| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical pickup device which can reduce occurrence of spherical aberration with reduced cost and size, in the optical pickup device compatible with a plurality of wavelengths. <P>SOLUTION: The optical pickup device 1 has a single objective lens 7 and copes with three wavelengths (λ1>λ2>λ3). Laser beams of wavelengths λ1 and λ2 are made incident in the objective lens 7 in a finite system and a laser beam of a wavelength λ3 is made incident in the objective lens 7 in an infinite system. The laser beams of wavelengths λ1 and λ2 are condensed on an optical recording medium 10 through a common optical path, reflected by the optical recording medium 10 and then condensed on an optical detector 9. The reflected beams from the optical recording medium 10 reach the optical detector 9 through a common optical path in respective wavelengths. A hologram element generating diffraction light of only the optical beam of the wavelength λ3 and correcting a focal position in an optical axis direction is disposed in a position through which only the reflected beams pass and before the optical detector 9. <P>COPYRIGHT: (C)2008,JPO&INPIT |
