7.8 A 1-inch 17Mpixel 1000fps Block-Controlled Coded-Exposure Back-Illuminated Stacked CMOS Image Sensor for Computational Imaging and Adaptive Dynamic Range Control

Abstract

In recent developments, image sensors are no longer simply a means for collecting optical signals, but rather, are increasingly expected to serve as intelligent systems with surrounding configurations. Coded exposure (CE) is one of the methods applied in intelligent systems approaches, and various functions can be realized by the selection of the integration variable in the plenoptic function. High DR can be realized if the integration variable is time. A variety of means to achieve high DR have been proposed in the literature, for example, a method that provides a plurality of detection capacitors (LOFIC, [1]) or a method of preventing saturation by adding low-sensitivity pixels [2]. These methods often require an enlarged pixel size. Alternatively, high-speed readout like an array parallel stacked structure [3] is useful for integrating multiple frames to realize high DR. However, this leads to an increase in noise and needs faster readout to reduce motion artifacts. In order to mitigate the adverse effects, a method has been proposed in which a pixel array is divided into a plurality of blocks and the signal integration time of each block is individually controlled [4]. Another method was described in which CE was demonstrated by using pixel level control of the exposure time [5]. However, in these methods, it was necessary to arrange the readout path and control circuitry within the same plane because these are non-stacked sensors, so the pixel size was relatively large and high resolution was difficult to realize. To overcome the above problems, we report a sensor that can simultaneously achieve 4K×4K resolution and 1000fps high-speed readout. Using a stacked structure, we demonstrate coded exposure capability by individually controlling exposure time for each block of pixels.