US4682862A — Projection lens

Claim 1

Independent Claim 148 words

A projection lens for a cathode ray tube having a semi-field angle of essentially thirty degrees or greater which consists of a first lens unit of weak positive power, a second lens unit including a biconvex glass element, and a third lens unit having a strongly concave image side surface and which contributes to correction of field curvature, and a meniscus corrector lens element having at least one aspheric surface and positioned to said second lens unit less than 0.1 percent of the equivalent focal length of the lens and having a surface convex to said second lens unit and contributing to correction of oblique spherical aberration, said meniscus corrector lens element having an axial optical power 0.05>K.sub.M /K.sub.0 >.sup.- 0.23 where K M is the optical power of said meniscus lens elements at the optical axis and K 0 is the optical power of the overall lens.

Claim 2

Dependent Claim 148 words

A projection lens for a cathode ray tube having a semi-field angle of essentially thirty degrees or greater which consists of a first lens unit of weak positive power, a second lens unit including a biconvex glass element, and a third lens unit having a strongly concave image side surface and which contributes to correction of field curvature, and a meniscus corrector lens element having at least one aspheric surface and positioned to said second lens unit less than 0.1 percent of the equivalent focal length of the lens and having a surface convex to said second lens unit and contributing to correction of oblique spherical aberration, said meniscus corrector lens element having an axial optical power 0.05>K.sub.M /K.sub.0 >.sup.- 0.23 where K M is the optical power of said meniscus lens elements at the optical axis and K 0 is the optical power of the overall lens.

Claim 3

Dependent Claim 30 words

The projection lens of claim 1 wherein said meniscus corrector lens element is on the image side of said second lens unit and forms part of said first lens unit.

Claim 4

Dependent Claim 22 words

The projection lens of claim 1 where said meniscus corrector lens element is on the object side of said second lens unit.

Claim 5

Dependent Claim 27 words

The projection lens system of claim 1 where said first meniscus element becomes concave to the image on its image side surface adjacent the clear aperture thereof.

Claim 6

Dependent Claim 51 words

The projection lens system of claim 2 wherein the optical power of said first lens unit is positive and 0.20>K.sub.1 /K.sub.0 >0.05 where K 1 is the combined power of said first and second meniscii of said first lens unit and K 0 is the overall power of the lens system.

Claim 7

Dependent Claim 29 words

The projection lens system of claim 1 further including a further corrector lens unit positioned between said second and third lens units and having at least one aspheric surface.

Claim 8

Dependent Claim 51 words

The projection lens of claim 6 where said further corrector lens unit is axially 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 and F 0 is the equivalent focal length of the lens.

Claim 9

Dependent Claim 23 words

The projection lens system of claim 6 where said further corrector lens unit is an overall meniscus element concave to the image side.

Claim 10

Dependent Claim 13 words

The projection lens system of claim 8 where said meniscus element is positive.

Claim 11

Dependent Claim 153 words

A projection lens system having a semi-field angle of essentially thirty degrees or greater adapted to project an image from a cathode ray tube and consisting from the image end of a first lens unit of weak optical power, a second lens unit of strong optical power and including a biconvex element, and a third lens unit of strongly negative optical power having a concave image side surface and serving to provide correction for field curvature, said first lens unit comprising a first meniscus shaped element having positive power at the optical axis having at least one aspheric surface and being convex to the image at the optical axis, and a second meniscus shaped element of weak optical power having at least one aspheric surface, said second element of said first lens unit being closely spaced to and convex to the second lens unit to contribute to correction of sagittal oblique spherical aberration.

Claim 12

Dependent Claim 153 words

A projection lens system having a semi-field angle of essentially thirty degrees or greater adapted to project an image from a cathode ray tube and consisting from the image end of a first lens unit of weak optical power, a second lens unit of strong optical power and including a biconvex element, and a third lens unit of strongly negative optical power having a concave image side surface and serving to provide correction for field curvature, said first lens unit comprising a first meniscus shaped element having positive power at the optical axis having at least one aspheric surface and being convex to the image at the optical axis, and a second meniscus shaped element of weak optical power having at least one aspheric surface, said second element of said first lens unit being closely spaced to and convex to the second lens unit to contribute to correction of sagittal oblique spherical aberration.

Claim 13

Dependent Claim 26 words

The projection lens system of claim 10 where the cathode ray tube has a curved face plate and contributes optical power to said third lens unit.

Claim 14

Dependent Claim 42 words

The projection lens system of claim 10 where 0.6>D.sub.12 /F.sub.3 >0.1 where D 12 is the axial spacing between said first meniscus shaped element and said second lens unit and F 3 is the equivalent focal length of said third lens unit.

Claim 15

Dependent Claim 36 words

The projection lens system of claim 10 where said first meniscus element becomes concave to the image side on its image side surface adjacent the clear aperture of the image side surface of said first meniscus.

Claim 16

Dependent Claim 51 words

The projection lens system of claim 10 wherein the optical power of said first lens unit is positive and 0.20>K.sub.1 /K.sub.0 >0.05 where K 1 is the combined power of said first and second meniscii of said first lens unit and K 0 is the overall power of the lens system.

Claim 17

Dependent Claim 28 words

The projection lens system of claim 10 including a further corrector lens unit positioned between said second and third lens units and having at least one aspheric surface.

Claim 18

Dependent Claim 50 words

The projection lens of claim 15 where said corrector lens unit is axially 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 and F 0 is the equivalent focal length of the lens.

Claim 19

Dependent Claim 22 words

The projection lens system of claim 15 where said further corrector lens unit is a meniscus element concave to the image side.

Claim 20

Dependent Claim 13 words

The projection lens system of claim 17 where said meniscus element is positive.

Claim 21

Dependent Claim 17 words

The projection lens system of claim 18 where said meniscus element is concave to the image side.

Claim 22

Dependent Claim 21 words

The projection lens of claim 10 where said second meniscus element is on the object side of said second lens unit.

Claim 23

Dependent Claim 20 words

The projection lens of claim 10 where said second meniscus is on the image side of said second lens unit.

Claim 24

Dependent Claim 181 words

A projection lens for a cathode ray tube having a semi-field angle of essentially thirty degrees or greater which consists of a first lens unit of weak positive power, a second lens unit including a biconvex glass element, and a third lens unit having a strongly biconcave surface and which contributes to correction of field curvature, and a meniscus corrector lens unit having at least one aspheric surface closely positioned to said second lens unit and having a surface convex to said second lens unit, said corrector lens unit being of meniscus form and of weak optical power, said first lens unit and said corrector lens unit each consisting of a single plastic element having at least one aspheric surface, and Tmax/Tmin<2.5 where Tmax is the maximum thickness of said plastic elements parallel to the optical axis of the lens and Tmin is the minimum thickness of said plastic elements parallel to the optical axis of said lens, and an additional plastic corrector element having at least one aspheric surface positioned between said second lens unit and said third lens unit.

Claim 25

Dependent Claim 181 words

A projection lens for a cathode ray tube having a semi-field angle of essentially thirty degrees or greater which consists of a first lens unit of weak positive power, a second lens unit including a biconvex glass element, and a third lens unit having a strongly biconcave surface and which contributes to correction of field curvature, and a meniscus corrector lens unit having at least one aspheric surface closely positioned to said second lens unit and having a surface convex to said second lens unit, said corrector lens unit being of meniscus form and of weak optical power, said first lens unit and said corrector lens unit each consisting of a single plastic element having at least one aspheric surface, and Tmax/Tmin<2.5 where Tmax is the maximum thickness of said plastic elements parallel to the optical axis of the lens and Tmin is the minimum thickness of said plastic elements parallel to the optical axis of said lens, and an additional plastic corrector element having at least one aspheric surface positioned between said second lens unit and said third lens unit.

Claim 26

Dependent Claim 17 words

The projection lens of claim 22 where said additional plastic corrector element also satisfies the condition Tmax/Tmin<2.5

Claim 27

Dependent Claim 150 words

A projection lens for a cathode ray tube having a semi-field angle of essentially thirty degrees or greater which consists of a first lens unit of weak positive power, a second lens unit including a biconvex glass element, and a third lens unit having a strongly concave image side surface and which contributes to correction of field curvature, said first lens unit including a first meniscus element having at least one aspheric surface and a further meniscus corrector lens element having at least one aspheric surface and being closely positioned to said second lens unit on the image side thereof and having a surface convex to said second lens unit, said first lens unit having an optical power 0.20>K.sub.1 /K.sub.0 >0.05 where K 1 is the combined power of said first and second meniscii of said first lens unit and K 0 is the overall power of the lens system.

Claim 28

Dependent Claim 150 words

A projection lens for a cathode ray tube having a semi-field angle of essentially thirty degrees or greater which consists of a first lens unit of weak positive power, a second lens unit including a biconvex glass element, and a third lens unit having a strongly concave image side surface and which contributes to correction of field curvature, said first lens unit including a first meniscus element having at least one aspheric surface and a further meniscus corrector lens element having at least one aspheric surface and being closely positioned to said second lens unit on the image side thereof and having a surface convex to said second lens unit, said first lens unit having an optical power 0.20>K.sub.1 /K.sub.0 >0.05 where K 1 is the combined power of said first and second meniscii of said first lens unit and K 0 is the overall power of the lens system.

Claim 29

Dependent Claim 32 words

The projection lens of claim 24 where said first meniscus element is convex to the image side at the optical axis and becomes concave to the image side adjacent its clear aperture.

Claim 30

Dependent Claim 34 words

The projection lens of claim 24 where said second lens unit consists of a biconvex element and another element which is of positive power at the optical axis, said biconvex element having spherical surfaces.

Claim 31

Dependent Claim 41 words

The projection lens of claim 24 where 0.6>D.sub.12 /F.sub.3 >0.1 where D 12 is the axial spacing between said first meniscus shaped element and said second lens unit and F 3 is the equivalent focal length of said third lens unit.

Claim 32

Dependent Claim 15 words

The projection lens of claim 24 where said second lens unit consists of two elements.

Claim 33

Dependent Claim 17 words

The projection lens of claim 28 where said elements of said second lens unit have spherical surfaces.

Claim 34

Dependent Claim 16 words

The projection lens of claim 24 where the surfaces of said second lens element are spherical.

Claim 35

Dependent Claim 124 words

A projection lens for a cathode ray tube having a semi-field angle of essentially thirty degrees or greater which consists of a first lens unit of weak positive power including a first meniscus element convex to the image side, a second lens unit including a biconvex glass element, and a third lens unit having a strongly concave image side surface and which contributes to correction of field curvature, a corrector lens element of meniscus form of weak optical power having at least one aspheric surface and closely positioned to said second lens unit and having a surface convex to said second lens unit, and a further corrector lens unit positioned between said second and third lens units and having at least one aspheric surface.

Claim 36

Dependent Claim 124 words

A projection lens for a cathode ray tube having a semi-field angle of essentially thirty degrees or greater which consists of a first lens unit of weak positive power including a first meniscus element convex to the image side, a second lens unit including a biconvex glass element, and a third lens unit having a strongly concave image side surface and which contributes to correction of field curvature, a corrector lens element of meniscus form of weak optical power having at least one aspheric surface and closely positioned to said second lens unit and having a surface convex to said second lens unit, and a further corrector lens unit positioned between said second and third lens units and having at least one aspheric surface.

Claim 37

Dependent Claim 29 words

The projection lens of claim 31 wherein said corrector lens element is on the image side of said second lens unit and forms part of said first lens unit.

Claim 38

Dependent Claim 20 words

The projection lens of claim 31 where said corrector lens is on the object side of said second lens unit.

Claim 39

Dependent Claim 27 words

The projection lens system of claim 31 where said first meniscus element becomes concave to the image on its image side surface adjacent the clear aperture thereof.

Claim 40

Dependent Claim 51 words

The projection lens system of claim 32 wherein the optical power of said first lens unit is positive and 0.20>K.sub.1 /K.sub.0 >0.05 where K 1 is the combined power of said first and second meniscii of said first lens unit and K 0 is the overall power of the lens system.

Claim 41

Dependent Claim 51 words

The projection lens of claim 31 where said further corrector lens unit is axially 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 and F 0 is the equivalent focal length of the lens.

Claim 42

Dependent Claim 22 words

The projection lens system of claim 31 where said further corrector lens unit is a meniscus element concave to the image side.

Claim 43

Dependent Claim 13 words

The projection lens system of claim 37 where said meniscus element is positive.

Claim 44

Dependent Claim 41 words

The projection lens of claim 31 where 0.6>D.sub.12 /F.sub.3 >0.1 where D 12 is the axial spacing between said first meniscus shaped element and said second lens unit and F 3 is the equivalent focal length of said third lens unit.

Claim 45

Dependent Claim 15 words

The projection lens of claim 31 where said second lens unit consists of two elements.

Claim 46

Dependent Claim 17 words

The projection lens of claim 40 where said elements of said second lens unit have spherical surfaces.

Claim 47

Dependent Claim 16 words

The projection lens of claim 31 where the surfaces of said second lens element are spherical.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1990-07-27	1991-01-26	1991-07-28	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1994-07-27	1995-01-26	1995-07-28	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1998-07-27	1999-01-26	1999-07-28	$7700.00	Window Closed / Lapsed

Projection lens

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