236 research outputs found
Monocular multi-view stereo imaging system
In this study, we present a single-camera, multi-view stereo imaging system for capturing three-dimensional (3D) information. First, we design a monocular, multi-view stereo imaging device composed of a fisheye lens, and planar mirrors placed around the lens. The fisheye lens has a wide view-angle. The captured image includes a centered region of direct observation and surrounding regions of mirrored observations. These regions can be considered as images captured by multiple cameras at different positions and orientations. Therefore, the proposed device is equivalent to a synchronous multiple-cameras configuration, in which all the cameras share the same physical characteristics.
In addition, we show how to place the mirrors in order to maximize the common view-angles, which is an important design consideration. Then, after calibrating the projection function of the fisheye lens, we obtain the positions and orientations of the virtual cameras from the external parameters. We also develop two multi-baseline stereo algorithms for the 3D measurement system.
The first algorithm transforms the captured image to perspective images, and uses the traditional method to perform stereo determination. The second algorithm directly uses the original captured image along with an analysis of the epipolar geometry.
Experimental results show that our system is more effective than traditional stereo methods that use a stereo pair, and it can achieve robust 3D reconstruction
Coincidence analysis to search for inspiraling compact binaries using TAMA300 and LISM data
Japanese laser interferometric gravitational wave detectors, TAMA300 and
LISM, performed a coincident observation during 2001. We perform a coincidence
analysis to search for inspiraling compact binaries. The length of data used
for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors
are operated simultaneously. TAMA300 and LISM data are analyzed by matched
filtering, and candidates for gravitational wave events are obtained. If there
is a true gravitational wave signal, it should appear in both data of detectors
with consistent waveforms characterized by masses of stars, amplitude of the
signal, the coalescence time and so on. We introduce a set of coincidence
conditions of the parameters, and search for coincident events. This procedure
reduces the number of fake events considerably, by a factor
compared with the number of fake events in single detector analysis. We find
that the number of events after imposing the coincidence conditions is
consistent with the number of accidental coincidences produced purely by noise.
We thus find no evidence of gravitational wave signals. We obtain an upper
limit of 0.046 /hours (CL ) to the Galactic event rate within 1kpc from
the Earth. The method used in this paper can be applied straightforwardly to
the case of coincidence observations with more than two detectors with
arbitrary arm directions.Comment: 28 pages, 17 figures, Replaced with the version to be published in
Physical Review
KAGRA: 2.5 Generation Interferometric Gravitational Wave Detector
The recent detections of gravitational waves (GWs) reported by LIGO/Virgocollaborations have made significant impact on physics and astronomy. A globalnetwork of GW detectors will play a key role to solve the unknown nature of thesources in coordinated observations with astronomical telescopes and detectors.Here we introduce KAGRA (former name LCGT; Large-scale Cryogenic Gravitationalwave Telescope), a new GW detector with two 3-km baseline arms arranged in theshape of an "L", located inside the Mt. Ikenoyama, Kamioka, Gifu, Japan.KAGRA's design is similar to those of the second generations such as AdvancedLIGO/Virgo, but it will be operating at the cryogenic temperature with sapphiremirrors. This low temperature feature is advantageous for improving thesensitivity around 100 Hz and is considered as an important feature for thethird generation GW detector concept (e.g. Einstein Telescope of Europe orCosmic Explorer of USA). Hence, KAGRA is often called as a 2.5 generation GWdetector based on laser interferometry. The installation and commissioning ofKAGRA is underway and its cryogenic systems have been successfully tested inMay, 2018. KAGRA's first observation run is scheduled in late 2019, aiming tojoin the third observation run (O3) of the advanced LIGO/Virgo network. In thiswork, we describe a brief history of KAGRA and highlights of main feature. Wealso discuss the prospects of GW observation with KAGRA in the era of O3. Whenoperating along with the existing GW detectors, KAGRA will be helpful to locatea GW source more accurately and to determine the source parameters with higherprecision, providing information for follow-up observations of a GW triggercandidate
Vibration isolation system with a compact damping system for power recycling mirrors of KAGRA
A vibration isolation system called the Type-Bp system used for power recycling mirrors has been developed for KAGRA, the interferometric gravitational-wave observatory in Japan. A suspension of the Type-Bp system passively isolates an optic from seismic vibration using three main pendulum stages equipped with two vertical vibration isolation systems. A compact reaction mass around each of the main stages allows for achieving sufficient damping performance with a simple feedback as well as vibration isolation ratio. Three Type-Bp systems were installed in KAGRA, and were proved to satisfy the requirements on the damping performance, and also on estimated residual displacement of the optics
Stable Operation of a 300-m Laser Interferometer with Sufficient Sensitivity to Detect Gravitational-Wave Events within our Galaxy
TAMA300, an interferometric gravitational-wave detector with 300-m baseline
length, has been developed and operated with sufficient sensitivity to detect
gravitational-wave events within our galaxy and sufficient stability for
observations; the interferometer was operated for over 10 hours stably and
continuously. With a strain-equivalent noise level of , a signal-to-noise ratio (SNR) of 30 is expected for
gravitational waves generated by a coalescence of 1.4 -1.4
binary neutron stars at 10 kpc distance. %In addition, almost all noise sources
which limit the sensitivity and which %disturb the stable operation have been
identified. We evaluated the stability of the detector sensitivity with a
2-week data-taking run, collecting 160 hours of data to be analyzed in the
search for gravitational waves.Comment: 5 pages, 4 figure
Application of independent component analysis to the iKAGRA data
We apply independent component analysis (ICA) to real data from a gravitational wave detector for the first time. Specifically, we use the iKAGRA data taken in April 2016, and calculate the correlations between the gravitational wave strain channel and 35 physical environmental channels. Using a couple of seismic channels which are found to be strongly correlated with the strain, we perform ICA. Injecting a sinusoidal continuous signal in the strain channel, we find that ICA recovers correct parameters with enhanced signal-to-noise ratio, which demonstrates the usefulness of this method. Among the two implementations of ICA used here, we find the correlation method yields the optimal results for the case of environmental noise acting on the strain channel linearly
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