JP3372335B2 - Information disk shape measuring method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape measuring method and apparatus suitable for shape evaluation of information disks, particularly magnetic disks using a glass substrate.

[0002]

2. Description of the Related Art In recent years, high density recording of hard disk devices has progressed, and the air gap of the flying head has been 0.1 to 0.0.
Miniaturization of 5 μm is required. Along with this, the demand for flatness of the hard disk surface is becoming more and more severe. As a disk material of this kind, a substrate obtained by metal-plating an aluminum alloy, a crystallized glass substrate, and the like have been developed. Regarding the glass substrate, the quality of the surface finish greatly affects the smoothness of the disk surface. It is known (Japanese Patent Laid-Open No. 5-89459). That is, the surface finishing step of glass is roughly divided into three steps of rough grinding, fine grinding, and polishing. Of these, polishing is called polishing, and conventionally, as a characteristic of this polishing step, as shown in FIG. In addition, it is known that the raised portion 42 is formed on the outer peripheral portion of the glass substrate and the outer peripheral portion is sagged. The height h of this raised part is 0.45
Since it is about μm, it has a great influence on the flying of the magnetic head, and there is a problem that the recording area is narrowed accordingly.

Therefore, in JP-A-5-89459, by appropriately adjusting the polishing processing pressure and the polishing processing time at the time of polishing, the occurrence of a raised portion at the outer peripheral edge portion of the glass substrate is suppressed as much as possible to obtain a high smoothness. Attempts have been made to obtain. In order to evaluate the quality of the product in this case, it is necessary to measure the shape of the glass substrate surface with high accuracy. As a shape measuring device capable of performing such a measurement, a stylus type surface roughness measuring device has been conventionally used on a trial basis.

[0004]

However, in the disk measuring method using the conventional stylus type shape measuring device, the displacement signal of the stylus is plotted by a recorder, and the inspector can visually check it from the plot result. Since the shape of the raised portion on the outer peripheral portion of the disk is evaluated, there are problems that the measurement results vary and the measurement takes time. In particular, the information about the position of the inflection point in the profile of the ridge is extremely important information for knowing the limit point of flying, the boundary point between the recording area and the end of the disc, the effective diameter of the disc, etc. Has a problem that it is difficult to accurately measure the position of the inflection point, because the profile of the bulge itself is sagging, and it takes experience in determining the range in the displacement direction. Therefore, conventionally, the shape of the disk is evaluated at an arbitrary radial position to judge whether the disk is good or defective, and the effective diameter of the disk is absolutely evaluated, and the tendency of the entire lot is known. I couldn't. Furthermore, when trying to obtain the center point of the disk and evaluate the shape of an arbitrary point in the x-axis direction of the disk, it is difficult to specify the x-axis value because the center point of the disk cannot be specified. There are also problems.

The present invention has been made in order to solve such a problem, and can accurately measure the positions of the inflection points in the ridges and sags of the outer peripheral portion caused by the polishing process of the information disk. An object of the present invention is to provide a device for measuring the shape of an information disc that can be used.

[0006]

According to the method of measuring the shape of an information disk according to the present invention, a measuring element is moved along the measuring surface of a disk to be measured, and a displacement signal output from the measuring element is sampled to obtain the shape. The step of storing as information, and the tilt angle of each minute range of the outer peripheral edge portion in the shape information is obtained from the shape information of the measured disk stored in this step, and the measured disk of the measured disk is determined based on these tilt angles. The inflection point in the shape information of the outer peripheral edge is defined as the radial position of the measured disk and the rotational axis direction.
And a step of calculating the data as the position data of the direction .

Further, the information disk shape measuring apparatus according to the present invention is arranged so as to be movable along the holding means for holding the measured disk and the measuring surface of the measured disk held by the holding means. A tracing stylus that outputs a displacement signal of a surface, a driving unit that moves the tracing stylus along the measuring surface in a state of sliding contact with the measuring surface of the measured disk, and along the measuring surface of the tracing stylus. Sampling means for sampling the displacement signal output from the tracing stylus at a predetermined timing during the movement, and storage means for storing the displacement signal sampled by the sampling means as the shape information of the measured disk, wherein stored in the storage means from the shape information of the measuring disc with obtaining the inclination angle of each micro range of the outer peripheral edge portion of the shape information, The point of inflection among shape information of the outer peripheral edge portion of the measured disk based on the inclination angle of these
Position of the measured disk in the radial direction and in the rotational axis direction
And an inflection point calculating means for calculating the position data .

As the inflection point calculating means, a straight line portion is extracted from the shape information of the disk to be measured stored in the storage means, and a point at which the inclination angle with respect to the straight line portion is equal to or more than a predetermined value It is possible to use an inflection point, or an inflection point at which the rate of change of the inclination angle is equal to or more than a value designated in advance. The tilt angle and its change rate are represented by the change amount Δz and the change thereof with respect to Δx, where x is the radial direction of the disk and z is the direction orthogonal to the measurement surface. Therefore, if Δx is constant, Δz The inflection point may be obtained by referring to only the value and its change amount.

Further, the reference sphere is positioned at the axial center of the disk, the stylus is moved in the x direction so as to pass substantially the center of the reference sphere, and the apex thereof is obtained. The position of the obtained apex in the x direction. May be determined as the center position of the disc.

[0010]

According to the present invention, the inclination angle of each minute range in the shape information is obtained from the shape information of the measured disk obtained by tracing the measurement surface of the measured disk and stored in the storage means. Since the inflection point in the shape information is obtained based on the inclination angle of, the desired inflection point can be accurately calculated without using a complicated curve fitting calculation. For this reason,
It is possible to obtain a correct evaluation result for the effective diameter of the disk to be measured, and it can also be applied to automatic inspection within a line where inspection speed is required.

When the disk edge is chamfered at a predetermined angle, information on the angle is designated in advance so that the tilt angle of the minute range becomes equal to or greater than the designated angle. Can be easily identified as the boundary point between the recording area and the end of the disc.

In general, at the inflection point including the boundary point, the angle of the tangent line of the profile may change abruptly. Therefore, the boundary point between the recording area and the end portion can be accurately detected by recognizing the point where the rate of change of the tilt angle is equal to or greater than the specified value or is the maximum as the inflection point.

When the inclination angle is represented by a change amount Δz with respect to Δx, and Δx is constant, calculation of these inflection points is performed.
By referring only to Δz, the arithmetic processing becomes simple.

Further, by disposing a reference sphere on the axis of the disc and tracing the substantially central position of the reference sphere, the center position of the disc can be easily and accurately determined, and the disc can be used. The effective diameter can be obtained extremely accurately.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hard disk shape measuring apparatus according to an embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an external view of this shape measuring apparatus. An inclination correction table 3 is placed on the table 2 of the shape measuring apparatus main body 1. A holding table 4 is fixed on the inclination correction table 3, and a measured disk 6 is held on a holding jig 5 fixed on the center of the upper surface of the holding table 4. The center hole of the measured disk 6 is the holding jig 5
In the state of being fitted to the convex portion of the above, it is sandwiched and fixed by the holding jig 5 and the fixing jig 7 arranged above. A spherical recess whose center of curvature is located on the axis of the measured disk 6 is formed at the upper end of the fixing jig 7, and a reference ball 8 is fitted into this spherical recess.

On the other hand, a column 12 to which a feed screw 11 is attached is fixed to the table 2, and a slider 13 is attached to this column 12. The column 12 is provided with a drive means such as a motor (not shown), and the feed screw 11 is rotated by this drive means to drive the slider 13 in the Z-axis direction in the drawing. A stylus arm 14 is attached to the slider 13. The stylus arm 14 is mounted on the slider 1 by driving means (not shown).
3 is driven in the X-axis direction in the figure. A stylus 15 is attached to the tip of the stylus arm 14, and the tip of the stylus 15 moves in the X direction while contacting the upper surface of the measured disk 6. Then, these configure the shape measuring device main body 1 including the table 2.

The stylus 15 is attached to the shape measuring apparatus main body 1.
A computer 20 is connected which samples a signal of the displacement of the tip of the to perform processing for shape evaluation.
The computer 20 includes a computer main body 21, a keyboard 22 and a mouse 23 as input means, and a display device 24. A printer 25 that outputs the measurement result is connected to the computer 20.

FIG. 2 is a functional block diagram of this measuring system. The displacement of the tip of the stylus 15 is detected by the detection unit 31.
Detected in. The detection unit 31 includes, for example, a differential transformer that works together with the stylus arm 14 and a synchronous detection circuit that synchronously detects the output of the differential transformer. The displacement signal from the detection unit 31 is sampled by the sampling unit 32 at regular time intervals. The sampling unit 32 is
For example, it is provided with an A / D converter for A / D converting the input displacement signal at a constant time interval, and an arc distortion removing section for removing the arc distortion caused by the arc movement of the stylus arm 14. The displacement data sampled by the sampling unit 32 is stored in the memory 33 as the shape information of the measured disk 6.

The arithmetic processing unit 34 calculates the inclination of the disk 6 to be measured from the shape information stored in the memory 33, and operates the drive mechanism 36 via the control unit 35,
The tilt angle of the tilt correction table 3 is corrected. Further, the control unit 35 operates the drive mechanism 37 to move the X of the stylus 15.
Control the axial position and the Y-axis position. Further, the arithmetic processing unit 34 detects a straight line portion from the shape information stored in the memory 33, calculates the position of the inflection point of the ridge portion of the outer peripheral edge portion of the disk 6, and displays the measurement result. Control for. Assuming that the measured disk 6 is a glass substrate for a hard disk, this measuring device has a minimum resolution in the Z-axis direction of 0.0005 to 0.05 μm,
It is preferable that the maximum magnification is 500,000 times and the maximum magnification in the X-axis direction can be selected up to 10,000 times.

Next, a method of measuring the shape of a hard disk using the system thus configured will be described.
First, by scanning the upper surface of the measured disk 6 with the stylus 15, the tilt angle of the stylus 15 with respect to the movement axis is roughly detected, and the tilt correction table 3 is actuated so that the measured surface of the measured disk 6 moves relative to the stylus 15. Are set to be parallel to each other. Next, the measurement process is executed in the measurement procedure as shown in FIG. First, according to the operator's instruction, the measurement pitch in the X-axis direction (for example, 3μ
The measurement conditions such as m) are set (S1). Subsequently, the uppermost position of the reference sphere 8 is traced with the stylus 15 in the X-axis direction to obtain the maximum Z-axis position, which is registered as the origin position in the X-axis direction (S2). This origin corresponds to the X-axis position of the rotation axis of the measured disk 6.

Next, the X coordinate of the measurement starting point (for example, 31 m
By specifying m), the stylus 15 is moved to the measurement start point by the drive mechanism 37 (S3). Then, when a measurement start command is given, the stylus 15 descends onto the measurement surface of the measured disk 6, contacts the measurement surface, and then stops at the position where the detection voltage of the detection unit 31 becomes a constant level. Subsequently, the stylus 15 moves in the X-axis direction, and the X-axis coordinate value and the Z-axis coordinate value are sampled by the sampling unit 32 at the designated measurement pitch and stored in the memory 33 (S4). Each measured value is plotted on the display device 24 and displayed as the shape information of the disk 6 (S5).

FIG. 4 is a diagram showing an example of a display mode of the shape information. The tilt of the measured disk 6 is roughly corrected by the tilt correction table. However, in this type of measurement, the Z-axis measurement range is as small as several tens of μm, so the measured values are shown in FIG. Inclination is inevitable as shown. Therefore, the diagonal position is designated by the cursor 41 of the mouse 23, and the range considered to be the straight line portion is A
1 is designated (S6). As a result, a regression line is calculated from the measurement data of the portion whose range is specified by the least squares method, and this straight line is highlighted as the reference line R in red, for example (S7). Next, by instructing the tilt correction,
As shown in FIG. 4B, the entire screen is corrected so that the reference line R is horizontally located at the substantially center of the display screen (S8).

Subsequently, as shown in FIG. 4 (b), an inflection point calculation area A2 is formed so as to surround the raised portion of the shape information.
Is designated by the mouse 23 (S9). After designating the inflection point calculation condition (S10), the inflection point calculation process is executed as follows (S11).

That is, the inflection point to be obtained here is
For example, there are the following points. (1) As shown in FIG. 8, when the height h of the raised portion 42 at the outer peripheral edge of the disk 6 is a problem, the peak position P1 of the raised portion 42. (2) As shown in FIG. 8, assuming that the height h of the raised portion 42 at the outer peripheral edge of the disk 6 is within the allowable range, the disk 6
To know the effective radius r of the boundary point P2 between the raised portion 42 and the outer peripheral edge portion.

In this embodiment, these inflection points are calculated based on the inclination angle of the minute range of the shape information. As shown in FIG. 5, the inclination angles of the minute range are straight lines L1 and L2 connecting two points separated by a fixed number of samples DX.
The inclination angles α1 and α2 with respect to the reference line R can be used. In addition, the rate of change Δα of the inclination angle is calculated by
Is the angle formed by. In this case, since the sample pitch ΔX in the X-axis direction is designated in advance, the following value can be used as the tilt angle.

[0026]

(1) (Z coordinate of data before p point)-(Z coordinate of current data)

The inflection point is defined as follows.
Of. (1) Point Pa at which the inclination angle α viewed from the reference line R is equal to or larger than a specified value. (2) Point P at which the rate of change in inclination angle Δα is greater than or equal to the specified value
b. (3) Point P at which the rate of change in tilt angle Δα is less than or equal to the specified value
c. (4) Point Pd at which the rate of change Δα of the tilt angle is maximized. (5) the rate of change Δα in the angle of inclination from the (+) (-) since the point P e. Of these inflection points, points Pa and Pb are shown in FIG. Which of these points should be determined may be determined according to the purpose of measurement.

When obtaining the inflection points Pa and Pb, the conditions to be specified in the calculation condition specifying step (S10) in FIG. 3 are the unit pitch number DX for the angle calculation, the inclination angle α and the change rate Δα. When these conditions are given, the processing shown in FIG. 7 is executed. First, the measurement start point Ps and the measurement end point Pe are obtained from the designated inflection point calculation area A2 (S21). Next, the corresponding distance z in the Z-axis direction from the designated inclination angle α is obtained as follows (S
22).

[0029]

[Formula 2] z = DX · tan α

Next, using i = DX + 1 as an initial value (S2
3), the following processing is sequentially executed from the i-th sample.
First, Δzi and Δzi-1 are calculated as follows (S2
4).

[0031]

## EQU3 ## .DELTA.zi = zi-DX-zi Δzi-1 = zi-DX-1-zi-1

Next, it is determined whether or not Δzi is greater than or equal to z (S25), Δαi is obtained as follows (S27), and it is determined whether Δαi is greater than or equal to Δα (S28).

[0033]

## EQU4 ## Δαi = tan-1 (Δzi / DX) −tan-1 (Δ
zi-1 / DX)

When zi is equal to or larger than z, the inflection point Pa is set to (xi, zi) (S26), and Δαi is Δ.
If it is equal to or greater than α, the inflection point Pb = (xi, zi) is set (S29). By executing the above processing for all the sample points within the designated range (S30, S31), it is possible to detect the data necessary for evaluating the quality of the hard disk, the effective recording radius, and the like.

The manual measurement procedure for interactively setting conditions by the operator has been described above.
When the measurement is performed on an actual line, the area condition and the measurement condition designated in advance are commonly used for a plurality of disks. In this case, since it is not necessary to perform complicated curve fitting calculation to calculate the inflection point, high-speed inspection is possible. Further, since the inclination angle change rate data itself is also effective for shape evaluation, the change rate data may be plotted and displayed on the display device for each sample.

[0036]

As described above, according to the present invention, the inclination angle of each minute range in the shape information is obtained, and
Since the inflection point in the shape information is obtained based on these inclination angles, the desired inflection point can be accurately calculated without using a complicated curve fitting calculation, and the measured disk It is possible to obtain a correct evaluation result for the effective diameter and the like, and it is also possible to apply to an automatic inspection in a line where inspection speed is required.

[Brief description of drawings]

FIG. 1 is an external view of a hard disk shape measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a functional block diagram of the device.

FIG. 3 is a flowchart showing a shape measuring procedure using the same apparatus.

FIG. 4 is a diagram showing a display example of shape information in the apparatus.

FIG. 5 is a diagram for explaining a method of calculating an inclination angle of shape information and a change rate thereof in the same apparatus.

FIG. 6 is a diagram showing an example of an inflection point obtained by the device.

FIG. 7 is a flowchart showing a procedure for calculating the inflection point.

FIG. 8 is a diagram showing a shape of a glass substrate after a polishing process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Shape measuring device main body, 3 ... Tilt correction table, 4 ... Holding table, 6 ... Measured disk, 15 ... Stylus, 20 ...
Computer, 25 ... Printer, 31 ... Detection unit, 32 ...
Sampling unit, 33 ... Memory, 34 ... Arithmetic processing unit, 3
5 ... control part, 36, 37 ... drive mechanism.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Kojima 2-7-5 Nakaochiai Shinjuku-ku, Tokyo Hoya Co., Ltd. (72) Inventor Yukihiro Sakata 1-20 Sakado, Takatsu-ku, Kawasaki-shi, Kanagawa No. 1 Mitutoyo Co., Ltd. (56) Reference JP-A-5-89459 (JP, A) JP-A-5-52548 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 21/20 G11B 5/84

Claims (8)

(57) [Claims] 1. A step of moving a probe along a measurement surface of a disk to be measured, sampling a displacement signal output from the probe and storing it as shape information, and a disk to be measured stored in this step. together with the shape information obtaining the inclination angle of each micro range of the outer peripheral edge portion in the shape information of the previous point of inflection among shape information of the outer peripheral edge portion of the measured disk on the basis of these inclination angles
The radial position of the measured disk and the rotational axis direction
And a step of calculating as position data, the method for measuring the shape of an information disc. 2. The step of calculating the inflection point extracts a straight line portion from the stored shape information of the measured disk, and each minute range of the outer peripheral edge portion with respect to the straight line portion.
2. The method for measuring the shape of an information disc according to claim 1, wherein the point at which the inclination angle is equal to or more than a predetermined value is set as an inflection point. 3. The step of calculating the inflection point comprises the steps of:
2. The method for measuring the shape of an information disc according to claim 1, wherein a point at which the rate of change of the inclination angle of each minute range of the outer peripheral edge portion is equal to or more than a value designated in advance is set as an inflection point. 4. An apex position of the reference sphere in the moving direction of the probe is obtained by locating a reference sphere at an axial center position of the disk to be measured and tracing a substantially central position of the reference sphere with the probe. , This vertex position of the inflection point
Claims 1 to 3 any one information disc shape measuring method according to, characterized in that further comprising a determined Mel step as the center position of the measuring disc for obtaining the radial position. 5. Holding means for holding the disk to be measured,
A tracing stylus which is movably arranged along the measuring surface of the measured disk held by the holding means and outputs a displacement signal of the measuring surface, and the measuring stylus is slid on the measuring surface of the measuring disk. Drive means for moving along the measuring surface in a state, sampling means for sampling a displacement signal output from the measuring element at a predetermined timing during the movement of the measuring element along the measuring surface, and the sampling means Storage means for storing the displacement signal sampled by the means as the shape information of the measured disk, and the inclination of each minute range of the outer peripheral edge in the shape information from the shape information of the measured disk stored in the storage means. with determining the angle, the measured inflection point among the shape information of the outer peripheral edge portion of the measured disk on the basis of these inclination angles di Disk radial position and rotation axis
An inflection point calculating means for calculating as data of a direction position, an information disk shape measuring device. 6. The inflection point calculation means extracts a straight line portion from the shape information of the measured disk stored in the storage means, and each minute portion of the outer peripheral edge portion with respect to the straight line portion.
6. The information disk shape measuring device according to claim 5, wherein a point at which the inclination angle of the range is equal to or more than a predetermined value is set as an inflection point. 7. The inflection point calculating means is configured to measure the outer peripheral edge portion.
6. The information disk shape measuring device according to claim 5, wherein a point at which the rate of change of the tilt angle in each minute range is equal to or more than a value designated in advance is set as an inflection point. 8. A reference sphere arranged in the holding means such that the center of curvature is located on the axial center of the disk to be measured, and the measuring element is traced to approximately the center position of the reference sphere. The apex position of the reference sphere in the moving direction of the child is obtained, and this apex position is set in the radial direction of the inflection point.
8. The information disk shape measuring device according to claim 5, further comprising a disk center calculating unit that calculates a center position of the measured disk when determining the position of .