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US 7,733,759 B2Granted
Optical pickup and optical disc apparatus
AssigneeHitachi Media Electronics Co., Ltd.
InventorsKenichi Shimada, Katsuhiko Izumi
Life of this patent
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Abstract
An optical system is disclosed including an optical pickup having a wavefront aberration-correcting element capable of correcting coma aberration and astigmatism, and an optical disc apparatus which uses the optical pickup. The optical pickup includes a laser light source for irradiating an optical disc with a light beam; an objective lens for focusing the light beam on the optical disc; a lens for correcting astigmatism; a second lens for correcting coma aberration; and a photodetector for receiving the light beam reflected from the optical disc. The astigmatism and the coma aberration are corrected independently of each other.
Claims18
An optical pickup comprising:
- a laser light source for irradiating an optical disc with a light beam;
- an objective lens for focusing the light beam emitted from the laser light source on the optical disc;
- a first lens for correcting astigmatism;
- a second lens for correcting coma aberration;
- and a photodetector for receiving the light beam reflected from the optical disc;
- wherein the astigmatism and the coma aberration are corrected independently of each other by using the first lens or the second lens, wherein at least one of:
- a Root Mean Square (RMS) value of the astigmatism that occurs when the first lens is moved in a direction perpendicular to an optical axis is greater than an RMS value of the coma aberration, and the RMS value of the coma aberration that occurs when the second lens is moved in a direction perpendicular to the optical axis is greater than the RMS value of the astigmatism.
4 more elements
An optical pickup comprising:
- a laser light source for irradiating an optical disc with a light beam;
- an objective lens for focusing the light beam emitted from the laser light source on the optical disc;
- a first lens for correcting astigmatism;
- a second lens for correcting coma aberration;
- and a photodetector for receiving the light beam reflected from the optical disc, wherein the astigmatism and the coma aberration are corrected independently of each other by using the first lens or the second lens, wherein when Root Mean Square (RMS) values of the astigmatism and coma aberration that occur when the first lens is moved in a direction perpendicular to an optical axis are represented by ΔWAS1 and ΔWCM1, respectively, and RMS values of the astigmatism and coma aberration that occur when the second lens is moved in a direction perpendicular to the optical axis are represented by ΔWAS2 and ΔWCM2, respectively, a relationship in which ΔWAS1 is at least ΔWCM1×2, or a relationship in which ΔWCM2 is at least ΔWAS2×2, is established.
2 more elements
An optical pickup comprising:
- a laser light source for irradiating an optical disc with a light beam;
- an objective lens for focusing the light beam emitted from the laser light source on the optical disc;
- a first lens for correcting astigmatism;
- a second lens for correcting coma aberration;
- and a photodetector for receiving the light beam reflected from the optical disc, wherein the astigmatism and the coma aberration are corrected independently of each other by using the first lens or the second lens, wherein:
- a shape of the first lens is represented using an expression of Z1 (h)=c1h2/[1{1−(K1+1)c12h2}0.5] (h is a distance from an optical axis, c1=0.22, K1=−0.63);
- and a shape of the second lens is represented using an expression of Z2 (h)=c2h21[1{1−(K2+1)c22h2}0.5] (h is a distance from the optical axis, c2=0.14, K2=+0.67).
4 more elements
An optical pickup comprising:
- a laser light source for irradiating an optical disc with a beam of light;
- an objective lens for focusing the light beam emitted from the laser light source on the optical disc;
- a first lens for correcting astigmatism;
- a second lens for correcting coma aberration;
- and a photodetector that receives the light beam reflected from the optical disc;
- wherein the first lens has characteristics which act on the astigmatism, but do not substantially act on the coma aberration when the first lens is moved perpendicularly to an optical axis, wherein a Root Mean Square (RMS) value of the astigmatism that occurs when the first lens is moved in a direction perpendicular to the optical axis is greater than an RMS value of the coma aberration, wherein the RMS value of the coma aberration that occurs when the second lens is moved in a direction perpendicular to the optical axis is greater than the RMS value of the astigmatism.
3 more elements
An optical pickup comprising:
- a laser light source for irradiating an optical disc with a beam of light;
- an objective lens for focusing the light beam emitted from the laser light source on the optical disc;
- a first lens for correcting astigmatism;
- a second lens for correcting coma aberration;
- and a photodetector that receives the light beam reflected from the optical disc, wherein the first lens has characteristics which act on the astigmatism, but do not substantially act on the coma aberration when the first lens is moved perpendicularly to an optical axis, wherein when Root Mean Square (RMS) values of the astigmatism and coma aberration that occur when the first lens is moved in a direction perpendicular to an optical axis are represented by ΔWAS1 and ΔWCM1, respectively, and RMS values of the astigmatism and coma aberration that occur when the second lens is moved in a direction perpendicular to the optical axis are represented by ΔWAS2 and ΔWCM2, respectively, a relationship in which ΔWAS1 is at least ΔWCM1×2, or a relationship in which ΔWCM2 is at least ΔWAS2×2, is established.
2 more elements
An optical pickup comprising:
- a laser light source for irradiating an optical disc with a beam of light;
- an objective lens for focusing the light beam emitted from the laser light source on the optical disc;
- a first lens for correcting astigmatism;
- a second lens for correcting coma aberration;
- and a photodetector that receives the light beam reflected from the optical disc, wherein the first lens has characteristics which act on the astigmatism, but do not substantially act on the coma aberration when the first lens is moved perpendicularly to an optical axis, wherein:
- a shape of the first lens is represented by Z1 (h)=c1h2/[1{1−(K1+1)c12h2}0.5] (where h is a distance from the optical axis, c1=0.22, K1=−0.63);
- and a shape of the second lens is represented by Z2 (h)=c2h2/[1{1−(K2+1)c22h2}0.5] (h is a distance from the optical axis, c2=0.14, K2=+0.67).
4 more elements
Dependencies are inferred from the claim text.