Ophthalmic lenses : dioptric formulae for combined cylindrical lenses, the prism-dioptry and other optical papers / by Charles F. Prentice.

  • Prentice, Charles F. (Charles Frederick), 1854-
Date:
1907
Catalogue details

Licence: In copyright

Credit: Ophthalmic lenses : dioptric formulae for combined cylindrical lenses, the prism-dioptry and other optical papers / by Charles F. Prentice. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    by parallelism of ZXMX and cxox; and, for similar reasons, < K = ZV.C, = 13. DXZX : Z,^/, = sin « : sin /?, Z^/, = A Fj. . \ DXZX: D1Vl — sin a : sin /?.(2) In the oblique plane DD.L F, we find A Vx : D2V2= DDx : DD2 ; or, as Z?A and Z>A are the focal distances fx and f2 of the cylinders C and c, respectively, D^-.D.V, =/,:/,.(3) Multiplying the equations (2) and (3), we obtain A A = sin^ A . (4) A F2 sin p fa Since Dlol is the radius of the circle indicated, we may, for convenience, ascribe to it the value 1. We shall then have AZi = sin <£ DxoxZv < A*iZi = A>iZi ~ < DxoxCv <£ DxoxZx = 90° — /J. Azi = s^n (90° — A) — cos z5* • • • C^) In the plane A we similarly find A F2 = sin <£ A^2 Z2) < A*« A = < — < A<w <A^A = 90°-«. . *. A F2 = sin (90°— «) = cos «. (6)