Large-cross-section, high-resolution flexible optical fiber imaging bundle and its preparation method and application

Abstract

The present invention relates to a large-cross-section, high-resolution flexible fiber optic imaging bundle, its preparation method, and its application. The flexible fiber optic imaging bundle comprises a plurality of flexible units, each of which comprises a densely packed array of imaging units, each of which comprises a glass fiber having a plurality of circular through-holes. The flexible fiber optic imaging bundle of the present invention has no cladding-based orderly isolation between the unit filaments, allowing crosstalk of optical signals transmitted between the unit filaments. The unit filament diameters can be as fine as submicron or even smaller. Compared with conventional flexible fiber optic imaging bundles, splicing interface traces can be effectively eliminated through bonding, fusion, and other processes, enabling the preparation of a large-cross-section, high-resolution flexible fiber optic imaging bundle.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber technology, in particular to a flexible optical fiber image transmission bundle with a large cross-section and high resolution, and a preparation method and application thereof, belonging to the field of optical fiber image transmission bundles. Background Art

[0002] Flexible optical fibers and their fiber optic image bundles are bendable, passive optical components. As a crucial component of fiber optic endoscope systems, they directly impact the performance and detection accuracy of fiber optic endoscopes. They are primarily used for image transmission, coupling, and display, and are key components of fiber optic endoscopes. Compared to traditional optical imaging components, they offer flexibility and flexibility, allowing for greater freedom of use. They enable real-time image acquisition, transmission, and processing within complex spatial structures, enabling observation of inaccessible cavities, narrow slits, or high-risk environments using fiber optic endoscopes, effectively expanding the scope of human observation. For example, fiber optic endoscope systems, bendable aiming systems, bendable periscope systems, and bendable radiation imaging systems based on flexible fiber optic image bundles have widespread applications in industrial manufacturing, medical diagnosis, aerospace, military defense, and other fields. However, flexible fiber optic image bundles still face technical difficulties in producing large cross-sections and high resolutions, severely limiting their development and application in related fields. There is an urgent need to address this difficulty in producing flexible fiber optic image bundles with large cross-sections and high resolutions.

[0003] Currently, there are two main methods for preparing flexible fiber optic image bundles: the stacking method and the acid dissolution method. The stacking method uses a direct "single-filament direct layout" process to arrange optical fibers into a specific shape and size to form a fiber bundle. This method is characterized by its simplicity and ability to produce large cross-sections. However, it suffers from the disadvantages of coarse unit fiber diameters, poor flexibility, and low resolution. When the unit fiber diameter is less than 50μm, the difficulty of fiber optic image bundle layout increases dramatically, and structural defects such as misalignment are easily generated. Therefore, the stacking method cannot produce high-resolution flexible fiber optic image bundles.

[0004] The acid dissolution method uses the "multifilament bundle making + unit fiber dispersion" process. The single optical fiber used in this method to manufacture a flexible optical fiber imaging bundle contains three glass materials: "core glass + cladding glass + outer acid-soluble glass". The three glasses are formed into a hard optical fiber bundle after fiber drawing. The hard optical fiber bundle is then acid-etched to become discrete single fibers, thereby producing a flexible optical fiber imaging bundle. The advantage of this method is that it can obtain a finer unit fiber diameter, so the resolution is higher. However, the disadvantages of the acid dissolution method are: 1. It is difficult to prepare large cross-sections, because the larger the cross-section of the optical fiber bundle, the more difficult it is for the acid solution to penetrate, resulting in poor unit fiber dispersion in the center of the optical fiber bundle, which directly affects the flexibility of the optical fiber bundle; 2. The broken wire rate is high. Since the unit fibers corresponding to the high resolution are too thin (generally the diameter is 6 to 10 μm), and they are also flexible unit fibers, it is very easy to produce unit fiber breakage during the acid dissolution process, resulting in dark areas in the image, which greatly affects the image resolution and imaging quality.

[0005] In summary, for large-cross-section, high-resolution flexible fiber optic imaging bundles, there is a conflict between increasing resolution and reducing unit filament diameter, as well as a conflict between increasing the cross-sectional area of the fiber bundle and increasing flexibility. Theoretically, the finer the unit filament diameter, the higher the resolution of the fiber bundle. However, as the unit filament diameter of the fiber bundle decreases, the strength of the unit filament gradually decreases, resulting in an increase in the breakage rate and a deterioration in the imaging quality of the fiber bundle. At the same time, theoretically, the larger the cross-sectional area of the fiber bundle, the larger the observation field, which is more conducive to observing and determining the target state. However, as the cross-sectional area of the fiber bundle increases, the acid solution cannot penetrate smoothly to corrode the acid-soluble glass material, resulting in residual acid-soluble glass and poor dispersion of the unit filaments. If the acid dissolution time is extended, the acid solution will corrode the inner cladding glass of the optical fiber, resulting in dark or broken filaments, resulting in a deterioration in the flexibility and image transmission quality of the large-cross-section fiber bundle. Therefore, how to manufacture large-cross-section, high-resolution flexible fiber bundles is currently a difficult problem in this technical field. Summary of the Invention

[0006] In view of this, the main purpose of the present invention is to provide a flexible fiber optic imaging bundle with a large cross-section and high resolution, and its preparation method and application. The technical problem to be solved is how to prepare a flexible fiber optic imaging bundle that meets both large cross-section and high resolution.

[0007] The objectives of the present invention and the technical problems solved therein are achieved by adopting the following technical solutions: The present invention provides a large-cross-section, high-resolution flexible fiber optic imaging bundle, comprising a plurality of flexible units, each of which comprises a plurality of closely packed imaging units, each of which comprises a glass fiber having a plurality of circular through-holes.

[0008] Preferably, in the aforementioned large-cross-section, high-resolution flexible optical fiber imaging bundle, the multiple circular through holes of the glass fiber are irregularly distributed micro-nano through hole structures.

[0009] Preferably, in the aforementioned flexible optical fiber imaging bundle with large cross-section and high resolution, the dense packing mode is a dense packing form of regular hexagons, squares or regular triangles.

[0010] Preferably, in the aforementioned large-section, high-resolution flexible optical fiber imaging bundle, the diameter of the circular through hole is 90-600 nm; the cross-sectional area of the circular through hole accounts for 20%-55% of the total cross-sectional area of the flexible unit fiber.

[0011] Preferably, in the aforementioned large-section, high-resolution flexible optical fiber imaging bundle, the flexible unit is a single fiber with a characteristic size of 50 to 200 μm, and the minimum bending radius allowed is 20 times the characteristic size of the single fiber.

[0012] Preferably, in the aforementioned large-section, high-resolution flexible optical fiber imaging bundle, the flexible optical fiber imaging bundle can transmit the wavelength range of 400nm to 1500nm, with a transmittance of 70% to 80% per meter; the end face characteristic size reaches more than 8mm, and the broken wire rate is less than 1‰.

[0013] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures. The present invention proposes a method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle, comprising the following steps:

[0014] S1: Arranging at least two glass tubes of the same material, uniform outer diameter, and different pore diameters randomly and closely in a certain quantity ratio, or arranging them closely in a pre-designed irregular distribution, into a glass tube bundle having a regular hexagonal or square cross-section, and tying and securing the glass tube bundle at both ends with copper wire or iron wire to obtain a porous preform;

[0015] S2: drawing the porous preform obtained in step S1 into a porous glass monofilament;

[0016] S3: cutting the porous glass monofilaments obtained in step S2 to a fixed length and randomly mixing and arranging them to obtain a monofilament fiber bundle, and then sleeved the monofilament fiber bundle with an acid-soluble glass sleeve of matching size to cover the side surface, and then tying and fixing the monofilament fiber bundle at both ends with copper wire or iron wire to obtain a primary composite rod;

[0017] S4: drawing the primary composite rod obtained in step S3 into primary multifilaments, cutting the primary multifilaments to a fixed length and arranging them into primary multifilament fiber bundles, and tying and fixing the primary multifilament fiber bundles at both ends with copper wire or iron wire to obtain secondary composite rods;

[0018] S5: drawing the secondary composite rod obtained in step S4 into secondary multifilaments, cutting the secondary multifilaments to a fixed length and arranging them into secondary multifilament fiber bundles, and performing an organic adhesive UV curing treatment on both ends of the secondary multifilaments to obtain a hard optical fiber bundle;

[0019] S6: The hard optical fiber bundle obtained in step S5 is subjected to acid etching and softening treatment to obtain the flexible optical fiber image transmission bundle blank;

[0020] S7: The flexible optical fiber image transmission bundle blank obtained in step S6 is cleaned and dried, and then both ends are pressed and formed to obtain a flexible optical fiber image transmission bundle blank with hard end faces at both ends;

[0021] S8: The flexible optical fiber image transmission bundle blank with hard end faces obtained in step S7 is subjected to end face cutting, fine carving, grinding, polishing, cleaning, and drying to obtain the flexible optical fiber image transmission bundle.

[0022] Preferably, in the aforementioned method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle, in step S1, the refractive index n of the glass tube is 1.47 to 1.53; the proportion of the cross-sectional area of the hollow through hole of the glass tube to the entire cross-sectional area of the glass tube is 4% to 70%; and the difference between the maximum and minimum values of the proportion of the cross-sectional area of the hollow through hole of the glass tube is greater than or equal to 5%.

[0023] Preferably, in the aforementioned method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, in step S2, an inert gas is passed through the porous preform during drawing.

[0024] Preferably, in the aforementioned method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle, in step S4, an inert gas is passed through the composite rod during drawing.

[0025] Preferably, in the aforementioned method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle, in step S5, an inert gas is passed through the secondary composite rod during drawing.

[0026] Preferably, in the aforementioned method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle, in steps S2, S4 and S5, the inert gas is selected from at least one of nitrogen, argon, neon and helium.

[0027] Preferably, in the aforementioned method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle, in step S2, the outer contour shape of the cross-section of the porous glass monofilament is one of a circle, a regular hexagon, an equilateral triangle or a square.

[0028] Preferably, in the aforementioned method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle, in step S3, the outer contour of the cross section of the monofilament fiber bundle is a regular hexagon or a square.

[0029] Preferably, in the aforementioned method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle, in step S4, the outer contour of the cross section of the primary multifilament fiber bundle is a regular hexagon or a square.

[0030] Preferably, in the aforementioned method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle, in step S5, the outer contour of the cross section of the secondary multifilament fiber bundle is a regular hexagon or a square.

[0031] Preferably, in the aforementioned method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle, in step S6, the acid etching and softening treatment includes: vertically suspending the hard optical fiber bundle solidified at both ends in an acidic corrosive liquid for corrosion treatment, and after the optical fiber bundle is completely dispersed, placing the softened optical fiber bundle in flowing deionized water for multiple cleaning treatments to remove the acidic corrosive liquid on the surface of the softened optical fiber bundle; tying the cleaned softened optical fiber bundle with cotton thread and then soaking the two ends in anhydrous ethanol or acetone to remove the ultraviolet curing glue at both ends, and then performing acid etching and softening treatment on both ends to obtain the flexible optical fiber imaging bundle blank.

[0032] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures: The present invention provides an endoscope, which includes the above-mentioned flexible optical fiber imaging bundle.

[0033] By means of the above technical solution, the present invention provides a large-cross-section, high-resolution flexible optical fiber imaging bundle and its preparation method and application, which have at least the following advantages:

[0034] The present invention uses a flexible optical fiber with an irregular micro-nano hole structure as the transmission medium, in which both the glass fiber and the air holes participate in light transmission, that is, the effective light transmission area participating in the optical signal input is 100%. Compared with the conventional flexible optical fiber with a "core + cladding" structure, the optical signal input area and optical signal input intensity are significantly improved;

[0035] The present invention transmits optical signals according to the mechanism of limited diffusion in the horizontal direction and free propagation in the vertical direction. Compared with conventional flexible optical fibers that have restrictions on the thickness of the optical fiber cladding, the diameter of the flexible optical fiber unit can be reduced to sub-micron or even smaller, significantly improving the resolution of the flexible optical fiber image bundle.

[0036] The flexible optical fiber image bundle of the present invention not only has multimode transmission characteristics but also has the characteristics of high lateral localization. Compared with conventional high-resolution flexible optical fiber image bundles, it has higher compatibility with wide-spectrum light sources and is more suitable for image coupling, transmission and display.

[0037] The flexible optical fiber imaging bundle of the present invention has no orderly isolation between the cladding layers and allows crosstalk of optical signals transmitted between the unit filaments. Compared with conventional flexible optical fiber imaging bundles, the bundles can be effectively fused through bonding, fusion, and other processes to eliminate splicing interface traces, and can be quickly spliced to achieve large-cross-section preparation of flexible optical fiber imaging bundles.

[0038] The flexible optical fiber imaging bundle of the present invention fundamentally solves the problem of splicing interface marks and is applicable not only to the field of large-section, high-definition flexible optical fiber imaging bundles, but also to the field of large-section, high-definition rigid optical fiber imaging bundles.

[0039] The flexible optical fiber imaging bundle of the present invention has a characteristic dimension of its flexible unit of 50 to 200 μm, and an allowable minimum bending radius of 20 times the characteristic dimension of a single fiber; the flexible optical fiber imaging bundle can transmit a wavelength range of 400 nm to 1500 nm, with a transmittance of 70 to 80% per meter; the characteristic dimension of the end face reaches more than 8 mm (can reach 32 mm or even larger), and the broken wire rate is less than 1‰.

[0040] The flexible optical fiber image transmission bundle of the present invention has a through hole diameter in a single flexible fiber of 90 to 600 nm, and an image resolution of up to 181 lp / mm.

[0041] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the cross section of glass tubes with the same outer diameter but different pore sizes;

[0043] Figure 2 Schematic diagrams of cross sections of porous preforms arranged from glass tubes of different pore sizes, where (a) is a porous preform with a regular hexagonal cross section, and (b) is a porous preform with a square cross section;

[0044] Figure 3 Schematic diagrams of cross-sections of monofilament fiber bundles arranged from porous glass monofilaments, wherein (a) is a monofilament fiber bundle with a regular hexagonal cross-section, and (b) is a monofilament fiber bundle with a square cross-section;

[0045] Figure 4 Schematic diagram of a cross section of an acid-soluble glass sleeve, wherein the outer contour of the acid-soluble glass sleeve is a circle (a, b), a regular hexagon (c, d), or a square (e, f), and the inner hole contour of the acid-soluble glass sleeve is a regular hexagon (a, c, e) or a square (b, d, f);

[0046] Figure 5 Schematic diagrams of cross sections of a primary composite rod and its outer circumference coated with an acid-soluble glass sleeve, wherein (a) is a schematic diagram of a monofilament fiber bundle with a regular hexagonal cross section being matched and nested in an acid-soluble glass sleeve with a circular outer contour, and (b) is a schematic diagram of a monofilament fiber bundle with a square cross section being matched and nested in an acid-soluble glass sleeve with a circular outer contour;

[0047] Figure 6 Schematic diagram of the cross section of a secondary composite rod formed by arranging primary multifilaments, wherein (a) is a schematic diagram of the circular primary multifilament arrangement, and (b) is a schematic diagram of the square primary multifilament arrangement;

[0048] Figure 7 Schematic diagram of the cross section of a rigid optical fiber bundle arranged by secondary multifilaments, wherein (a) is a schematic diagram of the arrangement of the secondary multifilaments in a regular hexagonal shape, and (b) is a schematic diagram of the arrangement of the secondary multifilaments in a square shape;

[0049] Figure 8 Schematic diagram of a flexible fiber optic image bundle with hard end faces at both ends. DETAILED DESCRIPTION

[0050] To further illustrate the technical means and effectiveness of the present invention in achieving its intended objectives, the following, in conjunction with preferred embodiments, provides a detailed description of a large-cross-section, high-resolution flexible fiber optic imaging bundle, its preparation method, and its specific implementation, structure, features, and effectiveness. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0051] The following materials or reagents, unless otherwise specified, were commercially available.

[0052] According to some embodiments of the present invention, a large-cross-section, high-resolution flexible fiber optic imaging bundle is provided, wherein the flexible fiber optic imaging bundle comprises a plurality of flexible units, each of which comprises a plurality of imaging units arranged in a densely packed manner, each of which comprises a glass fiber having a plurality of circular through holes.

[0053] It should be noted that, in the present invention, a flexible optical fiber image transmission bundle having a cross-sectional characteristic dimension greater than 2 mm can be referred to as a large cross-section; a flexible optical fiber image transmission bundle having a unit wire diameter less than 10 μm can be referred to as a high resolution (the corresponding resolution must be greater than 50 lp / mm).

[0054] In some embodiments, the plurality of circular through-holes in the glass fiber optionally comprise an irregularly distributed micro-nano through-hole structure. This structure is designed to form a light-transmitting medium composed of two different refractive indices, glass and air in the through-holes, within the glass fiber to form a transversely localized optical fiber for light transmission, thereby enabling the application of high-resolution, large-cross-section flexible optical fiber imaging bundles.

[0055] In some embodiments, the close packing mode is optionally a regular hexagon, a square or a regular triangle close packing mode. The purpose of such selection is that regular hexagon, a square or a regular triangle is the easiest to achieve close layout and is convenient for production operation.

[0056] In some embodiments, optionally, the cross-sectional side length (or width across the side) of the flexible unit is set as a characteristic dimension; the flexible unit is a single flexible fiber, and its characteristic dimension is 50 to 200 μm. The purpose of this dimension setting is to take into account both flexibility and light transmission needs. The smaller the characteristic dimension and the thinner the flexible unit, the better the fiber flexibility, but it also increases the risk of broken fibers. When the dimension is less than 50 μm, the lateral localization effect of the transmitted light wave in a single flexible unit will be less obvious, and the proportion of light waves passing through the flexible unit will increase significantly, affecting the output brightness and even causing broken fibers to cause missing data points. When the dimension is greater than 200 μm, the fiber flexibility begins to deteriorate, affecting the use effect of the flexibility. The cross-section of the flexible unit has many hollow glass fiber unit fibers and gaps between the densely packed unit fibers, where the diameter of the unit fibers is 3.3 to 6.5 μm; it can be seen that the characteristic dimension of a single flexible fiber is much larger than the diameter of the unit fibers in a single fiber.

[0057] In some embodiments, the aperture of the circular through hole is optionally 90 to 600 nm. Air hole sizes within this range can balance output resolution and operating wavelength range. When the aperture is less than 90 nm, it is easy to cause through hole interruption and increased light wave scattering during thermal processing, affecting output resolution and output light wave intensity. When the aperture is greater than 600 nm, since the large air holes are mainly introduced by the hollow holes of the glass tube, the larger the air hole diameter, the more concentrated the air holes are, which is not conducive to the lateral localization effect. Considering the flexibility of the optical fiber and the lateral localization effect, the cross-sectional area of the circular through hole accounts for 20% to 55% of the total cross-sectional area of the flexible unit fiber. When the ratio is less than 20%, the lateral localization effect is not obvious; when the ratio is greater than 55%, the proportion of the through hole is too large, resulting in poor flexibility of the optical fiber, which is not conducive to practical application.

[0058] In some embodiments, optionally, the total length of the flexible optical fiber image transmission bundle reaches at least 1m; the lengths of the hard areas at both ends are not less than 1cm respectively, the end face characteristic dimensions can reach at least 8mm, and the broken wire rate is less than 1‰.

[0059] In some embodiments, the flexible optical fiber imaging bundle optionally has a per-meter transmittance of 70-80%, enabling good transmission of visible light and near-infrared wavelengths in the range of 400nm to 1500nm. This transmission wavelength range is primarily determined by the glass material used. Most optical fiber imaging bundles are used in the visible light band, i.e., 400nm-800nm, with a few used in the near-infrared band, i.e., 800nm-1500nm. The present invention is primarily used in the visible to near-infrared band, so the transmission wavelength range of the present invention is 400nm-1500nm, and the minimum allowable bend radius is 20 times the characteristic dimension of a single fiber. This minimum bend radius reflects the flexibility of the flexible optical fiber imaging bundle of the present invention. A smaller multiple indicates greater flexibility. Use greater than the given value is safe, while use less than the given value is risky. Furthermore, when the bend radius is less than 20 times the given value, the smaller the bend radius, the greater the risk of breakage of the flexible optical fiber imaging bundle.

[0060] In some embodiments, optionally, the glass is composed of the following components in the following weight percentages: SiO2 65wt% to 75wt%; B2O3 10wt% to 15wt%; R2O 3wt% to 7wt% (R is at least one of Li, Na and K); ReO 5wt% to 8wt% (Re is at least one of Mg, Ca, Sr and Ba); Al2O3 3wt% to 5wt%; SnO2 0wt% to 2wt%; TiO2 0wt% to 2wt%; ZnO 0wt% to 2wt%; ZrO2 0wt% to 2wt%.

[0061] The flexible optical fiber and its large-section optical fiber image transmission bundle of the above-mentioned technical solution are prepared based on a transversely localized optical fiber. This transversely localized optical fiber is an optical fiber with a laterally irregular distribution of refractive index. It can produce strong transverse scattering of the light waves it transmits, causing the light waves to be locally confined in the laterally direction and propagate freely in the longitudinal direction. Therefore, this type of optical fiber not only has the multimode transmission characteristics of traditional large-core optical fibers, but also has the characteristics of highly localized most modes. At the same time, because this optical fiber does not have the traditional "core + cladding" unit fiber ordered arrangement structure and has no obvious fiber edges, it is very suitable for end-face transverse splicing. In theory, any number of them can be spliced together without a splicing seam. It is an ideal choice for the preparation and application of flexible optical fiber image transmission bundles that can meet large cross-section and high-resolution requirements.

[0062] According to some embodiments of the present invention, a method for preparing a flexible fiber optic imaging bundle with a large cross-section and high resolution is provided, comprising the following steps:

[0063] Step 1: Prepare at least two hollow glass tubes made of the same material, with the same outer diameter but different internal pore diameters. The refractive index n of the glass tubes is in the range of 1.47 to 1.53. The refractive index of the air medium in the hollow hole is 1, while the refractive index of glass is greater than that of air. Generally, when the refractive index difference between the two media is 0.5, the lateral localization effect of the transmitted light is most obvious, so the refractive index of the glass tube is preferably 1.50. When the refractive index difference changes to 0.03, the corresponding lateral localization radius of the transmitted light changes significantly. After comprehensive consideration, the refractive index of the glass tube is set to 1.50±0.03, that is, 1.47 to 1.53. The outer diameter of the glass tube can be 3mm to 6mm. The outer diameter of the glass tube is mainly selected based on the difficulty of glass tube preparation and the ease of typesetting and monofilament drawing. Generally, the production cost of glass tubes with an outer diameter less than 3mm is high, the technical requirements are high, and the consistency is difficult to control; although glass tubes with an outer diameter greater than 6mm are easier to produce, the larger the outer diameter, the more concentrated and sparse the distribution of hollow holes in the glass tube bundle, which is not conducive to lateral localized application; the cross-sectional area of the hollow through-holes of the single tube accounts for the proportion of the entire cross-sectional area of the glass tube (including the cross-sectional area of the hollow through-holes) between 4% and 70%; the proportion of the hollow hole area of the glass tube in the single tube is limited by the wall thickness of the glass tube and the size of the hollow hole diameter. For outer diameters of 3mm to 6mm, the wall thickness is generally controlled to be not less than 0.5mm, so the cross-sectional area of the hollow through-holes of the corresponding single tube accounts for a maximum of about 10% of the entire cross-sectional area of the glass tube. is 70%; the smaller the proportion of the hollow hole area of the glass tube in the single tube, the smaller the hollow hole diameter and the thicker the glass wall thickness, the less conducive it is to the dense and dispersed distribution of the air holes after typesetting, and the less conducive it is to lateral localized application. Therefore, taking comprehensive consideration, the proportion of the hollow through-hole cross-sectional area of the single tube to the entire cross-sectional area of the glass tube (including the hollow through-hole cross-sectional area) is selected to be between 4% and 70%, and the difference between the maximum and minimum values of the proportion of the hollow through-hole cross-sectional area of the single tube used is not less than 5%; the smaller the difference, the smaller the difference in hollow hole diameter, the more periodic the distribution of the hollow holes of the glass after typesetting, and the less conducive it is to lateral localized application. Therefore, the difference is required to be not less than 5%. In theory, the larger the difference, the more advantageous it is. In addition, the glass tube is composed of the following components in weight percentage: SiO2 65wt% to 75wt%; B2O3 10wt% to 15wt%; R2O 3wt% to 7wt% (R is at least one of Li, Na and K); ReO 5wt% to 8wt% (Re is at least one of Mg, Ca, Sr and Ba); Al2O3 3wt% to 5wt%; SnO2 0wt% to 2wt%; TiO2 0wt% to 2wt%; ZnO 0wt% to 2wt%; and ZrO2 0wt% to 2wt%.

[0064] Step 2: The glass tubes are randomly and densely arranged according to a certain number ratio, or arranged densely according to a pre-designed irregular distribution, to form a glass tube bundle with a regular hexagonal or square cross-section, and are tied and fixed at both ends of the glass tube bundle with copper wire or iron wire to obtain a porous preform rod; the ratio p of the cross-sectional area of the through holes to the total cross-sectional area of the single fiber is 20% to 55%; in order to arrange the cross-section with irregularly distributed hollow through holes occupying a certain proportion, for a glass tube with the same outer diameter, at least two different hollow hole diameters need to be used for ratio design. For example, for a glass tube with an outer diameter of Φ6 mm, in order to obtain a total p=55% micro-nano through-hole transversely localized glass fiber, it is necessary to use a single tube with a wall thickness of 0.7 mm at a ratio of 55% (the hollow hole area of the single tube accounts for 58.78%, and the area of the slit holes between the single tubes accounts for about 3.84%, so the comprehensive ratio of the through-hole area corresponding to the single tube is p=62.62%), and a single tube with a wall thickness of 1.1 mm at a ratio of 45% (the hollow hole area of the single tube accounts for 40.11%, and the area of the slit holes between the single tubes accounts for about 5.58%, so the comprehensive ratio of the through-hole area corresponding to the single tube is p=45.69%). It can be seen that for glass tubes with different outer diameters, the quantity ratios required for different wall thicknesses are different. According to the required glass tubes and their quantity ratio, an irregular distribution design is carried out, and then layout is carried out according to the design. Compared with random layout, the advantage of this method is that it can ensure that the irregular distribution of different batches is consistent, that is, it ensures good consistency of the lateral localization effect between different batches; the multi-hole refers to the different hollow holes of the glass tubes and the tube slit holes between the glass tube layout. The size of the glass tube hollow hole is determined by the selected glass tube hollow hole inner diameter, and the layout tube slit hole is determined by the selected glass tube outer diameter.

[0065] Step 3: Drawing the obtained porous preform rod into a porous glass monofilament at 800° C. to 1100° C.; wherein, when the temperature is lower than 800° C., the porous preform rod is not completely softened, has poor fluidity, tends to have an irregular cross-section, and cannot effectively control fiber molding; when the temperature is higher than 1100° C., the porous preform rod is highly softened, has strong fluidity, tends to have a droplet shape, and cannot effectively control drawing and molding; the outer contour shape of the cross section of the porous glass monofilament can be one of a circle, a regular hexagon, an equilateral triangle, or a square. Its characteristic dimensions are set to the values of the circle diameter, the distance between opposite sides of a regular hexagon, the height of an equilateral triangle or the side length of a square. In order to facilitate the control of the drawing shrinkage ratio and typesetting operations, the characteristic dimensions of the single wire are generally controlled at the order of 1 mm. During the drawing process, an inert gas is introduced into the porous preform rod; the inert gas can be selected from at least one of nitrogen, argon, neon and helium; the purpose of introducing the inert gas is to ensure that the hollow hole of the glass tube does not stick and break during the drawing process, and maintains the circular hole shape, and does not chemically react with the glass components.

[0066] Step 4: Cut the glass monofilaments to a fixed length and randomly mix and arrange them into glass fiber bundles with a regular hexagonal or square cross-section to obtain a monofilament fiber bundle, and put an acid-soluble glass sleeve of matching size on the outer periphery to cover its side, and then use copper wire or iron wire to tie and fix the two ends of the monofilament fiber bundle to obtain a composite rod. The acid-soluble glass can be corroded by at least one acid solution of hydrochloric acid, nitric acid, citric acid and sulfuric acid. The purpose of using the acid-soluble glass sleeve is to keep the monofilament fiber bundles isolated in the middle during the dense stacking process, and finally remove the acid-soluble glass through subsequent acid dissolution to make dispersed and flexible glass fibers. The size parameters of the sleeve are matched according to the outer diameter parameters of the fiber bundle to be coated. In addition, the acid-soluble glass is composed of the following components in the following weight percentages: B2O3 40wt% to 45wt%; BaO 35wt% to 40wt%; SiO2 5wt% to 8wt%; R2O3wt% to 7wt% (R is at least one of Li, Na and K); ReO 1wt% to 3wt% (Re is at least one of Mg, Ca and Sr); Al2O3 3wt% to 5wt%; La2O3 3wt% to 5wt%; and Y2O30wt% to 2wt%.

[0067] Step 5: Drawing the above-mentioned primary composite rod into a primary multifilament at 800°C to 1100°C, wherein, when the temperature is lower than 800°C, the primary composite rod is not completely softened, has poor fluidity, tends to have an irregular cross-section and cannot be effectively drawn into shape; when the temperature is higher than 1100°C, the primary composite rod has a high degree of softening and strong fluidity, tends to be drop-shaped and cannot effectively control the fiber molding; wherein nitrogen is passed through the porous primary composite rod during the drawing process, in order to facilitate the control of the drawing shrinkage ratio and layout operation, the characteristic size of the primary multifilament is generally controlled at the order of 1mm, the primary multifilament is cut to a fixed length and then arranged into a primary multifilament fiber bundle with a regular hexagonal or square cross-section, and copper wire or iron wire is used to tie and fix the two ends of the primary multifilament fiber bundle to obtain a secondary composite rod; the pressure of the nitrogen is 0.5 to 2kPa, and the purpose of this setting is to ensure that the through holes are conductive and circular during the drawing process, and do not react with the glass component. When the nitrogen pressure is less than 0.5kPa, the conformal properties are poor, and some through-holes may even be blocked. When the nitrogen pressure is greater than 2kPa, it is easy to cause the glass holes to break, resulting in poor light transmission performance of the final product.

[0068] Step six: Drawing the secondary composite rod into secondary multifilament at 800°C to 1100°C; wherein, when the temperature is lower than 800°C, the secondary composite rod is not completely softened, has poor fluidity, tends to have an irregular cross-section and cannot be effectively drawn into shape; when the temperature is higher than 1100°C, the secondary composite rod has a high degree of softening and strong fluidity, tends to be drop-shaped and cannot effectively control the fiber molding; during the drawing process, an inert gas is passed through the porous secondary composite rod. In order to facilitate the control of the drawing shrinkage ratio and layout operation, the characteristic size of the secondary multifilament is generally controlled at the order of 1mm. The secondary multifilament is cut to a fixed length and then arranged into a fiber bundle with a regular hexagonal or square cross-section, and an organic glue UV curing treatment is performed at both ends to obtain a hard optical fiber bundle; the pressure of the inert gas can be 0.5 to 2kPa; the purpose of passing the inert gas is to ensure that the through hole is conductive, maintains a circular shape, and does not react with the glass component. If the inert gas pressure is less than 0.5 kPa, the inert gas pressure is too low, resulting in poor conformal performance of the through-holes. If it is greater than 2 kPa, the inert gas pressure is too high, which can easily cause cracking of the porous glass and poor light transmission performance of the final product. The organic adhesive UV curing process is a conventional technique in the art, and the UV curing adhesive used is a commercially available product. The purpose is to solidify and fix the fiber bundles at both ends together, facilitating subsequent operations.

[0069] Step 7: The rigid optical fiber bundle with both ends solidified is subjected to an acid etching and softening treatment to obtain the flexible optical fiber image transmission bundle blank. The rigid optical fiber bundle with both ends solidified is vertically suspended in an acidic corrosive solution for etching treatment; after the optical fiber bundle is completely dispersed, the softened optical fiber bundle is placed in flowing deionized water for multiple cleaning treatments to remove the acidic corrosive solution on the surface of the softened optical fiber bundle; the cleaned softened optical fiber bundle is tied and fixed with cotton thread, and then both ends are soaked in anhydrous ethanol (or acetone) to remove the UV-curing glue on both ends, and then the un-etched areas at both ends are subjected to acid etching and softening treatment to obtain the flexible optical fiber image transmission bundle blank. The acid etching and softening treatment is as follows: using an acidic corrosive solution to corrode and remove the acid-soluble glass, so that the fibers separated by the acid-soluble glass are dispersed and thus have flexibility. The acidic corrosive solution is selected from at least one acid solution selected from hydrochloric acid, nitric acid, citric acid and sulfuric acid. The concentration of the acidic etching solution is 0.2-0.6 mol / L. The purpose of this setting is to reasonably control the acid etching reaction. If it is less than 0.2 mol / L, the acid concentration is too low, and the dispersion effect becomes worse; if it is greater than 0.6 mol / L, the acid concentration is too high, and the erosion of the glass fiber surface is aggravated; the immersion time is 30-180 min. The purpose of this setting is to reasonably control the acid etching reaction. If it is less than 30 min, the immersion time is too short, the dispersion effect becomes worse; if it is greater than 180 min, the immersion time is too long, and the erosion of the glass fiber surface is aggravated; the heating temperature is 30-50 ° C. The purpose of this setting is to effectively promote the acid etching. If it is less than 30 ° C, the heating temperature is too high. If the heating temperature is too low, the acid etching will be too slow, resulting in prolonged immersion time, which in turn will lead to increased erosion of the glass fiber surface; if it is greater than 50°C, the heating temperature is too high, the reaction between the glass fiber and the acid solution will intensify, the surface erosion will be aggravated, and the volatilization of the acid solution gas will intensify and the gas pollution will be aggravated; the flow rate of the acid etching solution is 0.5-1.5L / min. The purpose of this setting is to promote the acid etching and make the fibers fully dispersed. If it is less than 0.5L / min, the flow rate is too low, the acid etching will slow down, and the deviation of the acid etching process between the surface and the inside of the fiber bundle will become larger; if it is greater than 1.5L / min, the flow rate is too high, the acid etching solution will disturb the flexible fiber too much, aggravating the damage of the flexible fiber.

[0070] Step 8: The flexible optical fiber image transmission bundle blank is cleaned and dried, and then its two ends or the two ends of multiple identical flexible optical fiber image transmission bundle blanks aligned and fastened together are placed into a hot melt pressing mold, melt-pressed separately (melted separately or placed in a segmented melting furnace as a whole), and then pressed at high temperature to obtain a flexible optical fiber image transmission bundle blank with hard end faces at both ends; the cleaning and drying are conventional processing operations for glass products in this field; the purpose of the cleaning is to clean and remove residues, impurities, dust, etc. adhered or adsorbed on the surface of the product to make its surface clean; the purpose of the drying is to make the surface of the product free of moisture to improve the product's shelf life. The pressing pressure is 0.2-0.5MPa and the time is 2-8 hours; the purpose of this setting is to provide a certain extrusion force to the glass fiber bundle in accordance with the temperature and time, so that the fiber bundles are tightly attached together, and then adhere and fuse under a certain temperature and time; if it is less than 0.2MPa, the pressure is too small and the fusion effect is poor; if it is greater than 0.5MPa, the pressure is too high and micropores are easily deformed. If it is less than 2 hours, the time is too short and the fusion effect is poor; if it is more than 8 hours, the time is too long and the glass is prone to crystallization. The purpose of the separate melting and pressing is to only melt and press the two ends of the optical fiber bundle into a hard state to facilitate the use of the product, while the middle still maintains flexibility and bendability. The high temperature is set to 600-700℃, the purpose is to soften the glass surface and make it sticky, and then fuse it into one through pressing, thereby forming a flexible optical fiber image transmission bundle with both ends firmly and tightly fused. When the temperature is lower than 600℃, the glass softens poorly, making the pressed product prone to cracks or even unable to fuse, and the fusion effect is poor; when the temperature is higher than 700℃, the fusion effect is good, but it is easy to produce glass crystallization and microporous deformation.

[0071] Step nine: The flexible optical fiber image transmission bundle blank with the hard end face is subjected to end face cutting, fine carving, grinding, polishing, cleaning and drying to obtain a flexible optical fiber image transmission bundle with a hard end face having an irregularly distributed micro-nano through-hole structure. The total length of the flexible optical fiber imaging bundle can reach at least 3m, the lengths of the hard areas at both ends are not less than 1cm respectively, the characteristic dimensions of the end face can reach at least 8mm, and can be as large as 32mm (theoretically, any large cross-section can be spliced), the characteristic dimension D of a single fiber of the flexible optical fiber imaging bundle is in the range of 50-200μm, the broken wire rate is less than 1‰, the aperture d of the through hole in the flexible single fiber is in the range of 90-600nm, and the proportion of the through hole cross-sectional area in the total cross-sectional area of the single fiber is in the range of p=20%-55% (generally preferably 40%-50%), the transmittance per meter of the flexible optical fiber imaging bundle is T=70-80%, which can achieve good transmission of 400nm-1500nm visible light-near infrared, the highest resolution can reach 181lp / mm, and the minimum bending radius D×20 is allowed, which here refers to 20 times the characteristic dimension D of a single fiber, indicating the degree to which the flexible optical fiber can be bent. The end face cutting, fine carving, grinding, polishing, cleaning and drying processes are conventional techniques in the manufacturing process of glass products in this field. The purpose is to obtain the required length by cutting, obtain the required end face macromorphology by fine carving, obtain a flat and smooth end face morphology by grinding and polishing, clean and remove stains on the product surface during the processing, and dry the product to obtain a dry surface to improve the preservability.

[0072] According to some embodiments of the present invention, an endoscope is provided, which includes the aforementioned large-cross-section, high-resolution flexible fiber optic imaging bundle. Currently, the outer diameter of the cross-section of the glass flexible fiber optic imaging bundle used in high-resolution endoscopes is typically less than 8 mm, the diameter of the individual fiber filaments is generally 6 to 10 microns, the transmittance per meter is approximately 40 to 50%, the minimum allowable bending radius is approximately D×20, and the resolution is only a few dozen line pairs (lp / mm). However, the characteristic dimension of the cross-section of the fiber bundle in the present invention can be as large as 32 mm, the theoretical diameter of the individual fiber filaments is approximately 3 to 6.5 microns, and the optical fiber filaments are densely distributed with light-transmitting air holes with an aperture diameter of d=90 to 600 nm. Conventional image transmission bundles are periodic structures of a "core + cladding" array, and their light transmission units refer to each "core + cladding" unit fiber. However, the novel image transmission bundle of the present invention is an optical fiber with densely distributed air holes, and the air holes are irregularly distributed. Both the glass fiber and the air holes participate in light transmission, and crosstalk transmission is allowed. Its light transmission units can be simply understood as referring to the two medium units of glass fiber and air holes within the unit fiber. It can be seen that the unit fiber diameter of conventional image transmission bundles determines the resolution, while the size of both the glass fiber and the air holes within the unit fiber of the present invention jointly affects the resolution. Currently, the corresponding unit fiber diameter of conventional image transmission bundles with high resolution is generally 6 to 10 microns, while the unit fiber diameter of the present invention is between 3 and 6.5 microns (composed of glass fiber and air holes), and the unit fiber is densely distributed with air holes with an aperture range of d = 90 to 600 nm. It can be seen that in terms of resolution capability, the present invention is superior to conventional image transmission bundles. The transmittance per meter of the flexible optical fiber image transmission bundle is T=70~80%, the minimum bending radius allowed is D×20, and the resolution can reach up to 181lp / mm. It can be seen that the comprehensive performance of the flexible optical fiber image transmission bundle of the present invention is better.

[0073] The present invention provides these embodiments to make the present invention thorough and complete, and to fully express the scope of the present invention to those skilled in the art. It should be noted that: unless otherwise specifically stated, the relative arrangement of parts and steps, the composition of materials, numerical expressions and numerical values set forth in these embodiments should be interpreted as merely exemplary, and not as limiting.

[0074] The present invention will be further described below with reference to specific embodiments, but this should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0075] Unless otherwise specified, the materials and reagents mentioned below are commercially available products familiar to those skilled in the art. Unless otherwise specified, the methods described are all well-known methods in the art. Unless otherwise defined, technical or scientific terms used shall have the same meanings as those commonly understood by those skilled in the art.

[0076] Example 1

[0077] This embodiment provides a method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising the following steps:

[0078] Step 1: Prepare borosilicate glass tubes with a refractive index of n = 1.5, an outer diameter of 4 mm, and three different wall thicknesses (such as Figure 1 (as shown), wherein the number of glass tubes with a wall thickness of 0.5 mm accounts for 36%, the number of glass tubes with a wall thickness of 0.7 mm accounts for 44%, and the number of glass tubes with a wall thickness of 0.9 mm accounts for 20%; the composition of the borosilicate glass tubes and the proportions by weight are as follows: SiO2 70wt%; B2O3 12wt%; Li2O 1wt%; Na2O 2wt%; K2O 3wt%; MgO 1wt%; CaO1wt%; SrO 1wt%; BaO 3wt%; Al2O3 4wt%; SnO2 1wt%; ZrO2 1wt%.

[0079] Step 2: Arrange the three glass tubes in a pre-designed irregular distribution to form a glass tube bundle with a square cross section, and use copper wire to tie and fix the two ends of the glass tube bundle to obtain a porous preform with a characteristic size of about 36 mm (such as Figure 2 shown).

[0080] Step 3: Drawing the porous preform rod at 1000° C. into a porous glass monofilament with a characteristic size of 2 mm, wherein inert gas nitrogen is introduced into the glass tube bundle during the drawing process, and the positive pressure is controlled at 2 kPa.

[0081] Step 4: Cut the porous glass monofilament into 0.5m lengths and arrange them tightly according to the pre-designed irregular distribution to form glass fiber bundles with square cross sections (such as Figure 3 As shown), and an acid-soluble glass sleeve is placed on its periphery (as shown Figure 4 As shown) cover its side (as shown) Figure 5 The glass fiber bundle is then tied and fixed at both ends with copper wire to obtain a primary composite rod with a characteristic size of about 30 mm. The composition and proportion by weight of the acid-soluble glass are as follows: B2O3 42wt%; BaO 35wt%; SiO2 7wt%; Li2O 1wt%; Na2O 2wt%; K2O 3wt%; MgO 1wt%; CaO 1wt%; SrO 1wt%; Al2O3 3wt%; La2O3 3wt%; Y2O3 1wt%.

[0082] Step 5: Drawing the primary composite rod into a primary multifilament with a characteristic size of 2 mm at 950° C. During the drawing process, inert gas nitrogen is introduced into the primary composite rod, and the positive pressure is controlled at 1.6 kPa.

[0083] Step 6: Cut the primary multifilament into 0.5m lengths and arrange them into glass fiber bundles with square cross sections. Then use copper wire to tie and fix the two ends of the glass fiber bundles to obtain secondary composite rods with a characteristic size of about 20mm (such as Figure 6 shown).

[0084] Step 7: Drawing the secondary composite rod into a secondary multifilament with a characteristic size of 1 mm at 900° C. During the drawing process, inert gas nitrogen is introduced into the composite rod, and the positive pressure is controlled at 1.2 kPa.

[0085] Step 8: Cut the secondary multifilament into 2m lengths and arrange them into glass fiber bundles with square cross sections. UV-curing treatment is performed on both ends of the fiber bundles (glue type: UV curing glue (purchased from the market) and cured under UV light (wavelength of 365nm) for 8 minutes to obtain a hard fiber bundle with a characteristic size of about 16mm (such as Figure 7 shown).

[0086] Step nine: The hard optical fiber bundle with both ends solidified is subjected to acid etching and softening treatment to obtain a flexible optical fiber image transmission bundle blank. The hard optical fiber bundle with both ends solidified is vertically suspended in an acidic corrosive solution for corrosion treatment (using hydrochloric acid solution to corrode and remove acid-soluble glass, the concentration of hydrochloric acid solution is 0.3 mol / L, the soaking time is 150 minutes, the heating temperature is 50°C, and the acid flow rate is 1.0 L / min); after the optical fiber bundle is completely dispersed, the softened optical fiber bundle is placed in flowing deionized water for multiple cleaning treatments to remove the surface acidic corrosive liquid of the dispersed optical fiber bundle; the cleaned flexible optical fiber image transmission bundle is tied and fixed with cotton thread, and then the two end faces are placed in anhydrous ethanol and soaked for 30 minutes to remove the organic glue at both ends. The same acid etching and softening treatment is then performed on the glue-removed areas at both ends to obtain a flexible optical fiber image transmission bundle blank.

[0087] Step 10: Clean and dry the flexible optical fiber image transmission bundle blank, then load its two ends into a hot melt pressing mold, melt and press them separately, and then press them at a high temperature of 700°C (maintain a pressure of 0.2MPa for 8 hours for pressing and molding) to obtain a flexible optical fiber image transmission bundle blank with hard end faces at both ends.

[0088] Step 11: The flexible optical fiber image transmission bundle blank with a hard end face is subjected to end face cutting, fine carving, grinding, polishing, cleaning and drying to finally obtain a flexible optical fiber image transmission bundle with a hard end face with an irregular micro-nano through-hole structure (such as Figure 8 shown).

[0089] The flexible optical fiber imaging bundle obtained in this embodiment is 2m long, the length of the hard areas at both ends is 2cm respectively, the characteristic dimension of the end face is about 16mm, the characteristic dimension of the flexible single fiber of the optical fiber imaging bundle is D=100μm, the broken wire rate is 0.1‰, the unit wire diameter in the flexible single fiber is 6.5μm, the aperture of the densely distributed through holes inside is in the range of 150~580nm, the cross-sectional area of the through holes accounts for p=50%, the highest resolution can reach 181lp / mm, the transmittance per meter of the flexible optical fiber imaging bundle is about 78%, which can achieve good transmittance of 400nm~1500nm visible light-near infrared, and the minimum bending radius allowed is D×20.

[0090] Example 2

[0091] This embodiment provides a method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising the following steps:

[0092] Step 1: Prepare borosilicate glass tubes with a refractive index of n = 1.47, an outer diameter of 4 mm, and three different wall thicknesses, wherein the glass tubes with a wall thickness of 0.5 mm account for 36%, the glass tubes with a wall thickness of 0.7 mm account for 44%, and the glass tubes with a wall thickness of 0.9 mm account for 20%. The composition and proportion by weight of the borosilicate glass tubes are as follows: SiO2 75wt%; B2O3 10wt%; Li2O 1wt%; Na2O 2wt%; K2O 3wt%; MgO 1wt%; CaO 2wt%; SrO1wt%; BaO1wt%; Al2O3 3wt%; SnO2 1wt%.

[0093] Step 3: Drawing the porous preform rod into a porous glass monofilament with a characteristic size of 1 mm at 1100° C. During the drawing process, inert gas nitrogen is passed through the glass tube bundle and the positive pressure is controlled at 2 kPa.

[0094] Step 5: Drawing the primary composite rod into a primary multifilament with a characteristic size of 2 mm at 1000° C. During the drawing process, inert gas nitrogen is introduced into the primary composite rod, and the positive pressure is controlled at 1.6 kPa.

[0095] Step 7: Drawing the secondary composite rod into a secondary multifilament with a characteristic size of 2 mm at 950° C. During the drawing process, inert gas nitrogen is introduced into the composite rod, and the positive pressure is controlled at 1.2 kPa.

[0096] The other operations and steps are the same as those in Example 1, and a flexible optical fiber imaging bundle of the same size is obtained.

[0097] The flexible optical fiber imaging bundle obtained in this embodiment is 2m long, the length of the hard areas at both ends is 2cm respectively, the characteristic dimension of the end face is about 16mm, the characteristic dimension of the flexible single fiber of the optical fiber imaging bundle is D=100μm, the broken wire rate is 0.1‰, the unit wire diameter in the flexible single fiber is 6.5μm, the aperture of the densely distributed through holes inside is in the range of 150~580nm, the cross-sectional area of the through holes accounts for p=50%, the highest resolution can reach 161lp / mm, the transmittance per meter of the flexible optical fiber imaging bundle is about 78%, which can achieve good transmittance of 400nm~1500nm visible light-near infrared, and the minimum bending radius allowed is D×20.

[0098] Example 3

[0099] This embodiment provides a method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising the following steps:

[0100] Step 1: Prepare borosilicate glass tubes with a refractive index of n = 1.53, an outer diameter of 4 mm, and three different wall thicknesses, wherein the number of glass tubes with a wall thickness of 0.5 mm accounts for 36%, the number of glass tubes with a wall thickness of 0.7 mm accounts for 44%, and the number of glass tubes with a wall thickness of 0.9 mm accounts for 20%. The composition and proportion by weight of the borosilicate glass tubes are as follows: SiO2 65wt%; B2O3 15wt%; Li2O 1wt%; Na2O 2wt%; K2O 4wt%; MgO 1wt%; CaO 1wt%; SrO 1wt%; BaO3wt%; Al2O3 5wt%; SnO2 1wt%; TiO2 1wt%.

[0101] Step 3: Drawing the porous preform rod at 1000° C. into a porous glass monofilament with a characteristic size of 1 mm, wherein inert gas nitrogen is introduced into the glass tube bundle during the drawing process, and the positive pressure is controlled at 2 kPa.

[0102] Step 5: Drawing the primary composite rod into a primary multifilament with a characteristic size of 2 mm at 900° C. During the drawing process, inert gas nitrogen is introduced into the primary composite rod, and the positive pressure is controlled at 1.6 kPa.

[0103] Step 7: Drawing the secondary composite rod into a secondary multifilament with a characteristic size of 2 mm at 850° C. During the drawing process, inert gas nitrogen is introduced into the composite rod, and the positive pressure is controlled at 1.2 kPa.

[0104] The other operations and steps are the same as those in Example 1, and a flexible optical fiber imaging bundle of the same size is obtained.

[0105] The flexible optical fiber imaging bundle obtained in this comparative example is 2m long, the length of the hard areas at both ends is 2cm respectively, the characteristic dimension of the end face is about 16mm, the characteristic dimension of the flexible single fiber of the optical fiber imaging bundle is D=100μm, the broken wire rate is 0.1‰, the unit wire diameter in the flexible single fiber is 6.5μm, the aperture of the densely distributed through holes inside is in the range of 150~580nm, the cross-sectional area of the through holes accounts for p=50%, the resolution can reach up to 161lp / mm, the transmittance per meter of the flexible optical fiber imaging bundle is about 78%, which can achieve good transmittance of 400nm~1500nm visible light-near infrared, and allow a minimum bending radius of D×20.

[0106] Example 4

[0107] This embodiment provides a method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising the following steps:

[0108] Step 1: Prepare borosilicate glass tubes with a refractive index of n = 1.5, an outer diameter of 4 mm, and three different wall thicknesses, wherein the number of glass tubes with a wall thickness of 0.5 mm accounts for 0%, the number of glass tubes with a wall thickness of 0.7 mm accounts for 30%, and the number of glass tubes with a wall thickness of 0.9 mm accounts for 70%; the composition and proportion by weight of the borosilicate glass tubes are as follows: SiO2 70wt%; B2O3 12wt%; Li2O 1wt%; Na2O2wt%; K2O 3wt%; MgO 1wt%; CaO 1wt%; SrO 1wt%; BaO 3wt%; Al2O3 4wt%; SnO2 1wt%; ZrO2 1wt%.

[0109] The other operations and steps are the same as those in Example 1, and a flexible optical fiber imaging bundle of the same size is obtained.

[0110] The flexible optical fiber imaging bundle obtained in this comparative example is 2m long, the length of the hard areas at both ends is 2cm respectively, the characteristic dimension of the end face is about 16mm, the characteristic dimension of the flexible single fiber of the optical fiber imaging bundle is D=100μm, the broken wire rate is 0.1‰, the unit wire diameter in the flexible single fiber is 6.5μm, the aperture of the densely distributed through holes inside is in the range of 150~580nm, the cross-sectional area of the through holes accounts for p=40%, the resolution can reach up to 144lp / mm, the transmittance per meter of the flexible optical fiber imaging bundle is about 76%, which can achieve good transmittance of 400nm~1500nm visible light-near infrared, and allow a minimum bending radius of D×20.

[0111] Example 5

[0112] This embodiment provides a method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising the following steps:

[0113] Step 1: Prepare borosilicate glass tubes with a refractive index of n = 1.5, an outer diameter of 4 mm, and three different wall thicknesses, wherein the glass tubes with a wall thickness of 0.5 mm account for 58%, the glass tubes with a wall thickness of 0.7 mm account for 42%, and the glass tubes with a wall thickness of 0.9 mm account for 0%; the composition and proportion by weight of the borosilicate glass tubes are as follows: SiO2 70wt%; B2O3 12wt%; Li2O 1wt%; Na2O 2wt%; K2O 3wt%; MgO 1wt%; CaO 1wt%; SrO1wt%; BaO 3wt%; Al2O3 4wt%; SnO2 1wt%; ZrO2 1wt%.

[0114] The other operations and steps are the same as those in Example 1, and a flexible optical fiber imaging bundle of the same size is obtained.

[0115] The flexible optical fiber imaging bundle obtained in this comparative example is 2m long, the lengths of the hard areas at both ends are 2cm respectively, the characteristic dimension of the end face is about 16mm, the characteristic dimension of the flexible single fiber of the optical fiber imaging bundle is D=100μm, the broken wire rate is 0.1‰, the unit wire diameter in the flexible single fiber is 6.5μm, the aperture of the densely distributed through holes inside is in the range of 150~580nm, the cross-sectional area of the through holes accounts for p of 55%, the highest resolution can reach 161lp / mm, the transmittance per meter of the flexible optical fiber imaging bundle is about 78%, which can achieve good transmittance of 400nm~1500nm visible light-near infrared, and allow a minimum bending radius of D×20.

[0116] Example 6

[0117] This embodiment provides a method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising the following steps:

[0118] Step 1: Prepare borosilicate glass tubes with a refractive index of n = 1.47, an outer diameter of 5 mm, and two different wall thicknesses, of which the glass tubes with a wall thickness of 0.7 mm account for 36% and the glass tubes with a wall thickness of 0.9 mm account for 64%. The composition and proportions of the borosilicate glass tubes are as follows: SiO2 75wt%; B2O3 10wt%; Li2O 1wt%; Na2O 2wt%; K2O 3wt%; MgO 1wt%; CaO 2wt%; SrO 1wt%; BaO 1wt%; Al2O3 3wt%; SnO2 1wt%.

[0119] Step 2: Arrange the two glass tubes in a pre-designed irregular distribution to form a glass tube bundle with a regular hexagonal cross section, and use wire to tie and fix the two ends of the glass tube bundle to obtain a porous preform with a characteristic size of about 36 mm.

[0120] Step 3: Drawing the porous preform rod into a porous glass monofilament with a characteristic size of 1 mm at 1100° C. During the drawing process, inert gas nitrogen is introduced into the glass tube bundle and the positive pressure is controlled at 2 kPa.

[0121] Step 4: Cut porous glass monofilaments into 0.5-meter lengths and arrange them tightly in a pre-designed irregular pattern to form a glass fiber bundle with a regular hexagonal cross-section. An acid-soluble glass sleeve is placed around the outer periphery of the bundle to cover the sides. The bundle is then tied and secured at both ends with iron wire to form a primary composite rod with a characteristic dimension of approximately 35 mm. The composition and weight percentage of the acid-soluble glass are as follows: 42 wt% B2O3; 35 wt% BaO; 7 wt% SiO2; 1 wt% Li2O; 2 wt% Na2O; 3 wt% K2O; 1 wt% MgO; 1 wt% CaO; 1 wt% SrO; 3 wt% Al2O3; 3 wt% La2O3; and 1 wt% Y2O3.

[0122] Step 5: Drawing the primary composite rod into a primary multifilament with a characteristic size of 2 mm at 1000° C. During the drawing process, inert gas nitrogen is introduced into the primary composite rod, and the positive pressure is controlled at 1.6 kPa.

[0123] Step 6: Cut the primary multifilament into lengths of 0.5 m and arrange them into glass fiber bundles with regular hexagonal cross-sections. Then, use iron wire to tie and fix the two ends of the glass fiber bundles to obtain secondary composite rods with a characteristic size of about 20 mm.

[0124] Step 7: Drawing the secondary composite rod into a secondary multifilament with a characteristic size of 2 mm at 900° C. During the drawing process, inert gas nitrogen is introduced into the composite rod, and the positive pressure is controlled at 1.6 kPa.

[0125] Step 8: Cut the secondary multifilament into 1m lengths and arrange them into glass fiber bundles with regular hexagonal cross sections. UV-curing treatment with organic glue is performed on both ends (glue type: UV curing glue (purchased from the market) and the curing time is 10 minutes under ultraviolet light (wavelength of 365nm) to obtain a hard optical fiber bundle with a characteristic size of about 32mm.

[0126] Step nine: The hard optical fiber bundle with both ends solidified is subjected to acid etching and softening treatment to obtain a flexible optical fiber image transmission bundle blank. The hard optical fiber bundle with both ends solidified is vertically suspended in an acidic corrosive solution for corrosion treatment (using hydrochloric acid solution to corrode and remove acid-soluble glass, the acid concentration is 0.2 mol / L, the soaking time is 180 minutes, the heating temperature is 40°C, and the acid flow rate is 1.5 L / min); after the optical fiber bundle is completely dispersed, the softened optical fiber bundle is placed in flowing deionized water for multiple cleaning treatments to remove the acidic corrosive liquid on the surface of the dispersed optical fiber bundle; the cleaned flexible optical fiber image transmission bundle is tied and fixed with cotton thread, and then the two end faces are placed in acetone and soaked for 30 minutes to remove the organic glue at both ends. The same acid etching and softening treatment is then performed on the debonded areas at both ends (same as above) to obtain a flexible optical fiber image transmission bundle blank.

[0127] Step 10: Clean the above-mentioned flexible optical fiber image transmission bundle blank (hang the flexible optical fiber image transmission bundle blank fixed with the above-mentioned cotton thread vertically in pure water for cleaning, the water flow rate is 1.5L / min, the cleaning time is 180min, and then clean it with anhydrous ethanol, the anhydrous ethanol flow rate is 1.5L / min, and the cleaning time is 10min), dry it (hang the above-mentioned cleaned flexible optical fiber image transmission bundle blank vertically in a closed drying machine for drying, the drying temperature is 50°C, and the drying time is 30min), and then load its two ends into a hot melt pressing mold, melt-press them separately, and then press them at a high temperature of 700°C (heating rate of 5°C / min, pressure rising rate of 50Pa / min, 0.3MPa pressure maintained for 6 hours, press molding) to obtain a flexible optical fiber image transmission bundle blank with hard end faces at both ends.

[0128] Step 11: The flexible optical fiber image transmission bundle blank with a hard end face is subjected to end face cutting, fine carving, grinding, polishing, cleaning and drying to finally obtain a flexible optical fiber image transmission bundle with a hard end face having an irregular micro-nano through-hole structure.

[0129] The flexible optical fiber imaging bundle obtained in this embodiment is 1m long, the lengths of the hard areas at both ends are 3cm respectively, the characteristic dimension of the end face is about 32mm, the characteristic dimension of the flexible single fiber is D=200μm, the broken wire rate is 0.08‰, the unit wire diameter in the flexible single fiber is 6μm, the aperture of the densely distributed through holes inside is in the range of 160~600nm, the cross-sectional area of the through holes accounts for p of 50%, the highest resolution can reach 161lp / mm, the transmittance per meter of the flexible optical fiber imaging bundle is about 78%, which can achieve good transmittance of 400nm~1500nm visible light-near infrared, and the minimum bending radius allowed is D×20.

[0130] Example 7

[0131] This embodiment provides a method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising the following steps:

[0132] Step 1: Prepare borosilicate glass tubes with a refractive index of n = 1.5, an outer diameter of 6 mm, and two different wall thicknesses (such as Figure 1 ), wherein the number of glass tubes with a wall thickness of 0.8 mm accounts for 50%, and the number of glass tubes with a wall thickness of 1.2 mm accounts for 50%; the composition of the borosilicate glass tube and the proportions by weight are as follows: SiO2 70wt%; B2O3 12wt%; Li2O1wt%; Na2O 2wt%; K2O 3wt%; MgO 1wt%; CaO 1wt%; SrO 1wt%; BaO 3wt%; Al2O34wt%; SnO2 1wt%; ZrO2 1wt%.

[0133] Step 2: Arrange the above two glass tubes randomly and tightly into a glass tube bundle with a regular hexagonal cross section, and use iron wire to tie and fix the two ends of the glass tube bundle to obtain a porous preform with a characteristic size of about 36 mm (such as Figure 2 shown).

[0134] Step 3: Drawing the porous preform rod at 1000° C. into a porous glass monofilament with a characteristic size of 2 mm, wherein inert gas nitrogen is introduced into the glass tube bundle during the drawing process, and the positive pressure is controlled at 2 kPa.

[0135] Step 4: Cut the porous glass monofilament into 0.5m lengths and arrange them randomly and tightly into glass fiber bundles with regular hexagonal cross sections (such as Figure 3 As shown), and an acid-soluble glass sleeve is placed on its periphery (as shown Figure 4 As shown) cover its side (as shown) Figure 5 The glass fiber bundle is then tied and secured at both ends with iron wire to produce a primary composite rod with a characteristic size of approximately 30 mm. The composition and weight percentage of the acid-soluble glass are as follows: B2O3 42wt%; BaO3 5wt%; SiO2 7wt%; Li2O 1wt%; Na2O 2wt%; K2O 3wt%; MgO 1wt%; CaO 1wt%; SrO 1wt%; Al2O3 3wt%; La2O3 3wt%; Y2O3 1wt%.

[0136] Step 5: Drawing the primary composite rod into a primary multifilament with a characteristic size of 1 mm at 950° C. During the drawing process, inert gas nitrogen is introduced into the primary composite rod, and the positive pressure is controlled at 1.6 kPa.

[0137] Step 6: Cut the primary multifilament into 0.8m lengths and arrange them into glass fiber bundles with regular hexagonal cross sections. Then, use iron wire to tie and fix the two ends of the glass fiber bundles to obtain secondary composite rods with a characteristic size of about 20mm (such as Figure 6 shown).

[0138] Step 7: Drawing the secondary composite rod into a secondary multifilament with a characteristic size of 1 mm at 900° C. During the drawing process, inert gas nitrogen is introduced into the composite rod, and the positive pressure is controlled at 0.8 kPa.

[0139] Step 8: Cut the secondary multifilament into 3m lengths and arrange them into glass fiber bundles with regular hexagonal cross sections. Perform UV curing treatment on both ends of the fiber bundles (glue type: UV curing glue (purchased from the market), curing time is 3 minutes under UV lamp (wavelength of 365nm)), and obtain a hard optical fiber bundle with a characteristic size of about 8mm (such as Figure 7 shown).

[0140] Step nine: The hard optical fiber bundle with both ends solidified is subjected to acid etching and softening treatment to obtain a flexible optical fiber image transmission bundle blank. The hard optical fiber bundle with both ends solidified is vertically suspended in an acidic corrosive solution for corrosion treatment (using nitric acid solution to corrode and remove acid-soluble glass, the nitric acid concentration is 0.2 mol / L, the soaking time is 180 minutes, the heating temperature is 30°C, and the acid flow rate is 1.5 L / min); after the optical fiber bundle is completely dispersed, the softened optical fiber bundle is placed in flowing deionized water for multiple cleaning treatments to remove the acidic corrosive liquid on the surface of the dispersed optical fiber bundle; the cleaned flexible optical fiber image transmission bundle is tied and fixed with cotton thread, and then the two end faces are placed in anhydrous ethanol and soaked for 20 minutes to remove the organic glue at both ends. The same acid etching and softening treatment is then performed on the glue-removed areas at both ends to obtain a flexible optical fiber image transmission bundle blank.

[0141] Step 10: Clean and dry the flexible optical fiber image transmission bundle blank, then place both ends of the blank into a hot melt pressing mold and melt-press them separately, and then press-form them at a high temperature of 600°C (maintain a pressure of 0.4MPa for 4 hours for pressing and forming) to obtain a flexible optical fiber image transmission bundle blank with hard end faces at both ends.

[0142] Step 11: The flexible optical fiber image transmission bundle blank with a hard end face is subjected to end face cutting, fine carving, grinding, polishing, cleaning and drying to finally obtain a flexible optical fiber image transmission bundle with a hard end face with an irregular micro-nano through-hole structure (such as Figure 8 shown).

[0143] The flexible optical fiber imaging bundle obtained in this embodiment is 3m long, the length of the hard areas at both ends is 3cm respectively, the characteristic dimension of the end face is about 8mm, the characteristic dimension of the flexible single fiber of the optical fiber imaging bundle is about 50μm, the broken wire rate is 0.2‰, the unit wire diameter in the flexible single fiber is 3.3μm, the aperture of the densely distributed through holes inside is in the range of 110~420nm, the cross-sectional area of the through holes accounts for 50%, the resolution can reach 161lp / mm, the transmittance per meter of the flexible optical fiber imaging bundle is about 75%, and it can achieve good transmittance in the visible light-near infrared band of 400nm~1500nm, and the minimum bending radius allowed is D×20.

[0144] Example 8

[0145] This embodiment provides a method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising the following steps:

[0146] Step 1: Prepare borosilicate glass tubes with a refractive index of n = 1.5, an outer diameter of 3 mm, and two different wall thicknesses (such as Figure 1 ), wherein the number of glass tubes with a wall thickness of 0.8 mm accounts for 44%, and the number of glass tubes with a wall thickness of 1.2 mm accounts for 56%; the composition of the borosilicate glass tubes and the proportions by weight are as follows: SiO2 70wt%; B2O3 12wt%; Li2O 1wt%; Na2O2wt%; K2O 3wt%; MgO 1wt%; CaO 1wt%; SrO 1wt%; BaO 3wt%; Al2O3 4wt%; SnO2 1wt%; ZrO2 1wt%.

[0147] Step 2: Arrange the above two glass tubes randomly and tightly into a glass tube bundle with a square cross section, and use copper wire to tie and fix the two ends of the glass tube bundle to obtain a porous preform with a characteristic size of about 36 mm (such as Figure 2 shown).

[0148] Step 3: Drawing the porous preform rod at 950° C. into a porous glass monofilament with a characteristic size of 1.5 mm. During the drawing process, inert gas nitrogen is introduced into the glass tube bundle, and the positive pressure is controlled at 2 kPa.

[0149] Step 4: Cut the porous glass monofilament into 0.5m lengths and arrange them into glass fiber bundles with square cross sections (such as Figure 3 As shown), and an acid-soluble glass sleeve is placed on its periphery (as shown Figure 4 As shown) cover its side (as shown) Figure 5The glass fiber bundle is then tied and secured at both ends with copper wire to produce a primary composite rod with a characteristic dimension of approximately 30 mm. The composition and weight percentage of the acid-soluble glass are as follows: B2O3 42 wt%; BaO3 5 wt%; SiO2 7 wt%; Li2O 1 wt%; Na2O 2 wt%; K2O 3 wt%; MgO 1 wt%; CaO 1 wt%; SrO 1 wt%; Al2O3 3 wt%; La2O3 3 wt%; and Y2O3 1 wt%.

[0150] Step 5: Drawing the primary composite rod into a primary multifilament with a characteristic size of 2 mm at 950° C. During the drawing process, inert gas nitrogen is introduced into the primary composite rod, and the positive pressure is controlled at 1.6 kPa.

[0151] Step 6: Cut the primary multifilament into 0.5m lengths and arrange them into glass fiber bundles with square cross sections. Then use copper wire to tie and fix the two ends of the glass fiber bundles to obtain secondary composite rods with a characteristic size of about 20mm (such as Figure 6 shown).

[0152] Step 7: Drawing the secondary composite rod into a secondary multifilament with a characteristic size of 1 mm at 900° C. During the drawing process, inert gas nitrogen is introduced into the composite rod, and the positive pressure is controlled at 0.8 kPa.

[0153] Step 8: Cut the secondary multifilament into 1m lengths and arrange them into glass fiber bundles with square cross sections. UV-curing treatment is performed on both ends of the fiber bundles (glue type: UV curing glue (purchased from the market), and the curing time is 5 minutes under UV light (wavelength of 365nm)). A hard optical fiber bundle with a characteristic size of about 16mm is obtained (such as Figure 7 shown).

[0154] Step nine: The hard optical fiber bundle with both ends solidified is subjected to acid etching and softening treatment to obtain a flexible optical fiber image transmission bundle blank. The hard optical fiber bundle with both ends solidified is vertically suspended in an acidic corrosive solution for corrosion treatment (using sulfuric acid solution to corrode and remove acid-soluble glass, the concentration is 0.3 mol / L, the soaking time is 60 minutes, the heating temperature is 50 ° C, and the acid flow rate is 1.5 L / min). After the optical fiber bundle is completely dispersed, the softened optical fiber bundle is placed in flowing deionized water for multiple cleaning treatments to remove the acidic corrosive liquid on the surface of the dispersed optical fiber bundle; the cleaned flexible optical fiber image transmission bundle is tied and fixed with cotton thread, and then the two end surfaces are placed in anhydrous ethanol and soaked for 10 minutes to remove the organic glue at both ends. The same acid etching and softening treatment is then performed on the debonded areas at both ends to obtain a flexible optical fiber image transmission bundle blank.

[0155] Step 10: Clean and dry the above-mentioned flexible optical fiber image transmission bundle blank, then align the two ends of multiple identical flexible optical fiber image transmission bundle blanks and fasten them together, place the two ends into a hot melt pressing mold and melt-press them separately, and then press them at a high temperature of 600°C (maintain a pressure of 0.5MPa for 2 hours for pressing and molding) to obtain a flexible optical fiber image transmission bundle blank with hard end faces at both ends.

[0156] Step 11: The flexible optical fiber image transmission bundle blank with a hard end face is subjected to end face cutting, fine carving, grinding, polishing, cleaning and drying to finally obtain a flexible optical fiber image transmission bundle with a hard end face with an irregular micro-nano through-hole structure (such as Figure 8 shown).

[0157] The flexible optical fiber imaging bundle obtained in this embodiment is 1m long, the length of the hard areas at both ends is 1.5cm respectively, the characteristic dimension of the end face is about 16mm, the characteristic dimension of the flexible single fiber of the optical fiber imaging bundle is about 100μm, the broken wire rate is 0.1‰, the unit wire diameter in the flexible single fiber is 5.0μm, the aperture of the densely distributed through holes inside is in the range of 90~200nm, the cross-sectional area of the through holes accounts for 20%, the resolution can reach 90lp / mm, the transmittance per meter of the flexible optical fiber imaging bundle is about 70%, and it can achieve good transmittance of 400nm~1500nm visible light-near infrared, and the minimum bending radius allowed is D×20.

[0158] Four flexible optical fiber image transmission bundles with hard end faces of the same specifications as mentioned above are aligned at both ends and spliced to obtain a spliced piece, wherein the side surfaces at both ends that need to be spliced are polished and cleaned, the flatness of the splicing interface is 2 apertures, and the glass surface roughness is 5nm. After the two ends are aligned, optical adhesive bonding is performed, and then high-temperature fusion is performed at 500°C to finally obtain a flexible optical fiber image transmission bundle splicing piece with an end face characteristic size of about 32mm, a splicing interface seam width of about 8μm, and no obvious splicing marks. The end face characteristic size of the splicing piece is 1 times larger than the end face characteristic size of the single flexible optical fiber image transmission bundle before splicing, and other performance qualities are consistent with the single flexible optical fiber image transmission bundle before splicing. The preparation of a flexible optical fiber image transmission bundle with an enlarged cross-section is achieved through rapid splicing.

[0159] It can be seen from Examples 1-8 of the present invention that the aperture of the through hole in the flexible single fiber of the flexible optical fiber imaging bundle proposed by the present invention is between 90 and 600 nm, the image resolution can reach up to 181lp / mm, the broken wire rate is less than 1‰, and the end face characteristic size of the flexible optical fiber imaging bundle prepared by the flexible optical fiber of the present invention can reach 32 mm. Theoretically, any number of them can be spliced together to form a flexible optical fiber imaging bundle with a larger cross-section without obvious splicing seams. It is very suitable for quickly splicing to produce a flexible optical fiber imaging bundle with a large cross-section and high resolution.

[0160] In summary, the flexible optical fiber and its image transmission bundle proposed in the present invention adopt an irregular structure of micro-nano through holes, have high resolution, no obvious material edges, and can be spliced in any number of sections on the cross section. It is an ideal choice for the preparation and application of flexible optical fiber image transmission bundles that can meet the requirements of large cross-section and high resolution.

[0161] The necessary modifications and improvements made on the above-mentioned optical fibers and optical fiber bundles according to specific actual needs (such as coating a protective film or an optical functional film on the end face, or cutting and polishing the end face, or covering the outer side of the optical fiber or optical fiber bundle with a protective coating, etc.) should be included in the scope of protection of the present invention and will not be repeated here.

[0162] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0163] The numerical ranges described in the present invention include all values within the range, and include range values formed by any two values within the range. Different numerical values of the same indicator appearing in all embodiments of the present invention can be arbitrarily combined to form a range value.

[0164] The technical features in the claims and / or the specification of the present invention may be combined, and the manner of combination is not limited to the combination obtained by reference in the claims. The technical solutions obtained by combining the technical features in the claims and / or the specification are also within the scope of protection of the present invention.

[0165] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiment based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A flexible fiber optic imaging bundle with a large cross-section and high resolution, characterized in that: The flexible optical fiber image transmission bundle includes a plurality of flexible units, each of which includes a plurality of image transmission units arranged in a densely packed manner, each of which includes a glass fiber having a plurality of circular through holes; the plurality of circular through holes of the glass fiber are irregularly distributed micro-nano through hole structures; the densely packed manner is a regular hexagon, square, or regular triangle dense stacking form; The large-cross-section, high-resolution flexible optical fiber imaging bundle is prepared by the following steps: S1: Arranging at least two glass tubes of the same material, uniform outer diameter, and different pore diameters randomly and closely in a certain quantity ratio, or arranging them closely in a pre-designed irregular distribution, into a glass tube bundle having a regular hexagonal or square cross-section, and tying and securing the glass tube bundle at both ends with copper wire or iron wire to obtain a porous preform; S2: drawing the porous preform obtained in step S1 into a porous glass monofilament; S3: cutting the porous glass monofilaments obtained in step S2 to a fixed length and randomly mixing and arranging them to obtain a monofilament fiber bundle, and then sleeved the monofilament fiber bundle with an acid-soluble glass sleeve of matching size to cover the side surface, and then tying and fixing the monofilament fiber bundle at both ends with copper wire or iron wire to obtain a primary composite rod; S4: drawing the primary composite rod obtained in step S3 into primary multifilaments, cutting the primary multifilaments to a fixed length and arranging them into primary multifilament fiber bundles, and tying and fixing the primary multifilament fiber bundles at both ends with copper wire or iron wire to obtain secondary composite rods; S5: drawing the secondary composite rod obtained in step S4 into secondary multifilaments, cutting the secondary multifilaments to a fixed length and arranging them into secondary multifilament fiber bundles, and performing an organic adhesive UV curing treatment on both ends of the secondary multifilaments to obtain a hard optical fiber bundle; S6: The hard optical fiber bundle obtained in step S5 is subjected to acid etching and softening treatment to obtain the flexible optical fiber image transmission bundle blank; S7: The flexible optical fiber image transmission bundle blank obtained in step S6 is cleaned and dried, and then both ends are pressed and formed to obtain a flexible optical fiber image transmission bundle blank with hard end faces at both ends; S8: The flexible optical fiber image transmission bundle blank with hard end faces obtained in step S7 is subjected to end face cutting, fine carving, grinding, polishing, cleaning, and drying to obtain the flexible optical fiber image transmission bundle.

2. The large-cross-section, high-resolution flexible fiber optic imaging bundle according to claim 1, characterized in that: The pore diameter of the circular through hole is 90-600 nm; the cross-sectional area of the circular through hole accounts for 20%-55% of the total cross-sectional area of the flexible unit fiber.

3. The large-cross-section, high-resolution flexible fiber optic imaging bundle according to claim 1, characterized in that: The flexible unit is a single fiber with a characteristic size of 50~200 μm, and the minimum allowable bending radius is 20 times the characteristic size of the single fiber; the flexible optical fiber imaging bundle can transmit the wavelength range of 400 nm ~1500 nm, with a transmittance of 70~80% per meter; the end face characteristic size reaches more than 8 mm, and the broken wire rate is less than 1‰.

4. The large-cross-section, high-resolution flexible fiber optic imaging bundle according to claim 1, characterized in that: In step S1, the refractive index n of the glass tube is 1.47-1.53; the proportion of the cross-sectional area of the hollow through hole of the glass tube to the entire cross-sectional area of the glass tube is 4%-70%; and the difference between the maximum and minimum values of the proportion of the cross-sectional area of the hollow through hole of the glass tube is greater than or equal to 5%.

5. The large-cross-section, high-resolution flexible fiber optic imaging bundle according to claim 1, characterized in that: In step S2, an inert gas is passed through the porous preform rod during drawing; in step S4, an inert gas is passed through the primary composite rod during drawing; and in step S5, an inert gas is passed through the secondary composite rod during drawing.

6. The large-cross-section, high-resolution flexible fiber optic imaging bundle according to claim 5, characterized in that: In steps S2, S4 and S5, the inert gas is selected from at least one of nitrogen, argon, neon and helium.

7. The large-cross-section, high-resolution flexible fiber optic imaging bundle according to claim 1, characterized in that: In step S2, the outer contour shape of the cross section of the porous glass monofilament is one of a circle, a regular hexagon, an equilateral triangle or a square; in step S3, the outer contour shape of the cross section of the monofilament fiber bundle is a regular hexagon or a square; in step S4, the outer contour shape of the cross section of the primary multifilament fiber bundle is a regular hexagon or a square; in step S5, the outer contour shape of the cross section of the secondary multifilament fiber bundle is a regular hexagon or a square.

8. An endoscope, characterized in that: It comprises the flexible optical fiber imaging bundle according to any one of claims 1 to 7.

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