The Space-variant
CCD Sensor

This sensor has been realized as a collaboration between IMEC, the University of Genova and the University of Pennsylvania. It was the first Retina-like sensor of this kind in the world.

The prototype of the CCD sensor has the following structure: the pixels are arranged on 30 concentric circles each with 64 photosensitive sites. The pixel size increases from 30micron x 30micron for the inner circle to 412micron x 412micron for the outer circle. The total chip area is 11mm x 11mm. The video acquisition rate is 50 frames per second. The total amount of information is stored with less than 2Kbyte per frame. Thus, the chip realizes a good compromise between image resolution, amplitude of the visual field and size of the stored data. Computation of optical flow has been performed at a rate of about 4 Hz, using a common 386 PC 33MHz. This has allowed to perform some very simple, but not trivial, tasks such as computation of the time-to-impact of a target approaching a camera with the retinal sensor mounted in, and the control of the approaching velocity to avoid the collision.