Aberration correcting device and optical recording medium reproducing apparatus

• US 7,428,207 B2
• Filed: 08/12/2004
• Issued: 09/23/2008
• Est. Priority Date: 08/28/2003
• Status: Expired due to Fees

• Current Assignee: Pioneer Corporation
• Original Assignee: Pioneer Corporation
• Inventors: Sato, Makoto, Ogasawara, Masakazu
• Primary Examiner(s): Feild; Joseph
• Assistant Examiner(s): Agustin; Peter Vincent
• Application Number:
  US10/916,452
• Publication Number:
  US 20050047311A1
• Time in Patent Office: 1,503 Days
• Field of Search: None
• US Class Current: 369/112.02
• CPC Class Codes: G11B 2007/0006 adapted for scanning different types of carrier, e.g. CD & DVD
• CPC Class Codes: G11B 7/13925 active, e.g. controlled by electrical or mechanical means

Abstract

A disk reproducing apparatus for reproducing a disk that is any one of three kinds of disks, BD, DVD and CD, employing a BD objective lens, correct only aberration occurring inside the effective diameter of DVD, and leaves aberration outside the effective diameter, when reproducing DVD. Likewise, the disk reproducing apparatus corrects only aberration occurring inside the effective diameter of CD, and leaves aberration outside the effective diameter, when reproducing CD.

Claims

1. An aberration correcting device which corrects an aberration occurring when one objective lens is employed for a plurality of optical recording media at least one of recording density and thickness of a cover layer of which is different from each other, comprising:

a liquid crystal element disposed between the objective lens and a light source and controlled a refractive index thereof to be varied in accordance with an applied voltage; and

a voltage applying portion for applying voltage to the liquid crystal element so that a wavefront of light penetrated through the liquid crystal element forms a penetrated wavefront having a predetermined phase distribution, wherein the voltage applying portion applies voltage so that a penetrated wavefront having a phase distribution for correcting only an aberration occurring in an area inside an effective diameter in recording or reproducing the optical recording medium is formed,

wherein the voltage applying portion independently applies predetermined voltage to each of a plurality of electrodes arranged along the liquid crystal element to variably control a shape of the penetrated wavefront, in which the voltage applying portion applies predetermined voltage to a plurality of electrodes arranged in an area inside the effective diameter of the optical recording medium so that a penetrated wave having a shape corresponding to aberration occurring in the area is formed, and applies predetermined voltage to a plurality of electrodes arranged in an area outside the effective diameter of the optical recording medium so that a penetrated wave not having a shape corresponding to aberration occurring in the area is formed.

2. An aberration correcting device which corrects an aberration occurring when an objective lens exclusively used for a first optical recording medium is employed for a second optical recording medium having an effective diameter in recording or reproducing the optical recording medium smaller than an effective diameter of the first optical recording medium, and for a third optical recording medium having an effective diameter smaller than an effective diameter of the second optical recording medium, comprising:

a liquid crystal element disposed between the objective lens and a light source and controlled a refractive index thereof to be varied in accordance with an applied voltage; and

a voltage applying portion for applying voltage to the liquid crystal element so that a wavefront of light penetrated through the liquid crystal element forms a penetrated wavefront having a predetermined phase distribution, wherein the voltage applying portion applies voltage so that a penetrated wavefront having a phase distribution for correcting only an aberration occurring in an area inside a first effective diameter in recording or reproducing the second optical recording medium is formed when the objective lens is employed for the second optical recording medium, and applies voltage so that a penetrated wavefront having a phase distribution for correcting only an aberration occurring in an area inside a second effective diameter in recording or reproducing the third optical recording medium is formed when the objective lens is employed for the third optical recording medium.

3. The aberration correcting device according to claim 2, wherein the voltage applying portion independently applies predetermined voltage to a first area corresponding to inside of the second effective diameter and a second area corresponding to outside of the second effective diameter and inside of the first effective diameter to variably control only amplitude of penetrated wavefronts formed in each area, in which the voltage applying portion applies predetermined voltage to the first area and the second area so that a penetrated wavefront having an amplitude corresponding to aberration occurring in each area is formed when the objective lens is employed for the second optical recording medium, and applies predetermined voltage to the first area so that a penetrated wavefront having an amplitude corresponding to aberration occurring in the first area is formed and applies predetermined voltage to the second area so that a penetrated wavefront not having an amplitude corresponding to aberration occurring in the second area is formed when the objective lens is employed for the third optical recording medium.

4. The aberration correcting device according to claim 3, wherein the voltage applying portion applies predetermined voltage to the first area so that a penetrated wavefront having a predetermined amplitude ratio to the penetrated wavefront formed in the first area when the objective lens is employed for the second optical recording medium is formed, and applies predetermined voltage to the second area so that a penetrated wavefront having an amplitude ratio different from the predetermined amplitude ratio when the objective lens is employed for the third optical recording medium.

5. The aberration correcting device according to claim 3, wherein the voltage applying portion respectively applies equal voltage to an outermost circumference of the first area and an innermost circumference of the second area when the objective lens is employed for the second optical recording medium.

6. The aberration correcting device according to claim 2, wherein the voltage applying portion independently applies predetermined voltage to a first area corresponding to inside of the second effective diameter and a second area corresponding to outside of the second effective diameter and inside of the first effective diameter to variably control only amplitude of penetrated wavefronts formed in each area, in which the voltage applying portion applies predetermined voltage to the second area alone so that a penetrated wavefront having an amplitude corresponding to aberration occurring in the second area is formed when the objective lens is employed for the second optical recording medium, and applies predetermined voltage to the first area alone so that a penetrated wavefront having an amplitude corresponding to aberration occurring in the first area is formed when the objective lens is employed for the third optical recording medium.

7. The aberration correcting device according to claim 6, wherein the voltage applying portion applies voltage of fixed value to each of the first area and the second area.

8. The aberration correcting device according to claim 2, wherein the voltage applying portion integrally applies predetermined voltage to a first area corresponding to inside of the second effective diameter and a second area corresponding to outside of the second effective diameter and inside of the first effective diameter to variably control integrally only amplitude of penetrated wavefronts formed in each area, in which the voltage applying portion integrally applies predetermined voltage to the first area and the second area so that a envelop surface of the penetrated wavefront has in the first area a amplitude corresponding to aberration occurring in the first area, and has in the second area a plurality of step differences having a depth of integral times of a wavelength used in recording or reproducing the second optical recording medium when the objective lens is employed for the second optical recording medium, and the voltage applying portion integrally applies predetermined voltage to the first area and the second area so that a envelop surface of the penetrated wavefront has in the first area a amplitude corresponding to aberration occurring in the first area, and has in the second area a plurality of step differences having a depth except integral times of a wavelength used in recording or reproducing the third optical recording medium when the objective lens is employed for the third optical recording medium.

9. The aberration correcting device according to claim 2, wherein the voltage applying portion independently applies predetermined voltage to a first area corresponding to inside of the second effective diameter and a second area corresponding to outside of the second effective diameter and inside of the first effective diameter to variably control only amplitude of penetrated wavefronts formed in each area, in which the voltage applying portion independently applies predetermined voltage to the first area and the second area so that a envelop surface of the penetrated wavefront has in the first area a amplitude corresponding to aberration occurring in the first area, and has in the second area a plurality of step differences having a depth of integral times of a wavelength used in recording or reproducing the second optical recording medium when the objective lens is employed for the second optical recording medium, and the voltage applying portion independently applies predetermined voltage to the first area and the second area so that to form a envelop surface of the penetrated wavefront has in the first area a amplitude corresponding to aberration occurring in the first area, and has in the second area a plurality of step differences having a depth except integral times of a wavelength used in recording or reproducing the third optical recording medium when the objective lens is employed for the third optical recording medium.

10. An optical recording medium reproducing device which corrects an aberration occurring when an objective lens exclusively used for a first optical recording medium is employed for a second optical recording medium having an effective diameter in recording or reproducing the optical recording medium smaller than an effective diameter of the first optical recording medium, and for a third optical recording medium having an effective diameter smaller than an effective diameter of the second optical recording medium, and reproduces information recorded in each optical recording media, comprising:

a liquid crystal element disposed between the objective lens and a light source and controlled a refractive index thereof to be varied in accordance with an applied voltage; and

a voltage applying portion for applying voltage to the liquid crystal element so that a wavefront of light penetrated through the liquid crystal element forms a penetrated wavefront having a predetermined phase distribution, wherein the voltage applying portion applies voltage so that a penetrated wavefront having a phase distribution for correcting only an aberration occurring in an area inside a first effective diameter in recording or reproducing the second optical recording medium is formed when the objective lens is employed for the second optical recording medium, and applies voltage so that a penetrated wavefront having a phase distribution for correcting only an aberration occurring in an area inside a second effective diameter in recording or reproducing the third optical recording medium is formed when the objective lens is employed for the third optical recording medium.