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Browse Prior Art Database

TECHNIQUE FOR VARYING FOCAL LENGTH OF A LENS

IP.com Disclosure Number: IPCOM000023183D
Original Publication Date: 1976-Dec-31
Included in the Prior Art Database: 2004-Mar-27
Document File: 2 page(s) / 234K

Publishing Venue

Xerox Disclosure Journal

Abstract

The focal length of a compound lens is a function of several parameters, including the refractive index of the inter~lens media. The lens focal length can be changed by varying the refractive index of the medium between the lenses, which is temperature and pressure dependant in accordance with the

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Page 1 of 2

XEROX DISCLOSURE JOURNAL

TECHNiQUE FOR VARYING
FOCAL LENGTH OF A LENS
J. D. Rees

Proposed Classification
tJ,S, Cl. 350/180

mt. Cl. G02b 1/06

The focal length of a compound lens is a function of several
parameters, including the refractive index of the inter~lens media. The lens focal length can be changed by varying the
refractive index of the medium between the lenses, which is
temperature and pressure dependant in accordance with the
following relationship: ~ - 1 = no - 1 ~
wherein: 1 +O(t 760

        = index of refraction of gas at given
p temperature and pressure
no = index of refraction of gas at 0°Cand

760mm Hg

t = temperature in °C

= coefficient of thermal expansion of gas

p = pressure of gas in mm Hg

1,oo~

1.oo~

n~LO2 p~i5atm

6

/4

Volume 1 Numbers 11/12 November/December 1976 61

= number of atmospheres pressure

  p 760

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Page 2 of 2

TECHNIQUE FOR VARYING FOCAL LENGTH OF A LENS (Contd)
The resulting ~ n is then corelated to L~f by known optical
design methods. Focal length and magnification in an optical
system are related by the following equation:

          TC = [f + f/rn] + {f + fm] (thin lens approximation)
wherein:

TC = Total Conjugate

                        = lens focal length
m = magnification
[f + f/rn] = object conjugate
{f + frn] = image conjugate

62 XEROX DISCLOSURE J~JRNAL

Volume 1 Numbers 11/12 November/December 1976

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