Speckle

Speckle contrast reduction is essentially the creation of many independent speckle patterns, so that they average out on the retina/detector.

Speckle is usually quantified by the speckle contrast.

Subjective speckles When an image is formed of a rough surface which is illuminated by a coherent light (e.g. a laser beam), a speckle pattern is observed in the image plane; this is called a “subjective speckle pattern” – see image above.

On the other hand, the multiply scattered photons are generated via random deflections as the light passes through the material and show up as speckle noise in the reconstructed image.

After the revelation by politician Chishimba Kambwili last week, Valden Findlay denied ever knowing or meeting Goswami adding that his relationship with President Lungu was without any blemish or speckle and that it was mutual and personal.

Charles N. Christensen et al, Simple and robust speckle detection method for fire and heat detection in harsh environments, DOI: 10.1364/AO.

Every June and July, red, white and blue banners advertising firework stands at the nearest exit speckle highways around the Dallas-Fort Worth area.

Matt Patricia Maintains Strong Troll Game, Makes Lions Practice OutdoorsIf Matt Patricia has made anything clear this year, it's that he does not give one speckle of excreta what outside critics say about him.

Explanation The speckle effect is a result of the interference of many waves of the same frequency, having different phases and amplitudes, which add together to give a resultant wave whose amplitude, and therefore intensity, varies randomly.

If a photographic plate or another 2-D optical sensor is located within the scattered light field without a lens, a speckle pattern is obtained whose characteristics depend on the geometry of the system and the wavelength of the laser.

If the position of the imaging system is altered, the pattern will gradually change and will eventually be unrelated to the original speckle pattern.

In 1989, speckle interferometry was used to measure a dimension that varied between 498 and main during the rotational period.

In scientific applications, a spatial filter can be used to reduce speckle.

It is called "subjective" because the detailed structure of the speckle pattern depends on the viewing system parameters; for instance, if the size of the lens aperture changes, the size of the speckles change.

Laser speckle on a digital camera image from a green laser pointer.

Objective speckles A photograph of an objective speckle pattern.

Some fundamental properties of speckle.

Speckle contrast reduction in laser projection displays.

The "size" of the speckles is a function of the wavelength of the light, the size of the laser beam which illuminates the first surface, and the distance between this surface and the surface where the speckle pattern is formed.

The speckle pattern in the figure was obtained by pointing a laser beam at the surface of a mobile phone so that the scattered light fell onto an adjacent wall.