A focal cloud is the collection of focal points of any imperfect lens, whether optical, electrostatic or electromagnetic. This includes Parabolic antennas and lens-type reflective antennas of all kinds. The effect is analogous to the circle of confusion in photography.
In this focal cloud illustration, a perfect reflector would focus all beams into the blue spot. Due to imperfections of lens construction, the actual signal beams follow the red path to several different focal points, which form the focal cloud. Lens-reflector artifacts, geometry and other imperfections determine the actual radius of the focal cloud.
Read more about Focal Cloud: Satellite Dish Effects
Famous quotes containing the word cloud:
“Genius detects through the fly, through the caterpillar, through the grub, through the egg, the constant individual; through countless individuals the fixed species; through many species the genus; through all genera the steadfast type; through all the kingdoms of organized life the eternal unity. Nature is a mutable cloud which is always and never the same.”
—Ralph Waldo Emerson (1803–1882)