Compact afocal attachment for use with photographic objectives

Claim 2

A substantially afocal lens of Galilean form for use with a following objective lens to increase its focal length, said afocal lens consisting of no more than three lens elements the first of which is a positive meniscus element and the last of which is a negative plastic element spaced behind said positive meniscus element, the ratio of the radius of the front surface of said first positive meniscus element to the axial separation between the first surface of said first meniscus element and the last surface of said negative plastic element being no greater than 1.3 and the angular magnification of said afocal lens being no greater than 1.5.

Claim 3

The magnifying lens of claim 1 wherein the index of refraction of said positive meniscus is in the range from 1.43 to 1.652 and has an Abbe V-value in the range from 50 to 65.

Claim 4

A substantially afocal lens of Galilean form for use with a following objective lens to increase its focal length, said afocal lens consisting essentially of only two elements one of which is a positive meniscus element and the other of which is a negative plastic element air spaced behind said positive meniscus element, the ratio of the radius of the first surface of said positive meniscus element to the axial separation between the first surface of said positive meniscus element and the last surface of said negative plastic element being no more than 1.2 and the angular magnification of said afocal lens being no more than 1.5.

Claim 5

A substantially afocal lens of Galilean form for use with a following objective lens to increase its focal length, said afocal lens consisting essentially of only two elements one of which is a positive meniscus element and the other of which is a negative plastic element air spaced behind said positive meniscus element, the ratio of the radius of the first surface of said positive meniscus element to the axial separation between the first surface of said positive meniscus element and the last surface of said negative plastic element being no more than 1.2 and the angular magnification of said afocal lens being no more than 1.5.

Claim 6

The afocal lens of claim 3 wherein the overall axial length from the first to the last surface of said lens elements is no more than 37 mm.

Claim 7

The afocal lens of claim 3 wherein the index of refraction of said meniscus lens element is in the range from 1.43 to 1.65 and has an Abbe V-value in the range from 50 to 65.

Claim 8

The afocal lens of claim 3 wherein said optical plastic is selected from the group comprising plexiglass, polycarbonate, and polystyrene.

Claim 9

A two element substantially afocal lens for use with an objective of focal length, f o , said afocal lens having constructional data substantially in accordance with the following table: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ 1 .1901 .0850 1.4917 57.2 2 .8579 .0652 3 .5958 .0100 1.592 30.8 4 .1499 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number, and wherein surfaces 2 and 3 are aspheric in shape and have the general formula: ##EQU2## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 2 3 ______________________________________ beta 0.787 × 10.sup.1 -0.388 × 10.sup.1 gamma -0.707 × 10.sup.2 -0.588 × 10.sup.2 delta 0.964 × 10.sup.0 -0.137 × 10.sup.2 epsilon 0.658 × 10.sup.-2 -0.116 × 10.sup.0 zeta 0.000 × 10.sup.0 0.000 × 10.sup.0 ______________________________________

Claim 10

A two element substantially afocal lens for use with an objective of focal length, f o , said afocal lens having constructional data substantially in accordance with the following table: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ 1 .1901 .0850 1.4917 57.2 2 .8579 .0652 3 .5958 .0100 1.592 30.8 4 .1499 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number, and wherein surfaces 2 and 3 are aspheric in shape and have the general formula: ##EQU2## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 2 3 ______________________________________ beta 0.787 × 10.sup.1 -0.388 × 10.sup.1 gamma -0.707 × 10.sup.2 -0.588 × 10.sup.2 delta 0.964 × 10.sup.0 -0.137 × 10.sup.2 epsilon 0.658 × 10.sup.-2 -0.116 × 10.sup.0 zeta 0.000 × 10.sup.0 0.000 × 10.sup.0 ______________________________________

Claim 11

A convertible objective lens comprising a front substantially afocal component consisting of two air spaced elements and a rear component consisting of a single meniscus lens element of unit focal length, f o , said front component being mounted for movement into and out of coaxial alignment with said rear component to in combination therewith provide a system having a focal length greater than that of said rear component used above, said objective lens having the following constitutional data: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ FRONT 1 .1901 .0850 1.4917 57.2 2 .8579 .0652 3 .5958 .0100 1.592 30.8 4 .1499 .0400 REAR 5 .1824 .0306 1.4917 57.2 6 .2739 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number and wherein surfaces 2, 3 and 6 are aspheric in shape and have the general formula: ##EQU3## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 2 3 6 ______________________________________ beta 0.787 × 10.sup.1 -0.388 × 10.sup.1 0.517 × 10.sup.1 gamma -0.707 × 10.sup.2 -0.588 × 10.sup.2 0.151 × 10.sup.3 delta 0.964 × 10.sup.0 -0.137 × 10.sup.2 -0.900 × 10.sup.5 epsilon 0.658 × 10.sup.-2 -0.116 × 10.sup.0 0.838 × 10.sup.7 zeta 0.000 × 10.sup.0 0.000 × 10.sup.0 -0.296 × 10.sup.9 ______________________________________

Claim 12

A convertible objective lens comprising a front substantially afocal component consisting of two air spaced elements and a rear component consisting of a single meniscus lens element of unit focal length, f o , said front component being mounted for movement into and out of coaxial alignment with said rear component to in combination therewith provide a system having a focal length greater than that of said rear component used above, said objective lens having the following constitutional data: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ FRONT 1 .1901 .0850 1.4917 57.2 2 .8579 .0652 3 .5958 .0100 1.592 30.8 4 .1499 .0400 REAR 5 .1824 .0306 1.4917 57.2 6 .2739 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number and wherein surfaces 2, 3 and 6 are aspheric in shape and have the general formula: ##EQU3## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 2 3 6 ______________________________________ beta 0.787 × 10.sup.1 -0.388 × 10.sup.1 0.517 × 10.sup.1 gamma -0.707 × 10.sup.2 -0.588 × 10.sup.2 0.151 × 10.sup.3 delta 0.964 × 10.sup.0 -0.137 × 10.sup.2 -0.900 × 10.sup.5 epsilon 0.658 × 10.sup.-2 -0.116 × 10.sup.0 0.838 × 10.sup.7 zeta 0.000 × 10.sup.0 0.000 × 10.sup.0 -0.296 × 10.sup.9 ______________________________________

Claim 13

A two element substantially afocal lens for use with an objective of focal length, f o , said afocal lens having constructional data substantially in accordance with the following table: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ 1 .2543 .0850 1.652 58.5 2 .9005 .1221 3 1.0230 .0100 1.592 30.8 4 .1635 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number, and wherein surface 3 is aspheric in shape and has the general formula: ##EQU4## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 3 ______________________________________ beta -0.592 × 10.sup.1 gamma -0.594 × 10.sup.2 delta -0.137 × 10.sup.2 epsilon -0.116 × 10.sup.0 zeta 0.000 × 10.sup.0 ______________________________________

Claim 14

A two element substantially afocal lens for use with an objective of focal length, f o , said afocal lens having constructional data substantially in accordance with the following table: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ 1 .2543 .0850 1.652 58.5 2 .9005 .1221 3 1.0230 .0100 1.592 30.8 4 .1635 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number, and wherein surface 3 is aspheric in shape and has the general formula: ##EQU4## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 3 ______________________________________ beta -0.592 × 10.sup.1 gamma -0.594 × 10.sup.2 delta -0.137 × 10.sup.2 epsilon -0.116 × 10.sup.0 zeta 0.000 × 10.sup.0 ______________________________________

Claim 15

A convertible objective lens comprising a front substantially afocal component consisting of two air spaced elements and a rear component consisting of a single meniscus lens element of unit focal length, f o , said front component being mounted for movement into and out of coaxial alignment with said rear component to in combination therewith provide a system whose focal length is larger than that of the rear component by itself, said objective lens having the following constitutional data: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ FRONT 1 .2543 .0850 1.652 58.5 2 .9005 .1221 3 1.0230 .0100 1.592 30.8 4 .1635 .0400 REAR 5 .1824 .0306 1.535 41.5 6 .2739 1.4917 57.2 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number, and wherein surfaces 3 and 6 are aspheric in shape and have the general formula: ##EQU5## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 3 6 ______________________________________ beta -0.592 × 10.sup.1 0.517 × 10.sup.1 gamma -0.594 × 10.sup.2 0.151 × 10.sup.3 delta -0.137 × 10.sup.2 -0.900 × 10.sup.5 epsilon -0.116 × 10.sup.0 0.838 × 10.sup.7 zeta 0.000 × 10.sup.0 -0.296 × 10.sup.9 ______________________________________

Claim 16

A convertible objective lens comprising a front substantially afocal component consisting of two air spaced elements and a rear component consisting of a single meniscus lens element of unit focal length, f o , said front component being mounted for movement into and out of coaxial alignment with said rear component to in combination therewith provide a system whose focal length is larger than that of the rear component by itself, said objective lens having the following constitutional data: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ FRONT 1 .2543 .0850 1.652 58.5 2 .9005 .1221 3 1.0230 .0100 1.592 30.8 4 .1635 .0400 REAR 5 .1824 .0306 1.535 41.5 6 .2739 1.4917 57.2 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number, and wherein surfaces 3 and 6 are aspheric in shape and have the general formula: ##EQU5## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 3 6 ______________________________________ beta -0.592 × 10.sup.1 0.517 × 10.sup.1 gamma -0.594 × 10.sup.2 0.151 × 10.sup.3 delta -0.137 × 10.sup.2 -0.900 × 10.sup.5 epsilon -0.116 × 10.sup.0 0.838 × 10.sup.7 zeta 0.000 × 10.sup.0 -0.296 × 10.sup.9 ______________________________________

Claim 17

A two element substantially afocal lens for use with an objective of focal length, f o , said afocal lens having constructional data substantially in accordance with the following table: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ 1 .2196 .0850 1.4917 57.2 2 1.6069 .1221 3 1.3324 .0100 1.592 30.8 4 .1668 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number, and wherein surfaces 2 and 3 are aspheric in shape and have the general formula: ##EQU6## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 2 3 ______________________________________ beta 0.452 × 10.sup.1 -0.865 × 10.sup.1 gamma -0.507 × 10.sup.2 -0.591 × 10.sup.2 delta 0.964 × 10.sup.0 -0.137 × 10.sup.2 epsilon 0.658 × 10.sup.-2 -0.116 × 10.sup.0 zeta 0.000 × 10.sup.0 0.000 × 10.sup.0 ______________________________________

Claim 18

A two element substantially afocal lens for use with an objective of focal length, f o , said afocal lens having constructional data substantially in accordance with the following table: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ 1 .2196 .0850 1.4917 57.2 2 1.6069 .1221 3 1.3324 .0100 1.592 30.8 4 .1668 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number, and wherein surfaces 2 and 3 are aspheric in shape and have the general formula: ##EQU6## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 2 3 ______________________________________ beta 0.452 × 10.sup.1 -0.865 × 10.sup.1 gamma -0.507 × 10.sup.2 -0.591 × 10.sup.2 delta 0.964 × 10.sup.0 -0.137 × 10.sup.2 epsilon 0.658 × 10.sup.-2 -0.116 × 10.sup.0 zeta 0.000 × 10.sup.0 0.000 × 10.sup.0 ______________________________________

Claim 19

A convertible objective lens comprising a front substantially afocal component consisting of two air spaced elements and a rear component consisting of a single meniscus lens element of unit focal length, f o , said front component being mounted for movement into and out of coaxial alignment with said rear component to in combination therewith provide a system whose focal length is longer than that of said rear component by itself when in coaxial alignment therewith, said objective lens having the following constitutional data: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ FRONT 1 .2196 .0850 1.4917 57.2 2 1.6069 .1221 3 1.3324 .0100 1.592 30.8 4 .1668 .0400 REAR 5 .1824 .0306 1.4917 57.2 6 .2739 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number and wherein surfaces 2, 3 and 6 are aspheric in shape and have the general formula: ##EQU7## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 2 3 6 ______________________________________ beta 0.452 × 10.sup.1 -0.865 × 10.sup.1 0.517 × 10.sup.1 gamma -0.507 × 10.sup.2 -0.591 × 10.sup.2 0.151 × 10.sup.3 delta 0.964 × 10.sup.0 -0.137 × 10.sup.2 -0.900 × 10.sup.5 epsilon 0.658 × 10.sup.-2 -0.116 × 10.sup.0 0.838 × 10.sup.7 zeta 0.000 × 10.sup.0 0.000 × 10.sup.0 -0.296 × 10.sup.9 ______________________________________

Claim 20

A convertible objective lens comprising a front substantially afocal component consisting of two air spaced elements and a rear component consisting of a single meniscus lens element of unit focal length, f o , said front component being mounted for movement into and out of coaxial alignment with said rear component to in combination therewith provide a system whose focal length is longer than that of said rear component by itself when in coaxial alignment therewith, said objective lens having the following constitutional data: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ FRONT 1 .2196 .0850 1.4917 57.2 2 1.6069 .1221 3 1.3324 .0100 1.592 30.8 4 .1668 .0400 REAR 5 .1824 .0306 1.4917 57.2 6 .2739 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number and wherein surfaces 2, 3 and 6 are aspheric in shape and have the general formula: ##EQU7## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 2 3 6 ______________________________________ beta 0.452 × 10.sup.1 -0.865 × 10.sup.1 0.517 × 10.sup.1 gamma -0.507 × 10.sup.2 -0.591 × 10.sup.2 0.151 × 10.sup.3 delta 0.964 × 10.sup.0 -0.137 × 10.sup.2 -0.900 × 10.sup.5 epsilon 0.658 × 10.sup.-2 -0.116 × 10.sup.0 0.838 × 10.sup.7 zeta 0.000 × 10.sup.0 0.000 × 10.sup.0 -0.296 × 10.sup.9 ______________________________________

Claim 21

A two element substantially afocal lens for use with an objective of focal length, f o , said afocal lens having constructional data substantially in accordance with the following table: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ 1 .2750 .0850 1.652 58.5 2 .8383 .1449 3 -1.199 .0100 1.592 30.8 4 .2816 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction and V d is the Abbe dispersion number.

Claim 22

A two element substantially afocal lens for use with an objective of focal length, f o , said afocal lens having constructional data substantially in accordance with the following table: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ 1 .2750 .0850 1.652 58.5 2 .8383 .1449 3 -1.199 .0100 1.592 30.8 4 .2816 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction and V d is the Abbe dispersion number.

Claim 23

A convertible objective lens comprising a front substantially afocal component consisting of two air spaced elements and a rear component consisting of a single meniscus lens element of unit focal length, f o , said front component being mounted for movement into and out of coaxial alignment with said rear component to in combination therewith provide a system whose focal length is longer than that of said rear component by itself when in coaxial alignment therewith, said objective lens having the following constitutional data: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ FRONT 1 .2750 .0850 1.652 58.5 2 .8383 .1449 3 -1.199 .0100 1.592 30.8 4 .2816 .0400 REAR 5 .1824 .0306 1.4917 57.2 6 .2739 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number and wherein surface 6 is aspheric in shape and has the general formula: ##EQU8## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 6 ______________________________________ beta 0.517 × 10.sup.1 gamma 0.151 × 10.sup.3 delta -0.900 × 10.sup.5 epsilon 0.838 × 10.sup.7 zeta -0.296 × 10.sup.9 ______________________________________

Claim 24

A convertible objective lens comprising a front substantially afocal component consisting of two air spaced elements and a rear component consisting of a single meniscus lens element of unit focal length, f o , said front component being mounted for movement into and out of coaxial alignment with said rear component to in combination therewith provide a system whose focal length is longer than that of said rear component by itself when in coaxial alignment therewith, said objective lens having the following constitutional data: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ FRONT 1 .2750 .0850 1.652 58.5 2 .8383 .1449 3 -1.199 .0100 1.592 30.8 4 .2816 .0400 REAR 5 .1824 .0306 1.4917 57.2 6 .2739 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number and wherein surface 6 is aspheric in shape and has the general formula: ##EQU8## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 6 ______________________________________ beta 0.517 × 10.sup.1 gamma 0.151 × 10.sup.3 delta -0.900 × 10.sup.5 epsilon 0.838 × 10.sup.7 zeta -0.296 × 10.sup.9 ______________________________________

Claim 25

A three element substantially afocal lens for use with an objective of focal length, f o , said afocal lens having constructional data substantially in accordance with the following table: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ 1 .2628 .0650 1.517 64.2 2 .6309 .0100 3 .2628 .0650 1.517 64.2 4 .6309 .0582 5 -3.681 .0100 1.585 30.3 6 .1675 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number and wherein surface 5 is aspheric in shape and has the general formula: ##EQU9## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 5 ______________________________________ beta 0.512 × 10.sup.1 gamma -0.580 × 10.sup.2 delta -0.137 × 10.sup.2 epsilon -0.116 × 10.sup.0 zeta 0.000 × 10.sup.0 ______________________________________

Claim 26

A three element substantially afocal lens for use with an objective of focal length, f o , said afocal lens having constructional data substantially in accordance with the following table: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ 1 .2628 .0650 1.517 64.2 2 .6309 .0100 3 .2628 .0650 1.517 64.2 4 .6309 .0582 5 -3.681 .0100 1.585 30.3 6 .1675 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number and wherein surface 5 is aspheric in shape and has the general formula: ##EQU9## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 5 ______________________________________ beta 0.512 × 10.sup.1 gamma -0.580 × 10.sup.2 delta -0.137 × 10.sup.2 epsilon -0.116 × 10.sup.0 zeta 0.000 × 10.sup.0 ______________________________________

Claim 27

A convertible objective lens comprising a front substantially afocal component consisting of two air spaced elements and a rear component consisting of a single meniscus lens element of unit focal length, f o , said front component being mounted for movement into and out of coaxial alignment with said rear component to in combination therewith provide a system whose focal length is longer than that of said rear component by itself when in coaxial alignment therewith, said objective lens having the following constitutional data: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ FRONT 1 .2628 .0650 1.517 64.2 2 .6309 .0100 3 .2628 .0650 1.517 64.2 4 .6309 .0582 5 -3.681 .0100 1.585 30.3 6 .1675 .0400 REAR 7 .1824 .0306 1.4917 57.2 8 .2739 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number and wherein surfaces 5 and 8 are aspheric in shape and have the general formula: ##EQU10## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 5 8 ______________________________________ beta 0.512 × 10.sup.1 0.517 × 10.sup.1 gamma -0.580 × 10.sup.2 0.151 × 10.sup.3 delta -0.137 × 10.sup.2 -0.900 × 10.sup.5 epsilon -0.116 × 10.sup.0 0.838 × 10.sup.7 zeta 0.000 × 10.sup.0 -0.296 × 10.sup.9 ______________________________________

Claim 28

A convertible objective lens comprising a front substantially afocal component consisting of two air spaced elements and a rear component consisting of a single meniscus lens element of unit focal length, f o , said front component being mounted for movement into and out of coaxial alignment with said rear component to in combination therewith provide a system whose focal length is longer than that of said rear component by itself when in coaxial alignment therewith, said objective lens having the following constitutional data: ______________________________________ Separation Surface Radius Medium Air N.sub.d V.sub.d ______________________________________ FRONT 1 .2628 .0650 1.517 64.2 2 .6309 .0100 3 .2628 .0650 1.517 64.2 4 .6309 .0582 5 -3.681 .0100 1.585 30.3 6 .1675 .0400 REAR 7 .1824 .0306 1.4917 57.2 8 .2739 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separations are normalized to f o , N d is the index of refraction, V d is the Abbe dispersion number and wherein surfaces 5 and 8 are aspheric in shape and have the general formula: ##EQU10## where C is the reciprocal of the surface apex radius, Z represents the distance of a point on the aspheric surface measured from the surface vertex and parallel to the Z-axis, and S is the radial distance of the point measured perpendicular to the Z-axis and wherein the coefficients, β through ζ, normalized to f o , are given by the following table: ______________________________________ Surface 5 8 ______________________________________ beta 0.512 × 10.sup.1 0.517 × 10.sup.1 gamma -0.580 × 10.sup.2 0.151 × 10.sup.3 delta -0.137 × 10.sup.2 -0.900 × 10.sup.5 epsilon -0.116 × 10.sup.0 0.838 × 10.sup.7 zeta 0.000 × 10.sup.0 -0.296 × 10.sup.9 ______________________________________