3,096 research outputs found
Conceptual design study for a teleoperator visual system, phase 2
An analysis of the concept for the hybrid stereo-monoscopic television visual system is reported. The visual concept is described along with the following subsystems: illumination, deployment/articulation, telecommunications, visual displays, and the controls and display station
Surface wave control for large arrays of microwave kinetic inductance detectors
Large ultra-sensitive detector arrays are needed for present and future
observatories for far infra-red, submillimeter wave (THz), and millimeter wave
astronomy. With increasing array size, it is increasingly important to control
stray radiation inside the detector chips themselves, the surface wave. We
demonstrate this effect with focal plane arrays of 880 lens-antenna coupled
Microwave Kinetic Inductance Detectors (MKIDs). Presented here are near field
measurements of the MKID optical response versus the position on the array of a
reimaged optical source. We demonstrate that the optical response of a detector
in these arrays saturates off-pixel at the dB level compared to the
peak pixel response. The result is that the power detected from a point source
at the pixel position is almost identical to the stray response integrated over
the chip area. With such a contribution, it would be impossible to measure
extended sources, while the point source sensitivity is degraded due to an
increase of the stray loading. However, we show that by incorporating an
on-chip stray light absorber, the surface wave contribution is reduced by a
factor 10. With the on-chip stray light absorber the point source response
is close to simulations down to the dB level, the simulation based on
an ideal Gaussian illumination of the optics. In addition, as a crosscheck we
show that the extended source response of a single pixel in the array with the
absorbing grid is in agreement with the integral of the point source
measurements.Comment: accepted for publication in IEEE Transactions on Terahertz Science
and Technolog
Development of CUiris: A Dark-Skinned African Iris Dataset for Enhancement of Image Analysis and Robust Personal Recognition
Iris recognition algorithms, especially with the
emergence of large-scale iris-based identification systems, must
be tested for speed and accuracy and evaluated with a wide
range of templates – large size, long-range, visible and different
origins. This paper presents the acquisition of eye-iris images
of dark-skinned subjects in Africa, a predominant case of verydark-
brown iris images, under near-infrared illumination. The
peculiarity of these iris images is highlighted from the
histogram and normal probability distribution of their
grayscale image entropy (GiE) values, in comparison to Asian
and Caucasian iris images. The acquisition of eye-images for
the African iris dataset is ongoing and will be made publiclyavailable
as soon as it is sufficiently populated
Mt. Graham: Optical turbulence vertical distribution at standard and high vertical resolution
A characterization of the optical turbulence vertical distribution and all
the main integrated astroclimatic parameters derived from the CN2 and the wind
speed profiles above Mt. Graham is presented. The statistic includes
measurements related to 43 nights done with a Generalized Scidar (GS) used in
standard configuration with a vertical resolution of ~1 km on the whole 20-22
km and with the new technique (HVR-GS) in the first kilometer. The latter
achieves a resolution of ~ 20-30 m in this region of the atmosphere.
Measurements done in different periods of the year permit us to provide a
seasonal variation analysis of the CN2. A discretized distribution of the
typical CN2 profiles useful for the Ground Layer Adaptive Optics (GLAO)
simulations is provided and a specific analysis for the LBT Laser Guide Star
system ARGOS case is done including the calculation of the 'gray zones' for J,
H and K bands. Mt. Graham confirms to be an excellent site with median values
of the seeing without dome contribution equal to 0.72", the isoplanatic angle
equal to 2.5" and the wavefront coherence time equal to 4.8 msec. We provide a
cumulative distribution of the percentage of turbulence developed below H*
where H* is included in the (0,1 km) range. We find that 50% of the whole
turbulence develops in the first 80 m from the ground. The turbulence
decreasing rate is very similar to what has been observed above Mauna Kea.Comment: 12 pages, 6 figures, Proc. SPIE Conference "Ground-based and Airborne
Telescopes III", 27 June 2010, San Diego, California, US
Optical turbulence vertical distribution with standard and high resolution at Mt. Graham
A characterization of the optical turbulence vertical distribution (Cn2
profiles) and all the main integrated astroclimatic parameters derived from the
Cn2 and the wind speed profiles above the site of the Large Binocular Telescope
(Mt. Graham, Arizona, US) is presented. The statistic includes measurements
related to 43 nights done with a Generalized Scidar (GS) used in standard
configuration with a vertical resolution Delta(H)~1 km on the whole 20 km and
with the new technique (HVR-GS) in the first kilometer. The latter achieves a
resolution Delta(H)~20-30 m in this region of the atmosphere. Measurements done
in different periods of the year permit us to provide a seasonal variation
analysis of the Cn2. A discretized distribution of Cn2 useful for the Ground
Layer Adaptive Optics (GLAO) simulations is provided and a specific analysis
for the LBT Laser Guide Star system ARGOS (running in GLAO configuration) case
is done including the calculation of the 'gray zones' for J, H and K bands. Mt.
Graham confirms to be an excellent site with median values of the seeing
without dome contribution epsilon = 0.72", the isoplanatic angle theta0 = 2.5"
and the wavefront coherence time tau0= 4.8 msec. We find that the optical
turbulence vertical distribution decreases in a much sharper way than what has
been believed so far in proximity of the ground above astronomical sites. We
find that 50% of the whole turbulence develops in the first 80+/-15 m from the
ground. We finally prove that the error in the normalization of the
scintillation that has been recently put in evidence in the principle of the GS
technique, affects these measurements with an absolutely negligible quantity
(0.04").Comment: 11 figures. MNRAS, accepte
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