Speckles

When a laser beam eross a rough surface, the scattered light presents an granular aspect, which is call speckle. 

Often industry requires fast techniques to measure movements, deformations, etc. The optics methods, between them those based in speckle K gives quick solutions to this problems. 

First, the plane n(x,y) coincides with the diffuser mean plane of G, IT (x ,y ). When G is translated a distance x and rotated an angle Aa respect to the y axis of Il (x ,y ), we ob-a null movement of the speckle pattern on a circumference of center C and radius R ... 

As the dimensions of the speckle grain on the detectors is about 1,7 im, 4 times lesser than the pixel dimensions (for D = 350 mm illuminated area = 6,3mm x 2 mm magnification CCD = 0,05), the halo results not very clear. 

Sirohi, Speckle Metrology ,Marcel Dekker, Inc., New York (1993). 

We are interested in < E (0[,(t)i)E3(62,, where <> means the average over the ensemble of surfaces, the subindexes 1 and 2 refer to two different points of observation and the subindexes A and B belong to two different conditions of illumination, which for example arise from two different wavelengths, two different incident angles, etc.. If A = B and 1 = 2, the above expression gives the angular distribution of the mean scattered intensity, otherwise it turns to be the intensity correlation coefficient y from < E Eb >, assuming that we deal with fully developed speckle. 

Goldfisher, Autocorrelation function and power spectral density of laser-produced speckle pattern . J. Opt. Soc. Am., vol.55, p.247(1965). 

D. Leger, E. Mathieu and J. C. Perrin, Optical surface determmation usmg speckle correlation technique . Appl. Opt., Vol. 14, 872-877 (1975). 

Speckle shearing interferometry, or shearography, is a full field optical inspection teclmique that may be used for the nondestructive detection of surface and, sometimes, subsurface defects. Whilst being more sensitive in the detection of surface defects, it may also be considered for pipe inspection and the monitoring of internal conoslon. In contrast, laser ultrasound and other forms of ultrasound, are point by point measurement techniques, so that scanning facilities and significant data processing is required before information on local defects is extracted from any examination of extensive areas [1 - 3]. 

Figure 3. Sheared speckle image of a square aluminium plate clamped along all four sides...

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

The second conversion of GS to (GSi)r will be Case 4 of Table 5-10, the two-surface-zone enclosure with computation simphfied by assuming that the direct-view fac tor from any spot to a surface equals the fraction of the whole enclosure that the surface occupies (the speckled-furnace model). This case can be considered an ideahzation of many processing furnaces such as distilling and cracking coil furnaces, with parts of the enclosure tube-covered and part left refrac-toiy. (But the refractory under the tubes is not to be classified as part of the refractory zone.) Again, one starts with substitution into Eq. (5-173) of the terms GSi, GS, and S Si from Table 5-10, Case 4, with all terms first converted to their gray-phis-clear form. To indicate the procedure, one of the components, S Si, wil be formulated. 

Flaser,/. curl, speckle, streak flaw, flaseng, a. curled, speckled, streaked, Flattermine, /, (Mil.) land mine, contact mine, flattern, v.t. flutter, flicker float, wave dangle be flighty. 

Flcckfieber, n. spotted fever, specif, typhus, fleckig, a. spotted, speckled, stained, mottled, flawy freckled. — — warden, spot, stain. Fleck Schlerling, m. poison hemlock (Conium maculatum). seife,/. scouring soap. stein,... 

Maser, /. speckle, spot, mark grain (of wood) pi.) measles. 

Punkt, in. point dot spot, speck period. Punktcben, n. dot, speck, punkten, v.t. dot spot-weld, punkt-formig, a. in the form of points or a point, point-like, punctiform. -frei, a. (Dyeing) free from spots or specks, punktieren, v.t. point dot pimctuate speckle, spot, stipple. 

Spreng-wirkung, /. explosive effect, explosive action, -wolke, /. cloud from an explosion, bmst smoke, -zunder, m. detonating fuse. Sprenkel, m. speckle, spot, sprenkeln, v.t. sprinkle speckle, mottle, spot. Sprenkler, m. sprinkler, sparger, sprenkllg, a. speckled, spotted. 

Figure 3. A typical short-exposure speckle image of a 0.2arcsec binary star. The image width is about 2.2arcsec. (courtesy N.J. Wooder)...

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. 

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