Optical element for a radiographic imaging device, radiographic imaging device and X-ray imaging device

Abstract

Optical element for a radiation imaging device, comprising: a scintillator which receives radiation (100) to emit fluorescence light with a longer wavelength than the radiation (100) and which is uniformly formed on a radiation-incident substrate surface of a lens-shaped substrate (14) provided in an objective lens (10), wherein the scintillator is made of: a base material which is a solid optical material from which the lens-shaped substrate (14) is formed, and of a predetermined additive.

Description

Technical field

[0001] The present invention relates to an optical element for a radiation imaging device, for example for use in a synchrotron radiation facility, and relates to a radiation imaging device and an X-ray imaging device. State of the art

[0002] A synchrotron radiation facility is an oversized X-ray light source that generates highly directivity and high brightness X-rays. It is used as a powerful tool for observation and analysis in a wide range of fields, from materials science and life sciences to fundamental physics. To fully utilize the light source's capabilities, a high-precision X-ray detector with fast operation is required. In particular, an X-ray imaging system capable of simultaneously capturing X-ray signals over a wide area is used as an extremely versatile tool.

[0003] One aspect of the performance required in an X-ray imaging system is spatial resolution. In an X-ray imaging system, spatial resolution is a crucial parameter that determines the measurement limit, data quality, and the system's dimensions. Higher spatial resolution leads to greater acquisition accuracy.

[0004] Known X-ray imaging devices with a spatial resolution of 10 micrometers or less include a device comprising a scintillator, an imaging optical system, and an image sensor.

[0005] Fig. Figure 19 shows an overview layout of an X-ray imaging system using a scintillator. In the X-ray imaging system in Fig. In step 19, a sample 910 is irradiated with radiation, in this case X-rays; the radiation that penetrates or is scattered by the sample 910 strikes a scintillator 901. The scintillator 901 converts the incident light, i.e., the X-rays, into fluorescent light with a longer wavelength, which can be refracted by an optical lens. An image using the fluorescent light from the scintillator 901 is magnified (or reduced) by an imaging optical system 902 and then projected onto an image sensor 903. In this way, information about the structure of the sample 910 is acquired with a predetermined spatial resolution.

[0006] The theoretical limit of spatial resolution, as with light microscopes, is determined by a Rayleigh resolution limit. In an imaging device with a scintillator, the spatial resolution is limited by the diffraction of the scintillator fluorescence light, and the spatial resolution δ is determined by δ=0.61×λ / NA.

[0007] Here, λ represents the wavelength of the fluorescence light from the scintillator; NA represents the numerical aperture of the objective lens in the imaging optical system and is determined by NA=n⋅sin θ.

[0008] Here, n represents the refractive index of the medium located between the objective lens and the scintillator; θ represents the opening angle, which refers to the maximum angle of the rays incident on the objective lens from the sample (here the scintillator), which is the object being observed, relative to the optical axis.

[0009] Fig. Figure 20 shows a comparison between a dry objective lens and a liquid-encapsulated objective lens, both of which are used in the X-ray imaging device according to Fig. 19 are usable.

[0010] When a dry objective lens is used, the medium between the objective lens and the scintillator is a gas (typically air), or a vacuum is maintained between the objective lens and the scintillator. In these cases, the refractive index n is approximately 1.0 and the aperture angle θ is at most approximately 72 degrees. Therefore, when using a dry objective lens, the numerical aperture NA is at most approximately 0.95, which corresponds to 1 · sin 72°. Assuming the wavelength of the fluorescence light from the scintillator is 550 nm (nanometers), the spatial resolution δ is 0.61 × 550 × 10⁻⁶. -9 / 0.95 ≈ 353 × 10 -9 The limit is 353 nm.

[0011] When using a liquid-encapsulated objective lens, the medium between the lens and the scintillator is oil with a refractive index of approximately 1.52 or water with a refractive index of approximately 1.33. Thus, the refraction between the scintillator and the medium is lower compared to using a dry objective lens, allowing for signal acquisition at wider angles. The maximum aperture angle θ is approximately 72 degrees. Therefore, when using a liquid-encapsulated objective lens, the maximum numerical aperture NA is 1.44, which corresponds to 1.52 · sin 72°. Assuming a wavelength of 550 nm (nanometers) for the scintillator's fluorescent light, the spatial resolution δ is 0.61 × 550 × 10⁻⁶. -9 / 1.44 ≈ 233 × 10 -9 The limit is 233 nm.

[0012] With a view to achieving the Rayleigh resolution limit δ, which represents the theoretical limit, a method for forming a scintillator thin film and a structure of such a scintillator thin film are disclosed, which includes the elimination of defocused, i.e., unfocused, components and the suppression of light scattering at the scintillator interface (see JP 2016 - 045 183 A1). A technique is also known in which a scintillator is brought into the shape of a lens to align the emerging light parallel to itself (see JP 2007 - 024 584 A1).

[0013] Further examples of previously known designs can be found in JP 2009 - 222 578 A, JP 2006 - 162 293 A, US 2012 / 0 273 686 A1 and US 2006 / 0 192 129 A1. Summary of the invention: Technical problem

[0014] As explained above, the use of a dry objective lens results in a higher spatial resolution δ compared to the use of a liquid-encapsulated objective lens. However, liquid-encapsulated objective lenses have limited applications because they tend to lose focus due to temperature-dependent changes in the refractive index of the liquid component, the liquid becomes opaque due to turbidity under radiation, and the liquid is difficult to contain in applications where the objective lens is horizontally oriented. A problem in radiation imaging devices and the like is therefore that the spatial resolution can practically never be better than 353 nm, as is achievable with a dry objective lens.While the above explanations relate in particular to the background and the associated state of the art of X-ray imaging equipment, similar circumstances apply to radiation imaging equipment in general.

[0015] The object of the present invention is to propose an optical element for a radiographic imaging device, a radiographic imaging device and an X-ray imaging device, which contribute to improving spatial resolution. Solution to the problem

[0016] The above problem is solved by an optical element for a radiation imaging device according to the features of independent claim 1 and / or the features of independent claim 3 and / or a method for manufacturing an optical element for a radiation imaging device according to the features of independent claim 4 and / or a device according to any one of independent claims 6 to 8.

[0017] Further embodiments are described in the dependent claims. Advantageous effects of the invention

[0018] According to the present invention, it is possible to provide an optical element for a radiographic imaging device, a radiographic imaging device, and an X-ray imaging device that contribute to improving spatial resolution. Brief description of the drawings Fig. Figure 1 is a representation that conceptually shows an overall configuration of an imaging device according to an embodiment of the present invention; Fig. Figure 2 is a representation illustrating the structure of an imaging optical system according to an embodiment of the present invention; Fig. 3A and Fig. 3B are a perspective view or a side view of a front lens in a lens system; Fig. Figures 4A to 4D are illustrations that depict a method for manufacturing a front lens in a lens; Fig. Figures 5A to 5C are illustrations that depict the working distance of a lens; Fig. Figures 6A to 6G are illustrations showing various modified forms of a front lens in conjunction with a first practical example of the present invention; Fig. 7 is a representation showing a front lens in the form of a cemented lens in conjunction with a first practical example of the present invention; Fig. Figure 8 is a representation for reference to compare with a second practical example of the present invention; Fig. 9A and Fig. Figures 9B are sectional views of a lens-shaped substrate and a front lens according to the second practical example of the present invention; Fig. Figure 10 is a representation showing a spherical surface and its center in relation to the shape of the incidence surface of a front lens in conjunction with the second practical example of the present invention; Fig. 11 is a representation showing an example of the relationship between a sample, a front lens and the light diffracted by the sample in conjunction with the second practical example of the present invention; Fig. Figure 12 is a conceptual representation of an equidistance projection in connection with the second practical example of the present invention; Fig. 13 is a representation showing a further example of the relationship between a sample, a front lens and the light diffracted by the sample in conjunction with the second practical example of the present invention; Fig. 14 is a representation showing a further example of the relationship between a sample, a front lens and the light diffracted by the sample in conjunction with the second practical example of the present invention; Fig. Figure 15 shows a front lens with a convex lens arrangement formed on the exit surface in conjunction with a third practical example according to the present invention; Fig. 16 is a representation showing a front lens with a concave lens arrangement formed on the exit surface in conjunction with the third practical example according to the invention; Fig. Figure 17 is a representation showing the optical path of the fluorescence light in connection with the third practical example according to the invention; Fig. Figure 18 is a diagram showing the arrangement of an X-ray imaging device according to the fifth practical example of the invention; Fig. Figure 19 is a schematic representation of the setup of an X-ray imaging system with a scintillator in conjunction with conventional technology; and Fig. Figure 20 is a representation comparing a dry objective lens with a liquid-encapsulated objective lens in conjunction with conventional technique. Description of the embodiments

[0019] Examples embodying this invention are described in detail below with reference to the accompanying drawings. In the referenced drawings, the same parts are identified by the same reference numerals, and no overlapping descriptions of the same parts are repeated. For the sake of simplicity, symbols and other designations relating to information, signals, physical quantities, components, and the like are used in this description, with the names of the corresponding information, signals, physical quantities, components, and the like being omitted or abbreviated.

[0020] Fig. Figure 1 is a representation that conceptually shows a general arrangement of an imaging device 1 according to an embodiment of the present invention. The imaging device 1 comprises an objective lens 10, an imaging lens 20, an image sensor 30, a sensor drive / signal processor 40, a lens holder 50, and an imaging lens drive 60. The reference numeral "100" denotes light rays that are directed into the imaging device 1.

[0021] The objective lens 10 and the imaging lens 20 form an imaging optical system. The incident rays 100 first strike the objective lens 10 under the lenses that form the imaging optical system. The imaging optical system forms an image, based on the incident rays 100, onto the imaging surface of the image sensor 30.

[0022] The image sensor 30 is a fixed image sensor element comprising a CCD (charge-coupled device), CMOS (complementary metal-oxide semiconductor), or another image sensor. In response to the input of a sensor control signal, the image sensor 30 can output an image signal that conveys an image projected onto the imaging surface (optical image).

[0023] The sensor drive / signal processor 40 supplies the image sensor 30 with a sensor control signal for controlling and monitoring the image sensor 30 and thereby receives the above-mentioned image signal from the image sensor 30.

[0024] The lens holder 50 is a lens cylinder that supports the lenses, including the objective lens 10 and the imaging lens 20, which constitute the imaging optical system, at predetermined positions. It is assumed here that all lenses forming the imaging optical system are supported by a single lens holder 50. Likewise, the lens holder 50 can be composed of multiple lens holders. For example, the lens holder 50 can be composed of an objective lens holder supporting the objective lens 10 and an imaging lens holder supporting the imaging lens 20, and the objective lens holder and the imaging lens holder can be separate holders. The imaging device 1 can comprise a housing (not shown) that supports the imaging optical device and the image sensor 30.

[0025] The imaging lens drive 60 is a drive mechanism that moves the imaging lens 20 along the optical path of the fluorescence light, as described below.

[0026] With reference to Fig. Section 2 below describes in detail the setup of the imaging optical system, including the objective lens 10. Sample irradiation beams, such as X-rays, are directed onto a sample SS, and the sample irradiation beams that pass through the sample SS and are scattered by the sample SS strike the objective lens 10 as incident beams 100. The transmitted irradiation beams pertain to the sample irradiation beams that pass through the sample SS without being scattered by the sample SS. For the specific description, a three-dimensional rectangular coordinate system is assumed, defined by three mutually perpendicular axes: the X, Y, and Z axes. The direction of motion of the irradiation beams incident on the sample SS is parallel to the Z-axis.Accordingly, the direction of motion of the sample irradiation beams that passed through sample SS is also parallel to the Z-axis. The plane that lies parallel to the X and Y axes is called the XY plane, the plane that lies parallel to the Y and Z axes is called the YZ plane, and the plane that lies parallel to the Z and X axes is called the ZX plane.

[0027] The objective lens 10 comprises a front lens 11 and a non-front lens 12, i.e., each lens distinct from the front lens 11. To minimize aberrations throughout the objective lens 10, it is composed of multiple lenses. Of all the lenses that make up the objective lens 10, the front lens 11 is located closest to the point of incidence of the incident rays 100 (i.e., it is positioned closest to the sample SS). That is, the front lens 11 is closer to the point of incidence of the incident rays 100 than the non-front lens 12, and thus the incident rays 100 strike the front lens 11.

[0028] A fluorescent film 13 is provided as a scintillator on the surface of the front lens 11, which is located closer to the point of incidence of the incident rays 100. It is assumed here that the fluorescent film 13 is distributed in a plane perpendicular to the Z-axis. That is, it is assumed that the fluorescent film 13 is a planar film distributed in the XY plane and has a thickness in the direction of the Z-axis. In this embodiment, the scintillator formed on the surface of the front lens 11 has such a small thickness that it can be referred to as a film, and accordingly, the scintillator is called a fluorescent film. In practice, the scintillator can have any desired thickness and can then be referred to as a fluorescent element. The portion of the front lens 11 in which the fluorescent film 13 is not formed is referred to as the lens-shaped substrate 14.There is no gap between the lenticular substrate 14 and the fluorescent film 13. It is also possible to understand that the lenticular substrate 14 has formed the fluorescent film 13 on its surface in order to receive the incident rays 100 at the fluorescent film 13.

[0029] Because the fluorescent film 13 is positioned on the surface of the front lens 11 closer to the point of incidence of the incident rays 100, the incident rays 100, which are moving towards the objective lens 10, strike the fluorescent film 13. The irradiation rays of the sample and the incident rays 100 are light rays with a predetermined wavelength WL1, and are, for example, gamma rays, X-rays, or ultraviolet rays (e.g., especially extreme ultraviolet). The fluorescent film 13 is made of a scintillator material that generates fluorescent light upon receiving the incident rays 100. The wavelength WL2 of the fluorescent light is longer than the wavelength WL1, and the fluorescent light can, typically, be visible light. However, this does not preclude the possibility that the fluorescent light emitted by the fluorescent film 13 is in the ultraviolet range.When fluorescent light is mentioned in the following description of this embodiment, it refers to the fluorescent light generated in the fluorescent film 13.

[0030] The fluorescence light generated in the fluorescence film 13 travels in various directions, starting from the point of generation. At least some of the fluorescence light generated in the fluorescence film 13 penetrates the lens-shaped substrate 14 of the front lens 11 and enters the non-front lens 12.

[0031] The non-front lens 12 consists of one or more lenses. Together with the lens-shaped substrate 14 of the front lens 11, the non-front lens 12 aligns the fluorescence light from the fluorescent film 13 into parallel light and directs it onto the imaging lens 20. The imaging lens 20 uses the fluorescence light from the objective lens 10 to create an image on the imaging surface of the image sensor 30. Although in Fig. While the imaging lens 20 is shown as a single lens, the imaging lens 20, as well as the objective lens 10, can be composed of several lenses. Aberrations can be corrected by the non-front lens 12. In a case where aberrations can be sufficiently corrected by the front lens 11 and the imaging lens 20 alone, the non-front lens 12 can be omitted from the imaging optical system.

[0032] Photoelectric conversion pixels are arranged two-dimensionally on the imaging surface of the image sensor 30 for the photoelectric conversion of the image projected with the fluorescent light. The photoelectric conversion yields an image signal, which is an electrical signal. The image projected onto the image sensor 30 reflects the emission position and emission intensity of the fluorescent light onto the fluorescent film 13. The emission position and emission intensity of the fluorescent light onto the fluorescent film 13 depend on the incidence position and incidence intensity of the incident rays 100 onto the fluorescent film 13. Thus, an image is projected onto the image sensor 30 using the fluorescent light that reflects the incidence position and incidence intensity of the incident rays 100 onto the fluorescent film 13.The imaging optical system, including the objective lens 10 and the imaging lens 20, can project the image onto the imaging surface of the image sensor 30 with magnification (or reduction) using the fluorescence light generated in the fluorescence film 13.

[0033] Since the incident rays contain 100 pieces of information about the structure of sample SS (i.e., information about the external appearance and internal structure of sample SS), the image projected onto the image sensor 30 is a recording of sample SS encompassing structural information about sample SS. For example, if X-rays are used as irradiation rays for sample SS, an X-ray image of sample SS is projected onto the image sensor 30.

[0034] The front lens 11, including the lens-shaped substrate 14 and the fluorescent film 13, consists, in simplified terms, of a substance that transmits the fluorescent light but transmits the incident rays 100 either not at all or less than the fluorescent light. That is, the front lens 11, including the lens-shaped substrate 14 and the fluorescent film 13, consists of a substance that is transparent to the fluorescent light but has a lower transmittance to the incident rays 100 than to the fluorescent light. As long as it possesses these properties, any type of substance can be used to form the front lens 11. Here, it is assumed that the lens-shaped substrate 14 is made of LuAG. LuAG is an abbreviation for Lu3Al5O. 12 (Lutetium aluminum garnet).

[0035] The fluorescent film 13 is formed from a substance obtained by adding an additive in a predetermined ratio to the same substance as the lenticular substrate 14 (i.e., the material of the lenticular substrate 14). It is assumed that the fluorescent film 13 is formed from Pr:LuAG. Pr:LuAG is LuAG to which praseodymium has been added as an additive. As a result, the fluorescent film 13 emits fluorescent light with a wavelength of 305 nm when irradiated with the incident rays. The concentration of the additive in the fluorescent film 13 is, for example, approximately 0.5%.

[0036] A portion (a large portion, depending on the thickness of the fluorescent film 13) of the incident rays 100, such as radiation, is transmitted through the fluorescent film 13. If the incident rays 100, such as radiation or similar, reach the image sensor 30, they can degrade or destroy it. To prevent this, the lens-shaped substrate 14 is made sufficiently thick to adequately attenuate the incident rays 100 that pass through the fluorescent film 13.

[0037] On the other hand, the fluorescent film 13 is formed with a smaller thickness than that of the lens-shaped substrate 14, for example, a thickness in the range of 100 nm to 2 mm. Reducing the thickness of the fluorescent film 13 helps to suppress the variation in the emission point of the fluorescent light in the propagation direction of the incident rays 100, resulting in better spatial resolution of the imaging device 1. Conversely, increasing the thickness of the fluorescent film 13 helps to increase the amount of fluorescent light. The thickness of the fluorescent film 13 can be determined by considering the trade-off between spatial resolution and the amount of light.

[0038] The fluorescent film 13 is bonded to the lenticular substrate 14 in such a way that the refractive index continuity is maintained. Bonding the fluorescent film 13 to the lenticular substrate 14 while maintaining the refractive index continuity means that the interface between the fluorescent film 13 and the lenticular substrate 14 has a substantially uniform refractive index structure. For example, the difference in refractive index between the lenticular substrate 14 and the fluorescent film 13 is 0.1% or less, or on the order of 0.1% relative to the refractive index of the lenticular substrate 14. Thus, it can be stated that the interface between the fluorescent film 13 and the lenticular substrate 14 has a substantially uniform refractive index structure. This suppresses the scattering, refraction, and reflection of the fluorescent light at the interface.

[0039] Fig. 3A and Fig. Figure 3B is a perspective view or a side view of the front lens 11. Although in Fig. Figure 2 is not shown to avoid a complex illustration. An antireflective film 15 is arranged on the surface of the lenticular substrate 14 in the front lens 11. This film is not in contact with the fluorescent film 13, and likewise, an antireflective film 16 is arranged on the surface of the fluorescent film 13. This film is also not in contact with the lenticular substrate 14. That is, viewed in the direction of propagation of the incident rays 100 (ignoring scattering at the sample SS), the front lens 11 has the antireflective film 16, the fluorescent film 13, the lenticular substrate 14, and the antireflective film 15 in that order.

[0040] The antireflective film 15 is, for example, a thin film with a thickness corresponding to one-quarter of the wavelength of the fluorescent light. The antireflective film 15 prevents the reflection of the fluorescent light by canceling out the reflected light resulting from the reflection of the fluorescent light at the interface between the lens-shaped substrate 14 and the antireflective film 15 with the reflected light resulting from the reflection of the fluorescent light at the surface of the antireflective film 15. Alternatively, a multilayer film formed from two or more dielectric films can be used as the antireflective film 15.

[0041] The antireflective film 16 has the same structure as the antireflective film 15. The antireflective film 16 prevents the reflection of the fluorescent light by canceling out the reflected light resulting from the reflection of the fluorescent light at the interface between the fluorescent film 13 and the antireflective film 16 with the reflected light resulting from the reflection of the fluorescent light at the surface of the antireflective film 16.

[0042] With regard to the Fig. Sections 4A to 4C describe an example of the method for fabricating the front lens 11. It is assumed that in the lens-shaped substrate 14, the surface SF1 on which the fluorescent film 13 is formed is a planar surface parallel to the XY plane, and that the outer contour of the planar surface on the XY plane is circular. The outer contour can also be other than circular. The lens-shaped substrate 14 functions as a plano-convex lens, and in the lens-shaped substrate 14, the surface opposite surface SF1 is a convex surface SF2. As in Fig. Figure 4A shows the preparation of a fluorescent plate 13S, which is ultimately formed into the fluorescent film 13, and a lenticular substrate 14. The fluorescent plate 13S is a plate-shaped element with the same contour in the XY plane as the surface SF1 of the lenticular substrate 14 and is formed from the same substance as the fluorescent film 13. The lenticular substrate 14 acts as one of the lenses that make up the objective lens 10 and has a thickness, curvature, etc., that corresponds to the optical design of the objective lens 10. On the other hand, the fluorescent plate 13S can be made of any thickness, taking into account ease of handling, etc.

[0043] Using the fluorescent plate 13S and the separately prepared lens-shaped substrate 14, as described in Fig. As shown in Figure 4B, the surface SF1 of the lenticular substrate 14 is connected to a surface of the fluorescent plate 13S by solid-phase diffusion. Subsequently, the fluorescent plate 13S is thinned from the side opposite the side connected to the lenticular substrate 14. The thinned fluorescent plate 13S is the fluorescent film 13 (see Figure 4B). Fig. 4C). In the case that the fluorescent plate 13S has the same thickness as the fluorescent film 13 from the outset, the fluorescent plate 13S does not need to be thinned. Finally, as in Fig. As shown in 4D, for example by vacuum deposition, an antireflective film 15 is formed on the surface of the lenticular substrate 14, which is not in contact with the fluorescent film 13, and an antireflective film 16 is formed on the surface of the fluorescent film 13, which is not in contact with the lenticular substrate 14.

[0044] The method of joining by solid-phase diffusion is comparable to the method of joining a substrate and a fluorescent plate in JP 2016 45183 A1, and the pretreatment (polishing, cleaning, etc.) of the lenticular substrate 14 and the fluorescent plate 13S, which can be carried out before joining, as well as the method of thinning the fluorescent plate 13S, are also performed as disclosed in JP 2016 45183 A1. The in Fig. The process shown in Figures 4A to 4D for manufacturing the front lens 11 is only one example and allows for various modifications. For example, the sequence of the work steps can be changed as desired from the description. Specifically, it is possible, for instance, to first bond the fluorescent plate 13S and the substrate (hereinafter referred to as the raw substrate), which is ultimately formed into the lens-shaped substrate 14, by solid-phase diffusion, then to thin the fluorescent plate 13S to form the fluorescent film 13, and then to shape the raw substrate into a lens. The raw substrate processed in this way is now the lens-shaped substrate 14.

[0045] The above description concerns a case in which the lenticular substrate 14 and the fluorescent plate 13S, formed from a common base material, are joined together by solid-phase diffusion without the use of an admixture such as an adhesive. However, this does not preclude the possibility of joining the lenticular substrate 14 and the fluorescent plate 13S with an adhesive (after joining, the process continues as described above). It is even possible to join a lenticular substrate 14 and a fluorescent plate 13S made of different base materials.However, if the lenticular substrate 14 and the fluorescent plate 13S are bonded with an adhesive, the fluorescent light is scattered and reflected at the interface between the adhesive and the lenticular substrate 14 and at the interface between the adhesive and the fluorescent film 13 (the fluorescent plate 13S after thinning), resulting in a blurred image on the image sensor 30. To avoid this, solid-phase diffusion is preferable. However, any bonding technique can be used as long as the fluorescent film 13 can be bonded to the surface SF1 of the lenticular substrate 14. For example, the substance (here Pr:LuAG) from which the fluorescent film 13 is formed can be deposited on the surface SF1 of the lenticular substrate 14.In any case, the fluorescent film 13 is provided on the incidence side of the objective lens 10 (more precisely on the surface of the objective lens 10 that is closer to the point of incidence of the incident rays 100) in such a way that it forms a unit with the objective lens 10 (here the front lens 11).

[0046] On the surface of the fluorescent film 13 that is not in contact with the lens-shaped substrate 14, a reflective film can be provided instead of the antireflective film 16. This reflective film reflects the fluorescent light. The fluorescent light generated in the fluorescent film 13 propagates in various directions, starting from the point of generation. The reflective film reflects the fluorescent light propagating in its direction, thus directing the fluorescent light towards the non-front lens 12. The use of the reflective film helps to increase the amount of fluorescent light reaching the image sensor 30 and also helps to suppress the passage of other scattered light (e.g., visible light) through the front lens 11, but tends to result in lower spatial resolution.This means that when comparing a structure in which an antireflective film 16 is provided on the surface of the fluorescent film 13, which is not in contact with the lens-shaped substrate 14, with a structure in which a reflective film is provided, the latter is advantageous with respect to the amount of fluorescent light and the former with respect to the spatial resolution. Even when a reflective film is provided, making the fluorescent film 13 sufficiently thin helps to keep the reduction in spatial resolution to a negligible degree. Conversely, the fluorescent film 13 does not need to be made as thin if an antireflective layer 16 is provided.

[0047] In a conventional imaging setup (see Fig. 20) The medium between the lens and the scintillator is a gas or a liquid, or a vacuum exists between the lens and the scintillator. In the imaging device 1 of this embodiment, however, the medium between the lens and the scintillator is the lens-shaped substrate 14, which is a solid transparent to fluorescence light. Thus, in this embodiment, giving a substrate the shape of a lens, which is also required to attenuate the incident rays 100 (such as radiation), results in the medium between the lens and the scintillator being filled (supported) by the substrate (here, the lens-shaped substrate 14). This makes it possible to give the medium a higher refractive index n than with conventional dry objective lenses and liquid-encapsulated objective lenses.

[0048] Consider a case where, as described above, the lens-shaped substrate 14 is made of LuAG and the fluorescent film 13 emits fluorescent light with a wavelength λ of 305 nm. Since LuAG has a refractive index n of 2.03, assuming an opening angle θ of 72 degrees, the numerical aperture NA of the objective lens 10 is given by NA = n · sin θ = 2.03 × sin 72° ≈ 1.93, which is much larger than the conventional limit of the opening angle (0.95 for a dry lens). In this case, the spatial resolution 8 of the imaging optical system of the imaging device 1 is δ = 0.61 × λ / NA = 0.61 × 305 × 10-9 / 1.93 ≈ 96 × 10-9, which is far above the conventional limit of spatial resolution.

[0049] As previously described, the imaging device 1 of this embodiment makes it possible to significantly increase the numerical aperture of the objective lens and the spatial resolution of the imaging optical system compared to conventional standards. Furthermore, the use of a solid as the medium is expected to result in significantly improved temperature stability compared to a liquid-encapsulated objective lens. Moreover, unlike a liquid, a solid is neither fluid nor does it evaporate, thus achieving long-term mechanical stability.

[0050] To achieve a resolution below 100 nm, as in the calculation example above, it is necessary not only to increase the numerical aperture NA and shorten the wavelength λ of the fluorescent light, but also to reduce as much as possible the factors that lead to lower resolution. If a lenticular substrate 14 and a fluorescent film 13 made of a common base material (e.g., LuAG) are directly bonded together, the difference in refractive index between them is 0.1% or less; thus, the element resulting from the bonded lenticular substrate 14 and the fluorescent film 13 appears optically essentially as a single crystalline body. This helps to minimize the reduction in resolution at the interface between the lenticular substrate 14 and the fluorescent film 13.Accordingly, it is advantageous that the lens (here the lens-shaped substrate 14), which is contained in the objective lens 10 and which uniformly incorporates the fluorescent film 13, is made of a solid optical material (here LuAG) with a refractive index such that the difference in refractive index between this lens and the fluorescent film 13 has a predetermined value or less. The predetermined value can be 0.1% and can be any other value close to 0.1%.

[0051] In general, in imaging devices such as microscopes, the plane on which a sample lies as the imaging object is called the sample plane, and the distance from the front end of the objective lens to the sample plane with focus on the sample plane (in other words, the distance from the front end of the objective lens to the sample with focus on the sample) is called the working distance. In the imaging device 1 according to this embodiment, the fluorescent film 13 corresponds to the sample (i.e., the fluorescent film 13 serves as the light source and imaging target). In the imaging device 1, the sample plane is set on the fluorescent film 13, and the imaging optical system is designed such that the position at which the focus is achieved (focus point) is fixed on the fluorescent film 13 as the sample plane, so that the working distance of the objective lens 10 has a zero or negative value.

[0052] This means that the imaging optical system is designed such that the fluorescence light emanating from a specific emission point of the scintillator (here the fluorescent film 13) is imaged at a point on the image sensor 30. "A point" here is a term that covers an area corresponding to a circle of dispersion, with the fluorescent film 13 preferably being arranged within the depth of field of the imaging optical system.

[0053] In addition, the working distance of the objective lens 10 is now described. The fluorescent film 13 has a finite thickness t in the direction of the Z-axis. Therefore, if the focus point is set at the center of the fluorescent film 13, the working distance is equal to (-t / 2). That is, it can be said that the working distance has a negative value. As in Fig. As shown in Figure 5A, the working distance has a positive value when, according to an imaging device such as an ordinary microscope, the direction pointing from the sample plane to the front end of the objective lens 10 and the direction of the light propagating from the sample plane into the imaging optical system coincide. Conversely, the working distance has a negative value when, as shown in Figure 5A, the direction of light propagating from the sample plane to the front end of the objective lens 10 coincides. Fig. Figure 5B shows that the direction pointing from the sample plane to the front end of the objective lens 10 and the direction of the light propagating from the sample plane into the imaging optical system are opposite.

[0054] If the focus point in the imaging device 1 is set to the center of the fluorescence film 13, then, as described in Fig. Figure 5C shows a plane passing through the center of the fluorescent film 13 and parallel to the XY plane, the sample plane. The direction from the sample plane to the front end of the objective and the direction of the fluorescent light propagating from the sample plane into the imaging optical system are therefore opposite to each other, and the working distance has a negative value (-t / 2). Assuming that the incident rays 100 propagate from the negative to the positive side along the Z-axis, the front end of the objective lens 10 refers to the portion of the front lens 11 furthest towards the negative side along the Z-axis (in other words, the portion of the fluorescent film 13 furthest towards the negative side along the Z-axis). When the position of the front end of the objective lens 10 and the position of the sample plane coincide in the imaging optical system, the working distance is zero.

[0055] The focus can be adjusted precisely as follows, for example. In the beam path from the fluorescence scintillator (here the fluorescence film 13) to the image sensor 30, the imaging lens 20 is positioned between the objective lens 10 and the image sensor 30 such that the position of the imaging lens 20 along the optical axis of the beam path can be adjusted by the imaging lens drive 60. The position of the imaging lens 20 can then be adjusted and determined so that the image is projected onto the imaging surface of the image sensor 30 using the fluorescence light (i.e., so that the focus is on the fluorescence film 13; in other words, so that the image is projected sharply onto the image sensor 30 using the fluorescence light).Although the beam path from the fluorescence scintillator (here the fluorescence film 13) to the image sensor 30 is assumed to be a straight beam path, it can also be a curved or folded beam path, as is achieved with a reflective optic.

[0056] Aberrations (spherical, chromatic and other aberrations) that occur in the imaging optical system can be corrected in the objective lens 10 of the multitude of lenses that form the imaging optical system.

[0057] For the sake of simplicity, the design, operation, and other features of the imaging device 1 described so far are referred to as the basic practical example. The basic practical example is open to modifications and other techniques, as described below with reference to some practical examples. Unless otherwise stated or contradictory, the description of the basic practical example applies to the practical examples described below; for any specific description of one of the practical examples described later that differs from the basic practical example, the specific description of that practical example prevails. Unless contradictory, each feature described in connection with one of the practical examples described below applies to each of the other practical examples (i.e.,Two or more of the different practical examples can be combined. << First practical example >>

[0058] A first practical example is described. In this basic example, the lens-shaped substrate 14 is given the form of a plano-convex lens, so that the front lens 11 acts as a plano-convex lens. Depending on the design of the objective lens 10, the shape of the lens-shaped substrate 14, and thus also the shape of the front lens 11, can be changed as desired. For example, the shape of the lens-shaped substrate 14 can be defined such that the front lens 11 acts as a plano-concave lens, a biconvex lens, a biconcave lens, a meniscus lens, an achromatic lens, a bonded lens, or as an array of such lenses. These lenses do not necessarily have to have spherical surfaces, but can also have aspherical surfaces.

[0059] Specifically, for example, although the front lens 11 in the basic practical example has a flat surface on the incidence side and a convex surface on the exit side, each of the elements in the Fig. Front lenses 11a to 11g shown in sections 6A to 6G are used as front lens 11. Fig. Reference numerals 6A to 6G, “13a to 13g”, denote the fluorescent films 13 in the front lenses 11a to 11g, and reference numerals “14a to 14g” denote the lens-shaped substrate 14 in the front lenses 11a to 11g. For each front lens described in connection with the basic practical example, the first practical example, and the practical examples described later, the incidence surface denotes the surface of the front lens that is located on the incidence side of the incident rays 100 (i.e., the surface that receives the incident rays 100 and, with respect to the lens-shaped substrate, the surface through which the fluorescent light enters), and the exit surface denotes the surface of the front lens that is opposite the surface located on the incidence side of the incident rays 100 (with respect to the lens-shaped substrate, the surface through which the fluorescent light exits).

[0060] The front lens 11a has a flat surface on the incidence side and a concave surface on the exit side.

[0061] The front lens 11b has a concave surface on the incidence side and a flat surface on the exit side.

[0062] The front lens 11c has a concave surface on the incidence side and a concave surface on the exit side.

[0063] The front lens 11d has a concave surface on the incidence side and a convex surface on the exit side.

[0064] The front lens 11e has a convex surface on the incidence side and a flat surface on the exit side.

[0065] The front lens 11f has a convex surface on the incidence side and a concave surface on the exit side.

[0066] The front lens 11f has a convex surface on the incidence side and a convex surface on the exit side.

[0067] For each front lens described in connection with the basic practical example, the first practical example, and the practical examples described later, the fact that it has a concave or convex surface on the incidence side means that the incidence side has a concave or convex surface, but does not preclude the possibility that it may have a partially flat surface. Likewise, for each front lens described in connection with the basic practical example, the first practical example, and the practical examples described later, the fact that it has a concave or convex surface on the exit side means that it may have a concave or convex surface, but does not preclude the possibility that it may have a partially flat surface.

[0068] For each front lens described in connection with the basic practical example, the first practical example, and the practical examples described later, provided it has a concave or convex surface on the incident side, the image resulting from the fluorescent light from the fluorescent film on the front lens receiving the incident rays 100 is temporarily an image on a curved surface; the image on the curved surface is then converted by the objective lens 10, composed of several lenses, into an image on a flat surface (a planar image), so that the planar image is projected onto the image surface of the image sensor 30 via the imaging lens 20.The imaging optical system is designed such that, regardless of which of the front lenses described in connection with the basic practical example, the first practical example, and the practical examples described later is used, an image is projected onto the image surface of the image sensor 30 using the fluorescence light from the fluorescent film. In a case where the image is projected onto a curved surface, it can be projected onto the image sensor 30 using any method, including equidistance projection, solid angle projection, stereographic projection, and orthogonal projection. Lens configurations for converting an image on a curved surface with a concave or convex surface into an image on a planar surface are known; therefore, no details are given here.In a case where the image with the fluorescent light from the fluorescent film is an image on a flat surface, as when using a plano-convex lens as the front lens, the image with the fluorescent light can be projected onto the image sensor 30 by central projection.

[0069] Each anterior lens described in connection with the basic practical example, the first practical example, and the practical examples described later can be designed as a bonded lens. Fig. Figure 7 shows, as an example, a side view of the front lens 11 in the basic practical example, when it is designed as a bonded lens. Designing the front lens 11 as a bonded lens means that the lens-shaped substrate 14 of the front lens 11 is assembled by bonding several lenses together. Fig. 7. Two lenses are bonded together to form the lenticular substrate 14; alternatively, three or more lenses can be bonded together to form the lenticular substrate 14. The same applies in cases where a front lens other than the front lens 11 of the basic practical example is formed as a bonded lens. << Second practical example >>

[0070] A second practical example is described. This second practical example deals with specific modified techniques related to the shape of the lenticular substrate.

[0071] Assume that the sample's irradiation beams, such as X-rays, are directed onto the sample and diffracted. The angle between the vector indicating the propagation direction of the sample's irradiation beams before diffraction and the vector indicating the propagation direction of the sample's irradiation beams after diffraction is defined as the diffraction angle φ. The image of the diffracted light contains structural information about the sample SS, and this information has higher spatial resolution the further towards the wide-angle side (i.e., in a region of larger diffraction angles φ). Therefore, observing the diffracted components further towards the wide-angle side is essential for high resolution. To observe diffracted components as far as possible towards the wide-angle side, when using a detector with a flat detection surface, it is necessary either to bring the detection surface closer to the sample or to increase the size of the detection surface.However, bringing the detection area too close to the sample unfortunately results in insufficient resolution when measuring the diffraction angle. To avoid this, it is common practice to increase the size of the detection area while maintaining a sufficient distance for adequate resolution. Various methods for increasing the detection area have been investigated, such as enlarging the scintillator area and using a sensor array with two-dimensionally arranged image sensors. Fig. Figure 8 illustrates the concept of such procedures as a reference. Unfortunately, these procedures lead to an increase in costs and the size of the facility.

[0072] In light of this, the second practical example uses a front lens with a concave surface on the incidence side. Fig. Figure 9A is a sectional view of the lenticular substrate 14A through an arbitrary cutting plane perpendicular to the Z-axis. The lenticular substrate 14A has two opposing surfaces SF1A and SF2A, where the surfaces SF1A and SF2A correspond to the surfaces SF1 and SF2 in the basic practical example (see Figure 9A). Fig. 4A). That is, of the surfaces SF1A and SF2A, surface SF1A corresponds to the incidence side and surface SF2A to the exit side. Surface SF1A is a concave surface and surface SF2A is a convex surface. Fig. Figure 9B is a sectional view of the front lens 11A through an arbitrary sectioning plane perpendicular to the Z-axis. A fluorescent film 13A, acting as a scintillator, is connected to the concave surface SF1A of the lenticular substrate 14A, thereby forming the front lens 11A. That is, in the second practical example, the front lens 11A, the fluorescent film 13A, and the lenticular substrate 14A are used as the front lens 11, fluorescent film 13, and lenticular substrate 14, respectively. The concave surface SF1A corresponds to half of a spherical surface (hereinafter also referred to as a hemispherical surface), and in Fig. In section 10, the center of the spherical surface is designated by the reference symbol "SO". For the sake of simplicity, the concave surface SF1A is described in the above as being provided on the lens-shaped substrate 14A; likewise, the concave surface SF1A can be understood as the incidence surface of the front lens 11A, taking into account the entire front lens 11A.

[0073] As in Fig. As shown in Figure 11, a sample SS can be positioned at the center of the aforementioned spherical surface. The incident rays 100 then strike the fluorescent film 13A, which is shaped exactly like the concave surface SF1A, with diffraction angles φ of 90 degrees or less, and contribute to the emission of fluorescent light. Fig. The reference numeral “11” conceptually designates a component of a subsequent stage of the front lens 11A, whereby the representation is not to be understood as the actual shape of the component of the subsequent stage of the front lens 11 (the same applies to Fig. 13 and Fig. 14, which will be discussed later). Fig. Figure 11 shows a cross-sectional view through the front lens 11A and the component 18 of the subsequent stage; however, to avoid a cluttered representation, these are not shown hatched (the same applies to Fig. 13 and Fig. 14, which will be discussed later).

[0074] In the fluorescent film 13A, a spherical image is obtained from the incident rays 100 using the fluorescent light. The image from the fluorescent film 13A is converted from a spherical image (an image on a spherical surface) to a planar image (an image on a flat surface) by equidistant projection through the objective lens 10 and then imaged onto the image sensor 30. Fig. Figure 12 is a conceptual representation of the equidistant projection. As by comparing Fig. 8 as a reference and Fig. As can be understood from the second practical example, it is possible to observe diffracted components sufficiently far towards the wide-angle side (to capture diffraction signals of the incident rays 100 up to ultra-wide angles) in a space-saving manner and thus achieve a high spatial resolution.

[0075] The concave surface SF1A can be an ellipsoidal surface instead of a spherical one. That is, the concave surface SF1A can be one half of an ellipsoidal surface (hereinafter also referred to as a semi-ellipsoidal surface).

[0076] Taking into account maximizing the diffraction components captured on the wide-angle side, achieving the symmetry of the resulting image, etc., the sample SS can be placed at the center of the spherical or ellipsoidal surface; likewise, the sample SS can be placed at any other location. For example, if it is acceptable to limit the area in which diffracted components are captured on the wide-angle side, e.g., in a case where, for reasons related to the placement of the sample SS, a considerable amount of space must be left behind it, the sample SS can be placed at a position farther from the concave surface SF1A than the center of the spherical or ellipsoidal surface. More precisely, the sample SS can, as in Fig. As shown in Figure 13, the sample is placed at a position shifted by a predetermined distance from the center of the spherical or ellipsoidal surface in the direction opposite to the propagation direction of the irradiation rays on the sample. The position of the sample SS can be understood as indicating the position of the center of mass or geometric center of the sample SS. Fig. Reference numeral 13, denoted by "70", refers to a sample feeder that supplies the sample SS at the shifted position. It is also possible to place the sample SS at a position closer to the concave surface SF1A than the center of the spherical or ellipsoidal surface.

[0077] As mentioned previously, the concave surface SF1A can be formed in the shape of half a spherical surface (i.e., a hemispherical surface). Likewise, the concave surface SF1A can be part of a hemispherical surface. Suppose that a whole spherical surface is divided into two parts in a plane that does not pass through the center of the sphere; then the shape of the smaller of the two partial spherical surfaces (crowns) can be assigned to the concave surface SF1A. This is particularly advantageous when, for reasons related to the placement of the sample SS, a considerable amount of space must be left behind it. That is, if a placement such as in Fig. As illustrated in 13, it is assumed that it is possible, as in Fig. Figure 14 shows how to form the concave surface SF1A in the form of part of a hemispherical surface. Likewise, the concave surface SF1A can be formed in the form of part of a semi-elliptical surface.

[0078] In the first previously described practical example, the front lenses 11a to 11g are presented as modified examples of the front lens 11 in the basic practical example (see Fig. 6A to 6G). The front lens 11A in the second practical example also serves as an example for the front lens 11d in the first practical example. In the second practical example, the shape of the lens-shaped substrate 14A can be modified so that the exit surface of the front lens 11A is a flat or concave surface. << Third practical example >>

[0079] A third practical example is described. While the front lens 11 has a flat, concave or convex surface on the incidence side, the front lens 11 can have a convex lens arrangement on the exit side; likewise, the front lens 11 can have a flat, concave or convex surface on the incidence side, while the front lens 11 has a concave lens arrangement on the exit side. Fig. 15 and Fig. Figure 16 shows the front lenses 11P and 11Q as examples of the front lens 11, which uses a lens arrangement. The front lens 11P has a flat surface on the incidence side and a convex lens arrangement on the exit side. The front lens 11Q has a flat surface on the incidence side and a concave lens arrangement on the exit side. Fig. 15 and Fig. 16 The reference numerals “13P” and “13Q” denote the fluorescence films 13 in the front lenses 11P and 11Q respectively, and the reference numerals “14P” and “14Q” denote the lens-shaped substrates 14 in the front lenses 11P and 11Q respectively.

[0080] Although in Fig. As is not apparent from Figure 15, several convex surfaces are arranged along the X and Y axes on the exit side of the front lens 11P, forming a convex lens arrangement composed of several convex surfaces. However, this does not preclude the possibility that a multitude of convex surfaces are arranged along only one of the X and Y axes. Similarly, several concave surfaces are arranged along the X and Y axes on the exit side of the front lens 11Q, forming a concave lens arrangement composed of several concave surfaces. However, this does not preclude the possibility that a multitude of concave surfaces are arranged along only one of the X and Y axes.

[0081] Fig. Figure 17 schematically shows the optical path of the fluorescence light from the fluorescence film 13P in the case where the front lens 11P is used. Fig. In Figure 17, the imaging lens 20 is omitted from the illustration. The fluorescence light generated at a specific point on the fluorescence film 13P propagates through one of the convex surfaces that form the convex lens array and converges at a location on the image sensor 30 corresponding to the position of that specific point. Using the front lens 11P eliminates the need for the non-front lens 12. Using the front lens 11Q requires a separate optical system for imaging, such as a convex lens array positioned opposite the exit side of the front lens 11. In this practical example, the imaging device 1 does not have as high a spatial resolution as in the basic practical example, etc., but offers improved light convergence efficiency when using a large-area scintillator. << Fourth practical example >>

[0082] A fourth practical example is described. In the fourth practical example and in the practical examples described later, it is assumed that the front lens, the fluorescent film, and the lenticular substrate refer to the front lens, the fluorescent film, and the lenticular substrate that are presented in connection with one of the basic practical examples and the first to third practical examples described previously.

[0083] In imaging apparatus 1, the fluorescent film acts as a scintillator, while the lenticular substrate does not. This means that even if the incident rays 100 strike the lenticular substrate, no fluorescent light is generated within it. However, this does not preclude the possibility that faint fluorescent light is generated within the lenticular substrate when the incident rays 100 strike it.

[0084] In imaging device 1, the material of the lenticular substrate (i.e., the substance from which the lenticular substrate is formed) is the base material of the scintillator. While the above description deals with examples where LuAG is used as the material of the lenticular substrate, this is not intended to limit the material of the lenticular substrate; likewise, any of a variety of solid optical materials can be used as the material of the lenticular substrate. For example, any Y3Al5O can be used as the material of the lenticular substrate (i.e., as the solid optical material). 12 , Lu2SiO5, LuYSiO5, LuYSiO5, Gd3Ga5O 12 , CdWO4, Bi4Ge3O 12 , Gd2SiO5, Gd2O2S, Y2SiO5, Yb2SiO5, YAl1O3, LuAlO3, Gd3Al2Ga3O 12 , LaBr3, CeBr3, SrI2, GdAlO3, Cs2HfCl e , LiCaAlFe6 and Lu2O3 or a mixture of two or more of them may be used.

[0085] The fluorescent film is formed from a material obtained by adding a predetermined additive to the material of the lens-shaped substrate. The additive is not limited to the material mentioned above and can be any other material, as long as the fluorescent film acts as a scintillator; the type of additive can be determined by considering, for example, the required wavelength of the fluorescent light. The concentration of the additive in the fluorescent film can also be determined as required.

[0086] As described above, the base material and the additive for the scintillator can be modified in a variety of ways, and the fluorescent light produced in the fluorescent film can be any light classified as ultraviolet or visible light with a wavelength, for example, in the range of 200 nm to 700 nm.

[0087] If the lenticular substrate is made of LuAG and the fluorescent film is designed to emit fluorescent light with a wavelength λ of 305 nm, the lenticular substrate has a refractive index n = 2.03. This refractive index n naturally varies depending on the material and the fluorescence wavelength of the lenticular substrate, etc. << Fifth practical example >>

[0088] A fifth practical example is described. The sample irradiation rays and the incident rays 100 are radiation. Accordingly, the imaging device 1 can be called a radiation imaging device. Radiation includes gamma rays, X-rays, and ultraviolet rays (especially extreme ultraviolet rays). If the sample irradiation rays and the incident rays 100 are X-rays, the imaging device 1 can be used in X-ray imaging, X-ray CT, X-ray topography, X-ray imaging microscopes, etc. As in Fig. As shown in Figure 18, it is possible to design an X-ray imaging device comprising an X-ray generating device 2, which generates X-rays, and an imaging device 1. The X-rays generated by the X-ray generating device 2 are used as irradiation beams for the sample. << Sixth practical example >>

[0089] A sixth practical example is described. The above description generally assumes that the front lens consists of a lens-shaped substrate and a fluorescent film. However, the fluorescent film can also be considered as not being part of the front lens. That is, it can be understood as follows: the front lens is formed from a lens-shaped substrate, and a fluorescent film, which is not part of the front lens, is bonded to the lens-shaped substrate. << Seventh practical example >>

[0090] A seventh practical example is described. The imaging device 1, as a radiation imaging device, comprises an optical element for a radiation imaging device. The optical element for a radiation imaging device comprises at least one objective lens 10. The entire imaging optical system comprising the objective lens 10 can be understood as corresponding to the optical element for a radiation imaging device. The optical element for a radiation imaging device uses a scintillator (fluorescent film) to convert incident rays 100 with a comparatively short wavelength WL1 into fluorescent light with a comparatively long wavelength WL2 and uses the fluorescent light to project an image onto the imaging surface of an image sensor 30, enlarging or reducing it as needed. << Overview of the invention >>

[0091] The following is an overview of the present invention.

[0092] An optical element W1 for a radiation imaging device according to one aspect of the present invention is an optical element for a radiation imaging device comprising an objective lens (e.g. 10) that receives the incident radiation. A scintillator (e.g. 13), which receives the radiation in order to emit fluorescent light with a longer wavelength than the radiation, is provided as a single unit with the objective lens on the incidence side of the objective lens.

[0093] With this design, it is possible to greatly increase the numerical aperture of the objective lens compared to conventional dry and liquid-encapsulated objective lenses, thus capturing (imaging) incident rays with higher spatial resolution.

[0094] Specifically, for example, in the optical element W1 for a radiation imaging device, preferably a lens provided in the objective lens (e.g. 11), with which the scintillator is uniformly provided, is formed from such a solid optical material, so that the difference in the refractive index between the lens and the scintillator has a predetermined value or a lower value.

[0095] This helps to prevent scattering, refraction and reflection of the fluorescent light at the interface between the lens and the scintillator.

[0096] For another example, the optical element W1 for a radiation imaging device preferably comprises an imaging optical system that includes the objective lens and that images an image using the fluorescence light from the scintillator onto an imaging sensor (e.g. 30).

[0097] This setup makes it possible to obtain a high spatial resolution image from the image sensor.

[0098] In another example, the lens in the optical element W1 for a radiation imaging device preferably has a curved surface with a concave or convex surface on the side of the radiation incidence, and a curved image is generated on the curved surface using the fluorescence light from the scintillator. Preferably, the imaging optical system converts the curved image into an image on a flat surface and projects this image onto the image sensor.

[0099] In another example, the imaging optical system in the optical element W1 preferably comprises an objective lens in addition to the imaging lens, particularly for a radiation imaging device. Preferably, the imaging lens is arranged along the optical path from the scintillator, which generates the fluorescence light, to the image sensor in an adjustable position between the objective lens and the image sensor, such that by adjusting the position of the imaging lens, the image is focused onto the image sensor along with the fluorescence light.

[0100] For another example, in the optical element W1 for a radiation imaging device, the sample plane at the scintillator is preferably set such that the working distance of the objective lens has a zero or negative value.

[0101] A radiation imaging device W2 according to another aspect of the present invention comprises an image sensor and the optical element W1 for a radiation imaging device.

[0102] An X-ray imaging device W3 according to a further aspect of the present invention comprises an image sensor, the optical element W1 for a radiation imaging device and an X-ray generating device (e.g. 2) that generates X-rays as the radiation received by the optical element W1 for a radiation imaging device.

[0103] It should be noted that a setup in which a scintillator is integrated with the objective lens on its incident side corresponds to a state in which the medium between the lens and the scintillator is filled with the substance from which the lens is formed. That is, the above setup of the optical element W1 for a radiation imaging device can be understood as follows: in an optical element for a radiation imaging device comprising a scintillator that receives incident radiation to emit fluorescence light with a longer wavelength than the radiation, and an objective lens arranged in the stage downstream of the scintillator, the gap between the scintillator and the objective lens is filled with a solid optical material such that the difference in refractive index between the scintillator and the objective lens has a predetermined value (e.g.,0.1%) or a lower value. Such structures are also to be understood as belonging to the optical element W1 for a radiation imaging device. Reference symbol list 1 imaging device 10 objective lens 11, 11a-11g, 11A, 11P, 11Q front lens 12 Non-front lens 13, 13a-13g, 13A, 13P, 13Q fluorescent film 14, 14a-14g, 14A, 14P, 14Q lenticular substrate 20 Imaging lens 30 image sensor

Claims

[1] Optical element for a radiographic imaging device, comprising: a scintillator which receives radiation (100) to emit fluorescence light with a longer wavelength than the radiation (100) and which is uniformly formed on a radiation-incident substrate surface of a lens-shaped substrate (14) provided in an objective lens (10), wherein the scintillator is made of: a base material which is a solid optical material from which the lens-shaped substrate (14) is formed, and of a predetermined additive. [2] Optical element for a radiation imaging device according to claim 1, characterized by, that the lens-shaped substrate (14) is formed from a solid optical material with a refractive index whose difference to a refractive index of the scintillator, which is uniformly formed on the radiation-incident-side substrate surface of the lens-shaped substrate (14), is 0.1% or less. [3] Optical element for a radiographic imaging device, comprising: a scintillator which receives radiation (100) to emit fluorescence light with a longer wavelength than the radiation (100) and which is uniformly formed on a radiation-incident substrate surface of a lens-shaped substrate (14) provided in an objective lens (10), wherein a material of the lens-shaped substrate (14) and a base material of the scintillator are solid optical materials selected from the group consisting of Lu3AL5O 12 , Y3Al5O 12 , Lu2SiO5, LuYSiO5, LuYSiO5, Gd3Ga5O 12, CdWO4, Bi4Ge3O 12 , Gd2SiO5, Gd2O2S, Y2SiO5, Yb2SiO5, YAlO3, LuAlO3, Gd3Al2Ga3O 12 , LaBr3, CeBr3, SrI2, GdAlO3, Cs2HfCl6, LiCaAlF6 and Lu2O3 and a difference in a refractive index between the scintillator and the lenticular substrate (14) 0.1% or less. [4] Method for manufacturing an optical element for a radiation imaging device, comprising an objective lens (10) and receiving incident radiation (100), the method comprising: Preparing a raw substrate formed from a solid optical material, from which a lens is formed; Preparing a fluorescence plate (13S) from a material which uses as a base material a solid optical material which is substantially identical to the solid optical material of the raw substrate and wherein a predetermined additive has been added to the base material; Uniformly bonding the fluorescent plate (13S) to a first surface of the raw substrate and subsequently shaping a second surface of the raw substrate into the shape of a lens; and Manufacturing the optical element, as a front lens (11) of the objective lens (10), which is designed such that it has the fluorescent plate (13S) uniformly attached to one radiation-incidence side thereof. [5] Method for manufacturing an optical element for a radiation imaging device according to claim 4, characterized by , that the fluorescent plate (13S) is directly connected to the first surface of the raw substrate by solid-phase diffusion, and the second surface of the raw substrate is formed in the shape of a convex lens. [6] A radioimaging device comprising: a scintillator that receives radiation (100) with a predetermined wavelength in order to emit fluorescent light with a longer wavelength than the radiation (100); and a lens that is arranged in a subsequent stage to the scintillator, wherein a space between the scintillator and the lens is uniformly filled by a lens-forming substance having a refractive index whose difference to a refractive index of the scintillator is 0.1% or less. [7] A radioimaging device comprising: an image sensor (30); and the optical element for a radiation imaging device according to one of claims 1 to 3. [8] An X-ray imaging facility comprising: an image sensor (30); the optical element for a radiation imaging device according to one of claims 1 to 3; and an x-ray generating device that produces x-rays as the radiation received by the optical element for a radioimaging device.

Images