Two-Step Reset to Reduce the SNR Drop in the LOFIC CMOS Image Sensor

カテゴリ: 論文誌(論文単位)

グループ名: 【C】電子・情報・システム部門

発行日: 2024/04/01

タイトル(英語): Two-Step Reset to Reduce the SNR Drop in the LOFIC CMOS Image Sensor

著者名: Kazuki Tatsuta (Research Organization of Science and Engineering Ritsumeikan University), Ai Otani (Research Organization of Science and Engineering Ritsumeikan University), Ken Miyauchi (Brillnics Japan Inc.), Sang-Man Han (Brillnics Japan Inc.), Hideki

著者名(英語): Kazuki Tatsuta (Research Organization of Science and Engineering Ritsumeikan University), Ai Otani (Research Organization of Science and Engineering Ritsumeikan University), Ken Miyauchi (Brillnics Japan Inc.), Sang-Man Han (Brillnics Japan Inc.), Hideki Owada (Brillnics Japan Inc.), Isao Takayanagi (Brillnics Japan Inc.), Shunsuke Okura (Research Organization of Science and Engineering Ritsumeikan University)

キーワード: CMOS image sensor，LOFIC，HDR，correlated double sampling，SNR，reset noise

要約(英語): A lateral overflow integration capacitor (LOFIC) complementary metal oxide semiconductor (CMOS) image sensor can realize high-dynamic-range (HDR) imaging with combination of low-noise signals and high-full-well-capacity (high-FWC) signals. However, signal-to-noise ratio (SNR) drop at the switching point between the low-noise signals and the high-FWC signals is not negligible because pixel reset kTC noise to reset small in-pixel capacitor is not canceled in the high-FWC signals. In this paper, a reset circuit for the LOFIC CMOS image sensor is presented, which reduces the pixel reset noise with additional switch and large capacitor outside the pixel array. In order to further reduce the reset noise, an asymmetric structured in-pixel reset transistor is also proposed. Since the charge flow through the channel of in-pixel reset transistor is suppressed, the pixel reset kTC noise is reduced. A test chip of the reset circuit is fabricated with a 0.18 μm CMOS process. As an evaluation result, the pixel reset noise is reduced to 556 μVrms, which is 43.0 % lower than that of the conventional LOFIC pixel. The estimated SNR drop at the switching point is 6.5 dB, which is improved by 4.2 dB.

本誌: 電気学会論文誌C（電子・情報・システム部門誌） Vol.144 No.4 （2024） 特集Ⅰ：量子・情報・エレクトロニクスの医療/ヘルスケア応用　特集Ⅱ：電子回路関連技術

本誌掲載ページ: 337-343 p

原稿種別: 論文／英語

電子版へのリンク: https://www.jstage.jst.go.jp/article/ieejeiss/144/4/144_337/_article/-char/ja/