JPH07311160A - Method and device for preforming visual inspection - Google Patents

Abstract

PURPOSE:To only detect a defect of a transparent film even when the film is coated with a surface protective film so as to automate the visual inspection of the film by taking the picture of the transparent film of reflected ultraviolet rays and transmitted visible light rays by irradiating the sheet with ultraviolet rays and visible light rays and comparing and analyzing both pictures by processing the pictures. CONSTITUTION:A transparent film 1 is irradiated with visible light rays from a visible light source 4 and the image of the light transmitted through the film 1 is taken with a CCD camera 7 through a visible light transmitting filter 10 and sent to a picture processing section 15. On the other hand, the upper surface of the film 1 coated with a surface protective film 2 is irradiated with ultraviolet rays from an ultraviolet-ray source 5 and the image of the reflected light from the upper surface is taken with another CCD camera 8 after the reflected light is reflected by an ultraviolet-ray reflecting mirror 11 and passed through an ultraviolet-ray transmitting filter 13 and sent to the processing section 15. Similarly, the picture of the lower surface of the film 1 coated with another protective film 3 is taken with a third CCD camera 9 and sent to the processing section 15. The section 15 automatically detects the defect of the film 1 only by binarizing the picture signals and comparing the pictures taken with the cameras 7, 8, and 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent sheet, in particular, a visual inspection method capable of detecting air bubbles or foreign matter existing or mixed in a polarizing film having a surface protective film attached thereto, and an inspection apparatus used for the method. It is about.

[0002]

2. Description of the Related Art As a general method for producing a film,
There are casting method, melt extrusion method, drawing method, calendar method, cutting method, dispersion method, etc.,
If air bubbles or foreign substances are mixed in the produced film, it will result in a defective product. Therefore, an appearance inspection step for detecting such a defect in the film is required. In particular, in the case of a transparent film used for optical applications such as a polarizing film, the above-mentioned defect becomes a fatal defect of the product, so the inspection process is an extremely important process.

Usually, a polarizing film has a multi-layered structure in which a reinforcing film is laminated on both sides of a film-shaped polarizer that produces a polarizing effect, and is widely used in liquid crystal display devices and the like. In addition, a surface protective film is generally attached to the surface of the polarizing film to protect it from scratches during transportation and handling.

When the above-mentioned appearance inspection is performed on such a polarizing film, it must be carried out in a state where the surface protective film is laminated, but this surface protective film is peeled and removed at the time of use. Therefore, it is necessary to detect only the defect of the polarizing film without detecting the defect of the surface protection film at the time of the appearance inspection, but such inspection is extremely difficult.

From the above circumstances, it is difficult to automate the visual inspection of the polarizing film to which the surface protective film is attached,
Generally, visual inspection is performed by an inspector.

[0006]

However, the visual inspection by the current inspectors requires a skilled technique and it is difficult to unify the inspection levels among the inspectors. There is also a problem that it becomes difficult to make a visual determination when the defect size becomes small.

Further, when the surface of the film to be inspected is irradiated with visible light, defects in the surface protective film and the polarizing film are detected with similar signal intensities. Only was difficult to detect.

Therefore, according to the present invention, it is possible to automatically perform a visual inspection of a transparent film such as a polarizing film, and even if it is a structure covered with a surface protective film,
An object of the present invention is to provide a visual inspection method capable of detecting only defects in a polarizing film that is an inspection object.

It is another object of the present invention to provide an inspection device used in the above appearance inspection method.

[0010]

Therefore, the present inventors have used ultraviolet rays and visible rays in combination as the rays used for inspection, and image the reflected ultraviolet rays and the transmitted visible rays,
It was found that an inspection method and an inspection apparatus that can achieve the above-mentioned object can be obtained by comparing and judging these, and the present invention has been completed.

That is, according to the present invention, an image obtained by irradiating an ultraviolet ray on the surface of a transparent sheet and picked up an ultraviolet ray reflected by the transparent sheet, and an image obtained by picking up a visible ray on the surface of the transparent sheet by irradiating the visible ray and transmitting the visible ray, The present invention provides a visual inspection method characterized by comparative analysis by image processing.

Further, according to the present invention, an ultraviolet ray irradiating means for irradiating a transparent sheet as an inspected object with an ultraviolet ray, an ultraviolet ray image pickup means for picking up an image of the reflected ultraviolet ray, and a visible ray for a transparent sheet as an inspected object. And a visible light imaging means for imaging the transmitted visible light, and an image processing part for comparing and judging the image signals obtained by the ultraviolet light imaging means and the visible light imaging means. An inspection device is provided.

[0013]

Function: A film to be inspected having a surface protective film attached to the surface of a transparent film such as a polarizing film having a function of absorbing ultraviolet light is first irradiated with visible light to photograph transmitted light to An image containing defects in the film and defects in the surface protective film is obtained.

Next, an ultraviolet ray is irradiated and the reflected light is photographed to obtain an image of a defect only on the surface protective film attached to the irradiation side. When surface protective films are attached to both surfaces of the polarizing film, irradiation of ultraviolet rays is similarly performed from the other surface side, and the reflected light is also photographed.

Finally, a comparison judgment is made between an image containing defects of both the polarizing film and the surface protective film obtained from visible light transmitted, and an image containing defects of only the surface protective film obtained from ultraviolet ray reflected light. By doing so, it is possible to detect only defects in the polarizing film.

[0016]

Embodiments of the present invention will be specifically described below with reference to the drawings. However, the present invention is not limited to these and various applications can be made without departing from the technical idea of the present invention.
Deformation is possible.

FIG. 1 is a schematic diagram of a configuration showing an embodiment of the appearance inspection method and inspection apparatus of the present invention.

In FIG. 1, as the inspection light source as the light beam irradiation means, for example, a visible light source 4 such as a high frequency fluorescent lamp and ultraviolet light sources 5 and 6 such as a high frequency ultraviolet fluorescent lamp can be used.

Visible light from the visible light source 4 is applied to the polarizing film 1 to which the surface protective films 2 and 3 are attached,
The transmitted light is imaged by the CCD camera 7 as an image pickup means through the visible light transmission filter 10, and the image signal from the CCD camera 7 is input to the image processing unit 15.

On the other hand, an ultraviolet ray from the ultraviolet light source 5 is applied to one side (upper side in the figure) of the polarizing film 1 to which the surface protective film 2 is attached, and the reflected light is reflected by the ultraviolet ray reflecting mirror 11 to emit the ultraviolet ray. An image is taken by the CCD camera 8 as an imaging means through the transmission filter 13, and the image signal from the CCD camera 8 is input to the image processing unit 15.

Similarly, the ultraviolet ray of the ultraviolet ray 6 is applied to the other surface (the lower side in the figure) of the polarizing film 1 to which the surface protection film 3 is attached, and the reflected light is reflected by the ultraviolet ray reflecting mirror 12. An image is captured by the CCD camera 9 as an image capturing unit through the ultraviolet ray transmitting filter 14, and the image signal from the CCD camera 9 is input to the image processing unit 15.

The image signals input from the CCD cameras 7, 8 and 9 to the image processing section 15 are each subjected to threshold value processing to obtain a binary image, and the respective images are compared, whereby the polarizing film 1 is processed. Only inspect for defects.

FIG. 2 shows the CCD camera 7 in FIG.
8A and 8B are a binary image obtained by imaging and a binary image obtained by image processing.

FIG. 2A is a binary image obtained by imaging the transmitted light obtained by irradiating the visible light source 4 and performing threshold processing. In this image, defects of the polarizing film 1 and defects of the surface protective films 2 and 3 attached to the surface of the polarizing film 1 are detected.

FIG. 2B is a binary image obtained by imaging the reflected light obtained by irradiating the ultraviolet light source 5 and performing threshold processing. In this image, the defect of only the surface protection film 2 attached to one surface (upper side in the drawing) of the polarizing film 1 is detected, and the defect of the polarizing film 1 is not detected.

FIG. 2C is a binary image obtained by imaging the reflected light obtained by irradiating the ultraviolet light source 6 and performing threshold processing. In this image, the defect of only the surface protective film 3 attached to one surface (lower side in the figure) of the polarizing film 1 is detected, and the defect of the polarizing film 1 is not detected.

FIG. 2D is an image obtained by comparing the three binary images of FIGS. 2A to 2C, and FIG.
By subtracting the images of FIGS. 2B and 2C from the image of FIG. 2A, the defects of the surface protective films 2 and 3 attached to the surface of the polarizing film 1 are removed, and the defects of the polarizing film 1 are removed. Only detected.

The transparent film as an object to be inspected in the present invention is not limited to the above-mentioned polarizing film, and includes a film that transmits visible light and does not transmit ultraviolet light, and has a light transmittance in the visible light band of about 20% or more. Any of the above can be used for the inspection of the present invention. Further, it goes without saying that the appearance inspection method of the present invention can be applied even if it is not a covering structure in which a surface protective film or the like is attached to the transparent film.

[0029]

As described above, according to the inspection method and the inspection apparatus of the present invention, the appearance inspection of the transparent film having the surface covered with the protective film or the like can be inspected without peeling and removing the protective film. It can be inspected without being affected by the poor appearance. Therefore, in place of the conventional visual inspection by an inspector, the mechanization and automation of the inspection process can be facilitated, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a configuration showing an embodiment of an appearance inspection method and an inspection apparatus of the present invention.

2 (a) to 2 (c) are CCs in FIG.
Binary image obtained by imaging with D cameras 7, 8 and 9, FIG.
(D) is a binary image obtained by comparing these images.

[Explanation of symbols]

 1 Polarizing Film 2, 3 Surface Protection Film 4 Visible Light Irradiation Means (Visible Light Source) 5, 6 Ultraviolet Light Irradiation Means (Ultraviolet Light Source) 7, 8, 9 Imaging Means (CCD Camera) 10 Visible Light Transmission Filters 11, 12 Ultraviolet Light Reflector 13, 14 UV ray transmission filter 15 Image processing unit

Claims (4)

[Claims] 1. An image obtained by irradiating an ultraviolet ray on the surface of a transparent sheet with an image of an ultraviolet ray reflected and an image obtained by irradiating a visible ray on the surface of the transparent sheet with a visible ray transmitted through the image processing. A visual inspection method characterized by comparative analysis. 2. The appearance inspection method according to claim 1, wherein the transparent sheet is a polarizing film. 3. The appearance inspection method according to claim 1, wherein the transparent sheet is a covering structure having a protective film attached to the surface thereof. 4. An ultraviolet ray irradiating means for irradiating a transparent sheet as an inspected object with an ultraviolet ray, an ultraviolet ray imaging means for picking up an image of a reflected ultraviolet ray, and a visible ray for irradiating a transparent sheet as an inspected object. An inspection apparatus comprising: a visible light irradiating means, a visible light imaging means for imaging a transmitted visible light, and an ultraviolet ray imaging means and an image processing section for comparing and judging an image signal obtained by the visible light imaging means.