Inside the Camera: Traditional CCD or Tomorrow's CMOS Chip?

CMOS manufacturers debut a variety of chips that may change the 'guts' of surveillance


While our industry has installed many a camera, often not much thought at the dealer level is given to the actual guts of the camera. The focus is always on whether the camera can give you the images that the user requires, and often what price that will cost, and how simple it is to install and maintain.

However, there is a slight movement in our industry, at least among manufacturers, that is wrestling over the guts inside that camera. On many a camera's spec sheet, you'll notice a line about the sensor. It's either a CCD or CMOS, the two standard technologies used to capture light in such a way that it represents as close as possible to what the eye would see.

In the world of professional security cameras, the CCD has been the standard. The CCD, or charge coupled device, is basically a small chip that is sensitive to light. This silicon chip essentially receives light and turns it into voltage variations -- the data of an image. It's usually measured in inches -- the 1/3" CCD is the standard imager you'll find in video cameras used for professional security, but it's by no means the only one. Other sizes include 1/4", 1/3", 1/2" and even 2/3". In higher-end broadcast cameras, larger CCDs have been used and some of these high-fidelity manufacturers have even used three CCDs to expertly capture the image.

On the other side of the court is the CMOS chip, which was actually developed slightly before the CCD (both technologies were first developed in the 1960s and pushed forward by companies like Fairchild Semiconductor and RCA). CMOS stands for complementary metal oxide substrate, and at it's core, it does the same thing a CCD sensor does. It absorbs light and converts that into data. Like CCDs, CMOS chips are measured and usually size in inch measures, with 1/4" and 1/3" as the most common. The interesting thing about the CMOS chips it that they don't have to be used exclusively for imaging. They basically are memory chips, and are used that way in many devices, including personal computers.

OK, you say, what's so important about all this?

The key to keep in mind is that the CCD has been the standard for video cameras for a long time. If you've got a stack of old camera spec sheets, we'll venture to bet that you can find the CCD listed as the sensor on even your fairly old cameras, while you'd be highly unlikely to find a CMOS chip listed.

That just might be changing.

A variety of manufacturers, including Micron, Pixim and OmniVision, made a splash at the ISC West show in Las Vegas as they unveiled a variety of CMOS imagers designed specifically for surveillance cameras. CMOS chips are no stranger to surveillance cameras. Products from established companies like GE Security, Axis Communications, EverFocus and others have used CMOS chips in some of their cameras, but by and large, manufacturers have stayed transfixed on CCDs.

It's actually a tad surprising, since CMOS chips have had such a price lead on CCDs. The CCD has tended to add a cost of around $10 per camera; CMOS sensors, on the other hand, have been able to be produced for well less than $10 per sensor. But that slight price difference hasn't been enough to yet overthrow the CCTV market, where much of the cost still lies in the cabling and installation that support a surveillance camera.

And while many suspected that the cost issue would eventually override the CCD based purely on price point, even as CMOS chips were able to be manufactured less expensively, so were CCDs able to drop in price. And even though they couldn't quite keep up with the price drops that CMOS manufacturers could offer, that ability to chase them in prices has helped ensure the CCD's longevity in surveillance cameras.

There's also an issue of quality in many manufacturers eyes. CCD sensors have, most would agree, stayed a slight step ahead of CMOS sensors in terms of versatility.

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