JP2017009533A - Image inspection system - Google Patents

Abstract

For example, an image inspection system capable of performing an image inspection of a moving surface to be inspected with higher accuracy is obtained.
In the image inspection system according to the embodiment, the illumination unit that irradiates the inspection surface with light and the same position of the inspection surface are at the imaging positions that are shifted from each other in the relative movement direction with respect to the inspection surface. A plurality of imaging units that respectively capture images under different light illumination conditions, and an arithmetic processing unit that performs arithmetic processing based on a plurality of images obtained by capturing the same region by the plurality of imaging units.
[Selection] Figure 3

Description

  The present invention relates to an image inspection system.

  Conventionally, with a single camera, an image obtained when light is applied from one side to a moving object, an image obtained by applying light from the other, an image obtained by applying light from both, etc. are acquired, and abnormalities based on those images are obtained. Techniques for checking the presence or absence of the are known.

JP 2012-159382 A

  Shooting under different lighting conditions cannot be performed simultaneously with one camera. Therefore, in the image inspection system, when the object to be inspected is moving, the exact same position on the surface of the object to be inspected cannot be imaged under different illumination conditions. For this reason, for example, an imaging result at a slightly shifted position is used as an imaging result at the same position. However, in the case where the imaging result at a slightly shifted position is used as the imaging result at the same position as described above, for example, when the moving speed of the object to be inspected is high, the inspection accuracy is lowered or vice versa. In addition, there may be a problem that the moving speed of the object to be inspected is limited to ensure the inspection accuracy. Therefore, for example, it would be meaningful if a new image inspection system capable of performing image inspection of a moving surface to be inspected with higher accuracy is obtained.

  In the image inspection system according to the embodiment of the present invention, the illuminating unit that irradiates the inspection surface with light and the same position of the inspection surface at an imaging position that is shifted from each other in the relative movement direction with respect to the inspection surface. A plurality of imaging units that respectively capture images under different illumination conditions, and an arithmetic processing unit that performs arithmetic processing based on the plurality of images captured at the same position by the plurality of imaging units.

FIG. 1 is an exemplary schematic configuration diagram of a part of the image inspection system of the embodiment. FIG. 2 is an exemplary and schematic explanatory view of a change over time of a position to be imaged in a surface to be inspected in the image inspection system of the embodiment. FIG. 3 is an exemplary and schematic explanatory view of a temporal change of a captured position of a surface to be inspected in the image inspection system of the embodiment, a sample of a captured image, and a calculation process of the captured image. It is. FIG. 4 is an exemplary and schematic explanatory diagram showing that a protrusion is detected by an absolute difference between an image at the time of back irradiation and an image at the time of front irradiation in the image inspection system of the embodiment. FIG. 5 is an exemplary and schematic explanatory diagram showing that a pattern or dirt is not detected depending on an absolute difference between an image at the time of back irradiation and an image at the time of front irradiation in the image inspection system of the embodiment. . FIG. 6 is an exemplary schematic control block diagram of the image inspection system according to the embodiment. FIG. 7 is an exemplary schematic flowchart of an image inspection procedure performed by the image inspection system according to the embodiment.

  Hereinafter, exemplary embodiments of the present invention are disclosed. The configuration and control of the embodiment shown below, and the operation and result (effect) brought about by the configuration and control are examples. The present invention can be realized by other than the configuration and control disclosed in the following embodiments, and various effects obtained by the basic configuration and control can be obtained.

  An inspection system 1 shown in FIG. 1 inspects an inspection surface 10 a of an inspection object 10. The inspection system 1 determines the presence / absence of an abnormality such as unevenness on the surface 10a to be inspected by arithmetic processing on an image obtained by photographing the surface 10a to be inspected. The inspection object 10 is also referred to as an inspection object or an inspection object, the inspection surface 10a is also referred to as an inspection surface or an inspection object surface, and the inspection system 1 can also be referred to as an image inspection system. . The image is image data, and is a data group such as a luminance value at each of two-dimensional points (each coordinate and each pixel) discretized in a lattice shape.

  The inspection system 1 inspects the inspection surface 10a of the moving inspection object 10. The inspected object 10 (inspected surface 10a) is moved at a constant speed in a direction along the inspected surface 10a, that is, in the right direction in FIG. 1, by a drive unit 4 (see FIG. 6) not shown in FIG. . If the position of the inspected surface 10a at the imaging time can be detected by an encoder, a sensor, or the like, and the captured image data (luminance value) and the position of the inspected surface 10a can be associated, the moving speed is not constant. Also good. The inspected object 10 is a long object such as a hose, piping, sheet, film, cloth, paper, or board. In the following, for convenience, the moving direction of the device under test 10 may be referred to as a moving direction. Further, the front in the moving direction of the device under test 10 may be referred to as the front, and the back in the moving direction of the device under test 10 may be referred to as the back.

  The inspection system 1 includes an illumination unit 2 that illuminates the surface 10a to be inspected, and an imaging device 3 that images the surface 10a to be inspected.

  The illumination unit 2 has a plurality of light emitting units 21. In the present embodiment, the two light emitting portions 21 are arranged away from each other along the moving direction of the inspection object 10 and the inspection surface 10a (the right direction in FIG. 1). The light emitting unit 21r shown on the left side of FIG. 1 which is one of the two light emitting units 21 is obliquely rearward in the moving direction of the inspection object 10 with respect to the imaging positions Pf and Pr of the inspection surface 10a, that is, In FIG. 1, the light is emitted on the upper left side and obliquely forward toward the imaging positions Pf and Pr, that is, on the lower right side in FIG. 1. A light emitting unit 21f shown on the right side of FIG. 1 which is another of the two light emitting units 21 is obliquely forward in the moving direction of the inspection object 10 with respect to the imaging positions Pf and Pr of the inspection target surface 10a. That is, the light is located at the upper right in FIG. 1 and is emitted obliquely rearward toward the imaging positions Pf and Pr, that is, the lower left in FIG. The two light emitting portions 21 (21f, 21r) can be set so that, for example, the intensity of light on the surface 10a to be inspected and the absolute value of the incident angle with respect to the surface 10a to be inspected are substantially the same. The light emitting unit 21 is, for example, an LED (light emitting diode). Note that the light emitting unit 21 may be covered with a diffusion member that transmits light while diffusing the light so that variation due to the location of the intensity of light from the light emitting unit 21 is reduced.

  The imaging device 3 has a plurality of imaging units 31. In the present embodiment, the imaging device 3 includes two imaging units 31f and 31r arranged so as to be shifted in the movement direction. The imaging unit 31f positioned in front of the moving direction images the surface to be inspected 10a at the front imaging position Pf, and the imaging unit 31r positioned behind in the moving direction of the surface to be inspected 10a at the rear imaging position Pr. Shoot. The imaging positions Pf and Pr are shifted from each other in the movement direction. In the inspection system 1, the imaging device 3 and the drive are driven by the control unit 51 (see FIG. 6) not shown in FIG. 1 so that the same position (same area) of the surface 10a to be inspected is imaged at the imaging positions Pf and Pr. One, the other, or both of the parts 4 are controlled. In the inspection system 1, the same position of the surface 10a to be inspected is imaged by the imaging device 3 at the imaging positions Pf and Pr at different times and under different light illumination conditions.

  The imaging unit 31 (31f, 31r) is, for example, a line sensor extending in a direction orthogonal to the moving direction of the device under test 10, that is, in a direction perpendicular to the paper surface of FIG. In the present embodiment, the two imaging units 31f and 31r are arranged adjacent to each other in the movement direction. Therefore, the imaging device 3 is a dual line sensor (multi-line sensor) having two line sensors adjacent to each other in the moving direction, that is, the imaging units 31f and 31r. The imaging unit 31 acquires a digital image, that is, a luminance value (data) for each of a plurality of one-dimensional pixels. The imaging unit 31 includes an imaging element such as a complementary metal-oxide-semiconductor (CMOS) image sensor or a charge-coupled device (CCD) image sensor. In the following, the direction extending along the surface 10a to be inspected among the orthogonal directions to the moving direction may be simply referred to as an orthogonal direction.

  FIG. 2 shows positions where the imaging surface 3 is imaged by the imaging device 3 at a plurality of imaging times t. The “position” referred to here is a linear region extending in the direction orthogonal to the moving direction on the surface to be inspected 10a. Hereinafter, the imaging time may also be simply referred to as time. In the example of FIG. 2, the moving direction of the surface 10a to be inspected, that is, the position np in the longitudinal direction, is shown divided into 0 to 8. In FIG. 2, at time t = t0, the front imaging unit 31f images the position np: 3 of the surface 10a to be inspected, and the rear imaging unit 31r images the position np: 4 of the surface 10a to be inspected. At time t = t1, the front imaging unit 31f images the position np: 4 of the surface to be inspected 10a, and the rear imaging unit 31r images the position np: 5 of the surface to be inspected 10a. At time t = t2, the front imaging unit 31f images the position np: 5 of the surface to be inspected 10a, and the rear imaging unit 31r images the position np: 6 of the surface to be inspected 10a. At time t = t3, the front imaging unit 31f images the position np: 6 of the surface 10a to be inspected, and the rear imaging unit 31r images the position np: 7 of the surface 10a to be inspected. As will be apparent from FIG. 2, in the inspection system 1, the photographing by the plurality of imaging units 31 (31f, 31r) and the movement of the surface to be inspected 10a are synchronized. Then, each image is taken twice by the imaging device 3.

  In the present embodiment, as described above, the two imaging operations at the same position of the surface 10a to be inspected by the imaging device 3 are executed under different illumination conditions. FIG. 3 is an exemplary and schematic explanatory view (plan view) of a change over time of a position to be imaged on a surface to be inspected, a sample of a captured image, and a calculation process of the captured image. As shown in FIG. 3, shooting at time t = t0 is performed in a state where the light emitting unit 21r behind the moving direction emits light and the light emitting unit 21f ahead does not emit light, and shooting at time t = t1 is performed. The rear light emitting unit 21r in the moving direction does not emit light and the front light emitting unit 21f emits light, and shooting at time t = t2 is performed while the rear light emitting unit 21r in the moving direction emits light and the front light emitting unit 21f emits light. The photographing at the time t = t3 is performed in a state where the rear light emitting portion 21r in the moving direction does not emit light and the front light emitting portion 21f emits light. Thus, in the present embodiment, the light emission stop of the light emitting unit 21f and the light emission of the light emitting unit 21r (illumination condition 1) and the light emission of the light emitting unit 21f and the light emission stop of the light emitting unit 21r (illumination condition 2) are alternately performed. Repeated. Accordingly, all the positions in the surface 10a to be inspected are photographed under both the illumination condition 1 and the illumination condition 2. In this embodiment, an image of an absolute value of a difference between the two images is calculated from the two images taken at each position. The image data taken at the previous time is delayed by temporarily storing it in the storage unit 52 (see FIG. 6) not shown in FIG. 3 and then taken at the later time. It is used for the calculation. That is, the storage unit 52 can also be referred to as a delay unit.

  FIG. 4 illustrates the case where the protrusion Ip is present on the surface 10a to be inspected. The images at a plurality of positions photographed under the illumination condition 1, the images at the plurality of positions photographed under the illumination condition 2, and the illumination conditions. The image of the absolute value of the difference between the image captured at 1 and the image captured at illumination condition 2 is included. Each of the three images shown in FIG. 4 is a group of luminance values (image data) in which one-dimensional luminance values at each position on the inspection surface 10a are two-dimensionally arranged along the moving direction. In FIG. 4, the lower the value (luminance value) at each pixel in the image, the blacker the color, and the higher the value, the whiter. When the light emitting part 21 illuminates the protrusion Ip from an oblique direction, the light emitting part 21 side of the protrusion Ip becomes bright, and the side opposite to the light emitting part 21 of the protrusion Ip becomes shadow and dark. That is, in the image at the time of rear irradiation under the illumination condition 1, the region Apr behind the protrusion Ip is bright and the region Apf in front of the protrusion Ip is dark, and the image at the front irradiation in the illumination condition 2 is the protrusion Ip. The area Apf in front of is bright and the area Apr behind the protrusion Ip is dark. As described above, the brightness is inverted depending on the irradiation direction in the front area Apf and the rear area Apr of the protrusion Ip. Therefore, in the areas Apf and Apr, that is, in the area of the protrusion Ip, the absolute value of the difference in the luminance value of each pixel between the two images of the illumination condition 1 and the illumination condition 2 is a positive value. On the other hand, in the region where the projection Ip of the surface to be inspected 10a is not present, the difference in brightness depending on the direction of light irradiation from the light emitting unit 21 is small, and the absolute value of the difference between the luminance values of the pixels in the two images is approximately. 0 (zero). Therefore, a region having a large value in the image of the absolute value of the difference can be identified as the protrusion Ip.

  A recess (not shown) on the surface 10a to be inspected can also be identified from the image of the absolute value of the difference between the image photographed under the illumination condition 1 and the image photographed under the illumination condition 2, similarly to the protrusion Ip. . However, in the case of the concave portion, the position where the brightened area exists in each image at the time of rear irradiation and front irradiation is opposite to the case of the protrusion. That is, in the case of the concave portion, the light emitting portions 21f and 21r side becomes dark, and the side farther than the light emitting portions 21f and 21r becomes bright. Therefore, for example, the inspection system 1 can determine whether a protrusion or a recess is based on the position of a bright region or a dark region in an image at the time of rear irradiation or an image at the time of front irradiation.

  FIG. 5 illustrates the case where the pattern If and the stain Id exist on the surface 10a to be inspected. The images at a plurality of positions photographed under the illumination condition 1 and at the plurality of positions photographed under the illumination condition 2 are illustrated. An image and an image of an absolute value of a difference between an image taken under illumination condition 1 and an image taken under illumination condition 2 are included. The three images shown in FIG. 5 are the same as those in FIG. 4. In FIG. 5, the lower the value (luminance value) at each pixel in the image, the more black the image is, and the higher the white the image is. As shown in FIG. 5, the brightness (luminance value) of the pattern If and the stain Id is substantially the same in two images having different irradiation directions. Therefore, the absolute value of the difference between the luminance values of the pixels in the two images is approximately 0 (zero). Therefore, it can be understood from FIGS. 4 and 5 that according to the present embodiment, protrusions or recesses can be detected from the image of the absolute value of the difference between the image captured under the illumination condition 1 and the image captured under the illumination condition 2. Like.

  The inspection in the inspection system 1 can be controlled by the PC 5 as illustrated in FIG. The PC 5 is an example of an electronic device. The PC 5 includes a control unit 51, a storage unit 52, and the like. The control unit 51 can be configured as, for example, a CPU (central processing unit), a controller, or the like. The storage unit 52 may be configured as a random access memory (RAM), a read only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), or the like. That is, the storage unit 52 may include a nonvolatile rewritable storage device such as an HDD or an SSD.

  The control unit 51 includes a captured image acquisition unit 51d. The captured image acquisition unit 51 d acquires the luminance value acquired by the imaging device 3 at each position and stores it in the storage unit 52.

  The control unit 51 includes a difference absolute value image calculation unit 51e. The difference absolute value image calculation unit 51e calculates an image of the absolute value of the difference between the two images having different light illumination conditions stored in the storage unit 52. The difference absolute value image calculation unit 51e is an example of an arithmetic processing unit.

  The control unit 51 includes an abnormality determination unit 51j. The abnormality determination unit 51j determines the presence / absence of an abnormality in the inspection surface 10a from the difference absolute value image. The abnormality determination unit 51j uses a known image processing method such as filtering, hole filling, binarization, grouping, labeling, dilation processing, etc. Judgment can be made. The abnormality determination can be executed based on, for example, comparison with the luminance values of surrounding pixels, comparison with reference data of a normal shape or a standard shape, and the like. The abnormality determination unit 51j is an example of an arithmetic processing unit.

  The control unit 51 includes an output control unit 51k. The output control unit 51k can control the image output unit 53 so as to output an image indicating the result of the abnormality determination by the abnormality determination unit 51j. The image output unit 53 is a display device such as an LCD (liquid crystal display).

  In addition, the control unit 51 can include an imaging control unit 51a, a drive control unit 51b, an illumination control unit 51c, and the like. The imaging control unit 51a controls imaging of the surface 10a to be inspected by the imaging device 3 (imaging unit 31). The drive control unit 51 b controls the movement of the device under test 10 by the drive unit 4. The drive unit 4 can also be referred to as a moving mechanism, a transport mechanism, or the like. In addition, the illumination control unit 51c controls illumination of the surface 10a to be inspected by the illumination unit 2. The imaging control unit 51a, the drive control unit 51b, the illumination control unit 51c, and the like perform the position (movement) of the surface 10a to be inspected and the surface 10a to be inspected by the illumination unit 2 as illustrated in FIGS. Illumination, photographing by the imaging device 3, and the like are executed in synchronization. These synchronization controls can be performed based on, for example, a detection result by a sensor of the position of the object 10 to be inspected. In addition, the arithmetic processing in the inspection system 1 and the control of each unit may be controlled by an electronic device other than the PC 5. The control unit 51 alone or the control unit 51 and the storage unit 52 can be configured as an ECU (electronic control unit), a board, a unit, a device, or the like. In such a case, the control unit 51 is an example of an electronic device.

  The arithmetic processing and control described above by the control unit 51 may be executed by software, may be executed by hardware, arithmetic processing and control by software, and arithmetic processing and control by hardware. May be included. In the case of processing by software, the control unit 51 reads and executes a program stored in a ROM, HDD, SSD, or the like. In this case, the program can include modules corresponding to the respective units included in the control unit 51. When all or part of the control unit 51 is configured by hardware, the control unit 51 may include a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or the like.

  The inspection by the inspection system 1 is executed in the procedure as shown in FIG. First, the drive control unit 51b moves the surface to be inspected 10a to a predetermined position, and the illumination control unit 51c sets the illumination unit 2 to a predetermined illumination condition (S1). Next, the imaging control unit 51a controls the imaging device 3 to perform imaging (S2). Next, the captured image acquisition unit 51d acquires image data obtained by imaging from the imaging device 3, and stores it in the storage unit 52 (S3). S1 to S3 are continued until photographing within a predetermined range is completed (S4). That is, if No in S4, the process returns to S1.

  When S1 to S3 are completed for the predetermined range (Yes in S4), the difference absolute value image calculation unit 51e calculates the difference between the image data from a plurality of images (luminance values) corresponding to each position stored in the storage unit 52. Is calculated (S5). Next, the abnormality determination unit 51j performs abnormality determination based on the difference absolute value image (S6). The output control unit 51k controls the image output unit 53 so that the inspection result obtained in S6 is displayed (S7).

  As described above, in the present embodiment, the plurality of imaging units 31 are respectively at the imaging positions Pf and Pr that are shifted from each other in the moving direction of the surface to be inspected 10a (inspection surface) under illumination conditions of different lights. Take a picture. In addition, the difference absolute value image calculation unit 51e (calculation processing unit) calculates a difference absolute value image from a plurality of images obtained by photographing the same region by the plurality of imaging units 31. In other words, according to the present embodiment, the same position of the surface 10a to be inspected is photographed under different illumination conditions at a plurality of image capturing positions, and the abnormality of the surface 10a to be inspected by the arithmetic processing on the plurality of images obtained by the photographing. It can be determined whether or not. Therefore, for example, it may be possible to determine the presence or absence of an abnormality more efficiently or more accurately than when determining the presence or absence of an abnormality from only one image of the surface 10a to be inspected. Further, for example, it is easy to obtain a higher-accuracy image as compared with a case where shooting is performed under different illumination conditions by one imaging unit.

  In addition, according to the present embodiment, it is possible to determine whether there is an abnormality in the surface to be inspected 10a by performing arithmetic processing on a plurality of images having different light irradiation directions to the imaging positions Pf and Pr. Therefore, for example, it is possible to determine the presence / absence of unevenness more easily or more accurately from the image of the absolute value of the difference between a plurality of images taken in different light irradiation directions at the same position on the surface 10a to be inspected. .

  Further, according to the present embodiment, the imaging units 31f and 31r are line sensors that extend in a direction (cross direction) orthogonal to the moving direction of the surface 10a to be inspected, and the imaging device 3 includes a plurality of imaging units 31f. , 31r integrally. Therefore, for example, the imaging units 31f and 31r and the imaging device 3 can be realized with a relatively simple configuration.

  In addition, the inspection system 1 can be implemented by variously changing the configuration of each unit. For example, the light irradiation direction does not need to be in front of and behind the moving direction, and may be one or the other of the intersecting directions with the moving direction. Further, the imaging position Pf and the imaging position Pr may be separated from each other, and the imaging unit 31f and the imaging unit 31r may be separated from each other. The illumination conditions may be illumination conditions other than the irradiation direction, such as the wavelength (frequency) of light and the deflection direction. Even in such a case, for example, based on a plurality of images corresponding to a plurality of wavelengths or deflection directions, the presence or absence of an abnormality is easily determined more efficiently or more accurately. Further, the plurality of images with different illumination conditions may be three or more images, and the presence / absence of abnormality may be determined from images based on arithmetic processing other than the difference absolute value image. Moreover, in the said embodiment, although the to-be-inspected object 10 and the to-be-inspected surface 10a moved, the illumination part 2, the imaging device 3, and the to-be-inspected surface 10a should move relatively, and the inspection system 1 is, for example, A system in which the inspected object 10 and the inspected surface 10 a are fixed and the illumination unit 2 and the imaging device 3 move may be used. The inspected object 10 and the inspected surface 10 a, the illuminating unit 2, and the imaging device 3 may be used. It may be a system in which both move.

  Moreover, in the said embodiment, although it was comprised so that an irradiation direction may differ as a lighting condition in several imaging position, it is not limited to this, For example, in a some imaging position, light intensity | strength and light wavelength (( (Frequency) may be different. In this case, for example, each of the plurality of imaging positions may be irradiated with a plurality of lights having different colors.

  As mentioned above, although embodiment and the modification of this invention were illustrated, the said embodiment and modification are examples, Comprising: It is not intending limiting the range of invention. These embodiments and modifications can be implemented in various other forms, and various omissions, replacements, combinations, and changes can be made without departing from the spirit of the invention. These embodiments and modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof. In addition, the configuration and shape of each embodiment and each modification may be partially exchanged. In addition, the specifications (structure, type, direction, shape, size, length, width, thickness, height, number, arrangement, position, etc.) of each configuration and shape should be changed as appropriate. Can do.

  DESCRIPTION OF SYMBOLS 1 ... Inspection system (image inspection system), 2 ... Illuminating part, 31, 31f, 31r ... Imaging part, 51e ... Difference absolute value image calculation part (arithmetic processing part), 51j ... Abnormality judgment part (arithmetic processing part).

Claims (4)

An illumination unit for irradiating the inspection surface with light;
A plurality of imaging units that respectively shoot the same position of the inspection surface at imaging positions that are shifted from each other in the moving direction relative to the inspection surface under different light illumination conditions;
An arithmetic processing unit that performs arithmetic processing based on a plurality of images obtained by photographing the same position by the plurality of imaging units;
An image inspection system.   The image inspection system according to claim 1, wherein the illumination condition is an irradiation direction of light from the illumination unit to the imaging position.   The image inspection system according to claim 1, wherein the imaging unit is a line sensor extending in a direction intersecting with a moving direction of the inspection surface.   The image inspection system according to claim 3, further comprising a camera that integrally includes the plurality of imaging units.