29,308 research outputs found
Investigating reciprocity failure in 1.7-micron cut-off HgCdTe detectors
Flux dependent non-linearity (reciprocity failure) in HgCdTe NIR detectors
with 1.7 micron cut-off was investigated. A dedicated test station was designed
and built to measure reciprocity failure over the full dynamic range of near
infrared detectors. For flux levels between 1 and 100,000 photons/sec a
limiting sensitivity to reciprocity failure of 0.3%/decade was achieved. First
measurements on several engineering grade 1.7 micron cut-off HgCdTe detectors
show a wide range of reciprocity failure, from less than 0.5%/decade to about
10%/decade. For at least two of the tested detectors, significant spatial
variation in the effect was observed. No indication for wavelength dependency
was found. The origin of reciprocity failure is currently not well understood.
In this paper we present details of our experimental set-up and show the
results of measurements for several detectors.Comment: 11 pages, 10 figures, to appear in " Astronomical Telescopes and
Instrumentation: High Energy, Optical, and Infrared Detectors for Astronomy
IV", Proceedings of SPIE Vol. 774
On evolution of CMOS image sensors
CMOS Image Sensors have become the principal technology in majority of digital cameras. They started replacing the film and Charge Coupled Devices in the last decade with the promise of lower cost, lower power requirement, higher integration and the potential of focal plane processing. However, the principal factor behind their success has been the ability to utilise the shrinkage in CMOS technology to make smaller pixels, and thereby have more resolution without increasing the cost. With the market of image sensors exploding courtesy their inte- gration with communication and computation devices, technology developers improved the CMOS processes to have better optical performance. Nevertheless, the promises of focal plane processing as well as on-chip integration have not been fulfilled. The market is still being pushed by the desire of having higher number of pixels and better image quality, however, differentiation is being difficult for any image sensor manufacturer. In the paper, we will explore potential disruptive growth directions for CMOS Image sensors and ways to achieve the same
Optimizing floating guard ring designs for FASPAX N-in-P silicon sensors
FASPAX (Fermi-Argonne Semiconducting Pixel Array X-ray detector) is being
developed as a fast integrating area detector with wide dynamic range for time
resolved applications at the upgraded Advanced Photon Source (APS.) A burst
mode detector with intended \mbox{13 MHz} image rate, FASPAX will also
incorporate a novel integration circuit to achieve wide dynamic range, from
single photon sensitivity to x-rays/pixel/pulse. To achieve
these ambitious goals, a novel silicon sensor design is required. This paper
will detail early design of the FASPAX sensor. Results from TCAD optimization
studies, and characterization of prototype sensors will be presented.Comment: IEEE NSS-MIC 2015 Conference recor
Photosensor Characterization for the Cherenkov Telescope Array: Silicon Photomultiplier versus Multi-Anode Photomultiplier Tube
Photomultiplier tube technology has been the photodetector of choice for the
technique of imaging atmospheric Cherenkov telescopes since its birth more than
50 years ago. Recently, new types of photosensors are being contemplated for
the next generation Cherenkov Telescope Array. It is envisioned that the array
will be partly composed of telescopes using a Schwarzschild-Couder two mirror
design never built before which has significantly improved optics. The camera
of this novel optical design has a small plate scale which enables the use of
compact photosensors. We present an extensive and detailed study of the two
most promising devices being considered for this telescope design: the silicon
photomultiplier and the multi-anode photomultiplier tube. We evaluated their
most critical performance characteristics for imaging gamma-ray showers, and we
present our results in a cohesive manner to clearly evaluate the advantages and
disadvantages that both types of device have to offer in the context of GeV-TeV
gamma-ray astronomy.Comment: submitted to SPIE Optics+Photonics proceeding
High dynamic range perception with spatially variant exposure
In this paper we present a method capable of perceiving high dynamic range scene. The special feature of the method is that it changes the integration time of the imager on the pixel level. Using CNN-UM we can calculate the integration time for the pixels, and hence low dynamic range integration type CMOS sensors will be able to perceive high dynamic range scenes. The method yields high contrast without introducing non-existing edges
Neuronal imaging with ultrahigh dynamic range multiphoton microscopy
Multiphoton microscopes are hampered by limited dynamic range, preventing weak sample features from being detected in the presence of strong features, or preventing the capture of unpredictable bursts in sample strength. We present a digital electronic add-on technique that vastly improves the dynamic range of a multiphoton microscope while limiting potential photodamage. The add-on provides real-time negative feedback to regulate the laser power delivered to the sample, and a log representation of the sample strength to accommodate ultrahigh dynamic range without loss of information. No microscope hardware modifications are required, making the technique readily compatible with commercial instruments. Benefits are shown in both structural and in-vivo functional mouse brain imaging applications.R21 EY027549 - NEI NIH HH
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A 25 micron-thin microscope for imaging upconverting nanoparticles with NIR-I and NIR-II illumination.
Rationale: Intraoperative visualization in small surgical cavities and hard-to-access areas are essential requirements for modern, minimally invasive surgeries and demand significant miniaturization. However, current optical imagers require multiple hard-to-miniaturize components including lenses, filters and optical fibers. These components restrict both the form-factor and maneuverability of these imagers, and imagers largely remain stand-alone devices with centimeter-scale dimensions. Methods: We have engineered INSITE (Immunotargeted Nanoparticle Single-Chip Imaging Technology), which integrates the unique optical properties of lanthanide-based alloyed upconverting nanoparticles (aUCNPs) with the time-resolved imaging of a 25-micron thin CMOS-based (complementary metal oxide semiconductor) imager. We have synthesized core/shell aUCNPs of different compositions and imaged their visible emission with INSITE under either NIR-I and NIR-II photoexcitation. We characterized aUCNP imaging with INSITE across both varying aUCNP composition and 980 nm and 1550 nm excitation wavelengths. To demonstrate clinical experimental validity, we also conducted an intratumoral injection into LNCaP prostate tumors in a male nude mouse that was subsequently excised and imaged with INSITE. Results: Under the low illumination fluences compatible with live animal imaging, we measure aUCNP radiative lifetimes of 600 ÎŒs - 1.3 ms, which provides strong signal for time-resolved INSITE imaging. Core/shell NaEr0.6Yb0.4F4 aUCNPs show the highest INSITE signal when illuminated at either 980 nm or 1550 nm, with signal from NIR-I excitation about an order of magnitude brighter than from NIR-II excitation. The 55 ÎŒm spatial resolution achievable with this approach is demonstrated through imaging of aUCNPs in PDMS (polydimethylsiloxane) micro-wells, showing resolution of micrometer-scale targets with single-pixel precision. INSITE imaging of intratumoral NaEr0.8Yb0.2F4 aUCNPs shows a signal-to-background ratio of 9, limited only by photodiode dark current and electronic noise. Conclusion: This work demonstrates INSITE imaging of aUCNPs in tumors, achieving an imaging platform that is thinned to just a 25 ÎŒm-thin, planar form-factor, with both NIR-I and NIR-II excitation. Based on a highly paralleled array structure INSITE is scalable, enabling direct coupling with a wide array of surgical and robotic tools for seamless integration with tissue actuation, resection or ablation
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