Wave-front aberration compensation unit, wave-front aberration compensation device, and optical pickup

A wave-front aberration compensation unit which is located in an optical path between a light source and an objective lens to compensate wave-front aberrations of light emitted from said light source which are then output onto an on optical disk, comprising:

• an optical-path changing means which changes by a prescribed length an optical path of optical flux which enters said objective lens, based on an external voltage signal;
• wherein said optical-path changing means comprises:
• a refractive index changing means for changing a refractive index based on an application voltage due to said voltage signal;
• tilt detection means for detecting a tilt of said optical disk and outputting a tilt detection signal;
• and
• a voltage applying means for applying a voltage onto said refractive-index changing means to change an optical path length of light based on said tilt detection signal, said voltage applying means having a geometry corresponding to a wave-front aberration distribution given by an optical system.

A wave-front aberration compensation unit which is located in an optical path between a light source and an objective lens to compensate wave-front aberrations of light emitted from said light source which are then output on an optical disk, comprising:

• tilt detection means for detecting a tilt of said optical disk and outputting a tilt detection signal;
• rotation-angle/optical-path length changing means which rotates, by a prescribed angle based on an external voltage signal, a portion of an optical flux, which enters said objective lens, corresponding to a predetermined incident point and, at the same time, changes by a prescribed length an optical path of a portion of an optical flux whose wave-front aberrations are in excess of a prescribed standard value;
• wherein said rotation-angle/optical-path changing means comprises:
• means for changing both a rotation angle of and a refractive index of a changing surface based on said voltage signal;
• a first electrode which applies voltage onto said rotation-angle/refractive-index changing means by utilizing its own geometry determined based on a desired numerical aperture in order to rotate, by a prescribed angle, a portion of a polarization plane of light flux, which enters said objective lens, corresponding to a predetermined incident point;
• and
• a second electrode which is paired with said first electrode and also which applies voltage onto said refractive-index changing means to change an optical-path length of this portion of light flux by utilizing its own geometry corresponding to a wave-front aberration distribution given by an optical system;
• wherein said voltage is varied based on said tilt detection signal, such that a numerical aperture of said objective lens is changed to compensate for said wave-front aberrations due to disk tilt and differences in disk thickness.

A wave-front aberration compensation device, comprising:

• a wave-front aberration compensation unit which is located in an optical path between a light source and an objective lens to compensate wave-front aberrations of light emitted from said light source, including:
• an optical-path changing means which changes by a prescribed length an optical path of optical flux which enters said objective lens, based on an external voltage signal;
• wherein said optical-path changing means includes:
• a refractive index changing means for changing a refractive index based on an application voltage due to said voltage signal;
• and
• a voltage applying means for applying a voltage onto said refractive-index changing means to change an optical path length of light, said voltage applying means having a geometry corresponding to a wave-front aberration distribution given by an optical system;
• voltage application means which applies, based on external information, a prescribed value of voltage corresponding to said information, onto said refractive-index changing means;
• and
• tilt detection means which detects a tilt of an optical recording medium with respect to an optical axis and then sends out a detection signal to said voltage application means.

A wave-front aberration compensation device, comprising:

• a wave-front aberration compensation unit which is located in an optical path between a light source and an objective lens to compensate wave-front aberrations of light emitted from said light source, including:
• rotation-angle/optical-path length changing means which rotates, by a prescribed angle based on an external voltage signal, a portion of an optical flux, which enters said objective lens, corresponding to a predetermined incident point and, at the same time, changes by a prescribed length an optical path of a portion of an optical flux whose wave-front aberrations are in excess of a prescribed standard value;
• wherein said rotation-angle/optical-path changing means includes:
• means for changing both a rotation angle of and a refractive index of a changing surface based on said voltage signal;
• a first electrode which applies voltage onto said rotation-angle/refractive-index changing means by utilizing its own geometry determined based on a desired numerical aperture in order to rotate, by a prescribed angle, a portion of a polarization plane of light flux, which enters said objective lens, corresponding to a predetermined incident point;
• and
• a second electrode which is paired with said first electrode and also which applies voltage onto said refractive-index changing means to change an optical-path length of this portion of light flux by utilizing its own geometry corresponding to a wave-front aberration distribution given by an optical system;
• voltage application means which applies, based on external information, a prescribed value of voltage corresponding to said information onto said electrodes;
• and
• tilt detection means which detects a tilt of an optical recording medium with respect to an optical axis and then sends out a detection signal to said voltage application means.