Hitachi Maxell, Limited

Yoshiaki Minakawa

Yasuyuki Sugi

Tsuyoshi Maro

Koichiro Wakabayashi

Mitsuhiro Miyauchi

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.

Optical pickup system, optical head, optical disk apparatus, and objective lens

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.

Imaging lens unit

For use in combining and/or splitting a 3-wavelength multiplexed light, in which if central wavelengths of the three bands are denoted as &#x3bb;1, &#x3bb;2 and &#x3bb;3, in a relation that 0.92&#x2266;&#x3bb;2/&#x3bb;1&#x2266;1.08, 0.20&#x2266;&#x3bb;3/&#x3bb;1&#x2266;0.92 or 1.08&#x2266;&#x3bb;3/&#x3bb;1&#x2266;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 &#x3bb;3 and a 2-wavelength multiplexed light of &#x3bb;1 and &#x3bb;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 &#x3bb;1 and light of a band of &#x3bb;2, an optical edge filter is used for the filter A and an optical band-pass filter is used for the filter B.

Wavelength multiplexer/demultiplexing device

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, &#x3bb;, and &#x3bb;, satisfy: 0.92&#x2266;&#x3bb;&#x2266;1.08, and 0.20&#x2266;&#x3bb;&#x2266;0.92 or 1.08&#x2266;&#x3bb;&#x2266;5.00. The first optical filter combines or separates light of &#x3bb;and two-wavelength multiplexed light of &#x3bb;and &#x3bb;. The second optical filter combines or separates light of &#x3bb;and light of &#x3bb;

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Ibaraki, Japan

Yoshiaki Minakawa