TW202609809A - Micro-pore optics, associated manufacturing methods and x-ray imaging system - Google Patents

Abstract

The invention concerns micro pore optics (MPO) for X-ray focusing on an image plane positioned at a predetermined distance or for the creation of a parallel X-ray beam. The micro pore optics (MPO) comprising an array (23) integrates: a plurality of channels (10) through which X-rays can be transmitted and reflected; and a blocking zone in which the array (23) is opaque to X-rays, said blocking zone being arranged at least in a central zone of said micro pore optics (MPO).

Description

Microporous optical elements, their manufacturing methods and X-ray imaging systems

This invention relates to the field of X-ray imaging, and more specifically to micro-aperture optical elements (also known as MPOs) for X-ray focusing or for generating parallel X-ray beams. Furthermore, this invention relates to a method for manufacturing an MPO.

Although MPOs are traditionally used in X-ray telescopes, this invention can be used not only in the field of space imaging, but also in X-ray imaging and analysis applications, such as X-ray diffraction (XRD) or X-ray fluorescence (XRF) spectroscopy.

Therefore, this invention has a variety of potential applications.

In the field of space imaging, the goal is to observe the universe across the entire electromagnetic spectrum. To this end, astronomers use telescopes, parabolic antennas, microwave antennas, and other instruments to record electromagnetic waves from the universe.

However, X-ray observation is a major challenge because these electromagnetic waves are strongly absorbed by the Earth's atmosphere and cannot reach the Earth's surface. Furthermore, creating the optical systems used to capture and focus X-rays is extremely complex, and the extremely high energy of X-rays makes them difficult to manipulate using traditional optical techniques. To overcome these technical difficulties, satellites are designed to use grazing-incidence optical elements to observe X-rays.

Unlike optical telescopes that use refraction to deflect and focus light, grazing-incident optical elements use reflection.

Indeed, X-rays tend to penetrate matter rather than be refracted by it. However, if they strike a surface at a very small angle (almost parallel to the surface), they will be reflected. This angle is so small, usually measured in arcminutes or arcseconds, that it reflects the fact that the rays must be almost parallel to the reflecting surface.

To capture and focus X-rays in grazing-incidence optical elements, micropore optics (MPOs) have been developed. Because these MPOs have a structure similar to a lobster eye, they are also called "lobster eyes".

MPOs traditionally consist of thousands of straight, narrow channels arranged parallel to each other, typically with a square structure. This configuration can reflect and focus X-rays from different directions onto the detector or focal point, thereby improving X-ray capture efficiency.

Figure 1 of the prior art illustrates an MPO with channels (10) having a square cross-section. Each channel (10) has a side length of 20 micrometers and is also arranged in a square, with the wall (11) between each channel (10) having a thickness of 6 micrometers. For example, the length of each channel (10) is substantially equal to 1 millimeter.

MPO is typically made from drawn glass blocks. More specifically, the first fiber consists of an acid-soluble core (e.g., pure glass) and a cladding layer (e.g., leaded glass resistant to multiple acids) surrounding the core. These first fibers, called primary fibers, are obtained by drawing them to a first desired diameter and then assembling them into a preform composed of a large number of primary fibers.

Then, the preform is drawn to a second desired diameter to obtain secondary fibers from the first substrate, thereby forming a second slender substrate. Then, the second slender substrate is transversely cut along a given cutting plane.

This cutting step can form multiple substrates. These substrates are then immersed in acid to dissolve the fiber core, thereby exposing the microchannels. Thus, after the fiber core is dissolved, the substrate forms a microchannel plate, the body of which is formed by the fusion of the cladding of each fiber in the manufacturing process.

MPOs can be planar, but they can also be non-planar, meaning they are curved according to the radius of curvature, but they can also be elliptical or cylindrical. The channel can also be slightly deformed while maintaining its square appearance.

In order to achieve focusing using MPO, photons need to be reflected twice in two perpendicular directions. On the image plane, photons from the same source point, or from the same direction at infinite distance, will converge around a point called the spot, thus producing the focusing phenomenon.

As illustrated in Figure 3 of the prior art, photons from the same source penetrate different positions of the entrance segment of the channel (10): these positions are regions 0, 1, and 2 in Figure 3, respectively. The difference in the entrance point leads to a change in the number of reflections within the channel (10). Boxes 0, 1, and 2 of the image plane Pi are arranged at a distance F from the center of the channel (10) length L, respectively illustrating the portion that contacts the image plane Pi after zero, one, or two reflections. These numbers of reflections depend on the penetration point of the photon in the entrance segment Se of the channel (10) and the width d of the channel. The intensity captured on the image plane Pi also depends on the distance F of the image plane Pi relative to the channel (10).

It is not possible to determine whether each photon passing through the channel (10) actually undergoes two reflections, because the photon can pass through regions 0 and 1 at the entrance segment Se of the channel (10), resulting in zero or single reflections. In addition to the case shown in Figure 3, triple, quadruple, and other reflections can also be observed.

Rays that pass directly through channel (10) without being reflected or focused in any way are diffusely distributed to the image plane Pi.

As illustrated in Figure 2, some rays glide across the upper surface of the channel (10) and are reflected downwards to the detector (12). Similarly, some rays glide across the lower surface of the channel (10) and are reflected upwards to the detector (12). The rays from these two reflectors converge at the same height of the detector (12), but if they are not laterally focused, they will diffuse horizontally. Therefore, these rays appear as horizontal stripes of medium intensity on the detector (12). Likewise, some rays are reflected only by the vertical surface and not by the horizontal surface, forming vertical stripes on the image plane Pi.

Finally, some rays reach the corners, are first reflected by the vertical surface, then by the horizontal surface, and vice versa. These double-reflected rays travel diagonally toward the center of the detector, forming a very strong central focal point.

More specifically, as illustrated in Figure 4, a photon from the source point (13) passing through the channel (10) of the MPO may strike the image plane Pi without reflection (according to the impact R0), may undergo one reflection (according to the impact R1 forming a cross), or may undergo two reflections (resulting in a spot R2). The isosimilarity ratio between the source point (13), the MPO, and the image plane Pi remains constant. Therefore, there exists a ratio M corresponding to the distance L between the source point (13) and the image plane (Pi) divided by the distance Ls between the source point (13) and the MPO. This ratio M applies to the spatial difference between the MPO and the image plane Pi, and thus in Figure 4, X = M*x and Y = M*y, where X and Y are the reference coordinates of the image plane Pi, and x and y are the reference coordinates of the MPO.

Therefore, as illustrated in Figure 5, rays that are not focused will cause cross-shaped noise and diffuse background in the image plane.

The cross-shaped noise problem has been widely discussed in existing technologies and has not been truly solved for many years.

In the publication "X-ray focusing using square channel-capillary arrays" by H. N. Chapman, K. A. Nugent, and S. W. Wilkins, Rev. Sci. Instrum. (June 1, 1991); 62 (6): 1542–1561, the authors suggest optimizing the design of the MPO by limiting the cross-shaped noise effect by adjusting parameters such as the aspect ratio of the channel, surface reflectivity, and geometry.

Circular arrangements are also provided, for example, in the publications of G.J. Price, A.N. Brunton, M.W. Beijersbergen, G.W. Fraser, M. Bavdaz, J.-P. Boutot, R. Fairbend, S.-O. Flyckt, A. Peacock, and E. Tomaselli: X-ray focusing with Wolter microchannel plate optics, Nuclear Instruments and Methods in Physics Section A: Accelerators, Spectrometers, Detectors and Related Equipment, Vol. 490, No. 1-2, 2002, pp. 276-289, ISSN 0168-9002.

In this type of arrangement, the aim is to achieve single reflection on the channel walls that form the circular element. However, some photons may pass through such an MPO without any reflection. These photons then enter the diffuse background in the image plane.

Even though the intensity is not as high as in a square configuration, this diffuse background is still too strong for most optical applications.

In the publication "Optimization of square pore optics for the x-ray spectrometer on Bepi-Columbo" by R. Willingale, G. W. Fraser, and J. F. Pearson, Proc. SPIE 5900, EUV, X-ray and Gamma-ray Astronomical Optics II, 590012 (September 8, 2005), several channel arrangement structures were proposed to limit the influence of cross-shaped noise.

The publication "Aberrations in square pore micro-channel optics used for x-ray lobster eye telescopes" by R. Willingale, J. F. Pearson, A. Martindale, C. H. Feldman, R. Fairbend, E. Schyns, S. Petit, J. P. Osborne, and P. T. O’ Brien, Proc. SPIE 9905, Space Telescopes and Instruments 2016: Ultraviolet to Gamma Rays, 99051Y (July 18, 2016) describes the use of software models to manage noise or fuzzy concepts on a detector.

The publication by M. Gailhanou, P. Sarrazin, and D. Blake, "Modeling of x-ray fluorescence full field imaging using planar square pore micro-channel plate optics," Appl. Opt. 57, 6795-6807 (2018), provides two original solutions to limit the influence of cross-shaped noise. One is to capture X-rays while rotating the channel at a random angle, and the other is to extend the cross shape through continuous imaging operations by rotating the MPO, i.e., converting it into uniform noise. These solutions do not change the overall intensity of the noise, and more importantly, they do not eliminate noise near the spot.

The publication by Songwu Peng, Yizhong Ye, Fei Wei, Zuhua Yang, Yihong Guo, and Tianran Sun, “Numerical model built for the simulation of the earth magnetopause by lobster-eye-type soft X-ray imager onboard SMILE satellite”, Opt. Express 26, 15138-15152 (2018), describes a simulation method that incorporates channel manufacturing errors to more concretely characterize image quality.

The publication "Preliminary geometric parameters optimization of lobster-eye-type wide field of view soft x-ray imager" by Songwu Peng, Yizhong Ye, Fei Wei, Yihong Guo and Yizhong Ye, Opt. Eng. 58(9), 093101 (2019), analyzes the error of the channel curvature radius to limit the influence of cross-shaped noise.

The published paper "X-ray performance and simulation study of lobster eye optics" by Jin Li, Takanori Sakamoto, Motoko Serino, Daisuke Yonetoku, Tatsuya Sawano, Ikuyuki Mitsuish, and Tatehiro Mihara, Proc. SPIE 11444, Space Telescopes and Instruments 2020: Ultraviolet to Gamma Rays, 114447C (December 13, 2020), describes the use of software models to manage noise or fuzzy concepts on a detector while simultaneously addressing inhomogeneities in the curvature of the integral channel.

The publication of An, Siwen & Krapohl, David & Thörnberg, B & Roudot, R & Schyns, E & Norlin, Börje. (2023). Characteristics of micro-aperture optical elements for full-field X-ray fluorescence imaging. Instrumentation Journal. 18. C1017. 10.1088/1748-0221/18/01/C01017 provides a method for image processing via Fast Fourier Transform to limit the influence of crosshair noise.

In summary, although existing technologies offer various solutions to attenuate or diffuse this cross-shaped noise problem, such as rotating the channel at random angles or performing continuous imaging via a rotating MPO, these solutions only randomly diffuse the noise photons around the spot without significantly reducing the number of noise photons.

These solutions may be suitable for space applications with longer focal lengths due to relatively low noise. However, existing solutions are insufficient for shorter focal lengths, typically used for X-ray imaging and analysis applications such as X-ray diffraction or X-ray fluorescence spectroscopy.

Therefore, the technical problem of this invention is to find a way to significantly reduce noise from the MPO so that the MPO can be used in applications with relatively short focal lengths.

To address this technical problem, the present invention provides an opaque treatment of the central region of the MPO array, making it opaque to X-rays. Even if multiple possible reflections affect the image plane of the MPO, this solution appears to remove noise-generating photons from the area of strongest noise in the image plane (i.e., the area around the spot), the surface area of which is determined by the surface area of the noise region, and thus reduced on the image plane.

Furthermore, in applications that generate parallel beams, such as X-ray diffraction, this solution removes photons close to the optical axis, thereby improving the beam's divergence.

Therefore, according to the first embodiment, the present invention relates to a microaperture optical element for focusing X-rays onto an image plane located at a predetermined distance, or for generating a parallel X-ray beam, said microaperture optical element comprising an array integrating: a plurality of channels through which X-rays can be transmitted and reflected; and a shielding region, wherein the array is opaque to X-rays, said shielding region being arranged at least in a central region of said microaperture optical element.

Therefore, blocking the central area can reduce noise around the light spot.

The surface area of the central region can be determined based on the surface area of the noise region to be reduced in the image plane and the distance between the image plane and the micro-aperture optical element.

The occlusion effect is particularly effective when the array is arranged in a circular pattern. In this embodiment, the different pixels of the array are arranged according to a concentric circle pattern. The different pixels can be circular. In a circular arrangement, the pixels constituting the occlusion area include at least one circular area centered on the center of the array.

When the micro-aperture optical elements are arranged in a square pattern, the shading areas are preferably arranged in two orthogonal bands located at the center of the width and length of the array.

In this embodiment, the vertical band limits photons contributing to the horizontal branches of the crosshair, while the horizontal band limits photons contributing to the vertical branches of the crosshair. To define the width of each band, the size of the noise-to-reduced region on the image plane can be measured, and then the width of each band can be determined based on a ratio M, which is determined at least by the size of the noise-to-reduced region and the distance between the image plane and the microaperture optical element (MPO) (e.g., the ratio M described in Figure 4 in the prior art). Furthermore, the two orthogonal bands of the shading region limit photons that cause diffuse background noise around the spot.

As a variation or supplement, it may be more advantageous to apply opacity to both the vertical and horizontal bands, i.e., to occlude the region defined by the hyperbolic contour, thereby forming a cross with the hyperbolic contour. The mathematical definition of these hyperbolic contours can be achieved using the product of the channel positioning coordinates, x*y, as shown in Figure 4 of the prior art. Therefore, each channel whose product x*y is less than a constant can be occluded. In fact, the probability of a photon reaching the point (x, y) of the MPO and reflecting back to the spot is proportional to the product x*y. Therefore, this occlusion restricts noisy photons in the region surrounding the spot and further reduces the noise level outside that region, while having a very limited effect on the flux reaching the spot.

Furthermore, the source can be positioned on the focal plane of the microporous optical element to transmit a collimated beam.

In collimation applications, commonly used in X-ray imaging and analysis, the presence of a band centered on the width and length of the microaperture optical element removes noise photons with a divergence of less than 1/2*Δ/Ls in the vertical and horizontal planes, where Ls corresponds to the distance between the source and the MPO, as shown in Figure 4 of the prior art, where Δ is the size of the obscured area.

As a variation, the position of the source phase relative to the microporous optical element and its focal plane can be selected in a manner that generates a focused beam.

For some applications, the radius of curvature of a micro-aperture optical element along its optical axis can be positive or negative.

According to the first embodiment, the shielding area is formed by shielding plates located between a plurality of channels. In this embodiment, a plurality of conventional micro MPOs are assembled around an opaque structure. This results in an MPO that covers only a portion of the array, with all channels open at the four corners and the shielding plates forming a central cross. In this case, a single micro MPO can be placed at each corner of the array, or a plurality of micro MPOs can be placed at each corner, thus requiring the use of 4, 16, or 36 micro MPOs. In this embodiment, the rows and columns of the array are formed by shielding plates and different micro MPOs.

According to the second embodiment, the shielding area is formed by a shield attached to a portion of one of the plurality of channels. In this embodiment, the MPO array is formed in the first step, in which all channels are in an open state, and the shielding area is formed in the second step by installing the shield.

In both embodiments, the shield can be made of lead or any other material that is opaque to X-rays.

In the second embodiment, the shield can be printed on a thin film deposited on the microporous optical element or directly printed on the microporous optical element.

In the third embodiment, the obscuring region is formed by apodizing a portion of one of the plurality of channels. In this embodiment, certain channels in the array are thus obscuring by apodizing, i.e., the channels in the obscuring region are structurally modified before or after the array is formed, so that the apodized channels are opaque to X-rays.

To perform this apodization, a variety of different methods can be used. For example, three-dimensional printing technology can be used to obtain the apodization channel using a configured printing template, which is configured to form the channel, which forms the array of the occlusion areas.

The conventional manufacturing method for forming the shielding channels can also be modified. To this end, the method may include the following steps: forming a core soluble in an acid and a cladding surrounding the core insoluble in the same acid; forming a shielding fiber having a core and a cladding surrounding the core insoluble in the acid; assembling the transport fiber and the shielding fiber together such that the shielding fiber is arranged at least in a central region of the microporous optical element (MPO); transversely dicing the assembly to a desired thickness to form a substrate; and chemically etching the substrate to open only the channels of the transport fibers.

In the channel forming method, multiple drawings and continuous assemblies of transport and shielding fibers can be used, or specific treatments can be applied to the MPO, such as treatments designed to control the roughness of the open channel.

To this end, a metallization layer can be deposited inside the channel, or a glass-forming technique can be used, which involves heating the channel until it becomes soft enough to form the shape of the mold. This technique is also known as "slumping".

According to another embodiment, the present invention also relates to an X-ray imaging system for a sample, comprising: an X-ray source configured to irradiate the sample through a microporous optical element as described in the first embodiment of the present invention; and a detector placed on a reflective plane of the radiation originating from the sample.

As a variation, the X-ray imaging system for the sample includes: an X-ray source configured to irradiate the sample; a microporous optical element as in the first state of the present invention; and a detector placed on the image plane of the microporous optical element, the microporous optical element being configured to collect photons from the sample for transmission to the detector.

To improve the performance of micro-aperture optical elements, a mask can be used behind them. In this way, the mask can completely block the area in the image plane where "cross-shaped noise" photons reach (i.e., the area that is not protected from noise by the channel shield).

Preferably, the microporous optical element is placed between a first X-ray emitting element and a second X-ray receiving element, the first X-ray emitting element being, for example, the X-ray source or the sample, and the second X-ray receiving element being, for example, the sample or the detector; the first element is placed at a distance L1 from the microporous optical element and has a surface area formed by a first dimension A1 and a second dimension B1; the second element is placed at a distance L2 from the microporous optical element and has a surface area formed by a third dimension A2 and a fourth dimension B2; the shielding areas of the microporous optical element are arranged in two orthogonal bands, a first band having a minimum dimension d1 along a first axis and a second band having a minimum dimension d2 along a second axis; The first minimum dimension is equal to d1, which is greater than (L1A1+L2A2)/(5*(L1+L2)), especially greater than (L1A1+L2A2)/(3*(L1+L2)), and preferably greater than (L1A1+L2A2)/(L1+L2); the second minimum dimension is equal to d2, which is greater than (L1B1+L2B2)/(5*(L1+L2)), especially greater than (L1B1+L2B2)/(3*(L1+L2)), and preferably greater than (L1B1+L2B2)/(L1+L2).

As illustrated in Figures 7 to 10, the present invention therefore provides a microaperture optical element (MPO) for focusing X-rays onto an image plane Pi or generating a parallel X-ray beam. As illustrated in Figures 3 and 4 of the prior art, this microaperture optical element is intended to be positioned relative to the image plane Pi at a predetermined distance F. Unlike conventional microaperture optical elements, the microaperture optical element of the present invention comprises an array (23) having a shielding region that is opaque to X-rays within the shielding region. This shielding region may be simply the central region of the microaperture optical element (MPO), especially when the microaperture optical element has a circular arrangement. In addition to the shielding region, the array also integrates a plurality of channels (10) through which X-rays can be transmitted and reflected, just like the channels of conventional microaperture optical elements.

To determine the surface area of the central region, simply identify the noise area to be reduced on the image plane Pi, excluding the obstruction area of the microaperture optical element (MPO), and then apply the similarity principle regarding the distance F between the image plane Pi and the MPO. As shown in Figures 7 to 10, in a square arrangement, cross-shaped noise is better achieved by using two orthogonal band obstruction areas. These orthogonal bands are illustrated in Figure 7 as bands that obstruct two channels. As a variation or supplement, in addition to these two bands, a cross with a hyperbolic profile can also be used, as shown in Figure 8.

Crosses with straight or hyperbolic contours can be obtained through apodized channels (21). The apodization of these channels acts as a shield, making them opaque to X-rays. For this purpose, microporous optical element arrays can be formed using 3D printing technology, where the printing template integrates open channels (10) only in areas where apodization should not be performed.

As a variation, apodization can be performed after the microporous optical element has been formed, for example, by placing a lead shield over the desired shielding area.

Furthermore, the apodized channels (21) can be arranged in the desired positions by modifying the traditional manufacturing method, thereby forming a microporous optical element. For this purpose, the fiber formation of the microporous optical element traditionally includes the following steps: forming transport fibers having an acid-soluble core and an acid-insoluble cladding; and then assembling and drawing these fibers to obtain transport fibers with a predetermined diameter.

Furthermore, shielding fibers can be formed in the same way as these transport fibers, provided that the cladding and core are insoluble in acid. Then, as illustrated in the embodiments of Figure 7 or 8, the transport fibers and shielding fibers can be assembled together in the desired pattern to form an array (23).

At the end of the assembly phase, the component can be transversely cut to form a substrate according to the required thickness, and then a conventional step is performed in which the substrate is chemically etched to open channels for the transport fibers. As illustrated in Figure 7 or 8, at the end of this chemical etching process, the resulting MPO can be an MPO with shielding fibers that form atodial channels (21).

As illustrated in Figures 9 or 10, as a variation of this method, micro MPOs (25) can also be placed around the shielding plate (24) that forms the shielding area. In these embodiments, the cross-shaped shielding plate (24) is positioned at the center of the array (23), and the four corners of the array are formed by micro MPOs covering the rest of the array. In the example of Figure 9, one micro MPO is arranged at each corner of the array (23), while in the embodiment of Figure 10, four micro MPOs (25) are arranged at each corner of the array (23). As a variation, nine or more micro MPOs (25) can also be integrated at each corner of the array.

In addition, the baffle (24) may have other shapes that are different from those shown in Figures 9 and 10, such as having a hyperbolic profile or being arranged only in the central area of the MPO, for example when the MPO has a circular arrangement.

As illustrated in Figures 11 and 12, in addition to apodizing or occluding certain portions of the MPO array (23), a specific radius of curvature can be printed along the optical axis Ao of the MPO. In particular, in Figure 11, the MPO has a positive radius of curvature along the optical axis Ao to transmit a collimated beam (14) on the image plane Pi. As a variation, in the embodiment illustrated in Figure 12, the microaperture optical element MPO has a negative radius of curvature along the optical axis Ao to transmit a beam (15) focused on a point on the image plane Pi or at least a reduced space.

Therefore, the present invention is particularly applicable to limiting the noise generated in systems using MPOs. In fact, as illustrated in Figure 6, the cross-shaped noise generated by the square-arranged MPOs of the present invention is limited compared to prior art MPOs.

Currently, noise is a key factor in MPO, so this noise limitation allows us to envision new applications for MPO. For example, it is now possible to design a highly efficient X-ray imaging system to detect the characteristics of a sample (16). As illustrated in Figure 13, an X-ray source (17) can be placed opposite the sample (16) so that the X-rays on the sample (16) diffract through the MPO before reaching the detector (12).

As a variation of the X-ray imaging system illustrated in Figure 13, as shown in Figure 14, the MPO can also be placed between the X-ray source (17) and the sample (16), and the detector (12) directly captures the intensity of the reflection point of the sample (16).

Additionally, a mask can be placed between the micro-aperture optical element (MPO) and the detector to partially block the image plane, further limiting the noise measured on it.

In summary, this invention limits noise on the image plane, particularly around the spot, or improves the quality of parallel beams (especially around the main beam direction) by apodizing or opaque portions of the microaperture optical element array. Therefore, the reduction of image plane noise improves the overall performance of the microaperture optical element and holds promise for numerous new applications, especially X-ray analysis of samples. [Obscured Area Size]

Referring to Figure 15, one embodiment of the present invention is an X-ray imaging system, which includes an optical axis (18). This X-ray imaging system includes a first X-ray emitting element (19), a micro-aperture optical element (MPO), and a second X-ray receiving element (20) continuously along the optical axis (18).

Referring to Figure 13, the first X-ray emitting element (19) can be the sample (16) to be imaged. The second X-ray receiving element (20) can be a detector (12).

Referring to Figure 14, the first X-ray emitting element (19) can be an X-ray source (17). The second X-ray receiving element (20) can be the sample (16) to be imaged.

Referring to Figure 15, the first element (19) may have a first dimension equal to A1 on a plane perpendicular to the optical axis (18) and along the first axis, and a second dimension equal to B1 on a plane perpendicular to the optical axis (18) and along the second axis, which is perpendicular to the first axis. The first and second dimensions are, for example, the available dimensions of the first element (19).

The second element (20) may have a third dimension equal to A2 in a plane perpendicular to the optical axis (18) and along the first axis, and a fourth dimension equal to B2 in a plane perpendicular to the optical axis (18) and along the second axis, which is perpendicular to the first axis. The third and fourth dimensions are, for example, the available dimensions of the second element (20).

The first element (19) is placed along the optical axis (18) at a distance equal to L1 from the microporous optical element MPO. The second element (20) is placed along the optical axis (18) at a distance equal to L2 from the microporous optical element MPO.

As illustrated in Figure 15, a microporous optical element (MPO) may include a shielding region having two orthogonal bands located at the center of the width and length of the MPO array (23), respectively. Therefore, the MPO in Figure 15 includes a first band with a minimum dimension d1 along the first axis and a second band with a minimum dimension d2 along the second axis in a plane perpendicular to the optical axis (18).

The first minimum dimension is equal to d1, which can be greater than (L1A1+L2A2)/(5*(L1+L2)), especially greater than (L1A1+L2A2)/(3*(L1+L2)), and preferably greater than (L1A1+L2A2)/(L1+L2). Therefore, most of the photons that cause diffuse background noise along the first axis will be filtered out by the microporous optical element MPO.

The second minimum size is equal to d2, which can be greater than (L1B1+L2B2)/(5*(L1+L2)), especially greater than (L1B1+L2B2)/(3*(L1+L2)), and preferably greater than (L1B1+L2B2)/(L1+L2). Therefore, most of the photons that cause diffuse background noise along the second axis will be filtered out by the microporous optical element MPO.

0~2: Region 10: Channel 11: Wall 12: Detector 13: Source 14: Collimating Beam 15: Beam 16: Sample 17: X-ray Source 18: Optical Axis 19: First X-ray Emitting Element 20: Second X-ray Receiving Element 21: Apodized Channel 23: Array 24: Baffle 25: Miniature MPO Ao: Optical Axis A1: First Dimension A2: Third Dimension B1: Second Dimension B2: Fourth Dimension d: Width d1, d2: Minimum Dimension F, L1, L2: Distance L: Length MPO: Micro-aperture Optical Element Pi: Image Plane R0, R1: Impact R2: Spot Se: Entrance Section

The embodiments of the present invention and the advantages thereof can be better understood through the following examples of non-limiting instructions given in conjunction with the accompanying drawings. Figure 1 is a perspective view of the channel of a prior art micro-aperture optical element; Figure 2 shows a cross-sectional view of the channel of the micro-aperture optical element of Figure 1, which causes partial cross-shaped noise; Figure 3 shows a perspective view of possible reflections inside a prior art micro-aperture optical element; Figure 4 shows the dispersion between the source, the micro-aperture optical element, and the image plane according to the prior art; Figure 5 shows the image plane of a prior art micro-aperture optical element; Figure 6 shows the image plane obtained using a micro-aperture optical element according to an embodiment of the present invention; Figure 7 shows a top view of a micro-aperture optical element according to a first embodiment of the present invention; Figure 8 shows a top view of a micro-aperture optical element according to a second embodiment of the present invention; Figure 9 shows a top view of a micro-aperture optical element according to a third embodiment of the present invention. Figure 10 illustrates a top view of a micro-aperture optical element according to a fourth embodiment of the present invention; Figure 11 illustrates a cross-sectional view of a micro-aperture optical element having a first radius of curvature according to an embodiment of the present invention; Figure 12 illustrates a cross-sectional view of a micro-aperture optical element having a second radius of curvature according to an embodiment of the present invention; Figure 13 illustrates a simplified representation of a first X-ray imaging system of a sample integrating a micro-aperture optical element according to the present invention; Figure 14 illustrates a simplified representation of a second X-ray imaging system of a sample integrating a micro-aperture optical element according to the present invention; and Figure 15 schematically illustrates an X-ray imaging system according to an embodiment of the present invention, the system including a micro-aperture optical element according to an embodiment of the present invention.

10: Channel

23: Formation

24: Visor

25: Miniature MPO

MPO: Microporous Optical Components

Claims (15)

A micropore optics (MPO) for focusing X-rays onto an image plane (Pi) at a predetermined distance (F) or for generating a parallel X-ray beam, the MPO comprising an array (23) integrating: a plurality of channels (10) through which X-rays can be transmitted and reflected; and a shielding region, wherein the array (23) is opaque to X-rays, the shielding region being arranged at least in a central region of the micropore optics (MPO). For example, the microporous optical element (MPO) of claim 1, wherein the array (23) has a square arrangement. For example, the microporous optical element (MPO) of claim 2, wherein the shading region is arranged in two orthogonal bands located at the center of the width and length of the array (23). For example, the microporous optical element (MPO) of claim 2 or 3, wherein the shielding regions are arranged in a cross shape with a hyperbolic profile. For example, the microporous optical element (MPO) of claim 1, wherein the array (23) has a circular arrangement. For example, a microporous optical element (MPO) of any of claims 1 to 5, wherein the shielding area is formed by a shielding plate (24) between the plurality of channels (10). Microporous optical element (MPO) of any of claims 1 to 5, wherein the shielding area is formed by a shielding plate attached to a portion (10) of one of the plurality of channels. Microporous optical element (MPO) of any of claims 1 to 5, wherein the shielding area is formed by a portion of one of the plurality of channels (10). The microporous optical element (MPO) of any of claims 1 to 8, wherein the microporous optical element (MPO) has a positive or negative radius of curvature along an optical axis (Ao). A method for manufacturing a microporous optical element (MPO) as claimed in claim 8, wherein the method comprises the following steps: forming a core having an acid-soluble core and a cladding around the core that is insoluble in the same acid; forming a shielding fiber having a core and a cladding around the core that is insoluble in the acid; assembling the transport fiber and the shielding fiber together such that the shielding fiber is arranged at least in a central region of the microporous optical element (MPO); transversely dicing the assembly to a desired thickness to form a substrate; and chemically etching the substrate to open only the channels of the transport fiber. A method for manufacturing a microporous optical element (MPO) as claimed in claim 8, wherein the microporous optical element (MPO) is formed by three-dimensional printing using a printing template configured to form blocking channels (21) that form the blocking regions of the array (23). An X-ray imaging system for a sample (16) includes: an X-ray source (13, 17) configured to irradiate the sample (16) through a micro-aperture optical element (MPO) as claimed in any of claims 1 to 9; and a detector (12) placed on a reflective plane of the radiation originating from the sample (16). An X-ray imaging system for a sample (16) includes: an X-ray source (13, 17) configured to irradiate the sample (16); a microaperture optical element (MPO) as claimed in any one of claims 1 to 9; and a detector (12) placed on the image plane (Pi) of the microaperture optical element (MPO), the microaperture optical element (MPO) being configured to collect photons originating from the sample (16) for transmission to the detector (12). An X-ray imaging system of one of claims 12 or 13, wherein the imaging system includes a mask arranged between the microporous optical element (MPO) and the detector (12) to block a portion of the image plane (Pi) at the detector (12). An X-ray imaging system for a sample of any one of claims 12 to 14, wherein the microaperture optical element (MPO) is disposed between a first X-ray emitting element (19) and a second X-ray receiving element (20), the first X-ray emitting element (19) being, for example, the X-ray source (17) or the sample (16), and the second X-ray receiving element (20) being, for example, the sample (16) or the detector (12); the first element (19) is disposed at a distance L1 from the microaperture optical element (MPO) and has a surface area formed by a first dimension A1 and a second dimension B1; the second element (20) is disposed at a distance L2 from the microaperture optical element (MPO) and has a surface area formed by a third dimension A2 and a fourth dimension B2; The shielding region of the microporous optical element (MPO) is arranged in two orthogonal bands, a first band having a minimum dimension d1 along the first axis and a second band having a minimum dimension d2 along the second axis; the first minimum dimension is equal to d1, greater than (L1A1+L2A2)/(5*(L1+L2)), especially greater than (L1A1+L2A2)/(3*(L1+L2)), and preferably greater than (L1A1+L2A2)/(L1+L2); the second minimum dimension is equal to d2, greater than (L1B1+L2B2)/(5*(L1+L2)), especially greater than (L1B1+L2B2)/(3*(L1+L2)), and preferably greater than (L1B1+L2B2)/(L1+L2).