Optical disk apparatus which changes a tilt value of an objective lens and method of recording with such optical disk apparatus

• US 7,570,552 B2
• Filed: 01/26/2005
• Issued: 08/04/2009
• Est. Priority Date: 01/27/2004
• Status: Expired due to Fees

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Matsumoto, Shinji, Iwasaki, Satoshi, Fujishima, Hideyuki
• Primary Examiner(s): Feild; Joseph
• Assistant Examiner(s): HALEY, JOSEPH R
• Application Number:
  US11/042,201
• Publication Number:
  US 20050162998A1
• Time in Patent Office: 1,651 Days
• Field of Search: None
• US Class Current: 369/44.32
• CPC Class Codes: G11B 7/0945 Methods for initialising servos, start-up sequences
• 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

Abstract

During recording with an optical disk apparatus, an objective lens is moved toward the inner circumference and outer circumference of an optical disk in the radial direction thereof and also moved upward and downward, and the quantity of reflected light is measured at that time. Quantities of reflected light are determined taking advantage of the characteristic of laser heat that it is most efficiently used to provide the smallest quantity of reflected light when the relationship between the optical disk surface and the objective lens is closest to perpendicularity and when they are at a distance at which the point in focus is most closely approached. An optimum tilt value and focus position are learned from the result of the determination to allow operations to be performed at the optimum tilt and the optimum position of the point in focus.

Claims

1. An optical disk apparatus for recording data on a recordable type optical disk utilizing a pattern of emission of a laser, said optical disk apparatus comprising:

an objective lens that focuses laser light on the optical disk;

a focus control unit that changes tilt value of the objective lens in the radial direction of the optical disk; and

a reflected light measurement unit that measures a plurality of values of light quantity reflected on the optical disk, the plurality of values respectively corresponding to a plurality of the tilt values,

wherein the focus control unit corrects the tilt value of the objective lens by setting the tilt of the objective lens to a tilt value corresponding to the smallest value of the light quantity measured by the reflected light measurement unit,

wherein a process of tilting the objective lens so as to make the optical axis of the laser substantially perpendicular to the optical disk and a process of making the distance between the optical disk and the objective lens substantially equal to the focal length during recording are performed only in a data recording area of the optical disk by referring to a table for storing information on whether to permit or inhibit the process of tilting the objective lens relative to a position of the optical disk in the radial direction thereof so as to make the optical axis of the laser substantially perpendicular to the optical disk.

2. An optical disk apparatus according to claim 1, wherein reflected light from the optical disk under recording is received by the light-receiving unit and wherein a change in thermal efficiency of laser power during recording is detected from a change in the reflected light.

3. An optical disk apparatus according to claim 1, wherein the objective lens is tilted from the current state toward the outer circumference and inner circumference of the optical disk in the radial direction thereof during recording and wherein the quantity of a tilt of the optical axis of the laser relative to a surface of the optical disk is obtained from a change in reflected light at that time.

4. An optical disk apparatus according to claim 1, wherein

the measurement of a change in reflected light during recording is performed by measuring reflected light within one turn of the optical disk to prevent misdetection of the reflected light attributable to a runout component of the optical disk.

5. An optical disk apparatus according to claim 1, wherein a change in reflected light from the optical disk under recording is detected and in which the quantity of a tilt of the objective lens relative to the radial direction of the optical disk is controlled such that the optical disk and the optical axis of the laser are in a substantially perpendicular relationship.

6. An optical disk apparatus according to claim 1, wherein a process of operating the objective lens to make optical disk and the optical axis of the laser closest to perpendicularity during recording is performed during a recording operation.

7. An optical disk apparatus according to claim 1, wherein the objective lens is moved from a predetermined state upward and downward relative to a surface of the optical disk during recording to obtain the distance between the surface of the optical disk and the objective lens from a change in reflected light during recording at that time.

8. An optical disk apparatus according to claim 1, wherein a change in reflected light from the optical disk under recording is detected to control the distance between the optical disk and the objective lens such that it substantially equals the focal length.

9. An optical disk apparatus according to claim 1, wherein a process of making the distance between the optical disk and the objective lens substantially equal to the focal length during recording is performed during a recording operation.

10. An optical disk apparatus according to claim 1, wherein a process of tilting the objective lens so as to make the optical axis of the laser substantially perpendicular to the optical disk and a process of making the distance between the optical disk and the objective lens substantially equal to the focal length are performed during recording at each predetermined interval in the radial direction of the optical disk.

11. The optical disk apparatus according to claim 1, further comprising:

a temperature measurement unit that measures temperature,

wherein the focus control unit corrects the tilt value of the objective lens according to the temperature measured by the temperature measurement unit.

12. An optical disk apparatus according to claim 1, wherein selection can be made on whether to perform a process of tilting the objective lens so as to make the optical axis of the laser substantially perpendicular to the optical disk and a process of making the distance between the optical disk and the objective lens substantially equal to the focal length at each predetermined interval in the radial direction of the disk.

13. An optical disk apparatus according to claim 11, wherein a process of tilting the objective lens so as to make the optical axis of the laser substantially perpendicular to the optical disk and a process of making the distance between the optical disk and the objective lens substantially equal to the focal length are performed during recording and wherein the result of the processes in the form of a table showing the value of a tilt and a temperature associated with a position of the disk in the radial direction thereof or the result of tilt value acquisition at the time of activation is selected when the optical disk apparatus performs a reproduction operation or an additional write operation depending on the temperature at that time.

14. An optical disk apparatus according to claim 1, the optical disk apparatus using a result obtained during recording by a process of making the distance between the optical disk and the objective lens substantially equal to the focal length

when it starts a reproduction operation after finishing the recording.

15. An optical disk apparatus according to claim 11, wherein when a process of tilting the objective lens so as to make the optical axis of the laser substantially perpendicular to the optical disk and a process of making the distance between the optical disk and the objective lens substantially equal to the focal length are performed during recording, the value of a tilt associated with a position of the disk in the radial direction thereof and the temperature at that time are simultaneously acquired and stored in the form of a table.

16. The optical disk apparatus according to claim 1, wherein the focus control unit corrects the tilt value of the objective lens only in a data area of the optical disk.

17. A method for recording data on a recordable type optical disk utilizing a pattern of emission of a laser, said method comprising:

(a) employing an objective lens to focus laser light on the optical disk;

(b) controlling a focus of the laser light by changing a tilt value of the objective lens in the radial direction of the optical disk; and

(c) measuring a plurality of values of light quantity reflected on the optical disk, the plurality of values respectively corresponding to a plurality of the tilt values,

wherein in step (b) the tilt value of the objective lens is corrected by setting the tilt of the objective lens to a tilt value corresponding to the smallest value of the light quantity measured in step (c), and

wherein a process of tilting the objective lens so as to make the optical axis of the laser substantially perpendicular to the optical disk and a process of making the distance between the optical disk and the objective lens substantially equal to the focal length during recording are performed only in a data recording area of the optical disk by referring to a table for storing information on whether to permit or inhibit the process of tilting the objective lens relative to a position of the optical disk in the radial direction thereof so as to make the optical axis of the laser substantially perpendicular to the optical disk.