Layout Design of an Asynchronous Time-Based Image Sensor with Shared DVS Module

In the asynchronous time-based image sensor (ATIS), capture is performed asynchronously by each pixel when the dynamic vision sensor (DVS) module detects significant luminance change. The DVS module control aims at avoiding redundant capture. Furthermore, time-based capture allows for high dynamic range imaging. Each original ATIS pixel is composed by a capture module and a DVS module, resulting in a large pixel area and small fill factor. DVS module sharing reduces the pixel area and increases the fill factor. In this work, we present simulation results and layout design of an ATIS in which each 2×2 capture modules share a single DVS module. Corners, Monte Carlo, and post-layout simulations are presented. With the layout, designed in a 180 nm complementary metal-oxide semiconductor (CMOS) technology, we conclude that the DVS sharing saves approximately 33.68% area and the pixel fill factor is 7.7%. Simulation results indicate that the circuit operation is robust to fabrication errors and to layout parasitic components.

I. Introduction

Complementary metal-oxide semiconductor (CMOS) technology is commonly used for the fabrication of image sensors [1], [2]. An important characteristic of the CMOS technology is that it allows for the fabrication of transistors inside the pixel matrix. Conventional image sensors use this characteristic to improve signal-to-noise ratio by amplifying the photo-generated signal. In contrast to conventional CMOS video sensors, which are frame-based, the event-based sensors are asynchronous, and they have been acquiring increasing popularity over the last years [3]. They are now investigated or commercialized by a number of companies [4], and have been employed in several different event-based vision applications, ranging from robotics to astronomy [5]. In the asynchronous time-based image sensor (ATIS) [6], transistors are included inside the pixel matrix to measure light variations, and to perform event-based capture by measuring the photodiode capacitance discharge time.