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Digital Light Processing

January 17, 2002

Digital light processing, or DLP, produces sharper and brighter images for television, cinema and computer screens. The system projects light using a digital micromirror device, or DMD, a chip that contains as many as 1.3 million mirrors. Each mirror reflects light for one pixel of the projected image. Hinges tilt the mirrors to reflect or deflect light, thus producing light and dark pixels. A color wheel between the light source and the DMD spins several hundred times a minute; when the light source hits the wheel, color falls on the mirrors. The systems processor coordinates the positions of each mirror so the appropriate mirrors face the light source at the time the correct color is projected.

Conventional Television

Conventional televisions display images with a cathode ray tube. The cathode, or heated filament, creates a beam of electrons, which carry a negative charge and are attracted to a positive anode. When the beam hits the other end of the tube, its phosphor coating illuminates. Wires wrapped around the tube move the beam horizontally and vertically. Color televisions have three electron beams and three types of phosphors, one for each pixel: red, blue and green.

Condensing lens: Focuses light on color filter.

Shaping lens: Forms the light beam into a rectangular shape so it falls directly on the DMD. Color filter: Contains three colors: red, blue and green. Others are produced when the mirrors rotate to reflect multiple colors. Purple, for example, is created when a mirror rotates between red and blue.

DMD: Spans about 1 inch diagonally. Each mirror on the DMD is about one-fifth the width of a human hair.

Processor: Interprets incoming video signal and determines which mirrors should be turned on and off to reflect a certain color.

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Sources: Texas Instruments, www.howstuffworks.com

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Researched by CHRISTINE FREY / Los Angeles Times MARK HAFER / Los Angeles Times

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