JP3433565B2 - Refractive index measuring method and measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to the refractive index of the surface of an object,
In particular, the present invention relates to a refractive index measuring method for obtaining the refractive index of the skin surface as a non-destructive value as it is and an apparatus therefor.

[0002]

2. Description of the Related Art For the texture of the appearance of bare skin and makeup skin to an observer, particularly glossiness such as luster, acupuncture, powderyness, and fluffiness, the direction of light on the skin surface The scattering characteristic of the skin, which is the degree of scattering, has a great influence. Therefore, in order to objectively evaluate the glossiness of the skin, it is required to be able to quantify the scattering characteristics of the skin.

The surface shape and the refractive index of the skin can be cited as the determinants of the scattering property of the skin. That is, the distribution of the direction of scattering is determined by the surface shape of the skin. Further, the reflectance F (θ) is determined according to the following Fresnel's equation,
The larger the refractive index n, the larger the reflection intensity.

[0004]

[Equation 5] Here, the refractive index n is a value peculiar to the substance forming the skin surface.

Therefore, in order to quantify the scattering characteristic of the skin, it is necessary to be able to measure the refractive index of the skin.

Generally, as a refractive index measuring method, conventionally, a method of measuring a sample made of a single material by using the principle of Abbe's refractometer, or one or both of a liquid sample and a powder sample in a predetermined cell is used. Various methods are known, such as a method (liquid immersion method) of measuring the refractive index based on the presence or absence of a change in the refraction direction when filled in the.

[0007]

However, according to the conventional method for measuring the refractive index, it is not possible to measure a sample which is made of various constituents such as skin and whose surface is not flat, in a non-destructive state as it is. . Therefore, for bare skin, measure the refractive index of keratinocytes in the state at the time of the measurement, or for makeup skin, measure the refractive index as it is in the attached state where the foundation pigment or oil is attached on the keratinocytes. You cannot do it. Therefore, the scattering characteristics of the skin cannot be obtained.

The present invention is intended to solve the problems of the prior art as described above, and obtains scattering characteristics by measuring the refractive index of the skin, thereby objectively evaluating the texture such as glossiness of the skin. In order to be able to do so, the refractive index of a substance that is composed of various constituent substances, such as skin, and whose surface is not flat,
Its purpose is to enable non-destructive measurement as it is.

[0009]

Means for Solving the Problems The present inventors assume that the surface of the skin is a minute surface, and first, by changing the projection angle and the reception angle to obtain the reflection intensity, the projection angle is calculated. An angle θ (= (α + β) / of half of the sum of α and acceptance angle β)
2) and the reflection intensity R (θ,
φ) and the shape distribution function G (φ) as the reflection intensity proportional to the proportion of those having an azimuth angle φ among the minute bare surfaces, and the reflectance F when assuming that the skin surface is flat based on these (Θ) can be obtained, and the reflectance F (θ) thus obtained is fitted to the relationship between the reflectance F (θ) of the Fresnel equation and the refractive index n to obtain the refractive index of the sample. The inventors have found that n can be obtained, and have completed the present invention.

That is, according to the present invention, by projecting light on the surface of the sample a plurality of times at different projection angles α, and by receiving reflected light for each projection angle α at a plurality of different reception angles β, the projection angle An angle θ (= (α + β) / of half of the sum of α and acceptance angle β)
2) and the reflection intensity R (θ, φ) as a function of the azimuth angle φ of the minute surface constituting the sample surface, and the shape distribution function as the reflection intensity proportional to the proportion of the minute surface having the azimuth angle φ. G (φ) is calculated by the following formula

[0011]

## EQU6 ## The reflectance F (θ) of the sample is obtained based on R (θ, φ) = F (θ) G (φ), and this reflectance F
(Θ) and Fresnel's formula

[0012]

[Equation 7] Based on the above, there is provided a refractive index measuring method characterized by obtaining the refractive index n of a sample.

Further, as a measuring apparatus capable of suitably carrying out such a method, a light projecting means capable of projecting light from a light source onto a sample with a variable projection angle, and a sample for each projection angle Light receiving means consisting of a plurality of light receiving parts arranged at different installation angles with respect to the light projecting part of the sample so that the reflected light from the surface can be received simultaneously at a plurality of different light receiving angles. It has a converter for converting light into an electric signal corresponding to the light intensity, and a control calculation means, and the control calculation means responds to the light projection angle α, the light reception angle β, and the light intensity received by the light receiving part. Then, the angle θ (= (α + β) / 2), which is 1/2 of the sum of the projection angle α and the reception angle β, and the reflection intensity R (θ, θ as a function of the azimuth angle φ of the minute surface constituting the sample surface. φ), and as the reflection intensity proportional to the proportion of those having an azimuth angle φ among the minute surface. The shape distribution function G (φ) is calculated, and

[0014]

## EQU8 ## The reflectance F (θ) when the sample is flat is calculated based on R (θ, φ) = F (θ) G (φ),
This reflectance F (θ) and Fresnel's formula

[0015]

[Equation 9] Provided is a refractive index measuring device characterized in that the refractive index n of a sample is obtained based on the above.

The present invention will be described in detail below.

In the present invention, first, as shown in FIG. 2, the sample surface S such as the skin has many minute flat surfaces (for example,
It is assumed that it is composed of minute bare surfaces S1, S2, S3, S4). Such a minute bare surface has a predetermined projection angle α according to an azimuth angle φ which is an inclination with respect to a normal line of an average plane (reference surface) Sa of the refractive index measurement region of the sample surface S. Each of them reflects light in different directions.

On the other hand, the reflection intensity when light is projected onto a sample having a flat surface is, as shown in FIG. 3 (a), an azimuth angle φ = 0 °.
Can be considered as the reflection intensity of the minute surface S0 of the light source, and in this case, the reflectance at the projection angle α and the reception angle β is θ which is ½ of the sum of the projection angle α and the reception angle β. When doing
Fresnel formula

[0019]

[Equation 10] Accordingly, as shown in FIG. 3B, the angle θ increases and the refractive index n of the sample increases.

Therefore, like a skin surface or the like, light is projected onto a predetermined light projecting site on the sample surface S, which is considered to be a collection of minute bare surfaces of various azimuth angles φ, at different light projecting angles α, and at the light receiving angle β. The reflection intensity R (θ, φ) when receiving light is the azimuth angle φ and the angle θ (= (α + β) /
For example, the relationship shown in FIG. 4 depends on both of 2).

From FIG. 4, the reflection intensity R increases as the angle θ increases.
It can be seen that (θ, φ) is large, and it is further understood that the curves of the reflection intensity R (θ, φ) for different projection angles θ all have the same shape. Therefore, the angular distribution G ′ (φ) of the minute bare surface, which is the proportion of the fine bare surface having the azimuth angle φ among the bare bare surfaces forming the surface of the light projecting portion of the sample, is reflected by the reflection intensity R (θ, θ, The effect on φ) is constant regardless of the angle θ,

[0022]

It can be seen that the reflection intensity is expressed as R (θ, φ) = k · F (θ) · G ′ (φ) = F (θ) · G (φ). Here, k is a proportional constant having a dimension of the reflection intensity, which does not depend on the azimuth angle φ or the angle θ of each minute surface. In addition, G (φ) is

[0023]

## EQU00008 ## A shape distribution function represented by G (.phi.) = K.multidot.G '(. Theta.), Which represents the reflection intensity proportional to the ratio of the minute surface having the azimuth angle .phi ..

F (θ) corresponds to the reflectance when the sample is a flat plane with an azimuth angle of 0 °, and follows the Fresnel equation.
Therefore, the reflectance F (θ) is calculated from the shape distribution function G from FIG.
(Φ) can be obtained and obtained from the obtained shape distribution function G (φ) and the measured value of the reflection intensity R (θ, φ). In this case, as a method of obtaining the angular distribution G (φ) of the minute surface, for example, assuming a Gaussian distribution,

[0025]

[Equation 13] Can be obtained by finding the g and σ of

After the reflectance F (θ) is obtained, the reflectance F (θ) and the refractive index n of the Fresnel's equation are calculated from the values of the reflectance F (θ) and the corresponding angle θ. By fitting the relationship, the value of the refractive index n satisfying the relationship of the Fresnel equation is obtained. The value thus obtained is the refractive index n of the sample.

In obtaining the refractive index n of the sample in this way, as shown in FIG. 4, as a function of the azimuth angle φ and the angle θ (= (light projection angle α + light reception angle β) / 2) of the minute surface. As a method of obtaining the reflection intensity R (θ, φ), as shown in FIG. 5, light is projected onto the light projecting portion of the sample at a predetermined light projecting angle α 1 with respect to the reference surface Sa, and then the light is projected on the reference surface. Not only the light received at the acceptance angle β1 (the absolute value of the projection angle α1 = the absolute value of the acceptance angle β1) is received as reflected light and the received light intensity is determined, but also the projection light of the same projection angle α1 is obtained. On the other hand, the light received at the light receiving angle β2 may be received as the light reflected by a plurality of minute surface having different azimuth angles, for example, the minute surface having the azimuth angle φ1, and the received light intensity may be measured. Further, the projected angles of the projected light may be different, and the projected lights of different projected angles may be similarly received at different receiving angles and the received light intensity may be measured.
By combining these results, it is possible to obtain the reflection intensity R (θ, φ) as a function of the azimuth angle φ and the angle θ of the minute surface as shown in FIG.

The apparatus of the present invention can easily calculate the reflection intensity R (θ, φ) determined according to the azimuth angle φ of the minute surface and the angle θ which is 1/2 of the sum of the projection angle α and the reception angle β. It is a device that enables measurement and obtains the refractive index of a sample based on the result, and the system configuration can be as shown in FIG. 1, for example. That is, the device shown in FIG.
And a light receiving means 2 are integrated into a head portion 3, a converter 4 and a control operation portion 5, and the light emitting means 1
A light source 6 is connected to.

The light source 6 is not particularly limited, but it is preferable to use a light source that emits white light or visible light in order to evaluate the texture of normal skin.

The light source 6 is connected to a light projecting optical fiber 7 for guiding the light emitted from the light source. A bundle 8 is attached to the end portion of the light projecting optical fiber 7 inside the head portion 3 so that the light projecting angle α can be changed in a click manner at predetermined angular intervals. For example, the projection angle α can be changed in the range of 0 to 75 ° at 5 ° intervals. An irradiation lens 9 is attached to the end of the light projecting optical fiber inside the head unit 3 so that parallel light can be projected onto the sample.

The light-receiving means 2 in the head part 3 is in the same plane as the optical path of the projected light L projected from the projecting optical fiber to the projected portion of the sample surface S, and projected on the sample surface S. It is composed of a plurality of light receiving optical fibers 10 arranged at a predetermined installation angle on a concentric circle centered on the site. For example, 5 ° in the range of 15 to 75 ° around the projected portion of the sample S.
Thirteen light-receiving optical fibers arranged at intervals are arranged.

The converter 4 converts the light received by the plurality of light receiving optical fibers 10 into an electric signal according to the light intensity. As such a converter, a photoelectric converter connected to each light receiving optical fiber may be used, but from the viewpoint of shortening the processing time, the light received by a plurality of light receiving optical fibers is simultaneously processed. It is preferred to use a multi-channel converter that converts into an electrical signal.

The control calculation section 5 controls the value of the projection angle α projected by the projection means 1 so that the projection portion of the sample surface S is projected at a plurality of different projection angles α. . In addition, the control calculation unit 5 determines the azimuth angle φ of the micro bare surface corresponding to the signal from each light receiving optical fiber 10, the value of the projection angle α, and the installation angle of the light receiving optical fiber 10 that receives the signal (that is, ,
It is calculated according to the light receiving angles β 1 and β 2 in FIG. 5, and an angle θ that is ½ of the sum of the light projecting angle α and the light receiving angle β is calculated and stored. Then, the control calculation unit 5 obtains the relationship between the azimuth angle φ of the minute surface and the reflection intensity R (θ, φ) as shown in FIG. 4, further obtains the shape distribution function G (φ), and based on these, Obtaining the reflectance F (θ), the obtained reflectance F (θ)
The relationship between the angle θ and the angle θ is fitted to the Fresnel's equation, and the refractive index n of the sample is obtained. It should be noted that such a control calculation unit 5 can be configured using a personal computer.

According to the present invention, since the refractive index n of the sample is obtained as described above, it is possible to measure a sample, such as skin, whose surface is not flat, in a non-destructive state. Further, in this case, the refractive index of the bare skin is obtained, and then the refractive index of the makeup skin to which a cosmetic such as a foundation is applied is obtained, and by comparing the refractive indices of both, it affects the bare skin such as the covering power of the cosmetic. It is possible to evaluate the effect.

[0035]

According to the present invention, the sample is projected at different projection angles α, and the reflected light at each projection angle α is converted into a plurality of different reception angles β.
Since the light is received by, it becomes possible to obtain the reflection intensity R (θ, φ) on the minute surface of the azimuth angle φ when the sample surface is projected at the projection angle α, and the shape distribution function G ( φ) is obtained, and the reflectance F according to Fresnel's equation is calculated from the obtained reflection intensity R (θ, φ) and the shape distribution function G (φ).
It is possible to obtain (θ).

Then, the obtained reflectance F (θ) is calculated by the Fresnel equation.

[0037]

[Equation 14] Then, the refractive index n of the sample can be obtained.

Therefore, according to the present invention, a sample such as skin which is not flat can be used as a measurement target, and the refractive index of the sample can be measured in a non-destructive state as it is. Becomes

[0039]

EXAMPLES The present invention will be specifically described below based on examples.

Example 1 The refractive index of a skin replica formed using a dental impression material was determined using the apparatus of FIG. In this case, a halogen lamp is used as the light source, and the projection angle θ is 0 to 75 °.
° Changed at intervals. Further, the installation angles of the light receiving portions were set at 5 ° intervals in the range of 15 to 75 ° centering on the light projecting portion of the sample. The reflectance F (θ) thus obtained and the angle θ (=
FIG. 6 shows the relationship with (light projection angle α + light reception angle β) / 2).
Table 1 shows the refractive index n obtained by fitting this relationship to the Fresnel equation. For reference, the literature values of the refractive index of the constituent material of this replica are shown in Table 1.

Examples 2 to 4 The powder of Table 1 was applied to the surface of the replica (application amount 0.15 m).
The refractive index was measured in the same manner as in Example 1 with respect to that of g / cm ² ). Obtained reflectance F (θ) and angle θ
FIG. 6 shows the relationship with (= (projection angle α + reception angle β) / 2), and Table 1 shows the refractive index n obtained by fitting this relationship to the Fresnel equation. Table 1 shows literature values of the refractive index of each powder.

[0042]

[Table 1] Powder refractive index measurement value Refractive index literature value Example 1-1.445 1.40 Example 2 Plate-shaped mica (* 1) 1.998 1.58 Example 3 Granular titanium oxide (* 2) 2.821 2 .52 to 2.90 Example 4 Plate-shaped titanium oxide (* 3) 2.978 2.52 to 2.90 (* 1) Particle size 10 to 20 μm, Yamaguchi Mica Industry Co., Ltd., KY181 (* 2) Particle size about 1 μm, Teika Co., MT600KS (* 3) Particle size about 2 to 10 μm, Sumitomo Chemical Co., Ltd., Luxelen Silk D From the results in Table 1, it can be seen that the refractive index values obtained by the method of the present invention are in good agreement with the literature values. Therefore, according to the present invention, it can be seen that the refractive index of the sample whose surface is not flat can be measured.

Example 5 A commercially available powder foundation was coated on the replica of the skin formed by using the dental impression material in the coating amount shown in Table 2, and the refractive index was measured in the same manner as in Example 1. The obtained reflectance F (θ) and the angle θ (= (projection angle α + reception angle β) /
The relationship with 2) is shown in FIG. 7A, and the refractive index n obtained by fitting this relationship with the Fresnel equation is shown in Table 2. The relationship between the amount of powder foundation applied and the refractive index n in this case is shown in FIG.

[0044]

[Table 2] Coating amount of powder foundation (mg / cm ² ) Refractive index (n) −1.503 0.05 1.792 0.10 2.141 0.15 2.253 0.20 2.338 From the results of FIG. 7, the observed refractive index increases as the amount of powder foundation applied increases,
It can be seen that it approaches a certain value. Therefore, it can be seen that the hiding power and the feeling of finish of the powder foundation can be evaluated from the change in the applied amount and the refractive index of the powder foundation.

[0045]

EFFECTS OF THE INVENTION According to the present invention, it is possible to measure the refractive index of a substance which is made of various constituents such as skin and whose surface is not flat, in a non-destructive state.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an apparatus of the present invention.

FIG. 2 is an explanatory diagram of a minute surface and a reflection direction.

FIG. 3 is a relationship diagram between a refractive index n and a reflectance F (θ) of a sample.

FIG. 4 shows an angle θ (= (α + β) / 2) when light is projected onto a sample at a projection angle α and is received at a reception angle β, an azimuth angle φ of a minute surface and a reflection intensity R (θ, φ). FIG.

FIG. 5 is an explanatory diagram of a light projection angle, a light reception angle, and an azimuth angle of a minute surface.

FIG. 6 is a relationship diagram between an angle θ and a reflectance F (θ) in the example.

FIG. 7 is a diagram showing the relationship between the angle θ and the reflectance F (θ) in the example (FIG. 7A) and a diagram showing the relationship between the coating amount of the powder foundation and the refractive index n (FIG. 7B). .

[Explanation of symbols]

1 Projection means 2 Light receiving means 3 head 4 converter 5 Control calculation unit 6 light source 7 Optical fiber for projection 8 bundles 9 Lighting lens 10 Optical fiber for receiving light

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21/17-21/61 JISST file (JOIS) Practical file (PATOLIS) Patent File (PATOLIS)

Claims (5)

(57) [Claims] 1. A sample surface is projected a plurality of times at different projection angles α, and reflected light for each projection angle α is received at a plurality of different reception angles β.
Each of the light received at the angle .alpha. (= (. Alpha. +. Beta.) / 2), which is 1/2 of the sum of the projection angle .alpha. And the acceptance angle .beta., And the reflection as a function of the azimuth angle .phi. The intensity R (θ, φ) is obtained, and the shape distribution function G (φ) is obtained as the reflection intensity proportional to the proportion of the minute surface having the azimuth angle φ, and the following formula [Formula 1] R (θ, φ) = F (θ) · G (φ), the reflectance F (θ) of the sample is calculated, and this reflectance F
(Θ) and Fresnel's formula [Equation 2] The refractive index measurement method is characterized in that the refractive index n of the sample is obtained based on the above. 2. The refractive index measuring method according to claim 1, wherein the shape distribution function G (φ) is obtained based on a Gaussian distribution. 3. A light projecting unit capable of projecting light from a light source onto a sample with a variable projecting angle, and reflected light from the sample surface for each projecting angle can be simultaneously received at a plurality of different light receiving angles. A light receiving means comprising a plurality of light receiving portions arranged at different installation angles with respect to the light projecting portion of the sample, a converter for converting the light received by each light receiving portion into an electric signal according to its light intensity, And a control calculation means, and the control calculation means is 1 / the sum of the projection angle α and the reception angle β depending on the projection angle α, the reception angle β, and the light intensity received by the light receiving section. 2 angle θ (=
(Α + β) / 2), the reflection intensity R (θ, φ) as a function of the azimuth angle φ of the microscopic surface constituting the sample surface, and the reflection intensity proportional to the proportion of the microscopic surface having the azimuth angle φ. The shape distribution function G (φ) is obtained as
The reflectance F (θ) when the sample is flat is calculated based on the following equation: R (θ, φ) = F (θ) · G (φ)
This reflectance F (θ) and Fresnel's equation [Formula 4] A refractive index measuring device, characterized in that the refractive index n of the sample is obtained based on 4. A plurality of light-receiving portions of the light-receiving means are formed of a plurality of light-receiving optical fibers that are provided in a concentric circle centered on the light-projecting portion of the sample, in the same plane as the optical path of the light-projecting light. Item 3. The refractive index measuring device according to item 3. 5. The refractive index measuring device according to claim 4, wherein the converter is a multi-channel converter that simultaneously converts light received by the plurality of light receiving optical fibers into an electric signal.