Variable magnification lens system for finite conjugate distances

Claim 2

A variable magnification lens system for operation at relatively close conjugate distances comprising six lens elements, all air spaced, arranged symmetrically, elements 1 and 6 (as numbered consecutiveLy from front to rear) having positive power, elements 2 and 5 having negative power, the central elements 3 and 4 having positive power and being at a fixed axial distance from each other, characterized by the fact that said system is movable as a unit between fixed object and image planes, while elements 1 and 6 are simultaneously movable away from each other through equal distances to vary the magnification, such movement introducing curvature of field in one direction, and while elements 2 and 5 are simultaneously movable toward each other through equal distances to vary the magnification, such movement introducing curvature of field in an opposite direction, the curvature produced by movement of elements 1 and 6 being approximately compensated by the curvature produced by movement of elements 2 and 5.

Claim 3

A lens system as defined in claim 1, wherein elements 1 and 6 are plano-convex elements with their convex surfaces faced outwardly away from each other, and elements 2 and 5 are plano-concave elements with their concave surfaces faced inwardly toward each other.

Claim 4

A lens system as defined in claim 2, wherein elements 3 and 4 are meniscus elements with concave surfaces faced inwardly toward each other.

Claim 5

A lens system as defined in claim 1, wherein the axial distance of movement of elements 1 and 6, for producing any given change in magnification, is greater than the axial distance of movement of elements 2 and 5, for producing the same change in magnification.

Claim 6

A lens system as defined in claim 4, wherein the ratio of the axial movement of elements 1 and 6 to the axial movement of elements 2 and 5 is within the limits of 1.1:1 and 1.5:1.

Claim 7

A lens system as defined in claim 1, wherein the ratio of the axial movement of elements 1 and 6 to the axial movement of elements 2 and 5 is a linear ratio.

Claim 8

A lens system as defined in claim 1, wherein ratio of the axial movement of elements 1 and 6 to the axial movement of elements 2 and 5 is a non-linear ratio.

Claim 9

A lens system as defined in claim 1, wherein the powers of the respective lens elements are so chosen and the axial movements of the elements relative to each other for varying the magnification are so chosen that the total distance from an object to an image thereof formed by said lens system is substantially constant at all magnifications within the range of magnification variation.

Claim 10

A lens system as defined in claim 8, wherein said range of magnification variation is substantially 0.57X to 1.754X.

Claim 11

A lens system as defined in claim 9, wherein the conjugate distance from the lens system to the object and also to the image is not more than six times the equivalent focal length of the system.

Claim 12

A variable magnification lens system consisting essentially of six lens elements, all air spaced, arranged symmetrically, the characteristics of the elements and their spatial relationship to each other being substantially in the proportions indicated by the data in the following table: Lens ND V Radii Thicknesses R1 + 67.40 1 1.62032 60.3 T1 21.90 R2 Alpha S1 varies R3 Alpha 2 1.54873 45.4 T2 8.15 R4 + 48.84 S2 varies R5 + 76.60 3 1.62032 60.3 T3 7.50 R6 +121.43 S3 21.31 R7 -121.43 4 1.62032 60.3 T4 7.50 R8 - 76.60 S4 varies R9 - 48.84 5 1.54873 45.4 T5 8.15 R10 Alpha S5 varies R11 Alpha 6 1.62032 60.3 T6 21.90 R12 -67.40 wherein the lens elements are numbered in order from front to rear, the refractive indices of the respective elements for the D line of sodium are given in the column headed ND, the corresponding Abbe dispersive indices are given in the column headed V, the respective radii of curvature of the lens surfaces are indicated by R with a subscript numeral identifying the particular lens surface as numbered consecutively from front to rear, the respective axial thicknesses of the lenses are indicated by T with a subscript numeral identifying the particular lens, and the respective axial spaces between lenses are indicated by S with a subscript numeral identifying the particular space as numbered consecutively from front to rear, the linear dimensions of radii, thicknesses, and spacings being expressed proportionately in units of the same length.

Claim 13

A variable magnification lens system consisting essentially of six lens elements, all air spaced, arranged symmetrically, the characteristics of the elements and their spatial relationship to each other being substantially in the proportions indicated by the data in the following table: Lens ND V Radii Thicknesses R1 + 67.40 1 1.62032 60.3 T1 21.90 R2 Alpha S1 varies R3 Alpha 2 1.54873 45.4 T2 8.15 R4 + 48.84 S2 varies R5 + 76.60 3 1.62032 60.3 T3 7.50 R6 +121.43 S3 21.31 R7 -121.43 4 1.62032 60.3 T4 7.50 R8 - 76.60 S4 varies R9 - 48.84 5 1.54873 45.4 T5 8.15 R10 Alpha S5 varies R11 Alpha 6 1.62032 60.3 T6 21.90 R12 -67.40 wherein the lens elements are numbered in order from front to rear, the refractive indices of the respective elements for the D line of sodium are given in the column headed ND, the corresponding Abbe dispersive indices are given in the column headed V, the respective radii of curvature of the lens surfaces are indicated by R with a subscript numeral identifying the particular lens surface as numbered consecutively from front to rear, the respective axial thicknesses of the lenses are indicated by T with a subscript numeral identifying the particular lens, and the respective axial spaces between lenses are indicated by S with a subscript numeral identifying the particular space as numbered consecutively from front to rear, the linear dimensions of radii, thicknesses, and spacings being expressed proportionately in units of the same length.

Claim 14

A lens system as defined in claim 11 wherein, to obtain variation in magnification when the system is used for relatively close conjugate distances, S1 and S5 may be varied from about 0.200 to about 3.064, and S2 and S4 may be varied from about 5.260 to about 3.896, S1 and S5 increasing as S2 and S4 decrease, and vice versa.

Claim 15

A lens system as defined in claim 12 wherein, to obtain variations in magnification, the ratio of the axial movements of lens elements 1 and 6 to the axial movements of elements 2 and 5 is within the limits of 1.1:1 and 1.5:1.

Claim 16

A lens system as defined in claim 13 wherein the axial movements of elements 1 and 6, when varying the magnification from one power to another, are in a linear ratio to the axial movements of elements 2 and 5.

Claim 17

A lens system as defined in claim 13 wherein the axial movements of elements 1 and 6, when varying the magnification from one power to another, are in a non-linear ratio to the axial movements of elements 2 and 5.

Claim 18

A lens system as defined in claim 11 wherein, to obtain variation in magnification to the powers indicated in the following table, the spaces S1, S2, S4, and S5 are varied to the proportionate values indicated in the following table: Magnification S1 and S5 S2 and S4 0.65 3.010 3.950 0.70 2.0734 4.3866 0.75 1.4177 4.6923 0.85 0.5747 5.0853 1.0 0.200 5.260 1.175 0.5747 5.0853 1.333 1.4177 4.6923 1.426 2.0734 4.3866 1.539 3.010 3.950

Claim 19

A lens system as defined in claim 16 wherein, for the magnification powers indicated in claim 16, the conjugate distances from the lens system to the object and to the image are adjusted to the proportionate distances indicated in the columns headed L0 and L1, respectively, in the following table: Magnification L0 L1 0.65 561.600 344.100 0.70 543.145 363.5550.75 526.700 380.700 0.85 495.080 413.220 1.0 454.350 454.350 1.175 413.220 495.080 1.333 380.700 526.700 1.426 363.555 543.1451.539 344.100 561.600

Claim 20

A lens system as defined in claim 11 wherein, to obtain variation in magnification to the powers indicated in the following table, the spaces S1, S2, S4, and S5 are varied to the proportionate values indicated in the following table: Magnification S1 and S5 S2 and S4 0.65 3.064 3.896 0.70 2.033 4.427 0.75 1.350 4.760 0.85 0.543 5.117 1.0 0.200 5.260 1.175 0.543 5.117 1.333 1.350 4.760 1.426 2.033 4.427 1.539 3.064 3.896

Claim 21

A lens system as defined in claim 18 wherein, for the magnification powers indicated in claim 18, the conjugate distances from the lens system to the object and to the image are adjusted to the proportionate distances indicated in the columns headed L0 and L1, respectively, in the following table: Magnification L0 L1 0.65 562.58 343.18 0.70 542.30 364.43 0.75 524.79 382.63 0.85 493.43 414.90 1.0 454.35 454.35 1.175 414.90 493.43 1.333 382.63 524.79 1.426 364.43 542.30 1.539 343.18 562.58