Time-to-digital converters and histogram builders in SPAD arrays for pulsed-LiDAR

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. Pulsed-LiDAR is one of the most diffused LiDAR techniques which relies on the measurement of the round-trip travel time of an optical pulse back-scattered from a distant target. Besides the light source and the detector, Time-to-Digital Converters (TDCs) are fundamental components in pulsed-LiDAR systems, since they allow to measure the back-scattered photon arrival times and their performance directly impact on LiDAR system requirements (i.e., range, precision, and measurements rate). In this work, we present a review of recent TDC architectures suitable to be integrated in SPAD-based CMOS arrays and a review of data processing solutions to derive the TOF information. Furthermore, main TDC parameters and processing techniques are described and analyzed considering pulsed-LiDAR requirements

Fast-Gated 16 x 16 SPAD Array With 16 on-Chip 6 ps Time-to-Digital Converters for Non-Line-of-Sight Imaging

We present the design and characterization of a fully-integrated array of 16 x 16 Single-Photon Avalanche Diodes (SPADs) with fast-gating capabilities and 16 on-chip 6 ps time-to-digital converters, which has been embedded in a compact imaging module. Such sensor has been developed for Non-Line-Of-Sight imaging applications, which require: i) a narrow instrument response function, for a centimeter-accurate single-shot precision; ii) fast-gated SPADs, for time-filtering of directly reflected photons; iii) high photon detection probability, for acquiring faint signals undergoing multiple scattering events. Thanks to a novel multiple differential SPAD-SPAD sensing approach, SPAD detectors can be swiftly activated in less than 500 ps and the full-width at half maximum of the instrument response function is always less than 75 ps (60 ps on average). Temporal responses are consistently uniform throughout the gate window, showing just few picoseconds of time dispersion when 30 ns gate pulses are applied, while the differential non-linearity is as low as 250 fs. With a photon detection probability peak of 70% at 490 nm, a fill-factor of 9.6% and up to 1.6 . 10(8) photon time-tagging measurements per second, such sensor fulfills the demand for fully-integrated imaging solutions optimized for non-line-of-sight imaging applications, enabling to cut exposure times while also optimizing size, weight, power and cost, thus paving the way for further scaled architectures

SOLUS: An innovative multimodal imaging system to improve breast cancer diagnosis through diffuse optics and ultrasounds

To improve non-invasively the specificity in the diagnosis of breast cancer after a positive screening mammography or doubt/suspicious ultrasound examination, the SOLUS project developed a multimodal imaging system that combines: B-mode ultrasound (US) scans (to assess morphology), Color Doppler (to visualize vascularization), shear-wave elastography (to measure stiffness), and time domain multi-wavelength diffuse optical tomography (to estimate tissue composition in terms of oxy- and deoxy-hemoglobin, lipid, water, and collagen concentrations). The multimodal probe arranges 8 innovative photonic modules (optodes) around the US transducer, providing capability for optical tomographic reconstruction. For more accurate estimate of lesion composition, US-assessed morphological priors can be used to guide the optical reconstructions. Each optode comprises: i) 8 picosecond pulsed laser diodes with different wavelengths, covering a wide spectral range (635-1064 nm) for good probing of the different tissue constituents; ii) a large-area (variable, up to 8.6 mm2) fast-gated digital Silicon Photomultiplier; iii) the acquisition electronics to record the distribution of time-of-flight of the re-emitted photons. The optode is the basic element of the optical part of the system, but is also a stand-alone, ultra-compact (about 4 cm3) device for time domain multi-wavelength diffuse optics, with potential application in various fields

SOLUS: a novel multimodal approach to ultrasound and diffuse optics imaging of breast cancer

A multimodal instrument for breast imaging was developed, combining ultrasound (morphology), shear wave elastography (stiffness), and time domain multiwavelength diffuse optical tomography (blood, water, lipid, collagen) to improve the non-invasive diagnosis of breast cancer

A novel sub-10 ps resolution TDC for CMOS SPAD array

In this work, we present a novel Time-to-Digital Converter (TDC) for single-chip integration in Single-Photon Avalanche-Diode (SPAD) array and digital Silicon Photomultiplier (SiPM). Such novel detector-timing electronics combination will be suitable for Time-Correlated Single-Photon Counting (TCSPC) applications and direct Time-Of-Flight (TOF) measurements. The proposed TDC is based on a 200 MHz 4-bit counter that guarantees a Full-Scale Range of 80 ns. Two interpolators exploit the sliding scale technique to reduce the Differential Non-Linearity (DNL). Besides the coarse interpolation, the multi-stage interpolators have a novel dual-fine interpolation that guarantees a resolution as good as 7 ps, with a conversion time (< 50 ns) much shorter compared to typical architectures based on Vernier delay lines

Fast-gated 16 x 16 SPAD array with on-chip 6 ps TDCs for non-line-of-sight imaging

We present an array of 16 times 16 single-photon avalanche diodes (SPADs) with 16 shared 6 ps time-to-digital converters (TDCs), designed for non-line-of-sight imaging. It features a timing jitter of 60 ps (FWHM), fast-gated capabilities and up to 1.6·108 photon time-tagging measurements per second

Persone, famiglia e successioni nella giurisprudenza costituzionale

I saggi contenuti nel volume testimoniano al lettore l'ampiezza e la portat degli interventi che la Corte costituzionale ha dedicato agli istituti delle persone, della famiglia e delle successioni durante i cinquanta anni della sua attività

Event-driven SPAD camera with 60 ps IRF and up to 1.6 center dot 10(8) photon time-tagging measurements per second

We present a compact camera module based on an array of 16 x 16 single-photon avalanche diodes (SPADs) with fast-gating capabilities and hosting 16 shared time-to-digital converters (TDCs) with a least significant bit (LSB) of 6 ps. SPADs are gated with a rising-edge of less than 500 ps and show an average instrument response function (IRF) of 60 ps FWHM, including the TDCs, with less than 4 ps time-dispersion across a 30 ns gate window. Differential non-linearity (DNL) and integral non-linearity (INL) are as good as 0.04 LSB and 3.6 LSB, respectively. An event-driven readout protocol optimizes data transfer from the SPAD chip to the FPGA, handling the time-of-flight (TOF) pre-processing in order to minimize the dead-time of the TDCs, thus sustaining up to 1.6 center dot 10(8) conversions per second. TOF data can be transferred towards a PC via USB-C with a maximum throughput of about 6 Gbit/s.Our camera meets the requirements of an optimized multi-pixel solution for non-line-of-sight (NLOS) imaging, as it combines fast-gating with narrow IRF: the sub-nanosecond activation of the SPADs is exploited to reject spurious light pulses, like the first bounce one from the relay wall, and properly acquire multiply- scattered photons arriving from the hidden target, while its narrow IRF allows for centimeter-accurate NLOS reconstructions. Furthermore, while the high throughput paves the way towards real-time NLOS acquisitions at video-rates, the compact form-factor of our camera can optimize size, weight, power and cost of current state-of-art NLOS imaging systems

SPAD array for LiDAR with region-of-interest selection and smart TDC routing

Light Detection and Ranging (LiDAR) is a technique that can be applied to identify the position of objects in an industrial environment, which usually suffer by strong background illumination. In this work we present a novel architecture of a Single Photon Avalanche Diode (SPAD) array optimized for a direct Time Of Flight (dTOF) single-point rangefinder system, with a distance range of about 2 m and a resolution of a few centimeters. The ASIC has been implemented in a 0.16 μm Bipolar-CMOS-DMOS (BCD) technology and includes 10 × 40 pixels, 80 Time-to-Digital Converters (TDCs), and a histogram builder. The peculiarity of this work is the ability of performing a Region-Of-Interest (ROI) selection of just those pixels illuminated by the laser spot, as well as a smart sharing of timing electronics. ROI selection is performed through SPADconnected up/down counters, that are decremented whenever the connected SPAD is triggered within the time window where the laser spot is expected, whereas they are incremented when the connected SPAD is triggered within a time window where the laser pulse is not present. If the counter stores a negative value, the pixel is considered to be within the laser spot, and just those pixels might trigger a TDC during the following 500 samples frame. Each TDC is shared among 5 non-adjacent pixels that should not be hit at the same time, considering the expected laser spot dimension. The implemented TDCs have 75 ps resolution and 19.2 ns Full Scale Range (FSR)

Benzene and 2-ethyl-phthalate induce proliferation in normal rat pituitary cells

Purpose: Endocrine disruptors are known to modulate a variety of endocrine functions and increase the risk for neoplasia. Epidemiological data reported increased prevalence of pituitary tumors in high industrial areas while genotyping studies showed that mutations in the aryl hydrocarbon receptor (AhR) interacting protein (AIP)\u2014chaperone to the dioxin ligand AhR\u2014gene are linked to predisposition to pituitary tumor development. Aim of the present study was to establish whether endocrine pollutants can induce cell proliferation in normal rat pituitary cells. Methods: Pituitary primary cultures were incubated with 250, 650 and 1250 pM benzene or 2-ethyl-phthalate for up to 96 h and viability, energy content and cell proliferation assessed. Expression of pituitary tumor transforming gene (PTTG), cyclin D1 (Ccnd1), AhR and AIP was quantified by RT-qPCR. Results: Incubation with benzene or 2-ethyl-phthalate increased viability and energy content in pituitary cells. The endocrine disruptors also increased cell proliferation as well as Ccnd1 and PTTG expression. Increased AhR and AIP expression was observed after incubation with the two pollutants. Conclusions: Our findings indicate that benzene and 2-ethyl-phthalate activate AhR/AIP expression and stimulate proliferation in normal rat pituitary cells. This study is the first demonstration that pollutants can induce normal pituitary cells to proliferate and provides a link between epidemiological and genomic findings in pituitary tumors