JP2015021948A - Hole inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hole inspection device capable of preventing erroneous detection of a hole caused by cosmic ray particle.SOLUTION: The hole inspection device includes an image data acquisition unit, a hole detection unit, and a white noise determination unit. The image data acquisition unit acquires captured image data of an inspection object. The hole detection unit detects a section having luminance exceeding a hole candidate detection threshold among each of sections having a predetermined size determined according to a size of a hole to be inspected from captured image data for one line having a predetermined width determined according to the size of the hole to be inspected in a direction orthogonal to a conveyance direction of the inspection object as a hole candidate. The white noise determination unit determines that the hole candidate detected by the hole detection unit is a white noise when the hole candidate is detected in the captured image data for one line by the hole detection unit and the hole candidate is not detected in next captured image data for one line of the captured image data for one line.

Description

  Embodiments described herein relate generally to a hole inspection apparatus.

  Conventionally, in order to detect a hole generated in a steel plate, the illumination light that has passed through the through hole of the steel plate is captured by an imaging device in a state where the steel plate to be inspected is arranged between the illumination and the camera, and the captured image A technique for detecting a hole from a wide range is widely used.

JP 2001-249005 A

  However, in such a hole inspection apparatus, a CCD or CMOS image sensor is affected by cosmic ray particles (α rays, neutron rays, etc.), and a white spike on the output signal (video signal). Noise is generated randomly, and this white noise may be erroneously detected as a hole detection signal.

  The problem to be solved by the present invention is to provide a hole inspection device that can prevent erroneous detection of holes due to cosmic ray particles.

  The hole inspection apparatus according to the embodiment detects a through hole generated in an inspection object by detecting passage of light irradiated from the opposite side of the imaging surface of the inspection object, using captured image data obtained by imaging the inspection object. The hole inspection apparatus includes an image data acquisition unit, a hole detection unit, and a white noise determination unit. The image data acquisition unit acquires captured image data to be inspected. The hole detection unit is configured to detect one line of captured image data having a predetermined width determined according to the size of the hole to be detected in a direction orthogonal to the conveyance direction of the inspection target according to the size of the hole to be detected. Of each section having a predetermined size, a section having a luminance exceeding the hole candidate detection threshold is detected as a hole candidate. In the white noise determination unit, a hole candidate is detected in the captured image data for one line by the hole detection unit, and a hole candidate is detected in the captured image data for the next line of the captured image data for the one line. If not, the hole candidate detected by the hole detection unit is determined to be white noise.

FIG. 1 is a diagram illustrating an overall configuration including a hole inspection apparatus according to an embodiment and a steel plate to be inspected. FIG. 2 is a block diagram illustrating a hardware configuration example of the PC. FIG. 3 is a block diagram illustrating a functional configuration example of the PC. FIG. 4 is a diagram illustrating an example of captured image data. FIG. 5 is a diagram illustrating an example of captured image data for one scan (for one line). FIG. 6 is a flowchart for explaining processing related to removal of white noise caused by cosmic ray particles and detection of a true hole by the hole detection unit and the white noise determination unit.

  Hereinafter, a hole inspection apparatus according to an embodiment will be described with reference to the drawings.

  The hole inspection apparatus of this embodiment removes white noise caused by cosmic ray particles generated on an output signal (video signal) of a CCD camera or a CMOS camera (hereinafter referred to as a camera) by image processing. Prevents false detection of holes. In FIG. 1, the whole structure containing the hole inspection apparatus of this embodiment, the steel plate etc. of inspection object is shown. The inspection target is not limited to a steel plate, and any plate-like object can be used as the inspection target of the hole inspection apparatus of the present embodiment.

  The hole inspection device includes an illumination device 1 such as an LED or a fluorescent lamp (hereinafter referred to as illumination 1), a camera 2, and a PC 3 that performs image processing. At the inspection site, as shown in FIG. 1, the illumination light passing through the through hole 6 of the steel plate 4 is imaged by the camera 2 in a state where the steel plate 4 to be inspected is disposed between the illumination 1 and the camera 2. The steel plate 4 is conveyed at a constant speed in the Y-axis direction (the length direction of the steel plate 4 (conveying direction)) by a plurality of rollers 7.

  FIG. 2 shows a hardware configuration example of the PC 3. The PC 3 is an information processing apparatus such as a general personal computer, and includes a CPU 31, a ROM 32, a RAM 33, a storage unit 34, an operation unit 35, a display unit 36, and a camera I / F unit 37. Yes.

  The CPU 31 comprehensively controls the operation of each unit of the PC 3 by expanding and executing the basic program stored in the ROM 32 and the storage unit 34 in the RAM 33. In addition, the CPU 31 implements each functional unit described later by expanding and executing an application program stored in the ROM 32 or the storage unit 34 in the RAM 33.

  The ROM 32 stores various programs executed by the CPU 31 and setting information. The RAM 33 is a main storage device of the PC 3 and is also used for temporary storage of captured image data from the camera 2.

  The storage unit 34 is an auxiliary storage device such as an HDD (Hard Disk Drive), and stores various programs executed by the CPU 31 and setting information. The storage unit 34 also stores the results of image processing, which will be described later.

  The operation unit 35 is an input device such as a keyboard and a mouse, and outputs an operation input received from the user of the PC 3 to the CPU 31. The display unit 36 is a display device such as an LCD (Liquid Crystal Display), and displays characters, images, and the like under the control of the CPU 31. The camera I / F unit 37 receives a video signal from the camera 2 and passes the data to the CPU 31.

  Next, the functional configuration of the PC 3 will be described. FIG. 3 is a block diagram illustrating a functional configuration example of the PC 3. As shown in the figure, the PC 3 includes an image data acquisition unit 311, a hole detection unit 312, and functional units realized by the cooperation of the CPU 31 and the processing unit 310 including the RAM 33 as the main memory and the application program. A white noise determination unit 313. Data and processing results handled by each unit are stored in the storage device 320 (RAM 33 or storage unit 34).

  The image data acquisition unit 311 sequentially acquires captured image data 321 from the camera 2 via the camera I / F unit 37 and stores it in the storage device 320.

  The hole detection unit 312 performs processing such as hole candidate detection and white noise removal based on the captured image data 321 stored in the storage device 320. The hole candidate detection result (hole candidate detection result 322) is stored in the storage device 320.

  The white noise determination unit 313 determines whether or not the detected hole candidate is white noise based on the detection result by the hole detection unit 312.

  In the hole inspection apparatus of the present embodiment configured as described above, a video signal from the camera 2 is input to the PC 3. In the PC 3, the image data acquisition unit 311 stores the data (captured image data 321) of the video signal from the camera 2 as a two-dimensional image as shown in FIG. 4 in the storage device 320. When a one-dimensional CCD camera or a one-dimensional CMOS camera (line sensor) is used as the camera 2, the camera 2 faces one line in the X-axis direction (the width direction of the steel plate 4) of the steel plate 4 in the Y-axis direction. The scanning is sequentially performed according to the movement of the steel plate 4 being conveyed. Then, the image data acquisition unit 311 of the PC 3 sequentially acquires one-dimensional image data for each scan by the camera 2 and stores it in the storage device 320. The hole detection unit 312 and the white noise determination unit 313 sequentially perform each process each time the image data acquisition unit 311 acquires captured image data 321 for one line.

  FIG. 5 is an example of captured image data 321 for one line in the X-axis direction (corresponding to a line indicated by reference numeral 5 in FIG. 1). In FIG. 5, the position on the horizontal axis corresponds to the position in the X-axis direction shown in FIG. 1, and the vertical axis represents the luminance at each position. In the present embodiment, the luminance level is set to 256 gradations, and a portion having luminance exceeding a hole detection threshold (for example, 50) is handled as a hole candidate. In FIG. 4, the portion shown as a black section for illustration is a hole candidate. In FIG. 4, a hole candidate that is white noise is illustrated by a symbol A, and a hole candidate that is a true hole is illustrated by a symbol B.

  In addition, the scanning speed at the time of scanning the surface of the steel plate 4 with a line sensor is determined according to the conveyance speed of the steel plate 4 and the size of the hole to be detected. Here, assuming that a 1 mm hole is detected, scanning is performed so that one line in the captured image data 321 has a width of 0.5 mm. In this example, one section shown in a lattice shape in FIG. 5 has a width of 0.5 mm. In addition, the luminance indicated by each section in the captured image data 321 is determined by setting the value of the pixel at any position in the pixel group forming each section as the luminance (representative value) in this one section, or by calculating the average value. Let it be the brightness.

  Next, details of processing by the hole detection unit 312 and the white noise determination unit 313 will be described. FIG. 6 is a flowchart for explaining processing related to removal of white noise caused by cosmic ray particles and detection of a true hole by the hole detection unit 312 and the white noise determination unit 313.

  First, the hole detection unit 312 searches for hole candidates (step S101). Here, a portion having a luminance exceeding the hole detection threshold (for example, 50) in one scan data (data for one line in the X-axis direction) of the captured image data 321 stored in the PC 3 (a portion of one section in FIG. 4) Is detected (Yes in step S102), the portion is recognized as a hole candidate. If a hole candidate is not detected (No in step S102), the series of processing shown in FIG. 11 is performed in the reverse direction with respect to the Y-axis direction of the captured image data 321 (corresponding to the conveying direction of the steel plate 4). It carries out about the line.

When a hole candidate is detected here, the hole detection unit 312 stores the position coordinates (x _n , y _n ) of the hole candidate detected at this time in the storage device 320 as the hole candidate detection result 322 (step S103).

  Next, the hole detection unit 312 captures the captured image data 321 of the next scan (the captured image data of the next line; if a one-dimensional CCD camera is used, the captured image data of the next scanned line in the X-axis direction). Then, the hole candidates are further searched. Here, a hole candidate having a luminance exceeding the hole detection threshold is searched from the next line in the captured image data 321 (step S104).

Here, when a portion (one section) having a luminance exceeding the hole detection threshold value as a hole candidate is not detected (No in step S105), the white noise determination unit 313 detects (x _n , y _n ) in the previous scan. ) Is determined as white noise, and based on the determination result, the hole detection unit 312 removes the hole candidate from the captured image data 321 (step S106).

On the other hand, if there is a portion (one section) having a luminance exceeding the hole detection threshold (Yes in step S105), the hole detection unit 312 uses the position coordinates (x _{n + 1} , y _{n + 1} ) of the hole candidate detected at this time. The hole candidate detection result 322 is stored in the storage device 320 (step S107).

  Then, the white noise determination unit 313 further performs white noise determination under the following conditions (step S108).

(1) When | _{xn− xn + 1} |> white noise determination value (here, for example, about 5 sections (about 2.5 mm)) (Yes in step S108), the white noise determination unit 313 uses position coordinates ( x _n , y _n ) hole candidates are determined as white noise, and the hole detection unit 312 removes the hole candidates from the captured image data 321 based on the determination result (step S106).

(2) When | x _n −x _{n + 1} | ≦ white noise determination value (No in step S108), the white noise determination unit 313 determines a hole candidate having a position coordinate of (x _n , y _n ) as a real hole. (Step S109). In this case, the hole detection unit 312 determines that the corresponding hole candidate is a real hole and leaves the captured image data 321 as it is.

  Then, the above processing (steps S101 to S109) is sequentially performed on the subsequent lines in the opposite direction to the Y-axis direction (corresponding to the conveying direction of the steel plate 4) of the captured image data 321.

  The white noise and true hole determination described above are generally characterized in that white noise caused by cosmic ray particles does not occur continuously in the Y-axis direction, and in the X-axis direction. It has the feature that it does not occur and, in the case of a true hole (here, 1 mm or more), the feature is that the detected hole candidates are always continuous for 3 sections (here, 1.5 mm). As described above, the white noise and the true hole are discriminated.

  By the above image processing, white noise caused by cosmic ray particles can be detected and removed, and the accuracy of hole detection can be improved.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. In addition, the novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. This embodiment and its 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.

1 Illumination device 2 Camera 3 PC
4 Steel plate 5 Scan target line 6 Through hole 7 Roller 31 CPU
32 ROM
33 RAM
34 storage unit 35 operation unit 36 display unit 37 camera I / F unit 310 processing unit 311 image data acquisition unit 312 hole detection unit 313 white noise determination unit 320 storage device 321 captured image data 322 hole candidate detection result

Claims (6)

In the hole inspection apparatus for detecting a through hole generated in the inspection object by detecting the passage of light irradiated from the opposite side of the imaging surface of the inspection object, using the captured image data obtained by imaging the inspection object.
An image data acquisition unit for acquiring the captured image data of the inspection target;
A predetermined size determined according to the size of the hole to be detected from captured image data of one line having a predetermined width determined according to the size of the hole to be detected in a direction orthogonal to the conveyance direction of the inspection target. A hole detection unit that detects, as a hole candidate, a section having a luminance that exceeds a hole candidate detection threshold among the sections having a thickness;
When the hole detection unit detects a hole candidate in one line of captured image data, and no hole candidate is detected in the next line of captured image data of the one line of captured image data, A white noise determination unit that determines that the hole candidate detected by the hole detection unit is white noise;
A hole inspection apparatus. In the white noise determination unit, a first hole candidate is detected in the captured image data for one line by the hole detection unit, and further, the captured image for the next one line of the captured image data for the one line. When a second hole candidate is detected in the data, the positions of the first hole candidate and the second hole candidate in the direction orthogonal to the conveyance direction of the inspection target are respectively _xn and _{xn + 1} ,
| _{Xn− xn + 1} |> white noise judgment value,
When the condition is satisfied, it is determined that the first hole candidate is white noise; otherwise, it is determined as a hole.
The hole inspection apparatus according to claim 1.   The hole inspection apparatus according to claim 1, wherein the hole detection unit removes the hole candidate section determined to be white noise from the captured image data. When the imaging device that images the inspection object is an imaging device using a one-dimensional imaging device,
The image data acquisition unit acquires captured image data obtained by sequentially capturing the one line,
The hole detection unit and the white noise determination unit sequentially perform the processing of the hole detection unit and the white noise determination unit, respectively, each time the image data acquisition unit acquires the captured image data for one line.
The hole inspection apparatus of any one of Claims 1-3.   The hole inspection device according to claim 1, wherein the imaging device is a CCD camera or a CMOS camera.   The lighting device that irradiates light on one surface of the inspection target, and the imaging device that images the inspection target from the other surface side of the inspection target. The hole inspection device according to item.

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