JPH041938A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain an optical disk device guaranteed for its recording and reproducing with high reliability by controlling a recording laser with feedback of a monitor of the laser. CONSTITUTION:A current for driving a weak laser to densely irradiate a medium is supplied by a base power output circuit 5, and the reproducing is processed by using this weak laser. The density of such a laser is directly received by a photodetector 7 provided in the vicinity of a laser diode 6, and the density of the received beam is outputted by the photodetector 7 to obtain a monitor signal via an amplifier circuit 8 and a current/voltage converter circuit 9. Then, this monitor signal is converted by an A/D converter 11 into a digital signal and inputted to a controller 1, whereas its analog signal is inputted as it is via a sample-and-hold circuit 10 to the base power output circuit for the purpose of the feedback control of base power. By this method, the optical disk guaranteed for its recording and reproducing with high reliability is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The optical recording and reproducing device of the present invention relates to an optical recording and reproducing device that records information on a storage medium by optical means, and particularly has an erasing function and allows information to be rewritten. The present invention relates to an optical recording/reproducing device such as a magneto-optical disk device.

[Conventional technology]

In general, optical recording/reproducing devices such as magneto-optical disk devices use laser light for recording, erasing, and reproducing means, and a laser diode is generally used as the light source.

A light beam emitted from a laser diode is converged by an optical lens to become a polar light spot and irradiated onto a storage medium. On the other hand, an external magnetic field whose polarity is reversed during recording and erasing is applied to the medium, and the combination of the above-mentioned temperature rise on the medium surface due to the light beam and this external magnetic field causes magnetization on the medium corresponding to recording and erasing. A state is formed. That is,
During erasing, the medium is magnetized in one direction due to continuous irradiation of a light beam with a constant intensity and an external magnetic field with polarity in the erasing direction, and when recording, the medium is magnetized in a fixed direction due to erasure, as shown in Figure 2. As shown in the recording operation example, partial magnetization reversal is formed as shown in the figure from a light beam whose intensity is modulated in accordance with recorded data and an external magnetic field having a polarity opposite to that of erasing.

As mentioned above, since information is stored as partial magnetization reversal on the medium, its size is always required to be constant and optimal. If the diameter of magnetization reversal becomes small, the amplitude during information reproduction will be reduced, and if it is too large, interference will occur in the reproduced waveform, both of which will result in a decrease in the reproduced S/N ratio. For this reason, it is necessary to always ensure the optimal value for the optical power during recording, with a margin that the optical beam intensity (optical power) during erasing should be sufficient to ensure the erasing rate. occurs.

In the conventional recording method described above, the recording power is determined to be a constant value before data is recorded. However, the first
As shown in Figure 0, even if data is recorded on a recording medium with a constant recording power (Pw), the data may not be recorded on the recording medium due to various conditions such as the external environment or dirt on the lens used to converge the laser beam. There is a risk that the shape of the pit (the length and width of the magnetized portion) may change. When the bit shape changes, the waveform of the reproduced signal obtained when reproducing data changes. This has the disadvantage that the reliability of the reproduced data is reduced.

To explain using FIG. 10, the pit “l” on the recording medium
” is 501, the reproduced signal becomes like 504. 504
With a waveform like this, the position of the pit (the peak point of the waveform) cannot be detected accurately, and the amplitude H1 becomes small in areas with high pit density due to interference between pits, resulting in low reliability of reproduced data. Also, the number of pits on the recording medium is 50.
The reproduced signal at the time of 3 is as shown in 506. In a waveform such as 506, the amplitude value H1 is small and there is a possibility that pits cannot be identified. When the number of pits on the recording medium is 502, the reproduced signal becomes 505. Shake like 505 t/l1
If H2 is a thick signal, highly reliable data can be obtained from the signal 505 since there is no element that lowers the reliability of reproduced data as described above.

In other words, if data is recorded with a constant recording power,
There is a drawback that the bits recorded on the recording medium become 501° or 503 due to changes in various conditions such as the external environment, reducing the reliability of reproduced data.

There is also a method of directly monitoring and correcting the emitted light of the laser diode, but in this method, the driving current (1) - optical power (P) characteristic of the laser diode serving as the light source is
It has the characteristics shown in Figure 1, and is sensitive to changes in ambient temperature,
Alternatively, the threshold current I Tbp slope efficiency ΔP/ΔT generally changes over time. Therefore, in this type of recording apparatus, the following two methods have been used to correct the change in the characteristics of the laser diode and obtain a constant optical power during recording.

The first method allows changes in slope efficiency and corrects only changes in threshold current.The first method is to allow changes in slope efficiency and correct only changes in threshold current.The first method is to emit light at a low power (base power) that does not affect the medium during non-recording operations. This method converts optical power into an electrical signal using a photodetector and then feeds it back to the drive current.

During recording, this base power is held, and a drive current corresponding to the insufficient power is added.

The second method corrects both the threshold current and the slope efficiency, in which the optical power during recording is detected by a photodetector, and the drive current is corrected as in the first method.

In the first method, the target of correction control is the base power during non-recording, and the change in threshold current is not rapid, so the photodetector and control circuit are not required to be fast and are relatively simple. There are advantages that can be realized with this configuration. However, since there is no ability to correct for changes in slope efficiency, as mentioned above, the recording optical power changes due to changes in ambient temperature or over time, resulting in a decrease in the quality of the reproduced signal during information reproduction, resulting in a reproduction error rate. It has the disadvantage that it increases.

In addition, since the second method directly detects and controls the power during recording, the change in slope efficiency that was a problem with the first method is also corrected, as can be seen from the recording light beam waveform in Figure 2. , it becomes necessary to detect the peak level of a rapidly changing waveform. For this reason, the photodetector and the detection circuit have the drawback that they are required to be high-speed and have a complicated configuration, and conversely, they have the drawback that it is difficult to respond to the demand for increased speed of the device.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention proposes two types of configurations.

The first method is to determine the intensity of the recording light beam when the data was recorded from the reproduction signal, and adjust the intensity of the recording light beam. For this reason, the present invention includes a light beam recognition means for recognizing the intensity of the recording light beam from the reproduction signal, and a light beam control means for controlling the intensity of the light beam based on the recognition result.

The second method is to directly monitor the intensity of the erasing light beam and correct the characteristics of the laser diode. For this reason, the present invention includes a light beam recognition means for monitoring the intensity of the erasing beam, and a light beam control means for controlling the intensity of the light beam based on the recognition result.

〔Example〕

Next, one embodiment of the present invention will be described in detail with reference to the drawings. The present invention relates to laser power control, and the first embodiment is of a type in which recording power is corrected from the optimum values of base power and erasing power.

The configuration of this embodiment will be explained with reference to FIG.

The laser irradiated onto the medium is generated by a laser diode 6. This laser diode 6 is 3 depending on the operation.
Irradiate different types of lasers. Therefore, the laser diode 6
The drive current to is output from three types of output circuits. The recording output circuit 3 supplies a driving current during recording. The power of this drive current is applied from the controller 1 via the D/A converter 2, and is modulated with recording data. The erase output circuit 4 supplies a drive current during erasing. Similarly, the power of this drive current is determined by the controller l.

The base power output circuit 5 supplies a weak laser drive current that constantly irradiates the medium. In this embodiment, the regeneration process is performed using this weak laser.

The intensity of these laser beams is directly received by a photodetector 7 provided near the laser diode 6.

The photodetector 7 outputs the intensity of the received light, and the amplifier circuit 8
A monitor signal is obtained via the current-voltage conversion circuit 9, and this monitor signal 111 is converted into a digital signal by the A/D converter 11 and input to the controller. is input to the base power output circuit via.

Next, the operation of this embodiment will be explained.

The controller l has a recording command that instructs the recording and erasing of the reference power value and information corresponding to the target beam intensity at the time of erasing;
An erase command signal is supplied, and recording and erasing operation control and power control are performed here. First, when there is no recording or erasing command, standby signal 1 is sent from controller 1.
(10 is supplied to the sample-and-hold circuit 10, and the sample-and-hold circuit IO operates in sample mode, that is, to supply the monitor voltage 108 to the base power output circuit 5.The base power output circuit 5 uses the internal base power reference voltage and the supplied The base drive current 106 is supplied to the laser diode 6 while comparing the monitor voltage 108 that is generated.

The laser diode 6 emits laser light 4 at a small power level based on the base drive current 106, and the power level is detected by a monitoring photodetector 7 and amplified by an amplifier circuit 8 to obtain a power monitor current 107. The power monitor current 107 is converted to a voltage level by the current-voltage conversion circuit 9 and becomes the monitor voltage 108. Through the series of circuit operations described above, feedback control is performed so that the monitor voltage 108 matches the base power reference voltage, that is, the base power remains constant regardless of changes in the characteristics of the laser diode.

Next, in the erase operation that is performed prior to recording information, the supply of the erase command turns off the standby signal 1 (10), so the sample and hold circuit 10 changes to the hold mode, and the base power changes just before the erase operation starts. The power level 110 corresponding to the reference power value is then supplied to the D/A frequency converter 2, where an erase level voltage 102 which is an analog signal is created, and then the erase output circuit 4 erases the voltage. Drive current 1
05 and is added to the base drive current 106 and supplied to the laser diode 6. The erase power level during the erase operation is the same as the base power, and the photodetector 7
The signal is detected as a monitor voltage 108 via the amplifier circuit 8 and the current-voltage conversion circuit 9, and is converted into a digital erasure beam intensity signal 109 by the A/D converter 11 and then supplied to the controller (a). The controller 1 performs a comparison with a reference power value, and if there is a difference between the two, the power data 101 is corrected to correct the erase power.

As a result of the above operations, the operating state of the drive current vs. optical output characteristic of the laser diode 6 during the erasing operation is as shown in Figure 3, and changes in ambient temperature or changes in threshold current that occur over time are based on Due to the drive current 106,
The change in slope efficiency is corrected and controlled by the erase drive current 105. During the recording operation in which information is recorded, the standby signal 1 (10) is turned off and the base power is held in the same manner as during the erasing operation due to the supply of a recording command. Since the characteristic change has been corrected and the optical output characteristic with respect to the power data 101 is obtained as shown in FIG. 4, data corresponding to the optimum recording power is supplied to the D/A converter 2, and the recording level voltage 103 of the analog signal is
and is supplied to the recording output circuit 3. Recording output circuit 3
Then, the recording level voltage is set to 10 depending on the supplied recording data.
3 is turned on and off, and a recording drive current 104 corresponding to the recording light beam waveform shown in FIG. 2 is added to a base drive current 106 and supplied to the laser diode 6.

It can be seen from the operation of the above embodiment that characteristic changes in the threshold current and slope efficiency caused by ambient temperature and the like in the laser diode, which were a problem in the prior art, are corrected. Further, by using the erase power at a constant power level for correction of slope efficiency, which conventionally required high-speed response, there is an advantage that high-speed response is not required.

Furthermore, in the above embodiments, the configuration is shown under the condition that the erasing power level and the recording power level do not match.
When the two match, control over the base power becomes unnecessary, and the sample-and-hold circuit 10 can be omitted.

Next, a second embodiment of the present invention will be described.

In this embodiment, the laser power during recording is controlled by monitoring the reproduced signal, and in particular, the optimum value is determined based on the number of errors in the reproduced data.

This embodiment will be described with reference to FIGS. 5 to 7.

In this embodiment, unlike the first embodiment described above, the reproduction output circuit 34 and the erase output circuit 32 supply a constant drive current to the laser diode 35 according to instructions from the controller 30.

The drive current of the recording output circuit 33 is controlled by the controller 30 via the pulse generating circuit 31.

The photodiode 36 in this embodiment receives the light emitted from the laser diode 35 and reflected by a medium (not shown), and does not directly monitor the light as in the first embodiment. . The light received by the photodiode 36 is converted into digital data by a data reproducing circuit as in the conventional case. The memory circuit 40 holds the data to be recorded, the write pulse width, and the number of errors.

The count circuit 39 counts the number of discrepancies between the recorded data and the reproduced data compared by the data comparison circuit 38.

Next, the operation of this embodiment will be explained.

When record information 2 (10) is input to the hunt roller 30,
The controller 30 outputs the record data corresponding to information 2 (10) to the memory circuit 40 as memory data 217. The memory data 217 is stored in the memory circuit 40. The controller 30 outputs the record data 203 and the control signal to the pulse generation circuit 31. 204 to generate a write pulse width Pu+.The recording output circuit 33 outputs a recording current 208 to the laser diode 35 according to the write pulse signal 205 output from the pulse generation circuit 31 and the control signal 202 from the controller 30. The laser diode 6 changes the write pulse width Pu by the injected recording current (D).
It emits light at t. A recording output beam from the laser diode 35 is irradiated onto the medium, and recording data is recorded on the recording medium (not shown).

Controller 30 then resets count circuit 39 via reset signal 216. The controller 30 is
The reproduction output circuit 34 is operated by the control signal 206. The reproduction output circuit 34 injects a reproduction current 209' into the laser diode 35, so that the laser diode 35 irradiates the medium with a reproduction output beam.

A reproduced data signal 211 is obtained by receiving the reflected beam from the medium by the photodiode 36. The data reproducing circuit 37 converts the reproduced data signal 211 into reproduced data 212.

Next, the data comparison circuit 38 compares the data patterns of the recorded data 214 stored in the storage circuit 40 and the reproduced data 212 reproduced from the recording medium. A mismatch (error) signal 213 between the recorded data 214 and the reproduced data 212 from the data comparison circuit 38 is counted by a counter circuit 39. The counted error number Er is output to the storage circuit 40 through the error number signal 215. Number of errors Er.

The storage circuit 40 receives the write pulse width Pu+ used when recording data on the recording medium as storage data, and stores the error number Er and the write pulse width Pu as a pair.

Thereafter, the data on the recording medium is erased through the erase output circuit 32 in response to a control signal 217 from the controller 30.

The controller 30 repeats the above process using the recording data stored in the storage circuit 40 and using a write pulse width Pu2 different from the write pulse width Pu used in the above process. When the above process is repeated several tens of times for t1, a large number of pairs of the write pulse width Pu and the number of errors Er are stored in the memory circuit. The controller 30 finds out the write pulse width Pu used when the number of errors Er is small among the above, and uses the found write pulse width Pu to record data on the recording medium again.

A specific example of the pulse generating circuit 31 shown in FIG. 5 will be explained in detail using FIGS. 6 and 7.

When the recording data 203 enters the pulse generating circuit 31, the recording data 203 rises due to the integration circuit 42 composed of a coil and a resistor, and its fall becomes slow like the integral data 221. The control signal 204 from the outside is converted to the threshold value 220 of the comparator 43 by the D/A conversion circuit 41.
is determined, and the comparator 43 generates delayed data 222 from the integral data 221 using a threshold value 220.

A pulse signal 223 is generated by ANDing the recorded data 203 and the delayed data 222. In this embodiment, the threshold value 220 or the external control signal 204
Accordingly, a pulse signal 223 of arbitrary length can be created.

As explained above, in this embodiment, when storage data is given from the host device, the optimum pulse width is determined each time. Alternatively, a method may be considered in which the test is performed when the power is turned on or when the medium is inserted in the case of a convertible medium.

Next, a third embodiment will be described. Similar to the second embodiment described above, this embodiment optimizes the recording laser from the reproduction signal, but whereas the previous embodiment focused on the logical accuracy of the reproduction signal, in this embodiment the reproduction signal The method used is to monitor the amplitude of the recording laser and change the power of the recording laser.

This embodiment will be specifically described with reference to FIGS. 8 and 9.

The major difference in configuration between this embodiment and the second embodiment described above is that the pulse generation circuit 52 is different from the controller 50.
The second feature is that the drive current value is changed, and the second feature is that the playback monitor is configured to detect the amplitude of the playback signal rather than the data. The reproduction monitor receives light with a photodiode 57, and obtains a reproduction signal via an amplifier circuit. The amplitude value of this reproduced signal is detected by an AC detection circuit 59 and a peak detection circuit 61, and is stored in a storage circuit 62.

Next, the operation of this embodiment will be explained in detail.

When the recording data 3 (10) is input to the controller 50, the recording data 3 (10) becomes a storage signal 313 and is stored in the storage circuit 62.

For example, the test data with the highest density of recorded data is (2,
7), if modulation code is used, “1(101(
Test data of 101 (101 . . . ) is obtained from the data generation circuit 51.

The controller 50 includes a pulse generating circuit 52. The recording output circuit 53 is controlled through control signals 302 and 303.

The laser diode 56 emits light at the write power PW by the drive current 307 output from the recording output circuit 53. The output light from the laser diode 56 is irradiated onto the recording medium, and the test data is recorded on the recording medium.

Next, the hun)c=-ra 50 sends a control signal 305 to operate the reproduction output circuit 55. This output light is reflected by the recording medium and received by the photodiode 57, becoming a minute reproduction signal 308. A reproduced signal 309 is obtained by passing the minute reproduced signal 308 through the amplifier circuit 58. The AC component of this reproduced signal 309 is detected by the AC detection circuit 59. Regenerated AC signal 3 obtained from AC detection circuit 59
The peak value of 10 is detected by the peak detection circuit 61. The relationship between the write power Pw of the peak detection laser diode 56 and the peak value P of the reproduced AC signal 310 is stored. The controller 50 determines the peak value P of the reproduced AC signal 310 from the information stored in the storage circuit 62.
The light of the laser diode 56 when k reaches the maximum.
Find the power Pwo. Using the found write pulse Pwo, real recording data is read out from the storage circuit and recorded on the recording medium. Through the above process, the pits on the recording medium are recorded in the best condition. Finally, the contents of the memory circuit are cleared and returned to the initial state.

Although FIG. 9 shows an embodiment of the AC detection circuit 59, the peak detection circuit 61, and the memory circuit 62 shown in FIG. 8, the structure of each circuit is not limited.

FIG. 9 will be briefly explained. The DC component of the reproduced signal 309 input to the AC detection circuit 59 is cut by the capacitor CI and the resistor R1, and only the AC component passes through. The passed AC component becomes a regenerated AC signal 310.

The reproduced AC signal 310 input to the peak detection circuit has a diode peak value Pk stored in the storage circuit 62 as a pair with the write power Pw of the laser diode 56 used when recording test data on the recording medium. be done. Thereafter, the controller 50 outputs a control signal 304 to operate the erase output circuit 54, and the test data is erased from the recording medium.

As in the above process, the write power Pw of the laser diode 56 during recording is set to Pw 1 using the test data.
．． By performing this with several values such as P w 21 P W 3r '', the relationship between the write pulse Pw and the peak value Pk of the reproduced AC signal 310 at that time is stored in the storage circuit 62.

As previously explained using FIG. 10, the reproduced signal 50
In order to obtain highly reliable data from No. 4,505,506, the amplitude (Hl, H2°H3) in the figure should be large. When the amplitude is maximum (H2), it can be said that the pit condition on the recording medium is the best. In other words, it can be said that the pit condition on the recording medium is the best when the amplitude or peak value of the reproduced AC component is maximum.

From the above process, when data is recorded in the memory circuit 62, D
Regenerated AC signal 31 by L, capacitor C2 and resistor R2
A peak voltage of 0 is charged to capacitor C2. 9th
When the operational amplifier OP is connected as shown in the figure, the voltage charged in the capacitor C2, that is, the voltage applied to the positive input of the operational amplifier OPI, becomes the voltage output of the operational amplifier OP1. This voltage output is a value indicating the peak voltage value of the regenerated AC signal 310. This voltage representing peak value 19 is then input into a storage circuit, and the voltage value, ie peak value 312, is passed through A/D converter 64 and stored in memory 63. A storage signal 313 (recorded data and the value of the write power Pw of the laser diode 56 used during recording) input to the storage circuit 62 is also stored in the memory 63. The stored information is then read out through the storage/reproduction signal 314.

As explained above, in this example as well as in the second embodiment, there is no particular limitation on the timing of Test 1.

〔Effect of the invention〕

As described above, the present invention can be used for laser (recording or reproducing)
By configuring the recording laser to be controlled by feeding back the monitor to the recording laser, it is possible to provide an optical disk device that guarantees highly reliable recording and reproduction.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the first embodiment of the present invention, Figure 2 is a schematic diagram of magnetization reversal on the medium, and Figures 3 and 4 plot the current value on the horizontal axis and the laser power on the vertical axis. 5 is a block diagram of the second embodiment of the present invention, FIG. 6 is a circuit diagram showing a specific example of the pulse generation circuit in FIG. 5, and FIG. 7 is a block diagram of the second embodiment of the invention. 8 is a block diagram of the third embodiment of the present invention, and FIG. 9 is a detailed circuit diagram of the AC detection circuit, peak detection circuit, and storage circuit in FIG. 8. , FIG. 1O is a schematic diagram showing the shape of a bit and a reproduced signal, and FIG. 11 is a graph showing the characteristics of a laser diode similarly to FIGS. 3 and 4. Agent Patent Attorney Susumu Hara Uchihara Data /” ”/” ”0 ” ”/ ””θ” Hikari no Vwa Figure 3 Figure 4 ~ 161'l# Figure 5'' “θ” Figure 11

Claims (10)

[Claims] (1) recording means for recording data on an optical recording medium using a light beam generated by an electric-optical beam conversion means;
An optical recording and reproducing apparatus comprising erasing means for erasing the recorded data and reproducing means for reproducing the recorded data, comprising: a light beam recognition means for recognizing the intensity of the light beam used by the recording means; and a light beam control means for controlling the light beam in the recording means based on the recognition result of the light beam recognition means. (2) recording means for recording data on an optical recording medium using a light beam generated by an electric-optical beam conversion means;
In an optical recording and reproducing apparatus comprising erasing means for erasing the recorded data and reproduction means for reproducing the recorded data, a light beam recognition means for recognizing the intensity of the light beam used by the erasing means; and a light beam control means for controlling the light beam in the recording means based on the recognition result of the light beam recognition means. (3) The optical recording and reproducing apparatus according to claim 1 or 2, wherein the light beam control means controls the intensity of the current supplied to the electric-light beam conversion means. (4) The optical recording and reproducing apparatus according to claim 1 or 2, wherein the light beam control means controls the supply time of the drive current supplied to the electric-light beam conversion means. (5) Claim (1) characterized in that the light beam recognition means recognizes the light beam generated from the electricity-light beam conversion means as an electrical quantity by the light beam-electricity conversion means.
) or (2) or (3) or (4). (6) The optical recording and reproducing apparatus according to claim (5), wherein the light beam-to-electricity conversion means receives the light beam generated from the electricity-to-light beam conversion means without passing through the optical recording medium. . (7) The optical recording/reproducing apparatus according to claim (5), wherein the light beam recognition means is recognition means using a reproduction signal obtained from the reproduction means. (8) The optical recording and reproducing apparatus according to claim 7, wherein the reproduction signal is a reproduction signal of test data recorded in advance at a specific light beam intensity. (9) Claim (8) further comprising comparison means for comparing the reproduced signal and the test data before recording, and controlling the light beam control means based on the comparison result.
). (10) The optical recording and reproducing apparatus according to claim 8, further comprising an amplitude detecting means for detecting the amplitude of the alternating current component of the reproduction signal, and controlling the light beam controlling means based on the detection result.