Wide dynamic range linear-logarithmic CMOS image sensor using photogate and cascode MOSFET

• Published in: Electronics letters Vol. 52; no. 3; pp. 198 - 200
• Main Authors: Bae, M, Jo, S.-H, Choi, B.-S, Lee, H.H, Choi, P, Shin, J.-K
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 04.02.2016
• Subjects: cascode MOSFET; CMOS; CMOS image sensors; Dynamic range; Illumination; illumination level; Image and vision processing and display technology; Level (quantity); linear response regime; logarithmic response; MOSFET; MOSFETs; photogate MOSFET; photogate voltage; Pixels; Sensors; voltage‐light‐dependent active load; wide dynamic range linear‐logarithmic CMOS image sensor; MOSFET; photogate MOSFET; linear response regime; wide dynamic range linear-logarithmic CMOS image sensor; CMOS image sensors; illumination level; cascode MOSFET; logarithmic response; voltage-light-dependent active load; photogate voltage
• ISSN: 0013-5194; 1350-911X; 1350-911X
• DOI: 10.1049/el.2015.2907

A wide dynamic range CMOS image sensor is proposed, exhibiting a linear response at a low illumination level and a logarithmic response at a high illumination level. To maintain high sensitivity and to improve the dynamic range of the proposed pixel, a cascode MOSFET is integrated into the structure of the proposed pixel, along with a photogate. The applied photogate voltage reduces the sensitivity of the proposed pixel under the linear response regime, at a moderate illumination level. Under high illumination levels, the biased cascode MOSFET serves as a voltage-light-dependent active load and is responsible for logarithmic operation. The dynamic range of the proposed pixel can be improved by adjusting the sensitivity and the basis of the logarithmic response.