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{{ExpPsy}}
 
{{ExpPsy}}
'''Purkinje images''' are [[reflection]]s of objects from structure of the [[eye]]. They are also know as [[Purkinje reflexes]] and as [[Purkinje-Sanson images]]. There are at least four Purkinje images that are visible on looking at an eye. The [[first Purkinje image]] (P1) is the reflection from the outer surface of the [[cornea]]. The [[second Purkinje image]] (P2) is the reflection from the inner surface of the cornea. The [[third Purkinje image]] (P3) is the reflection from the outer (anterior) surface of the [[lens]]. The [[fourth Purkinje image]] (P4) is the reflection from the inner (posterior) surface of the lens. Unlike the others, P4 is an inverted image.
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'''Purkinje images''' are [[Reflection (physics)|reflection]]s of objects from structure of the [[eye]]. They are also known as Purkinje reflexes and as Purkinje-Sanson images. There are at least four Purkinje images that are visible on looking at an eye. The [[first Purkinje image]] (P1) is the reflection from the outer surface of the [[cornea]]. The [[second Purkinje image]] (P2) is the reflection from the inner surface of the cornea. The [[third Purkinje image]] (P3) is the reflection from the outer (anterior) surface of the [[lens (anatomy)|lens]]. The [[fourth Purkinje image]] (P4) is the reflection from the inner (posterior) surface of the lens. Unlike the others, P4 is an inverted image.
   
 
Purkinje-Sanson images are named after [[Czech people|Czech]] [[anatomist]] [[Jan Evangelista Purkyně]] (1787-1869) and after [[French people|French]] [[physician]] [[Louis Joseph Sanson]] (1790-1841).
 
Purkinje-Sanson images are named after [[Czech people|Czech]] [[anatomist]] [[Jan Evangelista Purkyně]] (1787-1869) and after [[French people|French]] [[physician]] [[Louis Joseph Sanson]] (1790-1841).
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The first and fourth Purkinje images are used by some [[eye tracker]]s, devices to measure the position of an eye.
 
The first and fourth Purkinje images are used by some [[eye tracker]]s, devices to measure the position of an eye.
   
==See also==
 
   
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== Brightness of Purkinje Images ==
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The brightness of the Purkinje images can be determined using Fresnel's equation where the
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<math>Intensity (Brightness)= (n'-n)^2/(n'+n)^2</math>
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Purkinje image I is the brightest of the four then PII, PIII and PIV (III and IV have about the same brightness).
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The Purkinje images can be used to assess the curvatures and separations of the surfaces in the eye.
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==See also==
 
*[[Red-eye effect]]
 
*[[Red-eye effect]]
   
 
==External links==
 
==External links==
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*[http://www.diku.dk/~panic/eyegaze/node9.html Explanation of using purkinje images for eye tracking.]
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{{Visual phenomena}}
   
*Explanation of using purkinje images for eye tracking (http://www.diku.dk/~panic/eyegaze/node9.html).
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[[Category:Optics]]
   
[[Category:Vision]]
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{{enWP|Purkinje images}}
 
{{enWP|Purkinje images}}

Latest revision as of 08:26, December 31, 2009

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Purkinje images are reflections of objects from structure of the eye. They are also known as Purkinje reflexes and as Purkinje-Sanson images. There are at least four Purkinje images that are visible on looking at an eye. The first Purkinje image (P1) is the reflection from the outer surface of the cornea. The second Purkinje image (P2) is the reflection from the inner surface of the cornea. The third Purkinje image (P3) is the reflection from the outer (anterior) surface of the lens. The fourth Purkinje image (P4) is the reflection from the inner (posterior) surface of the lens. Unlike the others, P4 is an inverted image.

Purkinje-Sanson images are named after Czech anatomist Jan Evangelista Purkyně (1787-1869) and after French physician Louis Joseph Sanson (1790-1841).

The third and fourth Purkinje images can be visible from within the eye itself. Light reflected away from the surfaces of the lens can in turn reflect back into the eye from the rear surface of the cornea. These images are, therefore, entoptic phenomena.

The first and fourth Purkinje images are used by some eye trackers, devices to measure the position of an eye.


Brightness of Purkinje Images Edit

The brightness of the Purkinje images can be determined using Fresnel's equation where the Intensity (Brightness)= (n'-n)^2/(n'+n)^2 Purkinje image I is the brightest of the four then PII, PIII and PIV (III and IV have about the same brightness). The Purkinje images can be used to assess the curvatures and separations of the surfaces in the eye.

See alsoEdit

External linksEdit

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