Choosing an IR illuminator for Night Vision
The best choice of wavelength of an IR Illuminator is dependent on the device and its usage.
Gen 1 Analogue tube device up to 760-780nm
Gen 2 Analogue tube device up to 850nm
Gen 2 High End up to 900nm
Gen 3 High End up to 1000nm
Digital Night Vision up to 950-980 nm
Basically two wavelengths are generally available as additional illuminators to give enhanced range above onboard IR.
But there are variant such as 875 or 915
850nm gives the greater range for digital Night Vision the wavelength is invisible to the eye but a slight red glow can be observed if viewed directly.
940nm is completely invisible to the eye and no discernable red Glow can be seen from the emitter but range is decreased by up to 40-50%
Depending on illuminator lens size/wattage/quality the distance viewed can be up to 400 metres and smaller units will be in the region of 200-250 meters
The ability of the unit to focus efficiently will affect the usable range.
Also there are two types of IR emitter LED and Laser (VCSEL)
The laser will give greater range but LED probably will be a cleaner image.
Also with the higher sensitivity of current Night Vision Units there can be a tendency for the image to be washed out at shorter ranges.
Ultimately performance is also affected by the price and quality of unit as the cost can vary from below £50 to some commercial units at £500-£600 or above.