JP3516174B2 - Physical quantity detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various physical objects except for directly detectable electric quantities such as temperature, humidity, speed (acceleration), weight, and the like. TECHNICAL FIELD The present invention relates to a physical quantity detector forming a transmission system for inputting an electrical signal including primary detection information obtained from various detection elements for detecting a physical state (referred to as a physical quantity) and providing the detection information for measurement. 2. Description of the Related Art Conventionally, a general physical quantity detector can detect various physical quantities with respect to an object to be detected, and a detection element (sensor) adapted to the detection of the physical quantity is used. I have. Also, new research and development for improving the detection function are constantly being attempted. The information detected by the detecting element of the physical quantity detector is usually converted into an electric signal and transmitted to the inside of the detector, and the output electric signal is used for measurement display or measurement such as recording. That is, in a physical quantity detector, detection information on a physical quantity to be detected is obtained as an electric electric signal by so-called primary detection by a detecting element, and the electric signal is transmitted as it is to perform reception, measurement, recording, and the like. ing. In order to detect such various physical quantities, a dedicated detection element is generally used for each detection target, and the detection is performed so that the detection can be easily performed. [0005] In the case of the above-mentioned physical quantity detector, since the electric signal including the detection information is transmitted as it is, the electric signal may not be transmitted faithfully due to various factors. In such a case, the detection accuracy of the physical quantity is deteriorated. For example, when the transmission path of an electric signal is formed of a conductor cable, noise from outside enters the electric signal and is superimposed on the electric signal depending on the environment at the time of use. May be leaked. Also, depending on the electric signal to be transmitted, it is not uncommon for the routing of the conductor cable to suddenly cause noise, or for the mismatch of the ground potential between the detection unit and the reception unit to occur, which is also a cause of noise generation. Become. Further, when performing remote detection, the usable distance is limited due to the transmission loss of the conductor cable. On the other hand, as a countermeasure against such noise, it may be used in an environment that can also suppress minute fluctuations in the electric field. However, such environmental conditions are rarely satisfied, and lightning strikes and the like occur even in such an environment. If the possibility is high, detection and transmission will be hindered. SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. A technical problem of the present invention is to provide a physical quantity detector capable of detecting a physical quantity with high accuracy without being affected by environmental conditions during use. To provide. According to the present invention, a detection element for generating an electric signal between a pair of detection terminals in response to detection of a predetermined physical quantity with respect to a detection target, a pair of detection terminals, A pair of modulation electrodes connected to each other, and the intensity of transmission light transmitted to an optical waveguide disposed near the pair of modulation electrodes changes depending on an electric signal applied to the pair of modulation electrodes. An optical modulator, an incident optical waveguide in an optical waveguide, a transmission light generating section for generating input transmission light transmitted to the incident optical waveguide, an output optical waveguide in the optical waveguide, and an output transmission light transmitted from the output optical waveguide. And a photodetector that photoelectrically converts the light into an output electric signal, wherein the optical modulator includes a first lens that collects input transmission light emitted from the incident optical waveguide, and a collected light. Input transmission A light polarizer that polarizes light, a light modulator having a polarizer attached to one end face, and a pair of modulation electrodes attached to the side face, and a modulated input transmission light attached to the other end face of the light modulation element. , And a physical quantity detector including a second lens that collects the output transmission light and transmits the output transmission light to the output optical waveguide. A physical quantity detector according to an embodiment of the present invention will be compared with physical quantity detectors according to some comparative examples which are technical preconditions, and will be described in detail with reference to the drawings. Will be described. [Comparative Example 1] The physical quantity detector of Comparative Example 1 can respond to the detection of a predetermined physical quantity with respect to a detection target with reference to its basic configuration shown in FIG. 1 and its main configuration shown in FIG. And a pair of detection terminals 3
A detection element 40 for generating an electric signal therebetween, and a pair of modulation electrodes electrically connected to each other via a pair of detection terminals 3 and a conductor 4, and an optical waveguide arranged near the pair of modulation electrodes An optical modulator that changes the intensity of transmitted light depending on an electric signal applied to a pair of modulation electrodes; an input optical fiber that forms an incident optical waveguide in the optical waveguide; A transmission light generating section for generating input transmission light, an output optical fiber 7 forming an emission optical waveguide in the optical waveguide, and a light receiving element for generating an output electric signal by photoelectrically converting output transmission light transmitted from the output optical fiber 7. And a vessel 13. The transmission light generator includes a light source 11 such as a semiconductor laser and a power supply 12 for the light source.
The optical modulator 1 is mounted on a substrate 20 as a mounting portion and housed in a thin cylindrical container 8 made of a resin of an organic polymer material. Further, the optical modulator 1 forms an interferometer that splits the input transmission light in the incident optical waveguide 22 into two phase-shifted optical waveguides 24 and combines the split light with the output transmission light in the output optical waveguide 23 again. By providing 25 near the two phase-shifted optical waveguides 24, it functions as a transmitted light interference type optical waveguide element. That is, here, the optical modulator 1 is configured as a one-way transmission type in which transmission relating to input transmission light and output transmission is performed by an input optical fiber 6 and an output optical fiber 7, respectively. A Mach-Zehnder interferometer is formed by providing two phase-shifting optical waveguides 24 on the surface of a substrate 20 made of a lithium niobate crystal as shown in FIG. Are formed on top of each other. Further, this physical quantity detector is configured as a physical quantity measuring instrument by being combined with an oscilloscope 16 as a measuring instrument capable of measuring an output electric signal according to a predetermined physical quantity via a conductor cable 15. In this physical quantity measuring device, an electric signal including detection information is applied from a detection terminal 3 of a detection element 40 to a pair of modulation electrodes 25 of the optical modulator 1 and a light source 1
1 is transmitted to the optical modulator 1 through the input optical fiber 6. Here, the input transmission light is split by the two phase-shifted optical waveguides 24, passes near the pair of modulation electrodes 25, and joins at the output optical waveguide 23. At this time, the input transmission light is The output optical fiber 7 is modulated by an electric signal input to the optical fiber 7 into output transmission light whose intensity is changed.
Is transmitted to the photodetector 13 via. That is, the detection terminal 3
Is generated in the two phase-shifting optical waveguides 24 via the pair of modulation electrodes 25, and locally changes the refractive index. A phase difference is generated in the transmission light, and the transmission light interferes with each other in the exit optical waveguide 23 where the transmission light and the transmission light merge. As a result, the output transmission light in the emission optical waveguide 23 becomes light having a change in intensity depending on the voltage of the applied electric signal. Further, in the photodetector 13, the output transmission light is photoelectrically converted, transmitted to the oscilloscope 16 as an output electric signal, and subjected to measurement processing. It should be noted that the output electric signal may be subjected to further signal processing or the like. The optical modulator 1 used in Comparative Example 1 had a length of 50 mm, a width of 3 mm, and a thickness of 0.5 mm. [Comparative Example 2] The physical quantity detector of Comparative Example 2 can respond to detection of a predetermined physical quantity with respect to a detection target by referring to its basic configuration shown in FIG. 3 and its main part configuration shown in FIG. And a pair of detection terminals 3
A detection element for generating an electric signal therebetween, and a pair of modulation electrodes electrically connected to each other via a pair of detection terminals and a conductor; An optical modulator 1 'that changes the intensity of output transmission light in a reflection optical waveguide that receives input transmission light and transmits output transmission light reflected at the other end surface depending on an electric signal applied to a pair of modulation electrodes. And a polarization maintaining fiber 5 forming an optical waveguide for input transmission light and output transmission light.
An optical circulator 17 as an optical directional separator for separating the input transmission light and the output transmission light in the polarization maintaining fiber 5; and a transmission light generation for generating the input transmission light to be transmitted to the polarization maintaining fiber 5. And a photodetector 13 that photoelectrically converts output transmission light transmitted from the polarization maintaining fiber 5 to generate an output electric signal. Here, the transmission light generating section also comprises a light source section 11 such as a semiconductor laser and a power supply section 12 for the light source. The optical modulator 1 'is mounted on a substrate 20 as a mounting section and is made of an organic polymer material. It is housed in a thin cylindrical container 8 made of resin. Further, the optical modulator 1 'branches the input transmission light into two phase-shifted optical waveguides 24 and couples the input transmission light to the output transmission light again by reflection at the total reflection film 26 disposed on the other end surface of the reflection optical waveguide. In addition, a pair of modulation electrodes 25 are provided in the vicinity of the two phase shift optical waveguides 24 to function as a reflected light interference type optical waveguide element. That is, here, the optical modulator 1 'is of a reflection type in which the transmission of the input transmission light and the output transmission is shared by the optical waveguide 21 by one polarization maintaining fiber 5, and is composed of niobium. Two phase shift optical waveguides 24 are provided on the surface of a substrate 20 made of a lithium oxide crystal, and a pair of modulation electrodes 25 are formed on the surface of the phase shift optical waveguide 24 branched into two. Further, this physical quantity detector is also configured as a physical quantity measuring instrument by being combined with an oscilloscope 16 as a measuring instrument capable of measuring an output electric signal according to a predetermined physical quantity via a conductor cable 15. In this physical quantity measuring device, a pair of modulating electrodes 25 in the optical modulator 1 'are connected from the detecting terminal 3 of the detecting element 40.
Is applied to the optical modulator 1 'through the optical circulator 17 and the polarization maintaining fiber 5, and the input transmission light from the light source unit 11 is transmitted to the optical modulator 1'. Here, the input transmission light is split by the two phase-shifted optical waveguides 24, passes near the pair of modulation electrodes 25, and is reflected on the surface of the total reflection film 26 provided on the other end surface of the optical modulator 1 '. The light is reflected and again passes through the vicinity of the pair of modulation electrodes 25 and joins in the polarization maintaining fiber 5. At this time, the input transmission light and the output transmission light are modulated by the electric signal input to the optical modulator 1 ′ and the intensity The changed output transmission light is transmitted to the optical receiver 13 via the polarization maintaining fiber 5 and the optical circulator 17. That is, the electric signal guided from the detection terminal 3 generates an electric field in the two phase shift optical waveguides 24 through the pair of modulation electrodes 25 and locally changes the refractive index. Wave path 24
A phase difference occurs between the input transmission light and the output transmission light passing through the optical waveguide 21 in a reciprocating process, and they interfere with each other in the optical waveguide 21 where these merge. As a result, the output transmission light in the optical waveguide 21 becomes light having a change in intensity depending on the voltage of the applied electric signal. Further, in the photodetector 13, the output transmission light is photoelectrically converted, transmitted to the oscilloscope 16 as an output electric signal, and subjected to measurement processing. The output electric signal obtained here can be subjected to further signal processing or the like. Incidentally, the optical modulator 1 'used in Comparative Example 2 had a length of 25 mm, a width of 3 mm and a thickness of 0.5 mm. Similar effects can be obtained by using an optical directional coupler instead of the optical circulator 17 used here. [Embodiment] On the other hand, the physical quantity detector according to the embodiment of the present invention has the basic configuration shown in FIG. 5 and the main configuration shown in FIG. Except for the configuration, the configuration is the same as that of the physical quantity detector of Comparative Example 1. As shown in FIG. 6, the optical modulator 2 includes an input optical fiber 6 forming an incident optical waveguide.
A lens (first lens) 34 for collecting the input transmission light emitted from the light source, a polarizer 32 for polarizing the collected input transmission light, and a polarizer 32 attached to one end surface.
A Pockels device 31 as a light modulation device having a pair of modulation electrodes 25 attached to the side surface, and a Pockels device 31 attached to the other end surface of the Pockels device 31 via a wavelength plate 35, and detects and outputs modulated input transmission light. It comprises an analyzer 33 for emitting transmission light, and a lens (second lens) 34 for collecting the emitted output transmission light and transmitting the collected output transmission light to the output optical fiber 7 forming an emission optical waveguide. The optical modulator 2 utilizes the property that the birefringence changes depending on the electric signal applied to the pair of modulation electrodes 25 by using the Pockels element 31. The chemical composition of the Pockels element 31 is Bi ₁₂
A hexahedral BGO crystal represented by GeO ₂₀ is used. A pair of modulation electrodes 25 are provided on two opposing side surfaces of the Pockels device 31, and two opposing optical surfaces (both end surfaces) are provided on the other two opposing optical surfaces. As described above, the polarizer 32 is arranged on the incident surface side, and the wave plate 35 and the analyzer 33 are arranged in this order on the emission surface side. In this physical quantity detector, the input transmission light from the light source unit 11 is collected by the lens 34 via the input optical fiber 6, then passes through the polarizer 32 to become linearly polarized light, and is transmitted to the Pockels element 31. Incident. The linearly polarized input transmission light is emitted as elliptically polarized light by the Pockels element 31, passes through the wavelength plate 35 and the analyzer 33, and is emitted as intensity-modulated linearly polarized output transmission light. Further, the output transmission light is transmitted to the light receiver 13 through the output optical fiber 7, and is converted into an electric signal by the light receiver 13 to obtain an output electric signal. The optical modulator 2 in the physical quantity detector
Also, it is attached to a mounting portion provided in a thin cylindrical container 8 made of a resin of an organic polymer material, and is housed and fixed in the container 8. Also, this physical quantity detector is combined with an oscilloscope 16 as a measuring instrument capable of measuring an output electric signal according to a predetermined physical quantity via a conductor cable 15 so that physical quantity measurement can be performed in the same manner as in each of the comparative examples described above. It is configured as a vessel. Comparative Example 3 The physical quantity detector of Comparative Example 3 has the basic structure shown in FIG. 7 and, in terms of the detection element 40 in the physical quantity detector of Comparative Example 2, sets the detection target to acceleration. And a detecting unit using the piezoelectric element 51. The detection section is constructed by attaching an elastic plate 52 to one side of a base 54 via a support, and providing a piezoelectric element 51 and a weight 53 on the elastic plate 52. In this detection unit, the piezoelectric element 51 and the pair of detection terminals 3 are connected to the conductor 4
, And the electric signal output from the piezoelectric element 51 is guided to the modulation electrode 25. Therefore, when the piezoelectric element 51 subjected to acceleration generates a surface charge due to distortion,
An electric signal to be transmitted to the external conductor 4 is extracted from the electrode, and the electric signal is transmitted to the optical modulator 1 '. That is, since the piezoelectric element 51 generates an electric signal depending on the magnitude of the applied acceleration in this physical quantity detector, it is configured as an acceleration detector. By combining a measuring device capable of measuring an electric signal output from the device as an acceleration, the device is configured as an acceleration measuring device. Incidentally, the piezoelectric element 51 of this acceleration detector
Is replaced with a detection element for detecting another physical quantity, a physical quantity detector for another detection target is configured. Comparative Example 4 The physical quantity detector of Comparative Example 4, referring to the main configuration shown in FIG. 8, relates to the detection element 40 of the physical quantity detector of Comparative Example 2 and sets the detection target to acceleration. For this purpose, the acceleration detecting element 50 and the optical modulator 1 ′ are attached to the mounting portion of the container 8 by using the acceleration detecting element 50 and stored and fixed in the container 8. That is, in the comparative example 4, the acceleration detecting element 5
0 and the optical modulator 1 'are attached to the container 8 and integrated to form an acceleration detector in which operability is improved by downsizing. However, as in the case of the comparative example 3, the acceleration detector is further provided. By combining a measuring device capable of measuring an output electric signal from the light receiver 13 as acceleration, the device is configured as an acceleration measuring device. Incidentally, when the acceleration detecting element 50 of this acceleration detector is replaced with a detecting element for detecting another physical quantity, a physical quantity detector for another object to be detected is constituted. In addition, the optical modulator 1, the optical modulator 2, and the detection element 40 described in the comparative example 1 and the example can also be configured to be attached to the attachment portion and housed and fixed in the container 8. COMPARATIVE EXAMPLE 5 The physical quantity detector of Comparative Example 5, referring to the main part configuration shown in FIG. 9, relates to the optical modulator 1 in the physical quantity detector of Comparative Example 1 and has one substrate 20. The acceleration detecting element 50 is housed in a storage part formed by cutting out the part, and two local parts of the pair of modulation electrodes 25 in the optical modulator 1 and two local parts of each electrode formed on both side surfaces of the acceleration detecting element 50 are provided. Are connected by strip conductors 61. The substrate 20 is made of a Z-plate lithium niobate crystal polarized in the thickness direction, and the light modulator 1 is formed on the surface thereof. In the case of the substrate 20, which is a piezoelectric material, the acceleration detecting element 50 can be constructed by forming a bending oscillator by performing slit processing by laser trimming and forming electrodes on the same surface. Incidentally, when the acceleration detecting element 50 of this acceleration detector is replaced with a detecting element for detecting another physical quantity, a physical quantity detector for another object to be detected is constituted. Also, the optical modulator 1 'described in the comparative example 2 and the embodiment.
The optical modulator 2, the light modulator 2, and the detection element 40 can also be configured to be attached to the attachment portion (substrate 20) and fixed. In each of the physical quantity detectors described in each of the above comparative examples and examples, the electrical detection between the detection unit and the measurement unit is performed, and the optical waveguide is used. Signals (voltages) can be faithfully transmitted in a low-loss state without noise. Further, by replacing a dedicated detection element for each detection target using a single measuring device, it can be configured as a physical quantity measuring device capable of detecting various physical quantities. As described above, according to the physical quantity detector of the present invention, a detection element that generates an electric signal between a pair of detection terminals in response to detection of a predetermined physical quantity for a detection target is provided. An electric signal applied to the pair of modulation electrodes, the intensity of transmission light transmitted to an optical waveguide disposed in the vicinity of the pair of modulation electrodes and including a pair of modulation electrodes electrically connected to the pair of detection terminals. An optical modulator that varies depending on the wavelength, an incident optical waveguide in the optical waveguide, a transmission light generator that generates input transmission light to be transmitted to the incident optical waveguide, an output optical waveguide in the optical waveguide, and transmission from the output optical waveguide. And a light receiver that photoelectrically converts the output transmission light to generate an output electric signal, the light transmitting from the incident optical waveguide in the optical waveguide disposed near the modulation electrode as an optical modulator. A first lens for collecting the collected input transmission light, a polarizer for polarizing the collected input transmission light, and a light having a polarizer attached to one end surface and a pair of modulation electrodes attached to the side surface. A modulating element, an analyzer attached to the other end face of the light modulating element, for analyzing the modulated input transmission light and emitting the output transmission light, and an emission optical waveguide for collecting the emitted output transmission light and collecting the output transmission light And a second lens that transmits to the pair of modulation electrodes, and utilizes the property that the birefringence changes depending on the electric signal applied to the pair of modulation electrodes.
After the optical modulator has a configuration using various optical elements, a physical quantity can be detected with high accuracy without being affected by environmental conditions at the time of use. In such a configuration, the electrical signal (voltage) primary detected by the detection element can be faithfully transmitted in a noise-free low-loss state by using the optical waveguide after electrically disconnecting the detection unit and the measurement unit. ,
By replacing a dedicated detection element for each detection target using a single measuring instrument, it becomes possible to configure a physical quantity measuring instrument capable of detecting various physical quantities other than electrical quantities with high accuracy. As a result, use in remote transmission becomes effective, and various physical quantities can be detected without being affected by the use environment. In particular, since this physical quantity detector does not require an external power supply, various physical quantities can be detected without any trouble even in a flammable or explosive gas atmosphere or in a use condition where there is a risk of lightning. Further, the acceleration detector and the acceleration measuring device using the acceleration detecting element as the detecting element can detect the acceleration more clearly than before.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a basic configuration of a physical quantity detector according to Comparative Example 1 of the present invention. FIG. 2 is an enlarged view of a main part configuration of the physical quantity detector shown in FIG. FIG. 3 shows a basic configuration of a physical quantity detector according to Comparative Example 2 of the present invention. FIG. 4 is an enlarged view showing a configuration of a main part of the physical quantity detector shown in FIG. 2; FIG. 5 shows a basic configuration of a physical quantity detector according to an embodiment of the present invention. FIG. 6 is an enlarged view of a main part configuration of the physical quantity detector shown in FIG. 5; FIG. 7 shows a basic configuration of an acceleration detector according to Comparative Example 3 of the present invention. FIG. 8 shows a main configuration of an acceleration detector according to Comparative Example 4 of the present invention. FIG. 9 shows a main configuration of an acceleration detector according to Comparative Example 5 of the present invention. [Description of Signs] 1, 1 ', 2 Optical modulator 3 Detection terminal 4 Conductor 5 Polarization maintaining fiber 6 Input optical fiber 7 Output optical fiber 8 Container 11 Light source unit 12 Power supply unit for light source 13 Receiver 15 Conductor cable 16 Oscilloscope 17 Optical circulator 20 Substrate 21 Optical waveguide 22 Incident optical waveguide 23 Outgoing optical waveguide 24 Phase shift optical waveguide 25 Modulation electrode 26 Total reflection film 31 Pockels element 32 Polarizer 33 Analyzer 34 Lens 35 Wave plate 40 Detection element 50 Acceleration detection element 51 Piezoelectric element 52 Elastic plate 53 Weight 54 Base 61 Strip conductor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-40512 (JP, A) JP-A-3-73916 (JP, A) JP-A-6-118357 (JP, A) JP-A-57- 105100 (JP, A) Fully open 1986-119732 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01D 5/26-5/38 G01B 11/00-11/30 G02B 6/00 G02F 1/00-1/125 G08C 13/00-25/04 G01P 15/08 G01L 1/00-25/00 G01K 1/00-19/00

Claims (1)

(57) [Claim 1] A detection element for generating an electric signal between a pair of detection terminals in response to detection of a predetermined physical quantity with respect to a detection target, and electrically connected to the pair of detection terminals Light including a pair of modulation electrodes, and changing the intensity of transmission light transmitted to an optical waveguide disposed near the pair of modulation electrodes depending on the electric signal applied to the pair of modulation electrodes. A modulator, an incident optical waveguide in the optical waveguide, a transmission light generator that generates input transmission light transmitted to the incident optical waveguide, an output optical waveguide in the optical waveguide, and an output transmitted from the output optical waveguide. A physical quantity detector comprising: a photodetector that photoelectrically converts transmission light to generate an output electric signal; wherein the optical modulator includes a first lens that collects the input transmission light emitted from the incident optical waveguide; and , Light collection A polarizer that polarizes the input transmission light, and the polarizer is attached to one end face, and a light modulation element having the pair of modulation electrodes attached to a side face, and attached to the other end face of the light modulation element. An analyzer that detects the modulated input transmission light and emits the output transmission light, and a second lens that collects the output transmission light and transmits the output transmission light to the emission optical waveguide. A physical quantity detector characterized by the above-mentioned.