Compact four element afocal lens

Claim 2

A four element Galilean magnifying lens for use with an objective of focal length fo comprising a first negative element, a second positive element, a third negative element, and a fourth positive element, said first and second elements being a cemented doublet with net positive power, said third and fourth elements being a cemented doublet with net negative power sufficient to render said lens substantially afocal and said first element having an index of refraction and a first surface with a radius such that the refracting power of said first surface is between 2.3/fo and 3.5/fo.

Claim 3

The lens of claim 1, in which said second and said third elements are cemented.

Claim 4

The lens of claim 1, in which said second and said third elements are air spaced.

Claim 5

The lens of claim 1, in which said first and third elements have indices of refraction greater than 1.6 and said second and fourth elements have indices of refraction less than 1.58, and in which the difference in index of refraction between successive elements is greater than 0.2

Claim 6

The lens of claim 2, in which said first and third elements have indices of refraction greater than 1.6 and said second and fourth elements have indices of refraction less than 1.58, and in which the difference in index of refraction between successive elements is greater than 0.2.

Claim 7

The lens of claim 3, in which said first and third elements have indices of refraction greater than 1.6 and said second and fourth elements have indices of refraction less than 1.58, and in which the difference in index of refraction between successive elements is greater than 0.2

Claim 8

The lens of claim 1, in which said first and third elements have indices of refraction substantially in the range between 1.6 and 1.88 and said second and fourth elements have indices of refraction substantially in the range between 1.40 and 1.58, and in which the difference in index of refraction between successive elements is substantially in the range between 0.2 and 0.4.

Claim 9

The lens of claim 2, in which said first and third elements have indices of refraction substantially in the range between 1.6 and 1.88 and said second and fourth elements have indices of refraction substantially in the range between 1.40 and 1.58, and in which the difference in index of refraction between successive elements is substantially in the range between 0.2 and 0.4.

Claim 10

The lens of claim 3, in which said first and third elements have indices of refraction substantially in the range between 1.6 and 1.88 and said second and fourth elements have indices of refraction substantially in the range between 1.40 and 1.58, and in which the difference in index of refraction between successive elements is substantially in the range between 0.2 and 0.4.

Claim 11

An afocal attachment for use with an objective having a focal length fo, said attachment comprising four lens elements, the first of said elements having an index of refraction and a first surface with a curvature R1 selected to produce a normalized refracting power φ1 between 2.3 and 3.5 where φ1 is normalized to fo, and said elements having a characteristic number Q1<1, where Q1=1000 [(0.098+Pa) R1] 2 in which Pa is the Petzval sum for the attachment, Pa also being normalized to fo, and having a barrel length and magnification such that Q2<1, where Q2=10(BL)/fo(fo)/fs 3 in which BL is the barrel length, and fs is the focal length of the system comprising the objective and the attachment.

Claim 12

An afocal attachment for use with an objective having a focal length fo, said attachment comprising four lens elements, the first of said elements having an index of refraction and a first surface with a curvature R1 selected to produce a normalized refracting power φ1 between 2.3 and 3.5 where φ1 is normalized to fo, and said elements having a characteristic number Q1<1, where Q1=1000 [(0.098+Pa) R1] 2 in which Pa is the Petzval sum for the attachment, Pa also being normalized to fo, and having a barrel length and magnification such that Q2<1, where Q2=10(BL)/fo(fo)/fs 3 in which BL is the barrel length, and fs is the focal length of the system comprising the objective and the attachment.

Claim 13

An afocal lens, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction higher than 1.65 and a first surface with a refracting power between 2.3/fo and 3.5/fo, said second element having a refractive index below 1.58, said first doublet having a cemented surface with a refracting power between -1.4/fo and -2.0/fo, said second doublet comprising a third negative element having a refractive index greater than 1.6 and a fourth positive element having a refractive index less than 1.58.

Claim 14

An afocal lens, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction higher than 1.65 and a first surface with a refracting power between 2.3/fo and 3.5/fo, said second element having a refractive index below 1.58, said first doublet having a cemented surface with a refracting power between -1.4/fo and -2.0/fo, said second doublet comprising a third negative element having a refractive index greater than 1.6 and a fourth positive element having a refractive index less than 1.58.

Claim 15

The lens of claim 11, in which said first doublet is cemented to said second doublet.

Claim 16

The lens of claim 11, in which said first doublet is air-spaced from said second doublet.

Claim 17

An afocal attachment for use with an objective having a focal length fo and a field greater than 40 degrees, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction higher than 1.65 and a first surface with a refracting power, normalized to fo, between 2.3 and 3.5, said second element having a refractive index below 1.58, said first doublet having a cemented surface with a refracting power, normalized to fo, between -1.4 and -2.0, said second doublet comprising a third negative element having a refractive index greater than 1.6 and a fourth positive element having a refractive index less than 1.58, said lens having a value Q1≦1, where Q1=1000 [(0.098+Pa) R1].sup.2, where Pa is the Petzval sum of the attachment and R1 is the radius of the first surface of said first element, both normalized to fo.

Claim 18

An afocal attachment for use with an objective having a focal length fo and a field greater than 40 degrees, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction higher than 1.65 and a first surface with a refracting power, normalized to fo, between 2.3 and 3.5, said second element having a refractive index below 1.58, said first doublet having a cemented surface with a refracting power, normalized to fo, between -1.4 and -2.0, said second doublet comprising a third negative element having a refractive index greater than 1.6 and a fourth positive element having a refractive index less than 1.58, said lens having a value Q1≦1, where Q1=1000 [(0.098+Pa) R1].sup.2, where Pa is the Petzval sum of the attachment and R1 is the radius of the first surface of said first element, both normalized to fo.

Claim 19

The lens of claim 14 in which said first doublet is cemented to said second doublet.

Claim 20

The lens of claim 14 in which said first doublet is air-spaced from said second doublet.

Claim 21

An afocal attachment for use with an objective having a focal length fo and a field greater than 40 degrees, said attachment comprising four elements alternately of negative and positive power, said negative elements having indices of refraction greater than 1.6, said positive elements having indices of refraction less than 1.58, the first of said elements having a first surface with a refracting power, normalized to fo, between 2.3 and 3.5, and said attachment having values of M1<1, where M1 is the root mean square of Q 1 and Q 2 where Q 1 =1000 [(0.098+P a ) R1] 2 in which P a is the Petzval sum for the attachment and R1 is the radius of said first element both normalized to fo, and where Q 2 =10(BL/fo)(fo/f s ) 3 in which BL is the barrel length and f s is the focal length of the system comprising the objective and the attachment.

Claim 22

An afocal attachment for use with an objective having a focal length fo and a field greater than 40 degrees, said attachment comprising four elements alternately of negative and positive power, said negative elements having indices of refraction greater than 1.6, said positive elements having indices of refraction less than 1.58, the first of said elements having a first surface with a refracting power, normalized to fo, between 2.3 and 3.5, and said attachment having values of M1<1, where M1 is the root mean square of Q 1 and Q 2 where Q 1 =1000 [(0.098+P a ) R1] 2 in which P a is the Petzval sum for the attachment and R1 is the radius of said first element both normalized to fo, and where Q 2 =10(BL/fo)(fo/f s ) 3 in which BL is the barrel length and f s is the focal length of the system comprising the objective and the attachment.

Claim 23

The afocal attachment of claim 17, in which said elements are cemented.

Claim 24

The afocal attachment of claim 17, in which said first and second elements form a first cemented doublet and said third and fourth elements form a second cemented doublet air spaced from said first cemented doublet.

Claim 25

A four element Galilean magnifying lens for use with an objective having a focal length fo, comprising a first negative element, a second positive element, a third negative element, and a fourth positive element, said first and second elements being a cemented doublet with net positive power, said third and fourth elements being a cemented doublet with net negative power sufficient to render said lens substantially afocal and said first element having an index of refraction and a first surface with a radius such that the refracting power φ of said first surface is between 2.3 and 3.5, in which said elements have radii and indices of refraction chosen to produce a small negative Petzval sum Pa between 0 and -0.2, where Pa and φ are normalized to fo.

Claim 26

A four element Galilean magnifying lens for use with an objective having a focal length fo, comprising a first negative element, a second positive element, a third negative element, and a fourth positive element, said first and second elements being a cemented doublet with net positive power, said third and fourth elements being a cemented doublet with net negative power sufficient to render said lens substantially afocal and said first element having an index of refraction and a first surface with a radius such that the refracting power φ of said first surface is between 2.3 and 3.5, in which said elements have radii and indices of refraction chosen to produce a small negative Petzval sum Pa between 0 and -0.2, where Pa and φ are normalized to fo.

Claim 27

The lens of claim 20, in which said second and said third elements are cemented.

Claim 28

The lens of claim 20, in which said second and said third elements are air spaced.

Claim 29

The lens of claim 20, in which said first and third elements have indices of refraction greater than 1.6 and said second and fourth elements have indices of refraction less than 1.58, and in which the difference in index of refraction between successive elements is greater than 0.2.

Claim 30

The lens of claim 21, in which said first and third elements have indices of refraction greater than 1.6 and said second and fourth elements have indices of refraction less than 1.58, and in which the difference in index of refraction between successive elements is greater than 0.2.

Claim 31

The lens of claim 22, in which said first and third elements have indices of refraction greater than 1.6 and said second and fourth elements have indices of refraction less than 1.58, and in which the difference in index of refraction between successive elements is greater than 0.2.

Claim 32

The afocal lens of claim 20, in which said elements are substantially in accordance with the following table: ______________________________________ Separations Glass Types Surface Radii Glass Air Nd Vd ______________________________________ 1 0.2721 0.1218 1.720 50.4 2 .1528 .0816 1.465 65.8 3 -1.922 .0214 4 -4.321 .0180 1.744 44.8 5 .2112 .0820 1.465 65.8 6 .7479 ______________________________________ 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 fo, Nd is the index of refraction, and Vd is the Abbe dispersion number.

Claim 33

The afocal lens of claim 20, in which said elements are substantially in accordance with the following table: ______________________________________ Separations Glass Types Surface Radii Glass Air Nd Vd ______________________________________ 1 .2579 .1218 1.720 50.4 2 .1612 .0816 1.465 65.8 3 -2.93 .0021 4 -2.00 .0180 1.717 48.0 5 .1853 .0820 1.465 65.8 6 .7580 ______________________________________ in which said surfaces are the surfaces of said elements in numerical order from object space to image space, said radii and separation are normalized to fo, Nd is the index of separation, and Vd is the Abbe dispersion number.

Claim 34

The afocal lens of claim 21, in which said elements are substantially in accordance with the following table: ______________________________________ Separations Glass Types Surface Radii Glass Air Nd Vd ______________________________________ 1 .2969 .1181 1.740 28.2 2 .1619 .0816 1.501 56.4 3 -1.732 .0305 4 -2.888 .0180 1.678 55.2 5 .1755 .0856 1.492 57.4 6 .5777 ______________________________________ 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 fo, Nd is the index of refraction, Vd is the Abbe dispersion number and surface 6 is an asphere having the given radius at the optical axis.

Claim 35

The afocal lens of claim 21, in which said elements are substantially in accordance with the following table: ______________________________________ Separations Glass Types Surface Radii Glass Air Nd Vd ______________________________________ 1 .2515 .1102 1.713 53.8 2 .1496 .0814 1.465 65.8 3 .5623 .0180 1.713 53.8 4 .1752 .0725 1.465 65.8 5 .4302 ______________________________________ 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 fo, Nd is the index of refraction, and Vd is the Abbe dispersion number.

Claim 36

The afocal lens of claim 21, in which said elements are substantially in accordance with the following table: ______________________________________ Separations Glass Types Surface Radii Glass Air Nd Vd ______________________________________ 1 .2603 .1290 1.713 53.8 2 .1454 .0850 1.465 65.8 3 2.53 .0180 1.713 53.8 4 .2155 .0715 1.465 65.8 5 .4783 ______________________________________ in which said surfaces are the surface of said elements in numerical order from object space to image space, said radii and separations are normalized to fo, Nd is the index of refraction, and Vd is the Abbe dispersion number.

Claim 37

The afocal lens of claim 21, in which said elements are substantially in accordance with the following table: ______________________________________ Separations Glass Types Surface Radii Glass Air Nd Vd ______________________________________ 1 .2255 .0841 1.720 50.4 2 .1364 .1065 1.487 70.4 3 1.705 .0180 1.788 50.5 4 .1723 .0739 1.541 47.2 5 .4067 ______________________________________ 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 fo, Nd is the index of refraction, and Vd is the Abbe dispersion number.

Claim 38

The afocal lens of claim 21, in which said elements are substantially in accordance with the following table: ______________________________________ Separations Glass Types Surface Radii Glass Air Nd Vd ______________________________________ 1 0.2606 .1290 1.720 50.4 2 .1509 .0955 1.465 65.8 3 -1.725 .0180 1.720 50.4 4 .2066 .0610 1.465 65.8 5 .6700 ______________________________________ 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 fo, Nd is the index of refraction, and Vd is the Abbe dispersion number.

Claim 39

The afocal lens of claim 21, in which said elements are substantially in accordance with the following table: ______________________________________ Separations Glass Types Surface Radii Glass Air Nd Vd ______________________________________ 1 0.2569 .1218 1.720 50.4 2 .1500 .0817 1.465 65.8 3 -2.21 .0180 1.720 50.4 4 .2009 .0820 1.465 65.8 5 .7332 ______________________________________ 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 fo, Nd is the index of refraction, and Vd is the Abbe dispersion number.

Claim 40

The afocal lens of claim 21, in which said elements are substantially in accordance with the following table: ______________________________________ Separations Glass Types Surface Radii Glass Air Nd Vd ______________________________________ 1 0.2537 0.1218 1.720 50.4 2 .1465 .0817 1.465 65.8 3 -1.87 .0180 1.720 50.4 4 .1954 .0820 1.465 65.8 5 .7883 ______________________________________ 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 fo, Nd is the index of refraction, and Vd is the Abbe dispersion number.

Claim 41

The lens of claim 20, in which said first and third elements have indices of refraction substantially in the range between 1.6 to 1.88 and said second and fourth elements have indices of refraction substantially in the range between 1.40 and 1.58, and in which the difference in index of refraction between successive elements is substantially in the range between 0.2 and 0.4.

Claim 42

The lens of claim 21, in which said first and third elements have indices of refraction substantially in the range between 1.6 and 1.88 and said second and fourth elements have indices of refraction substantially in the range between 1.40 and 1.58, and in which the difference in index of refraction between successive elements is substantially within the range between 0.2 and 0.4.

Claim 43

The lens of claim 22, in which said first and third elements have indices of refraction substantially in the range between 1.6 and 1.88 and said second and fourth elements have indices of refraction substantially within the range between 1.40 and 1.58, and in which the difference in index of refraction between successive elements is substantially within the range between 0.2 and 0.4.

Claim 44

An afocal attachment for use with an objective having a focal length fo, said attachment comprising four lens elements having a normalized Petzval sum Pa that is a negative number between 0 and -0.2, and the first of said elements having an index of refraction and a first surface with a curvature selected to produce a normalized refracting power φ1 between 2.3 and 3.5, in which Pa and φ1 are normalized to fo.

Claim 45

An afocal attachment for use with an objective having a focal length fo, said attachment comprising four lens elements having a normalized Petzval sum Pa that is a negative number between 0 and -0.2, and the first of said elements having an index of refraction and a first surface with a curvature selected to produce a normalized refracting power φ1 between 2.3 and 3.5, in which Pa and φ1 are normalized to fo.

Claim 46

An afocal lens for use with an objective of focal length fo inches, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction higher than 1.65 and a first surface with a refracting power between 2.3/fo and 3.5/fo, said second element having a refractive index below 1.58, said first doublet having a cemented surface with a refracting power between -1.4/fo and -2.0/fo, and said second doublet comprising a third negative element having a refractive index greater than 1.6 and a fourth positive element having a refractive index less than 1.58, said lens having a Petzval sum Pu in reciprocal inches such that Pufo=Pa and Pa is a negative number between 0 and -0.2.

Claim 47

An afocal lens for use with an objective of focal length fo inches, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction higher than 1.65 and a first surface with a refracting power between 2.3/fo and 3.5/fo, said second element having a refractive index below 1.58, said first doublet having a cemented surface with a refracting power between -1.4/fo and -2.0/fo, and said second doublet comprising a third negative element having a refractive index greater than 1.6 and a fourth positive element having a refractive index less than 1.58, said lens having a Petzval sum Pu in reciprocal inches such that Pufo=Pa and Pa is a negative number between 0 and -0.2.

Claim 48

The lens of claim 39, in which said first doublet is cemented to said second doublet.

Claim 49

The lens of claim 39, in which said first doublet is air-spaced from said second doublet.

Claim 50

An afocal lens, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction substantially in the range between 1.65 and 1.88 and a first surface with a refracting power between 2.3/fo and 3.5/fo, said second element having a refractive index substantially in the range between 1.40 and 1.58, said first doublet having a cemented surface with a refracting power between -1.4/fo and -2.0/fo, said second doublet comprising a third negative element having a refractive index substantially in the range between 1.6 and 1.88 and a fourth positive element having a refractive index substantially in the range between 1.40 and 1.58.

Claim 51

An afocal lens, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction substantially in the range between 1.65 and 1.88 and a first surface with a refracting power between 2.3/fo and 3.5/fo, said second element having a refractive index substantially in the range between 1.40 and 1.58, said first doublet having a cemented surface with a refracting power between -1.4/fo and -2.0/fo, said second doublet comprising a third negative element having a refractive index substantially in the range between 1.6 and 1.88 and a fourth positive element having a refractive index substantially in the range between 1.40 and 1.58.

Claim 52

An afocal attachment for use with an objective having a focal length fo and a field greater than 40 degrees, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction substantially in the range between 1.65 and 1.88 and a first surface with a refracting power, normalized to fo, between 2.3 and 3.5, said second element having a refractive index substantially in the range between 1.40 and 1.58, said first doublet having a cemented surface with a refracting power, normalized to fo, between -1.4 and -2.0, said second doublet comprising a third negative element having a refractive index substantially in the range between 1.6 and 1.88 and a fourth positive element having a refractive index substantially in the range between 1.40 and 1.58, said lens having a value Q1≦1, where Q1=1000[(0.098+Pa) R1].sup.2 where Pa is the Petzval sum of the attachment and R1 is the radius of the first surface of said first element, both normalized to fo.

Claim 53

An afocal attachment for use with an objective having a focal length fo and a field greater than 40 degrees, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction substantially in the range between 1.65 and 1.88 and a first surface with a refracting power, normalized to fo, between 2.3 and 3.5, said second element having a refractive index substantially in the range between 1.40 and 1.58, said first doublet having a cemented surface with a refracting power, normalized to fo, between -1.4 and -2.0, said second doublet comprising a third negative element having a refractive index substantially in the range between 1.6 and 1.88 and a fourth positive element having a refractive index substantially in the range between 1.40 and 1.58, said lens having a value Q1≦1, where Q1=1000[(0.098+Pa) R1].sup.2 where Pa is the Petzval sum of the attachment and R1 is the radius of the first surface of said first element, both normalized to fo.

Claim 54

An afocal lens of use with an objective of focal length fo inches, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction substantially in the range between 1.65 and 1.88 and a first surface with a refracting power between 2.3/fo and 3.5/fo, said second element having a refractive index substantially in the range between 1.40 and 1.58, said first doublet having a cemented surface with a refracting power between -1.4/fo and -2.0/fo, and said second doublet comprising a third negative element having a refractive index substantially in the range between 1.6 and 1.88 and a fourth positive element having a refractive index substantially in the range between 1.40 and 1.58, said lens having a Petzval sum Pu in reciprocal inches such that Pufo=Pa and Pa is a negative number between 0 and -0.2.

Claim 55

An afocal lens of use with an objective of focal length fo inches, comprising a first cemented doublet of net positive power and a second cemented doublet of net negative power, said first doublet comprising a first negative element and a second positive element, said first element having an index of refraction substantially in the range between 1.65 and 1.88 and a first surface with a refracting power between 2.3/fo and 3.5/fo, said second element having a refractive index substantially in the range between 1.40 and 1.58, said first doublet having a cemented surface with a refracting power between -1.4/fo and -2.0/fo, and said second doublet comprising a third negative element having a refractive index substantially in the range between 1.6 and 1.88 and a fourth positive element having a refractive index substantially in the range between 1.40 and 1.58, said lens having a Petzval sum Pu in reciprocal inches such that Pufo=Pa and Pa is a negative number between 0 and -0.2.