JP2015049091A - Rolled film concave-convex defect inspection device and inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect inspection device configured to accurately detect a surface defect of a rolled film completely with a simple and inexpensive configuration, and an inspection method.SOLUTION: A rolled film concave-convex defect inspection device includes: an illumination unit 2 for irradiating a surface 1 of a rolled film with slit light in a width direction of the rolled film; an imaging unit 4 which detects an image L1 of a bright line, on the basis of reflection light from the bright line L generated on the surface of the rolled film; and image processing units 7, 8 for detecting a distortion value of the bright line image L1 detected by the imaging unit 4, and performing concave-convex determination of the surface 1 of the rolled film, on the basis of the distortion value.

Description

  The present invention relates to an inspection apparatus and inspection method for surface irregularities of a roll film.

  The surface of the rolled-up film is not expressed in the film manufacturing process, but after winding the manufactured film into a roll, winding due to aging occurs, and irregularities on the surface of the film are found. May develop. Since this irregularity defect has a problem such as causing printing omission during printing, for example, an irregularity inspection of the surface of the roll film is necessary.

In many cases, the surface irregularity defect of the roll film is visually inspected by humans, but there is a risk of missing a defect because of human inspection. Therefore, an inspection apparatus and an inspection method using an optical method have been proposed in order to further improve detection accuracy.
In Patent Document 1, a specular reflection image of a reference surface having a predetermined periodic light / dark pattern (stripe pattern) on an inspection surface of an inspection object is picked up by an image pickup means, and the pattern shape of the obtained specular reflection image is obtained. A technique for detecting streaky irregularities on the surface to be inspected based on the distortion of the surface is disclosed.

Patent Document 2 also discloses a light irradiating means having a light emitting portion F having a predetermined shape for irradiating light to an object to be inspected that has a cylindrical side surface, has specular reflectivity, and has a curvature and / or a position of the surface to be inspected that changes with time. An imaging means for imaging an object to be inspected, and a surface inspection apparatus for inspecting the surface of the object to be inspected based on the captured image taken are disclosed.
Moreover, in patent document 3, when making parallel light through a lens from a light projector and irradiating this parallel light on the surface of a roll-shaped film along the "circumferential direction", it is light by the convex defect on the surface of a roll-shaped film. A defect detection method is proposed in which a shadow along the shape of a convex defect is detected by a light receiver, and an unevenness is determined by an image processing unit. In order to avoid erroneously detecting the step portion at the winding end portion of the roll film as irregularities, at least three sets of light projectors and light receivers are arranged in the circumferential direction, and at least two sets of them have the same roll width. If the position is determined to be convex, it is determined as a defect.

JP 2005-337857 A JP 2007-071562 A JP 2001-41898 A

  In Patent Document 1, a reference surface having a predetermined periodic light / dark pattern is prepared, and a specular reflection image picked up by the image pickup means is analyzed. In order to analyze the distortion of the periodic light / dark pattern, A portion having a certain two-dimensional area of a light and dark pattern must be photographed and recorded by an image pickup means (see FIG. 2B of the same document). Patent Document 2 also adopts a periodic bright / dark pattern for the light emitting part F, and images a portion having this two-dimensional area by an imaging means (see FIG. 21 of the same document).

  For this reason, in both Patent Documents 1 and 2, it is impossible to sufficiently squeeze the light emitted from the periodic light / dark pattern with a one-dimensional slit, and the light emitted from the periodic light / dark pattern undergoes secondary reflection and tertiary reflection. This results in stray light and entering the imaging means, which hinders the accuracy of inspection. Moreover, it is necessary to prepare software for performing a complicated stripe pattern analysis on the image pickup means side, which increases the cost due to software development costs.

  In the technique of Patent Document 3, the inspection object defect is a winding hump in which the roll-shaped film is continuously developed over the entire circumference in the circumferential direction. For this reason, while the roll-shaped film is stationary, the parallel light line sensor is moved in the width direction to detect defects in the winding bumps (or conversely, the parallel light line sensor is fixed and the roll-shaped film is stationary. Is moved in the width direction). In paragraph [0091] of Patent Document 3, there is a description that “the roll film may be rotated.” However, by simply rotating the roll film while the parallel light line sensor is stationary, The inspection cannot be continuously performed over the entire width of the roll, and it is difficult to deal with uneven defects that appear once in the width direction of the roll film.

Moreover, in the technique of patent document 3, in the defect of the shape long dented in the width direction of the roll-shaped film which is easy to generate | occur | produce in one shot, since the light is irradiated to the circumferential direction of a roll-shaped film, a difference with a normal part has a difference. There is a risk of detection failure.
Therefore, an object of the present invention is to provide a defect inspection apparatus and inspection method that can detect defects on the surface of a roll-shaped film with high accuracy with a simple and inexpensive configuration.

In view of the above circumstances, as a result of the study by the present inventors, a defect having a shape that is long and recessed in the width direction is accurately detected by performing a concavo-convex inspection based on the reflected light of a single bright line appearing on the roll film. In particular, the present invention has been completed.
The apparatus for inspecting unevenness of a roll-shaped film of the present invention has an illumination unit that irradiates the surface of a roll-shaped film with slit-shaped light that is elongated in the width direction of the roll-shaped film, and one that is expressed on the surface of the roll-shaped film. An image capturing unit that detects an image of the bright line based on reflected light from the bright line, and a distortion value of the bright line image detected by the image capturing unit is detected, and surface unevenness determination of the roll film is performed based on the distortion value. And an image processing unit to perform.

It is preferable that the illumination unit includes a slit plate having one elongated light-transmitting groove extending in the width direction of the roll film.
Specifically, the image processing unit performs surface unevenness determination by calculating a displacement amount from a reference line of the bright line image and a width of the displaced portion.
Preferably, the photographing unit is a device that photographs using an area sensor.

Moreover, the defect inspection apparatus of this invention WHEREIN: It is preferable that the said image sensor is arrange | positioned in the position which detects the regular reflection component of the reflected light in the surface of a roll-shaped film.
Moreover, in the defect inspection apparatus of this invention, it is preferable that it can test | inspect continuously in the outer peripheral direction of a roll-shaped film.
Moreover, the uneven | corrugated defect inspection method of the roll-shaped film of this invention is the process of irradiating the surface of a roll-shaped film with the slit-shaped light long and thin in the width direction of a roll-shaped film, and 1 expressed on the surface of the said roll-shaped film. A step of detecting an image of the bright line by the photographing unit based on the reflected light from the bright line of the book, a distortion value of the bright line image detected by the photographing unit, and a roll film based on the distortion value And a step of performing surface irregularity determination.

  According to the present invention, a long slit-like bright line irradiated on the surface of the roll film is photographed, the distortion value of the bright line image is detected, and the surface unevenness determination of the roll film is performed based on the distortion value. Thereby, the defect inspection apparatus and inspection method which detect the convex defect of the surface of a roll-shaped film and the concave defect long dented in the width direction with high precision are realizable.

(A) is a schematic perspective view which shows the basic composition of the uneven | corrugated defect inspection apparatus of the roll-shaped film which concerns on embodiment of this invention. (B) is a sectional side view of a concavo-convex defect inspection apparatus. (A) is an optical path figure of the incident light to a roll-shaped film. (B) is an optical path figure of the emitted light from a roll-shaped film. It is an optical path figure which shows the other example of the incident light to a roll-shaped film. It is a figure which shows the principal part of the screen which projected the image of the bright line L formed on the surface of a roll-shaped film on the display. It is the schematic which shows the concave defect of the surface of a roll-shaped film. It is the schematic which shows the convex defect of the surface of a roll-shaped film. It is the schematic which shows the distortion pattern of the bright line at the time of concave defect generation | occurrence | production.

Embodiments of the present invention will be described below with reference to the accompanying drawings. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
FIG. 1A is a schematic perspective view showing a basic configuration of a roll-shaped film unevenness inspection apparatus according to an embodiment of the present invention, and FIG. 1B is a side sectional view.

A film that is an object to be inspected is wound around the core tube 6 in a roll shape.
The surface 1 of the roll film is irradiated with one elongated light (referred to as slit light) that is spread one-dimensionally using the inspection illumination unit 2, and the reflected light 5 of the slit light on the surface 1 of the roll film is applied. It is detected by the imaging unit 4.
The inspection illumination unit 2 has a bright line L that extends in a one-dimensional manner on the surface 1 of the roll film in the width direction of the film, that is, in the direction of the center line of the core tube 6 (referred to as the “z direction”; see FIG. 1A). The configuration includes a light source portion 2a for irradiating light, a slit plate 2b having a light-transmitting groove formed in a one-dimensional shape, and a lens array 2c. The roll film can be rotated around the core tube 6.

  The inspection illumination unit 2 and the roll film may be installed in a state where both are fixed so that they cannot move along the z direction, and either or both of them are installed so as to be movable along the z direction. May be. However, at least during measurement, both are locked so that they cannot move relative to each other in the z direction. That is, during the measurement, the relative positions of the inspection illumination unit 2 and the roll film along the z direction are kept unchanged. During the measurement, the roll film may be rotated around the core tube 6 as appropriate.

  The light source unit 2a is not limited as long as it is a light emitter that emits light 3 having a predetermined wavelength. The shape may be a point light source, a planar light source, or a linear light source, but is preferably a linear light source along the z direction. Examples of the linear light source include a straight tube fluorescent lamp, a straight tube cold cathode tube, and a number of LED elements arranged in the z direction. The wavelength of the light source may be monochromatic light or light having a wavelength distribution in a certain range. In the latter case, white light including light in the visible light range (400-700 nm) may be used.

  The slit plate 2b has one elongated light transmission groove extending in the z direction. The arrangement position of the slit plate 2b is between the light source unit 2a and the lens array 2b as shown in FIG. The role of the slit plate 2b is to limit the light emitted from the light source unit 2a with a long and thin light-transmitting groove, thereby creating an image (bright line L) of the long and narrow light source. Further, it also has a role of blocking stray light that is reflected by each member in the room and directed toward the inspection object.

  The lens array 2c is a condensing element used to obtain a sharp bright line L, and includes a selfoc lens (selfock is a trademark or a registered trademark), a cylindrical lens, and the like arranged along the z direction. In order to form the image of the slit plate 2b on the surface 1 of the roll film, the lens is arranged such that one focal position of the lens array 2c is the slit plate 2b and the other focal position is the surface 1 of the roll film. The position of the array 2c may be determined.

In addition, even if the lens array 2c is not installed, the bright line L having the resolution necessary for the inspection may be obtained by using only the slit plate 2b. Therefore, the lens array 2c may be an optional component. it can.
An image sensor can be used for the photographing unit 4. For example, an area sensor camera is preferable. A computer 7 that processes an image signal detected by the photographing unit 4 is connected to the photographing unit 4.

2A is an optical path diagram of incident light from the concavo-convex defect inspection apparatus to the roll film, and FIG. 2B is an optical path diagram of emitted light from the roll film. In FIG. 2B, the direction in which the emitted light travels is y, and the direction perpendicular to the plane formed by the z direction and the y direction is x (right-handed coordinate system).
As shown in FIG. 2A, the light 3 emitted from the light source unit 2a passes through the light transmitting groove of the slit plate 2b, is condensed through the lens array 2b, and is applied to the surface 1 of the roll film. An image is formed as one linear bright line L extending in the z direction. The light reflected from the surface 1 of the roll film is received by the image sensor 4 as shown in FIG. 2B and forms an image in the image sensor 4 a built in the image sensor 4. The image sensor 4a extends two-dimensionally in the z direction and the x direction. Thereby, the image sensor 4a can detect a change in luminance in the z direction of the bright line L and also detect a change in luminance in the x direction.

  FIG. 3 is an optical path diagram when the lens array 2b is omitted. The light from the light source part 2a passes through the light transmitting groove of the slit plate 2b and forms an image on the surface 1 of the roll film as one linear bright line L extending in the z direction. In this case, since there is no lens, the sharpness of the bright line L is lower than that in the case of FIG. 2B, but it is sufficiently practical to acquire a defect determination parameter (described later).

  In addition, the incident angle of light on the surface 1 of the roll film and the emission angle to the image sensor 4 may be in the same regular reflection relationship or in an unequal relationship. When the surface of the roll film is smooth and only specular reflection light is strong, it is preferable to use specular reflection. When the surface of the roll film is rough and diffused light increases, it is possible to detect light other than specular reflection light. Can be targeted.

  The computer 7 receives the image signal detected by the photographing unit 4, performs image processing, and displays it on the display screen. The shape of the bright line L is displayed on the display screen. Although the content of the image processing is not limited, for example, edge sharpening processing may be performed to clearly display the shape of the bright line L, and binarization processing may be performed to reduce background noise.

  FIG. 4 is a diagram showing a screen on which the bright lines L formed on the surface of the roll film are projected on the display 8. The bright line image of the bright line L projected on the screen is indicated by “L1”. The direction of the horizontal line on the screen corresponds to the z direction, and the direction of the vertical line corresponds to the x direction (see FIG. 2B). A value indicating the height of the bright line image L1 corresponding to z is assumed to be x. That is, the coordinate value of the bright line image L1 is represented by (z, x).

A straight line (referred to as a reference line) indicating the average height of the bright line image L1 is indicated by “9”. The position of the reference line 9 can be obtained by processing with the least square method calculation software using the bright line image L1 as a calculation target curve. Also, the value of the height x of the bright line image L1 can be obtained by integrating in the z direction from the end z1 to the end z2 of the screen and dividing by (z2-z1).
The height in the x direction of the bright line image L1 with respect to the reference line 9 is referred to as “displacement from the reference line” or simply “displacement” of the bright line image L1. The amount of displacement is represented by “d”. When the surface state of the roll film is flat, the amount of displacement is zero in principle. However, when the surface state of the roll film is uneven, the shape of the bright line image L1 is distorted and displaced from the reference line 9. Defect determination is performed based on the amount of displacement d and the width w (referred to as defect width) w of the portion where the displacement occurs.

  A method for obtaining the defect width w will be described. A defect determination threshold th is set, and defect width determination lines 10 separated by the defect determination threshold th are provided above and below the reference line 9. A portion exceeding the defect width determination line 10 of the bright line image L1 is defined as a “defect region” (hatched portion in FIG. 4), and a width in the z direction of the defect region is defined as a defect width w. That is, the defect width w is the width of the bright line image L1 having a displacement of the defect determination threshold value th. In the defect area, the maximum value of the displacement amount d is referred to as a displacement amount dmax. These defect width w and displacement dmax are called defect determination parameters. When one end of the defect width w extends to the end of the roll film, the defect width w may be calculated by regarding the end of the roll film as one end of the defect width w.

In the defect inspection of the present invention, a defect inspection of the roll film is performed based on the defect determination parameters of the bright line image L1, that is, the displacement amount dmax and the defect width w.
Defects occurring on the surface 1 of the roll film include a width-direction concave defect 12 and a convex defect 14. As shown in FIG. 5, the widthwise concave defect 12 is a concave defect that is long in the width direction, that is, the z direction. In addition, as shown in FIG. 6, the convex defect is a convex shape that appears in a single line in the circumferential direction of the roll (the direction in which the roll is wound and is perpendicular to z), or that appears independently and discretely. It is a defect.

  Unlike the normal part, the defect surface has irregularities on the surface of the film. Therefore, the bright line image L1 is displaced from the straight line due to the irregularity shape at the position where the widthwise concave defect 12 or the convex defect 14 is generated. However, it is possible to inspect the unevenness of the film surface by detecting the distortion or the distortion.

<Example 1>
As shown in FIG. 7, the surface roughness of the film was inspected using an acrylic roll film (thickness: 50 to 150 μm) in which the widthwise concave defects 12 were intermittently generated in the circumferential direction.
A high-frequency fluorescent lamp illumination having a length of 2600 mm, which is long in the width direction (z direction) of the roll film, was used as a light source part of the unevenness inspection apparatus. A slit plate having a long translucent groove with a width of 3 mm was disposed between the film and the illumination to limit the light reaching the roll film (as in the configuration of FIG. 3). The line width of the bright line image L1 was about 5 mm.

  An area to be inspected on the roll film was irradiated, the core tube was rotated, and an image was taken once every 1 mm in the circumferential direction using an area sensor camera with 5 million pixels. Note that there is a slight step at the film end (film break) of the roll-shaped film, and when this portion is inspected, the bright line may be distorted and erroneous detection may occur. Therefore, in order to avoid this part, the core tube is stopped before making one rotation (angle 0 to 360 degrees). That is, the inspection is performed by rotating the core tube from 0 degree to 330 degrees. A total of 1005 bright line images L1 were obtained as samples.

As a result of the inspection under the above-described conditions, in the bright line image L1 corresponding to the defect portion in the inspection target region, distortion of the bright line image L1 is detected, the displacement dmax from the reference line is 1.9 mm, and the defect width w was 58.9 mm. The product of the displacement dmax and the defect width w, that is, the area w · dmax is 112 mm ² . Since such a large value was expressed, it was confirmed that the defect could be determined.

<Example 2>
Using a roll-shaped film in which convex defects having a maximum height difference of 0.5 to 1 mm and a diameter of 0.5 to 1 mm are scattered on the surface of the film, the surface roughness of the film was inspected. The apparatus configurations such as the inspection illumination unit and the imaging unit used are the same as those in the first embodiment.
As a result of the inspection under the conditions of Example 2, distortion of the bright line image L1 of the slit light is detected at the convex defect portion, the displacement dmax from the reference line is 0.8 mm, and the defect width w is 1.7 mm. Met. The product of the displacement dmax and the defect width w, that is, the area w · dmax is 1.36 mm ² . Since such a value was expressed, it was confirmed that the defect could be determined also in Example 2.

  In addition, in order to determine a defect using the area w · dmax of such a defect portion, it is necessary to set an area threshold (defect determination threshold), but it has a film having no defect and various uneven defects. It is considered that the defect determination threshold may be determined empirically so that the film can be inspected many times and a highly accurate defect determination can be performed.

DESCRIPTION OF SYMBOLS 1 ... Roll-shaped film surface, 2 ... Inspection illumination part, 2a ... Light source part, 2b ... Slit board, 2c ... Lens array, 3 ... Slit board, 4 ... Imaging | photography part, 6 ... Core tube, 7 ... Computer, 8 ... Display, 9 ... reference line, 10 ... defect width determination line, 12 ... width direction concave defect, 14 ... convex defect, L ... luminescent line, L1 ... luminescent line image

Claims (11)

An illumination unit that irradiates slit-shaped light that is elongated in the width direction of the roll film on the surface of the roll film,
An imaging unit for detecting an image of the bright line based on reflected light from one bright line expressed on the surface of the roll film;
An apparatus for inspecting a concavo-convex defect of a roll-shaped film, comprising: an image processing unit that detects a distortion value of a bright line image detected by the photographing unit and determines surface irregularities of the roll-shaped film based on the distortion value.   2. The defect inspection apparatus according to claim 1, wherein the illumination unit includes a slit plate having one elongated light transmission groove extending in a width direction of the roll film.   The defect inspection apparatus according to claim 1, wherein the image processing unit calculates a displacement amount from a reference line of the bright line image and a width of the displaced portion, and performs surface unevenness determination.   The defect inspection apparatus as described in any one of Claims 1-3 with which the said imaging | photography part image | photographs using an area sensor.   The defect inspection apparatus as described in any one of Claims 1-4 arrange | positioned in the position where the said imaging | photography part detects the regular reflection component of the reflected light in the surface of the said roll-shaped film.   The defect inspection apparatus as described in any one of Claims 1-5 which can test | inspect continuously in the outer peripheral direction of the said roll-shaped film. Irradiating the surface of the roll film with slit-like light elongated in the width direction of the roll film; and
A step of detecting an image of the bright line by the photographing unit based on reflected light from one bright line expressed on the surface of the roll-shaped film;
Detecting a distortion value of the bright line image detected by the photographing unit, and determining a surface irregularity of the roll film based on the distortion value.   The defect inspection method according to claim 7, wherein in the step of irradiating the light, the light is irradiated through one elongated light-transmitting groove extending in the width direction of the roll film.   The defect inspection method according to claim 7, wherein the inspection is performed while the roll film is rotating.   10. The surface unevenness determination according to claim 7, wherein the surface unevenness determination is performed by calculating a displacement amount from a reference line of the bright line image and a width of the displaced portion in the step of performing the surface unevenness determination. Defect inspection method.   The defect inspection method according to any one of claims 7 to 10, wherein in the step of detecting the image, a regular reflection component of reflected light on a surface of the roll film is detected.