JPH06109622A - Method and device for examining object surface - Google Patents

Abstract

PURPOSE:To make examination of presence of oil stain and surface condition possible by irradiating the space enclosed with a mirror face formed over the surface to be examined with light, taking out the light reflected multiple times and then examining the condition of the surface to be examined based upon that. CONSTITUTION:A light reflection space forming body 12, hemispherical, whose inside surface is gold plated is provided so that it encloses a surface to be examined 11, and an infrared ray is emitted through a light introducing opening 13 attached to the forming body 12. The infrared ray is reflected on a surface 11 to be examined, and the most of it hits on the inside surface of the forming body 12 to repeat reflections. The light of specific wave length is absorbed due to the stain sticking to the surface to be examined 11 in time, and so the difference of light quantity between non-absorption band and absorption band becomes larger. Thus the light containing constant light quantity over a brood wave length area is supplied, to make the light quantity difference, between absorbing band and non-absorbing band, conspicuous. Then it is taken out from the light take-out opening 14 of the forming body 12 for examination. Its pattern agrees with the spectrum obtained by directly irradiating the stain material with infrared ray. So, with this method, a trace of stain can be more conspicuous for its detection to be possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object surface inspection method and an inspection apparatus for detecting oil, rust, etc. adhering to the surface of an object such as a steel plate in a continuous annealing or cold rolling process.

[0002]

2. Description of the Related Art At present, in order to detect the surface condition of an object, for example, a flaw on the surface of a steel sheet during cold rolling or continuous annealing, H
A method of irradiating a steel plate surface with e-Ne laser light, semiconductor laser light, or the like and analyzing a speckle pattern generated by scattering of laser light has been put into practical use. Since the speckle pattern is generated by light scattering, it is particularly effective for detecting sharp scratches having unevenness on the steel plate surface.

[0003]

On the other hand, in the rolling process, when the steel sheet is passed between the rolling rolls, an oil mist is sprayed onto the rolling rolls, and this oil mist is rolled in a state of adhering to the surface of the steel sheet. And it becomes a pattern of dirt. In addition to the above, stains include oil spots such as rolling oil and pressure-regulating oil, striped stains called tiger marks, carbon adhesion, and rust.

[0004] Such stains are generally extremely thin film-like, and since no unevenness is formed on the surface of the steel sheet, no speckle pattern is generated. Further, even when the spot-shaped spots are attached, since the outline is generally unclear, the change from the non-dirt portion to the spot-attached portion is gentle and a speckle pattern is unlikely to occur. Furthermore, these stains exhibit various colors from yellowish brown to black depending on the type of stain, and may exhibit uneven gloss, but since the laser light is monochromatic light, the absorption wavelength of the stain is It cannot be detected unless it matches the laser beam. For example, in a flaw detection system using He-Ne laser light (wavelength λ = 6328Å),
Red stains cannot be detected.

As described above, in the conventional laser-based flaw detection system, like the oil stains on the steel plate surface,
Abnormalities in the surface state that do not cause unevenness on the surface cannot be detected.
This applies not only to the surface of the steel sheet but also to dirt attached to the surface of another object having no unevenness on the surface. The present invention has been made in view of such circumstances, and an object thereof is to provide an abnormality in which unevenness does not occur on an object surface, for example, an abnormality in a surface state caused by dirt such as oil adhesion. An object of the present invention is to provide an inspection method and an inspection device that can detect

[0006]

A method of inspecting an object surface according to the present invention comprises forming a space covered by a mirror surface on an inspection surface,
The space is irradiated with light, the light is multiple-reflected between the inspection surface and the mirror surface, the multiple-reflected light is extracted from the space, and the property of the inspection surface is inspected based on the extracted light. It is characterized.

Infrared rays or visible rays are used as the light, and the properties of the inspection surface are inspected based on the absorption spectrum of the extracted light. The object surface inspection apparatus of the present invention is a light reflection space forming body that covers an inspection surface with a mirror-finished inner wall surface to form an inspection space that multiple-reflects light between the inspection surface and the inner wall surface. The light reflection space forming body has a light inlet for taking in light into the inspection space, and a light outlet for taking out multiple reflected light between the inspection surface and the inner wall surface. It is characterized in that a light source is connected to the light intake opening, and an inspection unit for inspecting the properties of the inspection surface based on the extracted light is connected to the light extraction opening. .

[0008]

When light is irradiated on the inspection surface into the space covered by the mirror surface, the light is repeatedly reflected between the inspection surface and the mirror surface (hereinafter referred to as "multiple reflection"). On the other hand, of the irradiated light, light having a specific wavelength is absorbed by oil or the like attached to the inspection surface. The absorption of the light of the specific wavelength is repeated during the multiple reflection, so that the absorption amount is amplified.

Therefore, the light extracted from the space has less specific wavelength light. Therefore, by analyzing the absorption spectrum of the extracted light, the state of the inspection surface,
That is, it is possible to know the type and degree of dirt on the inspection surface.

[0010]

First, the background of the inspection method of the present invention will be described. In the inspection method of the present invention, in order to detect the property of the surface of the object, that is, stains having various colors such as oil and rust adhered to the surface (hereinafter, simply referred to as “contamination”), light in a wide wavelength range is detected. To use.

When light in a wide wavelength range is applied to dirt, light having a specific wavelength corresponding to the dirt component is absorbed. For example, in FIG.
As shown in Fig. 1, the container 1 made of SiO ₂
When the rolling oil 2 which is the one is put in, infrared light IRin is applied from the infrared light source 3 to this, and the light IRout transmitted through the rolling oil 2 is detected by the detector 5 through the filter or the spectroscope 4, As a result of a part being absorbed by the rolling oil 2, an absorption spectrum as shown in FIG. 7 is obtained. In FIG. 6, the vertical axis represents the reflectance R and the horizontal axis represents the wave number ν. In this absorption spectrum, an absorption band corresponding to a functional group derived from the rolling oil component is recognized. That is, 3350 cm ^-1 , 3680
cm ^-1, 1700cm ^-1, the absorption band of 1650cm ^-1 is,
In each order, it corresponds to the stretching motion of the NH group, the OH group, the C = O group, and the C = C group. Even when a similar measurement is performed using a prepared oil instead of the rolling oil, a similar absorption spectrum can be obtained because the prepared oil contains the functional group.

Therefore, if the inspection surface is irradiated with light in a wide wavelength range including a specific wavelength absorbed by dirt, for example, infrared rays,
It should be able to detect dirt on the inspection surface. Further, if attention is paid to the wave number and reflectance of the absorption band in the absorption spectrum, it should be possible to detect the type and degree of the dirt attached to the inspection surface. However, in practice, the spectrum of the reflected light obtained by directly irradiating the inspection surface with light in a wide wavelength range is not a satisfactory one for detecting dirt. For example, as shown in FIG. 8, the infrared light source 7 irradiates infrared rays IRin from above the steel plate 6 and the reflected light I
Even if Rout is detected by the detector 9 via the filter or the spectroscope 8, only the absorption spectrum as shown in FIG. 9 is obtained. In FIG. 9, the broken line is the absorption spectrum of a steel sheet having a clean surface without stains, and the solid line is the absorption spectrum of a steel sheet with stains, but there is almost no difference due to the presence or absence of stains on the steel plate. .

The present inventors have understood that this phenomenon is due to the fact that the reflectance of the steel sheet to be inspected is extremely high, but the amount of absorption due to dirt is small, and a method for making the absorption band remarkable is found. Thus, the present invention has been completed. That is, in the inspection method of the present invention, a space covered with a mirror surface is formed on the inspection surface, and light of a specific wavelength is absorbed in the space to make the absorption band noticeable.

In FIG. 1, in order to form a space covered with a mirror surface,
1 shows a basic configuration of an embodiment using a light reflection space forming body 12 whose inner surface is plated with gold (Au). The hemispherical light reflection space forming body 12 is installed so as to cover the inspection surface 11, and from the light intake port 13 opened in the light reflection space forming body 12,
An infrared ray IRin is incident on the inside of the light reflection space forming body 12. The incident infrared ray IRin is reflected by the inspection surface 11, and most of the reflected light hits the inner surface of the light reflection space forming body 12.
Since the inner surface of the light reflection space forming body 12 is plated with gold having a high reflectance with respect to the light rays in the infrared region, it is reflected and irradiates the inspection surface 11 again. In this way, infrared rays are repeatedly reflected in the light reflection space forming body 12 (this is referred to as "multiple reflection"). On the other hand, as the multiple reflections are repeated, stains adhering to the inspection surface 11 absorb light of a specific wavelength, so that the difference between the light amount in the non-absorption band wavelength region and the light amount in the absorption band wavelength region becomes large. When light having a uniform light amount over a wide wavelength range is given and the light IRout in which the light amount difference between the absorption band and the non-absorption band is remarkable is taken out from the taking-out port 14 of the light reflecting space body 12 and inspected, it is shown in FIG. Such an absorption spectrum is obtained. The obtained absorption spectrum has a slight shift in the wavelength of the absorption band due to multiple reflection, but the pattern is almost the same as the absorption spectrum obtained by directly irradiating the substance causing the stain with infrared rays. Therefore, according to the inspection method of the present invention, since the absorption band can be made conspicuous by repeating absorption, a minute amount of dirt that cannot be detected from the absorption spectrum of the reflected light obtained by simply irradiating light is used. Even if there is, it can be detected.

In FIG. 1, the light reflection space forming body 1 is shown.
Although a gap is provided between the inspection surface 11 and the inspection surface 11, the inspection surface in a wide range can be inspected by moving either the inspection surface 11 or the light reflection space forming body 12 in a non-contact manner. . Further, the inner surface of the light reflection space forming body 12 is
Any material may be used as long as it is a mirror surface capable of multiple reflection of incident light, and the material forming the mirror surface is appropriately selected according to the type of light used. When light in the infrared region is used, chromium or the like can be used instead of gold. In addition, as for the light used, infrared rays are effective for detecting oil stains, etc., but for stains such as carbon and rust that have greater absorption in the visible light range than the infrared range, visible light is used. It is more convenient to use with because it can be compared with the human sensory test. In this case, elements with color tones such as black, yellow-brown, or brown also come in, so white light may be emitted, and for stains such as oil mainly, 5000 Å ~ through a bandpass filter.
Visible light of about 7,000 Å may be selectively applied.
When using visible light, the light reflection space forming body 12
It is preferable to use barium oxide as the metal coating the inner surface. In the case of visible light, the roughness of the inspection surface (Ra)
Since the amount of absorption also differs depending on the type, it is preferable to prepare a calibration curve based on roughness in advance.

Next, an embodiment of the inspection apparatus of the present invention utilizing the above-mentioned basic structure will be described with reference to FIG. A hemispherical or bell-shaped cavity 21 having a diameter of about 100 mm as a light reflection space forming body on a steel plate 20 as an inspection object.
However, the opening of the cavity 21 is installed so as to face the steel plate 20. The cavity 21 is supported by a support 27 so that a predetermined space is provided between the cavity 21 and the steel plate 20, and the steel plate 20 can be freely moved. The inner surface of the cavity 21 is buffed and sufficiently smoothed, and then plated with gold. Also,
The cavity 21 has a double structure, and the cooling water is circulated inside the cavity 21 to prevent the cavity 21 itself from absorbing light and increasing in temperature, thereby generating infrared rays due to heat radiation. In FIG. 3, 21a and 21b are an inlet and an outlet of cooling water, respectively.

The cavity 21 has a light inlet 22.
And the light outlet 23 are opened respectively. The light inlet 22 is connected to the lens 3 by the optical fibers 25a and 25b.
0a, 30b and cut filters 31a, 31b are connected to light source lamps 32a, 32b. In the figure, 33 is a constant voltage device connected to the light source. As the optical fibers 25a and 25b, those having a small attenuation factor are preferably used, but the type thereof is not particularly limited.
When a quartz fiber is used, the attenuation is large in the infrared region of about 3 to 5 μm, but a fiber with a large opening is used and the distance between the light source lamps 32a and 32b and the cavity 21 is 4 to 5 m. If it is within the range, there is no problem in measurement.

The light extraction port 23 is connected to the inspection section 40 via an optical fiber 26. Optical fiber 2
It is preferable to use an optical fiber 6 having a large opening so that the extracted light can be sent to the inspection unit 40 without leakage. The inspection unit 40 is a device that analyzes the absorption spectrum of the light extracted from the cavity 21 and determines the type and degree of contamination. That is, the light extracted from the cavity 21 is focused by the lens 41 and sent to the infrared detector 44a and the visible light detector 44b by the half mirror 42. When the light enters each of the detectors 44a and 44b, the bandpass filters 43a and 43b cut off light other than the wavelength range suitable for the detectors 44a and 44b. Each of the detectors 43a and 43b converts light into an electric signal and inputs the electric signal to the calculator 45.

When mainly detecting oil stains on the surface of the steel sheet, the infrared bandpass filter 43a has a wavelength of 2.5 μm (wave number ν = 4000 cm ⁻¹ ) to a wavelength of 3.2 μm (wave number ν = 3100 cm ⁻¹ ) is used, and the detection element is germanium (Ge) or P.
bS is used. Wavelength 5000Å ~ 700 for visible light
A bandpass filter 43b of 0Å is used, and a photodiode is used as a detection element.

By using the inspection apparatus having the above-mentioned structure, the dirt can be detected as follows. Visible rays and infrared rays generated from the lamps 32a and 32b turned on by the constant voltage device 33 are filtered by the lenses 31a and 31b after the extra wavelength light is cut by the lenses 30a and 32b.
The light is focused by 30b, and is made incident on the inside of the cavity 21 from the light inlet 22 through the optical fibers 25a and 25b.

The incident light repeats multiple reflections in the space formed by the steel plate 20 and the inner surface of the cavity 21. During the multiple reflection, light of a specific wavelength is absorbed by dirt on the surface of the steel plate 20, and the amount of absorption is amplified by the multiple reflection. In this way, the light in which the light of the specific wavelength is absorbed while repeating the multiple reflection is transmitted from the light extraction port 23 to the optical fiber 26.
Through the inspection section 40. In the inspection unit 40, the light in the infrared region and the light in the visible light region are converted into electric signals I _(IR) and I _(VL) by the detectors 44a and 44b, respectively, and input to the calculator 45.

In the calculator 45, the detectors 44a and 44b are provided.
Infrared detection signal I _(IR) and visible detection signal I input from
_(VL) is standardized (the standardized infrared detection signal is shown by I _{0 (IR)} and the visible detection signal is shown by I _{0 (VL)} ), and the relationship between the type of stain and the amount of light created in advance is shown. Based on the database shown, for example, a calculation is performed according to the flowchart shown in FIG. 4 to determine the type and degree of dirt.

In FIG. 4, α and β are thresholds for determining the presence or absence of dirt with infrared rays or visible light, respectively, and when the light quantity is larger than the threshold value, it indicates that dirt is attached (steps 1 and 2). reference). Further, γ is a threshold value for distinguishing whether the stain is oil or something other than that, and when I _{0 (IR)} / I _{0 (VL)} is larger than γ, it means that it is oil stain. Shown (see step 3). In this way
The type of dirt is determined, and according to the size of I ₀ ,
The stain grade is determined and the result is output.

In the inspection apparatus as described above, since the cavities 21 are installed on the steel plate 20 so as to have a predetermined interval, the steel plates 20 are sequentially moved without damaging the surface of the steel plate or changing the contamination pattern. Can be made. Therefore, it is possible to inspect a wide range of steel plate surfaces with an inspection device having one cavity 21. Further, as shown in FIG. 4, if a plurality of cavities are arranged in parallel in the width direction of the steel sheet, the surface can be continuously inspected during the rolling process. Further, by using it together with the conventional laser-based flaw detection system, it is possible to automatically detect not only dirt but also scratches having unevenness.

In the above embodiment, the visible light and the infrared light are used together as the incident light, but only one of them may be used depending on the type of dirt or the like to be detected. When only visible light is used, a cavity whose inner surface is covered with barium oxide may be used. In this case, water cooling is not necessary, so that a cavity having a single structure can be used.

[0026]

According to the inspection method of the present invention, it is possible to inspect the property of the surface of an object such as the presence or absence of oil stain which cannot be detected by the conventional laser method. Moreover, the inspection method of the present invention is
It is possible to detect even a minute amount of dirt that cannot be detected by simply irradiating the surface of the object to be inspected with light in a wide wavelength range such as infrared rays. Further, by using the inspection method of the present invention in combination with various arithmetic units, it is possible to obtain various kinds of information regarding the properties of the object surface such as the type and degree of stains.

The inspection apparatus of the present invention can easily implement the inspection method of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic configuration of an inspection method of the present invention.

FIG. 2 is a diagram showing an absorption spectrum obtained by the method of FIG.

FIG. 3 is a configuration diagram showing an embodiment of an inspection apparatus of the present invention.

FIG. 4 is a flowchart for explaining a calculation in an inspection unit of the inspection device of this embodiment.

FIG. 5 is a diagram showing another embodiment of the inspection method of the present invention.

FIG. 6 is a diagram for explaining a laboratory inspection method for absorption spectra.

FIG. 7 is an absorption spectrum obtained by a laboratory measurement method.

FIG. 8 is a diagram for explaining an inspection method when a light reflection space forming body is not used.

FIG. 9 is an absorption spectrum obtained by the method shown in FIG.

[Explanation of symbols]

 11 Inspection Surface 12 Light Reflecting Space Forming Body 13 Red Intake Port 14 Light Extracting Port 15 Inspection Part 20 Steel Plate 21 Cavity 22 Light Intake Port 23 Light Extracting Port 32a Lamp 32b Lamp 40 Inspection Part

Claims (3)

[Claims] 1. A space covered by a mirror surface is formed on an inspection surface, light is irradiated into the space, the light is multiply reflected between the inspection surface and the mirror surface, and the multiple reflected light is A method of inspecting an object surface, which is characterized in that the property of an inspection surface is inspected on the basis of the extracted light. 2. The method for inspecting an object surface according to claim 1, wherein infrared rays or visible rays are used as the light, and the property of the inspection surface is inspected based on the absorption spectrum of the extracted light. 3. A light reflection space forming body which covers the inspection surface with a mirror-finished inner wall surface to form an inspection space for multiple reflection of light between the inspection surface and the inner wall surface, The reflection space forming body is provided with a light inlet for taking in light into the inspection space, and a light outlet for taking out light multiple-reflected between the inspection surface and the inner wall surface. A light source is directly or indirectly connected to the light intake port, and an inspection unit for inspecting a property of an inspection surface based on the extracted light is connected to the light extraction port. Object surface inspection device.