JPH11144281A - Disk reproducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detects a tangential tilt from the changeover point of a land part and a groove part. SOLUTION: The inclination with respect to the disk rotational direction (q) of an optical pickup device 17 is adjusted based on a detection output by detecting a tangential tilt in the disk rotational direction from a push-pull reproduced signal at the changeover point of the land part or the groove part in the disk rotational direction formed on a disk 11 or the rising point and falling point of pits formed on the disk. Thus, it is made possible to irradiate a beam vertically with respect to the surface of the disk and the error rate of a reproduced signal is prevented from being deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a disc reproducing apparatus capable of improving deterioration of an error rate due to tilt (tangential tilt) in a rotational direction of a disc on which marks having phase information are preformatted. More specifically, the reproduction rate of a mark or the like having phase information is determined to detect the tangential tilt amount, and mechanical or electrical correction is performed so as to reduce the tilt amount, thereby reducing the deterioration of the error rate. It is something that can be improved.

[0002]

2. Description of the Related Art In a disk recording / reproducing apparatus having a disk-shaped recording medium such as a magneto-optical disk, a disk 11 is rotated clockwise p in this example by a spindle motor 13 as shown in FIG. The recording and reproduction of data is performed by a movable optical pickup device 17 arranged so as to face the board surface.

A light source (not shown) such as a laser is built in the optical pickup device 17, and the data recording surface of the disk 11 is irradiated with laser through an objective lens 17a to record data. The recorded data is reproduced by using the return light of the laser.

[0004]

By the way, the disk 1
1 may be inclined with respect to the rotation direction p instead of the radial direction q. If the inclination (tilt) is hereinafter referred to as tangential tilt, the tangential tilt may be caused by the disc itself or may be caused by other factors.

[0005] As a case caused by the disk itself, there is surface deviation of the disk 11. Possible causes other than the disk 11 include a case where the disk is not mounted on the spindle motor 13 in a parallel manner, a case where the disk is correctly mounted, but the optical pickup device 17 is inclined with respect to the disk 11 in the rotation direction. Can be

In the latter case, if the rotation direction of the disk 11 is indicated by an arrow p in FIG. 16, if the relative positional relationship between the disk 11 and the optical pickup device 17 is accurate, the direction shown in FIG.
As shown in FIG. 6, the beam is irradiated perpendicularly to the disk surface.

However, if the relative positional relationship deviates, a tangential tilt occurs when the optical pickup device 17 is inclined by θ (radian) with respect to the vertical axis with respect to the rotation direction p as shown in FIG. 17, for example. Therefore, the beam is not irradiated perpendicularly to the disk surface.

When a laser beam is irradiated perpendicularly to the disk surface, a light intensity distribution symmetrical with respect to the optical axis is obtained as shown by a solid curve La in FIG. When the tangential tilt occurs as described above, the light intensity distribution becomes asymmetric with respect to the optical axis, for example, as shown by a chain line curve Lb in FIG.

Therefore, when a beam having a symmetrical light intensity distribution is applied to the pits formed on the disk surface as shown in FIG. 19A, a reproduced signal (FIG. 19B) without distortion as shown by a solid line Lc. As a result, a push-pull reproduction signal Spp described later is obtained.

However, when the beam is applied to the disk surface where the tangential tilt has occurred, the beam is not irradiated perpendicularly to the disk surface, resulting in an asymmetrical light intensity distribution. As a result, as shown by the chain line curve Ld in FIG. Only a reproduced signal Spp which is asymmetrical left and right and whose output level is lowered can be obtained. If the reproduction signal Spp is asymmetric, the data at the time of recording cannot be correctly reproduced, and the error rate deteriorates.

Conventionally, no improvement has been made for the deterioration of the error rate due to the tangential tilt. Such deterioration of the error rate becomes remarkable especially when a small-diameter disk for high-density recording is used.

In view of the above, the present invention has been made to solve such a conventional problem, and in particular, to provide a disk reproducing apparatus capable of improving the error rate deterioration due to tangential tilt.

[0013]

In a disk reproducing apparatus according to the present invention, a switching point of a land or a groove in a disk rotating direction formed on a disk or a rising point and a falling point of a pit formed on the disk. , The tangential tilt in the disk rotation direction is detected from the push-pull reproduction signal, and the tangential tilt is corrected based on the detected output.

In the present invention, focusing on the fact that the level of the push-pull reproduction signal at the switching point of the land portion or the groove portion changes depending on the amount of tangential tilt in the disk rotation direction, the tangential tilt amount is calculated from this reproduction signal. To detect. The tangential tilt is corrected based on the detected output. Specifically, the state of attachment of the spindle motor is adjusted, and the inclination of the optical pickup device with respect to the disk rotation direction is adjusted.
By this adjustment, the beam is irradiated in a state substantially perpendicular to the disk surface, whereby the error rate of the reproduced signal can be improved.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a disk reproducing apparatus according to the present invention applied to a magneto-optical disk apparatus (disk recording / reproducing apparatus). explain.

According to the present invention, the reproduction signal (push-pull reproduction signal) at the rising and falling points of the pits preformatted on the disk is asymmetrical in accordance with the amount of tilt in the disk rotation direction, that is, the tangential direction. By focusing on the tangential tilt amount and performing mechanical or electrical correction based on this detection signal, the light intensity distribution of the beam applied to the disk surface is almost symmetrical with respect to its optical axis. Thus, the error rate of the reproduction signal is improved.

In this example, the pit preformatted on the disk 11 indicates a clock mark by groove wobble. This is because a clock mark is formed by pits formed in grooves or lands as described later. The following is a case of a magneto-optical disk in which a clock mark is preformatted together with address information.

As shown in FIG. 8, in the magneto-optical disk 11, tracks 0 to n are formed spirally from the inner circumference toward the outer circumference, and each track has sectors 0 to m in the circumferential direction. It is included.

FIG. 9 shows a sector (wamble address frame) format. As described above, the groove portions 12G and the land portions 12L are alternately formed on the magneto-optical disk 11 in the radial direction, and data is recorded on one or both of the groove portions 12G and the land portions 12L.

As shown in FIG. 9A, one side of the groove portion 12G has, for example, address information ADM after biphase modulation.
Is wobbled according to. In this case, the address information ADM is frequency-modulated (FM), and the groove 12G is wobbled so as to correspond to the modulated signal. That is, the modulated signal is recorded as a groove wobble.

Since one side of the groove 12G is wobbled, one side of the land 12L is also wobbled in accordance with the address information ADM.

As shown in FIG. 10, the number of groove wobbles is four when the bit is "1" and three when the bit is "0", per one bit (one bit of the biphase) of the address information ADM. . Moreover, the amplitude of the groove wobble is changed in accordance with the frequency of the signal after modulation, and as shown in the enlarged view of FIG.
The inclination at the 0 cross point of the groove wobble corresponding to the joint between “1” and “0” of DM is not changed.

One sector (one wobble address frame)
The groove wobble in the period has data before bi-phase modulation, for example, 48-bit data. this,
As shown in FIG. 9B, the 48-bit data includes 4 bits of synchronization signal data, 24 bits of frame address data, 6 bits of reserved bits, and 14 bits of CRC.
(Cyclic redundancy check) code.

As shown in FIG. 9C, one sector is composed of, for example, 24 segments. At the boundary position of each segment, as shown in FIG. 9A, a clock mark CM is multiplexed into a groove wobble and preformatted. As shown in FIG. 9D, a 100-byte data area is provided in each segment, and a 10-byte fixed pattern area is provided corresponding to the boundary position of each segment. At the time of data writing, NRZI data is recorded in the data area as described later, but the fixed pattern area is synchronized with the NRZI data.
A fixed pattern signal of T is recorded (T is a data bit interval).

The above-described clock mark is formed as shown in FIG. In the figure, the area where the mark is formed is a switching point between the land and the groove. That is, instead of the groove of the groove portion 12G being formed as a land portion over a certain width (bit length) W, the same width W is formed as a clock mark groove at an adjacent land portion at this switching point.

When the land and the groove are switched in this way, for example, when the beam Ba scanning on the land 12L starts scanning the clock mark groove, the return light of the beam at that time is as shown in FIG. 12B. Among the four divided photodetectors Da to Dd, only two photodetectors in this example correspond to Dc and Dd (shown by oblique lines).

On the other hand, when the beam crosses the end of the clock mark groove, the diffraction of the return light is reversed. Therefore, the return light is one of the four photodetectors Da to Dd divided as shown in FIG. 12C. This corresponds to only the adjacent photodetectors Da and Db (shown by oblique lines). Therefore, four photodetectors D
If the signals Sa to Sd of a to Dd are output as push-pull signals as Spp = (Sa + Sb)-(Sc + Sd) (1), the land portion 12L and the groove portion 12 are output.
Can be obtained polarity different reproduced signal (clock mark signal) S _CM as shown in FIG. 11B in the switching point of the G. Pulse signal P _CM as shown from the reproduced signal S _CM in the drawing C is formed, P with reference to the pulse signal P _CM
A data clock signal is formed by an LL (phase-locked loop) circuit.

Now, the land portion 12L and the groove portion 12G
The clock mark CM can be formed by forming a pit at the switching point of the clock mark CM.
Such as the output level of by the clock mark signal S _CM was found to be dependent on the tangential tilt amount. For example, when no tangential tilt occurs, the signal is output as a vertically symmetric signal as shown in FIG. 11B, that is, the curve Lf in FIG.

However, when a tangential tilt occurs, the peak level differs between the plus side and the minus side as shown by the curve Lg in FIG.
Clock mark signal S _CM central portion raised asymmetric waveform is obtained. FIG. 13 shows a measurement example when the pit length W is 18 μm, the depth of the groove Gg is λ / 8 (λ is the recording wavelength), and the track pitch is 0.6 μm. The curve Lf is a measurement example when tilting by +20 mrad (milliradian: upward in the rotation direction) with respect to the rotation direction.

Here, the positive peak value of the clock mark signal S _CM is PK (+), and the negative peak value is P (P).
If K (-), PK (+) = Sa + Sb (2) PK (-) = Sc + Sd (3) Then, the sizes of PK (+) and PK (-) It can be seen that changes with the tangential tilt amount.

Now, assuming that the ratio (%) of the unbalance between PK (+) and PK (-) is a TPP signal, TPP = {PK (+)-PK (-)} / {PK (+) + PK (−)｝ × 100 (%) (4) As a result, a characteristic curve as shown in FIG. 14 is obtained.

The curve Lh has a pit length W shown in FIG.
The curve Li shows the unbalance amount when the pit length is 18 μm, which is twice the pit length. The curve in the first quadrant indicates the amount of imbalance when tilt occurs on the side where the disk 11 faces upward (the side opposite to the optical pickup device 17) with respect to the rotation direction, and the curve in the third quadrant faces downward. Shows the amount of unbalance when tilt occurs on the side.

[0033] Since the unbalance amount of TPP in relation to the direction and amount of tilt of the thus tangential tilt clock mark signal S _CM is obtained by multiplying the mechanical or electrical feedback thus unbalanced weight TPP is eliminated Thus, it is possible to correct the deterioration of the reproduced signal due to the tangential tilt.

First, the case where the mechanical correction means is applied to the above-described magneto-optical disk device will be described. As mechanical correction means, the mounting angle of the spindle motor 13 with respect to the disk rotation direction is adjusted according to the tangential tilt amount, or as shown in FIG. 2, the angle of the optical pickup device 17 with respect to the disk rotation direction is adjusted. I just need. FIG. 1 shows an example of the latter.

As shown in FIG. 1, a description will be given of a magneto-optical disk drive 10 as an example to which the present invention is applied. In FIG. 1, a frequency generator 1 for detecting the rotation speed is provided on the rotation shaft of a spindle motor 13 in order to rotate the disk 11 at a constant angular velocity during recording and reproduction.
4 is attached.

The magneto-optical disk drive 10 includes a magnetic head 15 for generating an external magnetic field, a magnetic head driver 16 for controlling the generation of a magnetic field of the magnetic head 15, a semiconductor laser,
The optical head device 17 includes an objective lens, a photodetector, and the like, and a laser driver 18 that controls light emission of a semiconductor laser of the optical head device 17. The magnetic head 15 and the optical head device 17 are disposed to face each other with the magneto-optical disk 11 therebetween. Laser driver 1
8, a laser power control signal _SPC is supplied from a servo controller 41 to be described later via the D / A converter 19, and the power of the laser beam output from the semiconductor laser of the optical head device 17 is changed during recording and reproduction. Each is controlled to be optimal.

To set the optimum power Pw at the time of recording and to set the optimum power Pr (Pw> Pr) at the time of reproduction, a power control signal corresponding to the recording / reproduction mode is supplied from the system controller 51 to the servo controller 41, which will be described later. Can be

At the time of data writing (at the time of recording), the recording data Dr and the fixed pattern signal _SFP are supplied to the magnetic head driver 16, and the recording data D
r and a magnetic field corresponding to the fixed pattern signal _SFP are generated, and the recording data Dr is recorded in the data area of the magneto-optical disk 11 in cooperation with the laser beam from the optical head device 17.
Is recorded, and the fixed pattern signal _SFP is recorded in the fixed pattern area corresponding to the data area where the recording data Dr is recorded.

When recording the recording data Dr, it is common practice to further modulate the laser beam modulated by the recording data Dr with the data clock signal DCK obtained from the data clock reproducing unit 70. For this purpose, the data clock signal DCK reproduced by the data clock reproducer 70 is supplied to the laser driver 18.

In the recording mode, the laser driver 18 is controlled to the reproduction mode during the period PB (corresponding to the width W) in which the clock mark CM is pre-formatted, and the laser beam is modulated by the data clock DCK only during this period PB. Interrupted.

As shown in FIG. 12, the photodetector 39 includes a photodetector 39m (B and C in FIG. 12) having the above-mentioned four divided photodetectors (such as photodiodes).
A photodetector 39i composed of two photodiodes,
39j (FIGS. A and D).

In response to the detection signals Sa to Sd of the four photodiodes Da to Dd, the detection signals of the photodiodes Di and Dj constituting the photodetectors 39i and 39j are represented by Si and
In the case of Sj, the following calculation is performed in the amplifier circuit unit (not shown) of the optical head device 17, and the reproduction signal S _MO from the recording area, the focus error signal S _{FE of the} astigmatism method, and the push-pull signal S _{A PP} is generated. S _MO = Si-Sj (5) S _FE = (Sa + Sc)-(Sb + Sd) (6) S _PP = (Sa + Sb)-(Sc + Sd) (7)

Returning to FIG. 1, the disk device 10
A servo controller 41 having a U (central processing unit) is provided. The focus error signal _SFE generated by the optical head device 17 is supplied to the servo controller 41 via the A / D converter 42. Further, the push-pull reproduction signal S _PP generated by the optical head device 17 includes a tracking error signal S _TE by the push-pull method, a wobble signal (FM signal) S _WB corresponding to the groove wobble of the magneto-optical disk 11, and an optical signal. a clock mark reproduced signal S _CM corresponding to the clock mark CM of the magnetic disk 11 is synthesized.

[0044] The servo controller 41, the push-pull reproduced signal S _PP from the tracking error signal extracted by the low-pass filter 43 S _TE is supplied through an A / D converter 44. This servo controller 41 includes:
Further, a frequency signal _SFG output from the frequency generator 14 described above is supplied.

The servo controller 41 controls an actuator 45 including a tracking coil, a focus coil, and a linear motor for moving the optical head device 17 in the radial direction, and performs tracking and focus servo. Apparatus 1
7 is controlled in the radial direction.

Further, the spindle motor 13 is controlled by the servo controller 41 so that the magneto-optical disk 11 is controlled so as to rotate at a constant angular velocity during recording and reproduction as described above.

The disk device 10 includes a system controller 51 having a CPU, a data buffer 52, and a SCSI (Small Computer System Interface) for transmitting and receiving data and commands to and from a host computer.
Interface 53. The system controller 51 controls the entire system.

The disk device 10 performs an error correction code addition process on write data supplied from the host computer via the SCSI interface 53, and performs an error correction process on output data of a data demodulator described later. ECC (error correction)
code) circuit 54 and the write data to which the error correction code has been added by the ECC circuit 54.
to Zero Inverted) data and record data Dr
And a data modulator 55 for generating the above-described fixed pattern signal _SFP .

The disk device 10 has an A / D converter 56 for converting the reproduction signal _SMO generated by the optical head device 17 into a digital signal, and an equalizer circuit for compensating the frequency characteristics of the digital signal. 57
A data discriminator 58 that digitally performs data discrimination processing on the frequency-compensated output data to obtain reproduced data Dp, and performs NRZI inverse conversion on the reproduced data Dp output from the data discriminator 58. A data demodulator 59 for processing to obtain read data. The data discriminator 58 includes a binarizing circuit, a Viterbi decoder, and the like.

[0050] Also, the disk device 10, ADIP to obtain a wobble signal S _WB from the frame synchronizing signal FD and the frame address data FAD included in the push-pull signal reproducing No. S _PP produced in the optical head apparatus 17 (Address
And In Pre-groove) decoder 60, a data clock reproducing obtaining data clock signal DCK from the push-pull reproduced signal S clock mark reproduction signal included in the _PP S _CM and a reproduction signal S _MO corresponding to the fixed pattern region of the magneto-optical disc 11 And a timing generator 90 that generates a timing signal necessary for each part of the system such as a read gate signal and a write gate signal using the frame synchronization signal FD, the frame address data FAD and the data clock signal DCK. ing. The frame address data FAD is also supplied to the servo controller 41, and the data clock signal DCK is supplied to the A / D converter 56 as a sampling clock.

According to the present invention, in addition to the above-described configuration, the tangential tilt amount is detected and corrected. In the following embodiment, the optical pickup device 17 can be tilt-adjusted with respect to the disk rotation direction as shown in FIG. 2 as a mechanical correction means.

For this reason, first, as shown in FIG. 1, the above-described push-pull reproduction signal _SPP is supplied to the low-pass filter 43 to output a band-limited reproduction signal _STE , and this reproduction signal _STE is subjected to A / D conversion. The digital data is supplied to the servo controller 41 after the digital conversion by the device 44. In the servo controller 41, the built-in CPU
The tangential tilt amount and the tilt direction are detected based on a control program stored in a ROM (neither is shown).

That is, the peak value PK shown in FIG.
(+) And PK (-) are calculated respectively, and the calculated peak values PK (+) and PK (-) are substituted into the equation (4) to obtain the unbalance amount TPP. A control signal indicating the obtained unbalance amount TPP is supplied to the tilt adjusting unit 100, and the tilt amount of the optical pickup device 17 is controlled according to the value.

FIG. 3 shows an example of the tilt adjusting means 100. In a well-known manner, a drive coil (not shown) for adjusting focus and tracking is provided on an inner casing 101 in which an objective lens 17a is arranged at the upper center thereof. (Not shown) is provided. Rotation shafts 102 are respectively attached to left and right side surfaces of the inner housing 101 which are positioned in a direction orthogonal to the disk rotation direction, and the left and right rotation shafts 102 are attached to the outer housing 103 as shown in FIG. Supported.

Although not shown, the outer casing 10
Reference numeral 3 is also used as a housing of a slide drive unit (not shown) for sliding the entire optical pickup device 17 in the disk radial direction, and constitutes a part of the slide drive unit. A linear motor or the like can be used as the slide driving means.

The tilt adjusting section 105 is provided on the front and rear side surfaces of the inner casing 101 located on the disk rotation side, in the illustrated example, on the front side surface. In this example, the tilt adjusting unit 105 includes an arc-shaped tooth (arc-shaped rack) 106 and a pinion gear 107 meshing with the arc-shaped tooth.
Is driven by a stepping motor 108.

When the tilt adjusting device 100 is configured as described above, of the unbalance amount TPP shown in FIG. 14, the unbalance amount obtained at a certain disk rotation angle is + TP in FIG.
When the pressure is Pa, a control signal (direction and amount of tilt correction) is generated based on the unbalanced signal + TPPa.
8 is controlled so that the tilt amount becomes zero.

For example, when a tilt (+ TPPa) on the plus side (upward) with respect to the disc rotation direction occurs as described above, the beam is perpendicular to the disc surface by tilting the optical pickup device 17 to the minus side. It will be irradiated.

In many cases, the tangential tilt amount is not uniform in the disk rotation direction. In this case, the unbalance amount TPP is calculated in accordance with the disk rotation angle position. Value.

The above example is an example in which the tangential tilt is corrected by mechanical control.
Tangential tilt can also be corrected by electrical correction. FIG. 5 shows an embodiment of the present invention. In this example, the frequency characteristic of the equalizer circuit 57 is corrected.

As shown in FIG. 18, when the beam does not hit the disk surface perpendicularly, the beam intensity on the disk surface becomes like a dashed line curve Lb, and the push-pull reproduction signal SPP obtained thereby is also shown in FIG. Is output as a blunted waveform. This waveform is corrected by the equalizer circuit 57 described above.

The curve shown in FIG. 19 is reproduced as a curve Lg in FIG. In the figure, a curve Lf is an output waveform when there is no tangential tilt. The curve Lf is almost symmetrical about the peak of the output waveform on the left and right, but the curve Lg when tilt occurs is asymmetrical about the peak on the left and right. Therefore, the equalizer circuit 57
In this case, the equalizer circuit 57 needs to correct the left-right asymmetry so that the right-left asymmetry is correctly corrected.

FIG. 7 shows a specific example of the equalizer circuit 57. The figure shows two cascaded delay elements 110, 1
11 shows a digital equalizer circuit composed of 11, three coefficient units 112, 113 and 114, and an adder 115. Assuming that the respective coefficients are ka to kc, the waveform position in FIG. 6 is corrected by these coefficients ka to kc. Now, each of the coefficients ka to kc when no tangential tilt occurs, When the output waveform when the tangential tilt is generated is equalized with the coefficient as it is, the above-mentioned curve Lg is obtained.

On the other hand, asymmetry correction is performed. For example, When the waveform is equalized by an asymmetric coefficient such as shown in FIG.

As is clear from comparison between the two curves Lf and Lh, it can be seen that the curve Lf is closer to the normal curve Lf than before the asymmetry correction is performed. In particular, the waveform on the right side of the peak almost coincides, and the left side also approaches the normal waveform.

If the waveform is equalized in this way, even if a tangential tilt occurs, the output waveform can be made closer to a normal output waveform, so that the error rate of the reproduced signal can be improved.

The tangential tilt is detected not only by using the switching point between the land 12L and the groove 12G, but also when the address formed on the disk surface is formed as pit information. Utilization can be used to detect tangential tilt.

In the above description, only one side of the groove portion 12G of the magneto-optical disk 11 is wobbled. However, the side portion of the groove portion 12G may be wobbled.

Although the clock mark CM is preformatted on the wobbled side of the groove portion 12G, the clock mark CM may be preformatted on the non-wobbled side. The CM may be pre-formatted.

"1" and "0" of address information ADM
The wave number of the groove wobble corresponding to is "4",
Although “3” is used, the present invention is not limited to this and may not be an integer.

Although the fixed pattern area of the recording area is provided in one-to-one correspondence with the recording position of the clock mark CM, it is not always necessary to make it correspond. For example, the number of fixed pattern areas may be smaller than the number of clock marks CM.

[0072]

As described above, according to the present invention, in the disc rotation direction in the disc rotation direction on the basis of the reproduction push-pull signal at the switching point of the land or groove section preformatted on the disc and the rising and falling points of the pits. This is to detect a tilt.

According to this, the tangential tilt can be detected without using any special tilt detecting means. By correcting the mounting position of the spindle motor and the tangential tilt angle of the optical pickup device based on the tilt detection output, the reproduced waveform is improved, and thus the error rate of the reproduced signal can be greatly improved. .

[Brief description of the drawings]

FIG. 1 is a block diagram (No. 1) showing a configuration of an embodiment of a disk reproducing apparatus according to the present invention.

FIG. 2 is a conceptual diagram of one embodiment according to the present invention.

FIG. 3 is a configuration diagram of a main part showing an embodiment of a tilt correction device.

FIG. 4 is a side view thereof.

FIG. 5 is a block diagram (part 2) showing a configuration of an embodiment of a disk reproducing apparatus according to the present invention.

FIG. 6 is a diagram illustrating an example of an output waveform of an equalizer circuit.

FIG. 7 is a system diagram showing an embodiment of an equalizer circuit.

FIG. 8 is a diagram showing a layout of sectors on a magneto-optical disk.

FIG. 9 is a diagram for explaining a sector (wobble address frame) format.

FIG. 10 is a diagram illustrating a configuration example of a groove wobble.

FIG. 11 is a diagram showing a relationship between a land portion, a groove portion, and a clock mark.

FIG. 12 is a diagram showing a configuration of a photodetector constituting an optical system and a spot formed thereon.

FIG. 13 is a characteristic diagram showing a relationship between a tangential tilt and an output waveform.

FIG. 14 is a diagram illustrating a relationship between a tangential tilt and an unbalanced signal.

FIG. 15 is an explanatory diagram of a tangential tilt.

FIG. 16 is an explanatory diagram when there is no tangential tilt.

FIG. 17 is an explanatory diagram when there is a tangential tilt;

FIG. 18 is a diagram showing a relationship between a spot and a beam intensity.

FIG. 19 is a diagram showing the influence of the tangential tilt on the output waveform.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Magneto-optical disk device, 11 ... Magneto-optical disk, 12G ... Groove part, 12L ... Land part, 15 ... Magnetic head for generating an external magnetic field, 16 ...
.Magnetic head driver, 17 ... optical head device, 1
8 Laser driver, 41 Servo controller, 51 System controller, 52 Data buffer, 53 SCSI interface, 54
... ECC circuit, 55 ... Data modulator, 57 ...
.Equalizer circuit, 100 ... Tilt control circuit, 10
2 ... Rotary axis

Claims (5)

[Claims] 1. A tangent in the disk rotation direction from a push-pull reproduction signal at a switching point of a land or a groove in the disk rotation direction formed on the disk or at a rising point and a falling point of a pit formed on the disk. A disc reproducing apparatus characterized by detecting a partial tilt and correcting the tangential tilt based on the detected output. 2. The disk reproducing apparatus according to claim 1, wherein when the tangential tilt is detected, the state of attachment of the spindle motor to the disk is corrected. 3. The disk reproducing apparatus according to claim 1, wherein when the tangential tilt is detected, the inclination of the optical pickup device with respect to the disk rotation direction is adjusted. 4. The disk reproducing apparatus according to claim 1, wherein when the tangential tilt is detected, an equalizer characteristic of the reproduced signal is controlled. 5. The disk reproducing apparatus according to claim 4, wherein said equalizer characteristic is corrected so as to be left-right asymmetric with respect to a peak value of a reproduction waveform.