JPWO2009031420A1 - Method and apparatus for detecting minute foreign matter inside transparent plate - Google Patents

Abstract

Light-blocking minute foreign matter inside the transparent plate is stably detected, and information on the depth of the fine foreign matter is obtained. A method of detecting by measuring bright spots E and F caused by scattering of a light beam 2 irradiated with a minute foreign substance 4 existing inside a transparent plate 1 having a uniform refractive index and a constant thickness. 2 is made to enter the inside of the transparent plate at a predetermined inclination angle with respect to the thickness direction of the transparent plate, and the internal light beam I that has entered and the internal light beam reflected by the surface of the transparent plate are reflected. II is formed inside the transparent plate, and the transparent plate and the light beam 2 are relatively moved (in the G direction) without changing the light beam entrance angle, so that the same minute foreign matter 4 is moved into the internal light beam. A bright spot E generated by irradiation with I and a bright spot F generated by irradiation with the internal light beam II are respectively measured from the thickness direction of the transparent plate to determine the position of the minute foreign matter in the transparent plate. Detects minute foreign matter inside the transparent plate To do.

Description

  The present invention relates to a method and apparatus for detecting minute foreign matter inside a transparent plate such as plate glass, and more particularly to a method and apparatus for detecting minute foreign matter such as nickel sulfide inside a plate glass. Moreover, this invention relates to the manufacturing method of plate glass including the process based on the method of detecting the micro foreign material inside plate glass.

  Fine foreign substances inside glass products are mainly translucent bubbles that transmit light, undissolved raw materials that block light, particles mixed in glass, etc., which become defects of glass products and reduce yield. . In a tempered glass product by so-called physical strengthening method that introduces compressive stress to the surface by prompting after heating the glass, there is nickel sulfide (hereinafter referred to as “NiS”) in which nickel and sulfur are combined. Especially problematic.

  Regarding the problem of NiS in tempered glass products, research from the 1960s has been scattered, for example, disclosed in Patent Document 1. NiS undergoes a structural phase transition from α-NiS to β-NiS depending on the temperature history received in the glass. At this time, since the volume of β-NiS becomes large, when the periphery of NiS is constrained as in the inside of glass, it becomes a cause of generating tensile stress in that portion. On the other hand, since the residual stress in the entire glass product is balanced inside the tempered glass product obtained by the physical strengthening method, a tensile stress remains inside the compressive stress remaining on the surface. NiS having a size of about 0.05 mm exists in the internal tensile stress layer, and a structural phase transition has occurred from α-NiS to β-NiS after a relatively long period of time after the tempered glass product is installed in a building or the like. When tensile internal stress occurs, cracks develop from there and the tempered glass product breaks suddenly. This is a phenomenon called so-called natural damage. This conversely means that spontaneous failure does not occur when NiS is in the surface compressive stress layer rather than the tensile stress layer.

  In order to prevent natural breakage of the tempered glass product, the tempered glass product is placed in a batch furnace and heated to about 280 ° C., thereby forcibly causing a structural phase transition from α-NiS to β-NiS in the furnace. A so-called heat soak process (referred to as heat soak test or HST) excluding glass mixed with NiS is employed.

  However, according to this heat soak treatment, it is necessary to heat the glass product again after manufacturing the tempered glass product, which increases the manufacturing cost.

  In such a situation, Patent Documents 2 and 3 propose a method and an apparatus that can detect the presence of NiS and other fine foreign matters inside the glass at the stage of the glass product before the physical strengthening treatment. In Patent Document 2, although NiS is not a target, laser light is incident in a direction perpendicular to the glass surface, and reflected light emitted in an oblique direction from the upper and lower surfaces of the glass, and sometimes inside the glass, is obtained by a camera. A method of detecting a minute foreign object by imaging and measuring its depth is disclosed. In Patent Document 3, a laser beam is incident on the surface of a glass product at a certain angle, and reflected light on the front and back surfaces is imaged by a camera at the position of the regular reflection light of the laser beam, whereby a fine foreign matter such as NiS is obtained. Is disclosed, and a method for measuring the depth thereof is disclosed.

Japanese Patent Publication No. 47-002113 Japanese National Patent Publication No. 06-510856 Japanese Patent Laid-Open No. 08-082602

  In Patent Documents 2 and 3, since the reflected image is captured by the camera from an oblique direction, the field of view of the camera is widened, reflection of reflected light and reflected light on the glass surface to be captured occurs, and the detection becomes unstable. is there. Further, since imaging is performed from an oblique direction, there is a problem that the square pixels are distorted and the resolution is deteriorated. In addition, this causes a problem that the detection sensitivity varies depending on the irradiation direction for minute foreign matters having different aspect ratios, such as elliptical fine foreign matters.

  In Patent Document 3, since it is necessary to install a camera at the position of the specularly reflected light of the laser beam, if there is a large change in the direction of the specularly reflected light due to the difference in warpage or surface properties of the glass product, There is a problem in that it is difficult to accurately measure the depth at which a minute foreign object is present. In addition, it is not preferable to capture the specularly reflected light of the laser beam directly with the camera in terms of the possibility of damage to the camera.

  Further, when detecting a minute foreign matter, it is necessary to distinguish whether the minute foreign matter contains a light-transmitting bubble or the like or contains light-shielding NiS. However, Patent Documents 2 and 3 have a problem that it is impossible to distinguish between a light-shielding property and a light-transmitting minute foreign matter.

  Furthermore, as described above, the natural breakage occurs when NiS is in the tensile stress layer of the tempered glass product, and when it is in the compressive stress layer near the surface of the glass product, it is not necessary to detect it as a fine foreign substance. For this reason, the existing depth information is important in detecting NiS.

  Furthermore, when detecting a minute foreign object, the higher the resolution of the camera used to obtain information on the shape and color of the minute foreign object, the better. However, a high-resolution camera is expensive and uses a large amount of image data. Therefore, there is a problem that the scanning speed of the object is also slowed down.

  The present invention has been made in view of the above problems, and in detecting minute foreign matter inside a transparent plate such as plate glass, the light-shielding and translucent minute foreign matter can be stably detected regardless of disturbance. It is an object of the present invention to provide a method and an apparatus for detecting minute foreign matters that can be identified. It is another object of the present invention to provide a method and an apparatus for detecting a minute foreign substance capable of obtaining information on the depth at which the light-shielding minute foreign substance containing NiS is present. Furthermore, the above method and apparatus can be realized even with a low-resolution camera in which it is difficult to recognize the shape of a minute foreign object. Furthermore, another object of the present invention is to provide a method for producing a plate glass containing NiS and having no light-shielding minute foreign matter as a raw plate glass before physical strengthening treatment for producing a tempered glass product.

  The present invention detects a minute foreign matter inside a transparent plate body such as a plate glass, particularly a minute foreign matter such as NiS inside a plate glass, and obtains information on the depth at which the minute foreign matter exists, and a method for detecting the minute foreign matter The invention is mainly related to the following invention. Furthermore, the present invention is mainly the following invention relating to a method for producing a plate glass that does not contain such a fine foreign material by removing the plate glass on which the detected fine foreign material exists.

  (1) A method of detecting by detecting a bright spot caused by scattering of a light beam irradiated with a minute foreign substance existing inside a transparent plate having a uniform refractive index and having a constant thickness, wherein the light beam is transparent A transparent plate body is made to enter the transparent plate body at a predetermined inclination angle with respect to the thickness direction of the body, and the internal light beam I and the internal light beam II reflected by the surface of the transparent plate body are transparent. A bright spot formed by irradiating the same minute foreign matter with the internal light beam I, formed inside the plate body, relatively moving the transparent plate body and the light beam without changing the light beam entrance angle; A bright spot generated by irradiation with the internal light beam II is detected from the thickness direction of the transparent plate, and the position of the minute foreign matter in the transparent plate is determined. A method to detect minute foreign matter.

  (2) A method of detecting by measuring a bright spot caused by scattering of a light beam irradiated with a minute foreign substance existing inside the plate glass, wherein the light beam is at a predetermined inclination angle with respect to the thickness direction of the plate glass. An irradiating means for forming an internal light beam I that has entered the interior and an internal light beam II reflected by the surface of the plate glass inside the plate glass; and a vertical direction from the plate glass surface to the surface. An imaging unit that images the emitted light on the light beam irradiation surface side or the non-irradiation surface side of the plate glass, an image processing unit that determines a position of a minute foreign substance inside the plate glass based on an image captured by the imaging unit, The same minute foreign matter is illuminated by the internal light beam I by moving the light beam irradiation position of the plate glass without changing the light beam entrance angle. The bright spot generated and the bright spot generated by irradiating with the internal light beam II are imaged by the imaging means, and the image processing means based on the image taken by the imaging means in the glass plate of the minute foreign matter A method for detecting a minute foreign substance inside a plate glass, wherein the position is determined.

  (3) A method of detecting by detecting a bright spot generated by scattering of a light beam irradiated with a minute foreign substance existing inside a plate glass, wherein the first light beam is inclined at a predetermined inclination with respect to the thickness direction of the plate glass. A first irradiating means for entering the inside of the plate glass at an angle, and forming an internal light beam I that has entered and an internal light beam II reflected by the surface of the plate glass inside the plate glass; and a second light beam To the inside of the glass sheet from the direction opposite to the inclination angle of the first light beam with respect to the thickness direction of the glass sheet, and the entered internal light beam I ′ and the internal light beam I ′ reflected by the surface of the glass sheet A second irradiation means for forming a light beam II ′ inside the plate glass, and light emitted from the plate glass surface in a direction perpendicular to the surface, on the light beam irradiation surface side or non-irradiation surface side of the plate glass Based on the imaging means for imaging, and based on the image taken by the imaging means, the image processing means for discriminating between the minute foreign matter inside the plate glass and the foreign matter such as dust on the surface of the plate glass, and determining the position of the minute foreign matter inside the plate glass; The same foreign matter is irradiated by the internal light beams I and I ′ by moving the light beam irradiation position of the plate glass without changing the entrance angles of the first and second light beams. The generated bright spot and the bright spot generated by irradiation with the internal light beams II and II ′ are imaged by the imaging means, and the first light is obtained by the image processing means based on the image captured by the imaging means. A foreign matter such as dust on the surface of the glass plate is discriminated based on the symmetry of the image of the bright spot by the same foreign material generated by the beam and the second light beam, and the position of the minute foreign material in the glass plate is determined. Board A method to detect minute foreign matter inside glass.

(4) A device for detecting minute foreign matter inside the plate glass, which makes the light beam enter the plate glass at a predetermined inclination angle with respect to the thickness direction of the plate glass, and enters the internal light beam I and the internal light beam. An irradiation device for forming an internal light beam II reflected on the surface of the plate glass inside the plate glass, a moving means for moving the light beam irradiation device relative to the plate glass in a direction parallel to the plane of the plate glass, and a plate glass An imaging apparatus for imaging light emitted from a surface in a direction perpendicular to the surface on a light beam irradiation surface side or a non-irradiation surface side of a plate glass, and the same minute foreign matter is irradiated by the internal light beam I An imaging device that captures the generated bright spot and the bright spot generated by irradiation with the internal light beam II, and a minute foreign object is determined based on the captured image connected to the imaging device An image processing means.
(5) A device for detecting minute foreign matter inside the glass sheet, the first light beam entering the inside of the glass sheet at a predetermined inclination angle with respect to the thickness direction of the glass sheet, and the entering internal light beam I and the A first irradiating device that forms an internal light beam II reflected by the surface of the glass sheet on the surface of the glass sheet, and a tilt of the first light beam with respect to the thickness direction of the glass sheet. A second irradiating device that enters the inside of the glass sheet from a direction opposite to the angle, and forms an internal light beam I ′ that has entered and an internal light beam II ′ that is reflected by the surface of the glass sheet inside the glass sheet; A moving means for moving the first and second irradiation devices relative to the plate glass in a direction parallel to the plane of the plate glass, and light emitted from the plate glass surface in a direction perpendicular to the surface. Light beam illumination An imaging device for imaging on a light emitting surface side or a non-irradiated surface side, wherein the same foreign matter is irradiated by the internal light beams I and I ′ and is generated by being irradiated by the internal light beams II and II ′ An image capturing apparatus that captures a bright spot, and an image processing unit that is connected to the image capturing apparatus and that determines a minute foreign object based on the captured image.

  (6) a step of detecting a minute foreign matter based on the method for detecting minute foreign matter inside the plate glass described above, and a step of determining whether or not to remove the plate glass containing the minute foreign matter detected by the detection step; And a removing step of removing the plate glass containing minute foreign substances based on the discrimination result of the discrimination step.

  (7) A step of manufacturing a continuous plate glass, a detection step of detecting a minute foreign matter in the continuous plate glass based on the method for detecting a minute foreign matter inside the plate glass described above, and a minute foreign matter detected by the detection step Discriminating step for discriminating whether or not to remove the plate glass containing, a cutting step for cutting the continuous plate glass into a predetermined size, and a cut plate glass containing minute foreign matter that should be removed based on the discrimination result of the discriminating step And a removing step for removing the glass.

  According to the present invention, the position of the minute foreign matter inside the transparent plate can be detected stably without being influenced by disturbance. Moreover, even if the minute foreign matter is light-shielding or translucent, it can be detected, and the type of these can be determined. In particular, it is possible to obtain information on the depth at which the light-shielding minute foreign matter containing NiS inside the plate glass is present, and it is also possible to distinguish it from other kinds of fine foreign matters such as bubbles. As a result, fine foreign matter containing NiS existing at a depth that may cause a problem from the surface of the plate glass is identified, and the plate glass containing such fine foreign matter is removed from the tempered plate glass manufacturing process, and natural damage may occur in the future. It is possible to suppress the production of tempered flat glass. Further, the detection of the above-mentioned minute foreign matter can be realized using a low-resolution camera that does not require shape recognition of the fine foreign matter.

The figure explaining the basic view of the method of detecting the micro foreign material inside the plate glass concerning the present invention. [1-1] and [1-2] are schematic cross-sectional views of the plate glass, [1-1] is when the minute foreign matter comes into contact with the internal light beam I, and [1-2] is the minute foreign matter. Sectional drawing at the time of contact with the internal light beam II. [1-3] and [1-4] are schematic plan views of the plate glass, [1-3] is the time indicated in [1-1], and [1-4] is [1-2]. FIG. The schematic diagram which shows the detail of the luminescent point (E, F) in FIG. 1 in case a micro foreign material is a light-shielding sphere. The figure explaining the manufacturing method of the plate glass which concerns on this invention. The figure explaining the method and apparatus which detect the micro foreign material inside the plate glass in conveyance which concerns on this invention. The figure explaining another method and apparatus which detect the micro foreign material inside the plate glass in conveyance which concerns on this invention. The figure explaining another method and apparatus which detect the micro foreign material inside the plate glass in conveyance which concerns on this invention. The figure explaining another method and apparatus which detect the micro foreign material inside the plate glass in conveyance which concerns on this invention. The figure explaining another manufacturing method of the plate glass which concerns on this invention. The figure explaining embodiment of another apparatus which detects the micro foreign material inside the plate glass which concerns on this invention. The figure explaining another method and apparatus which detect the micro foreign material inside the plate glass in conveyance which concerns on this invention. The figure which shows the image imaged by the method of detecting the micro foreign material inside the plate glass concerning this invention (when the micro foreign material exists on the internal light beam I with NiS). The figure which shows the image imaged by the method which detects the micro foreign material inside the plate glass concerning this invention (when a micro foreign material exists on the internal light beam II with NiS). The figure which shows the image imaged by the method of detecting the micro foreign material inside the plate glass concerning the present invention (when the micro foreign material is a bubble on the internal light beam I). The figure which shows the image imaged by the method of detecting the micro foreign material inside the plate glass which concerns on this invention (when a micro foreign material exists on the internal light beam II with a bubble).

Explanation of symbols

1: plate glass 2: linear laser beam 3: imaging means 4: minute foreign matter 5: irradiation means 6: image processing means 7: second linear laser beam 8: second irradiation means 10: irradiation surface 11: non-irradiation Surface 12: Plate glass moving means (roller)
13: Moving means 14: Table a ₁ : Distance between AB ′ in [1-1] in FIG. 1 or Distance between B ′ and C in [1-2] a ₂ : [1- in FIG. 1], the distance between A and E 'in [1], or the distance between F' and C in [1-2], d ₁ : the thickness d _{2 of the} plate glass, and the distance x from the irradiation surface of the minute foreign matter, x: parallel to the surface of the plate glass One of the two directions of the flat surface (in the case of a rectangle, the direction is parallel to each of two orthogonal sides, and in the case of a continuous plate glass, the length direction)
y: One of the two directions parallel to the surface of the plate glass (in the case of a rectangle, the direction is parallel to each of two orthogonal sides, and in the case of a continuous plate glass, the width direction)
z: Plate glass thickness direction A: Scattered light from the irradiated area formed on the irradiated surface, bright line extending in the y direction B: Scattered from the irradiated area formed by irradiating the non-irradiated surface from the inside side Bright line B ′ extending in the y direction with light: Line in which the z-direction light of the bright line (B) intersects the irradiation surface C: Scattered light from the irradiation region formed by irradiating the irradiation surface from the inside, y Bright line E extending in the direction: Bright spot E ′ due to scattered light or the like generated when the minute foreign matter is irradiated with the internal light beam I: Point F where the z-direction light of the bright spot (E) intersects the irradiated surface F: The minute foreign matter is inside Bright point F ′ due to scattered light or the like generated by irradiation with the light beam II: Point where the light in the z direction of the bright point (F) intersects the irradiation surface G: Movement (conveyance) direction of the plate glass H: Movement direction I by the moving means : Internal light beam I
II: Internal light beam II

  The transparent plate in the present invention is not limited to plate glass as long as it is made of a transparent material having a uniform refractive index and is a plate having a predetermined thickness. As long as it is transparent, it may be a transparent plate made of an inorganic material such as a metal oxide or ceramics or a plastic material such as an organic polymer material.

  The minute foreign matter inside the transparent plate may be made of a light-blocking solid material or a light-transmitting solid material having a refractive index different from that of the material of the transparent plate, and the material of the transparent plate made of a gaseous substance or a liquid substance And may be made of translucent materials having different refractive indexes. Further, it may be a portion where no substance exists. In short, the minute foreign material is optically different from the material of the transparent plate, and may be any material that scatters, reflects, or refracts light inside the transparent plate. The size of the minute foreign matter may be 1 mm or less, particularly 0.5 to 0.01 mm. It may be even smaller as long as its bright spot by optically scattered light or the like can be measured. Also, a size exceeding 1 mm can be detected. However, the foreign object in the transparent plate is usually a foreign object having a size of 1 mm or less.

  The light beam may be any light beam (bundle) with high directivity, but a laser light beam (hereinafter also referred to as a laser beam) is preferable. Visible light is preferred as the light. However, light other than visible light may be used as long as it can be measured by an imaging means or the like. The cross-sectional shape of the light beam may be linear or point (spot). In order to widen the detectable depth, the width of the line is preferably narrow, and the size of the point (spot) is preferably small. The linear laser beam can be obtained by, for example, a so-called line laser that emits a linear laser beam by providing a lens at the tip of a laser oscillator. In the case of a point light beam, it is preferable to form a beam that is substantially similar to a linear beam by moving the point light beam at high speed. As a means for converting the point light beam into a substantially linear beam, for example, there is a means using a polygon mirror.

  The light beam that irradiates the transparent plate preferably forms a linear irradiation area on the surface of the transparent plate that extends in a direction perpendicular to the axis of the light beam. In the case of a linear beam using a lens such as a line laser, it is possible to keep the width of the linear irradiation area constant and reduce the change in light intensity in the length direction. When the width of the linear irradiation area is not constant, the change in the light intensity of the bright spot due to the position in the line direction becomes large, and it may be difficult to determine the type of minute foreign matter by comparing the light intensity between the bright spots. .

  The light beam irradiation means is a means for generating the light beam as described above and irradiating the surface of the transparent plate at a predetermined incident angle, and oscillates the laser beam as a linear light beam or a substantially linear beam. What irradiates a transparent plate pair surface is preferable. The same applies to the light beam irradiation apparatus. By irradiating the surface of the transparent plate with a light beam at a predetermined incident angle, the light beam enters the transparent plate, and internal light beams I and II described later are formed.

  When scanning the surface of the transparent plate, in the case of a linear light beam, it is preferable to relatively move the linear light beam in a direction substantially perpendicular to the line. If the length of the linear light beam is less than the width of the surface, scan with a plurality of linear light beams, or scan the linear beam at high speed in the length direction of the linear light beam (that is, the linear light beam). It is preferable to scan by moving the beam at a higher speed than the relative moving speed of the beam. In the case of a point light beam, a beam substantially similar to a linear beam is formed as described above, and the surface of the transparent body is scanned using the substantial linear beam in the same manner as the linear beam. It is preferable to carry out. The relative moving direction of the transparent plate and the linear light beam is not limited to the above. Even when the moving direction is other than the substantially vertical direction, it is possible to distinguish whether or not two bright spots are formed from one minute foreign matter, and when the two bright spots are formed from one minute foreign matter. The type can be determined by comparing the light intensity (the position of the minute foreign matter can be determined from one bright spot).

  Hereinafter, a plate glass as a transparent plate, a non-transparent solid substance (NiS fine particles, etc.) and a gaseous substance (bubbles) of a size to be detected as a fine foreign substance, a linear laser beam as a light beam, The present invention will be described by way of example.

  FIG. 1 is a schematic diagram for explaining the basic concept of the method of the present invention for detecting minute foreign matter inside a plate glass. [1-1] and [1-2] in FIG. 1 are schematic cross-sectional views of the plate glass (1), and [1-1] shows a minute foreign matter (4) in contact with the internal light beam I (I). [1-2] is a cross-sectional view when the minute foreign matter (4) is in contact with the internal light beam II (II). [1-3] and [1-4] in FIG. 1 are schematic plan views of the plate glass (1), and [1-3] is the time indicated in [1-1], [1-4] These are top views at the time shown in [1-2].

  In FIG. 1, the thickness direction of the plate glass among the three orthogonal directions is hereinafter referred to as the z direction. Two directions of a plane parallel to the surface of the plate glass are hereinafter referred to as an x direction and a y direction. In the case of a rectangular plate glass, it is preferable that the directions parallel to the two orthogonal sides are the x direction and the y direction. In the glass ribbon (continuous plate glass) described later, it is preferable that the length direction of the glass ribbon is the x direction and the width direction is the y direction. Of the two surfaces of the plate glass (1), the surface (10) irradiated with the linear laser beam (2) is referred to as an irradiated surface, and the other surface (11) is referred to as a non-irradiated surface. The linear laser beam (2) irradiates the irradiation surface (10) from the x direction, and in FIG. 1, the beam portion irradiated with the minute foreign matter is indicated by a single line. In FIG. 1, it is assumed that the linear laser beam (2) forms a linear irradiation region extending in a direction perpendicular to the axis. That is, as shown in [1-3] and [1-4] in FIG. 1, the linear irradiation area formed on the irradiation surface (10) by irradiation of the linear laser beam (2) from the x direction is: The length direction of the line is the y direction.

  As shown in [1-1] and [1-2] in FIG. 1, the linear laser beam (2) that irradiates the plate glass from the direction inclined with respect to the z direction irradiates the irradiation surface (10). Laser beams are reflected, refracted and scattered. Scattering is caused by fine irregularities on the surface of the plate glass. The refracted laser beam enters the inside of the plate glass (1), and this laser beam that has entered is referred to as an internal light beam I. The internal light beam I (I) then reaches the inside of the non-irradiated surface (11) where it is reflected, refracted and scattered (refracted light is not shown). A laser beam that travels inside the plate glass (1) due to reflection of the internal light beam I (I) on the inside of the non-irradiated surface (11) is referred to as an internal light beam II. Accordingly, the internal light II reflected from the surface of the glass sheet by the internal light beam 1 (I) refers to the internal light II reflected from the inside of the non-irradiated surface. The internal light beam II (II) then reaches the inside of the irradiated surface (10), where it is reflected, refracted and scattered (the reflected light is not shown).

  A bright line extending in the y direction is generated by the scattered light from the irradiated region formed on the irradiated surface (10), and this bright line is hereinafter referred to as a bright line (A). Similarly, the internal light beam I (I) irradiates the non-irradiated surface (11) from the inner side to form a linear irradiation region. Hereinafter, the bright line generated by the scattered light from this irradiation region is the bright line (B). That's it. Further, the internal beam II (II) irradiates the irradiation surface (10) from the inside to form a linear irradiation region, and the bright line generated by the scattered light from this irradiation region is hereinafter referred to as a bright line (C). The bright lines A, B, and C shown in [1-3] and [1-4] in FIG. 1 are made of light emitted in the z direction from each irradiation region. Since the laser beam is attenuated by reflection, refraction, and scattering on each surface and absorption inside the plate glass, the light intensity of each emission line decreases in the order of emission line (A)> emission line (B)> emission line (C).

  In [1-1] and [1-3] in FIG. 1, a bright spot due to scattered light or the like generated by irradiating the minute foreign matter (4) with the internal light beam I (I) is referred to as a bright spot (E). Similarly, in [1-2] and [1-4], a bright spot due to scattered light or the like generated by irradiating the minute foreign matter (4) with the internal light beam II (II) is referred to as a bright spot (F). In [1-1], the point where the light in the z direction of the bright spot (E) intersects the irradiated surface (10) is defined as E ′. In [1-2], the light in the z direction of the bright spot (F) is irradiated on the irradiated surface ( Let F ′ be the point that intersects 10). In [1-1] and [1-2], B ′ is a line where the light in the z direction of the bright line (B) intersects the irradiated surface (10). The light emitted from the minute foreign matter (4) in the z direction includes light reflected in the z direction among scattered light, reflected light emitted in the z direction, refracted light emitted in the z direction, and the like.

  The measurement in the present invention is performed as follows. The plate glass (1) is relatively moved in the x direction from the right to the left (G direction in [1-1] in FIG. 1), and the bright line and the bright spot are measured from the z direction by an imaging means such as a camera. Imaging is performed when the minute foreign matter (4) is irradiated to the internal light beam I (I). [1-3] in FIG. 1 is a schematic diagram of an image at the time of the measurement. In the image captured before the time when the minute foreign matter (4) was irradiated to the internal light beam I (I), the bright lines (A), (B), and (C) exist, but the bright spot (E) does not exist. In the image of the schematic diagram of [1-3], bright lines (A), (B), (C) and a bright spot (E) exist, and the distance between the bright spot (E) and the bright line (A) (the bright spot ( E) and the bright line (B) may be measured). Since the distance between the bright lines (A) and (B) does not change, the distance between the bright lines (A) and (B) can be measured at this time or other time. Further, the bright lines (A) and (C) exist at positions symmetrical to the bright line (B). As described later, at this time, the distance between the bright spot (E) and the bright line (A) and the distance between the bright lines (A) and (B) are measured from the image shown in the schematic diagram of [1-3]. For example, the ratio of the depth (the distance from the irradiated surface (10)) of the minute foreign matter (4) to the thickness of the plate glass is found, and when the thickness of the plate glass is known, the absolute distance of the depth is found.

  Next, when the plate glass further moves and the minute foreign matter (4) is separated from the internal light beam I (I), the bright spot (E) disappears, and further the fine foreign matter (4) is irradiated to the internal light beam II (II). A bright spot (F) is generated at the position. [1-4] in FIG. 1 is a schematic diagram of an image at the time when the bright spot (F) occurs. In the image of the schematic diagram of [1-4], bright lines (A), (B), (C) and a bright spot (F) exist, and the distance between the bright spot (F) and the bright line (C) (the bright spot ( F) and bright line (B) may be measured). Each distance between the bright lines (A), (B), and (C) is equal to the image in the schematic diagram of [1-3], and the distance between the bright spot (F) and the bright line (C) is [1-3. ] Is equal to the distance between the bright spot (E) and the bright line (A) in the schematic diagram. That is, in both schematic diagrams, the bright spots (E) and (F) exist at positions symmetrical with respect to the bright line (B).

The distance between the bright lines (A), (B) measured from the image shown in [1-3] in FIG. 1 is the distance _{a 1} between A-B 'in [1-1] in FIG. 1, similar Further, the distance between the bright line (A) and the bright spot (E) is a distance a ₂ between AE ′. Assuming that the thickness of the plate glass is d ₁ and the distance of the minute foreign matter (4) from the irradiation surface (10) is d ₂ , d ₁ is known because a ₂ / a ₁ = d ₂ / d ₁ If there is, d ₂ is obtained from a ₁ and a ₂ measured from the image shown in [1-3] in FIG. Similarly, the distance a ₁ between B′-C measured from the image shown in [1-4] of FIG. 1 and the distance a ₂ between the distance F′-C between the bright line (C) and the bright spot (F). From this, d ₂ is obtained. The light intensity of the bright line (C) is weaker than that of the bright line (A), and it may be difficult to measure the position of the bright line (C), and the light intensity of the bright spot (F) is bright spot (E). The depth of the minute foreign matter (4) is preferably obtained from the image shown in [1-3] because the measurement of the position of the bright spot (F) may be difficult. Even if the thickness d _{1 of the} plate glass is unknown, it can be calculated from the angle of incidence of the internal light beam I (I) (the irradiation angle of the linear laser beam (2) with respect to the irradiation surface (10) and the refractive index of the glass. ) Is known, d ₂ can be obtained by calculating d ₁ from a _{1 and} this approach angle.

  FIG. 2 is a schematic diagram showing details of the bright spots (E) and (F) in FIG. 1 when the minute foreign matter (4) is a light-shielding sphere. The foreign object (4) corresponds to [1-1] in FIG. 1, the minute object (4) in [2-2] in FIG. 2 corresponds to [1-2] in FIG. 3] corresponds to [1-3] in FIG. 1, and the minute foreign substance (4) in [2-4] in FIG. 2 corresponds to [1-4] in FIG. As shown in these figures, when the internal light beams I and II are inclined with respect to the z direction and irradiate the minute foreign matter (4) from the opposite direction, light emission emitted to the irradiation surface (10) side in the x direction. The area is wide at the bright spot (E) and narrow at the bright spot (F). Therefore, the light intensity of the internal light beams I and II is different, and the light intensity of the bright spot (F) is considerably weaker than that of the bright spot (E). In addition, since the area of the light emitted perpendicularly to the non-irradiated surface (11) is opposite to the above, the difference in light intensity between the two bright spots due to the minute foreign matter (4) is smaller than in the above case. Become.

  If the minute foreign matter (4) is a translucent sphere such as a bubble, the bright spots (E) and (F) are formed by adding light emitted from the inside of the minute foreign matter in addition to the scattered light from the surface of the minute foreign matter. It is thought. The light emitted from the inside of the minute foreign matter refers to light that has entered the inside of the minute foreign matter or light reflected from the inner surface of the minute foreign matter has exited from the inside of the minute foreign matter due to refraction or scattering. For this reason, normally, the bright spots (E) and (F) due to the light-transmitting minute foreign matter (4) have higher light intensity than those due to the light-shielding minute foreign matter. In particular, in the bright spot (F), light is emitted also from the shadow portion of the minute foreign matter (4) shown in [2-4] in FIG. Thus, the light intensity is considered to increase. Therefore, when the ratio of the light intensity of the bright spot (F) to the bright spot (E) ([light intensity of the bright spot (F)] / [light intensity of the bright spot (E)]) is measured, it is usually translucent. In comparison with the light-shielding minute foreign matter, the ratio is close to 1, and sometimes exceeds 1. Therefore, by comparing the light intensity of the bright spots (E) and (F), it is possible to distinguish whether the minute foreign matter is light-shielding or translucent. The measurement is usually preferably performed from the irradiation surface (10) side because the difference in light intensity between the bright spots (E) and (F) is large in the case of a light-shielding minute foreign matter. In some cases, measurement can be performed simultaneously from the irradiated surface (10) side and the non-irradiated surface (11) side, and the bright spots (E) and (F) can be compared and compared.

  The incident angle of the linear laser beam (2) is determined by the resolution for detecting the depth of the minute foreign matter, the width of the laser beam, and the depth range where the detection of the fine foreign matter is necessary. In [1-1] and [1-2] in FIG. 1, when the incident angle is an angle with respect to the z direction, the distance between the bright line (A) and the bright line (B) in the captured image increases as the incident angle increases. The detection resolution of the depth information of the minute foreign matter is improved. However, the incident angle is limited by the range of the width of the linear laser beam (2) and the depth that requires detection of minute foreign matter.

  Since the widths of the bright lines (A), (B), and (C) are finite, when the image is taken from the z direction, the bright line (A) and the bright line become brighter as the position of the minute foreign matter (4) is closer to the irradiated surface (10). When the distance of the point (E) becomes short and the two approach below the resolution of the image, the distance cannot be measured. Similarly, when the position of the minute foreign matter (4) is close to the non-irradiated surface (11), it is difficult to measure the distance between the bright line (B) and the bright spot (E).

When the width of the linear laser beam (2) is W, the width of the irradiation area on the irradiation surface is W _S , and the incident angle is θ, W _S is expressed by W / cos θ. Thus, the depth T at which the minute foreign matter cannot be detected is expressed by 0.5 · W _S / tan θ _S, where θ _S is an incident angle changed by refraction on the irradiation surface. The depth T at which the minute foreign matter (4) cannot be detected does not depend on the plate thickness of the plate glass.

On the other hand, in the tempered glass as described above, since NiS in the region where the compression stress layer near the irradiated surface and the non-irradiated surface remains does not affect the natural breakage, the detection target depth is X, and the plate glass thickness is t. Then, W and θ need to satisfy T <(t−X) / 2. When the refractive index of the plate glass is 1.5, which is a general value, the incident angle is 49 degrees, the W / T is maximum, and the depth T at which a minute foreign matter cannot be detected for any W is minimum. It means that there is. It even if were possible to infinitely infinitely large incident angle theta made small W, the detection resolution of the depth of the fine foreign matter for percent change from Snell's law theta _S is rapidly reduced to dramatically improve There is no.

  Therefore, the incident angle is preferably 44 to 54 degrees, and more preferably 46 to 52 degrees where the undetectable depth is shallower. The width of the linear laser beam (2) may be about 0.25 mm when the plate glass is 4 mm thick. As the thickness of the glass plate increases, the area that need not be detected increases, so the width of the linear laser beam (2) may be relatively wide.

The measurement of the bright spot and the bright line is preferably performed by an imaging means (imaging device) such as a camera. An area scan camera (such as a CCD camera) that captures a two-dimensional image, converts the optical image into an electrical signal, and outputs the signal is preferable. Smaller foreign objects can be detected as the number of pixels increases. In the present invention, identification of the shape and color of the minute foreign matter is not essential. In addition, by blocking outside light by installing a dark room, etc., there is no optical signal outside the area where the laser beam is transmitted, and all noise that causes disturbance such as dust on the surface of the glass sheet is all on the irradiated and non-irradiated surfaces of the glass sheet. It is possible to use only the optical signal of For this reason, the S / N ratio (effective input signal / noise signal) in the image corresponding to the region inside the plate glass where the minute foreign matter is present is remarkably increased.
Therefore, if the signal of the bright spot or the bright line is sufficient, even if the size of the bright spot due to the minute foreign matter is less than one pixel, the minute foreign matter can be detected. That is, in the present invention, information from a minute foreign matter may be less than that in the prior art, so that even a low-resolution area scan camera can detect the information.

  It is preferable that images of bright spots and bright lines are captured continuously at short intervals and image data is captured rather than controlling the timing of imaging. The captured image data is sent to the image processing means. In the image processing means, the z-direction position (depth) and y-direction position (reference position) of the bright spot in each captured image based on the comparison between the image data stored in the memory in the numerical arithmetic unit and the captured image data. By combining any one or some of the three pieces of information of the position in the plane direction with respect to and the timing at which the bright spot appears, two types of images of the same minute foreign matter can be set. Since bright lines are always detected, information on the position (depth) in the z direction can be obtained relatively stably. Information on the position in the y direction can be obtained from the relative movement direction and movement speed of the plate glass. If a deviation in the movement direction or movement speed is expected, measures to prevent it or correct the deviation are taken. As for information on the timing at which a bright spot appears, it is not sufficient to set two types of images of the same minute foreign object alone, and at least the position (depth) of the bright spot in the z direction or the position in the y direction. It is necessary to combine the information. If the relative moving direction and moving speed of the plate glass are constant, two images to be set can be selected stably. However, if this is not the case, errors in the positions in the x, y and z directions are also accumulated. For this reason, it is preferable to take measures such as selecting two images to be set in consideration of data on the relative moving direction and moving speed of the plate glass sent from the area scan camera.

  Based on the data of the captured image, the position and type of the minute foreign matter are determined in the subsequent stage of the image processing means. Since image data is usually captured as digital data, this data is used to extract the bright spots and bright lines to be measured using an extraction routine that takes into account features such as bright spot and bright line positions. And the determination data is output. The position (depth) in the z direction is calculated from the distance between the bright line and the bright spot and the thickness of the plate glass as described above. The position in the x and y directions is calculated from the distance of the bright spot from the reference position in the x and y directions. At this time, the distance between the two bright spots (relative movement distance of the glass sheet), the time interval at which the two bright spots appear, the angle between the line connecting the two bright spots and the bright line (the relative movement direction of the glass sheet) ) Etc. are considered. The kind of minute foreign matter is determined from the light intensity ratio of two bright spots derived from the same minute foreign matter as described above. When the light intensity is digitized by the image gradation value, it is preferable to perform noise processing or the like.

  The image processing means comprises a numerical operation device such as a personal computer, a memory, and image processing software for identifying the image as described above. Alternatively, a numerical operation element incorporating these functions may be used. By this image processing means, it is possible to automatically and continuously perform the storage, extraction, determination and the like of the captured image.

  According to the present invention, in the production of a glass sheet, according to the presence / absence of a micro foreign material and the position and type of the micro foreign material, a micro foreign material containing plate glass that should not be a product is determined, and based on the result, a micro foreign material containing material that should not be a product is contained. The plate glass can be removed from the manufacturing process. The determination as to whether or not to be a product can be performed by comparing the determination data stored in the determination means in advance with the determination data of the minute foreign matter determined by the image processing means. The discrimination means can be incorporated in the image processing means, and the discrimination result can be used as output data of the image processing means. In the case of the plate glass after the plate glass to be discriminated is cut into a predetermined shape, the plate glass that is discriminated to be a product may be removed from the manufacturing process.

  The figure explaining one embodiment of the manufacturing method of the plate glass which concerns on FIG. 3 at this invention is shown. In addition, in this figure, the process which manufactures a continuous plate glass (henceforth a glass ribbon) and the plate-drawing process may be a well-known technique or any other technique. After manufacturing a glass ribbon from molten glass by the float method, etc., when cutting into a predetermined size to make a product, minute foreign objects are detected at the stage of the glass ribbon, and there are fine foreign objects that should not be included in the product. If detected, the cut plate glass containing the minute foreign matter is removed from the manufacturing process. At this time, it is preferable to increase the yield by cutting the glass ribbon so as to reduce the area of the cut glass sheet containing minute foreign matters that should not be included in the product as much as possible to reduce the area of the discarded glass sheet. When discriminating minute foreign matter in the glass ribbon, it is determined whether the detected minute foreign matter is a minute foreign matter that should not be included in the product by the determining means, and the minute foreign matter determined not to be included in the product The position in the glass ribbon (the position in the depth direction is negligible after the determination) is taken into the cutting control means from the output data of the image processing means and cut, and the cut plate glass containing the minute foreign matter is removed from the manufacturing process. The yield can be increased by incorporating in the cutting control means a program for reducing the area of the cutting plate glass containing minute foreign substances as much as possible.

  In addition, when detecting the micro foreign material in a glass ribbon, since the glass ribbon is moving continuously in the length direction (usually at constant speed), the plate glass and the light beam (or irradiation area) The relative movement can be performed with the light beam (or irradiation area) fixed. Further, as the moving means of the glass ribbon, the original moving means of the glass ribbon that is separated from the minute foreign matter detecting device is used.

  The method of the present invention does not require recognition of the shape and color as in the prior art in detecting the minute foreign matter, and is based only on the light signal as described above, so it is difficult to recognize the shape of the fine foreign matter. The area scan camera can be used. Compared to the conventional case where a minute foreign object is detected by a single light beam by using light of two paths (internal light beams I and II) derived from one light beam, the minute foreign object is light-shielding. Regardless of translucency, it is possible to detect stably including light-shielding and translucent minute foreign matter regardless of disturbance. In particular, it is difficult in Patent Documents 2 and 3 described above to easily and accurately distinguish between light-shielding and translucent minute foreign matters. In addition, since light from two surfaces, the irradiated surface and the non-irradiated surface, can be used, the measurement of the depth of the minute foreign matter can be performed stably and accurately without being influenced by disturbance. For this reason, it can be measured even when the transparent plate is dark. Depending on the irradiation direction of the light beam and the imaging direction of an imaging means such as an area scan camera, reflection from the surroundings on the irradiation surface to be imaged is reduced, and stable detection of minute foreign objects is possible regardless of disturbance. Since the irradiation position of the light beam and the position of the imaging means do not have to be on the same sheet glass surface side as in Patent Documents 2 and 3, the degree of freedom of installation is high.

  In addition, in the method of the present invention, unlike in Patent Documents 2 and 3, since the image is taken from the thickness direction of the plate glass, there is little change in resolution with respect to minute foreign matters depending on the irradiation direction. Even when reflection on the glass surface as a disturbance becomes a problem, it is easy to take measures. Furthermore, even with a light beam using a laser, specular reflection light on the surface of the plate glass is not taken into the imaging means, and there is little risk of damage to the imaging means by the laser beam.

  Hereinafter, the present invention will be described with examples.

  FIG. 4 to FIG. 7 are diagrams for explaining an embodiment of a method and apparatus for detecting minute foreign substances inside a plate glass by moving only the plate glass horizontally on the plate glass plane with the moving speed of the irradiation means and the imaging means being zero. Indicates. According to this embodiment, the above-described detection of minute foreign matters on the glass ribbon may be performed continuously, or even if necessary, detection of minute foreign matters on the sheet glass product after cutting stored before the strengthening step may be performed. Good.

  The plate glass (1) is placed on a roller (12), which is a known moving means, and moves in the transport direction (G). By this movement, the inner light beam I (I) that directly reaches the assumed detection location inside the plate glass from the irradiation surface (10) of the plate glass (1) by the irradiation means (5) is the lower surface of the plate glass at the same detection location. An internal light beam II (II) that arrives by reflection at the non-irradiated surface (11) scans the glass sheet. As a result, it is possible to detect minute foreign matter over the plane of the plate glass (1).

  The linear laser beam (2) is irradiated so that it is linear on the irradiation surface (10) and the irradiation direction has a moving direction component (G) or an inverse component. The linear light beam may be perpendicular to the moving direction (G) on the irradiation surface (10) as shown in FIG. 4, or the angle with respect to the direction perpendicular to the moving direction (G) as shown in FIG. The irradiation direction of the light beam may be from the opposite direction as shown in FIG. That is, the component on the irradiation surface (10) in the irradiation direction of the light beam may not be perpendicular to the movement direction (G). According to the width of the plate glass (1), it is preferable to install one or a plurality of irradiation means (5) as shown in FIG. One or a plurality of imaging means (3) may be installed according to the width of the glass sheet (1) so that the light from each irradiation means (5) is imaged from the irradiation surface (10) of the glass sheet (1). preferable. Thereby, the imaging means (3) continuously images the irradiation surface (10) of the plate glass (1) to be scanned by the movement of the plate glass (1) by the light of the linear irradiation means (5). Minute foreign matter can be detected.

  In the present embodiment, the case where the imaging means (3) is installed on the non-irradiated surface (11) side of the plate glass (1) is also within the scope of the present invention. Furthermore, the case where the illuminating means (5) and the imaging means (3) are provided on the lower surface side of the glass sheet with the upper surface of the glass sheet as the non-irradiated surface (11) and the lower surface of the glass sheet as the irradiated surface (10) are also within the scope of the present invention. is there. In the case of this embodiment, the influence of the reflection from the periphery is relatively small. However, care should be taken so that the irradiation means (5) and the imaging means (3) are not hindered by cracks during conveyance of the plate glass (1).

  According to the above embodiment, a known conveying means is used for moving the plate glass, the irradiation means and the imaging means are fixed, and the internal light beam I and the internal light beam II can be generated. Can be detected. In addition, according to the method of the present invention, the information on the distance between the front and back surfaces of the glass sheet can be obtained by the light on the upper or lower surface (irradiated surface, non-irradiated surface) of the plate glass. Even if it changes, the depth information of the internal minute foreign matter can be stably obtained with the same accuracy as the relative position from the glass surface. In addition, since it can be detected by a low-resolution imaging means that cannot recognize the shape of minute foreign matter, the image data capacity can be reduced, the scanning speed of the irradiation means can be increased, and the plate glass is conveyed at high speed. Yes.

  In FIG. 8, the figure explaining another embodiment of the manufacturing method of the plate glass which concerns on this invention is shown. In addition, in this figure, the process which manufactures a continuous plate glass (glass ribbon), and a plate-drawing process may be a well-known technique and any other technique. FIG. 9 shows a diagram illustrating another embodiment of the apparatus for this embodiment. These embodiments are a method and an apparatus that are assumed to detect minute foreign substances on a plate glass after the plate-making process in the plate glass manufacturing process, as compared with the embodiments of FIGS. 4 to 7. For this reason, it has a moving means of an irradiation means and an imaging means. In this apparatus, a linear laser beam (2) is caused to enter the inside of the glass sheet at a predetermined inclination angle with respect to the thickness direction of the glass sheet (1), and the entered internal light beam I (I) and the internal light beam I Irradiating means (5) for forming the internal light beam II (II) reflected by the surface of the glass sheet inside the glass sheet, and moving the irradiation means (5) relative to the glass sheet in a direction parallel to the plane of the glass sheet. A moving means (13) and an imaging device for imaging light emitted from a surface of a plate glass in a direction perpendicular to the surface on a light beam irradiation surface (10) side or a non-irradiation surface (11) side of the plate glass. An image pickup device (3) for picking up an image of a bright spot generated by irradiating the same minute foreign matter with the internal light beam I (I) and a bright spot generated by the internal light beam II (II); Connected to the device (3), An image processing unit 6 determines the fine foreign matter on the basis of the image image, an apparatus having a. The plate glass (1) may be supported on the table (14). Although not shown, the moving means (13) is fixed to a structure such as a table (14), and the irradiation means (5) and the imaging means (3) are movably installed. Irradiation may be performed such that the irradiation direction has a movement direction component (H) or its inverse component. Although FIG. 9 shows an apparatus that can only reciprocate in one direction (H), it is preferable that the apparatus can also move in a direction parallel to the plane of the glass sheet (1) when detection is not performed. In addition, the irradiation means (5) and the imaging means (3) are provided with a plurality of plate glasses on the moving means (13) so that they can be searched at once in the width direction according to the width of the plate glass (1). It is preferable to provide in the width direction of (1).

  According to the embodiment of the present invention described above, in particular, a plate glass can be stored after sampling, and minute foreign matters can be detected at a desired time. For this reason, it is desirable to perform detection before physical enhancement processing, but detection is possible even after physical enhancement processing. In addition, since it can be detected by a low-resolution imaging means that cannot recognize the shape of minute foreign matter, the image data capacity can be reduced, the scanning speed of the irradiation means, that is, the speed of movement by the moving means can be increased, and the large area Can be detected quickly with respect to flat glass. Furthermore, since the movement of the irradiation unit and the imaging unit can be controlled with high accuracy by the moving unit, the position coordinates of the minute foreign matter can be measured with high accuracy.

  In addition, in the method and apparatus for detecting minute foreign matter according to the present invention, and the method for producing a plate glass based on the method, in order to reduce the number of laser beams as the irradiation means, the number of them can be reduced as shown in FIGS. Thus, it is preferable to increase the length of the linear beam of the laser. For this purpose, it is necessary to increase the distance from the irradiation surface (10) of the plate glass (1) to the laser, or to adjust with a lens attached to the laser. However, the intensity of the laser beam in the unit length on the irradiation surface (10) by the laser is insufficient. This can be dealt with by increasing the output of the laser, but depending on how it is used, there are concerns about the effects on the human body, and the laser becomes expensive. Further, the intensity of the linear laser beam becomes weaker toward the end, and the intensity is uneven. In order to compensate for the shortage of laser output and unevenness in the intensity of the laser, it is preferable to irradiate with a plurality of lasers having the same incident angle and overlapping irradiation regions as shown in FIG. The accuracy with which the laser beam is superimposed has little effect on the identification of minute foreign objects and the measurement of depth unless the line is doubled. When the line width of the laser beam is increased, the undetectable areas near the front and back surfaces of the plate glass increase. In addition, this embodiment has an effect that the laser intensity can be adjusted with a simple wiring of the laser. Furthermore, the present embodiment can be applied to dark glass with low transmittance and also when light from a minute foreign matter by a laser beam becomes weak.

  Further, as another embodiment of the method and apparatus for detecting minute foreign matters inside the plate glass according to the present invention, as shown in FIG. 10, in addition to the irradiation unit 5 (first irradiation unit) of the plate glass 1, the irradiation unit The second irradiating means 8 for irradiating the second linear laser beam 7 (second light beam) from the direction opposite to the entry angle of the linear laser beam 2 (first light beam) by 5 is provided, and imaging means The image processing means 6 based on the image picked up in 3 causes the bright spot due to the same foreign matter generated by the linear laser beam 2 (first light beam) and the linear laser beam 7 (second light beam). Foreign matter such as dust on the surface of the plate glass is determined based on the symmetry of the image with respect to the axis orthogonal to the moving direction of the plate glass 1, the position of the minute foreign matter in the plate glass is determined, and the minute foreign matter is detected. As a result, foreign matter such as dust on the surface of the plate glass can be excluded from the detection target of minute foreign matter as erroneous detection. Foreign matter such as dust on the surface of the glass sheet is within the width of the laser beam in most cases, so it can be distinguished from the microscopic foreign material inside the glass sheet. There is a risk of false detection. For example, when a light beam is incident from the surface of a sheet glass, a relatively large amount of lint may be emitted to the outside of the sheet glass through the inside of the lint and become a bright spot (signal). is there. In addition, when the height of dust or the like is relatively high, part of the reflected light of the light beam may hit the dust or the like, and may become a bright spot (signal) there. Further, in the case of large dust or the like, there is a possibility that secondary scattering is caused by incident light or reflected light of a light beam to become a bright spot (signal). Foreign matter such as dust on the surface of the plate glass can be easily removed by blowing air on the plate glass before detection, but if this is not possible, there is a risk of erroneous detection as minute foreign matter inside the plate glass. In such a case, the present embodiment is effective in preventing erroneous detection of foreign matters such as relatively large dust attached to the surface of the plate glass.

  In this embodiment, foreign matter such as dust on the surface of the glass sheet is often in a shape that does not have symmetry on the surface of the glass sheet, so that an image of a bright spot (signal) for a light beam with a different irradiation direction is on the axis. Use the fact that they are often asymmetric. That is, in the present embodiment, in consideration of the feature of the bright spot (signal) of foreign matter such as dust, a signal is generated by two light beams, and the symmetry with respect to the axis is discriminated, whereby the surface of the plate glass Foreign matter such as dust adhering to the glass plate and minute foreign matter inside the glass plate, and if there is an asymmetry in the signal, the foreign material such as dust adhering to the glass plate surface is excluded as a false detection. be able to.

  In determining the symmetry of the signal by the two light beams, the second light beam is not only entered from the opposite direction to the angle of the first light beam, but also entered so that the angles are substantially the same. It is preferable to make it. With this configuration, the image obtained by capturing the bright spot and the bright line by the first light beam and the image obtained by capturing the bright spot and the bright line by the second light beam can be directly compared without performing correction processing. The symmetry of the bright spot (signal) due to the foreign matter can be determined. In particular, in setting the first irradiation means and the second irradiation means, it is more preferable that the bright lines generated by the light beams generated by the both are made parallel. Even if the first light beam and the second light beam have different entrance angles, foreign matter such as dust outside the plate glass can be obtained by correcting the image based on the difference in angle so that the two images can be compared. It can be determined as a false detection more easily. Note that the determination of the position of the minute foreign matter in the form of the light beam, irradiation means, imaging means, and image processing means in this embodiment is the same as in the basic embodiment described above.

  As described above, it is possible to distinguish between light-shielding and translucent minute foreign substances by the method and apparatus for detecting fine foreign substances according to the present invention and the method for manufacturing a plate glass based on the method. Furthermore, it is possible to distinguish between light-shielding NiS and other light-shielding minute foreign matters by utilizing the characteristics of the optical signal obtained from each minute foreign matter as described below. The NiS inside the glass is a smooth sphere or an ellipse close to a sphere, and has a strong metallic luster, and other light-shielding iron compounds, such as iron sulfide (FeS). Is not a smooth sphere, but a flat shape. Since the intensity of the optical signal from each minute foreign matter varies depending on the difference in shape and gloss, it can be distinguished by identifying based on the captured image. In particular, in the present invention, since the imaging by the imaging unit is performed from the thickness direction of the transparent plate, the resolution with respect to the minute foreign matter does not change depending on the irradiation direction of the light beam as described above. In addition, after detecting a light-shielding minute foreign matter containing NiS with the apparatus according to the present invention, NiS and other light-shielding minute foreign substances can be determined by visual inspection by an inspector or in combination with another apparatus having another high resolution. And can be distinguished.

  In a series of embodiments of the present invention, it is desirable to create a simple dark room by covering the irradiating means and the imaging means with a light-shielding curtain because it is less susceptible to the influence of the surroundings.

  In order to confirm the effectiveness of the method and apparatus for detecting fine foreign matter according to the present invention, an apparatus according to the present invention was manufactured, and NiS and bubbles in the plate glass were detected. However, the present invention is not limited to the following examples. As the laser as the light beam irradiation means, a class 2 laser having a wavelength of 635 nm, an energy of 1 mW, a divergence angle of 78 degrees, a focus, and a line width of the laser beam can be adjusted. The area scan camera as an imaging means is a CCD of 1/3 type IT system PS, a monochrome camera module capable of outputting an image of VGA class (640 × 480 pixels) at 60 fps (frame per second), a focal length of 50 mm, A lens having an F value of 2.8 indicating brightness was attached. The angle between the incident direction of the laser beam and the normal of the plate glass is 50 degrees, the width of the laser beam is 0.25 mm, the irradiation distance from the laser to the upper surface of the glass is 20 cm, and the area installed above the upper surface of the glass from the upper surface of the glass The distance to the line camera was 50 cm. Under this condition, the field of view of the area scan camera is 38 mm × 28 mm. In this detection, one pixel was set to 50 μm. At this resolution, the minute foreign matter targeted this time is about 2 × 2 pixels, and it is difficult to recognize the shape itself. In the case of stably recognizing the shape and color of a minute foreign substance having the same size by the conventional technique, 10 pixels × 10 pixels or more are required.

  The internal light beam I and the internal light beam II were formed by moving a plate glass and a laser beam relatively by placing and moving a plate glass as a transparent plate on a table. As the image processing means based on the captured image, a numerical computer having a memory mounted on a personal computer was used. Furthermore, an image input boat was attached to the numerical arithmetic unit, and images were captured. The analysis of the image was performed by obtaining the gradation value of each part of the image using commercially available image processing software installed in the numerical arithmetic unit.

[Example 1]
11 and 12 show images in which NiS is detected by the internal light beam I and the internal light beam II. As the plate glass, one containing ellipsoidal NiS having a size of 300 mm × 300 mm, a plate thickness of 6.8 mm, a major axis of 120 μm and a minor axis of 100 μm at a depth of 2.3 mm from the non-irradiated surface was prepared. The depth is a value based on the focal depth of NiS by a microscope.
FIG. 11 is an image obtained by capturing bright spots and bright lines by the internal light beam I. The uppermost line in the image is the bright line A on the glass surface that is the irradiated surface, the lower point is the bright point E of NiS, the lower line is the bright line B on the back of the glass, and the lower line is difficult to see It is a bright line C on the glass surface due to reflection from the back surface of the glass. From this image, it was confirmed that the NiS depth was 2.3 mm from the irradiated surface.
FIG. 12 is an image obtained by capturing bright spots and bright lines by the internal light beam II. The uppermost line in the image is the bright line A on the glass surface that is the irradiation surface, the lower line is the bright line B on the back side of the glass, the lower point is the bright point F of NiS, and the lower line is difficult to see It is a bright line C on the glass surface due to reflection from the back surface of the glass. Also from this image, it was confirmed that the NiS depth was 2.3 mm from the irradiated surface.

11 and 12, in the case of light-shielding NiS, it can be seen that the bright spot from the minute foreign matter by the internal light beam II is significantly weaker than the bright spot from the minute foreign matter by the internal light beam I.
In addition to this, even when the image was prepared by taking an image containing relatively small NiS having an ellipse size of 300 mm × 300 mm, plate thickness of 6.8 mm, major axis of 70 μm, minor axis of 60 μm, the NiS It was confirmed that bright spot detection and depth measurement were possible.

[Example 2]
13 and 14 show images in which bubbles are detected by the internal light beam I and the internal light beam II. As the plate glass, one containing a bubble having a size of 50 mm × 50 mm, a plate thickness of 3 mm, and a diameter of 200 μm at a depth of 1.0 mm from the non-irradiated surface was prepared. The depth is a value based on the depth of focus of the bubble by a microscope.
FIG. 13 is an image obtained by capturing bright spots and bright lines by the internal light beam I. The uppermost line in the image is the bright line A on the glass surface that is the irradiated surface, the lower point is the bright point E of the bubble, the lower line is the bright line B on the back of the glass, and the line below it is difficult to see It is a bright line C on the glass surface due to reflection from the back surface of the glass. From this image, it was confirmed that the bubble depth was 1.0 mm from the irradiated surface.
FIG. 14 is an image obtained by capturing bright spots and bright lines by the internal light beam II. The uppermost line in the image is the bright line A on the glass surface that is the irradiation surface, the lower line is the bright line B on the back surface of the glass, the lower point is the bubble and bright point F, and the lower line is difficult to see Is the bright line C on the glass surface due to reflection from the back surface of the glass. Also from this image, it was confirmed that the bubble depth was 1.0 mm from the irradiated surface.

  From FIG. 13 and FIG. 14, in the case of translucent bubbles, it can be seen that the intensity of the bright spot from the minute foreign matter by the internal light beam I and the internal light beam II is stronger by the internal light beam II.

[Example 3]
Whether the sample containing NiS and the sample containing bubbles can detect minute foreign matter, and each image can be captured with the internal light beam I and the internal light beam II to distinguish between light-shielding and translucent minute foreign matter. Confirmed. As the plate glass, 3 and 17 plates each having a size of 50 mm × 50 mm, a plate thickness of 3 mm, spherical NiS having a diameter of 80 to 200 μm, and bubbles having a diameter of 100 to 400 μm were prepared. In the identification, the part other than the minute foreign matter was used as the background signal. The signal intensity is represented by an 8-bit gradation value of the acquired image, and a gradation value of 256 or more is set to 255 as a range over. As a result, in the three samples containing NiS, the gradation value of the bright spot of the minute foreign matter by the internal light beam I is not recognizable by the noise level and becomes 255 over the range. The gradation value was almost zero, and partly 66. In 17 samples containing bubbles, the gradation value of the bright spot of the minute foreign matter by the internal light beam I is 123 on average, and the gradation value of the bright spot of the fine foreign object by the internal light beam II is almost over the range. 225. In this case, in the case of NiS, the gradation value of the bright spot of the minute foreign matter by the internal light beam I is over the range, but this changes depending on the size of NiS. The gradation value of the bright spot of the minute foreign matter by the internal light beam I is also within the range. That is, in distinguishing between light-shielding and translucent minute foreign matters, it is not sufficient to simply use the gradation value of the bright spot of each fine foreign matter.

  For this reason, the ratio of the light intensity of the bright spot from the same minute foreign matter by the internal light beam II to the light intensity from the fine foreign matter by the internal light beam I as an identification index was calculated. As a result, it was 0.26 or less in the case of NiS, and 1.4 or more in the case of bubbles, and the two could be distinguished by the difference in the ratio of the light intensity of the bright spots of the minute foreign matters by the two optical paths.

  As described above, according to the present invention, it is possible to detect and measure the depth of light-shielding NiS and translucent bubbles, and to identify light-shielding and translucent minute foreign objects by providing the above-described identification index. We have demonstrated that we can do it.

The present invention is effective not only for discriminating not only NiS inside a glass plate but also other relatively small bubbles or particulate foreign matter inside.

The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2007-229468 filed on Sep. 4, 2007 are cited here as disclosure of the specification of the present invention. Incorporated.

Claims (21)

  A method of detecting by detecting a bright spot caused by scattering of a light beam irradiated with a minute foreign substance existing inside a transparent plate having a uniform refractive index and having a constant thickness, and the thickness of the transparent plate The internal light beam I that has entered the transparent plate body at a predetermined inclination angle with respect to the vertical direction and the internal light beam II that is reflected by the surface of the transparent plate body are reflected inside the transparent plate body. The transparent plate and the light beam are relatively moved without changing the entrance angle of the light beam, and the bright spot generated by the same minute foreign matter being irradiated by the internal light beam I and the internal light Detecting the bright spot generated by the beam II from the thickness direction of the transparent plate and determining the position of the minute foreign matter in the transparent plate, How to detect.   The method according to claim 1, wherein the light beam is a light beam that forms a linear irradiation area extending in a direction perpendicular to the axis of the light beam on the surface of the transparent plate.   The method according to claim 1, wherein the direction in which the transparent plate and the light beam are relatively moved without changing the approach angle is a direction parallel to the surface of the transparent plate.   The light beam is a light beam that forms a linear irradiation area on the surface of the transparent plate extending in a direction perpendicular to the axis of the light beam, and the moving direction is the direction of the line of the linear irradiation area The method according to claim 3, wherein the method is substantially perpendicular to.   Furthermore, the method as described in any one of Claims 1-4 which determines the kind of minute foreign material by contrast of the light intensity of the said two luminescent spots.   The method according to any one of claims 1 to 5, wherein the transparent plate having a uniform refractive index and having a predetermined thickness is a plate glass. A method of detecting by detecting a bright spot caused by scattering of a light beam irradiated with a minute foreign substance existing inside a plate glass,
The light beam is allowed to enter the inside of the glass sheet at a predetermined inclination angle with respect to the thickness direction of the glass sheet, and the internal light beam I that has entered and the internal light beam II reflected by the surface of the glass sheet are reflected inside the glass sheet. Irradiation means to form;
Imaging means for imaging light emitted from the surface of the plate glass in a direction perpendicular to the surface on the light beam irradiation surface side or non-irradiation surface side of the plate glass;
An image processing means for determining the position of a minute foreign substance inside the plate glass based on an image picked up by the image pickup means, and using a detection device comprising:
The light beam irradiation position of the plate glass is moved without changing the light beam entrance angle, and the bright spot generated when the same minute foreign matter is irradiated with the internal light beam I and the internal light beam II are generated. The point is imaged by the imaging means,
The position of the minute foreign matter in the plate glass is determined by the image processing unit based on the image captured by the imaging unit.
A method for detecting minute foreign matter inside a plate glass. A method of detecting by detecting a bright spot caused by scattering of a light beam irradiated with a minute foreign substance existing inside a plate glass,
The first light beam is caused to enter the inside of the glass sheet at a predetermined inclination angle with respect to the thickness direction of the glass sheet, and the internal light beam I that has entered and the internal light beam II that is reflected from the surface of the glass sheet by the internal light beam I are obtained. A first irradiating means formed inside the plate glass;
The second light beam enters the plate glass from the direction opposite to the inclination angle of the first light beam with respect to the thickness direction of the plate glass, and the entered internal light beam I ′ and the internal light beam I ′ are converted into the plate glass. A second irradiation means for forming an internal light beam II ′ reflected on the surface inside the plate glass;
Imaging means for imaging light emitted from the surface of the plate glass in a direction perpendicular to the surface on the light beam irradiation surface side or non-irradiation surface side of the plate glass;
An image processing means for discriminating between minute foreign matters inside the plate glass and foreign matters such as dust on the surface of the plate glass based on an image picked up by the image pickup means, and an image processing means for judging the position of the fine foreign matter inside the plate glass Use
The light beam irradiation position of the plate glass is moved without changing the entrance angles of the first and second light beams, and the bright spot and the internal light generated when the same foreign matter is irradiated by the internal light beams I and I ′. The bright spots generated by irradiation with the beams II and II ′ are imaged by an imaging means,
Foreign matter such as dust on the surface of the glass plate due to the symmetry of the bright spot image by the same foreign matter generated by the first light beam and the second light beam by the image processing means based on the image picked up by the image pickup means And determining the position of the minute foreign matter in the plate glass,
A method for detecting minute foreign matter inside a plate glass.   The method of moving the light beam irradiation position of the plate glass without changing the approach angle of the light beam is a method of relatively moving the plate glass and the light beam irradiation means in a direction parallel to the surface of the plate glass. 9. The method according to 8.   The light beam is a light beam that forms a linear irradiation area on the surface of the plate glass extending in a direction perpendicular to the axis of the light beam, and the moving direction is relative to the direction of the line of the linear irradiation area. The method of claim 9, wherein the method is in a substantially vertical direction.   The method according to claim 7, wherein positions of the irradiation unit and the imaging unit are relatively fixed.   The method according to any one of claims 7 to 11, wherein a type of the minute foreign matter is further determined by an image processing unit based on an image captured by the imaging unit. An apparatus for detecting minute foreign matter inside a plate glass,
The light beam is allowed to enter the inside of the glass sheet at a predetermined inclination angle with respect to the thickness direction of the glass sheet, and the internal light beam I that has entered and the internal light beam II reflected by the surface of the glass sheet are reflected inside the glass sheet. An irradiation device to be formed;
Moving means for moving the light beam irradiation device relative to the plate glass in a direction parallel to the plane of the plate glass;
An imaging apparatus for imaging light emitted from a surface of a plate glass in a direction perpendicular to the surface on the light beam irradiation surface side or non-irradiation surface side of the plate glass, and the same minute foreign matter is irradiated by the internal light beam I An imaging device for imaging a bright spot generated by the internal light beam II and a bright spot generated by irradiation with the internal light beam II;
Image processing means connected to the imaging device for determining minute foreign matter based on the captured image;
Having a device. An apparatus for detecting minute foreign matter inside a plate glass,
The first light beam is caused to enter the inside of the glass sheet at a predetermined inclination angle with respect to the thickness direction of the glass sheet, and the internal light beam I that has entered and the internal light beam II that is reflected from the surface of the glass sheet by the internal light beam I are obtained. A first irradiation device formed inside the plate glass;
The second light beam enters the plate glass from the direction opposite to the inclination angle of the first light beam with respect to the thickness direction of the plate glass, and the entered internal light beam I ′ and the internal light beam I ′ are converted into the plate glass. A second irradiation device for forming an internal light beam II ′ reflected from the surface inside the plate glass;
Moving means for moving the first and second irradiation devices relative to the plate glass in a direction parallel to the plane of the plate glass;
An imaging device that images light emitted from a surface of a plate glass in a direction perpendicular to the surface on the light beam irradiation surface side or non-irradiation surface side of the plate glass, and the same foreign matter is caused by the internal light beams I and I ′ An imaging device that images the bright spots generated by irradiation and the bright spots generated by irradiation with the internal light beams II and II ′;
Image processing means connected to the imaging device for determining minute foreign matter based on the captured image;
Having a device.   The apparatus according to claim 13, wherein the image processing means is image processing means for determining a position of the minute foreign matter inside the plate glass based on an image of a bright spot imaged by the imaging device.   The image processing means is configured to detect the image of the surface of the glass plate based on the symmetry of the image of the bright spot caused by the same foreign matter generated by the first light beam and the second light beam based on the bright spot image captured by the imaging device. The apparatus according to claim 14, wherein the apparatus is an image processing unit that determines foreign matter such as dust and determines a position of the minute foreign matter in a plate glass.   The irradiation apparatus is an irradiation apparatus that forms a linear irradiation area on the surface of the plate glass that extends in a direction perpendicular to the axis of the light beam and extends in a direction substantially perpendicular to the moving direction of the moving means. The apparatus according to any one of 16.   The apparatus as described in any one of Claims 13-17 with which the position of the said irradiation apparatus and the said imaging device is fixed relatively.   The apparatus according to any one of claims 13 to 18, wherein the image processing means is an image processing means for further determining a type of the minute foreign matter based on an image of a bright spot imaged by the imaging device. .   A method for detecting minute foreign matter based on the method for detecting minute foreign matter inside a plate glass according to any one of claims 6 to 12, and whether or not the plate glass containing the minute foreign matter detected by the detection step should be removed. A method for manufacturing a plate glass, comprising: a determining step for determining; and a removing step for removing the plate glass containing minute foreign matters based on the determination result of the determining step.   A step of manufacturing a continuous plate glass, a detection step of detecting a minute foreign matter in the continuous plate glass based on the method of detecting a minute foreign matter inside the plate glass according to any one of claims 6 to 12, and the detection step The discriminating step for discriminating whether or not the plate glass containing the minute foreign matter detected by the step should be removed, the cutting step for cutting the continuous plate glass into a predetermined size, and the discriminating result of the discrimination step should be removed. And a removing step of removing the cut foreign glass containing minute foreign matter.

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