WO2013012106A1

WO2013012106A1 - Camera for detecting metal surface defects, device for detecting metal surface defects including the camera, and method for detecting metal surface defects

Info

Publication number: WO2013012106A1
Application number: PCT/KR2011/005282
Authority: WO
Inventors: 장유진; 이주섭
Original assignee: 동국대학교 경주캠퍼스 산학협력단; 주식회사 네드텍
Priority date: 2011-07-18
Filing date: 2011-07-19
Publication date: 2013-01-24
Also published as: KR101078404B1

Abstract

A camera for detecting a metal surface defect comprises: a polarizing separator; a first charge coupled device; and a second charge coupled device. When the polarizing separator simultaneously emits mutually intersecting linearly polarized lights onto a surface of a metal object, light reflected from the surface of the metal object is separated into vertically polarized light and horizontally polarized light. The first charge coupled device (CCD) acquires a vertically polarized image. The second charge coupled device acquires a horizontally polarized image.

Description

Camera for metal surface defect detection, metal surface defect detection apparatus including camera, and metal surface defect detection method

The present invention relates to a camera system for detecting metal surface defects, and more particularly, to a camera for metal surface defect detection, a metal surface defect detection apparatus including the camera, and a metal surface defect detection method.

In general, a method of detecting surface defects of a steel plate moving at a high speed includes a method of detecting surface defects by observing a surface of a steel plate being moved directly by an operator, and irradiating a laser light source to the surface and receiving a laser light receiving unit. To detect surface defects through constant signal processing, and to irradiate the surface of the steel sheet with illumination in the visible light region, to receive it with a line scan camera, and to detect surface defects through constant signal processing. There may be.

However, the defect detection method based on the operator's observation may be difficult to objectively detect because it is difficult to have consistent detection criteria among workers. Detecting defects using lasers can be susceptibly affected by external conditions, such as minor vibrations of continuously moving steel sheets.

The technical problem to be solved by the present invention relates to a metal surface defect detection technique and system, a surface for obtaining an image by simultaneously irradiating a stationary or moving metal surface with linearly polarized illumination without interference and orthogonal to each other A camera for defect detection, a metal surface defect detection apparatus including the camera, and a metal surface defect detection method are provided.

In order to achieve the above technical problem, the camera according to the embodiment of the present invention, when irradiating the surface of the metal object with the linearly polarized lights (horizontal wave and longitudinal wave) without interference and orthogonal to each other at the same time, the reflection on the surface of the metal object A polarization separator that separates the divided light into vertical polarization (longwave) and horizontal polarization (horizontal wave); A first charge coupled device obtaining an image of the vertical polarization; And a second charge coupling device for acquiring the image of the horizontal polarization.

The polarizer may be a polarizing beamsplitter cube.

In order to achieve the above technical problem, the metal surface defect detection apparatus according to an embodiment of the present invention, the first light source for irradiating the surface of the metal object with linearly polarized light in bright field conditions; A second light source for irradiating the surface of the metal object with the first light source simultaneously with the first light source in a dark field condition with the linearly polarized light orthogonal to each other and having the same wavelength as that of the linearly polarized light; And a camera for acquiring the light reflected from the surface of the metal object to acquire an image for inspecting the surface defect of the metal object.

The camera may include a polarization separator that separates light reflected from the surface of the metal object into vertical polarization (longwave) and horizontal polarization (horizontal wave) when the linearly polarized lights are irradiated on the surface of the metal object; A first charge coupled device obtaining the image of the vertical polarization; And a second charge coupling device for acquiring the image of the horizontal polarization. The metal object may be a stationary metal object or a moving metal object.

In order to achieve the above technical problem, a metal surface defect detecting apparatus according to another embodiment of the present invention, the first light source for irradiating the surface of the metal object with linearly polarized light of the first wavelength in bright field conditions; A second light source for irradiating a surface of the metal object with linearly polarized light having a second wavelength under dark field conditions; A third light source for irradiating a surface of the metal object with a linearly polarized light having a second wavelength orthogonal to the linearly polarized light of the second wavelength in a dark field condition; A fourth light source for irradiating the surface of the metal object with illumination of the linearly polarized first wavelength orthogonal to the linearly polarized illumination of the first wavelength in dark field conditions; And a camera unit which acquires the light reflected from the surface of the metal object to acquire an image for inspecting the surface defect of the metal object, wherein the first light source, the second light source, the third light source, and the The fourth light source can illuminate the lights at the same time.

The camera unit is disposed between the first light source and the fourth light source, and between the second light source and the third light source, wherein the first light source and the fourth light source are disposed with respect to the second light source and the third light source. It may be arranged to be orthogonal.

The camera unit reflects from the surface of the metal object when the illumination of the first light source, the illumination of the second light source, the illumination of the third light source, and the illumination of the fourth light source are simultaneously irradiated onto the surface of the metal object. A color screening mirror that separates the light into the light of the first wavelength and the light of the second wavelength; A first camera that obtains light of a first wavelength separated from the color-dividing mirror into vertical and horizontal polarizations, and acquires an image for inspecting surface defects of the metal object by using the obtained vertical and horizontal polarizations ; And a second light obtained by separating light having a second wavelength separated from the color-dividing mirror into vertical polarization and horizontal polarization and acquiring an image for inspecting surface defects of the metal object by using the obtained vertical polarization and horizontal polarization. It may include a camera.

In order to achieve the above technical problem, a metal surface defect detecting apparatus according to another embodiment of the present invention, the first light source for irradiating the surface of the metal object with linearly polarized light of the first wavelength at a first angle; A second light source for irradiating a surface of the metal object with linearly polarized light having a second wavelength at a second angle; A third light source for irradiating a surface of the metal object with the linearly polarized light of the second wavelength orthogonal to the linearly polarized light of the second wavelength at a third angle; A fourth light source for irradiating the surface of the metal object with the linearly polarized light of the first wavelength orthogonal to the linearly polarized light of the first wavelength at a fourth angle; And a camera unit which acquires the light reflected from the surface of the metal object to acquire an image for inspecting the surface defect of the metal object, wherein the first light source, the second light source, the third light source, and the The fourth light source irradiates the lights simultaneously, and the first angle, the second angle, the third angle, or the fourth angle may be an angle for brightfield illumination or darkfield illumination.

In order to achieve the above technical problem, the metal surface defect detection method according to an embodiment of the present invention, (a) irradiating the surface of the metal object with linearly polarized light in bright field conditions; (b) irradiating the surface of the metal object at the same time as the irradiation of the linearly polarized light in the bright field conditions orthogonal to the linearly polarized light in the dark field conditions and having the same wavelength as the wavelength of the linearly polarized light; Doing; (c) simultaneously acquiring an image of light reflected from the surface of the metal object; And (d) signal processing the obtained image to detect surface defects of the metal object.

In order to achieve the above technical problem, a metal surface defect detection method according to another embodiment of the present invention, (a) irradiating the surface of the metal object with a linearly polarized light of the first wavelength at a first angle; (b) irradiating a surface of the metal object with linearly polarized light of a second wavelength at a second angle; (c) irradiating a surface of the metal object with a linearly polarized light of a second wavelength orthogonal to the linearly polarized light of the second wavelength at a third angle; (d) irradiating a surface of the metal object with linearly polarized light of a first wavelength orthogonal to the linearly polarized light of the first wavelength at a fourth angle; (e) simultaneously acquiring an image of light reflected from the surface of the metal object; And (f) signal processing the obtained image to detect surface defects of the metal object, wherein the illumination of the first wavelength and the illumination of the second wavelength are simultaneously irradiated and the first angle The second angle, the third angle, or the fourth angle may be an angle for brightfield illumination or darkfield illumination.

A camera for detecting metal surface defects according to the present invention, a device for detecting metal surface defects including a camera, and a method for detecting metal surface defects are provided for a surface of a metal object, such as a metal steel sheet moving at a stationary or relatively high speed. An image of a same visual point may be obtained by minimizing the loss of light. Therefore, the present invention can obtain image information for a more sharp surface defect.

Since the present invention can acquire images of sharp surface defects, it is possible to improve the detection rate of the surface defects on the metal surface of the production product which is typically moving at high speed in the steel industry, and based on this, the quality control of the steel products is greatly improved. You can contribute.

Since the existing surface defect detection system relies mostly on foreign technology, it is possible to obtain the effect of import substitution and export through the present invention.

Compared to the image processing method obtained by the sequential irradiation of the light, the present invention moves at a higher speed or inspects surface defects of finer metals by acquiring images having two or four different positions and angles of light in one shot. To allow surface defect inspection of metals.

Since the present invention acquires the image of the simultaneous point, synchronization of the brightfield image and the darkfield image can be clearly performed. Since the present invention does not require an additional device such as an encoder for synchronizing positions of images, it is possible to reduce the complexity of the camera system, which is an optical system for surface defect detection, and to significantly reduce the configuration cost of the camera system.

In addition, the present invention, when using a light having two different wavelength bands by distinguishing the horizontal polarization (horizontal wave) and the vertical polarization (longwave) for the wavelength band of each of the illumination by the position of the four different lights and The image according to the angle can be acquired at the same time. Thus, the present invention can have an improved rate of detection of surface defects in metals.

In order to more fully understand the drawings used in the detailed description of the invention, a brief description of each drawing is provided.

1 is a view showing a surface defect detection apparatus 50 of a metal object compared with the present invention.

FIG. 2 is a diagram illustrating a method of operating the

light sources

20 and 30 shown in FIG. 1.

3 is a diagram illustrating an apparatus 90 for detecting surface defects of a moving metal object compared to the present invention.

4 shows a camera 95 compared with the present invention.

5 is a diagram illustrating a camera 100 for detecting metal surface defects according to an embodiment of the present invention.

6 is a view for explaining an embodiment of the polarization separator 115 shown in FIG.

7 is a view for explaining the metal surface defect detection apparatus 200 according to an embodiment of the present invention.

FIG. 8 is a view for explaining a method of operating the

light sources

205 and 210 shown in FIG. 7.

9 is a view for explaining a metal surface defect detection apparatus 300 according to another embodiment of the present invention.

FIG. 10 is a plan view illustrating an embodiment of an illumination arrangement of the metal surface defect detection apparatus 300 shown in FIG. 9.

FIG. 11A is a view for explaining the relationship between the surface defect form of the metal object shown in FIG. 9 and the illumination arrangement shown in FIG. 10.

FIG. 11B is a view for explaining another relationship between the surface defect shape of the metal object shown in FIG. 9 and the illumination arrangement shown in FIG. 10.

In order to fully understand the present invention and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate embodiments of the present invention and the contents described in the accompanying drawings.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail by explaining embodiment of this invention with reference to attached drawing. Like reference numerals in the drawings denote like elements.

In the steel industry, a system for detecting the shape and location of various defects on a moving metal surface is very important for quality control of product surfaces, and surface defect detection devices are commercially available.

A system for detecting the shape and location of metal surface defects may consist of one camera and two lights of different illumination angles and on the same plane. In such a system, the shape and location of surface defects are detected through two images obtained by sequentially blinking a bright field light and a dark field light.

In the production line, metal sheets are moving at high speeds and the surface defects vary, so depending on the location and angle of illumination, surface defects may or may not be captured in the camera image.

Therefore, it is necessary to develop a device that can increase the defect detection rate by adjusting the lighting position and angle. In addition, since the metal steel plate moves at a high speed, it is required to develop a device capable of acquiring images of the same point with a minimum amount of light loss.

In the steel industry, much effort has been made to improve the quality of finished products by increasing the detection rate of various defects on the surface of the final product and taking appropriate measures based on them, and related technology development is constantly required.

Before explaining the present invention, a comparative example to the present invention is described as follows.

1 is a view showing a surface defect detection apparatus 50 of a metal object compared with the present invention. Referring to FIG. 1, the surface defect detection apparatus 50 includes a camera 10, a first light source 20, and a second light source 30. The surface defect detection device 50 may be a multiview system.

The camera 10 is not a camera that distinguishes different wavelength bands, but is a single charge coupled device (CCD) camera. Therefore, the surface defect detection apparatus 50 constitutes the first light source 20 in the bright field condition and the second light source 30 in the dark field condition, and as shown in FIG. 2, the first light source 20 and the second light source. Acquiring an image by sequentially flashing the 30, and analyzing the acquired image through an image processing unit included in the surface defect detection device 50, to determine the surface of the stationary metal 40 as an object to be detected. Detect defects Therefore, when the method of the surface defect detection apparatus 50 is applied to a moving metal object, there is a problem in that the position difference of the image by the distance moved during the blinking time difference of the two

lights

20 and 30 occurs.

3 is a diagram illustrating an apparatus 90 for detecting surface defects of a moving metal object compared to the present invention. Referring to FIG. 3, the surface defect detection apparatus 90 of the metal object includes a first camera 60, a second camera 65, a first light source 70, and a second light source 75.

The first camera 60 or the second camera 65 is not a camera that distinguishes different wavelength bands, but is a single CCD camera. Thus, the two

lights

70, 75 alternately irradiate the surface of the moving metal object 80 as shown in FIG. 2.

When the metal object 80, which is a detection object, moves, a position error of an image corresponding to the distance moved during the blinking time difference of the

lights

70 and 75 in the surface defect detection apparatus 90 of the metal object occurs.

In order to eliminate the positional error of this image, the surface defect detection apparatus 90 of the metal object shown in FIG. 3 is used. The first camera 60 and the second camera 65 acquire images sequentially with respect to the moving direction of the metal object 80. That is, after the first camera 60 acquires the image by the illumination of the first light source 70 in the dark field condition, the second camera 65 is the illumination of the second light source 75 in the bright field condition. Acquire an image. Accordingly, the surface defect detection apparatus 90 of the metal object may be a multiview system.

Encoder or speed meter for measuring the position change of the metal object 80 to synchronize the position of the image between the image acquired by the first camera 60 and the image obtained by the second camera 65. An additional device such as) is required for the surface defect detection device 90 of the metal object. The surface defect detection device 90 synchronizes the positions of the images and analyzes the images acquired by the first camera 60 and the second camera 65 through an image processing unit therein to detect surface defects of the metal object 80. Detect.

4 shows a camera 95 compared with the present invention. Referring to FIG. 4, the camera 95 includes a lens 11, a prism (or beam splitter) 12, a first charge coupled device (CCD) 13, and a second CCD 14 is included.

Camera 95 may also be referred to as a two CCD type camera. The first CCD 13 and the second CCD 14 may each have a color filter for passing only light of a specific wavelength band provided in front of the first CCD 13 and the second CCD 14.

The prism 12 divides two lights of different wavelength bands (50%), which are surface reflections of the metal object incident through the lens 11, into the first CCD 13 and the second CCD 14, respectively. Each incident.

Therefore, the camera 95 may obtain the image of the simultaneous point by acquiring the light irradiated simultaneously to the surface of the metal object by two illuminations of different wavelength bands. The light irradiated is not polarized illumination.

The camera 95 equally divides the amount of light incident on the prism 12 through the lens 11 (or the intensity of light) by using the prism 12 and evenly divides the light by half (50%). The incident images of the same surface of the metal object can be obtained by injecting into 13 and the second CCD 14, respectively. Therefore, as the amount of light loss occurs as shown in FIG. 4, the camera 95 obtains an image at least 50% darker than the camera of FIG. 1 or 2 using a single CCD camera. Considering the filter installed in front of the first CCD 13 and the second CCD 14, the camera 95 acquires a darker image. When photographing the surface of the moving metal object by using the camera 95, as the speed of the metal object increases, the image may gradually become blurred. In order to obtain a clear image, the illumination should be brighter or the amount of light loss in the camera 95 should be reduced.

5 is a diagram illustrating a camera 100 for detecting metal surface defects according to an embodiment of the present invention. Referring to FIG. 5, the camera 100 includes a body 105, a lens 110, a polarization separator 115, a first charge coupled device (CCD) 120, and a second CCD 125. It includes.

The camera 100 obtains an image of a simultaneous point using the reflected light 130 which is irradiated on the surface of the metal object simultaneously with two illuminations (horizontal wave and longitudinal wave) that are linearly polarized to be orthogonal to each other in the same wavelength band. The reflected light 130 is linearly polarized light that is incident to the camera 100 through the lens 110 and has the same wavelength band and is orthogonal to each other and is free from interference.

The camera 100 includes two

CCDs

120 and 125 each having the same viewing angle, and each of the

CCDs

120 and 125 has a vertical polarization 135 according to the vibration direction of light in the surface reflection image. Image and horizontal polarization 140 are obtained. An image of horizontally polarized wave or horizontally polarized light and an image of vertically polarized wave or vertically polarized light are independent images. Therefore, the camera 100 may obtain two simultaneous point image information.

The polarization separator 115 passes the vertical polarization 135 of the reflected light 130 toward the first CCD 120 and reflects the horizontal polarization 140 of the reflected light 130 toward the second CCD 125 so that the camera 100 may be reflected. Vertical polarization (longwave) and horizontal polarization (horizontal wave) incident on the surface are separated with little loss of light amount. Therefore, the polarization separator 115 may suppress the loss of the amount of light generated by the prism 12 shown in FIG. 4.

6 is a view for explaining an embodiment of the polarization separator 115 shown in FIG. As shown in FIG. 6, the polarization separator 115 may be implemented as a cube-shaped polarizing beamsplitter cube.

If the light incident on the polarizing beam splitter cube is linearly polarized light, the light is separated into components perpendicular to each other according to the direction of the linearly polarized light. Therefore, when the light incident on the polarization beam splitter cube is linearly polarized light orthogonal to each other, when the direction of the polarization beam splitter cube is adjusted, the polarization beam splitter cube is vertically polarized (135) among the reflected light 130 incident on the polarization beam splitter cube. ) Passes through and reflects the horizontal polarization 140 of the reflected light 130. As a result, the camera 100 can obtain independent images with little loss of light and no interference with each other.

The polarizing beamsplitter cube includes two rectangular prisms. A dielectric coating layer 116 is disposed (formed) between the right prisms. The vertical polarization 135 may be generated by transmitting the reflected light 130 from the dielectric coating layer 140, and the horizontal polarization 140 may be generated by reflecting the reflected light 130 from the dielectric coating layer 140.

Referring back to FIG. 5, the first CCD 120 and the second CCD 125 each constitute an imaging device as a sensor. The first CCD 120 acquires an image (image information) of the vertical polarization 135 separated by the polarization separator 115, and the second CCD 125 obtains an image of the horizontal polarization 140. That is, the first CCD 120 converts the optical signal of the vertical polarization 135 into an electrical signal, and the second CCD 125 converts the optical signal of the horizontal polarization 140 into an electrical signal. Each of the first CCD 120 and the second CCD 125 may include a color filter array and a photodiode.

Therefore, since the camera 100 of the present invention includes a polarization separator 115, there is almost no loss of light compared to the camera 95 of FIG. 4 which acquires an image by two illuminations having different wavelength bands. Since illumination of the same wavelength band can be used to obtain a very bright image for detecting a surface defect of a metal object, surface defects of a metal object moving at high speed can be effectively detected.

7 is a view for explaining the metal surface defect detection apparatus 200 according to an embodiment of the present invention. Referring to FIG. 7, the metal surface defect detecting apparatus 200 may include a camera 100, a first light source 205, and a second light source 210.

The camera 100 includes the components of the camera 100 shown in FIG. 5.

Each of the first light source 205 and the second light source 210 may include a light emitted diode. A xenon lamp or a halogen lamp may be used instead of the light emitting diode (LED). The first light source 205 or the second light source 210 may include an optical filter. The optical filter may be installed on the front surface of the first light source 205 or on the front surface of the second light source 210.

The first light source 205 is illumination in a bright field condition and linearly polarized light, and the second light source 210 is illumination in a dark field condition and linearly polarized light. The bright field condition illumination and the dark field condition illumination are linearly polarized lights having the same wavelength band and orthogonal to each other. The first light source 205 irradiates the surface of the metal object 215 with linearly polarized light under bright field conditions. The first light source 205 may be brightfield illumination and should be disposed at an angle as close to 90 degrees as possible from the surface of the metal object 215 and at an angle of approximately 80 degrees in consideration of the installation of the illumination. May be

The second light source 210 irradiates the surface of the metal object 215 simultaneously with the first light source 205 with linearly polarized light that is orthogonal to the illumination of the first light source 205 in the dark field condition. The second light source 210 may be dark field illumination and may be disposed at an angle that is greater than 0 degrees and less than 45 degrees from the surface of the metal object 215, for example. The angle of the dark field illumination is effective to be adjusted according to the defect characteristics of the metal object.

Bright field illumination indicates illumination with a relatively high angle of illumination (light source). In other words, brightfield illumination is illuminating the light from a metal surface at a high angle so that shadows of metal surface defects do not occur. Dark field illumination indicates illumination with relatively low angles of illumination. In other words, dark field illumination is illumination from a low angle from the metal surface so that the shadow of the metal surface defect is generated as much as possible. These brightfield and darkfield illuminations can distinguish between a change in the image of the camera, whether it is a simple change in color or a defect in the metal surface.

For example, as illustrated in FIG. 7, the first light source 205 and the second light source 210 may be opposite to each other with respect to a vertical line from which the camera 100 acquires a surface reflection image of the metal object 215. Can be arranged. That is, when viewed from above the camera 100, the camera 100 may be disposed between the first light source 205 and the second light source 210.

FIG. 8 is a view for explaining a method of operating the

light sources

205 and 210 shown in FIG. 7. As shown in FIG. 8, the first light source 205 and the second light source 210 may be turned on at the same time and turned off at the same time.

Referring back to FIG. 7, the camera 100 simultaneously acquires a brightfield image and a darkfield image at the same point on the surface of the metal object 215. The camera 100 acquires light (or lights) that are simultaneously irradiated by the first light source 205 and the second light source 210 and reflected from the surface of the metal object 215 to inspect the surface defects of the metal object 215. Acquire an image for.

The metal object 215 may be a stationary metal object (eg, a metal sheet) or a moving metal object.

The metal surface defect detecting apparatus 200 obtains two independent images at the same time by irradiating two

independent lights

205 and 210 of the same wavelength band to the surface of the metal object 215. Each of the

lights

205, 210 includes two linearly polarized lights that are orthogonal to each other. The image signal processing apparatus (not shown) included in the metal surface defect detecting apparatus 200 receives the image information (image signal) acquired by the camera 100, analyzes the signal, and processes the surface of the metal object 215. Detect the type and location of the defect.

The image signal processing apparatus may be connected to a screen output device (not shown) included in the metal surface defect detecting apparatus 200. The screen output apparatus may output a screen of an image processed by the image signal processing apparatus. The image signal processing apparatus may be implemented by hardware, software, or a combination thereof, and may be implemented by a dedicated processor or a computer.

Therefore, the metal surface defect detecting apparatus 200 according to the present invention has two different illumination positions and angles in one shot, compared to the image processing method obtained by the sequential blinking method of illumination illustrated in FIG. 1 or 3. By acquiring, it is possible to inspect the surface defects of a more detailed metal object or to inspect the surface defects of a metal object moving at high speed.

In addition, since the metal surface defect detection apparatus 200 of the present invention acquires images of the simultaneous point, the bright field image and the dark field image may be clearly synchronized. Unlike the surface defect detection device 90 shown in FIG. 3, the present invention does not require an additional device such as an encoder for synchronizing positions of images, thereby reducing the complexity of the camera system, which is an optical system for surface defect detection. The construction cost of the camera system can be significantly reduced.

A metal surface defect detection method according to an embodiment of the present invention is described as follows. The metal surface defect detection method may be applied to the metal surface defect detection apparatus 200 shown in FIG. 7.

The metal surface defect detection method includes a first irradiation step, a second irradiation step, an acquisition step, and a detection step. Referring to FIG. 7, in the first irradiation step, the linearly polarized light in the bright field condition is irradiated onto the surface of the metal object 215 by the first light source 205. The metal object 215 may be a stationary metal object or a moving metal object.

According to the second irradiation step, the linearly polarized light having a wavelength perpendicular to the illumination of the first light source 205 and having the same wavelength as that of the illumination of the first light source 205 in the dark field condition is generated by the second light source 210. As shown in FIG. 8, the surface of the metal object 215 is irradiated at the same time as the bright field illumination by the first light source 205.

According to the obtaining step, the image of the light reflected from the surface of the metal object 215 is acquired by the camera 100 at the same time. The camera 100 may include a polarizing beamsplitter cube.

According to the detecting step, the image signal processing apparatus of the metal surface defect detecting apparatus 200 performs signal processing (for example, digital image signal processing) on the obtained image to detect a surface defect (surface defect image) of the metal object 215. Is detected.

9 is a view for explaining a metal surface defect detection apparatus 300 according to another embodiment of the present invention. Referring to FIG. 9, the metal surface defect detecting apparatus 300 may include a camera unit 305, a first light source 325, a second light source 330, a third light source 335, and a fourth light source. Light source 340.

Each of the first light source 325, the second light source 330, the third light source 335, and the fourth light source 340 may include a light emitting diode, a xenon lamp, or a halogen lamp. The first light source 325, the second light source 330, the third light source 335, or the fourth light source 340 may include an optical filter. The optical filter may be installed on the front surface of the first light source 325, the front surface of the second light source 330, the front surface of the third light source 335, or the front surface of the fourth light source 340.

The center wavelength band of the first light source 325 and the center wavelength band of the fourth light source 340 are the same as the first wavelength λ 1, and the first light source 325 and the fourth light source 340 are Linearly polarized lights that are orthogonal to one another. The center wavelength band of the second light source 330 and the center wavelength band of the third light source 335 are the same as the second wavelength λ2, and the second light source 330 and the third light source 335 are perpendicular to each other. Linearly polarized lights.

The first light source 325 irradiates the surface of the metal object 345 with linearly polarized light having a first wavelength λ 1 at a first angle, and the second light source 330 has a second wavelength λ 2 at a second angle. Linearly polarized light of the metal object 345 is irradiated to the surface of the metal object 345, the third light source 335 is irradiated to the surface of the metal object 345 of the linearly polarized light of the second wavelength (λ2) at a third angle, The light source 340 irradiates the surface of the metal object 345 with linearly polarized light having a first wavelength λ 1 at a fourth angle.

For example, the first angle may be an angle for brightfield illumination, and the second angle, the third angle, and the fourth angle may be an angle for darkfield illumination.

The brightfield illumination should be placed at an angle as close to 90 degrees as possible from the surface of the metal object 345 and may be arranged at an angle of approximately 80 degrees in consideration of the position of the illumination. The dark field illumination may be disposed at an angle that is greater than 0 degrees and less than 45 degrees from the surface of the metal object 345 according to the defect characteristics of the metal object.

The first light source 325, the second light source 330, the third light source 335, and the fourth light source 340 emit the polarizations (lights) in a manner similar to that shown in FIG. 8. Irradiate simultaneously on the surface.

The camera unit 305 includes a first camera 310, a second camera 315, and a dichroic mirror or dichroic beamsplitter 320. The camera unit 305 is irradiated simultaneously by the first light source 325, the second light source 330, the third light source 335, and the fourth light source 340 and reflected from the surface of the metal object 345 ( By acquiring light), an image for inspecting a surface defect of the metal object 345 is obtained.

The color screening mirror 320 separates the light reflected from the surface of the metal object 345 into light having a first wavelength λ 1 and light having a second wavelength λ 2. The dichroic mirror 320 transmits light in the wavelength band of λ1 and reflects light in the wavelength band of λ2 with little loss of light due to the interference effect of light in the multilayer thin film therein. Therefore, the first camera 310 and the second camera 315 can obtain a high-definition video image with little loss of light.

The first camera 310 obtains the light having the first wavelength λ1 separated by the color-dividing mirror 320 into vertical and horizontal polarizations, and uses the obtained vertical and horizontal polarizations to detect the metal object 345. Image for surface defect inspection). The second camera 315 is obtained by dividing the light of the second wavelength λ2 separated from the color-dividing mirror 320 into vertical and horizontal polarizations, and using the obtained vertical and horizontal polarizations, the metal object 345. Image for surface defect inspection). The first camera 310 or the second camera 315 includes the components of the camera 100 shown in FIG. 5.

The metal object 345 may be a stationary metal object (eg, a metal sheet) or a moving metal object.

The metal surface defect detecting apparatus 300 may simultaneously irradiate the surface of the metal object 345 with four independent polarization lights 325, 330, 335, and 340 of two different wavelength bands λ 1 and λ 2. Acquire four independent images of time at the same time.

The image signal processing apparatus (not shown) included in the metal surface defect detecting apparatus 300 receives the image information acquired by the camera unit 305, analyzes the signal, and processes the signal to form a surface defect of the metal object 345. Detect and position.

The image signal processing apparatus may be connected to a screen output device (not shown) included in the metal surface defect detecting apparatus 300. The screen output apparatus may output a screen of an image processed by the image signal processing apparatus. The image signal processing apparatus may be implemented by hardware, software, or a combination thereof, and may be implemented by a dedicated processor or a computer.

Therefore, the metal surface defect detecting apparatus 300 according to the present invention has an image having positions and angles of four different illuminations in one shot as compared to the image processing method obtained by the sequential blinking method of illumination illustrated in FIG. 1 or 3. By acquiring, it is possible to inspect the surface defects of a more detailed metal object or to inspect the surface defects of a metal object moving at high speed.

Since the metal surface defect detecting apparatus 300 of the present invention acquires an image of a simultaneous point, the bright field image and the dark field image may be clearly synchronized. Unlike the surface defect detection device 90 shown in FIG. 3, the present invention does not require an additional device such as an encoder for synchronizing positions of images, thereby reducing the complexity of the camera system, which is an optical system for surface defect detection. The construction cost of the camera system can be significantly reduced.

In addition, the metal surface defect detection apparatus 300 of the present invention uses four different illuminations by distinguishing horizontal polarization and vertical polarization for illuminations of the same wavelength band when the illumination having two different wavelengths is used. Images according to the position and angle of can be acquired simultaneously. Accordingly, the present invention may have an improved metal surface defect detection rate than the surface defect detection device 90 shown in FIG. 3.

Referring to FIG. 10, the first light sources λ1 and 325 and the fourth light sources λ1 and 340 are disposed to face each other with respect to the camera unit 305 (or to the center), and the second light sources λ2 and 330. ) And the third light sources λ2 and 335 are disposed to face each other with respect to the camera unit 305. The first light source λ1 and the fourth light source λ1, which are the first illumination pair, are disposed to be perpendicular to the second light source λ2 and the third light source λ2, which are the second illumination pair.

That is, when viewed from above the camera unit 305, the camera unit 305 is disposed between the first light source λ1 and the fourth light source λ1, and between the second light source λ2 and the third light source λ2. The first light source λ1 and the fourth light source λ1 are arranged perpendicularly (orthogonally) with respect to the second light source λ2 and the third light source λ2.

Referring to FIG. 11A, since the width of the defect DEFECT of the metal object is narrow in the direction of the first light source λ1 and the direction of the fourth light source, the defect is caused by the first light source λ1 and the fourth light source λ1. Although the detection probability of DEFECT is low, the width of the defect DEFECT of the metal object is wide in the direction of the second light source λ2 and the direction of the third light source λ2, so that the second light source λ2 and the third light source are By (λ2), the probability of detecting a defect is high.

Referring to FIG. 11B, since the width of the defect DEFECT of the metal object is narrow in the direction of the second light source λ2 and the direction of the third light source λ2, the second light source λ2 and the third light source λ2 may be formed. Although the detection probability of the defect DEFECT is low, the width of the defect DEFECT of the metal object is wide in the direction of the first light source λ1 and the direction of the fourth light source λ1. The fourth light source λ1 has a high probability of detecting a defect DEFECT.

Accordingly, the embodiment of the illumination arrangement shown in FIG. 10 can improve the probability of detecting a defect regardless of the shape of the defect or the direction of the defect.

A metal surface defect detection method according to another embodiment of the present invention is described as follows. The metal surface defect detection method may be applied to the metal surface defect detection apparatus 300 shown in FIG. 9.

The metal surface defect detection method includes a first irradiation step, a second irradiation step, a third irradiation step, a fourth irradiation step, an acquisition step, and a detection step. 9, in the first irradiation step, linearly polarized light having a first wavelength λ1 at a first angle is irradiated onto the surface of the metal object 345 by the first light source 325. The metal object 345 may be a stationary metal object or a moving metal object. The first angle may be an angle for brightfield illumination or darkfield illumination.

According to the second irradiation step, the linearly polarized light of the second wavelength λ2 at the second angle is irradiated onto the surface of the metal object 345 by the second light source 330. The second angle may be an angle for brightfield illumination or darkfield illumination.

According to the third irradiating step, the linearly polarized light of the second wavelength λ2 orthogonal to the linearly polarized light of the second wavelength λ2 at a third angle of the metal object 345 by the third light source 335. Irradiated to the surface. The third angle may be an angle for brightfield illumination or darkfield illumination.

According to the fourth irradiating step, the linearly polarized light of the first wavelength λ1 orthogonal to the linearly polarized light of the first wavelength λ1 at a fourth angle is transferred to the metal object 345 by the fourth light source 340. Irradiated to the surface. The fourth angle may be an angle for brightfield illumination or darkfield illumination.

In the first to fourth irradiation steps, the illumination of the first wavelength and the illumination of the second wavelength are simultaneously irradiated in a manner similar to that shown in FIG. 8.

According to the acquiring step, the illumination of the first to fourth irradiation steps is irradiated so that an image of light reflected from the surface of the metal object 345 is simultaneously acquired by the camera unit 305. The camera unit 305 includes a first camera 310, a second camera 315, and a color screening mirror 320.

According to the detecting step, the image signal processing apparatus of the surface defect detection apparatus 300 performs signal processing (for example, digital image signal processing) on the obtained image to detect surface defects (surface defect images) of the metal object 345. Detect.

As described above, the embodiments are disclosed in the drawings and the specification. Herein, specific terms have been used, but they are used only for the purpose of illustrating the present invention and are not used to limit the scope of the present invention as defined in the meaning or claims. Therefore, it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible from the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims

A polarization separator that separates light reflected from the surface of the metal object into vertically and horizontally polarized light when simultaneously irradiating orthogonal linearly polarized lights on the surface of the metal object;

A first charge coupled device obtaining an image of the vertical polarization; And

Camera comprising a second charge coupled device for obtaining the image of the horizontal polarization.
The method of claim 1,

Wherein the polarizer is a polarizing beamsplitter cube.
A first light source for irradiating the surface of the metal object with linearly polarized light under bright field conditions;

A second light source for irradiating the surface of the metal object with the first light source simultaneously with the first light source in a dark field condition with the linearly polarized light orthogonal to each other and having the same wavelength as that of the linearly polarized light; And

And a camera acquiring an image for inspecting a surface defect of the metal object by acquiring light reflected from the surface of the metal object.
The method of claim 3, wherein the camera,

A polarization separator that separates the light reflected from the surface of the metal object into vertical polarization and horizontal polarization;

A first charge coupled device obtaining the image of the vertical polarization; And

And a second charge coupling device for acquiring the image of the horizontal polarization.
The method of claim 4, wherein

And the polarization separator is a polarization beam splitter cube.
The method of claim 3,

The metal object is a metal surface defect detection device is a stationary metal object or a moving metal object.
A first light source for irradiating the surface of the metal object with linearly polarized light having a first wavelength in bright field conditions;

A second light source for irradiating a surface of the metal object with linearly polarized light having a second wavelength under dark field conditions;

A third light source for irradiating a surface of the metal object with a linearly polarized light having a second wavelength orthogonal to the linearly polarized light of the second wavelength in a dark field condition;

A fourth light source for irradiating the surface of the metal object with the linearly polarized light having a first wavelength orthogonal to the linearly polarized light having the first wavelength in a dark field condition; And

A camera unit which acquires an image for inspecting surface defects of the metal object by acquiring light reflected from the surface of the metal object;

And the first light source, the second light source, the third light source, and the fourth light source irradiate lights simultaneously.
The method of claim 7, wherein

The camera unit is disposed between the first light source and the fourth light source, and between the second light source and the third light source, wherein the first light source and the fourth light source are disposed with respect to the second light source and the third light source. Metal surface defect detection device arranged to be orthogonal.
The method of claim 7, wherein the camera unit,

A color screening mirror that separates the light reflected from the surface of the metal object into light of the first wavelength and light of the second wavelength;

A first camera that obtains light of a first wavelength separated from the color-dividing mirror into vertical and horizontal polarizations, and acquires an image for inspecting surface defects of the metal object by using the obtained vertical and horizontal polarizations ; And

A second camera obtained by dividing the light having the second wavelength separated from the dichroic mirror into vertical polarization and horizontal polarization and acquiring an image for inspecting the surface defect of the metal object using the obtained vertical and horizontal polarization; Metal surface defect detection device comprising a.
The method of claim 9, wherein the first camera,

A polarization separator that separates light of the first wavelength separated from the dichroic mirror into the vertical polarization and the horizontal polarization;

A first charge coupling device obtaining an image of vertical polarization separated by the polarization separator; And

Metal surface defect detection device comprising a second charge coupling device for obtaining an image of the horizontal polarization separated by the polarization separator.
The method of claim 9, wherein the second camera,

A polarization separator that separates light having a second wavelength separated from the dichroic mirror into the vertical polarization and the horizontal polarization;

A first charge coupling device obtaining an image of vertical polarization separated by the polarization separator; And

Metal surface defect detection device comprising a second charge coupling device for obtaining an image of the horizontal polarization separated by the polarization separator.
The method of claim 7, wherein

The metal object is a metal surface defect detection device is a stationary metal object or a moving metal object.
A first light source for irradiating the surface of the metal object with linearly polarized light having a first wavelength at a first angle;

A second light source for irradiating a surface of the metal object with linearly polarized light having a second wavelength at a second angle;

A third light source for irradiating a surface of the metal object with the linearly polarized light of the second wavelength orthogonal to the linearly polarized light of the second wavelength at a third angle;

A fourth light source for irradiating the surface of the metal object with the linearly polarized light of the first wavelength orthogonal to the linearly polarized light of the first wavelength at a fourth angle; And

A camera unit for acquiring an image for inspecting a surface defect of the metal object by acquiring light reflected from the surface of the metal object;

The first light source, the second light source, the third light source, and the fourth light source irradiate lights simultaneously, and the first angle, the second angle, the third angle, or the fourth angle is bright field. Metal surface defect detection device at an angle for illumination or dark field illumination.
(a) irradiating the surface of the metal object with linearly polarized light under bright field conditions;

(b) irradiating the surface of the metal object at the same time as the irradiation of the linearly polarized light in the bright field conditions orthogonal to the linearly polarized light in the dark field conditions and having the same wavelength as the wavelength of the linearly polarized light; Doing;

(c) simultaneously acquiring an image of light reflected from the surface of the metal object; And

(d) detecting a surface defect of the metal object by signal processing the obtained image.
(a) irradiating a surface of the metal object with linearly polarized light of a first wavelength at a first angle;

(b) irradiating a surface of the metal object with linearly polarized light of a second wavelength at a second angle;

(c) irradiating a surface of the metal object with a linearly polarized light of a second wavelength orthogonal to the linearly polarized light of the second wavelength at a third angle;

(d) irradiating a surface of the metal object with linearly polarized light of a first wavelength orthogonal to the linearly polarized light of the first wavelength at a fourth angle;

(e) simultaneously acquiring an image of light reflected from the surface of the metal object; And

(f) signal-processing the obtained image to detect surface defects of the metal object;

The illumination of the first wavelength and the illumination of the second wavelength are simultaneously irradiated and the first angle, the second angle, the third angle, or the fourth angle is an angle for brightfield illumination or darkfield illumination. Metal surface defect detection method.