Belt friction: Difference between revisions
en>Tapananand No edit summary |
en>Ward20 ce |
||
| Line 1: | Line 1: | ||
[[File:Système afocal téléobjectif.svg|thumb|right|350px|Diagram of the light path in an afocal system.]] | |||
In [[optics]] an '''afocal system''' (a system without focus) is an optical system that produces no net convergence or divergence of the beam, i.e. has an infinite [[effective focal length]].<ref>[http://books.google.com/books?id=4nxMduNT8-gC&pg=PA379&dq=afocal&lr=&cd=14#v=onepage&q=afocal&f=false Daniel Malacara, Zacarias Malacara, Handbook of optical design. Page 379]</ref> This type of system can be created with a pair of optical elements where the distance between the elements is equal to the sum of each element's [[focal length]] (''d'' = ''f''<sub>1</sub>+''f''<sub>2</sub>). A simple example of an afocal optical system is an [[optical telescope]] imaging a star, the light entering the system is at infinity and the image it forms is at infinity (the light is [[collimated]]).<ref>[http://books.google.com/books?id=Jg1JW4kWD1UC&pg=PA38&dq=afocal++without+focus&lr=&cd=5#v=onepage&q=afocal%20%20without%20focus&f=false Virendra N. Mahajan, Ray geometrical optics, page 38]</ref> Although the system does not alter the divergence of a collimated beam, it does alter the width of the beam, increasing [[magnification]]. The magnification of such a telescope is given by | |||
:<math>M = \frac{-f_2}{f_1},</math> | |||
Afocal systems are used in laser optics, [[Infrared]] and [[forward looking infrared]] systems, camera [[zoom lens]]es and telescopic lens attachments such as [[teleside converter]]s,<ref>[http://books.google.com/books?id=hcq_40I_7egC&pg=PA190&dq=early+afocal+photography&lr=&cd=12#v=onepage&q=afocal&f=false Rudolf Kingslake, Optics in photography, page 187]</ref> and photography setups combining cameras and telescopes ([[Afocal photography]]). | |||
==See also== | |||
* [[Lens (optics)]] | |||
* [[Teleside converter]] | |||
==References== | |||
{{reflist}} | |||
[[Category:Optics]] | |||
[[Category:Geometrical optics]] | |||
{{optics-stub}} | |||
Revision as of 15:56, 12 August 2013
In optics an afocal system (a system without focus) is an optical system that produces no net convergence or divergence of the beam, i.e. has an infinite effective focal length.[1] This type of system can be created with a pair of optical elements where the distance between the elements is equal to the sum of each element's focal length (d = f1+f2). A simple example of an afocal optical system is an optical telescope imaging a star, the light entering the system is at infinity and the image it forms is at infinity (the light is collimated).[2] Although the system does not alter the divergence of a collimated beam, it does alter the width of the beam, increasing magnification. The magnification of such a telescope is given by
Afocal systems are used in laser optics, Infrared and forward looking infrared systems, camera zoom lenses and telescopic lens attachments such as teleside converters,[3] and photography setups combining cameras and telescopes (Afocal photography).
See also
References
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.