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Open AccessFeature PaperArticle

An Optical Filter-Less CMOS Image Sensor with Differential Spectral Response Pixels for Simultaneous UV-Selective and Visible Imaging

Graduate School of Engineering, Tohoku University, 6-6-11-811, Aza-Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
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This manuscript is an extended version of the conference paper: A VGA Optical Filter-less CMOS Image Sensor with UV-selective and Visible Light Channels by Differential Spectral Response Pixels. In Proceedings of the International Image Sensor Workshop 2019, Snowbird, UT, USA, 23–27 June 2019.
Sensors 2020, 20(1), 13; https://doi.org/10.3390/s20010013
Received: 2 October 2019 / Revised: 13 December 2019 / Accepted: 17 December 2019 / Published: 18 December 2019
This paper presents a complementary metal-oxide-semiconductor (CMOS) image sensor (CIS) capable of capturing UV-selective and visible light images simultaneously by a single exposure and without employing optical filters, suitable for applications that require simultaneous UV and visible light imaging, or UV imaging in variable light environment. The developed CIS is composed by high and low UV sensitivity pixel types, arranged alternately in a checker pattern. Both pixel types were designed to have matching sensitivities for non-UV light. The UV-selective image is captured by extracting the differential spectral response between adjacent pixels, while the visible light image is captured simultaneously by the low UV sensitivity pixels. Also, to achieve high conversion gain and wide dynamic range simultaneously, the lateral overflow integration capacitor (LOFIC) technology was introduced in both pixel types. The developed CIS has a pixel pitch of 5.6 µm and exhibits 172 µV/e conversion gain, 131 ke full well capacity (FWC), and 92.3 dB dynamic range. The spectral sensitivity ranges of the high and low UV sensitivity pixels are of 200–750 nm and 390–750 nm, respectively. The resulting sensitivity range after the differential spectral response extraction is of 200–480 nm. This paper presents details regarding the CIS pixels structures, doping profiles, device simulations, and the measurement results for photoelectric response and spectral sensitivity for both pixel types. Also, sample images of UV-selective and visible spectral imaging using the developed CIS are presented. View Full-Text
Keywords: UV; CMOS; image; sensor; ultraviolet; imaging; differential; spectral; response; silicon UV; CMOS; image; sensor; ultraviolet; imaging; differential; spectral; response; silicon
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Sipauba Carvalho da Silva, Y.R.; Kuroda, R.; Sugawa, S. An Optical Filter-Less CMOS Image Sensor with Differential Spectral Response Pixels for Simultaneous UV-Selective and Visible Imaging. Sensors 2020, 20, 13.

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