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Special Issue "Advanced CMOS Image Sensors and Emerging Applications"

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: closed (28 February 2019)

Special Issue Editor

Guest Editor
Prof. Dr. Keiichiro Kagawa

Research Institute of Electronics, Shizuoka University, Japan
Website | E-Mail
Interests: biomedical, industrial, and agricultural applications of high-performance and functional CMOS image sensors; computational cameras

Special Issue Information

Dear Colleagues,

It is my pleasure to invite you to submit your technological contributions to this Special Issue, titled “Advanced CMOS Image Sensors and Emerging Applications”.

The progress in image sensor technologies and applications of image sensors is tremendous. The continuous progress and diversity in the engineering of image sensors and imaging systems, as well as state-of-the-art and emerging technologies for/in image sensors will be explored.

CMOS image sensors are now used in various fields such as computational photography, augmented reality, digital healthcare, biomedical imaging, and so on. These applications require CMOS image sensors to have new functions or new architecture to enhance their performance. On the other hand, new fabrication technologies like plasmonics will provide new features to sensor pixels.

This Special Issue aims to highlight advances in functional and high-performance CMOS image sensors. In addition, useful suggestions for image sensors from any technologies of image sensor applications, which can evolve or change the image sensor architecture, are also welcome. Topics include, but are not limited to:

  • Image sensor technologies: process, circuit, architecture
  • Image sensors for/in optics and photonics: nanophotonics, plasmonics, microscopy, spectroscopy
  • Image sensors for/in computational imaging and computational photography
  • Imaging systems with state-of-the-art image sensors
  • Image sensors for/in emerging applications and related topics of image sensors and imaging systems: Multi-spectral imaging, ultra-fast imaging, biomedical imaging, IoT, VR, deep learning, and so on

This Special Issue cooperate with the "4th International Workshop on Image Sensors and Imaging Systems (IWISS2018)", held in Tokyo, Japan, 28–29 November 2018. The authors of papers presented at this conference and within the scope of Sensors may submit a technically extended version to this Special Issue.

4th International Workshop on Image Sensors and Imaging Systems:
http://www.i-photonics.jp/meetings.html#20181128IWISS

Important Dates for IWISS2018:
October 5, 2018—Abstract Submission Deadline

Prof. Dr. Keiichiro Kagawa
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • CMOS image sensors
  • CMOS image sensor process
  • CMOS image sensor circuits
  • CMOS image sensor architecture
  • CMOS image sensor applications
  • Imaging systems

Published Papers (9 papers)

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Research

Open AccessArticle Effects of Offset Pixel Aperture Width on the Performances of Monochrome CMOS Image Sensors for Depth Extraction
Sensors 2019, 19(8), 1823; https://doi.org/10.3390/s19081823 (registering DOI)
Received: 28 February 2019 / Revised: 11 April 2019 / Accepted: 14 April 2019 / Published: 16 April 2019
PDF Full-text (1675 KB)
Abstract
This paper presents the effects of offset pixel aperture width on the performance of monochrome (MONO) CMOS image sensors (CISs) for a three-dimensional image sensor. Using a technique to integrate the offset pixel aperture (OPA) inside each pixel, the depth information can be [...] Read more.
This paper presents the effects of offset pixel aperture width on the performance of monochrome (MONO) CMOS image sensors (CISs) for a three-dimensional image sensor. Using a technique to integrate the offset pixel aperture (OPA) inside each pixel, the depth information can be acquired using a disparity from OPA patterns. The OPA is classified into two pattern types: Left-offset pixel aperture (LOPA) and right-offset pixel aperture (ROPA). These OPAs are divided into odd and even rows and integrated in a pixel array. To analyze the correlation between the OPA width and the sensor characteristics, experiments were conducted by configuring the test elements group (TEG) regions. The OPA width of the TEG region for the measurement varied in the range of 0.3–0.5 μm. As the aperture width decreased, the disparity of the image increased, while the sensitivity decreased. It is possible to acquire depth information by the disparity obtained from the proposed MONO CIS using the OPA technique without an external light source. Therefore, the proposed MONO CIS with OPA could easily be applied to miniaturized devices. The proposed MONO CIS was designed and manufactured using the 0.11 μm CIS process. Full article
(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)
Open AccessArticle Plasmonic Color Filter Array with High Color Purity for CMOS Image Sensors
Sensors 2019, 19(8), 1750; https://doi.org/10.3390/s19081750
Received: 5 March 2019 / Revised: 4 April 2019 / Accepted: 6 April 2019 / Published: 12 April 2019
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Abstract
We demonstrate the multiband color filtering of a standard RGB color and a complementary CMY color by a plasmonic color filter, composed of concentric corrugated metallic thin film rings. The surface plasmon resonance is excited by the periodic corrugation, and the coupled light [...] Read more.
We demonstrate the multiband color filtering of a standard RGB color and a complementary CMY color by a plasmonic color filter, composed of concentric corrugated metallic thin film rings. The surface plasmon resonance is excited by the periodic corrugation, and the coupled light is transmitted through the central subwavelength aperture. Color selectivity is achieved not only in the visible but also in the near-infrared (NIR) region. Therefore, simultaneous imaging with visible and NIR can be realized by the integration of plasmonic color filters with sensors. We investigate the angle of incidence dependence of the transmission color selectivity and the color purity of the fabricated plasmonic color filter array. Full article
(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)
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Open AccessArticle Averaging Pixel Current Adjustment Technique for Reducing Fixed Pattern Noise in the Bolometer-Type Uncooled Infrared Image Sensor
Sensors 2019, 19(7), 1653; https://doi.org/10.3390/s19071653
Received: 28 February 2019 / Revised: 25 March 2019 / Accepted: 4 April 2019 / Published: 6 April 2019
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Abstract
In this paper, we propose an averaging pixel current adjustment technique for reducing fixed pattern noise (FPN) in the bolometer-type uncooled infrared image sensor. The averaging pixel current adjustment technique is composed of active pixel, reference pixel, and calibration circuit. Polysilicon resistors were [...] Read more.
In this paper, we propose an averaging pixel current adjustment technique for reducing fixed pattern noise (FPN) in the bolometer-type uncooled infrared image sensor. The averaging pixel current adjustment technique is composed of active pixel, reference pixel, and calibration circuit. Polysilicon resistors were used in each active pixel and reference pixel. Resistance deviation among active pixels integrated with the same resistance value cause FPN. The principle of the averaging pixel current adjustment technique for removing FPN is based on the subtraction of dark current of the active pixel from the dark current of the reference pixel. The subtracted current is converted into the voltage, which contains pixel calibration information. The calibration circuit is used to adjust the calibration current. After calibration, the nano-ampere current is output with small deviation. The proposed averaging pixel current adjustment technique is implemented by a chip composed of a pixel array, a calibration circuit, average current generators, and readout circuits. The chip was fabricated using a standard 0.35 μm CMOS process and its performance was evaluated. Full article
(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)
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Open AccessArticle Fast Volumetric Feedback under Microscope by Temporally Coded Exposure Camera
Sensors 2019, 19(7), 1606; https://doi.org/10.3390/s19071606
Received: 27 February 2019 / Revised: 22 March 2019 / Accepted: 23 March 2019 / Published: 3 April 2019
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Abstract
We developed a temporally coded exposure (TeCE) camera that can cope with high-speed focus variations of a tunable acoustic gradient index (TAG) lens. The TeCE camera can execute a very short exposure multiple times at an arbitrary timing during one shot. Furthermore, by [...] Read more.
We developed a temporally coded exposure (TeCE) camera that can cope with high-speed focus variations of a tunable acoustic gradient index (TAG) lens. The TeCE camera can execute a very short exposure multiple times at an arbitrary timing during one shot. Furthermore, by accumulating the photoelectrons generated by each exposure, it is possible to maintain the brightness even with a short exposure time. By synchronously driving the TeCE camera and the TAG lens, different focal planes of an observation target can be acquired at high speed. As a result, high-speed three-dimensional measurement becomes possible, and this can be used for feedback of three-dimensional information. In the work described in this paper, we conducted a focus tracking experiment to evaluate the feedback performance of the TeCE camera. From the experimental results, we confirmed the feedback capability of the TeCE camera. Full article
(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)
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Open AccessArticle Front-Inner Lens for High Sensitivity of CMOS Image Sensors
Sensors 2019, 19(7), 1536; https://doi.org/10.3390/s19071536
Received: 28 February 2019 / Revised: 26 March 2019 / Accepted: 27 March 2019 / Published: 29 March 2019
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Abstract
Due to the continuing improvements in camera technology, a high-resolution CMOS image sensor is required. However, a high-resolution camera requires that the pixel pitch is smaller than 1.0 μm in the limited sensor area. Accordingly, the optical performance of the pixel deteriorates with [...] Read more.
Due to the continuing improvements in camera technology, a high-resolution CMOS image sensor is required. However, a high-resolution camera requires that the pixel pitch is smaller than 1.0 μm in the limited sensor area. Accordingly, the optical performance of the pixel deteriorates with the aspect ratio. If the pixel depth is shallow, the aspect ratio is enhanced. Also, optical performance can improve if the sensitivity in the long wavelengths is guaranteed. In this current work, we propose a front-inner lens structure that enhances the sensitivity to the small pixel size and the shallow pixel depth. The front-inner lens was located on the front side of the backside illuminated pixel for enhancement of the absorption. The proposed structures in the 1.0 μm pixel pitch were investigated with 3D optical simulation. The pixel depths were 3.0, 2.0, and 1.0 μm. The materials of the front-inner lens were varied, including air and magnesium fluoride (MgF2). For analysis of the sensitivity enhancement, we compared the typical pixel with the suggested pixel and confirmed that the absorption rate of the suggested pixel was improved by a maximum of 7.27%, 10.47%, and 29.28% for 3.0, 2.0, and 1.0 μm pixel depths, respectively. Full article
(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)
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Open AccessArticle A High Full Well Capacity CMOS Image Sensor for Space Applications
Sensors 2019, 19(7), 1505; https://doi.org/10.3390/s19071505
Received: 24 January 2019 / Revised: 24 March 2019 / Accepted: 26 March 2019 / Published: 28 March 2019
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Abstract
This paper presents a high full well capacity (FWC) CMOS image sensor (CIS) for space applications. The proposed pixel design effectively increases the FWC without inducing overflow of photo-generated charge in a limited pixel area. An MOS capacitor is integrated in a pixel [...] Read more.
This paper presents a high full well capacity (FWC) CMOS image sensor (CIS) for space applications. The proposed pixel design effectively increases the FWC without inducing overflow of photo-generated charge in a limited pixel area. An MOS capacitor is integrated in a pixel and accumulated charges in a photodiode are transferred to the in-pixel capacitor multiple times depending on the maximum incident light intensity. In addition, the modulation transfer function (MTF) and radiation damage effect on the pixel, which are especially important for space applications, are studied and analyzed through fabrication of the CIS. The CIS was fabricated using a 0.11 μm 1-poly 4-metal CIS process to demonstrate the proposed techniques and pixel design. A measured FWC of 103,448 electrons and MTF improvement of 300% are achieved with 6.5 μm pixel pitch. Full article
(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)
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Open AccessArticle Super Field-of-View Lensless Camera by Coded Image Sensors
Sensors 2019, 19(6), 1329; https://doi.org/10.3390/s19061329
Received: 28 February 2019 / Revised: 12 March 2019 / Accepted: 12 March 2019 / Published: 16 March 2019
PDF Full-text (3054 KB) | HTML Full-text | XML Full-text
Abstract
A lensless camera is an ultra-thin computational-imaging system. Existing lensless cameras are based on the axial arrangement of an image sensor and a coding mask, and therefore, the back side of the image sensor cannot be captured. In this paper, we propose a [...] Read more.
A lensless camera is an ultra-thin computational-imaging system. Existing lensless cameras are based on the axial arrangement of an image sensor and a coding mask, and therefore, the back side of the image sensor cannot be captured. In this paper, we propose a lensless camera with a novel design that can capture the front and back sides simultaneously. The proposed camera is composed of multiple coded image sensors, which are complementary-metal-oxide-semiconductor (CMOS) image sensors in which air holes are randomly made at some pixels by drilling processing. When the sensors are placed facing each other, the object-side sensor works as a coding mask and the other works as a sparsified image sensor. The captured image is a sparse coded image, which can be decoded computationally by using compressive sensing-based image reconstruction. We verified the feasibility of the proposed lensless camera by simulations and experiments. The proposed thin lensless camera realized super-field-of-view imaging without lenses or coding masks and therefore can be used for rich information sensing in confined spaces. This work also suggests a new direction in the design of CMOS image sensors in the era of computational imaging. Full article
(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)
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Open AccessArticle Compensation for Process and Temperature Dependency in a CMOS Image Sensor
Sensors 2019, 19(4), 870; https://doi.org/10.3390/s19040870
Received: 27 January 2019 / Revised: 14 February 2019 / Accepted: 17 February 2019 / Published: 19 February 2019
PDF Full-text (3559 KB) | HTML Full-text | XML Full-text
Abstract
This paper analyzes and compensates for process and temperature dependency among a (Complementary Metal Oxide Semiconductor) CMOS image sensor (CIS) array. Both the analysis and compensation are supported with experimental results on the CIS’s dark current, dark signal non-uniformity (DSNU), and conversion gain [...] Read more.
This paper analyzes and compensates for process and temperature dependency among a (Complementary Metal Oxide Semiconductor) CMOS image sensor (CIS) array. Both the analysis and compensation are supported with experimental results on the CIS’s dark current, dark signal non-uniformity (DSNU), and conversion gain (CG). To model and to compensate for process variations, process sensors based on pixel source follower (SF)’s transconductance gm,SF have been proposed to model and to be compared against the measurement results of SF gain ASF. In addition, ASF’s thermal dependency has been analyzed in detail. To provide thermal information required for temperature compensation, six scattered bipolar junction transistor (BJT)-based temperature sensors replace six image pixels inside the array. They are measured to have an untrimmed inaccuracy within ±0.5 °C. Dark signal and CG’s thermal dependencies are compensated using the on-chip temperature sensors by at least 79% and 87%, respectively. Full article
(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)
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Open AccessArticle An Analog-Front ROIC with On-Chip Non-Uniformity Compensation for Diode-Based Infrared Image Sensors
Sensors 2019, 19(2), 298; https://doi.org/10.3390/s19020298
Received: 24 November 2018 / Revised: 8 January 2019 / Accepted: 10 January 2019 / Published: 13 January 2019
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Abstract
This paper proposes a CMOS front-end readout-integrated circuit (ROIC) with on-chip non-uniformity compensation technique for a diode-based uncooled infrared image sensor. Two techniques are adopted to achieve on-chip non-uniformity compensation: a reference dummy metal line is introduced to alleviate the dominant non-uniformity with [...] Read more.
This paper proposes a CMOS front-end readout-integrated circuit (ROIC) with on-chip non-uniformity compensation technique for a diode-based uncooled infrared image sensor. Two techniques are adopted to achieve on-chip non-uniformity compensation: a reference dummy metal line is introduced to alleviate the dominant non-uniformity with IR-drop presented in large pixel array, and a current splitting architecture-based variable current source for diode bias is proposed to compensate other residual non-uniformity. A differential integrator is chosen as the main amplifier of readout circuit for its superior noise performance. For low power design, a pulse-powered row buffer is designed in this work. The proposed ROIC for 384 × 288 diode-based detector array is fabricated with a 0.35- μ m CMOS process. It occupies an area of 4.4 mm × 15 mm, and the power consumption is 180 mW. The measured result shows that with the proposed on-chip non-uniformity compensation, the output voltage variation is greatly reduced from 2.5 V to 60 mV. Full article
(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)
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