JPH02201108A - Physical quantity measuring instrument - Google Patents

Abstract

PURPOSE:To effectively suppress a drift by providing Fabry-Perot interference optical system in two systems and offsetting drift signal components at the time of obtaining difference information. CONSTITUTION:First and second Fabry-Perot interference optical systems 10A and 10B to obtain photoelectric converting signals I1S, I2S, and ICS to express interference light intensities E1 and E2 by generating interference lights LA3 and LA5 and photoelectric-converting them are provided. On side of a pair of reflecting surfaces to compose the optical systems is fixed to a first displacement detecting member 5, and the other reflecting surface is fixed to second displacement detecting members 4A and 4B. By obtaining difference information pieces IS and ICS corresponding to the relative displacement quantity of the detecting members 5, 4A and 4B based on the photoelectric converting signals I1S, I2S and ICS, the drift generated in a reflecting surface interval is offset, a measuring signal (e) is obtained, and thereby, the drift can effectively be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a physical quantity measuring device, and is particularly suitable for use in measuring minute changes in physical quantities.

[Summary of the invention]

According to the present invention, in a physical quantity measuring device having a Fabry-Perot interference optical system, by providing two series of Fabry-Perot interference optical systems, it is possible to reliably suppress a drift signal component that may occur in a measurement output signal.

[Conventional technology]

Conventionally, as a Fabry-Perot interferometric physical quantity measuring device, l
A configuration has been proposed in which a detection signal corresponding to a change in a physical quantity, for example, acceleration, is obtained based on a detection signal obtained from a series of optical interference optical systems (Patent Application No. 1983-2).
No. 35033).

This physical quantity measuring device detects the uniform displacement caused in the vibration-sensing member due to vibration as a change in interference light generated in a pair of semi-transparent mirrors, and charges and converts the interference light into a feedback signal for the vibration-sensing member. It is made to form.

In this way, a servo operation system is configured for the vibration-sensing member by the feedback signal, and the displacement of the vibration-sensing member is thereby controlled within a range such that the change in the photoelectric conversion signal that occurs when the vibration-sensing member is displaced is simply increased or decreased. This is done so that the amount can be controlled.

[Problem that the invention seeks to solve]

The physical m measuring device with this configuration has the advantage of being able to detect minute displacements of the vibration-sensing member with high sensitivity and precision; For example, if thermal expansion (or thermal contraction) occurs in the components of the vibration sensing member or wavelength fluctuation occurs in the light source that supplies measurement light to the interference optical system, this may be mixed into the measurement results as a disturbance signal component. be.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a physical quantity measuring device that can effectively reduce disturbance signal components that occur due to changes in the surrounding conditions. .

[Means for solving problems]

In order to solve such problems, in the first invention,
Between each pair of reflective surfaces, the reflective surface spacing 11,
Interference light intensity corresponding to 1g, E! Interference light LA exhibiting
3. By generating LA5 and photoelectrically converting the interference lights LA3 and LA5, a photoelectric conversion signal representing the interference light intensity 1, E is generated. , Its, the first and second to obtain IC3
The first and second Fabry-Perot interference optical systems 10A, 1 include Fabry-Perot interference optical systems 10A, IOB.
One of the pair of reflective surfaces constituting each of 0B is fixed to the first displacement detection member 5, and the other of the pair of reflection surfaces is fixed to the second displacement detection member 4A, 4.
A photoelectric conversion signal r+s, It is fixed to B and obtained from the first and second Fabry-Perot interference optical systems 10A and IOB.
s, difference information 1s corresponding to the relative displacement amount between the first and second displacement detection members 5, 4A, and 4B based on IC3.
, Ics, the measurement output signal e is obtained by canceling the drift displacement Δl that occurs in the reflective surface spacing e, , it.
Configure it to get .

Further, in the second invention, in addition to the first invention,
and second Fabry-Perot interference optical system 10A and IOB
are separate first and second photoelectric conversion elements 22A,
22B, and the first and second photoelectric conversion elements 22A
, 22B, the first and second photoelectric conversion signals 1+
The configuration is such that the difference information (2) is obtained by subtracting or adding s and Its.

Further, in the third invention, in addition to the first invention,
The second Fabry-Perot interference optical system 10A and IOB have a common photoelectric conversion element 22C, and the interference lights LA3 and LA5 generated in the first and second Fabry-Perot interference optical systems 10A and 10B are transferred to the common photoelectric conversion element. The configuration is such that a photoelectric conversion signal IC11 forming differential information is obtained by photoelectric conversion at 22C.

Further, in the fourth invention, in addition to the first invention,
and the cylinder 1 between the second displacement detection member 5 and 4A, 4B.
and displacement control means 25 and 27 that can change and control the relative positional relationship of the second displacement detection members 5, 4A, and 4B,
Feedback control signal S that suppresses changes in relative position based on photoelectric conversion signals I11, tts, and tcs
By controlling the displacement control means 25 and 27 by 2, the linearity of the change in the interference light intensity E, , E, when the amount of displacement between the first and second displacement detection members 5, 4A, and 4B changes. Configure to maintain.

Further, in the fifth invention, in addition to the first invention,
and the cylinder 1 between the second displacement detection member 5 and 4A, 4B.
and displacement control means 25 and 27 that can change and control the relative positional relationship of the second displacement detection members 5, 4A, and 4B,
The displacement control means 25 and 27 are configured to be able to set the relative positional relationship by applying a displacement setting signal.

Further, in the sixth invention, between the pair of reflective surfaces, the interference light intensity E corresponding to the reflective surface interval 1+, it,
, E, and by photoelectrically converting the interference lights LA3, LA5, the interference light intensities El, E! Photoelectric conversion signal representing ■4, ■□, yes
Fabry-Perot interference optics to get the best results! OA and IOB, one of the pair of reflective surfaces constituting the Fabry-Perot interference optical system 10A and IOB is fixed to the first displacement detection member 5, and the other of the pair of reflective surfaces is fixed to the first displacement detection member 5. The surfaces are fixed to the second displacement detection members 4A, 4B, and photoelectric conversion signals its, I! A measurement output signal e corresponding to the relative displacement between the first and second displacement detection members 5 and 4A, 4B is obtained based on the amount of change in ffi, rcs,
Reflection surface spacing at which the rate of change of interference light intensities Et and Ex is constant2. ．． 2. The value of is the reflective surface interval in a state where no relative displacement occurs between the first and second displacement detection members 5, 4A, and 4B! ,. , 2□. The configuration is configured so that the selection is made as follows.

[Effect]

First and second Fabry-Perot interference optical systems 10A, IO
The charging conversion signal obtained from B has a reflection surface interval of 1. ,
j! ! When a drift displacement Δ2 occurs in , a corresponding drift signal component is generated in the photoelectric conversion signal.

These drift signal components cancel each other out by performing processing such as determining difference information, and thus it is possible to effectively avoid the possibility of this occurring in the measurement output signal e.

Also, the reflective surface spacing 42.0 at which the rate of change of the interference light intensity E, , E, is constant. , f, and the reflective surface spacing r8,l! By selecting the center point of change as 7!1°, lto,
In practical terms, it is possible to obtain measurement results with even better linearity.

(Example〕 An embodiment of the present invention will be described in detail below with reference to the drawings.

[1] Structure of the first embodiment FIG. 1 shows an embodiment in which the present invention is applied to a servo acceleration type vibration detection device. It has a configuration that stores 3.

The vibration detecting unit main body 3 is fitted into the case 2 as shown in FIG. 2 to show the configuration of its vibration system, and includes a first annular fixing member 4A with one end closed, and a first fixing member 4A of this fixing member 4A. A cylindrical vibration sensing member 5 is provided at a concentric position inside the fixing members 4A and 4B.

An annular holder 6 is integrally fitted into the inner surface of the fixing member 4A, and a leaf spring 7 is fixed to the stepped portion of the inner surface.
A vibration-sensing member 5 is attached to the inner tip portion of the vibration-sensing member 5 so as to be able to freely vibrate in the axial direction.

A holding plate 8 is fixed inside the vibration-sensing member 5 so as to cross the central axis LCEjl'r, and a pair of movable half-transparent mirrors 9A and 9B are attached to both sides of the holding plate 8. Two Fabry-Perot interference optical systems 10A and 10B including transparent parts 9A and 9B are formed so as to run substantially parallel to the central axis L CENT of the vibration sensing member 5.

That is, a light source 15 made of, for example, a semiconductor laser is placed at a position outside the fixed member 4A on the central axis of the vibration sensing member 5, on □A.
Is the light provided? Measuring light LA emitted from fl15
I is converted into parallel light by the collimator 16 and then irradiated onto the movable semi-transparent mirrors 9A and 9B.

In this embodiment, the light [15 and the collimator 16 are attached to a mounting plate part I7 formed inside the case 2 so as to be orthogonal to the center line thereof, and a part of the parallel light emitted from the collimator 16 is The incident light flux LA2 passes through the through hole 18A provided in the closing plate part 14 of the fixed member 4A, and then passes through the fixed side semi-transparent mirror 19A provided inside the through hole 18A so as to cover it, and then passes through the movable side. The light is made to enter the semi-transparent mirror 9A.

Thus, the fixed side semitransparent mirror 19A and the movable side semitransparent fi9
A first interference light LA3 for the first fabric bellow interference optical system is generated between the reflective surfaces of A, and this first interference light LA3 is transmitted to the holding plate 8 at the position where the fixed side translucent II 1.19A is fixed. The light enters, for example, a photoelectric conversion element 22A through a through hole 20A formed in the hole 20A and a through hole 21A formed across the thickness of the fixing member 4B.

On the other hand, a part of the parallel light beam emitted from the collimator 16 passes through the through hole 1BB provided in the closing plate part 14 as a second incident light beam LA4, and then passes through the through hole 2 provided in the holding plate 8.
The light passes through 0B and enters the second movable semi-transparent mirror 9B.

The light flux passing through this movable semi-transparent mirror 9B is incident on the fixed semi-transparent m19B attached to the inner surface of the fixed member 4B so as to face the movable semi-transparent mirror 9B, and thus between the semi-transparent ff19B and 19B. The generated interference light LA5 passes from the stationary side semi-transparent mirror 19B through the through hole 21B drilled in the stationary member 9B. The light is input to the conversion element 22B.

In this way, the light source 15, collimator 16, through hole 18A
, semitransparent mirrors 19A, 9A, and through holes 20A.

A first Fabry-Perot interference optical system 10A is formed by the photoelectric conversion element 21A and the photoelectric conversion element 22A, and the light source 15, the collimator 16, and the through holes 1BB and 20B.

Semi-transparent mirrors 9B, 19B, through hole 21B, photoelectric conversion element 22
B forms a second Fabry-Perot interference optical system 10B. The fixing members 4A and 4 of the vibration sensing member 5 fit into this.
Interference lights LA3 and LA5 whose light intensity changes according to relative positional displacement with respect to B are obtained, and the photoelectric conversion signal Its
and Io as Fabry-Perot interference optical system 10A and IOB
The detection signal S1 is sent out as the detection signal S1.

An electromagnetic coil holding member 26 having an electromagnetic coil 25 fixed to its tip is attached to the outer surface of the vibration sensing member 5, and the electromagnetic coil 25 is provided on a ring-shaped magnetic circuit member 27 fixed to the inside of the holder 26. It is arranged so as to protrude into the space 11128.

Here, the blank [2B is cut in the left side end face in the right direction so as to extend in the direction along the central axis L C1HT of the vibration sensing member 5, and this causes the displacement given to the magnetic coil 25 from the drive control circuit 31. Displacement control means that controls the relative displacement position of the iM1 coil 25 with respect to the magnetic circuit member 27 (in the direction of the central axis L etNt), and therefore the displacement position of the vibration sensing member 5 with respect to the fixed members 4A and 4B, by the electromagnetic force generated by the control current S2. is formed.

The drive control circuit 31 generates photoelectric conversion signals It! obtained from the first and second Fabry-Perot interference optical systems 10A and IOB, respectively. and 10 as a subtraction circuit 3 having a differential amplifier circuit configuration.
Receive and subtract power in 2! , is phase-shifted to a predetermined phase in a phase shift circuit 33 having a differential circuit configuration, and then is caused to flow from the drive output amplification circuit 34 to the ground through the tM1 coil 25 and the load resistor 35 as a feedback output current I□.

Thus, the optical ti exchange signal It! and +, the first
and second Fabry-Perot interference optical system 10A and IOB
A servo drive circuit unit 36 is formed as a part of the drive control circuit 31 to obtain the feedback output current IFII by subtracting the difference information representing the difference between the detection signals of The voltage across the terminal is sent to the output terminal 37 as the measurement output signal e.

The drive control circuit 31 sends a light source drive signal S3 to the light source 15.
A printed circuit board 39 together with a light source circuit 38 that supplies
The photoelectric conversion elements 22A and 22B and the printed circuit board 3 are mounted on a case member 40 that closes the right end surface of the case 2, and both end surfaces of the case 2 are equipped with shield plates. 41 and 42.

The servo drive circuit section 36 has a displacement amount setting current source 45 which is a constant current source, and the displacement amount setting signal l5ty obtained at its output terminal is combined with the feedback output current I□ and sent out as a displacement control signal S2. Ru. In this way, the electromagnetic force generated between the electromagnetic coil 25 and the magnetic circuit member 27 is centered on the electromagnetic force caused by the displacement setting signal Iall, and N magnetic force caused by the feedback output current I□ is superimposed.

Therefore, the displacement amount setting signal I of the current source 45 for displacement amount setting. ,
If necessary, reset the reflection surface spacing of the semi-transparent mirrors 9A and 19A and 9B and 19B to 11° and j! when the feedback output current 1□ is Iym=O. □. (Therefore, the displacement position of the vibrating member 5) can be reset.

[2] Displacement detection operation In the vibration detection device 1 having the configuration shown in FIGS. 1 and 2, the vibration sensing member 5 is placed on the holding plate 8 as shown in FIG. When the movable half-transparent mirrors 9A and 9B fixed to the movable side mirrors 9A and 9B vibrate in the left-right direction along the center line L CENT as shown by arrow a, the amount of displacement is detected based on the operating principle described below.

Here, the positional relationship between the fixed side semi-transparent mirrors 19A and 19B is as follows:
Fixing member 4 in which the semi-transparent mirrors 19A and 19B are rigid bodies
Since they are rigidly connected to each other by A and 4B, even if the case 2 vibrates, the distance between the reflective surfaces of the semitransparent mirrors 19A and 19B does not change.Similarly, the movable semitransparent mirrors 9A and 9B are rigid bodies. Since they are firmly connected to each other by the retaining plate 8, the distance between the reflective surfaces of the translucent jis 19A and 9B does not change.

On the other hand, the vibration sensing member 5 and therefore the holding plate 8 are softly coupled to the holder 6 and therefore the fixed member 4A so that they can be displaced in the direction of the arrow a by the temporary spring 7, so that the movable side translucent m9A and 9B are The reflecting surfaces are displaced relative to the reflecting surfaces of the opposing stationary translucent mirrors 9A and 19B in accordance with the displacement of the vibration-sensing member 5, and thus the positional displacement of the vibration-sensing member 5 is the same as that of the semi-transparent mirrors 9A and 19A. and the reflective surface interval 1 of the semitransparent mirrors 9B and 19B.
It appears as a change in 1.

By the way, when configured as the first and second Fabry-Perot interference optical systems 10A and IOB in FIG. 3, the intensity reflectance of the semi-transparent mirror is generally assumed to be R1, the distance between reflective surfaces is l, and the light intensity of the light source is E. The light intensity E of the interference light obtained in this case can be expressed by a periodic function similar to a sine function with a period of 2π/λ, when the reflective surface spacing l is a variable, as shown in the following formula (1). Can be done.

Therefore, if the interference light intensity E expressed by equation (1) is expressed as a curve diagram using the intensity reflectance R as a parameter, it can be seen that there is a relationship as shown in FIG. 4.

In the curve diagram in Figure 4, the reflective surface spacing! In order to detect a small amount of change while maintaining good linearity, when the intensity reflectance R is specified, the reflective surface spacing l
It can be seen that it is sufficient to limit the area to a region where the interference light intensity E changes linearly with respect to a change in .

For example, the intensity reflectance R is R=0.25 (=25 (%)
), the center position l within the range where practically sufficient linearity can be obtained when the reflective surface spacing l changes.

However, from the diagram in Figure 4, it is clear that the point should be selected as shown in the following equation, and if the intensity reflectance R is selected to be less than a few [%], then in practice the relationship should be selected as shown in the following equation. You'll know what to do. Here m
is an integer (m-0, 1, 2...).

In the case of the embodiment shown in FIGS. 1 and 2, the center position i of the interval between the reflective surfaces of the first and second Fabry-Perot interference optical systems 10A and IOB. and Il. Semi-transparent @9A and 19A, 9B and 1 so as to satisfy λ
9B and the dimensions of the member joining these semi-transparent mirrors. In equations (4) and (5), m and m3 are selected to be approximately equal integers (equal values or nearby values), thus reflecting surface spacing L1
1 and 28 degrees are practically the same distance.

The reflective surface interval j set in this way! 1° and lt
When the vibration member 5 is located at the position corresponding to 6, the semi-transparent mirror 9
As the vibration sensing member 5 is displaced by the positional displacement δ to the right as shown by the arrow a1 from the state where the reflecting surfaces 9AX and 9BX of A and 9B are at the positions shown by the broken lines in FIG.
The reflective surfaces 9AX and 9BX are spaced apart as shown by solid lines! , and l.

Consider the case where the object moves to the position .

At this time, the reflective surface spacing 11 of the first Fabry-Perot interference optical system 10A is f, =jl! ,. +δ (6) In contrast, the distance 12 of the reflective surfaces of the second Fabry-Perot interference optical system 10B is j! , =2. . -δ ...... (7) It exhibits a change in which the distance δ decreases.

Therefore, by substituting equations (4) and (5) into equations (6) and (7), λ can be further expressed as the following equation, and by substituting this as the reflective surface spacing i in equation (1), , the interference light intensities E1 and E8 of the interference lights LA3 and LA5 obtained in the first and second Fabry-Perot interference optical systems can be determined.

However, in practice, it is possible to simplify the expressions by approximation in such arithmetic processing, and as a result of such simplification, the interference light intensities E1 and E2 can be simplified as shown in the following equations, and in the end, the interference light intensities E1 and E2 are the displacement amounts. It can be seen that there is a linear proportional relationship with respect to δ.

Therefore, the interference light L in the photoelectric conversion elements 22A and 22B
Photoelectric conversion signals its and ■ obtained by photoelectrically converting the interference light intensities E and E of A3 and LA5. can be expressed as a trigonometric function using the displacement amount δ of the reflecting surfaces 9AX and 98X as a variable, as shown in the following equation.

Equations (lO) and (11) further indicate that the displacement δ is 8/λ
If it is sufficiently smaller than , it can be expressed as the property of trigonometric functions.

Incidentally, although there are variations in sensitivity between the charge conversion elements 22A and 22B, this variation in sensitivity can be corrected in the servo drive circuit section 36, so that the first and second Fabry-Perot interference optical systems 10A and IOB's photoelectric conversion signal Il! It may be considered that and Its can be converted from equations (12) and (13) to the relationships of equations (14) and (15), respectively.

This photoelectric conversion signal■9. and■8. is subtracted by the subtraction circuit 32 of the servo drive circuit section 36, and as a result, the subtraction output I is proportional to the displacement amount δ, as shown in the following equation.
, can be obtained.

This subtracted output I is differentiated in a phase shift circuit 33 and shifted to a phase corresponding to a change in its rate of change, and then amplified in a drive output amplification circuit 34 and sent to the electromagnetic coil 25 as a feedback output current IFm. Given.

Thus, when the vibration sensing member 5, and thus the semitransparent mirrors 9A and 9B, vibrate in the direction of arrow a, the electromagnetic coil 25 performs a servo control operation that applies a suppressing force corresponding to the acceleration. The amount of displacement δ of the vibration sensing member 5 can be limited to a sufficiently modest value.

In fact, as mentioned above regarding equations (12) and (13), a value that is sufficiently compact to allow simplified calculations from equations (10) and (11), that is, a displacement that is sufficiently compact from 16/λ As a result, when the vibration sensing member 5 is displaced, the linearity between the displacement and the change in the interference light intensity that occurs in the first and second interference lights LA3 and LA5 can be suppressed to a practically sufficient level. It is possible to limit the displacement to a good range, and thus it is possible to convert the minute displacement of the vibration sensing member 5 into a subtracted output (2) with high accuracy.

In this way, from the servo drive circuit section 36 to the electromagnetic coil 2
The displacement control current S2 supplied to the terminal 5 flows to the ground through the load resistor 35, thereby generating a voltage drop corresponding to the displacement control current S2 across the load resistor 35, and this adjacent lower voltage is output as the measurement output signal e. The signal is sent to terminal 37.

In a servo vibration system with such a configuration, the mass of the movable part (mainly consisting of the bad news member 5 and the holding plate 8) is generally m
, the resistance value of the servo resistor (consisting of load resistor 35) is RL,
The t flow-force conversion coefficient At of the displacement control means (consisting of the magnetic coil 25 and the magnetic circuit member 27), the vibration member (bad news member 5)
When the amount of vibration (consisting of ) is set as a, the measurement output signal e can be obtained as an electrical signal that changes according to the magnitude of the amount of vibration a as shown in the following equation.

The sensitivity can be adjusted by setting ititm, the resistance value Rt, and the current-force conversion coefficient At as necessary, and thus the vibration to be measured can be accurately measured.

[3] Selection of reflective surface spacing Reflective surface spacing L11 and l, which are the center positions of the displacements described above for equations (4) and (5). When selecting the
The optimum condition can be determined as a condition in which the result of differentiating equation (1) twice with respect to the reflective surface spacing l is O.

Incidentally, in the characteristic curve of the interference light intensity E in Fig. 4, the range in which the interference light intensity E changes with good linearity with respect to a change in the reflective surface spacing 2 is the rate of change of the interference light intensity E expressed by equation (1). (Therefore, the value obtained by differentiating Equation (1) once) is a constant value in practice, and the center point is a point where the rate of change of the interference light intensity E is theoretically constant. This is because if the point where the value obtained by differentiating equation (1) twice is O), it can be said that there is a range in which linearity is good for the surrounding conditions in practice.

In this way, the reflective surface spacing representing the theoretically optimal center position can be determined by calculation as shown in Figure 10 according to the intensity reflectance R of the semi-transparent mirror. Change in interference light intensity E with good linearity,
Therefore, measurement detection results can be obtained.

Here, the center position can be set by resetting the current value of the displacement amount setting signal 7 of the displacement amount setting current source 45 in the drive control circuit 31 as necessary.

[4] Operation for suppressing disturbances such as thermal expansion When the vibration detection device l shown in FIGS. 1 and 2 performs the above-mentioned vibration detection operation, for example, the first and second Fabry-Perot interference optical systems 10A and When thermal expansion or contraction occurs in the constituent parts of the light source 10B, or when the wavelength λ of the measurement light LAl emitted from the light source 15 changes, an operation is enabled in which the measurement output signal e changes due to the fluctuation. It can be suppressed.

That is, in the configurations shown in FIGS. 1 and 2, the first and second Fabry-Perot interference optical systems 10A and IOB separately detect the displacement of the bad news member 5, and calculate the following equation (12) and It is possible to cause changes in the interference light intensities E and E2 as expressed by equation (13), but during this operation, the reflective surface interval 11
For example, if a spacing change Δi occurs in Rt and Rt (Fig. 3) due to thermal expansion, the reflecting surface spacing increases under the influence of this, and as shown in Fig. 6, equation (8) and ( 9) Reflection surface spacing 21 and 1□ described above for formula
In addition to this, the spacing change Δl due to thermal expansion occurs, so the spacing between reflective surfaces after thermal expansion! , and 1□ are the following equations... (19) As shown in (19), the vibration detection unit main body 3
The reflective surface spacing increases as the member constituting expands with a coefficient of thermal expansion α.

Here, the integers m and m2 are selected to be approximately equal to each other as described above, and the displacement δ of the bad news member 5 caused by vibration is suppressed to a small value, so (
It can be considered that the values of the second terms in equations 18) and (19) are approximately the same amount of change Δl, such as λ, and equations (18) and (19) are expressed by the following equations λ λ... ... (22) It can be expressed as follows.

Therefore, the first and second Fabry-Perot interference optical systems 10A
And the interference light intensities Ell and E□ of the first and second interference lights LA3 and LA5 that can be obtained at IOB are (
In the same way as described above for equations 10) and (11), it can be expressed as 3Δp... (20)... (23)... (24) can.

In reality, the ambient temperature θ changes slowly over a long period, so the interference light intensities E11 and E! 1 will cause a low frequency drift.

Interference lights LA3 and LA of these interference light intensities Ell and E□
Photoelectric conversion signals r+s and I obtained by photoelectrically converting 5 in photoelectric conversion elements 22A and 22B. When subtraction is performed in the subtraction circuit 32 of the servo drive circuit unit 36 (FIG. 1), the subtraction output I is difference information representing the difference between the detection signals of the first and second Fabry-Perot interference optical systems 10A and IOB. Become.

Then, the subtraction output I, is expressed by equations (12) and (13), and (1
By performing the same processing as described above for equations (4), (15), and (16), the reflective surface spacing and it are calculated based on thermal expansion as shown in the following equations.
The noise signal component of the interval change Δl that occurs in FIG. 3 is canceled out by the subtraction operation of the subtraction circuit 32, so that it can be processed so as not to be mixed into the subtraction output I.

As a result, it is possible to effectively avoid the possibility that a noise signal component due to thermal expansion, that is, a low frequency drift component, is generated in the measurement output signal e, and the accuracy of the vibration measurement result can be further improved.

In the above, the influence of drift during thermal expansion has been described, but even when thermal contraction occurs, the noise signal component can be effectively removed by the subtraction process of the subtraction circuit 32. The possibility of causing a drift in the output signal e can be effectively avoided.

In addition to this, if a thermal expansion phenomenon or a disturbance that causes a change in the wavelength λ of the measurement light LAI occurs in the light si5 in addition to the occurrence of a thermal expansion phenomenon, the measurement is performed based on this. It is possible to prevent drift from occurring in the output signal e.

The subtraction output I obtained at the output terminal of the subtraction circuit 32 is
As described above regarding equation (25), by being able to obtain a signal with the drift fluctuation component Δl canceled out, the possibility of drift occurring due to a change in the wavelength λ is effectively avoided.

In addition to this, in equation (25), the displacement δ is δ−0
When (this word indicates that the bad news member 5 is not vibrating), the subtraction output I is I.

-〇, thereby maintaining a state in which no electromagnetic force is applied to the magnetic circuit member 27, and hence the bad news member 5, based on the feedback output current I□.

Thus, even if the wavelength λ of the measurement light LAI emitted from the light source 15 fluctuates, the influence will be
It only affects the measurement sensitivity when the vibration displacement occurs.
By being able to always position the bad news member 5 at a predetermined initial position when the bad news member 5 is not vibrating, it is possible to prevent the measurement output signal e from drifting when there is no vibration, thereby achieving even higher accuracy. Vibration measurement results can be obtained with .

[5] Second Embodiment FIG. 7 shows a second embodiment of the present invention, and as shown by assigning the same reference numerals to corresponding parts to those in FIG.
Fabry-Perot interference optical system 1. Among the OA and IOB, one photoelectric conversion element 22C is commonly used in both systems as a means for photoelectrically converting the first and second interference lights LA3 and LA5.
Thus, the photoelectric conversion element 22G
The photoelectric conversion signal icy obtained by photoelectrically converting the combined light of the first and second interference lights LA3 and LA5 from the first and second Fabry-Perot interference optical systems 10A and I
The information is sent out as difference information representing the difference between the OB detection signals.

In the case of this embodiment, the reflective surface spacing 11 and I of the first and second Fabry-Perot interference optical systems 10A and IOB are
The reference values r1° and 18° when the bad news member 5 is not vibrating with respect to lt are given by the following formula: 1-15λ/
It was made possible to express the reflective surface spacing 1K by using the characteristics of the straight line section that slopes upward to the right, including the value at 16.
In this way, the photoelectric conversion process is performed at positions where the interference light intensities E and E of the interference lights LA3 and LA5 are shifted from each other by approximately π.

At this time, the interference light intensities E and El of the interference lights LA3 and LA5 are selected as shown in the following equations in the same manner as described above for equations (10) and (11). Thus, the light intensity E of the optical interference light LA3 of the first Fabry-Perot interference optical system 10A is:
In Figure 4,! The distance 11 between reflective surfaces can be expressed by using the conversion characteristics of the straight line portion that includes the value when =λ/16, that is, the straight line portion that changes downward to the right near l = 0. There is.

On the other hand, the light intensity E of the optical interference light LA5 of the second Fabry-Perot interference optical system 10B can be expressed as shown in FIG. The photoelectric conversion signal ICS obtained by charge conversion in can obtain the same effect as in the case.

There are many values corresponding to the sum of the changes in the intensity of the interference light generated in the interference lights LA3 and LA5, as shown in FIG.

As described above for the first embodiment ((16) 2), this relationship (30) 2 is related to the interference light LA3 and LA of the first and second Fabry-Perot interference optical systems tOA and IOB.
This means that it was possible to obtain a result equivalent to obtaining the deviation between 5 and 5 as the subtraction output I by the subtraction circuit 32.

Therefore, in the case of the embodiment shown in FIG.
Even if drift fluctuation occurs in the interference beams LA3 and L
The drift fluctuation components contained in each of A5 are canceled out by each other during the photoelectric conversion signal in the photoelectric conversion element 22C, and as a result, a detection signal in which the drift fluctuation component is effectively suppressed is obtained as a photoelectric conversion signal icx. Can be done.

Therefore, even if the configuration is as shown in FIG. 7, [6] Third Embodiment of the first embodiment, FIG. 8 shows the third embodiment, and corresponding parts to those in FIG. 3 are given the same reference numerals. As shown, parallel incident light beams LA2 and A4 obtained based on the measurement light LAI of the light source 15 (FIGS. 1 and 2) are incident on the through holes 18A and 18I3 through the beam splitter 5.

In this embodiment, the Fabry-Perot interference optical system 10 of the tube 1
The incident light beam LA2 on the A side passes through the semi-transparent fi19A and then enters the reflecting mirror 49 attached to the holding plate 8 so as to face the semi-transparent fi19A, and the reflective surface of this reflecting mirror 49 and the semi-transparent fi19A Optical interference is caused between the reflective surfaces, and the interference light LA3 thus obtained passes through the semi-transparent mirror 1.9A and the through hole 18A, is reflected by the beam splitter 5, and is extracted to the photoelectric conversion element 22A. .

On the other hand, the incident light beam LA4 on the second Fabry-Perot interference optical system 10B side passes through the beam splitter 51, passes through the through holes 18B and 20B, and enters the semi-transparent M9B. A reflecting mirror 50 is mounted on the fixed member 4B so as to face the semi-transparent mirror 9B.

In this way, optical interference occurs between the reflective surface of the reflective mirror 50 and the reflective surface of the semi-transparent mirror 9B, and the interference light LA5 is transmitted to the half mirror.
9B, beam splitter 5 through through hole 2OB118B
1 is drawn out to the charging conversion element 22B.

In this way, the charge conversion signal obtained in the photoelectric conversion elements 22A and 22B is 0. and 10 is a servo drive circuit section 36
subtraction circuit 32 (FIG. 1).

In the above configuration, when the bad news member 5 vibrates, the interference lights LA3 and LA5 obtained from the first and second Fabry-Perot interference optical systems 10A and IOB are expressed by equation (12) and It exhibits interference light intensities E1 and E8 as expressed by equation (13).

In addition to this, thermal expansion (or heat yield) and measurement light L
When a change occurs in the wavelength λ of the AI, an operation is performed to cancel out the drift signal component as expressed by equation (25) in the same manner as described above with reference to FIG.

Thus, the third embodiment can also provide the same effects as described above for the first embodiment.

[7] Fourth Embodiment FIG. 9 shows a fourth embodiment, in which corresponding parts to those in FIGS. 3 and 8 are denoted by the same reference numerals, and a first Fabry-Perot interference optical system 10A is shown. The incident light beam LA2 is passed through the beam splitter 52 to the through hole 18A, the semi-transparent mirror 19A,
By entering the reflecting mirror 49, the beam splitter 5
2 to obtain a photoelectric conversion signal ray by extracting the interference light LA3 to the photoelectric conversion element 22A,
In this respect, the configuration is similar to that of the embodiment shown in FIG.

On the other hand, regarding the second Fabry-Perot interference optical system 1OB, the semi-transparent mirrors 9B and 19 are
By extracting the interference light LA5 formed by B through the semi-transparent M19B, a photoelectric conversion signal I is generated from the photoelectric conversion element 22B. Configure it to get .

Even with the configuration as shown in FIG. 9, the same operation and effect as in the case of FIG. 8 can be obtained.

[8] Other embodiments (1) In the above embodiment, the displacement control current S2 is calculated based on the subtraction output Is (Figs. 3, 8, and 9) and the photoelectric conversion signal 1c3 (Fig. 7). In order to obtain
And/or the drive output amplification circuit 34 may be omitted.

(2) In the above embodiment, the servo drive circuit section 36
In order to suppress the vibration of the oscillating member 5 based on the displacement control signal S2 of By doing this, an electromagnetic force that acts as a control force for the bad news member 5 is generated.However, instead of this, an electromagnetic coil 25 is provided on the fixed part side, and 1! The magnetic circuit member 27 may be provided, or the electromagnetic circuit member 27 and the electromagnetic coil 25 may be integrated and provided on the fixed part side, and a magnetic material (
For example, a coupling member made of (such as iron) may be provided on the bad news member 5 side, or conversely, a magnetic material may be provided on the fixed part side, and a magnetic circuit member 27 and an electromagnetic coil 25 may be provided on the bad news member 5 side. If provided, various configurations can be applied.

Furthermore, various shapes, structures, and arrangements can be applied to the electromagnetic control force generating means such as the magnetic circuit member 27 and the electromagnetic coil 25, and the point is that there is mutual interaction between the case 2 side, that is, the fixed part side and the bad news member 5. It may be configured to generate a control force.

(3) In the above-mentioned embodiment, a configuration using electromagnetic force as a control force generation means for the bad news member 5 was described, but instead of this, an electrostatic force, a piezoelectric force, etc. are used. may be applied.

(4) In the above embodiment, the incident light beam LA2 enters the first and second Fabry-Perot interference optical systems 10A and IOB.
, LA4, the measurement light LAI emitted from one light source 15 provided in common to the first and second Fabry-Perot interference optical systems 10A and 1 and OB is passed through a collimator 16 and through holes 18A and 18B. However, instead of this, separate light sources are provided for the first and second Fabry-Perot interference optical systems 10A and IOH, and parallel light beams for each interference optical system are generated from each light source. or through hole 18 from the light source.
Various configurations may be applied, such as omitting the collimator 16 by generating a large-diameter parallel light beam that can irradiate A and 18B as a whole.

(5) In the above-mentioned embodiment, the interference light LA is
3. We have described the case where LA5 is obtained, but even if the distance between the reflective surfaces is set to several tens of pm or less and at the same time a diverging light beam is directly irradiated thereon, interference light representing the distance between the reflective surfaces can be obtained. Even in this case, the same effect as in the above case can be obtained.

(6) In the above embodiment, the first and second Fabry-Perot interference optical systems! Although the spacing between the pair of reflective surfaces constituting the OA and IOB was set as necessary by selecting the thickness of the members constituting the vibration detection unit main body 3, instead of this, the spacing between the reflective surfaces may be adjusted. A dedicated adjustment means may be provided for this purpose.

(7) In the above-described embodiment, in order to obtain interference light with interference light intensities E1 and Et from the first and second Fabry-Perot interference optical systems 10A and IOB, the intensities of the semi-transparent mirrors 9A and 9B, 19A and 19B are Reflectance R to 25 [%]
This was described as an example in the case where the intensity reflectance R
is not limited to this, and can be set to various values, and by setting the optimum reflective surface spacing for the various values, the same effect as in the above case can be obtained.

(8) In the second embodiment detailed with respect to FIG. 7, the first and second Fabry-Perot interference optical systems 10A and IO
In B, the reflective surface spacing Lo and i! in a state where the bad news member 5 is not vibrating! Engineering. As, (2G) Take and (2
7) As mentioned above for 2, while setting to give a phase difference of approximately π, each interference light LA3 and LA5 is combined by one photoelectric conversion element 22C provided in common, and then photoelectrically converted, thereby reducing drift. Although the components are configured to cancel each other out, instead of providing one photoelectric conversion element 22C, each of the interference lights LA3 and LA5 is photoelectrically converted by a separate charging conversion element, and then the converted outputs having a phase difference of π are added. Even if it is synthesized by
The same effect as in the case shown in the figure can be obtained.

(9) In the above embodiment, the servo drive circuit section 36
In the case where the amount of displacement of the bad news member 5 is limited to a region with good linearity by applying a suppressing force corresponding to the displacement control signal S2 obtained in (Fig. 1) to the bad news member 5. As described above, even if the present invention is applicable to a structure that does not suppress such servo operation,
Similar to the case described above, it is possible to obtain the effect of preventing the occurrence of drift signal components that may occur due to thermal expansion (or thermal contraction) or variations in the wavelength of the measurement light supplied from the light source.

This effect can be obtained when the Fabry-Perot interference optical system is constructed using only semi-transparent mirrors as in the case of FIGS. 1 to 6, and FIG. To obtain the same effect as when servo operation is performed in the case where an interference optical system is constructed, or when a Fabry-Perot interference optical system is constructed by combining a semi-transparent mirror and a reflecting mirror as described above with reference to FIG. Can be done.

00) In the above-mentioned embodiment, an embodiment was described in which the present invention was applied to an acceleration type vibration detection device, but the present invention is not limited to this, and in short, the present invention is applied to a pair of reflective surfaces constituting a Fabry-Perot interference optical system. The present invention can be widely applied when the interval between the two changes depending on the physical quantity to be measured.

00 In the equation (1) representing the interference light intensity E, the intensity reflectance R represents the reflectance when the reflectances of a pair of reflective surfaces are equal to each other, but the value R1 where the reflectances R are not equal to each other
and R2, the intensity reflectance R is expressed by the following formula C Effect of the invention] As described above, according to the present invention, two systems of Fabry-Perot interference optical systems are provided, and the displacement that can be obtained from each Fabry-Perot interference optical system is By canceling the drift signal component when obtaining differential information corresponding to the physical quantity to be measured based on the detection signal, thermal expansion (or thermal contraction),
It is possible to realize a physical quantity measuring device that can effectively suppress drift that may occur in measurement results based on fluctuations in the wavelength of a light source.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a first embodiment of the physical quantity measuring device according to the present invention, FIG. A partial vertical cross-sectional view showing the detailed configuration of the system, FIG. 4 is a characteristic curve diagram showing interference light intensity characteristics, and FIGS. 5 and 6 are used to explain changes in the spacing between reflective surfaces during vibration and thermal expansion. Route map, FIG. 7 is a partial longitudinal sectional view showing the second embodiment, FIG. 8 is a partial longitudinal sectional view showing the third embodiment, and FIG. 9 is a partial longitudinal sectional view showing the fourth embodiment. , FIG. 10 is a chart showing the optimum conditions for the spacing between reflective surfaces. ■...Vibration detection device, 2...Case,
3...Vibration detection unit main body, 4A, 4B...
・Fixing member, 5...Bad news member, 6...
Holder, 7...Temporary spring, 15...Light source, 16...Collimator, IOA, IOB...
...Fabry-Perot interference optical system, 9A, 9B, 19A
, 19B...Semi-transparent mirror, 9AX, 19BX...
...Reflecting surface, 49.50...Reflecting mirror, 22
A, 22B, 22C...Photoelectric conversion element. Agent Keiki Tanabe! Detailed structure of the optical system Fig. 3 Operation during vibration Fig. 5 Dynamics of thermal expansion A to Fig. 6 Fig. 4 Structure of r1 Fig. 3 Structure of practical example 8 Ward Nakanoshi I Tachiumi no Shu 6th IO Map

Claims (6)

[Claims] (1) Generate interference light exhibiting an interference light intensity corresponding to the distance between the reflective surfaces between each pair of reflective surfaces, and obtain a photoelectric conversion signal representing the interference light intensity by photoelectrically converting the interference light. first and second Fabry-Perot interference optical systems, one of the pair of reflective surfaces constituting the first and second Fabry-Perot interference optical systems, respectively;
and the other of the pair of reflective surfaces is fixed to a second displacement detection member, and the photoelectric conversion signal obtained from the first and second Fabry-Perot interference optical systems. By determining difference information corresponding to the amount of relative displacement between the first and second displacement detection members based on the above, a measurement output signal is obtained by canceling the drift displacement occurring in the spacing between the reflective surfaces. A physical quantity measuring device characterized by: (2) The first and second Fabry-Perot interference optical systems each have separate first and second photoelectric conversion elements, and the first and second 2. The physical quantity measuring device according to claim 1, wherein the difference information is obtained by subtracting or adding the photoelectric conversion signal. (3) The first and second Fabry-Perot interference optical systems have a common photoelectric conversion element, and the interference light generated in the first and second Fabry-Perot interference optical systems is transmitted to the common photoelectric conversion element. 2. The physical quantity measuring device according to claim 1, wherein the photoelectric conversion signal including the difference information is obtained by photoelectric conversion. (4) Displacement control means capable of changing and controlling the relative positional relationship between the first and second displacement detecting members is provided between the first and second displacement detecting members, and the relative position is controlled based on the photoelectric conversion signal. By controlling the displacement control means with a feedback control signal that suppresses a change in position, the change in the intensity of the interference light when the amount of displacement between the first and second displacement detection members changes. The physical quantity measuring device according to claim 1, characterized in that linearity is maintained. (5) Displacement control means capable of changing and controlling the relative positional relationship between the first and second displacement detection members is provided between the first and second displacement detection members, and a displacement amount setting signal is provided to the displacement control means. 2. The physical quantity measuring device according to claim 1, wherein the relative positional relationship can be set by providing a physical quantity. (6) Fabry-Perot generates interference light exhibiting an interference light intensity corresponding to the distance between the reflective surfaces between a pair of reflective surfaces, and photoelectrically converts the interference light to obtain a photoelectric conversion signal representing the interference light intensity. an interference optical system, one of the pair of reflective surfaces constituting the Fabry-Perot interference optical system is fixed to the first displacement detection member, and the other of the pair of reflective surfaces is fixed to the first displacement detection member; fixed to a second displacement detection member to obtain a measurement output signal corresponding to a relative displacement between the first and second displacement detection members based on the displacement amount of the photoelectric conversion signal; A value of the reflective surface spacing at which the rate of change in intensity is constant is selected as the reflective surface spacing in a state where no relative displacement occurs between the first and second displacement detection members. Physical quantity measuring device.