Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. When a curvature radius of an object-side surface of the fourth lens is R8, and a curvature radius of an image-side surface of the fourth lens is R9, and an Abbe number of the material of the third lens for d-line is ?d3, and an Abbe number of the material of the fifth lens for d-line is ?d5, the following conditional formulas (1) and (6) are satisfied: ?0.61<(R8+R9)/(R8?R9)<0.44 ??(1); and 38.1<?d3+?d5<45.1 ??(6).

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. When a curvature radius of an object-side surface of the fourth lens is R8, and a curvature radius of an image-side surface of the fourth lens is R9, and an Abbe number of the material of the third lens for d-line is ?d3, and an Abbe number of the material of the fifth lens for d-line is ?d5, the following conditional formulas (1) and (6) are satisfied: ?0.61<(R8+R9)/(R8?R9)<0.44??(1); and 38.1<?d3+?d5<45.1??(6).

Abstract: An imaging lens substantially consists of five lenses of a first lens having a meniscus shape with its convex surface facing an object side and negative refractive power, a second lens having negative refractive power, and the image-side surface of which has a convex shape facing an image side in the vicinity of an optical axis, a third lens having positive refractive power, a stop, a fourth lens having positive refractive power, and a fifth lens having negative refractive power. At least one of the surfaces of the first lens through the fifth lens is aspherical. A predetermined conditional formula about a distance on the optical axis from an object-side surface of the first lens to an image plane and a distance on the optical axis from the object-side surface of the first lens to the image-side surface of the second lens is satisfied.

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. When a curvature radius of an object-side surface of the fourth lens is R8, and a curvature radius of an image-side surface of the fourth lens is R9, and an Abbe number of the material of the third lens for d-line is ?d3, and an Abbe number of the material of the fifth lens for d-line is ?d5, the following conditional formulas (1) and (6) are satisfied: ?0.61<(R8+R9)/(R8?R9)<0.44??(1); and 38.1<?d3+?d5<45.1??(6).

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. When a curvature radius of an object-side surface of the fourth lens is R8, and a curvature radius of an image-side surface of the fourth lens is R9, and an Abbe number of the material of the third lens for d-line is ?d3, and an Abbe number of the material of the fifth lens for d-line is ?d5, the following conditional formulas (1) and (6) are satisfied: ?0.61<(R8+R9)/(R8?R9)<0.44 ??(1); and 38.1<?d3+?d5<45.1 ??(6).

Abstract: An imaging lens substantially consists of five lenses of a first lens having a meniscus shape with its convex surface facing an object side and negative refractive power, a second lens having negative refractive power, and the image-side surface of which has a convex shape facing an image side in the vicinity of an optical axis, a third lens having positive refractive power, a stop, a fourth lens having positive refractive power, and a fifth lens having negative refractive power. At least one of the surfaces of the first lens through the fifth lens is aspherical. A predetermined conditional formula about a distance on the optical axis from an object-side surface of the first lens to an image plane and a distance on the optical axis from the object-side surface of the first lens to the image-side surface of the second lens is satisfied.

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. When a curvature radius of an object-side surface of the fourth lens is R8, and a curvature radius of an image-side surface of the fourth lens is R9, and an Abbe number of the material of the third lens for d-line is ?d3, and an Abbe number of the material of the fifth lens for d-line is ?d5, the following conditional formulas (1) and (6) are satisfied: ?0.61<(R8+R9)/(R8?R9)<0.44??(1); and 38.1<?d3+?d5<45.1??(6).

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. An object-side surface of the second lens is concave, and an object-side surface of the third lens is concave. A predetermined conditional formula about a combined focal length of the fourth lens and the fifth lens is satisfied.

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. An object-side surface of the second lens has a shape having negative refractive power at a center, and including a part having positive refractive power in an area between the center and an effective diameter edge, and having negative refractive power at the effective diameter edge (concave shape facing the object side), and the refractive power at the effective diameter edge being weaker than the refractive power at the center. Further, an object-side surface of the third lens is convex toward the object side. Further, a predetermined conditional formula about a combined focal length of the first lens, the second lens and the third lens is satisfied.

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. When a curvature radius of an object-side surface of the fourth lens is R8, and a curvature radius of an image-side surface of the fourth lens is R9, and an Abbe number of the material of the third lens for d-line is ?d3, and an Abbe number of the material of the fifth lens for d-line is ?d5, the following conditional formulas (1) and (6) are satisfied: ?0.61<(R8+R9)/(R8?R9)<0.44??(1); and 38.1<?d3+?d5<45.1??(6).

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. An object-side surface of the second lens is concave, and an object-side surface of the third lens is concave. A predetermined conditional formula about a combined focal length of the fourth lens and the fifth lens is satisfied.

Abstract: An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. An object-side surface of the second lens has a shape having negative refractive power at a center, and including a part having positive refractive power in an area between the center and an effective diameter edge, and having negative refractive power at the effective diameter edge (concave shape facing the object side), and the refractive power at the effective diameter edge being weaker than the refractive power at the center. Further, an object-side surface of the third lens is convex toward the object side. Further, a predetermined conditional formula about a combined focal length of the first lens, the second lens and the third lens is satisfied.

Abstract: An imaging lens substantially consists of five lenses of a first lens having a meniscus shape with its convex surface facing an object side and negative refractive power, a second lens having negative refractive power, and the image-side surface of which has a convex shape facing an image side in the vicinity of an optical axis, a third lens having positive refractive power, a stop, a fourth lens having positive refractive power, and a fifth lens having negative refractive power. At least one of the surfaces of the first lens through the fifth lens is aspherical. A predetermined conditional formula about a distance on the optical axis from an object-side surface of the first lens to an image plane and a distance on the optical axis from the object-side surface of the first lens to the image-side surface of the second lens is satisfied.

Abstract: An objective lens for converging light emitted from a light source onto an optical recording medium to record and reproduce information consists of a single lens that has at least one aspheric surface. The following conditional expressions (1) and (2) are satisfied: ?0.90<R1/R2<?0.45??(1) 0.70<d/f<1.40??(2) where R1 denotes a radius of curvature (mm) of a light source side surface near an optical axis, R2 denotes a radius of curvature (mm) of an optical recording medium side surface near the optical axis, d denotes a thickness (mm) on an optical axis, and f denotes a focal length (mm).

Abstract: An objective lens consists of a single lens element, and has a light source side surface formed into a convex surface having a large curvature and an optical recording medium side surface has a small curvature. The both surfaces are aspheric surfaces. Also, the objective lens satisfies the following expressions (1) to (3): 0.7<NA<0.98??(1) 0.70<d/f<1.40??(2) 0.48<X<0.55??(3). where NA denotes a numerical aperture of the objective lens on an optical recording medium side, d denotes a thickness of the objective lens on an optical axis in mm, and f denotes a focal length of the objective lens in mm. X is equal to (X1?X2)·(n?1)/(NA·f), where X1 and X2 denote values relating to sag amounts in the respective surfaces, and n denotes a refractive index.

Abstract: An objective lens consists of a single lens element. A light source side surface is formed into a convex surface having a large curvature, and an optical recording medium side surface has a small curvature. The both surfaces are formed into aspheric surfaces. Also, the objective lens satisfies the following expressions (1) to (3): 0.70<NA<0.98??(1) 0.70<d/f<3.00??(2) 0.50<g/d<0.80??(3) where NA denotes a numerical aperture of the objective lens on an optical recording medium side, d denotes a thickness, in mm, of the objective lens on an optical axis, and g is a distance, in mm, from a tangential plane that is perpendicular to the optical axis and is tangent to a vertex of the light source side surface of the objective lens, to a center of gravity of the objective lens.

Abstract: An objective lens for converging light emitted from a light source on an optical recording medium to record and reproduce information consists of a single lens having at least one aspheric surface. The following conditional expressions (1) to (3) are satisfied: N?1.75??(1) 0.5<f/f1<0.6??(2) 0.8<d/(NA·De)<1.0??(3) where N denotes a refractive index, f denotes a focal length (mm), f1 denotes a focal length (mm) of a light source side surface, d denotes a thickness (mm) on an optical axis, NA denotes a numerical aperture on an optical recording medium side, and De denotes an effective aperture (mm) of the light source side surface.

Abstract: A laser beam output from a semiconductor laser light source 1 is transmitted through a cover glass 2 in the optical axis Z direction, is incident on a molded lens 4 in a state of divergent rays, is converted into convergent rays by the molded lens 4, and is applied onto a recording face 5 of the optical recording medium. A diaphragm 3 is arranged. An area of each lens surface onto which a luminous flux of the laser beam restricted by the diaphragm 3 is applied corresponds to an effective area. The following expression (1) is satisfied: d1?d0?0.04 mm??(1) where d0 denotes an effective aperture of one of the lens surfaces, and d1 denotes an outer diameter of the one of the lens surfaces.

Abstract: A molding material is heated and pressed plural times when molded is an optical element having a radius of curvature smaller than a radius of a sphere having the same volume as the optical element. When such an optical element is molded, a closed space is formed between a molding material and a transfer surface of a mold in a state where the molding material is placed thereon. Thus, an appearance defect such as a recess is easily generated on the molded optical element. However, since the molding material is molded plural times, it is possible to place the molding materials on the transfer surfaces of the molds after a size of the closed space is adjusted so as not to generate the appearance defect prior to each heating/pressing process. Thereby, it is possible to suppress generation of an appearance defect in the molded optical element.

Abstract: An objective optical system is formed of a diffractive optical element with a diffractive surface formed on a virtual plane and an objective lens for focusing three collimated light beams of three different wavelengths at three different numerical apertures onto desired positions of three different recording media with substrates that include different thicknesses, such as an AOD, a DVD, and a CD, that introduce different amounts of spherical aberration in the focused beams. The objective optical system provides compensating spherical aberration to the three light beams by varying the distance between the diffractive optical element and the objective lens with the recording medium being used. The objective optical system focuses second-order diffracted light of one wavelength and first-order diffracted light of the other two wavelengths. An optical pickup device includes the objective optical system, the recording media, and a light source that provides the three light beams.