JPH0894585A - Method for assaying magnetic particle inspection function and device for use in executing same - Google Patents

Abstract

PURPOSE: To enable assaying a magnetic-particle inspection function by picking up the image of fluorescence emitted from a fluorescent jig to which a fluorescent material of known brightness is affixed, then selecting a signal corresponding to the fluorescent material from among the signals produced, and measuring the average brightness from the signal selected. CONSTITUTION: A fluorescent jig 1 is conveyed by rotating a roller 2 as plural pieces of square timber are conveyed. A standard fluorescent material 7 and fluorescent tapes (a) to (d) which are affixed to the jig 1 are made to fluoresce when illuminated by an ultraviolet ray from an ultraviolet lamp 3. The image of the fluorescent material and the tapes are picked up by a CCD camera 4, a freezer 5 produces stationary images from signals indicating their brightness, and an image processing portion 6 processes the images. The images are then converted into binary images by a binarization means 61 according to a predetermined threshold, and a center area with the image of the fluorescent material 7 as its center is set by X-, Y-direction projection means 62, 63 and by a center area setting means 64. An average brightness setting means 65 and a half-value width measuring means 66 calculate the average brightness and the half-value width in the center area, respectively, and either feed correction signals to a gain correcting portion 8 or output signals indicating that an allowable gain range has been exceeded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for testing magnetic particle flaw detection function.

[0002]

2. Description of the Related Art Conventionally, in a fluorescent magnetic powder flaw detection inspection, a flaw in the inspected material is detected by spraying the magnetized inspection material with the fluorescent magnetic powder and visually observing the pattern of the adhered fluorescent magnetic powder. During this flaw inspection, the light intensity of the ultraviolet lamp, the fluorescent brightness of the fluorescent magnetic powder, the surface magnetic field strength of the material to be inspected, etc. are managed, and, for example, by measuring the fluorescent brightness in the fluorescent magnetic powder liquid, Fluorescent brightness is managed. In recent years, flaw detection inspection has been automated with the goal of high detectability and high speed, and flaw detection is performed using an image processing apparatus. In this automatic magnetic particle inspection, a fluorescent magnetic powder solution is sprayed while conveying a magnetized material to be inspected, and the fluorescent substance adhered to the flaw is irradiated with ultraviolet rays to emit light, and an image is captured by a CCD camera to perform image processing. To do.

In this image processing, the video signal captured by the camera is input to the freezer, and the still image obtained here is given to the image processing apparatus to obtain the luminance distribution on the screen. Such still images are continuously generated over time, and image processing is performed on these still images to automatically detect flaws in the material to be inspected.

[0004]

In the magnetic particle inspection as described above, it is not verified whether the functions of the camera and the image processing device are normal, and when the function is abnormal. Has a problem that an error occurs in the flaw detection result, and the reliability of the magnetic particle flaw detection is lowered.

The present invention has been made in view of the above circumstances, and provides a method and apparatus for testing a magnetic particle flaw detection function by imaging a fluorescent jig provided with a phosphor having a predetermined brightness. With the goal.

[0006]

According to a first aspect of the present invention, there is provided a magnetic particle flaw detection function inspection method, wherein an image pickup means captures an image of fluorescence from fluorescent magnetic particles attached to the surface of a material to be inspected, and based on the obtained signal. A method for verifying a function of performing magnetic particle flaw detection of the material to be inspected, comprising a step of capturing an image of fluorescence from a fluorescent jig provided with a phosphor having a known brightness by the image capturing means, and a step of obtaining the image by the image capturing means. It is characterized by including a step of selecting a signal corresponding to the phosphor among the signals and a step of measuring an average luminance from the selected signal.

The inspection method for the magnetic particle flaw detection function according to the second aspect of the invention is to image the fluorescence from the fluorescent magnetic powder adhering to the surface of the material to be inspected by the image pickup means, and based on the obtained signal, the magnetic powder of the material to be inspected. A method for testing the function of flaw detection,
A process of imaging fluorescence from a fluorescent jig provided with a phosphor having a known brightness by the imaging unit, a process of generating an image corresponding to the phosphor by a signal from the imaging unit, and a predetermined brightness of the image Counting the number of pixels having a brightness greater than the value.

The inspection device for the magnetic particle flaw detection function according to the third aspect of the present invention is an apparatus used for carrying out the inspection method for the magnetic particle flaw detection function of the first aspect of the present invention, in which the fluorescent substance in the signal obtained by the image pickup means is used. It is characterized by comprising means for selecting a corresponding signal and means for measuring an average luminance from the selected signal.

A magnetic particle flaw detection function inspection apparatus according to a fourth aspect of the present invention is an apparatus used for carrying out the magnetic particle flaw detection function inspection method of the second aspect of the present invention, in which an image corresponding to the phosphor is obtained by a signal from the image pickup means. And a means for counting the number of pixels having a brightness higher than a predetermined brightness value of the image.

[0010]

In the inspection method for the magnetic particle flaw detection function of the present invention and the apparatus used for carrying out the method, the image pickup means for picking up the material to be inspected picks up an image of a fluorescent jig provided with a phosphor of known brightness, and the average of the phosphors is taken. The brightness is measured to verify the function of the magnetic particle flaw detection. Thus, for example, when performing a flaw detection test on a plurality of inspection materials, the fluorescent jig is imaged during the flaw detection period to verify whether or not the function of the magnetic particle flaw detection is normal.

Further, in the inspection method for the magnetic particle flaw detection function of the present invention and the apparatus used for carrying out the method, the brightness distribution of the image is determined by the number of pixels having the brightness higher than the predetermined brightness value of the image corresponding to the phosphor. Then, the function of the magnetic particle flaw detection is verified by this.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing the configuration of the assay device of the present invention, and FIG. 2 is a perspective view showing the structure of a fluorescent jig used for carrying out the method of the present invention. As shown in FIG. 2, reference numeral 1 denotes a fluorescent jig, in which a standard fluorescent body 7 is attached to one surface of a rectangular parallelepiped square member, and four fluorescent tapes a, b, c are arranged so as to surround the standard fluorescent body 7. , D are attached. The standard phosphor 7 has a fluorescent brightness similar to that of the fluorescent magnetic powder used for the magnetic particle flaw detection inspection, and has a predetermined area smaller than the area of the fluorescent tapes a, b, c, d. The fluorescent tapes a and c have a length of 80 mm and a width of 10 mm, they are attached with a center-to-center distance of Y _S , and the fluorescent tapes b and d have a length of 80 mm and a width of 10 mm. , They are attached with a center-to-center distance of X _S. The fluorescent tapes a, b, c, and d have a dimensional accuracy of 10/100 mm or less, and are attached at intervals (X _S , Y _S ).
Is determined based on the number of fixed pixels included in the image processing unit described later. This fluorescent jig is for the case where the material to be inspected is a square material, but if the material to be inspected is not a square material, a fluorescent jig having the same shape as that of the material is prepared.

In FIG. 1, reference numeral 2 denotes a roller for conveying the material to be inspected and the fluorescent jig 1, and an ultraviolet lamp 3 is arranged diagonally above the fluorescent jig 1 conveyed on the roller 2. A CCD camera 4 is arranged in the vicinity of the ultraviolet lamp 3, and an image of the fluorescent material of the fluorescent jig 1 is picked up and the brightness signal thereof is detected by a freezer 5.
To enter. The input video signal is generated into a still image by the freezer 5 and given to the image processing unit 6. The binarizing unit 61 of the image processing unit 6 converts the video signal input from the freezer 5 into a binarized image based on a predetermined threshold value. The converted signal is given to the X-direction projection means 62 and the Y-direction projection means 63, and the numerical values obtained by the respective means are given to the central area setting means 64. In the central area setting means 64, the central area 9 centered on the image of the standard phosphor 7 is set based on the given numerical values, and is given to the average luminance measuring means 65 and the half width measuring means 66.

The video signal is input from the freezer 5 to the average luminance measuring means 65 and the half-value width measuring means 66, and the average luminance in the set central area 9 and the half-value width described later are respectively obtained to correct the gain. The data is output to the section 8. The binarizing means 61, the X-direction projection means 62, the Y-direction projection means 63, the central area setting means 64, the average luminance measuring means 65, and the half-value width measuring means 66 are components of the image processing section 6. In addition to this, the image processing unit 6 includes means (not shown) for converting the captured luminance signal into a signal indicating the degree of flaw, and is configured to perform a normal magnetic particle flaw detection inspection.

When the magnetic particle flaw detection function is verified by using the apparatus having the above-described structure, the roller 2 is rotated and the fluorescent jig 1 is conveyed between conveyance of a plurality of square pieces. The fluorescent jig 1 used is one stored in a dark place with low humidity in order to prevent deterioration of the standard phosphor 7. Ultraviolet rays are emitted from the ultraviolet lamp 3 and the standard phosphor 7 and the fluorescent tapes a, b, c and d attached to the fluorescent jig 1 emit light. The light intensity of the ultraviolet lamp 3 is set to 4500 μw / cm ² or more. CCD camera 4
The standard phosphor 7 and the fluorescent tapes a, b, c, d are imaged by. The CCD camera 4 has a shutter speed of 1/250
Second, aperture is set to 4 out of 8 stages. The freezer 5 generates a still image based on the luminance signal from the CCD camera 4, and the image processing unit 6 performs image processing. FIG. 3 is a flowchart showing a procedure for the image processing unit 6 to obtain the average brightness and the half-value width, and the operation of the image processing unit 6 will be described below based on this flowchart.

FIG. 3 is a flow chart showing a procedure for carrying out the image processing section 6 of the present invention. The procedure for detecting the brightness of the standard phosphor will be described with reference to this figure. Binarization means 61
The static image given to the
It is converted into a binarized image (step S11). The binarized image is expanded, reduced, and labeled. Then, in order to remove noise, the area of the light emitting portion is calculated, and a portion smaller than a predetermined area of the standard phosphor 7 is determined to be noise and converted to a dark portion (step S12).

FIG. 4 shows the binarized image on the coordinates.
It is a plan view in which the horizontal direction is the X direction and the vertical direction in the drawing.
Is in the Y direction. In this embodiment, X_SIZEIs in the X direction
512 pixels, Y_SIZE Has a fixed number of 240 pixels in the Y direction
I'm using one. Image of fluorescent tape a, b, c, d
The parameter that represents the position on the image is x_start, X_end, Y
_start, Y_endThen, the fluorescent tape a is (x₁, Y
_start) To (x₂, Y _start), B is (x_end, Y
₁) To (x_end, Y₂), C is (x₁, Y_{en d})
Et (x₂, Y_end), D is (x_start, Y₁) From
(X_start, Y₂) Located.

Then, in order to set the center position of the range surrounded by the fluorescent tapes a, b, c, d, first, the X-direction projection means 62 projects to measure the luminance in the X-direction (step S13). ). As a result of projection, prof-x for the X coordinate, that is, frequency, x
_Calculate the values of _start and x _end . Next, the Y-direction projection means 63 projects in the Y-direction to measure the brightness (step S14). Similar to the result of the X-direction projection, the values of y _start and y _end are obtained from prof-y, that is, the frequency with respect to the Y coordinate. x _start ,
The values of x _end , y _start and y _{en d} are calculated by the following formulas.

[0019]

[Equation 1]

Next, in order to set the central area 9, the X direction and Y of the range surrounded by the fluorescent tapes a, b, c and d.
The number of pixels H and W in each direction is calculated. H = x _end −x _start +1 W = y _end −y _start +1 Then, the average center (x ₀ , y ₀ ) of the image is calculated by x ₀ = x _start + H / 2 y ₀ = y _start + W / 2 (Step S15), the parameters alpha-x, alpha-y representing the central area 9 are obtained by the following equation (step S16). alpha-x = (x _end −x _start ) / 4 alpha-y = (y _end −y _start ) / 4

The pixel resolution can be calculated from the values of the numbers H and W of pixels. The pixel resolution in the X direction is αX _S /
The pixel resolution in the H and Y directions is calculated by αY _S / W. Note that αX _S and αY _S are fixed values of the image processing unit 6.

In the central area 9 thus set, a brightness histogram of the video signal input from the freezer 5 is created. FIG. 5 is a luminance histogram of a video signal, where the vertical axis represents frequency and the horizontal axis represents gradation. The average luminance measuring means 65 measures the average luminance of the standard phosphor 7 from this histogram (step S17). Next, the half width measuring means 66 obtains the half width F from this histogram (step S18). Here, the half-value width F is the number of pixels having a luminance of ½ or more of the maximum luminance. The histograms of A, B, and C in FIG. 5 all have the average brightness x _a , and even if the average brightness has the same value, the brightness distributions may differ. It is possible to know the difference in the luminance distribution in the case of.

As described above, the average luminance and the half-value width F of the standard phosphor are obtained, and these are input to the gain correction section 8. The gain correction unit 8 determines whether these values are within a predetermined allowable range, and if they are out of the range, outputs a signal for correcting the gain from the CCD camera 4 to the image processing unit. Alternatively, it outputs a signal notifying that the gain is out of the allowable range. As an example of the determination condition, the allowable range for the above-described gain correction is 40 ≦ x _a ≦ 50 for the average brightness x _a and 1400 for the half width F.
≦ F ≦ 1800.

In order to set the central area 9, x
X _start without using only the values of ₁ , x ₂ , y ₁ , y ₂
The values of x _end , y _start and y _end are _calculated as x ₁ , x
_{This is} because the values of ₂ , y ₁ and y ₂ easily cause a value error due to stains and chips of the fluorescent tapes a, b, c and d. Also,
If the area around the standard phosphor 7 of the fluorescent jig 1 can be set, the above formula is not limited.

Further, in the above-mentioned embodiment, the case where one CCD camera 4 for picking up an image of one surface of the fluorescent jig is provided is explained. However, in an actual magnetic particle flaw detector, a plurality of CCD cameras are to be inspected. The material may be imaged from various directions, each surface of the fluorescent jig may be imaged by an imaging device that images each surface of the material to be inspected, and the magnetic particle flaw detection function may be verified for each surface.

Further, in the above-described embodiment, the automatic flaw detection inspection apparatus for flaw detection while the material to be inspected is conveyed is explained, but the present invention is not limited to this, and any magnetic flaw detection apparatus for performing image processing can be applied. .

[0027]

As described above, in the present invention, the inspection of the magnetic particle flaw detection function is carried out in real time by imaging the fluorescent jig provided with the phosphor having the known brightness in the flaw detection inspection of the material to be inspected. Therefore, the present invention has excellent effects such as highly accurate magnetic particle flaw detection inspection.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a verification device according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a structure of a fluorescent jig used for carrying out the method of the present invention.

FIG. 3 is a flowchart showing an implementation procedure of an image processing unit of the present embodiment.

FIG. 4 is a plan view showing a binarized image according to the present embodiment on coordinates.

FIG. 5 is a luminance histogram of a video signal of this embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluorescent jig 2 Roller 3 Ultraviolet lamp 4 CCD camera 6 Image processing unit 7 Standard fluorescent substance 9 Central area 61 Binarizing means 65 Average brightness measuring means 66 Half width measuring means a, b, c, d Fluorescent tape

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Matsumoto 4-53-3 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd.

Claims (4)

[Claims] 1. A method for detecting fluorescence from fluorescent magnetic powder adhered to the surface of a material to be inspected by an image pickup means, and testing the function of performing magnetic particle flaw detection of the material to be inspected based on the obtained signal. A step of picking up an image of fluorescence from a fluorescent jig provided with a phosphor having a known brightness by the image pickup means, and a step of selecting a signal corresponding to the phosphor among the signals obtained by the image pickup means, And a step of measuring an average brightness from the generated signal. 2. A method for testing the function of performing magnetic particle flaw detection on a material to be inspected on the basis of the signal obtained by imaging the fluorescence from the fluorescent magnetic powder adhered to the surface of the material to be inspected with an imaging means. A step of capturing an image of fluorescence from a fluorescent jig provided with a phosphor having a known brightness by the image capturing means, a step of generating an image corresponding to the phosphor by a signal from the image capturing means, and a predetermined step of the image. And a step of counting the number of pixels having a brightness higher than the brightness value. 3. An apparatus used for carrying out the method for inspecting the magnetic particle flaw detection function according to claim 1, wherein the means for selecting a signal corresponding to the phosphor among the signals obtained by the imaging means, and the selection. And a means for measuring the average luminance from the generated signal. 4. An apparatus used for carrying out the method for inspecting the magnetic particle flaw detection function according to claim 2, wherein the means for generating an image corresponding to the phosphor by a signal from the imaging means,
And a means for counting the number of pixels having a luminance higher than a predetermined luminance value of the image, the inspection apparatus for the magnetic particle flaw detection function.