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An Optical Filter-Less CMOS Image Sensor with Differential Spectral Response Pixels for Simultaneous UV-Selective and
Yhang Ricardo Sipauba Carvalho da Silva1, Rihito Kuroda1, Shigetoshi Sugawa1
1Graduate School of Engineering, Tohoku University, 6-6-11-811, Aza-Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan.
Sensors (Basel, Switzerland)
|December 22, 2019
Summary
This study introduces a novel complementary metal-oxide-semiconductor (CMOS) image sensor (CIS) for simultaneous UV and visible light imaging without optical filters. It achieves UV-selective imaging by differentiating pixel responses, enabling new applications in variable lighting conditions.
Area of Science:
- Optoelectronics
- Semiconductor device physics
- Image sensor technology
Background:
- Simultaneous UV and visible light imaging is crucial for various applications but often requires complex optical filtering or multiple sensors.
- Existing CMOS image sensors (CIS) typically lack the capability for selective UV light capture alongside visible light imaging in a single exposure.
- The need for efficient UV imaging in diverse and variable lighting environments necessitates innovative sensor designs.
Purpose of the Study:
- To develop a novel CIS capable of capturing UV-selective and visible light images simultaneously from a single exposure.
- To design and implement a CIS architecture that eliminates the need for optical filters for UV/visible light separation.
- To characterize the performance of the developed CIS, including its spectral sensitivity, conversion gain, full well capacity, and dynamic range.
Main Methods:
- Designed a CIS with alternating high and low UV sensitivity pixel types in a checkerboard pattern.
- Utilized lateral overflow integration capacitor (LOFIC) technology in both pixel types for high conversion gain and wide dynamic range.
- Extracted UV-selective images via differential spectral response between adjacent pixels and visible light images from low UV sensitivity pixels.
Main Results:
- Achieved simultaneous UV-selective (200-480 nm) and visible light imaging without optical filters.
- The developed CIS features a 5.6 µm pixel pitch, 172 µV/e- conversion gain, 131 ke- full well capacity, and 92.3 dB dynamic range.
- Demonstrated spectral sensitivity ranges of 200-750 nm (high UV) and 390-750 nm (low UV) for individual pixel types.
Conclusions:
- The developed CIS successfully enables simultaneous UV-selective and visible light imaging in a single exposure, offering a filterless solution.
- The unique pixel design and LOFIC technology provide excellent performance metrics, suitable for demanding imaging applications.
- This technology advances UV imaging capabilities, particularly in variable light environments and applications requiring spectral differentiation.
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