A self-deforming deformable mirror based on transparent electrostrictive ceramics

Abstract

The present invention relates to a self-deforming deformable mirror based on transparent electrostrictive ceramics. The transparent electrostrictive ceramics serve as the mirror body of the self-deforming deformable mirror without the need for an additional driver.

Description

Technical Field

[0001] The present invention belongs to the field of adaptive optics, and in particular relates to a self-deforming deformable mirror based on transparent electrostrictive ceramics. Background Art

[0002] Adaptive optics is a technology that improves the performance of optical systems by correcting the wavefront distortion of light waves caused by atmospheric jitter. Adaptive optics systems primarily consist of a wavefront sensor, a real-time controller, and a wavefront corrector. The key component is the wavefront corrector, which corrects the phase of the light wavefront by changing the optical path length (deformable mirror) or the refractive index of the transmission medium (liquid crystal spatial light modulator) to alter the phase structure of the incident light wavefront. Most wavefront correctors achieve wavefront phase correction by changing the surface shape of the deformable mirror. Commonly used deformable mirrors include separate actuator deformable mirrors, spliced ​​sub-mirror deformable mirrors, piezoelectric deformable mirrors, MEMS electrostatically actuated (magnetically actuated) deformable mirrors, and thin-film deformable mirrors.

[0003] The core structure of the deformable mirror consists of a mirror surface and a driver, wherein the driver mainly includes a piezoelectric ceramic driver and an electrostrictive driver. The piezoelectric ceramic driver works by utilizing the inverse piezoelectric effect of piezoelectric ceramics, that is, when an external voltage is applied to the piezoelectric ceramics, deformation will occur along the polarization direction, but the piezoelectric ceramics must be pre-polarized, and if too high a reverse voltage is applied, depolarization will occur and even electrical breakdown will occur, destroying the function of the piezoelectric ceramics. Compared with the piezoelectric effect, the electrostrictive effect is a nonlinear phenomenon related to stress, strain and the quadratic term of the electric field. The advantage of electrostrictive materials is that they do not need to be pre-polarized like piezoelectric ceramics, and the strain is much larger than that of piezoelectric ceramics (can reach 10 -3 In the application of driving functional devices requiring low operating voltage, large strain and miniaturization, electrostrictive materials have better application characteristics than piezoelectric materials.

[0004] Typically, a deformable mirror uses an actuator to drive the mirror surface to deform, so there is a physical connection between the mirror and the actuator. Examples include piston deformable mirrors, piezoelectric deformable mirrors, bi-piezoelectric deformable mirrors, and voice coil deformable mirrors. However, this physical connection inevitably has adverse effects on the performance of the deformable mirror, including: 1) the deformation of the deformable mirror needs to be transmitted through the physical connection layer, which will leave traces of the actuator adhesion on the mirror surface, affecting the continuity of the mirror surface and introducing additional high-order distortion; 2) due to the difference in thermal expansion coefficients between the actuator and the mirror surface, when the ambient temperature changes, the mirror and actuator stack will produce thermally induced bending deformation, resulting in a decrease in the thermal stability of the surface. Therefore, there is an urgent need to provide a new deformable mirror that can deform the mirror surface without a physical connection and can be driven by electrostriction to achieve self-deformation. Summary of the Invention

[0005] To address the above-mentioned issues, the present invention provides an application of a transparent electrostrictive ceramic, which can be used as the mirror body of a self-deforming deformable mirror without requiring an additional actuator. Specifically, the present invention provides a self-deforming deformable mirror that integrates the mirror surface and actuator into one, eliminating the need for a separate physical connection between the mirror surface and the actuator. Specifically, the transparent electrostrictive ceramic, acting as the mirror surface, does not require an external actuator; instead, it exhibits significant strain under the action of an electric field, thereby achieving self-deformation of the mirror surface.

[0006] Preferably, the transparent electrostrictive ceramic can be PMN-PT transparent ceramic, PLMNT transparent ceramic, PZN-PT transparent ceramic or PLZT transparent ceramic, preferably PLZT transparent ceramic and PLMNT transparent ceramic.

[0007] Preferably, the transparent electrostrictive ceramic has a thickness of 0.5 to 10.0 mm and a diameter of 20 to 150 mm. If the thickness increases, the deformation increases, but the insertion loss also increases, causing the optical quality of the transparent electrostrictive ceramic to deteriorate.

[0008] The present invention uses transparent electrostrictive ceramics as its core. The ceramics not only have good light transmittance and a high refractive index in the visible to mid-infrared wavelength range, making them suitable for use as light transmission mirrors, but also exhibit excellent electrostrictive properties. Under the action of an external driving electric field, the strain is approximately 0.1% of the ceramic thickness, making them suitable for use as self-deformation actuators.

[0009] In one example, the deformable mirror with a self-deformable mirror surface further includes a metal electrode array disposed on one side of the transparent electrostrictive ceramic and a metal electrode layer disposed on the other side of the transparent electrostrictive ceramic.

[0010] In another example, the deformable mirror with self-deformable mirror surface further includes a reflective layer arranged on one side of the transparent electrostrictive ceramic, a transparent electrode layer arranged on the other side of the transparent electrostrictive ceramic, a metal electrode array arranged on the reflective layer, and an antireflection film arranged on the transparent electrode.

[0011] Beneficial effects

[0012] (1) Compared with conventional deformable mirrors, the self-deforming deformable mirror of the present invention combines the driver and the mirror into one, without the need for physical connection, thus simplifying the structure, significantly reducing the thickness of the mirror body, which is the core functional component, and making the deformation more continuous without physical connection of the mirror body.

[0013] (2) The self-deforming deformable mirror of the present invention can be a transmissive light-transmitting structure, which has an optical path amplification effect and can increase the modulation amplitude. The light beam passes through the transparent ceramic and then returns. The optical path is the product of the deformation and the refractive index (n≈2.5). A deformation of 1 micron can achieve an optical path difference of approximately 3 microns, thus achieving an optical path amplification effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the self-deformed mirror structure of the present invention;

[0015] Among them, 1-transparent electrostrictive ceramic, 2-reflective layer, 3-metal electrode unit, 4-transparent electrode, 5-antireflection film, 6-base;

[0016] Figure 2 is the transmittance curve of transparent electrostrictive PLZT ceramics;

[0017] Figure 3 The electric field intensity-strain curve of transparent electrostrictive PLZT ceramics;

[0018] Figure 4 This is a physical picture of the 7-unit and 19-unit metal Pt electrode structures of the self-deformable mirror;

[0019] Figure 5 The top view (1) and the tilted stereoscopic view (2) of each electrode unit of the 19-unit mirror body in Example 1;

[0020] Figure 6 This is a diagram showing the surface shape change when an electric field is applied simultaneously to multiple electrode units in Example 1;

[0021] Figure 7 This is an inclined stereoscopic view of the surface of each electrode unit of the 7-unit mirror body in Example 2;

[0022] Figure 8 These are the electric field strength-deformation curves of the 1# electrode unit and the 6# electrode unit in Example 2. DETAILED DESCRIPTION

[0023] To further illustrate the content, features and practical effects of the present invention, the present invention is described in detail below in conjunction with the embodiments. It should be noted that the modification method of the design of the present invention is not limited to these specific embodiments. Without departing from the spirit and connotation of the design of the present invention, equivalent replacements and modifications made by those skilled in the art based on the content of the present invention are also within the scope of the present invention.

[0024] The present invention uses transparent electrostrictive ceramics as the self-deformable mirror body to assemble a deformable mirror, without the need for an external driver. The assembled deformable mirror can be a conventional reflective type, for example, comprising a transparent electrostrictive ceramic as the self-deformable mirror body, a metal electrode array disposed on one side of the transparent electrostrictive ceramic, and a metal electrode layer disposed on the other side of the transparent electrostrictive ceramic. The assembled deformable mirror can also be a transmissive type, such as Figure 1 As shown, the present invention provides a deformable mirror with a self-deformable mirror surface. For ease of description, the thickness of the deformable mirror (i.e., the vertical direction) is considered the vertical direction, and the width of the deformable mirror (i.e., the radial direction, i.e., the left-right direction) is considered the horizontal direction. The specific structure of the deformable mirror may include: a transparent electrostrictive ceramic (deformable mirror body) 1, a reflective layer 2 disposed on one side of the transparent electrostrictive ceramic 1, and a transparent electrode 4 disposed on the other side of the transparent electrostrictive ceramic 1. Preferably, a metal electrode array 3 composed of multiple metal electrode units is disposed on the reflective layer 2, and an antireflection coating 5 is disposed on the transparent electrode 4. A base 6 is disposed on the outer periphery of the transparent electrostrictive ceramic 1 to support the transparent electrostrictive ceramic 1.

[0025] The transparent electrostrictive ceramic can be PMN-PT transparent ceramic, PLMNT transparent ceramic, PZN-PT transparent ceramic or PLZT transparent ceramic, preferably PLZT transparent ceramic and PLMNT transparent ceramic. The transparent electrostrictive ceramic can have a thickness of 0.5 to 10.0 mm and a diameter (width) of 20 to 150 mm.

[0026] A reflective layer 2 is formed on one side of the transparent electrostrictive ceramic 1 by a coating method such as evaporation or sputtering. The reflective layer 2 can be made of a dielectric reflective film, preferably a multilayer periodic reflective film of TiO2 (Ta2O5) and SiO2. The thickness of the reflective layer 2 can be 100 to 600 nm.

[0027] A transparent electrode 4 is formed on the other side of the transparent electrostrictive ceramic 1 by a coating method such as evaporation or sputtering. The transparent electrode 4 can be made of indium tin oxide (ITO) or a similar transparent conductive oxide film. The thickness of the transparent electrode 4 can be 200 to 500 nm.

[0028] An electrode array consisting of a plurality of metal electrode units 3 is formed on the reflective layer 2 by magnetron sputtering or evaporation. The material of the metal electrode can be Pt, Au, Ag, Cu, Al, etc. In order to reduce the boundary effect, the coverage area of ​​the electrode array 3 is slightly smaller than the area of ​​the transparent electrostrictive ceramic 1, for example, covering 60 to 90%. The electrode array can be composed of 7 to 200 electrode units. The shape of each electrode unit can be a regular hexagon, a fan, a circle, etc. For example, a plurality of electrode units can form a ring electrode array or a regular hexagonal electrode array pattern. In one example, the electrode array is composed of 19 electrode units, and each electrode unit is a regular hexagon (with a side length of 4 mm and an electrode spacing of 1.5 mm). The thickness of the electrode array can be 100-400 nm. The process parameters for preparing Pt electrodes by magnetron sputtering are: vacuum degree <6×10 -4 Pa, sputtering power is 95-105W, room temperature, sputtering atmosphere is pure Ar, and sputtering pressure is 0.95-1.05Pa.

[0029] Multiple discrete metal electrode units and transparent electrodes constitute a drive array for the deformable mirror; the multiple metal electrode units and the transparent electrodes are respectively connected to respective wires. When a voltage is applied to the one or more metal electrode units and the transparent electrode layer, the transparent ceramic mirror layer is deformed at the corresponding position of the discrete electrode unit due to the electrostrictive effect of the transparent ceramic.

[0030] An antireflection film 5 is formed on the transparent electrode 4 by a coating method such as evaporation or sputtering. The antireflection film 5 can be made of a multilayer antireflection film system, preferably a combination of SiO2 and HfO2, SiO2 and Al2O3, etc. The thickness of the antireflection film 5 is about 200-500 nm.

[0031] When the deformable mirror is in use, incident light passes through the antireflection film, the first transparent electrode, and the transparent ceramic in sequence, and is reflected back by the reflective layer. The reflected light then passes through the transparent ceramic, the transparent electrode, and the antireflection film in sequence to be emitted.

[0032] The base is made of high-strength engineering plastic with good rigidity and insulation as the fixed support structure of the mirror body, preferably polytetrafluoroethylene. The upper end of the base reserves an electrode access position at the edge of the transparent electrode to connect to the wire of the external circuit; the lower end of the base reserves a position to connect the driving end metal unit electrode to the external circuit wire.

[0033] Example 1

[0034] Based on the principle of reflective self-deformable mirror, a mirror self-deformable mirror body specifically includes a transparent electrostrictive PLZT ceramic, 19 metal Pt electrode units, and a metal electrode unit layer. The PLZT ceramic is polished on both sides to Φ50mm×1mm. After polishing, a metal surface electrode is magnetron sputtered on one side. To reduce the boundary effect, the electrode diameter is slightly smaller than the ceramic diameter, Φ44mm. 19 metal discrete electrode units are sputtered on the other polished surface of the ceramic. The electrode pattern is a regular hexagon (with a side length of 4mm and an electrode spacing of 1.5mm), covering an area of ​​approximately Φ40.63mm. Figure 4 ; Connect the metal electrode unit layer to the positive pole of the DC power supply, and lead out the respective wires of the 19 metal discrete electrode units on the other side. One or more electrode units are connected to the negative pole of the power supply to apply an electric field to a certain discrete electrode unit individually or to multiple discrete electrode units at the same time; fix the mirror body in the base.

[0035] Example 2

[0036] A reflective self-deformable mirror body comprises a transparent electrostrictive PLZT ceramic, seven metal Pt electrode units, and a metal electrode layer. The PLZT ceramic is polished on both sides to a diameter of 50 mm x 1 mm. A metal surface electrode with a diameter of 44 mm is magnetron sputtered onto one polished surface. Seven metal discrete electrode units are sputtered onto the other polished surface of the ceramic. The electrode pattern is a regular hexagon (with a side length of 7 mm and an electrode spacing of 1.5 mm), covering an area of ​​approximately 39.36 mm. Figure 4 ; Connect the metal electrode layer to the positive pole of the DC power supply, and lead out the respective wires of the 7 metal discrete electrode units on the other side. One or more electrodes are connected to the negative pole of the power supply to apply an electric field to a certain discrete electrode unit individually or to multiple discrete electrode units at the same time; fix the mirror body in the base.

[0037] Figure 2 FIG1 is a transmittance curve of a transparent electrostrictive PLZT ceramic. As can be seen from the figure, the transparent electrostrictive ceramic of the present invention has good transmittance and high refractive index in the wavelength range from visible light to mid-infrared, wherein 31% of the reflection loss is compensated by the specific wavelength anti-reflection film.

[0038] Figure 3 This is the electric field strength-strain curve of the transparent electrostrictive PLZT ceramic, which shows that the strain value in the longitudinal direction of the thickness of the ceramic changes under the action of the electric field. At an electric field strength of 10kV / cm, a strain of about 0.1% of the thickness is generated.

[0039] Figure 5 and Figure 6 These are surface diagrams of Example 1 in which a voltage of 1000 V is applied to different electrode units individually and a voltage of 1000 V is applied to multiple electrode units simultaneously, indicating that each electrode unit has a good deformation response.

[0040] Figure 7 This is an inclined stereoscopic image of the surface of each electrode unit of the 7-unit mirror body in Example 2, indicating that each electrode unit has an obvious deformation response.

[0041] Figure 8 The electric field strength-deformation curves of the 1# electrode unit and the 6# electrode unit in Example 2 show that as the applied voltage increases, the deformation of the electrode unit gradually increases. The deformation of the 1# electrode unit is slightly larger than that of the 6# electrode unit, and the deformation of the electrode unit is close to Figure 2 The amount of electrostrictive strain of the ceramic body shown.

[0042] In order to verify the feasibility of self-deformation of the mirror surface in practice, Examples 1 and 2 show a simple reflective deformable mirror assembled using a metal electrode layer. It should be understood that the metal electrode can also be replaced with a transparent electrode layer, and then a reflective layer and an anti-reflection layer are provided to assemble a transmissive deformable mirror.

Claims

1. A self-deforming deformable mirror, characterized in that: A transparent electrostrictive ceramic serves as a mirror body of the mirror self-deforming deformable mirror; the mirror self-deforming deformable mirror further comprises a reflective layer disposed on one side of the transparent electrostrictive ceramic, a transparent electrode layer disposed on the other side of the transparent electrostrictive ceramic, a plurality of metal electrode units disposed on the reflective layer, and an antireflection film disposed on the transparent electrode; in The plurality of metal electrode units and the transparent electrode are respectively connected to respective wires. When a voltage is applied to one or more of the plurality of metal electrode units and the transparent electrode layer, the transparent electrostrictive ceramic is deformed at a corresponding position of the corresponding electrode unit.

2. The mirror self-deforming deformable mirror according to claim 1, characterized in that: The transparent electrostrictive ceramic is selected from PMN-PT transparent ceramic, PLMNT transparent ceramic, PZN-PT transparent ceramic or PLZT transparent ceramic.

3. The mirror self-deforming deformable mirror according to claim 1 or 2, characterized in that: The transparent electrostrictive ceramic has a thickness of 0.5-10.0 mm and a diameter of 20-150 mm.

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