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Infrared light

IR light is light that is above the visible light spectrum and affects many different things. IR light cannot be seen. IR and heat is the same thing. The sun emits IR light (heat). Although IR cannot be seen, it can be measured, and some cameras recognise heat the same way that humans can see visible light.

For the most part in the industrial CCTV world, one works with NEAR IR. This is the light band ranging between visible red and actual IR and heat. Red light is 700 nm long -1 nano = 1 billionth therefore red light is 700 billionths of a metre. Each colour from violet to red is 50 nm longer than the preceding one.

Benefits of IR light

There are many situations where light available is limited. In this type of situation an IR lamp will solve the problem. The camera used must be IR sensitive at least at NEAR IR. Another example will be an area where visible light will cause problems, eg prisons, ATMs, defence force installations, night clubs etc.

IR lamp and LED

IR units come in both lamp and LED array. Indoor units should be limited to LED arrays. Lamps should be used for outdoor applications.

The advantage of LED over lamps is that lamps produce a lot of heat compared to LED arrays. The IR lamp operates at longer distances. Since IR lights diminishes with distance, as does visible light, it is recommended that one stay inside the manufacturers distance ratings by at least 10%, ie if a unit is specified at 60 m, the maximum distance should be 54 m. Most LED arrays units have a slight red glow from each LED, which is only visible when one is looking straight at the unit.

Serviceability

Serviceability of the unit is imperative. Some LED array units are rated for up to 100 000 hours. Most lamp style units are rated for 2000 to 4000 hours of usage. One will find that as time progresses, a camera will appear to have less and less sensitivity in the area that is illuminated by IR light. The bulbs in IR lamps can be replaced. The LED array can also be replaced. Daylight sensors can be used to turn off the lamp or LED array during the day when the IR is not required.

For further details contact Abie Ali, Frank Street, on tel: (011) 838 4515.

Infrared: 1100 nm and up

Near-infrared: 1100 nm and up

Red visible light: 700-750 nm

Orange visible light: 650-700 nm

Yellow visible light: 600-650 nm

Green visible light: 550-600 nm

Blue visible light: 500-550 nm

Indigo visible light: 450-500 nm

Violet visible light: 400-450 nm

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