JP6598194B2 - Sensing device - Google Patents

Description

The present invention relates to a sensing device that detects a physical quantity of a subject.

Conventionally, there has been a sensing technique for detecting a physical quantity of an object by using a surface acoustic wave (SAW) generated by a piezoelectric body, and specific examples thereof are described in, for example, Patent Documents 1 and 2. Has been.
Patent Document 1 describes a method of sensing by applying an electric signal to an input electrode to generate a surface acoustic wave on a piezoelectric body, measuring the velocity of the surface acoustic wave based on the electric signal generated at the output electrode. Has been. Japanese Patent Application Laid-Open No. 2004-228688 describes a method of sensing using an electric signal generated at an output electrode by generating an acoustic signal on a piezoelectric body by applying an electric signal to an input electrode.

JP-A-6-133759 JP 2007-85905 A

However, when an electrical signal is input to the input electrode, part of the energy of the electrical signal is output as electromagnetic waves in the space, and the output electrode may receive electromagnetic waves in the space and convert them into electrical signals. The methods described in Patent Documents 1 and 2 for detecting the physical quantity of the subject based on the electrical signal generated at the output electrode have a problem that stable detection cannot be performed.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a sensing device that stably measures a physical quantity of a subject by using a surface acoustic wave generated in a piezoelectric body.

The sensing device according to the present invention that meets the above-described object is a sensing device that generates a surface acoustic wave in a piezoelectric body to obtain a physical quantity of the subject that is in contact with the piezoelectric body, and that passes through the contact position of the subject. An input electrode for generating a surface acoustic wave in the piezoelectric body, a light reflecting piece provided on the downstream side of the contact position of the traveling path of the surface acoustic wave traveling through the piezoelectric body, and light on the light reflecting piece Irradiating means for irradiating ; and light detecting means for measuring the intensities of the r-th order diffracted light and the s-th order diffracted light generated when the light is reflected by the light reflecting piece in a state where the subject is in contact with the piezoelectric body. A calculator that calculates the amplitude of the surface acoustic wave based on the measured intensities of the r-order diffracted light and the s-order diffracted light, and obtains the physical quantity of the subject.

In the sensing device according to the present invention, it is preferable that the light reflecting piece includes a plurality of metal wire portions arranged in parallel.

In the sensing device according to the present invention, the computing unit may calculate the surface acoustic wave calculated based on the intensities of the r-order diffracted light and the s-order diffracted light measured in a state where the subject is in contact with the contact position. From the difference between the amplitude and the amplitude of the surface acoustic wave calculated based on the intensities of the r-th order diffracted light and the s-th order diffracted light measured in a state where the subject is not in contact with the piezoelectric body, It is preferable to determine the physical quantity of

In the sensing device according to the present invention, it is preferable that the r-order diffracted light is zero-order diffracted light, and the s-order diffracted light is first-order diffracted light.

The sensing device according to the present invention is measured by light detecting means for measuring the intensities of the r-th order diffracted light and the s-th order diffracted light generated by reflecting light downstream from the contact position of the surface acoustic wave traveling path of the piezoelectric body. And an arithmetic unit for calculating the physical quantity of the subject based on the intensities of the r-th order diffracted light and the s-order diffracted light and receiving the electromagnetic wave in the space to derive the physical quantity of the subject. Thus, it is not necessary to use an electrical signal that can be generated in this manner, and the physical quantity of the subject can be stably measured.

It is explanatory drawing of the sensing apparatus which concerns on one embodiment of this invention. It is explanatory drawing of an input electrode and a light reflection piece. It is explanatory drawing which shows the distortion of the surface of a piezoelectric material, and the diffraction of light. (A), (B) is explanatory drawing which shows the optical path difference by the displacement and inclination of a piezoelectric material surface, respectively. It is explanatory drawing of the sensing apparatus which changed the irradiation direction of light. It is a graph which shows the relationship between the intensity | strength of 1st-order diffracted light, and the density | concentration of glucose.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIG. 1 and FIG. 2, the sensing device 10 according to an embodiment of the present invention generates a surface acoustic wave W in the piezoelectric body 11 and determines the physical quantity of the subject T in contact with the piezoelectric body 11. It is a device to seek. Hereinafter, these will be described in detail.

As shown in FIG. 1, the sensing device 10 irradiates light toward a surface of the piezoelectric body 11 on which the subject T is placed, an input electrode 12 that generates a surface acoustic wave W on the piezoelectric body 11, and the surface of the piezoelectric body 11. Irradiating means 13, a light detecting means 14 for measuring the intensity of light, and a calculator 15 for obtaining a physical quantity of the subject T.
As shown in FIGS. 1 and 2, the piezoelectric body 11 is formed in a rectangular plate shape using a material that is distorted when an electric field is applied from the outside. The material of the piezoelectric body 11 of the present embodiment is lithium niobate, but is not limited thereto, and may be, for example, lead zirconate titanate or sodium tungstate.

The input electrode 12 and the light reflecting piece 16 are attached to the surface of the piezoelectric body 11 on both sides in the longitudinal direction, and the subject T is disposed between the input electrode 12 and the light reflecting piece 16 that reflects light. Hereinafter, the position where the subject T contacts on the surface of the piezoelectric body 11 is referred to as a contact position P. In the present embodiment, a liquid is used for the subject T. However, the subject T may be a solid or a gel. In the case of a solid or a gel, the subject T is brought into contact with the piezoelectric body 11. There is no change in making it.

The input electrode 12 includes a pair of metal comb-tooth members 17 and 18, and the comb-tooth members 17 and 18 include a plurality of metal wire portions 19 arranged in parallel and a plurality of metal wire portions similarly arranged in parallel. 20 respectively. The comb-tooth members 17 and 18 are provided so that the metal wire portions 19 and 20 are alternately arranged along the longitudinal direction of the piezoelectric body 11, and a signal for outputting an electric signal to the comb-tooth members 17 and 18. A generator 21 is connected.
The signal generator 21 is connected to the calculator 15 and outputs an electrical signal in response to a command signal transmitted from the calculator 15. The computing unit 15 is configured by an electronic computer that also controls the operation of the signal generator 21.

By outputting an electrical signal from the signal generator 21 to the comb-tooth members 17 and 18, an electric field is generated around the comb-tooth members 17 and 18, causing distortion in the piezoelectric body 11, and Is generated from the input electrode 12 through the contact position P toward the light reflecting piece 16. That is, the input electrode 12 is given an electrical signal and generates a surface acoustic wave W that passes through the contact position P in the piezoelectric body 11.
When the surface acoustic wave W passes through the contact position P, part of the energy is absorbed by the subject T provided at the contact position P, and the amplitude is reduced.

As shown in FIG. 2, the light reflecting piece 16 has a pair of metal comb-tooth members 22 and 23, similar to the input electrode 12, and the comb-tooth members 22 and 23 include a plurality of parallel-arranged comb-tooth members 22 and 23. The metal wire portions 24 and the plurality of metal wire portions 25 arranged in parallel are provided, and the metal wire portions 24 and 25 are alternately arranged along the longitudinal direction of the piezoelectric body 11. As shown in FIG. 1, a waveform measuring device 26 that detects the waveform of the surface acoustic wave W is connected to the comb members 22 and 23. When the surface acoustic wave W transmitted through the piezoelectric body 11 reaches the light reflecting piece 16, an electric signal is generated in the light reflecting piece 16. The waveform measuring device 26 can detect the generation of the surface acoustic wave W that has reached the light reflecting piece 16 by measuring an electric signal generated by the light reflecting piece 16.

The irradiation means 13 is arranged so as to irradiate light (in this embodiment, laser light) in an oblique direction with respect to the surface of the piezoelectric body 11 from a position away from the piezoelectric body 11. The irradiation unit 13 is connected to a controller 27 that controls the irradiation unit 13 according to a command signal given from the calculator 15 and a power supply 28 that supplies electric energy to the irradiation unit 13.
The irradiation unit 13 is supported by a support member (not shown), and the irradiation direction is adjusted so that the laser beam is irradiated to the light reflecting piece 16. Therefore, the irradiation means 13 irradiates the laser beam downstream from the contact position P of the traveling path of the surface acoustic wave W traveling on the piezoelectric body 11.

The light reflecting piece 16 is larger than the diameter of the laser light and totally reflects the laser light that has reached the comb-tooth members 22 and 23. Since the piezoelectric body 11 has translucency, part of the laser light that has reached the surface of the piezoelectric body 11 between the comb-tooth members 22 and 23 (for example, between the adjacent metal wire portions 24 and 25). The remaining light enters the piezoelectric body 11 after being reflected.
In the region where the comb-teeth members 22 and 23 and the surface of the piezoelectric body 11 are irradiated with laser light, periodic distortion is generated by the surface acoustic wave W. Therefore, the laser light is reflected in the region and diffraction of light occurs. . Hereinafter, the relationship between the light diffraction and the surface acoustic wave will be described.

As shown in FIG. 3, when the laser light is treated as a plurality of light beams traveling at an incident angle φ (an angle with respect to the surface of the piezoelectric body having no distortion) in a range of 0 ≦ x ≦ L of the surface of the piezoelectric body, With respect to the piezoelectric body surface that is distorted by the surface acoustic wave, as shown in FIGS. 4A and 4B, the optical path difference Δl due to the displacement of the piezoelectric body surface is reflected in the reflected light of each light beam. ₁ and an optical path difference Δl ₂ due to the inclination of the piezoelectric surface.
Δl ₁ and Δl ₂ are: a is the amplitude of the surface acoustic wave, ω ₁ is the angular frequency of the surface acoustic wave, θ is the displacement of the reflection angle of the reflected light due to the tilt of the surface of the piezoelectric body 11, λ is the wavelength of the light, k is a value of k = 2πcos φ / λ, and is expressed by the following formulas 1 and 2, respectively.

Therefore, the amplitude A (θ) of the reflected light is such that j _n is an nth-order Bessel function, K is the wave number of the surface acoustic wave, Λ is the wavelength of the surface acoustic wave, K = 2π / Λ, ω = (4πa / λ) Cosφ is expressed by the following Equation 3.

If β _n is a value defined by the following expression 4, A (θ) is expressed by the following expression 5.

Further, the intensity I _n (θ) of the _nth- order diffracted light (nth-order diffracted wave) due to the reflected light is expressed by the following formula 6, and the 0th-order diffracted light (0th-order diffracted wave) of n = 0 is θ = 0. The first order diffracted light (first order diffracted wave) with n = 1 has the maximum intensity at θ = ± K / k.

Since the relationship between the maximum value of the first-order diffracted light and the maximum value of the zero-order diffracted light is expressed by the following Equation 7, the incident angle of the laser light, the wavelength of the laser light, the intensity of the zero-order diffracted light, and the first-order diffracted light It can be seen that the amplitude of the surface acoustic wave can be calculated based on the intensity of the.

In the present embodiment, as shown in FIG. 1, the light detection means 14 is provided on the downstream side of the contact position P on the light reflection piece 16 (that is, on the traveling path of the surface acoustic wave W of the piezoelectric body 11). A light receiving section 29 for detecting the 0th order diffracted light and the 1st order diffracted light generated by the reflection of the laser light by the light reflecting piece 16), and a measurement for measuring each intensity of the 0th order diffracted light and the 1st order diffracted light detected by the light receiving section 29 The unit 30 is provided. The measurement unit 30 sends measured values of the intensities of the 0th-order diffracted light and the 1st-order diffracted light to the computing unit 15 connected via the digital multimeter 31. Note that the number of light receiving units 29 is not necessarily one, and may be two, for example.

Here, based on the magnitude of the electrical signal applied to the input electrode 12, the amplitude of the surface acoustic wave W generated in the piezoelectric body 11 in a state in which the subject T is not in contact with the material or shape of the piezoelectric body 11. It is theoretically possible to calculate the length. The amount of energy absorbed by the subject T by the surface acoustic wave W transmitted through the piezoelectric body 11 is determined according to the physical quantity (for example, concentration, viscosity, molecular weight) of the subject T, and the subject T absorbs the energy. The amount of change in the amplitude of the surface acoustic wave W due to this depends on the amount of energy absorbed by the subject T.
Therefore, the physical quantity of the subject T can be detected if the amount of change in the amplitude of the surface acoustic wave W that has become smaller due to the absorption of the energy of the subject T can be derived.

Based on the stored incident angle of the laser beam, the wavelength of the laser beam, and the intensities of the 0th-order diffracted light and the 1st-order diffracted light measured by the light detection unit 14, the computing unit 15 uses The amplitude of the surface acoustic wave W in which energy is absorbed by the specimen T (that is, the state where the subject T is in contact with the contact position P) is calculated, and energy is not absorbed (that is, the specimen T is not in contact). The physical quantity of the subject T is obtained from the difference between the amplitude of the surface acoustic wave W (in the state) and the amplitude of the surface acoustic wave W whose energy has been absorbed by the subject T.
In calculating the physical quantity of the subject T, a value obtained by converting a surface acoustic wave into an electrical signal by the output electrode is not used, so that the output electrode is not affected by the point of receiving electromagnetic waves in the space.

In the present embodiment, instead of calculating the magnitude of the amplitude of the surface acoustic wave W generated in the piezoelectric body 11 in a non-contact state with the subject T based on the magnitude of the electrical signal applied to the input electrode 12. Then, the intensity of the 0th-order diffracted light and the intensity of the 1st-order diffracted light are measured in a state where the subject T is not in contact with the piezoelectric body 11, and the surface acoustic wave W generated in the piezoelectric body 11 in the state where the subject T is not in contact is measured. The magnitude of the amplitude is obtained. By doing so, the value calculated from the magnitude of the electric signal applied to the input electrode 12 and the actual value for the magnitude of the amplitude of the surface acoustic wave W generated in the piezoelectric body 11 in a non-contact state with the subject T. There is no need to consider the differences that can occur between the two.

Hereinafter, a procedure for obtaining the physical quantity of the subject T in the present embodiment will be described.
First, the light detection means 14 measures the intensity of the 0th-order diffracted light and the intensity of the 1st-order diffracted light in a state where the subject T is not in contact with the piezoelectric body 11, and the computing unit 15 measures the intensity of the measured 0th-order diffracted light. Based on the intensity of the first-order diffracted light, the amplitude of the surface acoustic wave W (hereinafter, also referred to as “first amplitude”) is calculated using Equation 7. Next, the light detection unit 14 measures the intensity of the 0th-order diffracted light and the intensity of the 1st-order diffracted light in a state where the subject T is in contact with the contact position P of the piezoelectric body 11, and the calculator 15 measures the measured 0 Based on the intensity of the first-order diffracted light and the intensity of the first-order diffracted light, the amplitude of the surface acoustic wave W (hereinafter also referred to as “second amplitude”) is calculated using Equation 7. Then, the calculator 15 obtains the physical quantity of the subject T from the difference between the first amplitude and the second amplitude.

Since the amplitude of the surface acoustic wave can be calculated by a combination of diffracted light other than the intensity of the 0th-order diffracted light and the intensity of the 1st-order diffracted light, the calculator 15 is based on the intensities of the r-order diffracted light and the s-order diffracted light. The physical quantity of the subject T can be obtained. However, r and s are 0 or a natural number, and r ≠ s.
Since the n-th order diffracted light tends to decrease in intensity as the value of n increases, adopting the respective intensities of the 0th-order diffracted light and the first-order diffracted light is to obtain the physical quantity of the subject T stably. Is preferred.

Further, as shown in FIG. 5, the irradiation of the laser beam by the irradiation unit 13 may be performed on the downstream side from the contact position P of the traveling path of the surface acoustic wave W traveling through the piezoelectric body 11. There is no need to be made against. This is because r-order diffracted light and s-order diffracted light are generated even when the surface of the piezoelectric body 11 is irradiated with laser light. Therefore, the light reflecting piece 16 is not necessarily required in that the physical quantity of the subject is calculated based on the amplitude of the surface acoustic wave.

So far, the case where the subject is a liquid, a solid, and a gel has been described, but the subject may be a gas.
When a gas is adopted as the subject, the amplitude of the surface acoustic wave W calculated based on the intensities of the 0th-order diffracted light and the first-order diffracted light in a state where the subject gas is not touching the piezoelectric body 11, and the subject In the state where the contact position P of the piezoelectric body 11 is arranged in the atmosphere of the gas as the specimen (that is, the state where the subject is in contact with the contact position P of the piezoelectric body 11), the respective intensities of the 0th-order diffracted light and the first-order diffracted light are measured. The physical quantity of the subject is obtained from the amplitude of the surface acoustic wave W calculated based on the basis.
In addition, as a sensing apparatus whose liquid is a test object, a biosensor is mentioned, for example, As a sensing apparatus whose gas is a test object, a gas sensor is mentioned, for example. Further, a semiconductor is considered as an example of a solid object.

Next, an experiment conducted for confirming the effect of the present invention will be described.
In this experiment, a surface acoustic wave was generated by changing the magnitude of an electric signal applied to the input electrode on the piezoelectric body on which the sample was placed, and the intensity of the first-order diffracted light was measured.
The sample is glucose having a concentration of 7.3 wt%, 19.3 wt%, and 28.9 wt%. The graph of FIG. 6 shows the result of measuring the intensity of the first-order diffracted light for each sample.

In the graph of FIG. 6, the vertical axis represents the intensity of the first-order diffracted light. The horizontal axis of the graph represents the magnitude of the electric signal applied to the input electrode, but this is described as “surface wave amplitude” because it can be converted into the surface acoustic wave amplitude.
From the experimental results, the intensity of the first-order diffracted light depends on the concentration of the sample (one of the physical quantities) (that is, the relationship of the intensity of the first-order diffracted light of each sample is uniform at different surface acoustic wave amplitudes). It was revealed that the concentration of the sample was obtained from the intensity of the diffracted light.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and all changes in conditions and the like that do not depart from the gist are within the scope of the present invention.
For example, the piezoelectric body does not need to have a rectangular plate shape.
Moreover, when using a light reflection piece, the light reflection piece does not need to be provided with the some metal wire part, For example, you may employ | adopt a metal sheet | seat for a light reflection piece.
Further, the light applied to the piezoelectric body may not be radar light. For example, a high-intensity discharge lamp using arc discharge may be used. However, when a laser beam is used, the sensing device can be made compact and the design can be simplified.

DESCRIPTION OF SYMBOLS 10: Sensing apparatus, 11: Piezoelectric body, 12: Input electrode, 13: Irradiation means, 14: Light detection means, 15: Calculator, 16: Light reflection piece, 17, 18: Comb member, 19, 20: Metal Line part, 21: Signal generator, 22, 23: Comb member, 24, 25: Metal line part, 26: Waveform measuring instrument, 27: Controller, 28: Power supply, 29: Light receiving part, 30: Measuring part, 31: Digital multimeter, P: Contact position, T: Subject, W: Surface acoustic wave

Claims (4)

In a sensing device for generating a surface acoustic wave in a piezoelectric body and obtaining a physical quantity of an object in contact with the piezoelectric body,
An input electrode that causes the piezoelectric body to generate the surface acoustic wave that passes through the contact position of the subject;
A light reflecting piece provided on the downstream side of the contact position of the traveling path of the surface acoustic wave traveling through the piezoelectric body ;
Irradiating means for irradiating the light reflecting piece with light;
A light detection means for measuring the intensities of the r-th order diffracted light and the s-th order diffracted light generated by reflecting the light on the light reflecting piece in a state where the subject is in contact with the piezoelectric body ;
A sensing device comprising: a computing unit that calculates an amplitude of the surface acoustic wave based on the measured intensities of the r-order diffracted light and the s-order diffracted light, and obtains a physical quantity of the subject. The sensing device according to claim 1 , wherein the light reflecting piece includes a plurality of metal wire portions arranged in parallel. 3. The sensing device according to claim 1, wherein the computing unit calculates the elasticity calculated based on the intensities of the r-order diffracted light and the s-order diffracted light measured in a state where the subject is in contact with the contact position. From the difference between the amplitude of the surface wave and the amplitude of the surface acoustic wave calculated based on the intensities of the r-order diffracted light and the s-order diffracted light measured in a state where the subject is not in contact with the piezoelectric body, A sensing device for obtaining a physical quantity of the subject. In the sensing apparatus according to any one of claims 1 to 3, wherein r order diffracted light 0 a-order diffracted light, the s-order diffracted sensing device characterized in that 1 is diffracted light.

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