JP5837283B2 - Tire appearance inspection method and appearance inspection apparatus - Google Patents

Description

  The present invention relates to a tire appearance inspection method and an appearance inspection apparatus (hereinafter also simply referred to as “inspection method” and “inspection apparatus”), and more specifically, a tire capable of automatically inspecting the appearance shape of a product tire. The present invention relates to an appearance inspection method and an appearance inspection apparatus.

  Conventionally, an inspection method using a light cutting method as shown in FIG. 4 is known as a method for inspecting the quality of the appearance of a tire. In this inspection method, the tire 60 to be inspected is mounted on the rotating device 71 and rotated, and the light projecting device 72 using a semiconductor laser or the like irradiates the side portion 60K of the tire 60 with slit light, thereby the side portion 60K. After the slit image is taken by an area camera 73 such as a CCD camera, the shape of the side portion 60K is obtained from the image data (luminance data) of the slit image S, and this is compared with the reference image of the side portion 60K. The quality of the shape is determined.

  As a technique related to an appearance inspection of a tire or the like, for example, Japanese Patent Application Laid-Open No. H10-228867 includes a light projecting unit that irradiates slit light onto a surface to be inspected of a subject and an area camera that photographs the slit light irradiation unit. The subject and the subject are relatively moved to photograph the subject, and the coordinates and brightness of the subject are calculated from the pixel data of the photographed area camera to obtain the shape and shading of the subject. A method for inspecting the appearance and shape of a subject that is detected and simultaneously inspected for the shape and appearance of the subject is disclosed. Moreover, as a technique for accurately performing an appearance inspection of a tire or the like, for example, techniques disclosed in Patent Documents 2 to 4 are also known.

JP 2003-240521 A (Claims etc.) JP 2001-249012 A (claims, etc.) JP-A-2005-148010 (Claims etc.) JP 2008-232779 (Claims etc.)

  However, the conventional tire appearance inspection method is to obtain the shape data by processing the cross-sectional image data three-dimensionally (3D), so the amount of calculation required for the inspection of one tire is large, the processing is complicated, There was a problem that it took time. In addition, in the conventional visual inspection method using the light cutting method, the resolution is limited by the performance of the camera and the line width of the line laser, so the performance of both the laser and the camera must be used to detect fine irregularities. There was a need to improve. Therefore, there has been a demand for an inspection technique that can detect minute defects on the tire surface in a shorter time and with a simple processing method.

  Accordingly, an object of the present invention is to solve the above problems, and to inspect the external shape of the tire in a shorter time and with a simple processing method compared to the conventional method, and further, on the tire surface. An object of the present invention is to provide a tire appearance inspection method and appearance inspection apparatus that can detect even minute defects.

  As a result of intensive studies, the present inventor has found that the above problem can be solved by irradiating the tire surface with polarized light and analyzing the change in the polarization state of the reflected light, thereby completing the present invention. It came to.

  That is, in the tire appearance inspection method of the present invention, the polarized light is applied to the tire surface, and the polarized reflected light from the tire surface is provided with at least three polarizers in different directions. A tire appearance inspection method for detecting an unevenness of a tire surface from light intensity of reflected light received by a camera, wherein a line camera is used as the polarizing camera, and the tire surface is 54 to 60 ° with respect to the tire surface. In addition to irradiating polarized light from an angle, the polarizing camera is arranged in a direction perpendicular to the tire surface and continuously inspected while rotating the tire in the circumferential direction.

  The tire appearance inspection apparatus according to the present invention includes a light irradiating means for irradiating polarized light onto a tire surface, one polarization camera for receiving reflected light of the polarized light from the tire surface, and light received by the polarized camera. An unevenness detecting means for detecting unevenness on the tire surface from the light intensity of the reflected light, and a rotating means capable of rotating the tire in the circumferential direction, wherein the polarization camera is a line camera, and the polarization The camera is disposed in a direction perpendicular to the tire surface, and the light irradiation means is disposed so as to irradiate polarized light from an angle of 54 to 60 degrees with respect to the tire surface. And at least three or more polarizers in different directions.

  In the present invention, it is preferable to use linearly polarized light as the polarized light.

  According to the present invention, the inspection of the appearance shape of a tire can be performed in a shorter time and by a simple processing method compared to the conventional method, and the tire surface minuteness that has been impossible with the conventional method can be performed. A tire appearance inspection method and appearance inspection apparatus capable of detecting defects can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view showing a configuration example of a tire appearance inspection apparatus according to the present invention and a partial top view thereof. 4 is a graph showing a relationship between a polarizer direction θ and received light intensity (transmitted light intensity) I. It is the schematic perspective view which shows the other structural example of the external appearance inspection apparatus of the tire of this invention, and its partial top view. It is explanatory drawing which shows the external appearance inspection method of the tire using the conventional light cutting method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic perspective view showing a configuration example of a tire appearance inspection apparatus according to the present invention and a partial top view thereof. As shown in the drawing, the inspection apparatus of the present invention includes a light irradiation means 1 that irradiates polarized light L ₁ on the surface of the tire 10, a polarization camera 2 that receives reflected light L ₂ of polarized light from the surface of the tire 10, and and a concave-convex detecting means for detecting the unevenness of the surface of the tire 10 from the light intensity of the reflected light L ₂ received by the polarization camera 2 (not shown). X in the figure indicates the field of view of the polarization camera 2.

  When the surface of the tire 10 is irradiated with polarized light, the incident angle of the polarized light varies depending on the local shape and roughness of the surface, and the polarization state of the reflected light also changes locally. Therefore, when unevenness exists on the tire surface, the polarization state of the reflected light is different from the other portions in the uneven portion. In the present invention, by using this, a polarization camera is used to obtain and analyze a change in polarization state of reflected light of this polarized light, that is, a change in polarization angle, thereby obtaining uneven information on the surface of the tire 10. It is. This makes it possible to detect small defects on the tire surface that were impossible with conventional shape measurement methods, such as shallow small irregularities that are difficult to see visually, or defects in which different types of rubber were vulcanized. It becomes possible. Further, it is possible to acquire tire surface information at a high speed and with high accuracy by a simpler method than the conventional method, and it is possible to automatically determine a tire surface defect. Furthermore, the three-dimensional shape measurement by the conventional light cutting method is slightly affected by dirt and color unevenness on the tire surface, and particularly when detecting a micro defect, the influence of such dirt and color unevenness is affected. It is not considered small. On the other hand, the polarization angle of the polarized light used in the present invention is not affected by such stains and color unevenness, and is determined only by the surface irregularities. Therefore, in the present invention, the conventional method is also used. It is possible to carry out detection with higher accuracy than

In the present invention, first, irradiated with polarized L ₁ with respect to the surface of the tire 10. As the light irradiation means 1 for irradiating a polarized light L _1, as long as it can emit polarized light, it may use any illumination. Specifically, for example, a combination of a lighting fixture such as an LED (Light Emitting Diode) and a polarizing plate that polarizes light emitted from the lighting fixture can be used. Among them, it is preferable to use a combination of a red LED having a high light receiving sensitivity and a polarizing plate. In the present invention, any polarized light can be used as long as it can detect a change in the polarization angle in the reflected light of the polarized light reflected from the tire surface. However, the polarized light to be used is not particularly limited, but usually linearly polarized light is used. The polarization angle of the linearly polarized light is not particularly limited, but it is preferably 45 ° polarized light because information by the p wave and s wave can be obtained in a balanced manner.

Polarized reflected light L ₂ from the surface of the tire 10 is received by the polarization camera 2. The polarization camera 2 used in the present invention usually includes at least three or more polarizers in different directions before a sensor such as a CCD. By receiving the reflected light using such a polarization camera 2, the transmitted light intensity of the polarizer in three or more directions is obtained for each corresponding pixel unit, and the polarization angle of the reflected light is obtained from the transmitted light intensity. (Polarization major axis direction) can be imaged.

Detection of unevenness on the tire surface from the transmitted light intensity data of the reflected light received by the polarization camera is performed as follows. That is, the light intensity I transmitted through the polarizer at an angle θ (θ = 0 to 180 °) is expressed by the following equation:
I = M + Acos (2 (θ−α))
(In the formula, α indicates the direction in which the transmitted light intensity is greatest when the polarizer is rotated (polarization major axis direction), and A indicates the angle of the polarizer when the polarizer is rotated out of the light intensity. The amplitude (polarization amplitude) of the component that fluctuates accordingly is shown, M represents the component (average value) that does not vary even when the polarizer is rotated, and A / M represents the degree of polarization component (polarization degree). (See Fig. 2). Therefore, the polarization angle for each pixel unit can be derived by calculating using the direction and transmitted light intensity data of the polarizers in three or more directions based on the above formula, and therefore the polarization angles are different. It is possible to easily detect the uneven portion. In addition, if the polarization angle data for each pixel unit is output as, for example, a color image whose hue is changed according to the polarization direction, it can be obtained as image data in which the color of the uneven portion is displayed differently from the other portions. it can. Here, the angle of the polarizer in three or more directions can be, for example, a combination of 0 °, 90 °, and 135 °. The detection of the unevenness may be performed using a general arithmetic processing unit (PC) as the unevenness detecting means.

  By the image processing as described above, it is possible to detect minute irregularities on the surface of the tire 10, and also when there is a portion where the rubber 10 is vulcanized and molded without changing its shape on the surface of the tire 10. The detection can be performed.

  In the present invention, since it is necessary that the wavelength of the irradiated light and the wavelength of the reflected light are aligned, when using red light for the irradiated light, a red filter is also used on the polarizing camera side. It is necessary to receive only red light.

  In the present invention, as the polarization camera 2, an area camera or a line camera may be used, but a line camera is preferably used. By using a line camera as the polarization camera 2, as shown in the figure, it is possible to continuously perform inspection by performing imaging while rotating the tire 10 at a constant speed in the circumferential direction. The rotation of the tire 10 can be performed, for example, by placing the tire 10 on a turntable (not shown) and rotating the turntable. The rotating means of the tire 10 is not particularly limited to a turntable as long as the tire 10 can be rotated in the circumferential direction.

In the present invention the irradiation, the arrangement condition of the light irradiation means 1 and the polarizing camera 2, as shown in FIG. 1, to the surface of the tire 10, from the polarization L ₁ is an oblique, for example, from an angle of 54 - 60 ° It is preferable to arrange the light irradiation means 1 and arrange the polarization camera 2 in a direction perpendicular to the surface of the tire 10. With such an arrangement, the field of view X of the camera is along the tire radial direction, so that the image data obtained by the present invention is aligned with the tire shape data measured three-dimensionally according to the conventional method. This makes it possible to mask the design area of the tire surface. Further, as shown in FIG. 3, the light irradiation means 1 and the polarization camera 2 can be arranged so that the irradiation light is incident on the tire surface at a Brewster angle. In this case, the incident angle and the reflection angle are By bringing the angle closer to the Brewster angle, it is possible to maximize the change in the polarization angle at the defective portion and improve the detection accuracy. However, in the case of the arrangement shown in FIG. 3, since the tire surface is a curved surface, the field of view of the polarizing camera 2 is also curved as indicated by the symbol Y. Therefore, in this case, when the obtained image data is distorted and a character shape or the like is formed on the tire surface, it is difficult to correspond to the character shape data, and the character is captured because it is taken from an oblique direction. There is a drawback that a blind spot of the camera is generated on the back side of the convex part such as a part.

First light emitting means 2 polarization camera 10 tires _L 1, _{L 2} polarization X, the field of view of the Y polarization camera

Claims (4)

The polarized light is irradiated to the tire surface, and the reflected light of the polarized light from the tire surface is received by one polarization camera having at least three or more polarizers in different directions, and the light intensity of the received reflected light A tire exterior inspection method for detecting irregularities on the tire surface from a line camera as the polarization camera, irradiating polarized light from an angle of 54 to 60 degrees with respect to the tire surface, A method for inspecting the appearance of a tire , wherein the inspection is continuously performed while being arranged in a direction perpendicular to the tire surface and rotating the tire in a circumferential direction .   The tire appearance inspection method according to claim 1, wherein linearly polarized light is used as the polarized light. Light irradiation means for irradiating polarized light on the surface of the tire, one polarization camera for receiving the reflected light of the polarized light from the tire surface, and irregularities on the tire surface from the light intensity of the reflected light received by the polarized camera And a rotation means capable of rotating the tire in the circumferential direction, and the polarization camera is a line camera, and the polarization camera is in a direction perpendicular to the tire surface. And the light irradiating means is arranged to irradiate polarized light from an angle of 54 to 60 ° with respect to the surface of the tire, and the polarization camera includes at least three or more polarizers in different directions. A tire appearance inspection apparatus characterized by that. The tire appearance inspection apparatus according to claim 3 , wherein the polarized light is linearly polarized light.

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