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

Abstract

The invention 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 great application value in security inspection, medical imaging, non-destructive testing and other fields. At present, the most mature and commercially widely used is the indirect conversion FPXI composed of scintillator, a-Si detector and thin film transistor array (TFT) structure. The scintillator layer converts X-rays into visible light, which is then converted into electrical signals by the photodiode array composed of a-Si layer, and finally read out by TFT to obtain digital images. In order to obtain large-area X-ray images, it is necessary to prepare scintillators on large-area TFT arrays (Qiushui Chen, et al. All-inorganic perovskite nanocrystal scintillators, Nature, 2018, 561 (7721): 88-93.), which has a high preparation cost, especially high-definition images require high pixel resolution. At present, in order to improve the spatial feature resolution, there is a technical solution that uses a scintillator, a traditional optical lens group, and a CMOS or CCD image sensor to perform spatial resolution in an X-ray imaging device. The traditional optical lens group of this technology usually has a complex optical path, many discrete devices, and is not easy to integrate. And for a source of 14mm in size, it is estimated that the spatial resolution capability of only 50 microns can be achieved using traditional lenses (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, and also faces problems such as low scintillator conversion rate, low pixels, 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 to be solved. Summary of the invention

[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 view of the shortcomings of traditional optical lenses, this application introduces a superlens with miniaturization, light weight, integration and multifunctionality. This superlens can use its micro-nano structure to interact with electromagnetic waves to achieve effective regulation 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 prior art.

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

[0006] A high-definition X-ray imaging system based on a superlens 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 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 working 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 effectively detected light signals, thereby achieving the acquisition of X-ray images. Scintillators are usually selected from 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 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 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 moves X-rays that do not deposit energy on the scintillator out of the light 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 plurality of doublet and triplet lenses may be used to form a lens group. This type of lens can effectively eliminate imaging defects such as chromatic aberration, spherical aberration, and aberration.

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

[0018] Specifically, through photolithography and etching processes, a sub-wavelength 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. The above modulation of light 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 nanocolumns.

[0021] Optionally, any metalens that can achieve focusing function, has good focusing efficiency, and meets the designed working wavelength of the 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-nano structure 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, diamond, etc. is used as the sub-wavelength micro-nano structure. Preferably, the numerical aperture NA of the metalens satisfies the condition of 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-nano structure 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 superlens, 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 prior art, the present 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. At the same time, the high-resolution, small-size imaging module allows the resolvable line diameter to be close to the diffraction limit, and is expected to reach the sub-wavelength level. This superlens combined with a monochromatic scintillator with excellent fluorescence half-maximum full width can meet the requirements with a simpler structure, reducing the difficulty and cost of superlens manufacturing.

[0031] 4. For the metalens and scintillator, the half-width of the luminous 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, while at non-design wavelengths, the focusing effect is slightly poor, which is manifested 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 the half-width of the luminous peak of the scintillator to 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 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 diagram of the structure of Example 4 of the present application;

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

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

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

[0039] Figure 8 The cylindrical nanostructured superlens surface and simulation results of different design wavelengths for this application;

[0040] Fig. 9 The cylindrical nanostructured superlens surface with different unit lengths of this application and its simulation results;

[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 described embodiments 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 creative work 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 the X-ray 2 emitted by the X-ray emitter 1 into visible light 3, the visible light 3 is imaged through 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 and 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 working 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 superlens 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 superlens 7 and the second lens group 5-2 form an imaging lens group, the visible light 3 first enters the first lens group 5-1, passes through the superlens and enters the second lens group 5-2, and is then reflected by the reflector 6 and enters 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 figure).

[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 front optical system is usually outside the double focal length, so an inverted and reduced real image is presented between the focal length and the double focal length behind the metalens, which 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 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 the above-mentioned Embodiment 3 and Embodiment 4, when the super lens cannot be integrated into the surface of the imaging module, it can be combined with a traditional lens group, and a commercially available high-definition imaging module can be used to directly perform imaging. The advantages are that it can optimize the lens group structure, shorten the lens length, and achieve a higher magnification and a smaller resolvable line diameter. In addition, developers do not need to design additional imaging modules independently, but can use commercially available high-definition imaging modules to reduce R&D costs. It can also be designed to be detachable, which is convenient for use with different imaging modules. With the development of technology, it can even be used for shooting and imaging of daily equipment.

[0055] At the same time, thanks to the scintillator, the present application only needs the half-width of the luminescence peak of the scintillator to be within the range of ±10nm of the working wavelength of the superlens, and does not need to deal with the imaging chromatic aberration problem of the traditional superlens in a wide wavelength range. Furthermore, excellent focusing effect can be achieved without a particularly small unit structure, which reduces production difficulty, improves production efficiency, and reduces production costs.

[0056] Simulation test:

[0057] The basic structure of the superlens used in the simulation experiment is a silicon dioxide substrate as a light-transmitting substrate, titanium dioxide as a subwavelength micro-nano structure, and the titanium dioxide array is arranged on the silicon dioxide substrate. The focal length of the superlens is 11 μm, and the numerical aperture NA is 0.63 (satisfying numerical aperture 1>NA≥0.6) unless otherwise specified.

[0058] like Figure 5 As shown, a cylindrical simple nanostructure superlens with an operating wavelength of 520nm, 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 superlens under incident light of different wavelengths. 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-working wavelengths (405nm, 660nm), the focusing effect is slightly worse, manifested as focal length offset and energy dispersion, that is, there is obvious chromatic aberration. The same effect can also be seen in other types of simple nanostructure superlenses, such as square nanopillars, composite nanopillars, PB phase nanopillars and other superlenses.

[0059] Depend on Figure 5 It can be seen that the scintillator used in the indirect detection scenario emits monochromatic light or quasi-monochromatic light with a narrow full width at half maximum (FWHM), so the metalens does not need to consider the influence of chromatic aberration, but only needs the full width at half maximum of the luminous peak of the scintillator to 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 larger unit structure, the manufacturing cost of the micro-nano metalens is greatly reduced.

[0060] like Figure 6 As shown, Figure 6 (a) is the light intensity distribution of the focused Airy disk in the xy plane when the metalens meets the design conditions, that is, when the working wavelength of the metalens is equal to the wavelength of the incident light 520nm. Figure 6 (b) The x-axis intensity curve of the Airy disk formed by focusing the incident light with a wavelength of 500-540 nm under the superlens with an operating wavelength of 520 nm. Figure 6 It can be seen that: 1) when the working 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, that is, 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 working 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 of the Airy disk formed by the incident light with a wavelength of 500-540nm and irradiated by the superlens with an operating wavelength of 520nm in the xz plane. 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 onto the superlens. Figure 7 (c) is the focusing efficiency and focal length of the simulation experiment in (b). Figure 7It can be known 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 half-height full width of the luminous peak of the scintillator is within the working wavelength of the metalens ±10nm, 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 aggravated 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 ±10nm of the working wavelength of the superlens, the luminescence peak of the scintillator is narrow (FWHM≤20nm), and the imaging effect and spatial feature resolution of the superlens 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) superlens under equal intensity incident light, Figure 8 (e) is the z-axis field intensity distribution curve corresponding to the focusing of the (a)-(c) superlens under equal intensity incident light. Figure 8 It can be seen that the sub-wavelength micro-nano structure unit size of the designed metalens will change with different incident working wavelengths. 2 / m 2 ), a smaller unit length and a smaller structural size are required for a smaller incident wavelength (short-wavelength superlens); as the wavelength increases (long-wavelength superlens), the minimum required structural size gradually increases. At present, there are scintillators with narrow FWHM and peak wavelength greater than or equal to 520nm. The introduction of matching micro-nanostructure superlens can build a high-definition X-ray imaging system without considering the influence of chromatic aberration caused by covering a wide working wavelength range. At the same time, it simplifies the design difficulty of the superlens, and thanks to its simple and large unit structure, it greatly reduces the cost of micro-nano manufacturing.

[0064] like Fig. 9 As shown, Fig. 9(a) is the surface image of the superlens with a design wavelength of 405nm, a sub-wavelength micro-nanostructure unit length of 0.31μm, and a minimum nanocolumn diameter of 0.04μm. Fig. 9 (b) is the surface image of the superlens with a design wavelength of 405nm, a sub-wavelength micro-nanostructure unit length of 0.31μm, and a minimum nanocolumn diameter of 0.06μm. Fig. 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. Fig. 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. Fig. 9 (e) is the field intensity distribution curve along the z-axis corresponding to the incident light wavelength of 405nm. When the design wavelength is 405nm, the superlens with a sub-wavelength micro-nano structure unit length of 0.31μm satisfies the Nyquist sampling theorem; Fig. 9 (a) shows that a smaller nanorod structure is beneficial for light transmission, thereby focusing a stronger light spot, which is beneficial for imaging. Fig. 9 (b) shows that when the unit length is not changed and the diameter of the nanocolumn is slightly increased, the focusing effect is slightly worse, but the overall focusing function is still available and meets the usage conditions. Fig. 9 (c) shows that the superlens with a sub-wavelength micro-nano structure unit length of 0.45μm does not satisfy the Nyquist sampling theorem, and its focused light field is relatively dispersed. The light field intensity at the focal position is also much lower than that of the superlens with a sub-wavelength micro-nano structure unit length of 0.31μm that satisfies the Nyquist sampling theorem. Therefore, the use of a superlens 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-nano structure 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 superlens, respectively.

[0066] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that 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: It 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 half-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 enters the second lens group after passing through the super lens, 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 a sub-wavelength micro-nano structure.

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.

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