16-Channel Module Based on a Monolithic Array of Single-Photon Detectors and 10-ps Time-to-Digital Converters (original) (raw)
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IEEE Journal of Solid-State Circuits, 2000
An imager for time-resolved optical sensing was fabricated in CMOS technology. The sensor comprises an array of 128 2 128 single-photon pixels, a bank of 32 time-to-digital-converters, and a 7.68 Gbps readout system. Thanks to the outstanding timing precision of single-photon avalanche diodes and the optimized measurement circuitry, a typical resolution of 97 ps was achieved within a range of 100 ns. To the best of our knowledge, this imager is the first fully integrated system for photon time-of-arrival evaluation. Applications include 3-D imaging, optical rangefinding, fast fluorescence lifetime imaging, imaging of extremely fast phenomena, and, more generally, imaging based on time-correlated single photon counting. When operated as an optical rangefinder, this design has enabled us to reconstruct 3-D scenes with milimetric precisions in extremely low signal exposure. A laser source was used to illuminate the scene up to 3.75 m with an average power of 1 mW, a field-of-view of 5 and under 150 lux of constant background light. Accurate distance measurements were repeatedly achieved based on a short integration time of 50 ms even when signal photon count rates as low as a few hundred photons per second were available. Index Terms-Depth sensor, FCS, flash laser camera, fluorescence lifetime imaging microscopy (FLIM), Förster Resonance Energy Transfer (FRET), Geiger-mode avalanche photodiode, rangefinder, range imaging, single-photon avalanche diode, single-photon detector, solid-state 3-D imaging, SPAD, TCSPC, time-correlated single-photon counting, time-of-flight, 3-D image sensor.
IEEE Photonics Journal, 2017
In recent years, time-correlated single photon counting (TCSPC) has become the technique of choice in many life science analyses, where fast and faint luminous signals are recorded with picosecond accuracy. Nevertheless, the maximum operating frequency of a single TCSPC acquisition channel limits the measurement speed, especially when scanning point systems are exploited. In order to increase the speed of TCSPC experiments, many multichannel systems based on single photon avalanche diode arrays have been proposed in the literature, which integrate thousands of pixels on the same chip. Unfortunately, the huge number of data generated by this kind of system can easily bring to the saturation of the transfer bandwidth to the external processing unit. For this reason, several different readout architectures have been proposed in the literature, attempting to exploit at best the limited bandwidth under TCSPC operating conditions. In this paper, some typical readout approaches, namely clock-driven and event-driven readouts, are discussed and compared, along with a recently-introduced router-based algorithm that is specifically designed to obtain maximum bandwidth exploitation under any condition. Quantitative comparisons are performed starting from imager response of the systems, which is the rate of recorded events in the case of uniform illumination of the detector array.
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A compact single-photon counting module that can accurately control the bias voltage and hold-off time is developed in this work. The module is a microcontroller-based system which mainly consists of a microcontroller, a programmable negative voltage generator, a silicon-based single-photon avalanche diode, and an integrated active quench and reset circuit. The module is 3.8 cm × 3.6 cm × 2 cm in size and can communicate with the end user and be powered through a USB cable (5 V). In this module, the bias voltage of the single-photon avalanche diode (SPAD) is precisely controllable from −14 V ~ −38 V and the hold-off time (consequently the dead time) of the SPAD can be adjusted from a few nanoseconds to around 1.6 μs with a setting resolution of ∼6.5 ns. Experimental results show that the module achieves a minimum dead time of around 28.5 ns, giving a saturation counting rate of around 35 Mcounts/s. Results also show that at a controlled reverse bias voltage of 26.8 V, the dark count...
Optics Express, 2018
Time-Correlated Single Photon Counting (TCSPC) is an essential tool in many scientific applications, where the recording of optical pulses with picosecond precision is required. Unfortunately, a key issue has to be faced: distortion phenomena can affect TCSPC experiments at high count rates. In order to avoid this problem, TCSPC experiments have been commonly carried out by limiting the maximum operating frequency of a measurement channel below 5% of the excitation frequency, leading to a long acquisition time. Recently, it has been demonstrated that matching the detector dead time to the excitation period allows to keep distortion around zero regardless of the rate of impinging photons. This solution paves the way to unprecedented measurement speed in TCSPC experiments. In this scenario, the front-end circuits that drive the detector play a crucial role in determining the performance of the system, both in terms of measurement speed and timing performance. Here we present two fully integrated front-end circuits for Single Photon Avalanche Diodes (SPADs): a fast Active Quenching Circuit (AQC) and a fully-differential current pickup circuit. The AQC can apply very fast voltage variations, as short as 1.6ns, to reset external custom-technology SPAD detectors. A fast reset, indeed, is a key parameter to maximize the measurement speed. The current pickup circuit is based on a fully differential structure which allows unprecedented rejection of disturbances that typically affect SPAD-based systems at the end of the dead time. The circuit permits to sense the current edge resulting from a photon detection with picosecond accuracy and precision even a few picoseconds after the end of the dead time imposed by the AQC. This is a crucial requirement when the system is operated at high rates. Both circuits have been deeply characterized, especially in terms of achievable measurement speed and timing performance.
CMOS Imager With 1024 SPADs and TDCs for Single-Photon Timing and 3-D Time-of-Flight
IEEE Journal of Selected Topics in Quantum Electronics, 2014
We present a CMOS imager consisting of 32 × 32 smart pixels, each one able to detect single photons in the 300-900 nm wavelength range and to perform both photon-counting and photon-timing operations on very fast optical events with faint intensities. In photon-counting mode, the imager provides photonnumber (i.e., intensity) resolved movies of the scene under observation, up to 100 000 frames/s. In photon-timing, the imager provides photon arrival times with 312 ps resolution. The result are videos with either time-resolved (e.g., fluorescence) maps of a sample, or 3-D depth-resolved maps of a target scene. The imager is fabricated in a cost-effective 0.35-μm CMOS technology, automotive certified. Each pixel consists of a single-photon avalanche diode with 30 μm photoactive diameter, coupled to an in-pixel 10-bit time-to-digital converter with 320-ns full-scale range, an INL of 10% LSB and a DNL of 2% LSB. The chip operates in global shutter mode, with full frame times down to 10 μs and just 1-ns conversion time. The reconfigurable imager design enables a broad set of applications, like time-resolved spectroscopy, fluorescence lifetime imaging, diffusive optical tomography, molecular imaging, time-of-flight 3-D ranging and atmospheric layer sensing through LIDAR. Index Terms-Photon counting, CMOS imagers, single-photon avalanche diode (SPAD), 2-D imaging, 3-D ranging, time-of-flight, photon tagging, time-correlated single-photon counting (TCSPC), light detection and ranging (LIDAR).
A 32x32-pixel array with in-pixel photon counting and arrival time measurement in the analog domain
Solid-State Circuits European Conference, 2009
A Time-to-Amplitude Converter (TAC) with embedded analog-to-digital conversion is implemented in a 130-nm CMOS imaging technology. The proposed module is conceived for Single-Photon Avalanche Diode imagers and can operate both as a TAC or as an analog counter, thus allowing both time-correlated or time-uncorrelated imaging operation. A single-ramp, 8-bit ADC with two memory banks to allow high-speed, time-interleaved operation is
SPAD Smart Pixel for Time-of-Flight and Time-Correlated Single-Photon Counting Measurements
Ieee Photonics Journal, 2012
We present a smart pixel based on a single-photon avalanche diode (SPAD) for advanced time-of-flight (TOF) and time-correlated single photon counting (TCSPC) applications, fabricated in a cost-effective 0.35-m CMOS technology. The large CMOS detector (30-m active area diameter) shows very low noise (12 counts per second at room temperature at 5-V excess bias) and high efficiency in a wide wavelength range (about 50% at 410 nm and still 5% at 800 nm). The analog front-end electronics promptly senses and quenches the avalanche, thus leading to an almost negligible afterpulsing effect. The in-pixel 10-bit time-to-digital converter (TDC) provides 312-ps resolution and 320-ns full-scale range (FSR), i.e., 10-cm single-shot spatial resolution within 50-m depth range in a TOF system. The in-pixel 10-bit memory and output buffers make this smart pixel the viable building block for advanced single-photon imager arrays for 3-D depth ranging in safety and security applications and for 2-D fluorescence lifetime decays in biomedical imaging.
2006
The design and characterization of an imaging sensor based on single photon avalanche diodes is presented. The sensor was fully integrated in a 0.35µm CMOS technology. The core of the imager is an array of 4x112 pixels that independently and simultaneously detect the arrival time of photons with picosecond accuracy. A novel event-driven readout scheme allows parallel column-wise and non-sequential, on-demand row-wise operation. Both time-correlated and time-uncorrelated measurements are supported in the sensor. The readout scheme is scalable and requires only 11 transistors per pixel with a pitch of 25µm. A number of standard performance measurements for the imager are presented in the paper. An average dark count rate of 6Hz and 750Hz are reported at room temperature respectively for an active area diameter of 4µm and 10µm, while the dead time is 40ns with negligible crosstalk. A timing resolution better than 80ps over the entire integrated array makes this technique ideal for a fully integrated high resolution streak camera, thus enabling fast TCSPC experiments. Applications requiring low noise, picosecond timing accuracies, and measurement parallelism are prime candidates for this technology. Examples of such applications include bioimaging at cellular and molecular level based on fluorescence lifetime imaging and/or, fluorescence correlation spectroscopy, as well as fast optical imaging, optical rangefinders, LIDAR, and low light level imagers.
A Time-Resolved, Low-Noise Single-Photon Image Sensor Fabricated in Deep-Submicron CMOS Technology
IEEE Journal of Solid-State Circuits, 2000
We report on the design and characterization of a novel time-resolved image sensor fabricated in a 130 nm CMOS process. Each pixel within the 32 32 pixel array contains a low-noise single-photon detector and a high-precision time-to-digital converter (TDC). The 10-bit TDC exhibits a timing resolution of 119 ps with a timing uniformity across the entire array of less than 2 LSBs. The differential non-linearity (DNL) and integral non-linearity (INL) were measured at ±0.4 and ±1.2 LSBs, respectively. The pixel array was fabricated with a pitch of 50 µm in both directions and with a total TDC area of less than 2000 µm². The target application for this sensor is time-resolved imaging, in particular fluorescence lifetime imaging microscopy and 3D imaging. The characterization shows the suitability of the proposed sensor technology for these applications.