JP2009170087A5 - - Google Patents

Claims (10)

  An optical head for irradiating a light beam to an optical disk having a plurality of information recording layers stacked at a predetermined interval from each other and detecting a reflected light beam from the optical disk,
  With a light source;
  An objective lens for condensing the light beam emitted from the light source onto the optical disc;
  A splitting element for splitting the light beam reflected by the optical disc into a plurality of light beams;
  A condensing lens for condensing the light beam reflected by the optical disc;
  A photodetector for receiving the light beam collected by the condenser lens by a plurality of light receiving sections and converting the received light into an electrical signal;
  The dividing element is
  A first divided region disposed substantially in the center;
  A second divided region composed of four regions that are divided by the first dividing line and arranged so as to sandwich the first divided region along the direction of the first dividing line;
  It is divided by a second dividing line orthogonal to the first dividing line, and is composed of four regions arranged so as to sandwich the first dividing region along the direction of the second dividing line. A third divided region;
  When each of the first to third divided areas is focused on the target information recording layer of the optical disc, the reflected light beam from the target information recording layer is reflected on the light receiving portion of the photodetector. An optical head that is focused and configured so that a reflected light beam from a recording / reproducing layer other than the target information recording layer is not irradiated to the light receiving portion of the photodetector.   An optical head for irradiating a light beam to an optical disk having a plurality of information recording layers stacked at a predetermined interval from each other and detecting a reflected light beam from the optical disk,
  With a light source;
  An objective lens for condensing the light beam emitted from the light source onto the optical disc;
  A splitting element having a plurality of diffraction regions and diffracting a reflected light beam reflected by the optical disc in a plurality of directions;
  A photodetector that receives a plurality of reflected light beams diffracted by the dividing element by a plurality of light receiving sections and converts them into an electrical signal;
  The dividing element is
  A first region that includes the approximate center of the light beam incident on the split element and is positioned approximately in the center;
  A second region located on both sides of the first region;
  A third region comprising the first region and the remaining region of the second region;
  When the light beam is condensed on the target information recording layer of the optical disc, the reflected light beam diffracted in the second region and the third region of the splitting element is a focus error signal of the photodetector, respectively. When the light receiving unit that detects the tracking error signal is focused and defocused from the target information recording layer, the defocused reflected light beam is focused on the light collection position of the light receiving unit. An optical head configured to irradiate the outside of the optical head.   The optical head according to claim 2, wherein the second area is provided at a predetermined distance from the first area.   The optical head according to claim 2, wherein the second area is provided adjacent to the first area.   Of the dividing lines that divide the diffraction area of the dividing element, when the optical head is opposed to the optical disc, the optical head is substantially parallel to the track direction of the optical disc, and the approximate center of the light beam incident on the dividing element is When the dividing line that passes is the first dividing line,
  The dividing element is configured such that a part of a dividing line dividing the second area and the third area forms an angle of approximately 30 degrees with respect to the first dividing line. Item 5. The optical head according to any one of Items 2 to 4.   The optical head according to claim 2, wherein the dividing element is configured such that the second region includes four corners of the dividing element.   6. The optical head according to claim 2, wherein the dividing element is configured such that the third region includes four corners of the dividing element.   A focus error signal is detected by -1st order diffracted light diffracted in the second region;
  A tracking error signal is detected using + 1st order diffracted light diffracted in the second and third regions;
  Detecting an offset correction signal of the tracking error signal with the −1st order diffracted light diffracted in the third region;
  8. The optical head according to claim 2, wherein a reproduction signal is detected by a sum of + 1st order diffracted light diffracted in the first, second and third regions.   9. The optical head according to claim 8, wherein the diffraction grating is formed so that the light amount of the + 1st order diffracted light diffracted in each region of the dividing element is larger than the light amount of the -1st order diffracted light.   An optical head according to any one of claims 1 to 9,
  A laser drive circuit for driving the light source;
  A servo signal generation circuit for generating a servo signal from the output signal of the photodetector of the optical head;
  An information signal reproducing circuit for reproducing information recorded on the optical disc from an output signal of a photodetector of the optical head;
  An optical disk apparatus comprising: a system control circuit for controlling the laser drive circuit, the servo signal generation circuit, and the information signal reproduction circuit.