Modular manufacturing technology for gratings used in interferometric X-ray imaging

Abstract

A method for manufacturing a grating assembly (GA) from grating tiles for use in interferometric X-ray imaging, and related apparatus for facilitating the practice of the method, the method comprising applying (S350) a grating (GT) tile to a curved carrier substrate, or applying the curved carrier substrate to the grating tile, such that the curvature of the tile matches the curvature of the carrier substrate.

Description

Technical Field

[0001] The present invention relates to a manufacturing method of a grating component, a grating component, a device for manufacturing the grating component, and a manufacturing system. Background Art

[0002] Grating-based phase contrast and dark-field X-ray (DAX) imaging are promising technologies for enhancing the diagnostic quality of X-ray equipment, for example in mammography, chest imaging, and CT (computed tomography). As the name implies, grating-based imaging requires one or more (usually three) gratings as part of the imaging system. One such grating, often referred to as "G2," is located between the patient and the imaging system's detector.

[0003] One of the most challenging issues in building a clinical imaging system based on this technology is the fabrication of a full-field G2 grating. In particular, the relatively large area of ​​an X-ray detector used for chest examinations (almost 50 cm x 50 cm) is a major challenge, as it needs to be completely covered by the G2 grating.

[0004] Currently, one of the more mature processes for creating such gratings is the LIGA process. "LIGA" is the German acronym for "Lithographie, Galvanoformung, Abformung" (which translates to "lithography, plating, and forming"). In LIGA, the grating structure is fabricated from micron-scale gold structures onto a graphite substrate. Due to the limited space of the X-ray exposure system and the wafer handling limitations of the gold plating process used in the LIGA process, the maximum size of the existing grating is approximately 10 cm x 20 cm.

[0005] The fabrication of large wafer sizes that can completely cover an X-ray detector is currently unavailable. Therefore, current methods use a "stitching" process to mount several small grating tiles together to cover the entire front face of an X-ray detector.

[0006] Another challenge, particularly in DAX systems, is the desire to focus the grating to reduce signal loss, particularly for large-area imaging applications such as breast imaging. In such focused gratings, the cylindrical curvature radius of the G2 grating is approximately 2-3 m. However, individual grating wafers (which will be referred to herein as "grating tiles") are naturally flat during manufacture. Summary of the Invention

[0007] Therefore, alternative devices or systems may be needed to improve the fabrication of focusing gratings for imaging.

[0008] The objects of the invention are solved by the subject-matter of the independent claims, wherein further embodiments are incorporated in the dependent claims. It should be noted that the following described aspects of the invention apply equally to the apparatus for manufacturing a grating assembly, the manufacturing system, the computer program element and the computer-readable medium.

[0009] According to a first aspect of the present invention, there is provided a method for manufacturing a grating assembly from grating sheets for use in interferometric X-ray imaging, comprising the following steps:

[0010] - arranging the grating piece on a curved surface of a manufacturing apparatus so that the grating piece has a curvature, and then

[0011] - applying a (curved) grating tile to a curved carrier substrate, or applying the curved carrier substrate to the grating tile, such that the curvature of the tile matches the curvature of the carrier substrate. Preferably, a plurality of tiles are arranged in this manner, and then the curved carrier substrate is applied or being applied at once. The curved surface of the manufacturing apparatus is concave.

[0012] In an embodiment, the coefficient of thermal expansion of the carrier substrate corresponds to the coefficient of thermal expansion of the grating substrate.

[0013] In an embodiment, the carrier substrate comprises glass or graphite.

[0014] The carrier substrate can be obtained by bending a heated glass plate onto a (positive) mold. The mold can be made of aluminum, other metals, or other non-metallic materials. The mold can be produced with the desired curvature through additive manufacturing, 3D printing, CNC machining, etc. Graphite carrier substrates can be obtained through CNC machining.

[0015] In an embodiment, the glass is at least partially borosilicate glass.

[0016] In an embodiment, the grating substrate comprises graphite or silicon.

[0017] Material combinations for the carrier substrate and the grating substrate contemplated herein include "glass (carrier substrate) on graphite (grating substrate)", "glass on silicon", or "graphite on graphite", or "graphite on silicon". Of the glass combinations, glass on silicon may be preferred because one may find a glass material with a suitable thermal expansion coefficient that is better matched to silicon than graphite.

[0018] In an embodiment, the method comprises, before the applying step, the step of arranging the grating tile on a curved surface of a manufacturing device.

[0019] In an embodiment, the grating segments are arranged in groups as such.

[0020] In an embodiment, the arranging step comprises aligning at least one of the grating tiles using a stop edge of the fabrication apparatus, such as a raised edge of a working surface thereof. The edge may be removable so as to be repositionable to align one or more additional such grating tiles to fabricate the grating assembly.

[0021] In an embodiment, there is a gap between two adjacent grating tiles, and the method further comprises reducing a width of such gap.

[0022] In an embodiment, the method comprises arranging a separator or sealing element in the gap. This prevents glue from entering the gap and causing the piece to adhere undesirably to the work surface.

[0023] In an embodiment, the method comprises dispensing X-ray compatible glue on the carrier or on one or more of the grating tiles before the applying step.

[0024] According to the present invention, the grating block comprises two opposing surfaces, namely a first and a second surface. One of these surfaces, the second surface, includes a set of grooves, wherein the second surface is located distally from the curved carrier substrate. The grooved surface thus faces the working surface of the fabrication apparatus. This allows the thin slices of the grating block to be expanded, particularly when the working surface is concave, to promote uniform placement and focusing.

[0025] The proposed method allows for efficient fabrication of specifically focused, large-surface-area gratings with desired bend radii. The method facilitates precise assembly ("stitching") of individual grating tiles. The alignment of the grating tiles is preserved during fabrication. The proposed method eliminates the need for complex and time-consuming post-assembly alignment checks and / or adjustments, such as those based on lasers or other techniques.

[0026] In another aspect, there is provided a grating assembly comprising a glass carrier with a grating tile deposited therein, obtainable by a method according to any one of the preceding claims.

[0027] In another aspect, there is provided an apparatus for manufacturing a grating assembly from grating segments in an X-ray imaging apparatus, comprising:

[0028] A plurality of vacuum chucks have corresponding receiving segmented surfaces for receiving one or more grating segments, the segmented surfaces being curved to together form portions of a transverse cylindrical surface, the portions being concave.

[0029] In an embodiment, the vacuum chuck is configured to apply a vacuum suction force on the corresponding grating so as to bend and fix the corresponding grating segment to conform to the curvature of the corresponding curved segmented surface.

[0030] In an embodiment, the vacuum cups are movable in a motion relative to each other so as to increase or decrease the gap between the respective segmented surfaces.

[0031] In an embodiment, the motion is constrained to be linear motion.

[0032] In an embodiment, the linear motion is constrained such that the motion is parallel to the longitudinal direction of the ridges of the grating segment when the grating segment is fixed to a given segmented surface.

[0033] In an embodiment, the apparatus comprises a stop edge as an aid to align the grating tile on the at least one segmented surface.

[0034] In an embodiment, the stop edge is removably mountable on one of the segmented surfaces, removable from the segmented surface and mountable on a different one of the segmented surfaces or in a different position on the segmented surfaces.

[0035] In another aspect, a manufacturing system is provided, comprising: an apparatus according to any one of the embodiments described above, further comprising an arm or an apparatus having such an arm, which is configured to push a curved carrier substrate and / or the grating piece towards each other while the grating piece is arranged on and held by the vacuum chuck, so that the grating piece is clamped between the segmented surface and the carrier substrate.

[0036] In another aspect, a control logic is provided, which is configured to perform a method according to any one of the above-mentioned embodiments.

[0037] In another aspect, a computer program element is provided which, when run by at least one processing unit, is adapted to cause the processing unit to perform the method according to any of the above-mentioned embodiments.

[0038] In a further aspect, a computer readable medium having the program element stored thereon is provided.

[0039] In summary, what is presented here is a modular approach to mounting and aligning several gratings into a combined curved metasurface. In an embodiment, a mounting stage is used that comprises a plurality of blocks or "segments" of preferably identical (or at least similar) shape. The segments, in an embodiment a plurality of vacuum chucks, can be moved with high precision relative to each other in one direction. The geometric tolerances of the individual segments and the tolerances between the segments are preferably less than 50 μm. The top or receiving surface of each segment has a cylindrical surface with a curvature radius that matches the desired curvature radius of the grating assembly to be manufactured.

[0040] In an embodiment, a vacuum pump system is connected to some or each of the segments. Vacuum can be applied and released to each individual grating tile, which is placed on top of the curved receiving surface of the mounting segment. Precise alignment of each grating tile relative to a given segment can be achieved with the help of a stop edge. After placing an individual grating tile on the leading edge, the tile is fixed by activating the corresponding vacuum suction cup. As the leading edge moves from one segment to another, all segments are continuously loaded with grating tiles. In a final step, after removing the stop edge, the movable segments, each carrying one or more of the tiles, are pulled together to form a single combined curved surface of the G2 grating assembly, wherein the gaps between individual tiles are preferably less than 50 μm.

[0041] Advantages of the proposed modular manufacturing technology and supporting equipment / system as described herein to put this approach into practice include:

[0042] - Individual grating segments can be pre-aligned with high precision;

[0043] - the use of the stop edge facilitates the parallel placement of the individual grating segments;

[0044] - Fixing of individual grating pieces by vacuum is a versatile and non-destructive process;

[0045] - Maintaining the alignment / orientation of the gratings by securing the grating pieces with vacuum during the curing time of the glue;

[0046] - Fixing of all grating pieces in one single glue step rather than individual gluing steps eliminates orientation / alignment errors;

[0047] - securing the grating matrix to a supporting carrier substrate by glue to facilitate maintaining the orientation of the grating tiles;

[0048] - Customizations including replacement of grating segments of different sizes can be easily handled by adjusting the segments of the vacuum table accordingly,

[0049] Automation of part or all of the manufacturing method is possible, including any one or more (or all) of the following: placement of gratings, movement of the vacuum stage, application of glue, application of the carrier substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Exemplary embodiments of the present invention will now be described with reference to the following drawings, which are not to scale, in which:

[0051] Figure 1 shows a schematic diagram of an interferometric X-ray imaging device;

[0052] Figure 2A perspective view of a grating assembly assembled from grating segments is shown;

[0053] Figure 3 A flow chart illustrating a method of manufacturing a grating assembly;

[0054] Figure 4 shows a manufacturing chain for manufacturing a grating assembly;

[0055] Figure 5A -C shows an apparatus configured to facilitate assembly of a grating assembly;

[0056] Figure 6A -D illustrates the steps of arranging the grating tiles on the work surface in a plan view;

[0057] Figure 7A -C illustrates in side view a grating sheet arranged on a working surface of an apparatus to facilitate the manufacture of a grating assembly;

[0058] Figure 8A illustrates, in plan view, the steps of arranging a sealant in a system of grating tiles; and

[0059] Figure 8B is a cross-sectional view of a grating assembly with encapsulant included. DETAILED DESCRIPTION

[0060] refer to Figure 1 , which shows a schematic diagram of the components of the interferometric X-ray imaging device IA.

[0061] The apparatus IA comprises an X-radiation source S and an X-radiation sensitive detector D. Between the X-ray source and the detector D there is an examination region in which an object to be imaged (not shown) typically resides during imaging.

[0062] The imaging device IA further comprises an interferometer IF. Due to the interferometer IF (at least a portion of which is also arranged in the examination region between the source S and the detector D), the imaging device is capable of providing not only absorption images, but also phase contrast and / or dark field images. The latter two have been found to provide additional diagnostic value. The latter two images utilize a different contrast mechanism than absorption imaging, wherein they allow imaging of phase variations or small-angle scattering quantities, such as those caused by the object to be imaged (e.g., patient tissue), respectively. For example, in the medical field, as primarily contemplated herein, phase contrast imaging allows better imaging of soft tissues, where the contrast is typically too high for absorption-based imaging. On the other hand, dark field images have been found to provide good contrast for microstructures and may therefore be useful for detecting early stages of breast cancer.

[0063] In some embodiments, but not necessarily all, interferometer IF includes three grating structures, referred to herein as "G0," a source grating; "G1," a phase grating; and "G2," an analyzer grating. Source grating G0 is optional and is used to generate coherent X-ray radiation at source S. In other words, if source S generates naturally coherent radiation, grating G0 may not be required. Source grating G0 and analyzer grating G2 are absorption gratings, while grating G1, as its name implies, is a phase grating.

[0064] In operation, X-radiation is emitted from a source S and interacts with the object being imaged and with matter in the interferometer to cause a diffraction or moiré pattern that can be detected at a detector D. This pattern can then be analyzed using signal processing to calculate a dark field or phase contrast image and, if desired, a conventional absorption image.

[0065] The grating is usually rectangular or square in shape and is preferably as Figure 1 The focal spot shown is focused towards the light source. In other words, the gratings G0, G1 and G2 are curved, specifically forming corresponding cross sections of the side surfaces of three imaginary concentric cylinders with radii r0, r1 and r2, respectively. Focusing the gratings in this way provides better signal efficiency. Figure 1 In FIG, directions X and Z represent the two spatial dimensions of the grating, while direction Y is the imaging direction parallel to the optical axis OX of the system IA.

[0066] The imaging arrangement IA mainly envisaged herein is of the full-view type, in which the spatial dimensions of the grating G2 (when viewed in perspective along the optical axis) correspond to the shape and size of the radiation-sensitive surface of the detector D. In certain applications envisaged herein, such as breast imaging, the detector, and therefore G2, is quite large, up to 50 x 50 cm2 or even larger for non-medical applications (such as whole-body screeners). In other words, in the full-view system IA, the analyzer grating G2 has approximately the same size as the detector D. As mentioned earlier in the background, it is currently not possible to produce such large-sized full-view gratings. Instead, the analyzer grating G2 needs to be assembled or "stitched" together from smaller grating tiles GT in order to build up the analyzer grating G2 of the required size.

[0067] The fabrication of the grating tile GT itself is outside the scope of the present disclosure and has been described in detail elsewhere, such as in Mohr J et al., "High aspect ratio gratings for x-ray phase contrast imaging," published in AIP Conf. Proc., Vol. 1466, pp. 41-50 (2012), and David C et al., "Fabrication of diffraction gratings for hard x-ray phase contrast imaging," published in Microelectron. Eng., Vol. 84, pp. 1172-7 (2007). The grating tile GT used in the context of the present disclosure is currently available and is typically square or rectangular and has a thickness (in the Y direction) of approximately 1000 microns. As such, the grating tile GT itself is planar and includes two surfaces, a proximal surface and a distal surface, with the proximal surface being closer to the source S when used in the Y direction. The proximal surface of the grating tile may also be referred to herein as the "lower surface," while the other, opposite, distal surface may be referred to herein as the "upper surface."

[0068] The grating tile GT comprises a grating substrate or body having a top (or upper) surface and a bottom surface. The top surface of the grating substrate is scored to include a set of parallel lines or grooves, leaving ridges between any two adjacent grooves. These grooves can be obtained by etching or photolithography techniques as previously described. In addition, the grooves are partially or completely filled with a high-Z material, such as gold or lead, to obtain a set of parallel grating flakes of the grating tile GT. The grating substrate itself is made of a suitable material, such as silicone or graphite.

[0069] The proposed manufacturing method and the related apparatus allow efficient production of curved grating components from existing planar grating tiles, thereby building focusing gratings, in particular absorption gratings or phase gratings, of any desired size and / or for use in interferometric X-ray imaging.

[0070] Figure 2 One such grating assembly GA that can be built using the proposed method is schematically shown. The grating example GA comprises a plurality of grating tiles GT arranged in a matrix layout (in Figure 2 The number is 8 in the example of ). The tiles GT have their scribe patterns aligned in parallel in one direction, say X, and along the other direction Z have their scribe patterns aligned in register with each other, ie grooves at grooves and ridges at ridges.

[0071] The grating tile GT is fixed to a curved carrier substrate CS. In particular, the grating tile is glued to the carrier substrate CS. The curvature of the carrier substrate CS corresponds to the desired curvature of an imaginary transverse cylindrical surface with radius r2. The carrier substrate CS, to which glue (not shown) is applied, forces the grating to conform to the desired curvature because the grating itself is naturally planar, as mentioned previously.

[0072] It is desirable to maintain the X, Z alignment of the ruled surface of the grating during a range of operating conditions of the imaging device. Applicants have discovered that this can be achieved by having a coefficient of thermal expansion of the carrier substrate CS that corresponds to, and in particular is equal to, the coefficient of thermal expansion of the grating substrate of the tile GT. In particular, when the grating tile GT is made of silicon or graphite, it is advantageous to have a carrier substrate CS made of glass, in particular pure glass. More particularly, a curved plate of float glass, or more particularly borosilicate glass, having a coefficient of thermal expansion equal to that of graphite or silicone is used. Other material combinations for the carrier substrate and grating substrate may also be used, as long as their coefficients of thermal expansion are substantially equal or within tolerance of each other.

[0073] In an embodiment, the carrier substrate CS is a curved glass sheet having a desired curvature or bending radius r2, wherein its size (area surface) and shape are equal to (in perspective along direction Y) the size and shape of the radiation sensitive surface of the detector D.

[0074] Now refer to the flowchart Figure 3 , which illustrates the proposed manufacturing process such as Figure 2 The steps of the method for producing a grating assembly GA are shown. Although this article primarily contemplates the production of analyzer grating G2, the principles presented can equally be applied to source gratings and / or phase gratings, if desired. However, the primary interest in this article is indeed grating G2, as this is the largest grating. It should be understood that use in a full-view imager is not necessarily required, and grating assembly GA can still be used in raster scanning systems when larger grating structures are still required.

[0075] As previously mentioned, the proposed method allows for efficient assembly of a grating assembly GA of any desired size by combining or splicing together the desired number of grating tiles in a matrix configuration or layout. Initially, each grating tile, which is itself an absorption grating, is typically planar or has a natural curvature different from one of the desired r2 values, and the grating tiles are typically rectangular or square in shape. Other shapes are also contemplated herein. The grating tiles do not necessarily all have the same shape and / or size.

[0076] Broadly, at step S310, a desired number of grating segments are arranged on a working surface. The working surface is such that it allows the grating segments to be fixed and pre-bent from their natural planar shape to a desired curvature r2.

[0077] As will be explained in more detail below, the working surface can be formed by one or more surfaces in segments, such as the vacuum chucks of a vacuum assisted device, but any other working surface is also contemplated. The arrangement of the tiles GT can be done group by group, one by one, or all at once. Preferably, the submodule is first formed by arranging a group of two or more gratings on the working surface in a first step, and then further groups of grating tiles GT are so arranged in one or more subsequent steps. The tiles GT in each group can be applied one at a time or all at once. Preferably, the grating tiles GT are applied face down or upside down, wherein the upper surface faces the working surface, leaving the lower surface exposed. Stop edges can be used to assist in aligning the gratings.

[0078] For efficient manufacturing, gaps may be left between the tiles GT, particularly in different groups of tiles, and these gaps may be reduced in optional step S320. Again, specially designed tools may be used for this gap reduction. In one embodiment, gap reduction may be achieved by vacuum chucks that are movable toward each other, as will be explained more fully below.

[0079] At step S330, the remaining gaps, now of reduced width, are sealed so that the glue dispensed at the subsequent step S340 does not penetrate into the gaps between the grating tiles. The glue is dispensed in dots, lines, or other patterns onto the fixed grating tiles. In particular, the glue is applied to the lower surfaces of the grating tiles, as these can be held upside down as previously described.

[0080] At step S350, a curved carrier substrate, in an embodiment made of glass, is then applied to the pre-curved set of grating tiles arranged on the working surface. The curvature of the applied carrier substrate CS matches the curvature of the grating being held, and therefore the curvature of the working surface of the tool VT used to hold the grating tiles in place and under curvature. In other words, the curvature of the carrier substrate CS matches the curvature of the working surface to sandwich the grating tiles GT therebetween.

[0081] The step S350 of applying the curved carrier substrate CS to the pre-curved grating segment includes pushing the carrier substrate CS into contact with the glue to couple or bond the carrier substrate CS to the grating segment. Alternatively, the working surface with the grating segment thereon can be moved and pushed into contact with the stationary carrier substrate CS. Still alternatively, opposing motions can be applied to both the carrier substrate and the grating segment on the working surface to couple them together.

[0082] In step S360, the glue is then allowed to cure. The glue should be chosen so that the curing process does not start immediately, but can be extended over a certain time frame, which can allow the alignment of the grating piece to be adjusted in an optional step S370, if necessary. This optional alignment can be done, for example, with the help of a laser beam, which is projected onto the manufactured grating piece and adjusted by micrometer screws or other means so that a predefined diffraction pattern is obtained on the screen. However, for this purpose, it will be necessary to lift the assembled grating assembly GI from the work surface to allow it to be exposed to the interrogating laser beam. In addition, or as an alternative, the adjustment can be performed with the assistance of a microscope. However, it has been observed that the proposed method provides the highest accuracy and the alignment adjustment step is obsolete, thereby increasing the throughput of the proposed method.

[0083] Once the glue has fully cured, the grating assembly GA is ready for use. Preferably, and as mentioned, in the steps described above, the grating segments are arranged upside down on a concave (relative to the plan view direction Y) curved working surface, i.e., with the upper surface pointing towards the working surface SS and thus on the far side of the curved substrate. In other words, the glass CS is applied to the back side of the grating. Fixing the grating upside down on the concave working surface ensures that the grating segments are separated, as opposed to being compressed when curved convexly, thereby ensuring good focusing properties.

[0084] The glue used in step S340 needs to be X-ray compatible. In addition, a specific viscosity is desired within the range of 2000-10000 mPa·s (cP).

[0085] Although some or all of the steps mentioned above may be performed manually in an assembly line, at least partial or full automation of the proposed method is also envisaged herein. In this respect, reference is now made to an at least partially automated manufacturing chain MC, such as Figure 4 Diagrammatically shown.

[0086] Broadly speaking, the manufacturing chain MC comprises the aforementioned tool having a curved work surface, on which the grating tile GT is arranged. This tool may be referred to herein as a vacuum table VT, as will be explained in more detail below. The proposed method may be performed by a single or multiple robotic devices operating in coordination under the direction of control logic CL, such as implemented on a processing unit PU, such as a computing device.

[0087] One or more robotic devices may include a tile dispenser TD. The tile dispenser may include a suitable arm or delivery device A1, as explained above, which places the tiles one by one, at a time, or preferably in groups, onto the curved work surface of the vacuum table VT. The arm A1 may terminate in a suitable end effector that allows for dispensing grating tiles. Like a hand, an articulated structure may utilize a vacuum-based end effector.

[0088] In this embodiment, the curvature of the working surface of the vacuum table corresponds to the desired curvature of an imaginary transverse cylindrical surface of the intended imaging system IA, as described above with respect to Figure 1 mentioned.

[0089] A glue dispenser GD robotic unit with a third delivery component A3 (such as a robotic arm) is used to apply glue to a previously laid-out grating sheet on the work surface of a vacuum table VT. Suitable end effectors for the glue dispenser GD include a nozzle, possibly with a piezoelectric tip, through which the glue is expelled. Other end effectors are also contemplated.

[0090] In the schematic side view Figure 4 In an embodiment, the curvature of the vacuum table's working surface is concave, wherein a concave carrier substrate CS (curved glass sheet) is applied from above by a carrier substrate dispenser CD. In alternative embodiments, "double" embodiments or tables VT and carrier substrates with opposite curvatures are also envisioned. However, as mentioned above, placing the grating upside down against the concave surface ensures favorable diffusion of the flakes rather than less favorable compression.

[0091] Another robotic unit, a carrier substrate dispenser CD, may include a delivery component, such as a robotic arm A2, having a suitably formed end effector, such as a suction cup, which engages with a curved carrier substrate CS and applies glue from the top by pushing the carrier substrate onto the glue to couple it to the grating sheet arranged on the vacuum table VT. Once coupled, the process A2 releases the carrier substrate.

[0092] The carrier substrate can be obtained from a curved glass sheet formed to the desired curvature by bending it over a positive mold in an oven or kiln OV at a suitable temperature. The mold can be formed as a metal block, such as an aluminum block, or a clay block, preferably a graphite block, or other, having an exposed surface with the desired curvature, onto which the previously flat glass sheet is bent under the influence of heat.

[0093] As mentioned above Figure 4 The term "arm" as used in connection with the automated manufacturing system MC is to be interpreted broadly and includes any device or part thereof, whether articulated or not, which is capable of performing any one or more or all of the steps or actions described above.

[0094] Now refer to Figures 5A-5C , Figures 5A-5C More details of a manufacturing aid, the vacuum table VT, are shown.

[0095] Figure 5A is a schematic diagram of the vacuum table in a side view along the z direction, i.e. the longitudinal direction along which the lamellae / scribes of the grating extend, and Figure 5B It is a plan view along the optical axis direction Y. Figure 5C is another side view, where the view direction is perpendicular to Figure 5A The viewing direction.

[0096] The vacuum table comprises a frame TB. A set of vacuum cups VC1-VC4 are slidably arranged on a slide SI, preferably in a matrix configuration. The vacuum cups are blocks and form segments of the working surface. More specifically, vacuum cups VC1-4 each include a receiving surface SS1 and SS2, which together form a concave working surface in this embodiment, onto which a grating block can be received. Figure 5A Only one such suction cup VC1 is shown, extending along Figure 5A The view direction z in the drawing plane of obstructs the view of the other suction cups VC2-4 arranged in sequence behind the suction cup VC1.

[0097] Each vacuum chuck VC includes one or more suction ports SP1, SP2 formed in and preferably flush with the receiving surface SS1, SS2. The suction ports SP1, SP2 are communicatively coupled to a vacuum pump VP via a set of preferably flexible conduits, such as hoses or tubes. Upon application of a vacuum, as applied by the vacuum pump VP, the individual gratings GT, respectively disposed on the receiving surface SS1, SS2, are secured and forced into a curved shape by the vacuum suction force applied through the suction ports SP1, SP2. Each individual grating tile is then held in position and in the desired curved shape by the one or more suction ports, ready to receive a carrier substrate CS applied from above.

[0098] like Figure 5BAs shown by the double arrows in Figure 1 and Figure 2, the vacuum cups VC1-4 are movable so as to increase or decrease the gap between adjacent vacuum cups VC1, VC2, and therefore the gap between the pieces GT, by sliding the cups VC on a slide SA. The slide SA may be arranged as a set of rails or the like along which the vacuum cups can slide. The sliding may be performed automatically by a powered actuator, such as a servo or stepper motor, or other motorized device. Alternatively, the sliding may be achieved manually by the user by a suitable set of manual actuators, such as precision micrometer screws or others. In each embodiment, whether manual or externally powered, the SA preferably includes a sufficiently fine gear mechanism that allows the gap to be reduced in appropriately small steps to better manage proximity and more precise positioning.

[0099] The motion of the vacuum chuck is suitably constrained to be linear and preferably parallel to the course along which the scribe line extends. Figure 5A In other words, the motion of the vacuum chuck is constrained to the z direction, the same direction as the extended scribe line shown in FIG6 .

[0100] To facilitate conversion of the vacuum table VT for use in fabricating grating assemblies GA having a different curvature requirement, r'≠r2, in certain embodiments, the suction cups VC are removable and replaceable with a new set of suction cups (not shown) whose receiving surfaces SS' (not shown) are formed with a different (now required) curvature r'. In certain embodiments, a quick connector for connecting / reconnecting the conduit L to the suction port SP of the new suction cups may be provided to further facilitate conversion. Similar quick-release mechanisms are contemplated in certain embodiments for coupling / decoupling the suction cups to the slider SA and / or frame TB.

[0101] As previously mentioned, the gratings are preferably applied in groups, with one, two, or more being applied to the receiving surface SS1 of vacuum cup VC1. The next group of tiles is then applied to another vacuum cup VC2, for example. Once the vacuum is applied and secured, the adjacent cups are moved using a sliding mechanism to reduce the gap between the vacuum cups, and thus the gratings on both vacuum cups. This process can be repeated until all grating tiles are properly bent and separated by a reduced gap.

[0102] In order to properly align the grating of each vacuum chuck, a stop edge SE may be used.The edge SE may be fixedly arranged or preferably removably mounted on and removable from each of the chucks VC1 , VC2.

[0103] In more detail, in some (but not all) embodiments, the stop edge SE is substantially arcuate and curved to conform to the curvature of the receiving surface SS of the chuck VC. The stop edge SE allows for parallel alignment of the grating tiles GT1, 2 on the chuck VC1. In the arcuate embodiment, when mounted, the stop edge SE is raised relative to the receiving surfaces SS1, SS2, as shown in FIG. Figure 5C As shown. The stop edge SE allows the grating to be aligned by pushing the corresponding tile edge (preferably the longer tile edge GT1, 2) into abutment and against the stop edge SE. The grating tile is then secured by applying vacuum, at which point the stop edge SE can be removed and secured to the next sliding vacuum chuck VC2, and so on. For example, in some of the arcuate embodiments, the stop edge comprises a pin that mates with a hole in the receiving surface SS1 and SS2 of the vacuum chuck.

[0104] In an alternative and preferred embodiment, the stop edge SE is not attached to the receiving surfaces SS1, SS2, making more surface area SS1, SS2 available. In such an embodiment, the stop edge is not arched, but can be formed as part of a rectangular plate that is fixed to one of the corresponding side surfaces of the corresponding suction cup VC (the side surface with z as the normal), the upper edge of the plate not being flush, but rising to the corresponding (curved) edge of the corresponding vacuum cup. This raised portion of the plate then forms the stop edge SE.

[0105] The stop edge SE can be moved manually in manual assembly, or the stop edge SE can be moved by the action of a suitable end effector of the robot arm of the tile dispenser TD, as described above in conjunction with Figure 4 As mentioned. In this document it is assumed that the grating segments have a sufficiently precise orthogonal shape. Furthermore, it is assumed that the scribe lines are oriented parallel to one edge of the segment GT, preferably its short edge. The application of the stop edge SE then ensures sufficient alignment accuracy of all grating segments and a parallel orientation of all scribe lines within ±0.03°.

[0106] Figure 5B A plan view of the curved surface of table VC is shown (the curvature is not visible in this view) with the two suction ports of each vacuum cup exposed. Figure 5B In the illustration shown, the vacuum chucks have been moved to minimize the gap between them, thereby forming the working surface into a smooth, concavely curved surface that couples with the carrier substrate CS from above, thereby sandwiching the grating segment therebetween. The steps described above will now be described and illustrated in more detail with reference to Figures 6-8.

[0107] Now first refer to Figure 6A -D, these are shown in plan view as above combined Figure 35 and more details of the tile placement step and gap reduction step mentioned in the flowchart of FIG.

[0108] In particular, Figure 6A As shown in the plan view in FIG, two grating tiles G1, G2 are applied to the receiving surface SS1 of a first suction cup VC1. The two (or more) grating tiles GT1, 2 form a first group, or "submodule". The groups of gratings on the suction cups are aligned using stop edges SE. A small gap also exists between the tiles GT1, GT2 of each suction cup, and this gap is ensured by introducing a temporary distance piece, a feeler gauge (e.g., a foil of approximately 50 μm thickness), which is removed once the two adjacent tiles GT1, GT2 have been correctly positioned and spaced (preferably by their short edges).

[0109] Now through the suction port SP1 ( Figure 6A The vacuum is applied to the grating sheet (not shown in the figure because the middle grating sheet is in the middle) to push and fix the two gratings in shape and position respectively. The same steps are now repeated for the subsequent gratings GT3, GT4 on the next suction cup, in particular the adjacent suction cup VC2, and so on, until the entire surface of the vacuum table is laid out in the grating sheet.

[0110] The embodiment of FIG6 shows eight grating tiles being used, but this is to be understood as exemplary. In embodiments, a single grating tile is placed on each vacuum chuck, or more than two are placed on each grating tile. In embodiments, it may not be necessary to place the same number of grating tiles on each vacuum chuck, but in embodiments, the number may be different.

[0111] like Figure 6B As can be seen in FIG, the stop edge SE is repositioned to now be secured to the second vacuum chuck VC2 to facilitate alignment of the next set of grating tiles GT3, 4 on the second chuck VC2. Feeler gauges can be used to ensure correct grating spacing for the remaining chucks, etc. Once aligned and positioned, vacuum is applied to the second chuck VC2 to secure the grating tiles, and the stop edge SE / feeler gauges are removed.

[0112] Figure 6Cis an illustration of a gap reduction step in which a slide assembly SA has been used to move two of the suction cups on which their tiles are laid out closer together to reduce the gap between the two sets of tiles GT1, 2 and GT3, 4. The gap reduction step can be done last, after the entire work surface has been laid out with grating tiles, or it can be done incrementally for each two adjacent vacuum suction cups once the grating tiles have been laid out on their surfaces. The tiles GT1, GT3 on the two adjacent suction cups are positioned so that once the two adjacent suction cups VC1, VC2 are slid into abutment, the correct distance between the opposing edges of the tiles GT1, GT3 across the adjacent suction cups VC1, VC2 is achieved.

[0113] Figure 6D All gaps are now shown reduced after the vacuum cups have been drawn together, as facilitated by the slide arrangement SA. The example eight grating tiles GT1-GT8 are now arranged at suitable intervals and aligned.

[0114] Figure 7A -C shows further details of the arrangement step, where the grating is pre-bent to the desired curvature by operation of a vacuum pump.

[0115] Figure 7A A section of a vacuum table is shown in side view, wherein a vacuum chuck VC has two grating pieces GT1 and GT2 arranged on its surface SS1.

[0116] exist Figure 7B In the embodiment of the present invention, the glue is applied to the grating slices in dots or lines on each grating slice. As mentioned previously, the glue GL is preferably X-ray compatible so that it does not decompose upon X-ray exposure or decomposes only after a predefined lifetime of more than ten years or other predefined duty cycle.

[0117] Figure 7C The sub-step of applying a glass surface CS from the top in this case is shown, said glass surface cooperating with the concave surface of the receiving surfaces SS1, SS2 of the vacuum chucks VC1, 2. The curved glass surface CS is pushed against the vacuum table in order to spread the glue to facilitate fixation. The amount of glue applied is accurately calculated based on the viscosity and size of the grating tiles and the thickness of the sealing member AT (see FIG8 below) in order to achieve an even spreading of the glue on each grating tile. Preferably, each portion of glue applied to the respective grating tile should be spread substantially throughout the entire respective tile surface. The gradient of the curvature is taken into account when choosing the correct viscosity, since the glue tends to flow in a direction from the edge to the center of the grating tile when applied. The correct viscosity is preferred because if the viscosity is configured too low, the glue will be concentrated in the center of the grating tile (see FIG8 below). Figure 7A ). However, if the viscosity is configured too high, the glue GL will not be evenly distributed between the grating and the applied carrier substrate CS.

[0118] Preferably, in an embodiment, the glue is applied in the form of several dots / spots, the positions of which are determined to take into account the curvature of the (lower) surface of the grating tile and the viscosity of the glue.

[0119] In an embodiment, the glue GL is applied in discrete amounts to form a grid of preferably equidistant spots. The dispensing of the glue can be done sequentially or in parallel. Each dollop of glue, once applied, tends to flow and spread. If the glue GL is applied sequentially, the viscosity, dot volume and timing ensure that at the end of the dispensing process, the spots have not yet merged, but still preferably form a discrete pattern, although the spots applied earlier may now have spread more than once applied later. Only when the carrier substrate CS is applied and pushed against the grating tile GT will the spots spread and merge to form a uniform layer of glue covering the tile area (reducing the footprint of the sealing component AT, as discussed in Figure 8 below).

[0120] The thermal expansion coefficient of the glue will be different from that of the carrier CS and the grating block. However, this will not interfere adversely, as it has been observed that the glue forms a "floating" cushion or spacer between the carrier CS and the grating, thus avoiding misalignment that might otherwise be caused by certain temperature gradients.

[0121] In order to prevent the glue GL from accidentally overflowing into the inter-tile gap between two adjacent grating tiles GT1, 2, a sealing member AT is applied in the above-mentioned sealing step. In this step, a sealing material, such as an adhesive tape, is applied before applying the glue in order to seal the inter-tile gap and preferably also the outermost edge of the grating tile assembly, such as Figure 8A As shown in the plan view.

[0122] The adhesive type is preferably made of polyimide, such as Kapton(TM), and in an exemplary embodiment is approximately 50 μm thick and approximately 6-10 mm wide. Other dimensional measurements are also contemplated in other embodiments.

[0123] Side view Figure 8B Shown is an adhesive tape AT system that is applied to prevent glue from leaking onto the working surface of the suction cup. In particular, glue is prevented from leaking into the gaps between the tiles or beyond the outer edges of the assembly.

[0124] It is recommended in this article to leave the tape in place, e.g. Figure 8B As shown, in other words, the tape pattern forms an integral part of the prepared grating assembly GA, and the thickness of the tape defines the gaps to be filled by the glue.

[0125] Return Reference Figure 4 In the manufacturing chain, it will be understood that some or all steps can be completed by a single, two or more than three robotic cells. Figure 4 In the figures, each step has been shown to be performed by a dedicated robotic cell, but this is not necessarily the case, and some robotic cells may perform multiple or just one manufacturing step. The control logic CL may be located on a central computer, but may also be located across a network of more than one computer. The control logic may be located in a dedicated, hard-wired, or programmable microprocessor located at the respective robotic cell. The respective control logic of each robotic cell may communicate via a suitable network infrastructure to synchronize the operating steps.

[0126] In a further exemplary embodiment of the present invention, a computer program or a computer program element is provided, which is characterized by being adapted to perform the method steps of the method according to one of the preceding embodiments on a suitable system.

[0127] Thus, the computer program element may be stored on a computer unit, which may also be part of an embodiment of the present invention. The computer unit may be adapted to perform the steps of the method described above or to induce the performance of the steps of the method described above. Furthermore, it may be adapted to operate components of the apparatus described above. The computer unit may be adapted to automatically operate and / or execute user commands. The computer program may be loaded into a working memory of a data processor. The data processor may thus be equipped to perform the method of the present invention.

[0128] This exemplary embodiment of the invention covers both a computer program that right from the beginning uses the invention and a computer program that by means of an up-date turns an existing program into a program that uses the invention.

[0129] Furthermore, the computer program element can provide all necessary steps for implementing the procedures of an exemplary embodiment of the method as described above.

[0130] According to a further exemplary embodiment of the present invention, a computer-readable medium, such as a CD-ROM, is proposed, wherein the computer-readable medium has a computer program element stored on the computer-readable medium, the computer program element being described in the preceding section.

[0131] The computer program may be stored / distributed on a suitable medium (particularly, but not necessarily, a non-transitory medium), such as an optical storage medium or a solid-state medium provided with or as part of other hardware, but the computer program may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0132] However, the computer program may also be present on a network such as the World Wide Web and be downloadable from such a network into the working memory of a data processor. According to a further exemplary embodiment of the present invention, a medium for making a computer program element available for downloading is provided, wherein the computer program element is arranged to perform a method according to one of the previously described embodiments of the present invention.

[0133] It should be noted that embodiments of the present invention are described with reference to different subject matters. Specifically, some embodiments are described with reference to method-type claims, while other embodiments are described with reference to apparatus-type claims. However, those skilled in the art will appreciate from the above and following descriptions that, unless otherwise indicated, any combination of features relating to different subject matters, in addition to any combination of features belonging to one type of subject matter, is also considered disclosed by this application. However, all features can be combined to provide synergistic effects that exceed the simple sum of the features.

[0134] Although the present invention has been described and illustrated in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary rather than restrictive. The present invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention from a study of the drawings, the description, and the appended claims.

[0135] In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may perform the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A method for manufacturing a grating assembly from grating sheets for use in interferometric X-ray imaging, comprising the following steps: Arranging the grating piece on a curved surface of a manufacturing apparatus so that the grating piece has a curvature, and then applying the grating tile to a curved carrier substrate, or applying the curved carrier substrate to the grating tile, such that the curvature of the tile coincides with the curvature of the carrier substrate, wherein the curved surface of the manufacturing apparatus is a concave surface, and The grating block comprises two opposing surfaces, namely a first surface and a second surface, one of the surfaces, namely the second surface, comprises a set of grooves, wherein the second surface is on the far side of the curved carrier substrate, Wherein, there is a gap between two adjacent grating segments, and the method further comprises reducing the width of the gap.

2. The method according to claim 1, wherein The coefficient of thermal expansion of the carrier substrate corresponds to the coefficient of thermal expansion of the grating substrate.

3. The method according to claim 1 or 2, wherein: The carrier substrate comprises glass.

4. The method according to claim 3, wherein: The glass is at least partially borosilicate glass.

5. The method according to claim 2, wherein: The grating substrate includes graphite or silicon.

6. The method according to claim 1 or 2, wherein: The placing step includes aligning at least one of the grating tiles using a stop edge of the fabrication equipment.

7. The method according to claim 1 or 2, comprising dispensing an X-ray compatible glue on the carrier or on one or more of the grating tiles before the applying step.

8. A grating assembly comprising a glass carrier in which a grating block is deposited, said grating assembly being obtainable by a method according to any one of the preceding claims.

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