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Special Issue "Image Sensors"

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

Deadline for manuscript submissions: 1 December 2018

Special Issue Editors

Guest Editor
Prof. Dr. Lucio Pancheri

DII, University of Trento, Via Sommarive, 9, 38123 Trento, Italy
Website | E-Mail
Interests: Modeling and characterization of electron devices; CMOS integrated photodetectors and image sensors; Single-Photon Avalanche Diodes; 3D Imaging; Radiation detectors
Guest Editor
Dr. Matteo Perenzoni

Fondazione Bruno Kessler, Via Sommarive 14, 38123 Trento, Italy
Website | E-Mail
Interests: Image Sensors; Analog Integrated Circuits; Terahertz and Infrared Detectors; Microelectronics; Single Photon imaging
Guest Editor
Dr. Nicola Massari

Fondazione Bruno Kessler, Via Sommarive 14, 38123 Trento, Italy
Website | E-Mail
Interests: Image Sensors; Analog and Mixed-Signal integrated circuit design; Smart image sensors and AER imagers; Ultra-low power vision systems; X-ray imaging; Single photon

Special Issue Information

Dear Colleagues,

Although the quality of mainstream CMOS image sensors has reached outstanding levels in the last few years, new challenges are continuously pushing the image sensor research community. An increasing number of applications calls for dedicated image sensors with custom specifications in terms of space and time resolution, efficiency, power consumption and on-chip processing capabilities. These new requirements can often be met only with a combined effort of process, circuit, and system design. An interdisciplinary approach, involving research in material science, electronics and optics, is thus needed to push image sensors beyond the current state-of-the-art.

This Special Issue aims at providing an overview of current leading-edge research in image sensor technology, focusing on the following topics:

  • Image sensor process technology and packaging

  • Analog and digital circuits for image sensors

  • Image sensor characterization and modelling

  • Photon-counting image sensors

  • Ultra-high frame rate

  • Multispectral and hyperspectral imaging

  • Vision sensors: on-chip processing and computational imaging

  • Ultra-low power imaging

  • CMOS hybridization with organic and inorganic materials

  • Infrared and THz focal plane arrays

  • X-ray and charged particle image sensors

Prof. Lucio Pancheri
Dr. Matteo Perenzoni
Dr. Nicola Massari
Guest Editors

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 monthly 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

  • Pixel design

  • CMOS Image Sensors

  • CIS process technology

  • 3D stacking

  • Image sensor circuits and architectures

  • Quanta Image Sensors

  • 3D imaging

  • SPAD

  • Large-area image sensors

  • Hybrid image sensors

  • Vision sensors

  • Computational image sensors

  • Low-power image sensors

  • Frame-free vision sensors

  • Image sensor characterization

  • Infrared focal plane arrays

  • THz imaging

  • Above-CMOS detectors

  • Radiation imaging detectors

Published Papers (10 papers)

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Research

Open AccessArticle A Low-Noise Direct Incremental A/D Converter for FET-Based THz Imaging Detectors
Sensors 2018, 18(6), 1867; https://doi.org/10.3390/s18061867
Received: 20 March 2018 / Revised: 9 May 2018 / Accepted: 5 June 2018 / Published: 7 June 2018
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Abstract
This paper presents the design, implementation and characterization results of a pixel-level readout chain integrated with a FET-based terahertz (THz) detector for imaging applications. The readout chain is fabricated in a standard 150-nm CMOS technology and contains a cascade of a preamplification and
[...] Read more.
This paper presents the design, implementation and characterization results of a pixel-level readout chain integrated with a FET-based terahertz (THz) detector for imaging applications. The readout chain is fabricated in a standard 150-nm CMOS technology and contains a cascade of a preamplification and noise reduction stage based on a parametric chopper amplifier and a direct analog-to-digital conversion by means of an incremental ΣΔ converter, performing a lock-in operation with modulated sources. The FET detector is integrated with an on-chip antenna operating in the frequency range of 325–375 GHz and compliant with all process design rules. The cascade of the FET THz detector and readout chain is evaluated in terms of responsivity and Noise Equivalent Power (NEP) measurements. The measured readout input-referred noise of 1.6 μ V r m s allows preserving the FET detector sensitivity by achieving a minimum NEP of 376 pW/ Hz in the optimum bias condition, while directly providing a digital output. The integrated readout chain features 65-dB peak-SNR and 80-μ W power consumption from a 1.8-V supply. The area of the antenna-coupled FET detector and the readout chain fits a pixel pitch of 455 μm, which is suitable for pixel array implementation. The proposed THz pixel has been successfully applied for imaging of concealed objects in a paper envelope under continuous-wave illumination. Full article
(This article belongs to the Special Issue Image Sensors)
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Open AccessArticle Virtual Deformable Image Sensors: Towards to a General Framework for Image Sensors with Flexible Grids and Forms
Sensors 2018, 18(6), 1856; https://doi.org/10.3390/s18061856
Received: 17 April 2018 / Revised: 21 May 2018 / Accepted: 25 May 2018 / Published: 6 June 2018
PDF Full-text (8198 KB) | HTML Full-text | XML Full-text
Abstract
Our vision system has a combination of different sensor arrangements from hexagonal to elliptical ones. Inspired from this variation in type of arrangements we propose a general framework by which it becomes feasible to create virtual deformable sensor arrangements. In the framework for
[...] Read more.
Our vision system has a combination of different sensor arrangements from hexagonal to elliptical ones. Inspired from this variation in type of arrangements we propose a general framework by which it becomes feasible to create virtual deformable sensor arrangements. In the framework for a certain sensor arrangement a configuration of three optional variables are used which includes the structure of arrangement, the pixel form and the gap factor. We show that the histogram of gradient orientations of a certain sensor arrangement has a specific distribution (called ANCHOR) which is obtained by using at least two generated images of the configuration. The results showed that ANCHORs change their patterns by the change of arrangement structure. In this relation pixel size changes have 10-fold more impact on ANCHORs than gap factor changes. A set of 23 images; randomly chosen from a database of 1805 images, are used in the evaluation where each image generates twenty-five different images based on the sensor configuration. The robustness of ANCHORs properties is verified by computing ANCHORs for totally 575 images with different sensor configurations. We believe by using the framework and ANCHOR it becomes feasible to plan a sensor arrangement in the relation to a specific application and its requirements where the sensor arrangement can be planed even as combination of different ANCHORs. Full article
(This article belongs to the Special Issue Image Sensors)
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Open AccessArticle Sensitivity and Resolution Improvement in RGBW Color Filter Array Sensor
Sensors 2018, 18(5), 1647; https://doi.org/10.3390/s18051647
Received: 26 April 2018 / Revised: 17 May 2018 / Accepted: 19 May 2018 / Published: 21 May 2018
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Abstract
Recently, several red-green-blue-white (RGBW) color filter arrays (CFAs), which include highly sensitive W pixels, have been proposed. However, RGBW CFA patterns suffer from spatial resolution degradation owing to the sensor composition having more color components than the Bayer CFA pattern. RGBW CFA demosaicing
[...] Read more.
Recently, several red-green-blue-white (RGBW) color filter arrays (CFAs), which include highly sensitive W pixels, have been proposed. However, RGBW CFA patterns suffer from spatial resolution degradation owing to the sensor composition having more color components than the Bayer CFA pattern. RGBW CFA demosaicing methods reconstruct resolution using the correlation between white (W) pixels and pixels of other colors, which does not improve the red-green-blue (RGB) channel sensitivity to the W channel level. In this paper, we thus propose a demosaiced image post-processing method to improve the RGBW CFA sensitivity and resolution. The proposed method decomposes texture components containing image noise and resolution information. The RGB channel sensitivity and resolution are improved through updating the W channel texture component with those of RGB channels. For this process, a cross multilateral filter (CMF) is proposed. It decomposes the smoothness component from the texture component using color difference information and distinguishes color components through that information. Moreover, it decomposes texture components, luminance noise, color noise, and color aliasing artifacts from the demosaiced images. Finally, by updating the texture of the RGB channels with the W channel texture components, the proposed algorithm improves the sensitivity and resolution. Results show that the proposed method is effective, while maintaining W pixel resolution characteristics and improving sensitivity from the signal-to-noise ratio value by approximately 4.5 dB. Full article
(This article belongs to the Special Issue Image Sensors)
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Open AccessArticle The Dynamic Photometric Stereo Method Using a Multi-Tap CMOS Image Sensor
Sensors 2018, 18(3), 786; https://doi.org/10.3390/s18030786
Received: 28 December 2017 / Revised: 26 February 2018 / Accepted: 3 March 2018 / Published: 5 March 2018
PDF Full-text (1963 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The photometric stereo method enables estimation of surface normals from images that have been captured using different but known lighting directions. The classical photometric stereo method requires at least three images to determine the normals in a given scene. However, this method cannot
[...] Read more.
The photometric stereo method enables estimation of surface normals from images that have been captured using different but known lighting directions. The classical photometric stereo method requires at least three images to determine the normals in a given scene. However, this method cannot be applied to dynamic scenes because it is assumed that the scene remains static while the required images are captured. In this work, we present a dynamic photometric stereo method for estimation of the surface normals in a dynamic scene. We use a multi-tap complementary metal-oxide-semiconductor (CMOS) image sensor to capture the input images required for the proposed photometric stereo method. This image sensor can divide the electrons from the photodiode from a single pixel into the different taps of the exposures and can thus capture multiple images under different lighting conditions with almost identical timing. We implemented a camera lighting system and created a software application to enable estimation of the normal map in real time. We also evaluated the accuracy of the estimated surface normals and demonstrated that our proposed method can estimate the surface normals of dynamic scenes. Full article
(This article belongs to the Special Issue Image Sensors)
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Open AccessArticle The Design of a Single-Bit CMOS Image Sensor for Iris Recognition Applications
Sensors 2018, 18(2), 669; https://doi.org/10.3390/s18020669
Received: 10 January 2018 / Revised: 22 February 2018 / Accepted: 23 February 2018 / Published: 24 February 2018
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Abstract
This paper presents a single-bit CMOS image sensor (CIS) that uses a data processing technique with an edge detection block for simple iris segmentation. In order to recognize the iris image, the image sensor conventionally captures high-resolution image data in digital code, extracts
[...] Read more.
This paper presents a single-bit CMOS image sensor (CIS) that uses a data processing technique with an edge detection block for simple iris segmentation. In order to recognize the iris image, the image sensor conventionally captures high-resolution image data in digital code, extracts the iris data, and then compares it with a reference image through a recognition algorithm. However, in this case, the frame rate decreases by the time required for digital signal conversion of multi-bit digital data through the analog-to-digital converter (ADC) in the CIS. In order to reduce the overall processing time as well as the power consumption, we propose a data processing technique with an exclusive OR (XOR) logic gate to obtain single-bit and edge detection image data instead of multi-bit image data through the ADC. In addition, we propose a logarithmic counter to efficiently measure single-bit image data that can be applied to the iris recognition algorithm. The effective area of the proposed single-bit image sensor (174 × 144 pixel) is 2.84 mm2 with a 0.18 μm 1-poly 4-metal CMOS image sensor process. The power consumption of the proposed single-bit CIS is 2.8 mW with a 3.3 V of supply voltage and 520 frame/s of the maximum frame rates. The error rate of the ADC is 0.24 least significant bit (LSB) on an 8-bit ADC basis at a 50 MHz sampling frequency. Full article
(This article belongs to the Special Issue Image Sensors)
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Open AccessArticle Sub-THz Imaging Using Non-Resonant HEMT Detectors
Sensors 2018, 18(2), 543; https://doi.org/10.3390/s18020543
Received: 12 December 2017 / Revised: 2 February 2018 / Accepted: 6 February 2018 / Published: 10 February 2018
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Abstract
Plasma waves in gated 2-D systems can be used to efficiently detect THz electromagnetic radiation. Solid-state plasma wave-based sensors can be used as detectors in THz imaging systems. An experimental study of the sub-THz response of II-gate strained-Si Schottky-gated MODFETs (Modulation-doped Field-Effect Transistor)
[...] Read more.
Plasma waves in gated 2-D systems can be used to efficiently detect THz electromagnetic radiation. Solid-state plasma wave-based sensors can be used as detectors in THz imaging systems. An experimental study of the sub-THz response of II-gate strained-Si Schottky-gated MODFETs (Modulation-doped Field-Effect Transistor) was performed. The response of the strained-Si MODFET has been characterized at two frequencies: 150 and 300 GHz: The DC drain-to-source voltage transducing the THz radiation (photovoltaic mode) of 250-nm gate length transistors exhibited a non-resonant response that agrees with theoretical models and physics-based simulations of the electrical response of the transistor. When imposing a weak source-to-drain current of 5 μA, a substantial increase of the photoresponse was found. This increase is translated into an enhancement of the responsivity by one order of magnitude as compared to the photovoltaic mode, while the NEP (Noise Equivalent Power) is reduced in the subthreshold region. Strained-Si MODFETs demonstrated an excellent performance as detectors in THz imaging. Full article
(This article belongs to the Special Issue Image Sensors)
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Open AccessArticle Nuclear Radiation Degradation Study on HD Camera Based on CMOS Image Sensor at Different Dose Rates
Sensors 2018, 18(2), 514; https://doi.org/10.3390/s18020514
Received: 19 December 2017 / Revised: 23 January 2018 / Accepted: 6 February 2018 / Published: 8 February 2018
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Abstract
In this work, we irradiated a high-definition (HD) industrial camera based on a commercial-off-the-shelf (COTS) CMOS image sensor (CIS) with Cobalt-60 gamma-rays. All components of the camera under test were fabricated without radiation hardening, except for the lens. The irradiation experiments of the
[...] Read more.
In this work, we irradiated a high-definition (HD) industrial camera based on a commercial-off-the-shelf (COTS) CMOS image sensor (CIS) with Cobalt-60 gamma-rays. All components of the camera under test were fabricated without radiation hardening, except for the lens. The irradiation experiments of the HD camera under biased conditions were carried out at 1.0, 10.0, 20.0, 50.0 and 100.0 Gy/h. During the experiment, we found that the tested camera showed a remarkable degradation after irradiation and differed in the dose rates. With the increase of dose rate, the same target images become brighter. Under the same dose rate, the radiation effect in bright area is lower than that in dark area. Under different dose rates, the higher the dose rate is, the worse the radiation effect will be in both bright and dark areas. And the standard deviations of bright and dark areas become greater. Furthermore, through the progressive degradation analysis of the captured image, experimental results demonstrate that the attenuation of signal to noise ratio (SNR) versus radiation time is not obvious at the same dose rate, and the degradation is more and more serious with increasing dose rate. Additionally, the decrease rate of SNR at 20.0, 50.0 and 100.0 Gy/h is far greater than that at 1.0 and 10.0 Gy/h. Even so, we confirm that the HD industrial camera is still working at 10.0 Gy/h during the 8 h of measurements, with a moderate decrease of the SNR (5 dB). The work is valuable and can provide suggestion for camera users in the radiation field. Full article
(This article belongs to the Special Issue Image Sensors)
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Open AccessArticle Proton Radiation Effects on Dark Signal Distribution of PPD CMOS Image Sensors: Both TID and DDD Effects
Sensors 2017, 17(12), 2781; https://doi.org/10.3390/s17122781
Received: 27 September 2017 / Revised: 20 November 2017 / Accepted: 24 November 2017 / Published: 30 November 2017
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Abstract
Four-transistor (T) pinned photodiode (PPD) CMOS image sensors (CISs) with four-megapixel resolution using 11µm pitch high dynamic range pixel were radiated with 3 MeV and 10MeV protons. The dark signal was measured pre- and post-radiation, with the dark signal post irradiation showing a
[...] Read more.
Four-transistor (T) pinned photodiode (PPD) CMOS image sensors (CISs) with four-megapixel resolution using 11µm pitch high dynamic range pixel were radiated with 3 MeV and 10MeV protons. The dark signal was measured pre- and post-radiation, with the dark signal post irradiation showing a remarkable increase. A theoretical method of dark signal distribution pre- and post-radiation is used to analyze the degradation mechanisms of the dark signal distribution. The theoretical results are in good agreement with experimental results. This research would provide a good understanding of the proton radiation effects on the CIS and make it possible to predict the dark signal distribution of the CIS under the complex proton radiation environments. Full article
(This article belongs to the Special Issue Image Sensors)
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Open AccessArticle Design and Calibration of a Novel Bio-Inspired Pixelated Polarized Light Compass
Sensors 2017, 17(11), 2623; https://doi.org/10.3390/s17112623
Received: 9 September 2017 / Revised: 19 October 2017 / Accepted: 11 November 2017 / Published: 14 November 2017
Cited by 1 | PDF Full-text (1787 KB) | HTML Full-text | XML Full-text
Abstract
Animals, such as Savannah sparrows and North American monarch butterflies, are able to obtain compass information from skylight polarization patterns to help them navigate effectively and robustly. Inspired by excellent navigation ability of animals, this paper proposes a novel image-based polarized light compass,
[...] Read more.
Animals, such as Savannah sparrows and North American monarch butterflies, are able to obtain compass information from skylight polarization patterns to help them navigate effectively and robustly. Inspired by excellent navigation ability of animals, this paper proposes a novel image-based polarized light compass, which has the advantages of having a small size and being light weight. Firstly, the polarized light compass, which is composed of a Charge Coupled Device (CCD) camera, a pixelated polarizer array and a wide-angle lens, is introduced. Secondly, the measurement method of a skylight polarization pattern and the orientation method based on a single scattering Rayleigh model are presented. Thirdly, the error model of the sensor, mainly including the response error of CCD pixels and the installation error of the pixelated polarizer, is established. A calibration method based on iterative least squares estimation is proposed. In the outdoor environment, the skylight polarization pattern can be measured in real time by our sensor. The orientation accuracy of the sensor increases with the decrease of the solar elevation angle, and the standard deviation of orientation error is 0 . 15 at sunset. Results of outdoor experiments show that the proposed polarization navigation sensor can be used for outdoor autonomous navigation. Full article
(This article belongs to the Special Issue Image Sensors)
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Open AccessArticle A Multi-Resolution Mode CMOS Image Sensor with a Novel Two-Step Single-Slope ADC for Intelligent Surveillance Systems
Sensors 2017, 17(7), 1497; https://doi.org/10.3390/s17071497
Received: 9 May 2017 / Revised: 8 June 2017 / Accepted: 24 June 2017 / Published: 25 June 2017
Cited by 3 | PDF Full-text (3534 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present a multi-resolution mode CMOS image sensor (CIS) for intelligent surveillance system (ISS) applications. A low column fixed-pattern noise (CFPN) comparator is proposed in 8-bit two-step single-slope analog-to-digital converter (TSSS ADC) for the CIS that supports normal, 1/2, 1/4,
[...] Read more.
In this paper, we present a multi-resolution mode CMOS image sensor (CIS) for intelligent surveillance system (ISS) applications. A low column fixed-pattern noise (CFPN) comparator is proposed in 8-bit two-step single-slope analog-to-digital converter (TSSS ADC) for the CIS that supports normal, 1/2, 1/4, 1/8, 1/16, 1/32, and 1/64 mode of pixel resolution. We show that the scaled-resolution images enable CIS to reduce total power consumption while images hold steady without events. A prototype sensor of 176 × 144 pixels has been fabricated with a 0.18 μm 1-poly 4-metal CMOS process. The area of 4-shared 4T-active pixel sensor (APS) is 4.4 μm × 4.4 μm and the total chip size is 2.35 mm × 2.35 mm. The maximum power consumption is 10 mW (with full resolution) with supply voltages of 3.3 V (analog) and 1.8 V (digital) and 14 frame/s of frame rates. Full article
(This article belongs to the Special Issue Image Sensors)
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