What is a need of an IR illuminator?
A human eye cannot see the things in dark. The IR illuminators emit infrared light which is invisible to the human eye. But through this light a camera can see the things at night. It is useful in night surveillance. An illuminator contains an IR led around the camera which increase the performance of surveillance camera at night. This increase the night surveillance without any addition light .
I am using AXTON IR illuminator . I find it very useful at night surveillance. If you are thinking of buying any IR illuminator then go for it.
http://www.axtontech.com/at-7a-infrared-illuminator-940-nm/