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322:) can obtain information about the high-resolution structure of the object from the statistical properties of the speckle patterns. This technique was first implemented in 1971 at Palomar Observatory (200-inch telescope) by Daniel Y. Gezari, Antoine Labeyrie and Robert V. Stachnick. Methods developed in the 1980s allowed simple images to be reconstructed from this power spectrum information.
127:, whose random nature disrupts the single spot of the Airy disk into a pattern of similarly-sized spots scattered over a much larger area (see the adjacent image of a binary). For typical seeing, the practical resolution limits are at mirror sizes much less than the mechanical limits for the size of mirrors, namely at a mirror diameter equal to the
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One limitation of the technique is that it requires extensive computer processing of the image, which was hard to come by when the technique was first developed. This limitation has faded away over the years as computing power has increased, and nowadays desktop computers have more than enough power
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Speckle imaging in biology refers to the underlabeling of periodic cellular components (such as filaments and fibers) so that instead of appearing as a continuous and uniform structure, it appears as a discrete set of speckles. This is due to statistical distribution of the labeled component within
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The downside of the technique is that taking images at this short an exposure is difficult, and if the object is too dim, not enough light will be captured to make analysis possible. Early uses of the technique in the early 1970s were made on a limited scale using photographic techniques, but since
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The method involves calculation of the differential shifts of the images. This is easily accomplished in astronomical images since they can be aligned with the stars. Once the images are aligned they are averaged together. It is a basic principle of statistics that variation in a sample can be
267:
reduced by averaging together the individual values. In fact, when using an average, the signal-to-noise ratio should be increased by a factor of the square root of the number of images. A number of software packages exist for performing this, including
120:. A group of objects whose images are closer together than this limit appear as a single object. Thus larger telescopes can image not only dimmer objects (because they collect more light), but resolve objects that are closer together as well.
205:
into astronomy, which captures more than 70% of the light, lowered the bar on practical applications by an order of magnitude, and today the technique is widely used on bright astronomical objects (e.g. stars and star systems).
259:" method) is a form of speckle imaging commonly used for obtaining high quality images from a number of short exposures with varying image shifts. It has been used in astronomy for several decades, and is the basis for the
552:
Wong, M.H., A.A. Simon, J.W. Tollefson, I. de Pater, M.N. Barnett, A.I. Hsu, A.W. Stephens, G.S. Orton, S.W. Fleming, C. Goullaud, W. Januszewski, A. Roman, G.L. Bjoraker, S.K. Atreya, A. Adriani, and L.N. Fletcher (2020)
138:– about 20 cm in diameter for observations with visible light under good conditions. For many years, telescope performance was limited by this effect, until the introduction of speckle interferometry and
216:(whose smooth wavefront is an excellent simulation of the light from a distant star) on a surface, the resulting speckle pattern can be processed to give detailed images of flaws in the material.
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243:
images of
Jupiter at 5 μm, using stacks of individual Gemini Observatory frames each with a relatively long 309-msec exposure time, illustrate the principle that coherence time τ
172:, the movement of the atmosphere is too sluggish to have an effect; the speckles recorded in the image are a snapshot of the atmospheric seeing at that instant. Coherence time
209:
Many of the simpler speckle imaging methods have multiple names, largely from amateur astronomers re-inventing existing speckle imaging techniques and giving them new names.
673:"Speckle Interferometry : Diffraction-Limited Measurements of Nine Stars with the 200-inch Telescope", Daniel Y. Gezari, Antoine Labeyrie and Robert V. Stachnik, 1972,
38:) as seen through atmospheric turbulence. Each star should appear as a single point, but the atmosphere causes the images of the two stars to break up into two patterns of
50:
Slow-motion speckle imaging movie, showing how a high-magnification (negative) image of a star breaks up into multiple blobs (speckles), entirely an atmospheric effect.
767:
Baldwin, John; MacKay, C. D.; Titterington, D. J.; Sivia, D.; Baldwin, J. E.; Warner, P. J. (August 1987). "The First Images from
Optical Aperture Synthesis".
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from each of the short exposures. The "average bispectrum" can then be calculated and then inverted to obtain an image. This works particularly well using
97:
The principle of all the techniques is to take very short exposure images of astronomical targets, and then process those so as to remove the effects of
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All of these were obtained using infrared AO or IR interferometry (not speckle imaging) and have higher resolution than can be obtained with e.g. the
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photographic film captures only about 7% of the incoming light, only the brightest of objects could be viewed in this way. The introduction of the
647:, Antoine (May 1970). "Attainment of Diffraction Limited Resolution in Large Telescopes by Fourier Analysing Speckle Patterns in Star Images".
47:
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Jacquot, P.: Speckle interferometry: a review of the principal methods in use for experimental mechanics applications. Strain 44, 57–69 (2008)
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Baba, N; Isobe, Syuzo; Norimoto, Youji; Noguchi, Motokazu (May 1985). "Stellar speckle image reconstruction by the shift-and-add method".
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feature on some cameras. The short exposure images are aligned by using the brightest speckle and averaged to give a single output image.
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approach, only the best short exposures are selected for averaging. Early shift-and-add techniques aligned images according to the image
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that would otherwise appear as a single star to a visual observer working with a similar-sized telescope, and the first images of
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109:-like phenomena on other stars. Many of the techniques remain in wide use today, notably when imaging relatively bright targets.
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Baldwin, John; Haniff, C. A.; MacKay, C. D.; Warner, P. J. (April 1986). "Closure phase in high-resolution optical imaging".
345:. In this arrangement the telescope aperture is blocked except for a few holes which allow light through, creating a small
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enables real-time monitoring of dynamical systems and video image analysis to understand biological processes.
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495:(1966). "Optical Resolution Through a Randomly Inhomogeneous Medium for Very Long and Very Short Exposures".
42:. The speckles move around rapidly, so that each star appears as a single fuzzy blob in long exposure images.
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The resolution of a telescope is limited by the size of the main mirror, due to the effects of
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Weigelt, Gerd (April 1977). "Modified astronomical speckle interferometry 'speckle masking'".
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This improvement of resolution breaks down due to the practical limits imposed by the
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This section is about an imaging method. For the multiplication algorithm, see
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they drop to as little as 10 ms. When exposure times are shorter than τ
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techniques. The key to the technique, found by the
American astronomer
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Image quality, tip-tilt correction, and shift-and-add infrared imaging
578:, Applied Optics (ISSN 0003-6935), vol. 24, May 15, 1985, p. 1403-1405
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Stellar speckle image reconstruction by the shift-and-add method
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High-resolution UV/Optical/IR Imaging of
Jupiter in 2016–2019
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Gemini Gets Lucky and Takes a Deep Dive Into
Jupiter’s Clouds
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techniques based on the analysis of large numbers of short
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Another use of the technique is in industry. By shining a
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methods. These techniques can dramatically increase the
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One more recent type of speckle interferometry called
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Speckle imaging recreates the original image through
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unlabeled components. The technique, also known as
824:- freeware astronomical images processing software
574:Baba, N.; Isobe, S.; Norimoto, Y.; Noguchi, M.
34:Typical short-exposure image of a binary star (
142:provided a means of removing this limitation.
231:multiplication algorithm § Shift and add
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498:Journal of the Optical Society of America
409:Electronic speckle pattern interferometry
361:to make such processing a trivial task.
164:are on the order of 100 ms, but for the
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190:is a function of wavelength, because
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543:, NOIRLab press release, 2020-05-08.
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384:Aperture masking interferometry
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419:Holographic interferometry
404:Diffraction-limited system
247:increases with wavelength.
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675:The Astrophysical Journal
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255:method (more recently "
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261:image stabilisation
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118:Airy disk
63:exposures
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645:Labeyrie
631:20440355
468:MWC 349A
463:LKHa 101
378:See also
292:centroid
273:RegiStax
155:infrared
40:speckles
36:ζ Boötis
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779:Bibcode
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365:Biology
286:In the
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308:French
279:, and
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795:S2CID
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220:Types
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822:Iris
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269:IRAF
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