Apparatus and method for generating a tracking error signal using first through fourth optical detector elements

• US 6,345,020 B1
• Filed: 03/02/1999
• Issued: 02/05/2002
• Est. Priority Date: 06/25/1998
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Cho, Gea-ok, Kim, Chun-sup
• Primary Examiner(s): Psitos, Aristotelis M.
• Application Number:
  US09/260,020
• Time in Patent Office: 1,071 Days
• Field of Search: 369/44.32, 369/44.35, 369/44.41
• US Class Current: 369/44.32
• CPC Class Codes: G11B 7/0901 for track following only G11B7/0925, G11B7/094, G11B7/0941, G11B7/0943, G11B7/0945, G11B7/0946, G11B7/0948 take precedence
• CPC Class Codes: G11B 7/0943 Methods and circuits for performing mathematical operations on individual detector segment outputs

Abstract

An apparatus and method for adaptively generating a tracking error signal according to a phase error generated due to a nonuniform depth of pits formed in an optical disk. The apparatus includes a first adder to output a first added signal (A+C) among optical detection signals A, B, C and D output by four elements for detecting light beams reflected from the optical disk, a second adder to output a second added signal (B+D) among the optical detection signals A, B, C and D, a multiplexer to receive the optical detection signals A, B, C and D, the first added signal (A+C), and the second added signal (B+D), and to select and output the signals (A+C) and (B+D), A and B, or C and D, a phase detector to determine a difference between the two signals output by the multiplexer, and output the difference as a tracking error signal and determine whether the tracking error signal is normal, and a selection controller to control selection of the multiplexer according to the result of the determination of the phase detector. Therefore, an optimal tracking error signal is obtained by selecting appropriate optical detection signals according to the phase error between the selected optical detection signals.

Claims

1. An apparatus for generating a tracking error signal using first through fourth elements A, B, C, D, respectively, of an optical detector which detects light beams reflected from an optical disk, comprising:

a first adder to generate a first added signal (A+C) by adding first and third optical detection signals A and C output by the first and third elements, respectively;

a second adder to generate a second added signal (B+D) by adding second and fourth optical detection signals B and D output by the second and fourth elements, respectively;

a multiplexer to receive the optical detection signals A, B, C and D, the first added signal (A+C), and the second added signal (B+D), and to select and output a first group of the first and second added signals (A+C) and (B+D), a second group of the optical detection signals A and B, or a third group of the optical detection signals C and D;

a phase detector to determine a difference between the signals of the first, second or third group output by the multiplexer, and output the difference as a tracking error signal and determine whether the tracking error signal is normal; and

a selection controller to control selection of the first, second or third group by the multiplexer according to the determination of the normality of the tracking error signal by the phase detector.

2. The apparatus as claimed in claim 1, wherein the phase detector determines whether the tracking error signal is normal by determining a phase error between the signals of the selected group.

3. The apparatus as claimed in claim 2, wherein the selection controller selects a next one of the first through third groups if the phase error of a current one of the first through groups deviates from a predetermined range.

4. The apparatus as claimed in claim 3, wherein the phase detector detects a phase difference between the signals of the current group by determining zero-crossing points of the signals, and then determining a phase difference between the zero-crossing points.

5. The apparatus as claimed in claim 1, wherein the selection controller selects a next one of the first through third groups if the phase detector determines that the tracking error signal determined from a current one of the first through groups is not normal.

6. The apparatus as claimed in claim 1, wherein the phase detector determines whether the tracking error signal is normal by determining whether the tracking error signal, which is a sinusoidal wave, varies within a range between peak-to-peak values.

7. The apparatus as claimed in claim 2, wherein the phase detector determines whether the tracking error signal is normal by determining whether the tracking error signal, which is a sinusoidal wave, varies within a range between peak-to-peak values.

8. The apparatus as claimed in claim 1, wherein the selection controller initially selects a first one of the first through third groups, the phase detector determines whether the tracking error signal determined in response to reception of the first one of the first through third groups is normal, the selection controller selects a second one of the first through third groups if the tracking error signal determined from the reception of the first one of the first through third groups is not normal, the phase detector determines whether the tracking error signal determined in response to the second one of the first through third groups is normal, and the selection controller selects a third one of the first through third groups if the tracking error signal determined from the reception of the second one of the first through third groups is not normal.

9. The apparatus as claimed in claim 2, wherein the selection controller initially controls selection of a first one of the first through third groups, the phase detector determines whether a first phase error between signals of a first one of the first through third groups is within a predetermined range, the selection controller controls selection of a second one of the first through third groups if the first phase error is not within the predetermined range, the phase detector determines whether a second phase error between signals of a second one of the first through third groups is within the predetermined range, and the selection controller controls selection of a third one of the first through third groups if the second phase error is not within the predetermined range.

10. The apparatus as claimed in claim 1, further comprising:

first and second equalizers connected between the multiplexer and the phase detector, to respectively receive and equalize the signals from the first, second or third group output from the multiplexer, to generate equalized signals which are input to the phase detector.

11. The apparatus as claimed in claim 2, further comprising:

first and second equalizers connected between the multiplexer and the phase detector, to respectively receive and equalize the signals from the first, second or third group output from the multiplexer, to generate equalized signals which are input to the phase detector.

12. The apparatus as claimed in claim 5, further comprising:

first and second equalizers connected between the multiplexer and the phase detector, to respectively receive and equalize the signals from the first, second or third group output from the multiplexer, to generate equalized signals which are input to the phase detector.

13. The apparatus as claimed in claim 1, wherein the four elements are formed in a rectangular shape, and the elements which output the optical detection signals A and D are diagonal to each other in a track direction of the optical disk, and the elements which output the optical detection signals B and C are diagonal to each other in the track direction of the optical disk.

14. The apparatus as claimed in claim 2, wherein the four elements are formed in a rectangular shape, and the elements which output the optical detection signals A and D are diagonal to each other in a track direction of the optical disk, and the elements which output the optical detection signals B and C are diagonal to each other in the track direction of the optical disk.

15. An apparatus for generating a tracking error signal in response to a light beam reflected from an optical disk having an information recording surface with pits of varying pit depth, comprising:

an optical detector having a plurality of optical elements to receive the light beam reflected from the optical disk and to generate respective optical detection signals; and

a tracking error signal generator to compensate for changes in the optical detection signals caused by the varying pit depth of the pits, and to generate the tracking error signal in response to the optical detection signals by selecting between first, second and third groups of the optical detection signals,

the tracking error signal being based upon a phase difference between signals of a current selected group of the first through third groups while the phase difference is within a predetermined range, and then a group of the first through third groups next in order to the current selected group being selected in response to the phase difference being outside of the predetermined range.

16. The apparatus as claimed in claim 15, wherein:

the plurality of optical elements are first through fourth elements A, B, C, D, respectively, formed in a rectangular shape; and

the first and fourth elements output optical detection signals A and D and are diagonal to each other in a track direction of the optical disk, and the second and third elements which output optical detection signals B and C are diagonal to each other in the track direction of the optical disk; and

the tracking error signal generator comprises

a first adder to add the optical detection signals A and C to generate a first added signal,

a second adder to add the optical detection signals B and D to generate a second added signal,

a multiplexer to receive the first through fourth optical detection signals, and the first and second added signals, and to selectively output the first group comprising the first and second optical detection signals, the second group comprising the third and fourth optical detection signals, or the third group comprising the first and second added signals,

a phase detector to detect the phase difference between the signals of the current selected group, to generate the tracking error signal, and

a selection controller to control the selection of the multiplexer to the group of the first through third groups next in order to the current selected group if the phase difference is outside of the predetermined range.

17. The apparatus as claimed in claim 15, wherein:

the plurality of optical elements are first through fourth elements A, B, C, D, respectively, formed in a rectangular shape; and

the first and fourth elements which output optical detection signals A and D are diagonal to each other in a track direction of the optical disk, and the second and third elements which output optical detection signals B and C are diagonal to each other in the track direction of the optical disk; and

the tracking error signal generator selectively only uses the first group comprising the first and second optical detection signals, the second group comprising the third and fourth optical detection signals or the third group comprising sums of the first and second optical detection signals and the third and fourth optical detection signals to determine the tracking error signal, based upon whether the phase differences between signals of the first through third groups are within the predetermined range.

18. The apparatus as claimed in claim 17, wherein the tracking error signal generator initially selects the first group to determine whether the phase difference between the signals of the first group is within the predetermined range, selects the second group if not, and selects the third group if the phase difference between the signals of the second group is not within the predetermined range.

19. A method of generating a tracking error signal from first through fourth optical detection signals respectively output from first through fourth elements of an optical detector in response to a light beam reflected from an optical disk, comprising:

adding the first and third optical detection signals from the first and third elements which are adjacent to each other in a tracking direction of the optical disk to generate a first added signal, and the second and fourth optical detection signals from the second and fourth elements which are adjacent to each other to generate a second added signal;

determining the tracking error signal from a first group of the first and second optical detection signals, a second group of the third and fourth optical detection signals, or a third group of the first and second added signals; and

determining whether the tracking error signal is normal, and if not, selecting another one of the first through third groups to determine the tracking error signal.

20. The method as claimed in claim 19, wherein the step of determining whether the tracking error signal is normal comprises:

determining a phase difference between the two signals used to determine the tracking error signal; and

comparing the phase difference to a predetermined range.

21. The method as claimed in claim 20, wherein the step of determining the tracking error signal comprises:

receiving the first through fourth optical detection signals and the first and second added signals in a multiplexer; and

selectively controlling transmission of the first, second or third group based upon whether the phase difference of the signals of a currently selected one of the first, second or third group are within the predetermined range.

22. The method as claimed in claim 19, wherein the step of determining the tracking error signal comprises:

receiving the first through fourth optical detection signals and the first and second added signals in a multiplexer; and

selectively controlling transmission of the first, second or third group based upon whether the tracking error signal determined from a currently selected one of the first, second or third group is normal.