JP2024065001A - Surface state inspection method and surface state inspection device - Google Patents

Abstract

To provide a surface state inspection method and a surface state inspection device that make it easy to inspect the surface state of an inspection object with higher accuracy.SOLUTION: A surface state inspection method includes an irradiation step in which the surface of an inspection object is irradiated with illumination light L1 that is emitted from an illumination unit. The surface state inspection method inspects a surface state on the basis of the surface irradiated with illumination light L1. The illumination light L1 includes a gradation line part GL, of which the absolute value of a differential value in the light intensity data curve acquired by procedures 1 and 2 is within the range of 1.5/mm or smaller. In the procedure 1, the captured-image data of the sample to be inspected, which is irradiated with illumination light L1, is acquired. In the procedure 2, a light intensity data curve is acquired from the captured-image data, in which a relationship between at least one position on a linear line and light intensity is corrected so that maximum light intensity is 1.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method and device for inspecting a surface condition.

As described in Patent Document 1, a method for inspecting a transparent plate is known in which a stripe pattern of illumination light is irradiated onto the transparent plate and the shape of the transparent plate is evaluated from the reflected image. Also, as described in Patent Document 2, a device is known that uses multiple types of stripe patterns to measure the surface distortion of the measurement target surface.

JP 2005-345383 A JP 2007-147587 A

As described above, in conventional inspections of the surface condition of an object using stripe patterns, it is possible to detect a defect in the object if it exists at a position that straddles the light/dark boundary of the stripe pattern. However, if the object has a relatively fine defect, there is a risk that the defect cannot be detected because it overlaps with the stripe pattern. As such, there is still room for improvement in terms of inspecting the surface condition of an object with higher accuracy, such as detecting relatively fine defects that exist in the object.

The object of the present invention is to provide a surface condition inspection method and a surface condition inspection device that make it easier to inspect the surface condition of an object to be inspected with greater accuracy.

Various aspects of a surface condition inspection method and a surface condition inspection device that solve the above problems will be described.
The surface condition inspection method of aspect 1 includes an irradiation step of irradiating a surface of an inspection object with illumination light emitted from an illumination unit, and inspects the surface condition based on the surface irradiated with the illumination light, wherein the illumination light includes a gradation line portion in which the absolute value of a differential value in the light intensity data curve acquired by the following steps 1 and 2 is within a range of 1.5/mm or less. In step 1, imaging data of the inspection object sample illuminated by the illumination light is acquired. In step 2, a light intensity data curve is acquired from the imaging data in which the relationship between the position on at least one straight line and the light intensity is corrected so that the maximum light intensity is 1. According to this method, by inspecting the surface condition of the inspection object using the above-mentioned gradation line portion, it is possible to improve the accuracy of detecting finer defects, for example.

In the surface condition inspection method of aspect 2, in aspect 1, the illumination unit may include a plurality of light sources arranged along a predetermined direction, and a light diffusing member disposed between the plurality of light sources and the inspection object. This method makes it possible to efficiently inspect the surface of the inspection object using illumination light over a wider range.

In the surface condition inspection method of aspect 3, in aspect 2, the spacing between the multiple light sources may be 10 mm or less. This method makes it easy to ensure the amount of light between adjacent light sources.

In the surface condition inspection method of aspect 4, in any one of aspects 1 to 3, the illuminance of the illumination light in the irradiation step may be in the range of 500 lux or more and 2000 lux or less. According to this method, it becomes possible to easily detect defects using an imaging device or by visual inspection, for example.

The surface condition inspection method of aspect 5 is any one of aspects 1 to 4, and in the irradiation step, the illumination unit and the inspection object may be moved relatively along the gradation line portion. This method makes it possible to easily inspect the surface of the inspection object over a wider range.

The surface condition inspection method of aspect 6 is any one of aspects 1 to 5, and in step 1, the illuminance at the position of the sample to be inspected, which is 50 cm away from the illumination unit, may be set within a range of 500 lux or more and 2000 lux or less in an environment where the illuminance when the illumination unit is turned off is 500 lux or less.

The surface condition inspection device of aspect 7 is a surface condition inspection device equipped with an illumination unit that irradiates illumination light onto the surface of an inspection target, and the illumination light includes a gradation line portion in which the absolute value of the differential value in the light intensity data curve obtained by the following steps 1 and 2 is within a range of 1.5/mm or less. In step 1, imaging data of the inspection target sample illuminated by the illumination light is obtained. In step 2, a light intensity data curve is obtained from the imaging data by correcting the relationship between the position on at least one straight line and the light intensity so that the maximum light intensity is 1.

The present invention has the effect of making it easier to inspect the surface condition of the object to be inspected with greater accuracy.

FIG. 1 is a schematic diagram showing a surface condition inspection device according to an embodiment. FIG. 2 is an explanatory diagram illustrating the gradation line portion of the illumination light. FIG. 3 is a graph showing the relationship between the position and the light intensity in the gradation line portion of the illumination light and in the conventional stripe pattern. FIG. 4 is a graph showing the relationship between the position of the illumination light in the gradation line portion and the conventional stripe pattern and the absolute value of the differential value of the light intensity. FIG. 5 is a schematic diagram showing an example of a method for inspecting the surface state. 6(a) and 6(c) are surface images of Test Examples 1 and 2, and FIGS. 6(b) and 6(d) are graphs showing the relationship between the position of the surface images of Test Examples 1 and 2 and the light intensity. 7(a) and 7(c) are surface images of Test Examples 3 and 4, and FIGS. 7(b) and 7(d) are graphs showing the relationship between the position of the surface images of Test Examples 3 and 4 and the light intensity. 8(a) and 8(c) are surface images of Test Examples 5 and 6, and FIGS. 8(b) and 8(d) are graphs showing the relationship between the position of the surface images of Test Examples 5 and 6 and the light intensity. 9(a) and 9(c) are surface images of Test Examples 7 and 8, and FIGS. 9(b) and 9(d) are graphs showing the relationship between the position of the surface images of Test Examples 7 and 8 and the light intensity. FIG. 10 is a schematic diagram showing a surface condition inspection device in a modified example. FIG. 11 is a perspective view showing a lens member. FIG. 12 is a schematic diagram showing illumination light emitted from an illumination unit.

Below, an embodiment of a surface condition inspection method and a surface condition inspection device will be described with reference to the drawings. Note that in the drawings, for the sake of convenience, some of the components may be shown exaggerated or simplified. Furthermore, the dimensional ratios of each part may differ from the actual ones.

<Surface condition inspection device>
1, the surface condition inspection device 11 includes an illumination unit 12, an imaging device 13, and a computer 14. The illumination unit 12 irradiates illumination light L1 onto the surface Wa of the inspection object W. The imaging device 13 images the surface Wa of the inspection object W irradiated with the illumination light L1. The surface condition inspection device 11 includes a support table (not shown). The inspection object W is placed at a predetermined position on the support table.

(Illumination unit 12)
2, the illumination light L1 emitted from the illumination unit 12 in the surface condition inspection device 11 includes a gradation line portion GL. The gradation line portion GL can be defined based on a light intensity data curve. The light intensity data curve can be obtained by the following steps 1 and 2.

(Step 1) Acquire imaging data of a sample of an inspection object W illuminated with illumination light L1.
(Step 2) From the imaging data obtained in step 1, a light intensity data curve is obtained by correcting the relationship between the position on at least one line and the light intensity so that the maximum light intensity is 1.

In more detail, in the above step 1, first, a sample of the inspection object W is prepared. The surface condition of this sample of the inspection object W is recognized as normal. The conditions of the illuminance of the illumination light L1 in step 1 are not particularly limited, since the maximum light intensity is corrected to 1 in step 2. In step 1, for example, in an environment where the illuminance when the illumination unit 12 is turned off is 500 lux or less, it is preferable to set the illuminance at the position of the sample of the inspection object W, which is 50 cm away from the illumination unit 12, to a range of 500 lux or more and 2000 lux or less.

In FIG. 3, the light intensity data curve of the gradation line portion GL is shown by a solid line. Also, in FIG. 3, the light intensity data curve along the line width direction of the conventional stripe pattern is shown by a dashed line.

In Figure 4, the absolute values of the differential values in the light intensity data curve of the gradation line portion GL are plotted as black circles. Also in Figure 4, the absolute values of the differential values in the light intensity data curve of the conventional stripe pattern are plotted as white squares.

In the gradation line portion GL, the absolute value of the differential value in the light intensity data curve is within a range of 1.5/mm or less. The absolute value of the differential value in this light intensity data curve is more preferably within a range of 1.3/mm or less, and even more preferably within a range of 1.2/mm or less. Note that the differential value can be, for example, the amount of change in light intensity in a very small range of 1/3 of D, where D [mm] is the external dimension of the defect to be detected in the surface condition inspection.

In the gradation line portion GL, the absolute value of the differential value in the light intensity data curve is preferably 0.3/mm or more, and more preferably 0.4/mm or more. In this case, it is possible to further improve the inspection accuracy of the surface condition of the inspection object W.

Here, if the outer dimension of the defect to be detected in the surface condition inspection is D [mm], the gradation line portion GL can be set, for example, as follows. In the light intensity data curve shown in FIG. 3, the distance when the lower limit of the light intensity is 0.1 and the upper limit of the light intensity is 0.9 is ΔX [mm]. It is preferable that this ΔX satisfies the relationship "3D≦ΔX≦5D". Here, D [mm], which is the outer dimension of the defect, is, for example, in the range of 0.1 to 0.5. In this case, the above ΔX [mm] is in the range of 0.3 to 2.5.

The length dimension of the gradation line portion GL (the dimension along the Y direction shown in Figures 2 and 5) can be defined as the length dimension D1 at which the light intensity is 0.1 or more in the light intensity data curve, as shown in Figure 3.

The length dimension D1 of the gradation line portion GL is preferably 3 mm or more, and more preferably 5 mm or more. In this case, it is possible to set the absolute value of the differential value in the light intensity data curve to a smaller value. The upper limit of the length dimension D1 of the gradation line portion GL is not particularly limited, but is preferably, for example, 20 mm or less, and more preferably 15 mm or less.

The gradation line portion GL forms a predetermined range along the width direction (the direction along the Y direction shown in Figures 2 and 5) perpendicular to the length direction of the gradation line portion GL. That is, as shown in Figure 2, the illumination light L1 has an effective range R that satisfies the conditions of the gradation line portion GL on any parallel straight line. In the width direction, the effective range R that satisfies the conditions of the gradation line portion GL is preferably 5 mm or more, and more preferably 10 mm or more.

As shown in FIG. 1, the illumination unit 12 includes a light source 12a and a light diffusing member 12b arranged between the light source 12a and the inspection object W. Examples of the light source 12a include a point light source, a surface light source, and a line light source. The light source 12a is preferably an LED light source. The number of light sources 12a may be one or more. The illumination unit 12 preferably includes a plurality of light sources 12a arranged along a predetermined direction (the Y direction shown in FIG. 2 and FIG. 5). The spacing between the plurality of light sources 12a is preferably 10 mm or less.

The light diffusion member 12b diffuses the light emitted from the light source 12a. For example, the light diffusion member 12b may be a light diffusion sheet. The light diffusion sheet contains, for example, a light-transmitting resin and light-diffusing particles. The light diffusion member 12b may also be a cover member formed by applying a surface treatment such as painting or uneven processing to a light-transmitting base material.

(Imaging device 13 and computer 14)
The imaging device 13 in the surface condition inspection device 11 may be, for example, a camera equipped with an imaging element such as a CCD or a CMOS. The computer 14 includes a computer main body 14a and a display 14b. The computer main body 14a includes, for example, an image processing unit, an information storage unit, and a judgment unit. In the image processing unit, for example, image processing such as binarization processing and brightness correction processing can be performed as necessary on the image of the inspection object W captured by the imaging device 13. The information storage unit can store data of normal inspection object W (for example, light intensity data curve) and threshold values such as brightness values in advance. The judgment unit judges the presence or absence of a defect in the inspection object W based on, for example, the data stored in the information storage unit. The judgment unit can also be configured to judge the presence or absence of a defect in the inspection object W using a learning model constructed by learning through deep learning. The learning model may be, for example, an artificial intelligence (AI) model such as a neural network model. The computer main body 14a may be configured by a processor, memory, software, etc., which are not shown.

<Surface condition inspection method>
The surface condition inspection method includes an irradiation step of irradiating the surface Wa of the inspection object W with illumination light L1 emitted from the illumination unit 12. The surface condition inspection method inspects the surface condition based on the surface Wa of the inspection object W irradiated with the illumination light L1.

Examples of the substrate of the inspection object W include glass, ceramics, resin, and metal. The surface Wa of the inspection object W may be a flat surface or a curved surface. The surface Wa of the inspection object W may be formed by a substrate, or may be formed by a functional film laminated on the substrate.

The illuminance of the illumination light L1 in the irradiation process is preferably within a range of, for example, 500 lux or more and 2000 lux or less. This illuminance is the illuminance measured at the position of the inspection object W. For example, when the surface Wa of the inspection object W is placed at a position 50 cm away from the illumination unit 12, this refers to the illuminance at a position 50 cm away from the illumination unit 12.

As shown in FIG. 5, in the irradiation process of this embodiment, the illumination unit 12 and the inspection object W are moved relative to each other along the gradation line portion GL. For example, as shown by the white arrow in FIG. 5, the illumination unit 12 is moved along the surface Wa of the inspection object W. This makes it possible to detect defects over a wider range on the surface Wa of the inspection object W. For example, if defects exist in the range DA surrounded by the dashed line on the surface Wa of the inspection object W in FIG. 5, these defects can be easily detected by moving the illumination unit 12 along the surface Wa of the inspection object W. In the irradiation process, the inspection object W may be moved along the gradation line portion GL, or both the illumination unit 12 and the inspection object W may be moved along the gradation line portion GL. In addition, when the illumination unit 12 is moved, it is preferable to keep the relative position between the illumination unit 12 and the imaging device 13 constant.

In the surface condition inspection method of this embodiment, the surface Wa of the inspection object W irradiated with the illumination light L1 is imaged using the imaging device 13. In the surface condition inspection method, the surface condition of the inspection object W is inspected based on the image acquired by the imaging device 13. The surface condition inspection method includes a determination step of determining the presence or absence of defects on the surface Wa of the inspection object W based on the image acquired by the imaging device 13. This determination step can be executed by the computer main body 14a. Examples of defects on the surface Wa include localized distortion such as unevenness on the surface Wa, adhesion of foreign matter, and scratches on the surface Wa.

The surface condition inspection method may be an inspection to visually check defects on the surface Wa of the inspection object W irradiated with the illumination light L1 in the irradiation process, without using the imaging device 13 and the computer 14.

<Test Example>
Next, a test example will be described.
6 and 7 show test examples 1 to 4 in which the surface condition of the inspection object W was inspected using illumination light L1 including a gradation line portion GL. The inspection object W is a glass plate. In test example 1 shown in FIG. 6(a), the illumination light L1 is not irradiated onto the range DA in which the defect exists. As shown in FIG. 6(b), the light intensity data curve obtained from the result of the surface image analysis of test example 1 is a curve based on the gradation line portion GL.

In test example 2 shown in FIG. 6(c), at least a portion of the gradation line portion GL of the illumination light L1 is irradiated onto the range DA where the defect exists. As shown in FIG. 6(d), the light intensity data curve obtained from the results of the surface image analysis of test example 2 differs from the light intensity data curve of test example 1 shown in FIG. 6(b). This shows that in test example 2, defects on the surface Wa of the inspection object W can be detected.

In test example 3 shown in FIG. 7(a) and test example 4 shown in FIG. 7(c), at least a portion of the gradation line portion GL of the illumination light L1 is irradiated onto the range DA where the defect exists. As shown in FIG. 7(b) and FIG. 7(d), the light intensity data curves obtained from the results of the surface image analysis of test examples 3 and 4 differ from the light intensity data curve of test example 1 shown in FIG. 6(b). This shows that in test examples 3 and 4, defects on the surface Wa of the inspection object W can be detected.

Figures 8 and 9 show test examples 5 to 8 in which the surface condition of the inspection object W was inspected using illumination light with a conventional stripe pattern. The inspection object W is the same plate glass as in test examples 1 to 4 above. In test example 5 shown in Figure 8 (a), illumination light is not irradiated onto the area DA where the defect exists. As shown in Figure 8 (b), the light intensity data curve obtained from the results of image analysis of test example 5 is a curve based on the light and dark areas of the stripe pattern.

In Test Example 6 shown in FIG. 8(c) and Test Example 7 shown in FIG. 9(a), the range DA in which the defect of the inspection object exists is located across the light/dark boundary of the stripe pattern. As shown in FIG. 8(d) and FIG. 9(b), the light intensity data curve obtained from the results of the surface image analysis of Test Examples 6 and 7 is different from the light intensity data curve of Test Example 5 shown in FIG. 8(b). This shows that in Test Examples 6 and 7, defects on the surface Wa of the inspection object W can be detected.

In test example 8 shown in FIG. 9(c), the range DA in which the defect exists is located in the bright part of the stripe pattern. As shown in FIG. 9(d), the light intensity data curve obtained from the results of the surface image analysis of test example 8 does not have a clear difference from the light intensity data curve obtained from the results of the image analysis of test example 5, so the defect cannot be detected.

<Actions and Effects of the Present Embodiment>
Next, the operation and effects of this embodiment will be described.
(1) The method for inspecting the surface condition includes an irradiation step of irradiating the surface Wa of the inspection object W with illumination light L1 emitted from the illumination unit 12. The method for inspecting the surface condition inspects the surface condition based on the surface Wa irradiated with the illumination light L1. The illumination light L1 includes a gradation line portion GL. The absolute value of the differential value in the light intensity data curve of the gradation line portion GL is within a range of 1.5/mm or less. The light intensity data curve is acquired by the above-mentioned steps 1 and 2.

According to this method, by including an irradiation process in which the gradation line portion GL is irradiated onto the surface Wa of the inspection object W, it becomes easier to inspect the surface condition of the inspection object W with higher accuracy. In this embodiment, it is possible to improve the accuracy of detecting relatively fine defects present on the surface Wa of the inspection object W.

(2) In the surface condition inspection method, the illumination unit 12 preferably includes a plurality of light sources 12a arranged in a predetermined direction and a light diffusing member 12b disposed between the plurality of light sources 12a and the inspection object W. In this case, it becomes possible to efficiently inspect the surface Wa of the inspection object W using illumination light L1 over a wider range.

(3) The interval between the multiple light sources 12a of the illumination unit 12 is preferably 10 mm or less. In this case, it is easy to ensure the amount of light between adjacent light sources 12a.
(4) In the surface condition inspection method, the illuminance of the illumination light L1 in the irradiation step is preferably in the range of 500 lux or more and 2000 lux or less. In this case, for example, it becomes possible to easily detect defects using the imaging device 13 or visually detect defects.

(5) In the irradiation process, the illumination unit 12 and the inspection object W are moved relative to each other along the gradation line portion GL. In this case, it becomes possible to easily inspect a wider area of the surface Wa of the inspection object W.

<Example of change>
The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

- In the irradiation process in the above-mentioned surface condition inspection method, the illumination unit 12 and the inspection object W are moved relative to each other along the gradation line portion GL. However, for example, when inspecting only a portion of the surface Wa of the inspection object W or when the inspection object W is relatively small compared to the length dimension or effective range R of the gradation line portion GL, the irradiation process may be performed without moving the illumination unit 12 and the inspection object W relative to each other.

In the irradiation step of the above-described surface condition inspection method, the relative movement between the illumination unit 12 and the inspection object W may be performed automatically or manually.
In the irradiation step in the above-described method for inspecting the surface condition, a plurality of illumination units 12 may be used. This makes it possible to easily inspect a wider area of the surface Wa of the inspection object W.

The illumination light L1 emitted from the illumination unit 12 may be white light or colored light.
The surface condition inspection method may also be used for a product having fine irregularities on its surface Wa as the inspection object W. In other words, the surface condition inspection method may be applied to an inspection for checking the state of the fine irregularities on the surface Wa of the inspection object W.

-The illumination unit 12 of the surface condition inspection device 11 in the above embodiment can be modified, as in the surface condition inspection device 111 shown in FIG. 10. The illumination unit 112 in this modified example is provided with a light source 112a that emits light with a uniform light intensity in the length direction. Examples of the light source 112a include a line light source having an LED, a fluorescent lamp, and the like. The illumination unit 112 also includes a lens member 112b arranged between the light source 112a and the inspection object W. As shown in FIG. 10 and FIG. 11, the lens member 112b has a lens portion P having a convex surface. In more detail, the lens portion P is composed of, for example, a plano-convex lens having a flat surface arranged on the light source 112a side and a convex surface arranged on the inspection object W side. The number of lens portions P of the lens member 112b may be single or multiple. Examples of the lens member 112b include a microlens made of glass or resin. As shown in FIG. 10, in the surface condition inspection device 111, light incident on the lens member 112b from the light source 112a is focused by the lens member 112b. As a result, as shown in FIG. 12, the illumination light L1 including the gradation line portion GL similar to the above embodiment can be irradiated onto the surface of the inspection object.

REFERENCE SIGNS LIST 11, 111... Surface condition inspection device 12, 112... Illumination section 12a... Light source 12b... Light diffusion member GL... Gradation line section L1... Illumination light W... Inspection object Wa... Surface

Claims (7)

A method for inspecting a surface condition, comprising: an illumination step of irradiating an illumination light emitted from an illumination unit onto a surface of an inspection object; and inspecting a surface condition based on the surface irradiated with the illumination light,
The illumination light is generated by the following steps 1 and 2:
(Step 1) acquiring imaging data of the sample to be inspected illuminated by the illumination light; and (Step 2) acquiring a light intensity data curve from the imaging data, in which the relationship between the position on at least one straight line and the light intensity is corrected so that the maximum light intensity is 1. The absolute value of the differential value in the light intensity data curve acquired by the above steps is within a range of 1.5/mm or less. The surface condition inspection method according to claim 1, wherein the illumination unit includes a plurality of light sources arranged in a predetermined direction and a light diffusing member disposed between the plurality of light sources and the inspection object. The surface condition inspection method according to claim 2, wherein the spacing between the multiple light sources is 10 mm or less. The surface condition inspection method according to claim 1, wherein the illuminance of the illumination light in the irradiation step is in the range of 500 lux or more and 2000 lux or less. The surface condition inspection method according to claim 1, wherein in the irradiation step, the illumination unit and the inspection object are moved relative to each other along the gradation line portion. The surface condition inspection method according to claim 1, wherein in step 1, in an environment in which the illuminance of the illumination unit is 500 lux or less when the illumination unit is turned off, the illuminance at the position of the sample to be inspected, which is 50 cm away from the illumination unit, is set within a range of 500 lux or more and 2000 lux or less. A surface condition inspection device including an illumination unit that irradiates illumination light onto a surface of an inspection object,
The illumination light is generated by the following steps 1 and 2:
(Step 1) acquiring imaging data of the sample to be inspected illuminated by the illumination light; and (Step 2) acquiring a light intensity data curve from the imaging data, the relationship between the position on at least one straight line and the light intensity being corrected so that the maximum light intensity is 1. The absolute value of the differential value in the light intensity data curve acquired by the above-mentioned steps is within a range of 1.5/mm or less.

Images