CN109764804A - A kind of displacement sensor based on Fabry-Perot principle - Google Patents
A kind of displacement sensor based on Fabry-Perot principle Download PDFInfo
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- 238000006073 displacement reaction Methods 0.000 title claims abstract description 225
- 239000013307 optical fiber Substances 0.000 claims abstract description 35
- 239000000523 sample Substances 0.000 claims description 46
- 230000002829 reductive effect Effects 0.000 claims description 10
- 239000000758 substrate Substances 0.000 claims description 10
- 238000005259 measurement Methods 0.000 claims description 9
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- 230000009977 dual effect Effects 0.000 claims description 7
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- 230000033001 locomotion Effects 0.000 description 15
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- 230000005540 biological transmission Effects 0.000 description 7
- 230000001681 protective effect Effects 0.000 description 4
- 239000000835 fiber Substances 0.000 description 3
- 238000007789 sealing Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
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- 238000004891 communication Methods 0.000 description 1
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Abstract
The application discloses a kind of displacement sensor based on Fabry-Perot principle, and institute's displacement sensors include: shell, optical fiber, reflective mirror and displacement reduction structure；Wherein, the end of the optical fiber is the first reflecting surface, and the reflective mirror is the second reflecting surface；When first displacement knots modification occurs for the feeler lever of institute's displacement sensors, the first displacement knots modification reduction at second displacement knots modification and is driven second reflecting surface that second displacement knots modification occurs by the displacement reduction structure, the second displacement knots modification is less than the first displacement knots modification and linear with the first displacement knots modification, by measuring the interference cavity length variable quantity between first reflecting surface and second reflecting surface, determine the second displacement knots modification, and the first displacement knots modification is determined based on the relationship between the first displacement knots modification and the second displacement knots modification.
Description
Technical Field
The application relates to a measurement technology, in particular to a displacement sensor based on a Fabry-Perot principle.
Background
The displacement sensor can realize the measurement of distance, and the displacement sensor has different designs according to different measurement principles. However, displacement sensors designed on the basis of the current measurement principle have at least the following disadvantages: the structure is complicated, the precision is low, and the manufacturing cost is higher.
Content of application
In order to solve the above technical problem, an embodiment of the present application provides a displacement sensor based on a fabry-perot principle.
The displacement sensor based on the Fabry-Perot principle provided by the embodiment of the application comprises: the optical fiber displacement reduction device comprises a shell, a substrate arranged in the shell, an optical fiber, a reflector and a displacement reduction structure; wherein,
the end part of the optical fiber is a first reflecting surface, the reflector is a second reflecting surface, and the first reflecting surface is parallel to the second reflecting surface; the optical fiber is fixed on the substrate, the second reflecting surface can move along the axial direction of the second reflecting surface, and the axial direction of the second reflecting surface is parallel to the axial direction of the first reflecting surface; when a probe rod of the displacement sensor generates a first displacement change amount, the displacement reduction structure reduces the first displacement change amount into a second displacement change amount and drives the second reflecting surface to generate the second displacement change amount, the second displacement change amount is smaller than the first displacement change amount, the second displacement change amount is determined by measuring the interference cavity length change amount between the first reflecting surface and the second reflecting surface, and the first displacement change amount is determined based on the corresponding relation between the first displacement change amount and the second displacement change amount.
In an embodiment of the present application, the displacement reduction structure is a folding lever structure, the folding lever structure includes a plurality of folds, fixing points of the plurality of folds are fixed on the substrate, wherein M first folds are included between the fixing points and the second reflecting surface, N second folds are included between the fixing points and a probe rod of the folding lever structure, M and N are positive integers, and N is greater than or equal to M;
half of the length of the first fold is a and half of the length of the second fold is L; if the first displacement change amount of the probe rod of the folding lever structure is w, the interference cavity length change amount Δ d between the first reflecting surface and the second reflecting surface is:
in one embodiment of the present application, the larger the measurement range of the displacement sensor, the smaller the ratio of Na to ML; wherein the first amount of displacement change is directly proportional to the amount of interference cavity length change.
In one embodiment of the present application, the displacement reduction structure is a reduction gear structure comprising a gear and a rack; or, the reduction gear structure comprises a gear, a rack and a worm; the reduction gear structure can reduce a first displacement change generated by the probe rod into a second displacement change of the second reflecting surface, and the interference cavity length change between the first reflecting surface and the second reflecting surface is smaller than the first displacement change and is in direct proportion to the first displacement change.
In one embodiment of the present application, the probe rod of the reduction gear structure is provided with a first rack, the first rack is butted with a first gear on a double gear, a second gear on the double gear is butted with a second rack, the diameter of the first gear is larger than that of the second gear, and the end of the second rack is fixed with the reflector; wherein,
when the probe rod generates a first displacement change amount, the first rack is driven to move, and the first displacement change amount is subjected to displacement reduction through the double gears, so that the second rack with the reflector generates a second displacement change amount, and the second displacement change amount is smaller than the first displacement change amount; and the variation of the length of the interference cavity between the first reflecting surface and the second reflecting surface is the second displacement variation.
In one embodiment of the application, the reduction gear arrangement comprises one or more double gears, wherein, in case the reduction gear arrangement comprises a plurality of double gears, two adjacent double gears of the plurality of double gears are in abutment with each other by: the second gear of the double gear close to the probe rod is butted with the first gear of the double gear close to the reflector, and the diameter of the first gear is larger than that of the second gear.
In one embodiment of the present application, the probe rod of the reduction gear structure is provided with a first rack, the first rack is butted with a first gear with a worm, the first gear and the worm share a rotating shaft, the worm is butted with a second gear, the second gear is butted with a second rack, and the end of the second rack is fixed with the reflector; wherein,
when the probe rod generates a first displacement change amount, the first rack is driven to move, the first rack drives the first gear to rotate, the rotation of the first gear drives the worm to rotate, the worm performs displacement reduction on the first displacement change amount and drives the second gear to rotate, and therefore the second rack with the reflector generates a second displacement change amount.
In one embodiment of the application, the probe rod of the reduction gear structure is provided with a first rack which is butted with a first gear with a worm, the first gear and the worm share a rotating shaft, the end of the worm is fixed with the reflector, the normal line of the reflector is parallel to the axis of the worm, and the reflector moves along with the end of the worm; wherein,
the external screw thread of worm is twisted in a screw, when the probe rod takes place first displacement change volume, drive first rack removes, first rack drives first gear revolve, the rotation of first gear drives the worm rotates in the screw to drive the reflector of the tip of worm takes place to remove, through the worm is right first displacement change volume carries out the displacement and subtracts, makes the reflector of the tip of worm takes place the second displacement change volume.
In one embodiment of the present application, the displacement reducing structure comprises any combination of the following: gears, racks, worms; the reduction gear structure can reduce a first displacement change generated by the probe into a second displacement change of the second reflecting surface, and the interference cavity length change between the first reflecting surface and the second reflecting surface is smaller than the first displacement change.
In one embodiment of the present application, the displacement sensor further comprises a ramp;
an inclined hole perpendicular to the inclined plane is formed in the shell wall, a rod passes through the inclined hole, the top end of the rod is the reflector, a sliding block is fixed at the bottom of the rod, and the rod and the sliding block are integrated parts; the inclined plane, the bottom surface of the sliding block, the reflecting mirror at the top end of the rod and the end plane of the optical fiber are all parallel; when a probe rod of the displacement sensor generates a first displacement change amount in the horizontal direction, the inclined surface moves horizontally to drive the sliding block to move in the normal direction of the inclined surface, and finally the reflecting mirror at the top end of the rod is driven to move, so that the length delta d of an interference cavity between the plane of the end part of the optical fiber and the reflecting mirror is changed; wherein the inclination angle of the inclined plane is theta, and when the first displacement change amount is w, the change amount of the interference cavity length is delta d which is w sin theta; the first displacement change quantity and the cavity length change quantity are in a linear relation;
one end of a probe rod of the displacement sensor is connected with an anti-shaking lug, and the anti-shaking lug enables the inclined plane to axially move only along the direction of the first displacement variation.
In one embodiment of the present application, the contact manner of the bottom of the slider and the inclined surface is sliding friction contact or rolling friction contact; wherein,
the contact means of the sliding frictional contact includes: contacting with a point; or by a line contact; or with a planar contact; or two or more points which are arranged on the inclined plane at a certain distance are contacted, and the two or more points are arranged on the same plane; or two lines or a plurality of lines which are arranged on the inclined plane at a certain distance are contacted, and the two lines or the plurality of lines are arranged on the same plane; or two or more surfaces which are separated from each other by a certain distance on the inclined surface are contacted, and the two or more surfaces are on the same plane; the contact component of the bottom of the slide block and the inclined plane is in a sliding friction contact mode of any combination of points, lines and planes which do not rotate;
the contact manner of the rolling friction contact includes: contacting with a point; or two or more points which are arranged on the inclined plane at a certain distance are contacted, and the two or more points are arranged on the same plane; the bottom of the sliding block and a contact component of the inclined plane are in a rolling friction contact mode, the axis of a rigid rod connected with the top of the sliding block is perpendicular to the inclined plane and penetrates through an inclined hole with the axis perpendicular to the inclined plane, the normal of a reflector at the top of the rigid rod is perpendicular to the inclined plane, and the plane of the end part of the optical fiber is parallel to the reflector.
In one embodiment of the present application, the slider is in contact with the inclined surface in a point contact or surface contact manner; wherein,
the contact mode of point contact includes single-point contact or multipoint contact, wherein, when the multipoint contact, the projection of the connecting line of all contact points in the displacement direction has certain length, and under the condition that the slide block does not rotate, the measurement of the interference cavity length cannot be influenced additionally, and the measured displacement and the variation of the interference cavity length are in a linear relation.
In one embodiment of the present application, when the slider has two left and right point contacts or two plane contacts on the inclined surface:
the distance between the two action points is L, a spring is arranged above the sliding block, the sliding block can be extruded and attached to the inclined plane by the spring, the sliding block and the inclined plane have certain friction force, and the friction force is in direct proportion to the elasticity of the spring; when the probe rod of the displacement sensor generates a first displacement change amount, the distance L between the two action points is increased, or the friction coefficient between the sliding block and the inclined plane is reduced, or the elasticity of the spring is increased, so that the two action points are always in contact with the inclined plane, the sliding block does not rotate, and the reflecting mirror on the end face of the rigid rod above the sliding block is always parallel to the inclined plane.
The application provides a displacement sensor based on an Extrinsic Fabry-Perot interference (EFPI) principle, which is called as the Fabry-Perot displacement sensor for short, and the displacement sensor utilizes a folding lever or a gear, rack and worm and other structures to reduce larger displacement into smaller interference cavity length variation, and the displacement is in direct proportion to the interference cavity length variation, so that the interference cavity length variation can be measured according to the Fabry-Perot principle, and the displacement can be calculated. The displacement sensor has the advantages of high precision, strong anti-interference capability, strong durability and the like, and has a wide application prospect.
Drawings
Fig. 1 is a schematic diagram of an extrinsic fabry-perot interference (EFPI) principle according to an embodiment of the present disclosure;
fig. 2(a) is a spectrum diagram of an extrinsic fabry-perot interference (EFPI) principle according to an embodiment of the present application;
FIG. 2(b) is a graph of the linear relationship between the calibrated displacement and the interference cavity length based on the rack and dual gear structure provided by the embodiment of the present application;
FIG. 3 is a schematic diagram of a displacement sensor based on a folding lever structure according to an embodiment of the present disclosure;
FIG. 4 is a schematic diagram of a displacement sensor based on a rack and pinion configuration according to an embodiment of the present disclosure;
FIG. 5 is a schematic diagram of a first displacement sensor based on a gear, rack and worm structure according to an embodiment of the present disclosure;
FIG. 6 is a schematic diagram of a second displacement sensor based on a gear, rack and worm structure according to an embodiment of the present disclosure;
FIG. 7(a) is a first schematic diagram of a slope-based displacement sensor provided in an embodiment of the present application;
fig. 7(b) is a second schematic diagram of a displacement sensor based on a slope according to an embodiment of the present disclosure;
FIG. 8(a) is a first schematic view illustrating a contact relationship between a slider and a slope according to an embodiment of the present invention;
FIG. 8(b) is a second schematic view illustrating a contact relationship between a slider and a slope according to an embodiment of the present invention;
FIG. 8(c) is a third schematic view illustrating a contact relationship between a slider and a slope according to an embodiment of the present invention;
FIG. 8(d) is a fourth schematic view illustrating a contact relationship between a slider and a slope according to an embodiment of the present invention;
description of reference numerals:
1-an optical fiber; 2-fiber end face, i.e. first reflecting face; 3-mirror, second reflecting surface; 4-an optical fiber protective sleeve; 5-a carrier of a second reflective surface; 6-a substrate of the displacement sensor for fixing the component; 7-a spectral demodulation means; 8-a linear motion bearing fixed to the base plate; 9-a transmission rod of the displacement sensor; 10-fixed point of folding lever, this fixed point only limits the displacement, not the rotation; 11-first fold, referring to the folding lever between the fixed point 10 and the transmission rod 9 of the displacement sensor; 12-second fold, meaning the folding lever between the fixed point 10 and the feeler lever 14 of the displacement sensor; 13-the joint hinge between the second fold 12 and the feeler lever 14 of the displacement sensor; 14-probe rod of displacement sensor; 15-a first rack; a first gear on the 16-dual gear (i.e., a large diameter gear); 17-a second gear (i.e., a small diameter gear) on the dual gear; 18-a shaft with a gear or double gears fixed to the base plate; 19-a second rack; 20-a restraining device which only enables the probe rod 14 of the displacement sensor to move axially, a linear motion bearing and the like are commonly used; 21-common axis of rotation of gear and worm; 22-a first gear coaxial with the worm; 23-a worm coaxial with the first gear 22; 24-a second gear; 25-bearings constraining the shaft 21; 26-a screw hole with internal threads; 27-a sealing ring; 28-sealing plug; 29-a sensor housing; 30-a fixing device with an inclined hole; 31-spring 32-slide block, the bottom has a certain length, and the bottom is in multi-point contact or surface contact with the inclined plane; 33-a rigid rod, the bottom of which is rigidly connected with a sliding block and the top of which is provided with a reflector; 34-a bevel feature; 35-anti-wobble bumps; 36-limit bump.
Detailed Description
So that the manner in which the features and elements of the present embodiments can be understood in detail, a more particular description of the embodiments, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings.
The method combines the principle of extrinsic Fabry-Perot interference (EFPI), provides a combination folding lever, a gear, a double gear, a worm or a gear combination of multiple types, reduces the displacement, converts the larger displacement variable quantity into the smaller interference cavity length variable quantity through the folding lever or the gear, the worm and other components, and accordingly determines the size of the displacement by measuring the variable quantity of the interference cavity length.
Fig. 1 is a schematic diagram of the principle of extrinsic fabry-perot interference (EFPI), as shown in fig. 1, including: an optical fiber 1, a mirror 3; the optical fiber end face 2 of the optical fiber 1 constitutes a first reflecting surface, and the reflecting mirror 3 constitutes a second reflecting surface. FIG. 2(a) is a spectrum diagram of the principle of extrinsic Fabry-Perot interference (EFPI); FIG. 2(b) is a graph of the linear relationship between the calibrated displacement and the interference cavity length based on the rack and dual gear configuration.
Example 1: folding lever structure
As shown in fig. 3, according to the fabry-perot principle, the fiber end face 2 of the end of the optical fiber 1 is a first reflecting surface, the reflective mirror 3 is a second reflecting surface, and the two reflecting surfaces are parallel. On this basis, the optical fiber 1 is fixed to the substrate 6 inside the housing together with the fiber protective cover 4, and the mirror 3, in communication with the mirror carrier 5, is axially movable in the same direction as the axis of the end position of the optical fiber 1. A structure that can translate the mirror 3 without changing the reflection point is used to convert a large displacement into a small amount of cavity length change.
In this embodiment, the displacement is reduced by folding the lever structure. As shown in fig. 3, the folding lever structure has a plurality of rotating shafts 13, and since the variation of the fabry-perot interference cavity length (hereinafter referred to as interference cavity length) of the displacement sensor is small, the fixed point 10 of the folding lever structure is close to the reflective mirror 3, that is, the number of folds from the fixed point 10 to the reflective mirror 3 is small, there are M first folds 11, and fig. 3 illustrates the case where M is 1; the number of folds from the fixing point 10 to the probe 14 of the displacement sensor is large, and there are N second folds 12, and fig. 3 shows a case where M is 3. In addition, the length of the rods of each folded structure may be varied. In general, the second folds 12 of the fixing point 10 to the probe 14 of the displacement sensor are longer, half the length of each second fold being L; the first folds 11 of the fixing point 10 to the part of the mirror 3 are shorter, each one half the length of which is a. Assuming that the displacement of the probe 14 of the displacement sensor is w, the variation Δ d of the fabry-perot interference cavity length is:
because the change range of the Fabry-Perot interference cavity length is limited, the larger the measuring range of the displacement sensor is, the smaller the ratio of Na to ML is. Wherein, the displacement variation and the cavity length variation are always in direct proportion.
In the configuration of fig. 3, the probe 14 is moved to the left and the length of the interference cavity is increased. It is also possible to place the reflecting surface of the carrier 5 of the mirror to the right and the optical fibre 1 to the right of the second reflecting surface 3 of the mirror, so that the length of the interference cavity decreases when the probe 14 is moved to the left.
Example 2: gear structure
As shown in fig. 4, 5 and 6, according to the fabry-perot principle, the displacement is reduced by the reduction gear structure, so that a larger displacement variation is converted into a smaller interference cavity length variation. The mechanical structure comprises various combinations of gears, including different kinds of gears or double gears, racks, worms and the like. The larger displacement is reduced through a series of gears, racks, worms and other members, so that the length of the interference cavity is changed slightly. The displacement variation and the cavity length variation are always in direct proportion.
In fig. 4, the displacement reducing structure includes a gear and a rack, as shown in fig. 4, the probe 14 of the displacement sensor has a first rack 15, when the displacement changes, the first rack 15 is driven to move, the first rack 15 abuts against a first gear 16 (i.e. a large diameter gear) on the dual gear, a second gear 17 (i.e. a small diameter gear) on the dual gear abuts against a second rack 19, the end of the second rack is fixed with a carrier 5 of a reflector, the end of the carrier 5 is a second reflecting surface 3, the axis of the second reflecting surface 3 is parallel to the axis of the optical fiber 1, and the end of the optical fiber 1 and the optical fiber protective sleeve 4 are fixed on the substrate 6. The dual gear shaft 17 is fixed to the base plate 6. Linear motion bearings 8 fixed to the base plate 6 serve to limit the movement of the transmission rod 9 of the displacement sensor, ensuring that the transmission rod 9 moves only in the axial direction. The linear motion bearing 20, which is fixed to the base plate 6, serves to limit the motion of the probe 14 of the displacement sensor, ensuring that the probe 14 moves only in the axial direction. When the displacement changes greatly, the diameter of the double gears 16, 17 is different, and the displacement is reduced, so that the second rack 19 with the reflector 3 changes slightly, namely the length of the interference cavity changes slightly. Through calibration, a linear relation between the displacement variation and the cavity length variation can be obtained. If the measuring range of the displacement sensor is large, the reduction of the displacement of one double gear pair is not enough, and the displacement can be reduced through the combination of a plurality of double gears.
In fig. 5, the displacement reducing structure includes a gear, a worm and a rack, as shown in fig. 5, the displacement sensor probe 14 has a first rack 15, the first rack 15 is driven to move when the displacement of the probe 14 changes, the first rack 15 abuts against a first gear 22 having a worm 23, i.e. the first gear 22 and a worm 23 share a rotating shaft 21, and the first gear 22 rotates to drive the worm 23 to rotate. The worm 23 is abutted with the second gear 24, and at this time, the larger displacement is reduced through the worm 23 to drive the second gear 24 to rotate less. The second gear 24 abuts against the second rack 19, the end of the carrier transmission rod 9 of the second rack 19 is the carrier 5 of the mirror, the end of the carrier 5 is the second reflection surface 3, the axis of the second reflection surface 3 is parallel to the axis of the optical fiber 1, and the end of the optical fiber 1 and the optical fiber protective sleeve 4 are fixed on the substrate 6. A bearing 25 that constrains the first gear 22 and the rotation shaft 21 of the worm 23 is fixed to the base plate 6. Linear motion bearings 8 fixed to the base plate 6 serve to limit the wobble of the transmission rod 9 of the displacement sensor, ensuring that the transmission rod 9 only moves in the axial direction. The linear motion bearing 20, which is fixed to the base plate 6, serves to limit the motion of the probe 14 of the displacement sensor, ensuring that the probe 14 moves only in the axial direction. When the displacement changes greatly, the displacement is reduced through the worm 23 and the second gear 24, so that the second rack 19 with the reflector 3 has smaller displacement change, namely the interference cavity length changes slightly. Through calibration, a linear relation between the displacement variation and the cavity length variation can be obtained.
In fig. 6, the displacement sensor based on the fabry-perot principle uses a micrometer structure to convert the linear displacement into the rotation of the first gear 22 through the movement of the first rack 15, and has a worm 23 coaxial with the first gear 22, so that the larger gear rotation amount can be converted into the smaller axial movement amount of the worm. The worm 23 is in a structure of external thread and is placed in the screw hole 26, the screw hole 26 is fixed on the base plate 6 and does not move, the end part of the worm 23 is fixed with the reflecting mirror 3, the axis of the optical fiber 1 is perpendicular to the reflecting mirror 3 along with the movement of the end part of the worm 23, and the displacement can be determined by measuring the movement amount of the end part of the worm 23. The amount of displacement variation is proportional to the amount of cavity length variation.
It should be noted that, the present application, in combination with a gear, a double gear and a worm, can be made into a gear combination of various types, as long as the function of reducing displacement is achieved, that is, in combination with the fabry-perot principle, a method of converting a large displacement variation into a small interference cavity length variation through a gear, a worm and other components is within the protection scope of the present patent.
Example 3: inclined plane structure
As shown in fig. 7(a) and 7(b), the displacement is reduced by the slant according to the fabry-perot principle. FIG. 7(a) shows the working condition that the cavity length becomes shorter and shorter as the displacement increases, i.e. the working condition that theta is a positive number; the inclined plane hole can also be placed in reverse, that is, the cavity length is longer and longer with the increase of the displacement, that is, the working condition that theta is negative is shown in fig. 7 (b). The inclination angle theta of the inclined plane ranges from-90 deg. to +90 deg.. In fig. 7(a) and 7(b), the probe 14 of the displacement sensor is connected to the right and the left of the probe 14 of the displacement sensor by a limit bump 36, the left of the limit bump 36 is connected to a slope part 34, the housing wall 29 is provided with an inclined hole perpendicular to the slope, a linear motion bearing 3 is arranged in the inclined hole, a part is arranged above the slider 32 and the rigid rod 33, the rigid rod 33 penetrates through the linear motion bearing, the top end of the rigid rod 33 is provided with the reflector 3, and the rigid rod 33 and the slider are integrated. The plane of the inclined plane, the plane of the bottom surface of the slide block, the plane of the reflecting mirror 3 on the top surface of the rod and the plane of the optical fiber end part 2 are all parallel. As shown in fig. 8, fig. 8(a) and 8(d) show the condition where the slider 32 is in point contact with the inclined surface 34, and fig. 8(b) and 8(c) show the condition where the slider 32 is in surface contact with the inclined surface 34. The point contact includes a single point contact shown in fig. 8(a) and a multipoint contact shown in fig. 7 and 8(d), and when the multipoint contact is performed, a projection of a line connecting all the contact points in the displacement direction has a certain length. At this time, as long as the slider 32 does not rotate, even if the slider 32 slightly moves along the inclined surface due to the friction force, the variation of the interference cavity length is still a linear function of the displacement, and no additional variation of the interference cavity length exists. When the displacement changes in the horizontal direction, the inclined surface 34 translates in the horizontal direction to drive the sliding block 32 to move in the normal direction of the inclined surface, and finally the reflective mirror 3 at the end of the rigid rod 33 is driven to move, so that the length delta d of the interference cavity between the plane 2 at the end of the optical fiber and the reflective mirror 3 is changed. The inclination angle of the inclined plane is theta, and when the displacement variation is w, the variation of the interference cavity length is delta d which is w sin theta. The technical scheme of the application can enable the displacement and the cavity length variation to be in a linear relation.
To prevent the inclined surface from shaking, the shaking prevention protrusions 35 are used such that the inclined surface 34 is axially moved only in the direction of displacement, and is not normally moved. In addition, the spring 31 at the rigid rod 33 generates a downward elastic force to the slider 43 and the inclined plane part 34, so that the slider can be prevented from rotating under the action of friction force, and the inclined plane can be prevented from shaking. The spring 31 between the anti-rattle tab 35 and the sealing plug 28 compresses as the displacement decreases, causing the ramp element 34 to spring out to the right. In fig. 7(a) and 7(b), the parts 14, 34, 35, and 36 may be one part or a plurality of parts connected together. The limiting projection 36 is used to make the inclined surface 34 clamped at the right side of the inner part of the shell 29 when the inclined surface is pushed to a certain position by the spring 31.
The contact mode of the bottom of the slide block 32 and the inclined plane can be divided into sliding friction contact and rolling friction contact:
(1) the sliding friction may be contacted with a point; or by a line contact; or with a planar contact; or two or more points on the inclined plane at a certain distance are contacted, and the points are on the same plane; or two lines or a plurality of lines which are arranged on the inclined plane at a certain distance are contacted, and the lines are arranged on a plane; or two or more surfaces which are separated from each other by a certain distance on the inclined surface are contacted, and the surfaces are on the same plane; the contact member of the slider bottom and the inclined surface is a contact type of sliding friction such as a point, a line, a surface and the like which does not rotate. As shown in fig. 7 and 8.
(2) The rolling friction can be contacted by a point, or two or more points on the inclined plane at a certain distance, and the points are on a plane; in fig. 7, 8(a) and 8(b), the contact means of the bottom of the slider 32 and the inclined surface 34 can be regarded as balls, needles or other rolling friction contact means. The axis of the rigid rod 33 connected to the top of the slider 32 is perpendicular to the inclined surface 34 and passes through an inclined hole with the axis perpendicular to the inclined surface 34, the normal of the reflective mirror 3 on the top of the rigid rod 33 is also perpendicular to the inclined surface 34, and the optical fiber end plane 2 is parallel to the reflective mirror 3.
As shown in fig. 8, the slider 32 and the inclined surface 34 are in point contact or surface contact, the point contact includes single-point contact and multi-point contact, when the multi-point contact is performed, the projection of the connecting line of all the contact points in the displacement direction has a certain length, and at this time, as long as the slider does not rotate, even if the slider slightly moves along with the inclined surface due to friction, the slider does not have additional influence on the measurement of the length of the interference cavity, and the measured displacement and the variation of the length of the interference cavity have a linear relationship.
Preferably, as shown in fig. 8(b) and (c), when the slider 32 has two point contacts or two plane contacts on the inclined surface 34: the distance between the two action points is L, a spring 31 is arranged above the sliding block, the sliding block 32 can be extruded and attached to the inclined surface 34, the sliding block 32 and the inclined surface 34 have certain friction, and the friction is in direct proportion to the elastic force. When the displacement changes, in order to enable the two action points to be always contacted with the inclined surface 34 and the slide block 32 not to rotate, the reflecting mirror 3 on the end surface of the rigid rod 33 above the slide block 32 is always parallel to the inclined surface 34, and the displacement can be realized by increasing the distance L between the two action points, or reducing the friction coefficient between the slide block and the inclined surface, or increasing the elastic force of a spring and the like.
The technical solutions described in the embodiments of the present application can be arbitrarily combined without conflict.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application.
Claims (13)
1. A displacement sensor based on the fabry-perot principle, characterized in that it comprises: the optical fiber displacement reduction device comprises a shell, a substrate arranged in the shell, an optical fiber, a reflector and a displacement reduction structure; wherein,
the end part of the optical fiber is a first reflecting surface, the reflector is a second reflecting surface, and the first reflecting surface is parallel to the second reflecting surface; the optical fiber is fixed on the substrate, the second reflecting surface can move along the axial direction of the second reflecting surface, and the axial direction of the second reflecting surface is parallel to the axial direction of the first reflecting surface; when a probe rod of the displacement sensor generates a first displacement change amount, the displacement reduction structure reduces the first displacement change amount into a second displacement change amount and drives the second reflecting surface to generate the second displacement change amount, the second displacement change amount is smaller than the first displacement change amount, the second displacement change amount is determined by measuring the interference cavity length change amount between the first reflecting surface and the second reflecting surface, and the first displacement change amount is determined based on the corresponding relation between the first displacement change amount and the second displacement change amount.
2. The Fabry-Perot principle-based displacement sensor according to claim 1, wherein the displacement reduction structure is a folded lever structure comprising a plurality of folds, and a fixed point of the plurality of folds is fixed on the substrate, wherein M first folds are included between the fixed point and the second reflecting surface, N second folds are included between the fixed point and a probe rod of the folded lever structure, M and N are positive integers, and N is greater than or equal to M;
half of the length of the first fold is a and half of the length of the second fold is L; if the first displacement change amount of the probe rod of the folding lever structure is w, the interference cavity length change amount Δ d between the first reflecting surface and the second reflecting surface is:
3. the fabry-perot principle based displacement sensor of claim 2, wherein the larger the measurement range of the displacement sensor, the smaller the ratio of Na to ML; wherein the first amount of displacement change is directly proportional to the amount of interference cavity length change.
4. The fabry-perot principle based displacement sensor according to claim 1, wherein the displacement reduction structure is a reduction gear structure comprising a gear and a rack; or, the reduction gear structure comprises a gear, a rack and a worm; the reduction gear structure can reduce a first displacement change generated by the probe rod into a second displacement change of the second reflecting surface, and the interference cavity length change between the first reflecting surface and the second reflecting surface is smaller than the first displacement change and is in direct proportion to the first displacement change.
5. The fabry-perot principle based displacement sensor according to claim 4, wherein the probe of the reduction gear structure has a first rack that is abutted with a first gear on a dual gear that is abutted with a second gear, the first gear has a diameter larger than that of the second gear, and the mirror is fixed to an end of the second rack; wherein,
when the probe rod generates a first displacement change amount, the first rack is driven to move, and the first displacement change amount is subjected to displacement reduction through the double gears, so that the second rack with the reflector generates a second displacement change amount, and the second displacement change amount is smaller than the first displacement change amount; and the variation of the length of the interference cavity between the first reflecting surface and the second reflecting surface is the second displacement variation.
6. The fabry-perot principle based displacement sensor according to claim 5, wherein the reduction gear structure comprises one or more double gears, wherein in case the reduction gear structure comprises a plurality of double gears, two adjacent double gears of the plurality of double gears are interfaced with each other by: the second gear of the double gear close to the probe rod is butted with the first gear of the double gear close to the reflector, and the diameter of the first gear is larger than that of the second gear.
7. The fabry-perot principle-based displacement sensor according to claim 4, wherein the probe of the reduction gear structure has a first rack, the first rack is connected to a first gear having a worm, the first gear and the worm share a rotation axis, the worm is connected to a second gear, the second gear is connected to a second rack, and the end of the second rack is fixed with the reflective mirror; wherein,
when the probe rod generates a first displacement change amount, the first rack is driven to move, the first rack drives the first gear to rotate, the rotation of the first gear drives the worm to rotate, the worm performs displacement reduction on the first displacement change amount and drives the second gear to rotate, and therefore the second rack with the reflector generates a second displacement change amount.
8. The fabry-perot principle-based displacement sensor according to claim 4, wherein the probe of the reduction gear structure has a first rack that is abutted with a first gear having a worm, the first gear and the worm share a rotation axis, the end of the worm is fixed with the mirror, a normal of the mirror is parallel to an axis of the worm, and the mirror moves along with the end of the worm; wherein,
the external screw thread of worm is twisted in a screw, when the probe rod takes place first displacement change volume, drive first rack removes, first rack drives first gear revolve, the rotation of first gear drives the worm rotates in the screw to drive the reflector of the tip of worm takes place to remove, through the worm is right first displacement change volume carries out the displacement and subtracts, makes the reflector of the tip of worm takes place the second displacement change volume.
9. The fabry-perot principle based displacement sensor according to any of claims 4 to 8, wherein the displacement reduction structure comprises any combination of the following: gears, racks, worms; the reduction gear structure can reduce a first displacement change generated by the probe into a second displacement change of the second reflecting surface, and the interference cavity length change between the first reflecting surface and the second reflecting surface is smaller than the first displacement change.
10. The fabry-perot principle based displacement sensor according to claim 1, characterized in that the displacement sensor further comprises a ramp;
an inclined hole perpendicular to the inclined plane is formed in the shell wall, a rod passes through the inclined hole, the top end of the rod is the reflector, a sliding block is fixed at the bottom of the rod, and the rod and the sliding block are integrated parts; the inclined plane, the bottom surface of the sliding block, the reflecting mirror at the top end of the rod and the end plane of the optical fiber are all parallel; when a probe rod of the displacement sensor generates a first displacement change amount in the horizontal direction, the inclined surface moves horizontally to drive the sliding block to move in the normal direction of the inclined surface, and finally the reflecting mirror at the top end of the rod is driven to move, so that the length delta d of an interference cavity between the plane of the end part of the optical fiber and the reflecting mirror is changed; wherein the inclination angle of the inclined plane is theta, and when the first displacement change amount is w, the change amount of the interference cavity length is delta d which is w sin theta; the first displacement change quantity and the cavity length change quantity are in a linear relation;
one end of a probe rod of the displacement sensor is connected with an anti-shaking lug, and the anti-shaking lug enables the inclined plane to axially move only along the direction of the first displacement variation.
11. The Fabry-Perot principle based displacement sensor according to claim 10,
the contact mode of the bottom of the sliding block and the inclined plane is sliding friction contact or rolling friction contact; wherein,
the contact means of the sliding frictional contact includes: contacting with a point; or by a line contact; or with a planar contact; or two or more points which are arranged on the inclined plane at a certain distance are contacted, and the two or more points are arranged on the same plane; or two lines or a plurality of lines which are arranged on the inclined plane at a certain distance are contacted, and the two lines or the plurality of lines are arranged on the same plane; or two or more surfaces which are separated from each other by a certain distance on the inclined surface are contacted, and the two or more surfaces are on the same plane; the contact component of the bottom of the slide block and the inclined plane is in a sliding friction contact mode of any combination of points, lines and planes which do not rotate;
the contact manner of the rolling friction contact includes: contacting with a point; or two or more points which are arranged on the inclined plane at a certain distance are contacted, and the two or more points are arranged on the same plane; the bottom of the sliding block and a contact component of the inclined plane are in a rolling friction contact mode, the axis of a rigid rod connected with the top of the sliding block is perpendicular to the inclined plane and penetrates through an inclined hole with the axis perpendicular to the inclined plane, the normal of a reflector at the top of the rigid rod is perpendicular to the inclined plane, and the plane of the end part of the optical fiber is parallel to the reflector.
12. The fabry-perot principle based displacement sensor according to claim 11, wherein the slider is in point contact or surface contact with the inclined surface; wherein,
the contact mode of point contact includes single-point contact or multipoint contact, wherein, when the multipoint contact, the projection of the connecting line of all contact points in the displacement direction has certain length, and under the condition that the slide block does not rotate, the measurement of the interference cavity length cannot be influenced additionally, and the measured displacement and the variation of the interference cavity length are in a linear relation.
13. The fabry-perot principle based displacement sensor according to claim 11, wherein when the slider has two point contacts or two plane contacts on the slope:
the distance between the two action points is L, a spring is arranged above the sliding block, the sliding block can be extruded and attached to the inclined plane by the spring, the sliding block and the inclined plane have certain friction force, and the friction force is in direct proportion to the elasticity of the spring; when the probe rod of the displacement sensor generates a first displacement change amount, the distance L between the two action points is increased, or the friction coefficient between the sliding block and the inclined plane is reduced, or the elasticity of the spring is increased, so that the two action points are always in contact with the inclined plane, the sliding block does not rotate, and the reflecting mirror on the end face of the rigid rod above the sliding block is always parallel to the inclined plane.
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