Optical pickup apparatus

An optical pickup apparatus for reading recorded information from an optical recording medium, said optical pickup apparatus including an optical system which comprises:

• a single light intensity detection device having a quarter-split light receiving surface;
• two semiconductor lasers for emitting light beams of different wavelengths;
• an objective lens for directing each of said light beams onto an optical recording medium to form a light spot on a recording surface;
• and
• a holographic optical element located between said quarter-split light receiving surface and said objective lens, wherein said holographic optical element is operative to eliminate coma aberration and spherical aberration of a light beam traveled through said recording surface and said objective lens, thereby generating a predetermined amount of astigmatism, wherein said holographic optical element passes a light beam of a first wavelength launched from one of said semiconductor lasers, guides zero-order diffraction light of said light beam to said objective lens, diffracts said zero-order diffraction light of said first wavelength traveled through said recording surface, and guides positive first-order diffraction light, acquired by diffraction, to said quarter-split light receiving surface, and
• wherein the other one of said semiconductor lasers is located at such a position that said holographic optical element passes a light beam of a second wavelength launched from said other semiconductor laser, guides zero-order diffraction light of said light beam to said objective lens, diffracts said zero-order diffraction light of said second wavelength traveled through said recording surface, and guides positive first-order diffraction light, acquired by diffraction, to said quarter-split light receiving surface.

An optical pickup apparatus for reading recorded information from an optical recording medium, said optical pickup apparatus including an optical system which comprises:

• a single light intensity detection device having a quarter-split light receiving surface;
• two semiconductor lasers for emitting light beams of different wavelengths;
• an objective lens for directing each of said light beams onto an optical recording medium to form a light spot on a recording surface;
• and
• a holographic optical element located between said quarter-split light receiving surface and said objective lens, wherein said holographic optical element is operative to eliminate coma aberration and spherical aberration of a light beam traveled through said recording surface and said objective lens, thereby generating a predetermined amount of astigmatism, wherein said holographic optical element passes a light beam of a first wavelength launched from one of said semiconductor lasers, guides zero-order diffraction light of said light beam to said objective lens, diffracts said zero-order diffraction light of said first wavelength traveled through said recording surface, and guides positive first-order diffraction light, acquired by diffraction, to said quarter-split light receiving surface, and
• wherein the other one of said semiconductor lasers is located at such a position that said holographic optical element passes a light beam of a second wavelength launched from said other semiconductor laser, guides negative first-order diffraction light of said light beam to said objective lens, receives return light from a light spot on said recording surface, produced by said negative first-order diffraction light of said second wavelength, from said objective lens, diffracts said return light, and guides positive first-order diffraction light of said second wavelength, acquired by diffraction, to said quarter-split light receiving surface;
• and
• said optical system further includes an aberration correcting element, located between said holographic optical element and said objective lens, for passing said light beam of said second wavelength launched from said other semiconductor laser without acting on said light beam of said first wavelength, and guiding said light beam of said second wavelength to said objective lens while eliminating aberration from said light beam of said second wavelength.

An optical pickup apparatus for reading recorded information from an optical recording medium, said optical pickup apparatus including an optical system which comprises:

• a single light intensity detection device having a quarter-split light receiving surface;
• two semiconductor lasers for emitting light beams of different wavelengths;
• an objective lens for directing each of said light beams onto an optical recording medium to form a light spot on a recording surface;
• and
• a holographic optical element located between said quarter-split light receiving surface and said objective lens, wherein said holographic optical element is operative to eliminate coma aberration and spherical aberration of a light beam traveled through said recording surface and said objective lens, thereby generating a predetermined amount of astigmatism, wherein said holographic optical element passes a light beam of a first wavelength launched from one of said semiconductor lasers, guides zero-order diffraction light of said light beam to said objective lens, diffracts said zero-order diffraction light of said first wavelength traveled through said recording surface, and guides positive first-order diffraction light, acquired by diffraction, to said quarter-split light receiving surface, and
• wherein the other one of said semiconductor lasers is located at such a position that said holographic optical element passes a light beam of a second wavelength launched from said other semiconductor laser, guides negative first-order diffraction light of said light beam to said objective lens, receives return light from a light spot on said recording surface, produced by said negative first-order diffraction light of said second wavelength, from said objective lens, diffracts said return light, and guides positive first-order diffraction light of said second wavelength, acquired by diffraction, to said quarter-split light receiving surface;
• and
• said optical system further includes a light-source side aberration correcting element, located between said other semiconductor laser and said holographic optical element, for passing said light beam of said second wavelength launched from said other semiconductor laser, giving said light beam of said second wavelength such aberration as to cancel aberration, which occurs at a time said light beam of said second wavelength passes said holographic optical element, and guiding said light beam of said second wavelength to said holographic optical element, thereby eliminating aberration from said light beam of said second wavelength having passed said holographic optical element.

An optical pickup apparatus for reading recorded information from an optical recording medium, said optical pickup apparatus including an optical system which comprises:

• a single light intensity detection device having a quarter-split light receiving surface;
• two semiconductor lasers for emitting light beams of different wavelengths;
• an objective lens for directing each of said light beams onto an optical recording medium to form a light spot on a recording surface;
• and
• a holographic optical element located between said quarter-split light receiving surface and said objective lens, wherein said holographic optical element is operative to eliminate coma aberration and spherical aberration of a light beam traveled through said recording surface and said objective lens, thereby generating a predetermined amount of astigmatism, wherein said holographic optical element passes a light beam of a first wavelength launched from one of said semiconductor lasers, guides zero-order diffraction light of said light beam to said objective lens, diffracts said zero-order diffraction light of said first wavelength traveled through said recording surface, and guides positive first-order diffraction light, acquired by diffraction, to said quarter-split light receiving surface, and
• wherein said optical system further includes a second quarter-split light receiving surface;
• and
• the other one of said semiconductor lasers is located at such a position that said holographic optical element passes a light beam of a second wavelength launched from said other semiconductor laser, guides zero-order diffraction light of said light beam to said objective lens, diffracts said zero-order diffraction light of said second wavelength traveled through said recording surface, and guides positive first-order diffraction light, acquired by diffraction, to said second quarter-split light receiving surface.

An optical pickup apparatus for reading recorded information from an optical recording medium, said optical pickup apparatus including an optical system which comprises:

• a single light intensity detection device having a quarter-split light receiving surface;
• two semiconductor lasers for emitting light beams of different wavelengths;
• an objective lens for directing each of said light beams onto an optical recording medium to form a light spot on a recording surface;
• and
• a holographic optical element located between said quarter-split light receiving surface and said objective lens, wherein said holographic optical element is operative to eliminate coma aberration and spherical aberration of a light beam traveled through said recording surface and said objective lens, thereby generating a predetermined amount of astigmatism, wherein said holographic optical element passes a light beam of a first wavelength launched from one of said semiconductor lasers, guides zero-order diffraction light of said light beam to said objective lens, diffracts said zero-order diffraction light of said first wavelength traveled through said recording surface, and guides positive first-order diffraction light, acquired by diffraction, to said quarter-split light receiving surface, and
• wherein said optical system further includes a second quarter-split light receiving surface;
• and
• the other one of said semiconductor lasers is located at such a position that said holographic optical element passes a light beam of a second wavelength launched from said other semiconductor laser, guides negative first-order diffraction light of said light beam to said objective lens, receives return light from a light spot on said recording surface, produced by said negative first-order diffraction light of said second wavelength, from said objective lens, diffracts said return light, and guides positive first-order diffraction light of said second wavelength, acquired by diffraction, to said second quarter-split light receiving surface;
• and
• said optical system further includes an aberration correcting element, located between said holographic optical element and said objective lens, for passing said light beam of said second wavelength launched from said other semiconductor laser without acting on said light beam of said first wavelength, and guiding said light beam of said second wavelength to said objective lens while eliminating aberration from said light beam of said second wavelength.

An optical pickup apparatus for reading recorded information from an optical recording medium, said optical pickup apparatus including an optical system which comprises:

• a single light intensity detection device having a quarter-split light receiving surface;
• two semiconductor lasers for emitting light beams of different wavelengths;
• an objective lens for directing each of said light beams onto an optical recording medium to form a light spot on a recording surface;
• and
• a holographic optical element located between said quarter-split light receiving surface and said objective lens, wherein said holographic optical element is operative to eliminate coma aberration and spherical aberration of a light beam traveled through said recording surface and said objective lens, thereby generating a predetermined amount of astigmatism, wherein said holographic optical element passes a light beam of a first wavelength launched from one of said semiconductor lasers, guides zero-order diffraction light of said light beam to said objective lens, diffracts said zero-order diffraction light of said first wavelength traveled through said recording surface, and guides positive first-order diffraction light, acquired by diffraction, to said quarter-split light receiving surface, and
• wherein said optical system further includes a second quarter-split light receiving surface;
• the other one of said semiconductor lasers is located at such a position that said holographic optical element passes a light beam of a second wavelength launched from said other semiconductor laser, guides negative first-order diffraction light of said light beam to said objective lens, receives return light from a light spot on said recording surface, produced by said negative first-order diffraction light of said second wavelength, from said objective lens, diffracts said return light, and guides positive first-order diffraction light of said second wavelength, acquired by diffraction, to said second quarter-split light receiving surface;
• and
• said optical system further includes a light-source side aberration correcting element, located between said other semiconductor laser and said holographic optical element, for passing said light beam of said second wavelength launched from said other semiconductor laser, giving said light beam of said second wavelength such aberration as to cancel aberration, which occurs at a time said light beam of said second wavelength passes said holographic optical element, and guiding said light beam of said second wavelength to said holographic optical element, thereby eliminating aberration from said light beam of said second wavelength having passed said holographic optical element.