3,164 research outputs found
The ESPRI project: astrometric exoplanet search with PRIMA I. Instrument description and performance of first light observations
The ESPRI project relies on the astrometric capabilities offered by the PRIMA
facility of the Very Large Telescope Interferometer for the discovery and study
of planetary systems. Our survey consists of obtaining high-precision
astrometry for a large sample of stars over several years and to detect their
barycentric motions due to orbiting planets. We present the operation
principle, the instrument's implementation, and the results of a first series
of test observations. A comprehensive overview of the instrument infrastructure
is given and the observation strategy for dual-field relative astrometry is
presented. The differential delay lines, a key component of the PRIMA facility
which was delivered by the ESPRI consortium, are described and their
performance within the facility is discussed. Observations of bright visual
binaries are used to test the observation procedures and to establish the
instrument's astrometric precision and accuracy. The data reduction strategy
for astrometry and the necessary corrections to the raw data are presented.
Adaptive optics observations with NACO are used as an independent verification
of PRIMA astrometric observations. The PRIMA facility was used to carry out
tests of astrometric observations. The astrometric performance in terms of
precision is limited by the atmospheric turbulence at a level close to the
theoretical expectations and a precision of 30 micro-arcseconds was achieved.
In contrast, the astrometric accuracy is insufficient for the goals of the
ESPRI project and is currently limited by systematic errors that originate in
the part of the interferometer beamtrain which is not monitored by the internal
metrology system. Our observations led to the definition of corrective actions
required to make the facility ready for carrying out the ESPRI search for
extrasolar planets.Comment: 32 pages, 39 figures, Accepted for publication in Astronomy and
Astrophysic
The Palomar Testbed Interferometer
The Palomar Testbed Interferometer (PTI) is a long-baseline infrared
interferometer located at Palomar Observatory, California. It was built as a
testbed for interferometric techniques applicable to the Keck Interferometer.
First fringes were obtained in July 1995. PTI implements a dual-star
architecture, tracking two stars simultaneously for phase referencing and
narrow-angle astrometry. The three fixed 40-cm apertures can be combined
pair-wise to provide baselines to 110 m. The interferometer actively tracks the
white-light fringe using an array detector at 2.2 um and active delay lines
with a range of +/- 38 m. Laser metrology of the delay lines allows for servo
control, and laser metrology of the complete optical path enables narrow-angle
astrometric measurements. The instrument is highly automated, using a
multiprocessing computer system for instrument control and sequencing.Comment: ApJ in Press (Jan 99) Fig 1 available from
http://huey.jpl.nasa.gov/~bode/ptiPicture.html, revised duging copy edi
Harmonically-related diffraction gratings-based interferometer for quadrature phase measurements
We demonstrate the use of shallow diffraction gratings for quadrature phase interferometry. A single shallow diffraction grating-based Michelson interferometer yields only trivial (0° or 180°) phase shift between different output ports. In comparison, a combination of two parallel shallow diffraction gratings can be useful to achieve desired phase shifts (e.g., 90° for quadrature phase interferometry). We show that the phase at different output ports of a grating-pair based interferometer can be adjusted by shearing the two gratings with respect to each other. Two harmonically-related diffraction gratings are used to demonstrate phase shift control at the output ports of a modified Michelson interferometer. Our experimental data is in good agreement with theory
Implementation of in Process Surface Metrology for R2R Flexible PV Barrier Films
Thin functional barrier layers of aluminum oxide (Al2O3) that are used particularly in photovoltaic (PV) modules to prevent the possibility of water vapor ingress should be applied over the entire PV surface without any defects. However, for barrier layer thicknesses
within the sub-micrometer range (up to 50 nm)
produced through the atomic layer deposition (ALD) method, it is common for defects to occur during the production process. To avoid defective barriers from being incorporated in the final PV unit, defects need to be detected during the barrier production process.
In this paper, the implementation of in process inspection system capable of detecting surface defects such as pinholes, scratches, or particles down to a lateral size of 3 ÎŒm and a vertical resolution of 10 nm over a 500 mm barrier width is presented. The system has a built-in environmental vibration compensation capability, and can monitor ALD-coated films manufactured using roll-to-roll (R2R) techniques. Ultimately, with the aid of this in process measurement system, it should be possible to monitor the coating surface process of large-area substrates, and if necessary, carry out remedial work on the process parameters
The Fringe Detection Laser Metrology for the GRAVITY Interferometer at the VLTI
Interferometric measurements of optical path length differences of stars over
large baselines can deliver extremely accurate astrometric data. The
interferometer GRAVITY will simultaneously measure two objects in the field of
view of the Very Large Telescope Interferometer (VLTI) of the European Southern
Observatory (ESO) and determine their angular separation to a precision of 10
micro arcseconds in only 5 minutes. To perform the astrometric measurement with
such a high accuracy, the differential path length through the VLTI and the
instrument has to be measured (and tracked since Earth's rotation will
permanently change it) by a laser metrology to an even higher level of accuracy
(corresponding to 1 nm in 3 minutes). Usually, heterodyne differential path
techniques are used for nanometer precision measurements, but with these
methods it is difficult to track the full beam size and to follow the light
path up to the primary mirror of the telescope. Here, we present the
preliminary design of a differential path metrology system, developed within
the GRAVITY project. It measures the instrumental differential path over the
full pupil size and up to the entrance pupil location. The differential phase
is measured by detecting the laser fringe pattern both on the telescopes'
secondary mirrors as well as after reflection at the primary mirror. Based on
our proposed design we evaluate the phase measurement accuracy based on a full
budget of possible statistical and systematic errors. We show that this
metrology design fulfills the high precision requirement of GRAVITY.Comment: Proc. SPIE in pres
Metrology with Atom Interferometry: Inertial Sensors from Laboratory to Field Applications
Developments in atom interferometry have led to atomic inertial sensors with
extremely high sensitivity. Their performances are for the moment limited by
the ground vibrations, the impact of which is exacerbated by the sequential
operation, resulting in aliasing and dead time. We discuss several experiments
performed at LNE-SYRTE in order to reduce these problems and achieve the
intrinsic limit of atomic inertial sensors. These techniques have resulted in
transportable and high-performance instruments that participate in gravity
measurements, and pave the way to applications in inertial navigation.Comment: 7 pages, 5 figure
Quantum Technology: The Second Quantum Revolution
We are currently in the midst of a second quantum revolution. The first
quantum revolution gave us new rules that govern physical reality. The second
quantum revolution will take these rules and use them to develop new
technologies. In this review we discuss the principles upon which quantum
technology is based and the tools required to develop it. We discuss a number
of examples of research programs that could deliver quantum technologies in
coming decades including; quantum information technology, quantum
electromechanical systems, coherent quantum electronics, quantum optics and
coherent matter technology.Comment: 24 pages and 6 figure
In-Situ Surface Inspection Using White Light Channelled Spectrum Interferometer
We introduce a new environmentally robust optical interferometry system
for fast surface profile measurement. The proposed white light channelled spectrum
Interferometer (WLCSI) is effective for applications in on-line surface inspection
because it can obtain a surface profile in a single shot. Compared to the traditional
spectral interferometry techniques, cylindrical lens is used in the Michelson
interferometric objective of our system to achieve the measurement of long profiles.
Combined with a modern high speed CCD camera, general-purpose graphics
processing unit (GPGPU) and multi-core processors computing technology, large
dynamic measurement with a high signal-to-noise ratio is realized. The designed
prototype of WLCSI is presented and its performance was evaluated experimentally
by measuring two surface samples. The measuring results closely align with the
calibrated specifications given by the manufacturer as well as the measurement results
by the other commercial instrument, which shows that the proposed WLCSI could be
applied to production line like the roll-to-toll (R2R) surface inspection where only
defects on the film surface are concerned in terms of the quality contro
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