Video from

10/01/1998

Video from "camera-on-a-chip" technology, soon

Vanguard International Semiconductor, Hsinchu, Taiwan, has licensed high-performance CMOS "camera-on-a-chip" technology from Lucent Technologies` Bell Labs, Murray Hill, NJ. This technology is slated for marble-sized video cameras ideally suited for PC videoconferencing and security camera application. Each camera will use a single quarter-inch silicon chip, yet produce real-time video images that rival the quality of those produced by camcorders. With Vanguard producing the CMOS IC, a third-party camera and computer peripheral manufacturer will package them with a small lens. The final camera eventually will sell for less than $50.

Interestingly, Bell Labs is credited with developing charge-coupled device (CCD) technology used in conventional video cameras.

"While other companies have tried to use a single CMOS chip in a video camera, we`re the first group to show high-quality performance," said researcher Bryan Ackland of Bell Labs. The secret to this high performance is in "active pixel" technology using the same CMOS fabrication used for logic and memory devices.

The Bell Labs single chip includes an imaging array comprised of more than 100,000 optical sensors in a 2D grid on the silicon surface, fabricated on the same chip as the control circuitry. Each image site or pixel is accessed using a 2D arrangement of address and data buses, very similar to memory ICs. A small amplifier at each pixel helps reduce noise and distortion levels.

By developing a high-quality imaging array using conventional CMOS technology, the researchers integrated all of the functions associated with a camera - timing and control, analog-to-digital conversion, and the signal processing needed to provide exposure control and color balance - onto a single silicon chip.

"Although the active pixel approach was first proposed in the early 1970s," said Marc Loinaz at Bell Labs. "it`s only been in the last few years that IC design and fabrication technologies have progressed enough where transistors can be included in each pixel without significantly increasing the size of the array."

In the past, CMOS-based cameras have been plagued by a defect known as fixed pattern noise - an annoying stationary background pattern in the image that results from small differences in the behavior of the individual pixel amplifiers. Although some researchers believed this defect would prevent CMOS from ever seriously challenging CCDs, Bell Labs researchers have added circuits outside the sensor array that detect and cancel this noise.

Successful implementation of this technology into cameras will mean a 9 V battery can power a CMOS camera for up to 5 hrs. In addition, portions of the whole images are immediately accessible even before the entire image is captured.

While this technology will be used initially for computer and security cameras, future uses might include 3D imaging and collision avoidance, and possible integration into computer screens. "This camera might follow the same life-cycle as the digital clock," Ackland says, "which used to be an expensive stand-alone device, but is virtually everywhere now."

Because the camera-on-a-chip is an offshoot of silicon-chip technology, any semiconductor producer could make the chip at existing facilities, Ackland said. The same situation has not existed with CCD technology, which requires specially designed facilities. - P.B.