JP6339381B2 - Electrostatic drive variable mirror - Google Patents

Description

  The present invention relates to an electrostatic drive variable mirror, and more particularly to an electrostatic drive variable mirror that changes the shape of a reflecting surface with an electrostatic force.

  In order to obtain a high-definition image in fundus observation or astronomical observation, a wavefront compensation mirror is used. The wavefront compensation mirror corrects the wavefront shift of incident light during reflection by changing the shape of the reflecting surface.

  For example, in the electrostatic drive variable mirror shown in the cross-sectional view of FIG. 19, a plurality of electrodes 116 a to 116 e are arranged on the side opposite to the reflective film 115, and the voltage applied to the electrodes 116 a to 116 e is controlled by the voltage control circuit 120. Thus, the reflective film 115 is deformed (see, for example, Patent Document 1).

  For example, a variable mirror 111 shown in the explanatory diagram of FIG. 20 has been proposed as means for performing image blur correction in the photographing apparatus. In the variable mirror 111, an upper substrate 201 having a reflecting portion 204 is supported at one point by a pivot 261 of the lower substrate 201 and is connected through springs 251 to 254. The potential difference between the upper electrode 202 formed on the upper substrate 201 and the plurality of lower electrodes 222 to 225 formed on the lower substrate 201 is adjusted, and the electrostatic force between the upper electrode 203 and the lower electrodes 222 to 225 is adjusted. The tilt direction and tilt angle of the upper substrate 201 can be changed (see, for example, Patent Document 2).

JP 2005-221579 A International Publication No. 2004/109359

  When the wavefront compensation mirror is realized by a MEMS that produces a micro mechanical structure by a semiconductor microfabrication technique, among electrostatic, piezoelectric, electrostatic, and other driving systems, an electrostatic driving system such as Patent Document 1 is used. The device structure becomes relatively simple.

  However, in the electrostatic driving method, the electrostatic force used for driving is inversely proportional to the square of the electrode interval and proportional to the square of the driving voltage applied between the electrodes. Therefore, when a large deformation is required for wavefront compensation, the electrode interval is increased to ensure a stroke, and as a result, the drive voltage is increased to, for example, 100 V or more.

  When the mirror is supported at one point and electrostatically driven as in Patent Document 2, only the tilt of the mirror is changed, and a large displacement cannot be given to the mirror only by making an array. Further, when the electrode area is increased and the driving force is increased, the angle at which the mirror is tilted is reduced, and the deformation amount is reduced.

  In view of such circumstances, the present invention intends to provide an electrostatic drive variable mirror capable of increasing the amount of deformation of a reflecting surface even with a low drive voltage.

  In order to solve the above problems, the present invention provides an electrostatic drive variable mirror configured as follows.

The electrostatic drive variable mirror has (a) a mirror having a reflecting surface and a back surface opposite to the reflecting surface, and (b) a space between the back surface of the mirror and facing the back surface, A movable portion having an electrode facing the back surface, (c) a fixed portion that holds the movable portion so as to be movable toward and away from the mirror, and (d) the mirror and the movable portion. And a connecting portion that is disposed between the mirror and the movable portion and that maintains a distance between the mirror and the movable portion. An electrostatic force is generated by a potential difference between the electrode and the mirror, the mirror is tilted with respect to the movable portion by the electrostatic force, and the movable portion is moved in accordance with the tilt of the mirror. .

  In the above configuration, when a voltage is applied to the electrode of the movable part, an electrostatic force acts between the movable part and the mirror. At this time, since the distance between the mirror and the movable portion is maintained at the connection portion, the mirror is tilted with respect to the movable portion by electrostatic force, and the mirror is deformed. The movable part is held so as to be movable in a direction in which the movable part is in contact with or separated from the mirror. For this reason, the movable part moves in a direction in which the movable part comes into contact with or separates from the mirror with the deformation of the mirror. Note that the connecting portion may be formed integrally with one or both of the mirror and the movable portion, or may be elastically deformed.

  According to the above configuration, the distance between the electrode and the mirror is kept within a predetermined range by the connecting portion. Therefore, the mirror can be configured to be deformed even if the voltage applied to the electrode is lowered. Since the movable portion can move when the mirror is deformed, the amount of deformation of the mirror can be increased without being restricted by the distance between the mirror and the electrode without being restricted by the connecting portion. Therefore, the deformation amount of the reflecting surface can be increased even with a low driving voltage.

  In a preferred aspect, the connecting portion is fixed to both the mirror and the movable portion.

  In another preferable aspect, the connection portion is fixed to only one of the mirror and the movable portion. The movable portion and the fixed portion are connected, the movable portion is urged toward the mirror, and a support portion that holds the contact between the other of the mirror and the movable portion and the connecting portion is further provided.

Preferably, the fixed part accommodates the movable part with an interval between the movable part . The toward and away from the forward direction SL movable portion with respect to the mirror, are arranged with a distance from one another, further comprising a first and a second beam portion connected to the movable portion and the fixed portion.

  In this case, the first and second beam portions can suppress the inclination of the movable portion with respect to the direction in which the movable portion contacts and separates from the mirror. Moreover, the electrostatic drive variable mirror of MEMS structure can be produced easily.

Preferably, the apparatus includes one mirror, the plurality of movable portions, and the plurality of connection portions .

  In this case, by applying an arbitrary voltage to the electrode on the divided movable part, the deformation of the mirror by the adjacent movable part is largely deformed without restraining the movable part, and at that time, the movable part maintains a narrow distance from the mirror. Therefore, complicated deformation of the mirror is possible at a low voltage.

  According to the present invention, the amount of deformation of the reflecting surface can be increased even with a low driving voltage.

It is explanatory drawing which shows the basic composition of an electrostatic drive variable mirror. (First type) It is explanatory drawing which shows the basic composition of an electrostatic drive variable mirror. (Modification 1 of the first type) It is explanatory drawing which shows the basic composition of an electrostatic drive variable mirror. (Modification 2 of the first type) It is explanatory drawing which shows the basic composition of an electrostatic drive variable mirror. (Second type) It is explanatory drawing which shows the basic composition of an electrostatic drive variable mirror. (Third type) It is explanatory drawing at the time of arraying an electrostatic drive variable mirror. (Third type) It is a top view of an electrostatic drive variable mirror. Example 1 It is a principal part enlarged plan view of a lower board | substrate. Example 1 It is sectional drawing which shows the manufacturing process of an upper board | substrate. Example 1 It is sectional drawing which shows the manufacturing process of a lower board | substrate. Example 1 It is sectional drawing which shows the manufacturing process of a lower board | substrate. Example 1 It is (a) exploded sectional view of an electrostatic drive variable mirror, and (b) assembly sectional view. Example 1 It is an image figure of a simulation model. Example 1 It is an image figure of a simulation model. Example 1 It is an image figure of an actuator. Example 1 It is an image figure which shows a simulation result. Example 1 It is an image figure which shows a simulation result. Example 1 It is a graph which shows a simulation result. Example 1 It is sectional drawing which shows the structure of an electrostatic drive variable mirror. (Conventional example 1) It is explanatory drawing which shows the structure of a variable mirror. (Conventional example 2)

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the basic configuration of the electrostatically driven variable mirror of the present invention will be described with reference to FIGS.

  <First Type> FIGS. 1A and 1B are explanatory views showing a basic configuration of a first type electrostatic drive variable mirror 10a. FIG. 1A shows a disassembled state, and FIG. 1B shows an assembled state. As shown in FIGS. 1A and 1B, the mirror 12 has a reflecting surface 12a and a back surface 12b opposite to the reflecting surface 12a, and the movable portion 24 faces the back surface 12b of the mirror 12. Is arranged. Although the case where the periphery of the mirror 12 is constrained by the frame portion 36 is illustrated, it is possible to prevent the periphery of the mirror 12 from being constrained.

  The movable portion 24 is held by the fixed portion 22 so as to be movable in a mirror contacting / separating direction (for example, a normal direction of the back surface 12b of the mirror 12 before deformation) that approaches or separates from the mirror 12. A connecting portion 28a is fixed to the movable portion 24, and at least one electrode 25 is formed around the connecting portion 28a. The connection part 28a protrudes from the movable part 24 to the mirror 12 side. The movable part 24 is urged toward the mirror 12 by the support part 26.

  That is, in the first type electrostatic drive variable mirror 10a, the mirror 12 approaches the fixed portion 22, the movable portion 24 and the support portion 26 from the disassembled state shown in FIG. As shown in FIG. 1B, the connection portion 28 a is configured to contact the back surface 12 b of the mirror 12, and the state in which the connection portion 28 a contacts the back surface 12 b of the mirror 12 is maintained by the support unit 26. For example, the support unit 26 is configured to elastically pull the movable unit 24 toward the mirror 12 so that the state in which the connection unit 28 a is in contact with the back surface 12 b of the mirror 12 is maintained.

  The support part can be appropriately formed. For example, the surface 24b of the movable part 24 opposite to the mirror 12 may be pressed by an elastic member such as a spring or sponge, and the movable part is supported via a beam part as in Example 1 described later. May be.

  When a voltage is applied to the electrode 25 of the movable portion 24, an electrostatic force is generated due to a potential difference between the electrode on the mirror 12 side (for example, silicon forming the mirror 12) and the electrode 25. At this time, since the distance between the mirror 12 and the movable portion 24 is maintained in the connection portion 28a, the mirror 12 is inclined with respect to the movable portion 24 by the electrostatic force, and the mirror 12 is deformed. When a plurality of electrodes 25 are formed around the connection portion 28a and a voltage is selectively applied to the electrodes 25, the mirror 12 tilts in a direction corresponding to the electrode 25 to which the voltage is applied. The support portion 26 holds the connection portion 28a so as not to be separated from the mirror 12 even when the mirror is deformed, and allows the movable portion 24 to move according to the deformation of the mirror 12. If slippage is likely to occur between the connecting portion 28a and the back surface 12b of the mirror 12, the deformation of the reflecting surface 12a of the mirror 12 becomes smooth. The connecting portion 28a may be expanded and contracted or bent by elastic deformation.

  FIG. 2 is an explanatory diagram showing a basic configuration of the electrostatic drive variable mirror 10d of the first type of the first modification. As shown in FIG. 2, the connecting portion 28 d may be fixed to the back surface 12 b of the mirror 12 instead of the movable portion 24. Alternatively, a plurality of electrodes 25s may be formed on the mirror 12 side, and a single electrode 25t may be formed on the movable portion 24 side. In this case, the plurality of electrodes 25s on the mirror 12 side are formed around the connection portion 28d, and a voltage is selectively applied to the electrode 25s on the mirror 12 side. In addition, the support portion 26 does not pull the movable portion 24 toward the mirror 12, but the support portion 26 elastically presses the movable portion 24 toward the mirror 12, and the contact between the connecting portion 28d and the movable portion 24 is maintained. You may comprise so that.

  FIG. 3 is an explanatory diagram showing a basic configuration of the electrostatically driven variable mirror 10e according to the second type of the second modification. As shown in FIG. 3, the connection part 28e may be formed integrally with the movable part 24e. Alternatively, although not shown, the connecting portion may be formed integrally with the mirror. The electrode 25e on the movable part 24e side and the electrode on the mirror 12 side may not be parallel to each other.

  <Second Type> FIG. 4 is an explanatory diagram showing a basic configuration of a second type electrostatic drive variable mirror 10b. As shown in FIG. 4, in the second type electrostatic drive variable mirror 10b, the connecting portion 28b is fixed to both the mirror 12 and the movable portion 24, and the mirror 12 and the movable portion 24 move together. Therefore, it is not necessary to press the movable part 24 against the mirror 12 side.

  The movable part 24 is movable in the mirror contacting / separating direction (for example, the normal direction of the back surface 12b of the mirror 12 before deformation) by the fixed part 22, and is perpendicular to the mirror contacting / separating direction (for example, before deformation). Of the mirror 12 in a direction parallel to the back surface 12b of the mirror 12). The movable part 24 and the fixed part 22 may be in contact with each other so as to be relatively movable in the mirror contacting / separating direction, or provided with a gap that restricts the movement of the movable part 24 in the direction perpendicular to the mirror contacting / separating direction. , May be separated from each other.

  Since the distance between the mirror 12 and the movable portion 24 is maintained at the connection portion 28b, when a voltage is applied to the electrode 25 of the movable portion 24, the mirror 12 is inclined with respect to the movable portion 24 by electrostatic force, and the mirror 12 is deformed. The movable unit 24 moves in the mirror contacting / separating direction as indicated by the arrow 24x according to the deformation of the mirror 12. The connecting portion 28b may be expanded and contracted or bent by elastic deformation.

  <Third Type> FIG. 5 is an explanatory diagram showing a basic configuration of a third type electrostatic drive variable mirror 10c. As shown in FIG. 5, in the third type electrostatic drive variable mirror 10c, the connecting portion 28c is fixed to both the mirror 12 and the movable portion 24, and the mirror 12 and the movable portion 24 move together. The movable part 24 and the fixed part 22 are connected via a support part 26. The support part 26 allows the movement of the movable part 24 in the mirror contact / separation direction indicated by the arrow 24x when the mirror 12 is deformed. That is, since the distance between the mirror 12 and the movable portion 24 is maintained at the connection portion 28c, when a voltage is applied to the electrode 25 of the movable portion 24, the mirror 12 is inclined with respect to the movable portion 24 by electrostatic force, and the mirror 12 is The movable part 24 is deformed and moves in the mirror contacting / separating direction as indicated by the arrow 24x in accordance with the deformation of the mirror 12. The connecting portion 28c may be expanded and contracted or bent by elastic deformation.

  FIGS. 6A to 6C are explanatory diagrams when the third type electrostatic drive variable mirror 10c is arrayed. As shown in FIG. 6A, a third type basic configuration 10k in which the mirror 12 and the movable portion 24 are fixed is arranged at both ends of the connection portion 28c, and the mirror 12 and the fixed portion 22 are integrated. As shown in FIGS. 6B and 6C, when a voltage is applied only to one of the electrodes 25a and 25b, the mirror 12 tilts and at the same time, boundary conditions around the entire integrated mirror 12a As a result, a force to move the entire mirror 12a up and down acts. As a result, the entire mirror 12a moves up and down.

  The first and second types of electrostatic drive variable mirrors 10a and 10b can be similarly arrayed. Further, the basic configurations of the first to third types of electrostatic drive variable mirrors 10a, 10b, and 10c may be appropriately combined to form an array. Further, the second and third types of electrostatic drive variable mirrors 10b and 10c can be configured in the same manner as the first and second types of electrostatic drive variable mirror 10a.

  <Example 1> The electrostatic drive variable mirror 10 of Example 1 will be described with reference to FIGS. The electrostatic drive variable mirror 10 according to the first embodiment is an array of third type electrostatic drive variable mirrors.

  FIG. 7 is a plan view of the electrostatic drive variable mirror 10. FIG. 8 is an enlarged plan view of a main part of the lower substrate 20. FIG. 12A is an exploded cross-sectional view of the electrostatic drive variable mirror 10. FIG. 12B is an assembled cross-sectional view of the electrostatic drive variable mirror 10.

  As shown in FIGS. 7 and 12, in the electrostatic drive variable mirror 10, the lower substrate 20 on which the movable portion 24 is formed and the upper substrate 30 having the reflecting surface 34s are connected.

  The upper substrate 30 has a recess 32 formed on the opposite side of the lower substrate 20, a reflection film 34 is formed on the bottom surface of the recess 32, and the surface 34s of the reflection film 34 becomes the reflection surface 34s. Of the upper substrate 30, the portion between the back surface 30 x of the upper substrate 30 on the lower substrate 20 side and the reflecting surface 34 s becomes the mirror 12, and the frame portion 36 around the mirror 12 restrains the outer periphery of the mirror 12.

  As shown in FIGS. 8 and 12, the movable portion 24 is supported in the opening 23 formed in the lower substrate 20 via the first and second beam portions 26 a and 26 b, and A gap is formed between the peripheral surface 23 s and the outer peripheral surface 24 s of the movable portion 24. Of the lower substrate 20, a portion excluding the movable portion 24 and the first and second beam portions 26 a and 26 b becomes the fixed portion 22.

  The movable part 24 has a columnar shape. On the main surface 24a of the movable portion 24 on the upper substrate 30 side, the connecting portion 28 is formed in the center, and around the connecting portion 28, four electrodes 25 that are hatched in FIG.

  The first and second beam portions 26a and 26b are formed in pairs on the upper substrate 30 side of the lower substrate 20 and the opposite side thereof. The first and second beam portions 26a and 26b are relatively long first straight portions 26p extending along the sides of the main surface opposite to the main surface 24a on the upper substrate 30 side of the movable portion 24. The first straight line portion 26p is connected to the fixed portion 22 of the lower substrate 20, and the second straight line portion 26q is connected to the fixed portion 22 of the lower substrate 20. Is connected to the movable portion 24.

  The movable portion 24 is connected to the back surface 30x of the mirror 12 via the connection portion 28, and is in a direction in which the movable portion 24 is in contact with or separated from the mirror 12 by the four pairs of first and second beam portions 26a and 26b (hereinafter referred to as “mirror”). It is supported so as to be movable in the mirror contact / separation direction while suppressing the inclination with respect to the “contact / separation direction”).

  A wiring pattern 27 hatched in FIG. 8 is formed on the fixed portion 22 and the first beam portion 26a. The wiring pattern 27 is connected to the electrode 25, and a voltage can be applied to the electrode 25 through the wiring pattern 27 from the outside.

  Next, the operation of the electrostatic drive variable mirror 10 will be described. When a voltage is applied to the electrode 25 of the movable portion 24, an electrostatic force is generated due to a potential difference between the mirror 12 and the electrode 25 of the upper substrate 30, the mirror 12 is tilted, and the mirror 12 is deformed. The movable portion 24 connected to the mirror 12 moves in the mirror contacting / separating direction as the mirror 12 is deformed.

  When the electrode is fixed and the electrode does not move, the amount of deformation of the mirror is limited by the distance between the electrode and the mirror. On the other hand, since the movable part 24 having the electrode 25 is connected to the mirror 12 in the electrostatic drive variable mirror 10, the distance between the electrode 25 and the mirror 12 is kept within a predetermined range. Therefore, the mirror 12 can be configured to be deformed even when the voltage applied to the electrode 25 is lowered. Since the movable part 24 moves when the mirror 12 is deformed, the amount of deformation of the mirror 12 can be increased without being restricted by the distance between the mirror 12 and the electrode 25. Therefore, the deformation amount of the reflecting surface 34s can be increased even with a low driving voltage.

  Next, an example of the manufacturing process of the electrostatic drive variable mirror 10 will be described with reference to FIGS. The electrostatic drive variable mirror 10 is connected after the upper substrate 30 and the lower substrate 20 are formed.

  FIG. 9 is a cross-sectional view showing the manufacturing process of the upper substrate 30.

First, as shown in FIG. 9A, an SOI wafer 31 in which a SiO ₂ BOX layer 31b is sandwiched between an active layer 31a and a handle layer 31c is prepared, and a photo layer is formed on the handle layer 31c side of the SOI wafer 31. Resist is applied, exposed and developed to form a mask pattern 38 corresponding to the frame portion 36.

  Next, as shown in FIG. 9B, the handle layer 31c is removed through the mask pattern 38 by DRIE (Deep Reactive Ion Etching) to form the recess 32, and the BOX layer 31b is exposed. Let

  Next, as shown in FIG. 9C, the exposed portion of the BOX layer 31 b and the mask pattern 38 are removed, and the active layer 31 a is exposed in the recess 32.

  Next, as shown in FIG. 9D, a reflective film 34 is formed from the handle layer 31c side by metal deposition or the like. At this time, the metal film 35 is also formed on the frame portion 36. It is also possible to use the surface of the active layer 31a exposed in the recess 32 as a reflecting surface without forming the reflecting film 34.

  For example, an Al reflective film 34 having a thickness of 0.2 μm is formed using an SOI wafer 31 having an active layer 31a having a thickness of 2 to 5 μm, a BOX layer 31b having a thickness of 2 μm, and a handle layer having a thickness of 400 μm.

  10 and 11 are cross-sectional views showing the manufacturing process of the lower substrate 20.

  First, as shown in FIG. 10A, low stress SiN films 21a and 21b having a thickness of 0.3 μm are formed on both surfaces of a silicon wafer 21 by using LPCVD (low pressure chemical vapor deposition). To do.

Next, a photo resist is applied, exposed, and developed on the back side SiN film 21b to form a mask pattern corresponding to the second beam portion 26b, the fixed portion 22 and the movable portion 24, and CF ₄ gas is used. As shown in FIG. 10B, the second beam portion 26b is formed by removing the SiN film 21b through the mask pattern by RIE (Reactive Ion Etching) processing to be used.

  Next, as shown in FIG. 10C, a trench 21x having a depth about half the thickness of the silicon wafer 21 is formed along the second beam portion 26b by DRIE processing.

  Next, the SiN film 21a on the front surface side is processed in the same manner as the second beam portion 26b on the back surface side, and the first beam portion 21a is formed as shown in FIG.

  Next, an Al film having a thickness of 0.2 μm is formed by vapor deposition through a metal mask and the like, and an electrode 25 and a wiring pattern 27 are formed on the SiN film 21a as shown in FIG.

  Next, as shown in FIG. 11 (f), connecting parts 28 and 29 having a thickness of 5 μm are formed by applying, exposing, and developing SU-8, which is an epoxy-based negative photoresist.

  Next, as shown in FIG. 11G, trenches 21y having a depth about half the thickness of the silicon wafer 21 are formed by DRIE processing, as shown in FIG.

Next, isotropic dry etching using XeF ₂ gas is used to remove the space between the first and second beam portions 26a and 26b and between the upper and lower trenches 21x and 21y, as shown in FIG. 11 (h). Then, the first and second beam portions 26a and 26b are released. For example, using a silicon wafer 21 having a thickness of 525 μm, trenches 21x and 21y each having a depth of about 200 μm are formed from both sides, and about 100 μm remaining between the trenches 21x and 21y is etched by about 50 μm from both sides.

  As shown in FIG. 12A, the upper substrate 30 and the lower substrate 20 thus produced are shown in FIG. 12B with the back surface 30x of the upper substrate 30 and the connecting portions 28 and 29 of the lower substrate 20 facing each other. As described above, the mirror 12 and the movable portion 24 are connected via the connection portion 28, and the frame portion 36 and the fixed portion 22 are connected via the connection portion 29. For example, a recess 32 having an inner diameter of 8 mm is formed on the lower substrate 20 having a size of 16 mm × 16 mm, and the upper substrate 30 having a width of the frame portion 36 of 2 mm is connected.

  The electrostatic drive variable mirror 10 having the MEMS structure can be easily manufactured by the above steps. By forming the connection portion 28 using SU-8, a configuration in which the mirror and the movable portion 24 are connected can be easily manufactured. Further, due to the elastic deformation of the connecting portion 28, the deformation of the reflecting surface 34s becomes smooth.

  Next, the simulation of Example 1 will be described with reference to FIGS.

  13 and 14 are image diagrams of a simulation model. As shown in FIG. 13, the first model using 14 actuators 14a, 14b, and 14c and the second model using 7 actuators 14a, 14b, and 14c as shown in FIG. A 12x deformation was simulated. The outer periphery of the mirror 12x is constrained. Except that the mirror 12x is rectangular, the configuration is the same as in the first embodiment.

  FIG. 15 is an image diagram of one actuator 14. As shown in FIG. 15, in the actuator 14, as in the first embodiment, the columnar movable portion 24 has four L-shaped first and second beam portions 26a and 26b each having a width of 10 μm and a length of 340 μm. And is supported by a fixing portion (not shown). The main surface 24a of the movable part facing the mirror is a square of 320 μm × 320 μm, and four electrodes 25x approximated by a rectangle of 100 μm × 120 μm are arranged on the main surface 24a. In addition, although it was set as the rectangular electrode on the specification of simulation software, it calculated as the four electrodes 25x being electrically independent and generating an electrostatic force separately. The height of the connecting portion 28, that is, the initial interval between the mirror 12x and the movable portion 24 (electrode 25x) at the connecting portion 28 was 5 μm.

  16 to 18 show simulation results in the case where a voltage is applied only to the outer electrodes of the actuators 14a, 14b arranged on the outer side among the actuators 14a, 14b, 14c shown in FIGS. That is, in FIGS. 13 and 14, the actuator 14a applies a voltage to only one electrode farthest from the mirror center among the four electrodes 25x (see FIG. 15), and the actuator 14b includes the four electrodes 25x. A voltage is applied only to the two adjacent electrodes on the outer side far from the mirror center, and no voltage is applied to all the electrodes in the inner actuator 14c near the center.

  FIG. 16 is an image diagram showing a simulation result for the first model in the case of 14 actuators. FIG. 17 is an image diagram showing a simulation result for the second model when there are seven actuators. 16 and 17, it can be seen that the mirror 12x is deformed into a convex shape substantially concentrically.

  FIG. 18 is a graph showing simulation results. In FIG. 18, the horizontal axis represents the voltage applied to the electrode, the vertical axis represents the displacement at the center of the mirror 12x, and the direction of the displacement is perpendicular to the mirror surface (XY direction) before deformation (in the XY direction). Z direction). In FIG. 18, the symbol ■ indicates the first model with 14 actuators, and the symbol ♦ indicates the second model with 7 actuators. From FIG. 18, the amount of deformation of the mirror increases according to the magnitude of the voltage applied to the electrode, the voltage applied to the electrode is about 16 to 20 V, and the maximum displacement of the mirror 12 x is the same as that of the mirror 12 x at the connection portion 28. It can be seen that the initial distance of the movable portion 24 (electrode 25x) exceeds 5 μm.

  <Summary> As described above, the electrostatic drive variable mirror of the present invention in which the movable part is held so as to be movable in the direction of contact with and away from the mirror, the electrode is provided on the movable part, and the mirror is tilted by electrostatic force. The amount of deformation of the reflecting surface can be increased even with a low driving voltage.

  The present invention is not limited to the above embodiment, and can be implemented with various modifications.

  For example, an electrode may be formed inside the movable part. In addition, a mirror side electrode that faces the electrode of the movable part and generates a potential difference between the electrode of the movable part may be formed on the inside or the back surface of the mirror.

  Further, the present invention is not limited to control of the phase of light, but can also be used for control of light intensity and light direction.

10, 10a to 10e Electrostatic drive variable mirror 12, 12x mirror 12a Reflective surface 12b Back surface 20 Lower substrate 22 Fixed portion 24, 24e Movable portion 25, 25a, 25b, 25e, 25s, 25t, 25x Electrode 26 Support portion 26a, 26b Beam part (support part)
28, 28a-28e, 29 connection part 30 upper substrate 30x back surface 34s reflective surface

Claims (5)

A mirror having a reflective surface and a back surface opposite to the reflective surface;
A movable portion having an electrode facing the back surface with an interval between the mirror and the back surface, and facing the back surface;
A fixed portion that holds the movable portion so as to be movable in a direction in which the movable portion is in contact with or separated from the mirror;
A connecting portion disposed between the mirror and the movable portion, fixed to at least one of the mirror and the movable portion, and maintaining a distance between the mirror and the movable portion;
Equipped with a,
An electrostatic force is generated by a potential difference between the electrode and the mirror, the mirror is tilted with respect to the movable part by the electrostatic force, and the movable part is moved in accordance with the tilt of the mirror. An electrostatically driven variable mirror characterized by The fixed part is provided with a space between the movable part and accommodates the movable part,
The toward and away from the forward direction SL movable portion relative to the mirror that is disposed with a distance from one another, further comprising a first and a second beam portion connected to the movable portion and the fixed portion The electrostatic drive variable mirror according to claim 1 , wherein: Said connection unit, characterized in that it is fixed to both the mirror and the movable portion, the electrostatic driving variable mirror according to claim 1 or 2. The connection part is fixed to only one of the mirror and the movable part,
A support unit that connects the movable unit and the fixed unit, biases the movable unit toward the mirror, and maintains contact between the other of the mirror and the movable unit and the connection unit; wherein the electrostatic driving variable mirror according to claim 1 or 2. One of the mirrors;
A plurality of the movable parts ;
A plurality of the connecting portions;
The electrostatic drive variable mirror according to claim 1, further comprising: