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,
• wherein the third light flux which has passed through the first optical path difference providing structure forms a first best focus in which the third light flux forms a spot having a smallest diameter,
• the third light flux which passes through the first optical path difference providing structure forms a second best focus in which the third light flux forms a spot having a second smallest diameter, and
• the first best focus and the second best focus satisfy a following expression:
• 0 <L/f<0.05,
• where f (mm) is a focal length of the objective optical element for the third light flux which passes through the first optical path difference structure and forms the first best focus, and
• L (mm) is a distance between the first best focus and the second best focus,
• wherein the third light flux which passes through the objective optical element forms a spot on the information recording surface of the third optical disk, and
• the spot comprises, in order from a center to an outside of the spot when viewing the spot from a direction of an optical axis of the objective optical element:
• a central spot portion having a highest light density;
• an intermediate spot portion having a lower light density than the central spot portion;
• and
• a peripheral spot portion having a higher light density than the intermediate spot portion and having a lower light density than the central spot portion,
• wherein the central spot portion is used for recording and/or reproducing information for the third optical disk, and
• the intermediate spot portion and the peripheral spot portion are not used for recording and/or reproducing information for the third optical disk, and
• wherein the peripheral spot portion is formed on the information recording surface of the third optical disk by the third light flux which has passed through the second optical path difference providing structure of the objective optical element.

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
• 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,
• wherein the third light flux which passes through the first optical path difference providing structure forms a first best focus in which the third light flux forms a spot having a smallest diameter,
• the third light flux which passes through the first optical path difference providing structure forms a second best focus in which the third light flux forms a spot having a second smallest diameter, and
• the first best focus and the second best focus satisfy a following expression:
• 0<L/f<0.05,
• where f (mm) is a focal length of the objective optical element for the third light flux which passes through the first optical path difference structure and forms the first best focus, and
• L (mm) is a distance between the first best focus and the second best focus,
• wherein the third light flux which passes through the objective optical element forms a spot on the information recording surface of the third optical disk, and
• the spot comprises, in order from a center to an outside of the spot when viewing the spot from a direction of an optical axis of the objective optical element:
• a central spot portion having a highest light density;
• an intermediate spot portion having a lower light density than the central spot portion;
• and
• a peripheral spot portion having a higher light density than the intermediate spot portion and having a lower light density than the central spot portion, and
• wherein the central spot portion is used for recording and/or reproducing information for the third optical disk, and
• the intermediate spot portion and the peripheral spot portion are not used for recording and/or reproducing information for the third optical disk, and
• wherein the peripheral spot portion is formed on the information recording surface of the third optical disk by the third light flux which passes through the second optical path difference providing structure of the objective optical element.