Color corrected projection lens
AssigneeU. S. Precision Lens, Inc.
InventorMelvyn H. Kreitzer
Life of this patent
Estimating the term…
Abstract
A lens comprising from the image side a first lens unit which is a positive element with at least one aspheric surface; a three element lens unit consisting of a biconcave element, a biconvex element and another positive component, in that order; a third lens unit having a strongly concave image side surface and which serves as a field flattener and to correct the Petzval sum of the lens.
Claims59
A projection lens for use in combination with a cathode ray tube where the projection lens is closely coupled to the cathode ray tube, said lens comprising from the image end a first lens unit of positive optical power having at least one aspheric surface and contributing to correction of aperture dependent aberrations, a second lens unit providing a majority of the positive power of said lens, and a third lens unit having a strongly concave image side surface which provides correction for field curvature and Petzval sum of other units of said lens, said second lens unit consisting from the image end of a biconcave element, a biconvex element and a positive component, said biconcave element and said biconvex element forming a color correcting doublet and being of overall meniscus shape concave to the image end, said color correcting doublet being axially spaced from said positive component a distance less than 0.01 of the equivalent focal length of said lens.
A projection lens for use in combination with a cathode ray tube where the projection lens is closely coupled to the cathode ray tube, said lens comprising from the image end a first lens unit of positive optical power having at least one aspheric surface and contributing to correction of aperture dependent aberrations, a second lens unit providing a majority of the positive power of said lens, and a third lens unit having a strongly concave image side surface which provides correction for field curvature and Petzval sum of other units of said lens, said second lens unit consisting from the image end of a biconcave element, a biconvex element and a positive component, said biconcave element and said first biconvex element forming a color correcting doublet and being of overall meniscus shape concave to the image end, said positive component comprising two elements, one of said elements of said positive component having two aspheric surfaces and being of meniscus shape.
A projection lens for use in combination with a cathode ray tube where the projection lens is closely coupled to the cathode ray tube, said lens comprising from the image end a first lens unit of positive optical power having at least one aspheric surface and contributing to correction of aperture dependent aberrations, said first lens unit consisting of a single element, a second lens unit providing a majority of the positive power of said lens, and a third lens unit having a strongly concave image side surface which provides correction for field curvature and Petzval sum of other units of said lens, said second lens unit comprising from the image end a biconcave element, a biconvex element and a positive element, said biconcave element and said biconvex element forming a color correcting doublet and being of overall meniscus shape concave to the image end, and a corrector lens unit of weak optical power having at least one aspheric surface positioned between said second and third lens units, said corrector lens unit being axially spaced from said second lens unit a distance
- 0.4>D.sub.2C /F.sub.0 >0.15
- where D.sub.2C is the axial spacing distance between said second lens unit and said corrector element and F0 is the equivalent focal length of said lens.
A projection lens for use in combination with a cathode ray tube where the projection lens is closely coupled to the cathode ray tube, said lens comprising from the image end a first lens unit of postive optical power having at least one aspheric surface and contributing to correction of aperture dependent aberrations, a second lens unit providing a majority of the positive power of said lens, and a third lens unit having a strongly concave image side surface which provides correction for field curvature and Petzval sum of the other units of said lens, said second lens unit comprising from the image end a biconcave element, a biconvex element and a positive lens element, said biconcave element and said biconvex element forming a color correcting doublet and being of overall meniscus shape concave to the image end, a corrector lens unit positioned between said second and third lens units, said lens having a variable focus and said first lens unit, said second lens unit, and said corrector lens unit being movable axially in the same direction to change the focus of said lens, one of said first lens unit and said corrector lens unit moving differentially with respect to the other movable lens units.
A projection lens for use in combination with a cathode ray tube where the projection lens is closely coupled to the cathode ray tube, said lens comprising from the image end a first lens unit of positive optical power having at least one aspheric surface and contributing to correction of aperture dependent aberrations, a second lens unit providing a majority of the positive power of said lens, and a third lens unit having a strongly concave image side surface which provides correction for field curvature and Petzval sum of other units of said lens, said second lens unit comprising from the image end a biconcave element, a biconvex element and a positive element, said biconcave element and said biconvex element forming a color correcting doublet and being of overall meniscus shape concave to the image end, and a corrector lens unit of weak optical power having at least one aspheric surface positioned between said second and third lens units, said corrector lens unit being axially spaced from said second lens unit a distance
- 0.4>D.sub.2C /F.sub.0 >0.15
- where D.sub.2C is the axial spacing distance between said second lens unit and said corrector element and F.sub.0 is the equivalent focal length of said lens.
A projection lens for use in combination with a cathode ray tube where the projection lens is closely coupled to the cathode ray tube, said lens comprising from the image end a first lens unit of weak optical power having at least one aspheric surface and contributing to correction of aperture dependent aberrations, a second lens unit providing a majority of the positive power of said lens, said second lens unit being spaced from said first lens unit at least 0.1 of the equivalent focal length of the lens, and a third lens unit having a strongly concave image side surface which provides correction for field curvature and Petzval sum of other units of said lens, said second lens unit comprising from the image end a biconcave element, a biconvex element and a positive element, said biconcave element and said biconvex element forming a color correcting doublet and being of overall meniscus shape concave to the image end, and a corrector lens unit of weak optical power positioned between said second and third lens, said corrector lens unit having at least one aspheric surface, the configuration and the positioning 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 a surface of said corrector lens unit at a height H from the optical axis of said lens that is less than the clear aperture of said surface of said corrector lens unit, said corrector lens surface being configured to contribute to correction of aperture dependent aberrations within said height H, said surface of said corrector lens beyond said height H being configured to contribute to correction of aberrations due to off-axis rays.
A projection lens for use in combination with a cathode ray tube where the projection lens is closely coupled to the cathode ray tube, said lens comprising from the image end a first lens unit of positive optical power having at least one aspheric surface and contributing to correction of aperture dependent aberrations, said first lens unit comprising a front meniscus element convex toward the image end, a second lens unit providing a majority of the positive power of said lens, said second lens unit being spaced from said meniscus element at least 0.1 of the equivalent focal length of the lens, and a third lens unit having a strongly concave image side surface which provides correction for field curvature and Petzval sum of other units of said lens, said second lens unit consisting from the image end of a biconcave element, a biconvex element and a positive element, said biconcave element and said biconvex element forming a color correcting doublet and being of overall meniscus shape concave to the image end, and a corrector lens unit of weak optical power positioned between said second and third lens, the configuration and the positioning 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 a surface of said corrector lens unit at a height H from the optical axis of said lens that is less than the clear aperture of said surface of said corrector lens unit, said corrector lens surface being configured to contribute to correction of aperture dependent aberrations within said height H, said surface of said corrector lens beyond said height H being configured to contribute to correction of aberrations due to off-axis rays.
A projection lens for use in combination with a cathode ray tube where the projection lens is closely coupled to the cathode ray tube, said lens comprising from the image end a first lens unit of weak positive optical power having at least one aspheric surface and contributing to correction of aperture dependent aberrations, a second lens unit providing a majority of the positive power of said lens, and a third lens unit having a strongly concave image side surface which provides correction for field curvature and Petzval sum of other units of said lens, said second lens unit comprising from the image end a biconcave element, a biconvex element and a positive element, said biconcave element and said biconvex element forming a color correcting doublet and being of overall meniscus shape concave to the image end, and a corrector lens unit of weak optical power positioned between said second and third lens, the configuration and the positioning of said corrector lens unit from said second lens unit being such that the axial marginal rays from said second lens unit as traced from the long conjugate intersect a surface of said corrector lens unit at a height H from the optical axis of said lens that is less than the clear aperture of said surface of said corrector lens unit, said corrector lens surface being configured to contribute to correction of aperture dependent aberrations within said height H, said surface of said corrector lens beyond said height H being configured to contribute to correction of aberrations due to off-axis rays.
A projection lens system for use in combination with a cathode ray tube comprising:
- (a) a first lens at the image end of said lens system wherein the surface of said first lens on the image side is convex to the image on the axis of said first lens and is concave to the image at and near the clear aperture of said first lens and the other surface of said first lens is concave to the image;
- (b) a second lens adapted to be closely coupled to a cathode ray tube, said second lens having a concave image side surface;
- (c) a color correcting doublet located between said first and second lenses, said color correcting doublet being comprised of a biconcave lens and a biconvex lens;
- (d) a biconvex lens located between said color correcting doublet and said second lens;
- and
- (e) a corrector lens located between said biconvex lens and said second lens, said corrector lens being shaped and positioned to contribute to correction of spherical aberrations in the central portion thereof and to contribute to the correction of aberrations due to off axis rays beyond said central portion.
A projection lens system for use in combination with a cathode ray tube comprising
- (a) a first lens at the image end of said lens system wherein the surface of said first lens on the image side is convex to the image on the axis of said first lens and is concave to the image at and near the clear aperture of said first lens and the other surface of said first lens is concave to the image;
- (b) a second lens adapted to be closely coupled to the cathode ray tube, said second lens having a concave image side aspheric surface;
- (c) a color correcting doublet located between said first and second lenses, the color correcting doublet being comprised of a biconcave lens and a biconvex lens;
- (d) a biconvex lens located between said color correcting doublet and said biconvex lens;
- and
- (e) a meniscus lens convex to the image located between said doublet and said biconvex lens.
Dependencies are inferred from the claim text.