JPH0833342B2 - Metal tissue inspection method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for inspecting a metal structure using a microscope,
More specifically, the present invention relates to an inspection method suitable for detecting the area ratio of a specific component contained in the alloy structure.

2. Description of the Related Art For example, as a method for detecting the precipitation area ratio of Si (silicon) crystal part from the surface structure of aluminum alloy,
There is a method as shown in the figure.

This is for irradiating the sample 2 set on the surface plate 1 with the illumination light L ₁ of the internal illumination light source 7 reflected by the half mirror 6 through the lens barrel 4 and the objective lens 5 of the epi-illumination microscope 3, while the objective lens The two-dimensional solid-state image pickup device (for example, CCD
And the like) type camera 8. Then, the image captured by the camera 8 is binarized at a predetermined level by the image processing device 9, and the area of the bright portion corresponding to the above-described Si crystal portion is calculated to obtain the Si crystal portion. A deposition interview rate can be obtained.

That is, as shown in FIG. 3, the surface of the sample 2 is once finished to be smooth and then etched to obtain Si.
The exposed surface of the crystal part 10 remains a smooth surface close to a mirror surface, whereas the Al eutectic layer 11 is roughened by etching and becomes a rough surface. Therefore, when the surface of the sample 2 is irradiated with the internal illumination light L ₁ , the Al eutectic layer 11 is diffusely reflected due to the rough surface and a small part of the reflected light is incident on the objective lens 5 side, whereas the Si crystal is Since the part 10 has a smooth surface, the irradiation light is specularly reflected, and most of the reflected light is incident on the objective lens 5 side. That is, in the above-described binarized image, the portion where the specular reflection light is strong is recognized and extracted as the Si crystal portion 10.

However, in the conventional method, since it is a method of extracting the Si crystal portion 10 which is a smooth surface from the difference in the brightness of reflected light, the portion corroded by etching is not necessarily a rough surface. However, if it happens that the state becomes close to a smooth surface, the Si crystal part 10 and the Al eutectic layer 11 cannot be clearly distinguished. Therefore, it is extremely difficult to set the optimum threshold value for extracting the Si crystal portion 10, and a detection error is likely to occur. Moreover, the conventional method is easily affected by the external light, which is one of the causes of further increasing the detection error.

The present invention has been made in view of the above points, and an object thereof is to extract only mutually overlapping portions from, for example, a smooth surface of a tissue from three types of images with different illumination conditions. The present invention provides an inspection method with improved accuracy.

Means for Solving the Problems The present invention is a method for extracting and inspecting a specific component of a surface structure based on a difference in light reflection characteristics between a rough surface portion and a smooth surface of a sample surface, and a microscope for the sample. When the internal illumination light is emitted through the objective lens of, and the external illumination light is emitted from an oblique direction that forms a predetermined angle with the sample surface, both the internal illumination light and the external illumination light are emitted, and only the internal illumination light is emitted. , And the case of irradiating only the external illumination light, the surface texture of the sample captured by the objective lens is imaged by the imaging device, and the image of the internal illumination light irradiation and the image of the internal and external illumination light simultaneous irradiation are compared. Then, the bright part of both images that has no difference in brightness is extracted as the region of the specific component of the surface tissue, and the light and dark are inverted before binarization. Quantify and identify It is characterized in that the region of the component is extracted, the two binarized images are combined, and only the part where the regions extracted from the respective binarized images overlap each other is extracted as the true region of the specific component.

Action According to this method, if the illumination conditions are different, even if the same object is imaged, the region of the specific component extracted from each image is slightly different due to the fluctuation of the reflected light amount. Therefore, for example, for the region corresponding to the smooth surface of the metallographic structure, the image at the time of internal illumination light irradiation is compared with the image at the time of internal / external illumination light simultaneous irradiation, and there is no difference in brightness between both images,
That is, when the metallographic structure to be inspected is, for example, an aluminum alloy, the Si crystal part does not change in brightness even under the above two irradiation conditions, but the Al eutectic layer focuses on the change in brightness under both irradiation conditions. Then, in order to extract the Si crystal part, the bright part having no difference in brightness is extracted as the region of the specific component of the surface texture, the light and dark are inverted, and then the light and dark binarization is performed. Similarly, the image at the time of external illumination light irradiation is binarized to extract the region of a specific component. The extraction error is reduced by synthesizing the two binarized images and extracting only the portions where the regions extracted from the respective binarized images overlap each other as the true smooth surface region.

Example Figure 1 - Figure 7 is a diagram showing an embodiment of the present invention, the illumination light L ₂ from an oblique direction with respect to the sample 2 as a specific configuration of the inspection apparatus shown in FIG. 2 It is different from that of FIG. 9 in that an external illumination light source 12 for illuminating is provided.

First, as shown in FIGS. 2 and 3, only the internal illumination light source 7 is turned on, and the internal illumination light L ₁ is applied to the surface of the sample 2 through the objective lens 5. At this time, since the Al eutectic layer 11 has a rough surface due to etching as described above, the internal illumination light L ₁ is diffusely reflected and a small part of the reflected light enters the objective lens 5 side. On the other hand, since the surface of the Si crystal portion 10 is a smooth surface close to a mirror surface, the internal illumination light L ₁ is specularly reflected, and most of the reflected light is regarded as brightness and the objective lens 5
Incident on the side.

The diffusely reflected light from the Al eutectic layer 11 and the specularly reflected light from the Si crystal portion 10 returning to the objective lens 5 side are captured by the camera 8 as the brightness of each substance, and the image processing device 9 shown in FIG. It is stored in the image memory. For image brightness, one screen is sampled into 256 x 240 pixels by A / D converter,
It has been quantized into graded density levels.

Subsequently, the lighting state of the illumination light source is switched, and only the external illumination light source 12 is turned on as shown in FIGS. 2 and 4, and the external illumination light L ₂ is obliquely inclined with respect to the surface of the sample 2 at a predetermined angle θ. Irradiate from the direction. At this time, since the Al eutectic layer 11 is a rough surface, the external illumination light L ₂ is diffusely reflected, and a small part of the reflected light returns to the objective lens 5 side as brightness. On the other hand, since the Si crystal portion 10 is a smooth surface, the external illumination light L ₂ is regularly reflected at an angle equal to the incident angle θ, and thus the regular reflection light hardly returns to the objective lens 5 side. Then, the reflected light returning to the objective lens 5 side is captured by the camera 8 and stored in the image memory of the image processing device 9 as in FIG.

Next, in order to change the illumination condition again, both the internal illumination light source 7 and the external illumination light source 12 are turned on and the surface of the sample 2 is irradiated as shown in FIG. 1 (A). At this time, the reflection state at the Al eutectic layer 11 and the Si crystal portion 10 is a state in which the states of FIGS. 3 and 4 are combined, that is, only when the internal illumination light 7 is applied and when the external illumination light 12 is applied. It is in a combined state with that of the Al eutectic layer 11 returning to the objective lens 5 side and
The reflected light from the Si crystal portion 10 is captured by the camera 8 and stored in the image memory of the image processing device 9 as in the above.

The three types of images stored in the image processing device 9 by changing the illumination conditions as described above are as shown in FIGS. 5 to 7, for example. That is, FIG. 5 shows an image when only the internal illumination light 7 is applied, and FIG. 6 shows an image when only the external illumination light 12 is applied. Further, FIG. 7 shows the internal illumination. The image when both the light 7 and the external illumination light 12 are irradiated is shown.

As is clear from comparison of these three types of images, in FIGS. 5 and 7, since the specularly reflected light from the Si crystal portion 10 which is a smooth surface is incident on the objective lens 5 side, FIGS. In the figure, the Si crystal portion 10 is shown as a white portion, whereas in FIG. 6, the specularly reflected light of the Si crystal portion 10 is the objective lens 5
The Si crystal portion 10 appears as a black portion because it hardly enters the side.

Therefore, if the white portion recognized as the Si crystal portion 10 in FIGS. 5 and 7 and the black portion recognized as the Si crystal portion 10 in FIG. As is clear from the above figures, the shape of the region recognized as the Si crystal portion 10 on each image is slightly different due to the difference in reflection characteristics.

Therefore, as shown in FIG. 1 (B), the image processing device 9
Image P ₁ when the internal illumination light L ₁ is stored in
And the image P ₃ when both the internal illumination light L ₁ and the external illumination light L ₂ are irradiated, and the portion having no difference in brightness between the images P ₁ and P ₃ is recognized as the Si crystal portion 10. Then, reverse the black and white. That is, both images P ₁ and P ₃ are compared and each image P ₁ and P ₃ is compared.
Only the white portion having no difference in brightness among the above white portions is recognized as the Si crystal portion 10. In this case, if the Al eutectic layer 11 corroded by etching accidentally has a flat surface that is not rough as described above, this flat surface exhibits a reflection characteristic similar to that of the Si crystal portion 10 that is a smooth surface. For Si
It cannot be distinguished from the crystal part 10. As a result, there is a possibility that a portion other than the Si crystal portion 10 is actually recognized as the Si crystal portion 10 on the image P ₄ obtained by combining the images P ₁ and P ₃ .

Therefore, the composite image P ₄ and dark binarized While the binary image P _5, and brightness binarized image P ₂ in an external illumination light L ₂ irradiated, and the P ₆ both images P ₅ By comparison, among the black portions on each of the images P ₅ and P ₆ , only the portions that overlap each other are extracted and recognized as the true region E of the Si crystal portion 10 on the image P ₇ .

That is, on the image P ₂ when the external illumination light L _{2 is} irradiated, since the Si crystal portion 10 is in a state close to a mirror surface, most of the illumination light L ₂ is specularly reflected, and the illumination light itself is irradiated from an oblique direction. Therefore, the Si crystal part 10 appears as a black part. On the other hand, if the Al eutectic layer 11 has a flat surface portion that does not become a rough surface as described above, the flat surface portion of the Al eutectic layer 11 is metal and
The reflectance is higher than that of the crystal part 10, and the ratio of irregularly reflecting the illumination light L ₂ is high. Therefore, the plane portion of the Al eutectic layer 11 appears on the image P ₂ as a white portion brighter than the Si crystal portion 10.

Therefore, by utilizing this property, the binarized images P ₅ and P ₆
By taking the logical product of the black part between
Only the true region E of the Si crystal portion 10 is extracted as in the image P ₇ .

When the true region E of the Si crystal portion 10 is extracted, the image processing apparatus 9 obtains the area of the region E as the number of pixels, and the deposition of the Si crystal portion 10 is determined from the ratio of this number of pixels to the total number of pixels on the screen. The area ratio will be calculated and output.

The embodiment shown in FIG. 8 shows an example in which the cylindrical inner peripheral surface 22a of the sample 22 is inspected. The objective lens 25 is attached at a right angle to the axis of the lens barrel 24 while the external illumination light source not shown is shown. The illumination light L ₁₂ of the internal illumination light L ₁₁ is transmitted through the optical fiber 27.
It is irradiated so that it intersects with. 28 is a fiber holder,
Reference numeral 26 is a reflection mirror, 29 is a shaft portion for rotating the external illumination light L ₁₂ , and 30 is a set screw. The procedure of the image processing is the same as the case described above, and in the case of this embodiment, the same operational effect as that of the first embodiment can be obtained.

EFFECTS OF THE INVENTION As described above, according to the method of the present invention, a portion having no difference in brightness between both images by concealing the image at the time of irradiation of the internal illumination light and the image at the time of simultaneous illumination of the internal and external illumination light, When the metal structure to be inspected is an aluminum alloy, for example,
Although the Si crystal part does not change in brightness even under the above two irradiation conditions, the Al eutectic layer is focused on the fact that the brightness changes under both irradiation conditions, and in order to extract the Si crystal part, there is a difference in brightness. Extracts a non-bright part as a region of a specific component of the surface tissue, inverts the light and dark, and then binarizes it, and extracts the region of the specific component by binarizing the image during external illumination light irradiation.
By combining two binarized images and extracting only the part where the regions extracted from each binarized image overlap each other as the true region of a specific component, extraction by the influence of external light etc. The error can be reduced to extract the specific component with high accuracy, and the reliability of the inspection result is improved.

[Brief description of drawings]

FIG. 1 (A) is a diagram showing an embodiment of the present invention, and is an enlarged view of a main part of FIG. 2 during irradiation of internal and external illumination light, and FIG. 1 (B).
Is a schematic flow chart of an image processing process at the time of extracting a specific component, FIG. 2 is a schematic explanatory view of the entire system showing one embodiment of the present invention, and FIG. 3 is an enlarged view of a main part at the time of internal illumination light irradiation, FIG. 4 is an enlarged view of a main part when external illumination light is irradiated, FIG. 5 is an explanatory diagram showing an image example when internal illumination light is irradiated, and FIG. 6 is an explanatory diagram showing an image example when external illumination light is irradiated. FIG. 7 is an explanatory view showing an example of an image at the time of illuminating internal and external illumination light, and FIG.
FIG. 9 is an enlarged view of a main part showing another embodiment of the present invention, and FIG. 9 is a schematic explanatory view of the entire system for explaining a conventional inspection method. 2,22 …… Sample, 4,24 …… Body tube, 5,25 …… Objective lens, 7
...... Internal illumination light source, 8 ... Camera, 9 ... Image processing device, 10 ... Si crystal part (smooth surface), 11 ... Al eutectic layer (rough surface), 12 ... External illumination light source, L ₁ , L ₁₁ ...... Internal illumination light,
L ₂ , L ₁₂ …… External illumination light.

Claims (1)

[Claims] 1. A method for extracting and inspecting a specific component of a surface texture based on a difference in light reflection characteristics between a rough surface portion and a smooth surface of a sample surface, wherein the sample is internally illuminated through an objective lens of a microscope. Irradiate light with external illumination light from an oblique direction that forms a predetermined angle with the sample surface, and emit both internal illumination light and external illumination light, only internal illumination light, and external illumination light only. In each case, the surface texture of the sample captured by the objective lens is imaged by the imaging device, and the images of the internal illumination light irradiation and the images of the internal and external illumination light simultaneous irradiation are compared. Among them, the bright part with no difference in brightness is extracted as the area of the specific component of the surface tissue, and the light and dark are inverted, and then the light and dark binarization is performed. Area of Inspection method of a metal structure, wherein a region extracted from the binarized image by synthesizing the two binarized image to extract only the portion overlapping with each other as the true region of a particular component.