JP2000298011A - Method and apparatus for measuring shape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen effects of position change errors and highly accurately measure a shape of a surface of an object to be measured by setting a measurement point of one of two noncontact displacement gages to the surface of the object and a measurement point of the other gage to a smooth reference face, simultaneously moving the object and the reference face and obtaining a difference of displacement measured values. SOLUTION: Laser displacement gages 2 and 3 are held by Z-axis stages 4 and 5 on a substrate 1 respectively. A sample head 6 and a reference mirror 7 are held by an XYZ-axis motor pulse stage 10 via a rotary stage 14 and a biaxial inclined stage 8 and via a biaxial inclined stage 9 respectively. The stage 10 is operated to simultaneously move the sample head 6 and reference mirror 7 in an X-axis direction. Displacements of measurement points of the laser displacement gages 2 and 3 set to a slide face of the sample head 6 and a reference face of the reference mirror 7 are measured respectively. The obtained measured values are inputted to a computer 11. A difference of the measured value related to the sample head 6 and the measured value related to the reference face by the reference mirror is obtained for each point.

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 a shape of a sliding surface of a fixed head used in a magnetic tape device, for example.

[0002]

2. Description of the Related Art For example, a magnetic tape device for data backup includes a fixed head for recording data on a magnetic tape and reading the recorded data. Most of these types of fixed heads have a structure in which a plurality of recording / reproducing heads and sliding parts are combined and integrated, and at least a pair of opposing sides has a tape width (about 3.8 to 12.6 mm). It is set above.

[0003] In such a fixed head, it is known that the shape of the entire surface that slides on the tape affects various performances including the running property of the tape. There is no device capable of measuring the shape of the entire surface of the fixed head that slides on the tape (sliding surface) with high accuracy.

[0004]

When measuring the surface shape of an article, a displacement meter is often used. Displacement meters that measure by tracing the surface by bringing a pickup (detection needle) etc. into contact with the object to be measured (so-called contact type)
And those that perform measurement without contacting the surface of the object to be measured using optical means or the like (so-called non-contact type). When measuring the sliding surface of the fixed head, it is necessary to use the latter non-contact displacement meter because contact with the sliding surface must be avoided.

However, even when a non-contact displacement meter is used to measure the shape of the fixed head on the entire sliding surface as described above, a measurement point is set on the head sliding surface. With a fixed head or displacement gauge at least a few mm
The movement of the fixed head or the displacement meter (for example, a measurement error due to mechanical vibration or the like occurring during the operation of the moving mechanism) is added to the measured value of the displacement. There is a problem that it is difficult to achieve high precision. Conventionally, there is a device for measuring the shape of the surface of the object to be measured using a non-contact displacement meter, but the shape measurement in that case is limited to a relatively narrow range, and the entire surface of the fixed head sliding surface is measured. There is no known device capable of measuring a shape over a relatively wide range such as an area (for example, several mm to twenty and several mm).

According to the present invention, when one of the displacement meter and the object to be measured needs to be relatively moved when the shape of the surface of the object to be measured is measured using the displacement meter, the position accompanying the movement is required. An object of the present invention is to provide a method and an apparatus capable of measuring the shape of the surface of an object to be measured, for example, the shape in the entire area of the sliding surface of a fixed head with high accuracy while reducing the influence of a fluctuation error.

[0007]

In order to achieve the above object, the shape measuring method of the present invention uses two non-contact displacement meters,
The measurement point by one displacement meter is set on the surface of the object to be measured, and the measurement point by the other displacement meter is set on a smooth reference plane, respectively.
The object and the reference surface are simultaneously moved to measure respective displacements, and the surface shape of the object is measured based on a difference between the measured values.

Further, the shape measuring apparatus of the present invention comprises a non-contact displacement meter having a measurement point on the surface of the object, a non-contact displacement meter having a smooth reference surface as a measurement point, It is characterized by having means for moving the reference plane and means for obtaining the difference between the measured values obtained by the two displacement meters. Examples of non-contact displacement meters include a laser displacement meter that measures displacement using trigonometry and the Doppler effect, a laser focus displacement meter, and a displacement meter that measures displacement from reflectance using a photomic sensor. Can be used. A mirror having a smooth surface can be used as the smooth reference surface.

In the shape measuring method and apparatus according to the present invention, in order to reduce the influence of an error due to a tilt change due to the movement of the workpiece and the reference plane, the measurement point of the workpiece and the measurement point of the reference plane are connected. A straight line is set perpendicular to the moving surface of the device under test. In addition, 2 on the moving surface of the measured object and the reference surface
The axes are X axis and Y axis, and the axis perpendicular to the moving plane is Z axis.
The difference between the distance between the measurement point of the object to be measured and the measurement point of the reference plane from the Z axis may be set within 10 mm.

If the measurement range of the displacement meter used is relatively narrow and the surface of the object has irregularities exceeding the measurement range, the displacement is measured along the surface (measurement surface) of the object. During the movement, it is necessary to move the object to be measured or the displacement meter in the Z-axis direction (a direction perpendicular to the movement plane) so that the surface of the object to be measured is located within the measurement range of the displacement meter. In order to cope with this, the shape measuring apparatus of the present invention includes a means for moving the object to be measured, the reference surface, and the displacement meter in the Z-axis direction (a Z-axis stage and an XYZ-axis electric pulse stage in an embodiment described later). Means for recognizing the moving distance (computer in the embodiment described later).

For example, when it is necessary to measure the shape along the top of the ridge on the object to be measured having a ridge having an arc-shaped top on the surface, the measurement point by the displacement meter is always set. One of the object to be measured and the displacement meter must be relatively moved while being positioned on the top surface of the ridge. For this reason, the shape measuring apparatus of the present invention includes a means (a camera in the embodiment described later) for projecting the measurement surface of the object to be measured on the monitor screen at a magnification of 10 times or more, and rotating the object to be measured around the Z axis. Means (a rotary stage in the embodiment described later) and means for indicating a reference of the position of a scale, a marker or the like on a monitor screen.

When measuring the shape of the surface of an object to be measured,
If the device under test (or the reference surface) is inclined with respect to the moving surface, the surface shape of the device under test may not be able to be measured accurately. So, to deal with this situation,
The shape measuring apparatus of the present invention includes a means (a biaxial tilt stage in an embodiment described later) for adjusting the tilt of the object to be measured and the reference plane.

The present invention is suitable as a means for measuring the shape of a region on the entire sliding surface of a fixed head for a magnetic tape device.

[0014]

According to the present invention, since the object to be measured and the reference plane are simultaneously moved to measure the displacement and the difference between the measured values is obtained, the position fluctuation error due to the movement can be canceled. That is, when the displacement is measured by simultaneously moving the DUT and the reference plane as described above, the position fluctuation error accompanying the movement appears in both the measured values of the DUT and the reference plane in the same manner. By taking the difference, the positional fluctuation errors are canceled out, and the positional fluctuation errors due to the movement are removed from the measured values of the DUT. Thus, the shape of the surface of the measured object can be measured with high accuracy. In addition, when the straight line connecting the measurement point of the DUT and the measurement point of the reference plane is set perpendicular to the moving plane of the DUT, the influence of the error due to the tilt fluctuation due to the movement should be reduced. Can be.

[0015]

Embodiments of the present invention will be described below. In this embodiment, a fixed head (a sample head in the following example) provided in a magnetic tape device is used as an object to be measured, and the shape (head shape) in the entire sliding surface area is used.
Is measured.

<Shape Measuring Apparatus> FIG. 1 shows the configuration of a shape measuring apparatus used in this embodiment. In FIG. 1, the horizontal direction is the X-axis direction, the direction penetrating the paper is the Y-axis direction, and the vertical direction is the Z-axis direction.
The directions in which the sample head (fixed head used as a sample in this embodiment) 6 is moved during measurement are the X-axis direction and the Y-axis direction.

As shown in FIG. 1, a shape measuring apparatus according to this embodiment has a Z-axis in which laser displacement meters 2.3 (in this embodiment, based on a triangulation method) are respectively held on a base 1. X holding the stages 4 and 5 and the sample head 6 via a rotary stage 14 and a biaxial tilt stage 8, and holding the reference mirror 7 via a biaxial tilt stage 9.
The configuration is such that a YZ-axis electric pulse stage 10 is attached.

In the laser displacement meters 2.3, a straight line connecting the measurement point of the sample head 6 and the measurement point of the reference plane by the reference mirror 7 is perpendicular to the moving plane (XY plane) of the sample head 6. It is installed as follows. The reference mirror 7 constitutes a reference surface according to the present invention, and has a surface accuracy of 700 nm or less in this embodiment. Z-axis stage 4 that holds these laser displacement meters 2 and 3 respectively
5 is a drive source 4a, 5a composed of, for example, a pulse motor
And the laser displacement meters 2 and 3 can be moved in the Z-axis direction by the drive sources 4a and 5a.

The two-axis tilt stages 8.9 include a sample head 6
And to adjust the tilt of the reference mirror 7 around the X axis and the Y axis to set the sample head 6 and the reference mirror 7 in a predetermined state. On the side where the sample head 6 and the reference mirror 7 are mounted, The angles about the X axis and the Y axis can be finely adjusted manually.

The XYZ-axis electric pulse stage 10 holds the sample head 6 via the rotary stage 14 and the biaxial tilt stage 8 and the arm 10a which holds the reference mirror 7 via the biaxial tilt stage 9; 3 as a source
And two pulse motors 10b, 10c and 10d.
And these pulse motors 10b, 10c, 10d
The arm 10a in the X-axis direction, the Y-axis direction,
It can be moved in each axial direction.

The shape measuring apparatus further includes an operation control of the XYZ axis electric pulse stage 10 and a laser displacement meter 2.
A computer 11 for processing data output from 3; a camera 12 and a monitor 13 for monitoring the measurement surface of the sample head 6;

In the computer 11, the sample head 6 and the reference mirror 7, which are set in a predetermined positional relationship with respect to the laser displacement meters 2 and 3 at the time of measurement, move simultaneously along the X-axis direction or the Y-axis direction. As described above, the pulse motor 10b in the XYZ axis electric pulse stage 10
10c and 10d. Further, the computer 11 outputs a signal indicating the measurement value of the sample head 6 output from one laser displacement meter 2 at the time of measurement, and a signal indicating the measurement value of the reference mirror 7 output from the other laser displacement meter 3. The difference between the two is obtained based on the above, and the obtained result is written as data indicating the shape of the sample head 6 to a built-in or external storage device (not shown) or output to the outside via an output device. . In the illustrated example, since the sample head 6 and the reference mirror 7 are measured in a state where they are set in opposite directions, a difference between the two measured values may be obtained by simply adding the measured values.

The camera 12 is held on the Z-axis stage 4 in a state of being juxtaposed with the laser displacement meter 2, and sends an image of the measurement surface of the sample head 6 to the monitor 13 at the time of measurement, and displays the sample head on the screen. The measurement surface of No. 6 is projected at a magnification of 10 times or more (100 times in this example). In that case, monitor 13
On the screen, a scale or a marker is shown together with an image of the measurement surface of the sample head 6 so that the position and size level of the measurement surface of the sample head 6 reflected can be recognized.

<Measuring Method> Next, a method for measuring the shape of the entire sliding surface of the sample head 6 using such a shape measuring device will be described. First, as shown in FIG. 1, the sample head 6 and the reference mirror 7 are attached to the arm portion 10a of the XYZ-axis electric pulse stage 10 via the two-axis tilt stages 8 and 9, respectively. 3 is set at a predetermined height position. Then, the measurement point of one of the displacement meters 2 is set on the surface of the sample head 6, that is, the sliding surface, and the measurement point of the other displacement meter 3 is set on a reference mirror (reference surface) 7. The two-axis tilt stages 8.9 are manually operated to adjust the sample head 6 and the reference mirror 7 to be in a horizontal state. In this state, a straight line connecting the measurement point of the sample head 6 and the measurement point of the reference mirror 7 is perpendicular to the XY plane in the figure. When measuring the arc-shaped top (measurement example described later), the sample head 6 by the rotating stage 14 is viewed while looking at the marker on the monitor 13 so that the line connecting the top and the moving direction of the sample head 6 are parallel.
And the movement by the XYZ-axis electric pulse stage 10 are repeated to adjust until they become parallel.

Next, the XYZ-axis electric pulse stage 10
Is operated to simultaneously move the sample head 6 and the reference mirror 7 in the X-axis direction (or the Y-axis direction) while simultaneously moving the measurement point of one of the laser displacement meters 2 set on the sliding surface of the sample head 6 and the reference point. The displacement in the Z-axis direction of the measurement point of the other laser displacement meter 3 set on the mirror 7, that is, the reference surface, that is, the X-axis direction (or the Y-axis direction) of the sliding surface of the sample head 6 and the reference surface of the reference mirror 7. ) Is measured at each point along the Z-axis.

The measured values at the respective points on the sliding surface of the sample head 6 and the measured values at the respective points on the reference surface obtained by the reference mirror 7 are output as respective outputs from the laser displacement meters 2.3. It is input to the computer 11. The computer 11 compares the difference between the input measurement value for the sample head 6 and the measurement value for the reference plane with the sample head 6.
And for each point measured simultaneously on the reference plane. By taking the difference between the two measured values in this manner, the position fluctuation error due to the movement of the sample head 6 is canceled out, and as a result, the shape of the sliding surface of the sample head 6 is measured with high accuracy.

<Example of Shape Measurement> Next, an example of actual shape measurement of the sample head 6 will be described. FIG. 2 shows the sample head 6 used in this measurement example.
The scanning direction (relative moving direction) of the laser displacement meter 2 with respect to the sliding surface of the sample head 6 is also shown.

The sample head 6 shown in FIG. 2 has first to fifth five ridges 61 to 65 formed on the sliding surface thereof. Three ridges 62-64
Are provided with two gap portions CH1 and CH2 for the first channel and the second channel, respectively.
Here, for example, the first and fifth ridges 61 and 65 located at both ends are respectively outrigger portions, and the third ridge 63 located at the center is a head portion for reading.
The other second and fourth ridges 62 and 64 are write heads, respectively. The distance between the third ridge 63 and the second and fourth ridges 62 and 64 is 7.5 mm, and the width of the sample head 6 in the extending direction of each of the ridges 61 to 65 is 23 mm.

With respect to such a sliding surface of the sample head 6,
The shape was measured by the method described above using the shape measuring apparatus of FIG. The following shapes were measured. The shape in a direction passing through the gap CH1 for the first channel and orthogonal to the ridges 61 to 65 (the scanning direction of the laser displacement meter 2 in this case is indicated by an arrow A in FIG. 2). The shape of the direction which passes through the gap CH2 for the second channel and is orthogonal to each of the ridges 61 to 65 (the scanning direction of the laser displacement meter 2 is the same as that of the gap CH1). The shape along the top of each of the ridges 61 to 65 (the scanning direction of the laser displacement meter 2 in this case is indicated by an arrow B in FIG. 2).

The rough shape of is shown in FIGS. 3 and 4.
As shown in FIG. 3 shows the outline of the shape (almost the same in the case), and FIG. 4 shows the outline of the shape. In the top shapes of the second to fourth ridges shown in FIG. 4, the fact that the central portion is depressed indicates that this portion is worn by tape running.

<Measurement Results> FIGS. 5 to 11 show actual measurement results. FIG. 5 shows the measurement results of FIG. 6 among them. 7 to 11 show the measurement results of FIG. 7, FIG. 7 shows the first ridge 61, and FIG.
2, FIG. 9 shows a third ridge 63, FIG. 10 shows a fourth ridge 64,
FIG. 11 shows a measurement result of the shape along each top of the fifth ridge 65. In these figures, the solid line portion and the dotted line portion are caused by scanning (actually moving the sample head 6) by reciprocating the laser displacement meter 2 in a predetermined direction. The results are shown, and the dotted line indicates the return measurement result.

FIGS. 5 and 6 show that the shape of each ridge on the sliding surface of the sample head 6 is accurately measured. Since the shape of the head portion influences the performance of this type of head, the shape of the top of each of the second to fourth ridges is important in the sample head 6; It can be seen from FIG. 7 that the measurement results of the forward and backward scans (solid line) and the return (dotted line) of the laser beam from the laser displacement meter 2 for these top shapes agree with each other, and this point also indicates that the measurement accuracy is excellent. In FIG. 5 and FIG. 6, there are portions where the measurement results are different between the forward (solid line) and the backward (dotted line) scanning by the laser displacement meter 2 for the following reason. That is, in this example, since the laser displacement meter 2 having a relatively small measurement range is used, for example, when scanning from the second protrusion 62 to the third protrusion 63, one of the laser displacement meter 2 and the sample head 6 is used. The measurement is performed by moving the protrusion by a predetermined amount in the height direction (vertical direction in FIGS. 5 and 6). Here, when measuring one ridge, a portion having a low displacement falls outside the measurement range, and the measured value is held. Since the value to be held differs depending on the timing between the forward and backward scans, the above-described measurement results differ. However, as described above, such a difference is not important.

It can be seen from FIGS. 7 to 11 that the shape of each part is accurately measured. 8 and 11, there is a slight difference between the forward and backward scanning of the laser displacement meter 2, but the difference is at most about 1 to 2 μm. 8 to 10 showing the measurement results of the top shape of each of the second to fourth ridges 62 to 64, the two protrusions located near the center in the left-right direction are for the first channel and the second protrusion. This is for the gap portions CH1 and CH2 for two channels.

<Reference Example> FIG. 12 shows the result of measuring the shape of the surface of an optical flat glass in place of the sample head 6 using the same shape measuring apparatus and method as described above. From the results shown in FIG. 12, it can be confirmed that even when the laser displacement meter 2 scans a range of 2 × 10 ⁴ μm, a measurement error occurs only about 0.5 μm.

<Comparative Example> FIGS. 13 to 17 show the shape measurement apparatus of FIG. 1 in which only the shape of the sliding surface of the sample head 6 is measured by one laser displacement meter 2 and the reference is measured by the other laser displacement meter 3. It shows a measurement result when the shape measurement of the mirror 7 is not performed. 13 corresponds to FIG. 7 and relates to the top of the first ridge 61, FIG. 14 corresponds to FIG. 8 and relates to the top of the second ridge 62, and FIG. 16 relates to the top of the third ridge 63, FIG. 16 corresponds to FIG. 10 and relates to the top of the fourth ridge 64, and FIG. 17 corresponds to FIG. It relates to the top of the ridge 65. It can be seen from FIGS. 13 to 17 that the measured value of the displacement fluctuates relatively up and down in all the measurement ranges. This is considered to be caused by vibration or the like when the sample head 6 is moved in a predetermined direction to scan a predetermined range by the laser displacement meter 2. Since there is a position variation error due to the movement of the sample head 6 (or the laser displacement meter 2), FIGS.
In FIG. 17, it is almost impossible to recognize the shape of the top of each of the ridges 61 to 65 from the measurement result.

[0036]

As described above, according to the present invention, when measuring the shape of the surface of an object to be measured, two non-contact displacement meters are used to simultaneously move the object to be measured and the reference plane,
One displacement meter measures the displacement of the surface of the object to be measured and the other displacement meter measures the displacement of the reference plane, and the difference between the two measured values is calculated. The fluctuation error can be canceled out, and as a result, the shape of the surface of the measured object can be measured with high accuracy.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a configuration of a shape measuring device used in an embodiment of the present invention.

FIG. 2 is a perspective view of a sample head (measured object) used in an example of the present invention.

FIG. 3 is an explanatory view used to show a rough surface shape of a sliding surface of the sample head of FIG. 2 in a direction orthogonal to each ridge.

4 is an explanatory view used to show a rough surface shape along the top of each ridge on a sliding surface of the sample head of FIG. 2;

FIG. 5 is a table showing the results of measurement of the surface shape along the direction perpendicular to each ridge at the position of the gap for the first channel on the sliding surface of the sample head of FIG. 2;

FIG. 6 is a table showing the results of measuring the shape of the surface along the direction perpendicular to each ridge at the position of the gap for the second channel.

FIG. 7 is a table showing a result of measuring a surface shape along a top of a first ridge on a sliding surface of the sample head of FIG. 2;

FIG. 8 is a table showing the results of measuring the surface shape along the top of the second ridge.

FIG. 9 is a chart showing the results of measuring the surface shape along the top of the third ridge.

FIG. 10 is a table showing the results of measuring the surface shape along the top of the fourth ridge.

FIG. 11 is a table showing the results of measuring the surface shape along the top of the fifth ridge.

FIG. 12 is a table showing, as a reference example, the results of measuring the shape of the surface of an optical flat glass in place of the sample head in the examples of the present invention.

FIG. 13 shows a comparative example in which one laser displacement meter is used in FIG.
In the case where only the shape of the sliding surface of the sample head was measured (when the measurement of the reference surface was not performed simultaneously), the surface shape along the top of the first ridge on the sliding surface of the sample head was measured. It is a chart showing a result.

FIG. 14 is a chart showing the results of measuring the surface shape along the top of the second ridge on the sample head sliding surface.

FIG. 15 is a table showing the results of measuring the surface shape along the top of the third ridge on the sample head sliding surface.

FIG. 16 is a table showing the results of measuring the surface shape along the top of a fourth ridge on the sample head sliding surface.

FIG. 17 is a chart showing the results of measuring the surface shape along the top of the fifth ridge on the sample head sliding surface.

[Explanation of symbols]

2.3 Laser displacement meter (non-contact displacement meter) 4.5 Z-axis stage (means for moving the displacement meter in the Z-axis direction) 6 Sample head (fixed head that is the object to be measured) 7 Reference mirror (reference surface) 8.9 Two-axis tilt stage (means for adjusting the tilt of the workpiece and the reference plane) 10 XYZ-axis electric pulse stage (means of moving the workpiece and the reference plane) 11 Computer (means for obtaining the difference between the two measured values) Means for recognizing the movement amount) 12 camera (means for projecting the measurement surface of the object to be measured on the monitor screen at a magnification of 10 times or more, means for indicating the reference of the position of scales, markers, etc. on the monitor screen) 13 monitor 14 rotating stage (Means for rotating the DUT about the Z axis)

Claims (9)

[Claims] 1. Using two non-contact displacement gauges, a measurement point by one displacement gauge is set on the surface of the object to be measured, and a measurement point by the other displacement meter is set on a smooth reference surface. And a reference surface, which are simultaneously moved to measure respective displacements, and a surface shape of the object is measured based on a difference between the measured values. 2. A non-contact displacement meter having a surface of an object to be measured as a measurement point, a non-contact displacement meter having a smooth reference surface as a measurement point, and means for moving the object and the reference surface; Means for calculating a difference between values measured by the two displacement meters. 3. The shape measuring apparatus according to claim 2, wherein a straight line connecting the measurement point of the object to be measured and the measurement point of the reference plane is set perpendicular to the moving surface of the object to be measured. 4. An apparatus according to claim 1, wherein two axes on the moving surface of the object and the reference plane are an X axis and a Y axis, and an axis perpendicular to the moving surface is a Z axis. 3. The shape measuring apparatus according to claim 2, wherein a difference in distance from the Z axis is set within 10 mm. 5. The shape measuring apparatus according to claim 4, further comprising: means for moving the object to be measured, the reference plane, and the displacement meter in the Z-axis direction, and means for recognizing the movement distance. 6. A means for projecting a measurement surface of an object to be measured on a monitor screen at a magnification of 10 times or more; a means for rotating the object to be measured around the Z axis; The shape measuring apparatus according to claim 4, further comprising: 7. The shape measuring apparatus according to claim 2, further comprising means for adjusting the inclination of the object to be measured and the reference plane. 8. The shape measuring apparatus according to claim 2, wherein the surface of the object to be measured is a sliding surface of a magnetic head. 9. The shape measuring apparatus according to claim 8, wherein the magnetic head is a fixed head for a magnetic tape device.