JPS6250775B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for determining surface defects on high-temperature test materials.
Surface defects of high-temperature test materials such as hot steel pieces can be detected by surface temperature unevenness.
This allows reliable and quick detection regardless of the presence of scale.

As a method for inspecting surface defects on plate-shaped moving objects, the scanner method has traditionally been used, which images the surface condition with a camera, converts it into line information, and extracts defect signals by signal processing this line information. It is served to. The inspection method used in this type of surface inspection equipment is very effective for inspecting items with good surface conditions, but there are scales on the surface of high-temperature test materials such as hot steel pieces, and surface temperature unevenness can cause It is quite difficult to apply this method to materials with large variations in brightness.

The present invention has been made in view of such conventional circumstances, and it provides a reference pattern that corresponds to the temperature level of surface temperature spots, etc., without fixing the reference level for determining the quality of the surface condition. By setting the temperature and dividing the judgment into two stages: small sections and large sections, surface defects can be detected reliably and quickly regardless of the presence of surface temperature unevenness or scale. , is characterized by dividing the inspection surface of the high-temperature inspection material into a large number of pixels vertically and horizontally, and comparing each pixel with a reference pattern signal corresponding to the temperature level of the inspection surface to obtain pixel information. Next, while sequentially moving the small section corresponding to the number of pixels in the vertical and horizontal directions one pixel at a time, find the number of pixel information in the small section, and when this number of pixel information is greater than the set value, take the corresponding action. After determining the pixel information of each pixel as a defective part, the large sections corresponding to the number of vertical and horizontal pixels that are greater than the number of pixels of the small section are sequentially moved one pixel at a time, and after the small section processing within the large section. The defective portion is determined by determining the number of pixel information.

The method of the invention will now be described in detail with reference to the illustrated embodiments.

Now, for example, as shown in Figure 1, there is a defect.
A large section 4 is set on the surface of the high temperature test material 3 where the scale 1 and the scale 2 are present. This large section 4 divides the surface to be inspected into a large number of pixels vertically and horizontally, and collects the required number of pixels (16 x 16 pixels) vertically and horizontally. part like defect 1
Assume that scale 2 and scale 2 exist. This shaded area is a portion of the video signal obtained by imaging the surface to be inspected of the material 3 to be inspected, which is lower than the reference pattern signal corresponding to the temperature level of the surface to be inspected.

In the conventional detection method, the quality of the surface condition is determined by simply counting the number of diagonal lines in the large section 4, so if scale 2 exists, it is counted in the same way as defect 1. , resulting in errors in judgment. In the example of FIG. 2, the actual defect 1 has a size of 52 pixels, but with the addition of scale 2 (52 pixels in total), it is determined that a defect of 104 pixels exists within this large section 4.

However, in the method of the present invention, first, the small section (4 x 4 pixels) 5 as shown in FIG. If the number of defects is large, the small section 5 is determined to be a defective portion, and then the defective portions within the large section 4 are counted to determine whether the surface condition is good or bad. Therefore, when applied to the example shown in FIG. 2, a defect as shown in FIG. 4 is obtained by the determination based on the small section 5, and it is found that the defect 1 of 52 pixels exists in the large section 4.
This is the actual size of defect 1 excluding scale 2. However, the setting value for small section 5 was eight.
By inspecting the surface of the material 3 to be inspected in this manner, the defect 1 can be detected reliably and quickly regardless of the presence of the scale 2.

Next, an apparatus for carrying out the method of the present invention will be explained with reference to FIG. In FIG. 5, reference numeral 6 denotes a conveyance path for conveying the specimen 3, which is composed of a roller table and the like. Reference numeral 7 denotes an imaging device that scans the surface to be inspected in a direction substantially orthogonal to the conveying direction of the inspected material 3, captures a radiant light image of the inspected material 3, and generates a video signal VS.
Get 1. Video signal obtained by this imaging device 7
VS1 is sent to the recording device 8 and recorded therein, and is also converted into a digital video signal VS2 via the automatic sensitivity adjuster 9 and the A/D converter 10. Note that the automatic sensitivity adjuster 9 is used to eliminate differences in detection ability due to the temperature of the specimen 3. Reference numeral 11 denotes a storage circuit such as a shift register, which receives the digital video signal VS2 digitized by the A/D converter 10 and stores the digital video signal VS2.
2 by a certain period of time (multiple scanning lines). If the reference pattern signal (described later) corresponding to the surface temperature level of the test material 3 is directly subtracted from the digital video signal VS2, the target location will be shifted, so the reference pattern signal is passed through the digital video signal VS2 to the storage circuit 11. The digital video signal VS2 is delayed for as long as necessary to produce the digital video signal VS2. Reference numeral 12 denotes a reference pattern detection circuit, which receives the digital video signal VS2 digitized by the A/D converter 10 and generates a reference pattern indicating the temperature level in a normal case with no defects or scales on the surface of the material to be inspected 3. Create signal VS4. In other words, since there are temperature irregularities in the material 3 to be inspected, when determining defects, the level of radiant light on the surface of the material in a normal case excluding the effects of defects, scale, etc. is used as the reference pattern signal VS4, and the reference pattern signal VS4 We need to see how much the video signal deviates from that. Reference numeral 13 denotes a dark-area floating binarization circuit, in which a subtractor calculates the deviation between the delayed video signal VS3 taken out from the storage circuit 11 and a reference pattern signal VS4 taken out from the reference pattern detection circuit 12, and the difference signal is obtained by a comparator. Compare with a constant value. A constant value is set in the comparator in advance, and a logic 1 is output when the difference signal is lower than this constant value. This result is sent to the area determination circuit 14. The area determination circuit 14 calculates the flaw area according to the method of the present invention described above, compares it with a preset area, and outputs a logic 1 flaw signal FS to the flaw position detection circuit 15 when the area is larger than the set area. . The dark area floating binarization circuit 13 and the area determination circuit 14 are constructed as shown in FIG.

In FIG. 6, 16 is an 8-bit subtracter, which separates the delayed video signal VS3 and the reference pattern signal VS4.
The difference signal is compared with a constant value L by an 8-bit comparator 17. Comparator 17 outputs a logic 1 when the difference signal is lower than a certain value. 18-
1, 18-2, and 18-3 are 2048-bit shift registers, which receive the output of the comparator 17 and delay the signal by the time necessary for determining the subdivision 5. 19-1, 19-
2, 19-3, and 19-4 are 4-bit shift registers with parallel outputs, each consisting of 5 small sections [4 x 4 pixels].
Output the contents of. 20-1, 20-2, 20-
3, 20-4 and 21 are adders, and this small section 5
The 4-bit comparator 22 compares the result with a set number N, and outputs logic 1 when the number is greater than the set value N. 23
-1, 23-2, 23-4...23-15 is 2048
This is a bit shift register that receives the output of the comparator 22 and delays the signal by the time necessary to make a decision on the large section 4. 2
4-1, 24-2, 24-3...24-15 are 16-bit shift registers with parallel outputs,
Output the contents of large section [16 x 19 pixels] 4. 25
-1, 25-2, 25-3...25-16, and 26 are adders that read out and add all the contents of the large section 4, and the result is added to the area setting value S by the 16-bit comparator 27. By comparison, when the value is greater than the set value S, a logic 1 is output as a flaw signal.

In FIG. 5, 28 is a material edge detection circuit, which compares the reference pattern signal VS4 extracted from the reference pattern detection circuit 12 with a constant value using a comparator.
The portion higher than this certain value is regarded as the material to be inspected 3, and the material edge is detected. The flaw position detection circuit 15 receives the edge signal from the material edge detection circuit 28 and the flaw signal.
The flaw position is calculated from the flaw position, and the result is displayed on the printer 30 via the flaw position display circuit 29 and is also sent to the computer 31. 32 is a running state detection circuit which determines the running state of the material to be inspected 3 based on the material presence signal from the hot metal detector 33 and the material speed signal from the roller table speed meter 34. Reference numeral 35 denotes a material front and rear end detection circuit, which detects the front and rear ends of the material based on a signal from the running state detection circuit 32 and sends it to the computer 31. Based on the signals thus sent, the computer 31 controls (plays) the recording device 8 and displays it on the display device 36 if it is necessary to reproduce and view the state of the flaw. In addition, advanced judgments such as calculation of the total flaw area and judgment based on the flaw position are made, and these results are used for reject judgment, hot scarf control, spot scarf control, and steelmaking directives (flaw information, material shape).
It is used for etc. 37 is a dark area absolute binarization circuit, which outputs the delayed video signal taken out from the storage circuit 11;
A comparator compares VS3 with a constant value, and outputs logic 1 when the delayed video signal VS3 is lower than the constant value. This result is sent to the area determination circuit 38, and the flaw area is calculated based on the method of the present invention described above.
The area is compared with a preset area, and when the area is larger than this area, a logic 1 is output as a flaw signal. 39 is a binarization circuit based on signal width and depth, and memory circuit 1
The difference between the delayed video signal VS3 extracted from the reference pattern detection circuit 12 and the reference pattern signal VS4 extracted from the reference pattern detection circuit 12 is calculated, and the data of the signal width and signal depth of the difference signal are used as parameters to calculate whether the signal is defective or not. The result is sent to the connection determination circuit 40, which calculates the flaw length based on how the flaws are connected, and compares it with a preset length. When the length is longer than that length, a logic 1 is output as a flaw signal. 41 is a bright floating binarization circuit, and a memory circuit 11
Delayed video signal VS3 extracted from the reference pattern detection circuit 12 and reference pattern signal extracted from the reference pattern detection circuit 12
The deviation from VS4 is obtained by a subtracter, the difference signal is compared with a constant value by a comparator, and when the difference signal is higher than the constant value, a logic 1 is output. This result is sent to a connection determining circuit 42, which calculates the length of the flaw based on the way the flaws are connected, compares it with a preset length, and outputs logic 1 as a flaw signal when it is longer than the length.

Note that the dark area floating binarization circuit 13 and the area discrimination circuit 1
4 is a small heave flaw, dark area absolute binarization circuit 37, area discrimination circuit 38 is a large heave flaw, signal width/depth binarization circuit 39, connection discrimination circuit 40 is a root heave flaw, bright area The floating binarization circuit 41 and the connection determination circuit 42 are for detecting cracks, respectively.

As described in detail in the embodiments above, in the present invention, the surface to be inspected of the high-temperature specimen 3 is divided into a large number of pixels vertically and horizontally, and each pixel receives a reference pattern signal corresponding to the temperature level of the surface to be inspected. Next, the number of pixel information in the small section 5 is determined by sequentially moving the small section 5 corresponding to the number of pixels in the vertical and horizontal directions one pixel at a time. is greater than the set value, the pixel information of each corresponding pixel is set as a defective part, and then the large sections 4 corresponding to the number of pixels in the vertical and horizontal directions that are greater than the number of pixels in the small section 5 are sequentially moved one pixel at a time, while Since the number of pixel information after the small section processing in the large section 4 is determined to determine the defective part, it is possible to completely separate and extract defects on the surface of the material to be inspected, such as scab marks, from noise such as scale, It becomes possible to output a judgment proportional to the area of the defect, and surface defects can be detected reliably and quickly.

Incidentally, specific experimental results obtained by the method of the present invention are shown in FIG. This shows how defects of a certain size are detected with respect to the settings set for the small section and the large section. In setting A [small section 13/16, large section 208/256], only defects marked with ◎ were detected, and similarly in setting B [8/16, 160/25]
6], defects ◎ and ◎, defects ◎, 〇, and □ were detected in the setting C, and defects ◎, 〇, □, and △ were detected in the setting D. Also, defects marked with an "x" were not detected under these settings. As can be seen from this result, according to the present invention, it is possible to obtain an output corresponding to the area of defects such as bald spots.

Note that the size of the sections only indicates the relative relationship between the two sections, and does not indicate the size relationship with respect to the surface to be inspected.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a diagram showing the surface of a material to be inspected, FIGS. 2 to 4 are explanatory diagrams showing the relationship between pixels and sections, and FIG. 5 is an overall block diagram. , FIG. 6 is a block diagram of the main part, and FIG. 7 is a diagram showing the relationship between the size of the defect and the detection result. 1...Defect, 3...Test material, 4...Large section, 5
... Small section, 7 ... Imaging device, 12 ... Reference pattern detection circuit, 13 ... Dark area floating binarization circuit, 1
4, 38...area discrimination circuit, 37...dark area absolute 2
Value conversion circuit, 39...Binarization circuit based on signal width/depth, 40, 42...Connection determination circuit, 41...
Bright floating binarization circuit.

Claims (1)

[Claims] 1 Divide the inspection surface of the high-temperature inspection material 3 into a large number of pixels vertically and horizontally, and calculate pixel information for each pixel by comparing it with a reference pattern signal corresponding to the temperature level of the inspection surface. The number of pixel information in the small section 5 is calculated by sequentially moving the small section 5 corresponding to the number of pixels of , one pixel at a time, and when this number of pixel information is equal to or greater than the set value, the number of pixel information of each corresponding pixel is calculated. After the pixel information is set as a defective part, the large sections 4 corresponding to the number of vertical and horizontal pixels that are greater than the number of pixels of the small section 5 are sequentially moved pixel by pixel, and the small section processing within the large section 4 is performed. A surface defect determination method for a high-temperature test material, characterized in that a defective portion is determined by determining the number of pixel information.