Optical pickup unit and optical disk drive for accurate and stable information recording and reproduction

An optical disk drive unit for performing at least one of information recording, reproduction, and erasure with respect to an optical recording medium selected from disk-like optical recording media of a plurality of types using different wavelengths, the optical disk drive unit comprising:

• an optical pickup unit, the optical pickup unit comprising:
• a light source of a plurality of semiconductor laser chips of different light-emission wavelengths;
• a plurality of holograms provided to respective substrates, the holograms being placed between said light source and the optical recording medium, the holograms including at least one non-polarization hologram having a substantially uniform diffraction efficiency irrespective of a direction of polarization of incident light and at least one polarization hologram having a diffraction efficiency varying depending on a direction of polarization of incident light;
• and
• a wave plate provided closer to the optical recording medium than the polarization hologram is,
• wherein:
• a light beam emitted from a selected one of the semiconductor laser chips passes through said holograms to be focused onto a recording surface of the optical recording medium and reflected therefrom as a returning beam;
• the returning beam is diffracted by a corresponding one of said holograms so that a diffracted light of the returning beam is received by a light-receiving element;
• and
• said wave plate turns a direction of polarization of the returning beam to a different direction from that of the light beam emitted from the selected one of the semiconductor laser chips.

An optical pickup unit comprising:

• a plurality of light sources emitting light beams of different wavelengths;
• an optical system, the optical system comprising:
• an objective lens focusing any of the light beams onto a recording surface of an information recording medium attached to the optical pickup unit;
• a plurality of grating elements provided between said light sources and said objective lens, the grating elements corresponding to the different wavelengths, respectively, and dividing the light beams of the corresponding wavelengths traveling toward said objective lens each into a plurality of beams including a 0th-order light and diffracted lights;
• and
• a plurality of holograms corresponding to the different wavelengths, respectively, and guiding to a predetermined position the light beams of the corresponding wavelengths reflected from the recording surface;
• and
• a photodetector provided at the predetermined position,
• wherein one of the light sources which one emits a light beam of a wavelength corresponding to a type of the attached information recording medium is selected;
• and
• the light beam emitted from the selected one of the light sources is focused onto the recording surface and reflected therefrom to be received by said photodetector.

An optical disk unit performing information recording by emitting light onto a recording surface of an information recording medium, the optical disk unit comprising:

• an optical pickup unit, the optical pickup unit comprising:
• a plurality of light sources emitting light beams of different wavelengths;
• an optical system, the optical system comprising:
• an objective lens focusing any of the light beams onto the recording surface of the information recording medium;
• a plurality of grating elements provided between said light sources and said objective lens, the grating elements corresponding to the different wavelengths, respectively, and dividing the light beams of the corresponding wavelengths traveling toward said objective lens each into a plurality of beams including a 0th-order light and diffracted lights;
• and
• a plurality of holograms corresponding to the different wavelengths, respectively, and guiding to a predetermined position the light beams of the corresponding wavelengths reflected from the recording surface;
• and
• a photodetector provided at the predetermined position;
• and
• a processing device performing the information recording by using an output signal of said optical pickup unit,
• wherein one of the light sources which one emits a light beam of a wavelength corresponding to a type of the attached information recording medium is selected;
• and
• the light beam emitted from the selected one of the light sources is focused onto the recording surface and reflected therefrom to be received by said photodetector.