Superlens, endoscope and application thereof

Abstract

This invention relates to a superlens, an endoscope, and their applications. The superlens operates with a wavelength range of 780nm-850nm. Before surgery, patients are injected with a clinically approved indocyanine green solution, which acts as a fluorescent material entering the gastrointestinal mucosa. For the superlens of this invention, with its operating wavelength range of 780nm-850nm, after the 780nm laser output from the fiber bundle is focused onto the gastrointestinal mucosa by the superlens, the indocyanine green emits a fluorescence signal with a peak wavelength of 830nm and a receiving bandwidth of 810nm-850nm. This fluorescence signal returns to the fiber bundle via the superlens and is transmitted to an image processor for imaging. The fluorescence imaging mode employed by the endoscope of this invention enables high-resolution, high-contrast imaging of the gastrointestinal mucosa, thereby allowing for faster and more accurate identification of the location and nature of early-stage and precancerous lesions in the gastrointestinal mucosa during gastroscopy and colonoscopy, improving biopsy accuracy and efficiency while reducing the workload of biopsy procedures.

Description

Technical Field

[0001] This invention relates to the field of fluorescence endoscopic imaging, and in particular to a superlens, an endoscope, and their applications. Background Technology

[0002] After a biopsy of a lesion is sent to the pathology department, it undergoes a series of tedious steps, including tissue dehydration, paraffin embedding, staining, sectioning, and microscopic observation, taking about a week to obtain the "gold standard" test report. This process is time-consuming and labor-intensive, and the results can be biased due to errors in biopsy sampling. In particular, gastrointestinal tissue biopsies often involve multiple polyps and other lesions, making the workload especially enormous.

[0003] To address these issues, obtaining images of internal tissues via endoscopy before biopsy sampling allows for the determination of the location and nature of suspected lesions. This effectively reduces the workload of biopsy sampling and improves efficiency and accuracy. It's easy to understand that the extent to which the number of biopsies can be reduced, and the degree to which biopsy sampling accuracy can be improved, heavily depends on the imaging capabilities and quality of the endoscope.

[0004] While existing clinically used white-light or narrow-band light endoscopes can meet most examination needs in terms of image quality, they can only observe macroscopic lesions and cannot achieve pathological-level microscopic imaging. Furthermore, compared to other body tissues, they suffer from insufficient contrast when imaging the gastrointestinal mucosa. However, the most concerning early-stage cancers and precancerous lesions typically occur in the gastrointestinal mucosa. Therefore, current endoscopes have limited ability to identify the nature of digestive tract lesions, cannot effectively reduce the amount of tissue biopsies, and cannot effectively improve sampling accuracy and efficiency. Summary of the Invention

[0005] Therefore, it is necessary to provide a superlens, endoscope, and its application to address the problem of insufficient imaging capability of existing endoscopes for gastrointestinal mucosal tissue pathology.

[0006] The technical solution provided by this invention is as follows:

[0007] A superlens with an operating wavelength range of 780nm-850nm.

[0008] The superlens of the present invention includes a substrate and a first nanopillar array, wherein the first nanopillar array is located on one side of the substrate, and the material of the first nanopillar array is TiO2, Si3N4 or Si.

[0009] The substrate described in this invention is made of Si or SiO2.

[0010] The superlens of the present invention further includes a second nanopillar array, which is located on the side of the substrate opposite to the first nanopillar array, and the material of the second nanopillar array is TiO2, Si3N4 or Si.

[0011] The ratio of the object-side NA and the image-side NA of the superlens described in this invention is 1-2.

[0012] In the first nanopillar array of the present invention, the cross-sectional shape of the nanopillars is circular, annular, square, or square annular.

[0013] An endoscope includes an optical fiber bundle and the aforementioned superlens, wherein the end of the optical fiber bundle is disposed at a second nanopillar array.

[0014] The output wavelength of the optical fiber bundle described in this invention is 780nm.

[0015] The image area (NA) of the superlens described in this invention is matched with the NA of the fiber bundle.

[0016] An application of endoscopy in gastrointestinal mucosal imaging.

[0017] The beneficial effects of this invention are as follows:

[0018] Before the procedure, patients are injected with a clinically approved indocyanine green (ICG) solution, which acts as a fluorescent material entering the gastrointestinal mucosa. For the superlens of this invention, whose operating wavelength covers 780nm-850nm, the 780nm laser output from the fiber bundle is focused onto the gastrointestinal mucosa by the superlens. The indocyanine green then emits a fluorescence signal with a peak wavelength of 830nm and a receiving bandwidth of 810nm-850nm. This fluorescence signal returns to the fiber bundle via the superlens and is transmitted to the image processor for imaging.

[0019] The fluorescence imaging mode used in the endoscope of this invention can achieve high-resolution, high-contrast imaging of the gastrointestinal mucosa, thereby enabling faster and more accurate identification of the location and nature of early cancerous lesions and precancerous lesions in the gastrointestinal mucosa during gastroscopy and colonoscopy, improving the accuracy and efficiency of biopsy and reducing the workload of biopsy.

[0020] The superlens of this invention, due to its planar and aberration-free characteristics, enables the endoscope to greatly reduce the lens size while ensuring diffraction-limited focusing capability, and also reduces assembly difficulty. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the main view structure of the endoscope in Embodiments 1 and 2 of the present invention;

[0022] Figure 2This is the target phase / phase dispersion distribution map at the second nanopillar array in Embodiment 2 of the present invention;

[0023] Figure 3 This is the target phase / phase dispersion distribution map at the first nanopillar array in Embodiment 2 of the present invention;

[0024] Figure 4 This is the target phase and fitted phase diagram of the second nanopillar array in Embodiment 2 of the present invention;

[0025] Figure 5 This is the target phase and fitted phase diagram of the first nanopillar array in Embodiment 2 of the present invention;

[0026] Figure 6 This is a diagram showing the target phase dispersion and the fitted phase dispersion distribution of the second nanopillar array in Embodiment 2 of the present invention.

[0027] Figure 7 This is a diagram showing the target phase dispersion and the fitted phase dispersion distribution of the first nanopillar array in Embodiment 2 of the present invention.

[0028] Figure 8 This is the XZ-plane electric field distribution of the second nanopillar array at wavelengths of 780 nm and 830 nm in Embodiment 2 of the present invention;

[0029] Figure 9 This is the XZ-plane electric field distribution of the first nanopillar array at wavelengths of 780 nm and 830 nm in Embodiment 2 of the present invention;

[0030] Figure 10 This is the XY plane electric field distribution of the second nanopillar array at wavelengths of 780 nm and 830 nm in Embodiment 2 of the present invention;

[0031] Figure 11 This shows the XY plane electric field distribution of the first nanopillar array at wavelengths of 780nm and 830nm in Embodiment 2 of the present invention.

[0032] Figure label:

[0033] 1. Substrate; 2. First nanopillar array; 3. Second nanopillar array; 4. Fiber bundle. Detailed Implementation

[0034] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] To address the issue of insufficient imaging capability of existing endoscopes for the gastrointestinal mucosa, as pointed out in the background section, the inventors have discovered that the reason lies in the fact that existing endoscopic imaging is based on the principle of macroscopic imaging using reflected light. Illumination light is directed at the gastrointestinal mucosa, and imaging is then performed based on the light reflected from the mucosa. This only allows for the observation of macroscopic lesions, and its resolution is insufficient for observing the microscopic structure of the mucosal layer. Furthermore, due to the near-transparent nature of the gastrointestinal mucosa, the final image contrast is insufficient. Based on this research, the present invention provides subsequent embodiments to solve the problem of insufficient imaging quality of the gastrointestinal mucosa by existing endoscopes.

[0036] Example 1:

[0037] This embodiment provides an endoscope that images the gastrointestinal mucosa using fluorescence. Specifically, the endoscope in this embodiment includes an optical fiber bundle 4 and a superlens, with the end of the optical fiber bundle 4 disposed on one side of the superlens.

[0038] Before the procedure, patients are injected with a clinically approved indocyanine green (ICG) solution. ICG acts as a fluorescent material entering the gastrointestinal mucosa. The output wavelength of the fiber bundle 4 is 780 nm. After the output light is focused onto the gastrointestinal mucosa by a superlens, the ICG emits a fluorescence signal with a peak wavelength of 830 nm and a receiving bandwidth of 810 nm-850 nm. The fluorescence signal returns to the fiber bundle 4 via the superlens and is transmitted to the image processor for imaging. Therefore, in this embodiment, as long as the operating wavelength of the superlens covers 780 nm-850 nm, normal imaging of the gastrointestinal mucosa can be guaranteed. The fluorescence imaging mode used in this embodiment of the endoscope not only enables high-resolution imaging of the gastrointestinal mucosa, but also overcomes the shortcomings of existing endoscopes based on reflected light imaging. This overcomes the high transparency of the gastrointestinal mucosa during the imaging process, achieving high-contrast imaging of the gastrointestinal mucosa. As a result, during gastroscopy and colonoscopy, the location and nature of early cancerous lesions and precancerous lesions on the gastrointestinal mucosa can be identified more quickly and accurately, improving the accuracy and efficiency of biopsy and reducing the workload of biopsy.

[0039] The end of the fiber bundle 4 is positioned on the image side of the superlens. To further improve the imaging quality of the gastrointestinal mucosa, the numerical aperture (NA) of the fiber bundle 4 must match the image-side NA of the superlens; generally, the image-side NA of the superlens is equal to the NA of the fiber bundle 4. The image-side NA of the superlens is typically between 0.2 and 0.4, so that the fluorescence signal collected by the superlens can be efficiently coupled into the fiber bundle 4 and transmitted to the image processing terminal for signal processing. Furthermore, during the imaging process within the image processing terminal, the 780nm light is filtered to further enhance the imaging contrast of the gastrointestinal mucosa.

[0040] Considering that the imaging object is the gastrointestinal mucosa, the superlens needs to meet the requirements of cell-level resolution in order to achieve cell-level observation of the gastrointestinal mucosa. Therefore, the object-side NA of the superlens is between 0.4 and 0.8, and the overall effective resolution after matching with the fiber bundle is about 1.55μm-2.2μm.

[0041] Depending on the actual application requirements, the ratio of the object-side NA and the image-side NA of the superlens can be 1-2.

[0042] The diameter of the superlens is generally no more than the aperture of the fiber bundle 4, and the diameter of the superlens is generally less than 1mm.

[0043] The object-side working distance of a superlens is generally between 0μm and 300μm, which meets the requirements for depth observation of the gastrointestinal mucosa.

[0044] To enable the superlens to operate across a wavelength range of 780nm-850nm, this embodiment first provides a specific structure for the superlens, which effectively eliminates chromatic aberration. See also... Figure 1 The superlens comprises a substrate 1, a first nanopillar array 2, and a second nanopillar array 3, which are respectively disposed on opposite sides of the substrate 1. The end of the fiber bundle 4 is disposed at the second nanopillar array 3. Based on this, the operating wavelength of the superlens is determined by the materials of the substrate 1, the first nanopillar array 2, and the second nanopillar array 3.

[0045] The substrate 1 is made of Si or SiO2. In this embodiment, SiO2 can be used for the substrate 1 for ease of processing and assembly. Therefore, in this embodiment, when the superlens includes the substrate 1, the first nanopillar array 2, and the second nanopillar array 3, the final operating wavelength of the superlens is determined by the materials of the first nanopillar array 2 and the second nanopillar array 3. To ensure that the operating wavelength of the superlens can cover 780nm-850nm, the material of the first nanopillar array 2 is TiO2, Si3N4, or Si, and the material of the second nanopillar array 3 is also TiO2, Si3N4, or Si. It is worth noting that the first nanopillar array 2 and the second nanopillar array 3 can have the same material or different materials.

[0046] For example, when both the first nanopillar array 2 and the second nanopillar array 3 are made of TiO2, the actual operating wavelength of the superlens in this embodiment is 400nm-1000nm, which can effectively cover 780nm-850nm. As another example, when both the first nanopillar array 2 and the second nanopillar array 3 are made of Si3N4, the actual operating wavelength of the superlens is 600nm-1600nm, which also effectively covers 780nm-850nm.

[0047] It is easy to understand that the wavelength range of 780nm-850nm can be considered the ideal operating wavelength range of the superlens in this embodiment. The ideal operating wavelength range falls within the actual operating wavelength range of the superlens. The less the actual operating wavelength range of the superlens is outside the ideal operating wavelength range, the better the achromatic focusing performance of the light on the gastrointestinal mucosa, and the higher the image quality.

[0048] The superlens of this embodiment, due to its planar and aberration-free characteristics, enables the endoscope of this embodiment to greatly reduce the lens size while ensuring diffraction-limited focusing capability, and also reduces assembly difficulty.

[0049] Superlenses primarily rely on artificially designed subwavelength nanostructures to control parameters such as the amplitude, phase, and polarization state of light waves, enabling high degrees of freedom in shaping the incident wavefront and customizing the outgoing light field distribution. This is based on the generalized Snell's law. Superlenses achieve focusing by bending light through changes in phase gradient, which allows them to fundamentally eliminate spherical aberration, unlike glass lenses which require stacking lenses to reduce spherical aberration, thus simplifying the optical system. i n t θ i θ t Let represent the refractive index of the incident medium, the refractive index of the transmitting medium, the angle of incidence, and the angle of refraction, respectively, and λ0 be the wavelength of the incident light. The phase distribution of the superlens is given, and x represents the coordinates of the distance from the center.

[0050] right By integrating and defining the phase as 0 at the lens edge, the phase distribution formula of the superlens is obtained. Where w is the incident light angular frequency, c is the speed of light in a vacuum, R is the lens radius, and f is the focal length. Let be the phase modulation amount at a distance r from the center of the lens. In imaging applications, the incident light wavefront is converted into a converging spherical wavefront using the phase distribution formula of a superlens to achieve diffraction-limited focusing performance. The required phase modulation amount at each position can be achieved by selecting nanostructure units with appropriate height, lateral feature size, and lattice constant.

[0051] As shown in the phase distribution formula of a superlens, the target phase is linearly correlated with the incident light angular frequency. When the operating wavelength is a narrow band of light with a certain width, achromatic design needs to be considered if different wavelengths need to be focused at the same focal point. Assuming the minimum wavelength angular frequency of the operating wavelength is w1 and the maximum wavelength angular frequency is w2, substituting them into the superlens phase distribution formula and subtracting them, we obtain the phase dispersion formula. in This represents the phase dispersion.

[0052] The specific structural design process of the first nanopillar array 2 and the second nanopillar array 3 in this embodiment includes the following steps:

[0053] Step S1: In the finite element time-domain difference simulation software, the light source bandwidth is set to 780nm-850nm, and a TiO2 columnar nanostructure model with SiO2 as the substrate is constructed. The lattice constant, height, and cross-sectional shape of the nanostructure are set as variables, and a parameter scan is performed to obtain the scan result matrix. Using transmittance greater than 90% and phase modulation satisfying 0-2π as screening conditions, the lattice constant of the structural unit is determined to be 440nm, and the height to be 1.5μm.

[0054] Step S2: In the finite element time-domain difference simulation software, construct nanopillar models with circular, annular, square, and square ring cross-sections, respectively. The light source bandwidth, lattice constant, and height are consistent with those in Step S1. When the nanopillar cross-sections are circular, annular, square, and square rings, they are insensitive to incident light polarization. Set the transverse characteristic parameters as variables, ensuring their variation range is less than the lattice constant. Perform a parameter scan to obtain phase / phase dispersion libraries for the four models. Using linear fitting, remove data points with low transmittance and non-linear phase-frequency relationships from the library to obtain a new phase / phase dispersion library file for subsequent use.

[0055] Step S3: Select 780nm as the reference wavelength, set the diameter of the superlens and the aperture of the fiber bundle 4 to be the same, set the image-side NA of the superlens and the NA of the fiber bundle 4 to be the same, and set an appropriate magnification for the object-side NA and image-side NA of the superlens according to the actual magnification requirements, for example, 1-2 times. Generate the required reference wavelength phase distribution and narrowband phase dispersion distribution for the superlens, and based on the required reference wavelength phase distribution and narrowband phase dispersion distribution, filter from the phase / phase dispersion library obtained in step S2, and record the selected nanostructure characteristic parameters.

[0056] Step S4: Using the nanostructure feature parameters recorded in Step S3, construct a complete superlens in finite element time-domain difference simulation software and run the simulation to obtain the far-field distribution. Furthermore, to perform simulations of larger aperture superlenses and save computational resources, near-field data can be extracted from the scanning results of Step S2 based on the nanostructure features at various locations of the obtained superlens. The focused far-field distribution can then be obtained using near-field stitching and far-field projection.

[0057] Example 2:

[0058] See Figure 1 This embodiment also provides an endoscope, including an optical fiber bundle 4 and a superlens, with the end of the optical fiber bundle 4 disposed on one side of the superlens. The superlens includes a substrate 1, a first nanopillar array 2, and a second nanopillar array 3, which are respectively disposed on opposite sides of the substrate 1. The end of the optical fiber bundle 4 is disposed at the second nanopillar array 3. The superlens in this embodiment is designed using the design method described in Embodiment 1.

[0059] In this embodiment, the NA of fiber bundle 4 is 0.25, and the diameter of fiber bundle 4 is 40 μm. The image-side diameter of the superlens is 40 μm, the focal length is 80 μm, and the numerical aperture is 0.25. The object-side diameter of the superlens is 20 μm, the focal length is 20 μm, and the numerical aperture is 0.5. The height of the nanopillars in the first nanopillar array 2 and the second nanopillar array 3 is 1.5 μm, and the lattice constant is 440 nm.

[0060] In Matlab, phase distributions with a reference wavelength of 780 nm and phase dispersion distributions with a working wavelength range of 780 nm-850 nm were generated. Databases were constructed for nanopillars with four cross-sectional shapes: circular, toroidal, square, and square toroidal, each centered on phase / phase dispersion. See [link to Matlab documentation]. Figure 2 and Figure 3 Each data point corresponds to a nanostructure unit. The phase / phase dispersion data obtained by the parameter scanning can well cover and fit the phase / phase dispersion data required for theoretical calculation, proving that the four cross-sectional shapes of nanopillars—circular, annular, square, and square annular—can well meet the achromatic design requirements.

[0061] See Figures 4-7 For the first nanopillar array 2 and the second nanopillar array 3, the extracted phase / phase dispersion data has a good fitting effect when fitted to the phase / phase dispersion data required by the theory.

[0062] See Figures 8-11 The superlens in this embodiment can achieve diffraction-limited focusing capability, with a focus drift of 2.8% at 780nm and a focus drift of 2% at the fluorescence peak wavelength of 830nm.

[0063] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0064] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0065] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0066] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0067] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A superlens, characterized in that, The operating wavelength covers 780nm-850nm.

2. The superlens according to claim 1, characterized in that, The superlens includes a substrate (1) and a first nanopillar array (2), the first nanopillar array (2) being located on one side of the substrate (1), and the material of the first nanopillar array (2) being TiO2, Si3N4 or Si.

3. The superlens according to claim 2, characterized in that, The substrate (1) is made of Si or SiO2.

4. The superlens according to claim 3, characterized in that, The superlens also includes a second nanopillar array (3), which is located on the side of the substrate (1) away from the first nanopillar array (2). The material of the second nanopillar array (3) is TiO2, Si3N4 or Si.

5. The superlens according to claim 4, characterized in that, The ratio of the object-side NA to the image-side NA of the superlens is 1-2.

6. The superlens according to claim 4, characterized in that, The cross-sectional shape of the nanopillars in the first nanopillar array (2) is circular, annular, square, or square annular.

7. An endoscope, characterized in that, It includes an optical fiber bundle (4) and a superlens as described in claim 4, 5 or 6, wherein the end of the optical fiber bundle (4) is disposed at the second nanopillar array (3).

8. The endoscope according to claim 7, characterized in that, The output wavelength of the fiber bundle (4) is 780nm.

9. The endoscope according to claim 7, characterized in that, The image area NA of the superlens is matched with the NA of the fiber bundle (4).

10. An application of the endoscope as described in claim 7 in gastrointestinal mucosal imaging.

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