Object lens, optical pickup, and optical disc device

An optical disc device comprising:

• driving means configured to hold and rotationally drive an optical disc optionally selected from at least
• a first optical disc,
• a second optical disc of a different type from said first optical disc, and
• a third optical disc of a different type from said first and second optical discs;
• and
• an optical pickup configured to selectively irradiate multiple optical beams of different wavelengths to an optical disc rotationally driven by said driving means, so as to record and/or play information signals;
• said optical pickup including
• a first emitting unit configured to emit an optical beam of a first wavelength corresponding to said first optical disc,
• a second emitting unit configured to emit an optical beam of a second wavelength which is longer than said first wavelength, corresponding to said second optical disc,
• a third emitting unit configured to emit an optical beam of a third wavelength which is longer than said second wavelength, corresponding to said third optical disc,
• an object lens configured to condense optical beams emitted from said first through third emitting units onto a signal recording face of an optical disc, and
• a diffraction unit provided on one face of an optical element or said object lens, positioned on the optical path of said optical beams of the first through third wavelengths;
• wherein said diffraction unit includes a generally circular first diffraction region provided on the innermost perimeter, a ring zone shaped second diffraction region provided on the outer side of said first diffraction region, and a ring zone shaped third diffraction region provided on the outer side of said second diffraction region;
• wherein said first diffraction region has a first diffraction structure formed in a ring zone shape and having a predetermined depth, which
• emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens,
• emits diffracted light of an order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens, and
• emits diffracted light of an order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens;
• and wherein said second diffraction region has a second diffraction structure which is different from said first diffraction structure formed in a ring zone shape and having a predetermined depth, which emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens, emits diffracted light of an order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens, and emits diffracted light such that diffracted light of an order other than the order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens is dominant;
• and wherein said third diffraction region has a third diffraction structure which is different from said first and second diffraction structures formed in a ring zone shape and having a predetermined depth, which
• emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens,
• emits diffracted light such that diffracted light of an order other than the order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens is dominant, and
• emits diffracted light such that diffracted light of an order other than the order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens is dominant.

An object lens used with an optical pickup configured to irradiate optical beams on at least

• a first optical disc,
• a second optical disc of a different type from said first optical disc, and
• a third optical disc of a different type from said first and second optical discs,
• so as to record and/or play information signals, with said object lens condensing
• an optical beam of a first wavelength corresponding to said first optical disc,
• an optical beam of a second wavelength which is longer than said first wavelength, corresponding to said second optical disc, and
• an optical beam of a third wavelength which is longer than said second wavelength, corresponding to said third optical disc, onto a signal recording face of a corresponding optical disc, said object lens comprising:
• a diffraction unit provided on the input side face or output side face;
• wherein said diffraction unit includes a generally circular first diffraction region provided on the innermost perimeter, a ring zone shaped second diffraction region provided on the outer side of said first diffraction region, and a ring zone shaped third diffraction region provided on the outer side of said second diffraction region;
• wherein said first diffraction region has a first diffraction structure formed in a ring zone shape and having a predetermined depth, which
• emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens, emits
• diffracted light of an order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens, and emits
• diffracted light of an order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens;
• and wherein said second diffraction region has a second diffraction structure which is different from said first diffraction structure formed in a ring zone shape and having a predetermined depth, which
• emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens,
• emits diffracted light of an order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens, and
• emits diffracted light such that diffracted light of an order other than the order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens is dominant;
• and wherein said third diffraction region has a third diffraction structure which is different from said first and second diffraction structures formed in a ring zone shape and having a predetermined depth, which
• emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens,
• emits diffracted light such that diffracted light of an order other than the order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens is dominant, and
• emits diffracted light such that diffracted light of an order other than the order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens is dominant.

An optical disc device comprising:

• a driving unit configured to hold and rotationally drive an optical disc optionally selected from at least
• a first optical disc,
• a second optical disc of a different type from said first optical disc, and
• a third optical disc of a different type from said first and second optical discs;
• and
• an optical pickup configured to selectively irradiate multiple optical beams of different wavelengths to an optical disc rotationally driven by said driving unit, so as to record and/or play information signals;
• said optical pickup including
• a first emitting unit configured to emit an optical beam of a first wavelength corresponding to said first optical disc,
• a second emitting unit configured to emit an optical beam of a second wavelength which is longer than said first wavelength, corresponding to said second optical disc,
• a third emitting unit configured to emit an optical beam of a third wavelength which is longer than said second wavelength, corresponding to said third optical disc,
• an object lens configured to condense optical beams emitted from said first through third emitting units onto a signal recording face of an optical disc, and
• a diffraction unit provided on one face of an optical element or said object lens, positioned on the optical path of said optical beams of the first through third wavelengths;
• wherein said diffraction unit includes a generally circular first diffraction region provided on the innermost perimeter, a ring zone shaped second diffraction region provided on the outer side of said first diffraction region, and a ring zone shaped third diffraction region provided on the outer side of said second diffraction region;
• wherein said first diffraction region has a first diffraction structure formed in a ring zone shape and having a predetermined depth, which
• emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens,
• emits diffracted light of an order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens, and
• emits diffracted light of an order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens;
• and wherein said second diffraction region has a second diffraction structure which is different from said first diffraction structure formed in a ring zone shape and having a predetermined depth, which
• emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens,
• emits diffracted light of an order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens, and
• emits diffracted light such that diffracted light of an order other than the order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens is dominant;
• and wherein said third diffraction region has a third diffraction structure which is different from said first and second diffraction structures formed in a ring zone shape and having a predetermined depth, which
• emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens,
• emits diffracted light such that diffracted light of an order other than the order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens is dominant, and
• emits diffracted light such that diffracted light of an order other than the order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens is dominant.