1,720,983 research outputs found
15bit Time-to-Digital Converters with 0.9% DNLrms and 160ns FSR for single-photon imagers
No full textWe present a high precision Time-to-Digital Converter (TDC) architecture suitable for multi-channel implementations in monolithic arrays of single-photon avalanche diode (SPAD) detectors aimed at TCSPC applications (like FLIM, FCS, FRET), but also at photon timing and direct TOF measurements for 3D ranging applications (e.g. in LIDAR systems). A “smart-pixel” with a SPAD detector, an analog sensing and driving electronics and a TDC is able to detect single photons and to measure and record in-pixel the time delay between a START pulse (e.g., laser excitation, cell stimulus, or LIDAR flash) and a STOP pulse given by the detection of a single photon (e. g., fluorescence decay signal or back reflection from an object). We report on the design and characterization of prototype chips, fabricated in a 0.35 μm standard CMOS technology. With a 100 MHz reference clock, the TDC provides a time-resolution of 10 ps, a dynamic range of 160 ns and DNL <1% LSB rms
3D ranging with a single-photon imaging array
No full textSeveral applications require systems for 3D ranging acquisition, where both high frame-rate and high sensitivity (for either very dark environments or opaque objects) are a must. We exploited a monolithic chip with 32 x 32 Single-Photon Avalanche Diode smart-pixels for 3D ranging applications based on an Indirect Time-of-Flight (iTOF) technique. The scene is illuminated by a sinusoidally modulated LED and the reflected light is acquired by the imager in different timeslots, for measuring the phase delay of outgoing vs. incoming signal, hence computing the distance between the sensor and objects in the scene. All 1024 array pixels are synchronously enabled by a global gate signal, which allows photon counting in well-defined time-slots within each frame. The frame duration is set in accordance to the desired SNR. We report on measurements performed on chips fabricated in a standard high-voltage 0.35 μm CMOS technology, which feature 40% photon detection efficiency at 450 nm and 20% at 650nm. The single-photon sensitivity allowed the use of just few LEDs at 650 nm and 20MHz for acquiring a scene with a maximum distance of 7.5 m, with better than 10 cm distance resolution and frame-rates higher than 50 frames/s
Single-photon 3D ranging based on SPAD imagers
No full textThree dimensional (3D) ranging is a break through feature for imaging detectors. Increasing the spatial precision of 3D measurements and improving the system frame-rate are key objectives of research and industry, for novel exploitations of LIDAR. In this paper we present a 3D ranging system with single-photon sensitivity, based on a microelectronic Single-Photon Avalanche Diode array chip able to capture bidimensional (2D) images and to reconstruct distance information through time-gated photon counting and phase reconstruction
Single-photon pulsed light indirect time-of-flight 3D ranging
No full text"Indirect" time-of-flight is one technique to obtain depth-resolved images through active illumination that is becoming more popular in the recent years. Several methods and light timing patterns are used nowadays, aimed at improving measurement precision with smarter algorithms, while using less and less light power. Purpose of this work is to present an indirect time-of-flight imaging camera based on pulsed-light active illumination and a 32 x 32 single-photon avalanche diode array with an improved illumination timing pattern, able to increase depth resolution and to reach single-photon level sensitivity
Fast Sensing and Quenching of CMOS SPADs for Minimal Afterpulsing Effects
No full textWe present a single-photon avalanche diode (SPAD)
front-end circuitry, in a cost-effective 0.35 μm CMOS technology,
for single-photon detection in the visible wavelength range, aimed
at speeding up the sensing of detector ignition and at promptly
quenching the avalanche current buildup. The circuit allows the
reduction in detrimental effects of afterpulsing through reducing
any delays in the electronics intervention on the detector and
through a proper time-varying action of the MOS transistors on
the different SPAD’s operating conditions. The sensing time is
reduced down to a few hundreds of picoseconds, with an active
quenching transition of about 1 ns for 6 V excess bias, and a
final reset in just 3 n
Theoretical and experimental investigations into spatial correlations in spontaneous parametric downconversion
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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