JP2006003814A - Variable shape mirror element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shape variable mirror element which can change the shape of a mirror surface with high precision and in a variety of shapes. <P>SOLUTION: A shape variable mirror element 1 consists of a substrate 2, a shape variable part 3 which is integrally connected to the substrate 2, a lower electrode 4 for impressing a voltage on the shape variable part 3 and upper electrodes 5-1 and 5-2. By impressing a homopolar voltage, which is identical or is different, to each electrode, the shape variable part 3 can be controlled in the targeted variable shape. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a deformable mirror element that changes its shape by using a piezoelectric force or an electrostatic force as a driving force.

  As the deformable mirror element, there is an element in which a lead wire is soldered to a reflection mirror surface and an electrode on an upper surface of a ceramic piezoelectric material (see, for example, Patent Document 1). However, since the deformable mirror element uses a bulk material as the piezoelectric material, the thickness of the piezoelectric material is very large. As a result, it is easily guessed that a very high applied voltage is required to greatly change the shape.

  An example of a micro-variable shape variable mirror element is an element in which a piezoelectric film is attached to a reflection mirror plate (see, for example, Patent Document 2). As the reflection mirror plate, for example, a glass reflection mirror, a reflection mirror film, a silicon wafer or the like is used. In the case of this element as well, it is easily guessed that a very high applied voltage is required. That is, an element having a structure in which the piezoelectric film and the reflection mirror plate are simply bonded has a low adhesive strength, and cannot be self-supported by itself and is not suitable for practical use.

As a variable shape mirror element capable of a large change in shape with a low applied voltage, an element having a thin film diaphragm in the opening of a hollow portion of a substrate has been proposed. In the case of this variable shape mirror element using a thin film diaphragm, since the film thickness of the element can be 10 μm or less, a large shape change is possible at a low voltage.
Japanese Patent Laid-Open No. 10-10459 JP 2001-34993 A

  The variable shape mirror element having a thin film diaphragm in the opening of the hollow portion of the substrate has a single electrode on each of the upper and lower sides of the piezoelectric film, and a voltage is applied to the upper and lower electrodes, thereby applying a piezoelectric force to the piezoelectric film. By generating this, the shape of the mirror surface can be varied.

  Thus, in the case of a variable shape mirror element having a single electrode on each of the upper and lower sides, it can be changed to a shape determined by material properties such as film thickness and diaphragm diameter, shape dimensions, and piezoelectric power.

  However, although it is possible to predict and design material properties and dimensions that conform to the target variable shape in advance, the physical properties and dimensions cause manufacturing errors, so the variable shape mirror element can be deformed with extremely high accuracy. It is difficult to stably manufacture

  The present invention solves the above-described conventional problems, and an object thereof is to provide a deformable mirror element that can control the shape of a mirror surface to various shapes with extremely high accuracy.

  In order to solve the above problems, the deformable mirror element of the present invention has electrodes divided into a plurality of at least one surface of electrodes above and below the piezoelectric film, and each electrode has the same or different voltage with the same polarity. The main feature is that the deformable shape is controlled by application.

Further, the deformable mirror element of the present invention includes a piezoelectric power as a driving force for changing the shape and an electrostatic force means for applying an attractive force or a repulsive force to the shape variable portion, and uses the piezoelectric power and the electrostatic force to change the target. The main feature is that the voltage is controlled according to the shape.

  According to the variable shape mirror element of the present invention, the deformation of the piezoelectric film can be individually controlled by each electrode by applying the same or different voltage with the same polarity to each of the divided electrodes. It is possible to provide an excellent effect of providing a variable shape mirror element that can be varied to various shapes with high accuracy.

  Further, according to the deformable mirror element of the present invention, by operating the deformable mirror element with piezoelectric power and electrostatic force, the variable amount of the shape is larger than that of the piezoelectric power alone, and it is variable with high accuracy and various shapes. Therefore, it is possible to provide an excellent effect that a variable shape mirror element having excellent shape variable performance can be provided.

  A first invention made to solve the above-described problem is a shape comprising at least a piezoelectric film, electrode films disposed above and below the piezoelectric film, and a reflective mirror film disposed on any one of the electrode films. A variable shape mirror element comprising a variable portion and a substrate that supports the variable shape portion, wherein the electrode film on at least one surface is divided into a plurality of electrodes and is a variable shape mirror element. Since the shape of the mirror surface can be individually changed according to the electrode pattern divided into two, it is possible to correct the wavefront aberration such as spherical aberration and defocus of the circumferentially incident light. Furthermore, according to the deformable mirror element of the present invention, even if there is a manufacturing error such as the film thickness, stress, Young's modulus, etc. of the diaphragm constituted by the thin film, the manufacturing error is corrected by a plurality of electrodes to control the variable shape. Therefore, it is possible to obtain an excellent effect that a deformable mirror element having excellent quality can be stably manufactured.

  The second invention made in order to solve the above-mentioned problem is a shape comprising at least a piezoelectric film, electrode films disposed above and below the piezoelectric film, and a reflective mirror film disposed on any one of the electrode films. A variable shape mirror element comprising a variable portion and a substrate that supports the variable shape portion, wherein the variable shape mirror element is provided with an electrostatic electrode plate that applies attractive force or repulsive force to the variable shape portion. Since the electrostatic force is added to the electric power, deformation exceeding the piezoelectric power is possible, and a deformable mirror element having a large shape variable amount can be realized. Further, similarly to the first invention, since a plurality of electrodes of the piezoelectric film can be arranged, it can be changed to various shapes with extremely high accuracy. If the electrode of the electrostatic force means is divided into a plurality of parts, it can be changed into various shapes with higher accuracy.

  Hereinafter, embodiments of the variable shape mirror element of the present invention will be described with reference to the drawings. For the purpose of facilitating understanding, the film thickness, the substrate thickness, the shape variable amount, etc. in the drawings are different from the actual dimensions. Hereinafter, the same applies to all drawings.

(Embodiment 1)
FIG. 1 is a perspective view seen from the surface of a deformable mirror element according to Embodiment 1 of the present invention. The deformable mirror element 1 includes a substrate 2 that supports the deformable mirror element 1, a shape variable portion 3 that is integrally connected to the substrate 2, a lower electrode 4 and an upper electrode 5 that are used to apply a voltage to the shape variable portion 3. Consists of. In the deformable mirror element 1 according to the embodiment of the present invention, the upper electrode 5 is disposed on the inner and outer circumferences of the deformable portion, and includes an upper electrode 5-1 and an upper electrode 5-2. Although not shown, a reflection mirror film is provided on the uppermost part or the lowermost part of the shape variable part 3.

  FIG. 2 is a perspective view seen from the back surface of the deformable mirror element 1 according to the first embodiment of the present invention. The substrate 2 portion under the shape variable portion 3 is removed, and the shape variable portion 3 has a diaphragm structure.

  FIG. 3 is a cross-sectional view of a main part of the deformable mirror element 1 according to the first embodiment of the present invention. The laminated structure of the thin film on the upper surface of the substrate 2 has a structure in which a lower electrode 4, a piezoelectric film 6, and upper electrodes 5-1, 5-2 are arranged from the bottom. Although not shown, a reflection mirror film is provided on the uppermost part or the lowermost part of the shape variable part 3. Although an elastic plate film that determines the deformation direction of the deformable mirror element 1 is added as necessary, in the variable shape mirror element 1 according to the embodiment of the present invention, the reflection mirror film has a function of an elastic plate film. Therefore, the same member has the same configuration.

  Next, the manufacturing method of the variable shape mirror element of embodiment of this invention is demonstrated with reference to FIGS. 4 to 7 are cross-sectional views of the main part of the deformable mirror element 1 showing the manufacturing process of the deformable mirror element 1. FIG.

  As the material of the substrate 2, a single crystal material such as Si or MgO is preferably used because the piezoelectric properties of the piezoelectric film 6 are likely to be good, but is not particularly limited. However, when a process for high-temperature treatment is required in the process of manufacturing the deformable mirror element 1, a substrate material having good heat resistance may be selected. Moreover, since the substrate is removed by etching for forming the diaphragm, a relatively thin substrate is preferably used. In the embodiment of the present invention, a single crystal Si substrate having a substrate thickness of 300 μm was used.

  First, as shown in FIG. 4, the lower electrode 4 is formed on the substrate 2. As a material for the lower electrode 4, a metal having high conductivity is preferably used. In the case of using a process of performing high temperature processing in the process of manufacturing the deformable mirror element 1, a material resistant to high temperatures such as Pt, Ir, or an alloy thereof is desirable.

  Next, as shown in FIG. 5, a piezoelectric film 6 is formed on the lower electrode 4. As the material of the piezoelectric film 6, a material having a high piezoelectric constant and large deformation such as PZT (lead zirconium titanate) or a perovskite oxide containing Pb similar to PZT is preferably used. In addition, there are many methods for forming the electrode film and the piezoelectric film 6 such as sputtering, CVD (Chemical Vapor Deposition), or sol-gel, but there is no particular limitation as long as it is a technique capable of forming a film. In the embodiment of the present invention, an Ir—Ti alloy is used as the material of the lower electrode 4 and the film thickness is set to 0.1 μm. The material of the piezoelectric film 6 is PZT, and the film thickness is 3 μm. Ir—Ti alloy and PZT were both formed by sputtering, and the substrate temperature during Ir—Ti formation was 400 ° C., and the substrate temperature during PZT formation was 600 ° C.

  Next, as shown in FIG. 6, the upper electrode 5 is formed on the piezoelectric film 6. The material and forming method of the upper electrode 5 are the same as those of the lower electrode 4. In the embodiment of the present invention, Ti is used as the material and the film thickness is 0.1 μm. Ti was formed by sputtering, and the substrate temperature during Ti formation was normal temperature. Further, the upper electrode 5 is illustrated as being divided into two upper electrodes 5-1 and 5-2.

Next, although not shown, a reflection mirror film is formed on the upper electrode 5. Since the reflecting mirror film of the embodiment of the present invention has the function of an elastic plate film, the film thickness considers both characteristics of the reflecting mirror film and the elastic plate film, and the material is made of SiO ₂ and Ta ₂ O ₅ . The film thickness was 0.8 μm. The configuration of the reflecting mirror film is a laminated thin film having a thickness of retardation thickness λ / 4. The material of the reflection mirror film varies depending on the wavelength used for the mirror, but for example, a metal such as Au or Ag, or a low refractive index dielectric such as SiO ₂ / Ta ₂ O ₅ / a high refractive index dielectric λ / 4. A multilayer film is preferably used. As with the method for forming the piezoelectric film 6, there are many methods for forming the reflection mirror film, for example, a sputtering method or a vapor deposition method, but there is no particular limitation as long as it is a technique capable of forming a film. In the embodiment of the present invention, the reflection mirror film is provided with an elastic plate film function. However, as a material of the original elastic plate film, a material such as resin, metal, or ceramic can be used. The method of forming the elastic plate film is also the piezoelectric film 6
There are many methods such as a spin coating method, a sputtering method, and a vapor deposition method, as in the above-described forming method, but there is no particular limitation as long as it is a technology capable of forming a film.

  Finally, as shown in FIG. 7, the substrate 2 is removed by etching in order to make the shape variable portion 3 a diaphragm. There are many etching removal methods for the substrate 2, such as a wet etching method, a dry etching method, and machining, but there is no particular limitation as long as it is a technique capable of forming a diaphragm. In the embodiment of the present invention, the reactive ion etching technique is used from the back surface of the substrate 2. The diameter of the diaphragm was 1.5 mm. In the embodiment of the present invention, the formation of the diaphragm is the final process. However, when the reflection mirror film is formed under the lower electrode 4, the order of the reflection mirror film formation process and the diaphragm formation process is reversed. do it.

  The operation of the deformable mirror element manufactured as described above will be described with reference to the drawings. 8 to 11 are side sectional views showing the operation of the deformable mirror element 1 according to the embodiment of the present invention. FIG. 8 shows a non-operating state in which no voltage is applied. When the lower electrode 4 of the deformable mirror element 1 is set to a constant voltage (for example, 0V) and the same voltage (for example, 5V) is applied to the upper electrodes 5-1, 5-2, the cross-sectional shape shown in FIG. 9 is obtained. Next, when the voltage applied to the lower electrode 4 and the upper electrode 5-2 is the same voltage, and a high voltage (for example, 10 V) is applied only to the upper electrode 5-1, as shown in FIG. Further, the central portion is further bent, and the outer peripheral portion is slightly bent due to the influence of the central portion.

  In addition, when the voltage applied to the lower electrode 4 and the upper electrode 5-1 is the same voltage, and a high voltage (for example, 10 V) is applied only to the upper electrode 5-2, as shown in FIG. The outer peripheral portion is further bent, and the central portion is slightly bent due to the influence of the outer peripheral portion.

  When the curvature of the central part of the shape variable portion is compared for the above two voltage application methods, that is, when FIG. 10 and FIG. 11 are compared, the curvature of FIG. 10 is small, and the curvature of FIG. Becomes smaller. That is, when a voltage is applied to the central portion of the shape variable portion 3, the curvature changes greatly, and when a voltage is applied to the outer peripheral portion of the shape variable portion 3, the curvature changes slightly.

  Therefore, by applying the same voltage or different voltages to the upper electrodes 5-1 and 5-2, the curvature of the deformable shape 3 can be controlled with high resolution.

(Embodiment 2)
FIG. 12 is a perspective view of a deformable mirror element according to Embodiment 2 of the present invention. In the first embodiment, an example of the deformable mirror element in which the upper electrode is divided into two parts is shown. However, in the second embodiment, as shown in FIG. 12, the upper electrode of the deformable mirror element is concentrically formed. It is divided into multiple parts. In the second embodiment, by dividing the upper electrode into three or more in the radial direction, a voltage can be individually applied to each electrode, so that the degree of freedom of shape change is increased. Therefore, the variable shape can be controlled to a spherical shape. Furthermore, since it is possible to control an aspherical shape such as a paraboloid or a hyperboloid, it is also possible to correct spherical aberration as wavefront aberration. It can also be used as a reflective lens.

(Embodiment 3)
13 and 14 are perspective views showing a deformable mirror element according to Embodiment 3 of the present invention. In the example of FIG. 13, the upper electrode 5 is divided into four equal parts in the circumferential direction, and in the example of FIG. 14, the upper electrode 5 is divided into eight equal parts in the circumferential direction. In the variable shape mirror element according to the embodiment of the present invention, it is possible to control the variable shape in the angular direction from the center by the voltage applied to the electrode. For example, coma and astigmatism can be corrected as wavefront aberration, for example. It becomes possible.

(Embodiment 4)
15 and 16 are perspective views showing a deformable mirror element according to Embodiment 4 of the present invention. 15 and 16 show a case where the upper electrode 5 is divided into a plurality of radial directions and circumferential directions. In the example of FIG. 15, the dividing line in the circumferential direction of each electrode divided in the radial direction is shown. In the example of FIG. 16, the dividing lines in the circumferential direction are staggered. In the deformable mirror element according to the embodiment of the present invention, the variable shape in the radial direction and the circumferential direction can be controlled by the voltage applied to the electrode. It is also possible to correct.

  As described above, according to the variable shape mirror elements of the first to fourth embodiments, the upper electrode is divided into a plurality of electrodes, and the same or different voltage with the same polarity is applied to each electrode, so that the mirror surface It is possible to realize a variable shape mirror element whose shape can be varied with high accuracy.

(Embodiment 5)
Embodiment 5 of the deformable mirror element of the present invention will be described with reference to the drawings. FIG. 17 is a perspective view seen from the surface of the deformable mirror element according to the fifth embodiment of the present invention. FIG. 18 is an exploded view of the deformable mirror element according to the fifth embodiment of the present invention. The configuration of the deformable mirror element 1 according to the embodiment of the present invention is that an electrostatic electrode plate 7 for generating an electrostatic force is added to the deformable mirror element of the first embodiment. The electrostatic electrode plate 7 is firmly fixed to the substrate 2 with an adhesive or the like. FIG. 19 is a perspective view seen from the back surface of the electrostatic electrode plate 7. An electrostatic electrode 8 is formed on the electrostatic electrode plate 7, and is insulated from the electrostatic electrode 8 and the upper electrode 5 that applies a voltage to the piezoelectric film by an insulating plate 9. The insulating plate 9 maintains the distance between the electrostatic electrode 8 and the upper electrode 5 at a constant interval.

  The operation of the deformable mirror element configured as described above will be described with reference to the drawings. 20 to 24 are side sectional views showing the operation of the deformable mirror element 1. FIG. 20 shows a non-operating state in which no voltage is applied.

  When the voltage is not applied to the electrostatic electrode 8 and the potential is floating, the lower electrode 4 is set to a constant voltage (for example, 0V), and the same voltage (for example, 5V) is applied to the upper electrodes 5-1, 5-2. The cross-sectional shape shown in FIG.

  Next, when a voltage (for example, 5 V) is applied to the electrostatic electrode 8 and the lower electrode 4 and the upper electrodes 5-1 and 5-2 are set to the same voltage, the electrostatic electrode 8 is placed between the electrostatic electrode 8 and the upper electrode 5-2. Generates repulsive force as an electrostatic force. Since the electrostatic electrode 8 is fixed to the substrate 2, the shape variable portion 3 formed of a diaphragm is deformed by repulsive force as shown in FIG. Furthermore, if the voltage (for example, 10V) applied to the electrostatic electrode 8 is increased, a stronger repulsive force is generated, and the shape variable portion 3 is greatly deformed as shown in FIG.

  On the other hand, when the voltage applied to the electrostatic electrode 8 has a reverse polarity (for example, −10 V) and the upper electrodes 5-1 and 5-2 have the same voltage, the electrostatic electrode 8 and the upper electrode 5-2 have an attractive force. 24. As shown in FIG. 24, the deformation direction of the shape variable portion 3 may be reversed to have a convex shape. Therefore, if the sign of the voltage between the upper electrode 5 and the electrostatic electrode 8 is changed, the shape variable portion 3 can be deformed into a convex surface and a concave surface.

(Embodiment 6)
25 and 26 are perspective views seen from the back surface of the electrostatic electrode of the deformable mirror element according to Embodiment 6 of the present invention. The example of FIG. 25 shows an example in which the electrostatic electrode 8 is divided into four in the circumferential direction, and the example of FIG. 26 shows an example in which the electrostatic electrode 8 is divided into eight in the circumferential direction. In the sixth embodiment, since voltages can be individually applied to a plurality of electrostatic electrodes, the degree of freedom of shape variation is further increased as compared with the example of the fifth embodiment in which the electrostatic electrode 8 is not divided. Therefore, the variable shape can be controlled to a spherical shape. Further, since it is possible to control an aspherical shape such as a paraboloid or a hyperboloid shape, for example, spherical aberration, coma aberration, and astigmatism can be corrected as wavefront aberration. Further, it can be used as a reflection lens.

(Embodiment 7)
FIG. 27 is a cross-sectional view of the main part of the variable shape mirror element according to Embodiment 7 of the present invention. In this embodiment, the electrode shape of the electrostatic electrode 8 is a curved surface. Since the electrostatic force is determined by the voltage between the electrodes and the distance, if the target variable shape is determined in advance, the target variable can be achieved by partially changing the distance between the electrodes by making the electrode shape of the electrostatic electrode 8 a curved surface. Can be transformed into a shape. When a highly accurate variable shape is required, fine adjustment can be performed with piezoelectric power.

  As described above, according to Embodiments 5 to 7, it is possible to realize a variable shape mirror element that can change the shape of the mirror surface with high accuracy and variously by the configuration to which an electrostatic force is added.

  According to the variable shape mirror element of the present invention, the shape of the mirror surface can be varied with high accuracy according to the divided electrode pattern, and therefore, it can be applied to a reflection lens or a wavefront correction of light. For example, the present invention can be applied to applications such as a video projector, a digital camera, and an optical pickup component of an optical disk device that include an optical system including a variable optical element.

The perspective view seen from the surface of the form variable mirror element concerning Embodiment 1 of this invention The perspective view seen from the back surface of the variable shape mirror element concerning Embodiment 1 of this invention Sectional drawing of the principal part of the variable shape mirror element concerning Embodiment 1 of this invention Sectional drawing of the principal part of a deformable mirror element which shows the manufacturing process of the deformable mirror element which concerns on Embodiment 1 of this invention. Sectional drawing of the principal part of a deformable mirror element which shows the manufacturing process of the deformable mirror element which concerns on Embodiment 1 of this invention. Sectional drawing of the principal part of a deformable mirror element which shows the manufacturing process of the deformable mirror element which concerns on Embodiment 1 of this invention. Sectional drawing of the principal part of a deformable mirror element which shows the manufacturing process of the deformable mirror element which concerns on Embodiment 1 of this invention. Side sectional view showing the operation of the deformable mirror element according to the first embodiment of the present invention. Side sectional view showing the operation of the deformable mirror element according to the first embodiment of the present invention. Side sectional view showing the operation of the deformable mirror element according to the first embodiment of the present invention. Side sectional view showing the operation of the deformable mirror element according to the first embodiment of the present invention. The perspective view of a deformable mirror element when the upper electrode of the deformable mirror element according to Embodiment 2 of the present invention is divided into a plurality of concentric circles. A perspective view of a deformable mirror element according to a third embodiment of the present invention. A perspective view of a deformable mirror element according to a third embodiment of the present invention. A perspective view of a deformable mirror element according to a fourth embodiment of the present invention. A perspective view of a deformable mirror element according to a fourth embodiment of the present invention. The perspective view seen from the surface of the variable shape mirror element concerning Embodiment 5 of this invention Exploded view of the deformable mirror element according to the fifth embodiment of the present invention. The perspective view seen from the back surface of the electrostatic electrode of the deformable mirror element according to Embodiment 5 of the present invention Side sectional view showing the operation of the deformable mirror element according to the fifth embodiment of the present invention. Side sectional view showing the operation of the deformable mirror element according to the fifth embodiment of the present invention. Side sectional view showing the operation of the deformable mirror element according to the fifth embodiment of the present invention. Side sectional view showing the operation of the deformable mirror element according to the fifth embodiment of the present invention. Side sectional view showing the operation of the deformable mirror element according to the fifth embodiment of the present invention. The perspective view seen from the back surface of the electrostatic electrode of the deformable mirror element according to Embodiment 6 of the present invention The perspective view seen from the back surface of the electrostatic electrode of the deformable mirror element according to Embodiment 6 of the present invention Sectional drawing of the principal part of the deformable mirror element which concerns on Embodiment 7 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shape variable mirror element 2 Board | substrate 3 Shape variable part 4 Lower electrode 5 Upper electrode 5-1 Upper electrode 5-2 Upper electrode 6 Piezoelectric film 7 Electrostatic electrode plate 8 Electrostatic electrode 9 Insulating plate

Claims (2)

A variable shape portion including at least a piezoelectric film, electrode films disposed above and below the piezoelectric film, a reflective mirror film disposed on any one of the electrode films, and a substrate supporting the variable shape portion. A deformable mirror element comprising: a deformable mirror element, wherein an electrode film on at least one surface is divided into a plurality of electrodes. A variable shape portion including at least a piezoelectric film, electrode films disposed above and below the piezoelectric film, a reflective mirror film disposed on any one of the electrode films, and a substrate supporting the variable shape portion. A deformable mirror element, comprising: an electrostatic electrode plate that applies an attractive force or a repulsive force to the shape variable portion.

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