WO2011101893A1

WO2011101893A1 - Method and device for detecting flaw on surface of flexible object to be tested

Info

Publication number: WO2011101893A1
Application number: PCT/JP2010/000987
Authority: WO
Inventors: 浩次藤原
Original assignee: コニカミノルタホールディングス株式会社
Priority date: 2010-02-17
Filing date: 2010-02-17
Publication date: 2011-08-25

Abstract

In order to detect flaws on a surface of a flexible object to be tested thoroughly and easily even if the shapes of the flaws significantly vary, a device for detecting flaws on a surface of a flexible object to be tested comprises a conveying means that conveys the object while deforming the object such that the surface of the object is curved; an illuminating means that illuminates the surface of the object from a side of the object to which the surface of the object is convexed; an image capturing means that captures images of the surface of the illuminated object at predetermined time intervals; and an analyzing means that analyzes the images obtained by the image capturing means and detects flaws on the surface of the object.

Description

Method and apparatus for inspecting scratch on surface of inspection object having flexibility

The present invention relates to a method and apparatus for inspecting the surface of a test object having flexibility.

Conventionally, in a color image forming apparatus such as a copying machine or an MFP (Multi Function Peripherals) having an electrophotographic process, toner images of each color of YMCK are synthesized on an intermediate transfer belt and transferred onto a sheet. An intermediate transfer belt formed into a flexible sheet by injection molding may be used. The surface of the intermediate transfer belt is usually formed in a mirror surface, and it is necessary to inspect whether the surface is scratched.

2. Description of the Related Art Conventionally, there is a desire to increase the production yield of a sheet-like or paper-like object by in-line inspection for the presence or absence of scratches on the surface thereof. In the inspection, when the object is a specular surface, the inspection is difficult, and various methods have been proposed. There are two main methods for detecting a specular surface scratch.
(1) An illumination light source and a camera are arranged so as to capture specularly reflected light of a part of an object without a flaw, and a low-luminance part without specularly reflected light is detected as a flaw (2) specularly reflected light of a flaw of the object An illumination light source and a camera are arranged so as to capture the light, and a high-luminance portion with specular reflection light is detected as a scratch. Of these, in (1) above, if the positional relationship between the camera and the object changes even slightly, regular reflection There is a drawback that it is vulnerable to vibration when inspecting an object in-line, such as being unable to capture the part with a camera.

In the above (2), although the relative position between the object and the camera varies due to vibration or the like, it is relatively less affected, but the shape of the scratch varies. There is a drawback in that the optimal positional relationship of is different.

As a countermeasure for the above-mentioned defect (2), there has been proposed a method of irradiating light from various angles and arranging a plurality of cameras at positions where regular reflection light from a normal portion does not enter (for example, patents). Reference 1).

In order to inspect the scratches on the rubber roller, a linear light source is arranged in parallel with the axis, and the irregularly reflected light from the surface of the rubber roller by the light source is photographed with a line camera (one-dimensional imaging means) and processed. Has been proposed (Patent Document 2).

However, in the method of Patent Document 1, specularly reflected light does not enter the camera depending on the shape of the flaw and the like, so the rate of occurrence of flaw detection failure is high. In order to prevent this, it is necessary to install a large number of cameras, and there is a disadvantage that the apparatus becomes complicated.

In addition, when a sheet-like object is inspected with the object being spread out, the distance to the illumination light source is minimum at a position directly below the illumination light source, but as it goes to the periphery, And the irradiation angle also decreases. For this reason, there is a problem that the unevenness of illumination on the surface of the object is large.

In the method of patent document 2, it is devised so that an image of an originally cylindrical object such as a rubber roller may be emphasized and picked up. That is, according to the cited document 2, as described in the paragraph numbers 0004 to 0008, when the object is cylindrical, it is difficult to uniformly illuminate, so the illumination is placed near the end of the rubber roller. Hit Image processing is facilitated by photographing with a line camera between a bright part and a dark part generated by illumination.
JP2007-218889 JP 9-14942 A

The present invention provides a method and apparatus capable of easily inspecting a flaw on a surface of a test object having flexibility even if the flaw shape has a large variation, without omission. With the goal.

The apparatus according to the present invention is an apparatus for inspecting a scratch on the surface of an inspection object having flexibility, and conveying means for conveying the inspection object while deforming it so that the surface of the inspection object draws a curved surface. Illuminating means for illuminating the surface of the inspection object from the convex side of the curved surface, imaging means for imaging the surface of the illuminated inspection object at predetermined time intervals, and obtained by the imaging means. And analyzing means for analyzing the detected image to detect scratches on the surface of the inspection object.

It is a figure showing the composition of the inspection device concerning the embodiment of the present invention. It is a front view of the inspection apparatus which concerns on embodiment of this invention. It is a figure which shows the change of the incident angle of the illumination light by conveyance of a test subject. It is a figure which shows the difference in the angle of the regular reflection light by the shape of a flaw. It is a figure explaining a mode that a brightness picture is generated by superimposing a plurality of pictures. It is a figure which shows the example of the two produced | generated brightness | luminance images. It is a figure which shows the damage | wound which appeared in the image. It is a block diagram which shows the example of a structure of an analysis part. It is a flowchart which shows the outline of the process sequence in a test | inspection apparatus. It is a figure which shows the example of the area | region of regular reflection in a curved surface. It is a figure which shows the example which conveys an inspection target object so that two curved surfaces may be drawn.

Hereinafter, an embodiment of the inspection apparatus 1 that inspects the surface of the inspection object WK having flexibility will be described.

The inspection apparatus 1 of the present embodiment uses a flexible sheet-like object as the inspection object WK. In other words, the inspection object WK is in the form of a sheet and has flexibility, and the surface has a specularity such as a metallic luster.

The reflected light on the surface of the inspection object WK has a very large regular reflection component compared to the irregular reflection component. When there is a scratch on the surface of the inspection object WK, regular reflection does not occur at the scratched portion. In this case, local regular reflection occurs in a direction different from the normal regular reflection direction according to the shape or depth of the scratch.

Note that the inspection object WK may be in a strip shape having both ends, or may be endless (looped) by connecting both ends.

1, the inspection apparatus 1 includes a transport unit 11, an illumination unit 12, an imaging unit 13, a control unit 14, and the like.

The conveyance unit 11 conveys the inspection object WK while deforming it so that the surface of the inspection object WK is curved.

The conveyance unit 11 includes a columnar main roller 21,

auxiliary rollers

22a and 22b, a rotation drive device (not shown), and the like. As the main roller 21 rotates, the sheet-like inspection object WK wound around the main roller 21 is conveyed in the direction of the arrow X1.

In FIG. 1, the inspection object WK is wound around the main roller 21 by a half circumference, and the wound portion draws a cylindrical curved surface KM. That is, the cross section of the part is circular arc shape. The curved surface KM is a part of a cylindrical surface having an axis perpendicular to the transport direction X1, and is convex upward in the drawing.

The illumination unit 12 is disposed on the convex side of the curved surface KM, and illuminates the portion of the curved surface KM on the surface of the inspection object WK. The illumination unit 12 emits diffuse light such as normal white light. The illumination unit 12 is continuously lit during the inspection period.

The imaging unit 13 is an image sensor including an imaging element such as a CCD and a lens, and can image the entire curved surface KM of the inspection target WK. The imaging unit 13 images the surface of the curved surface KM of the inspection object WK illuminated by the illumination unit 12 at a predetermined time interval Δt.

The control unit 14 performs a calculation for detecting the presence or absence of a scratch on the surface of the inspection target WK based on the image obtained by the imaging unit 13 and controls the entire inspection apparatus 1.

Note that the imaging unit 13 has a time interval Δt set so that the same portion of the surface of the inspection object WK is imaged multiple times.

The control unit 14 includes a drive control unit 31, an analysis unit 32, an output unit 33, and the like.

The drive control unit 31 controls the main roller 21 to be driven at a predetermined speed and timing, controls the illumination unit 12 to be lit at a predetermined timing, and images the imaging unit 13 at a predetermined timing. Control.

The analysis unit 32 detects a scratch on the surface of the inspection object WK based on the state of the luminance values of a plurality of images obtained for the same portion of the surface of the inspection object WK.

For example, when the surface of the inspection object WK is a mirror surface, the analysis unit 32 uses the luminance of each of the plurality of images obtained for the same portion of the surface of the inspection object WK for an image that is not regularly reflected by a normal surface. When any of the values is higher than the first luminance threshold value TK1, the portion is extracted as a scratch or a scratch candidate portion.

In addition, when the surface of the inspection target object WK is a mirror surface, the analysis unit 32 uses each of a plurality of images obtained for the same part of the surface of the inspection target object WK with respect to an image that is regularly reflected by a normal surface. When any one of the luminance values is lower than the second luminance threshold value TK2, the portion is extracted as a scratch or a scratch candidate portion.

Also, the analysis unit 32 includes a calculation unit that calculates the degree of variation in luminance values of a plurality of images obtained for the same portion of the surface of the inspection object WK. When the degree of variation of the luminance value calculated by the calculation unit is higher than the variation threshold TH1, the portion is extracted as a scratch or a scratch candidate portion.

In addition, when the extracted candidate part of the scratch has a predetermined length and a predetermined thickness, the analysis unit 32 detects it as a scratch.

Further, a recording unit that records the scratches detected by the analysis unit 32 in association with the positional information on the inspection target WK may be included.

The output unit 3 displays the inspection result on the display surface or outputs it by voice. Further, when a flaw is detected, information on the position of the inspection object WK is also displayed or output.

The example illustrated in FIG. 1 illustrates a state in which the transport unit 11 transports the inspection object WK such that the curved surface KM is a part of a cylindrical surface having an axis perpendicular to the transport direction of the inspection object WK. ing. However, the inspection unit WK may be conveyed so that the conveyance unit 11 becomes a part of a cylindrical surface having an axis where the curved surface KM intersects at an acute angle with respect to the conveyance direction of the inspection object WK.

Further, the other one curved surface has an acute angle with respect to the conveyance direction of the inspection object WK so that the conveyance unit 11 becomes a part of a cylindrical surface having an axis perpendicular to the conveyance direction of the inspection object WK. The inspection object WK may be transported so as to draw two curved surfaces so as to be a part of a cylindrical surface having an axis intersecting with each other.

As the illuminating unit 12, a point light source or a linear light source extending linearly may be used, and the lighting unit 12 may be continuously lit. However, the illumination unit 12 may include a plurality of point light sources arranged in a direction parallel to the axis of the cylindrical surface forming the curved surface KM. In that case, you may control so that several point light sources light sequentially.

The following is a more detailed explanation.

2, the inspection object WK is bent into a convex shape along the main roller 21 and the

auxiliary rollers

22a and 22b, and is conveyed in the X1 direction at a constant speed V. The imaging unit 13 is a monochrome image sensor having a lens 25 and an area sensor 26. A half mirror 24 is provided in the optical path between the illumination unit 12 and the inspection object WK. The imaging unit 13 is attached so that the horizontal direction of the image obtained by imaging is aligned with the transport direction (X1 direction).

The surface of the inspection object WK is illuminated by the illumination unit 12, and the reflected light is reflected by the half mirror 24 and enters the imaging unit 13. The imaging unit 13 determines which part or which pixel in the image is a flaw part or a flaw candidate part according to the intensity (luminance) of incident light.

The inspection object WK receives illumination light from various angles as it is transported by the transport unit 11. In addition, since the inspection object WK is bent convexly toward the illumination unit 12, the range of the incident angle α of the illumination light at each part of the surface of the inspection object WK is not bent (that is, a plane surface). In the case of).

That is, as shown in FIG. 3, the illumination light LG from the illumination unit 12 is incident on the surface (curved surface KM) of the workpiece WK. The incident angle α of the illumination light LG on the work WK changes as α1, α2, α3, α4. That is, α1 <α2 <α3 <α4..., And the incident angle α gradually increases along the conveyance direction of the inspection object WK.

For example, in the vicinity of the center of the curved surface KM of the inspection object WK, the illumination light LG is incident from the front of the surface of the inspection object WK, and the incident angle α is approximately 90 degrees. However, at the end of the curved surface KM, the illumination light LG is incident at a very steep angle, and the incident angle α is close to 0 degree or 180 degrees.

That is, the incident angle α of the illumination light LG with respect to the curved surface KM of the inspection object WK is in a wide range of approximately 0 to 180 degrees.

On the other hand, if the inspection object WK is still in a flat state, the illuminating unit 12 is used to set the incident angle α in the range of 0 to 180 degrees with respect to the range corresponding to the curved surface KM. Must be in close proximity to the surface of the inspection object WK. In that case, since the distance from the illumination unit 12 varies greatly according to the surface of the inspection object WK, the amount of illumination light LG varies greatly and becomes non-uniform.

Now, as shown in FIGS. 4A to 4C, it is assumed that there is a scratch KA cut into a V shape on the surface of the inspection object WK.

FIG. 4A shows a relatively shallow scratch KA. In FIG. 4A, the light regularly reflected by the scratch KA passes through the optical path a and enters the imaging unit 13. This optical path a depends on the position and shape of the scratch KA.

FIG. 4 (B) shows a relatively deep scratch KB at the same position as the scratch KA shown in FIG. 4 (A). In FIG. 4B, the light regularly reflected by the scratch KB passes through the optical path b without passing through the optical path a, and therefore does not enter the imaging unit 13.

FIG. 4 (C) shows a state where the scratch KB shown in FIG. 4 (B) has further moved in the transport direction. In FIG. 4C, the light specularly reflected by the scratch KB passes through the optical path b ′ and enters the imaging unit 13. Therefore, at the position shown in FIG. 4C, the imaging unit 13 can capture the regular reflection of the scratch KB.

That is, the specularly reflected light from the scratch KA or the scratch KB can be captured by the imaging unit 13 at any position on the curved surface KM. That is, by transporting the inspection object WK along the curved surface KM, various shapes of scratches can be detected at any position on the curved surface KM.

In this way, by transporting the inspection object WK in a deformed state to the curved surface KM, the irradiation angle (incident angle α) of the illumination light LG with respect to the scratch K by the illumination unit 12 changes in a wide range, and various shapes are obtained. The regular reflection light with respect to the scratch can be captured by the imaging unit 13.

Therefore, even if the scratches on the surface of the inspection object WK have different shapes, the scratches can be easily inspected without omission.

Next, how to determine that the image is a flaw from the image obtained from the imaging unit 13 will be described.

In FIG. 5, three images G1, G2, and G3 captured by the imaging unit 13 are shown. Each image G is an image of a portion corresponding to the curved surface KM at each timing with respect to the inspection object WK.

Among these, the image G1 is an image captured at a specific time t1. The image G2 is an image captured at time t2 that is delayed by a time interval Δt from time t1. The image G3 is an image captured at a time t3 that is further delayed by a time interval Δt than the time t2. In this way, images G4, 5, 6.

In the image G1, a scratch image KG1 corresponding to the scratch K of the inspection object WK is shown. The wound image KG1 is a result of regular reflection of the wound K on the inspection object WK. Similarly, in the images G2 and G3, flaw images KG2 and 3 due to regular reflection of the flaw K of the inspection object WK are shown.

Since the scratch K of the inspection target WK is at the same position on the inspection target WK, these images G1 to G3 are combined by overlapping them in accordance with the coordinate system of the inspection target WK. That is, the luminance image GT is obtained by superimposing these images G1 to G3 in accordance with the position of the surface of the inspection object WK.

In the luminance image GT, the three images G1, G2, and G3 are sequentially shifted in the X direction by a distance Sx corresponding to the time interval Δt.

Here, the distance Sx is the shift amount of each image G and can be represented by the number of pixels on the image G. That is, the shift amount (number of pixels) Sx can be expressed by the following equation (1) using the conveyance speed V of the inspection object WK and the size Δx of one pixel along the conveyance direction X1 in the image G.

Sx = V · Δt / Δx (1)
When the angular velocity θ of the main roller 21 is used instead of the conveying speed V, the equation (1) is expressed by the following equation (2).

Sx = π · θ · Δt / Δx (2)
In the luminance image GT, the direction X in which the images G are sequentially shifted is the direction opposite to the conveyance direction X1 of the inspection target WK. Further, in the luminance image GT, the upper right end is the coordinate origin (0, 0), which is the Y direction downward from the origin (0, 0) and the X direction from the origin (0, 0) to the left.

In the luminance image GT, the flaw images KG1, 2, 3 overlap at the same coordinate position (x, y), that is, the same pixel position. Therefore, in the luminance image GT, the luminance value (density value) DR of each pixel is determined as follows.
(1) The maximum value (DRmax) among the luminance values DR of all the images corresponding to the pixel. (2) A value indicating the degree of variation in the luminance values DR of all the images corresponding to the pixel. For example, the ratio (DRmax / DRmin) between the maximum value DRmax and the minimum value DRmin among the luminance values DR of all the images corresponding to the pixel is used.

The luminance image GT in which the luminance value DR of each pixel is determined according to (1) above is the luminance image GTA shown in FIG. The luminance image GT in which the luminance value DR of each pixel is determined according to (2) above is the luminance image GTB shown in FIG.

Thus, two luminance images GTA and GTB in which the luminance value DR of each pixel is determined by different methods are generated.

Therefore, in FIG. 6A, the luminance value DR at each pixel position (x, y) is the maximum value (DRmax) among the luminance values DR of all the images corresponding to the pixel. In FIG. 6B, the luminance value DR at each pixel position (x, y) is the ratio (DRmax / DRmin) between the maximum value DRmax and the minimum value DRmin among the luminance values DR of all the images corresponding to the pixel. ).

Then, the luminance value DR of each pixel is checked for these two luminance images GTA and GTB. The method of checking is that when the luminance value DR is higher than the first luminance threshold value TK1 for the luminance image GTA and the luminance value DR is higher than the variation threshold value TH1 for the luminance image GTB, the pixel is determined. Extract as a candidate part of a wound.

Note that a value larger than the luminance due to irregular reflection and smaller than the luminance due to regular reflection is set as the first luminance threshold value TK1. An appropriate multiple value, for example, “1.5”, “2”, “3” or the like is set as the fluctuation threshold TH1.

In addition, since the intensity of the specularly reflected light changes depending on the position on the curved surface KM, these threshold values may be calibrated for each position and optimized according to the position.

For the luminance image GTA, the fact that the luminance value DR is higher than the first luminance threshold value TK1 means that it can be considered to be due to regular reflection light. Further, regarding the luminance image GTB, the fact that the luminance value DR is higher than the fluctuation threshold value TH1 means that it can be considered that there is specularly reflected light according to the transport position of the inspection object WK. In this way, a scratch candidate portion (scratch candidate pixel) is extracted.

FIG. 7 (A) shows a scratch candidate pixel or a continuous pixel in the image GW showing the inspection object WK as a scratch candidate image KKG.

7B, the length L1 and the thickness L2 of the scratch candidate image KKG are measured. When the measured length L1 and thickness L2 of the scratch candidate image KKG are not less than the predetermined length LL1 and not less than the predetermined thickness LL2, they are detected as scratches K.

Next, an example of the configuration of the analysis unit 32 of the control unit 14 will be described.

8, the analysis unit 32 includes an image input unit 321, an image composition unit 322, a scratch candidate extraction unit 323, a threshold storage unit 324, a determination unit 325, a threshold storage unit 326, and the like.

The image input unit 321 takes in the image G from the imaging unit 13 and temporarily stores it. That is, the imaging by the imaging unit 13 is continuously performed at a predetermined time interval Δt, but the captured image G is captured together with a reference time, for example, an elapsed time from when the inspection target WK passes the reference position.

At this time, each captured image G is converted into an image corresponding to a flattened cylindrical shape. The size (Δx, Δy) of the surface area of the inspection object WK corresponding to one pixel of the image G is obtained in advance.

The size (Δx, Δy) of one pixel of the image G may be obtained, for example, by imaging a grid chart having a known size instead of the inspection object WK.

Also, since the storage capacity of the memory of the image input unit 321 is limited, only the latest N predetermined images G are stored. When the number of captured images G exceeds N, the oldest image G at that time may be discarded in order.

The image composition unit 322 synthesizes the captured image G to generate luminance images GTA and GTB.

That is, since the conveyance speed V and the time interval Δt of the inspection object WK are constant, the shift amount Sx is also constant. The N images G are overlapped by shifting in the X direction (horizontal direction) by the shift amount Sx, and two luminance images GTA and GTB connected to each other are generated.

The scratch candidate extraction unit 323 extracts scratch candidate pixels. That is, in the two luminance images GTA and GTB, the luminance value DR of each pixel is compared with the first luminance threshold value TK1 and the variation threshold value TH1 stored in the threshold value storage unit 324, and both are Pixels larger than the threshold are extracted as scratch candidate pixels.

The determination unit 325 compares the scratch candidate pixel or the scratch candidate image KKG in which the scratch candidate pixel is continuous with the length LL1 and the thickness LL2, which are threshold values stored in the threshold storage unit 326, and the threshold is used. If it is greater than the value, it is determined to be a scratch K.

If it is determined that it is a scratch K, the inspection object WK outputs a display or an alarm indicating that the inspection target WK is defective due to the scratch K. Further, if necessary, an image of the scratch K is displayed on a display surface of a display device (not shown). Further, the image of the wound K is recorded in the recording unit 34 together with the position information on the inspection object WK.

For example, the position of the center of gravity (x, y) of the detected wound K is converted into coordinates on the inspection object WK, and the position of the damage K on the inspection object WK is specified. Then, the position of the specified wound K is recorded in the memory of the recording unit 34 together with the local image and imaging time of the wound K. At that time, the local image of the wound K may be recorded as the earliest image capturing time of the related image.

Note that the coordinates (X, Y) on the inspection target WK have the origin (0, 0) as the starting point of the first image captured at the start of the inspection of the inspection target WK, and the conveyance direction of the inspection target WK. The opposite direction may be X, and the direction orthogonal thereto may be Y (see FIG. 7).

Note that a position corresponding to the center of the first image captured at the start of inspection of the inspection object WK may be set as the origin.

Also, conversion from the coordinates (x, y) of the kth image taken from the start of the inspection to the coordinates (X, Y) on the inspection object WK can be performed as follows.

X = (k · Sx + x) · Δx
Y = y · Δy
Next, the inspection procedure for the scratch K on the inspection object WK by the inspection apparatus 1 will be described with reference to the flowchart shown in FIG.

In FIG. 9, a plurality of images G are captured from the imaging unit 13 (# 11). The plurality of images G are associated with the coordinate system of the inspection object WK to generate two luminance images GTA and GTB (# 12). Based on the luminance images GTA and GTB, the scratch K is detected (# 13). At that time, for example, a scratch candidate pixel or a scratch candidate image may be first extracted, and if it is larger than a threshold value, it may be determined that it is a scratch K.

The local image and the coordinate position of the detected scratch K are displayed and recorded in the memory (# 14).

These processes are repeated until all the inspection objects WK have been inspected (# 15).

As described above, according to the inspection apparatus 1 of the present embodiment, the surface of the sheet-like inspection object WK can be easily inspected even if the surface of the surface K has a large variation in the shape of the surface. Depending on the configuration, it can be easily performed in-line without leakage.

Moreover, by bending the inspection object WK into the curved surface KM, it is possible to reduce illumination unevenness as compared with the case where the inspection object WK remains flat, and to stably detect scratches.

Further, since the curved surface KM is formed while the inspection object WK is conveyed by the main roller 21, the inspection object WK can be inspected by illuminating at various angles in time series.

In addition, since the plurality of images G are obtained by partially overlapping and imaging while conveying the inspection object WK, each part is tracked based on the amount of movement of the inspection object WK to prevent double detection. be able to. Further, since the scratch K is detected from the change based on the plurality of images G, the detection of the scratch can be performed more robustly.
[Modification]
Next, modifications and supplementary items of the inspection apparatus 1 will be described.

In the inspection apparatus 1 described above, in the process of generating the luminance image GT from the plurality of images G, the portion of the image G that has a large amount of regular reflection light from the normal portion without the scratch K of the inspection target WK. Such a portion (area) may be excluded from processing.

The reason is that even if the target is not treated, it is sufficient if the specularly reflected light from the scratch K is captured in the other part (area). Further, even if there is specular reflection light in a region not to be processed, the scratches K are often relatively shallow scratches, that is, the depressions are often shallow, and the quality of the inspection target WK is a problem. This is because there is a high possibility that it will not be.

It should be noted that an area where there is a lot of specularly reflected light from the normal part without the scratch K of the inspection object WK is not excluded from the processing target, but the area is used for detection of the scratch K by another processing method. It may be combined with the method described in.

For example, as shown in FIG. 10, for the obtained image G, an area ER <b> 1 with much regular reflection light from the normal part is excluded from the processing target. Alternatively, for such a region ER1, a portion without specular reflection light is detected, and it is assumed that it is a scratch or a candidate portion thereof. In that case, for example, when the luminance value DR of each pixel included in the region ER1 is compared with the second luminance threshold value TK2 in FIG. 8, and the luminance value DR is lower than the second luminance threshold value TK2, What is necessary is just to extract the part as a flaw or a candidate part of a flaw.

In this case, a portion where regular reflection always occurs may be set as the region ER1. In this case, the second luminance threshold value TK2 may be set to a value larger than the luminance due to irregular reflection and smaller than the luminance due to regular reflection.

When the illumination unit 12 is a line light source and a line light source longer than the width dimension of the inspection object WK, the region ER1 having a large amount of regular reflection light from the normal part without the scratch K of the inspection object WK is shown in FIG. As shown, the inspection object WK has a rectangular or linear shape over the entire width. In this case, it is easy to detect regular reflection due to the scratch K in a portion other than the region ER1.

In addition, when the illumination unit 12 is a point light source, the region ER1 having a large amount of regular reflection light from the normal portion where there is no damage K on the inspection target WK is an extremely limited portion on the inspection target WK.

Also, when the scratch K is V-shaped and extends in a straight line in the conveyance direction (that is, the X1 direction) of the inspection object WK, it is difficult to detect the damage. The reason is that it may be difficult for the imaging unit 13 to capture the regular reflected light of the scratches K extending in a straight line in the transport direction even when the inspection object WK is transported.

In that case, for example, the following may be performed.
(1) As the illuminating unit 12, a plurality of point light sources are arranged in a line in the Y direction (direction parallel to the axis of the curved surface KM), and the point light sources are controlled so as to light up quickly and sequentially. By sequentially turning on the point light source, the direction of specularly reflected light due to the scratch K changes variously, and the specularly reflected light is easily captured by the imaging unit 13.
(2) After performing the inspection with the inspection apparatus 1 described above, another curved surface KM obtained by rotating the axis of the curved surface KM is formed on the inspection object WK, and the similar inspection is performed.

Next, the method (2) will be described.

FIG. 11 is a diagram illustrating an example of an inspection apparatus 1B that performs inspection by conveying the inspection object WK so as to draw two curved surfaces.

In FIG. 11, the inspection apparatus 1B is provided with two inspection apparatuses 1BA and 1BB.

One inspection device 1BA is substantially the same as the inspection device 1 described above. That is, the main roller 21 and the

auxiliary rollers

22a and 22b transport the inspection target WK in the transport direction X1, and form a curved surface KM1 that is a cylindrical surface having an axis along the direction Y perpendicular to the transport direction X1. The curved surface KM1 is illuminated by the illumination unit 12BA, which is a line light source extending in the axial direction, and the image G is captured by the imaging unit 13BA.

In the other inspection apparatus 1BB, the main roller 21B and the auxiliary rollers 22Ba, 22Bb have axes inclined with respect to the transport direction X1. Thus, a curved surface KM2 that is a cylindrical surface having an axis inclined with respect to the transport direction X1 is formed. The curved surface KM2 is illuminated by the illumination unit 12BB which is a line light source extending in the axial direction, and the image G is captured by the imaging unit 13BB.

In this case, since the main purpose of the main roller 21B and the auxiliary rollers 22Ba and 22Bb is to maintain the shape so as to draw the curved surface KM2 with respect to the inspection object WK, their surfaces slide relative to each other. It should be possible to move.

In this case, instead of transporting the inspection object WK in the same direction X1, the conveyance direction of the inspection object WK may be changed by the main roller 21B. For example, the inspection target WK may be bent at a right angle to the depth direction of the paper with respect to the transport direction X1 in FIG. Further, the inspection object WK may be bent at a right angle so as to face the upward direction in the drawing with respect to the transport direction X1 in FIG.

Suppose that the logical sum of the scratches K detected by these two inspection devices 1BA and 1BB is the scratch K of the inspection object WK.

Thus, since the direction of the axis of the curved surface KM changes by conveying the inspection object WK in a state of being twisted in the conveyance direction, it is possible to reliably detect the scratch K that extends in a straight line. .

In any of the forms described above, since the inspection object WK is bent so as to form a convex curved surface KM, the reflected light from the surface of the inspection object WK spreads more than in the case where it is not bent. . In order to compensate for this, the imaging unit 13 may be configured by arranging a plurality of cameras vertically above the half mirror 24.

In the embodiment described above, for the two luminance images GTA and GTB, when the luminance value DR of each pixel is higher than the first luminance threshold value TK1 and higher than the variation threshold value TH1, a candidate portion of a scratch Extracted as. However, only one luminance image GTA or luminance image GTB may be generated, and a scratch candidate portion may be extracted using only the generated one luminance image GTA or luminance image GTB.

In the embodiment described above, the case where the curved surface KM is a part of a cylindrical surface has been described, but a curved surface other than the cylindrical surface, for example, the cross section may be elliptical, parabolic, or the like.

In addition, the transport unit 11, the illumination unit 12, the imaging unit 13, the control unit 14, the analysis unit 32, or the configuration, the structure, the circuit, the shape, the number, the arrangement, and the like of each unit or the entire inspection apparatus 1 are the gist of the present invention. Can be changed accordingly.

Claims

A method for inspecting scratches on the surface of an inspection object having flexibility,
Transporting the inspection object while deforming it so that the surface of the inspection object draws a curved surface;
Illuminating the surface of the inspection object from the convex side of the curved surface;
Imaging the illuminated surface of the inspection object at predetermined time intervals using imaging means;
Analyzing the image obtained by the imaging means by analyzing means to detect a scratch on the surface of the inspection object;
A method for inspecting a scratch on the surface of an inspection object having flexibility.
The time interval is set so that the same part of the surface of the inspection object is imaged multiple times, the imaging means,
The analysis means detects a scratch on the surface of the inspection object based on the state of the brightness value of the plurality of images obtained for the same portion of the surface of the inspection object.
A method for inspecting a scratch on a surface of a flexible inspection object according to claim 1.
An apparatus for inspecting scratches on the surface of an inspection object having flexibility,
Transport means for transporting the inspection object while deforming it so that the surface of the inspection object draws a curved surface;
Illuminating means for illuminating the surface of the inspection object from the convex side of the curved surface;
Imaging means for imaging the surface of the illuminated inspection object at predetermined time intervals;
Analyzing means for analyzing the image obtained by the imaging means and detecting a scratch on the surface of the inspection object;
A device for inspecting scratches on the surface of an inspection object having flexibility.
The time interval is set so that the same part of the surface of the inspection object is imaged multiple times, the imaging means,
The analysis means detects a scratch on the surface of the inspection object based on the state of the brightness value of the plurality of images obtained for the same portion of the surface of the inspection object.
The apparatus which test | inspects the damage | wound of the surface of the flexible test | inspection target object of Claim 3.
When the surface of the object to be inspected is a mirror surface, the analyzing means is any one of the luminance values of a plurality of images obtained for the same part of the surface of the object to be inspected with respect to an image without normal reflection by a normal surface. When is higher than the first luminance threshold, the part is extracted as a flaw or a candidate part of a flaw,
The apparatus which test | inspects the damage | wound of the surface of the inspection object which has flexibility of Claim 4.
When the surface of the object to be inspected is a mirror surface, the analyzing unit is configured to determine which of the luminance values of the plurality of images obtained for the same part of the surface of the object to be inspected is an image that is regularly reflected by a normal surface When is lower than the second luminance threshold, the portion is extracted as a scratch or a candidate portion of a scratch,
The apparatus which test | inspects the damage | wound of the surface of the inspection object which has flexibility of Claim 5.
The analysis means includes means for calculating the degree of fluctuation of the luminance value of a plurality of images obtained for the same portion of the surface of the inspection object, and the degree of fluctuation of the calculated luminance value is based on a fluctuation threshold value. If it is too high, that part is considered as a wound or a candidate part of a wound,
The apparatus which test | inspects the damage | wound of the surface of the inspection target object which has flexibility of Claim 5 or 6.
The analysis means detects the scratch as a scratch when the extracted candidate portion of the scratch has a predetermined length and a predetermined thickness.
The apparatus which test | inspects the damage | wound of the surface of the test | inspection object which has flexibility in any one of Claim 5 thru | or 7.
Recording means for recording the wound detected by the analysis means in association with positional information on the inspection object;
The apparatus which test | inspects the damage | wound of the surface of the test | inspection object which has flexibility in any one of Claim 5 thru | or 8.
The transport means transports the inspection object so that the curved surface becomes a part of a cylindrical surface having an axis perpendicular to the transport direction of the inspection object.
The apparatus which test | inspects the damage | wound of the surface of the inspection object which has flexibility in any one of Claim 3 thru | or 9.
The illumination means includes a plurality of point light sources arranged in a direction parallel to the axis of the cylindrical surface,
The plurality of point light sources are controlled to be turned on sequentially.
The apparatus which test | inspects the damage | wound of the surface of the inspection target object which has the flexibility of Claim 10.
The conveying means conveys the inspection object so that the curved surface becomes a part of a cylindrical surface having an axis inclined with respect to the conveying direction of the inspection object;
The apparatus which test | inspects the damage | wound of the surface of the inspection target object which has flexibility in any one of Claim 3 thru | or 9.
The conveying means has an axis whose other curved surface is inclined with respect to the conveyance direction of the inspection object so that one curved surface becomes a part of a cylindrical surface having an axis perpendicular to the conveyance direction of the inspection object. Convey the inspection object so as to draw two curved surfaces to become a part of the cylindrical surface,
The apparatus which test | inspects the damage | wound of the surface of the inspection target object which has flexibility in any one of Claim 3 thru | or 9.