JP2012052998A - Optical measurement method and optical measurement device for measuring refraction factor of solid body having rough surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical measurement method and optical measurement device capable of measuring a refraction index of a rough surface of a solid body and a volume ratio γ of the solid body and a gas when the rough surface is regarded as a mixture layer of the solid body and the gas contacted to the solid body.SOLUTION: The optical measurement method includes a first step in which p-polarized light is incident on a rough surface 32 of a sample 30 which is in contact with the gas, and an apparent refraction index nof the rough surface 32 which is in contact with the gas is measured based on an incidence angle φwhere the intensity of the reflection light reflected from the rough surface 32 is minimum; and a second step in which the p-polarized light is incident on the rough surface 32 of the sample 30 which is in contact with a liquid, an apparent refraction index nof the rough surface 32 which is in contact with the liquid is measured based on an incidence angle φwhere the intensity of the reflection light reflected from the rough surface 32 is minimum, and a volume ratio γ in the mixture layer of the solid body and the gas and a refraction index nof the sample 30 when the rough surface 32 is regarded as a mixture layer of the solid body and the gas, based on the refraction indices of nand n.

Description

  The present invention relates to an optical measurement method and an optical measurement apparatus for measuring a refractive index of a solid having a rough surface.

  Conventionally, as a typical refractive index measurement method, a minimum deviation method, a critical angle method, an ellipsometry (an ellipsometry), an immersion method, and the like are known. The minimum deviation method (see Non-Patent Document 1) is a method for obtaining the refractive index by measuring the apex angle and the minimum deviation angle of a sample processed into a prism, and can measure the refractive index most precisely. The critical angle method (see Non-Patent Document 2) is suitable for measuring the refractive index of a liquid. The refractive index of the sample liquid is obtained as a relative value with respect to the reference prism. In ellipsometry (see Non-Patent Document 3), P-polarized light and S-polarized light are incident on a sample thin film on a substrate having a known refractive index, and the thickness, refractive index, and extinction of the thin film are determined from changes in the polarization state due to reflection. This is a method for obtaining a coefficient. The immersion method (see Non-Patent Document 4) uses a powder sample and a large number of transparent liquids whose refractive index changes stepwise, and mixes the liquid sample with these liquids to obtain a liquid in which the outline of the sample is most difficult to see. This is a method for obtaining the refractive index by selecting. In this method, the refractive index can be measured without mirror-treating the sample.

Everitt Charles, "Refraction." The Encyclopedia Britannica, 11th Ed. Vol. 23, The Encyclopedia Britannica Company, New York (1911) 26-27. Tilton, Leroy W., and John K. Taylor, "Refractive Index Measurement," in Physical Methods in Chemical Analysis Vol. 1, 2nd ed .; Walter G. Berl, editor (1961) 411-62. (E ABBE, " Carl's Repertorium der Physik ", Vol. 15, 643 (1879). C. PULFRICH," Zeitschrift fuer Instrumentenkunde ", Vol. 18, 107 (1898)) Hiroyuki Fujiwara, Spectroscopic Ellipsometry, Maruzen Co., Ltd. 2003, 7-124. Miyakonojo Akiho, Hisagi Ikuo, “Iwagaku I”, Kyoritsu Shuppan 2000, pp.90-93.

  The minimum deviation method has a problem that non-destructive measurement cannot be performed because the sample is processed into a prism. In addition, the critical angle method has problems that the refractive index of a solid sample cannot be measured, the measurement accuracy as low as the minimum deviation method cannot be obtained, and the refractive index larger than the refractive index of the reference prism cannot be measured. Ellipsometry is a method in which a solid or liquid whose surface is flattened by optical polishing or vapor deposition is used as a measurement sample, and is not suitable for measurement of a solid sample having a rough surface. In addition, the immersion method is a destructive inspection, limited to materials within the refractive index of the immersion liquid (1.44 to 1.88), and has problems such as inferior measurement accuracy compared to the previous three methods. ing.

  The present invention has been made in view of the above problems, and its object is to measure the refractive index of a solid having a rough surface without any processing on the rough surface of the solid. It is an object of the present invention to provide an optical measurement method and an optical measurement apparatus capable of performing the above.

(1) The present invention provides an optical measurement method for measuring a refractive index of a solid having a rough surface.
A first step of measuring an apparent refractive index n _cs of the solid rough surface by bringing a gas into contact with the rough surface of the solid;
A liquid having a large absorption coefficient or scattering coefficient is brought into contact with the solid rough surface, the apparent refractive index n _ci of the solid rough surface is measured, and the apparent refractive index n _cs of the rough surface with which the gas is in contact Based on the apparent refractive index n _ci of the rough surface in contact with the liquid, the volume ratio γ of the solid and the gas in the mixed layer when the rough surface of the solid is regarded as the mixed layer of the solid and the gas characterized by a second step of obtaining a refractive index n _m of the solid.

  Here, the refractive index actually felt when light incident on the solid rough surface is reflected or refracted on the rough surface is referred to as an apparent refractive index. The apparent refractive index is determined from the refractive index of the solid, the refractive index of the atmosphere surrounding it, and the uneven state of the rough surface, unlike the original refractive index of the solid. Of the return light from the interface between two media having different refractive indexes, the light that follows the law of reflection is called reflected light, and the other return light is called scattered light. In addition, among the light transmitted through the interface between two media having different refractive indexes, light complying with Snell's law is called transmitted light, and the other light is called scattered light. Furthermore, the ratio of the electric field of incident light and the electric field of reflected light is defined as electric field reflectance, and the ratio of incident light power and reflected light power is defined as power reflectance.

  According to the present invention, the refractive index of a solid having a rough surface can be measured nondestructively.

(2) In the present invention,
In the first step,
The p-polarized light whose electric field component of linearly polarized light vibrates in the incident plane is incident on the rough surface in contact with the gas at an incident angle φ ₁ , and the reflected light reflected at the reflection angle φ ₁ from the solid rough surface according to the law of reflection. It obtains the incident angle phi _min the strength is minimized, and the incident angle phi _min, based on the refractive index n _s of the gas in contact with the rough surface of the solid, the apparent rough surface on which the gas is in contact The refractive index n _cs may be obtained.

(3) In the present invention,
In the first step,
The apparent refractive index n _cs of the rough surface in contact with the gas may be obtained based on the above.

(4) In the present invention,
In the second step,
The liquid is brought into contact with the solid rough surface by pressing the transparent prism to the solid rough surface via the liquid, and the p-polarized light whose electric field component of linearly polarized light vibrates in the incident surface is incident on the transparent prism. The incident angle φ _i that minimizes the intensity of the reflected light reflected at the interface between the transparent prism and the solid rough surface according to the law of reflection is obtained, and the incident angle φ _i and the refractive index n of the transparent prism are determined. _g and, a top angle δ which faces the exit surface of the transparent prism, on the basis of the refractive index n _s of the gas in contact with the transparent prism, the refractive index n _ci apparent rough surface on which the liquid is in contact May be requested.

  Here, it is preferable that the transparent prism is a transparent prism obtained by optically polishing a light incident surface, an output surface, and a reflective surface.

(5) In the present invention,
In the second step,
The apparent refractive index n _ci of the rough surface in contact with the liquid may be obtained based on the above.

(6) In the present invention,
In the second step,
Based on the apparent refractive index n _cs of the rough surface in contact with the gas, the apparent refractive index n _ci of the rough surface in contact with the liquid, and the refractive index n _{i of the} liquid, the solid in the mixed layer The gas volume ratio γ may be obtained.

(7) In the present invention,
In the second step,
When the volume ratio of the solid volume V _m to the gas volume V _{s in} the mixed layer is γ = V _s / V _m ,
The refractive index n _cs apparent rough surface on which the gas is in contact, and the refractive index n _ci apparent rough surface on which the liquid is in contact, and a refractive index n _i of said liquid,

Represented by

The volume ratio γ may be obtained based on the above.

(8) In the present invention,
In the second step,
It said volume ratio gamma, on the basis of the refractive index n _cs apparent rough surface on which the gas is in contact, may be obtained refractive index n _m of the solid.

(9) In the present invention,
In the second step,
Refractive index and n _cs apparent rough surface on which the gas is in contact, the refractive index n _m of the solid,

Represented by

It may be obtained refractive index n _m of the solid based on.

(10) The present invention
In an optical measuring device for measuring the refractive index of a solid having a rough surface,
A light irradiator that causes p-polarized light whose electric field component of linearly polarized light oscillates in the incident plane to be incident on the solid rough surface;
A light detection unit for detecting the intensity of reflected light reflected according to the law of reflection from the rough surface of the solid contacted with gas or liquid;
A rotation drive unit that changes the incident angle of the p-polarized light by rotating the solid;
When the p-polarized light is incident on the rough surface in contact with the gas, the gas comes into contact based on an incident angle φ _min that minimizes the intensity of reflected light reflected from the solid rough surface according to the law of reflection. And calculating the apparent refractive index n _cs of the rough surface,
When the liquid is brought into contact with the rough surface of the solid by pressing the transparent prism to the rough surface of the solid through the liquid and the p-polarized light is incident on the transparent prism, the transparent prism and the solid Calculating an apparent refractive index n _cs of the rough surface in contact with the liquid, based on the incident angle φ _{i at} which the intensity of the reflected light reflected at the interface with the rough surface is minimized according to the law of reflection;
Based on the apparent refractive index n _cs of the rough surface in contact with the gas and the apparent refractive index n _ci of the rough surface in contact with the liquid, the solid rough surface is regarded as a mixed layer of the solid and the gas. wherein the volume ratio γ of the solid and gas in the mixed layer, characterized in that it comprises a processing unit for performing arithmetic processing for calculating the refractive index n _m of the solid when the.

  According to the present invention, the refractive index of a solid having a rough surface can be measured nondestructively.

The figure which shows typically the mode of reflection and scattering of the light in the solid surface which gas contacted. The figure which shows the model which considered the solid rough surface which gas contacted as the mixed layer of a solid and gas. The figure which shows the relationship between incident angle (phi) _min in the rough surface solid which gas contacted, and the scattering coefficient (alpha) of a mixed layer. The figure for demonstrating the apparent refractive index measurement of the rough surface solid which the liquid contacted. The figure for demonstrating the apparent refractive index measurement of the rough surface solid which the liquid contacted. The figure which shows an example of a structure of the optical measuring device of this embodiment. The side view which shows an example of a structure of the 1st rotation mechanism which rotates a sample stand, and the 2nd rotation mechanism which rotates a photodetector stand. The figure which shows the modification of an optical measuring device. The figure which shows the modification of an optical measuring device. The figure which shows the modification of an optical measuring device. The figure which shows one method of fixing a sample and a transparent prism. The figure which shows the positional relationship of a sample and a sample stand. The block diagram of a transparent prism, a transparent dove prism, and other prisms. 14A is an image obtained by imaging reflected light reflected by a light rough surface, and FIG. 14B is an image obtained by imaging reflected light reflected by a heavy rough surface. The figure for demonstrating the initial setting which determines the angle of incident light and a sample surface. The figure for demonstrating the initial setting which determines the angle of incident light and a sample surface. The figure for demonstrating the refractive index measurement of the liquid with a big absorption coefficient. The figure which shows the relationship between power reflectivity _Rp and incident angle (phi) _{1 of} LT crystal | crystallization put in the air. Drawing showing the relationship between the power reflectivity R _p of the contacted LT crystal large liquid the incident angle phi _i of the absorption coefficient.

  Hereinafter, this embodiment will be described. In addition, this embodiment demonstrated below does not unduly limit the content of this invention described in the claim. In addition, all the configurations described in the present embodiment are not necessarily essential configuration requirements of the present invention.

1. Measurement Principle The measurement principle employed by the optical measurement method and the optical measurement apparatus according to this embodiment will be described.

1-1. Measurement of apparent refractive index of solid rough surface (mixed layer of solid and gas) with gas in contact with rough surface irregularities (first step)
FIG. 1A schematically shows how light is reflected and scattered on a solid rough surface placed in a gas atmosphere. As shown in FIG. 1, the surface of frosted glass or as-cut crystal is a rough surface having fine irregularities, and has a structure in which a solid and a gas (for example, air) surrounding it are intricately complicated. Yes. When the fine portion of the rough surface structure is equal to or smaller than the wavelength of the incident light, the solid rough surface is regarded as a mixed layer of solid and gas as shown in FIG. Can do. This mixed layer exists, for example, between the upper surface and the lower surface when the surface that is in contact with the highest portion of the rough surface is the upper surface and the surface that is in contact with the lowest portion of the rough surface and is parallel to the upper surface is the lower surface. It is a layer which makes the solid (solid which comprises a rough surface) and gas (gas which is in contact with the rough surface) to constitute.

  In the first step in the present embodiment, the apparent refractive index of the solid rough surface in contact with the gas is measured using a model in which the solid rough surface is regarded as a mixed layer of solid and gas.

As shown in FIG. 2, the incident angle of the mixed layer p-polarized light incident on the (solid rough surface) (linear polarization electric field component vibrates in the plane of incidence) and phi _1, the refraction angle of the mixed layer and phi ₂ When the solid refraction angle is φ ₃ and the scattering coefficient and thickness of the mixed layer are α and d, respectively, the power reflectivity R _p φ ₁ of the mixed layer with respect to the incident light of p-polarized light is expressed as follows: Is done.

In equation (1), r ₁ is the amplitude reflectivity (reflectance of the electric field of light) due to Fresnel reflection when light enters the mixed layer from the gas, and r ₂ is the light at the boundary between the mixed layer and the solid. Is the amplitude reflectivity due to Fresnel reflection, and is expressed by the following equations, respectively.

Here, n _s is the refractive index of the gas, n _cs is the apparent refractive index of the mixed layer, and n _m is the refractive index of the solid.

  In Expression (1), L is a physical optical path length when light makes one round trip through the mixed layer, and Ψ is a phase difference between adjacent reflected lights, each represented by the following expression: . Where λ is the wavelength of the incident light.

Here, when the product αL of the scattering coefficient α and the optical path length L in the mixed layer is very small, not only the reflected light on the surface of the mixed layer (light ray 100 shown in FIG. 2) but also the reflection from the inside of the mixed layer according to the law of reflection. Since the presence of reflected light that cannot be ignored is also negligible, the power reflectivity R _p φ ₁ of the reflected light shows a periodic change with the change of φ ₁ according to the equation (1). On the other hand, when the αL is very large, the light incident on the mixed layer is scattered in various directions, and the reflected light from the inside of the mixed layer becomes extremely small. At this time, the reflected light of the mixed layer surface (ray 100 shown in FIG. 2) is, thus dominating the power reflectivity R _p phi ₁ of the reflected light from the mixed layer, the power reflectivity R _p of the reflected light,

It becomes.

Here, the scattered light is radiated in all directions as shown in FIG. 1, whereas the reflected light uses the optical system shown in FIGS. 6 to 10 described later in order to maintain the same reflection angle as the incident angle. For example, most of the scattered light can be blocked and the reflected light can be selectively extracted. If the main component of the light incident on the photodetector 40 shown in FIGS. 6 to 10 is reflected light, the apparent refractive index n _{cs of the} mixed layer (that is, the rough surface) is obtained using Brewster's law. Can be requested. When the Brewster angle at the interface between the mixed layer and the gas and phi _B, the refractive index n _cs of the mixed layer is expressed by the following equation.

At this time, since r ₁ = 0 by Brewster's law, the power reflectivity R _p φ _{B at} the Brewster angle φ _B is expressed by the following equation from the equation (1).

In order to find a condition for satisfying the equation (8), the equations (2) to (5) are substituted into the equation (1) to obtain a partial derivative ∂R _p φ ₁ ) / φ ₁ related to the variable φ ₁ , which is zero. Find the angle of incidence when Here, the solid refractive index n _m = 2.5, the gas refractive index n _s = 1, the mixed layer refractive index n _cs = 1.6 to 2.4, and the mixed layer thickness d = 1000 nm. And the calculation was performed under the condition that the wavelength λ of the incident light of p-polarized light was 632.8 nm.

FIG. 3 is a diagram showing an analysis result showing a relationship between the incident angle φ _{min at} which the power reflectivity R _p φ ₁ is the minimum value and the scattering coefficient α of the mixed layer. FIG. 3 shows that the incident angle φ _min becomes a constant value when αd> 2. Table 1 shows the results of calculating the incident angle φ _min by changing the refractive index n _cs of the mixed layer in the range of 1.6 to 2.4.

The incident angle φ _min shown in Table 1 is in agreement with the Brewster angle φ _B expressed by the equation (7). The analysis results in FIG. 3 and Table 1 are examples, and even if n _s , n _cs , n _m , d, and λ are changed, φ _min = φ _B is established as long as the mixed layer satisfies the condition of αd> 2. To do. Therefore, it is clear from this analysis that the refractive index n _cs of the mixed layer satisfying αd> 2 is obtained by the following equation.

Therefore, p-polarized light is incident on a solid rough surface in contact with gas, and the incident angle φ _{min at} which the intensity of reflected light reflected by the rough surface (ie, power reflectivity R _p φ ₁ ) is minimized is measured. By substituting the measured incident angle φ _min and the refractive index n _{s of the} gas into the equation (9), the refractive index n _cs of the mixed layer when the rough surface of the solid is regarded as a mixed layer of the solid and the gas ( That is, the apparent refractive index of the solid rough surface can be obtained.

  Thus, according to this embodiment, the apparent refractive index of the rough surface can be measured by regarding the rough surface of the solid as a mixed layer of a solid and a gas atmosphere.

1-2. Derivation of equations to the refractive index n _m of the solid rough surface gas contacts the irregularities of the rough surface of the solid and gas in (solid and mixed layer composed of gas) volume ratio γ and solid unknowns Next, the .alpha.d> 2 the derivation of equations describing relating the refractive index n _m of the solid and gas volume ratio γ and the solid in the mixed layer satisfying.

If the density of the solid is ρ _m , the density of the gas is ρ _s, and the density of the mixed layer is ρ _cs , the Lorentz-Lorentz (Lorentz-) From the Lorenz formula, the following relationship is established:

  Here, β is the weight (%) of the gas in the mixed layer.

It is also apparent that the following equation holds, where V _m is the solid volume, V _s is the gas volume, and V _cs is the volume of the mixed layer.

  From the equations (11) to (13), the following equation is obtained.

Here, γ is the ratio of the volume V _m of the solid and the volume V _s of the gas in the mixed layer.

Rewriting equation (13),
And rewriting equation (12),

It becomes. Substituting equation (17) into equation (16) yields:

  Substituting equation (14) into equation (18) yields:

Here, the functions f _m , f _s , f _cs of the refractive index n _m of the solid, the refractive index n _{s of the} gas, and the refractive index n _cs of the mixed layer are expressed as _follows :

And substituting Expression (20) and Expression (14) into Expression (10), the following expression is obtained.

  Substituting equation (19) into equation (21) yields:

Here, the refractive index of the gas n _s is approximately 1 (e.g., if air, 0 ° C., n _s = 1.000292 under the conditions of 1 atm) because it is a function f _s of the refractive index n _s from equation (20) Approximately 0. Therefore, by substituting f s _{= 0} in equation (22), as shown in the following equation, even if related functions f _m of the refractive index n _m of the volume ratio γ and solid solid and a gas in the mixed layer good.

1-3. Large liquid absorption coefficient or scattering coefficient, equation of solid rough surface in contact with the rough surface of the refractive index n _m of the volume ratio γ and a solid solid and the gas in the (mixed layer made of the solid liquid) and unknown Derivation and derivation of the volume ratio γ and the refractive index _nm of the solid (second step)
Next, the principle of simultaneously measuring the refractive index _nm (solid true refractive index) and volume ratio γ of a solid having a rough surface will be described.

Equation (22) and (23) are both include two variables γ and _{f m.} In order to determine these variables, another atmosphere (for example, liquid) other than air is brought into contact with the unevenness of the rough surface, and a new apparent refractive index n _ci corresponding to the equation (22) and the volume ratio γ are set. It is necessary to obtain an equation to be related and solve a simultaneous equation of this equation and Equation (22) or Equation (23).

  As another type of atmosphere other than air, (a) vacuum, (b) gas of the same pressure having a refractive index different from that of air, (c) air of different pressure or other gas, (d) liquid with high transparency, (E) A liquid having at least one of a large absorption coefficient and a large scattering coefficient is conceivable.

  (A) and (b) are not suitable because the difference in refractive index from the gas (for example, air) in the first step is very small. Although (c) can be measured because the difference in refractive index can be increased if the pressure difference between the two gases is greatly increased, the apparatus becomes large and is not suitable. (D) is not appropriate because the difference in refractive index between the solid and the liquid in the mixed layer is smaller than the difference in refractive index between the solid and air, and αd <2. In (e), the reflectance of the solid and the liquid in the mixed layer is lowered, but instead, the light propagating through the mixed layer is absorbed in the liquid, or is scattered in the liquid, or these two Because of the large attenuation due to the effect, the reflected light from inside the mixed layer can be ignored. That is, in the case of a sample that does not have a wet state, a liquid having at least one of a large absorption coefficient and a large scattering coefficient is most suitable.

  Here, a method of using a liquid having a high absorption rate (a liquid having a large absorption coefficient) as another type of atmosphere other than air will be described. Assuming that the absorption coefficient of the liquid is η, the following value is desirable for the absorption coefficient η from the analysis result of FIG.

  As shown in FIG. 4, a liquid having a high absorptance is uniformly applied to a solid rough surface, and a transparent prism (a transparent prism having an optically polished light incident surface, an output surface, and a reflective surface) is pressure-bonded thereon. Thus, a mixed layer having a thickness d is formed. The mixed layer is composed of a solid and a liquid having an absorption coefficient η.

As shown in FIG. 5, the mixed layer sandwiched between the solid and the transparent prism is irradiated with p-polarized light, and the incident angle φ ′ _min of the mixed layer at which the intensity of the reflected light from the mixed layer becomes the minimum value is obtained. Although the incident angle φ ′ _min cannot be directly measured, the incident angle φ _i of the transparent prism that minimizes the intensity of the reflected light can be measured, and φ _i and φ ′ _min can be related from Snell's law. .

Assuming that the refractive indexes of the transparent prism, the solid, and the mixed layer are n _g , n _m , and n _ci , respectively, the following equation is approximated when the intensity of the reflected light is minimized when Equation (24) is satisfied. It holds.

Further, a transparent prism, between the gas of the refractive index n _s (air), Snell's law of the following equation holds.

Here, φ _g is a refraction angle at the interface between the transparent prism and the gas as shown in FIG.

From the equations (25) and (26), the refractive index n _ci of the mixed layer can be obtained by the following equation.

  Here, as shown in FIG. 5, δ is an apex angle (angle formed by the incident surface of the transparent prism and the reflecting surface) facing the output surface of the transparent prism.

Accordingly, p-polarized light is incident on the incident surface of the transparent prism, and the incident angle φ _{i at} which the intensity of the reflected light reflected by the solid rough surface (interface between the transparent prism and the solid rough surface) is minimized is measured. in to the incident angle phi _i was, the refractive index n _g of transparent prisms, the apex angle δ of the transparent prism, the refractive index n _s of the gas by substituting the equation (27), and a liquid of solid and high absorption rate The refractive index n _ci (that is, the apparent refractive index of the solid rough surface in contact with the liquid having a high absorption rate) can be obtained.

Here, the respective functions f _m , f _i , and f _ci of the refractive index n _m of the solid, the refractive index n _i of the liquid having a high absorption rate, and the refractive index n _ci of the mixed layer are expressed as

Since the mixed layer is composed of a solid and a liquid, the following equation is established from the equation (22).

  Substituting equation (23) into equation (29) and rearranging results in the following equation.

Therefore, when the refractive index n _i (ie, the function f _{i of} n _i ) of the liquid having a high absorptance is clear, the refractive index n _cs (ie, n _cs of the mixed layer) which is the measurement value of the first step the function _{f cs),} the refractive index of the mixed layer is a measure of the second step _{n ci (i.e.,} the function _{f ci)} and _{n ci} by substituting the equation (30), solid in the mixed layer and the gas Can be obtained.

That is, f _cs is obtained by substituting the refractive index n _cs (apparent refractive index of the solid rough surface in contact with the gas) of the mixed layer obtained by the equation (9) into the equation (20). 27) Substituting the refractive index n _ci (apparent refractive index of the solid rough surface in contact with the liquid having a high absorption rate) of the mixed layer obtained by (27) into the equation (28), the f _ci was obtained and obtained. By substituting f _cs , f _ci and f _i into equation (30), the volume ratio γ of the solid and the gas in the mixed layer when the solid rough surface is regarded as a mixed layer of the solid and the gas can be obtained. .

Moreover, the volume ratio γ obtained by the equation (30), the refractive index of the mixed layer is a measurement of the first step _{n cs (i.e.,} the function _{f cs} of _{n cs)} and the formula (23) (or formula ( by substituting 22)), determine the function f _m of the refractive index n _m of solid, f _m obtained by substituting the equation (20) can be determined the true refractive index n _m of solid .

As described above, according to the present embodiment, the apparent refractive index n _cs of the rough surface in the gas atmosphere is measured in the first step, and the apparent refractive index of the rough surface in the liquid atmosphere having a high absorption rate in the second step. by measuring the n _ci, and a volume ratio γ of the refractive index n _m and the mixed layer of a solid can be measured nondestructively with a rough surface. Moreover, according to this embodiment, since the reflected light intensity is measured, the refractive index of a substance with large absorption can also be measured. In addition, in the conventional critical angle method and the liquid immersion method, the range of the refractive index that can be measured is limited. However, according to the present embodiment, as long as the mixed layer satisfies the condition of αd> 2, the refractive index in any range. Can be measured.

2. Configuration FIG. 6 is a diagram illustrating an example of the configuration of the optical measurement apparatus of the present embodiment.

The optical measuring device 1 of the present embodiment is a device that measures the apparent refractive index n _cs of the rough surface 32 of the sample 30 (solid having a rough surface) to be measured, and the volume ratio γ of the solid and gas in the mixed layer. It is. The optical measuring device 1 includes a light source 10 composed of a laser diode, a beam splitter 12, an aperture 14 having a circular aperture, a polarizer 20 and an analyzer 22 that transmit p-polarized light, and a photoelectric sensor (photo detector). First and second photodetectors 40 and 42, a chopper 50 for chopping continuous light, a chopper controller 52, a lock-in amplifier 54, a sample stage 60 on which the sample 30 is placed, and a first light A photodetector stage 62 on which the detector 40 is placed, a first rotation mechanism (not shown) for rotating the sample stage 60 around the rotation axis RA, and a photodetector stage 62 around the rotation axis RA. A second rotation mechanism (not shown) that rotates the first rotation mechanism, and an arithmetic unit 70. The rotation axis RA is parallel to the Z axis, exists in or near the rough surface 32 of the sample 30, and is orthogonal to the normal 33 of the rough surface 32.

  The light emitted from the light source 10 passes through the polarizer 20 and becomes p-polarized light that vibrates in a horizontal plane (a plane including the X axis and the Y axis in FIG. 6). That is, the p-polarized electric field vibrates on a horizontal plane including the normal line 33 of the rough surface 32 of the sample 30. The p-polarized light is pulse-modulated by the chopper 50 and is incident on the rough surface 32 of the sample 30. The intersection of the incident light and the reflected light is preferably coincident with the rotation axis RA or at least near the rotation axis RA.

  The p-polarized reflected light reflected by the rough surface 32 travels in the direction of the reflection angle φ equal to the incident angle φ as shown in FIG. On the other hand, scattered light is radiated in all directions from the intersection of incident light and reflected light. In order to measure the intensity of the reflected light and scattered light, an aperture 14, an analyzer 22 and a first light detector 40 having an opening having substantially the same diameter as the beam diameter of the incident light are installed on the light detector table 62. ing.

  The first photodetector 40 (light detector) receives the reflected light and scattered light reflected by the rough surface 32 as the photodetector base 62 rotates, and converts the intensity of the received light into a current or voltage ( Photoelectrically converted) and output to the lock-in amplifier 54 as light intensity information (detection signal).

  The chopper controller 52 outputs a control signal (drive signal) to the chopper 50 to control the drive of the chopper 50 and outputs the control signal to the lock-in amplifier 54 as a reference signal. The lock-in amplifier 54 detects a frequency component equal to the reference signal output from the chopper control unit 52 among the detection signals output from the first photodetector 40, and outputs the detected frequency component to the arithmetic device 70. By using the chopper 50, the chopper controller 52, and the lock-in amplifier 54, the measurement accuracy can be improved.

  The beam splitter 12 reflects a part of the light emitted from the light source 10. The second photodetector 42 receives the light reflected by the beam splitter 12, performs photoelectric conversion, and outputs a detection signal to the arithmetic device 70. The light detected by the first photodetector 40 due to the fluctuation of the emitted light intensity by detecting the fluctuation of the emitted light intensity from the light source 10 using the beam splitter 12 and the second photodetector 42. Variations in intensity can be compensated for and measurement accuracy can be improved.

  Although an example using a semiconductor laser as a light source is shown here, a gas laser, a dye laser, or a solid-state laser can be used instead of the semiconductor laser. A so-called incoherent light source such as a halogen lamp or a xenon lamp can also be used. However, since incoherent light generally has a very wide emission spectrum, it is necessary to insert an optical bandpass filter that narrows the spectrum between the light source 10 and the beam splitter 12.

  FIG. 7A is a side view showing an example of the configuration of a first rotation mechanism 61 that rotates the sample stage 60 and a second rotation mechanism 63 that rotates the photodetector stage 62.

  As shown in FIG. 7A, the sample stage 60 includes a first rotation mechanism 61 that rotates the sample stage 60, an tilt mechanism 64 (gonio) that adjusts the tilt angle of the sample stage 60, and the sample stage 60 as XYZ. It is provided on an XYZ moving mechanism 65 that moves in the axial direction. The XYZ moving mechanism 65 is supported by a first support pole 67.

  The photodetector base 62 is attached to a second rotation mechanism 63 that rotates the photodetector base 62. The photodetector base 62 includes a support pole (not shown) that supports the aperture 14, a second support pole 68 that supports the analyzer 22, and a vertical movement mechanism that vertically moves the first photodetector 40. 66 is provided, and the vertical movement mechanism 66 is provided with a third support pole 69 that supports the first photodetector 40. The first and second rotation mechanisms 61 and 63 can be configured by a manual rotation stage, an automatic rotation stage, or the like.

  The rotation axes RA of the first rotation mechanism 61 and the second rotation mechanism 63 coincide with each other, and the rotation axis RA coincides with the center of the circular sample stage 60. The sample stage 60 is rotated around the rotation axis RA by the first rotation mechanism 61, and the photodetector stage 62, the aperture 14, the analyzer 22, and the first photodetector 40 are rotated by the second rotation mechanism 63. It rotates around the rotation axis RA.

As described above, in this embodiment, the incident angle φ _min (or the incident angle φ _i ) that minimizes the intensity of the reflected light reflected by the rough surface of the sample 30 is obtained. Therefore, by rotating the sample stage 60 by the first rotating mechanism 61, the incident angle φ of the p-polarized light (see FIG. 6) is changed, and the second rotating mechanism is changed according to the change of the incident angle φ of the p-polarized light. By rotating the photodetector table 62 by 63, the reflected light reflected by the rough surface 32 of the sample 30 enters the first photodetector 40 via the aperture 14 and the analyzer 22. .

  FIG. 7B is a top view and a side view of the sample stage 60. As shown in FIG. 7B, the circular sample stage 60 shows a point indicating the rotation axis RA and a straight line passing therethrough. The sample 30 is placed so that the surface of the straight line and the rough surface 32 are flush with each other (illustration of devices necessary for installation is omitted).

Referring to FIG. 6 again, the arithmetic device 70 includes an arithmetic processing unit 72 and a storage unit 74. Based on the light intensity information output from the lock-in amplifier 60, the arithmetic processing unit 72 obtains the incident angle φ _min of p-polarized light that minimizes the intensity of the reflected light reflected by the rough surface 32 of the sample 30. Based on φ _min and the refractive index n _s of the gas, a calculation process (first calculation process) is performed to calculate the apparent refractive index n _cs of the rough surface 32 of the sample 30 in contact with the gas.

In addition, the arithmetic processing unit 72 receives the p-polarized light from the lock-in amplifier 60 when the p-polarized light is made incident on the rough surface 32 of the sample 30 through the liquid having the absorption coefficient η. Based on the output light intensity information, the incident angle φ _i of p-polarized light that minimizes the intensity of the reflected light reflected by the rough surface 32 of the sample 30 is obtained, and the incident angle φ _i and the refractive index of the transparent prism are obtained. and n _g, and the top angle δ of the transparent prism, on the basis of the refractive index n _s of the gas in contact with the transparent prism, the refractive index of the apparent rough surface 32 of the sample 30 in contact with the liquid n _ci is obtained, the apparent refractive index n _cs of the rough surface 32 in contact with the gas, the apparent refractive index n _ci of the rough surface 32 in contact with the liquid, and the refractive index n _{i of the} liquid. Based on the above, the rough surface 32 of the sample 30 is fixed. A calculation process (calculation process of the second step) is performed to calculate the volume ratio γ of the solid and the gas in the mixed layer when it is regarded as a mixed layer of body and gas. Further, the arithmetic processing unit 72, the volume ratio and gamma, based on the refractive index n _cs apparent rough surface 32 in contact with the gas, calculation processing for calculating a refractive index n _m of the sample 30 (second Step calculation processing).

  When the optical measurement device 1 does not include the chopper 50, the chopper control unit 52, and the lock-in amplifier 54, the arithmetic processing unit 72 is based on the light intensity information output from the first photodetector 40. Perform arithmetic processing.

  The storage unit 74 has a function of temporarily storing various data, and stores, for example, light intensity information output from the lock-in amplifier 60 in association with the incident angle φ of p-polarized light.

  8-10 is a figure which shows the modification of the optical measuring device 1. As shown in FIG.

  In the optical measuring device 1 shown in FIG. 8, the convex lens 16 is provided between the sample stage 60 and the aperture 14. Here, the distance between the convex lens 16 and the aperture 14 coincides with the focal length f of the convex lens 16. Therefore, the reflected light from the sample 30 that is parallel light passes through the opening of the aperture 14 and enters the first photodetector 40. On the other hand, the distance a between the sample 30 and the convex lens 16 is equal to or shorter than the focal length f of the convex lens 16, and scattered light from the sample 30 is blocked by the aperture 14. Further, according to the configuration shown in FIG. 8, the length of the photodetector base 62 in the direction along the optical path can be shortened as compared with the configuration shown in FIG.

  In the optical measuring apparatus 1 shown in FIG. 9, a beam expander 18 is provided between the light source 10 and the sample stage 60 to increase the beam diameter of the light emitted from the light source 10. By increasing the beam diameter of the p-polarized light incident on the sample 30, the reflected light from the sample 30 that is parallel light is condensed into a smaller spot by the convex lens 16, and thus compared with the configuration shown in FIG. The aperture of the aperture 14 can be made smaller, and the influence of scattered light from the sample 30 can be made smaller.

  In the optical measuring apparatus 1 shown in FIG. 10, an optical modulator 51 (for example, a photoelastic modulator) is provided instead of the chopper 50, and a signal generator 53 and an amplifier 55 are used instead of the chopper control unit 52. . By using the optical modulator 51, the intensity of light emitted from the light source 10 can be changed not only to a rectangular wave shape but also to a sine wave shape, and the modulation frequency can be freely selected from a low frequency to a high frequency. Can do.

  6 to 10 are configurations in the first step in which the rough surface contacts the gas. The second step is the same as the first step except that the liquid is brought into contact with the rough surface 32 of the sample 30 by pressing the transparent prism to the rough surface 32 of the sample 30 through the liquid having a large absorption coefficient. Measurements can be made with the configuration.

  An example of a technique for bringing the sample 30 and the transparent prism into contact is shown in FIG. The sample 30 and the transparent prism 110 are installed between the V-groove block 111 and the pedestal 112, and the sample 30, the transparent prism 110, the V-groove block 111, and the pedestal 112 are held together using a screw 113 and a spring 114. Is done. These are adjusted so that the straight line passing through the rotation axis RA of the sample stage 60 and the rough surface 32 coincide as shown in FIG. Here, illustration of an apparatus for installing the sample 30 and the V-groove block 111 for supporting the sample 30 on the sample stage 60 is omitted.

  As shown in FIG. 13A, the condition given to the transparent prism is that the incident surface, the reflection surface, and the output surface are mirror surfaces, and the apex angle δ facing the output surface is δ <90 °.

  FIG. 13B shows a transparent dove prism, and FIG. 13C shows other prisms. All of these are optical components that replace the transparent prism, and the surface facing the reflecting surface is parallel to the reflecting surface, so that the sample 30 and the contact with the sample using the parallel plate block instead of the V-groove block of FIG. The prism can be held stably and easily.

3. Measurement Method Prior to the measurement in the first step, initial setting for determining the angle between the incident light and the sample surface (rough surface 32 of the sample 30) is performed. First, the sample 30 is installed so that a straight line passing through the rotation axis RA of the sample stage 60 is included in an infinite plane including the rough surface 32 of the sample 30. Strictly speaking, the rough surface has fine irregularities, but even if this is regarded as a flat surface, the measurement accuracy is not affected.

  When the sample 30 has a light rough surface, as shown in FIG. 14A, the presence of reflected light (a bright portion near the center of the image shown in FIG. 14A) mixed with scattered light is recognized. It is done. In this case, the optical axis of the incident light and the normal of the sample surface can be matched by a very general method shown in FIG. That is, an aperture having an opening that substantially matches the diameter of the laser beam is provided between the light source 10 and the sample 30, and the angle of the sample stage 60 may be adjusted so that the reflected light from the sample 30 passes through this opening. If this state is set to 0 degree and the sample stage 60 is rotated about the rotation axis RA by the angle φ as shown in FIG. 15B, φ becomes the incident angle. At this time, if the photodetector base 62 is rotated about the rotation axis RA so that the reflected light from the sample 30 enters the first photodetector 40 via the aperture 14 and the analyzer 22, the incident light is incident. The intensity of the reflected light from the sample 30 in the case of the angle φ can be measured.

  Further, when the sample 30 has a severe rough surface, as shown in FIG. 14B, the scattered light and the reflected light cannot be distinguished with the naked eye. In this case, as shown in FIG. 16, convex lenses 101 and 102 are provided between the aperture and the sample 30, and between the beam splitter and the second photodetector 42, respectively, and the reflected light from the sample 30 is transmitted to the convex lens 101. And the reflected light from the beam splitter is incident on the second photodetector 42 via another convex lens 102. By adjusting the angle of the sample stage 60 so that the light intensity detected by the second photodetector 42 is maximized, the optical axis of the incident light and the normal line of the sample surface can be matched.

When the above initial settings are completed, the initial setting aperture and convex lens are removed from the optical path, and the first step measurement is performed. In other words, the incident angle φ of the p-polarized light is changed by rotating the sample stage 60, and the light detector stage 62 is rotated to reflect the light reflected by the rough surface 32 of the sample 30 by the first photodetector 40. measuring the intensity _{I R} of light. At this time, the intensity I _{i of} the light emitted from the light source 10 is also measured by the second photodetector 42, and a normalized power reflectance R _p of the following equation is calculated.

The reflected light intensity divided by the incident light intensity, it is possible to cancel the variation of the incident light intensity, it is possible to improve the measurement accuracy of the power reflectivity R _p. Then, the incident angle φ _min of the p-polarized light that minimizes the power reflectivity R _p is obtained, and the apparent refractive index n _{cs of} the rough surface 32 in contact with the gas (mixed layer of solid and gas) based on the incident angle φ _min Is calculated).

  Prior to the measurement in the second step, first, the refractive index of a transparent prism and a liquid having a large absorption coefficient is measured in advance.

  The most suitable method for measuring the refractive index of the transparent prism is the conventional minimum deflection angle method, and its measurement method is well known, and therefore the description thereof is omitted here.

Next, with reference to FIG. 17, described a technique for measuring the refractive index n _i of a large liquid absorption coefficient. The liquid is put into a container and covered with the transparent prism. At this time, the liquid and the transparent prism are brought into full contact so that air does not enter between the liquid and the substrate. As in FIG. 11, the transparent prism and the container are lightly pressure-bonded by the pedestal and the V-groove block, and this is attached to any one of the optical systems shown in FIGS. 6 to 10 in an infinite plane including the surface of the sample (liquid). The sample 30 is placed so that a straight line passing through the 60 rotation axes RA is included.

Then, by measuring the measurement procedure of the second step, it is possible to determine the refractive index n _i of the liquid. That is, if the incident angle at which the intensity of the reflected light is minimized is ξ _min (see FIG. 17), the following equation is approximately established when Equation (24) is satisfied.

Between the gas transparent prism and the refractive index n _s (air), Snell's law of the following equation holds.

Here, φ _g is a refraction angle as shown in FIG.

Equation (32), the equation (33), the refractive index _{n i} of a large liquid absorption coefficient can be calculated by the following equation.

  Here, δ is an apex angle opposite to the exit surface of the transparent prism, as shown in FIG.

When the refractive index measurement of the transparent prism and the liquid is completed, the liquid is sufficiently dropped on the rough surface solid that is the sample 30, and the transparent prism is brought into close contact with the rough surface. The sample 30 is placed so that the solid and the transparent prism are lightly pressed by the pedestal and the V-groove block shown in FIG. 11 and the straight line passing through the center RA of the sample table 60 is included in the infinite plane including the rough surface 32 of the sample 30. To do. Next, if the optical system is set in any one of the optical systems shown in FIGS. 6 to 10 and measured by the same measurement procedure as the first step, the apparent refractive index n _ci of the rough surface in contact with the liquid can be obtained. . That is, if the incident angle φ _i (see FIG. 5) at which the intensity of the reflected light is minimized is measured and substituted into the equation (27), the apparent refractive index n _ci of the rough surface in contact with the liquid can be obtained. it can.

  In this embodiment, an acrylic prism is used as the transparent prism. Moreover, the black ink liquid used for an ink jet printer was used as a liquid with a large absorption coefficient.

4). Measurement Results FIG. 18 and Table 2 show the measurement results at the first step in the optical measurement apparatus and the optical measurement method of the present embodiment. Here, in the optical measuring apparatus 1 shown in FIG. 6, the measurement was performed using an as-cut LiTaO ₃ crystal (LT crystal) as a sample and a 632.8 nm wavelength He—Ne laser as a light source.

FIG. 18 shows the relationship between the power reflectivity R _{p of the} LT crystal having a light rough surface and the incident angle φ ₁ . Based on the incident angle φ _min obtained from these measurement results, the apparent refractive index n _cs of the rough surface of the LT crystal having a light rough surface (the rough surface is a mixed layer of solid (crystal) and gas (air)) The refractive index of the mixed layer when considered). The measurement results are shown in Table 2.

  Next, FIG. 19 and Table 3 show the measurement results in the second step in the optical measurement apparatus and optical measurement method of the present embodiment. Here, similarly to the measurement result in the first step, the optical measurement apparatus 1 shown in FIG. 6 performs measurement using a light rough surface LT crystal as a sample and a He—Ne laser having a wavelength of 632.8 nm as a light source. It was.

FIG. 19 shows the relationship between the power reflectivity R _p and the incident angle φ _i of an LT crystal having a light rough surface. Based on the incident angle φ ′ _min = 52.7 ° at which the output light obtained from the measurement result is minimized, the apparent refractive index n _ci of the rough surface in contact with the black ink liquid of the LT crystal having a light rough surface is obtained. The refractive index of the mixed layer when the rough surface was regarded as a mixed layer of solid (crystal) and black ink liquid was determined. Table 3 shows the measurement results.

Table 2 and the refractive index n _cs apparent in Table _3, from n _ci, calculated refractive index and n _m of LT crystals, the volume ratio γ of the solid and gas in the mixed layer. Table 4 shows the measurement results.

It is well known that the published ordinary refractive index of LT crystal is 2.1774 at the same 632.8 nm as in the experiment (K. -H. Hellwege, Editor in chief, LANDOLT BOERNSTEIN, Numerical Data and Functional Relationships). in Science and Technology, New Series, Group III: Crystal and Solid State Physics, Vol.11, Elastic, Piezoelectric, Pyroelectric, Piezooptic, Electrooptic Constants, and Nonlinear Dielectric Susceptibilities of Crystals (Springer-Verlag Berlin, Heidelberg, New York 1979) (See p.616.) The results in Table 4 are only about 0.75% smaller than the published values. The measured value of the volume ratio γ of the rough LT crystal in contact with air was 0.230. The volume ratio γ determined by using the results in Table 2 and the known refractive index (2.1774) of the LT crystal was 0.241, and the difference between the two (4.6%) was small. These results indicate that the optical measurement apparatus and optical measurement method of the present embodiment can measure the refractive index _nm and volume ratio γ of a solid sample having a rough surface with high accuracy.

  The technical scope of the present invention is not limited to the above-described embodiment, and appropriate modifications can be made without departing from the spirit of the present invention.

  It can be used for refractive index measurement of samples that are not allowed to be processed, such as expensive substances, fossils, art works, and quantitative optical evaluation of cosmetics (foundation and powder). Also, since the refractive index of the rough surface can be accurately determined, the phone model often used in spectral image processing (see Yoichi Miyake, “Introduction to Spectral Image Processing”, The University of Tokyo Press 2006, pp. 37-61. ) Can be used for analysis. Since this model is connected to computer graphics (CG) technology, it can contribute to high image quality such as CG images and animations.

DESCRIPTION OF SYMBOLS 10 Light source, 12 Beam splitter, 14 Aperture, 16 Convex lens, 18 Beam expander, 20 Polarizer, 22 Analyzer, 30 Sample, 32 Rough surface, 33 Rough surface normal, 40 1st photodetector, 42 1st 2 photodetectors, 50 choppers, 51 optical modulators, 52 chopper controllers, 53 signal generators, 54 lock-in amplifiers, 55 amplifiers, 60 sample stands, 61 first rotation mechanism, 62 photodetector stands, 63 Second rotating mechanism, 70 arithmetic device, 72 arithmetic processing unit, 74 storage unit, 100 first reflected light from mixed layer, 101 convex lens, 102 convex lens, 110 transparent prism, 111 V groove block, 112 pedestal, 113 screw, 114 spring

Claims (10)

In an optical measurement method for measuring the refractive index of a solid having a rough surface,
A first step of measuring an apparent refractive index n _cs of the solid rough surface by bringing a gas into contact with the rough surface of the solid;
A liquid having a large absorption coefficient or scattering coefficient is brought into contact with the solid rough surface, the apparent refractive index n _ci of the solid rough surface is measured, and the apparent refractive index n _cs of the rough surface with which the gas is in contact Based on the apparent refractive index n _ci of the rough surface in contact with the liquid, the volume ratio γ of the solid and the gas in the mixed layer when the rough surface of the solid is regarded as the mixed layer of the solid and the gas an optical measuring method and a second step of obtaining a refractive index n _m of the solid. In claim 1,
In the first step,
The p-polarized light whose electric field component of linearly polarized light vibrates in the incident plane is incident on the rough surface in contact with the gas at an incident angle φ ₁ , and the reflected light reflected at the reflection angle φ ₁ from the solid rough surface according to the law of reflection. It obtains the incident angle phi _min the strength is minimized, and the incident angle phi _min, based on the refractive index n _s of the gas in contact with the rough surface of the solid, the apparent rough surface on which the gas is in contact An optical measurement method for obtaining the refractive index n _cs of the _film . In claim 2,
In the first step,
The optical measurement method which calculates _| requires apparent refractive index ncs of the rough surface which the said gas contacted based on. In claim 1 or 2,
In the second step,
The liquid is brought into contact with the solid rough surface by pressing the transparent prism to the solid rough surface via the liquid, and the p-polarized light whose electric field component of linearly polarized light vibrates in the incident surface is incident on the transparent prism. The incident angle φ _i that minimizes the intensity of the reflected light reflected at the interface between the transparent prism and the solid rough surface according to the law of reflection is obtained, and the incident angle φ _i and the refractive index n of the transparent prism are determined. _g and, a top angle δ which faces the exit surface of the transparent prism, on the basis of the refractive index n _s of the gas in contact with the transparent prism, the refractive index n _ci apparent rough surface on which the liquid is in contact Optical measurement method for obtaining In claim 4,
In the second step,
An optical measurement method for obtaining an apparent refractive index n _ci of the rough surface in contact with the liquid based on the above. In any one of Claims 1 thru | or 5,
In the second step,
Based on the apparent refractive index n _cs of the rough surface in contact with the gas, the apparent refractive index n _ci of the rough surface in contact with the liquid, and the refractive index n _{i of the} liquid, the solid in the mixed layer An optical measurement method for obtaining a gas volume ratio γ. In claim 6,
In the second step,
When the volume ratio of the solid volume V _m to the gas volume V _{s in} the mixed layer is γ = V _s / V _m ,
The refractive index n _cs apparent rough surface on which the gas is in contact, and the refractive index n _ci apparent rough surface on which the liquid is in contact, and a refractive index n _i of said liquid,
Represented by
An optical measurement method for obtaining the volume ratio γ based on the above. In claim 6 or 7,
In the second step,
It said volume ratio gamma, the gas on the basis of the refractive index n _cs apparent rough surface in contact, an optical measuring method for determining the refractive index n _m of the solid. In claim 8,
In the second step,
Refractive index and n _cs apparent rough surface on which the gas is in contact, the refractive index n _m of the solid,
Represented by
Optical measuring method for determining the refractive index n _m of the solid based on. In an optical measuring device for measuring the refractive index of a solid having a rough surface,
A light irradiator that causes p-polarized light whose electric field component of linearly polarized light oscillates in the incident plane to be incident on the solid rough surface;
A light detection unit for detecting the intensity of reflected light reflected according to the law of reflection from the rough surface of the solid contacted with gas or liquid;
A rotation drive unit that changes the incident angle of the p-polarized light by rotating the solid;
When the p-polarized light is incident on the rough surface in contact with the gas, the gas comes into contact based on an incident angle φ _min that minimizes the intensity of reflected light reflected from the solid rough surface according to the law of reflection. And calculating the apparent refractive index n _cs of the rough surface,
When the liquid is brought into contact with the rough surface of the solid by pressing the transparent prism to the rough surface of the solid through the liquid and the p-polarized light is incident on the transparent prism, the transparent prism and the solid Calculating an apparent refractive index n _ci of the rough surface in contact with the liquid, based on the incident angle φ _{i at} which the intensity of the reflected light reflected at the interface with the rough surface is minimized according to the law of reflection;
Based on the apparent refractive index n _cs of the rough surface in contact with the gas and the apparent refractive index n _ci of the rough surface in contact with the liquid, the solid rough surface is regarded as a mixed layer of the solid and the gas. optical measuring device which includes solids and a volume ratio γ of the gas, and a calculation processing unit for performing arithmetic processing for calculating the refractive index n _m of the solids in the mixed layer upon the.