Projection lens

Claim 2

A projection lens for use in combination with a cathode ray tube, which lens is positioned closely adjacent the faceplate of the cathode ray tube, said lens consisting of three lens units, the first lens unit from the image end including an overall meniscus shaped element of weak positive optical power at the optical axis of said lens and having at least one aspheric surface, a second lens unit comprising a biconvex element which supplies the majority of the positive optical power of said lens, a third lens unit closely adjacent said cathode ray tube and having a strongly concave image side surface and serving as a field flattener, said lens further comprising a corrector lens unit having at least one aspheric surface positioned between said second and third lens units, said first and second lens units being axially spaced 0.5>|D.sub.12 /F.sub.3 |>0.1 where D 12 is the axial spacing between said first and second lens units and F 3 is the equivalent focal length of said third lens unit, said corrector lens unit being constructed, arranged and spaced from said second lens unit such that the axial marginal rays from said second lens unit as traced from the long conjugate intersect the image side surface of said corrector lens unit at a height H from the optical axis that is less than the clear aperture of the image side surface of said corrector lens unit but at a height which will not affect the contribution of said corrector lens unit for correction of aperture dependent aberrations, said surfaces of said corrector lens unit above the height H being configured beyond said height H to contribute to correction of aberrations due to off-axis rays.

Claim 3

The lens of claim 1 where said first lens unit consists of a single element which is of positive optical power at the optical axis and changes to negative optical power adjacent its clear aperture.

Claim 4

The lens of claim 2 where said first lens unit has two aspheric surfaces.

Claim 5

The lens of claim 1 where said corrector lens unit consists of a single element having two aspheric surfaces.

Claim 6

The lens of claim 4 where said corrector lens unit has surfaces which are defined at the optical axis on radii which are substantially equal to or greater than the equivalent focal length of said lens.

Claim 7

The lens of claim 1 where said corrector lens unit has surfaces which are defined at the optical axis on radii which are substantially equal to or greater than the equivalent focal length of said lens.

Claim 8

The lens of claim 1 where said first lens unit and said corrector lens unit each consist of single elements.

Claim 9

The lens of claim 7 where both of said first lens unit and said corrector lens unit have two aspheric surfaces.

Claim 10

The lens of claim 1 satisfying the condition 0.92≧2H/CA>0.5 where CA is the clear aperture of the image side surface of said corrector lens unit.

Claim 11

The lens of claim 1 satisfying the condition 0.4>D.sub.2C /F.sub.0 >0.1 where D 2C is the axial distance between said second lens unit and said corrector lens unit and F 0 is the equivalent focal length of the lens.

Claim 12

The lens of claim 5 satisfying the condition 0.4>D.sub.2C /F.sub.0 >0.1 where D 2C is the axial distance between said second lens unit and said corrector lens unit and F 0 is the equivalent focal length of the lens.

Claim 13

The lens of claim 7 satisfying the condition 0.4>D.sub.2C F.sub.0 >0.1 where D 2C is the axial distance between said second lens unit and said corrector lens unit and F 0 is the equivalent focal length of the lens.

Claim 14

The lens of claim 8 satisfying the condition 0.4>D.sub.2C /F.sub.0 >0.1 where D 2C is the axial distance between said second lens unit and said corrector lens unit and F 0 is the equivalent focal length of the lens.

Claim 15

The projection lens of claim 1 further comprising another corrector lens unit consisting of a meniscus element having at least one aspheric surface positioned closely adjacent said secod lens unit and being convex toward said second lens unit.

Claim 16

The projection lens of claim 14 where said meniscus element of said another corrector lens unit is on the image side of said second lens unit and is part of said first lens unit.

Claim 17

The projection lens of claim 14 where said meniscus element of said another corrector lens unit is on the object side of said second lens unit.

Claim 18

The projection lens of claim 1 where said first lens unit is a single element and satisfies the condition |K.sub.CA /K.sub.A |>0.8 where K CA is the optical power of said meniscus element of said first lens unit at the clear aperture thereof and K A is the optical power of said meniscus element of said first lens unit at the optical axis thereof.

Claim 19

The projection lens of claim 3 where said first lens unit is a single element and satisfies the condition |K.sub.CA /K.sub.A |>0.8 where K CA is the optical power of said meniscus element of said first lens unit at the clear aperture thereof and K A is the optical power of said meniscus element of said first lens unit at the optical axis thereof.

Claim 20

The projection lens of claim 1 wherein said meniscus lens element of said first lens unit and said corrector lens unit are both convex to said second lens unit.

Claim 21

The projection lens of claim 3 wherein said meniscus lens element of said first lens unit and said corrector lens unit are both convex to said second lens unit.

Claim 22

The projection lens of claim 4 wherein said meniscus lens element of said first lens unit and said corrector lens unit are both convex to said second lens unit.

Claim 23

The projection lens of claim 5 wherein said meniscus lens element of said first lens unit and said corrector lens unit are both convex to said second lens unit.

Claim 24

The projection lens of claim 1 where said first lens unit is a meniscus element convex to the image side thereof with an aspheric surface which becomes concave to the image adjacent the clear aperture.

Claim 25

The projection lens of claim 1 where said first lens unit consists of a single element and satisfies the condition |K.sub.CA /K.sub.A |>0.8 where K CA is the optical power of said meniscus element of said first lens unit at the clear aperture thereof and K A is the optical power of said meniscus element at the optical axis thereof.

Claim 26

The projection lens of claim 3 where said first lens unit consists of a single element and satisfies the condition |K.sub.CA /K.sub.A |>0.8 where K CA is the optical power of said meniscus element of said first lens unit at the clear aperture thereof and K A is the optical power of said meniscus element at the optical axis thereof.

Claim 27

The lens of claim 1 where said second lens unit consists of a a biconvex element and another positive element.

Claim 28

The lens of claim 26 where the elements of said second lens unit have spheric surfaces.

Claim 29

The lens of claim 3 where the elements of said second lens unit have spheric surfaces.

Claim 30

The lens of claim 4 where the elements of said second lens unit have spheric surfaces.

Claim 31

The lens of claim 1 where said biconvex element of said second lens unit has spherical surfaces and is formed of glass.

Claim 32

The lens of claim 1 where said second lens unit comprises a plurality of lens units, all of which are glass and have spheric surfaces.

Claim 33

The lens of claim 1 where said corrector lens unit consists of a single element having surfaces which are defined at the optical axis on radii which are substantially equal to or greater than the equivalent focal length of said lens and said single element being biconvex at the optical axis.

Claim 34

A projection lens for use in combination with a cathode ray tube, which lens is positioned closely adjacent the faceplate of the cathode ray tube, said lens comprising three lens units, the first lens unit from the image end including an overall meniscus shaped element of weak positive optical power at the optical axis of said lens and having at least one aspheric surface, a second lens unit consisting of a biconvex element which supplies the majority of the positive optical power of said lens, a third lens unit closely adjacent said cathode ray tube and having a strongly concave image side surface and serving as a field flattener, said lens further comprising a corrector lens unit having at least one aspheric surface positioned between said second and third lens units, said first lens unit being spaced from second lens unit 0.5>|D.sub.12 /F.sub.3 |>0.1 where D 12 is the axial distance between said first and second lens units and F 3 is the equivalent focal length of said third lens unit, and 0.4>D.sub.2C /F.sub.0 >0.1 where D 2C is the axial distance between said second lens unit and said corrector lens unit, and F 0 is the equivalent focal length of the lens.

Claim 35

A projection lens for use in combination with a cathode ray tube, which lens is positioned closely adjacent the faceplate of the cathode ray tube, said lens comprising three lens units, the first lens unit from the image end including an overall meniscus shaped element of weak positive optical power at the optical axis of said lens and having at least one aspheric surface, a second lens unit consisting of a biconvex element which supplies the majority of the positive optical power of said lens, a third lens unit closely adjacent said cathode ray tube and having a strongly concave image side surface and serving as a field flattener, said lens further comprising a corrector lens unit having at least one aspheric surface positioned between said second and third lens units, said first lens unit being spaced from second lens unit 0.5>|D.sub.12 /F.sub.3 |>0.1 where D 12 is the axial distance between said first and second lens units and F 3 is the equivalent focal length of said third lens unit, and 0.4>D.sub.2C /F.sub.0 >0.1 where D 2C is the axial distance between said second lens unit and said corrector lens unit, and F 0 is the equivalent focal length of the lens.

Claim 36

The lens of claim 33 where said corrector lens unit consists of a single element having two aspheric surfaces and K.sub.C /K.sub.0 <0.3 where K C is the optical power of said corrector lens unit and K 0 is the optical power of said lens.

Claim 37

The lens of claim 34 where 0.92≧2H/CA>0.5 where CA is the clear aperture of said corrector lens unit and H is the height from the optical axis of said lens at which the axial marginal rays as traced from the long conjugate of said lens intersect the image side surface of said corrector lens unit.

Claim 38

The projection lens of claim 33 further including another corrector lens unit consisting of a meniscus element having at least one aspheric surface positioned closely adjacent said second lens unit and being convex toward said second lens unit.

Claim 39

The projection lens of claim 36 where said another corrector lens unit is on the image side of said second lens unit and is part of said first lens unit.

Claim 40

The projection lens of claim 36 where said another corrector lens unit is on the object side of said second lens unit.

Claim 41

The projection lens of claim 33 where said first lens unit consists of a single element and satisfies the condition |K.sub.CA /K.sub.A |>0.8 where K CA is the optical power of said meniscus element of said first lens unit at the clear aperture thereof and K A is the optical power of said meniscus element of said first lens unit at the optical axis thereof.

Claim 42

The projection lens of claim 33 wherein said meniscus lens element of said first lens unit and said corrector lens unit are both convex to said second lens unit.

Claim 43

The projection lens of claim 33 where said first lens unit is a meniscus element convex to the image side thereof with an aspheric surface which becomes concave to the image adjacent the clear aperture.

Claim 44

The projection lens of claim 33 where |K.sub.CA /K.sub.A |>0.8 where K CA is the optical power of said meniscus element of said first lens unit at the clear aperture thereof and K A is the optical power of said meniscus element at the optical axis thereof.

Claim 45

The lens of claim 33 where said corrector lens unit consists of a single element having two aspheric surfaces, and said second lens unit consists of a single biconvex element.

Claim 46

The lens of claim 33 where the surfaces of said biconvex element are spheric.

Claim 47

The lens of claim 33 where said first lens unit consists of a single element which is of positive optical power at the optical axis and changes to negative optical power adjacent its clear aperture, and has two aspheric surfaces.

Claim 48

The lens of claim 33 where said corrector lens unit consists of a single element having two aspheric surfaces.

Claim 49

The lens of claim 46 where said corrector lens unit has surfaces which are defined at the optical axis on radii which are substantially equal to or greater than the equivalent focal length of said lens.

Claim 50

The lens of claim 33 where said corrector lens unit consists of a single element having surfaces which are defined at the optical axis on radii which are substantially equal to or greater than the equivalent focal length of said lens, and both of said surfaces are aspheric.

Claim 51

The lens of claim 33 where said first lens unit and said corrector lens unit each consist of single elements.

Claim 52

The lens of claim 49 where both of said first lens unit and said corrector lens unit have two aspheric surfaces.

Claim 53

The lens of claim 33 satisfying the condition 0.92≧2H/CA>0.5 where CA is the clear aperture of the image side surface of said corrector lens unit and H is the height on the image side surface of said corrector lens unit measured from the optical axis where the axial marginal rays passing from said second lens unit as traced from the long conjugate intersect said image side surface of said corrector lens unit.

Claim 54

The projection lens of claim 46 wherein said meniscus lens element of said first lens unit and said corrector lens unit are both convex to said second lens unit.

Claim 55

The projection lens of claim 47 wherein said meniscus lens element of said first lens unit and said corrector lens unit are both convex to said second lens unit.

Claim 56

The lens of claim 33 where said corrector lens unit consists of a single element having surfaces which are defined at the optical axis on radii which are substantially equal to or greater than the equivalent focal length of said lens, said element being biconvex at the optical axis.

Claim 57

The lens of claim 33 where said biconvex element of said second lens unit has spherical surfaces and is formed of glass.

Claim 58

The lens of claim 33 where said second lens unit comprises a plurality of lens units, all of which are glass and have spheric surfaces.

Claim 59

A projection lens for use in combination with a cathode ray tube which lens is positioned closely adjacent the faceplate of the cathode ray tube, said lens comprising of three lens units, the first lens unit from the image end including an overall meniscus shaped element of weak optical power at the optical axis of said lens and having at least one aspheric surface, a second lens unit consisting of a biconvex element which supplies the majority of the positive optical power of said lens, said first lens unit being spaced from said second lens unit 0.5>|D.sub.12 /F.sub.3 |>0.1 where D 12 is the axial distance between said first and second lens units and F 3 is the equivalent focal length of said first lens unit, a third lens unit closely adjacent said cathode ray tube and having a strongly concave image side surface and serving as a field flattener, said lens further comprising a corrector lens element having two aspheric surfaces positioned between said second and third lens units, said corrector lens unit consisting of a single unit spaced from said second lens unit 0.4>D.sub.2C /F.sub.0 >0.1 where D 2C is the axial distance between said second lens unit and said corrector lens unit, F 0 is the equivalent focal length of said projection lens, and the surfaces of said corrector lens element are defined at the optical axis on radii which are substantially equal to or greater than the equivalent focal length of the lens, the positioning and shape of said corrector lens element from said second lens unit being such that the axial marginal rays from said second lens unit as traced from the long conjugate intersect the image side surface of said corrector lens unit at a height H from the optical axis that is less than the clear aperture of the image side surface of said corrector lens unit but at a height which will not affect the contribution of said corrector lens unit for correction of aperture dependent aberrations, said surfaces of said corrector lens unit above the height H being configured beyond said height H to contribute to correction of aberrations due to off-axis rays.

Claim 60

A projection lens for use in combination with a cathode ray tube which lens is positioned closely adjacent the faceplate of the cathode ray tube, said lens comprising of three lens units, the first lens unit from the image end including an overall meniscus shaped element of weak optical power at the optical axis of said lens and having at least one aspheric surface, a second lens unit consisting of a biconvex element which supplies the majority of the positive optical power of said lens, said first lens unit being spaced from said second lens unit 0.5>|D.sub.12 /F.sub.3 |>0.1 where D 12 is the axial distance between said first and second lens units and F 3 is the equivalent focal length of said first lens unit, a third lens unit closely adjacent said cathode ray tube and having a strongly concave image side surface and serving as a field flattener, said lens further comprising a corrector lens element having two aspheric surfaces positioned between said second and third lens units, said corrector lens unit consisting of a single unit spaced from said second lens unit 0.4>D.sub.2C /F.sub.0 >0.1 where D 2C is the axial distance between said second lens unit and said corrector lens unit, F 0 is the equivalent focal length of said projection lens, and the surfaces of said corrector lens element are defined at the optical axis on radii which are substantially equal to or greater than the equivalent focal length of the lens, the positioning and shape of said corrector lens element from said second lens unit being such that the axial marginal rays from said second lens unit as traced from the long conjugate intersect the image side surface of said corrector lens unit at a height H from the optical axis that is less than the clear aperture of the image side surface of said corrector lens unit but at a height which will not affect the contribution of said corrector lens unit for correction of aperture dependent aberrations, said surfaces of said corrector lens unit above the height H being configured beyond said height H to contribute to correction of aberrations due to off-axis rays.

Claim 61

The projection lens of claim 57 where said corrector lens unit is biconvex at the optical axis.

Claim 62

The projection lens of claim 57 where said first lens unit consists of a single element having two aspheric surfaces, and said element is of positive optical power at the optical axis and changes to negative optical power adjacent the clear aperture.

Claim 63

The projection lens of claim 57 further including another corrector lens unit consisting of a meniscus element having at least one aspheric surface positioned closely adjacent said second lens unit and being convex toward said second lens unit.

Claim 64

The projection lens of claim 60 where said another corrector lens unit is on the image side of said second lens unit and is part of said first lens unit.

Claim 65

The projection lens of claim 60 where said another corrector lens unit is on the object side of said second lens unit.

Claim 66

The projection lens of claim 57 where said first lens unit is a single element and satisfies the condition |K.sub.CA /K.sub.A |>0.8 where K CA is the optical power of said meniscus element of said first lens unit at the clear aperture thereof and K A is the optical power of said meniscus element of said first lens unit at the optical axis thereof.

Claim 67

The projection lens of claim 57 wherein said meniscus lens element of said first lens unit and said corrector lens unit are both convex to said second lens unit.

Claim 68

The lens of claim 57 where said biconvex element of said second lens unit has spherical surfaces and is formed of glass.

Claim 69

The lens of claim 57 where said second lens unit comprises a plurality of lens units, all of which are glass and have spheric surfaces.

Claim 70

A projection lens for use in combination with a cathode ray tube, which lens is positioned closely adjacent the faceplate of the cathode ray tube, said lens comprising from the image end a first lens unit of overall meniscus shape of weak positive optical power at the optical axis of said lens and having at least one aspheric surface, a second lens unit comprising a biconvex element which supplies the majority of the positive optical power of said lens, a third corrector lens unit having at least one aspheric surface, and a fourth lens unit closely adjacent the cathode ray tube having a strongly concave image side surface and serving as a field flattener, said first lens unit being spaced from second lens unit 0.5>|D.sub.12 /F.sub.4 |>0.1 where D 12 is the axial distance between said first and second lens units and F 4 is the equivalent focal length of said fourth lens unit, and 0.4>D.sub.2C /F.sub.0 >0.1 where D 2C is the axial distance between said second lens unit and said third corrector lens unit, and F 0 is the equivalent focal length of the lens.

Claim 71

A projection lens for use in combination with a cathode ray tube, which lens is positioned closely adjacent the faceplate of the cathode ray tube, said lens comprising from the image end a first lens unit of overall meniscus shape of weak positive optical power at the optical axis of said lens and having at least one aspheric surface, a second lens unit comprising a biconvex element which supplies the majority of the positive optical power of said lens, a third corrector lens unit having at least one aspheric surface, and a fourth lens unit closely adjacent the cathode ray tube having a strongly concave image side surface and serving as a field flattener, said first lens unit being spaced from second lens unit 0.5>|D.sub.12 /F.sub.4 |>0.1 where D 12 is the axial distance between said first and second lens units and F 4 is the equivalent focal length of said fourth lens unit, and 0.4>D.sub.2C /F.sub.0 >0.1 where D 2C is the axial distance between said second lens unit and said third corrector lens unit, and F 0 is the equivalent focal length of the lens.

Claim 72

The lens of claim 67 where said third corrector lens unit consists of a single element having two aspheric surfaces and K.sub.C /K.sub.0 >0.3 where K C is the optical power of said corrector lens unit and K 0 is the optical power of said lens.

Claim 73

The lens of claim 68 where 0.92≧2H/CA>0.5 where CA is the clear aperture of said corrector lens unit and H is the height from the optical axis of said lens at which the axial marginal rays as traced from the long conjugate of said lens intersect the image side surface of said third corrector lens unit.

Claim 74

The projection lens of claim 67 further including another corrector lens unit consisting of a meniscus element having at least one aspheric surface positioned closely adjacent said second lens unit and being convex toward said second lens unit.

Claim 75

The projection lens of claim 70 where said meniscus element of said another corrector lens unit is on the image side of said second lens unit and is part of said first lens unit.

Claim 76

The projection lens of claim 70 where said another corrector lens unit is on the object side of said second lens unit.

Claim 77

The projection lens of claim 68 where said first lens unit consists of a single element and satisfies the condition |K.sub.CA /K.sub.A |>0.8 where K CA is the optical power of said meniscus element of said first lens unit at the clear aperture thereof and K A is the optical power of said meniscus element of said first lens unit at the optical axis thereof.

Claim 78

The projection lens of claim 67 wherein said first lens unit consists of a single meniscus lens element and said first lens unit and said third corrector lens unit are both convex to said second lens unit.

Claim 79

The projection lens of claim 67 where said first lens unit is a meniscus element convex to the image side thereof with an aspheric surface which becomes concave to the image adjacent the clear aperture.

Claim 80

The projection lens of claim 75 where |K.sub.CA /K.sub.A |>0.8 where K CA is the optical power of said meniscus element of said first lens unit at the clear aperture thereof and K A is the optical power of said meniscus element at the optical axis thereof.

Claim 81

The lens of claim 67 where said corrector lens unit consists of a single element having two aspheric surfaces, and said second lens unit consists of a single biconvex element.

Claim 82

The lens of claim 67 where the surfaces of said biconvex element are aspheric.

Claim 83

The lens of claim 67 where said first lens unit consists of a single element which is of positive optical power at the optical axis and changes to negative optical power adjacent its clear aperture, and has two aspheric surfaces.

Claim 84

The lens of claim 67 where said third corrector lens unit consists of a single element having two aspheric surfaces.

Claim 85

The lens of claim 80 where said third corrector lens unit has surfaces which are defined at the optical axis on radii which are substantially equal to or greater than the equivalent focal length of said lens.

Claim 86

The lens of claim 67 where said third corrector lens unit consists of a single element having surfaces which are defined at the optical axis on radii which are substantially equal to or greater thant the equivalent focla length of said lens, and both of said surfaces are aspheric.

Claim 87

The lens of claim 67 where said first lens unit and said third corrector lens unit each consist of single elements.

Claim 88

The lens of claim 83 where both of said first lens unit and said third corrector lens unit have two aspheric surfaces.

Claim 89

The lens of claim 67 satisfying the condition 0.92≧2H/CA>0.5 where CA is the clear aperture of the image side surface of said corrector lens unit and H is the height on the image side surface of said corrector lens unit measured from the optical axis where the axial marginal rays passing from said second lens unit as traced from the long conjugate intersect said image side surface of said corrector lens unit.

Claim 90

The projection lens of claim 80 wherein said first lens unit and said corrector lens unit are both convex to said second lens unit.

Claim 91

The projection lens of claim 81 wherein said first lens unit and said corrector lens unit are both convex to said second lens unit.

Claim 92

The lens of claim 67 where said corrector lens unit consists of a single element having surfaces which are defined at the optical axis on radii which are substantially equal to or greater than the equivalent focal length of said lens, said element being biconvex at the optical axis.