Surface texture measuring device and surface texture measuring method

Abstract

To provide a surface property measuring device that can measure the desired surface properties regardless of the surface shape or layer structure. [Solution] The surface texture measuring device 1 comprises an imaging unit 2 for imaging the object to be measured S, a light source 3, an optical unit 4 that irradiates the object to be measured S with light output from the light source 3 and causes the reflected light from the object to be measured S to be incident on the imaging unit 2, and a retroreflective plate 7. The device further comprises a data processing device 8 for calculating the surface texture of the object to be measured S. The data processing device 8 calculates a value indicating the surface texture of the object to be measured S based on at least one of an image showing the specular reflection of the object to be measured S and an image showing the backscattered reflection of the object to be measured S, both of which are captured by the imaging unit 2.

Description

[Technical Field]

[0001] The present invention relates to a surface texture measuring device and a surface texture measuring method. [Background technology]

[0002] Surface properties include various measurement items such as surface roughness, surface color, gloss, and thickness. Measurement devices for each of these items have been proposed. For example, Patent Document 1 discloses a surface roughness measuring device that uses a quasi-blackbody to reduce the influence of reflections within the optical system. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-149286 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Incidentally, surface shapes include mirrored and roughened surfaces. Furthermore, surfaces may have one or more layers of film formed on them. To date, no device has been proposed that can measure the desired surface properties regardless of the surface shape or layer structure. Therefore, the object of the present invention is to provide a surface property measuring device that can measure the desired surface properties regardless of the surface shape or layer structure. [Means for solving the problem]

[0005] The surface property measurement device of the present invention includes an imaging unit that images a measurement object, a light source, an optical unit that irradiates the measurement object with the light output from the light source and makes the reflected light from the measurement object enter the imaging unit, and a retroreflective plate, and is a surface property measurement device further including a data processing device that calculates the surface property of the measurement object. The data processing device calculates a value indicating the surface property of the measurement object based on at least one of an image showing specular reflection of the measurement object and an image showing backscattering reflection of the measurement object, which are imaged by the imaging unit.

Effect of the Invention

[0006] The surface property measurement device of the present invention can provide a surface property measurement device that can measure the properties of a desired surface regardless of the shape or layer structure of the surface.

Brief Description of the Drawings

[0007] [Figure 1] It is a configuration diagram of the surface property measurement device according to an embodiment of the present invention. [Figure 2] It is a block diagram showing the hardware configuration of the data processing device. [Figure 3] It is a block diagram showing the functional configuration of the data processing device. [Figure 4A] It is a diagram showing an optical system where a blackboard is not installed. [Figure 4B] It is a diagram showing an optical system where a blackboard is installed. [Figure 5] It is a surface photograph of an aluminum shot blasting material. [Figure 6] It is a diagram showing the correlation between Rq of backscattering and abrasive grain #N. [Figure 7] It is a diagram showing the average value of #N, σ, and relative σ obtained by an approximate formula. [Figure 8] It is a diagram showing the specular reflectance and rough surface reflectance of each tile. [Figure 9A] It is a diagram showing the specular reflection chromaticity values of each tile. [Figure 9B] It is a diagram showing the backscattering reflection chromaticity values of each tile. [Figure 10] It is a diagram showing the reflectance of the mirror surface and the rough surface of the silicon oxide film at 6 levels. [Figure 11A] It is a diagram showing the theoretically calculated spectral reflectance of the mirror surface. [Figure 11B] It is a diagram showing the theoretically calculated spectral reflectance of the rough surface. [Figure 12A] It is a diagram showing the estimated film thickness, etc. when the silicon substrate is a mirror surface. [Figure 12B] It is a diagram showing the estimated film thickness, etc. when the silicon substrate is a rough surface. [Figure 13] It is a diagram showing the film thickness and reflection color value of the silicon oxide film. [Figure 14] It is a diagram showing the reflection color difference value with a film thickness pitch of 0.5 nm based on the film thickness of 0 of the silicon oxide film. [Figure 15] It is a graph plotting the values shown in FIG. 14. [Figure 16] It is a diagram showing the estimated film thickness, etc. of the decorative SUS oxide film. [Figure 17] It is a diagram showing the reflection color value of the decorative SUS oxide film. [Figure 18A] It is a diagram showing the chromaticity values from Color1 to 10 of the decorative SUS oxide film. [Figure 18B] It is a diagram showing the chromaticity values from Color11 to 23 of the decorative SUS oxide film. [Figure 19] It is a flowchart showing the process flow of the surface property measurement method. [Figure 20] It is a flowchart showing another process flow of the surface property measurement method.

Embodiments for Carrying Out the Invention

[0008] (Surface Property Measuring Apparatus) Embodiments for carrying out the present invention will be described with reference to the drawings. The content described below is exemplary. Referring to Figure 1, the configuration of the surface texture measuring device 1 according to an embodiment of the present invention will be described. Figure 1 is a configuration diagram of the surface texture measuring device 1. The surface texture measuring device 1 comprises an imaging unit 2, a light source 3, an optical unit 4, a retroreflective plate 7, and a data processing device 8. The surface texture measuring device 1 is a device for measuring the surface texture of an object S to be measured. Line OA1 indicates the optical axis OA1 of the imaging unit 2. Line OA2 indicates the optical axis OA2 of the retroreflective plate 7. The object S to be measured may be moved continuously.

[0009] The imaging unit 2 is a color camera. The imaging unit 2 is equipped with a CMOS type image sensor. The image sensor of the imaging unit 2 has, for example, 2048 × 1536 pixels for R, G, and B. The imaging unit 2 receives incident light on its light-receiving surface. The imaging unit 2 converts the optical image formed on the light-receiving surface into grayscale data for each pixel and outputs it. This output signal is called the RGB luminance signal.

[0010] The optical axis OA1 is tilted at an angle θ1 with respect to the perpendicular PL of the object S at point P on the surface of the object S. When the measurement distance of the telecentric lens 5 is 110 mm, the angle θ1 is, for example, between 10° and 15°. The exposure time of the imaging unit 2 is, for example, between 80 μsec and 700 μsec.

[0011] Light source 3 is a white LED light source. The brightness value of the white LED light source at wavelengths shorter than 400 nm is higher than that of other light sources. The brightness of the white LED light source is less affected by temperature. A portion of the LED light output from light source 3 is reflected by the beam splitter 6 and irradiated onto the object S to be measured. Light source 3 is powered by an LED power supply. The LED power supply is not shown in the diagram.

[0012] The optical unit 4 is the part that irradiates the object to be measured S with light output from the light source 3 and directs the reflected light from the object to be measured S into the imaging unit 2. The optical unit 4 includes a telecentric lens 5 and a beam splitter 6. The telecentric lens 5 is a coaxial incident lens designed so that the principal ray is parallel to the optical axis. The telecentric lens 5 is positioned so that the center of the lens coincides with the optical axis OA1.

[0013] The beam splitter 6 is an optical element that splits incident light into transmitted light and reflected light. The beam splitter 6 is installed between the telecentric lens 5 and the imaging unit 2. The beam splitter 6 is positioned so that its transmitting / reflecting surface is tilted at approximately 45° with respect to the optical axis OA1.

[0014] The retroreflective plate 7 is an optical component that reflects incident light along the incident light path. The optical axis OA2 is tilted at an angle θ2 with respect to the perpendicular PL at point P on the surface of the object S being measured. Angle θ2 is the same as angle θ1. Angle θ2 is between 10° and 15°. The retroreflective plate 7 reflects the light incident from the object S being measured back towards the object S being measured. By using the retroreflective plate 7, the effect of the tilt of the object S being measured can be reduced. The tilt of the object S being measured can be, for example, within a range of ±3° with respect to the reference plane.

[0015] In the optical system shown in Figure 1, a portion of the LED light output by the light source 3 is reflected by the beam splitter 6. The reflected light is irradiated onto the object to be measured S via the telecentric lens 5, as shown by the incident light L1. The incident light L1 irradiated onto the object to be measured S is reflected by the surface of the object to be measured S. The reflected light is incident on the retroreflective plate 7, as shown by the reflected light L2. The reflected light L2 incident on the retroreflective plate 7 is reflected by the surface of the retroreflective plate 7 and then incident on the surface of the object to be measured S as reflected light L3. The reflected light L3 incident on the surface of the object to be measured S is reflected by the surface of the object to be measured S. The reflected light is incident on the imaging unit 2 via the telecentric lens 5 and the beam splitter 6 as reflected light L4. An optical image of the reflected light L4 is formed on the light-receiving surface of the imaging unit 2. The formed optical image is converted into grayscale data, and the converted grayscale data is output.

[0016] (Data processing device) The data processing device 8 will be described with reference to Figure 2. Figure 2 is a block diagram showing the hardware configuration of the data processing device. The data processing device 8 is a device that controls the operation of the surface texture measuring device 1. The data processing device 8 controls, for example, the operation of the imaging unit 2 and the exposure time. The data processing device 8 also measures the surface texture of the object to be measured S. The surface texture measurement is performed based on image data obtained by photographing the object to be measured S.

[0017] As shown in Figure 2, the data processing device 8 includes a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a bus 14, an input / output interface 15, an output unit 16, an input unit 17, a storage unit 18, a communication unit 19, and a drive 20.

[0018] The CPU 11 is a device that executes various processes according to a program recorded in the ROM 12 or a program loaded into the RAM 13 from the storage unit 18. The RAM 13 is a device that stores data necessary for the CPU 11 to execute various processes. The bus 14 connects the CPU 11, ROM 12, and RAM 13 to each other.

[0019] The input / output interface 15 is connected to the bus 14. The output unit 16, input unit 17, storage unit 18, communication unit 19, and drive 20 are connected to the input / output interface 15. The output unit 16 is the part that outputs various types of information as images or sounds. The output unit 16 consists of a display, speaker, etc. The input unit 17 is the part that accepts input of various types of information. The input unit 17 consists of a keyboard, mouse, touch panel, etc. The storage unit 18 is the part that stores various types of data. The storage unit 18 consists of a hard disk and DRAM (Dynamic Random Access Memory), etc. The communication unit 19 is the part that communicates with other devices via a network. The network includes the internet. The drive 20 consists of a magnetic disk, optical disk, magneto-optical disk, or semiconductor memory, etc. A removable media 21 is installed in the drive 20. Programs read from the removable media 21 by the drive 20 are installed in the storage unit 18 as needed. The removable media 21 can store various types of data stored in the storage unit 18 in the same way as the storage unit 18.

[0020] Figure 3 is a block diagram showing the functional configuration of the data processing device 8. As shown in Figure 3, the data processing device 8 is electrically connected to the imaging unit 2 and the light source 3 via a communication cable. The data processing device 8 includes a CPU 11, a storage unit 18, and a communication unit 19. The CPU 11 comprehensively controls the operation of the data processing device 8. In each calculation process that identifies surface property items of the object to be measured S, the CPU 11 functions as an imaging control unit 31, a light source control unit 32, a data calculation unit 33, a film thickness calculation unit 34, a roughness index calculation unit 35, and a color value calculation unit 36. The imaging control unit 31 controls, for example, the operation of the imaging unit 2. The operation of the imaging unit 2 includes, for example, opening and closing the shutter and setting the exposure time. The light source control unit 32 controls, for example, the intensity of the LED light from the light source 3. The data calculation unit 33 calculates the retroreflective coefficient for each pixel in each imaging area based on the image captured by the imaging unit 2. The CPU 11 can also function as a glossiness calculation unit 37. The glossiness calculation unit 37 calculates, for example, the ratio of the intensity of incident light to specularly reflected light obtained by measurement. The glossiness calculation unit 37 may then determine the glossiness based on the calculated ratio, for example, by referring to a predetermined index.

[0021] (backscattered light) The measurement of backscattered light will be explained with reference to Figures 4A and 4B. Figure 4A shows an optical system without a blackboard. Figure 4B shows an optical system with a blackboard. As shown in Figure 4A, in specular reflection measurement, the first specular reflection of light emitted from the optical system at the object S to be measured is reflected by the retroreflector 7, and the reflected light from the retroreflector 7 is reflected a second time at the object S to be measured, and enters the imaging unit 2 as specular reflection L4. Specular reflection is measured based on this specular reflection L4 that enters the imaging unit 2. The reflectance of the retroreflector 7 is assumed to be 0.9.

[0022] If the surface of the object S to be measured is a perfect mirror surface, no backscattered reflected light is generated. If the surface of the object S to be measured is rough, backscattered reflected light is generated. When backscattered light is generated, in addition to the specularly reflected light L4, backscattered light L5 is incident on the imaging unit 2. To measure backscattering, a blackboard 9 is placed in front of the retroreflective plate 7, as shown in Figure 4B. By placing the blackboard 9, specularly reflected light L4 is not incident on the imaging unit 2, and backscattered light L5 is incident on the imaging unit 2. By not letting specularly reflected light L4 incident on the imaging unit 2, backscattering can be measured. Specularly reflected light L4 can be determined by subtracting the incident light (L5) in the optical system shown in Figure 4B from the incident light (L4+L5) in the optical system shown in Figure 4A. Note that the blackboard 9 is an example, and other items such as a black cloth or a diffusing blackboard may also be used.

[0023] (Surface roughness) This section explains the measurement of surface roughness. The materials used and measurement conditions are as follows. The material being measured is aluminum shot-blasted material. The types of abrasive grains (#N) used for blasting are #30, #80, #180, #220, and #320. Figure 5 shows surface photographs of the five types of aluminum shot-blasted material. The pixels used for imaging were the 2000 x 200 pixels in the central part of the imaging unit 2. The optical magnification was such that 1 pixel = 8 μm x 8 μm. A color reflectance image was obtained from the formed optical image. The shutter time was shortened for rougher surfaces to prevent the reflectance measurement from saturating. The correspondence between the type of abrasive grain and the shutter time is as follows: #30 is 80 μsec, #80 is 150 μsec, #180 is 200 μsec, #220 is 500 μsec, and #320 is 700 μsec.

[0024] Surface roughness can be determined based on the backscatter Rq. The procedure for calculating the backscatter Rq is as follows. The color reflectance image rφ(R, G, B) is converted to a monochrome reflectance image rφ(monochrome) using the following formula. rφ(monochrome) = 0.299rφ(R) + 0.587rφ(G) + 0.114rφ(B) Next, calculate Rq using the following formula. Rq=√(1 / N)xΣi=1~N|Zi―Rave| 2 Zi is the measured height. Rave is the average height of the surface. Next, divide Rq by the monochrome reflectance image rφ(monochrome)ave as shown in the following formula. This is because optical reflectance increases with reflectance, unlike normal Rq. Surface roughness = Rq(rφ(monochrome)) / rφ(monochrome)ave

[0025] Figure 6 shows the correlation between backscatter Rq and #N. Figure 6 shows the correlation between backscatter Rq and #N using a fifth-degree polynomial. The correlation between the obtained surface roughness, i.e., backscatter Rq, and #N is given by a fifth-degree polynomial with a correlation degree R. 2It is approximated to be ≒1.0. FIG. 7 shows the average #N, σ, and relative σ for each setting #N obtained by the approximation formula. The number of measurement points is 10, and the average value thereof is obtained. The values shown in FIG. 7 are calculated by the roughness data calculation unit 33.

[0026] The procedure for measuring Rq of the backscattering in the surface property measuring apparatus 1 is generally as follows. The backscattered light L5 is measured with the blackboard 9 inserted in front of the retroreflector 7. The imaging unit 2 images the combined optical image of the backscattered light L5. The imaging control unit 31 stores the captured image. Based on the stored data, the data calculation unit 33 calculates the Rq of the backscattering, and the roughness index calculation unit 35 calculates the values necessary for preparing the approximation formula. By registering the approximation formula in advance, the #N of the abrasive grains can be obtained by measuring the Rq of the backscattering. This makes it easy to evaluate whether stable rough surface treatment is being performed.

[0027] In order to obtain the Rq of the specular surface and the Rq of the backscattering with the surface property measuring apparatus 1, a mechanism for turning on and off the retroreflector 7 is required. The retroreflector 7 can be configured as follows. Black roughening treatment is performed on half of the retroreflector 7. Half of the surface of the retroreflector 7 is covered with a black cloth or a diffusing blackboard. A mechanical mechanism capable of turning on and off the retroreflector 7 is provided in front of the retroreflector 7.

[0028] (Reflected color value) The reflected color value will be explained. The reflected color value of the measurement object can be obtained by converting the three stimulus values X, Y, Z into the reflected color values L, a, b. The conversion of the reflected color value of the color reflectance rφ(R, G, B)% to the reflected color value Lab can be performed using the following formula. L = 116×(rφ(G) / 100.00) 1 / 3 -16 a = 500×[{rφ(R) / R 10} 1 / 3 -(rφ(G) / G 10 ) 1 / 3 b = 200×[{rφ(G) / G 10} 1 / 3 ​-(rφ(B) / B 10 ) 1 / 3 ] The R, G, and B components of the reference standard light source D65 are: 10 =94.811, G 10 =100.0, B 10 = 107.333. The color difference value can be calculated using the following formula after determining the reference color values. ΔE 2 =ΔL 2 +Δa 2 +Δb 2 ΔE = √(ΔL) 2 +Δa 2 +Δb 2 )

[0029] (Multilayer coating consisting of a coating film and a transparent film) Some coatings consist of a transparent film applied to the surface of a base coating. Such coatings are found in tiles, automobiles, and home appliances. Conventionally, when a transparent film is applied to the surface of a coating, it is difficult to individually measure the reflectance and color values ​​of the coating and the transparent film.

[0030] In the surface properties measuring device 1, the reflectance and reflective color value of the transparent film can be determined in the same way as the specular reflectance and reflective color value of the specular surface when measuring surface roughness. The reflectance and reflective color value of the underlying coating film can be determined in the same way as the backscattered reflectance and backscattered reflective color value when measuring surface roughness. In other words, the surface properties measuring device 1 can measure the reflectance and reflective color value of the underlying coating film and the reflectance and reflective color value of the transparent film individually.

[0031] Measurements can be performed with a pixel resolution of 8 μm per pixel. A retroreflective plate with one side blackened is used. By using such a retroreflective plate, specular reflectance and backscattered reflectance can be simultaneously determined from a single image measurement. For example, specular reflectance can be measured at the 400 x 200 pixels on the left edge of the imaging screen, and backscattered reflectance can be measured at the 400 x 200 pixels on the right edge at the same time. In the surface texture measuring device 1, the number of pixels can be arbitrarily set to 80,000 pixels (400 x 200) and 250,000 pixels (500 x 500), etc., with each pixel being 8 μm. Therefore, a variety of surface texture measurement results can be obtained.

[0032] The following are examples of measurements. In the following examples, thick tiles in milky white, light beige, green, and black were measured. Figure 8 shows the specular reflectance and backscatter reflectance of each tile. As shown in Figure 8, the specular reflectance is higher than the backscatter reflectance for all tiles. Also, the specular reflectance of the black tile is more than 1% lower than that of the other colored tiles. The backscatter reflectance of the black tile is approximately 0.7%.

[0033] Figure 9A shows the reflectance chromaticity values ​​of the specular surface. Figure 9B shows the reflectance chromaticity values ​​of the backscattered surface. The area occupied by the four points of the reflectance chromaticity values ​​of the specular surface is smaller than the area occupied by the four points of the reflectance chromaticity values ​​of the backscattered surface. From this, it can be concluded that evaluating the reflectance chromaticity values ​​of the backscattered surface is necessary to determine the reflectance chromaticity value of the underlying coating film.

[0034] Conventionally, in automobile production processes, the reflective color value of the underlying coating film is sometimes determined by visual inspection and touch after the application of a transparent film. In the surface property measuring device 1 of this embodiment, the specular reflectance and backscattered reflectance of the underlying coating film are measured during coating, and it is confirmed that both are within the control range. Then, the specular reflectance and backscattered reflectance are measured after the transparent film is applied. This enables production with a higher yield. Alternatively, the specular reflectance and backscattered reflectance of the substrate before the application of the underlying coating film may be measured, and the color difference value against the reference value of the color value may be determined.

[0035] (curved surface) The above explanation assumed that the object to be measured S was a flat plate. However, the surface of the object to be measured S may be curved. An example of a curved surface is the body of an automobile. When the surface of the object to be measured S is curved, it is preferable to switch between specular reflectance measurement and backscatter reflectance measurement using a mechanical shutter mechanism provided in front of the retroreflector, rather than switching using a retroreflector that has been partially blackened. This makes it easier to perform specular reflectance measurement and backscatter reflectance measurement on the same surface, i.e., at the same position, on the curved surface.

[0036] (Interference colors) This document describes how to simultaneously determine the film thickness and reflectance color value of a measurement object S that exhibits interference color. The interference color is calculated based on the specular reflectance. The measurement is performed with the retroreflective plate ON. The measurement object S used in the following description is a silicon wafer. A silicon oxide film is formed on the silicon wafer. The surface of the silicon oxide film is either specular or uniformly rough. The silicon oxide film thickness is available in six levels: 1.3 nm, 100 nm, 200 nm, 300 nm, 400 nm, and 500 nm. First, determine the refractive index of the substrate. The refractive index of the substrate can be calculated using the following formula. Nm = (1 + √Ro) / (1 - √Ro) Nm is the refractive index of the substrate. Ro is the reflectance at 550 nm. The refractive index of air is assumed to be 1.0.

[0037] Figure 10 shows the measured reflectance distribution for the six levels described above. Figure 10 shows the reflectance of the specular and rough surfaces of the silicon oxide film at the six levels. As shown in Figure 10, the specular reflectance of the silicon oxide film is 32.07%. The refractive index of the substrate on the specular surface is 3.61. The rough surface reflectance of the silicon oxide film is 6.77%. The refractive index of the substrate on the rough surface is 1.70. The Fresnel coefficient can be calculated using the following formula. ρ0 = (n0 - n) / (n0 + n) ρ1=(nn m ) / (n+n m ) n is the refractive index of the silicon oxide film. n0 is the refractive index of air. Let n0 be 1.0. The reflectance R can be calculated using the following formula. R=(ρ0 2 + ρ1 2 (+2ρ0ρ1cos2δ) / (1+(ρ0ρ1)) 2 (+2ρ0ρ1cos2δ) Here, δ = (2π / λ) × nd, where λ is the wavelength in the incident medium and d is the film thickness.

[0038] By setting the film thickness to 0 and calculating the reflectance in 1.5 nm increments from wavelength 400 nm to 700 nm, the reflectance distribution can be determined. The calculated reflectance is called the theoretically calculated spectral reflectance. Figure 11A shows the theoretically calculated spectral reflectance of a mirrored surface. Figure 11B shows the theoretically calculated spectral reflectance of a rough surface. Comparing Figures 11A and 11B, the distribution of theoretically calculated spectral reflectance for the mirrored surface and the distribution of theoretically calculated spectral reflectance for the rough surface are similar. This indicates that even for a rough surface, film thickness can be estimated in the same way as for a mirrored surface. Film thickness estimation is possible because the rough surface has a uniform rough surface shape.

[0039] Once the spectral reflectance distribution is determined, the light source color and luminous efficiency curve can be calculated to determine the tristimulus values ​​X, Y, and Z. This calculation method is based on the fact that the spectral characteristics of a CMOS color camera are equivalent to color matching functions. The retroreflectance can be determined from the tristimulus values. Furthermore, as mentioned above, the reflected color value can be determined from the retroreflectance.

[0040] The method for estimating film thickness is explained below. Film thickness can be estimated using the following formula. ΔW = √{(rφTe(R) - rφTx(R)) 2 +(rφTe(G)-rφTx(G)) 2 +(rφTe(B)-rφTx(B)) 2} ΔW is the error range in the estimated film thickness. Te is the set film thickness. The search width is set to ±50 nm, and a value is entered for Tx within this 100 nm width. The Tx value where ΔW = min(Tx) is taken as the estimated film thickness. The search width is set to ±50 nm to prevent a phenomenon called metamerism from occurring in interference colors, where the retroreflectance is the same even though the interference waveforms are different. Figures 12A and 12B show the estimated oxide film thickness, set film thickness, and estimated error width ΔW for mirror-finished and rough-finished silicon substrates. Figure 12A shows the estimated film thickness when the silicon substrate is mirror-finished. Figure 12B shows the estimated film thickness when the silicon substrate is rough-finished. As shown in Figures 12A and 12B, ΔW is generally small, and the oxide film thickness can be estimated, especially if the rough surface is uniform.

[0041] Film thickness can be estimated by estimating the film thickness difference from the reflectance color difference value. Specifically, the film thickness difference for measuring the silicon oxide film thickness of a silicon wafer can be determined by the following procedure. In the procedure below, the film thickness difference from a film thickness of 0 is expressed by the reflectance color difference value Δ(L, a, b, E). Figure 13 shows the calculated reflectance color values ​​for film thicknesses from 0 to 10 nm. Figure 14 shows the reflectance color difference values ​​for film thicknesses in 0.5 nm increments, with film thickness 0 as the reference. Figure 15 is a graph plotting the values ​​shown in Figure 14. From Figure 15, it can be seen that at ΔE ≈ 0.5, it is possible to distinguish between 0 nm and 9 nm. It can also be seen that at ΔE ≈ 0.05, it is possible to distinguish between 0 nm and 3 nm. Furthermore, ΔE increases non-linearly with increasing film thickness. Therefore, if 0 nm and 3 nm can be distinguished, a difference of 1 nm can also be distinguished around 10 nm. In addition, by increasing the number of average values, it is possible to distinguish even smaller differences in film thickness. For example, if the number of average values ​​is set to 10, σ becomes 1 / √10 ≈ 0.3, and ΔE ≦ 0.02, making it possible to distinguish between 0 nm and 2 nm.

[0042] Conventionally, the non-uniformity of silicon oxide film thickness in silicon wafer mirror polishing lines has been confirmed by visual inspection. Human discrimination ability is generally ΔE ≈ 1.0. Until now, no accurate and quantitative method for inspecting silicon oxide film thickness has been proposed. The surface property measuring device 1 enables accurate and quantitative inspection of silicon oxide film. As a result, product uniformity can be increased, and productivity can be improved.

[0043] The reflected color value of an object S that exhibits interference color can be determined based on the obtained spectral reflectance distribution. Specifically, the light source color and luminous efficiency curve are calculated, and the tristimulus values ​​X, Y, and Z are determined. Subsequently, the retroreflectance is determined according to the method described above, and then the reflected color value is determined. As described above, the surface texture measuring device 1 can simultaneously determine the film thickness and reflectance color value of a measurement target S that has interference colors.

[0044] (SUS) There is a technique for creating a coating by growing an oxide film on the surface of stainless steel (SUS). Changing the thickness of the coating produces interference colors. Therefore, this technique is also used as a decorative method. The surface property measuring device 1 can calculate the thickness of the oxide film on the surface of SUS using the technology described above. The calculation outline is as follows: First, the average color value of 400 x 400 pixels of the reflection image is determined. The average reflection color value and ΔE of each pixel are determined. Pixels where ΔE > N (N = 1 to 10) are excluded, and the average reflectance is calculated. The thickness is calculated from the average reflectance using the same method as for calculating the thickness of the silicon oxide film. In the experimental examples described below, images with ΔE > 4 were excluded, and the same processing as when calculating the thickness of the silicon oxide film was performed via retroreflectance. However, in the following examples, calculations were performed using rφ(R, G) instead of rφ(R, G, B). This is because, for decorative SUS oxide films, the values ​​obtained with rφ(R, G) are more stable than those obtained with rφ(B). Figure 16 shows the estimated film thickness Te, the set film thickness Ts, and the estimation error ΔT = Te - Ts of the decorative SUS oxide film after two adjustments to the set film thickness. As shown in Figure 16, the estimation error is small, |ΔT| ≤. This indicates that the film thickness estimation was performed with high accuracy. Figure 17 shows the reflective color values ​​of decorative SUS oxide films of different colors (Color 1 to 23). As shown in Figure 17, different reflective color values ​​were obtained for Color 1 to 23. This demonstrates that the color values ​​can be quantified.

[0045] Figure 18A shows the chromaticity values ​​for Color 1 to 10. Figure 18B shows the chromaticity values ​​for Color 11 to 23. As can be seen from comparing Figures 18A and 18B, the distribution range of chromaticity values ​​for Color 1 to 10 is smaller than the distribution range of chromaticity values ​​for Color 11 to 23. As shown in Figure 16, the film thickness of the decorative SUS oxide film for Color 1 to 10 and the film thickness of the decorative SUS oxide film for Color 11 to 23 differ. For example, the film thickness of Color 11 is approximately 100 nm greater than that of Color 10. It is thought that a large part of the difference in the size of the distribution range of chromaticity values ​​is due to the difference in the distribution range of film thickness. Thus, the surface texture measuring device 1 of the present invention can simultaneously measure film thickness and color value even when the shape of the substrate is non-uniform. This contributes to the stability and quality improvement of production in the decoration process.

[0046] As described above, the surface texture measuring device 1 of the present invention comprises an optical system consisting of a CMOS color camera, an LED light source, a telecentric lens, and a retroreflective plate. By changing the signal processing software in this configuration, the surface texture measuring device 1 can function as the devices described in (1) to (5) below. (1) Surface optical roughness measuring device. (2) A device for measuring the specular reflectance and reflective color value of a transparent film, and for measuring the reflectance and reflective color value of the underlying coating film separately. (3) A device for measuring interference film thickness (0-500 nm) and interference color value. (4) A measuring device that measures the film thickness of ultrathin films (0-10 nm) on a silicon wafer using the reflectance color difference value. (5) A device for simultaneously measuring the film thickness (0-500 nm) and reflectance color value of oxide films used as decorative techniques for SUS.

[0047] Furthermore, the surface texture measurement method of the present invention includes the following steps, which will be explained with reference to Figure 19. Figure 19 is a flowchart showing the processing flow of the surface texture measurement method. S1 indicates step 1. The same applies to S2 and subsequent steps. The steps described below can be executed by the control of the data processing device 8, in particular the imaging control unit 31. (S1) S1 is a retroreflective plate switching step. In S1, the presence or absence of reflection by the retroreflective plate is switched according to the surface properties of the object being measured. The switching of the presence or absence of reflection can be done by changing the position of the partially blackened retroreflective plate or by switching the mechanical shutter mechanism provided in front of the retroreflective plate. (S2) Step S2 is the image acquisition step. In S2, depending on whether or not there is reflection from the retroreflector, at least one of the following is acquired: an image showing the specular reflection of the object to be measured and an image showing the backscattered reflection of the object to be measured. If there is reflection from the retroreflector, it is easy to acquire an image showing the specular reflection. If there is no reflection from the retroreflector, it is easy to acquire an image showing the backscattered reflection. (S3) S3 is a surface texture calculation step. In S3, based on the image acquired in S2, at least one of the following is calculated as the surface texture: a value indicating surface roughness, reflectance, reflectance color value, and film thickness.

[0048] The surface properties measurement method of the present invention can be modified in various ways based on the above-described flow. An example of a modified example will be explained with reference to Figure 20. Figure 20 is a flowchart showing another flow of the surface properties measurement method. The flow shown in Figure 20 is for measuring the surface properties of the coating film and the transparent film individually for an object to be measured in which an undercoat and a transparent film are provided on the surface in that order. The undercoat is an example of a rough surface. The transparent film is an example of a mirror surface. (S11) S11 is the retroreflective plate switching determination step. In S11, a decision is made on whether to enable or disable the reflection of the retroreflective plate. For example, when measuring the surface properties of a mirror-like surface such as a transparent film, it is determined that it is a measurement of a mirror-like surface (transparent film). On the other hand, when measuring the surface properties of a rough surface such as an undercoat film, it is determined that it is a measurement of a rough surface (undercoat film). If it is determined that it is a measurement of a mirror-like surface (transparent film), the step proceeds to S12. (S12) S12 is the step of switching the retroreflective plate to a reflective state. (S13) S13 is the step of acquiring a specular (transparent film) reflection image. Since the retroreflective plate was switched to reflection mode in S12, a reflection image of the specular (transparent film) is acquired. (S14) Step S14 is the step to calculate the surface properties of the specular surface (transparent film). In S14, the surface properties of the specular surface (transparent film) are calculated based on the specular surface (transparent film) reflection image acquired in S13. (S15) If it is determined in S11 that the measurement is of a rough surface (underlying coating film), the step proceeds to S15. S15 is the step of switching the retroreflective plate to a non-reflective state. (S16) S16 is the step of acquiring a reflection image of the rough surface (underlying coating). Since the retroreflective plate was switched to non-reflective mode in S15, a reflection image of the rough surface (underlying coating) is acquired. (S17) Step S17 is a step in which the surface properties of the rough surface (underlying coating film) are calculated. In S17, the surface properties of the rough surface (underlying coating film) are calculated based on the reflection image of the rough surface (underlying coating film) acquired in S16. The flow from S12 to S14 and the flow from S15 to S17 can be performed consecutively. When performing them consecutively, the order in which each flow is performed can be arbitrarily determined. By performing the flow from S12 to S14 and the flow from S15 to S17, when a transparent film is applied to the surface of the coated film, the reflectance and reflectance color value of the coated film and the reflectance and reflectance color value of the transparent film can be measured separately.

[0049] The embodiments of the present invention have been described above. The present invention is not limited to the embodiments described above, and various modifications, variations, and combinations are possible.

[0050] Furthermore, the apparatus for measuring surface properties and the method for measuring surface properties of the present invention can also be expressed as follows. <1> A surface texture measuring device comprising: an imaging unit that captures a color image of an object having irregularities on its surface and acquires gradation data for each pixel; a light source; an optical unit that irradiates the object with light output from the light source and causes the reflected light from the object to enter the imaging unit; and a retroreflective plate; and a roughness calculation unit that calculates the retroreflective coefficient and optical surface roughness index for each pixel in the imaging area based on the image captured by the imaging unit. <2> An apparatus for determining specular color values ​​and substrate color values, comprising: an imaging unit that captures a color image of an object having a transparent coating film on a substrate coating film and acquires gradation data for each pixel; a light source; an optical unit that irradiates the object with light output from the light source and causes reflected light from the object to be incident on the imaging unit; and a retroreflective plate with one half blackened, and a color value calculation unit that calculates the color values ​​of the specular surface and substrate from the specular reflectance and backscattered reflectance using specular reflectance and backscattered reflectance data for each pixel in the imaging area based on the image captured by the imaging unit. <3> A silicon oxide film thickness measuring device comprising: an imaging unit that captures a color image of a silicon oxide film and acquires grayscale data for each pixel; a light source; an optical unit that irradiates the object with light output from the light source and causes the reflected light from the object to be incident on the imaging unit; and a retroreflective plate; and a film thickness calculation unit that calculates the refractive index of the substrate from the retroreflective coefficient of each pixel in the imaging area based on the image captured by the imaging unit, and calculates the difference in retroreflective coefficient rφ(R, G, B) with a set film thickness. <4> A film thickness measuring device comprising: an imaging unit that captures a color image of an ultrathin silicon oxide film on silicon and acquires grayscale data for each pixel; a light source; an optical unit that irradiates the object with light output from the light source and causes the reflected light from the object to be incident on the imaging unit; and a retroreflective plate; a color value calculation unit that calculates a reflected color value from the retroreflective coefficient of each pixel in the imaging area based on the image captured by the imaging unit, and calculates a color difference value with a film thickness of 0 nm as the reference; and a relationship formula between the reflected color difference value ΔE and the film thickness to measure an ultrathin film thickness. <5> The system includes an imaging unit that captures a color image of a stainless steel decorative sample and acquires gradation data for each pixel, a light source, an optical unit that irradiates the object with light output from the light source and causes the reflected light from the object to enter the imaging unit, and a retroreflective plate, and a data calculation unit that performs image defect removal processing based on the image captured by the imaging unit. The apparatus includes a film thickness calculation unit that calculates the refractive index of the substrate from the retroreflectance of each pixel after scratch removal in the imaging area and calculates the difference in retroreflectance rφ(R, G,) with the set film thickness, and a color value calculation unit, and simultaneously measures the film thickness and color value of a decorated sample. <6> A method for measuring surface properties using a surface property measuring device comprising: an imaging unit for capturing a color image of an object with an uneven surface; a light source; an optical unit and a retroreflective plate; and a roughness calculation unit for calculating retroreflectiveness and optical surface roughness index, wherein When determining the roughness index of an uneven surface, the process involves converting a color reflectance image to a monochrome reflectance image using equation (3), rφ(monochrome) = 0.299rφ(R) + 0.587rφ(G) + 0.114rφ(B) Equation (3) Rq=√(1 / N)xΣi=1~N|Zi―Rave| 2 Calculate the value of equation (4) in two dimensions, A surface texture measurement method comprising the step of dividing by the reflectance rφ(monochrome)ave to obtain an optical roughness index. <7> A method for determining color values ​​using an apparatus for determining specular color values ​​and substrate color values, comprising: an imaging unit for capturing a color image of an object having a transparent coating film on a substrate coating film; a light source; an optical unit and a retroreflective plate with one half blackened; and a color value calculation unit that calculates the color values ​​of the specular surface and the substrate from the specular reflectance and backscattered reflectance data; The process includes the step of acquiring a color image of an object having a transparent coating film on a base coating film, A measurement method for determining specular color values ​​and substrate color values ​​by measuring specular reflectance Mi_rφ(R, G, B) and backscatter Ro_rφ(R, G, B) reflectance in a single measurement, by using a retroreflective plate with one side blackened in the step of acquiring the aforementioned color image. <8> The system includes an imaging unit for capturing a color image of a silicon oxide film, a light source, an optical unit and a retroreflective plate, and a film thickness calculation unit that calculates the refractive index of the substrate from the retroreflectiveness and calculates the difference in retroreflectiveness rφ(R, G, B) with respect to a set film thickness. A method for measuring the thickness of a silicon oxide film and the interference color value using a silicon oxide film thickness measuring device, To determine the thickness and interference color of a silicon oxide film, set the target thickness Te, set the search width to ±50 nm, and then use the following formula (10) from that 100 nm width: ΔW = √{(rφTe(R)―rφTx(R)) 2 +(rφTe(G)―rφTx(G)) 2 +(rφTe(B)―rφTx(B)) 2} Formula (10) A method for measuring the thickness and interference color value of a silicon oxide film, where the estimated film thickness obtained by obtaining the minimum value of ΔW is used, and the interference color value is determined from its reflectance. <9> A film thickness measurement method for measuring an ultrathin film using a film thickness measuring device comprising an imaging unit for capturing a color image of an ultrathin silicon oxide film on silicon, a light source, an optical unit and a retroreflective plate, a color value calculation unit for determining the reflected color value from the retroreflectiveness and calculating the color difference value based on a film thickness of 0 nm, and a relationship formula between the reflected color difference value ΔE and the film thickness. The step includes acquiring a color image of an ultrathin silicon oxide film on silicon, In the step of acquiring the aforementioned color image, the temperature of the imaging unit and the light source unit are controlled to 0.1°C. A method for measuring ultrathin films that involves determining the ΔE of the reflectance color difference value after an average of 10 or more measurements, and using a relationship formula between ΔE and film thickness. <10> It comprises an imaging unit for capturing a color image of a stainless steel decorative sample, a light source, an optical unit and a retroreflective plate, and a data calculation unit for performing image defect removal processing. A method for simultaneously measuring the film thickness and color value of a decorative sample using an apparatus comprising a film thickness calculation unit that calculates the difference in retroreflectance rφ(R, G,) from a set film thickness and a color value calculation unit, A method for removing scratches from a color image of a stainless steel decorative sample, comprising the steps of: determining the average color values ​​(L, a, b) of the reflectance image; determining ΔE for each pixel based on the average reflectance color value, excluding points exceeding ΔE (1 to 10: select an appropriate value), recalculating the average reflectance, and calculating the film thickness and reflectance color value, thereby simultaneously measuring the film thickness and color value of the decorative sample. [Explanation of Symbols]

[0051] 1 Surface texture measuring device 2 Imaging Unit 3 light source 4 Optics Department 5 Telecentric lenses 6 Beam Splitter 7 Retroreflective panels 8 Data Processing Devices 9 Blackboard 11 CPU 12 ROM 13 RAM 14 bus 15 Input / Output Interfaces 16 Output section 17 Input section 18 Memory section 19 Communications Department 20 drives 21 Removable Media 31 Imaging control unit 32 Light source control unit 33 Data Calculation Unit 34 Film Thickness Calculation Unit 35 Index calculation section 36. Color Value Calculation Unit

Claims

1. A surface property measuring device comprising: an imaging unit for imaging an object to be measured; a light source; an optical unit for irradiating the object to be measured with light output from the light source and causing the reflected light from the object to be measured to enter the imaging unit; and a retroreflective plate, The system further comprises a data processing device for calculating the surface properties of the object to be measured, The data processing device calculates a value indicating the surface properties of the object to be measured based on at least one of the images captured by the imaging unit, which shows the specular reflection of the object to be measured and the image showing the backscattered reflection of the object to be measured. Surface texture measuring device.

2. The data processing device switches the image captured by the imaging unit between an image showing the specular reflection of the object to be measured and an image showing the backscattered reflection of the object to be measured by switching the presence or absence of reflection at the retroreflective plate. The surface texture measuring device according to claim 1.

3. The data processing device calculates a value indicating the surface roughness of the object to be measured based on an image showing the backscattered reflection of the object to be measured. The surface texture measuring device according to claim 1 or 2.

4. The surface of the object to be measured is provided with a coating film and a transparent film in that order. The aforementioned data processing device is Based on the image showing the specular reflection of the object to be measured, a value indicating the surface properties of the transparent film is calculated. Based on an image showing the backscattered reflection of the object to be measured, a value indicating the surface properties of the coating film is calculated. The surface texture measuring device according to claim 1 or 2.

5. The aforementioned surface properties include at least one of reflectance and reflectance color value. The surface texture measuring device according to claim 4.

6. The data processing device acquires the relationship between the film thickness difference with respect to film thickness 0 and the reflected color difference with respect to the reflected color value at film thickness 0. Based on the relationship obtained, the film thickness of the object to be measured is calculated. The surface texture measuring device according to claim 1 or 2.

7. A surface properties measurement method for measuring the surface properties of an object to be measured, using a surface properties measuring apparatus comprising: an imaging unit for imaging the object to be measured; a light source; an optical unit for irradiating the object to be measured with light output from the light source and causing the reflected light from the object to be measured to enter the imaging unit; and a retroreflective plate, wherein the surface properties of the object to be measured are measured. A retroreflective plate switching step that switches the presence or absence of reflection by the retroreflective plate according to the surface properties to be measured, Image acquisition step: Depending on whether or not reflection occurs at the retroreflective plate, an image acquisition step is taken to acquire at least one of an image showing specular reflection of the object to be measured and an image showing backscattered reflection of the object to be measured. The process includes a surface texture calculation step, in which, based on the acquired image, at least one of the following is calculated as the surface texture: a value indicating surface roughness, reflectance, reflectance color value, and film thickness. Surface texture measurement method.

8. The surface of the object to be measured is provided with a coating film and a transparent film in that order. In the retroreflective plate switching step, the reflection by the retroreflective plate is switched to none. In the image acquisition step, an image showing the backscattered reflection of the object to be measured is acquired. In the surface properties calculation step, a value indicating the surface properties of the coating film is calculated, Also, In the retroreflective plate switching step, the reflection by the retroreflective plate is switched to enabled. In the image acquisition step, an image showing the specular reflection of the object to be measured is acquired. In the above surface properties calculation step, a value indicating the surface properties of the transparent film is calculated. The method for measuring surface properties according to claim 7.

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