JP7136064B2 - Apparatus for inspecting surface of object to be inspected and method for inspecting surface of object to be inspected - Google Patents

Description

The present invention relates to a surface inspection apparatus for an object to be inspected and a surface inspection method for an object to be inspected.

In a surface inspection apparatus installed in a metal strip production line, it is common at present to illuminate an inspection point with a single light source and take an image with a single camera or a plurality of camera angles. These devices use a monochrome or color line scan camera to image the surface of the metal strip and detect defects such as scratches and stains. Many of the flaws on the surface of the metal strip have a long shape in the direction in which the strip advances.

As a surface inspection apparatus installed in a conventional metal strip production line as described above, Patent Document 1 discloses a surface inspection apparatus that irradiates an inspection point with a single light source and captures images with a single camera or multiple camera angles. It is

Further, in Patent Document 2, the same line in the width direction of the surface of the running metal strip is irradiated with light beams having different wavelengths from three or more linear light sources such as RGB light sources in parallel from different directions. A method for inspecting the surface of a metal strip is described in which the lines are scanned and imaged by a line scan camera capable of detecting the light.

In Patent Document 3, white illumination light is split by a spectroscopic prism, the split illumination light is condensed by a condensing lens, is irradiated onto a surface to be inspected, and the reflected light is imaged by a two-dimensional color sensor. discloses a method of detecting defects on a surface to be inspected and discriminating the types of defects from color video signals of different colors according to the types of defects.

JP-A-5-188010 JP 2019-39798 A JP-A-9-196859

In conventional surface inspection methods including Patent Document 1, a straight light source or an oblique light source is used as it is to irradiate the surface of an object to be inspected and image the brightness of a defective portion such as a flaw. Since it is necessary to determine the shape of a defect such as a flaw only from information on the brightness of the image, there is a problem that it is difficult to accurately estimate the shape of the defect.

In the inspection method of Patent Literature 2, it is possible to detect tilts in any direction with respect to surface defects, but three or more light sources are used, and the number of components in the apparatus increases, making the apparatus large. In addition, since all the light sources used are monochromatic light sources, it is difficult to obtain continuous information about the angle corresponding to the color that is the boundary between each color, and the information becomes discrete, which reduces the detection accuracy of the defect shape. trend.

In the inspection method of Patent Literature 3, a single spot light source is focused after being dispersed. It is difficult to adopt an inspection method that involves imaging. Also, the detection accuracy is lowered in a region distant from the condensing point.

The present invention is a surface inspection apparatus for an object to be inspected and an object to be inspected, which has a simple configuration using a single light source and is capable of using light composed of continuous wavelength components for detecting surface defects of the object to be inspected. It is an object of the present invention to provide a surface inspection method for

The gist of the present invention is as follows.
[1] A surface inspection device for an object to be inspected,
a light source that emits white parallel light;
spectroscopic means for dispersing the parallel white light emitted from the light source into continuous wavelength components;
Equipped with a color line scan camera,
The light source and the spectroscopic means are installed so that the light composed of continuous wavelength components separated by the spectroscopic means is irradiated in a line on the surface of the object to be inspected,
The color line scan camera is a surface inspection apparatus for an object to be inspected, which captures an image of reflected light of light composed of continuous wavelength components that is linearly irradiated onto the surface of the object to be inspected.
[2] The light source and the spectroscopy means are configured such that, when viewed from the front of the light source, the light of the wavelength component in the central region of the light composed of continuous wavelength components linearly irradiated onto the surface of the object to be inspected is The surface inspection apparatus for an object to be inspected according to [1], which is installed so that the surface of the object to be inspected is irradiated perpendicularly.
[3] The surface inspection apparatus for an object to be inspected according to [2], wherein the light of the wavelength component in the central region is green light.
[4] The surface inspection apparatus for an object to be inspected according to any one of [1] to [3], wherein the light source is an oblique light source.
[5] The device for inspecting the surface of the object to be inspected is a device for inspecting the surface of the object to be inspected that moves,
The light source and the spectroscopic means are arranged such that the light composed of continuous wavelength components separated by the spectroscopic means is irradiated onto the surface of the object to be inspected in a line perpendicular to the moving direction of the object to be inspected. The installed surface inspection apparatus for an object to be inspected according to any one of [1] to [4].
[6] Further comprising an arithmetic device having tilt angle calculation means for calculating the tilt angle of the surface of the object to be inspected based on the color image captured by the color line scan camera, [1] to [5] ] The surface inspection apparatus for an object to be inspected according to any one of
[7] A surface inspection method for an object to be inspected,
Parallel white light emitted from a light source is separated into continuous wavelength components,
irradiating the surface of the object to be inspected with the light composed of the continuous wavelength components separated into a line,
A method for inspecting the surface of an object to be inspected, wherein the surface of the object to be inspected is linearly irradiated and the reflected light of the light composed of continuous wavelength components is imaged by a color line scan camera.
[8] Light of wavelength components in a central region of light composed of continuous wavelength components irradiated linearly on the surface of the object to be inspected is perpendicular to the surface of the object to be inspected when viewed from the front of the light source. The surface inspection method for an object to be inspected according to [7], wherein the irradiation is performed so that the
[9] The surface inspection method for an object to be inspected according to [8], wherein the light of the wavelength component in the central region is green light.
[10] The surface inspection method for an object to be inspected according to any one of [7] to [9], wherein an oblique light source is used as the light source.
[11] The method for inspecting the surface of an object to be inspected is a method for inspecting the surface of a moving object to be inspected,
The object according to any one of [7] to [10], wherein the light composed of the dispersed continuous wavelength components is irradiated onto the surface of the object to be inspected in a line perpendicular to the moving direction of the object to be inspected. A method for inspecting the surface of an object to be inspected.
[12] The surface inspection of the object to be inspected according to any one of [7] to [11], wherein the inclination angle of the surface of the object to be inspected is calculated based on the color image captured by the color line scan camera. Method.

According to the present invention, there is provided a surface inspection apparatus for an object to be inspected, which has a simple configuration using a single light source and is capable of using light composed of continuous wavelength components for detecting surface defects of the object to be inspected. A method for inspecting the surface of an inspection object can be provided.

According to the present invention, continuous tilt angle information of the surface of an object to be inspected can be obtained by using light composed of continuous wavelength components for detecting surface defects of the object to be inspected. This makes it possible to further improve the detection accuracy of the defect shape.

FIG. 1 is a schematic diagram (side view) illustrating the configuration of a surface inspection apparatus for an object to be inspected according to one embodiment of the present invention. 2 is a front view of FIG. 1. FIG. FIG. 3 is a schematic diagram showing an example of an image captured by the surface inspection apparatus for an object to be inspected according to the present invention.

The present invention enables an optical camera and human eyes to recognize colors using three wavelength regions of RGB, and uses spectroscopy to detect light of a plurality of wavelength components at a plurality of angles on the same straight line on the surface of an object to be inspected. can be irradiated. That is, a collimated white light source of visible light that is long in the width direction with respect to an object to be inspected such as a metal band is used, and a spectroscopic means that disperses the collimated white light from the light source into continuous wavelength components is provided on the light source side. An image is acquired by irradiating the surface of an object with light of a plurality of wavelength components separated by a plurality of angles and capturing the reflected light with a color line scan camera.

According to the present invention, parallel white light emitted from a linear parallel white light source elongated in the width direction of an object to be inspected is dispersed into wavelength components that are continuous in the width direction of the object to be inspected. Since the incident angle of the wavelength component is uniformly divided for each wavelength component (color component) in , the hue and color imaged by the color line scan camera are determined depending on the incident angle of the reflected light with respect to the uneven surface of the object to be inspected. The color temperature will change, and it will be possible to detect surface defects and estimate the shape of the surface defects.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram (side view) illustrating the configuration of a surface inspection apparatus for an object to be inspected according to one embodiment of the present invention, and FIG. 2 is a front view thereof.

The object to be inspected in the present invention includes a metal band (metal plate), paper, and the like. The object to be inspected is preferably plate-shaped or sheet-shaped. In addition, in this embodiment, a steel strip (steel plate) will be described as an example of an object to be inspected. Specifically, in this embodiment, an example of detecting surface defects in a steel strip running in a continuous steel strip threading facility will be described. As shown in FIG. 1, in this embodiment, the steel strip S, which is the object to be inspected, is moving in the direction of the arrow.

A surface inspection apparatus 1 for an object to be inspected shown in FIG. A spectroscopic means 12 for dispersing light into specific wavelength components and a color line scan camera 14 are provided.

As shown in FIGS. 1 and 2, the light source 10 emits white parallel light L1. The white parallel light L1 includes wavelength components in the visible light region. As the light source 10, a light source containing a wide range of wavelength components is preferred. Further, the light source 10 is preferably a light source that emits white light with high directivity (straightness). Examples of the light source 10 include LED, halogen, metal halide, and the like. The light source 10 can be configured by arranging elements that emit white light, such as LEDs, in a line. Thereby, the light source 10 can emit uniform white parallel light in a line.

As shown in FIG. 2 , in this embodiment, an oblique light source is used as the light source 10 , and the light source 10 emits parallel white light L<b>1 obliquely to the irradiation surface 11 .

The spectral means 12 is arranged on the optical path of the white parallel light L1 and between the light source 10 and the object to be inspected (steel strip S). A prism or the like may be used as the spectroscopic means 12 . The spectroscopic means 12 can be configured by, for example, arranging small prisms in a line. A slit or the like may be arranged between the light source 10 and the spectroscopic means 12 .

The spectral means 12 splits the parallel white light L1 emitted from the light source 10 into continuous wavelength components. Then, the surface of the steel strip S is irradiated with light (hereinafter also referred to as "spectral light L2") composed of continuous wavelength components (continuous spectrum) that has been dispersed (see FIG. 2). It should be noted that the spectral light L2 by the spectroscopic means 12 may be obtained by discretizing the total spectral angle by 90 divisions or more. This is because, in order to detect surface defects of an object to be inspected, if it is divided into 90 or more, it can be considered that the spectrum is divided into continuous wavelength components.

The light source 10 and the spectroscopic means 12 are installed so that the surface of the steel strip S is irradiated with the spectral light L2 separated by the spectroscopic means 12 in a line. Such an installation method is not particularly limited. or adjusting the relative positions of the light source 10 and the spectroscopic means 12, and the like. Using an oblique light source as the light source 10 facilitates the adjustment. By such adjustment, the parallel white light L1 is split into continuous wavelength components in the same plane, and thereby the surface of the steel strip S is irradiated with the spectral light L2 in a line.

Furthermore, the light source 10 and the spectroscopic means 12, of the spectral light L2 linearly irradiated onto the surface of the steel strip S, emit light of wavelength components in the central region, as seen from the front of the light source 10, of the steel strip. It is preferably installed so that the S surface is illuminated perpendicularly. When installed in this manner, the wavelength components can be uniformly irradiated in the horizontal width direction of the steel strip S, which is the object to be inspected. This makes it easier to detect various angular changes on the surface of the object to be inspected.

In this embodiment, as shown in FIG. 2, the light source 10 and the spectroscopic means 12 are arranged so that the green light, which is the wavelength component in the central region of the spectral light L2, is projected onto the surface of the steel strip S when viewed from the front of the light source 10. Installed so that the light is emitted vertically. As a result, the wavelength components (color components) can be uniformly irradiated in the horizontal width direction of the steel strip S, which is the object to be inspected, with the green light at the center. That is, with green light at the center, continuous wavelength components from green to yellow and yellow to red from the center to the area on the right side of the paper, and continuous wavelength components from green to light blue and from light blue to blue from the center to the area on the left side of the paper. wavelength components can be irradiated. This makes it easier to detect various angular changes on the surface of the object to be inspected. Furthermore, it becomes easier to detect the various angular changes as changes in hue and color temperature.

Further, the light source 10 and the spectroscopic means 12 are preferably installed so that all wavelength components of the spectral light L2 are irradiated over the entire width direction of the object to be inspected. For example, as shown in FIG. 2, when viewed from the front of the light source 10, the right end in the width direction of the surface of the steel strip S, which is the object to be inspected, is irradiated with the blue wavelength component, and the left end is irradiated with the red wavelength component. When installed, the entire width of the steel strip S can be irradiated with all the wavelength components of the spectral light L2. This makes it easier to detect an angular change across the entire surface of the steel strip S in the width direction. Such an installation method is not particularly limited, but includes, for example, a method of adjusting the lengths of the light source 10 and the spectroscopic means 12 in the width direction.

When inspecting the surface of a moving inspection object as in this embodiment, the light source 10 is arranged so that the line of the spectral light L2 irradiated onto the surface is perpendicular to the moving direction of the inspection object. and spectroscopic means 12 are preferably installed. In particular, when the object to be inspected is a metal band, full-width inspection is often required, and the light source and camera field of view must cover the entire width of the metal band. In such a case, if the moving direction of the object to be inspected and the line of the spectral light L2 are not perpendicular to each other, it will be necessary to widen the light source and camera field of view by the angle. It becomes necessary to correct the position by the angle, and the inspection efficiency tends to decrease.

If the object to be inspected has warpage in the width direction, it is preferable to inspect the surface of the object to be inspected in a state in which the warpage is suppressed by restraining the object to be inspected with a roll or the like. Further, when the object to be inspected has warpage in the width direction, the obtained information such as the color temperature may be subjected to a band-pass filter to remove the influence of warpage.

The color line scan camera 14 is installed at a position capable of capturing the reflected light L3 of the spectral light L2 linearly irradiated as described above.

A color image obtained by the color line scan camera 14 is appropriately transferred to an arithmetic unit (not shown) such as a personal computer for processing. Then, the result is displayed on a monitor (not shown) connected to the arithmetic unit.

In the color image, the spectroscopic light L2 composed of continuous wavelength components is irradiated onto the surface of the object to be inspected. In a portion where the reflection angle differs from the normal portion due to such factors as the above, the reflection distribution has a different tendency depending on the wavelength component, resulting in a difference in hue. This makes it possible to detect surface defects of the object to be inspected.

Further, the surface inspection apparatus of the present embodiment includes an arithmetic device having image conversion means, tilt angle calculation means, uneven shape calculation means, and data coupling means.

The image conversion means performs a process of converting a color image acquired by a color line scan camera into a color temperature. The tilt angle calculation means performs a process of calculating the tilt angle from the color temperature. Thereby, the inclination angle of the surface of the object to be inspected can be obtained based on the color image.

Further, the concave-convex shape calculating means performs a process of calculating a two-dimensional or three-dimensional shape of the concave and convex from the inclination angle. The data combining means performs a process of converting the two-dimensional or three-dimensional shape into surface information. Through these processes, the detected uneven shape can be displayed on the monitor as surface information.

In this embodiment, the process of converting the color image into the color temperature is performed, and then the process of calculating the tilt angle is performed. However, the present invention is not limited to this. If the inclination angle can be calculated directly from the color image, the process of converting to color temperature may not be performed, or the process of converting to parameters other than color temperature may be performed. In addition, in the present embodiment, processing for converting the calculated two-dimensional or three-dimensional shape of unevenness into surface information is performed, but the present invention is not limited to this. For example, the color image may be converted into surface information and then converted into color temperature.

Next, as an example of the method for inspecting the surface of an object to be inspected according to the present invention, a surface inspection method for an object to be inspected (steel strip S) using the above-described surface inspection apparatus 1 is performed, as shown in FIG. A case where the cross-sectional concave defect 20 is imaged will be described.

In this case, a color image having color information as shown in FIG. 3(b) can be obtained. Note that the color image shown in FIG. 3(b) is obtained by converting linear data picked up by a color line scan camera into surface information and displaying it.

In FIG. 3B, the surface of the steel strip S, which is the object to be inspected, is irradiated with spectral light L2 composed of continuous wavelength components, so that the normal portion B (portion without surface defects such as unevenness) Get achromatic reflected light. In a portion where the reflection angle differs from that of a normal portion due to unevenness or the like, the reflection distribution has a different tendency depending on the wavelength component.

Specifically, in FIG. 3B, the central region in the width direction of the concave defect 20 exhibits white color corresponding to the wavelength components of the spectral light L2 shown in FIG. The hue tendency changes continuously from white to yellowish white and from yellowish white to red toward the area, and the hue tendency continuously changes from white to bluish white and from bluish white to blue from the central area to the area on the left side of the paper surface. An image in which is changed is obtained.

Furthermore, when a color image as described above is obtained, the wavelength of red or blue becomes extremely strong depending on the inclination and orientation in the width direction, resulting in a difference in color temperature. By analyzing this, it becomes possible to estimate whether the defect has an uneven surface and what kind of shape it has.

Specifically, when the above-described color image is converted into color temperature, the color temperature increases in regions where blue wavelengths are strong, and decreases in regions where red wavelengths are strong. Therefore, by associating the color temperature with the tilt angle, the tilt angle can be calculated from the color temperature. Furthermore, by calculating the two-dimensional or three-dimensional shape of the unevenness from the inclination angle, the two-dimensional or three-dimensional shape of the defect can be estimated.

In the present invention, since spectral light composed of continuous wavelength components is used for detecting surface defects, continuous information such as tilt angles can be obtained. Therefore, it becomes possible to detect the defect shape more precisely.

As described above, according to the surface inspection apparatus and the surface inspection method of an object to be inspected according to the present invention, the configuration is simple using a single light source, and the light composed of continuous wavelength components is applied. It can be used to detect surface defects of an object to be inspected. As a result, it is possible to obtain continuous information about the surface of the object to be inspected, and it is possible to further improve the detection accuracy of the shape of the defect.

In the present invention, the surface of an object to be inspected is irradiated with spectral light composed of continuous wavelength components, and the reflected light is imaged. This makes it possible to use incident light of a plurality of wavelength components that are incident at a plurality of angles, and to continuously detect changes in the inclination angles of the unevenness in more detail. This makes it possible to estimate the uneven shape with higher accuracy. According to the present invention, the unevenness of surface defects can be clearly detected, and the shape of fine unevenness can be detected. While improving the detection accuracy of surface defects, highly accurate defect detection is possible with a compact configuration. Become.

1 Surface Inspection Apparatus 10 for Inspection Object Light Source 12 Spectroscopic Means 14 Color Line Scan Camera L1 White Parallel Light L2 Spectroscopic Light L3 Reflected Light S Object (Steel Strip)

Claims (12)

A surface inspection device for an object to be inspected,
a light source that emits white parallel light;
spectroscopic means for dispersing the parallel white light emitted from the light source into continuous wavelength components;
Equipped with a color line scan camera,
The light source and the spectroscopic means are installed so that the light composed of continuous wavelength components separated by the spectroscopic means is linearly irradiated onto the surface of the object to be inspected, and the surface of the object to be inspected is installed so that the light of the wavelength component in the central region of the light composed of continuous wavelength components irradiated linearly to the light source is vertically irradiated to the surface of the object to be inspected when viewed from the front of the light source,
The color line scan camera is a surface inspection apparatus for an object to be inspected, which captures an image of reflected light of light composed of continuous wavelength components that is linearly irradiated onto the surface of the object to be inspected. 2. The surface inspection apparatus for an object to be inspected according to claim 1 , wherein the light of wavelength components in said central region is green light. 3. A surface inspection apparatus for an object to be inspected according to claim 1, wherein said light source is an oblique light source. A surface inspection device for an object to be inspected,
a light source that emits white parallel light;
spectroscopic means for dispersing the parallel white light emitted from the light source into continuous wavelength components;
Equipped with a color line scan camera,
The light source and the spectroscopic means are installed so that the light composed of continuous wavelength components separated by the spectroscopic means is irradiated in a line on the surface of the object to be inspected,
The color line scan camera captures reflected light of light composed of continuous wavelength components linearly irradiated onto the surface of the object to be inspected ,
A surface inspection apparatus for an object to be inspected , wherein the light source is an oblique light source . The apparatus for inspecting the surface of the object to be inspected is a surface inspection apparatus for the object to be inspected that moves,
The light source and the spectroscopic means are arranged such that the light composed of continuous wavelength components separated by the spectroscopic means is irradiated onto the surface of the object to be inspected in a line perpendicular to the moving direction of the object to be inspected. A surface inspection apparatus for an object to be inspected according to any one of claims 1 to 4, which is installed. 6. The apparatus according to any one of claims 1 to 5, further comprising an arithmetic unit having tilt angle calculation means for calculating the tilt angle of the surface of the object to be inspected based on the color image captured by the color line scan camera. A surface inspection apparatus for an object to be inspected as described. A surface inspection method for an object to be inspected,
Parallel white light emitted from a light source is separated into continuous wavelength components,
The surface of the object to be inspected is irradiated linearly with the light composed of the spectrally divided continuous wavelength components, and the center of the light composed of the continuous wavelength components linearly irradiated onto the surface of the object to be inspected irradiating the light of the wavelength component of the region so as to be perpendicular to the surface of the object to be inspected when viewed from the front of the light source;
A method for inspecting the surface of an object to be inspected, wherein the surface of the object to be inspected is linearly irradiated and the reflected light of the light composed of continuous wavelength components is imaged by a color line scan camera. 8. The surface inspection method for an object to be inspected according to claim 7 , wherein the light of the wavelength component in the central region is green light. 9. The surface inspection method for an object to be inspected according to claim 7 , wherein an oblique light source is used as said light source. A surface inspection method for an object to be inspected,
Parallel white light emitted from a light source is separated into continuous wavelength components,
irradiating the surface of the object to be inspected with the light composed of the continuous wavelength components separated into a line,
photographing the reflected light of the light composed of continuous wavelength components irradiated linearly on the surface of the object to be inspected with a color line scan camera ;
A surface inspection method for an object to be inspected , wherein an oblique light source is used as the light source . The method for inspecting the surface of the object to be inspected is a method for inspecting the surface of the object to be inspected that moves,
The object to be inspected according to any one of claims 7 to 10, wherein the surface of the object to be inspected is irradiated with the light composed of the dispersed continuous wavelength components in a line perpendicular to the moving direction of the object to be inspected. surface inspection method. 12. The surface inspection method of an object to be inspected according to claim 7, wherein the inclination angle of the surface of the object to be inspected is calculated based on the color image captured by the color line scan camera.

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