Occurrence
A familiar example is the random pattern created when a laser beam is scattered off a rough surface – see picture. A less familiar example of speckle is the highly magnified image of a star through imperfect optics or through the atmosphere (see speckle imaging). A speckle pattern can also be seen when sunlight is scattered by a fingernail.
The speckle effect is observed when radio waves are scattered from rough surfaces such as ground or sea, and can also be found in ultrasonic imaging. In the output of a multi-mode optical fiber, a speckle pattern results from a superposition of mode field patterns. If the relative modal group velocities change with time, the speckle pattern will also change with time. If differential mode attenuation occurs, modal noise results.
Read more about this topic: Speckle Pattern
Famous quotes containing the word occurrence:
“One is absolutely sickened, not by the crimes that the wicked have committed, but by the punishments that the good have inflicted; and a community is infinitely more brutalised by the habitual employment of punishment than it is by the occasional occurrence of crime.”
—Oscar Wilde (1854–1900)