Original Research

Thin lenses of asymmetric power

W. F. Harris, R. D. van Gool
African Vision and Eye Health | South African Optometrist: Vol 68, No 2 | a154 | DOI: https://doi.org/10.4102/aveh.v68i2.154 | © 2009 W. F. Harris, R. D. van Gool | This work is licensed under CC Attribution 4.0
Submitted: 13 December 2009 | Published: 13 December 2009

About the author(s)

W. F. Harris, PhD(Minnesota), South Africa
R. D. van Gool, DPhil(RAU), South Africa

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Abstract

It is generally supposed that thin systems, including refracting surfaces and thin lenses, have powers that are necessarily symmetric.  In other words they have powers which can be represented assymmetric dioptric power matrices and in the familar spherocylindrical form used in optometry and ophthalmology.  This paper shows that this is not correct and that it is indeed possible for a thin system to have a power that is not symmetric and which cannot be expressed in spherocylindrical form.  Thin systems of asymmetric power are illustratedby means of a thin lens that is modelled with small prisms and is chosen to have a dioptric power ma-trix that is antisymmetric.  Similar models can be devised for a thin system whose dioptric power matrix is any  2 2 ×  matrix.  Thus any power, symmetric, asymmetric or antisymmetric, is possible for a
thin system.  In this sense our understanding of the power of thin systems is now complete.


Keywords

dioptric power matrix; symmetric power; asymmetric power; antisymmetric power; prism

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