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By selection of different semiconductor materials, single-color LEDs can be made that emit light in a narrow band of wavelengths from near-infrared through the visible spectrum and into the ultraviolet range. The required operating voltages of LEDs increase as the emitted wavelengths become shorter (higher energy, red to blue), because of their ...
LED development began with infrared and red devices made with gallium arsenide. Advances in materials science have enabled making devices with ever-shorter wavelengths, emitting light in a variety of colors. LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface.
Remote controls and IrDA devices use infrared light-emitting diodes (LEDs) to emit infrared radiation which is focused by a plastic lens into a narrow beam. The beam is modulated, i.e. switched on and off, to encode the data. The receiver uses a silicon photodiode to convert the infrared radiation to an electric current. It responds only to the ...
To drive the LED, a computer-controlled pin is turned on and off at the right time. Cross-talk from the LED to the receiving PIN diode is extreme, so the protocol is half-duplex. To receive, an external interrupt bit is started by the start bit, then polled a half-bit time after following bits.
An early Xerox optical mouse chip, before the development of the inverted packaging design of Williams and Cherry. The first two optical mice, first demonstrated by two independent inventors in December 1980, had different basic designs: [1] [2] [3] One of these, invented by Steve Kirsch of MIT and Mouse Systems Corporation, [4] [5] used an infrared LED and a four-quadrant infrared sensor to ...
A single multicolor module may have three individual LEDs within that package, one each of red, green and blue, to allow many colors or shades of white to be selected, by varying the brightness of the individual LEDs. LED brightness may be increased by using a higher driving current, at the cost of reducing the device's lifespan.
The laser diode chip removed and placed on the eye of a needle for scale A laser diode with the case cut away. The laser diode chip is the small black chip at the front; a photodiode at the back is used to control output power.
An external yellow photographic filter is used (Wratten #12 or equivalent) to block the blue and violet wavelengths, which results in a false-color image by translating or remapping the captured spectrum (from green through infrared) to the visible spectrum: Infrared wavelengths are mapped to the red color, even though the infrared wavelengths ...