JPH09178669A - Surface inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate kind and degree of a flaw by continuously detecting a patterned flaw and unevenly shaped flaws on a moving steel plate surface on line. SOLUTION: The different polarized light of the reflected light from a steel plate is measured with a linear array camera. A signal process part 12 shading- corrects three species of image signals measured, and so normalizes a normal part as to be central concentration of the entire gradation for flattening, and converts into the light intensity signal indicating relative change to a normal part. The variation polarity and the variation amount of distribution of three species light intensity signals indicating relative change to the normal part are compared with a pattern set in advance, for detecting change of polarized light, and, based on the variation polarity and the variation amount to the normal part, the type of a flaw whose physical properties on the surface is different from a base material is decided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface inspection device for optically detecting surface defects such as thin steel plates.

[0002]

2. Description of the Related Art For example, as an apparatus for optically detecting a surface flaw of a steel sheet, a method of detecting a flaw by utilizing the scattering of laser light or the change of a diffraction pattern is often used. This method is an effective method for detecting flaws that form apparent irregularities on the surface of a steel sheet.

On the other hand, a flaw of a steel plate or the like does not have surface irregularities and has a pattern such as unevenness of physical properties, unevenness of microscopic roughness, local existence of thin oxide film or unevenness of coating film thickness. There is something called a flaw. Such pattern flaws are difficult to detect by scattering of laser light or changes in the diffraction pattern. For example, if there is an abnormal area with a thick oxide film of about 400Å locally on the surface of a steel sheet with an oxide film of about 100Å in the normal area, such an abnormal area will cause coating failure during the surface treatment process. Therefore, there is a request to detect and remove defects. However, the difference in the oxide film thickness between the abnormal portion and the normal portion is buried in the roughness of the steel sheet surface, and cannot be detected at all by the method utilizing light scattering or diffraction.

In order to detect a flaw that cannot be detected by a method utilizing light scattering or diffraction, a flaw inspection method using polarized light is disclosed in, for example, JP-A-52-138183 and JP-A-58-58.
No. 204356 is disclosed. The inspection method disclosed in Japanese Unexamined Patent Publication No. 52-138183 is to detect the presence or absence of a defect by determining whether or not the ratio of P-polarized light and S-polarized light reflected from the surface of the object to be inspected is higher than a predetermined comparison level. is there.
Further, the detection method disclosed in JP-A-58-204356 aims to improve the S / N ratio when detecting a surface defect by irradiating the surface of the inspection object with light at an incident angle of a specific angle. It is the one. Although not a flaw inspection method, a method of measuring the film thickness and surface physical properties using polarized light is disclosed in, for example, JP-A-62-293104 and JP-A-4-58138. The inspection method disclosed in Japanese Patent Application Laid-Open No. 62-293104 receives polarized light reflected from a sample through three analyzers having different azimuth angles, and determines the ellipso parameter at each position from the light intensities of three different kinds of polarized light. That is, the amplitude reflectance ratio tan Ψ and the phase difference Δ between the P-polarized light, which is a component of the reflected light in the direction of the incident surface, and the S-polarized light, which is a component in the direction perpendicular to the incident surface, are calculated and calculated on the surface to be inspected. It is a method to measure the oxide film, coating thickness or physical property values of the above with good accuracy. JP 4-58138
In the detection method disclosed in Japanese Patent Laid-Open Publication No. 2003-242242, the polarized light reflected from the sample is imaged through a phase shifter composed of a quarter wavelength plate and an analyzer.
When the light is guided to the image sensor, the position of the transmission axis of the retarder is changed by a predetermined angle, and the analyzer is rotated at each angle to obtain the polarization parameter for each pixel of the image sensor and accurately measure the birefringence distribution. Is the way to do it.

[0005]

The inspection methods disclosed in JP-A-52-138183 and JP-A-58-204356 use polarized light to discriminate between a normal part and an abnormal part. Only two polarization directions are measured. A flaw on the surface of a steel sheet or the like is often a portion whose optical properties are different from those of the normal portion, and since the types and forms thereof are various, the polarization state of light reflected by the steel sheet is also various. In such a case, the polarization characteristics of the measurement target cannot be uniquely expressed unless polarizations in three or more directions are measured. Therefore, even if an abnormal portion can be detected as an inspection result, it may be oil stains or oxidation. It was not possible to discriminate a large number of flaw species such as unevenness of the membrane or the attachment of some abnormal deposit, and the flaw species that could be applied were limited. Moreover, it has not been clarified what kind of method and apparatus using polarized light can discriminate a wide variety of flaws.

On the other hand, the inspection method disclosed in Japanese Unexamined Patent Publication No. 62-293104 uses the elliptic parameter amplitude reflectance ratio.
Since tan Ψ and phase difference Δ are used, there is a possibility that it is possible to discriminate oil stains, oxide film unevenness, and foreign matter adhesion. However, this method is basically point measurement and is not suitable for inspection of the entire surface of a steel plate or the like. If, for example, a large number of the devices disclosed in Japanese Patent Laid-Open No. 62-293104 are arranged in the width direction of the steel plate, or one device is scanned by means having a mechanism capable of moving at high speed in the width direction, Even if the whole surface can be scanned by the device, the signal processing unit calculates the amplitude reflectance ratio tan Ψ and phase difference Δ of the ellipsometer from the polarization intensity signal at all measurement points, and uses the image processing device to detect the defects. It is necessary to judge the grade of seeds and defects. However, it is necessary to process polarization intensity signals of 1000 points or more in one line in the width direction, and especially when the ellipso parameter calculation is performed by software, it takes about 10 seconds for calculation.
For example, it was not possible to continuously inspect online the surface of a sheet-like product such as a steel plate passing at a speed of several 100 m / min. For this reason, an arithmetic processing device such as a dedicated polarization parameter is required, and the device becomes expensive.

However, this method is very sensitive as an inspection method, and relatively weak detection strength from other kinds of flaws, stains, oil spots, scales, and the like, which does not give a pattern-like surface flaw. It was difficult to discriminate and detect only the information. In particular, when inspecting a steel sheet that has an oil film applied to the surface and moves on the production line, a polarization parameter that includes both the oil film unevenness and the surface defect that should be detected should be detected. It was not possible to discriminate and detect only the information of. For this reason, it is considered that there is no possibility that it can be used to detect surface flaws of ordinary steel sheets such as cold-rolled steel sheets, which often have an oil film applied to the surface for rust prevention. It has been considered impossible to detect such defects by optical means, and further to determine the type and grade of surface defects.

Further, this method is originally a method for measuring the film thickness or the physical property value, and for that purpose, ellipso parameters are used.
It was sufficient to measure the amplitude reflectance ratio tan Ψ and the phase difference Δ of the parameter.However, these parameters do not always correspond to the condition as seen by the human eye, and the human can recognize it as a flaw. However, the ellipsoparameter could not detect a flaw that did not change.

The inspection method disclosed in Japanese Unexamined Patent Publication No. 4-58138 is an ellipsometer used for thin film evaluation and the like.
In this case, the birefringence index is obtained for each pixel, and therefore the birefringence index is measured as different values between the normal part and the abnormal part, and the difference between the normal part and the normal part is determined. There is a possibility that the abnormal part can be discriminated. However, since the retarder and the analyzer are mechanically rotated for measurement, in order to measure the birefringence of each position of the inspection object, the inspection object should be stopped during at least one measurement. Had to be. For this reason, it is impossible to continuously inspect the surface of a sheet-like product continuously manufactured and sent, such as a steel plate, online.

The present invention has been made to solve the above-mentioned disadvantages, and it is possible to continuously detect online the pattern-like flaws and the uneven flaws on the surface of the sheet-like product with a simple structure, It is an object of the present invention to obtain a surface inspection device capable of discriminating its type and degree.

[0011]

A surface inspection apparatus according to the present invention has a light projecting section, a light receiving section, and a signal processing section. The light projecting section makes polarized light incident on a surface to be inspected, and at least the light receiving section. It has a plurality of light receiving optical systems that receive polarized light of different angles in three directions, detects the reflected light reflected on the surface to be inspected and converts it into an image signal, and the signal processing unit outputs the light output from each light receiving optical system. Normalize the intensity distribution so that the average value becomes a predetermined reference value, and compare the standardized change polarity and change amount of multiple light intensity distributions with a predetermined pattern to determine the defect type. Characterizing

Further, the signal processing unit normalizes the light intensity distribution output from each light receiving optical system so that the average value becomes a predetermined reference value, and changes the polarities and changes of the normalized plurality of light intensity distributions. The amount of light is compared with a predetermined pattern to determine the type of flaw, the light intensity change equivalent to visual observation is calculated from the light intensity distribution output from each light receiving optical system, and the calculated light intensity change is determined by the predetermined pattern. It is desirable to judge the grade of the flaw by comparing with.

[0013]

DETAILED DESCRIPTION OF THE INVENTION Polarized light is sensitive to the physical properties of reflective surfaces, especially thin films. In addition, the polarization direction of maximum intensity changes depending on the physical properties of the reflecting surface. The flaws on the metal surface have different surface characteristics from those of the normal portion, and the physical properties of the surface are different from those of the base material, resulting in flaws. There is something. The former can be detected by using polarized light, and the latter can be detected by a change in the amount of reflected light because the difference appears in reflectance.

Therefore, in the present invention, the light projecting portion is arranged so that polarized light is incident on the surface to be inspected at a constant incident angle over the entire width direction of the surface to be inspected, and the reflected light from the surface to be inspected is received. The light receiving section to be operated is arranged at a predetermined position. The light-receiving portion has three sets of, for example, a beam splitter that splits incident light into three beams and a CCD sensor that separately outputs the separated three beams and outputs an image signal. A linear array camera and an analyzer provided between the beam splitter and each linear array camera to convert the reflected light from the surface to be inspected into polarized light of different vibration planes are provided. The three analyzers are arranged so that the respective azimuth angles, that is, the angles formed by the transmission axis and the incident surface of the surface to be inspected are 0, π / 4 and −π / 4, for example.

The signal processing unit performs shading correction on the output image signal from each linear array camera to normalize and flatten the normal portion so that the normal portion has the central density of all the gradations, and changes relative to the normal portion. It is converted into the light intensity signal shown. A change in polarization is detected by comparing the change polarity and the change amount of the distribution of the three types of light intensity signals indicating the relative change with respect to the normal part with a predetermined pattern. Based on the change polarity of the three kinds of light intensity signals with respect to the normal part and the magnitude of the change amount, the flaw type of the flaw whose surface physical properties are different from those of the base material is determined.

In addition to the above processing, the signal processing unit also calculates a light amount change corresponding to visual observation, that is, the surface reflection intensity from the light intensity distribution output from each light receiving optical system, and compares the calculated light amount change with a predetermined pattern. Then, since the surface geometric shape is different from the normal portion such as unevenness based on the change polarity of the light amount change and the magnitude of the change amount, the flaw grade is determined.

[0017]

1 is a layout view showing an optical system according to an embodiment of the present invention. As shown in the figure, the optical system 1 includes the light projecting units 2 and 3.
It has a plate-type polarization linear array camera 3. The light projecting unit 2 is for injecting polarized light on the surface of the inspection object, for example, the steel plate 4, at a constant incident angle, and includes a light source 5 and a polarizer 6 provided in front of the light source 5. The light source 5 is composed of a rod-shaped light emitting device extending in the width direction of the steel plate 4, and emits light having a uniform intensity distribution over the width direction of the steel plate 4. The polarizer 6 is composed of, for example, a polarizing plate or a polarizing filter, and is arranged such that an angle α ₁ formed by the transmission axis P and the incident surface of the steel plate 4 is π / 4, as shown in the layout explanatory view of FIG. . The three-plate polarization linear array camera 3 has a beam splitter 7, three analyzers 8a, 8b and 8c, and three linear array sensors 9a, 9b and 9c, as shown in the configuration diagram of FIG. . The beam splitter 7 is composed of three prisms, and is provided with two semi-transmissive reflective surfaces having a dielectric multilayer film deposited on the incident surface.
The first reflection surface 7a on which the reflected light from the steel plate 4 is incident has a transmittance and a reflectance of 2: 1, and the second reflection surface on which the light transmitted through the first reflection surface 7a is incident. 7b has a 1: 1 ratio of transmittance and reflectance, and separates the reflected light from the steel plate 4 into three beams having the same light amount. Also,
The optical path lengths from the entrance surface of the beam splitter 7 to the exit surfaces of the three separated beams are the same. The analyzer 8a is the second
2 is provided in the optical path of the transmitted light of the reflecting surface 10b, and is arranged so that the azimuth angle, that is, the angle α ₂ formed by the transmission axis with the incident surface of the steel plate 4 is 0 degree, and the analyzer 8b is Second
Is provided in the optical path of the reflected light of the reflective surface 7b of the first reflective surface 7b, and the azimuth angle α ₂ is π / 4 degrees, and the analyzer 8c is provided in the optical path of the reflected light of the first reflective surface 7a. α ₂ is −π /
It is arranged to be 4. Linear array sensor 9
Reference numerals a, 9b and 9c are, for example, CCD sensors, and are arranged at the subsequent stages of the analyzers 8a, 8b and 8c, respectively. Between the beam splitter 7 and the analyzers 8a, 8b, 8c, slits 10a, 10b, 10c for cutting multiple reflected light and unnecessary scattered light in the beam splitter 7 are provided. A lens group 11 is provided in front of the optical splitter 7. In addition, the linear array sensors 9a, 9b,
The gain of 9c is adjusted so that the same signal is output when light with the same light intensity is incident.

The analyzers 8a to 8c and the linear array sensor 9 are arranged in the optical paths of the three beams that separate the incident light in this way.
Since a to 9c are integrally provided, when the linear array sensors 9a to 9c and the like are installed in the vicinity of the conveying path of the steel plate 4 and the reflected light from the steel plate 4 is detected, the linear array sensors 9a to 9c and the like. Position adjustment is not required, and
The reflected light from the same position on the steel plate 4 can be detected at the same timing. Further, since three sets of linear array sensors 9a to 9c are collectively housed in the three-plate type polarization linear array camera 3, the three-plate type polarization linear array camera 3 can be easily installed in the optical path of the reflected light of the steel plate 4. The optical system 1 can be arranged and the arrangement position can be arbitrarily selected, so that the degree of freedom in the arrangement of the optical system 1 can be improved.

The linear array sensors 9a to 9c of the three-plate polarization linear array camera 3 are connected to the signal processing unit 12 as shown in the block diagram of FIG. Signal processing unit 1
Reference numeral 2 denotes a signal preprocessing unit 13a, 13b, 13c, an I ₁ memory 14a, an I ₂ memory 14b, an I ₃ memory 14c, a defect parameter calculation unit 15, a pattern storage unit 16, and a light quantity storage unit 17. , The reference pattern storage unit 18, and the defect type determination unit 19
And a grade pattern storage unit 20, a defect grade determination unit 21 and an output unit 22. The signal preprocessors 13a to 13c perform shading correction and the like to correct sensitivity unevenness in the width direction of the polarized light intensity signals I ₁ , I ₂ and I ₃ output from the linear array sensors 9a to 9c. From the normal part signal as a reference level, the normal part signal is normalized to have 128 gradations, which is the central density of 255 gradations, and the normalized light intensity signals I ₁ , I ₂ , and I ₃ are respectively obtained. I ₁ memory 14a, I ₂
The data is stored in the memory 14b and the I ₃ memory 14c. The defect parameter calculation unit 15 sets the peak value of the defect represented by the distribution of the light intensity signals I ₁ , I ₂ and I ₃ stored in the I ₁ memory 14a to I ₃ memory 14c to the value of the normal part. A polar pattern that indicates whether it is positive or negative based on a certain 128 gradations and a value pattern that indicates the amount of change based on 128 gradations are calculated, and from the light intensity of the flaw Calculate the amount of light equivalent to visual observation. The pattern storage unit 16 stores the calculated polarity pattern and value pattern, and the light amount storage unit 17 stores the calculated visual equivalent light amount Imax. The reference pattern storage unit 18 stores in advance various polar patterns, value patterns, and flaw types corresponding to these. The defect type determination unit 19 is provided with the polarity pattern and the value pattern stored in the pattern storage unit 16.
And the various types of polarity patterns and the value patterns stored in the reference pattern storage unit 18 to determine the defect type. The grade pattern storage unit 20 stores in advance a grade reference pattern indicating the grade of the flaw with respect to the amount of light for each flaw type. The defect grade determination unit 21 grades the visual equivalent light amount Imax stored in the light intensity storage unit 17 and the defect type determined by the defect type determination unit 19 into a grade pattern.
The defect grade is judged by comparing with the grade reference pattern stored in the storage unit 20. The output unit 22 is the defect grade determination unit 21.
The defect type and the defect grade output from the device are output to a display device or a recording device (not shown).

Next, the operation of inspecting the surface of the steel sheet 4 with the surface inspection apparatus configured as described above will be described.

The polarized light emitted from the light projecting unit 2 and reflected on the surface of the steel plate 4 moving at a constant speed is received by the three-plate polarization linear array camera 3. The reflected light of the steel plate 4 incident on the three-plate polarization linear array camera 3 is separated by the beam splitter 7 and enters the linear array sensors 9a to 9c through the analyzers 8a, 8b and 8c. When the linear array sensors 9a to 9c detect the light intensity of the reflected light, the linear array sensors 9a to 9c are provided with analyzers 8a to 8c having different azimuth angles in front of the linear array sensors 9a to 9c. Detects the light intensities I ₁ , I ₂ , and I ₃ of different polarizations and sends them to the signal processing unit 12.

The signal preprocessors 13a to 13a of the signal processor 12
3c is Chez corrects the linear array sensor the light intensity signal I ₁ of the polarized light output from 9a to 9c, I _2, sensitivity unevenness in the width direction and the like of the I ₃ and the like - from performing loading correction, for example, in FIG. 5 As shown in the defect signal distribution chart, the signal in the normal part is 128
The light intensity signal I is normalized so as to have a gradation.
₁ , I ₂ , I ₃ are respectively I ₁ memory 14 a to I ₃ memory 1
4c. In FIG. 5, (a) shows the light intensity signal I.
₁ shows the distribution, (b) shows the distribution of the light intensity signal I ₂ , and (c) shows the distribution of the light intensity signal I ₃ . The defect parameter calculation unit 15 uses I ₁
Whether it is positive than 128 gradation is click value the value of the normal portion each - peak flaw portion appears in the distribution of memory 14A～I ₃ light intensities stored in the memory 14c signals I _1, I _2, I ₃ A polarity pattern showing whether it is negative and a value pattern showing the amount of change based on 128 gradations are calculated. In the example shown in FIG. 5, the peaks of the flaws of the normalized light intensity signals I ₁ , I ₂ , and I ₃ are shown.
All black values are more than 128 gradations, so polarity pattern
Is calculated as (+, +, +), and the amount of change in the peak value of the flaw portion of the light intensity signals I ₁ , I ₂ , I _{3 based on} 128 gradations is (+38, +10, +32). become. When this change amount is standardized with the maximum value as a reference, it becomes (1.0, 0.26, 0.84). A standard value based on the maximum value of this variation, for example (1.0, 0.2
6, 0.84) is calculated as the value pattern. Then, the calculated polarity pattern and value pattern are stored in the pattern storage unit 16. In addition, the defect parameter calculator 15 determines that the light intensity signal I
_From the distribution of ₁ , I ₂ , and I ₃ , the visual equivalent light amount Imax is calculated as Imax =
It is calculated by MAX [I ₂ (x) + I ₃ (x) −I ₁ (x)] and stored in the light quantity storage unit 17. For example, in the example shown in FIG. 5, since the amount of change in the peak value of the flaw portion of the light intensity signals I ₁ , I ₂ , and I ₃ is (+38, +10, +32), the visually equivalent light amount Imax is " 4 ”.

In the reference pattern storage unit 18, polar patterns and value patterns corresponding to a plurality of flaw types are experimentally determined according to the degree of flaws, and as shown in FIG. It is stored as a pattern. In FIG. 6, flaw types X to W are, for example, flaw types in the order of low to high degree of damage, and the polar patterns and the value patterns corresponding to the respective flaw types X to W. The standard value of the Further, in the grade pattern storage unit 20, the correlation showing the visual equivalent light quantity and the grade of the flaw is checked in advance in accordance with each flaw type X to the flaw type W, and stored as shown in the correlation diagram of FIG. 7, for example. is there.

The defect type judging unit 19 stores the polar pattern and the value pattern stored in the pattern storage unit 16, for example, in the case of the example shown in FIG. 5, the polar pattern (+, +, +). And the value pattern (1.0, 0.26, 0.84) and the reference pattern stored in the reference pattern storage unit 18 shown in FIG. 4 are compared to determine the defect type. For example, in the case of the example shown in FIG. 5, the defect type X is determined. FIG. 8 shows an example in which a plurality of different defect types A to H are determined by the polar pattern and the value pattern. When determining this flaw type, for example, even if flaw B and flaw C have the same polarity pattern (-,-,-), the flaw pattern Y having a low degree of harm and the flaw type having a high degree of harm according to the value pattern. It can be classified into Z, and the flaw type can be accurately determined. Depending on the state of the flaw, even if one of the three signs of the polar pattern is opposite as shown in flaw G, or even if it is "0", the flaw pattern can be accurately identified by using the value pattern together. can do. In addition, the polarity pattern and the value pattern are
Since the defect type is determined by the operation, the process for determining the defect type is simplified, and the defect type can be accurately determined in a short time.

On the other hand, the defect grade judging section 21 includes a light quantity storage section 17
The visual equivalent light amount Imax and the defect grade which are stored in the grade pattern storage unit 20 stored in the grade pattern storage unit 20 are the visual equivalent light amount Imax and the defect type determined by the defect type determination unit 19. Defect grade is judged by comparing with the correlation diagram showing. For example, as shown in FIG. 7, in the case of the flaw type X and the visually equivalent light amount Imax is “4”, the flaw grade is determined to be B, and the flaw type Y is the visually equivalent light amount Imax.
When is "37", the defect grade is judged as C. As described above, since the grade of the flaw is determined based on the visually equivalent light amount Imax and the flaw type, it is possible to accurately determine not only the pattern-like flaw having no unevenness generated on the surface of the steel plate 4 but also the degree of the uneven flaw. The defect grade determination unit 21 sends the defect grade determined to be the defect type determined by the defect type determination unit 19 to the output unit 22. The output unit 22 outputs the defect type and the defect grade output from the defect grade determination unit 21 to a display device or a recording device.

[0026]

As described above, according to the present invention, polarized light is incident on a surface to be inspected at a constant incident angle, a light intensity distribution of a plurality of polarized lights having different reflected lights is detected, and the detected intensity distribution is calculated. Normalize and calculate the change polarity and the change amount of the light intensity signal of polarized light of different flaws with respect to the normal part, and compare the calculated change polarity and change amount with the respective predetermined patterns to determine the flaw type. Since this is done, it is possible to quickly determine the defect type with a simple process.

Further, from the light intensity distribution output from each of the light receiving optical systems, the change in the light amount corresponding to the visual observation, that is, the surface reflection intensity in the non-polarized state is calculated, and the grade of the flaw is determined from the calculated change in the light amount. It is possible to accurately determine not only the pattern-like flaws having no unevenness but also the degree of the unevenness-like flaws by a simple process.

Furthermore, since the type of flaw and the grade of the flaw can be quickly judged by a simple process, the structure of the apparatus itself can be simplified and the surface of the sheet-like product moving at a high speed can be obtained. It is possible to accurately detect a certain abnormal part online.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an optical system according to an embodiment of the present invention.

FIG. 2 is an arrangement explanatory view showing the operation of the optical system.

FIG. 3 is a configuration diagram of a three-plate polarization linear array camera of the above embodiment.

FIG. 4 is a block diagram showing a signal processing unit of the above embodiment.

FIG. 5 is a light intensity distribution diagram showing a flaw signal.

FIG. 6 is a reference pattern diagram showing flaw types, flaw patterns, and value patterns.

FIG. 7 is a correlation diagram between a light intensity level and a defect grade.

FIG. 8 is an explanatory diagram showing a specific example of flaw types and grades of various flaws.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical system 2 Projection part 3 3 Plate-type polarization linear array camera 4 Steel plate 5 Light source 6 Polarizer 7 Beam splitter 8 Analyzer 9 Linear array sensor 12 Signal processing part 13 Signal preprocessing part 14a I ₁ memory 14b I ₂ memory 14c I ₃ memory 15 flaws parameters - data calculating unit 16 pattern - emission storage section 17 amount storage unit 18 reference pattern - emission storage unit 19 flaw type determination unit 29 grade pattern - emission storage unit 21 flaw grade determination unit

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Takahiko Oshige 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd.

Claims (2)

[Claims] 1. A light emitting unit, a light receiving unit, and a signal processing unit,
The light projecting unit has a plurality of light receiving optical systems that receive polarized light on the surface to be inspected and the light receiving unit receives polarized light of at least three different directions, and detects reflected light reflected by the surface to be inspected to generate an image signal. And the signal processing unit normalizes the light intensity distribution output from each light receiving optical system so that the average value becomes a predetermined reference value, and changes the polarity and the change amount of the standardized light intensity distributions. A surface inspection device characterized by determining a flaw type by comparing with a predetermined pattern. 2. A light emitting unit, a light receiving unit, and a signal processing unit,
The light projecting unit has a plurality of light receiving optical systems that receive polarized light on the surface to be inspected and the light receiving unit receives polarized light of at least three different directions, and detects reflected light reflected by the surface to be inspected to generate an image signal. And the signal processing unit normalizes the light intensity distribution output from each light receiving optical system so that the average value becomes a predetermined reference value, and changes the polarity and the change amount of the standardized light intensity distributions. Is compared with a predetermined pattern to determine the type of flaw and the grade of the flaw, calculate the light amount change equivalent to visual observation from the light intensity distribution output from each light receiving optical system, and calculate the calculated light amount change. -A surface inspection device characterized by judging the grade of a flaw by comparing with a surface.