JP2008032487A - Visual inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an visual inspection device for accurately detecting the defects developed on each face, independently of the surface shape of each face, where the surface of an inspected body is formed out of a multitude of faces, and in particular, where each developed on a corner part formed out of two faces. <P>SOLUTION: This visual inspection device is equipped with a lighting means 4 for applying light to the inspected body (a toothed wheel 2) with its surface formed from among a plurality of faces; imaging means 51 and 52 imaging the inspected body 2 at a position where a part of a surface, which is not a plane among the surfaces of the inspected body 2, appears as an outline along the surface shape and is imaged; an image processing means 7 image-processing subjected images taken by the imaging means 51 and 52 for detecting the defects on a surface which is not a plane of the inspected body 2; a first polarizing filter 61, disposed near the light-emitting part of the lighting means 4 to cause a light wave, having a specific vibrating direction, to pass therethrough; and a second polarizing filter 62, disposed near light receiving parts of the imaging means 51 and 52 to cause a light wave having the same vibrating direction as the polarizing filter 61 to pass therethrough. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an appearance inspection apparatus that inspects a defect on a surface that is not a plane in an object to be inspected, such as a gear, by image processing.

  An example of an object to be inspected having a plurality of surfaces is a gear. When manufacturing a gear, it is usually manufactured by sintering a powder alloy. Since the state of the gear before sintering is a green compact, chipping is likely to occur on the surface, and if it is sintered as it is, chipping remains on the surface. Further, if dust adheres to the soft surface of the gear during sintering, chipping may occur if the dust is burned during sintering. For example, if the chipping occurs at the tip edge portion of the tooth portion of the gear, there is a possibility that power transmission of the gear is insufficient.

  Moreover, when manufacturing a gear, a burr | flash may generate | occur | produce when removing a gear from a type | mold. In this way, when there are chips or burrs on the surface of the sintered gear, when the gear is rotated, the gear stops due to the burr biting, so the gear with burrs becomes a defective product. .

  Conventionally, when inspecting the surface of a gear, particularly the tip of a tooth portion, an operator determines whether there is a defect visually. However, when performing a visual inspection for humans, when a long-term inspection is performed, it is easy to miss or misjudgment because of fatigue due to tension, and because it depends on sensual feeling, there are large variations in judgment due to individual differences, stable It is not possible to guarantee the entire detection capability.

  Also, an apparatus for automatically inspecting surface defects has been proposed. In the case of automating inspection, for example, there is an apparatus that determines the quality by irradiating a gear with light, imaging regular reflection light / diffuse reflection light with an imaging unit, and processing the obtained image (for example, Patent Document 1). reference).

  A visual inspection apparatus disclosed in Patent Document 1 irradiates parallel light on a surface to be inspected from a certain direction, receives light reflected by the object to be inspected by an imaging unit, performs image processing, and monitors A light and dark pattern is displayed on the image, and the light and dark pattern is compared with a normal pattern to detect an abnormality of the surface to be inspected.

  In the appearance inspection apparatus disclosed in Patent Document 1, when the surface to be inspected is irradiated with parallel light from a certain direction, the light is inspected if there is no scratch or dirt on the surface to be inspected. Reflected in a certain direction due to the normal shape of the surface. However, when there is an abnormality on the surface to be inspected, the light that hits the defect portion is randomly scattered, so that the scattering state is different from the normal state. In the appearance inspection apparatus of Patent Document 1, a defect is detected by comparing this abnormal scattering state with a normal scattering state.

JP 05-157705 A

  By the way, the tooth portion of the gear may have a side surface formed by a curved surface, or the tip end side of the tooth on the axial end face may be a gently inclined shape instead of a plane perpendicular to the axial direction. .

  As described in Patent Document 1, when inspecting defects by irradiating parallel light onto the axial end surface of the gear, which is the surface to be inspected, when the axial end surface is a surface perpendicular to the axial direction, it is normal. In the portion, the reflected light is received by the image pickup means, and the defective portion is not received. Therefore, the defect can be detected in the portion by projecting the light / dark pattern.

  However, when the tip end side of the tooth on the axial end surface of the gear is an inclined surface, even if the inclined surface is in a normal state, the reflected light is not received by the imaging means because of the inclined surface, and the tip portion The gear teeth are imaged in a dark state. Therefore, when there is a defect on the surface of the inclined tip part, particularly when there is a chip or a burr at the corner part of the tip part, it is difficult to project a clear light-dark pattern, so it is very difficult to detect the defect. It becomes.

  Further, when oil adheres to the object to be inspected and is contaminated, it is difficult to detect a defect using regular reflection. When inspection is performed by receiving regular reflection, the reflected light cannot be received on the curved surface, so that the defect cannot be detected on the curved surface.

  Therefore, the present invention has been made in view of the above problems, and when the surface of the object to be inspected is formed of a large number of surfaces, the defects generated on each surface regardless of the surface shape of each surface, in particular, An object of the present invention is to provide an appearance inspection apparatus capable of accurately detecting defects generated at corners formed by surfaces.

  The appearance inspection apparatus according to the present invention includes a lighting unit that irradiates light to a test object having surfaces formed on a plurality of surfaces, and a part of the surface of the test object that is not a plane is along a surface shape. An imaging unit that images the object to be inspected at a position that appears as an outline, and an image processing unit that performs image processing on the captured image captured by the imaging unit and detects a defect on a surface other than the plane of the object to be inspected With.

  Furthermore, the present invention provides a first polarizing filter that is disposed near the light emitting unit of the illumination unit and transmits a light wave having a specific vibration direction, and is disposed near the light receiving unit of the imaging unit, and the first polarizing filter and the vibration direction. Includes a second polarizing filter that allows light waves in the same direction to pass therethrough.

  As the illumination means, a transmission illumination device is used. A surface-emitting type device is preferable as the transmission illumination device.

  Examples of the imaging means include a two-dimensional camera such as a CCD camera. The imaging means obtains a two-dimensional image using the visual field size as an imaging region. This two-dimensional image is sent to the image processing means.

  In order to cause the imaging unit to capture and image a part of the non-planar surface of the surface of the object to be inspected and imaged as a contour along the surface shape, for example, the optical axis of the imaging unit is the transmission direction of the transmitted illumination. It arranges in the position which becomes diagonal to. More specifically, the object to be inspected is arranged between the illumination means and the imaging means so that the optical axis of the imaging means is not perpendicular to the plane of the object to be inspected.

  When the object to be inspected is a gear, the illumination means is arranged so as to face one axial end face of the gear, and the imaging means is arranged with respect to the axial direction of the gear (the transmission direction of the transmitted illumination). And arranged on the other axial end face side of the gear so as to have an acute angle.

  When the illumination unit and the imaging unit are arranged in this way, defects on a non-planar surface of the surface of the object to be inspected, in particular, a corner formed by a non-plane and a non-plane, or a non-plane and a plane It is possible to reliably detect defects at the corners formed by.

  And even when the object to be inspected is a gear and the tooth portion forming portion on the axial end surface of the gear is not flat (inclined surface), it is formed by the tooth forming portion and the tooth side surface of the axial end surface of the gear. It is possible to reliably detect defects in the corners (edge portions).

  The image processing means performs image processing on the picked-up image picked up by the image pick-up means, and inspects a defect on a non-planar surface.

  The image processing means is configured by, for example, a computer, and can include an image processing unit and a determination unit. For example, the image processing unit pattern-searches the inspection target region from the captured image of the object to be inspected, and obtains a difference image between the reference image and the searched inspection target image using normal shape data as the reference image. And the particle | grain area of the site | part with a difference in the difference image is calculated | required.

  The determination unit determines pass / fail based on the data obtained by the image processing unit. For example, if the particle area of a part having a difference in the difference image obtained by the image processing unit is larger than a predetermined value, it is determined as a defect, and if it is equal to or smaller than a predetermined value, it is determined as not a defect.

  Further, the image processing means uses the first image (silhouette image) captured by the imaging means as a reference image, and then compares the image captured (silhouette image) with the reference image to determine the presence or absence of a defect. Also good. In this way, by using the first image as a reference image, it is possible to detect defects stably without being affected by dimensional variations (individual differences) between test objects. Further, when the object to be inspected is a gear, even if the tip shape changes due to a specification change or the like, there is an effect that it is not necessary to change the inspection software or re-register the reference image.

  Furthermore, in the case where the light of the transmitted illumination hits the surface of the object to be inspected, for example, a gear, the light may be irregularly reflected and received by the imaging means. The captured image at this time is an image in which the light-reflected surface is shined, and the contrast between the defective portion and the normal portion cannot be obtained, and there is a possibility that the defect generated in the shining portion cannot be inspected. Therefore, it is preferable to remove the light irregularly reflected on the surface of the object to be inspected with a filter before receiving the light with the imaging means.

  Therefore, in the present invention, the polarizing filter is disposed so as to reduce the image of the light irregularly reflected by hitting the surface of the object to be inspected by the imaging means. Specifically, as described above, the first polarizing filter that allows light waves in a specific vibration direction to pass is disposed near the light emitting unit of the illumination unit, and the first polarizing filter is disposed near the light receiving unit of the imaging unit. A second polarizing filter that allows light waves having the same vibration direction to pass is disposed.

  In the present invention, the light wave in the specific vibration direction out of the light irradiated from the illumination means is passed through the first polarizing filter, and only the light wave having the same vibration direction as the light wave that has passed through the first polarizing filter is passed through the second polarizing filter. Let it pass. As a result, even if the light wave hitting the surface of the object to be inspected is irregularly reflected and the vibration direction is scattered, most of the light wave can be cut by the second polarizing filter. As a result, the captured image is in a state where the shining portion is reduced, and an image with high contrast is obtained.

  By providing the polarizing filter in this way, it is possible to reduce the component that is irregularly reflected on the surface of the object to be inspected, and to improve the contrast ratio at the time of imaging.

  Further, when the object to be inspected is a gear, in one tooth portion of the gear, two imaging means are arranged so as to be symmetric with respect to a line parallel to the axial direction passing through the tooth tip portion, A first polarizing filter that allows light waves in a specific vibration direction to pass is arranged near the light emitting part of the illumination means, and light waves that have the same vibration direction as the first polarizing filter are passed near the light receiving part of each imaging means. It is preferable to arrange a second polarizing filter.

  By arranging the optical axes of the two imaging means so as to be oblique and symmetrical with respect to a line parallel to the axial direction passing through the tip of the tooth part, the front edge part and the back side of the gear tooth Since the edge portion can be imaged simultaneously on the left and right, it is possible to inspect all the edge portions for all the tooth portions of the gear with only one rotation of the gear.

  In addition, the appearance inspection apparatus of the present invention is not limited to the inspection of defects in the gear teeth, and even a turbine vane, a gear having a U-shaped groove, a rack bar having rack teeth, or the like can be formed only on a flat surface. However, if the object has an inclined surface or a curved surface, it is possible to inspect defects at the edge portion of the inclined surface or the curved surface.

  The appearance inspection apparatus according to the present invention has a defect that occurs on a non-planar surface, particularly a surface and a surface, even if the surface of the object to be inspected has a non-planar surface, such as an axial end face shape of a gear tooth. It is possible to reliably detect defects generated at the corners formed by.

  Embodiments of an appearance inspection apparatus according to the present invention will be described below with reference to the drawings. As shown in the schematic configuration diagram of FIG. 1, the appearance inspection apparatus 1 according to the present embodiment is an edge portion (a corner portion formed by an axial end surface and a side surface) of a tooth portion 21 of a gear 2 that is an object to be inspected. It is an apparatus for inspecting the generated defects.

  As shown in FIGS. 1 to 3, the gear 2 is formed with a through hole 23 at the center of a disc-shaped gear body 22, and the same inner diameter is coaxial with the through hole 23 on one axial surface of the gear body 22. The cylindrical portion 24 is projected and a tooth portion 21 is formed on the outer periphery.

  The appearance inspection apparatus 1 inspects the presence or absence of a defect in the edge portion of each tooth portion 21 while rotating the gear 2. The appearance inspection apparatus 1 includes a rotation mechanism 3 that rotates the gear 2, a transmission illumination device 4 that serves as illumination means, two first CCD cameras (imaging means) 51, and a second CCD camera (imaging means) 52, A first polarizing filter 61, a second polarizing filter 62, and an image processing means 7 are provided.

  As shown in FIG. 2, the rotation mechanism 3 is in contact with the rotation roller 31 that is rotated by a motor, and the rotation roller 31 and the outer peripheral surface of the cylindrical portion 24 of the gear 2. A transmission roller 32 that transmits force to the gear 2 and a support roller 33 that rotatably supports the cylindrical portion 24 of the gear 2 are provided.

  The transmission illumination device 4 uses a surface-emitting type transmission illumination device. As shown in FIGS. 1 and 3, the transmitted illumination device 4 is provided at a position where irradiation is performed toward the tooth portion 21 from one end face side in the axial direction of the gear 2.

  As shown in FIG. 1, the first CCD camera 51 and the second CCD camera 52 are arranged on the other end face side in the axial direction of the gear 2 so that the optical axis of the camera is an acute angle with respect to the axial direction of the gear 2. is doing. In the present embodiment, as shown in FIG. 1, the first CCD camera 51 and the second CCD camera 52 are arranged so as to be symmetric with respect to a line parallel to the axial direction passing through the tooth tip. And it arrange | positions so that an optical axis may become 45 degrees with respect to an axial direction. The angle of the optical axis is preferably in the range of 45 ° ± 10 °.

  The images picked up by the first CCD camera 51 and the second CCD camera 52 are two-dimensional images with the field of view size of the camera as the image pickup area. This two-dimensional image is sent to the image processing means.

  The first polarizing filter 61 allows light waves in a specific vibration direction to pass therethrough and is disposed near the light emitting unit of the transmissive illumination device 4, and has a size that covers the entire light emitting surface of the transmissive illumination device.

  The second polarizing filter 62 is disposed near the respective light receiving portions of the first CCD camera 51 and the second CCD camera 52, and allows light waves having the same vibration direction as that of the first polarizing filter 61 to pass therethrough.

  The image processing means 7 is composed of a computer and includes a monitor (not shown). The image processing means 7 includes a storage unit, an image processing unit, and a determination unit. The storage unit stores image data captured by the first CCD camera 51 and image data captured by the second CCD camera 52. The image processing unit searches the inspection target part from the captured image of the object to be inspected, obtains a difference image between the reference image and the searched examination target image, and obtains a particle area of a part having a difference in the difference image. The determination unit determines pass / fail based on the particle area of the defect portion obtained by the image processing unit.

  In the present embodiment, when the tooth portion 21 of the gear 2 is imaged, the reference image is the image of the tooth portion 21 (the silhouette image of the tooth portion) first captured as the reference image, and the reference image and the next image are captured. The image (silhouette image) of the tooth portion 21 is compared to determine whether the tooth portion 21 has a defect.

  Further, the appearance inspection apparatus 1 is provided with a light transmission type imaging trigger detection sensor 8 so as to face the tooth portion 21 of the gear 2. The light from the detection sensor 8 passes through the valley between the tooth portion 21 and the tooth portion 21, and a timing signal at which this light is blocked by the tooth portion 21 is input to the image processing means 7. It has become. Based on this timing signal, the image processing means controls the imaging timing of the first CCD camera 51 and the second CCD camera 52 so as to sequentially image the tooth portion 21.

  In the present embodiment, the gear 2 is set on the rotation mechanism 3, and first, one of the tooth portions 21 of the gear 2 is imaged by the first CCD camera 51 and the second CCD camera 52. The silhouette images of the tooth portion 21 captured by these cameras 51 and 52 are captured so that the axial end face and the side surface of the tooth portion 21 appear as shown in the circle of FIG. The edge portion between the end surface and the side surface appears as a contour. The image processing means 7 stores these images as reference images in the storage unit.

  Based on the detection result of the detection sensor 8, the adjacent tooth portions 21 are sequentially imaged in the same manner by the first CCD camera 51 and the second CCD camera 52. These images are also stored in the storage unit of the image processing means 7.

  The image processing means 7 reads out the reference image and one of the captured images of the other teeth captured thereafter from the storage unit, and the image processing unit pattern-searches the target tooth in the captured image frame, and the tooth 21 Then, a difference image from the reference image is obtained, and a particle area of a part having a difference in the difference image is obtained.

  Then, in the determination unit, when the particle area of the part having the difference is larger than a predetermined value, it is determined as a defect. When the particle area is equal to or smaller than the predetermined value, it is determined as not a defect, and the defect inspection process is performed. finish.

  The determination at this time is that the reference image, which is the first image, is missing or burred, and if any one of the remaining tooth images is normal, it will not match the reference image. Judged as a defect.

  In this embodiment, even if the tooth portion forming portion on the axial end surface of the gear is gently inclined and is not flat, the edge formed by the tooth forming portion and the tooth side surface of the axial end surface of the gear Since the contour of the part can be imaged, it is possible to reliably detect a defect generated at the edge part.

  Further, in the present embodiment, the front edge portion and the back edge portion of the tooth portion 21 of the gear 2 can be imaged with one camera, and the left and right edge portions are captured by the first CCD camera 51 and the second CCD camera 52. Can be imaged simultaneously. As a result, according to the appearance inspection apparatus of the present embodiment, the defect can be inspected for all the edge portions of all the tooth portions 21 of the gear 2 only by rotating the gear 2 once, so that the defect can be inspected at high speed. Yes.

  In addition, the appearance inspection apparatus of the present embodiment includes a first polarizing filter 61 and a second polarizing filter 62. As for the light emitted from the transmission illumination device 4, only the light wave in the specific vibration direction passes through the first polarizing filter 61. Even if the light wave that has passed through the first polarizing filter 61 hits the side surface of the gear 2 and is irregularly reflected, the second polarizing filter 62 allows only the light wave having the same vibration direction as that of the first polarizing filter 61 to pass. Most of the light wave is cut by the second polarizing filter 62. As a result, since the first CCD camera 51 and the second CCD camera 52 can capture an image with reduced diffuse reflection components on the side surfaces, the captured image has a good contrast. The contour of the edge portion to be formed surely appears.

  According to the appearance inspection apparatus of the present embodiment, since the axial end face of the tooth portion is an inclined surface, conventionally, even a gear that could not be inspected because the contrast between the defective portion and the good portion could not be taken. 4, defects such as chipping of the edge portion in the circle indicated by the dotted line in FIG. 4 and burrs in the edge portion in the circle indicated by the dotted line in FIG. 5 can be distinguished from the good portion with good contrast.

  The appearance inspection apparatus according to the present invention is suitable for inspecting defects generated at corners formed by surfaces of an object to be inspected having a non-planar surface such as a gear.

It is a schematic structure figure showing the whole appearance inspection device of the present invention. It is explanatory drawing which shows the positional relationship of the gearwheel and rotation mechanism in the external appearance inspection apparatus of this invention. It is explanatory drawing which shows the positional relationship of the gearwheel in the external appearance inspection apparatus of this invention, a CCD camera, and an illuminating device. It is a picked-up image which shows the state which the chip | tip generate | occur | produced in the edge part in the tooth | gear part of a gearwheel. It is a captured image which shows the state where the burr | flash generate | occur | produced in the edge part in the tooth | gear part of a gearwheel.

Explanation of symbols

1 Visual inspection device
2 Gear 21 Tooth 22 Gear body 23 Through hole 24 Tube
3 Rotating mechanism
31 Rotating roller 32 Transmission roller 33 Support roller
4 Transmitted illumination device
51 First CCD camera (imaging means) 52 Second CCD camera (imaging means)
61 First polarizing filter 62 Second polarizing filter
7 Image processing means 8 Detection sensor

Claims (4)

Illumination means for irradiating light to the object to be inspected having a plurality of surfaces, and
An imaging unit that images the inspection object at a position where a part of the surface of the inspection object that is not a plane appears as an outline along the surface shape and is imaged;
Image processing means for performing image processing on a picked-up image picked up by the image pickup means and detecting defects on a surface other than the flat surface of the inspection object;
A first polarizing filter disposed near the light emitting portion of the illumination means and passing a light wave in a specific vibration direction;
An appearance inspection apparatus comprising: a first polarizing filter and a second polarizing filter that is disposed near a light receiving unit of an imaging unit and transmits a light wave having the same vibration direction. The object to be inspected is a gear, and in the gear, the tooth portion forming portion on the axial end surface is not flat,
While arranging the illumination means so as to face one axial end face of the object to be inspected,
The imaging means is arranged on the other axial end face side of the inspection object so that the optical axis of the imaging means becomes an acute angle with respect to the axial direction of the inspection object,
The appearance inspection apparatus according to claim 1, wherein a defect in a corner portion formed by a tooth portion forming portion and a tooth side surface of an end surface in the axial direction of the inspection object is detected.   In one tooth portion of the gear, the two imaging means are arranged so as to be symmetric with respect to a line parallel to the axial direction passing through the tip portion of the tooth portion, and in a specific vibration direction near the light emitting portion of the illumination means. A first deflection filter that allows light waves to pass through is disposed, and a second deflection filter that allows light waves having the same vibration direction as that of the first deflection filter to be disposed near the light receiving portion of each imaging means. The visual inspection apparatus according to claim 2.   4. The image processing unit according to claim 1, wherein the first image picked up by the image pickup unit is used as a reference image, and the image picked up thereafter is compared with the reference image to determine the presence / absence of a defect. An appearance inspection apparatus according to any one of the above.

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