Optical pickup apparatus, objective optical element and optical information recording and/or reproducing apparatus

An objective optical element for use in an optical pickup apparatus, the optical pickup apparatus comprising

• a first light source for emitting a first light flux having a first wavelength λ1;
• a second light source for emitting a second light flux having a second wavelength λ2 (λ2>λ1);
• and
• a third light source for emitting a third light flux having a third wavelength λ3 (λ3>λ2), and
• conducting recording and/or reproducing information using the first light flux for a first optical disk having a protective substrate with a thickness t1,
• conducting recording and/or reproducing information using the second light flux for a second optical disk having a protective substrate with a thickness t2 (t1<t2), and
• conducting recording and/or reproducing information using the third light flux for a third optical disk having a protective substrate with a thickness t3 (t2<t3),
• the objective optical element comprising:
• an optical surface comprising a central area and a peripheral area surrounding the central area,
• wherein the central area comprises a first optical path difference providing structure,
• the peripheral area comprises a second optical path difference providing structure,
• wherein the objective optical element converges the first light flux which passes through the central area of the objective optical element onto the information recording surface of the first optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the first optical disk,
• the objective optical element converges the second light flux which passes through the central area of the objective optical element onto the information recording surface of the second optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the second optical disk,
• the objective optical element converges the third light flux which passes through the central area of the objective optical element onto the information recording surface of the third optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the third optical disk,
• the objective optical element converges the first light flux which passes through the peripheral area of the objective optical element onto the information recording surface of the first optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the first optical disk, and
• the objective optical element converges the second light flux which passes through the peripheral area of the objective optical element onto the information recording surface of the second optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the second optical disk, and
• wherein the first optical path difference providing structure comprises at least a first basic structure,
• the first basic structure is an optical path difference providing structure
• which emits a first order diffracted light flux with a larger light amount than any diffracted light fluxes with the other diffraction order, when the first light flux passes through the first basic structure,
• which emits a first order diffracted light flux with a larger light amount than any diffracted light fluxes with the other diffraction order, when the second light flux passes through the first basic structure, and
• which emits a first order diffracted light flux with a larger light amount than any diffracted light fluxes with the other diffraction order, when the third light flux passes through the first basic structure, and
• wherein the second optical path difference providing structure comprises a predetermined basic structure,
• the predetermined basic structure is an optical path difference providing structure
• which emits a x-th order diffracted light flux with a larger light amount than any diffracted light fluxes with the other diffraction order, when the first light flux passes through the predetermined basic structure,
• which emits a y-th order diffracted light flux with a larger light amount than any diffracted light fluxes with the other diffraction order, when the second light flux passes through the predetermined basic structure, and
• the predetermined basic structure satisfies a following expression:
• 0.9·(x·λ1)/(n1−1)≦(y·λ2)/(n2−1)≦1.2·(x·λ1)/(n1−1),
• where x is an integer excluding 0, y is an integer excluding 0, n1 is a refractive index of the objective optical element for the first light flux, and n2 is a refractive index of the objective optical element for the second light flux.

An optical information recording and/or reproducing apparatus, comprising:

• an optical pickup apparatus comprising:
• a first light source for emitting a first light flux having a first wavelength λ1;
• a second light source for emitting a second light flux having a second wavelength λ2 (λ2>λ1);
• a third light source for emitting a third light flux having a third wavelength λ3 (λ3>λ2);
• and
• an objective optical element
• for converging the first light flux onto an information recording surface of a first optical disk having a protective substrate with a thickness t1,
• for converging the second light flux onto an information recording surface of a second optical disk having a protective substrate with a thickness t2 (t1≦t2), and
• for converging the third light flux onto an information recording surface of a third optical disk having a protective substrate with a thickness t3 (t2<t3),
• wherein the optical pickup apparatus records and/or reproduces information by converging the first light flux onto the information recording surface of the first optical disk, by converging the second light flux onto the information recording surface of the second optical disk, and by converging the third light flux onto the information recording surface of the third optical disk,
• wherein the objective optical element comprises an optical surface comprising a central area and a peripheral area surrounding the central area,
• the central area comprises a first optical path difference providing structure, and
• the peripheral area comprises a second optical path difference providing structure,
• wherein the objective optical element converges the first light flux which passes through the central area of the objective optical element onto the information recording surface of the first optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the first optical disk,
• the objective optical element converges the second light flux which passes through the central area of the objective optical element onto the information recording surface of the second optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the second optical disk,
• the objective optical element converges the third light flux which passes through the central area of the objective optical element onto the information recording surface of the third optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the third optical disk,
• the objective optical element converges the first light flux which passes through the peripheral area of the objective optical element onto the information recording surface of the first optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the first optical disk, and
• the objective optical element converges the second light flux which passes through the peripheral area of the objective optical element onto the information recording surface of the second optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the second optical disk, and
• wherein the first optical path difference providing structure comprises at least a first basic structure,
• the first basic structure is an optical path difference providing structure
• which emits a first order diffracted light flux with a larger light amount than any diffracted light fluxes with the other diffraction order, when the first light flux passes through the first basic structure,
• which emits a first order diffracted light flux with a larger light amount than any diffracted light fluxes with the other diffraction order, when the second light flux passes through the first basic structure, and
• which emits a first order diffracted light flux with a larger light amount than any diffracted light fluxes with the other diffraction order, when the third light flux passes through the first basic structure, and
• wherein the second optical path difference providing structure comprises a predetermined basic structure,
• the predetermined basic structure is an optical path difference providing structure
• which emits a x-th order diffracted light flux with a larger light amount than any diffracted light fluxes with the other diffraction order, when the first light flux passes through the predetermined basic structure,
• which emits a y-th order diffracted light flux with a larger light amount than any diffracted light fluxes with the other diffraction order, when the second light flux passes through the predetermined basic structure, and
• the predetermined basic structure satisfies a following expression:
• 0.9·(x·λ1)/(n1−1)≦(y·λ2)/(n2−1)≦1.2·(x·λ1)/(n1−1)
• where x is an integer excluding 0, y is an integer excluding 0, n1 is a refractive index of the objective optical element for the first light flux, and n2 is a refractive index of the objective optical element for the second light flux.