Surface property measuring apparatus and surface property measuring method

Abstract

To provide a surface property measurement device and a surface property measurement method that can convert a strain of a reflected image into numbers to quantitatively evaluate the strain.SOLUTION: A surface property measurement device 10 is provided which has an irradiation unit 2 that irradiates a surface to be measured 1 with illumination light L1 having one or more bright areas and dark areas; a light detection unit 5 that focuses on a light source through the surface to be measured 1 to receive reflected light L2 that is reflected on the surface to be measured 1; a first processing unit 6 that, in a light intensity distribution of the reflected light L2 on the surface to be measured 1, determines a plurality of selection points obtained by connecting measurement points of light intensity of the reflected light L2 by using a predetermined light intensity threshold and specifies positions on the surface to be measured 1; a second processing unit 7 that creates a graph obtained by plotting the positions indicating the selection points with a first direction on the surface to be measured 1 as a transverse axis and a second direction orthogonal to the first direction as a vertical axis; a third processing unit 8 that determines a reference line based on a shape of the bright areas of the illumination light L1; and a fourth processing unit 9 that determines the difference between the points plotted in the graph and the reference line and converts a variation of the difference into numbers.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a surface property measuring apparatus and a surface property measuring method.

Background Art

[0002] The state of the surface of an object is an important factor related to the quality such as appearance and design. As a method for evaluating the surface state of an object, for example, a method of evaluating the distortion of a reflected image reflected on the surface of the object is known. Generally, the degree of distortion of the reflected image is evaluated visually.

[0003] The distortion of the reflected image is generated, for example, by unevenness or undulation on the object surface. For example, Patent Document 1 discloses a flatness measuring apparatus for measuring the flatness such as unevenness and undulation on the surface of an object to be measured, which projects a lattice image onto the surface of the object to be measured, detects the pitch of the lattice image, and uses the average value of the standard deviation of the pitch of the lattice image as the flatness.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with existing devices, the distortion of the reflected image cannot be sufficiently quantified.

[0006] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a surface property measuring apparatus and a surface property measuring method capable of quantifying the distortion of a reflected image and quantitatively evaluating it.

Means for Solving the Problems

[0007] One embodiment of the present disclosure includes an irradiation unit having a light source that irradiates an illumination light having one or more bright regions and dark regions onto a surface to be measured; focusing on the light source through the surface to be measured, receiving reflected light having one or more bright regions and dark regions corresponding to the bright regions and dark regions of the illumination light, and detecting a light intensity distribution of the reflected light on the surface to be measured; a first processing unit that, for each bright region in the light intensity distribution of the reflected light on the surface to be measured, determines a plurality of selection points located on a line connecting measurement points of the light intensity of the reflected light using a predetermined light intensity threshold, and specifies positions on the surface to be measured indicating the selection points; a second processing unit that, for each bright region, creates a graph plotting positions on the surface to be measured indicating the selection points, with a first direction on the surface to be measured as the horizontal axis and a second direction orthogonal to the first direction on the surface to be measured as the vertical axis; a third processing unit that, for each bright region, obtains a reference line based on the shape of the bright region of the illumination light; and a fourth processing unit that, for each bright region, obtains a difference between the points plotted on the graph and the reference line, and quantifies the variation of the difference for each bright region, and provides a surface property measurement device having the above components.

[0008] In the surface property measurement device of the present disclosure, it is preferable that the light detection unit is an imaging device.

[0009] In the surface property measurement device of the present disclosure, it is preferable that the illumination light has a linear bright region as the bright region, and the reflected light has a linear bright region corresponding to the linear bright region of the illumination light as the bright region.

[0010] In the above case, in the light detection unit, the surface to be measured is divided into M×N measurement regions, where there are N measurement regions in the longitudinal direction of the linear bright region of the reflected light and M measurement regions in the lateral direction of the linear bright region of the reflected light. The light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the surface to be measured. In the first processing unit, the light intensity distribution of the reflected light on the surface to be measured is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light in each divided region, for each linear bright region, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each linear bright region, a measurement point that is equal to or exceeds the light intensity threshold and shows the light intensity closest to the light intensity threshold is selected, or for each of the left-side light intensity distribution and the right-side light intensity distribution of each linear bright region, a measurement point that is equal to or exceeds the light intensity threshold and shows the light intensity closest to the light intensity threshold is selected. The measurement point may be used as the selected point.

[0011] Also, in the above case, in the light detection unit, the measurement surface is divided into M×N measurement regions, where there are N measurement regions in the longitudinal direction of the linear bright region of the reflected light and M measurement regions in the lateral direction of the linear bright region of the reflected light. The light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the measurement surface. In the first processing unit, the light intensity distribution of the reflected light on the measurement surface is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light for each divided region, for each linear bright region, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each linear bright region, a measurement point showing the light intensity closest to the light intensity threshold is selected, or for each of the left-side light intensity distribution and the right-side light intensity distribution of each linear bright region, a measurement point showing the light intensity closest to the light intensity threshold is selected, and the measurement point may be used as the selected point.

[0012] Also, in the above case, in the light detection unit, the measurement surface is divided into M×N measurement regions, where there are N in the longitudinal direction of the linear bright region of the reflected light and M in the lateral direction of the linear bright region of the reflected light. The light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the measurement surface. In the first processing unit, the light intensity distribution of the reflected light on the measurement surface is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light in each divided region, for each linear bright region, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each linear bright region, a measurement point that is equal to or less than the light intensity threshold or less than the light intensity threshold and shows the light intensity closest to the light intensity threshold, and a measurement point that is equal to or greater than the light intensity threshold or exceeds the light intensity threshold and shows the light intensity closest to the light intensity threshold are connected by a line, and a point indicating the light intensity threshold is selected. Alternatively, for each of the left-side light intensity distribution and the right-side light intensity distribution of each linear bright region, a measurement point that is equal to or less than the light intensity threshold or less than the light intensity threshold and shows the light intensity closest to the light intensity threshold, and a measurement point that is equal to or greater than the light intensity threshold or exceeds the light intensity threshold and shows the light intensity closest to the light intensity threshold are connected by a line, and a point indicating the light intensity threshold is selected. The point indicating the light intensity threshold may be used as the selected point.

[0013] Also, in the surface property measurement device of the present disclosure, in the third processing unit, an approximate expression may be obtained from the points plotted on the graph, and the approximate expression may be used as the reference line.

[0014] Also, in the surface property measurement device of the present disclosure, in the fourth processing unit, the standard deviation of the difference between the points plotted on the graph and the reference line can be calculated.

[0015] Further, the surface property measurement apparatus of the present disclosure can have a fifth processing unit that obtains the maximum value of the light intensity in the bright region and the minimum value of the light intensity in the dark region in the light intensity distribution of the reflected light on the measurement surface, and calculates the image sharpness according to the following formula (1). DOI=(M - m) / (M + m)×100 (1) (In the above formula, DOI represents image sharpness, M represents the maximum value of the light intensity in the bright region, and m represents the minimum value of the light intensity in the dark region.)

[0016] Another embodiment of the present disclosure uses a light source to irradiate the measurement surface with illumination light having one or more bright regions and dark regions, focuses on the light source through the measurement surface, receives reflected light having one or more bright regions and dark regions corresponding to the bright regions and dark regions of the illumination light reflected by the measurement surface, and detects the light intensity distribution of the reflected light on the measurement surface. In the light intensity distribution of the reflected light on the measurement surface, for each bright region, using a predetermined light intensity threshold, a plurality of selection points located on the line connecting the measurement points of the light intensity of the reflected light are determined, and a first processing step of specifying the positions on the measurement surface indicating the selection points is performed. For each bright region, a second processing step of creating a graph in which the positions on the measurement surface indicating the selection points are plotted with the first direction on the measurement surface as the horizontal axis and the second direction orthogonal to the first direction on the measurement surface as the vertical axis is performed. For each bright region, a third processing step of obtaining a reference line based on the shape of the bright region of the illumination light is performed. For each bright region, a fourth processing step of obtaining the difference between the points plotted on the graph and the reference line and quantifying the variation of the difference for each bright region is provided, and a surface property measurement method is provided.

[0017] Further, in the surface property measurement method of the present disclosure, it is preferable to use an imaging device in the light detection step.

[0018] Further, in the surface property measurement method of the present disclosure, it is preferable that the illumination light has a linear bright region as the bright region, and the reflected light has a linear bright region corresponding to the linear bright region of the illumination light as the bright region.

[0019] In the above case, in the light detection step, the measurement surface is divided into M×N measurement regions, where N is the number of regions in the longitudinal direction of the linear bright region of the reflected light and M is the number of regions in the transverse direction of the linear bright region of the reflected light. The light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the measurement surface. In the first processing unit, the light intensity distribution of the reflected light on the measurement surface is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light for each divided region, for each linear bright region, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each linear bright region, a measurement point that has a light intensity equal to or exceeding the light intensity threshold and is closest to the light intensity threshold is selected. Alternatively, for each of the left-side light intensity distribution and the right-side light intensity distribution of each linear bright region, a measurement point that has a light intensity equal to or exceeding the light intensity threshold and is closest to the light intensity threshold is selected, and this measurement point may be used as the selected point.

[0020] In addition, in the above case, in the light detection step, the measurement surface is divided into M×N measurement regions, where there are N measurement regions in the longitudinal direction of the linear bright region of the reflected light and M measurement regions in the lateral direction of the linear bright region of the reflected light. The light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the measurement surface. In the first processing unit, the light intensity distribution of the reflected light on the measurement surface is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light in each divided region, for each linear bright region, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each linear bright region, a measurement point indicating the light intensity closest to the light intensity threshold is selected, or for each of the left-side light intensity distribution and the right-side light intensity distribution of each linear bright region, a measurement point indicating the light intensity closest to the light intensity threshold is selected, and the measurement point may be used as the selected point.

[0021] Also, in the above case, in the light detection step, the surface to be measured is divided into M×N measurement regions, where N is in the longitudinal direction of the linear bright region of the reflected light and M is in the transverse direction of the linear bright region of the reflected light. The light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the surface to be measured. In the first processing unit, the light intensity distribution of the reflected light on the surface to be measured is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light for each divided region, for each linear bright region, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each linear bright region, a measurement point that is equal to or less than the light intensity threshold or less than the light intensity threshold and shows the light intensity closest to the light intensity threshold, and a measurement point that is equal to or greater than the light intensity threshold or exceeds the light intensity threshold and shows the light intensity closest to the light intensity threshold are connected by a line, and a point showing the light intensity threshold is selected. Alternatively, for each of the left-side light intensity distribution and the right-side light intensity distribution of each linear bright region, a measurement point that is equal to or less than the light intensity threshold or less than the light intensity threshold and shows the light intensity closest to the light intensity threshold, and a measurement point that is equal to or greater than the light intensity threshold or exceeds the light intensity threshold and shows the light intensity closest to the light intensity threshold are connected by a line, and a point showing the light intensity threshold is selected. The point showing the light intensity threshold may be used as the selected point.

[0022] Also, in the surface property measurement method of the present disclosure, in the third processing step, an approximate expression may be obtained from the points plotted on the graph, and the approximate expression may be used as the reference line.

[0023] Also, in the surface property measurement method of the present disclosure, in the fourth processing step, the standard deviation of the difference between the points plotted on the graph and the reference line can be calculated.

[0024] Further, the surface property measurement method of the present disclosure can have a fifth processing step of obtaining the maximum value of the light intensity in the bright region and the minimum value of the light intensity in the dark region in the light intensity distribution of the reflected light on the measurement surface, and calculating the image definition by the following formula (1). DOI = (M - m) / (M + m)×100 (1) (In the above formula, DOI represents the image definition, M represents the maximum value of the light intensity in the bright region, and m represents the minimum value of the light intensity in the dark region.)

Effect of the Invention

[0025] In the present disclosure, there is an effect that the distortion of the reflected image can be quantified and evaluated quantitatively.

Brief Description of the Drawings

[0026]

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Mode for carrying out the invention

[0027] Below, embodiments of this disclosure will be described with reference to the drawings and the like. However, this disclosure can be implemented in many different aspects, and it is not construed as being limited to the description content of the embodiments illustrated below. Further, in order to make the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual form, but this is only an example and does not limit the interpretation of this disclosure. Further, in this specification and each figure, the same elements as those described above with respect to the already shown figures may be given the same reference numerals, and detailed description may be omitted as appropriate.

[0028] Hereinafter, the surface property measurement apparatus and the surface property measurement method in this disclosure will be described in detail.

[0029] A. Surface property measurement apparatus The surface property measuring device in the present disclosure has a light source, an irradiation unit that irradiates the surface to be measured with illumination light having one or more bright regions and dark regions, focuses on the light source through the surface to be measured, receives reflected light having one or more bright regions and dark regions corresponding to the bright regions and the dark regions of the illumination light, and detects the light intensity distribution of the reflected light on the surface to be measured, in the light intensity distribution of the reflected light on the surface to be measured, for each bright region, using a predetermined light intensity threshold, determines a plurality of selection points located on a line connecting the measurement points of the light intensity of the reflected light, a first processing unit that specifies the positions on the surface to be measured indicating the selection points, for each bright region, with the first direction on the surface to be measured as the horizontal axis and the second direction perpendicular to the first direction on the surface to be measured as the vertical axis, a second processing unit that creates a graph plotting the positions on the surface to be measured indicating the selection points, for each bright region, a third processing unit that obtains a reference line based on the shape of the bright region of the illumination light, for each bright region, obtains the difference between the points plotted on the graph and the reference line, and for each bright region, a fourth processing unit that quantifies the variation of the difference.

[0030] The surface property measurement apparatus of the present disclosure will be described with reference to the drawings. FIG. 1 is a diagram illustrating the surface property measurement apparatus of the present disclosure. As shown in FIG. 1, the surface property measurement apparatus 10 includes a light source 3 and an irradiation unit 2 that irradiates the measurement surface 1 with illumination light L1 having one or more bright regions and dark regions. The light detection unit 5 focuses on the light source 3 through the measurement surface 1, receives the reflected light L2 having one or more bright regions and dark regions corresponding to the bright regions and dark regions of the illumination light L1 reflected by the measurement surface 1, and detects the light intensity distribution of the reflected light L2 on the measurement surface 1. In the light intensity distribution of the reflected light L2 on the measurement surface 1, for each bright region, a plurality of selection points located on the line connecting the measurement points of the light intensity of the reflected light L2 are determined using a predetermined light intensity threshold, and the first processing unit 6 that specifies the positions on the measurement surface indicating the selection points. For each bright region, with the first direction on the measurement surface 1 as the horizontal axis and the second direction orthogonal to the first direction on the measurement surface 1 as the vertical axis, the second processing unit 7 that creates a graph plotting the positions of the measurement surface 1 indicating the selection points. For each bright region, the third processing unit 8 that obtains a reference line based on the shape of the bright region of the illumination light L1. For each bright region, the fourth processing unit 9 that obtains the difference between the points plotted on the graph and the reference line and quantifies the variation of the difference for each bright region.

[0031] The irradiation unit 2 includes a light source 3 and a mask 4. For example, as shown in FIG. 2, the mask 4 has a plurality of rectangular transmission regions 11 and light-shielding regions 12, and further has a cross-shaped focusing transmission region 13. In the illumination unit 2, the light from the light source 3 passes through the mask 4, and the measurement surface 1 is irradiated with the illumination light L1 having a plurality of linear bright regions and dark regions.

[0032] When the measurement surface 1 is irradiated with the illumination light L1, the illumination light L1 is reflected by the measurement surface 1. As shown in FIG. 3, the reflected light L2 has a plurality of linear bright regions 21 and dark regions 22 corresponding to the linear bright regions and dark regions of the illumination light L1.

[0033] For example, in FIG. 1, when the light detection unit 5 is an imaging device, the light detection unit 5 focuses on the light source 3 through the surface 1 to be measured and images the reflected light L2. At this time, for example, by focusing on the cross-shaped light projected from the light source 3 through the cross-shaped focus adjustment transmission region 13 of the mask 4 of the illumination unit 2 on the surface 1 to be measured, the light source 3 is focused through the surface 1 to be measured. Thereby, for example, an image of the reflected light on the surface 1 to be measured as shown in FIG. 3 can be obtained. Further, in the imaging device (light detection unit 5), the light intensity of the reflected light L2 is detected for each pixel, and the light intensity distribution of the reflected light L2 on the surface 1 to be measured is detected.

[0034] In the first processing unit 6, for example, in FIG. 3, when the image of the reflected light on the surface to be measured has N×M pixels, where there are N pixels in the longitudinal direction D1 of the linear bright region of the reflected light and M pixels in the transverse direction D2 of the linear bright region of the reflected light, the image of the reflected light on the surface to be measured is divided into n divided regions A1 to An in the longitudinal direction D1 of the linear bright region of the reflected light. The number of pixels N in the longitudinal direction D1 of the linear bright region of the reflected light is the same as the number of divided regions n. Then, the light intensity distribution of the reflected light for each of the divided regions A1 to An is extracted. The light intensity distribution of the reflected light in each of the divided regions A1 to An is, for example, a scatter diagram as shown in FIG. 4. In the light intensity distribution shown in FIG. 4, the horizontal axis is the position of the pixels in the transverse direction D2 of the linear bright region of the reflected light.

[0035] Further, in the first processing unit 6, in the light intensity distribution of the reflected light in each of the divided regions A1 to An, for each linear bright region 21, a selection point located on the line connecting the measurement points of the light intensity of the reflected light is determined using a predetermined light intensity threshold. Then, the position on the surface to be measured indicating the selection point is specified.

[0036] An example of how to determine the selection point using the light intensity threshold will be described.

[0037] For example, FIG. 5(a) is an example of the light intensity distribution of the reflected light in the divided region A1. In the light intensity distribution of the reflected light in the divided region A1, for each of the linear bright regions 21a to 21d, the peak value of the light intensity is obtained, and for example, the light intensity value that is 50% of the peak value of the light intensity is used as the light intensity threshold T a1 ~T d1Let it be so. Also, in the light intensity distribution of the reflected light in the divided region A1, the light intensity distributions of each linear bright region 21a to 21d are divided into a left light intensity distribution L and a right light intensity distribution R with the peak value of each light intensity as the boundary. Selection point P L1 is a measurement point that is equal to or greater than the light intensity threshold value T a1 or greater than the light intensity threshold value T a1 and shows the light intensity closest to the light intensity threshold value T a1 in the left light intensity distribution L of the linear bright region 21a. Also, selection point P R1 is a measurement point that is equal to or greater than the light intensity threshold value T a1 or greater than the light intensity threshold value T a1 and shows the light intensity closest to the light intensity threshold value T a1 in the right light intensity distribution R of the linear bright region 21a. Similarly, selection point Q L1 is a measurement point that is equal to or greater than the light intensity threshold value T b1 or greater than the light intensity threshold value T b1 and shows the light intensity closest to the light intensity threshold value T b1 in the left light intensity distribution L of the linear bright region 21b. Also, selection point Q R1 is a measurement point that is equal to or greater than the light intensity threshold value T b1 or greater than the light intensity threshold value T b1 and shows the light intensity closest to the light intensity threshold value T b1 in the right light intensity distribution R of the linear bright region 21b. Similarly, selection point R L1 is a measurement point that is equal to or greater than the light intensity threshold value T c1 or greater than the light intensity threshold value T c1 and shows the light intensity closest to the light intensity threshold value T c1 in the left light intensity distribution L of the linear bright region 21c. Also, selection point R R1 is a measurement point that is equal to or greater than the light intensity threshold value T c1 or greater than the light intensity threshold value T c1 and shows the light intensity closest to the light intensity threshold value T c1 in the right light intensity distribution R of the linear bright region 21c. Similarly, selection point S L1 is a measurement point that is equal to or greater than the light intensity threshold value T d1 or greater than the light intensity threshold value T d1 and shows the light intensity closest to the light intensity threshold value T d1It is the measurement point showing the light intensity closest to R1 And the selection point S d1 is in the right light intensity distribution R of the linear bright region 21d, and is equal to or exceeds the light intensity threshold T d1 and is the measurement point showing the light intensity closest to the light intensity threshold T d1 .

[0038] Then, the positions (pixel positions) on the reflected light image indicating the selection points P L1、 P R1、 Q L1、 Q R1、 R L1、 R R1、 S L1、 S R1 are specified.

[0039] Also, for example, Fig. 5(b) is an example of the light intensity distribution of the reflected light in the divided region An. Also in the light intensity distribution of the reflected light in the divided region An, in the same manner as the light intensity distribution of the reflected light in the divided region A1, for each of the linear bright regions 21a to 21d and for each of the left light intensity distribution L and the right light intensity distribution R, the light intensity thresholds T an to T dn are used to determine the selection points P Ln、 P Rn、 Q Ln、 Q Rn、 R Ln、 R Rn、 S Ln、 S Rn are determined. Then, the positions (pixel positions) on the reflected light image indicating the selection points P Ln、 P Rn、 Q Ln、 Q Rn、 R Ln、 R Rn、 S Ln、 S Rn are specified.

[0040] In the first processing unit 6, for the light intensity distribution of the reflected light in each of the divided regions A1 to An, for each linear bright region and for each of the left light intensity distribution and the right light intensity distribution, selection points are determined using light intensity thresholds, and the positions (pixel positions) on the reflected light image indicating the selection points are specified. Note that the positions (pixel positions) on the reflected light image correspond to the positions on the surface to be measured.

[0041] In the second processing unit 7, a graph is created by plotting the position on the measurement surface indicating the selection point, with the first direction on the measurement surface as the horizontal axis and the second direction orthogonal to the first direction on the measurement surface as the vertical axis.

[0042] For example, in FIG. 6(a), regarding the left light intensity distribution L of the linear bright region 21a in the light intensity distribution of the reflected light of each divided region A1 to An, the selection points P L1 ~P Ln This is a graph obtained by plotting the positions (pixel positions) on the image of the reflected light indicating the selection points. In FIG. 6(a), the horizontal axis represents the pixel position in the longitudinal direction D1 of the linear bright region of the reflected light, and the vertical axis represents the pixel position in the short transverse direction D2 of the linear bright region of the reflected light. Note that the positions (pixel positions) on the image of the reflected light correspond to the positions on the measurement surface. In FIG. 6(a), the longitudinal direction D1 of the linear bright region of the reflected light image corresponds to the first direction on the measurement surface, and the short transverse direction D2 of the linear bright region of the reflected light image corresponds to the second direction on the measurement surface.

[0043] The second processing unit 7 creates a graph by plotting the positions (pixel positions) on the image of the reflected light indicating the selection points for each linear bright region and for each of the left light intensity distribution and the right light intensity distribution. For example, as shown in FIG. 3, when the image of the reflected light has four linear bright regions and each linear bright region is divided into two, namely the left light intensity distribution and the right light intensity distribution, eight graphs are created.

[0044] The third processing unit 8 obtains a reference line based on the shape of the linear bright region of the illumination light. For example, as shown in FIG. 2, when the illumination light L1 has a linear linear bright region, a linear approximation can be performed. For example, the points plotted on the graph shown in FIG. 6(a) are linearly approximated to obtain the linear approximation formula (solid line in FIG. 6) shown in FIG. 6(b). This linear approximation formula is used as the above-mentioned reference line.

[0045] In the third processing unit 8, a reference line based on the shape of the linear bright region of the illumination light is obtained for each linear bright region and for each of the left and right light intensity distributions. For example, as shown in FIG. 3, when the image of the reflected light has four linear bright regions 21 and each linear bright region is divided into two, i.e., the left and right light intensity distributions, eight reference lines are obtained.

[0046] In the fourth processing unit 9, the difference between the points plotted on the graph and the reference line is obtained for each linear bright region and for each of the left and right light intensity distributions. Then, for each linear bright region and for each of the left and right light intensity distributions, the variation of the above difference is quantified. Specifically, for each linear bright region and for each of the left and right light intensity distributions, the standard deviation of the above difference is calculated. These standard deviations are taken as the variation of the above difference for each linear bright region and for each of the left and right light intensity distributions. Also, the arithmetic mean value of the standard deviations of the above differences for each linear bright region and for each of the left and right light intensity distributions is calculated. This arithmetic mean value can be taken as the variation of the above difference for all the linear bright regions.

[0047] In the surface property measurement device of the present disclosure, the distortion of the reflected image of the surface to be measured can be quantified, for example, as the standard deviation of the above difference, and quantitatively evaluated.

[0048] Also, when obtaining the pitch of the bright regions as in the conventional device, the relative distortion between the bright regions due to the pitch is quantified. In this case, for example, when a plurality of bright regions are distorted in the same direction, the variation of the pitch of the bright regions tends to be small, so the distortion of the reflected image cannot be sufficiently evaluated. On the other hand, in the present disclosure, since the variation of the above difference is obtained for each bright region, the absolute distortion of each bright region can be quantified. Therefore, even when a plurality of bright regions are distorted in the same direction, the distortion of the reflected image can be quantitatively evaluated.

[0049] In addition, in the present disclosure, a reference line is obtained based on the shape of the bright region of the illumination light, and an analysis method that approximates based on the shape of the bright region of the illumination light is used. Therefore, a numerical value directly representing the distortion with respect to the light source can be calculated. In addition, even for distortion with a large period, it can be quantitatively evaluated.

[0050] Hereinafter, the configuration of the surface property measuring device of the present disclosure will be described.

[0051] 1. Illumination unit The illumination unit in the present disclosure has a light source and irradiates the surface to be measured with illumination light having one or more bright regions and dark regions.

[0052] In the illumination light irradiated by the illumination unit, the bright region and the dark region may each have one or more. Among them, the illumination light preferably has a plurality of bright regions. By irradiating such illumination light on the surface to be measured, the number of data (sample size) can be increased, and the surface properties of the surface to be measured can be accurately measured.

[0053] In addition, the shape of the bright region is not particularly limited, and examples include linear, planar, and dot-like shapes.

[0054] When the bright region is linear, the shape of the linear bright region is not particularly limited as long as it is linear, and for example, it may be linear or curved.

[0055] In addition, when the bright region is planar, the shape of the planar bright region is not particularly limited as long as it is planar, and examples include square, rectangular, circular, and elliptical shapes.

[0056] In addition, when the bright region is dot-like, the shape of the dot-like bright region is not particularly limited as long as it is dot-like, and examples include square and rectangular shapes.

[0057] Among them, the illumination light preferably has a linear bright region, and more preferably has a plurality of linear bright regions. In particular, when the illumination light has a plurality of linear bright regions, it preferably has stripe-shaped bright and dark regions. By irradiating such illumination light onto the surface to be measured, the number of data (sample size) can be increased, and the surface properties of the surface to be measured can be accurately measured.

[0058] Further, when the illumination light has a plurality of dot-shaped bright regions, it may be illumination light in which the bright regions are arranged in a grid pattern.

[0059] The illumination unit is not particularly limited as long as it has a light source and can irradiate illumination light having a bright region and a dark region. Examples thereof include an illumination unit having a light source and a mask having a transmission region and a light-shielding region, and a linear light source. Among them, it is preferable that the illumination unit has a light source and a mask having a transmission region and a light-shielding region. By using a mask, the shape of the bright region can be easily controlled.

[0060] When the illumination unit has a light source and a mask, the light source is not particularly limited, and examples thereof include an LED (light-emitting diode), an OLED (organic light-emitting diode), a halogen lamp, and a tungsten lamp. Among them, an OLED is preferable. The OLED light source has high light intensity uniformity.

[0061] Further, the mask has a transmission region and a light-shielding region. In the mask, the number of the transmission region and the light-shielding region may each be one or more.

[0062] Further, the shape of the transmission region is not particularly limited, and examples thereof include linear, planar, and linear.

[0063] When the transmission region is linear, the shape of the linear transmission region is not particularly limited as long as it is linear, and may be, for example, linear or curved.

[0064] Further, when the transmission region is planar, the shape of the planar transmission region is not particularly limited as long as it is planar, and examples thereof include a square shape, a rectangular shape, a circular shape, an elliptical shape, and the like.

[0065] Further, when the transmission region is dot-like, the shape of the dot-like bright region is not particularly limited as long as it is dot-like, and examples thereof include a square shape, a rectangular shape, and the like.

[0066] Among them, the mask preferably has a linear transmission region, and more preferably has a plurality of linear transmission regions. In particular, when the mask has a plurality of linear transmission regions, the transmission regions are preferably arranged in a stripe shape. By using such a mask, the number of data (sample size) can be increased, and the surface properties of the surface to be measured can be accurately measured.

[0067] Also, when the mask has a plurality of dot-like transmission regions, the transmission regions may be arranged in a grid pattern.

[0068] For example, FIG. 2 shows an example in which the transmission region 11 is linear and straight, and the transmission regions are arranged in a stripe shape. In this case, the planar shape of the transmission region 11 is rectangular. Further, for example, FIG. 7(a) shows an example in which the transmission region 11 is linear and curved. In this case, the planar shape of the transmission region 11 can be arc-shaped. Further, for example, FIG. 7(b) shows an example in which the transmission region 11 is planar, and the planar shape of the transmission region 11 is rectangular. Further, for example, FIG. 7(c) shows an example in which the transmission region 11 is dot-like, the transmission regions 11 are arranged in a grid pattern, and the planar shape of the transmission region 11 is square.

[0069] When the mask has a plurality of linear transmission regions and the transmission regions are arranged in a stripe shape, the line width, length, and pitch of the linear transmission regions may be the same or different, but among them, it is preferable that they are the same. The line width, length, and pitch of the linear transmission regions are not particularly limited and are set as appropriate.

[0070] In addition, when the mask has a planar transmission region, the size of the planar transmission region is not particularly limited and is appropriately set.

[0071] In addition, when the mask has a plurality of dot-like transmission regions and the transmission regions are arranged in a lattice pattern, the sizes of the dot-like transmission regions may be equal or different, but among them, it is preferably equal. The size of the dot-like transmission region is not particularly limited and is appropriately set. Among them, the size of the dot-like transmission region is preferably larger than the period of the distortion of the reflected image. The distortion of the reflected image can be represented by one dot-like bright region.

[0072] In addition, when the mask has a plurality of dot-like transmission regions and the transmission regions are arranged in a lattice pattern, the pitches of the dot-like transmission regions may be equal or different, but among them, it is preferably equal. The pitch of the dot-like transmission region is not particularly limited and is appropriately set. Among them, the pitch of the dot-like transmission region is preferably smaller than the period of the distortion of the reflected image. When the pitch of the dot-like transmission region becomes larger than the period of the distortion of the reflected image, it may become difficult to sufficiently and quantitatively evaluate the distortion of the reflected image.

[0073] In addition, the mask may further have a focusing transmission region. The planar shape of the focusing transmission region is not particularly limited as long as the light detection unit described later can focus on the light source through the surface to be measured. For example, it can have various shapes such as a cross shape.

[0074] The mask only needs to have a transmission region and a light-shielding region. For example, it may have a transparent substrate and a patterned light-shielding layer disposed on one surface of the transparent substrate, or it may have a light-shielding substrate and an opening penetrating the light-shielding substrate.

[0075] In addition, when the illumination unit is a light source, the light source includes, for example, a line light source, a point light source, a surface light source, etc. Among them, a line light source is preferable. The line light source can irradiate illumination light having a linear bright region.

[0076] Examples of the line light source include a fluorescent lamp, a linear LED light source, and a linear OLED light source.

[0077] Examples of the surface light source include a planar LED light source, a planar OLED light source, and the like.

[0078] Also, a display may be used as the lighting unit. In this case, the display displays a pattern having bright regions and dark regions.

[0079] The incident angle of the illumination light on the surface to be measured is not particularly limited as long as the light detection unit can receive the reflected light from the surface to be measured, and is usually less than 90°. Also, for each incident angle of the illumination light, the variation in the above difference may be quantified. Note that the incident angle of the illumination light on the surface to be measured is the angle formed by the incident direction of the illumination light on the surface to be measured and the normal direction of the surface to be measured.

[0080] The distance between the surface to be measured and the lighting unit is not particularly limited as long as the illumination light irradiated from the lighting unit is reflected by the surface to be measured and the light detection unit can receive the reflected light having bright regions and dark regions, and is appropriately set.

[0081] 2. Light detection unit The light detection unit in the present disclosure focuses on the light source through the surface to be measured, receives the reflected light having bright regions and dark regions corresponding to the bright regions and dark regions of the illumination light reflected by the surface to be measured, and detects the light intensity distribution of the reflected light on the surface to be measured.

[0082] The light detection unit is not particularly limited as long as it can focus on the light source through the surface to be measured, receive the reflected light from the surface to be measured, and detect the light intensity distribution of the reflected light on the surface to be measured. Examples thereof include a photoelectric conversion device that converts light into an electrical signal. Examples of the photoelectric conversion device include an imaging device, a photodiode array, and the like. Also, the photoelectric conversion device may be a device that scans a single photodiode using a driving device such as a stepping motor. Among them, a photoelectric conversion device is preferable, and an imaging device is more preferable.

[0083] In the imaging device, the light source is focused through the surface to be measured, and the reflected light having bright and dark regions corresponding to the bright and dark regions of the illumination light is imaged after being reflected by the surface to be measured. Then, from the obtained image, the light intensity distribution of the reflected light on the surface to be measured is obtained.

[0084] The imaging device has an imaging element. Examples of the imaging element include a CCD image sensor, a CMOS image sensor, etc. Examples of the imaging device include a digital camera, etc. Also, either an area camera or a line camera can be used as the imaging device. In the case of a line camera, when the reflected light has a linear bright region, it is preferable to scan in the longitudinal direction of the linear bright region of the reflected light. In the case of a line camera when the reflected light has a grid-like bright region, it is preferable to scan in the x-direction or y-direction of the grid points of the bright region of the reflected light.

[0085] The light detection unit receives the direct reflected light of the illumination light. Therefore, the light reception angle of the reflected light is equal to the incident angle of the illumination light. Note that the light reception angle of the reflected light refers to the angle with respect to the normal direction of the surface to be measured. Also, that the light reception angle θ2 of the reflected light is equal to the incident angle θ1 of the illumination light means that it is within θ1±10°, preferably within θ1±5°, and more preferably within θ1±3°.

[0086] The distance between the surface to be measured and the light detection unit is not particularly limited as long as the light detection unit can receive the reflected light having bright and dark regions, and is set as appropriate. The distance between the surface to be measured and the light detection unit may be the same as or different from the distance between the surface to be measured and the illumination unit.

[0087] When the light detection unit is an imaging device, the number of pixels of the imaging element can be set as appropriate.

[0088] In the light detection unit, the light source is focused on the surface to be measured through the surface to be measured. As a method of focusing the light source on the surface to be measured through the surface to be measured, for example, when the illumination unit has a light source and a mask, a mask having a transmission region for focusing is used, and the surface to be measured is focused on the light projected from the light source through the transmission region for focusing of the mask. Further, when the illumination unit is a light source, a method of arranging an alignment mark on the light source and focusing on the alignment mark projected on the surface to be measured can be mentioned.

[0089] The reflected light from the surface to be measured has one or more bright regions and dark regions corresponding to the bright region and the dark region of the illumination light. The bright region and the dark region in the reflected light are the same as the bright region and the dark region in the illumination light.

[0090] In the light detection unit, it is preferable to divide the surface to be measured into a plurality of measurement regions, detect the light intensity of the reflected light for each measurement region, and detect the light intensity distribution of the reflected light on the surface to be measured. For example, when the reflected light has a linear bright region, in the light detection unit, the surface to be measured is divided into M×N measurement regions, where N is in the longitudinal direction of the linear bright region of the reflected light and M is in the transverse direction of the linear bright region of the reflected light, and the light intensity of the reflected light is detected for each measurement region, and the light intensity distribution of the reflected light on the surface to be measured is detected. The number of data (sample size) can be increased, and the surface properties of the surface to be measured can be accurately measured.

[0091] The number of measurement regions is not particularly limited. For example, when the light detection unit is an imaging device, the number of pixels in the image of the reflected light can be set as the number of measurement regions. Specifically, when the reflected light has a linear bright region, in the image of the reflected light obtained by the imaging device, the number of pixels in the longitudinal direction of the linear bright region is N, the number of pixels in the transverse direction of the linear bright region is M, and the number of pixels in the image of the reflected light can be set as the number of measurement regions (M×N). That is, one measurement region on the surface to be measured can correspond to one pixel in the image of the reflected light. The larger the number of measurement regions, the larger the number of data (sample size) can be, and the surface properties of the surface to be measured can be accurately measured.

[0092] Here, the longitudinal direction of the linear bright region of the reflected light refers to the direction in which the linear bright region of the reflected light extends. For example, when the shape of the linear bright region of the reflected light is linear, the longitudinal direction of the linear bright region of the reflected light is the direction in which the linear linear bright region extends. Also, for example, when the shape of the linear bright region of the reflected light is curved, the longitudinal direction of the linear bright region of the reflected light is the direction in which the curved linear bright region extends.

[0093] For example, when the shape of the linear bright region of the reflected light is linear, the longitudinal direction of the linear bright region of the illumination light is the direction in which the linear linear bright region extends, and is indicated by reference numeral D1 in FIG. 3, for example. Also, for example, when the shape of the linear bright region of the reflected light is curved, the longitudinal direction of the linear bright region of the reflected light is the direction in which the curved linear bright region extends, and is indicated by reference numeral D1 in FIG. 8, for example.

[0094] Also, for example, when the reflected light has a lattice-like bright region, it is preferable that the size of the measurement region, that is, the size of one pixel, is smaller than the period of the distortion of the reflected image. In this case, as described above, it is preferable that the size of the dot-like bright region is larger than the period of the distortion of the reflected image. In such a case, the distortion of the reflected image can be represented by one dot-like bright region.

[0095] 3. First processing unit In the first processing unit in the present disclosure, in the light intensity distribution of the reflected light on the measurement surface, for each of the bright regions, using a predetermined light intensity threshold, a plurality of selection points located on the line connecting the measurement points of the light intensity of the reflected light are determined, and the positions on the measurement surface indicating the selection points are specified.

[0096] For example, when the reflected light has a linear bright region, the first processing unit divides the light intensity distribution of the reflected light on the surface to be measured into n divided regions in the longitudinal direction of the linear bright region of the reflected light, extracts the light intensity distribution of the reflected light for each divided region, and in the light intensity distribution of the reflected light for each divided region, for each bright region, using a predetermined light intensity threshold, determines a plurality of selection points located on the line connecting the measurement points of the light intensity of the reflected light, and preferably specifies the positions on the surface to be measured indicating the selection points. The number of data (sample size) can be increased, and the surface properties of the surface to be measured can be accurately measured.

[0097] In the above case, when the light intensity distribution of the reflected light on the surface to be measured is the light intensity distribution obtained by dividing the surface to be measured into M×N measurement regions, where there are N in the longitudinal direction of the linear bright region of the reflected light and M in the transverse direction of the linear bright region of the reflected light, and detecting the light intensity of the reflected light for each measurement region, the number of divided regions (n) is usually the same as the number of measurement regions (N) in the longitudinal direction of the linear bright region of the reflected light.

[0098] Note that the number (n) of divided regions does not have to be the same as the number (N) of measurement regions in the longitudinal direction of the linear bright region of the reflected light. For example, the number (n) of divided regions may be 1 / 2 of the number (N) of measurement regions in the longitudinal direction of the linear bright region of the reflected light. Specifically, when the measurement regions in the short-side direction of the linear bright region of the reflected light are regarded as rows and the measurement regions in the longitudinal direction of the linear bright region of the reflected light are regarded as columns, if the light intensity distribution of the reflected light is extracted every other column, the number (n) of divided regions will be 1 / 2 of the number (N) of measurement regions in the longitudinal direction of the linear bright region of the reflected light. In this case, the light intensity distribution of the even-numbered columns may be extracted, or the light intensity distribution of the odd-numbered columns may be extracted. Also, for example, when the measurement regions in the short-side direction of the linear bright region of the reflected light are regarded as rows and the measurement regions in the longitudinal direction of the linear bright region of the reflected light are regarded as columns, if the light intensity distribution of the reflected light is extracted every two columns, the number (n) of divided regions will be 1 / 3 of the number (N) of measurement regions in the longitudinal direction of the linear bright region of the reflected light, and if the light intensity distribution of the reflected light is extracted every three columns, the number (n) of divided regions will be 1 / 4 of the number (N) of measurement regions in the longitudinal direction of the linear bright region of the reflected light. In this case, it is preferable to set the number (n) of divided regions so that the pitch of each divided region is smaller than the period of the distortion of the reflected image. If the pitch of the divided region is larger than the period of the distortion of the reflected image, it may be difficult to sufficiently and quantitatively evaluate the distortion of the reflected image.

[0099] Also, for example, when the reflected light has a planar bright region, the first processing unit divides the light intensity distribution of the reflected light on the surface to be measured into n divided regions in an arbitrary direction, extracts the light intensity distribution of the reflected light for each divided region, and in the light intensity distribution of the reflected light for each divided region, for each bright region, using a predetermined light intensity threshold, determines a plurality of selection points located on the line connecting the measurement points of the light intensity of the reflected light, and can specify the positions on the surface to be measured indicating the selection points. The number of data (sample size) can be increased.

[0100] In the above case, the direction in which the light intensity distribution of the reflected light on the surface to be measured is divided into n divided regions is not particularly limited and is appropriately set according to the shape of the planar bright region. For example, as shown in FIG. 9(a), when the planar shape of the planar bright region 21 in plan view is rectangular, first, in the short side direction D4 of the rectangular bright region 21 of the image of the reflected light on the surface to be measured, the dark region 22, the bright region 21, and the dark region 22 are arranged in this order, and the image of the reflected light on the surface to be measured can be cut out with the frame line 26. In this case, for example, an image of the reflected light as shown in FIG. 9(b) can be obtained. Next, as shown in FIG. 9(b), the image of the reflected light may be divided into n divided regions A1 to An in the long side direction D3 of the original rectangular bright region 21 shown in FIG. 9(a). Alternatively, for example, as shown in FIG. 9(a), when the planar shape of the planar bright region 21 in plan view is rectangular, first, in the long side direction D3 of the rectangular bright region 21 of the image of the reflected light on the surface to be measured, the dark region 22, the bright region 21, and the dark region 22 are arranged in this order, and the image of the reflected light on the surface to be measured can be cut out with the frame line 26. In this case, for example, an image of the reflected light as shown in FIG. 9(c) can be obtained. Next, as shown in FIG. 9(c), the image of the reflected light may be divided into n divided regions A1 to An in the short side direction D4 of the original rectangular bright region 21 shown in FIG. 9(a).

[0101] In the above case, the number of divided regions (n) can be the same as in the case where the above reflected light has a linear bright region.

[0102] Further, for example, when the reflected light has a grid-like bright region, the first processing unit extracts, from the light intensity distribution of the reflected light on the surface to be measured, j partial regions including the bright region along the x-direction of the grid points of the bright region of the reflected light, divides each partial region into k divided regions along the x-direction of the grid points of the bright region of the reflected light, extracts the light intensity distribution of the reflected light for each divided region, and in the light intensity distribution of the reflected light for each divided region, for each bright region, determines a plurality of selection points located on the line connecting the measurement points of the light intensity of the reflected light by using a predetermined light intensity threshold, and can specify the position on the surface to be measured indicating the selection points. Alternatively, the first processing unit extracts, from the light intensity distribution of the reflected light on the surface to be measured, j partial regions including the bright region along the y-direction of the grid points of the bright region of the reflected light, divides each partial region into k divided regions along the y-direction of the grid points of the bright region of the reflected light, extracts the light intensity distribution of the reflected light for each divided region, and in the light intensity distribution of the reflected light for each divided region, for each bright region, determines a plurality of selection points located on the line connecting the measurement points of the light intensity of the reflected light by using a predetermined light intensity threshold, and can specify the position on the surface to be measured indicating the selection points.

[0103] In the above case, for example, as shown in Fig. 10(a), first, from the image of the reflected light on the surface to be measured, along the y-direction D6 of the lattice points of the bright region 21, j partial regions B1 to Bj including the bright region 21 can be extracted. In this case, the number of partial regions (j) is usually the same as the number of bright regions in the y-direction D6 of the lattice points of the bright region. Next, as shown in Fig. 10(b), each partial region B1 to Bj can be divided into k divided regions C1 to Ck in the y-direction D6 of the lattice points of the bright region of the reflected light. In this case, the number of divided regions (k) is usually the same as the number of measurement regions in the y-direction D6 of the lattice points of the bright region in each partial region. Alternatively, for example, as shown in Fig. 10(c), first, from the image of the reflected light on the surface to be measured, along the x-direction D5 of the lattice points of the bright region 21, j partial regions B1 to Bj including the bright region 21 can be extracted. In this case, the number of partial regions (j) is usually the same as the number of bright regions in the x-direction D5 of the lattice points of the bright region. Next, as shown in Fig. 10(d), each partial region B1 to Bj can be divided into k divided regions C1 to Ck in the x-direction D5 of the lattice points of the bright region of the reflected light. In this case, the number of divided regions (k) is usually the same as the number of measurement regions in the x-direction D5 of the lattice points of the bright region in each partial region. In these cases, it is preferable that the pitch of the dot-like bright region, that is, the pitch of each partial region, is smaller than the period of the distortion of the reflection image. When the pitch of the dot-like bright region is larger than the period of the distortion of the reflection image, it may be difficult to sufficiently quantitatively evaluate the distortion of the reflection image.

[0104] For example, when the light detection unit is an imaging device and the reflected light has a linear bright region, when dividing the image of the reflected light obtained by the imaging device into n divided regions in the longitudinal direction of the linear bright region of the reflected light, the angle of the image may be adjusted to perform an angle adjustment process so that the longitudinal direction of the linear bright region of the reflected light is horizontal or vertical.

[0105] Specifically, first, for noise removal, smoothing processing and binarization processing are sequentially performed on the image of the reflected light obtained by the imaging device. Examples of the smoothing processing method include the moving average method, the method of applying a Gaussian filter, etc. Next, for one linear bright region, in the case of a linear bright region, linear approximation is performed. At this time, in one linear bright region after binarization, for example, linear approximation can be performed using the data at one end in the longitudinal direction. Examples of the linear approximation method include the least squares method. Next, in the case of linear approximation, the image is rotated so that the slope of the approximated straight line becomes 0. Thereby, the longitudinal direction of the linear bright region of the reflected light can be made perpendicular. Also, when the image is further rotated by 90°, the longitudinal direction of the linear bright region of the reflected light can be made horizontal.

[0106] In the light intensity distribution of the reflected light in each divided region, the light intensity threshold value can be set for each bright region. For example, as shown in FIG. 3, when the reflected light has four linear bright regions, for example, as shown in FIG. 5(a), in the light intensity distribution of the reflected light in each divided region, for each of the linear bright regions 21a to 21d, four light intensity threshold values T a1 ~T d1 are set.

[0107] The light intensity threshold value may be smaller than the peak value (maximum value) of the light intensity of the bright region and larger than the peak value (minimum value) of the light intensity of the dark region. Among them, the light intensity threshold value is preferably a light intensity value that is 10% or more and 90% or less, further 30% or more and 70% or less, and particularly 40% or more and 60% or less of the peak value (maximum value) of the light intensity of the bright region.

[0108] In the first processing unit, in the light intensity distribution of the reflected light in each divided region, for each bright region, a plurality of selection points located on the line connecting the measurement points of the light intensity of the reflected light are determined using the above light intensity threshold value.

[0109] The method of determining the selection points using the light intensity threshold value will be described with examples.

[0110] The first method for determining the selection points using the light intensity threshold is, in the light intensity distribution of the reflected light in each divided region, for each bright region, the light intensity distribution of the bright region is divided into a left light intensity distribution and a right light intensity distribution with the peak value of the light intensity of each bright region as the boundary. For each left light intensity distribution and right light intensity distribution of each bright region, a measurement point that has a light intensity equal to or exceeding the light intensity threshold and that shows the light intensity closest to the light intensity threshold is selected, and the above measurement point is used as the selection point.

[0111] For example, FIG. 5(a) is an example of the light intensity distribution of the reflected light in the divided region A1, and is an example in which the reflected light has a linear bright region. In the light intensity distribution of the reflected light in the divided region A1, for each of the linear bright regions 21a to 21d, the peak value of the light intensity is obtained, and for example, a light intensity value that is 50% of the peak value of the light intensity is set as the light intensity threshold T a1 ~T d1 Let it be. Also, in the light intensity distribution of the reflected light in the divided region A1, the light intensity distributions of each of the linear bright regions 21a to 21d are divided into a left light intensity distribution L and a right light intensity distribution R with the peak value of each light intensity as the boundary. The selection point P L1 is a measurement point that has a light intensity equal to or exceeding the light intensity threshold T a1 in the left light intensity distribution L of the linear bright region 21a, and that shows the light intensity closest to the light intensity threshold T a1 Also, the selection point P a1 is a measurement point that has a light intensity equal to or exceeding the light intensity threshold T R1 in the right light intensity distribution R of the linear bright region 21a, and that shows the light intensity closest to the light intensity threshold T a1 Similarly, the selection point Q a1 is a measurement point that has a light intensity equal to or exceeding the light intensity threshold T a1 in the left light intensity distribution L of the linear bright region 21b, and that shows the light intensity closest to the light intensity threshold T L1 Also, the selection point Q b1 is a measurement point that has a light intensity equal to or exceeding the light intensity threshold T b1 in the right light intensity distribution R of the linear bright region 21b, and that shows the light intensity closest to the light intensity threshold T b1 and that shows the light intensity closest to the light intensity threshold T R1 is a measurement point that has a light intensity equal to or exceeding the light intensity threshold T b1 in the right light intensity distribution R of the linear bright region 21b, and that shows the light intensity closest to the light intensity threshold T b1 and that shows the light intensity closest to the light intensity threshold T b1is the measurement point showing the light intensity closest to []. Similarly, the selection point R L1 is, in the left light intensity distribution L of the linear bright region 21c, the light intensity threshold T c1 or more, or exceeds the light intensity threshold T c1 and is the measurement point showing the light intensity closest to the light intensity threshold T c1 . Also, the selection point R R1 is, in the right light intensity distribution R of the linear bright region 21c, the light intensity threshold T c1 or more, or exceeds the light intensity threshold T c1 and is the measurement point showing the light intensity closest to the light intensity threshold T c1 . Similarly, the selection point S L1 is, in the left light intensity distribution L of the linear bright region 21d, the light intensity threshold T d1 or more, or exceeds the light intensity threshold T d1 and is the measurement point showing the light intensity closest to the light intensity threshold T d1 . Also, the selection point S R1 is, in the right light intensity distribution R of the linear bright region 21d, the light intensity threshold T d1 or more, or exceeds the light intensity threshold T d1 and is the measurement point showing the light intensity closest to the light intensity threshold T d1 .

[0112] Also, the second method for determining the selection point using the light intensity threshold is, in the light intensity distribution of the reflected light in each divided region, for each bright region, dividing the light intensity distribution of the bright region into a left light intensity distribution and a right light intensity distribution with the peak value of the light intensity of each bright region as the boundary, and selecting, in either the left light intensity distribution or the right light intensity distribution of each bright region, the measurement point that is equal to or exceeds the light intensity threshold and shows the light intensity closest to the light intensity threshold, and using the above measurement point as the selection point.

[0113] For example, in the case of Fig. 5(a) described above, in the light intensity distribution of the reflected light in the divided region A1, extracting the left light intensity distribution L of each linear bright region 21a to 21d, and as the selection points, the selection points P L1 、Q L1 、R L1 、SL1 It may only use. Also, for example, in the case of FIG. 5(a) described above, in the light intensity distribution of the reflected light of the divided region A1, the right light intensity distribution R of each linear bright region 21a to 21d is extracted, and as the selection point, it is a measurement point that is equal to or exceeds the light intensity threshold value and shows the light intensity closest to the light intensity threshold value, the selection point P R1 , Q R1 , R R1 , S R1 It may only use.

[0114] Also, the third method for determining the selection point using the light intensity threshold value is that in the light intensity distribution of the reflected light of each divided region, for each bright region, the light intensity distribution of the bright region is divided into a left light intensity distribution and a right light intensity distribution with the peak value of the light intensity of each bright region as the boundary, and for each left light intensity distribution and right light intensity distribution of each bright region, a measurement point that is equal to or less than the light intensity threshold value and shows the light intensity closest to the light intensity threshold value is selected, and the above measurement point is used as the selection point.

[0115] Also, the fourth method for determining the selection point using the light intensity threshold value is that in the light intensity distribution of the reflected light of each divided region, for each bright region, the light intensity distribution of the bright region is divided into a left light intensity distribution and a right light intensity distribution with the peak value of the light intensity of each bright region as the boundary, and in either the left light intensity distribution or the right light intensity distribution of each bright region, a measurement point that is equal to or less than the light intensity threshold value and shows the light intensity closest to the light intensity threshold value is selected, and the above measurement point is used as the selection point.

[0116] Also, the fifth method for determining the selection point using the light intensity threshold value is that in the light intensity distribution of the reflected light of each divided region, for each bright region, the light intensity distribution of the bright region is divided into a left light intensity distribution and a right light intensity distribution with the peak value of the light intensity of each bright region as the boundary, and for each left light intensity distribution and right light intensity distribution of each bright region, a measurement point that shows the light intensity closest to the light intensity threshold value is selected, and the above measurement point is used as the selection point. In this case, the measurement point that shows the light intensity closest to the light intensity threshold value may be equal to or greater than the light intensity threshold value, or may be equal to or less than the light intensity threshold value.

[0117] For example, FIG. 11 shows an example of the light intensity distribution of the reflected light in the divided region A1, and is an example in which the reflected light has a linear bright region. In the light intensity distribution of the reflected light in the divided region A1, for each of the linear bright regions 21a to 21d, the peak value of the light intensity is obtained, and for example, the light intensity value that is 50% of the peak value of the light intensity is defined as the light intensity threshold T a1 ~T d1 Let it be so. Also, in the light intensity distribution of the reflected light in the divided region A1, the light intensity distributions of the respective linear bright regions 21a to 21d are divided into a left-side light intensity distribution L and a right-side light intensity distribution R with the peak value of each light intensity as the boundary. The selection point P L1 is the measurement point that shows the light intensity closest to the light intensity threshold T a1 in the left-side light intensity distribution L of the linear bright region 21a. Also, the selection point P R1 is the measurement point that shows the light intensity closest to the light intensity threshold T a1 in the right-side light intensity distribution R of the linear bright region 21a. Similarly, the selection point Q L1 is the measurement point that shows the light intensity closest to the light intensity threshold T b1 in the left-side light intensity distribution L of the linear bright region 21b. Also, the selection point Q R1 is the measurement point that shows the light intensity closest to the light intensity threshold T b1 in the right-side light intensity distribution R of the linear bright region 21b. Similarly, the selection point R L1 is the measurement point that shows the light intensity closest to the light intensity threshold T c1 in the left-side light intensity distribution L of the linear bright region 21c. Also, the selection point R R1 is the measurement point that shows the light intensity closest to the light intensity threshold T c1 in the right-side light intensity distribution R of the linear bright region 21c. Similarly, the selection point S L1 is the measurement point that shows the light intensity closest to the light intensity threshold T d1 in the left-side light intensity distribution L of the linear bright region 21d. Also, the selection point S R1 is the measurement point that shows the light intensity closest to the light intensity threshold T d1 in the right-side light intensity distribution R of the linear bright region 21d.

[0118] Also, the sixth method for determining the selection points using the light intensity threshold is, in the light intensity distribution of the reflected light in each divided region, for each bright region, the light intensity distribution of the bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each bright region, a measurement point showing the light intensity closest to the light intensity threshold is selected, and the above measurement point is used as the selection point. Also in this case, the measurement point showing the light intensity closest to the light intensity threshold may be equal to or higher than the light intensity threshold, or may be equal to or lower than the light intensity threshold.

[0119] For example, in the case of FIG. 11 described above, in the light intensity distribution of the reflected light in the divided region A1, the left-side light intensity distribution L of each linear bright region 21a to 21d is extracted, and as the selection points, selection points P L1 , Q L1 , R L1 , S L1 alone may be used. Also, for example, in the case of FIG. 11 described above, in the light intensity distribution of the reflected light in the divided region A1, the right-side light intensity distribution R of each linear bright region 21a to 21d is extracted, and as the selection points, selection points P R1 , Q R1 , R R1 , S R1 alone may be used.

[0120] Also, the seventh method for determining the selection points using the light intensity threshold is, in the light intensity distribution of the reflected light in each divided region, for each bright region, the light intensity distribution of the bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each bright region as the boundary. For each of the left-side light intensity distribution and the right-side light intensity distribution of each bright region, a point located on the line connecting the measurement point showing the light intensity equal to or lower than the light intensity threshold and closest to the light intensity threshold and the measurement point showing the light intensity equal to or higher than the light intensity threshold and closest to the light intensity threshold is selected, and the point showing the light intensity threshold is selected as the selection point. In this case, the point showing the light intensity threshold may or may not be a measurement point.

[0121] For example, Fig. 12 shows an example of the light intensity distribution of the reflected light in the divided region A1, where the reflected light has a linear bright region. In the light intensity distribution of the reflected light in the divided region A1, for each of the linear bright regions 21a to 21d, the peak value of the light intensity is obtained, and for example, the light intensity value that is 50% of the peak value of the light intensity is set as the light intensity threshold T a1 ~T d1 Let it be so. Also, in the light intensity distribution of the reflected light in the divided region A1, the light intensity distributions of each of the linear bright regions 21a to 21d are divided into a left-side light intensity distribution L and a right-side light intensity distribution R with the peak value of each light intensity as the boundary. The selection point P L1 is in the left-side light intensity distribution L of the linear bright region 21a, where the light intensity is below the light intensity threshold T a1 or less than the light intensity threshold T a1 and is the measurement point showing the light intensity closest to the light intensity threshold T a1 , and the measurement point showing the light intensity above the light intensity threshold T a1 or more than the light intensity threshold T a1 and is located on the line connecting the measurement point showing the light intensity closest to the light intensity threshold T a1 , and is the point showing the light intensity threshold T a1 . Also, the selection point P R1 is in the right-side light intensity distribution R of the linear bright region 21a, where the light intensity is below the light intensity threshold T a1 or less than the light intensity threshold T a1 and is the measurement point showing the light intensity closest to the light intensity threshold T a1 , and the measurement point showing the light intensity above the light intensity threshold T a1 or more than the light intensity threshold T a1 and is located on the line connecting the measurement point showing the light intensity closest to the light intensity threshold T a1 , and is the point showing the light intensity threshold T a1 . Similarly, the selection point Q L1 is in the left-side light intensity distribution L of the linear bright region 21b, where the light intensity is below the light intensity threshold T b1 or less than the light intensity threshold T b1 and is the measurement point showing the light intensity closest to the light intensity threshold T b1 , and the measurement point showing the light intensity above the light intensity threshold T b1 or more than the light intensity threshold T b1 and is located on the line connecting the measurement point showing the light intensity closest to the light intensity threshold T b1 , and is the point showing the light intensity threshold T b1is the point shown. Also, the selection point Q R1 is located on the line connecting the measurement point showing the light intensity below or less than the light intensity threshold T b1 in the right light intensity distribution R of the linear bright region 21b, and the measurement point showing the light intensity closest to the light intensity threshold T b1 and is the point showing the light intensity threshold T b1 . Similarly, the selection point R b1 is located on the line connecting the measurement point showing the light intensity below or less than the light intensity threshold T b1 in the left light intensity distribution L of the linear bright region 21c, and the measurement point showing the light intensity closest to the light intensity threshold T b1 and is the point showing the light intensity threshold T b1 . Also, the selection point R L1 is located on the line connecting the measurement point showing the light intensity below or less than the light intensity threshold T c1 in the right light intensity distribution R of the linear bright region 21c, and the measurement point showing the light intensity closest to the light intensity threshold T c1 and is the point showing the light intensity threshold T c1 . Similarly, the selection point S c1 is located on the line connecting the measurement point showing the light intensity below or less than the light intensity threshold T c1 in the left light intensity distribution L of the linear bright region 21d, and the measurement point showing the light intensity closest to the light intensity threshold T c1 and is the point showing the light intensity threshold T c1 . Also, the selection point R R1 is located on the line connecting the measurement point showing the light intensity below or less than the light intensity threshold T c1 in the right light intensity distribution R of the linear bright region 21c, and the measurement point showing the light intensity closest to the light intensity threshold T c1 and is the point showing the light intensity threshold T c1 . Similarly, the selection point S c1 is located on the line connecting the measurement point showing the light intensity below or less than the light intensity threshold T c1 in the left light intensity distribution L of the linear bright region 21d, and the measurement point showing the light intensity closest to the light intensity threshold T c1 and is the point showing the light intensity threshold T c1 . Similarly, the selection point S L1 is located on the line connecting the measurement point showing the light intensity below or less than the light intensity threshold T d1 in the left light intensity distribution L of the linear bright region 21d, and the measurement point showing the light intensity closest to the light intensity threshold T d1 and is the point showing the light intensity threshold T d1 . Also, the selection point S d1 is located on the line connecting the measurement point showing the light intensity below or less than the light intensity threshold T d1 in the left light intensity distribution L of the linear bright region 21d, and the measurement point showing the light intensity closest to the light intensity threshold T d1is located on the line connecting the measurement point indicating the light intensity closest to it and the light intensity threshold T d1 and is the point indicating it. Also, the selection point S R1 is in the right light intensity distribution R of the linear bright region 21d, where the light intensity is equal to or less than the light intensity threshold T d1 or less than the light intensity threshold T d1 and is located on the line connecting the measurement point indicating the light intensity closest to the light intensity threshold T d1 and the measurement point indicating the light intensity closest to the light intensity threshold T d1 equal to or greater than or exceeding the light intensity threshold T d1 and is the point indicating the light intensity threshold T d1 is located on the line connecting the measurement point indicating the light intensity closest to it and the light intensity threshold T d1 and is the point indicating it.

[0122] Also, the eighth method for determining the selection point using the light intensity threshold is, in the light intensity distribution of the reflected light of each divided region, for each bright region, the light intensity distribution of the bright region is divided into a left light intensity distribution and a right light intensity distribution with the peak value of the light intensity of each bright region as the boundary. In either the left light intensity distribution or the right light intensity distribution of each bright region, the measurement point indicating the light intensity equal to or less than the light intensity threshold or less than the light intensity threshold and closest to the light intensity threshold, and the measurement point indicating the light intensity equal to or greater than the light intensity threshold or exceeding the light intensity threshold and closest to the light intensity threshold are connected by a line, and the point indicating the light intensity threshold is selected, and the point indicating the above light intensity threshold is used as the selection point.

[0123] For example, in the case of FIG. 12 described above, in the light intensity distribution of the reflected light of the divided region A1, the left light intensity distribution L of each linear bright region 21a to 21d is extracted, and as the selection points, the measurement point indicating the light intensity equal to or less than the light intensity threshold or less than the light intensity threshold and closest to the light intensity threshold, and the measurement point indicating the light intensity equal to or greater than the light intensity threshold or exceeding the light intensity threshold and closest to the light intensity threshold are connected by a line, and the selection point P L1 、Q L1 、R L1 、S L1It may be used only. Also, for example, in the case of FIG. 12 described above, in the light intensity distribution of the reflected light in the divided region A1, the right light intensity distribution R of each linear bright region 21a to 21d is extracted, and as a selection point, it is below or less than the light intensity threshold, and the measurement point showing the light intensity closest to the light intensity threshold, and the light intensity is above or exceeds the light intensity threshold, and the measurement point showing the light intensity closest to the light intensity threshold are connected, and the selection point P which is the point showing the light intensity threshold R1 , Q R1 , R R1 , S R1 It may be used only.

[0124] In the first processing unit, the position on the measurement surface indicating the selection point is specified. For example, when the light detection unit is an imaging device, since the position (pixel position) on the image of the reflected light corresponds to the position on the measurement surface, the position (pixel position) on the image of the reflected light indicating the selection point may be specified.

[0125] 4. Second processing unit In the second processing unit in the present disclosure, for each bright region, a graph is created by plotting the position on the measurement surface indicating the selection point with the first direction on the measurement surface as the horizontal axis and the second direction orthogonal to the first direction on the measurement surface as the vertical axis.

[0126] For example, when the light detection unit is an imaging device, the position (pixel position) on the image of the reflected light corresponds to the position on the measurement surface. Therefore, for example, when the reflected light has a linear bright region, a graph is created by plotting the position (pixel position) on the image of the reflected light indicating the selection point with the longitudinal direction of the linear bright region of the image of the reflected light as the horizontal axis and the short transverse direction of the linear bright region of the image of the reflected light as the vertical axis. In this case, the longitudinal direction D1 of the linear bright region of the image of the reflected light corresponds to the first direction on the measurement surface, and the short transverse direction D2 of the linear bright region of the image of the reflected light corresponds to the second direction on the measurement surface.

[0127] In the first processing unit, when, in the light intensity distribution of the reflected light of each divided region, for each bright region, the light intensity distribution of the bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each bright region as the boundary, and when determining a selection point for each of the left-side light intensity distribution and the right-side light intensity distribution of each bright region, the second processing unit may create a graph plotting the positions on the measurement surface indicating the selection points for each bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution, or may create a graph plotting the positions on the measurement surface indicating the selection points for each bright region.

[0128] For example, FIG. 6(a) is a graph plotting the positions (pixel positions) on the reflected light image indicating the selection points P L1 ~P Ln for the left-side light intensity distribution L of the linear bright region 21a in the light intensity distribution of the reflected light of each divided region A1 to An as shown in FIGS. 5(a) to (b), FIG. 11, and FIG. 12. In the above case, when creating a graph plotting the positions on the measurement surface indicating the selection points for each linear bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution, a graph as shown in FIG. 6(a) is obtained.

[0129] Also, for example, FIG. 13(a) is a graph plotting the positions (pixel positions) on the reflected light image indicating the selection points P L1 ~P Ln 、P R1 ~P Rn for the linear bright region 21a in the light intensity distribution of the reflected light of each divided region A1 to An as shown in FIGS. 5(a) to (b), FIG. 11, and FIG. 12. In the above case, when creating a graph plotting the positions on the measurement surface indicating the selection points for each linear bright region, a graph as shown in FIG. 13(b) is obtained.

[0130] Note that in FIGS. 6(a) and 13(a), the horizontal axis is the pixel position in the longitudinal direction D1 of the linear bright region of the reflected light image, and the vertical axis is the pixel position in the short transverse direction D2 of the linear bright region of the reflected light image.

[0131] Further, in the first processing unit, in the light intensity distribution of the reflected light of each divided region, when the light intensity distribution of each bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each bright region as a boundary for each bright region, and when determining a selection point in either the left-side light intensity distribution or the right-side light intensity distribution of each bright region, the second processing unit may create a graph plotting the positions on the measurement surface indicating the selection points for each bright region.

[0132] 5. Third processing unit The third processing unit in the present disclosure obtains a reference line based on the shape of the bright region of the illumination light for each bright region.

[0133] The method for obtaining the reference line will be described with examples.

[0134] The first method for obtaining the reference line is a method of obtaining an approximation formula from the points plotted on the graph created by the second processing unit and using the approximation formula as the reference line. The approximation is based on the shape of the bright region of the illumination light. For example, when the bright region is linear and straight, linear approximation can be performed. Also, for example, when the bright region is planar and square or rectangular, linear approximation can also be performed. Also, for example, when the bright region is grid-like and square or rectangular, linear approximation can also be performed. Examples of the linear approximation method include the least squares method and the gradient descent method. Also, for example, when the bright region is linear and curved, curve approximation can be performed. Also, for example, when the bright region is planar and circular or elliptical, curve approximation can also be performed. Examples of the curve approximation method include polynomial regression. The coefficients of the polynomial regression can be determined, for example, by the least squares method.

[0135] In the case of the first method, in the first processing unit, in the light intensity distribution of the reflected light of each divided region, for each bright region, when the light intensity distribution of the bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each bright region as the boundary, and when determining a selection point for each of the left-side light intensity distribution and the right-side light intensity distribution of each bright region, in the second processing unit, when creating a graph plotting the position on the measurement surface indicating the selection point for each bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution, a reference line is obtained for each bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution. For example, in the graph shown in FIG. 6(b), when linearly approximating the plotted points, a linear approximation formula (the solid line in FIG. 6(b)) can be obtained, and this linear approximation formula can be used as the reference line.

[0136] Also, in the case of the first method, in the first processing unit, in the light intensity distribution of the reflected light of each divided region, for each bright region, when the light intensity distribution of the bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each bright region as the boundary, and when determining a selection point for each of the left-side light intensity distribution and the right-side light intensity distribution of each bright region, in the second processing unit, when creating a graph plotting the position on the measurement surface indicating the selection point for each bright region, a reference line is obtained for each bright region. For example, in the graph shown in FIG. 13(b), when linearly approximating the plotted points, a linear approximation formula (the solid line in FIG. 13(b)) can be obtained, and this linear approximation formula can be used as the reference line.

[0137] The second method for obtaining the reference line is a method of obtaining a reference line based on the shape of the bright region of the reflected light on the surface of a smooth reference substrate having a predetermined arithmetic mean roughness Ra. The method of obtaining the reference line is the same as the first method of obtaining the reference line described above when the measurement surface is the surface of the reference substrate. Specifically, by using the measurement surface as the surface of the reference substrate and passing through the above-described irradiation unit, light detection unit, first processing unit, and second processing unit, a graph can be created when the measurement surface is the surface of the reference substrate.

[0138] The arithmetic mean roughness Ra of the surface of the reference substrate is preferably, for example, 1 nm or less, more preferably 0.6 nm or less, and even more preferably 0.3 nm or less.

[0139] Here, the arithmetic mean roughness Ra of the surface of the reference substrate can be measured using an atomic force microscope (AFM) or a white light interferometer.

[0140] The reference substrate may be any substrate that satisfies the above flatness, and examples include glass substrates. Specifically, a glass substrate for a flat panel display can be mentioned. For example, the non-alkali glass substrate "OA-10G" manufactured by Nippon Electric Glass Co., Ltd. has an arithmetic mean roughness Ra of 0.2 nm and high smoothness.

[0141] 6. Fourth processing unit In the fourth processing unit in the present disclosure, for each of the above bright regions, the difference between the points plotted on the graph and the reference line is obtained, and for each of the above bright regions, the variation of the difference is quantified.

[0142] As the variation of the difference, for example, standard deviation, variance, deviation value, mean absolute deviation, etc. can be used. Among them, the standard deviation is preferable.

[0143] Also, for example, when obtaining the difference for each bright region and for each of the left and right light intensity distributions, when quantifying the variation of the difference for each bright region, for example, the variation of the difference can be obtained for each bright region and for each of the left and right light intensity distributions. In this case, the arithmetic mean value of the variation of the difference for each bright region and for each of the left and right light intensity distributions can be calculated, and the arithmetic mean value of the variation of the difference for each bright region and for each of the left and right light intensity distributions can be used as the variation of the difference for all the bright regions.

[0144] Further, for example, when obtaining the above difference for each bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution, when quantifying the variation of the above difference for each bright region, for example, the variation of the above difference can be obtained for each bright region and for each of the left-side light intensity distribution or the right-side light intensity distribution. In this case, the arithmetic mean value of the variation of the above difference for each bright region and for each of the left-side light intensity distribution or the right-side light intensity distribution is calculated, and the arithmetic mean value of the variation of the above difference for each bright region and for each of the left-side light intensity distribution or the right-side light intensity distribution can be set as the variation of the above difference for all the bright regions.

[0145] 7. Fifth processing unit As shown in FIG. 14, for example, the surface property measurement device of the present disclosure may include a fifth processing unit 31 that obtains the maximum value of the light intensity in the bright region and the minimum value of the light intensity in the dark region in the light intensity distribution of the reflected light on the surface to be measured, and calculates the image sharpness according to the following formula (1). DOI=(M - m) / (M + m)×100 (1) (In the above formula, DOI represents image sharpness, M represents the maximum value of the light intensity in the bright region, and m represents the minimum value of the light intensity in the dark region.)

[0146] The image sharpness is a degree to which the reflected image of the surface to be measured appears clearly and without distortion. At the same time as quantifying the variation of the above difference, the image sharpness can be measured, and the degree of distortion of the reflected image of the surface to be measured can be quantitatively evaluated.

[0147] The maximum value of the light intensity in the bright region and the minimum value of the light intensity in the dark region may be the maximum value of the light intensity in the bright region and the minimum value of the light intensity in the dark region in the entire light intensity distribution of the reflected light on the surface to be measured, or may be the maximum value of the light intensity in the bright region and the minimum value of the light intensity in the dark region in the light intensity distribution of the reflected light in one divided region.

[0148] 8. Display unit As shown in FIG. 14, for example, the surface property measurement device of the present disclosure may include a display unit 32 that displays the numerical value of the variation of the above difference. The display unit can also display the above image sharpness.

[0149] 9. Use The use of the surface property measuring device of the present disclosure is not particularly limited. The surface property measuring device of the present disclosure can be used, for example, for measuring the surface properties of a coating film, a film, a sheet, a painted surface, a processed surface, etc. Among them, the surface property measuring device of the present disclosure is preferably used for measuring the surface properties of an optical film, and more preferably used for measuring the surface properties of a surface member of a display device.

[0150] B. Surface property measurement method The surface property measurement method in the present disclosure includes an irradiation step of irradiating a surface to be measured with illumination light having one or more bright regions and dark regions using a light source, focusing on the light source through the surface to be measured, receiving reflected light having one or more bright regions and dark regions corresponding to the bright regions and the dark regions of the illumination light, and detecting the light intensity distribution of the reflected light on the surface to be measured; a first processing step of, for each bright region in the light intensity distribution of the reflected light on the surface to be measured, determining a plurality of selection points located on a line connecting the measurement points of the light intensity of the reflected light using a predetermined light intensity threshold value, and specifying the positions on the surface to be measured indicating the selection points; a second processing step of, for each bright region, creating a graph by plotting the positions on the surface to be measured indicating the selection points, with the first direction on the surface to be measured as the horizontal axis and the second direction perpendicular to the first direction on the surface to be measured as the vertical axis; a third processing step of, for each bright region, obtaining a reference line based on the shape of the bright region of the illumination light; and a fourth processing step of, for each bright region, obtaining the difference between the points plotted on the graph and the reference line, and quantifying the variation of the difference for each bright region.

[0151] FIG. 15 is a process diagram illustrating the surface property measurement method of the present disclosure, and is a process diagram showing the surface property measurement method executed by the surface property measurement apparatus 10 shown in FIG. 1, for example. As shown in FIGS. 1 and 15, first, in the irradiation step S11, using a light source, the measurement surface 1 is irradiated with illumination light L1 having one or more bright regions and dark regions. Next, in the light detection step S12, the light detection unit 5 focuses on the light source 3 through the measurement surface 1, receives reflected light L2 having one or more bright regions and dark regions corresponding to the bright regions and dark regions of the illumination light L1 reflected by the measurement surface 1, and detects the light intensity distribution of the reflected light L2 on the measurement surface 1. Next, in the first processing step S13, in the light intensity distribution of the reflected light L2 on the measurement surface 1, for each bright region, using a predetermined light intensity threshold, a plurality of selection points located on the line connecting the light intensity measurement points of the reflected light L2 are determined, and the positions on the measurement surface 1 indicating the selection points are specified. Next, in the second processing step S14, for each bright region, with the first direction on the measurement surface 1 as the horizontal axis and the second direction perpendicular to the first direction on the measurement surface 1 as the vertical axis, a graph is created by plotting the positions on the measurement surface 1 indicating the selection points. Next, in the third processing step S15, for each bright region, a reference line based on the shape of the bright region of the illumination light L1 is obtained. Next, in the fourth processing step S16, for each bright region, the difference between the points plotted on the graph and the reference line is obtained, and for each bright region, the variation of the difference is quantified.

[0152] In the surface property measurement method of the present disclosure, similar to the above-described surface property measurement apparatus, the distortion of the reflected image of the measurement surface can be quantified, for example, as the standard deviation of the above difference, and quantitatively evaluated.

[0153] Hereinafter, each step in the surface property measurement method of the present disclosure will be described.

[0154] 1. Illumination step In the light detection step in the present disclosure, using a light source, the measurement surface is irradiated with illumination light having one or more bright regions and dark regions.

[0155] The illumination step can be made the same as the content described in the section of the illumination unit in the above-described surface property measurement apparatus.

[0156] In the object to be measured having a surface to be measured, a light-shielding layer may be disposed on the surface opposite to the surface to be measured of the object to be measured. The light-shielding layer can suppress back surface reflection. The light-shielding layer is not particularly limited, and for example, a black resin film or a blackboard can be used. Further, a black resin composition may be applied to the surface opposite to the surface to be measured of the object to be measured to form a light-shielding layer.

[0157] 2. Light detection step In the light detection step in the present disclosure, the light source is focused through the surface to be measured, and the reflected light having one or more bright regions and dark regions corresponding to the bright region and the dark region of the illumination light is received after being reflected by the surface to be measured, and the light intensity distribution of the reflected light on the surface to be measured is detected.

[0158] Regarding the light detection step, it can be made the same as the content described in the section of the light detection unit in the above-described surface property measuring apparatus.

[0159] 3. First processing step In the first processing step in the present disclosure, in the light intensity distribution of the reflected light on the surface to be measured, for each bright region, using a predetermined light intensity threshold, a plurality of selection points located on the line connecting the measurement points of the light intensity of the reflected light are determined, and the positions on the surface to be measured indicating the selection points are specified.

[0160] Regarding the first processing step, it can be made the same as the content described in the section of the first processing unit in the above-described surface property measuring apparatus.

[0161] 4. Second processing step In the second processing step in the present disclosure, for each bright region, a graph is created by plotting the positions on the surface to be measured indicating the selection points with the first direction on the surface to be measured as the horizontal axis and the second direction orthogonal to the first direction on the surface to be measured as the vertical axis.

[0162] Regarding the second processing step, it can be made the same as the content described in the section of the second processing unit in the above-described surface property measuring apparatus.

[0163] 5. Third processing step In the third processing step in the present disclosure, for each bright region, a reference line based on the shape of the bright region of the illumination light is obtained.

[0164] The third processing step can be made the same as the content described in the section of the third processing unit in the above-described surface property measuring apparatus.

[0165] 6. Fourth Processing Step In the fourth processing step in the present disclosure, for each bright region, the difference between the points plotted on the graph and the reference line is obtained, and for each bright region, the variation of the difference is quantified.

[0166] The fourth processing step can be made the same as the content described in the section of the fourth processing unit in the above-described surface property measuring apparatus.

[0167] 7. Fifth Processing Step The surface property measurement method of the present disclosure may have, for example, as shown in FIG. 16, a fifth processing step S17 of obtaining the maximum value of the light intensity of the bright region and the minimum value of the light intensity of the dark region in the light intensity distribution of the reflected light on the surface to be measured, and calculating the image sharpness by the following formula (1). DOI=(M - m) / (M + m)×100 (1) (In the above formula, DOI represents the image sharpness, M represents the maximum value of the light intensity of the bright region, and m represents the minimum value of the light intensity of the dark region.)

[0168] The fifth processing step can be made the same as the content described in the section of the fifth processing unit in the above-described surface property measuring apparatus.

[0169] 8. Use The use of the surface property measurement method of the present disclosure is the same as that of the above-described surface property measuring apparatus.

[0170] Note that the present disclosure is not limited to the above-described embodiment. The above-described embodiment is an example, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits the same operational effects is included in the technical scope of the present disclosure.

Example

[0171] Hereinafter, the present disclosure will be specifically described with reference to Examples and Comparative Examples.

[0172] [Production Example 1] As the glass substrate, Gorilla Glass 3 manufactured by Corning was used. A black PET film was placed on the back surface of the glass substrate. This was designated as Sample 1. The surface to be measured of Sample 1 was the surface of the glass substrate.

[0173] [Production Example 2] As the glass substrate, Gorilla Glass 3 manufactured by Corning was used. On one surface of the glass substrate, a TAC film (Fuji TAC TG60UL manufactured by Fujifilm) was placed via an optically clear adhesive sheet (OCA, NCF-D692 manufactured by Lintec, thickness 5 μm). Also, a black PET film was placed on the other surface of the glass substrate. This was designated as Sample 2. The surface to be measured of Sample 2 was the surface of the TAC film.

[0174] [Production Example 3] As the glass substrate, Gorilla Glass 3 manufactured by Corning was used. On one surface of the glass substrate, an optically clear adhesive sheet (OCA, NCF-D692 manufactured by Lintec, thickness 5 μm) was placed. Also, a black PET film was placed on the other surface of the glass substrate. This was designated as Sample 3. The surface to be measured of Sample 3 was the surface of the optically clear adhesive sheet.

[0175] [Production Example 4] The foldable smartphone Galaxy Z Fold2 manufactured by Samsung Electronics was designated as Sample 4.

[0176] [Example] (1) Configuration of the surface property measuring device The OLED light source used was the EELM-SKY-300-W manufactured by Ecolight Co., Ltd. The mask used was a mask having a metal plate and rectangular and cross-shaped openings penetrating the metal plate. The mask had a transmission region consisting of four rectangular openings and a transmission region consisting of three cross-shaped openings. The rectangular transmission region had a length of 70 mm, a line width of 0.5 mm, and a pitch of 1.0 mm. The mask was directly attached to the OLED light source.

[0177] The camera used was the digital single-lens reflex camera D5600 manufactured by Nikon Corporation. The lens used was the AF-P DX NIKKOR 18-55mm f / 3.5-5.6G VR manufactured by Nikon Corporation. The camera settings were an aperture value of f / 22, an exposure time of 1 / 8 second, ISO-100, and a focal length of 55 mm.

[0178] The distance between the light source and the surface to be measured was 33 cm, and the incident angle of the illumination light irradiated from the illumination unit was 60°. Also, the distance between the camera and the surface to be measured was 33 cm, and the light receiving angle of the reflected light of the imaging device was 60°.

[0179] (2) Illumination and light detection By focusing on the cross part of the reflected image of the surface to be measured with the camera by autofocus, the focus was set on the light source. The surface to be measured was irradiated with light from the light source through the mask, and an image of the reflected light on the surface to be measured was taken with the camera.

[0180] (3) Processing For the image taken with the camera, a moving average was taken with 50 pixels vertically and horizontally, binarized with the maximum value / 1.3 as the threshold value to remove noise. For the cells at the left end of each row, a linear approximation was performed by the least squares method, and the image was rotated so that the slope of the approximate straight line became 0. From this, the angle of the image was adjusted.

[0181] Also, 1100 pixels were cut out in the longitudinal direction of the linear bright region and 500 pixels were cut out in the short transverse direction from the center of the image captured by the camera. With the longitudinal direction of the linear bright region as the column direction and the short transverse direction of the linear bright region as the row direction, the light intensity was obtained for each pixel. In the light intensity distribution of each column, for each linear bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution, the light intensity value of 50% of the peak value (maximum value) of the light intensity of the bright region was set as the light intensity threshold. Also, in the light intensity distribution of each column, for each linear bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution, the measurement point that was equal to or exceeded the light intensity threshold and was closest to the light intensity threshold was selected as the selection point. The position of the pixel indicating the selection point was specified. For each linear bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution, a graph was created in which the position of the pixel indicating the selection point was plotted with the position of the pixel in the longitudinal direction of the linear bright region on the horizontal axis and the position of the pixel in the short transverse direction of the linear bright region on the vertical axis. The points plotted on the graph were linearly approximated by the least squares method, and the linear approximation formula was used as the reference line. For each linear bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution, the difference between the points plotted on the graph and the reference line was obtained. Then, for each linear bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution, the standard deviation of the above difference was calculated. Next, the arithmetic mean value of the standard deviations of the above differences for each linear bright region and for each of the left-side light intensity distribution and the right-side light intensity distribution was calculated. This arithmetic mean value was regarded as the distortion of the reflected image of the surface to be measured.

[0182] The results of Samples 1 to 4 are shown in Table 1.

[0183] [Comparative Example] (1) Configuration of the surface property measuring device The configuration of the surface property measuring device was the same as that in Example 1.

[0184] (2) Illumination and light detection Illumination and light detection were performed in the same manner as in Example 1.

[0185] (3) Processing From the center of the image captured by the camera, 1100 pixels were cut out in the longitudinal direction of the linear bright region corresponding to the longitudinal direction of the bright region of the illumination light, and 500 pixels were cut out in the lateral direction of the linear bright region. Taking the longitudinal direction of the linear bright region as the column direction and the lateral direction of the linear bright region as the row direction, the light intensity was obtained for each pixel. For each column, the pitch of the bright region was obtained. At this time, the peak value of the light intensity of the bright region was obtained, and the distance between the peak values of the light intensity of adjacent bright regions was defined as the pitch of the bright region. For each column, the standard deviation δ of three-point data was obtained. Then, the arithmetic mean value of the standard deviation δ of the pitch of each column was calculated.

[0186] Note that the comparative example mimics the method using the flatness measuring device described in Patent Document 1.

[0187] [Reference Example] Instead of the camera, the reflected light on the surface to be measured was visually observed and evaluated according to the following criteria. A: No distortion of the reflected image B: Moderate distortion of the reflected image C: Large distortion of the reflected image

[0188]

Table 1

[0189] In the comparative example, the evaluation of Sample 3 was the same as that of Sample 1, and the distortion of the reflected image could not be sufficiently numerically evaluated. On the other hand, in the example, as in the reference example, the evaluations of Samples 2 to 4 were all different from that of Sample 1, and the distortion of the reflected image could be numerically evaluated. There is a long-period distortion in Sample 3. From this result, it was confirmed that the method of the present disclosure can also numerically evaluate long-period distortion.

Explanation of Reference Signs

[0190] 1... Surface to be measured 2... Illumination unit 3... Light source 4... Mask 5... Light detection unit 6... First processing unit 7... Second processing unit 8 … Third processing unit 9 … Fourth processing unit 10 … Surface property measurement device

Claims

1. An irradiation unit having a light source and irradiating the measurement surface with illumination light having one or more bright regions and dark regions; A light detection unit that focuses on the light source through the measurement surface, receives reflected light that is reflected by the measurement surface and has one or more bright regions and dark regions corresponding to the bright regions and dark regions of the illumination light, and detects the light intensity distribution of the reflected light on the measurement surface; In the light intensity distribution of the reflected light on the measurement surface, for each bright region, using a predetermined light intensity threshold, a plurality of selection points located on a line connecting the measurement points of the light intensity of the reflected light are determined, and a first processing unit that specifies the positions on the measurement surface indicating the selection points; A second processing unit that creates a graph plotting the positions on the measurement surface indicating the selection points with the first direction on the measurement surface as the horizontal axis and the second direction perpendicular to the first direction on the measurement surface as the vertical axis for each bright region; A third processing unit that obtains a reference line based on the shape of the bright region of the illumination light for each bright region; A fourth processing unit that obtains the difference between the points plotted on the graph and the reference line for each bright region, and quantifies the variation of the difference for each bright region; A surface property measurement apparatus comprising the above.

2. The surface property measurement apparatus according to claim 1, wherein the light detection unit is an imaging device.

3. The surface property measurement apparatus according to claim 1 or claim 2, wherein the illumination light has a linear bright region as the bright region, and the reflected light has a linear bright region corresponding to the linear bright region of the illumination light as the bright region.

4. In the light detection unit, the measurement surface is divided into M×N measurement regions, N in the longitudinal direction of the linear bright region of the reflected light and M in the lateral direction of the linear bright region of the reflected light, the light intensity of the reflected light is detected for each measurement region, and the light intensity distribution of the reflected light on the measurement surface is detected. In the first processing unit, the light intensity distribution of the reflected light on the measurement surface is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light in each divided region, for each linear bright region, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each of the linear bright regions, a measurement point that is equal to or greater than the light intensity threshold or exceeds the light intensity threshold and indicates the light intensity closest to the light intensity threshold is selected. Alternatively, for each of the left-side light intensity distribution and the right-side light intensity distribution of each of the linear bright regions, a measurement point that is equal to or greater than the light intensity threshold or exceeds the light intensity threshold and indicates the light intensity closest to the light intensity threshold is selected. The surface property measurement apparatus according to claim 3, wherein the measurement point is the selected point.

5. In the light detection unit, the surface to be measured is divided into M×N measurement regions, where there are N in the longitudinal direction of the linear bright region of the reflected light and M in the lateral direction of the linear bright region of the reflected light. The light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the surface to be measured. In the first processing unit, the light intensity distribution of the reflected light on the surface to be measured is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light in each divided region, for each linear bright region, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each of the linear bright regions, a measurement point that indicates the light intensity closest to the light intensity threshold is selected. Alternatively, for each of the left-side light intensity distribution and the right-side light intensity distribution of each of the linear bright regions, a measurement point that indicates the light intensity closest to the light intensity threshold is selected. The surface property measurement apparatus according to claim 3, wherein the measurement point is the selected point.

6. In the light detection unit, the surface to be measured is divided into M×N measurement regions, where there are N in the longitudinal direction of the linear bright region of the reflected light and M in the lateral direction of the linear bright region of the reflected light. The light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the surface to be measured. In the first processing unit, the light intensity distribution of the reflected light on the surface to be measured is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light in each of the divided regions, for each of the linear bright regions, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each of the linear bright regions, a measurement point that is equal to or less than the light intensity threshold or less than the light intensity threshold and shows the light intensity closest to the light intensity threshold, and a measurement point that is equal to or greater than the light intensity threshold or exceeds the light intensity threshold and shows the light intensity closest to the light intensity threshold are connected, and a point indicating the light intensity threshold is selected on the line connecting them. Alternatively, for each of the left-side light intensity distribution and the right-side light intensity distribution of each of the linear bright regions, a measurement point that is equal to or less than the light intensity threshold or less than the light intensity threshold and shows the light intensity closest to the light intensity threshold, and a measurement point that is equal to or greater than the light intensity threshold or exceeds the light intensity threshold and shows the light intensity closest to the light intensity threshold are connected, and a point indicating the light intensity threshold is selected. The surface property measuring device according to claim 3, wherein the point indicating the light intensity threshold is the selected point.

7. The surface property measuring device according to any one of claims 1 to 6, wherein the third processing unit obtains an approximation formula from the points plotted on the graph and uses the approximation formula as the reference line.

8. The surface property measuring device according to any one of claims 1 to 7, wherein the fourth processing unit calculates the standard deviation of the difference between the points plotted on the graph and the reference line.

9. The surface property measuring device according to any one of claims 1 to 8, further comprising a fifth processing unit that obtains the maximum value of the light intensity of the bright region and the minimum value of the light intensity of the dark region in the light intensity distribution of the reflected light on the surface to be measured, and calculates the image sharpness according to the following formula (1). DOI = (M - m) / (M + m) × 100 (1) (In the above formula, DOI represents the image sharpness, M represents the maximum value of the light intensity of the bright region, and m represents the minimum value of the light intensity of the dark region.)

10. An irradiation step of irradiating the surface to be measured with illumination light having one or more bright regions and dark regions using a light source. Focus on the light source through the surface to be measured, receive the reflected light that is reflected by the surface to be measured and has one or more bright regions and dark regions corresponding to the bright region and the dark region of the illumination light, and detect the light intensity distribution of the reflected light on the surface to be measured, which is a light detection step; In the light intensity distribution of the reflected light on the surface to be measured, for each bright region, using a predetermined light intensity threshold, determine a plurality of selection points located on the line connecting the measurement points of the light intensity of the reflected light, and a first processing step of specifying the positions on the surface to be measured indicating the selection points; For each bright region, taking the first direction on the surface to be measured as the horizontal axis and the second direction perpendicular to the first direction on the surface to be measured as the vertical axis, a second processing step of creating a graph plotting the positions on the surface to be measured indicating the selection points; For each bright region, a third processing step of obtaining a reference line based on the shape of the bright region of the illumination light; For each bright region, obtain the difference between the points plotted on the graph and the reference line, and for each bright region, a fourth processing step of quantifying the variation of the difference; A surface property measurement method comprising the above steps.

11. The surface property measurement method according to claim 10, wherein in the light detection step, an imaging device is used.

12. The surface property measurement method according to claim 10 or claim 11, wherein the illumination light has a linear bright region as the bright region, and the reflected light has a linear bright region corresponding to the linear bright region of the illumination light as the bright region.

13. In the light detection step, the surface to be measured is divided into M×N measurement regions, with N in the longitudinal direction of the linear bright region of the reflected light and M in the transverse direction of the linear bright region of the reflected light, and the light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the surface to be measured. In the first processing step, the light intensity distribution of the reflected light on the surface to be measured is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light in each divided region, for each linear bright region, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each of the linear bright regions, a measurement point that is equal to or greater than the light intensity threshold or exceeds the light intensity threshold and indicates the light intensity closest to the light intensity threshold is selected, or for each of the left-side light intensity distribution and the right-side light intensity distribution of each of the linear bright regions, a measurement point that is equal to or greater than the light intensity threshold or exceeds the light intensity threshold and indicates the light intensity closest to the light intensity threshold is selected. The surface property measurement method according to claim 12, wherein the measurement point is the selected point.

14. In the light detection step, the surface to be measured is divided into M×N measurement regions, where there are N in the longitudinal direction of the linear bright region of the reflected light and M in the transverse direction of the linear bright region of the reflected light. The light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the surface to be measured. In the first processing step, the light intensity distribution of the reflected light on the surface to be measured is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light in each divided region, for each linear bright region, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each of the linear bright regions, a measurement point that indicates the light intensity closest to the light intensity threshold is selected, or for each of the left-side light intensity distribution and the right-side light intensity distribution of each of the linear bright regions, a measurement point that indicates the light intensity closest to the light intensity threshold is selected. The surface property measurement method according to claim 12, wherein the measurement point is the selected point.

15. In the light detection step, the surface to be measured is divided into M×N measurement regions, where there are N in the longitudinal direction of the linear bright region of the reflected light and M in the transverse direction of the linear bright region of the reflected light. The light intensity of the reflected light is detected for each measurement region to detect the light intensity distribution of the reflected light on the surface to be measured. In the first processing step, the light intensity distribution of the reflected light on the surface to be measured is divided into n divided regions in the longitudinal direction of the linear bright region of the reflected light, and the light intensity distribution of the reflected light for each divided region is extracted. In the light intensity distribution of the reflected light in each of the divided regions, for each of the linear bright regions, the light intensity distribution of the linear bright region is divided into a left-side light intensity distribution and a right-side light intensity distribution with the peak value of the light intensity of each linear bright region as the boundary. In either the left-side light intensity distribution or the right-side light intensity distribution of each of the linear bright regions, a measurement point that has a light intensity equal to or less than the light intensity threshold or less than the light intensity threshold and shows the light intensity closest to the light intensity threshold, and a measurement point that has a light intensity equal to or greater than the light intensity threshold or greater than the light intensity threshold and shows the light intensity closest to the light intensity threshold are connected by a line, and a point indicating the light intensity threshold is selected. Alternatively, for each of the left-side light intensity distribution and the right-side light intensity distribution of each of the linear bright regions, a measurement point that has a light intensity equal to or less than the light intensity threshold or less than the light intensity threshold and shows the light intensity closest to the light intensity threshold, and a measurement point that has a light intensity equal to or greater than the light intensity threshold or greater than the light intensity threshold and shows the light intensity closest to the light intensity threshold are connected by a line, and a point indicating the light intensity threshold is selected. The surface property measurement method according to claim 12, wherein the point indicating the light intensity threshold is the selected point.

16. In the third processing step, an approximation formula is obtained from the points plotted on the graph, and the surface property measurement method according to any one of claims 10 to 15, wherein the approximation formula is used as the reference line.

17. In the fourth processing step, the standard deviation of the difference between the points plotted on the graph and the reference line is calculated, and the surface property measurement method according to any one of claims 10 to 16.

18. In the light intensity distribution of the reflected light on the surface to be measured, a fifth processing step of obtaining the maximum value of the light intensity of the bright region and the minimum value of the light intensity of the dark region, and calculating the image sharpness by the following formula (1) is provided, and the surface property measurement method according to any one of claims 10 to 17. DOI = (M - m) / (M + m) × 100 (1) (In the above formula, DOI represents image sharpness, M represents the maximum value of the light intensity of the bright region, and m represents the minimum value of the light intensity of the dark region.)

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