| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical head apparatus which is provided with an aperture control element recording and/or reproducing information of an optical disk of three kinds of HD, DVD, and CD using a single objective lens, and which is excellent in optical characteristics, and is suitable for being miniaturized and reduced in weight. <P>SOLUTION: In an aperture control element restricting a transmission region in accordance with light of wavelength λ<SB>1</SB>, λ<SB>2</SB>and λ<SB>3</SB>(λ<SB>1</SB><λ<SB>2</SB><λ<SB>3</SB>), a first multilayer film filter 12 in which incident light of wavelength λ<SB>1</SB>, λ<SB>2</SB>are transmitted and incident light of wavelength λ<SB>3</SB>is not transmitted is formed in a first circular ring region α obtained by subtracting the innermost circular region D<SB>3</SB>from an intermediate circular region D<SB>1</SB>, and a second multilayer film filter 13 in which incident light of wavelength λ<SB>2</SB>are transmitted and incident light of wavelength λ<SB>1</SB>, λ<SB>3</SB>are not transmitted is formed in a second circular ring region β obtained by subtracting the intermediate circular region D<SB>1</SB>from the outermost circular region D<SB>2</SB>. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
