1,720,987 research outputs found
Time-gated 128x1 and 8x8 SPAD cameras for 2D photon-counting and 3D time-of-flight maps
No full textWe present the development and the validation of two SPAD camera systems, based on two SPAD array chips (Figure 1), respectively with 8x8 and 128x1 high-performance CMOS SPAD pixels, able to acquire both photon-counting 2D "intensity" images and photon-timing 3D "time-resolved" (hence, also distance-resolved) maps. Each pixel integrates a 30 mu m SPAD detector, an 8-bit in-pixel counter (to counts the number of photons detected during user-selectable timeslots in the nanoseconds and microsecond range), and a 12-bit Time-to-Digital Converter (to timestamp the arrival time of the first photon detected by each SPAD, with sub-nanosecond resolution). In addition, the two array chips have the capability of actively gating the SPADs, driving the SPAD bias voltage above or below breakdown, with sub-nanosecond transitions allowing efficient time-domain filtering of incoming light. Active gating can be enabling in applications such as non-line of sight 3D ranging and time-domain functional Near-Infrared Spectroscopy (fNIRS), since it allows hiding unwelcome reflections, stray rays, or luminescence/fluorescence excitation signals. In fact, this feature allows the user to selectively avoid "early" photons, for instance those reflected by the sample surface, while measuring only the useful "late" photons, for instance those which interacted with the deeper biological tissue's layers, preventing the triggering due to the strong reflections, which would saturate the SPADs. For optimizing chip operation in many different applications, both systems are extremely versatile and allow the user to customize the cameras for various measurement setups. The cameras quantum sensitivity allows the reconstruction of faint optical signals through the Time-Correlated Single Photon Counting (1) (TCSPC) technique. In addition, they enable many quantum experiments where information on each photon arrival time is required for example to identify time-coincident events with entangled photons. The 128x1 linear array is perfectly suited for spectroscopy applications, particularly for advanced Raman techniques, thanks to on-chip time-gating and time-tagging capabilities
32 × 32 CMOS SPAD Imager for Gated Imaging, Photon Timing, and Photon Coincidence
No full textWe present the design and simulations of a single-photon sensitive imager based on single photon avalanche diodes (SPADs) with an innovative pixel architecture that includes four separate SPADs with independent active time-gating and quenching circuit, a shared time-to-digital converter (TDC) with 50-ps resolution, four independent photon counters, and multiple operation modes. The TDC is driven by smart arbitration logic, which preserves spatial information among the four detectors; furthermore, an alternative operation mode exploits photon-coincidence on multiple detectors to reduce the effect of high background levels, e.g., in light detection and ranging applications with strong ambient light. Key features are the ability to operate in simultaneous photon counting and timing modes for capturing 2-D and 3-D images of the scene in a single shot (frame), the option of a counting-only mode, reducing power consumption, and increasing achievable frame-rate when timing information is not needed, and the ability to individually shut down noisy detectors or to enable just some regions of interests
Design of a 24×24 SPAD imager for multi-photon coincidence-detection in super resolution microscopy
No full textMicroscopy resolution below the diffraction limit can be achieved by exploiting quantum light properties. NitrogenVacancy (NV) color centers in diamond, dye molecules and quantum dots are examples of single-photon emitters, whose antibunching property allows super-resolution imaging through the measurement of high-order autocorrelation functions. In this work, we present a novel Single Photon Avalanche Diode (SPAD) array architecture optimized for n-fold photon coincidence counting, in each point across the whole sensitive area. It is implemented in a 160 nm Bipolar-CMOS-DMOS (BCD) technology, and it includes 24 × 24 SPAD pixels with 50-μm pixel pitch and 10-μm SPAD diameter. Multi-photon coincidences (within time windows ranging from 2 ns to 500 ns) are identified by post-processing of the in-pixel timing data. Given the expected low photon rate on the detector in quantum imaging applications, on-chip logic discards unwanted information to limit readout throughput and data storage. In fact, reading the whole array would take 3 μs, while skipping rows detecting no photon reduces the readout time to 240 ns in case of no photon detected over the entire array. Moreover, we implemented a multi-gate approach, which avoids halting the array during readout, thus enabling multiple data acquisitions. Thanks to these power-saving expedients and efficient readout, the architecture is scalable towards multiple modules, such as 48 × 48 or 96 × 96-pixel arrays. Finally, it features the possibility of being coupled with a micro-lens array to reach a 78% equivalent fill-factor
Multi-photon coincidence-detection SPAD array for super-resolution microscopy
No full textWe designed a scalable and readout-efficient Single Photon Avalanche Diode (SPAD) array optimized to detect n-fold photon coincidences across a wide active area, aiming at super-resolution imaging through single-photon emitters and detection
SPAD 3D LiDAR sensors for automotive, industrial automation and surveillance
No full textLiDAR systems based on SPAD single-photon detectors are a key technology for autonomous driving, industrial automation and military surveillance. Different architectures are analyzed and compared to pave the way towards next-generation LiDAR SPAD imagers
32×32 SPAD camera for 2D photon-counting and 3D time-of-flight ranging
No full textWe present the development and characterization of a camera system based on an improved version of a previously developed 32×32 SPADs and TDCs array, with extended duty cycle (80%) and enhanced single-shot precision (175ps rms)
Linear SPAD array single- and multiple-photon coincidence- based Quantum Random Number Generator
No full textWe presents a 32 × 1 linear Single Photon Avalanche Diode array for quantum communication applications. The array provides the position of the single photon detected, and can identify multiple photon coincidences
Design of a 16 x 16 fast-gated SPAD imager with 16 integrated shared picosecond TDCs for non-line-of-sight imaging
Full text linkGoing 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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