Wide-Dynamic-Range CMOS Image Sensors—Comparative Performance Analysis

TLDR

A large variety of solutions for widening the dynamic range (DR) of CMOS image sensors has been proposed throughout the years. The authors propose criteria for a comparative analysis of wide‑DR sensor performance and discuss how technology advances affect these criteria. WDR sensors are classified into seven categories—companding, multimode, clipping, frequency‑based, time‑to‑saturation, global‑control‑over‑integration‑time, and autonomous‑control‑over‑integration‑time—and compared using consistent quantitative metrics of signal‑to‑noise ratio, DR extension, noise floor, transistor count, and sensitivity. The advantages and disadvantages of each category in terms of power consumption and data rate are discussed qualitatively.

Abstract

A large variety of solutions for widening the dynamic range (DR) of CMOS image sensors has been proposed throughout the years. We propose a set of criteria upon which an effective comparative analysis of the performance of wide-DR (WDR) sensors can be done. Sensors for WDR are divided into seven categories: 1) companding sensors; 2) multimode sensors; 3) clipping sensors; 4) frequency-based sensors; 5) time-to-saturation (time-to-first spike) sensors; 6) global-control-over-the-integration-time sensors; and 7) autonomous-control-over-the-integration-time sensors. The comparative analysis for each category is based upon the quantitative assessments of the following parameters: signal-to-noise ratio, DR extension, noise floor, minimal transistor count, and sensitivity. These parameters are assessed using consistent assumptions and definitions, which are common to all WDR sensor categories. The advantages and disadvantages of each category in the sense of power consumption and data rate are discussed qualitatively. The influence of technology advancements on the proposed set of criteria is discussed as well.