Objective lens and optical head device provided with the same
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United States of America Patent
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Oct 24, 2006
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N/A
app pub date -
Jul 1, 2005
filing date -
Jul 5, 2004
priority date (Note) -
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Abstract
According to the present invention, there is provided an objective lens for an optical head device which condenses two or more laser beams having wavelengths corresponding to two or more optical recording mediums having different thicknesses of transparent substrates on recording surfaces of the optical recording mediums via one optical condensing system to record information on the recording surfaces and/or reproduce the information on the recording surfaces, the objective lens comprising: a refractive surface including: a middle region which is formed in a middle portion of the refractive surface centering on an optical axis of the objective lens and which is used with respect to all of the optical recording mediums; one or more peripheral regions which are concentrically formed outside the middle region; and an aperture limiting ring band which is concentrically formed between the middle region and the peripheral region or between the peripheral regions.
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