Object lens for optical pickup device, optical pickup device and optical information recording/reproducing device

An objective lens used for an optical pickup device, the optical pickup device comprising:

• a light source;
• and
• a converging optical system including the objective lens for converging a light beam emitted from the light source to an information recording surface of an optical information recording medium,
• wherein the optical pickup device is capable of recording and/or reproducing information by converging the light beam emitted from the light source to the information recording surface of the optical information recording medium with the converging optical system,
• wherein the objective lens is a plastic single lens that comprises a ring-shaped phase structure on at least one optical surface, the ring-shaped phase structure comprising a plurality of ring surfaces and formed so that adjacent ring surfaces generate a predetermined optical path difference for incident light, and satisfies following formulas:
• NA≧0.8 (7)
• 1.3>f>0.2 (8)
• 0.8<d/f<1.8 (14)
• 500≧λ0≧350 (15)
• 0.40≦(X1−X2)·(N−1)/(NA·f·√(1+|m|))≦0.63 (16)
• where NA is an image-side numerical aperture of the objective lens, which is required for recording and/or reproducing information for the optical information recording medium, f (mm) is a focal length of the objective lens, λ0 (nm) is a design wavelength of the objective lens, d(mm) is a lens thickness in an optical axis of the objective lens, X1 (mm) is a distance in an optical axis direction between a plane that is perpendicular to an optical axis and tangent to a top of an optical surface on a light source side and an optical surface on the light source side in a most peripheral portion of an effective diameter (position of the NA on a surface on the light source side to which a marginal light beam is incident), X2 (mm) is a distance in an optical axis direction between a plane that is perpendicular to an optical axis and tangent to a top of an optical surface on an optical information recording medium side and an optical surface on the optical information recording medium side in a most peripheral portion of an effective diameter (position of the NA on a surface on the optical information recording medium side to which a marginal light beam is incident), N is a refractive index of the objective lens at the design wavelength λ0, and m is an image formation magnification of the objective lens,
• wherein X1 is a plus in a case of measuring X1 in a direction of the optical information recording medium with reference to the tangent plane, and minus in a case of measuring X1 in a direction of the light source, and
• wherein X2 is plus in a case of measuring X2 in a direction of the optical information recording medium with reference to the tangent plane and minus in a case of measuring X2 in a direction of the light source.

An optical pickup device comprising:

• a light source;
• and
• a converging optical system including an objective lens for converging a light beam emitted from the light source to an information recording surface of an optical information recording medium,
• wherein the optical pickup device is capable of recording and/or reproducing information by converging the light beam emitted from the light source to the information recording surface of the optical information recording medium with the converging optical system,
• wherein the objective lens is a plastic single lens and satisfies following formulas:
• NA≧0.8 (1)
• 1.0>f>0.2 (2)
• 500≧λ0≧350 (15)
• where NA is an image-side numerical aperture of the objective lens, which is required for recording and/or reproducing information to the optical information recording medium, f (mm) is a focal length of the objective lens, and λ0 (nm) is a design wavelength of the objective lens,
• wherein the optical device satisfies the following formulas:
• 0.8<d/f<1.8 (14)
• 0.40≦(X1−X2)·(N−1)/(NA·f·√(1+|m|))≦0.63 (16)
• where d (mm) is a lens thickness in an optical axis of the objective lens, X1 (mm) is a distance in an optical axis direction between a plane that is perpendicular to an optical axis and tangent to a top of an optical surface on a light source side and an optical surface on the light source side in a most peripheral portion of an effective diameter (position of the NA on a surface on the light source side to which a marginal light beam is incident), X2 (mm) is a distance in an optical axis direction between a plane that is perpendicular to an optical axis and tangent to a top of an optical surface on an optical information recording medium side and an optical surface on the optical information recording medium side in a most peripheral portion of an effective diameter (position of the NA on a surface on the optical information recording medium side to which a marginal light beam is incident), N is a refractive index of the objective lens at the design wavelength λ0, and m is an image formation magnification of the objective lens,
• wherein X1 is a plus in a case of measuring X1 in a direction of the optical information recording medium with reference to the tangent plane, and minus in a case of measuring X1 in a direction of the light source, and
• wherein X2 is plus in a case of measuring X2 in a direction of the optical information recording medium with reference to the tangent plane and minus in a case of measuring X2 in a direction of the light source.

An optical pickup device comprising:

• a light source;
• and
• a converging optical system including an objective lens for converging a light beam emitted from the light source to an information recording surface of an optical information recording medium,
• wherein the optical pickup device is capable of recording and/or reproducing information by converging the light beam emitted from the light source to the information recording surface of the optical information recording medium with the converging optical system,
• wherein the objective lens is a plastic single lens that comprises a ring-shaped phase structure on at least one optical surface, the ring-shaped phase structure comprising a plurality of ring surfaces and formed so that adjacent ring surfaces generate a predetermined optical path difference for incident light, and satisfies following formulas:
• NA≧0.8 (7)
• 1.3>f>0.2 (8)
• 500≧λ0≧350 (15)
• where NA is an image-side numerical aperture of the objective lens, which is required for recording and/or reproducing information for the optical information recording medium, f (mm) is a focal length of the objective lens, and λ0 (nm) is a design wavelength of the objective lens,
• wherein the optical device satisfies the following formulas:
• 0.8<d/f<1.8 (14)
• 0.40≦(X1−X2)·(N−1)/(NA·f·√(1+|m|))≦0.63 (16)
• where d (mm) is a lens thickness in an optical axis of the objective lens, X1 (mm) is a distance in an optical axis direction between a plane that is perpendicular to an optical axis and tangent to a top of an optical surface on a light source side and an optical surface on the light source side in a most peripheral portion of an effective diameter (position of the NA on a surface on the light source side to which a marginal light beam is incident), X2 (mm) is a distance in an optical axis direction between a plane that is perpendicular to an optical axis and tangent to a top of an optical surface on an optical information recording medium side and an optical surface on the optical information recording medium side in a most peripheral portion of an effective diameter (position of the NA on a surface on the optical information recording medium side to which a marginal light beam is incident), N is a refractive index of the objective lens at the design wavelength λ0, and m is an image formation magnification of the objective lens,
• wherein X1 is a plus in a case of measuring X1 in a direction of the optical information recording medium with reference to the tangent plane, and minus in a case of measuring X1 in a direction of the light source, and
• wherein X2 is plus in a case of measuring X2 in a direction of the optical information recording medium with reference to the tangent plane and minus in a case of measuring X2 in a direction of the light source.

An optical information recording/reproducing apparatus, the apparatus including an optical pickup device that comprises:

• a light source;
• and
• a converging optical system including an objective lens for converging a light beam emitted from the light source to an information recording surface of an optical information recording medium,
• wherein the apparatus is capable of recording and/or reproducing information by converging the light beam emitted from the light source to the information recording surface of the optical information recording medium with the converging optical system,
• wherein the objective lens is a plastic single lens and satisfies following formulas:
• NA≧0.8 (1)
• 1.0>f>0.2 (2)
• 500≧λ0350 (15)
• where NA is an image-side numerical aperture of the objective lens, which is required for recording and/or reproducing information for the optical information recording medium, f (mm) is a focal length of the objective lens, and λ0 (nm) is a design wavelength of the objective lens,
• wherein the apparatus satisfies the following formulas:
• 0.8<d/f<1.8 (14)
• 0.40≦(X1−X2)·(N−1)/(NA·f·√(1+|m|))≦0.63 (16)
• where d (mm) is a lens thickness in an optical axis of the objective lens, X1 (mm) is a distance in an optical axis direction between a plane that is perpendicular to an optical axis and tangent to a top of an optical surface on a light source side and an optical surface on the light source side in a most peripheral portion of an effective diameter (position of the NA on a surface on the light source side to which a marginal light beam is incident), X2 (mm) is a distance in an optical axis direction between a plane that is perpendicular to an optical axis and tangent to a top of an optical surface on an optical information recording medium side and an optical surface on the optical information recording medium side in a most peripheral portion of an effective diameter (position of the NA on a surface on the optical information recording medium side to which a marginal light beam is incident), N is a refractive index of the objective lens at the design wavelength λ0, and m is an image formation magnification of the objective lens,
• wherein X1 is a plus in a case of measuring X1 in a direction of the optical information recording medium with reference to the tangent plane, and minus in a case of measuring X1 in a direction of the light source, and
• wherein X2 is plus in a case of measuring X2 in a direction of the optical information recording medium with reference to the tangent plane and minus in a case of measuring X2 in a direction of the light source.

An optical information recording/reproducing apparatus comprising:

• an optical pickup device;
• wherein the optical pickup device includes
• a light source;
• and
• a converging optical system including an objective lens for converging a light beam emitted from the light source to an information recording surface of an optical information recording medium,
• wherein the optical pickup device records and/or reproduces information by converging the light beam emitted from the light source to the information recording surface of the optical information recording medium with the converging optical system,
• wherein the objective lens is a plastic single lens that comprises a ring-shaped phase structure on at least one optical surface, the ring-shaped phase structure comprising a plurality of ring surfaces and formed so that adjacent ring surfaces generate a predetermined optical path difference for incident light, and satisfies following formulas:
• NA≧0.8 (7)
• 1.3>f>0.2 (8)
• 500≧λ0≧350 (15)
• where NA is an image-side numerical aperture of the objective lens, which is required for recording and/or reproducing information for the optical information recording medium, f (mm) is a focal length of the objective lens, and λ0 (nm) is a design wavelength of the objective lens,
• wherein the apparatus satisfies the following formulas:
• 0.8<d/f<1.8 (14)
• 0.40≦(X1−X2)·(N−1)/(NA·f·√(1+|m|))≦0.63 (16)
• where d (mm) is a lens thickness in an optical axis of the objective lens, X1 (mm) is a distance in an optical axis direction between a plane that is perpendicular to an optical axis and tangent to a top of an optical surface on a light source side and an optical surface on the light source side in a most peripheral portion of an effective diameter (position of the NA on a surface on the light source side to which a marginal light beam is incident), X2 (mm) is a distance in an optical axis direction between a plane that is perpendicular to an optical axis and tangent to a top of an optical surface on an optical information recording medium side and an optical surface on the optical information recording medium side in a most peripheral portion of an effective diameter (position of the NA on a surface on the optical information recording medium side to which a marginal light beam is incident), N is a refractive index of the objective lens at the design wavelength λ0, and m is an image formation magnification of the objective lens,
• wherein X1 is a plus in a case of measuring X1 in a direction of the optical information recording medium with reference to the tangent plane, and minus in a case of measuring X1 in a direction of the light source, and
• wherein X2 is plus in a case of measuring X2 in a direction of the optical information recording medium with reference to the tangent plane and minus in a case of measuring X2 in a direction of the light source.