| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical head device suppressing interlayer crosstalk in a multilayer optical disk. <P>SOLUTION: The optical head device has a phase modulation element disposed in an optical path common to light having a wavelength λ<SB>1</SB>and light having a wavelength λ<SB>2</SB>between an objective lens and a photodetector, wherein the phase modulation element has a first region for emitting incident signal light with a first phase and a second region for emitting incident signal light with a second phase different from the first phase, both a first phase difference Δϕ<SB>1</SB>to be a phase difference between the first and second phases of the signal light having the wavelength λ<SB>1</SB>and a second phase difference Δϕ<SB>2</SB>to be a phase difference between the first and second phases of the signal light having the wavelength λ<SB>2</SB>are nearly π and the first and second regions of the phase modulation element are disposed line-symmetrically with respect to a linear line including an optical axis of the signal light. <P>COPYRIGHT: (C)2011,JPO&INPIT |
