An infrared receiver is a communications device that can respond to emissions very close and below the frequency of visible light. Found in items such as personal computers, home appliances, and cars, the infrared receiver usually relies on a digital coding scheme or a protocol to transfer information or commands across an infrared link. Infrared receivers were used in digital communications due to the ease of setup and the lack of need for licensing, unlike radio transmitters. During fog, rain, or snow, however, the infrared energy is absorbed heavily, leading to link outage. An infrared transmitter can be a semiconductor infrared device that transmits an invisible infrared beam.
The occurrence of a rainbow demonstrates wavelengths close to infrared. It displays the colors red, orange, yellow, green, blue, indigo, and violet (ROYGVIB), with red as the lowest frequency in the spectrum of visible light. If the frequency of red light is decreased, it will be in the invisible infrared spectrum.
Infrared technology is also used in thermal imaging. Popular night vision technology uses an infrared source that makes infrared bounce off targets in total darkness. The received image is then obtained using special lenses and a method of generating the image. These images may be still or displayed in real time video to show real-time images.
An infrared receiver may also work in conjunction with a data transmitter to form a data link. A very convenient way of transferring files to and from computers, accessories, and gadgets is the infrared link. One disadvantage of the infrared receiver is the need to align the transmitter beam to the receiver window. The infrared receiver-sensing element usually has a red filter on the outside, and this is partly to prevent ordinary light from desensing the receiver element.
A typical infrared transmitter is the television (TV) remote control, while the infrared receiver is on the TV itself. By coding the right-pulsed data, the user is able to send commands into the TV control. Different TV manufacturers use different codes on the remote control unit.
The infrared receiver is also used for detecting body temperature from a distance. This makes it possible to detect people with higher than normal body temperature, which is very useful in airports where most people are crossing borders into new countries. By using a real-time display and the various subparts of the infrared spectrum, surveillance for public safety can be done easily.