JPH0219420B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an apparatus for determining glossiness of an object surface,
In particular, it is suitable for use in measuring and managing the surface quality of steel sheets, and is suitable for use in object surface gloss determination devices that classify and grade gloss based on the visual sensation based on the light reflection intensity distribution on the object surface. Regarding improvements.

[Prior Art] Various types of light reflection measuring devices have been proposed as devices for determining the glossiness of an object's surface.A typical device measures the specular reflection intensity of a white beam projected at a fixed angle. A measuring device using specular gloss, a measuring device using contrastive gloss that uses the ratio of the specular reflection intensity and diffuse reflection intensity of white light projected at a certain angle (JISZ8741), and a measuring device that measures the reflected gloss by projecting another object onto the surface. There is a clear gloss measurement device that allows you to see the blur with the naked eye.

[Problems to be solved by the invention]

However, although the specular gloss measuring device is widely used industrially, it has the drawback that it does not match reality for specular objects with small surface roughness. In addition, the measuring device based on contrast glossiness has the characteristic of giving a glossiness close to visual perception even for objects of different colors, but this also tends to have lower judgment accuracy for objects that are close to mirror surfaces. . Furthermore, the above-mentioned clear gloss measuring device had a problem in that quantitative display could not be obtained.

[Purpose of the invention]

The present invention was made to solve the above-mentioned conventional problems, and has the same color (brightness may be different).
The object of the present invention is to provide a glossiness determination device for the surface of an object that closely matches the visual glossiness and can quantitatively determine the glossiness over a wide range of rough surfaces from specular to rough surfaces. shall be.

[Means to solve the problem]

The present invention uses the light reflection intensity distribution on the object surface to
In an object surface gloss determination device that classifies and grades the glossiness based on visual perception, as shown in Figure 1, the variance σ of the height distribution of the measured surface profile is expressed by the following equation: { (4πσ/λ ₁ )・cosθ ₁ } ² ≦1 …(1) {(4πσ/λ ₂ )・cosθ ₂ } ² ≧4 …(2) Wavelengths λ ₁ , λ ₂ (λ ₁ = λ ₂ ) onto the surface of the object to be measured 10 at incident angles θ ₁ and θ _{2 ,} respectively.
4A, 14B, and two light receivers 16A for detecting specular reflection intensities I ₁ , I ₂ and total reflection intensities S ₁ , S _{2 ,} respectively.
16B, the specular reflection intensities I ₁ , I ₂ and total reflection intensity
By including a calculation processing unit 18 that classifies the glossiness of the object to be measured 10 based on the coordinates of S _{1 and S 2 on a two-dimensional plane (I 1 /S 1 ,} I ₂ /S _{2 )} , the above-mentioned purpose can be achieved. has been achieved. Here, the specular reflection intensity I means the intensity of the luminous flux in a minute area in the optical specular reflection direction (α=0) with respect to the incident angle θ of the incident light, as shown in FIG. 10 and the following equation. do. I=∫ ⁺ 〓 _- 〓i(θ)dθ i(θ): Distribution of reflected luminous flux α: Receiving angle (direction of specular reflection α=0) Also, the total reflection intensity S is shown in Fig. 10 and the following formula. , it means the total intensity integrated over all directions of the optically reflected light beam with respect to the incident light. S=∫〓〓 _- 〓〓i(θ)dθ

[Effect]

The present invention was made based on the fact that the visual gloss of the surface of an object, such as a steel plate, depends on two surface roughness parameters: the average roughness and the average peak interval, and cannot be evaluated based on the average roughness alone. . That is, surface roughness is the main factor that determines the gloss of objects of substantially the same color, and it is basically considered that the degree of gloss can be evaluated by accurately grasping information on the surface roughness. Information on surface roughness can be roughly expressed by the variance σ of the height distribution of the surface profile and the autocorrelation distance T (distance at which the autocorrelation function is 1/e), and these quantities and the light reflection intensity The distribution includes e.g.
Published by Pergamon Press, P. Beckmann
and “The Scattering of
Electromagnetic Waves from Rough
There is a certain relationship as shown in ``Surfaces''.Furthermore, the results of detailed examination of these relationships by Yuichiro Asano et al. Accordingly, by satisfying each range of equations (1) and (2) above, the specular reflection intensities I ₁ and I ₂ under each condition have a relationship with the roughness parameters σ and T as shown in the following equation. I ₁ = f ₁ (σ) ... (3) I ₂ = f ₂ (σ, T) ... (4) However, the incident light intensity is assumed to be a unit intensity, and the total reflectance is assumed to be 1. Here, if the total reflectance is taken into account, the above (3),
The left side of equation (4) is I ₁ /S ₁ and I ₂ /S ₂ (S ₁ and S ₂ are
(1) and (2) (total reflection intensity under each condition), and the information on the roughness parameters σ and T is I ₁ /
It is definitely included in both S ₁ and I ₂ /S ₂ information. Therefore, the glossiness is determined by both information of I ₁ /S ₁ and I ₂ /S ₂ and can be quantified. That is, as shown in FIG. 1 above, from the two light sources 14A and 14B having wavelengths λ ₁ and λ ₂ and incident angles θ ₁ and θ ₂ that satisfy the conditions of equations (1) and (2), Luminous flux 12A,
12B onto the surface of the object to be measured 10, the specular reflection intensities I ₁ and I ₂ and the total reflection intensities S ₁ and S ₂ from the surface of the object to be measured 10 are detected by the receivers 16A and 16B. Based on the coordinates of the reflection intensities I ₁ , I ₂ and the total reflection intensities S ₁ , S ₂ on the two-dimensional plane (I ₁ /S ₁ , I ₂ /S ₂ ), the calculation processing unit 18 performs appropriate calculation processing. For example, the glossiness of the surface of the object to be measured 10 can be determined. As the light receivers 16A and 16B for detecting the specular reflection intensities I ₁ and I ₂ and the total reflection intensities S ₁ and S ₂ , for example, photodiodes 20A and 20 are used as shown in FIG.
B _, 20C, _. Reflection intensity S ₁ ,
It is conceivable to use light receivers 16A and 16B such that _S2 . At this time, photodiode 20
The spread (area) of the two-dimensional array of A, 20B, 20C, . . . must be large enough to receive the total reflected light. Further, as shown in FIG. 3, by providing a diaphragm 22 in front of the light receivers 16A, 16B and making the aperture area of the diaphragm 22 variable, the specular reflection intensities I ₁ , I ₂ and the total reflection intensity S ₁ , It is also conceivable to use light receivers 16A and 16B that detect _S2 . On the other hand, the specular reflection intensity I ₁ ,
As an arithmetic processing method for determining the glossiness of the surface of the object to be measured 10 from I ₂ and the total reflection intensities S ₁ and S ₂ , the method shown in FIG. As shown in , the two-dimensional plane (I ₁ /S ₁ ,
I ₂ /S ₂ ), plot the representative points of each visual gloss level, connect them smoothly, and determine the curve l obtained by drawing it on a drawing, for example, and draw a straight line m perpendicular to the curve l. As shown in FIG.
The evaluation method is based on the distance along the curve l from the reference point R on the curve l of the leg Q of the perpendicular drawn to the line (or an amount equivalent to this), or the method has already been proposed by the applicant in JP-A-61-130858. As proposed, as shown in Figure 6, a method is used in which a boundary line Z that minimizes the statistical overlap between two adjacent groups is derived using a discriminant function, and separation is performed using this boundary line Z. Can be done. The boundary line Z can be determined, for example, as shown in FIG. 7, so that when this two-dimensional distribution is projected onto the Zv axis perpendicular to the boundary line Z, the overlap thereon is minimized.

【Example】

Hereinafter, a first embodiment of the present invention will be described in detail, in which the glossiness of a stainless steel plate was evaluated using the method proposed in Japanese Patent Application Laid-Open No. 61-130857. This first embodiment is based on the conventional method of determining glossiness by visual judgment (4 levels of glossiness 1 to 4).
This was done to test the performance of automatic determination with the aim of replacing it with automatic determination by measuring the light reflection intensities I ₁ and I ₂ . The surface roughness parameter σ of the stainless steel plate treated here is 0.02 to 0.2 μm, and if an Ar laser beam of λ = 0.45 μm is used as the luminous flux, the incident angle θ = 75°, and the equation (1) above is used. can satisfy you, and
Equation (2) above can be satisfied when the incident angle θ=10°. In addition, in the case of the stainless steel plate treated here, the total reflectance is almost constant, and the two-dimensional plane (I ₁ /S ₁ , I ₂ /S ₂ ) used for gloss evaluation is equivalent to (I ₁ , I ₂ ). It is. FIG. 8 shows the results of the determination according to the first embodiment. Each sample was evaluated by multiple skilled judges.
The glossiness was classified into four levels from 1 to 4 based on visual judgment based on comparison with standard samples. In Figure 8, 〇, ▲, □, ● represent gloss levels of 1, 2, and 2, respectively.
Samples 3 and 4 are shown. On the other hand, for these samples, the specular reflection intensities I ₁ and I ₂ are measured, and for the samples belonging to each gloss level, the representative points (I ₁ , I ₂ ) on the two-dimensional plane (in the first example, the center of gravity) are measured. Points) After determining C ₁ to _{C 4} , they were smoothly connected on the drawing to draw a curve l. Next, appropriate boundaries are drawn perpendicularly to the curve l so that the samples are classified for each gloss level.
Ma, mb, and mc were determined. This boundary line ma, mb,
A practical method for determining mc is, for example, by plotting a large number of sample points and determining mc so that the number of false positive points for each adjacent group is minimized. As a result of automatically judging a large number of stainless steel plate samples using the judgment method determined in the above procedure, we were able to correctly judge approximately 97% of the samples.
It was confirmed that it had sufficient performance. In addition, as a method for more finely determining the glossiness, the glossiness of each of the representative points C ₁ , C ₂ , C ₃ , and C ₄ is set to 1.0,
2.0, 3.0, and 4.0, and the glossiness of each point is one reference point Rs, the intersection Ta of the curve l and the boundary line ma, the intersection Tb with the boundary line mb, the intersection Tc with the boundary line mc, and the other reference point Re. are respectively 0.5, 1.5, 2.5, 3.5, and 4.5,
Furthermore, the glossiness of any point on the curve l is determined by the curve l within each interval (0.5-1.0, 1.0-1.5,...4.0-4.5).
_The glossiness of any sample is defined as _the value proportionally interpolated along It can also be defined as the glossiness of a point. According to this method, analog glossiness determination is possible. Next, a second embodiment of the present invention will be described in which the glossiness of a cold-rolled steel sheet was evaluated using the method proposed in Japanese Patent Application Laid-Open No. 61-130858. The purpose of this second embodiment is also to replace the conventional visual judgment of glossiness (4 levels of glossiness 1 to 4) with automatic judgment by measuring the light reflection intensities I ₁ and I ₂ . This was done to test the performance of automatic judgment. Surface roughness parameter σ of cold rolled steel sheet treated here
is 0.1 to 0.5 μm, and if a He-Ne laser beam with a wavelength λ = 0.633 μm is used as the luminous flux, the above equation (1) can be satisfied at an incident angle θ = 75°,
Furthermore, the above equation (2) can be satisfied when the incident angle θ=10°. In addition, in the case of the cold-rolled steel sheet treated here, the total reflectance is almost constant, and the two-dimensional plane (I ₁ /S ₁ , I ₂ /S ₂ ) used for gloss evaluation is the same as the two-dimensional plane (I ₁ , I ₂ )
is equivalent to FIG. 9 shows the results of the determination according to this second embodiment. Each sample was evaluated by multiple skilled judges.
The glossiness was classified into four levels from 1 to 4 based on visual judgment based on comparison with standard samples. In Figure 9, 〇, ▲, □, and ● represent gloss levels of 1, 2, and 2, respectively.
Samples 3 and 4 are shown. On the other hand, for these samples, the specular reflection intensities I ₁ and I ₂ are measured, and for the samples belonging to each gloss level, discrimination is made between each gloss level group on the (I ₁ , I ₂ ) two-dimensional plane. The boundary line Z ₃₄ which is a function,
Z ₂₃ and Z ₁₂ were derived. The derived boundary line Z ₃₄ ,
Z ₂₃ and Z ₁₂ were represented by the following formula. Z ₃₄ =0.0043(I ₂ −1278) +0.0029(I ₁ −2269) ……(5) Z ₂₃ =0.0219(I ₂ −1017) −0.0035(I ₁ −2113) ……(6) Z ₁₂ = 0.03 (I ₂ −642) +0.0007 (I ₁ −2011) ...(7) The boundary lines Z ₃₄ , Z ₂₃ and
As a result of using Z ₁₂ to judge the brightness of a large number of cold-rolled steel sheet samples, the judgment was made correctly for about 90% of the samples, confirming that it has sufficient judgment ability. Note that in the above example, the present invention was applied to the determination of the glossiness of a stainless steel plate or a cold-rolled steel plate.
It is clear that the scope of application of the present invention is not limited to this, and can be similarly applied to determination of glossiness of the surface of a general object.

【Effect of the invention】

As explained above, according to the present invention, for objects of the same color (brightness may differ), the visual glossiness closely matches the visual glossiness and can be quantitatively measured over a wide roughness range from specular to rough surfaces. It becomes possible to determine the gloss level. Therefore, it is possible to accurately measure and manage the surface quality online, which has excellent practical effects such as prevention of defects.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the gist of the apparatus for determining the glossiness of an object surface according to the present invention, and FIG.
FIG. 3 is a perspective view showing an example of the structure of the light receiver used in the present invention, FIG. 3 is a perspective view showing another example of the structure of the light receiver, and FIGS. 4 to 7 are glossy FIG. 8 is a diagram for explaining an example of the gloss determination method of the present invention, and FIG. Similarly, the figure is a diagram showing the determination results of the second example in which the glossiness of a cold rolled steel sheet was determined, and FIG. 10 is a diagram for explaining the specular reflection intensity and the total reflection intensity. σ...dispersion, _λ1 , _λ2 ...wavelength, _θ1 , _θ2 ...incident angle, _I1 , _I2 ...specular reflection intensity, _S1 , _S2 ...total reflection intensity, 10...subject Measurement object, 12A, 12B...Light flux, 14A, 14B...Light source, 16A, 16B...
...Photoreceiver, 18...Arithmetic processing unit, 20A, 20
B, 20C,...Photodiode, 22...Aperture.

Claims (1)

[Claims] 1. In an object surface gloss determination device for classifying and grading gloss based on visual perception based on the light reflection intensity distribution on the object surface, the variance σ of the height distribution of the surface profile to be measured is ^The wavelengths λ ₁ ^and _{λ 2} ( _{λ 1 = λ 2 also} two _{light sources that} project _a luminous flux _{of (} including
two light receivers that detect the specular reflection intensities I ₁ , I ₂ and the total reflection intensities S ₁ , S ₂ .
An apparatus for determining the glossiness of an object surface, comprising: an arithmetic processing unit that classifies the glossiness of an object to be measured based on coordinates on a dimensional plane (I ₁ /S ₁ , I ₂ /S ₂ );