Kodak image sensor uses available light more efficiently

Stephen Withers
Friday, 15 June 2007 04:03

Your IT - Home IT

A relatively simple hardware change has allowed Kodak to make CMOS and CCD image sensors for digital cameras that are two to four times more sensitive to light, resulting in less colour noise when pictures in low light or a reduction in motion blur under better conditions.
Conventional single image sensors have a pattern of red, green and blue pixels in an arrangement determined by Kodak scientist Bryce Bayer in 1976. This is achieved by filtering the light before it reaches each pixel.

The new design keeps the Bayer ratio of two green pixels to every one red and one blue pixels, but for each group of four colour pixels there are another four that receive unfiltered light. The panchromatic (or clear) pixels therefore receive more photons of visible light as none are being filtered, so the overall sensitivity of the sensor is increased.

"In a low-light situation, these new patterns will produce a lot less color noise than a Bayer pattern sensor," said co-inventor John Hamilton, 'algorithm agitator' at Kodak. "You can run the shutter faster, which gets rid of a lot of motion artifacts. It will cut down on camera shake or, if you're taking a picture of a moving object there will be less blur."

Co-inventor and 'technology troublemaker' John Compton explained "The real advantage is that the panchromatic pixels are more sensitive, since they detect all wavelengths of visible light (rather than filtering light to detect color information)."

The algorithms used to convert the sensor measurements to a digital image must be changed to accommodate the panchromatic pixels. Since the number of sensor pixels in a repeat pattern has been increased from four to 16 by the addition of the panchromatic pixels, there's a risk that the averaging process used to convert sensor pixels to image pixels will result in colour bleed across edges within the image.

"[I]t's hard to get the right amount of cleaning ensuring that you reduce the noise, and at the same time, keep the edge definition reasonably good. And so there's been a lot of work done on finding the best way to do that," said Hamilton.

"This represents a new generation of image sensor technology and addresses one of the great challenges facing our industry – how to capture crisp, clear digital images in a poorly lit environment," said Chris McNiffe, General Manager of Kodak's image sensor solutions group.

Applications include cameras and camera phones plus industrial and scientific imaging.

The first Kodak sensor using the technology should be available in sample quantities in the first quarter of 2008.