Introduction
Our eye is in many respects different from a camera. For instance, it does not make sense at all to ask at what "frame rate" our eyes opperate. There are no frames! Every "pixel" opperates on its own timing, asynchronously. It conveys its information independently from all other pixels as a series of voltage pulses to the brain. In general, light intensity is encoded as the frequency of these pulses.
Our group and other researchers around the world have introduced vision sensors that are no longer frame based but instead use this asynchronous pulse transmission that is inspired by the nervous system. This communication is called "address event representation" (AER). However, so far all of those vision sensors have been monochrom (i.e. gray scale image sensors). Indeed, it is not so trivial to produce a colour camera chip the traditional way, that is with colour filters that are placed very precisely over the pixels. Complicated post processing of a CMOS chip is necessary to achieve this placement.
There is a more recent technique, though, that does not require any post processing at all. The company Foveon had the idea to use photo sensors that are burried in different depths below the surface of the silicon chip. Light of different colour/wavelength actually penetrates the silicon up to different depths. A photo sensor close to the surface will see blue light while one deeper down will only see red light. Conveniently, a light sensor in CMOS is nothing else but a PN-junction (a PN-diode) which is easily obtained in different depths in any normal CMOS chip production process. One can even have several of those diodes in the same 2D location, stacked on top of each other at different depths. Thus, one can get information on different colours from the very same pixel location instead of only one colour per pixel as with colour filters.
The Project
The aim of this project is to develop a frame less AER (asynchronous pulse communication) colour vision sensor with stacked photo-diodes.
Program
Informatikk