Optical pickup of tilt control type

• US 20020001282A1
• Filed: 05/21/2001
• Published: 01/03/2002
• Est. Priority Date: 05/24/2000
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Horinouchi, Shogo, Kojima, Kouki
• Granted Patent: US 6,804,186 B2
• Time in Patent Office: Days
• 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 7/0956 to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc
• CPC Class Codes: G11B 7/1369 Active plates, e.g. liquid crystal panels or electrostrictive elements
• CPC Class Codes: G11B 7/13925 active, e.g. controlled by electrical or mechanical means

Abstract

An optical pick-up composed of an objective lens and a liquid crystal element, for recording and reproduction of optical discs having different recording densities, the liquid crystal element having nine zones, including: zones 2, 4 located in center parts of half circles of a small diameter beam for a low density optical disc, zones 3, 5 laid along the outer peripheries of zones 2, 3 within the half circles so as to surround zones 2, 4, zones 6, 7 along the outer peripheries of zones 3, 5, between the outer periphery of the small diameter beam and a large diameter beam, extending along substantially half circumferential parts of the small diameter beam, zones 8, 9 extending along substantially half circumferential parts of the large diameter beam, a remainder first zone and including a diameter whose the direction is the same as a tilt direction to be corrected.

Claims

1. An optical pick-up composed of an objective lens and a liquid crystal element in combination, for recording and reproduction of optical discs having different recording densities,

the liquid crystal element having five zones in total, including:

zones 2, 4 located in center parts of half circles of a small diameter beam for a low density optical disc,

zones 3, 5 laid along the outer peripheries of the zones 2, 4 within the half circles, respectively, so as to surround the zones 2, 4, respectively, and

a first zone which is a remaining zone other than the zones 2, 3, 4, 5 and including a diameter,

wherein the direction of the diameter included in the first zone 1 is the same as a tilt direction to be corrected.

2. An optical pick-up as set forth in claim 1, characterized in that the zones 2 and 4, and zones 3 and 5 are arranged, symmetric to each other, respectively, with respect to the direction of the diameter contained in the zone 1.

3. An optical pick-up as set forth in claim 1 or 2, characterized in that there is provided voltage applying means for producing a reference voltage, a first voltage (V₂) having a predetermined potential difference from the reference voltage, a second voltage (V₃) having a absolute value equal to that of the first voltage but having a polarity reverse to that of the first voltage, a third voltage (V₁) having an absolute value greater than that of the first voltage, and a fourth voltage (V₄) having an absolute value equal to that of the third voltage and having a polarity reverse to that of the third voltage, the reference voltage is applied to the zone 1, the first voltage (V₂) is applied to the zone 3, second voltage (V₃) is applied to the zone 5, the third voltage (V₁) is applied to the zone 2, and the forth voltage (V₄) is applied to zone 4.

4. An optical pick-up device as set forth in any one of claims 1 to 3, characterized in that two liquid crystals are used, being joined to each other so that the directions of the diameters included in the first zones are orthogonal to each other.

5. An optical disc unit characterized in that the pick-up device as set forth in any one of claims 1 to 4 is used.

6. An optical pick-up composed of an objective lens and a liquid crystal element in combination, for recording and reproduction of optical discs having different recording densities, the liquid crystal element having seven zones in total, including:

zones 2, 4 located in center parts of half circles of a small diameter beam for a low density optical disc,

zones 3, 5 laid along the outer peripheries of the zones 2, 4 within the half circles, respectively, so as to surround the zones 2, 4, respectively,

zones 6, 7 along the outer peripheries of the zones 3, 5, between the outer periphery of the small diameter beam and a large diameter beam, extending along substantially half circumferential parts of the small diameter beam, respectively,

a zone 1 which is a remaining zone other than the zones 2, 3, 4, 5, 6, 7 and including a diameter, wherein the direction of the diameter included in the first zone 1 is at right angles to a tilt direction to be corrected.

7. An optical pick-up as set forth in claim 6, characterized in that the zones 2 and 4, zones 3 and 5, and zones 6 and 7 are arranged, symmetric to each other, respectively, with respect to the direction of the diameter contained in the zone 1.

8. An optical pick-up as set forth in claim 6 or 7, characterized in that there is provided voltage applying means for producing a reference voltage, a first voltage (V₂) having a predetermined potential difference to the reference voltage, a second voltage (V₃) having a absolute value equal to that of the first voltage but having a polarity reverse to that of the first voltage, a third voltage (V₁) having an absolute value greater than that of the first voltage, and a fourth voltage (V₄) having an absolute value equal to that of the third voltage and having a polarity reverse to that of the third voltage, the reference voltage is applied to the zone 1, the first voltage (V₂) is applied to the zones 3 and 6, second voltage (V₃) is applied to the zones 5 and 7, the third voltage is applied to the zone 2, and the forth voltage (V₄) is applied to zone 4.

9. An optical pick-up device as set forth in any one of claims 6 to 8, characterized in that two liquid crystals are used, being joined to each other so that the directions of the diameters included in the first zones are orthogonal to each other.

10. An optical disc unit characterized in that the pick-up device as set forth in any one of claims 6 to 9 is used.

12. An optical pick-up as set forth in claim 6, characterized in that the zones 2 and 4, zones 3 and 5, zone 6 and 7 and zones 8 and 9 are arranged, symmetric to each other, respectively, with respect to the direction of the diameter contained in the zone 1.

11. An optical pick-up composed of an objective lens and a liquid crystal element in combination, for recording and reproduction of optical discs having different recording densities,

the liquid crystal element having nine zones in total, including:

zones 2, 4 located in center parts of half circles of a small diameter beam for a low density optical disc,

zones 3, 5 laid along the outer peripheries of the zones 2, 4 within the half circles, respectively, so as to surround the zones 2, 4, respectively,

zones 6, 7 along the outer peripheries of the zones 3, 5, between the outer periphery of the small diameter beam and a large diameter beam, extending along substantially half circumferential parts of the small diameter beam,

zones 8, 9 extending along substantially half circumferential parts of the large diameter beam, respectively,

a first zone which is a remaining zone other than the zones 2, 3, 4, 5, 6, 7, 8, 9 and including a diameter,

wherein the direction of thee diameter included in the first zone 1 is at right angles to a tilt direction to be corrected.

13. An optical pick-up as set forth in claim 11 or 12, characterized in that there is provided voltage applying means for producing a reference voltage, a first voltage (V₂) having a predetermined potential difference to the reference voltage, a second voltage (V₃) having a absolute value equal to that of the first voltage but having a polarity reverse to that of the first voltage, a third voltage having an absolute value greater than that of the first voltage, and a fourth voltage (V₄) having an absolute value equal to that of the third voltage and having a polarity reverse to that of the third voltage, the reference voltage is applied to the zone 1, the first voltage (V₂) is applied to the zones 3 and 6, second voltage (V₃) is applied to the zones 5 and 7, the third voltage (V₁) is applied to the zones 2 and 9, and the forth voltage (V₄) is applied to zones 4 and 8.

14. An optical pick-up device as set forth in any one of claims 11 to 13, characterized in that two liquid crystals are used, being joined to each other so as that the directions of the diameters included in the first zones are orthogonal to each other.

15. An optical disc unit characterized in that the pick-up device as set forth in any one of claims 11 to 13 is used.