Patent ID: 7848210
Filing Date: 2010-12-07
Classification: G11B

Abstract:
1. An optical head, comprising: a first light source emitting a first light having a first wavelength and a second polarization state; a second light source emitting a second light having a second wavelength different from the first wavelength and a first polarization state approximately perpendicular to the second polarization state; a third light source emitting a third light having a third wavelength different from the first and the second wavelengths and the first polarization state; a first optical element having an optical characteristic of reflecting a light of the first wavelength and transmitting lights of the second and the third wavelengths, on said first optical element the first light from said first light source being incident; a second optical element having an optical characteristic of transmitting the light of the first wavelength, reflecting the light of the second or the third wavelength in the first polarization state and transmitting a light of the second or the third wavelength in the second polarization state, a first surface on which the first light reflected by said first optical element is incident, a second surface on which the second and the third lights from said second and said third light sources are incident, and a third surface emitting the first light incident from the first surface and the second and the third lights incident from the second surface, said second optical element reflecting a part of the first light from the first light source and transmitting a part of the second and the third lights from the second and the third light sources; an optical system leading the first, the second and the third lights emitted from the third surface to an optical disk; a third optical element converting a polarization state of the second and the third lights reflected by the optical disk from the first polarization state to the second polarization state, said third optical element converting a polarization state of the first light reflected by the optical disk from the second polarization state to the first polarization state, said third optical element being disposed between the optical disk and said second optical element; a fourth optical element transmitting a light in the second polarization state and reflecting a light in the first polarization state, said fourth optical element being disposed between said first light source and said first optical element; a first light-receiving element receiving the first light reflected by the optical disk, transmitted through said second optical element and reflected by said first and said fourth optical elements; a second light-receiving element receiving the second and the third lights reflected by the optical disk, converted in the polarization state by said third optical element and transmitted through said second and said first optical elements; and a third light-receiving element receiving the part of the first light reflected by said second optical element and the part of the second and the third lights transmitted through said second optical element.