JP5816008B2 - Bimorph optical element - Google Patents

Description

  The present invention provides a bimorph optical element controlled by an oppositely actuated piezoelectric ceramic active element.

  Patent Document 1 relates to a bimorph mirror having two ceramic layers having electrodes and separated by a central core.

  Such mirrors are constructed in the form of a laminate structure with two so-called “skin” layers, at least one of which is used as a mirror, with two ceramic layers and a central core of two skin layers. It is sandwiched between.

  It is relatively complex and difficult to implement a laminated structure.

  The concept of the laminated structure used in the bimorph mirror limits the size of the mirror to the size of the ceramic element and its multiple, and the presence of the laminated structure limits the quality of mirror polishing.

  Solutions known in the prior art have always been based on the assembly of ceramic elements on a plane parallel to the working optical surface.

  In any situation, the ceramic is bonded to a surface parallel to the optical surface, and is laminated in a direction perpendicular to the optical surface.

  This also applies to Patent Document 2, where the ceramic is bonded to a surface facing the optical surface.

  If the ceramic rod is bimorph, i.e. comprises two ceramic pieces that are bonded together, the stability of the bimetal effect limits stability as the assembly temperature changes.

  Also, if the size of the deformable mirror is larger than the size of the ceramic element (as is often the case with the size of commercially available ceramics), the manufacturer may have multiple dimensions to obtain the required size. It is necessary to connect the ends of the ceramic pieces, and in Patent Document 2, the junction point between the ceramic pieces is located on the rear surface, which is a non-optical surface of the mirror, but in order to change the curvature of the mirror, This discontinuity becomes apparent when pressure is applied.

European Patent Application EP1723461 Document EP 1835302

  The present invention adopts a structure in which the piezoelectric element is arranged in a lateral direction with respect to the optical element when the structure includes the piezoelectric element, at least partially. Thus, at least one of the above disadvantages is to be avoided.

  The present invention thus provides a bimorph optical device comprising an optical element that can be deformed and an active element made of a piezoelectric ceramic with electrodes, the elements being controlled in pairs, thereby a set of elements. A compression movement of the first element and an extension movement of the set of second elements are produced, the device comprising a first main surface in which the optical element is optically active and a second main surface facing the first main surface. With at least first and second opposing sides, and wherein the ceramic active element comprises at least two sets of piezoceramic rods disposed facing each other on the first and second sides, The set has two bars arranged on one of the first and second side surfaces on either side of the central surface forming the neutral axis of the optical element.

  In the device according to the invention, the principle described above consists of a set of opposing ceramics arranged on either side of the neutral axis of the optical element in which it can be deformed, whereby one element is compressed and the other element Is inevitably bimorph because is actuated in the opposite direction, such as stretching and vice versa.

  Also, the ceramic is glued to the lateral side rather than to a plane parallel to the optical surface or between planes parallel to the optical surface. Therefore, this is not a laminated structure.

  Unlike prior art devices, such as the device described in US Pat. No. 6,057,049, ceramic curvature is no longer used directly for mirror curvature.

  The ceramic rods are bonded to the side surfaces of the optical element via their own side surfaces. In the prior art, the bonding surface is not flat, but along the curvature at which the mirror is bent.

  In the present invention, the side of the bar remains flat and the length of the ceramic bar is changed by actuation of the ceramic bar. Curvature is produced by the action of the bar of varying length. Contrary to expectation, the curvature caused by the actuation of the side bars of the mirror spreads uniformly against the center of the mirror.

  Thus, the present invention arises from a new functional analysis.

  This structure also has several advantages.

  The most important thing is that the ceramic elements are arranged on the outer surface, so that they are arranged as far as possible from either side of the neutral axis compared to the laminated structure described in US Pat. It is possible to maximize the effect on.

  The improved connection between the ceramic and the mirror improves accuracy and stability when the mirror is bent.

  Since the ceramic is not below or above the optical surface, the connections between the ceramic elements are less visible, and such connections are smooth over the entire width of the mirror.

  In contrast to the description in US Pat. No. 6,057,089, the structure of the present invention is symmetrical with respect to the neutral axis of the optical element, avoiding the thermal effects of bimetal (industrial bars are bonded to each other). This provides excellent thermal stability, even in the case of a plurality of ceramic elements.

  Solutions that use ceramic (monomorph or bimorph) on the back are not excellent solutions, have a small operating range, and are exposed to the thermal effects of bimetal, so these advantages transform conventional mirrors into bimorph mirrors Is particularly important when

  At least one control bar may have a surface that is coplanar with the main surface.

  The apparatus has at least one major surface intersecting the first and second side surfaces along a straight portion, and at least some of the ceramic rods are straight, and are arranged parallel to the straight portion. Can be characterized.

  The apparatus has at least one major surface intersecting the first and second side surfaces along a curved portion that is a concave or convex portion, and at least some of the ceramic rods are straight, It may be characterized by being arranged parallel to the average direction.

  The apparatus includes at least one major surface intersecting the first and second side surfaces along a curved portion that is a concave or convex portion, and at least some of the ceramic rods are curved, It can be characterized by being arranged along.

  The at least one ceramic rod may comprise at least two piezoceramic elements arranged end to end connected and / or stacked.

  Advantageously, the optical element is a rectangular parallelepiped, preferably a square or rectangular shape, and if the element is rectangular, the first and second side surfaces extend along their long sides.

  The ratio of the length L to the width l of the rectangular parallelepiped is advantageously in the range 1 to 100, more specifically in the range 3 to 50, preferably in the range 3 to 25.

  The width l can be, for example, in the range of 10 millimeters (mm) to 80 mm.

  The length L can be in the range of 40 mm to 1500 mm, for example.

  The thickness e of the optical element can be in the range of 5 mm to 100 mm, for example.

  The optical device may also include at least two sets of the above-mentioned piezoceramic rods that are similarly disposed on the third and fourth opposing sides.

  The device of the present invention can be implemented with any optical device that can be deformed, since it is an implementation of a counteracting piezoelectric actuator that is simply attached to two or four sides.

  As an example, the optical element may be a mirror body on which at least the first main surface is polished.

  As an example, the optical element may be a diffraction grating in which at least a first major surface forms at least one grating pattern.

  Other features and advantages of the present invention will become more apparent by referring to the following description in conjunction with the drawings.

FIG. 1 is a perspective view of an apparatus of the present invention, such as a mirror. FIG. 2 is a side view of FIG. FIG. 3 shows a modification in which the bar is offset from the surface of the optical element. Figures 4a and 4b are two different embodiments of electrode pairs. FIG. 5 shows electrode pairs mounted on four sides. Figures 6a to 6c are different embodiments in which at least one major surface is curved.

  FIG. 1 shows a rectangular deformable optical element 1 with two main side surfaces 2 and 3 and two end side surfaces 4 and 5 along the long side of the rectangle. The top surface 6 carries an optical function, for example it is polished to form a mirror that is flat or curved (concave or convex) in the longitudinal and / or lateral direction, or on the long side of, for example, a rectangle Diffraction with one or more grating patterns with lines that are perpendicular or parallel to it, thereby flat or curved (concave or convex) in the longitudinal and / or lateral direction and functioning in reflection or diffraction A lattice is formed.

  Side 2 is relative to the central plane P of optical element 1 (indicated by the dashed line in FIG. 2) that defines the neutral axis (when planes 6 and 7 are flat or only slightly curved). Supports a first set of piezoelectric rods 21, 22 that are substantially parallel and preferably symmetrically spaced. The same applies to the bars 31 and 32 fixed to the side surface 3. If at least one surface is curved, the neutral axis is a non-flat central surface.

The surface 6 can be planar, cylindrical, toroidal, spherical or aspherical (eg elliptical, parabolic or hyperbolic) and thus has a constant or non-constant radius of curvature. In the illustrated embodiment, the surface 6 is a plane and is defined by straight portions 6 ₂ , 6 ₃ , 6 ₄ , 6 ₅ .

  The bottom surface 7 can optionally have an optical function and, like the top surface 6, can be planar or curved (concave or convex).

  The radius of curvature of the surface 6 (and / or 7) is, for example, in the range of 10 mm to ∞ (plane) in the direction not supporting the piezoelectric rod (here, the lateral surfaces 4 and 5) and supporting the piezoelectric rod. The direction (here, the longitudinal planes 2 and 3) ranges from 100 mm to ∞.

  This curvature can also be implemented for the square optical element 1.

  The curvature is oriented in the same direction as or perpendicular to the curvature produced by the set of piezoelectric elements 21, 22, 31, 32.

  Each of the rods 21, 22, 31, and 32 is made of one member of piezoelectric ceramic or a plurality of members that are arranged end to end.

  These piezoelectric rods 21, 22, 31, 32 are preferably flush with the surfaces 6 and 7, separating them as far as possible from the neutral axis and thereby optically with a predetermined control signal applied to the rods. The maximum curvature of the element 1 is obtained while the stress at the bar joint is minimized.

  Since the rods 21 and 22 are opposed, for example, when the same control signal is given to their electrodes (not shown), the rod 21 is compressed, the rod 22 is expanded, or vice versa, as shown in FIG. FIG. 2 is a diagram showing (exaggeratedly) the curvature of the optical element 1 for changing the curvature of the optically active surface 6 so as to provide a concave shape C starting from a plane.

  When starting from a surface 6 that is concave or convex, it is possible to shift the range of curvature change without correcting the width of the change.

  The bars 21, 22, 31, 32 are glued to the side surfaces 2 and 3. They preferably extend over the entire length of this face. In the mirror, the bonding takes place after the surface 6 has been polished, so that, in particular, the component 1 is easy to manufacture because it is a single piece.

  This feature makes it possible to transform an existing passive mirror into an active mirror, which is not possible with a laminated structure.

  In other optical elements, in particular diffraction gratings, the piezoelectric rods 21, 22, 31, 32 can be glued after finishing the surface 6, i.e. after being given optical properties here.

Compared to a mirror with a laminated structure, the ceramic member used does not cover the surface of the mirror, so it is smaller and the cost is reduced. Therefore, its dimensions are configured to a desired value for curvature. For example, the bar can have a width l _{0 in} the range of 2 mm to 30 mm and a height h ₀ in the range of 2 mm to 30 mm. In addition, since there is no electrode under the thin surface layer constituting the mirror, local deformation due to the connection between the electrodes no longer occurs.

  The optical element 1 can be made of any material that is suitable in optics. For example, glass, silica, silicon, silicon carbide, germanium, laser glass, ZnS and ZnSe, metal.

  FIG. 3 shows a variant in which the ceramic bars 21, 22, 31, 32 are separated from the faces 6 and 7 by a distance d, for example smaller than 10 mm, for example in the range from 0.1 mm to 4 mm. . This is particularly suitable when the surface 6 is concave or convex.

4a and 4b are arranged end-to-end (FIG. 4a) and / or overlapped (FIG. 4b) (reference numerals 21, 21 ′, 22, 22 ′) each bar 21 ₁ , 21 ₂ , An embodiment of a variation of the invention having 21 ₃ , 22 ₁ , 22 ₂ , 22 ₃ , 31 ₁ , 31 ₂ , 31 ₃ etc. is shown.

  When a plurality of piezoceramic rods are connected end-to-end and bonded together (for a long mirror), the connecting portions formed on the side surfaces 2 and 3 of the optical element 1 are defective in the planar structure of the optically active surface 6 Does not cause. Such a malfunction cannot occur after time has passed (FIG. 4a).

  The bars 21, 22, 31, 32 can be formed by superimposing two individual bars to be bonded (FIG. 4b).

  FIG. 5 is glued to the faces 4 and 5 of the optical element 1 which is square or rectangular, preferably spaced symmetrically by a central plane P which forms a neutral axis when the faces 6 and 7 are flat or slightly curved. FIG. 2 shows a bimorph mirror that can be curved along two vertical axes by having additional piezoelectric rods 41, 42, 51, 52 to be made. These bars 41, 42, 51, 52 are preferably coplanar with surfaces 6 and 7, or have surfaces offset therefrom, as shown in FIG. Surfaces 6 and / or 7 can be flat or curved in one or two directions of curvature caused by the set of piezoelectric elements, or perpendicular to that direction. The radius of curvature can be in the range of 100 mm to ∞.

  Double actuation with two sets of side piezoelectric actuators is particularly suitable for use with optical components having a square or rectangular shape. The ratio of L / l can be in the range of 1 (square) to 5.

  FIG. 6a shows a mirror with a polished top surface 6 that is concave in both the longitudinal and transverse directions. The rods 21, 22, 31, and 32 are linear and are arranged in the longitudinal direction.

These are parallel to each other and are oriented in the average direction of the curved portion 62 or 63 which is the contact point between the upper surface 6 and the side surface 2 or 3. The curved portions 64 and 65 correspond to the contact points between the upper surface 6 and the side surfaces 4 and 5, respectively. In the illustrated embodiment, this direction is parallel to the bottom surface 7 and this surface is a plane, but it can also be convex or concave in the longitudinal and / or transverse direction. This direction is generally parallel to the tangent plane at the vertex S, particularly for curved sections that are in the form of parabolas or hyperbolas. This configuration can be similarly implemented when the upper surface 6 is curved only in the longitudinal direction (FIG. 6b). The intersection of the upper surface 6 and the side surfaces 4 and 5 then occurs along the straight sections 6 ₄ and 6 ₅ .

  FIG. 6 c shows a mirror having a polished top surface 6 that is concave in the longitudinal direction. The bars 210 and 310 adjacent to the surface 6 are along a curved portion 62 or 63 that is a contact point between the upper surface 6 and the side surface 2 or 3. The bars 22 and 32 are straight and extend along a longitudinal direction that is parallel to the bottom surface 7. In the illustrated embodiment, the bars 21 and 31 are separated from the upper surface 6 by the distance d described above. These may be on the same plane as the curved portion.

Therefore, the straight or curved bar is constant or otherwise in the straight part (6 ₂ , 6 ₃ , 6 ₄ , 6 ₅ ) or curved part (62, 63, 64, 65) However, they are arranged close to each other at a distance d of 10 mm or less, in particular 4 mm.

Claims (14)

An optical element that is deformable and an active element made of a piezoceramic with electrodes, the elements are paired so as to produce a compressive movement with respect to a set of first elements and an expansion movement with respect to a set of second elements. In the bimorph optical device controlled in the opposite direction, the device comprises at least a first main surface (6) in which the optical element (1) is optically active and a second main surface (7) opposite the first main surface. Comprising at least two sets of piezoceramic rods (provided with first and second opposing side faces (2, 3)) and ceramic active elements facing each other on said first and second side faces (2, 3) 21, 22; 31, 32), and each pair is disposed on one of the first and second side surfaces (2, 3) on either side of the central surface forming the neutral axis of the optical element (1) 2 With two bars (21, 22; 31, 32); Bimorph optical device according to claim. At least one of the main surfaces (6, 7) intersects the first and second side surfaces (2, 3) along straight portions (6 ₂ , 6 ₃ , 6 ₄ , 6 ₅ ), and the ceramic 2. Bimorph optical device according to claim 1, characterized in that at least some of the bars (21, 31) are linear and are arranged parallel to the linear part. At least one of the main surfaces (6, 7) intersects the first and second side surfaces (2, 3) along a curved portion (62, 63, 64, 65) that is a concave or convex portion; The bimorph optical device according to claim 1, characterized in that at least some of the ceramic rods (21, 31) are linear and are arranged parallel to the average direction of the curved portion. At least one of the main surfaces (6, 7) intersects the first and second side surfaces (2, 3) along a curved portion (62, 63, 64, 65) that is a concave or convex portion; The bimorph optical device according to claim 1, characterized in that at least some of the ceramic rods (210, 310) are curved and arranged along the curved portion. At least one ceramic rod, end to end is arranged to be connected _{(21 1, 21 2,} 21 _{3, 22} 1, 22 _2, 22 3, 31 _1, 31 2, 31 ₃₎ or superimposed The bimorph optical device according to claim 1, characterized in that it comprises at least two piezoelectric ceramic elements (21, 21 ', 22, 22', 31, 31 ', 32, 32'). 6. The optical element (1) having a rectangular parallelepiped shape, and the first and second side surfaces (2, 3) extending along a long side of a rectangle. The bimorph optical device according to any one of the above. The bimorph optical device according to claim 6, wherein the ratio of the length L to the width l of the rectangular parallelepiped is in the range of 1 to 100. 8. The bimorph optical device according to claim 7, wherein the width l is in a range of 10 mm to 80 mm. 9. The bimorph optical device according to claim 7, wherein the length L is in a range of 40 mm to 1500 mm. The width l ₀ of the rod (21, 22, 31, 32, 41, 42, 51, 52) is in the range of 2 mm to 30 mm, and the height h ₀ is in the range of 2 mm to 30 mm. The bimorph optical device according to any one of claims 1 to 9, characterized in that: 11. A method according to any one of claims 6 to 10, characterized in that it also includes third and fourth opposing side surfaces (4, 5) comprising a set of at least two of said piezoelectric ceramic rods (41, 42, 51, 52). The bimorph optical device according to one item. The bimorph optical device according to any one of claims 1 to 11, characterized in that the thickness e of the optical element (1) is in the range of 5 mm to 100 mm. 13. The bimorph optical device according to claim 1, wherein the optical element is a mirror body and at least the first main surface (6) is polished. 13. 13. Bimorph optical device according to any one of the preceding claims, characterized in that the optical element is a grating and at least the first main surface (6) comprises at least one grating pattern. .

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