Infrared Use in Video Security

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Infrared lighting is one key component of several in video security system design. Others are camera selection and placement, lens selection and general lighting.

Determining lighting for any given scene is absolutely essential and infrared light or infrared security cameras could play a part. Light is typically measured in video security by the Lux level. The lower the Lux level, the lower the amount of light for a given scene.

IR light is invisible to the human eye. Light that we can see is measured by nanometers on a scale of 400nm to approximately 700nm. IR light is in the range of 700nm to 1100nm. The light we see is only a small fraction of the actual light waves that exist.

We experience IR when we feel heat from the sun or from a fire. That is thermal infrared. A very common use of IR is in remote controls and motion detectors.

LED’s or light emitting diodes are most often used to create Infrared light. LED’s are lights that do not have a filament and do not typically get very warm light a normal light bulb would. They are illuminated solely by the movement of electrons over a semiconductor material. They last as long as a standard transistor and are very energy efficient. They can be made to display infrared light or visible light.

IR LED’s may be built into a camera to support the cameras night vision capabilities. Infrared illuminators or arrays may also be used to give additional distance and increased area of coverage.

IR imaging is used in both civilian and military applications. Military applications include target acquisition, night vision, homing and tracking. IR imaging should not be confused with thermal imaging.

Active infrared night vision combines infrared illumination in the spectral range of 700nm to 1000nm which is just below the visible spectrum to the human eye. CCD cameras are sensitive to this light when the IR cut off filter is removed. The resulting scene, which is apparently dark to a human observer, appears as a monochrome image on a normal display device.

Key considerations for using Infrared in video security are the effective distance of the IR LED’s being used and the reflectivity of objects in the scene. You need to find out for sure what the effective distance of the IR LED’s used in the camera will be when making your selection. It will help determine which camera will work for a given scene. Infrared light is absorbed by things like asphalt, grass, etc., while it is reflected by other objects. Only items that create a reflection will be seen by the camera.

The wavelength for most security cameras of the Infrared light is in the 700nm to 850nm range. At this level the LED’s on the camera will glow a slight red.

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