JP5519067B1 - Optical interferometer and Fourier transform spectrometer using the same - Google Patents

Abstract

【Task】
In the wishbone interferometer, there has been a problem that the data accuracy of the interference intensity signal is lowered due to the axial displacement of the rotating shaft that occurs during the rotational scanning of the moving mirror.
[Solution]
The present invention provides a wishbone type interferometer provided with an “axis misalignment correcting mechanism” for correcting an axis misalignment during rotational scanning.
The shaft misalignment correction mechanism includes a radial correction unit, a radial displacement detection unit, and a radial displacement correction control unit.
The radial correction unit is composed of a radial displacement sensor and an electrostatic actuator for correcting shaft misalignment.
The radial displacement detection unit detects an axis shift of the rotation center based on a sensor signal from the radial displacement sensor, transmits the detection signal to the radial displacement correction control unit, and the radial displacement correction control unit Based on the detection signal, the position of the rotary shaft is corrected and controlled so as to eliminate the radial axial deviation of the rotation center via the electrostatic actuator.
[Selection] Figure 1

Description

  The present invention relates to an optical interferometer and a Fourier transform spectrometer using the same.

  Interfering light obtained by an optical interferometer (for example, a Michelson interferometer or a wishbone interferometer) composed of a beam splitter and a moving mirror is applied to a Fourier transform spectrometer. In obtaining the interference light intensity signal, it is important to accurately measure the position of the movable mirror corresponding to the interference intensity measurement point. In the case of a Fourier transform type spectrometer, the spectral accuracy (resolution) is determined by the optical path difference corresponding to the displacement (movement amount) of the moving mirror, and the higher the optical path difference, the higher the resolution.

  On the other hand, developments for downsizing the above-mentioned interferometer and the Fourier transform type spectrometer using the interferometer and making it a compact system are underway. In particular, the wishbone type interferometer is advantageous for miniaturization because the optical path difference is the same even if the movement amount of the moving mirror is half that of the Michelson type interferometer. In addition, the mechanical elements that make up the wishbone interferometer are manufactured by applying MEMS (Micro Electro-Mechanical System) technology to develop a miniaturized Fourier transform spectrometer. (See Non-Patent Document 1).

  FIG. 8 shows an example of a conventional wishbone interferometer 800. This drawing is an explanatory diagram showing a schematic plan view of the interference optical system portion and the rotary scanning mechanism portion. In this example, the main mechanism element members are manufactured by applying MEMS technology. A beam splitter 801 is provided, and corner cube mirrors are used for the two movable mirrors 802 and 803. The moving mirror is connected to the rotation shaft 805 by an arm 804.

  The rotating shaft is fixed by four springs 807 each having one end fixed by an anchor 808. The spring 807 is a leaf spring, and the drawn line in the drawing is an image of the thickness of the leaf spring. Assuming that the width of the leaf spring appears in the front and back direction of the drawing, the spring 807 is a wide leaf spring. It has a large moment of inertia in the cross section in the front and back direction. For this reason, the rotating shaft 805 and the members (moving mirrors 802, 803, etc.) connected to the rotating shaft are firmly fixed in a “hanging state” by these four springs.

  On the other hand, an arm 804 connected to the movable mirror 802 is provided with an electrostatic actuator 821 having comb-shaped electrodes for rotationally scanning the movable mirror. The electrostatic actuator 821 is actuated by a predetermined output from the electrostatic drive power source 820, and the rotary shaft 805 having the rotation center 806 rotates, whereby the movable mirrors 802 and 803 are rotationally scanned.

  The arm 804 connected to the moving mirror 803 is provided with a capacitance type displacement sensor 826 having a comb-shaped electrode in order to detect displacement of the moving mirror. Based on the sensor signal from the displacement sensor 826, the capacitance displacement meter 825 measures the position (displacement) of the moving mirror.

  The parallel light from the light source 809 is guided to the beam splitter 801, and the incident light is separated into light in two orthogonal directions by the beam splitter. The separated lights are guided to the movable mirrors 802 and 803 and reflected, and then the lights are combined again by the beam splitter and emitted as interference light.

Young-Min Lee et al., “Micro Wishbone interferometer for Fourier transform infrared spectrometry”, Journal of Micromechanics and Microengineering 21, 065039, 2011.

  In the above-described conventional wishbone interferometer, although the position of the moving mirror by rotational scanning is accurately measured by a capacitance displacement meter, the relationship between the optical path difference and the interference intensity is often used. There is a problem that variations occur and the accuracy of the interference intensity data decreases. As a result of studying to solve this problem, it has been found that the main cause of the decrease in the accuracy of the interference intensity data is the axial displacement of the rotating shaft that occurs during rotational scanning. An object of the present invention is to eliminate the axial displacement of the rotating shaft in the radial direction and improve the accuracy of interference intensity data.

  In order to achieve the above object, the wishbone interferometer according to the present invention is provided with an “axial deviation correcting mechanism” for eliminating the radial deviation (radial direction) of the rotational axis with respect to the rotational scanning mechanism. ing. The shaft misalignment correction mechanism is composed of two sets of the same form consisting of a radial correction unit, a radial displacement detector, and a radial displacement correction controller.

  The radial correction unit has a structure in which a capacitance type radial displacement sensor and a radial displacement correction electrostatic actuator adjacent to the electrostatic capacitance type radial displacement sensor are combined, and this is attached to a rotating shaft by a connecting member.

  Axial misalignment of the rotation axis in the radial direction (radial direction) may occur not only in a specific direction but also in all directions. For this reason, in the present invention, radial correction units are provided at two locations in order to detect an axial shift and correct the displacement.

  Accordingly, in laying out the two radial displacement sensors, the mounting angle of the fixed electrode (fixed sensor electrode) of the sensor (the angle formed by two line segments connecting the fixed electrode and the rotation center) is roughly set. It arrange | positioned so that it might become 90 degree | times. The radius of rotation of these radial correction units from the center of rotation is arbitrary, and the radius of rotation may be determined in consideration of the overall structure of the wishbone interferometer.

  In addition, as the radial displacement correcting electrostatic actuator arranged adjacent to the radial displacement sensor, two types of electrostatic actuators called “radial outward electrostatic actuator” and “radial inward electrostatic actuator” are used. A combined type actuator is used. The “radial outward electrostatic actuator” generates a driving force in the radial direction outward from the rotation center, and the “radial inward electrostatic actuator” generates a driving force in the radial direction toward the rotation center.

  Further, the rotational trajectory planes of the two radial correction units including the radial displacement sensor are the same as, or adjacent to or parallel to the rotational trajectory planes of the two moving mirrors in the wishbone interferometer of the present application. To be a face. In addition, the “rotating orbit” referred to in the present application may refer to the case of the entire circumference of the rotating orbit circle, or in fact, a part of the “arc-shaped orbit”, but it is self-evident. Therefore, even in the case of “arc-shaped orbit”, the term “rotating orbit” is used for convenience.

  The radial displacement detection unit detects an axial shift of the rotation center based on a sensor signal from the radial displacement sensor, and transmits the detection signal to the radial displacement correction control unit. Based on the detection signal, the radial displacement correction control unit corrects the rotation axis to the normal position so as to eliminate the radial displacement of the rotation center in the radial direction via the correction electrostatic actuator in the radial correction unit. ·Control.

Furthermore, the present invention provides an arrangement method of a radial correction unit for detecting the rotational axis deviation with the highest sensitivity. First, an orthogonal XY coordinate axis having the rotation center as the origin is virtually set on the rotation track surface of the radial correction unit. Regarding the X-axis and Y-axis directions at this time, the direction of the XY orthogonal coordinate axes is set so as to be parallel and perpendicular to the optical path in the wishbone interferometer--that is, the optical path from the beam splitter to each moving mirror. To do.
Also, when the coordinate axes corresponding to the four quadrants of XY orthogonal coordinates are defined as the X axis, -X axis, Y axis, and -Y axis, and the clockwise or counterclockwise direction is traced around the origin The fixed sensor electrodes of the radial displacement sensors may be arranged on the two coordinate axes adjacent to each other.

  The wishbone interferometer according to the present invention can be applied to the “optical interferometer” portion of the “Fourier transform spectrometer”.

  According to the present invention, it is possible to eliminate axial misalignment during rotational scanning in a wishbone interferometer, so that the accuracy of interference intensity data is improved. Further, if the wishbone type interferometer provided with the “axis deviation correction mechanism” according to the present invention is applied to the “Fourier transform type spectrometer”, the resolution of the spectrometer can be improved.

It is a schematic explanatory view showing a basic embodiment of the present invention. It is drawing which shows an example of the radial correction unit of this invention, FIG. 2 (A) is a model perspective view, FIG.2 (B) is a model plane sectional view, FIG.2 (C) is a model top view which shows a comparative example. . FIG. 3A is an explanatory diagram of the axial displacement displacement, FIG. 3B is an analysis explanatory diagram of the axial displacement amount, and FIG. 3C is a graph showing the relative sensitivity of the radial displacement sensor. It is a model top view which shows suitable arrangement | positioning of the radial displacement sensor by this invention. It is a schematic explanatory view showing an embodiment of the present invention. It is a schematic explanatory drawing which shows the Example of this invention. It is a schematic explanatory drawing which shows the Example which applied this invention to the Fourier-transform type | mold spectrometer. It is a schematic explanatory view showing an example of a conventional wishbone interferometer.

  First, a basic embodiment of the present invention will be described. FIG. 1 is a schematic explanatory view showing a basic embodiment of a wishbone interferometer 100 of the present invention. The interference optical system 110, which is the same as the conventional configuration, includes a light source 109, a beam splitter 101, movable mirrors 102 and 103, an arm 104, a rotary shaft 105, and the like. The illustration of the rotational scanning mechanism including it is omitted. Further, since the operation of the interference optical system 110 is the same as the description of the background art using FIG. 8 described above, the description thereof is omitted here.

  The shaft misalignment correcting mechanism 150 according to the present invention has the same type consisting of three units of radial correction units -1, -2 (160, 170), radial displacement detectors 181 and 186, and radial displacement correction controllers 182 and 187. The radial correction units (160, 170) are connected to the rotating shaft 105 by a connecting arm 130.

  Next, the detailed structure of the radial correction unit-1 (160) will be described with reference to FIGS. FIG. 4A is a perspective view showing a schematic structure of the radial correction unit, and FIG. 4B is a schematic plan sectional view. The radial displacement sensor 161 is a capacitance type displacement sensor and is disposed adjacent to the electrostatic actuator 165 for correcting radial displacement. An electrostatic capacitance type radial displacement sensor 161 for detecting an axial deviation in the radial direction is composed of a fixed sensor electrode 162 and a movement sensor electrode 163 that is opposed to this and has a gap d. In addition, the electrostatic actuator 165 for correcting the axial displacement displacement in the radial direction includes a radial outward electrostatic actuator 166 and a radial inward electrostatic actuator 168.

  The radial outward electrostatic actuator and the radial inward electrostatic actuator are opposed to the correction moving electrode 164 common to both of them, and are separated from the outward driving fixed electrode 167 on the both sides of the correction moving electrode 164 by an appropriate distance. An orientation drive fixed electrode 169 is disposed. Further, as shown in the figure, the correction moving electrode 164 and the moving sensor electrode 163 are integrated and attached to a rotating shaft (not shown) via a connecting member (connecting arm 130).

  The radial displacement detectors 181 and 186 shown in FIG. 1 detect a shaft misalignment of the rotation center based on sensor signals from the radial displacement sensors 161 and 171 and transmit the detection signals to the radial displacement correction controllers 182 and 187. Based on the detection signal, the radial displacement correction control unit drives and controls the actuator via the axial displacement correcting electrostatic actuators 165 and 175 so as to eliminate the axial displacement displacement of the rotation center in the radial direction. That is, the radial displacement correction control unit determines whether to operate a radial outward electrostatic actuator or a radial inward electrostatic actuator in the actuator based on the input detection signal, and then Is driven to correct and control the rotation axis to the normal position.

  In the example shown in FIGS. 2A and 2B, the adjacent arrangement of the radial displacement sensor 161 and the electrostatic actuator 165 for correction is “actuator → sensor” when viewed clockwise with respect to the rotation center. Although it is in order, it is not limited to this, and the reverse of the above may be used. Also, the adjacent positional relationship between the radial displacement sensor and the correction electrostatic actuator does not necessarily have to be the same between the radial correction units -1 and -2 shown in FIG.

  As shown in FIG. 1, in laying out the two radial correction units-1 and -2 (160 and 170), the fixed sensor electrodes (162 and 172) of the two radial displacement sensors have the center of rotation. The mounting angle to be viewed, that is, the angle (mounting angle) formed by the straight lines (layout lines L1 and L2) connecting the fixed sensor electrodes 162 and 172 and the rotation center 106 is approximately 90 degrees.

  Further, the radius of the rotation trajectory from the rotation center of the radial correction unit is arbitrary, and may be determined in consideration of the structure of the existing wishbone interferometer. In this example, the radius of the rotational trajectory 120 of the radial correction unit is smaller than the radius of the rotational trajectory 115 of the moving mirror, but is not limited thereto.

  Furthermore, the rotational trajectory surface of the radial correction unit including the two radial displacement sensors may be a trajectory surface adjacent to and parallel to the rotational trajectory surfaces of the two moving mirrors. It is not necessary to coincide with the rotation orbital surface of the moving mirror, and it may be determined in consideration of the overall structure mainly including the interference optical system.

(Comparative example)
As described above, in the present invention, an actuator of a type in which two types of electrostatic actuators of “radial outward electrostatic actuator” and “radial inward electrostatic actuator” are combined is used as an axial displacement correcting electrostatic actuator. ing. Below, the case where the electrostatic actuator for correction | amendment is comprised with an actuator of either one of a radial outward electrostatic actuator or a radial inward electrostatic actuator is considered as a comparative example.

  In FIG. 2C, the correction electrostatic actuators in the radial correction units -3 and 4 (160-C, 170-C) arranged on the rotating track 120 are shown as radial outward electrostatic actuators (165-C). 175-C) shows a comparative example configured using only one type. Here, a case where an axis deviation ΔR occurs in the direction of the range (angle range shown by hatching) between the two layout lines (L1, L2) will be considered.

  The radial displacement sensors 161 and 171 detect the axial deviation ΔR from the center of rotation toward the outside in the radial direction, and the radial displacement detector transmits the detection signal from the radial displacement sensor to the radial displacement correction controller as shown in FIG. To do. At this time, the radial displacement correction control unit attempts to execute a “radial direction inward correction operation” based on the detection signal. However, in this comparative example, since the function of the electrostatic actuator for correction that is provided is only “outward operation”, the axial displacement correction operation in the radial direction is impossible.

  In other words, with respect to the axial misalignment toward the hatched area shown in the figure, it is impossible to correct the misalignment in the radial direction with only one type of “radial outward electrostatic actuator”. It turns out that it is necessary to equip.

  Similarly, when the hatched area shown in the figure has a 180 degree “rotationally symmetric” positional relationship with the rotation center 106 as a symmetric point, one type of “radial inward electrostatic actuator” is detected with respect to the axis deviation toward this area. It can be seen that the rotational axis misalignment correction operation is impossible only with this. By constructing an electrostatic actuator for correcting axial misalignment by combining two types of electrostatic actuators so that a driving force in the radial direction is generated in two directions, an “axis misalignment correction is impossible” axis misalignment direction The existence of a specific range of “” can be eliminated.

  Next, a preferred arrangement method of the radial displacement sensor according to the present invention will be described with reference to FIGS. FIG. 3 is a schematic diagram in which the shaft misalignment of the rotating shaft is analyzed. FIG. 3A is an explanatory diagram of the axial displacement displacement, FIG. 3B is an analysis explanatory diagram of the axial displacement amount, and FIG. 3C is a graph showing the relative sensitivity of the radial displacement sensor.

  The X-Y coordinate system in FIG. 3A is parallel to the optical path-1 (111) of the interference optical system in FIG. 1, and the X axis is parallel to the optical path-2 (112). Thus, the Y axis is virtually set so that the rotation center 106 is the coordinate origin. Here, the magnitude and direction of the axial displacement amount ΔR of the rotation center 106 in the rotation shaft 105 is assumed as indicated by an arrow, and the radial displacement sensor is fixed at a position rotated counterclockwise by an angle β from the X axis. Assume that the sensor electrode 162 is disposed.

  The amount of displacement that can be detected by the radial displacement sensor at this time will be examined with reference to FIG. In the following, an axial deviation amount ΔX that can be detected as an X-direction component by a radial displacement sensor (161 shown in FIGS. 1 and 2) having a fixed sensor electrode 162 is obtained.

  If the X-axis direction component of the axial deviation amount ΔR is ΔX as shown in the figure, this ΔX becomes an error factor of the optical path difference in the optical path-1 (111) direction shown in FIG. However, since the radial displacement sensor is on the layout line L1 inclined by the angle β from the X axis, the displacement displacement amount ΔXb that can be actually detected by the radial displacement sensor is a value obtained by projecting ΔX onto the layout line L1 as shown in the figure. That is, a value obtained by multiplying ΔX by cos β. The Y-axis direction component ΔYb that can be actually detected by a radial displacement sensor (not shown) arranged on the layout line L2 rotated 90 degrees counterclockwise from the layout line L1 is exactly the same as that in the X-axis direction. It can be obtained as ΔY · cos β according to the concept.

  If the error amount affected by the optical path difference of the interference optical system shown in FIG. 1 is δ, when the above-described axial deviation (ΔX, ΔY) occurs, the error amount δ is δ = 2 (ΔX− ΔY). Here, in the positive and negative signs attached to ΔX and ΔY, the traveling direction of light toward the reflecting mirror (moving mirror) is a positive sign, and in the reverse direction, a negative sign is attached.

  Furthermore, the above-described axial misalignment not only causes the above error in the optical path difference, but also adversely affects the position measurement of the moving mirror. That is, the position of the moving mirror at the time of regular rotational scanning is measured with the above-described capacitance-type displacement sensor and capacitance-type displacement meter. Since an error is mixed in the sensor signal from the mold displacement sensor, the position of the moving mirror cannot be measured accurately, and the measurement accuracy is lowered.

  FIG. 3C is a graph showing a simulation result of the influence of the angle β formed by the layout line L1 of the fixed sensor electrode 162 of the radial displacement sensor and the X axis on the detection sensitivity of the radial displacement sensor. is there. The vertical axis of the graph represents the relative sensitivity (ΔXb / ΔX) normalized by the maximum sensitivity of the radial displacement sensor (that is, the sensitivity when the sensor is on the X axis). As shown in the figure, it can be seen that the sensitivity decreases as the installation position of the radial displacement sensor is laid out away from the X axis. Also, since the rate of decrease in sensitivity is cos β, the rate of decrease increases as β increases. At this time, if β is about ± 10 °, it can be seen that the rate of decrease in sensitivity is only a few percent.

  In the above, the detection sensitivity of the axial deviation in the X-axis direction has been described, but the same analysis result is obtained in the Y-axis direction. That is, the detection sensitivity of the displacement displacement in the Y-axis direction of the radial displacement sensor (not shown) arranged on the layout line L2 is maximized when the radial displacement sensor is arranged on the Y-axis.

  Next, FIG. 4 shows the arrangement method of the radial displacement sensor for detecting the rotational axis deviation with the highest sensitivity found from the above results. The interference optical system and the rotary scanning mechanism in the upper left of the drawing are the same as those in FIG. Further, the XY coordinate axes in the figure are set with the same definition as in FIG. Four points P1 to P4 in the figure are suitable arrangement points of the radial displacement sensor, and all are on the X axis or the Y axis.

  Actually, since the displacements in the X and Y directions are detected using two radial displacement sensors, each sensor (strictly speaking, a fixed sensor electrode of the radial displacement sensor) is placed on the rotational scanning track 120. What is necessary is just to arrange | position to any two adjacent points of the points of P1-P4. There are four combinations of P1 / P2, P2 / P3, P3 / P4, and P4 / P1. Which combination should be laid out may be determined in consideration of the overall structure mainly composed of the interference optical system.

  Even if the points P1 to P4 described above are off by several degrees from the X axis or the Y axis, the decrease in detection sensitivity of the sensor is only a few percent as shown in FIG. This is often acceptable. Similarly, the angle at which the two radial displacement sensors look at the center of rotation (mounting angle between the two radial displacement sensors) is set to “approximately” 90 degrees for the above reason.

  Another embodiment of the shaft misalignment correcting mechanism according to the present invention is shown in FIG. The illustrated set of shaft misalignment correction mechanisms 550 is composed of a radial correction unit 560, a radial displacement detection unit 581, and a radial displacement correction control unit 582. The feature of this embodiment is that the electrostatic actuator for correction 565 in the radial correction unit 560 is configured such that comb-shaped electrostatic actuators are symmetrically arranged on both sides of the layout line L1.

  As shown in the figure, the radial displacement sensor 561 is a capacitance type displacement sensor including a fixed sensor electrode 562 and a movement sensor electrode 563. A comb-shaped outward electrostatic actuator 566 is arranged adjacent to the displacement sensor, and the actuator is two comb-shaped electrostatic actuators that generate a driving force outward in the radial direction. The actuators are arranged symmetrically on both sides of L1 so that the layout line L1 is an axis of line symmetry. The two actuators at this time are composed of an outward driving fixed electrode 567 and a correction comb-shaped moving electrode 564 connected to the connecting arm 530.

  Further, a comb-shaped inward electrostatic actuator 568 is disposed adjacent to the comb-shaped outward electrostatic actuator 566. The symmetrical arrangement method of the inward electrostatic actuator is the same as that of the outward electrostatic actuator described above, and is configured by an inward drive fixed electrode 569 and a correction comb-shaped moving electrode 564.

  When the axial displacement in the radial direction occurs, the radial displacement detection unit 581 detects the axial displacement of the rotation center based on the sensor signal from the radial displacement sensor 561, and transmits the detection signal to the radial displacement correction control unit 582. . The radial displacement correction control unit determines whether to operate the comb-shaped radial outward electrostatic actuator 566 or the comb-shaped radial inward electrostatic actuator 568 based on the detection signal, and then determines the rotation center. The actuator is driven so as to eliminate the axial displacement displacement in the radial direction, and the rotation axis is corrected and controlled to the normal position.

  By using a comb-shaped actuator as the electrostatic actuator for correction as in this example, a larger driving force can be obtained compared to the single electrode actuator shown in FIGS. In addition, in this example, the radial outward / inward electrostatic actuators are arranged opposite to each other so as to be line-symmetric with respect to the layout line, so that the driving force in the rotational trajectory direction generated when each actuator operates is reduced. Canceled.

  If the radial outward actuator and the radial inward actuator are not symmetrically arranged and only one is arranged on each side, the correction comb-tooth-shaped moving electrode 564 is not connected to the correction comb-shaped moving electrode 564 when each actuator is operated. There arises a problem that a driving force is also generated in the direction of the rotation trajectory due to the suction force between the direction or inward driving fixed electrode (567 or 569).

  In the present invention, as described above, each of the radial outward / inward electrostatic actuators is arranged in a line-symmetric arrangement facing each other with respect to the layout line, so that the rotational trajectory direction generated when each actuator operates can be reduced. The generated driving force is canceled to solve the above problem.

  FIG. 6 shows an embodiment of the present invention. This drawing is a schematic explanatory diagram of a wishbone type interferometer of the present invention constituted by an interference optical system portion, a rotary scanning mechanism, and two types of axial deviation correction mechanisms. The wish splitter type interference optical system is constituted by the beam splitter 601 and the two movable mirrors 602 and 603. Here, a corner cube mirror is used for two moving mirrors. The two moving mirrors are connected to the rotation shaft 605 by an arm 604.

  The rotating shaft is connected and fixed to four springs 607 each having one end fixed by an anchor 608. The spring 607 is a leaf spring, and if the drawing line is an image of the thickness of the leaf spring and the width of the leaf spring appears in the front and back direction of the drawing, the spring 607 is a wide leaf spring and the front and back direction of the drawing. Have a large moment of inertia in cross section. For this reason, the rotating shaft 605 and the members connected to the rotating shaft (arms 604, 630, moving mirrors 602, 603, radial correction units 660, 670, etc.) are suspended by these four springs. It is firmly fixed.

  Further, in order to rotationally scan the moving mirror, an electrostatic actuator 621 having a comb-shaped electrode is provided on an arm 604 connected to the rotating shaft of the moving mirror. The coupling arm 604 of the moving mirror 603 is provided with a capacitance type displacement sensor 626 having a comb-shaped electrode in order to detect displacement of the moving mirror.

  The electrostatic actuator 621 is actuated by a predetermined output from the electrostatic drive power source 620, and the movable mirrors 602 and 603 are rotationally scanned about the rotation center 606. In this example, for example, a range of about 20 degrees is rotationally scanned, whereby the optical path difference is varied.

  The parallel light from the light source 609 is guided to the beam splitter 601, and the incident light is separated by the beam splitter into light in two orthogonal directions of optical path-1 (611) and optical path-2 (612). The separated lights of the optical path-1 and the optical path-2 are guided and reflected by the moving mirrors 602 and 603, and then the lights are combined again by the beam splitter 601 and emitted as interference light.

  The radial correction units -1, -2 (660, 670) are composed of radial displacement sensors 661, 671 and correction electrostatic actuators 665, 675, and are arranged with reference to the layout lines L1, L2. . The correcting electrostatic actuators 665 and 675 are the same as those shown in FIG. 5, and a detailed description thereof will be omitted here. The cooperative operation of the radial correction unit (660, 670), the radial displacement detection unit (681, 686), and the radial displacement correction control unit (682, 687) is as already described with reference to FIGS. Therefore, explanation here is omitted.

  In the present embodiment, the radial displacement sensors 661 and 671 are laid out so that the detection sensitivity becomes the highest. In addition, it is devised so that the deviation between the center of gravity and the rotation center of a rotating body composed of moving mirrors, various sensors, radial correction units, arms, etc. that rotate around the rotation axis is minimized. .

  That is, in the schematic diagram shown in FIG. 6, when the XY coordinates are virtually set according to the same definition as in FIG. 4, the present embodiment is located at the diagonal of the second quadrant where the beam splitter 601 is arranged. Fixed sensor electrodes (662, 672) of the radial displacement sensor are respectively arranged on the X axis and the -Y axis belonging to the fourth quadrant.

  If the straight line passing through the intermediate position between the moving mirrors 602 and 603 and the rotation center 606 is S in the figure, the arrangement of the members connected to the rotation shaft 605 and involved in the rotational movement is substantially line symmetric with respect to the straight line S. It can be seen that the combined center of gravity of the members involved in the rotational movement exists at a position close to the straight line S. Furthermore, by adjusting the size and the rotation radius of the radial correction unit, it is possible to further reduce the deviation between the combined center position of the member and the rotation center related to the rotational movement.

  As described above, the shaft misalignment correction mechanism according to the present embodiment is effective in improving the symmetry of the mechanism member related to the rotational movement, and the shaft at the time of rotational scanning caused by the mass imbalance of the rotating member. It can also contribute to reduction of displacement.

  Further, in this embodiment, the interference optical system to which the axial deviation correction mechanism of the present invention is applied is manufactured by a manufacturing method mainly based on MEMS technology, and has a very small size. Similarly, since the radial correction unit (660, 670) according to the present invention can be manufactured by using the MEMS technology, both of the manufacturing methods are well matched and it is convenient for downsizing the interferometer.

  FIG. 7 shows another embodiment of the present invention. This drawing is a schematic explanatory view showing an example in which a wishbone interferometer according to the present invention is applied to a Fourier transform spectrometer. In the illustrated Fourier transform spectroscope 700, interference light obtained from the wishbone interferometer 600 provided with the axial deviation correction mechanism shown in FIG. 6 is guided to the sample cell 780. The wishbone interferometer here is the same as the embodiment already described with reference to FIG.

  The interference light transmitted through the sample cell 780 containing the analysis object is detected by the photodetector 785, and the detected light intensity signal is transmitted to the calculation / control unit 790. In addition, the position information (symbol: Δ box “a” in the figure) of the moving mirror from the capacitive displacement meter 625 is also transmitted to the calculation / control unit.

  The calculation / control unit performs predetermined data processing and Fourier transform based on the transmitted data signal, transmits the obtained results (spectral waveform data, etc.) to the output unit 795, and displays the analysis result from the output unit. Is done.

  In the Fourier transform type spectrometer of the present embodiment, a wishbone type interferometer is used in which the reduction in the accuracy of interference intensity data due to the axial displacement of the rotary scanning mechanism is eliminated. Thereby, the resolution can be improved without impairing the advantage of the ultra-small Fourier transform spectrometer.

  As described above, in the description of the present application, the optical parts / mechanical parts / members constituting the interference optical system and the axis deviation correction mechanism are mainly manufactured by applying the MEMS technology. However, the present invention is limited to these manufacturing methods. It is not a thing. Of course, the present invention can also be implemented using optical parts, mechanism parts, and members manufactured by ordinary machining.

100, 600 ... Wishbone interferometers 101, 601, 801 ... Beam splitters 102, 103, 602, 603, 802, 803 ...・ Movement mirrors 105, 605, 805... Rotating shafts 106, 606, 806... Rotation centers 109, 609, 809. ........ Shaft correction mechanism 160, 660 ... Radial correction unit
161, 171, 561, 661, 671 ... Radial displacement sensors 165, 175, 565, 665, 675 ... electrostatic actuator 166 for correction ... ... Radial outward electrostatic actuators 170, 670 ... Radial correction unit-2
181, 186, 581, 681, 686... Radial displacement detection unit 182, 187, 582, 682, 687... Radial displacement correction control unit 566.・ ・ ・ ・ Comb-tooth type radial outward electrostatic actuator 568 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Comb-tooth type radial inward electrostatic actuator 607, 807・ ・ ・ ・ Springs 620 and 820 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Electrostatic drive power supplies 621 and 821 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Electrostatic actuators 625 and 825 .... Capacitance type displacement sensors 626, 826 ..... Capacitance type displacement sensor 700 .....・ Fourier transform spectrometer 780 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Sample cell 785 ・・ ・ ・ ・ ・ ・ ・ ・ ・ Photodetector 790 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Operation and control unit 795 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・... Output section

Claims (5)

In a wishbone interferometer including a moving mirror, a beam splitter, and a rotational scanning mechanism for rotationally scanning the moving mirror,
An axial deviation correction mechanism for correcting an axial deviation in the radial direction (radial direction) of the rotation center in the rotational scanning mechanism,
The axis deviation correction mechanism is composed of two combinations of a radial correction unit, a radial displacement detector, and a radial displacement correction controller.
The radial correction unit includes a radial displacement sensor and an electrostatic actuator adjacent to the radial displacement sensor.
The radial displacement sensor is a capacitance-type displacement sensor for detecting axial misalignment in the radial direction, and includes a fixed sensor electrode and a moving sensor electrode disposed opposite to the fixed sensor electrode. Furthermore, the movement sensor electrode is connected to a rotating member in the rotary scanning mechanism using a connecting member,
In addition, the electrostatic actuator for correcting the axial misalignment in the radial direction to a normal position,
An electrostatic actuator called a “radial outward electrostatic actuator” that generates a radial driving force outward from the center of rotation, and a “radial inward electrostatic that generates a radial driving force toward the rotational center. It consists of two types of electrostatic actuators called electrostatic actuators called “actuators”
Further, the radial outward and inward electrostatic actuators are arranged adjacent to the radial displacement sensor, and the correction moving electrodes of the radial outward and inward electrostatic actuators are rotated and scanned. Connect to the rotating body member in the mechanism using a connecting member,
Furthermore, in arranging the fixed sensor electrode of each radial displacement sensor described above,
The fixed sensor electrode of the above radial displacement sensor is arranged with arbitrary rotation radius at two places on the rotation track surface of the moving mirror or on the rotation track surface adjacent to and parallel to the rotation mirror surface,
Further, the mounting angle of the fixed sensor electrodes of the two radial displacement sensors (the angle formed by two line segments (layout lines) connecting the fixed sensor electrode and the rotation center) is approximately 90 degrees,
Further, the radial displacement detection unit detects an axial shift of the rotation center based on a sensor signal from the radial displacement sensor, and transmits the detection signal to the radial displacement correction control unit.
The radial displacement correction control unit adjusts the position of the rotation axis so as to eliminate the radial displacement of the rotation center in the radial direction via the electrostatic actuator in the radial correction unit based on the detection signal. A wishbone interferometer provided with the axis misalignment correcting mechanism, wherein correction and control are performed. In disposing the fixed sensor electrode of each radial displacement sensor included in each radial correction unit on the rotating track surface,
First, an orthogonal XY coordinate axis having the rotation center as an origin is virtually set on the rotation orbit plane, and at this time, the optical path in the wishbone interferometer with respect to the directions of the X axis and the Y axis is as follows. That is, the direction of the XY orthogonal coordinate axes is set so as to be parallel and orthogonal to the optical path from the beam splitter to each moving mirror,
The coordinate axes corresponding to the four quadrants of the XY orthogonal coordinates are defined as the X axis, the −X axis, the Y axis, and the −Y axis, and the clockwise or counterclockwise direction is traced around the origin. 2. The wishbone interferometer according to claim 1, wherein fixed sensor electrodes of the radial displacement sensors are arranged on two coordinate axes that are sometimes adjacent to each other.   3. The fixed sensor electrode of each of the radial displacement sensors according to claim 2, wherein the fixed sensor electrodes of the radial displacement sensors are arranged on two coordinate axes belonging to a quadrant (non-adjacent quadrant) having a diagonal relationship with a quadrant of the coordinates where the beam splitter exists. The wishbone interferometer according to claim 2, wherein the wishbone interferometer is arranged. In the electrostatic actuator for correcting the axial deviation in the radial direction to a normal position,
Assuming a “layout line” connecting the rotation center and the fixed sensor electrode of the radial displacement sensor,
Further, the radial outward and inward electrostatic actuators are configured by a comb-shaped structure, and these are referred to as “comb-shaped radial outward electrostatic actuator” and “comb-shaped radial inward electrostatic actuator”,
In proximity to the radial displacement sensor, the comb-teeth radial outward electrostatic actuators are symmetrically arranged on both sides of the layout line so that the layout line is an axis of line symmetry,
Similarly, in proximity to the comb-shaped outward electrostatic actuator, the comb-shaped inward electrostatic actuators are symmetrically arranged on both sides of the layout line so that the layout line is an axis of line symmetry. And
Furthermore, the correction moving electrodes of the comb-shaped outward and inward electrostatic actuators are connected to the rotating member in the rotary scanning mechanism using a connecting member,
The wishbone interferometer according to any one of claims 1 to 3, wherein the electrostatic actuator for correcting an axial misalignment in a radial direction to a normal position is configured.   A Fourier transform spectrometer using the wishbone interferometer according to any one of claims 1 to 4 as an interferometer included in the Fourier transform spectrometer.

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