JP2000040245A - Laser power controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cancel the decrease of apparent laser power by defocusing and to enable the irradiation with a laser beam at an adequate power by correcting the intrinsic laser power value which is a reference value in accordance with the defocusing quantity obtd. from a focus error signal. SOLUTION: The correction value signal obtd. in accordance with the out-of- focus quantity of the focus error signal FE and the signal indicating the intrinsic laser power value as the reference are inputted to an adder 52. The output signal of the adder 52 of this time indicates the signal that the correction value changing according to the state of defocusing fluctuating momentarily with the time is added to the intrinsic laser power value. The correction value meeting the defocusing quantity is added to the intrinsic laser power value, thereby, the apparent power of the laser beam cast to the disk controlled nearly constant regardless of a change in the defocusing quantity and the apparent power of the laser beam is confined within the range of the margin to the optimum value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser provided in, for example, a disk drive device and controlling the laser power of a laser beam applied to a signal recording surface of a recording medium for recording and reproduction to be optimal. The present invention relates to a power control device.

[0002]

2. Description of the Related Art For example, a disk medium such as a magneto-optical disk is an optical recording medium, and it is necessary to irradiate a laser beam to a signal surface of the disk with an objective lens as an output end in order to perform recording and reproduction. It is.

In order to properly record or reproduce data on or from a disk medium such as the above-described magneto-optical disk, the output power (laser power) of the laser beam applied to the disk signal surface at this time is required. It needs to be set properly. For this reason, as the laser power, for example, an appropriate laser power value according to recording or reproduction is obtained in advance, and laser emission is performed by setting this laser power value fixedly.

[0004]

However, media such as the above-described magneto-optical discs are in a state of increasing their recording density by using various techniques. Accordingly, the margin of the optimal laser power has been reduced.

[0005] Further, the applicant has previously proposed a magnetic super-resolution (MSR) as a magneto-optical disk.
upper resolution) method has been proposed. This MSR
In brief, the method is a technique of reading recorded information in an area smaller than the laser spot diameter using a plurality of layers of magnetic films having different temperature characteristics. It is possible to increase the recording density without intentionally pushing down the size. However, this MSR method requires a high laser power at the time of reproduction, and in this case also, the margin of the laser power is reduced.

As described above, when the margin of the laser power as the optimum value becomes smaller, for example, the laser irradiation is performed by using the laser power value set in advance as appropriate as described above. Even if you go,
It has been found that the shift of the focus servo, that is, the adverse effect due to defocusing cannot be ignored. In other words, in a state where the focus servo is shifted and the focus on the signal surface tends to be out of focus, the apparent power of the laser light applied to the signal surface decreases accordingly.
In a situation where the margin of the laser power as the optimum value is small, the possibility that the power of the laser beam reduced by this defocusing is out of the range of the margin becomes higher, resulting in proper data recording, reproduction, and erasing. May not be possible.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a recording / reproducing apparatus corresponding to an optical recording medium, which can properly record data irrespective of an apparent change in laser power due to defocus. , Reproduction, etc. are performed.

For this reason, a focus error signal indicating a focus state of a laser beam is provided as a laser power control device for controlling a laser power of a laser beam applied to a recording medium with an objective lens as an output end for recording or reproduction. A defocus amount detecting means for detecting a defocus amount that is a deviation amount from a just focus state, and a laser power value using at least a predetermined laser power reference value set according to a recording / reproducing situation. Laser power setting means for setting the laser power, and laser light output means for outputting the laser light based on the laser power value set by the laser power setting means. The laser power reference value is compensated based on the defocus amount detected by the focus amount detection means. It was be configured to run the laser power value correction setting for setting a laser power value by.

According to the above configuration, for example, a laser obtained based on a focus error signal (that is, a signal that is varied according to the degree of defocus) with respect to a laser power reference value set according to a recording / reproducing situation. The laser power can be set by performing correction using the power correction value. This makes it possible to correct an apparent change in laser power due to defocus.

[0010]

Embodiments of the present invention will be described below. The reproducing apparatus according to the embodiment of the present invention makes it possible to make a magneto-optical disk compatible with a disk based on the MSR system (hereinafter referred to as an MSR disk) and a conventional disk not supporting the MSR system (hereinafter referred to as an MO disk). An example in which the apparatus is mounted on a disk drive device having a configuration capable of recording and reproducing data will be described.

Here, before describing the disk drive device of the present embodiment, an MSR disk will be described first. In the MSR disk, a data string formed on a track of the disk has a continuous unit of a sector. And one sector is Figure 1
As shown in (1), it is roughly divided into a header and an MO area.

The header is a read-only area in which data based on so-called emboss pits is recorded, and an address and the like are recorded as described later. The MO area is an area in which magneto-optical recording / reproduction is possible, in which user data and the like are recorded.

In the case of this MSR disk, the MO area is an area on which an MSR recording film is formed, that is, data is reproduced by the MSR reproduction method. Therefore, the data recording density is the same as the conventional MO disk (for example, 8 times dense disk)
About twice the density can be realized. As a data modulation method, for example, a (1-7) run-length limited code modulation method (hereinafter, referred to as “(1-7) RLL”) is adopted. Since the recording clock frequency is about twice as high as that of the conventional MO disk, the frequency of the reproduction clock is about twice that of the conventional MO disk. For example, assuming that the clock frequency in the case of the conventional MO disk is fc, the frequency of the reproduction clock in the MO area in this example is 2fc.

Next, an MSR (magnetic super-resolution) reproducing method will be described with reference to FIG. FIG. 2A shows a recording track Dt and a laser beam spot B irradiated thereon.
s, and FIG. 2B shows a part of a cross section of the magneto-optical disk. To obtain the MSR effect, as shown in FIG. 2B, the magneto-optical disk needs to have a recording layer and a reproducing layer, each of which has different magnetic characteristics depending on the temperature. The reproducing layer is a layer that masks the recording layer Ms from the beam spot Bs of the laser beam Lb. Then, as can be seen from FIGS. 2A and 2B, a small window (aperture Ap) is formed on the reproducing layer by irradiating the reproducing layer with a laser beam having a reproducing power. The magnetization direction mt of the recording bit Rb of the lower recording layer is transferred. By observing the direction mt of the magnetization transferred to the reproducing layer, the recording bit Rb recorded at a high density even with the laser beam Lb having a large spot diameter.
Can be read.

By irradiating the laser beam Lb with the reproducing laser power in this way, the magnetization direction mt is transferred from the recording layer to the reproducing layer, and the size of the aperture Ap is determined by the reproducing laser power at that time. In other words, since the area where the transfer is performed from the recording layer to the reproduction layer can be controlled, if the reproduction laser power is properly controlled, the frequency characteristics of the signal reproduced from the disk can be extended. If such an MSR technique is used, for example, high-density recording and reproduction twice or more can be performed even if the beam spot diameter is the same as the conventional one. In the disc of the present embodiment, such recording and reproduction by the MSR method is performed in the MO area of FIG.
Note that recording is possible if, for example, a magnetic field modulation method is adopted.

Next, the disk drive of the present embodiment will be described with reference to FIG. The disk 1 shown in this figure is, for example, the MO disk or MS described above.
One of the R disks is rotated by a spindle motor 2. The rotation speed of the spindle motor 2 is controlled by a spindle servo control circuit (not shown).

The optical pickup 3 receives a laser diode serving as a light source for emitting laser light, an objective lens serving as an output end of the laser light, and receives reflected light (laser light) from a disk and converts it into an electric signal. Photo detector,
An optical system composed of a beam splitter, a cylindrical lens, and the like for guiding the reflected light to the photodetector, and a biaxial support for movably supporting the objective lens in a disk radial direction (tracking direction) and a direction in which the objective lens comes into contact with or separates from the disk surface (focus direction). It has a mechanism and the like.

Also, a bias magnet (magnetic head)
Numeral 4 is arranged at a position facing the optical pickup 3 with the disk 1 interposed therebetween. In this case, for example, the magnetic disk 4 has such a size that a magnetic field can be applied to the entire area in the radial direction of the disk. In the present embodiment,
The bias magnet 4 is provided to generate an external magnetic field and apply the magnetic field to the disk during recording on the disk 1. When the disk 1 is compatible with the MSR method, first, FIG. M explained
In order to obtain a reproduction effect as SR, a bias magnetic field having a required constant intensity is generated even during reproduction. That is, in the MSR method described with reference to FIG. 2, it is necessary to apply a magnetic field for forming the mask Ms layer on the reproducing layer. In the disk drive device of the present embodiment, this magnetic field is applied to the bias magnet (magnetic head). ) 4). The magnetic field generation control for the bias magnet 4 is performed, for example, by a DSP (Digital Signal Process).
r) 16 is realized by controlling the magnetic head driver 7 via the DSP bus. In the magnetic head driver 7,
Control by DSP bus (or input recording data W
In accordance with D), a drive current is caused to flow to the bias magnet 4, whereby a magnetic field having a required intensity and polarity is generated in the bias magnet 4.

The above-described optical pickup 3 is supported by a sled mechanism (not shown) so as to be movable in the disk radial direction. In this case, the movement of the thread mechanism is realized by the DSP 16 performing thread servo control. In other words, the DSP 16 generates a thread control signal according to the reproduction status, and outputs a PW signal from the DSP bus.
The signal is output to the thread mechanism as a thread drive signal SD via the M circuit 15. Thus, for example, control is performed such that movement according to a change in the playback position during playback or movement during seek is performed.

The laser diode of the optical pickup 3 is driven by a laser driver 6 to emit light.
As a result, the laser beam is emitted to the disk 1 with the objective lens as the output end. This irradiation light is reflected on the disk surface, returns again as reflected light via the objective lens, and is condensed on the photodetector via a beam splitter, a cylindrical lens, and the like. The photodetector receives the reflected light, obtains a detection signal, and outputs the detection signal to the IV conversion matrix circuit 5. The detection signal obtained by the photo detector is a current signal. The IV conversion matrix circuit 5 converts the detection signal as a current into a voltage signal and executes various matrix arithmetic processing as described later, thereby generating various servo signals and a reproduction signal MO.

FIG. 4 shows the structure of a photodetector provided in the optical pickup 3.
As shown in this figure, the photodetector PD receives the 0th-order light spot SP0 obtained by reflection from the disk 1, and is divided into four light-receiving elements A, B, C, and D by a beam splitter. Light spot SP1, SP
2 for receiving the light beams 2 respectively. These light receiving elements are arranged in the track direction in the arrangement shown in the figure.

The IV conversion matrix circuit 5 performs various arithmetic operations on the detection signals obtained by the light-receiving elements A, B, C, D, I, and J, for example, in the following manner. The servo signal and the reproduction signal MO are obtained. If it is a tracking error signal for performing a tracking servo, (A + D)
− (B + C) can be obtained. Such a calculation method is also called a “radial push-pull method” in the push-pull method, and the tracking error signal obtained by the above calculation is referred to as an RPP signal here. In addition, the reproduction signal MO can be obtained by calculating MO = I−J using the detection signals obtained by the light receiving elements I and J for the magneto-optical disk.

In the IV conversion matrix circuit 5,
A push-pull operation along the disk tangential direction is also performed. That is, the calculation of (A + B)-(C + D) is also performed. Such a push-pull method is also called a tangential push-pull method, and a signal obtained by the above calculation based on the tangential push-pull method is hereinafter referred to as a TPP signal.

A focus error signal FE for performing focus servo is obtained as shown in FIG. FIG. 5A shows the internal structure of the optical pickup 3 and the positional relationship with the disk 1. For example, as shown in this figure, the optical pickup 3 outputs a laser beam using a laser diode LD as a light source. The laser light output from the laser diode LD is applied to the signal surface of the disk 1 with the objective lens 3a as an output end. The laser beam (reflected light) reflected on the signal surface of the disk 1 has its optical path converted by the beam splitter 3b, and is guided to the photodetector PD via the cylindrical lens 3c.

As the photodetector PD for obtaining the focus error signal, A, B, C, and C shown in FIG.
Among the light receiving elements D, I, and J, the light receiving elements A, B, C,
D is used. Here, FIG. 5B shows the light receiving elements A,
B, C, and D are shown. Then, the focus error signal FE is given by FE for the light receiving elements A, B, C and D.
= (A + C)-(B + D).

Here, in the structure shown in FIG.
Actually, the position of the photodetector PD is fixed,
For example, when the distance between the disc signal surface and the objective lens is used as a reference, the distance to the objective lens (detector position in FIG. 5A) on the photodetector PD side relatively depends on the focus state of the laser light on the signal surface. It can be seen as changing. Then, in the case of a focus state where the detector position is closer to the objective lens than the focal length, as shown in FIG.
The reflected light (zero-order light spot SP0) is received by B, C, and D. That is, the light receiving elements A, C are more than the light receiving elements B, D.
, A large number of light receiving areas can be obtained. In the case of the detector position corresponding to the just focus, FIG.
As shown in (1), a substantially uniform light receiving area is obtained for the light receiving elements A, B, C, and D. Further, if the detector position is in a focus state in which the detector position is closer to the objective lens than the focal length, more light is received by the light receiving elements B and D than the light receiving elements A and C as shown in FIG. The area is obtained.

In this manner, the light receiving areas in the light receiving elements A, B, C, and D change according to the focus state. The result of performing the above-described calculation for such light receiving elements A, B, C, and D is as follows. 5 (f), the focus error signal FE as shown by the solid line is obtained. In this case, the reference value Vref varies in a positive region with respect to the reference value Vref according to the defocus if it is closer than the just focus state, and conversely, the reference value Vref according to the defocus if it is farther than the just focus state. Is a signal that fluctuates in a negative region.

The description returns to FIG. Focus error signal FE, RPP signal, and TP obtained as described above
Each of the P signals is once input to an AGC (Automatic Gain Control) circuit 5 to perform gain adjustment. And
The focus error signal FE is converted into a digital signal by the A / D converter 13 and then converted to a digital signal via the DSP bus.
The signal is input to an SP (Digital Signal Processor) 16. R
The PP signal is sent to the address decoder 12, the A / D converter 1
3 is input. The RPP signal converted into a digital signal through the A / D converter 13 is input to the DSP 16 and used as a tracking error signal. Further, in the present embodiment, the focus error signal FE
Is also branched and supplied to the laser driver 6.
The focus error signal FE input to the laser driver 6 is used for correcting a laser power value according to defocus as described later. The TPP signal is PL
Input to the L circuit 11. The reproduction signal MO is AG
It is input to the C circuit 9.

The PLL circuit 11 is provided for extracting clock information using a clock mark signal included in the TPP signal. FIG. 6 shows an operation of extracting clock information by the PLL circuit 11. For example, the MO disk and the MSR disk to which the present embodiment corresponds have a physical disk format as shown in FIG. This figure shows a state where the clock mark CM is formed on the land portion. The clock marks CM are provided, for example, in a predetermined number in one round of the disk. In this case, the groove becomes a data recording area (track). Although not shown in this figure, the grooves are formed such that wobbling (meandering) is given by, for example, FM-modulated or FSK-modulated address information. That is, address information is recorded by forming wobbling for the groove.

Here, the disk 1 having the disk format shown in FIG.
Assuming that a P signal has been obtained, this TPP signal has an S signal as shown in FIG.
A character curve is obtained.

The PLL circuit 11 detects the S-shaped curve of the TPP signal shown in FIG. 6B as a clock mark signal, and detects the center zero-cross position ZX and the internal VCO.
(Voltage Controlled Oscillator; voltage-controlled oscillator circuit), by synchronizing the phase of the frequency signal output with the frequency-divided signal, thereby synchronizing the detection timing of the clock mark signal with the internal clock. Then, this clock is output as a reference clock.

The clock generated by the PLL circuit 11 is output to a timing generator (TG) 17. The timing generator (TG) 17 generates and outputs a timing signal for generating and detecting a data synchronization signal and an address position signal based on the input clock. In this case, the timing signals are a bit timing signal BT output to the encode / PRML decode circuit 18 and a frame synchronization signal FT output to the address decoder 12.

The address decoder 12 is supplied with the RPP signal via the AGC circuit 8, and extracts address information from the RPP signal using the frame synchronization signal FT. That is, the high-frequency portion of the RPP signal contains address information recorded by the wobbling of the groove, and the address information contained in the RPP signal binarizes the RPP signal to perform bi-phase conversion and CRC. It is taken out by checking. This address information AD is transmitted by the DSP 16.

The DSP 16 performs seek control at the time of data reading, and manages and controls sector positions for recording and reproduction based on the address information AD. Further, the required laser power is set according to the recording / reproducing situation, and the optical pickup 3 is set.
And the like, and the laser emission control and the like.

The DSP 16 also executes various servo controls. For example, the DSP 16 generates focus control data for driving and controlling the focus coil of the biaxial mechanism based on the input focus error signal FE. This focus control data is transmitted to a PWM (pulse width modulation) circuit 15, where it is converted into a focus coil drive signal FD and output to the focus coil. Thereby, focus pull-in control for pulling the position of the objective lens into focus on the signal surface and focus servo control by a closed loop for maintaining a state where the position of the objective lens is focused on the signal surface are executed. .

Tracking servo control for controlling a laser beam spot to properly trace a track is performed, for example, as follows. The tracking error signal is a low frequency component of the RPP signal. For this reason, the DSP 16 removes the high-frequency component from the input RPP signal, extracts the low-frequency component, and obtains this as a tracking error signal. Then, based on the tracking error signal, tracking control data for driving and controlling the tracking coil of the two-axis mechanism is generated and transmitted to the PWM circuit 15. The tracking control data is supplied as a tracking coil drive signal TD via the PWM circuit 15 to the tracking coil. As a result, tracking servo control is performed. Further, the DSP 16 also executes a thread servo control for controlling the movement of the sled mechanism so that the optical pickup 3 accesses or moves to a required position according to the reproduction state.

The reproduction signal MO generated by the IV conversion matrix circuit 5 is sent to the A / D converter 10 after the amplitude fluctuation is adjusted by the AGC circuit 9. This A
The / D converter 10 operates based on the clock generated by the PLL circuit 11. That is, the A / D converter 10 outputs the reproduced signal M as the input RF signal.
O is sampled and digitized at a sampling frequency generated based on the clock, and waveform equalization is performed by a built-in digital equalizer or the like.
It is sent to the PRML decoding unit of the encoding / PRML decoding circuit 18.

The PRML decoding section of the encoding / PRML decoding circuit 18 decodes the waveform signal of the reproduction signal MO output from the A / D converter 10 by PRML. The PRML is a partial response system (P) which is one of the waveform equalization systems that can reproduce data even when waveform interference occurs between waveforms corresponding to data.
R; Partial Response) and a Viterbi composite system that reproduces the most probable data sequence when the waveform contains noise. The encode / PRML decode circuit 18 converts the binarized data obtained by the Viterbi compound into NRZl (Non
Modulation processing is performed using Return to Zero Inverted, and the like, and further, ECC (Error Correcting Code) is solved and output as reproduction data.

Encoding / PRML decoding circuit 1
In step 8, a read gate signal is generated according to the current operation state when a read (reproduction) operation is being performed, and a write gate signal is generated according to the current operation state during a write operation. The read gate signal and the write gate signal are output to a required circuit unit in the encoding / PRML decoding circuit 18 or the encoding / PRML, for example.
It is used for operation control of required functional circuit units other than the decode circuit 18. In the present embodiment, these areas
The d gate signal and the write gate signal are also supplied to the laser driver 6 as signals for setting the validity / invalidity of a laser power correction operation described later.

The encoding / PRML decoding circuit 1
The reproduced data output from the control unit 8 is transmitted via an I / F control circuit 20 as an interface circuit to, for example, an SC.
The data is sent to the host computer 23 via a signal line of SI (Small Computer System Interface). Also, data recorded on the disk 1 is a so-called MPEG (M
oving Picture Experts Group), the above-described encoding / PRML
The compressed reproduction data output from the decoding circuit 18 is MP
It is sent to the EG decoder 22. This MPEG Recorder 2
In step 2, the compressed and reproduced data is decompressed and decoded according to the MPEG standard. The reproduced video data is then sent to, for example, the monitor 24 and displayed.

When data is recorded on the disk 1, for example, data supplied from the host computer 23 is sent to the encoding unit of the encoding / PRML decoding circuit 18 via the 1 / F control circuit 20.

In the encoding section, the data from the 1 / F control circuit 20 is subjected to addition of an error correction code and a predetermined encoding process, and further, a predetermined modulation process for recording on the disk 1 is performed. For example, a recording signal WD synchronized with the bit timing signal BT is generated. Here, if recording is performed on the disk 1 which is, for example, a magneto-optical disk by the optical modulation overwrite method, the recording signal WD is supplied to the DSP 16. The DSP 16 generates laser drive control data modulated by the recording signal WD, and outputs it to the laser driver 6 via the DSP bus. In the laser driver 6,
A laser diode drive voltage LDB is generated based on the supplied laser drive control data, and the laser diode of the optical pickup 3 is driven. Thereby, the recording data W is output from the laser diode of the optical pickup 3.
Pulse emission modulated by D is performed. On the other hand, for example, in the DSP 16, by controlling the magnetic head driver 7 via the DSP bus, for example, a required constant level magnetic field is generated from the bias magnet 4 and applied to the disk 1. Thereby, data recording by the light modulation overwrite method is realized.

If recording is performed by a magnetic field modulation overwrite method (here, a simple magnetic field modulation method is taken as an example), the recording signal WD generated by the encoding unit of the encoding / PRML decoding circuit 18 is transferred to a magnetic head. The data is supplied to the driver 7. This recording signal WD
, The magnetic head driver 7 drives the bias magnet 4 to generate an N or S magnetic field corresponding to the recording data from the bias magnet 4 and apply it to the disk. At the same time, the DSP 16 generates laser drive control data in which a laser power corresponding to a required recording level is set, and outputs it to the laser driver 6. As a result, light is emitted from the laser diode of the optical pickup 3 by the laser power corresponding to the recording level. In this manner, by applying the external magnetic field modulated by the recording data and irradiating the laser beam with the laser power of the recording level, the recording can be performed by the magnetic field modulation overwriting method. As a magnetic field modulation overwrite method, a so-called laser strobe magnetic field modulation method has been proposed which achieves a higher recording density than the simple magnetic field modulation method. The DSP 16 may perform control so that the modulated external magnetic field is applied and the laser light is pulsed according to the clock timing (bit timing signal BT) of the recording data.

As can be said in any of the recording methods described above, the optical pickup 3 at the time of recording generates a laser beam having a power sufficient to raise the temperature on the recording surface of the disk 1 to a so-called Curie point. The bias magnet 4 applies a magnetic field to the recording surface of the disk 1 whose temperature has risen to the Curie point due to the laser light, and then the temperature of the recording surface decreases as the disk 1 rotates. The applied magnetic field remains, which means that recording has been performed.

The power of the laser diode during recording (here, erasing operation is also included in recording) and reproduction is set. Normally, the disk 1 has the outermost peripheral portion, innermost peripheral portion, etc. ROM area (PEP (Pha
In the “Se Encorded Part” zone), an optimum laser power value of the laser beam applied to the disc is recorded. Therefore, the DSP 16 can set the power of the laser beam to be actually applied to the disk by giving the laser driver 6 a laser power value read from the PEP zone of the optical disk. In the present embodiment, as described later, for example, the laser power value read from the PEP zone as described above is used as a reference value, and the laser power value obtained based on the focus error signal FE with respect to this reference value. And the final laser power value can be set.

The CPU 19 is connected to the DSP 16 and the I / F control circuit 20 via, for example, a CPU bus to control the operation of the entire disk drive. For example, various control processes executed in the DSP 16 are also performed under the overall control of the CPU 19.

Next, the configuration of laser power control, which is a feature of the embodiment of the present invention, will be described. In the present embodiment, the laser power value is corrected using the focus error signal FE as described later. The grounds for this will be described with reference to FIGS.

FIG. 10 shows the relationship between the laser power (Write Power) at the time of recording and the bit error rate when data recorded by this laser power is reproduced. As shown in the figure, assuming that the optimum value of the laser power is set, the laser power margin of this optimum value corresponds to a specific bit error rate value as indicated by the range of the arrow in the figure. Is obtained.

FIG. 11 shows the relationship between the defocus value and the bit error rate when the focus state is perturbed under the condition that the laser power of the optimum value shown in FIG. 10 is fixedly set. It shows the relationship. This figure shows that the bit error rate increases with an increase in defocus based on just focus (defocus 0%). In this case, the margin of the defocus range corresponds to the same specific bit error rate value as in FIG.
It is represented by the range indicated by the arrow 1. Such a change in the bit error rate according to the defocus is caused by the laser power of the laser light irradiated on the signal surface due to the defocus fluctuating so as to decrease in appearance. In other words, on the signal surface, the recording is performed with the laser power deviated from the optimum value in accordance with the defocus, so that the bit error rate for the recording data increases accordingly.

For example, if the fluctuation range of the defocus due to the actual focus servo control is within the margin shown in FIG. 12, the bit error rate is also within the allowable range, which is not a problem. As described above, the margin of the laser power is strict for a disk having a high recording density, including an MO disk, and a disk requiring a high laser power during reproduction, such as an MSR disk. This means that the defocus margin shown in FIG. 11 also becomes smaller. Here, the case of recording is described as an example, but such a relationship between laser power and defocus can be similarly applied to reproduction and further to data erasure.

Therefore, in the present embodiment, irrespective of the fluctuation of the defocus, the irradiation power of the laser beam on the signal surface is kept almost at the optimum value and constant, so that the proper data recording (including erasing) or always The following configuration is adopted so that data reproduction is performed.

FIG. 7 shows an example of the internal configuration of the laser driver 6 according to this embodiment. In this figure, L
PC (Laser Power Controller)
oller) 31 is basically a laser drive control data (PEP) transmitted from the DSP 16 via the DSP bus.
(This is the data of the laser power value read from the zone.)
And outputs a laser drive signal S-LD as an analog signal at a level corresponding to. The LPC 31 receives a focus error signal FE, a read gate signal, and a write gate signal. Furthermore, D
Through the SP bus, an enable signal and a disable signal for instructing validity / invalidity of the laser power value correction operation are input. The focus error signal FE is used to obtain a correction value for correcting the laser power value read from the PEP zone as a reference value (correction target value). Also, the read gate signal / write
e gate signal and enable signal / disab signal
Based on the le signal, the LPC 31 selects an operation for validating the laser power value correction or an operation for invalidating the correction, which will be described later.

APC (Autmatic Power Controller) 3
2 is a laser drive signal S-LD from the LPC 31
Is input, and a signal Im corresponding to the amount of reflected light obtained by the photodetector PD in the optical pickup 3.
Is fed back and input. The APC 32 outputs a laser drive current Iout. This laser drive current Iout
Has a level based on the laser drive signal S-LD. The drive element 33 is driven by the laser drive current Iout, so that the laser diode LD in the optical pickup 3 is driven to emit light. In this configuration, when the diode LD is driven to emit light, the signal I of the reflected light amount of the laser light applied to the disk is emitted.
m is fed back to the APC 32,
The PC 32 controls the level of the actual laser drive current Iout so that the relationship of Iout = Im × k (k is a coefficient based on a predetermined value) is obtained between the laser drive current Iout and the signal Im corresponding to the amount of reflected light. Will be.

FIG. 8 shows an example of the configuration inside the LPC 31 shown in FIG. In the LPC 31, a register 45 is provided first. This register 45 has a DSP
Data transmitted from the DSP 16 via the DSP bus is set, and the set data is supplied to required functional circuits in the LPC 31 via the register bus. Here, the data that the register 45 should receive and process from the DSP 16 include data of each laser power value (laser drive control data) corresponding to recording (write), reproduction (read), and erasing (erase), and focus to be described later. Fcs offset data indicating the offset amount, and e for controlling the operation of the gate enabler 44
The signal is a enable signal, a disable signal, or the like. Further, a switching control signal for controlling signal selection in each of the selectors (50, 51) described later is also supplied from the register 45 to the selector via the register bus.

Of the data set in the register 45, the data of each laser power value set corresponding to write, read, and erase are processed as follows. The laser power values corresponding to the write, read, and erase are supplied to D / A converters 47, 48, and 49, respectively. The D / A converters 47, 48, and 49 convert the input laser power value data into analog signals and supply the analog signals to the selector 50.
The outputs of the D / A converters 47, 48 and 49 are
The signal is branched and supplied to the selector 51. In the selector 51, these D / A converters 47, 48, 4
9 is selected and supplied to the VGA 43, which will be described later.

The selector 50 selectively selects one of the supplied signals indicating the laser power values and supplies the selected signal to one input of the adder 52. The selection control of this signal is performed by a switching control signal output from the register 45 according to the operation mode of the disk drive device. That is, at the time of write (data writing), the output of the D / A converter 47 is selected and supplied to the adder 52. Similarly, read (data reproduction)
Sometimes, the output of the D / A converter 48 is selected and era
At the time of se (data erasing), the output of the D / A converter 49 is selected. Accordingly, the current operation mode (any of data writing, reproduction, and erasing) of the disk drive device is given to the adder 52.
, A signal indicating the laser power value considered to be suitable for the operation mode is supplied. And
The laser power value output from the selector 50 in this manner is obtained based on the laser power value included in the information read from the PEP zone, for example, as described above. The power value (reference value) will be used.

The fcs offset data indicating the focus offset amount obtained by the register 45 is supplied to the absolute / limiter 42, which will also be described later.

On the other hand, the focus error signal FE input to the LPC 31 is first band-limited via the filter 41, and then input to the absolute / limiter 42. The absoluteizer / limiter 42 converts the input focus error signal FE into an absolute value, and for example, thereafter, limits the absolute value of the focus error signal FE. Focus error signal F
The absolute value of E is a process of setting a level in a region more negative than the reference level Vref set corresponding to the just focus as a positive level, as shown by a broken curve in FIG. 5F, for example. is there. As a result, the amount of focus shift from just focus is obtained based on the focus error signal FE. Then, the level obtained by slicing the absolute value of the focus error signal FE obtained in this manner with a predetermined limiting level LM is set to VGA (V
oltage control gain (Amp) 43.

The focus error signal FE input to the LPC 31 is used to obtain a correction value for correcting a laser power value as a reference value, as described later. By performing limiting on the signal FE, even if an unnecessarily large defocus amount due to, for example, impact or vibration is detected, an appropriate correction value can be obtained regardless of this. Although not shown here, the limiting level can be configured to be set externally by an instruction of the DSP 16, for example.
The setting can be arbitrarily made by estimating the maximum operation according to the disk drive device.

The above-mentioned fcs offset level is input to the absolute / limiter 42,
An offset can be given to the reference level Vref corresponding to the just focus shown in FIG.

For example, although the focus error signal FE is actually detected as shown in FIG. 5, the actual focus state when a reference signal level corresponding to just focus is obtained is not necessarily just focus. There are cases. That is, as is well known, the focus error signal FE has a DC offset amount. For this reason, in an actual disk drive device, this offset amount is detected by performing a required calibration operation. Then, the actual focus servo control is executed based on the focus error signal FE in consideration of the offset amount. Therefore,
Even when an attempt is made to obtain a correction value of the laser power based on the focus error signal FE input to the LPC 32, if this is to be strictly performed, it is necessary to consider the offset amount. Accordingly, in the present embodiment, an offset is given based on the fcs offset level as described above so that the reference level Vref, which is a reference for absolute value conversion, matches the actual focus state. Thus, an accurate correction value can be obtained.

The focus error signal FE that has been subjected to the processing described above is supplied to the VGA 43, where the gain is adjusted. This gain adjustment is
The output is performed using the output from the selector 51 as a parameter.
In the selector 51, the outputs of the D / A converters 47, 48, and 49 (that is, w
write, read, and erase laser power values) are input. Then, similarly to the selector 50, wr
At the time of the item, the output of the D / A converter 47 (write
Is selected and output.
At the time of d, the output of the D / A converter 48 (laser power value corresponding to read) and the output of the D / A converter 49 (laser power value corresponding to erase) are selected and output.

Accordingly, in the VGA 43, the gain is set for the focus error signal FE in accordance with the input laser power value. That is, writ
Different gain settings are made for e, read, and erase. In other words, w
Gains suitable for write, read, and erase are given. However, the gain setting here is defined so that a predetermined ratio (for example, 5%) becomes the maximum value in terms of laser power in consideration of the fact that excessive gain setting is not performed. And

The focus error signal FE, which has been subjected to the gain adjustment by the VGA 43, is provided at a subsequent stage with a correction value for correcting the laser power value as a reference value obtained from the selector 50 described above. Is treated as The signal as a correction value (hereinafter also referred to as a “correction value signal”) obtained by the VGA 43 in this manner is supplied to the gate enabler 44.

For the gate enabler 44, in addition to the correction value signal, a write gate signal / read gate signal as a control signal, and an enable signal / disable signal from the register 45 via the register bus.
The e signal is input. The gate enabler 44 uses the above w
In accordance with the input state of the write gate signal / read gate signal and the enable signal / disable signal, the correction value signal currently input from the VGA 43 is passed through and supplied to the other input of the adder 52.
ble mode, and disab which does not output the correction value signal currently input from the VGA 43 to the adder 52.
Switching to the le mode is executed.

Here, the gate enabler 44 is en
The case where the mode is the able mode will be described. In this case, the correction value signal obtained based on the deviation amount of the focus error signal FE from Vref and the signal indicating the original laser power value as the reference value are input to the adder 52. . The adder 52 adds these two input signals and outputs the result to the APC 32 (see FIG. 7) as a laser drive signal S-LD. At this time, the output signal of the adder 52 is a defocus which fluctuates every moment. Is a signal added to the original laser power value. That is, as described above, the power of the laser beam applied to the disk apparently decreases according to the degree of defocus, but in the present embodiment, the correction value according to the defocus amount is originally smaller. , The apparent power of the laser beam applied to the disk is controlled to be substantially constant regardless of the change in the defocus amount. In practice, the apparent power of the laser beam can be kept within a margin with respect to the optimum value shown in FIG. Thus, in the present embodiment, appropriate data writing, reproduction,
Alternatively, erasing can be performed.

The gate enabler 44 is dis
In the case of the enable mode, the correction value signal is not output from the gate enabler 44. Therefore, only the signal indicating the original laser power value as the reference value is output from the adder 52. Become.

In the present embodiment, as described above, the enable mode and the dis
The switching to the able mode is performed in consideration of the following circumstances. For example, during the period when the actual recording / reproducing operation is being performed, the laser light is output based on only the original laser power value as the reference value without using the laser power value corrected by the correction value signal. There are times when it should be.

For example, at the time of so-called focus pull-in control for shifting from a state where the focus is out of focus to focus servo control by a normal closed loop, the laser light is corrected by using the laser power value corrected by the correction value signal. When irradiating, it is not possible to obtain a focus error signal corresponding to the focus pull-in situation. That is, it is necessary to emit laser light using only the original laser power value as the reference value.

Further, the above-mentioned focus error signal FE
In order to detect the offset amount, even during calibration for so-called focus bias detection, it is necessary to obtain reflected light according to the defocus state, and use only the original laser power value as a reference value. Laser light must be emitted.

Also, due to the characteristics of the MO disk, the MSR disk, and the like, it is sometimes preferable to use only the original laser power value as a reference value during recording.

In the disk drive according to the present embodiment, the write
ON of the output of the gate signal / read gate signal /
It is turned off or the enable signal / disable
Signal switching is performed.

For example, during the focus pull-in control or the calibration for detecting the focus bias, a read operation or a wr
item operation is enabled and read gat
The DSP 16 outputs the disable signal via the register 45 even when the signal e or the write gate signal is being input.
The gate enabler 44 sets the disable mode based on the disable signal input at this time, so that laser emission is performed based only on the original laser power value as the reference value.

In the case where only the original laser power value as the reference value is used at the time of recording, if data is written to the disk, D
The SP 16 outputs a disable signal via the register 45, and the gate enabler 44 outputs di.
The sable mode may be set. In this case, a write gate signal is always input when writing data to the disk.
The gate enabler 44 may monitor the write gate signal, and may set the disable mode when the write gate signal is obtained.

Further, depending on the configuration including the standard setting of the disk drive device, operations such as the above-described calibration for focus pull-in control and focus bias detection are executed in a state where the enable signal is obtained. , Instead, a read gate signal,
Alternatively, the write gate signal may be set to be turned off. In such a case, in the gate enabler 44, when the enable signal is obtained and the read gate signal or the write signal
When the e gate signal is on, the enable mode is set for the first time.
Even if the enable signal is obtained, read g
If the ate signal or the write gate signal is off, the disable mode is set. In this manner, similarly to the above case, when the calibration operation for focus pull-in control or focus bias detection is being performed, laser emission based on only the original laser power value that is the reference value is performed. Can be done.

FIG. 9 shows another configuration example of the LPC of the present embodiment. LPC31A shown in this figure
In, the input focus error signal FE is output to the comparator block 65 via the filter 61 and the absolute / limiter 62. The filter 61 and the absolute / limiter 62 may have the same configuration as the filter 41 and the absolute / limiter 42 shown in FIG. Here, the fcs offset level set in the offset register 63 for the absolute / limiter 62 is input via the D / A converter 64, and the V
The ref offset is realized.

The comparator block 65 includes comparators 71, 72, to which the focus error signal FE input from the absolute / limiter 62 is input in parallel.
73, 74, and 75 are provided at the preceding stage. These comparators 71, 72, 73, 74, and 75 have different thresholds (Vref1, 2, 3, 4, and 5), respectively, and the result of comparison with the thresholds is input to the register / selector circuit 76. . In other words, with this configuration,
The level of the focus error signal FE input from the absolute / limiter 62 is detected stepwise. In this case, the comparators 71, 72, 7
By providing 5, 3, 74, and 75, six levels of detection can be performed in accordance with the defocus amount, including a state corresponding to just focus. The detection result is output from the register / selector circuit 76 to the gate enabler 77.

The gate enabler 77 here is also
Since a configuration similar to that of the gate enabler 44 shown in FIG. 8 may be employed, the description thereof will be omitted. Actually, in the circuit shown in FIG.
Are transmitted to the required functional circuit unit via the register bus (for example, an enable signal / disab input to the gate enabler 44).
le signal, etc.), but illustration here is omitted.

Then, the gate enabler 77
In the case of the le mode, the input detection information of the level of the focus error signal FE is output as a control signal to the selector 67.

The values set in the registers 66 a to 66 e of the laser power register 66 are input to the selector 67. The values set in the registers 66a to 66e are respectively 5%, 4%, 3%, and 2% with respect to the original laser power value which is the currently set reference value.
%, 1%, and 0%. In the selector 67, the registers 66a to 66e are controlled according to the control signal output from the gate enabler 77.
Of these, the correction laser power value set in the required register is selected, and the laser drive signal S-LD is output to the APC 32 via the D / A converter 68.

The gate enabler 77 is disab
If the mode is the le mode, the corrected laser power value given the 0% increase set in the register 66e (that is, the laser power value as a reference value without correction)
Is output.

In this configuration, when compared with the configuration shown in FIG. 8, the laser power can be corrected only stepwise instead of linearly. However, in practice, for example, the configuration shown in FIG. Detection by the number of steps is sufficient. Further, in the case of the configuration shown in FIG.
In some cases, the need for the GA may cause a gain linearity or offset, which may cause the correction amount to be inaccurate. However, in the configuration shown in FIG. 9, the focus error signal FE Since the correction values set in the registers 66a to 66e are used as digital values based on the defocus amounts detected stepwise based on the correction amount, the correction amounts caused by the VGA operation as described above are used. Can be eliminated. Further, the circuit configuration shown in FIG. 9 can be obtained more simply than the configuration shown in FIG. Although the configuration shown in FIG. 9 employs a configuration in which the defocus amount can be detected and the laser power value can be corrected in six stages, the number of stages may be changed according to actual use conditions and the like. Things.

The present invention is not limited to the configuration of the above embodiment. For example, the disk drive device according to the above embodiment has a configuration in which the MO disk and the MSR disk can be recorded and reproduced with compatibility, but the present invention is not limited to this. A configuration capable of recording or reproduction may be employed.

[0084]

As described above, according to the present invention, the original laser power value, which is the reference value, is corrected based on the defocus amount obtained from the focus error signal. By canceling the apparent decrease in the laser power, it is possible to irradiate the signal surface with laser light with a substantially constant appropriate power. Thus, appropriate data recording (including erasing) and reproduction can be performed regardless of defocus. With such a configuration, for example, recording or reproduction is performed on a disk having a condition that a margin of an appropriate laser power is small, such as a disk with a high recording density or an MSR disk that requires a high laser power during reproduction. It is particularly effective in such cases.

As a configuration for correcting the laser power value, when a correction value is obtained from the detected defocus amount and is added to the laser power reference value, the correction value is adjusted according to the defocus amount. Correction can be performed linearly (steplessly). In the case where a required correction laser power value is selected from the correction laser power values set stepwise based on the detected defocus amount, for example, the correction laser power value is set stepwise. It is possible to actually hold the corrected laser power value as a digital value in a register or the like.In this case, it becomes possible to avoid unstable operation due to analog signal processing, and However, it is possible to obtain a reliable correction value.

In detecting the amount of defocus, a limiter is applied to the focus error signal, and the defocus amount is obtained based on the limited focus error signal. , It is possible to detect the defocus amount whose influence has been canceled. If the correction is performed following the defocus obtained by shock or vibration, the correction amount may actually be excessive, which may hinder proper data recording and reproduction. By using the limiter as described above, such inconveniences can be avoided.

The laser power reference value is, for example, a laser power set in advance so as to be suitable for recording / reproduction operations such as recording, reproduction, and erasing. The laser power correction value is determined based on the laser power reference value. Is made variable, it is possible to obtain a value suitable for the recording / reproducing operation as the laser power correction value.

Further, a valid instruction signal / invalid instruction signal (en
an operation of correcting a laser power reference value based on an enable signal and a disable signal to set a laser power value, and an operation of setting an uncorrected laser power reference value as a laser power value without performing the correction. , Or an external gate signal (read ga) corresponding to a recording or reproducing operation.
The above-described switching of the laser power value setting operation is performed according to the presence / absence of the input of the te signal / writegate signal). For example, a focus error for writing data to a recording medium or a focus servo control is performed. If the corrected laser power value, such as bias adjustment for the signal or focus pull-in control, would cause malfunction or erroneous detection, the laser power reference value is operated so as not to be corrected, Laser emission based on the laser power reference value can be performed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a disk according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an MSR in the disk of the embodiment.

FIG. 3 is a block diagram illustrating a configuration of a disk drive device according to the present embodiment.

FIG. 4 is an explanatory diagram showing a structural example of a photodetector provided in the disk drive device of the present embodiment.

FIG. 5 is an explanatory diagram illustrating a focus error signal and a generation process thereof.

FIG. 6 is an explanatory diagram for explaining a clock generation operation based on a clock mark on a disk.

FIG. 7 is a block diagram illustrating an internal configuration of a laser driver 6 according to the present embodiment.

FIG. 8 is a block diagram illustrating an example of an internal configuration of an LPC according to the present embodiment.

FIG. 9 is a block diagram illustrating another example of the internal configuration of the LPC according to the embodiment.

FIG. 10 is an explanatory diagram showing a relationship between a laser power and a bit error rate.

FIG. 11 is an explanatory diagram showing a relationship between a defocus amount and a bit error rate under a condition that a laser power is fixed as an optimum value.

[Explanation of symbols]

1 disk, 2 spindle motor, 3 optical pickup, 4 bias magnet, 3 optical pickup, 5 IV conversion matrix circuit, 6 laser driver, 7 magnetic head driver, 11 PLL circuit, 12
Address decoder, 18 encode / PRML decode circuit, 19 CPU, 20 I / F control circuit, 22 MPEG decoder, 23 host computer, 31, 31A APC, 41, 61 filter, 4
2,62 absolute / limiter, 43 VGA,
44,77 Gate enabler, 45 register, 5
0, 51, 67 selector, 52 adder, 61 filter, 65 comparator block, 66 laser power register, 66a-66e register, 76 register / selector circuit, 77 gate enabler

Claims (9)

[Claims] 1. A laser power control device for controlling a laser power of a laser beam irradiated to a recording medium with an objective lens as an output end for recording or reproduction, a focus error indicating a focus state of the laser beam. A defocus amount detecting means for detecting a defocus amount which is a deviation amount from a just focus state based on a signal; and a laser power using at least a predetermined laser power reference value set according to a recording / reproducing state. A laser power setting unit capable of setting a value, and a laser light output unit that outputs the laser light based on the laser power value set by the laser power setting unit. The laser power base based on the defocus amount detected by the defocus amount detection means Setting the laser power value by correcting the value, the laser power control apparatus characterized by being configured to be able to execute the laser power value correction settings. 2. The laser power setting means obtains a correction value corresponding to the defocus amount detected by the defocus amount detection means as the laser power value correction setting, and sets the correction value to the laser power reference value. The laser power control device according to claim 1, wherein the laser power value is set by adding the laser power value to the value. 3. The laser power setting means holds a plurality of corrected laser power values which are set by giving different predetermined correction amounts to the laser power reference value, respectively. A required correction laser power value is selected from among the plurality of correction laser power values based on the defocus amount detected by the defocus amount detection means, and this selected correction laser power value is The laser power control device according to claim 1, wherein the power value is set as a power value. 4. The defocus amount detection means includes limiter means for limiting the focus error signal at a required level, and the defocus amount is determined based on the focus error signal limited by the limiter means. The laser power control device according to claim 1, wherein the laser power control device is configured to obtain the following. 5. A laser power correction value varying means capable of varying an increase / decrease rate of the laser power correction value based on a laser power reference value currently set by the laser power setting means. The laser power control device according to claim 1, wherein: 6. The laser power setting means is capable of inputting a validity instruction signal / invalidity instruction signal for instructing validity / invalidity of a required operation in accordance with a recording or reproduction situation, and obtaining the validity instruction signal. When the laser power value correction setting is executed, the laser power value correction setting is executed. When the invalidation instruction signal is obtained, the laser power value non-correction setting for setting the laser power value based on the laser power reference value not corrected by the laser power correction value is performed. 2. The laser power control device according to claim 1, wherein the laser power control device is configured to perform the following. 7. When the invalidation instruction signal is obtained, at least one of data writing to a recording medium, bias adjustment for a focus error signal for focus servo control, or focus pull-in control is executed. 7. The laser power control device according to claim 6, wherein the operation is performed. 8. The laser power setting means is capable of inputting an external gate signal indicating an operation state in which a recording operation or a reproducing operation is enabled, and when the external gate signal is input, the laser power setting means outputs the laser power. When a value correction setting is executed and an external gate signal is not input, a laser power value non-correction setting for setting a laser power value based on a laser power reference value not corrected by the laser power correction value is executed. The laser power control device according to claim 1, wherein: 9. When the invalid instruction signal is obtained, at least one of data writing to a recording medium, bias adjustment for a focus error signal for focus servo control, or focus pull-in control is executed. The laser power control device according to claim 8, wherein the operation is performed.