JP3782188B2 - Retry device for optical disk playback system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disk reproducing system for reproducing an optical disk such as a CD (Compact Disk) or a DVD, and in particular, when a track jump occurs due to scratches or dirt on the optical disk, the track is automatically reproduced again. The present invention relates to an improvement of the retry device.
[0002]
[Prior art]
As is well known, in the optical disk reproduction system as described above, when reading the recorded information from the optical disk, first, the objective lens of the optical pickup is moved from the initial position to the vicinity of the in-focus position. A focus search operation is performed, then focus servo is performed to hold the objective lens at the in-focus position, and then tracking servo is applied to the objective lens.
[0003]
FIG. 4 shows such a conventional optical disc reproducing system. That is, the optical disk 11 is driven to rotate at a predetermined rotational speed by the disk motor 12. An optical pickup 13 is installed on the signal recording surface side of the optical disc 11. The optical pickup 13 is supported so as to be movable in the radial direction of the optical disk 11 by a driving force of a pickup feed motor (not shown).
[0004]
This optical pickup 13 focuses the irradiation light from the semiconductor laser 13a on the signal recording surface of the optical disk 11 by guiding it to the objective lens 13d through various optical systems such as a collimator lens 13b and a deflection beam splitter 13c. The reflected light is bent at a substantially right angle by the deflecting beam splitter 13c and received by the photoelectric conversion element 13e, so that the information recorded on the optical disk 11 is electrically read out.
[0005]
The output signal of the optical pickup 13 is supplied to a focus error detection circuit 14, a tracking error detection circuit 15, and a signal processing circuit 16, respectively. Among these, the focus error detection circuit 14 detects a focus error of the objective lens 13 d based on the input signal, generates a focus error signal according to the detection result, and supplies the focus error signal to one fixed contact 17 a of the switch 17. Output to the focus search control circuit 18.
[0006]
The focus search control circuit 18 determines whether or not the focus error of the objective lens 13d exceeds a preset allowable value from the input focus error signal. If it is determined that the focus error is exceeded, the focus search control circuit 18 switches a predetermined focus search signal. 17 is operated to switch the movable contact piece 17c of the switch 17 to the fixed contact 17b side.
[0007]
Therefore, in a state where the objective lens 13d is in the initial position, the focus search control circuit 18 determines that the focus error of the objective lens 13d exceeds the allowable value, so that the focus search signal is switched to the switch 17 and the phase compensation circuit 19. Then, it is supplied to a focus actuator coil (not shown) in the optical pickup 13 via the drive circuit 20. Thereby, the objective lens 13d is forcibly moved in the focus direction from the initial position toward the in-focus position, and a focus search is performed here.
[0008]
Assume that this focus search brings the objective lens 13d close to the in-focus position, and the focus search control circuit 18 determines that the focus error of the objective lens 13d has reached an allowable value. Then, the focus search control circuit 18 operates to switch the movable contact piece 17c of the switch 17 to the fixed contact 17a side. For this reason, the focus error signal output from the focus error detection circuit 14 is supplied to the focus actuator coil in the optical pickup 13 via the switch 17, the phase compensation circuit 19 and the drive circuit 20. Focus servo for holding 13d at the in-focus position is performed.
[0009]
The tracking error detection circuit 15 detects a tracking error of the objective lens 13d based on the input signal, generates a tracking error signal according to the detection result, and supplies the tracking error signal to one fixed contact 21a of the switch 21. Output to the track jump control circuit 22. As will be described in detail later, the track jump control circuit 22 outputs a predetermined track jump signal to the other fixed contact 21b of the switch 21 and a movable contact 21c of the switch 21 when a track jump is requested. Is switched to the fixed contact 21b side.
[0010]
That is, in a normal reproduction state where no track jump is requested, the tracking error detection circuit 15 operates to switch the movable contact piece 21c of the switch 21 to the fixed contact 21a side. For this reason, the tracking error signal output from the tracking error detection circuit 15 is supplied to a tracking actuator coil (not shown) in the optical pickup 13 via the switch 21, the phase compensation circuit 23, and the drive circuit 24. Tracking servo is performed on the objective lens 13d.
[0011]
Here, continuous tracks are spirally formed on the signal recording surface of the optical disk 11. For convenience, five tracks Tn-2, Tn-1, Tn, Tn + 1, and Tn + 2 are defined on the signal recording surface of the optical disk 11 as indicated by dotted lines in FIG. It is assumed that the optical pickup 13 reaches the part A having scratches or dirt on the optical disk 11 while tracing the track Tn.
[0012]
Then, since a sufficient amount of reflected light cannot be obtained from the scratched or dirty portion A of the optical disk 11, the signal output from the optical pickup 13 becomes unstable, and an accurate tracking error signal is generated. Can not do. For this reason, correct tracking servo cannot be performed, so that the optical pickup 13 leaves the track Tn that was originally traced, and moves to a trace such as the track Tn + 1 adjacent to the outer peripheral side. Track jumping will occur.
[0013]
Therefore, the signal processing circuit 16 decodes the address information from the output signal of the optical pickup 13 and outputs it to the track skip detection circuit 25. This address information is recorded in advance on the optical disc 11 so as to change sequentially at a constant rate when the optical disc 11 is correctly reproduced. The track skip detection circuit 25 detects the occurrence of an undesired track jump by checking the rate of change of the input address information, and detects the direction information and the distance traveled. A detection signal including information is generated and output to the track jump number calculation circuit 26.
[0014]
The track jump number calculating circuit 26 traces a track (for example, Tn-1, Tn-2,...) Preceding the track Tn where the track jump occurred based on the input detection signal. A track jump number signal indicating how many tracks should be jumped from the current position, that is, the position where the track Tn + 1 is traced, is generated and output to the track jump control circuit 22. is doing.
[0015]
For this reason, the track jump control circuit 22 determines that the track jump has been requested by the input of the track jump number signal, and the track jump signal including the direction in which the objective lens 13d makes the track jump and the number of the track jumps. Is generated and output to the fixed contact 21b of the switch 21, and the movable contact piece 21c of the switch 21 is operated to be switched to the fixed contact 21b side.
[0016]
As a result, the track jump signal is supplied to the tracking actuator coil in the optical pickup 13 via the switch 21, the phase compensation circuit 23, and the drive circuit 24, where the objective lens 13d is currently tracking the track. The track jump is performed from Tn + 1 to the position where the track preceding the track Tn where the track jump occurred is traced.
[0017]
FIG. 5B shows a state in which the objective lens 13d is track-jumped from the currently traced track Tn + 1 to a track preceding the track Tn where the track jump occurred. In the example shown in FIG. 5 (b), the track jump is made from the current track Tn + 1 to the track Tn-3 four times ahead as the track preceding the track Tn where the track jump occurred. ing.
[0018]
Thereafter, if the track jump control circuit 22 switches the movable contact piece 21c of the switch 21 to the fixed contact 21a side to start tracking servo, the objective lens 13d traces from the track Tn-3 after the track jump. , And a so-called retry operation can be performed in which the track Tn on which the track jump has occurred is reproduced again.
[0019]
Then, by performing this retry operation, as shown in FIG. 5C, even if the objective lens 13d reaches the scratch or dirt portion A on the optical disk 11 again and the tracking servo becomes unstable, When the tracking servo functions normally after exiting the portion A, there is a possibility that the track Tn can be reproduced by being drawn into the target track Tn.
[0020]
However, in the conventional optical disc reproducing system having the retry function as described above, the objective lens 13d may be able to correctly reproduce the target track Tn as a result of performing the retry operation. There is a case where the track jumps in the track, and there is a problem that the target track Tn cannot be surely reproduced.
[0021]
[Problems to be solved by the invention]
As described above, in the conventional optical disc playback system having the retry function, even if the retry operation is performed, the target track is not always reliably reproduced, and the reliability of the retry operation is low. have.
[0022]
Therefore, the present invention has been made in consideration of the above circumstances, and can improve the reliability of the retry operation by increasing the success rate of reproducing the target track when the retry operation is performed. An object of the present invention is to provide a retry device for an optical disc reproduction system.
[0023]
[Means for Solving the Problems]
The retry device of the optical disk reproduction system according to the present invention comprises:
An optical pickup that reads information recorded on the optical disc by irradiating the optical disc with a light beam through an objective lens and receiving reflected light from the optical disc with a photodetector;
Based on the output signal obtained from the photodetector of this optical pickup, a tracking error signal corresponding to the tracking error of the objective lens with respect to the track formed on the optical disc is generated, and based on the tracking error signal, the tracking error signal is generated. Tracking servo means for performing tracking servo to trace the track with respect to the objective lens;
Address decoding means for decoding address information from the output signal of the photodetector;
Based on the address information, the tracking servo means determines that the objective lens has caused a track jump from the first track to another track while the objective lens is tracing the first track. A track jump detection means to detect;
Based on the detection result of the track jump detection means, the tracking servo for the objective lens is stopped, and the objective lens is moved to the second track located before the first track where the track jump has occurred. It is a track jump, and the retry means for resuming the trace from said second track the tracking servo is started to said tracking servo means,
Based on the address information before and after the track jump, direction detection means for detecting the track jump direction and distance,
By said tracking servo means, wherein when the objective lens has resumed trace from the second track, control means for applying an offset based on the direction and distance of the track jump is detected by said direction detecting means with respect to said objective lens Are provided.
[0024]
According to the above configuration, when the optical pickup reads information from the second track by the retry means, an offset based on the direction and distance of the track jump is given to the objective lens. During reproduction by retry, it is possible to prevent as much as possible an unwanted track jump from occurring again in the same direction as before in the objective lens. For this reason, when the retry operation is performed, the success rate at which the target track can be reproduced can be increased, and the reliability of the retry operation can be improved.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1, the same parts as those in FIG. 4 are denoted by the same reference numerals. That is, the address information output from the signal processing circuit 16 is supplied to the track deviation direction detection circuit 27. The track deviation direction detection circuit 27 generates a detection signal indicating a direction in which an undesired track jump occurs and a distance traveled based on the change rate of the input address information, and sends it to the offset amount calculation circuit 28. Output.
[0026]
Although the details will be described later, the offset amount calculation circuit 28 calculates an offset amount in the tracking direction to be given to the objective lens 13d at the time of retry reproduction and its direction based on the input detection signal, and calculates the calculation result. This is output to the offset signal generation circuit 29.
[0027]
The offset signal generation circuit 29 generates an offset signal according to the calculation result of the input offset amount and its direction when the track jump control circuit 22 generates a track jump signal, that is, at the start of a retry operation. And output. The offset signal output from the offset signal generation circuit 29 is added to the tracking error signal output from the tracking error detection circuit 15 by the adding circuit 30 and used for tracking servo in the retry operation.
[0028]
Here, FIGS. 2A to 2C specifically show that an offset signal is added to a tracking error signal during reproduction by a retry operation. 2A and 2B are the same as FIGS. 5A and 5B, respectively. That is, FIG. 2A shows that the objective lens 13d traces the track Tn and reaches the scratched or dirty portion A on the optical disk 11 and a track jump occurs on the track Tn + 1. Indicates the state. FIG. 2B shows a state in which the objective lens 13d is track-jumped from the track Tn + 1 to the track Tn-3 after it is detected that the track jump has occurred.
[0029]
In this case, the track deviation direction detection circuit 27 detects that the direction in which the undesired track jump occurs in the objective lens 13d is the direction toward the outer periphery of the optical disc 11, and the distance traveled is one track. Therefore, the offset amount and direction for correcting the direction and distance are calculated by the offset amount calculation circuit 28, and an offset signal corresponding to the calculation result is output from the offset signal generation circuit 29 and added to the tracking error signal. Will be.
[0030]
More specifically, as shown in FIG. 2C, the objective lens 13d is slightly placed on the inner peripheral side of the optical disc 11 for each of the tracks Tn-3 to Tn traced after the track jump for retry. An offset is given so as to be biased. For this reason, even if the objective lens 13d reaches the scratch or dirt portion A on the optical disc 11 and a track jump corresponding to one track toward the outer peripheral side of the optical disc 11 occurs in the objective lens 13d, A relative shift amount with respect to the track Tn can be suppressed small. As a result, the objective lens 13d is quickly returned to the original position having the offset after exiting from the scratch or dirt portion A.
[0031]
In short, if the objective brick 13d causes a track jump in a predetermined direction due to scratches or dirt on the optical disk 11, the same track jump may occur again when the same scratch or dirt part is reproduced by retry. In anticipation of the high level, an offset in a direction to suppress the track skip is added in advance to the tracking error signal at the time of reproduction by retry. For this reason, the direction and amount of the offset are controlled in accordance with the direction and distance of the track jump.
[0032]
Then, when the track skip detection circuit 25 determines that the track Tn in which the track jump has occurred is correctly reproduced by the reproduction by the retry, the generation of the offset signal is stopped, and thereafter it is output from the tracking error detection circuit 15. Normal tracking servo is performed only by the tracking error signal.
[0033]
FIG. 3 shows a flowchart summarizing the retry operations described above. First, when started (step S1), the process waits for the address information to be updated in step S2. When the address information is updated, the updated address information and the previous address information are updated in step S3. Is greater than the address difference corresponding to one rotation of the optical disk 11, and if not so (NO), the process returns to step S2.
[0034]
If the difference between the address information updated in step S3 and the address information before the update is larger than the address difference for one rotation of the optical disc 11 (YES), it is determined that a track jump has occurred. At this time, in step S4, it is determined whether or not the flag indicating the number of retries is “0”. If it is “0” (YES), the flag indicating the number of retries is set to “+1” in step S5. In step S6, the offset amount is set to a predetermined value.
[0035]
Thereafter, in step S7, it is determined whether or not the track jump direction is on the outer peripheral side of the optical disc 11, and if it is on the outer peripheral side (YES), in step S8, the polarity of the offset signal is set to positive polarity and on the inner peripheral side. If there is (NO), in step S9, the polarity of the offset signal is set to negative polarity.
[0036]
On the other hand, if the flag indicating the number of retries is not “0” in step S4 (NO), in step S10, it is determined whether or not the direction of the track jump generated this time is the same as the direction of the track jump generated last time. If they are the same (YES), the offset amount is set large in step S11. If they are not the same (NO), the offset amount is set small in step S12.
[0037]
Then, after step S8, S9, S11, S12, a track jump for retry based on the offset signal is executed in step S13, and in step S14, the track that could not be correctly traced by the track jump earlier. Is reproduced correctly. If reproduction is not possible (NO), the process returns to step S4. If reproduction is possible (YES), a flag indicating the number of retries is set to “0” in step S15. Is set to "" and the process ends (step S16).
[0038]
Therefore, according to the above-described embodiment, when reproducing by retry, an offset in a direction to suppress the previously generated track jump is added in advance to the tracking error signal. Therefore, at the time of reproducing by retry, the objective lens 13d. On the other hand, it is possible to prevent unwanted track jumps in the same direction as before. For this reason, when the retry operation is performed, the success rate at which the target track can be reproduced can be increased, and the reliability of the retry operation can be improved.
The present invention is not limited to the above-described embodiment, and can be variously modified and implemented without departing from the scope of the invention.
[0039]
【The invention's effect】
As described above in detail, according to the present invention, a very good optical disk reproducing system capable of increasing the success rate of reproducing the target track when the retry operation is performed and improving the reliability of the retry operation. A retry device can be provided.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram for explaining an embodiment of a retry device of an optical disk reproducing system according to the present invention.
FIG. 2 is a view for explaining a retry operation in the same embodiment;
FIG. 3 is a flowchart for explaining a retry operation in the embodiment;
FIG. 4 is a block diagram showing a conventional optical disc playback system having a retry function.
FIG. 5 is a view for explaining a retry operation in the conventional system.
[Explanation of symbols]
11 ... Optical disc,
12 ... disk motor,
13: Optical pickup,
14: Focus error detection circuit,
15 ... Tracking error detection circuit,
16: Signal processing circuit,
17 ... switch,
18 ... focus search control circuit,
19: Phase compensation circuit,
20 ... Drive circuit,
21 ... switch,
22 ... Track jump control circuit,
23: Phase compensation circuit,
24 ... Drive circuit,
25. Track skip detection circuit,
26: Track jump number calculation circuit,
27. Track deviation direction detection circuit,
28: Offset amount calculation circuit,
29. Offset signal generation circuit,
30: Adder circuit.

Claims (5)

An optical pickup that reads information recorded on the optical disc by irradiating the optical disc with a light beam through an objective lens and receiving reflected light from the optical disc with a photodetector;
Based on the output signal obtained from the optical detector of the optical pickup, a tracking error signal corresponding to the tracking error of the objective lens with respect to the track formed on the optical disc is generated, and based on the tracking error signal, the tracking error signal is generated. Tracking servo means for performing tracking servo to trace the track with respect to the objective lens;
Address decoding means for decoding address information from the output signal of the photodetector;
Based on the address information, the tracking servo means determines that the objective lens has caused a track jump from the first track to another track while the objective lens is tracing the first track. A track jump detection means to detect;
Based on the detection result of the track jump detection means, the tracking servo for the objective lens is stopped, and the objective lens is moved to the second track located before the first track where the track jump occurs. It is a track jump, and the retry means for resuming the trace from said second track the tracking servo is started to said tracking servo means,
Based on the address information before and after the track jump, direction detection means for detecting the track jump direction and distance,
By said tracking servo means, wherein when the objective lens has resumed trace from the second track, control means for applying an offset based on the direction and distance of the track jump is detected by said direction detecting means with respect to said objective lens A retry device for an optical disk playback system, comprising: The control means generates an offset signal for biasing the objective lens in the direction opposite to the direction in which the track jumping detected by the track jump detection means occurs with respect to the second track. 2. The retry device for an optical disk reproduction system according to claim 1, wherein the retry error signal is added to the tracking error signal. When the control unit detects that a track jump has occurred again in the state of reading information by the retry unit, the direction of the track jump and the direction of the track jump that occurred before that are detected. 3. The retry device of the optical disk reproducing system according to claim 1, wherein the offset amount by the control means is increased when the directions are the same. When the control unit detects that a track jump has occurred again in the state of reading information by the retry unit, the direction of the track jump and the direction of the track jump that occurred before that are detected. 3. The retry device of the optical disk reproducing system according to claim 1, wherein the offset amount by the control means is reduced when is in the reverse direction. The track skip detection means determines that a track skip occurs when the change rate of the address information included in the output signal of the optical pickup corresponds to one rotation or more of the optical disc. The retry device of the optical disk reproducing system according to claim 1.

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