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Surveillance-camera-sensor: what should I know? The Surveillance-camera-sensor or imager of surveillance cameras, translates a visual image, projected on its surface by a Camera lens, into an electronic one made of pulses capable of being collected, transmitted, stored and retrieved. Modern cameras are based on reliable and inexpensive solid state devices as their imagers. As explained in the following, two types of chips compete for primacy. The Surveillance-camera-sensor for CCTV Surveillance Cameras uses either one of two different technologies represented by CMOS (Complementary Metal Oxide Semiconductor) or CCD (Charge Coupled Device) chips. They perform essentially the same function of converting light photons into electrons. The whole surface of the Surveillance-camera-sensor is divided into tiny picture elements or pixels. Each such element is called a photodiode. Upon exposure, every pixel becomes charged with electrons, proportionally to the intensity of light. They accumulate signal charge in each pixel proportional to the local illumination intensity. The video signal to be further transmitted, is obtained by scanning the image on the Surveillance-camera-sensor pixel by pixel, according to a well defined protocol, and collecting the information on brightness and color in a streaming waveform. See Fundamental Concepts. It should be understood that the current polemics on advantages and disadvantages of a Surveillance-camera-sensor employing one technology vs. the other one is highly technical and not clearly cut. As with many other applications, each one deals better with a certain set of conditions, while a compromise is accepted for other cases. The proponents of each one have strong interests and huge investments to defend. Therefore opinions sustained with force and determination by their champions must be considered with a critical eye. Some of the opinions are reflected in the next paragraphs, which may be probably challenged by more recent or future progress. One should also consider that the field is very dynamic and that improvements are constantly being introduced, driven by market forces, so that what appeared as an advantage for one type at a certain time, may be no more valid at another time. At the present time CMOS-based Surveillance-camera-sensors perform well in environments where the light is consistent, like in an inner office where the same interior lights are always on. It is not considered quite suitable for outside use in bright sunlight. It is also less sensitive in low light situations, making this chip technology less than desirable for outdoor night use. CMOS chips (less expensive), provide lesser quality images, but with much less power consumption, an important consideration for battery operated units. CCD chips are typically designed to satisfactorily collect images in environments where the light level is either low or high and variable.
Tiny and/or low price CCTV cameras usually use CMOS technology for Surveillance-camera-sensor. They produce limited quality video and have relatively poor light sensitivity. Higher quality and better CCTV cameras use CCD technology for general applications. But this is not a static situation, in that incremental progress is constantly implemented and prices are in a down trend. A technical article that throws more light on the subject, and other publications with further reference on relative merits and drawbacks of both technologies, can be found online at The struggle for pre-eminence has benefited both technologies, with both striving to improve quality and reduce costs and at this time the race is not yet clearly cut. The electronics embedded in the chips and accessory circuits is complex, including synchronizing and accessory functions. Any further discussion becomes soon too highly technical to be useful for a presentation conducted in general terms.
Format The size of the Surveillance-camera-sensor chip is normally 1/4", 1/3" or 1/2". As a rule of thumb, the larger the size, the higher the quality of the image produced and the higher the price. However, higher density 1/4" and 1/3" CCD chips can now produce as good an image as many older 1/3" or 1/2" chips. The make of the Surveillance-camera-sensor in the camera is important. Known and respected manufacturers produce higher quality chips, even if the specifications are the same than those of less renowned firms. 3CCD Although probably too expensive to be adopted for home surveillance, one more solution for high end products should be mentioned here. For color video capturing at high resolution, if needed, one should investigate the 3CCD Surveillance-camera-sensor technology. It reproduces color in great fidelity, with three separate CCDs for reds, greens and blues (RGB) that are divided using special prisms. The same technology is used in professional broadcasting equipment. It is available with 540 lines of resolution. This gain is somewhat reduced by the fact that the format is usually smaller (probably to contain costs).
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