JP4464375B2 - Mirror control device - Google Patents

Description

  The present invention relates to a mirror control device used for an optical switch for communication and the like.

  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 340 a to 340 d are formed in circles concentric with the mirror 230 of the opposing mirror substrate 200 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. An insulating layer 311 made of silicon oxide or the like is formed on the surface of the base 310, and electrodes 340a to 340d, lead lines 341a to 341d, and wirings 370 are formed on the insulating layer 311.

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

  The mirror 230 has an electrostatic attraction generated by a potential difference between the four electrodes 340a to 340d and a restoring force of the torsion springs 211a, 211b, 221a, and 221b that attempts to return the position of the mirror 230 against the electrostatic attraction. When is balanced, stop at a certain angle. When the drive voltage applied to the electrodes 340a to 340d is increased and the inclination angle of the mirror 230 is increased, the distance between the mirror 230 and the electrodes 340a to 340d is decreased. The electrostatic attractive force generated between the mirror 230 and the electrodes 340a to 340d is inversely proportional to the square of the distance between the mirror 230 and the electrodes 340a to 340d. Therefore, as the distance between the mirror 230 and the electrodes 340a to 340d decreases, the electrostatic attractive force increases. On the other hand, the restoring force of the torsion springs 211 a, 211 b, 221 a, 221 b that resists electrostatic attraction increases in proportion to the tilt angle of the mirror 230. Therefore, when the inclination angle of the mirror 230 increases, the electrostatic attractive force and the restoring force of the torsion springs 211a, 211b, 221a, 221b are not balanced, and the rotation of the mirror 230 does not stop as shown in FIG. A phenomenon called pull-in occurs in which 230 contacts the insulating layer 311 and the electrodes 340a to 340d.

  If the insulating layer 311 is polarized by applying a voltage to the electrodes 340a to 340d or charged for some reason, the mirror 230 is fixed to the insulating layer 311 when the mirror 230 contacts the insulating layer 311. was there. Once this sticking due to electrostatic attraction occurs, even if the potential of the electrodes 340a to 340d is subsequently reduced to zero or a voltage is applied to the electrodes 340a to 340d so that the mirror 230 rotates on the opposite side, There was a problem that the mirror 230 did not move while being fixed to the insulating layer 311.

  Further, when there is a potential difference between the mirror 230 and the electrodes 340a to 340d when the mirror 230 comes into contact with the electrodes 340a to 340d, a current flows from the power source that supplies the drive voltage to the electrodes 340a to 340d in a short time. The mirror 230 and the electrodes 340a to 340d are electrodeposited. When this electrodeposition occurs, the mirror 230 cannot be returned, as in the case of fixation by electrostatic attraction. In order to prevent such electrodeposition, the surface of the electrodes 340a to 340d or the surface of the mirror 230 is covered with an insulating layer so that no current flows even if the mirror 230 and the electrodes 340a to 340d come into contact with each other. Conceivable. However, if this insulating layer contacts the mirror 230 or the electrodes 340a to 340d, the mirror 230 may be fixed to the insulating layer as in the case of the contact between the insulating layer 311 and the mirror 230 described above. It was.

  In addition, it is conceivable to increase the distance between the mirror 230 and the electrodes 340a to 340d so that pull-in does not occur under any conditions. However, if the distance between the mirror 230 and the electrodes 340a to 340d is increased, In the case of the drive type mirror control device 100, there is a problem that a very large drive voltage is required.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a mirror control device capable of eliminating the sticking of the mirror during pull-in and returning the mirror to the initial position.

The present invention relates to a mirror control device including a mirror rotatably supported and a plurality of electrodes spaced apart from the mirror, and pull-in release for instructing release of fixation between the mirror and the electrode When a command signal is input from the outside, AC voltage application means for applying an AC voltage to at least one of the mirror and the electrode, and whether or not the reflected light of the mirror is incident on a port to be incident is detected. And detecting the pull-in release command signal to the AC voltage applying means when it is determined that the reflected light of the mirror is not incident on the port where the light should be incident. Determination means.
Further, the present invention provides an instruction to release the fixation between the mirror and the electrode in a mirror control device including a mirror that is rotatably supported and a plurality of electrodes that are spaced apart from the mirror. When a pull-in release command signal is input from the outside, AC voltage applying means for applying an AC voltage to at least one of the mirror and the electrode, a sensor electrode disposed away from the mirror , and the sensor electrode And a determination unit that outputs the pull-in release command signal to the AC voltage application unit when the detected tilt angle exceeds a predetermined threshold value. .
In one configuration example of the mirror control device of the present invention, the AC voltage is a voltage having a substantially zero DC component. The AC voltage may be a rectangular wave voltage, a sine wave voltage, or a voltage in which a positive potential, a zero potential, and a negative potential are periodically switched.

  According to the present invention, when a pull-in release command signal is input from the outside, the mirror is prevented from sticking due to electrostatic attraction by providing an AC voltage applying means for applying an AC voltage to at least one of the mirror and the electrode. Thus, the mirror can be returned to the initial position. As a result, in the present invention, in order to prevent the occurrence of pull-in, it is not necessary to increase the distance between the mirror and the electrode, and it is not necessary to increase the drive voltage as the distance between the mirror and the electrode increases.

  In the present invention, the detection means for detecting whether or not the reflected light of the mirror is incident on the port to be incident and the pull-in cancellation when it is determined that the reflected light of the mirror is not incident on the incident port By providing the determination means for outputting the command signal to the AC voltage application means, it is possible to eliminate the sticking of the mirror due to electrostatic attraction and automatically return the mirror to the initial position.

  In the present invention, the tilt angle of the mirror is detected based on the sensor electrode and the signal of the sensor electrode, and when the detected tilt angle exceeds a predetermined threshold, a pull-in release command signal is output to the AC voltage applying means. By providing the determination means, the mirror can be prevented from sticking due to electrostatic attraction and the mirror can be automatically returned to the initial position.

  Further, in the present invention, by making the DC component of the AC voltage substantially zero, the charge accumulated in the insulating layer under the electrode or the insulating layer covering the surface of the electrode can be brought closer to zero on a time average, Mirror sticking due to electrostatic attraction can be eliminated.

[ First Reference Example ]
Hereinafter, reference examples 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 reference example 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 reference example , single crystal silicon), and the mirror 230 is a mirror substrate. 200 is supported 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.

This reference example is characterized in that a periodic voltage (AC voltage) is applied to the electrodes 340a to 340d when pull-in occurs. FIG. 3 is a block diagram showing an electrical connection relationship of the mirror control device of this reference example .
In a normal operation, the mirror voltage application unit 400 applies a ground potential to the mirror 230 via the frame part 210, the torsion springs 211a and 211b, the movable frame 220, and the torsion springs 221a and 221b.

  On the other hand, the drive voltage application unit 401 applies a drive voltage to at least one of the electrodes 340a to 340d in a normal operation. 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 drive voltage is applied to the electrodes 340a to 340d via lead lines 341a to 341d.

Here, when the monitor finds that pull-in has occurred in the mirror 230, the monitor inputs a pull-in release command signal to the mirror voltage application unit 400 and the drive voltage application unit 401. Upon receiving the pull-in release command signal, the mirror voltage application unit 400 puts the mirror 230 into an open state (floating state). In this reference example , when a pull-in release command signal is input, the drive voltage application unit 401 serving as an AC voltage application unit applies an AC voltage having substantially zero DC component as shown in FIG. 4 to all the electrodes 340a to 340d. Apply. The reason why the mirror 230 is in an open state is to prevent a current from flowing from the driving voltage applying unit 401 to the mirror 230 via the electrodes 340a to 340d.

When an AC voltage having substantially zero DC component is applied to the electrodes 340a to 340d in a state where pull-in occurs, the charge accumulated in the insulating layer 311 can be brought close to zero on the time average. As a result, in this reference example , the fixation of the mirror 230 due to electrostatic attraction can be eliminated, and the mirror 230 can be returned to the initial position (horizontal position in FIG. 2).

[ Second Reference Example ]
In the first reference example , when pull-in occurs, an AC voltage having a substantially zero DC component is applied to the electrodes 340a to 340d, but may be applied to the mirror 230. In this case, the drive voltage application unit 401 that has received the pull-in release command signal opens all the electrodes 340a to 340d. In this reference example , the mirror voltage application unit 400 serving as an AC voltage application unit applies an AC voltage having substantially zero DC component as shown in FIG. 4 to the mirror 230 when a pull-in release command signal is input. Thus, also in this reference example , the mirror 230 can be returned to the initial position.

[ Third reference example ]
In the first and second reference examples , an AC voltage is applied to one of the electrodes 340a to 340d and the mirror 230, but it may be applied to both. In this case, the mirror voltage applying means 400 that has received the pull-in release command signal applies an AC voltage having substantially zero DC component as shown in FIG. 5A to the mirror 230 and also receives the pull-in release command signal. The voltage application unit 401 applies an AC voltage having substantially zero DC component as shown in FIG. 5B to all the electrodes 340a to 340d. The AC voltage applied to the mirror 230 and the AC voltage applied to the electrodes 340a to 340d may have the same phase, but a difference may be provided between the amplitudes of the two. Thereby, also in this reference example , the mirror 230 can be returned to the initial position.

In the first to third reference examples , when the mirror 230 and the electrodes 340a to 340d come into contact with each other, a current flows from the driving voltage applying unit 401 to the mirror 230 via the electrodes 340a to 340d, and the mirror 230 and the electrode 340a When ˜340d is electrodeposited, this electrodeposition cannot be resolved and the mirror 230 cannot be returned to the initial position. However, if there are naturally formed oxide films or moisture on the surfaces of the electrodes 340a to 340d, these act as an insulating layer, so that electrodeposition between the mirror 230 and the electrodes 340a to 340d can be avoided.

  Further, in order to prevent electrodeposition between the mirror 230 and the electrodes 340a to 340d, an insulating layer covering the surface of the electrodes 340a to 340d, the surface of the mirror 230, or both may be provided in advance. In this case, since the mirror 230 and the electrodes 340a to 340d are not in electrical contact, it is not necessary to open the mirror 230 or the electrodes 340a to 340d when pull-in occurs.

[ First Embodiment ]
In the first to third reference examples , when the monitor finds that pull-in has occurred in the mirror 230, a pull-in release command signal is input to the mirror voltage application unit 400 and the drive voltage application unit 401. It is also possible to detect the occurrence of pull-in and automatically generate a pull-in release command signal. FIG. 6 is a perspective view showing a configuration of an optical switch to which the mirror control device of the present embodiment is applied.

  In FIG. 6, 11a is an input port, 11b is an output port, 12a is an input side collimator array, 12b is an output side collimator array, 13a is an input side mirror array, and 13b is an output side mirror array. The input port 11a and the output port 11b are each composed of a plurality of optical fibers that are two-dimensionally arranged, and the collimator arrays 12a and 12b are each composed of a plurality of microlenses that are two-dimensionally arrayed. 13b includes a plurality of mirror control devices 100 that are two-dimensionally arranged. The arrows in FIG. 6 indicate the traveling direction of the light beam.

  An optical signal emitted from a certain input port 11a is converted into collimated light by a microlens of the input-side collimator array 12a, sequentially reflected by the input-side mirror array 13a and the output-side mirror array 13b, and the microlens of the output-side collimator array 12b. Is condensed and guided to the output port 11b. By appropriately controlling the inclination angle of the mirror 230 of the mirror control device 100 of each of the mirror arrays 13a and 13b, it is possible to connect between any two-dimensionally arranged input port 11a and output port 11b. And the optical path can be switched.

In the present embodiment, in such an optical switch, output light detection means is provided for each output port 11b. FIG. 7 is a block diagram showing an electrical connection relationship of the mirror control device of the present embodiment. The same components as those in FIG. However, in the example of FIG. 7, only one mirror control device 100 is described.
The output light detection means 402 of each output port 11b detects whether or not the output light is incident on its own output port 11b.

For example, the determination unit 403 including a control device that controls the entire optical switch recognizes which port of the plurality of output ports 11b should receive the output light.
The determination unit 403 receives the output light detection result by the output light detection unit 402 of each output port 11b, and when the output light is not incident on the output port 11b to which the output light is incident, the determination unit 403 is on the path of the output light. Assuming that pull-in has occurred in a certain mirror control device 100, a pull-in release command signal is output to the mirror voltage application unit 400 and the drive voltage application unit 401 of the mirror control device 100. Subsequent operations are as described in the first to third reference examples . Thus, according to the present embodiment, when pull-in occurs in the mirror 230, the mirror 230 can be automatically returned to the initial position.

[ Second Embodiment ]
In the first embodiment, it is determined whether or not pull-in has occurred in the mirror 230 using the output light detection result by the output light detection means. However, the mirror 230 is detected by detecting the tilt angle of the mirror 230. It may be determined whether or not a pull-in has occurred. FIG. 8 is a block diagram showing the electrical connection relationship of the mirror control device of the present embodiment. The same components as those in FIG.

In the present embodiment, apart from the electrodes 340a to 340d, the sensor electrode 404 is provided on the insulating layer 311 of the base 310 of the mirror control device 100 so as to face the mirror 230.
The determination unit 405 detects the attitude of the mirror 230, that is, the tilt angle, by detecting the capacitance according to the distance between the mirror 230 and the sensor electrode unit 404 that changes according to the tilt angle of the mirror 230. Then, when the detected tilt angle of the mirror 230 exceeds a predetermined threshold, the determination unit 405 considers that the pull-in has occurred in the mirror 230, and cancels the pull-in to the mirror voltage applying unit 400 and the drive voltage applying unit 401. A command signal is output. Subsequent operations are as described in the first to third reference examples . Thus, also in the present embodiment, the mirror 230 can be automatically returned to the initial position as in the first embodiment .

[ Third Embodiment ]
In the first to third reference examples and the first and second embodiments, a rectangular wave is used as an AC voltage applied to at least one of the mirror 230 and the electrodes 340a to 340d when pull-in occurs. A sine wave voltage or a triangular wave voltage may be used.
In addition, as shown in FIG. 9, an alternating voltage in which a positive potential, a zero potential, and a negative potential are periodically switched may be applied to at least one of the mirror 230 and the electrodes 340a to 340d. In this case, the DC component can be made zero by making the amplitude and application time width of the positive potential and the negative potential equal.

  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 reference example 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 which concerns on the 1st reference example of this invention. It is a wave form diagram which shows the alternating voltage applied to an electrode at the time of pull-in generation | occurrence | production in the 1st reference example of this invention. It is a wave form diagram which shows the alternating voltage applied to a mirror and an electrode at the time of pull-in generation | occurrence | production in the 3rd reference example of this invention. It is a perspective view which shows the structure of the optical switch which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the electrical connection relation of the mirror control apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the electrical connection relation of the mirror control apparatus which concerns on the 2nd Embodiment of this invention. It is a wave form diagram which shows the alternating voltage applied to at least one among a mirror and an electrode at the time of pull-in occurrence in the 3rd Embodiment of this invention. It is sectional drawing explaining the pull-in phenomenon in which a mirror contacts an electrode or an insulating layer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... 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 ... Electrode, 400: mirror voltage application means, 401: drive voltage application means, 402: output light detection means, 403, 405 ... determination means, 404 ... sensor electrode.

Claims (6)

In a mirror control device comprising a mirror that is rotatably supported and a plurality of electrodes that are spaced apart from the mirror,
AC voltage application means for applying an AC voltage to at least one of the mirror and the electrode when a pull-in release command signal instructing release of fixation between the mirror and the electrode is input from the outside ;
Detecting means for detecting whether or not the reflected light of the mirror is incident on a port to be incident;
And a determination unit that outputs the pull-in release command signal to the AC voltage application unit when it is determined that the reflected light of the mirror is not incident on the port to be incident upon receiving the detection result by the detection unit. A mirror control device characterized by that. In a mirror control device comprising a mirror that is rotatably supported and a plurality of electrodes that are spaced apart from the mirror,
AC voltage application means for applying an AC voltage to at least one of the mirror and the electrode when a pull-in release command signal instructing release of fixation between the mirror and the electrode is input from the outside;
A sensor electrode disposed away from the mirror;
Determining means for detecting the tilt angle of the mirror based on the signal of the sensor electrode, and outputting the pull-in release command signal to the AC voltage applying means when the detected tilt angle exceeds a predetermined threshold value. A mirror control device characterized by that. In the mirror control device according to claim 1 or 2 ,
A mirror control device characterized in that the AC voltage has a DC component substantially zero . In the mirror control device according to any one of claims 1 to 3,
The mirror control device according to claim 1, wherein the AC voltage is a rectangular wave voltage . In the mirror control device according to any one of claims 1 to 3 ,
The mirror control device, wherein the AC voltage is a sine wave voltage . In the mirror control device according to any one of claims 1 to 3 ,
The AC voltage is a mirror control device characterized in that a positive potential, a zero potential, and a negative potential are periodically switched .

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