JPH11142331A - Measurement of pearl glossiness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for properly measuring the brightness of the interference part of a pearl characterizing the brightness by the interference of the pearl in order to properly measure the brightness as a jewel of the pearl. SOLUTION: The image of a light source 7 is reflected on the surface of a pearl P and taken by an imaging element to calculate brightness distribution and glossiness is measured from the brightness distribution. In this method, a slit light source is used so that the width of the image of a light source part (A) is narrowed and an interference part (B) appears in the vicinity of the vertex of the pearl and the surface image of the pearl at this time is taken to calculate a brightness distribution curve. By this constitution, a practical method extremely coinciding with the judgment of brightness by a skilled expert is provided as a method for measuring the glossiness of the pearl P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for automatically measuring the glossiness of a pearl.

[0002]

2. Description of the Related Art A pearl has a very thin layer of crystal formed around a pearl nucleus, and light applied to the pearl is divided into light transmitted and reflected by each layer. Are complexly synthesized and interfere to form a gem-like shine.

[0003] The brilliance of pearls is mainly explained by factors such as surface gloss, internal gloss and interference color. The surface gloss is determined by the state of the pearl surface, and the smoother the surface, the stronger the surface gloss. The inner gloss is determined by the amount of light reflected by the crystal layer inside the pearl. If the crystal layer is distorted or disturbed, the light causes diffuse reflection, reducing the total amount of light and weakening the gloss. The brightness of the pearl is determined by the total amount of light from the surface gloss and the inner gloss. However, the brilliance of a pearl is not determined solely by brightness, and the phenomenon of interference of reflected light inside the crystal layer with each other characterizes the brilliance peculiar to the pearl. The interference color is caused by interference due to the difference in the optical path length of the light reflected by the inner crystal layer, and the specific wavelength is strengthened and appears as a color. Variations in thickness and crystal layer distortion and turbulence, which are important factors in pearl brilliance.

[0004] Attempts have been made to automatically measure the shine of pearls using a glossiness measuring device, but the problem of inconsistency with the expert's judgment cannot be eliminated. .

A generally known method for measuring gloss is a method for measuring the gloss of a flat object, and a commercially available gloss measuring device includes a gloss meter for measuring the gloss of a metal mirror surface. However, this type of gloss meter has been developed to measure the specular reflection of a flat metal surface and is not suitable for measuring the gloss of spherical objects.

[0006] In view of the fact that the conventional gloss measurement only targets a flat object, Japanese Patent Application Laid-Open No. 61-230045 proposes a method for measuring the gloss of a spherical object or a curved surface. When light is applied to the spherical body using a light source, an image of the light source is reflected on the spherical body. The image has a high brightness at the center, and blurs toward the periphery, and the brightness tends to decrease. The above image is received by a photoelectric detector, and the distribution of the amount of light is measured, and the glossiness is determined from the characteristics of the distribution.

In general, an image of a light source reflected on a spherical body has a luminance distribution tendency of the amount of received light which has a peak at the center and decreases at both ends. The higher the height of the peak of this curve, and the more the luminance distribution of the curve The narrower the width, the higher the gloss. In JP-A-61-230045, the magnitude of gloss is detected by detecting the peak of the distribution curve of the amount of received light and the width of the distribution curve.

In JP-A-61-230045, this method is also applied to the measurement of pearl gloss.
However, the above-mentioned measurement method focuses on the surface gloss and the inner surface gloss, and it is not satisfactory as a method for measuring the glossiness of a pearl because the factor of interference is not sufficiently considered.

[0009]

FIG. 5 shows an example of an image in which a spherical light source image is projected on a pearl. It is divided into a light source part (A) having a high luminance on which the image of the central light source is reflected, a part (B) surrounding the light source part having a low luminance, and a peripheral part (C) in which the outermost ground color appears. These portions do not have clear boundaries. For example, the brightness decreases as the periphery of the portion (A) decreases, and the portion (B) in which the interference color becomes clear gradually appears.

In the light source section (A) at the center of the image, the total amount of the reflected light on the pearl surface and the amount of reflection of the light that has entered the pearl appears as the intensity of the brightness. The effects of the two factors appear remarkably. The center light source (A) is also affected by interference, but the surface gloss and the inner gloss are strongly affected, while the interference (B) clearly shows the interference. That is, the luster peculiar to the pearl caused by the structure in which the thin crystal layers are superposed many times is reflected in the luminance distribution of the interference part (B).

As a result of repeated experiments, the present inventor has found that the shine of a pearl jewel is characterized by the interference portion (B) as described above, and the brightness of the interference portion (B) is reduced. If the measurement could be performed properly, it was confirmed that the measurement result was correlated with the evaluation of a pearl expert. Therefore, in order to measure the glossiness of the pearl, it is necessary to measure the surface gloss and the inner surface gloss, and to appropriately measure the luminance of the pearl interference portion (B) that characterizes the pearl interference.

[0012]

According to the present invention, in order to measure the above-mentioned specific pearl gloss, the surface gloss and the inner gloss are measured, and the luminance of the pearl interference part (B) which characterizes the pearl shine is measured. It is an object of the present invention to provide a method and an apparatus for measuring the temperature.

According to a first aspect of the present invention, there is provided a method of projecting an image of a light source on a surface of a pearl, capturing the image of the light source with an image sensor to obtain a luminance distribution, and measuring a glossiness from the luminance distribution. This is a method for measuring pearl gloss, wherein a slit-shaped light source is used.

A second aspect of the present invention is a method for measuring pearl luster, wherein the luminous flux of a slit light source used as a light source is a parallel luminous flux.

According to a third aspect of the present invention, a strip-shaped or oval image of a pearl surface includes a high-brightness portion at the center of the image. For example, there is provided a method for measuring pearl luster, wherein a window for image processing having a long side in a short axis direction is provided, and a luminance distribution curve is obtained from image element data in the window.

According to a fourth aspect of the present invention, the captured image is green, yellow,
This is a method for measuring pearl luster, characterized in that it is decomposed into light of three colors of blue and a luminance distribution curve is obtained only by green light.

[0017]

According to the first aspect of the present invention, the image of the slit light source is projected on the pearl surface to consolidate the surface gloss and the inner surface gloss at the center, and the luminance of the interference portion (B) can be measured appropriately. According to the second aspect of the present invention, the use of a parallel light beam as a light source allows the interference effect to appear more clearly in the interference section (B). The invention according to claim 3 is an image processing method for efficiently obtaining a luminance distribution from a captured image, and the luminance distribution can be obtained efficiently. According to the fourth aspect of the present invention, by obtaining a luminance distribution curve only with green light, a luminance distribution similar to the intensity of luminance felt by a human can be obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A measuring method according to an embodiment of the present invention will be described with reference to FIGS. This embodiment shows an example of the embodiment of the present invention, and the present invention is not limited to this.

FIG. 1A is a cross-sectional view of a pearl glossiness measuring device 1. A frame 3 is mounted on an optical bench 2, and a pearl mounting box 4 for mounting pearls is provided on the upper portion of the frame 3, and the frame 3 shields disturbance light from entering an optical system disposed on the optical bench 2. doing.

The pearl mounting box 4 is provided with a pearl mounting table 5 for mounting a pearl P whose glossiness is to be measured. The pearl mounting table 5 is provided with an oval through hole 6 having a width smaller than the diameter of the pearl and having arcs at both ends, and a pearl P for measuring glossiness.
Is placed on the through hole 6, illuminated from below through the through hole 6, and an image of the pearl surface is observed from below through the through hole 6.

If the edge of the upper end of the through hole 6 is sharp, there are problems such as damage and poor stability of the pearl. To prevent this, the upper end of the through hole 6 may be chamfered.
The pearl P placed in the through-hole 6 is irradiated with light from the light source 7, and the light reflected from the pearl at this time is received by the CCD area sensor camera 14 equipped with a two-dimensional CCD element, and the image is processed. Find the luminance distribution.

The light source 7 of this embodiment is a straight tube type fluorescent lamp 8
And a slit section 9 for restricting light emitted from the fluorescent lamp 8
And arranged so as to irradiate the optical path from the pearl P whose glossiness is to be measured to the prism 10 from a direction inclined by about 10 to 15 degrees. It is desirable to use a light source composed of parallel rays. However, as shown in this embodiment, a slit section 9 is provided in front of a straight tube type fluorescent lamp 8 to limit the width of emitted light, so that the width is close to parallel rays. You may comprise and use the light source of a light beam.

The prism box 11 is arranged directly below the pearl mounting table 5 on which the pearl P is mounted.
1 is equipped with a prism 10 and plays a role of reflecting the reflected light from the pearl in a right angle direction and guiding it to the CCD area sensor camera 14.

In the present embodiment, the prism 10 is used to bend the optical path once and lead the CCD area sensor camera 14 to the CCD area sensor camera 14 in order to prevent the apparatus from becoming longer in the vertical direction. Even if the CCD area sensor camera 14 is directly opposed to the pearl P without using the pearl P, there is no problem.

The reflected light from the pearl P can be adjusted by the zoom lens 12 mounted on the CCD area sensor camera 14 so that the light receiving range can be taken in an optimum range.
The CCD area sensor camera 14 incorporates an area sensor in which CCD image elements are arranged two-dimensionally in the camera, and is an image detecting means capable of rapidly processing the light and dark information of a minute section. It is sent to the device 16 via the signal cable connection port 15.

Next, a method of measuring the pearl gloss will be described. When a pearl is irradiated with light using a light source, if the diameter of the light source is large, the image of the light source is greatly reflected on the pearl surface as shown in FIG. , And the influence of the interference of the interference part (B) cannot be properly observed.

In order to properly observe the brightness of the interference part (B), it is necessary to select a light source so that the interference part appears near the zenith of the pearl. In order to solve this problem, in the present invention, the width of the image of the light source unit (A) is reduced by reducing the width of the light source using a slit, so that the interference unit (B) appears near the zenith of the pearl. Tried.

As a result, as shown in FIG. 2, when the slit-shaped light source is transferred to the pearl, the light source portion (A), which is the image of the central light source, has a substantially elliptical shape and the interference portion (B ) Can be projected near the zenith of the pearl.

The interference part (B) can be observed by using a slit light source as a light source. However, by using a slit light source composed of parallel light beams, it is possible to make the effect of interference appear more clearly. it can.

FIG. 6 is a schematic diagram of the image processing apparatus 16.
An image received by the CCD is separated into three colors of red (R), green (G), and blue (B), and subjected to data processing. Green (G)
By performing processing using only signals, it is possible to obtain a result close to the luminance that human eyes perceive.

A method for obtaining a luminance distribution will be described.
A two-dimensional image received by the area sensor is set in a rectangular window Wd by the image processing device 16, and pixel data in the window Wd is subjected to arithmetic processing to obtain a luminance distribution.

In the image processing, the center of the window Wd is aligned with the center of the luminance of the image of the light source, that is, the center of the light source section (A) in FIG. Next, the long axis of the image of the light source is Y
The window Wd is set so that the long side of the window Wd is in the X-axis direction, assuming that the axis is the axis and the direction orthogonal to the axis is the X-axis.

FIG. 3A shows an example in which the window Wd of the range for executing the image processing is set as described above, and FIG. 3B shows the data of the pixels arranged in one column in the Y-axis direction. It is a luminance distribution curve showing the luminance distribution based on the X axis after addition. As shown in FIG. 3B, data of a luminance distribution that is higher at the center and lower at both ends is obtained.

Comparing the brightness distribution curve with the glossiness perceived by humans, it is known that the higher the peak and the narrower the lower side, the higher the glossiness is determined. Calculate the parameters used to determine the gloss.

FIG. 4 is an explanatory diagram of parameters for determining the glossiness. Ymax is a maximum value, Ymin is a minimum value, and a threshold level value T is calculated from a parameter d between 0 and 1, a difference H between Ymax and Ymin, and Ymax. W is the width of the luminance distribution curve when the luminance is at the threshold level value T.

The parameter Ymax indicates the surface gloss and the inner gloss among the factors characterizing the pearl luster, and the higher the luminance of the light source unit (A), the larger the value of the parameter Ymax. In terms of pearl shine, the parameter Ym
A larger value of ax indicates that the pearl has a larger brightness. On the other hand, the value of the parameter W indicates the luminance of the interference part (B), and the smaller the value, the more the pearl-like shine appears. Conversely, when the parameter W becomes large, it indicates that blur occurs in the interference part (B), and the pearl shine quality is inferior.

The evaluation of the shine of the pearl can be performed by comparing the parameter Ymax derived from the luminance distribution with the parameter W. In other words, if the parameter Ymax is the same, the smaller the parameter W is, the better the shine is determined to be. If the parameter W is the same, the larger the parameter Ymax is, the better the pearl is determined to be.
FIG. 7 shows the correlation between the ratio of the parameter Ymax and the parameter W as a judgment index and visual evaluation by an expert, and shows that the present measurement method is practical.

[0038]

The measurement method according to the present invention focuses on the characteristics of the structure of the pearl and measures the brightness. A practical method is provided as a measuring method.

Further, although the standard of the conventional expert judgment has not been standardized and unified, according to the measuring method of the present invention, it greatly contributes to the improvement of pearl quality accuracy.

[Brief description of the drawings]

1A is an external view using a partial cross section of a pearl gloss measuring device for realizing a pearl gloss measuring method of the present embodiment, and FIG. 1B is a cross-sectional view of a light source unit viewed from a side. .

FIG. 2 is an explanatory diagram illustrating an image of a light source on a pearl surface.

FIG. 3A is an explanatory diagram showing a relationship between a pearl image and a window, and FIG. 3B is a luminance distribution curve obtained through image processing.

FIG. 4 is an explanatory diagram for determining the luster of a pearl.

FIG. 5 is an explanatory diagram illustrating an image of a light source on a pearl surface.

FIG. 6 is an explanatory diagram illustrating an outline of an image processing apparatus.

FIG. 7 is a correlation diagram between a measurement result according to the present invention and a judgment result by an expert.

[Explanation of symbols]

 Reference Signs List 1 pearl glossiness measuring device 2 optical bench 3 frame 4 pearl mounting box 5 pearl mounting table 6 through hole 7 light source 8 straight tube fluorescent lamp 9 slit section 10 prism 11 prism box 12 zoom lens 13 camera mounting base 14 CCD area sensor camera Reference Signs List 15 signal cable connection port 16 image processing device 17 AD converter 18 data processing unit 19 DA converter 20 monitor 21 printer P pearl ball Wd window

Claims (4)

[Claims] 1. A method of projecting an image of a light source on a surface of a pearl, capturing an image of the light source with an image sensor to obtain a luminance distribution, and measuring glossiness from the luminance distribution, wherein the light source is a slit light source. A method for measuring pearl luster, characterized by using: 2. The pearl gloss measuring method according to claim 1, wherein the light beam of the slit light source is a parallel light beam. 3. A high-brightness portion at the center of a strip-shaped or oval image of the pearl surface. The strip-shaped image has a short side direction, and the oval image has a short-axis direction. 3. The method according to claim 1, wherein a window for image processing having long sides is provided, and a luminance distribution curve is obtained from image element data in the window. 4. An image taken by the image pickup device is decomposed into light of three colors of green, yellow and blue, and a luminance distribution curve is obtained only by green light. The pearl gloss measurement method described.