JP2002109745A - Optical disk apparatus and method for of adjusting reproducing power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk apparatus and a method of adjusting reproducing power, in which power margin of a laser beam can be obtained with clear both ends. SOLUTION: In the optical disk apparatus 200, an optical pickup 102 detects a magneto-optical signal from a magneto-optical recording medium 100 with a variety of power of the laser beam. The magneto-optical signal is processed with a reproduction process using reproduction circuits (BPF106-BCH decoder 112). A controller 114 determines the power of laser beam in which an error rate becomes minimum as provisional optimum power, on the basis of error rates inputted from the BHC decoder 112. The controller 114 varies the power again around the provisional optimum power, and determines a suitable range for laser beam power and a central value of the suitable range as the optimum power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for reproducing a signal by determining an optimum power of a laser beam when reproducing a signal from an optical disk, and a method of adjusting a reproduction power.

[0002]

2. Description of the Related Art Optical disks, such as magneto-optical disks and phase change disks, are formed with grooves and lands alternately in the radial direction (radial direction), and are recorded at a high density by recording signals on both the grooves and lands. Is being planned.

[0003] Signals having various signal lengths are recorded and / or reproduced on the optical disc. For example, recently, AS-MO (Advanced Storage) which is one of standardized magneto-optical disks has been developed.
In the Magneto Optical Disk standard, a magneto-optical disk is irradiated with a laser beam having a predetermined intensity, each magnetic domain recorded on a recording layer of the magneto-optical disk is transferred to a reproducing layer, and the magnetic domain transferred to the reproducing layer is converted into a laser beam. This is done by detecting That is, a magnetic material that is an in-plane magnetic film at room temperature and changes to a perpendicular magnetic film at a predetermined temperature or higher is used for the reproducing layer. Then, the power of the laser light applied to the reproducing layer is controlled so that the area smaller than the spot diameter of the laser light changes from the in-plane magnetization film to the perpendicular magnetization film. In the area where the in-plane magnetic film changes to the perpendicular magnetic film, the magnetic domain of the recording layer is transferred, and the transferred magnetic domain is detected by the laser beam.

On the other hand, in a semiconductor laser that emits laser light, the power of the emitted laser light changes depending on the ambient temperature. Then, the power of the laser beam in the reproducing layer also changes, and the region where the in-plane magnetic film changes to the perpendicular magnetic film also changes. The power margin of the laser light applied to the magneto-optical disk is generally set to be wide so that a constant reproduction characteristic can be obtained even when the power of the laser light fluctuates. That is, the error rate of the reproduced signal when the power of the laser light is changed is detected, and the error rate is hardly changed with respect to the power of the laser light in an area where the error rate is lower than a predetermined reference value. Is the power margin of the laser beam.

[0005]

However, when the error rate of the reproduced signal when the power of the laser light is sequentially changed from a lower power to a higher power is detected, the error rate is almost equal to the power of the laser light. It changes parabolically. Then, in a region where the error rate is equal to or less than a predetermined reference value, the power of the laser light when the error rate sharply increases becomes unclear, and there is a problem that the power margin of the laser light cannot be determined accurately. This problem is particularly noticeable in a low power region.

Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide an optical disk apparatus and a reproducing power adjusting method capable of obtaining a clear laser beam power margin at both ends. It is to be.

[0007]

SUMMARY OF THE INVENTION An optical disk apparatus according to the present invention provides a signal from an optical disk having a track on which a fine clock mark as a reference for generating a reproduction clock for reproducing a signal is formed at a constant period. An optical head for reproducing laser light, focusing and irradiating a laser beam onto an optical disk by an objective lens and detecting the reflected light, and a fine clock mark signal detected by the optical head due to the fine clock mark. A clock generation circuit for generating a reproduction clock, a reproduction processing circuit for performing reproduction processing of a magneto-optical signal detected from the optical disk by the optical head in synchronization with the reproduction clock, and determining a suitable range of laser light power. A control circuit for setting the power of the laser beam within the determined preferred range. Is input from the reproduction processing circuit the error rate of the reproduction signal when the intensity of the laser light is changed, determines the power of the laser light at which the error rate is minimized as the temporary optimum power, and centers on the temporary optimum power. The preferred range is determined based on the error rate of the reproduced signal when the power of the laser beam is changed.

In the optical disk device according to the present invention, the power at which the error rate of the reproduction signal when the power of the laser light is changed is minimized is determined as the temporary optimum power. Then, the relationship between the error rate of the reproduction signal and the power of the laser light is determined again around the temporary optimum power, and a suitable range of the power of the laser light is determined.

Therefore, according to the present invention, a suitable range can be clearly determined even in a region where the power of the laser beam is low. As a result, a suitable range can be set wider.

Preferably, the control circuit of the optical disk device further determines a center value of a suitable range as the optimum power, and sets the center value of the laser light at the optimum power to set the power of the laser light at the optimum power. And a signal is reproduced from the optical disk using the determined optimum power.

Therefore, according to the present invention, a reproduced signal having a low error rate can be obtained. Also, even if the power deviates from the optimum power of the laser beam, the signal can be reproduced at a constant error rate within a suitable range.

Preferably, the control circuit of the optical disk device detects a minimum error rate from a plurality of error rates lower than a predetermined reference value, and determines the power of the laser beam realizing the error rate as a temporary optimum power. I do.

An error rate of a reproduced signal is detected for each power of the laser beam. Then, an error rate lower than a predetermined reference value is selected from among the error rates for the changed laser beam power, and the power that realizes the minimum error rate among the selected error rates is the temporary optimum power. Is determined.

Therefore, according to the present invention, the power of the laser beam realizing the error rate lower than the predetermined reference value is determined as the tentative optimum power, so that the reproduction signal having the error rate lower than the predetermined reference value is obtained. Can be obtained.

Preferably, the control circuit of the optical disk device detects the power of the first and second laser beams at which the error rate of the reproduction signal matches a predetermined reference value, and compares the power of the first laser beam with the second laser beam. The average value with the power of the laser light is determined as a temporary optimum power.

When the error rate of the reproduction signal is detected by changing the power of the laser light, a parabolic relational diagram is generally obtained in which the error rate has a minimum value as the power of the laser light increases. . Then, there are two laser beam powers whose error rates match the predetermined reference value, and the average value of the two is determined as the temporary optimum power.

Therefore, according to the present invention, the provisional optimum power can be determined by a simple method.

A method for adjusting a reproduction power according to the present invention is a method for adjusting a reproduction power of a laser beam in an optical disc apparatus for reproducing a signal from an optical disc by using a laser beam. , A second step of detecting an error rate of the reproduced signal reproduced in the first step, and a minimum error rate detected from the error rate detected in the second step. A third step of determining the power of the laser beam for realizing the error rate as the temporary optimum power; and a fourth step of reproducing the signal from the optical disk by changing the power of the laser beam around the temporary optimum power. Determining a suitable range based on the error rate of the reproduced signal reproduced in the step and the fourth step, and calculating a center value of the suitable range. And a fifth step of determining a suitable power.

In the reproduction power adjusting method according to the present invention, the power at which the error rate of the reproduction signal when the power of the laser light is changed is minimized is determined as the temporary optimum power. Then, the relationship between the error rate of the reproduction signal and the power of the laser light is determined again around the temporary optimum power, and a suitable range of the power of the laser light is determined. When a suitable range is determined, the center value is determined as the optimum power of the laser beam.

Therefore, according to the present invention, a suitable range can be clearly determined even in a region where the power of the laser beam is low. As a result, the optimum power can be determined accurately.

Preferably, in the third step, among the error rates lower than a predetermined reference value, the power of the laser beam that realizes the minimum error rate is determined as the temporary optimum power.

Among the error rates of the reproduced signal detected for each power of the laser light, the minimum error rate is detected from among error rates lower than a predetermined reference value. Then, the power that realizes the detected minimum error rate is determined as the temporary optimum power.

Therefore, according to the present invention, the power of the laser beam is determined so that a reproduced signal having an error rate lower than a predetermined reference value is detected.

Preferably, in the third step, the powers of the first and second laser beams at which the error rate of the reproduced signal reproduced in the first step matches a predetermined reference value are detected. The average value of the power of the laser light and the power of the second laser light is determined as the temporary optimum power.

When the error rate of the reproduced signal is detected by changing the power of the laser light, a parabolic relational diagram is generally obtained in which the error rate has a minimum value as the power of the laser light increases. . Then, there are two laser beam powers whose error rates match the predetermined reference value, and the average value of the two is determined as the temporary optimum power.

Therefore, according to the present invention, the provisional optimum power can be determined by a simple method.

Preferably, in the first step, a signal is reproduced in synchronization with a reference clock generated by detecting a clock mark formed on the optical disk at a constant period.

A reproduction signal for adjusting the power of the laser light is detected in synchronization with a reference clock generated based on the fine clock mark detected from the optical disk.

Therefore, according to the present invention, the preferred range of the laser beam can be determined based on the reproduced signal detected accurately.
And the optimal power.

[0030]

Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions have the same reference characters allotted, and description thereof will not be repeated.

With reference to FIG. 1, a description will be given of a magneto-optical recording medium on which data is recorded and / or reproduced by the optical disc apparatus according to the present invention. Magneto-optical recording medium 100
, Frames (Frames) as recording units are arranged at equal intervals, and each frame is composed of 39 segments (Segments) S0, S1, S2,..., S38.

The magneto-optical recording medium 100 has a planar structure in which grooves 1 and lands 2 are alternately formed in the radial direction, and the grooves 1 and lands 2 are arranged in a spiral or concentric manner. And the length of each segment is 53
2DCB (Data Channel Bit), and a fine clock mark (FCM: Fine Clock Mark) 3 indicating phase information of a clock for recording and reproducing data is formed at the beginning of each segment. The fine clock mark 3 is formed by providing lands of a fixed length at regular intervals on the groove 1 and providing grooves of a constant length at regular intervals on the lands 2. In the segment S0, which is the head of the frame, the address information (A) indicating the address on the magneto-optical recording medium 100 follows the fine clock mark 3.
address is preformatted by the wobbles 4 to 9 when the magneto-optical recording medium 100 is manufactured.

Wobbles 4 and 5, wobble 6 and wobble 7, and wobble 8 and wobble 9 are formed on opposite walls of groove 1 and record the same address information. Such a recording method of address information is referred to as a one-sided staggered method, and a tilt or the like occurs in the magneto-optical recording medium 100 by employing the one-sided staggered method,
Even when the laser beam deviates from the center of the groove 1 or the land 2, the address information can be accurately detected.

The area where the address information is recorded and the area where the fine clock mark 3 is formed are not used as areas for recording user data. Segment S
n is the fine clock mark 3 and the user data Use
r Data n-1.

Referring to FIG. 2, a detailed configuration of the segment will be described. Each segment S constituting the frame
0, S1, S2,..., S38, the segment S0 is an address segment preformatted on the magneto-optical recording medium 100, and the segments S1 to S38 are data segments secured as user data recording areas. is there. Segment S0 is 12DCB
The segment S is composed of a fine clock mark area FCM of the
1 is a 12DCB fine clock mark area FCM
, 4DCB Pre-Write, 512DCB Data, and 4DCB Post-Write.

Pre-Write indicates that data is to be written out. For example, the predetermined pattern "001"
The Post-Write indicates the end of the data. For example, the Post-Write indicates a predetermined pattern “1”.
100 ".

The user data area of the segment S1 is provided with a header (Header) which is a fixed pattern for performing data position confirmation during reproduction, position compensation of a reproduction clock, adjustment of laser power, and the like. The fixed pattern to be recorded in the header is a pattern in which a DC component is suppressed. For example, a pattern in which a predetermined number of 2T domains are formed at intervals of 2T and a pattern in which a predetermined number of 8T domains are formed at intervals of 8T are recorded. You.

Then, phase compensation is performed by adjusting the sampling timing of the analog signal obtained by reproducing the 2T domain so as to match the phase of the clock used for data recording and reproduction, thereby performing the 2T domain and the 2T domain. The 8T domain is reproduced, and the laser power is adjusted so that the ratio of the 2T domain reproduced signal strength to the 8T domain reproduced signal strength becomes 50% or more. Also, by confirming whether or not the position of the digital signal obtained by reproducing the 8T domain and binarizing the reproduced signal matches the position of the digital signal of the 8T domain predicted in advance, the position of the data at the time of reproduction can be confirmed. Do. Further, each pattern of Pre-Write, Post-Write, and Header is recorded continuously with the user data when recording the user data.

The segments S2 to S38 are composed of a 12DCB fine clock mark area FCM and a 4DCB Pr
e-Write, 512DCB Data, 4DC
B-Post-Write.

The preformatted area such as the fine clock mark FCM and the address Address is called a "preformatted area".

Referring to FIG. 3, an optical disk device according to the present invention will be described. The optical disc device 200 includes a spindle motor 101, an optical pickup 102, a fine clock mark detection circuit (FCM detection circuit) 103
, A PLL circuit 104, an address detection circuit 105,
BPF 106, AD converter 107, waveform equalization circuit 1
08, a Viterbi decoding circuit 109, an unformat circuit 110, a data demodulation circuit 111, a BCH decoder 112, a header detection circuit 113, and a controller 11
4, a timing generation circuit 115, a BCH encoder 116, a data modulation circuit 117, a format circuit 126, a magnetic head drive circuit 123, a laser drive circuit 124, and a magnetic head 125. The format circuit 126 includes a pattern generation circuit 119 and a selector 120.

The spindle motor 101 rotates the magneto-optical recording medium 100 at a predetermined rotation speed. The optical pickup 102 irradiates the magneto-optical recording medium 100 with a laser beam,
The reflected light is detected. The FCM detection circuit 103 detects that the optical pickup 102 detects the fine clock mark detection signal FCMT indicating the position of the fine clock mark 3 on the magneto-optical recording medium 100, and outputs the detected fine clock mark detection signal FCMT to the PLL circuit 104 and the timing. Output to the generation circuit 115. Also, the PLL circuit 104 generates a clock CK based on the fine clock mark detection signal FCMT output from the FCM detection circuit 103, and uses the generated clock CK with the address detection circuit 105, the AD converter 107, and the waveform equalization. Circuit 1
08, Viterbi decoding circuit 109, unformat circuit 1
10, the data demodulation circuit 111, the controller 114, the timing generation circuit 115, the data modulation circuit 117, and the pattern generation circuit 119 of the format circuit 126.

In the address detection circuit 105, the optical pickup 102 detects that the segment S of the magneto-optical recording medium 100
From 0, the address signal AD detected by the radial push-pull method is input, the address signal AD is detected in synchronization with the clock CK input from the PLL circuit 104, and the address detection signal ADF indicating that the address signal AD has been detected. At the final position of the address signal. The detected address signal AD is sent to the controller 114.
And outputs the generated address detection signal ADF to the header detection circuit 113 and the timing generation circuit 115.

The BPF 106 is a magneto-optical recording medium 1
The high and low frequencies of the reproduction signal RF reproduced from 00 are removed. The AD converter 107 converts the reproduction signal RF from an analog signal to a digital signal in synchronization with the clock CK from the PLL circuit 104.

The waveform equalizing circuit 108 is a PLL circuit 104
PR (1, 1) waveform equalization is performed on the reproduced signal RF converted into a digital signal in synchronization with the clock CK from the CPU.

The Viterbi decoding circuit 109 includes a PLL circuit 10
The reproduction signal RF is converted from multi-valued data to binary data in synchronization with the clock CK from Step 4, and the converted reproduction signal RF is output to the unformat circuit 110 and the header detection circuit 113.

The unformat circuit 110 pre-writes (Pre-Write) and post-writes (Post-Write) recorded in the user data area of the magneto-optical recording medium 100 based on the timing signal input from the header detection circuit 113. , And the header (Heade
r) is removed. Then, the unformat circuit 110
Outputs the removed header to the controller 114.

The data demodulation circuit 111 is a PLL circuit 10
In response to the clock CK from Step 4, an unformatted reproduction signal RF is input, and demodulation is performed to release digital modulation performed during recording.

The BCH decoder 112 corrects the error of the demodulated reproduced signal, outputs the reproduced signal as reproduced data, and outputs the error rate of the reproduced signal, that is, the error rate, to the controller 114. Header detection circuit 113
Detects the position of the header included in the reproduction signal based on the address signal input from the controller 114 and the address detection signal ADF input from the address detection circuit 105, and reproduces the header in synchronization with the clock CK from the PLL circuit 104. Pre-Write from signal
And a header (Header) timing signal. Then, it outputs the generated header (Header) timing signal to the unformat circuit 110 and the data demodulation circuit 111.

The controller 114 receives the address signal AD detected by the address detection circuit 105, controls a servo mechanism (not shown) based on the address signal AD, and causes the optical pickup 102 to access a desired position. When adjusting the reproduction power, the controller 114 controls the laser drive circuit 124 via the timing generation circuit 115 to change the power of the laser light emitted from the semiconductor laser (not shown). Further, when the error rate of the reproduction signal is input from the BCH decoder 112, the controller 114 determines a preferable range and an optimum power of the reproduction power by a method described later, and the controller 114 outputs the optimum range from the semiconductor laser via the timing generation circuit 115. The laser driving circuit 124 is controlled so that the power of the laser beam becomes the optimum power.

The timing generation circuit 115 controls the FCM detection circuit 103 based on the control from the controller 114.
Fine clock mark detection signal FCM input from
T and the timing signal SS based on the address detection signal ADF input from the address detection circuit 105, in synchronization with the clock CK input from the PLL circuit 104.
And outputs the generated timing signal SS to the pattern generation circuit 119 and the selector circuit 120 of the format circuit 126, the magnetic head drive circuit 123, and the laser drive circuit 124.

The BCH encoder 116 adds an error correction code to recording data. The data modulation circuit 117 modulates the recording data into a predetermined format. Format circuit 1
Reference numeral 26 denotes a pre-write (Pre-Write), a header (Header), and a recording data from the data modulation circuit 117, which are synchronized with the clock CK from the PLL circuit 104 and based on the timing signal SS from the timing generation circuit 115. And post light (Post-W
write) to format the recording data to match the user data area. Then, the format circuit 126 selectively outputs the formatted recording data and the pattern data to be recorded in the preformat area to the magnetic head drive circuit 123 based on the timing signal SS from the timing generation circuit 115.

The pattern generation circuit 119 outputs from the PLL circuit 104 pattern data to be recorded in the pre-format area and pattern data as pre-write (Pre-Write), header (Header), and post-write (Post-Write). Clock (C
K), and outputs the generated data pattern to the selector circuit 120.

The selector circuit 120 selects the recording data from the data modulation circuit 117 and the pattern data from the pattern generation circuit 119 based on the timing signal SS from the timing generation circuit 115, and sends the selected data to the magnetic head drive circuit 123. Output.

The magnetic head drive circuit 123 drives the magnetic head 125 in synchronization with each timing of the timing signal SS from the timing generation circuit 115 and based on the output from the format circuit 126.

The laser drive circuit 124 drives a semiconductor laser (not shown) in the optical pickup 102 based on the timing signal SS from the timing generation circuit 115.

The magnetic head 125 is driven by a magnetic head driving circuit 123 and applies a magnetic field modulated by recording data or a data pattern to the magneto-optical recording medium 10.
Apply to 0. The memory 128 stores 8T, as described later.
The reproduction condition (power of the laser beam, equalizer coefficient, and phase of the clock CK) at which the amplitude ratio between the signal of (1) and the signal of 2T becomes larger than 50% is stored in correspondence with the plurality of amplitude ratios.

Referring to FIG. 4, address signal AD and fine clock mark signal F from magneto-optical recording medium 100 are provided.
The detection of the CM and the magneto-optical signal RF will be described.
The area 10 and the area 30 constitute a preformat area that is preformatted when the magneto-optical recording medium 100 is manufactured. In the area 10, wobbles 4 to 7 and a fine clock mark 3 are formed. In the area 30, the fine clock mark 3 is formed. The area 20 constitutes a user data area, in which user data is recorded.

The photodetector 1020 in the optical pickup 102 for irradiating the magneto-optical recording medium 100 with a laser beam and detecting its reflected light has six detection areas 1020A and 1020A.
0B, 1020C, 1020D, 1020E, 1020
F. Area A1020A and area B1020B, area C1020C and area D1020D, and area E10
The area 20E and the area F1020F are arranged in the tangential direction DR2 of the magneto-optical recording medium 100, and the area A1020
A and the area D1020D, and the area B1020B and the area C1020C are in the radial direction D of the magneto-optical recording medium 100.
It is located at R1.

Areas A1020A, B1020B, C1020C, and D1020D detect reflected light of laser light LB applied to magneto-optical recording medium 100 in areas A, B, C, and D, respectively. I do. Further, a region E1020E and a region F102
0F transmits the laser light reflected by the entire laser light LB in the A region, the B region, the C region, and the D region in two directions having different polarization planes by a Wollaston prism (not shown) of the optical pickup 102. The diffracted laser light is detected.

The reproduction signal RF of the magneto-optical signal recorded in the area 20 which is the user data area includes the laser light intensity [E] detected in the area E1020E of the photodetector 1020 and the laser light intensity detected in the area F1020F. It is detected by calculating the difference from [F]. That is, the circuit 4
The zero differentiator 400 calculates a difference between the laser light intensity [E] detected in the region E1020E and the laser light intensity [F] detected in the region F1020F, and obtains a reproduction signal RF =
[E]-[F] is output.

Area 10 Constituting Preformat Area
Information AD recorded by wobbles 4 to 7 of
Is detected by the radial push-pull method, and the laser beam intensity [A] detected in the area A1020A
And the sum of the laser beam intensity [C] detected in the region C1020C and the laser beam intensity [D] detected in the region D1020D is subtracted from the sum of the laser beam intensity [B] detected in the region B1020B. Is detected. That is, the address information AD is added to the adder 5 forming the circuit 50.
00, 501 and a subtractor 502. The adder 500 outputs [A + B] obtained by adding the laser light intensity [A] detected in the region A 1020A and the laser light intensity [B] detected in the region B 1020B. Adder 5
01 outputs [C + D] obtained by adding the laser beam intensity [C] detected in the region C1020C and the laser beam intensity [D] detected in the region D1020D. Then, the subtractor 502 subtracts the output [C + D] of the adder 501 from the output [A + B] of the adder 500, and outputs a reproduced signal AD = [A + B] − [C + D] of the address information.

The fine clock mark FCM in the area 30 constituting the preformat area is detected by the tangential push-pull method, and the area A1020 is detected.
Laser light intensity [A] detected at A and area D1020D
From the sum with the laser beam intensity [D] detected in the area B10
Laser light intensity [B] detected at 20B and area C102
It is detected as a value obtained by subtracting the sum with the laser light intensity [C] detected at 0C. That is, the fine clock mark FCM is added to the adders 503 and 504 constituting the circuit 50.
And a subtractor 505. Adder 503
Is the laser beam intensity [A] detected in the area A1020A.
And [A + D] obtained by adding the laser beam intensity [D] detected in the area D1020D. The adder 504 outputs [B + C] obtained by adding the laser light intensity [B] detected in the region B1020B and the laser light intensity [C] detected in the region C1020C. And the subtractor 505
The output [B + C] of the adder 504 is subtracted from the output [A + D] of the adder 503 to output a fine clock mark reproduction signal FCM = [A + D] − [B + C].

Referring to FIG. 5, the configuration of PLL circuit 104 forming optical disk device 200 shown in FIG. 3 will be described. The PLL circuit 104 includes a phase comparison circuit 1041 and L
PF 1042 and voltage controlled oscillator (VCO) 1043
And a 1/532 frequency divider 1044. 1/532
The frequency divider 1044 includes a voltage controlled oscillator (VCO) 1043
The clock (CK) output from is divided by 1/532. The phase comparator 1041 is a 1/532 frequency divider 1044
Is compared with the phase of the fine clock mark detection signal FCMT, and an error voltage corresponding to the phase difference is generated. Therefore, this PL
The L circuit 104 outputs the fine clock mark detection signal FC
A clock CK synchronized with MT and having a period of 1/532 of the fine clock mark detection signal FCMT is generated.

Referring to FIG. 6, detection of fine clock mark FCM and generation of clock CK will be described. The light detection unit 1020 of the optical pickup 102 detects the fine clock mark signal FCM by the tangential push-pull method as described with reference to FIG.
M is output to the FCM detection circuit 103. The FCM detection circuit 103 receives the input fine clock mark signal FC
M based on the fine clock mark detection signal FCMT
Generate That is, in the FCM detection circuit 103, the fine clock mark signal FCM is compared at a predetermined level and converted into a signal FCMC. Then, the signal FCMC is inverted to the signal / FCMC. Thereafter, the rising edge is synchronized with the position of the point P where the polarity of the fine clock mark signal FCM switches, and 6
A detection window signal DEWIN having an amplitude width of DCB is generated, and a logical product of signal / FCMC and detection window signal DEWIN is calculated to generate signal FCMP. Then,
A fine clock mark detection signal FCMT having an amplitude width of 1 DCB synchronized with the rise of the signal FCMP is generated.

The fine clock mark signal FCM shown in FIG. 6 has been described as the fine clock mark signal detected when the laser beam travels in the groove 1 of the magneto-optical recording medium 100. The fine clock mark signal detected when the laser beam travels on the land 2 only changes its polarity, and the position of the point P does not change. Therefore, even when the laser beam travels on the land 2, the signal FCMP and the fine clock mark detection signal FCMT can be similarly generated.

The FCM detection circuit 103 outputs the detected fine clock mark detection signal FCMT to the PLL circuit 104.
Output to The PLL circuit 104 outputs the fine clock mark detection signal FCM as described with reference to FIG.
T and the fine clock mark detection signal F
A clock CK obtained by dividing the CMT by 1/532 is generated.

Referring to FIG. 7, address detection circuit 105
The detection of the address information and the generation of the address detection signal will be described. The optical pickup 102 detects the address signal AD recorded by wobble by the radial push-pull method as described with reference to FIG. 4, and the address signal AD is input to the address detection circuit 105. The address detection circuit 105 outputs the address signal AD
Is generated, and a binary signal ADD is generated.
The address information ADIF is detected based on the DD. At the same time, the address detection circuit 105 outputs the binarized signal AD
An address detection signal ADF indicating the final position F of the address signal is generated in synchronization with the clock CK from the PLL circuit 104 based on D and the address information ADIF. The address detection signal ADF is generated by determining a fixed length T including the final position F of the address information ADIF. That is, the last position F of the address signal is calculated from the component of the clock CK synchronized with the first position of the binarized signal ADD.
Are counted up to the component of the clock CK synchronized with the clock CK. Then, the count value at the final position F is set to K, and a fixed length T is set between the count value K−m and the count value K + m, which are shifted forward and backward by m counts around the count value K.
The address detection signal ADF is generated such that a pulse component having

Referring to FIGS. 8 and 9, a method of adjusting the power of the laser beam will be described. By changing the power of the laser beam within a predetermined range, the magneto-optical recording medium 100
To reproduce the signal from Then, the error rate of the reproduced signal is detected. In this case, the power of the laser light is increased in the range of 2.2 to 3.4 mW for each 0.04 mW.

FIG. 8 shows the relationship between the error rate and the power of the laser beam, which shows a substantially parabolic relationship. Based on the curve shown in FIG. 8, in the region where the error rate is 10 ⁻⁴ or less, the power of the laser beam when the minimum error rate ERmin is realized is determined as the temporary optimum power Prkopt. In this case, the power of the laser beam when the error rate is equal to 10 ^-4 is Pr
k1 and Prk2, and the average value of Prk1 and Prk2 may be determined as the tentative optimum power Prkopt.

When the provisional optimum power Prkopt is determined, the provisional optimum power Prkopt is centered on the provisional optimum power Prkopt again.
The signal is reproduced from the magneto-optical recording medium 100 by changing the power of the laser light. FIG. 9 shows the relationship between the error rate of the reproduced signal and the power of the laser beam. The error rate hardly changes when the power of the laser beam is between Pr3 and Pr4. Therefore,
The average value of the power Pr3 of the laser light and the power Pr4 of the laser light is determined as the optimum power Propt. The powers Pr3 and Pr4 of the laser light are powers at which the error rate starts to increase rapidly. Therefore,
A suitable range of the power of the laser light is between the powers Pr3 and Pr4 of the laser light. Then, the optical pickup 10
Even if the power of the laser beam emitted from the semiconductor laser fluctuates due to a change in the temperature around 2 and the power after the fluctuation falls within the range of Pr3 to Pr4, the minimum error rate in the reproduced signal is reduced. As a result, there is no problem in the signal reproduction characteristics.

As described above, in the relationship between the power of the laser beam and the error rate of the reproduction signal, the wider the range of the power of the laser beam where the error rate of the reproduction signal does not fluctuate is more stable from the magneto-optical recording medium 100. The signal can be reproduced, and the margin of the reproduction power is wide.

Therefore, as described with reference to FIGS. 8 and 9, by using the power adjusting method according to the present invention, the powers Pr3 and Pr4 of the laser beam at which the error rate of the reproduction signal sharply increases are clearly detected. And the margin of the reproduction power can be widened.

Further, the power of the laser beam when the error rate matches 10 ^-4 may be set to Pr1 and Pr2, and the average value of Pr1 and Pr2 may be determined as the optimum power Propt.

As described above, in the present invention, the temporary optimum power is once obtained, and then, based on the error rate of the reproduced signal reproduced by changing the power of the laser beam around the obtained temporary optimum power. Find the optimum power and power margin of the laser beam.

Referring to FIG. 10, a method of adjusting the reproduction power according to the present invention will be described. When the adjustment of the reproduction power is started, the controller 114 of the optical disk device 200 controls the laser drive circuit 124 so that the power of the laser light is changed within a predetermined range to irradiate the magneto-optical recording medium 100. The laser drive circuit 124 controls the optical pickup 1 so as to emit a laser beam whose power has been changed within a predetermined range under the control of the controller 114.
The semiconductor laser (not shown) in 02 is driven. Then, a signal is reproduced from the magneto-optical recording medium 100 by irradiating the laser beam with the changed power (step S1). The reproduced signal is reproduced via a BPF 196, an AD converter 107, a waveform equalizing circuit 108, a Viterbi decoding circuit 108, an unformat circuit 110, a data demodulating circuit 111, and a BCH decoder 112. Then, the BCH decoder 112 outputs the error rate, that is, the error rate of the reproduced signal, to the controller 114. Thereby, the error rate of the reproduced signal is detected (step S2). Thereafter, the provisional optimum power Prkopt is obtained by the method described above.
Is determined (step S3).

When the temporary optimum power Prkopt is obtained, the signal is reproduced by changing the power of the laser beam around the temporary optimum power Prkopt (step S).
4) Based on the error rate of the reproduced signal, a suitable range is determined by the method described above (step S5). Then, the optimum power is determined by the method described above (step S6). Then, the adjustment of the reproduction power ends.

Referring again to FIG. 3, the operation of recording data on magneto-optical recording medium 100 in optical disk device 200 according to the present invention will be described. Magneto-optical recording medium 10
When the optical disk device 200 is mounted on the optical disk device 200, the controller 114 controls a servo mechanism (not shown) so as to rotate the spindle motor 101 at a predetermined number of rotations, and outputs laser light of a predetermined intensity from the optical pickup 102. The laser drive circuit 124 is controlled via the timing generation circuit 115 so as to emit light.

Then, the servo mechanism (not shown)
The spindle motor 101 is rotated at a predetermined rotation speed, and the spindle motor 101 rotates the magneto-optical recording medium 100 at a predetermined rotation speed. Also, the optical pickup 102
Irradiates a laser beam of a predetermined intensity onto the magneto-optical recording medium 100 by an objective lens (not shown) and detects the reflected light. Then, the optical pickup 102 outputs a focus error signal and a tracking error signal to a servo mechanism (not shown), and the servo mechanism outputs a focus servo of the objective lens of the optical pickup 102 based on the focus error signal and the tracking error signal. And turn on the tracking servo.

Thereafter, the optical pickup 102 detects the fine clock mark signal FCM from the magneto-optical recording medium 100 by the tangential push-pull method, and outputs the detected fine clock mark signal FCM to the FCM detection circuit 120. The FCM detection circuit 120 uses the fine clock mark signal FC
M, a fine clock mark detection signal FCMT is detected, and the detected fine clock mark detection signal FCMT is detected.
MT to PLL circuit 104 and timing generation circuit 11
Output to 5 The PLL circuit 104 generates a clock CK based on the fine clock mark detection signal FCMT, and outputs the generated clock CK to the address detection circuit 10.
5. Output to the AD converter 107, the waveform equalizer 108, the Viterbi decoder 109, the unformat circuit 110, the data demodulator 111, the controller 114, the timing generator 115, the data modulator 117, and the format circuit 126.

The address detection circuit 105 is arranged so that the optical pickup 102 is connected to the segment S of the magneto-optical recording medium 100.
From 0, the address signal detected by the radial push-pull method is input, and the address signal AD is detected in synchronization with the clock CK input from the PLL circuit 104.
An address detection signal ADF indicating that the address signal AD has been detected is generated at the last position of the address information. Then, it outputs the detected address signal AD to the controller 114, and outputs the generated address detection signal ADF to the header detection circuit 113 and the timing generation circuit 115.

On the other hand, the BCH encoder 116 adds an error correction code to the recording data,
Is synchronized with the clock CK from the PLL circuit 104.
The recording data from the CH encoder 116 is modulated into a predetermined format. Then, the data modulation circuit 117 outputs the modulated recording data to the format circuit 126.

The timing generation circuit 115 determines the address based on the address information input from the address detection circuit 105.
A timing signal for generating a recording signal to be recorded in the data area of the magneto-optical recording medium 100 is generated. And
The timing generation circuit 115 outputs the generated timing signal to the selector circuit 120, the magnetic head drive circuit 123, and the laser drive circuit 124.

The selector circuit 120 selects a recording signal input from the data modulation circuit 117 based on the timing signal, and outputs it to the magnetic head driving circuit 123. Then, the magnetic head drive circuit 123 drives the magnetic head 125 so as to generate a magnetic field modulated by the recording signal in synchronization with the timing signal. On the other hand, the laser drive circuit 124 drives a semiconductor laser (not shown) in the optical pickup 102 in synchronization with the timing signal, and the optical pickup 102 transmits the laser light to the magneto-optical recording medium 100 by an objective lens (not shown). Is focused and irradiated. And
The magnetic head 125 applies a magnetic field modulated by a recording signal to the magneto-optical recording medium 100. Thus, the recording data is recorded on the magneto-optical recording medium 100.

Next, the operation of reproducing a signal from the magneto-optical recording medium 100 using the optical disk device 200 will be described. The operation until the magneto-optical recording medium 100 is mounted on the optical disk device 200, focus servo and tracking servo of the objective lens are performed, the clock CK is generated, and the address information is detected is the same as the signal recording operation. . The detected address information is input to the controller 114.

Then, the controller 114 moves the optical pickup 102 to the calibration area (not shown) of the magneto-optical recording medium 100 based on the detected address information.
To access. Then, power adjustment of the laser beam is performed according to the flowchart described with reference to FIG. Once the optimal power is determined, the controller 114
Controls the laser drive circuit 124 via the timing generation circuit 115, and the semiconductor laser in the optical pickup 102 emits a laser beam having an optimum power.

After that, focus servo and tracking servo of the objective lens are performed in the same manner as the signal recording operation by the laser beam having the optimum power, the clock CK is generated, and the address information is detected.

The header detection circuit 113 includes the controller 1
14, the position of the header included in the reproduction signal is detected based on the address information AD input from the address signal 14 and the address detection signal ADF input from the address detection circuit 105.
A pre-write (Pre-Write) and a timing signal of a header (Header) are generated from the reproduction signal in synchronization with the clock CK from the LL circuit 104. Then, the generated header (Header) timing signal is transmitted to the unformat circuit 110 and the data demodulation circuit 1.
Output to 11

On the other hand, the optical pickup 102 outputs the detected reproduction signal to the BPF 106, and the BPF 106 cuts the high band and the low band of the reproduction signal. AD converter 1
07 converts the reproduced signal output from the BPF 106 from an analog signal to a digital signal in synchronization with the clock CK from the PLL circuit 104.

The waveform equalization circuit 108 performs PR (1, 1) waveform equalization on the reproduced signal converted into a digital signal in synchronization with the clock CK from the PLL circuit 104. That is, the data before and after the detection signal are equalized so as to cause one-to-one waveform interference.

Thereafter, the Viterbi decoding circuit 109 outputs the PLL
In synchronization with the clock CK from the circuit 104, the reproduced signal subjected to waveform equalization is converted from multi-valued data to binary data, and the converted reproduced signal is output to the unformat circuit 110 and the header detection circuit 113.

Then, the header detection circuit 113 outputs the address information ADIF input from the controller 114.
And the position of the header included in the reproduction signal is detected based on the address detection signal ADF input from the address detection circuit 105, and the pre-write (Pre-Write) and the header ( (Header) timing signal. Then, it outputs the generated header (Header) timing signal to the unformat circuit 110 and the data demodulation circuit 111.

The unformat circuit 110 pre-writes (Pre-Write) and post-writes (Post-Write) recorded in the user data area of the magneto-optical recording medium 100 based on the timing signal input from the header detection circuit 113. , And the header (Heade
r) is removed.

The data demodulation circuit 111 receives the unformatted reproduction signal in synchronization with the clock CK from the PLL circuit 104, and performs demodulation for canceling the digital modulation applied at the time of recording. Then, the BCH decoder 112 corrects the error of the demodulated reproduced signal and outputs it as reproduced data.

In the present invention, a suitable range and an optimum power of the laser beam may be determined for each of the groove and the land.

Further, in the above description, the magneto-optical recording medium has been described as an example. However, the optical disk apparatus and the reproducing power adjusting method according to the present invention are not intended only for the magneto-optical recording medium, It goes without saying that optical discs are also targeted.

According to the embodiment of the present invention, the temporary optimum power of the laser beam at which the error rate of the reproduction signal is minimized is determined, and the power of the laser beam is changed again around the temporary optimum power. Thus, the suitable range and the optimum power of the laser beam in which the error rate of the reproduction signal is reduced are determined, so that the suitable range can be set wide and the optimum power can be determined accurately.

In the present invention, the BPF 106,
The AD converter 107, the waveform equalization circuit 108, the Viterbi decoding circuit 109, the unformat circuit 110, the data demodulation circuit, and the BCH decoder 112 constitute a "reproduction processing circuit".

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description of the embodiments, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[Brief description of the drawings]

FIG. 1 is a plan view showing a magneto-optical recording medium and its format.

FIG. 2 is a schematic diagram showing a format of a recording data string.

FIG. 3 is a block diagram of an optical disk device.

FIG. 4 is a diagram for explaining reproduction of data from a preformat area and a user data area.

FIG. 5 is a block diagram of a PLL circuit.

FIG. 6 is a diagram for explaining generation of a fine clock mark detection signal and a clock.

FIG. 7 is a diagram for explaining detection of address information and generation of an address final position detection signal.

FIG. 8 is a diagram illustrating a relationship between an error rate of a reproduction signal and power of laser light.

9 is a diagram showing the relationship between the error rate of the reproduced signal and the power of the laser beam when the power of the laser beam is changed around the temporary optimum power obtained from the relationship diagram shown in FIG.

FIG. 10 is a flowchart showing a method for adjusting the power of laser light according to the present invention.

[Explanation of symbols]

1 groove, 2 lands, 3 fine clock mark, 4 to 9 wobbles, 10, 30 preformat area, 20 user data area, 40, 50 circuits, 10
0 magneto-optical recording medium, 101 spindle motor, 10
2 Optical pickup, 103 FCM detection circuit, 104
PLL circuit, 105 address detection circuit, 106 B
PF, 107 AD converter, 108 waveform equalization circuit, 1
09 Viterbi decoding circuit, 110 unformatting circuit,
111 data demodulation circuit, 112 BCH decoder, 1
13 header detection circuit, 114 controller, 115
Timing generation circuit, 116 BCH encoder, 1
17 data modulation circuit, 119, 121 pattern generation circuit, 120 selector circuit, 123 magnetic head drive circuit, 124 laser drive circuit, 125 magnetic head,
126 format circuit, 200 optical disk device,
400 subtractor, 500, 501, 503, 504 adder, 502, 505 subtractor, 1020 photodetector,
1020A to 1020F region, 1041 phase comparison circuit, 1042 LPF, 1043 voltage-controlled oscillator,
44 1/532 divider.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kanichi Furuyama 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. F-term (reference) 5D075 AA03 CD11 5D090 AA01 BB05 BB10 CC04 DD03 EE11 HH01 KK03 5D119 AA12 BA01 BB05 DA05 HA54 5F073 BA06 EA15 FA01 GA02 GA12 GA14

Claims (8)

[Claims] 1. An optical disk apparatus for reproducing a signal from an optical disk having a track on which a fine clock mark serving as a reference for generating a reproduction clock when reproducing a signal is formed at a constant period, comprising: An optical head that collects and irradiates laser light and detects reflected light thereof; a clock generation circuit that generates a reproduction clock based on a fine clock mark signal detected by the optical head due to the fine clock mark; A reproduction processing circuit for performing a reproduction process in synchronization with the reproduction clock with a magneto-optical signal detected from the optical disk by the optical head; and determining a suitable range of the power of the laser light, and setting the laser to the determined preferable range. A control circuit for setting the power of light, wherein the control circuit has an intensity of the laser light. The error rate of the reproduced signal when changed is input from the reproduction processing circuit, the power of the laser beam at which the error rate is minimized is determined as the temporary optimum power, and the laser light is centered on the temporary optimum power. The preferred range is determined based on the error rate of the reproduced signal when the power of is changed,
Optical disk device. 2. The optical disk device according to claim 1, wherein the control circuit further determines a center value of the preferable range as an optimum power, and sets the power of the laser beam to the optimum power. 3. The control circuit detects a minimum error rate from a plurality of error rates lower than a predetermined reference value, and determines the power of the laser beam realizing the error rate as the temporary optimum power. Claim 1 or Claim 2
An optical disk device according to claim 1. 4. The control circuit detects a power of the first and second laser lights at which an error rate of the reproduction signal matches the predetermined reference value, and detects a power of the first laser light and a power of the first laser light. 3. The optical disk device according to claim 1, wherein an average value of the power of the second laser light and the average power is determined as the temporary optimum power. 5. A method for adjusting a reproduction power of a laser beam in an optical disc apparatus for reproducing a signal from an optical disc using a laser beam, the method comprising: changing a power of the laser beam to reproduce a signal from the optical disc. And a second step of detecting an error rate of the reproduction signal reproduced in the first step; and detecting a minimum error rate from the error rates detected in the second step, A third step of determining the power of the laser light for realizing the temporary optimum power; and a fourth step of changing the power of the laser light around the temporary optimum power to reproduce a signal from the optical disk. Determining a suitable range based on an error rate of the reproduction signal reproduced in the fourth step, and determining a center value of the preferable range; Adjustment method of reproducing power and a fifth step of determining a suitable power. 6. The method according to claim 5, wherein, in the third step, a power of the laser beam that realizes a minimum error rate among error rates lower than a predetermined reference value is determined as the temporary optimum power. How to adjust the playback power. 7. The method according to claim 3, wherein in the third step, the first
Detecting the powers of the first and second laser beams whose error rate of the reproduced signal reproduced in the step (b) matches the predetermined reference value, and comparing the power of the first laser beam with the second laser beam.
6. The reproducing power adjusting method according to claim 5, wherein an average value of the power of the laser light and the power of the laser light is determined as the temporary optimum power. 8. The method according to claim 5, wherein in the first step, a signal is reproduced in synchronization with a reference clock generated by detecting a clock mark formed on the optical disk at a constant period. A method for adjusting the reproduction power according to any one of the preceding claims.