JP2003317414A - Device and method for writing servo information and magnetic disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize a deviation influence with no reproducibility on a disk in writing servo information on the disk. <P>SOLUTION: This servo information writing device which is applied to a magnetic disk drive 100 having a magnetic disk 1 rotated by a spindle, a magnetic head 3 for recording information on the magnetic disk or reading the information from the magnetic disk and an actuator 6 for moving the magnetic head in the radial direction of the magnetic disk and writes servo information for performing position control of the magnetic head at a position of each track of the magnetic disk is provided with an optical detection device 50 for detecting rotation position information on the outmost circumferential side face of the magnetic disk in a noncontact manner and a controller 70 for writing the servo information on the magnetic disk by the magnetic head on the basis of detection results of the optical detection device. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting angular position (circumferential direction) position information on a continuously rotating disk-shaped rotating object with high accuracy, and more particularly to detecting rotational position information of a continuously rotating hard disk or the like. The present invention relates to an apparatus for writing servo track information on a disk while detecting it with high accuracy.

[0002]

2. Description of the Related Art At present, for example, a hard disk drive (HDD) having a disk coated with a magnetic material is mainly used as a recording / reproducing means used in an information processing apparatus such as a computer. When a signal (information) is written on this disk (magnetic disk) by using a magnetic head, it is necessary to write information for positioning the magnetic head, a so-called servo track signal, on the magnetic disk with high accuracy.

FIG. 5A is an image diagram of a servo pattern on the magnetic disk, and FIG. 5B is an example of the servo pattern. In the servo pattern of this example, writing is performed with a resolution of 1/2 of the data track.

In order to write the servo track signal on the magnetic disk with high accuracy by the magnetic head, not only the position information of the magnetic head in the radial direction (track direction) of the magnetic head but also the position information in the rotating direction of the magnetic disk is highly accurate. Therefore, it is necessary to write the magnetic signal at a desired position on the magnetic disk.

As a method for controlling the position of the magnetic head in the track direction with high accuracy, as shown in FIG.
A method of forcibly fixing the rotational position of the drive to a rotational position corresponding to a desired track by a rotary positioner (not shown) is mainly used.

As a method for detecting the rotational direction of the magnetic disk with high accuracy, a method using a magnetic clock head is mainly used in addition to the original magnetic head for writing information.

FIG. 7 is a block diagram of essential parts of a method using a magnetic clock head.

In this method, first, the magnetic clock head 7 enters the HDD 100 through the opening 8 and writes a rotational signal (clock signal) in the outermost peripheral portion of the magnetic disk 1. While reading the clock signal again by the magnetic clock head, the disk rotation position is detected and the servo track signal corresponding to each track is written by the information writing magnetic head.

[0009]

However, in today's mass production of HDDs, the above clock head has to enter tens of thousands of HDDs and write clock signals in a short period of time. Don't
As a result, maintenance such as replacement of the clock head is required, and the clock head itself becomes a consumable item, which causes a cost increase. Further, since the gap between the magnetic disk and the clock head needs to be kept very small, an abnormal situation such as contact between the magnetic disk and the clock head may occur due to some cause, and mass production of HDDs can be performed efficiently. The situation was unfavorable in terms of structure in terms of economic performance.

Further, a GMR head or the like has come to be used as a magnetic head due to the influence of high densification in recent years. However, since the magnetic film formation of the magnetic disk is also different from the conventional one, the clock head is also the internal magnetic head. Will need to be adjusted to. However, as the head becomes compatible with higher density, it becomes necessary to make the flying gap between the magnetic disk and the head smaller, so that the handling becomes severe, and the increase in the frequency of replacement of the clock head becomes a big problem. .

As a method for solving this problem, Japanese Patent Application Laid-Open No. 7-29229 discloses a method using a laser Doppler system for irradiating a light diffusing object with a laser beam to detect rotational position information of a rotating object.

According to the laser Doppler system, the hub of the magnetic disk may be irradiated with a laser beam,
There is no need to attach a special object such as a scale, and since it is non-contact, the detector does not wear and is in an ideal state in terms of structure.

FIG. 8 is a diagram showing an example of the laser Doppler velocimeter.

The laser Doppler velocimeter utilizes the effect (Doppler effect) of irradiating a moving object with laser light and causing the frequency of light scattered by the moving object to shift in proportion to the moving speed. A device for measuring the moving speed of the moving object.

In FIG. 8, reference numeral 51 is a laser, 52 is a collimator lens, 53 is a parallel light beam, 54 is a beam splitter, 55a and 55b are light beams, 56a and 56b are mirrors, and 57 is a velocity V in the direction of the arrow. An object to be measured, 58 is a condenser lens, and 59 is a photodetector.

The laser light emitted from the laser 51 is converted into a parallel light flux 53 by the collimator lens 52 and is applied to the beam splitter 54, and the two light fluxes 55a and 55 are generated.
After being divided into b and reflected by the mirrors 56a and 56b, two beams are irradiated at an incident angle θ to the object to be measured 57 moving at a velocity V. The scattered light from the object is collected by the condenser lens 58.
Is detected by the photodetector 59. The frequencies of the light scattered by the two light fluxes are + Δf and −Δ, respectively, in proportion to the moving speed V.
Receive a Doppler shift of f. Here, if the wavelength of the laser light is λ, Δf can be expressed by the following equation (1).

Δf = V · sin θ / λ (1) The scattered light subjected to the Doppler shift of + Δf, −Δf is
They interfere with each other to cause changes in brightness and darkness on the light receiving surface of the photodetector 9, and the frequency F thereof is given by the following equation (2).

F = 2 · Δf = 2 · V · sin θ / λ (2) From the equation (2), if the frequency F of the photodetector 59 (hereinafter referred to as Doppler frequency) is measured, the speed of the object 57 to be measured. V is required.

Velocity V when the object 57 to be measured is a rotating object
When the irradiation radius is r and the rotation speed is Wrpm, V = 2 · π · r · W / 60 (3), and the equation (2) finally becomes as follows.

F = π · r · W · sin θ / 15λ (4) Converting this into the number of pulses N per rotation, N = 4 · π · r · sin θ / λ (5) The rotational position information can be detected by detecting this pulse signal.

On the other hand, when the magnetic disk 1 of the HDD 100 rotates, an NRRO (Non-Repeatable Run Out) so-called non-reproducible shaft run-out of about 0.1 micron occurs, and the influence of this NRRO is suppressed to the maximum. Forming a signal is an important item in writing a stable servo track signal.

FIG. 9 shows a method for maximizing the influence of NRRO, which is already filed by the applicant of the present invention.
It is a principal part block diagram of the apparatus disclosed by 001-141432 gazette.

The track direction of the magnetic head 6 is sequentially controlled by a rotary positioner (not shown) corresponding to each track, and LDV (Laser Doppler Velocimeter)
The servo track signal for each track is written on the magnetic disk based on the rotational position information of the magnetic disk 1 obtained by the signal processing logic 60 for processing the Doppler signal from the optical head 50.

The signal in FIG. 10A shows the signal amplitude of the Doppler signal from the LDV optical head 50 with respect to the rotational position. This signal amplitude is reproducible with respect to the rotational position if the laser beam irradiation area of the disk hub 2 is the same. FIG. 10B shows a Doppler signal (upper part) near the rotational position origin signal (lower part) and a waveform shaping signal (middle part) obtained by comparing the Doppler signal. The frequency of the Doppler signal is proportional to the rotation speed if the radius of the laser beam irradiation position on the disk hub 2 is always the same.

The magnetic disk 1 has a reproducible shake (RRO) and a non-reproducible shake (NRRO), and the reproducible RRO is similarly displaced at the same rotational position. Even if the shake exists as a detection error, it does not cause a writing error in writing the servo track signal because the same detection error is put on each track. On the other hand, NRRO, which does not have reproducibility, has detection errors randomly appearing on each track. Therefore, suppressing the detection errors as much as possible is the key to improving the accuracy of servo track signal writing.

FIG. 11 is a diagram for explaining the positional relationship between the magnetic disk 1 and the magnetic recording head (slider) 3 in the detection direction of the LDV optical head.

With the direction of the magnetic recording head 3 with respect to the center of the magnetic disk 1 as the X axis, X with respect to the vibration width e of NRRO.
The vibration component in the axial direction is ex, the vibration component in the Y axis direction is ey,
The angle of the normal to the X-axis in the LDV detection direction is α, LDV
Assuming that the radius from the center of the magnetic disk 1 at the detection position is r, the detection error component S that the NRRO influences in the LDV detection direction is S = −ex · sinα + ey · cosα (6).

Further, the radius error component V that the NRRO influences in the LDV detection vertical direction is as follows: V = excosα + eysinα (7)

Therefore, assuming that the distance between the disk rotation center and the slider 3 is R, the LDV detection error E due to NRRO at the slider 3 is: E = (R / r) .S. (R + V) / r V.ltoreq. Since e << r, it can be approximated as follows.

E≈ (R / r) S = (R / r)  (-exsinα + eycosα) (8) On the other hand, the disk 1 is offset by ey in the rotational normal direction with respect to the slider 3. Therefore, the relative position detection deviation (writing position deviation) W in the disk rotation direction relative to the slider 3 is W = E−ey = (R / r) · (−ex · sinα + ey · cosα) −ey (9) The writing position shift is converted into the writing angle shift ω as follows.

Ω = W / R = (1 / r) · (−ex · sinα + ey · cosα) −ey / R (10) Generally, NRRO has a vibration width e that does not depend on the direction,
The angle β takes a random value (0 ≦ β <2π). When the conceptual diagram is shown in FIG. 12, it means that the disk center is randomly displaced within the range of the area A in FIG.

At this time, the vibration component ex of the NRRO in the X-axis direction and the vibration component ey of the Y-axis direction are described by e and β as follows.

Ex = e · cosβ, ey = e · sinβ (11) Substituting the equation (11) into the equation (10), ω = (e / r) · {−cosβ · sinα + sinβ · (cosα−r / R)} (12) Here, since the angle β can take a random value within the range of 0 ≦ β <2π, the writing angle deviation | ω | of NRRO at the installation angle α of the LDV optical head 50 The possible value is equal to the maximum value of β in the equation (13) below.

[0034]     │ω│ = ｜ (e / r) ・ {-cosβ ・ sinα + sinβ ・ (cosα-r / R)} |                                                         …(13) The necessary condition for the maximum value of β in equation (13) is       A = -cosβ ・ sinα + sinβ ・ (cosα-r / R) (14) Then, dA / dβ = 0.

When dA / dβ is obtained, it can be transformed as follows.

DA / dβ = sinβ · sinα + cosβ · (cosα−r / R) = cos (β−α) − (r / R) · cosβ = sin (β + π / 2−α) − (r / R) · cosβ Here, c = sin (π / 2−α) −r / R = cosα−r / R, d = cos (π / 2−α) = sinα, sinΦ = c / {√ (c2 + d2)}, cosΦ = If d / {√ (c2 + d2)} (15), then dA / dβ = (√ (c2 + d2)) sin (β + Φ) (16) =-
Φ.

From equation (15), sin β = −c / {√ (c2 + d2)} cosβ = d / {√ (c2 + d2)} (17) Equation (17) gives the maximum value of β in equation (13). It is a necessary condition for taking.

Substituting equation (17) into equation (14), A = {-d.sinα-c. (Cosα-r / R)} / {√ (c2 + d2)} =-{sin2α + (cosα-r / R) 2} / √ {sin2α + (cosα-r / R) 2} = -√ {sin2α + (cosα-r / R) 2} (18) Therefore, the maximum value ωma of the write angle deviation | ω |
x is ωmax = | − (e / r) · √ {sin2α + (cosα−r / R) 2} | = (e / r) · √ {1+ (r / R) 2-2 · (r / R)・ Cosα} (19) From equation (19), if R is a constant, ωm when α = 0 rad
It can be seen that ax becomes the minimum.

According to the description of the above publication, the LDV detection direction is in the vicinity of a vertical line to the straight line connecting the center of the rotating object and the information recording head (slider), and the detection position is on the information recording head side with respect to the center of the rotating object. In this case, it is shown that the clock signal can be formed by the LDV that is least affected by the detection error due to the NRRO.

However, the technique described in the above publication presupposes that the NRRO behavior between the surface of the disk hub 2 and the surface of the disk 1 under the magnetic head 3 is rigid. In a 2.5-inch HDD with a single disk, the surface of the disk 1 and the surface of the disk hub 2 are almost the same, and this premise is almost true. For example, a 3.5-inch disk with multiple disks
In the HDD, a mode in which the behavior of the surface of the disk hub 2 and the surface of the disk 1, which have different axial heights, has no correlation is generated due to the shaft runout of the spindle bearing.

Focusing on the NRRO modes having no correlation only in the Y-axis direction, NRRO; e1 of the surface of the disk 1 and NRRO; e2 of the surface of the hub 2 are obtained. Like

Ω = e1 / R + e2 / r (20) Since e1 and e2 have values peculiar to each HDD, and R depends on the position of the slider 3, the LDV detection position radius has a degree of freedom. It can be said that only r. As can be seen from equation (20), in order to reduce the writing angle deviation ω, LD
The V detection position radius r may be increased.

However, the radius of the disk hub surface is generally smaller than that of the disk information surface, and there is a limit, and the disk surface is mirror-finished, and it is very difficult to optically detect the position. .

Therefore, the present invention has been made in view of the above-mentioned problems, and an object thereof is to minimize the influence of non-reproducible shake of the disk in writing servo information to the disk. .

[0045]

[Means for Solving the Problems]
To achieve the object, a servo information writing apparatus according to the present invention includes a magnetic disk rotated by a spindle, a magnetic head for recording information on the magnetic disk or reading information from the magnetic disk, and Applied to a magnetic disk device having an actuator for moving a head in the radial direction of the magnetic disk, and writing servo information for writing servo information for controlling the position of the magnetic head at each track position of the magnetic disk. In the apparatus, an optical detection device that detects rotational position information of the outermost peripheral side surface of the magnetic disk in a non-contact manner, and based on the detection result of the optical detection device, the magnetic head causes the servo information to be recorded on the magnetic disk. And a control device for writing the data.

Further, in the servo information writing apparatus according to the present invention, the optical detecting apparatus is characterized by detecting rotational position information of the outermost peripheral surface of the magnetic disk by using a laser Doppler method.

Further, in the magnetic disk device according to the present invention, in the magnetic disk device in which the servo information is written by using the above-mentioned servo information writing device, the outermost circumference of at least one magnetic disk attached to the spindle. It is characterized in that a measurement surface to be detected by the optical detection device is formed on the side surface.

Further, the magnetic disk device according to the present invention is characterized in that the measurement surface is a light scattering surface.

Further, the magnetic disk drive according to the present invention is characterized in that a scale is formed on the measurement surface.

Further, in the magnetic disk device according to the present invention, a plurality of the magnetic disks are provided, and the optical system is provided on the outermost peripheral surface of at least one magnetic disk located substantially at the center of the plurality of magnetic disks. It is characterized in that a measurement surface to be detected by the detection device is formed.

Further, the magnetic disk device according to the present invention is characterized in that the measuring surface is a light scattering surface.

Further, the magnetic disk drive according to the present invention is characterized in that a scale is formed on the measurement surface.

Further, in the servo information writing method according to the present invention, a magnetic disk rotated by a spindle, a magnetic head for recording information on the magnetic disk or reading information from the magnetic disk, and the magnetic head are used. A servo information writing method applied to a magnetic disk device having an actuator for moving the magnetic disk in a radial direction, for writing servo information for controlling position of the magnetic head at each track position of the magnetic disk. The rotation position information of the outermost peripheral side surface of the magnetic disk is detected in a non-contact manner, and the servo information is written to the magnetic disk by the magnetic head based on the detection result.

Further, in the servo information writing method according to the present invention, when the rotational position information of the outermost peripheral side surface of the magnetic disk is detected in a non-contact manner, it is detected by using the laser Doppler method.

[0055]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below.

First, the outline of the embodiment will be described.

In this embodiment, even when a mode in which the behavior of NRRO on the surface of the disk hub 2 and the behavior of NRRO on the surface of the disk 1 are not correlated, a clock signal that minimizes the influence of NRRO is formed. It is possible.

Specifically, by detecting the position information of the outermost peripheral side surface of the magnetic disk, the rotation NRRO of the magnetic disk is detected.
It is possible to reduce the effect of. As another effect, since the information recording / reproducing area on the disk surface and the clock area are separated, it is possible to maximize the potential of both the magnetic head and the clock head.

Further, by forming the measurement surface for the optical clock head on the outermost peripheral side surface of at least one magnetic disk mounted on the spindle, the servo information writing apparatus is more stable and does not depend on the film formation of the disk information surface. Can be configured.

Further, since the optical clock head is of the laser Doppler type, it is not necessary to provide a special object such as a scale on the outermost peripheral side measuring surface.

Further, only by setting the outermost peripheral side surface of the magnetic disk to be a light scattering surface, it is possible to obtain an optimum structure as a laser Doppler type measurement surface.

The embodiments of the present invention will be specifically described below.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 6 is a block diagram of a main part of the device of the embodiment, which is an example applied to a servo track writer of a hard disk.

The LDV optical head 50 is arranged so as to irradiate the side surface of the disk 1 made of an aluminum material. The side surface of a general aluminum disk is cut out and serves as a light-scattering surface without any special processing, so that there is no problem as an LDV detection surface.

The track direction of the magnetic head 3 is sequentially controlled by a rotary positioner (not shown) corresponding to each track, and obtained by the signal processing logic circuit 60 for processing the Doppler signal from the LDV optical head 50. The sector servo pattern writing control device 70 controls the magnetic head 3 based on the rotational position information of the magnetic disk 1 to write the servo track signal for each track on the magnetic disk 1.

Assuming that the optical resolution of the LDV optical head 50 is p, p = λ / 2 · sin θ (21) as can be seen from the equation (2).

The optical system of the LDV optical head 50 is set to p = 5 μ
Designed to be m, the device indicated by reference numeral 100 is 3.5inc
With hHDD, the irradiation radius r is about 47 mm. In this case, the number of pulses N per rotation is N = 2 · π · r / p≈59062 (22) Rotation speed W of 3.5inch HDD100 is 7200r
Assuming pm, the Doppler frequency F to be processed is
From the equations (4), (21) and (22), F = N · W · / 60 (23) and the Doppler frequency F is about 7 MHz.

The nature of the signal is the same as that described with reference to FIG. 10, and by processing this pulse signal by the signal processing logic circuit 60 as in FIG. 9, the rotational position information of the side surface of the magnetic disk 1 is obtained. It becomes possible to detect, and the servo track signal for each track can be written on the magnetic disk.

FIG. 2 is a diagram for explaining the runout of the disk 1 and the hub 2 due to the runout of the spindle bearing of the spindle motor unit 10 inside the HDD, where 11 is the stator (fixed) part and 12 is the rotor (rotating) part. , 13a, 13
Reference characters b denote upper and lower bearings that connect the rotor and the stator, respectively.

The disc 1 is sandwiched by the disc spacer 21 and the disc hub 2, and the mounting screw 22 is attached.
Is fixed by. Here, motor elements such as coils and permanent magnets are omitted.

FIG. 2 (a) shows a state in which there is no runout of the bearing portion, FIG. 2 (b) shows the rotor 12 falling counterclockwise, and FIG. 2 (c) shows the rotor 12 portion clockwise. Shows the case when it falls. This is an example in which the disk fixing position is located at the center of the shaft shake fulcrum, and for the NRRO; e2 of the surface of the hub 2,
The NRRO; e1 on the surface of the disk 1 is small, and it can be seen that there is no correlation in the NRRO mode. In practice, the fixed position of the disk 1 is not necessarily located at the center of the shaft shake fulcrum, but due to the different shaft heights, NRROs having no correlation occur due to a similar mechanism.

Further, if a plurality of discs are fixed, since the axial heights are different, it can be understood that the NRRO modes are slightly different between the individual discs.

Equation (20) described above is the NR of the surface of the disk 1.
The formula is based on the assumption that RO; e1 and NRRO; e2 of the surface of the hub 2. However, considering the embodiment of the present invention as shown in FIG. 1, the NRRO at the LDV detection position radius r with a degree of freedom of change.
It is important to minimize the detection angle deviation ω ′ caused by the above in order to suppress the writing angle deviation.

If NRRO at the LDV detection position is e ', then ω' = e '/ r (24). Therefore, when the disk side with the largest r is set as the detection position, the above-mentioned mode is used. It is possible to minimize the detection angle deviation due to the NRRO.

As a matter of course, since the NRRO correlation is high between the disc information side and the disc side,
As proposed in Japanese Patent No. 41432, the LDV detection direction is in the vicinity of a vertical line to the straight line connecting the center of the rotating object and the information recording head (slider), and the detection position is on the information recording head side with respect to the center of the rotating object. With such a configuration, it is possible to further suppress the detection error due to NRRO.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
FIG. 4 is a diagram showing an embodiment of the present invention, in which the optical clock head serves as an encoder head 70 and the side surface of the disk 1 serves as a scale 31. Encoder head 70
The structure of is generally the same as that of the LDV, but is omitted here. The other components are shown in FIG.
Is the same as that of the first embodiment. The structure in which the side surface of the disk is a scale is an effective means because molding processing including the scale is possible when the disk material is made of plastic, for example.

Although the detection surface is scaled in the second embodiment, the influence of NRRO is similar to that of the first embodiment, and has the same effect as that of the first embodiment.

(Third Embodiment) FIG. 4 shows the first embodiment of the present invention.
FIG. 13 is a diagram showing a third embodiment which is a modified example of the embodiment of FIG. 3, in which the HDD has a three-disk configuration, and only one side surface (the middle disk) of the three disks has a light-scattering surface. It is processed so that it becomes 32. That is, the configuration of the first embodiment is applied to the center disk.

At present, aluminum disk materials are the mainstream, but HDDs using glass material disks are also increasing due to the demand for smoothness of the disk information surface. In this case, the side surface of the disk may not necessarily be the light scattering surface. In that case, if one side surface of the plurality of disks is made to be a light scattering surface in some form, it can function as the measurement surface of the LDV optical head 50, and the optical clock head can be used without processing all the disk side surfaces. Can be configured.

The form of the light scattering surface may be any form such as mechanical processing, chemical processing, and application of magic ink. Of course, even for aluminum disc materials,
Such a form may be adopted in order to improve the signal stability of the detection surface.

As described above, the above embodiment is
By using the optical clock head and using the side of the disk as the measurement surface, the performance of both the magnetic head and the clock head for recording / reproducing on the disk can be maximized, and the effect of NRRO is minimized. It is possible to generate the clock signal.

Specifically, by detecting the position information on the outermost peripheral side surface of the magnetic disk, the rotation NRRO of the magnetic disk is detected.
It is possible to reduce the effect of. As another effect, since the information recording / reproducing area on the disk surface and the clock area are separated, it is possible to maximize the potential of both the magnetic head and the clock head.

Further, by forming the measuring surface for the optical clock head on the outermost peripheral side surface of at least one magnetic disk mounted on the spindle, the servo information writing apparatus is more stable and does not depend on the film formation of the disk information surface. Can be configured.

Further, since the optical clock head is of the laser Doppler type, it is not necessary to provide a special object such as a scale on the outermost peripheral side measuring surface.

Further, only by forming the outermost side surface of the magnetic disk as a light scattering surface, it is possible to obtain an optimum structure as a measurement surface of the laser Doppler system.

[0086]

As described above, according to the present invention,
In writing the servo information to the disc, it is possible to minimize the influence of non-reproducible shake of the disc.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating whirling of a spindle bearing.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment which is a modification of the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a servo pattern on a magnetic disk.

FIG. 6 is a top view of a hard disk drive.

FIG. 7 is a block diagram of a main part of a configuration using a magnetic clock head.

FIG. 8 is a diagram showing an example of a laser Doppler velocimeter.

FIG. 9 is a diagram showing a method for maximizing the influence of non-reproducible shaft shake.

FIG. 10 is a diagram illustrating a Doppler signal with respect to a rotational position.

FIG. 11: Magnetic disk, magnetic recording head (slider)
FIG. 6 is a diagram illustrating a positional relationship in the detection direction of the LDV optical head with respect to FIG.

FIG. 12 is a conceptual diagram of shaft shake without reproducibility.

[Explanation of symbols]

1 magnetic disk 2 disk hub 3 slider 4 Magnetic head arm 5 Voice coil motor 6 magnetic head 7 Magnetic clock head 8 openings 10 Spindle motor unit 11 Stator 12 rotor 13 bearings 21 disk spacer 22 mounting screws 50 LDV optical head 51 laser diode 52 Collimator lens 53 parallel light flux 54 Beam splitter 55 luminous flux 56 mirror 57 DUT 58 Condensing lens 59 Photodetector 60 signal processing logic 70 Encoder head 100 HDD

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F065 AA03 AA07 DD06 FF04 JJ03                       JJ26 QQ02 QQ03 QQ14 QQ25                 5D096 WW03

Claims (10)

[Claims] 1. A magnetic disk rotated by a spindle, a magnetic head for recording information on or reading information from the magnetic disk, and an actuator for moving the magnetic head in a radial direction of the magnetic disk. And a servo information writing device for writing servo information for controlling position of the magnetic head at each track position of the magnetic disk, wherein the outermost peripheral side surface of the magnetic disk rotates. An optical detection device that detects position information in a non-contact manner, and a control device that writes the servo information to the magnetic disk by the magnetic head based on a detection result of the optical detection device. Servo information writing device. 2. The servo information writing device according to claim 1, wherein the optical detection device detects rotational position information on the outermost peripheral surface of the magnetic disk by using a laser Doppler method. 3. A magnetic disk device in which the servo information is written by using the servo information writing device according to claim 1, wherein the optical disk is provided on an outermost peripheral side surface of at least one magnetic disk attached to the spindle. A magnetic disk device, wherein a measurement surface to be detected by the detection device is formed. 4. The magnetic disk drive according to claim 3, wherein the measurement surface is a light scattering surface. 5. The magnetic disk drive according to claim 3, wherein a scale is formed on the measurement surface. 6. A measurement surface to be detected by the optical detection device, comprising a plurality of the magnetic disks, and the outermost peripheral surface of at least one magnetic disk located substantially at the center of the plurality of magnetic disks. 4. The magnetic disk drive according to claim 3, wherein the magnetic disk drive is formed. 7. The magnetic disk device according to claim 6, wherein the measurement surface is a light scattering surface. 8. The magnetic disk drive according to claim 6, wherein a scale is formed on the measurement surface. 9. A magnetic disk rotated by a spindle, a magnetic head for recording information on the magnetic disk or reading information from the magnetic disk, and an actuator for moving the magnetic head in a radial direction of the magnetic disk. A servo information writing method for writing servo information for controlling the position of the magnetic head at each track position of the magnetic disk, wherein the outermost side surface of the magnetic disk rotates. A servo information writing method, wherein position information is detected in a non-contact manner, and the servo information is written to the magnetic disk by the magnetic head based on the detection result. 10. The servo information writing method according to claim 9, wherein when the rotational position information of the outermost peripheral side surface of the magnetic disk is detected in a non-contact manner, the rotational position information is detected using a laser Doppler method.