JP2014169988A - Defect inspection device of transparent body or reflection body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect inspection device configured to detect a defect of light-shielding performance or light diffusion performance of a transparent body or a tabular body of a mirror surface and a defect of transparency including ametropia, in the same optical condition.SOLUTION: A defect inspection device of a transparent body or a mirror-surface body irradiates an object to be inspected through a mask body having light-shielding parts and transparent parts alternately with light emitted from a lighting device arranged on one side of the object, images the object by an imaging apparatus arranged on the other side of the object, and detects a defect by means of image processing means. The defect inspection device adjusts lens aperture of the imaging apparatus and a distance between the mask body and the object, while the imaging apparatus focuses the object, to form a background image having a luminance waveform in which dark gray and light gray successively occur with small changes around a gray level center, without extremely changing the waveform.

Description

  The present invention provides a transparent body (for example, an object that can exhibit transparency such as glass, resin, or a deposited mirror) or a reflective body (for example, a reflective surface such as a mirror surface or a glossy surface). In particular, it is related to defect inspection equipment, such as “foreign matter”, “dirt”, “scratches”, etc., with light-shielding properties (light travel is blocked) or light-diffusing properties (light travel is changed in multiple directions) The present invention relates to a defect inspection apparatus that optically detects defects such as “bubbles”, “dents”, “sink marks”, and the like, and refractive defects (the light travels bends).

  Techniques for detecting light-blocking and light-diffusing defects and refractive defects present in a plate-like transmissive body or reflector, such as detecting defects as light shadows, or using reflected light from defects And those that capture the distortion of the background lines by utilizing the difference in light refraction at the defect. Hereinafter, a technique relating to a conventional method for detecting a light-blocking property, a light diffusing property, and a refractive property existing in a transmissive body or a reflective body will be described.

Japanese Patent Application Laid-Open No. 07-11490 Japanese Patent Laid-Open No. 07-110302 Japanese Patent Laid-Open No. 08-220021 JP-A-10-1112252 JP 2002-286656 A JP2012-2792A

  As a conventional means for detecting a refractive defect, there are some proposals that illuminate through a striped mask or slit that alternately repeats a transparent portion and an opaque portion. In the technique of extracting a specific defect by utilizing the lens effect (refractive abnormality) of the defect point with respect to the defect proposed in Patent Document 1 or Patent Document 3, there is an application for finding a specific defect called distortion. It is excellent, but it is difficult to detect defects such as dirt and sharp scratches because the focus is not on the object to be inspected.

  In the technique proposed in Patent Document 2, the focus is on the object to be inspected, but the defect can be detected in the bright region, but has no detection power in the dark region. For this reason, in order to inspect the entire region, it is necessary to perform imaging a plurality of times.

  The technique for detecting the defect by detecting the chart line distortion of the grid chart proposed in Patent Document 6 exhibits a high effect on the distortion, but does not generate a lens action or dust that does not hang on the chart. It is difficult to detect defects due to contamination with foreign matter.

  The technique proposed in Patent Document 4 efficiently extracts fine streak defects called thread lines, but the width and interval of the band light source is as wide as 5 to 50 mm, and is limited to thread line defect detection. It is.

  The technique proposed in Patent Document 5 can efficiently detect a defect of a fine projection called a linear crater generated on a glass substrate and can detect a defect accompanied by refraction or scattering, but a dark region due to a slit. It is difficult to detect a light-shielding defect at.

  As described above, the conventional means can detect only defects having specific refractive anomalies (distortion, thread line, crater, etc.), or detect both light-shielding or light-diffusing defects and refractive defects. Therefore, it was necessary to change the optical system and perform multiple imaging. That is, in the conventional method, defects such as “foreign matter”, “dirt”, and “scratch”, and light-reflective or light-diffusing defects, and refractive properties such as “bubbles”, “dents”, and “sinks” (the progression of light is bent). It was difficult to detect the defect (1) under the same optical conditions.

  In the present invention, light-blocking or light-diffusing defects such as “foreign matter”, “dirt”, and “scratches” that have been difficult in the past, and refractive defects such as “bubbles”, “dents”, and “sinks” that include refractive errors It is an object of the present invention to provide a defect inspection apparatus for a transmissive body or a reflector that can detect various defects of the above by imaging the inspection object once under the same optical conditions.

In order to achieve the above object, according to the first aspect of the present invention, in the invention of claim 1, the light to be inspected is irradiated to the object to be inspected through a mask body having alternately light-shielding portions and light-transmitting portions. In the defect inspection apparatus in which the inspection object is imaged by an imaging apparatus disposed at a position opposite to the illumination apparatus with the inspection object interposed therebetween, and the defect is detected by the image processing apparatus, the focus of the imaging apparatus is focused on the inspection object. In the combined state, the imaged luminance waveform is a gray image that is the center of the light and shade level. It is characterized by inspecting defects of light and light diffusivity and refractive defects.

  According to a second aspect of the present invention, in the first aspect of the present invention, the mask body is provided so as to be movable back and forth in the optical axis direction between the inspection object and the illumination device.

  According to the third aspect of the present invention, imaging is performed by irradiating the object to be inspected with the light irradiated from the illumination device through a mask body having alternately light-shielding portions and light-transmitting portions, and imaging reflected light from the object to be inspected. In a defect inspection apparatus having an apparatus and detecting a defect by an image processing apparatus, with respect to a gray state where a luminance waveform to be imaged is in the center of a gray level in a state where the imaging apparatus is focused on an object to be inspected The background image in which the dark gray and the light gray in the vicinity continuously occur is used to inspect the light shielding and light diffusing defects and the refractive defects existing in the reflector. .

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the mask body is provided so as to be movable back and forth in the optical axis direction between the object to be inspected and the illumination device.

  According to the first aspect of the present invention, various defects such as a light-blocking or light-diffusing defect and a refractive defect are captured in the entire imaging region by once imaging a transmission body as an inspection object under the same optical conditions. Therefore, it is possible to provide a defect inspection apparatus that can detect various types of defects contained in the transmission body in a short time without being limited to the types of defects.

  According to the invention of claim 2, in the invention of claim 1, the mask body is provided between the object to be inspected and the illuminating device so as to be movable back and forth in the optical axis direction, so that the transparent body having different refractive index and thickness is provided. Can be inspected by the same defect inspection apparatus.

  According to the invention of claim 3, various defects such as a light diffusive defect and a refractive defect can be detected in the entire imaging region by once imaging a reflector as an inspection object under the same optical conditions. Therefore, without being limited to the type of defect, it is possible to provide a defect inspection apparatus that can detect various defects included in the reflector in a short time.

  According to the invention of claim 4, in the invention of claim 3, the mask body is provided so as to be able to advance and retract in the optical axis direction between the object to be inspected and the illumination device, so that the reflector having a different refractive index and thickness is provided. Can be inspected by the same defect inspection apparatus.

Configuration diagram of defect inspection apparatus of the present invention The principal part perspective view of the defect inspection apparatus in Example 1 of this invention The principal part perspective view of the defect inspection apparatus in Example 2 of this invention Luminance waveform with extreme translucency and shading at the object focus Brightness waveform adjusted to dark gray and light gray as proposed in the present invention A chart showing a processing flow of the defect detection processing unit 10

  Hereinafter, an embodiment of a defect inspection apparatus according to the present invention will be described with reference to the drawings. Note that each drawing referred to in the present specification is schematically represented by exaggerating some of the components in order to facilitate understanding of the present invention. For this reason, the dimension, ratio, etc. between each component may differ.

  FIG. 1 is a block diagram of a defect inspection apparatus according to the present invention. As shown in FIG. 1, the defect inspection apparatus is not shown because it does not directly affect the gist of the present invention, since the line light source 2, the mask body 4, the one-dimensional imaging apparatus 1, the defect detection processing section 10, and the control section 11 are not directly affected. However, it is equipped with a device for gripping and transporting an object to be inspected.

  FIG. 2 shows an embodiment of the present invention, which is a configuration example of a transmission optical system in which a one-dimensional imaging device 1 and a line-shaped light source 2 are arranged to face each other with an inspection object 3 interposed therebetween.

  The line-shaped light source 2 irradiates diffused light toward the inspection object 3 and is formed in a rectangular parallelepiped shape extending in a direction orthogonal to the direction A in which the inspection object 3 is conveyed. In this case, the line light source 2 is formed longer than the length in the width direction of the inspection target region of the inspection target 3.

  Further, a diffusion plate (not shown) is attached to the light emitting surface of the line-shaped light source 2, so that the irradiated light has a uniform brightness. The line light source 2 is configured by incorporating a white LED, and the brightness is controlled by a control unit 11 described later. The line light source 2 may be a light emitter other than an LED, such as a halogen lamp or a metal halide lamp. That is, the line light source 2 corresponds to the illumination device according to the present invention.

  A mask body 4 is provided above the line light source 2 so as to be able to advance and retract in the optical axis direction B so as to cover the light emitting surface. The mask body 4 transmits a part of the light projected from the line light source 2 and blocks the other part, and is a plate shape for forming a background image in which dark gray and light gray continuously occur. It is a member. More specifically, the mask body 4 is formed of a transparent resin plate having a rectangular shape corresponding to the light emitting surface of the line light source 2. Then, on the surface of the mask body 4, light shielding portions 4 a and light transmitting portions 4 b extending in the direction orthogonal to the longitudinal direction (inspected object transport direction) are alternately and repeatedly formed along the longitudinal direction of the mask body 4. Yes.

  The light shielding portion 4a is a portion that shields and blocks light emitted from the line light source 2, and is colored black. On the other hand, the translucent part 4b is a transparent part that transmits the light emitted from the line light source 2 as it is. In the present embodiment, the light shielding portion 4a is formed to 0.75 mm, for example, and the light transmitting portion 4b is formed to 0.25 mm. The widths of the light-shielding part 4a and the light-transmitting part 4b of the mask body 4 are variously determined based on the respective conditions such as the defect to be detected and the opening and arrangement of the lenses constituting the one-dimensional imaging device 1. Yes, as described above, the light shielding portion 4a is not limited to 0.75 mm, and the light transmitting portion 4b is not limited to 0.25 mm.

  Above the mask body 4, the one-dimensional imaging device 1 is disposed oppositely. The one-dimensional imaging device 1 is imaged by scanning while transporting the inspection object 3 that is arranged above the line light source 2 and the mask body 4 and irradiated with light from the line light source 2 through the mask body 4. It is an optical device that performs electrical output and outputs an electrical signal representing a captured image. In the present embodiment, the one-dimensional imaging device 1 is configured by a line CCD or CMOS image sensor and a lens. The one-dimensional imaging apparatus 1 is supported above the mask body 4 by a support body (not shown).

  In this case, the one-dimensional imaging device 1 is adjusted so as to be focused on the inspection object 3 conveyed by a conveyance device (not shown), and is installed so that the imaging resolution is, for example, 20 μm. Note that the imaging resolution of the one-dimensional imaging apparatus 1 is determined based on various conditions such as the defect to be detected and the size of the inspection target range of the inspection target 3, and is limited to 20 μm as described above. is not. That is, the one-dimensional imaging device 1 corresponds to the imaging device according to the present invention.

  The defect detection processing unit 10 processes an image signal output from the one-dimensional imaging device 1 to detect a defect. The defect detection processing unit 10 is connected to a display monitor (not shown), and can display a defect detection result and an image signal output from the one-dimensional imaging device 1 continuously as a luminance waveform. That is, the defect detection processing unit 10 corresponds to the image processing apparatus according to the present invention.

  The object to be inspected 3 is held by a conveying device (not shown) directly or via a work folder (not shown) and is at a height between the one-dimensional imaging device 1 and the mask body 4 in a direction A perpendicular to the longitudinal direction of the line light source 2. Be transported. The work folder holds one or a plurality of inspection objects 3 in a detachable manner, and is configured by forming a through-hole corresponding to a portion to be inspected of the inspection objects 3 on a resin plate or the like. .

  A conveyance device (not shown) holds the object 3 and conveys it at a speed corresponding to the scanning period and imaging resolution of the one-dimensional imaging device 1, and everything from the front end to the end of the inspection object 3 is the same as that of the one-dimensional imaging device 1. The operation is controlled by the control unit 11 so as to pass below.

  The control unit 11 controls various operations of the defect inspection apparatus by executing a control program stored in advance according to an instruction from the operator. Specifically, the control unit 11 controls each operation of a conveyance device (not shown), the one-dimensional imaging device 1, the line light source 2, and the defect detection processing unit 10. For example, the control unit 11 controls a transport device (not shown) to transport the inspection object 3 and to control the start and end of processing of an image signal output from the one-dimensional imaging device 1 of the defect detection processing unit 10.

  Next, the detection principle of the defect inspection apparatus according to the present invention will be described. First, the inspection object 3 is imaged, and a background image in which dark gray and light gray are continuously generated is adjusted. Specifically, the inspection object 3 is moved by the transport device, and the inspection target area of the inspection object 3 is positioned below the one-dimensional imaging apparatus 1. Next, light is emitted from the line light source 2 and the luminance waveform of the image signal output from the one-dimensional imaging device 1 is observed. As a result, the light emitted from the line-shaped light source 2 has a square wave shape in which light and dark portions are alternately repeated by the light transmitted through the light transmitting portion 4b in the mask body 4 and the shadow blocked by the light shielding portion 4a. A luminance waveform is observed.

  In this case, in the luminance waveform, when the luminance difference between the bright part and the dark part is large with respect to the average luminance as in the waveform of FIG. 4, the brightness of the line light source 2, the lens aperture of the one-dimensional imaging device 1, the mask By adjusting the distance between the body 4 and the object 3 to be inspected, the brightness difference between the bright part X and the dark part Y is reduced with respect to the average brightness as shown in the waveform of FIG. In the present embodiment, adjustment is performed so that the average luminance of the luminance waveform is in the middle of the maximum gradation, and the luminance difference between the bright portion X and the dark portion Y is within a range of about 10% of the maximum luminance gradation. . The average luminance of the luminance waveform and the difference between the bright part X and the dark part Y are appropriately adjusted according to the characteristics of the defect desired to be detected by the defect detection processing unit 10 and the detection conditions. The luminance difference between the part X and the dark part Y is not limited to the numerical value of the present embodiment.

  Thus, by reducing the difference between the bright part X and the dark part Y of the brightness, the bright part ranges from a defect whose brightness level becomes dark like a light-shielding defect such as dust or foreign matter to a defect whose brightness level becomes brighter due to diffusion. Since the contrast is also generated in the defect having the refractive error due to the effect of the mask body 4 while maintaining the sensitivity in the entire region of the X region, the dark portion Y region, and the intermediate region, all the defects can be detected.

  After adjusting the luminance waveform as described above, the inspection object 3 is transported in a predetermined manner, and imaging from the front end to the end of the inspection object 3 is performed, and the defect detection processing unit 10 performs defect detection processing on the image. . FIG. 6 is a chart showing a flow of defect detection processing in the defect detection processing unit 10 of the present embodiment. The flow is performed in the order of image data acquisition, filter processing, threshold processing, defect data processing, and classification processing.

  The defect detection is performed by canceling a dark gray background corresponding to the dark portion Y and a light gray background corresponding to the bright portion X by the filter processing and performing threshold processing for detecting an abnormal image of a predetermined level or more. In addition, since the focus of the one-dimensional imaging device 1 is focused on the inspection object 3, feature quantities such as defect position coordinates, dimensions, and areas can be accurately acquired. By processing, it is possible to identify and classify defect types.

  As shown in FIG. 3, the linear light source 2 is disposed above the inspection object 3 with the longitudinal direction inclined as an axis, and the reflected light of the light irradiated onto the inspection object 3 through the mask body 4 is one-dimensionally imaged. This is a configuration example of a reflection optical system arranged so as to capture an image with the apparatus 1, and the main point is the same as that of the first embodiment. In this case, even if the inspection object 3 is a reflector, a light-blocking or light-diffusing defect or a refractive defect adhering to the surface (upper surface) can be detected in the same manner as in the first embodiment. Thus, it can be used not only for a transmissive body but also for a reflective body.

  In the two embodiments, the mask body 4 uses a transparent resin plate, but may be another material such as glass as long as it is a transparent material.

  Further, although the light shielding portion 4a of the mask body 4 of the two embodiments is formed in parallel with the transport direction of the inspection object 3, the invention is not limited to this. It may be one that intersects at an angle or a lattice. That is, it is only necessary that the light shielding portions and the light transmitting portions are alternately and repeatedly formed in the longitudinal direction of the mask body 4.

DESCRIPTION OF SYMBOLS 1 ... One-dimensional imaging device 2 ... Line-shaped light source 3 ... Inspected object (transmissible or mirror-like plate-shaped body)
DESCRIPTION OF SYMBOLS 4 ... Mask body 4a ... Light-shielding part 4b ... Translucent part 10 ... Defect detection process part 11 ... Control part A ... Direction B in which the to-be-inspected object 3 is conveyed ... Optical axis direction X ... Bright part (light gray)
Y ... dark part (dark gray)

Claims (4)

  Imaging in which light irradiated from an illuminating device is irradiated to an object to be inspected through a mask body having alternately light-shielding portions and light-transmitting portions, and arranged at a position facing the illuminating device with the object to be inspected in between In a defect inspection apparatus that images an object to be inspected by an apparatus and detects a defect by an image processing apparatus, a luminance waveform to be imaged is a gray color that is the center of a gray level in a state where the object to be inspected is in focus. By using a background image in which dark gray and light gray in the vicinity of the state continuously occur, the light shielding and light diffusing defects and refractive defects present in the transmissive body were inspected. A defect inspection apparatus for a transparent body characterized by the above.   2. The defect inspection apparatus for a transmissive body according to claim 1, wherein the mask body is provided so as to be movable back and forth in the optical axis direction between the inspection object and the illumination device.   The image processing apparatus includes an imaging device that irradiates light to be inspected through a mask body having alternately light-shielding portions and light-transmitting portions and illuminates light reflected from the inspection device, and images reflected light from the inspection object. In the defect inspection apparatus for detecting defects by the apparatus, in the state in which the imaging apparatus is focused on the object to be inspected, the dark waveform in the vicinity of the gray state where the luminance waveform to be imaged is the center of the gray level and A reflector defect inspection apparatus characterized by inspecting light-blocking and light-diffusing defects and refractive defects existing in a reflector by using a background image in which light gray is continuously generated.   4. The reflector defect inspection apparatus according to claim 3, wherein the mask body is provided so as to be movable back and forth in the optical axis direction between the object to be inspected and the illumination device.

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