JP2010096597A - Optical sensor measuring device and optical sensor measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sensor measuring device improving measurement accuracy by correcting each detection error of a plurality of optical detection means by a simple method. <P>SOLUTION: This device includes: a Mach-zehnder interferometer 50 for allowing reflected light of light entering a wavelength changing type optical sensor 30 from a wide band light source 10 to interfere; a beam splitter 60 for splitting output light output from the Mach-zehnder interferometer 50 into each light having each different phase; a first photodetection means 21, a second photodetection means 22 and a third photodetection means 23 for detecting each output light having each different phase splitted by the beam splitter 60; a light intensity modulation means 1 for modulating the intensity of light so as not to interfere by the Mach-zehnder interferometer 50; and an MPU 3 for determining a detection value of incoherent light obtained by the light intensity modulation means 1, by the first photodetection means 21, the second photodetection means 22 and the third photodetection means 23, using it as a correction value, and correcting a measured value based on the correction value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical sensor measurement apparatus that measures physical quantities such as acceleration, displacement, and tilt, and a measurement method thereof.

Optical fibers are widely used mainly for communication, but extensive research has been conducted in the measurement field, and various optical fiber sensors have been put into practical use.
Among them, the wavelength change type optical sensor called FBG (Fiber Bragg Grating) has the features common to optical fiber sensors such as excellent resistance to lightning strike and electromagnetic noise, and excellent weather resistance. In addition, a plurality of optical sensors can be remotely measured by wavelength division multiplexing (WDM), and the distortion measurement accuracy is improved. Utilizing these features, many applications of optical fiber sensors to strain and displacement measurement have been studied and put into practical use.

As this optical fiber sensor, there is a conventional example shown in Non-Patent Document 1. A conventional example having the same configuration as the conventional example of Non-Patent Document 1 is shown in FIG.
In FIG. 10, the optical sensor measurement apparatus includes a broadband light source 10, a circulator 20 through which light emitted from the broadband light source 10 passes, and an FBG installed on the object to be measured after the light passing through the circulator 20 enters. The optical sensor 30 is provided. Then, the light reflected or transmitted only at a specific wavelength by the optical sensor 30 passes through the circulator 20 again, is sent to the optical element 40 that demultiplexes the reflected light, is branched into two, and enters the Mach-Zehnder interferometer 50. The Mach-Zehnder interferometer 50 has two optical paths 51 and 52 for providing an optical path difference. Lights that have passed through the different optical paths 51 and 52 are combined again by the beam splitter 60 and then branched into three. . The three-branched light has a phase difference of (2π / 3), and the light is converted into electric signals by three photoelectric converters 71, 72, 73 connected to the beam splitter 60, respectively. Amplification is performed by amplifiers 81, 82, and 83 connected to photoelectric converters 71, 72, and 73, and digital signals are converted by AD converters 91, 92, and 93, and calculated by MPU 100 to obtain a measured value.
The light intensity detected by the photoelectric converters 71, 72, 73 draws a sine wave as the wavelength of the optical sensor 30 changes. The phase change Δφ of the sine wave can be expressed by Equation (1).

In Equation (1), λ is the wavelength of the optical sensor, n is the refractive index of the optical fiber, d is the difference in optical path length between the two optical paths 51 and 52 of the Mach-Zehnder interferometer 50, and Δλ is the wavelength change of the optical sensor 30. Amount.
As can be seen from Equation (1), if the phase change is known, the wavelength change amount can be calculated. The phase change is demodulated using the output voltages of the amplifiers 81, 82 and 83. There are three amplifiers 81, 82, and 83, and each output voltage Vn can be expressed by Equation (2).

In Expression (2), α _n is a disturbance component due to a transient intensity change of light, C is a numerical value obtained by adding the dark current of the photoelectric converters 71, 72, and 73 and the DC component of the amplifier, and n is three amplifiers 81, 82, and 83 are shown, and n = 1-3. For example, V ₁ is the voltage value of the amplifier 81. The amount of phase change can be calculated from the outputs of the three amplifiers 81, 82, and 83 using Equation (3).

  Therefore, the MPU 100 performs the calculation of the formula (3), calculates the phase change amount from the three outputs of the amplifiers 81, 82, and 83, and then performs the calculation of the formula (1) to calculate the wavelength change amount. be able to. A measured value is obtained by converting the wavelength change amount into a physical quantity by the optical fiber sensor.

MDTodd, GAJohnson and CCChang, “Passive, light intensity-independent interferometric method for fiber Bragg grating interrogation”, ELECTRONINC LETTERS, 1999, Vol.35, No.22, p.1970-1971 (Publisher: “Institution of Engineering and Technology; Stevenage "

In the conventional example, as a precondition for performing the calculation of Expression (3), the outputs V ₁ , V ₂ , and V ₃ from the amplifiers 81, 82, and 83 need to have the same voltage amplitude amount and offset position. is there.
However, in reality, as shown in FIG. 11, the gain characteristics of the amplifiers 81, 82, and 83, the branch characteristics of the beam splitter 60, the characteristics of the photoelectric converters 71, 72, and 73, Due to variations in reflection characteristics of the optical sensor 30 to be measured, the amplitude amounts and offset positions of the three voltage outputs cannot be made uniform, and the measurement accuracy cannot be improved sufficiently.
Therefore, conventionally, before the measurement, the wavelength of the optical sensor 30 to be measured is changed until the phase angle of the formula (1) is rotated by 360 ° or more, and the output characteristics from the amplifiers 81, 82, 83 are grasped. Correction is performed before the calculation according to (3).

  In order to change the wavelength of the optical sensor 30, it is necessary to change a physical quantity that the optical sensor 30 is to measure, for example, acceleration, etc. Therefore, for example, the optical acceleration sensor after being installed in a structure is used as a conventional device. When the measurement is to be performed, it is necessary to actually change the wavelength by shaking the optical sensor 30 after the optical sensor 30 is connected. In practice, the structure is often large and the optical sensor 30 cannot be vibrated greatly. As a result, the wavelength change is insufficient, and the three amplifiers 81, 82, and 83 are rotated when the phase angle is rotated by 360 ° or more. Since the output characteristics cannot be grasped, there is a problem that the calculation of the formula (3) cannot be performed.

  An object of the present invention is to provide an optical sensor measurement device and an optical sensor measurement method that can improve measurement accuracy by correcting detection errors of a plurality of optical detection means by a simple method.

  The optical sensor measurement device of the present invention includes a light source, a wavelength change type optical sensor that is incident on the light that is emitted from the light source, and a reflection of the light that is incident on the wavelength change type optical sensor. An interferometer that makes light or transmitted light incident and interferes with the reflected light or transmitted light, a beam splitter that branches output light output from the interferometer into light of different phases, and is branched by the beam splitter. A plurality of light detecting means for detecting output lights having different phases, a light intensity modulating means for modulating light intensity so as not to cause interference by the interferometer, and interference by the interferometer obtained by the light intensity modulating means. And a calculation means for correcting a measurement value detected by the light detection means based on the correction value. That.

  In the optical sensor measurement method of the present invention, light emitted from a light source is incident on a wavelength-variable optical sensor installed on an object to be measured, and reflected or transmitted light of the light incident on the wavelength-variable optical sensor is used. Light that interferes with an interferometer, splits the output light output from the interferometer into light with different phases by a beam splitter, and detects output light with different phases branched by the beam splitter by a plurality of light detection means A sensor measurement method, wherein before measurement, the intensity of light is modulated so as not to interfere with the interferometer, the light that does not interfere is obtained by the light detection means as a correction value, and the light is calculated based on the correction value. The measurement value obtained by the detection means is corrected.

In the present invention having the above configuration, light is not interfered by the interferometer by the light intensity modulation means before the measurement. In this state, light from the light source is incident on the wavelength-variable optical sensor, and the reflected light or transmitted light incident on the wavelength-variable optical sensor is allowed to pass through the interferometer. Then, after the output light output from the interferometer is branched by a beam splitter, it is detected by a plurality of light detection means, and this detection value is used as a correction value.
In actual measurement, first, the light intensity modulation means is set so as to cause light interference with the interferometer, and then the measurement operation is performed as usual. That is, the light from the light source is incident on the wavelength change type optical sensor, and the reflected light or transmitted light of the light incident on the wavelength change type optical sensor is caused to interfere with the interferometer. After the output light output from the interferometer is branched into light having different phase differences by the beam splitter, the branched light is detected by the light detection means. The detected value is calculated by the calculation means, and in this calculation, a corrected numerical value is calculated based on the correction value.
Therefore, in the present invention, the light intensity modulation means prevents light interference by the interferometer, and the detection value detected by the light detection means in this state is used as a correction value, and the light detection means based on this correction value. Since the required measurement value is corrected, an appropriate measurement value can be easily obtained without changing the wavelength of the wavelength-changing optical sensor to be measured.
In the present invention, examples of the interferometer include a Mach-Zehnder interferometer and a Michelson interferometer (Twiman Green interferometer).

Here, in the present invention, the interferometer is a Mach-Zehnder interferometer, and the Mach-Zehnder interferometer preferably includes a plurality of optical paths, and the light intensity modulation means is provided in one of the optical paths. .
In the invention of this configuration, since the light intensity adjusting means is provided in one optical path of the Mach-Zehnder interferometer, it is possible to reliably achieve non-interference of light in the Mach-Zehnder interferometer, and to obtain a more accurate measurement value. Correction can improve the measurement accuracy.

The light source is a light source that irradiates light having a broad wavelength, and the wavelength change type optical sensor includes a plurality of light reflecting or transmitting lights having different wavelengths, and one measuring unit is constituted by the plurality of light detecting means. A configuration is preferably provided in which a branching unit is provided between these measurement units and the light source so as to divide and branch in a certain wavelength region.
In the invention of this configuration, light having a broad wavelength is emitted from the light source. Then, each of the plurality of wavelength change type optical sensors reacts at a predetermined wavelength, and reflects or transmits light corresponding to the wavelength. The reflected or transmitted light is branched for each predetermined region by a beam splitter, for example, branched into a high wavelength region and a low wavelength region, and is incident on each measurement unit. In each measurement unit, detection is performed in a high wavelength region and a low wavelength region, respectively. Therefore, in the present invention, detection is performed by dividing the wavelength region, so that the measurement accuracy is further improved.

The light intensity modulation means includes a switching element using bend loss of an optical fiber, a switching element using switching by a mirror, a switching element using refractive index change by an electro-optic effect, a switching element using switching by an acousto-optic effect, Either a switching element using a change in refractive index due to a temperature change or a switching element by inserting a light shielding material may be used, and among these, a switching element by inserting a light shielding material is preferable.
If a switching element by inserting a light shield is used, the structure of the switching element is simple and light switching can be performed reliably.

The light intensity modulating means preferably has a configuration that completely blocks the one optical path.
In the invention of this configuration, since one optical path of the Mach-Zehnder interferometer is completely blocked, light non-interference in the Mach-Zehnder interferometer can be achieved more reliably, and measurement accuracy is improved. Can be achieved.

The light source preferably has a light intensity modulation function.
In the invention of this configuration, when there is a change in the offset level of the photoelectric converter and the amplifier in the value (voltage value) detected by the light detection means, it is possible to perform highly accurate measurement.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, in the description of each embodiment, the same components are denoted by the same reference numerals, and description thereof is omitted or simplified.
[First Embodiment]
FIG. 1 shows a first embodiment of the present invention.
In FIG. 1, the optical sensor measurement apparatus of the first embodiment includes a broadband light source 10, an optical fiber F through which light emitted from the broadband light source 10 passes, a circulator 20 provided in the optical fiber F, and an optical fiber. And a wavelength change type optical sensor 30 provided on the other end side of F. The broadband light source 10 has the same structure as that of the conventional example, and irradiates the laser light into the optical fiber F with a predetermined period over a predetermined wavelength region.

The wavelength change type optical sensor 30 is a wavelength change type optical sensor called FBG (Fiber Bragg Grating), and is installed on an object not shown.
The circulator 20 is also connected to the optical fiber F. The circulator 20 sends the light emitted from the broadband light source 10 to the wavelength changing optical sensor 30 and reflects the reflected light of a predetermined wavelength reflected by the wavelength changing optical sensor 30 to the optical fiber. Send to F.
The optical fiber F is provided with an optical element 40, a Mach-Zehnder interferometer 50 having two optical paths 51 and 52 for providing an optical path difference, and a beam splitter 60.
The optical element 40 is a beam splitter that branches the reflected light sent from the circulator 20 to the two optical paths 51 and 52 of the Mach-Zehnder interferometer 50.
The Mach-Zehnder interferometer 50 includes two optical paths 51 and 52 each made of an optical fiber, and causes reflected light to interfere by the optical path difference between these optical paths 51 and 52.

The light intensity modulation means 1 is provided in one of the two optical paths 51 and 52 of the Mach-Zehnder interferometer 50, for example, in the optical path 52.
The light intensity modulation means 1 modulates the intensity of light so that the reflected light does not interfere with the Mach-Zehnder interferometer 50, and its specific means is not limited. For example, the configuration shown in FIG. 2 can be employed.
FIG. 2 shows a schematic configuration of the light intensity modulation means 1.
The light intensity modulation means 1 shown in FIG. 2A is an example of a switching element using a bend loss of an optical fiber.
In FIG. 2A, the light intensity modulation means 1 has a configuration in which an optical path 52 formed of an optical fiber is bent in a substantially ring shape and the bending radius _ro is adjusted. Pulling means (not shown) is provided on both sides of the optical path 52. When the light intensity modulating means 1 is operated, the light passing through the optical path 52 with a bending radius r (r < _ro ) is blocked. When the light intensity modulation means 1 is not operated, the tension means is loosened to allow the passage of light inside the optical path 52. The bending radius r when light is blocked is 10 mm or less, although it depends on the diameter of the optical path 52.

The light intensity modulation means 1 shown in FIG. 2B is an example of a switching element by inserting a light shielding object.
In FIG. 2B, the light intensity modulation means 1 divides an optical path 52 formed of an optical fiber into an optical path 52A and an optical path 52B, and a shielding object 1A is provided between the optical path 52A and the optical path 52B. It is a structure to insert or withdraw. The shield 1A may be of any material or shape as long as it shields light.
The shielding object 1A includes an advancing / retreating mechanism (not shown), for example, a nut fixed to the shielding object 1A, a ball screw screwed to the nut, and a motor connected to the ball screw. When operating, as shown by the imaginary line in FIG. 2B, the shielding object 1A is inserted between the optical path 52A and the optical path 52B, and when the light intensity modulation means 1 is not operated, FIG. As shown by the solid line B), the shield 1A is extracted from between the optical path 52A and the optical path 52B.

The light intensity modulation means 1 shown in FIG. 2C is an example of a switching element using switching by a mirror.
In FIG. 2C, the light intensity modulation means 1 divides an optical path 52 composed of an optical fiber into an optical path 52A and an optical path 52B, and the optical path 52A and the optical path 52B are respectively separated from the mirror 1B. In this configuration, the angles β1 and β2 are arranged. The mirror 1B can be rotated by a motor (not shown). The light emission angle β1 from the optical path 52A with respect to the mirror 1B and the light reflection angle β2 reflected from the mirror 1B toward the optical path 52B are the rotation angles of the mirror 1B. It depends on. When the light intensity modulation means 1 is operated, as shown by the imaginary line in FIG. 2C, the mirror 1B prevents the angle β1 and the angle β2 from matching. Thereby, even if the light emitted from the optical path 52A is reflected by the mirror 1B, it is not incident on the optical path 52B, and the light is blocked. On the other hand, when the light intensity modulating means 1 is not operated, as shown by the solid line in FIG. 2 (C), the mirror 1B makes the angle β1 and the angle β2 coincide with each other. Thereby, the light emitted from the optical path 52A is reflected by the mirror 1B and then enters the optical path 52B.

The light intensity modulation means 1 shown in FIG. 2D is a switching element that uses a change in refractive index due to an electro-optic effect or a switching element that uses a change in refractive index due to a temperature change.
In FIG. 2D, the light intensity modulation means 1 divides an optical path 52 formed of an optical fiber into an optical path 52A and an optical path 52B, and the refractive index is different between the optical path 52A and the optical path 52B. Two types of substances 1CA and 1CB are provided, and the refractive indexes n _A and n _B of these substances 1CA and 1CB are changed. In order to change the refractive indexes n _A and n _B of the substances 1CA and 1CB, the method using the refractive index change due to the electro-optic effect applies an electric field to one of the substances 1CA and 1CB, and the refractive index due to a temperature change. In the method using the change, one of the substances 1CA and 1CB is heated or cooled.

When the light intensity modulating means 1 is operated, the refractive index n _A of the substance 1CA and the refractive index n of the substance 1CB are utilized using the electro-optic effect and the temperature change, as shown by the imaginary line in FIG. _When the light emitted from the optical path 52A is totally reflected at the boundary surface between the substance 1CA and the substance 1CB and the light intensity modulation means 1 is not operated, the light intensity modulation means 1 is not operated as shown by the solid line in FIG. As shown in the drawing, the light emitted from the optical path 52A with the refractive index n _A of the substance 1CA and the refractive index n _{B of} the substance 1CB made the same by utilizing the electro-optic effect and the temperature change is the boundary surface between the substance 1CA and the substance 1CB. Is transmitted and incident on the optical path 52B.
In the present embodiment, besides the one shown in FIG. 2, a switching element using switching due to the acousto-optic effect can be adopted as the light intensity modulation means 1.

In FIG. 1, a beam splitter 60 branches output light output from the Mach-Zehnder interferometer 50 into light having different phases, and includes a first light detection means 21, a second light detection means 22, and a third light detection. Connected to means 23. The first light detection means 21, the second light detection means 22, and the third light detection means 23 are for detecting output light whose phase is branched into three by the beam splitter 60 and is different by (2π / 3). The detection signal is sent to the MPU 3 which is a calculation means.
The first light detection means 21 includes a first photoelectric converter 71 that converts the light transmitted from the beam splitter 60 into an electric signal, and a first amplifier 81 that amplifies the signal output from the first photoelectric converter 71. The first AD converter 91 converts the analog signal output from the first amplifier 81 into a digital signal.
The second light detection means 22 includes a second photoelectric converter 72 that converts the light transmitted from the beam splitter 60 into an electric signal, and a second amplifier 82 that amplifies the signal output from the second photoelectric converter 72. The second AD converter 92 converts the analog signal output from the second amplifier 82 into a digital signal.
The third light detection means 23 includes a third photoelectric converter 73 that converts the light transmitted from the beam splitter 60 into an electric signal, and a third amplifier 83 that amplifies the signal output from the third photoelectric converter 73. The third AD converter 93 converts the analog signal output from the third amplifier 83 into a digital signal.

The MPU 3 performs a predetermined calculation based on signals output from the first AD converter 91, the second AD converter 92, and the third AD converter 93, respectively.
At this time, the light intensity detected by the first photoelectric converter 71, the second photoelectric converter 72, and the third photoelectric converter 73 draws a sine wave with the wavelength change of the wavelength change type photosensor 30. The phase change Δφ of the sine wave can be expressed by the above-described equation (1). Then, the respective output voltages Vn of the first amplifier 81, the second amplifier 82, and the third amplifier 83 can be obtained from the above equation (2). Further, the phase angle φ (t) is calculated based on the voltage output of the first amplifier 81, the second amplifier 82, and the third amplifier 83 from the above equation (3).
The MPU 3 of the present embodiment obtains a detection value of light that does not interfere with the obtained Mach-Zehnder interferometer 50 by using the first light detection means 21, the second light detection means 22, and the third light detection means 23, and uses it as a correction value. A correction process for correcting the measurement value based on the correction value is performed.
Therefore, the light intensity modulation means 1 is operated so that there is no interference in the Mach-Zehnder interferometer 50, and voltage outputs from the first amplifier 81, the second amplifier 82, and the third amplifier 83 in a state without this interference are obtained. Let it be V _n-ref .

The output voltage V _n-ref calculated as a result of the modulation indicates the intensity of the reflected light from the wavelength change type photosensor 30 and the branching characteristics of the beam splitter 60 that are different for each wavelength change type photosensor 30. Therefore, the characteristics are grasped using V _n-ref , and the voltage output in the MPU 3 is corrected using equations (4-1), (4-2), and (4-3) at the time of actual measurement.

In Equation (4), V _nc represents the corrected voltage value. That is, V _1-c is the corrected voltage value of the first amplifier 81, V _{2 -c} is the corrected voltage value of the second amplifier 82, and V _{3 -c} is the corrected third amplifier 83. Is the voltage value. By applying these to Equation (3), the phase angle can be calculated.
In the first embodiment, before the measurement, the light intensity modulation means 1 is operated to modulate the light intensity so as not to interfere with the Mach-Zehnder interferometer 50. And the light which does not interfere is calculated | required by the 1st light detection means 21, the 2nd light detection means 22, and the 3rd light detection means 23, and it is set as a correction value.
Thereafter, the Mach-Zehnder interferometer 50 is brought into a state where interference does not occur without operating the light intensity modulation means 1, and a normal measurement operation is performed. The detection values detected by the first light detection means 21, the second light detection means 22, and the third light detection means 23 are corrected by the correction values described above and are calculated by the MPU 3 as correct measurement values.

Here, in this embodiment, normally, the light intensity is completely blocked and the voltage level after intensity modulation is V _n-ref , and the equations (4-1), (4-2), and (4-3) are directly applied. However, in a modulation method that cannot completely block light, for example, when the bendross shown in FIG. 2A is used as the light intensity modulation means 1, Equations (4-1) (4) using Equation (5) -2) The _coefficient V _n-ref used in (4-3) can be obtained. In Equation (5), V _n-ref is an output voltage (n = 1, 2, 3) when there is no interference, Vn is a voltage value before intensity modulation, and V _n-att is intensity modulation. , Attr indicates the intensity modulation ratio, and its change range is 0 <Attr ≦ 1.
That is, by using Expression (5), Expressions (4-1), (4-2), and (4-3) can be applied without completely eliminating interference.

Therefore, 1st Embodiment can have the following effects.
(1) A broadband light source 10, a wavelength change optical sensor 30 on which light emitted from the broadband light source 10 is incident and placed on the object to be measured, and reflection of light incident on the wavelength change optical sensor 30 A Mach-Zehnder interferometer 50 that makes light incident and interferes with reflected light, a beam splitter 60 that branches output light output from the Mach-Zehnder interferometer 50 into light having different phases, and a beam splitter 60 that branches the light. Light intensity modulation for modulating the light intensity so as not to interfere with the first light detection means 21, the second light detection means 22, the third light detection means 23, and the Mach-Zehnder interferometer 50. The detected value of the light which does not interfere with the means 1 and the light intensity modulating means 1 is used as the first light detecting means 21, the second light detecting means 22 and the third light detecting means 2. And an MPU 3 that corrects the measurement value based on this correction value, and calculates the correction value by modulating the light intensity so as not to interfere with the Mach-Zehnder interferometer 50 before measurement, Since a correction process for correcting the measurement values obtained by the first light detection means 21, the second light detection means 22, and the third light detection means 23 is performed based on the correction values, the wavelength change type optical sensor to be measured Appropriate measurement values can be easily obtained without changing the 30 wavelengths. Therefore, unlike the conventional case, it is not necessary to change the wavelength of the wavelength change type optical sensor to be measured, and therefore, an appropriate measurement value can be easily obtained.

(2) Since the Mach-Zehnder interferometer 50 includes two optical paths 51 and 52, and the light intensity modulation means 1 is provided in one of the optical paths 51 and 52, the non-light of the Mach-Zehnder interferometer 50 Interference can be reliably achieved. Therefore, the measurement accuracy can be improved by correcting the measurement value more accurately.

(3) If a switching element by insertion of the light shield 1A is used as the light intensity modulating means 1, the structure of the switching element is simplified, and light can be shielded and passed reliably. For this reason, the light intensity modulation means 1 operates reliably, and an accurate correction value can be obtained to improve measurement accuracy.

Next, a second embodiment of the present invention will be described with reference to FIG.
[Second Embodiment]
FIG. 3 shows a second embodiment of the present invention. The second embodiment is different from the first embodiment in the configuration of the light detection means, but the other configurations are the same as those in the first embodiment.
In FIG. 3, in the optical sensor measurement device of the second embodiment, the light detection means is composed of a first light detection means 21 and a second light detection means 22, and between the circulator 20 and the optical element 40. An optical element 41 for branching the reflected light sent from the circulator 20 to the optical element 40 and the fourth photoelectric exchanger 74 is provided. The fourth photoelectric exchanger 74 converts the light sent from the optical element 41 into an electric signal. Therefore, the light emitted from the broadband light source 10 passes through the circulator 20 and enters the wavelength change optical sensor 30, but the light reflected by the wavelength change optical sensor 30 only through the specific wavelength passes through the circulator 20 again. Then, the optical element 41 branches the light toward the fourth photoelectric converter 74 and the optical element 40. The light traveling toward the optical element 40 is branched into two by the optical element 40 and enters the Mach-Zehnder interferometer 50. The light that has passed through the Mach-Zehnder interferometer 50 is combined by the beam splitter 60 and split into two again. The bifurcated light has a phase difference of (2π / 3), and the light having different phases is converted by the first light detection means 21 and the second light detection means 22 and is calculated by the MPU 3.

At this time, the light intensity detected by the first photoelectric converter 71 of the first light detection means 21 and the second photoelectric converter 72 of the second light detection means 22 is the wavelength change in the wavelength change type photosensor 30. Along with this, a sine wave is drawn. The phase change Δφ of the sine wave can be expressed using Equations (6-1) (6-2) and Equation (7).
The DC offsets of the output signals of the first amplifier 81 and the second amplifier 82 are set to Voffset-1 and Voffset-2, the amplitudes are set to Vpp1 and Vpp2, and at the time of measurement, the MPU 3 uses the equations (6-1) and (6-2). The measurement data is processed by the method, and the phase angles φ ₁ and φ ₂ are calculated by the method shown in Equation (7).

In Equations (6-1) and (6-2), V _adi indicates data after processing, V ₁ indicates the output voltage of the first amplifier 81, and V ₂ indicates the output voltage of the second amplifier 82. In Equation (7), V _{pp represents} the amplitude of V _adi , and V _ref represents the output of the fourth photoelectric converter 74.
Which of φ ₁ and φ ₂ is used as measurement data is determined by whether or not the SelectFlag value in Expression (8) is 0 or more.
If the amount of light changes during measurement, an error occurs. Therefore, the fourth photoelectric converter 74 monitors and corrects the amount of light.
In the second embodiment, correction and measurement are performed in the same procedure as in the first embodiment.

Therefore, in 2nd Embodiment, there can exist the following effect other than the same effect as (1)-(3) of 1st Embodiment.
(4) The light detecting means is composed of the first light detecting means 21 and the second light detecting means 22, and the light is branched between the circulator 20 and the optical element 40 to the optical element 40 and the fourth photoelectric exchanger 74. Since the optical element 41 to be provided is provided, the third light detection means 23 required in the first embodiment is not required, and the structure of the apparatus is simplified.

Next, a third embodiment of the present invention will be described with reference to FIG.
[Third Embodiment]
FIG. 4 shows a third embodiment of the present invention. The third embodiment is different from the first embodiment in that there are a plurality of wavelength-changing optical sensors that reflect light of different wavelengths, and the first light detection means 21, the second light detection means 22, and the third light detection means 23. Are different from the first embodiment in that one measuring unit is configured, and a branching unit is provided between these measuring units and the broadband light source 10, and the other configurations are the same as those in the first embodiment. .

In FIG. 4, in the third embodiment, there are two types of wavelength-changing photosensors: a wavelength-changing photosensor 31 that reacts in the region of the high wavelength λ1 and a wavelength-changing photosensor 32 that reacts at the low wavelength λ2. Is provided.
In the third embodiment, one measurement is performed from the optical element 40, the Mach-Zehnder interferometer 50, the light intensity modulation means 1, the beam splitter 60, the first light detection means 21, the second light detection means 22, and the third light detection means 23. A unit is configured, and these measurement units are provided with two types of first measurement unit 2A and second measurement unit 2B.
Between the first measurement unit 2A and the second measurement unit 2B and the circulator 20, a WDM coupler 4 is provided as a branching unit that branches into two parts in a certain wavelength region.

  The WDM coupler 4 separates the reflected light of wavelength λ1 that reacts with the wavelength-changing optical sensor 31 and the reflected light of wavelength λ2 that reacts with the wavelength-changing optical sensor 32, and reflects the reflected light of wavelength λ1 on the measurement unit 2A side. The reflected light having the wavelength λ2 is sent to the optical element 40 and sent to the optical element 40 on the measurement unit 2B side. In the measurement unit 2A and the measurement unit 2B, correction and measurement are performed in the same procedure as in the first embodiment. In the third embodiment, two wavelength change type optical sensors and two measurement units are used. However, the present invention is not limited to this, and may be three or more according to the measurement target.

Therefore, in the third embodiment, the following operational effects can be achieved in addition to the same operational effects as (1) to (3) of the first embodiment.
(5) A plurality of wavelength-changing photosensors 31 and 32 having different reacting wavelengths are provided, and the reflected light of wavelength λ1 reflected from the wavelength-changing photosensor 31 and the reflected light of wavelength λ2 reflected from the wavelength-changing photosensor 32 are provided. An optical element 40, a Mach-Zehnder interferometer 50, a light intensity modulation means 1, a beam splitter 60, and a WDM coupler 4 for branching the reflected light are provided, and measurement is performed based on the wavelength λ1 branched by the WDM coupler 4. In order to configure the measurement unit 2A from the first light detection means 21, the second light detection means 22, and the third light detection means 23 and perform measurement based on the wavelength λ2 branched by the WDM coupler 4, the optical element 40, Mach-Zehnder interferometer 50, light intensity modulating means 1, beam splitter 60, first light detecting means 21, second light detecting means 22 and third light detecting means 23 to measuring unit 2B Configuration was. Therefore, the wavelength change type optical sensors 31 and 32 can be connected in series to one optical fiber F to perform measurement.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
[Fourth Embodiment]
FIG. 5 shows a fourth embodiment of the present invention. The fourth embodiment differs from the third embodiment in the arrangement position of the WDM coupler 4, and the other configurations are the same as those of the third embodiment.
In FIG. 5, in the fourth embodiment, one measurement unit is constituted by the first light detection means 21, the second light detection means 22, and the third light detection means 23. These measurement units are the first measurement unit 2C and the first measurement unit 2C. Two types of second measurement unit 2D are provided.
A WDM coupler 4 is provided between the first measurement unit 2 </ b> C and the second measurement unit 2 </ b> D and the beam splitter 60.

  This WDM coupler 4 separates the reflected light of wavelength λ1 and the reflected light of wavelength λ2, sends the reflected light of wavelength λ1 to measurement unit 2C, and sends the reflected light of wavelength λ2 to measurement unit 2D. In the measurement unit 2C and the measurement unit 2D, correction and measurement are performed in the same procedure as in the first embodiment.

Therefore, in the fourth embodiment, the following operational effects can be achieved in addition to the same operational effects as (1) to (3) and (5) of the third embodiment.
(6) Since the WDM coupler 4 is provided between the first measurement unit 2C and the second measurement unit 2D and the beam splitter 60, the optical element 40, the Mach-Zehnder interferometer 50, the light intensity modulation means 1, and the beam splitter 60. Therefore, the structure of the apparatus is simpler than that of the third embodiment.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
[Fifth Embodiment]
FIG. 6 shows a fifth embodiment of the present invention. The fifth embodiment differs from the first embodiment in the configuration of the wavelength change optical sensor, and the other configurations are the same as those in the first embodiment.
In FIG. 6, the wavelength change type optical sensor 33 of the fifth embodiment is a sensor using Fabry-Perot interference, and the wavelength change type optical sensor 33 is provided at a predetermined position of the optical fiber F.
In the fifth embodiment, the light emitted from the broadband light source 10 to one end of the optical fiber F reacts and is transmitted by the wavelength change type optical sensor 33, and this transmitted light enters the optical element 40. In this optical element 40, similarly to the first embodiment, the transmitted light is branched into two, and after the branched transmitted light passes through the Mach-Zehnder interferometer 50, the beam splitter 60 changes the phase to (2 / 3π). It is shifted and sent to the first light detection means 21, the second light detection means 22, and the third light detection means 23. In the first light detection means 21, the second light detection means 22, and the third light detection means 23, correction and measurement are performed in the same procedure as in the first embodiment.

Therefore, in the fifth embodiment, in addition to the same operational effects as (1) to (3) of the first embodiment, the following operational effects can be achieved.
(7) Since the wavelength change type optical sensor 33 is a sensor using Fabry-Perot interference and measurement is performed using the transmitted light of this sensor, a circulator is not required compared to the first embodiment. The structure of the device is simplified.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
[Sixth Embodiment]
FIG. 7 shows a sixth embodiment of the present invention. The sixth embodiment is different from the first embodiment in the configuration of the broadband light source and the correction method in the MPU 3, and the other configurations are the same as those in the first embodiment.
In FIG. 7, the broadband light source 11 of the sixth embodiment is a light source having a light intensity modulation function. The light emitted from the broadband light source 11 passes through the circulator 20, the light of a specific wavelength reacts with the wavelength change type optical sensor 30, and is sent to the optical element 40 and the Mach-Zehnder interferometer 50 by the circulator 20 as reflected light. Then, the beam splitter 60 splits the light into three lights by shifting the phase by (2π / 3), and the branched light is supplied to the first light detection means 21, the second light detection means 22, and the third light detection means 23. Sent to be processed by the MPU 3.

In the sixth embodiment, Expression (5) and Expressions (4-1), (4-2), and (4-3) are used for the calculation in the MPU3. Here, the calculations of the mathematical expressions (4-1), (4-2), and (4-3) are performed by the voltage offset levels of the amplifier circuits of the first photoelectric converter 71, the second photoelectric converter 72, and the third photoelectric converter 73. Only under conditions where no change occurs. When the offset level changes, an offset level correction value is obtained by applying intensity modulation to the broadband light source 11, and is set to V _n-ref obtained by Equations (4-1), (4-2), and (4-3). Subtract the offset level correction value. This correction value is obtained from Equation (9).

In Equation (9), V _n-offset represents an offset level correction value, and n = 1, 2, 3. n = 1 is the offset level correction value of the first photoelectric converter 71, n = 2 is the offset level correction value of the second photoelectric converter 72, and n = 3 is the offset level correction value of the third photoelectric converter 73. Value.
V _n-san represents the voltage values of the first amplifier 81, the second amplifier 82, and the third amplifier 83 after the intensity modulation of the broadband light source 11, SA _ttr represents the intensity modulation ratio of the light source, and 0 <SA _ttr <1. It is.
Using the correction values described above, the calculation in the MPU 3 is performed.

Therefore, in the sixth embodiment, in addition to the same operational effects as (1) to (3) of the first embodiment, the following operational effects can be achieved.
(8) Since the broadband light source 11 is a light source having light intensity modulation means, the voltage offset levels of the amplifier circuits of the first photoelectric converter 71, the second photoelectric converter 72, and the third photoelectric converter 73 are changed. However, it is possible to perform highly accurate measurement by calculating the correction value based on Equation (9).

Next, a seventh embodiment of the present invention will be described with reference to FIG.
[Seventh Embodiment]
FIG. 8 shows a seventh embodiment of the present invention. The seventh embodiment is different from the first embodiment in the configuration of the light source and the optical fiber provided with the wavelength change type optical sensor 30, and the other configurations are the same as those in the first embodiment.
In FIG. 8, the light source of the seventh embodiment is an excitation light source 12. In the middle of the optical fiber F, a rare earth-doped optical fiber EDF is provided. In this rare earth-doped optical fiber EDF, the rare earth is excited by the pumping light, and broadband spontaneous emission light is generated. The generated spontaneous emission light is incident on the wavelength change type optical sensor 30. The light reflected by the wavelength change type optical sensor 30 only at a specific wavelength is incident on the rare earth-doped optical fiber EDF doped with a rare earth such as erbium. Here, since the rare earth-doped optical fiber EDF is in an excited state, stimulated emission occurs when reflected light of a specific wavelength is incident. The reflected light from the wavelength-change optical sensor 30 whose light intensity has increased due to stimulated emission is incident on the circulator 20, the optical element 40, and the Mach-Zehnder interferometer 50, and then is branched into three by the beam splitter 60. After being converted into an electric signal by the means 21, the second light detection means 22, and the third light detection means 23, it is processed by the MPU 3.

Therefore, in the seventh embodiment, in addition to the same operational effects as (1) to (3) of the first embodiment, the following operational effects can be achieved.
(9) By providing the rare earth doped optical fiber EDF in the middle of the optical fiber F, the pumping light source 12 is used as the light source, an expensive broadband light source is unnecessary, and the cost of the apparatus can be reduced. Since an increase in the amount of reflected light of 10 dB or more can be expected as compared with the use of a broadband light source, an optical system with a large SN ratio can be constructed.

Next, an eighth embodiment of the present invention will be described with reference to FIG.
[Eighth Embodiment]
FIG. 9 shows an eighth embodiment of the present invention. The eighth embodiment is different from the first embodiment in the configuration of the interferometer, and the other configurations are the same as those in the first embodiment.
In FIG. 9, the interferometer of the eighth embodiment is a Michelson interferometer 53. The Michelson interferometer 53 reflects two light paths 51 and 52 and light emitted from these light paths 51 and 52, respectively. And a mirror 54 for returning to the optical paths 51 and 52. The light path 52 is provided with the light intensity modulation means 1. In the present embodiment, the Michelson interferometer includes an interferometer called a Twiman Green interferometer.
An optical element 40 composed of a beam splitter is provided at the ends of the optical paths 51 and 52. The optical element 40 is connected to the first light detection means 21 via the circulator 20, and further, the second light detection means 22 and the second light detection means 22 The three light detection means 23 are respectively connected.

  In the eighth embodiment, the light emitted from the broadband light source 10 passes through the circulator 20 and enters the wavelength change type optical sensor 30. The light reflected only at a specific wavelength by the wavelength change type optical sensor 30 passes through the circulator 20 again, is branched into two by the optical element 40 composed of a beam splitter, and enters the Michelson interferometer 53. The light incident on the Michelson interferometer 53 passes through the optical paths 51 and 52, is reflected by the mirror 54, and returns to the optical element 40. In this optical element 40, the lights incident from the optical path 51 and the optical path 52 are combined and then branched into three. The three-branched light is different in phase by (2π / 3), and one of these lights is sent to the first photoelectric converter 71 of the first light detection means 21 via the circulator 20, and the remaining two are Directly sent to the second photoelectric converter 72 of the second light detection means 22 and the third photoelectric converter 73 of the third light detection means 23. Then, similarly to the first embodiment, calculation processing is performed by the MPU 3.

Therefore, in the eighth embodiment, the same operational effects as the (1) to (3) of the first embodiment can be achieved, and the following operational effects can be achieved.
(10) Since the Michelson interferometer 53 is used as the interferometer, the yield is improved when all are constructed with an optical fiber optical system. Usually, when the optical path difference of a Mach-Zehnder interferometer is specified and manufactured, the intersection of the optical path differences is about 0.5 mm. However, it is difficult to produce a Mach-Zehnder interferometer with a 0.5 mm intersection by connecting beam splitters by fusion splicing. On the other hand, when the Michelson interferometer is used, the fusion splicing step is not necessary, and it is easy to suppress the crossing to 0.5 mm.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, in the present invention, the circulator 20 used in each of the above embodiments may be replaced with a beam splitter (coupler). Since the circulator 20 has a larger light quantity than the beam splitter, an optical system having a large S / N ratio can be constructed. On the other hand, since the beam splitter is cheaper than the circulator, the cost of the apparatus can be reduced. In the present invention, the circulator and the beam splitter are properly used depending on the apparatus.
Further, the interferometer of the present invention is not limited to a specific structure as long as it is configured to enter the reflected light or transmitted light of the light incident on the wavelength change type optical sensor and to interfere with the reflected light or transmitted light. The Mach-Zehnder interferometer and the Michelson interferometer (Twiman Green interferometer) are not limited to the above.
Furthermore, the wavelength change type optical sensor is a sensor using FBG (fiber Bragg grating) in the first to fourth embodiments, the sixth embodiment, and the seventh embodiment, and the Fabry-Perot in the fifth embodiment. In the present invention, the reverse, that is, in the first embodiment to the fourth embodiment, the sixth embodiment, and the seventh embodiment are sensors that use Fabry-Perot interference, and the fifth embodiment. In a form, it is good also as a sensor using FBG.

  The present invention can be used for measuring physical quantities such as strain, temperature, acceleration, displacement, inclination, pressure, and sound wave.

1 is a schematic configuration diagram of a first embodiment of the present invention. (A) to (D) are schematic configuration diagrams showing different light intensity modulation means. The schematic block diagram of 2nd Embodiment of this invention. The schematic block diagram of 3rd Embodiment of this invention. The schematic block diagram of 4th Embodiment of this invention. The schematic block diagram of 5th Embodiment of this invention. The schematic block diagram of 6th Embodiment of this invention. The schematic block diagram of 7th Embodiment of this invention. The schematic block diagram of 8th Embodiment of this invention. The schematic block diagram of a prior art example. The graph which shows the relationship between the output from the amplifier in conventional example, and time.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light intensity | strength modulation means, 1A ... Light shielding object, 2A, 2B, 2C, 2D ... Measurement unit, 3 ... MPU (calculation means), 4 ... WDM coupler (branch means), 10 ... Broadband light source, 11 ... Light intensity modulation Light source having function, 20 ... circulator, 21 ... first light detecting means, 22 ... second light detecting means, 23 ... third light detecting means, 30, 31, 32, 33 ... wavelength change type optical sensor, 50 ... Mach Zender interferometer, 51, 52, 52A, 52B ... optical path, 53 ... Michelson interferometer, 60 ... beam splitter, 71 ... first photoelectric converter, 72 ... second photoelectric converter, 73 ... third photoelectric converter, 74 ... 4th photoelectric exchanger, 81 ... 1st amplifier, 82 ... 2nd amplifier, 83 ... 3rd amplifier, 91 ... 1st AD converter, 92 ... 2nd AD converter, 93 ... 3rd AD converter, F ... light Fiber, EDF ... rare earth added Fiber

Claims (7)

  A light source, a wavelength-variable optical sensor that is incident on the object to be measured while the light emitted from the light source is incident, and the reflected or transmitted light of the light incident on the wavelength-variable optical sensor is incident on the light source. An interferometer that interferes with reflected light or the transmitted light, a beam splitter that branches output light output from the interferometer into light of different phases, and output light of different phases branched by the beam splitter are detected. A plurality of light detection means; a light intensity modulation means for modulating the light intensity so as not to interfere with the interferometer; and a light detection value obtained by the light intensity modulation means that does not interfere with the interferometer. An optical sensor measurement apparatus comprising: a calculation unit that calculates a correction value obtained by the unit and corrects a measurement value detected by the light detection unit based on the correction value. The optical sensor measurement apparatus according to claim 1,
The interferometer is a Mach-Zehnder interferometer, and the Mach-Zehnder interferometer includes a plurality of optical paths, and the optical intensity modulation means is provided in one of the optical paths. In the optical sensor measurement device according to claim 1 or 2,
The light source is a light source that irradiates light having a broad wavelength, and the wavelength change type optical sensor includes a plurality of light reflecting or transmitting lights having different wavelengths, and one measuring unit is constituted by the plurality of light detecting means. An optical sensor measuring apparatus, wherein a branching unit that branches in a predetermined wavelength region is provided between the measuring unit and the light source. In the optical sensor measurement device according to claim 2 or 3,
The optical sensor measuring device, wherein the light intensity modulating means has a switching element by inserting a light blocking object. The optical sensor measurement device according to claim 4,
The optical sensor measuring device, wherein the light intensity modulating means completely blocks the one optical path. The optical sensor measurement apparatus according to claim 1,
The optical sensor measurement apparatus, wherein the light source has a light intensity modulation function. The light emitted from the light source is incident on a wavelength change optical sensor installed on the object to be measured, and the reflected or transmitted light of the light incident on the wavelength change optical sensor is caused to interfere with the interferometer. The output light output from the light beam is split into light beams having different phases by a beam splitter, and the output light beams having different phases branched by the beam splitter are detected by a plurality of light detection means,
Before the measurement, the intensity of light is modulated so as not to interfere with the interferometer, the light that does not interfere is obtained as a correction value by the light detection means, and the measurement value obtained by the light detection means based on the correction value A method for measuring an optical sensor, wherein:

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