JP4877355B2 - Defect detection method and apparatus for transparent plate - Google Patents

Description

  The present invention relates to a detection method and a detection device for a defect occurring in a transparent plate-like body such as a plate glass.

  The defects of transparent plate-like bodies such as glass include defects existing on the surface such as scratches and dirt on the surface and defects such as foreign matter in the plate-like body, and the plate-like body is transparent. As described in Reference 1, optical means such as illuminating the transparent plate from a direction nearly perpendicular to the surface of the transparent plate and a direction parallel to the surface and detecting defects with a CCD camera have been frequently used. It was.

  In the optical method shown in Patent Document 1, many light sources are required for illumination of the transparent plate-like body. In addition, it is not possible to distinguish between scratches on the surface of the transparent plate-like body, defects such as foreign matter and bubbles in the transparent plate-like body, and foreign matters such as dirt on the surface of the transparent plate-like body and dust attached to the surface, Inspection was difficult only after the transparent plate was washed. That is, when the inspection is performed without cleaning, there is a possibility that the transparent plate-like body that is simply soiled is discarded as a product.

  Therefore, in order to distinguish defects that can be removed by cleaning such as dirt and dust on the surface of the transparent plate from defects that cannot be removed by cleaning such as scratches and foreign matter, the transparent plate such as glass must be cleaned. After that, only the defect was detected without being affected by dust and dirt by keeping the transparent plate-like body clean. Alternatively, it is necessary to adopt a method such as inspecting only a specific defect that can be detected even when it is dirty.

  Patent Document 2 discloses a method for distinguishing and detecting stains that can be removed by cleaning as described above and defects such as scratches and foreign matters. However, with this method, it is difficult to clearly distinguish between dust and dirt on the surface and scratches on the surface, and it is necessary to clean the transparent plate-like body to be detected in order to reliably detect defects. It was.

  Patent Document 3 discloses a method for propagating light from an edge into a transparent plate-like body. However, in a glass having a large absorption, light does not reach the center of the transparent plate-like body, and a transparent plate having a small thickness. It was difficult for light to enter the edge from the edge.

Japanese Patent Laid-Open No. 11-337504 JP 2002-214158 A JP 2003-75367 A

   In the conventional defect detection method using light transmitted through the plate and light reflected from the surface, it is difficult to distinguish surface defects from dirt.

  The present invention provides a defect detection method capable of easily distinguishing between dirt and defects.

  The defect detection method and the detection apparatus according to the present invention is a method for efficiently detecting only defects regardless of the cleanliness of the glass. Among the signals input to the light receiving element for detecting defects, the luminance difference is only detected in the defects. This provides an inspection method that does not cause a difference in brightness between dust and dirt.

Specifically, the light irradiated to the glass is guided to the inside of the glass and is totally reflected, so that only the glass surface and the defects existing in the glass are shined, and the dust and dirt adhering to the glass surface are not shining. By adopting this method, we will adopt a method that reliably detects only defects without being affected by the cleanliness of the glass.
That is, in a defect detection method for illuminating a transparent plate to detect a defect in the transparent plate, a scattering means for scattering illumination light is provided on the surface of the transparent plate, and the scattering means is a transparent plate. A roller-like scattering reflector that is in contact with the surface opposite to the surface on which the illumination light is incident. The scattering means illuminates the scattering means and totally reflects and propagates through the transparent plate. A defect detection method characterized by illuminating a defect in a transparent plate-like body with illumination light.

  Delete

  Delete

  The present invention also provides a defect detection apparatus used in the defect detection method, wherein a light source that illuminates a transparent plate-like body and a roller-like scattering reflection formed by dispersing particles that scatter light in a resin. A defect detection apparatus comprising a body and a CCD camera for detecting light from the defect.

   The transparent plate defect detection method and apparatus according to the present invention can detect defects that can be removed by cleaning such as dirt and dust on the surface and defects that cannot be removed such as foreign matter in the transparent plate and scratches on the surface. A method and an apparatus thereof are provided, the step of cleaning the transparent plate-like body before detection is omitted, and furthermore, there is no need to detect defects in a place where a clean atmosphere is maintained. Improvement and reduction of manufacturing cost.

It is a schematic side view which shows the method of detecting a defect with the light which propagates by totally reflecting in the transparent plate-shaped object. The schematic diagram which shows the illumination light illuminated in a line form. The schematic diagram which shows Snell's law. The schematic diagram which shows the illumination light scattered by a droplet. The schematic diagram which shows the distance of the position which illumination light injects, and a detection position. The schematic diagram which shows the illumination light scattered by a droplet. The schematic diagram which shows the illumination light scattered by a scattering reflector. The schematic diagram which shows the range which a CCD camera focuses.

  The defect detection method of the transparent plate-shaped body of the present invention is not particularly limited, but can be applied to an apparatus for detecting defects of the transparent plate-shaped body with an optical system as shown in FIG. In the optical system shown in FIG. 1, the illuminator 1 desirably illuminates the transparent plate-like body 3 in a line shape as shown in FIG. A line-shaped range is photographed by the CCD camera 4 with respect to the strip-shaped illumination range. The illuminator 1 uses a light source such as a halogen lamp, a xenon lamp, a high-pressure mercury lamp, a sodium lamp, or an LED lamp, blocks light from the light source, or uses a plate-shaped or rod-shaped light guide to form a transparent plate-shaped body 3. Are illuminated in a line as shown in FIG. Although it is desirable to use light with little scattering as the light incident on the transparent plate-like body 3, a diffuser such as frosted glass is used, or illumination light is irradiated with a light guide, and unevenness processing is performed on the exit side of the light guide. And may be scattered light. A rod-like fluorescent lamp can also be used as the light source.

  The total reflected light 6 is light that propagates through the transparent plate at an angle equal to or greater than the critical angle θ. FIG. 3 is a diagram illustrating Snell's law. The incident light 20 is refracted at the interface between the transparent plate-like body 3 and air to become refracted light 21. At this time, the incident angle θ1 of the incident light 20 and the refraction angle θ2 of the refracted light 21 use the refractive index n1 of air and the refractive index n2 of the transparent plate, and Snell's law is n1sinθ1 = n2sinθ2.

When the refractive index n1 of air is 1, sin θ1 = n2sin θ2, and the refraction angle θ2 is obtained by θ2 = sin− ¹ (sin θ1 / n2). The maximum θ1 is 90 °, and the refraction angle θ2 when θ1 = 90 ° is also maximum. When θ1 = 90 °, θ2 is obtained by θ2 = sin− ¹ (1 / n2), and θ2 when θ1 = 90 ° is the critical angle θ. When the transparent plate is soda lime glass such as float glass, n2 = 1.52 and the critical angle θ is 41.8 °.

  FIG. 4 shows a case where a droplet 8 is used as a means for scattering illumination light on the surface of the transparent plate-like body on the same side as the illuminator 1. The droplets 8 are formed in a range illuminated by the illumination light 2 of the transparent plate 3 by spraying mist-like droplets onto the transparent plate 3 using a spray device (not shown). As shown in FIG. 4, the incident angle of the illumination light 2 to the transparent plate-like body 3 does not necessarily have to be vertical, and may be illuminated at an angle that facilitates illumination.

  Since the droplets attached to the surface of the transparent plate-like body have a curved surface shape due to surface tension, the illumination light is scattered in the transparent plate-like body. A part of the illumination light scattered in the transparent plate is scattered at an angle greater than the critical angle θ with respect to the normal of the transparent plate, and is totally reflected and propagates in the transparent plate. .

  The droplets attached to the surface of the transparent plate are preferably water droplets and desirably have a particle size as small as possible. Using an electric sprayer or sprayer, the generated mist is sprayed on the surface of the transparent plate-like body, and water droplets are attached to the surface of the transparent plate-like body.

  The totally reflected light 6 propagates through the transparent plate 3 almost without being affected by dirt, dust, dust, etc. adhering to the surface of the transparent plate 3, and a defect 7 existing in the transparent plate 3. Scattered due to scratches on the surface.

  By detecting light scattered by defects 7 and scratches on the surface of the transparent plate 3 using the detector 4, dirt, dust, dust, etc. adhering to the surface of the transparent plate 3 are removed. Without detection, it is possible to detect only the defects 7 and the scratches on the surface existing in the transparent plate-like body 3.

  The detector 4 is desirably a CCD camera. Further, the CCD camera may be a normal camera, but it is preferable to perform data processing on an image with uniform brightness, and it is desirable to use a line camera that captures only one scanning line.

  Since the detection of the defect by the detector 4 is performed by the total reflection light 6, the position a shown in FIG. 5 where the illumination light 2 enters the transparent plate 3, the position b detected by the detector 4, the position a and the position With respect to the distance d from b, the thickness of the transparent plate 3 is t, and the droplet 8 is attached to the surface of the transparent plate 3 on the same side as the illuminator 1 as shown in FIG. In the case of scattering 2, it is preferable that the distance d is 2 t × tan θ or more.

  As shown in FIG. 6, when the droplet 8 is attached to the surface of the transparent plate 3 opposite to the illuminator 1 for scattering of the illumination light 2, the interval d is preferably t × tan θ or more. .

  When detecting defects by moving the transparent plate, the droplets attached to the surface of the transparent plate move to the detection position of the detector and do not interfere with the detection. It is desirable to arrange the detector and the illuminator in this order in the traveling direction.

  FIG. 7 shows a case where a light scattering body 9 is formed by dispersing particles that scatter light in an elastic resin, and the light scattering body 9 is used as a means for scattering illumination light. In FIG. 7, the light scatterer 9 formed into a cylinder is configured in a roller shape and brought into contact with the surface of the transparent plate 3, and the light scatterer 9 is rotated in accordance with the movement of the transparent plate 3. It is a thing. The light scatterer 9 is preferably in the form of a roller so that it can be rotated, but it may be used in the form of a sheet.

  The resin that molds the light scatterer 9 is preferably elastic, and is preferably transparent or milky white, and uses an acrylic or silicone elastic rubber-like resin. be able to. An opaque resin may be used as the resin.

  As particles to be mixed into the resin, a resin having a relatively large refractive index such as polycarbonate or polystyrene may be used as a powder.

  It is desirable to surround the detector 1 with a light shielding plate 5 so that light other than the light scattered by the defect does not enter the detector.

  When the transparent plate-shaped body 3 is continuously produced, it is desirable to arrange the detector and the spraying device in this order in the direction in which the transparent plate-shaped body proceeds.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

    FIG. 1 shows an optical system of this embodiment.

Example 1
The defect detection method of the present invention was used for a float glass 3 having a thickness of 5 mm that is continuously produced in a float glass production line. In the inspection, the place that came out of the cooling room was surrounded by a black screen, so that there was no light other than the illuminator 1.

  Fog was sprayed on the lower surface of the float glass with an electric sprayer (not shown), and a droplet 8 ′ composed of water droplets was attached to the lower surface side of the transparent plate-like body 3 as shown in FIG. 5. The portion to which the droplet 8 ′ was attached was illuminated with the illumination light 2 from the illuminator 1. The illuminator 1 was a halogen lamp. When the refractive index of the float glass is n2 = 1.52, the critical angle is 41.8 °, and when t = 5 mm, t × tan (θ) = 5 × tan (41.8 °) = 4.5 mm. From this numerical value, the detector 4 and the illuminator 1 are installed in this order in the direction of movement of the float glass, and the position b and the illuminating light 2 detected by the detector 4 shown in FIG. The distance d to the position b to be set was 7 mm, which is about 1.5 times 4.5 mm.

  A CCD camera 10 was used as the detector 4. The focus of the CCD camera was adjusted to the area on the line 11 shown in FIG. 8 near the surface of the transparent plate-like body 3.

  The light that is totally reflected and propagated in the scattered illumination light 6 was scattered by a foreign matter in the transparent plate or a scratch on the surface, and could be detected as a defect. Further, there was no detection of dirt or dust on the surface of the transparent plate as a defect.

Example 2
A polystyrene resin powder was mixed in a transparent silicone resin, formed into a cylindrical shape, and used as the scattering reflector 9 shown in FIG. The scattering reflector 9 was supported so as to be able to rotate as a roller and was brought into contact with the transparent plate 3, and the contacted portion was illuminated with the illumination light 2.

  The same procedure as in Example 1 was performed except that the scattering reflector 9 was used as means for scattering the illumination light.

  Also in the present embodiment, as in the first embodiment, the light that is totally reflected and propagated in the scattered illumination light 6 is scattered by the foreign matter in the transparent plate or scratches on the surface, and can be detected as a defect. . Further, there was no detection of dirt or dust on the surface of the transparent plate as a defect.

DESCRIPTION OF SYMBOLS 1 Illuminator 2 Illumination light 3 Transparent plate-like body 4 Detector 5 Light-shielding plate 6 Total reflection light 7 Defect 8, 8 'Droplet 9 Scattering reflector

Claims (2)

In a defect detection method for illuminating a transparent plate to detect a defect in the transparent plate, a scattering means for scattering illumination light is provided on the surface of the transparent plate, and the scattering means is a transparent plate. Is a roller-like scattering reflector brought into contact with the surface opposite to the surface on which the illumination light is incident, and the roller-like scattering reflector disperses particles that scatter light, and the scattering means The defect detection method is characterized by illuminating a defect in the transparent plate with the scattered illumination light propagating through the total reflection in the transparent plate.   It consists of a light source that illuminates the transparent plate, a roller-shaped scattering reflector formed by dispersing particles that scatter light in the resin, and a CCD camera for detecting light from defects. The apparatus used for the defect detection method according to claim 1.