Varifocal objective system

Claim 1

AN OPTICAL OBJECTIVE SYSTEM CONSTITUTED BY A FIXEDFOCUS REAR LENS GROUP AND A FORWARD LENS GROUP CONSISTING OF A SUBSTANTIALLY FIXED POSITIVE FIRST COMPONENT, AN AXIALLY MOVABLE NEGATIVE SECOND COMPONENT, AN AXIALLY MOVABLE NEGATIVE THIRD COMPONENT AND A FIXED POSITIVE FOURTH COMPONENT, SAID FIRST COMPONENT CONSISTING OF THREE AIRSPACED POSITIVE LENSES AND A DISPERSIVE FRONT LENS PRECEDING SAID LENSES, SAID SECOND COMPONENT CONSISTING OF TWO AIRSPACED DISPERSIVE LENS MEMBERS, SAID THIRD COMPONENT CONSISTING OF A SINGLE DISPERSIVE LENS MEMBER, SAID FOURTH COMPONENT CONSISTING OF A SINGLE COLLECTIVE LENS MEMBER, SAID SECOND AND THIRD COMPONENTS BEING MOVABLE RELATIVELY TO EACH OTHER AND TO SAID FIRST AND FOURTH COMPONENTS INTO A FIRST POSITION WHEREIN SAID SYSTEM HAS A RELATIVELY SHORT FOCAL LENGTH, AN INTERMEDIATE POSITION WITH AN INTERMEDIATE FOCAL LENGTH AND A THIRD POSITION WITH A RELATIVELY LARGE FOCAL LENGTH, THE FIRST DISPERSIVE LENS MEMBER OF SAID SECOND COMPONENT AND THE DISPERSIVE LENS MEMBER CONSTITUTING SAID THIRD COMPONENT ARE DOUBLETS WITH POSITIVELY REFRACTIVE CEMENTED SURFACES, SAID REAR LENS GROUP CONSISTING OF A FIRST POSITIVE SINGLET, A POSITIVE DOUBLET WITH A NEGATIVELY REFRACTIVE CEMENTED SURFACE, A NEGATIVE SINGLET AND A SECOND POSITIVE SINGLET FOLLOWING ONE ANOTHER IN THE ORDER NAMED, THE CEMENTED SURFACES OF SAID FIRST DISPERSIVE LENS MEMBER, SAID THIRD COMPONENT AND SAID POSITIVE DOUBLET BEING RESPECTIVELY CONCAVE, CONVEX AND CONCAVE AS SEEN FROM THE OBJECT SIDE OF THE SYSTEM, THE NUMERICAL VALUES OF THE RADII OF CURVATURE R1 TO R27 OF SAID DISPERSIVE FRONT LENTS L1, SAID THREE AIR-SPACED POSITIVE LENSES L2, L3, L4, THE FIRST DISPERSIVE LENS MEMBER L5, L6 AND THE SECOND DISPERSIVE LENS MEMBER L7 OF SAID SECOND COMPONENT, SAID THIRD COMPONENT L3, L9, SAID FOURTH COMPONENT L10, SAID FIRST POSITIVE SINGLET L11, SAID POSITIVE DOUBLET L12, L13, SAID NEGATIVE SINGLET L14 AND SAID SECOND POSITIVE SINGLET L15, AND OF THE AXIAL THICKNESSES AND SEPARATIONS D1 TO D26 THEREOF, BASED UPON A NUMERICAL VALUE OF 150 FOR AN INTERMEDIATE OVERALL FOCAL LENGTH OF THE SYSTEM AT SAID INTERMEDIATE POSITION, THE REFRACTICE INDICES ND OF THE LENSES L1 TO L15 AND THEIR ABBE NUMBERS V BEING SUBSTANTIALLY AS GIVEN IN THE FOLLOWING TABLE, WHEREIN D3, D13 AND D16 ARE GIVEN FOR SAID INTERMEDIATE POSITION: