Objective optical element, optical pick-up apparatus, and optical information recording reproducing apparatus

An objective optical element for use in an optical pickup apparatus which comprises a first light source to emit a light flux having a wavelength λ1 for conducting recording or reproducing information for a first information recording medium with a transparent substrate having a thickness t1, a second light source to emit a light flux having a wavelength λ2 (λ1<λ2) for conducting recording or reproducing information for a second information recording medium with a transparent substrate having a thickness t2 (t1<t2), and a light converging system including the objective optical element to converge the light flux emitted from the first and second light sources onto an information recording plane through the respective transparent substrates of the first and second information recording mediums, the objective optical element comprising:

• an objective lens to converge the light flux emitted from the first and second light sources;
• and
• an optical functional surface to provide an optical action to the light flux and the optical functional surface including a common region including an optical axis and used for recording and/or reproducing information for both of the first and second information recording mediums and an exclusive region mainly used for recording and/or reproducing information for the first information recording medium;
• wherein the objective optical element forms a spot on a first recording medium with the diameter of the spot determined by an effective diameter and a focal length of the objective optical element,
• wherein when the first optical information medium is used, a sine condition unsatisfied-amount whose value is maximum exists on the common region,
• wherein the following formula is satisfied:
• 0.5<COMA2/COMA1<1.0
• where COMA1 is a coma aberration (λ1 rms) when a light flux goes slantingly to be incident with a view angle of 1° onto the objective optical element when the first optical information medium is used, and
• COMA2 is a coma aberration (λ2 rms) when a light flux goes slantingly to be incident with a view angle of 1° onto the objective optical element when the second optical information medium is used.

An objective optical element for use in an optical pickup apparatus which comprises a first light source to emit a light flux having a wavelength λ1 for conducting recording or reproducing information for a first information recording medium with a transparent substrate having a thickness t1, a second light source to emit a light flux having a wavelength λ2 (λ1<λ2) for conducting recording or reproducing information for a second information recording medium with a transparent substrate having a thickness t2 (t1<t2), and a light converging system including the objective optical element to converge the light flux emitted from the first and second light sources onto an information recording plane through the respective transparent substrates of the first and second information recording media, the objective optical element comprising:

• an objective lens to converge the light flux emitted from the first and second light sources;
• and
• an optical functional surface to provide an optical action to the light flux and the optical functional surface including a common region including an optical axis and used for recording and/or reproducing information for both of the first and second information recording mediums and an exclusive region mainly used for recording and/or reproducing information for the first information recording medium;
• wherein the objective optical element forms a spot on a first recording medium with the diameter of the spot determined by an effective diameter and a focal length of the objective optical element,
• wherein in the case that a height from the optical axis is placed on the vertical line (x), a sine condition unsatisfied amount when the second optical information recording medium is used is placed on the horizontal line (y) and a differential value (dy/dx) on a curve representing a relationship between the height from the optical axis and the sine condition unsatisfied amount on the common region is obtained, when a height of a light ray passing an outermost peripheral section of an effective diameter of the objective optical element is hCDNA from the optical axis, the following formula is satisfied:
• (dy/dx)≦0 when h<0.6hCDNA, and
• when at a first height on the curve, a straight line having an inclination corresponding to the differential value at the first height is drawn, the curve has a region residing at a positive side of the straight line on a farther side than the height from the optical axis.

An objective optical element for use in an optical pickup apparatus which comprises a first light source to emit a light flux having a wavelength λ1 for conducting recording or reproducing information for a first information recording medium with a transparent substrate having a thickness t1, a second light source to emit a light flux having a wavelength λ2 (λ1<λ2) for conducting recording or reproducing information for a second information recording medium with a transparent substrate having a thickness t2 (t1<t2), and a light converging system including the objective optical element to converge the light flux emitted from the first and second light sources onto an information recording plane through the respective transparent substrates of the first and second information recording media, the objective optical element comprising:

• an objective lens to converge the light flux emitted from the first and second light sources;
• and
• an optical functional surface to provide an optical action to the light flux and the optical functional surface including a common region including an optical axis and used for recording and/or reproducing information for both of the first and second information recording mediums and an exclusive region mainly used for recording and/or reproducing information for the first information recording medium;
• wherein the objective optical element forms a spot on a first recording medium with the diameter of the spot determined by an effective diameter and a focal length of the objective optical element,
• wherein when the first information recoding medium is used, and when an infinite object distance light ray with a height h from the optical axis is emitted from the objective optical element, U is an angle formed by the emitted infinite object distance light ray and the optical axis and a sine condition unsatisfied-amount is defied by a formula of SC1(h)=h/sinU−f (f is a focal length of the objective optical element when the first optical information recording medium is used), the following formulas are satisfied:
• SC1(h0/2)≦SC1out(h0)
• SC1(h0/2)≦0
• SC1(hmax)≦0
• where a height of an innermost peripheral light ray passed through an innermost section of the exclusive region is h0 from the optical axis, the sine condition unsatisfied-amount of the innermost peripheral light ray is SC1out(h0), and a height of a light ray passed through an outermost section of the effective diameter of the objective optical element is hmax from the optical axis.

An objective optical element for use in an optical pickup apparatus which comprises a first light source to emit a light flux having a wavelength λ1 for conducting recording or reproducing information for a first information recording medium with a transparent substrate having a thickness t1, a second light source to emit a light flux having a wavelength λ2 (λ1<λ2) for conducting recording or reproducing information for a second information recording medium with a transparent substrate having a thickness t2 (t1<t2), and a light converging system including the objective optical element to converge the light flux emitted from the first and second light sources onto an information recording plane through the respective transparent substrates of the first and second information recording media, the objective optical element comprising:

• an objective lens to converge the light flux emitted from the first and second light sources;
• and
• an optical functional surface to provide an optical action to the light flux;
• wherein a light source side optical functional surface of the objective optical element comprises a diffractive structure having a center on the optical axis,
• wherein an optical information recording medium side optical functional surface of the objective optical element comprises a common region including an optical axis and used for recording and/or reproducing information for both of the first and second information recording mediums, an exclusive region provided at an outside of the common region and mainly used for recording and/or reproducing information for the first information recording medium and a stepped section adjoining the common region and the exclusive region and provided to be almost parallel to the optical axis and to face toward an outside in terms of the optical axis, and
• wherein the objective optical element forms a spot on a first recording medium with the diameter of the spot determined by an effective diameter and a focal length of the objective optical element.