The Bend Sensor Sony
The sensors in digital cameras are generally flat. The realization of a sensor plate is obviously linked to problems mainly productive and not qualitative, since a bend sensor would ensure a higher sensitivity, better image quality as well as allow for use of the lenses of construction simpler.
Some time ago, at the VLSI Symposium 2012, Kazuichiro Itonaga (Sony device Manager) showed a full-frame sensor curved, as well as a reduced version (a 2/3 “), always curved http://smilesmultimedia.com. The first sensor is obviously intended to reflex high-level, while the second is dimensioned so as to be housed in compact cameras smartphone or even of high level.
In the presentation it has not been shown the production process, but from what has been able to understand, the sensor has been created flat, and only subsequently, through the use of a machine ad hoc, was added the curvature and a ceramic substrate the whose function is, precisely, to provide rigidity to the sensor and then keep it curved in time.
Why a curved sensor?
In a few words, a bend sensor is designed to counteract the curvature of field (also known as field curvature Petzval) associated alenti simple coupled with floors or flat sensors. The curvature of field is related to the fact that the effective focal length of the light rays decreases as the light beams move away from the optical axis of the lens (therefore towards the outside of the lens, for instance, being the optical axis of lens imaginary line perpendicular to the lens itself that passes through its center exact).
In other words, more light rays furthest from the optical axis have, the more it moves forward the focal plane (in practice falling behind the sensor itself and putting out fire those light rays).
In the image above you can see how the flat surface of the sensor is imagined as a curve (and just call Petzval surface) and not as flat (the theoretical level that you see all right in the drawing).
The lens manufacturers do their best to fight the curvature of field with the introduction of elements designed ad hoc (do you remember the curvature barrel? Here, is one of the distortions that must be corrected!). Moreover, these elements designed ad hoc often introduce other aberrations: for example there is a compromise between the well-known astigmatism and field curvature.
Sony, when he realized the bend sensor, has set a very clear question: what if instead of working to correct the curvature of the field sfruttassimo introducing a curvature in real sensor instead of just imagining it? The use of optical sensors curved design would allow more simple since the light rays entering the lens from oblique angles should not be corrected to be projected on a flat surface.