JP2015143666A - Dielectric refraction index detection method and apparatus therefor, film thickness detection method and apparatus therefor, and surface roughness detection method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric refraction index detection method capable of highly accurately detecting a refraction index of a dielectric or the like in a case of detecting the refraction index of the dielectric or the like by reflection of an electromagnetic wave.SOLUTION: A terahertz wave is incident perpendicularly on a rough surface 13A of a dielectric 13 via a lens 8, and an intensity signal I representing intensity of the terahertz wave reflected by the rough surface 13A is detected. On the other hand, the terahertz wave is incident perpendicularly on a mirror surface 12A of a metallic plate 12 via the lens 8, and an intensity signal Irepresenting intensity of the terahertz wave reflected by the mirror surface 12A is detected. Furthermore, the intensity signals I and Iare each detected at a plurality of viewing angles φ of the lens 8, respectively, a ratio (I/I) of the intensity signal I to the intensity signal Iat each viewing angle φ is obtained and a characteristic curve representing the ratio (I/I) for the viewing angle φ is obtained, and the characteristic curve is extrapolated toward a viewing angle φ=0, whereby a mirror surface reflectivity Rat the viewing angle φ=0 is obtained and a refractive index of a measurement sample 13 is detected on the basis of the mirror surface reflectivity R.

Description

  The present invention relates to a method and an apparatus for detecting a refractive index of a dielectric, a film thickness detecting method and an apparatus therefor, and a surface roughness detecting method and an apparatus therefor, for example, the refractive index and film thickness of a top coat of a thermal barrier coating for a gas turbine. It is useful when applied to the detection of surface roughness.

  In recent years, non-destructive inspection applications of terahertz waves (frequency 0.1 to 10 THz), which are electromagnetic waves in the frequency region between light waves and radio waves, have advanced. Since terahertz waves pass through dielectrics such as plastic, ceramic, wood, and paint relatively well, they are used for film thickness measurement as well as imaging internal structures and detecting internal defects (see Non-Patent Document 1).

  When terahertz waves are applied to the dielectric film thickness measurement, the refractive index of the dielectric material to be measured in the terahertz band is required. Typically, the refractive index is measured by terahertz time domain spectroscopy (THz-TDS) in a transmissive configuration. In THz-TDS, a refractive index is calculated from changes in amplitude and phase of a transmitted wave before and after insertion of a measurement object of a known length in a terahertz wave propagation path. Accordingly, the dielectric on the metal surface cannot be applied because a transmitted wave cannot be obtained, and in this case, measurement by a reflection type arrangement is required.

  For example, a thermal barrier coating (TBC) is applied to the surface of the base material to be a blade in order to protect the base material of a high-temperature component used in a combustion environment, such as a gas turbine blade. TBC is applied by spraying ceramics on the metal surface. In this case, the refractive index of the TBC ceramic layer changes depending on the thermal spraying conditions and subsequent sintering in a high temperature environment. Therefore, even if the refractive index of the ceramic, which is the material of TBC, is known, it does not always coincide with the refractive index of the ceramic layer. In addition, since the ceramic layer is integrally sprayed on the metal substrate, transmission measurement cannot be performed.

  Thus, the refractive index of a dielectric such as TBC integrated with a metal needs to be obtained by reflection measurement using electromagnetic waves such as terahertz waves. However, the result of the reflection measurement is affected by the surface roughness of the dielectric that is the measurement target. Therefore, when obtaining the refractive index of the dielectric by reflection of terahertz waves, special measures such as assuming the surface roughness of the dielectric to be measured have been required (see Non-Patent Document 2).

Measurement of topcoat thickness of thermal barrier coating for gas turbines using terahertz waves Tetsuo Fukuchi et al. (5 persons); Electrical Engineering A Vol. 132, No. 2, P166-172 2012 Measurement of top coat thickness of gas turbine blade thermal barrier coating using terahertz waves Tetsuo Fukuchi et al. (6 persons); Electrical Engineering A 133, No. 7, P395-401 2013

  However, since the surface roughness assumed in Non-Patent Document 2 is different from the true value and often cannot be said to reflect the true value with high accuracy, the detected refractive index value and its true value The deviation is large, and as a result, the error of the detected value of the film thickness using the refractive index becomes large.

  In view of the above-mentioned points, the present invention provides a method for detecting a refractive index of a dielectric, a device for detecting the refractive index, and the like, which can detect the refractive index of the dielectric by reflection of electromagnetic waves with high accuracy. It is an object of the present invention to provide a method and an apparatus thereof, a surface roughness detection method and an apparatus thereof.

  In the present invention that achieves the above object, it is essential to measure the refractive index of a dielectric that has a rough surface by utilizing the reflection characteristics of electromagnetic waves such as terahertz waves in the measurement of high-precision refractive index. As a result, a method for removing the influence of the surface roughness in the measurement was examined. In other words, in order to detect the refractive index of a dielectric with high accuracy using electromagnetic waves such as terahertz waves, it is important to remove as much as possible the influence of the surface roughness of the dielectric, which is a rough surface. In order to do so, the inventors have come up with the idea that the substantial specular reflectance of the dielectric should be obtained. To obtain the specular reflectivity of a dielectric, specular reflection returns along the same path as the incident wave, and since scattering has a wider angular distribution than the incident wave, only a part of it returns along the same path as the incident wave. Can be used.

  Therefore, as shown in FIG. 1, a field stop 02 for limiting the viewing angle φ of the lens 01 is arranged in front of the transceiver, and the reflected wave from the mirror surface 03A of the metal plate 03 is changed while changing the viewing angle φ. A reflected wave from the rough surface 04A of the dielectric 04 is measured. 1A shows a case where the reflected wave from the mirror surface 03A is measured at a large viewing angle φ, and FIG. 1B shows a case where the reflected wave from the rough surface 04A is measured at a large viewing angle φ. FIG. 1D conceptually shows a case where the reflected wave from the mirror surface 03A is measured with a small viewing angle φ, and FIG. 1D conceptually shows a case where the reflected wave from the rough surface 04A is measured with a small viewing angle φ.

In the cases shown in FIGS. 1 (a) and 1 (c), the reflected wave intensity signal I _M obtained from the mirror surface 03A passes through the field stop 02 and reaches the mirror surface 03A. It represents the intensity of the reflected wave that passes through the aperture 02 and reaches the receiver from the lens 01 via the beam splitter 05. Here, the reflectance R _S = 1 of the mirror surface 03A is 1, which is the maximum intensity that can be received at the viewing angle φ. On the other hand, the intensity signal I of the reflected wave obtained from the rough surface 04A is the intensity of the reflected wave similarly reaching the receiver, but the specular reflectance R _S of the rough surface 4A is R _S <1, Is taken into consideration, I <I _{M at} all viewing angles φ.

Regardless of the viewing angle φ, the specular reflected wave with respect to the electromagnetic wave that has passed through the field stop 02 at the time of transmission returns to the receiver through the field stop 02 again in principle. On the other hand, since the scattered electromagnetic wave has a wider angular distribution, only a part thereof (only the electromagnetic wave scattered at an angle close to specular reflection) can pass through the field stop 02 again. That is, as shown in FIG. 1 (d), if the viewing angle φ is sufficiently small, most of the scattering returns outside the field of view and is not received. That is, most of the received intensity signal I is due to specular reflection. Therefore, if I / I _M is extrapolated to the minimum viewing angle φ = 0 (the reflected wave cannot be measured if φ = 0 is actually measured, the influence of scattering is removed). it can. Therefore, Expression (1) is established.

If the specular reflectance _RS is obtained, the refractive index of the dielectric can be obtained from the equation (2).

Conversely, when the viewing angle φ is large, the ratio of scattering to specular reflection increases, and the ratio of incident waves that return to the receiver due to loss due to scattering decreases. That is, the apparent reflectance decreases. Here (can not measure the reflected wave to be actually phi = [pi, measured to a sufficiently large viewing angle φ) I / I _M a extrapolating up view angle phi = [pi lever, the reflectivity of the apparent R _D Is a value that includes the maximum effect of scattering. The apparent reflectance _RD is given by equation (3).

From this examination result, it can be seen that the apparent reflectance I / I _M depends on the viewing angle φ. From the equations (1) and (3), it is assumed that the dependency of I / _{IM on} the viewing angle φ is as shown in FIG. That is, the ratio (I / I _M) mirror reflectivity R _S at the point where the viewing angle dependence characteristic curve is viewing angle phi = 0 representing the is given with respect to the viewing angle phi, the equation of this specular reflectivity R _S (2 ) To obtain a refractive index n that eliminates the effect of the surface of the dielectric 04 being a rough surface 04A.

The first aspect of the present invention based on such knowledge is as follows:
An electromagnetic wave is vertically incident on the rough surface of the measurement sample, which is a dielectric, through a lens, and a first intensity signal I representing the intensity of the electromagnetic wave reflected by the rough surface is detected, while the first surface is reflected on the mirror surface of the metal plate. It is incident perpendicularly the electromagnetic wave through the lens, detecting a second intensity signal I _M indicating the intensity of the electromagnetic waves reflected by the mirror surface,
Further, the first and second intensity signals I and I _M are detected at a plurality of viewing angles of the lens, respectively, and a ratio of the first and second intensity signals I and I _M at each viewing angle is obtained. Obtaining a characteristic curve representing the ratio to the viewing angle;
Wherein the viewing angle by extrapolating the calculated specular reflectivity R _S when the zero detecting the refractive index of the measurement sample based on said mirror surface reflectivity R _S toward the curve on the viewing angle zero And a method of detecting the refractive index of the dielectric.

  According to this aspect, the influence of the surface roughness of the rough surface can be substantially removed when detecting the refractive index of the dielectric that is the rough surface using the reflection of electromagnetic waves. The refractive index of the dielectric can be detected with high accuracy.

The second aspect of the present invention is:
In the method for detecting a refractive index of a dielectric according to the first aspect,
The extrapolation is a characteristic curve in which a ratio of the first and second intensity signals I and I _M is constant at a plurality of measurement points in a range of a viewing angle smaller than a viewing angle that gives a bending point in the characteristic curve. A method of detecting a refractive index of a dielectric is characterized in that one end is directed toward a viewing angle of zero.

  According to this aspect, the extrapolation of the characteristic curve can be accurately performed toward the viewing angle = 0.

The third aspect of the present invention is:
When the refractive index detected in the method for detecting the refractive index of a dielectric according to the first or second aspect is n, the speed of light is c, and the time for which the electromagnetic wave makes one round trip through the dielectric is Δt, the measurement sample In this method, the thickness d of the dielectric is obtained by d = (c · Δt / 2n).

  According to this aspect, since the film thickness d given by d = (c · Δt / 2n) can be obtained using the refractive index n detected with high accuracy, the film thickness can also be detected with high accuracy.

The fourth aspect of the present invention is:
An electromagnetic wave is vertically incident on the rough surface of the measurement sample, which is a dielectric, through the lens, and a first intensity signal I in the time domain representing the time characteristic of the intensity of the electromagnetic wave reflected by the rough surface is obtained from the lens. While detecting at each of a plurality of viewing angles, the electromagnetic wave is vertically incident on the mirror surface of the metal plate via the lens, and the second intensity in the time domain representing the time characteristic of the intensity of the electromagnetic wave reflected by the mirror surface to detect the signal _{I M,}
Furthermore the first intensity signal I with obtaining a third intensity signal I (f) in the frequency domain by Fourier transform, the fourth frequency region by Fourier transform to the second intensity signal I _M Obtaining an intensity signal I _M (f),
The ratio between the third intensity signal I (f) and the fourth intensity signal I _M (f) is expressed by the equation (4).
The method of detecting the surface roughness of the dielectric is characterized in that the surface roughness δ is obtained as the slope of the equation (4) using the above relationship.

  According to this aspect, accurate surface roughness can be obtained easily and appropriately simply by substituting the refractive index of the dielectric detected with high accuracy into a known equation. That is, the surface roughness of the desired measurement sample can be detected in a non-contact manner without contacting the surface of the measurement sample, compared to the case where a palpation type roughness meter is used. Therefore, it is particularly useful when the measurement sample is an art work or the like.

According to a fifth aspect of the present invention,
An electromagnetic wave is vertically incident on the rough surface of the measurement sample, which is a dielectric, via a lens, and a first intensity signal I representing the intensity of the electromagnetic wave reflected by the rough surface is detected, and on the mirror surface of the metal plate It is incident perpendicularly the electromagnetic wave through the lens, and the reflected wave detection means for detecting a second intensity signal I _M indicating the intensity of the electromagnetic waves reflected by the mirror surface,
A field stop means for adjusting a viewing angle of the lens so as to stop the electromagnetic wave irradiated from the lens toward the rough surface and the mirror surface;
Storage means for storing time-axis characteristics of the intensity of the first intensity signal and the second intensity signal respectively detected at a plurality of the viewing angles;
The information of the first and second intensity signals I and I _M at each viewing angle is read from the storage means, and the ratio of the first and second intensity signals I and I _M is obtained to determine the ratio with respect to the viewing angle. with obtaining the characteristic curves representing the ratio, the characteristics the viewing angle by extrapolating curves toward the viewing angle zero is determined specular reflectivity R _S when the zero, the measurement on the basis of said mirror surface reflectivity R _S An apparatus for detecting a refractive index of a dielectric has an arithmetic means for calculating a refractive index of a sample.

  According to this aspect, the influence of the surface roughness of the dielectric can be substantially removed when detecting the refractive index of the measurement sample using reflection of electromagnetic waves, so that the measurement sample is generally rough. Even for a certain dielectric, the refractive index can be detected with high accuracy.

The sixth aspect of the present invention is:
In the dielectric refractive index detection device according to the fifth aspect,
The extrapolation is a characteristic curve in which a ratio of the first and second intensity signals I and I _M is constant at a plurality of measurement points in a range of a viewing angle smaller than a viewing angle that gives a bending point in the characteristic curve. An apparatus for detecting a refractive index of a dielectric is characterized in that one end is directed toward a viewing angle of zero.

  According to this aspect, the extrapolation of the characteristic curve can be appropriately performed toward the viewing angle = 0.

The seventh aspect of the present invention is
When the refractive index detected in the dielectric refractive index detection device according to the fifth or sixth aspect is n, the speed of light is c, and the time for which the electromagnetic wave makes one round trip of the measurement sample is Δt, the measurement sample An apparatus for detecting a dielectric film thickness is characterized in that the calculation means is configured to obtain the film thickness d of the following: d = (c · Δt / 2n).

  According to this aspect, since the film thickness d given by d = (c · Δt / 2n) can be obtained using the refractive index n detected with high accuracy, the film thickness can also be detected with high accuracy.

The eighth aspect of the present invention is
The computing means described in the fifth or sixth aspect further obtains a third intensity signal I (f) in the frequency domain by Fourier-transforming the first intensity signal I, and the second intensity signal. The fourth intensity signal I _M (f) in the frequency domain is obtained by Fourier transforming I _M , and the ratio of the third intensity signal I (f) and the fourth intensity signal I _M (f) is expressed by the equation (5)
The dielectric surface roughness detecting device is characterized in that the surface roughness δ is obtained as the slope of the equation (5) by utilizing the above relationship.

  According to this aspect, accurate surface roughness can be obtained easily and appropriately simply by substituting the refractive index of the dielectric detected with high accuracy into a known equation. That is, the surface roughness of the desired measurement sample can be detected in a non-contact manner without contacting the surface of the measurement sample, compared to the case where a palpation type roughness meter is used. Therefore, it is particularly useful when the measurement sample is an art work or the like.

  According to the present invention, the influence of the surface roughness of the dielectric can be substantially removed, and the refractive index of the dielectric that is a rough surface can be accurately detected. In addition, the film thickness and surface roughness of the dielectric can be obtained with high accuracy using such a refractive index.

It is explanatory drawing for demonstrating the principle of this invention. And the viewing angle, the intensity signal I, is a characteristic diagram showing the relationship between the ratio of I _M. It is a block diagram which shows the detection apparatus of the refractive index of the dielectric material concerning embodiment of this invention. FIG. 6 is a characteristic diagram showing time characteristics of an intensity signal I (solid line) and an intensity signal I _M (dotted line) using a plurality of aperture diameters o and viewing angles φ of the field stop as parameters. Intensity signal I in the measurement were carried out by varying the viewing angle, it is a characteristic view showing characteristic curves representing the ratio of I _M. It is explanatory drawing which shows the aspect in the case of measuring the film thickness of a dielectric material by irradiation of a terahertz wave.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Detection of refractive index of dielectric>
FIG. 3 is a block diagram showing an apparatus for detecting a refractive index of a dielectric according to an embodiment of the present invention. As shown in the figure, the dielectric refractive index detection device according to this embodiment includes a reflected wave detection unit 1, a terahertz wave transmitter 2, a terahertz wave receiver 3, a storage unit 4, a calculation unit 5, and a display. Part 6. The reflected wave detection unit 1 has two lenses 7 and 8 disposed at two positions above and below the same vertical optical axis, and the surface of the metal plate 12 disposed below the lens 8. The terahertz wave is converged and vertically incident on the mirror surface 12A or the rough surface 13A of the dielectric 13 as the measurement sample. Here, for example, a SUS plate can be suitably used as the metal plate 12, and the dielectric 13 is a member that forms a top coat of a thermal barrier coating (TBC) sprayed on, for example, a turbine blade, and the surface thereof is rough. 13A. This dielectric 13 is an object for measuring the refractive index. Here, the surface roughness of the rough surface 13A of the dielectric 13 is unknown.

  Below the lens 8, a field stop 10 that restricts the field of the lens 8 is disposed. Here, the structure of the field stop 10 is not particularly limited as long as it can stop the terahertz wave directed from the lens 8 toward the surface of the reference sample 12 or the measurement sample 13. For example, it can be suitably configured by applying a diaphragm structure of a normal camera lens.

  The beam splitter 9 is disposed between the lenses 7 and 8 with an inclination of 45 ° with respect to the optical axes of the lenses 7 and 8. Thus, the terahertz wave reflected by the mirror surface 12A of the metal plate 12 or the rough surface 13A of the dielectric 13 and returned through the lens 8 is bent by 45 ° by the beam splitter 9 and is incident on the lens 11.

  The lens 11 causes the reflected wave of the terahertz wave to enter the receiver 3. The reflected wave incident on the receiver 3 is converted into an electric signal representing the time characteristic of the reflection intensity and stored in the storage unit 4.

Hereinafter, the reflection intensity of the reflected wave reflected by the mirror surface 12A of the metal plate 12 is represented by I _M , and the reflection intensity of the reflected wave reflected by the rough surface 13A of the dielectric 13 serving as a measurement sample is represented by the symbol I.

Detected by the receiver 3, the time characteristic of the intensity signal I and the intensity signal I _M that is stored in the storage unit 4 shown in FIG. In the drawing, the time characteristic of the solid line intensity signal I, the dotted line indicates the time characteristic of the intensity signal I _M, respectively. Each time characteristic indicates a plurality of aperture diameters o and viewing angles φ of the field stop 10 shown in FIG. 4 as parameters.

The time characteristics as described above are stored as data in the storage unit 4 by controlling the laser pulse generator 12, the delay device 14 and the storage unit 4 with the controller 13. More specifically, the laser pulse generator 12 generates a laser pulse according to a control signal of the controller 13, irradiates the terahertz wave from the transmitter 2 with this laser pulse, and operates the receiver 3 via the delay device 14. Thus, the reflected wave of the terahertz wave is received. Here, the laser pulse is delayed by the delay device 14 by a predetermined time. As a result, the reflected wave capturing timing in the receiver 3 is sequentially delayed. Thus, the receiver 3 obtains data representing the intensity of the reflected wave as a discrete value scanned on the time axis, and the data is read into the storage unit 4. As a result, intensity signals I and I _M shown in FIG. 4 are generated. The read timing of the storage unit 4 is controlled by the controller 13 so as to be synchronized with the reflected wave capture timing in the receiver 3.

The calculation unit 5 performs a predetermined calculation based on the data representing the time characteristic of the intensity signal I and the time characteristic of the intensity signal I _M stored in the storage unit 4 to thereby make the refractive index n of the dielectric 13 as a measurement sample. Ask for. That is, the characteristic curve as shown in FIG. 5 representing the ratio (I / I _M ) of the intensity signals I and I _M to the viewing angle φ is obtained by obtaining the ratio of the intensity signals I and I _M at each viewing angle φ. Thereafter, the specular reflectance _RS when the viewing angle φ = 0 is obtained by extrapolating the characteristic curve toward the viewing angle φ = 0. Finally, the refractive index n of the dielectric 13 is calculated based on the specular reflectance R _S. Here, extrapolation is performed for the first and second intensity signals I and I _M at a plurality of measurement points in a range of a viewing angle φ smaller than the viewing angle φ giving the bending point P in the characteristic curve shown in FIG. This is performed by extending one end of a characteristic curve with a constant ratio toward a viewing angle of zero.

Here, the refractive index n of the rough surface 13A of the dielectric 13 to be measured is an expression of the specular reflectance R _S obtained by extrapolating the characteristic curve shown in FIG. 5 toward the viewing angle φ = 0. Obtained by substituting in 6).

  The calculation result by the calculation unit 5 is displayed on the display unit 6.

In this embodiment, first, with the metal plate 12 disposed below the lens 8, the terahertz wave irradiated from the transmitter 2 is incident vertically on the mirror surface 12 </ b> A via the lenses 7 and 8. Next, it is detected and stored in the storage unit 4 the intensity signal I _M indicating the intensity of the terahertz wave reflected by the mirror surface 12A. The same operation is repeated a plurality of times while changing the viewing angle φ with the field stop 10.

  Further, a terahertz wave is vertically incident on the rough surface 13A via the lenses 7 and 8 in a state where the dielectric 13 having the rough surface 13A is disposed below the lens 8 instead of the metal plate 12, and the rough surface 13A The intensity signal I representing the intensity of the terahertz wave reflected by is detected and stored in the storage unit 4. The same operation is repeated a plurality of times as in the case of the metal plate 12 by changing the viewing angle φ by the field stop 10.

Finally, by calculating the ratio between the two based on I _M and I stored in the storage unit 4, creating a characteristic diagram shown in FIG. 5, and extrapolating the characteristic curve toward the viewing angle φ = 0 The specular reflectance R _S when the viewing angle φ = 0 is obtained. Subsequently, a predetermined calculation is performed based on the specular reflectance R _S to obtain the refractive index n of the dielectric 13, and the result is displayed on the display unit 6.

<Dielectric film thickness detection>
The film thickness of the dielectric 13 having the rough surface 13A can be detected by the following principle. As shown in FIG. 6, the reflected wave when the dielectric 13 is irradiated with the terahertz wave is reflected from the surface of the dielectric 13 (see FIG. 6A) and from the inside or the back of the dielectric 13. It is separated into reflected waves (see FIG. 5B). Here, the time T required for the terahertz wave to reciprocate once through the dielectric 13 having the film thickness d and the refractive index n is given by T = (2nd / c (c is the speed of light)). Accordingly, the film thickness d is measured by the width of the pulse of the front surface reflection and the pulse of the back surface reflection (see FIG. 5C), that is, the time T required for the terahertz wave to make one round trip through the dielectric 13 having the refractive index n. By doing so, it can be obtained as d = (cT / 2n).

Therefore, in the present embodiment, by calculating the time T based on the intensity signal I or I _M and using the time T and the refractive index n obtained in the above-described embodiment,
The film thickness d can be accurately obtained by configuring the calculation unit 5 shown in FIG. 3 so as to perform the calculation of the equation d = (cT / 2n).

<Detection of surface roughness of dielectric>
The intensity signal I shown in FIG. 4 along with obtaining intensity signals I (f) in the frequency domain by Fourier transform, to obtain the intensity signal I _{M (f)} in the frequency domain by Fourier transform of the intensity signal I _M it can.

On the other hand, the ratio (I (f) / I _M (f)) between the intensity signal I (f) and the intensity signal I _M (f) satisfies the relationship of the expression (7).

  Therefore, if the relationship of Expression (7) is used, the surface roughness δ can be obtained as the slope of Expression (7).

Accordingly, in this embodiment, the arithmetic unit 5 shown in FIG. 3, on the basis of the intensity signal I and the intensity signal I _M in the time domain stored in the storage unit 4 the intensity signals of the Fourier transform the frequency domain If I (f) and the intensity signal I _M (f) are generated and the ratio between the two (I (f) / I _M (f)) is obtained, the relationship of the above equation (7) is used. Thus, the surface roughness δ of the rough surface 13A can be obtained.

  In the above embodiment, the case where a terahertz wave is used as an electromagnetic wave has been described. However, the present invention is not limited to this. An electromagnetic wave having an appropriate wavelength may be selected depending on the surface roughness of the dielectric to be measured.

  The present invention detects the refractive index, film thickness, surface roughness, etc. of the dielectric film integrated with the substrate by thermal spraying or the like, for example, the top coat of a thermal barrier coating for a gas turbine, according to the present invention. Can be used in industrial fields.

I, I _M Reflection intensity 1 Reflected wave detection unit 2 Transmitter 3 Receiver 4 Storage unit 5 Calculation unit 7, 8 Lens 9 Beam splitter 10 Field stop 12 Metal plate 12A Mirror surface 13 Dielectric body 13A Rough surface

Claims (8)

An electromagnetic wave is vertically incident on the rough surface of the measurement sample, which is a dielectric, through a lens, and a first intensity signal I representing the intensity of the electromagnetic wave reflected by the rough surface is detected, while the first surface is reflected on the mirror surface of the metal plate. It is incident perpendicularly the electromagnetic wave through the lens, detecting a second intensity signal I _M indicating the intensity of the electromagnetic waves reflected by the mirror surface,
Further, the first and second intensity signals I and I _M are detected at a plurality of viewing angles of the lens, respectively, and a ratio of the first and second intensity signals I and I _M at each viewing angle is obtained. Obtaining a characteristic curve representing the ratio to the viewing angle;
Wherein the viewing angle by extrapolating the calculated specular reflectivity R _S when the zero detecting the refractive index of the measurement sample based on said mirror surface reflectivity R _S toward the curve on the viewing angle zero A method for detecting the refractive index of a dielectric. The method for detecting a refractive index of a dielectric according to claim 1,
The extrapolation is a characteristic curve in which a ratio of the first and second intensity signals I and I _M is constant at a plurality of measurement points in a range of a viewing angle smaller than a viewing angle that gives a bending point in the characteristic curve. A method for detecting a refractive index of a dielectric, wherein one end is directed toward a viewing angle of zero.   When the refractive index detected in the method for detecting a refractive index of a dielectric according to claim 1 or 2 is n, the speed of light is c, and the time for which the electromagnetic wave makes a round trip through the dielectric is Δt, the measurement sample A method for detecting a film thickness of a dielectric material, wherein the film thickness d of the dielectric layer is obtained by d = (c · Δt / 2n). An electromagnetic wave is vertically incident on the rough surface of the measurement sample, which is a dielectric, through the lens, and a first intensity signal I in the time domain representing the time characteristic of the intensity of the electromagnetic wave reflected by the rough surface is obtained from the lens. While detecting at each of a plurality of viewing angles, the electromagnetic wave is vertically incident on the mirror surface of the metal plate via the lens, and the second intensity in the time domain representing the time characteristic of the intensity of the electromagnetic wave reflected by the mirror surface to detect the signal _{I M,}
Furthermore the first intensity signal I with obtaining a third intensity signal I (f) in the frequency domain by Fourier transform, the fourth frequency region by Fourier transform to the second intensity signal I _M Obtaining an intensity signal I _M (f),
The ratio of the third intensity signal I (f) and the fourth intensity signal I _M (f) is expressed by the equation (1).
A method for detecting the surface roughness of a dielectric, characterized in that the surface roughness δ is obtained as the slope of the equation (1) by utilizing the above relationship. An electromagnetic wave is vertically incident on the rough surface of the measurement sample, which is a dielectric, via a lens, and a first intensity signal I representing the intensity of the electromagnetic wave reflected by the rough surface is detected, and on the mirror surface of the metal plate It is incident perpendicularly the electromagnetic wave through the lens, and the reflected wave detection means for detecting a second intensity signal I _M indicating the intensity of the electromagnetic waves reflected by the mirror surface,
A field stop means for adjusting a viewing angle of the lens so as to stop the electromagnetic wave irradiated from the lens toward the rough surface and the mirror surface;
Storage means for storing time-axis characteristics of the intensity of the first intensity signal and the second intensity signal respectively detected at a plurality of the viewing angles;
The information of the first and second intensity signals I and I _M at each viewing angle is read from the storage means, and the ratio of the first and second intensity signals I and I _M is obtained to determine the ratio with respect to the viewing angle. with obtaining the characteristic curves representing the ratio, the characteristics the viewing angle by extrapolating curves toward the viewing angle zero is determined specular reflectivity R _S when the zero, the measurement on the basis of said mirror surface reflectivity R _S An apparatus for detecting a refractive index of a dielectric, comprising: an arithmetic means for calculating a refractive index of a sample. In the apparatus for detecting a refractive index of a dielectric according to claim 5,
The extrapolation is a characteristic curve in which a ratio of the first and second intensity signals I and I _M is constant at a plurality of measurement points in a range of a viewing angle smaller than a viewing angle that gives a bending point in the characteristic curve. An apparatus for detecting a refractive index of a dielectric, wherein one end is directed toward a viewing angle of zero.   The measurement sample when the refractive index detected in the dielectric refractive index detection device according to claim 5 or 6 is n, the speed of light is c, and the time for which the electromagnetic wave makes a round trip of the measurement sample is Δt. An apparatus for detecting a film thickness of a dielectric material, characterized in that the calculation means is configured to obtain a film thickness d of the following: d = (c · Δt / 2n). The calculating means according to claim 5 or 6 further obtains a third intensity signal I (f) in the frequency domain by performing a Fourier transform on the first intensity signal I, and the second intensity. obtain a fourth intensity signal I _M in the frequency domain _(f) by Fourier transformation of the signal I _M, the ratio of the third intensity signal I (f) and a fourth intensity signal I _{M (f)} is Formula (2)
A device for detecting the surface roughness of a dielectric material, characterized in that the surface roughness δ is obtained as the slope of the equation (2) by utilizing the above relationship.