Speckle interferometry

Specific resistance Specific rotation Specific speed Specific viscosit Specimen contrast Speckle interferometry Spectazole... 

Interferometry in astronomy is used to surpass the limitations on angular resolution set by the Earth s atmosphere (i. e., speckle interferometry), or by the diffraction of the aperture of a single telescope. We will focus in this lecture on interferometry with multiple telescope arrays with which it is possible to obtain information on spatial scales of the source beyond the diffraction limit of its member telescopes. 

Interferometric measured displacement (d) is calculated d = nk 0.51, where n is the number of interference fringes between the displaced point and a fixed point on the object. In holographic, or speckle, interferometry, A is a light source from which spherical waves radiate outward while B is a point of observation, or a light sink, toward which spherical waves move inward (see Fig. 6). In that case the hyperbolas will move with a velocity greater than light while the ellipses are... 

R. Navarro, F.J. Puentes, M. Nieto-Vesperinas, Simulated annealing image reconstruction in photolimited stellar speckle interferometry. Astronomy and Astrophysics, 208 (1989) 374. 

As experimental techniques for measuring displacement and strain become increasingly accurate at micro- and nano- length scales, experiments must be performed to verify the accuracy of predictions of models of material behavior at these scales. In particular, the use of diffraction techniques for measurements of lattice distortion [20] combined with surface measurement techniques such as micro-Moire [21], speckle interferometry [22] and displacement mapping [23] promise to provide essential information on the local deformation behavior of metals and alloys in the vicinity of grain boundaries, voids and second phase particles. These techniques must be further developed and applied to the analysis of real materials to increase our knowledge of material behavior at these length scales. 

Fig. 10,1. Left Hubble Space Telecsope image of tlie Eskimo nebula. The filaments visible above consist of material ejected by the central star (now a white dwarf) during its AGB phase. Right Speckle interferometry of the carbon star IRC 10216 at 1.125 /im. The structure of the dust shell around the star can be clearly seen. Credit J. Hester, P. Scowen (ASU), HST, NASA...

Full-field speckle interferometry is similar to holographic interferometry except that the speckles are observed on the specimen surface by illuminating it with laser light or by establishing an optically speckled surface (for example by painting it). 

R. Jones and C. Wykes, Holographic and Speckle Interferometry, 2nd ed., Cambridge University Press, Cambridge, 1989. 

V. Shchepinov and V. Pisarev, eds.. Strain and Stress Analysis by Holographic and Speckle Interferometry, John Wiley Sons, Inc., New York, 1996. 

Non-contact strain measuring methods are generally based on optical principles. The principal methods addressed in the literature include MI or SI (moire or speckle interferometry), and DIG (digital image correlation). Amongst their advantages, whole-field, non-contact or remote measurement... 

Read, D. T. (1998), Young s modulus of thin films by speckle interferometry. Measurement Science and Technology 9, 676-685. 

Yang, W. J. 2001. Handbook of Flow Visualization, 2nd ed. New York Taylor Francis. Covers techniques used to visualize flow in liquids and gasses. Includes both underlying theory and experimental applications. Techniques presented include Schlieren, shadowgraph, speckle, interferometry, light sheet, and plasma fluorescence. Numerous applications are given in subsequent chapters medical, aerospace, wind tunnels, turbines, and indoor airflow. 

In 1970, the French astronomer and optical physicist Antoine Labeyrie pointed out an elegantly simple method for circiunventing atmospheric seeing conditions to achieve diffraction-limited resolutioa Labeyrie s method, which he named speckle interferometry, takes advantage of the detailed marmer in which the blmring occitrs in order to cancel out the seeing-induced effects. 

A speckle pictirre of abright star is shown in Fig. 2. Had Labeyrie s idea occitrred fully to the previous generation of astronomers who had only photographic emulsions at their disposal, they would have been frustrated by the lack of technology that would enable speckle interferometry to be carried out beyond a demonstration stage. 

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