Objective for video disks

Claim 2

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks satisfying the following conditions: (1) 1.15 > f.sub.1 /f > 0.97 (2) 1.5 >|r.sub.2 | /d.sub.1 >1.1 (3) n.sub.2 - n.sub.3 > 0.28 (4) 1.01 > r.sub.4 /f > 0.85 (5) 0.91 > d.sub.2 /f > 0.57 wherein reference symbol f represents the focal length of the lens system as a whole, reference symbol f 1 represents the focal length of the front lens component, reference symbol r 2 represents the radius of curvature of the surface on the image side of the front lens component, reference symbol r 4 represents the radius of curvature of the cemented surface of the rear lens component, reference symbol d 1 represents the thickness of the front lens component, reference symbol d 2 represents the airspace between the front lens component and rear lens component, and reference symbols n 2 and n 3 respectively represent refractive indices of respective lenses constituting the rear lens component.

Claim 3

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks having the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.372 n.sub.1 = 1.51462 ν.sub.1 = 64.1 r.sub.2 = -0.524 d.sub.2 = 0.832 r.sub.3 = 1.642 d.sub.3 = 0.151 2 = 1.77861 ν.sub.2 = 25.7 r.sub.4 = 0.859 d.sub.4 = 0.305 n.sub.3 = 1.48601 ν.sub.3 = 70.1 r.sub.5 = -1.555 f = 1 , β = -35x , N.A. = 0.33 WD = 0.103 , ΣP = 0.1902 , f.sub.1 = 1.02 ______________________________________ wherein reference symbols r 1 through r 5 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 4 respectively represent thicknesses of respective lenses and airspace between respective lens components, reference symbols n 1 , n 2 and n 3 respectively represent refractive indices of respective lenses for the wavelength of 632.8 nm, reference symbols ν 1 , ν 2 and ν 3 respectively represent Abbe's numbers of respective lenses for d line, reference symbol f represents the focal length of the lens system as a whole, reference symbol β represents magnification, reference symbol N.A. represents numerical aperture, reference symbol WD represents work distance, reference symbol ΣP represents Petzval's sum, and reference symbol f 1 represents the focal length of the front lens component.

Claim 4

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks having the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.372 n.sub.1 = 1.51462 ν.sub.1 = 64.1 r.sub.2 = -0.524 d.sub.2 = 0.832 r.sub.3 = 1.642 d.sub.3 = 0.151 2 = 1.77861 ν.sub.2 = 25.7 r.sub.4 = 0.859 d.sub.4 = 0.305 n.sub.3 = 1.48601 ν.sub.3 = 70.1 r.sub.5 = -1.555 f = 1 , β = -35x , N.A. = 0.33 WD = 0.103 , ΣP = 0.1902 , f.sub.1 = 1.02 ______________________________________ wherein reference symbols r 1 through r 5 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 4 respectively represent thicknesses of respective lenses and airspace between respective lens components, reference symbols n 1 , n 2 and n 3 respectively represent refractive indices of respective lenses for the wavelength of 632.8 nm, reference symbols ν 1 , ν 2 and ν 3 respectively represent Abbe's numbers of respective lenses for d line, reference symbol f represents the focal length of the lens system as a whole, reference symbol β represents magnification, reference symbol N.A. represents numerical aperture, reference symbol WD represents work distance, reference symbol ΣP represents Petzval's sum, and reference symbol f 1 represents the focal length of the front lens component.

Claim 5

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks having the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.372 n.sub.1 = 1.56671 ν.sub.1 = 56.2 r.sub.2 = -0.549 d.sub.2 = 0.906 r.sub.3 = 1.632 d.sub.3 = 0.145 n.sub.2 = 1.77861 ν.sub.2 = 25.7 r.sub.4 = 0.865 d.sub.4 = 0.301 n.sub.3 = 1.48601 ν.sub.3 = 70.1 r.sub.5 = -1.632 f = 1 , β = -35x , N.A. = 0.35 WD = 0.096 , ΣP = 0.188 , f.sub.1 = 0.97 ______________________________________ wherein reference symbols r 1 through r 5 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 4 respectively represent thicknesses of respective lenses and airspace between respective lens component, reference symbols n 1 , n 2 and n 3 respectively represent refractive indices of respective lenses for the wavelength of 632.8 nm, reference symbols ν 1 , ν 2 and ν 3 respectively represent Abbe's numbers of respective lenses for d line, reference symbol f represents the focal length of the lens system as a whole, reference symbol β represents magnification, reference symbol N.A. represents numerical aperture, reference symbol WD represents work distance, reference symbol ΣP represents Petzval's sum, and reference symbol f 1 represents the focal length of the front lens component.

Claim 6

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks having the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.372 n.sub.1 = 1.56671 ν.sub.1 = 56.2 r.sub.2 = -0.549 d.sub.2 = 0.906 r.sub.3 = 1.632 d.sub.3 = 0.145 n.sub.2 = 1.77861 ν.sub.2 = 25.7 r.sub.4 = 0.865 d.sub.4 = 0.301 n.sub.3 = 1.48601 ν.sub.3 = 70.1 r.sub.5 = -1.632 f = 1 , β = -35x , N.A. = 0.35 WD = 0.096 , ΣP = 0.188 , f.sub.1 = 0.97 ______________________________________ wherein reference symbols r 1 through r 5 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 4 respectively represent thicknesses of respective lenses and airspace between respective lens component, reference symbols n 1 , n 2 and n 3 respectively represent refractive indices of respective lenses for the wavelength of 632.8 nm, reference symbols ν 1 , ν 2 and ν 3 respectively represent Abbe's numbers of respective lenses for d line, reference symbol f represents the focal length of the lens system as a whole, reference symbol β represents magnification, reference symbol N.A. represents numerical aperture, reference symbol WD represents work distance, reference symbol ΣP represents Petzval's sum, and reference symbol f 1 represents the focal length of the front lens component.

Claim 7

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks having the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.562 n.sub.1 = 1.61655 ν.sub.1 = 36.3 r.sub.2 = -0.693 d.sub.2 = 0.655 r.sub.3 = 1.944 d.sub.3 = 0.142 n.sub.2 = 1.77861 ν.sub.2 = 25.7 r.sub.4 = 0.95 d.sub.4 = 0.304 n.sub.3 = 1.49668 ν.sub.3 = 65.0 r.sub.5 = -1.62 f = 1 , β = -35x , N.A. = 0.37 WD = 0.102 , ΣP = 0.165 , f.sub.1 = 1.12 ______________________________________ wherein reference symbols r 1 through r 5 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 4 respectively represent thicknesses of respective lenses and airspace between respective lens components, reference symbols n 1 , n 2 and n 3 respectively represent refractive indices of respective lenses for the wavelength of 632.8 nm, reference symbols ν 1 , ν 2 and ν 3 respectively represent Abbe's numbers of respective lenses for d line, reference symbol f represents the focal length of the lens system as a whole, reference symbol β represents magnification, reference symbol N.A. represents numerical aperture, reference symbols WD represents work distance, reference symbol ΣP represents Petzval's sum, and reference symbol f 1 represents the focal length of the front lens component.

Claim 8

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks having the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.562 n.sub.1 = 1.61655 ν.sub.1 = 36.3 r.sub.2 = -0.693 d.sub.2 = 0.655 r.sub.3 = 1.944 d.sub.3 = 0.142 n.sub.2 = 1.77861 ν.sub.2 = 25.7 r.sub.4 = 0.95 d.sub.4 = 0.304 n.sub.3 = 1.49668 ν.sub.3 = 65.0 r.sub.5 = -1.62 f = 1 , β = -35x , N.A. = 0.37 WD = 0.102 , ΣP = 0.165 , f.sub.1 = 1.12 ______________________________________ wherein reference symbols r 1 through r 5 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 4 respectively represent thicknesses of respective lenses and airspace between respective lens components, reference symbols n 1 , n 2 and n 3 respectively represent refractive indices of respective lenses for the wavelength of 632.8 nm, reference symbols ν 1 , ν 2 and ν 3 respectively represent Abbe's numbers of respective lenses for d line, reference symbol f represents the focal length of the lens system as a whole, reference symbol β represents magnification, reference symbol N.A. represents numerical aperture, reference symbols WD represents work distance, reference symbol ΣP represents Petzval's sum, and reference symbol f 1 represents the focal length of the front lens component.

Claim 9

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks having the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.731 n.sub.1 = 1.72309 ν.sub.1 = 28.5 r.sub.2 = -0.831 d.sub.2 = 0.577 r.sub.3 = 2.007 d.sub.3 = 0.135 n.sub.2 = 1.77861 ν.sub.2 = 25.7 r.sub.4 = 0.986 d.sub.4 = 0.308 n.sub.3 = 1.49668 ν.sub.3 = 65.0 r.sub.5 = -1.969 f = 1 , β = -35x , N.A. = 0.38 WD = 0.098 , ΣP = 0.151 , f.sub.1 = 1.15 ______________________________________ wherein reference symbols r 1 through r 5 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 4 respectively represent thicknesses of respective lenses and airspace between respective lens components, reference symbols n 1 , n 2 and n 3 respectively represent refractive indices of respective lenses for the wavelength of 632.8 nm, reference symbols ν 1 , ν 2 and ν 3 respectively represent Abbe's numbers of respective lenses for d line, reference symbol f represents the focal length of the lens system as a whole, reference symbol β represents magnification, reference symbol N.A. represents numerical aperture, reference symbol WD represents work distance, reference symbol ΣP represents Petzval's sum, and reference symbol f 1 represents the focal length of the front lens component.

Claim 10

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks having the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.731 n.sub.1 = 1.72309 ν.sub.1 = 28.5 r.sub.2 = -0.831 d.sub.2 = 0.577 r.sub.3 = 2.007 d.sub.3 = 0.135 n.sub.2 = 1.77861 ν.sub.2 = 25.7 r.sub.4 = 0.986 d.sub.4 = 0.308 n.sub.3 = 1.49668 ν.sub.3 = 65.0 r.sub.5 = -1.969 f = 1 , β = -35x , N.A. = 0.38 WD = 0.098 , ΣP = 0.151 , f.sub.1 = 1.15 ______________________________________ wherein reference symbols r 1 through r 5 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 4 respectively represent thicknesses of respective lenses and airspace between respective lens components, reference symbols n 1 , n 2 and n 3 respectively represent refractive indices of respective lenses for the wavelength of 632.8 nm, reference symbols ν 1 , ν 2 and ν 3 respectively represent Abbe's numbers of respective lenses for d line, reference symbol f represents the focal length of the lens system as a whole, reference symbol β represents magnification, reference symbol N.A. represents numerical aperture, reference symbol WD represents work distance, reference symbol ΣP represents Petzval's sum, and reference symbol f 1 represents the focal length of the front lens component.

Claim 11

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks having the following numerical data: r.sub.1 = ∞ d.sub.1 = 0.758 n.sub.1 = 1.77861 ν.sub.1 = 25.7 r.sub.2 = -0.878 d.sub.2 = 0.606 r.sub.3 = 2.07 d.sub.3 = 1.149 n.sub.2 = 1.77861 ν.sub.2 = 25.7 r.sub.4 = 1.004 d.sub.4 = 0.305 n.sub.3 = 1.49668 ν.sub.3 = 65.0 r.sub.5 = -2.029 f = 1 , β = -35x , N.A. = 0.4 WD = 0.099 , ΣP = 0.146 , f.sub.1 = 1.13 ______________________________________ wherein reference symbols r 1 through r 5 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 4 respectively represent thicknesses of respective lenses and airspace between respective lens components, reference symbols n 1 , n 2 and n 3 respectively represent refractive indices of respective lenses for the wavelength of 632.8 nm, reference symbols ν 1 , ν 2 and ν 3 respectively represent Abbe's numbers of respective lenses for d line, reference symbol f represents the focal length of the lens system as a whole, reference symbol β represents magnification, reference symbol N.A. represents numerical aperture, reference symbol WD represents work distance, reference symbol ΣP represents Petzval's sum, and reference symbol f 1 represents the focal length of the front lens component.

Claim 12

An objective for video disks comprising a front lens component and a rear lens component, said front lens component being an approximately hemispherical lens with its plane surface positioned toward the object side, said rear lens component being a cemented doublet lens consisting of a concave lens and a convex lens, said objective for video disks having the following numerical data: r.sub.1 = ∞ d.sub.1 = 0.758 n.sub.1 = 1.77861 ν.sub.1 = 25.7 r.sub.2 = -0.878 d.sub.2 = 0.606 r.sub.3 = 2.07 d.sub.3 = 1.149 n.sub.2 = 1.77861 ν.sub.2 = 25.7 r.sub.4 = 1.004 d.sub.4 = 0.305 n.sub.3 = 1.49668 ν.sub.3 = 65.0 r.sub.5 = -2.029 f = 1 , β = -35x , N.A. = 0.4 WD = 0.099 , ΣP = 0.146 , f.sub.1 = 1.13 ______________________________________ wherein reference symbols r 1 through r 5 respectively represent radii of curvature of respective surfaces of respective lenses, reference symbols d 1 through d 4 respectively represent thicknesses of respective lenses and airspace between respective lens components, reference symbols n 1 , n 2 and n 3 respectively represent refractive indices of respective lenses for the wavelength of 632.8 nm, reference symbols ν 1 , ν 2 and ν 3 respectively represent Abbe's numbers of respective lenses for d line, reference symbol f represents the focal length of the lens system as a whole, reference symbol β represents magnification, reference symbol N.A. represents numerical aperture, reference symbol WD represents work distance, reference symbol ΣP represents Petzval's sum, and reference symbol f 1 represents the focal length of the front lens component.