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

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


"It's getting better, and it's getting very close in quality," said Fredrik Nilsson, general manager for network camera manufacturer Axis Communications. "For indoors, CMOS is really as good [as CCD technology], but for outdoors it's not as good because it's not as light sensitive."

The CCD chips, note Nilsson, are so sensitive to light that they are excellent for low-light situations. That ultra sensitivity even requires that the cameras use auto-irises so that too much light isn't fed onto the CCD chips, which could cause streaking in the image.

The CMOS chip of 2006, however, isn't the CMOS chip of old. The old chips were notorious for lacking light sensitivity and for having resolution problems of "noise" on the chip. Today's chips may not have quite the light sensitivity of CCDs, but some manufacturers, such as Pixim's new chips, are able to capture color images at light levels down to 0.5 lux. Along the way, the signal-to-noise ration dropped as well, offering less noisy images, and the width of the dynamic range increased.

But even as they improved, the CMOS chips still primarily found their way into low-end still cameras and started to take over the camera-phone market.

Part of the reason is not only the cost, but the size. CMOS chips actually are able to receive the light and convert that into the data right on one chip. The "logic" is actually embedded in the silica. A CCD, on the other hand, actually converts the light into analog electrical variation, and then needs a second analog-to-digital (A/D) converter chip to "flip" that data back to digital if it's going to be used in an IP-camera. However, that analog functionality was a featured that solidified the CCD's position in video surveillance, when the market was almost exclusively analog cameras. Because it requires that extra conversion chip, CCD cameras will always be slightly larger than cameras that solely use CMOS sensors.

That's allowed CMOS to hit the market of smaller cameras, according to Micron's Director of Market Development Paul Gallagher. The low cost, adds Gallagher, has also enabled CMOS chip manufacturers to help drop the cost on lower-end cameras, such as those used for residential surveillance, and has had a similar effect in thermal imaging cameras as well. Now, says Gallagher, the CMOS chips are showing up in very high-resolution cameras -- the so-called "multi-megapixel" cameras, and even the high-resolution fisheye style cameras that allow users to operate with a digital pan, tilt and zoom, moving through the field of view with full resolution without ever having to mechanically change the camera's position.

So for now, where does that leave us?

Here's a quick summary:

CCD: Higher-priced, but great for cameras that may require vision in near darkness. The lack of noise has helped solidify this camera technology's market share lead, and with big manufacturers like Sony producing the CCDs, they have huge staying power. They still offer a slight advantage in image quality over CMOS chips, and your buyers are likely rather familiar with this tried-and-true technology.

CMOS: Lower prices and improving quality. Great for fixed-light environments, and the lower cost will help these chips take off in cameras used for residential installations and lower-end commercial facilities, especially for cameras used to verify intrusion alarms. The size makes them attractive for compact cameras, and the direct-to-digital format will likely seize upon the growing network camera market.

Finally, we asked Axis' Nilsson, how he expects to see the market share between the two sensors change. He says his company is already using CMOS sensors in some of its cameras, but still heavily relies upon CCD sensors. He adds that while he knows the change is coming, but he's not so sure that there will be a rapid change from CCD to CMOS.

"In 1999, we said it would take two years before CMOS started to be prevalent in the professional surveillance market," said Nilsson. "Now, in 2006, we still say two years. It's estimated that 95 percent of surveillance cameras are still CCD cameras, so there is a big market that has to change."