JP2012173045A - Evaluation apparatus for surface checkup apparatuses and evaluation method for surface checkup apparatuses - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluation apparatus for surface checkup apparatuses and an evaluation method for surface checkup apparatuses that can reliably evaluate performances of surface checkup apparatuses for checking minute surface defects to make possible appropriate calibration.SOLUTION: A calibration device 30 retreats a ring illumination 11 and a camera 13 of a surface checkup apparatus 10 with their relative positional relationship at the time of checkup maintained as it is to separate them from a checkup face 1a, where a calibration plate 40 is arranged. In this process, the distance from the calibration plate 40 to the ring illumination 11 is kept equal to that from the checkup face 1a to the ring illumination 11. Further, a hole 41 of a level equivalent to minute surface defects of a checkup object is formed in advance in the calibration plate 40. In this state, a surface image of the calibration plate 40 is shot with the camera 13 and the image is processed in the same way as at the time of checkup to ascertain whether or not the hole 41 of the calibration plate 40 is appropriately checked thereby to evaluate the checkup performance of the surface checkup apparatus 10.

Description

  The present invention relates to an evaluation apparatus and an evaluation method for evaluating the inspection performance of a surface inspection apparatus for inspecting minute defects existing on the surface of an inspection object such as a steel plate.

Conventionally, as a surface inspection apparatus for detecting minute defects existing on the surface of a steel sheet, for example, there is a technique described in Patent Document 1. This technique uses a ring illumination and an area camera that images the steel plate surface through a central opening of the ring illumination to inspect minute defects such as scale residue on the steel plate surface.
FIG. 8 is a diagram showing an outline of a general surface inspection apparatus using a ring illumination and an area camera. As shown in FIG. 8, the surface inspection apparatus 100 images the surface of the steel sheet through the ring illumination 101 arranged in parallel to the inspection surface of the steel sheet 1, the light source 102 of the ring illumination 101, and the central opening of the ring illumination 101. A high-resolution CCD camera 103 and an image processing device 104 that detects a minute defect using a binarization threshold after performing a series of image processing on a steel plate surface image captured by the CCD camera 103.

  Here, the detection target is a minute dot defect of φ0.1 mm to φ0.5 mm, and the resolution of the CCD camera 103 is 0.03 mm. Further, since it is necessary to narrow the camera field of view in order to achieve high resolution, the distance between the CCD camera 103 and the inspection surface of the steel plate 101 is 200 mm, and the distance between the light emitting portion 102 of ring illumination and the inspection surface of the steel plate 101 is Is as short as 80 mm, and the camera field of view is 40 mm (w) × 30 mm (l).

  By the way, normally, the inspection performance of the surface inspection apparatus is lower than that at the time of installation due to contamination and deterioration of the illumination unit and the imaging unit. Such performance abnormalities tend to deteriorate over time, and are often difficult to notice in a short time. Therefore, it is desirable to periodically perform an inspection operation to confirm whether or not the apparatus is normal and to calibrate the apparatus as necessary. In addition, it is ideal to carry out this calibration procedure with a short cycle such as once per day. However, in a surface inspection apparatus installed in the immediate vicinity of the production line, it is generally only performed when the line is stopped. It was difficult to calibrate.

  Therefore, as a method for calibrating the surface inspection apparatus without stopping the operation during the operation of the production line, for example, there is a technique described in Patent Document 2. This technology irradiates the surface of a steel plate with light, detects the reflected light from the surface with a light receiver, and calibrates the optical system of the surface inspection device that inspects the surface of the steel plate based on the intensity of the received light signal. is there. Here, an opening of φ10 mm penetrating the steel plate is provided in the steel plate, and the optical system of the surface inspection apparatus is calibrated based on the magnitude of the reflected light intensity in this opening.

JP 2010-210322 A JP-A-11-132967

  However, in the calibration method of the surface inspection apparatus described in Patent Document 2, the surface inspection apparatus is calibrated using a calibration opening formed each time. Therefore, the size of the opening may not always be constant, and the calibration reliability is low. Further, in the case of a surface inspection apparatus that performs surface inspection with one camera, only one opening may be used. However, in the case of an apparatus using a plurality of cameras, an opening must be formed in each camera viewing area.

Furthermore, since the opening size is φ10 mm, when the inspection target is a micro defect of about φ1.0 mm, the inspection size at the time of calibration is 10 times larger than the inspection target, and the inspection performance is not sufficiently confirmed. is there. In order to sufficiently check the inspection performance, it is necessary to form a minute opening corresponding to the defect size which is the inspection target. However, an opening of about φ1.0 mm is formed with accuracy each time. Have difficulty.
Accordingly, the present invention provides an evaluation apparatus for a surface inspection apparatus and an evaluation method for the surface inspection apparatus capable of performing a highly reliable performance evaluation so as to appropriately calibrate the surface inspection apparatus for inspecting minute surface defects. It is an issue to provide.

  In order to solve the above-described problems, an evaluation apparatus for a surface inspection apparatus according to the present invention includes an illumination device that irradiates an inspection object at a predetermined inspection distance, and a surface image of the inspection object that is irradiated by the illumination device. A surface inspection apparatus comprising: a camera that picks up images; and an image processing device that performs predetermined image processing on a surface image of the inspection object imaged by the camera and inspects minute surface defects of the inspection object In the evaluation apparatus, the illumination device and the camera are moved by the inspection distance or more in a direction orthogonal to the surface of the inspection object while maintaining a relative positional relationship during the inspection of the minute surface defect. The distance between the moving means for separating from the camera and the illumination device after being moved by the moving means within the field of view of the camera is a large equivalent to the minute surface defect at a position where the inspection distance is obtained. Calibration plate placement means for placing a calibration plate having a calibration surface defect formed thereon, imaging means for taking a surface image of the calibration plate placed by the calibration plate placement means with the camera, and the imaging Evaluation means for evaluating the performance of the surface inspection apparatus by performing the same processing as the image processing in the image processing apparatus on the surface image of the calibration plate imaged by the means, and inspecting the calibration surface defect It is characterized by providing these.

  In this way, since the performance evaluation of the surface inspection apparatus is performed using a calibration plate prepared in advance, the size of the surface defect for calibration used for the evaluation can always be constant, and the stability of the evaluation / calibration of the surface inspection apparatus Can be improved. In addition, since the calibration surface defect formed on the calibration plate has the same size as the micro surface defect to be inspected, the reliability of the evaluation / calibration of the surface inspection apparatus can be improved. Furthermore, in the performance evaluation, the calibration plate is moved to a position where the calibration surface defect can be inspected under the same conditions as the inspection, so in the case of a surface inspection apparatus using a plurality of cameras, the field of view of each camera This can be done by moving the calibration plate inside.

Further, in the above, a plurality of calibration surface defects having different sizes are formed on the calibration plate, and the evaluation means has a defect corresponding to the calibration surface defect in the surface image of the calibration plate. A plurality of evaluation regions that individually include image regions are set, and the calibration surface defect is inspected for each of the evaluation regions.
In this way, the evaluation area is set for each size of the calibration surface defect, and the performance of the surface inspection apparatus is evaluated by inspecting the calibration surface defect for each evaluation area. Therefore, the degree of deterioration of the surface inspection apparatus can be ascertained, for example, defects up to a predetermined size can be inspected, but defects smaller than the predetermined size cannot be inspected.

Further, in the above, a plurality of calibration surface defects of the same size are formed on the calibration plate, and the evaluation means includes a plurality of defect image areas corresponding to the calibration surface defects of the same size. The evaluation area is grouped as one evaluation area.
As described above, since a plurality of calibration surface defects having the same size are grouped and the evaluation region is set and inspected, the evaluation accuracy is improved as compared with the case where only one minute calibration surface defect is used. Can do.

In the above, the evaluation means detects a black pixel portion in the binarized image obtained by binarizing the surface image of the calibration plate as the calibration surface defect, and the surface image of the calibration plate It is characterized in that the quality of the surface inspection apparatus is determined according to whether the average luminance and the number of black pixels are within the respective allowable ranges.
Thus, since the average luminance is used as the evaluation index of the surface inspection device, for example, when the average luminance is equal to or lower than the allowable lower limit value, whether the light amount of the lighting device is reduced due to contamination or deterioration of the lighting device, It can be determined that the amount of light received by the camera is reduced due to contamination. Further, since the number of black pixels is used as the evaluation index of the surface inspection apparatus, for example, when the number of black pixels is equal to or greater than the allowable upper limit value, it can be determined that the camera is dirty or deteriorated. Accordingly, it is possible to appropriately evaluate the performance of the surface inspection apparatus.

Furthermore, in the above, the illumination device is configured by ring illumination having a ring-shaped light emitting portion disposed in parallel with the surface of the inspection object, and the camera is disposed on a center line of the ring illumination, The inspection object is imaged from a central opening of the ring illumination.
As described above, it is possible to appropriately perform the performance evaluation of the surface inspection apparatus for the surface inspection apparatus that uses the ring illumination as the illumination apparatus and irradiates the surface of the inspection target object evenly to inspect the minute surface defect. .

Further, in the above, the illuminating device includes a light shielding unit having an optical opening concentric with the light emitting unit and having a smaller diameter than the light emitting unit between the light emitting unit and the inspection object. It is characterized by having a board.
As described above, for a surface inspection apparatus that accurately inspects minute surface defects by using ring illumination including a light shielding plate as an illuminating apparatus so that light is not directly irradiated onto the inspection target, Performance evaluation can be performed appropriately.

Furthermore, the evaluation method of the surface inspection apparatus according to the present invention includes an illumination device that irradiates an inspection object at a predetermined inspection distance, a camera that captures a surface image of the inspection object irradiated by the illumination device, and In an evaluation method for a surface inspection apparatus, comprising: an image processing apparatus that performs predetermined image processing on a surface image of the inspection object imaged by the camera and inspects a minute surface defect of the inspection object; After moving the illumination device and the camera more than the inspection distance in the direction orthogonal to the surface of the inspection object while maintaining the relative positional relationship at the time of inspection of the micro surface defect, after moving away from the inspection object, A calibration plate in which a calibration surface defect having a size equivalent to the minute surface defect is formed in a position where the inspection distance is within the field of view of the camera and the illumination device. By capturing a surface image of the calibration plate with the camera, performing the same processing as the image processing in the image processing device on the captured surface image of the calibration plate, and inspecting the surface defect for calibration The performance of the surface inspection apparatus is evaluated.
Thereby, performance evaluation with high stability and reliability can be performed on a surface inspection apparatus for inspecting minute surface defects.

  According to the present invention, it is possible to perform performance evaluation with high stability and reliability in order to appropriately calibrate a surface inspection apparatus that inspects a minute surface defect of an inspection object.

It is a figure which shows the structure of the evaluation apparatus of the surface inspection apparatus at the time of a test | inspection. It is a figure which shows the structure of ring illumination. It is a side view which shows the structure of a calibration board. It is a figure which shows the structure of the evaluation apparatus of the surface inspection apparatus at the time of calibration. It is a flowchart which shows the calibration process procedure performed with a calibration apparatus. It is a figure explaining the evaluation method using a calibration board. It is a figure which shows an example of an evaluation result display screen and the quality determination content. It is a figure which shows the outline | summary of the general surface inspection apparatus using a ring illumination and an area camera.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Constitution)
1A and 1B are diagrams showing a configuration of a surface inspection apparatus and its evaluation apparatus in the present embodiment, wherein FIG. 1A is a plan view and FIG. 1B is a side view.
In the figure, reference numeral 1 denotes a steel plate (inspection object) being conveyed on the production line, and reference numeral 10 denotes a surface inspection apparatus for inspecting minute surface defects such as scale residue existing on the surface (inspection surface) 1a of the steel plate 1. It is. FIG. 1 shows a state when the inspection surface 1 a is inspected by the surface inspection apparatus 10.
The surface inspection device 10 includes a ring illumination 11, a light source 12, a camera 13, a camera case 14, and an image processing device 15. The ring illumination 11 is arranged parallel to the inspection surface 1 a of the steel plate 1 to irradiate the inspection surface 1 a and is connected to the light source 12. As the light source 12, a xenon strobe device or the like is suitable.

The camera 13 is a high-resolution CCD camera that is arranged on the same axis as the ring illumination 11 and images the surface of the inspection surface 1 a through the central opening of the ring illumination 11. In the present embodiment, a micro defect having a diameter of 0.1 mm to 1.0 mm is to be inspected, and the spatial resolution of the camera 13 is at least 0.1 mm or less, preferably about 0.03 mm to 0.05 mm. Furthermore, in order to achieve high resolution, it is necessary to narrow the camera field of view, for example, 40 mm (w) × 30 mm (l). Therefore, here, the distance in the front-rear direction from the inspection surface 1 a to the ring illumination 11 (FIG. 1 ( a) The distance in the left-right direction) D1 is set to 80 mm, and the front-rear direction distance D2 from the inspection surface 1a to the camera 13 is set to 200 mm.
The light source 12 and the camera 13 are configured to receive an image capturing command output from the image processing device 15 and perform synchronous imaging of the inspection surface 1a. The surface image of the inspection surface 1 a captured by the camera 13 is input to the image processing device 15.

Next, the configuration of the ring illumination 11 will be specifically described with reference to FIG.
As shown in FIG. 2A, the ring illumination 11 includes a light emitting portion 11a arranged in a ring shape. The light emitting unit 11a is configured by arranging LEDs in a ring shape or distributing an optical fiber bundle connected to the light source 12 in a ring shape. The light emitting portion 11a is arranged to be inclined inward by a predetermined angle so that the irradiation light wraps even if the working distance to the inspection surface 1a is short.
In order to suppress the occurrence of image noise due to fine irregularities on the surface of the steel plate, it is necessary to irradiate the inspection surface 1a of the steel plate 1 with the ring illumination 11 as uniformly as possible. Therefore, diffuse illumination with low condensing property is applied as the ring illumination 11. This can be realized by installing a light diffusion plate in front of the light emitting portion 11a.

  In addition, the angle α serving as an index of the arrangement of the ring illumination 11 is approximately 17 ° to 34 °. Here, the angle α is an angle satisfying tan α = R / D, where R is the radius of the light emitting portion 11 a and D is the distance between the light emitting portion 11 a and the inspection surface 1 a of the steel plate 1. In this manner, by arranging the ring illumination 11 so that the angle α is 17 ° or more and 34 ° or less, it is possible to suppress excessive detection and improve the detection SN ratio of a minute surface defect.

  In addition, as the ring illumination 11, as shown in FIG. 2B, it is possible to apply a light shielding plate 11 b provided between the light emitting portion 11 a and the steel plate 1. The light shielding plate 11b has an optical ring-shaped opening that is concentric with the light emitting portion 11a and has a smaller diameter than the light emitting portion 11a. The light shielding plate 11b may be made of any material as long as it is optically opaque. For example, an aluminum material whose surface is black anodized can be used. If the transmittance of the illumination light is sufficiently small, it can be used even if it is not a complete light shielding plate.

  With such a configuration, a dark light-shielding portion 11d is formed inside the bright ring-shaped illumination portion 11c on the inspection surface 1a. At this time, the size of the light shielding part 11d is set so that the entire camera visual field region enters the light shielding part 11d. Thereby, the direct reflected light from the ring illumination 11 does not enter the camera 13. That is, the diffracted light enters the camera 13 after being diffusely reflected back. Since the reflection intensity of the back-diffused reflected light is substantially constant even if there is a minute change in the angle of the inspection surface 1a, a brightness pattern of bright and dark spots is not generated, and a minute surface defect can be inspected more accurately. it can.

  Returning to FIG. 1, the image processing device 15 includes a microcomputer or the like (not shown) having a CPU, a memory, and the like. Based on the surface image of the inspection surface 1 a acquired from the camera 13, the image processing device 15 detects minute surface defects on the inspection surface 1 a. Execute the surface inspection process to be inspected. In this surface inspection process, first, preprocessing such as shading correction is performed on the acquired surface image, then binarization processing is performed, and a portion below a threshold level set in advance by an experiment or the like is extracted, It is determined that the pixel is a black dot pixel (black pixel) corresponding to the surface defect. This utilizes the fact that the defective part is photographed darker than the healthy part.

In the camera case 14, the ring illumination 11 and the camera 13 are fixed on the installation base 21, and the installation base 21 can slide on the drive stage 22 in the front-rear direction (left-right direction in FIG. 1B). It is configured. In the following description, the left direction in FIGS. 1A and 1B is defined as the front direction, and the right direction is defined as the rear direction.
Further, on the front side of the drive stage 21 and in the vicinity of the arrangement position of the ring illumination 11 at the time of inspection, a drive stage 23 extending in the left-right direction of the drive stage 21 (the direction orthogonal to the plane of FIG. 1B) is arranged. Has been. A part of the drive stage 23 is arranged in a storage box 24 connected to the front side portion of the camera case 14. On the drive stage 23, an installation base 25 is slidably movable on the drive stage 23. At the time of inspection, the installation base 25 is stored in a storage box 24 that is outside the camera visual field area. A calibration plate 40 is fixed on the installation base 25.

FIG. 3 is a side view (camera 13 side view) showing the configuration of the calibration plate 40.
The calibration plate 40 has a configuration in which the same product as the steel plate 1 as an inspection object is processed into a predetermined size (here, 50 mm × 50 mm) and a plurality of holes 41 are formed on the surface thereof. The hole 41 is sized according to the defect size targeted for inspection. In this embodiment, since the inspection target is set to φ0.1 mm to φ0.5 mm, the hole 41 is a hole of the same size (for example, φ0.5 mm) and its peripheral size.

Specifically, a plurality of (here, five) holes 41 of the same size are formed in a horizontal row, and a plurality of holes 41 of different sizes are formed vertically (here, five rows). In this example, the size of the hole 41 is gradually reduced from the top to the bottom, and each size is set to φ0.9 mm, φ0.7 mm, φ0.5 mm, φ0.3 mm, and φ0.1 mm in order from the top.
Although the case where the calibration hole 41 is formed in the calibration plate 40 has been described here, an equivalent black spot may be drawn by metal plating or the like instead of the hole 41.

  In FIG. 1, the movement of the installation bases 21 and 25 is realized by the calibration device 30 driving and controlling an actuator 31 composed of, for example, a motor. The calibration device 30 starts execution of calibration processing of the surface inspection device 10 when an operator presses a calibration button or the like (not shown). When performing calibration processing, the actuator 31 is driven to control the drive stage 22 and The installation bases 21 and 25 on 23 are moved from the arrangement state at the time of inspection shown in FIG. 1 to the arrangement state at the time of calibration shown in FIG.

  The calibration device 30 first moves the installation base 21 backward by D1 = 80 mm with respect to the arrangement state at the time of inspection shown in FIG. 1, so that the ring illumination 11 and the camera 13 are maintained in the relative positional relationship at the time of inspection. It is separated from the inspection surface 1a, and it is set as the arrangement state at the time of calibration shown in FIG. At this time, since the installation base 21 is separated from the drive stage 23, the calibration device 30 moves the installation base 25 here. That is, at the time of calibration, as shown in FIG. 4, the calibration plate 40 is arranged so that the center position of the calibration plate 40 coincides with the central axis of the camera 13. In this state, the front-rear direction distance from the inspection surface of the calibration plate 40 to the ring illumination 11 is D1 = 80 mm, which is the same as the front-rear direction distance from the inspection surface 1a of the steel plate 1 to the ring illumination 11 at the time of inspection. As a result, the calibration plate 40 can be imaged by the camera 13 under the same conditions as the inspection.

Here, the amount of movement of the installation base 21 is detected by the position detection sensor 32 disposed on the rear side of the drive stage 22. The position detection sensor 32 is installed at a position where the rear end of the installation base 21 reaches at the time of calibration. The calibration device 30 receives a detection signal indicating that the rear end of the installation base 21 has been detected from the position detection sensor 32. By inputting, it is detected that the installation base 21 has reached the position at the time of calibration. Although not specifically shown, the same applies to the detection of the movement amount of the installation base 25.
Then, the calibration device 30 outputs an image capturing command of the calibration plate 40 to the light source 12 and the camera 13 in the arrangement state at the time of calibration, and the surface inspection is performed based on the surface image of the calibration plate 40 obtained thereby. The inspection performance of the apparatus 10 is evaluated, and the result is displayed on the monitor 33. The operator performs calibration as necessary based on the evaluation result displayed on the monitor 33.

Hereinafter, the calibration process of the surface inspection apparatus 10 will be specifically described.
FIG. 5 is a flowchart showing a calibration processing procedure executed by the calibration device 30. As described above, the calibration process starts when the operator presses a calibration button or the like during the inspection.
First, in step S1, the calibration device 30 moves the ring illumination 11 and the camera 13 to the calibration position, and proceeds to step S2. That is, the calibration device 30 drives and controls the actuator 31 to retract the installation base 21 from the inspection position shown in FIG. 1 to the calibration position shown in FIG.

In step S2, the calibration device 30 moves the calibration plate 40 to the calibration position, and proceeds to step S3. That is, the calibration device 30 drives and controls the actuator 31, and moves the installation base 25 from the inspection position shown in FIG. 1 to the calibration position shown in FIG.
In step S <b> 3, the calibration device 30 outputs an image capturing command to the light source 12 and the camera 13. Thereby, strobe light is emitted and a surface image of the calibration plate 40 is captured.

Next, in step S4, the calibration device 30 acquires the surface image of the calibration plate 40 captured by the camera 13 in step S3, stores this in the memory, and proceeds to step S5.
In step S5, the calibration device 30 performs the same image processing as the image processing on the surface image of the inspection surface 1a at the time of inspection on the surface image of the calibration plate 40 stored in the memory in step S4. At this time, the surface image of the calibration plate 40 is divided into a plurality of evaluation areas, and image processing is performed for each of the evaluation areas. Here, the evaluation area is an area that individually includes the holes 41 (for example, a rectangular area), and a plurality of evaluation areas that include the holes 41 of the same size are grouped into one evaluation area.

That is, in the case of the calibration plate 40 shown in FIG. 3, as shown in FIG. 6, it is composed of five holes 41 of the same size formed in a horizontal row and its peripheral region in the surface image of the calibration plate 40. A rectangular area is set as the evaluation area. Since this evaluation region is set for each size of the hole 41, in this example, five ranges (range 1 to range 5) are set as the evaluation region. Then, a series of image processing is executed for each of the ranges 1 to 5, and the average luminance [cd / m ² ] and the number of black spot pixels [pieces] for each range are calculated. The calculated average luminance and the number of black spots are stored in the memory.

Next, in step S6, the calibration device 30 captures a predetermined number (for example, 10) of surface images of the calibration plate 40 and determines whether or not it has been acquired. If the predetermined number has not been acquired, the process proceeds to step S3. If the predetermined number has been acquired, the process proceeds to step S7.
In step S7, the calibration device 30 calculates an average value for each of the average luminance and the number of black spot pixels calculated based on the predetermined number of surface images of the calibration plate 40, and proceeds to step S8.

In step S8, the calibration device 30 compares the numerical values of the average luminance and the number of black dots calculated in step S7 with predetermined management values, and determines whether the inspection performance of the surface inspection device 10 is good or bad. . The above control values include the upper and lower permissible values of each numerical value, the allowable difference from the previous calibration value (difference from the previous time), and the allowable difference from the previous calibration value (the difference from the previous month) ) And when all of the following three conditions are satisfied, the pass / fail result is set to “good”.
[1] Allowable lower limit value <Numerical value <Allowable upper limit value [2] Difference within ± X% (for example, within ± 1.0%) with respect to the previous calibration value
[3] Difference within ± Y% (for example, within ± 2.0%) of the value at the time of calibration one month ago
This pass / fail determination is performed for each of the ranges 1 to 5.

  Next, in step S9, the calibration device 30 displays the pass / fail judgment result performed in step S8 on the monitor 33. An example of the pass / fail judgment result screen is shown in FIG. FIG. 7 shows an example in which the management values (allowable lower limit, allowable upper limit, difference from the previous time, difference from the previous month) and pass / fail judgment results (pass / fail) in each range 1 to 5 are displayed. The pass / fail judgment result screen is not limited to the display format shown in FIG. 7 as long as at least pass / fail judgment results (pass / fail) in each range 1 to 5 are displayed.

  The operator performs calibration treatment of the surface inspection apparatus 10 based on the quality determination result displayed on the monitor 33. Specifically, when it is determined that the pass / fail result is “No” based on the average luminance, the cause may be a deterioration of the lamp of the light source 12 or the ring illumination 11, contamination of the camera 13 or the illumination unit, and the like. As a calibration procedure, the lamp of the light source 12, the ring illumination 11, and the camera 13 are replaced or cleaned. On the other hand, when it is determined that the pass / fail result is “No” based on the number of black dots, the cause of the deterioration is the pixel contamination of the camera 13 that is contaminated with the lens. Do work.

Next, in step S10, the calibration device 30 moves the calibration plate 40 to the inspection position, and proceeds to step S11. That is, the calibration device 30 drives and controls the actuator 31 to move the installation base 25 from the calibration position shown in FIG. 4 to the inspection position shown in FIG.
In step S11, the calibration device 30 moves the ring illumination 11 and the camera 13 to the inspection position, and ends the calibration process. That is, the calibration device 30 drives and controls the actuator 31 to advance the installation base 21 from the calibration position shown in FIG. 4 to the inspection position shown in FIG. Thereby, it returns to the state which can start the surface test | inspection of the test | inspection surface 1a of the steel plate 1. FIG.
In FIG. 5, step S1 corresponds to the moving means, step S2 corresponds to the calibration plate arranging means, step S3 corresponds to the imaging means, and steps S5 to S8 correspond to the evaluating means.

(Operation)
Next, the operation of this embodiment will be described.
As shown in FIG. 1, the surface inspection apparatus 10 is arranged so that the front-rear direction distance D1 from the inspection surface 1a to the ring illumination 11 is 80 mm at the time of normal inspection. A micro defect existing in 1a is inspected. When the image processing device 15 outputs an image capturing command to the light source 12 and the camera 13, the camera 13 captures an image of the inspection surface 1a of the steel sheet 1 that is transporting the production line, and the captured surface image of the inspection surface 1a is an image. Input to the processor 15. At this time, the image processing apparatus 15 performs a series of image processing on the surface image acquired from the camera 13, and then extracts a minute surface defect that appears as a black spot using a binarization threshold.
In the present embodiment, the ring illumination 11 having the configuration shown in FIG. 2 is used as the illumination unit of the surface inspection apparatus 10, and the high-resolution camera 13 having a spatial resolution of 0.03 mm to 0.1 mm is used as the imaging unit. Therefore, it is possible to accurately inspect a minute dot-like defect having a diameter of about 0.1 mm to 1.0 mm.

  For example, when the operator presses the calibration button to perform the calibration process of the surface inspection apparatus 10 at an arbitrary timing such as when the steel plate 1 that is not the inspection target is being conveyed, the calibration apparatus 30 starts executing the calibration process. To do. First, the calibration device 30 retracts the installation base 21 from the inspection position shown in FIG. 1 by D1 = 80 mm and moves to the calibration position shown in FIG. 4 (step S1 in FIG. 5). Then, since the installation base 21 placed on the drive stage 23 at the time of inspection moves away from the drive stage 23, the calibration device 30 moves the installation base 25 to this position (step S2). As a result, as shown in FIG. 4, the calibration plate 40 has a longitudinal distance from the ring illumination 11 between the ring illumination 11 and the steel plate 1 after being moved to the calibration position on the central axis of the camera 13. It arrange | positions in the position used as D1 = 80mm.

  Thus, the calibration process of the surface inspection apparatus 10 can be started without stopping the operation during the operation of the production line. The timing for starting the calibration process can be arbitrarily determined by the operator. In addition, since the movement of the ring illumination 11, the camera 13, and the calibration plate 40 between the two positions of the inspection position and the calibration position is completely automated by the actuator 31, a highly accurate arrangement work can be performed in a short work time. Can do.

Therefore, in the case of a system that calibrates the surface inspection device when the production line is stopped, or a system that places the calibration plate at the calibration position through the manual operation during the calibration process, due to time constraints or lack of manpower, For example, the necessity of the performance of the surface inspection apparatus 10 can be confirmed only with a span of about once per month, whereas in the present embodiment, the surface inspection apparatus 10 with a short span of about once per day. It can be confirmed whether the performance is good. Therefore, device abnormalities such as a decrease in the amount of light due to contamination of the illumination unit and lamp deterioration, a decrease in the amount of received light due to camera contamination, and camera deterioration can be detected at an early stage.
Further, the calibration plate 40 used for the calibration processing is stored in the storage box 24 outside the camera visual field area so as not to affect the inspection at the time of the inspection by the surface inspection apparatus 10, and automatically in the camera visual field area at the time of calibration. Move on. Therefore, the calibration process can be performed by arranging the same calibration plate 40 at a predetermined calibration position every time.

  By the way, conventionally, in the surface treatment line of a steel plate, an opening for calibration is provided in an area where the product yield of the steel plate is not affected, and the optical system of the surface inspection apparatus is calibrated based on the magnitude of the reflected light intensity in this opening. There is something. However, in this case, the size of the opening may be different for each calibration, and the calibration stability is low. Further, due to the meandering of the steel plate, the positional deviation of the opening, and the like, the calibration may not be possible because the opening does not pass through the narrow camera visual field at the time of calibration. Furthermore, when calibrating a surface inspection apparatus having a plurality of cameras, a plurality of openings are required so that the openings pass through the camera visual field regions.

On the other hand, in the present embodiment, the calibration process can be performed by arranging the same calibration plate 40 at a predetermined calibration position every time as described above, so that the stability of calibration can be improved. Further, even in the case of a surface inspection apparatus having a plurality of cameras, it can be dealt with only by moving the calibration plate 40 into each camera visual field region.
In the arrangement state at the time of calibration shown in FIG. 4, when the calibration device 30 outputs an image capturing command to the light source 12 and the camera 13 (step S <b> 3), the surface image of the calibration plate 40 captured by the camera 13 is the calibration device 30. (Step S4), the calibration device 30 performs the same series of image processing on the surface image as in the inspection. At this time, the surface image of the calibration plate 40 is divided into five ranges as shown in FIG. 6, and the average luminance and the number of black spot pixels used as the evaluation index of the surface inspection apparatus 10 are calculated for each range (step S5).

  Then, when 10 surface images of the calibration plate 40 are captured and the evaluation indexes are calculated based on the surface images of the 10 calibration plates 40 (Yes in step S6), the average value of each evaluation index is calculated, These are used as evaluation indexes of the final surface inspection apparatus 10 (step S7). As described above, since an average value of a plurality of sheets is used, a highly reliable evaluation index can be obtained even when strobe shorts are uneven.

  When the surface inspection apparatus 10 is evaluated, it is determined whether or not the numerical values of the average luminance and the number of black spots are within allowable ranges. When no apparatus abnormality has occurred in the surface inspection apparatus 10, the average luminance and the number of black spots in each of the ranges 1 to 5 in FIG. 6 are within the allowable ranges, and satisfy the above conditions [1] to [3]. To do. Accordingly, each of the ranges 1 to 5 is determined as “good” (step S8), and this is displayed on the monitor 33 (step S9).

  On the other hand, for example, when the ring illumination 11 is contaminated as an apparatus abnormality, the amount of irradiation light is lower than that in a normal state, and thus the average luminance value in each of the ranges 1 to 5 is low. When this numerical value is less than or equal to the allowable lower limit value, the pass / fail determination result is determined as “No”, and this is displayed on the monitor 33. Therefore, the operator can recognize that the ring illumination 11 is contaminated by checking the monitor 33. As a result, the operator can take appropriate measures such as cleaning the ring illumination 11 as a calibration procedure for the surface inspection apparatus 10.

  For example, when the camera 13 is deteriorated as a device abnormality, the number of black spot pixels in each range 1 to 5 increases. When this numerical value is equal to or lower than the allowable lower limit value, the pass / fail determination result is determined as “No”, and this is displayed on the monitor 33, so that the operator can recognize that the camera 13 has deteriorated. Therefore, the operator can take appropriate measures such as replacement of the camera 13 as a calibration procedure for the surface inspection apparatus 10.

  In the present embodiment, the surface image of the calibration plate 40 is divided into five ranges, and the evaluation index is calculated for each range to evaluate the surface inspection apparatus 10. At that time, each range includes only holes 41 of the same size. Therefore, for example, when the number of black spot pixels in the range 1 is less than or equal to the allowable lower limit value and the number of black spot pixels in the range 2 to 5 is within the allowable range, the hole 41 having a diameter of 0.3 mm or more can be appropriately inspected. Yes, it can be determined that only the hole 41 having a diameter of 0.1 mm cannot be inspected. Thus, the inspectable range (or the degree of deterioration) of the surface inspection apparatus 10 can be recognized appropriately.

  Therefore, for example, if the steel plate 1 to be inspected does not require high-level inspection and the surface inspection apparatus 10 can inspect even a micro defect of φ0.3 mm, there is no problem. However, if the pass / fail result is “good” in the range 2 to 5, the surface inspection of the steel plate 1 is continued without performing the calibration procedure as it is, and the steel plate 1 to be inspected needs a high level inspection. In such a case, the operator can take action according to the required level, for example, if any one of the ranges 1 to 5 is “No”, the calibration process is promptly performed.

  When the calibration process of the surface inspection apparatus 10 using the calibration plate 40 is completed, the calibration apparatus 30 moves the installation base 25 from the calibration position shown in FIG. 4 to the inspection position shown in FIG. 1 (step S10). Thereafter, the calibration device 30 advances the installation base 21 from the calibration position shown in FIG. 4 by D1 = 80 mm and moves to the inspection position shown in FIG. 1 (step S11). Thereby, the surface inspection of the inspection surface 1a of the steel plate 1 by the surface inspection apparatus 10 can be resumed.

(effect)
Thus, in the said embodiment, the performance evaluation and calibration of the surface inspection apparatus which test | inspects the micro surface defect of a steel plate can be performed at arbitrary timing, without stopping a production line. Therefore, for example, the quality of the surface inspection apparatus can be determined periodically with a short span of about once per day, and early detection of apparatus abnormality is possible. Therefore, the quality assurance system can be improved.

  In addition, using a calibration plate prepared in advance, the ring illumination, the camera, and the calibration plate are automatically arranged at the calibration position so that the surface of the calibration plate can be inspected under the same conditions as the inspection. Accordingly, the same calibration plate can be accurately placed at a predetermined calibration position each time, and the calibration process can be performed, so that the stability of evaluation and calibration can be improved. In addition, since a series of operations at the time of calibration can be automated, the operation time can be greatly shortened as compared with a case where a person performs a task of arranging a calibration plate in front of the camera. Furthermore, since the calibration surface defect formed on the calibration plate has the same size as the minute surface defect to be inspected, the reliability of the evaluation / calibration of the surface inspection apparatus can be improved.

Furthermore, since the average brightness and the number of black spots of the surface image of the calibration plate are used as indicators for evaluating the performance of the surface inspection apparatus, the surface inspection apparatus can be determined by determining whether or not these numerical values are within an allowable range. As the apparatus abnormality, it is possible to find phenomena such as a decrease in the amount of light due to illumination contamination and lamp deterioration, a decrease in the amount of received light due to camera contamination, and camera deterioration.
At this time, in the surface image of the calibration plate, an evaluation area is set for each size of the surface defect for calibration, and the performance evaluation of the surface inspection apparatus is performed for each evaluation area, so it is possible to inspect even a predetermined size defect. However, the degree of deterioration of the surface inspection apparatus can be grasped, for example, a defect smaller than the predetermined size cannot be inspected.

(Application examples)
In the above-described embodiment, the case where the ring illumination 11 is used as the illumination device has been described. However, for example, a surface inspection device that irradiates spot illumination symmetrically from both sides of the inspection surface can be used.
Moreover, in the said embodiment, although the case where this invention was applied to the evaluation apparatus of the surface inspection apparatus 10 which test | inspects the micro defect which exists on the surface of a steel plate was demonstrated, a test object is not limited to a steel plate.

  DESCRIPTION OF SYMBOLS 1 ... Steel plate (inspection object), 1a ... Inspection surface, 10 ... Surface inspection apparatus, 11 ... Ring illumination (illumination device), 11a ... Light emission part, 11b ... Light-shielding plate, 12 ... Light source, 13 ... Camera, 14 ... Camera case, 15 ... Image processing device, 21 ... Installation base, 22 ... Drive stage, 23 ... Drive stage, 24 ... Storage box, 25 ... Installation base, 30 ... Calibration device, 31 ... Actuator, 32 ... Position detection sensor, 33 ... monitor, 40 ... calibration plate, 41 ... hole (calibration surface defect)

Claims (7)

An illumination device that irradiates an inspection object at a predetermined inspection distance, a camera that captures a surface image of the inspection object that is irradiated by the illumination device, and a surface image of the inspection object that is captured by the camera In an evaluation apparatus for a surface inspection apparatus comprising: an image processing apparatus that performs predetermined image processing and inspects a minute surface defect of the inspection object;
Moving means for moving the illumination device and the camera more than the inspection distance in a direction perpendicular to the surface of the inspection object while maintaining a relative positional relationship at the time of inspection of the minute surface defect, and moving away from the inspection object When,
A calibration surface defect having a size equivalent to the minute surface defect is formed in a position where the distance from the illumination device after moving by the moving means is the inspection distance within the field of view of the camera. Calibration plate placement means for placing the calibration plate;
With the camera, an imaging unit that captures a surface image of the calibration plate arranged by the calibration plate arrangement unit;
The same processing as the image processing in the image processing apparatus is performed on the surface image of the calibration plate imaged by the imaging unit, and the performance of the surface inspection apparatus is evaluated by inspecting the calibration surface defect. An evaluation device for a surface inspection apparatus, comprising: an evaluation means. The calibration plate has a plurality of calibration surface defects of different sizes,
The evaluation means sets a plurality of evaluation areas individually including a defect image area corresponding to the calibration surface defect in the surface image of the calibration plate, and each of the evaluation areas is inspected for the calibration surface defect. The apparatus for evaluating a surface inspection apparatus according to claim 1, wherein: The calibration plate is formed with a plurality of calibration surface defects of the same size,
3. The surface inspection apparatus evaluation according to claim 2, wherein the evaluation unit groups a plurality of evaluation regions including a defect image region corresponding to the calibration surface defect having the same size as one evaluation region. apparatus.   The evaluation means detects a black pixel portion in a binarized image obtained by binarizing the surface image of the calibration plate as the calibration surface defect, and the average luminance and blackness of the surface image of the calibration plate are detected. The evaluation of the surface inspection apparatus according to any one of claims 1 to 3, wherein the quality of the surface inspection apparatus is determined according to whether or not the number of pixels is within an allowable range. apparatus. The illumination device is configured by ring illumination having a ring-shaped light emitting portion arranged in parallel with the surface of the inspection object,
The surface inspection apparatus according to claim 1, wherein the camera is disposed on a center line of the ring illumination and images the inspection object from a central opening of the ring illumination. Evaluation device.   The illuminating device includes a light shielding plate having an optical opening that is concentric with the light emitting part and smaller in diameter than the light emitting part between the light emitting part and the inspection object. The apparatus for evaluating a surface inspection apparatus according to claim 5, wherein the apparatus is an evaluation apparatus. An illumination device that irradiates an inspection object at a predetermined inspection distance, a camera that captures a surface image of the inspection object that is irradiated by the illumination device, and a surface image of the inspection object that is captured by the camera In an evaluation method of a surface inspection apparatus, comprising: an image processing apparatus that performs predetermined image processing and inspects a minute surface defect of the inspection object,
After moving the illuminating device and the camera more than the inspection distance in a direction orthogonal to the surface of the inspection object while keeping the relative positional relationship at the time of inspection of the micro surface defect, and after moving away from the inspection object A calibration plate in which a calibration surface defect having a size equivalent to the minute surface defect is formed in the field of view of the camera and at a position where the distance from the illumination device is the inspection distance;
By capturing a surface image of the calibration plate with the camera, performing the same processing as the image processing in the image processing device on the captured surface image of the calibration plate, and inspecting the surface defect for calibration A method for evaluating a surface inspection apparatus, comprising evaluating the performance of the surface inspection apparatus.

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