Deformable mirror assembly and two-dimensional optical system

Abstract

The invention provides a deformable mirror assembly comprising a deformable mirror body, the back of which is provided with a telescopic piezoelectric actuator comprising a plurality of linearly arranged actuating units; the cushion block is arranged on the back surface of the deformable mirror body; the control system is used for providing actuating alternating current voltage for the telescopic piezoelectric actuator, so that sinusoidal vibration of different actuating units adopts random amplitude and random phase; the maximum peak-valley amplitude, caused by sinusoidal vibration, of the mirror surface of the deformable mirror body overcomes the Rayleigh criterion, the periodicity of the spatial frequency is destroyed through the randomness of the phase of the actuating unit, and therefore homogenization of light beam speckles is achieved when the deformable mirror body is used for light beam deflection. The invention also provides a corresponding two-dimensional optical system. According to the deformable mirror assembly, the speckle uniformity in the imaging process is improved, and the influence of speckles is reduced.

Description

Technical Field

[0001] The present invention relates to a deformable mirror assembly and a two-dimensional optical system for realizing high-frequency surface modulation, and specifically to the design, device realization, piezoelectric element arrangement design and control scheme of a grazing-incidence piezoelectric actuator mirror used in X-ray, ultraviolet and other wavebands. Background Art

[0002] Compared with the third-generation synchrotron radiation sources, new large-scale advanced light sources, such as X-ray free electron lasers (XFELs) and fourth-generation synchrotron radiation facilities, provide significantly enhanced brightness and coherence. For example, high-gain FELs operating in self-amplified spontaneous emission (SASE) mode can produce coherent X-ray pulses with gigawatt-level power and femtosecond time intervals. These technological advances have greatly promoted a series of X-ray technologies, including high-resolution full-field imaging, time-resolved imaging, scanning coherence imaging, projection holography, spectroscopy, etc., and promoted the development of cutting-edge scientific research.

[0003] However, the increased coherence of the beam also introduces speckle, a granular or noisy pattern produced by the interference of coherent wavefronts with the uneven surfaces of optical components. Speckle introduces noise and reduces the signal-to-noise ratio, thereby affecting image quality, contrast and resolution, especially in diffraction-limited and phase-contrast imaging. In addition, speckle may also affect the accuracy of X-ray spectra by changing the intensity distribution across the spectrum. The short and intense X-ray pulses generated by XFELs are particularly sensitive to speckle, and the pulse fluctuations caused by speckle may affect the reliability of time-resolved studies. Therefore, solving the speckle problem is crucial to further optimize and advance the application of X-rays in scientific research.

[0004] In order to reduce the impact of speckle, a variety of strategies have been proposed and applied in visible light, including the use of mobile diffusers, changing the polarization of the beam, using multiple beams with different angles or wavelengths, and deformable mirrors as part of the optical decoherence scheme. In the field of visible light projection, deformable mirrors play an important role in reducing speckle noise during imaging. These mirrors are composed of multiple actuators, each of which can independently manipulate the mirror surface to cause the desired deformation and correct the wavefront aberration.

[0005] In short-wavelength optics such as X-rays, wavefront modulation requires higher surface control accuracy. In the X-ray field, deformable mirrors have been successfully used in diffraction-limited focusing systems to achieve perfect wavefronts and compensate for wavefront errors. Due to the use of actuators operating in bimorph mode, the response time of such mirrors is relatively slow. For the decoherence requirements of the beam, very high mirror vibration frequencies are required to meet the frequency range of MHz for synchrotron beams and the high repetition rates of hundreds of kilohertz (kHz) for XFELs.

[0006] Based on this, it is necessary to develop a deformable mirror for realizing high-frequency surface modulation, which can improve the uniformity of speckle during imaging and allow the speckle of coherent light beams to be destroyed under dynamic mirror conditions to reduce the influence of speckle. Summary of the invention

[0007] The object of the present invention is to provide a deformable mirror assembly and a two-dimensional optical system to improve the uniformity of speckle during imaging and reduce the influence of speckle.

[0008] In order to achieve the above-mentioned purpose, the present invention provides a deformable mirror assembly, comprising: a deformable mirror body, a telescopic piezoelectric actuator is provided on the central meridian of the back side of the deformable mirror body, and the telescopic piezoelectric actuator includes a plurality of linearly arranged actuating units; a pad, which is provided on the back side of the deformable mirror body, so that one side of the telescopic piezoelectric actuator is bonded to the plane provided by the pad, and the other side is bonded to the back side of the deformable mirror body; and a control system, the control system is used to provide an actuating AC voltage to the telescopic piezoelectric actuator to control the sinusoidal vibration of different actuating units to adopt random amplitude and random phase; wherein the peak-to-valley maximum amplitude of the mirror surface of the deformable mirror body caused by the sinusoidal vibration overcomes the Rayleigh criterion, and the periodicity of the spatial frequency is destroyed by the randomness of the phase of the actuating unit, thereby achieving homogenization of the beam speckle when the deformable mirror body is used for beam deflection.

[0009] The actuating unit of the telescopic piezoelectric actuator adopts a piezoelectric ceramic with a laminated structure, and its vibration frequency is continuously adjustable, the maximum vibration frequency reaches kilohertz to megahertz, and the maximum peak-to-valley amplitude is in the range of hundreds of nanometers to micrometers.

[0010] The peak-to-valley maximum amplitude of the mirror surface of the deformable mirror body overcomes the Rayleigh criterion, which means that the minimum peak-to-valley maximum amplitude Δd allowed by the mirror surface of the deformable mirror body satisfies: 2kΔdsinθ>π / 2, wherein k=2π / λ is the wave vector, λ is the wavelength of light incident on the deformable mirror body, Δd is the minimum peak-to-valley maximum amplitude allowed by the mirror surface of the deformable mirror body, and θ is the grazing incidence angle.

[0011] Preferably, the amplitude and phase of the actuating AC voltage of each actuating unit are completely random.

[0012] Preferably, the phase of the actuating AC voltage of each actuating unit is preset, and the preset phase distribution is obtained in the following manner: the actuating units are grouped by treating a specified number of adjacent actuating units as an actuating unit group; in each actuating unit group, a maximum phase difference is maintained between adjacent actuating units, and a random phase difference is maintained between different actuating unit groups, so as to destroy the periodicity of the spatial frequency through the randomness of the phase of the actuating unit group; the number of actuating units in each actuating unit group is determined according to the requirements of the spatial frequency.

[0013] The back of the deformable mirror body is provided with long flat-plate piezoelectric actuators arranged along the length direction of the mirror on both sides of the central meridian of the back of the deformable mirror body; the control system provides a DC voltage to the flat-plate piezoelectric actuator so that the displacement of the flat-plate piezoelectric actuator is stabilized at a fixed value to adjust the overall curvature of the mirror surface of the deformable mirror body.

[0014] The deformable mirror assembly also includes a base plate and a clamping mechanism, and the cushion block is supported on the base plate through a three-point support structure; the clamping mechanism is fixed on the four sides of the base plate, and is used to lock and fix the deformable mirror body and the cushion block on the base plate.

[0015] The clamping mechanism has adjustment hinges at both ends and both sides of the deformable mirror body.

[0016] The telescopic piezoelectric actuator is arranged on the central meridian of the back side of the deformable mirror body, and an optical reflective film is provided on the central meridian of the front side of the deformable mirror body; and / or the material of the deformable mirror body is single crystal silicon and the thickness is less than 5 mm; and / or the material of the pad is stainless steel; and / or the roughness Ra of the upper surface of the pad is 0.03~0.005μm, and the flatness is 0.005, and the roughness Ra of the lower surface is 0.03~0.005μm, and the flatness is 0.01; and / or the pad is provided with a chamfer.

[0017] On the other hand, the present invention provides a two-dimensional optical system, which includes a light source arranged in sequence along the optical path, a deformable mirror for deflecting the light beam in the vertical direction, a deformable mirror for deflecting the light beam in the horizontal direction, a slit device, and a surface detector; the deformable mirror for deflecting the light beam in the vertical direction and the deformable mirror for deflecting the light beam in the horizontal direction are both based on the deformable mirror assembly described above.

[0018] The deformable mirror assembly of the present invention adopts linearly arranged telescopic piezoelectric actuators to replace the bimorph piezoelectric actuators commonly used in the X-ray field. A control system is used to provide an actuating AC voltage to the actuator to control the sinusoidal vibrations of different actuating units with random amplitudes and random phases. The peak-to-valley maximum amplitude of the mirror surface of the deformable mirror body caused by the sinusoidal vibration overcomes the Rayleigh criterion, and the periodicity of the spatial frequency is destroyed by the randomness of the phase of the actuating unit, thereby achieving homogenization of the beam speckle when the deformable mirror body is used for beam deflection.

[0019] In addition, the two-dimensional optical system of the present invention eliminates speckle, weakens coherence and homogenizes the light field by adding a grazing-incidence deformable mirror assembly in the optical path, and generates high-frequency sinusoidal vibrations with random amplitude and random phase for the surface shape, thereby artificially destroying the speckle of a single pulse coherent light beam, differentiating the morphology of speckles of multiple pulse coherent light beams, and ultimately achieving a homogenization effect of the speckle within the imaging time, thereby realizing the so-called decoherence effect.

[0020] In summary, the present invention can effectively destroy the coherence of X-rays and reduce the generation of speckles through the above technical solutions, thereby significantly improving the uniformity and quality of imaging. At the same time, the method of the present invention achieves high-precision and wide-range modulation of the mirror shape through precise piezoelectric actuator control and mirror posture adjustment, meeting the strict requirements of homogenized optical imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a principle diagram of the optical path of a typical usage scenario of the deformable mirror assembly of the present invention.

[0022] Figure 2 Schematic diagram of the overall structure of a deformable mirror assembly according to an embodiment of the present invention.

[0023] Figure 3 Yes Figure 2 The structural exploded diagram of the deformable mirror mechanical part of the deformable mirror assembly is shown.

[0024] Figure 4 Yes Figure 2 The deformable mirror body and piezoelectric ceramic distribution diagram of the deformable mirror assembly are shown.

[0025] Figure 5 Yes Figure 2 A rear view of the deformable mirror body of the deformable mirror assembly is shown, which shows the piezoelectric actuator arrangement structure.

[0026] Figure 6 This is a test result diagram of the mirror height obtained by two telescopic piezoelectric actuators (located at the edge and middle area respectively) under different voltage actuation.

[0027] Figure 7This is a graph of measured data of the high-frequency vibration of the mirror above a telescopic piezoelectric actuator within 0.01 seconds.

[0028] Figure 8 This is a comparison of the vibration spectra of telescopic piezoelectric actuators in different channels of the mirror under 50V and 50kHz signal excitation.

[0029] Fig. 9 This is a simulation diagram of the double-slit interference experiment of light beams under different deformation amplitudes.

[0030] Fig.10 This is the spot image after being modulated by the deformable KB mirror and homogenized after multiple acquisitions. From left to right, the imaging is acquired after 1, 5, 100 and 500 deformations respectively. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with specific examples. It should be understood that the following examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0032] The present invention provides a deformable mirror assembly, which is used to realize high-frequency surface modulation, thereby improving the uniformity of speckles in an imaging process and reducing the influence of speckles. Figure 1 This is a light path diagram of a typical use scenario of the deformable mirror assembly of the present invention, which shows a two-dimensional optical system implemented based on the deformable mirror assembly of the present invention, wherein the two-dimensional optical system includes two deformable mirrors arranged along the direction of the light path, and the two deformable mirrors are respectively used for deflecting the light beam in the vertical and horizontal directions (that is, the central meridians of the two deformable mirrors are respectively perpendicular to the vertical plane and the horizontal plane, so that the light beam is deflected in the vertical plane and the horizontal plane respectively), and both are used to achieve high-frequency surface modulation. Therefore, by orthogonally arranging two such deformable mirror assemblies that achieve high-frequency surface modulation, decoherence, speckle elimination and image homogenization of the imaging of the two-dimensional optical system can be achieved.

[0033] like Figure 1 As shown, in this embodiment, the two-dimensional optical system is used for the X-ray band, and specifically includes an X-ray light source 101 arranged in sequence along the optical path of the X-ray 102, a deformable mirror 103 for deflecting the light beam in the vertical direction, a deformable mirror 104 for deflecting the light beam in the horizontal direction, a slit device 105, and a surface detector 106.

[0034] Among them, the X-ray light source 101 is preferably an undulator light source of synchrotron radiation or free electron laser. The slit device 105 is a double-slit or single-slit device, which can be used for beam coherence measurement. Except for the difference in the clamping mechanism caused by the placement direction of the mirror, the internal structures (such as actuators and power supplies) of the deformable mirrors 103 and 104 are basically the same. The deformable mirrors 103 and 104 are both deformable mirror assemblies described in detail below, which realize the homogenization of beam speckles when used for beam deflection.

[0035] In one embodiment, the deformable mirrors 103, 104 are large-size KB grazing incidence mirrors.

[0036] like Figure 2 As shown, the deformable mirror assembly includes a deformable mirror mechanical part 201 and a control system 203 connected to the deformable mirror mechanical part 201 via a control cable 202. Figure 2 and Figure 3 As shown, the deformable mirror mechanical part 201 includes a deformable mirror body 301 and a fixing component of the deformable mirror body 301 .

[0037] The fixing assembly of the deformable mirror body 301 includes a pad 302 arranged on the back of the deformable mirror body 301, a base plate 303 and a clamping mechanism, wherein the pad 302 is supported on the base plate 303 by a three-point support structure; the clamping mechanism is fixed on all sides of the base plate 303, and is used to lock and fix the deformable mirror body 301 and the pad 302 on the base plate 303.

[0038] The three-point support structure includes semi-buried steel balls with a radius of 5 mm at three points. The three-point support positioning is a mature market practice with accurate positioning, good repeatability, and easy control of the parallelism of the two planes. The lower surface of the pad 302 is provided with a cone, a V groove and a plane corresponding to the three-point support structure to keep the pad absolutely stable.

[0039] In addition, the clamping mechanism clamps the two ends and both sides of the deformable mirror body 301, which can achieve push bending with sub-micron precision, and realize the correction of micron-level deformation of the thin deformable mirror body 301 caused by processing or stress. Specifically, the clamping mechanism has several adjustment hinges at both ends and both sides of the deformable mirror body 301, which are used to fix or fine-tune a part of the mirror position, so as to apply pressure on both ends of the deformable mirror body 301 to form a convex shape and pressure on both sides to form a concave shape, so that the deformable mirror body 301 produces an overall bending effect to prevent the light spot from being excessively divergent or focused. The adjustment hinge can be located at the two end points of the mirror along the length direction, can be one or more at the midline; or can be located at the midpoint of the mirror length along the wide position.

[0040] The bottom plate 303 is mounted on any adjustment mechanism so that the deformable mirror assembly is located in the optical path; in this embodiment, the bottom plate 303 is mounted on a mirror body posture adjustment mechanism, and the pad 302 is connected to the mirror body posture adjustment mechanism through the bottom plate 303 to achieve the adjustment of the projection angle, light cutting, roll angle and other dimensions of the reflector. In other embodiments, the clamping mechanism and the mirror body posture adjustment mechanism can be two different mechanisms, or two functions of the same mechanism.

[0041] In this embodiment, the material of the deformable mirror body 301 is single crystal silicon and the thickness is less than 5 mm, so as to ensure that the deformable mirror body 301 can have a large driving deformation and response frequency. After mirror polishing, the mirror roughness of the front surface of the deformable mirror body 301 is better than 0.5 nm, and the back surface of the deformable mirror body 301 is also properly polished to ensure close adhesion with the piezoelectric actuator 305.

[0042] In the present invention, the material of the pad 302 is stainless steel, and the thickness of the pad 302 is usually several tens of millimeters, so that the pad 302 and the very thin deformable mirror body 301 are fixed in the clamping mechanism together to maintain its stability during high-frequency vibration. The stainless steel pad 302 needs to be very flat to ensure that when the deformable mirror body 301 is fixed, the deformable mirror body 301 will not be deformed due to the additional gravity or deformation of the pad 302. The pad 302 is made of stainless steel and has a thickness of not less than 10mm. The upper and lower surfaces of the pad 302 are ultra-precision machined, and the roughness Ra of the upper surface is 0.03-0.005μm, the surface finish is above level 8, and the flatness is 0.005. The roughness Ra of the lower surface is 0.03-0.005μm, and the flatness is 0.01.

[0043] like Figure 4 As shown, an optical reflective film 304 is provided on the central meridian of the front side of the deformable mirror body 301, and a piezoelectric actuator 305 is provided on the back side of the deformable mirror body 301. Thus, the piezoelectric actuator 305 is located between the back side of the deformable mirror body 301 and the cushion block 302, and one side of the piezoelectric actuator 305 is bonded to the plane provided by the cushion block 302, and the other side is bonded to the back side of the deformable mirror body 301.

[0044] The optical reflective film 304 is used to make the light beam obtain a reflectivity of better than 90% at about 10 keV. The optical reflective film 304 is located on the central meridian of the front of the deformable mirror body 301. The material of the optical reflective film 304 can be selected from but not limited to gold, rhodium, and platinum.

[0045] See also Figure 2 and Figure 3In this embodiment, one or both sides of the upper surface of the pad 302 have chamfers, and the width of the upper surface of the pad 302 with chamfers is at least 1.2 times the width of the piezoelectric actuator. The chamfers are used to facilitate the installation and wiring of the piezoelectric actuator 305.

[0046] like Figure 5 As shown, in this embodiment, the piezoelectric actuator 305 on the back of the deformable mirror body 301 can be divided into two categories, including a telescopic piezoelectric actuator 3051 arranged along the central meridian of the back of the deformable mirror body 301 and a long flat-plate piezoelectric actuator 3052 arranged along the mirror length direction on both sides of the central meridian of the back of the deformable mirror body 301. The telescopic piezoelectric actuator 3051 plays the role of pushing and pulling the mirror surface to generate high-frequency vibration. The actuating unit of the telescopic piezoelectric actuator 3051 is preferably a piezoelectric ceramic with a laminated structure, which realizes a telescopic design effect and can achieve an amplitude of hundreds of nanometers or even micrometers and a vibration frequency of at least kilohertz. The flat-plate piezoelectric actuator 3052 is used to correct the overall curvature of the mirror to prevent the light spot from being excessively divergent or focused, and it is preferably a flat-plate piezoelectric ceramic.

[0047] In this embodiment, the telescopic piezoelectric actuator 3051 is connected to a high-power AC control power supply to be driven thereby, and the flat piezoelectric actuator 3052 is connected to a high-voltage DC power supply to be driven thereby.

[0048] In this embodiment, the telescopic piezoelectric actuator 3051 includes a plurality of linearly arranged actuating units, which are arranged in a row along the center line of the mirror body, for realizing high-frequency surface modulation of the mirror surface. The number of actuating units is 10-30, the side length of each actuating unit is about 10 mm, and the interval between adjacent actuating units is no more than 2 mm. All actuating units of the telescopic piezoelectric actuator 3051 must cover the effective length of the deformable mirror body 301, and the stroke of each actuating unit is in the order of hundreds of nanometers.

[0049] In this embodiment, the deformable mirror body 301, the telescopic piezoelectric actuator 3051 and the cushion block 302 are firmly bonded by epoxy resin glue to form a whole, and then fixed together in the clamping mechanism. The flat piezoelectric actuator 3052 is fixed to the deformable mirror body 301 by epoxy resin and is not connected to the cushion block 302.

[0050] When one end of each actuating unit of the telescopic piezoelectric actuator 3051 is fixed to the back of the deformable mirror body 301, and the other end is fixed to the pad 302 with good rigidity, and different voltages are applied to each actuating unit of the telescopic piezoelectric actuator 3051, a telescopic effect will be generated independently, thereby driving the mirror surface of the deformable mirror body 301 to produce a convex and concave effect, and a stacked piezoelectric effect can be generated within the range of each electrode of the telescopic piezoelectric actuator 3051.

[0051] The flat piezoelectric actuator 3052 disposed on the back of the deformable mirror body 301 adjusts the overall curvature of the mirror surface of the deformable mirror body 301, so that the entire mirror surface is bent along the meridian. In other embodiments, the flat piezoelectric actuator 3052 can be omitted.

[0052] The control system 203 is used to provide an actuating AC voltage to the telescopic piezoelectric actuator 3051 to control the sinusoidal vibration of different actuating units to adopt random amplitude and random phase. The peak-to-valley maximum amplitude of the mirror surface of the deformable mirror body 301 caused by the sinusoidal vibration overcomes the Rayleigh criterion, and the random phase of different actuating units destroys the periodicity of the spatial frequency, thereby achieving the homogenization of the beam speckle when the deformable mirror body is used for beam deflection.

[0053] In addition, the control system 203 provides a DC voltage to the flat piezoelectric actuator 3052 so that the displacement of the flat piezoelectric actuator 3052 is stabilized at a fixed value, so as to adjust the overall curvature of the mirror surface of the deformable mirror body 301 .

[0054] The peak-to-valley maximum amplitude of the mirror surface of the deformable mirror body 301 overcomes the Rayleigh criterion, which means that the minimum peak-to-valley maximum amplitude Δd allowed by the mirror surface of the deformable mirror body satisfies:

[0055] 2kΔdsinθ>π / 2, where k=2π / λ is the wave vector, λ is the wavelength of the light incident on the deformable mirror body, Δd is the minimum allowable peak-to-valley maximum amplitude of the mirror surface of the deformable mirror body, and θ is the grazing incidence angle. That is, the peak-to-valley maximum amplitude of the mirror surface of the deformable mirror body 301 can be set according to the relationship between the incident light wavelength and the mirror grazing incidence. The actuating AC voltage is substantially proportional to the peak-to-valley maximum amplitude of the telescopic piezoelectric actuator 3051.

[0056] Therefore, under the drive of the control system, each actuator unit performs sinusoidal vibration within its maximum peak-to-valley amplitude, and the phase of the actuator AC voltage of different actuator units is random, so as to destroy the periodicity of the spatial frequency, so that the mirror surface shape of the deformable mirror body 301 produces a random vibration effect, thereby achieving the homogenization of the beam speckle when the deformable mirror body 301 is used for beam deflection.

[0057] In this embodiment, the vibration frequency of the telescopic piezoelectric actuator 3051 is continuously adjustable, the maximum vibration frequency reaches kilohertz to megahertz, and the maximum peak-to-valley amplitude is hundreds of nanometers to micrometers.

[0058] In one embodiment, the amplitude and phase of the actuating AC voltage of each actuating unit are completely random.

[0059] In another embodiment, the phase of the actuating AC voltage of each actuating unit is preset, and the preset phase distribution is obtained in the following manner: the actuating units are grouped by taking a specified number of adjacent actuating units as an actuating unit group; in each actuating unit group, the maximum phase difference is maintained between adjacent actuating units, and there is a random phase difference between different actuating unit groups to destroy the periodicity of the spatial frequency. Thus, the phase relationship between the actuating units can be destroyed after a few actuating units are separated, so that there is no significant phase correlation between these actuating units. The number of actuating units in each actuating unit group can be determined according to the requirements of the spatial frequency. For example, if it is believed that the spatial frequency lower than one tenth of the mirror length will have a greater impact on the spatial coherence, then the number of actuating units in the actuating unit group is the total number of actuating units divided by 10.

[0060] The phase difference between electrodes of different actuation units may be fixed or may vary with time.

[0061] In this embodiment, the control system 203 includes a high-power AC control power supply and a high-voltage DC power supply, and the frequency of the AC control power supply can reach up to hundreds of kilohertz or even megahertz. In some embodiments, since the flat piezoelectric actuator 3052 can be omitted, the DC power supply can be omitted.

[0062] In this embodiment, the control system 203 includes a main control part, a power transfer part, and a power supply part. The main control part is composed of a control chip and peripheral circuits, a control screen, a DAC control, and a network port communication; the power transfer part includes power transfer, heat dissipation, and a chassis; and the power supply part is a high-power AC control power supply and a high-voltage DC power supply.

[0063] Device effect test:

[0064] The overall surface characteristics of the optical reflective film 304 surface under the action of static voltage are tested using a Fizeau interferometer. The test results of the mirror heights of the two telescopic piezoelectric actuators (located at the edge and the middle area, respectively) under different voltage actuation are shown in FIG. Figure 6 shown. Figure 6 In the process, actuators at different positions push the mirrors at corresponding positions to undergo Gaussian-like surface deformation under different voltage actuation. The height of the mirrors after surface deformation is between tens and hundreds of nanometers. Figure 6 In the figure, 16 and 24 marked in the upper right corner refer to the actuator numbers. The two actuators are located at 35mm and 80mm of the mirror respectively. 17V and 33V refer to the maximum amplitude values ​​of the actuating voltage.

[0065] The high-frequency vibration of the mirror is tested based on a laser interferometer, and the data acquisition frequency can reach up to MHz. The test results are as follows: Figure 7and Figure 8 shown. Figure 7 It is the high-frequency vibration data of the mirror above a telescopic piezoelectric actuator measured within 0.01 seconds. Its horizontal axis represents the vibration of the mirror above the actuator. Figure 7 The results demonstrate that ultra-high frequency surface vibration can be measured in a very short time, proving the effectiveness of the relevant device. Figure 8 The comparison results of vibration spectra of telescopic piezoelectric actuators in different channels of the mirror under 50V and 50kHz signal excitation are shown. Figure 8 It is proved that 50kHz vibration can be achieved in different positions, but the vibration amplitude of the response is different due to different positions. Figure 8 In the figure, ch13, ch19 and ch25 marked in the upper right corner are the actuator numbers, and 18nm, 39nm and 48nm refer to the maximum amplitude of the height measured under 50V conditions.

[0066] The X-ray online test simulation results of the whole system are as follows: Figure 9-10 shown. Fig. 9 In the figure, the 200 sampling average refers to the point obtained by taking the average value after 200 samplings, and the following 2-18nm refers to the local height peak and valley value of the mirror given by the telescopic piezoelectric actuator. Fig. 9 It is shown that for random vibrations with different maximum amplitudes, the interference fringes displayed by the reflected light after double-slit interference are significantly modulated. When the maximum amplitude overcomes the requirements of the Rayleigh criterion, the visibility of the interference fringes is significantly reduced and the fringes almost disappear. For a mirror with a maximum peak-to-valley (PV) amplitude of 18nm, after hundreds of samplings (corresponding to the effect of beam repetition rate), its speckle visibility and contrast can be reduced to 0.18 and 0.04 respectively. Fig.10 For the simulated speckle two-dimensional imaging, it can be observed that with the increase in the number of sampling times, the uniformity of the image is significantly improved and the speckle phenomenon gradually disappears, which significantly improves the quality of the imaging experiment.

[0067] The deformable mirror assembly of the present invention adopts linearly arranged telescopic piezoelectric actuators to replace the actuators of the dual-crystal piezoelectric film mode commonly used in the X-ray field, and utilizes a control system to provide an actuating AC voltage to the actuator to control the sinusoidal vibrations of different actuating units to adopt random amplitudes and random phases. The peak-to-valley maximum amplitude of the mirror surface of the deformable mirror body caused by the sinusoidal vibration overcomes the Rayleigh criterion, and the periodicity of the spatial frequency is destroyed by the randomness of the phase of the actuating unit, thereby achieving homogenization of the beam speckle when the deformable mirror body is used for beam deflection.

[0068] In addition, the two-dimensional optical system of the present invention eliminates speckle, weakens coherence and homogenizes the light field by adding a grazing-incidence deformable mirror assembly in the optical path, and generates high-frequency sinusoidal vibrations with random amplitude and random phase for the surface shape, thereby artificially destroying the speckle of a single pulse coherent light beam, differentiating the morphology of speckles of multiple pulse coherent light beams, and ultimately achieving a homogenization effect of the speckle within the imaging time, thereby realizing the so-called decoherence effect.

[0069] In summary, the present invention can effectively destroy the coherence of X-rays and reduce the generation of speckles through the above technical solutions, thereby significantly improving the uniformity and quality of imaging. At the same time, the method of the present invention achieves high-precision and wide-range modulation of the mirror shape through precise piezoelectric actuator control and mirror posture adjustment, meeting the strict requirements of homogenized optical imaging.

[0070] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiments of the present invention can also be modified in various ways. All simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A deformable mirror assembly, characterized in that: include: A deformable mirror body, on the back of which a telescopic piezoelectric actuator is provided, wherein the telescopic piezoelectric actuator comprises a plurality of linearly arranged actuating units; A pad is provided on the back of the deformable mirror body, so that one side of the telescopic piezoelectric actuator is bonded to the plane provided by the pad, and the other side is bonded to the back of the deformable mirror body; as well as A control system is used to provide an actuating AC voltage to a telescopic piezoelectric actuator to control the sinusoidal vibrations of different actuating units to adopt random amplitudes and random phases; wherein the peak-to-valley maximum amplitude of the mirror surface of the deformable mirror body caused by the sinusoidal vibration overcomes the Rayleigh criterion, and the periodicity of the spatial frequency is destroyed by the randomness of the phase of the actuating unit, thereby achieving homogenization of the beam speckle when the deformable mirror body is used for beam deflection.

2. The deformable mirror assembly according to claim 1, characterized in that: The actuating unit of the telescopic piezoelectric actuator adopts a piezoelectric ceramic with a laminated structure, and its vibration frequency is continuously adjustable, the maximum vibration frequency reaches kilohertz to megahertz, and the maximum peak-to-valley amplitude is in the range of hundreds of nanometers to micrometers.

3. The deformable mirror assembly according to claim 1, characterized in that: The peak-to-valley maximum amplitude of the mirror surface of the deformable mirror body overcomes the Rayleigh criterion, which means that the minimum peak-to-valley maximum amplitude Δd allowed by the mirror surface of the deformable mirror body satisfies: 2kΔdsinθ>π / 2, Among them, k = 2π / λ is the wave vector, λ is the wavelength of the light incident on the deformable mirror body, Δd is the minimum peak-to-valley maximum amplitude allowed by the mirror surface of the deformable mirror body, and θ is the grazing incidence angle.

4. The deformable mirror assembly according to claim 1, characterized in that: The amplitude and phase of the actuating AC voltage of each actuating unit are completely random.

5. The deformable mirror assembly according to claim 1, characterized in that: The phase of the actuating AC voltage of each actuating unit is preset, and the preset phase distribution is obtained in the following manner: the actuating units are grouped by treating a specified number of adjacent actuating units as an actuating unit group; in each actuating unit group, the maximum phase difference is maintained between adjacent actuating units, and there is a random phase difference between different actuating unit groups, so as to destroy the periodicity of the spatial frequency through the randomness of the phase of the actuating unit group; the number of actuating units in each actuating unit group is determined according to the requirements of the spatial frequency.

6. The deformable mirror assembly according to claim 1, characterized in that: The back of the deformable mirror body is provided with long strip-shaped flat-plate piezoelectric actuators arranged along the length direction of the mirror on both sides of the central meridian of the back of the deformable mirror body; The control system provides a DC voltage to the flat piezoelectric actuator, so that the displacement of the flat piezoelectric actuator is stabilized at a fixed value, so as to adjust the overall curvature of the mirror surface of the deformable mirror body.

7. The deformable mirror assembly according to claim 1, characterized in that: It also includes a base plate and a clamping mechanism, wherein the cushion block is supported on the base plate through a three-point support structure; the clamping mechanism is fixed on the four sides of the base plate, and is used to lock and fix the deformable mirror body and the cushion block on the base plate.

8. The deformable mirror assembly according to claim 7, characterized in that: The clamping mechanism has adjustment hinges at both ends and both sides of the deformable mirror body.

9. The deformable mirror assembly according to claim 1, characterized in that: The telescopic piezoelectric actuator is arranged on the central meridian of the back side of the deformable mirror body, and an optical reflective film is arranged on the central meridian of the front side of the deformable mirror body; and / or The deformable mirror body is made of single crystal silicon and has a thickness of less than 5 mm; and / or The material of the cushion block is stainless steel; and / or The upper surface of the pad has a roughness Ra of 0.03 to 0.005 μm and a flatness of 0.005, and the lower surface has a roughness Ra of 0.03 to 0.005 μm and a flatness of 0.01; and / or The cushion block is provided with a chamfer.

10. A two-dimensional optical system, characterized in that: It includes a light source arranged in sequence along the optical path, a deformable mirror for deflecting the light beam in the vertical direction, a deformable mirror for deflecting the light beam in the horizontal direction, a slit device, and a surface detector; the deformable mirror for deflecting the light beam in the vertical direction and the deformable mirror for deflecting the light beam in the horizontal direction are both deformable mirror assemblies according to any one of claims 1-9.

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