JPH109820A - Method and equipment for measuring eccentricity of information recording disc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the eccentricity easily and accurately in a short time by measuring the eccentricity based on the coordinates at the centers of the information recording region, and the inner and outer circumferential fringes of an information recording disc. SOLUTION: A magnetic disc 1 is mounted on a rotary disc 112 and turned at a predetermined period. A pickup drive section 122 shifts an optical pickup 121 to an arbitrary position of a data track DT and delivers a tracking signal for 1 turn while a spindle motor 111 detects the GP transmitting position of the rotary disc 112 and generates a GP signal. Based on a radial displacement signal detected 132a from these signals, a signal analyzing section 132a determines the radial displacement of the track DT (difference between the center of rotation A and the center of the track). Similarly, the differences determined between the centers N, G (center of outside diameter) of the inner and outer fringes of the disc 1) and the center of rotation A. Finally, the distance between the center of track T and the center of inside diameter N is measured as the eccentricity of the disc 1 at the time of conversion into a spatial coordinate having the center of outside diameter G as the center of coordinate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the eccentricity of an information recording disk on which information such as data and programs is recorded in an information recording area formed in advance.

[0002]

2. Description of the Related Art For example, in a computer system, a hard disk device is used as an information recording disk device. Magnetic films are formed on both surfaces of a magnetic disk, which is an information recording disk built in this hard disk device, and the magnetic head is mounted on a head slider floating above the surface of the magnetic disk. And the like are recorded in a track shape, and the data and the like recorded in the track shape on the magnetic film are reproduced.

In recent years, miniaturization and large recording capacity of hard disk drives have been desired.
It is necessary to improve the positioning accuracy of the magnetic head, that is, the tracking accuracy. In a normal tracking servo, a tracking signal written on a magnetic disk is read by a magnetic head, and the movement of a head slider is controlled based on the tracking signal to position the magnetic head at the center of the track. I have.

Since the tracking accuracy of the tracking servo system depends on the accuracy of writing a tracking signal on a magnetic disk by a magnetic head, a head feeding mechanism dedicated to writing a high-precision tracking signal is required to improve the tracking accuracy. Required. However, since the head feed mechanism is a mechanical type, and its accuracy is limited, there is a problem that a desired hard disk drive cannot be reduced in size and increased in recording capacity. Therefore, a so-called pre-emboss type magnetic disk in which a data recording area (hereinafter, referred to as a data zone) and a control signal recording area (hereinafter, referred to as a servo zone) formed of uneven portions on both surfaces of the magnetic disk are respectively formed radially. Proposed.

FIG. 7 is a plan view showing an example of the pre-emboss type magnetic disk, and FIG. 8 is a plan view showing a detailed example thereof. On both surfaces of a substrate made of synthetic resin, glass, aluminum, or the like of the magnetic disk 1, a data zone and a servo zone each formed of an uneven portion are formed radially.

[0006] In the data zone, concentric data tracks DT for recording data and the like are formed so as to be convex portions, and guard bands GB for separating adjacent data tracks DT are formed in concave portions. It is formed so that it becomes. In the servo zone, a burst portion serving as a reference when generating a servo clock and a data track D are provided.
Servo patterns SP such as an address portion for specifying T and a fine pattern portion for tracking control of the magnetic head are formed so as to be convex portions or concave portions.

[0007] The data zone and the servo zone are transferred and formed on the surface between the outer peripheral edge and the inner peripheral edge of the substrate by a stamper attached to a molding die when the ring-shaped substrate is injection-molded. You. Then, a magnetic film is formed on those surfaces, and signals of opposite polarities m1 and m2 are written into the concave and convex portions. As described above, since the servo patterns SP are formed in advance on the magnetic disk 1 with the uneven portions, the tracking accuracy depends on the patterning accuracy of the uneven portions. Since the irregularities are patterned using photolithography or the like, the patterning accuracy of the irregularities can be made higher than the feed accuracy of the conventional head feed mechanism, and the desired hard disk drive can be made smaller and have a larger recording capacity. Can be achieved.

When the pre-embossed magnetic disk 1 having such a structure is used, as shown in FIG. 9, when a stamper for molding is manufactured, when the stamper is attached to a molding die, and when the stamper is punched out. When punching out a center hole of the formed magnetic disk 1 in a misalignment error (hereinafter, referred to as a stamper-related error) in various processes such as
This includes factors of positional deviation errors (hereinafter referred to as magnetic disk-related errors) in various processes such as when the magnetic disk 1 is mounted on a spindle. The center of the DT may be shifted from the rotation center of the magnetic disk 1.

Since the eccentricity due to this shift adversely affects the tracking servo, it is necessary to minimize the amount of eccentricity in each of the above-described steps and manage the final eccentricity to be equal to or less than a predetermined value. . The measurement of the eccentricity of the conventional pre-embossed magnetic disk 1 is performed by, in the final stage of the manufacturing process, mounting the magnetic disk 1 on a spindle to reproduce information, detecting the reproduced signal, and deriving the amount of eccentricity. Have been.

[0010]

According to the conventional method for measuring the eccentricity of the pre-embossed magnetic disk 1, the eccentricity is clarified only in the final stage of the manufacturing process. It will be shipped as a product. Therefore, the yield of the magnetic disk 1 is relatively low, and there is a problem that the manufacturing cost is high.

[0011] Further, there is also a problem that the eccentricity inherent in the ring-shaped data track DT cannot be measured because of the mounting error when the magnetic disk 1 is mounted on the spindle. Further, there is a problem that it is difficult to determine whether the cause of the eccentricity of the magnetic disk 1 is on the stamper side or the magnetic disk side.

In view of the foregoing, it is an object of the present invention to provide an information recording disk eccentricity measuring method and apparatus capable of easily and accurately measuring eccentricity in a short time.

[0013]

According to the present invention, when measuring the eccentricity of an information recording disk on which an information recording area is formed in advance, the information recording area and the inner peripheral edge of the information recording disk are measured. In addition, a coordinate position of a center point with respect to an outer peripheral edge of the information recording disk is obtained from a tracking signal of an optical unit, and the eccentricity of the information recording disk is measured based on the coordinate position of each center point.

According to the above arrangement, since the eccentricity of the information recording disk is measured by the optical means, the amount of eccentricity can be clarified at a relatively early stage of the manufacturing process. Furthermore, since the eccentricity is measured after calculating the coordinate position of the center point with respect to the information recording area, the inner peripheral edge of the information recording disk, and the outer peripheral edge of the information recording disk,
It is possible to clarify the exact amount of eccentricity and the cause of eccentricity.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiments described below are preferred specific examples of the present invention,
Although various technically preferred limitations are given, the scope of the present invention is not limited to these forms unless otherwise specified in the following description.

FIG. 1 is a block diagram showing an embodiment of an eccentricity measuring apparatus for an information recording disk according to the present invention, and a magnetic disk 1 shown in FIG. 7 will be described as an example of an information recording disk. This information recording disk eccentricity measuring device 100
The measuring unit 120 measures the magnetic disk 1 mounted on the rotating unit 110, and the eccentricity of the magnetic disk 1 is measured by the measuring unit 130. Rotating part 11
Numeral 0 is for mounting and fixing the magnetic disk 1 on a rotating disk 112 connected to a spindle motor 111 and rotating the disk.

The measuring unit 120 includes an optical pickup 121
Is moved in the radial direction of the magnetic disk 1 by the pickup drive unit 122, and the trajectory of the data track DT or the like on the magnetic disk 1 is measured by the optical pickup 121. The optical pickup 121 is a general one including a light emitting element, an optical element, a photodetector, and the like. The surface of the magnetic disk 1 is irradiated with, for example, a laser beam, and the reflected light is detected. The tracking of the data track DT on the disk 1 and the inner and outer peripheral edges of the magnetic disk 1 and the like is performed, and the displacement in the radial direction during the tracking is measured.

The measuring unit 130 controls the rotating unit 110 and the measuring unit 120 by the control unit 131, and controls the rotating unit 110
And a signal from the measuring unit 120 is detected, analyzed, and displayed by the processing unit 132. And the control unit 1
The system controller 133 integrally controls the 31 and the processing unit 132. The control unit 131
A spindle control signal from the system controller 133 and an external frequency servo signal are added by an adder 131a, amplified by an amplifier 131b, and output as a spindle servo signal to a spindle motor 111 for control.

Further, a search control signal from the system controller 133 and a tracking error signal from the optical pickup 121 via the amplifier 131c, the matrix circuit 131d and the tracking error detecting section 131e are added by an adder 131f to form a tracking servo signal. , The optical pickup 12
1 to perform tracking control. On the other hand, a search control signal from the system controller 133, an amplifier 131c from the optical pickup 121, and a matrix circuit 13
1d and the tracking error signal passed through the tracking error detection unit 131e are added by an adder 131h, and the added result is output to the pickup drive unit 122.

Further, the focus search signal from the focus search section 131i and the focus signal from the optical pickup 121 via the amplifier 131c and the matrix circuit 131d are added by an adder 131j to form a focus servo signal, which is amplified by the amplifier 131k. Output to the optical pickup 121 for focus control.

The processing section 132 includes an optical pickup 121
Tracking signal from the pickup drive unit 122
And a radial position signal based on the rotation center A of the optical pickup 121 from the optical pickup 121 are input to the signal detecting unit 132a to detect the radial displacement, and the PG signal from the spindle motor 111 is detected by the signal detecting unit 132a. To be entered. Then, the displacement signal and the PG signal are input and analyzed by the signal analysis unit 132b to determine the eccentricity and the eccentricity factor of the magnetic disk 1, and the eccentricity and the eccentricity factor of the magnetic disk 1 are displayed on the display unit 132c. ing.

An operation example of such a configuration will be described with reference to a flowchart of FIG. First, the magnetic disk 1 is placed and fixed on the rotary disk 112 and rotated at a constant period while the reference point of the magnetic disk 1 to be measured coincides with the PG transmission position of the rotary disk 112 (step STP).
1, 2). Note that the reference point of the magnetic disk 1 and the rotating disk 112
If you can not match the PG transmission position of
The phase difference between the reference point of the magnetic disk 1 and the PG transmission position of the turntable 112 is confirmed when the magnetic disk 1 is mounted.

Next, the pickup drive section 122 controls the optical pickup 121 to, for example, an arbitrary data track DT.
And the position signal at that time is detected by the signal detection unit 1.
32a (step STP4). Control unit 131
Controls the optical pickup 121 based on, for example, the tracking condition shown in FIG. 4A (step STP5). Then, a tracking signal for one round of the disk at the time of on-tracking is transmitted to the signal detection unit 132a (step STP6). In this tracking condition, the output difference between the photodetectors A and B for detecting the 0th-order light beam spot is 0, and the output difference between the photodetectors C and D for detecting the ± 1st-order light beam spot is 0. Condition.

The spindle motor 111 detects the PG signal from the signal detection unit 1 when the PG transmission position of the rotary disk 112 comes on the movement line of the optical pickup 121 in the radial direction.
32a. The signal detection unit 132a performs twice integration and processing of an FET and the like on the tracking signal from the optical pickup 121, extracts only the primary component, and detects a radial displacement signal as shown in FIG. (Step STP7). This displacement signal corresponds to the data track D including the eccentricity detected by the optical pickup 121.
The trajectory of T is shown. Then, the signal detection unit 132a
Sends the detected displacement signal to the signal analyzing unit 132b together with the position signal from the pickup driving unit 122 and the PG signal from the spindle motor 111.

The signal analyzer 132b calculates the difference between the maximum value of the displacement signal and the average of the maximum value and the minimum value, and converts the difference into a radial displacement amount. This converted value corresponds to the amount of eccentricity of the magnetic disk 1, and the rotation center A and the data track DT
(Hereinafter referred to as the track center) T. The signal analyzer 132b also detects the time from the appearance of the PG signal to the appearance of the maximum value of the displacement signal at the same time. This time is the phase difference θt (= 360 · maximum value appearance time / one cycle time) until the track center T appears with reference to the PG signal (step STP8).

Here, the rotation center A is the data track DT
5, the point B at which the distance from the rotation center A to the data track DT is the minimum and the point C at which the distance from the rotation center A is the maximum always exist on a straight line, and the track center T is It always exists between the center A and the point C where the distance from the data track DT is maximum. Also,
The distance δt between the rotation center A and the track center T is equal to the rotation center A
From the rotation center A to the point B and the distance B from the rotation center A to the point B.

From the difference .delta.t between the rotation center A and the track center T obtained in this way and the phase difference .theta.t until the track center T appears with reference to the PG signal, the track center T is calculated as shown in FIG. (Xt, Yt) in the coordinate space AA where the rotation center A is the coordinate center (0, 0).
Can be expressed as Here, the rotation center A
Assuming that the distance from (0, 0) to the arbitrary point (x, y) is δ and the phase difference is θ, x and y are expressed by Equations 1 and 2. Therefore, the coordinate points Xt and Yt of the track center T can also be obtained by Expressions 1 and 2.

(Equation 1)

(Equation 2) By performing the above series of processes, the relationship between the rotation center A and the track center T can be obtained.

Next, the pickup drive unit 122 moves the optical pickup 121 to the position on the inner peripheral edge of the magnetic disk 1, and sends out the position signal at that time to the signal detection unit 132a (steps STP9, STP9, STP4). Then, the control unit 131 performs tracking control of the optical pickup 121 on the inner peripheral edge of the magnetic disk 1 based on, for example, the tracking conditions shown in FIG. 3B (step ST).
P5, 6), by performing the same processing as the above-described processing, the center δ of the inner peripheral edge of the magnetic disk 1 (hereinafter referred to as the inner diameter center) N is also determined by the difference δ between the rotation center A and the inner diameter center N.
n and a phase difference θn until the center N of the inner diameter with respect to the PG signal appears (step STP7,
8).

After that, the pickup driving section 122
The optical pickup 121 is moved to the position of the outer peripheral edge of the magnetic disk 1, and the position signal at that time is detected by the signal detection unit 132.
a (step STP11, 12, 4). Then, the control unit 131 performs tracking control of the optical pickup 121 on the outer peripheral edge of the magnetic disk 1 based on, for example, the tracking conditions shown in FIG. 3C (steps STP5 and STP6), and performs the same processing as the processing described above. By doing so, the center G of the outer peripheral edge of the magnetic disk 1 (hereinafter referred to as the center of the outer diameter) is also changed to the center of rotation A and the center of the outer diameter G.
Δg, and the outer diameter center G based on the PG signal
And the phase difference θg up to the appearance of (Step STP
7, 8).

These tracking conditions are such that the output difference between the photodetectors A and B for detecting the zero-order light beam spot is 0, and the output sum of the photodetectors C and D for detecting the ± first-order light beam spots. Is 0. Then, as shown in FIG. 6, the center of the inner diameter N (X) on the coordinate space AA where the rotation center A is the coordinate center (0, 0).
By expressing them as n, Yn) and the outer diameter center G (Xg, Yg), not only the relationship with the rotation center A but also the relationship with the track center T (Xt, Yt) can be obtained.

Each center T (X
t, Yt), N (Xn, Yn), G (Xg, Yg)
The coordinate space AA having the rotation center A as the coordinate center (0, 0) is converted into a coordinate space GG having the outer diameter center G (Xg, Yg) as the coordinate center (0, 0) (step STP13). The conversion from the coordinate space AA to the coordinate space GG is performed when the center of the magnetic disk 1 has no center hole or the data track DT.
And becomes the original center of the magnetic disk 1. Here, assuming that the distance from the outer diameter center G ′ (0,0) to the arbitrary point (x ′, y ′) is δ and the phase difference is θ,
x ′ and y ′ are expressed by Equations 3 and 4. Therefore, the coordinate points Xt ′ and Yt ′ of the track center T ′ and the coordinate points Xn ′ and Yn ′ of the inner diameter center N ′ can also be obtained by Expressions 3 and 4.

(Equation 3)

(Equation 4) By performing the above series of processing, the outer diameter center G ′
The track center T ′ (Xt ′, Yt ′) of the magnetic disk 1 and the center N ′ (X
n ′, Yn ′).

The track center T ′ (Xt ′, Yt ′) and the inner diameter center N ′ (Xn ′, Y) obtained by the above processing are obtained.
By calculating the distance to the magnetic disk 1, the original eccentricity δh of the magnetic disk 1, that is, the eccentricity δh when the magnetic disk 1 is mounted on a spindle or the like with no mounting error can be measured. The track center T '(Xt', Y
t ′) and the center of outer diameter G ′ (Xg ′, Yg ′) are determined, so that the stamper can be prepared, the stamper can be attached to a mold, the magnetic disk 1 can be punched (injection molding), and the like. The resulting stamper-related error S can be measured. Further, by calculating the distance between the center N ′ (Xn ′, Yn ′) of the inner diameter and the center G ′ (Xg ′, Yg ′) of the outer diameter, an error relating to the magnetic disk caused by punching of the center hole of the magnetic disk 1 or the like can be obtained. U can be measured (step STP14).

At this time, there is no problem if the amount of eccentricity δh is smaller than a certain reference value, but if it is larger than the reference value, it is necessary to analyze what caused the eccentricity (step STP15). ). However, even when the amount of eccentricity δh is smaller than the reference value, if the error S and the error U are larger than the reference value, it is necessary to analyze what caused the error.

By grasping the magnitudes of the errors S and U, it is possible to determine whether or not the magnetic disk 1 is within the standard or to compare the magnitudes of the errors S and U to determine which one. It is possible to determine how much eccentricity the factor has affected. Further, since each error S and U is standardized as a numerical value, each factor can be easily normalized as a numerical value. For example, comparing the magnitudes of the errors S and U, if the error S is larger, it can be estimated that the eccentricity is caused by the stamper-related error, and conversely, the error U If it is larger, it can be assumed that the eccentricity is caused by an error related to punching of the center hole.

The effects of these errors S and U on the amount of eccentricity can be normalized by equations (5) and (6). Then, by taking the product of the results obtained by Equations 5 and 6 and the amount of eccentricity δh, a substantial error amount given to the amount of eccentricity δh can be obtained.

(Equation 5)

(Equation 6)

The centers G '(0,0) and T' (X
t ', Yt') and N '(Xn', Yn ') can be visually grasped in a coordinate space.
It also facilitates troubleshooting such as correction of the displacement of the stamper. Furthermore, a plurality of magnetic disks 1 of the same lot
Track center T '(Xt', Yt ') and inner diameter center N'
By calculating the average value (deviation amount) and dispersion (variation) of (Xn ′, Yn ′), it is possible to further clarify the eccentricity error factors estimated from one magnetic disk. Further, by obtaining them statistically, it is possible to grasp the pattern forming ability of an injection molding machine or a stamper, the accuracy of punching a center hole by a cutter, and the like. For example, the track center T ′ (Xt ′,
If the average value of Yt ') is large, it becomes clear that the stamper-related error affects the eccentricity, and if the variance is large, it becomes clear that the magnetic disk-related error affects the eccentricity.

Each center G '(0,
0), T '(Xt', Yt '), N' (Xn ', Y
n '), the magnetic disk 1 having the respective error amounts exceeding the specified values when the position deviation error amount, the eccentric error amount, and the like are specified.
, The yield can be easily predicted. Further, it is possible to accumulate useful data when manufacturing or developing the magnetic disk 1 with the eccentric amount suppressed (steps STP16, 17, 18, 19).

In the above embodiment, the measurement of the eccentricity of the pre-emboss type magnetic disk as the information recording disk has been described. However, the present invention is not limited to this. If so, for example, eccentricity of an optical disk, a magneto-optical disk, or the like can be measured.

[0039]

As described above, according to the present invention,
With a simple configuration, the eccentricity of the magnetic disk can be measured easily and in a short time, and the number of inspection steps for the magnetic disk can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an eccentricity measuring device for an information recording disk according to the present invention.

FIG. 2 is a flowchart showing an embodiment of a method for measuring eccentricity of an information recording disk according to the present invention.

FIG. 3 is a diagram showing an example of tracking conditions used in the eccentricity measuring device shown in FIG.

FIG. 4 is a waveform chart showing a signal example in the eccentricity measuring device shown in FIG.

FIG. 5 is a diagram showing an example of eccentricity measurement in the eccentricity measuring device shown in FIG.

FIG. 6 is a diagram showing an example of processing of eccentricity measured by the eccentricity measuring device shown in FIG. 1;

FIG. 7 is a plan view showing an example of a general magnetic disk.

FIG. 8 is a partially enlarged view of the magnetic disk shown in FIG. 7;

FIG. 9 is a view showing an example of eccentricity of the magnetic disk shown in FIG. 7;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk, 100 ... Eccentricity measuring device, 1
10: rotating unit, 120: measuring unit, 130:
Measuring unit, 111 ... spindle motor, 112 ...
Rotating disk, 121 ... Optical pickup, 122 ...
Pickup drive unit, 131 ... Control unit, 132 ...
.Processing unit, 133 ... System controller, 132
a: signal detection unit, 132b: signal analysis unit, 13
2c ... Display unit

Claims (2)

[Claims] When measuring the eccentricity of an information recording disk in which an information recording area is formed in advance, a coordinate position of a center point with respect to the information recording area, an inner peripheral edge of the information recording disk, and an outer peripheral edge of the information recording disk. And measuring the eccentricity of the information recording disk based on the coordinate position of each of the center points. 2. A rotating unit for mounting and rotating an information recording disk on which an information recording area is formed in advance, and a measuring unit disposed above the rotating unit and capable of tracking the information recording disk. A control unit that drives and controls the rotating unit and the measuring unit; and a drive control of the rotating unit and the measuring unit that is performed by the control unit, the information recording area, an inner peripheral edge of the information recording disk, and an outer peripheral edge of the information recording disk. And a processing unit for determining a coordinate position of the center point with respect to the tracking signal of the measuring unit and measuring the eccentricity of the information recording disk based on the coordinate position of each center point. Disk eccentricity measuring device.