JP2012088199A - Method and apparatus for inspecting foreign matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for inspecting a foreign matter, capable of surely detecting only a foreign matter attached to a circuit board.SOLUTION: A method for inspecting a foreign matter, comprises: for each pixel of a digital image of a circuit board to be inspected, setting a pixel group having a small area including the pixel; calculating the amount indicating a dispersion degree of a luminance value of each pixel with respect to the pixel group, as a luminance confirmation value for each pixel, by comparing the luminance value of each pixel with the luminance value of the pixel group including the pixel; and then determining the presence or the absence of the foreign matter based on the luminance confirmation value. While the circuit board has a low dispersion degree of the luminance value, the foreign matter that is a naturally-formed object having an irregular shape entirely has a high dispersion degree of the luminance value including gradation. Accordingly, the foreign matter can be sharply distinguished by calculating the luminance confirmation value to utilize the difference in dispersion degree of the luminance value between a product and the foreign matter.

Description

  The present invention relates to a foreign matter inspection apparatus and a foreign matter inspection method.

  For example, when inspecting foreign matters such as solder balls, mold debris, and fiber scraps attached between the leads of an integrated circuit, a conventional inspection apparatus performs a technique of imaging a substrate and performing image processing. For example, the foreign matter inspection apparatus disclosed in Patent Document 1 differentiates an AD-converted digital image and binarizes it. Then, the binarized image data is parallel to the longitudinal direction of the substrate lead. A value of “1” in the direction is measured to generate measurement data, and the measurement data is further binarized to generate projection binarized data. When determining the quality of a product, count all consecutive numbers of “0” and “1” in the binarized projection data, and set the upper and lower limits for the preset numbers of “0” and “1” respectively. If there is even one continuous number outside the range, it is determined that foreign matter is attached.

  When binarization is immediately performed from an AD-converted image, it is difficult to detect a foreign matter portion having a low reflectance or a foreign matter portion having a high transmittance, whereas the technique disclosed in Patent Document 1 uses image data. Since the edge is emphasized by the differential processing, the detection of the foreign matter portion is enhanced in the subsequent processing.

JP-A-7-128249

  However, in the configuration of Patent Document 1, since the lead of the substrate is also evaluated with the same value as the foreign matter, when the foreign matter overlaps the lead or when the shape of the foreign matter is aligned with the lead, the edge of the foreign matter Is difficult to detect, and foreign matter cannot be reliably detected.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a foreign matter inspection apparatus and a foreign matter inspection method that can detect foreign matter more reliably.

  In order to solve the above problems, the present invention is a foreign matter inspection apparatus for inspecting the presence or absence of foreign matter on a substrate that has undergone a surface treatment including a printing process, and imaging means that images the substrate and outputs an analog signal; AD conversion means for converting the output analog signal into a digital image, pixel group setting means for setting a pixel group of a small area including the pixel for each pixel of the converted digital image, and luminance in the pixel group A luminance check value calculation means for calculating for each pixel a quantity representing a degree of variation in value as a luminance check value of the pixel, and a determination means for determining the presence or absence of a foreign substance based on the luminance check value Is a foreign matter inspection apparatus characterized by

  In this aspect, the luminance confirmation value calculation means calculates an amount representing the degree of variation in the luminance value of each pixel as the luminance confirmation value. When each pixel is a product, the amount of change in the boundary is large, so the variation amount is converged to 0. In contrast, in the case of a foreign object, various values are used for the gradation of the foreign object. Diverge. As a result, it becomes easy to extract pixels only in the foreign matter portion, and the foreign matter can be reliably detected.

  In a preferred aspect, the determination means performs a ternarization process on the luminance confirmation value of each pixel. In this aspect, the brightness confirmation value of the product portion is further converged to 0, and the brightness confirmation value of the foreign matter can be made to stand out. Moreover, it is preferable to further include a median processing means for performing median processing on the calculated luminance confirmation value.

  A foreign matter inspection apparatus according to a preferred aspect includes a display unit that displays an image of the substrate, and a GUI that surrounds a portion corresponding to the foreign matter with a window in the image displayed by the display unit when the determination unit determines that the foreign matter is present. And processing means. In this aspect, the foreign substance determination result can be displayed easily.

  In a preferred aspect, the determination means determines that the pixel block having the luminance confirmation value having a large degree of variation is a foreign object when it has a predetermined area. In this aspect, it is possible to determine only foreign substances that require detection by removing noise. In the present invention, since a luminance confirmation value is set for each pixel, depending on the aspect of the luminance confirmation value, there is a possibility that a thing that is confused with noise or a foreign object is determined as a foreign object. When a cluster of pixels having a luminance confirmation value with a large degree of variation has a predetermined area, it is possible to reliably distinguish such noise from foreign matters. As an area evaluation method, for example, it is possible to determine whether or not an area having a predetermined size (5 pixels × 8 pixels) is inscribed in a block of pixels having a luminance confirmation value with a large degree of variation. Alternatively, it is determined whether or not an area of 4 pixels × 3 pixels moves within a range of pixels having a luminance confirmation value with a large variation degree, and the quality is determined based on the moving distance or the area of the moving range. It may be. Furthermore, as another method, a rectangle of an area of 5 pixels × 8 pixels may be tilted to determine whether or not the pixel block having a luminance confirmation value with a large degree of variation is inscribed. Further, the pixel area for evaluating a cluster of pixels having a luminance confirmation value with a large degree of variation is not limited to a rectangle. Employing the method as described above is particularly effective when the shape of the foreign matter is known in advance.

  In a preferred aspect, the luminance check value calculation means is configured to calculate, for each pixel, a sum of absolute values of differences between a luminance value of each pixel and an average value of luminance values of the pixel group set for the pixel as the luminance check value. It is to calculate. In this aspect, it is possible to obtain a high-accuracy luminance confirmation value using parameters that can be calculated relatively quickly.

  In a preferred aspect, the luminance confirmation value calculation means calculates an amount representing a degree of variation while ignoring the minimum and maximum luminance values of the pixels in the pixel group. In this aspect, since the maximum value and the minimum value of the luminance values of the pixels that statistically cause noise are ignored at the stage of the luminance confirmation value calculation step, the calculation at the determination step is speeded up and simplified.

  Another aspect of the present invention is a foreign matter inspection method for inspecting the presence or absence of foreign matter on a substrate that has undergone a surface treatment including a printing process, and an imaging step for imaging the substrate and outputting an analog signal is output. An AD conversion step for converting an analog signal into a digital image, a pixel group setting step for setting a pixel group of a small area including the pixel for each pixel of the converted digital image, and a degree of variation in luminance value in the pixel group A luminance confirmation value calculation step for calculating for each pixel a luminance confirmation value for the pixel, and a determination step for determining the presence or absence of a foreign substance based on the luminance confirmation value. This is a foreign matter inspection method.

  In a preferred aspect, the luminance confirmation value calculation step calculates an amount representing a degree of variation while ignoring the minimum and maximum luminance values of the pixels in the pixel group. In this aspect, since the maximum value and the minimum value of the luminance values of the pixels that statistically cause noise are ignored at the stage of the luminance confirmation value calculation step, the calculation at the determination step is speeded up and simplified.

  As described above, in the present invention, foreign matter determination can be performed with a very high probability by paying attention to the difference in the degree of variation between the luminance value of the pixel relating to the product and the luminance value of the pixel relating to the foreign matter. The remarkable effect that it can detect more reliably is produced.

It is a section schematic diagram showing the important section of a foreign substance inspection device concerning one embodiment of the present invention. It is a block diagram which shows schematic structure of the foreign material inspection apparatus of FIG. It is a schematic diagram of the board | substrate used as a test object. It is a flowchart which shows the operation example of the foreign material inspection apparatus of FIG. It is a flowchart which shows the pass / fail judgment subroutine of the flowchart of FIG. It is the schematic which shows the example of a display by the execution result of the flowchart of FIG. It is a schematic diagram of the board | substrate in the 1st-4th Example of this invention. It is a schematic diagram which shows the example of the luminance average value in the 1st-4th Example of this invention. It is a principal part enlarged view of FIG. It is a flowchart which shows the brightness | luminance confirmation value calculation subroutine of FIG. 4 by 1st Example. It is a schematic diagram which shows the example of the luminance average value by the execution result of the flowchart of FIG. It is a principal part enlarged view of FIG. It is a schematic diagram which shows the example of the luminance average value by the execution result of the flowchart of FIG. It is a graph of the profile which shows a brightness | luminance average value (brightness ratio). It is a graph of the difference profile which shows the difference of a brightness | luminance average value. It is a graph which shows the difference absolute value of a brightness | luminance average value. It is the graph which gave ternarization to the difference absolute value of the luminance average value. It is the graph which performed the median process of 3 pixels to the difference absolute value of the luminance average value. It is the graph which performed the median process of 3 pixels and the ternarization to the difference absolute value of the luminance average value. It is a flowchart which shows the brightness | luminance confirmation value calculation subroutine of FIG. 4 by 2nd Example. It is a schematic diagram which shows the example of the luminance average value by the execution result of the flowchart of FIG. It is a principal part enlarged view of FIG. It is a schematic diagram which shows the example of the luminance average value by the execution result of the flowchart of FIG. It is a flowchart which shows the brightness | luminance confirmation value calculation subroutine of FIG. 4 by 3rd Example. It is a schematic diagram which shows the example of the luminance average value by the execution result of the flowchart of FIG. It is a principal part enlarged view of FIG. It is a schematic diagram which shows the example of the luminance average value by the execution result of the flowchart of FIG. It is a flowchart which shows the brightness | luminance confirmation value calculation subroutine of FIG. 4 by 4th Example. It is a schematic diagram which shows the example of the luminance average value by the execution result of the flowchart of FIG. It is a principal part enlarged view of FIG. It is a schematic diagram which shows the example of the luminance average value by the execution result of the flowchart of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the structure of an appearance inspection apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS. The appearance inspection apparatus 100 according to the present embodiment is an example of the “foreign substance inspection apparatus” in the present invention. This appearance inspection apparatus 100 determines whether or not a foreign matter such as a solder ball, dross, component debris, or fiber debris is attached to the surface of the substrate W as a substrate that has undergone a surface treatment including a printing process. When there is a foreign object, it has a function of displaying it.

  With reference to FIG. 1, the foreign matter inspection apparatus according to the present embodiment includes a stage 11 on which a substrate W to be inspected is placed in a housing 10. The stage 11 is embodied by a conveyor mechanism, and can be moved in a transport direction along a predetermined horizontal direction and a horizontal direction orthogonal to the transport direction by a drive mechanism (not shown). In the following description, the transport direction of the stage 11 is referred to as the X direction, and the horizontal direction perpendicular thereto is referred to as the Y direction. The stage 11 is configured to be able to stop and hold the substrate W at a predetermined inspection position. The stage 11 is configured so that the substrate W that has been inspected can be transported in the X direction from a predetermined inspection position, and the substrate W can be unloaded from the appearance inspection apparatus 100.

  On the upstream side of the stage 11 in the X direction, a carry-in conveyor 12 for carrying the substrate W into the stage 11 is provided. Further, an unloading conveyor 14 for unloading the substrate W from the stage 11 is provided on the downstream side of the stage 11 in the X direction. The carry-in conveyor 12 carries the substrates W one by one onto the stage 11 after completing a predetermined process. The carry-out conveyor 14 carries out the substrate W that has been subjected to the inspection process in the appearance inspection apparatus 100 from the stage 11.

  The housing 10 includes an optical camera 20 that images the surface of the substrate W and outputs an analog signal thereof, and an illumination device 30 that illuminates the substrate W on the stage 11 captured by the optical camera 20. ing. The optical camera 20 and the illumination device 30 are configured to be movable in the XY directions above the stage 11 by a driving mechanism (not shown).

  The optical camera 20 is composed of, for example, a CCD camera. The optical camera 20 is configured to stop right above the inspection position and direct the lens 21 directly below it to image the substrate W on the stage 11.

  On the other hand, the illumination device 30 has a dome-like shape in which an opening 321 facing the lens 21 of the optical camera 20 from above is formed at the top, and a plurality of illuminations divided vertically are provided on the inner surface side of the dome. Is provided. Specifically, an upper illuminating unit 322, a middle illuminating unit 323, and a lower illuminating unit 324 are provided in order from the apex side where the opening 321 is provided, and each of the illuminating units 322 to 324 includes: A plurality of white LEDs are arranged in the circumferential direction. In addition, the upper illumination unit 322 is provided with infrared illumination that emits infrared illumination light. Therefore, the optical camera 20 captures the upper surface of the substrate W from the opening 321 using the illumination light emitted from the illumination device 30 to the substrate W, and outputs a two-dimensional (planar) analog signal. It is configured. In this photographing by the optical camera 20, RGB images corresponding to red R, green G, and blue B are obtained under illumination light from a white LED described later, and an infrared image is obtained under infrared illumination light. . In the present embodiment, an average brightness value obtained by averaging the brightness values of red R, green G, and blue B among the brightness values of the digital image generated after image capturing by the optical camera 20 is used as a calculation parameter.

  Referring to FIG. 2, appearance inspection apparatus 100 is configured to be controlled by control device 40. The control device 40 logically includes a stage control unit 41, a conveyor control unit 42, a camera control unit 43, a display control unit 45, and an illumination control unit 46. Further, in order to execute an inspection process described later, an image processing unit 410, an inspection determination processing unit 420, and a GUI processing unit 430 are logically configured. Furthermore, the control device 40 includes a CPU that executes logical operations, a ROM (Read Only Memory) that stores programs for controlling the CPU, and a RAM (Random Access Memory) that temporarily stores various data during operation of the device. And a storage device 50 composed of an auxiliary storage device for storing programs and various data (parameters).

  Each of the control units 41 to 46 is executed by the microprocessor according to a program or data stored in the storage device 50, whereby the stage 11, the conveyors 12 and 14, the optical camera 20, the illumination device 30, and the display unit 60. It is a logical module that controls Here, the display unit 60 is embodied by a liquid crystal display, for example, and displays the processing contents of the control device 40. Further, an input device such as a pointing device (not shown) is connected to the display unit 60 so that an operator can input necessary settings and data according to a program stored in the storage device 50 as appropriate. It has become.

  Each of the processing units 410 to 430 performs processing on the board based on an analog signal that is output when the optical camera 20 captures an image by the microprocessor executing processing according to a program or data stored in the storage device 50. This is a logical module for performing a foreign matter inspection of W.

  The image processing unit 410 includes an AD conversion unit 411, a pixel processing unit 412, a pixel group setting unit 413, and a luminance check value processing unit 414. The AD conversion unit 411 has a function of obtaining a digital image from an analog signal output from the optical camera 20. The pixel processing unit 412 has a function of acquiring an address and a luminance value for each pixel from the digital image converted by the AD conversion unit 411 and storing the acquired address and luminance value in a storage area set in advance in the storage device 50. In the present embodiment, the luminance value is stored for each RGB corresponding to red R, green G, and blue B, and “luminance average value” obtained by averaging these luminance values is also stored. Yes. The pixel group setting unit 413 has a function of setting, for each pixel processed by the pixel processing unit 412, a pixel group GR of a small region including the pixel. For example, for a pixel whose coordinates in the X direction and the coordinate in the Y direction are (100, 100), a small region of 3 pixels × 3 pixels is set around this pixel, and for this (100, 100) pixel, A pixel group GR having a start position (99, 99) and an end position (101, 101) is set. The luminance check value processing unit 414 has a function of calculating a value for evaluating the variation degree of the luminance value of each pixel (this value is referred to as “brightness check value”) for each pixel and storing it in the storage device 50.

  The inspection determination processing unit 420 has a function of determining whether or not a foreign object is included in the image based on the image data processed by the image processing unit 410.

  The GUI processing unit 430 has a function of displaying various graphical user interfaces (GUIs) on the display unit 60 based on the processing content of the display control unit 45. The GUI processing unit 430 according to the present embodiment functions so as to surround the foreign matter determined by the examination determination processing unit 420 with, for example, a red window when there is a foreign matter in the image displayed by the display unit 60.

  Referring to FIG. 3, in the substrate W, a plain glass epoxy substrate is etched to form a copper foil portion A1, and then a resist printing portion A2 by resist printing and a silk printing portion A3 by silk printing are formed. Is. A0 is a plain part, and A4 is an overlapping part of the copper foil part A1 and the resist printing part A2. Since each of the portions A0 to A4 is partitioned by a linear boundary, the luminance variation degree is reduced.

  A case where the foreign substance Ob adheres to the substrate W will be described. The foreign object Ob is overwhelmingly solder balls and then has a lot of dross. In addition, there may be rare cases where part debris and fiber scraps are attached. Since these foreign substances Ob are naturally formed irregular objects, they have a characteristic of a high degree of variation in luminance accompanied by gradients as a whole. In view of this, in the present embodiment, image processing that distinguishes foreign matters is performed by using the difference in brightness variation between the product and the foreign matter.

  Next, an example of the foreign substance inspection processed by the control device 40 will be described.

  Referring to FIGS. 1 and 4, control device 40 reads product data based on an inspection program (step S <b> 1). Next, a variable N is set based on the product information (step S2). Here, the variable N is the number of images that need to be inspected. Since imaging of the substrate W may be performed a plurality of times as necessary, in this embodiment, the number of imaging can be determined for each product.

  Further, the imaging position is changed by moving the optical camera 20 (the illumination device 30 as necessary) according to the number of times of imaging.

  Next, the control device 40 drives the stage 11, the carry-in conveyor 12, and the carry-out conveyor 14 (if necessary), and fixes the substrate W to the inspection position on the stage 11 (step S3). Thereby, as shown in FIG. 1, the substrate W is fixed immediately below the illumination device 30, so that the optical camera 20 can image the substrate W through the opening 321 of the illumination device 30. .

  Next, the control device 40 initializes a variable J for counting the number of times of imaging to 1 (step S4), and moves the optical camera 20 (and the illumination device 30 as necessary) to the J-th imaging position (step S4). Step S5). Next, the control device 40 images the substrate W with the optical camera 20 (step S6), and processes the image data.

  The captured analog signal is converted into a digital image by the AD conversion unit 411 of the image processing unit 410 (step S7).

  Thereafter, the control device 40 determines pass / fail of the imaged substrate W in a pass / fail determination subroutine S8 to be described in detail later, increments the variable J (step S9), and determines whether or not the number of times of image capture has reached the required number. (Step S10). If it is determined that the required number is not reached, the control device 40 returns to step S5 and repeats the above-described processing. On the other hand, if it is determined that the number of inspected images has reached the required number, the control device 40 drives the stage 11 and the carry-out conveyor 14 and carries out the inspected substrate W (step S11). Next, the control device 40 determines whether or not there is a foreign object (step S12). If it is determined that there is a foreign object, the control device 40 displays a window surrounding the foreign object in the image captured in step S6 (step S14).

  Next, referring to FIG. 5, in the pass / fail judgment subroutine (step S <b> 8), control device 40 calculates the RGB luminance average values corresponding to red R, green G, and blue B of the image data obtained from the digital signal. Calculation is performed for each pixel (step S801). Next, the control device 40 executes a brightness check value calculation subroutine, and calculates a brightness check value for each pixel (step S802). As described above, the substrate W has a low degree of luminance variation when there is no foreign matter, and when there is a foreign matter, the portion has a high degree of luminance variation. Therefore, for example, the absolute value of the difference from the average value, the variance, the sum of squared deviations, the difference between the maximum value and the minimum value, etc. are calculated, and the calculated value is used as the determination data as the luminance confirmation value. .

  Next, the control device 40 performs a filtering process on the luminance confirmation value of each pixel to remove noise (step S803). Examples of the noise removal method include a ternarization process or a median process. Here, the ternarization processing means that when the pixels are arranged in order of the luminance value, the pixel value between the upper limit value (for example, 30) and the lower limit value (for example, 5) is set to 1. And other values are set to 0. The median process is a process for acquiring the value of the luminance value of the center pixel when a plurality of pixels are arranged in the order of the luminance value. In this process, when the number of pixels is an odd number, the value of the central luminance value is used, and when the number is an even number, the average value of the luminance values of the two central pixels is used.

  By these filter processes, the determination value of the part with a small variation degree becomes 0, and the determination value of the part with a large variation degree takes a value according to the variation degree.

  Next, the control device 40 identifies an area of pixels whose determination value is greater than 0 (step S804). Next, the control device 40 counts the number of areas Ac (step S805). Thereafter, the control device 40 initializes a variable K for counting the area to 1 (step S806), and determines whether or not the Kth area is within the allowable range (step S807).

  Various specific determination methods can be employed.

  For example, it is possible to set a determination frame of 5 pixels × 8 pixels, determine whether or not the determination frame is inscribed in the area, and in the case of inscribed, it is possible to adopt a method of determining a foreign object. . In this determination, the determination frame may be rotated to determine whether it is inscribed. When the shape of a foreign object that needs to be detected can be specified in advance, there is an advantage that the determination of the foreign object becomes easy and reliable by setting such a determination frame and changing the angle to verify the area.

  Also, a determination frame of 4 pixels × 3 pixels is set, whether or not this determination frame can be moved within the area, and if it can be moved, whether or not it is a foreign object is determined based on the size of the movable area. A determination method may be adopted.

  Alternatively, it is verified whether or not the determination frame of 4 pixels × 3 pixels can move within the area, and if it can move, whether or not it is a foreign object based on the movable distance in the X direction and the movable distance in the Y direction You may employ | adopt the method of determining.

  A determination frame other than a rectangle, such as a circle or an ellipse, may be employed.

  Usually, the size of the foreign object Ob is 200 μm or more, and the size of one side of the pixel is 19 μm. Therefore, foreign matter detection is performed with extremely high accuracy by making a determination using a determination frame of 5 pixels × 8 pixels.

  As a result of the foreign object determination in step S807, when it is determined that the object is not a foreign object, the control device 40 makes a normal determination for the Kth area (step S808). Foreign matter determination is made for (step S809). Next, the control device 40 increments the value of the variable K (step S810), determines whether all areas have been inspected (step S811), and returns to step S807 if there is an undetermined area. The above process is repeated. On the other hand, when the determination is completed for all areas, the process returns to the main routine.

  Referring to FIG. 6, control device 40 causes display unit 60 to display an image as shown in FIG. 6, for example, through the process of step S14 of the main routine (flowchart of FIG. 4). FIG. 6 is a display example of an image when the substrate W as shown in FIG. 3 is imaged. In the illustrated example, the red display window Wd is circumscribed by the foreign object Ob to facilitate visual recognition.

  As described above, the appearance inspection apparatus 100 according to the present embodiment is an appearance inspection apparatus 100 that inspects the presence or absence of the foreign matter Ob on the substrate W that has been subjected to the surface treatment including the printing process. An optical camera 20 as an imaging means for outputting an analog signal, an AD conversion unit 411 for converting the output analog signal into a digital image, and a pixel in a small region including the pixel for each pixel of the converted digital image A pixel group setting unit 413 that sets the group GR, a luminance check value processing unit 414 that calculates, for each pixel, a luminance check value Vp of the pixel group GR as a luminance check value Vp of the pixel, and a luminance check value Vp And an inspection determination processing unit 420 for determining the presence or absence of the foreign object Ob.

  Another aspect of the present embodiment is a foreign matter inspection method for inspecting the presence or absence of foreign matter Ob on the substrate W that has been subjected to surface treatment including printing processing, and an imaging step of outputting an analog signal of the substrate W (step S6). And an AD conversion step (step S7) for converting the output analog signal into a digital image, and a pixel group GR setting step for setting a pixel group GR of a small region including the pixel for each pixel of the converted digital image (Step S801), a luminance confirmation value calculation step (Step S802) for calculating, for each pixel, the amount representing the variation degree of the luminance value in the pixel group GR as the luminance confirmation value Vp of the pixel, and the luminance confirmation value Vp. And a determination step (step S808) for determining whether or not the foreign object Ob exists.

  For this reason, in this embodiment, the luminance confirmation value processing unit 414 serving as the luminance confirmation value calculation means calculates, as the luminance confirmation value Vp, an amount representing the variation degree of the luminance value of each pixel, so that each pixel is a product. In some cases, since the amount of change in the boundary is large, the variation amount is converged to 0, whereas in the case of the foreign object Ob, it diverges to various values due to the gradient of the foreign object Ob. As a result, it becomes easy to extract pixels only for the foreign object Ob, and the foreign object Ob can be reliably detected.

  In addition, the appearance inspection apparatus 100 according to this embodiment includes a display unit 60 as a display unit that displays an image of a substrate, and an inspection determination as a determination unit when there is a foreign object Ob in the analog signal displayed by the display unit 60. And a GUI processing unit 430 surrounding the foreign object Ob determined by the processing unit 420 with a window. For this reason, in this embodiment, the determination result of the foreign object Ob can be displayed easily.

  In the present embodiment, the inspection determination processing unit 420 determines that the pixel block having the luminance confirmation value Vp having a large degree of variation in the digital image is a foreign object Ob when the pixel block has a predetermined area. Therefore, in the present embodiment, it is possible to determine only foreign objects Ob that need to be detected by removing noise. In the present embodiment, since the luminance confirmation value Vp is set for each pixel, depending on the aspect of the luminance confirmation value Vp, there is a possibility that a noise or a foreign object Ob may be determined as the foreign object Ob. When a cluster of pixels having the luminance confirmation value Vp having a large degree of variation has a predetermined area, it is possible to reliably distinguish such noise from the foreign object Ob.

  As described above, according to the present embodiment, it is possible to reliably detect a foreign object.

  Next, examples according to the present invention will be described.

  The substrate W described in FIG. 3 was imaged using the apparatus described in FIGS. 1 and 2. After the imaged analog signal of the substrate W was converted into a digital image, the luminance value of each part was obtained and the average luminance value was calculated. The calculation result was as shown in FIG. In the figure, the numerical value prefixed with “Ave” is the RGB luminance average value corresponding to the red R, green G, and blue B of the image data, and the parenthesized values are the RGB luminance values.

  FIG. 8 is a diagram schematically showing the calculated luminance average value, and FIG. 9 is an enlarged view of a main part of FIG. As shown in FIG. 8, in the portions A4, A2, A3, and A2, the average luminance values are Ave 150, Ave 158, Ave 255, and Ave 158 in order from the left. For the foreign object Ob, as shown in FIG. 9, the average luminance value at the center is the highest, 150, and gradually decreases with the gradient, and the outer peripheral portion is zero.

Next, the first to fourth embodiments were implemented in executing the luminance confirmation value calculation subroutine of FIG.
(First embodiment)
In the first embodiment, the subroutine shown in FIG. 10 is executed.

  Referring to FIG. 10, in this subroutine, first, a variable P for counting pixels is initialized with 1 (step S8021), and a pixel group GR of 3 pixels × 3 pixels centering on the Pth pixel is set. (Step S8022).

  Then

  Was calculated as Vp (step S8023). In this calculation process, the maximum value and the minimum value are ignored among the luminance values of the pixels constituting the pixel group. This Vp is registered as the luminance confirmation value of the Pth pixel (step S8024). Next, the value of P is incremented (step S8025), and it is determined whether or not the luminance confirmation values for all the pixels have been set (step S8026). If there is an undetermined pixel, the process returns to step S8022, and the above-described processing is repeated. After the determination for all the pixels is completed, the process returns to the subroutine of FIG.

  FIG. 11 is a diagram schematically showing the calculated luminance confirmation value in the range surrounded by Ar in FIG. 7, and FIG. 12 is an enlarged view of the main part in FIG. 11. As shown in FIG. 11 and FIG. 12, as a result of calculating the luminance confirmation value, each portion A4, A2, A3, A2 has a variation degree of 0, and thus becomes 0, and a difference remains only in a part of the boundary portion. Further, for the foreign object Ob, since the variation degree of the luminance average value is large, the luminance confirmation value is also a value indicating a large difference. In particular, in the first embodiment, when the luminance confirmation value is calculated, the maximum value and the minimum value of the luminance value of the pixel are ignored in the pixel group GR. It was found that only the part can be extracted.

  Next, in executing the subroutine of FIG. 5, in the filtering process in step S803, a median filter for 5 pixels is applied to calculate the median value. As a result, as shown in FIG. 13, the boundaries of the portions A4, A2, A3, and A2 are 0, and only the foreign object Ob is exposed in white.

  In the first embodiment, the luminance check value processing unit 414 calculates the sum of the absolute values of the differences between the average value of the pixel group GR as a population and the luminance value of each pixel, as shown by the equation (1). The confirmation value Vp is calculated for each pixel. For this reason, in the present embodiment, it is possible to obtain a high-accuracy luminance confirmation value Vp using parameters that can be calculated relatively quickly.

  In the first embodiment, the maximum value and the minimum value of the luminance value of the pixel that statistically causes noise are ignored at the stage of the luminance confirmation value calculation step, so that the calculation in the determination step is accelerated. Simplify.

  Next, variations of the first embodiment will be described with a graph. The graphs shown in FIG. 14 to FIG. 19 are obtained by plotting and verifying the luminance values of the pixels on the line (horizontal line passing right above the foreign object Ob) L in FIG.

  Referring to FIG. 14, at the stage where the average brightness value is calculated (the stage where step S801 in FIG. 5 is executed), the average brightness value corresponding to each part of the substrate W is distributed flatly without variation, and the boundary part is Shows high contrast. On the other hand, in the portion where the foreign object Ob is present, the luminance average value varies in a mountain shape due to the characteristics accompanied by the gradient, and the contrast is low. Therefore, it was confirmed that the variation degree of the luminance average value was increased only in the foreign substance Ob portion and decreased in each portion of the substrate W.

  Next, as shown in FIG. 15, when the difference in luminance average value is taken, that is,

  In the difference profile at the stage where the above is calculated, pixels having a large variation in luminance average value are detected.

  As shown in FIG. 16, after taking the absolute value of the difference value obtained by the equation (2), a method for removing noise was considered.

  As shown in FIG. 17, when the difference value obtained by equation (2) is ternarized with the lower limit value 5 and the upper limit value 30, a slight noise remains, but the pixel value of the foreign matter portion is set to 1, and the residual value This part could be 0.

  As shown in FIG. 18, when the median process of 3 pixels was performed on the difference value obtained by Expression (2), noise was clearly removed, and a value corresponding to the luminance of only the foreign matter portion could be obtained.

  In addition, as shown in FIG. 19, even when the difference value obtained by Equation (2) is subjected to a median process of 3 pixels and then further ternarized, noise is clearly removed and only the foreign matter portion is removed. A characteristic of 1 could be obtained.

  Thus, in 1st Example, the test | inspection determination process part 420 contains the aspect which ternarizes the brightness | luminance confirmation value Vp of each pixel. In this aspect, the brightness confirmation value Vp of the product portion is further converged to 0, and the brightness confirmation value Vp of the foreign object Ob can be made to stand out.

In particular, in the first embodiment, when the luminance confirmation value is calculated, the maximum value and the minimum value of the luminance values of the pixels of the pixel group GR are ignored. Therefore, as shown in FIG. 11, it is possible to obtain a luminance characteristic capable of detecting a foreign substance without necessarily requiring a filtering process.
(Second embodiment)
Referring to FIG. 20, in executing the luminance check value calculation subroutine of FIG. 5, in the second embodiment, instead of the expression (1),

  Was used to calculate the variance value.

  As shown in FIG. 21, also in the second embodiment, each of the portions A4, A2, A3, A2 has a low degree of variation, and thus becomes 0, and the difference remains only in a part of the boundary portions. Further, as shown in FIG. 22, the foreign substance Ob has a large variation degree of the luminance average value, and thus the luminance confirmation value is also a value indicating a large variation degree.

Next, in executing the subroutine of FIG. 5, in the second embodiment, the median value is calculated by applying a median filter for five pixels in the filter processing in step S803. As a result, as shown in FIG. 23, the boundaries of the portions A4, A2, A3, and A2 are 0, and only the foreign object Ob is exposed in white.
(Third embodiment)
Referring to FIG. 24, in executing the brightness check value calculation subroutine of FIG. 5, in the third embodiment, instead of the expression (1),

  Was used to calculate the deviation sum of squares.

  As shown in FIGS. 25 and 26, also in the third example, the portions A4, A2, A3, and A2 are 0 because the degree of variation is low, and the difference remains only in a part of the boundary portions. Further, for the foreign object Ob, since the variation degree of the luminance average value is large, the luminance confirmation value is also a value indicating a large variation degree.

Next, in executing the subroutine of FIG. 5, in the third embodiment, the median value is calculated by applying a median filter for five pixels in the filter processing in step S803. As a result, as shown in FIG. 27, the boundaries of the portions A4, A2, A3, and A2 are 0, and only the foreign object Ob is exposed in white.
(Fourth embodiment)
Referring to FIG. 28, in executing the brightness check value calculation subroutine of FIG. 5, in the fourth embodiment, instead of the expression (1),
Vp = MAX (GR) −MIN (GR) (5)
Was used to calculate the difference between the maximum and minimum luminance values of the pixels.

  As shown in FIGS. 29 and 30, as a result of calculating the luminance confirmation value, in the fourth embodiment, each portion A4, A2, A3, A2 is 0 because the degree of variation is low, and only the boundary portion is the difference. Remained. Further, for the foreign object Ob, since the degree of variation in the average luminance value is large, the luminance confirmation value is also a value indicating a large difference.

  Next, in executing the subroutine of FIG. 5, the median value was calculated by applying a median filter for three pixels in the filter processing of step S803. As a result, as shown in FIG. 31, the boundaries of the portions A4, A2, A3, and A2 are 0, and only the foreign object Ob is exposed in white.

  The above-described embodiment is merely a preferred specific example of the present invention, and the present invention is not limited to the above-described embodiment. In addition to the above-described embodiments or examples, various aspects can be adopted.

  For example, as a specific mode, a plurality of pieces of image data having different illumination angles may be acquired by selectively turning on any one of a plurality of illuminations irradiated from different angles.

  Alternatively, a plurality of pieces of image data having different emission wavelengths may be acquired by selectively turning on any one of the plurality of illuminations having different emission wavelengths.

  Furthermore, a filter having a spectroscopic function may be provided in the camera for imaging the substrate W, and a plurality of image data having different light receiving wavelengths may be acquired for one illumination.

  And a plurality of image data having different illumination angles, a plurality of image data having different emission wavelengths, a plurality of image data having different light reception wavelengths, or a plurality spanning at least two of the illumination angle, the emission wavelength, and the light reception wavelength The image data obtained by performing image calculation processing such as addition / subtraction / division / division on the image data is subject to inspection. As described above, in order to inspect a plurality of image data, in this embodiment, the number of times of imaging can be determined for each product.

  In the first embodiment, when the luminance confirmation value is calculated, the maximum value and the minimum value of the luminance values of the pixels of the pixel group GR are ignored, but this may be omitted. Alternatively, on the contrary, in the second and third embodiments, when calculating the luminance confirmation value, the maximum value and the minimum value of the luminance values of the pixels of the pixel group GR may be ignored.

  In each embodiment, the average value of RGB corresponding to red R, green G, and blue B is used as the basis of calculation, but the luminance confirmation value is obtained from the luminance value of the black and white data depending on the foreign substance inspection mode. Calculation may be performed, or only one of red R, green G, and blue B may be employed. Infrared data may also be adopted.

  In executing the brightness check value calculation subroutine of FIG.

  The luminance confirmation value may be calculated using.

  It goes without saying that various modifications can be made within the scope of the claims of the present invention.

DESCRIPTION OF SYMBOLS 20 Optical camera 30 Illuminating device 40 Control apparatus 60 Display unit 100 Appearance inspection apparatus (an example of a foreign material inspection apparatus)
410 Image processing unit 411 AD conversion unit 412 Pixel processing unit 413 Pixel group setting unit 414 Luminance confirmation value processing unit 420 Inspection determination processing unit 430 GUI processing unit A0 Plain part A1 Copper foil part A2 Resist printing part A3 Silk printing part A4 Overlapping part Ob Foreign matter Vp Brightness confirmation value W Substrate Wd Display window

Claims (8)

A foreign matter inspection apparatus for inspecting the presence or absence of foreign matter on a substrate subjected to surface treatment including printing processing,
Imaging means for imaging the substrate and outputting an analog signal;
AD conversion means for converting the output analog signal into a digital image;
Pixel group setting means for setting a pixel group of a small area including the pixel for each pixel of the converted digital image;
A luminance confirmation value calculation means for calculating, for each pixel, an amount representing a variation degree of the luminance value in the pixel group as a luminance confirmation value of the pixel;
A foreign substance inspection apparatus comprising: a determination unit that determines the presence or absence of a foreign substance based on the luminance confirmation value. The foreign matter inspection apparatus according to claim 1,
The foreign matter inspection apparatus, wherein the determination means performs a ternarization process on a luminance confirmation value of each pixel. The foreign matter inspection apparatus according to claim 1 or 2,
Display means for displaying an image of the substrate;
A foreign substance inspection apparatus comprising: a GUI processing means that surrounds a portion corresponding to a foreign substance in an image displayed by the display means when the determination means determines a foreign substance. In the foreign material inspection apparatus according to any one of claims 1 to 3,
The foreign substance inspection apparatus, wherein the determination means determines that the pixel block having the luminance confirmation value having a large variation degree is a foreign object when the predetermined area is present. In the foreign material inspection apparatus according to any one of claims 1 to 4,
The luminance check value calculation means calculates, for each pixel, the sum of absolute values of differences between the luminance value of each pixel and the average value of the luminance values of the pixel group set for the pixel as the luminance check value. A foreign substance inspection device characterized by that. In the foreign material inspection apparatus according to any one of claims 1 to 5,
The foreign substance inspection apparatus, wherein the luminance check value calculation means calculates an amount representing a degree of variation while ignoring a minimum value and a maximum value of luminance values of pixels in the pixel group. A foreign matter inspection method for inspecting for the presence or absence of foreign matter on a substrate subjected to surface treatment including printing processing,
An imaging step of imaging the substrate and outputting an analog signal;
AD conversion step for converting the output analog signal into a digital image;
A pixel group setting step for setting a pixel group of a small area including the pixel for each pixel of the converted digital image;
A luminance confirmation value calculation step for calculating, for each pixel, an amount representing a degree of variation in luminance value in the pixel group as a luminance confirmation value of the pixel;
A foreign substance inspection method comprising: a determination step of determining the presence or absence of a foreign substance based on the luminance confirmation value. The foreign matter inspection method according to claim 7,
The foreign matter inspection method, wherein the luminance confirmation value calculation step calculates an amount representing a degree of variation while ignoring a minimum value and a maximum value of luminance values of pixels in the pixel group.