A Sun-Tracking CMOS Image Sensor With Black-Sun Readout Scheme

• Published in: IEEE transactions on electron devices Vol. 68; no. 3; pp. 1115 - 1120
• Main Author: Kim, Hyeon-June
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-03-2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Analog-digital conversion; Black-sun phenomenon; black-sun readout scheme; CMOS; CMOS imager sensor (CIS); column-parallel single-slope (SS) analog-to-digital convertor (ADC); Detectors; Electronic devices; Energy conversion efficiency; Lighting; Photodiodes; Prototypes; SS ADC; Sun; sun-tracking CIS; Timing; Tracking
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2021.3052450

This article presents a black-sun readout scheme for CMOS image sensors (CISs) that utilizes the black-sun effect caused by a strong illumination condition. Based on the analysis of the black-sun phenomenon in CISs, the proposed CIS extracts the black-sun indication and its strength images while providing normal images without any degradation. By effectively utilizing the black-sun readout capability, a prototype CIS with the proposed readout scheme was identified as a useful solution to track the brightest source of light. In addition, the proposed black-sun readout scheme is reversible to the conventional readout scheme such that it can be used for various purposes in several electronic devices using CISs. The proposed readout scheme was verified in the typical CIS structure, and it shows the feasibility of utilizing it in sun tracking sensor applications for improving energy conversion efficiency. The prototype chip was implemented in a 0.11-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> 1P4M CIS process with a 2.9-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> pitch.