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An infrared light-emitting diode (LED) is a type of electronic device that emits infrared light not visible to the naked eye. An infrared (IR) LED operates like a regular LED, but may use different materials to produce infrared light. This infrared light may be used for a remote control, to transfer data between devices, to provide illumination for night vision equipment, or for a variety of other purposes.
An infrared LED is, like all LEDs, a type of diode, or simple semiconductor. Diodes are designed so that electric current can only flow in one direction. As the current flows, electrons fall from one part of the diode into holes on another part. In order to fall into these holes, the electrons must shed energy in the form of photons, which produce light.
The wavelength and color of the light produced depend on the material used in the diode. Infrared LEDs use material that produces light in the infrared part of the spectrum, that is, just below what the human eye can see. Different IR LEDs may produce infrared light of differing wavelengths, just like different LEDs produce light of different colors.
A very common place to find an infrared LED is in a remote control for a television or other device. One or more LEDs inside the remote transmit rapid pulses of infrared light to a receiver on the television. The receiver then decodes and interprets these pulses as a command and carries out the desired operation.
Infrared light can also be used to transfer data between electronic devices. Mobile phones, personal digital assistants (PDAs), and some laptops may have an infrared LED and receiver designed for short-range data transfer. Some wireless keyboards and computer mice also use an IR LED and receiver to replace a cable.
Although invisible to human eyes, many types of cameras and other sensors can see infrared light. This makes infrared LED technology well-suited to applications like security systems and night vision goggles. Many security cameras and camcorders use IR LEDs to provide a night-vision mode. Hunters may use similar equipment to spot game at night, and some companies sell flashlights with an infrared LED to provide extra illumination for night-vision cameras or devices.
Infrared LEDs can be used for a variety of other purposes. The U.S. Food and Drug Administration has approved several products with IR LEDs for use in medical or cosmetic procedures. Robots may use an infrared LED to detect objects, and some utility meters even have an IR LED to transmit data to a tool for easy meter reading.
A lot of Sony cameras have a "night shot" mode which is near-IR. If you add a Wrattan #87 filter it brings it up to full IR capacity. You can get some really interesting photographs this way from what I've seen.
Infrared light is also used in crime scenes. It's capable of doing interesting things like visualizing gunshot residue or the writing of a burned document.
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