The ePix100A camera is a 0.5 megapixel (704 x 768 pixels) camera for low noise x-ray detection applications requiring high spatial and spectral resolution. The camera is built around a hybrid pixel detector consisting of 4 ePix100a ASICs ip-chip bonded to one sensor. The pixels are 50 μm x 50 μm (active sensor size ~ 35:4mm x 38:6 mm), with a noise of ~ 180 eV rms, a range of 100 8 keV photons, and a current frame rate of 240 Hz (with an upgrade path towards ~ 10 kHz). This performance leads to a camera combining a high dynamic range, high signal to noise ratio, high speed and excellent linearity and spectroscopic performance. While the ePix100A ASIC has been developed for pulsed source applications (e.g., free-electron lasers), it performs well with more common sources (e.g., x-ray tubes, synchrotron radiation). Several cameras have been produced and characterized and the results are reported here, along with x-ray imaging applications demonstrating the camera performance.
KEYWORDS: Prototyping, Sensors, Analog electronics, High dynamic range imaging, Liquid crystal lasers, Photons, Cameras, Signal processing, Image resolution, Free electron lasers
ePix10k is a variant of a novel class of integrating pixel ASICs architectures optimized for the processing of signals in second generation LINAC Coherent Light Source (LCLS) X-Ray cameras. The ASIC is optimized for high dynamic range application requiring high spatial resolution and fast frame rates. ePix ASICs are based on a common platform composed of a random access analog matrix of pixel with global shutter, fast parallel column readout, and dedicated sigma-delta analog to digital converters per column. The ePix10k variant has 100um×100um pixels arranged in a 176×192 matrix, a resolution of 140e- r.m.s. and a signal range of 3.5pC (10k photons at 8keV). In its final version it will be able to sustain a frame rate of 2kHz. A first prototype has been fabricated and characterized. Performance in terms of noise, linearity, uniformity, cross-talk, together with preliminary measurements with bump bonded sensors are reported here.
ePix100 is the first variant of a novel class of integrating pixel ASICs architectures optimized for the processing of signals in second generation LINAC Coherent Light Source (LCLS) X-Ray cameras. ePix100 is optimized for ultra-low noise application requiring high spatial resolution. ePix ASICs are based on a common platform composed of a random access analog matrix of pixel with global shutter, fast parallel column readout, and dedicated sigma-delta analog to digital converters per column. The ePix100 variant has 50μmx50μm pixels arranged in a 352x384 matrix, a resolution of 50e- r.m.s. and a signal range of 35fC (100 photons at 8keV). In its final version it will be able to sustain a frame rate of 1kHz. A first prototype has been fabricated and characterized and the measurement results are reported here.
We present a compact time-resolved spectrometer suitable for optical spectroscopy from 400 nm to 1 μm wavelengths.
The detector consists of a monolithic array of 16 high-precision Time-to-Digital Converters (TDC) and Single-Photon
Avalanche Diodes (SPAD). The instrument has 10 ps resolution and reaches 70 ps (FWHM) timing precision over a 160
ns full-scale range with a Differential Non-Linearity (DNL) better than 1.5 % LSB. The core of the spectrometer is the
application-specific integrated chip composed of 16 pixels with 250 μm pitch, containing a 20 μm diameter SPAD and
an independent TDC each, fabricated in a 0.35 μm CMOS technology. In front of this array a monochromator is used to
focus different wavelengths into different pixels. The spectrometer has been used for fluorescence lifetime spectroscopy:
5 nm spectral resolution over an 80 nm bandwidth is achieved. Lifetime spectroscopy of Nile blue is demonstrated.
KEYWORDS: Picosecond phenomena, Luminescence, Clocks, Field programmable gate arrays, Electronics, Power supplies, Fluorescence lifetime imaging, Time metrology, Interfaces, Data acquisition
We present a low-power Time-to-Digital Converter (TDC) chip, fabricated in a standard cost-effective 0.35 μm CMOS
technology, which provides 160 ns dynamic range, 10 ps timing resolution and Differential Non-Linearity better than
0.01 LSB rms. This chip is the core of a compact TDC module equipped with an USB 2.0 interface for user-friendly
control and data-acquisition. The TDC module is suitable for a wide variety of applications such as Fluorescence
Lifetime Imaging (FLIM), time-resolved spectroscopy, Diffuse Optical Spectroscopy (DOS), Optical Time-Domain
Reflectometry (OTDR), quantum optics, etc. In particular, we show the application of our TDC module to fluorescence
lifetime measurements.
We present a "smart-pixel" suitable for implementation of monolithic single-photon imaging arrays aimed at 3D ranging
applications by means of the direct time-of-flight detection (like LIDAR systems), but also for photon timing applications
(like FLIM, FCS, FRET). The pixel includes a Single-Photon Avalanche Diode (SPAD) and a Time-to-Digital Converter
(TDC) monolithically designed and manufactured in the same chip, and it is able to detect single photons and to measure
in-pixel the time delay between a START signal (e.g. laser excitation, LIDAR flash) and a photon detection (e.g. back
reflection from a target object). In order to provide both wide dynamic range, high time resolution and very high
linearity, we devised a TDC architecture based on an interpolation technique. A "coarse" counter counts the number of
reference-clock rising-edges between START and STOP, while high resolution is achieved by means of two
interpolators, which measure the time elapsed between START (and STOP) signal and a successive clock edge. In an
array with many pixels, multiple STOP channels are needed while just one START channel is necessary if the START
event is common to all channels. We report on the design and characterization of prototype circuits, fabricated in a 0.35 μm
standard CMOS technology containing complete conversion channels (i.e. 20-μm active-area diameter SPAD, quenching circuitry,
and TDC). 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.
We present a novel "smart-pixel" able to measure and record in-pixel the time delay (photon timing) between a START
(e.g. given by laser excitation, cell stimulus, or LIDAR flash) and a STOP (e.g. arrival of the first returning photon from
the fluorescence decay signal or back reflection from an object). Such smart-pixel relies of a SPAD detector and a Timeto-
Digital Converter monolithically designed and manufactured in the same chip. Many pixels can be laid out in a rows
by columns architecture, to give birth to expandable 2D imaging arrays for picoseconds-level single-photon timing
applications. Distance measurements, by means of direct TOF detection (used in LIDAR systems) provided by each
pixel, can open the way to the fabrication of single-chip 3D ranging arrays for scene reconstruction and intelligent object
recognition. We report on the design and characterization of prototype circuits, fabricated in a 0.35 μm standard CMOS
technology containing complete conversion channels, "smart-pixel" and ancillary electronics with 20 μm active area
diameter SPAD detector and related quenching circuitry. With a 100 MHz reference clock, the TDC provides timeresolution
of 10 ps, dynamic range of 160 ns and very high conversion linearity.
Scientific experiments often demand the detection of very weak light signals at high-speed or to precisely measure the
time of arrival of single photons. Arrays of Single-Photon Avalanche Diodes (SPAD) are ideal candidates when high
sensitivity is required together with high frame-rate or precise photon-timing resolution. We designed a linear 32x1
SPAD array using a high-voltage CMOS technology able to provide both good SPAD performance and fast electronics.
During frame acquisition all pixels work in parallel, each of them being equipped with anything necessary for photon
counting. The array architecture is capable of fully parallel operation of all pixels allowing free running acquisition at
high frame-rate. With a low-speed 10 MHz clock frequency, one pixel is read out in 100 ns while the whole array is
readout in 320 ns, corresponding to a frame-rate of 312.5 kframe/s. The frame-rate can top to 4 Mframe/s with a clock of
128 MHz. The photon timing modality employs the photon time-of-arrival information provided by each of the 32
outputs. All 32 "timing" outputs feed external Time-Correlated Photon Counting boards. The Full-Width at Half-
Maximum using very short laser pulses is 55 ps with few kcps counting rate.
We present a novel "smart-pixel" 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). This smart-pixel represents the
basic building block of SPAD arrays aimed at time-correlated single photon counting (TCSPC) applications (like FLIM,
FCS, FRET), but also at photon timing and direct Time-of-Flight (dTOF) measurements for 3D ranging applications
(e.g., in LIDAR systems). The pixel comprises a Single-Photon Avalanche Diode (SPAD) detector, an analog sensing
and driving electronics, and a Time-to-Digital Converter monolithically designed and manufactured into the same chip.
We report on the design and characterization of prototype circuits, fabricated in a 0.35 μm standard CMOS technology
containing complete conversion channels, smart-pixels and ancillary electronics with 20 μm active area diameter SPAD
detectors and related quenching circuitry. With a 100 MHz reference clock, the TDC provides a time-resolution of 10 ps,
a dynamic range of 160 ns and very high conversion linearity.
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