CMOS imagers target camera applications

Although they still lack the dynamic range of their CCD counterparts, CMOS image sensors are finding use in markets other than consumer products and low-cost security systems. But the latest CMOS devices differ radically from the standard 30-frame/s VGA-resolution-type imagers now being produced by vendors such as Eastman Kodak Co. (Rochester, NY), Agilent Technologies (Palo Alto, CA), and National Semiconductor (Dallas, TX). These latest devices feature variable frame rates and resolutions and wide nonlinear dynamic ranges and target applications in high-speed camera designs, often with frame rates in excess of 10,000 frames/s.

Nowhere was this trend more evident than at the recent VISION 2001 trade show in Stuttgart, Germany, where several companies displayed devices and cameras based on CMOS technology. At the show, companies such as IMS Chips (Stuttgart, Germany), the Fraunhofer

Institute (Duisburg, Germany), and Silicon Vision (Boxdorf, Germany) announced CMOS devices aimed at niche machine-vision markets. At these companies' booths and elsewhere, camera vendors such as Photonic Science (Robertsbridge, East Sussex, England) and Weinberger (Dietikon, Switzerland) also demonstrated cameras based on the technology.

Automotive air-bag detonation is an example of an application that uses the SpeedCam camera from Weinberger. The camera uses a CMOS sensor built by the Fraunhofer Institute to capture three 10-bit color images at 1536 x 1024-pixel resolution and at a data rate of approximately 1000 frames/s.

At the Fraunhofer Institute booth, Robert Dinkelbach explained how this new generation of CCDs is filling needs in the machine-vision market. "In high-speed image-processing applications," he says, "it is necessary to use devices that can be electronically windowed to produce a number of different resolutions at different frame speeds." The company's latest product, the IMS 1M 1024 x 1024 CMOS sensor, for example, features an electronic rolling shutter and programmable multiwindow readout capability. The device also uses a patented multiple-exposure technique to obtain a high dynamic range. Dinkelbach also showed an unannounced camera from Photonic Science that uses the device to obtain region-of-interest images at rates to 800 frames/s.

One Fraunhofer Institute custom-made product appeared in the booth of high-speed machine-vision vendor Weinberger. The SpeedCam imager uses a CMOS sensor built by Fraunhofer to capture three 10-bit color images at 1536 x 1024-pixel resolution and at a data rate of approximately 1000 frames/s. "To capture this amount of information," explains Jorn Mehlmann, European sales manager at Weinberger, "images are read from the camera and buffered in 4

Start-up Silicon Vision also announced a high-resolution CMOS imager with 2464 x 1632-pixel resolution capable of 2.5 frames/s at full resolution and 30 frames/s at VGA resolution. According to Christina Tassev, Silicon Vision marketing manager, the device will be ready sometime next year.

European vendors are not the only companies looking at such markets. Last month, Photobit (Pasadena, CA) announced its PB-MV40, a 2352 x 1728-pixel imager with a 4:3 aspect ratio capable of image-processing rates to 240 frames/s. The device can also operate in partial scan mode to achieve frame rates of 2000 frames/s.