Optical recording and reproducing apparatus

An apparatus for optically recording and reproducing information on and from first and second media having first and second areal densities, respectively, the first density being higher than the second density, said apparatus comprising:

• a first light source for emitting a first light beam having a first wavelength;
• a second light source for emitting a second light beam having a second wavelength larger than said first wavelength;
• an optical system for guiding said first and second light beams from said first and second light sources to an optical recording medium, separating said first and second light beams reflected from said optical recording medium and guiding the same to first and second optical detecting means, respectively, wherein said optical system includes an objective lens for converging said first and second light beams as a first light spot and a second light spot on said optical recording medium, said optical system further including at least one beam splitter disposed between said first and second light sources and said objective lens, for reflecting all said first light beam, transmitting at least part of a P-polarized component of said second light beam, and reflecting all in S-polarized component of said second light beam, and a quarter wavelength plate disposed in an optical path between said beam splitter and said objective lens, said optical system further including a diffracting element for diffracting said first and second light beams to allow the same to be incident on said first and second optical detecting means, respectively, and wherein said first light source is used for recording and reproducing information on and from said first medium, and said second light source is used for recording and reproducing information on and from said second medium.

An apparatus for optically recording and reproducing information on and from first and second media having first and second areal densities, respectively, the first density being higher than the second density, said apparatus comprising:

• a first light source for emitting a first light beam having a first wavelength;
• a second light source for emitting a second light beam having a second wavelength larger than said first wavelength;
• an optical system for guiding said first and second light beams from said first and second light sources to an optical recording medium, separating said first and second light beams reflected from said optical recording medium and guiding the same to first and second optical detecting means, respectively, said optical system including an objective lens for converging said first and light beams as a first light spot and a second light spot on said optical recording medium, and said optical system further including a first beam splitter disposed between said first and second light sources and said objective lens, for reflecting all of said first light beam, transmitting at least part of a P-polarized component of said second light beam, and reflecting all of and S-polarized component of said second light beam, a second beam splitter disposed between said first and second light sources and said objective lens, for reflecting all of said first light beam, transmitting all of a P-polarized component of said second light beam, and reflecting all of and S-polarized component of said second light beam, and a quarter wavelength plate disposed in an optical path between said beam splitter and said objective lens, wherein said first light source is used for recording and reproducing information on and from said first medium, and said second light source is used for recording and reproducing information on and from said second medium.

An apparatus for optically recording and reproducing information on and from first and second media having different thicknesses and having first and second areal densities, respectively, the first density being higher than the second density, said apparatus comprising:

• a first light source for emitting a first light beam having a first wavelength and being incident on an objective lens as a parallel light beam along an optical axis;
• a second light source for emitting a second light beam having a second wavelength longer than said first wavelength and being incident on said objective lens as a divergent light beam along said optical axis;
• and
• an optical system for guiding said first and second light beams to an optical recording medium and guiding said first and second light beams upon reflection from said optical recording medium to a first optical detector and a second optical detector, said optical system including an objective lens for converging said first and second light beams as a first light spot and a second light spot on said optical recording medium.