JP3339416B2 - Quality inspection equipment using epi-illumination - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a quality inspection apparatus for judging the presence or absence of surface flaws on printed sheets or films, foreign substances, and the like.

[0002]

2. Description of the Related Art Conventionally, there has been known a quality inspection apparatus which irradiates an inspection surface of an inspection object with light and determines the quality of the inspection surface based on a light intensity distribution of a reflected image. This type of quality inspection apparatus is capable of printing errors on a printing surface such as a sheet-fed printed material, for example, lack of shading of a printed portion, a pinhole of a printed portion,
It is possible to inspect the presence or absence of foreign matter such as hair, and to inspect the film surface for defects such as scratches and dirt.

FIG. 7 shows a schematic configuration of a conventional example of such a quality inspection device 40. According to FIG. 7, the sheet 41 to be inspected is conveyed in the direction indicated by the arrow 43 while the upper and lower surfaces are pinched by a number of conveying rollers 42a,. Have been. In order to inspect the surface state of the sheet 41, it is necessary to irradiate inspection light to the sheet surface through the gap 44 between the transport rollers. Therefore, the quality inspection device 40 includes a light source 45, a half mirror 47 for vertically emitting light 46 emitted from the light source 45, and an imaging camera 48 for capturing a surface image of the sheet 41.
And determination means 49 for determining the surface state based on the light intensity distribution of the surface image. The half mirror 47 is used to convey the sheet 41 (width in the depth direction of the drawing).
In order to provide the reflected light 50 of the linear region over the imaging camera 48, the shape must be a line shape corresponding to the linear region. Therefore, the imaging camera 48
In order to image the linear area,
(Charge-coupled devices) are often used as line sensors. In addition, as a specific example of the sheet 41, a sheet-fed printing paper having a thickness of about 0.2 to 1.0 mm is exemplified.

Hereinafter, an inspection method using the conventional quality inspection apparatus 40 will be briefly described. First, the outgoing light 4 of the light source 45
6 is reflected by the half mirror 47 inclined at a predetermined angle, passes through the gap 44 between the conveying rollers, and
4 falls vertically onto the inspection surface of the sheet 41 underneath. The reflected light 50 on the inspection surface passes through the gap 44 and the half mirror 47, is received by the imaging camera 48, and gives a surface image of the inspection surface. Next, the image data of the picked-up surface image is transferred to the judging means 49, and is processed as multi-tone image data in pixel units. The determination means 49 compares the density level at each pixel of the multi-tone image data with the density level at each pixel of the master image data having a good surface condition that has been created in advance, thereby performing an inspection. The quality of the surface condition of the surface is determined.

[0005]

As described above, in the conventional quality inspection apparatus, in order to obtain an image of the inspection surface below the gap between the transport rollers, the inspection light is vertically projected onto the inspection surface. I have. Not limited to such conventional examples, in a situation where it is difficult to irradiate the inspection surface obliquely with the inspection light due to the presence of a light-shielding material,
The vertical epi-illumination method using a half mirror was commonly used. However, there is a disadvantage in using a half mirror.

The disadvantages of using a half mirror include the following (1) to (3). (1) In order to obtain a surface image that can clearly determine the quality of the surface condition of the inspection surface,
The light intensity of the surface image must be above a certain level. However, when a half mirror is used, the intensity of the light emitted from the light source is reflected on the half mirror, and the intensity of the reflected light on the inspection surface is transmitted through the half mirror. May fall below the above-mentioned certain level. (2) When dust adheres to the half mirror due to long-term use of the device, the intensity of light reaching the imaging camera becomes weaker. (3) In general, the line-shaped half mirror is very expensive and difficult to manufacture, which causes a significant increase in the manufacturing cost of the quality inspection device. For example, in the surface inspection of a sheet-fed printed material, 420 over the transport width (width in the depth direction of the drawing) is used.
In order to inspect a linear area of about 1,250 mm,
It is necessary to prepare half mirrors of the same size, but this type of half mirror is difficult and expensive to manufacture.

SUMMARY OF THE INVENTION In view of the above-mentioned disadvantages, the present invention provides a method for clarifying an inspection surface without using a vertical mirror system using a half mirror in a situation where it is difficult to irradiate inspection light obliquely to the inspection surface due to the presence of a light shielding object. It is an object of the present invention to provide a quality inspection device capable of obtaining a proper image.

[0008]

In order to achieve the above object, a quality inspection apparatus according to the present invention is arranged outside an angle of view of an imaging means, and illuminates one or a plurality of light sources on an inspection surface of an inspection object by epi-illumination. Imaging means for receiving reflected light of the linear area of the inspection surface illuminated by incident light and imaging the linear area; and determining the quality of the inspection plane based on the light intensity distribution of the reflected image of the linear area. It is Bei Ete and a determination means for.

[0009] Then, the above light source, a line-shaped region as well as incident illumination through Kyosuki between shaders, shooting the
Patent that the image means, for capturing a reflection image of the line-shaped region
It is a sign .

[0010] It is more preferable that a lens for refracting the light emitted from the light source and irradiating the linear area of the inspection surface with uniform illuminance is provided.

As a determining means of such a quality inspection apparatus, the density level of the multi-tone image data obtained from the intensity distribution of the reflected image picked up by the image pick-up means is compared with the reference density level of the master image data. What determines the quality of the inspection surface can be used.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, various exemplary embodiments according to the present invention will be described with reference to the drawings. 1 and 2 are schematic configuration diagrams showing one embodiment of a quality inspection apparatus according to the present invention, and FIG. 2 is a view taken along the line CC of FIG. According to FIG. 2, the sheet 1 to be inspected is conveyed in the direction of the arrow 3 while holding the upper and lower surfaces thereof by a number of conveying rollers 2a,..., 2b,. Have been. Gap distance between transport rollers (t)
Is about 5 to 30 mm. Further, according to FIG. 1, the sheet 1 is conveyed toward the front of the drawing while the upper and lower surfaces are sandwiched by the conveying rollers 2a and 2b.

The quality inspection apparatus 4 of this embodiment for inspecting the surface condition of the sheet 1 includes an imaging camera 5 and illuminators 6a and 6b arranged outside the angle of view of the imaging camera 5.
And determination means 7 for determining the surface state based on the surface image of the inspection surface. In addition, the illuminators 6a, 6
b is disposed directly above the gap 8 and on both sides of the imaging camera 5 shown in FIG. 1 to illuminate the gap 8 between the transport rollers with light. With this arrangement, it is possible to inspect the object under the gap between the light-shielding objects through a gap of about 5 mm in the same manner as in the above-described vertical epi-illumination method using the half mirror.

The arrangement of the illuminators 6a and 6b in the present embodiment is such that a surface image (hereinafter, referred to as a dark-field image) mainly based on a scattered light component on the inspection surface is given to the imaging camera. However, in the present invention, the arrangement of the illuminator is not limited to this, and the arrangement of the illuminator is mainly determined by a surface image (hereinafter referred to as a bright image) of a specularly reflected light component (a light component reflected from the surface at a reflection angle equal to the incident angle of incident light). (Referred to as a field-of-view image) may be given to the imaging camera, or an arrangement in which the imaging camera appropriately contains both a scattered light component and a regular reflection light component may be given to the imaging camera.

As the illuminator, various lenses for refracting light from a light source and irradiating an inspection surface with uniform illuminance can be used. One embodiment is shown in FIG. The illuminator 10 shown in FIG. 3 mainly has a cylindrical main body 1.
1, a light entrance 13 provided at the rear end of the main body 11 for receiving light 12 from a light source such as a lamp, a first condenser lens 14 having convex surfaces on both sides, and a second condenser lens having convex surfaces on both sides. The lens 15 and the second condenser lens 15
A third condenser lens 16 having a concave shape corresponding to the convex shape on both sides, and a light exit port 17 are provided.

As the illuminator according to the present invention, a line light source or a straight tube lamp can be used. Specific examples of such a light source include a fluorescent lamp and a light guide type illuminator (an illuminator that guides the light of the light source to the vicinity of the light irradiation area with a light guide such as an optical fiber). Further, as a light source for irradiating the linear region with light, a light source such as a laser oscillator that linearly irradiates a light beam through a lens, or a linear mirror using a polygon mirror that rotates the light beam may be used. Irradiation may be performed sequentially.

Among these illuminators, the light guide type illuminator guides the light of the light source to the vicinity of the inspection surface to easily produce uniform outgoing light of various shapes such as a line shape and a spot shape, and to provide the inspection light. It is preferable from the viewpoint that the angle of incidence can be easily adjusted. 4 to 6 show a schematic configuration of an embodiment of a quality inspection apparatus using a light guide type illuminator. FIG. 5 is a view taken in the direction of arrows D-D in FIG. 4. FIG. 6 shows a modification of the quality inspection apparatus shown in FIGS. Except for the illuminator of these embodiments, the configuration and mechanism of each part are substantially the same as those of the embodiment of FIGS. 1 and 2 described above.

According to FIG. 4 and FIG.
Light guide type illuminator 21a, 2 provided with 2a, 22b
1b is the lower surface 24a, 24b of the main body 23a, 23b.
Are provided with a large number of slit-shaped light emitting ports. The light guide type illuminators 21a and 21b have the lower surfaces 24a and 24b facing the irradiation area of the inspection surface of the inspection object 28, and are directly above the gap 25 between the transport rollers, and are shown in FIG. It is arranged near the inspection surface on both the left and right sides of the imaging camera 26.

In FIG. 6, a light guide type illuminator 3 is shown.
0a and 30b are outside the angle of view of the imaging camera 31,
An example is shown in which they are arranged along the maximum angle of view. By paying attention to the maximum angle of view of the imaging camera and arranging the illuminators 30a and 30b along this maximum angle of view as in the present embodiment, the inspection surface can be efficiently illuminated.

As the imaging camera according to the present invention, it is preferable to use a line sensor from the viewpoint that a linear area of the conveyance width of the inspection object can be imaged at a time. As this line sensor, an array of solid-state imaging devices such as a CCD (charge coupled device) and a photodiode can be used. For example, 256 pixels, 5
A high-precision image can be obtained by a line sensor having 12, 1024, 2048, 4096, and 8192 pixels. Also, as a line sensor,
It is not limited to a monochrome plane imaging apparatus, but a color plane imaging apparatus can be used.

In addition, examples of the inspection object according to the present invention include a sheet material and a continuous sheet. The quality inspection apparatus according to the present invention provides a surface property (scratch, chip,
Material defects, dents, wrinkles, breaks, etc.) can be inspected. Further, offset printing, gravure printing, flexo printing, screen printing, or the like may be performed on these inspection objects, and the printing state of the printing surface may be simultaneously inspected. The inspection surface suitable for the inspection based on the dark field image includes a surface printed with color ink and an aluminum laminate surface. In particular, in the case of a printing surface using color ink, since the light intensity is too strong from the reflection image of the specular reflection light component to make it difficult to identify the color component, it is desirable to obtain a reflection image mainly containing a scattered light component.

Inspection surfaces and inspection objects suitable for the inspection based on the bright-field image include transparent and translucent films and sheets, coated paper, and substrates obtained by vacuum-depositing aluminum or silver on a substrate. Alternatively, a thin film formed by depositing metal particles on the surface by sputtering may be used.

Such a reflected image of the object to be inspected is picked up by an image pickup camera, transferred to the judgment means, and processed there. As a preferable judging means, processing is performed on a pixel-by-pixel basis as multi-tone image data based on a light intensity distribution, and a density level of each pixel of the multi-tone image data and a reference of master image data of a previously imaged defect-free surface. A method in which the quality of an inspection surface is determined by comparing and collating with a density level is exemplified. This determination result may be transferred to a speaker and output as a warning sound or the like, or may be output to image display means such as a CRT to display an abnormal portion or the like.

In each of the above embodiments, only one inspection surface is inspected. However, the present invention is not limited to this, and the quality inspection apparatus according to the present invention may be installed on the back side or both sides of the inspection object. It may be provided to inspect the back surface or both surfaces.

In each of the embodiments described above, the light-shielding material is present, but the light-shielding material according to the present invention is not particularly limited. May be.

[0026]

As described above, the quality inspection apparatus of the present invention
One or more light sources that are arranged outside the angle of view of the imaging means and illuminate the inspection surface of the inspection object with incident light, and receive the reflected light of the linear region of the illuminated inspection surface and image the linear region. Because it is equipped with an imaging means, it is possible to achieve high inspection accuracy and low cost without employing a vertical epi-illumination method using a half mirror or the like, and it is possible to perform an inspection equivalent to an inspection using the vertical epi-illumination method. Was.

[0027]And, Such a quality inspection deviceLight source
Illuminates the linear area through the gap between the shades.
ToWith the imaging means,Take a reflection image of the line-shaped area
ImageBecauseInspection of the inspection surface under the gap between the light shielding objects
It becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a quality inspection apparatus according to the present invention.

FIG. 2 is a view as viewed in the direction of arrows CC in FIG. 1;

FIG. 3 is a schematic configuration diagram showing a cross section of the illuminator according to the present invention.

FIG. 4 is a schematic configuration diagram showing an embodiment including a light guide type illuminator, which is a quality inspection apparatus according to the present invention.

FIG. 5 is a view as seen in the direction of the arrows D in FIG. 4;

FIG. 6 is a diagram showing a modification of the embodiment shown in FIGS. 4 and 5;

FIG. 7 is a schematic configuration diagram showing a conventional vertical-emission type quality inspection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Sheet 2a, 2b Conveyance roller 3 Arrow direction 4 Quality inspection apparatus 5 Imaging camera 6a, 6b Illuminator 7 Judgment means 8 Interspace 10 Illuminator 11 Main body 12 Light of light source 13 Light entrance 14 First condenser lens 15 Second condenser Lens 16 Third condenser lens 17 Light exit 20 Quality inspection device 21a, 21b Light guide illuminator 22a, 22b Light guide 23a, 23b Light guide illuminator main body 24a, 24b Lower surface of light guide illuminator main body 25 Transport roller Intermediate gap 26 Imaging camera 27a, 27b Transport roller 28 Inspection object 30a, 30b Light guide type illuminator 31 Imaging camera 40 Quality inspection device 41 Sheet 42a, 42b Transport roller 43 Arrow direction 44 Intersection 45 Light source 46 Emitting light 47 Half mirror 48 Imaging camera 9 determining unit 50 the reflected light

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-282239 (JP, A) JP-A-2-245644 (JP, A) JP-A-59-74354 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) G01N 21/89-21/892 B41F 33/14

Claims (4)

(57) [Claims] A light source disposed outside the angle of view of the imaging means for illuminating the inspection surface of the inspection object, and receiving reflected light of a linear area of the illuminated inspection surface; in the inspection apparatus using an imaging means for imaging the linear region, the epi-illumination and a determination means for determining the quality of the inspection surface of the light intensity distribution based on the reflected image of the line-shaped region
And wherein the light source passes through the gap between the light-shielding objects to form the linear region.
And epi-illumination, and the imaging means captures a reflected image of the linear region.
A quality inspection apparatus using epi-illumination. 2. The inspection method according to claim 1, wherein the light emitted from said light source is refracted.
Equipped with a lens that illuminates the linear area of the surface with uniform illuminance
A quality inspection device using the epi-illumination according to claim 1. 3. The method according to claim 2, wherein the light source includes a light guide.
An article using the epi-illumination according to claim 1 or 2.
Quality inspection equipment. 4. The apparatus according to claim 1 , wherein said determining means includes :
Multi-tone image data obtained from the intensity distribution of the captured reflected image
Data density level is the reference density level of the master image data.
2. The quality of the inspection surface is determined by comparing with
A quality inspection device using the epi-illumination according to any one of claims 1 to 3.
Place.