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Speckle, speckle pattern, or speckle noise designates the granular structure observed in coherent light, resulting from random interference. Speckle patterns are used in a wide range of metrology techniques, as they generally allow high sensitivity and simple setups.
An important example is the speckle noise commonly observed in radar imagery. Examples of multiplicative noise affecting digital photographs are proper shadows due to undulations on the surface of the imaged objects, shadows cast by complex objects like foliage and Venetian blinds , dark spots caused by dust in the lens or image sensor, and ...
Aperture masking interferometry (or Sparse aperture masking) is a form of speckle interferometry, that allows diffraction limited imaging from ground-based telescopes (like the Keck Telescope and the Very Large Telescope), and is a high contrast imaging mode on the James Webb Space Telescope.
Salt and pepper noise or spike noise, scattered very dark or very light pixels; Fixed pattern noise, that is tied to pixel sensors; Shadow noise, made visible by increasing brightness or contrast; Speckle noise, typical of radar imaging and interferograms; Film grain in analog photography
This upper bound signal-to-noise ratio of unity is only for absolute magnitude measurement: it can have signal-to-noise ratio better than unity for phase, frequency or time-varying relative-amplitude measurements in a stationary speckle field.
NASA scientists believe the ominous noises could potentially be the "background noise" of the Earth otherwise known as "Ambient Earth Noise." Since this still lacks scientific confirmation ...
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The primary disadvantage of CSLDV is the additional laser speckle noise that occurs if the laser spot scans the structure too quickly. Speckle noise is caused by micro-scale irregularities in the surface that change the intensity pattern of the laser light received by the LDV as it scans the surface.