JP5825278B2 - Defect inspection apparatus and defect inspection method - Google Patents

Description

  The present invention relates to an apparatus and method for inspecting an inner layer defect of an inspection object.

  A technique for detecting defects by performing image processing based on an image obtained by irradiating a sheet-like article with light and receiving transmitted light or reflected light with a camera is known. Here, when the object to be inspected is a polarizing film (optical film) used in a liquid crystal display, it is desired to determine whether a defect exists on the surface or an inner layer. This is because a polarizing film or the like is inspected in a state where a protective sheet is stuck on the surface and finally the protective sheet is peeled off.

  Japanese Patent Application Laid-Open No. H10-228707 describes that the surface layer and the inner layer are photographed while the focal positions are shifted, and the surface defect and the inner layer defect are distinguished based on the plurality of images. However, there is a problem that it is necessary to perform imaging a plurality of times at the surface layer position and the inner layer position, and it takes time for inspection. In addition, a mechanism for adjusting the focal point to each position is required, which increases the cost. In addition, since the focus position accuracy is important because the determination is based on the focus position, it is necessary to suppress the position fluctuation of the inspection object. Therefore, the stage for suppressing the position fluttering leads to an increase in cost, and the inspection object needs to be stationary to suppress the position fluttering, resulting in a long inspection tact.

  Patent Document 2 describes that a surface defect and an inner layer defect are distinguished based on an image captured by irradiating coaxial illumination and an image captured by diffusing illumination. However, since it is necessary to take an image twice by sliding the illumination system, there is a problem that the inspection takes time. In addition, a mechanism for sliding the illumination is required, which increases the cost. Furthermore, since a large member such as illumination is driven, maintenance of the drive unit is required.

JP 2005-98970 A JP 2001-108639 A

  The present invention has been made in view of the above-described problems, and an object thereof is to perform an inspection capable of discriminating between surface defects and inner layer defects at low cost and at high speed.

In order to solve the above problems, a defect inspection apparatus according to one aspect of the present invention is provided.
A defect inspection apparatus for inspecting defects in a sheet-like inspection object,
First irradiation means for irradiating the inspection object with first light;
Second irradiation means for irradiating the inspection object with second light;
Photographing means for photographing the reflected light of the first light to obtain photographing data relating to the reflected light , photographing the transmitted light of the second light and obtaining photographing data relating to the transmitted light ;
By dividing the value of the imaging data related to the reflected light acquired by the imaging means by the value when there is no defect, the reflected light luminance ratio is obtained, and the value of the imaging data related to the transmitted light acquired by the imaging means is calculated. Processing means for determining the transmitted light luminance ratio by dividing the value by the value when there is no defect;
Detection means for detecting a surface defect and an inner layer defect of the inspection object based on the reflected light luminance ratio and the transmitted light luminance ratio at the same position of the inspection object;
With
The imaging means, the first irradiation means, and the second irradiation means are arranged so that the imaging means images the diffuse reflection light of the first light and the indirect transmitted light of the second light. It is,
The detection means includes
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the transmitted light luminance ratio is larger than the reflected light luminance ratio, it is determined as an inner layer defect,
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the reflected light luminance ratio is equal to or greater than the transmitted light luminance ratio, it is determined that the surface defect is present .

  That is, the positional relationship between the second irradiating means and the photographing means is such that the regular transmitted light of the light emitted from the second irradiating means does not enter the photographing means and the indirect transmitted light enters the photographing means. It is preferable that Indirectly transmitted light refers to transmitted light that is reflected or scattered by a defect present in the inspection object and deviates from the normal transmission direction. By doing so, dark field imaging of defects can be realized and the dynamic range is improved. In this case, the indirectly transmitted light transmitted through the inner layer defect is detected more strongly than the indirectly transmitted light transmitted through the surface defect.

By adopting the configuration as described above, it is possible to determine an inner layer defect based on imaging data corresponding to the intensity of reflected light and imaging data corresponding to the intensity of indirect transmitted light. That is, it can be seen that there is some defect in the portion where reflected light or indirect transmitted light is strongly detected, and if the indirect transmitted light luminance ratio is larger than the reflected light luminance ratio for the same defect, the defect is an inner layer defect. Can be determined.

  As described above, when photographing indirectly transmitted light of the second light, it is preferable to shorten the wavelength of the second light. This is because, as the light has a shorter wavelength, the scattering effect at the defect becomes larger, and therefore, the intensity of transmitted light transmitted through the defect is improved. In addition, although the scattering effect becomes larger as the second light has a shorter wavelength, it is preferable to use blue light (in the vicinity of a wavelength of 450 nm) considering the availability of the light source and the light receiving element.

A defect inspection apparatus according to another aspect of the present invention includes:
A defect inspection apparatus for inspecting defects in a sheet-like inspection object,
First irradiation means for irradiating the inspection object with first light;
Second irradiation means for irradiating the inspection object with second light;
Photographing means for photographing the reflected light of the first light to obtain photographing data relating to the reflected light , photographing the transmitted light of the second light and obtaining photographing data relating to the transmitted light ;
By dividing the value of the imaging data related to the reflected light acquired by the imaging means by the value when there is no defect, the reflected light luminance ratio is obtained, and the value of the imaging data related to the transmitted light acquired by the imaging means is calculated. Processing means for determining the transmitted light luminance ratio by dividing the value by the value when there is no defect;
Detection means for detecting a surface defect and an inner layer defect of the inspection object based on the reflected light luminance ratio and the transmitted light luminance ratio at the same position of the inspection object;
With
The imaging means, the first irradiation means, and the second irradiation means are arranged so that the imaging means images the diffuse reflection light of the first light and the regular transmitted light of the second light. And
Between the inspection object and the second irradiating means, and, between the inspection object and the imaging means, polarization filter transmission axes are orthogonal to each other are provided, respectively,
The detection means includes
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the transmitted light luminance ratio is larger than the reflected light luminance ratio, it is determined as an inner layer defect,
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the reflected light luminance ratio is equal to or greater than the transmitted light luminance ratio, it is determined that the surface defect is present .

  Thus, it is also preferable that the positional relationship between the second irradiating unit and the photographing unit is a positional relationship such that the regular transmitted light of the light emitted from the second irradiating unit is incident on the photographing unit. That is, it can be configured such that the imaging means captures the transmitted light that travels straight without scattering or the like in the inspection object. In this case, polarizing filters whose transmission axes are orthogonal to each other are provided between the second irradiation unit and the inspection object and between the imaging unit and the inspection object, respectively. Light that has passed through the part with no defect in the object to be inspected is blocked by the polarizing filter, whereas light that has passed through the defective part is disturbed in polarization when passing through the defective part. Incident on the photographing means. Even with such a configuration, dark field imaging of a defect is possible. Further, the regular transmitted light that has passed through the inner layer defect is detected more strongly than the regular transmitted light that has passed through the surface defect.

By adopting the configuration as described above, it is possible to detect the inner layer defect based on the imaging data corresponding to the reflected light intensity from the first irradiation means and the imaging data corresponding to the intensity of the regular transmitted light. . In other words, it can be seen that there is some defect in the portion where reflected light or specular transmitted light is detected strongly, and if the normal transmitted light luminance ratio is larger than the reflected light luminance ratio for the same defect, the defect is an inner layer defect. Can be determined.

  The defects include foreign matters, holes, wrinkles, unevenness, scratches, and the like. The surface defect is a defect that exists in the vicinity of the surface of the inspection object, and is a defect that exists in the outermost layer when the inspection object has a multilayer structure. The inner layer defect is a defect existing inside the inspection object, and when the inspection object has a multilayer structure, it is a defect existing outside the outermost layer. However, the inspection object does not necessarily have a multilayer structure. When the object to be inspected does not have a multilayer structure, defects existing within a predetermined distance from the surface correspond to surface defects, and defects present inside the defects correspond to inner layer defects.

  In the present invention, the speed of inspection can be increased by employing a configuration in which the reflected light of the first light reflected by the inspection object and the transmitted light of the second light transmitted through the inspection object are simultaneously measured. In order to measure simultaneously, there are a method using two cameras as a photographing means and a method using one camera. In the case where measurement is performed simultaneously using two cameras, it is preferable that the irradiation position of the first light and the irradiation position of the second light are different places. In this case, in the defect device, it is necessary to provide an alignment means for aligning the imaging data relating to the reflected light and the imaging data relating to the transmitted light. In the case where the reflected light and the transmitted light are measured simultaneously using one camera, it is preferable that the color (wavelength) of the first light and the second light are made different to be photographed with a color camera. In any case, since there is no need to move the irradiation means or the like, high-speed inspection is possible, and the configuration of the apparatus is simplified, so that manufacturing costs and maintenance costs can be suppressed.

  When one camera is used as the photographing means, the first irradiating means irradiates light from one side of the inspection object, and the second irradiating means irradiates light from the other side of the inspection object. The photographing means photographs the reflected light of the first light and the transmitted light of the second light from the one side. On the other hand, when two cameras are employed as the photographing means, the first and second irradiating means irradiate light from the same side of the object to be inspected, and the first reflected light of the first light is photographed. The imaging means and the second imaging means for imaging the transmitted light (indirectly transmitted light or regular transmitted light) of the second light may be arranged on different sides of the object to be inspected. Of course, even when two cameras are employed, the first and second irradiation means may be arranged on different sides, and the first and second imaging means may be arranged on the same side.

  The irradiation position of the first light by the first irradiation means and the irradiation position of the second light by the second irradiation means may be the same or different.

  When the irradiation positions are different, two cameras that capture the respective irradiation positions may be used. In this case, an alignment unit that aligns the imaging data related to the reflected light of the first light and the imaging data related to the transmitted light of the second light is further provided, and based on the two imaging data after the alignment. Detect inner layer defects.

  On the other hand, when the irradiation position of 1st light and 2nd light is made the same, the color (wavelength) of each light is varied. For example, one of red light (near wavelength 650 nm), green light (near wavelength 550 nm), and blue light (near wavelength 450 nm) can be selected. Here, in the case of a configuration in which indirectly transmitted light from the second irradiation unit is photographed, it is preferable to employ blue light as described above in the second irradiation unit, so that red is used in the first irradiation unit. Light or green light may be employed. In addition, when the irradiation position of 1st light and 2nd light is made the same, an imaging | photography means can be made into one color camera provided with the several linear light receiving element which light-receives each light. Further, the photographing unit may be a single color camera having a spectroscopic element that splits incident light and a plurality of light receiving elements that respectively acquire the light intensity after the splitting. In addition, when a plurality of line-shaped light receiving elements are used, the imaging position is different, and thus alignment is necessary. It becomes unnecessary.

  The present invention can be understood as a defect inspection apparatus having at least a part of the above means. The present invention can also be understood as a defect inspection method including at least a part of the above processing or a program for realizing the method. Each of the above means and processes can be combined with each other as much as possible to constitute the present invention.

As one aspect of the present invention, a defect inspection method includes:
A defect inspection method for inspecting a sheet-like inspection object for defects,
An irradiation step of irradiating the inspection object with the first light and the second light;
An imaging step of imaging the reflected light of the first light to acquire imaging data relating to the reflected light , imaging the transmitted light of the second light, and acquiring imaging data relating to the transmitted light ;
By dividing the value of the imaging data relating to the reflected light acquired in the imaging step by the value when there is no defect, the reflected light luminance ratio is obtained, and the value of the imaging data relating to the transmitted light acquired in the imaging step is calculated. Determining the transmitted light luminance ratio by dividing the value by the value when there is no defect ;
A detection step of detecting surface defects and inner layer defects of the inspection object based on the reflected light luminance ratio and the transmitted light luminance ratio at the same position of the inspection object;
Including
In the photographing step, the diffuse reflected light of the first light is photographed and the indirectly transmitted light of the second light is photographed.
In the detecting step,
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the transmitted light luminance ratio is larger than the reflected light luminance ratio, it is determined as an inner layer defect,
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the reflected light luminance ratio is equal to or greater than the transmitted light luminance ratio, it is determined that the surface defect is present .

As one aspect of the present invention, a defect inspection method includes:
A defect inspection method for inspecting a sheet-like inspection object for defects,
An irradiation step of irradiating the inspection object with the first light and the second light;
An imaging step of imaging the reflected light of the first light to acquire imaging data relating to the reflected light , imaging the transmitted light of the second light, and acquiring imaging data relating to the transmitted light ;
By dividing the value of the imaging data relating to the reflected light acquired in the imaging step by the value when there is no defect, the reflected light luminance ratio is obtained, and the value of the imaging data relating to the transmitted light acquired in the imaging step is calculated. Determining the transmitted light luminance ratio by dividing the value by the value when there is no defect ;
A detection step of detecting surface defects and inner layer defects of the inspection object based on the reflected light luminance ratio and the transmitted light luminance ratio at the same position of the inspection object;
Including
In the imaging step, thereby capturing the diffused reflected light of the first light, photographing the regular transmission light of the second light,
The second light is irradiated on the object to be inspected with the second light through the first polarizing filter, and after passing through the object to be inspected, the transmission axis of the first polarizing filter is orthogonal to the first light. Taken through the second polarizing filter ,
In the detecting step,
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the transmitted light luminance ratio is larger than the reflected light luminance ratio, it is determined as an inner layer defect,
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the reflected light luminance ratio is equal to or greater than the transmitted light luminance ratio, it is determined that the surface defect is present .

  According to the present invention, a defect inspection in which surface defects and inner layer defects are distinguished can be performed at high speed and at low cost.

The figure which shows the whole outline | summary of a defect inspection system. The figure which shows the structure of the defect inspection apparatus which concerns on 1st Embodiment. The figure explaining the reflected light (a) and indirect transmitted light (b) in a surface defect and an inner layer defect in 1st Embodiment. The figure explaining the brightness | luminance ratio of the defect (a) which exists in a to-be-inspected object, and reflected light (b) at the time of image | photographing this to-be-inspected object, and indirect transmitted light (c). The flowchart which shows the flow of the defect inspection method which concerns on 1st Embodiment. The figure which shows the structure of the defect inspection apparatus which concerns on 2nd Embodiment. The figure explaining the transmitted light which permeate | transmits a surface defect and an inner layer defect in 2nd Embodiment. The figure which shows the structure of the defect inspection apparatus which concerns on 3rd Embodiment. The figure which shows the structure of the defect inspection apparatus which concerns on 4th Embodiment. The figure which shows the structure of the optical system of the defect inspection apparatus which concerns on the modification of 3rd and 4th embodiment. The figure explaining the method of the defect detection which concerns on 5th Embodiment. The figure which shows the structure of the optical system of the defect inspection apparatus which concerns on the modification of 1st and 2nd embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified.

  A schematic configuration of the entire defect inspection system according to the present invention is shown in FIG. The defect inspection system is a system that inspects the sheet-like inspection object S conveyed by the conveyance roller 400. The inspection object S is, for example, a polarizing film used for a liquid crystal display. In the inspection stage, the polarizing film has a multilayer structure in which a protective sheet is provided on a sheet-like polarizing element. The defect inspection system according to the present embodiment detects a defect existing in the inner layer (polarization element layer) of the inspection object S, thereby performing appropriate defect detection that suppresses over-observation (defect detection).

  In the defect inspection system according to the present embodiment, two light sources 101 and 102 for irradiating the inspection object S with light are provided. The light source 101 irradiates the inspection object S with light from the same side as the camera 200. The light source 102 irradiates the inspection object S with light from the side opposite to the camera 200. The camera 200 captures the reflected light of the light irradiated from the light source 101 on the surface of the inspection object and the transmitted light irradiated from the light source 102 and transmitted through the inspection object. Although only one camera 200 is shown in the figure, two cameras that respectively capture reflected light and transmitted light may be employed. Shooting data shot by the camera 200 is sent to the signal processing unit 300 to detect defects in the inspection object S. At this time, the signal processing unit 300 determines whether the detected defect exists in the inner layer or the surface of the inspection object S based on the intensity of the reflected light and transmitted light.

  Here, the outline of the defect inspection system has been briefly described, but individual embodiments will be described in detail below.

<First Embodiment>
FIG. 2 is a diagram illustrating a configuration of the defect inspection apparatus according to the first embodiment. The defect inspection apparatus includes light sources 101 and 102, cameras 201 and 202, and a signal processing unit 300.

  The light source 101 irradiates the inspection object S with light 101 a from the same side as the camera 201. The wavelength of the light 101a irradiated by the light source 101 is not particularly limited, and may be visible light, ultraviolet light, infrared light, or the like. The light 101a may not be a single wavelength light. In the present embodiment, for example, green light is used as the light 101a. The light source 101 is arranged so that the light 101a is irradiated obliquely with respect to the inspection object S. The camera 201 is a line sensor camera, and may be a color camera or a monochrome camera. The camera 201 is disposed in a direction orthogonal to the conveyance direction of the inspection object S, and is disposed so as to photograph the irradiation position of the light 101a from the vertical direction. The positional relationship between the light source 101 and the camera 201 is preferably such that the regular reflection light of the light 101a does not enter the camera 201 and the diffuse reflection light 101b enters. By doing in this way, the defect of the to-be-inspected object S can be imaged by dark field, and a defect can be imaged with high contrast. Note that the positional relationship between the light source 101 and the camera 201 may be other than the above as long as dark field imaging can be realized. The light source 101 and the camera 201 are referred to as a reflection optical system in this specification.

The light source 102 irradiates the inspection object S with light 102a from the side opposite to the camera 202.
The wavelength of the light 102 a emitted from the light source 102 may be arbitrary as in the case of the light source 101, but blue light is preferably used in the present embodiment. The reason why blue light is desirable will be described later. The light source 102 is arranged so that the light 102a is irradiated obliquely with respect to the inspection object S. In the present embodiment, the irradiation positions of the light 101a and the light 102a are shifted in the transport direction. The camera 202 is a line sensor camera and may be a color camera or a monochrome camera. The camera 202 is disposed in a direction orthogonal to the conveyance direction of the inspection object S, and is disposed so as to photograph the irradiation position of the light 102a from the vertical direction. The positional relationship between the light source 102 and the camera 202 is preferably a positional relationship in which the normally transmitted light of the light 102a does not enter the camera 202 and the indirect transmitted light 102b enters. By doing in this way, the defect of the to-be-inspected object S can be imaged by dark field, and a defect can be image | photographed with high contrast. Note that the positional relationship between the light source 102 and the camera 202 may be other than the above as long as dark field imaging can be realized. The light source 102 and the camera 202 are referred to as an indirect transmission optical system in this specification.

  The signal processing unit 300 is a computer including a CPU (Central Processing Unit), a main storage device such as a RAM, an auxiliary storage device such as an HDD or an SSD, an input / output device such as a mouse, a keyboard, or a display. When the CPU of this computer executes the computer program, it functions as a reflection optical system signal processing unit 301, a transmission optical system signal processing unit 302, an alignment processing unit 303, a defect detection unit 304, a comparison determination unit 305, and an output unit 306. To do.

  The reflection optical system signal processing unit 301 acquires the shooting data output from the camera 201 and obtains the luminance ratio from the shooting data. In the present embodiment, since a green light source is used as the light source 101, when the camera 201 is a color camera, the luminance ratio of the G signal may be obtained. Note that the luminance ratio is a value obtained by dividing the charge (imaging data) of each light receiving element by the charge (imaging data) of each light receiving element when an object having no defect is targeted. That is, photographing data of the inspection object S having no defect is obtained in advance, and a ratio of photographing data at the time of inspection to this value is defined as a luminance ratio. The “charge of each light receiving element when there is no defect” may be an average value of the charge of each light receiving element when imaging is performed a plurality of times. The luminance ratio becomes a value close to 1 when there is no defect, and becomes a value larger than 1 when diffuse reflection light enters the defect when there is a defect. In this specification, the luminance ratio calculated by the reflective optical system signal processing unit 301 is referred to as a reflected light luminance ratio.

  The transmission optical system signal processing unit 302 acquires the shooting data output from the camera 202 and obtains the luminance ratio from the shooting data in the same manner as described above. In the present embodiment, since a blue light source is used as the light source 102, when the camera 202 is a color camera, the luminance ratio of the B signal may be obtained. Similarly to the above, the luminance ratio obtained here becomes a value close to 1 when there is no defect, and becomes a value larger than 1 when indirect transmitted light is incident when there is a defect. In this specification, the luminance ratio calculated by the transmission optical system signal processing unit 302 is referred to as a transmitted light luminance ratio.

  The alignment processing unit 303 performs alignment processing of the data of the reflected light luminance ratio and the transmitted light luminance ratio. Since the shooting positions of the camera 201 and the camera 202 are different, it takes time for the portion shot by the camera 201 to reach the position shot by the camera 202. In order to compare the luminance ratio of the same location obtained from the camera 201 and the camera 202, the alignment processing unit 303 performs alignment processing based on the conveyance speed of the inspection object and the acquisition time of the imaging data.

The defect detection unit 304 detects a defect from each of the reflected light luminance ratio data and the transmitted light luminance ratio data. The defect detection unit 304 detects all defects without distinguishing whether the defect is an inner layer defect or a surface defect. Specifically, the defect detection unit 304 determines that a defect exists when the luminance ratio is equal to or greater than a predetermined threshold. This threshold value can be set from the outside as a detection parameter.

  The comparison determination unit 305 determines whether the defect detected by the defect detection unit 304 is an inner layer defect or a surface defect based on the reflected light luminance ratio and transmitted light luminance ratio at the defect portion. The comparison determination unit 305 determines that a defect having a transmitted light luminance ratio larger than the reflected light luminance ratio is an inner layer defect, and a defect having a reflected light luminance ratio larger than the transmitted light luminance ratio is a surface defect. Is determined.

  The reason why the inner layer defect and the surface defect can be discriminated by the above method will be described with reference to FIGS.

FIG. 3A is a diagram for explaining the reflected light in the defect of the light 101 a emitted from the light source 101. Light 101a emitted from the light source 101 is diffusely reflected at the surface defect _{D S} and the internal defect _{D I,} the diffuse reflection light _R S, _{R I} is captured by the camera 201. Here, while the diffuse reflection out strongly in surface defects D _S, is characterized in that the inner layer defect D _I In diffuse reflection exits weaker. Therefore, the intensity of the reflected light R _{S at} the surface defect D _S is detected to be stronger than the intensity of the reflected light R _{I at} the inner layer defect D _I.

FIG. 3B is a diagram for explaining indirect transmitted light in the defect of the light 102 a irradiated from the light source 102. Light 102a emitted from the light source 102 is scattered in the surface defect _{D S} and the internal defect _{D I,} deviated from the positive transmission direction. The indirect transmitted light T _S and T _I are photographed by the camera 202. Here, while the strong scattering in the inner defect D _I, the surface defect D _S scattering has a feature that weak. Therefore, the intensity of the indirectly transmitted light T _{I at} the inner layer defect D _I is detected to be stronger than the intensity of the indirectly transmitted light T _{S at} the surface defect D _S.

  This scattering effect is the reason why it is preferable to use a blue light source for the light source 102. The shorter the wavelength of the light 102a, the stronger the scattering effect on the inner layer defect, and the stronger the indirectly transmitted light incident on the camera 202. For this reason, it is preferable that the wavelength of the light irradiated from the light source 102 is short. Considering the availability and cost of the light source and the light receiving element, the light 102a emitted from the light source 102 is preferably blue light.

  FIG. 4 is a diagram for explaining the difference in luminance ratio between the inner layer defect and the surface defect. FIG. 4A is a diagram showing the object to be inspected from the vertical direction. A surface flaw (surface defect) 41 and an inner layer foreign matter (inner layer defect) 42 are present at the photographing position 43 of the cameras 201 and 202. Represents. FIG. 4B is a diagram illustrating the reflected light luminance ratio (the luminance ratio calculated by the reflective optical system signal processing unit 301) captured by the camera 201 for each pixel position. As described above, since the reflected light intensity at the surface scratch 41 is larger than the reflected light intensity at the inner layer foreign matter 42, the luminance ratio at the position of the surface scratch 41 is large, and the luminance at the position of the inner layer foreign matter 42. The ratio is small. On the other hand, FIG. 4C is a diagram showing the indirect transmitted light luminance ratio (the luminance ratio calculated by the transmission optical system signal processing unit 302) captured by the camera 202 for each pixel position. As described above, since the indirect transmitted light intensity at the inner layer foreign matter 42 is larger than the indirect transmitted light intensity at the surface scratch 41, the luminance ratio at the position of the inner layer foreign matter 42 is large, and at the position of the surface scratch 41. The luminance ratio is small.

  Thus, as for the luminance ratio at the position of the inner layer foreign matter 42, the transmitted light luminance ratio is larger than the reflected light luminance ratio. On the other hand, as for the luminance ratio at the position of the surface scratch 41, the reflected light luminance ratio is larger than the transmitted light luminance ratio. Therefore, the comparison / determination unit 305 can determine a defect having a transmitted light luminance ratio larger than the reflected light luminance ratio as an inner layer defect.

In the description of FIG. 3 and FIG. 4, in order to simplify the description, the case where the surface defect is on the front side (light source 101 side) is taken as an example. This phenomenon holds. Even if the inner layer defect and the surface layer defect are present at the same position, the transmitted light luminance ratio of the detected defect can be adjusted by appropriately adjusting the light amount of the light source 102 and the threshold value for defect detection. Can be made larger than the reflected light luminance ratio. Therefore, even when the inner layer defect and the surface layer defect are present at the same location, the presence or absence of the inner layer defect can be determined by the above principle.

  When a defect is detected, the output unit 306 outputs information indicating a position where the defect exists and whether the defect is an inner layer defect or a surface defect to a display device or the like. Send data to Note that the output unit 306 may notify that a defect exists only when an inner layer defect exists.

  A defect inspection method using the defect inspection apparatus according to the present embodiment will be described with reference to the flowchart of FIG. In step S <b> 51, reflected light of the light emitted from the light source 101 to the inspection object S is imaged by the camera 201, and transmitted light of the light irradiated from the light source 102 to the inspection object S is imaged by the camera 202. Further, the reflection optical system signal processing unit 301 and the transmission optical system signal processing unit 302 calculate the luminance ratio of the reflected light and the transmitted light. Since the inspection object S is conveyed, a two-dimensional luminance ratio distribution is obtained by this photographing. In step S52, the alignment processing unit 303 performs alignment processing of the reflected light luminance ratio and the transmitted light luminance ratio, and obtains the reflected light luminance ratio and the transmitted light luminance ratio at the same position. In step S53, the defect detection unit 304 detects a defect from each of the reflected light luminance ratio data and the transmitted light luminance ratio data of the same photographing location. When the luminance ratio is larger than the threshold value given as the imaging parameter, the defect detection unit 304 determines that there is a defect. Here, the defect detection is performed after the alignment process, but the alignment process may be performed after the defect detection.

  In step S54, the comparison determination unit 305 determines whether or not the transmitted light luminance ratio is greater than the reflected light luminance ratio for the defect detected by the defect detection unit 304. If the transmitted light luminance ratio is larger, the process proceeds to step S55, and the comparison / determination unit 305 determines that the defect is an inner layer defect. On the other hand, when the reflected light luminance ratio is larger, the process proceeds to step S56, and the comparison / determination unit 305 determines that the defect is a surface defect. Thereafter, in step S57, the output unit 306 outputs the position, defect type, and the like of the detected defect. However, information regarding defects may be output only when the defects are inner layer defects, and information may not be output regarding surface defects.

  According to the defect inspection apparatus according to the present embodiment, since two types of imaging of reflected light and indirect transmitted light can be performed simultaneously, high-speed inspection is possible. In addition, since a driving unit for moving the optical system is unnecessary, manufacturing costs and maintenance costs can be suppressed. Furthermore, by determining the defect based on the difference between the reflected light intensity and the indirect transmitted light intensity, it is possible to determine with high accuracy. In particular, the use of short-wavelength light such as blue light, which has a high scattering effect on defects, as the transmitted light increases the indirect transmitted light, further improving the accuracy of classification determination.

<Second Embodiment>
FIG. 6 shows the configuration of the defect inspection apparatus according to the second embodiment. The defect inspection apparatus according to this embodiment is basically the same as that of the first embodiment, but the configuration of the optical system for transmitted light imaging is different. While indirect transmitted light is imaged in the first embodiment, regular transmitted light is imaged in this embodiment.

In the present embodiment, in order to photograph regular transmitted light, the light source 102 and the camera 202 are arranged so that the irradiation direction of the light source 102 and the photographing direction of the camera 202 coincide. For example, it is preferable that the light source 102 irradiates light on the inspection object S vertically from below, and the camera 202 images the inspection object S vertically from above.

  In the present embodiment, a polarizing filter 401 is disposed between the light source 102 and the inspection object S and a polarizing filter 402 is disposed between the camera 202 and the inspection object S for dark field imaging. Here, the polarizing filter 401 and the polarizing filter 402 are arranged so that their transmission axes are orthogonal to each other (crossed Nicols arrangement). Therefore, the light emitted from the light source 102 is blocked by the polarization filter 402 and does not reach the camera 202 when there is no disturbance in the polarization in the inspection object S.

FIG. 7 is a diagram for explaining the intensity of transmitted light when light emitted from the light source 102 passes through the inspection object S. FIG. The transmitted light T _{0 that} has passed through the part having no defect is blocked by the polarizing filter 402 because the polarization does not disturb in the inspection object S. On the other hand, the transmitted lights T _I and T _S transmitted through the inner layer defect D _I and the surface defect D _S pass through the polarization filter 402 because the polarization is disturbed when passing through the defect. Here, there is a feature that the polarization disturbance when transmitting through the inner layer defect is larger than the polarization disturbance when transmitting through the surface defect. Therefore, in the camera 202, the intensity of the transmitted light T _I transmitted through the inner layer defect D _I is detected to be stronger than the intensity of the transmitted light T _S transmitted through the surface defect D _S. Note that since the degree of polarization disturbance due to defects does not depend on the wavelength of light, the wavelength (color) of light emitted from the light source 102 may be arbitrary.

  Also in the present embodiment, as in the first embodiment, the defect is an inner layer defect or a surface defect based on the intensity of reflected light imaged by the camera 201 and the intensity of transmitted light imaged by the camera 202. Can be determined. Since the configuration of the signal processing unit 300 is the same as that of the first embodiment, description thereof is omitted.

  The effect by this embodiment is the same as the effect by 1st Embodiment.

<Third Embodiment>
In the first and second embodiments, shooting is performed using two cameras. In this embodiment, shooting is performed using one camera.

  FIG. 8 shows the configuration of the defect inspection apparatus according to this embodiment. The configuration of FIG. 8 is a modification based on the configuration of the first embodiment. As shown in FIG. 8, the defect inspection apparatus performs imaging with only one camera 200. Therefore, the irradiation position of the light source 101 and the irradiation position of the light source 102 are made the same, and the wavelengths (colors) of the light emitted from the light source 101 and the light emitted from the light source 102 are different. As described in the first embodiment, when photographing indirectly transmitted light, it is preferable to use a blue light source as the light source 102. Therefore, if the light source 102 is a blue light source and the light source 101 is a red light source or a green light source. Good.

  FIG. 8 also shows a detailed configuration of the camera 200 in the present embodiment. The camera 200 is a color camera including line-shaped light receiving elements 200R, 200G, and 200B that receive light of different wavelengths. All of the line-shaped light receiving elements are arranged in a direction orthogonal to the conveyance direction of the inspection object S. In the drawing, three light receiving elements that respectively receive R, G, and B light are shown. However, two types of optical elements corresponding to the light source 101 and the light source 102 are sufficient.

FIG. 8 shows a configuration in which changes are made based on the first embodiment, but similar changes can be made to the second embodiment. The configuration in that case is shown in FIG. Also in this case, the light source 101 and the light source 102 irradiate the same position with light of different wavelengths, and photographing is performed by one camera 200. Further, a polarizing filter 401 is provided between the light source 102 and the inspection object S, and a polarizing filter 402 is provided between the camera 200 and the inspection object S. The configuration of the camera 200 and the light emitted from the light source are the same as described above.

  According to the defect apparatus according to the present embodiment, since one camera can be used, space saving can be achieved.

<Fourth Embodiment>
In the present embodiment, as with the third embodiment, a single camera is used for shooting.

  FIG. 9 shows the configuration of the defect inspection apparatus according to the present embodiment. The configuration of FIG. 9 is a modification based on the configuration of the first embodiment, as in the third embodiment, and is substantially the same except for the configuration of the camera 200 as compared to the third embodiment. It is the same. The camera 200 in this embodiment includes dichroic mirrors 211 and 212 and R, G, and B light receiving elements 210R, 210G, and 210B. In the configuration shown in the figure, the dichroic mirror 211 reflects only blue light and transmits other light. The dichroic mirror 212 reflects only green light and transmits other light. The red light (R), green light (G), and blue light (B) after being split by the dichroic mirrors 211 and 212 are received by the light receiving elements 210R, 210G, and 210B, respectively.

  Note that, here, a configuration in which light is split into three colors of light is shown, but a configuration in which light is split into two colors of light emitted by the light source 101 and the light source 102 may be adopted. Further, as the spectroscopic element, a dichroic prism, a grating, or the like may be employed instead of the dichroic mirror.

  FIG. 9 shows a configuration in which changes are made based on the first embodiment, but the same configuration can be added to the second embodiment to adopt the configuration of the optical system as shown in FIG. .

  According to the present embodiment, there is an advantage that space can be saved because shooting can be performed with one camera as in the third embodiment. Furthermore, since the reflected light and the transmitted light are photographed at exactly the same position, the alignment processing unit 303 is not necessary in the signal processing unit 300. Furthermore, since no positional deviation occurs, even if there is a change in the conveyance speed of the inspection object S, accurate defect detection without positional deviation can be performed.

<Fifth Embodiment>
In the present embodiment, the processing for detecting a defect in the signal processing unit 300 is different from the other embodiments, and the configuration of the other parts is the same. Specifically, the processing contents of the reflection optical system signal processing unit 301, the transmission optical system signal processing unit 302, the defect detection unit 304, and the comparison determination unit 305 are different.

  In the first to fourth embodiments, a defect is detected based on whether or not the luminance ratio is larger than a threshold value. However, in the present embodiment, a defect is detected based on a luminance ratio histogram. When a luminance ratio histogram is calculated for pixels of one line imaged by a line camera, if a defect exists, a peak appears in a portion other than the luminance ratio 1 (defect-free portion). Therefore, a defect can be detected based on the peak appearing in the histogram.

  The reflection optical system signal processing unit 301 and the transmission optical system signal processing unit 302 in this embodiment calculate a histogram of luminance ratios from the captured data of reflected light and transmitted light. An example of the calculated histogram is shown in FIG.

FIGS. 11A and 11B are histograms obtained from shooting data obtained by shooting the light emitted from the light source 101. FIG. 11A is a histogram when a surface defect is present, and FIG. 11B is a histogram when an inner layer defect is present. In the figure, the peak at the luminance ratio of 1 is omitted. As shown in the figure, the peak width W is wider in the case of surface defects than in the case of inner layer defects.

  FIGS. 11C and 11D are histograms obtained from photographing data obtained by photographing light emitted from the light source 102. FIG. 11C is a histogram when a surface defect is present, and FIG. 11D is a histogram when an inner layer defect is present. In this case, the peak width W is wider in the case of the inner layer defect than in the case of the surface defect.

  The defect detection unit 303 in the present embodiment determines that a defect exists in the inspection object S when the peak width in the histogram obtained from the imaging data is equal to or greater than a predetermined threshold. This threshold value can be set from the outside as a detection parameter.

  For the defect detected by the defect detection unit 304, the comparison determination unit 305 compares the width of the reflected light histogram at the defect portion with the width of the transmitted light histogram. As described above, if the peak width in the histogram of transmitted light is wider, it can be determined as an inner layer defect, and vice versa, it can be determined as a surface defect.

  Here, the defect detection and type determination are performed based on the width of the peak appearing in the histogram, but the defect can be similarly detected based on the peak area. That is, the defect detection unit 304 determines that a defect exists when a peak having an area equal to or larger than a predetermined threshold exists, and the comparison determination unit 305 determines that the inner layer defect is larger if the peak area in the transmitted light histogram is larger. It is determined that

  The defect detection and type determination based on the histogram employed in this embodiment can be used as an alternative to the defect detection and type determination based on the luminance ratio in the first to fourth embodiments, but by combining both methods Also good. By using these two methods at the same time, it becomes possible to detect defects and classify with higher accuracy.

<Others>
In the above description, a polarizing film used for a liquid crystal display or the like as an inspection object has been described as an example. However, the inner layer defect can be detected for any article as long as it is a transparent material that at least partially transmits light.

  In the above description, the defect is detected and the defect type is determined based on the luminance ratio of the reflected light and transmitted light. However, since the processing may be performed based on the reflected light intensity and transmitted light intensity, A similar process can be performed based on the luminance value itself instead of the ratio.

  Further, the specific arrangement of the optical system described above is merely an example, and those skilled in the art can easily understand that various modifications are possible within the scope of the technical idea of the present invention. . For example, in the first and second embodiments using two cameras, the respective cameras are arranged on the same side with respect to the object to be inspected. Any arrangement may be used as long as the reflected light and the transmitted light can be photographed. For example, as a modification of the first embodiment, as shown in FIG. 12A, the light source 101 and the light source 102 are arranged on the same side of the inspection object S, and the camera 201 and the camera 202 are connected to the inspection object S. It may be arranged on the different side. Similarly, as a modification of the second embodiment, a configuration as shown in FIG. 12B can be adopted.

S Inspected object 101 Light source (first light source)
102 Light source (second light source)
DESCRIPTION OF SYMBOLS 201 Camera 202 Camera 300 Signal processing part 301 Reflective optical system signal processing part 302 Transmission optical system signal processing part 303 Position alignment processing part 304 Defect detection part 305 Comparison determination part 306 Output part 401 Polarizing filter 402 Polarizing filter

Claims (12)

A defect inspection apparatus for inspecting defects in a sheet-like inspection object,
First irradiation means for irradiating the inspection object with first light;
Second irradiation means for irradiating the inspection object with second light;
Photographing means for photographing the reflected light of the first light to obtain photographing data relating to the reflected light , photographing the transmitted light of the second light and obtaining photographing data relating to the transmitted light ;
By dividing the value of the imaging data related to the reflected light acquired by the imaging means by the value when there is no defect, the reflected light luminance ratio is obtained, and the value of the imaging data related to the transmitted light acquired by the imaging means is calculated. Processing means for determining the transmitted light luminance ratio by dividing the value by the value when there is no defect;
Before SL on the basis of the reflected light luminance ratio and the transmitted light intensity ratio at the same position of the object to be inspected, and detecting means for detecting the surface defects and the internal defects of the object to be inspected,
With
The imaging means, the first irradiation means, and the second irradiation means are arranged so that the imaging means images the diffuse reflection light of the first light and the indirect transmitted light of the second light. It is,
The detection means includes
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the transmitted light luminance ratio is larger than the reflected light luminance ratio, it is determined as an inner layer defect,
A defect inspection apparatus that determines a surface defect when the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the reflected light luminance ratio is equal to or greater than the transmitted light luminance ratio . The second light is blue light;
The defect inspection apparatus according to claim 1. A defect inspection apparatus for inspecting defects in a sheet-like inspection object,
First irradiation means for irradiating the inspection object with first light;
Second irradiation means for irradiating the inspection object with second light;
Photographing means for photographing the reflected light of the first light to obtain photographing data relating to the reflected light , photographing the transmitted light of the second light and obtaining photographing data relating to the transmitted light ;
By dividing the value of the imaging data related to the reflected light acquired by the imaging means by the value when there is no defect, the reflected light luminance ratio is obtained, and the value of the imaging data related to the transmitted light acquired by the imaging means is calculated. Processing means for determining the transmitted light luminance ratio by dividing the value by the value when there is no defect;
Detection means for detecting a surface defect and an inner layer defect of the inspection object based on the reflected light luminance ratio and the transmitted light luminance ratio at the same position of the inspection object;
With
The imaging means, the first irradiation means, and the second irradiation means are arranged so that the imaging means images the diffuse reflection light of the first light and the regular transmitted light of the second light. And
Between the inspection object and the second irradiating means, and, between the inspection object and the imaging means, polarization filter transmission axes are orthogonal to each other are provided, respectively,
The detection means includes
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the transmitted light luminance ratio is larger than the reflected light luminance ratio, it is determined as an inner layer defect,
A defect inspection apparatus that determines a surface defect when the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the reflected light luminance ratio is equal to or greater than the transmitted light luminance ratio . The first irradiation means irradiates the inspection object with the first light from one side of the inspection object,
The second irradiation means irradiates the inspection object with the second light from the other side different from the one side,
The imaging means is disposed on the one side of the inspection object.
The defect inspection apparatus in any one of Claims 1-3. The first irradiation means and the second irradiation means irradiate the inspection object with the first light and the second light, respectively, from one side of the inspection object,
The imaging means is arranged on the one side of the object to be inspected, the first imaging means for imaging the reflected light of the first light, and the other side different from the one side of the object to be inspected And a second photographing means for photographing the transmitted light of the second light.
The defect inspection apparatus in any one of Claims 1-3. The irradiation position of the first light and the irradiation position of the second light are different,
The photographing means includes two cameras, a camera that photographs the irradiation position of the first light and a camera that photographs the irradiation position of the second light.
The defect inspection apparatus in any one of Claims 1-5. The irradiation position of the first light and the irradiation position of the second light are the same,
The first light and the second light are light having different wavelengths,
The photographing means is a single color camera having a plurality of line-shaped light receiving elements that receive light of different wavelengths.
The defect inspection apparatus in any one of Claims 1-4. The irradiation position of the first light and the irradiation position of the second light are the same,
The first light and the second light are light having different wavelengths,
The photographing means is a single color camera having a spectroscopic element that separates light incident on the photographing means and a plurality of light receiving elements that respectively obtain the light intensity after the spectrum.
The defect inspection apparatus in any one of Claims 1-4. The second light is blue light;
The first light is red light or green light.
The defect inspection apparatus according to claim 7 or 8. It further comprises alignment means for aligning the photographing data related to the reflected light and the photographing data related to the transmitted light,
The detection means detects surface defects and inner layer defects of the inspection object based on imaging data after alignment.
The defect inspection apparatus according to claim 6 or 7. A defect inspection method for inspecting a sheet-like inspection object for defects,
An irradiation step of irradiating the inspection object with the first light and the second light;
An imaging step of imaging the reflected light of the first light to acquire imaging data relating to the reflected light , imaging the transmitted light of the second light, and acquiring imaging data relating to the transmitted light ;
By dividing the value of the imaging data relating to the reflected light acquired in the imaging step by the value when there is no defect, the reflected light luminance ratio is obtained, and the value of the imaging data relating to the transmitted light acquired in the imaging step is calculated. Determining the transmitted light luminance ratio by dividing the value by the value when there is no defect ;
Before SL on the basis of the reflected light luminance ratio and the transmitted light intensity ratio at the same position of the inspection object, a detection step for detecting surface defects and the internal defects of the object to be inspected,
Including
In the photographing step, the diffuse reflected light of the first light is photographed and the indirectly transmitted light of the second light is photographed.
In the detecting step,
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the transmitted light luminance ratio is larger than the reflected light luminance ratio, it is determined as an inner layer defect,
A defect inspection method for determining a surface defect when the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the reflected light luminance ratio is equal to or greater than the transmitted light luminance ratio . A defect inspection method for inspecting a sheet-like inspection object for defects,
An irradiation step of irradiating the inspection object with the first light and the second light;
An imaging step of imaging the reflected light of the first light to acquire imaging data relating to the reflected light , imaging the transmitted light of the second light, and acquiring imaging data relating to the transmitted light ;
By dividing the value of the imaging data relating to the reflected light acquired in the imaging step by the value when there is no defect, the reflected light luminance ratio is obtained, and the value of the imaging data relating to the transmitted light acquired in the imaging step is calculated. Determining the transmitted light luminance ratio by dividing the value by the value when there is no defect ;
Before SL on the basis of the reflected light luminance ratio and the transmitted light intensity ratio at the same position of the object to be inspected, and a detection step of detecting the surface defects and the internal defects of the object to be inspected,
Including
In the imaging step, thereby capturing the diffused reflected light of the first light, photographing the regular transmission light of the second light,
The second light is irradiated on the object to be inspected with the second light through the first polarizing filter, and after passing through the object to be inspected, the transmission axis of the first polarizing filter is orthogonal to the first light. Taken through the second polarizing filter ,
In the detecting step,
When the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the transmitted light luminance ratio is larger than the reflected light luminance ratio, it is determined as an inner layer defect,
A defect inspection method for determining a surface defect when the reflected light luminance ratio or the transmitted light luminance ratio is equal to or greater than a threshold value and the reflected light luminance ratio is equal to or greater than the transmitted light luminance ratio .

Images