JP4445563B2 - Defect inspection apparatus and defect inspection method - Google Patents

Description

  The present invention relates to a defect inspection apparatus and a defect inspection method. More specifically, the present invention relates to a defect inspection apparatus and a defect inspection method for inspecting the surface of an inspection object using an optical technique.

Conventionally, in the inspection of surface defects of sheet-like products such as steel sheets, the surface of the steel sheet or the like is irradiated with light, and the presence or absence of defects is judged based on the intensity of the received light signal of the reflected light reflected from the surface of the steel sheet or the like. Was done.
However, in steel plates, etc., oil may be applied to the surface for the purpose of rust prevention in the manufacturing process, and in this case, detection errors of defects may occur due to the influence of oil present in the steel plate. There is sex. For example, when oil is scattered on the surface of a steel plate or the like, the reflected light from the oil part is lower in signal intensity than the reflected light from the part where no oil is present. The phenomenon occurs. Then, a detection error that misidentifies the oil as a defect occurs, so that the defect inspection accuracy is lowered.

As a technique for suppressing the influence of oil existing on the surface of a steel plate or the like on the defect inspection accuracy, there is a technique disclosed in Patent Document 1.
In this document, a light projecting unit that makes a polarized light beam incident on a surface to be inspected, a light receiving unit that extracts three different polarization components from reflected light reflected by the surface to be inspected and converts them into image signals, and a surface to be inspected. There is disclosed a defect inspection apparatus including an incident angle variable unit that changes an incident angle of an incident polarized light beam and a light receiving angle variable unit that changes a light receiving angle for receiving reflected light reflected by a surface to be inspected.
In this defect inspection apparatus, the incident angle and the light receiving angle are changed to the predetermined optimum incident angle and light receiving angle based on the presence or absence of oil applied to the steel plate and the type of oil to be applied. There is a description that the surface of the steel sheet can be inspected in a state where the signal level of the light reception signal is the highest, irrespective of the state, that is, the presence of oil, and a stable inspection can be performed.

However, in the technique of Patent Document 1, by adjusting the incident angle and the light receiving angle, the signal level of the entire light receiving signal is increased to facilitate detection of the defect signal, and the influence itself of the oil contained in the light receiving signal is reduced. It cannot be removed.
In addition, the angle of the light projecting part and the light receiving part must be changed according to the surface condition of the steel sheet, and the angle adjustment is complicated. In addition, since the incident angle variable part, the light receiving angle variable part, and the control mechanism for the incident angle variable part must be provided, the apparatus becomes complicated and large.

JP-A-9-159621

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a defect inspection apparatus and a defect inspection method capable of suppressing the influence of oil or the like and increasing surface defect detection accuracy without complicating the apparatus configuration. .

(Defect inspection equipment)
A defect inspection apparatus according to a first aspect of the present invention is an apparatus for inspecting defects on the surface of an object to be inspected in the presence of a liquid, and includes an incident-side polarizing member and a light source that irradiates light to the object to be inspected. An incident side polarizing member of the light projecting means , comprising: a light means, a light receiving side polarizing member, and a light receiving portion that receives light reflected on the surface of the inspection object through the light receiving side polarizing member. Is arranged on the optical axis of the light source so that a part of the light emitter of the light source can be seen when viewed from the optical axis direction, and is directed from the light source toward the object to be measured. Is provided so that a part of the emitted light is directly irradiated on the surface of the object to be measured without passing through the incident-side polarizing member, and is irradiated on the object to be inspected from the light source. By reflection at the part where the liquid exists And the total amount of light incident on the serial light-receiving unit, characterized in that the difference between the total light quantity, are arranged so as to be smaller incident on the light receiving portion by reflecting at a portion where the liquid is absent.
The defect inspection apparatus according to a second aspect of the present invention is characterized in that, in the first aspect, the imaging means includes a filter that transmits light in a specific wavelength region.
(Defect inspection method)
The defect inspection method of the third invention is an inspection method for inspecting a surface defect of the inspection target based on reflected light of light irradiated from a light source on the surface of the inspection target in a state where a liquid exists. An incident-side polarizing member disposed between the light source and the object to be inspected, and a light-receiving side polarizing member provided between the object to be inspected and an imaging means for receiving reflected light on the liquid surface. The total amount of light incident on the light receiving unit due to the reflection at the portion where the liquid exists in the light irradiated to the object to be inspected from the light source and the liquid does not exist A part of the light emitted from the light source is transmitted through the incident-side polarizing member so as to reduce the difference between the total amount of light incident on the light receiving unit due to reflection at the part, and irradiated on the inspection target; Of light emitted from the light source Parts irradiated directly the object to be inspected, the light reflected by the surface to be inspected, characterized in that it received through the light receiving side polarizing member.
The fourth bright defect inspection method is characterized in that, in the third invention, light is received through a filter that transmits light in a specific wavelength range.

(Defect inspection equipment)
According to the first aspect of the invention, the scattered light of the light directly irradiated from the light source to the surface of the object to be measured while removing the influence of the reflection on the liquid surface such as oil by the polarizing member provided in the light projecting means and the photographing means. Due to this, the difference between the amount of light entering the imaging means from the liquid portion and the amount of light entering the imaging means from a portion where no liquid exists can be reduced. Then, in the reflected light received by the light receiving unit of the photographing means, the influence of reflection on the liquid surface is reduced, so that the detection accuracy of the surface defect of the measurement target can be increased. In addition, since only the polarizing member is provided in the light projecting means and the photographing means, the apparatus can be prevented from becoming complicated, and the apparatus can also be made compact.
According to the second invention, even when the contrast between the liquid and the surface to be inspected is strong, it is possible to reduce the influence of the liquid contained in the reflected light.
(Defect inspection method)
According to the third aspect of the present invention, the polarizing member provided on the light source side and the light receiving side removes the influence of reflection on the liquid surface such as oil, and the light amount from the liquid portion toward the light receiving side and the portion where no liquid exists. It is possible to reduce the difference from the amount of light traveling toward the light receiving side. Then, since the reflected light in which the influence of reflection on the liquid surface is reduced is received, the detection accuracy of the surface defect of the measurement object can be increased.
According to the fourth aspect, even when the contrast between the liquid and the surface to be inspected is strong, the influence of the liquid contained in the reflected light can be reduced.

  FIG. 1A is a schematic explanatory view of a defect inspection apparatus 1 according to an embodiment of the present invention, and FIG. 1B is a view taken along line BB in FIG. In FIG. 1, in order to make it easy to understand the arrangement of the devices and the like, the relative sizes are described with dimensions different from actual ones.

In FIG. 1, the code | symbol S has shown to-be-inspected objects, such as a sheet-like member consisting of a film, a metal, etc. conveyed continuously. This inspection target S is a surface inspection in a state where a liquid such as oil or water is present on the surface thereof. For example, since various oils such as rolling oil and rust preventive oil are used in the copper foil manufacturing process, the inspection is performed in a state where the oil is present on the sheet surface.
Moreover, in FIG. 1, the code | symbol R has shown the roller provided in order to apply tension | tensile_strength with respect to the to-be-inspected object S conveyed.

Next, the defect inspection apparatus 1 of the present embodiment will be described.
The defect inspection apparatus 1 according to the present embodiment includes a light projecting unit 10 that irradiates light to the inspection target S and an imaging unit 20 that receives reflected light reflected by the surface of the inspection target S.

First, the light projecting means 10 will be described.
As shown in FIG. 1A, the light projecting means 10 includes a light source 11 that emits light toward the surface of the inspection target S, and an incident side provided between the light source 11 and the inspection target S. And a polarizing member 12.

  As shown in FIG. 1B, the light source 11 includes a horizontally long light emitter 11a extending along the width direction of the inspection target S (the direction perpendicular to the paper surface in FIG. 1A). The light emitter 11a is, for example, a fluorescent lamp or an LED, but is not particularly limited as long as it can irradiate light toward the inspection target S.

The incident-side polarizing member 12 is, for example, a polarizing filter or a polarizing film that transmits and polarizes light emitted from the light emitter 11 a and is provided on the optical axis LA of the light source 11. The incident-side polarizing member 12 is formed so that its shape is horizontally long, and is arranged so that the axial direction thereof coincides with the axial direction of the light emitter 11a (the left-right direction in FIG. 1B). Has been.
And this incident side polarizing member 12 is formed so that the height H1 may become lower than the height H2 of the light-emitting body 11a. That is, the incident-side polarizing member 12 has a light emitter 11a of the light source 11 that is not completely hidden by the incident-side polarizing member 12 when the light projecting means 10 is viewed from the front, and is a part of the light emitter 11a of the light source 11. It is arranged so that can be seen.

Therefore, if light is emitted from the light emitter 11a of the light source 11 in the light projecting unit 10 toward the inspection target S, a part of the emitted light is transmitted through the incident side polarization member 12 and polarized. Although the surface of the inspection object S is irradiated, a part of the light is directly irradiated on the surface of the inspection object S.
Hereinafter, among the light emitted from the light emitter 11a of the light source 11 toward the inspection target S, the light transmitted through the incident-side polarizing member 12 and applied to the inspection target S is polarized irradiation light, the inspection target. The light directly irradiated on the surface of S is referred to as direct irradiation light.

  Although not shown, the defect inspection apparatus 1 is a mechanism for moving the light projecting means 10 along the direction of the optical axis LA to move the light projecting means 10 closer to and away from the inspection target S, such as a jack or a cylinder. A moving mechanism such as a ball screw is provided for the reason described later.

Next, the photographing means 20 will be described.
As shown in FIG. 1, the imaging means 20 includes a light receiving unit 21 that receives reflected light reflected by the inspection target S, and a light receiving side polarizing member 22 provided between the light receiving unit 21 and the inspection target S. And.

  The light receiving unit 21 is, for example, an imaging device such as a line sensor or a CCD area camera. However, the light receiving unit 21 is not particularly limited as long as it is a device that can detect reflected light that is reflected by the inspection target S and transmitted through the light receiving side polarizing member 22.

  The light-receiving-side polarizing member 22 is, for example, a polarizing filter or a polarizing film that transmits light having a predetermined polarization among the reflected light reflected by the inspection target S. The light receiving side polarizing member 22 is provided between the light receiving unit 21 and the inspection target S, and is disposed so as to completely cover the light detection unit of the light receiving unit 21. That is, the light receiving side polarizing member 22 is provided so that only the reflected light that has passed through the light receiving side polarizing member 22 enters the light receiving unit 21.

Next, inspection work by the defect inspection apparatus 1 of the present embodiment will be described.
First, the light projecting means 10 and the photographing means 20 are installed on the same side of the inspection object S (FIG. 1). At this time, the photographing unit 20 is arranged so that the light emitted by the light projecting unit 10 receives the reflected light that is regularly reflected by the inspection target S. That is, the optical axis LA of the light projecting means 10 is arranged so that the axis that is regularly reflected by the inspection target S and the optical axis LA1 of the imaging means 20 coincide with each other. In addition, the photographing unit 20 adjusts so as to photograph a region of the inspection target S that is irradiated with the polarized irradiation light of the light projecting unit 10. In other words, the photographing unit 20 adjusts so as to receive only the reflected light reflected in the region irradiated with the polarized irradiation light.

Next, the incident side polarizing member 12 is provided in the light projecting means 10, and the light receiving side polarizing member 22 is also provided in the photographing means 20. Then, the liquid existing on the surface of the inspection target S during the inspection of oil or the like is arranged in the imaging region of the imaging means 20 on the surface of the inspection target S. Then, adjustment is made so that a portion where the liquid exists (liquid portion) and a portion where the liquid does not exist (non-liquid portion) exist in the imaging region.
In this state, the light-receiving side polarizing member 22 of the photographing unit 20 is adjusted so that the influence of the reflected light on the liquid surface contained in the light reception signal of the light receiving unit 21 is reduced. Specifically, the light receiving side polarizing member 22 is rotated around the optical axis LA1, and the polarization angle of the light receiving side polarizing member 22 with respect to the optical axis LA1 of the photographing unit 20 is changed, so that the reflectance in the liquid part and the non-liquid part are changed. Adjust so that the reflectance at is equal. That is, the light receiving unit 21 of the photographing unit 20 is adjusted so that light from which the influence of reflection on the surface of the liquid is removed enters.

When the polarization angle of the light-receiving side polarizing member 22 is adjusted, the distance D from the light projecting means 10 to the inspection object S is adjusted by moving the light projecting means 10 along the optical axis LA by the moving mechanism.
The polarized irradiation light irradiated to the imaging region is reflected by the surface of the object S to be inspected and enters the imaging means 20, but the polarized irradiation light irradiated to the liquid part passes through the liquid and is inspected. After being irradiated on the object S and reflected on the surface of the object S to be inspected, the liquid is again transmitted to the imaging unit 20. That is, since the reflected light reflected by the liquid part is transmitted through the liquid, the amount of polarized irradiation light incident on the light receiving unit 21 of the photographing means 20 by reflection on the liquid part (hereinafter referred to as liquid part direct incident light amount) is The amount of light becomes smaller than the amount of polarized irradiation light incident on the light receiving unit 21 due to reflection of the non-liquid part (hereinafter referred to as non-liquid part directly incident light amount).
However, by adjusting the distance D from the light projecting means 10 to the object S to be inspected, the contrast between the liquid part and the non-liquid part due to the effect of the direct irradiation light irradiated from the light projecting means 10 to the object S to be inspected. That is, the total amount of light incident on the light receiving unit 21 due to reflection at the liquid part (hereinafter referred to as the total liquid amount of liquid part) and the total amount of light incident on the light receiving unit 21 due to reflection at the non-liquid part (hereinafter referred to as non-liquid). Difference with the total light quantity).

When the adjustment is completed, the surface of the inspection target S is inspected by the defect inspection apparatus 1 of the present embodiment while conveying the inspection target S. Then, even if liquid is present on the surface of the object S to be inspected, the reflected light received by the light receiving unit 21 of the imaging unit 20 is removed from the influence of the liquid surface reflection, and the total light amount of the liquid part is not. The difference from the liquid part total light amount is reduced.
That is, since the light receiving unit 21 of the photographing unit 20 receives the reflected light in which the influence of the liquid is reduced, the detection accuracy of the surface defect of the measurement target S can be increased.

  Moreover, since only the polarizing members 12 and 22 and the moving mechanism are provided in addition to the light projecting means 10 and the photographing means 20, the apparatus can be prevented from becoming complicated, and the apparatus has a compact configuration. be able to.

  Here, the reason why the difference between the liquid part total light quantity and the non-liquid part total light quantity can be reduced by adjusting the distance D from the light projecting means 10 to the inspection target S will be described.

  First, in the defect inspection apparatus 1 of this embodiment, both the polarized irradiation light and the direct irradiation light are irradiated from the light projecting unit 10 to the inspection target S, but the photographing unit 20 is irradiated with the polarized irradiation light. The shooting area is adjusted so as to shoot the area that has been set. For this reason, of the light reflected on the surface of the inspection object S, only the reflected light of the polarized irradiation light directly enters the imaging unit 20, and the reflected light of the direct irradiation light does not enter the imaging unit 20 directly.

  However, since the direct irradiation light irradiated on the part other than the imaging region is irregularly reflected on the surface of the inspection object S, a part of the irregularly reflected light is incident on the imaging region. Then, the irregularly reflected light incident on the imaging area is re-reflected in the imaging area. If the direction in which the re-reflected light moves coincides with the optical axis LA1 direction of the imaging means 20, it is re-reflected. The light enters the light receiving unit 21 of the photographing unit 20. That is, the reflected light of the direct irradiation light also enters the light receiving unit 21 indirectly. Then, the amount of reflected light incident on the light receiving unit 21 is the sum of the amount of polarized irradiation light directly incident on the light receiving unit 21 and the amount of direct irradiation light incident on the light receiving unit 21 indirectly. (Total light intensity).

  Here, the amount of direct irradiation light that indirectly enters the light receiving unit 21 is higher than the amount of light that enters the light receiving unit 21 due to reflection at the non-liquid part (hereinafter referred to as non-liquid part indirect incident light amount). The amount of light incident on the light receiving unit 21 due to reflection at the portion (hereinafter referred to as liquid portion indirect incident light amount) is increased. This is because, due to the presence of liquid, scattering is more likely to occur in the liquid part than in the non-liquid part, and the probability that the direction of the scattered light coincides with the direction of the optical axis LA1 of the imaging unit 20 is increased. .

  Then, as described above, since the amount of polarized irradiation light directly incident on the light receiving unit 21 of the photographing unit 20 is larger than the liquid unit direct incident light amount, the non-liquid portion direct incident light amount is larger. If the light quantity of the direct irradiation light that indirectly enters 21 is changed, the difference between the liquid part total light quantity and the non-liquid part total light quantity can be adjusted. In other words, the difference between the non-liquid portion direct incident light amount and the liquid portion direct incident light amount can be reduced by the difference between the non-liquid portion indirectly incident light amount and the liquid portion indirect incident light amount.

The light amount of the direct irradiation light that indirectly enters the light receiving unit 21 of the photographing unit 20 varies depending on the area of the inspection target S that is directly irradiated with the irradiation light. For example, if the distance D from the light projecting means 10 to the inspection target S is changed, the area of the inspection target S that is directly irradiated with irradiated light can be increased or decreased. Then, since the liquid part indirect incident light amount can be increased or decreased with the increase or decrease of the area irradiated with the direct irradiation light, if the area irradiated with the direct irradiation light is adjusted, the liquid part total light amount and the non-liquid part total The difference from the light quantity can be reduced, and the erroneous detection of the defect due to the light quantity difference of the reflected light can be prevented.
In addition, if the irradiation light is directly incident on the light receiving unit 21 of the photographing unit 20, the amount of reflected light entering the light receiving unit 21 increases as a whole, so that the defect signal is more easily detected. An effect is also obtained.

  The method of adjusting the light amount of the direct irradiation light is not limited to the above method, and the height H1 of the incident side polarizing member 12 is adjusted so that the area where the incident side polarizing member 12 covers the light emitter 11a of the light source 11 is adjusted. Even if it is changed, it can be adjusted.

Also, in the part where the liquid is dry (boundary part) at the boundary between the liquid part and the non-liquid part, the difference in reflected light intensity from the non-liquid part is larger than that in other liquid parts, and the boundary part is It may be mistaken for a defect.
However, as shown in FIG. 2, if the imaging means 20 is provided with a filter 23 that transmits light in a specific wavelength range, the filter 23 can selectively remove light contained in reflected light from the boundary. Since it can do, the influence of the boundary part contained in reflected light can be reduced.

  For example, if the inspection target S is a copper plate and oil is present on the surface of the inspection target S, the filter 23 transmits the red wavelength region that is included in the reflected light of the copper plate. If the red filter that can be used is used, the frequency component contained in the reflected light at the boundary portion can be removed to some extent, and the contrast between the boundary portion and other portions can be weakened. That is, since the difference between the reflected light intensity at the boundary portion and the reflected light intensity at the other portion can be reduced, the possibility of misidentifying the boundary portion as a defect can be reduced, and the surface defect detection accuracy can be increased.

  In FIG. 3, the example of the image which image | photographed the copper plate with which oil adhered to the surface by the defect inspection apparatus 1 of this embodiment is shown. The photographed copper plate is in a state in which the outer peripheral portion of the attached oil is slightly dried and the contrast between the boundary portion and other portions is increased.

  FIG. 3 (A) is an image photographed by the defect inspection apparatus of the present invention in which the photographing means is provided with a red filter. The difference between the location where oil is present and the location where there is no oil, and the boundary portion between the two are shown. It can be confirmed that there is almost no image affected by oil.

  FIG. 3B is an image taken by the defect inspection apparatus of the present invention in the absence of a red filter, and the difference in color intensity between the location where oil is present and the location where there is no oil is reduced. It can be confirmed that the influence of oil is suppressed. However, the contrast between the boundary portion and other portions is strong. In other words, when the contrast is strong between the location where oil is present and the location where there is no oil, it can be confirmed that a filter that transmits light in a specific wavelength region is effective.

  On the other hand, FIG. 3C shows a defect inspection apparatus according to the present invention, in which the photographing means includes a red filter, but the light emitting body of the light source of the light projecting means is completely covered by the polarizing member. It is the image which photographed. That is, it is an image when there is no direct irradiation light. In the case of this image, since the boundary portion cannot be confirmed as clearly as in FIG. 3B, it is considered that the effect of reducing the contrast by the red filter is obtained. However, the overall image is dark, and the difference in color density between the location where oil is present and the location where there is no oil is large. In other words, since there is no direct irradiation light, the amount of light received by the photographing means is insufficient, and since there is no irregular reflection light of the direct irradiation light, the difference in light amount between the location where oil is present and the location where there is no oil. Can be seen to remain large.

  From the above results, the defect inspection apparatus according to the present invention is suitable for surface defect inspection of an inspection target in which a liquid such as oil is present, and there is a strong contrast between a location where oil is present and a location where there is no oil. In this case, it can be confirmed that a filter that selectively transmits light in a specific wavelength region is effective.

  The defect inspection apparatus of the present invention is suitable for surface defect inspection in a sheet-like member having a liquid such as oil or water attached to the surface.

(A) is a schematic explanatory drawing of the defect inspection apparatus 1 concerning one Embodiment of this invention, (B) is a BB arrow directional view of (A). It is a schematic explanatory drawing of the defect inspection apparatus 1 concerning other embodiment. It is an example of the image which image | photographed the copper plate which the oil adhered to the surface by the defect inspection apparatus 1 of this embodiment, (A) is an image image | photographed with the defect inspection apparatus of this invention, (B) is the defect of this invention. (C) is an image taken with the light emitter of the light source completely covered with a polarizing member in the defect inspection apparatus of the present invention.

DESCRIPTION OF SYMBOLS 1 Defect inspection apparatus 10 Light projection means 11 Light source 12 Polarizing member 20 Imaging means 21 Light-receiving part 22 Polarizing member 23 Filter S Inspection object

Claims (4)

An apparatus for inspecting a surface defect of an inspection target in a state where a liquid exists ,
A light projecting means comprising an incident-side polarizing member and a light source that irradiates light to the object to be inspected;
A light receiving side polarizing member, and a photographing means including a light receiving unit that receives light reflected on the surface of the inspection target through the light receiving side polarizing member,
The incident side polarizing member of the light projecting means is
The light source is disposed on the optical axis of the light source so that a part of the light emitter of the light source can be seen when viewed from the optical axis direction, and is emitted from the light source toward the object to be measured. Is provided so that a part of the light to be directly irradiated on the surface of the object to be measured without passing through the incident side polarization member,
Of the light emitted from the light source to the object to be inspected, the total amount of light incident on the light receiving portion by reflection at the portion where the liquid exists, and the light incident on the light receiving portion by reflection at the portion where the liquid does not exist The defect inspection apparatus is arranged so that a difference between the total light quantity and the total light quantity to be reduced is reduced . The photographing means includes
The defect inspection apparatus according to claim 1, further comprising a filter that transmits light in a specific wavelength range. An inspection method for inspecting a defect on the surface of the object to be inspected based on reflected light of light irradiated from a light source on the surface of the object to be inspected in a state where liquid exists ,
An incident-side polarizing member disposed between the light source and the object to be inspected, and a light-receiving side polarizing member provided between the object to be inspected and an imaging unit that receives reflected light. Remove the effect of reflections,
Of the light emitted from the light source to the object to be inspected, the total amount of light incident on the light receiving portion by reflection at the portion where the liquid exists and the light receiving portion by reflection at the portion where the liquid does not exist A part of the light emitted from the light source is transmitted through the incident-side polarizing member to irradiate the object to be inspected so that the difference from the total amount of incident light is small, and the light emitted from the light source Directly irradiate part of the subject
A defect inspection method, wherein light reflected by the surface of the inspection target is received through the light-receiving side polarizing member. 4. The defect inspection method according to claim 3, wherein the light is received through a filter that transmits light in a specific wavelength range.