JP2007178194A - Differential pressure measurement system and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a differential pressure measurement system for measuring a differential pressure in an optically wide dynamic range. <P>SOLUTION: This differential pressure measurement system includes a light source 4, a first sensor 5 for changing the light intensity of an application beam emitted by the light source 4 with a first pressure sensitivity according to a first external pressure P<SB>O1</SB>to output the application beam as a first measurement beam, a second sensor 15 for changing the light intensity of the first measurement beam with a second pressure sensitivity given a sign of polarity opposite to that of a first pressure sensitivity according to a second external pressure P<SB>O2</SB>to output the first measurement beam as a second measurement beam, and a measurement module 17A for measuring a differential pressure between the external pressures P<SB>O1</SB>and P<SB>O2</SB>by measuring the light amount of the second measurement beam. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pressure measurement technique, and more particularly to a differential pressure measurement system and a differential pressure measurement method.

When controlling an oil plant or the like, it may be necessary to measure the differential pressure of the fluid at different locations within the oil plant. As a conventional differential pressure measurement method, a method has been proposed in which a Fabry-Perot interferometer is arranged at a measurement position and a change in the optical path difference of the Fabry-Perot interferometer caused by pressure is read from interference fringes (for example, see Patent Document 1). . However, the interference fringe signal is superimposed on the light intensity component signal that does not depend on the optical path difference. Therefore, when the interference fringe signal superimposed on the signal of the light intensity component is converted from analog to digital signal, the interference fringe signal is assigned to only some bits of the digital signal, and the other bits are used for differential pressure measurement. A signal with an irrelevant light intensity component is assigned. Therefore, the method of reading the change in the optical path difference of the Fabry-Perot interferometer from the interference fringes has a problem that the dynamic range of the differential pressure measurement is lowered.
Japanese Patent Laid-Open No. 2003-166890

  An object of the present invention is to provide a differential pressure measuring system and a differential pressure measuring method capable of measuring a differential pressure with an optically high dynamic range.

  According to the first aspect of the present invention, the light source, the first sensor that changes the light intensity of the irradiation light emitted by the light source according to the first external pressure with the first pressure sensitivity, and outputs the first measurement light as the first sensor light; A second sensor that changes the light intensity of the first measurement light in accordance with the second external pressure with a second pressure sensitivity that is opposite in sign to the first pressure sensitivity, and outputs the second measurement light as a second measurement light; A differential pressure measurement system is provided that includes a measurement module that measures the differential pressure between the first and second external pressures by measuring the light intensity of the light. The light intensity of the second measurement light directly reflects the differential pressure between the first and second external pressures. Therefore, the differential pressure measurement system according to the first aspect of the present invention can measure the differential pressure between the first and second external pressures with a high dynamic range by measuring the light intensity of the second measurement light. To do.

  According to the second aspect of the present invention, the step of irradiating the irradiation light and the light intensity of the irradiation light emitted from the light source according to the first external pressure with the first pressure sensitivity are changed and output as the first measurement light. A step of changing the light intensity of the first measurement light in accordance with the second external pressure with a second pressure sensitivity having a sign opposite to that of the first pressure sensitivity, and outputting the second measurement light as a second measurement light; Measuring a light intensity of the measurement light, and measuring a differential pressure between the first and second external pressures. The light intensity of the second measurement light directly reflects the differential pressure between the first and second external pressures. Therefore, the differential pressure measurement method according to the second aspect of the present invention can measure the differential pressure between the first and second external pressures with a high dynamic range by measuring the light intensity of the second measurement light. To do.

  According to the present invention, it is possible to provide a differential pressure measuring system and a differential pressure measuring method capable of measuring a differential pressure with an optically high dynamic range.

  Embodiments of the present invention will be described below. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic. Therefore, specific dimensions and the like should be determined in light of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(First embodiment)
Differential pressure measurement system according to the first embodiment, as shown in FIG. 1, a light source 4, by changing the light intensity of the irradiation light source 4 is emitted in response to the first external pressure P _O1 at a first pressure sensitivity the first sensor 5 for outputting a first measurement light, the sign of the positive and negative by changing the light intensity of the first measuring beam in response to a second external pressure P _O2 at a second pressure sensitivity opposite to the first pressure sensitive, A second sensor 15 that outputs the second measurement light and a measurement module 17A that measures the differential pressure between the first and second external pressures P _O1 and P _O2 by measuring the light intensity of the second measurement light are provided.

  The light source 4 includes a xenon lamp, a light emitting diode, a super luminescent diode, a semiconductor laser resonator, a multimode laser diode, and a single mode laser diode capable of supporting a continuous spectrum from the ultraviolet region to the infrared region (185 nm to 2000 nm). Etc. can be used. An optical waveguide 30 such as an optical fiber that propagates the irradiation light is connected to the light source 4. Connected to the optical waveguide 30 is a first splitter 21 that divides the irradiated light in two directions. The first splitter 21 is connected to an optical waveguide 31 that propagates one of the divided irradiation lights.

The first sensor 5 is connected to the optical waveguide 31. As shown in FIG. 2, the first sensor 5 includes a first condensing unit 24 that is a lens or the like that condenses the irradiation light emitted from the end of the optical waveguide 31. The first light collector 24 is disposed with a first interval d ₁ with respect to the end of the optical waveguide 31. Further, the first sensor 5 is a first pressure sensing unit such as a diaphragm arranged on the optical axis of the first light collecting unit 24 so as to be movable closer to the first light collecting unit 24 than the focal point of the first light collecting unit 24. 25. That is, the first pressure sensing unit 25 has a distance (FL _1I -L ₁ ) obtained by subtracting the first pressure-dependent distance L ₁ from the focal length FL _1I of the first light collecting unit 24 with _respect to the first light collecting unit 24. Are arranged. The first pressure sensing unit 25 receives the first external pressure _PO1 and moves on the optical axis of the first light collecting unit 24. The movable range of the first pressure sensing unit 25 is from the main surface of the first light collecting unit 24 to the focal point of the first light collecting unit 24. When the first external pressure P _O1 is increased first pressure sensing 25 is moved to the first condensing unit 24 directions, the first pressure-dependent distance L ₁ is longer. When the first external pressure P _O1 is lowered first pressure sensing 25 is moved in the focus direction of the first condenser section 24 to the opposite, first pressure-dependent distance L ₁ is shorter. Further, for example, a chromium oxide film or the like is deposited on the surface of the first pressure sensing unit 25, and the first pressure sensing unit 25 reflects the irradiation light collected by the first light collecting unit 24. The irradiation light reflected by the first pressure sensing unit 25 enters the optical waveguide 31 again as the first measurement light through the first light collecting unit 24.

  Incidentally, when the z-axis of the x-y-z space is the optical axis, a basic Gaussian beam as shown in FIG. 3 is expressed by the following equation (1).

E = (2 / π) ^1/2 (1 / w (z)) × exp [-i (kz-φ (z))-r ² ((1 / w ² (z)) + (ik / 2R ( z))}]… (1)
In Eq. (1), E is the electric field, w (z) is the function of the beam radius in the optical axis (z) direction, i is the imaginary number, k is the wave number, and φ (z) is the function of the phase in the optical axis (z) direction. , R is the distance from the optical axis, and R (z) is a function of the radius of curvature of the wavefront in the direction of the optical axis (z). The beam radius function w (z) is given by the following equation (2).

w (z) = w ₀ {1 + (λz / πw ₀ ² ) ² } ¹ / ² … (2)
In equation (2), λ is the wavelength, and w ₀ is the minimum value of the beam radius. A position where the beam radius becomes the minimum value w ₀ is called a beam waist. The function R (z) of the radius of curvature of the wavefront in the above equation (1) is the following equation (3), the phase function φ (z) is the following equation (4), and the distance r from the optical axis is the following equation (5). Given.

R (z) = z {1 + (λz / πw ₀ ² ) ² }… (3)
φ (z) = tan ^-1 (λz / πw ₀ ² )… (4)
r = (x ² + y ² ) ^1/2 … (5)
The complex beam parameter q (z) of the Gaussian beam given by the above equation (1) is given by the following equation (6).

1 / q (z) = 1 / R (z)-i (λ / πw ² (z))… (6)
At the beam waist (z = 0), the radius of curvature R (0) of the wave front becomes infinite. Therefore, the complex beam parameter q (0) at the beam waist is given by the following equation (7).

1 / q (0) = 0-i (λ / πw ² (z))
∴q (0) = i (πw ² (0) / λ)… (7)
If complex beam parameters before and after passing through an element represented by a ray matrix of geometric optics with A, B, C, and D as matrix elements are defined as q ₁ and q ₂ , respectively, complex beam parameters q ₁ and q ₂ Is given by the following equation (8).

q ₂ = (Aq ₁ + B) / (Cq ₁ + D)… (8)
Also, assuming that the distance from the optical axis of the light beam before and after passing through the element represented by the light matrix is r ₁ , r ₂ , and the slope dr / dz is r ₁ ′, r ₂ ′, the relationship is as follows ( It is given by the determinant of 9).

For example, as shown in FIG. 4, the relationship between the distances r ₁ and r ₂ from the optical axis of the light beams before and after the space d spaced in the optical axis (z) direction, and the inclinations r ₁ ′ and r ₂ ′. Is given by the determinant of the following equation (10).

Assuming that the lens 29 shown in FIG. 5 is a thin lens having a focal length FL, the distance r ₁ and the inclination r ₁ ′ from the optical axis of the light beam incident on the lens 29 and the optical axis of the light beam emitted from the lens 29 The relationship between the distance r ₂ and the slope r ₂ ′ is given by the determinant of the following equation (11).

Now, the irradiation light emitted from the end face of the optical waveguide 31 shown in FIG. 2 can be regarded as a Gaussian beam having the end face of the optical waveguide 31 as a beam waist. Therefore, the complex beam parameter of the irradiation light on the end face of the optical waveguide 31 is given by the above equation (7). Here, since the optical waveguide 31 and the first condensing unit 24 is disposed at a first distance d _1, the optical waveguide 31 with respect to light of the irradiation light space between the first condensing unit 24 Can be represented by a ray matrix M _I1 given by the following equation (12). Further, when the first condensing unit 24 having the focal length FL _1I is regarded as a thin lens, the first condensing unit 24 with respect to the light beam of the irradiation light can be represented by a light ray matrix M _I2 given by the following equation (13). Furthermore, the space between the first light collecting unit 24 and the first pressure sensing unit 25 for the light rays of the irradiation light can be expressed by a light ray matrix M _I3 given by the following equation (14).

When the surface of the first pressure sensing 25, a reflectance of 100% of the flat mirror surface, the first pressure sensing 25 for light of the irradiation light can be expressed by the ray matrix M _R given by the following equation (15).

The space between the first pressure-sensitive part 25 and the first light collecting part 24 with respect to the light beam of the irradiation light reflected by the first pressure-sensitive part 25 is represented by a light matrix M _O1 given by the following equation (16). Can do. Further, assuming that the focal length of the first light collecting unit 24 on the side of the optical waveguide 31 is FL _1O , the first light collecting unit 24 with respect to the light beam of the irradiation light reflected by the first pressure sensing unit 25 is given by the following equation (17). It can be represented by a ray matrix M _O2 . Further, the space between the first light collecting unit 24 and the optical waveguide 31 with respect to the light beam of the irradiation light reflected by the first pressure sensing unit 25 can be represented by a light beam matrix _MO3 given by the following equation (18). it can.

Therefore, the space until the irradiation light emitted from the end face of the optical waveguide 31 reaches the end face of the optical waveguide 31 again is the light matrix M _I1 , M _I2 , M given by the above equations (12) to (18). It can be expressed by a ray matrix M _T given by the following equation (19) which is a product of _I3 , M _R , M _O1 , M _O2 , and M _O3

M _T = M _O3 M _O2 M _O1 M _R M _I3 M _I2 M _I1 … (19)
Therefore, from the complex beam parameters and ray matrix M _T given above (19) at the end of the light guide 31, the irradiation light arrived inside the first sensor 5 to the end of the light guide 31 again and forth complex The beam parameter can be calculated using the above equation (8). Furthermore, the beam radius of the irradiation light that has reached the end of the optical waveguide 31 can be calculated again using the above equation (6).

FIG. 6 shows that the distance (FL _1I -L ₁ ) from the main surface of the first light collecting unit 24 to the first pressure sensing unit 25 is 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.8 mm, and 0.9 mm. In this case, the beam diameter of the irradiation light reflected by the first pressure sensing unit 25 is shown. The focal length FL _1I of the first light collecting unit 24 is 1 mm, and the end of the optical waveguide 31 is the origin (z = 0). As shown in FIG. 6, the closer the distance (FL _1I -L ₁ ) from the main surface of the first light collecting unit 24 to the first pressure sensing unit 25 approaches the focal length FL _1I (1 mm), the first pressure sensing unit. The beam diameter of the irradiation light reflected by 25 is reduced.

As shown in FIG. 7, when the first pressure sensing unit 25 is arranged at the focal position of the first light collecting unit 24, the optical path of the irradiation light incident on the first pressure sensing unit 25, and the first pressure sensing The optical path of the irradiation light reflected from the portion 25 as a whole matches. Therefore, the beam diameter of the irradiation light that re-enters the optical waveguide 31 as the first measurement light is minimized, and the light intensity of the first measurement light is maximized. On the other hand, the first pressure sensing unit 25 of the first sensor 5 is arranged closer to the first light collecting unit 24 than the focal position of the first light collecting unit 24. For this reason, the optical path of the irradiation light reflected from the first pressure sensing unit 25 as a whole does not match. Therefore, the light intensity of the first measurement light that re-enters the optical waveguide 31 is weaker than when the first pressure-sensitive part 25 is disposed at the focal position of the first light collecting part 24. When the first external pressure _PO1 further increases, the first pressure sensing unit 25 moves toward the first light collecting unit 24, and comes closer to the first light collecting unit 24 from the focal position of the first light collecting unit 24. Therefore, the distance (FL _1I -L ₁ ) from the main surface of the first light collecting unit 24 to the first pressure sensing unit 25 is shorter than the focal length FL _1I, and reenters the optical waveguide 31. The light intensity of the measurement light is further weakened. On the other hand, when the first external pressure _PO1 decreases, the first pressure sensing unit 25 approaches the focal position of the first light collecting unit 24. Therefore, the distance (FL _1I -L ₁ ) from the main surface of the first light collecting unit 24 to the first pressure sensing unit 25 approaches the focal length FL _1I, and the light intensity of the first measurement light reentering the optical waveguide 31 Will strengthen. As described above, in the first sensor 5, when the first external pressure P _O1 increases, the light intensity of the first measurement light decreases, and when the first external pressure P _O1 decreases, the light intensity of the first measurement light decreases. Strengthen. That is, the first pressure sensitivity that is the pressure sensitivity of the first sensor 5 is set so that the first external pressure _PO1 and the light intensity of the first measurement light have a negative correlation.

  The first measurement light output from the first sensor 5 is propagated through the optical waveguide 31 and the optical waveguide 32 connected to the first splitter 21, and reaches the second splitter 22 connected to the optical waveguide 32. The second splitter 22 divides the first measurement light of the first sensor 5 in two directions. The second splitter 22 is connected to an optical waveguide 33 that propagates one of the divided first measurement lights. One of the divided first measurement lights is propagated to the second sensor 15 by the optical waveguide 33.

As shown in FIG. 8, the second sensor 15 includes a second condensing unit 124 that is a lens or the like that condenses the first measurement light emitted from the end of the optical waveguide 33. The second light collector 124 is disposed at a second interval d ₂ with respect to the end of the optical waveguide 33. Further, the second sensor 15 includes a second pressure sensing unit 125 such as a diaphragm disposed on the optical axis of the second light collecting unit 124 so as to be distant from the focal point of the second light collecting unit 124. That is, the second pressure sensing 125 whereas the second condensing section 124, the distance plus the second pressure-dependent distance L ₂ to the focal length FL _2I of the second condensing unit 124 (FL _2I + L ₂₎ Contact Are arranged. Second pressure sensing 125 moves on the optical axis of the second condensing unit 124 receives the second external pressure P _O2. The movable range of the second pressure sensing unit 125 is a range of the same distance as the focal length FL _2I from the focal point of the second light collecting unit 124 to the far side. When the second external pressure P _O2 is increased second pressure sensing 125 is moved in the focus direction, the second pressure-dependent distance L ₂ becomes shorter. When the second external pressure P _O2 is decreased second pressure sensing 125 moves away more from the focal point of the second condensing section 124 in the opposite, second pressure-dependent distance L ₂ becomes longer. Further, for example, a chromium oxide film or the like is deposited on the surface of the second pressure sensing unit 125, and the second pressure sensing unit 125 reflects the first measurement light collected by the second light collecting unit 124. The first measurement light reflected by the second pressure sensing unit 125 passes through the second light collecting unit 124 and again enters the optical waveguide 33 as the second measurement light.

Here, the second pressure sensing unit 125 of the second sensor 15 is disposed farther from the focal position than the second light collecting unit 124. Therefore, the light intensity of the second measurement light re-entering the optical waveguide 33 is compared with the case where the second pressure sensing unit 125 is disposed at the focal position of the second light collecting unit 124 as described in FIG. And weak. However, when the second external pressure _PO2 increases, the second pressure sensing unit 125 approaches the focal position of the second light collecting unit 124. Therefore, the distance (FL _2I + L ₂ ) from the main surface of the second light collecting unit 124 to the second pressure sensing unit 125 approaches the focal length FL _2I, and the light intensity of the second measurement light reentering the optical waveguide 33 Will strengthen. On the other hand, when the second external pressure _P02 decreases, the second pressure sensing unit 125 moves further away from the focal point of the second light collecting unit 124. Therefore, the distance (FL _2I + L ₂ ) from the main surface of the second light collecting unit 124 to the second pressure sensing unit 125 is longer than the focal length FL _2I and re-enters the optical waveguide 33. The light intensity of the measurement light is weakened. As shown in FIG. 9, in the first sensor 5, when the first external pressure _PO1 rises, the first pressure sensitivity is set so that the light intensity of the first measurement light is weakened, whereas the second sensor In FIG. 15, when the second external pressure P _O2 increases, the light intensity of the second measurement light increases, and when the second external pressure P _O2 decreases, the light intensity of the second measurement light decreases. That is, the second pressure sensitivity that is the pressure sensitivity of the second sensor 15 is set so that the second external pressure _PO2 and the light intensity of the second measurement light have a positive correlation. Therefore, the first pressure sensitivity and the second pressure sensitivity have a relationship in which the positive and negative signs are opposite.

FIG. 10 shows the distance (FL _1I -L ₁ ) from the main surface of the first light collecting unit 24 of the first sensor 5 to the first pressure sensing unit 25, the main surface of the second light collecting unit 124 of the second sensor 15. 3 shows the relationship between the distance (FL _2I + L ₂ ) from the first pressure sensing unit 125 to the light intensity of the second measurement light. In the first sensor 5, the light intensity of the second measurement light increases as the distance (FL _1I -L ₁ ) from the first light collecting unit 24 to the first pressure sensing unit 25 increases and approaches the focal length FL _1I. . In the second sensor 15, the light intensity of the second measurement light increases as the distance (FL _2I + L ₂ ) from the second light collecting unit 124 to the second pressure sensing unit 125 decreases and approaches the focal length FL _2I. Become. FIG. 11 shows the relationship between the difference Δ (L ₁ −L ₂ ) between the first pressure-dependent distance L ₁ and the second pressure-dependent distance L ₂ and the light intensity of the second measurement light. The greater the difference Δ (L ₁ −L ₂ ), the weaker the light intensity of the second measurement light, and the smaller the difference Δ (L ₁ −L ₂ ), the greater the light intensity of the second measurement light.

The second measurement light output from the second sensor 15 shown in FIG. 1 is propagated to the light receiving element 151 through the optical waveguide 34 connected to the second splitter 22. The light receiving element 151 receives the second measurement light propagated through the optical waveguide 34 and measures the light intensity of the second measurement light. A signal processing device 7A is connected to the light receiving element 151, and the measured light intensity of the second measurement light is transmitted to the signal processing device 7A. The measurement module 17A is included in the signal processing device 7A. The principle of measuring the differential pressure between the first and second external pressures P _O1 and P _{O2 by} the measurement module 17A measuring the light intensity of the two measurement lights will be described below.

FIG. 12 shows the relationship between the distance (FL _1I -L ₁ ) from the main surface of the first light collecting unit 24 of the first sensor 5 to the first pressure sensing unit 25 and the reflectance of the first sensor 5. Yes. Here, the “reflectance” of the first sensor 5 is a value obtained by dividing the light intensity of the first measurement light output from the first sensor 5 by the light intensity of the irradiation light incident on the first sensor 5. FIG. 12 also shows the relationship between the distance (FL _2I + L ₂ ) from the main surface of the second light collecting unit 124 of the second sensor 15 to the second pressure sensing unit 125 and the reflectance of the second sensor 15. ing. Here, the “reflectance” of the second sensor 15 is a value obtained by dividing the light intensity of the second measurement light output from the second sensor 15 by the light intensity of the first measurement light incident on the second sensor 15. . Further, FIG. 12 shows the relationship between the reflectance of each of the first and second sensors 5 and 15 and the light intensity of the second measurement light received by the light receiving element 151. Each of the focal length FL _1I of the first light collector 24 and the focal length FL _2I of the second light collector 124 is 1 mm.

In the initial state, the distance from the first light collector 24 to the first pressure sensor 25 (FL _1I -L ₁ ) is 0.5 mm, and the distance from the second light collector 124 to the second pressure sensor 125 (FL _2I + L ₂ ) is 1.5 mm. In this case, the reflectance of the first sensor 5 is 0.809, and the reflectance of the second sensor 15 is 0.832. The light intensity of the second measurement light is 0.673. When the first external pressure _PO1 decreases and the distance (FL _1I -L ₁ ) from the first light collecting unit 24 to the first pressure sensing unit 25 becomes 0.6 mm, the light intensity of the first measurement light increases. Therefore, the reflectance of the first sensor 5 increases to 0.817. At the same time, when the second external pressure P _O2 decreases while keeping the differential pressure with the first external pressure P _O1 constant, the distance (FL _2I + L ₂ ) from the second light collecting unit 124 to the second pressure sensing unit 125 is 1.6. mm. Then, since the light intensity of the second measurement light is weakened, the reflectance of the second sensor 15 is reduced to 0.825. In this case, although the reflectance of the first sensor 5 is increased, the reflectance of the second sensor 15 is decreased, so that the light intensity of the second measurement light remains 0.673. Thereafter, similarly, when each of the first external pressure P _O1 and the second external pressure P _O2 decreases while the differential pressure is kept constant, the increase in the reflectance of the first sensor 5 and the decrease in the reflectance of the second sensor 15 simultaneously. Arise. Therefore, as long as the differential pressure between the first external pressure P _O1 and the second external pressure P _O2 is constant, the light intensity of the second measurement light continues to maintain 0.673. On the other hand, even when each of the first external pressure P _O1 and the second external pressure P _O2 rises while keeping the differential pressure constant, the light intensity of the second measurement light does not change. Therefore, if the light intensity of the second measurement light is constant, the measurement module 17A determines that the differential pressure between the first external pressure P _O1 and the second external pressure P _O2 is constant.

In FIG. 13, in the initial state, the distance (FL _1I -L ₁ ) from the first light collecting unit 24 to the first pressure sensing unit 25 is 0.8 mm, and the second light collecting unit 124 to the second pressure sensing unit 125 The distance (FL _2I + L ₂ ) is 1.5 mm. In this case, the reflectance of the first sensor 5 is 0.828, and the reflectance of the second sensor 15 is 0.83. The light intensity of the second measurement light is 0.69. When the first external pressure _PO1 rises and the distance (FL _1I -L ₁ ) from the first light collecting unit 24 to the first pressure sensing unit 25 becomes 0.7 mm, the light intensity of the first measurement light is weakened. For this reason, the reflectance of the first sensor 5 decreases to 0.823. At the same time, when the second external pressure _PO2 decreases, the distance (FL _2I + L ₂ ) from the second light collecting unit 124 to the second pressure sensing unit 125 becomes 1.6 mm. Then, since the light intensity of the second measurement light is weakened, the reflectance of the second sensor 15 is reduced to 0.825. In this case, since the reflectances of both the first sensor 5 and the second sensor 15 are reduced, the light intensity of the second measurement light is reduced to 0.676. Thereafter, similarly, when the first external pressure P _O1 increases and the second external pressure P _O2 decreases to increase the differential pressure, the light intensity of the second measurement light further decreases. On the other hand, when the first external pressure P _O1 decreases and the second external pressure P _O2 increases and the differential pressure narrows, the light intensity of the second measurement light increases. Note that when the first external pressure P _O1 increases and the second external pressure P _O2 is constant, the light intensity of the second measurement light is weakened. When the first external pressure P _O1 is constant and the second external pressure P _O2 is increased, the light intensity of the second measurement light is increased. Therefore, when the light intensity of the second measurement light changes, the measurement module 17A determines that the differential pressure between the first external pressure P _O1 and the second external pressure P _O2 has changed.

Furthermore, for example, in advance and the differential pressure of the first external pressure P _O1 and the second external pressure P _O2, if acquires a relational expression or a comparison table or the like between the light intensity of the second measurement light, a second measurement light measured It is possible to calculate the differential pressure between the first external pressure P _O1 and the second external pressure P _O2 by substituting the above light intensity into the relational expression. Signal processor 7A in connected data storage device 170A, the measurement module 17A is used to calculate the differential pressure of the first external pressure P _O1 and the second external pressure P _O2, and a first external pressure P _O1 obtained in advance and the differential pressure of the second external pressure P _O2, stores a relational expression or the like between the light intensity of the second measurement light.

In the conventional differential pressure measurement system, the first measurement pressure P _O1 and the second measurement pressure are obtained by dividing the second measurement light in two directions and causing interference with an interferometer, and analyzing the interference fringes formed by the interferometer with a computer. The pressure difference with P _O2 was obtained. For this reason, there is a problem that it takes time to identify the interference fringe position. In contrast, the differential pressure measurement system according to the first embodiment measures the differential pressure between the first external pressure P _O1 and the second external pressure P _O2 by measuring the light intensity of the second measurement light. No complicated processing such as identification of interference fringes is required. Further, the interference fringe signal measured by the conventional differential pressure measurement system is superimposed on the light intensity component signal that does not depend on the optical path difference. Therefore, there has been a problem that the dynamic range of the interference fringe signal necessary for measuring the differential pressure is low. In contrast, the light intensity of the second measurement light measured by the differential pressure measurement system according to the first embodiment directly reflects the differential pressure between the first external pressure P _O1 and the second external pressure P _O2 . . Therefore, the differential pressure between the first external pressure P _O1 and the second external pressure P _O2 can be measured with a high dynamic range, and a slight change in differential pressure can be measured accurately. For each of the optical waveguides 30, 31, 32, 33, 34, a single mode or multimode optical fiber or the like can be used. For each of the first splitter 21 and the second splitter 22, an optical fiber coupler, a half mirror, a thin film waveguide branching device, or the like can be used.

  Next, the differential pressure measurement method according to the first embodiment will be described with reference to FIG.

  (a) In step S101, irradiation light in a wide wavelength band is irradiated onto the optical waveguide 30 from the light source 4 shown in FIG. In step S102, the irradiation light is propagated to the first sensor 5 through the optical waveguide 31 through the optical waveguide 30 and the first splitter 21. In step S 103, the irradiation light irradiated from the end of the optical waveguide 31 is collected by the first light collecting unit 24 of the first sensor 5.

In (b) step S104, than the focal point of the first condenser section 24 is placed near, the first pressure sensing 25 which moves on the optical axis of the first condensing section 24 in response to the first external pressure P _O1 , The condensed irradiation light is reflected. In step S105, the reflected irradiation light is condensed by the first condensing unit 24, and the condensed irradiation light is incident on the optical waveguide 31 again as the first measurement light. Since the first pressure sensing unit 25 is disposed closer to the focal point of the first light collecting unit 24, the first external pressure _PO1 and the light intensity of the first measurement light have a negative correlation.

  (c) In step S106, the first measurement light is propagated to the second sensor 15 through the optical waveguide 33, the first splitter 21, the optical waveguide 32, and the second splitter 22. In step S107, the first measurement light emitted from the end of the optical waveguide 33 is collected by the second light collecting unit 124 of the second sensor 15.

(d) in step S108, is located farther than the focal point of the second condensing section 124, the second pressure sensing 125 which moves on the optical axis of the second condensing section 124 in response to the second external pressure P _O2 The collected first measurement light is reflected. In step S109, the reflected first measurement light is collected by the second light collecting unit 124, and the collected first measurement light is incident on the optical waveguide 33 again as the second measurement light. Since the second pressure sensing unit 125 is disposed farther than the focal point of the second light collecting unit 124, the second external pressure _PO2 and the light intensity of the second measurement light have a positive correlation.

  (e) In step S 110, the second measurement light is propagated to the light receiving element 151 through the optical waveguide 34 through the optical waveguide 33 and the second splitter 22. The light receiving element 151 receives the second measurement light and measures the light intensity of the second measurement light. The light receiving element 151 electrically transmits the light intensity of the second measurement light to the measurement module 17A of the signal processing device 7A.

(f) measurement module 17A in step S111 reads the differential pressure of the first external pressure P _O1 and the second external pressure P _O2 obtained in advance, the relationship between the light intensity of the second measurement light from the data storage device 170A. Next, the measurement module 17A substitutes the measurement value of the light intensity of the second measurement light into the relational expression, calculates the differential pressure between the first external pressure P _O1 and the second external pressure P _O2 , and relates to the first embodiment End the differential pressure measurement method.

According to the differential pressure measurement method according to the first embodiment described above, the first external pressure P is calculated from the light intensity of the second measurement light that directly reflects the differential pressure between the first external pressure P _O1 and the second external pressure P _O2. A differential pressure between _O1 and the second external pressure P _O2 is measured. Therefore, it is possible to measure the differential pressure between the first external pressure P _O1 and the second external pressure P _O2 with a high dynamic range.

(Modification of the first embodiment)
In the first embodiment, the first pressure sensitivity of the first sensor 5 shown in FIG. 1 is set so that the first external pressure _PO1 and the light intensity of the first measurement light have a `` negative '' correlation, An example has been described in which the second pressure sensitivity of the second sensor 15 is set so that the second external pressure _PO2 and the light intensity of the second measurement light have a “positive” correlation. On the other hand, the first pressure sensitivity of the first sensor 5 is set so that the first external pressure P _O1 and the light intensity of the first measurement light have a “positive” correlation, and the second external pressure P _O2 and the second measurement The second pressure sensitivity of the second sensor 15 may be set so that the light intensity of light has a “negative” correlation.

Specifically, the first pressure-sensing unit 25 of the first sensor 5 according to the modification of the first embodiment is configured such that the first light collecting unit with respect to the first light collecting unit 24, as shown in FIG. They are arranged with a distance (FL _1I + L ₁ ) obtained by adding the first pressure-dependent distance L ₁ to 24 focal lengths FL _1I . When the first external pressure P _O1 is increased first pressure sensing 25 is moved toward the focal point of the first condenser section 24, the first pressure-dependent distance L ₁ is shorter. Therefore, the light intensity of the first measurement light is increased. When the first external pressure P _O1 is lowered first pressure sensing 25 moves away from the focal point of the first condenser section 24 to the opposite, first pressure-dependent distance L ₁ is longer. For this reason, the light intensity of the first measurement light is weakened.

Further, the second pressure sensing unit 125 of the second sensor 15 according to the modification of the first embodiment is configured so that the second pressure from the focal length FL _2I of the second light collecting unit 124 with respect to the second light collecting unit 124. They are arranged at a distance (FL _2I -L ₂ ) obtained by subtracting the dependency distance L ₂ . When the second external pressure P _O2 is increased second pressure sensing 125 is moved toward the second condenser section 124, a second pressure-dependent distance L ₂ is longer. Therefore, the light intensity of the second measurement light is weakened. When the second external pressure P _O2 is decreased second pressure sensing 125 is moved toward the focal point of the second condensing section 124 in the opposite, second pressure-dependent distance L ₂ becomes shorter. Therefore, the light intensity of the second measurement light is increased.

Also in the modification of the first embodiment, the second pressure sensitivity has a sensitivity that is opposite in sign to the first pressure sensitivity. Therefore, as long as the differential pressure of the first external pressure P _O1 and the second external pressure P _O2 it is constant, even if the first external pressure P _O1 and the second external pressure P _O2 is varied light intensity of the second measurement light is constant. Therefore, even if respective values of the first external pressure P _O1 and the second external pressure P _O2 is varied, to accurately measure the differential pressure of the first external pressure P _O1 and the second external pressure P _O2 first embodiment This is also possible in the modified example.

(Second embodiment)
The light source 204 according to the second embodiment shown in FIG. 17 is the same as the light source 4 of FIG. Irradiation light emitted from the light source 204 is propagated to the first sensor 105 through the optical waveguide 130. As shown in FIG. 18, the first sensor 105 according to the second embodiment has a first pressure sensing part 225 that receives the first external pressure _PO1 . The first pressure sensing unit 225 is arranged so that the incident angle of the irradiation light emitted from the end of the optical waveguide 130 is 30 degrees. In addition the normal direction of the first pressure sensing 225, the first pressure sensing 225 and the optical waveguide 130 is disposed at a first radial distance H ₁ in the initial state. When the first external pressure P _O1 is increased, as shown in FIG. 19, the first pressure sensing 225 the first pressure-dependent distance L ₁ from the initial state positively increased in the normal direction of the first pressure sensing 225 Move like so. Therefore, the distance between the first pressure sensing unit 225 and the optical waveguide 130 is a distance (H ₁ −L ₁ ) obtained by subtracting the first pressure-dependent distance L ₁ from the first radiation distance H ₁ . When the first external pressure P _O1 is decreased, the first pressure sensing 225 is moved so that the first pressure-dependent distance L ₁ is decreased in the normal direction of the first pressure sensing 225.

The optical waveguide 131 into which the irradiation light reflected by the first pressure sensing unit 225 enters as the first measurement light is disposed adjacent to the optical waveguide 130. When the diameter of each cross section of the optical waveguides 130 and 131 is Q, the distance between the center of the end face of the optical waveguide 130 and the center of the end face of the optical waveguide 131 is in a direction parallel to the main surface of the first pressure sensing part 225. Corresponds to twice the length of the diameter Q. Here, when the first pressure-dependent distance L ₁ is 0 as shown in FIG. 18, the peak of the light intensity of the reflected illumination light from the center of the end face of the optical waveguide 130, the main surface of the first pressure sensing 225 It is set to appear at a point spaced 1.5 times the diameter Q in the parallel direction. Therefore, as shown in FIG. 20, the first measurement light incident on the optical waveguide 131 does not include an optical component on the optical axis at which the light intensity reaches a peak among the irradiated light. Here the first external pressure P _O1 is increased, when the first pressure sensing 225 increases the first pressure-dependent distance L ₁ as shown in FIG. 19 approaches the optical waveguide 130, 131, as shown in FIG. 21 The position where the peak of the light intensity of the irradiation light reflected by the first pressure sensing unit 225 appears is farther from the optical waveguide 131. Conversely irradiation, the first external pressure P _O1 is lowered, the first pressure sensing 225 the first pressure-dependent distance L ₁ is decreased moves away from the optical waveguide 130, 131, reflected by the first pressure sensing 225 The position where the peak of the light intensity appears approaches the optical waveguide 131.

Accordingly, in the first sensor 105, when the first external pressure P _O1 increases, the light intensity of the first measurement light decreases, and when the first external pressure P _O1 decreases, the light intensity of the first measurement light increases. That is, the first pressure sensitivity, which is the pressure sensitivity of the first sensor 105, is set so that the first external pressure _PO1 and the light intensity of the first measurement light have a negative correlation. In other words, as shown in FIG. 22, the reflectance of the whole of the first sensor 105 as the first external pressure P _O1 is increased is reduced, the overall reflection of the first sensor 105 as the first external pressure P _O1 is reduced The rate goes up.

The first measurement light is propagated to the second sensor 115 through the optical waveguide 131 shown in FIG. As shown in FIG. 23, a second sensor 115 according to the second embodiment has a second pressure sensing 325 for receiving a second external pressure P _O2. The second pressure sensing unit 325 is arranged so that the incident angle of the first measurement light emitted from the end of the optical waveguide 131 is 30 degrees. In addition the normal direction of the second pressure sensing 325, and the second pressure sensing 325 and the optical waveguide 131 is disposed at a second radial distance H ₂ in the initial state. The second radial distance H ₂ may be the same as the first radial distance H _1. When the second external pressure P _O2 is increased, as shown in FIG. 24, the second pressure sensing 325 the second pressure-dependent distance L ₂ from the initial state positively increased in the normal direction of the second pressure sensing 325 Move like so. Therefore, the distance between the second pressure sensing unit 325 and the optical waveguide 131 is a distance (H ₂ −L ₂ ) obtained by subtracting the second pressure dependent distance L ₂ from the second radiation distance H ₂ . When the second external pressure P _O2 is decreased, the second pressure sensing 325 is moved so that the second pressure-dependent distance L ₂ decreases in the normal direction of the second pressure sensing 325. Note that the first pressure-dependent distance ratio of L ₁ to the first external pressure P _O1, are set to be equal to the second pressure-dependent distance L ₂ of the ratio for the second external pressure P _O2.

The optical waveguide 132 in which the first measurement light reflected by the second pressure sensing unit 325 is incident as the second measurement light is disposed adjacent to the optical waveguide 131. When the diameter of the cross section of each of the optical waveguides 131 and 132 is Q, the distance between the center of the end face of the optical waveguide 131 and the center of the end face of the optical waveguide 132 is in a direction parallel to the main surface of the second pressure sensing unit 325. The length is equal to the diameter Q. Here, if the second pressure-dependent distance L ₂ is 0 as shown in FIG. 23, from the center of the end face of the peak of the light intensity of the first measurement light reflected optical waveguide 131, the second pressure sensing 325 It is set to appear at a point 1.5 times the diameter Q in the direction parallel to the main surface. Therefore, as shown in FIG. 25, the second measurement light incident on the optical waveguide 132 does not include an optical component on the optical axis at which the light intensity peaks among the first measurement light. Wherein the second external pressure P _O2 is increased, the second pressure-dependent distance L ₂ second pressure sensing 325 increases as shown in FIG. 24 approaches the optical waveguide 131, 132, as shown in FIG. 26 The position at which the peak of the light intensity of the first measurement light reflected by the second pressure sensing unit 325 appears approaches the optical waveguide 132. Conversely, the second external pressure P _O2 is decreased, the second pressure sensing 325 a second pressure-dependent distance L ₂ is decreased away from the optical waveguide 131, 132, reflected by the second pressure sensing 325 the 1 The position where the peak of the light intensity of the measurement light appears moves away from the optical waveguide 132.

Therefore, in the second sensor 115, when the second external pressure P _O2 increases, the light intensity of the second measurement light increases, and when the second external pressure P _O2 decreases, the light intensity of the second measurement light decreases. That is, the second pressure sensitivity, which is the pressure sensitivity of the second sensor 115, is set so that the second external pressure _PO2 and the light intensity of the second measurement light have a positive correlation. In other words, as shown in FIG. 27, the reflectance of the entire second sensor 115 as the second external pressure P _O2 rises rises, the overall reflection of the second sensor 115 as the second external pressure P _O2 is reduced The rate drops. Therefore, as shown in FIG. 28, the first pressure sensitivity and the second pressure sensitivity have a relationship in which positive and negative signs are opposite to each other.

As shown in FIG. 29, the first external pressure P _O1 is increased, the light intensity of the second measuring beam as the first pressure-dependent distance L ₁ is longer weakens. In contrast, the second external pressure P _O2 is increased, the light intensity of the second pressure-dependent distance L approximately _two longer second measuring light intensified. However, the difference between the first pressure-dependent distance L ₁ and the second pressure-dependent distance L ₂ (L ₁ - L ₂₎ as long as the constant, the first pressure-dependent distance L ₁ and the second pressure as shown in FIG. 30 It is varied each dependent distance L ₂ is, the light intensity of the second measuring beam is not changed. Therefore, the light intensity of the second measurement light accurately reflects the differential pressure between the first external pressure P _O1 and the second external pressure P _O2 .

The second measurement light is propagated to the light receiving element 251 through the optical waveguide 132. The light receiving element 251 receives the second measurement light and electrically transmits the light intensity of the second measurement light to the signal processing device 7A. Since a method of measuring module 17A of the signal processing unit 7A calculates the light intensity of the second measuring beam between the first external pressure P _O1 of the differential pressure between the second external pressure P _O2 is the same as in the first embodiment described Is omitted. Note that the first pressure sensitivity of the first sensor 105 shown in FIG. 17 is set so that the first external pressure _PO1 and the light intensity of the first measurement light have a positive correlation, and the second external pressure _PO2 2 The second pressure sensitivity of the second sensor 115 may be set so that the light intensity of the measurement light has a “negative” correlation.

  Next, a differential pressure measurement method according to the second embodiment will be described with reference to FIG.

(a) In step S201, irradiation light is irradiated onto the optical waveguide 130 from the light source 204 shown in FIG. In step S202, the irradiation light is propagated to the first sensor 105 through the optical waveguide 130. Irradiation light is emitted from the end of the optical waveguide 130. In step S203, the irradiation light is reflected by the first pressure-sensing unit 225 that moves according to the first external pressure _PO1 . In step S204, the reflected irradiation light is incident on the optical waveguide 131 as the first measurement light. Since the optical waveguide 131 is arranged farther from the optical waveguide 130 than the position where the peak of the light intensity of the irradiation light reflected in the initial state appears, the first external pressure _PO1 and the light intensity of the first measurement light Has a negative correlation.

(b) In step S205, the first measurement light is propagated to the second sensor 115 through the optical waveguide 131. The first measurement light is emitted from the end of the optical waveguide 131. In step S206, it reflects the first measuring beam at a second pressure sensing 325 to move in response to a second external pressure P _O2. In step S207, the reflected first measurement light is incident on the optical waveguide 132 as the second measurement light. Since the optical waveguide 132 is disposed closer to the optical waveguide 131 than the position where the peak of the light intensity of the first measurement light reflected in the initial state appears, the second external pressure _PO2 and the light of the second measurement light There is a positive correlation with intensity.

  (c) In step S208, the second measurement light is propagated to the light receiving element 251 through the optical waveguide 132. The light receiving element 251 receives the second measurement light and measures the light intensity of the second measurement light. The light receiving element 251 electrically transmits the light intensity of the second measurement light to the measurement module 17A of the signal processing device 7A. Thereafter, step S209 is performed in the same manner as step S111 in FIG. 14, and the differential pressure measurement method according to the second embodiment is terminated.

(Modification of the second embodiment)
As shown in FIG. 32, a first condensing unit 301 such as a lens that condenses the irradiation light emitted from the optical waveguide 130 may be disposed between the optical waveguide 130 and the first pressure sensing unit 225. . By disposing the first light collecting unit 301, the irradiation light is collected, and the spread of the light intensity shown in FIG. 20 of the irradiation light reflected by the first pressure sensing unit 225 is narrowed. Therefore, the amount of change in the light intensity of the first measurement light accompanying the movement of the first pressure sensing unit 225 is increased, and the change in the first external pressure _PO1 can be detected with higher sensitivity. In this case, also in the second sensor 115, as shown in FIG. 33, the second condensing unit 302 such as a lens for condensing the first measurement light emitted from the optical waveguide 131 is connected to the optical waveguide 131 and the second sensor. It is good to arrange between the pressure parts 325.

(Other embodiments)
As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques should be apparent to those skilled in the art. For example, in the first embodiment, as shown in FIG. 2, the first light collecting portion 24 of the first sensor 5 is arranged at a first interval d ₁ from the optical waveguide 31. On the other hand, the first condensing unit 24 may be provided at the end of the optical waveguide 31 by polishing the end of the optical waveguide 31 such as an optical fiber into a lens shape. Similarly, in the second sensor 15 shown in FIG. 8, the second condensing unit 124 may be provided at the end of the optical waveguide 33 by polishing the end of the optical waveguide 33 such as an optical fiber into a lens shape. .

  Further, Fresnel reflection can occur at the end of the optical waveguide 31 due to the difference between the refractive index of the material of the optical waveguide 31 and the refractive index of the medium around the optical waveguide 31 such as air. The irradiation light reflected by Fresnel travels through the optical waveguide 31 toward the first splitter 21. Therefore, a phase difference proportional to the distance between the end of the optical waveguide 31 and the first pressure sensing unit 25 occurs between the irradiation light reflected by Fresnel and the first measurement light output from the first sensor 5. If the reciprocating distance between the end of the optical waveguide 31 and the first pressure sensing unit 25 is within the coherence length of the irradiation light, the Fresnel reflected irradiation light and the first measurement light interfere with each other. For this reason, interference fringes are generated, which may cause an error in measuring the light intensity of the second measurement light. The same applies to the end of the optical waveguide 33. In order to prevent interference, the reciprocating distance between the end of the optical waveguide 31 and the first pressure sensing unit 25 and the reciprocating distance between the end of the optical waveguide 33 and the second pressure sensing unit 125 are respectively , The coherence length of the irradiation light should be longer Further, the difference between the reciprocating distance between the end of the optical waveguide 31 and the first pressure-sensitive part 25 and the reciprocating distance between the end of the optical waveguide 33 and the second pressure-sensitive part 125 is also the coherence of the irradiation light. Make it longer or longer. Alternatively, interference can also be prevented by subjecting the respective end portions of the optical waveguides 31 and 33 to an oblique polishing process based on the numerical aperture or by depositing an antireflection film on the respective end portions of the optical waveguides 31 and 33. It becomes possible.

  In addition, the irradiation light reciprocated once between the end portion of the optical waveguide 31 and the first pressure-sensitive portion 25 and the irradiation light reciprocated twice are also between the end portion of the optical waveguide 31 and the first pressure-sensitive portion 25. Interference may occur due to the optical path difference corresponding to the round-trip distance between the two. Figure 34 shows the relationship between the optical path difference scan amount and the error, with the difference between the measured value of the first measurement light intensity and the theoretical value when interference is ignored divided by the theoretical value as an error. It is a graph. When the end portion of the optical waveguide 31 is not subjected to the antireflection treatment, an error occurs according to the scanning amount of the optical path difference due to interference. On the other hand, when the end of the optical waveguide 31 is obliquely polished to prevent interference, the error is almost 0%.

Furthermore, in the second embodiment, the interval between the optical waveguide 130 and the optical waveguide 131 in the first sensor 105 is set to 2Q, and the interval between the optical waveguide 131 and the optical waveguide 132 is set to Q in the second sensor 115. It has been explained that the correlation between the pressure and the light intensity defined by the first pressure sensitivity and the second pressure sensitivity is reversed. In contrast, such as by the distance between the optical waveguide 131 and the optical waveguide 132 in the second sensor 115 similarly to the Q and the first sensor 105, the second radial distance between H ₂ first two times the radial distance H ₁ However, it is possible to reverse the sign of the correlation between the pressure and the light intensity defined by the first pressure sensitivity and the second pressure sensitivity, respectively.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

1 is a schematic diagram of a differential pressure measurement system according to a first embodiment of the present invention. It is a 1st schematic diagram of the 1st sensor concerning a 1st embodiment of the present invention. It is a schematic diagram of a basic Gaussian beam according to the first embodiment of the present invention. It is a 1st schematic diagram of the light ray which concerns on the 1st Embodiment of this invention. It is a 2nd schematic diagram of the light ray which concerns on the 1st Embodiment of this invention. It is a graph which shows the beam diameter of the irradiation light which concerns on the 1st Embodiment of this invention. It is the 2nd schematic diagram of the 1st sensor concerning a 1st embodiment of the present invention. It is a schematic diagram of the 2nd sensor which concerns on the 1st Embodiment of this invention. It is a graph which shows the relationship between the 1st pressure sensitivity which concerns on the 1st Embodiment of this invention, and 2nd pressure sensitivity. It is a graph which shows the relationship between the distance from the condensing part which concerns on the 1st Embodiment of this invention, and a pressure sensitive part, and the optical intensity of 2nd measurement light. It is a graph which shows the relationship between the difference of the 1st and 2nd pressure dependence distance which concerns on the 1st Embodiment of this invention, and the optical intensity of 2nd measurement light. It is a 1st graph which shows the relationship between the reflectance of the 1st and 2nd sensor which concerns on the 1st Embodiment of this invention, and the optical intensity of 2nd measurement light. It is a 2nd graph which shows the relationship between the reflectance of the 1st and 2nd sensor which concerns on the 1st Embodiment of this invention, and the optical intensity of 2nd measurement light. It is a flowchart which shows the differential pressure | voltage measurement method which concerns on the 1st Embodiment of this invention. It is a schematic diagram of the 1st sensor which concerns on the modification of the 1st Embodiment of this invention. It is a schematic diagram of the 2nd sensor which concerns on the modification of the 1st Embodiment of this invention. It is a schematic diagram of the differential pressure measurement system which concerns on the 2nd Embodiment of this invention. It is the 1st schematic diagram of the 1st sensor concerning a 2nd embodiment of the present invention. It is the 2nd schematic diagram of the 1st sensor concerning a 2nd embodiment of the present invention. It is a 1st graph which shows the light intensity distribution of the irradiation light reflected inside the 1st sensor which concerns on the 2nd Embodiment of this invention. It is a 2nd graph which shows the light intensity distribution of the irradiation light reflected inside the 1st sensor which concerns on the 2nd Embodiment of this invention. It is a graph which shows the reflectance of the 1st sensor which concerns on the 2nd Embodiment of this invention. It is the 1st schematic diagram of the 2nd sensor concerning a 2nd embodiment of the present invention. It is the 2nd schematic diagram of the 2nd sensor concerning a 2nd embodiment of the present invention. It is a 1st graph which shows light intensity distribution of the 1st measurement light reflected inside the 2nd sensor which concerns on the 2nd Embodiment of this invention. It is a 2nd graph which shows light intensity distribution of the 1st measurement light reflected inside the 2nd sensor which concerns on the 2nd Embodiment of this invention. It is a graph which shows the reflectance of the 2nd sensor which concerns on the 2nd Embodiment of this invention. It is a graph which shows the reflectance of the 1st sensor and 2nd sensor which concern on the 2nd Embodiment of this invention. It is a 1st graph which shows the light intensity of the 2nd measurement light based on the 2nd Embodiment of this invention. It is a 2nd graph which shows the light intensity of the 2nd measurement light based on the 2nd Embodiment of this invention. It is a flowchart which shows the differential pressure | voltage measurement method which concerns on the 2nd Embodiment of this invention. It is a schematic diagram of the 1st sensor which concerns on the modification of the 2nd Embodiment of this invention. It is a schematic diagram of the 2nd sensor which concerns on the modification of the 2nd Embodiment of this invention. It is a graph explaining the influence of the interference which may arise with the 1st sensor concerning other embodiments of the present invention.

Explanation of symbols

4, 204… Light source
5, 105 ... 1st sensor
7A ... Signal processing device
15, 115… Second sensor
17A… Measurement module
21 ... 1st splitter
22 ... Second splitter
24, 301 ... 1st condensing part
25, 225 ... 1st pressure sensing part
29 ... Lens
30, 31, 32, 33, 34, 130, 131, 132… optical waveguide
124, 302… Second light collector
125, 325 ... 2nd pressure sensing part
151, 251 ... Light receiving element
170A ... Data storage device

Claims (18)

A light source;
A first sensor that changes light intensity of irradiation light emitted from the light source in response to a first external pressure with a first pressure sensitivity, and outputs the first measurement light as a first measurement light;
A second sensor that changes the light intensity of the first measurement light in accordance with a second external pressure with a second pressure sensitivity opposite in sign to the first pressure sensitivity, and outputs the second measurement light as a second measurement light;
A differential pressure measurement system comprising: a measurement module that measures a differential pressure between the first and second external pressures by measuring a light intensity of the second measurement light. The differential pressure measurement system according to claim 1, wherein the first pressure sensitivity is set so that the first external pressure and the light intensity of the first measurement light have a negative correlation. The first sensor is
A first light collecting part for collecting the irradiation light;
It is arranged to be movable closer to the first light collecting unit than the focal point of the first light collecting unit, and moves on the optical axis of the first light collecting unit according to the first external pressure, and the light is collected. The differential pressure measuring system according to claim 1, further comprising: a first pressure sensing unit that reflects the irradiated light. 4. The second pressure sensitivity is set so that the second external pressure and the light intensity of the second measurement light have a positive correlation. 5. Differential pressure measurement system. The second sensor is
A second condensing unit that condenses the first measurement light;
It is arranged so as to be movable farther than the focal point of the second light collecting part, moves on the optical axis of the second light collecting part according to the second external pressure, and reflects the collected first measurement light The differential pressure measurement system according to any one of claims 1 to 4, further comprising: a second pressure sensing unit. The differential pressure measurement system according to claim 1, wherein the first pressure sensitivity is set so that the first external pressure and the light intensity of the first measurement light have a positive correlation. The first sensor is
A first light collecting part for collecting the irradiation light;
The first condensing unit is movably arranged farther than the focal point of the first condensing unit, moves on the optical axis of the first condensing unit according to the first external pressure, and reflects the collected irradiation light. The differential pressure measuring system according to claim 1, further comprising: 1 pressure sensing unit. 8. The second pressure sensitivity is set so that the second external pressure and the light intensity of the second measurement light have a negative correlation. The differential pressure measurement system described in 1. The second sensor is
A second condensing unit that condenses the first measurement light;
It is arranged to be movable closer to the second light collector than the focal point of the second light collector, moves on the optical axis of the second light collector according to the second external pressure, and is condensed. The differential pressure measurement system according to claim 1, further comprising: a second pressure sensing unit that reflects the first measurement light. Irradiating with irradiation light;
Changing the light intensity of the irradiation light emitted from the light source according to the first external pressure with the first pressure sensitivity, and outputting the first measurement light as the first measurement light;
Changing the light intensity of the first measurement light in accordance with a second external pressure with a second pressure sensitivity having a positive / negative sign opposite to the first pressure sensitivity, and outputting the second measurement light as a second measurement light;
Measuring the differential pressure between the first and second external pressures by measuring the light intensity of the second measurement light. The differential pressure measurement method according to claim 10, wherein the first pressure sensitivity is set so that the first external pressure and the light intensity of the first measurement light have a negative correlation. The step of outputting as the first measurement light comprises:
Condensing the irradiation light with a first condensing unit;
A first pressure-sensitive part that is arranged so as to be movable closer to the first light-collecting part than the focal point of the first light-collecting part and moves on the optical axis of the first light-collecting part according to the first external pressure The method for measuring a differential pressure according to claim 10, further comprising: reflecting the condensed irradiation light. 13. The second pressure sensitivity is set so that the second external pressure and the light intensity of the second measurement light have a positive correlation. Differential pressure measurement method. The step of outputting as the second measurement light comprises:
Condensing the first measurement light with a second condensing unit;
The second condensing portion is disposed so as to be distant from the focal point of the second light collecting portion, and is condensed by a second pressure sensing portion that moves on the optical axis of the second light collecting portion according to the second external pressure. The method for measuring differential pressure according to claim 10, further comprising: reflecting one measurement light. The differential pressure measurement method according to claim 10, wherein the first pressure sensitivity is set so that the first external pressure and the light intensity of the first measurement light have a positive correlation. The step of outputting as the first measurement light comprises:
Condensing the irradiation light with a first condensing unit;
Irradiated by the first pressure-sensitive part, which is arranged so as to be movable farther than the focal point of the first light-collecting part and moves on the optical axis of the first light-collecting part according to the first external pressure. The method for measuring differential pressure according to claim 10, further comprising: reflecting light. The said 2nd pressure sensitivity is set so that the said 2nd external pressure and the light intensity of the said 2nd measurement light may have a negative correlation, The any one of Claim 10, 15, 16 characterized by the above-mentioned. 2. The differential pressure measuring method described in 1. The step of outputting as the second measurement light comprises:
Condensing the first measurement light with a second condensing unit;
A second pressure-sensitive part that is arranged so as to be movable closer to the second light-collecting part than the focal point of the second light-collecting part and moves on the optical axis of the second light-collecting part according to the second external pressure The differential pressure measuring method according to claim 10, further comprising: reflecting the condensed first measuring light.

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