High-definition X-ray imaging system based on super lens

Abstract

The utility model relates to a high-definition X-ray imaging system based on a super lens. The high-definition X-ray imaging system comprises a scintillator, an imaging lens group and an imaging module, the scintillator converts incident X-rays into visible light, the visible light is focused through the imaging lens group, and the imaging module performs image acquisition; the imaging lens group comprises a lens group, a super lens and a reflective mirror; the full width at half maximum of the luminescence peak of the scintillator is within the range of + / -10nm of the working wavelength of the super lens; by introducing the super-lens with the characteristics of miniaturization, light weight, integrability and multifunction, higher spatial resolution imaging can be obtained, integration is facilitated, the difficulty in the prior art is solved, and the super-lens has important significance in promoting the practicability of the super-lens.

Description

Technical Field

[0001] The present application relates to the field of radiation imaging, and in particular to a high-definition X-ray imaging system based on a superlens. Background Art

[0002] Flat-panel X-ray imager (FPXI) technology has enormous application value in security inspections, medical imaging, nondestructive testing, and other fields. Currently, the most mature and commercially widely used FPXI is an indirect conversion scintillator, consisting of a scintillator, an a-Si detector, and a thin-film transistor (TFT) array. The scintillator layer converts X-rays into visible light, which is then converted into an electrical signal by a photodiode array composed of an a-Si layer. Finally, a digital image is read out through a TFT. In order to obtain large-area X-ray images, it is necessary to prepare scintillators on a large-area TFT array (Qiushui Chen, et al. All-inorganic perovskite nanocrystal scintillators, Nature, 2018, 561(7721):88-93.), which is expensive to prepare, especially since high-definition images require high pixel resolution. At present, in order to improve the spatial feature resolution, a technical solution is to use a scintillator, a traditional optical lens group, a CMOS or CCD image sensor to combine to perform spatial resolution of the X-ray imaging device. The traditional optical lens group of this technology usually has a complex optical path, many discrete components and is not easy to integrate. And for a 14mm source, the spatial resolution capability of the traditional lens is expected to only reach the order of 50 microns (a large-area high spatial and temporal resolution ultra-hard X-ray imaging system, patent publication number: CN116594051A). The existing technical solution usually requires the integration of a sensor array of the same size behind the scintillator, which undoubtedly increases the manufacturing cost and space size. It also faces problems such as low scintillator conversion rate, low pixel count, or X-ray damage to the sensor.

[0003] Therefore, how to obtain higher spatial feature resolution imaging while facilitating integration, reducing costs, and reducing weight is an urgent problem that needs to be solved. Utility Model Content

[0004] The purpose of this application is to solve the above technical problems and provide a high-definition X-ray imaging system based on a superlens. In response to the shortcomings of traditional optical lenses, this application introduces a superlens with miniaturization, lightweight, integration and multifunctionality. This superlens can use its micro-nano structure to interact with electromagnetic waves to achieve effective control of electromagnetic wave amplitude, polarization and phase characteristics. Combined with an X-ray source and a scintillator with excellent fluorescence half-maximum full width, as well as a compatible high-resolution CMOS or CCD image sensor, it is expected to achieve a spatial feature resolution of 450 nanometers or even smaller. Therefore, by introducing a superlens, this application can achieve higher spatial feature resolution imaging while facilitating integration, thus solving the difficulties of the existing technology.

[0005] Specifically, this application is implemented through the following technical solutions:

[0006] A high-definition X-ray imaging system based on a superlens includes a scintillator, an imaging lens group, and an imaging module; the scintillator converts incident X-rays into visible light, the visible light is focused by the imaging lens group, and the imaging module performs image acquisition; the imaging lens group includes a lens group, a superlens, and a reflector; the full width at half maximum of the luminescence peak of the scintillator is within the range of ±10nm of the operating wavelength of the superlens.

[0007] Specifically, the scintillator is a material that can convert incident X-rays into visible light, which is used to convert X-rays into more efficiently detected light signals, thereby achieving the acquisition of X-ray images. Scintillators are usually made of materials with high atomic numbers. Common scintillator materials include but are not limited to the following compounds and their doped modifications, quantum dots, such as CsI, CaWO4, Gd2O2S:Tb, Gd3Ga3Al2O 12 、Lu3Al5O 12 、Gd3Al2Ga3O 12 :Ce + , CsPbBr3 quantum dots, etc. These materials are highly sensitive to X-rays and can produce high light output efficiency. Optionally, any material and structure that can convert X-rays into visible light can be used in this application.

[0008] Furthermore, the visible light first passes through the lens group, is reflected by the reflector and enters the super lens, and after passing through the super lens, is imaged on the imaging module and image collection is performed.

[0009] Furthermore, the visible light is first reflected by the reflector and enters the lens group, and then forms an image on the imaging module after passing through the super lens.

[0010] Furthermore, the lens group includes two groups, the visible light first enters the first lens group, passes through the super lens and then enters the second lens group, and is then reflected by the reflector and enters the imaging module to form an image.

[0011] Furthermore, the lens group includes two groups, the visible light is first reflected by the reflector into the first lens group, passes through the super lens, enters the second lens group, and is then imaged by the imaging module.

[0012] Furthermore, the positions of the super lens and the second lens group are exchanged.

[0013] Furthermore, the reflector reflects visible light and simultaneously moves X-rays that do not deposit energy on the scintillator out of the optical path.

[0014] Specifically, the reflector reflects visible light, changes its propagation direction, and moves residual X-rays out of the optical path to prevent the X-rays from damaging subsequent components.

[0015] Furthermore, the lens group collects, focuses and forms an image of the visible light, and after processing, it can present an inverted reduced real image, an inverted magnified real image, and an upright magnified real image; and transmits these images to the next component.

[0016] Optionally, a lens group can be composed of several doublet and triplet lenses. This type of lens can effectively eliminate imaging defects such as chromatic aberration, spherical aberration, and aberration.

[0017] Furthermore, the metalens is a metasurface lens containing sub-wavelength micro-nano structures.

[0018] Specifically, through photolithography and etching processes, a subwavelength structure is formed on the surface, thereby changing the amplitude, phase, and polarization direction of the outgoing light wavefront to meet the target wavefront phase profile that can be focused. The target phase value at any point on the metalens surface can be determined by the following formula:

[0019]

[0020] Where φ(x,y) is the phase value at any point on the metalens surface, λ is the wavelength of the incident light, and f is the focal length of the metalens. This light modulation is achieved by adjusting the morphology, size, and arrangement of the surface nanostructures, including but not limited to the shape, size, and density of the nanopillars.

[0021] Optionally, any metalens that can achieve focusing function, has good focusing efficiency, and meets the designed working wavelength of this optical system can be used in this application.

[0022] Preferably, the basic structure of the metalens includes a light-transmitting substrate and a sub-wavelength micro-nanostructure arrayed on the light-transmitting substrate; preferably, a silicon dioxide substrate is selected as the light-transmitting substrate, and a high-refractive-index material such as titanium dioxide, aluminum oxide, or diamond is selected as the sub-wavelength micro-nanostructure. Preferably, the numerical aperture NA of the metalens satisfies the condition 1>NA≥0.6, under which condition the imaging quality can be guaranteed. Preferably, the metalens also satisfies the Nyquist sampling theorem, which can make the focusing effect more excellent. The Nyquist sampling theorem is specifically:

[0023]

[0024] Among them, U is the length of the subwavelength micro-nanostructure unit, λ is the wavelength of the incident light, NA is the numerical aperture, r and f are the radius and focal length of the metalens, respectively.

[0025] Furthermore, the imaging module converts optical signals into electrical signals.

[0026] Optionally, as long as it has excellent ability to convert optical signals into electrical signals, high resolution and other characteristics, it can be used in this application, including but not limited to traditional grayscale CMOS, CCD, SPAD, and other photoelectric sensor arrays.

[0027] Beneficial effects:

[0028] 1. Thanks to the small size advantage of the metalens, the same or even higher imaging quality can be achieved with a smaller imaging lens group, or the imaging surface can be reduced without increasing the size of the lens group, and a smaller, higher-resolution imaging module can be used to achieve the same or even higher imaging quality.

[0029] 2. Compared with the existing technology, this application focuses light to make the imaging surface brighter, making it more convenient for sensors to detect, while also avoiding the problem of X-ray damage to subsequent devices.

[0030] 3. Furthermore, the high-resolution, compact imaging module allows for resolvable line diameters close to the diffraction limit, potentially reaching subwavelength levels. This metalens, combined with a monochromatic scintillator with excellent fluorescence full-width at half-maximum (FWHM), can meet these requirements with a simpler structure, reducing the difficulty and cost of metalens manufacturing.

[0031] 4. For the metalens and scintillator, the half-width of the luminescence peak of the scintillator is within the range of ±10nm of the working wavelength of the metalens, and when the metalens satisfies the Nyquist sampling theorem, the focusing effect is excellent. However, at non-design wavelengths, the focusing effect is slightly poor, which manifests as focal length offset and energy dispersion, that is, there is obvious chromatic aberration. Generally speaking, the scintillator used in high-resolution indirect detection scenarios has quasi-monochromatic light with a narrow half-width, so the metalens does not need to consider the influence of chromatic aberration, but only requires that the half-width of the luminescence peak of the scintillator be within the range of ±10nm of the working wavelength of the metalens, which greatly simplifies the design difficulty of the metalens. Compared with the achromatic metalens, thanks to its simple and larger unit structure, the difficulty of photolithography and etching is greatly reduced, effectively reducing the manufacturing cost of the metalens. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the structure of Example 1 of the present application;

[0033] Figure 2 This is a schematic diagram of the structure of Example 2 of the present application;

[0034] Figure 3 This is a schematic diagram of the structure of Example 3 of the present application;

[0035] Figure 4 This is a schematic structural diagram of Example 4 of the present application;

[0036] Figure 5 This is a diagram of the cylindrical nanostructured superlens structure and its simulation results in this application;

[0037] Figure 6 This is a simulation result diagram of the Airy disk formed by incident light of different wavelengths under the same metalens in this application;

[0038] Figure 7 This is a simulation result of the focusing effect of scintillators with different luminous wavelengths under the same superlens in this application;

[0039] Figure 8 The cylindrical nanostructured metalens surface and its simulation results for different design wavelengths in this application;

[0040] Figure 9 Surfaces of cylindrical nanostructured metalenses with different unit lengths and their simulation results for this application;

[0041] Reference numerals:

[0042] 1 X-ray emitter; 2 X-ray; 3 Visible light; 4 Scintillator; 5 Lens group; 5-1 First lens group; 5-2 Second lens group; 6 Reflector; 7 Super lens; 8 Imaging module. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] Example 1

[0045] like Figure 1 As shown, the high-definition X-ray imaging system based on the superlens provided in Example 1 includes a scintillator 4, a lens group, and an imaging module 8. The scintillator 4 converts X-rays 2 emitted by the X-ray emitter 1 into visible light 3, which is imaged by the lens group, and the imaging module 8 performs imaging acquisition. The lens group includes a lens group 5, a superlens 7, and a reflector 6. In Example 1, the visible light 3 first passes through the lens group 5, is reflected by the reflector 6, enters the superlens 7, and is imaged on the imaging module 8 after passing through the superlens 7. The full width at half maximum of the luminescence peak of the scintillator 4 is within the range of ±10nm of the operating wavelength of the superlens 7.

[0046] Example 2

[0047] like Figure 2 As shown, the high-definition X-ray imaging system based on the superlens provided in Example 2 is different from that in Example 1 in that the visible light 3 in Example 2 is first reflected by the reflector 6 into the lens group 5, and then passes through the superlens 7 to form an image on the imaging module 8.

[0048] Example 3

[0049] like Figure 3 As shown, the high-definition X-ray imaging system based on the metalens provided in Example 3 is different from that in Example 1 in that the lens group in Example 3 includes a first lens group 5-1 and a second lens group 5-2, the metalens 7 and the second lens group 5-2 form an imaging lens group, and the visible light 3 first enters the first lens group 5-1, passes through the metalens, enters the second lens group 5-2, and is then reflected by the reflector 6 into the imaging module 8 for imaging.

[0050] Example 4

[0051] like Figure 4 As shown, the high-definition X-ray imaging system based on the superlens provided in Example 4 is different from that in Example 3 in that the visible light 3 in Example 4 is first reflected by the reflector 6 and enters the first lens group 5-1, passes through the superlens 7 and enters the second lens group 5-2, and is then imaged by the imaging module 8.

[0052] Furthermore, the positions of the super lens 7 and the second lens group 5 - 2 in Examples 3 and 4 can be interchanged to meet different requirements (not shown in the figures).

[0053] In the above-mentioned embodiments 1 and 2, from the perspective of optical imaging, since the focal length of the metalens is usually small, the imaging surface of the preceding optical system is usually outside the double focal length. Therefore, an inverted and reduced real image is presented between the double focal length and the double focal length behind the metalens. This means that after further focusing by the metalens, the light can be further focused and the Airy disk can be reduced in a very limited space. At the same time, thanks to the short focal length, the metalens can be placed close to the imaging module, and even the two can be integrated together. This application benefits from the further focusing of the metalens, and the required sensor size is greatly reduced, the imaging area is reduced, and the production efficiency of the imaging module is improved. The introduction of the metalens can not only reduce the area of ​​the required imaging module, but also shorten the length of the lens space and reduce costs.

[0054] In Examples 3 and 4 above, when the metalens cannot be integrated into the imaging module surface, it can be combined with a traditional lens assembly and directly imaged using a commercially available high-definition imaging module. This has the advantage of optimizing the lens assembly structure, shortening the lens length, achieving higher magnification and smaller resolvable line diameters, and eliminating the need for developers to independently design their own imaging modules; instead, they can use commercially available high-definition imaging modules, reducing R&D costs. Furthermore, the metalens can be designed to be detachable, making it easier to use with different imaging modules. With technological advancements, it can even be used for imaging in everyday devices.

[0055] Furthermore, this application benefits from the scintillator, requiring only that the full width at half maximum of the scintillator's luminescence peak be within ±10 nm of the metalens' operating wavelength, eliminating the need to address the wide-wavelength imaging chromatic aberration issues of conventional metalens. Furthermore, excellent focusing can be achieved without requiring a particularly small unit structure, reducing production complexity, improving efficiency, and lowering costs.

[0056] Simulation test:

[0057] The basic structure of the metalens used in the simulation experiments all consisted of a silicon dioxide substrate as the light-transmitting base and titanium dioxide as the subwavelength micro-nanostructure. The titanium dioxide array was placed on the silicon dioxide substrate. The focal length of each metalens was 11 μm, and the numerical aperture (NA) was 0.63 (satisfying the condition 1 > NA ≥ 0.6) unless otherwise specified.

[0058] like Figure 5 As shown, a cylindrical simple nanostructured superlens with an operating wavelength of 520 nm is Figure 5 (a) is a top view of the 3D structure of a cylindrical nanostructured superlens. Figure 5(b) is the xz plane light field distribution diagram of the metalens under different wavelengths of incident light. Figure 5 (c) is the z-axis field intensity distribution curve corresponding to different incident light wavelengths. Figure 5 It can be seen that at an incident wavelength of 520nm, the focusing effect is excellent, while at non-operating wavelengths (405nm and 660nm), the focusing effect is slightly poor, manifested as focal length shift and energy dispersion, that is, obvious chromatic aberration. The same effect is also observed in other types of simple nanostructured metalenses, such as square nanopillars, composite nanopillars, and PB phase nanopillars.

[0059] Depend on Figure 5 As can be seen, the scintillator used in indirect detection scenarios emits monochromatic light or quasi-monochromatic light with a narrow full-width at half-maximum (FWHM). Therefore, the metalens does not need to consider the influence of chromatic aberration. Instead, it only needs the full-width at half-maximum of the scintillator's emission peak to be within ±10nm of the metalens' operating wavelength, which greatly simplifies the design of the metalens. Compared with achromatic metalens, the simpler larger unit structure greatly reduces the manufacturing cost of micro-nano metalens.

[0060] like Figure 6 As shown, Figure 6 (a) is the light intensity distribution in the xy plane of the focused Airy disk formed by the metalens when the design conditions are met, that is, when the operating wavelength of the metalens is equal to the wavelength of the incident light, 520 nm. Figure 6 (b) The x-axis intensity curve of the Airy disk formed by the incident light with a wavelength of 500 to 540 nm and irradiated by the super lens with an operating wavelength of 520 nm. Figure 6 It can be seen that: 1) When the operating wavelength of the metalens is equal to the wavelength of the incident light, the FWHM of the Airy disk can be reduced to 440.3nm, which means that the spatial feature resolution is expected to reach the order of 440.3nm; 2) When the wavelength of the incident light is offset by ±10nm compared to the operating wavelength of the metalens, the FWHM of the Airy disk differs by only 3%.

[0061] like Figure 7 As shown, Figure 7 (a) is the light intensity distribution in the xz plane of the Airy disk formed by the incident light with a wavelength of 500-540 nm and irradiated by the superlens with an operating wavelength of 520 nm. Figure 7 (b) is the z-axis intensity curve corresponding to x=0 when the incident light has a wavelength of 490 to 550 nm and is irradiated on the metalens. Figure 7 (c) is the focusing efficiency and focal length of the simulation experiment in (b). Figure 7It can be seen that: 1) When the wavelength of the incident light is offset by ±10nm (510nm to 530nm) compared to the working wavelength of the metalens, that is, the full width at half maximum of the luminous peak of the scintillator is within the range of ±10nm of the working wavelength of the metalens, the focal length offset is less than 1%, and the focusing efficiency decreases within 10%; 2) When the incident light exceeds this range, the smaller the incident wavelength, the faster the focusing efficiency of the metalens decreases, the faster the focal length increases, and the second focus appears, which seriously affects the focusing effect; conversely, the larger the incident wavelength, the slower the focusing efficiency of the metalens increases, but the focal length decreases rapidly. In summary, the increased offset of the focusing focal length will affect the spatial feature resolution of the system.

[0062] Figure 6 and Figure 7 It is shown that when the full width at half maximum of the luminescence peak of the scintillator is within the range of ±10 nm of the operating wavelength of the superlens, the scintillator luminescence peak is narrow (FWHM≤20 nm), and the superlens imaging effect and spatial feature resolution are optimal.

[0063] like Figure 8 As shown, Figure 8 (a) Surface image of cylindrical nanostructured superlens with an operating wavelength of 405 nm. Figure 8 (b) Surface image of cylindrical nanostructured superlens with an operating wavelength of 520 nm. Figure 8 (c) Surface image of cylindrical nanostructured superlens with an operating wavelength of 635 nm. Figure 8 (d) is the xz plane light field distribution diagram corresponding to the focusing of the (a)-(c) super lens under equal intensity incident light, Figure 8 (e) is the z-axis field intensity distribution curve corresponding to the focusing of the (a)-(c) super lens under equal intensity incident light. Figure 8 It can be seen that the size of the sub-wavelength micro-nano structure unit of the designed metalens will change with different incident working wavelengths. 2 / m 2 ), smaller incident wavelengths (short-wavelength superlenses) require smaller unit lengths and smaller structural dimensions; as the wavelength increases (long-wavelength superlenses), the required minimum structural dimensions gradually increase. Currently, scintillators with narrow FWHM and peak wavelengths greater than or equal to 520nm are available. Introducing a matching micro-nanostructure superlens can build a high-definition X-ray imaging system without considering the effects of chromatic aberration caused by covering a wide operating wavelength range. This simplifies the design difficulty of the superlens and, thanks to its simple and large unit structure, significantly reduces the cost of micro-nano manufacturing.

[0064] like Figure 9 As shown, Figure 9(a) is a surface image of a superlens with a design wavelength of 405 nm, a sub-wavelength micro-nanostructure unit length of 0.31 μm, and a minimum nanocolumn diameter of 0.04 μm. Figure 9 (b) is the surface image of the superlens with a design wavelength of 405 nm, a sub-wavelength micro-nanostructure unit length of 0.31 μm, and a minimum nanocolumn diameter of 0.06 μm. Figure 9 (c) is the surface image of the superlens with a design wavelength of 405nm, a sub-wavelength micro-nanostructure unit length of 0.45μm, and a minimum nanocolumn diameter of 0.08μm. Figure 9 (d) is the xz plane light field distribution diagram corresponding to the above three super lenses focusing at an incident light wavelength of 405nm. Figure 9 (e) is the corresponding z-axis field intensity distribution curve for an incident light wavelength of 405 nm. When the design wavelength is 405 nm, the superlens with a sub-wavelength micro-nanostructure unit length of 0.31 μm satisfies the Nyquist sampling theorem. Figure 9 (a) shows that the smaller nanopillar structure is conducive to light transmission, thereby focusing a stronger light spot, which is beneficial for imaging. Figure 9 (b) shows that when the unit length is not changed and the diameter of the nanocolumns is slightly increased, the focusing effect is slightly worse, but the overall focusing function is still available and meets the usage conditions. Figure 9 Figure (c) shows that a metalens with a subwavelength micro-nanostructure unit length of 0.45μm does not satisfy the Nyquist sampling theorem. Its focused light field is relatively dispersed, and the light field intensity at the focal position is much lower than that of a metalens with a subwavelength micro-nanostructure unit length of 0.31μm that satisfies the Nyquist sampling theorem. Therefore, using a metalens that does not satisfy the Nyquist sampling theorem will result in poor focusing effect and basically cannot meet the focusing performance requirements.

[0065] The Nyquist sampling theorem is specifically: U<λ / 2NA, Among them, U is the length of the subwavelength micro-nanostructure unit, λ is the wavelength of the incident light, NA is the numerical aperture, r and f are the radius and focal length of the metalens, respectively.

[0066] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-definition X-ray imaging system based on a superlens, characterized in that: The invention comprises a scintillator, an imaging lens group and an imaging module; the scintillator converts incident X-rays into visible light, the visible light is focused by the imaging lens group, and the imaging module collects images; the imaging lens group comprises a lens group, a super lens and a reflector; the full width at half maximum of the luminescence peak of the scintillator is within the range of ±10nm of the working wavelength of the super lens.

2. The high-definition X-ray imaging system based on a superlens according to claim 1, characterized in that The visible light first passes through the lens group, is reflected by the reflector and enters the super lens, and after passing through the super lens, is imaged on the imaging module and image collection is performed.

3. The high-definition X-ray imaging system based on a superlens according to claim 1, characterized in that The visible light is first reflected by the reflector and enters the lens group, and then forms an image on the imaging module after passing through the super lens.

4. The high-definition X-ray imaging system based on a superlens according to claim 1, characterized in that The lens group includes two groups. The visible light first enters the first lens group, passes through the super lens, enters the second lens group, and is then reflected by the reflector into the imaging module to form an image.

5. The high-definition X-ray imaging system based on a superlens according to claim 1, characterized in that The lens group includes two groups. The visible light is first reflected by the reflector and enters the first lens group, then passes through the super lens and enters the second lens group, and is then imaged by the imaging module.

6. The high-definition X-ray imaging system based on a superlens according to claim 4 or 5, characterized in that: The positions of the super lens and the second lens group are exchanged.

7. The high-definition X-ray imaging system based on a superlens according to claim 1, characterized in that: The mirror reflects visible light while moving X-rays that do not deposit energy on the scintillator out of the light path.

8. The high-definition X-ray imaging system based on a superlens according to claim 1, characterized in that: The lens group collects, focuses and forms an image of visible light, and after processing, it can present an inverted reduced real image, an inverted magnified real image, and an upright magnified real image; and transmits these images to the next component.

9. The high-definition X-ray imaging system based on a superlens according to claim 1, characterized in that: The superlens is a lens composed of a supersurface containing sub-wavelength micro-nano structures.

10. The high-definition X-ray imaging system based on a superlens according to claim 1, characterized in that: The imaging module converts optical signals into electrical signals.

Images