capable of steering photons with unparalleled accuracy. This digital micro-mirror - greatly refined - is the basis of modern DLP technology. In 2002 Dr. Hornbeck was elected Fellow of the International Society for Optical Engineering. The first commercial sub-systems using DLP were shipped in 1996 by nView for use in projectors. In 2001 the one-millionth DLP sub-system was shipped. By 2003 the number of DLP shipments reached 2 million.

How Does DLP Technology Work?
THE DLP SEMICONDUCTOR
At the heart of every DLP™ projection system is an optical semiconductor known as the Digital Micromirror Device, or DMD chip.

The DMD chip is probably the world's most sophisticated light switch. It contains a rectangular array of up to 1.3 million hinge-mounted microscopic mirrors; each of these micromirrors measures less than one-fifth the width of a human hair, and corresponds to one pixel in a projected image.

When a DMD chip is coordinated with a digital video or graphic signal, a light source, and a projection lens, its mirrors can reflect an all-digital image onto a screen or other surface. The DMD and the sophisticated electronics that surround it are what we call Digital Light Processing™ technology.

DIGITAL LIGHT PROCESSING I: THE GRAYSCALE IMAGE
A DMD panel's micromirrors are mounted on tiny hinges that enable them to tilt either toward the light source in a DLP™ projection system (ON) or away from it (OFF)-creating a light or dark pixel on the projection surface.

The bit-streamed image code entering the semiconductor directs each mirror to switch on and off up to several thousand times per second. When a mirror is switched on more frequently than off, it reflects a light gray pixel; a mirror that's switched off more frequently reflects a darker gray pixel.

In this way, the mirrors in a DLP™ projection system can reflect pixels in up to 1,024 shades of gray to convert the video or graphic signal entering the DMD into a highly detailed grayscale image.

DIGITAL LIGHT PROCESSING II: ADDING COLOR
The white light generated by the lamp in a DLP™ projection system passes through a color wheel as it travels to the surface of the DMD panel. The color wheel filters the light into red, green, and blue, from which a single-chip DLP™ projection system can create at least 16.7 million colors. And the 3-DMD chip system found in DLP Cinema™ projection systems is capable of producing no fewer than 35 trillion colors.

The on and off states of each micromirror are coordinated with these three basic building blocks of color. For example, a mirror responsible for projecting a purple pixel will only reflect red and blue light to the projection surface; our eyes then blend these rapidly alternating flashes to see the intended hue in a projected image.

What Is The Estimated Life-Span of a DLP Television?
A DLP-based HDTV set should last indefinitely because the digital micromirror device behind it is very reliable. There is no maintenance or alignment required for DLP based sets as they age. The only consumer replaceable component is the DLP light source (lamp) which will last for 8,000 hours and costs around $250 to replace. The micro-mirrors used in DLP are not subject to degradation due to heat, humidity, vibration or "burn-in".

According to Lars Yoder of Texas Instruments "To test hinge failure, approximately 100 different DMD's (i.e. the DLP chip) were subjected to a simulated 1-year operational period. Some devices have been tested for more than 1 trillion cycles, equivalent to 20 years of operation. Inspection of the devices after these tests showed no broken hinges on any of the devices. Hinge failure is not a factor in DMD reliability".

"The DMD has passed all standard semiconductor qualification tests. It has also passed a barrage of tests meant to simulate actual DMD environmental operating conditions, including thermal shock, temperature cycling, moisture resistance, mechanical shock, vibration, and acceleration testing. Based on thousands of hours of life and environmental testing, the DMD and DLP systems exhibit inherent reliability".

Why Do DLP Television Sets Appear Brighter Than Projection HDTV Sets?
Because the DMD (Digital Micro Device) is a reflective device, it has a light efficiency of greater than 60%, making DLP™ systems more efficient than LCD projection displays. This efficiency is the product of reflectivity; fill factor, diffraction efficiency, and actual mirror "on" time.

LCDs are polarization-dependent, so one of the polarized light components is not used. This means that 50% of the lamp light never even gets to the LCD because it is filtered out by a polarizer. Other light is blocked by the transistors, gate, and source lines in the LCD cell. In addition to these light losses, the liquid crystal material itself absorbs a portion of the light. The result is that only a small amount of the incident light is transmitted through the LCD panel and onto the screen. Recently, LCDs have experienced advances in apertures and light transmission, but their performance is still limited because of their dependence on polarized light.

Seamless Picture Advantage
The square mirrors on DMD's are 16 µm˛, separated by 1 µm gaps, giving a fill factor of up to 90%. In other words, 90% of the pixel/mirror area can actively reflect light to create a projected image. Pixel size and gap uniformity are maintained over the entire array and are independent of resolution. LCDs have, at best, a 70% fill factor. The higher DMD™ fill factor gives a higher perceived resolution, and this, combined with the progressive scanning, creates a projected image that is much more natural and lifelike than conventional projection displays.

A leading video graphics adapter (VGA) LCD projector was used to project the image of the parrot shown below, the pixelated, screen-door effect common to LCD projectors can be easily seen.

The same image of the parrot was projected using a DLP™ projector and is displayed in the right image. Because of the high fill factor of DLP™, the screen-door effect is gone. What is seen is a digitally projected image made up of square pixels of information. With DLP, the human eye sees more visual information and perceives higher resolution, although, as demonstrated, the actual resolution shown in both projected images is the same.

Can A DLP Set Be Used As A PC Monitor?
This depends upon the DLP television set, the current Samsung DLP models are equipped with a PC input 15 pin D-sub jack. This is the same jack that is on the back of your analog PC monitor. Below are the main standards of resolution. The resolution is the number of 'pixels' that the DLP units capable are of displaying. Pixels are the individual dots that make up the image on your computer.SVGA, XGA and SXGA are terms that describe common resolutions used by computers and projectors. The table below shows you the number of pixels that are displayed in each common resolution.

Resolution	Pixels horizontally	Pixels vertically	Approx. total pixels (thousands)
SVGA	800	600	480
XGA (Samsung DLP)	1024	768 (720)	786 (737)
SXGA	1280	1024	1311
UXGA	1600	1200	1920

What size DLP TV screen should I purchase?
The optimal screen size to choose is a function of your viewing distance from the screen - usually constrained by the size of your living room. The "rule of thumb" formula to determine screen size is:

• divide the diagonal screen measurement in half to get an approximate screen height for 16:9 aspect ratio HDTVs
• multiply the height by 3.2 to determine optimal viewing distance for 1080i content, or multiply by 4.8 to get the optimal distance for 720p content.

For example, take a 720p Samsung 43" diagonal HLN4365W, the screen height is roughly 21 inches, which when multiplied by 4.8 yields 100.8 inches, or 8.4 feet as an optimal viewing distance. At a typical living room distance of 10 feet, this screen would be too small to see fine detail on the screen. Backing out the optimal screen size, 10ft is 120 inches, and dividing by 4.8, that would require a 25 inch vertical height, or approximately a 50 inch diagonal HDTV for optimal perception of the 720p screen resolution from 10ft.

Is "Screen Burn" A Problem With DLP Sets?
No. DLP uses a mirror reflective technology so there is no possibility of screen burn. Conventional TV's using CRT's or Plasma displays can sustain after-image damage (i.e. "screen burn") if a static image is left on the screen for too long. There are no phosphors present in DLP sets which can degrade over time.



Further Resources:

	The Digital Display Technology of the Future Abstract: When we compare DLP™ to today's display technologies, it's easy to see why DLP™ has a promising future. Because the technology is digital, DLP™ is able to reproduce life-like color images with precision accuracy. Seamless picture reproduction, high brightness, inherent reliability, the ability to show PC graphics and TV video, and other DLP™ advantages are discussed below. Read this White Paper
	The State of the Art in Projection Display: An Introduction to the Digital Light Processing Technology Abstract: This paper presents an overview of Digital Light Processing (DLP™). It describes the advantages of DLP™ and the fundamental benefits of a digital display system along with system reliability. The way DLP™ works and the advantages of a digital projection system are pieces of information essential to understanding our increasingly digital world. Read this White Paper
	Why is the Texas Instruments Digital Micromirror Device™ so reliable? Abstract: For many people, it is difficult to believe that the Digital Micromirror Device (DMD) is sufficiently reliable for use in today's demanding commercial products. This paper looks at how the DMD 'breaks the rules', and how it attains a level of reliability that enables TI to project that it will have a lifetime in a typical commercial application of greater than twenty-five years. Read this White Paper
	Digital Light Processing™ for High-Brightness, High-Resolution Applications Abstract: This paper describes the design, operation, performance, and advantages of DLP™-based projection systems for high-brightness, high-resolution applications. It also presents the current status of high-brightness products that will soon be on the market. Read this White Paper
	Video Processing for DLP™ Display Systems Abstract: Texas Instruments' Digital Light Processing™ (DLP™) technology provides all-digital projection displays that offer superior picture quality in terms of resolution, brightness, contrast, and color fidelity. This paper provides an overview of the digital video processing solutions that have been developed by Texas Instruments for the all-digital display. The video processing solutions include: progressive scan conversion, digital video resampling, picture enhancements, color processing, and gamma processing. Read this White Paper

Click Here for a Macromedia Flash Movie from Texas Instruments explaining DLP Technology
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DLP TV RESOURCES, REVIEWS AND BUYING TIPS
DLP technology is the only display solution that enables an entirely digital connection between a graphic or video source and the screen in front of you. The result is a picture whose clarity, brilliance and color must be seen to be believed.

• View the current selection of DLP Televisions available at DTVCity
• Background into DLP Technology
• Compare DLP TVs to Direct View, Projection and Plasma Screen TVs.
• Selecting the correct DLP TV screen size.
• Read the latest DLP television reviews
• DLP TV Links
• Read customer testimonials on DTVCity's excellent service

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