CN118859512A - Deformable mirror and adaptive optical system - Google Patents

Abstract

The present disclosure provides a deformable mirror and an adaptive optics system, the deformable mirror comprising: a base; a plurality of driving columns vertically disposed on the base in an array manner, each driving column comprising: a plurality of piezoelectric drivers axially stacked, each piezoelectric driver being configured to lengthen or contract in an axial direction in response to an external control signal, so that each driving post lengthens or contracts in the axial direction; and a mirror surface provided on each driving post and configured to change a reflection angle of externally inputted signal light at a junction of the mirror surface and each driving post following extension and/or contraction of each driving post.

Description

Deformable mirror and adaptive optical system

Technical Field

The present disclosure relates to the field of adaptive optics technology, and in particular to a deformable mirror and an adaptive optics system.

Background Art

When using a telescope to observe distant targets, the state of the atmosphere may affect the observation effect. For example, when the magnification is large, the imaging spot is blurred and jittery, which greatly affects the observation resolution. This is the result of dynamic wavefront errors caused by atmospheric turbulence. In order to overcome dynamic influences such as atmospheric disturbances and obtain a resolution close to the diffraction limit of the system, an adaptive optical system architecture has been proposed. The adaptive optical system has three basic components: a wavefront sensor, a wavefront controller, and a wavefront corrector. The essence of the wavefront corrector is to change the wavefront shape of the incident light beam, and the correction function is mainly achieved through a deformable mirror.

As the distance of the target in the imaging system continues to increase and the spectral range continues to improve, the deformable mirror needs to have the ability to compensate for the high-amplitude phase error of long-distance atmospheric disturbances, so the deformable mirror needs to meet a larger stroke and higher precision. Currently, the stroke of the deformable mirror on the market is mostly less than 50μm and the precision is less than 20nm. Since increasing the stroke of the deformable mirror will cause the mirror stress to exceed the allowable stress, the mirror surface is prone to cracking.

Summary of the invention

In order to solve the technical problems in the prior art, the present invention provides a deformable mirror, which uses a plurality of stacked piezoelectric drivers as driving columns, and the driving columns are vertically arranged on a base in an array manner. The mirror surface is optimized through three processing processes to achieve a high-flatness mirror surface shape, thereby increasing the stroke of the deformable mirror and improving the accuracy of the deformable mirror.

In one aspect of the embodiments of the present disclosure, a deformable mirror is provided, comprising a base, a plurality of drive posts, and a mirror surface. The plurality of drive posts are vertically arranged on the base in an array, and each of the drive posts comprises: a plurality of axially stacked piezoelectric drivers, each of the piezoelectric drivers being configured to extend or contract in the axial direction in response to an external control signal, so that each of the drive posts is extended or contracted in the axial direction; and a mirror surface is arranged on each of the drive posts, and is configured to change the reflection angle of the external input signal light at the junction of the mirror surface and each of the drive posts following the extension or contraction of each of the drive posts.

According to an embodiment of the present disclosure, each of the driving columns further comprises a shell, which covers both sides of the piezoelectric driver to form an elastic sawtooth structure with a pre-tightening force, so as to reduce the resistance of the piezoelectric driver to extend in the axial direction and improve the rigidity of the driving column.

According to an embodiment of the present disclosure, the mirror surface is circular, and the ratio of the diameter to the thickness of the mirror surface is not greater than 500.

According to an embodiment of the present disclosure, the manufacturing process of the mirror surface includes: grinding the substrate so that the surface shape of the ground substrate is within 10 wavelengths of the signal light; performing magnetorheological shaping on the ground substrate so that the surface shape of the modified substrate is within 1 wavelength of the signal light; performing ion beam polishing on the modified substrate so that the surface shape of the polished substrate is within 0.01 wavelength of the signal light, thereby obtaining the mirror surface.

According to an embodiment of the present disclosure, an isolation block is provided between two housings covering two adjacent piezoelectric drivers of each driving column, so that the two adjacent piezoelectric drivers of each driving column are electrically isolated.

According to an embodiment of the present disclosure, pads are respectively provided at both ends of the shell facing the mirror surface and the base, and the bottom of the shell is screwed or bonded to the base through the pads.

According to an embodiment of the present disclosure, the deformable mirror further includes:

A plurality of joints are mounted on the driving column through a spacer on the top of each housing and are flexibly connected to the mirror.

According to an embodiment of the present disclosure, the thermal expansion coefficient of the joint is equal to or close to the thermal expansion coefficient of the mirror.

According to an embodiment of the present disclosure, the portion of the joint that is connected to the mirror surface is spherical, hemispherical or ellipsoidal.

According to an embodiment of the present disclosure, the thermal expansion coefficient of the housing is lower than that of the piezoelectric driver, so as to reduce the interference of the housing on the extension or contraction stroke of the piezoelectric driver.

According to an embodiment of the present disclosure, the upper and lower surfaces of the mirror are coated with reflective films to increase the reflectivity of the mirror.

Another aspect of the disclosed embodiments provides an adaptive optical system, comprising any one of the above-described deformable mirrors, a wavefront detector, and a wavefront controller. The deformable mirror is suitable for correcting the wavefront aberration of incident signal light, the wavefront detector is suitable for detecting the wavefront aberration of the signal light, and the wavefront controller is suitable for outputting a control signal according to the measurement result of the wavefront detector to control the extension and/or contraction of the drive column of the deformable mirror.

According to the deformable mirror of the embodiment of the present disclosure, the travel of the deformable mirror is increased by stacking multiple piezoelectric drivers as driving columns. By vertically arranging the driving columns in an array on a base, the mirror surface follows each driving column to extend or contract in the axial direction, thereby improving the correction accuracy of the deformable mirror to the signal light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 schematically shows an axial cross-sectional view of a deformable mirror according to an embodiment of the present disclosure;

FIG2 schematically shows an arrangement diagram of a deformable mirror drive column according to an embodiment of the present disclosure; and

FIG. 3 schematically shows a system diagram of an adaptive optical system according to an embodiment of the present disclosure.

Description of reference numerals:

1- base;

2- driving column;

21- piezoelectric actuator;

22-housing;

23-isolation block;

24- Pad;

3- Mirror surface; and

4-Connector.

DETAILED DESCRIPTION

In order to make the purpose, technical scheme and advantages of the present disclosure more clear, the present disclosure is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. However, the present disclosure can be implemented in different forms and should not be construed as being limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and fully convey the scope of the present disclosure to those skilled in the art. In the accompanying drawings, for clarity, the sizes and relative sizes of layers and regions may be exaggerated, and the same reference numerals represent the same elements throughout.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and/or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

In order to facilitate those skilled in the art to understand the technical solution of the present disclosure, the following technical terms are explained.

In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and/or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and/or A, B, C, etc.).

Deformable mirrors, also known as wavefront correctors, are mainly used in various adaptive optical systems. They change the phase structure of the incident light wavefront by changing the optical path of the light wavefront transmission or the refractive index of the transmission medium, thereby achieving the purpose of correcting the light wavefront phase.

Fig. 1 schematically shows an axial cross-sectional view of a deformable mirror according to an embodiment of the present disclosure, and Fig. 2 schematically shows an arrangement diagram of drive columns of a deformable mirror according to an embodiment of the present disclosure, wherein the numbers in Fig. 2 are the numbers of the drive columns.

According to one aspect of the embodiments of the present disclosure, a deformable mirror is provided, as shown in FIGS. 1 and 2 , comprising a base 1, a plurality of drive posts 2, and a mirror 3. The plurality of drive posts 2 are vertically arranged on the base 1 in an array manner, and each drive post comprises a plurality of axially stacked piezoelectric drivers 21, and each piezoelectric driver 21 is configured to extend or contract in the axial direction in response to an external control signal (for example, a control signal sent by a wavefront controller), so that each drive post 2 extends or contracts in the axial direction. The mirror 3 is disposed on each drive post 2, and is configured to change the reflection angle of the external input signal light at the junction of the mirror and each drive post 2 following the extension or contraction of each drive post 2, thereby correcting the wavefront aberration of the signal light.

According to the deformable mirror of the embodiment of the present disclosure, the stroke of the deformable mirror is increased by stacking multiple piezoelectric drivers 21 as part of the driving column 2. By vertically arranging the driving columns 2 in an array between the base 1 and the mirror surface, the mirror surface 3 follows each driving column 2 to extend or shrink in the axial direction, thereby improving the correction accuracy of the deformable mirror for the wavefront aberration of the signal light. With the characteristics of large stroke (more than 80um) and high precision (less than 5nm), the mirror surface shape can be accurately and largely adjusted to achieve the correction of various orders of wavefront aberrations, so that the imaging system has the ability to compensate for the high-amplitude phase error of long-distance atmospheric disturbances, and can achieve the problem of focusing on the target object without the need for a complex lens group.

According to the embodiments of the present disclosure, it is found in the process of implementing the present disclosure that the mirror stress is related to the mirror thickness of the deformable mirror and the position distribution of the driver, and these parameters will affect the fitting accuracy of the deformable mirror. In order to meet the requirements of large travel (more than 80um) and high precision (less than 5nm) of the deformable mirror, in the deformable mirror of the embodiment of the present disclosure, the parameters of the drive column and the mirror are designed by constructing a numerical model, and the mirror is prepared by micro-nano processing technology, so as to greatly and accurately adjust the surface shape of the mirror and improve the imaging quality.

According to an embodiment of the present disclosure, the mirror surface 3 is circular, and the ratio of the diameter to the thickness of the mirror surface 3 is not greater than 500.

According to an embodiment of the present disclosure, the numerical model of the driving column 2 includes: stiffness K _act and stroke ΔU:

Wherein, _Fb is the output force (i.e., the force of the driving column without deformation under the maximum voltage _Vmax ), _ΔU0 is the maximum stroke of the driving column under the maximum voltage _Vmax , and V is the input voltage of the driving column.

According to the embodiment of the present disclosure, in order to achieve the target stroke, the rigidity of the driving column should be more than 20 times greater than the rigidity of the mirror surface, and the driving column stroke should exceed the target stroke by more than 4%. The target stroke is a stroke set according to actual needs.

According to an embodiment of the present disclosure, the numerical model of the mirror surface 3 includes: stiffness K _m , stroke Δ _L and stress σ _FP .

Wherein, _Em is the Young's modulus of the mirror, _tm is the mirror thickness, _vm is the Poisson's ratio of the mirror, d is the spacing between two adjacent driving columns, _Kact is the stiffness of the driving column, and _ΔU0 is the maximum stroke of the driving column under the maximum voltage _Vmax .

According to an embodiment of the present disclosure, the driving columns 2 are arranged in an array between the substrate 1 and the mirror 3, so that the spacing between two adjacent driving columns is equal. For example, as shown in FIG. 2, the spacing between the 16th driving column and the 11th driving column is equal to the spacing between the 16th driving column and the 22nd driving column.

It can be seen from formulas (3)-(5) that the equivalent stiffness K m , stroke Δ L and stress σ _FP of the mirror can be determined according to the stiffness K _act of the driving column, the maximum stroke ΔU ₀ at the maximum voltage V _max and the distance d between two adjacent driving _columns , and according to the Young's modulus _Em , thickness t _m and _Poisson 's ratio v _m of the mirror.

According to the embodiments of the present disclosure, in order to meet the application of large stroke, the stiffness of the mirror 3 should be smaller than the stiffness of the driving column, and the stress of the mirror 3 should not exceed the breaking stress of the material selected for the mirror.

In an illustrative embodiment, in an illustrative embodiment, the target stroke is 80 μm, and the stiffness of the driving column 2 is determined to be 15.14 N/μm according to formulas (1) and (2), and the maximum stroke of the driving column 2 is 84.4 μm. According to formula (3), the stiffness of the mirror is determined to be 0.35 N/μm.

According to an embodiment of the present disclosure, the mirror surface 3 is prepared by a micro-nano processing technology, and the micro-nano processing technology includes:

The substrate is ground so that the surface shape of the ground substrate is within 10 wavelengths of the signal light. For example, the substrate can be ground using a single-axis grinder.

The ground substrate is subjected to magnetorheological modification so that the surface shape of the modified substrate is within one wavelength of the signal light.

The modified substrate is subjected to ion beam polishing to make the surface shape of the polished substrate within 0.01 wavelength of the signal light, thereby obtaining the desired mirror surface.

According to the embodiments of the present disclosure, the mirror surface is optimized through three processing steps to achieve a mirror surface shape with high flatness (less than 5 nm).

According to an embodiment of the present disclosure, the material of the mirror includes any one of single crystal silicon, SiC, metal, etc.

According to an embodiment of the present disclosure, the upper and lower surfaces of the mirror are coated with reflective films to increase the reflectivity of the mirror.

According to an embodiment of the present disclosure, the material of the reflective film includes any one of aluminum, silver, gold, and the like.

In an exemplary embodiment, the mirror is made of single crystal silicon, and to ensure stress control of the mirror, the upper and lower surfaces are coated with reflective films. The flatness of the mirror is less than 5nm, and to improve the reflectivity, the reflective film uses metal aluminum, so that the reflectivity of the mirror is above 90%.

According to an embodiment of the present disclosure, the accuracy of the driving column 2 is linearly related to the number of piezoelectric drivers 21 .

In an exemplary embodiment, the accuracy of the drive column 2 is better than 1/10000 of the full stroke of the piezoelectric driver 21 .

According to an embodiment of the present disclosure, all driving columns 2 are arranged vertically and equidistantly in an array between the base 1 and the mirror 3 .

According to an embodiment of the present disclosure, each driving column 2 further includes a housing 22. As shown in FIG1 , the housing 22 covers both sides of the piezoelectric driver 21 to form an elastic sawtooth structure with a pre-tightening force to reduce the resistance of the piezoelectric driver to extend in the axial direction and to improve the rigidity of the driving column 2.

According to an embodiment of the present disclosure, by forming an elastic serration structure with a pre-tightening force on both sides of the piezoelectric driver 21, the elastic serration structure with a pre-tightening force can be extended along the axial direction of the piezoelectric driver following the piezoelectric driver, and provide a contraction elastic force during the process of the piezoelectric driver contracting after extension, so that the piezoelectric driver can quickly contract to the target position, thereby reducing the response time of the piezoelectric driver.

According to an embodiment of the present disclosure, the housing 22 is an elastic serrated structure with a pre-tightening force and is made of a high-strength material to improve the overall rigidity of the drive column and meet the requirements of a large stroke.

In an exemplary embodiment, the shell 22 may be made of a metal material, such as stainless steel or Kovar.

According to the embodiment of the present disclosure, pads 24 are respectively provided at both ends of the housing 22 facing the mirror surface 3 and the base 1 , and the bottom of the housing is screwed or bonded to the base through the pads 24 .

According to an embodiment of the present disclosure, the thermal expansion coefficient of the housing 22 is lower than that of the piezoelectric driver, so as to reduce the interference of the housing 22 on the extension or contraction stroke of the piezoelectric driver 21 .

According to an embodiment of the present disclosure, in order to reduce the influence of temperature change on the deformable mirror, the base 1 is made of a material with a low thermal expansion coefficient, such as Invar.

According to an embodiment of the present disclosure, the material of the piezoelectric driver 21 includes stacked piezoelectric sheets or electrostrictive materials.

According to an embodiment of the present disclosure, each driving column may include 3, 4, 5, 7, etc. piezoelectric drivers stacked axially.

In an illustrative embodiment, as shown in FIG1 , the drive column is composed of two axially stacked piezoelectric drivers.

In an illustrative embodiment, as shown in FIG. 2 , the deformable mirror includes 31 driving columns, which are substantially hexagonal in shape and are vertically and evenly arranged on the base 1 in an array.

According to an embodiment of the present disclosure, an isolation block 23 is provided between two housings 22 covering two adjacent piezoelectric drivers 21 of each driving column 2, so that two adjacent piezoelectric drivers of each driving column are electrically isolated.

In an illustrative embodiment, the isolation block 23 and/or the cushion block 24 are integrally provided with the housing 22 .

According to an embodiment of the present disclosure, the deformable mirror further comprises a plurality of joints 4, which are mounted on the driving column 2 via a spacer 24 at the top of each housing and are flexibly connected to the mirror surface.

According to an embodiment of the present disclosure, the flexible connection between each joint 4 and the mirror 3 includes bonding with epoxy adhesive.

According to an embodiment of the present disclosure, the portion of the joint 4 that is connected to the mirror 3 is spherical, hemispherical or ellipsoidal.

In an illustrative embodiment, in order to reduce the contact area between the joint 4 and the mirror surface 3 and improve the accuracy of the deformable mirror, the portion of the joint 4 that is connected to the mirror surface 3 is spherical.

According to an embodiment of the present disclosure, the thermal expansion coefficient of the joint 4 is equal to or close to the thermal expansion coefficient of the mirror 3 .

According to an embodiment of the present disclosure, the joint 4 and the mirror 3 may be made of the same material or different materials.

In an illustrative embodiment, the joint 4 is made of Invar, and the mirror surface 3 is made of single crystal silicon.

FIG. 3 schematically shows a system diagram of an adaptive optical system according to an embodiment of the present disclosure.

Another aspect of the disclosed embodiment provides an adaptive optical system, as shown in Fig. 3, comprising any of the above-mentioned deformable mirrors (wavefront correctors), wavefront detectors, and wavefront controllers. The deformable mirror is suitable for correcting the wavefront aberration of the incident signal light, the wavefront detector is suitable for detecting the wavefront aberration of the signal light, and the wavefront controller is suitable for outputting a control signal according to the measurement result of the wavefront detector to control the extension and/or contraction of the drive column of the deformable mirror.

In an illustrative embodiment, the telescope shown in FIG3 adopts the adaptive optical system provided by the embodiment of the present disclosure to overcome the influence of atmospheric disturbances. The wavefront controller converts the wavefront distortion obtained by the wavefront sensor into a control signal for the wavefront corrector, thereby realizing closed-loop control of the adaptive optical system. Each driving column of the wavefront corrector (deformable mirror) executes the control command of the wavefront controller to extend or contract, and the mirror follows the extension or contraction of each driving column to adjust the surface shape of the mirror, thereby improving the imaging quality of the telescope.

The deformable mirror according to the embodiment of the present disclosure can also be used in laser nuclear fusion systems to increase laser intensity, reduce bit error rates in space optical communication systems, and be used in extreme adaptive optics systems to detect extrasolar planets, etc.

So far, the embodiments of the present disclosure have been described in detail in conjunction with the accompanying drawings. It should be noted that the implementation methods not shown or described in the drawings or the body of the specification are all forms known to ordinary technicians in the relevant technical field and are not described in detail. In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and ordinary technicians in the field can simply change or replace them.

Based on the above description, those skilled in the art should have a clear understanding of the deformable mirror and adaptive optical system provided by the present disclosure.

In summary, the present disclosure provides a deformable mirror that can achieve a large stroke and high precision of the deformable mirror. By constructing a numerical model to design the deformable mirror and preparing the mirror surface through micro-nano processing technology, the surface shape of the mirror surface can be adjusted to a large extent and accurately to improve the imaging quality.

It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only reference directions of the drawings and are not intended to limit the scope of protection of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure, and the shapes and sizes of the components in the drawings do not reflect the actual size and proportion, but only illustrate the contents of the embodiments of the present disclosure.

Unless otherwise indicated, the numerical parameters in this specification and the appended claims are approximate values and can vary according to the desired properties obtained through the content of the present disclosure. Specifically, all numbers used in the specification and claims to express the content of the composition, reaction conditions, etc., should be understood to be modified by the term "about" in all cases. In general, the meaning of the expression is to include a variation of ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments by a specific number.

The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., to modify the corresponding elements, do not themselves mean that the elements have any ordinal numbers, nor do they represent the order of one element and another element, or the order in the manufacturing method. The use of these ordinal numbers is only used to clearly distinguish a component with a certain name from another component with the same name.

In addition, unless the steps are specifically described or must occur in sequence, the order of the above steps is not limited to the above list, and can be changed or rearranged according to the required design. And the above embodiments can be mixed and matched with each other or with other embodiments based on design and reliability considerations, that is, the technical features in different embodiments can be freely combined to form more embodiments.

The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims (10)

1. A deformable mirror comprising:

A base (1);

A plurality of drive columns (2) arranged vertically in an array on the base, each of the drive columns (2) comprising: a plurality of piezoelectric drivers (21) axially stacked, each of the piezoelectric drivers (21) being configured to lengthen or contract in an axial direction in response to an external control signal, so that each of the driving posts (2) lengthens or contracts in the axial direction; and

-A mirror (3) arranged on each of said drive posts (2) and configured to vary the angle of reflection of externally input signal light at the junction of said mirror and each of said drive posts (2) following extension and/or contraction of each of said drive posts (2).

2. Deformable mirror according to claim 1, wherein each of the driving posts (2) further comprises:

A housing (22) covering both sides of the piezoelectric driver (21) to form an elastic serration structure having a preload force to reduce a resistance of extension of the piezoelectric driver (21) in an axial direction and to improve rigidity of the driving post (2),

Preferably, the mirror surface (3) is circular, the ratio of the diameter to the thickness of the mirror surface (3) is not more than 500,

Preferably, the manufacturing process of the mirror surface (3) comprises the following steps:

Grinding the substrate to enable the surface shape of the ground substrate to be within 10 wavelengths of the signal light;

performing magnetorheological modification on the ground substrate to enable the surface shape of the modified substrate to be within 1 wavelength of the signal light;

and (3) performing ion beam polishing on the modified substrate to enable the surface shape of the polished substrate to be within 0.01 wavelength of the signal light, thereby obtaining the mirror surface (3).

3. Deformable mirror according to claim 2, wherein an isolating block (23) is provided between two housings (22) covering two adjacent piezoelectric drivers (21) of each driving post (2), electrically isolating two adjacent piezoelectric drivers (21) of each driving post (2).

4. A deformable mirror according to claim 3, wherein two ends of the housing (22) facing the mirror surface (3) and the base (1) are respectively provided with a cushion block (24), and the bottom of the housing (22) is screwed or adhered to the base (1) through the cushion blocks (24).

5. The deformable mirror of claim 4, further comprising:

And a plurality of joints (4) which are arranged on the driving column (2) through cushion blocks (24) at the top of each shell (22) and are flexibly connected with the mirror surface (3).

6. Deformable mirror according to claim 5, wherein the coefficient of thermal expansion of the joint (4) is equal or similar to the coefficient of thermal expansion of the mirror surface (3).

7. Deformable mirror according to claim 5, wherein the joint (4) is spherical, hemispherical or ellipsoidal in its point of termination with the mirror surface (3).

8. Deformable mirror according to claim 2, wherein the thermal expansion coefficient of the housing (22) is lower than the thermal expansion coefficient of the piezoelectric driver (21) to reduce stroke disturbances of the housing (22) for extension or contraction of the piezoelectric driver (21).

9. Deformable mirror according to any one of claims 1-8, wherein the upper and lower surfaces of the mirror surface (3) are coated with reflective films to increase the reflectivity of the mirror surface (3).

10. An adaptive optics system, comprising:

the deformable mirror of any one of claims 1-9 for correcting wavefront aberration of incident signal light;

A wavefront detector adapted to detect wavefront aberration of the signal light; and

And the wavefront controller is suitable for outputting a control signal according to the measurement result of the wavefront detector to control the extension and/or contraction of the driving column of the deformable mirror.