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11 pages, 3342 KiB

Open AccessArticle

Effects of Offset Pixel Aperture Width on the Performances of Monochrome CMOS Image Sensors for Depth Extraction

by Jimin Lee, Byoung-Soo Choi, Sang-Hwan Kim, Jewon Lee, Junwoo Lee, Seunghyuk Chang, JongHo Park, Sang-Jin Lee and Jang-Kyoo Shin

Sensors 2019, 19(8), 1823; https://doi.org/10.3390/s19081823 - 16 Apr 2019

Cited by 6 | Viewed by 4251

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)

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10 pages, 24337 KiB

Open AccessArticle

Plasmonic Color Filter Array with High Color Purity for CMOS Image Sensors

by Atsutaka Miyamichi, Atsushi Ono, Keiichiro Kagawa, Keita Yasutomi and Shoji Kawahito

Sensors 2019, 19(8), 1750; https://doi.org/10.3390/s19081750 - 12 Apr 2019

Cited by 20 | Viewed by 9866

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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12 pages, 3060 KiB

Open AccessArticle

Averaging Pixel Current Adjustment Technique for Reducing Fixed Pattern Noise in the Bolometer-Type Uncooled Infrared Image Sensor

by Sang-Hwan Kim, Byoung-Soo Choi, Jimin Lee, Junwoo Lee, Jewon Lee, Jae-Hyoun Park, Kyoung-Il Lee and Jang-Kyoo Shin

Sensors 2019, 19(7), 1653; https://doi.org/10.3390/s19071653 - 6 Apr 2019

Cited by 3 | Viewed by 4502

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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13 pages, 2571 KiB

Open AccessArticle

Fast Volumetric Feedback under Microscope by Temporally Coded Exposure Camera

by Kazuki Yamato, Toshihiko Yamashita, Hiroyuki Chiba and Hiromasa Oku

Sensors 2019, 19(7), 1606; https://doi.org/10.3390/s19071606 - 3 Apr 2019

Cited by 7 | Viewed by 3538

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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9 pages, 3419 KiB

Open AccessArticle

Front-Inner Lens for High Sensitivity of CMOS Image Sensors

by Godeun Seok and Yunkyung Kim

Sensors 2019, 19(7), 1536; https://doi.org/10.3390/s19071536 - 29 Mar 2019

Cited by 5 | Viewed by 6043

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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16 pages, 5782 KiB

Open AccessArticle

A High Full Well Capacity CMOS Image Sensor for Space Applications

by Woo-Tae Kim, Cheonwi Park, Hyunkeun Lee, Ilseop Lee and Byung-Geun Lee

Sensors 2019, 19(7), 1505; https://doi.org/10.3390/s19071505 - 28 Mar 2019

Cited by 16 | Viewed by 8905

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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13 pages, 3054 KiB

Open AccessArticle

Super Field-of-View Lensless Camera by Coded Image Sensors

by Tomoya Nakamura, Keiichiro Kagawa, Shiho Torashima and Masahiro Yamaguchi

Sensors 2019, 19(6), 1329; https://doi.org/10.3390/s19061329 - 16 Mar 2019

Cited by 16 | Viewed by 7860

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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15 pages, 3559 KiB

Open AccessArticle

Compensation for Process and Temperature Dependency in a CMOS Image Sensor

by Shuang Xie and Albert Theuwissen

Sensors 2019, 19(4), 870; https://doi.org/10.3390/s19040870 - 19 Feb 2019

Cited by 7 | Viewed by 6237

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 g_m_,SF have been proposed to model and to be compared against the measurement results of SF gain A_SF. In addition, A_SF’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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13 pages, 6673 KiB

Open AccessArticle

An Analog-Front ROIC with On-Chip Non-Uniformity Compensation for Diode-Based Infrared Image Sensors

by Mao Ye, Gongyuan Zhao, Yao Li and Yiqiang Zhao

Sensors 2019, 19(2), 298; https://doi.org/10.3390/s19020298 - 13 Jan 2019

Cited by 5 | Viewed by 5820

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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Review

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16 pages, 3758 KiB

Open AccessReview

Light-In-Flight Imaging by a Silicon Image Sensor: Toward the Theoretical Highest Frame Rate

by Takeharu Goji Etoh, Tomoo Okinaka, Yasuhide Takano, Kohsei Takehara, Hitoshi Nakano, Kazuhiro Shimonomura, Taeko Ando, Nguyen Ngo, Yoshinari Kamakura, Vu Truong Son Dao, Anh Quang Nguyen, Edoardo Charbon, Chao Zhang, Piet De Moor, Paul Goetschalckx and Luc Haspeslagh

Sensors 2019, 19(10), 2247; https://doi.org/10.3390/s19102247 - 15 May 2019

Cited by 30 | Viewed by 9218

Abstract

Light in flight was captured by a single shot of a newly developed backside-illuminated multi-collection-gate image sensor at a frame interval of 10 ns without high-speed gating devices such as a streak camera or post data processes. This paper reports the achievement and [...] Read more.

Light in flight was captured by a single shot of a newly developed backside-illuminated multi-collection-gate image sensor at a frame interval of 10 ns without high-speed gating devices such as a streak camera or post data processes. This paper reports the achievement and further evolution of the image sensor toward the theoretical temporal resolution limit of 11.1 ps derived by the authors. The theoretical analysis revealed the conditions to minimize the temporal resolution. Simulations show that the image sensor designed following the specified conditions and fabricated by existing technology will achieve a frame interval of 50 ps. The sensor, 200 times faster than our latest sensor will innovate advanced analytical apparatuses using time-of-flight or lifetime measurements, such as imaging TOF-MS, FLIM, pulse neutron tomography, PET, LIDAR, and more, beyond these known applications. Full article

(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)

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