JP6628185B2 - Inspection method for transparent objects - Google Patents

Description

  The present invention relates to a method for inspecting a transparent body such as a glass plate or a resin plate.

  In the process of manufacturing a transparent body such as a glass plate or a resin plate, foreign substances and bubbles may be mixed into the transparent body. The contaminants and air bubbles cause performance degradation when the transparent body is used for optical components. For this reason, it is required to inspect the transparent body for foreign matter or air bubbles.

  On the other hand, since the optical effect differs between the case where the contaminant is a foreign substance and the case where the contaminant is a bubble, it is desirable that the method be able to distinguish between the two as the inspection method.

  As an inspection method corresponding to such a point, there is a method disclosed in Patent Document 1. This is because, when binarizing an image obtained by photographing a transparent body, in consideration of the occurrence of a ring-shaped low-luminance portion for a round bubble, the binarization level should be set to a level at which a ring shape can be obtained. This allows the bubbles to be identified.

JP-A-8-285789

  However, bubbles are not always round (spherical), and when binarized at a predetermined binarization level, binarization that is indistinguishable from foreign matter despite being bubbles In many cases, only information can be obtained, and as a result, bubbles cannot be distinguished from foreign matters.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a transparent body inspection method that can more reliably perform an inspection while distinguishing bubbles and foreign matter mixed in a transparent body. I do.

  In the method for inspecting a transparent body according to the present invention, in the method for inspecting a transparent body which detects an impurity contained in a transparent body by performing image processing on an image of the transparent body, the transparent body is imaged in the image processing. From the image, the luminance is obtained in segment units consisting of one pixel or a plurality of pixels. When the luminance difference between adjacent segments is large, the contaminant is a foreign substance, and when the luminance difference is small, the contaminant is Is characterized in that it is determined to be a bubble.

  In the present invention, irrespective of the size and shape of bubbles, it is possible to identify whether the particles are foreign substances or bubbles. It can be done reliably.

It is a block diagram showing the outline of the inspection device for carrying out the inspection method of the present invention. A is an explanatory diagram of a captured image, B is an explanatory diagram of size detection by edge detection, and C is an explanatory diagram of segment scanning. FIG. 7 is an explanatory diagram of an example of segment scanning in the order of t1, t2, t3, and t4. A is a line graph showing a change in the luminance difference, and B is a graph showing a change in the primary differential value of the change in the luminance difference. FIG. 9 is an explanatory diagram showing a result of determining whether a defect or a defect is present. 5 is a flowchart for one embodiment of the present invention.

  The present invention relates to a method for inspecting a transparent body, which performs image processing on an image of a transparent body and detects contaminants contained in the transparent body. The luminance is obtained in segment units composed of pixels. When the luminance difference between adjacent segments is large, it is determined that the contaminant is a foreign substance, and when the luminance difference is small, it is determined that the contaminant is a bubble. .

  Then, in addition to the image processing for obtaining the luminance, the size of the contaminant is determined by performing edge detection of an image of the transparent body, and the size of the contaminant is determined. It is preferable to determine whether the contaminant is defective or non-defective by determining whether the contaminant is a bubble.

  Alternatively, the size of the contaminant may be determined by detecting the edge of an image of the transparent body, and the luminance may be obtained in segment units having a size corresponding to the obtained size.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 shows an inspection device for inspecting a resin transparent body 1 formed as a so-called light guide. An illuminator 2 for illuminating the light from above, an imaging unit 3 including a CCD camera or the like for photographing light transmitted through the transparent body 1, a processing circuit 4 for processing an image obtained by the imaging unit 3 and performing a determination process based on the processing result. Consists of As the processing circuit 4, a computer can be suitably used.

  The contaminant 5 mixed in the transparent body 1 may be a foreign substance 51 or a bubble 52, which appear in the image as shown in FIG. 2A. Note that, in the case of the bubble 52, since a part of light passes through, the decrease in luminance is less than that in the case of the foreign matter 51. Here, the foreign matter 51 is indicated by black coating and the bubble 52 is hatched. ing.

  The processing circuit 4 temporarily stores the luminance signal of the image sent from the imaging unit 3 in the storage unit 41, and then detects the stored luminance of each pixel in the x and y directions as shown in FIG. 2B. Then, the size S of the contaminant 5 (foreign matter 51, bubble 52) is detected. In this process, the processing circuit 4 detects the size with the edge sensitivity (binary level) that can detect not only the foreign matter 51 but also the bubble 52.

  If the size S of the foreign matter 51 and the bubble 52 is smaller than the minute size Smin, the processing circuit 4 does not determine that the foreign matter 51 and the bubble 52 are defective. Is determined.

  Next, the processing circuit 4 performs re-scanning of the luminance of each pixel stored in the storage unit 41 with respect to the foreign matter 51 and the bubble 52 that have been the temporary defects. In this re-scanning, however, the processing circuit 4 calculates an average luminance value in each segment 6 for each segment 6, as shown in FIG.

  Now, as shown in FIG. 3, a change in the average luminance of each segment 6 when the region having the contaminant 5 as a temporary defect is scanned in the order of t1, t2, t3, and t4 in units of segments as shown in FIG. It becomes what is shown in. Here, the line 5a indicates the case where the contaminant 5 is the foreign matter 51, and the line 5b indicates the case where the contaminant 5 is the bubble 52. That is, the average luminance difference between the adjacent segments 6 is large when the contaminant 5 is the foreign substance 51 and is small when the contaminant 5 is the bubble 52.

  This is because the difference between the bubble 52 and the foreign matter 51 is small when the brightness of the peripheral portion of the contaminant 5 is compared between the bubble 52 and the foreign matter 51. However, the central portion of the contaminant 5 has a higher luminance than the portion of the foreign matter 51 because light easily passes through the bubble 52. Therefore, the difference between the portion at t4 when the central portion of the contaminant 5 is extracted and the portions at t1, t2 and t3 where the peripheral portion of the contaminant 5 is mainly extracted is due to the foreign matter 51 This is due to the larger part.

  Therefore, as shown in FIG. 4B, when the primary differential value of the change in the average luminance due to the scanning is larger than the predetermined value K, the temporary defect is caused by the foreign matter 51, and the primary differential value is smaller than the predetermined value K. In the case of, it can be determined that the temporary defect is caused by the bubble 52.

  As described above, since the processing circuit 4 can determine whether the contaminant 5 is the foreign substance 51 or the bubble 52, when the contaminant 5 is the foreign substance 51, The criteria for determining a defect can be set separately between and.

  Incidentally, FIG. 5 shows that the contaminant 5 which was determined to be a temporary defect is a defect F because the upper left contaminant 5 and the upper right contaminant 5 were both determined to be foreign matter 51 as a result of the above-mentioned determination, and the lower right contaminant 5 was determined. Is determined to be a bubble 52 as a result of the determination, but is determined to be a defect F because the size S is equal to or larger than the predetermined size Smax, and the contaminant 5 at the lower left is determined to be the bubble 52 as a result of the determination, and An example is shown in which the value S is smaller than the predetermined size Smax and thus is determined as a non-defective NF. FIG. 6 shows a flowchart of the above-described determination operation performed by the processing circuit 4.

  At the stage where the size of the contaminant 5 is determined by edge detection, if the size S of the contaminant 5 (the foreign matter 51 and the bubble 52) is equal to or larger than a predetermined size Smax, the processing circuit 4 regards all of them as defects. The processing based on the luminance difference may be skipped for the contaminant 5 having a size equal to or larger than Smax.

  In addition, the contaminant 5 having a size smaller than the extremely small size Smin may not be detected by adjusting the edge sensitivity in the above-described edge detection stage.

  Here, the size of the segment 6 as a set of a plurality of pixels is determined from the relationship between the size of the size Smin and the predetermined value K. In addition, the size of the segment may be changed according to the size of the contaminant 5 obtained by the edge detection.

  By the way, in the scanning of the segment 6 shown in FIG. 3, some pixels are overlapped by the adjacent segments 6 and 6 by setting segment size> segment moving amount. Although this is to increase the resolution, the segment size may be set equal to the segment moving amount, or the segment size may be set to be smaller than the segment moving amount to improve the calculation speed.

  In any case, in order to detect whether the bubble 52 or the foreign matter 51 is based on the average luminance in the segment 6 as a set of a plurality of pixels, the bubble 52 is adjusted by adjusting the edge sensitivity (binary level). Compared to the conventional example in which the bubble 52 is distinguished, it is possible to distinguish the foreign matter 51 or the bubble 52 regardless of the size and the shape of the bubble 52.

  If it is necessary to determine whether the contaminant 5 having a size smaller than the extremely small size Smin is the foreign matter 51 or the bubble 52, the segment may be one pixel. In this case, the foreign matter 51 and the bubble 52 are identified based on the luminance difference between adjacent pixels.

DESCRIPTION OF SYMBOLS 1 Transparent body 2 Illuminator 3 Imaging means 4 Processing circuit 5 Contaminant 6 Segment 51 Foreign material 52 Air bubble

Claims (2)

A method for inspecting a transparent body that detects contaminants contained in the transparent body by performing image processing on an image of the transparent body,
In the image processing, the luminance is obtained in segments each consisting of one pixel or a plurality of pixels from an image obtained by capturing the transparent body, and when the luminance difference between adjacent segments is large, the contaminant is a foreign substance, and when the difference is small is a method of determining the said contaminant is an air bubble,
A method of inspecting a transparent body , comprising detecting an edge of an image of a transparent body, determining the size of a contaminant, and obtaining the luminance in segment units having a size corresponding to the obtained size . In addition to the image processing for obtaining the luminance, the size of the contaminant is determined by performing edge detection of an image of the transparent body, and the size of the contaminant is determined. 2. The method for inspecting a transparent body according to claim 1, wherein whether the contaminant is a defect or a non-defect is determined by determining whether the contaminant is present .

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