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Invited Review Article: Review of centrifugal microfluidic and bio-optical disks

Nolte, David D.
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Artigo de Revista Científica
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Spinning biodisks have advantages that make them attractive for specialized biochip applications. The two main classes of spinning biodisks are microfluidic disks and bio-optical compact disks (BioCD). Microfluidic biodisks take advantage of noninertial pumping for lab-on-a-chip devices using noninertial valves and switches under centrifugal and Coriolis forces to distribute fluids about the disks. BioCDs use spinning-disk interferometry, under the condition of common-path phase quadrature, to perform interferometric label-free detection of molecular recognition and binding. The optical detection of bound molecules on a disk is facilitated by rapid spinning that enables high-speed repetitive sampling to eliminate 1∕f noise through common-mode rejection of intensity fluctuations and extensive signal averaging. Multiple quadrature classes have been developed, such as microdiffraction, in-line, phase contrast, and holographic adaptive optics. Thin molecular films are detected through the surface dipole density with a surface height sensitivity for the detection of protein spots that is approximately 1 pm. This sensitivity easily resolves a submonolayer of solid-support immobilized antibodies and their antigen targets. Fluorescence and light scattering provide additional optical detection techniques on spinning disks. Immunoassays have been applied to haptoglobin using protein A∕G immobilization of antibodies and to prostate specific antigen. Small protein spots enable scalability to many spots per disk for high-throughput and highly multiplexed immonoassays.

Interferometric Dynamic Measurement: Techniques Based on High-Speed Imaging or a Single Photodetector

Fu, Yu; Pedrini, Giancarlo; Li, Xide
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
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In recent years, optical interferometry-based techniques have been widely used to perform noncontact measurement of dynamic deformation in different industrial areas. In these applications, various physical quantities need to be measured in any instant and the Nyquist sampling theorem has to be satisfied along the time axis on each measurement point. Two types of techniques were developed for such measurements: one is based on high-speed cameras and the other uses a single photodetector. The limitation of the measurement range along the time axis in camera-based technology is mainly due to the low capturing rate, while the photodetector-based technology can only do the measurement on a single point. In this paper, several aspects of these two technologies are discussed. For the camera-based interferometry, the discussion includes the introduction of the carrier, the processing of the recorded images, the phase extraction algorithms in various domains, and how to increase the temporal measurement range by using multiwavelength techniques. For the detector-based interferometry, the discussion mainly focuses on the single-point and multipoint laser Doppler vibrometers and their applications for measurement under extreme conditions. The results show the effort done by researchers for the improvement of the measurement capabilities using interferometry-based techniques to cover the requirements needed for the industrial applications.

Synthetic Aperture Radar Interferometry with 3 satellites; InSAR with 3 satellites

Wong, Wallace D. (Wallace Dazheng)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 128 p.; 6805700 bytes; 6811039 bytes; application/pdf; application/pdf
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Our study investigates interferometric SAR (InSAR) post-processing height retrieval techniques. We explore the possible improvements by adding a third satellite to the two already in orbit, and examine some potential uses of this setup. As such, we investigate three methods for height retrieval and compare their results with the original 2-satellite method. The first approach is data averaging; a simple method that extends from the results obtained using the 2-satellite method. The 3 sets of data obtained per sampling look are grouped into pairs, and the 2 statistical best pairs are selected to be averaged, producing a better estimate of the digital elevation map (DEM) height. The second approach is the unambiguous range magnification (URM) method, which seeks to ease the reliance on phase unwrapping steps often necessary in retrieving height. It does so by expanding the wrapped phase range without performing any phase unwrapping, through the use of different wrapping speeds of the 3 sets of satellite pairings. The third method is the maximum likelihood estimation technique, an asymptotically efficient method which employs the same phase expansion property as the URM to predict the closest phase estimate which best fits most (if not all) of the data sets provided.; (cont.) Results show that for a handful of flyover looks...

Phase diversity for segmented and multi-aperture systems

Bolcar, Matthew R. (1979 - ); Fienup, James R.
Fonte: University of Rochester. Publicador: University of Rochester.
Tipo: Tese de Doutorado Formato: Number of Pages:xxx, 180 leaves
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Thesis (Ph. D.)--University of Rochester. Institute of Optics, 2009.; As telescopes become larger, segmented and multi-aperture designs are being implemented to meet cost, size and weight constraints. These systems require alignment of the segments or sub-apertures to within fractions of a wavelength. We investigate the performance of phase diversity, a technique of image-based wavefront sensing, for characterizing and aligning segmented and multi-aperture systems. Supporting work developing the core phase-diversity algorithm is also presented. The modification of phase diversity to incorporate a broadband object model is discussed. Through digital simulation, we show a benefit to using a broadband, gray-world algorithm, as opposed to the conventional monochromatic algorithm, when bandwidths greater than 20% are used for imaging. We further demonstrate that knowledge of the gray-world object spectrum is not required to achieve improved performance. Using digital simulation, three regularization techniques for phase-diversity metrics are compared to the conventional phase-diversity algorithm. For low signal-to-noise ratio (SNR), we demonstrate an improvement in both the phase estimation accuracy and convergence properties of the algorithm when a regularization based on the object and noise power spectra is used. We present a novel implementation of phase diversity unique to segmented and multi-aperture systems that utilizes individual sub-aperture piston phases in the pupil. Through digital simulation...

Robust image-based wavefront sensing

Zielinski, Thomas P. (1982 - ); Fienup, James R.
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xxii, 171 leaves; Illustrations:ill. (some col.)
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Thesis (Ph. D.)--University of Rochester. Institute of Optics, 2011.; Several planned future optical systems, such as the James Webb Space Telescope (JWST), rely on image-based wavefront sensing for alignment, testing, and control of optical surfaces during operation. The focus of this work is on characterizing the effects of various non-idealities on the performance of image-based wavefront sensing algorithms, developing techniques to mitigate those effects, and demonstrating these techniques in computer simulations and in the lab. Two new techniques for algorithmically determining the proper sampling factor for optical propagation are presented and tested against experimental data collected in the lab and during JWST ground-based testing. A new method for mitigating against the effects of vibration on phase retrieval is discussed, implemented, and tested in simulation. The use of an alternative type of diversity, called transverse translation, is explored for use in the JWST and shown to be a promising technique through simulation. A method for extending the capture range of phase retrieval algorithms is presented and tested both in simulation and with experimental data collected in the lab. A benchmark of a phase retrieval algorithm running on a graphics card is presented and the practical implications for JWST testing are discussed. Finally...

Design of a phase sampled interferometry antenna using the robust symmetrical number system

York, Nathan S.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
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This research has examined the benefits of using the Robust Symmetrical Number System (RSNS) to resolve ambiguities in phase sampling interferometry. A compact, high resolution direction finding antenna architecture based on the RSNS was developed to demonstrate experimentally the elimination of phase errors using a minimum amount of hardware. Previous work has determined that phase errors in the system will degrade the system performance. Several improvements were made to the original RSNS prototype antenna to provide enhanced performance. Adding isolators and supplementing the ground plane with copper tape (between the antenna elements), a reduction in the mutual coupling effects was accomplished. Mounting the microwave components on a brass plate also reduced errors contributed by vibrations and temperature. Tailor cutting all semi-rigid coaxial lines also helped reduce the number of connectors required to assemble the microwave circuit, also a source of phase errors. Matching the front-end amplifiers in each amplification stage rather than matching the characteristics of two cascaded amplifiers in each signal line has reduced relative phase errors between channels as well as matching the power outputs of the amplifiers. Two printed circuit boards were designed and built for the RSNS signal processor. The printed circuit boards provide a decrease in the electrical noise floor over the original design (assembled on breadboards). The new design has reduced the phase errors that were present in the first prototype system. The RSNS signal processing technique is able to provide a high-resolution phase sampled direction finding capability with an angular resolution of 1.9 degrees by using only three receiving elements (two interferometers)

Application of the robust symmetrical number system to high resolution direction finding interferometry

Wickersham, David J.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
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To reduce the number of phase sampling comparators in a direction finding (DF) interferometer antenna, a new array based on a robust symmetrical number system (RSNS) is described. The RSNS is used to decompose the spatial filtering operation into a number of parallel sub-operations that are of smaller computational complexity. Each sub-operation (interferometer) symmetrically folds the phase with folding period equal to 2Nm(i) where N is the number of channels that are used and n(i) the channel modulus. A small comparator ladder mid-level quantizes each folded phase response. Each sub-operation only requires a precision in accordance with that modulus. A much higher DF resolution is achieved after the N different RSNS moduli are used and the results of these low precision sub-operations are recombined. The parallel use of phase waveforms increases the antenna resolution without increasing the folding rate of the system. The new antenna is constructed and tested in an anechoic chamber, and the results are compared with the experimental results of a previously tested optimum symmetrical number system (OSNS) array. Although the dynamic range of the RSNS is somewhat less than the OSNS, the inherent Gray code properties make it attractive for error control in phase sampling interferometry.

Mixed signal processor for a robust symmetrical number system direction finding antenna

Babb, Charles F.
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Formato: xvi, 100 p. : ill. (some col.) ; 28 cm.
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Approved for public release; distribution is unlimited.; Approved for public release; distribution is unlimited.; This applied research project has designed, simulated, constructed and tested the performance of a processing system for a prototype direction finding antenna. A mixed signal architecture to derive the direction of arrival from a Robust Symmetrical Number System (RSNS) encoded direction finding array is based on a new phase sampling interferometer approach that can be easily incorporated into established techniques to provide a high resolution, small-baseline array with few number of phase sampling comparators. The approach is based on preprocessing the received signal using the RSNS. The preprocessing is used to decompose the spatial filtering operation into a number of parallel suboperations (moduli) that are of smaller computational complexity. A much higher direction finding spatial resolution is achieved after the N different moduli are used and the results of the low precision suboperations are recombined, in addition to the reduction of the number of possible encoding errors due to the RSNS' inherent Gray-coding properties. This has resulted in a four inch antenna array being able to attain an angular resolution of less than 1.8 degrees with a continuous field of view of 120 degrees. The accompanying electronics occupy two 6 inch by 8 inch printed circuit boards...

The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations

Dexter, Jason; Agol, Eric; Fragile, P. Chris; McKinney, Jonathan C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/05/2010 Português
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Recent high resolution observations of the Galactic center black hole allow for direct comparison with accretion disk simulations. We compare two-temperature synchrotron emission models from three dimensional, general relativistic magnetohydrodynamic simulations to millimeter observations of Sgr A*. Fits to very long baseline interferometry and spectral index measurements disfavor the monochromatic face-on black hole shadow models from our previous work. Inclination angles \le 20 degrees are ruled out to 3 \sigma. We estimate the inclination and position angles of the black hole, as well as the electron temperature of the accretion flow and the accretion rate, to be i=50+35-15 degrees, \xi=-23+97-22 degrees, T_e=(5.4 +/- 3.0)x10^10 K and Mdot=(5+15-2)x10^-9 M_sun / yr respectively, with 90% confidence. The black hole shadow is unobscured in all best fit models, and may be detected by observations on baselines between Chile and California, Arizona or Mexico at 1.3mm or .87mm either through direct sampling of the visibility amplitude or using closure phase information. Millimeter flaring behavior consistent with the observations is present in all viable models, and is caused by magnetic turbulence in the inner radii of the accretion flow. The variability at optically thin frequencies is strongly correlated with that in the accretion rate. The simulations provide a universal picture of the 1.3mm emission region as a small region near the midplane in the inner radii of the accretion flow...

Near and mid-IR sub-arcsecond structure of the dusty symbiotic star R Aqr

Tuthill, P. G.; Danchi, W. C.; Hale, D. S.; Monnier, J. D.; Townes, C. H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/03/2000 Português
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The results of a high-resolution interferometric campaign targeting the symbiotic long-period variable (LPV) R~Aqr are reported. With both near-infrared measurements on baselines out to 10m and mid-infrared data extending to 32m, we have been able to measure the characteristic sizes of regions from the photosphere of the LPV and its extended molecular atmosphere, out to the cooler circumstellar dust shell. The near-infrared data were taken using aperture masking interferometry on the Keck-I telescope and show R~Aqr to be partially resolved for wavelengths out to 2.2 microns but with a marked enlargement, possibly due to molecular opacity, at 3.1 microns. Mid-infrared interferometric measurements were obtained with the U.C. Berkeley Infrared Spatial Interferometer (ISI) operating at 11.15 microns from 1992 to 1999. Although this dataset is somewhat heterogeneous with incomplete coverage of the Fourier plane and sampling of the pulsation cycle, clear changes in the mid-infrared brightness distribution were observed, both as a function of position angle on the sky and as a function of pulsation phase. Spherically symmetric radiative transfer calculations of uniform-outflow dust shell models produce brightness distributions and spectra which partially explain the data...

Quantum dynamics in ultra-cold atomic physics

He, Q. Y.; Reid, M. D.; Opanchuk, B.; Polkinghorne, R.; Rosales-Zárate, Laura E. C.; Drummond, P. D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/12/2011 Português
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We review recent developments in the theory of quantum dynamics in ultra-cold atomic physics, including exact techniques, but focusing on methods based on phase-space mappings that are appli- cable when the complexity becomes exponentially large. These phase-space representations include the truncated Wigner, positive-P and general Gaussian operator representations which can treat both bosons and fermions. These phase-space methods include both traditional approaches using a phase-space of classical dimension, and more recent methods that use a non-classical phase-space of increased dimensionality. Examples used include quantum EPR entanglement of a four-mode BEC, time-reversal tests of dephasing in single-mode traps, BEC quantum collisions with up to 106 modes and 105 interacting particles, quantum interferometry in a multi-mode trap with nonlinear absorp- tion, and the theory of quantum entropy in phase-space. We also treat the approach of variational optimization of the sampling error, giving an elementary example of a nonlinear oscillator.

Detection noise bias and variance in the power spectrum and bispectrum in optical interferometry

Gordon, J. A.; Buscher, D. F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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Long-baseline optical interferometry uses the power spectrum and bispectrum constructs as fundamental observables. Noise arising in the detection of the fringe pattern gives rise to both variance and biases in the power spectrum and bispectrum. Previous work on correcting the biases and estimating the variances for these quantities typically includes restrictive assumptions about the sampling of the interferogram and/or about the relative importance of Poisson and Gaussian noise sources. Until now it has been difficult to accurately compensate for systematic biases in data which violates these assumptions. We seek a formalism to allow the construction of bias-free estimators of the bispectrum and power spectrum, and to estimate their variances, under less restrictive conditions which include both unevenly-sampled data and measurements affected by a combination of noise sources with Poisson and Gaussian statistics. We used a method based on the moments of the noise distributions to derive formulae for the biases introduced to the power spectrum and bispectrum when the complex fringe amplitude is derived from an arbitrary linear combinations of a set of discrete interferogram measurements. We simulated interferograms with different combinations of photon noise and read noise and with different fringe encoding schemes to illustrate the effects of these biases. We have derived formulae for bias-free estimators of the power spectrum and bispectrum which can be used with any linear estimator of the fringe complex amplitude. We have demonstrated the importance of bias-free estimators for the case of the detection of faint companions (for example exoplanets) using closure phase nulling. We have derived formulae for the variance of the power spectrum and have shown how the variance of the bispectrum could be calculated.; Comment: 9 pages...

An image-plane algorithm for JWST's non-redundant aperture mask data

Greenbaum, Alexandra Z.; Pueyo, Laurent; Sivaramakrishnan, Anand; Lacour, Sylvestre
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/11/2014 Português
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The high angular resolution technique of non-redundant masking (NRM) or aperture masking interferometry (AMI) has yielded images of faint protoplanetary companions of nearby stars from the ground. AMI on James Webb Space Telescope (JWST)'s Near Infrared Imager and Slitless Spectrograph (NIRISS) has a lower thermal background than ground-based facilites and does not suffer from atmospheric instability. NIRISS AMI images are likely to have 90 - 95% Strehl ratio between 2.77 and 4.8 micron. In this paper we quantify factors that limit the raw point source contrast of JWST NRM. We develop an analytic model of the NRM point spread function which includes different optical path delays (pistons) between mask holes and fit the model parameters with image plane data. It enables a straightforward way to exclude bad pixels, is suited to limited fields of view, and can incorporate effects such as intra-pixel sensitivity variations. We simulate various sources of noise to estimate their effect on the standard deviation of closure phase, sigma_CP (a proxy for binary point source contrast). If sigma_CP < 10^-4 radians --- a contrast ratio of 10 magnitudes --- young accreting gas giant planets (e.g. in the nearby Taurus star-forming region) could be imaged with JWST NIRISS. We show the feasibility of using NIRISS' NRM with the sub-Nyquist sampled F277W...

The radio remnant of SN1993J: an instrumental explanation for the evolving complex structure

Heywood, Ian; Blundell, Katherine M.; Kloeckner, Hans-Rainer; Beasley, Anthony J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/10/2008 Português
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We present simulated images of Supernova 1993J at 8.4 GHz using Very Long Baseline Interferometry (VLBI) techniques. A spherically symmetric source model is convolved with realistic uv-plane distributions, together with standard imaging procedures, to assess the extent of instrumental effects on the recovered brightness distribution. In order to facilitate direct comparisons between the simulations and published VLBI images of SN1993J, the observed uv-coverage is determined from actual VLBI observations made in the years following its discovery. The underlying source model only exhibits radial variation in its density profile, with no azimuthal dependence and, even though this model is morphologically simple, the simulated VLBI observations qualitatively reproduce many of the azimuthal features of the reported VLBI observations, such as appearance and evolution of complex azimuthal structure and apparent rotation of the shell. We demonstrate that such features are inexorably coupled to the uv-plane sampling. The brightness contrast between the peaks and the surrounding shell material are not as prominent in the simulations (which of course assume no antenna- or baseline-based amplitude or phase errors, meaning no self-calibration procedures will have incorporated any such features in models). It is conclusive that incomplete uv-plane sampling has a drastic effect on the final images for observations of this nature. Difference imaging reveals residual emission up to the 8 sigma level. Extreme care should be taken when using interferometric observations to directly infer the structure of objects such as supernovae.; Comment: 14 pages...

Image Deblurring Using Derivative Compressed Sensing for Optical Imaging Application

Rostami, Mohammad; Michailovich, Oleg; Wang, Zhou
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/07/2011 Português
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Reconstruction of multidimensional signals from the samples of their partial derivatives is known to be a standard problem in inverse theory. Such and similar problems routinely arise in numerous areas of applied sciences, including optical imaging, laser interferometry, computer vision, remote sensing and control. Though being ill-posed in nature, the above problem can be solved in a unique and stable manner, provided proper regularization and relevant boundary conditions. In this paper, however, a more challenging setup is addressed, in which one has to recover an image of interest from its noisy and blurry version, while the only information available about the imaging system at hand is the amplitude of the generalized pupil function (GPF) along with partial observations of the gradient of GPF's phase. In this case, the phase-related information is collected using a simplified version of the Shack-Hartmann interferometer, followed by recovering the entire phase by means of derivative compressed sensing. Subsequently, the estimated phase can be combined with the amplitude of the GPF to produce an estimate of the point spread function (PSF), whose knowledge is essential for subsequent image deconvolution. In summary, the principal contribution of this work is twofold. First...

Comparison of fringe-tracking algorithms for single-mode near-infrared long-baseline interferometers

Choquet, Élodie; Menu, Jonathan; Perrin, Guy; Cassaing, Frédéric; Lacour, Sylvestre; Eisenhauer, Frank
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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To enable optical long baseline interferometry toward faint objects, long integrations are necessary despite atmospheric turbulence. Fringe trackers are needed to stabilize the fringes and thus increase the fringe visibility and phase signal-to-noise ratio (SNR), with efficient controllers robust to instrumental vibrations, and to subsequent path fluctuations and flux drop-outs. We report on simulations, analysis and comparison of the performances of a classical integrator controller and of a Kalman controller, both optimized to track fringes under realistic observing conditions for different source magnitudes, disturbance conditions, and sampling frequencies. The key parameters of our simulations (instrument photometric performance, detection noise, turbulence and vibrations statistics) are based on typical observing conditions at the Very Large Telescope observatory and on the design of the GRAVITY instrument, a 4-telescope single-mode long baseline interferometer in the near-infrared, next in line to be installed at VLT Interferometer. We find that both controller performances follow a two-regime law with the star magnitude, a constant disturbance limited regime, and a diverging detector and photon noise limited regime. Moreover...

Extracting seismic core phases with array interferometry

Lin, Fan-Chi; Tsai, Victor C.; Schmandt, Brandon; Duputel, Zacharie; Zhan, Zhongwen
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Article; PeerReviewed Formato: application/pdf; text/plain; application/msword
Publicado em 28/03/2013 Português
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Seismic body waves that sample Earth's core are indispensable for studying the most remote regions of the planet. Traditional core phase studies rely on well-defined earthquake signals, which are spatially and temporally limited. We show that, by stacking ambient-noise cross-correlations between USArray seismometers, body wave phases reflected off the outer core (ScS), and twice refracted through the inner core (PKIKP^2) can be clearly extracted. Temporal correlation between the amplitude of these core phases and global seismicity suggests that the signals originate from distant earthquakes and emerge due to array interferometry. Similar results from a seismic array in New Zealand demonstrate that our approach is applicable in other regions and with fewer station pairs. Extraction of core phases by interferometry can significantly improve the spatial sampling of the deep Earth because the technique can be applied anywhere broadband seismic arrays exist.