DLP (Digital Light Processing) is a rear projection technology that uses a chip with hundreds of thousands of tiny mirrors to reflect light and produce a picture. This chip is produced exclusively by Texas Instruments and is called a DMD (Digital Micromirror Device) chip. The picture below shows a DMD chip with a zoomed in section showing the microscopic mirrors in comparison to an ant leg.
Each mirror in the DMD chip above represents one or two (depending on the chipset) pixels. Each mirror can tilt very rapidly to reflect light onto the screen or off the screen. When the mirror is tilted away from the screen, the pixel corresponding to the mirror will be black. When the mirror is tilted onto the screen, the pixel will light up with the reflected color. Each mirror can tilt over a thousand time per second, which is too fast for our eyes to see. A matrix of these rapidly moving mirrors is what produces an image.
Older DLP models used a spinning color wheel to add color to the image. The color wheel consists of multiple colors making up red, green, and blue that change the reflected light off of the mirror to a specific color. The mirrors tilting with reflected light is timed precisely with a specific color in the rapidly rotating color wheel; therefore, producing a colored pixel. Newer LED based models get rid of the color wheel and use red, green ,blue LEDs instead.
To Wobble or Not to Wobble
That is the question … Wobulation is the humorously coined term when a single mirror is used for two pixels. The mirror spends 1/120th of a second on one pixel and then wobbles over to the adjacent pixel, and spends 1/120th of a second there. Therefore, using the same mirror to produce 2 pixels in 1/60th of a second. Once again, this rapid motion is too fast for our eyes to see. The advantage of wobulation is a reduction in manufacturing costs since only half the mirrors are needed. Some also say that the picture is smoother and flows better. The disadvantage of wobulation is lower sharpness and clarity levels.
Know your DLP chipsets. There are noticeable picture quality differences between each chipset. There are also noticeable cost differences. As time goes on, Texas Instruments improves the quality of each chipset. Below is a list of DLP chipsets with HD2 being the oldest and xHD4 being the newest.
- HD2 – 1280 x 720 mirrors, no wobulation is used to produce a resolution of 720p with a 1500:1 contrast ratio.
- HD3 – 640 x 720 mirrors, wobulation is used to produce a resolution of 720p with a 2000:1 contrast ratio.
- HD2+ - 1280 x 720 mirrors, no wobulation is used to produce a resolution of 720p with a 2500:1 contrast ratio.
- HD4 - 640 x 720 mirrors, wobulation is used to produce a resolution of 720p with a 2500:1 contrast ratio.
- xHD4 - 960 x 1080 mirrors, wobulation is used to produce a resolution of 1080p with a 10,000:1 contrast ratio.
Production UpdateMitsubishi is the last of the DLP rear projection manufactures and they are now focusing more on their LaserVue technology. DLP models from the last two years have moved towards the use of LED backlighting instead of a bulb and color wheel. LED backlighting reduces the need to replace bulbs and increases the reliability of TVs with the removal of the spinning color wheel. The lack of a color wheel also eliminates the "rainbow effect" which a small portion of the population experinced.
- Great contrast ratio
- Great colors
- Great picture quality
- No burn-in. Important if you watch a lot of 4:3 images or use a HTPC
- High brightness levels – viewable in bright room
- No motion blur – important for sport fanatics
- Rainbows - quick flashes of colored light on the edge of sharp transitions from black to white. Could be very aggravating, but only a small amount of people see them. Not a problem with newer LED based DLP TVs.
- Low vertical viewing angles.
- Changing a bulb required approximately every 4000 hours. Not a problem with newer LED based DLP TVs.
- Typically around 15 inches in depth, so not wall mountable.
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