JP2000011481A - Reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the reproduction always corresponding to the reproduction sensitivity of a recording medium by reproducing recording data by the electric signal formed corresponding to the reflected light of the light that an optical pickup irradiates the recording medium, monitoring the reproduction sensitivity and changing the operation conditions of the optical pickup when a prescribed change is detected. SOLUTION: Control sections 11, 12 set the reproducing power and recording power of the laser beam by the results of the test reproducing and test recording in the respective prescribed regions on a magneto-optical disk 2. When these control sections 11, 12 reproduce the prescribed region of the magneto-optical disk 2 by the instruction of a host computer, the sections monitor the amplitude value from an amplitude detection circuit 23 as the reproduction sensitivity. The control sections 11, 12 compare the monitored amplitude value with a predetermined reference value and changes the power set value of the reproducing beam to be applied to an LD drive circuit 19 according to whether the value is above the reference value or below. As a result, the lowering of the transfer rate of the data is suppressed without interrupting the reproduction operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a reproducing apparatus for reproducing data from a recording medium by irradiating light.

[0002]

2. Description of the Related Art At present, an optical disk is known as a recording medium on which information can be recorded at a high density. Among these optical disks, a system including a magneto-optical disk capable of repeatedly rewriting information and an optical disk drive (reproducing device) is rapidly spreading particularly as an external memory of a computer.

The most recent magneto-optical disk is a magnetically induced super resolution (MSR).
n) is applied (hereinafter, this magneto-optical disk is referred to as "MSR magneto-optical disk"). The magneto-optical disk of this MSR makes it possible to reproduce information at a high resolution by utilizing a temperature distribution generated in the magnetic film, so that information can be recorded at a higher density.

[0004]

On the other hand, the magneto-optical disk of the MSR has a drawback that the reproduction sensitivity is easily changed by the environmental temperature since the reproduction principle depends on the temperature distribution of the magnetic film. For this reason, the power margin of the light to be irradiated becomes narrower in the optical disk drive on the reproducing side. Therefore, when the temperature of the magneto-optical disk of the MSR changes, a reproduction error or a decrease in signal amplitude is likely to occur. This is particularly noticeable when the temperature difference between the magneto-optical disk of the MSR and the optical disk drive is large immediately after loading.

In order to cope with such a magneto-optical disk having an MSR, the read sensitivity is measured by irradiating reference data previously written in a predetermined region of the magneto-optical disk a plurality of times (test reproduction), and irradiation is performed. A method of resetting the light power to an optimal value has been proposed. But,
In test reproduction, it is necessary to move the optical pickup, which is the light emission system, to a predetermined area of the magneto-optical disk.
During this time, the reproduction operation that should be performed is interrupted. The movement of the optical pickup is time-consuming because it is performed mechanically, and the frequent test reproduction reduces the data transfer rate of the optical disk drive.

It is also conceivable to use a thermometer to obtain the reproduction sensitivity. However, it is difficult to directly measure the temperature of a rotating magneto-optical disk,
It is known that the non-contact temperature measurement cannot reliably obtain the reproduction sensitivity of the magneto-optical disk.
Therefore, an object of the present invention is to provide a reproducing apparatus that can always perform reproduction corresponding to the reproduction sensitivity of a recording medium without lowering a data transfer rate.

[0007]

According to the first aspect of the present invention, an optical pickup means for irradiating a recording medium with light and generating an electric signal in accordance with the reflected light of the light, and based on the electric signal, Reproducing means for reproducing data recorded on the recording medium, monitoring means for monitoring the reproduction sensitivity of the recording medium,
Changing means for changing the operating condition of the optical pickup means when a predetermined change in the reproduction sensitivity is detected.

In the present invention, "monitoring of reproduction sensitivity"
Means the measurement of the reproduction sensitivity performed without interrupting the operation related to the data reproduction. Therefore, a device that interrupts the data reproduction operation by an operation of reading out the reference data, such as measurement of the reproduction sensitivity by test reproduction, is not included in the “monitoring of the reproduction sensitivity”. According to a second aspect of the present invention, in the reproducing apparatus according to the first aspect, the monitoring unit monitors an amplitude of an electric signal generated by the optical pickup unit as an index of a reproduction sensitivity of the recording medium. .

According to a third aspect of the present invention, in the reproducing apparatus according to the first aspect, the monitoring means monitors an error correction frequency performed by the reproducing means in a data reproducing process as an index of the reproduction sensitivity of the recording medium. It is characterized by doing.

According to a fourth aspect of the present invention, in the reproducing apparatus according to any one of the first to third aspects, the recording medium is a magneto-optical recording medium to which a technique of magnetic super-resolution reproduction is applied. It is characterized by being.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> First, a first embodiment according to the present invention will be described.
An embodiment will be described with reference to FIGS. Note that the first embodiment corresponds to claims 1, 2, and 4. FIG. 1 is a diagram showing a main configuration of an optical disk drive (playback apparatus) according to the first embodiment. An optical disk drive 1 shown in FIG. 1 performs magnetic super-resolution reproduction (MSR) and recording corresponding to a magneto-optical disk 2 of MSR.

The optical disk drive 1 includes the following components. That is, the control unit 11 (corresponding to a monitoring unit, a reproducing unit, and a changing unit) that operates each unit in response to a command from the host computer, and a laser beam (reproduction beam,
An optical pickup 13 (corresponding to an optical pickup means) for irradiating a recording beam (recording beam) and generating an electric signal corresponding to the reflected light of the laser light; a rotating mechanism (not shown) for rotating the magneto-optical disk 2; An optical pickup moving mechanism 15 for moving the optical pickup 13 in the radial direction of the magneto-optical disk 2 based on the servo signal obtained from the optical disc 2, and a modulation for converting a data bit string input from the control unit 11 into a recording waveform according to a predetermined modulation method. A circuit 17, a laser drive circuit (LD drive circuit) 19 for driving the light source of the laser light emitted by the optical pickup 13 in accordance with the recording waveform, and a data bit sequence corresponding to an electric signal obtained from the optical pickup 13 for control. A demodulation circuit 21 (corresponding to a reproducing means) provided to the section 11 , And the like (corresponding to the monitoring means) amplitude detection circuit 23 for detecting the amplitude of the electrical signal.

Note that the optical pickup 13 is connected to the demodulation circuit 2
The electric signal given to 1 is an electric signal indicating the intensity of a specific polarization component in the reflected light obtained from the magneto-optical disk 2 by the optical pickup 13. The demodulation circuit 21 amplifies the electric signal and then modifies the signal waveform to generate a data bit string. Further, the amplitude detection circuit 23 receives an electric signal similar to that input to the demodulation circuit 21, generates an amplitude value indicating the amplitude of the electric signal, and sequentially supplies the amplitude value to the control unit 11. The control unit 11 can monitor the reproduction sensitivity of the magneto-optical disk 2 based on the amplitude value.

FIG. 2 shows a control unit 11 according to the first embodiment.
4 is an operation flowchart of FIG. First, step S in FIG.
In 1, S2, S3, S4, S5, and S6, the control unit 11
Works as follows. That is, when the magneto-optical disk 2 is loaded into the optical disk drive 1 (YES in step S1 in FIG. 2), the control unit 11 rotates the magneto-optical disk 2 and irradiates a reproduction beam having a constant power to move the optical pickup. 15 starts the tracking servo. The power of the reproduction beam is set to a relatively low predetermined value.

At the time of setting the reproducing power in step S2 of FIG.
Is moved to cause the reproduction beam to follow the recording track in the test reading area of the magneto-optical disk 2. At this time, a predetermined reproducing magnetic field is applied in order to perform magnetic super-resolution reproduction (MSR) corresponding to the magneto-optical disk 2. In this state, the reference data, which is a continuous and repeated data pattern, is read from the test reading area of the magneto-optical disk 2.

The control unit 11 reads this reference data a plurality of times while changing the power of the reproduction beam (test reproduction). Based on the result of the test reproduction, the control unit 11 reads out the reproduction beam having the lowest probability of occurrence of a read error. Find the power setting. Then, the value is stored in a memory (not shown) as a reproduction power to be used at the time of reproduction (step S5 in FIG. 2) described later (setting of the reproduction power).

At the time of setting the recording power in step S3 in FIG. 2, the control unit 11 moves the irradiation position of the reproduction beam to the recording track in the test writing area of the magneto-optical disk 2. At this time, a recording beam whose intensity has been modulated is applied while applying a predetermined recording magnetic field in order to write reference data, which is a continuous and repeated data pattern, to the test writing area. The control unit 11 reads the reference data written in this manner by magnetic super-resolution reproduction (MSR). At the time of this reading, the power of the reproducing beam is set to the set reproducing power, and the above-mentioned reproducing magnetic field is applied.

The control unit 11 performs the writing and reading of the reference data a plurality of times while changing the power of the recording beam (test recording). Based on the result of the test recording, the recording that minimizes the probability of occurrence of a writing error is performed. Find the beam power setting. Then, the value is stored in a memory (not shown) as a recording power to be used at the time of recording (step S6 in FIG. 2) described later (setting of recording power).

When the setting of the recording power is completed, the control section 11 causes the reproducing beam set to the reproducing power to follow any one of the recording tracks. In general,
This follow-up is performed in order to immediately shift to a reproduction or recording operation when a reproduction or recording instruction is issued. In this state, the control unit 11 waits for an instruction from the host computer (Step S4 in FIG. 2), and at the time of receiving the instruction, reproduces (Step S5 in FIG. 2) or records (Step S6 in FIG. 2).
I do.

At the time of reproduction in step S5 of FIG. 2, the control unit 11 applies a reproduction magnetic field to a recording track in a designated area, which is input together with a reproduction command from a host computer, and applies a reproduction beam set to reproduction power. Let them follow. The control unit 11 extracts data to be reproduced from the data bit string obtained from the demodulation circuit 21 in this state,
The data is sent to the host computer after error correction only when necessary.

At the time of recording in step S6 in FIG. 2, the control unit 11 causes the reproducing beam set to the reproducing power to follow the recording track in the designated area input together with the recording command from the host computer. Then, a recording beam set to a recording power is applied to the designated area while applying a recording magnetic field. The data bit string provided by the control unit 11 to the modulation circuit 17 to irradiate the recording beam is obtained by adding an error correction code to data to be recorded input from the host computer.

As described above, steps S2 and S2 in FIG.
In the state where the powers of the reproduction beam and the recording beam are set in 3, data reproduction and recording are performed in steps S <b> 5 and S <b> 6 of FIG. 2. The control unit 11 of the first embodiment operates as follows, particularly in a standby state where there is no instruction from the host computer (NO in step S4 in FIG. 2).

That is, at the time of standby (step S4NO in FIG. 2)
Side), the control unit 11 applies a reproducing magnetic field while following the reproducing beam set to the reproducing power to any of the recording tracks as described above (step S in FIG. 2).
9). This is performed by a magnetic field generating source (not shown) in the optical pickup 13, and the reproducing magnetic field has the same value as that during the above-described reproduction (Step S5 in FIG. 2).

As a result, the magneto-optical disk 2 is kept in the same state as that at the time of the immediately preceding reproduction (step S5 in FIG. 2). In this state, the controller 11 controls the magneto-optical disk 2
The amplitude value obtained from the amplitude detection circuit 23 is monitored as the reproduction sensitivity of, and the monitored amplitude value is compared with a predetermined reference value (step S7 in FIG. 2).

As a result of this comparison, the control unit 11 determines that the amplitude value exceeds the reference value (step S7N in FIG. 2).
O) considers that appropriate reproduction is possible under the current reproduction power, that is, the reproduction power stored in the memory (not shown). On the other hand, when the amplitude value falls below the reference value (YES in step S7 in FIG. 2), the control unit 11
It is considered that proper reproduction is difficult under the reproduction power, and the process in step S8 in FIG. 2 is performed.

In step S8, the control unit 11
Changes the power setting value of the reproduction beam given to the LD drive circuit 19 while monitoring the amplitude value. The LD drive circuit 19 supplies a steady drive current of a value corresponding to the set value to the light source of the optical pickup 13. In this way, the control unit 11 changes the power setting value of the reproduction beam in a direction in which the monitored amplitude value is sufficiently higher than the reference value.

Then, the control unit 11 stores the reproduction power set value at the time when the monitored amplitude value becomes a sufficient value as a new reproduction power in a memory (not shown). As a result, the reproduction power of the optical disk drive 1 is changed to an appropriate value. When the reproduction power needs to be changed as described above (step S7Ye in FIG. 2).
Generally, in s), the recording power needs to be changed. For this reason, the control unit 11 executes step S3 of FIG. 2 again to reset the recording power.

As described above, in the first embodiment,
As an index of the reproduction sensitivity, the amplitude of an electric signal which is relatively easily changed according to the reproduction sensitivity is monitored. This makes it possible to monitor the reproduction sensitivity during standby (NO in step S4 in FIG. 2), which was not possible with test reproduction involving reading of reference data. Further, the change of the reproduction power (step S8 in FIG. 2) is realized without performing the test reproduction according to the monitoring result.

Therefore, the optical disk drive 1 can flexibly adapt to the reproduction sensitivity and the recording sensitivity of the magneto-optical disk 2 without lowering the data transfer rate. It should be noted that the recording track on which the reproduction beam follows during the standby (NO in step S4 in FIG. 2) is not limited to the recording track on which data is recorded. Therefore, when following a recording track on which no data is recorded, the reproduction sensitivity is monitored as follows.

That is, the control section 11 monitors the amplitude value of the electric signal corresponding to the VFO region among the amplitude values given from the amplitude detection circuit 23. The VFO area is provided for each sector of the magneto-optical disk 2, and a continuous repetitive data pattern (clock signal) is magnetically recorded in order to give write / read timing to the apparatus in advance. .

That is, the control section 11 can monitor the reproduction sensitivity of the magneto-optical disk 2 based on the amplitude value obtained when the magnetically recorded clock signal is read. Therefore, in the first embodiment, the monitoring of the reproduction sensitivity during standby (NO in step S4 in FIG. 2) is reliably performed regardless of whether data is recorded in each user area of the magneto-optical disk 2.

In the first embodiment, the reproduction beam irradiated during standby (NO in step S4 in FIG. 2) is set to the reproduction power stored in the memory (not shown) at that time. However, it is not limited to this. For example,
The reproducing beam in the standby state (NO in step S4 in FIG. 2) may be set sufficiently lower than the reproducing power stored in the memory (not shown) so as to be easily affected by the temperature change of the magneto-optical disk 2. Since a large amplitude change occurs with a small change in the reproduction sensitivity, the reproduction power and the recording power can be made to correspond to the magneto-optical disk 2 more flexibly.

However, in this case, the change of the reproducing power is realized by performing test reproduction. Also in this case, the power setting value of the reproduction beam in the standby state is set within a range where at least tracking servo is possible and the address portion on the magneto-optical disk 2 can be recognized.

In the first embodiment, the reproducing beam continuously follows the same recording track during standby (NO in step S4 in FIG. 2). May change, the recording track to be followed may be changed as appropriate to prevent a decrease in monitoring accuracy. <Second Embodiment> Next, a second embodiment according to the present invention will be described.
A description will be given based on FIGS. It should be noted that the second embodiment corresponds to claims 1, 2, and 4.

Here, only the differences from the first embodiment will be described, and the description of the other parts will be omitted. In the second embodiment, the optical disk drive 1 shown in FIG. 1 is used as in the first embodiment, but the operation of the control unit 12 is different from that of the first embodiment. FIG. 3 is an operation flowchart of the control unit 12 in the second embodiment.

The control unit 12 performs a reproduction operation under an instruction from the host computer (step S5 'in FIG. 3).
Next, the reproduction sensitivity of the magneto-optical disk 2 is monitored. In step S5 ', the control unit 12 monitors the amplitude value given from the amplitude detection circuit 23 as an index of the reproduction sensitivity while performing the reproduction in the same manner as in step S5 of FIG. Then, the control unit 12 obtains the amount of data (amplitude reduction data amount) in which the corresponding amplitude value is lower than a predetermined reference value among the data being read, and determines the amplitude of the unit data amount as the amplitude reduction frequency. Calculate the reduced data amount.

Thereafter, the control unit 12 compares the frequency of the amplitude decrease thus obtained with a predetermined reference value (step S7 'in FIG. 3). Then, when the frequency of the decrease in the amplitude is lower than the predetermined reference value (step S in FIG. 3).
At 7′NO), the control unit 12 determines that the change of the reproduction power is unnecessary.

On the other hand, when the frequency of the amplitude decrease exceeds the reference value (step S7'YES in FIG. 3), the control unit 12 considers that the reproduction power or the recording power needs to be changed, and again executes FIG. Steps S2 and S3 are executed. As described above, in the second embodiment, the amplitude value, which is an index of the reproduction sensitivity, is monitored during reproduction. Although the instantaneous amplitude value varies depending on the content of the data to be reproduced, the reproduction sensitivity of the magneto-optical disk 2 can be reliably obtained by obtaining the average amplitude value as described above.

Then, only when it is necessary to change the reproduction power or the recording power based on the monitoring result, test reproduction or test recording is performed to make these changes. As a result, the number of times of relatively long test reproduction and test recording is kept to a minimum, and
And the recording sensitivity. In addition,
In the second embodiment, the reproduction power is changed after the end of the reproduction (step S5 ′ in FIG. 3), but may be changed during the reproduction.

For example, in step S5 ', the controller 12 changes the power setting value of the reproduction beam in a direction where the monitored amplitude value exceeds the reference value, as in step S8 in FIG. 2 of the first embodiment. Let it. Then, the power set value at the time when the amplitude value sufficiently exceeds the reference value is stored in a memory (not shown) as a new reproduction power. In this case, since it is not necessary to perform the second and subsequent test reproductions, a decrease in the data transfer rate can be prevented as in the first embodiment.

In the second embodiment, since the change in the reproduction sensitivity is not monitored during standby (NO in step S4 in FIG. 3), the reproduction magnetic field for realizing the magnetic super-resolution reproduction (MSR) is not monitored. The application (step S9 in FIG. 2) is not essential. In the first and second embodiments,
When determining the reproduction power or the recording power in test reproduction or test recording, the amplitude value obtained from the amplitude detection circuit 23 may be referred to when the reference data is read. In this case, the reproducing power or the recording power may be set to a value at which the amplitude value becomes sufficiently large.

Third Embodiment Next, a third embodiment according to the present invention will be described.
An embodiment will be described with reference to FIGS. Note that the third embodiment corresponds to claims 1, 3, and 4. Here, only differences from the second embodiment will be described, and description of the other portions will be omitted.

FIG. 4 is a diagram showing a main configuration of an optical disk drive (playback apparatus) according to the third embodiment. Unlike the optical disk drive 1 (see FIG. 1), the optical disk drive 3 does not include the amplitude detection circuit 23. The control unit 32 is similar to the control unit 12 according to the second embodiment.
Recording and reproduction are performed according to the procedure shown in FIG. 3. The frequency of error correction performed during reproduction is monitored as an index of the reproduction sensitivity of the magneto-optical disk 2.

In general, at the time of reproduction (step S5 'in FIG. 3), a predetermined calculation is performed on each read data, and it is determined from the calculation result whether or not an error has occurred in the reading. Then, as described in the first embodiment,
Error correction is performed only when an error has occurred.
Therefore, unlike the second embodiment, the control unit 32 of the third embodiment performs such a reproduction (step S5 'in FIG. 3)
The number of read errors that have occurred is counted, and the number of errors in the unit data amount is determined as the frequency of error correction. Assuming that data is properly recorded, the reproduction sensitivity of the magneto-optical disk 2 can be monitored based on the frequency of the error correction.

Then, the control section 32 compares the error correction frequency thus obtained with a predetermined reference value (step S7 'in FIG. 3). When the frequency of this error correction is lower than the reference value (step S7'N in FIG. 3)
In O), the control unit 32 considers that it is not necessary to change the reproduction power.

On the other hand, if the frequency of the error correction is higher than the reference value (step S7'YES in FIG. 3), the control unit 32 considers that the reproduction power or the recording power needs to be changed and re-executes. The processing in steps S2 and S3 in FIG. 3 is executed. As described above, in the third embodiment, the index of the reproduction sensitivity performed at the time of reproduction is the frequency of error correction in the reproduction. Although the instantaneous error number varies depending on the content of the data to be reproduced, the reproduction sensitivity of the magneto-optical disk 2 can be reliably obtained by obtaining the average error number as described above.

Then, based on the result of the monitoring, only when it is necessary to change the reproducing power or the recording power, these changes are made. As a result, it is possible to adapt to the reproduction sensitivity and recording sensitivity of the magneto-optical disk 2 while minimizing the number of times of relatively long test reproduction and test recording required. Further, the optical disk drive 3 of the third embodiment
4 (see FIG. 4) does not need to include the amplitude detection circuit 23 unlike the optical disk drive 1 (see FIG. 1), and thus has an advantage that the hardware configuration is simplified.

In the above embodiments, the reproduction power and the recording power are changed in order to adjust the reproduction condition and the recording condition corresponding to the reproduction sensitivity and the recording sensitivity of the magneto-optical disk 2, respectively. However, the reproducing condition and the recording condition can be changed by the reproducing magnetic field and the recording magnetic field, respectively. In this case, a memory (not shown) of the control unit is provided with an area for storing the value of the reproducing magnetic field in addition to the reproducing power and the recording power, and an area for storing the value of the recording magnetic field, and the contents are appropriately changed. Is done.

In addition, the wavelength of the light source of the optical pickup 13 may be changed, and the reproduction condition combining the change of the wavelength may be changed. Further, in each of the above embodiments, the test recording is always performed when it is necessary to change the reproducing power, but the recording sensitivity of the magneto-optical disk 2 is less affected by the temperature change than the reproducing sensitivity. In such a case, the frequency of test recording may be reduced as follows.

That is, a reference value for determining whether or not to perform test recording (a reference value for the amplitude value in the first embodiment, a reference value for the frequency of amplitude reduction in the second embodiment, and an error correction value in the third embodiment). (A frequency reference value) is set, and the reference value is made gentler than a reference value for determining the necessity of changing the reproduction power. Then, test recording is performed by judging the necessity based on the reference values provided in this manner. As a result, the number of times of test recording, which requires more time than test reproduction, can be minimized, and the data transfer rate is improved.

In each of the above embodiments, if the change in the recording sensitivity of the magneto-optical disk 2 can be neglected, the setting of the recording power for the second and subsequent times may be omitted. In each of the above embodiments, if the recording sensitivity of the magneto-optical disk 2 can be considered to change in the same manner as the reproduction sensitivity, the second and subsequent test recordings are omitted, and the recording power is changed by a value corresponding to the change in the reproduction power. May be changed. As a result, the data transfer rate is further improved.

In the above embodiments, the change in the reproduction sensitivity is monitored at the time of standby or data reproduction, but may be performed at the time of verification performed immediately after data recording in a general optical disk drive. Further, in each of the above embodiments, the method of rotating the magneto-optical disk 2 assumes that the linear velocity of the laser beam with respect to the magneto-optical disk 2 is constant, but the present invention is not limited to this. When the rotation speed of the magneto-optical disk is constant, the linear velocity changes depending on the radial position of the magneto-optical disk. Will be done.

Although the magneto-optical disk 2 loaded in each of the above embodiments is a magneto-optical disk of the MSR, any optical disk can be used as long as the reproduction sensitivity changes. Can be

[0055]

As described above, according to the first aspect of the present invention, since the reproduction sensitivity of the recording medium is monitored, the operating conditions of the optical pickup means can be adapted to the recording medium. Moreover, this monitoring realized without the test reproduction does not interrupt the operation related to the reproduction of the apparatus, so that a decrease in the data transfer rate can be suppressed.

According to the second aspect of the invention, the monitoring of the reproduction sensitivity is performed based on the electric signal generated by the optical pickup means. That is, the monitoring of the reproduction sensitivity can be performed during the operation related to the reproduction. According to the third aspect of the invention, the monitoring of the reproduction sensitivity is performed based on the error correction by the reproduction means. That is, the monitoring of the reproduction sensitivity can be performed during the reproduction. In particular, since the monitoring of the frequency of error correction can be performed on software, it is easily realized.

According to the fourth aspect of the present invention, a magneto-optical recording medium to which a technique of magnetic super-resolution reproduction is applied is used as a recording medium. The reproducing apparatus according to any one of claims 1 to 3, wherein the reproducing sensitivity of the magneto-optical recording medium is easily changed by the environmental temperature, and the reproducing apparatus can adapt to the fluctuating reproducing sensitivity. Suitable for reproduction.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a main configuration of an optical disk drive (playback apparatus) according to a first embodiment and a second embodiment.

FIG. 2 is an operation flowchart of a control unit 11 according to the first embodiment.

FIG. 3 illustrates a control unit 12 and a third unit according to the second embodiment.
5 is an operation flowchart of a control unit 32 in the embodiment.

FIG. 4 is a diagram illustrating a main configuration of an optical disk drive (playback apparatus) according to a third embodiment.

[Explanation of symbols]

 1, 3 optical disk drive 2 magneto-optical disk 11, 12, 32 control unit 13 optical pickup 15 optical pickup moving mechanism 17 modulation circuit 19 LD drive circuit 21 demodulation circuit 23 amplitude detection circuit

Claims (4)

[Claims] An optical pickup means for irradiating a recording medium with light and generating an electric signal in accordance with the reflected light of the light, and reproducing data recorded on the recording medium based on the electric signal. A reproducing unit; a monitoring unit that monitors a reproduction sensitivity of the recording medium; and a changing unit that changes an operating condition of the optical pickup unit when a predetermined change is detected in the reproduction sensitivity. Playback device. 2. The reproducing apparatus according to claim 1, wherein the monitoring unit monitors an amplitude of an electric signal generated by the optical pickup unit as an index of a reproduction sensitivity of the recording medium. apparatus. 3. The reproducing apparatus according to claim 1, wherein the monitoring unit monitors, as an index of the reproduction sensitivity of the recording medium, a frequency of an error correction performed by the reproducing unit in a data reproduction process. Playback device. 4. The reproducing apparatus according to claim 1, wherein the recording medium is a magneto-optical recording medium to which a magnetic super-resolution reproducing technique is applied. Playback device.