Locally adaptive active pixel sensors

In this paper we describe two circuits for implementing local adaptation in active pixel sensors. In addition to increasing the dynamic range, local adaptation provides finer resolution. The first photoreceptor circuit consists of an active pixel sensor which is operated at three different shutter speeds given sequentially. The decision to use the next shutter speed is determined locally by the controlling circuit of each pixel. The other circuit uses a multimode photodetector in which the gain is set depending on the light intensity. In this implementation the adaptive circuit controls a set of four pixels. For both circuits the pixel output consists of (1) region of operation and (2) the output voltage corresponding to the light intensity