JPH1172605A - Mirror and lens with variable curvature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small-size inexpensive mirror with variable curvatures by using a single electrostriction crystal to constitute the mirror, shaping the faces perpendicular to the electrostriction direction of the crystal into concave or convex faces, and applying a mirror coating on the curved face. SOLUTION: This reflection mirror 1 consists of a single electrostriction element. The reflection mirror 1 has a cross section like a hand drum having parallel top and bottom lines and concave sides. Positive voltage is applied on the upper face 1a, while negative voltage is applied on the lower face 1b. Metal thin films are deposited by vapor deposition on the upper and lower faces 1a, 1b, and voltage is uniformly applied on the electrostriction element to effectively cause deformation. Either of the concave faces 1c is coated with a mirror coating 2. As for the mirror coating 2, a vapor deposition plating film of a metal is used. By adding voltage in the perpendicular direction to the electrostriction direction of the single electrostriction crystal having a drum- like cross section, the curvature of the concave face 1c changes due to the difference in the thickness in the cross section along the height direction. Thus, the curvature of the mirror face also changes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a variable curvature mirror and a lens which change the curvature of the surface by applying a voltage to an electrostrictive crystal.

[0002]

2. Description of the Related Art When a temperature environment or posture changes, the surface shape of a large-aperture reflector such as an astronomical telescope changes, and the performance as an imaging system deteriorates. It is necessary to make the mirror material thicker in order to prevent the mirror surface from deforming due to changes in posture,
This leads to an increase in weight due to an increase in cost and a negative effect on thermal deformation. For this reason, a plurality of actuators are provided on the back surface of the mirror surface, and correction control is performed according to the deformation of the mirror surface shape. As the actuator, an electromechanical method using a servomotor and a ball screw, a piezo method using an electrostrictive element, an electrostatic method, and the like are used.

FIG. 5 is a conceptual diagram of an apparatus for changing the curvature of a mirror surface using a large number of electrostrictive elements. (A) is a concave mirror,
(B) is a convex mirror. The mirror surface is made of a flexible material, a large number of electrostrictive elements are arranged on the back surface, a voltage application device and a displacement measuring device (not shown) are provided for each electrostrictive device, and a control device controls each electrostrictive device. The mirror surface is deformed accurately by feedback control of the displacement. FIG. 5 shows two dimensions,
Some devices are spread three-dimensionally. In this case, a three-dimensionally arranged electrostrictive element controls three-dimensional deformation of a mirror surface.

[0004]

As described above, the conventional mirror surface for changing the curvature and the shape requires a complicated apparatus for controlling each of the electrostrictive elements by using a large number of electrostrictive elements. They were large and expensive. Further, since a large number of electrostrictive elements are arranged on the back surface of the mirror surface, it cannot be used as a half mirror that partially transmits light through the mirror surface or as a lens.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a structure in which a single electrostrictive element constitutes a mirror surface, a translucent mirror surface, or a lens, and the curvature of the curved surface is changed by applying a voltage. It is intended to provide a variable mirror or lens.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a single electrostrictive crystal is formed with a concave or convex surface perpendicular to the direction of electrostriction of the crystal. , A mirror coating is applied to the surface.

When a voltage is applied in a direction perpendicular to the direction of electrostriction of a single electrostrictive crystal whose cross section looks like a drum or a drum, the thickness of the cross section differs in the height direction, so that a concave curved surface or The curvature of the convex surface changes. This also changes the curvature of the mirror surface.

[0008] In the invention of claim 2, the concave surface or the convex surface is a concave spherical surface or a convex spherical surface.

By making the concave or convex surface a concave spherical surface or a convex spherical surface, processing of a curved surface becomes easy and accurate.

According to a third aspect of the present invention, a metal thin film is attached to both sides of the electrostrictive crystal where voltage is applied.

By attaching a metal thin film to both surfaces facing each other to which a voltage is applied, a voltage can be uniformly applied to the electrostrictive crystal, and the curved surface can be accurately deformed.

In the invention according to claim 4, the electrostrictive crystal is transparent and the mirror coating is translucent.

A half mirror can be formed by making the electrostrictive crystal transparent and the mirror surface coating translucent.

According to a fifth aspect of the present invention, a single transparent electrostrictive crystal is formed, and a surface orthogonal to the direction of electrostriction of the crystal is formed as a concave surface or a convex surface.

Since the electrostrictive crystal is transparent and the surface orthogonal to the direction of electrostriction of the crystal is formed as a concave surface or a convex surface, it is possible to obtain a lens whose focal length can be varied by applying a voltage. .

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of the reflecting mirror 1 of the first embodiment. The reflecting mirror 1 is composed of a single electrostrictive element. The reflecting mirror 1 has a drum-shaped cross section with a parallel top and bottom and a concave curve on the left and right. A positive voltage is applied to the upper surface 1a and a negative voltage is applied to the lower surface 1b. A metal thin film is adhered to the upper and lower surfaces 1a and 1b by vapor deposition or the like, so that a voltage is uniformly applied to the electrostrictive element and the element can be effectively deformed. A mirror coating 2 is applied to one of the left and right concave curved surfaces 1c. As the mirror surface coating 2, a metal vapor deposition plating or the like is used.

FIG. 2 shows a concave surface 1 due to the piezoelectric effect of the reflecting mirror 1.
It is a figure explaining the curvature change of c. When stress is applied to the crystal of the electrostrictive element, a polarization (electric dipole in 1 m ³ ) of a magnitude proportional thereto is generated. When both ends of the crystal are electrically open, a voltage is generated therebetween, and when short-circuited, a flow of electric charge occurs during the application of stress. Conversely, when a voltage is applied between a pair of faces of the crystal, the crystal is distorted. These two effects opposite to each other are called a piezoelectric effect. A necessary condition for piezoelectricity is that the crystal structure has no center of symmetry.

As shown in FIG. 2, the thickness of the reflecting mirror 1 differs depending on the position in the height direction due to the concave curved surface 1c. As described above, since the thickness differs depending on the position in the height direction, when a voltage is applied from the upper and lower surfaces 1a and 1b, the deformation is not uniform, the curvature changes as indicated by the broken line, and the radius of curvature changes from R0 to R1. Change. Assuming that the material, shape, and size of the reflecting mirror 1 are constant, there is a fixed relationship between the change in curvature and the applied voltage. By obtaining these in advance, it is possible to obtain a desired curvature and an applied voltage that generates this. You know the value.

Next, a second embodiment will be described. This embodiment is the same as the first embodiment, except that the electrostrictive element is made of transparent quartz or the like, the mirror coating is a translucent film, and is provided on one of the left and right concave curved surfaces 1c. It is. Thereby, a half mirror can be formed. By applying a voltage, the curvature of the half mirror can be changed as in the first embodiment.

Next, a third embodiment will be described. This embodiment shows a case in which a translucent mirror coating is used as a lens in the second embodiment. By applying a voltage, the curvature of the lens can be changed as in the first embodiment. In the above embodiment, both surfaces are concave curved surfaces, but the curved surface can be deformed on only one surface,
Either surface is concave or convex.

FIG. 3 shows a modification of the first to third embodiments.
In the first to third embodiments, the left and right curved surfaces of the electrostrictive element are concave curved surfaces, but are formed as convex curved surfaces. Even if the surface is a convex curved surface, the curvature can be changed as shown by a broken line by applying a voltage from the upper and lower surfaces. Also in this case, only one side may be a convex surface.

FIG. 4 shows another modification of the first to third embodiments. In the first to third embodiments, the left and right curved surfaces of the electrostrictive element are concave curved surfaces, but these are concave spherical surfaces. By making it a concave spherical surface, processing becomes easy and processing accuracy improves. By applying a voltage, the spherical surface can be deformed. Also in this case, only one side may be spherical. Further, it may be a convex spherical surface.

[0023]

As is apparent from the above description, the present invention comprises a single electrostrictive crystal, and forms a concave or convex surface perpendicular to the direction of electrostriction of the crystal and applies a voltage. Thereby, the concave or convex curved surface can be changed. A mirror having a curved surface can be obtained by coating the concave or convex surface with a mirror surface, and a half mirror having a curved surface can be obtained by making the electrostrictive element a transparent crystal and applying a semi-transparent mirror surface coating. In addition, a lens having a curved surface can be obtained by using the electrostrictive element as a transparent crystal and using it as it is without performing mirror coating. When the curved surface is a spherical surface, it is easy to process and a highly accurate curved surface can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment.

FIG. 2 is a diagram illustrating a change in curvature.

FIG. 3 is a diagram showing a case where a curved surface is a convex surface.

FIG. 4 is a diagram showing a case where a curved surface is a spherical surface.

FIG. 5 is a diagram showing a configuration for performing conventional mirror surface deformation, and FIG.
Indicates a concave mirror, and (B) indicates a convex mirror.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflecting mirror 1a Upper surface 1b Lower surface 1c Concave curved surface 2 Mirror coating

Claims (5)

[Claims] 1. A variable curvature mirror comprising a single electrostrictive crystal, a surface orthogonal to the direction of electrostriction of the crystal is formed as a concave surface or a convex surface, and the surface is mirror-coated. . 2. The variable curvature mirror according to claim 1, wherein the concave or convex surface is a concave or convex spherical surface. 3. The variable curvature mirror according to claim 1, wherein a metal thin film is attached to both sides of the electrostrictive crystal where voltage is applied. 4. The variable curvature mirror according to claim 1, wherein said electrostrictive crystal is transparent, and said specular coating is translucent. 5. A variable curvature lens comprising a single transparent electrostrictive crystal, wherein a surface orthogonal to the direction of electrostriction of the crystal is formed as a concave surface or a convex surface.