Objective lens system for optical reading device

Claim 2

An objective lens system with a single lens element for use in a device for optically reading digital data on an optical disk, said single lens element including: a light source side aspherical surface having a positive refractive power; and a disk side surface having a positive refractive power; and wherein said objective lens system is used with the projecting magnification β, -1/2<β<-1/8 and the objective lens system fulfills the following conditions: 0.9≦(N.sub.1 -1)r.sub.1 /f≦3.9 1.4≦d.sub.1 r.sub.1 /f.sup.2 ≦4.0 1.4≦d.sub.1.sup.2 /f.sup.2 (N.sub.1 -1)≦4.0 wherein: f represents the focal length of the single lens element; r 1 represents the paraxial radius of curvature of the light source side surface of the single lens element; N 1 represents the refractive index of the single lens element; and d 1 represents the axial thickness of the single lens element.

Claim 3

An objective lens system as claimed in claim 1, wherein said disk side surface is an aspherical surface.

Claim 4

An objective lens system as claimed in claim 2, wherein the objective lens system further fulfills the following condition: 0≦f(N.sub.1.sup.2 -N.sub.1 -1)/|r.sub.2 |≦1.2 wherein: r 2 represents the radius of curvature of the disk side surface of the single lens element.

Claim 5

An objective lens system with a single lens element for use in a device for optically reading digital data on an optical disk; said single lens element including: a light source side aspherical surface having a positive refractive power; and a disk side surface having a positive refractive power; and wherein said objective lens system is used with the projecting magnification β, -1/2<β<-1/8 and the objective lens system fulfills the following conditions: 1.4≦(N.sub.1 -1)r.sub.1 /f≦3.9 1.6≦d.sub.1 r.sub.1 /f.sup.2 ≦4.0 wherein: f represents the focal length of the single lens element; r 1 represents the paraxial radius of curvature of the light source side surface of the single lens element; N 1 represents the refractive index of the single lens element; and d 1 represents the axial thickness of the single lens element.

Claim 6

An objective lens system with a single lens element for use in a device for optically reading digital data on an optical disk; said single lens element including: a light source side aspherical surface having a positive refractive power; and a disk side surface having a positive refractive power; and wherein said objective lens system is used with the projecting magnification β, -1/2<β<-1/8 and the objective lens system fulfills the following conditions: 1.4≦(N.sub.1 -1)r.sub.1 /f≦3.9 1.6≦d.sub.1 r.sub.1 /f.sup.2 ≦4.0 wherein: f represents the focal length of the single lens element; r 1 represents the paraxial radius of curvature of the light source side surface of the single lens element; N 1 represents the refractive index of the single lens element; and d 1 represents the axial thickness of the single lens element.

Claim 7

An objective lens system as claimed in claim 4, wherein the objective lens system further fulfills the following condition: 0≦f (N.sub.1.sup.2 -N.sub.1 -1)/|r.sub.2 |≦1.2 wherein: r 2 represents the radius of curvature of the disk side surface of the single lens element.

Claim 8

An objective lens system with a single lens element for use in a device for optically reading digital data on an optical disk, said single lens element including: a light source side aspherical surface having a positive refractive power; and a disk side surface having a positive refractive power; and wherein the objective lens system fulfills the following conditions:

Claim 9

An objective lens system with a single lens element for use in a device for optically reading digital data on an optical disk, said single lens element including: a light source side aspherical surface having a positive refractive power; and a disk side surface having a positive refractive power; and wherein the objective lens system fulfills the following conditions:

Claim 10

9≦(N 1 -1)r 1 /f≦3.9 1.2≦d.sub.1 r.sub.1 /f.sup.2 ≦4.0 0.7≦r.sub.1 (N.sub.1 -1)(1+|β|)/-r.sub.2 =3.0 wherein: f represents the focal length of the single lens element; r 1 represents the paraxial radius of curvature of the light source side surface of the single lens element; N 1 represents the refractive index of the single lens element; d 1 represents the axial thickness of the single lens element; r 2 represents the radius of curvature of the disk side surface of the single lens component; and β represents the magnification of the single lens element.

Claim 11

9≦(N 1 -1)r 1 /f≦3.9 1.2≦d.sub.1 r.sub.1 /f.sup.2 ≦4.0 0.7≦r.sub.1 (N.sub.1 -1)(1+|β|)/-r.sub.2 =3.0 wherein: f represents the focal length of the single lens element; r 1 represents the paraxial radius of curvature of the light source side surface of the single lens element; N 1 represents the refractive index of the single lens element; d 1 represents the axial thickness of the single lens element; r 2 represents the radius of curvature of the disk side surface of the single lens component; and β represents the magnification of the single lens element.

Claim 12

An objective lens system as claimed in claim 6, wherein said disk side surface is an aspherical surface.

Claim 13

An objective lens system as claimed in claim 6, wherein the objective lens system further fulfills the following conditions:

Claim 14

4≦(N 1 -1)r 1 /f≦3.9 1.6≦d.sub.1 r.sub.1 /f.sup.2 ≦4.0.

Claim 15

4≦(N 1 -1)r 1 /f≦3.9 1.6≦d.sub.1 r.sub.1 /f.sup.2 ≦4.0.

Claim 16

An objective lens system with a single lens element for use in a device for optically reading digital data on an optical disk, said single lens element including: a light source side aspherical surface having a positive refractive power; and a disk side surface having a positive refractive power; and wherein said objective lens system is used with the projecting magnification β, -1/2<β<-1/8 and wherein the objective lens system fulfills the following conditions: 0.9<(N.sub.1 -1)r.sub.1 /f<3.9 0.6<r.sub.1 /-r.sub.2 ·(N.sub.1 -1)<1.7 0.5<ε<1.5 wherein: f represents the focal length of the single lens element; r 1 represents the paraxial radius of curvature of the light source side surface of the single lens element; N 1 represents the refractive index of the single lens element; r 2 represents the radius of curvature of the disk side surface of the single lens element; and ε represents the conic constant.

Claim 17

An objective lens system with a single lens element for use in a device for optically reading digital data on an optical disk, said single lens element including: a light source side aspherical surface having a positive refractive power; and a disk side surface having a positive refractive power; and wherein said objective lens system is used with the projecting magnification β, -1/2<β<-1/8 and wherein the objective lens system fulfills the following conditions: 0.9<(N.sub.1 -1)r.sub.1 /f<3.9 0.6<r.sub.1 /-r.sub.2 ·(N.sub.1 -1)<1.7 0.5<ε<1.5 wherein: f represents the focal length of the single lens element; r 1 represents the paraxial radius of curvature of the light source side surface of the single lens element; N 1 represents the refractive index of the single lens element; r 2 represents the radius of curvature of the disk side surface of the single lens element; and ε represents the conic constant.

Claim 18

An objective lens system with a single lens element for a device for optically reading digital data on an optical disk, comprising the following design parameters: ______________________________________ NA = 0.47 f = 1.0 β = -0.17 ______________________________________ radius of axial refractive curvature distance index ______________________________________ rg.sub.1 ∞ dg.sub.1 0.067 Ng 1.49000 rg.sub.2 ∞ dg.sub.2 6.643 r.sub.1 * 1.2686 d.sub.1 1.356 N.sub.1 2.10000 r.sub.2 * -3.6447 d.sub.2 0.440 rp.sub.1 ∞ d.sub.p 0.267 Np 1.57147 rp.sub.2 ∞ ______________________________________ aspherical surface coefficients ______________________________________ r.sub.1 * ε = 1.0 C.sub.1 = 0.0 C.sub.2 = -0.62371 × 10.sup.-1 C.sub.3 = -0.35855 × 10.sup.-1 C.sub.4 = -0.34573 × 10.sup.-1 C.sub.5 = -0.10152 × 10.sup.-2 r.sub.2 * ε = 1.0 C.sub.1 = 0.0 C.sub.2 = 0.94476 × 10.sup.-1 C.sub.3 = -0.31391 C.sub.4 = -0.34388 × 10.sup.-4 C.sub.5 = 0.26302 × 10.sup.-4 ______________________________________ wherein NA is the numerical aperture, f is the focal length, β is the magnification, subletter g refers to a cover glass, subletter p refers to a plate glass, and the aspherical surface is defined as follows: ##EQU2## wherein, x represents a coordinate along the optical axis measured from an imaginary plane tangent to the aspherical surface perpendicularly to an optical axis, h represents the coordinate perpendicular to the optical axis measured from the optical axis, Co represents paraxial curvature (1/r 1 ) of the light source side surface of the lens (L), ε represents the conic constant and c i represents the aspherical surface coefficients.

Claim 19

An objective lens system with a single lens element for a device for optically reading digital data on an optical disk, comprising the following design parameters: ______________________________________ NA = 0.47 f = 1.0 β = -0.17 ______________________________________ radius of axial refractive curvature distance index ______________________________________ rg.sub.1 ∞ dg.sub.1 0.067 Ng 1.49000 rg.sub.2 ∞ dg.sub.2 6.643 r.sub.1 * 1.2686 d.sub.1 1.356 N.sub.1 2.10000 r.sub.2 * -3.6447 d.sub.2 0.440 rp.sub.1 ∞ d.sub.p 0.267 Np 1.57147 rp.sub.2 ∞ ______________________________________ aspherical surface coefficients ______________________________________ r.sub.1 * ε = 1.0 C.sub.1 = 0.0 C.sub.2 = -0.62371 × 10.sup.-1 C.sub.3 = -0.35855 × 10.sup.-1 C.sub.4 = -0.34573 × 10.sup.-1 C.sub.5 = -0.10152 × 10.sup.-2 r.sub.2 * ε = 1.0 C.sub.1 = 0.0 C.sub.2 = 0.94476 × 10.sup.-1 C.sub.3 = -0.31391 C.sub.4 = -0.34388 × 10.sup.-4 C.sub.5 = 0.26302 × 10.sup.-4 ______________________________________ wherein NA is the numerical aperture, f is the focal length, β is the magnification, subletter g refers to a cover glass, subletter p refers to a plate glass, and the aspherical surface is defined as follows: ##EQU2## wherein, x represents a coordinate along the optical axis measured from an imaginary plane tangent to the aspherical surface perpendicularly to an optical axis, h represents the coordinate perpendicular to the optical axis measured from the optical axis, Co represents paraxial curvature (1/r 1 ) of the light source side surface of the lens (L), ε represents the conic constant and c i represents the aspherical surface coefficients.