In
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing '' signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...
, the term multiplicative noise refers to an
unwanted random signal that gets multiplied into some relevant
signal
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...
during capture, transmission, or other processing.
An important example is the
speckle noise commonly observed in
radar
Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
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 blind
A window blind is a type of window covering. There are many different kinds of window blinds which use a variety of control systems. A typical window blind is made up of several long horizontal or vertical slats of various types of hard mate ...
s, dark spots caused by dust in the lens or image sensor, and variations in the gain of individual elements of the
image sensor
An image sensor or imager is a sensor that detects and conveys information used to make an image. It does so by converting the variable attenuation of light waves (as they pass through or reflect off objects) into signals, small bursts of c ...
array.
[
Maria Petrou, Costas Petrou (2010]
Image Processing: The Fundamentals
John Wiley & Sons. 818 pages.
References
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Signal processing