JP6632852B2 - X-ray imaging apparatus and X-ray imaging method - Google Patents

Description

  The present invention relates to an X-ray imaging device and an X-ray imaging method.

  The X-ray absorption coefficient differs depending on the X-ray energy even for the same substance. Therefore, in the X-ray imaging apparatus, the energy region of the X-ray to be used is selected according to the constituent material of the sample. For example, Patent Literature 1 discloses a light collecting device including an aspherical mirror and a vent mechanism. The vent mechanism selects the radius of curvature of the aspherical mirror in the longitudinal direction according to the X-ray energy by adjusting the bending of the aspherical mirror in the longitudinal direction.

  Note that Patent Documents 2 and 3 describe X-ray microscopes. The X-ray microscope described in Patent Literature 3 includes an illumination optical system having two reflection regions having different reflection angles in the optical axis direction, and moving means for moving the illumination optical system in the optical axis direction. In this X-ray microscope, the bright-field observation mode and the dark-field observation mode can be switched by moving the illumination optical system in the optical axis direction.

JP 2014-163667 A JP 2008-96273 A JP 2006-343535 A

  In the condensing device described in Patent Document 1, the incident angle of X-rays on a sample changes according to the energy of X-rays. Therefore, when an imaging optical system and a detector are provided behind the sample, X-rays from the sample are imaged on the detector by the imaging optical system. Alignment of the optical system and the detector is required. In the X-ray microscope described in Patent Document 3, there is no mention of selecting the energy of X-rays.

  An object of the present invention is to provide an X-ray imaging apparatus and an X-ray imaging method that can easily observe a sample while selecting an X-ray energy region.

  The X-ray imaging apparatus according to the present invention, an X-ray source that emits X-rays for irradiating the sample, a detector that detects X-rays from the sample, and are arranged on a reference line from the X-ray source to the detector, A condensing optical system having a first reflecting surface and a second reflecting surface for converging X-rays emitted from an X-ray source onto a sample by total internal reflection, and arranged on a reference line to detect X-rays from the sample The state of the imaging optical system that forms an image on the container and the state of the light collection optical system are as follows: a first state in which X-rays totally reflected by the first reflection surface are collected on the sample; And a control unit for performing control to switch between a second state in which the X-rays are focused on the sample, the sample being held at a predetermined distance from the X-ray source on the reference line, and The angle formed between the reflection surface and the reference line and the angle formed between the second reflection surface and the reference line are different from each other, and the first reflection occurs in the first state. The angle formed by the optical axis of the X-ray totally reflected by the reference line and the reference line and the angle formed by the optical axis of the X-ray totally reflected by the second reflection surface in the second state and the reference line are equal to each other. is there.

  This X-ray imaging apparatus includes a control unit that switches the state of the light collecting optical system. The control unit switches between a first state in which X-rays are totally reflected by the first reflection surface and incident on the sample, and a second state in which X-rays are totally reflected by the second reflection surface and incident on the sample. The angle formed by the first reflection surface and the reference line is different from the angle formed by the second reflection surface and the reference line. Further, in the first state, the angle between the optical axis of the X-ray totally reflected by the first reflecting surface and the reference line, and in the second state, the optical axis of the X-ray totally reflected by the second reflecting surface. The angles formed with the reference line are equal to each other. Therefore, the oblique incidence angle of X-rays on the first reflection surface in the first state and the oblique incidence angle of X-rays on the second reflection surface in the second state are different from each other due to a geometric relationship. If the oblique incidence angle of X-rays on the reflecting surface is different, the energy region of X-rays totally reflected on the reflecting surface is different. Thus, by switching between the first state and the second state, the X-rays used for observing the sample are converted to the X-rays of the energy region totally reflected by the first reflection surface and the energy totally reflected by the second reflection surface. And X-rays in the region. As described above, in the first state and the second state, the angle between the optical axis of the X-ray totally reflected on the first reflection surface and the reference line, and the light of the X-ray totally reflected on the second reflection surface The angle between the axis and the reference line is equal to each other. For this reason, the state of incidence of X-rays on the imaging optical system does not change between the first state and the second state. Therefore, there is no need to align the imaging optical system and the detector according to the selection of the X-ray energy. As described above, in this X-ray imaging apparatus, a sample can be easily observed while selecting an energy region of X-rays.

  In this X-ray imaging apparatus, the first optical element including the first reflecting surface and the second optical surface are integrated with the first optical element in a state of being aligned with the first optical element along the reference line. The control unit may include a second optical element, and may switch between the first state and the second state by moving the first optical element and the second optical element along a reference line. In this case, since the first optical element and the second optical element are integrated, the state of the condensing optical system can be switched by moving the first optical element and the second optical element by a common moving mechanism. .

  In this X-ray imaging apparatus, the condensing optical system includes a first optical element including a first reflecting surface, and a second optical element including a second reflecting surface and configured separately from the first optical element. The control unit may switch between the first state and the second state by moving the first optical element and the second optical element. In this case, since the first optical element and the second optical element are configured separately, the first optical element and the second optical element can be respectively moved. Therefore, the first optical element and the second optical element can be easily arranged at positions for converging the X-ray emitted from the X-ray source on the sample by total reflection.

  In this X-ray imaging apparatus, a first shielding member for shielding X-rays from the X-ray source toward the second reflecting surface and a second shielding member for shielding X-rays from the X-ray source toward the first reflecting surface are provided. A shielding member, wherein the control unit shields X-rays from the X-ray source toward the second reflection surface using the first shielding member, and performs first reflection from the X-ray source using the second shielding member. The state may be switched between the first state and the second state by selecting one of the states that block the X-rays traveling toward the surface. In this case, there is no need to move the first reflection surface and the second reflection surface.

  In this X-ray imaging apparatus, the imaging optical system may have a third reflection surface that totally reflects X-rays from the sample and forms an image on the detector. In this case, it is not necessary to change the optical elements constituting the imaging optical system and their arrangement according to the selection of the X-ray energy.

  In this X-ray imaging apparatus, the third reflecting surface may totally reflect X-rays in the entire energy region which are totally reflected on the first reflecting surface and the second reflecting surface. In this case, it is possible to suppress the X-rays in the energy region used for observation of the sample from being removed by the imaging optical system.

  The X-ray imaging apparatus includes a filter that is disposed on the reference line and that removes X-rays on the low energy region side among X-rays in the energy region totally reflected on the first reflection surface and the second reflection surface. Is also good. In this case, since the X-rays in the low energy region which are not used for observation of the sample can be removed, the contrast of the obtained X-ray image can be improved.

  The X-ray imaging apparatus may include a third shielding member that is arranged on the reference line and shields X-rays that enter the detector without passing through the focusing optical system. In this case, since the X-rays in the energy region that are not used for observation of the sample are suppressed from being incident on the detector, the contrast of the obtained X-ray image can be further improved.

  An X-ray imaging method according to the present invention is an X-ray imaging method using the above-mentioned X-ray imaging apparatus, wherein the state of the focusing optical system is set to one of a first state and a second state by a control unit. A step of selecting X, an emission step of emitting X-rays for irradiating the sample from the X-ray source, a focusing step of focusing the X-rays emitted in the emission step on the sample by a focusing optical system, and forming an image. An imaging step of forming an X-ray from a sample on a detector by an optical system and a detection step of detecting the X-ray imaged in the imaging step by a detector are included.

  Since this X-ray imaging method uses the above-described X-ray imaging apparatus, the sample can be easily observed while selecting the energy region of X-rays.

  According to the X-ray imaging apparatus and the X-ray imaging method according to the present invention, it is possible to easily observe a sample while selecting an energy region of X-rays.

FIG. 2 is a diagram illustrating a configuration of the X-ray imaging apparatus according to the first embodiment. FIG. 3 is a diagram illustrating a configuration of a light collecting optical system and a control unit. FIG. 3 is a diagram illustrating dimensions of an optical element. FIG. 3 is a diagram illustrating a relationship between a critical angle of total reflection of X-rays and energy of X-rays. It is a figure showing the composition of the X-ray imaging device concerning a modification of a 1st embodiment. It is a figure showing the composition of the X-ray imaging device concerning a 2nd embodiment. It is a figure showing the composition of the X-ray imaging device concerning a 3rd embodiment. FIG. 4 is a diagram illustrating a configuration of an X-ray imaging apparatus according to a comparative example. It is a figure which shows the relationship between the energy of X-rays, a transmittance | permeability, and a reflectance. It is a figure which shows the relationship between the energy of X-rays, a transmittance | permeability, and a reflectance.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference characters, and redundant description will be omitted.

(1st Embodiment)
An X-ray imaging apparatus according to the first embodiment will be described with reference to FIGS. FIG. 1 is a diagram illustrating a configuration of the X-ray imaging apparatus according to the first embodiment. More specifically, FIG. 1A is a diagram illustrating a case where the state of the light collecting optical system is a first state, and FIG. 1B is a state where the state of the light collecting optical system is a second state. It is a figure showing a case. FIG. 2 is a diagram illustrating dimensions of the optical element.

  As shown in FIG. 1, the X-ray imaging apparatus 10A includes an X-ray source 1, a filter 2, a condensing optical system 3A, a shielding member (third shielding member) 4, and a shielding member (third shielding member). ) 5, an imaging optical system 6, a detector 7, and a control unit 8 (see FIG. 3). The X-ray imaging device 10A is, for example, a soft X-ray 3D microscope. The sample S is held at a distance L0 from the X-ray source 1 and at a distance L3 from the detector 7 on a reference line A from the X-ray source 1 to the detector 7, and is held by a sample holding unit (not shown). I have.

  The X-ray absorption coefficient differs depending on the X-ray energy even for the same substance. Therefore, in the X-ray imaging apparatus 10A, the energy of the X-ray used for observation is selected according to the constituent material of the sample S. For example, for observation of a material with a low atomic number (Z) (light element material), X-rays in an energy range of 1 keV to several keV are used. For observation of a biological sample containing water, X-rays in an energy range of 285 eV to 543 eV called a “water window” are used. The X-ray imaging apparatus 10A can observe the light element material and the internal structure of the biological sample by using X-rays in such an energy region. By rotating the sample S, the sample S can be observed three-dimensionally. The rotation axis B of the sample S is perpendicular to the reference line A, for example. When the energy of the X-ray used is low (（5 keV), the X-ray imaging apparatus 10 </ b> A may be installed in a vacuum vessel (not shown) to avoid the attenuation of the X-ray by air.

  The X-ray source 1 emits X-rays 20 that irradiate the sample S. The X-ray source 1 is, for example, an electron beam excitation type (electron beam impact type) X-ray source, a plasma X-ray source using laser and gas discharge, and the like. The X-ray source 1 is an X-ray in an energy range (285 eV to 543 eV) used for observation of a biological sample as described above, an X-ray in an energy range (1 keV to several keV) used for observation of a light element material, or the like. Is emitted. When an electron beam excitation type X-ray source is used as the X-ray source 1, the emitted X-rays 20 include characteristic X-rays and bremsstrahlung X-rays. The characteristic X-ray has a high intensity, and the energy is determined by a substance constituting the target. Bremsstrahlung X-rays have low intensity and their energy is determined by the acceleration voltage. Characteristic X-rays are used for observation. As a target having the characteristic X-ray in the energy region as described above, for example, an oxide target, a Ti target, or the like is used.

  The filter 2 is arranged on the reference line A. The filter 2 is, for example, a metal filter of Be, Ti, or the like. The filter 2 allows the X-rays 20 in the energy region higher than the energy E0 to pass therethrough and removes the X-rays 20 in the energy region lower than the energy E0. That is, the filter 2 restricts the X-rays 20 emitted from the X-ray source 1 to the X-rays 20 having the energy E0 or more, and emits the X-rays 20 to the focusing optical system 3A. The energy E0 serving as the threshold is determined by the material and thickness of the filter 2. Therefore, the material and thickness of the filter 2 are determined according to the energy of the X-rays 20 used for observation. A plurality of types of filters 2 are prepared, and can be replaced relatively easily by disposing and retracting them on the optical path of the X-rays 20 by a moving mechanism (not shown).

  The focusing optical system 3A focuses the X-rays 20 emitted from the X-ray source 1 and passing through the filter 2 onto the sample S. The condensing optical system 3A has an optical element 30A. The optical element 30A is, for example, an aspherical mirror. The optical element 30 </ b> A is, for example, a cylindrical oblique incidence reflection mirror, and is arranged on the reference line A so that the center axis coincides with the reference line A. The optical element 30A collects light by reflecting the X-ray 20 on its inner surface. The optical element 30A is a reflection optical system using total reflection, and is, for example, a Walter mirror including a spheroid and a hyperboloid, a spheroid, a paraboloid of revolution, and the like. Here, the optical element 30A includes a first optical element 31, a second optical element 32, and a connection pipe 33.

  The first optical element 31 is a cylindrical oblique incidence reflecting mirror, and is arranged on the reference line A such that the central axis coincides with the reference line A. The first optical element 31 is, for example, a spheroid mirror. The first optical element 31 includes an end 31a, an end 31b, and a first reflection surface 31c for condensing the X-rays 20 emitted from the X-ray source 1 on the sample S by total internal reflection. . The end 31a is arranged on the X-ray source 1 side, and the end 31b is arranged on the detector 7 side. The end 31a is arranged at a distance L1 from the X-ray source 1 along the reference line A.

  The first reflection surface 31c is a curved surface forming the inner surface of the first optical element 31, and connects the end 31a and the end 31b. The first reflection surface 31c is a surface that is arranged on the reference line A and is for condensing the X-rays 20 emitted from the X-ray source 1 on the sample S by total internal reflection. The first reflection surface 31c is line-symmetric with respect to the reference line A. That is, the first optical element 31 collects light by reflecting the X-rays 20 on the first reflection surface 31c. The first reflection surface 31c is inclined at a first inclination angle α1 with respect to the reference line A.

  The second optical element 32 is integrated with the first optical element 31 in a state where the second optical element 32 is aligned with the first optical element 31 along the reference line A. The second optical element 32 is a cylindrical oblique incidence reflection mirror, and is arranged on the reference line A such that the central axis coincides with the reference line A. The second optical element 32 is, for example, a spheroidal mirror. The second optical element 32 includes an end 32a, an end 32b, and a second reflection surface 32c for condensing the X-rays 20 emitted from the X-ray source 1 on the sample S by total internal reflection. . The end 32a is arranged on the X-ray source 1 side, and the end 32b is arranged on the detector 7 side. The end 32a is arranged at a distance L2 from the X-ray source 1 along the reference line A.

  The second reflection surface 32c is a curved surface that forms the inner surface of the second optical element 32, and connects the end 32a and the end 32b. The second reflection surface 32c is a surface arranged on the reference line A for converging the X-rays 20 emitted from the X-ray source 1 on the sample S by total internal reflection. The second reflection surface 32c is line-symmetric with respect to the reference line A. That is, the second optical element 32 condenses the X-rays 20 by reflecting the X-rays on the second reflection surface 32c. The second reflection surface 32c is inclined at a second inclination angle α2 with respect to the reference line A. The second inclination angle α2 is different from the first inclination angle α1. Since the first optical element 31 is disposed closer to the X-ray source 1 than the second optical element 32 and has a larger inner diameter as described later, the second inclination angle α2 is larger than the first inclination angle α1.

  The connection pipe 33 is a tubular member that connects the first optical element 31 and the second optical element 32, and is arranged so that the central axis coincides with the reference line A. The connection pipe 33 includes an end 33a and an end 33b. The end 33a is arranged on the first optical element 31 side and is connected to the end 31b. The end 33b is arranged on the second optical element 32 side and is connected to the end 32a. The inner surface of the connection pipe 33 may be coated with a substance that does not reflect the X-rays 20 and absorbs the X-rays 20. This suppresses the X-rays reflected on the inner surface of the connection pipe 33 from entering the imaging optical system 6.

  Here, as shown in FIG. 2A, the dimensions of the first optical element 31 are the length L6 along the reference line A (see FIG. 1), the inner diameter D1 of the end 31a, and the inner diameter of the end 31b. D2. The inside diameter D1 is larger than the inside diameter D2. The dimensions of the second optical element 32 are a length L8 along the reference line A, an inner diameter D3 of the end 32a, and an inner diameter D4 of the end 32b. The inside diameter D3 is smaller than the inside diameter D2 and larger than the inside diameter D4. The dimensions of the connection pipe 33 are a length L7 along the reference line A, an inner diameter D2 of the end 33a, and an inner diameter D3 of the end 33b.

  Returning to FIG. 1, the description will be continued. The condensing optical system 3A has a first state shown in FIG. 1A and a second state shown in FIG. 1B depending on the position of the optical element 30A. The values of the distance L1 and the distance L2 are different between the first state and the second state. The distance L1 in the first state (hereinafter, referred to as distance L1 (S1)) is longer than the distance L1 in the second state (hereinafter, referred to as distance L1 (S2)). The first state distance L2 (S1) is longer than the second state distance L2 (S2).

  In the first state, the first reflecting surface 31c is used for collecting the X-rays 20. That is, in the first state, the X-rays 20 are incident on the first reflection surface 31c at the first oblique incidence angle β1, and the X-rays 20 totally reflected by the first reflection surface 31c are collected on the sample S. The first oblique incidence angle β1 is defined as an angle formed between the optical axis C3 of the X-ray 20 incident on the center position of the first reflection surface 31c in the direction along the reference line A and the first reflection surface 31c.

  In the second state, the second reflection surface 32c is used for collecting the X-rays 20. That is, in the second state, the X-rays 20 are incident on the second reflection surface 32c at the second oblique incidence angle β2, and the X-rays 20 totally reflected by the second reflection surface 32c are collected on the sample S. The second oblique incidence angle β2 is defined as an angle formed between the optical axis C4 of the X-ray 20 incident on the center position of the second reflection surface 32c in the direction along the reference line A and the second reflection surface 32c.

  In the condensing optical system 3A, by setting the length L7 of the connection pipe 33, the arrangement of the first reflection surface 31c and the second reflection surface 32c in the first state causes X reflected by the second reflection surface 32c. The line 20 is set so that it does not enter the imaging optical system 6, and in the second state, the X-ray 20 reflected by the first reflection surface 31 c does not enter the imaging optical system 6. The condensing optical system 3A includes a shielding member 4 and a shielding member 5, which will be described later. In the first state, the X-rays 20 reflected by the second reflection surface 32c do not enter the imaging optical system 6, and In the second state, the X-rays 20 reflected by the first reflection surface 31c may be set so as not to enter the imaging optical system 6.

  The optical axis C1 of the X-ray 20 (hereinafter, referred to as first incident light) totally reflected by the first reflection surface 31c in the first state forms an angle γ with the reference line A. The optical axis C1 is defined as the optical axis of the X-ray 20 emitted to the sample S from the center position of the first reflection surface 31c in the direction along the reference line A. In the second state, the optical axis C2 of the X-ray 20 (hereinafter, referred to as second incident light) totally reflected by the second reflection surface 32c and the reference line A form an angle γ. The optical axis C2 is defined as the optical axis of the X-ray 20 emitted to the sample S from the center position of the second reflection surface 32c in the direction along the reference line A.

  As described above, the angle between the optical axis C1 of the first incident light and the reference line A and the angle between the optical axis C2 of the second incident light and the reference line A are both the angle γ, and are equal to each other. It is. That is, the first incident light and the second incident light have a common optical path. More specifically, the optical path of the first incident light and the optical path of the second incident light have overlapping portions. In other words, the numerical apertures of the first optical element 31 and the second optical element 32 are both equal to the numerical aperture of the imaging optical system 6. Further, as described above, the first inclination angle α1 and the second inclination angle α2 are different from each other. From the geometric relationship between the angle γ, the first inclination angle α1, and the first oblique incidence angle β1, and the geometric relationship between the angle γ, the second inclination angle α2, and the second oblique incidence angle β2, the first oblique incidence is obtained. The angle β1 and the second oblique incidence angle β2 are different from each other. The configuration for switching between the first state and the second state of the condensing optical system 3A will be described later with reference to FIG.

  The shielding member 4 and the shielding member 5 are arranged on the reference line A. The shielding member 4 and the shielding member 5 have a circular shape when viewed from a direction along the reference line A. The outer diameter of the shielding member 4 is smaller than the inner diameter D4 (see FIG. 2A). The outer diameter of the shielding member 5 is smaller than the inner diameter D5 described later (see FIG. 2B). The shielding member 4 is disposed on the X-ray source 1 side of the sample S on the reference line A. The shielding member 5 is disposed closer to the detector 7 than the sample S on the reference line A.

  The shielding member 4 is disposed inside the optical path of the first incident light and the optical path of the second incident light (on the side of the reference line A), and shields the X-rays 20 incident on the detector 7 without passing through the condensing optical system 3A. I do. The shielding member 5 is disposed inside the optical path of the X-ray 20 incident on the reflection surface 61c from the sample S (on the side of the reference line A), and is incident on the detector 7 without passing through the focusing optical system 3A. Shield. According to the shielding member 4 and the shielding member 5, the X-rays 20 that do not contribute to imaging, such as scattered X-rays from the surroundings, can be removed.

  The imaging optical system 6 is arranged on the reference line A, and enlarges the X-ray 20 from the sample S to form an image on the detector 7. The imaging optical system 6 has a third optical element 60. The third optical element 60 is, for example, an aspherical mirror. The third optical element 60 is, for example, a cylindrical oblique incidence reflection mirror, and is arranged on the reference line A such that the central axis coincides with the reference line A. The third optical element 60 reflects the X-rays 20 on its inner surface to collect light. The third optical element 60 is a reflection optical system using total reflection, and is, for example, a Walter mirror including a spheroid and a hyperboloid.

  The third optical element 60 includes a first portion 61 and a second portion 62. The first portion 61 includes an end 61a, an end 61b, and a reflection surface (third reflection surface) 61c. The end 61a is arranged on the sample S side, and the end 61b is arranged on the detector 7 side. The end 61a is located at a distance L4 from the sample S along the reference line A. The reflection surface 61c of the first portion 61 corresponds to, for example, the hyperboloid of rotation of the Walter mirror, and is inclined at a third inclination angle α3 with respect to the reference line A. The reflecting surface 61c is line-symmetric with respect to the reference line A. The third inclination angle α3 is larger than the second inclination angle α2 and the first inclination angle α1.

  The second portion includes an end 62a, an end 62b, and a reflection surface 62c. The end 62a is arranged on the sample S side, and the end 62b is arranged on the detector 7 side. The end 62a is arranged at a distance L5 from the X-ray source 1 along the reference line A. The reflection surface 62c of the second portion 62 corresponds to, for example, a spheroid of the Walter mirror. The reflection surface 62c is line-symmetric with respect to the reference line A. The end 61b and the end 62a are connected to each other.

  Here, as shown in FIG. 2B, the dimensions of the first portion 61 of the third optical element 60 are a length L9 along the reference line A (see FIG. 1), an inner diameter D5 of the end 61a, and The inner diameter D6 of the end 61b. The dimensions of the second portion 62 of the third optical element 60 are a length L10 along the reference line A, an inner diameter D6 of the end 62a, and an inner diameter D7 of the end 62b.

  Returning to FIG. 1, the description will be continued. The detector 7 detects X-rays 20 from the sample S. The detector 7 has a light receiving surface, and detects the X-rays 20 formed on the light receiving surface by the imaging optical system 6 after transmitting through the sample S. The detector 7 includes, for example, an X-ray detection element such as a CCD element. By rotating the sample S and taking an image with the detector 7, and performing image reconstruction, three-dimensional observation of the sample S is also possible.

  FIG. 3 is a diagram illustrating a configuration of the light-converging optical system and the control unit. As shown in FIG. 3, the condensing optical system 3A further includes a stage 11, a holder 12, and a drive motor 13. The holder 12 holds the optical element 30 </ b> A on the outer peripheral surface of the connection pipe 33 on the stage 11. The holder 12 is arranged on the stage 11 so as to be movable along the reference line A. The drive motor 13 is, for example, a pulse motor, and moves the holder 12 on the stage 11 along the reference line A.

  The control unit 8 is electrically connected to the drive motor 13. The control unit 8 is configured by a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, for example. The control unit 8 sends a control signal to the drive motor 13 to drive the drive motor 13. The control unit 8 switches between the first state and the second state by moving the first optical element 31 and the second optical element 32 along the reference line A (for example, in parallel). That is, the control unit 8 changes the state of the condensing optical system 3A into a first state in which the X-rays 20 totally reflected on the first reflection surface 31c are condensed on the sample S, and a total reflection on the second reflection surface 32c. Control is performed to switch between the X-ray 20 that has been focused and the second state in which the X-ray 20 is focused on the sample S.

  Subsequently, an X-ray imaging method using the X-ray imaging apparatus configured as described above will be described. In the X-ray imaging method according to the present embodiment, first, the state of the condensing optical system 3A is selected from the first state and the second state (selection step). Thereby, the energy region of the X-rays 20 to be removed by the focusing optical system 3A can be selected for the following reasons.

FIG. 4A is a diagram illustrating the oblique incidence angle of X-rays, and FIG. 4B is a graph illustrating the relationship between the energy of X-rays and the reflectance. As shown in FIG. 4A, when X-rays are incident on a certain material plane, total reflection occurs when an oblique incidence angle θ, which is an angle formed between the plane and the X-rays, is equal to or smaller than a predetermined value. The maximum angle at which this total reflection occurs is called the total reflection critical angle θc. The magnitude of the critical angle for total reflection θc is determined by the material on the reflection plane and the X-ray energy, and using the density ρ (g / cm ³ ) and the X-ray wavelength λ (nm) of the material on the reflection plane, Equation (1) Indicated by
θc (°) = 94.2 × 10 ⁻¹ × λ × (ρ) ^1/2 (1)

The relationship between the X-ray energy E and the X-ray wavelength λ is represented by Expression (2).
E (eV) = 1240 / λ (2)

  As shown in FIG. 4B, when the oblique incident angle is θa, the X-ray energy is Ea, and the reflectance sharply decreases. When the oblique incident angle is θb (θa> θb), the X-ray energy is reduced. Eb sharply lowers the reflectance. That is, if the oblique incident angle is set to θa, X-rays having an X-ray energy of Ea or more are removed, and if the oblique incident angle is set to θb, X-rays having an X-ray energy of Eb or more are removed. Understand. As described above, by selecting the oblique incident angle, the energy region of the X-ray to be removed without being reflected can be selected.

  When the first state is selected in the selecting step, the control unit 8 does not switch the state of the light collecting optical system 3A if the state of the light collecting optical system 3A is the first state in advance. Further, when the state of the condensing optical system 3A is the second state, the control unit 8 drives the drive motor 13 to move the first optical element 31 and the second optical element 32 along the reference line A (for example, , Parallel). Thereby, the state of the condensing optical system 3A is switched to the first state. On the other hand, similarly, when the second state is selected in the selection step, the control unit 8 does not switch the state of the light collecting optical system 3A if the state of the light collecting optical system 3A is the second state in advance. Further, when the state of the condensing optical system 3A is the first state, the control unit 8 drives the drive motor 13 to move the first optical element 31 and the second optical element 32 in parallel with the reference line A. . Thereby, the state of the condensing optical system 3A is switched to the second state.

  Subsequently, X-rays 20 for irradiating the sample S are emitted from the X-ray source 1 (emission step). X-rays 20 emitted from the X-ray source 1 enter the filter 2. Among the X-rays 20 incident on the filter 2, the X-rays 20 in the lower energy region lower than the energy E0 are removed, and the X-rays 20 in the energy region higher than the energy E0 are emitted from the filter 2.

  Subsequently, the X-rays 20 transmitted through the filter 2 are focused on the sample S by the focusing optical system 3A (a focusing step). In the case of the first state, the X-rays 20 transmitted through the filter 2 are totally reflected by the first reflection surface 31c and are collected on the sample S. At this time, the X-rays 20 having energy equal to or higher than the energy E1 with the first oblique incident angle β1 as the total reflection critical angle are hardly reflected by the first reflection surface 31c (reflectance is 30% or less). Therefore, the X-rays 20 having energy equal to or higher than E1 are removed by the focusing optical system 3A, and the other X-rays 20 are focused on the sample S.

  On the other hand, in the case of the second state, the X-rays 20 transmitted through the filter 2 are totally reflected by the second reflection surface 32c and are collected on the sample S. At this time, the X-rays 20 having energy equal to or higher than the energy E2 having the second oblique incidence angle β2 as the critical angle for total reflection are hardly reflected by the second reflection surface 32c (reflectance is 30% or less). Therefore, the X-rays 20 having energy equal to or higher than E2 are removed by the focusing optical system 3A, and the other X-rays 20 are focused on the sample S.

  That is, here, the X-rays 20 on the low energy side are removed by the filter 2, and the X-rays 20 on the high energy side are removed by the focusing optical system 3A. Thus, the X-rays 20 in a predetermined range between the low energy side and the high energy side (E0 to E1 in the first state, and E0 to E2 in the second state) are selected. As can be derived from the above equations (1) and (2), the energy E2 is higher than the energy E1 (E2> E1). Note that, in both the first state and the second state, the X-rays 20 that pass through the filter 2 and travel toward the sample S without passing through the focusing optical system 3A are shielded by the shielding member 4.

  Subsequently, an X-ray 20 from the sample S is imaged by the imaging optical system 6 (imaging step). In the imaging optical system 6, the X-ray 20 is reflected twice on each of the reflection surface 61c and the reflection surface 62c. As described above, since the first incident light and the second incident light have a common optical path, the optical path of the X-ray 20 from the sample S is also common in the first state and the second state. Therefore, in both the first state and the second state, in the imaging optical system 6, the X-rays 20 from the sample S are incident on the reflection surface 61c at the third oblique incidence angle β3. Therefore, in any of the first state and the second state, it is not necessary to move the positions of the sample S, the imaging optical system 6, and the detector 7. Also, since the imaging optical system 6 and the detector 7 are not moved, the magnification does not change. The third oblique incident angle β3 is defined as an angle formed between the optical axis C5 of the X-ray 20 incident on the central position of the reflecting surface 61c in the direction along the reference line A and the reflecting surface 61c. Here, the reflecting surface 62c is set so that the X-rays 20 from the reflecting surface 61c are incident at an oblique incident angle equal to the third oblique incident angle β3.

  Here, as described above, the third inclination angle α3 is larger than the second inclination angle α2 and the first inclination angle α1. From the geometrical relationship with the third oblique incidence angle β3 and the like, the third oblique incidence angle β3 is smaller than the first oblique incidence angle β1 and the second oblique incidence angle β2. Therefore, the energy E3 having the third oblique incident angle β3 as the critical angle for total reflection is higher than the energy E1 and the energy E2 (E3> E1, E2). That is, the reflecting surface 61c totally reflects the X-rays 20 in the entire energy region totally reflected by the first reflecting surface 31c and the second reflecting surface 32c and forms an image on the detector 7. The X-rays 20 traveling from the sample S to the detector 7 without passing through the imaging optical system 6 are shielded by the shielding member 5.

  Finally, the X-rays 20 formed in the imaging step are detected by the detector 7 (detection step). In the case of the first state, in the detection step, an image captured by the X-ray 20 having energies of E0 to E1 is obtained. In the case of the second state, an image captured by the X-rays 20 having energies E0 to E2 is obtained from the detector 7.

  FIG. 5 is a diagram illustrating a configuration of an X-ray imaging apparatus according to a modification of the first embodiment. As shown in FIGS. 1 and 5, the X-ray imaging apparatus 10A includes a focusing optical system 3A, whereas the X-ray imaging apparatus 10B according to the modification includes a focusing optical system 3B. ing. The light-collecting optical system 3A is different from the light-collecting optical system 3B in that the light-collecting optical system 3B includes an optical element 30B. Further, the optical element 30A is different in that the optical element 30B has a connection pipe 34, while the optical element 30B has a connection pipe 34.

  The connection pipe 34 differs from the connection pipe 33 in the shape. The connection pipe 34 includes a parallel portion 35 parallel to the reference line A and an intersection 36 intersecting the reference line A. As described above, since the connection pipe 34 includes the parallel portion 35, the connection pipe 34 is easily held by the holder 12 (see FIG. 3).

(2nd Embodiment)
FIG. 6 is a diagram illustrating a configuration of an X-ray imaging apparatus according to the second embodiment. As shown in FIGS. 1 and 6, the X-ray imaging apparatus 10A according to the first embodiment includes a condensing optical system 3A, whereas the X-ray imaging apparatus 10C according to the second embodiment includes a condensing optical system. The difference is that the system 3C is provided.

  The condensing optical system 3C includes a first optical element 31 including a first reflecting surface 31c, and a second optical element 32 including a second reflecting surface 32c and configured separately from the first optical element 31. ing. That is, the condensing optical system 3A has the first optical element 31 and the second optical element 32 as one integrated optical element 30A, whereas the condensing optical system 3C is separated as a separate body. It differs from the condensing optical system 3A in that it has a first optical element 31 and a second optical element 32 configured as described above.

  The first optical element 31 and the second optical element 32 are provided so as to be movable in a direction crossing the reference line A by a moving mechanism (not shown) such as a stage. Here, the first optical element 31 and the second optical element 32 are provided movably in a direction orthogonal to the reference line A. The control unit 8 sends a control signal to the moving mechanism, and arranges the first reflection surface 31c at a position where the X-rays 20 emitted from the X-ray source 1 are collected on the sample S by total internal reflection. As a result, the state of the condensing optical system 3C becomes the first state. Further, the control unit 8 retracts the second reflection surface 32c from the light condensing position. The control unit 8 retracts the second reflection surface 32c to a place isolated from the X-ray source 1, for example.

  Further, the control unit 8 retracts the first reflection surface 31c from a position for converging the X-rays 20 emitted from the X-ray source 1 on the sample S by total reflection. As a result, the state of the condensing optical system 3C becomes the second state. The control unit 8 retracts the first reflection surface 31c to a place isolated from the X-ray source 1, for example. Further, the control unit 8 arranges the second reflection surface 32c at a position for condensing the X-rays 20 emitted from the X-ray source 1 on the sample S by total reflection. As described above, in the X-ray imaging apparatus 10C, the control unit 8 switches between the first state and the second state by moving one of the first optical element 31 and the second optical element 32.

(Third embodiment)
FIG. 7 is a diagram illustrating a configuration of an X-ray imaging apparatus according to the third embodiment. As shown in FIGS. 6 and 7, the X-ray imaging apparatus 10C according to the second embodiment includes a condensing optical system 3C, whereas the X-ray imaging apparatus 10D according to the third embodiment includes a condensing optical system. The difference is that the system 3D is provided. Further, the X-ray imaging apparatus 10D differs from the X-ray imaging apparatus 10C in further including a shielding member 15 and a shielding member 16.

  In the condensing optical system 3D, the first optical element 31 is fixedly held at a position where the first reflection surface 31c condenses the X-rays 20 emitted from the X-ray source 1 on the sample S by total internal reflection. . The second optical element 32 is fixedly held at a position where the second reflection surface 32c focuses the X-rays 20 emitted from the X-ray source 1 on the sample S by total internal reflection. The X-ray imaging apparatus 10D is otherwise identical to the X-ray imaging apparatus 10C.

  The shielding member 15 is used to shield the X-rays 20 traveling from the X-ray source 1 toward the second reflection surface 32c. The shielding member 15 has a circular shape when viewed from a direction along the reference line A. The control unit 8 is on the optical path of the X-ray 20 from the X-ray source 1 to the second reflection surface 32c and is inside the optical path of the X-ray 20 from the X-ray source 1 to the first reflection surface 31c (reference line A). Side), the shielding member 15 is arranged. Thus, the shielding member 15 shields the X-rays 20 traveling from the X-ray source 1 to the second reflection surface 32c while passing the X-rays 20 traveling from the X-ray source 1 to the first reflection surface 31c. That is, the condensing optical system 3D is in the first state.

  The shielding member 16 is used to shield the X-rays 20 traveling from the X-ray source 1 toward the first reflection surface 31c. The shielding member 16 has an annular shape when viewed from a direction along the reference line A. The control unit 8 is on the optical path of the X-ray 20 traveling from the X-ray source 1 to the first reflecting surface 31c, and the inner edge of the shielding member 16 is traveling along the optical path of the X-ray 20 traveling from the X-ray source 1 to the second reflecting surface 32c. The shielding member 16 is disposed outside the device. Thus, the shielding member 16 shields the X-rays 20 traveling from the X-ray source 1 to the first reflection surface 31c while passing the X-rays 20 traveling from the X-ray source 1 to the second reflection surface 32c. That is, the condensing optical system 3D is in the second state.

  As described above, the control unit 8 shields the X-rays 20 traveling from the X-ray source 1 toward the second reflection surface 32 c using the shielding member 15 and the first reflection from the X-ray source 1 using the shielding member 16. The first state and the second state are switched by selecting any one of the states for shielding the X-rays 20 toward the surface 31c.

  As described above, the X-ray imaging apparatuses 10A to 10D according to the present embodiment include the control unit 8 that switches the states of the light collection optical systems 3A to 3D. The control unit 8 controls the first state in which the X-ray 20 is totally reflected by the first reflection surface 31c and is incident on the sample S, and the second state in which the X-ray 20 is totally reflected by the second reflection surface 32c and is incident on the sample S. Switch between states. The first inclination angle α1 of the first reflection surface 31c and the second inclination angle α2 of the second reflection surface 32c are different from each other. The angle formed between the optical axis C1 of the first incident light and the reference line A and the angle formed between the optical axis C2 of the second incident light and the reference line A are both angles γ, which are equivalent to each other. . Therefore, the first oblique incidence angle β1 of the X-rays 20 on the first reflection surface 31c in the first state and the second oblique incidence angle β2 of the X-rays 20 on the second reflection surface 32c in the second state are mutually different. different.

  As described with reference to FIG. 4, when the oblique incidence angle θ of the X-ray to the reflecting surface is different, the energy region of the X-ray totally reflected by the reflecting surface is different. Thus, by switching between the first state and the second state, the X-rays 20 used for observation of the sample S are totally reflected by the X-rays in the energy region totally reflected by the first reflection surface 31c and the second reflection surface 32c. X-rays in the energy region to be reflected.

  As described above, the angle between the optical axis C1 of the first incident light and the reference line A and the angle between the optical axis C2 of the second incident light and the reference line A are both angles γ, and Are equivalent. For this reason, the state of incidence of the X-rays 20 on the imaging optical system 6 does not change between the first state and the second state. Therefore, there is no need to align the imaging optical system 6 and the detector 7 according to the selection of the energy of the X-rays 20. As described above, in the X-ray imaging apparatuses 10A to 10D, the sample S can be easily observed while selecting the energy region of the X-ray 20.

  Since the condensing optical systems 3A to 3D are configured to select the energy region of the X-rays 20 to be removed by using total reflection, the selective reflection characteristics of the multilayer mirror as described in Patent Document 2 are used. The use efficiency of the X-rays 20 can be improved as compared with the configuration used. For example, the reflectance in the “water window” region of the multilayer mirror is several tens of percent, and the utilization efficiency is low. Further, in an energy region higher than that, the utilization efficiency is further reduced.

  FIG. 8 is a diagram illustrating a configuration of an X-ray imaging apparatus according to a comparative example. As shown in FIGS. 1 and 8, the X-ray imaging apparatus 100 according to the comparative example is different from the X-ray imaging apparatus 10A according to the first embodiment in that the X-ray imaging apparatus 100 includes an optical element 103 as a light collecting optical system. . The optical element 103 is a spheroid mirror. When changing the energy of the X-rays 20 used for observing the sample S by changing the target substance, the X-ray imaging apparatus 100 replaces not only the filter 2 but also the optical element 103 and replaces the optical element 103. It is necessary to change the material and the angle of oblique incidence. The work of replacing the optical element 103 requires highly accurate position adjustment, which takes time.

  When changing the oblique incidence angle of the optical element 103 and the third optical element 60, it is necessary to allow the X-rays 20 condensed by the optical element 103 to efficiently enter the third optical element 60. In other words, the numerical apertures of the optical element 103 and the third optical element 60 need to be equal. Therefore, the positions of the focal points of the optical element 103 and the third optical element 60 change, and accordingly, the positions of the X-ray source 1, the sample S, and the detector 7 may change. Therefore, in the X-ray imaging apparatus 100 according to the comparative example, it is not easy to observe the sample S while selecting the energy region of the X-ray 20 like the X-ray imaging apparatuses 10A to 10D according to the present embodiment. .

  In the X-ray imaging apparatuses 10A to 10D, the imaging optical system 6 totally reflects the X-rays 20 in the entire energy region totally reflected on the first reflection surface 31c and the second reflection surface 32c to form an image on the detector 7. Let it. For this reason, the removal of the X-rays 20 in the energy region used for observation of the sample S by the imaging optical system 6 can be suppressed. Further, since the imaging optical system 6 forms an image by totally reflecting the X-rays 20, it is not necessary to change the third optical element 60 and its arrangement according to the selection of the energy of the X-rays 20. On the other hand, in an imaging optical system using a multilayer mirror, it is necessary to change the thickness and material of the multilayer film for each X-ray energy. That is, in a system using a plurality of energy regions, such as the X-ray imaging apparatuses 10A to 10D, it is necessary to prepare a plurality of multilayer mirrors by the number of energy regions to be used. Further, in the imaging optical system using the zone plate (ZP), the efficiency is lower than that of the imaging optical system 6 of the present embodiment, and the focal length changes depending on the energy of the X-ray. Unlike optical elements such as a multilayer mirror and a zone plate, a reflection optical system using total reflection uses a single optical element to provide a plurality of energies under the condition that the oblique incident angle is smaller than the oblique incident angle of the condensing optical system. It can correspond to an area.

  Since the X-ray imaging apparatuses 10A to 10D include the filter 2, it is possible to remove the X-rays 20 in the low energy region that are not used for observation of the sample S. Thereby, the contrast of the obtained X-ray image can be improved. Furthermore, the X-ray imaging apparatuses 10A to 10D include a shielding member 4 and a shielding member 5. For this reason, since the X-rays 20 in the energy region not used for observation of the sample S are suppressed from being incident on the detector 7, the contrast of the obtained X-ray image can be further improved.

  In the X-ray imaging apparatuses 10A and 10B, the first optical element 31 and the second optical element 32 are integrated. For this reason, the control unit 8 moves the first optical element 31 and the second optical element 32 by one common moving mechanism including the stage 11, the holder 12, the drive motor 13, and the like, so that the condensing optical system 3A, 3B can be switched. Therefore, the configuration of the X-ray imaging apparatuses 10A and 10B can be simplified.

  In the X-ray imaging apparatus 10C, since the first optical element 31 and the second optical element 32 are configured separately, the first optical element 31 and the second optical element 32 can be moved. Therefore, the control unit 8 can easily arrange the first optical element 31 and the second optical element 32 at positions for converging the X-rays 20 emitted from the X-ray source 1 on the sample S by total internal reflection. it can. Further, the control unit 8 can retreat the unused first optical element 31 and second optical element 32 to a place isolated from the X-ray source 1. Therefore, there is no possibility that the X-rays 20 totally reflected by the unused first optical element 31 and second optical element 32 will be incident on the imaging optical system 6. Furthermore, since there is no connecting tube, there is no possibility that the X-rays 20 totally reflected by the connecting tube enter the imaging optical system 6.

  In the X-ray imaging apparatus 10D, the control unit 8 switches between the first state and the second state by using one of the shielding member 15 and the shielding member 16. Therefore, it is not necessary to move the first optical element 31 and the second optical element 32. Further, since the first optical element 31 and the second optical element 32 are formed separately and there is no connecting pipe, the X-ray 20 totally reflected by the connecting pipe is formed into an image forming optical system, similarly to the X-ray imaging apparatus 10C. There is no danger of entering the system 6.

  Further, since the X-ray imaging method according to the present embodiment uses the X-ray imaging apparatus 10A, the sample S can be easily observed while selecting the energy region of the X-rays 20. Note that the same applies to the case where the X-ray imaging apparatuses 10B to 10D are used.

  The X-ray imaging apparatuses 10A to 10C and the X-ray imaging method according to the present embodiment have been described above, but the present invention is not limited thereto. For example, if the distance L0 is sufficiently long and the optical element can be further installed, the condensing optical systems 3A to 3D have three or more reflecting surfaces and can select three or more X-ray energies. It may be. If it is not necessary to remove the X-rays 20 on the low energy region side, the filter 2 may not be provided. Further, the position of the filter 2 is not limited to between the X-ray source 1 and the sample S, but may be between the sample S and the detector 7. Further, the position of the shielding member 4 and the shielding member 5 is on the reference line A, and any position that shields the X-ray 20 incident on the detector 7 without passing through the focusing optical systems 3A to 3D. Good. Further, only one of the shielding member 4 and the shielding member 5 may be provided. Further, if the first inclination angle α1 and the second inclination angle α2 are larger than the third inclination angle α3, the first inclination angle α1 may be larger than the second inclination angle α2. Further, in the X-ray imaging apparatuses 10A and 10B, the shape of the connection pipe is not limited to the connection pipes 33 and 34 and is arbitrary.

  In the X-ray imaging apparatus 10C, the second optical element 32 is located on the optical path of the X-ray 20 totally reflected on the first reflection surface 31c, and the X-ray 20 totally reflected on the first reflection surface 31c is converted into a second optical element. If it can be shielded by the element 32, the controller 8 does not have to retract the second optical element 32 in the second state. Further, the place where the first reflection surface 31c and the second reflection surface 32c are retracted is not limited to the place isolated from the X-ray source 1, and the X-rays 20 emitted from the X-ray source 1 are reflected on the sample S by total reflection. It does not have to be a position for focusing.

  In the X-ray imaging apparatus 10D, the second optical element 32 is located on the optical path of the X-ray 20 totally reflected by the first reflection surface 31c, and the X-ray 20 totally reflected by the first reflection surface 31c is converted into the second optical element. If the shield can be performed by the element 32, the control unit 8 may not use the shielding member 16 in the second state. Further, the first optical element 31 and the second optical element 32 may be integrated.

(Example 1)
Example 1 A case in which a light element material is observed will be described as Example 1. As the X-ray imaging device, an X-ray imaging device corresponding to the X-ray imaging device 10A according to the first embodiment is used. The condensing optical system is accurately adjusted in position at the time of installation, and a high-precision stage using a pulse motor is used for moving the condensing optical system. Thereby, the positional accuracy when the first reflection surface and the second reflection surface are rearranged is maintained.

  In observation, L-lines (0.93 keV, 0.95 keV) of characteristic X-rays when Cu (copper) is used as a target are used as X-rays in an energy region having a large absorption coefficient for light elements of several keV or less, and The characteristic X-ray M line (around 1.78 keV) when W is used as the target is used.

  If Cu is used as a target and the acceleration voltage is 10 kV, the characteristic X-rays K-line (8.05 keV, 8.9 keV) and L-line (0.93 keV, 0.95 keV), and 10 keV or less as the bremsstrahlung X-ray Continuous X-rays are emitted. Here, the energy region (0.9 keV to 1 keV) of the L line of the characteristic X-ray is used as efficiently as possible, and the other characteristic X-rays and continuous X-rays are removed. This suppresses a decrease in contrast due to a difference in X-ray absorption. Therefore, a Be foil having a thickness of 1 μm is used as a filter having a transmittance of 80% or more at 0.9 keV to 1 keV and removing X-rays of 400 eV or less.

Further, the material and the oblique incidence angle of the condensing optical system are set so that the reflectivity is high at 0.9 keV to 1 keV, and characteristic X-rays and continuous X-rays exceeding 1 keV can be removed as much as possible. Here, the first optical element is formed of SiO ₂ (ρ = 2.2 g / cm ³ ), and the first oblique incidence angle β1 is 1.55 °. The X-ray energy having a total reflection critical angle of 1.55 ° is 1.1 keV, and X-rays of 1.1 keV or more are not reflected. Therefore, continuous X-rays of 8.05 keV and 8.9 keV, which are the characteristic X-rays, and 1.1 keV or more can be removed. As described above, observation in the X-ray energy region of 400 eV to 1.1 keV including the energy of the characteristic X-ray L line of 0.93 keV and 0.95 keV becomes possible.

Next, a case where W is used as a target will be described. The above-described Be foil having a thickness of 1 μm has a transmittance of 90% or more near 1.78 keV. The second optical element is formed of SiO ₂ (ρ = 2.2 g / cm ³ ), and the second oblique incidence angle β2 is set to 0.85 °. The X-ray energy having a total reflection critical angle of 0.85 ° is 1.9 keV, and X-rays of 1.9 keV or more are not reflected. As described above, observation in the X-ray energy region of 400 eV to 1.9 keV including the vicinity of the energy of the characteristic X-ray M-ray of 1.78 keV becomes possible.

As described above, the condensing optical system and the imaging optical system need to satisfy the following conditions (1) to (3).
(1) The distances L0 in the first state and the second state are equal to each other.
(2) An angle formed between the optical axis C1 of the first incident light and the reference line A and an angle formed between the optical axis C2 of the second incident light and the reference line A are both angles γ, and are equal to each other. (That is, the numerical apertures of the first optical element and the second optical element are equal to the numerical aperture of the imaging optical system).
(3) The third oblique incidence angle β3 is smaller than the second oblique incidence angle β2.

  When the specifications of the condensing optical system and the imaging optical system are determined so as to satisfy these conditions, L0 = 337 mm, L1 (S1) = 170 mm, L2 (S1) = 317 mm, L1 (S2) = 155 mm, L2 (S2) = 302 mm, L3 = 3280 mm, L4 = 71 mm, L5 = 80 mm, L6 = 25 mm, L7 = 122 mm, L8 = 10 mm, L9 = 9 mm, L10 = 10.07 mm, D1 = 9.3 mm, D2 = 9. 2 mm, D3 = 1.86 mm, D4 = 1.6 mm, D5 = 4.06 mm, D6 = 4.53 mm, D7 = 4.57 mm, β1 = 1.55 °, β2 = 0.85 ° and β3 = 0. 41 °.

  When the X-ray imaging devices corresponding to the X-ray imaging devices 10C and 10D according to the second embodiment and the third embodiment are used as the X-ray imaging device, the focusing optics is set so as to satisfy the above condition. When the specifications of the system and the imaging optical system are determined, L0 = 337 mm, L1 (S1) = 170 mm, L2 (S2) = 302 mm, L3 = 3280 mm, L4 = 71 mm, L5 = 80 mm, L6 = 25 mm, L8 = 10 mm, L9 = 9 mm, L10 = 10.07 mm, D1 = 9.3 mm, D2 = 9.2 mm, D3 = 1.86 mm, D4 = 1.6 mm, D5 = 4.06 mm, D6 = 4.53 mm, D7 = 4. 57 mm, β1 = 1.55 °, β2 = 0.85 ° and β3 = 0.41 °.

  FIG. 9 is a diagram showing the relationship between the energy of X-rays and the transmittance and reflectance. FIG. 9A shows the relationship between the energy of X-rays and the transmittance of a filter (Be foil having a thickness of 1 μm), the energy of X-rays and the first optical element (β1 = 1.55 °) of the focusing optical system. ) And the reflectance of the second optical element (β2 = 0.85 °), and the relationship between the energy of X-rays and the reflectance of the imaging optical system (β3 = 0.41 °). . Here, since the imaging optical system reflects the X-ray twice on each of the two reflecting surfaces, it is indicated as “twice”. Note that the reflectance is affected by the absorption edges (543 eV, 1.8 keV) of oxygen and silicon contained in the substances of the condensing optical system and the imaging optical system, and thus the reflectance shown in FIG. Is slightly different from the reflectance graph shown in FIG.

  FIG. 9B shows the transmission wavelength characteristics of the entire X-ray imaging apparatus in the first state and the second state, and the difference therebetween. The transmission wavelength characteristic of the entire X-ray imaging apparatus in the first state is obtained by multiplying the transmittance of the filter, the reflectance of the first optical element, and the reflectance of the imaging optical system. In addition, the transmission wavelength characteristic of the entire X-ray imaging apparatus in the second state is obtained by multiplying the transmittance of the filter, the reflectance of the second optical element, and the reflectance of the imaging optical system.

  As shown in FIG. 9B, in the first state, X-rays in the energy region of 400 eV to 1.2 keV can be used for observation. In the second state, X-rays in the energy range of 400 eV to 1.8 keV can be used for observation. Therefore, in the first state, the M-line (around 1.78 keV) of the characteristic X-ray when W is used as the target can be used for observation. In the second state, L-lines (0.93 keV, 0.95 keV) of characteristic X-rays when Cu (copper) is used as a target can be used for observation. As described above, by switching between the first state and the second state, it is possible to see a difference in observation between two different energy regions using X-rays.

  In this example, the X-ray images of the two energy regions overlap on the low energy side. Therefore, as shown in FIG. 9B, according to the difference obtained by subtracting the transmission wavelength characteristic of the entire X-ray imaging device in the first state from the transmission wavelength characteristic of the entire X-ray imaging device in the second state. , 1.0 keV to 1.8 keV. Actually, since the size of the visual field focused on the sample and the X-ray intensity are different between the first optical element and the second optical element, the image obtained by simple subtraction between the images is shown in FIG. It is slightly different from the difference image shown in b).

(Example 2)
Second Embodiment A case where a biological sample is observed will be described as a second embodiment. As the X-ray imaging device, an X-ray imaging device corresponding to the X-ray imaging device 10A according to the first embodiment is used. Biological samples are often observed using X-rays in the “water window” region (285 eV-543 eV). In the “water window” region, absorption of X-rays by water is reduced, and absorption by biological substances such as proteins and nucleic acids is increased. Therefore, an image of a biological sample containing water can be obtained with high contrast. X-rays having an energy other than the area of the “water window” are required to be removed as much as possible in order to reduce the contrast of the image.

  If Ti (titanium) is used as the target and the acceleration voltage is 10 kV, L lines (0.45 keV and 0.46 keV) of characteristic X-rays are emitted in the “water window” region. In addition, K-rays (4.51 keV, 4.93 keV) and bremsstrahlung X-rays of 10 keV or less are emitted. A Ti foil having a thickness of 0.05 μm is used as a filter which has a high transmittance at several 100 eV and can remove X-rays of less than 10 eV.

  When the specifications of the condensing optical system and the imaging optical system are determined so as to satisfy the above conditions (1) to (3), L0 = 266 mm, L1 (S1) = 136 mm, L2 (S1) = 259 mm, L1 (S2) = 128 mm, L2 (S2) = 251 mm, L3 = 3030 mm, L4 = 20 mm, L5 = 30 mm, L6 = 10 mm, L7 = 113 mm, L8 = 10 mm, L9 = 10 mm, L10 = 14.89 mm, D1 = 25 .13 mm, D2 = 25.02 mm, D3 = 1.86 mm, D4 = 1.6 mm, D5 = 4.19 mm, D6 = 5.62 mm, D7 = 6.25 mm, β1 = 5.4 °, β2 = 2. 65 ° and β3 = 1.35 °.

  When the X-ray imaging devices corresponding to the X-ray imaging devices 10C and 10D according to the second embodiment and the third embodiment are used as the X-ray imaging device, the focusing optics is set so as to satisfy the above condition. When the specifications of the system and the imaging optical system are determined, L0 = 266 mm, L1 (S1) = 136 mm, L2 (S2) = 251 mm, L3 = 3030 mm, L4 = 20 mm, L5 = 30 mm, L6 = 10 mm, L8 = 10 mm, L9 = 10 mm, L10 = 14.89 mm, D1 = 25.13 mm, D2 = 25.02 mm, D3 = 2.63 mm, D4 = 2.17 mm, D5 = 4.19 mm, D6 = 5.62 mm, D7 = 6. 25 mm, β1 = 5.4 °, β2 = 2.65 ° and β3 = 1.35 °.

  The first oblique incidence angle β1 is 5.4 °, and the X-ray energy with 5.4 ° as the total reflection critical angle is 287 eV. This is near the low energy end of the "water window" region. On the other hand, the second oblique incidence angle β2 is 2.65 °, and the X-ray energy having a total reflection critical angle of 2.65 ° is 530 eV. This is near the high energy end of the "water window" region.

  FIG. 10 is a diagram showing the relationship between the energy of X-rays and the transmittance and reflectance. FIG. 10A shows the relationship between the X-ray energy and the transmittance of the filter (Ti foil having a thickness of 0.05 μm), the X-ray energy and the first optical element (β1 = 5. 4 °) and the reflectance of the second optical element (β2 = 2.65 °), and the relationship between the energy of X-rays and the reflectance of the imaging optical system (β3 = 1.35 °). ing. FIG. 10B shows the transmission wavelength characteristics of the entire X-ray imaging apparatus in the first state and the second state, and the difference therebetween.

  As shown in FIG. 10A, the K-line (4.51 keV, 4.93 keV) of the characteristic X-ray can be almost removed. According to the second state, it is possible to observe with the L line (0.45 keV, 0.46 keV) of the characteristic X-ray which is the “water window” region. As shown in FIG. 10B, according to the difference between the transmission wavelength characteristics of the entire X-ray imaging apparatus in the first state and the second state, the energy component of 284 eV or less outside the “water window” region is reduced. , The contrast of the X-ray image is improved.

  When observing a dry and relatively thick biological sample that does not contain water, the target may be a substance composed of C (carbon) such as graphite and DLC, and observation may be performed using carbon K-rays (282 eV). it can. With carbon K-rays, the transmittance to the living body increases, and the internal structure of the sample can be observed even with a thick sample. This is particularly effective for CT imaging. On the other hand, when observed in a “water window” region having energy equal to or higher than the carbon K-ray, the transmittance for carbon is low. Therefore, it is necessary to remove X-rays exceeding 282 eV as much as possible. In this case, when observation is performed using the first state, X-rays of 287 eV or more can be selectively removed. As described above, by using two light-collecting optical systems, more information can be obtained, and the utility is high, as compared with the X-ray imaging apparatus of the comparative example using one light-collecting optical system.

DESCRIPTION OF SYMBOLS 1 ... X-ray source, 2 ... Filter, 3A-3D ... Condensing optical system, 4 ... Shielding member (1st shielding member), 5 ... Shielding member (2nd shielding member), 6 ... Imaging optical system, 7 ... Detector, 8: control unit, 10A to 10C: X-ray imaging device, 15: shielding member (third shielding member), 16: shielding member (third shielding member), 31: first optical element, 32: second Optical element, 31c: first reflecting surface, 32c: second reflecting surface, 61c: reflecting surface (third reflecting surface), A: reference line, C1, C2: optical axis, S: sample.

Claims (9)

An X-ray source for emitting X-rays for irradiating the sample,
A detector for detecting X-rays from the sample;
A collector disposed on a reference line from the X-ray source to the detector and having a first reflection surface and a second reflection surface for converging the X-rays emitted from the X-ray source onto the sample by total internal reflection; Optical optics,
An imaging optical system arranged on the reference line and imaging an X-ray from the sample on the detector;
The state of the condensing optical system is defined as a first state in which X-rays totally reflected on the first reflection surface are condensed on the sample, and an X-ray totally reflected on the second reflection surface in the sample. A control unit that performs control for switching between a second state in which light is condensed, and
With
The sample is held on the reference line at a predetermined distance from the X-ray source,
An angle formed between the first reflection surface and the reference line and an angle formed between the second reflection surface and the reference line are different from each other,
The angle between the optical axis of the X-ray totally reflected by the first reflecting surface in the first state and the reference line, and the optical axis of the X-ray totally reflected by the second reflecting surface in the second state And the angle formed by the reference line are equivalent to each other,
X-ray imaging device. The condensing optical system includes a first optical element including the first reflecting surface, and a first optical element including the second reflecting surface and arranged alongside the first optical element along the reference line. An integrated second optical element,
The X-ray imaging according to claim 1, wherein the control unit switches between the first state and the second state by moving the first optical element and the second optical element along the reference line. apparatus. The condensing optical system has a first optical element including the first reflecting surface, and a second optical element including the second reflecting surface and configured separately from the first optical element,
The X-ray imaging apparatus according to claim 1, wherein the control unit switches between the first state and the second state by moving the first optical element and the second optical element. A first shielding member for shielding X-rays from the X-ray source toward the second reflection surface;
A second shielding member for shielding X-rays from the X-ray source toward the first reflection surface;
With
The control unit is configured to shield the X-rays from the X-ray source toward the second reflection surface using the first shielding member, and to perform the first reflection from the X-ray source using the second shielding member. 2. The X-ray imaging apparatus according to claim 1, wherein the first state and the second state are switched by selecting any one of states in which X-rays directed to a surface are shielded. 3.   The X-ray imaging according to any one of claims 1 to 4, wherein the imaging optical system has a third reflection surface that totally reflects X-rays from the sample and forms an image on the detector. apparatus.   The X-ray imaging apparatus according to claim 5, wherein the third reflection surface totally reflects X-rays in a total energy region which are totally reflected on the first reflection surface and the second reflection surface. A filter that is disposed on the reference line and that removes X-rays in a low-energy region side among X-rays in an energy region totally reflected by the first reflection surface and the second reflection surface,
The X-ray imaging apparatus according to claim 1.   The X-ray imaging apparatus according to any one of claims 1 to 7, further comprising a third shielding member that is arranged on the reference line and shields X-rays that enter the detector without passing through the light-collecting optical system. . An X-ray imaging method using the X-ray imaging apparatus according to any one of claims 1 to 8,
A selecting step of selecting which of the first state and the second state by the control unit the state of the condensing optical system;
An emission step of emitting X-rays for irradiating the sample from the X-ray source,
A focusing step of focusing the X-rays emitted in the emitting step on the sample by the focusing optical system,
An imaging step of imaging the detector with X-rays from the sample by the imaging optical system;
A detection step of detecting, by the detector, the X-rays formed in the imaging step.

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