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CONVERTER MEANS FOR VARYING FOCAL LENGTH

IP.com Disclosure Number: IPCOM000024209D
Original Publication Date: 1979-Dec-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 2 page(s) / 79K

Publishing Venue

Xerox Disclosure Journal

Abstract

Reflective lenses (half lenses) are not satisfactory for use with add on elements to change focal lengths. In systems where half the lenses were used for reduction, the method often adopted was to vary the conjugate to obtain the correct optical path. This results in longer path lengths and requires moving several mirrors as well as moving the lens.

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3EROX DISCLOSURE JOURNAL

CONVERTER MEANS FOR VARYING FOCAL LENGTH
David K. Shogrcn

Proposed Classification

U.S. Cl. 355/8

Int. C1. G03g 15/28

Volume 4 Number 6 November/December 1979 789

[This page contains 1 picture or other non-text object]

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CONVERTER MEANS FOR VARYING FOCAL LENGTH (Cont'd)

Reflective lenses (half lenses) are not satisfactory for use with add on elements to change focal lengths. In systems where half the lenses were used for reduction, the method often adopted was to vary the conjugate to obtain the correct optical path. This results in longer path lengths and requires moving several mirrors as well as moving the lens.

Referring to Figure 1, a conventional half lens scanning system is illustrated. Shown in dashed lines are two additional elements. In particular, a second half lens 1 is mounted integral with the first or 1X lens, and an auxiliary mirror 2 is provided.

When the system is set for reduction, the lens is moved to a new position (Figure 2). When the lens is moved, the auxiliary mirror 2 is moved into place where the plane of the lens mirror originally was positioned and the lens mirror 3 is removed from the lens. In this configuration the sum of the powers of the two halves of the lens is less than twice the power of the first. This is given by the relationship (to the first order)

ff

fl-fT

l/f2 = (1 -d ) ( T 1).

3 -

where d is the separation between lenses; f is the focal length of the original half lens; and fT is the ne...