Anamorphic mirror assembly and two-dimensional optical system

Abstract

The application provides a deformable mirror assembly, comprising: a deformable mirror mirror body, a back surface of which is provided with a telescopic piezoelectric actuator, which comprises a plurality of linearly arranged actuating units; a pad, which is arranged on the back surface of the deformable mirror mirror body; a control system, which is used for providing an actuating alternating voltage to the telescopic piezoelectric actuator, so that the sinusoidal vibration of different actuating units adopts random amplitude and random phase; the peak-to-valley maximum amplitude of the mirror surface of the deformable mirror mirror body caused by the sinusoidal vibration overcomes the Rayleigh criterion, and the periodicity of the spatial frequency is destroyed through the randomness of the phase of the actuating unit, so that the homogenization of the light beam speckle is realized when the deformable mirror mirror body is used for light beam deflection. The application also provides a corresponding two-dimensional optical system. The deformable mirror assembly of the application improves the speckle homogeneity in the imaging process and reduces the influence of the speckle.

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 implementation, piezoelectric element arrangement design and control scheme of a grazing-incidence piezoelectric actuator mirror used in X-ray, ultraviolet and other bands. Background Art

[0002] Compared to 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, offer significantly enhanced brightness and coherence. For example, high-gain FELs operating in self-amplified spontaneous emission (SASE) mode can generate coherent X-ray pulses with gigawatt-level power and femtosecond time intervals. These technological advances have greatly facilitated a range of X-ray techniques, including high-resolution full-field imaging, time-resolved imaging, scanning coherence imaging, projection holography, and spectroscopy, driving the development of cutting-edge scientific research.

[0003] However, the enhanced coherence of the beam also introduces speckle, a granular or noisy pattern caused 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] To reduce the effects of speckle, various strategies have been proposed and applied internationally 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 induce the desired deformation and correct wavefront aberrations.

[0005] In short-wavelength optics, such as X-rays, wavefront modulation requires higher surface control precision. 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, a very high mirror vibration frequency is required to meet the MHz frequency range of synchrotron radiation beams and the high repetition rates of hundreds of kilohertz (kHz) of XFELs.

[0006] Based on this, it is necessary to develop a deformable mirror for achieving high-frequency surface modulation, which can improve the speckle uniformity during the imaging process and allow the speckle of the coherent light beam to be destroyed under dynamic mirror conditions to reduce the impact 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 objectives, 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, the telescopic piezoelectric actuator comprising 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, whose vibration frequency is continuously adjustable, with a maximum vibration frequency reaching kilohertz to megahertz, and a peak-to-valley maximum amplitude 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 by grouping the actuating units 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 random phase difference is provided between different actuating unit groups to destroy the periodicity of the spatial frequency by randomness of the phase of the actuating unit group; the number of actuating units in each actuating unit group is determined according to the requirement of the spatial frequency.

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

[0014] The deformable mirror assembly further comprises a base plate and a clamping mechanism, the cushion block is supported on the base plate through a three-point support structure; the clamping mechanism is fixed around the base plate, and is used for locking and fixing the deformable mirror mirror body and the cushion block on the base plate.

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

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

[0017] In another aspect, the application provides a two-dimensional optical system, which comprises a light source, a deformable mirror for vertical deflection of a light beam, a deformable mirror for horizontal deflection of the light beam, a slit device, and a plane detector arranged in sequence along the light path; the deformable mirror for vertical deflection of the light beam and the deformable mirror for horizontal deflection of the light beam are both according to the deformable mirror assembly described above.

[0018] The deformable mirror assembly of the present application adopts a telescopic piezoelectric actuator arranged in a linear array to replace the actuator of the double-crystal piezoelectric sheet mode commonly used in the field of X-rays, and provides an actuating alternating voltage to the actuator by a control system to control the sinusoidal vibration of different actuating units with random amplitude and random phase. The peak-to-valley maximum amplitude of the mirror surface of the deformable mirror 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, so that the speckle of the light beam is homogenized when the deformable mirror is used for light beam deflection.

[0019] In addition, the two-dimensional optical system of the present application adds a grazing incidence deformable mirror assembly in the optical path, generates high-frequency sinusoidal vibration with random amplitude and random phase for the surface shape, to eliminate speckle, weaken coherence and homogenize the light field, artificially destroy the speckle of a single pulsed coherent light beam, differentiate the shapes of multiple pulsed coherent light beams, and achieve the effect of speckle homogenization in the imaging time, realizing the so-called de-coherence effect.

[0020] In summary, the present application can effectively destroy the coherence of X-rays, reduce the generation of speckle, and significantly improve the imaging uniformity and quality by the above technical solutions. At the same time, the method of the present application realizes high-precision and large-range modulation of the mirror surface shape through precise piezoelectric actuator control and mirror body attitude adjustment, meeting the strict requirements of homogenized optical imaging. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a typical use scenario of the deformable mirror assembly of the present application.

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

[0023] Figure 3 is a schematic diagram of the overall structure of the deformable mirror assembly according to an embodiment of the present application. Figure 2

[0024] Figure 4 is a schematic diagram of the overall structure of the deformable mirror assembly according to an embodiment of the present application. Figure 2

[0025] Figure 5 is a schematic diagram of the overall structure of the deformable mirror assembly according to an embodiment of the present application. Figure 2

[0026] Figure 6 is a schematic diagram of the overall structure of the deformable mirror assembly according to an embodiment of the present application.

[0027] Figure 7 ​​​is a measured data graph of high-frequency vibration of a mirror on a certain telescopic piezoelectric actuator within 0.01 seconds.

[0028] Figure 8 is a comparison result graph of vibration spectrum of telescopic piezoelectric actuators in different channels of a mirror under excitation of a 50-volt and 50-kHz signal.

[0029] Figure 9 is a simulation graph of a light beam double-slit interference experiment under different deformation amplitudes.

[0030] Figure 10 is a light spot graph after deformation KB mirror modulation and multiple collection and homogenization, from left to right, after 1, 5, 100 and 500 times of deformation imaging collection. DETAILED DESCRIPTION

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

[0032] The application provides a deformation mirror assembly for realizing high-frequency surface shape modulation, thereby being capable of improving speckle uniformity in an imaging process and reducing the influence of speckle. Figure 1 is an optical path diagram of a typical use scenario of the deformation mirror assembly of the application, which shows a two-dimensional optical system realized based on the deformation mirror assembly of the application, the two-dimensional optical system including two deformation mirrors arranged along the direction of the optical path, the two deformation mirrors being respectively used for deflection of a light beam in a vertical direction and a horizontal direction (that is, the central meridian of the two deformation mirrors is respectively perpendicular to a vertical plane and a horizontal plane, so that the light beam is deflected in the vertical plane and the horizontal plane, respectively), and both being used for realizing high-frequency surface shape modulation. Thus, by orthogonally arranging two such deformation mirror assemblies realizing high-frequency surface shape modulation, de-coherence, elimination of speckle and homogenization of an image of the two-dimensional optical system can be realized.

[0033] As shown in Figure 1 , in the embodiment, the two-dimensional optical system is used in an X-ray waveband, and specifically includes, in sequence along the direction of the optical path of X-rays 102, an X-ray source 101, a deformation mirror 103 used for deflection of a light beam in a vertical direction, a deformation mirror 104 used for deflection of a light beam in a horizontal direction, a slit device 105, and a plane detector 106.

[0034] The X-ray source 101 is preferably a synchrotron or free electron laser undulator source. The slit device 105 is a double slit or single slit device, which can be used for measuring the coherence of the light beam. The deformable mirrors 103, 104 are basically the same in internal structure (e.g. actuator, power supply) except for the clamping mechanism due to the different orientations of the mirrors. The deformable mirrors 103, 104 are both deformable mirror assemblies as will be described in detail below, which achieve speckle homogenization of the light beam when used for light beam deflection.

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

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

[0037] The fixing assembly of the deformable mirror body 301 comprises a cushion block 302 provided on the back of the deformable mirror body 301, a bottom plate 303 and a clamping mechanism, the cushion block 302 being supported on the bottom plate 303 through a three-point support structure; the clamping mechanism being fixed around the periphery of the bottom plate 303 and being used for locking and fixing the deformable mirror body 301 and the cushion block 302 on the bottom plate 303.

[0038] The three-point support structure comprises three half-buried steel balls with a radius of 5 mm at the three points. The three-point support positioning belongs to a mature market practice, which is accurate and has good repeatability, and the parallelism of the two planes is easy to control. The lower surface of the cushion block 302 is provided with a conical surface, a V-shaped groove and a flat surface corresponding to the three-point support structure, so as to keep the cushion block absolutely stable.

[0039] In addition, the clamping mechanism clamps the two ends and the two sides of the deformable mirror body 301, and can achieve sub-micron precision pushing and bending, and correct the micron-level deformation of the thin deformable mirror body 301 caused by machining or stress. Specifically, the clamping mechanism has a plurality of adjusting hinges at the two ends and the two sides of the deformable mirror body 301, which are used for fixing or fine-tuning a part of the mirror position, so as to give the deformable mirror body 301 a pressure at the two ends for forming a convex surface type and a pressure at the two sides for forming a concave surface type, so that the deformable mirror body 301 produces an overall bending effect to prevent the light spot from being excessively divergent or focused. The adjusting hinges can be located at the two endpoints of the mirror along the length direction, can be one at the middle line, or can be several; or can be located at the middle points of the mirror length along the width position.

[0040] Base plate 303 is mounted on any adjustment mechanism to position the deformable mirror assembly in the optical path. In this embodiment, base plate 303 is mounted on a mirror body posture adjustment mechanism, and pad 302 is connected to the mirror body posture adjustment mechanism via base plate 303 to enable adjustment of the reflector's projection angle, light cutting, roll angle, and other dimensions. In other embodiments, the clamping mechanism and the mirror body posture adjustment mechanism can be two separate mechanisms, or they can serve two functions of the same mechanism.

[0041] In this embodiment, the deformable mirror body 301 is constructed of single-crystal silicon and is less than 5 mm thick, ensuring a large actuation deformation and high response frequency. After polishing, the front surface of the deformable mirror body 301 has a surface roughness better than 0.5 nm. The back surface of the deformable mirror body 301 is also polished to ensure a tight bond with the piezoelectric actuator 305.

[0042] In the present invention, the pad 302 is made of stainless steel and is typically several tens of millimeters thick. This allows the pad 302 to be fixed together with the very thin deformable mirror body 301 in the clamping mechanism, maintaining 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 additional weight or deformation of the pad 302 does not cause additional deformation of the deformable mirror body 301. The pad 302 is made of stainless steel and has a thickness of not less than 10 mm. The upper and lower surfaces of the pad 302 are ultra-precision machined, with a roughness Ra of 0.03 to 0.005 μm on the upper surface, a surface finish of level 8 or higher, and a flatness of 0.005. The lower surface has a roughness Ra of 0.03 to 0.005 μm and a flatness of 0.01.

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

[0044] The optical reflective film 304 is used to achieve a reflectivity of better than 90% at about 10 keV. The optical reflective film 304 is located on the central meridian of the front surface 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 top surface of the spacer 302 are chamfered. The width of the top surface of the spacer 302 with the chamfer is at least 1.2 times the width of the piezoelectric actuator. The chamfer facilitates the installation and wiring of the piezoelectric actuator 305.

[0046] like Figure 5 As shown, in this embodiment, the piezoelectric actuators 305 on the back of the deformable mirror body 301 can be divided into two categories: telescopic piezoelectric actuators 3051 arranged along the central meridian of the back of the deformable mirror body 301, and long, flat-plate piezoelectric actuators 3052 arranged along the length of the mirror on both sides of the central meridian of the back of the deformable mirror body 301. The telescopic piezoelectric actuators 3051 push and pull the mirror surface to generate high-frequency vibration. The actuating unit of the telescopic piezoelectric actuators 3051 preferably utilizes a laminated piezoelectric ceramic structure, achieving a telescopic design effect, capable of achieving amplitudes of hundreds of nanometers or even microns and vibration frequencies of at least kilohertz. The flat-plate piezoelectric actuators 3052 are used to correct the overall curvature of the mirror to prevent excessive divergence or focusing of the light spot, and are preferably constructed of 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 comprises multiple linearly arranged actuating units, arranged in a single row along the centerline of the deformable mirror body, to achieve high-frequency surface modulation of the mirror surface. The number of actuating units ranges from 10 to 30, with each actuating unit having a side length of approximately 10 mm and a spacing of no more than 2 mm between adjacent actuating units. All actuating units of the telescopic piezoelectric actuator 3051 must cover the effective length of the deformable mirror body 301, and the travel of each actuating unit is on the order of hundreds of nanometers.

[0049] In this embodiment, the deformable mirror body 301, the telescopic piezoelectric actuator 3051, and the spacer 302 are firmly bonded together with epoxy glue to form a single unit, which is then secured together in a clamping mechanism. The flat piezoelectric actuator 3052 is fixed to the deformable mirror body 301 with epoxy glue and is not connected to the spacer 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 plate piezoelectric actuator 3052 arranged on the back of the mirror body 301 is used to adjust the overall curvature of the mirror surface of the mirror body 301, so that the mirror surface is bent as a whole in the direction along the meridian. In other embodiments, the plate piezoelectric actuator 3052 can be omitted.

[0052] The control system 203 is used to provide actuation alternating voltage to the telescopic piezoelectric actuator 3051, so as to control the sinusoidal vibration of different actuation units with random amplitude and random phase. In this way, the peak-to-valley maximum amplitude of the mirror surface of the mirror body 301 caused by the sinusoidal vibration overcomes the Rayleigh criterion, and the random phase of different actuation units destroys the periodicity of spatial frequency, so as to realize the homogenization of beam speckle when the mirror body is used for beam deflection.

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

[0054] In this way, the peak-to-valley maximum amplitude of the mirror surface of the mirror body 301 overcomes the Rayleigh criterion, which means that the minimum peak-to-valley maximum amplitude Δd of the mirror surface of the 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 mirror body, Δd is the minimum peak-to-valley maximum amplitude of the mirror surface of the mirror body, and θ is the grazing incidence angle. That is, the peak-to-valley maximum amplitude of the mirror surface of the mirror body 301 can be set according to the wavelength of the incident light and the grazing incidence relationship of the mirror. The actuation alternating voltage is substantially proportional to the peak-to-valley maximum amplitude of the telescopic piezoelectric actuator 3051.

[0056] Therefore, under the driving of the control system, each actuation unit performs sinusoidal vibration within its peak-to-valley maximum amplitude, and the phase of the actuation alternating voltage of different actuation units is random, so as to destroy the periodicity of spatial frequency, so that the mirror surface of the mirror body 301 generates random vibration effect, and the homogenization of beam speckle is realized when the mirror body 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 peak-to-valley maximum amplitude is in the order of hundred nanometers to microns.

[0058] In one embodiment, the amplitude and phase of the actuation alternating voltage of each actuation 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 by grouping the actuating units by grouping 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. In this way, 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 spatial frequency requirements. For example, if it is believed that the spatial frequency below one-tenth of the mirror length will have a greater impact on 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 the 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. The AC control power supply has a frequency of up to hundreds of kilohertz or even megahertz. In some embodiments, the DC power supply can be omitted because the flat-plate piezoelectric actuator 3052 can be omitted.

[0062] In this embodiment, the control system 203 includes a main control unit, a power transfer unit, and a power supply unit. The main control unit consists of a control chip and peripheral circuits, a control panel, DAC control, and network communication ports. The power transfer unit includes power transfer, heat dissipation, and a chassis. The power supply unit includes 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 under the action of static voltage were 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 voltages were as follows: Figure 6 shown. Figure 6 In the experiment, actuators at different positions drive the mirrors at corresponding positions to undergo Gaussian-like surface deformation under different voltages. 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. These two actuators are located at 35mm and 80mm positions of the mirror respectively. 17V and 33V refer to the maximum amplitude values ​​of the actuation 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 This is the high-frequency vibration data of the mirror above a telescopic piezoelectric actuator measured within 0.01 seconds. The 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 the vibration spectra of the 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 height amplitudes measured under 50V conditions.

[0066] The X-ray online test simulation results of the entire system are as follows: Figure 9-10 shown. Figure 9 In the figure, the 200-sample average refers to the point obtained by taking the average value after 200 samples, and the 2-18nm below refers to the local height peak and valley values ​​of the mirror given by the telescopic piezoelectric actuator. Figure 9 The results show that for random vibrations of varying maximum amplitudes, the interference fringes exhibited by reflected light after double-slit interference are significantly modulated. When the maximum amplitude overcomes the Rayleigh criterion, the visibility of the interference fringes decreases significantly, nearly disappearing. For a mirror with a maximum peak-to-valley (PV) amplitude of 18nm, after several hundred sampling cycles (corresponding to the effect of beam repetition rate), the speckle visibility and contrast can be reduced to 0.18 and 0.04, respectively. Figure 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 mode 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 vibration of different actuating units with random amplitude and random phase. 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 adds 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 to eliminate speckle, weaken coherence, and homogenize the light field. This artificially destroys the speckle of a single pulse coherent light beam, differentiates the morphology of the speckle of multiple pulse coherent light beams, and ultimately achieves the effect of homogenizing the speckle within the imaging time, realizing the so-called decoherence effect.

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

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Various modifications are possible. Any simple, equivalent changes and modifications made in accordance with the claims and description of the present invention are within the scope of protection of the patent claims. Anything not fully described in this invention is conventional technology.

Claims

1. A deformable mirror assembly, characterized in that: include: The deformable mirror body has a telescopic piezoelectric actuator on its back, and the telescopic piezoelectric actuator includes a plurality of linearly arranged actuating units; A spacer 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 spacer and the other side is bonded to the back of the deformable mirror body; as well as A control system for providing an actuating AC voltage to the telescopic piezoelectric actuator to control the sinusoidal vibrations of different actuating units to adopt random amplitudes and random phases; wherein the maximum peak-to-valley amplitude of the deformable mirror body caused by the sinusoidal vibration overcomes the Rayleigh criterion, and the randomness of the phase of the actuating unit destroys the periodicity of the spatial frequency, thereby achieving uniformity of the beam speckle when the deformable mirror body is used for beam deflection; The deformable mirror assembly further includes a base plate and a clamping mechanism, wherein the pad is supported on the base plate via a three-point support structure; the clamping mechanism is fixed around the base plate and is used to lock and fix the deformable mirror body and the pad to the base plate; Driven by the control system, each actuator unit performs sinusoidal vibration within its maximum peak-to-valley amplitude, and the phase of the actuating AC voltage of different actuator units is random, so as to destroy the periodicity of the spatial frequency and make the mirror surface of the deformable mirror produce a random vibration effect, thereby improving the speckle uniformity during the imaging process and reducing the impact of speckle.

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

3. The deformable mirror assembly according to claim 1, wherein: The maximum peak-to-valley 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, 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 peak-to-valley amplitude allowed by the deformable mirror body, and θ is the grazing incidence angle.

4. The deformable mirror assembly according to claim 1, wherein: 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, wherein: 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, wherein: 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-plate piezoelectric actuator, so that the displacement of the flat-plate piezoelectric actuator is stabilized at a fixed value, thereby adjusting the overall curvature of the mirror surface of the deformable mirror body.

7. The deformable mirror assembly according to claim 1, wherein: The clamping mechanism has adjustment hinges at both ends and both sides of the deformable mirror body.

8. The deformable mirror assembly according to claim 1, wherein: 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 pad 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 pad is provided with a chamfer.

9. 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 one of claims 1-8.

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