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An infrared (IR) light emitting diode (LED) is an electronic method of creating infrared light. This makes an IR LED illuminator a method of lighting up an area using infrared light. Since infrared is outside the visual range of the vast majority of people, this is essentially bathing an area in totally invisible light. On the other hand, if the area is monitored by a device capable of seeing into the IR range, then the area may be brightly lit to that device alone. It is possible to find an IR LED illuminator in several places, but they are likely most common in security systems.
Infrared sits just below visible light in the electromagnetic spectrum. While some humans and a few species of animals can see into the IR spectrum, this is a very uncommon ability. For most people, anything making infrared light is just as dark as an unplugged lamp. Though we can’t see it, we interact with and emit infrared radiation all the time, mostly through heat.
A light emitting diode is a type of semiconductor. One end of the diode is designed to generate photons as electricity passes through a gap. The size of the gap determines the color of visible light or the band of non-visible light created by the diode. In addition to visible and infrared, an LED can create ultraviolet or mixed band light.
Since infrared light exists outside of human vision, it can be all around without anyone seeing it. Most household remote controls operate by pulsing very bright bursts of IR light. These bursts can be ‘seen’ by a receiver on the associated device and translated into commands. If humans could see this light it would be distracting and troublesome, but it is outside human vision range.
An IR LED illuminator works on the same basic principle. These devices work like floodlights of IR light. They can blanket large areas in constant IR illumination that is outside a human’s ability to perceive. Typically, cameras are set up that record in the IR spectrum but translate the image to one humans can recognize.
These IR LED illuminator and camera setups are used heavily in security systems. Since the light is invisible, and there may be no visible light sources nearby, people will let their guard down because they believe they can’t be seen. This will make ordinarily careful criminals make common mistakes, such as showing their faces to the camera. From the system’s point of view, the IR LED illuminator has made the area bright as day.