JP2005345230A - Optical interference type sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easily miniaturizable optical interference type sensor having a simple optical system and high measurement accuracy. <P>SOLUTION: This sensor has a substrate 12 such as a glass plate, and a body part 20 having a hollow part 22 and provided with a movable part such as a weight 24 on the center. The sensor is equipped with a laser light source 44 such as a laser diode; beam splitters 14, 15, 16 fixed directly or indirectly to the body part 20, for splitting light from the laser light source 44; a fixed reflection part 32 for reflecting laser light b on one side split by the beam splitters 14, 15, 16; and a movable reflection part 30 moved by movement of the weight 24 of the body part 20, for reflecting laser light b on the other side split by the beam splitters 14, 15, 16. Laser light b reflected by the fixed reflection part 32 and laser light b reflected by the movable reflection part 30 are guided respectively onto the same axis and allowed to interfere with each other by the beam splitters 14, 15, 16. The sensor is also equipped with a light receiving element 46 for receiving the interference light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical interference sensor that optically detects pressure and acceleration.

  Conventionally, for example, as a sensor for detecting acceleration, there is a capacitance type semiconductor acceleration sensor. As disclosed in Patent Document 2, this acceleration sensor has a rectangular insulating substrate such as a glass plate, a silicon having a hollow portion and a weight that moves by acceleration at the center thereof, and has substantially the same shape as the insulating substrate. It consists of a semiconductor body. The body is provided with an electrode that swings due to the weight, and the electrode on the insulating substrate and the electrode provided on the weight face each other in a state where the body is joined to the insulating substrate.

An acceleration sensor using a semiconductor laser is disclosed in Patent Document 1. In this acceleration sensor, the light emitting surfaces of a pair of semiconductor lasers are arranged facing each other at a predetermined interval, a cantilever reflecting member is provided at an intermediate position between them, and the laser light is fed back to the semiconductor laser, so that the opposite side There is a technique for measuring the displacement of the cantilever beam by the difference in the intensity of the laser beam from the light emitting surface and obtaining the acceleration.
Japanese Patent Laid-Open No. 5-18988 JP 2003-152162 A

  The conventional capacitance type acceleration sensor detects acceleration by the capacitance between the electrodes facing each other, but the capacitance is easily affected by an external electric field, magnetic field, circuit wiring pattern, etc. It is difficult to increase accuracy. Furthermore, in order to suppress stray capacitance due to wiring, the sensor main body and the drive circuit system must be arranged close to each other. In the case of an integrated module, it may not be used at a detection location with a limited size. In addition, it is necessary to take out the electrode terminals from the insulating substrate and the main body, and it is difficult to arrange the lead wiring and to join the main body and the insulating substrate with the lead wiring interposed therebetween. In addition, there is a problem that the distance between the electrodes facing each other is narrow, and the electrodes are in contact with each other during the manufacturing process.

  On the other hand, the optical acceleration sensor disclosed in Patent Document 1 is to detect an interval by a difference in received light intensity using feedback of a laser beam to a light source to obtain an acceleration. When it is difficult to detect acceleration in three axes, a laser light source and a photodetector are required inside the sensor, so that the structure is complicated and the apparatus becomes large.

  The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide an optical interference sensor that is a simple optical system, has high measurement accuracy, and can be easily downsized.

  The present invention includes a substrate such as a glass plate, a body portion such as a silicon semiconductor having a hollow portion and a movable portion such as a weight and a diaphragm provided at the center thereof, a laser light source such as a laser diode, and the body portion. A beam splitter that is directly or indirectly fixed to branch the light from the laser light source, a fixed reflecting portion that reflects one of the laser beams branched from the beam splitter, and a movable portion that moves by the movement of the main body portion. Interfering light that reflects the other laser beam branched by the beam splitter, the laser light reflected by the fixed reflecting portion, and the laser light reflected by the movable reflecting portion coaxially and interfering with each other Forming means and a light receiving element for receiving the interference light by the interference light forming means, optically detecting the displacement of the movable reflecting portion, Or an optical interference sensor for detecting the acceleration.

  The interference light forming means is the beam splitter, and the fixed reflecting portion is provided on one side surface of the beam splitter. The movable reflecting portion is provided on a lower surface of a weight which is the movable portion and a lower surface of a cantilever movable plate extending symmetrically from the weight. The cantilever-like movable plate extends symmetrically in four directions, and the beam splitter faces each of the pair of movable plates positioned at right angles to each other and the movable reflecting portions of the weights. doing.

  The invention also includes a substrate such as a glass plate, a body portion such as a silicon semiconductor having a hollow portion and a movable portion such as a weight or a diaphragm that moves by acceleration at the center thereof, and a pair of wavelengths slightly different from each other. From a laser light source such as a laser diode, a first beam splitter that branches the laser light from each of the laser light sources and interferes the laser light from each of the laser light sources coaxially, and from the first beam splitter A first light receiving element that receives the interference light, a second beam splitter that branches the laser light from each of the laser light sources, and a fixed that reflects the laser light branched to one side by the second beam splitter. It is possible to reflect the laser beam branched to the other by the second beam splitter while moving by the movement of the reflecting portion and the movable portion of the main body portion. The reflection part and the laser light of the one laser light source are reflected light from the fixed reflection part, and the laser light from the other laser light source is reflected as a reflection light from the movable reflection part, respectively, and are caused to interfere with each other on the same axis. An interference light forming means for guiding the light to the second light receiving element; and a second light receiving element for receiving the interference light from the interference light forming means. It is an optical interference type sensor that detects

  The interference light forming means includes the second beam splitter formed of a polarization beam splitter and an analyzer. The movable reflecting portion is provided on the lower surface of the weight which is the movable portion and the lower surface of the cantilever movable plate extending symmetrically from the weight. The cantilevered movable plates extend in four directions symmetrically to each other, and the quarter-wave plate faces each of a pair of movable plates positioned perpendicular to each other and the movable reflecting portion of the weight. doing.

  The weight is held in the hollow portion of the main body via a beam. The weight, the movable plate, and the beam are integrally formed by a semiconductor process such as etching when the main body is formed.

  The optical interference sensor according to the present invention may be any sensor as long as the movable reflecting portion is displaced by acceleration or force, and can be used as an acceleration sensor, a pressure sensor, etc., and is not affected by an external electric field or magnetic field. Therefore, accurate measurement is possible even in these noisy locations. In addition, there is no influence of stray capacitance or the like due to wiring, and the sensor and the drive circuit can be arranged separately. In addition, the sensor body does not require an electrode, is easy to manufacture, has no trouble due to the electrode, and has a good yield and can be efficiently manufactured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show an embodiment of an optical interference type sensor of the present invention. The optical interference type sensor of this embodiment relates to an acceleration sensor. The acceleration sensor 10 of this embodiment includes a transparent substrate 12 such as a glass plate, three beam splitters 14, 15, 16 disposed at predetermined positions on the back surface of the substrate 12, and the beam splitters 14, 15, It comprises a holding plate 18 holding 16.

  A main body 20 made of silicon is bonded to the surface of the substrate 12. As shown in FIGS. 1 and 2, the main body 20 is formed in a quadrangular shape, a hollow portion 22 is provided at the center, and a weight 24 that is a movable portion is provided at the center of the hollow portion 22. The weight 24 is supported on all sides by thin beams 26 extending from the corners of the main body 20, and a fan-shaped cantilever thin movable plate 28 is formed integrally with the weight 24 between the beams 26. . The main body 20, the weight 24, the beam 26, and the movable plate 28 are integrally formed of silicon. The back surfaces of the weight 24 and the movable plate 28 are formed flush with each other.

  The back surfaces of the weight 24 and the movable plate 28 are formed in a mirror surface by a metal vapor deposition film or the like to constitute the movable reflecting portion 30. Further, the side surfaces of the beam splitters 14, 15, and 16 are also formed in a mirror surface in the same manner, and constitute a fixed reflecting portion 32.

  The upper surface opening of the main body 20 is sealed with a cover lid 34 such as a glass plate or a silicon plate. Each adhesion between the substrate 12 and the main body 20 and the cover lid 34 is tightly fixed in an airtight state by low melting point glass or the like, and the inside of the hollow portion 22 of the main body 20 is sealed in a vacuum state. Further, the substrate 12 and the holding plate 18 are fixed to the main body 20 via a frame member 36. The beam splitters 14, 15, and 16 are fixed with one side surface positioned on the back surface side of the holding plate 18, and optical connectors 38 project from the back surface side of the holding plate 18. An optical fiber 40 is connected to each optical connector 38.

  Each optical fiber 40 is connected to an optical connector 43 of a drive detection circuit unit 42 provided separately from the main body unit 20. The drive detection circuit unit 42 includes a laser light source 44 such as a laser diode and a light receiving element 46 such as a photodiode that detects the reflected laser beam b. Between the optical connector 43 and the laser light source 44 and the light receiving element 46, the laser light b from the laser light source 44 is branched into three optical connectors 43, and further receives the laser light b incident through each optical connector 43. An optical branching unit 48 including a beam splitter (not shown) or the like that is directed toward the element 46 is provided. Then, the signal received by the light receiving element 46 is detected as a displacement of the movable reflecting portion 30 by the processing method described later through the signal converting portion 50, and the acceleration is calculated.

  The operation of the acceleration sensor 10 of this embodiment is as follows. First, the laser beam b emitted from the laser light source 44 is sent to the three optical connectors 43 through the optical branching section 48, and the three beams are transmitted through the optical fibers 40. The light enters the splitters 14, 15 and 16. In the beam splitters 14, 15, and 16, the laser light b incident on the beam splitters 14, 15, and 16 is divided into two at the half mirror portion, and one is formed on one side surface of the beam splitters 14, 15, and 16, respectively. It goes to the fixed reflection part 32. The other laser beam b is emitted to the movable reflector 30 on the back surface of the weight 24 and each movable reflector 30 of the pair of movable plates 28.

  Reflected light from the movable reflecting portion 30 and the fixed reflecting portion 32 is coaxially matched in the beam splitters 14, 15, and 16, and returns to the optical connector 43 from the optical connector 38 through the optical fiber 40, respectively. From 48 to the light receiving element 46. Then, the reflected light from the movable reflecting portion 30 and the fixed reflecting portion 32 interfere with each other and become interference light. Here, in this embodiment, the displacement is detected using Michelson interference, the optical path difference of each reflected light from the movable reflecting portion 30 and the fixed reflecting portion 32 is L, and the laser from the laser light source 44 is used. Assuming that the wavelength of the light b is λ, the number of times of light and dark of the interference light due to the fluctuation of the optical path difference for one wavelength detected by the light receiving element 46 is N, and the fraction of light and dark less than 1 is ε, the optical path difference L is 1).

L = 1/2 · λ (N + ε) (1)
By this equation (1), the optical path difference L can be obtained by obtaining the number N of bright and dark interference light captured by the light receiving element 46 and its fraction ε. The optical path difference L is the deflection of the beam 26 or the deflection of the movable plate 28, and the force F is obtained from the deflection amount, and the obtained force F is a value determined by the acceleration α applied to the weight 24. Therefore, the acceleration α can be obtained by obtaining the number N of bright and dark interference light captured by the light receiving element 46 and its fraction ε. This is calculated independently in the XYZ three-axis directions in FIG. 1, and the movable reflecting portion 30 on the back surface of the weight 24 is displaced by the deflection of the beam 26 due to the acceleration in the Z-axis direction, and by the acceleration in the X and Y-axis directions. The movable plates 28 facing the beam splitters 14 and 15 are displaced, and the acceleration sensor 10 can detect acceleration in the XYZ triaxial directions.

  According to the acceleration sensor 10 of this embodiment, the movable reflector 30 is displaced by receiving the acceleration, thereby detecting the optical path difference of the laser beam b with high accuracy below the wavelength of the light. Since the force is obtained from the deflection of the movable plate 28 and the acceleration is calculated, the acceleration detection can be performed with extremely high sensitivity. In addition, the electrical part is provided in the drive detection circuit part 42, and the main body part 20 of the acceleration sensor 10 is not affected by an external magnetic field or electric field. From this point of view, highly accurate detection is possible. Become. Moreover, the beam splitters 14, 15, and 16 can have a side of 0.5 mm or less, and the size of the acceleration sensor 10 can be extremely small. In addition, the material of the main body 20, the holding plate 18, and the cover lid 34 can be appropriately selected, and any material can be used as long as the substrate 12 can transmit the laser beam b. Yes, it can be manufactured at low cost.

  The shape of the movable plate 28 of the acceleration sensor 10 may be a substantially triangular shape as shown in FIG. 3 or a substantially pentagonal shape as shown in FIG. 24 may be formed symmetrically about the X axis and the Y axis.

  Further, as shown in FIG. 5, the main body portion 20 is formed so that the beam 26 holding the weight 24 is connected to the center portion in the Z-axis direction of the weight 24, and extends symmetrically in the XY-axis direction on the lower surface of the weight 24. The movable reflector 30 may be connected. The movable reflecting portion 30 is, for example, a metal thin plate or a glass thin plate having a mirror surface. Further, the holding plate 18 may be omitted, and the laser beam b may be transferred from the substrate 12 through the optical connector 38.

  Further, as shown in FIG. 6, the optical paths connected to the beam splitters 14, 15, 16 are positioned on the side of the main body 20, and the optical connectors 38 are disposed on the side surfaces of the beam splitters 14, 15, 16 and the side of the frame member 36. It may be provided.

  Next, a second embodiment of the present invention will be described with reference to FIGS. Here, the same members as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted. This embodiment also relates to an acceleration sensor. The acceleration sensor 60 of this embodiment is arranged on the substrate 12 fixed to the main body 20 instead of the beam splitters 14, 15, and 16 of the above embodiment. A wave plate 62 is provided, and the main body 20 is provided with a movable reflector 30 on the lower surface of the weight 24 and the lower surface of the movable plate 28 integral with the weight, as in the above embodiment. Three quarter-wave plates 62 are provided to face the lower surface of the weight 24 and the lower surfaces of the pair of movable plates 28 extending orthogonally to each other. The quarter-wave plate 62 emits circularly polarized light when linearly polarized laser light is incident, and emits linearly polarized light when circularly polarized laser light is incident.

  As shown in FIG. 9, the drive detection circuit unit 64 of the acceleration sensor 60 of this embodiment includes a pair of laser light sources 66 and 67 such as laser diodes having slightly different wavelengths, and lasers from the laser light sources 66 and 67. A first beam splitter 68 for splitting the light beams b1 and b2 and partially transmitting the laser beams b1 and b2 from the laser light sources 66 and 67 and reflecting a part thereof. On the optical path of the interference light from the first beam splitter 68, an analyzer 72 and a first light receiving element 70 such as a photodiode for receiving the interference light from the first beam splitter 68 are provided.

  Further, of the laser beams b1 and b2 from the laser light sources 66 and 67 incident from the first beam splitter 68 adjacent to the first beam splitter 68, one of the lasers depends on the direction of the polarization plane of the laser beam. A second beam splitter 76, which is a polarization beam splitter that transmits the laser beam b1 from the light source 66, reflects the laser beam b2 from the other laser light source 67, and directs the laser beam b2 to the fixed reflection unit 74 described later, is provided. In this embodiment, assuming that the plane of polarization of the laser beam b1 of the laser light source 66 is in the vertical direction on the drawing, the plane of polarization of the laser beam b2 of the laser light source 67 is set in the horizontal direction on the drawing. Accordingly, the laser beams b1 and b2 from the laser light sources 66 and 67 are selectively transmitted or reflected by the second beam splitter 76.

  On the optical path of the laser beam b2 of the laser light source 67 reflected by the second beam splitter 76, a quarter-wave plate 80 and a fixed reflection unit 74 are provided, and the laser beam b2 reflected by the fixed reflection unit 74 is Return to the second beam splitter 67 and transmit. Further, the laser light b 1 of the laser light source 66 that has passed through the second beam splitter 76 is emitted from the optical connector 43 through the condensing ball lens 84 in the drive detection circuit unit 64.

  In addition, the laser beam b1 of the laser light source 66 reflected and returned by the movable reflecting unit 30 is reflected by the second beam splitter 76 to the drive detection circuit unit 64, and the laser beams b1 and b2 of the laser light sources 66 and 67 are reflected. The optical paths are consistent. On the optical path, an analyzer 78 and a second light receiving element 82 such as a photodiode for receiving the interference light are provided.

  A signal converter 50 that processes signals received by the light receiving elements 70 and 82 is connected to the drive detection circuit unit 64. The signal conversion unit 50 detects the displacement of the movable reflection unit 30 and calculates the acceleration by a processing method described later.

  The detection method of the acceleration sensor 60 of this embodiment uses interference of laser beams b1 and b2 from a pair of laser light sources 66 and 67 having slightly different wavelengths. That is, using heterodyne interference of light, the laser light sources 66 and 67 such as a pair of laser diodes from the laser light b 1 that is reflected light from the movable reflecting portion 30 of the main body portion 20 and the fixed reflecting portion 74. The displacement of the movable reflecting portion 30 is obtained from the interference light by the laser light b2 that is the reflected light of the same and the similar interference light by the fixed optical path.

  In this embodiment, the laser beams b1 and b2 from a pair of laser light sources 66 and 67 such as a pair of laser diodes having slightly different wavelengths are passed through an analyzer 72 by a first beam splitter 68 on a fixed optical path. Then, the light enters each of the first light receiving elements 70, and the intensity changes at a predetermined period due to interference. The change in the intensity I is expressed by the following formula (2). Similarly, the laser beams b1 and b2 from the laser light sources 66 and 67 such as a pair of laser diodes are divided by the second beam splitter 76 into laser beams b1 and b2 that are directed to the fixed reflecting portion 74 and the movable reflecting portion 30. Each of the reflected lights returns to the second beam splitter 76, the optical paths are matched, and the interference light passes through the analyzer 78 and enters the second light receiving element 82. This change in intensity I is also expressed by the following formula (2).

I = A ₁ ² + A ₂ ² + 2A ₁ A ₂ cos [(ω ₂ −ω ₁ ) t + (φ ₂ −φ ₁ )] (2)
A ₁ , ω ₁ , and ψ ₁ are the amplitude, angular velocity, and phase of the laser light b ₁ of the laser light source 66, and A ₂ , ω ₂ , and ψ ₂ are the amplitude, angular velocity, and phase of the laser light b ₂ of the laser light source 67.

  Thus, the laser beam is detected by detecting a delay in the change in the intensity I of the interference light in the second light receiving element 82 with respect to the change in the intensity I of the interference light serving as a reference in the first light receiving element 70. The optical path difference due to the movement of the movable reflector 30 of the laser beams b1 and b2 of the light sources 66 and 67 can be measured.

  Therefore, the movement of the laser beams b1 and b2 of the laser light sources 66 and 67 in this embodiment will be described in detail. First, in this embodiment, the polarization plane of the laser beam b1 of the laser light source 66 is in the vertical direction on the drawing, and the polarization plane of the laser beam b2 of the laser light source 67 is set in the horizontal direction on the drawing. The laser light b 1 of the laser light source 66 that has passed through the beam splitter 68 and the laser light b 2 of the laser light source 67 that has been reflected by the first beam splitter 68 are incident on the analyzer 72 with their polarization planes perpendicular to each other. The analyzer 72 has a plane of polarization set at an angle of 45 ° in the drawing, and transmits each laser beam component along the plane of polarization of the analyzer 72 out of each of the laser beams b1 and b2, thereby causing interference light. And is incident on the first light receiving element 70. The incident interference light changes its intensity I according to the equation (2).

  Of the laser beams b1 and b2 incident on the second light receiving element 82, the laser beam b2 from the laser light source 67 is transmitted through the beam splitter 68, reflected by the second beam splitter 76, and further, a fixed reflecting portion. 74 is reflected back. Since this laser beam b2 reciprocates through the quarter-wave plate 80 facing the fixed reflector 74, the polarization plane of the laser beam b reflected by the fixed reflector 74 is rotated by 90 °, and the second beam splitter 76 is rotated. Transparent.

  On the other hand, the laser beam b 1 from the laser light source 66 that has passed through the second beam splitter 76 is collected by the ball lens 84 and travels to the optical connector 38 through the optical fiber 40. Further, the laser beam b 1 passes through the quarter wavelength plate 62 from the optical connector 38, is reflected by the movable reflecting portion 30, passes through the quarter wavelength plate 62 again, and returns to the optical fiber 40. The returned laser beam b 1 is incident on the second beam splitter 76 through the optical connector 43 in the drive detection circuit unit 64. The laser beam b <b> 1 returning from the movable reflecting unit 30 reciprocates through the quarter wavelength plate 62 of the main body unit 20, so that the polarization plane is rotated by 90 ° and is reflected by the second beam splitter 76.

  As a result, of the laser beams b1 and b2 from the laser light sources 66 and 67, the optical path of the laser beam b2 reflected by the fixed reflector 74 and the laser beam b1 reflected by the movable reflector 30 is unified by the second beam splitter 76. Then, the light enters the analyzer 78. The laser light b1 of the laser light source 66 that has passed through the second beam splitter 76 and the laser light b2 of the laser light source 67 that has been reflected by the second beam splitter 76 have polarization planes that are perpendicular to each other. The plane of polarization is set at an angle of 45 ° on the drawing, and each laser beam component along the plane of polarization of the analyzer 78 is transmitted, whereby interference light is formed. The intensity I of the interference light incident on the second light receiving element 82 changes according to the equation (2).

  The interference light incident on the first light receiving element 70 is interference light by the laser beams b1 and b2 whose optical paths are fixed, and the intensity I of the interference light changes at a constant timing. This is the reference value. Moreover, the interference light incident on the second light receiving element 82 includes the reflected light from the movable reflecting portion 30, and the optical path length thereof changes as the movable reflecting portion 30 moves due to acceleration. The difference in the optical path length appears as a deviation of the received light intensity change of the second light receiving element 82 from the reference value, and the acceleration is calculated by obtaining the difference between the received light intensity change of the second light receiving element 82 and the reference value. can do.

  The acceleration sensor 60 of this embodiment can obtain the same effect as that of the first embodiment, and can detect acceleration with higher accuracy.

  In the acceleration sensor 60 of this embodiment, as shown in FIG. 10, the main body portion 20 is formed so that the beam 26 holding the weight 24 is connected to the center portion of the weight 24, and the lower surface of the weight 24 is arranged in the XY axis direction. You may connect the movable reflection part 30 extended symmetrically. The movable reflecting portion 30 is, for example, a metal thin plate or a glass thin plate having a mirror surface. Also in this embodiment, the holding plate 18 may be omitted, and the laser beam b <b> 1 may be exchanged from the substrate 12 via the optical connector 38.

  Furthermore, as shown in FIG. 11, the optical path connected to each quarter-wave plate 62 may be positioned on the side of the main body 20, and the optical connector 38 may be provided on the side of the frame member 36.

  The optical interference sensor of the present invention is not limited to the above-described embodiment, and can be used as a pressure sensor by replacing weights, beams, and movable plates with thin diaphragms. Also in this case, a change in the position of the diaphragm is optically detected, and the same effect as that of the above-described embodiment is obtained as compared with the capacitance type pressure sensor. In addition, it can be suitably used for a sensor for detecting physical distortion.

  In addition, the wavelength of the laser light, the laser element, the light receiving element, and other optical elements can be selected as appropriate, and the arrangement of the optical system can also be set as appropriate.

It is a longitudinal cross-sectional view which shows the outline of the optical interference type sensor of 1st embodiment of this invention. It is a top view of the state which removed the cover lid of the optical interference type sensor of 1st embodiment of this invention. It is a top view of the state which removed the cover lid of the optical interference type sensor of the other example of 1st Embodiment of this invention. It is a top view of the state which removed the cover lid of the optical interference type sensor of the other example of 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the outline of the optical interference type sensor of the other example of 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the outline of the optical interference type sensor of the other example of 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the outline of the optical interference type sensor of 2nd embodiment of this invention. It is a top view of the state which removed the cover lid of the optical interference type sensor of 2nd embodiment of this invention. It is a schematic block diagram which shows the drive detection circuit part of the optical interference type sensor of 2nd embodiment of this invention. It is a longitudinal cross-sectional view which shows the outline of the optical interference type sensor of the other example of 2nd embodiment of this invention. It is a longitudinal cross-sectional view which shows the outline of the optical interference type sensor of the other example of 2nd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Acceleration sensor 12 Board | substrate 14,15,16 Beam splitter 20 Main-body part 24 Weight 26 Beam 28 Movable plate 30 Movable reflection part 32 Fixed reflection part 44 Laser light source 46 Light receiving element

Claims (8)

  A main body provided with a movable part that receives a force or acceleration at the center thereof, a laser light source, and a beam splitter that is directly or indirectly fixed to the main body and branches light from the laser light source A fixed reflecting portion that reflects one laser beam branched from the beam splitter, a movable reflecting portion that moves by the movement of the movable portion of the main body portion and reflects the other laser light branched by the beam splitter, and An interference light forming unit that guides the laser beam reflected by the fixed reflecting unit and the laser beam reflected by the movable reflecting unit on the same axis to interfere with each other, and a light receiving element that receives the interference light by the interference light forming unit. An optical interference sensor, wherein the displacement of the movable reflector is optically detected to detect force or acceleration.   2. The optical interference type sensor according to claim 1, wherein the interference light forming means is the beam splitter, and the fixed reflecting portion is provided on one side surface of the beam splitter.   2. The optical interference sensor according to claim 1, wherein the movable reflecting portion is provided on a lower surface of a weight which is the movable portion and a lower surface of a cantilever movable plate extending symmetrically from the weight. .   The cantilevered movable plate extends in four directions symmetrically to each other, and the beam splitter faces each of a pair of movable plates positioned at right angles to each other and each movable reflecting portion of the weight. The optical interference sensor according to claim 3.   A main body portion provided with a movable portion receiving a force or acceleration at the center thereof, a pair of laser light sources having slightly different wavelengths, and a laser beam from each of the laser light sources is branched and each of the lasers A first beam splitter that causes the laser light from the light source to be coaxially interfered with each other, a first light receiving element that receives the interference light from the first beam splitter, and the laser light from each of the laser light sources is branched. The second beam splitter, the fixed reflecting portion that reflects the laser beam branched to one side by the second beam splitter, and the second beam splitter that moves by the movement of the movable portion of the main body portion and the other by the second beam splitter. A movable reflecting portion that reflects the laser beam branched into the first and second laser light sources is reflected from the fixed reflecting portion, and the other laser beam Interference light forming means for guiding the laser light from the light source as reflected light from the movable reflecting portion on the same axis to the second light receiving element, and second light for receiving the interference light from the interference light forming means An optical interference sensor, wherein the displacement of the movable reflecting portion is optically detected to detect force or acceleration.   6. The optical interference sensor according to claim 5, wherein the interference light forming means comprises the second beam splitter comprising a polarization beam splitter and an analyzer.   6. The optical interference sensor according to claim 5, wherein the movable reflecting portion is provided on a lower surface of a weight which is the movable portion and a lower surface of a cantilever movable plate extending symmetrically from the weight. . The cantilevered movable plates extend in four directions symmetrically to each other, and a pair of movable plates positioned perpendicularly to each other and a movable reflecting portion provided on the weight each have the ¼ wavelength. 6. The optical interference sensor according to claim 5, wherein the plates face each other.

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