JPH10134373A - Servo signal processor and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply accurate focus servo in spite of deviations in assembly in a servo signal processor and an optical disk device. SOLUTION: A servo signal processor 1 is constituted of a circuit 5 for forming a first offset cancellation signal corresponding to an offset generating in a tracking error signal, a circuit 8 for detecting a focusing error signal, a matrix processing circuit 9 for forming a second offset cancellation signal corresponding to an offset generating in the focusing error signal based on the first offset cancellation signal from the circuit 5, and a second subtracter for subtracting the second offset cancellation signal from the focusing error signal. In this structure, the servo signal processor 1 cancels the offset generating in the focusing error signal on the basis of the first offset cancellation signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a focusing state based on return light from a disk-shaped recording medium,
The present invention relates to a servo signal processing device that performs focus servo and an optical disk device including the servo signal processing device.

[0002]

2. Description of the Related Art Conventionally, a servo signal processing device performs a servo process by detecting a focus error signal and a tracking error signal.

This servo signal processing device irradiates a laser beam to an optical disk or a magneto-optical disk and detects a focus error signal and a tracking error signal based on return light from the optical disk or the magneto-optical disk. Then, the servo signal processing device performs focus servo and tracking servo so that the focus error signal and the tracking error signal become zero.

The above-mentioned servo signal processing apparatus is, for example, shown in FIG.
As shown in FIG. 5, a microprism detector 202 that emits laser light to the optical disk 201 and receives the return light, and a photodetector that is disposed on the microprism detector 202 and receives the return light and outputs a light detection signal A tracking error detection circuit 205 for detecting a tracking error signal based on the light detection signal; a tracking servo processing circuit 206 for performing tracking servo based on the tracking error signal; A focus error detection circuit 207 that detects a focus error signal based on the detection signal;
A focus servo processing circuit 208 that performs focus servo based on the focus error signal, an objective lens 209 that focuses the laser beam on the optical disc 201, and a tracking servo processing circuit 206 and a focus servo processing circuit 208 that are controlled by the objective lens 209. And a two-axis actuator 210 for moving operation.

Also, a micro prism detector 202
Is a substrate 21 on which the photodetectors 203 and 204 are disposed.
1, a semiconductor laser 212 mounted on the base body 211 and emitting laser light, and a reflecting surface 213 such that the laser light emitted by the semiconductor laser 212 is directed toward the optical disc 201.
Is formed. The prism 214 has a semi-transmissive reflection surface 215 and an opposing reflection surface 2 so that each of the photodetectors 203 and 204 can receive return light.
16 are formed.

With such a configuration, the servo signal processing device 200 receives the return light at each of the photodetectors 203 and 204, and according to the amount of the received light, returns each of the photodetectors 203 and 20.
The tracking error signal and the focus error signal are detected based on the light detection signal output from the reference numeral 4. The servo signal processing device 200 performs servo processing based on the tracking error signal and the focus error signal.

[0007]

By the way, an optical pickup device, which is a part of the servo signal processing device 200 and includes, for example, the micro prism detector 202 and the objective lens 209, has small components. Therefore, high-precision alignment is required.
In particular, since the semiconductor laser 212 is a light source that emits a laser beam that irradiates a recording track formed on the optical disk 201 at a pitch of only 1.6 μm, a high-precision mount is required. However, it is difficult to completely mount the semiconductor laser 212 at the design center.

For example, if the semiconductor laser 212 is mounted on the base 211 with a slight deviation from the center of the design, even if the servo signal processing device 200 performs the focus servo so that the focus error signal is set to 0, the just focus is not performed. I will. This causes a problem that the servo signal processing device 200 is always defocused.

Further, when a plurality of the optical pickup devices are manufactured, the displacement of the mount as described above differs for each device, so that it is difficult to correct the mount.

Further, in the conventional focus servo system, defocus may occur even if the lens is shifted from the center due to eccentricity of the disk.

Accordingly, the present invention has been made in view of the above circumstances, and cancels an offset generated in a focus error signal due to misalignment of an assembly or eccentricity of a disk-shaped recording medium such as an optical disk, thereby achieving accurate focusing. It is an object of the present invention to provide a servo signal processing device for realizing servo and an optical disk device using the servo signal processing device.

[0012]

In order to solve the above-mentioned problems, a servo signal processing device according to the present invention has a focus error detecting means for detecting a focus error signal and a tracking error signal based on a push-pull method. In this case, the tracking error detection unit includes an offset cancellation amount generation unit that generates a first offset cancellation amount corresponding to the offset amount generated in the tracking error signal due to the spot movement of the return light in the light receiving unit; A matrix processing unit for generating a second offset cancellation amount corresponding to an offset generated in the focus error signal in accordance with the spot movement in the light receiving unit, based on the first offset cancellation amount of 2 offset cancellation The and a subtraction means for subtracting.

With such a configuration, the servo signal processing device cancels an offset generated in the focus error signal based on the first offset cancellation amount.

The optical disk apparatus according to the present invention has a focus error detecting means for detecting a focus error signal and a tracking error signal detected by a push-pull method. A tracking error detection unit including an offset cancellation amount generation unit that generates a first offset cancellation amount corresponding to an offset generated in the signal; and a light receiving unit based on the first offset cancellation amount from the offset cancellation amount generation unit. A matrix processing unit that generates a second offset cancellation amount corresponding to an offset generated in the focus error signal in accordance with the spot movement in the step (a), and a subtraction unit that subtracts the second offset cancellation amount from the focus error signal.

With such a configuration, the optical disc apparatus cancels the offset generated in the focus error signal based on the first offset cancellation amount.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings.

First, the first embodiment is a servo signal processing device for detecting a tracking error signal and a focus error signal based on return light from a magneto-optical disk.
Here, the magneto-optical disk is a disk-shaped recording medium having a recording track in which a meandering guide groove is formed.

This servo signal processing device generates a second offset cancel signal based on a first offset cancel signal for canceling an offset generated in a push-pull signal obtained by a push-pull method,
The second offset cancel signal is used to cancel an offset generated in the focus error signal. Note that, as will be described later, the offset referred to here is, for example, an offset generated when a lens shift occurs in an objective lens in a state where a semiconductor laser that irradiates a disk with laser light is slightly deviated from a design center.

In the push-pull method, the intensity distribution of return light diffracted and reflected in a guide groove or pit formed in a recording track of a disk is determined by the relative position between the guide groove or pit and the spot. By utilizing the fact that the light changes depending on the relationship, the return light is received by a plurality of light receiving units, and a tracking error signal is detected based on the difference in the amount of light received by each light receiving unit.

As shown in FIG. 1, the servo signal processing device outputs a light detection signal output from the first light detector 2 and the second light detector 3 based on the return light from the magneto-optical disk 61. A push-pull signal detecting circuit 4 for detecting a push-pull signal based on the above, an offset canceling amount generating circuit 5 for generating a first offset canceling signal for canceling the above-described offset from the push-pull signal, A tracking error detection circuit 7 is provided which comprises a first subtractor 6 for subtracting the first offset cancellation signal from the push-pull signal and outputting a tracking error signal in which the offset has been canceled.

Further, the servo signal processing device 1 is generated by a focus error detection circuit 8 for detecting a focus error signal based on the light detection signals from the photodetectors 2 and 3 and an offset cancellation amount generation circuit 5. A matrix processing circuit 9 for generating a second offset cancellation signal based on the first offset cancellation signal
And a second subtractor 10 that subtracts the second offset cancel signal from the focus error signal and outputs a focus error signal in which the offset has been canceled.
And

The servo signal processor 1 comprises a microprism detector 11 for irradiating the magneto-optical disk 61 with laser light, an objective lens 12 for focusing the laser light on the signal recording surface of the magneto-optical disk 61, and an objective lens 1
A two-axis actuator 13 for moving the actuator 2 in the tracking direction and the focusing direction, and a tracking servo processing circuit 1 for controlling the two-axis actuator 13 based on a tracking error signal output from the first subtractor 6.
4 and a focus servo processing circuit 15 for controlling the biaxial actuator 13 based on a focus error signal output from the second subtractor 10.

Further, the micro prism detector 1
Reference numeral 1 denotes a base 16 on which the photodetectors 2 and 3 are disposed, and a semiconductor laser 1 mounted on the base 16 and emitting laser light.
7 and a prism 19 having a reflection surface 18 formed so as to direct the laser light emitted from the semiconductor laser 17 toward the magneto-optical disk 61.

The prism 19 includes a transflective surface 20 formed so as to cover the first photodetector 2 and an opposing reflective surface 21 formed to face the transflective surface 20. . Here, the semi-transmissive reflection surface 20 has an optical characteristic that transmits 50% of the return light incident from the reflection surface 18 to the first photodetector 2 and reflects the remaining return light toward the opposite reflection surface 21. Have. The opposing reflection surface 21 has an optical characteristic of reflecting the return light reflected by the transflective surface 20 toward the second photodetector 3.

The first photodetector 2, as shown in FIGS. 2 and 3, forms a light receiving portion composed of four light receiving elements 2a, 2b, 2c, 2d such as photodiodes. I have. These four light receiving elements 2a, 2b, 2c, 2d
Are each formed in a substantially rectangular shape. The two light receiving elements 2b and 2c disposed on the inner side are formed to have narrower short sides than the light receiving elements 2a and 2d disposed on the outer side. These light receiving elements 2a, 2b, 2c, 2d
They are arranged so that their longitudinal directions are parallel to each other. The light receiving elements 2a, 2b, 2c, 2d output light detection signals V _2a , V _2b , V _2c , V _2d according to the received light.

As shown in FIG. 3, the second photodetector 3 is formed in the same shape as the first photodetector 2. In other words, a light receiving section composed of four light receiving elements 3a, 3b, 3c, 3d such as photodiodes is formed. These four light receiving elements 3a, 3b, 3c, 3d
Each one is formed in a substantially rectangular shape. The two light receiving elements 3b and 3c disposed on the inner side are formed to have narrower short side widths than the light receiving elements 3a and 3d disposed on the outer side. These light receiving elements 3a, 3b, 3c, 3d are arranged so that their longitudinal directions are parallel to each other. The light receiving elements 3a, 3b, 3c, 3d output light detection signals V _3a , V _3b , V _3c , V _3d according to the received light.

Then, the tracking error detection circuit 7
_Are the light detection signals V _2a , V _2b , V from the first photo detector 2
_A tracking error signal is detected and output based on _2c and V _2d . Further, the focus error detection circuit 8 detects the light detection signals V _2a , V _2b , V _2c , V _2d , and V 2 from the photodetectors 2 and 3.
_A focus error signal is detected and output based on _3a , _V3b , _V3c and _V3d .

The tracking error detecting circuit 7 detects an effective tracking error signal when a tracking servo is applied to a magneto-optical disk 61 having a recording track in which a meandering (wobble) guide groove is formed. It is a detection circuit. The tracking error detection circuit 7 utilizes the fact that the amplitude of the wobble frequency component changes depending on the position of the objective lens 12, detects the amplitude of the wobble frequency component, obtains the position of the objective lens 12, and obtains the offset generated in the tracking error signal. To cancel the so-called WPP (Woble Push-Pull)
Has been applied.

As shown in FIG. 2, the configuration includes a push-pull signal detection circuit 4, an offset cancellation amount generation circuit 5, and a first subtractor 6. Here, the push-pull signal detection circuit 4 detects the push-pull signal, and the offset cancellation amount generation circuit 5 generates a first offset cancellation signal corresponding to the offset included in the push-pull signal.

As shown in FIG. 4, the magneto-optical disk 61 has a pre-group 62 corresponding to a groove and a land 63 corresponding to a land, and a boundary between the pre-group 62 and the land 63 is meandering at a predetermined cycle. The above push-pull signal detection circuit 4
Detects the push-pull signal based on the return light of the spot 64 irradiated on the pre-groove 62.

The above push-pull signal detection circuit 4
, Adders 31, 32, 33 and a subtractor 34
And a divider 35. In the push-pull signal detection circuit 4, the adder 31 adds the light detection signal V _2a and the light detection signal V _2b , while the adder 32 adds the light detection signal V _2c and the light detection signal V _2d. . Then, the subtractor 34 outputs the signal V _2a + V _2b output from the adder 31.
_Is subtracted from the signal V _2c + V _2d output from the adder 32. The adder 33 adds the signals V _2a + V _2b and V _2c + V _2d output from the adders 31 and 32.
The divider 35 divides the signal output from the subtractor 34 using the signal output from the adder 33 as a divisor.
Thus, the push-pull signal detection circuit 4 outputs a push-pull signal TE ₁ shown in (1).

TE ₁ = ((V _2a + V _2b ) − (V _2c + V _2d )) / (V _2a + V _2b + V _2c + V _2d ) (1) Also, the offset cancellation amount generation circuit 5 has a wobble amplitude. Detectors 36, 37, 38, subtractors 39, 40,
It comprises a divider 41 and a coefficient multiplier 42.
In the offset cancellation amount generating circuit 5, the wobble amplitude detector 36 detects the wobble amplitude component signal V _2aw of the light detection signal V _2a , and the wobble amplitude detector 37 outputs the wobble amplitude component signal V _2dw of the light detection signal V _2d. To detect. Then, the subtractor 39 subtracts the signal V _2dw output from the wobble amplitude detector 37 from the signal V _2aw output from the wobble amplitude detector ₃₆ to obtain a signal V _2aw −V _2dw . Moreover, the wobble amplitude detector 38, the wobble amplitude component signal of the signal V _2a -V _2d obtained from the light detection signal V _2a by subtracting the optical detection signal V _2d in a subtractor 40 (V _2a -V _{2d) w}
Is detected. Then, the divider 41 uses the signal (V _2a −V _2d ) _w output from the wobble amplitude detector 38 as a divisor to output the signal V _2aw −V _2dw output from the subtractor 39.
Is divided by Signal divided by the divider 41, the coefficient multiplier 42 is predetermined coefficient K _w is multiplied. The signal output from the coefficient multiplier 42 is (2)
The offset shown in the equation and included in the push-pull signal,
For example the first offset cancel signal CSL ₁₁ corresponding to the offset due to lens shift.

CSL ₁₁ = K _w (V _2aw −V _2dw ) / (V _2a −V _2d ) _w (2) The first offset cancel signal CSL ₁₁ is
Is input to the subtractor 6 and the matrix processing circuit 9. First subtractor 6 from the push-pull signal TE ₁ outputted from the push-pull signal detecting circuit 4 by subtracting a first offset cancel signal CSL ₁₁ the tracking error signal TE _w as shown by (3) Output.

TE _w = ((V _2a + V _2b ) − (V _2c + V _2d )) / (V _2a + V _2b + V _2c + V _2d ) −K _w (V _2aw −V _2dw ) / (V _2a −V _2d ) _w (3) The tracking error signal TE _w is a tracking error signal in which an offset due to, for example, a lens shift has been canceled. Then, the tracking error signal TE _w offset is canceled is inputted to the tracking servo processing circuit 14.

On the other hand, the first offset cancel signal CSL ₁₁ input to the matrix processing circuit 9, where for example, the constant α is multiplied. This matrix processing circuit 9
Output signals from, the second offset cancel signal CSL ₂₁ corresponding to the offset of the focus error signal as described later. The constant α is determined in accordance with the condition for generating the offset, and is set and input to the matrix processing circuit 9 in advance when the device is manufactured.

As shown in FIG. 3, the focus error detecting circuit 8 for detecting the focus error signal detects the focus error signal based on the light detection signals output from the photodetectors 2 and 3. It is configured. The focus error detection circuit 8 includes a first calculation unit 71 to which a light detection signal from the first light detector 2 is input and a second operation unit to which a light detection signal from the second light detector 3 is input. , And a subtractor 73. And the first
Is composed of adders 74 and 75 and a subtractor 76. Further, the second arithmetic unit 72 includes the adder 7
7, 78 and a subtractor 79.

In the first arithmetic unit 71, the adder 74 adds the light detection signal V _2b and the light detection signal V _2c , while the adder 75 adds the light detection signal V _2a and the light detection signal V _2d . to add. The subtractor 76 outputs the signal V _2b output from the adder 74.
The signal V _2a + V _2d output from the adder 75 is subtracted from + V _2c . In the second arithmetic unit 72, the adder 77 adds the light detection signal V _3b and the light detection signal V _3c , while the adder 78 adds the light detection signal V _3a and the light detection signal V _3d. . The subtractor 79 outputs the signal V _3b output from the adder 77.
The signal V _3a + V _3d output from the adder 78 is subtracted from + V _3c .

Then, the subtractor 73 is connected to the first arithmetic unit 71
The signal output from the second arithmetic unit 72 is subtracted from the signal output from the second arithmetic unit 72. As a result, the signal output from the subtractor 73 becomes a focus error signal FE as shown in Expression (4).

FE = (V _2a + V _2d + V _3b + V _3c ) − (V _2b + V _2c + V _3a + V _3d ) (4) The second subtractor 10 uses the focus error signal F
Subtracting the matrix processing circuit 9 the output from the second offset cancel signal CSL ₂₁ from E. Thus a focus error signal FE, the offset is canceled by the second offset cancel signal CSL _21. That is, the focus error signal FE is
So that the offset is canceled by the second offset cancel signal CSL ₂₁ generated based on the offset cancellation signal CSL ₁₁ of. Note that the offset generated in the focus error signal described here is
As will be described later, for example, the offset is generated when a lens shift occurs when the semiconductor laser 17 is slightly deviated from the design center.

Here, the offset caused by the lens shift will be described with reference to FIGS.

For example, the position of the semiconductor laser 17, the position of the objective lens 12, the position of the reflection surface 18 of the prism 19, and the principal ray 91 of the laser light from the objective lens 12 to the photodetectors 2 and 3 (broken line in FIG. ) Are shown in FIGS. 5 to 9 in form. Also, as shown in FIGS. 5 to 9,
The virtual light emitting point 92 of the semiconductor laser 17 (marked by x in the figure) is usually the center line 93 of the photodetectors 2 and 3 (dashed line in the figure).
Located in. The photodetectors 2 and 3 shown below FIGS. 5 to 9 are views seen from above the light receiving surface, and return light spots S2 and S3 are formed on the photodetectors 2 and 3, respectively. You. Spots S2, formed on the photodetectors 2, 3,
In step S3, when the objective lens 12 moves in the tracking direction, the objective lens 12 moves symmetrically about the virtual light emitting point 92.

First, in the on-track state, the virtual light emitting point 92 and the centers of the spots S2 and S3 are located on the center line 93 of the photodetectors 2 and 3, as shown in FIG. For example, when the objective lens 12 shakes in the tracking direction due to the lens shift, the spots S2 and S3 move around the virtual light emitting point 92 as shown in FIG. In this case the push-pull signal TE ₁ detected output a push-pull signal detection circuit 4, the offset due to a lens shift occurs. However, the offset due to this lens shift is caused by the first offset cancel signal CS
It is canceled by L _11.

The first offset cancel signal C
Offset cancellation amount corresponding to SL ₁₁ (CSL ₁₁ )
_x can be represented by, for example, a linear expression as a function of the lens shift LS as shown in Expression (5), and is represented by a relationship as shown in FIG. Here, β is a constant.

(CSL ₁₁ ) _x = β × LS (5) On the other hand, regarding the focus error signal FE, even if the lens shift shown in FIG. Due to the shift, FE = 0. Therefore, there is no defocus at this time.

On the other hand, as shown in FIG. 7, when the semiconductor laser 17 is mounted on the base 16 of the microprism detector 11 slightly displaced in the arrow Y direction from the design center during assembly, the virtual light emitting point 92 Center line 9 of detectors 2 and 3
It deviates from 3. When the semiconductor laser 17 is shifted from the design center and a lens shift occurs, for example, in the outer peripheral direction of the magneto-optical disk, as shown in FIG. Spot S
2, the shift amount of the center of S3 is different, and the focus error signal FE shown in the equation (4) becomes FE <0, and an offset occurs in the focus error signal FE. Similarly, with the semiconductor laser 17 shifted from the design center,
For example, if a lens shift occurs in the inner circumferential direction of the magneto-optical disk, as shown in FIG. 9, the amount of movement of the centers of the spots S2 and S3 from the center line 93 of the photodetectors 2 and 3 is different. The focus error signal FE in the expression 4) is FE
> 0, and an offset occurs in the focus error signal FE. When focus servo is applied so that the focus error signal FE becomes 0 in a state where these offsets are generated, defocus occurs.

As described above, if the lens shift occurs when the semiconductor laser 17 is slightly deviated from the design center, an offset occurs in the focus error signal FE, and the focus is shifted so that the focus error signal FE becomes zero. Defocusing occurs even when servo is applied.

For example, the defocus amount (DF)
_x can be represented by, for example, a linear expression as a function of the lens shift LS as shown in Expression (6), and is represented by a relationship as shown in FIG. Here, γ is a constant.

(DF) _x = γ × LS (6) As described above, Expression (6) is a function of the lens shift LS similarly to Expression (5). From these relations, the constant α used in the matrix processing circuit 9 can be determined as shown in equation (7). Note that the defocus amount (DF) _x and the offset cancel amount (CSL) in the equation (7)
₁₁ ) _x is the same for lens shift values.

Α = (DF) _x / (CSL ₁₁ ) _x (7) By determining the constant α in this manner, the second offset cancel signal CSL ₂₁ is converted into a defocus amount generated by the lens shift LS. (DF) It can be set to correspond to _x . Therefore, for example, the semiconductor laser 17
Is slightly deviated from the design center and the lens shift occurs, the second offset cancel signal CSL ₂₁
The offset caused by the cause can be canceled from the focus error signal FE. Also, the first
As a function of the offset cancel signal CSL ₁₁ of the second
Since the offset cancel signal CSL ₂₁ is generated, the offset can be canceled even if the lens shift amount changes.

The focus error signal whose offset has been canceled as described above is input to the focus servo processing circuit 15. The servo signal processing device 1 performs servo processing so that the focus error signal and the tracking error signal become zero. Therefore, the servo signal processing device 1 can perform accurate focus servo.

Further, the servo signal processing device 1 converts the second offset cancellation signal CSL ₂₁ based on the first offset cancellation signal CSL ₁₁ output from the offset cancellation amount generation means 5 provided in the tracking error detection circuit 7. Since it can be generated, the offset included in the focus error signal can be canceled without increasing the number of components.

Next, a servo signal processing device according to a second embodiment of the present invention will be described.

The second embodiment is a servo signal processing device for detecting a tracking error signal and a focus error signal based on return light from an optical disk. Here, the optical disk is a disk-shaped recording medium in which recording tracks are formed by pits.

This servo signal processing apparatus, like the first embodiment, performs the second offset cancellation based on the first offset cancellation signal for canceling the offset generated in the push-pull signal obtained by the push-pull method. A signal is generated, and the offset generated in the focus error signal is canceled using the second offset cancel signal. This servo signal processing device is configured in the same manner as the first embodiment except for the tracking error detection circuit 7 shown in FIG. 1, and includes a focus error detection circuit 8 and a matrix processing circuit 9
, A second subtractor 10, a tracking servo processing circuit 14, a focus servo processing circuit 15, a microprism detector 11, an objective lens 12, and a biaxial actuator 13. Here, the description of the same components as those in the first embodiment will be omitted.

The tracking error detection circuit 7 is an error detection circuit for detecting a tracking error signal effective when a tracking servo is applied to an optical disk having a recording track formed with pits. The tracking error detection circuit 7 utilizes the fact that the envelope of the RF signal is slightly modulated, and in particular, detects a change in the peak value of the envelope and multiplies it by a predetermined coefficient to obtain an offset, that is, a so-called TPP. (To
p hold Push-Pull) is applied.

The configuration includes a push-pull signal detection circuit 101, an offset cancellation amount generation circuit 102, and a first subtractor 6, as shown in FIG.
Here, the push-pull signal detection circuit 101 detects the push-pull signal and outputs the offset cancel amount generation circuit 1
02 generates a first offset cancel signal corresponding to the offset included in the push-pull signal.

The push-pull signal detection circuit 101
It comprises adders 103 and 104 and a subtractor 105. In the push-pull signal detection circuit 101, the adder 103 adds the light detection signal V _2a and the light detection signal V _2b while the adder 104 adds the light detection signal V _2c and the light detection signal V _2b.
Add _2d . Then, the subtracter 105 is connected to the adder 10.
The signal V _2c + V _2d output from the adder 104 is subtracted from the signal V _2a + V _2b output from 3. Thus, the push-pull signal detecting circuit 101 outputs the push-pull signal TE ₂ indicated by (8).

TE ₂ = (V _2a + V _2b ) − (V _2c + V _2d ) (8) On the other hand, the offset cancellation amount generation circuit 102 includes peak hold circuits 106 and 107, a coefficient multiplier 108,
109 and a subtractor 110. In the offset cancellation amount generation circuit 102, the peak hold circuit 106 sets the peak value (V _2a +) of the signal output from the adder 103 included in the push-pull signal detection circuit 101.
V _2b ) _p , while the peak hold circuit 107 obtains the peak value (V _2c + V _2d ) _p of the signal output from the adder 104 of the push-pull signal detection circuit 101. Then, the coefficient multiplying circuit 108
Multiplied by the coefficient K _t the peak value output from the 6. Also,
Coefficient multiplying circuit 109 multiplies the coefficient K _t the peak value output from the peak hold circuit 107. Then, the subtractor 110 subtracts the signal output from the coefficient multiplier 109 from the signal output from the coefficient multiplier 108. Signal output from the subtracter 110, (9) shown by the formula, the first offset cancel signal CSL ₁₂ corresponding to the offset by the offset, for example, a lens shift included in the push-pull signal.

CSL ₁₂ = K _t (V _2a + V _2b ) _p −K _t (V _2c + V _2d ) _p (9) The first offset cancel signal CSL ₁₂ is
Is input to the subtractor 6 and the matrix processing circuit 9. First subtractor 6, the push-pull signal detected from the push-pull signal TE ₂ output from the circuit 101 subtracts the first offset cancel signal CSL ₁₂ (10) a tracking error signal TE _t as shown by the formula Is output.

TE _t = ((V _2a + V _2b ) − (V _2c + V _2d )) − (K _t (V _2a + V _2b ) _p −K _t (V _2c + V _2d ) _p ) (10) tracking error signal TE _t is a tracking error signal canceling the offset, for example by the lens shift. Then, the tracking error signal TE _t that the offset is canceled is inputted to the tracking servo processing circuit 14.

[0061] On the other hand, the first offset cancel signal CSL ₁₂ input to the matrix processing circuit 9, as in the first embodiment, the constant α is multiplied. Note that the constant α can be obtained based on the offset cancel amount (CSL ₁₂ ) _x and the defocus amount (DF) _x for the lens shift LS, as in the first embodiment. Thereby, the second offset cancel signal CSL ₂₂ can be set to correspond to the defocus amount (DF) _x caused by the lens shift LS.

Therefore, for example, when a lens shift occurs with the semiconductor laser 17 slightly deviated from the design center,
The focus error signal F offset caused by its cause by the second offset cancel signal CSL ₂₂
You can cancel from E. Further, in order to the second offset cancel signal CSL ₂₂ is generated as a function of the first offset cancel signal CSL _12, even if the lens shift amount is changed, it is possible to cancel the offset.

The focus error signal from which the offset has been canceled as described above is input to the focus servo processing circuit 15. Thus, the servo signal processing device 1 can perform accurate focus servo servo based on the focus error signal.

Further, the servo signal processing device 1 converts the second offset cancel signal CSL ₂₂ based on the first offset cancel signal CSL ₁₂ output from the push-pull signal detecting circuit 101 provided in the tracking error detecting circuit 7. Since it can be generated, the offset included in the focus error signal can be canceled without increasing the number of components.

Next, an optical disc device according to a third embodiment of the present invention will be described.

In the third embodiment, an information signal is recorded by performing servo processing on the magneto-optical disk having meandering guide grooves and recording tracks formed thereon using the servo signal processing device. Or an optical disk device for reproducing.

This optical disk device has a servo signal processing device 122 as shown in FIG. And
This servo signal processing device 122 has the same configuration as that of the first embodiment. That is, the tracking error detection circuit 7 of the servo signal processing device 122, as shown in FIG.
It is configured by applying the tracking error detection method by the WPP. The description of the same components as in the first embodiment is omitted.

As shown in FIG. 13, the optical disk device 121 emits a laser beam to the signal recording surface of the magneto-optical disk 61, and an optical pickup device 123 to which the return light is incident, and the optical pickup device 123 to transmit the return light. a tracking error detecting circuit 7 for detecting a push-pull signal TE ₁ and the first offset cancel signal CSL ₁₁ on the basis, generating a second offset cancel signal CSL ₂₁ based on the first offset cancel signal CSL ₁₁ Matrix processing circuit 9, a focus error detection circuit 8 for detecting and outputting a focus error signal FE based on the return light, and a second subtraction for subtracting the second offset cancel signal CSL ₂₁ from the focus error signal FE. And a focus error signal output from the second subtractor 10. A focus servo processing circuit 15 for performing Susabo, and a tracking servo processing circuit 14 for performing based on the tracking servo tracking error signal output from the tracking error detecting circuit 7.

Here, the tracking error detection circuit 7
As described above, the push-pull signal detection circuit 4 is configured by applying the tracking error detection method by WPP.
, An offset canceling amount generating circuit 5 and a first subtractor 6. As shown in FIG. 1, the optical pickup device 123 includes a micro prism detector 11 in which the first photo detector 2 and the second photo detector 3 and the like are disposed, an objective lens 12, and a biaxial An actuator 13 is provided.

As shown in FIG. 13, the optical disk device 121 includes a spindle motor 124 for rotating the magneto-optical disk 61 and a digital signal processing circuit 1 to be described later.
A spindle servo processing circuit 126 for controlling the rotation of the spindle motor 124 based on the control signal from the optical detector 25;
Processing circuit 1 for shaping the electric signal output from
27, and a digital signal processing circuit 125 for converting an electric signal output from the signal processing circuit 127 into a digital signal.
And a D / A converter 12 for converting a digital signal output from the digital signal processing circuit 125 into an analog signal.
8 and a system controller 129 that controls the focus servo processing circuit 15 and the tracking servo processing circuit 14 based on the input control signal.

The optical disk device 121 having the above configuration
Can perform recording or reproduction of information signals on the magneto-optical disk while performing servo processing.

The optical disk device 121 is based on the first offset cancellation signal CSL ₁₁ generated by the offset cancellation amount generation circuit 5 provided in the tracking error detection circuit 7 as in the first embodiment. the second offset cancel signal CSL ₂₁ corresponding to the offset included in the focus error signal FE can be generated.

As a result, the optical disk device 121
From the focus error signal FE including the offset to the second offset cancel signal C
By subtracting the SL _21, it is possible to cancel the offset that occurs when the lens shift occurs while for example a semiconductor laser 17 is slightly deviated from the designed center of the focus error signal FE. Therefore, the optical disk device 121 can accurately apply the focus servo based on the focus error signal in which the offset has been canceled.

The light detection signals output from the photodetectors 2 and 3 are input to a signal processing circuit 127 and output as, for example, audio through a digital signal processing circuit 125 and a D / A converter 128. . Since the audio signal is obtained based on the light detection signal obtained by performing accurate focus servo, deterioration of the audio is prevented.

Therefore, even if the semiconductor laser 17 slightly shifts from the design center and a lens shift occurs, the optical disk device 121 can perform accurate focus servo without defocusing. Thereby, the optical disk device 121 can reduce the deterioration of the information signal recorded or reproduced on the magneto-optical disk.

Next, an optical disc device according to a fourth embodiment of the present invention will be described.

The fourth embodiment is an optical disk apparatus for reproducing information signals by performing servo processing on the optical disk on which recording tracks are formed by pits using the servo signal processing apparatus.

This optical disk device includes a servo signal processing device 122 as in the third embodiment. The servo signal processing device 122 has the same configuration as that of the second embodiment. That is, the tracking error detection circuit 7 of the servo signal processing device 122
As shown in FIG. 12, a push-pull signal detection circuit 101, an offset cancellation amount generation circuit 102,
And a first subtractor 6.

With this configuration, the optical disk device 121 can reproduce the information signal from the optical disk while performing the servo processing.

The optical disk device 121 is provided with an offset cancel amount generation circuit 102 provided in the tracking error detection circuit 7 in the same manner as in the second embodiment.
The first offset cancel signal CSL ₁₂ generated at
, The second offset cancel signal CSL ₂₂ corresponding to the offset included in the focus error signal.
Can be generated.

As a result, the optical disk device 121
The second offset cancel signal CSL is obtained from the focus error signal including the offset in the subtractor 6 of FIG.
By subtracting ₂₂ from the focus error signal FE, for example, an offset that occurs when a lens shift occurs when the semiconductor laser 17 is slightly deviated from the design center can be canceled. Thus, the optical disk device 121 can accurately apply the focus servo based on the focus error signal from which the offset has been canceled.

The light detection signals output from the photodetectors 2 and 3 are input to a signal processing circuit 127 and output as, for example, audio through a digital signal processing circuit 125 and a D / A converter 128. . Since the audio signal is obtained based on the light detection signal obtained by performing accurate focus servo, deterioration of the audio is prevented.

Therefore, even if the semiconductor laser 17 deviates from the design center and a lens shift occurs, the optical disk device 121 can apply accurate focus servo without defocusing. Thereby, the optical disc device 121 can reduce the deterioration of the information signal reproduced from the optical disc.

In the servo signal processing device and the optical disk device, when the relationship between the lens shift and the offset cancel amount or the relationship between the lens shift and the defocus amount can be expressed by a quadratic expression or a quadratic or higher expression, respectively. However, the offset generated in the focus error signal can be canceled. In this case, the matrix processing circuit 9 generates a second offset cancellation signal by polynomial approximation based on the first offset cancellation signal.

Further, the servo signal processing device and the optical disk device can cancel the offset generated in the focus error signal due to the eccentricity or skew of the magneto-optical disk or the optical disk. In this case, the constant α is determined so that a second offset cancel signal corresponding to an offset caused by eccentricity or skew of the magneto-optical disk or optical disk can be generated.

[0086]

The servo signal processing apparatus according to the present invention includes a matrix processing section for generating a second offset cancellation amount based on a first offset cancellation amount for canceling an offset generated in a tracking error signal. Therefore, even if assembly variations occur in the optical pickup or the like, the offset due to the influence can be canceled and accurate focus servo can be applied.

Further, the optical disk device according to the present invention includes a matrix processing unit that generates a second offset cancellation amount based on a first offset cancellation amount that cancels an offset generated in a tracking error signal, thereby providing an optical disk device. Even if there is assembly variation or the like in the pickup or the like, it is possible to cancel the offset due to the influence and perform accurate focus servo.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a servo signal processing device according to first and second embodiments of the present invention.

FIG. 2 is a circuit diagram showing a tracking error detection circuit provided in the servo signal processing device configured to be applied to a magneto-optical disk.

FIG. 3 is a circuit diagram showing a focus error detection circuit provided in the servo signal processing device.

FIG. 4 is a sectional perspective view of a signal recording surface of the magneto-optical disk.

FIG. 5 is a configuration diagram showing a relationship between a photodetector, an objective lens, a semiconductor laser, and a principal ray of a laser emitted from the semiconductor laser in a normal state.

FIG. 6 is a configuration diagram showing a relationship between a photodetector, an objective lens, a semiconductor laser, and a principal ray of laser light emitted from the semiconductor laser when the objective lens is shifted.

FIG. 7 is a configuration diagram illustrating a positional relationship between a photodetector, an objective lens, a semiconductor laser, and a principal ray of laser light emitted from the semiconductor laser when the semiconductor laser is shifted from a design center.

FIG. 8 shows a main part of a photodetector, an objective lens, a semiconductor laser, and laser light emitted from the semiconductor laser when the objective lens is shifted in the outer peripheral direction of the magneto-optical disk with the semiconductor laser deviated from the design center. FIG. 3 is a configuration diagram illustrating a positional relationship between light rays.

FIG. 9 shows a photodetector, an objective lens, a semiconductor laser, and laser light emitted from the semiconductor laser when the objective lens shifts in the inner circumferential direction of the magneto-optical disk with the semiconductor laser deviated from the design center. FIG. 3 is a configuration diagram illustrating a positional relationship between principal rays.

FIG. 10 is a characteristic diagram illustrating a relationship between an offset cancellation amount and a lens shift.

FIG. 11 is a characteristic diagram showing a relationship between a defocus amount and a lens shift.

FIG. 12 is a circuit diagram showing a tracking error detection circuit provided in the servo signal processing device configured to be applied to an optical disc.

FIG. 13 is a block diagram of an optical disc device according to third and fourth embodiments of the present invention.

FIG. 14 is a configuration diagram of a conventional servo signal processing device.

[Explanation of symbols]

4 push-pull signal detection circuit, 5 offset cancellation amount generation circuit, 7 tracking error detection circuit, 8
Focus error detection circuit, 9 matrix processing circuit,
10 Second subtractor

Claims (8)

[Claims] 1. A servo signal processing device for performing focus servo and tracking servo based on a light detection signal output by a light detection means according to an amount of return light received from a disk-shaped recording medium, comprising: A focus error detecting means for detecting a focus error signal by detecting a tracking error signal by a push-pull method based on the light detection signal; A tracking error detection unit including an offset cancellation amount generating unit that generates a first offset cancellation amount corresponding to the offset amount generated in the above; and the tracking error detection unit based on the first offset cancellation amount from the offset cancellation amount generation unit. Up according to the spot movement at the light receiving section A matrix processing unit that generates a second offset cancellation amount corresponding to an offset generated in the focus error signal; and a subtraction unit that subtracts the second offset cancellation amount from the focus error signal. Servo signal processing device. 2. The light detecting means comprises at least two light detectors, and the offset canceling amount generating means detects the light out of the return light of one spot beam applied to the disk-shaped recording medium. 2. The method according to claim 1, wherein the first offset canceling amount is generated based on a light detection signal detected based on the return light received by any one of the photodetectors. Servo signal processing device. 3. The offset canceling amount generating means generates the first offset canceling amount based on return light from the disk-shaped recording medium having a recording track on which a meandering guide groove is formed. 3. The servo signal processing device according to claim 2, wherein: 4. The offset cancel amount generating means generates the first offset cancel amount based on return light from the disk-shaped recording medium having a recording track on which pits are formed. Item 3. The servo signal processing device according to Item 2. 5. An optical disk device for performing focus servo and tracking servo based on a light detection signal output by a light detection means in accordance with an amount of return light received from a disk-shaped recording medium, wherein the focusing is performed based on the light detection signal. Focus error detection means for detecting an error signal; and when the tracking error signal is detected by the push-pull method based on the light detection signal, the tracking error signal is generated by spot movement of return light in a light receiving portion of the light detection means. A tracking error detection unit including an offset cancellation amount generation unit that generates a first offset cancellation amount corresponding to the offset; and the light receiving unit based on the first offset cancellation amount from the offset cancellation amount generation unit. Depending on the spot movement at An optical disc comprising: a matrix processing unit that generates a second offset cancellation amount corresponding to an offset generated in an focus error signal; and a subtraction unit that subtracts the second offset cancellation amount from the focus error signal. apparatus. 6. The light detecting means comprises at least two light detectors, and the offset canceling amount generating means detects the light in the return light of one spot beam applied to the disk-shaped recording medium. 6. The method according to claim 5, wherein the first offset cancellation amount is generated based on a photodetection signal detected based on the return light received by any one of the photodetectors. Optical disk device. 7. The offset canceling amount generating means generates the first offset canceling amount based on return light from the disk-shaped recording medium having a recording track on which a meandering guide groove is formed. 7. The optical disk device according to claim 6, wherein: 8. The method according to claim 1, wherein the offset cancellation amount generating means generates the first offset cancellation amount based on return light from the disk-shaped recording medium having a recording track on which pits are formed. Item 7. An optical disk device according to item 6.