JP6358884B2 - Inspection device - Google Patents

Description

  The present invention relates to an inspection apparatus for automatically inspecting a display panel having a spindle portion.

 2. Description of the Related Art Conventionally, a technique for automatically inspecting defects due to contamination of foreign matters that occur during a manufacturing process is generally well known.

  Patent Document 1 discloses a technique in which a band-shaped light emitted from a light irradiation device is irradiated on the surface of an object to be inspected, and the amount of reflected light from the surface layer is detected by a line sensor. In this device, the amount of reflected light is detected while rotating the object to be inspected at a constant speed, and when the surface of the object to be inspected has defects such as unevenness and foreign matter adhesion, the reflected scattered light is detected to detect surface layer defects. I try to detect it.

  In patent document 2, the technique which test | inspects the printing state of the display panel attached to the surface side of a vehicle meter is disclosed. In this case, while irradiating light using a light source from the front and back surfaces of the substrate of the display panel, the display panel is photographed with a camera from above while the substrate surface is conveyed so that the photographed image is taken. Based on this, the printing state of the display panel is inspected.

  Moreover, the technique of a nonpatent literature 1 is disclosed as a technique regarding a phase only correlation method.

Japanese Patent No. 2712940 JP2013-160544A

Takafumi Aoki and three others, “High-precision machine vision based on phase-only correlation”, Fundamentals Review, Vol.1, No.1, p.30-39, 2007.

  In technologies such as those disclosed in Patent Documents 1 and 2, the light amount reflected from the object to be inspected and the surface density of the object to be inspected are extracted from the imaging result of the camera while irradiating light on the front and back surfaces of the object to be inspected. If there is a defect, the extraction result is different from the normal state, so that the defect can be detected.

  By the way, for the purpose of producing a calm shine and luxury in the dial face (display panel) of a car or the face of a clock, a pattern decoration (hereinafter referred to as a fine concentric groove) is formed on its surface. In some cases, a spindle portion is also provided. Since the spindle portion has a circular groove portion, that is, a curved edge portion, there is a problem that image processing and image analysis for detecting defects taking into account reflection of light at the edge portion become complicated. .

  In view of the above points, an object of the present invention is to facilitate the determination of the presence or absence of a defect without requiring a complicated analysis in the inspection of a display panel having a spindle portion.

  The inspection apparatus according to the present invention performs polar coordinate conversion of a captured image by a conversion unit, detects a density pattern based on the converted image, and performs determination based on the detected density pattern.

  That is, according to the first aspect of the present invention, in the inspection apparatus that inspects the inspection object having the first groove portion in which a plurality of concentric grooves are formed on the surface, the light source that irradiates the surface of the inspection object with light. An imaging unit that images the surface of the inspection object irradiated by the light source while moving relative to the inspection object in a direction along the surface of the inspection object, and the image captured by the imaging unit A conversion unit that detects the center coordinates of the first groove and converts the first groove into a second groove formed of a plurality of linear grooves, and is adjacent to the darkest part of the second groove A determination unit that detects at least one density pattern that is a change in density from the darkest part or a change in density from the brightest part to the adjacent brightest part, and determines whether there is a defect based on the density pattern; It is characterized by being.

  According to this aspect, the density pattern is detected based on the image that has been polar-coordinate-converted into the second groove part formed by the linear groove by the conversion part, and the determination based on the detected density pattern is performed. The presence or absence of a defect can be easily determined without performing complicated image processing.

  According to a second aspect of the present invention, in the inspection apparatus according to the first aspect, the determination unit is based on a comparison result between the detected density pattern and a density pattern detected from an adjacent site or a density pattern in a normal state. And determining the presence or absence of defects.

  According to this aspect, the inspection is performed based on collation with a density pattern detected from a plurality of adjacent sites or a density pattern in a normal state. That is, since this mode is a determination using comparison between density patterns, for example, the processing in the determination unit is lightened compared to a method for determining the presence / absence of a defect by analyzing a change in the detected density pattern. be able to. Thereby, inspection time can be shortened.

  According to a third aspect of the present invention, in the inspection apparatus according to the first aspect, whether or not the maximum density value of the density pattern is greater than or equal to a predetermined first threshold value and the minimum density value of the density pattern is a first value. It is characterized in that the presence or absence of a defect is determined based on at least one of whether or not it is equal to or lower than a second threshold value that is lower than the first threshold value.

  According to this aspect, the presence or absence of a defect is determined based on a comparison between the first and second threshold values and the maximum value and / or minimum value of the density of the density pattern. That is, the determination of the presence / absence of a defect can be realized by a simple comparison process of comparing the maximum value and / or minimum value of the density with a predetermined threshold value, so that the process in the determination unit can be further reduced. . In addition, by applying the determination based on the threshold value to a density pattern row composed of a plurality of density patterns, it is possible to easily detect even a defect having a small density change such as a stain.

  According to the present invention, since the presence / absence of a defect is determined based on the density pattern after the polar coordinate conversion, the presence / absence of a defect can be easily determined without performing complicated image processing at the edge portion.

It is a figure showing the schematic structure of the inspection device concerning an embodiment. It is a front view of the display panel inspected with the inspection device concerning an embodiment. It is a flowchart at the time of the test | inspection of the test | inspection apparatus which concerns on embodiment. It is a figure for demonstrating the polar coordinate conversion of the spindle part of a display panel. It is the figure which showed an example of the density pattern extracted with the inspection apparatus. It is the figure which showed the other example of the density pattern extracted with the test | inspection apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its scope of application, or its application.

(Configuration of inspection equipment)
FIG. 1 shows a schematic configuration of an inspection apparatus according to the embodiment. The inspection apparatus 1 is a display panel 2 (see FIG. 2) attached to the surface side of a vehicle meter (not shown) provided in front of the driver's seat of the vehicle. The display panel 2 is inspected for defects on the surface of the display panel 2.

  As shown in FIG. 2, the display panel 2 is a resin plate extending in the vehicle width direction when viewed from the front. The display panel 2 is provided with a tachometer display portion 21 on the left side in the vehicle width direction, and a speed meter on the right side in the vehicle width direction. A display unit 25 is provided. On the surface of the display portion 21 of the tachometer, a substantially circular connecting hole 22 for connecting the pointer and the movement is formed at the center thereof, and a plurality of concentric circular shapes extending outward from the connecting hole 22 as the center. A spindle part 23 made of fine grooves is formed. Reference numeral 23 a denotes a convex portion of the spindle portion 23, and reference numeral 23 b denotes a groove portion of the spindle portion 23. Similarly, a substantially circular connecting hole 26 for connecting the pointer and the movement is formed at the center of the surface of the display portion 25 of the speedometer, and a concentric circular shape that spreads outward with the connecting hole 26 as the center. A spindle portion 27 made of a plurality of fine grooves is formed. 27 a is a convex part of the spindle part 27, and 27 b is a groove part of the spindle part 27. Reference numerals 29, 29, and 29 denote attachment holes for attaching the display panel 2 to the vehicle meter. In the vehicle instrument, after the display panel 2 is mounted through the mounting holes 29, 29, 29, the display units 21, 25 are transmitted by transmitting light such as LEDs from the back side of the display panel 2 (front side of the vehicle). The letters and scales are lit up at night. In the present disclosure, the defect on the surface of the display panel is a generic term for a state in which the defect is present in comparison with a normal display panel surface. It is a concept including defects due to dirt, unevenness, and the like.

  Returning to FIG. 1, the inspection apparatus 1 includes a transport unit 11, a light source 12 arranged to irradiate light from a predetermined angle with respect to the surface of the transport unit 11, and a surface of the transport unit 11 in a direction perpendicular to the surface. And an image pickup unit 13 arranged to pick up images from.

  The display unit 2 is placed on the transport unit 11, and the imaging unit 13 and the surface of the display panel 2 (the spindle units 23 and 27 of the display units 21 and 25) face each other. And the conveyance part 11 conveys the display panel 2 in the horizontal direction (scanning direction of FIG. 1) along the surface.

  The light source 12 is, for example, an LED lighting device, and irradiates light from a predetermined angle onto the surface of the display panel 2 transported by the transport unit 11. The intensity of light from the light source 12 and the irradiation angle can be arbitrarily set so that imaging by the imaging unit 13 can be suitably performed. The light source 12 is not limited to the LED lighting device, and may be another light source. For example, a fluorescent lamp or an incandescent lamp may be used. Moreover, the irradiation angle of the light source may be fixed, or the angle may be adjustable. Further, the number of light sources is not limited to one. For example, a plurality of light sources that irradiate from different angles may be used.

  The imaging unit 13 is a CCD (Charge Coupled Device) line sensor camera, for example, and images the surface of the display panel 2 transported by the transport unit 11 from the perpendicular direction. The imaging unit 13 has an imaging area that is wider than the width of the display panel 2 in the vertical direction (front-rear direction in FIG. 1). The transport unit 11 transports the display panel 2 so that the imaging unit 13 can capture images from one end to the other end of the display units 21 and 25 in the horizontal direction. Thereby, the entire surface of the display panel 2 including the display units 21 and 25 can be imaged by the imaging unit 13. The imaging unit 13 is not limited to a CCD line sensor camera, and may be another imaging unit (imaging device). For example, it may be a CMOS line sensor camera or a CCD or CMOS area sensor camera. Moreover, although the imaging part 13 shall image the surface of the display panel 2 from a perpendicular direction, it is not limited to this. For example, the surface of the display panel 2 may be imaged from a predetermined angle other than the plane.

  In the present embodiment, the display unit 2 is transported so that the transport unit 11 can capture images from one end to the other end of the display units 21 and 25 in the horizontal direction by the image capturing unit 13, but the present invention is not limited thereto. The imaging unit 13 only needs to be configured to image the surface of the display panel 2 irradiated by the light source 12 while relatively moving in the direction along the surface of the display panel 2. For example, the surface of the display panel 2 may be imaged while moving the imaging unit 13 in the scanning direction or in the opposite direction (right direction in FIG. 1) with the transport unit 11 stopped. The surface of the display panel 2 may be imaged while moving the imaging unit 13 in the direction opposite to the scanning direction (rightward in FIG. 1) while transporting the display panel 2 in the scanning direction.

  The imaging unit 13 is connected to the control panel 14. The control panel 14 captures an image picked up by the image pickup unit 13 and, based on the image, detects a center coordinate of the spindle units 23 and 27 of the display units 21 and 25, and a spindle unit 23. , 27, a polar coordinate conversion unit 15b that performs polar coordinate conversion, a determination unit 16 that determines the presence or absence of a defect, and a storage unit 17 that stores a master image and the like to be described later. A conversion unit 15 includes a center coordinate detection unit 15a and a polar coordinate conversion unit 15b.

  The inspection apparatus 1 is provided with a monitor 18 that displays an image of the display panel imaged by the imaging unit 13, a result of processing by the conversion unit 15, a determination result by the determination unit 16, and the like.

(Inspection of display panel)
Next, the inspection flow when inspecting the display panel 2 by the inspection apparatus 1 will be described in detail based on the flowchart of FIG. In the initial state, the left end of the display panel 2 is located on the right side of the imaging unit 13 below.

  First, in step S <b> 1, the display panel 2 is transported in the scanning direction by the transport unit 11, while the imaging unit 13 captures an image of the display panel 2. The image captured by the imaging unit 13 is taken into the center coordinate detection unit 15 a of the conversion unit 15. For example, the display panel 2 is divided at a plurality of locations in the scanning direction, and captured images are sequentially captured for each divided region. The capturing of the image from the imaging unit 13 is not limited to each region, and may be performed in real time, or may be performed collectively after the capturing of the entire region is completed.

  Next, in step S2, the center coordinate detection unit 15a that has received the image transfer recognizes the center coordinates of the spindle units 23 and 27 based on the phase-only correlation method. Specifically, the center coordinates of the spindle part of the reference display panel image (hereinafter also referred to as a master image) stored in the storage unit 17 by the calculation based on the phase-only correlation method, and the captured display panel 2 A deviation amount from the center coordinates of the spindle portions 23 and 27 can be detected, and the center coordinates of the spindle portions 23 and 27 of the display panel 2 are recognized based on the deviation amount. As a conventional method for recognizing the center coordinate, a method of recognizing the center coordinate using at least three feature points, for example, the positional relationship between the three attachment holes 29, 29, 29 is conceivable. It is necessary to wait until the feature point is imaged. On the other hand, the phase-only correlation method has an advantage that the time until recognition of the center coordinates can be shortened because the amount of deviation can be detected if a partial image of the spindle unit 23 is captured.

  In step S3, the polar coordinate conversion unit 15b converts the image of the spindle unit 23 into a plurality of linear shapes based on the center coordinates of the spindle unit 23 detected by the center coordinate detection unit 15a, as shown in FIG. The polar coordinates are converted into a polar image (hereinafter also referred to as a stripe portion 33) composed of a convex portion 33a (see FIG. 4C) and a plurality of linear grooves 33b (see FIG. 4C). At this time, the length of the stripe portion 33 in the Y direction is the length between the outer peripheral side of the spindle portion 23 (right side in FIG. 4A) and the inner peripheral side of the spindle portion 23 (left side in FIG. 4A). In order to make the same, an interpolation process is performed for a gap portion (see the right diagram of FIG. 4A) generated on the inner peripheral side of the spindle portion 23. In the interpolation processing, for example, interpolation is performed using the value of the nearest pixel of the same θ coordinate in polar coordinates. FIG. 4B is a diagram illustrating an example of the stripe portion 33 generated by polar coordinate conversion, and FIG. 4C is an enlarged view of the area AR1 in FIG. 4B. Similarly, the polar coordinate conversion unit 15 b performs polar coordinate conversion on the spindle unit 27 to generate a stripe unit 37. Note that the interpolation processing method is not limited to this method, and may be another method. For example, interpolation processing may be performed based on the values of a plurality of adjacent pixels with θ coordinates.

  In step S4, the determination unit 16 extracts at least one density pattern that is a density change in the X direction (hereinafter also simply referred to as a density pattern) between at least two adjacent grooves 33b and 33b of the stripe part 33, and The presence / absence of a defect on the surface of the spindle unit 23 is determined based on the extracted density pattern. There are various methods for determination by the determination unit 16, but here, as an example of the determination method, (1) determination using a local region and (2) determination using a threshold will be described in detail.

(1) Determination Using Local Area In determination using a local area, the determination unit 16 determines an image of the local area AR2 (for example, 50 × 50 pixels) including the two grooves 33b and 33b from the image of the stripe part 33. Cut out and collate at least one density pattern detected from the image of the local area AR2 (see FIG. 4C). Specifically, a density pattern (hereinafter also simply referred to as a density pattern) that is a change in density from the darkest part of one groove 33b to the darkest part of the adjacent groove 33b is detected, and the detected density pattern is collated. . At this time, for example, a density pattern in a normal display panel (referred to as a reference pattern in FIG. 3) is stored in advance in the storage unit 17, and this normal density pattern is compared with the detected density pattern. Alternatively, for example, a plurality of density patterns may be detected from the local area AR2, and the detected density patterns may be compared with each other for comparison.

  FIG. 5 is a diagram in which the density pattern in the determination using the local region is plotted, and FIG. 5A shows the density from the darkest part of one groove 33b to the darkest part of the adjacent groove 33b in the local area without a defect. FIG. 5B shows an example of a density pattern from the darkest part of one groove 33b to the darkest part of the adjacent groove 33b in a local region having a defect (for example, foreign matter). Here, FIG. 5 shows an example in which four density patterns are detected from the local area AR2 and displayed in a superimposed manner. That is, density changes (density patterns) in the X direction are detected at four different locations in the Y direction of the local area AR2, and these are superimposed and displayed.

  In FIG. 5 (a), the four density patterns almost overlap, whereas in FIG. 5 (b), one density pattern is significantly different from the other density patterns, indicating that there is a defect. (See region P in FIG. 5B). In this way, the inspection is performed based on the density pattern matching in the local region. Note that it is possible to arbitrarily set whether or not to determine a defect when the mutual patterns are shifted.

  Further, it may be a method of determining a defect when the density is shifted by Q% (Q is a real number) as compared with the reference pattern. In this way, for the determination using comparison between density patterns, for example, the processing in the determination unit is lightened compared with a means for determining the presence / absence of a defect by analyzing a change in the detected density pattern. Therefore, the inspection time can be shortened. Further, if the method detects a plurality of patterns from within the local region and compares the detected density patterns with each other, the process in the determination unit can be further reduced as compared with the method of comparing with the reference pattern.

  Note that the detection target is not limited to a plurality of different locations in the Y direction, and density changes may be detected at a plurality of different locations in the X direction. Specifically, for example, a local region adjacent to the local region AR2 in the X direction is provided, and a change in density (density pattern) in the X direction is detected over a plurality of local regions at the same or adjacent positions in the Y direction. It may be displayed in a superimposed manner.

(2) Determination Using Threshold In determination using a threshold, the determination unit 16 cuts out an image of an area AR3 (for example, 30 × 200 pixels) including a plurality of grooves 33b from the image of the stripe part 33, and this area AR3 A density pattern sequence consisting of repetition of a constant density change is collated for the image in the image (see FIG. 4C). Specifically, for example, a threshold SU on the higher density side and a threshold SL on the lower density side are determined, and the presence or absence of a defect is determined based on these threshold values SU and SL. The criterion for determining a defect can be arbitrarily set. For example, the minimum value of the density of the groove portion for each of the grooves 33b and 33b is at least one of the threshold value SL and the maximum value of the density of the convex portion for each of the convex portions 33a and 33a is at least one of the threshold values SU. A method of determining a defect when the state continues for a certain period or more (for example, three or more times) is conceivable.

  FIG. 6 is a drawing in which a density pattern sequence in determination using a threshold value is plotted, FIG. 6A is a density pattern sequence in a defect-free area AR3, and FIG. 6B is a defect (for example, a stain). The example of the density | concentration pattern row | line in area | region AR3 which has is shown. Here, FIG. 6 shows an example in which continuous density pattern rows in the area AR3 are displayed.

  In FIG. 6A, the density of the groove part is lower than the threshold value SL for each of the grooves 33b and 33b over the entire region, and the density of the convex part exceeds the threshold value SU for each of the convex parts 33a and 33a. On the other hand, in FIG. 6B, the density of the groove portion is lower than the threshold value SL for each of the grooves 33b and 33b. On the other hand, when viewed for each of the convex portions 33a and 33a, The state where the density of the groove portion is equal to or less than the threshold value SU continues four times, and it can be seen that there is a defect. Thus, by providing a predetermined threshold and determining the presence or absence of a defect based on the threshold, it is possible to easily detect a defect with a small density change such as a stain. In FIG. 6, the determination unit 16 detects the presence / absence of a defect in the density pattern row of the region including the plurality of grooves 33b. However, one or more grooves 33b and one or more protrusions 33a are included. Also in the included region, the presence / absence of a defect is determined based on at least one of whether the density of the groove 33b in the density pattern is equal to or higher than the threshold value SU and whether the density of the convex portion 33a is equal to or lower than the threshold value SL. Can be detected.

  The result of determination by the determination unit 16 is displayed on the monitor 18 in step S5, and the inspection ends.

  As described above, according to the present embodiment, the density pattern is detected based on the image subjected to the polar coordinate conversion by the conversion unit, and the determination based on the detected density pattern is performed, so that complicated image processing is not performed. The presence or absence of defects can be easily determined. Furthermore, in the inspection apparatus according to the present disclosure, in order to make a determination based on comparison with the reference pattern and mutual comparison with other density patterns, the amount of light emitted from the light source for dividing the defective portion and the reflection of the edge There is no need to fine tune the camera or adjust the camera sensitivity. That is, a complicated and fine setting of the inspection apparatus is unnecessary, and the display panel can be easily inspected.

  In the above embodiment, the detected density pattern is a change in density from the darkest part of one groove 33b to the darkest part of the adjacent groove 33b. However, the present invention is not limited to this. Specifically, other patterns may be used as long as a periodic density change can be obtained. For example, a change in density from the brightest part of one convex part 33a to the brightest part of the adjacent convex part 33a may be applied as the density pattern. Further, as a density pattern, a change in density to the darkest part of the groove 33b located at a predetermined distance from the darkest part of one groove 33b or a predetermined distance away from the brightest part of the one convex part 33a. The brightest portion of the convex portion 33a at the position may be a single density pattern. The predetermined distance at this time is, for example, a distance to the darkest part of the groove part 33b at a position two or more away from the darkest part of the one groove 33b or two or more away from the brightest part of the one convex part 33a. It is the distance to the brightest part of the convex part 33a in the position. Also, a density pattern that can obtain a periodic density change with reference to a portion other than the darkest part or the brightest part may be used.

  Further, the determination by the determination unit 16 is not limited to (1) determination using a local region and (2) determination using a threshold, and may be any method that can find a defect from a density pattern. It may be.

  Further, in the processing in the center coordinate detection unit 15a, polar coordinate conversion unit 15b, and determination unit 16, the image G1 including the display unit 21 and the image G2 including the display unit 25 are displayed on the boundary X1 in FIG. And parallel processing using the respective images may be executed. Thereby, processing time can be shortened.

  The present invention can facilitate inspection of an inspection object having a plurality of concentric grooves formed on the surface, and thus is extremely useful in inspection of a display panel for an automobile meter having a spindle portion, for example. is there.

1 Inspection device 2 Display panel (inspection object)
DESCRIPTION OF SYMBOLS 11 Conveyance part 12 Light source 13 Imaging part 15 Conversion part 16 Determination part 23,27 Spindle part (1st groove part)

Claims (3)

An inspection apparatus for inspecting an object to be inspected having a first groove portion in which a plurality of concentric grooves are formed on a surface,
A light source for irradiating light on the surface of the inspection object;
An imaging unit that images the surface of the inspection object irradiated by the light source while moving relative to the inspection object in a direction along the surface of the inspection object;
A conversion unit that detects a center coordinate of the first groove imaged by the imaging unit, and converts the first groove part into a second groove part including a plurality of linear grooves;
Detecting at least one density pattern which is a change in density from the darkest part of the second groove to the adjacent darkest part or a density change from the brightest part to the adjacent brightest part ; An inspection apparatus comprising: a determination unit that determines the presence or absence of a defect based on a comparison with a reference value . The inspection apparatus according to claim 1,
The determination unit determines the presence / absence of a defect based on a comparison result between the detected density pattern and a density pattern detected from an adjacent part as the reference value or a density pattern in a normal state as the reference value. Inspection apparatus characterized by that. The inspection apparatus according to claim 1,
The determination unit determines whether the maximum density value of the density pattern is equal to or greater than a predetermined first threshold value as the reference value , and the minimum density value of the density pattern is a first value as the reference value. An inspection apparatus that determines the presence or absence of a defect based on at least one of whether or not a second threshold value is lower than a threshold value.

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