Optical pickup apparatus with objective optical system and guiding optical system

An optical pickup apparatus comprising:

• a first light source for emitting a first light flux having first wavelength λ1 (430 nm>λ1>380 nm);
• a second light source for emitting a second light flux having second wavelength λ2 (λ2>λ1);
• an objective optical system having a phase structure thereon, the objective optical system for converging the first light flux on a surface of a first recording medium having recording density ρ1 for recording and/or reproducing information onto or from the first recording medium and for converging the second light flux on a surface of a second recording medium having recording density ρ2 (ρ2<ρ1) for recording and/or reproducing information onto or from the second recording medium;
• and
• an optical system including a movable common optical element, the optical system guiding both the first light flux from the first light source and the second light flux from the second light source respectively to pass through the movable common optical element and to enter the objective optical system,
• wherein the movable common optical element is moved in a direction parallel to an optical axis to shape both the first light flux and the second light flux entering the objective optical system into an approximately parallel light flux respectively such that the objective optical system satisfies M1=M2=0, where:
• M1 denotes a first magnification of the objective optical system for recording and/or reproducing the information on or from the first recording medium;
• and
• M2 denotes a second magnification of the objective optical system for recording and/or reproducing the information on or from the second recording medium, and
• wherein the first light source and the second light source are configured into a single body,
• wherein the optical system is configured in one of a first structure and a second structure such that:
• in the first structure, the optical system further includes a collimator for shaping a light flux having a predetermined wavelength into a parallel light flux or an approximately parallel light flux, and
• the collimator is moved as the movable common optical element so as to correct a chromatic aberration of the collimator due to difference in wavelength between the first light flux and the second light flux and the collimator satisfies a following condition,
• 0.01<|δCL/fCL<0.05
• where δCL denotes a moving distance of the collimator lens;
• fCL denotes a focal length for the first wavelength λ1, and
• in the second structure the optical system further includes a collimator for shaping a light flux having a predetermined wavelength into a parallel light flux or an approximately parallel light flux and an aberration correction device having two lenses, at least one of the two lenses is moved as the movable common optical element so as to correct a chromatic aberration of the collimator due to difference in wavelength between the first light flux and the second light flux, and that the aberration correction device satisfies a following condition,
• 0.001<|δBEML/fBEML|<0.02
• where, δBEML denotes a moving distance of the movable common optical element in the aberration correction device and fBEML denotes a focal length of the movable common optical element in the aberration correction device for the first light flux having the first wavelength λ1.