Abstract: An optical pickup system for reading information of three kinds of optical recording media. The optical pickup system has a wavelength selective filter that includes an outer area for shielding one light beam of light beams having three kinds of wavelengths and an inner area for allowing all the light beams to pass through. The optical pickup system also has an objective lens that focuses each light beam having passed through the wavelength selective filter on each light recording medium. An optical head and an optical disk apparatus have the optical pickup system.

Abstract: An imaging lens unit comprising, in order from the object side, a first lens having a meniscus shape with its convex surface on the object side, an aperture stop and a second lens having a meniscus shape with its convex surface on the image side. A maximal value of a tangent angle within a range of a lens surface effective diameter of the surface on the object side of the first lens is 70 to 90 degrees. A maximal value of a tangent angle within a range of a lens surface effective diameter of the surface on the image side of the second lens is 70 to 90 degrees.

Abstract: An imaging lens unit includes, from an object side, a diaphragm, a first lens, and a second lens placed on an image side of the first lens. The first lens is a positive meniscus lens convex toward the object side, and at least one side of the first lens has an aspherical surface. The second lens is a meniscus lens convex toward the image side, and at least one side of the second lens has an aspherical surface. Further, a maximum value of an angle between a tangent to a surface on the image side of the second lens and a normal to an optical axis is in a range of 65° to 90° within an effective diameter of the second lens.

Abstract: An imaging lens unit comprising, in order from the object side, a first lens having a meniscus shape with its convex surface on the object side, an aperture stop and a second lens having a meniscus shape with its convex surface on the image side. A maximal value of a tangent angle within a range of a lens surface effective diameter of the surface on the object side of the first lens is 70 to 90 degrees. A maximal value of a tangent angle within a range of a lens surface effective diameter of the surface on the image side of the second lens is 70 to 90 degrees.

Abstract: An imaging lens unit comprising, in order from the object side, a first lens having a meniscus shape with its convex surface on the object side, an aperture stop and a second lens having a meniscus shape with its convex surface on the image side. A maximal value of a tangent angle within a range of a lens surface effective diameter of the surface on the object side of the first lens is 70 to 90 degrees. A maximal value of a tangent angle within a range of a lens surface effective diameter of the surface on the image side of the second lens is 70 to 90 degrees.

Abstract: For use in combining and/or splitting a 3-wavelength multiplexed light, in which if central wavelengths of the three bands are denoted as ?1, ?2 and ?3, in a relation that 0.92??2/?1?1.08, 0.20??3/?1?0.92 or 1.08??3/?1?5.00, the wavelength multiplexing and demultiplexing device comprises two optical filters of different characteristics, supported by one of more optical substrates combined in a single package, wherein, when a 3-wavelength multiplexed light is led to a first filter A for splitting the 3-wavelength multiplexed light into light of a band of ?3 and a 2-wavelength multiplexed light of ?1 and ?2, and when the 2-wavelength multiplexed light is led to a second filter B for splitting the 2-wavelength multiplexed light into light of a band of ?1 and light of a band of ?2, an optical edge filter is used for the filter A and an optical band-pass filter is used for the filter B.

Abstract: An imaging lens unit comprising, in order from the object side, a first lens having a meniscus shape with its convex surface on the object side, an aperture stop and a second lens having a meniscus shape with its convex surface on the image side. A maximal value of a tangent angle within a range of a lens surface effective diameter of the surface on the object side of the first lens is 70 to 90 degrees. A maximal value of a tangent angle within a range of a lens surface effective diameter of the surface on the image side of the second lens is 70 to 90 degrees.

Abstract: The wavelength division multiplexer includes a single optical substrate or a plurality of optical substrates integrated together, on which the first optical filter and the second optical filter are placed. The center wavelengths of three wavelength bands, ?1, ?2, and ?3, satisfy: 0.92??2/?1?1.08, and 0.20??3/?1?0.92 or 1.08??3/?1?5.00. The first optical filter combines or separates light of ?3 and two-wavelength multiplexed light of ?1 and ?2. The second optical filter combines or separates light of ?1 and light of ?2.

Abstract: An optical pickup system for reading information of three kinds of optical recording media. The optical pickup system has a wavelength selective filter that includes an outer area for shielding one light beam of light beams having three kinds of wavelengths and an inner area for allowing all the light beams to pass through. The optical pickup system also has an objective lens that focuses each light beam having passed through the wavelength selective filter on each light recording medium. An optical head and an optical disk apparatus have the optical pickup system.

Abstract: An optical pickup system for reading information of three kinds of optical recording media. The optical pickup system has a wavelength selective filter that includes an outer area for shielding one light beam of light beams having three kinds of wavelengths and an inner area for allowing all the light beams to pass through. The optical pickup system also has an objective lens that focuses each light beam having passed through the wavelength selective filter on each light recording medium. An optical head and an optical disk apparatus have the optical pickup system.

Abstract: The wavelength division multiplexer includes a single optical substrate or a plurality of optical substrates integrated together, on which the first optical filter and the second optical filter are placed. The center wavelengths of three wavelength bands, ?1, ?2, and ?3, satisfy: 0.92??2/?1?1.08, and 0.20??3/?1?0.92 or 1.08??3/?1?5.00. The first optical filter combines or separates light of ?3 and two-wavelength multiplexed light of ?1 and ?2. The second optical filter combines or separates light of ?1 and light of ?2.

Abstract: For use in combining and/or splitting a 3-wavelength multiplexed light, in which if central wavelengths of the three bands are denoted as ?1, ?2 and ?3, in a relation that 0.92??2/?1?1.08, 0.20??3/?1?0.92 or 1.08??3/?1?5.00, the wavelength multiplexing and demultiplexing device comprises two optical filters of different characteristics, supported by one of more optical substrates combined in a single package, wherein, when a 3-wavelength multiplexed light is led to a first filter A for splitting the 3-wavelength multiplexed light into light of a band of ?3 and a 2-wavelength multiplexed light of ?1 and ?2, and when the 2-wavelength multiplexed light is led to a second filter B for splitting the 2-wavelength multiplexed light into light of a band of ?1 and light of a band of ?2, an optical edge filter is used for the filter A and an optical band-pass filter is used for the filter B.