JP2003166891A - Physical quantity measuring method and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of measuring accurately the differential value of a physical quantity generated on the positions at a distance without being influenced by a surrounding environment or the like and without being influenced by a physical quantity which is not a measuring object. <P>SOLUTION: Light from a light source is inputted into a sensor pair constituted by a combination between a sensor generating the optical path difference in input light corresponding to the physical quantity which is a measuring object and the physical quantity which is not the measuring object and a sensor generating the optical path difference in input light corresponding to the physical quantity which is not the measuring object. Then, the light having the generated optical path difference outputted in response to the input is inputted into a sensor pair having the same optical path difference generation function prepared separately, and the light having the generated optical path difference outputted in response to the input is branched dually, and interference fringes are generated therefrom. The moving quantity corresponding to the differential value of the physical quantity which is the measuring object is detected by subtracting the moving quantity corresponding to the differential value of the physical quantity which is not the measuring object, to thereby measure the differential value of the physical quantity which is the measuring object. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a physical quantity measuring method and apparatus for measuring a difference value of a physical quantity such as pressure, and more particularly, to a difference value of a physical quantity generated at positions distant from each other in an ambient environment. TECHNICAL FIELD The present invention relates to a physical quantity measuring method and an apparatus for accurately measuring the physical quantity without being affected by the physical quantity of the non-measurement target.

[0002]

2. Description of the Related Art When controlling a plant such as a petroleum plant, it is sometimes required to measure a differential value of pressures of process fluids existing at positions distant from each other.

Conventionally, in such a case, FIG.
As shown in, by adopting a configuration in which a pressure gauge is provided at each of two measurement positions, by transmitting the measured values (electrical signals) of the two pressure gauges to an arithmetic circuit and performing difference processing, Two
The pressure difference generated at each measurement position is measured.

In addition to the above, as shown in FIG. 36B, a differential pressure gauge for measuring a differential value of pressure is prepared,
By using a pressure guiding tube to introduce the process fluid from each of the two measuring positions into the differential pressure gauge, the difference value of the pressure generated at the two measuring positions is measured.

The method using such a pressure guiding tube has a problem that the pressure guiding tube becomes clogged and measurement becomes impossible, or if the pressure guiding tube is damaged, the process fluid flows out to the outside.

Therefore, as shown in FIG. 36 (c), the pressure of the process fluid is propagated from each of the two measuring positions to the differential pressure gauge by using a remote seal for enclosing a filling liquid such as silicone oil. Then, the difference value of the pressure generated at the two measurement positions may be measured.

[0007]

However, a method is adopted in which a pressure gauge is prepared at each of two measurement positions, and differential processing is performed on the measurement values of the two pressure gauges by an arithmetic circuit. If so, it is necessary to prepare two expensive pressure gauges, which causes a problem of high cost.

On the other hand, when the method of introducing the process fluid into the differential pressure gauge from each of the two measuring positions by using the pressure guiding tube is used, the pressure guiding tube becomes clogged and the measurement cannot be performed. If the pressure tube is damaged, the process fluid will flow out.

On the other hand, when the method of transmitting the pressure of the process fluid from each of the two measuring positions to the differential pressure gauge by using the remote seal is used, clogging of the pressure guiding pipe and the process fluid flow out to the outside. Although there is no risk of it being damaged, since the two remote seals are arranged in different environments, there is a problem that the measurement accuracy is lowered due to the influence of temperature and the like. Moreover, this method has a problem that the sealed liquid leaks to the outside when the remote seal is broken.

There is a demand for the construction of a physical quantity measuring technique for solving such a problem. In constructing this physical quantity measuring technique, it is necessary to measure accurately without being affected by the physical quantity of the non-measurement target. We have to go.

The present invention has been made in view of the above circumstances, and makes it possible to accurately measure the difference value of physical quantities generated at positions distant from each other without being affected by the surrounding environment and the like. It is an object of the present invention to provide a new physical quantity measurement technique that enables accurate measurement without being affected by the physical quantity of the measurement target.

[0012]

To achieve this object, according to the present invention, a sensor for generating an optical path difference in input light according to a physical quantity of a measurement target and a physical quantity of a non-measurement target according to a reflection structure, According to the reflection structure, a plurality of sensor pairs configured by a combination of a sensor that generates an optical path difference in the input light according to the physical quantity of the non-measurement target, and the sensor pair provided in association with the sensor pair at the front stage, An optical path for transmitting the light emitted from the light source to the pair and an optical fiber means provided in association with each sensor pair other than the frontmost sensor pair and reversely transmitting the optical fiber means provided in association with the front sensor pair. Generation of an optical path difference that reversely transmits the optical fiber means for transmitting the light having the difference generated as an input to the pair of sensors and the optical fiber means provided in correspondence with the sensor pair at the last stage The detected light as an input, the optical means for demultiplexing the light into two, the detection means for detecting the interference fringes generated by the two demultiplexed light emitted from the optical means, and the detecting means. It is configured to include a calculating unit that calculates the difference value of the physical quantity of the measurement target from the fringe position of the detected interference fringes without being affected by the physical quantity of the non-measurement target.

When this configuration is adopted, a sensor pair which is a transmission destination of light of each optical fiber means is a sensor which generates an optical path difference in the input light according to the physical quantity of the measurement object and the physical quantity of the non-measurement object, A sensor in which a sensor that generates an optical path difference in input light is connected in parallel according to the physical quantity of the non-measurement target, or a sensor in which such a sensor is connected in series may be used.

In order to achieve this object, according to the present invention, according to the transmission structure, a sensor for generating an optical path difference in the input light according to the physical quantity of the measurement object and the physical quantity of the non-measurement object, and the transmission structure, A sensor pair configured by a combination of a sensor that generates an optical path difference in input light according to the physical quantity of the non-measurement target and a sensor pair in the front stage are provided in association with each other, and the light source emits light to the sensor pair. The optical fiber means for transmitting light and the sensor pair other than the frontmost sensor pair are provided in association with each other, and are connected in series to the front sensor pair, and the light having the optical path difference generated by the sensor pair is connected. An optical fiber means for transmitting the light to a pair of sensors as an input, and an optical means for demultiplexing the light into two by taking the light having an optical path difference generated by the sensor pair at the last stage as an input; Means Detection means for detecting an interference pattern generated by being branched into two emitted light,
And a calculating unit that calculates a difference value of the physical quantity of the measurement target without being affected by the physical quantity of the non-measurement target from the fringe position of the interference fringe detected by the detection unit.

When this configuration is adopted, a sensor pair serving as a transmission destination of light of each optical fiber means is a sensor that changes the optical path length given to the input light according to the physical quantity of the measurement object and the physical quantity of the non-measurement object. In some cases, a sensor that changes the optical path length given to the input light according to the physical quantity of the non-measurement target and an optical fiber means that bypasses these sensors are connected in parallel.

According to the present invention having such a configuration, the sensor for generating an optical path difference in the input light according to the physical quantity of the measurement object and the physical quantity of the non-measurement object, and the input light according to the physical quantity of the non-measurement object. At least two sensor pairs that are configured in combination with a sensor that generates an optical path difference are prepared, and one sensor of the sensor pair at the forefront stage has an optical path difference n ₁ ×
L ₁ (n ₁ is a refractive index, L ₁ is a length) generating function, and one sensor associated with that of the sensor pair in the next stage has an optical path difference n ₂ × L ₂ (n ₂ is a refractive index, If L ₂ is described in the example of having the function of generating length), through an optical fiber provided in association with the forefront of the sensor pairs, the emission light of the light source in the forefront stage sensor inputs Then, due to the function of generating the optical path difference n ₁ × L ₁ of the sensor at the forefront stage, if explained with a sensor having a reflection structure, the light whose optical path length does not change and the optical path length changes n ₁ × L ₁ And light is emitted.

These two lights are input to the sensor of the next stage through an optical fiber provided in association with the sensor pair of the next stage, and the optical path difference n ₂ × L ₂ of the sensor of the next stage is generated. According to the function, if a sensor having a reflective structure is used, light whose optical path length does not change and light whose optical path length changes by n ₂ × L ₂ are generated with this input light as a starting point.

Then, the sensor at the front stage receives the change in the optical path length of n ₁ × L ₁ and is input to the sensor at the next stage, where it is transmitted without being changed in the optical path length of n ₂ × L _2. And the light input to the sensor of the next stage without being affected by the change of the optical path length of n ₁ × L _{1 by} the sensor of the front stage, and there is the light transmitted by receiving the change of the optical path length of n ₂ × L _2. by doing,
A phase difference having a factor of (n ₁ × L ₁ −n ₂ × L ₂ ) occurs, which causes an optical path difference (n ₁ × L ₁ −n ₂ ×).
An interference fringe corresponding to L ₂ ) is generated on the sensor.

The fringe position of the interference fringe corresponding to this optical path difference (n ₁ × L ₁ −n ₂ × L ₂ ) causes an optical path difference in the input light depending on the physical quantity of the measurement object and the physical quantity of the non-measurement object. In the case of a sensor that makes the difference between the physical quantity of the measurement target and the difference value of the physical quantity of the non-measurement target, on the other hand, a sensor that generates an optical path difference in the input light according to the physical quantity of the non-measurement target. In the case of, it corresponds to the difference value of the non-measurement target physical quantity.

From now on, when the physical quantity to be measured is pressure and the physical quantity to be non-measured is temperature,
The position D _12a of the former interference fringe and the position D of the latter interference fringe
_12b is D _12a = D _12a (P, T) D _12b = D _12b (T) where P = P ₁ -P ₂ P ₁ : Pressure generated at the sensor position at the front stage P ₂ : The sensor at the next stage Pressure generated at the position T = T ₁ −T ₂ T ₁ : Temperature at the sensor position of the front stage T ₂ : Represented by a temperature at the sensor position of the next stage.

Therefore, the interference fringe position D _12a generated by one of the pair of sensors is ΔD _12a = C _12a ^(P) × ΔP + C _12a ^(T) × ΔT when the pressure difference and the temperature difference change. And changes.

Here, C _12a ^(P) represents the sensitivity with respect to the differential pressure, and can be obtained in advance by experiments as the moving amount of the interference fringes per unit differential pressure amount, which is obtained under the condition that the temperature difference is constant. it can. Further, C _12a ^(T) represents the sensitivity with respect to the temperature difference, and can be previously obtained by an experiment as the movement amount of the interference fringes per unit temperature difference obtained under the condition of the constant pressure difference.

On the other hand, the interference fringe position D _12b generated by the other sensor of the sensor pair changes as ΔD _12b = C _12b ^(T) × ΔT when the temperature difference changes.

Here, C _12b ^(T) represents the sensitivity with respect to the temperature difference, and it can be obtained in advance by an experiment as the movement amount of the interference fringes per unit temperature difference obtained under the condition that the differential pressure is constant. .

From this, in the present invention, first, the moving amount of the interference fringe position D _12b generated by the sensor which reacts only to the temperature in the sensor pair is obtained, and this is obtained in advance by the sensitivity C _12b ^{( The} temperature difference ΔT is obtained by dividing by ^T) .

Subsequently, the fringe position D _12a produced by the sensor responsive to both pressure and temperature within the sensor pair.
The moving amount ΔD _12a thus obtained, the temperature difference ΔT previously obtained, and the sensitivity C _12a ^(P) ,
C _12a ^(T) and ΔD _12a = C _12a ^(P) × ΔP + C _12a ^(T) × ΔT derived ΔP = (ΔD _12a −C _12a ^(T) × ΔT) / C _12a ^(P) By doing so, the differential pressure ΔP is measured.

As described above, according to the present invention, when measuring the difference value of the physical quantity measured at the distanced position, the optical fiber is used instead of the pressure guiding tube or the remote seal, and the optical interference is used. Since the difference value of the physical quantity is measured while canceling the influence of the physical quantity of the non-measurement target at the same time, the difference value of the physical quantity of the non-measurement target is cancelled. It becomes possible to accurately measure the difference value of the physical quantity to be measured without being influenced by the surrounding environment and the like, and to accurately measure the physical quantity of the non-measurement target.

That is, since all the light waves transmitted through the optical fiber undergo the same phase fluctuation, the interference due to the disturbance cancels each other out. Therefore, according to the present invention, they are generated at positions distant from each other. It becomes possible to accurately measure the difference value of the physical quantity without being influenced by the surrounding environment and the like, and also to accurately measure the difference value of the physical quantity without being influenced by the physical quantity of the non-measurement target.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to an embodiment in which a differential value of pressures generated at measurement points separated by a distance is measured.

FIG. 1 illustrates an embodiment of the present invention.

This embodiment example uses a first sensor pair 100 installed at a first measurement point and a second sensor pair 200 installed at a second measurement point to make a first measurement. The configuration is such that the difference value between the pressure generated at the point and the pressure generated at the second measurement point is measured.

The first sensor pair 100 is affected by the temperature at the first measurement point and at the first pressure temperature which causes an optical path difference in the input light in accordance with the pressure generated at the first measurement point. It is composed of a sensor 100a and a first temperature sensor 100b that generates an optical path difference in the input light according to only the temperature at the first measurement point.

On the other hand, the second sensor pair 200 is affected by the temperature at the second measurement point, and at the same time, the second pressure that causes an optical path difference in the input light according to the pressure generated at the second measurement point. It is composed of a temperature sensor 200a and a second temperature sensor 200b that generates an optical path difference in the input light according to only the temperature at the second measurement point.

The first pressure / temperature sensor 100a is a total reflection mirror 10 set on a pressure receiving member such as a diaphragm.
1a and a semi-transmissive mirror 102a, which is provided so as to face the total reflection mirror 101a and reflects a part of the input light, and transmits the remaining part, and the light transmitted through the semi-transmissive mirror 102a, are collimated. The lens 103a for irradiating the total reflection mirror 101a, and the semi-transmission mirror 102a and the total reflection mirror 101a.
If the distance to a is represented by L _1a , for the input light,
The case where the light is reflected by the semi-transmissive mirror 102a and the case where the light is totally reflected
2n _1a L _1a (n _1a is a semi-transparent mirror 1
Refractive index of the substance between 02a and the total reflection mirror 101a)
Optical path difference.

The first temperature sensor 100b is a total reflection mirror 101 set on a pressure receiving member such as a diaphragm.
b and a semi-transmissive mirror 102b which is provided so as to face the total reflection mirror 101b and reflects a part of the input light and transmits the remaining part of the input light, and the light transmitted through the semi-transmissive mirror 102b is collimated. It is composed of a lens 103b for irradiating the total reflection mirror 101b, and a semi-transmission mirror 102b and a total reflection mirror 101b.
If the distance between and is represented by L _1b , 2n _1b L _1b (n _1b is a half Transmission mirror 10
An optical path difference called a refractive index of a substance existing between 2b and the total reflection mirror 101b is generated.

On the other hand, the second pressure temperature sensor 200a is
It has the same structure as the first pressure temperature sensor 100a,
Total reflection mirror 2 set on a pressure receiving member such as a diaphragm
01a and a semi-transmissive mirror 202a that is provided so as to face the total reflection mirror 201a and reflects a part of the input light and transmits the remaining part of the input light, and collimates the light that passes through the semi-transmissive mirror 202a. Lens 203a for irradiating the total reflection mirror 201a
And a semi-transmissive mirror 202a and a total reflection mirror 20.
If the distance to 1a is represented by L _2a , the input light is reflected by the semi-transmissive mirror 202a and the total reflection mirror 20.
An optical path difference of 2n _2a L _2a (n _2a is a refractive index of a substance between the semi-transmissive mirror 202a and the total reflection mirror 201a) is generated between when reflected by 1a.

Further, the second temperature sensor 200b is
The total reflection mirror 201b having the same structure as that of the temperature sensor 100b and set on a pressure receiving member such as a diaphragm.
And a semi-transmissive mirror 202b, which is provided so as to face the total reflection mirror 201b and reflects a part of the input light and transmits the remaining part of the light, and the light transmitted through the semi-transmissive mirror 202b is collimated into a total light. If the distance between the semi-transmissive mirror 202b and the total reflection mirror 201b is represented by L _2b , the light is reflected by the semi-transmission mirror 202b. 2n _2b L _2b (n _2b is a semi-transmissive mirror 202) depending on whether it is reflected by the total reflection mirror 201b.
The optical path difference of (b) and the total reflection mirror 201b, which is the refractive index of the substance, is generated.

In the following, for convenience of explanation, “n _1a = n _2a ” is assumed, and when there is no pressure difference or temperature difference between the first measurement point and the second measurement point, “L _1a = L”. It is assumed that the first pressure / temperature sensor 100a and the second pressure / temperature sensor 200a which are _2a ″ are used.

For convenience of explanation, “n _1b = n _2b ” is assumed and “L _1b = L _2b ” when there is no temperature difference between the first measurement point and the second measurement point. It is assumed that the first temperature sensor 100b and the second temperature sensor 200b are used.

In the case of such a configuration, the first
When there is no pressure difference and temperature difference between the pressure and temperature generated at the measurement point of 1 and the pressure and temperature generated at the second measurement point, “L _1a = L _2a ”, and the semitransparent mirror 102a Since the substance between the total reflection mirror 101a and the substance between the semi-transmission mirror 202a and the total reflection mirror 201a is the same, "n _1a = n _2a " is obtained. Optical path difference 2n _1a L _1a generated by the temperature sensor 100a and optical path difference 2n _2a L generated by the second pressure temperature sensor 200a.
It matches _2a .

On the other hand, when there is a pressure difference between the pressure generated at the first measurement point and the pressure generated at the second measurement point, there is a difference between these two optical path differences. Moreover, this optical path difference is affected by temperature.

On the other hand, when there is no temperature difference between the temperature at the first measurement point and the temperature at the second measurement point,
“L _1b = L _2b ”, and the semi-transmissive mirror 102b and the total reflection mirror 1
01b and the material between the semi-transmissive mirror 202b and the total reflection mirror 201b are the same, so that "n
_1b = n _2b ”, the first temperature sensor 100b
Thus, the optical path difference 2n _1b L _1b generated by the above and the optical path difference 2n _2b L _2b generated by the second temperature sensor 200b coincide with each other.

On the other hand, when there is a temperature difference between the temperature at the first measurement point and the temperature at the second measurement point, there is a difference between the two optical path differences.

In the embodiment shown in FIG. 1, the difference between the pressure generated at the first measurement point and the pressure generated at the second measurement point is determined by detecting the difference between these optical path differences. And the second
The measurement is performed without being affected by the temperature at the measurement point.

In order to realize this, in the embodiment shown in FIG. 1, a light source 1 composed of an LED or the like which emits low coherent light (a light source 1 composed of a so-called white light source).
And a single mode optical fiber 2 for extracting the light emitted from the light source 1 and the first sensor pair 100 are provided so as to correspond to each other.
Optical fiber 3a for transmitting to 00, an optical demultiplexing coupler 50a for demultiplexing the light transmitted through the optical fiber 3a into two and inputting to the first sensor pair 100, and the optical fiber 2. An optical demultiplexer 4a that couples the optical fiber 3a and demultiplexes the light that is reversely transmitted through the optical fiber 3a, and a single-mode optical fiber 5 that extracts the light that is demultiplexed by the optical demultiplexer 4a. And a single mode optical fiber 3b that is provided in association with the second sensor pair 200 and that transmits the light extracted by the optical fiber 5 to the second sensor pair 200, and the light that transmits the optical fiber 3b. The optical demultiplexing coupler 50b that splits the light into two and inputs it to the second sensor pair 200 is coupled with the optical fiber 5 and the optical fiber 3b, and the light that is reversely transmitted through the optical fiber 3b is demultiplexed. Optical demultiplexing coupler 4 When an optical fiber 6 of the single-mode light is taken out for demultiplexing the optical demultiplexing coupler 4b, the optical demultiplexing coupler 7 which branched into two light extracted with the optical fiber 6,
A single-mode optical fiber 8a for extracting one of the demultiplexed lights of the optical demultiplexer 7 and a single-mode optical fiber 8 for extracting the other light of the optical demultiplexer 7 to be demultiplexed.
b, the line image sensor 9 that detects the interference fringes generated by the light emitted from the optical fibers 8a and 8b, and the fringe position of the interference fringes that the line image sensor 9 detects, at the first measurement point. An arithmetic unit 10 for calculating a pressure difference between the generated pressure and the pressure generated at the second measurement point.

As will be described later, the optical fibers 3a,
Regarding 3b, it is not necessary to be limited to the single mode, and it is also possible to use the multi mode.
Correspondingly, the optical fibers 2, 5, 6, 8a, 8b need not be limited to single-mode ones, and multimode ones can be used.

In the present invention having such a configuration, the first pressure temperature sensor 100a and the second pressure temperature sensor 200 are provided.
To explain in relation to a, as shown in FIG. 2A, after being reflected by the total reflection mirror 101a, the total reflection mirror 201a is reflected.
As shown in FIG. 2B, the transmission pattern of light reflected by and transmitted by the semitransparent mirror 102a.
2C, a transmission pattern (second transmission pattern) of light that is reflected by the semi-transmissive mirror 202a and then transmitted.
As shown in FIG. 5, a transmission pattern of light that is reflected by the semi-transmissive mirror 102a and then reflected by the total reflection mirror 201a (third
2) and a transmission pattern (fourth transmission pattern) of light that is reflected by the total reflection mirror 101a and then reflected by the semi-transmission mirror 202a to be transmitted, as shown in FIG. 2D. There will be a light transmission pattern.

Therefore, the phase difference of the light emitted toward the line image sensor 9 is generated by the combination of the first transmission pattern and the second transmission pattern as shown in (a) FIG. Phase difference = k × 2 (n _1a L _1a +
n _2a L _2a ) and (b) as shown in FIG. 4, a combination of the second transmission pattern and the fourth transmission pattern ((a) in the figure), the first transmission pattern and the third transmission pattern. Phase difference generated by combination with transmission pattern ((b) in the figure) = k
X2n _1a L _1a and (c) As shown in FIG. 5, a combination of the second transmission pattern and the third transmission pattern ((a) in the figure), the first transmission pattern and the fourth transmission pattern. Phase difference generated by combination with transmission pattern ((b) in the figure) = k
X2n _2a L _2a and (d) As shown in FIG. 6, the phase difference generated by the combination of the third transmission pattern and the fourth transmission pattern = k × 2 (n _1a L _1a −n _2a L _2a ),
There will be four types of phase differences.

Similarly, the first temperature sensor 100
b also in the relationship between the second temperature sensor 200b
There are four types of light transmission patterns shown in 2.
4 types corresponding to those shown in FIGS.
Phase difference k × 2 (n_1bL_1b+ N _2bL_2b), K × 2n
_1bL_1b, K × 2n_2bL_2b, K × 2 (n_1bL_1b-N
_2bL_2b) Will exist.

On the other hand, between the light emitted from the optical fiber 8a and the light emitted from the optical fiber 8b, which reaches an arbitrary point (z, 0) on the line image sensor 9, FIG.
There is an optical path difference Δ calculated according to the formula (Young's interferometer formula). Here, “h” indicates the distance between the line image sensor 9 and the tips of the optical fibers 8a and 8b, and “2a” indicates the distance between the tips of the optical fibers 8a and 8b.

From now on, the first pressure temperature sensor 100a
If if is described in relation to the second pressure temperature sensor 200a, the interference fringes produced on the line image sensor 9, if represents the coherence length of the emitted light of the light source 1 at l _c, l _c ≧ Δ-2 (n _1a L _1a + n _2a L _2a ) l _c ≧ Δ-2 (n _1a L _1a −n _2a L _2a ) l _c ≧ Δ-2n _1a L _1a l _c ≧ Δ-2n _2a L _2a l _c ≧ Δ + 2 (n _1a L _1a + n _2a L _2a ) l _c ≧ Δ + 2 (n _1a L _1a −n _2a L _2a ) l _c ≧ Δ + 2n _1a L _1a l _c ≧ Δ + 2n _2a L _2a = 2 (n _1a L _1a + n _2a L _2a ) Δ = 2 (n _1a L _1a −n _2a L _2a ) Δ = 2n _1a L _1a Δ = 2n _2a L _2a will show strong interference intensity. .

The intensity of the interference fringes generated on the line image sensor 9 can be simulated according to a model formula as shown in FIG. 8 if a beam having a beam intensity of Gaussian distribution is assumed.

Here, this model formula shows interference fringes generated by the first pressure temperature sensor 100a and the second pressure temperature sensor 200a, and n _1a included in the formula.
L _1a , n _2a L _2a will change with pressure and temperature.

The first temperature sensor 100b and the second temperature sensor 100b
Interference fringes generated by the temperature sensor 200b
Is the n of this model formula_1aL_1a, N_2aL_2aThat
N _1bL_1b, N_2bL_2b(This changes only with temperature
The strength will be calculated by the model formula in place of

FIG. 9 shows an example of the simulation.

Here, the simulation shown in FIG.
H shown in FIG. 7 is 100 mm, and a shown in FIG. 7 is 10 m
Letting m and n _1a be the refractive index of air 1 and n _2a be the refractive index of air 1, (a) L _1a = 150 μm, L _2a = 15
The interference fringes generated at 0 μm and (b) L _1a = 15
The simulation was performed by simulating the interference fringes generated when 0 μm and L _2a = 200 μm and (c) the interference fringes generated when L _1a = 150 μm and L _2a = 250 μm.

The symbol shown in the figure appears at a fixed position in the center.
The central interference fringes are 2 (n_1aL_1a-N_2aL_2a) Light
The interference fringe based on the road difference factor is 2n_1aL_1aOptical path difference
Interference fringes based on factors, is 2n_2aL_2aOptical path difference factor
Interference fringes based on _1aL_1a+ N_2aL_2a)
It is an interference fringe based on an optical path difference factor.

As can be seen from this simulation,
The interference fringes appear symmetrically and move in opposite directions as L _2a increases.

The optical path difference factor of 2 (n _1a L _1a −n _2a L _2a ) is the pressure generated at the first measurement point where the first pressure temperature sensor 100a is placed, and the second pressure temperature sensor 200.
The differential pressure from the pressure generated at the second measurement point where a is placed is shown, from which the moving amount of the interference fringes based on the optical path difference factor of 2 (n _1a L _1a −n _2a L _2a ) is detected. By doing so, the differential pressure can be measured.

[0060] However, since the first pressure temperature sensor 100a and the second pressure temperature sensor 200a is affected by the temperature, the interference fringe based on the optical path difference factor of the _{2 (n 1a L 1a -n 2a} L 2a) If the differential pressure is calculated based on the detected amount of movement of the differential pressure, the differential pressure measurement is affected by the temperature.

On the other hand, similarly, in the relationship between the first temperature sensor 100b and the second temperature sensor 200b, Δ = 2 (n _1b L _1b + n _2b L _2b ) Δ = 2 (n _1b L _1b −n _2b L _2b ) Δ = 2n _1b L _1b Δ = 2n _2b L _{2b A} strong interference intensity is exhibited.

The optical path difference factor of 2 (n _1b L _1b −n _2b L _2b ) is the temperature at the first measurement point where the first temperature sensor 100b is placed, and the second temperature sensor 20.
It shows the temperature difference from the temperature at the second measurement point where 0b is placed, from which this 2 (n _1b L _1b −n _2b L _2b )
The temperature difference can be measured by detecting the movement amount of the interference fringes based on the optical path difference factor.

The following condition l _c ≤ Δ-2 (n _1a L _1a -n _1b L _1b ) l _c for preventing the first pressure temperature sensor 100a and the first temperature sensor 100b from interfering with each other. ≦ Δ + 2 (n _1a L _1a −n _1b L _1b ) is satisfied, and the following condition l _c for preventing the second pressure temperature sensor 200a and the second temperature sensor 200b from interfering with each other is provided. The configuration is such that ≦ Δ−2 (n _2a L _2a −n _2b L _2b ) l _c ≦ Δ + 2 (n _2a L _2a −n _2b L _2b ).

The arithmetic unit 10 uses 2 (n _1a L _1a -n
_2a L _2a ), the movement amount of the interference fringes based on the optical path difference factor is detected, and the movement amount of the interference fringes based on the optical path difference factor 2 (n _1b L _1b −n _2b L _2b ) is detected and Based on this, the process of calculating the differential pressure between the pressure generated at the first measurement point and the pressure generated at the second measurement point is performed without being affected by the temperature.

10 and 11 show the processing contents of the arithmetic unit 10 in the form of flowcharts.

The arithmetic unit 10 performs the processing of the flowchart shown in FIG. 10 before starting the actual measurement,
The calculation parameter required for the actual measurement is calculated and stored in the memory.

That is, as shown in the flow chart of FIG.
First, in step 1, a differential pressure condition serving as a measurement reference is determined and stored in a memory.

Then, in step 2, the determined criteria
Under the condition of differential pressure of 2 (n_1aL_1a-N _2aL_2a) Optical path
Actually detecting the position of the interference fringe based on the difference factor
2 (n_1bL_1b-N_2bL_2b) Optical path difference factor
Actually detect the positions of the interference fringes and determine them
Save to memory as initial value of.

Here, from the simulation result of FIG.
As can be seen, there is no pressure between the first and second measurement points.
If there is no difference in force and temperature, "n_1aL_1a= N_2aL_2a"When
First pressure temperature sensor 100a and second pressure temperature
When using the sensor 200a, 2 (n_1aL_1a-N_2a
L_2aThe fringe position based on the optical path difference factor of 2) is 2 (n
_1aL_1a+ N_2aL_2a) And 2n_1aL_1aAnd 2n_2aL_2aLight
Closer to the center fringe than the position of the fringe due to the road difference factor
Be in position. And between the first measurement point and the second measurement point
If there is no temperature difference between the_1bL_1b= N_2bL_2bWill be
First temperature sensor 100b and second temperature sensor 200
When using b, 2 (n_1bL_1b-N _2bL_2b)
The interference fringe position based on the optical path difference factor is 2 (n_1bL_1b+ N_2b
L_2b) And 2n_1bL_1bAnd 2n_2bL_2bBased on the optical path difference factor
The position is closer to the central interference fringe than the position of the subsequent interference fringe.

On the other hand, the interference fringe position based on the optical path difference factor of 2 (n _1a L _1a −n _2a L _2a ) and 2 (n _1b L _1b −n _2b L)
_2b ) which of the interference fringe positions based on the optical path difference factor is closer to the central interference fringe is basically L _1a (which coincides with L _2a when there is no differential pressure and temperature difference) and L _{1a. 1b} (matches L _2b when there is no temperature difference)
It is determined by the size relationship between

As can be seen from this, the central interference fringes are
The order of appearance of the interference fringes as the starting point depends on design matters.
Can be uniquely determined, and from this, 2 (n_1a
L_1a-N_2aL_2a) The position of the interference fringes based on
And 2 (n_1bL_1b-N_2bL _2b) Optical path difference factor
The position of the interference fringes
Since it is possible, in Step 2, the determined differential pressure
Under the conditions, the positions of these interference fringes are actually detected and
Save these in memory as the initial value of the interference fringe position
To process.

The position of the interference fringes at this time is detected by, for example, taking the differential value of the pixel value output from the line image sensor 9 and detecting the position of the differential maximum value appearing in the prescribed order from the central interference fringe. Done in. In addition, in order to improve the resolution, it is preferable to detect the object at the symmetrical position.

Here, when the standard differential pressure condition is zero differential pressure, the central interference fringe becomes the initial value of the position of the interference fringe, so that the process of step 2 can be omitted.

Then, in step 3, in the vicinity of the determined standard differential pressure condition, the differential pressure is actually changed under the condition that the temperature difference is constant, and 2 (n _1a L _1a −n _2a L) at that time is changed. According to the movement amount of the interference fringe position based on the optical path difference factor _2a ), the sensitivity C _12a ^(P) regarding the differential pressure, which is obtained as the movement amount of the interference fringes per unit pressure difference amount, is obtained and stored in the memory.

Then, in step 4, the temperature difference is actually changed under the condition of constant differential pressure in the vicinity of the determined standard differential pressure condition, and 2 (n _1a L _1a −n _2a L at that time is changed. According to the movement amount of the interference fringe position based on the optical path difference factor _2a ), the sensitivity C _12a ^(T) relating to the temperature, which is obtained as the movement amount of the interference fringe per unit temperature difference, is obtained and stored in the memory.

Then, in step 5, in the vicinity of the determined standard differential pressure condition, the temperature difference is actually changed under the condition of constant differential pressure, and 2 (n _1b L _1b −n _2b L) at that time is changed. According to the movement amount of the interference fringe position based on the optical path difference factor _2b ), the sensitivities C _12b ^(T) relating to the temperature, which are obtained as the movement amount of the interference fringes per unit temperature difference, are obtained and those sensitivities are stored in the memory.

On the other hand, the arithmetic unit 10 measures the differential pressure without being affected by the temperature by performing the processing of the flowchart shown in FIG. 11 when the actual measurement is performed.

That is, when the arithmetic unit 10 starts the actual measurement, as shown in the flowchart of FIG. 11, first, in step 1, the optical path difference of 2 (n _1b L _1b −n _2b L _2b ) is calculated. The position of the interference fringe is detected based on the factor.

The position of the interference fringes at this time is detected by, for example, taking the differential value of the pixel value output from the line image sensor 9 and detecting the position of the differential maximum value appearing in the prescribed order from the central interference fringe. Done in. In addition, in order to improve the resolution, it is preferable to detect the object at the symmetrical position.

Then, in step 2, the difference value between the detected interference fringe position and the initial value of the corresponding interference fringe position stored in the memory is calculated to obtain 2 (n _1b L _1b -n _2b
The movement amount ΔD _12b from the initial value of the interference fringe position based on the optical path difference factor of L _2b ) is calculated.

Subsequently, in step 3, the calculated movement amount ΔD _12b is divided by the sensitivity C _12b ^(T) relating to the temperature stored in the memory to obtain the temperature at the first measurement point and the second The temperature difference ΔT from the temperature at the measurement point is calculated.

Then, in step 4, 2 (n _1a L _1a −n
_2a L _2a ) The position of the interference fringe based on the optical path difference factor is detected.

The position of the interference fringes at this time is detected, for example, by taking the differential value of the pixel value output from the line image sensor 9 and detecting the position of the differential maximum value that appears from the central interference fringes in a prescribed order. Done in. In addition, in order to improve the resolution, it is preferable to detect the object at the symmetrical position.

Then, in step 5, the difference value between the detected interference fringe position and the initial value of the corresponding interference fringe position stored in the memory is calculated to obtain 2 (n _1a L _1a −n _2a
The movement amount ΔD _12a from the initial value of the interference fringe position based on the optical path difference factor L _2a ) is calculated.

Subsequently, in step 6, the calculated movement amount ΔD _12a , the temperature difference ΔT calculated previously, the sensitivity C _12a ^(P) relating to the pressure stored in the memory, and the memory C are stored in the memory. From the sensitivity C _12a ^(T) related to the temperature and the standard differential pressure condition stored in the memory according to the above-described calculation formula of ΔP = (ΔD _12a −C _12a ^(T) × ΔT) / C _12a ^(P). The displacement of the differential pressure of is calculated.

Subsequently, in step 7, the current differential pressure is calculated by adding the calculated displacement of the differential pressure and the reference differential pressure condition stored in the memory, and the calculated differential pressure is used as the measurement result. Output.

In this way, the arithmetic unit 10 has 2 (n
It detects the amount of movement of the interference fringes based on optical path difference factor of _{1a L 1a -n 2a L 2a)} , 2 (n 1b L 1b -n 2b L 2b)
The movement amount of the interference fringe based on the optical path difference factor is detected,
Based on them, the pressure difference between the pressure generated at the first measurement point and the pressure generated at the second measurement point is calculated and output without being affected by the temperature.

In the embodiment described above, when there is no pressure difference or temperature difference between the first measurement point and the second measurement point, "n _1a L _1a = n _2a L _2a " is satisfied. It is assumed that the first pressure temperature sensor 100a and the second pressure temperature sensor 200a are used.

In this case, as can be seen from the simulation result of FIG. 9, 2 (n _1a L _1a −n _2a L) indicating the pressure difference and the temperature difference between the first measurement point and the second measurement point is shown. _2a )
The interference fringes based on the optical path difference factor are to move away from the central interference fringes as the absolute value of the differential pressure increases, starting from the position of the central interference fringes based on Young's interferometer. Become.

The present invention is not limited to the use of the first pressure / temperature sensor 100a and the second pressure / temperature sensor 200a having such a configuration, and it is possible to use the first measurement point and the second measurement point. The first pressure / temperature sensor 1 that has “n _1a L _1a ≠ n _2a L _2a ” when there is no pressure difference and temperature difference between the two.
00a and the second pressure temperature sensor 200a can also be used, in which case negative pressure can be measured.

That is, the first measurement point and the second measurement point
If there is no pressure difference or temperature difference between the_1aL_1a≠ n_2a
L_2aThe first pressure temperature sensor 100a and the second pressure temperature sensor 100a
When the pressure temperature sensor 200a is used, it is shown in FIG.
So that 2 (n_1aL_1a-N _2aL_2a) Optical path difference factor
Based on the position of the interference fringes other than the center interference fringe
And then 2 (n_1aL_1a-N_2aL_2a) Has a sign
The first measurement point and the second measurement point
For negative pressure such that the pressure difference between the measuring point is reversed
You will be able to measure.

However, the first pressure temperature sensor 100a is
Basically, the optical path difference is changed in response to the pressure generated at the first measurement point, and the second pressure temperature sensor 200
Since a basically changes the optical path difference in response to the pressure generated at the second measurement point, the temperature difference is not taken into consideration, and the difference between the first measurement point and the second measurement point is a. The first pressure temperature sensor 100a and the second pressure temperature sensor 200a are “n _1a L _1a ≠ n _2a L _2a ” when there is no pressure difference between the two.
Also by using, it is possible to measure a negative pressure such that the pressure difference between the first measurement point and the second measurement point is reversed.

As described above, the arithmetic unit 10 sets the reference differential pressure condition, detects the initial value of the interference fringes under the reference differential pressure condition, and detects the displacement therefrom.
Since the configuration is such that the pressure difference value is measured while considering the temperature difference, even with respect to the movement of the interference fringes showing the movement as shown in FIG. 12, the movement difference is detected to obtain the pressure difference pressure value. It can be measured.

Similarly, in the embodiment described above,
The first temperature sensor 10 having “n _1b L _1b = n _2b L _2b ” when there is no temperature difference between the first measurement point and the second measurement point.
0b and the second temperature sensor 200b are assumed to be used, the present invention is not limited to the use of the first temperature sensor 100b and the second temperature sensor 200b having such a configuration. When there is no temperature difference between the first measurement point and the second measurement point, the first temperature sensor 100b and the second temperature sensor 2 that satisfy “n _1b L _1b ≠ n _2b L _2b ”.
It is also possible to use 00b.

Further, in the embodiment described above, it is assumed that the single mode fiber is used as the optical fibers 3a and 3b, but it is also possible to use the multimode fiber.

Since the core diameter of the multimode optical fiber is larger than the core diameter of the single mode optical fiber, when the multimode optical fibers 3a and 3b are used, the first sensor pair having the Fabry-Perot structure is used. 10
The light returned from 0 is efficiently returned to the core of the optical fiber 3a (more precisely, the core of the optical fiber connected to the semi-transmissive mirrors 102a and 102b), and also returned from the second sensor pair 200 having the Fabry-Perot structure. The light is efficiently transmitted to the core of the optical fiber 3b (more precisely, the semi-transmissive mirrors 202a, 202a).
The advantage is that it is returned to the core of the optical fiber connected to b).

That is, as shown in FIG. 13, part of the light returned from the first sensor pair 100 or the second sensor pair 200 having the Fabry-Perot structure is returned to the cladding of the optical fiber 3a or the optical fiber 3b. However, if the core diameter of the optical fiber 3a or the optical fiber 3b is large, the proportion of the light returned to the clad becomes small, so that the light returned from the first sensor pair 100 or the second sensor pair 200. Is effectively returned to the core of the optical fiber 3a or the optical fiber 3b.

On the other hand, as can be seen from the model expression of the intensity of the interference fringes shown in FIG. 8, the interference fringes generated on the line image sensor 9 are called γ (A) having the attenuation coefficient defined by the coherence length l _c. It has a width defined by the coherence length l _c according to the attenuation term.

Therefore, if the interference fringes based on the optical path difference factor of 2 (n _1a L _1a −n _2a L _2a ) do not deviate from the width of the central interference fringe based on Young's interferometer, 2 (n _1a L _1a −
The movement of the interference fringes based on the optical path difference factor of n _2a L _2a ) cannot be detected.

If the interference fringes based on the optical path difference factor of 2 (n _1b L _1b −n _2b L _2b ) do not deviate from the width of the central interference fringe based on Young's interferometer, 2 (n _1b L _1b − n _2b
The movement of the interference fringes based on the optical path difference factor of L _2b ) cannot be detected.

From now on, it is necessary to increase the length of L _1a , L _2a , L _1b and L _2b , and at that time, the optical fiber 3
a and the optical fiber 3b so that the light can be efficiently returned to the core of the optical fiber 3a and the optical fiber 3b.
It is necessary to increase the core diameter of b.

In this way, when the multimode optical fibers 3a and 3b are used, the first sensor pair 1
The light returned from 00 is efficiently returned to the core of the optical fiber 3a, and the light returned from the second sensor pair 200 is efficiently returned to the core of the optical fiber 3b. Obtained, whereby L _1a ,
By increasing the lengths of L _2a , L _1b and L _2b , it becomes possible to accurately measure the movement of the interference fringes based on the optical path difference factor of 2 (n _1a L _1a −n _2a L _2a ). At the same time, there is an advantage that the movement of the interference fringes based on the optical path difference factor of 2 (n _1b L _1b −n _2b L _2b ) can be accurately measured.

Next, the first pressure temperature sensor 100a, the second pressure temperature sensor 200a, and the first temperature sensor 100a.
The result of the simulation performed for the light amount loss based on b and the gap length L of the second temperature sensor 200b will be described.

This simulation is based on the beam propagation method (Beam Propagation Method) for solving Maxwell's electromagnetic wave equation.
thod) is mounted on a commercially available software package, the outer diameter of the optical fiber is 100 μm, the refractive index of the core of the optical fiber is 1.45, the refractive index of the cladding of the optical fiber is 1.447, and the wavelength of light is 0.4. The medium between 84 μm and the gap length L is the air layer, and the core diameter φ of the optical fiber is 10/20.
/ 40/60 μm, and the gap length L of the first sensor 100a and the second sensor 100b is 0.5 / 1 / 2.5 / 5/10.
/ 25/50/100 μm.

The results of this simulation are shown in FIGS. 14 to 16. Here, FIG. 15 shows a partially enlarged view of the simulation result of FIG. 14, and FIG. 16 shows a partially enlarged view of the simulation result of FIG.

In FIGS. 14 to 16, the horizontal axis represents the ratio (L / φ) of the gap length L and the core diameter φ, and the vertical axis represents the reflection with respect to the amount of incident light at the position where the light propagates backward in the optical fiber by 1 mm. The light amount loss (%) defined by the ratio with the light amount is shown.

As can be seen from the simulation result of FIG. 15, when the light quantity loss of 0.1% is used as a guide, the core diameter φ
Is 10 μm, the upper limit of the ratio (L / φ) between the gap length L and the core diameter φ is about 0.5, and it can be seen that the upper limit of the gap length L is about 5 μm. When the core diameter φ is 20 μm, the upper limit of the ratio (L / φ) between the gap length L and the core diameter φ is about 0.8.
Therefore, the upper limit of the gap length L is about 16μ.
It turns out that it is m. When the core diameter φ is 40 μm, the upper limit value of the ratio (L / φ) between the gap length L and the core diameter φ is about 1.2, and the upper limit value of the gap length L is about 48 μm. I know there is. When the core diameter φ is 60 μm, the upper limit value of the ratio (L / φ) between the gap length L and the core diameter φ is about 1.5,
It can be seen that the upper limit of the gap length L is approximately 90 μm.

As can be seen from the simulation results of FIG. 16, when the light amount loss of 0.01% is used as a guide and the core diameter φ is 10 μm, the ratio of the gap length L and the core diameter φ (L It can be seen that the upper limit of the gap length L is about 2 μm, since the upper limit of / φ) is about 0.2. When the core diameter φ is 20 μm,
The upper limit of the ratio (L / φ) between the gap length L and the core diameter φ is about 0.2, and it can be seen that the upper limit of the gap length L is about 4 μm. Also, the core diameter φ is 40
In the case of μm, the ratio of the gap length L and the core diameter φ (L /
It can be seen that the upper limit of φ) is about 0.4, and the upper limit of the gap length L is about 16 μm. Further, when the core diameter φ is 60 μm, the upper limit value of the ratio (L / φ) between the gap length L and the core diameter φ is about 0.5, and the upper limit value of the gap length L is about 30 μm. I know there is.

As described above, from the viewpoint of loss of light quantity, when the core diameter of the optical fiber 3a or the optical fiber 3b is given, the first pressure temperature sensor 100a, the second pressure temperature sensor 200a, or the first temperature sensor. There is an upper limit value for the gap length L of 100b and the second temperature sensor 200b.

For example, when using a commercially available single-mode optical fiber having a core diameter φ of 12.5 μm, in order to suppress the light quantity loss to 0.1%, the ratio of the gap length L to the core diameter φ is set. Since the upper limit of (L / φ) is about 0.6, the gap length L needs to be 7.5 μm or less. When using a commercially available multimode optical fiber having a core diameter φ of 50 μm, in order to suppress the light amount loss to 0.1%, the ratio of the gap length L to the core diameter φ (L / φ) Since the upper limit value of is about 1.35, the gap length L needs to be 67 μm or less. However, it is needless to say that the upper limit value is larger than this when allowing the loss of light amount to be large.

This condition is based on the assumption of the first pressure temperature sensor 100a, the second pressure temperature sensor 200a, the first temperature sensor 100b and the second temperature sensor 200b having the Fabry-Perot structure. Needless to say, when the pressure receiving portion has another structure such as an optical waveguide, the pressure receiving portion is not limited to such an upper limit value.

As described above, the first pressure / temperature sensor 1
00a and the gap length L of the second pressure temperature sensor 200a
When (L _1a, L _2a ) is increased, 2 (n _1a L _1a −n _2a L
_The interference fringes based on the optical path difference factor _2a ) greatly deviate from the width of the central interference fringes based on Young's interferometer.
This is advantageous because the movement of the interference fringe can be accurately detected.

Then, the first temperature sensor 100b and the second temperature sensor 100b
When the gap length L (L _1b, L _2b ) of the temperature sensor 200b of No. 2 is increased, the interference fringes based on the optical path difference factor of 2 (n _1b L _1b −n _2b L _2b ) become the central interference fringes based on the Young's interferometer. When the width of the interference fringe is greatly deviated, the movement of the interference fringe can be accurately detected, which is advantageous.

For example, the simulation result shown in FIG. 17A was performed based on the model formula shown in FIG. 8 with "L _1a = 6 μm, L _1b = 5 μm" assuming a single mode optical fiber. Simulation results are shown. In this case, since L _{1a and} L _2a are small, the interference fringes based on the optical path difference factor of 2 (n _1a L _1a −n _2a L _2a ) are based on Young's interferometer. It falls within the width of the central interference fringe, and the movement of the interference fringe cannot be substantially detected.

On the other hand, in the simulation result shown in FIG. 17B, assuming that a multimode optical fiber is used, "L _1a = 60 μm, L _1b = 35 μm" is obtained.
The simulation result based on the model formula shown in FIG. 8 is shown. In this case, the optical path difference of 2 (n _1a L _1a −n _2a L _2a ) can be obtained by making L _{1a and} L _2a large. When the interference fringes based on the factor deviate from the width of the central interference fringe based on the Young's interferometer, the movement of the interference fringes can be detected.

Here, the simulation results shown in FIGS. 17A and 17B are as follows: h = 100 mm, a = 1.0 mm, center wavelength λ ₀ = 850 nm, full width at half maximum of emission band Δλ = 22n
m, coherence length l _c (0.44 × λ ₀ ² / Δλ) = 14
.mu.m and sensor element length = 8 mm were assumed.

The coherence length l _c shown in the figure should not be compared with the sensor element length, but merely shows the width of the interference fringes defined by the coherence length l _c .

From the results of this simulation, it is concluded that a single mode optical fiber cannot be used, but this is not the case.

For example, the simulation result shown in FIG. 18 is set as “L _1a = 20 μm, L _1b = 7 μm” by assuming a single mode optical fiber, and the simulation result obtained based on the model formula shown in FIG. 8 is used. In this case, the interference fringes based on the optical path difference factor of 2 (n _1a L _1a −n _2a L _2a ) deviate from the width of the central interference fringe based on Young's interferometer, and the interference The movement of stripes can be detected.

Here, the simulation result of FIG. 18 shows that under conditions other than L _{1a and} L _2a , FIG.
This is the same as the simulation result shown in (b).

As can be seen from the simulation result of FIG. 18, the optical fiber does not have to be multimode, and a single mode fiber can be used.

Next, each constituent element of the present invention shown in FIG. 1 will be described in detail.

(A) Structure of Light Source 1 The light source 1 is a white light source that emits low coherent light. This is because when using light of high coherency, that the central interference fringe is not easily damped, its width is increased, _{thereby, 2 (n 1a L 1a -n} 2a L 2a) interference fringes based on optical path difference factor of Position or 2 (n _1b L _1b −n _2b L
_This is because it is impossible to accurately detect the position of the interference fringe based on the optical path difference factor _2b ).

19 to 22, 2 (n _1a L _1a -n
_2a L _2a ) is a specific example of the position of the interference fringe based on the optical path difference factor, and the result of the simulation performed to verify this is illustrated.

In this simulation, h shown in FIG. 7 is 100 mm, a shown in FIG. 7 is 10 mm, and n is n.
_1a is the refractive index of air 1, n _2a is the refractive index of air 1, the emission wavelength of the light source 1 is 850 nm, L _1a = 50 μm,
L _2a = 150 μm, 200 μm, 250 μm,
(A) The interference fringes generated when the full width at half maximum of the emission band of the light source 1 is 0.44 nm, and (b) the interference fringes generated when the full width at half maximum of the emission band of the light source 1 is 2.2 nm. ) Light source 1
The interference fringes generated when the emission band full width at half maximum of 22 nm was 22 nm, and the interference fringes generated when (d) the emission band full width at half maximum of the light source 1 was 44 nm were simulated.

The simulation result shown in FIG. 19 is the interference fringes generated when the full width at half maximum of the emission band of the light source 1 is 0.44 nm, and the simulation result shown in FIG. 20 is at the full width at half maximum of the emission band of the light source 1 of 2.2 nm. 21 is an interference fringe generated when the full width at half maximum of the light emission band of the light source 1 is 22 nm, and the simulation result shown in FIG. It is an interference fringe generated when the full width at half maximum is 44 nm.

Here, the coherence length l of the light source 1_cIs
Emission wavelength λ₀From the emission band full width at half maximum Δλ, l_c= 0.44 x (λ₀ ²/ Δλ) As shown in FIG. 19, the simulation shown in FIG.
Resulting coherence length l _cIs 722 μm, as shown in FIG.
Simulation result coherence length l_cIs 144μ
m, coherence of simulation results shown in FIG.
Long l_cIs 14 μm, the simulation result shown in FIG.
Coherence length l_cIs 7 μm.

From this simulation result, if the light source 1 that emits light with low coherency having a full width at half maximum of emission band of about 22 nm is prepared, 2 (n _1a L _1a −n _2a L _2a )
It has been verified that it is possible to detect the position of the interference fringe based on the optical path difference factor. Therefore, 2 (n _1b
It was verified that it is possible to detect the position of the interference fringe based on the optical path difference factor of L _1b −n _2b L _2b ).

That is, as the coherence length l _c increases, the width of the central interference fringes having the width defined by the coherence length l _c increases, so that 2 (n _1a L _1a −n
_The interference fringes based on the optical path difference factor of _2a L _2a ) are buried inside the central interference fringes, and it becomes impossible to detect the position of the interference fringes, so light of low coherency is emitted. It is necessary to use the light source 1.

In order to realize such low coherency light emission, as shown in FIG. 23, a plurality of light sources 1 having different emission wavelengths are prepared and transmitted to the optical demultiplexing coupler 4a. May be taken.

(B) Configuration of the first sensor pair 100 / second sensor pair 200 The first pressure / temperature sensor 100a constituting the first sensor pair 100 is of the same configuration except that a single pressure / temperature sensor 100a is used. You may make it use what is comprised by connecting in parallel a some thing with a structure using an optical fiber.

If such a plurality of parallel-connected structures are used as the first pressure / temperature sensor 100a, each sensor produces the same optical path difference of 2n _1a L _1a with respect to the input light. Since the average value is calculated, the pressure generated at the first measurement point can be detected with high accuracy.

Further, as the first temperature sensor 100b constituting the first sensor pair 100, a single temperature sensor having a single structure may be used, or a plurality of sensors having the same structure may be connected in parallel using an optical fiber. You may make it use what is comprised.

When such a plurality of parallel-connected configurations are used as the first temperature sensor 100b, each sensor produces the same optical path difference of 2n _1b L _1b with respect to the input light, and thus the optical temperature difference is increased. Since the average value has been calculated, the temperature at the first measurement point can be detected with high accuracy.

On the other hand, as the second pressure / temperature sensor 200a constituting the second sensor pair 200, one having a single structure is used, and a plurality of those having the same structure are connected in parallel using an optical fiber. You may make it use what is comprised.

When such a plurality of parallel-connected structures is used as the second pressure / temperature sensor 200a, each sensor produces the same optical path difference of 2n _2a L _2a with respect to the input light. Since the average value is calculated, the pressure generated at the second measurement point can be detected with high accuracy.

Further, as the second temperature sensor 200b forming the second sensor pair 200, in addition to using a single temperature sensor, a plurality of sensors having the same structure are connected in parallel by using an optical fiber. You may make it use what is comprised.

When such a plurality of parallel-connected structures is used as the second temperature sensor 200b, each sensor produces the same optical path difference of 2n _2b L _2b with respect to the input light, which results in an optical Since the average value is calculated, the temperature at the second measurement point can be detected with high accuracy.

(C) Structure of Young's Interferometer In the embodiment shown in FIG. 1, the optical demultiplexer coupler 7 is used.
Young's interferometer is configured by demultiplexing the light reversely transmitted from the second sensor pair 200 into the optical fiber 8a and the optical fiber 8b.

The method of constructing the Young's interferometer is not limited to such a construction method, and various construction methods as shown in FIGS. 24 and 25 can be used.

In the method of constructing Young's interferometer shown in FIG. 24, instead of the optical fibers 8a and 8b connected to the optical fiber 6 through the optical demultiplexing coupler 7, two optical fibers are provided on the front surface of the optical fiber 6. Light shield plate 12 with slits or pinholes
The Young's interferometer is configured by including.

In the method of constructing the Young's interferometer shown in FIG. 25, the Young's interferometer is constructed by connecting the two-mode optical fiber 13 instead of the single-mode optical fibers 8a and 8b. There is.

Here, 14 shown in FIG. 25 is a connector for connecting the optical fiber 6 and the optical fiber 13, and 15a, 1a.
Reference numeral 5b is a total reflection mirror that irradiates the line image sensor 9 with light emitted from the two-mode optical fiber 13.

(D) Configuration of Young's interferometer for expanding the measurement range In the embodiment shown in FIG. 1, the optical demultiplexer coupler 7 is used.
Young's interferometer is configured by demultiplexing the light reversely transmitted from the second sensor pair 200 into the optical fiber 8a and the optical fiber 8b.

In this case, the position of the interference fringes changes depending on the distance (2a shown in FIG. 7) between the tips of the optical fibers 8a and 8b. The simulation result shown in FIG. 9 is the result of the simulation performed with a = 10 mm.

FIG. 26 shows the result of a simulation performed with a = 20 mm and other conditions unchanged from the simulation shown in FIG. The upper part of the figure shows the result of the simulation performed with a = 20 mm, and the lower part shows the result of the simulation performed with a = 10 mm (the one shown in FIG. 9).

As can be seen from the results of this simulation, when the distance between the tips of the optical fibers 8a and 8b is reduced, the spread of the spread of the interference fringe positions increases.

As can be seen from this, when the pressure difference to be measured is large, it is better to increase the distance between the tips of the optical fibers 8a and 8b. This is because if the distance is reduced, the pixel range of the line image sensor 9 may deviate when the pressure difference to be measured is large. On the other hand, when the pressure difference to be measured is small, it is better to reduce the distance between the tips of the optical fibers 8a and 8b. This is because if this distance is made small, the resolution will be improved.

Therefore, as shown in FIG. 27, the optical fiber 8a is used as a starting point, and the optical fiber 8b is constructed by a hierarchical structure of one or a plurality of stages of optical fibers that split the input light into two. From the starting point, the line image sensor 9 (may be composed of one or may be composed of a plurality. May be done)
It is preferable to adopt a configuration in which the measurement range is expanded by using the optical fibers in the final stage which emit light to have different emission intervals.

When this structure is used, the arithmetic unit 10
For example, first, the differential pressure is measured with the one having the largest differential pressure measurement range, and then, from the measured differential pressure, the most differential pressure measurement range within the pixel range of the line image sensor 9 is measured. By selecting a differential pressure measurement range with high resolution and using it to measure the differential pressure again, processing is performed so as to measure the final differential pressure.

(E) Configuration for Realizing Miniaturization of Device To realize miniaturization of the device for implementing the embodiment shown in FIG. 1, as shown in FIG. 28, an optical fiber 2 / optical demultiplexing coupler is used. 4a / optical fiber 5 / optical demultiplexing coupler 4b / optical fiber 6 / optical demultiplexing coupler 7 / optical fiber 8a / optical fiber 8
It is preferable to adopt a configuration in which b is integrated on one platform.

Further, even when the configuration for expanding the measurement range shown in FIG. 27 is used, as shown in FIG.
It is preferable to adopt a configuration integrated on one platform.

Here, the optical fiber 3a connected to the first sensor pair 100 and the optical fiber 3b connected to the second sensor pair 200 can be integrated on the platform to the extent possible. preferable.

In the embodiment shown in FIG. 1, a first pressure-temperature sensor 100a and a first pressure-temperature sensor 100a are used as the first sensor pair 100.
Of the second sensor pair 200, in which the second pressure temperature sensor 200a and the second temperature sensor 200b are connected in parallel by an optical fiber. Although the configuration of using is adopted, as shown in FIG. 30, as the first sensor pair 100, one in which a first pressure temperature sensor 100a and a first temperature sensor 100b are connected in series by an optical fiber is used, It is also possible to adopt a configuration in which the second pressure / temperature sensor 200a and the second temperature sensor 200b are connected in series by an optical fiber as the second sensor pair 200.

In the case of adopting this structure, in order to realize the series connection, the first pressure / temperature sensor 100a (first
In the case where the temperature sensor 100b) of 1) is in the former stage, the one in which the total reflection mirror 101a (total reflection mirror 101b) of the temperature sensor 100b) is replaced with a semitransparent mirror is used, and the second pressure temperature sensor 200a (second In the case where the temperature sensor 200b) is provided in the front stage, a total reflection mirror 201a (total reflection mirror 201b) of the temperature sensor 200b) is replaced with a semitransparent mirror.

Also in the case of adopting this configuration, in order to improve the measurement accuracy by calculating the optical average value, the first pressure temperature sensor 100a and the second pressure temperature sensor 200 are used.
a, the first temperature sensor 100b, and the second temperature sensor 20
As for 0b, it is also possible to use a device configured by connecting a plurality of devices having the same structure in parallel using an optical fiber.

Next, another embodiment of the present invention will be described. FIG. 31 illustrates another embodiment of the present invention.

Although there are two measurement points in the embodiment shown in FIG. 1, there are five measurement points in this embodiment.

In accordance with this, the embodiment shown in FIG.
In addition to the first sensor pair 100 and the second sensor pair 200, a third sensor pair 300 installed at a third measurement point
And a fourth sensor pair 400 installed at the fourth measurement point
And a fifth sensor pair 500 installed at the fifth measurement point.

The third sensor pair 300 has the same structure as that of the first sensor pair 100, and produces an optical path difference of 2n _3a L _3a in response to input light in response to pressure and temperature. At the same time, it reacts only with temperature to generate an optical path difference of 2n _3b L _3b .

On the other hand, the fourth sensor pair 400 has the same structure as the first sensor pair 100, and produces an optical path difference of 2n _4a L _4a in response to pressure and temperature with respect to input light. At the same time, it reacts only with temperature to generate an optical path difference of 2n _4b L _4b .

On the other hand, the fifth sensor pair 500 has the same structure as the first sensor pair 100, and produces an optical path difference of 2n _5a L _5a in response to pressure and temperature with respect to input light. At the same time, it reacts only with temperature to generate an optical path difference of 2n _5b L _5b .

In addition to preparing the third sensor pair 300 / fourth sensor pair 400 / fifth sensor pair 500, in addition to the configuration shown in FIG.
The single mode optical fiber 5α for extracting the demultiplexed light of b and the third sensor pair 300 are provided so as to correspond to each other, and the light extracted by the optical fiber 5α is provided for the third sensor pair 30.
A single-mode optical fiber 3c for transmitting to 0, an optical demultiplexing coupler 50c for demultiplexing the light transmitted through the optical fiber 3c into two and inputting to the third sensor pair 300, and an optical fiber 5α. An optical demultiplexing coupler 4c that couples the optical fiber 3c and demultiplexes the light that is reversely transmitted through the optical fiber 3c, and a single-mode optical fiber 5β that extracts the demultiplexed light of the optical demultiplexing coupler 4c. And the fourth sensor pair 400
The single mode optical fiber 3d for transmitting the light extracted from the optical fiber 5β to the fourth sensor pair 400 and the light transmitted through the optical fiber 3d are
The optical demultiplexing coupler 50d that splits the light into two and inputs it to the fourth sensor pair 400 is coupled with the optical fiber 5β and the optical fiber 3d, and the light that is reversely transmitted through the optical fiber 3d is demultiplexed. An optical demultiplexing coupler 4d, a single mode optical fiber 5γ for extracting the light demultiplexed by the optical demultiplexing coupler 4d,
A single-mode optical fiber 3e, which is provided in association with the fifth sensor pair 500 and transmits the light extracted by the optical fiber 5γ to the fifth sensor pair 500, and the optical fiber 3e.
The fifth sensor pair 50 is obtained by demultiplexing the transmitted light into two.
The optical demultiplexing coupler 50e input to 0, the optical fiber 5γ and the optical fiber 3e are coupled to each other, and the optical fiber 3e
And an optical demultiplexing coupler 4e that demultiplexes the light that is reversely transmitted, and the optical fiber 6 shown in FIG. 1 extracts the demultiplexed light of the optical demultiplexing coupler 4e and The configuration of transmitting to the wave combiner 7 is adopted.

According to this configuration, on the line image sensor 9, interference fringes based on the optical path difference factor of 2 (n _1a L _1a −n _2a L _2a ) and 2 (n _1a L _1a −n _3a L _3a ) are displayed. An interference fringe having an interference fringe position associated with the pressure difference between any two measurement points, such as an interference fringe based on the optical path difference factor, is generated.

As described above, by using the present invention of this embodiment, it becomes possible to measure the differential pressures at a plurality of measuring points at once with a sensor having a single structure, as shown in FIG.

The position of the interference fringes depends on the pressure difference (optical path difference).
Since the smaller the value, the closer the fringes are to the central fringe, the order of appearance of the fringes may change.However, in the case of normal measurement targets, the order of pressure differences may not change. Since it does not exist, the differential pressure measurement of such a plurality of measurement points according to the present invention becomes possible.

Here, even when the configuration of the embodiment shown in FIG. 31 is used, it is not necessary to limit the use of a single mode optical fiber to the optical fiber, and it is also possible to use a multimode optical fiber. is there.

Even when the configuration of the embodiment of FIG. 31 is used, the interference fringes generated when there is no pressure difference between the two measurement points will not coincide with the central interference fringe. It goes without saying that a sensor that produces interference fringes as shown can be used.

In the embodiment described above, the first pressure temperature sensor 100a having the function of changing the optical path difference given to the input light by moving the total reflection mirror 101a in response to the pressure is used. , The pressure difference is measured.

If the total reflection mirror 101a or the like moves in response to the magnetic field strength, the magnetic field strength difference can be measured by using the present invention. If the total reflection mirror 101a or the like moves in response to the electric field strength, By using the present invention, the difference in electric field strength can be measured. Thus, the invention is not limited in its application to measuring pressure differentials.

On the other hand, in the present invention, even if the total reflection mirror 101a or the like does not move, the total reflection mirror 101a and the semi-transmission mirror 10 are not changed.
By changing the refractive index of the substance between 2a, etc.,
A sensor having a function of changing the optical path difference given to the input light can also be used.

For example, depending on the type of high-molecular weight polymer, FIG.
As shown in FIG. 3, there is one in which the refractive index is changed depending on the temperature. If a polymer having such characteristics is placed between the total reflection mirror 101a and the semi-transmission mirror 102a, the temperature difference can be measured.

In general, a substance changes in temperature, changes in pressure, changes in concentration, changes in magnetic field,
When the electric field changes, its refractive index and length change,
As a result, the phase difference of passing light is changed.

From now on, a substance which is sensitive to such an external factor and changes the refractive index and the length is used.
By placing it between 1a etc. and the semi-transparent mirror 102a etc.,
Even if the total reflection mirror 101a or the like does not move, the pressure difference or the like can be measured by using the present invention.

Further, in the case of using a substance which changes the refractive index and the length sensitively to such an external factor, reflection such as the first pressure temperature sensor 100a shown in FIG. 1 is used. As shown in FIG. 34, transparent glass plates are arranged in parallel in place of the type sensor, and the refractive index and the length are changed between the two glass plates in response to such external factors. In some cases, a transmissive sensor that provides a change in the optical path length to the input light by placing a substance that causes the transmission is prepared.

FIG. 35 shows an embodiment of the present invention which is suitable for using such a transmission type sensor.

In this example embodiment, the first sensor pair 10
0 is a transmission type first pressure temperature having a structure as shown in FIG. 34 in which the optical path length is changed according to the pressure generated at the first measurement point while being influenced by the temperature at the first measurement point. A sensor 100a, a transmission-type first temperature sensor 100b having a structure as shown in FIG. 34 that changes the optical path length depending only on the temperature at the first measurement point, and a single-mode light that bypasses those sensors. Fiber 62
The configuration is such that one configured by parallel connection with a is used.

Then, as the second sensor pair 200, a structure as shown in FIG. 34 is used in which the optical path length is changed according to the pressure generated at the second measurement point while being influenced by the temperature at the second measurement point. Second pressure-temperature sensor 2 having
00a, a transmission-type second temperature sensor 200b having a structure as shown in FIG. 34 that changes the optical path length depending only on the temperature at the second measurement point, and a single-mode optical fiber that bypasses these sensors. The configuration is such that one configured by parallel connection with 62b is used.

In this case, the first pressure / temperature sensor 10
0a is an optical path length of n _1a L _1a (n _1a is a refractive index of a substance between the two glass plates) when passing through, if the distance between the two glass plates is represented by L _1a. If the first temperature sensor 100b expresses the distance between the two glass plates as L _1b , then n _1b L _1b (n _1b is between the two glass plates) when passing through the input light. (Refractive index of material) gives the optical path length.

On the other hand, the second pressure temperature sensor 200a is
If the distance between two glass plates is represented by L _2a , an optical path length of n _2a L _2a (n _2a is a refractive index of a substance between two glass plates) is given to the input light when passing through, If the second temperature sensor 200b expresses the distance between the two glass plates as L _2b , the second temperature sensor 200b receives the input light when passing through,
An optical path length of n _2b L _2b (n _2b is a refractive index of a substance between two glass plates) is given.

Hereinafter, for convenience of explanation, “n _1a = n _2a ” is assumed, and when there is no pressure difference or temperature difference between the first measurement point and the second measurement point, “L _1a = L It is assumed that the first pressure / temperature sensor 100a and the second pressure / temperature sensor 200a which are _2a ″ are used. Then, for convenience of explanation, “n _1b = n _2b ” is assumed, and when there is no temperature difference between the first measurement point and the second measurement point, “L _1b = L 2
It is assumed that the first temperature sensor 100b and the second temperature sensor 200b which are _2b "are used.

In the case of such a configuration, the first
When there is no pressure difference or temperature difference between the pressure and temperature generated at the measurement point of 1 and the pressure and temperature generated at the second measurement point, “L _1a = L _2a ” and the first pressure temperature Sensor 1
Since the substance between the two glass plates of 00a and the substance between the two glass plates of the second pressure / temperature sensor 200a are the same, “n _1a = n _2a ” is obtained. The optical path length n _1a L _1a given by the pressure temperature sensor 100a and the optical path length n _2a L _2a given by the second pressure temperature sensor 200a coincide.

On the other hand, when there is a pressure difference between the pressure generated at the first measurement point and the pressure generated at the second measurement point, the two optical path lengths differ. Moreover,
This optical path length will be affected by temperature.

On the other hand, the temperature generated at the first measurement point and the second
When there is no temperature difference between the temperatures generated by the measurement points, "L _1b = L _2b", and the first temperature sensor 100b
Since the substance between the two glass plates held by and the substance between the two glass plates held by the second temperature sensor 200b are the same, “n _1b = n _2b ” is obtained.
Optical path length n _1b L _1b given by the temperature sensor 100b of
And the optical path length n _2b L _2b given by the second temperature sensor 200b coincides.

On the other hand, when there is a temperature difference between the temperature generated at the first measurement point and the temperature generated at the second measurement point, the two optical path lengths are different.

In the embodiment shown in FIG. 35, the difference between the pressure generated at the first measurement point and the pressure generated at the second measurement point is determined by detecting the difference in these optical path differences. And a configuration in which the measurement is performed without being affected by the temperature at the second measurement point.

In order to realize this, in the embodiment shown in FIG. 32, the light source 1 composed of an LED or the like which emits low coherent light (the light source 1 composed of a so-called white light source).
And the light emitted from the light source 1 is taken out to obtain the first sensor pair 1
A single mode optical fiber 60a for transmitting to 00,
The light transmitted through the optical fiber 60a is demultiplexed into three, and the first
The optical demultiplexer coupler 61a input to the sensor pair 100, the optical demultiplexer coupler 63a that couples the three lights output from the first sensor pair 100, and the light that the optical demultiplexer coupler 63a couples to each other. A single mode optical fiber 60b that transmits to the second sensor pair 200, an optical demultiplexing coupler 61b that demultiplexes the light transmitted through the optical fiber 60b into three, and inputs to the second sensor pair 200; An optical demultiplexer coupler 63b for coupling the three lights output from the second sensor pair 200, and an optical demultiplexer coupler 63
The single mode optical fiber 6 for extracting the light to be coupled by b, the optical demultiplexing coupler 7 for demultiplexing the light extracted by the optical fiber 6 into two, and one of the demultiplexed light of the optical demultiplexing coupler 7 A single-mode optical fiber 8a to be taken out, a single-mode optical fiber 8b to take out the other light demultiplexed by the optical demultiplexing coupler 7, an optical fiber 8a and an optical fiber 8
From the line image sensor 9 that detects the interference fringes generated by the light emitted from b, and the fringe position of the interference fringes that the line image sensor 9 detects, the pressure generated at the first measurement point and the second measurement point And a calculation device 10 for calculating a pressure difference between the pressure and the pressure generated in.

According to this embodiment, the first pressure temperature sensor 100a and the second pressure temperature sensor 200a are used.
The first pressure temperature sensor 1
After passing through 00a, the second pressure temperature sensor 200a
And a transmission pattern of light transmitted through the optical fiber 62a that bypasses the first pressure / temperature sensor 100a and then the optical fiber 62b that bypasses the second pressure / temperature sensor 200a, First
Optical fiber 6 bypassing the pressure temperature sensor 100a of
2a, the transmission pattern of the light transmitted through the second pressure temperature sensor 200a, and the second pressure temperature sensor 200a transmitted through the first pressure temperature sensor 100a.
There are four types of light transmission patterns, that is, a light transmission pattern for transmitting the optical fiber 62b that bypasses a.

Considering that the optical path lengths given by the optical fibers 62a and 62b are fixed, when transmitted by the transmission pattern of, the optical path length of n _2a L _2a is given to the input light and transmitted by the transmission pattern of The input light is n _1a
An optical path length of L _1a is given, and thus, a phase difference of k × (n _1a L _1a −n _2a L _2a ) is included in the phase difference of the light emitted toward the line image sensor 9. Will exist.

The optical path difference factor of (n _1a L _1a −n _2a L _2a ) is the first path where the first pressure temperature sensor 100a is placed.
Of the pressure generated at the measurement point of the second pressure temperature sensor 20
Represents the differential pressure of the pressure and generated in the second measurement point to be placed with 0a, now, for detecting the amount of movement of the interference fringes based on optical path difference factor of the _{(n 1a L 1a -n 2a L} 2a) Therefore, the differential pressure can be measured.

However, since the first pressure temperature sensor 100a and the second pressure temperature sensor 200a are affected by the temperature, the interference fringes based on the optical path difference factor (n _1a L _1a −n _2a L _2a ) are generated. If the moving amount is detected and the differential pressure is calculated based on the moving amount, the differential pressure measurement affected by the temperature is performed.

On the other hand, in the relationship between the first temperature sensor 100b and the second temperature sensor 200b, the first temperature sensor 100b may be transmitted or bypassed, and then the second temperature sensor 200b may be transmitted or bypassed. Then, there are four types of light transmission patterns as described above, and as a result, the phase difference = k × (n _1b L _1b −n _2b L _2b )
There will be a phase difference.

The optical path difference factor of (n _1b L _1b −n _2b L _2b ) is the temperature at the first measurement point where the first temperature sensor 100b is placed and the second temperature sensor 200b where the second temperature sensor 200b is placed. Shows the temperature difference from the temperature at the measurement point, and the temperature difference is measured by detecting the movement amount of the interference fringe based on the optical path difference factor (n _1b L _1b −n _2b L _2b ). can do.

Therefore, even in the embodiment of FIG. 35,
While detecting the movement amount of the interference fringes based on the optical path difference factor of (n _1a L _1a −n _2a L _2a ), (n _1b L _1b −n
_2b L _2b ). The amount of movement of the interference fringes based on the optical path difference factor is detected, and based on them, the pressure generated at the first measurement point and the second measurement point are measured without being affected by temperature. It becomes possible to measure the pressure difference with the generated pressure.

Here, even in the case of using the configuration of the embodiment shown in FIG. 35, it is not necessary to limit the use of the single mode optical fiber to the optical fiber, and it is also possible to use the multimode optical fiber. is there.

Even when the configuration of the embodiment of FIG. 35 is used, the interference fringes generated when there is no pressure difference between the two measurement points will not coincide with the central interference fringe. It goes without saying that a sensor that produces interference fringes as shown can be used.

Also in the case of adopting the configuration of the embodiment shown in FIG. 35, in order to improve the measurement accuracy by calculating the optical average value, the first pressure / temperature sensor 100a and the second pressure / temperature sensor 100a are used.
Pressure temperature sensor 200a and first temperature sensor 100b
Alternatively, the second temperature sensor 200b may be configured by connecting a plurality of second sensors having the same structure in parallel using an optical fiber.

Further, in the embodiment of FIG. 35, the number of measurement points is two, but when the number of measurement points is three or more, an optical fiber and a sensor pair are connected in series. An optical demultiplexer coupler will be provided.

Further, also in realizing the embodiment shown in FIG. 35, as shown in FIG. 27, one or a plurality of stages of optical fibers for splitting the input light into two from the optical fiber 8a as a starting point. Of the optical fiber 8b as a starting point, the optical fiber 8b is used as a starting point, and the optical fiber 8b is divided into two. The optical fiber in the final stage that emits light has different emission intervals, and the measurement range is expanded. Is preferred.

Also in realizing the embodiment shown in FIG. 35, in order to achieve miniaturization, as shown in FIG. 28, as many optical fibers and optical demultiplexing couplers as possible are combined into one platform. It is preferable to adopt a configuration of integration.

[0201]

As described above, in the present invention, an optical fiber is used in place of a pressure guide tube, a remote seal, or the like when measuring a difference value of physical quantities measured at positions distant from each other. In addition to adopting a configuration in which the difference value is measured using interference, at the same time, a configuration is adopted in which the difference value of the physical quantity is measured in a form that cancels the influence of the physical quantity that is not the measurement target. It becomes possible to accurately measure the difference value of the physical quantity generated at a different position without being affected by the surrounding environment and the like, and also to accurately measure the physical quantity of the non-measurement target physical quantity.

That is, since all light waves transmitted through the optical fiber undergo the same phase fluctuation, interference due to disturbances cancel each other out. Therefore, according to the present invention, they are generated at positions distant from each other. It becomes possible to accurately measure the difference value of the physical quantity without being influenced by the surrounding environment and the like, and also to accurately measure the difference value of the physical quantity without being influenced by the physical quantity of the non-measurement target.

Further, according to the present invention, the difference value of the physical quantity measured at three or more positions distant from each other by distance,
This enables simultaneous and accurate measurement without being affected by the surrounding environment, etc., and also enables accurate measurement without being affected by the physical quantity of the non-measurement target.

[Brief description of drawings]

FIG. 1 is an example of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a light transmission pattern.

FIG. 3 is an explanatory diagram of a light transmission pattern.

FIG. 4 is an explanatory diagram of a light transmission pattern.

FIG. 5 is an explanatory diagram of a light transmission pattern.

FIG. 6 is an explanatory diagram of a light transmission pattern.

FIG. 7 is an explanatory diagram of a Young's interferometer.

FIG. 8 is a model formula of the intensity of interference fringes.

FIG. 9 is an explanatory diagram of a simulation result of interference fringe generation.

FIG. 10 is an explanatory diagram of an execution process of the arithmetic device.

FIG. 11 is an explanatory diagram of an execution process of the arithmetic device.

FIG. 12 is an explanatory diagram of movement of interference fringes.

FIG. 13 is an explanatory diagram of a sensor having a Fabry-Perot structure.

FIG. 14 is an explanatory diagram of a simulation result of light amount loss of a sensor having a Fabry-Perot structure.

FIG. 15 is an explanatory diagram of a simulation result of light amount loss of a sensor having a Fabry-Perot structure.

FIG. 16 is an explanatory diagram of a simulation result of light amount loss of a sensor having a Fabry-Perot structure.

FIG. 17 is an explanatory diagram of a simulation result of interference fringe generation.

FIG. 18 is an explanatory diagram of a simulation result of interference fringe generation.

FIG. 19 is an explanatory diagram of a simulation result of light source coherency.

FIG. 20 is an explanatory diagram of a simulation result of light source coherency.

FIG. 21 is an explanatory diagram of a simulation result of light source coherency.

FIG. 22 is an explanatory diagram of a simulation result of light source coherency.

FIG. 23 is an exemplary embodiment of a light source configuration.

FIG. 24 is an explanatory diagram of a method of configuring a Young's interferometer.

FIG. 25 is an explanatory diagram of a method of configuring a Young's interferometer.

FIG. 26 is an explanatory diagram of a simulation result of interference fringe generation.

FIG. 27 is an example of an embodiment of a configuration for expanding the measurement range.

FIG. 28 is an exemplary embodiment of an integrated configuration.

FIG. 29 is an exemplary embodiment of an integrated configuration.

FIG. 30 is another configuration example of the sensor pair.

FIG. 31 is another embodiment example of the present invention.

FIG. 32 is an explanatory diagram of a usage pattern of the present invention.

FIG. 33 is an explanatory diagram of characteristics of a high molecular polymer.

FIG. 34 is an explanatory diagram of a transmissive sensor that gives an optical path difference to input light.

FIG. 35 is another embodiment example of the present invention.

FIG. 36 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

1 light source 2 optical fiber 3a optical fiber 3b optical fiber 4a Optical demultiplexer coupler 4b Optical demultiplexer coupler 5 optical fiber 6 optical fiber 7 Optical demultiplexer coupler 8a optical fiber 8b optical fiber 9 line image sensor 10 arithmetic unit 50a Optical demultiplexer coupler 50b Optical demultiplexer coupler 100 First sensor pair 100a First pressure temperature sensor 100b First temperature sensor 101a total reflection mirror 101b Total reflection mirror 102a Semi-transparent mirror 102b Semi-transparent mirror 103a lens 103b lens 200 Second sensor pair 200a Second pressure temperature sensor 200b Second temperature sensor 201a total reflection mirror 201b Total reflection mirror 202a semi-transparent mirror 202b Semi-transparent mirror 203a lens 203b lens

Continued front page    (72) Inventor Takaro Kuroiwa             2-12-19 Shibuya, Shibuya-ku, Tokyo Stock market             Takeyama F term (reference) 2F055 AA40 BB05 CC02 DD20 EE31                       FF02 FF34 FF38 GG32

Claims (17)

[Claims] 1. A sensor for generating an optical path difference in input light according to a physical quantity of a measurement target and a physical quantity of a non-measurement target, and a sensor for generating an optical path difference in input light according to a physical quantity of the non-measurement target. The light emitted from the light source is input to the sensor pair composed of a combination, and the light generated in the optical path difference by the sensor pair output in response to the input is the same as that prepared separately from the sensor pair. It is input to a sensor pair having an optical path difference generation function, and the light having an optical path difference generated by the other sensor pair is split into two to generate an interference fringe. A physical quantity measurement method characterized by calculating the difference value of the physical quantity of the measurement target without being affected by the physical quantity of. 2. A sensor for generating an optical path difference in input light according to a physical quantity of a measurement target and a non-measurement target, and a sensor for generating an optical path difference in input light according to a physical quantity of the non-measurement target. A plurality of sensor pairs composed of a combination, an optical fiber means for transmitting the light emitted from the light source to the frontmost sensor pair, and a light with an optical path difference generated by the front sensor pair to the pair of sensors Optical fiber means, optical means for demultiplexing the light having the optical path difference generated by the last pair of sensors, and detection means for detecting the interference fringes generated by the two demultiplexed light. And a calculation unit that calculates a difference value of the physical quantity of the measurement target from the fringe position of the interference fringes without being affected by the physical quantity of the non-measurement target. 3. A sensor that generates an optical path difference in input light according to a physical quantity of a measurement target and a physical quantity of a non-measurement target according to a reflection structure, and an input light according to a physical quantity of the non-measurement target according to a reflection structure. A plurality of sensor pairs constituted by a combination with a sensor for generating an optical path difference, an optical fiber means provided in association with the sensor pair at the frontmost stage and transmitting the light emitted from the light source to the sensor pair, Provided in association with each sensor pair other than the preceding sensor pair, as an input, the light generated optical path difference reverse transmission of the optical fiber means provided corresponding to the preceding sensor pair,
The optical fiber means for transmitting the light to the pair of sensors and the optical fiber means for the reverse transmission of the optical fiber means provided in correspondence with the sensor pair at the last stage are input, and the two light beams are input. The optical means for demultiplexing into two, the detecting means for detecting the interference fringes generated by the above-mentioned two demultiplexed light, and the fringe position of the above interference fringes are measured without being affected by the physical quantity of the non-measurement target. A physical quantity measuring device comprising: a calculating unit that calculates a difference value of a target physical quantity. 4. The physical quantity measuring device according to claim 3, wherein, as the sensor pair, a sensor that generates an optical path difference in input light according to a physical quantity of a measurement target and a physical quantity of a non-measurement target, and the sensor pair of the non-measurement target A physical quantity measuring device characterized in that a sensor that is connected in parallel with a sensor that generates an optical path difference in input light according to a physical quantity is used. 5. The physical quantity measuring device according to claim 3, wherein, as the sensor pair, a sensor that generates an optical path difference in input light according to a physical quantity of a measurement target and a physical quantity of a non-measurement target, and A physical quantity measuring device characterized in that a sensor that is connected in series with a sensor that generates an optical path difference in input light according to a physical quantity is used. 6. The physical quantity measuring device according to claim 4, wherein a plurality of sensors having the same structure are used as a sensor for generating an optical path difference in the input light according to the physical quantity of the measurement target and the physical quantity of the non-measurement target. A physical quantity measuring device characterized in that the two are connected in parallel. 7. The physical quantity measuring device according to claim 4, wherein a plurality of sensors having the same structure are connected in parallel as a sensor for generating an optical path difference in input light according to the physical quantity of the non-measurement target. A physical quantity measuring device characterized by using. 8. The physical quantity measuring device according to claim 3, wherein as the sensor, a gap length for realizing a reflection structure is defined by a core diameter of the optical fiber means forming a pair. A physical quantity measuring device characterized by using a material within the length. 9. A sensor for generating an optical path difference in input light according to a physical quantity of a measurement target and a physical quantity of a non-measurement target according to a transmission structure, and an input light according to a physical quantity of the non-measurement target according to a transmission structure. A plurality of sensor pairs constituted by a combination with a sensor for generating an optical path difference, an optical fiber means provided in association with the sensor pair at the frontmost stage and transmitting the light emitted from the light source to the sensor pair, A sensor that is provided in association with each sensor pair other than the preceding sensor pair, is connected in series to the preceding sensor pair, and receives the light with the optical path difference generated by the sensor pair as an input, and forms a pair of that light. Optical fiber means for transmitting to the pair, optical means for inputting the light having the optical path difference generated by the last sensor pair, and splitting the light into two, and generating by the light split into the two. Interference fringes A detecting means for detecting that, the fringe position of the interference fringes, further comprising a calculating means for calculating a difference value of the physical quantity to be measured without being affected by a physical quantity of non-analyte, the physical quantity measuring device according to claim. 10. The physical quantity measuring device according to claim 9, wherein, as the sensor pair, a sensor that changes an optical path length given to input light according to a physical quantity of a measurement target and a physical quantity of a non-measurement target, and the non-measurement target A physical quantity measuring device using a sensor in which a sensor that changes the optical path length given to the input light according to the physical quantity of and the optical fiber means that bypasses these sensors are connected in parallel. 11. The physical quantity measuring device according to claim 10, wherein a plurality of sensors having the same structure are used as sensors for changing the optical path length given to the input light according to the physical quantity of the measurement target and the physical quantity of the non-measurement target. A physical quantity measuring device characterized by using those connected in parallel. 12. The physical quantity measuring device according to claim 10, wherein a sensor in which a plurality of sensors having the same structure are connected in parallel is used as a sensor for generating an optical path difference in input light according to the physical quantity of the non-measurement target. A physical quantity measuring device characterized by the above. 13. The physical quantity measuring device according to claim 2, wherein as a combination of sensors that generate an optical path difference in input light according to the physical quantity of the measurement target and the physical quantity of the non-measurement target. A physical quantity measuring device characterized by using an apparatus that does not generate the same optical path difference when the difference value of the physical quantity of the measurement target is zero. 14. The physical quantity measurement device according to claim 2, wherein the physical quantity of the non-measurement target is a combination of sensors that generate an optical path difference in input light according to the physical quantity of the non-measurement target. A physical quantity measuring device characterized by using one that does not generate the same optical path difference when the difference value of is zero. 15. The physical quantity measuring device according to claim 2, wherein the light split into two by the optical means is input.
The optical means is composed of one or a plurality of stages of optical means for demultiplexing the input light into two, and the final stage optical means for emitting light to the detection means has different emission intervals. A physical quantity measuring device characterized by the above. 16. The physical quantity measuring device according to claim 2, wherein a part or all of the optical fiber means is formed on one substrate. And a physical quantity measuring device. 17. The physical quantity measuring device according to claim 2, wherein the calculating means detects the movement amount of the interference fringes pointed to by the difference value of the non-measurement target physical quantity in a merged form. The movement amount of the interference fringes indicated by the difference value of the physical quantity of the measurement target is detected, and the movement amount of the interference fringes indicated only by the difference value of the physical quantity of the non-measurement target is detected, and according to the detected movement amount. ,
A physical quantity measuring device characterized by calculating a difference value of a physical quantity of a measurement target without being affected by a physical quantity of a non-measurement target.