Micro-imaging system of radiation-damage-resistant thick X-ray scintillator

Abstract

The invention discloses a radiation-damage-resistant microscopic imaging system of a thick X-ray scintillator, which is characterized by comprising the scintillator used for absorbing X-rays penetrating through a sample and converting the X-rays into visible light; the reflective microscope objective is used for amplifying and imaging the luminous pattern of the scintillator to obtain primary imaging information of the sample and focusing the primary imaging information to the light field imaging module through an imaging lens; the light field imaging module is used for extracting light field information from the primary imaging information by using a light field imaging method to obtain secondary imaging of the sample and inputting the secondary imaging into the data processing module; and the data processing module is used for extracting light field information from the secondary image, resolving the extracted light field information through a light field reconstruction algorithm, and reconstructing to obtain a high-resolution image of the sample. According to the invention, the problems of high-efficiency fluorescence conversion coefficient and high spatial resolution of the high-energy X-ray are solved, and the light conversion efficiency of the high-energy X-ray is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of X-ray imaging, and relates to a microscopic imaging system of a thick X-ray scintillator resistant to radiation damage. Background Art

[0002] X-rays have strong penetrating power for matter. X-ray penetrating imaging combined with wavelength conversion and optical microscopy systems is a powerful tool for high-resolution observation of the internal structure of opaque objects.

[0003] In order to obtain high spatial resolution beyond visible light, a better method is to directly image and amplify the transmitted X-ray beam through X-ray optical devices and image it by an X-ray area detector. It is necessary to amplify the X-ray beam passing through the sample, usually in the following ways:

[0004] 1) X-ray lens magnification imaging method (imaging magnification)

[0005] Similar to traditional microscopes, Figure 1 As shown, an X-ray lens (zone plate) is used to magnify the light beam and make an image, and an X-ray detector is used to record the image.

[0006] The problem is that the optical devices that can be used for high-energy X-rays have poor performance, so high-energy X-rays cannot be used for illumination, which affects the penetration of X-rays and can only be used for materials with weaker or thinner absorption.

[0007] 2) Point source spherical wave amplification imaging

[0008] This method does not require a microscope magnification device. It uses a spherical wave emitted by a point light source to illuminate the sample. Within the geometric propagation distance range, the closer the sample is to the point light source and the farther the imaging detector is from the sample, the greater the imaging magnification. However, the luminous flux of a point light source is often not easy to increase, so high-magnification imaging is also difficult.

[0009] 3) Indirect amplification method of wavelength conversion.

[0010] If the illumination X-ray is strong enough, the X-ray projection image can be further magnified by using a scintillator to convert the X-ray into visible light. This technology requires the use of a thin scintillator to convert the X-ray projection into fluorescence in the visible light band, because the visible light microscope lens has a depth of field requirement, and a thick scintillator will make the image blurred.

[0011] In terms of optical path layout, Figure 2As shown in the figure, there are two configuration modes of the microscope objective lens, online and offline. The scintillator converts X-rays into visible light and emits it towards the full solid angle. The former directly enters the microscope imaging lens for magnification and imaging, while the latter visible light enters the microscope imaging lens through the deflection mirror. In these two schemes, in order to prevent the detector from being irradiated by direct X-rays, the visible light image detector is generally configured to deviate from the incident X-ray optical axis.

[0012] For online microscopic imaging systems, since strong X-rays will also irradiate the microscope head, its glass material will change color after being irradiated, affecting the transmittance of visible light. For offline microscopic imaging systems, the objective lens is far away from the scintillator, making it difficult to achieve a high-magnification and compact imaging system.

[0013] Scintillator materials less than ten microns thick have greatly limited absorption and conversion capabilities for higher energy X-rays. The fatal weakness of the scintillator wavelength conversion-microscope imaging method is that the wavelength conversion and light receiving efficiency are too low (less than 1%), and the resolution is limited by visible light, and it is impossible to exceed the resolution specified by the scintillator emission wavelength. Not only does the characteristics of the X-ray probe not make good use of, but the excessive X-ray input will also cause radiation damage to the sample.

[0014] The reason for using thin scintillators is to match the depth of field (focal depth) of the microscope. However, the absorption wavelength conversion ability of scintillator materials less than ten microns thick for higher energy X-rays is greatly limited. That is, although thick scintillators have better absorption efficiency for X-rays, the detection efficiency of detectors is also higher; however, the aberration terms and focal depth terms that affect the spatial resolution of the optical system are related to the thickness of the scintillator. Because the scintillator is too thick, there will be aberrations and focal depth, and the imaging is not in the same plane, which is a blurred 2D image. Summary of the invention

[0015] Considering the characteristics of X-ray scintillators and microscopic optical systems, in X-ray imaging technology, high-efficiency X-ray-fluorescence conversion and high spatial resolution are two aspects that need to be balanced. The present invention provides a microscopic imaging system with a thick X-ray scintillator that is resistant to radiation damage, aiming to solve the dilemma of the contradiction between improving the low X-ray absorption efficiency by thickening the scintillator and the shallower focal depth of high-resolution microscopic imaging. At the same time, since general microscopic imaging lenses use glass materials, the lenses will be damaged by radiation after strong X-rays are incident. The present invention uses a reflective microscope lens, which can better solve this problem.

[0016] The present invention utilizes a reflective microscope lens to optimize the online microscopic imaging system, thereby simplifying the entire structure while avoiding the problem of radiation damage to lens materials. At the same time, a detector for monitoring the X-ray beam can be embedded in the optical axis.

[0017] The present invention utilizes a light field imaging method to achieve high spatial resolution imaging of a thick scintillator, improve the light conversion efficiency of high-energy X-rays, and solve the difficulty of both high-efficiency fluorescence conversion coefficient and high spatial resolution of high-energy X-rays.

[0018] The technical solution of the present invention is:

[0019] A microscopic imaging system of a thick X-ray scintillator resistant to radiation damage, characterized in that it comprises

[0020] Scintillator, which absorbs the X-rays that pass through the sample and converts them into visible light;

[0021] A reflective microscope objective lens is used to magnify and image the luminous pattern of the scintillator, obtain primary imaging information of the sample and focus it to the light field imaging module through an imaging lens;

[0022] A light field imaging module, used to extract light field information from the primary imaging information using a light field imaging method, obtain a secondary image of the sample and input it into a data processing module;

[0023] The data processing module is used to extract light field information from the secondary imaging, and then to solve the extracted light field information through a light field reconstruction algorithm to reconstruct a high-resolution image of the sample.

[0024] Furthermore, the reflective microscope objective lens includes a first reflector and a second reflector, and the scintillator is located on the focal plane of the second reflector; the second reflector is used to receive the visible light converted by the scintillator and make it incident on the first reflector, and the first reflector is used to convert the incident light into a parallel light beam that is incident on the imaging lens.

[0025] Furthermore, the light field imaging module includes a microlens array, a relay lens and an image sensor; wherein the microlens array is used to obtain the light field distribution of the scintillator, and the relay lens is used to image the light field distribution on the focal plane of the microlens array onto the image sensor to obtain the secondary imaging.

[0026] The advantages of the present invention are as follows:

[0027] The present invention utilizes a light field imaging method. Since light field imaging is 4D imaging, the focal depth of the microscope can be ignored and a thick scintillator can be used to achieve efficient detection of high-energy X-rays.

[0028] The present invention utilizes the characteristic of reflective lens that it does not need to transmit light, and can prevent the transparency of the lens from being damaged by radiation when placed in the light path; thereby making the entire system compact and facilitating the production of large-diameter lenses (in principle, reflective lenses can be made larger).

[0029] The present invention uses a reflective microscope lens and light field imaging to use thickened scintillators, improves the low absorption rate of x-rays, and uses light field imaging to not care about the depth of focus of the microscope, making the imaging clearer and solving the above-mentioned dilemma. The advantage of this system is that an x-ray monitoring instrument can be embedded in the optical path to monitor the intensity and position of the incident light. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of lens magnification imaging method.

[0031] Figure 2 Schematic diagram of the indirect amplification method of wavelength conversion;

[0032] (a) Online microscopic magnification imaging system, (b) offline microscopic imaging magnification system.

[0033] Figure 3 It is a schematic diagram of the structure of the X-ray illumination light field microscope of the present invention.

[0034] Figure 4 This is the structural diagram of the light field imaging module.

[0035] Figure 5 This is a structural diagram of a reflective microscope objective.

[0036] Figure 6 Schematic diagram of commonly used X-ray beam monitoring methods;

[0037] (a) The scintillator is placed at an angle, (b) a deflecting reflector is used. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention but not to limit the scope of the present invention.

[0039] The system is Figure 3 As shown, the main components include:

[0040] Scintillator absorbs X-rays passing through the sample and converts them into visible light, which is detected by conventional light field imaging modules. Its luminous intensity is proportional to the incident X-rays, and the conversion efficiency is proportional to the scintillator thickness by the integral of exp(-μt). Where μ is the linear absorption coefficient of the scintillator for X-rays, and t is the thickness.

[0041] A reflective microscope objective lens is used to magnify and image the luminous pattern of the scintillator.

[0042] The imaging lens acts as a transition lens to converge the image to the light field imaging module.

[0043] The light field imaging module includes an optical lens (group) for performing secondary imaging on the output image of the microscope objective lens, and uses a light field imaging method to extract light field information from the output image to obtain a secondary imaging of the sample.

[0044] The data processing module extracts light field information from the signal collected by the light field imaging module, and obtains a high-resolution image of scintillator luminescence-X-ray imaging through data processing.

[0045] The specific technical details include the following:

[0046] The optimized design parameters of the scintillator include luminous efficiency and thickness. The former determines the conversion efficiency and luminous direction of visible light emitted after absorbing X-rays, and the latter determines the total absorption of X-rays.

[0047] The reflective microscope objective lens is based on the traditional Schwarzschild design, and its structure is as follows: Figure 5 As shown, after correction of third-order spherical aberration, coma and astigmatism, higher-order aberrations can be neglected, resulting in high resolution with diffraction-limited performance. Depending on the main emission wavelength of the scintillator, different coatings can be selected to improve the efficiency of the reflector. X-rays are absorbed by the block material on the back of the reflector and cannot pass through the microscope objective. Reflective microscope objectives have the following characteristics:

[0048] a. Longer working distance relative to magnification;

[0049] b. Large numerical aperture can improve light gathering ability.

[0050] A reflective microscope objective lens + scintillator is used to detect the position of the incident light; an X-ray photoelectric detector is installed in front of the first reflector to monitor the changes in the intensity and position of the incident X-ray light. The present invention uses a microscope objective lens and light field imaging to use a scintillator with high luminous efficiency and a thicker thickness, without worrying about damage to the instrument due to the high luminous efficiency; when using a thick scintillator, there is no need to worry about the problem of low scintillator absorption efficiency caused by the thin scintillator and the penetration of x-rays into the scintillator. At the same time, the light field imaging technology will not cause blurred imaging due to the high thickness of the scintillator not meeting the imaging depth requirement.

[0051] The light field imaging module is used to re-image the primary imaging of the microscope objective lens. The structure of the light field imaging module is as follows: Figure 4 As shown, the light field can be imaged using a tube lens and a microlens array, thereby obtaining the light field distribution of the scintillator, that is, obtaining the angular distribution and spatial distribution information of the luminous intensity from the scintillator, solving the problem that the imaging focal depth of traditional microscopes is very small and thick scintillators cannot be used. The relay lens images the light field distribution on the focal plane of the microlens array onto the image sensor.

[0052] The data processing module is used to obtain the intensity distribution of the scintillator on different sampling planes through the light field reconstruction algorithm based on the light field distribution information measured by the image sensor, and finally obtain the light field distribution of the incident X-ray based on the path accumulation. Light field imaging can solve the imaging depth problem, solve the imaging blur, and eliminate the diffusion effect of luminescence; because the diffusion effect of luminescence is eliminated, a high spatial resolution image of the luminescence from the thick scintillator can be obtained, and then the incident X-ray distribution information with high spatial resolution can be obtained.

[0053] The system also has the advantage of being able to serve as a high-precision X-ray monitoring instrument, simultaneously monitoring the intensity and position of incident light. Figure 6 It is a commonly used method for X-ray beam monitoring. Figure 6 (a) The scintillator is placed at an angle, which causes the X-ray displacement to have different effects. Figure 6 (b) A deflecting mirror is needed to separate the fluorescence from the X-ray optical path. A microscope lens + fluorescent body is used to detect the position of the incident light; Figure 5 An X-ray photoelectric detector is installed in front of the reflector 1 to detect the intensity change of the incident X-ray light. Based on this, high-precision morphology distribution and intensity change can be obtained at the same time. Advantages: Compact structure.

[0054] Although the specific embodiments of the present invention are disclosed for the purpose of illustration, the purpose is to help understand the content of the present invention and implement it accordingly, those skilled in the art will understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the best embodiment, and the scope of the present invention is subject to the scope defined in the claims.

Claims

1. A microscopic imaging system of a thick X-ray scintillator resistant to radiation damage, characterized in that: include Scintillator, which absorbs the X-rays that pass through the sample and converts them into visible light; A reflective microscope objective lens is used to magnify and image the luminous pattern of the scintillator, obtain primary imaging information of the sample and focus it to the light field imaging module through an imaging lens; A light field imaging module, used to extract light field information from the primary imaging information using a light field imaging method, obtain a secondary image of the sample and input it into a data processing module; The data processing module is used to extract light field information from the secondary imaging, and then to solve the extracted light field information through a light field reconstruction algorithm to reconstruct a high-resolution image of the sample.

2. The microscopic imaging system according to claim 1, characterized in that: The reflective microscope objective lens includes a first reflector and a second reflector, and the scintillator is located on the focal plane of the second reflector; the second reflector is used to receive the visible light converted by the scintillator and make it incident on the first reflector, and the first reflector is used to convert the incident light into a parallel light beam and make it incident on the imaging lens.

3. The microscopic imaging system according to claim 1 or 2, characterized in that: The light field imaging module includes a microlens array, a relay lens and an image sensor; wherein the microlens array is used to obtain the light field distribution of the scintillator, and the relay lens is used to image the light field distribution on the focal plane of the microlens array onto the image sensor to obtain the secondary imaging.

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