The image sensor – the heart of a video camera

One of the most important components in a video camera is the image sensor. Two types of sensors are the most widespread: CCD and CMOS.

CCD (charge coupled device)

CCD sensors generate voltages according to the amount of incoming light. After exposure, the charges are shifted incrementally, just like a bucket chain (which is where the term “bucket brigade device” comes from), until they finally reach the output amplifier as a charge package – one after the other. After this, electric voltage is output which corresponds to the charges or the amount of light. Due to this “analog shift register” in video surveillance CCD sensors are generally used for analog cameras. CCDs are characterized by low noise and high light sensitivity. CCDs do however require additional processors to allow image processing functions to be used.

CCD sensor

CMOS (complementary metal oxide semiconductor)

CMOS sensors, also know as active pixel sensors, collect the charges produced by incoming light, just like CCD sensors. There is an output amplifier on every single pixel, which amplifies the signal and assigns it a digital value. Based on the technology, the biggest different between CMOS image sensors and CCD sensors is that each and every pixel is read out. CMOS sensors are less expensive to manufacture than their CCD counterparts and consume considerably less power – as a number of models only require ten percent of the energy of a CCD sensor. In addition, there is only a very slight blooming effect with CMOS sensors. This means that overexposed areas of the image do not obscure the surrounding areas as much, because the excess light is not transferred to the pixel adjacent to the overexposed pixel.

Each pixel tells a story of its own – improving picture quality with Pixim

Is a high contrast ratio expected at the place of use, for example when a gate opens and shuts and causes the area being monitored to change from very dark to very light due to backlight, or is a room which is usually dark occasionally lit up by bright artificial light? Using a special, adaptable adjustment technology is therefore recommended for situations like this, because optimum picture quality depends on every pixel. The day/night cameras in the ABUS Profiline series are therefore equipped with image sensors from Pixim, among other things.

The next generation of CMOS sensors made by the manufacturer Pixim analyse every single pixel and adapt them fully automatically for optimal exposure. This patented technology allows the individual pixels from the surveillance camera with a Pixim sensor to act almost as if they were all self-contained cameras, which adapt to the prevailing light conditions again with every picture made.

The highest resolution, natural colours, absolute clarity and the elimination of visual faults such as glare or reflections are the result. Pixim sensors are far superior to traditional sensors when there is extreme backlight, unpredictable or constantly changing light conditions. The only prerequisite for the use of these sensors is good, sufficient lighting. If the ambient light is too dim, you should place your trust in the good old cameras with CCD image sensors.

ABUS is one of the few Pixim technology partners and therefore involved directly in the ongoing development of this chip technology. This is know-how which benefits our customers.

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