A Method for Detecting Timing of Photodiode Saturation without In-Pixel TDC for High-Dynamic-Range CMOS Image Sensor

Yuji INAGAKI; Yasuyuki MATSUYA

doi:10.1587/transele.2020CTP0001

A Method for Detecting Timing of Photodiode Saturation without In-Pixel TDC for High-Dynamic-Range CMOS Image Sensor

Yuji INAGAKI, Yasuyuki MATSUYA

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A method for detecting the timing of photodiode (PD) saturation without using an in-pixel time-to-digital converter (TDC) is proposed. Detecting PD saturation time is an approach to extend the dynamic range of a CMOS image sensor (CIS) without multiple exposures. In addition to accumulated charges in a PD, PD saturation time can be used as a signal related to light intensity. However, in previously reported CISs with detecting PD saturation time, an in-pixel TDC is used to detect and store PD saturation time. That makes the resolution of a CIS lower because an in-pixel TDC requires a large area. As for the proposed pixel circuit, PD saturation time is detected and stored as a voltage in a capacitor. The voltage is read and converted to a digital code by a column ADC after an exposure. As a result, an in-pixel TDC is not required. A signal-processing and calibration method for combining two signals, which are saturation time and accumulated charges, linearly are also proposed. Circuit simulations confirmed that the proposed method extends the dynamic range by 36 dB and its total dynamic range to 95 dB. Effectiveness of the calibration was also confirmed through circuit simulations.

Publication: IEICE TRANSACTIONS on Electronics Vol.E104-C No.10 pp.607-616

Publication Date: 2021/10/01

Publicized: 2021/04/09

Online ISSN: 1745-1353

DOI: 10.1587/transele.2020CTP0001

Type of Manuscript: Special Section PAPER (Special Section on Analog Circuits and Their Application Technologies)

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Authors

Yuji INAGAKI
Aoyama Gakuin University
Yasuyuki MATSUYA
Aoyama Gakuin University

Keyword

CMOS image sensor (CIS), high dynamic range (HDR), photodiode saturation time, timing detection

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Yuji INAGAKI, Yasuyuki MATSUYA, "A Method for Detecting Timing of Photodiode Saturation without In-Pixel TDC for High-Dynamic-Range CMOS Image Sensor" in IEICE TRANSACTIONS on Electronics, vol. E104-C, no. 10, pp. 607-616, October 2021, doi: 10.1587/transele.2020CTP0001.
Abstract: A method for detecting the timing of photodiode (PD) saturation without using an in-pixel time-to-digital converter (TDC) is proposed. Detecting PD saturation time is an approach to extend the dynamic range of a CMOS image sensor (CIS) without multiple exposures. In addition to accumulated charges in a PD, PD saturation time can be used as a signal related to light intensity. However, in previously reported CISs with detecting PD saturation time, an in-pixel TDC is used to detect and store PD saturation time. That makes the resolution of a CIS lower because an in-pixel TDC requires a large area. As for the proposed pixel circuit, PD saturation time is detected and stored as a voltage in a capacitor. The voltage is read and converted to a digital code by a column ADC after an exposure. As a result, an in-pixel TDC is not required. A signal-processing and calibration method for combining two signals, which are saturation time and accumulated charges, linearly are also proposed. Circuit simulations confirmed that the proposed method extends the dynamic range by 36 dB and its total dynamic range to 95 dB. Effectiveness of the calibration was also confirmed through circuit simulations.
URL: https://globals.ieice.org/en_transactions/electronics/10.1587/transele.2020CTP0001/_p

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@ARTICLE{e104-c_10_607,
author={Yuji INAGAKI, Yasuyuki MATSUYA, },
journal={IEICE TRANSACTIONS on Electronics},
title={A Method for Detecting Timing of Photodiode Saturation without In-Pixel TDC for High-Dynamic-Range CMOS Image Sensor},
year={2021},
volume={E104-C},
number={10},
pages={607-616},
abstract={A method for detecting the timing of photodiode (PD) saturation without using an in-pixel time-to-digital converter (TDC) is proposed. Detecting PD saturation time is an approach to extend the dynamic range of a CMOS image sensor (CIS) without multiple exposures. In addition to accumulated charges in a PD, PD saturation time can be used as a signal related to light intensity. However, in previously reported CISs with detecting PD saturation time, an in-pixel TDC is used to detect and store PD saturation time. That makes the resolution of a CIS lower because an in-pixel TDC requires a large area. As for the proposed pixel circuit, PD saturation time is detected and stored as a voltage in a capacitor. The voltage is read and converted to a digital code by a column ADC after an exposure. As a result, an in-pixel TDC is not required. A signal-processing and calibration method for combining two signals, which are saturation time and accumulated charges, linearly are also proposed. Circuit simulations confirmed that the proposed method extends the dynamic range by 36 dB and its total dynamic range to 95 dB. Effectiveness of the calibration was also confirmed through circuit simulations.},
keywords={},
doi={10.1587/transele.2020CTP0001},
ISSN={1745-1353},
month={October},}

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TY - JOUR
TI - A Method for Detecting Timing of Photodiode Saturation without In-Pixel TDC for High-Dynamic-Range CMOS Image Sensor
T2 - IEICE TRANSACTIONS on Electronics
SP - 607
EP - 616
AU - Yuji INAGAKI
AU - Yasuyuki MATSUYA
PY - 2021
DO - 10.1587/transele.2020CTP0001
JO - IEICE TRANSACTIONS on Electronics
SN - 1745-1353
VL - E104-C
IS - 10
JA - IEICE TRANSACTIONS on Electronics
Y1 - October 2021
AB - A method for detecting the timing of photodiode (PD) saturation without using an in-pixel time-to-digital converter (TDC) is proposed. Detecting PD saturation time is an approach to extend the dynamic range of a CMOS image sensor (CIS) without multiple exposures. In addition to accumulated charges in a PD, PD saturation time can be used as a signal related to light intensity. However, in previously reported CISs with detecting PD saturation time, an in-pixel TDC is used to detect and store PD saturation time. That makes the resolution of a CIS lower because an in-pixel TDC requires a large area. As for the proposed pixel circuit, PD saturation time is detected and stored as a voltage in a capacitor. The voltage is read and converted to a digital code by a column ADC after an exposure. As a result, an in-pixel TDC is not required. A signal-processing and calibration method for combining two signals, which are saturation time and accumulated charges, linearly are also proposed. Circuit simulations confirmed that the proposed method extends the dynamic range by 36 dB and its total dynamic range to 95 dB. Effectiveness of the calibration was also confirmed through circuit simulations.
ER -