BASICS OF CCTV CAMERAS

All CCTV CAMERAS are composed of three basic elements:

IMAGE SENSOR – Converts light Image to electric signals

LENSES – Gathers light reflected from a subject.

IMAGE PROCESSING CIRCUITRY – Organizes, Optimizes, and transmits signals.

 

The heart of the modern CCTV camera is the Charge Coupled Device (CCD) sensor. A CCD consists of a flat array of tiny, light-sensitive photodiodes that converts light into an electrical signal. Each diode produces a voltage that’s directly proportional to the amount of light falling on it. No light would produce zero voltage, and therefore, a black level. Maximum light would produce a maximum voltage (a white level). In between these extremes are shades of grey. In the case of a color camera, a chrominance signal is superimposed onto the luminance signal to carry the color information.

The camera processes this electrical signal and converts it to a video signal output, which is then recorded or displayed on a monitor. The range of light levels that a CCD can handle is somewhat limited, so the light range that the CCD receives must be restricted within certain

limits.

LENSES:

Lenses are the “eyes” of a CCTV system. They are essential for creating video functions. Lenses perform two main functions: First, it determines the scene that will be shown on the monitor –this is a function of the focal length. Second, it controls the amount of light reaching the sensor – this is a function of the iris. Focal length can be fixed or variable (e.g., a zoom lens). The iris

may be manually adjusted or automatically controlled by the camera.

Lens can be classified in to 4 types they are

1)    Fixed focal length lenses

2)    Varifocal Lenses

3)    IR corrected Lenses

4)    Motorized Zoom Lenses.

IMAGE PROCESSING CIRCUITRY:

organizes, optimizes, and transmits signals

 

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