JP2007139630A - Surface inspection device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface inspection device and a method having a function for determining an abnormality of optical arrangement by simultaneous determination of a plurality of cameras in a metal belt width direction and by angle determination in a camera width direction. <P>SOLUTION: This surface inspection device for inspecting optically the surface of a specimen formed by connecting a plurality of metal belts by welding is equipped with a self-diagnosis device for receiving reflected light from a weld zone of the specimen, and determining whether the optical arrangement of a light source and/or a light receiving device of the surface inspection device is normal or not based on a reflected light intensity distribution of the weld zone. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface inspection apparatus and method for optically inspecting a surface defect of a metal strip in a continuous conveyance line installed in a manufacturing process or an inspection process of a metal strip such as a steel plate.

  Although there are various apparatuses for inspecting wrinkles on the surface of a metal strip, a surface inspection apparatus as shown in FIG. 1 is generally used. FIG. 1 is a diagram showing an outline of a linear sensor camera type surface inspection apparatus. FIG. 1A shows a side view, and FIG. 1B shows a top view. The light source 1 that irradiates linear light in the plate width direction, and the reflected light reflected by the irradiation light band 4 ′ on the surface of the metal band 4 from the light source 1, the regular reflection position (angle) and the diffuse reflection position (angle) ) And one-dimensional cameras (linear sensor cameras) 2 and 3 as imaging devices that receive light. These linear sensor cameras generally use a linear sensor camera type surface inspection apparatus that is configured by arranging a plurality of linear sensor cameras in the plate width direction. FIG. 1B shows an example in which two one-dimensional cameras (regular reflection positions) 2a and 2b are arranged in the width direction.

  The inspection performance of these surface inspection devices may deteriorate due to slight misalignment of the light source or light receiver, contamination of the light projection window of the light source or light reception window of the light receiver, or a reduction in light quantity or failure due to deterioration of the light source over time. For this reason, calibration of optical systems is usually performed regularly.

  For example, Patent Document 1 discloses a conventional technique related to self-diagnosis (calibration) for determining whether or not the optical arrangement (optical axis) of the surface inspection apparatus is normal. FIG. 2 is a view showing a welded portion between metal bands and an opening hole provided in the vicinity thereof. In this technique, as shown in FIG. 2, an opening hole 6 is formed in a welded portion (welded portion) 5 at the front end (following coil 7) and rear end (preceding coil 8) of each lot in a continuous line of metal bands. The opening hole 6 is inspected by a surface inspection device.

FIG. 3 is a diagram schematically showing the intensity of reflected light from the opening hole. When the optical system of the apparatus is sufficiently adjusted as shown in FIG. 3A, the difference in reflected light intensity from the opening and the portion without the opening becomes large, but as shown in FIG. If the optical system of the apparatus is not sufficiently adjusted, the difference in reflected light intensity is reduced. In this method, a “calibration threshold value” is provided in advance, and whether or not the optical system in the surface inspection apparatus needs to be calibrated is determined based on whether or not the threshold value is exceeded during measurement. In addition, the opening is opened in the vicinity of the welded portion of each lot of the metal strip, and this range is usually scrapped by a cutting machine, so that the area to be inspected is not affected by the product yield. A method of forming an opening that penetrates the body is performed.
JP-A-11-132967

  However, in the technique disclosed in Patent Document 1, in order to determine whether or not calibration is necessary, it is necessary to first provide an opening, and a camera that captures reflected light uses the provided opening as its field of view. It is mandatory to do. FIG. 4 is a diagram for explaining the relationship between the visual field of a plurality of cameras (width direction) and the positioning of the opening. FIG. 4A shows a top view, and FIG. 4B shows the reflected light intensity. In this example, only the camera 2a can scan the opening hole 6 of the metal band 4, but the camera 2b cannot scan the opening hole 6. As described above, the configuration of a general surface inspection apparatus in which a plurality of units are installed in the width direction of the metal strip has a problem that determination cannot be performed.

  Further, since only one or several openings are used, there is a problem that it is impossible to determine the inclination of the visual field of the linear sensor camera (inclination with respect to the width direction).

  The present invention has been made in view of the above circumstances, and provides a surface inspection apparatus and method having a function of determining abnormality in optical arrangement by simultaneous determination of multiple cameras in the metal band width direction and angle determination in the camera width direction. With the goal.

  The invention according to claim 1 of the present invention is a surface inspection apparatus that optically inspects the surface of a subject formed by welding a plurality of metal bands, and receives reflected light from a welded portion of the subject. A surface inspection device comprising: a self-diagnosis device that determines whether the optical arrangement of the light source and / or the light receiving device of the surface inspection device is normal based on a reflected light intensity distribution of the welded portion It is.

  According to a second aspect of the present invention, in the surface inspection apparatus according to the first aspect, the self-diagnosis device may be configured so that the reflected light intensity is within a predetermined intensity range in the reflected light intensity distribution. Based on this, it is determined whether or not the optical arrangement of the surface inspection apparatus is normal.

  According to a third aspect of the present invention, in the surface inspection apparatus according to the first aspect, the self-diagnosis device calculates a reflected light intensity change rate, which is an inclination of the reflected light intensity distribution, and calculates the calculated reflection. The surface inspection apparatus is characterized in that it is determined as abnormal when the light intensity change rate is not within a predetermined range.

  According to a fourth aspect of the present invention, in the surface inspection apparatus according to the third aspect, the rate of change in the reflected light intensity is the reflected light intensity at the end of the reflected light intensity distribution and the center of the visual field of the light receiving device. The surface inspection apparatus is calculated on the basis of the distance between the edge portion and the edge portion.

  Furthermore, the invention according to claim 5 of the present invention is a surface inspection method for optically inspecting the surface of an object formed by welding a plurality of metal bands, and receives reflected light from a welded portion of the object. The surface inspection method is characterized in that a self-diagnosis is performed to determine whether the optical arrangement of the light source and / or the light receiving device is normal based on the reflected light intensity distribution of the weld.

  In the surface inspection apparatus in which a plurality of linear sensor cameras are installed in the width direction of the weld line, the present invention is based on an image signal obtained by imaging a weld line (welded portion) of a metal strip with a linear sensor camera. Optical system abnormalities such as travel direction angle and width direction parallel angle are determined for all metal strip weld lines, so it is possible to quickly detect abnormalities in surface inspection equipment. It is possible to minimize re-inspection. In addition, since the weld line is inspected online through the transport line, it is not necessary to stop the transport line, and simple and quick self-diagnosis can be performed.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 6 is a diagram schematically showing metal bands connected by welding. The leading end (following coil 7) and tail end (leading coil 8) of the metal band are welded and connected at the entrance side of the production line or inspection line, and are continuously conveyed. This welded portion (welded portion) 5 is called a weld line or welded portion, and is welded linearly in the width direction perpendicular to the metal strip conveyance direction. In order to ensure high-speed stability, the width direction angle with respect to the traveling direction is substantially a right angle. The weld line has the same length as the width of the metal strip.

  The dimensions of the weld line in the traveling direction L and the width direction W vary depending on the steel type and thickness of the lot to be manufactured, or other welding equipment, but usually L is about 20 mm, and W is from the width of the metal strip. The length is obtained by subtracting the edge trimming margin in the width direction.

  In the present invention, the welding lines that are in a uniform state over the entire width direction of the metal strip are imaged by all of the linear sensor cameras arranged in the width direction, and based on the captured image signal. It is intended to determine whether the optical arrangement of the linear sensor camera (imaging device or light receiving device) or illumination device (light source) of the surface inspection device is normal.

  When the welding line is imaged with a linear sensor camera for imaging the reflected light at the specular reflection angle, if the optical system of the device is sufficiently adjusted, the reflection intensity at the welding line will be welded to other regions, i.e., welded. It is significantly smaller than the metal band stationary part of the metal band surface that is not. FIG. 7 is a diagram schematically showing a difference in reflected light intensity distribution between metal bodies. In the figure, A represents the reflected light intensity distribution from other than the weld line, and B and C represent the reflected light intensity distribution from the weld line. This difference is because, at the regular reflection angle, generally, the weld line has a lower reflectance than the metal band stationary part. However, depending on the metal strip material and welding conditions, the magnitude relationship of the reflection intensity may be reversed, and is not limited to this example.

If the optical arrangement (optical axis) of the linear sensor camera is shifted from the adjusted and set optical axis as the initial setting and is not normal, the relative position of the light source, linear sensor camera, and metal strip Since the positional relationship is abnormal, the intensity distribution in the metal band width direction of the reflected light from the weld line obtained by the linear sensor camera decreases unlike normal times (from B to C in FIG. 7).
Examples of optical system misalignment include the following.

  1) This is a case where the optical axis is shifted in the traveling direction of the metal band in any one of the linear sensor cameras arranged in the width direction. FIG. 8 is a diagram showing the intensity of reflected light received by a linear sensor camera whose optical axis is shifted and normal reflected light intensity. Compared with a linear sensor camera having a normal optical axis, the reflected light amount is reduced. In the example of FIG. 8, the optical axis of the camera 2 is shifted. This is because the observation position of the linear sensor camera is shifted outside the irradiation area on the surface of the metal band of the light source, and the reflected light of the light source cannot be obtained.

  2) This is a case where the parallelism of the field of view of the linear sensor camera deteriorates with the width direction of the metal strip (the direction perpendicular to the metal strip transport direction). FIG. 5 is a diagram schematically illustrating the case of a linear sensor camera in which the optical axis is shifted. In this case, as shown in FIG. 5, the reflection intensity distribution in the width direction is non-uniform. FIG. 5 shows an example in which the reflected light intensity is extremely reduced at the end portion although it is normal in the central portion of the visual field. This is because the irradiation area on the surface of the metal band is observed in the central part of the visual field, but the edge part deviates from the irradiation area.

  In the present invention, an image of a welding line is captured in advance under normal optical axis conditions, and a normal reflection intensity value or intensity distribution is stored based on the image signal. Based on the value of the reflection intensity and the intensity distribution, an intensity value “abnormality determination threshold” for determining an abnormality is determined in advance in consideration of variations in a normal state. For example, a value indicated by a broken line in FIG. 8 is an “abnormality determination threshold value”, and in a welding line image signal obtained by a plurality of linear sensor cameras, a range exceeding the “abnormality determination threshold value” is a welding line. Whether the optical system arrangement (optical axis) of the linear sensor camera of the surface inspection apparatus is normal or abnormal may be determined based on whether or not the value is equivalent to the width (for example, the weld line width-α). Note that α shown above may be determined in consideration of the resolution of the optical system.

  In the example shown in FIG. 7, the threshold value is set with the same value in the width direction, but the reflection intensity is not constant, for example, the edge becomes slightly darker than the center due to the influence of shading under normal conditions. May be set to have different values at positions in the width direction.

  FIG. 9 is a diagram showing an apparatus configuration example when the present invention is applied to a continuous treatment line (surface treatment line or the like) of a metal strip. In the figure, 11 is an entry side dispensing reel, 12 is an entry side welding machine, 13 is a process line, 14 is an exit side take-up reel, 15 is a host computer, 16 is an encoder, 17 is a welding line tracking device, and 18 is a self-diagnosis. Reference numeral 19 denotes a display device, and reference numeral 25 denotes a surface inspection device.

  The metal strip 4 paid out from the entry-side delivery reel 11 is subjected to a process such as alloying in the process line 13 and taken up on the delivery-side take-up reel 14. Between the process line 13 and the take-up take-up reel 14, an encoder 16 for detecting a transport distance, a light source 1, a one-dimensional camera (regular reflection position) 2, and a one-dimensional camera (diffuse reflection position) 3 (see FIG. 1 (see (a)) is installed.

  The welding line welded to connect the leading coil tail end and the trailing coil as shown in FIG. 6 by the inlet side welding machine 12 installed on the inlet side of the continuous production line is a metal strip. For example, it has a size of 1200 mm in the width direction and 20 mm in the transport direction. This weld line is inspected by the four line sensor cameras in the width direction in the surface inspection device 25.

  At the timing when welding is performed by the entrance side welding machine 12 installed on the entrance side, the conveyance of the metal strip 4 is stopped, and at the timing when the entrance side welding operation is completed, the welding completion signal is sent to the host computer 15 or the entrance computer that manages the line. It is output from the side welder 12 to the weld line tracking device 17. At this timing, the weld line tracking device 17 resets the distance at the entry side welding position, that is, sets the position of the weld line at the entry side welder position to 0 m for inspection of the weld line.

  When conveyance of the metal band 4 is started after completion of the entry side welding operation, the conveyance distance signal from the encoder 16 counts the conveyance distance of the metal band, and on the line until the surface inspection device 25 on the exit side is reached. Track the transport position. The distance between the installation position of the surface inspection apparatus 25 and the installation position of the entry side welding machine 12 is measured in advance, and the conveyance distance counted by the encoder 16 and the distance between the surface inspection apparatus 25 and the entry side welding machine 12 measured in advance are measured. By comparing with the distance interval, it is determined whether or not the weld line reaches the position of the surface inspection device 25.

  The self-diagnosis device 18 receives the weld line arrival signal from the weld line tracking device 17, extracts the images before and after the weld line, and extracts the extracted image and the metal band specification information input from the host computer 15. Based on this, whether the optical arrangement of the surface inspection device 25 is normal or abnormal is determined. Then, the determination result in the self-diagnosis device 18 is displayed on the display device 19. Further, it may be output to the host computer 15.

  For example, four line sensor cameras are arranged in order to inspect the entire width of the metal strip, and the visual field in the width direction is divided into four. An example of determination by observing the weld line is shown in FIG. The area range (width) in which the reflected light intensity at each welding line exceeds the abnormality determination threshold is (L1 + L2 + L4), which is smaller than the width (L = L1 + L2 + L3 + L4) corresponding to the actual welding line. This is because the camera 3 has a range L3 in which the reflected light intensity does not exceed the threshold value. For example, based on the metal band width in the metal band specification information input from the host computer 15, the width threshold of the region exceeding the abnormality determination threshold is set as metal band width −β (predetermined value), If the value is higher than that, it is judged as normal, and if it is less than that, it is judged as abnormal.

  FIG. 11 is a diagram showing an example of determination by observing a weld line (the reflected light intensity distribution has an inclination). When such an inclination (change rate in the width direction of the reflected light intensity distribution) is abnormal, the width at which the reflected light intensity at the welding line exceeds the abnormality determination threshold is L1 + L2 + (L3−L3 ′) + L4. The width of the weld line is smaller than L1 + L2 + L3 + L4. This is because the camera 3 has a range L3 'in which the reflected light intensity does not exceed the threshold value.

Furthermore, since the reflected light intensity distribution has an inclination, the camera 3 may determine the abnormality of the optical axis based on the inclination. FIG. 12 is a diagram illustrating determination of an optical axis abnormality based on inclination. As shown in FIG. 12, the inclination angle Θ (change rate) of the reflected light intensity distribution is calculated from the following equation (1).
tan Θ = h / d (1)
However,
h: “Intensity difference between the reflection intensity at the edge of the luminance distribution and the abnormality determination threshold”
d: “Pixel difference between the edge of the reflected light intensity distribution used for calculating h and the center of the camera field of view (distance in the width direction)”
If the value of Θ is not within the preset allowable range, it is determined that there is an abnormality.

  Then, the judgment result of the self-diagnosis device 18 described above is judged by the operator who is operating at the manufacturing site with the display device 19. As a result of this, the operator has not been able to inspect the metal strip normally, so that the subsequent passing process is performed so that the operator transports to a line (for example, a recoil line, an inspection line, etc.) capable of performing another surface inspection. Give instructions to change. Further, based on the determination result in the self-diagnosis device 18, an alarm (warning) may be output and the result may be output to the host computer 15.

  And it inspects again by the surface inspection apparatus installed in the line, or visual inspection. For an abnormal camera, an instruction to adjust the position angle in the flow direction and the parallel angle in the width direction is issued so that the optical axis is normal.

It is a figure which shows the outline | summary of a linear sensor camera type surface inspection apparatus. It is a figure which shows the opening part provided in the welding part between metal strips, and its vicinity. It is the figure which showed typically the reflected light intensity from an opening hole. It is a figure explaining the relationship of multiple camera (width direction) visual field and positioning of an opening part. It is a figure which shows typically the case of the linear sensor camera from which the optical axis shifted | deviated. It is the figure which represented typically the metal strip connected by welding. It is a figure which shows typically the difference in the reflected light intensity distribution in a metal body. It is a figure which shows the reflected light intensity received with the linear sensor camera from which the optical axis shifted | deviated, and normal reflected light intensity. It is a figure which shows the apparatus structural example at the time of applying this invention to the continuous treatment line (surface treatment line etc.) of a metal strip. It is a figure which shows the example of the determination which observed the weld line. It is a figure which shows the example of the determination which observed the weld line (the reflected light intensity distribution has inclination). It is a figure explaining the optical axis abnormality determination based on inclination.

Explanation of symbols

1 Light source 2 One-dimensional camera (regular reflection position)
2a, 2b One-dimensional camera (regular reflection position) width direction 3 One-dimensional camera (diffuse reflection position)
4 Metal band 4 'Irradiation light band 5 Welded part (welded part)
6 Opening hole 7 Subsequent coil 8 Predecessor coil 11 Incoming delivery reel 12 Incoming welding machine 13 Process line 14 Outgoing take-up reel 15 Host computer 16 Encoder 17 Welding line tracking device 18 Self-diagnosis device 19 Display device 25 Surface inspection device

Claims (5)

In a surface inspection apparatus that optically inspects the surface of a subject formed by welding a plurality of metal bands,
Self-diagnosis for receiving reflected light from the welded portion of the subject and determining whether the optical arrangement of the light source and / or the light receiving device of the surface inspection device is normal based on the reflected light intensity distribution of the welded portion Equipment,
A surface inspection apparatus comprising: The surface inspection apparatus according to claim 1,
The self-diagnosis device determines whether or not the optical arrangement of the surface inspection device is normal based on the size of a region where the reflected light intensity falls within a predetermined intensity range in the reflected light intensity distribution. Surface inspection equipment. The surface inspection apparatus according to claim 1,
The self-diagnosis device calculates a reflected light intensity change rate that is an inclination of the reflected light intensity distribution, and determines that the surface inspection device is abnormal when the calculated reflected light intensity change rate is not within a predetermined range. . In the surface inspection apparatus according to claim 3,
The surface inspection apparatus characterized in that the reflected light intensity change rate is calculated based on the reflected light intensity at the end of the reflected light intensity distribution and the distance between the center of the field of view of the light receiving device and the end. In the surface inspection method for optically inspecting the surface of an object formed by welding a plurality of metal bands,
Receiving reflected light from the welded portion of the subject, and performing self-diagnosis to determine whether the optical arrangement of the light source and / or the light receiving device is normal based on the reflected light intensity distribution of the welded portion. Surface inspection method.