JP4528850B2 - Defect detection apparatus, defect detection method, defect detection program, and computer-readable recording medium recording the program - Google Patents

Description

  The present invention provides a luminance value of a pixel to be inspected included in an image obtained by imaging an inspection object, and a luminance value of a pixel to be compared that is included in the image and is a target for comparing the luminance value with the pixel to be inspected. The present invention relates to a defect detection device or the like that detects a defect of the inspection object on the basis of the deviation.

  Main defects of display devices using flat panels, such as LCD (Liquid Crystal Display) display devices, PDP (Plasma Display Panel) display devices, EL (Electro Luminescence) display devices, and liquid crystal projectors, include line defects and point defects. It is done. A point defect is caused by a defect of each pixel of the display device, and a line defect is caused by a short circuit of adjacent signal lines, a contact defect, a drive driver element defect, or the like.

  When detecting the line defect and point defect of the display device as described above, the presence or absence of the defect and the position of the defect are obtained by imaging the display device to be inspected and analyzing the image obtained by the imaging. The method of detecting is widely used. According to this method, since the defect inspection can be automated, the time required for the defect inspection can be reduced, and the labor cost required for the defect inspection can be reduced to reduce the manufacturing cost of the display device. .

  As described above, since there is a great merit in the method of detecting defects by analyzing an image obtained by imaging an apparatus to be inspected, this inspection method is applied to other than the display apparatus. For example, a defect of an image sensor of an image pickup apparatus is detected by the above inspection method. In recent years, the resolution of an image pickup apparatus has been rapidly improved, and accordingly, a defect of an image pickup element such as a CCD is likely to occur. For this reason, the above-described inspection method is applied. The above inspection method is also applied to inspection of circuits such as ICs.

  By the way, when the defect detection of the display device is performed by the above inspection method, the image display surface of the display device is imaged by an imaging device such as a camera. Here, in recent years, since the size of the image display surface of the display device is rapidly increasing, the aberration of the lens of the imaging device, the distance between the lens of the imaging device and the center of the image display surface, and the imaging device The distance difference between the lens and the edge of the image display surface often increases.

  Thereby, there may be a case where an image in which a distortion is generated in a portion where the vicinity of the center of the image display surface is imaged and a portion where the vicinity of the end is imaged is acquired. In addition, in an image obtained by capturing an image display surface, shading may occur in which the luminance value near the edge portion is lower than that near the center portion of the image display surface. Further, when the display device is an LCD display device using a transmissive liquid crystal panel, uneven brightness due to the arrangement of a plurality of backlights may occur. Therefore, for example, when a defect is detected by binarizing an image obtained by imaging an inspection target, there is a problem that the processing result is not stable due to a variation in luminance value between pixels.

Here, shading and luminance unevenness will be described with reference to FIG. FIG. 16 is a diagram for explaining the influence of shading and luminance unevenness on an image obtained by capturing an image display surface. In the same figure, the relationship between the position on the image which imaged the image display surface of the display apparatus, and a luminance value is shown. x _p is an axis that indicates the position in the horizontal direction (lateral direction in the drawing), y _p is an axis that indicates the position in the vertical direction (vertical direction in drawing). Further, x _l and y _l are axes indicating luminance values.

A _x indicates a profile of the luminance value in the horizontal direction, B _x indicates a profile of the luminance value in the horizontal direction in an image darker (a luminance value is lower) than A _x , and C _x is when there is uneven illumination. A profile of luminance values in the horizontal direction is shown. A _y indicates a profile of the luminance value in the vertical direction, and B _y indicates a profile of the luminance value in the vertical direction in an image darker (a luminance value is lower) than A _y .

  It should be noted that the luminance value when displaying an image on the display device is set uniformly over the entire image display surface both when displaying a bright image and when displaying a dark image. In this way, when the luminance value is set so that the luminance value of the entire surface of the image display surface is uniform, it is included in the image obtained by imaging the image display surface unless shading or luminance unevenness occurs. The luminance value of the pixel becomes uniform.

However, as shown in the figure, in the dark image profile B _x and profile B _y , and the bright image profile A _x and profile A _y , there are differences in luminance values near the center and near the edge of the image. Further, in the profile C _{x in the} case where there is uneven illumination, the luminance value varies irregularly depending on the position in the horizontal direction.

  As described above, even when the luminance value of the entire image display surface is set to be uniform, when shading or uneven luminance occurs, the luminance value varies depending on the portion of the image display surface. . For this reason, when a display defect (for example, a line defect or a point defect) of a display device is detected using such an image, it is necessary to perform shading correction or the like.

  For example, in the case of detecting a point defect in an LCD display device, a technique for detecting a defect by performing shading correction has been conventionally used. In this method, a predetermined display pattern is displayed on the LCD display device to be inspected, the displayed pattern is imaged by the imaging device, and shading correction is performed on the image obtained by imaging. Then, in the image after the shading correction, a portion having a luminance value equal to or higher than a predetermined threshold is detected as a bright spot defect, and a portion below the predetermined threshold is detected as a black spot defect.

  As described above, when performing defect detection of an inspection object based on an image obtained by capturing an image display surface, defects are accurately detected by reducing the influence of shading and luminance unevenness by shading correction. be able to. However, in this method, when the size of the image display surface is large, it is necessary to perform shading correction using a large-size smoothing filter or the like.

  Also in Patent Document 1 below, a point defect is detected using an image obtained by capturing an image display surface of a display device. Specifically, in Patent Document 1, a difference image between an image captured by displaying a white lighting display pattern and an image captured by displaying a black lighting display pattern is created. Then, in the created difference image, a luminance equal to or higher than a predetermined threshold is detected as a bright spot defect, and a luminance equal to or lower than the predetermined threshold is detected as a black spot defect.

  Here, when performing defect detection using the difference of the image obtained by imaging the image display surface in a state where different display patterns are displayed as in Patent Document 1, it takes an extra imaging time, There is a drawback that the processing time becomes long. Further, although the shading amount is reduced by taking the difference, the shading is not completely lost. Therefore, in the technique of Patent Document 1, it is necessary to perform shading correction in order to improve the detection accuracy. When shading correction is performed, the processing time naturally becomes longer.

  For example, the shading correction is performed as follows. That is, a plurality of non-defective (non-defective) inspection target images are sampled in advance, and an average luminance value of corresponding pixels of the plurality of images obtained by the sampling is calculated. Then, an image having the calculated average luminance value as the luminance value of each pixel is generated, and the image is smoothed by a smoothing filter, thereby creating a reference image for performing shading correction. By taking a difference between this reference image and an image obtained by imaging an inspection object whose unknown whether or not it has a defect, it is possible to cancel the influence of shading and accurately detect the presence or absence of the defect.

  Here, the above-described shading correction is premised on that the imaging conditions at the time of capturing the reference image and the imaging conditions of the imaging performed at the time of inspection match. However, defect inspection is usually performed on a plurality of inspection objects, and the imaging conditions of the inspection object are changed every moment due to aging of the backlight, external illumination, etc., maintenance of the measuring device, etc. It will be different.

  For this reason, in order to maintain the accuracy of the inspection, it is necessary to periodically update the reference image so that the imaging condition for the reference image and the imaging condition for the image for inspection are as close as possible. Therefore, it is necessary to periodically sample non-defective inspection objects and update the reference image database.

  That is, in the above conventional defect inspection method, the defect inspection accuracy can be improved by taking the defect inspection time, but it is difficult to shorten the time required for the defect inspection while maintaining the accuracy of the defect inspection. The shorter the time required for defect inspection, the better, and the higher the accuracy of defect inspection, the better. Therefore, a method for shortening the time required for defect inspection while maintaining the accuracy of defect inspection has been proposed.

  For example, when detecting defects of an inspection object using an image obtained by imaging an inspection object including many repetitive patterns, such as a display unit of a CCD, a display device, or an IC, the luminance of adjacent pixels in the image is detected. A method of detecting a defect by comparing values is known. Specifically, in this method, the defect of the pixel to be inspected is determined based on whether or not the difference between the luminance value of the pixel to be inspected and the luminance value of the pixel adjacent to the pixel to be inspected is within a predetermined range. Determine the presence or absence. According to this method, the inspection object may be imaged only once, and the presence or absence of a defect in each pixel is detected, so that the defect position of the inspection object can be obtained with high accuracy.

  Here, according to the above-described method, when the adjacent pixel is a pixel that is generated by imaging a portion where there is no defect of the inspection object, defect detection can be normally performed. However, when the adjacent pixel is a pixel generated by imaging a defective part of the inspection target, normal determination cannot be performed. That is, there is a problem of so-called pseudo defects in which normal pixels are detected as defective pixels. In particular, when the inspection object has a line defect, a pseudo defect is likely to occur in the peripheral portion of the line defect.

  In order to suppress the occurrence of this pseudo defect, for example, the difference between the pixel to be inspected and each of a plurality of adjacent pixels (upper and lower, left and right, diagonal eight pixels) is calculated, and the calculated difference values are sorted in order of size. Thus, it is possible to use a method using a difference value having a predetermined order (Patent Document 2 below).

  Also, a comparison operation is performed on the luminance values of two neighboring pixels (three types, upper, lower, left, and right) adjacent to each other with the pixel to be inspected, and the two surroundings that are determined to have substantially the same luminance value as a result of the comparison operation A method of determining the presence or absence of a defect in the pixel to be inspected by comparing the average value of the luminance values in the pixel and the luminance value of the pixel to be inspected (Patent Document 3 below) can also be used.

  Further, the difference between the average value of the luminance values of two neighboring pixels (upper, left, right, and diagonal) adjacent to the pixel to be inspected and the luminance value of the pixel to be inspected is calculated and obtained by calculation. By selecting one difference value from the three difference values, the occurrence of pseudo defects can be suppressed. Below, this method is demonstrated based on FIG.

  FIG. 17 is a diagram illustrating a method of determining the presence or absence of a defect in the pixel P0 to be inspected by performing a comparison operation between the pixel P0 to be inspected and three sets of pixels selected from the peripheral pixels P1 to P8. In the illustrated example, the defect detection device 200 shown on the right side of the figure determines the presence or absence of a defect of the pixel P0 to be inspected based on the pixel P0 and the peripheral pixels P1 to P8 having the positional relationship shown on the left side of the figure. To do. As illustrated, the defect detection apparatus 200 includes comparison operation units 201a to 201c, a selection unit 202, and a defect determination unit 203.

  The comparison operation unit 201a performs comparison operation 1 for obtaining a difference between the pixel to be inspected P0 and the average value of the luminance values of the peripheral pixels P4 and P5 located in the horizontal direction with the pixel to be inspected P0 as the center. Further, the comparison operation unit 201b performs a comparison operation 2 for obtaining a difference between the pixel to be inspected P0 and the average value of the luminance values of the peripheral pixels P1 and P8 located in the oblique direction with the pixel to be inspected P0 as the center. Then, the comparison operation unit 201c performs a comparison operation 3 for obtaining a difference between the pixel to be inspected P0 and the average value of the luminance values of the peripheral pixels P2 and P7 positioned in the vertical direction with the pixel to be inspected P0 as the center. The comparison calculation results of the comparison calculation units 201a to 201c are sent to the selection unit 202.

  Here, it is assumed that the luminance values of P0 to P8 are theoretically the same value when an inspection object having no defect is imaged. Therefore, if no defect occurs in the inspection object, theoretically, the brightness values of P0 to P8 are all the same value (hereinafter referred to as normal values), and the comparison calculation results of the comparison calculation units 201a to 201c are all 0. become.

  It should be noted that in an image obtained by actually capturing an image of an inspection object, it is extremely rare that the luminance values completely match. For this reason, it is very rare that the result of the comparison operation becomes 0 even when the inspection object has no defect. Therefore, actually, when the comparison calculation result is a value within a predetermined range from 0, the comparison calculation result is regarded as 0. That is, when the luminance values of P0 to P8 are substantially equal, and the comparison calculation result is substantially zero, a defect occurs at a position corresponding to the pixel to be inspected of the inspection target. I consider it not.

  On the other hand, if a defect has occurred in the inspection object, the luminance values of P0 to P8 are different from the normal values. For example, when a defect occurs only at a position corresponding to the inspection pixel P0 of the inspection target, the luminance values of the peripheral pixels P1 to P8 are normal values, and only the inspection pixel P0 has a luminance different from the normal value. Value. In this case, the comparison calculation results of the comparison calculation units 201a to 201c all have the same value other than zero. If the comparison calculation result is not zero, it can be determined that the pixel P0 to be inspected has a defect.

  As described above, when a defect occurs only at a position corresponding to the inspection target pixel P0 of the inspection target, the inspection target pixel can be accurately detected using any of the comparison calculation results of the comparison calculation units 201a to 201c. The presence or absence of a P0 defect can be determined.

  However, when a defect occurs at a position corresponding to the peripheral pixels P1 to P8 of the inspection target, the comparison calculation results of the comparison calculation units 201a to 201c are different values. Therefore, in order to accurately determine the presence / absence of a defect in the pixel P0 to be inspected, it is necessary to select an appropriate result from the comparison calculation results of the comparison calculation units 201a to 201c, and the selection of the comparison calculation result is appropriate. Otherwise, there is a possibility of erroneously determining that there is a defect even though there is no defect at the position corresponding to the pixel P0 to be inspected. That is, a pseudo defect occurs.

  The selection unit 202 selects one calculation result from the comparison calculation results of the comparison calculation units 201 a to 201 c according to a predetermined selection rule, and sends the selected calculation result to the defect determination unit 203. Then, the defect determination unit 203 uses the calculation result received from the selection unit 202 to determine whether there is a defect in the pixel P0 to be inspected.

Here, for example, when the line defects such as L ₁ has occurred, P3, P5, luminance values of three neighboring pixels P8 will be different from the normal value. In this case, P3, P5 or the operation result of the comparison operation 1 and 2 using the luminance values of P8, is affected by _{L 1.} Therefore, in this case, selection unit 202, by selecting the comparison operation result of the comparison operation unit 201c not affected by L _1, the defect determination unit 203 accurately the presence or absence of a defect in the inspected pixel P0 It becomes possible to judge. That is, no pseudo defect occurs.
JP 7-175442 A (published July 14, 1995) JP 2006-145232 A (released on June 8, 2006) JP 2004-28836 A (published January 29, 2004)

  As a method of selecting a comparison calculation result that is not affected by the defect of the peripheral pixels from the comparison calculation results of the comparison calculation units 201a to 201c, for example, as disclosed in Patent Document 3, two adjacent pixels with the pixel to be inspected in between are used. It is conceivable to select a result of comparison operation performed using two peripheral pixels determined to have substantially the same luminance value among the three peripheral pixels (upper, left, right, and diagonal three types).

  However, in the above method, since the comparison calculation is performed using the average luminance value of two adjacent pixels adjacent to each other with the pixel to be inspected, the average luminance value becomes unstable due to the influence of noise or display noise during imaging. There is a factor.

  Further, for example, in the example of FIG. 17, when a line defect occurs at a position corresponding to P2, P0, and P7 of the inspection object, both P2 and P7 correspond to the same defect site. Thus, the luminance values of both become substantially equal. Therefore, there is a possibility that the defect determination of the pixel P0 to be inspected is performed using the comparison calculation result (by the comparison calculation unit 201c) using P2 and P7 corresponding to the defective part. There is a possibility that it is erroneously determined that a defect does not occur at a position corresponding to the pixel P0 to be inspected, and the defect is overlooked.

Furthermore, as shown in FIG. 17, when a line defect of L ₂ occurs in addition to L ₁ , the comparison calculation results of the comparison calculation units 201a to 201c are all affected by the line defect L ₁ or L _2. Therefore, there is a possibility that a pseudo defect may occur.

  Further, as another method for selecting a comparison calculation result that is not affected by the defect of the peripheral pixels, for example, as in Patent Document 2, the difference between the pixel to be inspected P0 and each of the peripheral pixels P1 to P8 is calculated and calculated. It is also conceivable to sort the difference values in order of magnitude and use the difference values having a predetermined rank.

  However, the above method has a problem that the amount of calculation increases. That is, in the above method, first, it is necessary to perform an operation for calculating the difference between the pixel to be inspected P0 and each of the peripheral pixels P1 to P8. Then, it is necessary to perform an operation for sorting the calculated 8 operation results in order of size. The number of operations required for sorting varies depending on the number of surrounding pixels and the order of difference values to be used.

  For example, in the case of using eight neighboring pixels, when using the fourth difference value, the comparison operation is 22 (7 + 6 + 5 + 4) times, and when using the fifth difference value, the comparison operation is 25 (7 + 6 + 5 + 4 + 3) times. It is necessary to sort. When the amount of calculation increases, there is a problem that the processing time becomes long when the calculation is performed by software, and there is a problem that the scale of the processing circuit becomes large when the calculation is performed by hardware.

  Here, if the number of peripheral pixels for calculating the difference from the pixel P0 to be inspected is reduced, the amount of calculation required for sorting can be reduced. However, when the number of peripheral pixels for calculating the difference from the pixel P0 to be inspected is reduced, the accuracy of the calculation result is lowered, which may cause a pseudo defect.

Further, in the method of calculating the difference between the pixel P0 to be inspected and each of the surrounding pixels P1 to P8, sorting the calculated difference values in order of magnitude, and using the difference values having a predetermined rank, as shown in FIG. In addition, when a line defect of L ₂ in addition to L ₁ occurs, the probability that an erroneous determination will occur increases. For this reason, it is difficult to completely prevent the occurrence of pseudo defects.

  The present invention has been made in view of the above-mentioned problems, and its purpose is to generate pseudo defects when detecting defects on the inspection object based on an image obtained by imaging the inspection object. An object of the present invention is to realize a defect detection device or the like that prevents and maintains high defect detection accuracy.

  In order to solve the above problem, the defect detection apparatus according to the present invention is an image obtained by imaging an inspection object, and the luminance value of the pixel to be inspected extracted from an image having a pattern in which the luminance value repeats at a constant cycle A defect detection device for detecting a defect of the inspection object based on a luminance value extracted from the image of a comparison target pixel selected from a pixel separated from the inspection pixel by a certain period. In addition, the pixel to be inspected includes a plurality of comparison target pixels, and a plurality of different comparison target pixel groups are associated with each other, and the luminance value of each comparison target pixel included in the comparison target pixel group is The index calculation means for calculating the index indicating the magnitude of the deviation from the luminance value of the pixel to be inspected for each of the plurality of comparison target pixel groups, and the absolute value of the indices calculated by the index calculation means is Corresponding to the pixel to be inspected of the inspection object based on the size relationship between the index selection means for selecting a smaller index as a defect detection index, the defect detection index selected by the index selection means, and a predetermined threshold value And defect determination means for determining the presence / absence of a defect at the position to be detected.

  Further, in order to solve the above problem, the defect detection method according to the present invention is an image obtained by imaging an inspection object, and the luminance of an inspected pixel extracted from an image having a pattern in which luminance values repeat at a constant cycle Defect detection for detecting a defect of the inspection object based on the value and the luminance value extracted from the image of the comparison target pixel selected from the pixel separated from the inspection pixel by the certain period A defect detection method executed by the apparatus, wherein the pixel to be inspected includes a plurality of pixels to be compared and a plurality of different pixel groups to be compared with each other, and is included in the pixel group to be compared. An index calculation step for calculating an index indicating a magnitude of a deviation between the luminance value of each comparison target pixel and the luminance value of the pixel to be inspected for each of the plurality of comparison target pixel groups; and the index calculation step From the index selection step for selecting the index having the smallest absolute value as the index for defect detection among the indices calculated in the process, the magnitude relationship between the index for defect detection selected in the index selection step and a predetermined threshold value, And a defect determination step of determining whether or not there is a defect at a position corresponding to the pixel to be inspected of the inspection object.

  Here, conventionally, the luminance value of the pixel to be inspected extracted from an image obtained by imaging the inspection object and having a pattern in which the luminance value repeats at a constant period, and the constant value for the pixel to be inspected. Detection of a defect of the inspection object is performed based on a luminance value extracted from the image of a comparison target pixel selected from pixels separated by a period.

  That is, if the image obtained by imaging the inspection object is an image having a pattern in which the luminance value repeats at a constant cycle, the inspection object extracted from the image is theoretically provided that there is no defect in the inspection object. The luminance value is the same as the luminance value of the comparison target pixel selected from the pixels separated from the pixel to be inspected by the certain period.

  By using this, the difference between the luminance value of the comparison target pixel and the luminance value of the pixel to be inspected is calculated, and the defect of the inspection target is determined by comparing the calculated difference with a predetermined threshold value. Can be detected. Here, the luminance value of the pixel to be inspected or the pixel to be compared when there is no defect at the corresponding position of the inspection object is referred to as a normal value.

  More specifically, when no defect occurs at any of the position corresponding to the inspection target pixel of the inspection target and the position corresponding to the comparison target pixel of the inspection target, the inspection target pixel and the comparison target pixel Both luminance values are normal values, and in this case, the difference is theoretically zero. However, since it is rare that the difference is completely zero due to an error or the like, the presence or absence of a defect is determined by comparison with a threshold value. In short, as long as the luminance value of the pixel to be inspected and the luminance value of the pixel to be compared can be regarded as substantially the same, it is determined that there is no defect at the position corresponding to the pixel to be inspected of the inspection target. it can.

  Further, when a defect has occurred at a position corresponding to the pixel to be inspected of the inspection target and no defect has occurred at a position corresponding to the comparison target pixel of the inspection target, the luminance value of the pixel to be inspected Becomes a value different from the normal value, and the luminance value of the comparison target pixel becomes a normal value. In this case, the difference is theoretically not zero. In other words, if the luminance value of the pixel to be inspected and the luminance value of the comparison target pixel are within a range that can be considered to be substantially different, it is determined that the position corresponding to the pixel to be inspected of the inspection target is defective. Can do.

  However, if a defect does not occur at a position corresponding to the inspection target pixel of the inspection target and a defect occurs at a position corresponding to the comparison target pixel of the inspection target, the inspection target inspection is performed. The difference does not theoretically become zero even though there is no defect at the position corresponding to the pixel. For this reason, there exists a possibility of misjudging that there exists a defect in the position corresponding to the to-be-inspected pixel of a test subject. That is, in this case, a pseudo defect may occur.

  The occurrence of the pseudo defect is, as in the above configuration, by using an index indicating the magnitude of deviation between the luminance value of each comparison target pixel included in the comparison target pixel group and the luminance value of the pixel to be inspected. It is reduced. That is, by using the comparison target pixel group including a plurality of comparison target pixels, a defect occurs in a part of the comparison target pixel included in the comparison target pixel group at a position corresponding to the comparison target pixel of the inspection target. Even if a pixel having a luminance value different from the normal value is included, the influence is canceled by the comparison target pixel having a normal luminance value.

  As a result, it is possible to suppress the occurrence of pseudo defects, but when the comparison target pixels of the comparison target pixel group include many pixels whose luminance values are different from the normal values, the luminance values different from the normal values are If the influence cannot be completely cancelled, there is a possibility that a pseudo defect may occur.

  Therefore, in the above configuration, the index is calculated for each of the plurality of pixel groups to be compared, and the defect detection index, which is the index having the smallest absolute value among the calculated indices, is used. It is determined whether or not there is a defect at a position corresponding to the pixel to be inspected.

  Here, the index indicates the magnitude of deviation between the luminance value of each comparison target pixel included in the comparison target pixel group and the luminance value of the pixel to be inspected. Therefore, according to the above configuration, the presence / absence of a defect is determined using the comparison target pixel group having the smallest deviation from the luminance value of the pixel to be inspected.

  The smallest deviation from the luminance value of the pixel to be inspected means that the deviation in luminance value is close to zero. Therefore, according to the above configuration, it is determined that the pixel to be inspected is defective. Is less likely. Therefore, according to said structure, generation | occurrence | production of a pseudo defect can be prevented.

  Furthermore, according to said structure, compared with the method of the said patent document 2, a defect can be determined with a small calculation amount. For example, in the above configuration, when two sets of comparison target pixel groups 1 and 2 including four comparison target pixels are used, first, an operation for calculating indices of the pixel to be inspected and the comparison target pixel group 1; An operation for calculating an index between the pixel to be inspected and the comparison target pixel group 2 is performed. Then, among the calculated indices, an index having the smallest absolute value is determined as a defect determination index, and the presence / absence of a defect at a position corresponding to the inspection target pixel of the inspection target is determined using the defect determination index.

  On the other hand, in the method of Patent Document 2, when using the eight neighboring pixels, when using the difference value of the fourth size, when using the difference value of the fifth size 22 (7 + 6 + 5 + 4) times, The presence / absence of a defect at the position corresponding to the pixel to be inspected of the inspection object is determined using the difference value determined by performing the comparison operation and the sorting of 25 (7 + 6 + 5 + 4 + 3) times. Thus, in the method of Patent Document 2, the amount of calculation required for sorting is large, so the total amount of calculation is very large compared to the configuration of the present invention.

  Here, the ratio of pixels in which defects are not generated is generally large between the pixels in which defects are generated and the pixels in which defects are not generated. For this reason, by increasing the number of comparison target pixels, it is possible to reduce the proportion of pixels in the comparison target pixel in which no defect has occurred, and to reduce the influence of the defective pixel on defect detection.

  That is, according to the above configuration, since the amount of calculation when the number of comparison target pixels is increased is small, the defect detection accuracy can be easily improved by increasing the number of comparison target pixels.

  Moreover, it is preferable that the defect detection apparatus includes a comparison target pixel setting unit that sets the comparison target pixel while avoiding an outer edge portion of the image.

  Here, when the size of the inspection target is relatively large, distortion may occur in the outer edge portion of the captured image due to the influence of aberration or the like of the imaging device that images the inspection target. If a pixel where distortion occurs is set as a comparison target pixel, the influence of the distortion is reflected on the luminance value used for calculation of the index, which reduces the reliability of the index, which is not preferable.

  Therefore, according to the above configuration, the comparison target pixel is set avoiding the outer edge portion of the image. As a result, it is possible to eliminate the influence of the distortion on the luminance value used for calculating the index, so that even when the image is distorted, defect detection can be performed with high accuracy.

  The defect detection apparatus includes a defect position storage unit that stores defect position data indicating a position on the image corresponding to a defect position of the inspection object, and the comparison target pixel is stored in the defect position storage unit. It is preferable to include comparison target pixel changing means for changing the comparison target pixel to a pixel other than the position indicated by the defect position data when the position matches the position indicated by the stored defect position data.

  As described above, the occurrence of pseudo defects can be suppressed by determining the presence / absence of defects using the defect detection index, which is the index having the smallest absolute value among the calculated indices. Here, when the comparison target pixel group includes a pixel at a position corresponding to the defect position of the inspection target, it is considered that the defect determination accuracy is lowered due to the influence of the pixel and a pseudo defect is generated. It is done.

  So, according to said structure, the defect position data which show the position on the image corresponding to the defect position of a test target object are previously stored in a defect position memory | storage part, and the comparison object pixel is stored in the defect position. When included in the position indicated by the data, the comparison target pixel is changed to a pixel other than the position indicated by the defect position data.

  Thereby, the pixel at the position corresponding to the defect position of the inspection object can be excluded from the comparison target pixels. Therefore, even when the set comparison target pixel group includes a pixel at a position corresponding to the defect position of the inspection object, the defect determination accuracy is maintained and the generation of the pseudo defect is surely prevented. be able to.

  The defect determination means stores the position of the pixel to be inspected on the image when it is determined that the inspection object is defective in the defect position storage unit as the defect position data, and the comparison target pixel Preferably, the changing unit changes the comparison target pixel using the defect position data stored in the defect position storage unit by the defect determining unit.

  According to said structure, the comparison result pixel is changed using the determination result of the said defect determination means as defect position data. Therefore, according to the above configuration, even if the pixel group to be compared includes a pixel at a position corresponding to the defect position of the inspection object, a high defect can be obtained without separately creating defect position data. The determination accuracy can be maintained and the occurrence of pseudo defects can be reliably prevented.

  In addition, the defect detection device may include a pixel to be inspected that is located in a region other than the nearest region where the pixel is generated by imaging the imaging device and the inspection target at the closest distance in the image, and / or The comparison target pixel is corrected so that the extraction position of the luminance value of the pixel to be inspected and / or the comparison target pixel is closer to the nearest part, and the correction amount is in a position far from the nearest part. It is preferable to provide an extraction position correcting hand that makes the pixel and / or the comparison target pixel larger.

  Here, the image is generated by imaging an inspection object with an imaging device. More specifically, the image is obtained by converting the reflected light reflected by the inspection object into an electrical signal by a plurality of imaging elements included in the imaging device, and the electrical signal generated by each imaging element indicates the luminance value of each pixel. It is generated as data to show.

  Usually, an imaging apparatus having a sufficient number of imaging elements for imaging an inspection object is used. Therefore, the image is an electrical signal (a signal indicating a luminance value) generated by each imaging element, that is, data in which pixels (imaging pixels) are arranged at equal intervals.

  However, when an image of an inspection object is picked up by an image pickup apparatus that does not include a sufficient number of image pickup elements, a difference occurs in the image pickup area per image pickup element depending on the distance between the image pickup element and the inspection target. As a result, the pixel interval in the image may change depending on the position in the image.

  More specifically, as the distance between the image sensor and the inspection target increases, the image area per image sensor increases, and as the image area per image sensor increases, the interval between pixels in the image decreases. Become. In other words, in the image, the interval between adjacent pixels becomes narrower as the distance from the part (nearest neighbor part) imaged at the closest distance to the imaging device increases.

  As a result, the pixel located farther from the nearest part shifts to a position closer to the nearest part. As a result, the size of the image is reduced as compared with an image in which all pixels in the image are arranged at equal intervals. For this reason, when the luminance value is extracted from the image without considering the interval between the pixels, the luminance value at a position different from the pixel from which the luminance value should actually be extracted may be extracted. . Therefore, in this case, the defect detection accuracy may be reduced.

  Therefore, according to the above configuration, in the image, for the pixel located outside the nearest part, the extraction position of the luminance value of the pixel is corrected to be closer to the nearest part, and the correction amount is The pixel farther from the nearest part is made larger. Thereby, even when the pixel interval in the image changes according to the position in the image, it becomes possible to always perform highly accurate defect detection by canceling the influence of the pixel interval deviation.

  In addition, the index calculation means uses the difference between the average value of the luminance values of the comparison target pixels included in the comparison target pixel group and the luminance value of the pixel to be inspected, and the comparison target pixel group as the index. In the target pixel group, the difference between the average value of the luminance values of the remaining comparison target pixels excluding at least one of the comparison target pixel having the maximum luminance value or the minimum comparison target pixel and the luminance value of the pixel to be inspected, Among the comparison target pixels included in the comparison target pixel group, the average value of the luminance values of the remaining comparison target pixels excluding the comparison target pixel whose luminance value deviation value is larger than a predetermined value, and the luminance value of the pixel to be inspected Or the difference between the luminance value at the position of the pixel to be inspected and the luminance value of the pixel to be inspected, obtained by linear interpolation of the luminance value of the pixel to be compared included in the comparison target pixel group. Is preferable

  When calculating the difference between the average value of the luminance values of the comparison target pixels included in the comparison target pixel group and the luminance value of the pixel to be inspected as the index, the index can be calculated by a simple calculation. . Also, the accuracy of defect detection can be easily improved by increasing the number of comparison target pixels included in each comparison target pixel group.

  Then, as the index, the luminance of the remaining comparison target pixels excluding at least one of the comparison target pixel having the maximum luminance value or the minimum comparison target pixel in the comparison target pixel group from the comparison target pixel group. When calculating the difference between the average value of the values and the luminance value of the pixel to be inspected, the influence of noise or the like can be reduced to improve the accuracy of defect detection.

  This is because there is a possibility that noise has occurred in the comparison target pixel having the maximum luminance value and the comparison target pixel having the minimum luminance value. This is because it may correspond to a defect.

  Further, as the index, among the comparison target pixels included in the comparison target pixel group, the average value of the luminance values in the remaining comparison target pixels excluding the comparison target pixels whose luminance value deviation value is larger than a predetermined value; Even when the difference from the luminance value of the pixel to be inspected is calculated, the influence of noise or the like can be reduced to improve the accuracy of defect detection.

  This is because, in general, there are more places where defects in the inspection object have not occurred than places where defects have occurred. However, when the deviation value is small, the luminance value of the pixel is highly likely to be a normal value, and when the deviation value is large. This is because the possibility of being abnormal is high.

  Then, as the index, the difference between the luminance value at the position of the pixel to be inspected and the luminance value of the pixel to be inspected obtained by linear interpolation of the luminance value of the pixel to be compared included in the group of pixels to be compared is calculated. In this case, the reliability of the comparison calculation process can be improved by canceling the gradient of the luminance value due to shading.

  This is because, when shading is occurring, it can be canceled by linear interpolation that the luminance value of the pixel in the image changes stepwise according to its position. In particular, when the position of the pixel to be compared is set at a position away from the pixel to be inspected, or when the pixel to be inspected and the pixel to be compared are included in the outer edge portion of the image, the influence of shading increases. It is preferable to use linear interpolation.

  The defect detection apparatus may be realized by a computer. In this case, a control program for realizing the defect detection apparatus by a computer by operating the computer as each unit of the defect detection apparatus, and A computer-readable recording medium on which it is recorded also falls within the scope of the present invention.

  As described above, in the defect detection apparatus according to the present invention, the pixel to be inspected includes the plurality of comparison target pixels, and a plurality of different comparison target pixel groups are associated with each other. Index calculating means for calculating an index indicating the magnitude of deviation between the brightness value of each comparison target pixel and the brightness value of the pixel to be inspected for each of the plurality of comparison target pixel groups, and the index calculating means From the index selection means for selecting the index having the smallest absolute value among the indices calculated as the defect detection index, the magnitude relationship between the defect detection index selected by the index selection means and a predetermined threshold value, Defect determining means for determining the presence or absence of a defect at a position corresponding to the pixel to be inspected of the inspection object.

  In the defect detection method according to the present invention, as described above, the pixel to be inspected includes a plurality of comparison target pixels, and a plurality of different comparison target pixel groups are associated with each other. An index calculating step for calculating an index indicating the magnitude of deviation between the luminance value of each comparison target pixel included in the group and the luminance value of the pixel to be inspected for each of the plurality of comparison target pixel groups; and the index From the index selection step for selecting the index with the smallest absolute value as the index for defect detection among the indices calculated in the calculation step, the magnitude relationship between the index for defect detection selected in the index selection step and a predetermined threshold value And a defect determination step for determining whether or not there is a defect at a position corresponding to the pixel to be inspected of the inspection object.

  Therefore, even if the comparison target pixel includes a pixel whose luminance value is different from the normal value, it is possible to prevent the occurrence of a pseudo defect and maintain high defect detection accuracy.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS. The defect detection apparatus according to the present embodiment compares a luminance value with a peripheral pixel of each pixel of an image obtained by imaging an inspection object, thereby detecting a pixel having an abnormal luminance value (different from a normal value). A pixel having a luminance value) is specified, and thereby a point / line defect of the inspection object is detected. Hereinafter, a pixel that is a target for determining whether or not a luminance value is normal is referred to as a pixel to be inspected, and a pixel that is to be compared with the pixel to be inspected is referred to as a comparison target pixel. Also, normal (as set) luminance values are referred to as normal values, and abnormal (higher or lower than set luminance values) luminance values are referred to as abnormal values.

  When determining whether or not the luminance value of the pixel to be inspected is normal by comparing the luminance value of the pixel to be inspected and the luminance value of the comparison target pixel around the pixel to be inspected, It is necessary that there is a comparison target pixel that theoretically has the same luminance value as the pixel to be inspected. Therefore, the inspection object needs to be such that a pixel having the same luminance value as the pixel appears around each pixel in an image obtained by imaging the inspection object. Specifically, this requirement is satisfied if the inspection object has a repeated pattern.

  Hereinafter, an example in which the inspection target is the display device P will be described. Since the RGB pixels are regularly arranged on the display screen of the display device P (having RGB repeating patterns), it is suitable as an inspection object. For example, an LCD display device, an EL display device, a PDP display device, a liquid crystal projector, a CRT (Cathode Ray Tube) display device, or the like can be used as the inspection object. Further, the inspection object only needs to have a repeated pattern, and may be, for example, an IC, a CCD, or the like.

  In an image obtained by imaging such an inspection object, a repeated pattern in which the luminance value repeats at a constant cycle appears. For this reason, when one pixel is extracted from the image, a pixel at a position away from the pixel by the certain period theoretically has the same luminance value as the extracted pixel. Accordingly, a pixel at a position away from the pixel to be inspected by the certain period can be set as a comparison target pixel.

[Images used for defect detection]
Here, first, an image obtained by imaging the inspection object and the positional relationship between the pixel to be inspected and the comparison target pixel in the image will be described with reference to FIG. FIG. 2 is a diagram for explaining the relationship between the inspection object and an image obtained by imaging the inspection object, and the positional relationship between the pixel to be inspected and the comparison target pixel in the image obtained by imaging the inspection object.

  In FIG. 2, a rectangular rectangle indicates a display pixel of the display device P, and a square rectangle indicates a pixel (imaging pixel) in an image obtained by imaging the display device P. There are three types of display pixels, R, G, and B, which are arranged in the horizontal direction (the left-right direction in the figure) in the order of R, G, and B. Then, display pixels of the same color are arranged in the vertical direction (vertical direction in the figure). One pixel of the display device P is formed by three display pixels of R, G, and B.

  As shown in the drawing, six imaging pixels are assigned to one pixel (three display pixels R, G, and B) of the display device P in the horizontal direction, and one of the display devices P in the vertical direction. Three are assigned to the pixels. That is, as shown in the figure, six imaging pixels are assigned to one display pixel. For this reason, the luminance value of one display pixel is reflected in the six imaging pixels assigned to the display pixel. Note that the allocation of imaging pixels is not limited to this example as long as at least one imaging pixel is allocated to one display pixel.

  In the example shown in the figure, the horizontal pixel interval (cm) which is the horizontal interval is 6 and the vertical pixel interval (cn) which is the vertical interval is 6 for the pixel to be inspected selected from the imaging pixels. The imaging pixel at the position is set as a comparison target pixel.

  The reason why the horizontal pixel interval is 6 is that, in the left-right direction, six imaging pixels are assigned to one pixel (three display pixels R, G, and B) of the display device P. This is because the image pickup pixels at positions six away from the pixels in the left-right direction correspond to the same positions of the display pixels of the same color.

  That is, in the example shown in the figure, the pixel to be inspected corresponds to the upper right of the R display pixel, and two comparison target pixels adjacent in the horizontal direction of the pixel to be inspected also correspond to the upper right of the R display pixel. ing. Thus, by setting the position of the comparison target pixel to the same position of the display pixel of the same color as the pixel to be inspected, it is possible to determine whether or not the luminance value of the pixel to be inspected is normal.

  The position of the comparison target pixel only needs to be the same position of the display pixel of the same color as the pixel to be inspected. In other words, in the example shown in the figure, any pixel that is an image pixel located at an integer multiple of 6 in the left-right direction with respect to the pixel to be inspected can be a comparison target pixel.

  Similarly, in the vertical direction, imaging pixels at positions that are six positions away from the pixel to be inspected in the vertical direction are set as comparison target pixels. In the vertical direction, an imaging pixel at a position that is an integer multiple of 3 away from the pixel to be inspected in the vertical direction can be a comparison target pixel.

  Therefore, for example, an imaging pixel at a position three away from the pixel to be inspected in the vertical direction can be set as a comparison target pixel. However, when a defect occurs in one display pixel, the same defect may occur in a display pixel adjacent to the display pixel. This possibility is particularly high when a line defect has occurred.

  For this reason, the position of the comparison target pixel is preferably a position corresponding to a display pixel other than the display pixel adjacent to the display pixel corresponding to the pixel to be inspected. Therefore, in the example shown in the drawing, the imaging pixels at positions that are separated by six in the vertical direction with respect to the pixel to be inspected are set as comparison target pixels.

[Outline of defect detection method]
The defect detection apparatus according to the present embodiment uses the image obtained by performing imaging so that the imaging pixels are allocated to the display pixels of the display apparatus P to be inspected as described above, and uses the display apparatus P. Detect defects.

  Here, an outline of the defect detection method performed by the defect detection apparatus will be described with reference to FIG. FIG. 3 is a diagram for explaining the outline of the defect detection method of the present embodiment. In the figure, the pixel to be inspected is indicated by P0, the comparison target pixel 1 is indicated by P1 to P8, and the comparison target pixel 2 is indicated by P1a to P8a. In FIG. 3, for simplicity, the pixels between the pixel to be inspected and the comparison target pixel are not shown. That is, also in FIG. 3, as shown in FIG. 2, pixels are arranged between the pixel to be inspected and the comparison target pixel.

  As illustrated, the comparison target pixel 1 (P1 to P8) is a comparison target pixel located in the upper, lower, left, and right directions of the inspected pixel P0. The comparison target pixel 2 (P1a to P8a) is above the comparison target pixel P2, below P7, left of P4, right of P5, upper left of P1, upper right of P3, lower left of P6, And P8 are pixels to be compared that are located obliquely below and to the right of P8.

  In the defect detection method of the present embodiment, it is determined whether the luminance value of the pixel P0 to be inspected is normal based on the comparison target pixel 1 (P1 to P8) and the comparison target pixel 2 (P1a to P8a). Thus, it is determined whether or not the display pixel at the position corresponding to the pixel P0 to be inspected has a display defect (such as a line defect or a point defect).

  Here, as described above, if there is no defect in the inspection object (in this case, the display device P), the luminance value of the pixel to be inspected P0 is equal to the luminance value of the comparison target pixels 1 and 2, and the inspection object If there is a defect at a position corresponding to the pixel P0 to be inspected, a difference occurs between the luminance value of the pixel P0 and the luminance values of the comparison target pixels 1 and 2. Therefore, for example, whether or not the luminance value of the pixel to be inspected P0 is normal can be determined from the difference between the luminance value of the pixel to be inspected P0 and the luminance value of the comparison target pixel 1 or 2.

  However, as shown in FIG. 3, when a line defect occurs, the luminance values of P3, P5, and P8 of the comparison target pixel 1 are different from the normal values. In this case, the difference between the average value of the pixel to be inspected P0 and the comparison target pixel 1 (P1 to P8) reflects P3, P5, and P8 that are different from the normal values. For this reason, when it is determined whether or not the luminance value of the pixel P0 to be inspected is normal using this difference value, a pseudo defect may occur.

  Therefore, in the defect detection method, the difference between the average value of the pixel to be inspected P0 and the comparison target pixel 1 (P1 to P8) is calculated, and the average value of the pixel to be inspected P0 and the comparison target pixel 2 (P1a to P8a). The difference between is calculated. Then, the absolute values of the two difference values obtained by the calculation are compared, and a difference value having a small absolute value is selected as a difference value for determining the pixel P0 to be inspected.

  Then, the selected difference value is compared with a predetermined threshold value (for bright spot defect determination), and when the difference value is larger than the threshold value, it is determined that the pixel P0 to be inspected has a bright spot defect. Further, the selected difference value is compared with a predetermined threshold value (for black spot defect determination), and when the difference value is smaller than the threshold value, it is determined that the pixel P0 to be inspected has a black point defect.

  According to the configuration described above, the smaller of the two difference values is selected as the difference value for determining the pixel P0 to be inspected. As a result, the presence / absence of a defect is determined using a difference value that is less likely to be determined to have a defect. Therefore, even when the comparison target pixel includes a pixel having a luminance value different from the normal value, the occurrence of a pseudo defect can be prevented.

  Moreover, according to said structure, the space | interval of the to-be-tested pixel P0 and the comparison object pixels 1 and 2 is a comparatively narrow space | interval of about 6 pixels-12 pixels. In the case of performing comparative calculation processing in such a relatively small region, there is almost no influence of shading that occurs due to factors such as the lens characteristics of the imaging device 2 and illumination conditions. That is, according to the above configuration, it is not necessary to perform shading correction by filter processing as in the conventional case. In addition, one image is necessary to perform the inspection of the display device P. Therefore, according to said structure, a defect can be detected at high speed and with high precision.

  Further, according to the above configuration, it is not necessary to perform shading correction using the reference image. For this reason, even when the imaging conditions of the display device P change due to a change in illumination conditions, device maintenance, or the like, it is possible to detect defects constantly and stably.

  Further, according to the above configuration, the comparison target pixel is set to a pixel having the same color as the pixel to be inspected that is located at a certain distance from the pixel to be inspected. Thereby, when a line defect has occurred in the pixel to be inspected and / or the periphery thereof, it is possible to prevent most of the luminance values of the comparison target pixel from being different from normal values. For this reason, defect detection accuracy is improved, and defect detection can be performed stably.

  3 shows an example in which two sets of comparison target pixels (comparison target pixels 1 and 2) are used. However, as the number of comparison target pixels used increases, the accuracy of defect detection can be increased. . This means that as the number of comparison target pixels increases, the presence or absence of a defect is determined using a difference value calculated using a comparison target pixel that does not include a comparison target pixel having a luminance value different from the normal value. This is because the probability of being made increases.

[Outline of Inspection System 100]
Next, an overview of the inspection system 100 of the present embodiment will be described based on FIG. FIG. 4 is a block diagram showing a main configuration of the inspection system 100 according to the present embodiment. As illustrated, the inspection system 100 includes a defect detection device 1 and an imaging device 2. The defect detection device 1 includes an image input unit 10, an image memory 11, a difference value calculation unit 12, a defect determination. A part (defect determination means) 13 and a display control unit 14 are included. The display device P is disposed within the imaging range of the imaging device 2, the display device drive circuit 4 is connected to the display device P, and the pattern generator 3 is connected to the display device drive circuit 4. Connected.

  The display device P is an inspection target of the inspection system 100. The display device driving circuit 4 drives the display device P based on the display pattern generated by the pattern generator 3 so that an image corresponding to the display pattern is displayed on the display device P.

  The imaging device 2 captures an image displayed on the display device P and outputs image data (digitized gray image) obtained by the imaging to the image input unit 10. As illustrated, the imaging device 2 moves in a direction perpendicular to the image display surface of the display device P (a direction indicated by an arrow A) and in a direction parallel to the image display surface of the display device P (a direction indicated by an arrow B). It is possible. Thereby, imaging can be performed at an appropriate position according to the imaging range of the imaging device 2 and the size of the display device P.

  The imaging device 2 may be an area sensor or a line sensor. However, when the size of the display device P is large, the TDI / line sensor (time delay integration) is used in terms of resolution. Type line sensor) is preferably used. However, when the imaging device 2 is a line sensor, it is necessary to provide a mechanism for relatively moving the imaging device 2 and the display device P.

  The image input unit 10 is an interface that captures image data acquired by the imaging device 2 into the defect detection device 1. The image data acquired by the imaging device 2 is captured into the defect detection device 1 via the image input unit 10, and the captured image data is stored in the image memory 11. Transmission of image data from the imaging device 2 to the defect detection device 1 may be performed by wired communication or wireless communication, and the configuration of the image input unit 10 depends on the transmission method of the image data. Determined.

  The image memory 11 is a recording medium that stores image data captured by the image input unit 10. The image memory 11 only needs to be capable of writing and reading data. In the inspection system 100, the defect detection result is also stored in the image memory 11. The defect detection result may be recorded on a recording medium different from the image memory 11.

  The difference value calculation unit 12 reads the image data stored in the image memory 11, calculates a difference value serving as a criterion for determining the presence or absence of a defect in the display device P based on the read image data, and calculates the calculated difference value. Is sent to the defect determination unit 13. The difference value calculation method will be described in detail later.

  The defect determination unit 13 determines the presence or absence of a defect included in the display device P based on the difference value calculated by the difference value calculation unit 12. Specifically, the defect determination unit 13 determines the presence / absence of a defect by comparing the difference value with a predetermined threshold value. If it is determined that there is a defect, the defect determination unit 13 stores the position of the defect in the image memory 11.

  Moreover, the defect determination part 13 determines whether it is necessary to change the display pattern displayed on the display apparatus P based on the determination result of the presence or absence of a defect, and when it determines that it needs to change, Then, the display control unit 14 is instructed to change the display pattern.

[Detailed Configuration of Defect Detection Apparatus 1]
Next, a more detailed configuration of the defect detection apparatus 1 will be described with reference to FIG. FIG. 1 is a block diagram showing a main configuration of the defect detection apparatus 1, and particularly shows details of the difference value calculation unit 12 and the defect determination unit 13.

  As illustrated, the difference value calculation unit 12 includes a first address control circuit (comparison target pixel setting unit, extraction position correction unit) 20, an image data reading circuit 21, buffers 22a to 22i ′, a first difference calculation circuit (index). A calculation unit) 23a, a second difference calculation circuit (index calculation unit) 23b, a comparison / selection circuit (index selection unit) 24, a comparison pixel position determination table 25, and a pixel interval determination table 26. The defect determination unit 13 includes a defect determination processing circuit 30, an output buffer 31, an image data writing circuit 32, and a second address control circuit 33.

  The first address control circuit 20 is a circuit for designating a reading position when the image data reading circuit 21 reads a luminance value from the image stored in the image memory 11 into the difference value calculation unit 12. More specifically, the first address control circuit 20 sends the reading position (address) of the pixel to be inspected and the reading position (address) of the comparison target pixel to the image data reading circuit 21. As a result, the image data reading circuit 21 reads the luminance value of the pixel at the position specified by the address into the difference value calculation unit 12 in the image of the display device P stored in the image memory 11.

  Here, the first address control circuit 20 first determines the upper left pixel of the image as the pixel to be inspected, and sends the address to the image data reading circuit 21. Then, the first address control circuit 20 determines the positions of a plurality of comparison target pixels corresponding to the positions of the pixel to be inspected, and sends the addresses to the image data reading circuit 21. A method for determining the position of the comparison target pixel will be described later.

  Next, the first address control circuit 20 determines the next pixel to the right of the first pixel to be inspected as the next pixel to be inspected, and sends the address to the image data reading circuit 21. Then, the first address control circuit 20 determines the positions of a plurality of comparison target pixels corresponding to the newly determined position of the pixel to be inspected, and sends the addresses to the image data reading circuit 21.

  When this process is repeated and the position of the pixel to be inspected reaches the right end of the image, the first address control circuit 20 determines the position of the left end one pixel below in the vertical direction as the position of the next pixel to be inspected. This process is repeated, and the defect detection process for the image ends when all the pixels of the image become the pixel to be inspected once. The first address control circuit 20 only needs to specify an address so that all the pixels of the image become the pixel to be inspected at least once, and the order in which the pixels to be inspected are specified in the above example. Not limited.

  In accordance with an instruction from the first address control circuit 20, the image data reading circuit 21 reads the luminance value of the image obtained by capturing the display device P, which is stored in the image memory 11, into the difference value calculation unit 12, and buffers 22a to 22i. And 22b 'to 22i'. That is, the image data reading circuit 21 reads the luminance value at the position specified by the first address control circuit 20 of the image stored in the image memory 11, and the read luminance values are respectively stored in the buffers 22a to 22i and 22b. Output to “˜22i”.

  Specifically, the first address control circuit 20 outputs the position (address) in the image of the pixel to be inspected and the position (address) in the image of the comparison target pixel to the image data reading circuit 21, and the image data Based on this address, the reading circuit 21 reads the luminance value from the image stored in the image memory 11, and outputs the read luminance value to the buffers 22a to 22i and 22b 'to 22i', respectively.

  Note that the luminance value of the pixel to be inspected (P0) is read into the buffer 22a, the luminance value of the comparison target pixel 1 (P1 to P8) is read into the buffers 22b to 22i, and the comparison is performed with the buffers 22b ′ to 22i ′. It is assumed that the luminance value of the target pixel 2 (P1a to P8a) is read.

  Here, the image data reading circuit 21 basically performs an operation of storing the luminance value for each pixel in each buffer, but the luminance values of a plurality of pixels may be transferred to the buffer at a time. As a result, it is possible to achieve efficient memory transfer and high transfer speed. Such processing can also be realized by using, for example, a 64-bit bus DDR / DDR2 memory frequently used in recent years.

  The first difference calculation circuit 23a calculates the luminance value of the pixel to be inspected (P0) stored in the buffer 22a and the average value of the luminance values of the comparison target pixels 1 (P1 to P8) stored in the buffers 22b to 22i. The difference is calculated and output to the comparison / selection circuit 24.

  Similarly, the second difference calculation circuit 23b includes the luminance value of the pixel to be inspected (P0) stored in the buffer 22a and the luminance value of the comparison target pixel 2 (P1a to P8a) stored in the buffers 22b ′ to 22i ′. The difference from the average value is calculated and output to the comparison / selection circuit 24.

  The comparison / selection circuit 24 compares the absolute value of the difference value received from the first difference calculation circuit 23a with the absolute value of the difference value received from the second difference calculation circuit 23b, and determines the smaller difference value as a defect determination. The data is sent to the processing circuit 30. As a result, a defect is determined using a difference value having a smaller absolute value.

  By determining the defect using a difference value having a smaller absolute value, the luminance value of the pixel to be inspected is a normal value, and the luminance value of the comparison target pixel is an abnormal value, thereby increasing the difference value. In this case, it is possible to prevent erroneous determination that the luminance value of the pixel to be inspected is an abnormal value, thereby preventing a pseudo defect from occurring.

  Here, the reason why the absolute values of the difference values are compared is that the defect of the display device P includes a bright spot defect in which the display pixel has a luminance value larger than a normal value and a black spot defect in which the display pixel does not light up. This is because the sign of the difference value is reversed between when a bright spot defect occurs and when a black spot defect occurs.

  The comparison pixel position determination table 25 is a table in which the position (address) of the pixel to be inspected is associated with the position (address) of the comparison target pixel corresponding to the position. After determining the position of the pixel to be inspected, the first address control circuit 20 refers to the comparison pixel position determination table 25 to determine the position of the comparison target pixel corresponding to the determined position of the pixel to be inspected.

  The position of the pixel to be compared corresponding to the position of the pixel to be inspected is the position to be compared with the pixel to be inspected (the normal value of the luminance value of the pixel at that position and the normal value of the luminance value of the pixel to be inspected). Are theoretically the same value) and are not particularly limited, but the position of the pixel to be compared is preferably changed according to the position of the pixel to be inspected on the image. Since changing the position of the comparison target pixel according to the position of the pixel to be inspected on the image is not an essential process, this process will be described later.

  The pixel interval determination table 26 is a table for correcting the position of the pixel to be inspected determined by the first address control circuit 20 and the position of the comparison target pixel according to the position on the image. By using the pixel interval determination table 26, even when the pixel pitch is different between the center portion and the end portion of the image due to the aberration or distortion of the lens of the imaging device 2, the defect is detected with high accuracy. be able to. Since the pixel interval determination table 26 is not an essential component of the defect detection apparatus 1, details of the pixel interval determination table 26 will be described later.

  The defect determination processing circuit 30 uses the difference value received from the comparison / selection circuit 24 to determine whether the luminance value of the pixel to be inspected is a normal value or an abnormal value. If the luminance value of the pixel to be inspected is a normal value, it indicates that there is no defect in the position corresponding to the pixel to be inspected on the display device P, and if it is an abnormal value, it corresponds to the pixel to be inspected on the display device P. Indicates that the position is defective.

  Specifically, the defect determination processing circuit 30 compares the difference value received from the comparison / selection circuit 24 with a bright spot detection threshold value stored in advance, and the difference value is equal to or greater than the bright spot detection threshold value. If it is a value, it is determined that there is a bright spot defect at a position corresponding to the pixel to be inspected on the display device P, and a determination value indicating the determination result is stored in the output buffer 31.

  Further, the defect determination processing circuit 30 compares the difference value received from the comparison / selection circuit 24 with the previously stored black point detection threshold value, and if the difference value is equal to or smaller than the black point detection threshold value, It is determined that there is a black spot defect at a position corresponding to the pixel to be inspected on the display device P, and a determination value indicating the determination result is stored in the output buffer 31.

  In addition, the defect determination processing circuit 30 determines that the difference value received from the comparison / selection circuit 24 is smaller than the bright spot detection threshold value and larger than the black spot detection threshold value. It is determined that there is no defect at the corresponding position, and a determination value indicating the determination result is stored in the output buffer 31. Note that only the position where the black spot defect or the bright spot defect is detected may be output to the output buffer 31.

  The image data writing circuit 32 stores the determination value stored in the output buffer 31 at an address designated by the second address control circuit 33 of the image memory 11. As described above, the first address control circuit 20 designates an address so that all the pixels of the image stored in the image memory 11 become the pixels to be inspected. For this reason, finally, data in which determination values are stored for all the pixels of the image is stored in the image memory 11.

[Defect detection process flow]
Next, the flow of defect detection processing performed in the defect detection apparatus 1 will be described with reference to FIG. FIG. 5 is a flowchart illustrating an example of the defect detection process. In the flowchart of FIG. 5, a display pattern for defect detection is displayed on the display device P, the display pattern is picked up by the image pickup device 2, and an image obtained by the image pickup is displayed via the image input unit 10 in the image memory 11. Shows the processing after being stored in.

  First, the first address control circuit 20 sets a vertical address counter (Vcnt) indicating a vertical position (address) in an image stored in the image memory 11 to zero (S1). Here, as described above, since it is assumed that defect inspection is performed in order from the upper left end of the image, the reading position when the vertical address counter is set to zero is the upper end of the image.

  Subsequently, the first address control circuit 20 sets a horizontal address counter (Hcnt) indicating a horizontal position (address) in the image stored in the image memory 11 to zero (S2). Here, as described above, since it is assumed that defect inspection is performed in order from the upper left end of the image, the reading position when the horizontal address counter is set to zero is the left end of the image.

  That is, in S1 and S2, the vertical address counter and horizontal address counter are set to zero, so that the reading position becomes the upper left corner of the image. The reading position determined here is the reading position of the luminance value of the pixel to be inspected. When the reading position of the luminance value of the pixel to be inspected is determined, the first address control circuit 20 refers to the comparison pixel position determination table 25 and compares the pixel to be compared corresponding to the reading position of the luminance value of the pixel to be inspected. The reading position of the brightness value of is determined.

  Then, the first address control circuit 20 displays the reading position of the luminance value of the pixel to be inspected (value of the vertical address counter and horizontal address counter) determined as described above and the reading position of the luminance value of the comparison target pixel. The data is sent to the data reading circuit 21.

  The image data reading circuit 21 that has received the reading position of the luminance value of the pixel to be inspected and the reading position of the luminance value of the pixel to be compared reads the luminance read from the image memory 11 in accordance with the reading position of the luminance value of the pixel to be inspected. The value (P0) is stored in the buffer 22a. Further, the image data reading circuit 21 stores the luminance values (P1 to P8) read from the image memory 11 in the buffers 22b to 22i according to the received reading position of the luminance value of the comparison target pixel (S3) and the image memory. The luminance values (P1 ′ to P8 ′) read from 11 are stored in the buffers 22b ′ to 22i ′ (S4).

  When the luminance value (P0) is stored in the buffer 22a and the luminance values (P1 to P8) are stored in the buffers 22b to 22i, the first difference calculation circuit 23a executes the difference calculation 1 and compares the calculation results. The data is sent to the selection circuit 24. Specifically, the first difference calculation circuit 23 a performs a calculation for obtaining a difference between the luminance value (P 0) and the average value of the luminance values (P 1 to P 8), and sends the calculation result to the comparison / selection circuit 24.

  When the luminance value (P0) is stored in the buffer 22a and the luminance values (P1 ′ to P8 ′) are stored in the buffers 22b ′ to 22i ′, the second difference calculation circuit 23b executes the difference calculation 2. The calculation result is sent to the comparison / selection circuit 24. Specifically, the second difference calculation circuit 23 b performs a calculation for obtaining a difference between the luminance value (P 0) and the average value of the luminance values (P 1 ′ to P 8 ′), and sends the calculation result to the comparison / selection circuit 24. (S5). Hereinafter, the calculation result of the difference calculation 1 is referred to as a difference calculation value 1, and the calculation result of the difference calculation 2 is referred to as a difference calculation value 2.

  The comparison / selection circuit 24 that has received the difference calculation values 1 and 2 performs a magnitude comparison between the absolute value of the difference calculation value 1 and the absolute value of the difference calculation value (S6). If the absolute value of the difference calculation value 1 is smaller than the absolute value of the difference calculation value 2 (YES in S6), the comparison / selection circuit 24 selects the difference calculation value 1 as the difference value (S7). .

  On the other hand, when the absolute value of the difference calculation value 2 is less than or equal to the absolute value of the difference calculation value 1, the comparison / selection circuit 24 selects the difference calculation value 2 as the difference value (S8). Here, an example is shown in which the difference calculation value 2 is selected when the difference calculation values 1 and 2 are equal. However, when the difference calculation values 1 and 2 are equal, the difference calculation values 1 and 2 are selected. Either of these may be selected.

  As described above, either one of the difference calculation values 1 and 2 is selected as a difference value and sent to the defect determination processing circuit 30. Then, the defect determination processing circuit 30 that has received the difference value determines whether or not the received difference value is equal to or greater than Th1 (bright spot detection threshold) (S9). If the difference value is equal to or greater than the bright spot detection threshold value (YES in S9), the defect determination processing circuit 30 determines the determination value of the pixel to be inspected as a bright spot defective pixel (S10).

  On the other hand, when the difference value is smaller than the bright spot detection threshold (NO in S9), the defect determination processing circuit 30 determines whether or not the difference value is equal to or less than Th2 (black spot detection threshold) (S11). . Here, when the difference value is equal to or smaller than the black point detection threshold value (YES in S11), the defect determination processing circuit 30 determines the determination value of the pixel to be inspected as a black point defective pixel (S12). When the difference value is larger than the black point detection threshold (NO in S11), the defect determination processing circuit 30 determines the determination value of the pixel to be inspected as a normal pixel (S13).

  As described above, the defect determination processing circuit 30 determines the determination value of the pixel to be inspected as a bright spot defective pixel, a black spot defective pixel, or a normal pixel, and stores the determined determination value in the output buffer 31 (S14). ). Then, the image data writing circuit 32 writes the determination value stored in the output buffer 31 to an address designated by the second address control circuit 33 of the image memory 11 (S15).

  Although not shown in FIG. 1, the first address control circuit 20 and the second address control circuit 33 are connected. The address of the pixel to be inspected determined by the first address control circuit 20 is also sent to the second address control circuit 33. Thereby, the second address control circuit 33 can specify the address of the pixel to be inspected as the write destination of the determination value.

Further, the second address control circuit 33 transmits the determination value to the first address control circuit 20 after designating the write destination of the determination value. As a result, the first address control circuit 20 recognizes that the determination for the pixel to be inspected previously has been completed, and proceeds to determination of the next pixel to be inspected.
That is, the first address control circuit 20 increments the vertical address counter (Vcnt) by 1 (S16).

  Subsequently, the first address control circuit 20 determines whether or not the horizontal address counter (Hcnt) is within the number of horizontal calculation pixels (S17). The number of horizontal calculation pixels is the number of pixels in the horizontal direction of the image. That is, in S17, it is determined whether or not the right end of the image has been reached. If the value of the horizontal address counter is within the number of horizontal calculation pixels (YES in S17), the process returns to S3 and defect detection processing is performed. In this case, the next pixel to be inspected is the pixel immediately to the right of the pixel to be inspected, which was previously used for determining whether or not there is a defect.

  On the other hand, when the horizontal address counter exceeds the number of horizontal calculation pixels (NO in S17), the first address control circuit 20 increments the vertical address counter (Vcnt) by 1 (S18).

  Then, the first address control circuit 20 determines whether or not the incremented vertical address counter value is within the number of vertical calculation pixels (S19). The number of vertical calculation pixels is the number of pixels in the vertical direction of the image. That is, in S19, it is determined whether or not the lower end of the image has been reached.

  If the vertical address counter is within the number of vertical calculation pixels (YES in S19), the process returns to S2 and defect detection processing is performed. In this case, the leftmost pixel in the next row below the pixel to be inspected that has been used to determine whether or not there is a defect is the next pixel to be inspected. On the other hand, if the value of the vertical address counter is larger than the number of vertical operation pixels (NO in S19), the first address control circuit 20 determines that all pixels of the image have been subjected to defect detection processing, and performs defect detection processing. finish.

[Method for determining the position of the comparison target pixel]
As described above, the position of the comparison target pixel is determined in advance according to the position of the pixel to be inspected, and the position of the comparison target pixel corresponding to the position of the pixel to be inspected is stored in the comparison pixel position determination table 25. ing. The position of the comparison target pixel may be determined without considering the position of the pixel to be inspected in the image, but by changing the position of the comparison target pixel according to the position of the pixel to be inspected in the image, Detection accuracy can be increased.

  Here, an example in which the position of the comparison target pixel is changed according to the position in the image of the pixel to be inspected will be described with reference to FIGS. FIG. 6 is a diagram illustrating a relationship between distortion generated in an image captured by the display device P and a block for setting the position of the comparison target pixel.

  By the way, when the display screen of the display device P is large, when the display screen is picked up by the area sensor type image pickup device 2, mold distortion or the like is generated in the picked-up image due to the influence of lens aberration or the like. It is known. In particular, image sensors such as area sensors and TDI / line sensors used for FA applications tend to increase the amount of distortion due to the relatively large size of the image sensor. Also, when a wide-angle lens is used, the amount of distortion tends to increase.

  When the barrel distortion occurs, as shown in the figure, the edge portion of the image has a rounded image shape. Thus, when detecting a defect using a distorted image, the position of the pixel to be compared is set between the vicinity of the center of the image without distortion and the end of the image with distortion. If they are set in the same way, there is a risk that the accuracy of defect detection will be reduced.

  In order to avoid such a situation, it is necessary to change the position of the comparison target pixel according to the position of the pixel to be inspected in the image. For example, as shown in the figure, by dividing the image into nine blocks and setting the position of the comparison target pixel for each block, it is possible to prevent a decrease in defect detection accuracy and maintain high detection accuracy.

  In the example shown in the figure, an image is represented by an upper left corner (a), an upper end (b), an upper right corner (c), a left end (d), a center (e), a right end (f), a lower left corner ( g), divided into nine blocks, a lower end (h) and a lower right corner (i). When the blocks are divided in this way, a comparison position determination table corresponding to each block is prepared in advance.

  Since no distortion occurs in the central portion (e), it is not necessary to determine the position of the comparison target pixel in consideration of the influence of the distortion. Therefore, the position of the comparison target pixel at the center (e) may be set as in the example of FIG. That is, the comparison position determination table for the central portion (e) is a table indicating the position of the comparison target pixel having the arrangement shown in FIG. 3 with respect to the position of the pixel to be inspected.

  In this case, when the first address control circuit 20 determines the position of the pixel to be inspected, if the determined position is included in the central portion (e), the comparison for the central portion (e) is performed. The comparison target pixel may be determined using the position determination table. Thereby, the pixel having the positional relationship shown in FIG. 3 with respect to the position of the pixel to be inspected is determined as the comparison target pixel.

  On the other hand, the upper left corner (a), the upper right corner (c), the lower left corner (g), and the lower right corner (i) are distorted. It is necessary to determine the position of the pixel. For these blocks, the position of the comparison target pixel may be set as in the example of FIG.

  FIG. 7 is a diagram illustrating a setting example of the position of the comparison target pixel in the corner portion of the image. In the drawing, the positional relationship among the pixel to be inspected (P0), the comparison target pixel 1 (P1 to P4), the comparison target pixel 2 (P1a to P4a), and the comparison target pixel 3 (P1b to P4b) is shown. . Although not shown, the horizontal interval (horizontal direction) of each pixel is cm = 6 (see FIG. 2), and the vertical interval (vertical direction) of each pixel is cn = 6 (see FIG. 2). ).

  Here, in the example of FIG. 3, two sets of comparison target pixels (comparison target pixels 1 and 2) are used, but in the example of FIG. 7, three sets of comparison target pixels (comparison target pixels 1 to 3) are used. Yes. When three comparison target pixels are used, the lowest absolute value is selected from the three sets of difference calculation values, and the pixel to be inspected is inspected. In this example, the number of comparison target pixels is four per set, but the number of comparison target pixels per set may be eight as in the example of FIG. Other numbers may be used.

  Thus, the number of sets of comparison target pixels used in the defect detection process and the number of comparison target pixels constituting each set can be changed as appropriate. Although the reliability of the defect detection result can be improved by increasing the number of sets of comparison target pixels and the number of comparison target pixels constituting each set, the amount of calculation also increases at the same time. Therefore, the number of sets of comparison target pixels and the number of comparison target pixels constituting each set may be selected according to the reliability required for defect inspection and the allowable inspection time (arithmetic circuit scale).

  In the example of FIG. 7, in the upper left corner (a), the comparison target pixel is set to be positioned in the lower right direction with respect to the pixel to be inspected. This is because, as shown in FIG. 6, in the upper left corner (a), the distortion is larger in the upper left pixel and is smaller in the lower right pixel.

  For the same reason, in the upper right corner (c), the comparison target pixel is set to be positioned in the lower left direction with respect to the pixel to be inspected, and in the lower left corner (g), the comparison target pixel is set to be inspected. The pixel is set to be positioned in the upper right direction with respect to the pixel, and the comparison target pixel is set to be positioned in the upper left direction with respect to the pixel to be inspected in the lower right corner portion (i).

  In this case, the comparison position determination tables for the upper left corner (a), the upper right corner (c), the lower left corner (g), and the lower right corner (i) On the other hand, this is a table indicating the positions of the comparison target pixels in the arrangements shown in (a), (c), (g), and (i) of FIG.

  In this case, when the first address control circuit 20 determines the position of the pixel to be inspected, the determined positions are the upper left corner (a), the upper right corner (c), and the lower left corner (g). Alternatively, if it is included in the lower right corner (i), the comparison target pixel may be determined using the comparison position determination table for that block. Thereby, a pixel having a positional relationship shown in FIG. 7 with respect to the position of the pixel to be inspected is determined as a comparison target pixel.

  As described above, in the upper left corner (a), upper right corner (c), lower left corner (g), and lower right corner (i), the comparison target pixel has less distortion than the pixel to be inspected. It is set to be a position in the direction. In other words, the first address control circuit 20 sets the comparison target pixel while avoiding the outer edge portion having a large influence of distortion in the image (from pixels other than the outer edge portion).

  Thereby, since the influence of the distortion in the comparison target pixel is reduced, even when the image is distorted, it is possible to prevent the defect detection accuracy from being lowered and to maintain high detection accuracy. The position of the comparison target pixel is not limited to the illustrated example as long as it is set so as to reduce the influence of distortion.

  Moreover, as shown in FIG. 6, distortion has arisen also in the upper end part (b), the left end part (d), the right end part (f), and the lower end part (h). Therefore, for these blocks, it is necessary to determine the position of the comparison target pixel in consideration of the influence of distortion. For these blocks, the position of the comparison target pixel may be set as in the example of FIG.

  FIG. 8 is a diagram illustrating a setting example of the position of the comparison target pixel in the upper end portion (b), the left end portion (d), the right end portion (f), and the lower end portion (h) of the image. In the drawing, the positional relationship among the pixel to be inspected (P0), the comparison target pixel 1 (P1 to P4), the comparison target pixel 2 (P1a to P4a), and the comparison target pixel 3 (P1b to P4b) is shown. . Similar to the example of FIG. 7, the number of sets of comparison target pixels used in the defect detection process and the number of comparison target pixels constituting each set can be changed as appropriate. Although not shown, the horizontal interval (horizontal direction) of each pixel is cm = 6 (see FIG. 2), and the vertical interval (vertical direction) of each pixel is cn = 6 (see FIG. 2). ).

  As illustrated, in the upper end portion (b), the comparison target pixel is set so as to be positioned downward with respect to the pixel to be inspected. This is because, as shown in FIG. 6, in the upper end portion (a), distortion occurs in the upper pixel of the block, and distortion hardly occurs in the lower pixel.

  For the same reason, the comparison target pixel is set to be positioned in the right direction with respect to the pixel to be inspected at the left end portion (d), and the comparison target pixel is set to the pixel to be inspected at the right end portion (f). On the other hand, the pixel to be compared is set to be in the left direction, and the comparison target pixel is set to be in the upper direction with respect to the pixel to be inspected at the lower end (h).

  In this case, the comparison position determination tables for the upper end part (b), the left end part (d), the right end part (f), and the lower end part (h) are shown in FIG. 8 is a table showing the positions of the comparison target pixels in the arrangement shown in (b), (d), (f), and (h).

  In this case, when the first address control circuit 20 determines the position of the pixel to be inspected, the determined position is the upper end (b), left end (d), right end (f), or lower end. If included in the part (h), the comparison target pixel may be determined using the comparison position determination table for the block. Thereby, the pixel having the positional relationship shown in FIG. 8 with respect to the position of the pixel to be inspected is determined as the comparison target pixel.

  Thus, at the upper end (b), the left end (d), the right end (f), and the lower end (h), the comparison target pixel is positioned in a direction with less distortion with respect to the pixel to be inspected. Is set as follows. In other words, the first address control circuit 20 sets the comparison target pixel while avoiding the outer edge portion that is greatly affected by distortion in the image (from pixels other than the outer edge portion).

  Thereby, since the influence of the distortion in the comparison target pixel is reduced, even when the image is distorted, it is possible to prevent the defect detection accuracy from being lowered and to maintain high detection accuracy. The position of the comparison target pixel is not limited to the illustrated example as long as it is set so as to reduce the influence of distortion.

[Correction of reading position of inspected pixel and comparison target pixel]
As described above, when the size of the display device P that is an inspection object is large, distortion may occur in an image obtained by imaging the display device P, and the defect detection is performed using the image in which the distortion has occurred. For this, it is effective to change the position of the comparison target pixel in accordance with the position of the pixel to be inspected.

  Here, when the image is distorted, the influence of the distortion is further reduced by correcting the reading position of the pixel to be inspected and the comparison target pixel according to the position of the pixel to be inspected in the image. Can do. Hereinafter, a method for correcting the reading positions of the pixel to be inspected and the pixel to be compared in accordance with the position in the image of the pixel to be inspected will be described with reference to FIG.

  FIG. 9 illustrates the relationship between the position on the display device P and the pixel pitch in the image generated by imaging the position when the display device P is imaged by the TDI / line sensor type imaging device 2. FIG. In the figure, the entire image display surface of the display device P is imaged by relatively moving the TDI / line sensor type imaging device 2 and the display device P in the horizontal direction (direction indicated by the arrow B). Assumes that

  As described above, when the imaging device 2 and the display device P are relatively moved in the direction indicated by the arrow B, the imaging device 2 holds the row of imaging elements so as to be always perpendicular to the arrow B. Take an image. Since the TDI / line sensor type imaging device 2 is generally used for imaging of a large display device P, the number of imaging elements included in a row reaches several thousand. In addition, a wide-angle lens is often used to further expand the imaging range.

  In such a case, the imaging area per imaging element of the imaging device 2 differs depending on the distance between the imaging target portion of the display device P and the imaging element. That is, as shown in the drawing, the image is captured in the state where the distance between the imaging device 2 and the display device P is the longest than the part (A) imaged in the state where the distance between the imaging device 2 and the display device P is the shortest. The imaged area per image sensor is larger in the portion (C) that has been made. In other words, the imaging density is high at the central portion where the distance to the imaging device 2 is short, and the imaging density is low at the end portion where the distance from the imaging device 2 is far.

  For this reason, the pixel spacing in the vertical direction is narrower in the region (B) closer to the edge of the image than in the region (A) near the center of the image, and more vertical in the region (C) closer to the edge. The pixel spacing in the direction becomes narrower.

For example, in the illustrated example, site and the pixel A ₁ and A ₂ contained the (A) to the image captured is the spacing in the horizontal direction cm, vertical spacing is cn. On the other hand, the pixels C ₁ and C ₂ included in the image obtained by imaging the part (C) have a horizontal interval of cm and the same as the part (A), but the vertical interval is cn ′ (cn ′ <Cn). Thus, the closer to the edge of the image the distance from the imaging device 2 is, the narrower the pixel spacing in the vertical direction.

  Therefore, when the luminance value is read from the image without considering such a difference in pixel interval, the luminance value at a position shifted from the position from which the luminance value should be originally read is read. If the defect is detected based on the above, the defect detection accuracy may be reduced.

  In order to avoid such a situation, for example, it is conceivable to perform correction by shifting the reading position of the pixel to be inspected and the comparison target pixel in accordance with the position on the image. Specifically, after the first address control circuit 20 determines the reading position of the pixel to be inspected and the comparison target pixel using the comparison pixel position determination table 25, the position on the image and the correction amount corresponding to the position The determined reading position may be corrected using the pixel interval determination table 26 in which is associated with.

  As a result, even when the pixel interval is different between the center and the edge of the image used for defect detection due to lens aberration, distortion, etc., the reading position of the luminance value from the image is appropriately corrected. Thus, high-quality comparison calculation processing can be realized, and defects can be detected with high accuracy.

  Note that the correction amount of the reading position of the luminance value is continuously set according to the distance (distance in the vertical direction) from the part (A) imaged in a state where the distance between the imaging device 2 and the display device P is the shortest. The image may be changed, or the image may be divided into a plurality of blocks according to the distance from the part (A), and the correction amount may be determined in advance for each block.

[Embodiment 2]
In the above embodiment, the difference calculation between each of the two (or three or more) comparison target pixels and the pixel to be inspected is performed, and the defect detection is performed using the difference calculation result having the smallest absolute value among the difference calculation results. An example of performing the determination has been described. According to the above configuration, since the difference calculation result in which the pseudo defect is least likely to occur is used from among the plurality of difference calculation results, the comparison target pixels include those whose luminance value is an abnormal value. Even if it exists, generation | occurrence | production of a pseudo defect can be suppressed.

  However, when the comparison target pixel includes a pixel whose luminance value is an abnormal value (a pixel in which the luminance value at the defect position of the display device P is reflected), the abnormal value is reflected in the comparison calculation result. As a result, the defect detection accuracy may be reduced.

  Therefore, in the defect detection apparatus 1 of the present embodiment, when the luminance value of the comparison target pixel is predicted to be an abnormal value, the comparison target pixel is changed to another pixel. Thereby, it is possible to prevent the abnormal value from being reflected in the comparison calculation result, and to further improve the reliability of defect detection.

[Outline of defect detection method]
Here, an outline of the defect detection method performed by the defect detection apparatus 1 ′ of the present embodiment will be described with reference to FIG. FIG. 10 is a diagram for explaining the outline of the defect detection method of the present embodiment. In the figure, the pixel to be inspected is indicated by P0, the comparison target pixel 1 is indicated by P1 to P8, the comparison target pixel 2 is indicated by P1a to P8a, and the comparison target pixel 3 is indicated by P1b to P8b.

  Thus, here, three sets of comparison target pixels of comparison target pixels 1 to 3 are used. Then, in a stage before performing the difference calculation, a pixel whose luminance value is predicted to be an abnormal value is extracted from the comparison target pixels. It should be noted that the position where the luminance value is predicted to be an abnormal value in the image is stored in advance so that the defect detection apparatus 1 ′ can read it.

  Then, the extracted comparison target pixel is replaced with another comparison target pixel (a comparison target pixel whose luminance value is not an abnormal value), and a difference calculation is performed using the replaced comparison target pixel. Thereby, it is possible to prevent the abnormal value from being reflected in the comparison calculation result, and to further improve the reliability of defect detection.

  For example, in the illustrated example, the comparison target pixel 1 (P1 to P8) and the comparison target pixel 2 (P1a to P8a) are set in the same arrangement as the example of FIG. 3, and the comparison target pixel 3 (P1b to P8b) is set. ) Is set. The comparison target pixel 3 (P1b to P8b) has P1b on the left side of P1a, P2b on the top side of P2a, P3b on the top side of P3a, P4b on the bottom left side of P4a, P5b on the top right side of P5a, and P6b on the bottom side of P6a. , P7a is set to P7b, and P8a is set to P8b.

  As shown in the figure, line defects are generated on the straight lines passing through P3, P5, and P8. That is, here, it is assumed that the luminance values of P3, P5, and P8 included in the comparison target pixel 1 are not normal. In such a case, if the comparison operation is performed using the comparison target pixel 1 (P1 to P8) and the comparison target pixel 2 (P1a to P8a), the comparison using the comparison target pixel 1 (P1 to P8) is performed. The luminance values of P3, P5, and P8 that are abnormal values are reflected in the calculation result.

  Therefore, as illustrated, P3, P5, and P8 of the comparison target pixel 1 are replaced with P3a, P5a, and P8a of the comparison target pixel 2 or P3b, P5b, and P8b of the comparison target pixel 3. Thereby, it is possible to prevent the luminance values of P3, P5, and P8, which are abnormal values, from being reflected in the comparison calculation result.

  In the illustrated example, the replacement candidate for the comparison target pixel 1 (P1 to P8) is the comparison target pixel 2 (P1a to P8a) or the comparison target pixel 3 (P1b to P8b), but this is not the only example. Absent. The replacement candidate may be a pixel at a position where the luminance value is expected to be normal (a pixel that is not stored as an abnormal luminance value).

  Further, in the example shown in the figure, an example is shown in which three sets of comparison target pixels 1 to 3 each consisting of eight comparison target pixels are used. However, as shown in FIG. There may be four. FIG. 11 shows an example of changing the comparison target pixel at the position of the defect to the comparison target pixel at the position having no defect when using three sets of comparison target pixels 1 to 3 each consisting of four comparison target pixels. Is shown. 11, P2, P4, P5, P7, P2a, P4a, P5a, P7a, P2b, P4b, P5b, and P7b are removed from the comparison target pixel in FIG.

[Detailed Configuration of Defect Detection Device 1 ']
Next, a detailed configuration of the defect detection apparatus 1 ′ that executes the defect detection method will be described with reference to FIG. FIG. 12 is a block diagram showing a main configuration of the defect detection apparatus 1 ′ of the present embodiment. In addition, about the structure similar to the defect detection apparatus 1 of the said embodiment shown in FIG. 1, the same reference number is attached | subjected and the description is abbreviate | omitted.

  The defect detection apparatus 1 ′ has the same configuration as the defect detection apparatus 1 shown in FIG. 1 except that the difference value calculation unit 12 is replaced with the difference value calculation unit 12 ′. Further, the difference value calculation unit 12 ′ includes a defect position memory (defect position storage unit) 27 and a selection circuit (comparison target pixel changing unit) 28 in addition to the configuration provided in the difference value calculation unit 12. It is a configuration.

  The defect position memory 27 is a memory for storing the position of the defect in the image obtained by imaging the display device P that is the object of defect detection. The defect position memory 27 may store a defect position detected in advance before the defect detection process, or may store a defect position detected in the defect detection process. The process of storing the defect position detected in the defect detection process in the defect position memory 27 will be described later.

  The selection circuit 28 receives the position of the comparison target pixel from the first address control circuit 20, and determines whether or not the received position matches the defect position stored in the defect position memory 27. Then, the selection circuit 28 replaces the comparison target pixel at a position that matches the defect position with a pixel at a position other than the defect position. The pixel to be replaced is a pixel that can be a comparison target pixel, that is, when the luminance value of the pixel is a normal value (when there is no defect in the position of the display device P corresponding to the pixel), Any pixel that has the same luminance value as that of the pixel to be inspected may be used.

[Flow of comparison target pixel replacement processing]
The process of determining the comparison target pixel by replacing the comparison target pixel at a position that matches the defect position with a pixel at a position other than the defect position can also be realized as shown in FIG. 13, for example. FIG. 13 is a flowchart illustrating an example of processing for determining a comparison target pixel.

  First, the selection circuit 28 reads out a defect position stored in the defect position memory 27 (S30). Subsequently, the selection circuit 28 reads the positions of P1 to P8 of the comparison target pixel 1 and the positions of P1a 'to P8a' of the comparison target pixel 2 from the first address control circuit 20 (S31).

  Next, the selection circuit 28 determines whether or not the positions of P1 to P8 of the comparison target pixel 1 read in S31 coincide with the defect position read in S30 (S32). If it is determined that they do not match (NO in S32), the selection circuit 28 instructs the first address control circuit 20 to read the luminance values at the positions P1 to P8.

  Upon receiving the instruction, the first address control circuit 20 causes the image data reading circuit 21 to read the luminance values at the positions P1 to P8. Thereby, the luminance values at the positions P1 to P8 are stored in the buffers 22b to 22i and output to the first difference calculation circuit 23a (S35).

  On the other hand, if it is determined that they match (YES in S32), the selection circuit 28 first changes the luminance value of the position that matches the defect position among P1 to P8 and the luminance value other than the defect position. An instruction is given to the address control circuit 20 (S33).

  Upon receiving the instruction, the first address control circuit 20 replaces the position of the reading position of P1 to P8 that matches the defect position with another position. As a result, the position where the image data reading circuit 21 reads the luminance value changes, and the replaced luminance value is stored in the buffers 22b to 22i and output to the first difference calculation circuit 23a (S34).

  For example, in the example of FIG. 10, P3, P5, and P8 coincide with the defect positions. Therefore, in this case, the reading position of P3 is replaced with the reading position of P3a or P3b, and P5 and P8 are similarly replaced. Here, if the comparison target pixel 3 (P1b to P8b) is exclusively used for replacement, P1, P2, P3b, P4, P5b, P6, P7, and P8b are stored in the buffers 22b to 22i, respectively. It will be. If P3b, P5b, and P8b include those that match the defect position, other positions (for example, P3a, P5a, and P8a) are set as reading positions.

  As described above, when the luminance value is output to the first difference calculation circuit 23a, the selection circuit 28 detects the positions P1 ′ to P8 ′ of the comparison target pixel 1 read in S31 and the defect position read in S30. Is matched (S36). If it is determined that they do not match (NO in S36), the selection circuit 28 instructs the first address control circuit 20 to read the luminance values at the positions P1 'to P8'.

  Upon receiving the instruction, the first address control circuit 20 causes the image data reading circuit 21 to read the luminance values at the positions P1 'to P8'. Accordingly, the luminance values at the positions P1 'to P8' are stored in the buffers 22b 'to 22i' and output to the second difference calculation circuit 23b (S39).

  On the other hand, when it is determined that they match (YES in S36), the selection circuit 28 replaces the luminance value at the position that matches the defect position and the luminance value other than the defect position among P1 ′ to P8 ′. The first address control circuit 20 is instructed (S37).

  Upon receiving the instruction, the first address control circuit 20 replaces the position of the reading position of P1 'to P8' that matches the defect position with another position. As a result, the position where the image data reading circuit 21 reads the luminance value changes, and the replaced luminance value is stored in the buffers 22b ′ to 22i ′ and output to the second difference calculation circuit 23b (S38). ).

  By performing the processing as described above, the comparison target pixel can be configured only by pixels that are not in the defect position (the luminance value is a normal value), thereby preventing the abnormal value from being reflected in the comparison calculation result. Can do. In addition, you may make it perform the process of S32-S35, and the process of S36-S39 simultaneously.

  Since the selection circuit 28 is provided, as described above, in addition to the effect of preventing the luminance value of an abnormal pixel from being reflected in the comparison calculation result, the buffers 22a to 22i and 22a 'to 22i' It is also possible to perform a comparison operation using a set of arbitrary luminance values selected from the above. In other words, the provision of the selection circuit 28 can increase the number of combinations of comparison target pixels to be subjected to a comparison operation, and thus can improve versatility.

  For example, the four luminance values selected from the buffers 22a to 22i and the four luminance values selected from the buffers 22a ′ to 22i ′ are output to the first difference calculation circuit 23a, and the remaining eight luminance values are output to the second difference. Processing such as output to the arithmetic circuit 23b is also possible. As described above, since the calculated difference calculation value becomes a different value by changing the combination of the luminance values, the defect detection accuracy can be further increased by performing the inspection a plurality of times with different combinations.

[Example of detection method of defect position stored in defect position memory 27]
When the defect positions to be stored in the defect position memory 27 are obtained in advance, a defect detection process is performed from an image obtained by imaging the display device P before the above-described defect detection process (see FIG. 5). It is necessary to keep. This process only needs to be able to detect a point defect and a line defect from an image, and a conventionally used general method can also be used.

Here, an example of a method for detecting a defect position stored in the defect position memory 27 will be described with reference to FIGS. FIG. 14 is a diagram illustrating an example of a defect position detection method, and is a diagram illustrating integrated luminance values in the vertical and horizontal directions of the display device P. In the figure, the integrated value profile of the vertical luminance value at each position in the horizontal direction of the display device P is indicated by a _x , and the integrated value profile of the horizontal luminance value at each position in the vertical direction of the display device P is indicated by a _This is indicated by _y .

As shown in the figure, it is assumed here that a line defect L ₁ has occurred in the display device P. When a line defect occurs, the luminance value of the pixel in the line defect portion becomes an abnormal value. For this reason, when the luminance values are integrated in the vertical direction or the horizontal direction at the location where the line defect occurs, the integrated value also becomes a value different from the normal value. More specifically, at a location where a line defect occurs in the vertical direction, the integrated value of the vertical luminance value including that location is different from the normal value, and a location where the line defect occurs in the horizontal direction. In this case, the integrated value of the luminance values in the horizontal direction including that portion is different from the normal value.

In the illustrated example, different since line defects L ₁ from the left to the pixel in the fourth column is generated, the normal integrated value of luminance values in the vertical direction at a position corresponding to the pixel in the fourth column from the left value It becomes. The figure shows a normal value of the integrated value of the luminance values in the vertical direction by N _x. In the integrated value profile corresponding to the location where the line defect L ₁ occurs, as shown by a ₁ in the figure, the integrated value of the luminance value exceeds N _x or as shown by a ₂ , so that the integrated value is smaller than N _x.

For this reason, the location where the display defect occurs in the display device P can be specified based on the integrated value profiles a _x and a _y . Note that when the integrated value of luminance values exceeds N _x , it can be determined that a bright line defect has occurred, and when it is smaller than N _x , it is determined that a black line defect has occurred. can do.

FIG. 15 is also a diagram illustrating an example of a defect position detection method similar to FIG. 14, and is a diagram illustrating integrated luminance values in the vertical and horizontal directions of the display device P. In the figure, the integrated value profile of the vertical luminance value at each position in the horizontal direction of the display device P is indicated by b _x , and the integrated value profile of the horizontal luminance value at each position in the vertical direction of the display device P is b. _This is indicated by _y .

As shown, here it is assumed that line defects L ₂ in the horizontal direction is generated in the display device P. Therefore, the integrated value profile b _x vertical luminance values, influence of L ₂ is reflected. That is, the luminance value at the position corresponding to the line defect L ₂ in the integrated value profile b _x is smaller (b ₁ ) or larger (b ₂ ) than the normal value Ny.

  As described above, the display defect occurring in the display device P can be detected and the position of the display defect can be specified by obtaining the integrated value of the luminance values in the vertical direction and the horizontal direction of the display device P. it can. Then, by storing the position thus obtained in the defect position memory 27, the pixel at the defect position can be excluded from the comparison target pixels.

  The means for detecting the defect position by the above method may be included in the defect detection apparatus 1 ′, or the defect position is detected by the above method in an apparatus outside the defect detection apparatus 1 ′. The detected result may be sent to the defect position memory 27. Further, the defect position detection method is not limited to the above example.

[Feedback of defect detection results]
Here, as described above, when a defect is detected as a pre-process of the defect detection process, there is a problem that the processing time becomes long. Therefore, the defect detection apparatus 1 ′ shown in FIG. 12 can exclude the pixel at the defect position from the comparison target pixel by feeding back the defect detection result to the comparison target pixel setting process.

  That is, as shown in FIG. 12, in the defect detection device 1 ′, the result of the defect determination processing circuit 30 determining the defect is output to the output buffer 31 and is stored in the defect position memory 27. Is also output. As a result, since the defect position is stored in the defect position memory 27, the selection circuit 28 can exclude the pixel at the position where the defect determination processing circuit 30 has detected the defect from the comparison target pixels.

  That is, according to the above configuration, the pixel at the defect position can be excluded from the comparison target pixels without performing defect detection preprocessing. Therefore, the accuracy of defect detection can be improved and the generation amount of pseudo defects can be greatly reduced without increasing the time required for the defect detection processing.

[Modification of comparison operation]
In the above-described example, the example in which the comparison calculation process is performed by calculating the difference between the arithmetic average (arithmetic mean) value of the luminance value of the comparison target pixel and the luminance value of the pixel to be inspected has been described. When the arithmetic average value is used, since the arithmetic processing is simple, it is easy to speed up the comparison arithmetic processing. In addition, when the arithmetic average value is used, the reliability of the result of the comparison calculation process can be easily increased by increasing the number of comparison target pixels.

  However, the comparison calculation process is not limited to the method of calculating the difference between the arithmetic average value of the luminance values of the comparison target pixels and the luminance value of the pixel to be inspected. For example, the comparison calculation process may calculate the difference between the arithmetic average value of the luminance values excluding the maximum value and / or the minimum value of the luminance values of the comparison target pixel and the luminance value of the pixel to be inspected. Thereby, for example, the influence of the luminance value that has become an abnormal value due to the occurrence of noise or the like can be eliminated, and the reliability of the result of the comparison calculation process can be improved.

  Further, the deviation value of the luminance value of the comparison target pixel may be obtained, and the one used for the comparison calculation process may be selected based on the obtained deviation value. That is, in general, a portion where the defect of the display device P does not occur (a portion displayed with a normal luminance value) is a portion where a defect occurs (a portion displayed with a luminance value different from the normal luminance value). ) More. For this reason, when a plurality of comparison target pixels are set, there is a high possibility that the number of pixels having normal values is larger than the number of pixels having abnormal values.

  Therefore, when the deviation value is small, the luminance value of the pixel is highly likely to be normal, and when the deviation value is large, the possibility that the luminance value is abnormal is high. For this reason, there is a possibility that the luminance value with respect to the result of the comparison calculation process is an abnormal value by obtaining the deviation value of the luminance value of the comparison target pixel and excluding those where the obtained deviation value is larger than a predetermined value. This can reduce the influence of high pixels.

  Furthermore, a difference between the luminance value at the position of the pixel to be inspected and the luminance value of the pixel to be inspected obtained by linear interpolation from the luminance values of the plurality of comparison target pixels may be used as the difference calculation value. In this case, it is possible to cancel the gradient of the luminance value due to shading and improve the reliability of the comparison calculation process.

  For example, at the comparison target pixel position in the example of FIG. 8D, the luminance value becomes lower as the pixel on the left side of FIG. 8 is affected by shading. For example, let us consider a case in which there is a gradient of luminance values such that the luminance value of P0 is 60, the luminance value of P2 is 70, and the luminance value of P4 is 80. It is assumed that the luminance value of P0 is normal (no defect has occurred at a position corresponding to P0 of the display device P).

  In this case, the arithmetic average of the luminance value of P2 and the luminance value of P4 is (70 + 80) / 2 = 75. Therefore, when the difference between the luminance value of the pixel to be inspected and the arithmetic average value of the luminance values of the comparison target pixels is taken, the difference calculation value is (60−75) = − 15 (because of the negative value, the black spot defect ) In this case, a pseudo defect may occur due to the fact that the difference calculation value is not zero.

  On the other hand, the luminance value at the position of P0 obtained by linear interpolation from the luminance value of P2 and the luminance value of P4 is (2 × 70) −80 = 60. Therefore, when linear interpolation is performed, the difference calculation value is (60-60) = 0. Since the difference calculation value is zero, in this case, there is no possibility that a pseudo defect occurs.

  As described above, by using linear interpolation, it is possible to cancel the gradient of the luminance value due to shading and improve the reliability of the comparison calculation process. In particular, when the position of the pixel to be compared is set at a position away from the pixel to be inspected, or when the pixel to be inspected and the pixel to be compared are in a corner portion or an end portion (region other than the central portion in the example of FIG. 6) If it is included, it is preferable to use linear interpolation since the influence of shading becomes large.

  In addition, the defect detection process is performed by appropriately combining the above-described comparison calculation processes, such as performing a difference calculation using an arithmetic average value in the central part where the influence of shading is small, and performing a difference calculation using linear interpolation in other parts. You may make it perform. Further, as shown in FIG. 16, due to the influence of shading, the luminance value at the central portion of the image and the luminance value at the peripheral portion are different values. Therefore, the luminance value may be corrected (normalized) according to the part in the image, and the difference calculation may be performed using the corrected luminance value.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  Finally, each block of the defect detection devices 1 and 1 ′, particularly the difference value calculation unit and the defect determination unit, may be configured by hardware logic, or may be realized by software using a CPU as follows. Good.

  That is, the defect detection apparatus 1 or 1 ′ includes a CPU (central processing unit) that executes instructions of a control program that realizes each function, a ROM (read only memory) that stores the program, and a RAM (random) that expands the program. access memory), a storage device (recording medium) such as a memory for storing the program and various data. The object of the present invention is to record the program code (execution format program, intermediate code program, source program) of the control program of the defect detection apparatus 1 or 1 ′, which is software that realizes the above-described functions, in a computer-readable manner. This can also be achieved by supplying the recording medium to the defect detection apparatus 1 or 1 ′ and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include tapes such as magnetic tapes and cassette tapes, magnetic disks such as floppy (registered trademark) disks / hard disks, and disks including optical disks such as CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  The defect detection apparatus 1 or 1 'may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Further, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  According to the defect detection apparatus of the present invention, the occurrence of a pseudo defect can be suppressed when a defect of the inspection object is detected based on an image obtained by imaging the inspection object. This defect detection apparatus is particularly suitable for detecting point defects and line defects in a display device, but can be applied to defect detection of any inspection object as long as it has a repeated pattern.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, showing an embodiment of the present invention, is a block diagram illustrating a main configuration of a defect detection apparatus. It is a figure explaining the positional relationship of a to-be-inspected pixel and a comparison object pixel in the image which image | photographed the test target object and the image which image | photographed the test target object. It is a figure explaining the outline | summary of the defect detection method which the said defect detection apparatus performs. It is a block diagram which shows the principal part structure of the inspection system containing the said defect detection apparatus. It is a flowchart which shows an example of the said defect detection process. It is a figure which shows the relationship between the distortion which arises in the image which imaged the display apparatus, and the block for setting the position of a comparison object pixel. It is a figure which shows the example of a setting of the position of the comparison object pixel in the corner part of an image. It is a figure which shows the example of a setting of the position of the comparison object pixel in the upper end part of an image, a left end part, a right end part, and a lower end part. It is a figure explaining the relationship between the position on a display apparatus and the pitch of the pixel in the image produced | generated by imaging this position when a display apparatus is imaged with the TDI / line sensor type imaging device. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows embodiment of this invention and demonstrates the outline | summary of the defect detection method different from the above. The figure explaining the example which changes the comparison object pixel of the position of a defect into the comparison object pixel of a position without a defect, when one set uses 3 sets of comparison object pixels 1-3 comprised by four comparison object pixels. It is. It is a block diagram which shows the principal part structure of the defect detection apparatus which performs the said defect detection method. It is a flowchart which shows an example of the process which determines a comparison object pixel. It is a figure which shows a prior art and shows an example of the detection method of a defect position. It is a figure which shows a prior art and shows an example of the detection method of a defect position. It is a figure explaining the influence of the shading and brightness nonuniformity with respect to the image which imaged the image display surface. It is a figure explaining the method of determining the presence or absence of the defect of a to-be-inspected pixel by performing the comparison calculation with to-be-inspected pixel and 3 sets of pixels selected from the surrounding pixel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Defect detection apparatus 12 Difference value calculation part 13 Defect determination part (defect determination means)
20 First address control circuit (comparison target pixel setting means, extraction position correction means)
21 Image data reading circuits 22a to 22i ′ Buffer 23a First difference calculation circuit (index calculation means)
23b Second difference calculation circuit (index calculation means)
24 comparison / selection circuit (index selection means)
27 Defect position memory 28 selection circuit (comparison target pixel changing means)

Claims (9)

An image obtained by imaging an inspection object, the luminance value of the pixel to be inspected extracted from an image having a pattern in which the luminance value repeats at a constant cycle, and a pixel separated from the pixel to be inspected by the predetermined cycle A defect detection device for detecting a defect of the inspection object based on a luminance value extracted from the image of the selected comparison target pixel,
The pixel to be inspected is composed of a plurality of comparison target pixels, and a plurality of different comparison target pixel groups are associated with each other,
Index calculating means for calculating an index indicating the magnitude of deviation between the luminance value of each comparison target pixel included in the comparison target pixel group and the luminance value of the pixel to be inspected for each of the plurality of comparison target pixel groups. When,
An index selection means for selecting an index having the smallest absolute value as an index for defect detection among the indices calculated by the index calculation means;
Defect determining means for determining the presence or absence of a defect at a position corresponding to the pixel to be inspected of the inspection object from the magnitude relationship between the defect detection index selected by the index selecting means and a predetermined threshold value ,
The index calculation means obtains the luminance value of the comparison target pixel included in the comparison target pixel group by linear interpolation as the index when the pixel to be inspected is included in a corner portion or an end portion of the image. A defect detection apparatus that calculates a difference between a luminance value at the position of the pixel to be inspected and a luminance value of the pixel to be inspected .   The defect detection apparatus according to claim 1, further comprising comparison target pixel setting means for setting the comparison target pixel while avoiding an outer edge portion of the image. A defect position storage unit for storing defect position data indicating a position on the image corresponding to the defect position of the inspection object;
When the comparison target pixel matches the position indicated by the defect position data stored in the defect position storage unit, the comparison target pixel is changed to a pixel other than the position indicated by the defect position data. The defect detection apparatus according to claim 1, further comprising a changing unit. The defect determination means stores the position on the image of the pixel to be inspected when it is determined that the inspection object has a defect in the defect position storage unit as the defect position data,
The defect detection apparatus according to claim 3, wherein the comparison target pixel changing unit changes the comparison target pixel using the defect position data stored in the defect position storage unit by the defect determination unit.   In the above image, at least one luminance of the pixel to be inspected and the pixel to be compared is determined for at least one of the pixel to be inspected and the pixel to be compared located other than the closest part that is the part closest to the imaging device at the time of imaging. It is characterized by comprising an extraction position correction means for correcting the value extraction position so as to be closer to the nearest part and increasing the correction amount as the position becomes farther from the nearest part. The defect detection apparatus according to any one of claims 1 to 4. When the pixel to be inspected is not included in a corner portion or an end portion of the image , the indicator calculation means, as the indicator,
The difference between the average luminance value of each comparison target pixel included in the comparison target pixel group and the luminance value of the pixel to be inspected,
From the comparison target pixel group, in the comparison target pixel group, at least one of the comparison target pixel having the maximum brightness value or the minimum comparison target pixel is excluded, and the average value of the brightness value and the target value of the remaining comparison target pixels are excluded. The difference in the luminance value of the inspection pixel,
Or, among the compared pixels included in the comparison pixel group, and the average value of the luminance values in the remaining comparison target pixel deviation of the luminance values except the compared pixel greater than a predetermined value, the pixel under test The difference from the brightness value,
The defect detection apparatus according to claim 1, wherein the defect detection apparatus calculates a defect. An image obtained by imaging an inspection object, the luminance value of the pixel to be inspected extracted from an image having a pattern in which the luminance value repeats at a constant cycle, and a pixel separated from the pixel to be inspected by the predetermined cycle A defect detection method executed by a defect detection device that detects a defect of the inspection object based on a luminance value extracted from the image of the selected comparison target pixel,
The inspected pixel includes a plurality of comparison target pixels, and a plurality of different comparison target pixel groups are associated with each other,
An index calculation step for calculating an index indicating the magnitude of deviation between the luminance value of each comparison target pixel included in the comparison target pixel group and the luminance value of the pixel to be inspected for each of the plurality of comparison target pixel groups. When,
An index selection step of selecting an index having the smallest absolute value as an index for defect detection among the indices calculated in the index calculation step;
A defect detection index selected in the index selection step, from the magnitude relation between the predetermined threshold, saw including a defect determination step of determining presence or absence of a defect at a position corresponding to the pixel under test in the test object ,
In the index calculation step, when the pixel to be inspected is included in a corner portion or an end portion of the image, a luminance value of a comparison target pixel included in the comparison target pixel group is obtained by linear interpolation as the index. A defect detection method comprising calculating a difference between a luminance value at the position of the pixel to be inspected and a luminance value of the pixel to be inspected . A defect detection program for operating the defect detection apparatus according to any one of claims 1 to 6,
A defect detection program for causing a computer to function as each of the above means.   A computer-readable recording medium on which the defect detection program according to claim 8 is recorded.

Images