An improved smart readout technique based on temporal redundancies suppression designed for logarithmic CMOS image sensor

Abstract

In this paper we present an improved version of the readout technique proposed in [7]. It concerns a continuous operating logarithmic image sensor with 120dB of Dynamic Range (DR). The pixel element presents also improved characteristics, compared to the standard logarithmic pixel, especially in terms of Fixed Pattern Noise compensation and extended output voltage swing. The first goal of this readout technique is to reduce the data temporal redundancies in order to reduce the dataflow outgoing from the sensor. The main idea lies in the distribution of the sensor into macro-pixels composed of nxn pixel elements. Each macro-pixel generates the mean value of all its pixels luminosities, and then an event detector is used to detect any variation in this mean value. A positive reaction of this event detector triggers the readout of the block pixel elements. The Matlab emulation results show the intended dataflow reduction rate. The pixel schematic and layout designed in the CMOS 0.35μm AMS technology, the event detector architecture and the bloc diagram of the system are detailed later through the different sections of this paper.