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LED printer

An electrophotographic printer that uses a matrix of LEDs as its light source. The LED mechanism is much simpler than its laser printer counterpart. A stationary array of LEDs is used instead of numerous moving parts, and the LEDs are selectively beamed onto the drum. LED printers are available from inexpensive personal printers to huge digital printing presses that print more than 700 pages per minute (ppm). See LED.

LED Vs. Laser Printing
The LED mechanism is much simpler, because it is a stationary array of light emitting diodes (LEDs) rather than a number of moving parts.

Personal LED Printer
One of the first LED printers, the OKIPAGE 4w was introduced in 1996 at a breakthrough low price of USD $299. At 4 ppm, it printed a respectable 600 dpi. (Image courtesy of Okidata.)

High-Speed LED Printer
These earlier Oce digital printing presses used LEDs to print up to 420 ppm at 300 dpi on continuous forms or roll-fed paper. With a 17" LED array, two letter-sized pages were printed simultaneously. (Image courtesy of Oce Printing Systems USA, Inc.)


(Light Emitting Diode) A display and lighting technology used in almost every electrical and electronic product on the market, from a tiny on/off light to digital readouts, flashlights, traffic lights and perimeter lighting. LEDs are also used as the light source in multimode fibers, optical mice and laser-class printers. See LED lightbulb.

In the early 1970s, red LEDs were used in the first digital watches, but were superseded by lower-power LCDs within a few years. LEDs still use more power than LCDs, but less power than incandescent bulbs. They also last for decades and are virtually indestructible.

LEDs and LCDs coexist on countless devices where the LEDs provide the status lights, and the LCDs display data. In addition, white or red, green and blue LEDs are used as the backlight source on many LCD TV sets. See LCD, LED TV and flat panel TV.

Several Colors
LEDs are semiconductor diodes that typically emit a single wavelength of light when charged with electricity. Originally red, today, several colors can be generated based on the material used for the tips of the probes. Aluminum indium gallium phosphide (AlInGaP) is used for red and yellow. Indium gallium nitride (InGaN) is used for green and blue, and with the addition of phosphor, for white light as well. See digital billboard, OLED, IRED, LED printer, fiber optics glossary and Nixie tube.

An LED Unit
The LED is the semiconductor die, which sits in a reflective cup that is also a heat sink. Voltage is applied to the LED, and electrons and holes in the two semiconductor layers are attracted to each other at the junction. When they combine, photons are created.

LEDs and LCDs Are Used Together
Small alphanumeric readouts can be LED or LCD, but the indicator lights on countless products are LEDs.

First LED Watch
The Synchronar 2100 was the first LED watch and the first solar powered watch. It preceded Hamilton's famous Pulsar LED watch in 1970. (Image courtesy of the private collection of Peter Wenzig.)

LEDs Offer Flexibility
A flick of a switch changes the ambience in this Los Angeles bedroom (top), while the Westin Hotel staircase in Shanghai (bottom) cycles colors or becomes a musical light show. (Images courtesy of Color Kinetics, Inc., Bedroom design and photo by Steven Cordrey. Staircase by Light Directions Hong Kong, photo by Friendly Light.)

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