JP4773300B2 - Mirror control method - Google Patents

Description

The present invention relates are used in the optical switch and the like for communication Rumi error control method.

  In the field of optical networks, which are the foundation of Internet communication networks, optical MEMS (Micro Electro Mechanical System) technology is in the spotlight as a technology that realizes multi-channel, wavelength division multiplexing (WDM), and cost reduction. An optical switch has been developed using this technique (see, for example, Patent Document 1). The most characteristic component of the MEMS type optical switch is a mirror array. The mirror array is a two-dimensional arrangement of a plurality of mirror control devices. FIG. 1 is an exploded perspective view showing a configuration of a mirror control device according to a first embodiment of the present invention, and FIG. 2 is a sectional view of the mirror control device of FIG. Since the configuration is the same, a conventional mirror control device will be described with reference to FIGS.

The mirror control device 100 has a structure in which a mirror substrate (upper substrate) 200 on which a mirror is formed and an electrode substrate (lower substrate) 300 on which an electrode is formed are arranged in parallel.
The mirror substrate 200 has a plate-like frame portion 210 having a substantially circular opening in a plan view and a substantially circular opening in a plan view, and is disposed in the opening of the frame portion 210 by a pair of torsion springs 211a and 211b. The movable frame 220 includes a mirror 230 having a substantially circular shape in a plan view and disposed in the opening of the movable frame 220 by a pair of torsion springs 221a and 221b. The frame part 210, the torsion springs 211a, 211b, 221a, 221b, the movable frame 220, and the mirror 230 are integrally formed of, for example, single crystal silicon. For example, three Ti / Pt / Au layers are formed on the surface of the mirror 230. A frame-shaped member 240 is formed on the upper surface of the frame portion 210 so as to surround the movable frame 220 and the mirror 230.

The pair of torsion springs 211 a and 211 b connect the frame part 210 and the movable frame 220. The movable frame 220 can rotate about the movable frame rotation axis x of FIG. 1 passing through the pair of torsion springs 211a and 211b.
Similarly, the pair of torsion springs 221 a and 221 b couple the movable frame 220 and the mirror 230. The mirror 230 can rotate about the mirror rotation axis y of FIG. 1 passing through the pair of torsion springs 221a and 221b. The movable frame rotation axis x and the mirror rotation axis y are orthogonal to each other. As a result, the mirror 230 rotates about two orthogonal axes.

  The electrode substrate 300 includes a plate-like base portion 310 and a terrace-like protrusion portion 320 that protrudes from the surface (upper surface) of the base portion 310 and is formed at a position facing the mirror 230 of the opposing mirror substrate 200. The base 310 and the protrusion 320 are made of, for example, single crystal silicon. The protrusion 320 includes a second terrace 322 having a truncated pyramid shape formed on the upper surface of the base 310, a first terrace 321 having a truncated pyramid shape formed on the upper surface of the second terrace 322, and the first terrace 321. It is composed of a pivot 330 having a columnar shape formed on the upper surface of one terrace 321. The pivot 330 is formed so as to be positioned approximately at the center of the first terrace 321. Accordingly, the pivot 330 is disposed at a position facing the center of the mirror 230.

  Four electrodes 340a to 340d are formed in a circle concentric with the mirror 230 of the mirror substrate 200 facing each other at the four corners of the protrusion 320 and the upper surface of the base 310 following the four corners. In addition, a pair of convex portions 360 a and 360 b arranged side by side so as to sandwich the protruding portion 320 is formed on the upper surface of the base portion 310. Furthermore, wirings 370 are respectively formed at locations between the protrusions 320 on the upper surface of the base 310 and the protrusions 360a and 360b. The wirings 370 are connected to electrodes via lead lines 341a to 341d. 340a to 340d are connected.

The mirror substrate 200 and the electrode substrate 300 as described above are arranged such that the lower surface of the frame portion 210 and the upper surfaces of the convex portions 360a and 360b are disposed so that the mirror 230 and the electrodes 340a to 340d corresponding to the mirror 230 are disposed to face each other. 2 is configured to constitute a mirror control device 100 as shown in FIG.
In such a mirror control device 100, the mirror 230 is grounded, a positive voltage is applied to the electrodes 340a to 340d, and an asymmetrical potential difference is generated between the electrodes 340a to 340d, whereby the mirror 230 is electrostatically attracted. And the mirror 230 can be rotated in an arbitrary direction.

JP 2003-57575 A

  In the mirror control device 100 shown in FIG. 1 and FIG. 2, it is necessary to apply a large drive voltage corresponding to the tilt angle of the mirror 230 to the electrodes 340a to 340d during driving. Depending on the distance between the mirror 230 and the electrodes 340a to 340d, the restoring force of the torsion spring that supports the mirror 230, the area of the electrodes 340a to 340d, the relationship between the driving voltage and the electrostatic attractive force, or the inclination angle of the driving voltage and the mirror 230 However, as the drive voltage applied to the electrodes 340a to 340d, a high voltage of about several tens of volts to several hundreds of volts is necessary. Therefore, there is a problem that a power source capable of generating a high voltage is required.

The present invention has been made to solve the above problems, and an object thereof is to provide a luminal error control method can achieve lower the driving voltage of the mirror.

The present invention is directed to a mirror control device including a mirror that is rotatably supported and a plurality of electrodes that are spaced apart from the mirror, by applying a driving voltage to the electrodes, a mirror control method for controlling a bias voltage applying step of applying a bias voltage of the non-zero on the mirror, one of the electrodes to be paired involved in driving of the mirror, the bias voltage and synchronization to one electrode A drive voltage applying step of applying a drive voltage of the same polarity and applying a drive voltage of opposite polarity synchronized with the bias voltage to the other electrode , wherein the bias voltage and the drive voltage are alternating voltages It is a feature .
The DC component of the AC voltage is preferably zero. An example of the AC voltage is a rectangular wave voltage.

  According to the present invention, since the drive voltage can be lowered by applying a non-zero bias voltage to the mirror, the bias voltage application means and the drive voltage application means have a lower voltage output than the conventional one. A power supply can be used. Further, by applying a drive voltage having a polarity opposite to the bias voltage to at least one of the plurality of electrodes, the force for driving the mirror can be increased.

  In addition, among the pair of electrodes involved in driving the mirror, by applying a driving voltage having the same polarity as the bias voltage to one electrode and applying a driving voltage having the opposite polarity to the bias voltage to the other electrode, The driving force can be increased.

  Further, when an AC voltage is applied as a bias voltage and a drive voltage, the occurrence of vibrations in the mirror can be reduced by setting the AC voltage to have a DC component of zero. Further, in the present invention, by setting the bias voltage and the drive voltage to an alternating voltage having a direct current component of zero, the charge accumulated in the stray capacitance such as an insulating layer existing between the electrode and the mirror can be brought close to zero. Therefore, it is possible to suppress the occurrence of mirror drift caused by the charge accumulated in the stray capacitance.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view showing a configuration of a mirror control device according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view of the mirror control device of FIG. As described above, the frame portion 210, the torsion springs 211a, 211b, 221a, 221b, the movable frame 220, and the mirror 230 are integrally formed of a conductive material (in this embodiment, single crystal silicon), and the mirror 230 is a mirror. The substrate 200 is supported so as to be rotatable. On the other hand, an insulating layer 311 made of silicon oxide or the like is formed on the surface of the base 310 made of single crystal silicon or the like, and electrodes 340a to 340d, lead lines 341a to 341d, and wirings 370 are formed on the insulating layer 311. Has been.

  The major difference between this embodiment and the conventional mirror control device is that the mirror 230 is grounded in the conventional mirror control device, whereas a non-zero voltage is applied to the mirror 230 in this embodiment. Is a point. The voltage applied to the mirror 230 is a voltage (bias voltage) that does not depend on the tilt angle of the mirror 230. Hereinafter, differences between the present embodiment and a conventional mirror control device will be described in more detail.

  FIG. 3 is a block diagram showing an electrical connection relationship of the mirror control device of the present embodiment. In the present embodiment, a bias voltage is applied from the bias voltage applying unit 400 to the mirror 230, and the driving voltage is applied from the driving voltage applying unit 401 to at least one of the electrodes 340a to 340d. The drive voltage application unit 401 has a table in which the relationship between the tilt angle of the mirror 230 and the drive voltage value is set in advance, and acquires the drive voltage value corresponding to the desired tilt angle of the mirror 230 from the table. Then, a drive voltage is applied to the electrodes 340a to 340d. A bias voltage is applied to the mirror 230 via the frame portion 210, the torsion springs 211a and 211b, the movable frame 220, and the torsion springs 221a and 221b. A driving voltage is applied to the electrodes 340a to 340d through the lead lines 341a to 341d.

  For example, it is assumed that −Vm is applied as a bias voltage to the mirror 230, −Vx is applied as a drive voltage to the electrode 340b, and + Vx is applied as a drive voltage to the electrode 340d. As a result, the mirror 230 rotates so as to be drawn toward the electrode 340d as shown in FIG. The voltage application at this time is equivalent to 0 V applied to the mirror 230, the drive voltage (Vm−Vx) applied to the electrode 340b, and the drive voltage (Vm + Vx) applied to the electrode 340d in the conventional mirror control device. Therefore, focusing on the voltage value, the conventional mirror control device requires a maximum voltage of Vm + Vx, whereas in the present embodiment, either the voltage Vm or Vx is the maximum voltage. The drive voltage can be lowered compared to the above.

  As described above, in this embodiment, since the drive voltage can be reduced, it is possible to use a power supply with a lower voltage output than the conventional one for the bias voltage application unit 400 and the drive voltage application unit 401. it can.

  Note that when a non-zero bias voltage is applied to the mirror 230 as in the present embodiment, it is desirable to apply a drive voltage having a polarity opposite to the bias voltage to at least one of the electrodes 340a to 340d. The reason is that if a driving voltage having the opposite polarity to the bias voltage is applied to at least one of the electrodes 340a to 340d, the electrodes 340a to 340a to 340a to 340d are compared to the case where the driving voltage having the same polarity as the bias voltage is applied. This is because the potential difference between 340d can be increased and the force for driving the mirror 230 can be increased.

  For the same reason, when a drive voltage is applied to the pair of electrodes related to driving of the mirror 230 (the electrodes 340b and 340d in the example of the present embodiment), a bias voltage is applied to one of the pair of electrodes. And a drive voltage having the opposite polarity to the bias voltage may be applied to the other electrode. Thereby, the mirror 230 rotates so as to be attracted to the electrode to which the drive voltage having the opposite polarity to the bias voltage is applied, but the driving force at this time can be increased.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 5 is an exploded perspective view showing the configuration of the mirror control device according to the second embodiment of the present invention. In the first embodiment, the movable frame rotation axis x and the mirror rotation axis y are arranged so that the dividing lines of the electrodes 340a to 340d intersect at 45 degrees. On the other hand, in the mirror control device 100a of the present embodiment, the movable frame rotation axis x passing through the torsion springs 211c and 211d, the mirror rotation axis y passing through the torsion springs 221c and 221d, and the division of the electrodes 340a to 340d. It is arranged so that the line is parallel.

  Also in the present embodiment, the electrical connection relationship of the mirror control device is as shown in FIG. 3, and the bias voltage application unit 400 applies −Vm to the mirror 230 as a bias voltage. If the drive voltage necessary to rotate the mirror 230 about the movable frame rotation axis x is Vx, and the drive voltage necessary to rotate the mirror 230 about the mirror rotation axis y is Vy (Vx, Vy). Drive voltage application means 401 applies a drive voltage (Vx + Vy) to electrode 340a, a drive voltage (Vx−Vy) to electrode 340b, and a drive voltage (−Vx−Vy) to electrode 340c. And a drive voltage (−Vx + Vy) is applied to the electrode 340d. Thereby, the mirror 230 rotates in the direction according to the potential difference between the electrodes 340a to 340d.

  The voltage application at this time is 0 V for the mirror 230, the drive voltage (Vm + Vx + Vy) for the electrode 340a, the drive voltage (Vm + Vx-Vy) for the electrode 340b, and the drive voltage (Vm-Vx-Vy) for the electrode 340c in the conventional mirror control device. This is equivalent to applying a drive voltage (Vm−Vx + Vy) to the electrode 340d. Therefore, while the conventional mirror control device requires a voltage of Vm + Vx + Vy at the maximum, in this embodiment, the larger voltage of Vm or Vx + Vy is the maximum voltage, so that it is driven as compared with the conventional mirror control device. The voltage can be lowered. Thus, also in this embodiment, the same effect as that of the first embodiment can be obtained.

[Third Embodiment]
In the first and second embodiments, the bias voltage and the drive voltage are DC, but they may be periodic voltages (AC voltages). For example, in the first embodiment, a periodic bias voltage as shown in FIG. 6A is applied to the mirror 230, and a periodic drive voltage as shown in FIG. 6B synchronized with the bias voltage is applied to the electrode 340b. When a periodic drive voltage as shown in FIG. 6C synchronized with the bias voltage is applied to the electrode 340d, the mirror 230 rotates so as to be drawn toward the electrode 340b.

  At this time, it is preferable that the bias voltage and the drive voltage are AC voltages having zero DC component. When the DC component of the bias voltage and the drive voltage is not zero, the mirror 230 may vibrate according to the frequency of the bias voltage and the drive voltage. This is particularly noticeable when the frequency of the drive voltage is smaller than the mirror resonance frequency. However, such a vibration of the mirror 230 can be reduced by reducing the DC component of the drive voltage to zero. In the case of a rectangular wave voltage, the vibration of the mirror 230 can be suppressed at any frequency regardless of the mirror resonance frequency in principle by setting the DC component to zero.

  Similarly to the first embodiment, when a drive voltage is applied to a pair of electrodes related to driving of the mirror 230, a drive voltage having the same polarity synchronized with the bias voltage is applied to one of the pair of electrodes. Is applied, and a driving voltage having the opposite polarity synchronized with the bias voltage is applied to the other electrode, so that the driving force of the mirror 230 can be increased as in the first embodiment. In the example of FIG. 6, a drive voltage having the opposite polarity to the bias voltage is applied to the electrode 340b, and a drive voltage having the same polarity as the bias voltage is applied to the electrode 340d.

  The AC voltage applied to the mirror 230 and the electrodes 340a to 340d is preferably a rectangular wave from the viewpoint that the driving force can be increased, but may be a sine wave or the like other than the rectangular wave.

  The present invention can be applied to a mirror control device and a mirror array in which a plurality of mirror control devices are two-dimensionally arranged.

It is a disassembled perspective view which shows the structure of the mirror control apparatus which concerns on the 1st Embodiment of this invention. It is sectional drawing of the mirror control apparatus of FIG. It is a block diagram which shows the electrical connection relation of the mirror control apparatus of the 1st Embodiment of this invention. It is sectional drawing which shows a mode that a mirror rotates in the 1st Embodiment of this invention. It is a disassembled perspective view which shows the structure of the mirror control apparatus which concerns on the 2nd Embodiment of this invention. FIG. 10 is a waveform diagram of a bias voltage applied to a mirror and a drive voltage applied to an electrode in the third embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100,100a ... Mirror control apparatus, 200 ... Mirror board | substrate, 211a, 211b, 211c, 211d, 221a, 221b, 221c, 221d ... Torsion spring, 220 ... Movable frame, 230 ... Mirror, 300 ... Electrode board, 340a-340d ... Electrodes, 400... Bias voltage applying means, 401.

Claims (3)

A mirror that controls the movement of the mirror by applying a driving voltage to the electrode with respect to a mirror control device that includes a mirror that is rotatably supported and a plurality of electrodes that are spaced apart from the mirror. A control method,
A bias voltage application step of applying a non-zero bias voltage to the mirror;
Of the pair of electrodes involved in driving the mirror, one electrode is applied with the same polarity driving voltage synchronized with the bias voltage, and the other electrode is applied with the opposite polarity driving voltage synchronized with the bias voltage. And a driving voltage applying step
The mirror control method, wherein the bias voltage and the drive voltage are alternating voltages . The mirror control method according to claim 1,
A mirror control method, wherein a DC component of the AC voltage is zero . In the mirror control method according to claim 1 or 2,
The mirror control method, wherein the bias voltage and the drive voltage are rectangular wave voltages .

Images