Vendors form alliances to develop CMOS image sensors
With the promise of high-level integration, low power, low cost, and ease of fabrication, camera and silicon vendors are now scrambling to develop CMOS cameras-on-a-chip. Integrated with sensor, timing, and control functions, analog-to-digital conversion, and exposure and color-balance controls, such integrated circuits (ICs) are incorporating many of the functions that currently require a multichip approach in CCD-based devices.
Even with high-level integration, CMOS-based cameras have been plagued by fixed-pattern noise, which results from small differences in the behavior of individual pixel amplifiers used at each sensing site. And, although some industry experts believe that such defects would prevent CMOS imagers from ever challenging CCDs, researchers at Bell Labs (Murray Hill, NJ) are convinced they have conquered the problem by integrating circuits outside the sensor array for detecting and canceling this noise.
"Because the camera-on-a-chip is an offshoot of today`s technology, any semiconductor manufacturer could produce the chip at existing facilities," says Bryan Ackland of Bell Labs, which recently licensed its camera-on-a-chip technology to Vanguard International Semiconductor (San Jose, CA).
Other companies are also forging alliances to promote integrated image sensors. VLSI Vision (Edinburgh, Scotland), a pioneer in the development of CMOS image sensors, recently licensed color-filter and microlens technologies from Polaroid Corp. (Cambridge, MA) to make desktop digital cameras for PC teleconferencing.
While many companies see low-cost camera systems targeting the videoconferencing and security markets, others are looking to broaden their role in traditional industrial markets. In such a move, Dalsa (Waterloo, Ontario, Canada) and Semiconductor Insights (SI; Kanata, Ontario, Canada) signed an agreement last year to develop CMOS image-sensor technology.
Recently, Semiconductor Insights released its vision-system roadmap, detailing its product plans for the next two years. Like other semiconductor manufacturers, SI will integrate much of the functionality currently associated with digital cameras and frame grabbers into a series of ICs, allowing camera manufacturers to develop fully integrated machine-vision cameras. "Developing functions such as frame grabbers, digital cameras, vision modules, accelerators, and input/output controls as a series of intellectual property cores will allow us to offer a number of easily configurable CMOS devices to OEMs," says Larry Lam, SI director of research and development.
First out of the SI gate will be a monochrome digital camera IC capable of 1280 ¥ 1024 resolution, on-board timing, black-level control, and RS-170 video output. Within two years, SI hopes to introduce a color version of the camera with on-board automatic exposure, contrast stretching, thresholding, analog-to-digital conversion, and digital output.
"With companies such as Intel (Santa Clara, CA), Motorola (Chandler, AZ), and Eastman Kodak (Rochester, NY) already developing product," says Les Thurlow, SI director of business development, "it is highly likely that the technical challenges faced by combining analog CMOS sensors with digital circuits will be overcome very soon."