Laser Converging Apparatus, Optical Pickup Device, and Optical Disc Recording/Reproducing Apparatus

An optical pickup device comprising:

• (1) a semiconductor laser that emits laser light;
• and
• (2) a laser converging assembly including:
• a nonpolarizing hologram element having a first area defined by a numerical aperture corresponding to a thickness of a first protective layer of a first disk medium and a second area inside the first area, the second area defined by a numerical aperture corresponding to a thickness of a second protective layer (>the thickness of the first protective layer) of a second disk medium, the second area having a hologram pattern for diffracting the laser light into zero order light and high-order diffracted light having the order of primary or higher;
• an objective lens having the numerical aperture corresponding to the thickness of the first protective layer, the objective lens converging the laser light having passed through apart of the first area other than the second area and the zero order light having passed through the second area onto an information surface on one side of the first protective layer, the objective lens converging the high-order diffracted light having passed through the second area onto an information surface on one side of the second protective layer;
• and
• a holder that holds the nonpolarizing hologram element and the objective lens.

A laser converging apparatus comprising:

• a polarizing hologram element having a first area defined by a numerical aperture corresponding to a thickness of a first protective layer of a first disk medium and a second area inside the first area, the second area defined by a numerical aperture corresponding to a thickness of a second protective layer (>the thickness of the first protective layer) of a second disk medium, the second area having a polarizing hologram pattern for transmitting first laser light linearly polarized in a first direction without diffracting the first laser light, diffracting and transmitting second laser light that is linearly polarized in a second direction crossing the first direction, the second laser light having the same wavelength as the first laser light, and transmitting third laser light having a wavelength different from that of the first and second laser light without diffracting the third laser light;
• a wavelength selecting nonpolarizing hologram element having a third area defined by a numerical aperture corresponding to a thickness of a third protective layer (>the thickness of the first protective layer) of a third disk medium, the third area having a nonpolarizing hologram pattern for transmitting the first and second laser light without diffracting the first and second laser light while diffracting the third laser light into high-order diffracted light having the order of primary or higher;
• an objective lens having the numerical aperture corresponding to the thickness of the first protective layer, the objective lens converging the first laser light having passed through the first area including the second area onto an information surface on one side of the first protective layer, the objective lens converging the second laser light having passed through the second area onto an information surface on one side of the second protective layer, the objective lens converging the high-order diffracted light having passed through the third area onto an information surface on one side of the third protective layer;
• and
• a holder that holds the polarizing hologram element, the nonpolarizing hologram element, and the objective lens.

An optical pickup device comprising:

• (1) a first semiconductor laser that emits a first laser light linearly polarized in a first direction;
• (2) a polarizing direction switching element that transmits the first laser light while maintaining a polarizing direction of the first laser light or that transmits a second laser light created by turning the polarizing direction of the first laser light to a second direction crossing the first direction;
• (3) a second semiconductor laser that emits third laser light having a wavelength different from that of the first and second laser light;
• and
• (4) a laser converging assembly including:
• a polarizing hologram element having a first area defined by a numerical aperture corresponding to a thickness of a first protective layer of a first disk medium and a second area inside the first area, the second area defined by a numerical aperture corresponding to a thickness of a second protective layer (>the thickness of the first protective layer) of a second disk medium, the second area having a polarizing hologram pattern for transmitting the first laser light without diffracting the first laser light, diffracting and transmitting the second laser light, and transmitting the third laser light without diffracting the third laser light;
• a wavelength selecting nonpolarizing hologram element having a third area defined by a numerical aperture corresponding to a thickness of a third protective layer (>the thickness of the first protective layer) of a third disk medium, the third area having a nonpolarizing hologram pattern for transmitting the first and second laser light without diffracting the first and second laser light while diffracting the third laser light into high-order diffracted light having the order of primary or higher;
• an objective lens having the numerical aperture corresponding to the thickness of the first protective layer, the objective lens converging the first laser light having passed through the first area including the second area onto an information surface on one side of the first protective layer, the objective lens converging the second laser light having passed through the second area onto an information surface on one side of the second protective layer, the objective lens converging the high-order diffracted light having passed through the third area onto an information surface on one side of the third protective layer;
• and
• a holder that holds the polarizing hologram element, the nonpolarizing hologram element and the objective lens.

A laser converging apparatus comprising:

• a wavelength selecting first nonpolarizing hologram element having a first area defined by a numerical aperture corresponding to a thickness of a first protective layer of a first disk medium and a second area inside the first area, the second area defined by a numerical aperture corresponding to a thickness of a second protective layer (>the thickness of the first protective layer) of a second disk medium, the second area having a first hologram pattern for diffracting first laser light into zero order light and first high-order diffracted light having the order of primary or higher while transmitting second laser light having a wavelength different from that of the first laser light without diffracting the second laser light;
• a wavelength selecting second nonpolarizing hologram element having a third area defined by a numerical aperture corresponding to a thickness of a third protective layer (>the thickness of the first protective layer) of a third disk medium, the third area having a second hologram pattern for transmitting the first laser light without diffracting the first laser light while diffracting the second laser light into second high-order diffracted light having the order of primary or higher;
• an objective lens having the numerical aperture corresponding to the thickness of the first protective layer, the objective lens converging the first laser light having passed through a part of the first area other than the second area and zero order light having passed through the second area onto an information surface on one side of the first protective layer, the objective lens converging first high-order diffracted light having passed through the second area onto an information surface on one side of the second protective layer, the objecting lens converging the second high-order diffracted light having passed through the third area onto an information surface on one side of the third protective layer;
• and
• a holder that holds the first nonpolarizing hologram element, the second nonpolarizing hologram element, and the objective lens.

An optical pickup device comprising:

• (1) a first semiconductor laser that emits first laser light;
• (2) a second semiconductor laser that emits second laser light having a wavelength different from that of the first laser light;
• and
• (3) a laser converging assembly including:
• a wavelength selecting first nonpolarizing hologram element having a first area defined by a numerical aperture corresponding to a thickness of a first protective layer of a first disk medium and a second area inside the first area, the second area defined by a numerical aperture corresponding to a thickness of a second protective layer (>the thickness of the first protective layer) of a second disk medium, the second area having a first hologram pattern for diffracting the first laser light into zero order light and first high-order diffracted light having the order of primary or higher while transmitting the second laser light without diffracting the second laser light;
• a wavelength selecting second nonpolarizing hologram element having a third area defined by a numerical aperture corresponding to a thickness of a third protective layer (>the thickness of the first protective layer) of a third disk medium, the third area having a second hologram pattern for transmitting the first laser light without diffracting the first laser light while diffracting the second laser light into second high-order diffracted light having the order of primary or higher;
• an objective lens having the numerical aperture corresponding to the thickness of the first protective layer, the objective lens converging the first laser light having passed through a part of the first area other than the second area and zero order light having passed through the second area onto an information surface on one side of the first protective layer, the objecting lens converging first high-order diffracted light having passed through the second area onto an information surface on one side of the second protective layer, the objective lens converging second high-order diffracted light having passed through the third area onto an information surface on one side of the third protective layer;
• and
• a holder that holds the first nonpolarizing hologram element, the second nonpolarizing hologram element, and the objective lens.