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Speckle imaging and eye testing using speckle also use the speckle effect. Speckle is the chief limitation of coherent lidar and coherent imaging in optical heterodyne detection. In the case of near field speckles, the statistical properties depend on the light scattering distribution of a given sample.
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. Speckle imaging comprises a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of ...
A monochromatic light source, usually a laser, is shot through a polarizer and into a sample. The scattered light then goes through a second polarizer where it is collected by a photomultiplier and the resulting image is projected onto a screen. This is known as a speckle pattern (Figure 1). [4] Figure 1. Typical speckle pattern.
Figure 1 shows a sequence of speckle patterns in a corn seed in the start of its germination process where the dynamic effect is higher in the areas where the scattering centers are expected to be more active as is the case of the embryo and in a break in the endosperm region of the seed. The embryo is in the lower left side and the break is a ...
It was later realized that speckle patterns could carry information about the object's surface deformations. Butters and Leendertz developed the technique of speckle pattern interferometry in 1970, [97] and since then, speckle has been exploited in a variety of other applications. A photograph is made of the speckle pattern before deformation ...
Since the speckle pattern is perceived by the brain to be on the retina, the effect is of parallax; the speckle pattern appears to be nearer to the eye than the surface and hence moves in the same direction as the surface, but faster than the surface.
Laser speckle contrast imaging (LSCI), also called laser speckle imaging (LSI), is an imaging modality based on the analysis of the blurring effect of the speckle pattern. The operation of LSCI is having a wide-field illumination of a rough surface through a coherent light source.
This technique either uses a camera to detect many speckle grains (see speckle pattern) or a ground glass to create a large number of speckle realizations (Echo-DWS [6]). In both cases an average over a large number of statistically independent intensity values is obtained, allowing a much faster data acquisition time.