JP4168023B2 - Optical disc apparatus and servo system adjustment method - Google Patents

Description

  The present invention relates to an optical disk apparatus that reproduces an optical disk at a plurality of speeds and a servo system adjustment method thereof, and in particular, a technique suitable for setting a servo system by changing a reproduction laser power according to each speed. About.

  In an optical disc apparatus, data reading speed has been increased. Therefore, an optical disc is rotated at a high speed N times the standard speed to reproduce a signal. At this time, the S / N in the high band is lowered due to the increase in the high frequency noise level due to shot noise and the like, as well as the increase in the high frequency noise accompanying the digital signal processing in the apparatus.

  It has been conventionally known that the S / N of the reproduction signal is increased by increasing the reproduction laser power to reduce the S / N during high-speed reproduction. In Patent Document 1, a laser power setting table is provided, and when switching from low-speed reproduction to high-speed reproduction, laser power is controlled by setting the laser power stepwise according to the reproduction speed ratio. Is done.

  On the other hand, if the set value of the servo system at the time of low speed reproduction is used as it is at the time of high speed reproduction, the followability of the servo system may become unstable. Therefore, when changing the reproduction speed, it is necessary to learn the optimum value of the servo system and reset the servo system conditions. However, if learning is performed every time the playback speed is switched, the preparation time (ready time) becomes longer. Therefore, Patent Document 2 discloses that when a speed different from the current playback speed is requested, only a learning process correlated with the deterioration in playback performance accompanying the speed change is disclosed.

JP 2003-187451 A JP 2004-164788 A

  Japanese Patent Application Laid-Open No. 2005-228561 describes that the reproduction laser power is changed in accordance with the reproduction speed change, but further does not describe the correction of the servo system. Furthermore, when the reproduction laser power is excessively increased, some optical discs may cause quality degradation due to repeated reproduction many times, but this must be taken into consideration.

  In Patent Document 2, although the average preparation time (ready time) at the time of changing the playback speed can be shortened, if there is a correlation with performance degradation and learning processing is required, the playback operation is interrupted and the learning operation is stopped. Doing so increases the preparation time.

  An object of the present invention is to shorten the preparation time and improve the convenience for the user when setting a servo system in accordance with a change in reproduction speed and reproduction laser power in an optical disc apparatus.

  In the optical disk apparatus and the servo system adjustment method according to the present invention, the first rotation speed and the first reproducing laser power are given to the mounted optical disk, and the servo system first is calculated from the error signal reproduced by the optical head. Gain value and first offset value are obtained. Further, the second rotation speed and the second reproducing laser power are given to the optical disc, and the second gain value and the second offset value of the servo system are obtained from the reproduced error signal and stored. The gain value and the offset value of the servo system for the desired rotation speed and the desired reproduction laser power for reproducing data from the optical disc, the first gain value and the first offset value stored, and the first 2 is obtained by calculation based on the gain value of 2 and the second offset value. The servo system is set with the value obtained by calculation, and data is reproduced from the optical disk.

  Also, information about the speed limit of the optical disc is read from the optical disc. If the desired rotational speed exceeds the limit speed, change the desired rotational speed to be less than or equal to the limit speed, calculate the servo system gain and offset values for this, and set the servo system again. To do.

  Further, a test signal is recorded in the trial writing area of the optical disc, and the test signal is continuously and repeatedly reproduced with a test reproduction laser power set in accordance with the desired reproduction laser power. It is determined whether the quality degradation of the reproduced signal after the predetermined number of reproductions is within an allowable value. When the deterioration amount exceeds the allowable value, the desired reproduction laser power is changed to a value below the allowable value, the gain value and the offset value of the servo system corresponding to this are obtained by calculation, and the servo system is set again.

  According to the present invention, stable servo performance can be ensured even when the reproduction speed and the reproduction laser power are changed, and the convenience of the user can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of an optical disk apparatus according to the present invention. An optical disc is an optical disc device that performs playback processing at multiple multiples of the disc rotation speed based on the disc standard, and performs learning processing related to the servo system, when there is an instruction to change the double speed from outside the device such as a personal computer or user In addition, the learning process associated with the double speed change is executed. As a learning process associated with the double speed change, the present embodiment is characterized by adjustment relating to the gain value and offset value of the servo system during reproduction.

  Hereafter, each block and operation | movement are demonstrated concretely using FIG. As shown in the figure, the present optical disk apparatus reproduces data and information from the disk 1 by rotating the optical disk 1 at a plurality of speeds (double speed) by a spindle motor 4. The optical head 2 is moved in the radial direction of the disk 1 by the sled mechanism 3, irradiates the disk 1 with laser light, and condenses the reflected laser light. The laser power irradiated by the optical head 2 is driven by a laser power driving circuit 6. The laser power detection circuit 5 detects the intensity of the laser power, and the laser power control circuit 7 controls the laser power driving circuit 6 based on the detected value.

  Based on the reflected light from the disk 1, the reproduction signal demodulation circuit 11 demodulates the reproduced data, and the reproduction error information detection circuit 13 analyzes the error rate of the data, and these are controlled by the reproduction processing control circuit 12. Is done.

  The servo system error signal detection circuit 8 detects a tracking error signal and a focus error signal based on the reflected light from the disk 1. For each detected error signal, the servo system gain variable circuit 15 and the servo system offset variable circuit 16 obtain the optimum gain value and offset value so that the amplitude thereof becomes a predetermined value. Store in the second memory 18. The servo system control circuit 19 reads the gain value and the offset value from the first memory 17 and the second memory 18, generates a servo signal based on this, and sends it to the optical head drive circuit 9. The optical head drive circuit 9 drives the optical head 2 with a servo signal, and performs tracking and focus control.

  In this embodiment, when the optical disc 1 is loaded (mounted) on the apparatus, learning of the servo system is performed according to the procedure described later. When the disk rotation speed (double speed) at the time of data reproduction is designated from the outside of the apparatus such as a personal computer or a user, the apparatus control circuit 10 compares the designated double speed with the current double speed. When it is necessary to change the double speed, the spindle motor 4 is caused to change the double speed, and the laser power control circuit 7 is instructed to change the reproduction laser power. Then, the servo system control circuit 19 is caused to adjust the servo system in accordance with the double speed change.

  That is, the servo system control circuit 19 performs learning processing of servo system constants related to tracking control and focus control at two points that are representative of laser power during reproduction after disk loading, and stores them in the first memory 17 and the second memory 18. Keep it. Then, when new double speed and laser power conditions are given from the device control circuit 10 and the laser power control circuit 7, they are stored in the first memory 17 and the second memory 18 without newly performing servo learning work. The optimum servo system constant is obtained by calculation based on the learning value, and the servo system is set to that value.

  FIG. 2 is a flowchart showing an example of a servo system adjustment method in the optical disc apparatus according to the present invention. This embodiment is a basic flow in the case of multi-disk support.

  When a disk is loaded (mounted) in step S20, it is determined in step S21 which format medium the disk is of. This is because the laser power value set in the subsequent servo learning is determined according to the type of the medium. Note that the laser power for discrimination is the lowest power among the media handled so as not to deteriorate the recorded data on the disc.

  In step S22, the first servo learning condition is set. The first learning is usually performed under the condition of the minimum double speed. Assuming that the speed at this time is V1 and the power is P1, these conditions are used because the specifications are determined for each medium. In FIG. 1, the apparatus control circuit 10 controls the spindle motor 4 to have this speed V1, and the laser power control circuit 7 controls the laser power driving circuit 6 to have this power P1.

  In step S23, the first servo learning is executed. The procedure is as follows. The servo system error signal detection circuit 8 detects a tracking error signal and a focus error signal from the signal of the optical head 2. Here, the amplitude of each detected error signal basically depends on the laser power to be irradiated, but depends on the disk speed and mechanical conditions. Therefore, the servo system gain variable circuit 15 obtains an optimum servo system gain value so that the detected amplitude becomes a predetermined value. Further, since there is an offset in the servo system, the servo system offset variable circuit 16 obtains an optimum offset value in accordance with the obtained gain value. The obtained servo values S1 (gain value G1 and offset value Z1) are stored in the first memory 17 in step S24.

  In step S25, disc information is read from a predetermined area of the disc. This describes the maximum speed of the disc and the recommended power value at that time.

  In step S26, a second servo learning condition is set. Since the second learning is performed under the condition of the maximum double speed, the speed V2 and the power P2 are set according to the read maximum double speed and the recommended power. If these are not described on the disc, or if the second learning condition is set separately, the speed V2 and the power P2 can be set independently. Note that the power P2 at this time is preferably set to be approximately proportional to √ (V2 / V1) in consideration of the influence of the increase in speed with reference to the first learning condition P1.

  In step S27, the second servo learning is executed. The procedure is the same as the first learning described in step S23. The servo value S2 (gain value G2 and offset value Z2) obtained as a result of the second learning is stored in the second memory 18 in step S28.

  In step S29, conditions (speed Vx and power Px) for actual data reproduction are set. This speed Vx is designated by a personal computer or a user. Further, the power Px at that time is designated from the outside or is arbitrarily set. Here, it is preferable to set Px substantially proportional to √ (Vx / V1) in consideration of the increase in speed with reference to P1.

  In step S30, the optimum servo system conditions Sx (gain value Gx and offset value Zx) under actual data reproduction conditions (speed Vx and power Px) are obtained by calculation. Servo values S1 and S2 that have been learned in advance and stored in the first memory 17 and the second memory 18 are read out, and are calculated from them by an interpolation method.

  FIG. 3 shows the principle of the calculation of the servo system conditions in step S30. The horizontal axis represents the reciprocal 1 / P of the reproduction power, and the vertical axis represents the gain G and the offset Z. Here, as a basic property, the error signal amplitude is proportional to the power P, and the gain G is determined so as to make the signal amplitude constant. Therefore, the power P and the gain G are in an inversely proportional relationship. Therefore, when the reciprocal 1 / P of the reproduction power is taken on the horizontal axis as shown in the figure, the gain G changes linearly. Since the offset Z is compensated in proportion to the gain G, it also changes linearly. The servo constant S1 (G1, Z1) for the first power P1 and the servo constant S2 (G2, Z2) for the second power P2 are plotted, and these are connected by a straight line. The servo constant Sx (Gx, Zx) can be obtained by reading the value on the straight line for the desired power Px. In this calculation, the servo system control circuit 19 can read the servo values S1 and S2 from the first memory 17 and the second memory 18, and obtain the servo constant Sx by simple interpolation calculation.

  In step S31, the servo system is set with the servo constant Sx (Gx, Zx) obtained by calculation. Servo pull-in is performed in step S32, and when it is stabilized, data reproduction is started in step S33.

  As described above, in this embodiment, the learning process related to the servo system conditions is executed in advance at two points that are representative of the reproduction speed and the laser power. Then, when new speed and laser power conditions are given, the optimum servo system conditions are obtained by calculation based on the stored learning values without performing servo learning work each time. Therefore, it is possible to quickly set the servo condition for the speed change, the preparation time can be shortened, and the convenience for the user is improved.

  As a modification of the above embodiment, based on servo conditions S1 and S2 obtained by learning, optimum servo conditions for power conditions (Px1, Px2,...) Of typical double speeds (Vx1, Vx2,...) (Sx1, Sx2,...) May be obtained by an interpolation method and stored in a memory. By doing so, it is not necessary to calculate servo conditions each time the speed changes, and the preparation time can be further reduced.

  Further, the servo learning condition is not limited to the above embodiment. Although the minimum power value and the maximum power value are applied as P1 and P2, an intermediate power value may be used, and in this case, an external interpolation method is used. In addition, the number of learnings may be three or more, and a more accurate servo value can be set.

  Next, FIG. 4 shows a process when the playback speed is limited, which is an additional flow to the basic flow of FIG. For example, as in a DVD-RAM, information that restricts the playback speed may be written in a DIZ (Disk Information Zone) area. If the reproduction speed is reduced by the information, it is necessary to reduce the reproduction power, and it is necessary to adjust the servo system again. This step is executed after the flow of FIG. 2 is completed (step S33) (A) or in the middle of step S29 (B).

  In step S40, the presence / absence of information relating to the playback speed limit is read from the disc. For example, if the information is “present”, it is determined in step S41 whether the speed Vx to be reproduced exceeds the speed limit Vc. If it exceeds (Vx> Vc), the playback speed is changed to a speed Vx ′ that is equal to or lower than Vc in step S42, and the power Px ′ is set for that. In step S43, the optimum servo condition Sx 'for the changed power Px' is obtained by calculation (interpolation). In step S44, the servo system is set with the servo value Sx 'obtained by the calculation. Servo pull-in is performed in step S45, and when it is stabilized, data reproduction is started in step S46.

  By adding the process of FIG. 4, a normal servo system can be set within the allowable speed and allowable power specific to the disk, and the disk protection and data reliability can be improved.

  Next, FIG. 5 shows an additional flow to the basic flow of FIG. 2 and shows processing when the reproduction laser power is limited. In this embodiment, if the reproduction power is excessively increased in each disk, the reproduction signal may gradually deteriorate and the S / N may decrease when the same part is reproduced continuously. It corresponds to. That is, there is a possibility that a disc has a reproduction tolerance (reproduction quality degradation due to repeated reproduction) lower than the standard, and this is checked to set the reproduction power. This step is executed after the flow of FIG. 2 is completed (step S33) (A) or in the middle of step S29 (B).

  In the procedure, first, in step S50, a test signal is recorded in the test writing area. In step S51, the reproduction power is set as a test condition. In the test, the desired reproduction power Px is set to about 1.5 to 3 times higher. In step S52, reproduction is continuously repeated a predetermined number of times. The number of times is 1000, for example. In step S53, the reproduction quality after a predetermined number of reproductions is evaluated. As an evaluation method, for example, the number of PI (Parity Innercode) errors is measured.

  In step S54, it is determined whether the quality deterioration is within an allowable value. In the case of DVD, for example, the number of PI errors corresponding to data to CLK jitter = 13% = 100 is set as a threshold value, and it is determined whether or not this value is exceeded. If it does not exceed, it is determined that there is no problem with the desired reproduction power Px. If it has exceeded, there is a problem and the setting of the reproduction condition is changed in step S55, and the reproduction power is lowered to Px '. Then, the reproduction test is repeated and confirmed again with the newly set reproduction power Px ′. Alternatively, the safe reproduction power Px ′ can be obtained by calculation from the quality deterioration amount obtained by the test using an empirical formula, and can be set by this.

  In step S56, the optimum servo condition Sx 'for the changed power Px' is obtained by calculation (interpolation). In step S57, the servo system is set with the servo value Sx 'obtained by the calculation. Servo pull-in is performed in step S58, and when it is stabilized, data reproduction is started in step S59.

  The above-described test of the reproduction resistance is an example, and if the acceleration test is performed by further increasing the reproduction power as a test condition in step S51, the evaluation can be performed in a short time with a small number of repetitions. In steps S53 and S54, as a reproduction quality evaluation method, reproduction jitter, error rate, CD system C1 error, etc. may be measured as evaluation items instead of PI error.

  According to the present embodiment, it is possible to limit the reproduction power switching to a range in which the reproduction durability does not deteriorate with respect to a non-standard disk or the like. Then, it is possible to prevent the recorded data from being deteriorated by continuous reproduction. As a result, the protection and reliability of the disk can be improved.

1 is a block diagram showing an embodiment of an optical disc apparatus according to the present invention. The flowchart figure which shows an example of the servo system adjustment method by this invention. The figure explaining the calculation method (step S30) of the conditions of the servo system in FIG. The figure which shows the processing flow when there exists a restriction | limiting in reproduction speed as another example of the servo system adjustment method by this invention. The figure which shows the processing flow when there exists a restriction | limiting in reproduction | regeneration power as another example of the servo system adjustment method by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Optical head, 4 ... Spindle motor, 6 ... Laser power drive circuit, 7 ... Laser power control circuit, 8 ... Servo system error signal detection circuit, 9 ... Optical head drive circuit, 10 ... Device control circuit, DESCRIPTION OF SYMBOLS 15 ... Servo system gain variable circuit, 16 ... Servo system offset variable circuit, 17 ... 1st memory, 18 ... 2nd memory, 19 ... Servo system control circuit.

Claims (6)

In an optical disc device capable of reproducing at a plurality of rotational speeds,
An optical head for reproducing a signal from reflected light by irradiating a reproducing laser on an optical disc;
A spindle motor for rotating the optical disc at a predetermined rotational speed;
A laser power driving circuit for supplying a predetermined laser power to the optical head;
An optical head driving circuit for performing tracking and focusing operations of the optical head;
A servo system variable circuit for obtaining a gain value and an offset value of the servo system from an error signal obtained from the optical head at a predetermined rotation speed and laser power for reproduction;
A memory for storing a gain value and an offset value obtained by the servo system variable circuit;
A servo system control circuit that sends servo signals for tracking and focus control to the optical head drive circuit;
The servo system variable circuit calculates the gain value and offset value of the servo system at the first rotation speed and the first reproduction laser power, and the second rotation speed and the second reproduction laser power, respectively. Store in memory,
The servo system control circuit sets the servo system by calculating the servo system gain and offset values for the desired rotation speed and desired laser power for reproduction based on the gain and offset values stored in the memory. An optical disc apparatus characterized by: The optical disk apparatus according to claim 1, wherein
A device control circuit for controlling the device by a reproduction signal of the optical head;
The optical head reads information on the speed limit of the optical disc from the optical disc,
The apparatus control circuit, when the desired rotational speed exceeds the read speed limit, changes the desired rotational speed below the speed limit and changes the desired reproduction laser power,
The servo system control circuit calculates the servo system gain value and offset value for the changed rotation speed and changed playback laser power by calculation, and sets the servo system again. The optical disk apparatus according to claim 1, wherein
A device control circuit for controlling the device by a reproduction signal of the optical head;
The optical head records a test signal in a test writing area of the optical disc, and continuously reproduces the test signal with a test reproduction laser power set according to the desired reproduction laser power,
The apparatus control circuit determines whether or not the quality degradation of the reproduction signal after reproduction for a predetermined number of times is within an allowable value, and if the deterioration amount exceeds the allowable value, the desired reproduction laser power is changed to an allowable value or less. ,
The optical disc apparatus, wherein the servo system control circuit obtains a gain value and an offset value of the servo system with respect to the desired rotation speed and the changed reproduction laser power by calculation, and sets the servo system again. In the servo system adjustment method of an optical disk device that can be reproduced at a plurality of rotational speeds,
A first rotation speed and a first reproduction laser power are given to the mounted optical disk, and a first gain value and a first offset value of the servo system are obtained from the reproduced error signal,
A second rotation speed and a second laser power for reproduction are given to the optical disc, and a second gain value and a second offset value of the servo system are obtained from the reproduced error signal,
The servo system gain value and offset value for the desired rotational speed and desired reproduction laser power when reproducing data from the optical disc, the first gain value, the first offset value, and the second gain. A calculation based on the value and the second offset value,
A servo system adjustment method for an optical disc apparatus, wherein a servo system is set by a gain value and an offset value obtained by the calculation. In the servo system adjustment method of the optical disk device according to claim 4,
Read information about the speed limit of the optical disc from the optical disc,
If the desired rotational speed exceeds the read speed limit, the desired rotational speed is changed to be equal to or lower than the speed limit and the desired reproduction laser power is changed,
A servo system adjustment method for an optical disk apparatus, comprising: calculating a gain value and an offset value of a servo system with respect to a changed rotation speed and a changed reproduction laser power, and setting the servo system again. In the servo system adjustment method of the optical disk device according to claim 4,
Recording a test signal in the test writing area of the optical disc,
The test signal is continuously and repeatedly played back with a test playback laser power set according to the desired playback laser power,
Determine if the quality of the playback signal after the specified number of playbacks is within an acceptable value,
If the amount of deterioration exceeds an allowable value, the desired reproduction laser power is changed to an allowable value or less,
A servo system adjustment method for an optical disc apparatus, wherein the servo system gain value and offset value for the desired rotation speed and the changed reproduction laser power are obtained by calculation, and the servo system is set again.

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