Interference fringes obtained on VEGA with two optical telescopes

Labeyrie, A.

doi:10.1086/181747

Cited by 191 publications

(113 citation statements)

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“…The introduction of single aperture speckle interferometry (Labeyrie 1970) and long baseline interferometry (Labeyrie 1975) demonstrated the potential of the technique which uses the instantaneous fine structure in object images ("speckles") to attain angular resolution close to the diffraction limit of the instrument, despite atmospheric turbulence. Beckers (1982) described a technique of narrow spectral band speckle interferometry which derives spatial information with a resolution higher than the instrument diffraction limit, using the variations in the spectrum across the astronomical object under study.…”

Section: Differential Interferometry Methodsmentioning

confidence: 99%

Interferometric-Doppler imaging of stellar surface structure

Jankov

Vakili

Souza

et al. 2001

A&A

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Abstract. In this paper we discuss the combination of two basic approaches which should potentially generate images of spatially unresolved stars: differential interferometry and classical spectroscopy. Doppler Imaging provides indirect observational information on stellar surface structures by modeling the rotational modulation of the observed flux distribution across spectral lines. Similarly, differential interferometry makes it possible to measure the disturbances of photocentroid location of an unresolved star as a function of wavelength and to deduce the corresponding stellar map. We present the general formalism to reconstruct images from spectroscopy and differential interferometry data for sources with spatially unresolved structures, and we discuss how their combination improves the image reconstructions. This technique, that we call Interferometric-Doppler Imaging (IDI), leads to significant progress in solving some long-standing problems of Doppler Imaging, such as latitude smearing and bias as well as the non-uniqueness of the solution in the special case of an equator-on star. We treat explicitly the most delicate case of non-radial stellar pulsations, for which the cancellation of opposite sign temperature or velocity fields introduces additional difficulties. The performance of the method is demonstrated, using the indirect imaging code built on the basis of the developed approach to reconstruct an input image from a series of generated noisy spectra. The problem of image reconstruction from two-aperture interferometry data has been particularly addressed since it represents the case of most presently operating interferometers.

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Section: Differential Interferometry Methodsmentioning

confidence: 99%

Interferometric-Doppler imaging of stellar surface structure

Jankov

Vakili

Souza

et al. 2001

A&A

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“…The CERGA prototype long baseline interferometer (I2T) [21,22], which employs two 26-cm aperture telescopes, has been used with baselines in the range 6 to 40 m to measure the angular sizes of 10 stars with accuracies in the range 7 to 14$ [23,24]. The more recent determination of diameters of equivalent uniform disks are based on the visual detection of very low contrast fringes for the largest possible baseline.…”

Section: C) Visual Long Baseline Interferometrymentioning

confidence: 99%

9. Instruments and Techniques

Livingston¹,

Humphries²,

Bhattacharyya³

et al. 1985

Trans. Int. Astron. Union

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Between the Patras and New Delhi General Assemblies no meetings were directly sponsored by Commission 9 because the discipline was amply covered by the following: - “Eighth Symposium on Photoelectronic Image Devices,” Imperial College (London) 5-7 September 1983 (B. L. Morgan, Ed., Academic Press, London, 1984).- “Advanced Technology Optical Telescopes II” Imperial College, 5-7 September 1983.- “Instrumentation in Astronomy V” 7-9 September 1983 (A. Boksenberg and D. Crawford, Eds., Proc. SPIE 415).- IAU Symposium No. 109: “Astrometric Techniques,” 9-12 January 1984, Gainsville (Florida).- “Astronomical Photography 1984,” Edinburgh, 4-6 April 1984 (E. Sim and K. Ishida, Eds., Number 14 of Occasional Reports of the Royal Observatory, Edinburgh).- “IAU Colloquium No. 79: “Very Large Telescopes, Their Instrumentation and Programs,” Garching bei München, 9-12 April 1984 (M. H. Ulrich and K. Kjär, Eds.)

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“…This advancement has taken a long time from the early measurement of Betelgeuse's diameter by Michelson & Pease (1921), to the use of two coherent telescopes (Labeyrie 1975;Mourard et al 1994) and the development of stellar interferometers such as CHARA (ten Brummelaar et al 2005;Mourard et al 2009) and VLTI (Ohnaka et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Strategies for the deconvolution of hypertelescope images

Aimé

Lantéri

Diet

et al. 2012

A&A

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Aims. We study the possibility of deconvolving hypertelescope images and propose a procedure that can be used provided that the densification factor is small enough to make the process reversible. Methods. We present the simulation of hypertelescope images for an array of cophased densified apertures. We distinguish between two types of aperture densification, one called FAD (full aperture densification) corresponding to Labeyrie's original technique, and the other FSD (full spectrum densification) corresponding to a densification factor twice as low. Images are compared to the Fizeau mode. A single image of the observed object is obtained in the hypertelescope modes, while in the Fizeau mode the response produces an ensemble of replicas of the object. Simulations are performed for noiseless images and in a photodetection regime. Assuming first that the point spread function (PSF) does not change much over the object extent, we use two classical techniques to deconvolve the images, namely the Richardson-Lucy and image space reconstruction algorithms. Results. Both algorithms fail to achieve satisfying results. We interpret this as meaning that it is inappropriate to deconvolve a relation that is not a convolution, even if the variation in the PSF is very small across the object extent. We propose instead the application of a redilution to the densified image prior to its deconvolution, i.e. to recover an image similar to the Fizeau observation. This inverse operation is possible only when the rate of densification is no more than in the FSD case. This being done, the deconvolution algorithms become efficient. The deconvolution brings together the replicas into a single high-quality image of the object. This is heuristically explained as an inpainting of the Fourier plane. This procedure makes it possible to obtain improved images while retaining the benefits of hypertelescopes for image acquisition consisting of detectors with a small number of pixels.

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Interference fringes obtained on VEGA with two optical telescopes

Cited by 191 publications

References 0 publications

Interferometric-Doppler imaging of stellar surface structure

Interferometric-Doppler imaging of stellar surface structure

9. Instruments and Techniques

Strategies for the deconvolution of hypertelescope images

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