JPH0245814B2 - HANTOMEIBUTSUTAINONAIBUSHOKUSOKUTEIHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring method capable of non-destructively measuring the color inside a translucent object.

For example, an artificial veneer 1 with a wood grain pattern on the surface as shown in FIG. Make diagonal cuts 4,
It is manufactured by slicing it so that it contains 4,.... Therefore, the color of each dyed veneer 2 has a great influence on the quality of the product. The dyed veneer 22 has a rotary lace, for example, thickness.
It can be obtained by dyeing a 0.8 to 1.0 mm material veneer to the desired color, but in this case, color differences may occur due to differences in the dyeing characteristics of the material or differences in the amount of dye mixed, or the interior may not match the desired color. There were many cases where the dye did not get dyed and it smudged. Even if the inside is not dyed the desired color, the surface of the veneer is still dyed, so
It was not possible to determine internal staining defects from the appearance. For this reason, destructive tests were carried out on samples for each dyeing lot, but the dyeability of wood varies depending on the lot of raw wood, and even within the same lot, it varies depending on whether the wood is core material or sapwood. In addition, it is also affected by the contained ingredients, so sampling inspections often miss defective products.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an inspection method capable of non-destructively inspecting the dyeing state inside such translucent materials. This will be explained below.

The method for measuring the internal color of a translucent object according to the present invention involves irradiating light perpendicularly to the surface of a sample made of a translucent object, and placing a blackboard in close contact with the back surface of the sample to prevent transmitted light from returning. Using an integrating sphere, measure the reflected light in the state and the light transmitted through the specimen, calculate the tristimulus values in a non-destructive state from the measurement results, and compare these values with the values obtained by actually destroying the specimen. Compare the measured internal tristimulus values and find a relational expression that relates the two in advance from the necessary multiple sets of data. The feature is that the tristimulus values are measured in a broken state, and the internal color is determined from the results using the above relational expression.

The principle of this internal color measurement method is to apply the color mixing theory (also called absorption/diffusion theory) used in color matching. In other words, when light is incident on an object, we consider the absorption (K) and diffusion (S) inside the object, and from the optical density K/S, we can calculate the color of the object on the back side of the object when the thickness is infinite (∞). The ideal reflectance R∞ when there is no influence of
is determined according to the well-known theory of Kubelka, Munk, etc. When this R _∞ is determined over the entire visible region, it can be displayed as a color by calculating the tristimulus values using the following formula.

Here, Pλ is the spectral distribution of the illumination that illuminates the sample,
Xλ, λ, λ are CIE (Commission Internationale de l'Eclairage) spectral tristimulus values.

In this way, find R _∞ from K/S and use it as a color.
The method for determining X _R∞ , Y _R∞ , and Z _R∞ is applied to a wood veneer as follows. That is, as mentioned above, the dyeing in the thickness direction of the veneer is not uniform, and when expressed in terms of brightness, it becomes as shown in FIG. 3. The reflectance when a blackboard is closely attached to the back side of such an object to be measured and white light is irradiated perpendicularly to the surface (the transmitted light is absorbed by the blackboard and does not return to the front side), Calculate K/S from the reflectance measured by placing a white board in close contact with the blackboard (in this case, the transmitted light is reflected by the white board and returning),
When X _{R∞ ,} Y _R∞ , and Z _R∞ are determined from R ∞, values obtained by averaging the distribution in the thickness direction are obtained. The X _R∞ , Y _R∞ , and Z _R∞ obtained in this way and the values actually measured using a colorimeter after destroying the dyed veneer that is the object to be measured (usually is the center value of the thickness, but is not limited thereto) It was found that there is the following relationship between X, Y, and Z.

X=f _x (X _R∞ , Y _R∞ , Z _R∞ ) Y=f _y (X _R∞ , Y _R∞ , Z _R∞ ) Z=f _z (X _R∞ , Y _R∞ , Z _R∞ ) ... Therefore, X _R∞ , Y _R∞ , Z _R∞ found from K/S
By using , it is possible to calculate and estimate the internal color (X, Y, Z) without destroying the object to be measured. However, in the above relationship or the relationship described below, each function f _x , f _y , f _z
Although it is better to use all three variables (X, Y, and Z) for better accuracy, it is also possible to use only one or two of them.

The above is based on the measured values obtained from the spectrum in _the visible light range using a _{spectrophotometer} .
This method calculates Z _R∞ , but as it is, it takes a long time to measure and the calculation is complicated.
It is not very suitable for practical use online. Therefore, based on the following knowledge discovered by the inventors, the method is usually performed as described below. That is, using a photometer with a structure similar to a color difference meter equipped with a tristimulus value filter in advance, K/S _(x) ,
By calculating K/S _(y) and K/S _(z) and using the R _∞(x) , R _∞(y) , and R _∞(z) obtained from these, the result is the same as the above formula. The results were obtained. Furthermore, the measured values of the X, Y, and Z tristimulus value regions when the blackboard is brought into close contact with the back side are taken as X _B , Y _B , and Z _B , and the measured values when the white board is brought into close contact are taken as X _W , Y _W , _{If Z W , ( internal color ) _ _ _ _ _ W} , Z _W ) Z=f _z (X _B , Y _B , Z _B , X _W , Y _W , Z _W ) ... It was also found that there is a relationship. Therefore, when making measurements, a photometer equipped with a tristimulus value filter is used. In this way, the internal color can be calculated and estimated directly from the measured values without having to calculate K/S from the reflectance and tristimulus values from R _∞ as described above, making it possible to go online. This is because it is extremely advantageous for measurement. An example of implementing this method will be described below.

FIG. 4 shows an example of the configuration of a measuring device used when carrying out this measuring method, and the white light emitted from the white light source 5 through the slit 6 is
The light beam passes through the collimator lens 7 and becomes a light beam having an appropriate beam diameter, and is irradiated perpendicularly to the surface of the dyed veneer 2, which is the object to be measured, by the mirror 8. Blackboards 9 or whiteboards 10 are alternately brought into close contact with the back side of the dyed veneer 2. The reflected light from the dyed veneer 2 is reflected by the integrating sphere 1
1 and measured by a photometer 13 equipped with a filter 12. The photometer 13 is
It has a built-in photoelectric conversion element, and as shown in Figure 4b, three sets are provided at 120 degree intervals, and each photometer is equipped with one type of filter for X, Y, and Z. There is. Therefore,
The reflected light from the object to be measured is received by an integrating sphere, decomposed into tristimulus values of X, Y, and Z and measured.

When using this device _, first sample the required _number of stained veneers _from various lots that are _thought to represent various dyeing conditions, and then select _the Measure six variables of _W. Next, the sample subjected to measurement is destroyed, and measurements are taken on the areas where the color actually becomes a problem, to obtain the respective X, Y, and Z values. Once the measured values are obtained, use a method such as multivariate analysis to set the objective variables as X, Y, and Z, and set the explanatory variables as X _B ,
The above relational expression is determined using Y _B , Z _B , X _W , Y _W , and Z _W . Once this relational expression is obtained, X _B , Y _B , Z _B , X _W , Y _W ,
The internal colors X, Y, and Z can be estimated (calculated) simply by measuring _ZW . This measurement method (referred to as the first method) is shown in FIG. 5 as a block diagram. In the figure, A represents the relational expression creation part, and B represents the estimation part of the internal color of the unknown sample.

In the first method, the measurement takes too much time because it is necessary to replace the blackboard and the whiteboard and repeat the measurement. Furthermore, when measuring the object while moving it in the plane direction, it is difficult to match the measurement points on the blackboard with the measurement points on the whiteboard, so the reliability of the estimated value tends to deteriorate. Therefore, in order to avoid such a thing,
You can do it like this: In other words, in the measurement method shown in FIGS. 4 and 5, if we consider the case where the white board is brought into close contact with the back surface of the object to be measured, the light incident on the dyed veneer 2 as shown in FIG. There is some attenuation due to absorption and some attenuation due to scattering, but the light that has completely passed through the veneer is reflected back into the veneer by the white plate 10 on the back of the veneer.
It can be seen that this light is also received as reflected light. This means that the measured value when the white board is brought into close contact with the back surface portion measures the amount of transmitted light. Therefore, the measurement value when the white board is in close contact with the first method is the measurement value of the true transmitted light obtained by not applying the white board to the back side (the transmitted light is decomposed into tristimulus values, X _t , Y _t , Z _t )
By changing it to , we obtained the following relational expression, similar to the above expression.

X=f _x (X _B , Y _B , Z _B , X _t , Y _t , Z _t ) Y=f _y (X _B , Y _B , Z _B , X _t , Y _t , Z _t ) Z=f _z (X _B , Y _B , Z _B , X _t , Y _t , Z _t ) ... In this way, it is possible to calculate and estimate the internal color even by measuring the true transmitted light value. However, an example of the configuration of a measuring device for carrying out such a measuring method is shown in FIG. In the figure, the white light source 5 is collimated to an appropriate beam diameter,
Light is irradiated onto the object 2 to be measured from the vertical direction. The reflected diffused light and the transmitted light at this time are received by integrating spheres 11 and 11' placed on the front and back surfaces of the object to be measured, respectively, and decomposed into tristimulus values X, Y, and Z, respectively. In the figure, 13' is a photometer equipped with a filter 12'. Three photometers 13, 13' are attached to the integrating spheres 11, 11' at 120 degree positions as shown in Figure 4b, and each photometer is one for X and one for Y.
It has filters for Z and Z.

Using the six variables obtained in this way, the internal color X,
After estimating and calculating Y and Z, for example, X ^* , a ^* , b ^*
The color display system is converted to a color display system such as , and quality is judged based on the pigment, hue difference, etc. with the target standard color. A block diagram of this measurement method (referred to as the second method) is shown in FIG. In the figure, L ^* , a ^* , b ^* , and ΔE are calculated using the following formula.

L ^* = 116× ³ √−16 a ^* = 500× ( ³ √− ³ √) b ^* = 200× ( ³ √− ³ √) ΔE=√ ( ^* − _ST ) ² + ( ^* − _ST )
² + ( ^* - _ST ) ² (L _ST , a _ST , b _ST are standard values.) According to the second method above, six variables can be measured at the same point at the same time, making high-speed processing easy. It is also highly accurate, making it an excellent online testing method.

Next, there is a third method which will be described below as a further improvement on the second method. That is, in the first and second methods, if there is a large difference in the moisture content of the object to be measured, there is a problem that the error in the estimated value becomes large. When the surface roughness of objects differs,
Since there is a possibility that measurement errors may occur due to scattered light, it is necessary to correct these errors. For this purpose, the six variables (X, Y,
In addition to Z), a photometer equipped with a filter that has a generally known water absorption wavelength of around 1450nm or around 1950nm, and a wavelength in the near-infrared region other than these water absorption wavelengths, such as 1100nm.
Preferably, a photometer equipped with a filter around m is added to the apparatus, and a total of 10 variables including the measured values (transmission, reflection) obtained by these are used for estimation. In this case, the wavelength is 1450nm or
The 1950nm filter peaks at these values.
It is sufficient if it has a width of about 20 nm. Also,
For wavelengths other than the water absorption range, a certain width is acceptable as long as the water absorption range is not included. Here, if the reflected light and transmitted light in the water absorption region are respectively W _B and W _t , and the reflected light and transmitted light at near-infrared wavelengths that do not include the water absorption region are _IRB and IR _t , then
Between _{the internal colors} X _{, Y , and Z ,}
, W _t , IR _t ) Y=f _y (X _B , Y _B , Z _B , W _B , I R _B , X _t , Y _t , Z _t
, W _t , IR _t ) Z=f _z (X _B , Y _B , Z _B , W _B , I R _B , X _t , Y _t , Z _t
, W _t , IR _t ) holds true. Since this relational expression incorporates a moisture correction term and a surface unevenness correction term, it is possible to correct the moisture content and surface roughness, and it is possible to estimate the internal color with higher accuracy.

As is clear from the above description, the method for measuring the internal color of a translucent object according to the present invention is capable of estimating the internal color of the object without destroying the object. It is highly practical and suitable for inspection of staining conditions such as. It goes without saying that this measurement method can be used to estimate the internal color of other translucent objects.

[Brief explanation of the drawing]

Figure 1 is an external view of the artificial veneer, Figure 2 is an explanatory diagram of the manufacturing method of this veneer, Figures 3a and b are explanatory diagrams showing the internal staining state of the dyed veneer, and Figure 4a is an example of a measuring device. Fig. 4b is an explanatory diagram showing the relationship between the integrating sphere and the photometer, Fig. 5 is a block diagram of the first measurement method, Fig. 6 is an explanatory diagram of the principle of measuring reflected light, Fig. 7 The figure is a block diagram showing another example of the measuring device, and FIG. 8 is a block diagram of the second measuring method. 1... Substrate, 2... Dyed veneer, 3... Adhesive layer, 5... White light source, 6... Slit, 7... Collimator lens, 8... Mirror, 9... Blackboard, 1
0... White board, 11,11'... Integrating sphere, 12,1
2'...Filter, 13,13'...Photometering tool.

Claims (1)

[Claims] 1. Light is irradiated perpendicularly to the surface of a sample made of a semi-transparent object, and reflected light is obtained when a blackboard is placed in close contact with the back surface of the sample to prevent the transmitted light from returning; The light that passes through the specimen is measured using an integrating sphere, and the tristimulus values in a non-destructive state are determined from the measurement results, and this value is compared with the internal tristimulus values measured by actually destroying the sample. A relational expression relating the two is found in advance from multiple sets of data, and then the tristimulus values in the above non-destructive state are calculated for an actual object to be measured consisting of a similar translucent object. 1. A method for measuring the internal color of a translucent object, comprising performing a measurement and determining the internal color from the result using the above relational expression. 2. Claim 1, in which the light transmitted through the object to be measured is measured by measuring the light reflected from the object using an integrating sphere with a white plate in close contact with the back surface of the object to be measured. Method for measuring internal color of translucent objects as described in Section 1. 3 Place integrating spheres on both sides of the object to be measured, and measure the reflected light of the light irradiated to the object with the integrating sphere on the front side, and measure the transmitted light of the same irradiated light with the integrating sphere on the back side. A method for measuring the internal color of a translucent object according to claim 1. 4. Any one of claims 1 to 3, in which the tristimulus values of reflected light and transmitted light from the object to be measured are measured using three sets of photometers each equipped with a tristimulus value filter. A method for measuring the internal color of a translucent object as described in . 5 A photometer equipped with a filter for water absorption wavelengths and a photometer equipped with a filter for wavelengths in the near-infrared region other than the water absorption wavelength are provided, and in addition to the tristimulus values, a photometer equipped with a filter for water absorption wavelengths and other near-infrared regions is provided. 5. A method for measuring an internal color of a translucent object according to claim 4, wherein the intensity of reflected light and transmitted light is measured, and these data are added to a relational expression to determine the internal color of the object.