Business Wire: Aptina announces a new Clarity+ 13MP sensor for smartphones, the AR1331CP, featuring 1.1um pixel with Clarity+ technology, which is said to boost the pixel sensitivity by a factor of two without introducing the image artifacts that have limited similar approaches from other sensor makers.
"Clarity+ technology uses a Bayer-like pattern with high-fidelity clear pixels that collect two times the light compared to standard green, resulting in a significant improvement in captured signal," said Bob Gove, President and CTO of Aptina. "Clarity+ technology provides the leap necessary to take artifacts and noise out of the equation enabling a world-class image sensor in the mobile-ready, tiny form factor that OEMs need."
Aptina has published a whitepaper on Clarity+ technology. Clarity+ starts with the standard 2x2 Bayer RGB color filter pattern commonly used in image sensors throughout the industry, and then replaces all of the green color filters with carefully optimized clear filters. This pattern preserves the high-frequency spatial information of the Bayer pattern, eliminating the aliasing artifacts that are inevitably introduced when both green and clear filters are used in larger kernel (4x4) patterns. The green color is determined through the image processing algorithms that use subtractive and interpolation techniques. Specialized noise reduction is then applied, resulting in a 3dB improvement in low-light SNR, relative to that possible with the RGB Bayer pattern.
"Aptina’s Clarity+ CFA pattern (RC/CB) is unique in that we have the same number of B and R pixels as Bayer, but determine G through a subtraction of R and B from C. Because we have the same number of C pixels as other 50% C schemes, we can extract the same SNR improvement. However, because we have the same configuration as Bayer, we uniquely maintain the high fidelity of luma information and low level of chromatic artifacts to which the industry is accustomed. Because G is determined through a subtraction, there is a tendency to amplify noise in the conversion to the standard RGB (sRGB) representation. This is addressed by image processing algorithms that are part of the Clarity+ technology."
"As with other patterns involving C pixels, there is a very slight trade-off (a few tenths of a dB) in visual noise when compared to Bayer in bright light situations, but this is not noticeable in those situations, because SNR is high and does not typically limit quality. There is the benefit in bright light situations, that Clarity+’s increased sensitivity will result in exposure times that are half that for Bayer and this is useful for capturing action shots with less blur and motion artifacts. The 50% RGBC patterns (including Clarity+) are also more sensitive to flare and other stray light issues, but this can be managed through appropriate pixel, lens, and packaging design."
The whitepaper also has many actual pictures comparing Bayer CFA sensor with the Clarity+ one.
The AR1331CP is available now for sampling in die form with raw output for use in systems that are enabled for Clarity+ processing. The AR1331CP is also available for sampling with Clarity+ coprocessors that can either fully process the unique Clarity+ images into industry standard camera formats or “pre-process” the Clarity+ images into Bayer format for compatibility with standard image and application processors.