Sony's Back-Illuminated CMOS Sensor Increases Sensitivity, Reduces Noise Dramatically

Sony has developed a new CMOS technology that may revolutionize consumer video camcorders and cameras: a 5-megapixel, 60 frames per second back-illuminated sensor. As you can see in this test image, the sensor nearly duplicates light sensitivity while reducing the signal-to-noise ratio. The idea is apparently simple, but it dramatically increases the quality of the picture in low-illumination conditions. How does it work?

As you can see, previous CMOS designs had the photoreceptive diodes behind the transistor layer. The transistor layer allowed some light to go through but reflected some of it, resulting in a lower sensitivity and increased noise.


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In the new design, however, most of the photons goes through the on-chip lens and color filter directly into the new photo-diode structure, while the transistor layer sits at the bottom of the sensor. According to Sony, "that achieves a higher sensitivity of +6dB and a lower random noise of -2dB without light by reducing noise, dark current and defect pixels compared to the conventional front-illuminated structure."

Sony is planning on introducing the new technology in their next generation cameras, and hopefully we will see it in other products, especially cellphones. [Sony]

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