JPS5816465B2 - Running object surface inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a regular object surface inspection device for detecting surface flaws on a moving inspected material, that is, a moving object.

Surface inspection of moving objects has conventionally been performed directly visually, and technology for automatic or remote inspection has not yet been established.

In order to inspect the surface of a moving object directly by visual inspection, the object's running speed must be maintained at a low speed, which is a factor in reducing efficiency.

Various technologies are being considered for inspecting the surface of objects traveling at high speed with greater accuracy than direct visual inspection, one of which is
One method is to convert a moving object into an image using an imaging device such as a television camera, and then inspect it automatically or visually.

However, in the case of a so-called moving image captured by a normal television camera while driving, there is no difference from direct visual observation.

Although it is possible to obtain a clear image by stopping the object and photographing it, this poses a significant problem in terms of efficiency and is meaningless.

In order to inspect the surface of an object moving at high speed with a higher precision than direct visual inspection, it is necessary to obtain an image with a resolution as clear as that of a so-called still image, which is an image taken while the moving object is stopped.

Further, the area of the surface of the moving object that can be imaged is determined by the size of the object to be inspected, such as a surface flaw.

If we want to inspect a flaw several millimeters in size, the area of the surface of the moving object that can be imaged is 200 to 300 m.
It will be about m square.

For this reason, it is generally used as a moving object. It is impossible to photograph the entire body surface in one image, and it is necessary to separate the images into multiple images.

In this case, it is necessary to ensure that the images do not overlap or separate, and that the entire surface of the moving object is photographed.

There are two conventional techniques for obtaining still images of moving objects: (1) taking pictures with a regular television camera and recording and reproducing them with a video recorder; and (2) taking pictures with a high-speed camera.

However, in method (2), the exposure time of the television camera is long, at several tenths of a second, and the image is blurred due to the effects of afterimages.

The faster the object travels, the more blurred the image becomes, making it difficult to obtain a clear image.

Furthermore, although it is possible to obtain images with less blur in the method (2), there are drawbacks such as recording and reproducing cannot be performed automatically and takes time, making it unsuitable for industrial equipment.

This invention was devised in view of these points, and its first purpose is to use an imaging device such as a television camera to compare images of a moving object while it is in a running state, so that the running speed of the moving object changes. It is possible to separate the images into multiple still images so that they do not overlap or separate even when the image is taken apart, and it is also possible to automatically recognize the position on the moving object corresponding to the separated still images. The second object of the present invention is to provide a surface inspection device for a moving object that can inspect the surface of an object running at high speed with higher accuracy and efficiency than direct visual inspection, and that can later perform indirect visual inspection using images. The object of the present invention is to provide a moving object surface inspection device that can automatically inspect the surface of a moving object with high accuracy and efficiency.

That is, the present invention divides the surface of a running object into parts with a constant area and photographs them using an imaging device such as a television camera.
The photographed image of each part is obtained as a still image with the same level of clarity as a photographed image of a stationary object, and the images do not overlap or separate even if the traveling speed changes, and at the same time, the This automatically recognizes which part of the moving object the image corresponds to.

As a result, the surface of a moving object can be inspected using a still image captured by an imaging device such as a television camera, which not only improves the accuracy and efficiency of surface inspection but also enables automatic inspection of the surface of a moving object.

In other words, as a solution to the shortcomings of the conventional technology, the advantage of imaging devices such as television cameras is the immediacy of image recording and playback, and the ability of high-speed cameras to obtain images with less blur even when photographing moving objects. We have developed a method that combines the features of

Specifically, for example, a television camera and a mechanical shutter are combined, and the shutter is opened and closed according to the movement of the moving object, thereby taking time-series images of the moving object.

By shortening the opening time of this shutter, the exposure time of the television camera is shortened, so it is possible to obtain clear still images with less blur.

In addition, by synchronizing the timing of opening and closing the shutter with the distance traveled by the moving object, the shooting surface of the moving object can be divided into multiple parts, and still images of each part can be obtained without the images overlapping or separating. be able to.

An embodiment of the present invention will be described below with reference to the drawings.

First, an example of the configuration of the imaging section of the present invention will be described with reference to FIG.

The mechanical shutter 1 is composed of a rotating disk 5 having one or more microscopic slits 4 installed between the optical lens 2 and the television camera 3. The shutter opens when the object passes through the gap.

The surface of the object 6 traveling at a speed V is the area S that is the field of view of the television camera 3 (S is set according to the object to be inspected).
In order to divide the image into parts 6 □ , 6 □ , 63 . . . and capture images of each part without overlapping or dispersing even if the speed ■ changes, the field of view of the television camera 3 must be If the length in the moving direction of parts 61゜6□, 63... of a certain area S is a, then the opening/closing interval of the shutter 1 is a/v.
It is necessary to do so.

Therefore, if the number of slits in the rotating disk 5 is one,
The rotating disk 5 may be rotated at a rotation speed of n=-.

For this purpose, the running speed V of the running object 6 is detected by a speed detector 7 (for example, a laser for direct detection, a pulse transmitter, speed generator, etc. for indirect detection such as ultrasonic waves),
The motor control circuit 8 causes the rotation speed of the rotating disk 5 to be set to v/
The speed of the motor 9 that rotates the rotary disk 5 is controlled so that

Furthermore, when a is small and v is large, the number of slits may be increased.

On the other hand, the width d of the slit 4 is determined from the smallest image to be inspected, where C is the allowable amount of blurring of the image, and d=2πr- (where r is the average radius from the center of the rotating disk 5 to the slit 4).
This is uniquely determined from the size of the rotating disk 5, the field of view of the television camera 3, and the allowable amount of image blur, regardless of the moving speed of the object.

A scanning signal generator 10 scans the image of the television camera 3 using this signal, and an amplified video signal is output from an amplifier 11.

12 is a timing detector for opening the shutter; 13 is a recording device; the recording device 13 uses the output signal of the scanning signal generator 10 and the detection signal of the timing detector 12 to record the U-th (after the detection signal of the timing detector 12); (U is selected depending on the image quality) A video signal corresponding to one screen is recorded.

Then, the images recorded in the storage device 13 are transferred to the monitor TV 1.
Play on 4.

Note that a clear image can be obtained by using an external light source for illumination when the shutter speed is fast and the illuminance is insufficient, or by using an external light source with a specific wavelength and a filter in the case of a high-temperature object.

In this way, even if the moving speed V of the running object 6 changes, the image blur will not increase and the clarity will be the same as that of a photographed image of a stationary object, and the images will not overlap or become separated. , it becomes possible to take a still image of the entire surface of the running object 6 in the running direction.

This makes it possible to visually inspect the surface of the moving object 6 by converting it into a still image instead of visually inspecting it directly, making it easier to inspect the surface of the moving object 6 even when traveling at high speeds, improving efficiency. , which also improves accuracy.

It is also possible to automatically inspect the surface of the moving object 6 using still images.

In addition, when the field of view in the direction perpendicular to the moving direction of the television camera 3 is insufficient, the same device as shown in FIG. 1 is used, as shown in FIG. Just put them side by side so they don't get separated.

Now, even if the surface of the moving object 6 is visually or automatically inspected from the still image taken in this way,
If it is not possible to determine which position of the moving object the still image corresponds to, the value of the information as an inspection result is halved.

Next, FIG. 3 shows an example of the configuration of the position detecting section of the present invention that automatically associates a still image with a position on a moving object when a plurality of TV cameras with mechanical shutters as described above are installed. Refer to and explain.

The y-axis is a direction perpendicular to the moving direction of the running object 6, with point A at the tip of the running object 6 as the origin.

Assuming a plane with the moving direction as the y-axis, the mechanical shutter 1. Television camera 151.1 with mechanical shutter consisting of optical lens 2 and television camera 3
52. The still image photographed at 153 is associated with the position on the running object 6 using coordinate points x and y.

Then, the X coordinate of each TV camera 15. ．． 15□,
With the number 153, the X coordinate is determined by the number of images from the tip of the running object 6.

That is, the size of the field of view of the television camera 151, 152, 153 is aXb (a: the lengthwise size of the running object,
b (the size in the width direction of the running object), then the X coordinate of the mth 1 still image taken by the No. n television camera 15n is (n 2 ) x b, and the y coordinate is (m-7). )xa, and can be associated with the position on the traveling object 6 using the coordinate points ((n-1 Σ)b, (m-7)a).

That is, for example, a television camera 15. To explain the still images taken in , the number m of still images is calculated by counting the number of shutter openings of the television camera 151 using the adder 16, and the television camera number n is the value corresponding to the number of the television camera 151. Set with the setting device 17, input each to the computing unit 18, and the computing unit 18 calculates (n) b, (rn 2
) Compute a.

Then, this calculated value, ie, the coordinates Xy, is input to the function generator 19.

The function generator 19 outputs a video signal corresponding to the coordinates X and y in synchronization with the signal from the scanning signal generator 10.

The amplifier 1 which is a video signal of a photographed image from a television camera 151 synchronized with this signal and the scanning signal generator 10
1 is mixed by the signal mixer 20 to produce an image as shown in FIG. 4, in which x and y coordinate points indicating the correspondence with the position on the moving object 6 are superimposed on a still image of the moving object 6. Create.

The created image is then stored in the image storage device 13 as described above and reproduced on the monitor television 14.

The contact point 21 is used to align the first image taken by the television camera 151 with the tip of the running object 6, and is used to detect an object installed on the front line f of the field of view of each television camera 151, 152, 153. When the detector 22 detects the tip of the running object 6, it is turned on and starts inputting the detection signal of the speed detector 7 to a part of the shutter of the television camera 15, thereby starting the opening/closing operation of the shutter and detecting the object. The shutter is opened in synchronization with the detection of the tip of the running object 6 by the detector 22, and when the object detector 22 detects the tail end of the running object 6, it is turned off and the television camera 15□ receives the detection signal of the speed detector 7. By stopping the input to a part of the shutter, the opening/closing operation of the shutter is stopped, and the shutter is closed.

The above description has been made by taking as an example a still image photographed by the television camera 151, but the same may be applied to still images photographed by the other television cameras 15□ and 153.

By doing this, each television camera 15□,
15□, When inspecting the still image photographed in disassembly at 153 visually or automatically, it becomes possible to determine the position on the traveling object 6 corresponding to the still image.

Next, an example will be described in which surface flaws on a red-hot slab were inspected using the above-described apparatus.

The inspection target is a red-hot slab with a surface temperature of 600 to 1200℃ on the blooming surface.
The inspection was carried out during transportation at a speed of 60 m/in.

Initially, the field of view of the television camera was set to 2501 m><250 mv for the purpose of observing flaws larger than 1 mm.
t, the image blur was designed to be within 1 mm.

For this reason, the mechanical shutter has a width of 0.5 mm (lit.
) radius 20mm (40mrrt
), the running speed of the slab is detected by a speed generator attached to the table roller for transferring slabs, and the running speed of the slab is adjusted to 60 m/min in proportion to this detection signal.
The speed was controlled by an electric motor so that it rotated at 240 OrPM when .

In addition, a Carnicon image pickup tube is used as a television camera,
Since the target was a slab with a width of up to 10,100 mm, four television cameras were installed in a direction perpendicular to the running direction of the slab.

In addition, a 250W light source was placed 3m above the slab.
Twelve lighting devices using ultra-high pressure mercury lamps were installed, and the illumination intensity on the slab surface was approximately 110,000 LX.

The light source was placed at a position off the transport roller table in order to form an image on the microflow, and the light source was projected at an irradiation opening angle of 30° with respect to the axis perpendicular to the slab surface.

In addition, HM is used as a slab detector to detect the passage of slabs.
D was used.

With this device, the running speed of the slab is 30 to 60 m/mi.
It is possible to separate and photograph the entire surface of the slab into very clear still images even if the value changes by n, without the images overlapping or scattering. Scratches etc. were confirmed.

We also tried the following three methods to recognize the presence or absence of flaws and the extent of flaws from images of the slab surface taken in disassembly using this device.

■ Visual discrimination ■ Automatic discrimination ■ Semi-visual discrimination (semi-automatic discrimination) In addition, in the automatic discrimination described in ■, in order to automatically identify flaws, dark areas on the image are A method of counting area was used.

FIG. 5 shows the configuration of this automatic discrimination device, which is composed of a converting section 23, an arithmetic section 24, and a determining section 25, and the functions of each section are as follows.

1) Conversion unit 23 For example, as shown in FIG. 6a, an analog signal of brightness and darkness proportional to the unevenness of the object surface generated by scanning the object surface, that is, a video signal S of the object surface imaged by an imaging device
As shown in FIG. 6, it is compared with the slice level SL set externally for each unit area using a pulse signal PS, and when it is bright, it is converted into a white digital signal, and when it is dark, it is converted into a black digital signal DS.

2) Arithmetic unit 24 The white and black digital signals DS obtained from the conversion unit 23 are stored in a memory device (1...i+i+1,
1-1-2...m address) as shown in FIG. 6C.

Then, from this data, the number of black parts and their respective sizes are calculated.

3) Judgment unit 25 compares the number of black parts and their respective sizes obtained by the calculation unit 24 with the maximum allowable number MN of flaws set from the outside and the maximum value MS of the size of flaws, and outputs a judgment signal JS. issue.

This automatic discrimination device is disassembled by the device described above.

By inputting the photographed video signal of the surface of the moving object (red-hot slab), the surface of the moving object (red-hot slab) can be automatically inspected.

Now, according to the results of inspecting the slab surface using the three methods mentioned above, the number of images is too large for the visual judgment (■).

Because of the large number of slabs (approximately 160 slabs on average), the burden on the inspector is heavy, and when the rolling pitch is fast, the inspection time becomes a bottleneck.

Automatic discrimination (2) can be processed at the same time as the image is taken, but the inspection accuracy is lower than that of visual discrimination.

Therefore, visual inspection and automatic discrimination are combined. The semi-visual discrimination (semi-automatic discrimination) method described in (2) was used.

This is the maximum allowable number MN of flaws and the maximum value M of the size of flaws that are set from the outside of the automatic discrimination device shown in Figure 5.
For images where the S setting is set to two levels, large and small, and the number or total area of dark images exceeds each large setting,
It automatically determines that a flaw needs to be cleaned unconditionally, and only images that exceed a small setting are played back on the monitor, allowing the inspector to visually determine whether or not the flaw needs to be cleaned. .

As a result, the burden on the inspector was reduced, and flaw inspection could be performed with the same accuracy as visual judgment.

The coordinate point X, y representing the position on the slab of the image determined to require flaw cleaning using the above method can be placed on a card, tape, or
Record it with a computer or other device and send it to the next flaw removal process.

In the flaw removal process, spot scarfing is performed by selecting hole nozzles or by other suitable methods based on the stored x and y information.

In this way, the entire surface of the moving red-hot slab is photographed separately into clear still images without overlapping or dispersing images, and from these still images the existence and extent of surface flaws on the slab can be determined automatically, semi-automatically, or visually. and automatically detect the slab surface position corresponding to the still image that requires flaw removal.
By storing these information, it is possible to perform spot scarfing only on the necessary areas using this memorized information, which can eliminate the reduction in yield due to excess or shortage of hot scarves, reduce the unit consumption of hot scarves, and eliminate the need for cold scarves. did it.

This invention applies not only to red-hot slabs, but also to hot steel products manufactured in hot strip mills, thick plate mills, section steel mills, bar and wire thickening mills, pipe rolling mills, cold mills, skin pass mills, pickling mills, etc. It can be used to inspect surface flaws on cold-worked steel sheets produced on the Metsuki line, etc.

In these cases, the presence or absence and type of light source, the structure of the mechanical shutter, etc. may be considered depending on each situation.

As described above, according to the present invention, a plurality of images of a moving object captured by an imaging device such as a television camera while the moving object is in a running state are not overlapped or separated even if the running speed of the moving object changes. In addition to being able to separate and photograph individual still images, it is also possible to automatically recognize the position on a moving object that corresponds to the separated still images, making it possible to inspect the surface of an object moving at high speed better than by direct visual inspection. Therefore, it is possible to provide a moving object surface inspection device that can inspect the surface of a moving object with high accuracy and efficiency, and later allows indirect visual inspection using images.

Furthermore, it is possible to provide a moving object surface inspection device that can automatically inspect the surface of the moving object with high accuracy and efficiency.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an imaging section according to an embodiment of the present invention;
FIG. 2 is a diagram showing a schematic configuration when a plurality of imaging devices are provided, FIG. 3 is a diagram showing the configuration of the position detection section of the same embodiment, and FIG. 4 is an example of an image of the same embodiment. Figure 5 is a diagram showing the configuration of the automatic discrimination device of the same embodiment, Figure 6 a, b
, C are diagrams for explaining the operation of the automatic discrimination device of the same embodiment. 110101, mechanical shutter, 3...TV camera, 4...slit, 5...
Rotating disk, 6... Running object, 7... Speed detector, 8... Motor control circuit, 9...
...Motor, 12...Timing detector, 13
...Storage device, 14...Monitor television, 151.15□, 153...Television camera with mechanical shutter, 16...Adder, 17
... Camera NO setting device, 18 ... Arithmetic unit, 19 ... Function generator, 2
0... Signal mixer, 22... Object detector, 23... Conversion section, 24... Arithmetic section, 25... Judgment MS...video signal, SL...slice level, DS...
・Digital signal, MN...Maximum allowable flaw number setting value, MS...Maximum allowable flaw size setting value, JS
...Judgment signal.

Claims (1)

[Claims] 1. The surface of a moving inspected material is captured as a still image by a shutter-equipped imaging device that combines an imaging device with a shutter that opens and closes at a predetermined period, and the still image is inspected for defect inspection. In a device that performs inspection, one or a plurality of imaging devices with shutters are arranged so that the imaging range is not dispersed in the width direction of the inspected material, a speed detector that detects the traveling speed of the inspected material, and this speed. controlling the opening/closing cycle of the shutter of the shutter-equipped imaging device according to the detection output of the detector;
a shutter control device that synchronizes the opening/closing period with the traveling speed of the material to be inspected; a scanning signal generator that scans the image captured by the imaging device; a timing detector that detects the timing of opening the shutter; a storage device for storing an image captured by the imaging device as a still image having a constant area in response to a signal and a signal from the scanning signal generator, and outputting the image signal as desired; A counting circuit that counts the number of captured still images of the material to be inspected, and a position of the material to be inspected corresponding to the still image captured by the imaging device is detected from the counting output of this counting circuit and the imaging position of the imaging device with a shack. What is claimed is: 1. A moving object surface inspection device comprising a position detection device. 2 In the case where the surface of the moving inspected material is imaged as a still image by a shutter-equipped imaging device that combines an imaging device with a shack that opens and closes at a predetermined period, and the defect inspection is performed by inspecting the still image, 1 or a plurality of imaging devices with shacks arranged so that the imaging range is not dispersed in the width direction of the material to be inspected, one speed detector for detecting the traveling speed of the material to be inspected, and the detection output of this speed detector. a shutter control device that controls the opening/closing period of the shutter of the shutter-equipped imaging device according to the shutter speed and synchronizes the opening/closing period with the traveling speed of the inspected material; a scanning signal generator that scans the image taken by the imaging device; A timing detector detects the opening timing, and in response to the signal of this timing detector and the signal of the scanning signal generator, the image captured by the imaging device is stored as a still image with a constant area, and the image is stored as desired. A storage device that outputs a signal, a counting circuit that counts the number of still images of the inspected material taken by the shutter-equipped imaging device, and a counting output of this counting circuit and an imaging position of the shutter-equipped imaging device. a position detection device that detects the position of the inspected material corresponding to a still image captured by the imaging device; a conversion device that converts an imaging signal from the shutter-equipped imaging device into a digital signal according to brightness; An arithmetic device that counts the number and size of dark areas in an image capture screen based on the number of signals corresponding to dark areas of a digital signal output by the device and their positional relationship on the image capture screen, and an arithmetic output of this arithmetic device. A traveling object surface inspection device comprising: a determination device that compares a predetermined value with a preset value to determine the presence or absence of this condition.