JP5239561B2 - Substrate appearance inspection method and substrate appearance inspection apparatus - Google Patents

Description

  The present invention relates to a method of performing an appearance inspection on a component main body and a soldering portion on a component mounting board after soldering, and a board appearance inspection apparatus for performing this method.

  The applicant has previously developed a number of substrate visual inspection apparatuses that employ an inspection method called a “color highlight method”. This color highlight type substrate visual inspection apparatus (hereinafter simply referred to as “inspection apparatus”) is different from the two-dimensional color camera and the red, green, and blue color lights from each direction surrounding the optical axis of the camera. Using a lighting device that irradiates the substrate with an incident angle, a color image is generated in which each soldered part is represented by a color pattern corresponding to each illumination color, and an inspection based on the suitability of the color pattern is automatically performed. is there. Further, in this inspection apparatus, in addition to the inspection for the soldered part, the component main body is subjected to checking whether there is a mounting error, a lack, a positional deviation, or the like.

  In this type of inspection apparatus, inspection area setting data (indicating the position and size of the area), a binarized threshold value used for extracting the characteristics (generally color) of the region to be inspected, and extracted features A determination reference value or the like for determining the suitability of the product is registered as inspection data for each part. At the time of inspection, after imaging a substrate to be inspected, an inspection region is set based on the inspection data, and feature extraction, measurement, and determination processing are executed for each inspection region.

  However, the position of the soldering portion on the substrate is not constant, and often varies due to a shift of the component when the component is mounted by the mounter or a contraction of the substrate due to heat in the soldering process. Therefore, in the conventional inspection apparatus, for each part, a search window that is large enough to include the part is set, and an area having a brightness higher than the surrounding area is detected as a soldering part in the window. The setting position of the inspection area is adjusted based on the detection result (see paragraphs 0006 to 0009 of Patent Document 1 below).

Japanese Patent No. 3599023

  When imaging the board to be inspected, it is necessary to adjust the illumination intensity so that the image of the soldered part with high specular reflectivity does not saturate. Generated. For this reason, when a plurality of types of component bodies having different colors are distinguished from each other by the difference in color, considerable effort is required to set a threshold value for detecting each color.

  As a method of solving the above problem, set the lighting conditions suitable for the component body and the lighting conditions suitable for the soldering part in order, and perform imaging under each lighting condition, and use the image according to the former condition A method of inspecting a part and inspecting a soldering site using an image under the latter condition is conceivable. However, at the site where this kind of inspection is performed, the method in which the worker visually confirms the image used for the inspection, the inspection standard is too strict and the part judged to be defective although it is a non-defective product, and the inspection standard is not good. For this reason, there are many cases where a component whose defect has been overlooked is detected, and when two images are generated, there is a possibility that this visual confirmation operation may be hindered.

  Regarding the above point, Patent Document 2 describes that a subject is imaged under two illumination conditions having different illumination intensities, and images generated by the respective imaging are compared for each pixel having the same coordinate, and the median value of brightness It is described that it is possible to select a pixel having a brightness close to (the average value of the maximum value and the minimum value of the luminance value) and to use this image composition processing for the inspection of the mounting state of the circuit board ( Paragraphs 0049, 0057-0062, 0070-0075, etc.).

JP 2001-292370 A

  If the invention described in Patent Document 2 is applied to the inspection of a component mounting board, it is generated according to each illumination condition after imaging with an illumination condition suitable for the component main body and an illumination condition suitable for the soldered part. By synthesizing the images, it is possible to obtain a clear image of both the component main body and the soldering site. In addition, since the images generated by the two imaging operations are integrated into one, visual confirmation of the images can be easily performed.

  However, the invention described in Patent Document 2 only assumes that the brightness of the dark area can be raised to the vicinity of the center level, and the brightness width of the component main body is sufficient to distinguish the difference in color. I am wondering if it can be set to size.

  In addition, according to the invention described in Patent Document 2, since the brightness closer to the median brightness is selected for each of the component main body and the soldering portion, the soldering portion and the component main body in the image are selected. The brightness relationship does not reflect the actual relationship (see paragraph 0045 of Patent Document 2). Moreover, since the brightness of the soldering site and the component main body in the image both approach the median value, it may be difficult to set a threshold value used for detecting the soldering site.

  As described above, even if the invention described in Patent Document 2 is applied to generation of an image for inspection of a component mounting board, it is difficult to improve the performance of the inspection apparatus. Increasing the number of times of imaging increases the inspection time, but there is no merit of increasing the number of times of imaging if the performance of the inspection apparatus cannot be improved.

  The present invention pays attention to the above-mentioned problems and generates an automatic appearance by generating an image in which both the soldering part and the component main body have sufficient brightness and accurately represent the relationship between the actual brightness of both. It is an object to reduce the labor related to the setting of the inspection so that the inspection can be performed with high accuracy.

In order to solve the above-described problems, in the present invention, the component mounting board after soldering is imaged by an imaging device under a predetermined illumination condition, and the generated image is used for the component main body and the soldering part on the board . In the method of performing an appearance inspection, the relationship between the reflected light incident on the imaging device from the component main body on the substrate and the brightness of the corresponding portion in the image is linear before the inspection, but is incident on the imaging device from the soldered part. The relationship between the first illumination condition adjusted to the illumination intensity at which the reflected light is saturated and the brightness of the corresponding light in the image and the reflected light incident on the image pickup device from various parts of the board including the soldered part is linear. made as in the second illumination condition adjusted to weak illumination intensity than the first illumination condition, respectively imaging the same imaging object, located in correspondence between images obtained by the imaging and By measuring the luminance of a portion not saturated even at deviations of the image, setting each measurement value as a reference luminance in the lighting condition corresponding. In the test, the substrate to be inspected after captured respectively lighting conditions of the two ways, and the subject image by the imaging under the first illumination condition, reach the saturation level in the image pixel data executes image conversion processing for replacing the multiplication value of the ratio between the luminance data and the reference of the corresponding pixels in the image by the imaging under the second illumination condition, the image generated by the image conversion process Perform visual inspection using.

In the above method, a substrate to be inspected is illuminated under two illumination conditions with different illumination light intensities, an image is taken for each illumination condition, and one inspection image is generated from the two generated images. It is. The image generated here is based on an image obtained by imaging under the first illumination condition. However, a pixel that has reached a saturation level in the image is obtained by imaging under the second illumination condition. A value obtained by multiplying the data of the corresponding pixel of the image by the ratio between the reference luminances corresponding to each illumination condition is applied. Therefore, with the illumination intensity adjusted so that the components are sufficiently bright as the first illumination condition, the saturated portion of the image generated when the substrate is imaged under illumination according to the first illumination condition It can be replaced with an image representing the actual brightness under illumination. Further, since the image data based on the first illumination condition is maintained for the component main body, an image reflecting the actual brightness relationship between the component main body and the soldered portion can be obtained. In addition, since a wide range of luminance levels output from the camera can be associated with the component main body, the brightness width of the component main body can be set sufficiently.

Note that the “ imaging object” in imaging before inspection is preferably a plate-like body with uniform color and reflectance, but is not limited to this.

In a preferred embodiment of the above method, the imaging object is imaged under the first and second illumination conditions prior to imaging of the substrate to be inspected, and is generated for each illumination condition by imaging under the illumination condition. The illumination intensity is adjusted based on the difference between the luminance in the image and the reference luminance. In this way, even when the illumination intensity varies with time, the illumination intensity can be readjusted to the level at which the reference luminance is set, so that the substrate to be inspected can be stably illuminated. It becomes possible to image below.

In another preferred embodiment of the above method, a CCD camera is used as the imaging device, and the intensity of reflected light incident on the CCD camera from the object to be imaged is a linear region of the input / output characteristics of the CCD camera (light incident on the CCD). The illumination intensity under the first illumination condition and the second illumination condition is set within a range included in the range in which a proportional relationship is established between the intensity of the image signal and the intensity of the output image signal.

  According to the above aspect, in the imaging under the second illumination condition, a proportional relationship is established between the amount of light received by each pixel of the CCD and the intensity of the image data output from the CCD. Further, even in the case of imaging under the first illumination condition where the illumination intensity is high, a proportional relationship is established between the received light amount that has not reached the saturation level and the output image data. Therefore, since the luminance ratio of the non-saturated portion between the images can be made constant, an image conversion process using the luminance ratio and the image under the second illumination condition can be used under the first illumination condition. An image having a relationship proportional to the amount of light received by the CCD can be obtained.

Next, in another preferred embodiment, the image used for the appearance inspection is corrected so that the maximum luminance in the image is within a predetermined upper limit value, and the corrected image is displayed or output.
According to the above image conversion processing, the number of bits of the image after conversion becomes larger than that before conversion, but when the image is displayed on the display device to check the inspection result after the inspection, or the image is transmitted to the external device In some cases, these devices may not be able to process the converted image. According to the above aspect, since the converted image can be converted into an image having the number of bits corresponding to the processing capability of the display device or the external device, processing such as display can be performed without any problem.

Next, in the above method, the illumination conditions are limited to two. However, the present invention is not limited to this, and three or more illumination conditions may be set. In the substrate appearance inspection method in this case, prior to the inspection, the same imaging target is used in each of the first and second illumination conditions and at least one illumination condition adjusted to the illumination intensity between these two illumination conditions. Image the object, measure the luminance of the part that has a correspondence between the images obtained by each imaging and is not saturated in any image, and set each measured value as the reference luminance in the corresponding lighting condition . In tests, the substrate to be inspected after imaging by the respective lighting conditions, by combining the lighting conditions in order illumination intensity is low by two such overlapping occurs between each pair, for each combination, the set For the image obtained under the illumination condition with the higher illumination intensity , the corresponding pixel in the image obtained under the illumination condition with the lower illumination intensity for the pixel data that has reached the saturation level in the target image It executes the image transformation processing for replacing according to the data and the combination to the multiplication value of the ratio between the luminance of the reference of each lighting conditions. Then , an appearance inspection is executed using an image generated by an image conversion process that targets an image captured under the first illumination condition in the last combination.

For example, in addition to the first illumination condition and the second illumination condition, when a third illumination condition adjusted to the illumination intensity between these illumination conditions is set , under each illumination condition After imaging the substrate, first, paying attention to the combination of the second illumination condition and the third illumination condition , the data of the pixel saturated in the image for the image under the third illumination condition An image conversion process is executed in which the pixel value corresponding to the image is multiplied by a multiplication value of the reference luminance ratio of the combination under consideration . Next, focusing on the combination of the third illumination condition and the first illumination condition, a similar image conversion process is executed. At this stage, the saturated pixel in the image according to the first illumination condition has a second value. The multiplication value of the data of the corresponding pixel in the image generated by the image conversion processing related to the combination of the illumination condition and the third illumination condition and the ratio of the reference luminance related to the combination under consideration is applied. Become.

  According to the above processing, finally, it is possible to generate an image reflecting the brightness of each part when the substrate is imaged under a state where the illumination intensity is the highest, and to perform an inspection using the image. . Therefore, for example, even when multiple lighting conditions are set according to the color and reflectance of each component as the lighting conditions suitable for the component main body on the board, when imaging is performed under the lighting conditions that match the darkest component It is possible to generate an image that accurately represents the brightness of each component main body and the soldered part, and to perform an inspection using the image.

Next, an apparatus for carrying out the above-described board appearance inspection method includes an imaging apparatus for imaging the component mounting board after soldering, an illumination apparatus for illuminating the field of view of the imaging apparatus, and the first described above. And an imaging control means for sequentially setting the second illumination condition in the illumination device and causing the imaging device to perform imaging under illumination with each illumination intensity , a component main body on the board using an image generated by the imaging device, and Inspection execution means for executing an appearance inspection on the soldered portion.

Further, this apparatus uses images captured under the illumination under the first illumination condition and the second illumination condition before the inspection, so that each image has a corresponding relationship and is not saturated in any image. Measuring means for measuring the luminance of the location, luminance ratio calculating means for calculating the ratio of each measured luminance, and registration means for registering the luminance ratio calculated by the luminance ratio calculating means are further provided. The test execution means, the target image by the imaging in the first illumination conditions, of the corresponding pixels of the image data of the pixel has reached the saturation level in the image by the imaging under the second illumination condition An image conversion process is performed to replace the product with a multiplication value of the data and the luminance ratio registered in the registration unit, and an appearance inspection is performed using an image generated by the image conversion process .

  According to the above apparatus, by appropriately setting the first and second illumination conditions in advance, both the component and the soldering part are used by using an image generated by imaging under illumination under each illumination condition. It is possible to automatically generate an image that clearly appears and reflects the relationship between the actual brightness of the two, and to perform an accurate inspection using the image.

  According to the appearance inspection method and the appearance inspection apparatus described above, after the substrate to be inspected is imaged under a plurality of illumination conditions with different illumination intensities, a sufficient brightness is given to the component body from the images obtained by each imaging. An image reflecting the relationship between the actual brightness of the component main body and the soldering part can be generated. Therefore, it is possible to easily set a threshold value used for determining the color of the component main body and a threshold value for identifying the soldering site from the surroundings, and to perform an accurate inspection.

  In addition, it is only necessary to set illumination conditions suitable for each of the component main body and the soldered part without considering the capability of the imaging apparatus, so that the illumination conditions can be easily set.

FIG. 1 shows a configuration example of a substrate visual inspection apparatus.
This board appearance inspection apparatus (hereinafter simply referred to as “inspection apparatus”) is for inspecting the suitability of the position and orientation of each component, the soldering state, etc. for the printed circuit board 5 after soldering. The camera 1, the illumination device 2, the control processing device 3, the substrate stage 4, the input unit 6, the display unit 7, etc.

  The substrate stage 4 includes a substrate support table 41 including a pair of conveyor portions 43 and 43 (shown in FIG. 2), and the substrate support table 41 is arranged along the length direction of the substrate 5 (left and right direction in the drawing). And a stage unit 42 that is movably supported.

  The camera 1 is a CCD camera that generates a color still image. The illuminating device 2 has a configuration in which three annular light sources 2R, 2G, and 2B having different diameters are sequentially arranged so that the diameter increases from the top to the bottom. The light source 2R arranged at the highest position emits red light, the central light source 2G emits green light, and the light source 2B arranged at the bottom emits blue light.

  The camera 1 is arranged above the substrate stage 4 with the light receiving surface facing directly below. The illumination device 2 is arranged between the substrate stage 4 and the camera 1 so that the center of each light source 2R, 2G, 2B It arrange | positions in the state match | combined with the optical axis. By arranging the camera 1 and the illumination device 2 in this way, a so-called “color highlight system” optical system is set.

  Furthermore, the camera 1 and the illumination device 2 are supported by a support unit and a stage unit (not shown) so as to be movable along a direction orthogonal to the moving direction of the substrate support table 41 while maintaining the above relationship.

  The control processing device 3 includes an image input unit 31, an imaging control unit 32, an illumination control unit 33, an XY stage control unit 34, a memory 35, an inspection result output unit 36, etc., in addition to a computer control unit 30.

  The illumination control unit 33 controls the lighting / extinguishing operation of each of the light sources 2R, 2G, and 2B of the lighting device 2 and adjusts the light amount. The XY stage control unit 34 controls the timing and amount of movement of the stage unit 42 of the substrate stage 4 and the stage unit on the optical system side.

  The memory 35 stores a program in which a series of processing procedures related to the inspection are described, an inspection data file, and the like. In the inspection data file, for each region to be inspected, setting data for the inspection region, a binary threshold value for extracting the feature of the region to be inspected in the inspection region, and the suitability of the measurement value for the extracted feature are determined. For example, a determination reference value is stored. Further, in the memory 35 of this embodiment, information relating to the setting of two illumination conditions described later (the amount of light of each light source 2R, 2G, 2B, the brightness value of the image of the internal reference plate described later), and the brightness between the images. The ratio etc. are preserved.

  The control unit 30 controls the movement of each stage unit via the XY stage control unit 34 to align the camera 1 and the illumination device 2 with a predetermined imaging target area of the substrate 5. When the alignment is completed, the camera 1 is caused to take an image while adjusting the light quantity of each of the light sources 2R, 2G, and 2B of the illumination device 2. The color image generated by this imaging is A / D converted by the image input unit 31 and stored in the internal memory (RAM) of the control unit 30. The control unit 30 uses the inspection data file to set an inspection region for each region to be inspected in the color image stored in the internal memory, and sequentially executes feature extraction, measurement, and determination processing for each inspection region. To do.

  When the processing for all the parts to be inspected on the substrate 5 is completed, the control unit 30 outputs the measurement result and the determination result for each part to be inspected to the external device via the inspection result output unit 36. In addition, an image used for the inspection (hereinafter referred to as “inspection image”) is stored in the memory 35.

  Furthermore, the control unit 30 appropriately receives an image call from the input unit 6 or an external device, reads an inspection image from the memory 35, and displays it on the display unit 7 or outputs it to the external device.

  In the above inspection, the hourly imaging target area includes a part body of a predetermined number of parts and a soldered part. Among these, for the soldered portion, regular reflection becomes dominant with respect to illumination light from each of the light sources 2R, 2G, and 2B, and strong reflected light enters the camera 1. On the other hand, since the diffused reflection is generally dominant and the color of the component main body is dark, the intensity of the reflected light incident on the camera 1 becomes weak.

In view of the above points, in the inspection apparatus of this embodiment, the illumination conditions suitable for imaging the component main body and the illumination conditions suitable for imaging the soldering part are individually set, and these two illumination conditions are set in order. Then, the same imaging target area is imaged twice. Furthermore, the images generated by the respective imaging are integrated, and the image after integration is used for inspection (hereinafter, the image after integration is referred to as “inspection image”).
The illumination condition setting process and the inspection image generation process will be described below.

  Regarding the setting of illumination conditions, in this embodiment, images of two types of reference plates are used. Each reference plate is a white ceramic plate and is placed on the substrate support table 41 and imaged by the camera 1.

FIG. 2 shows a state of the substrate support table 41 when setting illumination conditions.
Reference numerals 51 and 52 in the figure are reference plates. As with the substrate 5, one reference plate 51 is carried into the substrate support table 41 from the outside, and is positioned in a state where both end edges are supported by the conveyor portions 43 and 43. The other reference plate 52 is smaller than the reference plate 51 and is fixedly arranged on the upper surface of one conveyor unit 43 so that images can be appropriately captured between inspections.

  Hereinafter, the reference plate 51 carried in from the outside is referred to as “external reference plate 51”, and the reference plate 52 fixedly arranged in the apparatus is referred to as “internal reference plate 52”.

  In this embodiment, first, while imaging the external reference plate 51, the light amounts of the light sources 2R, 2G, and 2B are adjusted until the luminance of the external reference plate 51 in the image reaches a predetermined reference value. When this adjustment is completed, the camera 1 and the lighting device 2 are moved above the internal reference plate 52 while maintaining the adjusted illumination intensity, and the reference plate 52 is imaged. Then, the brightness of the generated image of the internal reference plate 52 is measured, and the measured value is registered in the memory 35 as the reference brightness. This series of processing is performed individually for each of the two illumination conditions described above, and illumination control data (control amounts for the light sources 2R, 2G, and 2B) regarding the setting of each illumination condition is registered in the memory 35.

  In the inspection, imaging is performed by alternately setting each illumination condition based on the registered illumination control data. However, the illumination intensity of each light source 2R, 2G, 2B may vary with time. In order to cope with this problem, in this embodiment, prior to imaging of the substrate 5, the internal reference plate 52 is imaged according to each illumination condition, the luminance in the generated image is measured, and the measured value is a reference value. When it is different from the luminance, the illumination light quantity is adjusted so that the difference disappears. According to such processing, the illumination conditions set using the external reference plate 51 can be maintained, so that each substrate 5 can be imaged under stable illumination.

  In addition, the measurement of the brightness | luminance of the image of each reference | standard board 51 and 52 is specifically performed for every image data of r, g, and b which comprises a color image. Similarly, the inspection image generation processing described below is performed for each of the r, g, and b image data.

  Next, in this embodiment, under the above two illumination conditions, the light amount of light within the linear region of the input / output characteristics is incident on the camera 1 based on the reflectance of the component body and the soldered part. Set the illumination intensity. By such illumination condition setting processing and image conversion processing described below, an inspection image in which both the component body and the soldering part are clear and the brightness relationship between the two in the image matches the actual relationship is generated. can do.

  FIG. 3 shows a histogram (upper stage) of the intensity (light reception amount) of light incident on the imaging device (CCD) of the camera 1 from the substrate 5 and a graph (lower stage) showing the relationship between the luminance and the light reception amount in the image. It is shown in correspondence. In any graph, the amount of light received on the horizontal axis is normalized and shown with a maximum value of 100%, whereby the amount of light received corresponding to the two illumination conditions (the amount of light received with respect to reflected light based on the same reflectance). ) Is assigned the same coordinates on the horizontal axis.

  In the upper part, the histograms are divided into those corresponding to the reflected light from the component main body and those corresponding to the reflected light from the soldered part. The intensity distribution of these histograms is a schematic representation of the actual reflection state of each part. According to this model, the intensity of light incident on the camera 1 from the component main body is included in the range of 0 to 50%, while the majority of light incident on the camera 1 from the soldering site has an intensity exceeding 50%. Have.

In the lower graph, the solid lines of the line L _A, illumination conditions (hereinafter, referred to as "illumination condition A" or "condition A".) Suitable component body of the CCD at the time of setting the amount of light received and the image of the luminance of Show the relationship. Dotted line L _B, the illumination conditions suitable for soldering site (hereinafter, referred to as. "Illumination condition B" or "condition B") shows a relationship between the luminance of the CCD light-receiving amount and an image as set by. Here, it is assumed that an image having an 8-bit configuration is generated under any condition.

According to the line L _A, the illumination condition A, the light of 50% strength of the light incident on the CCD is set as represented by the maximum luminance (255). According to this setting, an image in which the component main body is bright but most of the soldering portions are saturated is generated.

On the other hand, according to the line L _B, the illumination condition B is the amount of light received intensity of 100% is set as represented by maximum brightness. According to this setting, the soldering portion is clearly shown, but the component main body is considerably darker than the image of the condition A.

In the above, the illumination conditions A, B, since the light that is included in the linear region of the input-output characteristic of the CCD is set to be incident, corresponding to 0-50% of the amount range of the line L _A portion and the line L _B are both made proportional straight line. Therefore, it is considered that the luminance ratio between the corresponding points of these proportional lines (two points having the same coordinate on the horizontal axis) is uniform. Therefore, by applying the saturated portion above luminance ratio data of the corresponding line L _B (the portion corresponding to 50-100% of the light quantity range) of the line L _A, part of which is saturated with the image by the illumination condition A it is considered possible to obtain a line L _C that represents the original brightness.

  Next, assuming that the reference luminances measured from the images of the internal reference plate 52 when setting the illumination conditions A and B are a and b, respectively, the reference luminances a and b are the same internal reference plate 52. 3 corresponds to the same coordinate on the horizontal axis representing the amount of received light, as shown in FIG. Moreover, since the reference brightness | luminances a and b are for setting the illumination conditions A and B appropriately, it is thought that all fall below a saturation level. Therefore, the luminance ratio between the proportional lines can be obtained from the reference luminances a and b.

Based on the above principle, in this embodiment, a value P (P = a / b) obtained by dividing the reference luminance a corresponding to the illumination condition A by the reference luminance b corresponding to the illumination condition B is obtained as the luminance ratio. The pixel data that has reached the saturation level in the image under the condition A is replaced with a value obtained by multiplying the data of the corresponding pixel in the image according to the condition B by the luminance ratio P. Image data corresponding to the line L _C by the conversion process can be obtained.

  According to the above processing, a portion where saturation occurs in the image under the condition A can be replaced with data representing the original brightness under the condition A. Further, since the image data according to the condition A is reflected as it is for the portion where the saturation does not occur, an image reflecting the actual brightness of the component main body and the soldering can be obtained.

  Further, since the reference luminances a and b are measured and registered when setting the illumination conditions A and B, the luminance ratio P may be obtained and registered at that time. As described above, in this embodiment, since the illumination conditions A and B are maintained using the internal reference plate 52, it is assumed that the registered luminance ratio P fits an image according to each hourly condition with high accuracy. Conceivable. Therefore, it is possible to easily and accurately generate an inspection image.

Next, a processing procedure for setting illumination conditions will be described with reference to FIG.
In this process, first, an illumination condition suitable for the component main body (hereinafter referred to as “illumination condition A”) is set by imaging the external reference plate 51 (ST11). Specifically, while continuously imaging the external reference plate 51, the light amounts of the light sources 2R, 2G, and 2B are adjusted until the luminance of the external reference plate 51 in the image reaches a predetermined reference value.

  Next, the internal reference plate 52 is imaged under the illumination condition A set by the above processing, the luminance of the internal reference plate 52 in the image is measured, and the measured value is set as the reference luminance a (ST12, 13). .

  Next, an illumination condition (hereinafter referred to as “illumination condition B”) suitable for the soldered part is set again with the external reference plate 51 as an imaging target (ST14). The specific process is the same as ST11, but the set illumination intensity is lower than that in the illumination condition A.

  When the illumination condition B is set, the internal reference plate 52 is imaged under illumination by the illumination condition B, the luminance of the internal reference plate 52 in the image is measured, and the measured value is set as the reference luminance b ( ST15, 16).

  Thereafter, the luminance ratio P is calculated by calculation using the reference luminances a and b (ST17), and the reference luminances a and b and the luminance ratio P are registered in the memory 35 (ST18). Furthermore, for the lighting conditions A and B, lighting control data used for setting the conditions is registered (ST19), and the process ends.

  In each step of ST11 and ST14, when measuring the luminance of the image for light quantity adjustment, the luminance of the same coordinate is measured. Similarly, in the measurements of ST13 and ST16, the coordinates of the measurement target are matched. Further, in these steps, specifically, an average value of luminance for each of the r, g, and b images is calculated for a region having a predetermined size.

  FIG. 5 shows a procedure of processing at the time of inspection. In order to simplify the description, this flowchart mainly illustrates processing related to generation of an inspection image with a single imaging target region.

Referring to step numerals in the figure, the substrate 5 to be inspected is loaded onto the substrate stage 4 is first (ST21), by performing the imaging by setting a lighting condition A, corresponding to the line L _A of FIG. 3 to generate an image _{G a} to (ST22). Then, by switching the illumination condition to the condition B by performing a second imaging (ST23), and it generates an image G _B corresponding to the line L _B of FIG. These images _G A, _{G B} are both stored in the RAM in the controller 30.

  Although omitted from FIG. 5, in ST22 and ST23, the internal reference plate 52 is imaged before the substrate 5 is imaged, the luminance in the image is measured, and the measured value is used as the reference luminance a or b. The process to be compared with is executed. If the measured value is different from the reference luminance, the illumination light quantity is adjusted so that the two values coincide with each other, and then the process proceeds to imaging of the substrate 5.

Then, set the counter i indicating the target pixel in the first initial value (ST24), reads out the data _G A (i) of the i th pixel of image _{G A,} and checks the value (ST25,26) . Here, _{if G} A (i) has reached the 255 upper limit (ST26 is "NO"), reads the i-th pixel data _G B image _{G B} (i) (ST27), the G Data G _A (i) is replaced with a value obtained by multiplication of _B (i) and luminance ratio P (ST28). On the other hand, when the data G _A (i) is smaller than 255 (ST26 is “YES”), the value of G _A (i) is maintained as it is.

Hereinafter, by changing the target pixel by updating the value of i (ST29,30), by executing the same processing for each pixel, the data of the pixel has reached the saturation level in the image G _A, image replaced with the multiplication value between the data and the luminance value P of the corresponding pixel in the G _B. Thus, the image G _A is converted into an image that combines data corresponding to the data and the line L _C that corresponds to the portion that is not saturated in the line L _A of FIG.

Thereafter, using the converted image _{G A,} performs image processing and determination for the test (ST31), and outputs the check result (ST32). Finally, store the image _{G A} used in the test (ST33), and ends the process.

  The loop of ST25 to 29 is actually performed for each of r, g, and b images. However, the procedure shown in FIGS. 4 and 5 can be applied not only to this embodiment but also to a monochrome image generated under monochromatic illumination.

  According to the setting process shown in FIG. 4, it is only necessary to pay attention to each of the component main body and the soldering part and to set the illumination condition suitable for the attention part, so that the setting can be easily performed. . In the inspection, after performing imaging under each illumination condition in order, the soldered part in the image under the condition A with the higher illumination intensity is converted into an original brightness image (an image without saturation). By doing so, it is possible to generate an image reflecting the actual brightness relationship between the component body and the soldered part. Therefore, it is possible to easily set a threshold value for discriminating between a component and a soldering site, and it is possible to perform a process of detecting the soldering site for adjusting the setting position of the inspection region without any trouble.

  In addition, if the first illumination condition is determined so that the amount of reflected light from the brightest color of the various component bodies corresponds to the maximum value of the output of the CCD, the brightness range of the component body can be sufficiently increased. It is possible to increase the threshold value, and it is possible to easily set a threshold value for determining a difference in color.

  Further, in the above embodiment, the illumination conditions A and B are maintained using the internal reference plate 52, and the reference luminances a and b obtained from the image of the internal reference plate 52 are used to reduce the distance between the substrate images according to each illumination condition. Since the luminance ratio P that conforms to the relationship (limited to a portion that is not saturated) is calculated, accurate image conversion processing can be performed.

  However, if the variation amount of the illumination intensity is within an allowable value, the illumination conditions A and B are adjusted using only the external reference plate 51 without introducing the internal reference plate 52 into the apparatus, and used for the adjustment. The luminance ratio P may be obtained from the image and used for image conversion processing. Further, when the internal reference plate 52 is not provided in the apparatus, the luminance ratio is calculated using the luminance of the specific part in the image generated under each illumination condition A and B for each substrate to be inspected. The image conversion process may be performed using the luminance ratio. However, it is necessary to match the coordinates of the measurement target part in each image. In addition, a part that is highly likely to be saturated with an image according to the illumination condition A, such as a soldering part, or a part that has a large variation in luminance cannot be measured.

  Next, according to the example of FIG. 3, the inspection image generated by the image conversion process has a 9-bit configuration (511 gradations), but the data capacity of the inspection image is limited to this. Instead, it fluctuates according to the width of the received light amount represented by the image under the illumination condition B.

  However, when an image with an irregular data capacity is displayed or output to an external device in this way, it is necessary to convert the image into a format that can be recognized by the display device or the external device. With regard to this point, in this embodiment, the inspection image is converted into a standard 8-bit image by a conversion process (for example, a logarithmic conversion process) that reduces the compression ratio for a relatively low luminance range, and displayed. Or output to the outside. According to such a conversion process, while maintaining the brightness of the component of the inspection image, it is possible to reduce the image of the high luminance region corresponding to the soldered portion to a luminance level at which the color can be easily viewed. When the inspection result is visually confirmed in the inspection apparatus or the external apparatus, an image that can be easily viewed can be displayed.

  Next, in the above-described embodiment, each of the two illumination conditions A and B is used for imaging. However, when three or more illumination conditions are set, the images according to the conditions are combined in the order of the illumination intensity. By executing processing similar to that shown in FIGS. 3 and 6, one inspection image can be generated.

  For example, in addition to the above-described illumination conditions A and B, when a condition X based on an intermediate illumination intensity between these conditions is set, the condition B and the condition X are first combined to saturate the image under the condition X After the pixel data that has reached the level is converted, the pixel data that has reached the saturation level in the image according to the condition A may be converted using the converted image.

  As described above, if three or more lighting conditions are set, for example, a plurality of lighting conditions for the component main body are set according to the color of the component main body, and the brightness range of the component main body is further widened. Can be generated.

It is a block diagram of a board | substrate external appearance inspection apparatus. It is a figure which shows the example of arrangement | positioning of the reference board in a board | substrate support table. It is a figure which matches and shows the graph which shows the characteristic of the image corresponding to each illumination condition, and the image for a test | inspection, and the histogram which divided | segmented the received light quantity of CCD into the component main body and the soldering site | part. It is a flowchart regarding the setting process of illumination conditions. It is a flowchart regarding the process at the time of a test | inspection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera 2 Illuminating device 3 Control processing device 5 Board | substrate 7 Display part 30 Control part 31 Image input part 33 Illumination control part 35 Memory 36 Test result output part 51 External reference board 52 Internal reference board a, b Reference | standard brightness | luminance

Claims (7)

A method of imaging a component mounting board after soldering with an imaging device under a predetermined illumination condition, and performing an appearance inspection on a component main body and a soldering site on the board using the generated image,
Prior to the inspection, the relationship between the reflected light incident on the imaging device from the component main body on the substrate and the brightness of the corresponding portion in the image is linear, but the reflected light incident on the imaging device from the soldered portion becomes a saturation level. The first illumination condition adjusted to the illumination intensity, and the first illumination condition so that the relationship between the reflected light incident on the image pickup apparatus from various parts of the substrate including the soldering part and the brightness of the corresponding part in the image is linear. In the second illumination condition adjusted to a weaker illumination intensity, the brightness of a portion where the same imaging object is imaged and there is a correspondence between the images obtained by each imaging and is not saturated in any image , And set each measured value as the reference brightness in the corresponding lighting conditions,
The substrate to be inspected after captured respectively in the first and second illumination conditions, the target image by the imaging under the first illumination condition, the data of the pixel has reached the saturation level in the image It executes image conversion processing for replacing the multiplication value of the ratio between the luminance of the data and the reference of the corresponding pixels in the image by the imaging under the second illumination condition, using the image generated by the image conversion process Performing the appearance inspection;
A method for inspecting the appearance of a substrate. The method of claim 1, wherein
A substrate visual inspection method using a plate-like body having a uniform color and reflectance as the imaging object . The method according to claim 1 or 2, wherein
Prior to imaging the substrate to be inspected, the imaging object is imaged under the first and second illumination conditions, and the luminance in the image generated by imaging under the illumination condition and the reference for each illumination condition Substrate visual inspection method that adjusts the illumination intensity based on the difference from the luminance of the substrate. The method according to claim 1 or 2, wherein
A CCD camera is used as the imaging device , and the first illumination condition and the first illumination condition are within a range in which the intensity of reflected light incident on the CCD camera from the imaging object is included in the linear region of the input / output characteristics of the CCD camera. A substrate visual inspection method for setting the illumination intensity under the illumination condition of 2 . The method of claim 1, wherein
A substrate visual inspection method for correcting an image used for the visual inspection so that the maximum luminance in the image is within a predetermined upper limit, and displaying or outputting the corrected image. A method of imaging a component mounting board after soldering under a predetermined illumination condition and performing an appearance inspection on a component main body and a soldering site on the board using the generated image,
Prior to the inspection, the relationship between the reflected light incident on the imaging device from the component main body on the substrate and the brightness of the corresponding portion in the image is linear, but the reflected light incident on the imaging device from the soldered portion becomes a saturation level. The first illumination so that the relationship between the first illumination condition adjusted to the illumination intensity, the reflected light incident on the imaging device from various parts of the board including the soldering part, and the brightness of the corresponding part in the image is linear. The same imaging object in each of the second illumination condition adjusted to an illumination intensity weaker than the condition and at least one illumination condition adjusted to an illumination intensity between the first illumination condition and the second illumination condition Image the object, measure the luminance of the part that is in a correspondence relationship between the images obtained by each imaging and is not saturated in any image, and set each measured value as the reference luminance in the corresponding lighting condition ,
After each of the substrates to be inspected is imaged under each illumination condition , each illumination condition is combined in such a way that there is an overlap between each pair in order of decreasing illumination intensity. the subject image obtained by the square lighting conditions, data and the combination of the corresponding pixel in the image to obtain a data of a pixel has reached the saturation level in the target image in lighting conditions towards the illumination intensity is weak By performing image conversion processing to be replaced with a multiplication value with the ratio between the reference luminances of each illumination condition according to the image conversion processing for an image obtained by imaging under the first illumination condition in the last combination A substrate appearance inspection method, wherein the appearance inspection is executed using a generated image. An imaging device for imaging the component mounting board after soldering, an illuminating device for illuminating the field of view of the imaging device, reflected light incident on the imaging device from the component body on the substrate, and corresponding locations in the image Although the relationship with brightness is linear, the reflected light incident on the imaging device from the soldering site is adjusted to the illumination intensity at which the reflected light reaches a saturation level, and the board including the soldering site to the imaging device. Second illumination conditions adjusted to an illumination intensity weaker than the first illumination condition so that the relationship between incident reflected light and the brightness of corresponding portions in the image is linear are sequentially set in the illumination device. , it checks to perform the imaging control unit to perform imaging on the imaging device under the illumination by the illumination intensity, a visual inspection for a component body and soldering site on the substrate using an image generated by the imaging device ; And a line means,
Prior to the inspection, using the images captured under the illumination under the first illumination condition and the second illumination condition, the brightness of the portion that is in a corresponding relationship in each image and is not saturated in any image Measuring means for measuring, brightness ratio calculating means for calculating the ratio of each measured brightness, and registration means for registering the brightness ratio calculated by the brightness ratio calculating means,
It said test execution means, the image targeting of the imaging of the first lighting conditions, the corresponding pixel of the image data of the pixel has reached the saturation level in the image by the imaging under the second illumination condition The image conversion process is performed to replace the product with the multiplication value of the luminance ratio registered in the registration unit, and the appearance inspection is performed using the image purified by the image conversion process .
A substrate visual inspection apparatus characterized by the above.

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