117,930 research outputs found
Assessment of stereoscopic optic disc images using an autostereoscopic screen - experimental study
No full textBACKGROUND: Stereoscopic assessment of the optic disc morphology is an important part of the care of patients with glaucoma. The aim of this study was to assess stereoviewing of stereoscopic optic disc images using an example of the new technology of autostereoscopic screens compared to the liquid shutter goggles.
METHODS: Independent assessment of glaucomatous disc characteristics and measurement of optic disc and cup parameters whilst using either an autostereoscopic screen or liquid crystal shutter goggles synchronized with a view switching display. The main outcome measures were inter-modality agreements between the two used modalities as evaluated by the weighted kappa test and Bland Altman plots. RESULTS: Inter-modality agreement for measuring optic disc parameters was good [Average kappa coefficient for vertical Cup/Disc ratio was 0.78 (95% CI 0.62-0.91) and 0.81 (95% CI 0.6-0.92) for observer 1 and 2 respectively]. Agreement between modalities for assessing optic disc characteristics for glaucoma on a five-point scale was very good with a kappa value of 0.97.
CONCLUSION: This study compared two different methods of stereo viewing. The results of assessment of the different optic disc and cup parameters were comparable using an example of the newly developing autostereoscopic display technologies as compared to the shutter goggles system used. The Inter-modality agreement was high. This new technology carries potential clinical usability benefits in different areas of ophthalmic practice
Design of back-illuminated voltage-domain global shutter pixels with dual in-pixel storage
No full textGlobal shutter pixels are indispensable for applications wherein the minimisation of
motion artefacts is of critical importance. However, these pixels are more complex
than the common rolling shutter type pixels and require some form of per-pixel storage.
They are almost invariably reliant upon metal light shielding in order to protect their
in-pixel memory nodes and this prevents them from taking advantage of some of the
latest developments in CMOS image sensor technology. Backside-illumination is the
most prominent example of such a technology. The greater sensitivity afforded by the
reduced optical stack height is indispensable for many applications, particularly in the
mobile market where form factor and power consumption are constrained. The design
challenge is to exploit these advantages offered by backside-illumination without making
use of metal shielding of the per-pixel memory.
The research in this thesis covers the design, implementation and characterisation of
a back-illuminated voltage-domain global shutter pixel. The pixel architecture is a
novel 10 transistor-per-pixel architecture with dual independent in-pixel storage nodes.
Beginning with the pixel architecture, the design is developed through TCAD-driven
photodiode and pixel layout co-optimisation. The behaviour of pixels with differential
parasitic light sensitivity (PLS) behaviour is analysed in greater detail than previously
reported and a prediction model is developed based upon this.
The 10T pixel is characterised and found to have excellent PLS of -73:5 dB native
and -82:5 dB differential PLS at 940 nm. The dual in-pixel storage enables the pixel to
operate either in a low noise correlated double sampling mode with differential PLS, or
in an exposure-bracketed high dynamic range imaging (HDR) mode. This HDR mode
is successfully demonstrated and yields substantial enhancement of the pixel dynamic
range
Shutter Fastener.
No full textPatent for a new and improved shutter fastener. This design "has for its object the production of a simple and efficient device, and one that can be conveniently operated from the inside of the blind, but not readily tampered with or opened from the outside without removing some of the slats of the blind. . . . one part—a bolt—is carried by the blind, and the other part—a catch—is secured to the windowsill and locks the bolt, so as to unfasten the blind both hands are required—one hand to operate the catch, the other hand to operate the bolt" (lines 16-30)
Rolling shutter detector data flow strategies to push the limits of AO performance
No full textAdaptive Optics (AO) improves the image quality of ground-based telescopes, by compensating in real-time for the blurring effects of atmospheric turbulence. AO systems of future Extremely Large Telescopes (ELTs) will have to operate at much bigger scales (in terms of degrees of freedom) and faster control rates (in terms of loop frequency) to realise their full potential. We have investigated and simulated an AO control methodology to stream pixels "as they come" using a rolling-shutter sCMOS camera to reconstruct 2D images. Compared to a traditional global shutter implementation, the initial results indicate the rolling shutter can reduce control loop latency by a factor of two to four, using existing hardware. This means we can detect twice the number of photons while sampling twice as slowly. Nevertheless, significant technical challenges remain in implementing the rolling functionality, especially when integrating off- The -shelf software and hardware, which is often constricted by a closed-source code base. Furthermore, as the rolling shutter readout is asynchronous, questions remain about coupling and aliasing of telescope vibrations into the imaging system, causing distortions of time and space. If successfully implemented in practice, the rolling shutter approach has the potential to allow astronomers and engineers to capture better scientific observations closer to the diffraction limit
Wide-angle monochromatic x-ray beam shutter : a design study.
No full textA novel design of a wide-angle monochromatic x-ray beam shutter is discussed. The shutter is designed as a compact unit capable of providing users with the means of shutting off the beam in secondary beamlines that are at an angle to the primary beamline and to each other. The single-unit design used the fact that all the secondary beamlines will be closed at the same time. The main challenge was to fit the shutter in the limited space of the existing Advanced Photon Source IMMW-CAT hutch. Space limitations led to the change in position of the actuator subassembly as compared to the standard shutter design. Although the actuator subassembly is placed underneath the shutter, fail-safe shutting is achieved by placing tungsten blocks above the beam while the shutter is open and using gravity to close the shutter in case of pneumatic failure. Redundancy required by safety concerns was achieved by duplicating the tungsten block/actuator subunits. Tungsten blocks of uneven length were used to counteract the increase in the center-to-center distance among secondary beamlines due to their angular offset. A special support table was designed to facilitate assembly and adjustability of the shutter position in the available space. To provide a radiation-tight hutch, a non-standard guillotine system was designed. In this paper, the design, specifications and optical ray tracing of the shutter assembly are presented
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
High-speed, low-cost laser-triggered plasma shutter
No full textDesign and construction of a CO2 laser-triggered plasma shutter is described. An inexpensive pyroelectric detector and a novel needle-resistor spark gap, requiring an applied voltage of less than 500 V, are employed. The total electronic delay can be made to be less than 15 ns with subnanosecond jitter. This plasma shutter finds applications in producing picosecond CO 2 laser pulses and in optical isolation.</p
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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Development of a plasma retropulse shutter for Shiva and Nova
No full textA plasma shutter is being developed for a Nd:glass laser fusion system which, at an output spatial filter pinhole, produces a plasma of 10/sup 21/ cm/sup -3/ to block target-reflected light from reentering the laser. A pulser using low-inductance capacitors and elastomer dielectric is switched with uv preilluminated railgaps to resistively heat a wire producing a plasma. The plasma generated within a nozzle and configured in a railgun geometry is projected across the optical beam path at 3.9 cm/..mu..s. The optics are protected from the plasma. A scaled experiment is characterized, and a prototype shutter module is described
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