JP2014149286A - Surface roughness measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement device that can detect surface roughness with high accuracy in order to accurately discriminate a slight difference in a color or color unevenness.SOLUTION: The measurement device comprises: an optical system (101) that includes a light source (1011); an imaging section (103); and a data process section (105). The measurement device is configured so as to: irradiate a measurement object (201) with the optical system; acquire an image of the measurement object by the imaging section; and process the image of the measurement object by the data process section. The data process section is configured so as to: calculate correction reflection luminance that eliminates reflection inside the optical system as to each pixel of the image of the measurement object from data on the image of the measurement object and data on an image of a sub black body, and calculate surface roughness of the measurement object, using the correction reflection luminance.

Description

  The present invention relates to a measuring apparatus that obtains the surface roughness of a measuring object by using the reflection luminance of light irradiated to the measuring object. The present invention also relates to a measuring apparatus that obtains a reflected color value together with the surface roughness of the measuring object by using the reflection luminance of the light irradiated to the measuring object.

  In recent years, in products such as automobiles, home appliances, mobile phones, and compact cameras, users are placing more emphasis on the appearance. For this reason, the request | requirement with respect to the external appearance of a product is very high.

  Regarding the appearance of the product, it is important to accurately discriminate slight color differences and color unevenness of the product. Conventionally, slight color differences and color unevenness of such products have been visually determined. This is because there has conventionally been no measuring apparatus that can accurately discriminate slight color differences and color unevenness of products.

  For example, in the case of a rolled stainless steel plate having a mirror surface (with rolling streaks) and the back surface of which has been subjected to shot blasting, the difference between the front surface and the back surface can be expressed quantitatively. It is not possible with the measuring device.

  In addition, for an extruded metal product, the gloss (surface roughness) may change due to the extrusion process even though the color of the material does not change, and it may appear as if the color has changed. For example, since the purity of aluminum material is high, the color of the base material does not change by the extrusion process. However, it is considered that the inner surface of the mold is rough immediately after the start of use of the mold, but if the number of uses increases, the unevenness of the inner surface is reduced, the molded product has a smooth surface, and the reflectance is increased. For this reason, color unevenness may occur in a metal extrusion-molded product. However, there is no measuring device that can quantitatively measure such color unevenness.

  As for the resin product, the molded product is produced using a mold. Recently, the surface of the resin with a metallic luster has been increasing. As in the case of the metal described above, since the change in roughness of the inner surface of the mold is transferred to the molded product, the reflected color value of the molded product changes and a phenomenon called color unevenness occurs.

  It is also said that when developing a new molded product, a color difference occurs between a prototype molded product and a mass-produced molded product. This is because a prototype molded product has a small number of samples, so it can be manufactured even with a low-durability mold. However, since durability is required at the time of mass production, the mold material at the time of mass production may be different from that at the time of producing a prototype. In this case, the gloss (surface roughness) of the prototype molded product may not match the gloss (surface roughness) of the molded product during mass production, and a product with a different gloss (surface roughness) from the prototype may be produced. . In such a case, even if the materials are the same, the human eye feels uneven color and color differences.

  For example, manufacturers that produce aluminum casings such as mobile phones and digital cameras use sandpaper with a linear roughness (mirror surface) to change the surface condition of the aluminum, and make it rough by shot blasting. Use what you did. This is colored by electrodeposition, but the color is affected by gloss (surface roughness). A measuring apparatus that can measure such a color difference has not been developed. Therefore, a total of 25 samples having 5 levels of surface roughness and 5 levels of color density are made, and these are used as samples for color management. The operator visually determines the quality of the product compared to the samples. doing. Due to such a visual inspection, the inspection yield deteriorates due to factors such as individual differences and changes over time due to eye fatigue.

  Also, a PET (polyethylene terephthalate) film laminated on paper and a mirror surface produced by aluminum vapor deposition is commercially available as package-coated paper and label-coated paper. In these coated papers, the change in PET thickness affects the generation of heat due to aluminum vapor deposition, and the gloss (roughness) of the underlying surface of the vapor deposition surface changes, and the reflected color value may change. Conventionally, there is no measuring apparatus that can measure such a color difference.

  Here, a conventional reflection color measuring apparatus will be described. The conventional reflection colorimeter assumes that the surface is close to the diffusing surface. The reason is that it is an integrating sphere method or a diffuse reflection colorimeter with a light projecting / receiving angle of 45 ° / 0 °. Such reflective colorimeters are not suitable for specular measurements where the rolling streaks are clearly visible like metal surfaces. Even if the material is paper, a material having a deposited film formed on the surface cannot be measured for the same reason.

  In addition, a measuring apparatus that obtains the surface roughness of a measuring object by using the reflection luminance of light irradiated to the measuring object has already been developed (for example, Patent Documents 1 to 3). However, since the conventional measuring apparatus does not consider the influence of reflection inside the optical system, there is a problem in the measurement accuracy of the surface roughness. In addition, a measuring apparatus that can measure both surface roughness and reflected color value from image data to be measured has not been developed.

JP-T-2002-544497 JP 2003-161608 A JP-A-6-213953

  Therefore, there is a need for a measuring apparatus that can measure surface roughness with high accuracy in order to accurately discriminate slight color differences and color unevenness. There is also a need for a measuring device that can measure both surface roughness and reflected color values.

  A measurement apparatus according to a first aspect of the present invention includes an optical system including a light source, an imaging unit, and a data processing unit, irradiates a measurement target with the optical system, and outputs an image of the irradiated measurement target to the imaging unit. And the data processing unit is configured to process the measurement target image by the data processing unit, wherein the data processing unit includes the measurement target image data, the quasi-blackbody image data, and The corrected reflection brightness obtained by removing the reflection inside the optical system is obtained for each pixel of the image to be measured, and the surface roughness of the measurement object is obtained using the corrected reflection brightness. .

  The measuring apparatus according to the present aspect obtains a corrected reflection luminance obtained by removing reflection inside the optical system for each pixel of the measurement target image from the measurement target image data and the quasi-blackbody image data, and the corrected reflection Since the luminance is used to determine the surface roughness of the measurement target, the surface roughness can be determined with high accuracy even for a measurement target having a low reflectance.

  In the measurement apparatus according to the embodiment of the present invention, the optical system irradiates light in a direction substantially perpendicular to the surface of the measurement object, and the imaging unit is substantially perpendicular to the surface of the measurement object. Configured to receive light reflected in various directions.

  In the measurement apparatus according to the present embodiment, an image by light reflected in a direction substantially perpendicular to the surface to be measured is used, so that the surface roughness is obtained with high accuracy and is not easily affected by ambient external light. be able to.

  In the measurement apparatus according to the embodiment of the present invention, the imaging unit is a color video camera, and the data processing unit is configured to further obtain a reflection color value from the measurement target image.

  In the measurement apparatus according to the present embodiment, the surface roughness and the reflected color value of the measurement object can be obtained simultaneously from the image of the measurement object.

  In the measurement apparatus according to the embodiment of the present invention, the imaging unit includes a first imaging apparatus configured to receive light reflected in a direction perpendicular to the surface of the measurement target, and the measurement target. A second imaging device configured to receive light reflected in a direction inclined by 20 degrees to 30 degrees from a direction perpendicular to the plane.

  According to the measuring apparatus according to the present embodiment, the reflected color value of the measurement object that cannot measure the reflected color value depending on the light reflected perpendicularly to the surface of the measurement object, such as a color tile with a transparent film on the surface. Can be measured.

  In the measurement apparatus according to the embodiment of the present invention, the data processing unit is configured to obtain the surface roughness of the measurement target using a standard deviation of the corrected reflected luminance for each pixel.

  In the measuring apparatus according to the present embodiment, the surface roughness of the measurement object can be obtained by simple calculation.

  In the measurement apparatus according to the embodiment of the present invention, the data processing unit defines an x-axis and a y-axis in the measurement target image, and the corrected reflection of each point in the y direction for each point on the x-axis of the image. The average value of the luminance is obtained, the surface roughness in the x-axis direction is obtained using the standard deviation of the average value of the reflected luminance at each point in the y-direction for each point on the x-axis, and the image on the y-axis is obtained. The average value of the corrected reflected luminance at each point in the x direction is obtained for each point, and the standard deviation of the average value of the reflected luminance at each point in the x direction is obtained for each point on the y axis. It is comprised so that roughness may be calculated | required.

  According to the measuring apparatus according to the present embodiment, the direction of the roughness of the measurement target surface can be quantified using the surface roughness in the x-axis direction and the surface roughness in the y-axis direction.

  In the measurement apparatus according to the embodiment of the present invention, the data processing unit is configured to create an image composed of reflection luminance obtained by multiplying the corrected reflection luminance by a predetermined magnification.

  According to the measurement apparatus according to the present embodiment, even when the measurement target surface has a low reflectance, the luminance value of the difference image is multiplied by a predetermined magnification to provide an image of the measurement target surface that can be easily identified by the naked eye. can do.

  The inspection apparatus according to the second aspect of the present invention uses the measuring apparatus according to the first aspect of the present invention.

  The inspection apparatus according to the second aspect of the present invention uses the data digitized by the measuring apparatus according to the first aspect of the present invention to inspect the appearance of a product that could only be performed by visual observation in the past. Can do.

It is a figure which shows the structure of the measuring apparatus by one Embodiment of this invention. It is a flowchart which shows the method of calculating | requiring reference | standard reflection brightness | luminance from the image data of a calibration board with a measuring apparatus. It is a figure which shows the spectral luminance distribution of a light source, and the transmittance | permeability distribution of the RGB filter of the color video camera used as an imaging part. It is a flowchart for demonstrating the method of calculating | requiring the average value and standard deviation of the reflectance of a measuring object. It is a figure which shows the image by the digital camera of the area | region containing the character of a black envelope. It is a figure which shows the image which multiplied 8 times the luminance value of the difference image of the measuring object calculated | required in step S2040 of FIG. It is a figure which shows the image which multiplied 32 times the luminance value of the difference image of the measuring object calculated | required in step S2040 of FIG. It is a figure which shows the value of the vertical reflectance Rv (R), Rv (G), and Rv (B) of the character part which printed the varnish on the background of the quasi-black body, the black envelope, and the black envelope. It is a figure which shows the image which shows the rolling stripe of the stainless steel plate calculated | required by the imaging part. It is a figure which shows the image of the mirror surface of the stainless steel plate calculated | required by the imaging part. It is a figure which shows the image of the rough surface of the stainless steel plate calculated | required by the imaging part. It is a figure which shows the reflective color value and glossiness index of the stainless steel plate mirror surface and rough surface which were calculated | required with this measuring apparatus. It is a figure which shows the condition of the measurement of the square angle of aluminum by this measuring apparatus. It is a figure which shows the image of the sample 1 calculated | required by the imaging part. It is a figure which shows the image of the sample 2 calculated | required by the imaging part. . It is a figure which shows distribution of the long side direction of the relative value Rela. (Sigma) xy of vertical reflectance Rv (G) and the standard deviation value of the part enclosed with the rectangle of the image of FIG.14 and FIG.15. It is a figure which shows distribution of the long side direction of the reflective color value L, a, and b of the part enclosed with the rectangle of the image of FIG.14 and FIG.15. It is a figure which shows the image of the sample 3 calculated | required by the imaging part. It is a figure which shows the image of the sample 4 calculated | required by the imaging part. It is a figure which shows the reflective color value L, a, b of the sample 3 and the sample 4 which were calculated | required with this measuring apparatus, glossiness index Rela. (Sigma) xy, and ratio (alpha). It is a figure which shows the image of the sample 5 calculated | required by the imaging part. It is a figure which shows the image of the sample 6 calculated | required by the imaging part. It is a figure which shows the reflective color value L, a, b of the sample 5 and the sample 6, the glossiness index Rela. (Sigma) xy, and ratio (alpha) which were calculated | required with this measuring apparatus. It is a figure which shows the image of the sample 7 calculated | required by the imaging part. It is a figure which shows the image of the sample 8 calculated | required by the imaging part. It is a figure which shows the image of the sample 9 calculated | required by the imaging part. It is a figure which shows the reflective color value L, a, b of the sample 7 thru | or sample 9, the glossiness index | exponent Rela. (Sigma) xy, and ratio (alpha) which were calculated | required with this measuring apparatus. It is a figure which shows the structure of the measuring apparatus by other embodiment of this invention. It is a figure which shows the image by the light of an orange tile reflected perpendicularly to the surface of a measuring object. It is a figure which shows the image which image | photographed the diffuse reflected light whose angle with respect to the normal line of the surface of a measurement object of an orange tile is 25 degrees. It is a figure which shows Rela. (Sigma) xy of the average value Rv (G) of the vertical reflectance Rv (G) * (sigma) xy, and the glossiness index | exponent of 10 types of color tiles including an orange tile calculated | required with the measuring apparatus. . It is a figure which shows the distribution of diffuse reflection color value L, a, b of ten types of color tiles including an orange tile calculated | required with the measuring apparatus.

  FIG. 1 is a diagram showing a configuration of a measuring apparatus 100 according to an embodiment of the present invention. The measuring apparatus 100 includes an optical system 101, an imaging unit 103, a data processing unit 105, and a data storage unit 107.

  The optical system 101 includes a light source 1011, a beam splitter 1013, and a telecentric lens 1015. The light source 1011 may be a light emitting diode (LED) light source having emission luminance in a wavelength range of 430 nanometers to 700 nanometers.

  The imaging unit 103 may be a color video camera provided with an electronic shutter mechanism. The color video camera signal is divided into R, G, and B color signals, and a numeric value of 0 to 4095 is stored as a (R, G, B) value corresponding to each pixel by a 12-bit AD converter. The The number of pixels in the horizontal direction X = 1600 of the screen and the vertical direction Y = 1200 is used, but is not limited to this. (R, G, B) data is obtained as image data for each point (X, Y). With the optical system 101, the measurement visual field is about 14 mm × 11 mm, and the RGB information of a small spot is obtained with the visual field of one pixel being about 9 μm × 9 μm. Approximately 90,000 points of RGB data (12 bits) can be obtained when the final measurement area of the measurement field of view is approximately 3 mm x 3 mm.

  The data processing unit 105 may be a personal computer having a monitor (not shown). You may comprise so that the various images demonstrated later may be displayed with a monitor.

After the light from the light source 1011 is reflected by the beam splitter 1013, the surface of the object 201 is irradiated as parallel light substantially perpendicular to the surface through the telecentric lens 1015. The light reflected in the direction perpendicular to the surface of the object 201 passes through the telecentric lens 1015 and the beam splitter 1013 and reaches the imaging unit 103. The telecentric lens 1015 forms parallel light substantially perpendicular to the surface of the target 201 and sends only the light reflected in a direction substantially perpendicular to the surface of the target 201 to the imaging unit 103. In this way, a two-dimensional image of the target 201 irradiated by the light source 1011 is collected by the imaging unit 103. The collected two-dimensional image data is sent to the data processing unit 105 for processing. The processed data is stored in the data storage unit 107 and used again by the data processing unit 105 as necessary.

  Since the measuring apparatus 100 has a wide range of reflectance of light reflected perpendicularly to the surface of the object 201, that is, a vertical reflectance of 0.01% to 99%, the imaging unit 103 is as described above. Must have an electronic shutter function.

  In order to obtain the vertical reflectance from the image data acquired by the imaging unit 103, a calibration plate is used.

  Further, in the measurement apparatus 100, when the light reflected by the object 201 is measured by the imaging unit 103, there is a problem that the light emitted from the light source 1011 and reflected inside the optical system 101 is also measured. For this reason, especially when the vertical reflectance is low, the measurement accuracy is significantly lowered.

  Therefore, in this embodiment, the measurement device 100 measures an image of a cylindrical black body cavity as a quasi-black body to obtain image data of internal reflection of the optical system 101, and this image data is used as an image to be measured. By subtracting from the data, the influence of internal reflection of the optical system 101 is removed.

  The quasi-blackbody is a cylindrical blackbody cavity with a cavity diameter of about 40 millimeters and a cavity depth of about 69 millimeters. The bottom is conical, the zenith angle is 60 °, the cone height is about 35 millimeters, and the cylindrical part is integrated by screwing. The inner surfaces of the cylindrical part and the conical part are painted black.

  FIG. 2 is a flowchart showing a method for obtaining the reference reflection luminance from the image data of the calibration plate by the measuring apparatus 100. In the present embodiment, a low reflectance calibration plate is used as the calibration plate. The low reflectivity calibration plate has a reflectivity of 4.43-4.25% for wavelengths of 400-700 nm. Depending on the object to be measured, a high reflectance calibration plate having a reflectance of approximately 90% for a wavelength of 400 to 700 nm may be used.

  In step S1010 of FIG. 2, the brightness of the light source is set. As the light source 1011, an LED (light emitting diode) light source, specifically, a model MCEC-CW8 (maximum rating 0.15A, for MML coaxial epi-illumination) manufactured by Moritex Corporation was used.

  FIG. 3 is a diagram illustrating the spectral luminance distribution of the light source 1011 and the transmittance distribution of the RGB filter of the color video camera used as the imaging unit 103. The color video camera includes an infrared cut filter. The above spectral luminance distribution is after the infrared cut by the infrared cut filter.

  In step S1020 in FIG. 2, the shutter time of the imaging unit 103 when measuring the calibration plate is set. As an example, the shutter time is 0.5 milliseconds.

  In step S1030 in FIG. 2, image data of the low reflectance calibration plate is acquired by the imaging unit 103.

  In step S1040 of FIG. 2, the imaging unit 103 acquires quasi-blackbody image data.

  In step S1050 of FIG. 2, the data processing unit 105 subtracts the quasi-blackbody image data acquired in step S1040 from the image data of the low reflectance calibration plate acquired in step S1030. The image data obtained by subtraction in this way is referred to as calibration plate difference image data.

  In step S1060 of FIG. 2, the data processing unit 105 calculates the average values R1 (R) and R1 (G) R1 (B) of the R, G, and B values in the measurement area of the difference image data on the calibration plate.

  In step S1070 of FIG. 2, the data processing unit 105 uses the above-described average values R1 (R), R1 (G) R1 (B), and the reflectance of the calibration plate to reflect 1% with a shutter time of 1 millisecond. The reference reflection luminances Rs1 (R), Rs1 (G), and Rs1 (B) corresponding to the reflection luminance when the measurement object is measured are calculated. The reference reflection luminances Rs1 (R), Rs1 (G), and Rs1 (B) are sent to and stored in the data storage unit 107. The reflectance of the calibration plate is shown in Table 1.

  FIG. 4 is a flowchart for explaining a method of obtaining the average value and standard deviation of the reflectance of the measurement target.

  In step S2010 of FIG. 4, the shutter time of the imaging unit 103 at the time of measurement is set. As an example, the shutter time is 2 milliseconds.

  In step S2020 of FIG. 4, quasi-blackbody image data is acquired by the imaging unit 103.

  In step S2030 in FIG. 4, the image data to be measured is acquired by the imaging unit 103.

  In step S2040 of FIG. 4, the data processing unit 105 subtracts the quasi-blackbody image data acquired in step S2030 from the measurement target image data acquired in step S2040. The image data obtained by subtraction in this way is called difference image data to be measured.

  In step S2050 of FIG. 4, the data processing unit 105 uses the average values R2 (R), R2 (G), R2 (B), and R of the R, G, and B values in the difference image measurement area. A standard deviation R2 (G) σ is calculated. The standard deviation R2 (G) σ is calculated by the following procedure.

  As an example, the coordinates of the start point of the measurement area are (Xs, Ys) = (650, 450), and the coordinates of the end point are (Xe, Ye) = (950, 750). The coordinate points of this two-dimensional measurement area are 301 × 301 = 90,601 points. At this time, for the 301 points of coordinates X = 650, 651, 652 ---- 948, 949, 950, the average value in the Y direction is obtained, respectively, and the standard deviation value of the average value of the 301 points is R2 (G) • σx. This R2 (G) · σx is referred to as an X-direction standard deviation value. Similarly, an average value in the X direction is obtained for 301 points at coordinates Y = 450,451,452 ----- 748,749,750, and the standard deviation value of the average value of the 301 points is R2 (G) · σy. This R2 (G) · σy is referred to as a Y-direction standard deviation value.

The value of R2 (G) · σxy as the standard deviation value in the measurement area is calculated using the following formula.
R2 (G) · σxy = √ {R2 (G) · σx} ² + {R2 (G) · σy} ²

  In step S2060 of FIG. 4, the data processing unit 105 uses the reference reflection luminances Rs1 (R), Rs1 (G), and Rs1 (B) stored in the storage unit 107 to calculate the average value Rv ( R), Rv (G), Rv (B) and three types of standard deviations Rv (G) · σx, Rv (G) · σy, Rv (G) · σxy are obtained and stored in the storage unit 107.

For example, the average value Rv (R) of the vertical reflectance is calculated according to the following formula.
Rv (R) = R2 (R) / (2 × Rs1 (R))
In the above formula, the reference reflection luminance Rs1 (R) is doubled in order to correct the shutter time. Other average values and standard deviations are also calculated by the same formula.

Moreover, a relative value standard deviation is calculated | required by the following formula | equation, and let this value be a glossiness index | exponent.
Rela.σxy ＝ Rv (G) ・ σxy / Rv (G)
The gloss index corresponds to the roughness of the surface. The larger the gloss index, the greater the roughness and the lower the gloss.

Further, a ratio between the X-direction standard deviation value and the Y-direction standard deviation value is α.
α = Rv (G) · σx / (Rv (G) · σy)
α is used to determine whether the roughness has a direction. When α is close to 1, there is no directionality, and when α is 2 or more, there is a clear directionality in roughness. α will be described later according to a specific example.

  In the present embodiment, the standard deviation for the G value is obtained, but the standard deviation for the R value or B value may be obtained. Alternatively, a standard deviation of luminance values of a monochrome image may be obtained using a monochrome imaging device.

  Here, the measurement result by the method shown in FIG. 4 will be described.

  The object to be measured is a black envelope on which characters are printed with varnish. It is difficult to identify such characters to be measured with the naked eye.

  FIG. 5 is a diagram illustrating an image obtained by a digital camera in an area including characters of a black envelope.

  FIG. 6 is a diagram illustrating an image obtained by multiplying the luminance value of the difference image to be measured obtained in step S2040 of FIG. 4 by eight.

  FIG. 7 is a diagram showing an image obtained by multiplying the luminance value of the difference image to be measured obtained in step S2040 of FIG. 4 by 32 times. In the image of FIG. 7, the background of the black envelope and the character portion can be easily distinguished by the naked eye. As described above, even if the measurement target surface has a low reflectance, an image of the measurement target surface that can be easily identified by the naked eye can be provided by multiplying the luminance value of the difference image by a predetermined magnification. That is, “visualization” of the image can be realized.

  FIG. 8 is a diagram showing the values of vertical reflectances Rv (R), Rv (G), and Rv (B) of a character portion in which a varnish is printed on a quasi-black body, a black envelope, and a black envelope. It is.

Table 1 shows the reflectivity of the low reflectivity calibration plate, and the vertical reflectivity Rv (R) and Rv (G) of the character part in which the varnish is printed on the quasi-black body, the background of the black envelope, and the background of the black envelope , Rv (B) values.

  The values of the vertical reflectances Rv (R), Rv (G), and Rv (B) of the character portion in which the varnish is printed on the background of the black envelope and the background of the black envelope shown in FIG. It is obtained by the method shown in FIG. The vertical reflectance of the quasi-blackbody is obtained by the same procedure as steps S2050 and S2060 in FIG. 4 using the quasi-blackbody image data obtained in step S2020 in FIG. The influence of the internal reflection of the optical system by the quasi-blackbody is about 1%, and cannot be ignored as an error. In particular, the influence on the measurement accuracy of a measurement object having a low reflectance is very large.

  As described above, the data processing unit 105 calculates the X-direction standard deviation and the Y-direction standard deviation of the image data. When the direction of roughness is quantified by the X-direction standard deviation and the Y-direction standard deviation, the screen has a direction so that the direction of the measurement target, such as rolling rebar, coincides with the X-direction or Y-direction of the screen. Need to be set. Specifically, for example, the screen is set so that the rolling bars coincide with the horizontal direction or the vertical direction of the screen.

  FIG. 9 is a view showing an image showing the rolling stripes of the stainless steel plate obtained by the measuring apparatus 100. FIG. FIG. 9A is a diagram showing an image in a state in which the rolling stripe is inclined 10 degrees in the clockwise direction with respect to the vertical direction of the screen. FIG. 9B is a diagram showing an image in a state where the rolling stripes coincide with the vertical direction of the screen. FIG. 9C is a diagram showing an image in a state in which the rolling stripe is inclined 5 degrees in the counterclockwise direction with respect to the vertical direction of the screen. According to the measuring apparatus 100, it is possible to set the screen so that the rolling bar coincides with the horizontal direction or the vertical direction of the screen while viewing the image showing the rolling bar of the stainless plate obtained by the measuring apparatus 100.

  Here, a method for obtaining the reflection color value from the average values Rv (R), Rv (G), and Rv (B) of the vertical reflectance will be described.

The color matching functions x ₁₀ , y ₁₀ and z ₁₀ corresponding to the human diopter curve used for the reflected color tristimulus values XYZ are similar to the sensitivity curves of the R, G and B filters shown in FIG. ing. Therefore, according to JIS, etc., the diffuse reflection color is determined from L *, a *, b * from the reflection color tristimulus values of XYZ, and the average values of vertical reflectances Rv (R), Rv (G), Rv From (B), the reflected color value is calculated.

The formulas for calculating L *, a *, b * from the reflected color tristimulus values X, Y, Z are literature (for example, JIS usage series, “Common sense of color”, Motoro Kawakami and Hitoshi Komatsubara, published by the Japanese Standards Association, P163-164) and the following formula is used.
L * = 116 (Y / Yn) ^1/3 -16 (1)
a * = 500 [(X / Xn) ¹ /3-(Y / Yn) ^1/3 ] (2)
b * = 200 [((Y / Yn) ¹ /3-(Z / Zn) ^1/3 ] (3)
X / Xn> 0.008856 Y / Yn> 0.008856, Z / Zn> 0.008856 (4)
Equation (4) is a common condition for equations (1) to (3).

  When a D65 standard light source is assumed as the light source, the values of Xn = 94.811, Yn = 100.00, Zn = 107.333 are described in JIS-Z-8722.

  In the present embodiment, the lightness value is expressed as L, and the color saturation is expressed as a and b. In this embodiment, an LED is used as the light source, but the constant of the calculation formula uses the same value as the D65 standard light source.

  According to JIS, different formulas are used depending on whether the formula (4) is satisfied or not (4). When the expression (4) is satisfied, it substantially corresponds to the case where the average values Rv (R), Rv (G), and Rv (B) of the vertical reflectance are all 1% or more.

Calculation formula when formula (4) is satisfied (when Rv (R), Rv (G), and Rv (B) are all 1% or more)
L = 116 (Rv (G) / 100) ^1/3 -16 (5)
a = 500 {(Rv (R) /94.81) ^1/3 − (Rv (G) / 100) ^1/3 } (6)
b = 200 {(Rv (G) / 100) ^1/3 − (Rv (B) /107.3) ^1/3 } (7)
The above formulas (5) to (7) correspond to the formulas (1) to (3).

Calculation formula when equation (4) is not satisfied (when Rv (R), Rv (G), or Rv (B) is less than 1%)
L = 903.29 (Rv (G) / 100) (8)
a = 3894 {(Rv (R) /94.81) − (Rv (G) / 100)} (9)
b = 1557 {(Rv (G) / 100) − (Rv (B) /107.3)} (10)
As described above, reflection from the average values Rv (R), Rv (G), and Rv (B) of the vertical reflectivity using the equations (5) to (7) or the equations (8) to (10). The color values L, a, and b are calculated.

  The measurement result by the measuring apparatus 100 will be described below. The image data described below is so-called difference image data obtained in step S2040 of FIG. 4 except for the images shown in FIGS.

  First, the measurement results of the mirror surface and the rough surface of the stainless steel plate will be described.

  FIG. 10 is a diagram showing an image of the mirror surface of the stainless steel plate obtained by the measuring apparatus 100. FIG. The rolling streaks appear on the mirror surface.

  FIG. 11 is a diagram showing an image of the rough surface of the stainless steel plate obtained by the measuring apparatus 100. FIG. The rough surface is formed by erasing the rolling streaks with shot blasting.

  One pixel of the images in FIGS. 10 and 11 is about 9 μm, and the field of view of the screen is about 14 mm × 11 mm.

  FIG. 12 is a diagram showing the reflection color values and gloss index of the stainless steel plate mirror surface and rough surface obtained by this measuring apparatus. Regarding the color value, the value of the mirror surface is larger than the value of the rough surface in all of L, a, and b. The gloss index corresponds to the roughness, and the gloss index of the mirror surface is smaller than the gloss index of the rough surface. As for the ratio α, the value of the mirror surface where the rolling bars appear clearly is 18.67, which is larger than the value of the rough surface. As described above, the measurement apparatus realizes the numerical values corresponding to the observation with the naked eye of the color and the gloss (roughness).

  In the example in which the variation of the color value during 10 consecutive measurements is measured, ΔEab <0.05 in terms of color difference value is extremely small. This is because, when the measurement area is 3 mm × 3 mm as described above, the color value is an average value of 90,000 points, so that there is an effect of reducing the noise level of AD conversion and the accuracy is improved. . As described above, since the stability of the reflected color value is high, a minute color difference value can be determined.

  Next, the measurement results of the square angle (40 mm × 40 mm) of aluminum formed by extrusion will be described.

  FIG. 13 is a diagram showing a photograph of the situation of measuring the square angle of aluminum by this measuring apparatus. The diameter of the irradiation range by the light source is about 25 mm.

  FIG. 14 is a diagram illustrating an image of the sample 1 obtained by the measuring apparatus 100.

  FIG. 15 is a diagram illustrating an image of the sample 2 obtained by the measuring apparatus 100.

  According to the images of FIGS. 14 and 15, the processing streaks due to the mold during the extrusion process can be clearly seen. Further, the processing streaks have uneven brightness. Furthermore, the conditions of the processing streaks of sample 1 and sample 2 are different.

FIG. 16 is a diagram illustrating a distribution in the long side direction of the relative value Rela.σxy of the vertical reflectance Rv (G) and the standard deviation value in a portion surrounded by a rectangle in the images of FIGS. 14 and 15. The horizontal axis in FIG. 16 indicates the coordinates in the X direction (long side direction), and the vertical axis indicates the relative values of the vertical reflectance and the standard deviation. The unit of the vertical axis is percent. Here, the vertical reflectance Rv (G) at a certain X coordinate is an average value of all pixels in the Y direction having the X coordinate in a rectangle. The relative value Rela.σxy of the standard deviation value at a certain X coordinate Xi calculates the standard deviation σxy (Xi) of the vertical reflectance Rv (G) of 41 pixels from Xi-20 to Xi + 20, I asked for it.
Rela. σxy = σxy (Xi) / Rv (Xi)

  FIG. 17 is a diagram illustrating the distribution in the long side direction of the reflected color values L, a, and b in the portion surrounded by the rectangle in the images of FIGS. 14 and 15. The horizontal axis in FIG. 17 indicates the coordinates in the X direction (long side direction), and the vertical axis indicates the reflected color values L, a, and b. Here, the reflection color values L, a, and b at a certain X coordinate are average values of all pixels in the Y direction having the X coordinate in the rectangle.

  According to FIG. 16, the glossiness index Rela.σxy is slightly larger on the left side of the figure and smaller on the right side from the center. This means that the gloss on the right side from the center is high (the roughness is small).

  According to FIG. 17, the lightness value L of samples 1 and 2 is smaller in the left side (X coordinate N = 200 to 500) in the figure than the value in the right side. In the range of X = 500 to 700, the lightness value of sample 2 is larger than the lightness value of sample 1. In the range of X = 1100 to 1400, the lightness value of sample 1 is larger than the lightness value of sample 2. For samples 1 and 2, the difference in saturation values a and b is relatively small.

  Next, measurement results of a sample of coated paper for packaging or labeling, in which polyethylene terephthalate is laminated on paper and aluminum deposition is performed, will be described.

  FIG. 18 is a diagram illustrating an image of the sample 3 obtained by the measuring apparatus 100. Sample 3 has a laminated polyethylene terephthalate thickness of 25 micrometers.

  FIG. 19 is a diagram illustrating an image of the sample 4 obtained by the measuring apparatus 100. Sample 4 has a laminated polyethylene terephthalate film thickness of 12 micrometers.

  Comparing the image of FIG. 18 with the image of FIG. 19, the surface of the sample 3 shown in FIG. 18 is smoother and less uneven than the surface of the sample 4 shown in FIG. 19. The reason why the surface of the sample 4 has many irregularities is considered to be that the film thickness of polyethylene terephthalate is small, so that the heat during the deposition of aluminum affects the base and the irregularities increase. The surface irregularities of the samples 3 and 4 cannot be identified by observation with the naked eye. With this measuring apparatus, as shown in the images of FIGS. 18 and 19, it is possible to identify irregularities on the surfaces of the sample 3 and the sample 4.

  FIG. 20 is a diagram showing the reflected color values L, a, and b, the gloss index Rela.σxy, and the ratio α of Sample 3 and Sample 4 obtained by this measuring apparatus. The gloss index Rela.σxy of sample 4 is larger than that of sample 3. This means that the glossiness of the sample 4 is smaller than that of the sample 3, that is, the roughness of the sample 4 is larger than that of the sample 3. The ratio α of sample 3 is 3.21, and the ratio α of sample 4 is 1.194. This means that the roughness in the X direction with respect to the roughness in the Y direction is larger in the sample 3 than in the sample 4, that is, the sample 3 has a sharper stripe in the Y direction. As described above, the result of digitization by this measuring apparatus coincides with the identification result by the images of FIGS. 18 and 19. The lightness value L of the reflected color value is 93.45 for sample 3 and 80 for sample 4. There is almost no difference in saturation values a and b between samples 3 and 4.

  Next, the measurement result of the pearl coated paper for labels will be described. Since pearl coated paper is colored using the coherence of pearl particles, the color cannot be distinguished at all by integrating all reflection angles as in the integrating sphere method. In this measurement apparatus, since the image of the vertically reflected light (0 ° / 0 °) is captured by the imaging unit 103, imaging of interference colors can be easily realized.

  FIG. 21 is a diagram illustrating an image of the sample 5 obtained by the measuring apparatus 100. Sample 5 is a red sample.

  FIG. 22 is a diagram illustrating an image of the sample 6 obtained by the measuring apparatus 100. Sample 6 is a blue sample.

  In the images of FIGS. 21 and 22, pearl particle groups appear, and the directionality of roughness (gloss) is hardly seen.

  FIG. 23 is a diagram showing the reflected color values L, a, and b, the glossiness index Rela.σxy, and the ratio α of the samples 5 and 6 obtained by this measuring apparatus. There is almost no difference between the sample 5 and the sample 6 in the gloss index Rela.σxy and the ratio α. The values α of Sample 5 and Sample 6 are approximately 1.0, indicating that there is no directionality. On the other hand, regarding the reflected color values of Sample 5 and Sample 6, the difference in lightness value L is small, but since the saturation values a and b are red and blue, a large difference clearly appears. In addition to the RED (red) and BLUE (blue) samples, WHITE, GLEY, GOLD, GREEN, and LILAC samples were also measured. Similarly, the difference in the color values clearly appears as numerical values.

  According to this measuring device, it is possible to measure interference colors that were impossible with conventional reflection colorimeters, and also to visualize and quantify glossiness (roughness). The application of can be expected.

  Next, measurement results of commercially available small pieces of rolled material of phosphor bronze, brass, and copper having different colors will be described.

  FIG. 24 is a diagram illustrating an image of the sample 7 obtained by the measuring apparatus 100. Sample 7 is a small piece of phosphor bronze rolled material.

  FIG. 25 is a diagram illustrating an image of the sample 8 obtained by the measuring apparatus 100. Sample 8 is a small piece of brass rolled material.

  FIG. 26 is a diagram illustrating an image of the sample 9 obtained by the measuring apparatus 100. Sample 9 is a small piece of rolled copper material.

  According to FIGS. 24 to 26, the rolling bars of brass (sample 8) and copper (sample 9) clearly appear, but the rolling bars of phosphor bronze (sample 7) appear slightly blurred.

  FIG. 27 is a diagram showing the reflected color values L, a, and b, the gloss index Rela.σxy, and the ratio α of Samples 7 to 9 obtained by this measuring apparatus. Regarding the gloss index Rela.σxy, phosphor bronze (sample 7) is as large as 21.72, and it can be seen that the gloss is low (roughness) among the three samples. It can be said that the directivity ratio α is almost the same in all three samples and there is no difference. The reflected color values are three samples, and the L value, a value, and b value are all different. Copper alloy is easy to oxidize, so its color is easy to change. A minute change in color can be digitized by using this measuring apparatus, and determination and classification can be performed based on the result.

  FIG. 28 is a diagram showing a configuration of a measurement apparatus 150 according to another embodiment of the present invention. The measurement apparatus 150 includes a first optical system 151A, a first imaging unit 153A, a second optical system 151B, a second imaging unit 153B, a data processing unit 155, and a data storage unit 157. Including.

  Compared with the measurement apparatus 100, the measurement apparatus 150 is different in that it includes a second optical system 151B and a second imaging unit 153B. The second optical system 151B and the second imaging unit 153B are used to measure the reflection color value of the measurement object that cannot measure the reflection color value by the light reflected perpendicularly to the surface of the measurement object. . Such a measurement object will be described later. The first optical system 151A and the first imaging unit 153A are the same as the optical system 101 and the imaging unit 103 of the measuring apparatus 100, respectively.

  The second optical system 151B includes a telecentric lens 1515B, and is installed so as to receive light reflected in a direction of an angle of 20 degrees to 30 degrees with respect to the normal line of the surface of the measurement target 201. The second imaging unit 153 </ b> B may be a color video camera provided with the same electronic shutter mechanism as the imaging unit 103 of the measurement apparatus 100.

The light from the light source 1511 is reflected by the beam splitter 1013 and then irradiated as parallel light substantially perpendicular to the surface of the object 201 through the telecentric lens 1515A. The light reflected in the direction perpendicular to the surface of the target 201 passes through the telecentric lens 1515A and the beam splitter 1513 and reaches the first imaging unit 153A. The telecentric lens 1515A forms parallel light substantially perpendicular to the surface of the target 201 and sends only light reflected in a direction substantially perpendicular to the surface of the target 201 to the first imaging unit 153A. In this way, a two-dimensional image of the target 201 irradiated by the light source 1511 is collected by the first imaging unit 153A. In addition, part of the light diffusely reflected by the surface of the target 201 passes through the telecentric lens 1515B, reaches the second imaging unit 153B, and is irradiated by the light source 1511 from the second imaging unit 153B. A two-dimensional image is acquired. The collected two-dimensional image data is sent to the data processing unit 155 for processing. The processed data is stored in the data storage unit 157 and used again by the data processing unit 155 as necessary.

  For the measurement by the first imaging unit 153A, the reference reflection luminance is obtained from the image data of the calibration plate by the method shown in FIG. 2, and the average value and standard value of the reflectance of the measurement object are obtained by the method shown in FIG. Find the deviation.

  A diffuse reflection calibration plate is used for the measurement by the second imaging unit 153B. However, since the second optical system 151B does not have a light source, correction by a quasi-black body for removing the internal reflection of the light source is unnecessary. Therefore, a method in which the reference reflection luminance is obtained from the image data of the calibration plate by a method in which the process related to the quasi-black body is excluded from the flowchart shown in FIG. Thus, the average value of the reflectance of the measurement object is obtained. The diffuse reflectance calibration plate is composed of a white tile, and the reflectance when the white tile is used in an integrating sphere method is 100%.

  Here, a description will be given of measurement results of a color tile in which a reflection color value cannot be measured by light reflected perpendicularly to the surface to be measured and a transparent film is attached to the surface.

  FIG. 29 is a diagram showing an image of the orange tile reflected by light perpendicular to the measurement target surface. The ground of the image is close to black, and the protrusions shine white. Measurements were made on 10 types of color tiles, but this sample has the widest shade and the unevenness looks intense. It was confirmed by visual inspection of the sample that the orange tile base was very uneven. The reason why the image due to the light reflected perpendicularly to the surface to be measured is not colored is because there is a transparent film on the base, the transparency of the transparent film is large, and the reflection of the base color is small. Can be estimated.

  FIG. 30 is a diagram illustrating an image obtained by photographing diffuse reflected light having an angle of 25 ° with respect to the normal line of the surface to be measured of the orange tile. This image has an orange color. For materials with a transparent film on the surface, as shown in this example, it has been demonstrated that gloss (roughness) needs to be measured by the vertical reflection method and color by the diffuse reflection method. It was.

  Here, when the angle of the diffuse reflection light with respect to the normal of the surface to be measured is smaller than 20 °, the vertical reflection component becomes stronger than the diffuse reflection component, and the measurement sensitivity of the diffuse reflection color decreases. On the other hand, if the angle of the diffuse reflected light with respect to the normal of the surface to be measured is larger than 30 °, the deviation of the irradiation position when the distance between the measuring device and the measurement target fluctuates increases, and the accuracy of the diffuse reflectance measurement is increased. descend. In addition, since the illuminance on the surface to be measured decreases, it is necessary to lengthen the shutter time of the imaging unit. In the case of measurement in a production line, it is preferable that the shutter time is short. Therefore, it is preferable that the imaging unit 153 be installed so as to receive reflected light having an angle with respect to the normal of the surface to be measured in the range of 20 ° to 30 °.

  FIG. 31 shows the average value Rv (G), the standard deviation value Rv (G) · σxy, and the gloss index Rela.σxy of ten types of color tiles including the orange tile, which are obtained by the measuring device 150. FIG. The horizontal axis of FIG. 31 indicates the color tile color, and the vertical axis of FIG. 31 indicates the gloss index (right scale), the average value of the vertical reflectance, and the standard deviation (left scale). The colors of the color tiles were arranged in descending order of the Rela.σxy value of the gloss index from the left side along the horizontal axis. The orange tile has the smallest vertical reflectance Rv (G) and the standard deviation value Rv · σxy (G) is not large, but the relative value Rela.σxy is 0.95, which is far greater than other samples. It can be seen that the glossiness is low (roughness is large). When the vertical reflectance Rv (G) is large, the glossiness index Rela.σxy is relatively small, and the tendency of high glossiness (low roughness) is in good agreement with the image by vertical reflection.

  FIG. 32 is a diagram illustrating the distribution of diffuse reflection color values L, a, and b of 10 types of color tiles including orange tiles, which are obtained by the measurement apparatus 150. The horizontal axis in FIG. 32 indicates the color of the color tile, and the vertical axis in FIG. 32 indicates the reflected color values L, a, and b. The color tile colors are arranged in descending order of the saturation value a from the left side along the horizontal axis. In 10 samples, L, a, and b values are different from each other.

  FIG. 31 and FIG. 32 show that visualization and quantification can be realized by combining the vertical reflection method and the diffuse reflection method in the measurement of the reflection color value and glossiness of the measurement object having the transparent film on the surface. Yes.

  The inventor of the present application is perpendicular to the surface of the measurement object based on the inventor's knowledge that the slight color difference and color unevenness of the product depend on the reflection color value and the gloss (roughness) of the surface. We developed a measuring device that irradiates light, acquires an image of the reflected light, and quantifies the reflected color value and surface gloss (roughness) from the image. According to this measuring apparatus, it is possible to discriminate slight color differences and color unevenness of products by converting the reflected color value and surface gloss (roughness) into numerical values. Further, by displaying the above-described image, “visualization” of gloss (roughness) in particular is realized.

  One of the advantages of irradiating light perpendicularly to the surface of the measurement object is that it is less susceptible to ambient external light. In the actual measuring apparatus, the optical system has a distance of 110 mm from the lens to the sample. Since the vertical reflected light (0 ° / 0 °) is measured, the camera body has a shielding effect against external light, and the LED light source is also large. The effect of is negligible. This point is particularly advantageous when used at a manufacturing site.

  As described above, this measurement apparatus can quantify the reflection color value of the measurement target and the gloss (roughness) of the surface. Therefore, appropriate reference values for the reflection color value and the gloss (roughness) of the surface are determined and stored in the data storage unit 107 or 157, and numerical values obtained by measuring the reflection color value and the gloss (roughness) of the surface and the reference value are stored. Is configured to be compared by the data processing unit 105 or 155, the measurement apparatus can be used as an inspection apparatus for inspecting slight color differences or color unevenness of the measurement target. According to the inspection apparatus using this measuring apparatus, it is possible to improve the accuracy of guaranteeing the product color that is symmetrical to the measurement.

  An inspection apparatus using this measuring apparatus can be substituted for visual inspection of products in a wide range of fields such as metals, chemicals, resins, films, paper, textiles, ceramics, agricultural products, and marine products.

DESCRIPTION OF SYMBOLS 101 ... Optical system, 1011, 1511 ... Light source, 1013, 1513 ... Beam splitter, 103 ... Imaging part, 153A ... First imaging part, 153B ... Second imaging , 105, 155 ... data processing unit, 107, 157 ... data storage unit

Claims (8)

An optical system including a light source, an imaging unit, and a data processing unit, irradiating a measurement target by the optical system, obtaining an image of the irradiated measurement target by the imaging unit, and acquiring the measurement target image as the data A measuring device configured to process by a processing unit,
The data processing unit obtains a corrected reflection luminance obtained by removing reflection inside the optical system for each pixel of the measurement target image from the measurement target image data and the quasi-blackbody image data, and the correction A measuring apparatus configured to obtain the surface roughness of the measurement object using reflection luminance.   The optical system irradiates light in a direction substantially perpendicular to the surface of the measurement object, and the imaging unit receives light reflected in a direction substantially perpendicular to the surface of the measurement object. The measuring device according to claim 1 configured.   The measuring apparatus according to claim 1, wherein the imaging unit is a color video camera, and the data processing unit is configured to further obtain a reflected color value from the image to be measured.   The imaging unit includes a first imaging device configured to receive light reflected in a direction perpendicular to the surface of the measurement target, and 20 from a direction perpendicular to the surface of the measurement target. And a second imaging device configured to receive light reflected in a direction inclined by 30 degrees from 5 degrees.   The measurement apparatus according to claim 1, wherein the data processing unit is configured to obtain a surface roughness of the measurement target using a standard deviation of the corrected reflected luminance for each of the pixels. .   The data processing unit defines an x-axis and a y-axis in the measurement target image, obtains an average value of the corrected reflected luminance at each point in the y direction for each point on the x-axis of the image, and The surface roughness in the x-axis direction is obtained using the standard deviation of the average value of the reflected luminance of each point in the y direction for each point, and the correction of each point in the x direction for each point on the y axis of the image An average value of reflected luminance is obtained, and a surface roughness in the y-axis direction is obtained using a standard deviation of an average value of reflected luminance of each point in the x direction for each point on the y axis. 5. The measuring device according to 5.   The measurement apparatus according to claim 1, wherein the data processing unit is configured to create an image including reflection luminance obtained by multiplying the corrected reflection luminance by a predetermined magnification.   An inspection apparatus using the measuring apparatus according to claim 1.

Images