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

Deadline for manuscript submissions: closed (30 April 2021) | Viewed by 89553

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Prof. Dr. Lucio Pancheri

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DII, University of Trento, Via Sommarive, 9, 38123 Trento, Italy
Interests: modeling and characterization of electron devices; CMOS integrated photodetectors and image sensors; single-Photon Avalanche Diodes; 3D Imaging; radiation detectors
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Dr. Matteo Perenzoni

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Sony Europe Technology Development Centre, Via Sommarive 18, 38123 Trento, Italy
Interests: image sensors; analog integrated circuits; terahertz and infrared detectors; microelectronics; single photon imaging
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Special Issue Information

Dear Colleagues,

In recent years, integrated sensors based on single-photon avalanche diodes (SPADs) have definitely entered the market, providing optical detector systems with low-noise and picosecond timing resolution. An increasing amount of work is steadily going on in academia as well as in the industry to increase sensor performance and functionality towards time-resolved single-photon imaging. The simultaneous optimization of fabrication processes, circuits, and architectures is required to advance the state-of-the-art of art in this field and to enable an increasing number of applications in basic physics, biomedical, industrial, and consumer domains.

This Special Issue aims at providing an overview of the latest developments in CMOS-integrated SPAD pixel arrays, including work on detectors, pixels, readout circuits, chip architectures, and related applications. Submissions can span from technology processes to design and circuit innovations, from system-level analysis and optimization to electrical and optical characterization, all in relation to SPAD image sensors.

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

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Keywords

Single-photon avalanche diode
Geiger-mode avalanche photodiode
SPAD Image Sensor
SPAD array
CMOS
Single-photon imaging
Photon counting
Photon timing
Time-resolved imaging

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Published Papers (10 papers)

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19 pages, 1533 KiB

Open AccessArticle

Numerical Model of SPAD-Based Direct Time-of-Flight Flash LIDAR CMOS Image Sensors

by Alessandro Tontini, Leonardo Gasparini and Matteo Perenzoni

Sensors 2020, 20(18), 5203; https://doi.org/10.3390/s20185203 - 12 Sep 2020

Cited by 59 | Viewed by 10488

Abstract

We present a Montecarlo simulator developed in Matlab^® for the analysis of a Single Photon Avalanche Diode (SPAD)-based Complementary Metal-Oxide Semiconductor (CMOS) flash Light Detection and Ranging (LIDAR) system. The simulation environment has been developed to accurately model the components of a flash LIDAR system, such as illumination source, optics, and the architecture of the designated SPAD-based CMOS image sensor. Together with the modeling of the background noise and target topology, all of the fundamental factors that are involved in a typical LIDAR acquisition system have been included in order to predict the achievable system performance and verified with an existing sensor. Full article

(This article belongs to the Special Issue SPAD Image Sensors)

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21 pages, 6962 KiB

Open AccessArticle

Temporal and Spatial Focusing in SPAD-Based Solid-State Pulsed Time-of-Flight Laser Range Imaging

by Juha Kostamovaara, Sahba S. Jahromi and Pekka Keränen

Sensors 2020, 20(21), 5973; https://doi.org/10.3390/s20215973 - 22 Oct 2020

Cited by 19 | Viewed by 4112

Abstract

The relation between signal and background noise strengths in single-photon avalanche diode (SPAD)-based pulsed time-of-flight 3-D range imaging is analyzed on the assumption that the SPAD detector is operating in the single photon detection mode. Several practical measurement cases using a 256-pixel solid-state pulsed time-of-flight (TOF) line profiler are presented and analyzed in the light of the resulting analysis. It is shown that in this case it is advantageous to concentrate the available optical average power in short, intensive pulses and to focus the optical energy in spatial terms. In 3-D range imaging, this could be achieved by using block-based illumination instead of the regularly used flood illumination. One modification of this approach could be a source that would illuminate the system FOV only in narrow laser stripes. It is shown that a 256-pixel SPAD-based pulsed TOF line profiler following these design principles can achieve a measurement range of 5–10 m to non-cooperative targets at a rate of ~10 lines/s under bright sunlight conditions using an average optical power of only 260 µW. Full article

(This article belongs to the Special Issue SPAD Image Sensors)

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15 pages, 8605 KiB

Open AccessArticle

Current-Assisted SPAD with Improved p-n Junction and Enhanced NIR Performance

by Gobinath Jegannathan, Thomas Van den Dries and Maarten Kuijk

Sensors 2020, 20(24), 7105; https://doi.org/10.3390/s20247105 - 11 Dec 2020

Cited by 12 | Viewed by 6147

Abstract

Single-photon avalanche diodes (SPADs) fabricated in conventional CMOS processes typically have limited near infra-red (NIR) sensitivity. This is the consequence of isolating the SPADs in a lowly-doped deep N-type well. In this work, we present a second improved version of the “current-assisted” single-photon avalanche diode, fabricated in a conventional 350 nm CMOS process, having good NIR sensitivity owing to 14 μm thick epilayer for photon absorption. The presented device has a photon absorption area of 30 × 30 µm², with a much smaller central active area for avalanche multiplication. The photo-electrons generated in the absorption area are guided swiftly towards the central area with a drift field created by the “current-assistance” principle. The central active avalanche area has a cylindrical p-n junction as opposed to the square geometry from the previous iteration. The presented device shows improved performance in all aspects, most notably in photon detection probability. The p-n junction capacitance is estimated to be ~1 fF and on-chip passive quenching with source followers is employed to conserve the small capacitance for bringing monitoring signals off-chip. Device physics simulations are presented along with measured dark count rate (DCR), timing jitter, after-pulsing probability (APP) and photon detection probability (PDP). The presented device has a peak PDP of 22.2% at a wavelength of 600 nm and a timing jitter of 220 ps at a wavelength of 750 nm. Full article

(This article belongs to the Special Issue SPAD Image Sensors)

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15 pages, 5320 KiB

Open AccessArticle

A Low-Resources TDC for Multi-Channel Direct ToF Readout Based on a 28-nm FPGA

by Mojtaba Parsakordasiabi, Ion Vornicu, Ángel Rodríguez-Vázquez and Ricardo Carmona-Galán

Sensors 2021, 21(1), 308; https://doi.org/10.3390/s21010308 - 5 Jan 2021

Cited by 24 | Viewed by 5900

Abstract

In this paper, we present a proposed field programmable gate array (FPGA)-based time-to-digital converter (TDC) architecture to achieve high performance with low usage of resources. This TDC can be employed for multi-channel direct Time-of-Flight (ToF) applications. The proposed architecture consists of a synchronizing input stage, a tuned tapped delay line (TDL), a combinatory encoder of ones and zeros counters, and an online calibration stage. The experimental results of the TDC in an Artix-7 FPGA show a differential non-linearity (DNL) in the range of [−0.953, 1.185] LSB, and an integral non-linearity (INL) within [−2.750, 1.238] LSB. The measured LSB size and precision are 22.2 ps and 26.04 ps, respectively. Moreover, the proposed architecture requires low FPGA resources. Full article

(This article belongs to the Special Issue SPAD Image Sensors)

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31 pages, 7518 KiB

Open AccessReview

3D Photon-To-Digital Converter for Radiation Instrumentation: Motivation and Future Works

by Jean-François Pratte, Frédéric Nolet, Samuel Parent, Frédéric Vachon, Nicolas Roy, Tommy Rossignol, Keven Deslandes, Henri Dautet, Réjean Fontaine and Serge A. Charlebois

Sensors 2021, 21(2), 598; https://doi.org/10.3390/s21020598 - 16 Jan 2021

Cited by 27 | Viewed by 7507

Abstract

Analog and digital SiPMs have revolutionized the field of radiation instrumentation by replacing both avalanche photodiodes and photomultiplier tubes in many applications. However, multiple applications require greater performance than the current SiPMs are capable of, for example timing resolution for time-of-flight positron emission tomography and time-of-flight computed tomography, and mitigation of the large output capacitance of SiPM array for large-scale time projection chambers for liquid argon and liquid xenon experiments. In this contribution, the case will be made that 3D photon-to-digital converters, also known as 3D digital SiPMs, have a potentially superior performance over analog and 2D digital SiPMs. A review of 3D photon-to-digital converters is presented along with various applications where they can make a difference, such as time-of-flight medical imaging systems and low-background experiments in noble liquids. Finally, a review of the key design choices that must be made to obtain an optimized 3D photon-to-digital converter for radiation instrumentation, more specifically the single-photon avalanche diode array, the CMOS technology, the quenching circuit, the time-to-digital converter, the digital signal processing and the system level integration, are discussed in detail. Full article

(This article belongs to the Special Issue SPAD Image Sensors)

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15 pages, 533 KiB

Open AccessArticle

A Scaling Law for SPAD Pixel Miniaturization

by Kazuhiro Morimoto and Edoardo Charbon

Sensors 2021, 21(10), 3447; https://doi.org/10.3390/s21103447 - 15 May 2021

Cited by 14 | Viewed by 5245

Abstract

The growing demands on compact and high-definition single-photon avalanche diode (SPAD) arrays have motivated researchers to explore pixel miniaturization techniques to achieve sub-10 μm pixels. The scaling of the SPAD pixel size has an impact on key performance metrics, and it is, thereby, critical to conduct a systematic analysis of the underlying tradeoffs in miniaturized SPADs. On the basis of the general assumptions and constraints for layout geometry, we performed an analytical formulation of the scaling laws for the key metrics, such as the fill factor (FF), photon detection probability (PDP), dark count rate (DCR), correlated noise, and power consumption. Numerical calculations for various parameter sets indicated that some of the metrics, such as the DCR and power consumption, were improved by pixel miniaturization, whereas other metrics, such as the FF and PDP, were degraded. Comparison of the theoretically estimated scaling trends with previously published experimental results suggests that the scaling law analysis is in good agreement with practical SPAD devices. Our scaling law analysis could provide a useful tool to conduct a detailed performance comparison between various process, device, and layout configurations, which is essential for pushing the limit of SPAD pixel miniaturization toward sub-2 μm-pitch SPADs. Full article

(This article belongs to the Special Issue SPAD Image Sensors)

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23 pages, 4532 KiB

Open AccessReview

SPADs and SiPMs Arrays for Long-Range High-Speed Light Detection and Ranging (LiDAR)

by Federica Villa, Fabio Severini, Francesca Madonini and Franco Zappa

Sensors 2021, 21(11), 3839; https://doi.org/10.3390/s21113839 - 1 Jun 2021

Cited by 108 | Viewed by 15939

Abstract

Light Detection and Ranging (LiDAR) is a 3D imaging technique, widely used in many applications such as augmented reality, automotive, machine vision, spacecraft navigation and landing. Achieving long-ranges and high-speed, most of all in outdoor applications with strong solar background illumination, are challenging requirements. In the introduction we review different 3D-ranging techniques (stereo-vision, projection with structured light, pulsed-LiDAR, amplitude-modulated continuous-wave LiDAR, frequency-modulated continuous-wave interferometry), illumination schemes (single point and blade scanning, flash-LiDAR) and time-resolved detectors for LiDAR (EM-CCD, I-CCD, APD, SPAD, SiPM). Then, we provide an extensive review of silicon- single photon avalanche diode (SPAD)-based LiDAR detectors (both commercial products and research prototypes) analyzing how each architecture faces the main challenges of LiDAR (i.e., long ranges, centimeter resolution, large field-of-view and high angular resolution, high operation speed, background immunity, eye-safety and multi-camera operation). Recent progresses in 3D stacking technologies provided an important step forward in SPAD array development, allowing to reach smaller pitch, higher pixel count and more complex processing electronics. In the conclusions, we provide some guidelines for the design of next generation SPAD-LiDAR detectors. Full article

(This article belongs to the Special Issue SPAD Image Sensors)

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16 pages, 5818 KiB

Open AccessArticle

Design and Characterization of an Asynchronous Fixed Priority Tree Arbiter for SPAD Array Readout

by Enagnon Aguénounon, Safa Razavinejad, Jean-Baptiste Schell, Mohammadreza Dolatpoor Lakeh, Wassim Khaddour, Foudil Dadouche, Jean-Baptiste Kammerer, Laurent Fesquet and Wilfried Uhring

Sensors 2021, 21(12), 3949; https://doi.org/10.3390/s21123949 - 8 Jun 2021

Cited by 4 | Viewed by 4299

Abstract

The usage of single-photon avalanche diode arrays is becoming increasingly common in various domains such as medical imaging, automotive vision systems, and optical communications. Nowadays, thanks to the development of microelectronics technologies, the SPAD arrays designed for these applications has been drastically well-facilitated, allowing for the manufacturing of large matrices. However, there are growing challenges for the design of readout circuits with the needs of reducing their energy consumption (linked to the usage cost) and data rate. Indeed, the design of the readout circuit for the SPAD array is generally based on synchronous logic; the latter requires synchronization that may increase the dead time of the SPADs and clock trees management that are known to increase power consumption. With these limitations, the long-neglected asynchronous (clockless) logic proved to be a better alternative because of its ability to operate without a clock. In this paper, we presented the design of a 16-to-1 fixed-priority tree arbiter readout circuit for a SPAD array based on asynchronous logic principles. The design of this circuit was explained in detail and supported by simulation results. The manufactured chip was tested, and the experimental results showed that it is possible to record up to 333 million events per second; no reading errors were detected during the data extraction test. Full article

(This article belongs to the Special Issue SPAD Image Sensors)

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13 pages, 14325 KiB

Open AccessArticle

An Ultrafast Active Quenching Active Reset Circuit with 50% SPAD Afterpulsing Reduction in a 28 nm FD-SOI CMOS Technology Using Body Biasing Technique

by Mohammadreza Dolatpoor Lakeh, Jean-Baptiste Kammerer, Enagnon Aguénounon, Dylan Issartel, Jean-Baptiste Schell, Sven Rink, Andreia Cathelin, Francis Calmon and Wilfried Uhring

Sensors 2021, 21(12), 4014; https://doi.org/10.3390/s21124014 - 10 Jun 2021

Cited by 9 | Viewed by 5679

Abstract

An ultrafast Active Quenching—Active Reset (AQAR) circuit is presented for the afterpulsing reduction in a Single Photon Avalanche Diode (SPAD). The proposed circuit is designed in a 28 nm Fully Depleted Silicon On Insulator (FD-SOI) CMOS technology. By exploiting the body biasing technique, the avalanche is detected very quickly and, consequently, is quenched very fast. The fast quenching decreases the avalanche charges, therefore resulting in the afterpulsing reduction. Both post-layout and experimental results are presented and are highly in accordance with each other. It is shown that the proposed AQAR circuit is able to detect the avalanche in less than 40 ps and reduce the avalanche charge and the afterpulsing up to 50%. Full article

(This article belongs to the Special Issue SPAD Image Sensors)

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19 pages, 1359 KiB

Open AccessArticle

Noise and Breakdown Characterization of SPAD Detectors with Time-Gated Photon-Counting Operation

by Hiwa Mahmoudi, Michael Hofbauer, Bernhard Goll and Horst Zimmermann

Sensors 2021, 21(16), 5287; https://doi.org/10.3390/s21165287 - 5 Aug 2021

Cited by 4 | Viewed by 4195

Abstract

Being ready-to-detect over a certain portion of time makes the time-gated single-photon avalanche diode (SPAD) an attractive candidate for low-noise photon-counting applications. A careful SPAD noise and performance characterization, however, is critical to avoid time-consuming experimental optimization and redesign iterations for such applications. Here, we present an extensive empirical study of the breakdown voltage, as well as the dark-count and afterpulsing noise mechanisms for a fully integrated time-gated SPAD detector in 0.35-

μ

m CMOS based on experimental data acquired in a dark condition. An “effective” SPAD breakdown voltage is introduced to enable efficient characterization and modeling of the dark-count and afterpulsing probabilities with respect to the excess bias voltage and the gating duration time. The presented breakdown and noise models will allow for accurate modeling and optimization of SPAD-based detector designs, where the SPAD noise can impose severe trade-offs with speed and sensitivity as is shown via an example. Full article

(This article belongs to the Special Issue SPAD Image Sensors)

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