Lenses with distortion

Claim 2

An objective lens which introduces barrel distortion at the edges of its field of view, the lens comprising a front part of positive power consisting of at least one positive lens element, a middle part of negative power consisting of at least two lens elements, one of which is of negative power and of a dispersive material and the other of which is of positive power but less powerful and of a less dispersive material than the negative power element, a back part of positive power and consisting of at least two components of positive power and with front convex surfaces, at least one of the components being a doublet which corrects residual lateral chromatic aberration, and a field-flattening element of negative power, wherein the middle part of negative power corrects residual spherical aberration of the front and back positive parts and lowers the residual Petzval sum which is further reduced by the negative field-flattening element, and wherein the front convex surfaces of the components of the back part of positive power contribute to barrel distortion.

Claim 3

A lens according to claim 1 wherein the front part consists of a single positive lens element.

Claim 4

A lens according to claim 1 wherein the front part consists of a plurality of lens elements.

Claim 5

A lens according to claim 3 wherein the front part includes a doublet having a positive element with a refractive index at least as high as that of a negative element to which it is cemented.

Claim 6

A lens according to claim 1 wherein the middle negative part consists of a powerful negative element made of a dispersive flint glass type and a weaker positive element made of a less dispersive crown glass type.

Claim 7

A lens according to claim 1 wherein at least one of the front convex surfaces of the components of the back part which contributes to barrel distortion has a radius of curvature less than the focal length of the complete lens.

Claim 8

A lens according to claim 1 wherein the air gap between the middle and back parts of the lens is the largest air gap in the lens.

Claim 9

A lens according to claim 7 wherein the air gap between the middle and back parts of the lens is about three quarters of the focal length of the complete lens.

Claim 10

A lens according to claim 1 wherein the focal length of the front part is in the range +1.4F to +2.3F; the focal length of the middle part is in the range -1.4F to -8F; the focal length of the back part is in the range +0.7F to +0.9F; and the field-flattening element has a focal length in the range -0.7F to -3F (where F is the focal length of the complete lens).

Claim 11

A lens according to claim 1 incorporating a prism to bend the light path through the lens.

Claim 12

A lens according to claim 10 wherein the prism is interposed between the front and middle parts of the lens.

Claim 13

A lens according to claim 10 wherein the prism is interposed between the back part and the field-flattening element.

Claim 14

An objective lens which introduces barrel distortion at the edges of its field of view having axially spaced components comprising from front to back in the order given a positive singlet meniscus element convex to the front, a positive doublet comprising a positive convex-plano element cemented to a negative plano-concave element, the refractive index of the positive element in the positive doublet being at least as high as that of the negative element, a negative doublet comprising a negative bi-concave element cemented to a positive bi-convex element, the positive element in the negative doublet being less powerful and of a less dispersive material than the negative element, a further positive singlet meniscus element convex to the front, a further positive doublet comprising a positive bi-convex element cemented to a negative bi-concave element, and a negative singlet concave-plano field flattening element, wherein said negative doublet corrects residual spherical aberration of the positive components of the lens and lowers the residual Petzval sum which is further reduced by said negative field flattening element, said further positive doublet corrects residual lateral chromatic aberration, and the front convex surfaces of said further positive singlet meniscus element and said further positive doublet contribute to barrel distortion.

Claim 15

An objective lens which introduces barrel distortion at the edges of its field of view having axially spaced components comprising from front to back in the order given a positive singlet meniscus element convex to the front, a positive doublet comprising a positive convex-plano element cemented to a negative plano-concave element, the refractive index of the positive element in the positive doublet being at least as high as that of the negative element, a negative doublet comprising a negative bi-concave element cemented to a positive bi-convex element, the positive element in the negative doublet being less powerful and of a less dispersive material than the negative element, a further positive singlet meniscus element convex to the front, a further positive doublet comprising a positive bi-convex element cemented to a negative bi-concave element, and a negative singlet concave-plano field flattening element, wherein said negative doublet corrects residual spherical aberration of the positive components of the lens and lowers the residual Petzval sum which is further reduced by said negative field flattening element, said further positive doublet corrects residual lateral chromatic aberration, and the front convex surfaces of said further positive singlet meniscus element and said further positive doublet contribute to barrel distortion.

Claim 16

A lens according to claim 13 wherein the refractive indices (Nd) and Abbe numbers (Vd) of the elements, identified as 1 to 9, and the radii of curvature of and spacings between successive surfaces, identified as R1 to R15, are substantially in accordance with the following table: ______________________________________ Con- Axial strin- Sur- Radius of Thickness/ Refractive gence Element face Curvature Separation Index Nd Vd ______________________________________ R1 +186.739 1 2.374 1.788309 47.39 R2 +730.801 0.990 R3 +112.084 2 21.778 1.788309 47.39 R4 PLANO 3 6.827 1.698951 30.07 R5 +103.252 24.252 R6 -117.029 4 6.480 1.748400 27.71 R7 +242.508 5 18.808 1.788309 47.39 R8 -177.686 21.782 R9 +72.840 6 17.224 1.69734 56.19 R10 +377.704 22.563 R11 +79.802 7 20.491 1.69734 56.19 R12 -79.802 8 5.400 1.698951 30.07 R13 +202.900 11.047 R14 -66.238 9 4.356 1.805182 25.43 R15 PLANO 2.792 ______________________________________ Focal length F=100

Claim 17

Aperture F/0.8 Field of View 40 degrees Barrel Distortion 3.8% Stop position 13.66 behind R5.

Claim 18

Aperture F/0.8 Field of View 40 degrees Barrel Distortion 3.8% Stop position 13.66 behind R5.

Claim 19

An objective lens which introduces barrel distortion at the edges of its field of view having axially spaced components comprising from front to back in the order given, a positive singlet meniscus element convex to the front, a positive doublet comprising a positive bi-convex element cemented to a negative bi-concave element, the positive element in the positive doublet having a refractive index at least as high as that of the negative element, a negative singlet bi-concave element, a positive singlet bi-convex element which is less powerful and of a less dispersive material than said negative singlet bi-concave element, two positive doublets each comprising a positive bi-convex element cemented to a negative meniscus element concave to the front, and a negative singlet concave-plano field flattening element, wherein said negative singlet bi-concave element and said positive singlet bi-convex element are in combination of negative power and correct residual spherical aberration of the positive components of the lens and lower the residual Petzval sum which is further reduced by said negative field flattening element, said two positive doublets correct residual lateral chromatic aberration, and the front convex surfaces of said two positive doublets contribute to barrel distortion.

Claim 20

An objective lens which introduces barrel distortion at the edges of its field of view having axially spaced components comprising from front to back in the order given, a positive singlet meniscus element convex to the front, a positive doublet comprising a positive bi-convex element cemented to a negative bi-concave element, the positive element in the positive doublet having a refractive index at least as high as that of the negative element, a negative singlet bi-concave element, a positive singlet bi-convex element which is less powerful and of a less dispersive material than said negative singlet bi-concave element, two positive doublets each comprising a positive bi-convex element cemented to a negative meniscus element concave to the front, and a negative singlet concave-plano field flattening element, wherein said negative singlet bi-concave element and said positive singlet bi-convex element are in combination of negative power and correct residual spherical aberration of the positive components of the lens and lower the residual Petzval sum which is further reduced by said negative field flattening element, said two positive doublets correct residual lateral chromatic aberration, and the front convex surfaces of said two positive doublets contribute to barrel distortion.

Claim 21

A lens according to claim 15 wherein the refractive indices (Nd) and Abbe numbers (Vd) of the elements, identified as 10 to 19, and the radii of curvature of and spacings between successive surfaces, identified as R1 to R17, are substantially in accordance with the following table: ______________________________________ Con- Axial strin- Sur- Radius of Thickness/ Refractive gence Element face Curvature Separation Index Nd Vd ______________________________________ R1 +164.764 10 11.500 1.784272 41.30 R2 +426.423 0.500 R3 +124.141 11 22.440 1.788309 47.39 R4 -238.359 12 5.880 1.698951 30.07 R5 +215.330 16.648 R6 -173.697 13 6.255 1.647689 33.85 R7 +84.938 11.559 R8 +135.873 14 13.183 1.696800 56.18 R9 -413.673 14.164 R10 +104.714 15 28.610 1.696800 56.18 R11 -180.357 16 5.004 1.584064 37.04 R12 -582.824 0.500 R13 +195.284 17 32.537 1.696800 56.18 R14 -70.124 18 5.004 1.698951 30.07 R15 -391.939 17.069 R16 -77.911 19 4.003 1.917613 21.51 R17 +667.205 3.729 ______________________________________ Focal length F=100 Aperture F/1.0 Field of View 50 degrees Barrel Distortion 5.7% Stop position 12.65 behind R5.

Claim 22

An objective lens which introduces barrel distortion at the edges of its field of view having axially spaced components comprising from front to back in the order given, a positive singlet meniscus element convex to the front, a negative singlet bi-concave element, a positive singlet plano-convex element which is less powerful and of a less dispersive material than said negative singlet bi-concave element, a further positive singlet meniscus element convex to the front, a positive doublet comprising a positive bi-convex element cemented to a negative bi-concave element, and a negative singlet bi-concave field-flattening element, wherein said negative singlet bi-concave element and said positive singlet plano-convex element are in combination of negative power and correct residual spherical aberration of the positive components of the lens and lower the residual Petzval sum which is further reduced by said negative field-flattening element, said positive doublet corrects residual lateral chromatic aberration, and the front convex surfaces of said further positive singlet meniscus element and said positive doublet contribute to barrel distortion.

Claim 23

An objective lens which introduces barrel distortion at the edges of its field of view having axially spaced components comprising from front to back in the order given, a positive singlet meniscus element convex to the front, a negative singlet bi-concave element, a positive singlet plano-convex element which is less powerful and of a less dispersive material than said negative singlet bi-concave element, a further positive singlet meniscus element convex to the front, a positive doublet comprising a positive bi-convex element cemented to a negative bi-concave element, and a negative singlet bi-concave field-flattening element, wherein said negative singlet bi-concave element and said positive singlet plano-convex element are in combination of negative power and correct residual spherical aberration of the positive components of the lens and lower the residual Petzval sum which is further reduced by said negative field-flattening element, said positive doublet corrects residual lateral chromatic aberration, and the front convex surfaces of said further positive singlet meniscus element and said positive doublet contribute to barrel distortion.

Claim 24

A lens according to claim 17 further comprising a prism element and a filter disposed between said positive singlet meniscus element and said negative singlet bi-concave element, wherein the refractive indices (Nd) and Abbe numbers (Vd) of the elements, identified as 20 to 28, and the radii of curvature of and spacings between successive surfaces, identified as R1 to R17, are substantially in accordance with the following table: ______________________________________ Con- Axial strin- Sur- Radius of Thickness/ Refractive gence Element face Curvature Separation Index Nd Vd ______________________________________ R1 +84.656 20 8.738 1.788309 47.39 R2 +237.497 3.280 R3 PLANO 21 67.327 1.805182 25.43 R4 PLANO 4.318 R5 PLANO 22 2.927 1.516800 64.17 R6 PLANO 4.463 R7 -106.926 23 3.615 1.805182 25.43 R8 +138.238 8.599 R9 PLANO 24 7.201 1.689002 49.48 R10 -103.696 0.366 R11 +67.010 25 10.787 1.620411 60.33 R12 +304.786 19.398 R13 +64.840 26 28.629 1.620411 60.33 R14 -64.840 27 3.659 1.647689 33.85 R15 +199.056 17.247 R16 -99.945 28 2.883 1.698951 30.07 R17 +195.763 4.806* ______________________________________ *For object distance of 32,465 Focal length F=100 Aperture F/1.42 Field of View 50 degrees Barrel Distortion 21.7% Stop position 1.56 behind R6.

Claim 25

An objective lens which introduces barrel distortion at the edges of its field of view having axially spaced components comprising from front to back in the order given, a positive singlet meniscus element convex to the front, a negative singlet bi-concave element, a positive singlet bi-convex element which is less powerful and of a less dispersive material than said negative singlet bi-concave element, a further positive singlet bi-convex element, a positive doublet comprising a positive bi-convex element cemented to a negative bi-concave element, and a negative singlet meniscus field-flattening element convex to the front, wherein said negative singlet bi-concave element and said positive singlet bi-convex element are in combination of negative power and correct residual spherical aberration of the positive components of the lens and lower the residual Petzval sum which is further reduced by said negative field-flattening element, said positive doublet corrects residual lateral chromatic aberration, and the front convex surfaces of said further positive singlet bi-convex element and said positive doublet contribute to barrel distortion.

Claim 26

An objective lens which introduces barrel distortion at the edges of its field of view having axially spaced components comprising from front to back in the order given, a positive singlet meniscus element convex to the front, a negative singlet bi-concave element, a positive singlet bi-convex element which is less powerful and of a less dispersive material than said negative singlet bi-concave element, a further positive singlet bi-convex element, a positive doublet comprising a positive bi-convex element cemented to a negative bi-concave element, and a negative singlet meniscus field-flattening element convex to the front, wherein said negative singlet bi-concave element and said positive singlet bi-convex element are in combination of negative power and correct residual spherical aberration of the positive components of the lens and lower the residual Petzval sum which is further reduced by said negative field-flattening element, said positive doublet corrects residual lateral chromatic aberration, and the front convex surfaces of said further positive singlet bi-convex element and said positive doublet contribute to barrel distortion.

Claim 27

A lens according to claim 19 further comprising a prism element disposed between said positive doublet and said field-flattening element, wherein the refractive indices (Nd) and Abbe numbers (Vd) of the elements, identified as 30 to 37, and the radii of curvature of and spacings between successive surfaces, identified as R1 to R15, are substantially in accordance with the following table: ______________________________________ Con- Axial strin- Sur- Radius of Thickness/ Refractive gence Element face Curvature Separation Index Nd Vd ______________________________________ R1 +70.271 30 14.684 1.748400 27.71 R2 +116.870 37.968 R3 -133.776 31 5.130 1.748400 27.71 R4 +106.926 5.990 R5 +1566.026 32 9.584 1.517421 52.20 R6 -108.898 75.260 R7 +158.527 33 12.472 1.788309 47.39 R8 -1431.138 5.775 R9 +76.027 34 32.777 1.788309 47.39 R10 -102.083 35 4.208 1.805182 25.43 R11 +231.409 5.990 R12 PLANO 36 56.891 1.805182 25.43 R13 PLANO 0.737 R14 +79.992 37 5.775 1.62049 36.24 R15 +53.640 8.885 ______________________________________ Focal length=100 Aperture F/1.40 Field of View 40 degrees Barrel Distortion 25.6% Stop position 5.5 behind R6.