Patent ID: 7616550
Filing Date: 2009-11-10
Classification: G11B

Abstract:
1. An optical pickup unit comprising: a first light-emitting element configured to emit a first-wavelength light; a second light-emitting element configured to emit a second-wavelength light longer in wavelength than the first-wavelength light; a liquid crystal element configured to change a state of polarization of the first-wavelength light; a polarizing mirror configured to transmit or reflect the first-wavelength light based on the state of polarization of the first-wavelength light, and to reflect the second-wavelength light; a first objective lens configured to converge the first-wavelength light passing through the polarizing mirror on a first medium; a second objective lens configured to converge the first-wavelength light and the second-wavelength light both reflecting from the polarizing mirror on a second medium; and a quarter-wave plate with aperture limit through which the first-wavelength light and the second-wavelength light both reflecting from the polarizing mirror pass so as to reach the second objective lens, the quarter-wave plate with aperture limit being configured to pass the first-wavelength light reflecting from the polarizing mirror without change and configured to act on the second-wavelength light reflecting from the polarizing mirror.