JPS61230778A - Classification of color of pearl utilizing complementary color of pearl - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION As shown in FIG. 1, cultured pearls have an artificial nucleus of a shell in the center, and the surface thereof is covered with a translucent multilayer nacre. If strong light is applied to the surface of such a pearl from one side, strong specular reflection will occur in the direction of specular reflection. This reflected portion of specularly reflected light is called a highlight.

However, according to the conventional theory, the highlighted area shines almost exclusively from the reflected light from the light source, and the color of this area reflects the color of the light source and has little to do with the color of the pearl. On the other hand, from the periphery of the highlight, transmitted waves [E radiation light], which are closely related to the color of the pearl, are generated, giving rise to the unique color of the pearl.

Visual appraisers have determined the color of pearls by observing the color of this area.

Therefore, in conventional pearl color sorting equipment, the reflected light from the highlights is removed as much as possible, and the spectral characteristics of the transmitted diffuse reflected light emitted from the surrounding areas of the highlights are measured. I'm trying to do color classification.

With this method, for example, it is possible to classify Akoya pearls into three types: black, yellow, and white (white pearls consist of three types: white, pink, and green pearls), but on the other hand, the colors of white pearls are very similar. Therefore, it takes a considerable amount of time to subdivide white pearls into white, pink, and green pearls using this method.

There are some drawbacks.

In addition, white, pink, and green pearls all belong to the white color system according to the CrE international standard color test, pink pearls are pale reddish white, green pearls are white pearls with a thin edge, and ordinary It is almost impossible to subdivide pearls into white, pink, and green pearls depending on the spectrophotometric needle.

In the method of the present invention, only almost pure specularly reflected light appears from the very small surface of 10 to 20 degrees near the center of the highlight part of the pearl surface.

We have found new information that the colors that can be determined based on the spectral characteristics of this specularly reflected light are complementary to the color of pearls that humans perceive (the color caused by transmitted diffusely reflected light), so we will utilize this new information. This allows white pearls to be subdivided into three types: white, pink, and green pearls. Such subdivision into three types is easy, and misjudgment is extremely rare.

A specific example of the present invention is shown below. The method of the present invention consists of two operations: detecting complementary color information of pearls and classifying pearls based on the detection results.

First, the method of the present invention will be explained with reference to FIG.

The light emitted from the light source 1 passes through an optical filter or a spectroscope 2 such as a diffraction grating to produce near-monochromatic light (wavelength width approximately 1
When the position of the pearl 3 is adjusted so that the center of the pearl 3 coincides with the optical axis of this light (below 0++ m), an image of the light source is generated on the surface of the pearl. The intensity of the reflected light from this portion of the image (highlight portion) is detected by a charge detector 4 such as a CCD line sensor or a video camera. This detection is performed by sequentially changing the wavelength of the spectroscopic light 82, and the reflected light intensity-wavelength characteristics detected in this way are collected by the color feature extraction unit 5.
When the wavelength characteristics of the light source 1 spectrometer and charge detector are used to calculate the relative spectral characteristics shown in Figure 3, the relative spectral characteristics shown in Figure 3 can be obtained. Alternatively, the one-color feature extraction unit 5 converts it into a color evaluation amount, and uses the difference in color evaluation amount to explain that there is a white relationship. The intensity of the light incident from the light source on the microscopic surface near the center of the highlight part of the pearl is I, N (8), and the intensity of the specularly reflected light from the 41 microscopic surface is Green Yo F (, k), the microscopic surface. Let the intensity of light entering the inside of the pearl be ■Ding K (entering).

There is a relationship: I, N (in) = I, EF (in > + x,, (in) (1).

The reflectance of specularly reflected light on the pearl surface is J) (in), and on the other hand, the light that enters the pearl is repeatedly reflected and absorbed by the nacre membrane and nucleus, and then comes out again to the pearl surface (transmitted diffused). Let the total transmittance of reflected light) be t (on).

■Ryu FOX) = J) (in) IIN (in) (2) ITRC
In') = '[: (in) IIN (in) (3).

However, since I-k(^) is reflected many times within the nacre and exits to the outside, the direction of reflection changes during that time.

Therefore, the proportion of pearl highlights that appear outside is
The proportion of pearls that come out from around the pearl highlights is much higher.

In conventional eye appraisal, the color of a pearl is determined by the light emitted from the surrounding area of the pearl highlight.

The color of the pearl is determined by I-C (in) in equation (3), and it can be said that the overall transmittance 'C (in) of the pearl controls the color of the pearl.

Here, if we substitute equations (2) and (3) into equation (1) and divide both sides by FIN (8).

1 = f (in) + t (in) (4) and substituting equation (4) into equation (2) in the second order gives IREF
'In)=I, N(λ>-''c (In)・IIN (In). What is detected by one device is the refining (in) of equation (5), which is the result of the pearl incident light. Intensity 'IN (in) minus the color of the pearl, I, N (in) is 1
M station, the complementary color of the pearl color will be the amount of rain.

Figure 4 shows the position of the pearl surface, a is the highlighted part,
b is the periphery of the highlight. Curve (a) in Fig. 5 represents the relative spectral characteristics of the highlight area a, and curve (b) represents the relative spectral characteristics of the transmitted diffuse reflected light from the highlight peripheral area.
In addition, curve (C) indicates the value obtained by subtracting the relative spectral intensity from the highlight peripheral area (the value of curve (b)) from 1.0.
Comparing the shapes of curve (c) and curve (a), they are almost the same, which shows that the color of curve (a) and the color of curve (b) are complementary to each other.1 In the present invention, pearl Since the specularly reflected light from the microscopic surfaces in the highlight area is detected, it is possible to detect the complementary color of the pearl color as described above.

In contrast, conventional spectrophotometers detect reflected light from a fairly wide area of the highlight and the surrounding area of the highlight. Since the transmitted diffusely reflected light is captured, the reflected light intensity-wavelength characteristic curve shows almost the same shape regardless of the color of the pearl, as shown in Figure 6, and from this we can subdivide the color of the pearl. That is impossible.

Next, the color fringe classification process of the method according to the present invention and its effects will be explained.

(a) Figure 7 shows an example of classification of white, pink, and green pearls.
After being raised from the beach, the treated pearl oyster light characteristic curve was measured at wavelength 50.
It is shown in the range of 0 to 650 nm.

As can be seen from FIG. 7, the shapes of the relative spectral characteristic curves of white, pink, and green pearls are completely different.

For example, wavelength 550. Let the relative spectral intensities at 65On+s be D (550) and D (650), respectively, and the ratio PP l:I D (550)/D (650
) is about 1 for white pearls and 1 for pink pearls.
．． It is 2 to 2.5. On the other hand, the P of green pearl is 0.
．． It is as small as about 5, so by comparing the P value, green pearls (white and pink pearls) can be completely classified.

(Note) White pearls and pink pearls can generally be classified using the method in (a) of other classification examples, but a more reliable classification example is the area surrounded by one curve and the horizontal axis in the relative spectral characteristic curve in Figure 7. If (the area of the hatch part) is S, the S (P) of pink pearls is much larger than the S (W) of white pearls.Therefore, by comparing the value of S, pink pearls and white pearls can be classified. Being touched.

If you use methods (a) and (b) above together.

White pearls can be subdivided into three types: white, pink, and green pearls. The results of this classification were consistent with the classification by pearl appraisers.

[Brief explanation of the drawing]

Figure 1 shows an example of the structure of cultured pearls, Figure 2 shows a schematic diagram of the device used for color classification of pearls, and Figure 3 shows an example of the measurement results of relative spectral characteristics from the highlight area of pearls. , Figure 4 shows the position of the pearl surface, Figure 5 shows a comparison of the relative spectral characteristics of the highlight 1lia and the surrounding area of the highlight (complementary color relationship), and Figure 6 shows the comparison of the relative spectral characteristics of the highlight 1lia and the surrounding area of the highlight. Figure 7 shows the relative spectral characteristics measured from the highlight part of the pearl at a wavelength of 500mm and 65mm.
A drawing shown in the 0 nm range. Each is shown below.

Claims (1)

[Claims] In accordance with the principle of the present invention, the color of the light reflected from the center of the highlight part of the pearl (the part where the image of the light source is projected and appears to shine) is complementary to the color of the pearl that humans perceive. The center of the highlight area (minimum area 10-20
mm^2), the intensity of the light reflected from the wavelength 450 to 7
A method in which the reflected light intensity-wavelength characteristics (spectral characteristics) are determined by measuring in the 00 nm range, and the color classification of white pearls into white pearls, pink pearls, and green pearls is performed using the difference in the shape of the spectral characteristic curve. .