Optical pickup and optical disc drive

A composite optical element comprising:

• a diffraction element for transmitting a light beam emitted toward an optical disc from a light source and diffracting a return light beam reflected by the optical disc;
• light splitting means arranged at a position where the return light beam diffracted by the diffraction element is incident and adapted for splitting the return light beam into a plurality of beams and leading the plurality of beams to light receiving means having a plurality of light receiving areas;
• and
• reflection means for reflecting the light beam emitted from the light source to the diffraction element and/or reflecting the return light beam diffracted by the diffraction element to the light splitting means.

An optical pickup device comprising:

• a light source for emitting light of a predetermined wavelength;
• an objective lens for condensing the light beam emitted from the light source onto an optical disc and condensing a return light beam from the optical disc;
• a composite optical element having a diffraction element for transmitting the light beam emitted from the light source and diffracting the return light beam from the optical disc, and light splitting means arranged at a position where the return light beam diffracted by the diffraction element is incident and made up of a prism constituted by a plurality of planes or curved surfaces for splitting the return light beam into a plurality of beams;
• and
• light receiving means for receiving each return light beam split by the light splitting means, in a plurality of light receiving areas, in order to acquire a focusing error signal.

An optical pickup device comprising:

• a light source for emitting light of a predetermined wavelength;
• an objective lens for condensing the light beam emitted from the light source onto an optical disc and condensing a return light beam from the optical disc;
• a composite optical element having a diffraction element for transmitting the light beam emitted from the light source and diffracting the return light beam from the optical disc, and light splitting means arranged at a position where the return light beam diffracted by the diffraction element is incident and adapted for splitting the return light beam into a plurality of beams;
• light receiving means for receiving each return light beam split by the light splitting means, in a plurality of light receiving areas, in order to acquire a focusing error signal;
• and
• reflection means for reflecting the light beam emitted from the light source to the diffraction element and/or reflecting the return light beam diffracted by the diffraction element to the light splitting means.

An optical disc device having an optical pickup for recording and/or reproducing information signals to and/or from an optical disc, and disc rotational driving means for rotationally driving the optical disc,

• the optical pickup comprising:
• a light source for emitting light of a predetermined wavelength;
• an objective lens for condensing the light beam emitted from the light source onto the optical disc and condensing a return light beam from the optical disc;
• a composite optical element having a diffraction element for transmitting the light beam emitted from the light source and diffracting the return light beam from the optical disc, and light splitting means arranged at a position where the return light beam diffracted by the diffraction element is incident and made up of a prism constituted by a plurality of planes or curved surfaces for splitting the return light beam into a plurality of beams;
• and
• light receiving means for receiving each return light beam split by the light splitting means, in a plurality of light receiving areas, in order to acquire a focusing error signal.

An optical disc device having an optical pickup for recording and/or reproducing information signals to and/or from an optical disc, and disc rotational driving means for rotationally driving the optical disc,

• the optical pickup comprising:
• a light source for emitting light of a predetermined wavelength;
• an objective lens for condensing the light beam emitted from the light source onto the optical disc and condensing a return light beam from the optical disc;
• a composite optical element having a diffraction element for transmitting the light beam emitted from the light source and diffracting the return light beam from the optical disc, and light splitting means arranged at a position where the return light beam diffracted by the diffraction element is incident and adapted for splitting the return light beam into a plurality of beams;
• and
• light receiving means for receiving each return light beam split by the light splitting means, in a plurality of light receiving areas, in order to acquire a focusing error signal;
• the composite optical element having reflection means for reflecting the light beam emitted from the light source to the diffraction element and/or reflecting the return light beam diffracted by the diffraction element to the light splitting means.

A light beam detection method comprising:

• transmitting through a diffraction element a light beam emitted toward an optical disc from a light source;
• diffracting a return light beam incident on the optical disc and reflected by the optical disc, by the diffraction element;
• splitting the return light beam diffracted by the diffraction element into a plurality of light beams by a prism constituted a plurality of planes or curved surfaces;
• and
• receiving the plurality of light beams by light receiving elements for receiving the respective light beams.

A light beam detection method comprising:

• reflecting a light beam emitted toward an optical disc from a light source and thus leading the light beam to a diffraction element;
• causing the light beam transmitted through the diffraction element to be incident on the optical disc;
• causing a return light beam reflected by the optical disc to be incident on the diffraction element so as to diffract the return light beam, and splitting the return light beam into a plurality of light beams by a prism constituted by a plurality of planes or curved surfaces;
• and
• receiving the plurality of split light beams by light receiving elements for receiving the respective light beams.

A light beam detection method comprising:

• leading to a diffraction element a light beam emitted toward an optical disc from a light source;
• causing the light beam transmitted through the diffraction element to be incident on the optical disc;
• causing a return light beam reflected by the optical disc to be incident on the diffraction element so as to diffract the return light beam;
• reflecting the diffracted return light beam and thus causing the diffracted return light to be incident on a prism constituted by a plurality of planes or curved surfaces, and splitting the return light beam into a plurality of light beams by the prism;
• and
• receiving the plurality of split light beams by light receiving elements for receiving the respective light beams.

A light beam detection method comprising:

• reflecting a light beam emitted toward an optical disc from a light source and thus leading the light beam to a diffraction element;
• causing the light beam transmitted through the diffraction element lobe incident on the optical disc;
• causing a return light beam reflected by the optical disc to be incident on the diffraction element so as to diffract the return light beam;
• reflecting the diffracted return light beam and thus causing the diffracted return light to be incident on a prism constituted by a plurality of planes or curved surfaces, and splitting the return light beam into a plurality of light beams by the prism;
• and
• receiving the plurality of split light beams by light receiving elements for receiving the respective light beams.