Sony Publishes Details About New Exmor R CMOS Sensors

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Submitted by lalit on March 1, 2010 - 2:29pm.

Sony released cameras based on their new Exmor R back-illuminated CMOS sensor last month. According to Sony, the new sensor will allow better low-light photography, high-speed image processing, decreased power consumption and better HD video recording. The company has now published a paper highlighting the technological advancements made in designing the new image sensor.

In the paper, Sony says that Exmor R CMOS sensor was developed to offer high-speed imaging with lower sensitivity to noise ratio. And the new sensor offers sensitivity characteristics that are improved by approximately a factor of two from current front illuminated image sensors by adopting a newly developed back-illuminated structure.  Sony explains:

Since the incident light entering current CMOS image sensors passes through gaps in the metal wiring layer, the light is obstructed by that metal wiring layer and cannot be delivered efficiently to the photodiodes. In particular, since light that comes in at an angle is reflected back, problem such as the outer areas of image being darker or the sensitivity not increasing as the aperture is opened wider occur.
Sony has now developed a back-illuminated structure that differs from the current pixel structure (the front-illuminated structure) in that the metal wiring is placed below the photodetectores. In the back-illuminated structure, light is projected onto the rear surface of silicon substrate (the back side) and as a result, the amount of light entering each unit pixel is increased since it is not affected by wiring and other circuits. This structure increases the light collecting efficiency even under imaging conditions where high angles of incidence are common.

Sony says that in future back-illuminated CMOS sensors will offer even further improvements in speed and performance as they make it possible to use multi-layer metal wirings and arbitrary transistor structures. You can read the whole PDF of the paper here.

Along with Sony many other companies like OnmiVision are developing back-illuminated CMOS sensors for devices like cellphones and webcams, which would bring better image quality to those devices also.