Cramer-Rao lower bound and object reconstruction performance evaluation for intensity interferometry

Dolne, Jean J.; Gerwe, David R.; Crabtree, Peter N.

doi:10.1117/12.2063418

Cited by 4 publications

(5 citation statements)

References 5 publications

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“…Theoretical and numerical simulations of such observations have been made for several types of objects (Nuñez et al, 2012a,b;Rou et al, 2013;Dolne et al, 2014). Here, we report on their experimental verification.…”

Section: Introductionsupporting

confidence: 52%

Long-baseline optical intensity interferometry

Dravins

Lagadec

Nuñez

2015

A&A

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Context. A long-held vision has been to realize diffraction-limited optical aperture synthesis over kilometer baselines. This will enable imaging of stellar surfaces and their environments, and reveal interacting gas flows in binary systems. An opportunity is now opening up with the large telescope arrays primarily erected for measuring Cherenkov light in air induced by gamma rays. With suitable software, such telescopes could be electronically connected and also used for intensity interferometry. Second-order spatial coherence of light is obtained by cross correlating intensity fluctuations measured in different pairs of telescopes. With no optical links between them, the error budget is set by the electronic time resolution of a few nanoseconds. Corresponding light-travel distances are approximately one meter, making the method practically immune to atmospheric turbulence or optical imperfections, permitting both very long baselines and observing at short optical wavelengths. Aims. Previous theoretical modeling has shown that full images should be possible to retrieve from observations with such telescope arrays. This project aims at verifying diffraction-limited imaging experimentally with groups of detached and independent optical telescopes. Methods. In a large optics laboratory, artificial stars (single and double, round and elliptic) were observed by an array of small telescopes. Using high-speed photon-counting solid-state detectors and real-time electronics, intensity fluctuations were cross-correlated over up to 180 baselines between pairs of telescopes, producing coherence maps across the interferometric Fourier-transform plane. Results. These interferometric measurements were used to extract parameters about the simulated stars, and to reconstruct their twodimensional images. As far as we are aware, these are the first diffraction-limited images obtained from an optical array only linked by electronic software, with no optical connections between the telescopes. Conclusions. These experiments serve to verify the concepts for long-baseline aperture synthesis in the optical (somewhat analogous to radio interferometry) and to optimize the instrumentation and observing procedures for future observations with large arrays of Cherenkov telescopes, aiming at order-of-magnitude improvements of the angular resolution in optical astronomy.

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Section: Introductionsupporting

confidence: 52%

Long-baseline optical intensity interferometry

Dravins

Lagadec

Nuñez

2015

A&A

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“…Imaging methods specifically for intensity interferometry have been worked out for one 56 and two dimensions [57][58] . Such phase recovery techniques have been applied to reconstruct images from simulated intensity interferometry observations [59][60][61][62] , demonstrating that also rather complex images can be reconstructed. One remaining limitation is the non-uniqueness between the image and its mirrored reflection.…”

Section: Aperture-synthesis Imaging With Large Optical Arraysmentioning

confidence: 99%

Intensity interferometry: optical imaging with kilometer baselines

Dravins

2016

SPIE Proceedings

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Optical imaging with microarcsecond resolution will reveal details across and outside stellar surfaces but requires kilometer-scale interferometers, challenging to realize either on the ground or in space. Intensity interferometry, electronically connecting independent telescopes, has a noise budget that relates to the electronic time resolution, circumventing issues of atmospheric turbulence. Extents up to a few km are becoming realistic with arrays of optical air Cherenkov telescopes (primarily erected for gamma-ray studies), enabling an optical equivalent of radio interferometer arrays. Pioneered by Hanbury Brown and Twiss, digital versions of the technique have now been demonstrated, reconstructing diffraction-limited images from laboratory measurements over hundreds of optical baselines. This review outlines the method from its beginnings, describes current experiments, and sketches prospects for future observations.

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“…Realizing that potential, various theoretical simulations of intensity interferometry observations with extended telescope arrays have been made 7 8 9 10 11 , in particular examining the overall sensitivity and limiting stellar magnitudes. Different studies conclude that, with current electronic performance and current Cherenkov telescope designs, one night of observation in one single wavelength band permits measurements of hotter stars down to visual magnitude about m v =8, giving access to thousands of sources.…”

Section: Resultsmentioning

confidence: 99%

“…Theoretical simulations have verified that, provided the Fourier-transform plane is well filled with data, two-dimensional image restoration becomes feasible 8,9,11 . The pattern of secondorder coherence is equivalent to the intensity pattern produced by diffraction of light in a correspondingly sized aperture, and it is already intuitively clear that a thorough mapping of that pattern must put stringent constraints on the source geometry.…”

Section: Image Reconstruction Principlesmentioning

confidence: 90%

Optical aperture synthesis with electronically connected telescopes

2015

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Highest resolution imaging in astronomy is achieved by interferometry, connecting telescopes over increasingly longer distances and at successively shorter wavelengths. Here, we present the first diffraction-limited images in visual light, produced by an array of independent optical telescopes, connected electronically only, with no optical links between them. With an array of small telescopes, second-order optical coherence of the sources is measured through intensity interferometry over 180 baselines between pairs of telescopes, and two-dimensional images reconstructed. The technique aims at diffraction-limited optical aperture synthesis over kilometre-long baselines to reach resolutions showing details on stellar surfaces and perhaps even the silhouettes of transiting exoplanets. Intensity interferometry circumvents problems of atmospheric turbulence that constrain ordinary interferometry. Since the electronic signal can be copied, many baselines can be built up between dispersed telescopes, and over long distances. Using arrays of air Cherenkov telescopes, this should enable the optical equivalent of interferometric arrays currently operating at radio wavelengths.

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Cramer-Rao lower bound and object reconstruction performance evaluation for intensity interferometry

Cited by 4 publications

References 5 publications

Long-baseline optical intensity interferometry

Long-baseline optical intensity interferometry

Intensity interferometry: optical imaging with kilometer baselines

Optical aperture synthesis with electronically connected telescopes

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