EP4551930A1 - Imageur plénoptique pour rayons x à cristaux de diffraction - Google Patents
Imageur plénoptique pour rayons x à cristaux de diffractionInfo
- Publication number
- EP4551930A1 EP4551930A1 EP23744366.8A EP23744366A EP4551930A1 EP 4551930 A1 EP4551930 A1 EP 4551930A1 EP 23744366 A EP23744366 A EP 23744366A EP 4551930 A1 EP4551930 A1 EP 4551930A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- crystal
- source
- curved crystal
- curved
- curvature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
- G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/56—Cameras or camera modules comprising electronic image sensors; Control thereof provided with illuminating means
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/95—Computational photography systems, e.g. light-field imaging systems
- H04N23/957—Light-field or plenoptic cameras or camera modules
Definitions
- the present invention relates to a plenoptic imaging system for acquiring an image of an object. It finds a particularly interesting application in the field of biological imaging ranging from cells to small animals, but also in materials science.
- the invention aims to improve so-called plenoptic or “lightfield” cameras.
- plenoptic imaging consists of refocusing an image digitally from a single physical acquisition. This refocusing makes it possible to reconstruct a scene in three dimensions and if the object is transparent (which is the case when using X-rays) we can reconstruct the volume in three dimensions.
- the plenoptic camera is composed of a lens or a set of lenses, for example a microscope objective, followed by a matrix of lenses then a pixelated detector.
- This set creates numerous sub-images of the same scene or an object which, after digital processing, allows digital refocusing to the desired distance.
- the present invention aims to design a plenoptic camera for use with X-rays. This makes it possible to visualize certain objects transparently and thus carry out 3D reconstructions.
- the first problem concerns the lateral and longitudinal resolutions which vary in 1/NA and 1/NA2 respectively, with NA the numerical aperture of the optical system.
- Optics for hard X-rays therefore for energies of photons greater than a few keV (which is equivalent to wavelengths less than 1 nm) currently have numerical apertures of 10' 4 typically.
- the lateral resolution is equivalent to approximately 10,000 times the wavelength (i.e. 100 nm at 1 keV), which is very poor compared to visible optics which easily reach an NA of 1 and even slightly greater than 1 with submerged microscopes.
- the most efficient commercial visible microscopes have spatial resolutions well below 100 nm. As it stands, there is no point in switching to the X, which are technically much more complex to manage than the visible.
- the first problem is linked to the aspect ratio between the lateral and longitudinal resolutions which varies in 1/NA and then produces voxels having an anamorphosis of 10,000. This anamorphosis prevents reconstruction in three dimensions. In such a case, performing plenoptics under X-rays is no longer of interest.
- the second problem prevents the use of the X-ray plenoptic with table sources which emit polychromatic radiation and therefore produce blurred images.
- the present invention aims to provide a new plenoptic imaging system under X-rays allowing the production of high-quality three-dimensional reconstructions.
- Another aim of the invention is a new high-resolution plenoptic camera.
- At least one of the objectives is achieved with a plenoptic imaging system for acquiring an image of an object, this system comprising:
- the main optical device comprises at least one curved crystal.
- photodetector network we mean for example any detector capable of capturing in a spatially distinct manner the X-ray beams coming from the matrix of lenses or holes. Such a detector is for example a CCD sensor.
- the present invention makes it possible to produce an X-ray camera capable of producing 3D views using the plenoptic technique.
- the optical system for X-rays according to the invention proposes a main optical device equipped with a numerical aperture greater than the systems of the prior art. Compared to X-ray systems using Fresnel lenses for example, the system according to the invention makes it possible to achieve a numerical aperture of around 0.3, which improves the lateral resolution by a factor of 3000 and a factor of 9 million the longitudinal resolution. Furthermore, the anamorphosis of the voxels is only a factor of 3, which is easily compensable numerically. These characteristics allow the production of true 3D reconstructions from a single acquisition.
- the ratio between the longitudinal resolution and the lateral resolution varies in 1/NA, with NA the numerical aperture.
- the X-ray source and the curved crystal are determined so that the ratio 1/NA is less than 10, therefore NA greater than 0.1
- a useful surface surface of the curved crystal capable of reflecting the incident X-ray beam of the curved crystal large enough to ensure a high NA greater than 0.1.
- the X-ray beam reflected by the curved crystal forms an image of the object beyond the image focal plane of the curved crystal; the matrix of lenses or holes being placed beyond this image focal plane.
- the source, the curved crystal and the orientation of the curved crystal can be determined so that the X-ray beam is reflected according to the diffraction law known as the law. from Bragg:
- the source can be positioned on a first virtual circle, known as the Rowland circle, with a radius R equal to half the radius of a second virtual circle in which a crystal plane of the curved crystal.
- the two virtual circles are concentric, the Rowland circle being adjacent to the central point of the curvature produced on the curved crystal.
- the surface of the curved crystal can be polished according to a curvature identical to the curvature of a crystal plane of the curved crystal according to a geometry called Johann geometry.
- the polishing carried out on the useful surface of the curved crystal makes it possible to obtain a surface said to be parallel to the crystallographic planes of the curved crystal. This achievement makes it possible to improve the numerical aperture, but on only part of the surface presented by the curved crystal.
- the surface of the curved crystal can be polished according to a curvature identical to the curvature of the Rowland circle according to a geometry called Johansson geometry.
- the polishing carried out on the useful surface of the curved crystal makes it possible to obtain a surface which crosses crystallographic planes of the curved crystal. Such an achievement ensures a good numerical aperture over almost the entire polished surface presented by the curved crystal.
- the source is ideally positioned on the Rowland circle but we can consider positioning it inside or outside the circle.
- the matrix of lenses or holes can be a one-dimensional matrix and each photodetector is a one-dimensional photodetector.
- the matrix of lenses or holes can be a two-dimensional matrix and each photodetector is a two-dimensional photodetector.
- the curved crystal can be of the toric type.
- the toroidal crystal has two advantages: a large effective diffraction surface, leading to a high numerical aperture and good collection of the beam flux, beneficial for the quality of the image.
- the curved crystal can be of cylindrical or spherical type.
- the curved crystal can be a single crystal with a single radius of curvature.
- the curved crystal can be a single crystal with double perpendicular radii of curvature.
- the main optical device can comprise two crystals, each having a single radius of curvature, the two radii of curvature being perpendicular.
- the source can be a monochromatic source.
- Any type of X-ray monochromator can be used, such as for example a crystal or diffraction grating monochromator.
- the reflectivity of the curved crystal can be very high, several tens of percent compared to a polychromatic source.
- the monochromatic source can be a source point obtained from a polychromatic source illuminating a second curved crystal whose image focal plane constitutes said source point.
- Such an arrangement makes it possible to use a second curved crystal to make the incident X-ray radiation monochrome.
- This second curved crystal may have identical or possibly different parameters from the first curved crystal.
- This second curved crystal is placed between the source and the object. This solution ensures that the X-rays passing through the object are reflected with very good efficiency by the curved crystal, strongly limiting the absorbed dose.
- a new plenoptic camera comprising the system as described above and a processing unit for the digital reconstruction of images at different depths of field.
- FIG. 1 is a schematic view of the system according to the invention.
- FIG. 2 Figure 2 is a schematic top view of the system according to the invention illustrating the path of the X-radiation according to Johann geometry
- Figure 3 Figure 3 is a schematic view illustrating Johann's geometry
- Figure 4 is a schematic top view of the system according to the invention illustrating the path of the X radiation according to Johansson geometry
- Figure 5 is a schematic view illustrating Johansson geometry
- Figure 6 is a schematic view of a monochromator based on a curved crystal in the system according to the invention.
- Figure 1 we can see a source 1 capable of emitting a beam of rats X towards an object 2 to be imaged.
- the X-ray beam is then reflected by a curved crystal 3 suitably designed and positioned in alignment with the source 1 and the object 2.
- the reflected X-ray beam then reaches a lens matrix then a detector 5. It This is a plenoptic system in which the main lens has advantageously been replaced by a curved crystal having a high numerical aperture.
- an intermediate image 6 is simply illustrated for information purposes. It represents the image of the object, this image being contained in the reflected X-ray beam.
- a single acquisition thus makes it possible to obtain several spatially separated flows at the detector.
- Digital processing then makes it possible to carry out three-dimensional reconstructions in a conventional manner.
- the X-ray source is a source at, for example, 11 keV.
- the invention can be applied to any type of X-rays.
- we speak of X-rays as soon as the optical index of the material is less than 1. Typically, this corresponds to around 20-30 eV.
- the curved crystal 3 has a surface 3 A which has been polished and positioned to serve as a useful surface, that is to say the surface which receives and reflects the X-ray beam.
- the curved crystal geometry can be divided into two main aspects: the curvature of the internal planes of the crystal lattice and the curvature of the 3 A effective surface. Both can affect the imaging quality of the crystal, such as aberration, image fluence and numerical aperture . Adjusting the curvature of the planes of the internal crystal lattice optimizes the focusing performance of the crystal. Polishing in a toric curve has been found to achieve excellent results.
- a crystal reflects X-rays by diffraction on crystal planes which behave like a network.
- the diffraction law is the so-called Bragg law:
- each wavelength corresponds to a diffraction angle. Outside of this angle the crystal does not reflect X-rays of this wavelength.
- the crystals are not perfect: the reticular planes are not all spaced at the same distance, creating an angular widening for which a crystal will reflect monochromatic radiation.
- This angular band is commonly called the oscillation curve or “rocking curve” in English, and obviously depends on each crystal.
- the “rocking curve” has a width at half height of 0.00383° or 6.5xl0' 5 rad. This is a very low numerical aperture.
- the curved crystal behaves like a curved mirror for X-rays.
- the curved crystals according to the invention are advantageously concave curved.
- a curved crystal has a “focus circle” in the horizontal plane tangent to its central point.
- the radius of this circle is equal to half the radius of curvature of the crystal (radius of curvature of the crystal planes).
- This circle is called Rowland's circle and was defined for a concave lattice in visible light. If a point source is on the Rowland circle of a concave curved crystal, it will be focused at another point on that circle.
- the Rowland circle 7 is tangent to the center of the curved crystal 3.
- the source 1 is positioned on this circle.
- the object to be imaged is located between the source and the curved crystal, inside the Rowland circle 7.
- the intermediate image 6 is located outside the Rowland circle in the optical axis of the reflected X-ray beam.
- Figure 2 is a very schematic geometric representation in top view of the system according to the invention.
- Source A illuminating an object C to be imaged.
- Source A can be real or a source point created by a real, remote source and whose image is relayed to this point.
- the beam of X-rays coming from A and passing through C reaches an area of the curved crystal B.
- the reflected beam is directed towards a matrix of lenses E before reaching the detector F.
- the angle between the straight lines B1-B0-B2 and A-Bo satisfies the Bragg condition, Bo being the central bridge of the curved surface of the curved crystal.
- the curved crystal B has a polished surface in accordance with the so-called Johann geometry, that is to say the polishing is parallel to a crystal plane inside the curved crystal.
- a Rowland G circle is represented. This circle has a radius equal to the half the radius of curvature of the polished surface of the curved crystal. With such a circle, the source point A placed on the circle has its focal point A' also placed on the same Rowland circle.
- Figure 3 illustrates the principle of Johann geometry. The rays from the crystal surface and the crystal plane P are the same, so only rays reaching an area near the center of the crystal satisfy the Bragg condition.
- Figure 4 is also a very schematic geometric representation in top view of the system according to the invention. The principle and elements are identical to those in Figure 2 except the curved crystal is different.
- the X-ray beam coming from A and passing through C reaches the entire surface of the curved crystal B.
- the reflected beam is directed towards the lens matrix E before reaching the detector F.
- the curved crystal B has a polished surface in accordance with the so-called Johansson geometry, that is to say the polishing presents a curve identical to the curvature of the Rowland G circle.
- Figure 5 illustrates the principle of Johansson geometry.
- the radius of the inner surface of the crystal is equal to half the radius of its crystal plane P. Due to the theorem of the inscribed angle of a circle, such geometry allows the rays of the source to arrive over the entire surface of the crystal at the Bragg angle.
- the source can advantageously be positioned on the Rowland circle.
- Figure 6 shows the geometry of a two-crystal plenoptic camera making it possible to very significantly reduce the dose received by the sample/animal/person.
- Figure 2 shows the elements of Figure 2 with a crystal B polished according to Johann geometry. But one or both crystals can be polished according to Johann or Johansson geometry.
- the source A is a source point formed from a real, remote source A’.
- This real source A' is polychromatic and illuminates a second curved crystal B' so that the beam reflected by this second crystal is monochromatic.
- the focusing point of the beam reflected by the second crystal B’ is the source point A.
- plenoptic X-ray imaging potentially affects all the fields normally covered by X-ray tomography, ranging from medical to biology, materials science, metallurgy, mechanics, plasma physics, agri-food, cultural heritage etc.
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- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Multimedia (AREA)
- Analytical Chemistry (AREA)
- Physics & Mathematics (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Computing Systems (AREA)
- Theoretical Computer Science (AREA)
- Analysing Materials By The Use Of Radiation (AREA)
Abstract
Description
Claims
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR2206921A FR3137767B1 (fr) | 2022-07-06 | 2022-07-06 | Imageur plénoptique pour rayons X à cristaux de diffraction |
| PCT/EP2023/068609 WO2024008824A1 (fr) | 2022-07-06 | 2023-07-05 | Imageur plénoptique pour rayons x à cristaux de diffraction |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP4551930A1 true EP4551930A1 (fr) | 2025-05-14 |
Family
ID=84362432
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP23744366.8A Withdrawn EP4551930A1 (fr) | 2022-07-06 | 2023-07-05 | Imageur plénoptique pour rayons x à cristaux de diffraction |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP4551930A1 (fr) |
| FR (1) | FR3137767B1 (fr) |
| WO (1) | WO2024008824A1 (fr) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2623964A1 (fr) * | 2012-02-06 | 2013-08-07 | Jürgen Kupper | Appareil de radiographie et procédé radiographique pour l'examen d'un objet de recherche en trois dimensions |
| FR3076655B1 (fr) * | 2018-01-09 | 2020-01-17 | Alpyx | Dispositif optique pour rayons x |
-
2022
- 2022-07-06 FR FR2206921A patent/FR3137767B1/fr active Active
-
2023
- 2023-07-05 EP EP23744366.8A patent/EP4551930A1/fr not_active Withdrawn
- 2023-07-05 WO PCT/EP2023/068609 patent/WO2024008824A1/fr not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| WO2024008824A1 (fr) | 2024-01-11 |
| FR3137767A1 (fr) | 2024-01-12 |
| FR3137767B1 (fr) | 2024-12-13 |
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