### point-spread function

**(PSF)**
(function describing an optical system's response to a point of light)

A **point-spread function** (**PSF**) is a description of the
response of an optical system (such as a telescope) to
incoming light from a point, consisting of a mathematical
function describing the light-pattern expected on the focal plane.
An example would be a function that describes an Airy disk.

There are theories associating specific mathematical
functions to particular aperture shapes (e.g., rectangles, slits, circles)
and sizes.

**PSF subtraction** (for **point spread function subtraction**)
is post-processing designed to sharpen images.
Airy disks from images of lone stars taken with the same
instrument are then used to help sort out the images of the
stars with overlapping Airy disks.

(*telescopes,optics,function*)
**Further reading:**

http://en.wikipedia.org/wiki/Point_spread_function

http://www.stsci.edu/itt/review/dhb_v4/NICMOS/nic_ch56.html

**Referenced by pages:**

PSF fitting

speckle suppression

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