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Press release: https://ala.associates/corporate/lynred-acquires-new-imaging-technologies-to-consolidate-leadership-in-infrared-sensors/

Acquisition of Paris-based SWIR imaging provider expands Lynred’s product portfolio to include coveted large format shortwave sensors with small pixel pitch

Grenoble, France, October 7, 2024 – Lynred, a leading global provider of high-quality infrared sensors for the aerospace, defense and commercial markets, today announces its acquisition of New Imaging Technologies, a Paris-based shortwave infrared (SWIR) imaging modules and sensors provider. In a strategic move to consolidate its leadership in infrared sensors, Lynred’s product portfolio will expand to include high-definition large array SWIR sensors in small pixel pitch, bolstering its product offering across all wavelength bands (short to very longwave). The transaction is expected to close in Q4, 2024 and is subject to customary conditions.

The deal includes New Imaging Technologies’ large and innovative portfolio of SWIR products (imaging sensors and modules) and a portfolio of wide dynamic range patents. This enables Lynred to offer global customers large format SWIR sensors with advanced capabilities for applications in markets where AI, deep learning and multispectral imaging are driving growth.
New Imaging Technologies (NIT) is the only European firm to manufacture and market a SWIR HD1080p array and associated module at a pixel size of 8µm, a key asset for several applications that Lynred will now leverage.

“Lynred’s acquisition of NIT is a growth accelerator. We will shorten time to market and leverage synergies in offering state-of-the-art SWIR products. The global market for SWIR infrared imaging for machine vision is growing fast, as well as for defense applications, such as laser detection and in new space,” said Hervé Bouaziz, executive president at Lynred. “NIT brings to Lynred the agility of a small, innovative organization, with an extensive product offering able to cater to our large customer base. As we share complementary industrial supply chains and technical skills, we can deliver highly competitive SWIR imaging sensors and modules to customers.” 

This strategic acquisition is yet another significant investment Lynred is making in order to strengthen its leadership in infrared, a critical technology for a growing range of commercial applications and sovereign activities. In parallel, Lynred is investing significantly in its ongoing Campus project. Campus includes the construction of state-of-the-art clean rooms that will double Lynred’s current capacity.

Lynred and NIT will attend Vision Stuttgart in Germany (October 8-10), booth #8C46, and AUSA (October 14-16), in Washington DC, booth #8015, showcasing products based on the companies’ latest technological achievements. These two important trade shows will give them the opportunity to share further information and answer any questions about the acquisition.

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Thesis title: A Scientific Event Camera: Theory, Design, and Measurements
Author: Rui Garcia
Advisor: Tobi Delbrück

 See also, earlier post about the PhD thesis abstract and full text link: https://image-sensors-world.blogspot.com/2024/08/phd-thesis-on-scidvs-event-camera.html

The full thesis text is available here after the embargo ends in July 2026: https://www.research-collection.ethz.ch/handle/20.500.11850/683623

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Neil Na et al from Artilux and UMass Boston have published a paper titled "Room-temperature photonic quantum computing in integrated silicon photonics with germanium–silicon single-photon avalanche diodes" in APL Quantum.

Abstract: Most, if not all, photonic quantum computing (PQC) relies upon superconducting nanowire single-photon detectors (SNSPDs) typically based on niobium nitride (NbN) operated at a temperature <4 K. This paper proposes and analyzes 300 K waveguide-integrated germanium–silicon (GeSi) single-photon avalanche diodes (SPADs) based on the recently demonstrated normal-incidence GeSi SPADs operated at room temperature, and shows that their performance is competitive against that of NbN SNSPDs in a series of metrics for PQC with a reasonable time-gating window. These GeSi SPADs become photon-number-resolving avalanche diodes (PNRADs) by deploying a spatially-multiplexed M-fold-waveguide array of M GeSi SPADs. Using on-chip waveguided spontaneous four-wave mixing sources and waveguided field-programmable interferometer mesh circuits, together with the high-metric SPADs and PNRADs, high-performance quantum computing at room temperature is predicted for this PQC architecture.

Link: https://doi.org/10.1063/5.0219035

Schematic plot of the proposed room-temperature PQC paradigm with integrated SiPh using the path degree of freedom of single photons: single photons are generated through SFWM (green pulses converted to blue and red pulses) in SOI rings (orange circles), followed by active temporal multiplexers (orange boxes that block the blue pulses), and active spatial multiplexers (orange boxes that convert serial pulses to parallel pulses) (quantum sources), manipulated by a FPIM using cascaded MZIs (quantum circuits), and measured by the proposed waveguide GeSi SPADs as SPDs and/or NPDs (quantum detectors). An application-specific integrated circuit (ASIC) layer is assumed to be flipped and bonded on the PIC layer with copper (Cu)–Cu pillars (yellow lines) connected wafer-level hybrid bond, or with metal bumps (yellow lines) connected chip-on-wafer-on-substrate (CoWoS) packaging. The off-chip fiber couplings are either for the pump lasers or the optical delay lines.

 

 (a) Top view of the proposed waveguide GeSi SPAD, in which the materials assumed are listed. (b) Cross-sectional view of the proposed waveguide GeSi SPAD, in which the variables for optimizing QE are illustrated.

 

 

(a) QE of the proposed waveguide GeSi SPAD without the Al back mirror, simulated at 1550 nm as a function of coupler length and Ge length. (b) QE of the proposed waveguide GeSi SPAD with the Al back mirror, simulated at 1550 nm as a function of gap length and Ge length. (c) QE of the proposed waveguide GeSi SPAD with the Al back mirror, simulated as a function of wavelength centered at 1550 ± 50 nm (around the C band) and 1310 ± 50 nm (around the O band), given the optimal conditions, that is, coupler length equal to 1.4 μm, gap length equal to 0.36 μm, and Ge length equal to 14.2 μm. While the above data are obtained by 2D FDTD simulations, we also verify that for Ge width >1 μm and mesa design rule <200 nm, there is little difference between the data obtained by 2D and 3D FDTD simulations.

Dark current of GeSi PD at −1 V reverse bias, normalized by its active region circumference, plotted as a function of active region diameter. The experimental data (blue dots) consist of the average dark current between two device repeats (the ratio of the standard deviation to the average is <2%) for five different active region diameters. The linear fitting (red line) shows the bulk dark current density and the surface dark current density with its slope and intercept, respectively.

For the scheme of photon-based PQC: (a) The probability of successfully detecting N photon state and (b) the fidelity of detecting N photon state, using M spatially-multiplexed waveguide GeSi SPADs at 300 K as an NPD. (c) The difference in the probabilities of successfully detecting N photon state, and (b) the difference in the fidelities of detecting N photon state, using M spatially-multiplied waveguide GeSi SPADs at 300 K and NbN SNSPDs at 4 K as NPDs. Note that no approximation is used in the formula for plotting these figures.

For the scheme of qubit-based PQC: (a) The probability of successfully detecting N qubit state, and the fidelity of detecting N qubit state, using single waveguide GeSi SPADs at 300 K as SPDs. (b) The difference in the probabilities of successfully detecting N qubit state, and the difference in the fidelities of detecting N qubit state, using single waveguide GeSi SPADs at 300 K and NbN SNSPDs at 4 K as SPDs. Note that no approximation is used in the formula for plotting these figures.

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RSNA 2024  - 1-5 December 2024 - Chicago, Illinois, USA - Website

21st Annual IEEE International Conference on Sensing, Communication, and Networking - 2-4 Dec 2024 - Phoenix, Arizona, USA - Website

Asia-Pacific Remote Sensing - 2-5 December 2024 - Kaohsiung, Taiwan - Website

International Technical Exhibition on Image Technology and Equipment (ITE) - 4-6 Dec 2024 - Yokohama, Japan - Website

IEEE International Electron Devices Meeting - 7-11 Dec 2024 - San Francisco, CA, USA - Website

17th International Conference on Sensing Technology (ICST2024) - 9-11 Dec 2024 - Sydney, Australia - Website

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Eric Fossum, Nobukazu Teranishi, and Albert Theuwissen have published a review paper titled "Digital Image Sensor Evolution and New Frontiers" in the Annual Review of Vision Science.

Link: https://doi.org/10.1146/annurev-vision-101322-105538

Abstract:

This article reviews nearly 60 years of solid-state image sensor evolution and identifies potential new frontiers in the field. From early work in the 1960s, through the development of charge-coupled device image sensors, to the complementary metal oxide semiconductor image sensors now ubiquitous in our lives, we discuss highlights in the evolutionary chain. New frontiers, such as 3D stacked technology, photon-counting technology, and others, are briefly discussed.

Figure 1  Illustration of a four-phase charge-coupled device diagram, a potential well diagram, and clock charts. As four clocks switch sequentially, the potential wells move rightward together with the charge packets.

Figure 2  Illustration of a (three-phase) interline-transfer (ILT) charge-coupled device (CCD) showing (left) a unit cell with a photodiode (PD) and vertical CCD and (right) the entire ILT CCD image sensor. The photosignal moves from the PD into the vertical CCD, and then into the horizontal CCD to the sense node and output amplifier.

Figure 3  A pinned PD in an interline-transfer CCD with one phase of the CCD shift register (VCCD) shown. (a) A physical cross-section and (b) a potential diagram showing the electrons transferring from the PD to the VCCD. Abbreviations: CCD, charge-coupled device; CS, channel stop; PD, photodiode; TG, transfer gate; VCCD, vertical CCD.

Figure 4  Microlenses to concentrate light on the photoactive area of a pixel. (a) Top view. (b) Cross-sections for different thermal-flow times. Images courtesy of NEC Corp.

Figure 5  A 16-Mpixel stitched complementary metal oxide semiconductor image sensor on a 6-inch-diameter wafer. Figure reproduced from Ay & Fossum (2006).

Figure 6  (a) Complementary metal oxide semiconductor (CMOS) image sensor block diagram. (b) Photograph of early Photobit CMOS image sensor chip for webcams. (Left) Digital logic for control and input-output (I/O) functions. (Top right) The pixel array. (Bottom right) The column-parallel analog signal processing and analog-to-digital converter (ADC) circuits. Photo courtesy of E.R.F.

Figure 7  An illustrative PPD 4-T active pixel with intrapixel charge transfer. (a) A circuit schematic (Fossum & Hondongwa 2014). (b) A band diagram looking vertically through the PPD showing the photon, electron–hole pair, and SW. (c) A physical cross-section showing doping levels (Fossum 2023). Abbreviations: COL BUS, column bus line; FD, floating diffusion; PPD, pinned photodiode; RST, reset gate; SEL, select gate; SF, source-follower; SW, storage well; TG, transfer gate.

Figure 8  Illustrative example of (a) a frontside-illuminated pixel and (b) a backside-illuminated (BSI) pixel showing the better light gathering capability of the BSI pixel.

Figure 9  Illustrative cross-sectional comparison of (a) a backside-illuminated device and (b) 3D stacked image sensors where the lower layer is used for additional circuitry.

Figure 10  Quanta image sensor concept showing the spatial distribution of jot outputs (left), an expanded view of jot output bit planes at different time slices (center), and gray-scale image pixels formed from spatiotemporal neighborhoods of jots (right). Figure adapted from Ma et al. (2022a).

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Press release: https://www.hamamatsu.com/us/en/news/featured-products_and_technologies/2024/20240531000000.html

Acquisition completion of NKT Photonics. Accelerating growth in the semiconductor, quantum, and medical fields through laser business enhancement.

Hamamatsu Photonics K.K. (hereinafter referred to as “Hamamatsu Photonics”) is pleased to announce the completion of the previously published acquisition of NKT Photonics A/S (hereinafter referred to as “NKT Photonics”).
 
NKT Photonics is the leading supplier of high-performance fiber lasers and photonic crystal fibers. Based on their unique fiber technology, the laser products fall within three major product lines:

1.  Supercontinuum White Light Lasers (SuperK): The SuperK lasers deliver high brightness in a broad spectral range (400 nm-2500 nm), and are used within bio-imaging, semiconductor metrology, and device-characterization.
2.  Single-Frequency DFB Fiber Lasers (Koheras): The Koheras lasers have extremely high wavelength stability and low noise, and are ideal for fiber sensing, quantum computing, and quantum sensing.
3.  Ultra-short pulse Lasers (aeroPULSE and Origami): This range of lasers consists of picosecond and femtosecond pulsed lasers with excellent beam quality and stability. The lasers are mainly used within ophthalmic surgery, bio-imaging, and optical processing applications.

 
The acquisition enables us to combine Hamamatsu Photonics’ detectors and cameras with NKT Photonics' lasers and fibers, thereby offering unique system solutions to the customers.
 
One special market of interest is the rapidly growing quantum computing area. Here NKT Photonics’ Koheras lasers serve customers with trapped ions systems requiring high power narrow linewidth lasers with extremely high wavelength stability and low noise. The same customers use Hamamatsu Photonics’ high-sensitivity cameras and sensors to detect the quantum state of the qubits. Together, we will be able to provide comprehensive solutions including lasers, detectors, and optical devices for the quantum-technology market.
 
Another important area of collaboration is the semiconductor market. With the trend toward more complex three-dimensional semiconductor devices, there is an increasing demand for high precision measurement equipment covering a wide range of wavelengths. By combining NKT Photonics' broadband SuperK lasers with Hamamatsu Photonics’ optical sensors and measuring devices, we can supply expanded solutions for semiconductor customers needing broader wavelength coverage, multiple measurement channels, and higher sensitivity.
 
Finally, in the hyperspectral imaging market, high-brightness light sources with a broad spectral range from visible to near-infrared (400 nm-2500 nm) are essential. Additionally, unlike halogen lamps, since no heat generation occur, the demand for NKT Photonics' SuperK is increasing. We can provide optimal solutions by integrating it with Hamamatsu Photonics’s image sensors and cameras, leveraging the unique compound semiconductor technologies.
 
With this acquisition, Hamamatsu Photonics Group now possesses a very broad range of technologies within light sources, lasers, and detectors. The combination of NKT Photonics and Hamamatsu Photonics will help us to drive our technology to the next level. NKT Photonics will continue their operating structure and focus on providing superior products and solutions to their customers.

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6th International Workshop on Image Sensors and Imaging Systems (IWISS2024) - 8 Nov 2024 - Tokyo, Japan - Website

Photonics Spectra Sensors & Detectors Summit 2024 - 13 Nov 2024 - Online - Website

SEMI MEMS & Imaging Sensors Summit - 14 Nov 2024 - Munich, Germany - Website

Eleventh International Workshop on Semiconductor Pixel Detectors for Particles and Imaging (Pixel2024) - 18-22 Nov 2024 - Strasbourg, France - Website

The 6th International Workshop on new Photon-Detectors (PD24) - 19-21 Nov 2024 - Vancouver, BC, Canada - Website

Coordinating Panel for Advanced Detectors Workshop - 19-22 Nov 2024 - Oak Ridge, Tennessee, USA - Website

Compamed - 11-14 Nov 2024 - Dusseldorf, Germany - Website

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From GlobeNewswire: https://www.globenewswire.com/news-release/2024/09/13/2945864/0/en/SeeDevice-Inc-Files-Complaint-In-U-S-District-Court-Against-Korean-Broadcasting-System.html

SeeDevice Inc. Files Complaint In U.S. District Court Against Korean Broadcasting System

ORANGE, California, Sept. 13, 2024 (GLOBE NEWSWIRE) -- SeeDevice Inc. (“SeeDevice”), together with its CEO and founder Dr. Hoon Kim, has filed a Complaint in the U.S. District Court for the Central District of California against Korean Broadcasting System (KBS), and its U.S. subsidiary KBS America, Inc. (collectively, “KBS”) for trade libel and defamation. The claims are based on an August 25, 2024, broadcast KBS is alleged to have published on its YouTube channel and KBS-america.com (“The KBS Broadcast”).

The complaint asserts that KBS Broadcast published false and misleading statements regarding the viability and legitimacy of SeeDevice and Dr. Kim’s QMOS™ (quantum effect CMOS) SWIR image sensor, as a result of having omitted the fact that in 2009, and again in 2012, the Seoul High Court and Seoul Administrative Court found Dr. Kim’s sensor to be legitimate.

Dr. Kim’s QMOS™ sensor has garnered industry praise and recognition and is the subject of numerous third-party awards. In the past year alone, SeeDevice has been recognized with four awards for outstanding leadership and innovative technology: "20 Most Innovative Business Leaders to Watch 2023" by Global Business Leaders, "Top 10 Admired Leaders 2023" by Industry Era, "Most Innovative Image Technology Company 2023" by Corporate Vision, and “Company of the Year” of the Top 10 Semiconductor Tech Startups 2023 by Semiconductor Review. 

In their lawsuit, SeeDevice and Dr. Kim seek retraction of KBS’s defamatory broadcast, and a correction of the record, in addition to significant monetary damages and injunctive relief preventing further misconduct by KBS.

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Dissertation defense by B. McReynolds on his thesis titled "Benchmarking and Pushing the Boundaries of Event Camera Performance for Space and Sky Observations," PhD, ETH Zurich, 2024

Courtesy: Prof. Tobi Delbruck

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Press release from Quantum Solutions:

September 19, 2024

QUANTUM SOLUTIONS and TOPODRONE Unveil TOPODRONE x Q.Fly: A Cost-Effective, DJI- Ready Quantum Dot SWIR Camera for UAV Applications

Quantum Solutions and Topodrone are excited to announce the launch of the Q.Fly, a next- generation camera with Quantum Dot Short Wave Infrared (SWIR) imaging capability designed specifically for UAV (drones) platforms. The Q.Fly is fully DJI-ready, working seamlessly out of the box with DJI Matrice 300 and DJI Matrice 350 RTK, offering real-time video streaming, control, and configuration directly from the DJI remote controller.

Developed to make SWIR technology more accessible and affordable for drone service companies and drone users, Q.Fly delivers a ready-to-use solution that eliminates the complexities of integrating advanced sensors into UAV platforms. The camera system also includes an RGB camera and/or a thermal camera for enhanced vision capabilities. With plug- and-play compatibility and unmatched spectral imaging performance, Q.Fly redefines what’s possible for a wide range of airborne applications.

This unique product combines the Quantum Solutions’ Quantum Dot SWIR Imaging technology with TOPODRONE’s UAV expertise, providing a cost-effective alternative to traditional SWIR cameras. Q.Fly covers a broad spectral range from VIS-SWIR (400–1700 nm), making it ideal for a variety of airborne applications that demand precise, high-resolution imaging.

·       Built-In RGB Cameras with optional Thermal imager: Includes a 16 MP RGB camera for visual positioning and a thermal imager (640 x 512 pixels, 30 Hz) for enhanced versatility

·       High-precision spectral images geo-referencing

·       High-Speed Spectral Imaging: Capable of operating at 220 Hz, delivering superior spectral imaging performance in real-time

·       Lightweight Design: Weighing only 650g with its 3-axis gyrostabilized gimbal, Q.Fly allows for flight times of up to 35 minutes per battery cycle

·       Built-In Linux Computer: Facilitates easy camera control and supports a variety of protocols, including DJI PSDK and Mavlink

·       Filter Flexibility: Supports quick installation of spectral filters to adapt to specific use cases

Q.Fly is designed to serve industries that require precise, reliable, and easy-to-use drone-based imaging solutions, including:

• Agriculture
•  Fire Safety and Rescue
•  Security&surveillance
•  Industrial Inspection and Surveying

 

Product Launch at INTERGEO 2024
The TOPODRONE x Q.Fly will be officially unveiled at the INTERGEO 2024 exhibition in Stuttgart from September 24–26. This breakthrough technology will be showcased, highlighting its cost-effectiveness and how it can transform UAV imaging for various industries.
Attendees are invited to visit TOPODRONE Booth: Booth Hall 1 - Booth: B1.055 to experience the Q.Fly and learn more about its unparalleled ease of use and advanced SWIR capabilities.
 
Unparalleled Ease of Use for Drone Operators
Q.Fly is designed with drone operators in mind, offering a hassle-free solution that simplifies the often-complex process of integrating advanced sensors into UAV platforms. With its plug- and-play compatibility with DJI drones, users can quickly deploy the Q.Fly for a wide range of applications without the need for complex setup procedures.

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The 6th International Workshop on Image Sensors and Imaging Systems (IWISS2024) will be held at the Tokyo University of Science on Friday November 8, 2024.

In this workshop, people from various research fields, such as image sensing, imaging systems, optics, photonics, computer vision, and computational photography/imaging, come together to discuss the future and frontiers of image sensor technologies in order to explore the continuous progress and diversity in image sensors engineering and state-of-the-art and emerging imaging systems technologies.


Date: November 8 (Fri), 2024
Venue: Forum-2, Morito Memorial Hall, Building 13, Tokyo University of Science / Online
Access: https://maps.app.goo.gl/LyecM4XUYazco5D79
Address: 4-2-2, Kagurazaka, Shinjuku-ku, Tokyo 162-0825, JAPAN

 

Online registration fees information is available here.
Registration is necessary because the number of seats in person is limited. Online viewing via Zoom is also offered.
Registration deadline is Nov. 5 (Tue).
Register and pay online from the following website: [Online registration page]

[Plenary Talk]
"CMOS Direct Time-of-Flight Depth Sensor for Solid-Sate LiDAR Systems"
by Jaehyuk Choi (SolidVue, Inc., Korea & Sungkyunkwan Univ. (SKKU), Korea)

[8 Invited Talks]
Invited-1 “Plasmonic Color Filters for Multi-spectral Imaging” by Atsushi Ono (Shizuoka Univ., Japan)
Invited-2 (online) “Intelligent Imager with Processing-in-Sensor Techniques” by Chih-Cheng Hsieh (National Tsing Hua Univ. (NTHU), Taiwan)
Invited-3 “Designing a Camera for Privacy Preserving” by Hajime Nagahara (Osaka Univ., Japan)
Invited-4 “Deep Compressive Sensing with Coded Image Sensor” by Michitaka Yoshida (JSPS, Japan), et al.
Invited-5 “Event-based Computational Imaging using Modulated Illumination” by Tsuyoshi Takatani (Univ. of Tsukuba, Japan)
Invited-6 “Journey of Pixel Optics Scaling into Deep Sub-micron and Migration to Meta Optics Era” by In-Sung Joe (Samsung Electronics, Korea)
Invited-7 “Trigger-Output Event-Driven SOI pixel Sensor for X-ray Astronomy” by Takeshi Tsuru (Kyoto Univ., Japan)
Invited-8 “New Perspectives for Infrared Imaging Enabled by Colloidal Quantum Dots” by Pawel E. Malinowski (imec, Belgium), et al.

Sponsored by:
Technical Group on Information Sensing Technologies (IST), the Institute of Image Information and Television Engineers (ITE)
Co-sponsored by:
International Image Sensor Society (IISS)

Group of Information Photonics (IPG) +CMOS Working Group, the Optical Society of Japan
General Chair: Keiichiro Kagawa (Shizuoka Univ., Japan)
Technical Program Committee (Alphabetical order): Keiichiro Kagawa (Shizuoka Univ., Japan), Hiroyuki Suzuki (Gunma Univ., Japan), Hisayuki Taruki (Toshiba Electronic Devices & Storage Corporation, Japan), Min-Woong Seo (Samsung Electronics, Korea), Sanshiro Shishido (Panasonic Holdings Corporation, Japan)

Contact for any question about IWISS2024
E-mail: iwiss2024@idl.rie.shizuoka.ac.jp (Keiichiro Kagawa, Shizuoka Univ., Japan)

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Anduril Industries Chief Engineer, Imaging	Lexington, Massachusetts, USA	Link
Purdue University Assistant Professor of Physics and Astronomy	West Lafayette, Indiana, USA	Link
RTX Raytheon Mixed Signal IC Design Senior Engineer	Goleta, California, USA	Link
Sandia National Laboratories Postdoctoral Appointee - Optoelectronic and Microelectronic Device Fabrication, Onsite	Albuquerque, New Mexico, USA	Link
Apple Electrical Engineer - Camera Hardware	San Diego, California, USA	Link
University of Birmingham Professor of Silicon Detector Instrumentation for Particle Physics	Birmingham, England, UK	Link
Google Imaging Systems Engineer, Devices and Services	Mountain View, California, USA	Link
Institute of Physics in Prague Postdoctoral research associate in ATLAS	Prague, Czech Republic	Link
Marvell Silicon Photonics Engineer	Ottawa, Ontario, Canada	Link

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Thesis Title: Advanced techniques for SPAD-based CMOS d-ToF systems
Author: Alessandro Tontini
Affiliation: University of Trento and FBK

Full text available here: [link]

Abstract:

The possibility to enable spatial perception to electronic devices gave rise to a number of important development results in a wide range of fields, from consumer and entertainment applications to industrial environments, automotive and aerospace. Among the many techniques which can be used to measure the three-dimensional (3D) information of the observed scene, the unique features offered by direct time-of-flight (d-ToF) with single photon avalanche diodes (SPADs) integrated into a standard CMOS process result in a high interest for development from both researchers and market stakeholders. Despite the net advantages of SPAD-based CMOS d-ToF systems over other techniques, still many challenges have to be addressed. The first performance-limiting factor is represented by the presence of uncorrelated background light, which poses a physical limit to the maximum achievable measurement range. Another problem of concern, especially for scenarios where many similar systems are expected to operate together, is represented by the mutual system-to-system interference, especially for industrial and automotive scenarios where the need to guarantee safety of operations is a pillar. Each application, with its own set of requirements, leads to a different set of design challenges. However, given the statistical nature of photons, the common denominator for such systems is the necessity to operate on a statistical basis, i.e., to run a number of repeated acquisitions over which the time-of-flight (ToF) information is extracted. The gold standard to manage a possibly huge amount of data is to compress them into a histogram memory, which represents the statistical distribution of the arrival time of photons collected during the acquisition. Considering the increased interest for long-range systems capable of both high imaging and ranging resolutions, the amount of data to be handled reaches alarming levels. In this thesis, we propose an in-depth investigation of the aforesaid limitations. The problem of background light has been extensively studied over the years, and already a wide set of techniques which can mitigate the problem are proposed. However, the trend was to investigate or propose single solutions, with a lack of knowledge regarding how different implementations behave on different scenarios. For such reason, our effort in this view focused on the comparison of existing techniques against each other, highlighting each pros and cons and suggesting the possibility to combine them to increase the performance. Regarding the problem of mutual system interference, we propose the first per-pixel implementation of an active interference-rejection technique, with measurement results from a chip designed on purpose. To advance the state-of-the-art in the direction of reducing the amount of data generated by such systems, we provide for the first time a methodology to completely avoid the construction of a resource-consuming histogram of timestamps. Many of the results found in our investigations are based on preliminary investigations with Monte Carlo simulations, while the most important achievements in terms of interference rejection capability and data reduction are supported by measurements obtained with real sensors.

Contents

Contents
1 Introduction 1
1.1 Single Photon Avalanche Diode (SPAD)
1.1.1 Passive quenching
1.1.2 Active quenching
1.1.3 Photon Detection Efficiency (PDE)
1.1.4 Dark Count Rate (DCR) and afterpulsing

2 Related work
2.1 Pioneering results
2.2 Main challenges
2.3 Integration challenges

3 Numerical modelling of SPAD-based CMOS d-ToF sensors
3.1 Simulator architecture overview
3.2 System features modeling
3.2.1 Optical model
3.2.2 Illumination source - modeling of the laser emission profile
3.3 Monte Carlo simulation
3.3.1 Generation of SPAD-related events
3.3.2 Synchronous and asynchronous SPAD model
3.4 Experimental results
3.5 Summary

4 Analysis and comparative evaluation of background rejection techniques
4.1 Background rejection techniques
4.1.1 Photon coincidence technique
4.1.2 Auto-Sensitivity (AS) technique
4.1.3 Last-hit detection
4.2 Results
4.2.1 Auto-Sensitivity vs. photon coincidence
4.2.2 Comparison of photon coincidence circuits
4.2.3 Last-hit detection characterization
4.3 Automatic adaptation of pixel parameters
4.4 Summary


5 A SPAD-based linear sensor with in-pixel temporal pattern detection for interference and background rejection with smart readout scheme
5.1 Architecture
5.1.1 Pixel architecture
5.1.2 Readout architecture
5.2 Characterization
5.2.1 In-pixel laser pattern detection characterization
5.2.2 Readout performance assessment
5.3 Operating conditions and limits
5.4 Summary

6 SPAD response linearization: histogram-less LiDAR and high photon flux measurements
6.1 Preliminary validation
6.1.1 Typical d-ToF operation
6.1.2 Histogram-less approach
6.2 Mathematical analysis
6.3 Acquisition schemes
6.3.1 Acquisition scheme #1: Acquire or discard
6.3.2 Acquisition scheme #2: Time-gated
6.3.3 Discussion on implementation, expected performance and mathematical analysis
6.3.4 Comparison with state-of-the-art
6.4 Measurement results
6.4.1 Preliminary considerations
6.4.2 Measurements with background light only
6.4.3 Measurements with background and laser light and extraction of the ToF
6.5 Summary

7 Conclusion
7.1 Results
7.1.1 Modelling of SPAD-based d-ToF systems
7.1.2 Comparative evaluation of background-rejection techniques
7.1.3 Interference rejection
7.1.4 Histogram-less and high-flux LiDAR
7.2 Future work and research
Bibliography

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