JPH10141933A - Method and apparatus for measuring flatness - Google Patents

Abstract

(57) [Problem] To provide a flatness measuring method capable of accurately measuring the flatness of a surface to be measured regardless of the surface state. An inspection light is condensed in a spot shape at a plurality of measurement points on a measurement target surface, and an image of each measurement point is formed by an optical system by reflected light of the collected inspection light. . The amount of unevenness from a fixed reference position at each measurement point on the measurement target surface 11 is obtained based on the focal position adjustment amount for forming an image at each measurement point at the set position. The flatness of the measurement target surface 11 is calculated based on the obtained unevenness amount from the reference position.

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 optically measuring the flatness of, for example, a material surface of a recording medium substrate in a non-contact manner.

[0002]

2. Description of the Related Art For example, a carbon substrate is extremely excellent as a material for a substrate for a recording medium, such as being lighter in weight, superior in impact resistance and heat resistance, and thinner than an aluminum substrate or a glass substrate. When the surface of such a carbon substrate is polished, it is desired that those having a low flatness on the surface be excluded from the objects to be polished to reduce the polishing cost.

As a conventional method for optically measuring the flatness of the surface of such a substrate or the like, a method is employed in which a single wavelength light beam is incident on the surface to be measured from a vertical direction or an oblique direction at an arbitrary angle. There is a vertical or oblique laser interferometry in which the reflected light interferes with the reflected light when a light beam similarly enters the reference surface, and the flatness is obtained from the sparse density of the obtained interference fringes.

[0004]

However, in the above-mentioned conventional method, accurate measurement cannot be performed unless the unevenness of the surface to be measured is uniform and the reflectance is uniform and high. Therefore, the surface to be measured had to be polished or surface-treated in advance. For example, when the difference between the height of the concave portion and the height of the convex portion on the measurement target surface is locally about 10 μm or more, the interference fringes there are extremely disturbed or overcrowded, so that the measurement becomes impossible. In addition, if the surface to be measured has no gloss, the reflectance is low, and the reflectance is uneven, the measurement becomes difficult. For example, when a carbon substrate has not been subjected to surface treatment or polishing, the surface state of the substrate is poor, and the flatness cannot be measured by the conventional method in some cases. That is, the surface condition of the measurement target surface is limited to a narrow range.

An object of the present invention is to provide a method and an apparatus for measuring flatness which can solve the above-mentioned problems.

[0006]

According to the flatness measuring method of the present invention, inspection light is condensed in a spot shape at a plurality of measurement points on a surface to be measured, and reflected light of the converged inspection light is used. The image of each measurement point is formed by an optical system, and the unevenness from a fixed reference position at each measurement point on the measurement target surface is determined based on the focal position adjustment amount for forming the image of each measurement point at a set position. The amount is obtained, and the flatness of the surface to be measured is calculated based on the obtained amount of unevenness from the reference position.
The flatness can be obtained from the difference between the maximum value and the minimum value of the unevenness amount from the reference position at each measurement point. The flatness measuring device of the present invention is a light source that emits inspection light,
Means for converging the inspection light in a spot shape on the measurement point on the measurement target surface, an optical system for forming an image of the measurement point by reflected light of the collected inspection light, and an image of the measurement point. Means for adjusting the focal position of the optical system so that an image can be formed at a set position, and the amount of unevenness from a fixed reference position at a measurement point on the surface to be measured based on the adjustment amount of the focal position. Means for changing the measurement points, and means for calculating the flatness of the surface to be measured based on the amount of unevenness from the reference position at the plurality of measurement points. According to the flatness measuring method of the present invention, the flatness can be obtained based on the amount of unevenness from a reference position at an arbitrary measurement point on the measurement target surface. That is, since there is no need to form interference fringes as in the related art, the flatness of the surface to be measured can be accurately measured regardless of the surface state. According to the flatness measuring device of the present invention, the flatness measuring method of the present invention can be implemented.
Furthermore, since the flatness measuring device of the present invention includes the automatic focus adjustment mechanism, the focus can be quickly adjusted without manual operation. In addition, since the flatness measuring apparatus of the present invention includes an automatic change mechanism of the measurement point, the measurement of the flatness can be speeded up.

In the flatness measuring method according to the present invention, it is preferable that an image of the measurement point is taken, and the focus position is adjusted based on the clarity of the image of the taken measurement point. In this case, the flatness measuring apparatus according to the present invention includes an image capturing unit for the image of the measurement point and a display unit for displaying the image of the captured measurement point. Thereby, the focus adjustment can be easily performed.

In the method for measuring flatness according to the present invention, the focal position is adjusted by adjusting the distance from the measurement point of the objective lens constituting the optical system, and the optical system and the surface to be measured are oriented along the surface to be measured. It is preferable that the measurement points are changed by relatively moving the measurement points, and the adjustment distance of the objective lens at each measurement point corresponds to the amount of unevenness from the reference position. in this case,
The optical system in the flatness measuring apparatus of the present invention has an objective lens and an eyepiece, the focal position is adjusted by adjusting the distance from the measurement point of the objective lens, and the optical system and the measurement target surface are measured. The measurement point can be changed by relative movement in the direction along the surface, and the adjustment distance from the measurement point of the objective lens for the focal position adjustment corresponds to the unevenness amount from the reference position at the measurement point. Is done. Thereby, the focus adjusting mechanism can be easily configured.

In the method of the present invention, it is preferable to change the amount of the inspection light according to the reflectance of the surface to be measured. Thus, when the reflectance is low, the amount of the inspection light is increased so that the image by the reflected light is clearly formed, and when the reflectance is high, the amount of the inspection light is reduced and the brightness of the image by the reflected light is reduced. Can be prevented from becoming excessive. In this case, the flatness measuring apparatus of the present invention includes means for determining the reflectance of the surface to be measured, and means for adjusting the light amount of the inspection light to a set amount according to the determined reflectance. .

In the flatness measuring method of the present invention, it is preferable to change the spot diameter of the inspection light focused on the measuring point in accordance with required accuracy and roughness of the surface to be measured. Accordingly, when the required accuracy is low or when the surface to be measured is rough, the spot diameter of the inspection light can be increased, and the influence of minute unevenness that is not necessary for calculating the flatness can be eliminated. On the other hand, when the required accuracy is high or the roughness of the surface to be measured is small, the spot diameter of the inspection light is reduced, so that the amount of unevenness that affects the flatness can be reliably obtained. In this case, the flatness measuring device of the present invention can change the spot diameter of the inspection light focused on the measurement point.

In the flatness measuring method of the present invention, it is preferable to change the depth of focus of the optical system in accordance with the required accuracy and the roughness of the surface to be measured. This makes it possible to increase the depth of focus when the required accuracy is low or when the surface to be measured is rough, and to eliminate the influence of minute irregularities that are not necessary for calculating the flatness. On the other hand, when the required accuracy is high or the roughness of the surface to be measured is small, the depth of focus is made shallow, so that the unevenness amount that affects the flatness can be reliably obtained. in this case,
The flatness measuring apparatus of the present invention includes an interchangeable objective lens as an optical system, and changes the depth of focus by exchanging the objective lens.

In the method of measuring flatness according to the present invention, when a change in the amount of unevenness from the reference position at each measurement point with respect to the amount of unevenness from the reference position at an adjacent measurement point is equal to or greater than a preset value, It is preferable to exclude the unevenness amount from the reference position at the measurement point from the basis of the calculation of the flatness. Thereby, even if there is a measurement point where the amount of unevenness rapidly changes locally on the measurement target surface, the entire flatness can be accurately obtained.

In the method of measuring flatness according to the present invention, the surface of the object to be measured is placed on the object supporting member with the surface opposite to the surface to be measured as the lower surface, and based on the amount of irregularities from the reference position at each measurement point. The inclination of the measurement target surface with respect to the mounting surface of the test object support member is obtained, and the amount of unevenness from the reference position at each measurement point is corrected so that the inclination becomes zero, and the measurement target surface is determined based on the correction value. Is preferably calculated. Thus, it is possible to prevent the thickness unevenness of the test object, the flatness of the surface opposite to the measurement target surface, and the error based on the flatness of the mounting surface of the test object support member from affecting the calculation of the flatness. .

In the method of measuring flatness according to the present invention, the test object is placed on the test object support member with the surface to be measured facing downward.
Preferably, an optical system is arranged below the support member, and a through hole formed in the support member is used as a light path between the optical system and the measurement point. Accordingly, it is possible to prevent the thickness unevenness of the test object and the flatness error of the surface of the test object on the side opposite to the measurement target surface from affecting the flatness measurement accuracy. in this case,
In the flatness measuring apparatus of the present invention, a support member is disposed above the optical system, and a test object can be placed on the upper surface of the support member with the surface to be measured as the lower surface. A through hole serving as a light path between the measurement point and the measurement point is formed.

In the method for measuring flatness according to the present invention, it is preferable that the amount of unevenness from a reference position of a measurement point within a preset range from the end of the surface to be measured is excluded from the basis of the flatness calculation. Thus, it is possible to prevent a sudden change in the amount of unevenness at the end of the measurement target surface of the test object having a finite size from affecting the calculation of the flatness.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

The flatness measuring device 1 shown in FIG. 1 has an optical system 4 mounted on a mounting base 2 via a first moving mechanism 3, and a light source device 5 for emitting inspection light to the optical system 4.
An imaging device 6 for photographing a flatness measurement point via the optical system 4; and a test object support member 9 attached to the attachment base 2 via a second moving mechanism 7 and a third moving mechanism 8. And The test object support member 9 is disposed below the optical system 4, and a test object 10 is placed on the upper surface of the test object support member 9.
It is set to 1.

The optical system 4 transmits the inspection light emitted from the light source device 5 to the surface 1 to be measured as shown by a two-dot chain line in FIG.
The light is condensed in a spot shape on the measurement point 1 and an image of the measurement point is formed at a set position by reflected light at the measurement point on the measurement target surface 11. In the present embodiment, the image at the measurement point is formed on the light receiving unit of the imaging device 6. The optical system 4 includes, for example, a half mirror 4a
And an optical microscope such as a differential interference metal microscope (for example, Nikon Optiphoto 100S) having an objective lens 4b and an eyepiece 4c. That is, the optical path of the inspection light emitted from the light source device 5 is changed by the half mirror 4a, condensed by the objective lens 4b, and the reflected light is reflected by the objective lens 4b, the half mirror 4a,
The image is guided to the imaging device 6 via the eyepiece 4c to form an enlarged image of the measurement point. The magnification may be arbitrarily selected, and may be, for example, about 1000 times.

The objective lens 4b is replaceable. Accordingly, when the required accuracy is low or when the measurement target surface 11
When is small, the depth of focus can be increased by using an objective lens 4b having a small numerical aperture (NA) to eliminate the influence of minute irregularities that are not necessary for calculating the flatness. On the other hand, if the required accuracy is high or the roughness of the measurement target surface 11 is small, the depth of focus is reduced by using a large numerical aperture (NA) as the objective lens 4b to reduce the depth of focus. Can be reliably obtained. The depth of focus becomes the measurement accuracy of the flatness. For example, when a lens having a magnification of 100 and an NA of 0.9 is used as the objective lens 4b, the depth of focus can be 1 μm.

The light source device 5 emits inspection light of a light amount corresponding to the applied power. For example, a high-intensity halogen lamp of about 50 W or the like can be used, and is connected to the light amount adjusting device 5a of the inspection light. You. The diameter of the exit of the inspection light can be changed, and the spot diameter at the measurement point of the inspection light can be set arbitrarily. For example, when the required accuracy is low or when the measurement target surface 11 is rough, the spot diameter of the inspection light can be increased to eliminate the influence of minute irregularities that are not necessary for calculating the flatness. On the other hand, when the required accuracy is high or when the roughness of the measurement target surface 11 is small, the amount of unevenness affecting the flatness can be reliably obtained by reducing the spot diameter of the inspection light.

The imaging device 6 is a two-dimensional CCD camera (for example, XC-75CE manufactured by SONY) or the like, and can be configured to send a video signal of the captured image to the TV monitor 15. A sensor 6a for detecting the amount of reflected light incident on the imaging device 6 is provided.

The first moving mechanism 3 displaces the optical system 4 in the Z-axis direction orthogonal to the surface 11 to be measured. In this embodiment, the displacement is determined by manual operation by an operator. The direction is the vertical direction. Due to the displacement of the optical system 4 in the Z-axis direction, focus adjustment for forming an image of the measurement point on the light receiving unit of the imaging device 6 is performed. The amount of displacement of the optical system 4 in the Z-axis direction corresponds to the amount of unevenness from a predetermined fixed reference position at a measurement point on the measurement target surface 11. A Z-axis displacement sensor 3a for detecting the displacement of the optical system 4 in the Z-axis direction by the first moving mechanism 3 is provided.

The second moving mechanism 7 changes the measurement point in the X-axis direction by displacing the test object supporting member 9 in the X-axis direction parallel to the measurement target surface 11 with respect to the optical system 4. In this embodiment, the displacement is caused by the manual operation of the operator, and the X-axis direction is the horizontal direction. An X-axis displacement sensor 7a for detecting the displacement of the object support member 9 in the X-axis direction by the second moving mechanism 7 is provided.

The third moving mechanism 8 displaces the object support member 9 and the second moving mechanism 7 with respect to the optical system 4 in the Y-axis direction parallel to the surface 11 to be measured. In this embodiment, the displacement is made by a manual operation of an operator, and the Y-axis direction is a horizontal direction orthogonal to the X-axis direction. A Y-axis displacement sensor 8a for detecting a displacement of the test object support member 9 in the Y-axis direction by the third moving mechanism 8 is provided.

The light amount adjusting device 5a, the light amount sensor 6a,
Z-axis displacement sensor 3a, X-axis displacement sensor 7
a and the Y-axis direction displacement amount sensor 8a
It is connected to the. The control device 20 is constituted by a computer, and stores the amount of unevenness from the reference position at each measurement point and measures the amount of unevenness from the reference position at a plurality of measurement points based on a previously stored program, as described below. The flatness of the target surface 11 is calculated, and the calculation result is output to the output device 21. The output device 21 is
It can be constituted by a CRT display, a printer, or the like.

In order to obtain the flatness by the above configuration, first, the second moving mechanism 7 and the third moving mechanism 8 move the test object supporting member 9 on which the test object 10 is mounted from a preset reference position. The inspection light emitted from the light source device 5 is condensed via the optical system 4 at the first measurement point on the measurement target surface 11 by being displaced in the X and Y axis directions. At this time, the control device 20 stores the X and Y coordinates of the measurement point based on signals from the X-axis displacement amount sensor 7a and the Y-axis displacement amount sensor 8a. In addition, an enlarged image of the measurement point is formed by the reflected light of the inspection light condensed at the measurement point, and the image is captured by the imaging device 6 and displayed on the monitor 15.

Next, the optical system 4 is displaced in the Z-axis direction from a preset reference position by the first moving mechanism 3, and focus adjustment is performed so that the image displayed on the monitor 15 can be clearly recognized. At this time, the controller 20 controls the Z-axis displacement sensor 3
From the signal from a, the Z coordinate of the measurement point, ie,
The amount of unevenness from the reference position at the measurement point on the measurement target surface 11 is stored.

Next, the test object support member 9 is displaced in the X and Y axis directions, and the inspection light emitted from the light source device 5 is emitted to the second measurement point on the measurement target surface 11 via the optical system 4. Focus,
Repeat the above operation.

In the process of obtaining the Z coordinate of the measurement point, the measurement target surface 1 detected by the light amount detection sensor 6a
The detected value of the amount of reflected light from 1 is input to the control device 20. The control device 20 calculates the reflectance of the measurement target surface 11 according to the input value, and controls the light amount adjusting device 5a according to the reflectance, thereby controlling the light amount of the inspection light emitted from the light source device 5. We are trying to optimize. That is, when the reflectance of the measurement target surface 11 with respect to the amount of the inspection light is lower than a preset value, the amount of the emitted light is increased so that an image by the reflected light is clearly formed, and the reflectance is set in advance. If the value is higher than the set value, the amount of the emitted light is reduced to prevent the luminance of the image due to the reflected light from becoming excessive.

When the Z coordinates at all the measurement points have been obtained, the control device 20 performs a filtering process. That is, when the amount of unevenness from a reference position at a part of the measurement points of the measurement target surface 11 rapidly changes with respect to the amount of unevenness from a reference position at an adjacent measurement point, the entire flatness is accurately obtained. Can not. The Z coordinate of such a measurement point, that is, the amount of unevenness is excluded from the basis of flatness calculation so that such a sudden change in the amount of unevenness does not affect the calculation of flatness. For example, FIG. 2 shows the relationship between the Y coordinate and the Z coordinate of each measurement point (shown by a black point in the figure) on the measurement target surface 11 of the disk-shaped test object 10 having a center hole. Here, each measurement point is located only on the Y coordinate, and the zero point of the Z coordinate is a reference position. In this figure, the Z coordinate of the measurement point A where the amount of unevenness rapidly changes with respect to the amount of unevenness from a reference position at an adjacent measurement point is excluded from the basis of flatness calculation. It is to be noted that the inclination at each measurement point is determined as to whether or not the amount of unevenness is suddenly changed. If the inclination is equal to or greater than a preset inclination, it is determined that the amount of unevenness is suddenly changed. The test object 10 in FIG. 2 is an unpolished carbon blank for a hard disk having a diameter of 1.89 ″, which is obtained by curing a thermosetting resin and carbonizing the same.
1.4 mm, outer diameter 48.5 mm, thickness 1.46 mm, 4
The reflectance of the inspection light of 00 to 800 nm is 20% or less, the surface roughness is 1 μm or less, and the flatness is 200 μm or less.

When the Z coordinates at all the measurement points have been obtained, the controller 20 performs a tilt correction process. That is, the test object 10 is placed on the surface 1 on the side opposite to the measurement target surface 11.
When 1 ′ is placed on the test object support member 9 with the lower surface, the Z coordinate at each measurement point indicates the thickness unevenness of the test object 10,
The flatness of the surface 11 'on the opposite side, the test object support member 9
Includes an error based on the flatness of the mounting surface 9 '. The Z coordinate is corrected so that such an error does not affect the calculation of the flatness. For example, the broken line B in FIG. 2 corresponds to a linear relational expression of the Y coordinate and the Z coordinate of the measurement point obtained by the least square method or the like as described above. The inclination in the relational expression corresponds to the inclination of the measurement target surface 11 with respect to the mounting surface 9 'of the test object support member 9, and becomes zero if there is no error. Therefore, FIG.
As shown in (2), the Z coordinate is corrected so that the slope becomes zero as shown by the broken line C in the figure.

When the Z coordinates at all the measurement points have been obtained, the control unit 20 performs an end mask process. That is, since the size of the test object 10 is finite, the amount of unevenness rapidly changes at the end of the measurement target surface 11. With such a sudden change in the amount of unevenness,
The entire flatness cannot be determined accurately. In order to prevent such a sudden change in the amount of unevenness from affecting the calculation of the flatness, the Z coordinate of the end, that is, the amount of unevenness is excluded from the basis of the calculation of the flatness. For example, D in FIG.
Points E, F, and G indicate the Y coordinate of a position inward from the end of the test object 10 by a predetermined dimension in advance. The Z coordinates of the measurement points excluding the measurement point between the points D and E and the measurement point between the points F and G are excluded from the basis of the flatness calculation.

After performing the above-described filtering, inclination correction, and edge masking, the control unit 20 calculates the flatness based on the processed Z coordinates. The calculation is performed based on the difference between the maximum value and the minimum value of the Z coordinate, that is, the difference between the highest point and the lowest point of the unevenness on the measurement target surface 11.

According to the above-described configuration, the flatness can be obtained without forming interference fringes as in the related art, based on the amount of unevenness from a reference position at an arbitrary measurement point on the measurement target surface 11. Thereby, the flatness of the measurement target surface 11 can be accurately measured regardless of the surface state. For example, a difference in height between a concave portion and a convex portion on a measurement target surface such as a carbon substrate used as a material of a hard disk is locally about 10 μm.
As described above, there is uneven reflection, low reflectivity, no gloss, and even in a poor surface state where the flatness cannot be measured by the conventional laser interference method, the flatness can be obtained with a measurement accuracy of about ± 1 μm. Further, even when such a carbon substrate is subjected to surface processing such as texture formation, grinding, polishing, thin film formation, etching, and pattern formation, the flatness can be measured. Of course, the flatness can be measured with high accuracy even on a mirror-finished surface to be measured. Furthermore, the depth of focus, the effective spot diameter, and the amount of inspection light are optimized in accordance with the unevenness of the measurement target surface 11, and the filtering, tilt correction, and edge mask processing are performed. The flatness on the surface can be measured with the same accuracy as before.

In FIG. 4, the vertical axis indicates the flatness obtained by the measuring method according to the embodiment of the present invention, and the horizontal axis indicates the flatness obtained by the conventional oblique laser interferometry. The points correspond to the measurement points according to the measurement method of the embodiment of the present invention, and the solid lines in the figure correspond to the measurement positions according to the conventional method. According to the present invention, the measurement position becomes discontinuous, unlike the case where measurement is performed at a continuous position as in the conventional method, but the measurement result is correlated with the conventional method, and with the same accuracy as the conventional method. It is confirmed that the flatness can be measured accurately. The surface to be measured in FIG. 4 was obtained by carbonizing a cured thermosetting resin so that the surface state was as poor as possible within a range where the method of the present invention and the conventional method could be compared. A carbon blank having reduced reflectance unevenness and irregularities of about 10 μm or more was used as much as possible.

FIG. 5 shows a second embodiment of the present invention. In the first embodiment, instead of the first to third moving mechanisms 3, 7, 8 manually operated by an operator, a control device 2
First to third drive mechanisms 3 ', 7', 8 'driven by a signal from 0 are provided, and a focus detection sensor 3 which forms an automatic focus adjustment mechanism with the first drive mechanism 3'.
0 is connected to the control device 20. Each drive mechanism 3 ',
7 'and 8' can be constituted by a known mechanism. The control device 20 transmits the light source device 5 to a plurality of predetermined measurement points.
The test object support member 9 is driven in the X and Y axis directions by the second drive mechanism 7 'and the third drive mechanism 8 so that the inspection light emitted from the light source is sequentially collected, and the measurement point is automatically changed. I do.
The X- and Y-axis displacements of the object support member 9 by the second drive mechanism 7 'and the third drive mechanism 8' are measured by an X-axis displacement sensor 7a.
Is detected by the Y-axis displacement amount sensor 8a.
A coordinate and a Y coordinate are obtained. The focus detection sensor 30
Is for detecting an amount corresponding to the amount of defocus, and may be constituted by, for example, a sensor for detecting the sharpness of an image captured by the imaging device 6. The control device 20 calculates the amount of defocus according to the input value from the focus detection sensor 30,
The optical system 4 is driven by the first drive mechanism 3 'according to the calculation result.
Is driven in the Z-axis direction to perform automatic focus adjustment. On this occasion,
The image displayed on the monitor 15 can be used to monitor whether the automatic focus adjustment is properly performed.
Monitoring by 5 is not mandatory. The displacement of the optical system 4 in the Z-axis direction by the first drive mechanism 3 'is detected by the Z-axis displacement amount sensor 3a, and the Z coordinate of each measurement point is obtained. Other parts are the same as those of the above embodiment, and the same parts are denoted by the same reference numerals.

FIG. 6 shows a third embodiment of the present invention. First
The difference from the embodiment is that the test object support member 9 is disposed above the optical system 4, and the lower surface of the test object 10 placed on the upper surface thereof is the measurement target surface 11. In addition, the test object support member 9
Is formed with a through-hole 9a serving as a light passage between the optical system 4 and the measurement point. In the example shown in the figure, the measurement points are arranged in parallel along the cross as indicated by the black dots in the figure, so that a cross-shaped Through hole 9
a is formed. Other configurations are the same as those of the first embodiment, and the same portions are denoted by the same reference numerals. According to the third embodiment,
The Z coordinate at each measurement point is determined by the thickness unevenness of the test object 10,
Since no error based on the flatness of 1 'is included, the accuracy of measuring the flatness can be improved.

The present invention is not limited to the above embodiment. For example, the measurement points are not limited to those arranged along a straight line on the measurement target surface, and may be arranged along a curve or randomly arranged. Optical system 4
The object support member 9 may be moved in the Z-axis direction by moving the object support member 9 in the X-axis, Y-axis, and Z-axis directions. May be moved. In addition, the test object is not limited to the carbon substrate,
It has a certain degree of smoothness on the surface of magnetic disk substrates, semiconductor wafers, liquid crystal substrates, optical disks, stampers, magnetic tapes, floppy disks, metal substrates, ceramic substrates, plastic substrates, films, etc. The flatness can be measured if it is several percent or more in white light, single light, or a specific wavelength region.

[0039]

According to the method of the present invention, the flatness of the surface to be measured can be accurately measured regardless of the surface condition, and the apparatus of the present invention can implement the method of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a flatness measuring apparatus according to a first embodiment of the present invention;

FIG. 2 is a diagram showing the relationship between the position of each measurement point measured by the flatness measuring device and the amount of unevenness of a measurement target surface before a tilt correction process.

FIG. 3 is a diagram showing the relationship between the position of each measurement point measured by the flatness measuring device and the amount of unevenness of the measurement target surface after the inclination correction processing.

FIG. 4 is a diagram showing a relationship between flatness measured by a flatness measuring device of the embodiment and flatness measured by a conventional measuring device.

FIG. 5 is a configuration explanatory view of a flatness measuring device according to a second embodiment of the present invention.

FIG. 6 is a configuration explanatory view of a flatness measuring device according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 3 First moving mechanism 4 Optical system 5 Light source device 6 Imaging device 7 Second moving mechanism 8 Third moving mechanism 11 Measurement target surface 20 Control device

Claims (16)

[Claims] An inspection light is condensed in a spot shape at a plurality of measurement points on a measurement target surface, and an image of each measurement point is formed by an optical system by reflected light of the collected inspection light. Based on the focus position adjustment amount for forming the image of each measurement point at the set position, the amount of unevenness from a fixed reference position at each measurement point on the measurement target surface is calculated, and the amount of unevenness from the determined reference position is calculated. A flatness measurement method, wherein a flatness of a measurement target surface is calculated based on the flatness. 2. The flatness measurement method according to claim 1, wherein an image of the measurement point is captured, and the focus position is adjusted based on clarity of the captured image of the measurement point. 3. A focal point is adjusted by adjusting a distance from a measurement point of an objective lens constituting the optical system, and the optical system and the measurement target surface are relatively moved in a direction along the measurement target surface to thereby measure the measurement point. The flatness measurement method according to claim 1 or 2, wherein the distance of adjustment of the objective lens at each measurement point is made to correspond to the amount of unevenness from the reference position. 4. The method for measuring flatness according to claim 1, wherein the light amount of the inspection light is changed according to the reflectance of the surface to be measured. 5. The method according to claim 1, wherein the spot diameter of the inspection light focused on the measurement point is changed according to the roughness of the surface to be measured.
The method for measuring flatness according to any one of the above. 6. The method of measuring flatness according to claim 1, wherein the depth of focus of the optical system is changed according to the roughness of the surface to be measured. 7. The flatness is determined from the difference between the maximum value and the minimum value of the amount of unevenness from each reference point at each measurement point.
7. The method for measuring flatness according to any one of 6. 8. When the amount of unevenness from the reference position at each measurement point to the amount of unevenness from the reference position at an adjacent measurement point is greater than or equal to a preset value, the difference from the reference position at that measurement point is determined. The method for measuring flatness according to any one of claims 1 to 7, wherein the amount of unevenness is excluded from the basis of the calculation of flatness. 9. The flatness according to claim 1, wherein the amount of unevenness from the reference position of the measurement point within a preset range from the end of the measurement target surface is excluded from the basis of the flatness calculation. How to measure the degree. 10. The test object is placed on the test object support member with the surface opposite to the surface to be measured facing downward, and the test object support member is placed on the basis of the amount of irregularities from the reference position at each measurement point. The method according to claim 1, further comprising: calculating an inclination of the measurement target surface with respect to the mounting surface, correcting an amount of unevenness from a reference position at each measurement point so that the inclination becomes zero, and calculating a flatness of the measurement target surface based on the correction value. 10. The method for measuring flatness according to any one of 1 to 9. 11. A test object is placed on a test object support member with the surface to be measured facing downward, an optical system is disposed below the support member, and a through hole formed in the support member is measured with the optical system. The method for measuring flatness according to claim 1, wherein the path is a light path between the point and the point. 12. A light source for emitting inspection light, means for condensing the inspection light in a spot shape at a measurement point on a measurement target surface, and an image of the measurement point is formed by reflected light of the collected inspection light. An optical system to form an image, a means for adjusting a focal position of the optical system so that an image of the measurement point can be formed at a set position, and an amount of adjustment of the focal position. Means for storing the amount of unevenness from a fixed reference position at a measurement point, means for changing the measurement point, and means for calculating the flatness of the surface to be measured based on the amount of unevenness from the reference position at a plurality of measurement points. A flatness measuring device comprising: 13. The flatness measuring apparatus according to claim 12, further comprising: an imaging unit for capturing an image of the measurement point; and a display unit for displaying the captured image of the measurement point. 14. The flatness measuring apparatus according to claim 12, further comprising an automatic focus adjustment mechanism. 15. The flatness measuring apparatus according to claim 14, further comprising an automatic change mechanism of the measuring point. 16. A support member is disposed above the optical system, and a test object can be placed on the upper surface of the support member with the surface to be measured facing the lower surface. 13. A through hole, which is a light passage between them, is formed.
16. The apparatus for measuring flatness according to any one of claims 15 to 15.