JP5476824B2 - Illuminance stabilization mechanism for surface defect inspection equipment - Google Patents

Description

  The present invention is an optical type for inspecting the surface of an inspection object such as a metal plate, paper, roll or the like by image processing in the manufacture of a metal plate such as a thin steel plate or a thick steel plate, or in the manufacture of paper or a roll. The present invention relates to an illuminance stabilization mechanism of a surface defect inspection apparatus that can be suitably used for a surface defect inspection apparatus.

When the surface of the inspection target is inspected by image processing using an optical surface defect inspection apparatus, the illumination is preferably uniform. As an illuminance stabilization mechanism for obtaining uniform illumination, there is an optical fiber system, for example.
As illustrated in FIG. 5, the illuminance stabilization mechanism 101 includes a necessary number of light source units 102, and a reflector 104 and a lamp 103 are provided in each light source unit 102. Then, the light from the lamp 103 is collected by the lens 105, and the collected light is uniformly incident on one end face of the bundle of optical fibers 106. The other ends of the plurality of optical fibers 106 are connected to the light distribution unit 107. In this light distribution unit 107, the optical fibers 106 are arranged in portions where illumination is necessary so that the optical fibers 106 are uniformly distributed in the vicinity of the irradiation surface. Has been.

  In this illuminance stabilization mechanism 101, in order to reduce the variation of the optical fiber 106 and the variation at the time of incident light, the optical fiber 106 is made thin and uniform with a large number of optical fibers, and at the exit of the optical fiber 106. In order to make the variation uniform, the rod-shaped lens 108 is further provided in the light distribution unit 107, and uniform illumination can be obtained if the light attenuation in the optical path of the optical fiber 106 is substantially the same. ing.

  Here, conventionally, when inspecting a flaw on a strip-shaped inspection target surface such as a metal plate by image processing, as shown in FIG. 6, the optical surface defect inspection apparatus is a one-dimensional CCD camera 10 as a light receiver. Is used. Then, as shown in FIG. 7 as viewed in the direction of the arrow X in FIG. 6, when the inspection target K is long like a strip-shaped metal plate, a plurality of CCD cameras 10 (reference characters A and B) are arranged, Uniform illumination is obtained by arranging the light distribution unit 107 of the illuminance stabilization mechanism 101 with respect to the scanning direction of the CCD camera 10. Then, while uniformly illuminating the surface of the inspection target K, the inspection target K is moved at an angle of 90 degrees with respect to the scanning direction of the plurality of CCD cameras 10, and the surface of the inspection target K is continuously scratched. We are inspecting.

Here, FIG. 8 shows the received light intensity (gain) of a plurality of one-dimensional CCD cameras 10 when the illuminance stabilization mechanism 101 shown in FIGS. 5 to 7 is used.
As shown in FIG. 2A, the above-described optical fiber illumination is distributed so that the illumination is uniform in the CCD scanning direction of the two cameras 10 (reference numerals A and B). However, the CCD of a one-dimensional CCD camera usually has a light receiving characteristic at its center that is brighter than its surrounding light receiving characteristics. Therefore, when the reflection of this uniform light distribution is received by the two one-dimensional CCD cameras 10, the received light intensity is different at the central portion and the peripheral portion of the CCD as shown in FIG. Will be. For this reason, conventionally, the illuminance stabilization mechanism used in this type of surface defect inspection apparatus has been provided with a gain adjuster (not shown), and the light received by each one-dimensional CCD camera 10 is converted into an electrical signal by the gain adjuster. In other words, as shown in FIG. 5C, the gain is adjusted by normalization at each point so that the same output is obtained. Since the edge portion of the camera 10 has an abnormal value, it is deleted (not inspected).

  In this type of optical surface defect inspection apparatus, for example, the received light amount intensity in a state normalized by the gain adjuster is monitored as a reference received light amount intensity. When the scratched portion (defective portion) passes, the scratched portion causes an abnormal reflection with respect to the reference received light intensity. Therefore, the output is not uniform at this scratched part. Therefore, threshold values are provided above and below the reference received light intensity that has been corrected to a uniform output, and those exceeding these threshold values can be detected as abnormal (having scratches) (for example, Patent Documents 1 to 3). reference).

JP 58-204356 A JP 58-204355 A JP 58-216938 A

  By the way, in this type of optical surface defect inspection apparatus, considerable brightness is required to obtain a high-quality image or to inspect a surface defect at a high speed. Therefore, the above-mentioned optical fiber type illuminance stabilization mechanism concentrates the light on the back and side surfaces of the inspection object on the front surface of the inspection object using equipment such as optical fibers and lenses, and ensures uniform illumination while ensuring brightness. Was to be tested.

  However, such a condensing device needs to be installed in the vicinity of the inspection target. In addition, in the case of using a condensing device such as an optical fiber or a lens as described above for the purpose of uniform light distribution, the distance between the light projector and the inspection object can be increased while obtaining the necessary brightness. Can not. For example, in the illuminance stabilization mechanism 101 exemplified above, as shown in FIG. 6, even if the distance b between the inspection target K and the CCD camera 10 can be secured (for example, 700 to 2000 mm), the inspection target K and the light distribution unit 107. It was difficult to sufficiently separate the distance a (for example, 100 to 200 mm). Therefore, in the illuminance stabilization mechanism 101 exemplified above, the condensing device is an obstacle to the installation configuration (design).

  On the other hand, in order to obtain a powerful light source, a plurality of projectors equipped with a lamp and a simple reflecting mirror are arranged along the CCD scanning direction instead of an optical fiber illumination, and the plurality of projectors are inspected. A configuration that secures a sufficient distance from the target may be considered. However, with such a plurality of projectors, the light distribution from the plurality of projectors on the light receiver side is not uniform. Therefore, although a powerful light source can be obtained while separating the distance between the projector and the inspection object, the light quantity becomes uneven.

  Here, the unevenness in the amount of light can be corrected by, for example, the gain adjuster. However, since the degree of correction is larger than in the example of the optical fiber type illumination, the gain is increased in the portion where the gain is increased. The deterioration of the S / N ratio is also increased. In other words, when the gain is increased, ambient external noise and noise inherent to the CCD camera may be increased, and a signal exceeding the threshold value due to noise may be generated even in an uninspected part to be inspected, resulting in malfunction (false detection). Increase.

  Therefore, the present invention has been made paying attention to such problems, and it is possible to obtain a strong light source, while ensuring a sufficient distance of the inspection target with respect to the projector and suppressing unevenness in the amount of light. The purpose is to provide a mechanism.

In order to solve the above problems, the present invention, the surface of the test object in the illumination stable mechanism used in an optical surface defect inspection apparatus for inspecting the image processing, the light of the lamp and the lamp in the test object side A plurality of projectors each having a reflecting plate to be reflected and having a light projecting characteristic in the center that is brighter than that of the surroundings, and reflected light that has been projected from the plurality of projectors and reflected from the surface of the inspection object It is arranged to receive light, and is a one-dimensional CCD camera with a plurality of light receivers having a light receiving characteristic in the center of itself that is brighter than that of its surroundings, and gains of the plurality of light receivers are normalized by normalization An illuminance stabilizing mechanism including a gain adjuster, wherein the plurality of light projectors are spaced apart from each other along one direction and more than the number of the plurality of light receivers. , Wherein the the one direction is arranged to fit a central position of the projector in the middle position of the light receiver adjacent alternately and a plurality of light receivers when seen from a direction perpendicular to its own central brighter than said own surroundings The light emitting characteristic of the light projector and the light receiving characteristic of the one-dimensional CCD camera whose center is brighter than its surroundings work in a complementary manner to suppress unevenness in the amount of light as a whole illuminance stabilization mechanism .

According to the illuminance stabilization mechanism according to the present invention, since a configuration including a plurality of projectors is used instead of using devices such as optical fibers and lenses, it is possible to obtain a powerful light source while sufficiently securing a distance to be inspected with respect to the projectors. it can.
The plurality of projectors have a light projection characteristic in the center that is brighter than that in the surrounding area. On the other hand, the plurality of light receivers have a light reception characteristic in the center that is brighter than that in the surrounding area. Furthermore, the plurality of light projectors is disposed more than the number of the plurality of light receivers, and the light projectors are arranged in an intermediate position between the light receivers alternately and adjacent to the plurality of light receivers. Since the central positions are aligned, even if the light distribution from multiple projectors is not uniform, the projector's light projection characteristics and CCD light reception can be achieved by arranging multiple projectors for multiple receivers. The unevenness in the amount of light is complemented by the combination of the alternating arrangement with the characteristics. Therefore, unevenness in the amount of light can be suppressed.

  Since the gain adjuster normalizes the gains of the plurality of light receivers in which the unevenness of the light amount is suppressed by normalization, the degree of correction is reduced and the influence of ambient external noise and noise specific to the CCD camera is reduced. It becomes difficult to receive. Therefore, the surface defect inspection apparatus using the illuminance stabilization mechanism according to the present invention is suitable for obtaining a high-quality image or performing high-speed inspection.

Here, the illuminance stabilization mechanism according to the present invention, for example, the optical path between said plurality of light receivers and the plurality of projectors, have a scattering plate for scattering light from the projector, facing the center of the projector If the light shielding plate arranged at the position to be inclined is inclined with respect to the light projecting direction, it is more preferable in suppressing unevenness in the amount of light.

  As described above, according to the illuminance stabilization mechanism according to the present invention, it is possible to secure a sufficient distance of the inspection target with respect to the projector and suppress unevenness in the amount of light while obtaining a powerful light source.

It is a schematic diagram which shows the illumination intensity stabilization mechanism of this invention. It is a schematic diagram (X arrow view in FIG. 1) which shows the illuminance stabilization mechanism of this invention, and the same figure has shown together the image of the intensity | strength of the light distribution by a several projector. It is a figure explaining the light reception intensity | strength (gain) in the illumination intensity stabilization mechanism of this invention, the figure (a) is a figure of light distribution intensity, (b) is a figure of received light quantity, and (c) is an image of gain adjustment. FIG. It is a figure explaining the modification of the illumination intensity stabilization mechanism of this invention, The figure (a) is a schematic diagram which shows the illumination intensity stabilization mechanism of a modification, (b) is a figure which shows the image of the gain adjustment of a test | inspection waveform. It is a perspective view which shows the conventional optical fiber type light source typically. It is a schematic diagram which shows the conventional illumination intensity stabilization mechanism. It is a schematic diagram (X arrow view in FIG. 6) which shows the conventional illumination intensity stabilization mechanism. It is a figure explaining the light reception intensity | strength (gain) in the conventional illumination intensity stabilization mechanism, The figure (a) is a figure of a light distribution intensity, (b) is a figure of a received light quantity, and (c) is a gain adjustment of a test waveform. FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.
In FIG. 1, the schematic diagram of the illumination intensity stabilization mechanism of the surface defect inspection apparatus which concerns on this invention is shown.
This illuminance stabilization mechanism 1 is an example used in an optical surface defect inspection apparatus for inspecting the surface of an inspection object k by image processing. As shown in the figure, a projector 2 and a one-dimensional CCD camera are used. 10.

As shown in FIG. 2, a plurality of (three in this example) projectors 2 are arranged. Each projector 2 includes a lamp 3 and a reflector 4 that reflects light from the lamp 3 toward the inspection target K side. Have Here, the floodlight 2 has a light projection characteristic at its center that is brighter than that of its surroundings.
As shown in FIG. 1, the one-dimensional CCD camera 10 is arranged as a light receiver that receives reflected light projected from the plurality of light projectors 2 and reflected from the surface of the inspection object K. As shown in FIG. 2, a plurality of (two in this example) one-dimensional CCD cameras 10 are also arranged. This one-dimensional CCD camera 10 has a CCD whose light receiving characteristic at the center is brighter than that around itself. The intensity of light distribution acquired through the CCD of the one-dimensional CCD camera 10 is sent to a gain adjuster (not shown). In the gain adjuster, the gains of a plurality of one-dimensional CCD cameras 10 are made uniform by normalization.

  Here, as shown in FIG. 2, in the illuminance stabilization mechanism 1 of the present embodiment, the plurality of projectors 2 have the width direction of the inspection target K as one direction and are separated along this one direction (mutually Three projectors 2 are arranged, one more than the number of the two one-dimensional CCD cameras 10 (with a distance L1). Further, as shown in FIG. 2 (in the direction of the arrow X in FIG. 1), the plurality of projectors 2 are arranged in an intermediate position (separation distance L2) between the two one-dimensional CCD cameras 10 alternately and adjacent to each other. The central position of the projector 2 is aligned with ½).

Next, the operation and effect of this illuminance stabilization mechanism will be described.
The illuminance stabilization mechanism 1 includes two one-dimensional CCD cameras 10, a gain adjuster that equalizes the gains of the two CCD cameras 10 by normalization, and three projectors 2. A powerful light source can be obtained while ensuring a sufficient distance of the inspection object K from the projector 2. Specifically, as shown in FIG. 1, a distance b (for example, 700 to 2000 mm) between the inspection target K and the CCD camera 10 is ensured in the same manner as in the past, and further, a distance a between the inspection target K and the projector 2 is also secured. For example, it has become possible to sufficiently separate to about 1000 to 5000 mm.

These three projectors 2 are arranged one more than the number of the two one-dimensional CCD cameras 10 and are alternately arranged between the two one-dimensional CCD cameras 10 and between the adjacent cameras 10. Since the central position of the projector 2 is aligned with the position, unevenness in the amount of light can be suppressed as a whole of the illuminance stabilization mechanism 1 by this arrangement.
That is, as shown in FIG. 3A, in the illumination of the three projectors 2 described above, the illumination characteristic at the center of itself is brighter than that of its surroundings, so that the illumination is 3 in the CCD scanning direction of the camera 10. The light is distributed so that it becomes one “mountain”. On the other hand, the CCDs of the two cameras 10 have a light reception characteristic at the center that is brighter than the light reception characteristics around the CCD. Therefore, when the reflection of this uniform light distribution is received by the two one-dimensional CCD cameras 10, the intensity of the received light amount is different between the center portion and the peripheral portion as shown in FIG. It works in a complementary manner to the lighting.

  In other words, the high part of the above three “mountains” (the part brighter than the surroundings) is alleviated by the light receiving characteristics around the CCD, while the “valley” part between the “mountains” and the “mountains” (more than the surroundings). The dark portion) is also compensated by the light receiving characteristic at the center of the CCD, and as a result, the two one-dimensional CCD cameras 10 as a whole receive light as the “lighted” amount of received light. Therefore, as shown in the figure (c), this “normalized” light is converted into an electric signal by a gain adjuster, and the gain is adjusted by normalization at each point so that the same output is obtained. This can be done with minor adjustments. Since the edge portion of the camera 10 has an abnormal value, it is deleted (not inspected).

  As a result, according to the illuminance stabilization mechanism 1 of the present embodiment, fine adjustment of the gain is sufficient, and the influence of ambient external noise and noise inherent to the CCD camera is mitigated. Therefore, according to the surface defect inspection apparatus provided with the illuminance stabilization mechanism 1, it is possible to perform inspection at a high speed while obtaining a good image. Further, there is no problem that a signal exceeding the threshold value due to noise is generated and a malfunction (false detection) occurs in a portion where the surface to be inspected is not damaged.

As described above, according to the illuminance stabilization mechanism 1, it is possible to obtain a strong light source and to sufficiently secure the distance of the inspection target K with respect to the projector 2 while suppressing unevenness in the amount of light. In particular, it is advantageous when inspecting minute scratches in an apparatus in which the projector of the optical surface defect inspection apparatus is separated.
The illuminance stabilization mechanism of the surface defect inspection apparatus according to the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, if there is still a difference in light amount even when the plurality of projectors 2 are arranged in a staggered manner and the gain is uneven in the width direction of the inspection target K, a plurality of light shielding plates as shown in FIG. A configuration using (or scattering plate) 6 is more suitable for suppressing unevenness in the amount of light.
In the example of the figure, among the plurality of light shielding plates 6, one light shielding plate 6a disposed at a position facing the center of the central projector 2 is inclined with respect to the light projecting direction. Among the two “mountains”, the summit portion (the Y portion in the figure) of the central “mountain” is made low (dark). That is, if such a plurality of light shielding plates 6 are appropriately disposed between the plurality of projectors 2 and the plurality of one-dimensional CCD cameras 10 and adjusted individually according to the situation, the gain of the gain adjuster is uniform. It is possible to make the amount of light physically (optically) uniform before the adjustment, and it is possible to more surely prevent gain unevenness. As a result, variation in CCD gain before gain equalization by the gain adjuster can be reduced as much as possible, and noise can be reduced by gain correction by the gain adjuster.

DESCRIPTION OF SYMBOLS 1 Illuminance stabilization mechanism 2 Floodlight 3 Lamp 4 Reflecting plate 6 Light-shielding plate 10 CCD camera 11 Lens K Inspection object

Claims (2)

In the illuminance stabilization mechanism used in the optical surface defect inspection apparatus for inspecting the surface of the inspection object by image processing,
A plurality of projectors each having a lamp and a reflector for reflecting the light of the lamp to the inspection object side, and having a light projecting characteristic at the center that is brighter than that of the surroundings, and light projected from the plurality of projectors A plurality of light receivers arranged so as to receive reflected light reflected by the surface of the inspection object, and having a CCD having a light receiving characteristic in the center of the one-dimensional CCD camera that is brighter than that of its surroundings; An illuminance stabilization mechanism including a gain adjuster that equalizes gains of a plurality of light receivers by normalization,
The plurality of light projectors are spaced apart from each other along one direction and disposed more than the number of the plurality of light receivers, and the plurality of light projectors are viewed from a direction orthogonal to the one direction . The light emitting device is arranged in the middle position between the light receiving devices alternately and adjacent to each other, and the light emitting characteristics of the light emitting device whose center is brighter than its surroundings, and whose center is brighter than its surroundings. An illuminance stabilization mechanism for a surface defect inspection apparatus, wherein the light reception characteristics of a one-dimensional CCD camera work in a complementary manner to suppress unevenness in the amount of light as the entire illuminance stabilization mechanism. The optical path between said plurality of light receivers and the plurality of projectors, have a scattering plate for scattering light from the projector with respect to the light projection direction of the light-shielding plate disposed in a position facing the center of the projector The illuminance stabilization mechanism of the surface defect inspection apparatus according to claim 1, wherein the illuminance stabilization mechanism is inclined .

Images