The human eye can detect light wavelengths from approximately 380 to 740 nanometers. This spectrum is also called the visible light. Wavelengths of light that are beyond the visible spectrum (visible light) are longer wavelengths and are called infrared wavelengths, or infrared light.
An infrared illuminator is simply said a flashlight that emits light in an infrared spectrum.
It is invisible to the human eye, but visible for night vision devices.
IR illuminators are available in different wavelengths, which tells us also, in combination with what kind of night vision they are designed to be used.
LED infrared illuminators are the most common illuminators on the market. An LED is a semiconductor light source that emits light when current flows through.
LED infrared illuminators feature one or more Light Emitting Diodes (LEDs) which produce the infrared light.
Pulsar AL-915T IR Illuminator
The older LEDs gave a small amount of light, but the newer are extremely strong. They almost completely replaced the older illuminators with an incandescent bulb because of many advantages.
Compared to the older illuminators with an incandescent bulb, they do not need an additional lens which lets through only the light in the infrared spectrum. LED 's can be built so that they radiate the light in a very narrow wavelength spectrum. They are also a lot more resistant to shocks, which is especially important if they are mounted on a clip-on night vision device, or directly on a rifle.
They have a very good infrared light output for a very small amount of energy used. That means, with a single battery the illuminator can work for many hours without a noticeable difference in power.
Most LED infrared illuminators on the market are very small and easy to mount on a night vision device or directly on the rifle. Of course, there are some exceptions, but the bigger illuminators are designed for extreme distance observations and feature a high infrared light output.
The energy LED 's use is very small, so a single battery can be used for many hours.
LEDs are also a lot more resistant to shocks compared to an incandescent bulb infrared illuminator. Because the light output is not "coherent", one illuminator can be used for many types of night visions. This means a LED illuminator with an advertised wavelength of 875nm radiates light from approximately 850nm up to 900nm. Because of that, it is visible for Gen. 2 and Gen. 3 night vision devices, but also for digital night vision devices.
Because the light out of an LED illuminator is not "coherent", this can also be a disadvantage:
For example, an LED illuminator with a given wavelength of 850nm can radiate light from approximately 825nm up to 875nm.
As we know, some animals can detect the light up to 850nm wavelength, so for them, it could be visible.
This is especially noticeable on cheap infrared illuminators, where the radiation has a much bigger spectrum, for example from 800nm up to 900nm.
Another disadvantage is especially noticeable on adjustable beam illuminators. When the light is focused on a small point for long-distance observations, the light gets a square shape. Normally it does not affect the image quality, but some users do not like it.
When buying an infrared illuminator, you have to be cautious what is the maximal wavelength your night vision can detect. If the emitted light of your infrared illuminator is beyond the spectrum, it is invisible for such a device.
For Gen. 1 NV devices an IR illuminator with a wavelength between 750nm and 780nm,
For Gen. 2 an illuminator an IR illuminator with a wavelength of 850nm, or even higher (up to 900nm) if you own a high-quality IIT in your device.
For Gen. 3 an IR illuminator is mostly not needed, but one with a wavelength of 850nm - 900nm would work perfectly
For a digital night vision devices an IR illuminator with a wavelength between 850nm and 980nm
Night vision optics are mostly used for hunting purposes. Because of that, the manufacturers developed many types of mounting solutions for their IR illuminators.
The most common are IR illuminators with a 30mm main tube, so a normal rifle scope mounting ring can be used. This one can be then attached to the optic itself, or directly on the rifle.
The most common mounting solutions on NV optics are short 11-millimeter dovetail rails or short Picatinny rails.
For mounting on the rifle, it is the easiest way to use a mounting ring for a Picatinny rail. Thanks to that, it can be mounted anywhere on the rail.
If you don´t have a Picatinny rail mounting solution on your rifle, then a clamp-mount can be used. This can be clamped directly on your rifle scope or the rifle barrel.
A short presentation of LED IR Illuminators is available here.