JP4258330B2 - Film thickness measuring method and film thickness measuring apparatus - Google Patents

Description

  The present invention relates to a film thickness measuring method and a film thickness measuring apparatus. More specifically, the present invention relates to a film thickness measurement method and a film thickness measurement apparatus that can measure the film thickness of a film with high accuracy.

  Conventionally, from the viewpoint of improving the corrosion resistance of the base material, a film is formed on the surface of the base material by plating or the like. If this film thickness is not the specified film thickness, the desired corrosion resistance is ensured. Will not be. For this reason, various methods and apparatuses for measuring the film thickness of such a coating have been proposed.

  For example, in Patent Document 1, the surface of the coating is irradiated to image the irradiated portion, and chromaticity coordinate values x, y in the XYZ color system or X of tristimulus values in the XYZ color system based on the imaging signal. , Y, and a method and apparatus for measuring the film thickness based on the chromaticity coordinate values x, y or the tristimulus values X, Y have been proposed.

However, in the film thickness measurement device shown in the example of Patent Document 1, when the object to be measured is a metal and the surface is in a mirror state, the occurrence of reflection in the camera and uniform illumination cannot be easily realized. Since it is difficult to stably image the surface color of an object, there is a problem that accurate film thickness measurement cannot be performed.
Japanese Patent Laid-Open No. 2003-147581

  The present invention has been made in view of the problems of the prior art, and an object thereof is to provide a film thickness measuring method and a film thickness measuring apparatus that can use various light sources and can accurately measure the film thickness. It is said.

The film thickness measurement method of the present invention comprises a non-coated part where no film is formed, a non-stable film part where the film thickness of the film continuing to the non-coating part is unstable, and a continuous part to the unstable film part. A film thickness measuring method for measuring a film thickness of a substrate having a stable film thickness portion where the film thickness of the coating film is stable,
While transporting the base material in a predetermined direction, the film thickness of the unstable film thickness portion is measured by a direct measurement device that directly measures the film thickness spot-wise, and the unstable film thickness portion is measured by a predetermined light source. Extracting specific color information from a color image captured while indirectly illuminating, obtaining a correlation between the film thickness measured by the direct measurement device and the extracted specific color information for each substrate,
The film thickness of the substrate is determined online based on the specific color information extracted from the color image obtained by imaging the film thickness stable part following the imaging of the film thickness unstable part and the correlation. It is characterized by measuring.

The film thickness measuring device of the present invention includes a non-coated part where no film is formed, a non-stable film part where the film continuous to the non-coated part is unstable, and a non-stable part. A film thickness measuring device for measuring the film thickness of a substrate having a film thickness stable portion where the film thickness of the coating film is stable online,
A color reference film thickness measurement unit that measures film thickness based on a color image, a film thickness direct measurement unit that directly measures film thickness in a spot manner, and an output unit,
The color reference film thickness measurement unit includes an illuminating unit having a predetermined light source, a color imaging unit that captures a film irradiated by the illuminating unit, and a specific color obtained from a color image captured by the color imaging unit Calculating a correlation between the information and the measured value measured by the film thickness direct measurement unit for each base material, and a control / arithmetic processing device that calculates the film thickness based on the calculated correlation,
The correlation is calculated based on a measurement value and a captured image of the film thickness direct measurement unit in the film thickness unstable part.

  According to the first embodiment of the film thickness measuring apparatus and the film thickness measuring method of the present invention, it is possible to measure the film thickness such as plating inexpensively and easily with high accuracy using a light source such as a fluorescent lamp. An excellent effect is obtained.

  Further, according to the second embodiment of the film thickness measuring apparatus and the film thickness measuring method of the present invention, the film thickness measured by the color reference during the film thickness measurement is directly corrected by the film thickness, so that calibration for each lot is performed. An excellent effect is obtained that the productivity is improved because it is unnecessary.

  Furthermore, according to the third embodiment of the film thickness measuring apparatus and the film thickness measuring method of the present invention, the thickness of the film such as plating can be obtained online without obtaining the correlation between the specific color information such as chromaticity and the film thickness in advance. It is possible to measure, and an excellent effect is obtained that the working efficiency is further improved and the productivity is further improved.

  Hereinafter, although the present invention is explained based on an embodiment, referring to an accompanying drawing, the present invention is not limited only to this embodiment.

Embodiment 1
A film thickness measuring apparatus applied to the film thickness measuring method of Embodiment 1 of the present invention is shown in FIG.

  As shown in FIG. 1, the film thickness measuring apparatus A captures a color image of the illumination device 1, the indirect illumination means 2 that indirectly irradiates the measurement target by irregularly reflecting the light from the illumination device 1, and the measurement target P. The color imaging means 3, the output means (output device) 4, and the control / arithmetic processing device 5 are provided as main components.

  The illumination device 1 is a surface light source composed of, for example, a fluorescent lamp or a white LED. Here, the type of the light source and the lighting method thereof are appropriately selected according to the imaging speed of the imaging means 3 to be used. For example, when a normal video camera is used as the imaging means 3, a method of lighting with a commercial frequency power source using a fluorescent lamp is adopted from the viewpoint of cost reduction. Also, the exposure time is shortened and the lighting cycle of the light source is reduced by increasing the electronic shutter speed, imaging using a high-speed camera, or scanning a line sensor (such as a one-dimensional CCD) at high speed. Depending on the exposure time and cost effectiveness, the fluorescent lamp may be turned on at a high frequency and blinked at a cycle shorter than the exposure time, or the white LED may be turned on by a DC power source. To prevent flashing.

  The indirect illumination means 2 diffuses light from the light source of the illumination device 1 to uniformly illuminate the measurement region. For example, as shown in FIGS. The arc surface is formed with a white irregular reflection surface 2a. The size of the circular arc surface is appropriately adjusted according to the measurement region. If the measurement region is, for example, 300 mm × 250 mm, the width is 500 mm and the curvature radius is 250 mm.

  The color imaging means 3 is, for example, a color CCD camera that can image a measurement region. When the measurement object P moves in one direction, the color imaging means 3 can be a one-dimensional line sensor arranged orthogonal to the movement direction of the measurement object P.

  The output means 4 is, for example, a digital display device or a liquid crystal display device that displays the film thickness calculated by the control / arithmetic processing device 5. The output unit 4 may be a printer.

  The control / arithmetic processing unit 5 is, for example, a personal computer, and controls the illumination device 1, the color imaging unit 3, and the output unit 4, and performs a film thickness calculation process described later.

  Hereinafter, the film thickness calculation process will be described.

  In color televisions and color CCD cameras, various colors are expressed by mixing the three primary colors. That is, various colors are expressed by appropriately mixing R (red), G (green), and B (blue). For example, when RGB three colors are mixed, it becomes colorless or white, when RG two colors are mixed, it becomes yellow, when GB two colors are mixed, it becomes light blue, and when RB two colors are mixed, it turns purple. Become. Further, a color that is located at the center of the mixture of the three primary colors of RGB and has a point-symmetrical relationship with respect to white or white is referred to as a complementary color. For example, yellow is complementary to blue. In other words, it becomes yellow when the blue color is reduced from colorless or white. Further, when the degree of reduction of blue color from colorless or white is adjusted, the degree of yellow obtained is also changed.

  For example, when a gold plating F is applied to a stainless steel substrate B (surface color is colorless) B and irradiated with white light, blue is absorbed by the gold plating F, that is, the blue reflectance is reduced and the reflected light looks yellow. And yellow becomes dark from the place where the fall of the reflectance of blue increases as the film thickness of the gold plating F increases. This is schematically shown in FIG.

  This means that the film thickness of the gold plating F can be measured by irradiating the base material B on which the gold plating F has been made with white light and measuring the degree of blue of the reflected light. FIG. 5 shows the results obtained by measuring the film thickness of the gold plating F and the degree of blue, that is, b chromaticity (= B / (R + G + B)) based on such knowledge. Here, “chromaticity” refers to the degree of color excluding brightness.

  FIG. 5 shows that the film thickness and b chromaticity have a good linear relationship. That is, it can be seen that the film thickness of the gold plating F can be measured accurately (for example, the measurement error is 5 nm or less) by measuring the b chromaticity.

  In addition, the following merits can be obtained by using chromaticity for film thickness measurement. In other words, the measurement accuracy is not affected by fluctuations or irregularities in the absolute amount of light, tilt of the measurement object, or vertical fluctuations, and there is also the advantage that color aging such as light sources can be easily corrected. It is done.

  Next, the film thickness measurement of the gold plating by the film thickness measuring apparatus A having such a configuration will be described.

(1) The relationship between the film thickness and b chromaticity is measured in advance to create a b chromaticity-film thickness function (or b chromaticity-film thickness map).

(2) The measurement object P is indirectly irradiated with white light.

(3) The measurement object P that is indirectly irradiated with white light is imaged by a color CCD camera.

(4) The b chromaticity of the captured color image is measured.

(5) The film thickness is calculated by the b chromaticity-film thickness function prepared in advance based on the measured b chromaticity.

  Thus, according to the film thickness measuring apparatus A of Embodiment 1, the film thickness of the gold plating F can be accurately measured using various light sources.

Embodiment 2
A film thickness measuring apparatus A1 applied to the film thickness measuring method according to Embodiment 2 of the present invention is shown in a block diagram in FIG. The second embodiment is obtained by modifying the first embodiment, and measures the plated film thickness after plating in a gold plating process on-line.

  As shown in FIG. 6, the film thickness measuring apparatus A1 includes a color reference film thickness measuring unit 10 that measures the film thickness based on the b chromaticity obtained from the color image captured by the color imaging unit, and the film thickness. A film thickness direct measurement unit 20 that directly measures, a film thickness correction unit 30 that corrects a film thickness measured by the color reference film thickness measurement unit 10 with a film thickness measured by the film thickness direct measurement unit 20, and an output unit 40 It is supposed to comprise. In addition, the code | symbol R in FIG. 6 shows a plating roll material.

  FIG. 7 shows a more specific configuration of the film thickness measuring device A1.

  The color reference film thickness measuring unit 10 includes an illumination device 11, a color imaging unit 12, and a control / arithmetic processing device 50. In addition, the code | symbol 11a in FIG. 7 shows an indirect lighting fixture.

  The illuminating device 11 is, for example, a fluorescent lamp that is turned on by a commercial power supply, and its longitudinal direction is orthogonal to the conveying direction of the plating roll material R, and is disposed at a predetermined position above the plating roll material R. It is supposed to illuminate. The light source may be a light source in which a three-color light source of red, green, and blue is lit in a predetermined time division.

  The color image pickup means 12 is, for example, a color CCD camera 12A, and is arranged so as to pick up an image of the portion of the plating roll material R irradiated by the illumination device 11 from obliquely above. The color images continuously captured by the color CCD camera 12A are transmitted to the control / arithmetic processing unit 50.

  The control / arithmetic processing unit 50 is, for example, a personal computer, performs image processing on a color image transmitted from the color CCD camera 12A, measures b chromaticity, and stores b chromaticity stored in advance based on the b chromaticity. The film thickness, that is, the color reference film thickness is calculated by the film thickness function (or b chromaticity-film thickness table). The control / arithmetic processing unit 50 also receives a film thickness measurement value from the film thickness direct measurement unit 20, and corrects the color reference film thickness based on the measured film thickness value. That is, the control / arithmetic processing unit 50 also functions as the film thickness correction unit 30. In addition, the control / arithmetic processing unit 50 also controls the color reference film thickness measurement unit 10, the film thickness direct measurement unit 20, and the output unit 40.

  The film thickness direct measurement unit 20 is, for example, a spectral interference film thickness measurement device 21 and measures the plating film thickness of the plating roll material R in a spot manner, for example, at a cycle of 100 milliseconds. The film thickness measured by the film thickness direct measurement unit 20 (hereinafter also referred to as direct film thickness) is transmitted to the control / arithmetic processing device 50 as described above.

  When there is a difference between the color reference film thickness and the direct film thickness, the film thickness correction unit 30 corrects the color reference film thickness so as to directly match the film thickness. More specifically, this correction is performed as follows.

  For example, if the direct film thickness is A, the color reference film thickness is B, and the allowable limit value of the difference between them is C, as shown in FIG. 8A, the width exceeding the allowable limit value C (specifically, When the time or length (x) is equal to or greater than the specified width (specifically, the specified time or specified length) X, an appropriate part is extracted from an interpolation curve or interpolation line such as a preset spline curve. The color reference film thickness B (color reference film thickness curve) where the difference between the color reference film thicknesses B exceeds the allowable limit value C is corrected by the extracted curve or straight line.

  This correction may be performed immediately when the width x in which the difference between the two exceeds the allowable limit value C becomes equal to or greater than the specified width X, or the difference between the two exceeds the allowable limit value C. The inspector checks the surface for any abnormalities based on the time, the time exceeded, and the position (these are automatically recorded as a database). It may be made like.

  The output unit 40 is an output device 41 such as a digital display device or a liquid crystal display device that displays the film thickness corrected by the control / arithmetic processing device 50. The output unit 40 may be a printer.

  Thus, in this film thickness measuring apparatus A1, while the film thickness is continuously measured by the color reference film thickness measuring unit 10, that is, the film thickness is measured over the entire range of the plating roll material R. The film thickness directly measured by the thickness direct measurement unit 20 is spot-measured, and then the film thickness measured by the color reference film thickness measurement unit 10 is corrected by the direct film thickness measured spot by the film thickness direct measurement unit 20. It is supposed to be. For this reason, there is no need to obtain the relationship between the chromaticity and the film thickness in advance for each lot. Conversely, if the relationship between the b chromaticity and the film thickness is obtained once, the plating roll is determined according to the relationship. It is possible to accurately measure the film thickness over the entire range of the material R. Therefore, productivity is improved.

  In addition, by performing threshold processing on the measured film thickness with an appropriate threshold, it is possible to detect non-plating, color unevenness, and the like.

Embodiment 3
A film thickness measuring apparatus A2 applied to the film thickness measuring method according to Embodiment 3 of the present invention is schematically shown in FIG. The third embodiment is a modification of the second embodiment, and the plating film thickness after plating is measured online without obtaining the relationship between chromaticity and film thickness in advance in the gold plating process. It is supposed to be.

As shown in FIG. 9, the hoop-shaped plating roll material R includes a non-plated portion (front unplated portion) R ₁ where the tip portion is not plated, and a film in which the film thickness immediately after the start of plating is not stable. Thickness unstable part (front film thickness unstable part) R ₂ , subsequent film thickness stable part R ₃ where film thickness is stable, and subsequent film thickness unstable part where film thickness is not stable immediately after the end of plating (Rear film thickness unstable part) R ₄ and subsequent non-plated part (rear non-plated part) R ₅ exist.

Therefore, in the third embodiment, the control / arithmetic processing unit 50 uses the b chromaticity obtained from the color image obtained by imaging the front film thickness unstable portion R ₂ by the color imaging means 12 and the front film thickness unstable. A correlation (see FIG. 10) with the film thickness obtained by measuring the portion R ₂ by the film thickness direct measurement unit 20 is obtained, and the film thickness of the film thickness stabilizing portion R ₃ is determined based on the correlation. The thickness is measured by the thickness measuring unit 10. Here certain thickness stabilizer R ₃ is, for example, measurement of the film thickness directly measuring section 20 is a stable point.

  As described above, in Embodiment 3, the thickness of the gold plating of the hoop-shaped plating roll material R is measured without obtaining the relationship between the chromaticity and the film thickness in advance, so that the work efficiency is improved and the productivity is improved. Will improve.

  As mentioned above, although this invention has been demonstrated based on embodiment, this invention is not limited only to this embodiment, A various change is possible. For example, in the embodiment, the film thickness is measured by measuring the b chromaticity, but the r chromaticity and the g chromaticity may be set according to the type of the film of the measurement target P.

  In addition, since the RGB color system and the XYZ color system can be converted into each other by simple matrix conversion, the film thickness is measured by the chromaticity of the XYZ color system instead of the chromaticity of the RGB color system. May be.

  Furthermore, the film thickness correction unit 30 of the second embodiment may be added to the third embodiment.

It is a block diagram of the film thickness measuring apparatus which concerns on Embodiment 1 of this invention. It is the schematic of the indirect illumination means used for the film thickness measuring apparatus. It is the sectional view on the AA line of FIG. It is explanatory drawing which shows a mode that yellow becomes dark as the film thickness of gold plating becomes thick. It is an example of the graph which shows the relationship between b chromaticity and a film thickness. It is a block diagram of the film thickness measuring apparatus which concerns on Embodiment 2 of this invention. It is the same schematic. It is explanatory drawing of the correction method by the direct film thickness of the color reference film thickness in Embodiment 2 of this invention. It is the schematic block of the film thickness measuring apparatus which concerns on Embodiment 3 of this invention. It is a graph which shows correlation with chromaticity and a film thickness.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Illuminating device 2 Indirect illumination means 2a Diffuse reflection surface 3 Color imaging means 4 Output means, output device 5 Control / arithmetic processing apparatus 10 Color reference film thickness measurement part 11 Illumination apparatus 12 Color imaging means 12A Color CCD camera 20 Film thickness direct measurement part 21 Spectral Interference Film Thickness Measurement Device 30 Film Thickness Correction Unit 40 Output Unit 41 Output Device A Film Thickness Measurement Device B Base Material F Gold Plating P Measurement Object R Plating Roll Material

Claims (2)

The film-free part where the film is not formed, the film thickness unstable part where the film thickness of the film continuous to the filmless part is not stable, and the film thickness of the film continuous to the film thickness unstable part are stable A film thickness measuring method for measuring a film thickness of a substrate having a film thickness stabilizing portion that is online,
While transporting the base material in a predetermined direction, the film thickness of the unstable film thickness portion is measured by a direct measurement device that directly measures the film thickness spot-wise, and the unstable film thickness portion is measured by a predetermined light source. Extracting specific color information from a color image captured while indirectly illuminating, obtaining a correlation between the film thickness measured by the direct measurement device and the extracted specific color information for each substrate,
The film thickness of the substrate is determined online based on the specific color information extracted from the color image obtained by imaging the film thickness stable part following the imaging of the film thickness unstable part and the correlation. A film thickness measuring method characterized by measuring. The film-free part where the film is not formed, the film thickness unstable part where the film thickness of the film continuous to the filmless part is not stable, and the film thickness of the film continuous to the film thickness unstable part are stable A film thickness measuring device that measures the film thickness of a substrate having a film thickness stabilizing portion that is online,
A color reference film thickness measurement unit that measures film thickness based on a color image, a film thickness direct measurement unit that directly measures film thickness in a spot manner, and an output unit,
The color reference film thickness measurement unit includes an illuminating unit having a predetermined light source, a color imaging unit that captures a film irradiated by the illuminating unit, and a specific color obtained from a color image captured by the color imaging unit Calculating a correlation between the information and the measured value measured by the film thickness direct measurement unit for each base material, and a control / arithmetic processing device that calculates the film thickness based on the calculated correlation,
The film thickness measuring apparatus, wherein the correlation is calculated based on a measurement value and a captured image of the film thickness direct measurement unit in the film thickness unstable portion.

Images