scholarly journals Statistical Modelling of SPADs for Time-of-Flight LiDAR

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4481
Author(s):  
Alfonso Incoronato ◽  
Mauro Locatelli ◽  
Franco Zappa
Keyword(s):  
Single Photon ◽  
Time Of Flight ◽  
Statistical Modelling ◽  
Operating Conditions ◽  
Single Photons ◽  
Distance Measurements ◽  
Distance Information ◽  
High Background ◽  
Lidar Return ◽  
Storage Cells

Time-of-Flight (TOF) based Light Detection and Ranging (LiDAR) is a widespread technique for distance measurements in both single-spot depth ranging and 3D mapping. Single Photon Avalanche Diode (SPAD) detectors provide single-photon sensitivity and allow in-pixel integration of a Time-to-Digital Converter (TDC) to measure the TOF of single-photons. From the repetitive acquisition of photons returning from multiple laser shots, it is possible to accumulate a TOF histogram, so as to identify the laser pulse return from unwelcome ambient light and compute the desired distance information. In order to properly predict the TOF histogram distribution and design each component of the LiDAR system, from SPAD to TDC and histogram processing, we present a detailed statistical modelling of the acquisition chain and we show the perfect matching with Monte Carlo simulations in very different operating conditions and very high background levels. We take into consideration SPAD non-idealities such as hold-off time, afterpulsing, and crosstalk, and we show the heavy pile-up distortion in case of high background. Moreover, we also model non-idealities of timing electronics chain, namely, TDC dead-time, limited number of storage cells for TOF data, and TDC sharing. Eventually, we show how the exploit the modelling to reversely extract the original LiDAR return signal from the distorted measured TOF data in different operating conditions.

scholarly journals Modeling and Analysis of a Direct Time-of-Flight Sensor Architecture for LiDAR Applications

Sensors ◽  
2019 ◽  
Vol 19 (24) ◽  
pp. 5464 ◽  
Author(s):  
Preethi Padmanabhan ◽  
Chao Zhang ◽  
Edoardo Charbon
Keyword(s):  
Background Noise ◽  
3D Imaging ◽  
Dynamic Range ◽  
Time Of Flight ◽  
Operating Conditions ◽  
Exposure Limits ◽  
Depth Sensing ◽  
Wide Dynamic Range ◽  
High Background ◽  
Time Gating

Direct time-of-flight (DTOF) is a prominent depth sensing method in light detection and ranging (LiDAR) applications. Single-photon avalanche diode (SPAD) arrays integrated in DTOF sensors have demonstrated excellent ranging and 3D imaging capabilities, making them promising candidates for LiDARs. However, high background noise due to solar exposure limits their performance and degrades the signal-to-background noise ratio (SBR). Noise-filtering techniques based on coincidence detection and time-gating have been implemented to mitigate this challenge but 3D imaging of a wide dynamic range scene is an ongoing issue. In this paper, we propose a coincidence-based DTOF sensor architecture to address the aforementioned challenges. The architecture is analyzed using a probabilistic model and simulation. A flash LiDAR setup is simulated with typical operating conditions of a wide angle field-of-view (FOV = 40 ° ) in a 50 klux ambient light assumption. Single-point ranging simulations are obtained for distances up to 150 m using the DTOF model. An activity-dependent coincidence is proposed as a way to improve imaging of wide dynamic range targets. An example scene with targets ranging between 8–60% reflectivity is used to simulate the proposed method. The model predicts that a single threshold cannot yield an accurate reconstruction and a higher (lower) reflective target requires a higher (lower) coincidence threshold. Further, a pixel-clustering scheme is introduced, capable of providing multiple simultaneous timing information as a means to enhance throughput and reduce timing uncertainty. Example scenes are reconstructed to distinguish up to 4 distinct target peaks simulated with a resolution of 500 ps. Alternatively, a time-gating mode is simulated where in the DTOF sensor performs target-selective ranging. Simulation results show reconstruction of a 10% reflective target at 20 m in the presence of a retro-reflective equivalent with a 60% reflectivity at 5 m within the same FOV.

Vacuum Ultraviolet Single-Photon Ionization Time-of-Flight Mass Spectrometer

2011 ◽  
Vol 39 (10) ◽  
pp. 1470-1475 ◽  
Author(s):  
Guo-Bin TAN ◽  
Wei GAO ◽  
Zheng-Xu HUANG ◽  
Yi HONG ◽  
Zhong FU ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Vacuum Ultraviolet ◽  
Single Photon ◽  
Time Of Flight ◽  
Ionization Time ◽  
Single Photon Ionization ◽  
Flight Mass Spectrometer ◽  
Photon Ionization

scholarly journals Observing quantum coherence from photons scattered in free-space

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Shihan Sajeed ◽  
Thomas Jennewein
Keyword(s):  
Free Space ◽  
Quantum Coherence ◽  
Quantum Communication ◽  
Single Photon ◽  
Detector Array ◽  
Line Of Sight ◽  
Background Suppression ◽  
Single Photon Detector ◽  
High Background ◽  
Non Line Of Sight

AbstractQuantum channels in free-space, an essential prerequisite for fundamental tests of quantum mechanics and quantum technologies in open space, have so far been based on direct line-of-sight because the predominant approaches for photon-encoding, including polarization and spatial modes, are not compatible with randomly scattered photons. Here we demonstrate a novel approach to transfer and recover quantum coherence from scattered, non-line-of-sight photons analyzed in a multimode and imaging interferometer for time-bins, combined with photon detection based on a 8 × 8 single-photon-detector-array. The observed time-bin visibility for scattered photons remained at a high 95% over a wide scattering angle range of −450 to +450, while the individual pixels in the detector array resolve or track an image in its field of view of ca. 0.5°. Using our method, we demonstrate the viability of two novel applications. Firstly, using scattered photons as an indirect channel for quantum communication thereby enabling non-line-of-sight quantum communication with background suppression, and secondly, using the combined arrival time and quantum coherence to enhance the contrast of low-light imaging and laser ranging under high background light. We believe our method will instigate new lines for research and development on applying photon coherence from scattered signals to quantum sensing, imaging, and communication in free-space environments.

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

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 598
Author(s):  
Jean-François Pratte ◽  
Frédéric Nolet ◽  
Samuel Parent ◽  
Frédéric Vachon ◽  
Nicolas Roy ◽  
...  
Keyword(s):  
Large Scale ◽  
Single Photon ◽  
Time Of Flight ◽  
Digital Signal ◽  
Liquid Argon ◽  
Cmos Technology ◽  
System Level ◽  
Superior Performance ◽  
Digital Converter ◽  
Positron Emission

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.

scholarly journals Quantum Structured Light: Non-classical Spin Texture of Twisted Single-photon Pulses

2021 ◽  
Author(s):  
Li-Ping Yang ◽  
Zubin Jacob
Keyword(s):  
Spin Density ◽  
Electromagnetic Waves ◽  
Single Photon ◽  
Structured Light ◽  
Three Dimensional ◽  
Quantum Spin ◽  
Single Photons ◽  
Spin Order ◽  
Spin Noise ◽  
Spin Texture

Abstract Classical structured light with controlled polarization and orbital angular momentum (OAM) of electromagnetic waves has varied applications in optical trapping, bio-sensing, optical communications and quantum simulations. The classical electromagnetic theory of such structured light beams and pulses have advanced significantly over the last two decades. However, a framework for the quantum density of spin and OAM for single-photons remains elusive. Here, we develop a theoretical framework and put forth the concept of quantum structured light for space-time wavepackets at the single-photon level. Our work marks a paradigm shift beyond scalar-field theory as well as the paraxial approximation and can be utilized to study the quantum properties of the spin and OAM of all classes of twisted quantum light pulses. We capture the uncertainty in full three-dimensional (3D) projections of vector spin demonstrating their quantum behavior beyond the conventional concept of classical polarization. Even in laser beams with high OAM along the propagation direction, we predict the existence of large OAM quantum fluctuations in the transverse plane which can be verified experimentally. We show that the spin density generates modulated helical texture beyond the paraxial limit and exhibits distinct statistics for Fock-state vs. coherent-state twisted pulses. We introduce the quantum correlator of photon spin density to characterize the nonlocal spin noise providing a rigorous parallel with fermionic spin noise operators. Our work paves the way for quantum spin-OAM physics in twisted single photon pulses and also opens explorations for new phases of light with long-range spin order.

scholarly journals Techniques for X-Ray Diffraction Studies of Radioactive Materials

1958 ◽  
Vol 2 ◽  
pp. 261-274
Author(s):  
W. V. Cummings ◽  
W. J. Gruber
Keyword(s):  
Energy Spectrum ◽  
Radiation Damage ◽  
Background Level ◽  
Operating Conditions ◽  
Limiting Factor ◽  
X Ray Diffraction ◽  
Radioactive Materials ◽  
High Background ◽  
X Ray

AbstractMany materials, both fissionable and non-fissionable, become very radioactive when subjected to nuclear radiations. This radioactivity results in a high background level in X-ray diffraction studies and becomes a limiting factor in an analysis of radiation damage. A description is given of special techniques that are used to minimize this background and produce optimum diffraction conditions. The radioactive intensity of irradiated X-ray specimens varies from levels that are only mildly troublesome to levels that are extremely hazardous to personnel. The diffraction methods employed at the various levels are explained. An example of the radioactive energy spectrum of a specimen is given to show the method of selecting the best operating conditions and techniques.

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