Mirror device

Abstract

To improve a numerical aperture of an optical system with less chromatic aberration.SOLUTION: A mirror device 10 includes a first mirror 12 having a first reflection surface 22 on which a light beam 20 is incident, and a second mirror 14 located away from the first reflection surface 22 in a normal direction of the first reflection surface 22. The second mirror 14 has a second reflection surface 24 on which the light beam 20 is incident and a surface 26 on the opposite side of the second reflection surface 24, the surface 26 on the opposite side faces the first reflection surface 22, and the second reflection surface 24 is variable in a shape.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to Japanese Patent Application No. 2023-036579, filed March 9, 2023, and Japanese Patent Application No. 2023-074850, filed April 28, 2023, the entireties of which are incorporated herein by reference.

[0002] (Technical field) The present disclosure relates to mirror devices, optical devices, and laser fusion reactors. [Background technology]

[0003] X-ray analysis technology is widely used in both academia and industry. In recent years, X-ray microspectroscopic imaging, which uses XAFS (X-ray Absorption Fine Structure) and fluorescent X-rays to analyze the local structure of each element of a target object, has been attracting attention. X-ray microspectroscopic imaging uses a wide range of X-ray wavelengths, so an X-ray optical system with minimal chromatic aberration is required.

[0004] Optical elements used in X-ray optical systems include compound refractive lenses that utilize refraction, Fresnel zone plates that utilize diffraction, and grazing-incidence total-reflection mirrors that utilize reflection. Of these, grazing-incidence total-reflection mirrors have the advantages of high X-ray utilization efficiency and little chromatic aberration. Furthermore, an AKB (Advanced Kirkpatrick-Baez) mirror optical system, which uses four grazing-incidence total-reflection mirrors, is an optical system that is free of coma aberration. Furthermore, to make the optical characteristics of X-ray optical systems variable, deformable mirrors are also used, in which a piezoelectric element is attached to a total-reflection mirror and the shape of the reflecting surface is controlled by the amount of deformation of the piezoelectric element (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-21897 Summary of the Invention [Problem to be solved by the invention]

[0006] In X-ray microspectroscopic imaging, a spatial resolution of approximately 30 nm has been reported, but there is a demand for even higher spatial resolution. Increasing the numerical aperture (NA) of the X-ray optical system is an effective way to improve spatial resolution. However, increasing the numerical aperture increases the grazing incidence angle of X-rays on the grazing incidence total reflection mirror, which no longer satisfies the total reflection condition. Using a multilayer mirror that utilizes Bragg reflection makes it possible to increase the grazing incidence angle of X-rays, but this results in chromatic aberration.

[0007] The present disclosure has been made in view of these problems, and one of its exemplary purposes is to provide a technique for improving the numerical aperture of an optical system with little chromatic aberration. [Means for solving the problem]

[0008] A mirror device according to an embodiment of the present disclosure includes a first mirror having a first reflecting surface on which a light ray is incident, and a second mirror positioned away from the first reflecting surface in the normal direction of the first reflecting surface. The second mirror has the second reflecting surface on which the light ray is incident and a surface opposite the second reflecting surface, the surface facing the first reflecting surface, and the second reflecting surface is deformable.

[0009] A mirror device according to another embodiment of the present disclosure includes a piezoelectric substrate having a reflecting surface on which light rays are incident and a surface opposite the reflecting surface, a first electrode provided on the reflecting surface, a second electrode provided on the opposite surface, and a power source that applies a voltage between the first and second electrodes. The piezoelectric substrate includes a first piezoelectric layer having the reflecting surface and a second piezoelectric layer having the opposite surface. The second piezoelectric layer is made of the same material as the first piezoelectric layer and has a polarization direction opposite to that of the first piezoelectric layer.

[0010] An optical device according to yet another aspect of the present disclosure includes an optical system including the mirror device according to an aspect of the present disclosure, and a detection unit that detects a light beam emitted from the optical system.

[0011] An optical device according to yet another aspect of the present disclosure includes an optical system including the mirror device according to an aspect of the present disclosure, and a sample holder that holds a sample to be irradiated with a light beam emitted from the optical system.

[0012] An optical device according to yet another aspect of the present disclosure includes a laser light source that outputs laser light, a deformable mirror that compensates for the wavefront of the laser light, and a focusing optical element that focuses the laser light reflected by the deformable mirror. The deformable mirror has a reflective surface on which the laser light is incident and a surface opposite to the reflective surface, and includes a piezoelectric substrate made of single-crystal lithium niobate (LN), a first electrode provided on the reflective surface, a second electrode provided on the opposite surface, a dielectric multilayer film mirror provided on the first electrode and that reflects the laser light, and a power source that applies a voltage between the first electrode and the second electrode.

[0013] Yet another aspect of the present disclosure is a laser fusion reactor, comprising: an optical device according to an aspect of the present disclosure; and a reaction vessel having an internal space into which laser light output from the optical device is introduced and containing fuel for causing nuclear fusion when irradiated with the laser light.

[0014] Any combination of the above components, or mutual substitution of the components or expressions of the present disclosure between methods, systems, etc., are also valid aspects of the present disclosure. [Effects of the Invention]

[0015] According to certain aspects of the present disclosure, the numerical aperture of an optical system with reduced chromatic aberration can be improved. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view schematically showing the configuration of an X-ray mirror device according to a first embodiment. [Figure 2] FIG. 10 is a cross-sectional view schematically showing the configuration of a variable-shape mirror according to a second embodiment. [Figure 3]3(a) to 3(c) are diagrams schematically showing an example of a method for forming a domain inversion layer. [Figure 4] 10 is a graph showing an example of the amount of deformation of the reflecting surface of a deformable mirror. [Figure 5] FIG. 10 is a top view schematically showing the configuration of a variable-shape mirror according to a third embodiment. [Figure 6] FIG. 10 is a cross-sectional view schematically showing the configuration of a variable-shape mirror according to a fourth embodiment. [Figure 7] FIG. 10 is a bottom view schematically showing the configuration of a variable-shape mirror according to a fifth embodiment. [Figure 8] FIG. 13 is a bottom view schematically showing the configuration of a variable-shape mirror according to a sixth embodiment. [Figure 9] FIG. 13 is a cross-sectional view schematically showing the configuration of a variable-shape mirror according to a seventh embodiment. [Figure 10] FIG. 13 is a top view schematically showing the configuration of a variable-shape mirror according to an eighth embodiment. [Figure 11] 10 is a graph showing an example of the amount of deformation of the reflecting surface of a deformable mirror. [Figure 12] 12(a) and 12(b) are diagrams schematically illustrating an example of the operation of the deformable mirror. [Figure 13] FIG. 13 is a cross-sectional view schematically showing the configuration of an X-ray mirror device according to a ninth embodiment. [Figure 14] FIG. 20 is a cross-sectional view schematically showing the configuration of an X-ray mirror device according to a tenth embodiment. [Figure 15] FIG. 22 is a cross-sectional view schematically showing the configuration of an X-ray mirror device according to an eleventh embodiment. [Figure 16] FIG. 23 is a perspective view schematically showing the configuration of an X-ray apparatus according to a twelfth embodiment. [Figure 17] FIG. 22 is a diagram schematically illustrating the configuration of an optical device according to a thirteenth embodiment. [Figure 18] FIG. 22 is a diagram showing a schematic configuration of a laser fusion reactor according to a fourteenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Before describing the present disclosure in detail, an overview will be provided. The present disclosure relates to an X-ray mirror device that reflects X-rays. The X-ray mirror device according to the present disclosure includes an outer mirror (also referred to as a first mirror) and an inner mirror (also referred to as a second mirror) that is positioned between the optical axis and the outer mirror. In other words, the X-ray mirror device has a nested structure that combines the outer mirror and the inner mirror. According to the present disclosure, by combining the outer mirror and the inner mirror, it is possible to improve the numerical aperture of the X-ray optical system while suppressing the grazing incidence angle of X-rays incident on each mirror to an angle at which total reflection is possible (e.g., 10 mrad) or less.

[0018] In X-ray optical systems, because the oblique incidence angle of the mirror is extremely small, the distance from the optical axis to the outer mirror is also extremely small, and can be, for example, 5 mm or less. In this case, to place the inner mirror between the optical axis and the outer mirror, the inner mirror must be extremely thin, for example, 1 mm or less, or 500 μm or less. Furthermore, the shape accuracy of the reflective surface required in X-ray optical systems is 10 nm or less, or 5 nm or less. Therefore, the inner mirror must meet the extremely difficult specification of maintaining the shape accuracy of the surface of an extremely thin substrate to 10 nm or less.

[0019] In this disclosure, the inner mirror is formed from a piezoelectric substrate, and electrodes are formed on both sides of the piezoelectric substrate, making the shape of the reflective surface formed by the surface of the piezoelectric substrate variable in response to an applied voltage. In other words, a deformable mirror is used as the inner mirror. By using a very thin piezoelectric substrate, the inner mirror can be placed in the limited space between the optical axis and the outer mirror. Furthermore, by using a deformable mirror as the inner mirror, deviations from the ideal shape of the inner mirror can be compensated for, improving the shape accuracy of the reflective surface of an inner mirror that uses a thin substrate.

[0020] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description, the same elements are designated by the same reference numerals, and redundant description will be omitted as appropriate. Furthermore, to facilitate understanding of the description, the dimensional ratios of the components in the drawings do not necessarily correspond to the actual dimensional ratios.

[0021] In the following embodiments, an X-ray mirror device for reflecting X-rays will be described, but the present disclosure can also be used as a mirror device for reflecting X-rays or light rays having wavelengths different from X-rays. In this case, the light rays may be visible light, infrared light, ultraviolet light, or extreme ultraviolet light. The light rays may also be gamma rays, which have a shorter wavelength than X-rays. The light rays may also be laser light. The mirror device can be used in any optical device that uses light rays. In a mirror device, the surface onto which light rays are incident may be referred to as the incident surface or the reflecting surface.

[0022] (First embodiment) FIG. 1 is a cross-sectional view schematically showing the configuration of an X-ray mirror device 10 according to a first embodiment. The X-ray mirror device 10 includes an outer mirror (or first mirror) 12 and an inner mirror (or second mirror) 14. The X-ray mirror device 10 is configured to reflect X-rays 20 from a first focal point F1 and focus them at a second focal point F2. In FIG. 1, the straight line connecting the first focal point F1 and the second focal point F2 is defined as an optical axis 18. The direction approaching the optical axis 18 is sometimes referred to as the inward direction, and the direction away from the optical axis 18 is sometimes referred to as the outward direction.

[0023] The X-ray mirror device 10 in FIG. 1 can be used as an objective lens. For example, a sample is placed at a first focal point F1, and X-rays from the sample are magnified and imaged at a second focal point F2. An X-ray detection device is placed at the second focal point F2 to detect a magnified image (X-ray image) of the sample. The X-ray mirror device 10 increases the total angular range α1, α2 (i.e., numerical aperture) of the X-rays 20 from the first focal point F1 that can be focused by the X-ray mirror device 10 through a combination of an outer mirror 12 and an inner mirror 14. This improves the spatial resolution of the sample being observed, achieving, for example, a spatial resolution of 10 nm or less or 5 nm or less.

[0024] The outer mirror 12 has an outer reflective surface (or first reflective surface) 22 onto which the X-rays 20 are obliquely incident. The inner mirror 14 has an inner reflective surface (or second reflective surface) 24 onto which the X-rays 20 are obliquely incident, and a surface (or back surface) 26 opposite the inner reflective surface 24. Each of the outer reflective surface 22 and the inner reflective surface 24 is, for example, an elliptical concave curved surface having two foci coinciding with a first focal point F1 and a second focal point F2.

[0025] Each of the outer reflective surface 22 and the inner reflective surface 24 can be a convex or concave curved surface that is arc-shaped, elliptical, hyperbolic, or parabolic. Each of the outer reflective surface 22 and the inner reflective surface 24 may have curvature in only one direction (e.g., the optical axis direction). Each of the outer reflective surface 22 and the inner reflective surface 24 may be a curved surface that has curvature in two directions, or may be a flat surface.

[0026] The outer mirror 12 is positioned away from the optical axis 18, with the outer reflecting surface 22 facing inward. The outer mirror 12 is positioned so that the optical axis 18 is in the normal direction of the outer reflecting surface 22 when viewed from the outer reflecting surface 22.

[0027] The inner mirror 14 is disposed between the optical axis 18 and the outer mirror 12. The inner mirror 14 is disposed so that the inner reflective surface 24 faces inward and the back surface 26 faces outward. The inner mirror 14 is disposed so that the optical axis 18 is in the normal direction of the inner reflective surface 24 when viewed from the inner reflective surface 24. The inner mirror 14 is disposed away from the outer reflective surface 22 in the normal direction of the outer reflective surface 22. The back surface 26 of the inner mirror 14 faces the outer reflective surface 22.

[0028] The outer reflective surface 22 and the inner reflective surface 24 are preferably grazing-incidence total reflection mirrors free of chromatic aberration. The outer reflective surface 22 and the inner reflective surface 24 are formed of a metal thin film made of a single metal material such as nickel (Ni), chromium (Cr), rhodium (Rh), platinum (Pt), or gold (Au). In order to avoid chromatic aberration, the outer reflective surface 22 and the inner reflective surface 24 are preferably configured without a multilayer mirror that utilizes Bragg reflection. The multilayer mirror is formed, for example, by a multilayer film in which multiple first layers made of heavy elements and multiple second layers made of light elements are alternately and periodically stacked.

[0029] The outer reflective surface 22 and the inner reflective surface 24 may be provided with a multilayer mirror in applications where chromatic aberration is acceptable. However, to mitigate the effects of chromatic aberration, it is preferable to set the number of layers in the multilayer mirror (e.g., the sum of the number of first layers and the number of second layers) to 100 or less, 30 or less, or 15 or less. In applications where X-ray absorption near edge structure (XANES) is measured, optical characteristics where chromatic aberration is negligible in an energy range of, for example, about ±100 eV are required, and in this case, it is preferable to set the number of layers in the multilayer mirror to 100 or less. In applications where extended X-ray absorption fine structure (EXAFS) is measured, optical characteristics where chromatic aberration is negligible in an energy range of, for example, about ±500 eV are required, and in this case, it is preferable to set the number of layers in the multilayer mirror to 30 or less or 15 or less.

[0030] Alternatively, one of the outer reflecting surface 22 and the inner reflecting surface 24 may be a total reflection mirror, and the other of the outer reflecting surface 22 and the inner reflecting surface 24 may be a multilayer mirror. For example, the outer reflecting surface 22, where the oblique incident angle is relatively large, may be a multilayer mirror, and the inner reflecting surface 24, where the oblique incident angle is relatively small, may be a total reflection mirror.

[0031] The outer reflective surface 22 reflects the X-ray flux 20a within a first angular range α1 from the first focal point F1 toward the second focal point F2. The first angular range α1 can be expressed as α1≈θ1-θ2, where θ1 is the maximum and minimum values ​​of the oblique incidence angle of the X-rays 20 incident on the outer reflective surface 22. To totally reflect the X-rays 20 at the outer reflective surface 22, the maximum oblique incidence angle θ1 must be equal to or smaller than the critical angle. The magnitude of the critical angle depends on the energy (i.e., wavelength) of the X-rays 20, and the greater the energy of the X-rays 20, the smaller the critical angle. For example, if the X-ray energy is 10 keV, the magnitude of the critical angle is approximately 7 mrad. From the viewpoint of maximizing the first angular range α1, it is preferable that the maximum oblique incidence angle θ1 at the outer reflective surface 22 be as large as possible. Therefore, it is preferable that the maximum oblique incidence angle θ1 at the outer reflective surface 22 be as close as possible to the critical angle, which is the upper limit.

[0032] The inner reflective surface 24 reflects the X-ray flux 20a within a second angular range α2 from the first focal point F1 toward the second focal point F2. The second angular range α2 is an angular range different from the first angular range α1. The second angular range α2 can be expressed as α2≈θ3-θ4, where θ3 is the maximum and θ4 values ​​of the oblique incidence angle of the X-rays 20 incident on the inner reflective surface 24. Because the inner reflective surface 24 is disposed more inward than the outer reflective surface 22, the maximum θ3 value of the oblique incidence angle on the inner reflective surface 24 is smaller than the maximum θ1 value of the oblique incidence angle on the outer reflective surface 22. For example, the maximum θ3 value of the oblique incidence angle on the inner reflective surface 24 can be smaller than the critical angle.

[0033] When the oblique incidence angle of the X-rays 20 is small, the shape accuracy required for the reflective surface is relaxed. Therefore, the shape accuracy of the inner reflective surface 24 may be lower than that of the outer reflective surface 22. The shape accuracy (PV; Peak-to-Valley) of the outer reflective surface 22 and the inner reflective surface 24 is 10 nm or less or 5 nm or less. The shape accuracy (PV) of the outer reflective surface 22 is preferably 3 nm or less, for example, about 2 nm. The shape accuracy (PV) of the inner reflective surface 24 may be 3 nm or more, for example, about 5 nm. The shape accuracy (PV) of the outer reflective surface 22 and the inner reflective surface 24 can be achieved by performing rough processing such as cutting or mechanical polishing, followed by known precision processing such as EEM (Elastic Emission Machining).

[0034] The first distance D1 is small due to constraints such as keeping the maximum oblique incidence angle θ1 at the outer reflecting surface 22 equal to or less than the critical angle (e.g., 10 mrad) and keeping the X-ray optical system within a practical size (e.g., 1 m to 10 m). The first distance D1 from the optical axis 18 to the outer reflecting surface 22 is, for example, 10 mm or less, 5 mm or less, 3 mm or less, or 1 mm or less. The first distance D1 is, for example, 100 μm or more, 200 μm or more, 300 μm or more, or 500 μm or more.

[0035] The first distance D1 corresponds to the sum of the second distance D2 from the optical axis 18 to the inner reflective surface 24, the thickness t of the inner mirror 14 from the inner reflective surface 24 to the rear surface 26, and the third distance D3 from the inner mirror 14 to the outer reflective surface 22 (i.e., D1 = D2 + t + D3). To maximize the sum of the first angular range α1 and the second angular range α2, it is preferable to make the thickness t of the inner mirror 14 as small as possible. The thickness t of the inner mirror 14 is, for example, 1 mm or less, 500 μm or less, 300 μm or less, or 200 μm or less. The thickness t of the inner mirror 14 is, for example, 10 μm or more, 50 μm or more, 100 μm or more, 150 μm or more, or 200 μm or more. Each of the second distance D2 and the third distance D3 is, for example, 50 μm or more, 100 μm or more, 200 μm or more, or 500 μm or more. The second distance D2 and the third distance D3 are each, for example, 5 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less. The third distance D3 is, for example, greater than the second distance D2. The third distance D3 may be the same as the second distance D2 or may be smaller than the second distance D2.

[0036] The inner mirror 14 is configured as a deformable mirror using a piezoelectric substrate. By making the inner mirror 14 a deformable mirror, it is possible to achieve both an extremely thin thickness t and high shape accuracy for the inner reflective surface 24. Details of deformable mirrors that can be used for the inner mirror 14 will be described separately later. On the other hand, since there are no thickness restrictions on the outer mirror 12, any type of mirror can be used as long as the shape accuracy of the outer reflective surface 22 can be achieved.

[0037] The outer mirror 12 may be a deformable mirror using a piezoelectric material, or may be a normal mirror that does not use a piezoelectric material (i.e., is not deformable). When the outer mirror 12 is a normal mirror, it is made of a substrate made of any material whose surface shape can be precisely processed, such as silicon or glass. When the outer mirror 12 is a deformable mirror, it may be made by attaching a piezoelectric element to the surface of a substrate having an outer reflecting surface 22, or it may be made of a piezoelectric substrate having an outer reflecting surface 22.

[0038] (Second embodiment) Figure 2 is a cross-sectional view schematically showing the configuration of a deformable mirror 30 according to a second embodiment. The deformable mirror 30 in Figure 2 can be used as the inner mirror 14 in Figure 1. The deformable mirror 30 in Figure 2 may also be used as the outer mirror 12 in Figure 1. The deformable mirror 30 includes a piezoelectric substrate 32, a reflective surface electrode (or first electrode) 34, a back surface electrode (or second electrode) 36, and a power source 38.

[0039] 2, the x-direction is the direction perpendicular to both the incident direction and the reflection direction of the X-rays 20 in the deformable mirror 30. The z-direction is the thickness direction of the piezoelectric substrate 32, and the y-direction is the direction perpendicular to both the x-direction and the z-direction. The y-direction corresponds to the direction in which the optical axis 18 of the X-rays 20 extends (also referred to as the optical axis direction). The coordinate axes shown in the figure are set to facilitate understanding of the explanation, and do not limit the orientation of the deformable mirror 30 when in use.

[0040] The piezoelectric substrate 32 has a reflecting surface 40 and a surface (or back surface) 42 opposite the reflecting surface 40. A reflecting surface electrode 34 is provided on the reflecting surface 40, and a back surface electrode 36 is provided on the back surface 42. The thickness of the piezoelectric substrate 32 is 10 μm or more and 10 mm or less, for example, 50 μm or more and 1 mm or less. The thickness of the piezoelectric substrate 32 may be 100 μm or more, 200 μm or more, or 250 μm or more. The thickness of the piezoelectric substrate 32 may be 500 μm or less, 400 μm or less, or 300 μm or less.

[0041] The piezoelectric substrate 32 is made of a piezoelectric material, such as a piezoelectric single crystal material such as lithium niobate (LN) or lithium tantalate (LT). The piezoelectric substrate 32 may be, for example, a 127.86-degree Y-cut LN substrate, a 140-degree Y-cut LN substrate, or a 36-degree Y-cut LN substrate.

[0042] The piezoelectric substrate 32 deforms in response to a voltage applied between the reflective surface electrode 34 and the rear surface electrode 36. The piezoelectric substrate 32 includes a first piezoelectric layer 44 and a second piezoelectric layer 46. The first piezoelectric layer 44 and the second piezoelectric layer 46 expand and contract in the y direction in response to a voltage applied in the z direction. The first piezoelectric layer 44 and the second piezoelectric layer 46 are made of the same material but have opposite polarization directions. In the example shown in FIG. 2, the polarization direction A1 of the first piezoelectric layer 44 is the -z direction, and the polarization direction A2 of the second piezoelectric layer 46 is the +z direction. When a voltage is applied to expand the first piezoelectric layer 44, the second piezoelectric layer 46 contracts. Conversely, when a voltage is applied to contract the first piezoelectric layer 44, the second piezoelectric layer 46 expands. As a result, the piezoelectric substrate 32 functions like a bimorph piezoelectric element. The first piezoelectric layer 44 and the second piezoelectric layer 46 preferably have approximately the same thickness.

[0043] The piezoelectric substrate 32 can be formed, for example, by preparing two substrates corresponding to the first piezoelectric layer 44 and the second piezoelectric layer 46, and bonding the two substrates together so that their polarization directions are opposite to each other. The first piezoelectric layer 44 and the second piezoelectric layer 46 are preferably bonded together by a method that does not use adhesive, such as optical contact.

[0044] The piezoelectric substrate 32 may be formed by heat treating a substrate with a fixed polarization direction. It is known that in LN and LT substrates, a polarization inversion layer in which the polarization direction is reversed is formed by heat treatment at a temperature near the Curie point.

[0045] 3(a) to 3(c) are schematic diagrams illustrating an example of a method for forming a polarization inversion layer 56 using an LN substrate. FIG. 3(a) shows an LN substrate 50 before heat treatment. The LN substrate 50 has a positive surface 52 and a negative surface 54. The polarization direction A2 of the LN substrate 50 is from the negative surface 54 to the positive surface 52. FIG. 3(b) shows the LN substrate 50 during heat treatment. The heat treatment forms a polarization inversion layer 56 near the positive surface 52. The heat treatment temperature is, for example, 1100 to 1150°C. The thickness t1 of the polarization inversion layer 56 depends on the heat treatment time, and the thickness t1 increases as the heat treatment time increases. FIG. 3(c) shows the LN substrate 50 after heat treatment. By adjusting the heat treatment time, the thickness t1 of the polarization inversion layer 56 can be reduced to half the thickness t of the LN substrate 50. For example, when the thickness t of the LN substrate 50 is 200 μm, the heat treatment conditions required to make the thickness t1 of the domain-inverted layer 56 100 μm are 1150° C. and about 6 hours.

[0046] When using an LT substrate as the piezoelectric substrate 32, it is necessary to apply a proton exchange method, in which the LT substrate is immersed in benzoic acid or pyrophosphoric acid before heat treatment to exchange lithium ions (Li+) on the substrate surface for protons (H+). After proton exchange, the LT substrate is heat treated at 550°C to 600°C to form the first piezoelectric layer 44 and the second piezoelectric layer 46, which have opposite polarization directions. When an LT substrate is used, the polarization direction is opposite to that when an LN substrate is used, with the polarization direction of the first piezoelectric layer 44 being in the +z direction and the polarization direction of the second piezoelectric layer 46 being in the -z direction. This is thought to be because protons diffuse into the crystal during heat treatment, forming a polarization inversion layer on the negative side, not the positive side.

[0047] It should be noted that a non-bimorph piezoelectric material may be used as the piezoelectric substrate 32. In this case, the polarization direction of the entire piezoelectric substrate 32 may be uniform. If the piezoelectric substrate 32 is not a bimorph, the piezoelectric substrate 32 may be configured to expand and contract in the z direction in response to a voltage applied in the z direction.

[0048] 2, the reflecting surface 40 has the shape precision and surface roughness required for a grazing incidence total reflection mirror. The shape precision (PV) of the reflecting surface 40 is, for example, 10 nm or less, and preferably 2 nm or more and 5 nm or less. The surface roughness (Rms) of the reflecting surface 40 is, for example, 0.5 nm or less, and preferably 0.05 nm or more and 0.2 nm or less.

[0049] The reflecting surface 40 is, for example, an arc-shaped, elliptical, hyperbolic, or parabolic convex or concave curved surface, and has curvature in only one direction (for example, the y direction). In the example of FIG. 2, the reflecting surface 40 is a concave curved surface. The reflecting surface 40 may be a flat surface or a curved surface having curvature in two directions (for example, the x direction and the y direction). The back surface 42 is, for example, a polished flat surface.

[0050] The reflecting surface electrode 34 is provided on the reflecting surface 40. The reflecting surface electrode 34 has a thickness of, for example, 10 nm or more and 100 nm or less. The reflecting surface electrode 34 is provided, for example, to cover the entire reflecting surface 40 and to have a uniform thickness over the entire reflecting surface 40. Since the reflecting surface electrode 34 has a uniform thickness, the surface of the reflecting surface electrode 34 has a shape corresponding to the reflecting surface 40 and has the same shape precision and surface roughness as the reflecting surface 40. The reflecting surface electrode 34 functions as an electrode for applying a voltage to the piezoelectric substrate 32, and also functions as a total reflection mirror that totally reflects the X-rays 20.

[0051] The reflective surface electrode 34 can be made of a material such as nickel (Ni), chromium (Cr), rhodium (Rh), platinum (Pt), or gold (Au). The reflective surface electrode 34 may be made of a metal thin film of a single material, or may be made of a laminate of multiple metal thin films made of different materials. The reflective surface electrode 34 may have, for example, an adhesive layer made of Cr, Ti, or the like that contacts the reflective surface 40, and a reflective layer made of Rh, Pt, Au, or the like that is formed on the adhesive layer. The reflective surface electrode 34 can be formed using a vapor deposition method or a sputtering method.

[0052] The back electrode 36 is provided on the back surface 42. The back electrode 36 includes a plurality of electrodes 36a, 36b, 36c, 36d, 36e, 36f, 36g, 36h, and 36i arranged at intervals in the optical axis direction (e.g., the y direction). The width w of the plurality of electrodes 36a to 36i in the optical axis direction (e.g., the y direction) is, for example, 0.5 mm to 10 mm, and preferably 1 mm to 6 mm. The interval d of the plurality of electrodes 36a to 36i in the optical axis direction (e.g., the y direction) is, for example, 0.1 mm to 5 mm, and preferably 0.5 mm to 4 mm. The pitch p (the sum of the width w and the interval d) of the plurality of electrodes 36a to 36i in the optical axis direction (e.g., the y direction) is, for example, 1 mm to 15 mm, and preferably 1.5 mm to 10 mm.

[0053] The multiple electrodes 36a-36i are configured, for example, so that their width w, spacing d, and pitch p in the optical axis direction (e.g., y direction) are constant. At least one of the width w, spacing d, and pitch p of the multiple electrodes 36a-36i may be configured so that they are different from one another. For example, if the angle θ of the X-rays 20 obliquely incident on the reflecting surface 40 varies depending on the position in the optical axis direction, the pitch p of the multiple electrodes 36a-36i may be made different from one another so that the effective pitch p×θ when viewed from the X-rays 20 is constant.

[0054] The back surface electrode 36 is made of a metal material, such as nickel (Ni), chromium (Cr), copper (Cu), silver (Ag), gold (Au), etc. The thickness of the back surface electrode 36 is not particularly limited, but is, for example, not less than 100 nm and not more than 1000 nm.

[0055] The power supply 38 applies a DC voltage between the reflective surface electrode 34 and the back surface electrode 36. The power supply 38 is configured to be able to apply different voltages to each of the multiple electrodes 36a-36i. In FIG. 2, to avoid complication of the drawing, the power supply 38 is connected to only one electrode 36a of the multiple electrodes 36a-36i. In reality, the power supply 38 is connected to each of the multiple electrodes 36a-36i. The power supply 38 is configured to independently control the voltage applied to each of the multiple electrodes 36a-36i. The power supply 38 applies a DC voltage that is variable within a range of, for example, −1 kV to +1 kV. By individually variably controlling the voltage applied to each of the multiple electrodes 36a-36i, the power supply 38 controls the amount of deformation of the piezoelectric substrate 32 at positions corresponding to each of the multiple electrodes 36a-36i, thereby variably controlling the shape of the reflective surface 40.

[0056] FIG. 4 is a graph showing an example of the deformation amount of the reflecting surface 40 of the deformable mirror 30. FIG. 4 shows the deformation amount of the reflecting surface 40 when the height of the reflecting surface 40 when no voltage is applied to the electrodes 36a-36i is used as a reference and when the magnitude of the voltage applied to the electrodes 36a-36i is 10V, 20V, 30V, 40V, 50V, and 100V. The voltage applied to the electrodes 36a-36i alternates between positive and negative in the optical axis direction (e.g., y direction). The vertical axis of the graph represents the deformation amount [nm] in the thickness direction (z direction), and the horizontal axis represents the position [mm] in the optical axis direction (e.g., y direction). In the example shown in FIG. 4, the width w of the electrodes 36a-36i is 5 mm, and the spacing d is 1 mm. A bimorph LN substrate with a thickness of 250 μm is used as the piezoelectric substrate 32.

[0057] As shown in FIG. 4, after deformation, convex and concave portions of the reflecting surface 40 appear approximately every 6 mm, indicating that the reflecting surface 40 has been deformed to correspond to the positions of the multiple electrodes 36a-36i arranged at a 6 mm pitch. When the voltage applied to the multiple electrodes 36a-36i is 100 V, the height difference between the convex and concave portions is approximately 1 mm, demonstrating the large deformation amount inherent in the bimorph structure. It also shows high linearity between the applied voltage and the amount of deformation. Furthermore, unlike piezoelectric ceramic materials such as PZT, no hysteresis is observed, and no drift, in which the amount of deformation changes over time despite a fixed applied voltage, is observed. Therefore, with the deformable mirror 30 according to this embodiment, the amount of deformation can be uniquely determined according to the applied voltage, enabling stable and highly reproducible control of the shape of the reflecting surface 40.

[0058] According to this embodiment, the shape of the reflecting surface 40 can be variably controlled while irradiating the reflecting surface 40 with X-rays 20, and therefore the shape of the reflecting surface 40 can be adjusted afterward to be optimal for the X-ray mirror device 10 in which the deformable mirror 30 is incorporated. For example, by measuring the shape of the reflecting surface 40 by a pencil beam method using X-rays, it is possible to precisely measure and adjust the shape of the reflecting surface 40 on the spot when the deformable mirror 30 is applied to the X-ray mirror device 10.

[0059] When a deformable mirror 30 is used as the inner mirror 14, the thickness of the piezoelectric substrate 32 is very small, and therefore distortion caused by the support force for supporting the inner mirror 14 can occur on the inner reflective surface 24. According to this embodiment, because the inner mirror 14 is a deformable mirror 30, distortion caused by the support force of the inner reflective surface 24 can be compensated for, and the inner reflective surface 24 can be deformed to have an ideal shape. For example, by accurately predicting the distortion of the inner reflective surface 24 caused by the support force of the inner mirror 14 using a simulation such as the finite element method, the distortion can be compensated for with high precision.

[0060] (Third embodiment) 5 is a top view schematically showing the configuration of a deformable mirror 30A according to the third embodiment. In the third embodiment, a reflecting surface electrode 33 and a reflecting film 35 are provided on the reflecting surface 40 of a piezoelectric substrate 32. The reflecting surface electrode 33 includes a plurality of electrodes 33a, 33b, 33c, 33d, 33e, 33f, 33g, 33h, and 33i arranged at intervals in the optical axis direction (e.g., the y direction). This embodiment will be described mainly focusing on the differences from the above-described embodiments, and a description of the commonalities will be omitted as appropriate.

[0061] The deformable mirror 30A includes a piezoelectric substrate 32, a reflecting surface electrode 33, a reflecting film 35, a back surface electrode 36 (see FIG. 2), and a power supply 38 (see FIG. 2). The reflecting surface electrode 33 and the reflecting film 35 are provided on a reflecting surface 40 of the piezoelectric substrate 32. The reflecting film 35 is disposed at the center in the x-direction of the reflecting surface 40 on which the X-rays 20 are incident. The reflecting film 35 functions as a total reflection mirror that totally reflects the X-rays 20. The reflecting film 35 can be made of the same material and with the same thickness as the reflecting surface electrode 34 according to the above-described embodiment.

[0062] The reflective surface electrode 33 is disposed on both sides of the reflective film 35 in the x direction. The reflective surface electrode 33 is disposed away from the reflective film 35 in the x direction. The reflective surface electrode 33 includes a plurality of electrodes 33a to 33i. The plurality of electrodes 33a to 33i may have the same width w, spacing d, and pitch p as the plurality of electrodes 36a to 36i of the back surface electrode 36 according to the above embodiment. The reflective surface electrode 33 may be made of the same material and thickness as the reflective surface electrode 34 according to the above embodiment. The reflective surface electrode 33 may also be made of the same material and thickness as the back surface electrode 36 according to the above embodiment.

[0063] In this embodiment, the rear surface electrode 36 can include a plurality of electrodes 36a to 36i, as in the above-described embodiment. In this case, the width w, spacing d, and pitch p of the plurality of electrodes 36a to 36i of the rear surface electrode 36 are preferably the same as the width w, spacing d, and pitch p of the plurality of electrodes 33a to 33i of the reflective surface electrode 33.

[0064] In this embodiment, the back surface electrode 36 does not have to include the multiple electrodes 36a to 36i as in the above-described embodiment. In this case, the back surface electrode 36 may be formed uniformly over the entire back surface 42 (see FIG. 2) of the piezoelectric substrate 32 and function as a common electrode.

[0065] The power supply 38 is configured to be able to apply different voltages to each of the multiple electrodes 33a to 33i of the reflective surface electrode 33. When the rear surface electrode 36 includes multiple electrodes 36a to 36i, the power supply 38 applies a voltage between pairs of opposing electrodes of the reflective surface electrode 33 and the rear surface electrode 36 (for example, the pair of electrode 33a and electrode 36a, the pair of electrode 33b and electrode 36b, etc.).

[0066] In this embodiment, the same effects as those of the above-described embodiment can be achieved.

[0067] (Fourth embodiment) 6 is a cross-sectional view schematically showing the configuration of a deformable mirror 30B according to the fourth embodiment. In the fourth embodiment, an intermediate electrode 48 is further provided between the first piezoelectric layer 44B and the second piezoelectric layer 46B. This embodiment will be described mainly focusing on the differences from the above-described embodiments, and a description of the commonalities will be omitted as appropriate.

[0068] The deformable mirror 30B includes a piezoelectric substrate 32B, a reflective surface electrode (or first electrode) 34, a back surface electrode (or second electrode) 37, a power source 38B, and an intermediate electrode 48 (or third electrode). The reflective surface electrode 34 is configured in the same manner as in the above-described embodiment. The back surface electrode 37 is formed uniformly over the entire back surface 42 of the piezoelectric substrate 32 and functions as a common electrode.

[0069] The piezoelectric substrate 32B includes a first piezoelectric layer 44B and a second piezoelectric layer 46B, with an intermediate electrode 48 provided between the first piezoelectric layer 44B and the second piezoelectric layer 46B. The first piezoelectric layer 44B and the second piezoelectric layer 46B are made of the same material and have the same polarization direction. In the example of FIG. 6, the polarization direction B1 of the first piezoelectric layer 44B is the −z direction, and the polarization direction B2 of the second piezoelectric layer 46B is also the −z direction. The polarization directions B1 and B2 of the first piezoelectric layer 44B and the second piezoelectric layer 46B are not limited to those shown in the figure and may be, for example, the +z direction.

[0070] The intermediate electrode 48 includes a plurality of electrodes 48a, 48b, 48c, 48d, 48e, 48f, 48g, 48h, and 48i arranged at intervals in the optical axis direction (e.g., the y direction). The plurality of electrodes 48a to 48i may have the same width w, spacing d, and pitch p as the plurality of electrodes 36a to 36i of the back surface electrode 36 according to the above-described embodiment. The intermediate electrode 48 may be made of the same material and with the same thickness as the reflective surface electrode 34 and the back surface electrode 36 according to the above-described embodiment.

[0071] The intermediate electrode 48 can be formed by, for example, forming a first metal film on the bonding surface of the first piezoelectric layer 44B using a vapor deposition method or a sputtering method, forming a second metal film on the bonding surface of the second piezoelectric layer 46B, and then bonding the first metal film and the second metal film together. The bonding method for the first metal film and the second metal film is not particularly limited, and any bonding technique can be used. For example, solid-state bonding techniques such as room-temperature bonding and diffusion bonding can be used. Alternatively, the first metal film and the second metal film may be electrically and mechanically bonded together using a binder material such as a conductive adhesive or metal nanoparticles. The first metal film and the second metal film may be mechanically bonded together using an insulating adhesive or adhesive layer. The intermediate electrode 48 may be formed by a metal film formed on only one bonding surface of the first piezoelectric layer 44B or the second piezoelectric layer 46B. In these cases, the bonding method between the first piezoelectric layer 44B and the second piezoelectric layer 46B is not particularly limited, and any adhesive or adhesive layer made of any material may be used, or a bonding method without adhesive may be used.

[0072] The power supply 38B applies a DC voltage between the reflective surface electrode 34 and the intermediate electrode 48, and also applies a DC voltage between the intermediate electrode 48 and the rear surface electrode 37. In the example of FIG. 6, the power supply 38B is connected so that the reflective surface electrode 34 and the rear surface electrode 37 have the same potential. In a modified example, a second power supply that applies a DC voltage between the intermediate electrode 48 and the rear surface electrode 37 may be used in addition to a first power supply that applies a DC voltage between the reflective surface electrode 34 and the intermediate electrode 48. In other words, the first voltage applied between the reflective surface electrode 34 and the intermediate electrode 48 and the second voltage applied between the intermediate electrode 48 and the rear surface electrode 37 may be individually controllable.

[0073] 6, the direction of the electric field applied to the first piezoelectric layer 44B is upside down and the direction of the electric field applied to the second piezoelectric layer 46B is upside down. Because the first piezoelectric layer 44B and the second piezoelectric layer 46B have the same polarization direction, applying voltages in opposite directions to each other causes them to function like a bimorph piezoelectric element.

[0074] In this embodiment, the same effects as those of the above-described embodiment can be achieved.

[0075] In a modification of the configuration shown in FIG. 6, the reflecting surface electrode 33 and the reflecting film 35 shown in FIG. 5 may be provided on the reflecting surface 40 of the first piezoelectric layer 44B. That is, multiple electrodes 33a-33i may be provided on the reflecting surface 40 of the first piezoelectric layer 44B. Furthermore, the back surface electrode 36 according to the above embodiment may be provided on the back surface 42 of the second piezoelectric layer 46B. That is, multiple electrodes 36a-36i may be provided on the back surface 42 of the second piezoelectric layer 46B. In this case, the intermediate electrode 48 may include multiple electrodes 48a-48i, or may not include multiple electrodes 48a-48i. In the latter case, the intermediate electrode 48 may function as a common electrode formed on the entire bonding surface of the first piezoelectric layer 44B and the second piezoelectric layer 46B. The power source 38B may be configured to apply different voltages to each of the multiple electrodes 33a-33i of the reflecting surface electrode 33. The power supply 38B may be configured to be able to apply different voltages to the plurality of electrodes 36a to 36i of the rear surface electrode 36, respectively.

[0076] (Fifth embodiment) FIG. 7 is a bottom view schematically illustrating the configuration of a deformable mirror 30C according to a fifth embodiment. In the fifth embodiment, rear electrodes 36 are arranged in a two-dimensional array in the x and y directions. In the fifth embodiment, by applying different voltages to the two-dimensional array of rear electrodes 36, the shape of the reflecting surface 40 can be variably controlled in two dimensions. In the example shown in FIG. 7, the piezoelectric substrate 32 has a circular outer shape, but the outer shape of the substrate 32 is not particularly limited. The piezoelectric substrate 32 may also have a rectangular outer shape.

[0077] (Sixth embodiment) 8 is a bottom view schematically illustrating the configuration of a deformable mirror 30D according to the sixth embodiment. In the sixth embodiment, the piezoelectric substrate 32 has a circular outer shape, and the rear surface electrodes 36 are arranged in a two-dimensional array in the radial and circumferential directions. In the sixth embodiment, too, the shape of the reflecting surface 40 can be variably controlled in two dimensions by applying different voltages to each of the two-dimensionally arrayed rear surface electrodes 36.

[0078] (Seventh embodiment) 9 is a cross-sectional view schematically showing the configuration of a variable-shape mirror 30E according to the seventh embodiment. The seventh embodiment differs from the above-described embodiments in that a multilayer mirror 58 is further provided on the reflective surface electrode 34. This embodiment will be described mainly focusing on the differences from the above-described embodiments, and a description of the commonalities will be omitted as appropriate.

[0079] The deformable mirror 30E includes a piezoelectric substrate 32, a reflective surface electrode 34, a back surface electrode 36, a power supply 38, and a multilayer mirror 58. The multilayer mirror 58 is configured to reflect the light beam 20E incident thereon with high reflectivity. When the light beam 20E is ultraviolet, visible, or infrared light, the multilayer mirror 58 may be a dielectric multilayer film configured to have a reflectivity of 99% or more, e.g., 99.9% or more, for the light beam 20E. The material of the dielectric multilayer film is not particularly limited, but oxide materials such as Al2O3, SiO2, and HfO2, and fluoride materials such as LaF3, MgF2, and AlF3 can be used. The thickness of the multilayer mirror 58 is not particularly limited, but is, for example, smaller than the thickness of the piezoelectric substrate 32. The thickness of the multilayer mirror 58 is, for example, 1 μm or more, 5 μm or more, or 10 μm or less, for example, 50 μm or less, 20 μm or less, or 10 μm or less.

[0080] The deformable mirror 30E does not include an additional dielectric layer between the reflective surface electrode 34 and the multilayer mirror 58. Therefore, the thickness of the dielectric material between the reflective surface 40 of the piezoelectric substrate 32 and the top surface 59 of the multilayer mirror 58 is the same as the thickness of the multilayer mirror 58. The deformable mirror 30E may include an additional dielectric layer between the reflective surface electrode 34 and the multilayer mirror 58. The material of the additional dielectric layer may be the same as the dielectric multilayer. The thickness of the additional dielectric layer is, for example, 1 μm or more, 5 μm or more, or 10 μm or less, such as 50 μm or less, 20 μm or less, or 10 μm or less. In these cases, the thickness from the reflective surface 40 of the piezoelectric substrate 32 to the top surface 59 of the multilayer mirror 58 is 1 mm or less, for example, 200 μm or less, 100 μm or less, or 50 μm or less.

[0081] (Eighth embodiment) 10 is a top view schematically showing the configuration of a deformable mirror 30F according to the eighth embodiment. In the eighth embodiment, similar to the third embodiment shown in FIG. 5, a reflecting surface electrode 33 and a reflecting film 35 are provided on the reflecting surface 40 of a piezoelectric substrate 32. The eighth embodiment differs from the third embodiment in that the outer peripheral shapes of the reflecting surface electrode 33 and the reflecting film 35 are polygonal with rounded corners. This embodiment will be described mainly focusing on the differences from the above-mentioned embodiments, and a description of the commonalities will be omitted as appropriate.

[0082] The outer peripheral shape of each of the multiple electrodes 33a to 33h that make up the reflecting surface electrode 33 is a polygon with rounded corners 33r, for example, a rectangle with rounded corners 33r. The radius of curvature of the corners 33r of each of the electrodes 33a to 33h is, for example, 1% or more, 5% or more, or 10% or more of the width w of each of the electrodes 33a to 33h in the optical axis direction (for example, the y direction), and is 50% or less, 30% or less, or 20% or less of the width w. By rounding the corners 33r of each of the electrodes 33a to 33h that make up the reflecting surface electrode 33, electric field concentration at the corners 33r can be alleviated, and discharge that may occur when a high voltage is applied can be suppressed.

[0083] The outer peripheral shape of the reflective film 35 is a polygon with rounded corners 35r, for example, a rectangle with rounded corners 35r. The radius of curvature of the corners 35r of the reflective film 35 is the same as or larger than the radius of curvature of the corners 33r of each of the electrodes 33a to 33h that make up the reflective surface electrode 33. The radius of curvature of the corners 35r of the reflective film 35 is, for example, 1% or more, 5% or more, or 10% or more of the width w of each of the electrodes 33a to 33h in the optical axis direction (e.g., the y direction), and is 100% or less, 50% or less, or 30% or less of the width w. By rounding the corners 35r of the reflective film 35, electric field concentration at the corners 35r can be alleviated, and discharge that may occur between the reflective surface electrode 33 and the reflective film 35 can be suppressed.

[0084] In the deformable mirrors 30, 30A, 30B, 30C, 30D, and 30E according to the other embodiments, the outer periphery of at least one of the reflective surface electrodes (or first electrodes) 33 and 34, the reflective film 35, and the rear surface electrodes (or second electrodes) 36 and 37 may be a polygon or rectangle with rounded corners. For example, in the deformable mirrors 30C and 30E shown in FIGS. 7 and 8, the corners of the rear surface electrode 36 may be rounded.

[0085] FIG. 11 is a graph showing an example of the deformation amount of the reflective surface of the deformable mirror 30F. The dashed curve G1 indicates the surface shape of the reflective film 35 when no voltage is applied to the multiple electrodes 33a-33h of the deformable mirror 30F. The solid curve G2 indicates the surface shape of the reflective film 35 when a predetermined voltage is applied to the multiple electrodes 33a-33h of the deformable mirror 30F. The vertical axis of the graph indicates the error from the ideal shape of the surface of the reflective film 35. The shape accuracy (PV) before voltage application shown by curve G1 is about 140 nm. On the other hand, the shape accuracy (PV) after voltage application shown by curve G2 is 3 nm, which shows that a shape accuracy preferable for an X-ray mirror has been achieved.

[0086] The shape accuracy shown in FIG. 11 can be achieved not only by the deformable mirror 30F according to this embodiment, but also by the deformable mirrors 30, 30A, 30B, 30C, 30D, and 30E according to the other embodiments.

[0087] 12(a) and (b) are diagrams schematically illustrating an example of the operation of the deformable mirror 30F. Fig. 12(a) illustrates a case in which the reflecting surface 40 of the deformable mirror 30F is a concave curved surface, and the X-rays 20 incident on the reflecting surface 40 are focused at a specific point 39a on the sample 39. Fig. 12(b) illustrates a case in which the reflecting surface 40 of the deformable mirror 30F is a convex curved surface, and the X-rays 20 incident on the reflecting surface 40 are diverged toward a wide range 39b on the sample 39.

[0088] The deformable mirror 30F according to this embodiment exhibits a large amount of deformation of the reflecting surface 40 in response to changes in the voltage applied to the electrodes 33a to 33h. Therefore, simply by changing the voltage, the mirror can be switched between the state shown in FIG. 12(a) and the state shown in FIG. 12(b). In the state shown in FIG. 12(a), the beam width of the X-rays 20 at the specific point 39a can be focused to approximately 200 nm. On the other hand, in the state shown in FIG. 12(b), the size of the range 39b irradiated with the X-rays 20 can be diverged to 1 mm or more or 10 mm or more. For example, while the sample 39 is fixed, the mirror can be switched between a focused mode in which the X-rays 20 are irradiated only to the specific point 39a on the sample 39 and a divergent mode in which the X-rays 20 are irradiated to a wide range 39b on the sample 39. This allows instantaneous switching between local and global measurements of the sample 39, improving user convenience.

[0089] The operational example shown in Figures 12(a) and (b) can be realized not only in the variable-shape mirror 30F of this embodiment, but also in the variable-shape mirrors 30, 30A, 30B, 30C, 30D, and 30E of the other embodiments.

[0090] (Ninth embodiment) Fig. 13 is a cross-sectional view schematically showing the configuration of an X-ray mirror device 10A according to the ninth embodiment. The ninth embodiment differs from the X-ray mirror device 10 in Fig. 1 in that the thickness of the inner mirror 14A is configured to change in a tapered shape in the optical axis direction. The following description of this embodiment will focus on the differences from the above-mentioned embodiments, and a description of the commonalities will be omitted as appropriate.

[0091] The X-ray mirror device 10A includes an outer mirror 12 and an inner mirror 14A. The outer mirror 12 is configured similarly to the above-described embodiment. The inner mirror 14A includes an inner reflective surface 24A and a back surface 26A. The inner reflective surface 24A can be configured similarly to the inner reflective surface 24 of the above-described embodiment.

[0092] The inner mirror 14A has a first end 25 located on the incident side of the X-rays 20 (the first focal point F1 side) and a second end 27 located on the exit side of the X-rays 20 (the second focal point F2 side). The inner mirror 14A extends along the optical axis 18 from the first end 25 to the second end 27. The inner mirror 14A is configured so that the thickness ta of the first end 25 is different from the thickness tb of the second end 27, and the thickness changes in a tapered manner from the first end 25 to the second end 27. The thickness of the inner mirror 14A is configured to increase or decrease monotonically in the optical axis direction. In the example of FIG. 13, the thickness ta of the first end 25 is smaller than the thickness tb of the second end 27, and the thickness is configured to increase monotonically from the first end 25 to the second end 27. In an example different from that shown in FIG. 13, the thickness ta of the first end 25 may be greater than the thickness tb of the second end 27, and the thickness may be configured to decrease monotonically from the first end 25 to the second end 27.

[0093] According to this embodiment, by varying the thickness of the inner mirror 14A in a tapered manner, the thickness ta of the first end 25 or the thickness tb of the second end 27 can be made smaller than when the thickness is constant. As a result, the angular range δ of X-rays 20 that cannot be effectively used because they are blocked by the inner mirror 14A can be made smaller, and the first angular range α1 can be made larger. The angular range δ that cannot be effectively used is, for example, the range between the first angular range α1 and the second angular range α2. This further improves the numerical aperture of the X-ray mirror device 10A and improves the spatial resolution.

[0094] In the example of FIG. 13 , the distance from the X-ray mirror device 10A to the first focal point F1 is closer than the distance to the second focal point F2. Therefore, the angular ranges α1 and α2 of the X-ray beams 20a and 20b incident on the X-ray mirror device 10A are relatively large, and the angular ranges β1 and β2 of the X-ray beams 20c and 20d emerging from the X-ray mirror device 10A are relatively small. In such a case, the space between the X-ray beam 20a incident on the outer mirror 12 and the X-ray beam 20b incident on the inner mirror 14A is particularly limited. On the other hand, there is a relatively large space between the X-ray beam 20c emerging from the outer mirror 12 and the X-ray beam 20d emerging from the inner mirror 14A. In the example of FIG. 13 , reducing the thickness ta of the first end 25 prevents the X-ray beam 20a in the first angular range α1 from being blocked by the inner mirror 14A, thereby contributing to an improvement in the numerical aperture of the X-ray mirror device 10A. Furthermore, by increasing the thickness tb of second end portion 27, the mechanical strength of inside mirror 14A can be improved.

[0095] 13, in a configuration in which the distance from X-ray mirror device 10A to second focal point F2 is shorter than the distance to first focal point F1, it is possible to increase the thickness ta of first end portion 25 and decrease the thickness tb of second end portion 27. This makes it possible to improve both the numerical aperture of X-ray mirror device 10A and the mechanical strength of inner mirror 14A.

[0096] (Tenth embodiment) 14 is a cross-sectional view schematically showing the configuration of an X-ray mirror device 110 according to a tenth embodiment. The X-ray mirror device 110 includes an outer mirror (or first mirror) 112, an inner mirror (or second mirror) 114, and an intermediate mirror 116 (or third mirror). The tenth embodiment differs from the first embodiment in that an intermediate mirror 116 is added between the outer mirror 112 and the inner mirror 114. The following description of the tenth embodiment will focus on the differences from the above-described embodiments, and a description of the commonalities will be omitted where appropriate.

[0097] The outer mirror 112 has an outer reflective surface (or first reflective surface) 122 onto which the X-rays 120 are obliquely incident. The outer reflective surface 122 reflects the X-ray flux 120a within a first angular range α1 from the first focal point F1 toward the second focal point F2. The outer mirror 112 can be configured similarly to the outer mirror 12 according to the first embodiment described above.

[0098] The inner mirror 114 has an inner reflective surface (or second reflective surface) 124 onto which the X-rays 120 are obliquely incident, and a surface (or back surface) 126 opposite the inner reflective surface 124. The inner reflective surface 124 reflects the X-ray flux 120b within the second angular range α2 from the first focal point F1 toward the second focal point F2. The inner mirror 114 can be configured similarly to the inner mirror 14 according to the first embodiment described above.

[0099] The intermediate mirror 116 has an intermediate reflective surface (or third reflective surface) 128 onto which the X-rays 120 are obliquely incident, and a surface (or back surface) 130 opposite the intermediate reflective surface 128. The intermediate reflective surface 128 reflects the X-ray flux 120c in a third angular range α3 from the first focal point F1 toward the second focal point F2. The third angular range α3 is an angular range different from the first angular range α1 and the second angular range α2. The intermediate mirror 116 is disposed between the outer mirror 112 and the inner mirror 114. The intermediate reflective surface 128 of the intermediate mirror 116 faces the inner mirror 114. The back surface 130 of the intermediate mirror 116 faces the outer mirror 112.

[0100] Like the inner mirror 114, the intermediate mirror 116 needs to be thin due to space limitations. Like the inner mirror 114, the intermediate mirror 116 preferably has a shape precision (PV) of 10 nm or less or 5 nm or less for the intermediate reflective surface 128. By configuring the intermediate mirror 116 in the same way as the inner mirror 114, it is possible to achieve both an extremely thin thickness and high shape precision for the intermediate reflective surface 128. As the intermediate mirror 116, for example, the deformable mirrors 30, 30A, 30B shown in FIG. 2, FIG. 5, or FIG. 6 can be used.

[0101] According to this embodiment, the X-ray mirror device 110 has a nested structure combining three mirrors, which increases the total angular range α1, α2, α3 (i.e., the numerical aperture) of the X-rays 120 from the first focal point F1 that can be focused by the X-ray mirror device 110. This improves the spatial resolution, and makes it possible to achieve a spatial resolution of, for example, 10 nm or less or 5 nm or less.

[0102] In a modified example, multiple intermediate mirrors may be placed between outer mirror 112 and inner mirror 114. Also, deformable mirrors 30, 30A, and 30B can be used as the multiple intermediate mirrors placed between outer mirror 112 and inner mirror 114. This makes it possible to achieve both an extremely thin thickness and high shape accuracy of the reflective surface for each of the multiple intermediate mirrors.

[0103] In a modified example, the thickness of at least one of the inner mirror 114 and the intermediate mirror 116 may be changed in a tapered manner, similar to the inner mirror 14A shown in Fig. 13. Only the thickness of the inner mirror 114 may be changed in a tapered manner, or only the thickness of the intermediate mirror 116 may be changed in a tapered manner, or the thicknesses of the inner mirror 114 and the intermediate mirror 116 may each be changed in a tapered manner. Also, the thicknesses of multiple intermediate mirrors arranged between the outer mirror 112 and the inner mirror 114 may be changed in a tapered manner.

[0104] (Eleventh embodiment) 15 is a cross-sectional view schematically showing the configuration of an X-ray mirror device 210 according to the eleventh embodiment. The X-ray mirror device 210 includes a first outer mirror (or first mirror) 212, a first inner mirror (or second mirror) 214, a second outer mirror (or fourth mirror) 232, and a second inner mirror (or fifth mirror) 234. The third embodiment differs from the above-described embodiments in that an outer mirror and an inner mirror are disposed on both sides of an optical axis 218. The following description of the eleventh embodiment will focus on the differences from the above-described embodiments, and a description of the commonalities will be omitted as appropriate.

[0105] The first outer mirror 212 has a first outer reflecting surface (or first reflecting surface) 222 onto which the X-rays 220 are obliquely incident. The first outer reflecting surface 222 reflects the X-ray flux 220a within a first angular range α1 from the first focal point F1 toward the second focal point F2. The first outer mirror 212 can be configured similarly to the outer mirror 12 according to the first embodiment described above.

[0106] The first inner mirror 214 has a first inner reflective surface (or second reflective surface) 224 onto which the X-rays 220 are obliquely incident, and a surface (or first back surface) 226 opposite the first inner reflective surface 224. The first inner reflective surface 224 reflects the X-ray flux 220b within the second angular range α2 from the first focal point F1 toward the second focal point F2. The first inner mirror 214 can be configured similarly to the inner mirror 14 according to the first embodiment described above.

[0107] The second outer mirror 232 is disposed on the opposite side of the optical axis 218 from the first outer mirror 212. The second outer mirror 232 can be disposed in a position symmetrical to the first outer mirror 212 with respect to the optical axis 218. The second outer mirror 232 has a second outer reflecting surface 242 (or a fourth reflecting surface) onto which the X-rays 220 are obliquely incident. The second outer reflecting surface 242 reflects the X-ray flux 220c within a third angular range α3 from the first focal point F1 toward the second focal point F2. The second outer reflecting surface 242 may have a shape symmetrical to the first outer reflecting surface 222 with respect to the optical axis 218. In this case, the third angular range α3 is an angular range symmetrical to the first angular range α1 with respect to the optical axis 218. The second outer mirror 232 can be configured in the same manner as the outer mirror 12 according to the first embodiment described above.

[0108] The second inner mirror 234 is disposed on the opposite side of the optical axis 218 from the first inner mirror 214. The second inner mirror 234 can be disposed at a position symmetrical to the first inner mirror 214 with respect to the optical axis 218. The second inner mirror 234 is disposed between the optical axis 218 and the second outer mirror 232. The second inner mirror 234 has a second inner reflective surface (or a fifth reflective surface) 244 onto which the X-rays 220 are obliquely incident, and a surface (or a second back surface) 246 opposite the second inner reflective surface 244. The second back surface 246 faces the second outer mirror 232. The second inner reflective surface 244 faces the first inner reflective surface 224. The second inner reflective surface 244 reflects the X-ray flux 220d within a fourth angular range α4 from the first focal point F1 toward the second focal point F2. The second inner reflective surface 244 may have a shape that is symmetrical to the first inner reflective surface 224 across the optical axis 218. In this case, the fourth angular range α4 is an angular range that is symmetrical to the second angular range α2 across the optical axis 218. The second inner mirror 234 can be configured in the same way as the inner mirror 14 according to the first embodiment described above.

[0109] According to this embodiment, by arranging an additional outer mirror and an additional inner mirror on opposite sides of the optical axis, it is possible to increase the total angular range α1, α2, α3, and α4 (i.e., the numerical aperture) of the X-rays 220 from the first focal point F1 that can be focused by the X-ray mirror device 210. This makes it possible to improve the spatial resolution, achieving, for example, a spatial resolution of 10 nm or less or 5 nm or less.

[0110] In a modified example, the thickness of the first inner mirror 214 and the second inner mirror 234 may be changed in a tapered shape, similar to the inner mirror 14A shown in FIG.

[0111] In a modified example, one or more first intermediate mirrors (or sixth mirrors) may be arranged between the first outer mirror 212 and the first inner mirror 214. Also, one or more second intermediate mirrors (or seventh mirrors) may be arranged between the second outer mirror 232 and the second inner mirror 234. The one or more second intermediate mirrors may be arranged symmetrically with the one or more first intermediate mirrors across the optical axis 218. The first intermediate mirror and the second intermediate mirror may be configured in the same manner as the intermediate mirror 216 according to the tenth embodiment shown in FIG. 14. In a modified example, the thicknesses of the first inner mirror 214 and the second inner mirror 234 may be tapered, as in the inner mirror 14A shown in FIG. 13, or the thicknesses of the first intermediate mirror and the second intermediate mirror may be tapered.

[0112] (Twelfth embodiment) 16 is a perspective view schematically showing the configuration of an X-ray device 60 according to a twelfth embodiment. The X-ray device 60 is an example of an optical device that uses X-rays, and is an X-ray microscope having a so-called imaging type microscope configuration. The X-ray device 60 includes an illumination optical system 62, a sample holder 64, an imaging optical system 66, and an X-ray detection unit 68. The X-ray device 60 is configured to irradiate a sample 88 with X-rays 92 generated by an X-ray source 90, and to detect an enlarged image of X-rays 96 that have passed through the sample 88 with the X-ray detection unit 68.

[0113] The X-ray source 90 generates X-rays 92 for observing the sample 88. The type of X-ray source 90 is not particularly limited, and an X-ray tube, a large-scale synchrotron radiation facility such as SPring-8, an X-ray free electron laser, or the like can be used. When a small device such as an X-ray tube is used as the X-ray source, the X-ray device 60 may include the X-ray source 90. On the other hand, when a large device such as a synchrotron radiation facility is used as the X-ray source 90, the X-ray device 60 does not need to include the X-ray source 90. The X-ray source 90 is configured to output hard X-rays of, for example, 2 keV or higher. The X-ray source 90 may generate monochromatic X-rays that are monochromatized to a specific wavelength, or may generate continuous X-rays (white X-rays) containing various wavelength components.

[0114] The illumination optical system 62 is disposed between the X-ray source 90 and the sample holder 64. The illumination optical system 62 is configured to focus X-rays 92 from the X-ray source 90 onto the sample holder 64. The illumination optical system 62 is configured with so-called Kirkpatrick-Baez (KB) mirrors and includes a horizontal concave mirror 70 and a vertical concave mirror 72. The horizontal concave mirror 70 and the vertical concave mirror 72 are disposed so that the normal directions of their respective reflective surfaces are orthogonal. The reflective surfaces of the horizontal concave mirror 70 and the vertical concave mirror 72 are configured, for example, as elliptical concave surfaces with a focal point at the position of the sample holder 64. The illumination optical system 62 may be configured with four curved mirrors, similar to the imaging optical system 66 described below.

[0115] The sample holder 64 holds a sample 88 that is irradiated with X-rays 94 emitted from the illumination optical system 62. The sample holder 64 holds the sample 88 to be observed on the optical path of the X-rays 94. The configuration of the sample holder 64 is not particularly limited, and any configuration for fixing the position of the sample 88 can be used depending on the characteristics of the sample 88. The sample holder 64 includes, for example, a stage device for adjusting the position of the sample 88 with respect to the optical path of the X-rays 94.

[0116] The imaging optical system 66 is disposed between the sample holder 64 and the X-ray detector 68. The imaging optical system 66 is configured to image the X-rays 96 from the sample holder 64 onto the X-ray detector 68. The imaging optical system 66 is a so-called AKB (Advanced Kirkpatrick-Baez) mirror optical system, and includes four curved mirrors 74, 76, 78, and 80. The imaging optical system 66 is configured to achieve an image magnification of, for example, approximately 100 to 1,000 times.

[0117] The imaging optical system 66 can be configured as a Wolter I mirror, for example, a combination of a hyperbolic concave mirror and an elliptical concave mirror. In this case, the first curved mirror 74 is a horizontal hyperbolic concave mirror and has a reflective surface formed by a hyperbolic concave surface with a focus at the position of the sample holder 64. The second curved mirror 76 is a vertical hyperbolic concave mirror and has a reflective surface formed by a hyperbolic concave surface with a focus at the position of the sample holder 64. The third curved mirror 78 is a horizontal elliptical concave mirror and has a reflective surface formed by an elliptical concave surface with a first focus at the position of the X-ray detector 68 and a second focus shared with the first curved mirror 74. The fourth curved mirror 80 is a vertical elliptical concave mirror and has a reflective surface formed by an elliptical concave surface with a first focus at the position of the X-ray detector 68 and a second focus shared with the second curved mirror 76.

[0118] In the example of FIG. 16 , four curved mirrors 74-80 are arranged from the sample holder 64 toward the X-ray detector 68 in the following order: horizontal hyperbolic concave mirror, vertical hyperbolic concave mirror, horizontal elliptical concave mirror, and vertical elliptical concave mirror. However, the arrangement order is not limited to this. For example, the horizontal hyperbolic concave mirror may be arranged next to the horizontal elliptical concave mirror, or the vertical hyperbolic concave mirror may be arranged next to the vertical elliptical concave mirror. The imaging optical system 66 can also be configured as a Wolter III mirror, which combines an elliptical concave mirror and a hyperbolic convex mirror. In this case, the first curved mirror 74 can be a horizontal elliptical concave mirror, the second curved mirror 76 can be a vertical elliptical concave mirror, the third curved mirror 78 can be a horizontal hyperbolic convex mirror, and the fourth curved mirror 80 can be a vertical hyperbolic convex mirror.

[0119] The X-ray detection unit 68 detects X-rays 98 emitted from the imaging optical system 66. The X-ray detection unit 68 is, for example, an X-ray camera that detects a two-dimensional image of the X-rays 98. The configuration of the X-ray detection unit 68 is not particularly limited, and for example, a direct conversion type or indirect conversion type image sensor (CCD or CMOS sensor) can be used. In order to further increase the resolution, the X-ray detection unit 68 may include an optical element such as a lens for magnifying the visible light image converted by the scintillator, and an image sensor that visualizes the magnified visible light image.

[0120] At least one of the illumination optical system 62 and the imaging optical system 66 can include the X-ray mirror device 10, 10A, 110 or 210 according to the above-described embodiment or modification.

[0121] At least one of the horizontal concave mirror 70 and the vertical concave mirror 72 that constitute the illumination optical system 62 may be configured by the X-ray mirror device 10, 10A, 110, or 210. The X-ray mirror device 10, 10A, 110, or 210 may be applied to only the horizontal concave mirror 70, only the vertical concave mirror 72, or both the horizontal concave mirror 70 and the vertical concave mirror 72.

[0122] At least one of the four curved mirrors 74 to 80 that make up the imaging optical system 66 may be configured with the X-ray mirror device 10, 10A, 110, or 210. The X-ray mirror device 10, 10A, 110, or 210 may be applied to any one, two, three, or all of the four curved mirrors 74 to 80. By using the X-ray mirror device 10, 10A, 110, or 210 in at least one of the illumination optical system 62 and the imaging optical system 66, the characteristics of the X-ray optical system can be improved, and spatial resolution can be increased.

[0123] The X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure is preferably applied to the imaging optical system 66, which requires a higher numerical aperture. In particular, it is preferable to apply the X-ray mirror device 10, 10A, 110, or 210 to each of the horizontal and vertical curved mirrors that are disposed near the sample holder 64 and serve as the objective lens of the imaging optical system 66. In the configuration of FIG. 16 , it is preferable to apply the X-ray mirror device 10, 10A, 110, or 210 to one or both of the first curved mirror 74, which is a horizontal hyperbolic concave mirror, and the second curved mirror 76, which is a vertical hyperbolic concave mirror. This is because the numerical aperture of the imaging optical system 66 must be increased to increase the resolution of the imaging optical system 66. By applying the X-ray mirror device 10, 10A, 110, or 210 to the curved mirror that serves as the objective lens of the X-ray optical system, the spatial resolution of the X-ray device 60 can be effectively improved.

[0124] The imaging optical system 66 may be configured with a KB mirror consisting of a horizontal concave mirror and a vertical concave mirror, similar to the illumination optical system 62. In this case, by using the X-ray mirror device 10, 10A, 110 or 210 for at least one of the horizontal concave mirror and the vertical concave mirror, the characteristics of the imaging optical system 66 can be improved, and the spatial resolution of the X-ray device 60 can be improved.

[0125] The X-ray device 60 may further include an X-ray spectrometer (not shown) disposed between the X-ray source 90 and the illumination optical system 62. The X-ray spectrometer is configured to monochromatize the X-rays 92 from the X-ray source 90. The X-ray spectrometer may be a crystal spectrometer such as a double crystal monochromator, and may be configured to tune the X-ray wavelength by changing the crystal angle. The X-ray device 60 can provide XAFS (X-ray Absorption Fine Structure) imaging by tuning the X-ray wavelength. Because the X-ray device 60 is configured with an X-ray optical system with little chromatic aberration, it can provide high-resolution XAFS images (e.g., 10 nm or less or 5 nm or less) simply by changing the X-ray wavelength.

[0126] The X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure can be applied to any X-ray device, and in particular to an X-ray optical system such as a focusing optical system or an imaging optical system provided in an X-ray device. Examples of the X-ray device include the imaging X-ray microscope illustrated in Fig. 16, as well as a scanning X-ray microscope and an X-ray telescope.

[0127] The scanning X-ray microscope includes a focusing optical system that focuses X-rays on a sample holder, and at least one of the X-ray mirrors constituting the focusing optical system may be the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure. In the case of a scanning X-ray microscope, the resolution is determined by the beam size of the X-rays focused by the focusing optical system. Using the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure can improve the characteristics of the focusing optical system and thereby improve the resolution of the scanning X-ray microscope. The focusing optical system of the scanning X-ray microscope can use a horizontal concave mirror 70 and a vertical concave mirror 72 similar to those in the illumination optical system 62 of FIG. 16 , and at least one of these can be the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure. The focusing optical system of the scanning X-ray microscope can also use an AKB mirror optical system including four curved mirrors, and at least one of the four curved mirrors can be the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure.

[0128] The X-ray telescope includes an imaging optical system that focuses X-rays from a celestial object to be observed on an X-ray detector, and at least one of the X-ray mirrors constituting the imaging optical system may be the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure. The imaging optical system of the X-ray telescope may be, for example, an AKB mirror optical system similar to the imaging optical system 66 in FIG. 16 . If the sample 88 in FIG. 16 is considered to be the celestial object to be observed, a Wolter 1-type imaging optical system may be used, in which the first curved mirror 74 and the second curved mirror 76 are parabolic concave mirrors and the third curved mirror 78 and the fourth curved mirror 80 are hyperbolic concave mirrors. Alternatively, a Wolter 3-type imaging optical system may be used, in which the first curved mirror 74 and the second curved mirror 76 are parabolic convex mirrors and the third curved mirror 78 and the fourth curved mirror 80 are elliptical concave mirrors. When the Wolter 3 type is used, it is easy to ensure the distance from the optical axis to the elliptical concave mirror, making it easy to place the inner mirror between the optical axis and the outer mirror. In these cases, the X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure can be used for at least one of the four curved mirrors.

[0129] The X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure may be used as a wavefront compensation optical element in any X-ray device. When used as a wavefront compensation optical element, the substantially flat reflecting surface is slightly deformed, for example, to have a shape opposite to the wavefront aberration of obliquely incident X-rays, thereby compensating for the wavefront aberration of the incident X-rays. The X-rays whose wavefront aberration has been compensated for by the X-ray mirror device 10, 10A, 110, or 210 may be further processed by X-ray optical elements such as lenses or mirrors, may be irradiated onto a sample held in a sample holder, or may be detected by an X-ray detection unit.

[0130] The X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure may be applied to an optical lithography apparatus that uses X-rays. The optical lithography apparatus includes, for example, an illumination optical system for irradiating a pattern mask with X-rays from an X-ray source, and an imaging optical system for imaging the X-rays patterned by the pattern mask onto a sample such as a wafer. The X-ray mirror device 10, 10A, 110, or 210 according to the present disclosure can be applied to at least one of the illumination optical system and the imaging optical system of the optical lithography apparatus.

[0131] The deformable mirror 30, 30A, 30B, 30C, 30D, or 30E according to the present disclosure can be used as a wavefront adaptive optical element for compensating for wavefront aberration of a laser beam, for example, as a wavefront adaptive optical element for an ultra-high intensity laser used in laser fusion.

[0132] (Thirteenth embodiment) 17 is a diagram schematically illustrating the configuration of an optical device 300 according to a thirteenth embodiment. The optical device 300 includes a laser light source 302 and an irradiation optical system 304. The optical device 300 is used to irradiate a fuel capsule 306 held in a sample holder 308 with laser light 332 provided by the laser light source 302, thereby causing nuclear fusion in the fuel capsule 306. The fuel capsule 306 contains, for example, deuterium and tritium as fuel. When deuterium and tritium undergo nuclear fusion, helium and fast neutrons (approximately 10.6 MeV) are produced, and the thermal energy extracted from the fast neutrons is used to generate electricity.

[0133] The laser light source 302 is configured to output high-intensity laser light having a peak output of, for example, 1 TW (10 W) or more or 1 PW (10 W) or more. The output wavelength of the laser light source 302 is not particularly limited, but is configured to output, for example, near-infrared light such as 1053 nm or 1064 nm, or a harmonic (second harmonic, third harmonic, or fourth harmonic) of near-infrared light. The laser light source 302 is a pulsed laser and outputs laser light 332 having a pulse width of 10 ns or less, 1 ns or less, 100 ps or less, or 10 ps or less. The pulse energy of the laser light 332 is, for example, 100 J or more, 1 kJ or more, 10 kJ or more, 100 kJ or more, or 1 MJ or more. The beam diameter of the laser light 332 provided from the laser light source 302 to the irradiation optical system 304 is, for example, 10 cm or more, 30 cm or more, 50 cm or more, 80 cm or more, or 100 cm or more.

[0134] Irradiation optical system 304 includes first folding mirror 310, second folding mirror 312, steering mirror 314, and collecting mirror 316. Laser light 332 from laser light source 302 is reflected by first folding mirror 310 and second folding mirror 312 and then enters steering mirror 314. Steering mirror 314 focuses the laser light toward intermediate focal point 318 located between steering mirror 314 and collecting mirror 316. Collecting mirror 316 reflects the laser light from intermediate focal point 318 and focuses it on fuel capsule 306. Steering mirror 314 is, for example, a parabolic mirror, and collecting mirror 316 is, for example, an elliptical mirror. Steering mirror 314 and collecting mirror 316 are examples of focusing optical elements that focus laser light 332. The focusing optical elements are not limited to reflective elements and may be transmissive optical elements such as lenses.

[0135] The optical elements (first folding mirror 310, second folding mirror 312, steering mirror 314, and collecting mirror 316) included in irradiation optical system 304 have sizes corresponding to the beam diameter of laser light 332. The size of the optical elements included in irradiation optical system 304 is equal to or larger than the beam diameter of laser light 332, for example, 20% or more larger than the beam diameter. The size of the optical elements included in irradiation optical system 304 is, for example, 10 cm or more, 15 cm or more, 30 cm or more, 40 cm or more, 50 cm or more, 60 cm or more, 80 cm or more, or 100 cm or more.

[0136] The irradiation optical system 304 is disposed inside a housing 320 for blocking fast neutrons coming from the fuel capsule 306. The irradiation optical system 304 may include a housing 320. A folded optical path for the laser beam 332 to pass through is provided inside the housing 320. A narrow passage 328 having an optical path width narrower than other locations is formed near the intermediate focus 318. The narrow passage 328 functions as a neutron filter for blocking fast neutrons. By forming the narrow passage 328, it is possible to prevent fast neutrons from directly irradiating the steering mirror 314, the second folding mirror 312, and the first folding mirror 310, which are located upstream of the narrow passage 328.

[0137] On the other hand, it is difficult to prevent direct irradiation of fast neutrons to collector mirror 316, which is located downstream of narrow passage 328. Therefore, the surface of collector mirror 316 is easily damaged by irradiation with fast neutrons, making it impossible to maintain the surface shape accuracy required to accurately focus laser beam 334 on fuel capsule 306. In other words, damage to the surface of collector mirror 316 causes disturbances in the wavefront of laser beam 334, reducing the focusing accuracy of laser beam 334. To compensate for such disturbances in the wavefront of laser beam 334, at least one of first folding mirror 310 and second folding mirror 312 can be a wavefront adaptive optical element. That is, the deformable mirror 30, 30A, 30B, 30C, 30D, 30E, or 30F according to the above-described embodiment can be used for at least one of first folding mirror 310 and second folding mirror 312.

[0138] Illumination optical system 304 may further include a beam splitter 322 disposed between second folding mirror 312 and steering mirror 314, and a detector 324 that detects light reflected by beam splitter 322. Beam splitter 322 is disposed to guide the returning light from fuel capsule 306 to detector 324. Detector 324 measures damage to the surface of collector mirror 316 by detecting the light that has passed from fuel capsule 306 through collector mirror 316 and steering mirror 314. The measurement result of detector 324 can be used to control wavefront compensation in at least one of first folding mirror 310 and second folding mirror 312.

[0139] The irradiation optical system 304 includes a deformable mirror (at least one of a first folding mirror 310 and a second folding mirror 312) that reflects the laser beam 332 provided by the laser light source 302, and a focusing mirror 316 that focuses the laser beam reflected by the deformable mirror toward the fuel capsule 306 held in the sample holder 308. At least one of the first folding mirror 310 and the second folding mirror 312 can be configured similarly to the deformable mirror 30, 30A, 30B, 30C, 30D, 30E, or 30F according to the above-described embodiments. By using a piezoelectric single crystal material such as LN or LT as the deformable mirror, hysteresis and drift can be suppressed, and the shape of the reflecting surface can be uniquely determined according to the applied voltage. Therefore, wavefront disturbance of the laser beam 334 irradiated onto the fuel capsule 306 can be compensated for with high precision, and the effects of damage to the surface of the focusing mirror 316 can be mitigated. This allows the maintenance cycle of the collector mirror 316 to be extended, contributing to the realization of a laser fusion reactor that can operate stably for a long period of time.

[0140] (Fourteenth embodiment) 18 is a diagram showing a schematic configuration of a laser fusion reactor 400 according to the fourteenth embodiment. The laser fusion reactor 400 includes a laser light source 402, an irradiation optical system 404, a fuel supply device 408, a reaction vessel 410, a blanket 412, a containment vessel 414, a laser inlet 416, and a fuel inlet 418.

[0141] The laser light source 402 and the irradiation optical system 404 may be configured similarly to the laser light source 302 and the irradiation optical system 304 described above. The laser light 424 output from the irradiation optical system 404 is introduced into the internal space 420 of the reaction vessel 410 through the laser inlet 416. The laser light 424 is irradiated onto the fuel capsule 406 introduced into the internal space 420 of the reaction vessel 410. In the example shown in FIG. 18 , four laser light sources 402 and irradiation optical systems 404 are used to irradiate the fuel capsule 306 with the laser light 424 from four directions. However, the number of laser light irradiated onto the fuel capsule 306 is not particularly limited and may be three or less, or five or more. The number of laser light irradiated onto the fuel capsule 306 may be ten or more, or twenty or more. The laser light irradiated onto the fuel capsule 306 may be a combination of a compression laser light for compressing the fuel and an ignition laser light for igniting the fuel.

[0142] A fuel supply device 408 introduces a fuel capsule 406 into an internal space 420 of a reaction vessel 410 through a fuel inlet 418. The reaction vessel 410 has an internal space 420 into which the fuel capsule 406 and a laser beam 424 are introduced. A blanket 412 is provided inside the reaction vessel 410. The blanket 412 absorbs fast neutrons generated by the nuclear fusion reaction in the fuel capsule 406 and converts them into heat. The blanket 412 includes a material capable of regenerating fuel. The blanket 412 includes, for example, a solid material (e.g., lithium titanate) or a liquid material (e.g., titanium lead, lithium beryllium fluoride) containing lithium (Li) and is configured to regenerate tritium by capturing neutrons. A containment vessel 414 is disposed outside the reaction vessel 410. A neutron shielding material 422, such as water, is contained inside the containment vessel 414.

[0143] The heat generated in the blanket 412 is transferred to a fluid flowing inside a pipe 428 introduced into the reaction vessel 410, and is sent to a steam generator 430. The fluid flowing inside the pipe 428 is circulated by a pump or the like (not shown). The steam generator 430 generates steam by utilizing the heat from the fluid flowing inside the pipe 428. The steam generated in the steam generator 430 is sent to a steam turbine 432 and drives the steam turbine 432. A generator 434 generates electricity using the driving force generated by the steam turbine 432.

[0144] The present disclosure has been described above based on the embodiments. It will be understood by those skilled in the art that the present disclosure is not limited to the above embodiments, and that various design changes and modifications are possible, and that such modifications are also within the scope of the present disclosure. [Industrial Applicability]

[0145] According to certain aspects of the present disclosure, the numerical aperture of an optical system with reduced chromatic aberration can be improved. [Explanation of symbols]

[0146] 10, 10A... X-ray mirror device, 12... outer mirror, 14, 14A... inner mirror, 18... optical axis, 20... X-ray, 22... outer reflective surface, 24... inner reflective surface, 26, 26A... rear surface, 30, 30A, 30B, 30C, 30D, 30E, 30F... deformable mirror, 32, 32B... piezoelectric substrate, 33, 34... reflective surface electrode, 36, 37... rear surface electrode, 38... power supply, 40... reflective surface, 42... rear surface, 44, 44B... first piezoelectric layer, 46, 46B... second piezoelectric layer, 48... intermediate electrode, 60... X-ray microscope, 62... illumination optical system, 64... sample holder, 66... ​​imaging optics System, 68...X-ray detection unit, 110...X-ray mirror device, 112...outer mirror, 114...inner mirror, 116...intermediate mirror, 120...X-rays, 122...outer reflective surface, 124...inner reflective surface, 126...back surface, 128...intermediate reflective surface, 130...back surface, 210...X-ray mirror device, 212...first outer mirror, 214...first inner mirror, 218...optical axis, 220...X-rays, 222...first outer reflective surface, 224...first inner reflective surface, 226...first back surface, 232...second outer mirror, 234...second inner mirror, 242...second outer reflective surface, 244...second inner reflective surface.

Claims

1. a first mirror having a first reflecting surface onto which the light beam is incident; a second mirror positioned away from the first reflecting surface in a normal direction of the first reflecting surface, a mirror device in which the second mirror has a second reflecting surface onto which a light ray is incident and a surface opposite to the second reflecting surface, the opposite surface facing the first reflecting surface, and the second reflecting surface having a deformable shape;

2. The mirror device according to claim 1 , wherein at least one of the first reflecting surface and the second reflecting surface is a total reflection mirror.

3. 2. The mirror device according to claim 1, wherein at least one of the first reflecting surface and the second reflecting surface is a multilayer mirror having 100 or less layers.

4. The mirror device according to claim 1 , wherein each of the first reflecting surface and the second reflecting surface has a curvature at least in the optical axis direction.

5. 2. The mirror device according to claim 1, wherein the second mirror has a thickness of 10 [mu]m or more and 1 mm or less.

6. 2. The mirror device according to claim 1, wherein the distance between the first mirror and the second mirror is not less than 50 [mu]m and not more than 5 mm.

7. The second mirror is a piezoelectric substrate having the second reflecting surface and the opposite surface; a first electrode located on the second reflecting surface; a second electrode located on the opposite surface; The mirror device according to claim 1 , further comprising: a power supply that applies a voltage between the first electrode and the second electrode.

8. The mirror device according to claim 7 , wherein the outer periphery of at least one of the first electrode and the second electrode is a polygon with rounded corners.

9. 8. The mirror device according to claim 7, wherein the thickness of the piezoelectric substrate is not less than 10 [mu]m and not more than 1 mm.

10. 8. The mirror device according to claim 7, wherein the thickness of the piezoelectric substrate changes in a tapered shape in the optical axis direction.

11. At least one of the first electrode and the second electrode includes a plurality of electrodes arranged at intervals in the optical axis direction, The mirror device according to claim 7 , wherein the power source is capable of applying different voltages to each of the plurality of electrodes.

12. The mirror device according to claim 11 , wherein the outer periphery of each of the plurality of electrodes is a polygon with rounded corners.

13. 8. The mirror device according to claim 7, wherein the piezoelectric substrate is made of a piezoelectric single crystal material.

14. 14. The mirror device of claim 13, wherein the piezoelectric single crystal material is lithium niobate (LN) or lithium tantalate (LT).

15. 8. The mirror device of claim 7, wherein the piezoelectric substrate comprises a first piezoelectric layer having the second reflecting surface and a second piezoelectric layer having the opposite surface, the second piezoelectric layer being made of the same material as the first piezoelectric layer and having a polarization direction opposite to that of the first piezoelectric layer.

16. the piezoelectric substrate includes a first piezoelectric layer having the second reflecting surface and a second piezoelectric layer having the opposite surface, the second piezoelectric layer being made of the same material as the first piezoelectric layer; the second mirror further comprises a third electrode located between the first piezoelectric layer and the second piezoelectric layer; The mirror device according to claim 7 , wherein the power supply applies a voltage between the first electrode and the third electrode, and applies a voltage between the third electrode and the second electrode.

17. The mirror device according to claim 1 , further comprising a third mirror located between the first mirror and the second mirror.

18. a fourth mirror located on the opposite side of the optical axis from the first mirror; The mirror device according to claim 1 , further comprising: a fifth mirror located on the opposite side of the optical axis from the second mirror.

19. At least one of the first electrode and the second electrode comprises a plurality of electrodes; the power source is capable of applying different voltages to the plurality of electrodes; 8. The mirror device according to claim 7, wherein the piezoelectric substrate is made of a single piezoelectric single crystal substrate in which a first piezoelectric layer having the second reflecting surface and a second piezoelectric layer having the opposite surface are integrated, and the second piezoelectric layer has a polarization direction opposite to that of the first piezoelectric layer.

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