JP5196582B2 - Movable mirror mechanism - Google Patents

Description

  The present invention relates to a movable mirror mechanism that is a component of an optical input / output unit of an optical communication device that performs communication using a light beam propagating in free space.

  In general, as a communication method using free space propagation optical communication, a diffusion communication method and a narrow beam communication method are known. The diffusion communication method is mainly used for optical communication at a short distance, and the narrow beam communication method is often used for optical communication at a long distance. In particular, it is known that there are the following problems when optical communication is performed between an artificial satellite and the ground.

For example, since the artificial satellite is moving with respect to the base station, it is necessary to constantly monitor each other and adjust the emission direction of the beam. Further, in propagation in the atmosphere, the optical path is constantly disturbed by fluctuations in the atmosphere. Since this disturbance includes a frequency component of 1 kHz or more, it needs to be an adjustment mechanism capable of high-speed response operation.
For this reason, especially when optical communication is performed between the artificial satellite and the ground, it is necessary to align the optical axis with a narrow beam and extremely high accuracy. As a means for aligning the optical axis, a light reflecting mirror is inserted into the optical path by a movable mirror mechanism, and the normal direction is adjusted at high speed to align the optical axis.

  A mechanism for adjusting an optical axis such as a laser processing apparatus is known as FPM (fine positioning mirror), and for example, a galvanometer mirror is usually used. In general, a galvanometer mirror is a mirror fixed to one rotation axis. For example, the irradiation point position can be selected from points on the plane by arranging the irradiating part of the laser beam on two axes that are orthogonal to each other. However, since it is necessary to use a reflector having a large aperture for optical communication between an artificial satellite and the ground, a sufficiently high-speed response characteristic cannot be obtained with a conventional galvanometer mirror.

  As a polarizer having a high-speed response characteristic, there is a disclosure of Patent Document 1 (US Pat. No. 5,215,056). This is because a piezoelectric material is arranged in parallel and fixed to the reflecting mirror using a plastic adhesive, and this is placed on the substrate and a voltage is applied so as to perform a push-pull operation, so that a reflecting mirror with a large area can be obtained. Even when used, the resonance frequency can be set high.

  A device using a piezoelectric substance actuator is disclosed in Patent Document 2 (US Pat. No. 7,212,494). This is an optical scanning device that drives a platform by attaching an actuator and a spring to a platform that moves around a rotation axis on which a reflecting mirror is mounted. The actuator and spring are arranged on the left and right of the rotation axis, and the repulsive force of the spring The platform is held by an actuator. The actuator and the platform are in contact with each other by ball bearings, and the contact angle can be freely changed.

  Patent Document 3 (Japanese Patent Application Laid-Open No. 2007-184706) describes an optical wireless transmission device that can adjust the optical axis. The optical wireless transmission slave described therein specifies the optical axis direction of the guide light from the master unit based on the imaging data, and the moving direction and moving amount of the reflecting surface of the reflecting plate are first determined from the optical axis direction. The movement direction and the movement amount of the reflecting surface of the reflecting plate are respectively acquired as second movement information from the first direction detection unit to be acquired as the movement information of the first and the received light data of the guide light received by the 4-split PD. Based on the first direction information and the second movement information acquired by the second direction detection unit and the first and second direction detection units, the reflection surface of the reflection plate is moved via the piezo actuator. And a drive control unit that substantially matches the optical axis direction of the guide light from the machine and the optical axis direction of the collimating lens.

  A schematic diagram of a conventional example relatively close to the present invention is shown in FIG. In this configuration, the light reflecting mirror 27 is placed on the support substrate 21, and the support substrate 21 is held on the two piezoelectric drive elements 23 by the two springs 35. Considering the uniaxial driving, the moment of inertia of the piezoelectric driving element 23 includes the light reflecting mirror 27, the support substrate 21, and the spring 35. Is not fast enough. Alternatively, in order to achieve a sufficiently high speed, it is necessary to increase the size of the piezoelectric drive element 23 for driving, which increases power consumption. For this reason, the drive circuit becomes very large. For example, in order to move 20 milliradians at 1 kHz, 75 W per element of the piezoelectric driving element 23, and a total of 300 W is required. However, since the apparatus becomes large and power consumption increases in this way, it is desired to reduce power consumption for mounting on a satellite.

  Further, as a conventional example, there is a conventional example similar to FIG. 1, in which four piezoelectric drive elements are moved linearly by applying a pulling force by four springs to move the reflecting mirror. Specifically, two axes move one axis, and two are overlapped to form a two-axis drive. In such an optical axis adjusting mechanism, the shafts are moved separately and four springs are used, which is complicated and disadvantageous for reduction in size and weight. In addition, since the moment of inertia when swinging a spring, a light reflecting mirror, or the like becomes very large, there is a problem that high-speed response is poor, the fluctuation of communication light cannot be handled, and reception is unstable. In order to solve this problem, for example, a mechanism that drives two axes at the same time is known. However, a complicated joint is required, which is disadvantageous for reduction in size and weight.

  FIG. 14A shows a cross-sectional view of the fine tracking mechanism described in Non-Patent Document 1. This is one in which a mirror is fixed on an inner movable part supported by a rotary rod, and the inner movable part is driven by an electromagnetic suction actuator. FIGS. 14B and 14C show the measurement results of the closed-loop circuit transfer function frequency characteristics of the optical path difference correction mechanism configured using this fine tracking mechanism. (B) is a gain-frequency characteristic, and (c) is a phase-frequency characteristic. In this result, the upper limit of the frequency characteristic is about 600 Hz.

US Pat. No. 5,215,056 US Pat. No. 7,212,494 JP 2007-184706 A

2008, 52nd Space Science and Technology Conference, pages 484-486

  An object of the present invention is to provide a movable mirror mechanism capable of correcting a shift of the axis of communication light in optical communication using free space propagation with high frequency response.

  In order to achieve the above object, a movable mirror mechanism according to the present invention is a movable mirror mechanism that performs optical axis alignment of communication light using an input unit or an output unit of an optical communication device, and is fixed to a holding substrate. A reflecting mirror; an actuator for moving the holding substrate to adjust a normal direction thereof; a pulling means for connecting the actuator and the holding substrate in connection with the holding substrate; the pulling means; A support substrate for holding the actuator and a controller for controlling the actuator are provided. However, the controller drives the actuator so that the portion connecting the holding substrate and the pulling means is a fixed point when adjusting the orientation in the normal direction.

  When a spring mechanism for pivotally connecting the pulling means and the holding substrate is provided, the spring mechanism can be realized by a leaf spring having rotational symmetry such as an annular leaf spring. The spring mechanism is for connecting the actuator and the holding substrate. The pulling means and the holding substrate are pivoted through this spring mechanism and can move freely.

  The spring mechanism can also be realized by a tension type or compression type coil spring.

  The pulling means may be a pull rod or a pull wire.

  The actuator is desirably an element that responds linearly to an input voltage, but can be used also with a piezoelectric drive element that exhibits nonlinearity and hysteresis characteristics.

  The actuator is a plurality of three or more, and is arranged so as to surround the tension means, whereby the actuator and the holding substrate can be brought into pressure contact with each other. In this case, the orientation of the reflecting mirror can be set within two dimensions.

  When the orientation of the reflecting mirror is set within one dimension, the number of actuators is set to 2, and a holding rod for holding the holding substrate is used. Also in this case, it is desirable that the actuator and the holding rod are arranged so as to surround the tension means. The holding rod and the pulling means may be configured coaxially.

    By providing the portion for connecting the pulling means and the holding substrate at the center of gravity of the holding substrate to which the reflecting mirror is fixed, the moment of inertia of the rotational motion can be minimized.

  More specifically, for example, the holding substrate of the light reflecting mirror swinging in the biaxial direction, and the holding substrate are driven by three or four linearly driven piezoelectric drive elements, and the holding substrate and the piezoelectric drive are driven. Between the connection to the element, three or four spherical joint members are arranged in series, these piezoelectric drive elements are arranged at the apex of the triangle or the four corners, and a pulling rod is arranged in the central gap to apply pressure. Add it.

In the movable mirror mechanism having the above-described configuration, high frequency response characteristics can be realized when adjusting the normal direction of the light reflecting mirror.

It is sectional drawing which shows the basic structure of the conventional movable mirror mechanism. It is sectional drawing which shows the basic structure of the movable mirror mechanism concerning a 1st Example. It is sectional drawing which shows the detailed structure of the movable mirror mechanism concerning a 1st Example. It is sectional drawing which shows the detailed structure of the spherical-joint member vicinity of the movable mirror mechanism concerning a 1st Example. It is a three-dimensional wire frame figure which shows the whole structure of the movable mirror mechanism concerning a 1st Example. It is the solid wire frame figure which looked at the whole structure of the movable mirror mechanism concerning a 1st Example from another angle. It is a perspective view of the whole structure of the movable mirror mechanism concerning a 1st Example. It is a block diagram explaining the application example of the movable mirror mechanism concerning a 1st Example. It is sectional drawing which shows the detailed structure of the movable mirror mechanism concerning a 2nd Example. It is sectional drawing which shows the detailed structure of the spherical joint member vicinity of the movable mirror mechanism concerning a 2nd Example. It is a figure which shows the example which uses (a) compression spring and (b) tension spring for a tension | pulling means. It is a figure which shows the example which uses a wire for a tension | pulling means. (A) shows the specifications of the manufactured movable mirror mechanism, and (b) shows the measurement system used for the measurement. In the example of this invention, (a) The figure which shows the example of the preload value dependence of a resonant frequency, (b) The figure which shows the frequency dependence of an amplitude. It is sectional drawing of the example of the conventional fine tracking mechanism, and a figure which shows the frequency characteristic example of the optical path difference correction mechanism comprised using it.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, devices having the same function or similar functions are denoted by the same reference numerals unless there is a special reason.

  FIG. 2 is a cross-sectional view showing the basic structure according to the first embodiment of the movable mirror mechanism of the present invention. FIG. 3B is a cross-sectional view taken along line A-A ′ in FIG. 3A, and the same reference numerals indicate the same members. FIG. 4 is a cross-sectional view showing a detailed structure near the spherical joint member of the movable mirror mechanism. In FIG. 3B, 21 is a support substrate, 22 is a tension bar, and screws are cut at both ends. In the piezoelectric drive element 23 which is an actuator, when a DC voltage (for example, within 150 V) is applied, the piezoelectric drive element 23 extends about several tens of microns. In the spherical joint member 24, a spherical body having a diameter of several millimeters is bonded on a truncated cone. In the positioning nut 25, one side of a normal nut has a conical shape, and is fitted into the central hole 28 via an annular leaf spring 31. In the light reflecting mirror holding member 26, the aluminum material is cut into a cup shape. The diameter of the light reflecting mirror 27 is, for example, 20 mm. A central hole 28 is formed in the bottom of the light reflecting mirror holding member 26, and a ball receiving hole 29 is formed in the bottom edge of the light reflecting mirror holding member 26 and into which the sphere of the spherical joint member 24 is fitted. . The sleeve 30 is a cylindrical sleeve that is screwed on the inner side and screwed into the tension bar 22.

  In FIG. 2, a single pulling rod 22 passes through a center hole 28 opened in the center of the light reflecting mirror holding member 26 and a hole opened in the center of the support substrate 21, and is tightened from both by a positioning nut 25. On the other hand, the sphere of the spherical joint member 24 is fitted into the four holes opened in the light reflecting mirror holding member 26 so as to be rotatable. The light reflecting mirror holding member 26 moves around the central hole 28 by the expansion and contraction of the piezoelectric driving element 23 and changes its orientation. Compared with the conventional example of FIG. 1, it can be seen that the moment of inertia generated when the light reflecting mirror holding member 26 swings is reduced by the amount that the spring 35 is not located away from the center of motion.

  FIG. 3 is a sectional view showing the detailed structure of the movable mirror mechanism. Four piezoelectric driving elements 23 are arranged on the support substrate 21 at points corresponding to the apexes of the quadrangle, and the light reflecting mirror holding member 26 is arranged thereon. In the light reflecting mirror holding member 26, the pulling rod 22 is passed through the center, and the light reflecting mirror holding member 26 is pulled by the positioning screws 25 at both ends. As a result, pressure is applied to the piezoelectric driving element 23 through the spherical indirect member 24. This pressure is best in the range of 100 kg to 160 kg when the total mass of the support substrate 21 and the light reflecting mirror 27 is 5 g, for example.

  The pulling rod may be a rod-shaped object having no resonance point in the driving frequency band, but may be a wire 36 as shown in FIG. However, it is assumed that sufficient tension is applied and the natural vibration frequency is higher than the driving frequency band. For example, when the above-described light reflecting mirror holding member is used, it is pulled with a force of 800 to 1000 N. However, when the resonance frequency may be low, the pulling force can be further reduced.

  FIG. 4 illustrates the periphery of the spherical joint member 24 which is a part of the above-described mechanism. The light reflecting mirror 27 is attached to the light reflecting mirror holding member 26. The end of the pull rod 22 is passed through the central hole 28 and is tightened with the positioning nut 25 with the annular leaf spring 31 interposed therebetween. Since the tip of the positioning nut has a conical shape, the positioning nut fits into the central hole 28 of the light reflecting mirror holding member 26 and is fixed at the center. On the other hand, since the positioning tube 30 is screwed into the pulling member 22 on the opposite side through the light reflecting mirror holding member 26, the positional deviation of the light reflecting mirror holding member 26 can be prevented.

  A spherical joint member 24 is rotatably engaged with the piezoelectric drive element 23, and a light reflecting mirror holding member 26 to which a light reflecting mirror 27 is fixed is loosely fitted to the spherical joint member 24 so as to be capable of fine rotation. ing. As shown in FIG. 8, the voltage output of the control drive circuit 9 is applied to the piezoelectric drive element 23. The piezoelectric drive element 23 can drive the light reflecting mirror holding member 26 in two axial directions.

  5 and 6 are wire frame diagrams of the overall appearance of the movable mirror mechanism, in which the inner support member 33 is sandwiched between the light reflecting mirror holding member 26 and the outer support member 32. FIG. The outer support member 32 is cylindrical and the bottom is screwed to the support substrate 21. This structure can withstand vibration and impact environments. FIG. 7 shows a perspective view thereof.

  FIG. 8 shows an application example of the movable mirror mechanism described above. The communication light is collected by the condenser 2 and enters the movable mirror mechanism 1. This reflected light is incident on the beam splitter 4. On the other hand, the transmission light and the reception light of the laser 5 are separated here. Next, the beam is reduced by the lens 3, passes through the half mirror 6, and is received by the light receiving element 7. Further, the position of the light incident on the position detection element 8 is detected by the drive control circuit 9, and the movable mirror mechanism 1 is driven and controlled so that the light beam is incident on the light receiving element 7 at a predetermined position. A method for controlling this series of operations is already well known.

  As a result of measurement using the measurement system shown in FIG. 13B for the movable mirror mechanism manufactured with the specification of FIG. 13A, FIG. 14A shows an example of the preload value dependency of the resonance frequency. FIG. 14B shows an example of the frequency dependence of the amplitude. Here, the resonance frequency is a natural frequency of the movable mirror mechanism. From this result, it can be seen that the resonance frequency increases as the preload, which is the force with which the pulling rod presses the light reflecting mirror holding member against the piezoelectric driving element, increases. When the preload is 900 N, the upper limit of the frequency characteristic is about 6 kHz. Compared with the case of this example shown in FIG. 15, it can be seen that the frequency characteristics are greatly improved. FIG. 15A shows an optical path difference correction mechanism having a two-axis integrated configuration using an electromagnetic suction actuator and a flexible pivot, and FIG. 15B shows its frequency characteristics.

  Further, as shown in FIG. 14A, in order to realize a high resonance frequency, it is necessary to increase the preload value. However, as in the above known example, when a plurality of pulling means such as springs are used for this purpose, it is desirable that the force be applied uniformly. This is because if it is non-uniform, it is necessary to apply extra power to the piezoelectric drive element to eliminate the non-uniformity.

  However, in the present invention, the pulling means is single, and the piezoelectric driving elements are arranged around the pulling means. Therefore, a uniform pressure is applied to each piezoelectric driving element. As a result, the light reflecting mirror holding member on which the light reflecting mirror is placed is moved in a state where the rotational moment is small, and a higher frequency characteristic than that of the conventional one can be realized.

  Next, an example using three actuators will be described. FIG. 9 is a structural view of the second embodiment, and FIG. 10 is a cross-sectional view taken along the line AA ′ of FIG. 9. Three ball joint members 24 are rotatably engaged with the pull bar 22. The spherical joint member 24 is rotatably engaged with a light reflector holding portion 34 to which a light reflector 27 is fixed. Further, pressure is applied to the three piezoelectric driving elements 23 by the pulling rod 22. As described above, the number of the piezoelectric drive elements 23 of the first embodiment is changed from 4 to 3. Other components are the same as those in the first embodiment. This three-piece structure is advantageous in reducing the size and weight and further improving the high-speed response. Then, the frequency response of optical axis deviation correction is improved, and the power consumption of the apparatus is reduced and the entire apparatus is downsized.

  Even when one of the three actuators is stopped and used as a holding rod, the orientation can be adjusted.

  In the first and second embodiments, the piezoelectric driving element 23 is used as the actuator. However, it is generally known that the piezoelectric element has a hysteresis characteristic and gives a nonlinear transition to the applied voltage. However, in the control, it is easier to have a piezoelectric element having a linear response characteristic. In such a case, it is possible to use a piezo element with position feedback control in which the expansion response to the input voltage is linear. Such operation control is performed by the control drive circuit 9 of FIG.

  The actuator need not be limited to the above-described piezoelectric element, and can be applied to the present invention as long as it is an actuator capable of high-speed operation such as a moving coil or a magnetostrictive element.

  In the above embodiment, an example in which the tension rod 22 and the leaf spring 31 are used as the tension means has been shown. However, as shown in FIGS. 11A and 11B, the leaf spring 31 is a compression spring 34 or a tension spring 35. Can also be used. Further, instead of the pull bar 22, a wire can be used as shown in FIG. In particular, the spring can be substituted by using an elastic wire.

  Furthermore, although the example using a spring was shown in said tension | pulling means, when the movable range of the direction of a mirror may be small, said spring can be abbreviate | omitted.

  In the above configuration, when changing the orientation of the reflecting mirror, it is desirable to set the driving amount of each actuator so that the position of the central hole 28 of the support substrate 21 is a fixed point that does not change. This operation control is performed by the control drive circuit 9 of FIG.

  As described above, the movable mirror mechanism of the present invention improves the performance and reduces the size and weight of the optical communication device. In particular, it may be applied to an optical communication device for an artificial satellite in which severe conditions are imposed on weight and volume. When optical space communication is performed between the universe and the ground, fluctuations due to the atmosphere become a major problem. It is known that the frequency component of this fluctuation extends to about 2 kHz. Therefore, the frequency response of the movable mirror mechanism needs to be 2 kHz or more. In the conventional biaxial galvanometer mirror, since the frequency response limit is about 50 to 100 Hz, the effect of applying the present invention is great. Furthermore, when the movable mirror mechanism shown in FIG. 2 was prototyped and evaluated, it was confirmed that the desired performance was obtained, and it was confirmed that the weight could be reduced by 40% or more.

DESCRIPTION OF SYMBOLS 1 Movable mirror mechanism 2 Condenser 3 Lens 4 Beam splitter 5 Laser 6 Half mirror 7 Light receiving element 8 Position detection element 9 Control drive circuit 21 Support board 22 Pull rod 23 Piezoelectric drive element 24 Spherical joint member 25 Positioning nut 26 Light reflecting mirror Holding member 27 Light reflecting mirror 28 Center hole 29 Ball receiving hole 30 Positioning tube 31 Leaf spring 32 Outer support member 33 Inner support member 34 Compression spring 35 Tension spring 36 Wire

Claims (3)

A movable mirror mechanism having a frequency response limit of 2 kHz or more and performing optical axis alignment of communication light using an input unit or an output unit of an optical communication device;
A reflector fixed to the holding substrate;
An actuator that moves the holding substrate and adjusts the direction of its normal direction;
A pulling means for pivotally connecting the holding substrate and connecting the actuator and the holding substrate;
A support substrate for holding the pulling means and the actuator;
A controller for controlling the actuator;
With
The controller state, and are not part of pivotally and the holding substrate and the pulling means for driving the actuator such that the fixed point,
A spring mechanism for pivotally connecting the pulling means and the holding substrate;
The spring mechanism, Ri Oh a leaf spring having a rotational symmetry,
The tension means, Ri pull rod or pull wire der,
The actuator is Ri Oh piezoelectric drive element,
The actuator is a plurality of three or more ,
Furthermore, including a holding rod for holding the holding substrate,
The actuator and the holding rod are arranged so as to surround the pulling means.
A movable mirror mechanism , wherein a spherical joint member is rotatably engaged with the actuator, and the holding substrate is fitted to the spherical joint member . The movable mirror mechanism according to claim 1, wherein the actuator has a position feedback control in which an expansion amount response to an input voltage is linear. 3. The movable mirror mechanism according to claim 1, wherein a portion connecting the pulling means and the holding substrate is located at the center of gravity of the holding substrate to which the reflecting mirror is fixed .

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