| Stokes lens | |
|---|---|
| Synonyms | Stokes' lens |
| Test of | Astigmatism |
Stokes lens also known as variable power cross cylinder lens[1] is a lens used to diagnose a type of refractive error known as astigmatism.
Lens design[edit]
The Stokes lens also known as variable power cross cylinder lens, in its standard version, is a lens combination consisted of equal but opposite (one plano-convex and other plano-concave) power cylindrical lenses attached together in a way so that the lenses be rotated in opposite directions.[2][3] When the axes are parallel, the two powers cancel each other out to achieve the resulting power zero; When the axes are vertical, a sphero-cylindrical lens with maximum power is obtained.[3]
Uses[edit]
Stokes lens is a lens used to diagnose and measure astigmatism.[4][5]
Adaptations[edit]
American ophthalmologist Edward Jackson revised the Stokes lens concept and made a cross cylinder lens to refine power and axis of astigmatism.[2] This lens combination is known as Jackson cross cylinder.[2] Based on the Stokes lens, James P. Foley and Charles E. Campbell made a variable power astigmatic lens which is combination of two identical cylindrical powers instead of equal and opposite powers.[2][6]
History[edit]
In 1837, English mathematician and astronomer George Biddell Airy invented the cylindric lens and used it to correct astigmatism.[3] Irish English physicist and mathematician George Stokes invented Stokes lens in 1849.[3]
References[edit]
- ^ Ferrer-Altabás, Sara; Micó, Vicente (10 April 2020). "Characterization of a compact low-cost Stokes lens for astigmatism compensation in optical instruments". Applied Optics. 59 (11): 3347–3352. Bibcode:2020ApOpt..59.3347F. doi:10.1364/AO.386247. ISSN 2155-3165. PMID 32400444. S2CID 216493169.
- ^ a b c d Ferrer-Altabás, Sara; Thibos, Larry; Micó, Vicente (14 March 2022). "Astigmatic Stokes lens revisited". Optics Express. 30 (6): 8974–8990. Bibcode:2022OExpr..30.8974F. doi:10.1364/OE.450062. ISSN 1094-4087. PMID 35299337. S2CID 245785084.
- ^ a b c d Wunsh, Stuart E. (10 July 2016). "The Cross Cylinder". Ento Key.
- ^ "Stokes lens". TheFreeDictionary.com.
- ^ Dennett, WS (1885). "The Stokes' Lens for Measuring Astigmatism". Transactions of the American Ophthalmological Society. 4: 106–10. PMC 1326669. PMID 25258975.
- ^ Foley, James; Campbell, Charles (1999-10-01). "An Optical Device with Variable Astigmatic Power". Optometry and Vision Science. 76 (9): 664–7. doi:10.1097/00006324-199909000-00025. PMID 10498009.