Interferometric method for image formation: the basic ideas and computer simulation
As it is known, the key resolution limit of an astronomical instrument is determined by diffraction of a received wave on the instrument aperture. However, by performing observations from the Earth surface in a short-wave part of the wave band, it is seldom possible to achieve this limit because of...
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| Published in: | Кинематика и физика небесных тел |
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| Date: | 2005 |
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| Language: | English |
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Головна астрономічна обсерваторія НАН України
2005
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| Cite this: | Interferometric method for image formation: the basic ideas and computer simulation / Yu. Kornienko, V. Pugach // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 534-536. — Бібліогр.: 6 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860120050095095808 |
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| author | Kornienko, Yu. Pugach, V. |
| author_facet | Kornienko, Yu. Pugach, V. |
| citation_txt | Interferometric method for image formation: the basic ideas and computer simulation / Yu. Kornienko, V. Pugach // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 534-536. — Бібліогр.: 6 назв. — англ. |
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| container_title | Кинематика и физика небесных тел |
| description | As it is known, the key resolution limit of an astronomical instrument is determined by diffraction of a received wave on the instrument aperture. However, by performing observations from the Earth surface in a short-wave part of the wave band, it is seldom possible to achieve this limit because of phase distortions arising by the propagation of a wave in the Earth’s atmosphere which is caused by fluctuations of the refraction index. There is a series of ideas how to form an astronomical image decreasing or excluding the influence of phase distortions during the observation. One of such methods is the interferometric imaging method. We describe this technique and present results of simulated observations of various objects and their images reconstructed for various atmospheric distortions. The advantage of a multi-beam interferometer, both by obtaining of instantaneous images and by using time accumulation is well-visible.
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| first_indexed | 2025-12-07T17:38:51Z |
| format | Article |
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INTERFEROMETRIC METHOD FOR IMAGE FORMATION:
THE BASIC IDEAS AND COMPUTER SIMULATION
Yu. Kornienko, V. Pugach
Usikov Institute of Radiophysics and Electronics, NAS of Ukraine
12 Ac. Proskura Str., Kharkiv, Ukraine
As it is known, the key resolution limit of an astronomical instrument is determined by diffraction of
a received wave on the instrument aperture. However, by performing observations from the Earth
surface in a short-wave part of the wave band, it is seldom possible to achieve this limit because of
phase distortions arising by the propagation of a wave in the Earth’s atmosphere which is caused by
fluctuations of the refraction index. There is a series of ideas how to form an astronomical image
decreasing or excluding the influence of phase distortions during the observation. One of such
methods is the interferometric imaging method. We describe this technique and present results of
simulated observations of various objects and their images reconstructed for various atmospheric
distortions. The advantage of a multi-beam interferometer, both by obtaining of instantaneous
images and by using time accumulation is well-visible.
One of the main tasks of the observational astronomy is to increase resolution of astronomical instruments.
As it is known, the key resolution limit of an astronomical instrument is determined by diffraction of a received
wave on the instrument aperture. However, by performing observations from the Earth surface in a short-
wave part of the wave band, it is seldom possible to achieve this limit because of phase distortions arising
by the propagation of a wave in the Earth’s atmosphere which is caused by fluctuations of the refraction
index. There is a series of ideas how to form an astronomical image decreasing or excluding the influence
of phase distortions during the observation (for example, [1, 5]). One of such methods is the interferometric
imaging method proposed in [2, 6] and described in details in [3]. The point of this method is that an image
is not formed directly in the telescope focal plane, as it is done by the traditional method. Instead of this,
the interferometer entrance aperture is divided into sub-apertures. Each pair of sub-apertures transmits its
spatial-frequency window in the image space spectrum. However, contributions of these pairs are not summed
up, as in the traditional telescope, but are registered independently. The periscope system serves this purpose,
which transfers the frequency window passed by the pair to another region of the frequency plane. The periscope
system outputs form in the aggregate the exit aperture of the interferometer, which should be irredundant for
the correct functioning.
a) b)
Figure 1. (a) Configuration of a multimirror telescope and the input aperture interferometer (dotted line shows a contour
of the aperture of a traditional telescope); (b) configuration of the output aperture of the interferometer and the scheme
of mapping the input apertures on the output one
c© Yu. Kornienko, V. Pugach, 2004
534
a) b) c) d)
Figure 2. The interferograms of a point (a) and a multiple star (c) for different levels of atmospheric distortion (b), (d)
a)
b)
c)
Figure 3. Images of the multiple star obtained by means of a conventional telescope (left), a multi-mirror telescope
(center) and a multi-beam interferometer (right) with a root-mean-square value of phase atmospheric distortion equal
to 0 (a) and ±2π (instantaneous images (b)), and by time accumulation (c)
535
The image reconstruction from an interferogram obtained requires to remove unknown phase distortions
from several independent measurements of the coherence function by different pairs of sub-apertures and find
true values of the Fourier-components of the object brightness. Moreover, it is necessary to solve the algebraic
system of equations connecting the results of measurements of the coherence function phases with their true
values and phase distortions in the atmosphere.
This idea may be verified well using a computer model of the optical system, when the brightness distribution
over the object is known exactly and may be compared with the image reconstructed. In [4] this technique is
described in more details, and results of simulated observations of various objects and their images reconstructed
are adduced for various atmospheric distortions.
For simulation of an interferometer, the configuration of the input aperture was chosen consisting of 21 sub-
apertures with diameter of 50 cm. It is presented in Fig. 1a. The dotted line shows a contour of the aperture
of a traditional telescope with diameter of 6 m. Images obtained with three instruments – this telescope,
the multi-beam interferometer, and the multi-mirror telescope with the aperture similar to the aperture of
the interferometer – were compared.
The configuration of the output aperture of the interferometer and the scheme of mapping the input apertures
on the output one are shown in Fig. 1b. Figure 2 presents the interferograms of a point and a multiple
star for different levels of atmospheric distortions. Comparison of images of the multiple star obtained with
the three above-mentioned telescopes and a root-mean-square value of phase atmospheric distortions equal to 0
and ±2π, is presented in Fig. 3. These figures also present results of time accumulation 50 instantaneous
images. The advantage of the multi-beam interferometer, both in case of instantaneous images and with time
accumulation is well-visible.
[1] Jennison R. C. Phase sensitive interferometer technique for the measurement of the Fourier transforms of spatial
brightness of small angular extent // Mon. Notic. Roy. Astron. Soc.–1958.–118.–P. 176.
[2] Kornienko Yu. V., Uvarov V. N. Signal accumulation at observation of an astronomical object through the turbulent
atmosphere // Reports of Academy of Science of Ukraine.–1987.–Ser. A, N 4.–P. 60–63.
[3] Kornienko Yu. V. Interferometric approach to the problem of turbulent atmosphere effects in astronomical obser-
vations // Kinematics and Physics of Celestial Bodies.–1994.–10, N 2.–P. 98–106.
[4] Pugach V. V. Interferometric method for image formation: review of results and computer simulation // Radio-
physics and Electronics.–2004.–9.–P. 140–153.
[5] Rhodes W. T., Goodman J. W. Interferometric technique for recording and restoring images by unknown aberra-
tion // J. Opt. Soc. Amer.–1973.–63, N 6.–P. 647–657.
[6] Roddier F. Redundant versus nonredundant beam recombination in an aperture synthesis with coherent arrays //
J. Opt. Soc. Amer.–1987.–A4, N 8.–P. 1396–1401.
536
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| id | nasplib_isofts_kiev_ua-123456789-79716 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0233-7665 |
| language | English |
| last_indexed | 2025-12-07T17:38:51Z |
| publishDate | 2005 |
| publisher | Головна астрономічна обсерваторія НАН України |
| record_format | dspace |
| spelling | Kornienko, Yu. Pugach, V. 2015-04-03T20:16:38Z 2015-04-03T20:16:38Z 2005 Interferometric method for image formation: the basic ideas and computer simulation / Yu. Kornienko, V. Pugach // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 534-536. — Бібліогр.: 6 назв. — англ. 0233-7665 https://nasplib.isofts.kiev.ua/handle/123456789/79716 As it is known, the key resolution limit of an astronomical instrument is determined by diffraction of a received wave on the instrument aperture. However, by performing observations from the Earth surface in a short-wave part of the wave band, it is seldom possible to achieve this limit because of phase distortions arising by the propagation of a wave in the Earth’s atmosphere which is caused by fluctuations of the refraction index. There is a series of ideas how to form an astronomical image decreasing or excluding the influence of phase distortions during the observation. One of such methods is the interferometric imaging method. We describe this technique and present results of simulated observations of various objects and their images reconstructed for various atmospheric distortions. The advantage of a multi-beam interferometer, both by obtaining of instantaneous images and by using time accumulation is well-visible. en Головна астрономічна обсерваторія НАН України Кинематика и физика небесных тел MS6: New Trends, Research Directions, and Perspective Programs in the Field of Astronomy and Astrophysics Interferometric method for image formation: the basic ideas and computer simulation Article published earlier |
| spellingShingle | Interferometric method for image formation: the basic ideas and computer simulation Kornienko, Yu. Pugach, V. MS6: New Trends, Research Directions, and Perspective Programs in the Field of Astronomy and Astrophysics |
| title | Interferometric method for image formation: the basic ideas and computer simulation |
| title_full | Interferometric method for image formation: the basic ideas and computer simulation |
| title_fullStr | Interferometric method for image formation: the basic ideas and computer simulation |
| title_full_unstemmed | Interferometric method for image formation: the basic ideas and computer simulation |
| title_short | Interferometric method for image formation: the basic ideas and computer simulation |
| title_sort | interferometric method for image formation: the basic ideas and computer simulation |
| topic | MS6: New Trends, Research Directions, and Perspective Programs in the Field of Astronomy and Astrophysics |
| topic_facet | MS6: New Trends, Research Directions, and Perspective Programs in the Field of Astronomy and Astrophysics |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79716 |
| work_keys_str_mv | AT kornienkoyu interferometricmethodforimageformationthebasicideasandcomputersimulation AT pugachv interferometricmethodforimageformationthebasicideasandcomputersimulation |