Intensity mappings within the context of near-sensor image processing

In the original near-sensor image processing (NSIP) concept, intensity level for an individual sensor element is mapped onto the time axis so that the time to reach the threshold is inversely proportional to the intensity. In many cases this is favorable, in some cases there is a need for another mapping between time and intensity. We will show in this paper that such mappings can be achieved by either inserting delays or by varying the threshold voltage. The result is that to achieve a linear mapping it is much more favorable to use variable threshold since the processing power of the sensor is then better utilized. An interesting result, when it comes to adaptive mapping, is that the traditionally time consuming operation histogram equalization can be accomplished almost for free in the NSIP concept. We will also show that other histogrambased, i.e., data-dependent, mapping can be easily implemented.