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CMOS Camera Won’t Be Blinded by the Light

Photonics Spectra
Sep 1999
Jörg Schwartz

DUISBURG, Germany — Photographers commonly find themselves in situations with too little or too much light. An inability to deal with changing brightness is a weakness of amateur and professional cameras.

techBlinded.jpg
Cars could use recently developed CMOS imaging technology for glare-free rear vision, as demonstrated in this comparison of a traditional CCD image, left, and a picture from a CMOS camera, right.

The problem relates to dynamic range, which is typically between 50 and 70 dB for a standard charge-coupled device camera. Using complementary metal oxide semiconductor (CMOS) technology, researchers at the Fraunhofer Institut für Mikroelektronische Schaltungen und Systeme IMS have moved toward the human eye's 200-dB dynamic range, developing an imager with a dynamic range of 120 dB and local, on-chip brightness adaptation.

A CMOS sensor can amplify individual pixels in response to their respective illumination conditions. Dark areas are amplified, while pixels that receive high signal levels remain unchanged. Multiple-pixel access enables the user to select up to four integration intervals, improving picture quality by choosing the best exposure time for each pixel.

The researchers received the Philip Morris Research Award for their innovation. Project financing came from carmaker BMW -- no accident, considering that several applications can be found in the automotive sector. One, noted project leader Michael Schanz, is glare-free rear vision.

The team is improving the camera and developing a color version. The first-generation chips contained 256 × 256 pixels with a fill factor of 65 percent. Since then, 0.5-µm twin-well CMOS technology has improved resolution by a factor of eight.


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