Looking at the Expanding Sensor Market

The big question in the sensor market remains the same: CCD or CMOS? The answer remains the same: It depends upon the application. Cameras and sensors are everywhere, from cell phones to Formula One racing cars, to medical offices and even orbiting the earth.

But that doesn't mean the sensor market is stagnant. Kodak, for example, has new developments in both CCD and CMOS. The Rochester, N.Y. company deployed its high-ISO color filter pattern, or sparse color filter array, on its latest generation of CMOS chips. It also released a PMOS, or hole detector that, contrary to more conventional sensors that detect electrons, actually senses the absence of electrons.

The PMOS actually is a re-engineering of the fundamental design and architecture of traditional CMOS pixels. In a standard pixel, the signal is measured by detecting electrons that are generated when light interacts with the sensor surface. As more light strikes the sensor, more electrons are generated, resulting in a higher signal at each pixel. In the Kodak PMOS the underlying polarity of the silicon is reversed, so the absence of electrons is used to detect a signal.

On the CCD side, Kodak has new interline products with smaller pixel and faster frame rates that they are deploying into different sensor sizes for full-frame, medical and photographic applications.

In another development, aimed at the mobile handset industry, OmniVision (Sunnyvale, Calif.) introduced the OV3642, a ¼-inch, 3mp CMOS sensor with its TrueFocus™ technology embedded on-chip that is well-suited for low-light performance. The camera phone's point-and-shoot capability keeps the entire scene—from 20cm to infinity, including video capture—in focus.

The sensor features an embedded image stabilization function to prevent image blur, which is, of course, important in low-light situations where cameras need longer exposure time.

Other hot news came in March when Samsung Electronics Ltd., unveiled an 8.4mp CMOS sensor. The chip provides a high signal-to-noise ratio through a photo diode technology to achieve higher light sensitivity and saturation levels.

Samsung says the new sensor provides the same image quality as the CCDs used in most digital cameras and camcorders because it uses only one-tenth the power of a CCD. The company is targeting the mobile phone, digital camera and camcorder markets with the new sensors in the second half of the year. It may trigger what some deem "Megapixel Wars."

"A lot depends on the application," says Michael DeLuca, marketing manager for Kodak's CCD group. "Consumers want resolution and low-light production. At the industrial level, it's frame rate. We have to reconcile how to take different needs customers have identified and get to market. The way you meet that need is to make the pixels work better. You can improve sensitivity and dynamic range, make them smaller and decrease noise. Then, once you have what I call 'pixel good-will' you can deploy the application in different ways, depending on the market."

Brian Benamati, CMOS product manager at Kodak, adds: "We see the industry force moving to high-definition video in mobile applications. The high-end will have a feature set consistent with the low end of point-and-shoot—8mp 10mp, xenon flash, optical zoom and high-definition video, even 1080p. The midrange will be 720p mobile video phone with three- to five-times optical zoom." The low-end, he says, will feature a smaller chip of 3-5mp for economy. "What we're looking for is low-light sensitivity, high-speed and high-definition video."

Customers trying to decide between CMOS and CCD need to consider a number of questions.

"We have those conversations all the time as customers come to us with different needs," says Antonio Ciccarelli, Worldwide Marketing Manager CCD Image Sensor Business, Image Sensor Solutions at Kodak. "One way it's different: resolutions, frame rate, specs? What about packaging? How is it set in the housing? What kind of glass is used to cover the sensor? Do they want coatings to cut reflection? Do they want bare silicon because they're working with fiber optics? We really work to understand those needs."

What's coming up down the road? Perhaps, Benamati says, you may see CMOS and CCD cohabitate. On the CCD side, the capabilities are more on sensitivity and dynamic range. They could meet in the same home security system, some sensors on the inside, others on the outside.

"From the camera designer's perspective, they're different technologies," he adds. "Consumers, they don't care. Other than people who are techies, consumers are looking for images, high quality and high dynamic range. You can equate it to wireless. The technical [aspects] might be different, but they're doing the same things."

author: By Barry Hochfelder, Editor - Advanced Imaging