Speckle noise

speckleImage Despeckling
Speckle is a granular 'noise' that inherently exists in and degrades the quality of the active radar, synthetic aperture radar (SAR), medical ultrasound and optical coherence tomography images.wikipedia
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Synthetic-aperture radar

synthetic aperture radarSARsynthetic aperture
Speckle is a granular 'noise' that inherently exists in and degrades the quality of the active radar, synthetic aperture radar (SAR), medical ultrasound and optical coherence tomography images.
Unfortunately, the phase differences between adjacent image picture elements ("pixels") also produce random interference effects called "coherence speckle", which is a sort of graininess with dimensions on the order of the resolution, causing the concept of resolution to take on a subtly different meaning.

Dynamic speckle

The speckle can also represent some useful information, particularly when it is linked to the laser speckle and to the dynamic speckle phenomenon, where the changes of the speckle pattern, in time, can be a measurement of the surface's activity.
Speckle noise

Speckle pattern

specklelaser specklespeckle noise
The speckle can also represent some useful information, particularly when it is linked to the laser speckle and to the dynamic speckle phenomenon, where the changes of the speckle pattern, in time, can be a measurement of the surface's activity.
Speckle noise

Radar

radar stationradarsradar system
Speckle is a granular 'noise' that inherently exists in and degrades the quality of the active radar, synthetic aperture radar (SAR), medical ultrasound and optical coherence tomography images.

Medical ultrasound

ultrasoundultrasonographysonogram
Speckle is a granular 'noise' that inherently exists in and degrades the quality of the active radar, synthetic aperture radar (SAR), medical ultrasound and optical coherence tomography images.

Optical coherence tomography

OCTOptical Coherence Tomography (OCT)Gaussian envelope
Speckle is a granular 'noise' that inherently exists in and degrades the quality of the active radar, synthetic aperture radar (SAR), medical ultrasound and optical coherence tomography images.

Capillary wave

ripplesripplecapillary gravity waves
In SAR oceanography, for example, speckle noise is caused by signals from elementary scatterers, the gravity-capillary ripples, and manifests as a pedestal image, beneath the image of the sea waves.

Adaptive filter

adaptive filteringadaptedadaptive
A second method involves using adaptive and non-adaptive filters on the signal processing (where adaptive filters adapt their weightings across the image to the speckle level, and non-adaptive filters apply the same weightings uniformly across the entire image).

Mean

mean valuepopulation meanaverage
There are two forms of non-adaptive speckle filtering: one based on the mean and one based upon the median (within a given rectangular area of pixels in the image).

Median

averagesample medianmedian-unbiased estimator
There are two forms of non-adaptive speckle filtering: one based on the mean and one based upon the median (within a given rectangular area of pixels in the image).

Variance

sample variancepopulation variancevariability
The sample mean and variance of a single pixel are equal to the mean and variance of the local area that is centred on that pixel.

Gaussian noise

Gaussianwhite Gaussian noiseGaussian random noise
Gaussian noise

Salt-and-pepper noise

salt and pepper noisepepper noise
Salt and pepper noise

Noise (signal processing)

noisenoisybackground noise
Speckle noise, typical of radar imaging and interferograms

Project 1640

The instrument uses the chromatic nature of the speckle noise to distinguish it from any true astrophysical companions, including a software which increases sensitivity by 10-20 times.

Median filter

Medianmedian smoothingrunning-median filter
However, its performance is not that much better than Gaussian blur for high levels of noise, whereas, for speckle noise and salt-and-pepper noise (impulsive noise), it is particularly effective.

Multiplicative noise

multiplicative
An important example is the speckle noise commonly observed in radar imagery.

Continuous-scan laser Doppler vibrometry

The primary disadvantage of CSLDV is the additional laser speckle noise that occurs if the laser spot scans the structure too quickly.

Amplified spontaneous emission

superluminescencesuperluminescentASE
This results in low temporal coherence, offering reduced speckle noise when compared with a laser.

Ultrasound computer tomography

For high resolution and speckle noise reduced reflectivity imaging Synthetic Aperture Focusing Techniques (SAFT), similar to radar's SAR and sonar's SAS, are widely used.

Fixed-pattern noise

pixel response non-uniformity
The main challenge is to generate a flat field illumination for short time exposures and wavelengths, to avoid speckle (in monochromatic light conditions) and statistical fluctuations of the light stream that become most obvious at short integration times.