Mimicking Nature once more

CMOS curved sensor designed to mimic the retina to maximise image quality. Credit: Sony

Researchers at Sony have been able to manufacture a curved CMOS sensor with a bit of biomimicry that simplifies the lens system and support higher sensitivity.

The eyes of animals are curved and the retina, the part acting as light sensor, follows the curvature. The mechanics of the eye is simpler than the one you see in a camera lens, thanks to this curvature (of course the alteration to the shape of the eye ball results in difficulties in vision, something we call myopia, hyperopia, presbyopia...).

They have been able to create the curved CMOS sensor using a bending machine they invented. After the bending the back of the sensor is covered in ceramic to stabilise the curvature. According to the researchers they can achieve a curvature similar to the one of the retina in the human eye.  

So far all CMOS sensors have been planar. The curvature makes it possibile to decrease the curvature in the lens system which in turns makes it possible to reduce distortion and increases the amount of light that can reach the sensor. They measured an increase of 1.4 times the amount of light reaching the center of the sensor and twice the amount of light reaching the edges of the sensor (the periphery of the sensor, because of the geometry of the lens, always gets less light, which creates the "vignetting" phenomena).

An added benefit of the curved geometry is an increase in the band gap between the pixels, which results in a decrease in dark currents, flow of electrons that occur  between neighbour pixels causing noise in the image.

Sony has manufactured the CMOS sensor in two sizes, one 43mm, similar to a full frame digital camera, and the other 11mm that can easily fit in a smartphone.

Author - Roberto Saracco

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