GB1386175A - Lenses - Google Patents

Abstract

1386175 Zoom lenses RANK ORGANISATION Ltd 31 May 1973 [2 June 1972] 25792/72 Heading G2J A copying lens of continuously variable magnification, with constant image plane for a stationary object, comprises a convergent inner member 30 having a plurality of components forming on at least approximately symmetrical arrangement about a central component or central air space, and two substantially similar divergent members 40, 40a symmetrically arranged with respect to the inner member 30 respectively to the front and to the rear thereof, the complete system being movable along the optical axis in conjunction with equal and opposite displacement of the outer members 40, 40a relative to the inner member 30 in order to vary the magnification of the system, the outer members 40, 40a moving outwardly to reduce the magnification and inwardly to increase it, the inner member 30 having parameters selected substantially to balance aberration residuals of the outer members in all relative positions in the range of movements. Optical data are given for the example shown in Figure 2. In another example Figure 1, (not shown) the inner member consists of two singlet and two doublet meniscus components symmetrically arranged with respect to a diaphragm, and concave to it; the outer members are negative singlets or negative doublets (cemented or air spaced.)