JP2002140989A - Inspecting device of metal thin plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspecting device capable of detecting a defect of an aperture grill, which has been performed by a complicated visual inspection by an inspecting person, in relatively simple structure and operation. SOLUTION: This inspecting device comprises a lighting means for radiating light to one direction of the aperture grill 1, an image pickup device 20 that is disposed on the other side of the aperture grill and photographs a transparent illumination image of the aperture grill from a direction tilting with respect to the aperture grill surface in a place orthogonal to the longitudinal direction of a through hole of the aperture grill, a moving means for moving the aperture grill in the longitudinal direction of the through hole, and an image processing device 22 for detecting a micro defect based on the image data provided by the image pickup device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a plurality of slit-like elongated through holes parallel to each other, such as an aperture grill used for a color cathode ray tube such as a trinitron tube (registered trademark of Sony Corporation). The present invention relates to a metal sheet inspection apparatus for inspecting whether a periodically formed metal sheet has minute defects on its surface.

[0002]

2. Description of the Related Art An aperture grill has a structure in which a large number of narrow tapes (grids) are integrally connected in a blind. This aperture grill is manufactured by performing a series of photo-etching processes on a metal sheet material to form a plurality of elongated through holes (slits) parallel to each other in the metal sheet. In the manufacturing process, a narrow tape is used. Minute defects such as chipping and tapered pits may occur.

FIG. 7 (a) shows a front view of an aperture grill, and FIGS. 7 (b) and 7 (c) show an enlarged front view and an enlarged vertical sectional view of a portion A of FIG. 7 (a), respectively. 6 is the effective area 2 of the aperture grill 1
A part of the narrow tape 3 formed in the above is a defect that is extremely small and chipped. 4 in FIG. 7 is a through-hole (slit).

At present, the detection of these chips and taper pits is mainly performed by a visual inspection of an inspector. In this visual inspection, first, tension is applied to the aperture grill in the vertical direction (the longitudinal direction of the narrow tape 3) in the same manner as when the aperture grill is incorporated into a color cathode ray tube, and the aperture grill is placed on a light table in that state. I do.
When the aperture grill is observed from the front, it can be seen if the chip is relatively large, but it is difficult to detect it with a small chip, and the taper pit must be detected from the front. Can not. Therefore, taking advantage of the fact that the cross section of the effective area of the aperture grill in the width direction (the direction orthogonal to the longitudinal direction of the narrow tape 3) has a shape in which trapezoids are periodically arranged, the aperture grill is moved in the horizontal direction. Observation is performed from a low angle (a direction substantially orthogonal to the longitudinal direction of the narrow tape 3). According to such an observation method, the amount of light directly transmitted through the slit enters the eyes, and it becomes easy to recognize the light transmitted through the chipped or tapered pit.
In this case, as shown in FIG. 8, the central portion and the peripheral portion in the width direction of the effective area 2 of the aperture grill 1 are:
The cross-sectional shapes of the narrow tapes 3a, 3b, and 3c in the respective portions (a), (b), and (c) are different, and the cross-sectional shape of the narrow tape 3 gradually changes in the width direction. For this reason, the optimal observation angle changes depending on the observation position on the aperture grill 1. Therefore, in the visual inspection,
As shown in FIG. 9, the effective area 2 of the aperture grill 1 is adjusted while adjusting the viewpoint 7 and the depression angle when observing the transmitted light 8 of the slit 4 according to the observation position on the aperture grill 1.
Inspection is performed over the entire surface.

[0005]

As described above, at present, defects of the aperture grill and defects of the taper pit are detected by visual inspection. However, as the definition of the color cathode ray tube becomes higher, some defects need to be detected. As a result, the defect cannot be sufficiently detected by visual inspection. Further, in the visual inspection, there is also instability of the inspection result due to fatigue and individual differences, and automation of the inspection is desired in order to solve the problem and reduce the inspection cost by hand.

[0006] In the inspection for detecting the lack of the aperture grille or the tapered pit, it is necessary to flexibly adjust the position and the line of sight of the inspector, and if the imaging means is to have the same movement as the inspector. As a result, the configuration of the inspection apparatus becomes complicated and the cost increases. Japanese Patent No. 2911619 discloses an invention in which a method for automatically controlling the angle and viewpoint of an image pickup apparatus is applied to a defect inspection of a large hole diameter of a shadow mask for a color CRT in the same manner as the above-described visual inspection. Therefore, it is conceivable to apply the invention to an inspection device for detecting chipping of an aperture grille and taper pits. However, in the inspection apparatus described in the same publication, the configuration of the apparatus becomes complicated due to the need to change the angle and the viewpoint of the imaging apparatus, and the inspection time becomes longer.
There is such a problem. An apparatus for automating visual inspection by measuring obliquely transmitted light using a line sensor approaching an aperture grille is disclosed in Japanese Patent Application Laid-Open No.
-45197. However,
The inspection apparatus described in the same publication requires a long contact-type line sensor, and also has a problem that the position adjustment between the line sensor and the light source is complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has a relatively simple configuration and a relatively simple structure. An object of the present invention is to provide an inspection apparatus for a metal sheet that can be performed by an operation.

[0008]

The invention according to claim 1 is
In a metal sheet inspection apparatus for detecting minute defects in a metal sheet in which a plurality of elongated through holes are periodically formed in parallel with each other, illumination means for irradiating light to one surface of the metal sheet, and the other surface of the metal sheet Disposed on the side, an imaging means for photographing the transmitted illumination image of the metal sheet in a plane perpendicular to the longitudinal direction of the through hole from a direction inclined with respect to the metal sheet surface, and the metal sheet, Moving means for relatively moving the image pickup means in a direction along the longitudinal direction; and defect detection means for detecting minute defects in the metal sheet based on image data obtained by the image pickup means. It is characterized by.

According to a second aspect of the present invention, in the inspection apparatus according to the first aspect, the imaging means is inclined to one side with respect to the surface of the sheet metal in a plane orthogonal to the longitudinal direction of the through hole of the sheet metal. First imaging means for photographing a transmission illumination image of the metal sheet from a direction, and a transmission illumination image of the metal sheet from a direction inclined to the other side with respect to the metal sheet surface in a plane orthogonal to the longitudinal direction of the through hole of the metal sheet. And a second imaging means for photographing the image.

According to a third aspect of the present invention, in the inspection apparatus according to the second aspect, the transmitted illumination images of the same imaging region other than the central portion of the thin metal plate in the width direction orthogonal to the longitudinal direction of the through hole are respectively provided. The first imaging unit and the second imaging unit that capture images have different depression angles facing the imaging region.

According to a fourth aspect of the present invention, in the inspection apparatus according to the second or third aspect, the thin metal plate is divided into a plurality of imaging regions in a width direction orthogonal to a longitudinal direction of the through hole. In order to photograph the transmitted illumination image of the imaging region from both sides, a plurality of the first imaging means and a plurality of the second imaging means are provided.

According to a fifth aspect of the present invention, in the inspection apparatus according to any one of the first to fourth aspects, a tension is applied to the thin metal plate in a direction along a longitudinal direction of the through hole. It is characterized by further comprising means.

According to a sixth aspect of the present invention, in the inspection apparatus according to any one of the first to fifth aspects, the imaging means is separated in a width direction orthogonal to a longitudinal direction of the through hole of the thin metal plate. It is characterized in that each of the two points is set in a range where the respective detectable angle ranges overlap each other.

In the inspection apparatus according to the first aspect of the present invention, light is applied to one surface of the thin metal plate by the illumination means, and a transmitted illumination image on the other surface side of the thin metal plate is photographed by the imaging means. At this time, since the imaging means performs imaging from a direction inclined with respect to the metal thin plate in a plane orthogonal to the longitudinal direction of the elongated through hole of the metal thin plate, the amount of light directly transmitted from the through hole to the imaging means is obtained. Is small enough. Therefore, transmitted light from a minute defect such as a chip or a tapered pit can be observed with good S / N. Then, while the metal thin plate is moved by the moving means in the direction along the longitudinal direction of the through-hole with respect to the imaging means, the imaging means takes the transmitted illumination image a plurality of times. As a result, image data is obtained over the entire longitudinal direction of the through hole of the thin metal plate, and a defect is detected by performing a differentiation process or the like by a defect detection unit based on the image data.

In the inspection apparatus according to the second aspect of the present invention, the first
Since the imaging means and the second imaging means take transmission illumination images of the metal sheet from respective directions inclined to opposite sides in a plane orthogonal to the longitudinal direction of the metal sheet through-hole, the image is sandwiched between the holes. It is possible to detect defects occurring on either side of the elongated metal portion.

In the inspection apparatus according to the third aspect of the present invention, when the shape of the cross section of the elongated metal portion sandwiched between the through holes in the direction orthogonal to the longitudinal direction is not symmetric, the first imaging means and the With the two imaging means, it is possible to observe transmitted light from the defect with good S / N.

In the inspection apparatus according to the fourth aspect of the present invention, the plurality of divided imaging regions are photographed by the same number of the first imaging unit and the second imaging unit, and image data is obtained over the entire width of the thin metal plate. .

In the inspection apparatus according to the fifth aspect of the present invention, the inspection can be performed by flattening a thin metal plate in which a large number of narrow tapes are connected like a blind, like an aperture grill.

According to the inspection apparatus of the present invention, an imaging area including two points separated in the width direction orthogonal to the longitudinal direction of the through hole of the thin metal plate can be imaged by one imaging means.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a schematic side view showing an example of an embodiment of the present invention, and showing a schematic configuration of an inspection device for a thin metal plate, for example, an aperture grill. Aperture grill 1
Has a structure in which a large number of narrow tapes are connected in a cord-like manner as described above, so that it does not become a flat plate by waving in a natural state. Therefore, the inspection apparatus is provided with a tension applying mechanism as shown in a schematic side view in FIG.

The tension applying mechanism of the aperture grill 1
The narrow tape 3 (slit 4) has a pair of clamps 10, 10 for gripping two sides perpendicular to the longitudinal direction of the narrow tape 3, respectively. The clamp 10 includes a pair of upper and lower plate-like grippers 12, 14.
It is constituted by. Each of the plate-like grippers 12 and 14 has an elongated rectangular shape having a length equivalent to a dimension of a side of the aperture grille 1 perpendicular to the longitudinal direction of the narrow tape 3 (a side in a direction perpendicular to the paper surface). Further, the plate-like grippers 12, 14
Is finished by attaching a stainless steel thin plate 16 on the side contacting the aperture grill 1 so that the effective area 2 is not damaged when the aperture grill 1 is gripped strongly. Further, when the aperture grill 1 is gripped by the plate-like grippers 12 and 14, the gripping force acts evenly on the effective area 2 of the aperture grill 1, so that the gripping force is slightly fixed on the back surface side of the stainless steel thin plate 16. The rubber plate 18 is joined so that the gripping force is absorbed and dispersed by the rubber plate 18.

Although not shown, the pair of clamps 10 and 10 are attached to a clamp table, and the upper and lower plate-like grippers 12 and 14 are moved toward and away from each other.
The one plate-like gripper 12 is reciprocated in the vertical direction by a cylinder. The pair of clamps 10 and 10 are configured to be moved by a small distance in a direction away from each other by a cylinder while holding two sides of the aperture grill 1. The tension can be applied in a direction along the longitudinal direction of the width tape 3.

The clamp table to which the clamps 10 and 10 are attached is moved by a moving mechanism (not shown) to the clamp 1.
A direction along the longitudinal direction of the narrow tape 3 of the aperture grill 1 (direction indicated by an arrow D in FIG. 2) in a state where the aperture grill 1 is gripped by 0 and 10 and tension is applied thereto.
And the aperture grill 1 can be transported.

Aperture grill 1 set in a state where it is gripped and tensioned by a tensioning mechanism and is flattened.
An illumination light source (not shown) for irradiating the lower surface of the aperture grill 1 with light is disposed on the lower surface side of the aperture grill 1. On the other hand, as shown in FIG. 1, a plurality of imaging devices 20 are arranged on the upper surface side of the aperture grill 1.

Here, the basic concept when installing the imaging device 20 will be described. As schematically shown in FIG. 4 in which the taper pits 6 of the aperture grille 1 are detected, the imaging device 20 is arranged in the same manner as in the conventional visual inspection, in which the longitudinal direction of the narrow tape 3 (the direction orthogonal to the plane of the drawing) is taken. A transmitted illumination image of the aperture grille 1 is taken from a direction inclined with respect to the surface of the aperture grille 1 in a plane orthogonal to the plane.
In this case, if tapered pits 6 are generated in the narrow tape 3, the angle at which the illumination light is not transmitted when the narrow tape 3 is normal (from the imaging device 20 to the aperture grill 1).
An angle θ1 (hereinafter, referred to as a “defect detection minimum angle”) that is smaller than an angle θ1 (hereinafter referred to as a “defect detection minimum angle”) is referred to as a depression angle when facing the upper observation position, and as an elevation angle when facing the imaging device 20 from the observation position on the aperture grill 1. However, the transmitted light from the tapered pit 6 can be observed by the imaging device 20. On the other hand, if the amount of the direct transmitted light from the slit 4 incident on the imaging device 20 is sufficiently small, the transmitted light from the tapered pit 6 can be detected with good S / N.
The angle at which the directly transmitted light from the slit 4 almost does not enter the imaging device 20 is defined as the maximum defect detection angle θ2.
These defect detection minimum angle θ1 and defect detection maximum angle θ2
If the imaging device 20 is arranged in an angle range between θ2 and θ1 (which is an angle range of θ2−θ1 and is referred to as a “defect detectable angle range” in this document) and the observation position on the aperture grill 1 is observed. The transmitted light from the tapered pit 6 can be observed with good S / N. The above description is for the case where the defect is the taper pit 6, but the same can be said for the chipping.

Here, the cross-sectional shape of the narrow tape 3 in a direction orthogonal to the longitudinal direction is symmetrical at the center in the width direction of the aperture grille 1, but is located left and right from the center. Is shifted, the degree of asymmetry increases as the distance from the center to the left or right. Therefore, the minimum defect detection angle θ1 and the maximum defect detection angle θ2 change depending on the observation position on the aperture grill 1. Therefore, the minimum defect angle at a position A at the center of the aperture grill 1 shown in FIG. 5 is θ1 (A), the maximum defect detection angle is θ2 (A), and the defect at a position B away from the center of the aperture grill 1 is shown. The minimum detection angle is θ1 (B) and the maximum defect detection angle is θ2
(B), if the cross-sectional shape of the narrow tape 3 monotonously changes between the position A and the position B, as shown in FIG. The range (θ2 (A) −θ1 (A) angle range) and the defect detectable angle range for position B (θ2 (B) −θ1)
If the imaging device 20 is arranged in a range where the angle range of (B) overlaps (the hatched portion in FIG. 6), a defect existing between the position A and the position B can be detected by one imaging device. 20
Can be detected. By installing one imaging device 20 in each of the plurality of imaging regions E1 to E4 divided in the width direction of the aperture grill 1 shown in FIG. A transmitted illumination image can be taken.

As can be seen from FIGS. 4 and 6, if the image is taken only from a direction inclined to one side with respect to the surface of the aperture grille in a plane orthogonal to the longitudinal direction of the narrow tape 3, the narrow width is obtained. Only defects on one side of the tape 3 (taper pits 6 on the right side and chips on the left side in the examples shown in FIGS. 4 and 6) can be detected. Therefore, in order to detect all the defects that have occurred in the aperture grill 7, it is necessary to arrange a plurality of imaging devices 20 symmetrically in the width direction of the aperture grill 1.

Then, while the aperture grill 1 is conveyed in the vertical direction along the longitudinal direction of the narrow tape 3, a plurality of image pickup devices 20 are installed on the left and right sides, respectively, thereby taking pictures. Effective area 2
Can be detected over the entire area.

Based on the above concept, a plurality of imaging devices 20 are provided as shown in FIG. Imaging device 2
0 indicates, for example, a CCD camera (eg, 640 horizontal pixels, 480 vertical pixels) and a taking lens (eg, a focal length of 75 m).
m). Then, the imaging device 20
Are installed on each side of the aperture grille 1 in the width direction orthogonal to the longitudinal direction of the narrow tape 3, six in total, 12 in total. In addition, the imaging devices 20 are installed in the left and right directions from the center of the aperture grill 1, for example, at a position of a distance of 1.8 m, for example, in a vertical direction.

The CCD camera of the image pickup device 20 sets the horizontal direction of the aperture grill 1 (the direction orthogonal to the longitudinal direction of the narrow tape 3) to the vertical direction of the image, and the vertical direction of the aperture grill 1 (the longitudinal direction of the narrow tape 3). Photographing is performed with the transport direction D) along the direction as the horizontal direction of the image. Each of the six CCD cameras of the imaging devices 20 performs imaging while equally sharing the imaging regions S1 to S6 in the width direction of the aperture grill 1, so that the width dimension of each imaging region S1 to S6 is:
The width is one sixth of the width of the effective area 2 of the aperture grill 1, for example, about 70 mm in a 21-inch high-definition aperture grill. The focal length of the imaging lens is selected such that the imaging range is larger than the width of the imaging regions S1 to S6. And the height of each imaging device 20 is
The imaging device 20 is set so as to fall within the defect detectable angle range determined by the method described above, and the inclination of the CCD camera is in a range of about 30 ° to 40 °.

The image pickup area in the transport direction of the aperture grill 1 is uniquely determined because the position of the CCD camera of the image pickup device 20 and the focal length of the photographing lens are determined. For example, about 100 m in a 21-inch high-definition aperture grill.
m. Therefore, when the aperture grill 1 is conveyed in the vertical direction and an image is taken at least once while the aperture grill 1 advances by 100 mm, it is possible to detect defects on the entire effective area 2 without omission.

If there is a defect in the transmitted illumination image taken by the imaging device 20, it appears as a bright spot on the screen. The signal of the transmitted illumination image of the aperture grill taken by each imaging device 20 is transmitted to the image processing device 2.
2 respectively. The image processing device 22 performs a horizontal differentiation process on the image based on the obtained image data, extracts a defect signal, and detects a chip or a tapered pit.

When there is no particular need to detect a defect over the entire surface of a thin metal plate such as an aperture grill,
The imaging devices 20 may be installed only on one side in the horizontal direction of the thin metal plate, or one imaging device 20 may be arranged on each of the left and right sides of the thin metal plate.
Further, when the present invention is applied to a shadow mask or the like in which a number of elongated slot holes are formed, it is not particularly necessary to provide a tension applying mechanism.

[0035]

By using the metal sheet inspection apparatus according to the first aspect of the present invention, it is possible to detect a defect such as an aperture grill which has been conventionally performed by a complicated visual inspection by an inspector.
The operation can be performed by a simple operation with a relatively simple device configuration, and the time required for the inspection can be reduced. When the inspection is performed while fixing the imaging means and moving the metal sheet, other defects (projection, pit,
This is advantageous in configuring an inspection system including a detection device for unevenness, spots, and the like, and also enables inline inspection.

In the inspection apparatus according to the second aspect of the present invention, it is possible to detect a defect occurring on any side of the elongated metal portion sandwiched between the through holes.

In the inspection apparatus according to the third aspect of the present invention, when the cross-sectional shape of the elongated metal portion sandwiched between the through-holes in the direction orthogonal to the longitudinal direction is not symmetrical, the transmitted light from the defect is removed. Each can be observed with good S / N.

In the inspection apparatus according to the fourth aspect of the invention, image data can be obtained over the entire width of the thin metal plate.

In the inspection apparatus according to the fifth aspect of the present invention, an accurate inspection can be performed by flattening a metal thin plate in which a large number of narrow tapes are connected in a blind pattern like an aperture grill.

In the inspection apparatus according to the sixth aspect of the present invention, an imaging area including two points separated in the width direction orthogonal to the longitudinal direction of the through hole of the thin metal plate can be imaged by one imaging means. The number of means can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing an example of an embodiment of the present invention and showing a schematic configuration of an aperture grill inspection apparatus.

FIG. 2 is a front view of an aperture grill.

FIG. 3 is a side view showing a schematic configuration of a tension applying mechanism which is one of components of the aperture grill inspection apparatus.

FIG. 4 is a schematic diagram for explaining a basic concept when installing an imaging device in the aperture grill inspection apparatus.

FIG. 5 is also a view for explaining a basic concept when installing the imaging device, and is a front view of an aperture grill.

FIG. 6 is a schematic diagram for explaining a basic concept when installing an imaging device.

FIGS. 7A and 7B are diagrams for explaining a defect occurring in the aperture grill, wherein FIG. 7A is a front view of the aperture grill;
(B) and (c) are an enlarged front view and an enlarged vertical sectional view of a portion A in (a).

FIG. 8 is a view showing that the cross-sectional shape of the narrow tape is different between the central portion and the peripheral portion in the width direction of the aperture grill.

FIG. 9 is a schematic diagram for explaining a conventional aperture grill inspection method.

[Explanation of symbols]

 Reference Signs List 1 aperture grill 2 effective area of aperture grill 3 narrow tape 4 slit (through hole) 6 taper pit (defect) 10 clamp 12, 14 plate-like gripper 20 imaging device 22 image processing device D arrow indicating the transport direction of aperture grill S1 To S6, E1 to E4 Imaging area θ1, θ1 (A), θ1 (B) Defect detection minimum angle θ2, θ2 (A), θ2 (B) Defect detection maximum angle

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshiharu Asai 4-chome Tenjin Kitamachi 1-chome, Horikawa-dori-Terauchi, Kamigyo-ku, Kyoto F-term (reference) 2F065 AA49 BB02 BB18 CC06 CC25 DD06 FF02 HH13 HH15 JJ03 JJ05 JJ08 JJ26 MM03 PP11 PP12 2G051 AA90 AB02 CA04 CA07 CB02 DA06 5C012 AA02 BE03

Claims (6)

[Claims] 1. A metal sheet inspection apparatus for detecting minute defects in a metal sheet in which a plurality of elongated through holes are periodically formed in parallel with each other, comprising: an illuminating means for irradiating one surface of the metal sheet with light; An imaging unit disposed on the other surface side of the metal sheet, for photographing a transmitted illumination image of the metal sheet from a direction inclined with respect to the metal sheet surface in a plane orthogonal to the longitudinal direction of the through hole; Moving means for relatively moving with respect to the imaging means in a direction along the longitudinal direction of the through hole; and defect detecting means for detecting minute defects in the metal sheet based on image data obtained by the imaging means. And a metal sheet inspection apparatus. 2. A first imaging means for photographing a transmitted illumination image of a metal sheet from a direction inclined to one side with respect to a surface of the metal sheet in a plane orthogonal to a longitudinal direction of the through hole of the metal sheet as the imaging means. And a second imaging means for taking a transmitted illumination image of the metal sheet from a direction inclined to the other side with respect to the metal sheet surface in a plane orthogonal to the longitudinal direction of the through hole of the metal sheet. Metal sheet inspection equipment. 3. The first image pickup means and the second image pickup means for respectively taking a transmitted illumination image of the same image pickup area other than a central portion in a width direction orthogonal to a longitudinal direction of the through hole of the thin metal plate. 3. The metal thin plate inspection apparatus according to claim 2, wherein the depression angles facing the imaging areas are different. 4. A first thin metal plate is divided into a plurality of imaging regions in a width direction orthogonal to a longitudinal direction of the through hole, and a transmission illumination image of each imaging region is taken from both sides. The metal sheet inspection apparatus according to claim 2 or 3, wherein a plurality of means and the second imaging means are provided. 5. The metal sheet inspection apparatus according to claim 1, further comprising tension applying means for applying a tension to the metal sheet in a direction along a longitudinal direction of the through hole. . 6. The image pickup means is installed in a range where respective defect detectable angle ranges at two points separated in a width direction orthogonal to a longitudinal direction of the through-hole of the metal thin plate overlap with each other. Item 6. An inspection device for a metal sheet according to any one of Items 5.