Introduction to time-of-flight imaging

Charbon, Edoardo

doi:10.1109/icsens.2014.6985072

Cited by 11 publications

(8 citation statements)

References 31 publications

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“…In fact, these circuits encode information based on the difference between instants of time in which digital events occur rather than based on the values of the voltages at the nodes or currents in the branches of the electrical networks. In this scenario, TDC circuits are consequently the core of modern Time-of-Flight (ToF) [1] measurements, which are last generation solutions in medical diagnostics (e.g. TOF Positron Emission Tomography, ToF-PET [2], [3]), in automotive (e.g.…”

Section: Introductionmentioning

confidence: 99%

Time-to-Digital Converter IP-Core for FPGA at State of the Art

et al. 2021

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The Field Programmable Gate Array (FPGA) structure poses several constraints that make the implementation of complex asynchronous circuits such as Time-Mode (TM) circuits almost unfeasible. In particular, in Programmable Logic (PL) devices, such as FPGAs, the operation of the logic is usually synchronous with the system clock. However, it can happen that a very high-performance specifications demands to abandon this paradigm and to follow an asynchronous implementative solution. The main driver forcing the use of programmable logic solutions instead of tailored Application Specific Integrated Circuits (ASIC), best suiting an asynchronous design, is the request coming from the research community and industrial R&D of fast-prototyping at low Non Recursive Engineering (NRE) costs. For instance in the case of a high-resolved Time-to-Digital Converter (TDC), a signal clocked at some hundreds of MHz implemented in FPGA allows implementing a TDC with resolution at ns. If a higher resolution is required, the signal frequency cannot be increased further and one of the aces up the designer's sleeve is the propagation delay of the logic in order to quantize the time intervals by means of a so-called Tapped Delay-Line (TDL). This implementation of TDL-based TDC in FPGAs requires special attention by the designer both in making the best use of all available resources and in foreseeing how signals propagate inside these devices. In this paper, we investigate the implementation of a high-performance TDL-TDC addressed to 28-nm 7-Series Xilinx FPGA, taking into account the comparison between different technological nodes from 65-nm to 20-nm. In this context, the term high-performance means extended dynamic-range (up to 10.3 s), high-resolution and single-shot precision (up to 366 fs and 12 ps r.m.s respectively), low differential and integral non-linearity (up to 250 fs and 2.5 ps respectively), and multi-channel capability (up to 16).

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Section: Introductionmentioning

confidence: 99%

Time-to-Digital Converter IP-Core for FPGA at State of the Art

et al. 2021

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“…Time Correlated Single Photon Counting [15], the measurement of the decay time of particles is used to properly identify materials. Instead, in TOF imaging [16], such as LIDAR [17] and FIGURE 1. Energy coupling due to the XT translates into a temporal shift in time of digital signal edges.…”

Section: Introductionmentioning

confidence: 99%

Cross-Talk Issues in Time Measurements

Lusardi¹,

Corna

Garzetti

et al. 2021

IEEE Access

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The enormous diffusion of Time-Mode circuits, in particular Time-to-Digital Converter (TDC) time measurement circuits, and at the same time the dizzying increase in parallel channels required by the most recent applications, for example in the automotive and digital imaging fields, brings the problem of electromagnetic interference between channels ever more to the fore. This phenomenon, generally known as Cross-Talk (XT), is particularly critical given the increase in the operating frequency and density of systems components, and its effect on the timing parameters in TDC measurements is investigated. Considering the time measurements, XT creates temporal shift on the physical events from which the timestamps are extracted; in this manner, an error in the measurements is generated. In order to detect the XT phenomena, a methodical analysis based on Code-Density Test (CDT) is performed; in this terms, two different typologies of XTs are investigated, which are correlated and uncorrelated XT. Furthermore, a TDC board is used as case study and all the XT sources are detected and classified. Thus, a classification of the importance of the different sources of XT is achived and a solution to minimize the different causes is proposed.INDEX TERMS Cross-Talk (XT), Time Measurement, Time-to-Digital Converter (TDC), Code-Density Test (CDT), Linearity.

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“…An ITOF lidar sensor continuously emits amplitude modulated light, similar to traditional laser-based phase difference lidar sensors. However, instead of measuring phase delay through direct comparison or mixing of the return signal with a version of the emitted signal, ITOF relies on quadrature sampling of the return energy [ 16 , 17 ]. The amount of return energy is integrated four times per period, i.e., at 90-degree phase intervals (see Figure 1 ), the timing of which is aligned with the phase of the emitted signal.…”

Section: Introductionmentioning

confidence: 99%

Radiometric Calibration of an Inexpensive LED-Based Lidar Sensor

Laughlin

Hartzell

Glennie

et al. 2020

Sensors

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Radiometric calibration of laser-based, topographic lidar sensors that measure range via time of flight or phase difference is well established. However, inexpensive, short-range lidar sensors that utilize non-traditional ranging techniques, such as indirect time of flight, may report radiometric quantities that are not appropriate for existing calibration methods. One such lidar sensor is the TeraRanger Evo 60 m by Terabee, whose reported amplitude measurements do not vary smoothly with the amount of return signal power. We investigate the performance of a new radiometric calibration model, one based on a neural network, applied to the Evo 60 m. The proposed model is found to perform similarly to those applied to traditional lidar sensors, with root mean square errors in predicted target reflectance of no more than ±6% for non-specular surfaces. The radiometric calibration model provides a generic approach that may be applicable to other low-cost lidar sensors that report return signal amplitudes that are not smoothly proportional to target range and reflectance.

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Introduction to time-of-flight imaging

Cited by 11 publications

References 31 publications

Time-to-Digital Converter IP-Core for FPGA at State of the Art

Time-to-Digital Converter IP-Core for FPGA at State of the Art

Cross-Talk Issues in Time Measurements

Radiometric Calibration of an Inexpensive LED-Based Lidar Sensor

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