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Special Issue "The International SPAD Sensor Workshop"

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

Deadline for manuscript submissions: closed (30 September 2018)

Special Issue Editors

Guest Editor
Prof. Dr. Edoardo Charbon

Advanced Quantum Architecture Laboratory (AQUA), EPFL, Neuchatel, Switzerland
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Guest Editor
Dr. Alberto Tosi

Politecnico di Milano, Department of Electronics, Milan, Italy
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Guest Editor
Dr. Alberto Gola

Fondazione Bruno Kessler, Trento, Italy
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Guest Editor
Dr. David Stoppa

Advanced Optical Solutions division, ams AG, Rueschlikon, Switzerland
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Guest Editor
Prof. Dr. Robert Henderson

University of Edinburgh, School of Engineering, Edinburgh, United Kingdom
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Guest Editor
Dr. Claudio Bruschini

Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland
Website | E-Mail
Interests: photonic/electronic quantum devices; single photon detectors (SPAD arrays) and corresponding applications; medical physics

Special Issue Information

Dear Colleagues,

The scope of the workshop is as follows (issw.epfl.ch):

The International SPAD Sensor Workshop focuses on the study, modeling, design, fabrication, and characterization of SPAD sensors. The workshop welcomes all researchers, practitioners, and educators interested in SPADs, SPAD imagers, and associated applications, not only in imaging but also in other fields. The first edition of the workshop will gather experts in all areas of SPADs and SPAD-related applications in the Swiss Alps, where over 20 invited speakers will animate three days of study, information dissemination, and debates. Authentic alpine activities will complete the event, which will take place in a spectacular setting. The workshop is supported by the International Image Sensor Society (IISS).

Prof. Dr. Edoardo Charbon
Dr. Alberto Tosi
Dr. Alberto Gola
Dr. David Stoppa
Prof. Dr. Robert Henderson
Dr. Claudio Bruschini
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 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.

Published Papers (7 papers)

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Research

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Open AccessArticle Time-of-Flight Imaging at 10 ps Resolution with an ICCD Camera
Sensors 2019, 19(1), 180; https://doi.org/10.3390/s19010180
Received: 30 November 2018 / Revised: 20 December 2018 / Accepted: 4 January 2019 / Published: 6 January 2019
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Abstract
ICCD cameras can record low light events with extreme temporal resolution. Thus, they are used in a variety of bio-medical applications for single photon time of flight measurements and LIDAR measurements. In this paper, we present a method which allows improvement of the [...] Read more.
ICCD cameras can record low light events with extreme temporal resolution. Thus, they are used in a variety of bio-medical applications for single photon time of flight measurements and LIDAR measurements. In this paper, we present a method which allows improvement of the temporal resolution of ICCD cameras down to 10 ps (from the native 200 ps of our model), thus placing ICCD cameras at a better temporal resolution than SPAD cameras and in direct competition with streak cameras. The higher temporal resolution can serve for better tracking and visualization of the information carried in time-of-flight measurements. Full article
(This article belongs to the Special Issue The International SPAD Sensor Workshop)
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Open AccessArticle Background Light Rejection in SPAD-Based LiDAR Sensors by Adaptive Photon Coincidence Detection
Sensors 2018, 18(12), 4338; https://doi.org/10.3390/s18124338
Received: 30 October 2018 / Revised: 3 December 2018 / Accepted: 6 December 2018 / Published: 8 December 2018
Cited by 1 | PDF Full-text (6025 KB) | HTML Full-text | XML Full-text
Abstract
Light detection and ranging (LiDAR) systems based on silicon single-photon avalanche diodes (SPAD) offer several advantages, like the fabrication of system-on-chips with a co-integrated detector and dedicated electronics, as well as low cost and high durability due to well-established CMOS technology. On the [...] Read more.
Light detection and ranging (LiDAR) systems based on silicon single-photon avalanche diodes (SPAD) offer several advantages, like the fabrication of system-on-chips with a co-integrated detector and dedicated electronics, as well as low cost and high durability due to well-established CMOS technology. On the other hand, silicon-based detectors suffer from high background light in outdoor applications, like advanced driver assistance systems or autonomous driving, due to the limited wavelength range in the infrared spectrum. In this paper we present a novel method based on the adaptive adjustment of photon coincidence detection to suppress the background light and simultaneously improve the dynamic range. A major disadvantage of fixed parameter coincidence detection is the increased dynamic range of the resulting event rate, allowing good measurement performance only at a specific target reflectance. To overcome this limitation we have implemented adaptive photon coincidence detection. In this technique the parameters of the photon coincidence detection are adjusted to the actual measured background light intensity, giving a reduction of the event rate dynamic range and allowing the perception of high dynamic scenes. We present a 192 × 2 pixel CMOS SPAD-based LiDAR sensor utilizing this technique and accompanying outdoor measurements showing the capability of it. In this sensor adaptive photon coincidence detection improves the dynamic range of the measureable target reflectance by over 40 dB. Full article
(This article belongs to the Special Issue The International SPAD Sensor Workshop)
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Open AccessArticle A CMOS SPAD Imager with Collision Detection and 128 Dynamically Reallocating TDCs for Single-Photon Counting and 3D Time-of-Flight Imaging
Sensors 2018, 18(11), 4016; https://doi.org/10.3390/s18114016
Received: 5 October 2018 / Revised: 14 November 2018 / Accepted: 15 November 2018 / Published: 17 November 2018
Cited by 4 | PDF Full-text (9910 KB) | HTML Full-text | XML Full-text
Abstract
Per-pixel time-to-digital converter (TDC) architectures have been exploited by single-photon avalanche diode (SPAD) sensors to achieve high photon throughput, but at the expense of fill factor, pixel pitch and readout efficiency. In contrast, TDC sharing architecture usually features high fill factor at small [...] Read more.
Per-pixel time-to-digital converter (TDC) architectures have been exploited by single-photon avalanche diode (SPAD) sensors to achieve high photon throughput, but at the expense of fill factor, pixel pitch and readout efficiency. In contrast, TDC sharing architecture usually features high fill factor at small pixel pitch and energy efficient event-driven readout. While the photon throughput is not necessarily lower than that of per-pixel TDC architectures, since the throughput is not only decided by the TDC number but also the readout bandwidth. In this paper, a SPAD sensor with 32 × 32 pixels fabricated with a 180 nm CMOS image sensor technology is presented, where dynamically reallocating TDCs were implemented to achieve the same photon throughput as that of per-pixel TDCs. Each 4 TDCs are shared by 32 pixels via a collision detection bus, which enables a fill factor of 28% with a pixel pitch of 28.5 μm. The TDCs were characterized, obtaining the peak-to-peak differential and integral non-linearity of −0.07/+0.08 LSB and −0.38/+0.75 LSB, respectively. The sensor was demonstrated in a scanning light-detection-and-ranging (LiDAR) system equipped with an ultra-low power laser, achieving depth imaging up to 10 m at 6 frames/s with a resolution of 64 × 64 with 50 lux background light. Full article
(This article belongs to the Special Issue The International SPAD Sensor Workshop)
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Open AccessArticle 0.16 µm–BCD Silicon Photomultipliers with Sharp Timing Response and Reduced Correlated Noise
Sensors 2018, 18(11), 3763; https://doi.org/10.3390/s18113763
Received: 20 September 2018 / Revised: 23 October 2018 / Accepted: 30 October 2018 / Published: 3 November 2018
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Abstract
Silicon photomultipliers (SiPMs) have improved significantly over the last years and now are widely employed in many different applications. However, the custom fabrication technologies exploited for commercial SiPMs do not allow the integration of any additional electronics, e.g., on-chip readout and analog (or [...] Read more.
Silicon photomultipliers (SiPMs) have improved significantly over the last years and now are widely employed in many different applications. However, the custom fabrication technologies exploited for commercial SiPMs do not allow the integration of any additional electronics, e.g., on-chip readout and analog (or digital) processing circuitry. In this paper, we present the design and characterization of two microelectronics-compatible SiPMs fabricated in a 0.16 µm–BCD (Bipolar-CMOS-DMOS) technology, with 0.67 mm × 0.67 mm total area, 10 × 10 square pixels and 53% fill-factor (FF). The photon detection efficiency (PDE) surpasses 33% (FF included), with a dark-count rate (DCR) of 330 kcps. Although DCR density is worse than that of state-of-the-art SiPMs, the proposed fabrication technology enables the development of cost-effective systems-on-chip (SoC) based on SiPM detectors. Furthermore, correlated noise components, i.e., afterpulsing and optical crosstalk, and photon timing response are comparable to those of best-in-class commercial SiPMs. Full article
(This article belongs to the Special Issue The International SPAD Sensor Workshop)
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Open AccessArticle A 250 m Direct Time-of-Flight Ranging System Based on a Synthesis of Sub-Ranging Images and a Vertical Avalanche Photo-Diodes (VAPD) CMOS Image Sensor
Sensors 2018, 18(11), 3642; https://doi.org/10.3390/s18113642
Received: 31 August 2018 / Revised: 19 October 2018 / Accepted: 24 October 2018 / Published: 27 October 2018
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Abstract
We have developed a direct time-of-flight (TOF) 250 m ranging Complementary Metal Oxide Semiconductor (CMOS) image sensor (CIS) based on a 688 × 384 pixels array of vertical avalanche photodiodes (VAPD). Each pixel of the CIS comprises VAPD with a standard four transistor [...] Read more.
We have developed a direct time-of-flight (TOF) 250 m ranging Complementary Metal Oxide Semiconductor (CMOS) image sensor (CIS) based on a 688 × 384 pixels array of vertical avalanche photodiodes (VAPD). Each pixel of the CIS comprises VAPD with a standard four transistor pixel circuit equipped with an analogue capacitor to accumulate or count avalanche pulses. High power near infrared (NIR) short (<50 ns) and repetitive (6 kHz) laser pulses are illuminated through a diffusing optics. By globally gating the VAPD, each pulse is counted in the in-pixel counter enabling extraction of sub-photon level signal. Depth map imaging with a 10 cm lateral resolution is realized from 1 m to 250 m range by synthesizing subranges images of photon counts. Advantages and limitation of an in-pixel circuit are described. The developed CIS is expected to supersede insufficient resolution of the conventional light detection and ranging (LiDAR) systems and the short range of indirect CIS TOF. Full article
(This article belongs to the Special Issue The International SPAD Sensor Workshop)
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Open AccessArticle Mutually Coupled Time-to-Digital Converters (TDCs) for Direct Time-of-Flight (dTOF) Image Sensors
Sensors 2018, 18(10), 3413; https://doi.org/10.3390/s18103413
Received: 21 August 2018 / Revised: 27 September 2018 / Accepted: 3 October 2018 / Published: 11 October 2018
Cited by 3 | PDF Full-text (3531 KB) | HTML Full-text | XML Full-text
Abstract
Direct time-of-flight (dTOF) image sensors require accurate and robust timing references for precise depth calculation. On-chip timing references are well-known and understood, but for imaging systems where several thousands of pixels require seamless references, area and power consumption limit the use of more [...] Read more.
Direct time-of-flight (dTOF) image sensors require accurate and robust timing references for precise depth calculation. On-chip timing references are well-known and understood, but for imaging systems where several thousands of pixels require seamless references, area and power consumption limit the use of more traditional synthesizers, such as phase/delay-locked loops (PLLs/DLLs). Other methods, such as relative timing measurement (start/stop), require constant foreground calibration, which is not feasible for outdoor applications, where conditions of temperature, background illumination, etc. can change drastically and frequently. In this paper, a scalable reference generation and synchronization is provided, using minimum resources of area and power, while being robust to mismatches. The suitability of this approach is demonstrated through the design of an 8 × 8 time-to-digital converter (TDC) array, distributed over 1.69 mm2, fabricated using TSMC 65 nm technology (1.2 V core voltage and 4 metal layers—3 thin + 1 thick). Each TDC is based on a ring oscillator (RO) coupled to a ripple counter, occupying a very small area of 550 μ m2, while consuming 500 μ W of power, and has 2 μ s range, 125 ps least significant bit (LSB), and 14-bit resolution. Phase and frequency locking among the ROs is achieved, while providing 18 dB phase noise improvement over an equivalent individual oscillator. The integrated root mean square (RMS) jitter is less than 9 ps, the instantaneous frequency variation is less than 0.11%, differential nonlinearity (DNL) is less than 2 LSB, and integral nonlinearity (INL) is less than 3 LSB. Full article
(This article belongs to the Special Issue The International SPAD Sensor Workshop)
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Review

Jump to: Research

Open AccessReview NUV-Sensitive Silicon Photomultiplier Technologies Developed at Fondazione Bruno Kessler
Sensors 2019, 19(2), 308; https://doi.org/10.3390/s19020308
Received: 16 October 2018 / Revised: 9 December 2018 / Accepted: 30 December 2018 / Published: 14 January 2019
Cited by 1 | PDF Full-text (9651 KB) | HTML Full-text | XML Full-text
Abstract
Different applications require different customizations of silicon photomultiplier (SiPM) technology. We present a review on the latest SiPM technologies developed at Fondazione Bruno Kessler (FBK, Trento), characterized by a peak detection efficiency in the near-UV and customized according to the needs of different [...] Read more.
Different applications require different customizations of silicon photomultiplier (SiPM) technology. We present a review on the latest SiPM technologies developed at Fondazione Bruno Kessler (FBK, Trento), characterized by a peak detection efficiency in the near-UV and customized according to the needs of different applications. Original near-UV sensitive, high-density SiPMs (NUV-HD), optimized for Positron Emission Tomography (PET) application, feature peak photon detection efficiency (PDE) of 63% at 420 nm with a 35 um cell size and a dark count rate (DCR) of 100 kHz/mm2. Correlated noise probability is around 25% at a PDE of 50% at 420 nm. It provides a coincidence resolving time (CRT) of 100 ps FWHM (full width at half maximum) in the detection of 511 keV photons, when used for the readout of LYSO(Ce) scintillator (Cerium-doped lutetium-yttrium oxyorthosilicate) and down to 75 ps FWHM with LSO(Ce:Ca) scintillator (Cerium and Calcium-doped lutetium oxyorthosilicate). Starting from this technology, we developed three variants, optimized according to different sets of specifications. NUV-HD–LowCT features a 60% reduction of direct crosstalk probability, for applications such as Cherenkov telescope array (CTA). NUV-HD–Cryo was optimized for cryogenic operation and for large photosensitive areas. The reference application, in this case, is the readout of liquid, noble-gases scintillators, such as liquid Argon. Measurements at 77 K showed a remarkably low value of the DCR of a few mHz/mm2. Finally, vacuum-UV (VUV)-HD features an increased sensitivity to VUV light, aiming at direct detection of photons below 200 nm. PDE in excess of 20% at 175 nm was measured in liquid Xenon. In the paper, we discuss the specifications on the SiPM related to different types of applications, the SiPM design challenges and process optimizations, and the results from the experimental characterization of the different, NUV-sensitive technologies developed at FBK. Full article
(This article belongs to the Special Issue The International SPAD Sensor Workshop)
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