U-shaped light cone, preparation method and application thereof, and integrated hot bending die

Abstract

The present invention relates to a U-shaped light cone, its preparation method and application, and an integrated hot bending mold. The U-shaped light cone includes a large end portion, a small end portion, and a straight optical fiber portion arranged between the large end portion and the small end portion. The axis of the large end portion is parallel to the axis of the small end portion, and the angles between the axis of the large end portion and the axis of the small end portion and the axis of the straight optical fiber portion are both greater than or equal to 90°; the cone ratio of the U-shaped light cone is (1-5):1. The shape of the U-shaped light cone is free of collapse; the magnification is (1.0-5.0):1; the shear distortion is less than or equal to 50μm; the image displacement is less than or equal to 60μm, and there are no dark spots with a diameter of more than 150μm inside; the transmittance at a wavelength of 500nm is greater than or equal to 50%; the contrast is less than or equal to 2.0%; the optical surface roughness is less than or equal to 30nm; the coupling efficiency is 40-55%; and the coupling resolution is 39-51lp / mm. The pixel diameter of the U-shaped light cone is 4-10μm. The technical problem to be solved is to achieve high-efficiency and high-precision coupling in complex environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing optical fiber image transmission elements, and in particular relates to a U-shaped light cone, a preparation method and application thereof, and an integrated hot bending mold. Background Art

[0002] Light cones are widely used in the coupling of charge-coupled devices (CCDs), image intensifiers, and photomultiplier tubes in the fields of national defense, scientific research, criminal investigation, aerospace, and medical treatment, and are also used in radiographic imaging, new fingerprint recognition, high-definition television imaging, and advanced office equipment imaging. In recent years, with the rapid development of digital image processing technology, the acquisition, storage, and transmission of high-fidelity images have become very convenient, and have become an important symbol of mankind entering the digital age. However, in the process of war, scientific research, production, and medical treatment, people often need to observe, analyze, and process weak images and events that are invisible to the naked eye. For example, they need to monitor and observe at night under no lighting conditions; they need to conduct imaging research on objects that emit rays; they need to track and identify high-speed moving aircraft, and so on. In these cases, the brightness of the image is usually only 10 -3 ~10 -4 Candela, or even lower. Therefore, image enhancement is essential before observation, processing, and analysis. Conventional image digitization techniques are no longer sufficient. Utilizing fiber tapers coupled to CCDs, photomultiplier tubes, and image intensifiers is the optimal solution for digitizing low-light-level imaging and reducing device size. my country began developing fiber tapers in the 1990s. However, there is a significant quality gap compared to those developed by US companies INCOM and SCHOTT. The most critical difference lies in low coupling efficiency with CCDs, poor coupling resolution, and image clarity. The reasons for this are multifaceted. Foreign fiber tapers generally utilize a square wire structure, with a large-end wire diameter of less than 5 microns, internal defects controlled to less than 50 microns, and distortion controlled to less than 3%. This structural approach ensures efficient coupling with the CCD.

[0003] The light cone is a tapered optical fiber array material made by melting, pressing and stretching tens of millions of glass fibers at high temperature, which can achieve 1.5 to 5 times of magnification or reduction. Figure 1As shown, the input end face 1' and the output end face 2' of a conventional light cone are coaxial, and are primarily used in straight-tube optoelectronic coupling devices. The image of the input end face is reduced by a specific factor and then transmitted to the CCD / CMOS to achieve the electronic and digitalization of the optical image. However, for some complex coupling devices, the positional relationship between the image output surface and the photosensitive surface is not simply on the same optical axis, but rather there is a certain spatial misalignment, and their relative position cannot be adjusted. As a result, the coupling strength of conventional flexible fiber bundle coupling devices is low, and they cannot operate normally under high temperature conditions. Therefore, there is a demand for special-shaped light cones to achieve efficient coupling between the image input device of complex high-precision detection equipment and the photosensitive element, which is of great significance to the fields of national defense and scientific research. Summary of the Invention

[0004] In view of this, the main purpose of the present invention is to provide a U-shaped light cone, its preparation method and application, and an integrated hot bending mold. The technical problem to be solved is to achieve spatial misalignment of the positional relationship between the image output surface and the photosensitive element, not being on the same optical axis, and high-efficiency and high-precision coupling under complex environments such as high temperature or corrosion.

[0005] The objectives of the present invention and the technical problems solved therein are achieved by adopting the following technical solutions. A U-shaped light cone proposed in the present invention comprises a large end portion, a small end portion, and an optical fiber portion disposed between the large and small end portions. The axis of the large end portion is parallel to the axis of the small end portion, and the angles between the axis of the large and small end portions and the axis of the optical fiber straight portion are both greater than or equal to 90°. The cone ratio of the U-shaped light cone is (1 to 5):1.

[0006] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0007] Preferably, the aforementioned U-shaped light cone, wherein the large end portion, the small end portion and the optical fiber portion all include tens of millions or even hundreds of millions of micron-sized glass fibers, each of which is composed of a high-refractive-index core and a low-refractive-index cylindrical cladding, the cladding being uniformly coated on the cylindrical surface of the core, the refractive index of the core being 1.80 to 1.81, and the refractive index of the cladding being 1.50 to 1.51.

[0008] Preferably, in the aforementioned U-shaped light cone, the diameter of the glass fiber is 4 to 10 microns, the diameter of the core is 0.8 to 0.85 times the diameter of the glass fiber, and the thickness of the cladding is 0.15 to 0.2 times the diameter of the glass fiber.

[0009] Preferably, in the aforementioned U-shaped light cone, the inner diameter of the large end portion is the same as the inner diameter of the optical fiber portion.

[0010] Preferably, in the aforementioned U-shaped light cone, the optical surface roughness of the U-shaped light cone is less than or equal to 30 nm.

[0011] Preferably, the aforementioned U-shaped light cone, wherein the shape of the U-shaped light cone is not collapsed; the magnification is (1.0~5.0):1; the shear distortion is less than or equal to 50μm; the image displacement is less than or equal to 60μm, and there are no dark spots with a diameter of more than 150μm inside; the transmittance at a wavelength of 500nm is greater than or equal to 50%; the contrast is less than or equal to 2.0%; the optical surface roughness is less than or equal to 30nm; the coupling efficiency is 40~55%, and the coupling resolution is 39~51lp / mm.

[0012] Preferably, in the aforementioned U-shaped light cone, the pixel diameter of the U-shaped light cone is 4-10 μm.

[0013] The purpose of the present invention and the technical problem solved are also achieved by adopting the following technical solutions. According to the method for preparing a U-shaped light cone proposed by the present invention, the method comprises the following steps:

[0014] S1. The first glass member is drawn into a monofilament; the light-absorbing glass rod is drawn into a light-absorbing glass monofilament; the skin glass rod is drawn into a gap wire;

[0015] S2. Arranging multiple monofilaments in a hexagonal close-packed manner, and inserting light-absorbing glass monofilaments and interstitial wires into the gaps formed by the multiple monofilaments, using one light-absorbing glass monofilament for every two fiber cores, and inserting interstitial wires into the remaining gaps to obtain a composite rod;

[0016] S3. The primary composite rods are bundled and drawn into a primary multifilament having a side dimension of 1.0 to 1.05 mm; the primary multifilament is then cut into 630 to 800 mm, and the hexagonal closest-packed arrangement and bundled to obtain a secondary composite rod;

[0017] S4. The secondary composite rod is drawn to obtain a hexagonal prism-shaped melt fiber bundle having a side dimension of 20 to 50 mm, which is then cut to length into melt fiber rods having a length greater than 350 mm, and then rounded to obtain a cylindrical blank having a diameter of 10 to 45 mm;

[0018] S5. The cylindrical blank is stretched at a temperature of 780 to 800°C and a tensile force of 300 to 400N. After stretching, it is cut from the center to obtain two symmetrical light cone blanks.

[0019] S6. Fix the light cone blank, and then place the gravity slider on top of the light cone blank so that the circular through hole on the lower side of the slider completely matches the light cone;

[0020] S7 step S6 of the light cone blank is subjected to high temperature hot bending forming, so that the light cone blank is hot bent at a temperature higher than the softening point of the core, skin and light absorbing glass;

[0021] S8. After cooling completely, take out the U-shaped light cone blank after hot bending and perform optical finishing on its shape. Then determine the optical axis, process the input and output end faces, and then use the machining center to perform optical polishing on the input and output end faces.

[0022] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0023] Preferably, in the aforementioned preparation method, in step S1, the first glass member comprises a glass rod and a skin glass tube of adapted size after screening, the core glass rod is cylindrical, and the skin glass tube is a hollow round tube; the skin glass tube is nested on the surface of the core glass rod to obtain the first glass member; the light-absorbing glass rod is cylindrical, and the absorption coefficient per millimeter of length in the 500-600nm band is greater than 95%.

[0024] Preferably, in the aforementioned preparation method, in step S1, the diameter of the core glass rod is 30±1.0 mm, the inner diameter of the skin glass tube is 31.0-31.5 mm, and the thickness of the skin tube is 3.5-4.0 mm; the diameter of the light absorbing glass rod is 30±1.0 mm; and the diameter of the skin glass rod is 30±1.0 mm.

[0025] Preferably, in the aforementioned preparation method, in step S1, the diameter of the monofilament is 2.00-2.05 mm; the diameter of the light-absorbing glass monofilament is 0.3-0.5 mm; and the diameter of the interstitial filament is 0.3-0.5 mm.

[0026] Preferably, in the aforementioned preparation method, in step S1, the refractive index of the skin glass tube is 1.50-1.51; the refractive index of the glass rod is 1.80-1.81.

[0027] Preferably, in the aforementioned preparation method, in step S6, during the fixing process, a boron nitride solution is coated on the surface of the light cone blank, and then a mica sheet is used to isolate the mold and the light cone blank.

[0028] Preferably, in the aforementioned preparation method, in step S6, the boron nitride solution is prepared by combining three components: nitrocellulose, boron nitride and alcohol, with a volume ratio of nitrocellulose: boron nitride: alcohol = 1: (2-3): (15-20).

[0029] Preferably, in the aforementioned preparation method, in step S7, the high-temperature hot bending forming specifically includes: raising the temperature of the light cone blank in step S6 to 700-720° C. and keeping the temperature for 5-6 hours.

[0030] The objectives of the present invention and the technical problems solved therein are also achieved by adopting the following technical solutions. According to the present invention, an integrated heat bending mold for preparing a U-shaped light cone is proposed, the integrated heat bending mold includes a base, the base has a slide groove adapted to the gravity slider, and the bottom of the slide groove has a boss structure;

[0031] Before placing the light cone blank, the gravity slider and the light cone blank fixing fixture are completely separated from the base, and the gravity slider and the light cone blank fixing fixture are respectively arranged above the slide groove of the base, and the gravity slider moves freely in the slide groove along the z direction and is limited by the boss structure;

[0032] After the light cone blank is placed, and the gravity slider is placed in the slide groove of the base, the lower end of the gravity slider contacts the light cone blank, and the weight of the gravity slider is supported by one end of the light cone blank; the light cone blank fixing fixture is connected to the base by bolts, and the center of the base has a semi-cylindrical groove, and the semi-cylindrical groove of the light cone blank fixing fixture is located directly above the semi-cylindrical groove at the center of the base. The two semi-cylindrical grooves are connected to form a circular through hole, and the light cone blank is placed in the circular through hole.

[0033] Preferably, in the aforementioned integrated hot bending mold for preparing a U-shaped light cone, the slide groove and the boss structure are respectively integrally formed with the base.

[0034] The purpose of the present invention and the technical problems solved therein are also achieved by adopting the following technical solutions: According to a charge coupled device proposed by the present invention, the charge coupled device adopts the aforementioned U-shaped light cone.

[0035] The purpose of the present invention and the technical problems solved therein are also achieved by adopting the following technical solutions: According to an image intensifier proposed by the present invention, the image intensifier adopts the aforementioned U-shaped light cone.

[0036] The purpose of the present invention and the technical problems solved therein are also achieved by adopting the following technical solutions: According to a photomultiplier tube proposed in the present invention, the photomultiplier tube adopts the aforementioned U-shaped light cone.

[0037] By means of the above technical solution, the U-shaped light cone, its preparation method and application, and the integrated hot bending mold proposed in the present invention have at least the following advantages:

[0038] The U-shaped light cone provided by the present invention, its preparation method and application, and integrated hot bending mold can achieve spatial misalignment of the positional relationship between the image output surface and the photosensitive element, and they are not on the same optical axis, and achieve high-efficiency and high-precision coupling in complex environments such as high temperature or corrosion.

[0039] The structure of the U-shaped light cone provided by the present invention comprises three parts: a large end portion, a small end portion and a straight section of the optical fiber; the cone ratio of the U-shaped light cone can reach (1-5):1. The axis of the large end portion is parallel to the axis of the small end portion, and the angles α1 and α2 between the axis of the large end portion and the axis of the small end portion and the axis of the straight section of the optical fiber are respectively greater than or equal to 90°. The shape of the U-shaped light cone is free of collapse. The magnification of the U-shaped light cone can be distributed within the range of (1.0-5.0):1; the shear distortion is less than or equal to 50μm; the image displacement is less than or equal to 60μm, and there are no dark spots with a size exceeding 150μm inside; the transmittance at a wavelength of 500nm is greater than or equal to 50%; and the contrast is less than or equal to 2.0%. The optical surface roughness of the U-shaped light cone is less than or equal to 30nm. The pixel diameter of the U-shaped light cone is 4-10μm. The coupling efficiency of the U-shaped light cone is 40-55%, and the coupling resolution is 39-51lp / mm.

[0040] The present invention designs an integrated hot bending mold, combines the thermophysical properties of the U-shaped light cone, and proposes a matching heat treatment process. The multi-point bending process of the U-shaped light cone is formed in one hot bending mold at one time, and high-precision forming of the U-shaped light cone can be achieved.

[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 with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of the structure of a normal light cone;

[0043] Figure 2 This is one of the schematic diagrams of the U-shaped light cone structure of the present invention;

[0044] Figure 3 This is a process flow chart for preparing a U-shaped light cone according to the present invention;

[0045] Figure 4A It is an insertion diagram of the absorption filament and interstitial filament of the ordinary light cone;

[0046] Figure 4B This is a diagram of the insertion of the U-shaped light cone light absorbing filament and the interstitial filament of the present invention;

[0047] Figure 5 This is a structural diagram of the U-shaped light cone integrated molding die of the present invention;

[0048] Figure 6 This is a cross-sectional view of the integrated hot bending die of the present invention;

[0049] Figure 7 This is a top view of the integrated hot bending die of the present invention;

[0050] Figure 8 This is one of the schematic diagrams of the wire insertion method of Comparative Example 1 of the present invention;

[0051] Figure 9 This is the second schematic diagram of the wire insertion method of Comparative Example 2 of the present invention; DETAILED DESCRIPTION

[0052] To further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail a U-shaped light cone, its preparation method and application, and an integrated hot bending mold proposed in accordance with the present invention, as well as its specific implementation method, structure, characteristics, and effects.

[0053] Unless otherwise specified, the materials and reagents mentioned below are all commercially available products familiar to those skilled in the art; unless otherwise specified, the methods described are all methods well known in the art. Unless otherwise defined, technical or scientific terms used should have the same meanings as those of ordinary skill in the art. Where specific experimental procedures or conditions are not specified below, the procedures or conditions described in the literature in this field can be followed.

[0054] Some embodiments of the present invention provide a U-shaped light cone, such as Figure 2 As shown, it includes a large end portion 2, a small end portion 1 and an optical fiber straight section 3 arranged between the large end portion 2 and the small end portion 1; wherein the length of the small end portion 1 is h1, the length of the large end portion 2 is h2, and the length of the optical fiber straight section 3 is l; the large end portion 2 is parallel to the small end portion 1, and the axis L of the large end portion y1 With the axis L of the small end face y2 Parallel to the axis L of the large end face y1 , small end face axis L y2 Respectively with the optical fiber straight section axis L x The included angles α1 and α2 must be greater than or equal to 90°. If the included angles are less than 90°, the mold hot bending method of the present invention cannot be used to form the U-shaped light cone. This will cause the outer optical fibers of the large and small end portions to break, reducing the transmittance of the outer optical fibers and causing non-uniform light transmission in the U-shaped light cone, which cannot meet the transmittance performance requirements of the U-shaped light cone. The U-shaped light cone is a type of rigid optical fiber image transmission element and is widely used in optoelectronic coupling devices due to its high coupling efficiency.

[0055] In the above-mentioned technical solution, the large end portion 2, the small end portion 1, and the straight fiber section 3 each comprise tens of millions, or even hundreds of millions, of micron-sized glass fibers. Each glass fiber is composed of a high-refractive-index core and a low-refractive-index cylindrical cladding, with the cladding uniformly covering the cylindrical surface of the core. The refractive index of the core ranges from 1.80 to 1.81, and the refractive index of the cladding ranges from 1.50 to 1.51. Theoretically, to ensure sufficiently high light-collecting power and improve the transmittance of the U-shaped light cone, the core refractive index should be as high as possible or the cladding glass refractive index as low as possible. However, if the core refractive index is higher than 1.81, the core glass is prone to crystallization. If the core refractive index is lower than 1.80 and the cladding refractive index is higher than 1.51, the numerical aperture is too small, resulting in a decrease in the light-collecting power of the fiber. The present invention ensures that the numerical aperture of the optical fiber is above 0.98, thereby maximizing the transmittance and coupling efficiency of the U-shaped light cone.

[0056] Furthermore, the diameter of the glass fiber d is 4-10 microns. For the light cone, the finer the fiber diameter, the better, and the finer the fiber cone, the higher the resolution. If the diameter is less than 4 microns, the other properties of the light cone will be impaired and will not meet the required performance. When the fiber diameter is greater than 10 microns, the resolution is less than 57 lp / mm, which has no practical value. Therefore, the fiber diameter d of the present invention is designed to be between 4-10 microns. The corresponding core diameter is 0.8-0.85d, and the cladding thickness is 0.15-0.2d microns. If the core diameter is greater than 0.85d, that is, the cladding thickness is less than 0.15d, crosstalk between the fibers will be aggravated, affecting contrast performance. If the cladding thickness is greater than 0.2d, the effective light transmission area of ​​the light cone will be reduced, and the overall transmittance of the light cone will decrease, affecting performance.

[0057] In addition, the inner diameter of the large end surface portion 2 is the same as the inner diameter of the optical fiber straight section 3, and there is no diameter change from the large end surface portion 2 to the optical fiber straight section 3, which can ensure that the transmittance loss of the U-shaped optical fiber cone is reduced and has sufficient transmittance.

[0058] After testing, the shape of the U-shaped light cone is not collapsed; the magnification can be distributed in the range of (1.0-5.0):1; the shear distortion is less than or equal to 50μm; the image displacement is less than or equal to 60μm, and there are no dark spots with a size exceeding 150μm inside; the transmittance at a wavelength of 500nm is greater than or equal to 50%; the contrast is less than or equal to 2.0%; the resolution is greater than or equal to 90lp / mm; the optical surface roughness of the U-shaped light cone is less than or equal to 30nm; the pixel diameter of the U-shaped light cone is 4-10μm.

[0059] like Figure 2The U-shaped light cone shown is made by bending the input and output end faces of a conventional light cone at a certain angle. The structure of the light cone can also be designed according to the assembly conditions of the coupling device to achieve high-efficiency and high-precision coupling in complex environments. The U-shaped light cone is made of hard optical fiber image transmission material, and the core and sheath glass transition points are both above 600°C to ensure that the U-shaped light cone can operate normally under 400°C. The structural parameters of the U-shaped light cone can be designed and adjusted according to product requirements, and U-shaped light cones with different outer diameters and magnifications can be produced. However, due to its special U-shaped structure, it is necessary to apply heat bending treatment to two locations of the light cone blank. By bending at various angles and in multiple directions, other special-shaped light cones can also be produced. At the same time, to ensure that the U-shaped light cone does not lose a lot of optical performance after heat bending, the bending radius of the bent portion is required, which requires the blank to have a certain length, satisfying the blank length L>h1+h2+l. In reality, the length of conventional light cones currently mass-produced is relatively short, making it impossible to produce other special-shaped structures during the taper drawing process, without having to consider bends greater than 90° and the effects of blank length. The optical fibers that comprise the light cones are all multimode fibers, and their light transmission performance degrades to a certain extent with increasing length. Therefore, based on the structural characteristics and optical performance requirements of U-shaped light cones, appropriate improvements to the material properties and production process are needed. Specifically, the material performance requires that the transmittance of the core glass is higher than 85%, the transmittance of the skin glass is higher than 92%, and the light absorption rate of the light-absorbing glass is not lower than 95%. If the absorption rate of the light-absorbing glass is lower than 95%, it cannot effectively absorb the stray light emitted from the optical fiber, and the contrast performance of the U-shaped light cone will be reduced. If the absorption performance of the light-absorbing glass is required to be higher than 95%, more colorants need to be added during the glass melting process, which will increase the difficulty of melting. The crystallization defects are very likely to increase during the glass melting, resulting in a lower yield. In the preparation process, the number of light-absorbing glass filaments inserted in the gap is appropriately reduced from the conventional 27 light-absorbing filaments to 18 light-absorbing filaments to ensure that the overall transmittance of the U-shaped light cone is improved while absorbing stray light. For the specific process, see the subsequent material composition design and preparation method.

[0060] like Figure 3 As shown, according to some embodiments of the present invention, a method for preparing a U-shaped light cone is provided, comprising the following steps:

[0061] 1. Preparation of Light Cone Blanks

[0062] The light cone blanks in this step are made from tens of millions or even hundreds of millions of micron-sized glass fibers arranged in a tightly packed, regular pattern and then melt-pressed at high temperature. The glass fibers consist of a high-refractive-index core and a low-refractive-index cladding glass. The core refractive index is between 1.80 and 1.81, and the cladding refractive index is between 1.50 and 1.51. The cladding is evenly coated on the cylindrical surface of the cylindrical core. The core refractive index should be as high as possible, or the cladding refractive index should be as low as possible. However, if the core refractive index is higher than 1.81, the core glass is prone to crystallization. If the core refractive index is lower than 1.80 or the cladding refractive index is higher than 1.51, the numerical aperture is too small, resulting in a decrease in the optical fiber's light-collecting ability, and thus a decrease in the overall transmittance of the fiber cone. The core diameter is 0.8-0.85d, and the cladding thickness is 0.15-0.2d. Each glass fiber acts as a pixel, independently transmitting the optical image from the input end to the output end.

[0063] The preparation of the light cone blank specifically includes the following steps:

[0064] 101 The first glass piece is drawn into a monofilament; the light-absorbing glass rod is drawn into a light-absorbing glass monofilament. The glass component ratio of the light-absorbing glass rod is shown in Table 1.

[0065] Among them, the first glass piece in this step includes a screened core glass rod and a skin glass tube. The core glass rod is cylindrical and the skin glass tube is a hollow round tube to avoid scratches, bumps and other defects on the surface of the core glass rod and the skin glass tube that affect the imaging quality of the optical fiber cone. The diameter of the core glass rod is selected to be 30±1.0mm. The common process of the current wire drawing forming equipment uses a core glass rod with a diameter of 30mm. The inner diameter of the glass tube is 31.0~31.5mm, mainly to match the core glass rod. If it is lower than 31.0mm, it cannot be used. If it is higher than 31.5mm, the subsequent plate making accuracy will be reduced, affecting the imaging effect; the thickness of the skin tube is controlled between 3.5-4.0mm. If the thickness is greater than 4.0mm, the overall transmittance of the optical fiber cone will be seriously reduced, which does not meet the use requirements. If the wall thickness is less than 3.5mm, it will lead to an increase in the crosstalk of the optical fiber and a decrease in the imaging contrast; the selected skin glass tube is nested on the surface of the core glass rod to obtain the first glass piece, and then a high-temperature wire drawing furnace is used to draw The production temperature is 780-790°C. When the drawing temperature is higher than 790°C, the glass softens to a high degree, and a fast drawing speed easily leads to low fiber molding accuracy. If the temperature is lower than 780°C, the drawing speed is too slow and seriously reduces the preparation efficiency. It is drawn into a single wire with a wire diameter of 2.00-2.05mm, and the drawing tolerance is controlled within the range of 0.05mm, which is beneficial to improving the light transmission uniformity of the optical fiber cone. Exceeding this range will cause defects in the wire diameter and microstructure uniformity of the optical fiber cone and cause defects in imaging performance. It is cut into short wires with a length of 1000±5mm. The length tolerance does not affect the imaging performance of the optical fiber cone blank, but will reduce the utilization efficiency of the fiber wire. Controlling it within the error range of 10mm helps to reduce production costs. Among them, the refractive index of the sheath glass tube is 1.50~1.51; the refractive index of the core glass rod is 1.80~1.81, the numerical aperture NA ≥ 1.0, the core refractive index should be as high as possible or the cladding glass refractive index should be as low as possible, but when the core refractive index is higher than 1.81, the core glass is prone to crystallization; when the core refractive index is lower than 1.80 and the cladding refractive index is higher than 1.51, the numerical aperture is too small, resulting in a decrease in the optical fiber's light collecting ability, and thus a decrease in the overall transmittance of the optical fiber cone. The light-absorbing glass rod is cylindrical, and the glass used has good light absorption performance. The absorption rate per millimeter of length in the 500-600nm band is more than 95%. The light absorption rate of the light-absorbing glass directly affects the contrast of the optical fiber cone. In order to ensure that the optical fiber cone has high transmittance and contrast, it is necessary to increase the absorption rate of the light-absorbing glass fiber and reduce the number of insertions in the fiber gap. When it is lower than 95%, the number of insertions needs to be increased, and the stray light escaping from the optical fiber cannot be effectively absorbed. The contrast performance of the U-shaped light cone will be reduced. If the absorption performance of the light-absorbing glass is required to be higher than 95%, more colorants need to be added during the glass melting process, which will increase the difficulty of melting the light-absorbing glass and cause glass crystallization, thereby reducing the yield of the light-absorbing glass rod.The diameter of the light-absorbing glass rod is 30mm±1mm, mainly considering the precision requirements and tolerance range of existing glass rod drawing equipment. When it is higher than 31mm, the existing equipment needs to be adjusted, and the process stability deteriorates; when it is lower than 29mm, the diameter of the drawn light-absorbing glass monofilament is between 0.3 and 0.5mm. Within this range, it can be relatively perfectly filled in the gaps between multiple fibers. If the diameter is higher than 0.5mm, the light-absorbing glass filament is likely to cause wear of adjacent fibers during insertion, resulting in defects such as defects. When the diameter is less than 0.3mm, it cannot fill the gap well, resulting in a certain gap between the fibers. During subsequent hot processing and forming, the fibers are easily deformed and the fiber structure will be poor; the skin glass rod is the same as the light-absorbing glass rod when in use, with a diameter of 30mm±1mm, mainly considering the output size, precision requirements and tolerance range of existing glass rod drawing equipment. The diameter of the drawn gap wire monofilament is also controlled within the range of 0.3 to 0.5mm, filling the same gap as the light-absorbing wire. The skin glass tube, core glass rod, and light-absorbing glass are all multicomponent borosilicate glasses. The composition ratios are detailed in Table 1. All three glass materials have high expansion coefficients. Specifically, in the range of 30 to 300°C, the expansion coefficient of the core glass is (92±2)×10. -7 1 / ℃, the expansion coefficient of the cladding glass is (87±2)×10 -7 1 / ℃, the expansion coefficient of light absorbing glass is (86±2)×10 -7 1 / ℃. Softening temperature T of core glass f 700~710℃; the softening temperature of the cladding glass is T f 650~660℃; the softening temperature of light absorbing glass is T f It is 620~630℃.

[0066] Table 1 Composition of core, skin and light absorbing glass

[0067]

[0068] 102 Arrange multiple monofilaments in a hexagonal close-packed manner, and insert light-absorbing glass fibers and white interstitial fibers into the gaps formed by the multiple monofilaments. In order to ensure the transmittance of the U-shaped light cone, it is designed that every two fiber cores share a light-absorbing glass fiber, and white interstitial fibers are inserted into the remaining gaps. For details, see Figure 4BThe U-shaped light cone wire insertion diagram shown in the figure is then used to obtain a primary composite rod; after the primary composite rod is bundled, it is drawn on a high-temperature wire drawing machine into a primary multifilament with a side size of 1.0 to 1.05 mm. If the side size of the multifilament is higher than 1.05 mm or lower than 1.00 mm, it will increase the difficulty of the wire arrangement process, and the poor uniformity of the wire diameter will lead to poor stability of the overall structure of the optical fiber cone; the primary multifilament is then regularly cut into a length of 630 to 800 mm. If the length of the primary multifilament is less than 630 mm, the number of wire arrangement times will increase, resulting in an increase in process steps and a decrease in the yield rate; after it is greater than 800 mm, the degree of bending during fiber arrangement is greater, and the difficulty of wire arrangement increases, so it is preferably within the range of 630 to 800 mm. After the hexagonal closest arrangement and bundling, a secondary composite rod is obtained. The length of the U-shaped light cone is large, and the light transmission loss increases accordingly. At this time, it is necessary to reduce the number of light-absorbing wires inserted to increase the transmittance of the U-shaped light cone blank. The specific operation method is as follows Figure 4A 、 Figure 4B As shown in the inserted wire structure diagram, compared with the conventional light cone multifilament structure, the number of light absorbing wires is reduced from 27 to 19, a reduction of 17.6%. The conventional light cone is a fiber structure composed of a core 30, a cladding 40, a light absorbing wire 20 and a gap wire 10; wherein, the inserted light absorbing wire 20 and the gap wire 10 are inserted between the core 30 and the cladding 40 (see Figure 4A ), the light absorbing filament 20 can absorb stray light, and the interstitial filament 10 can reduce the porosity. The U-shaped light cone is a fiber structure composed of a core 30a, a cladding 40a, a light absorbing filament 20a and an interstitial filament 10a; wherein the light absorbing filament 20a and the interstitial filament 10a are inserted between the core 30a and the cladding 40a (see Figure 4B ), the light absorbing wire 20a can absorb stray light, and the gap wire 10a can reduce the porosity ratio.

[0069] To ensure the optical performance and resolution of the final fiber optic imaging element, a double drawing process is required to obtain a multifilament. In both steps, a high-precision glass fiber forming machine is used to heat and draw the glass components. The heating rate during the heating process is 40-50°C / min. A heating rate lower than 40°C / min reduces the drawing efficiency; a rate higher than 50°C / min can cause the glass rod tube to crack. When the temperature reaches 740-750°C, it is held for 30-40 minutes. The initial heating rate is high, resulting in a temperature difference between the center and edge of the rod tube. Once the temperature reaches a certain level, the heating rate needs to be reduced for holding. A temperature lower than 740°C affects the subsequent fine heating time, while a temperature higher than 750°C prevents good drawing results. A holding time of less than 30 minutes prevents the temperature difference between the center and edge from being balanced. A holding time longer than 40 minutes exacerbates the diffusion of components between the core and sheath. Then continue to heat up at 8-10℃ / min, and this heating reaches the wire drawing forming temperature. If it is lower than 8℃ / min, the heating time will be extended. If it is higher than 10℃ / min, there will still be the problem of inconsistent temperature between the center and the edge, which affects the precision of wire drawing. The drawing temperature of single filament and single multifilament is 780-800℃. If it is lower than 780℃, the core glass has not fully reached the softening forming temperature, and the wire drawing speed is low, which affects the drawing efficiency. If it is higher than 800℃, the softening degree of the core glass is too high, and the dimensional accuracy of the formed fiber is poor, resulting in a wire diameter drawing accuracy of ≤0.05mm.

[0070] Among them, the primary composite rod and the secondary composite rod are both regular hexagonal prism structures. In the step of bundling multiple monofilaments after hexagonal closest arrangement to obtain a primary composite rod, and in the step of bundling multiple primary composite wires after hexagonal closest arrangement to obtain a secondary composite rod, it is necessary to regularly cut multiple monofilaments or primary composite wires. The length of the monofilament is 1000±10mm. The diameter of the monofilament is relatively thick. 1000mm has sufficiently high strength while ensuring better rod arrangement efficiency. The allowable error is within the range of 10mm, which can improve the utilization rate of the primary wire. The length of the primary multifilament is 630-800mm. If the length of the primary multifilament is less than 630mm, the number of wire arrangement times will increase, resulting in an increase in process steps and a decrease in yield rate. When the length is greater than 800mm, the degree of bending during fiber arrangement is greater, and the difficulty of wire arrangement increases. After cutting, a regular hexagonal mold is used to arrange the wires. After the arrangement is completed, the wires are bundled to obtain a primary composite rod or a secondary composite rod.

[0071] 103 It should be noted that in the subsequent secondary composite rod, a molten fiber bundle can be directly obtained through the plate drawing process. This is mainly due to the large axial size of the U-shaped light cone, and the hot pressing process cannot guarantee the uniform pressing of the composite fiber bundle with a longer length, which is prone to distortion and magnification problems. In the wire drawing process, it can be directly drawn into a molten fiber bundle with arbitrary length and uniform structure; the only thing to worry about is the air tightness of the light cone blank prepared by the plate drawing process, but by testing the air tightness of the U-shaped light cone before and after hot bending, it was found that the light cone blank had an air leakage problem before stretching, but after the stretching was completed, the air leakage problem of all U-shaped light cones disappeared, indicating that this defect was well solved in the multi-point hot bending process. In addition, it is necessary to consider the requirement of directly achieving the design pixel size during the plate drawing process in the early design. After obtaining the molten fiber bundle, it is mechanically processed to obtain a cylindrical blank. Specifically, the secondary composite rod is placed in a high-precision glass fiber forming machine, and the pixel size and external size requirements of the U-shaped light cone (such as Figure 5 As shown in the figure, a hexagonal shaped molten fiber bundle with a side dimension of 20 to 50 mm is drawn. The size is drawn according to the required product size requirements. The commonly used product range is between 10 and 20 mm, so it is better to design the side dimension to be 20 to 50 mm. According to the length parameters of the U-shaped light cone, it is cut into a fixed length of molten fiber rods with a length of ≥350 mm. If it is less than 350 mm, the requirements of the two bending radii cannot be met when the U-shaped light cone is hot-bent. The length can be further increased and then rounded on a lathe to obtain a cylindrical blank with a diameter of 10-45 mm. This size is designed according to current product requirements and can be appropriately increased or reduced.

[0072] 104 Place the cylindrical blank into a high-temperature stretching furnace. The stretching temperature is set to 780-800°C. If the temperature is lower than 780°C, the blank is not completely softened, making it difficult to form, and damaging the fibers with large deformation at the edge. If the temperature is higher than 800°C, the blank softens too much, resulting in poor forming accuracy. Figure 5 The cone ratio of the U-shaped light cone shown can reach the range of 1 to 5. When the cone ratio is less than 1, the input and output ends are the same size, the zoom function cannot be realized, and the use requirements are not met. When the cone ratio increases to greater than 5, based on the existing material system and preparation level, the transmittance of the U-shaped light cone is too low to be used normally. The applied tensile force is 300 to 400N. When it is less than 300N, the stretching speed is slow. When it is greater than 400N, the stretching forming process is rapid and the shape cannot be controlled. After the stretching is completed, it is cut from the center position to obtain two symmetrical light cone blanks.

[0073] For other quartz optical fibers, the bending process mostly uses a hot flame spray gun, which can be bent after heating at room temperature, and will not cause stress explosion. However, for the U-shaped light cone in the present invention, this preparation method is not applicable, because when the light cone is heated by a flame spray gun, it is very easy to explode due to its high expansion coefficient. At the same time, this method has low control accuracy of the bending radius and angle during the bending process, and it is difficult to meet the requirements of preparing high-precision U-shaped light cones. Therefore, the present invention proposes an integrated mold hot bending process based on the physical properties of the U-shaped light cone, which forms the multi-point bending process of the U-shaped light cone in one hot bending mold at one time. According to the design of the mold, the bending forming of various special-shaped light cones can be achieved. First, according to the structure of the U-shaped light cone, an integrated forming mold is designed. Figure 5 The connection between the components can also refer to Figure 6 、 Figure 7 The cross-sectional view and top view of the integrated hot bending mold shown. Specifically, the integrated molding mold includes a base 1. First, the base 1 has slide grooves 4 and 5 that respectively match the geometric shapes of the gravity sliders 2 and 3. The slide grooves 4 and 5 are provided with boss structures a and b below, and the slide grooves 4 and 5, the boss structures a and b are all integrally formed with the base 1. The base 1 is made of heat-resistant stainless steel (2520 steel) to avoid the deformation of the mold itself during the hot bending process, which causes errors in the structure of the U-shaped light cone. Before the light cone blank is placed, the gravity sliders 2 and 3 are completely separated from the base 1. The gravity slider 2 is arranged directly above the slide groove 4 of the base 1. The gravity slider 2 can move freely in the slide groove 4 of the base 1 along the z direction. When no upward pulling force is applied, the gravity slider 2 slowly slides downward along the z direction in the slide groove 4 of the base 1. Before placing the light cone blank, the slider 2 needs to be pulled out of the slide groove 4, as shown in FIG. Figure 5 As shown in , the boss structure a of the base 1 is a limiting device for the movement of the gravity slider 2 in the z direction. The gravity slider 2 stops moving when it is stuck in the boss structure a, and the weight of the gravity slider 3 is supported by the boss structure a; the gravity slider 3 is arranged directly above the slide groove 5 of the base 1, and the gravity slider 3 can move freely in the slide groove 5 of the base 1 along the z direction. When no upward pulling force is applied, the gravity slider 3 slowly slides downward along the z direction in the slide groove 5 of the base 1. Before placing the light cone blank, the slider 3 needs to be pulled out of the slide groove 5. The boss structure b of the base 1 is a limiting device for the movement of the gravity slider 3 in the z direction. The gravity slider 3 stops moving when it is stuck in the boss structure b, and the weight of the gravity slider 3 is supported by the boss structure b. The light cone blank fixing fixture 6 is separated from the base 1 and is arranged directly above the base 1. There is a semi-cylindrical groove 7 at the center of the lower side of the light cone blank fixing fixture 6. The light cone blank fixing fixture 6 can be connected to the base 1 by a bolt 9 (see Figure 6 and Figure 7), the base 1 has a semi-cylindrical groove 8 at its center. The semi-cylindrical groove 7 of the light cone blank fixing fixture 6 is located directly above the semi-cylindrical groove 8 at the center of the base 1. The semi-cylindrical groove 7 and the semi-cylindrical groove 8 are butted together to form a circular through-hole. The inner diameter of the circular through-hole is the same as the outer diameter of the light cone blank, and the light cone blank can be placed in the circular through-hole. The light cone blank is fixed to the circular through-hole formed by the semi-cylindrical groove 7 of the light cone blank fixing fixture 6 and the semi-cylindrical groove 8 of the base 1 by bolts 9. This can effectively prevent sliding or warping displacement caused by the subsequent application of pressure, thereby improving processing accuracy.

[0074] During the hot bending forming process, first place the light cone blank into the circular through hole; tighten the bolt 9 to fix the light cone blank so that it does not slide or warp; place the gravity slider 2 in the slide groove 4 of the base 1, and the lower end of the gravity slider 2 contacts the light cone blank, and the weight of the gravity slider 2 is supported by one end of the light cone blank; place the gravity slider 3 in the slide groove 5 of the base 1, and the lower end of the gravity slider 3 contacts the other end of the light cone blank, and the weight of the gravity slider 3 is supported by the light cone blank. When the temperature continues to rise, the role of the gravity sliders 2 and 3 is to apply external pressure for hot bending when the light cone reaches the softening temperature. When the optical fiber blank begins to soften, it will gradually bend. The weight of the two sliders can be adjusted by adding weights. This method can be used for bending U-shaped light cones of different diameters by adjusting the inner diameter of the circular through hole. When the optical fiber blank reaches the softening point, U-shaped bending is achieved under the action of the gravity sliders 2 and 3. When the gravity sliders 2 and 3 stop at the limit, no gravity is applied to the light cone blank. The diameter of the semi-cylindrical groove 8 at the center of the base 1 and the semi-cylindrical groove 7 of the light cone blank fixing fixture 6 are the same as the outer dimensions of the designed U-shaped light cone, which suppresses other unexpected radial deformations of the light cone during the hot bending process, and can effectively ensure the outer shape accuracy of the U-shaped light cone after the hot bending is completed. After the design is completed, the engraving machine is used according to Figure 5-Figure 7 The integrated hot bending forming mold is processed by precision engraving and milling, and the material used for the mold is 2520 heat-resistant stainless steel.

[0075] During the integrated molding process, the mold is placed in a high-temperature furnace, the temperature of the furnace is set, and continuous heating is performed until the light cone reaches its softening temperature. The ends of the light cone are then subjected to the pressure of a gravity slider to complete the thermal bending process. During this process, the light cone and the mold are placed in the same environment, allowing all parts of the U-shaped light cone to be heated evenly. By setting a holding time and performing integrated thermal bending after the temperature stabilizes, the phenomenon of collapse can be effectively prevented. Furthermore, the circular through-hole formed by the semi-cylindrical grooves 7 and 8, which form the fixing grooves of the light cone, is designed based on the structural parameters of the target U-shaped light cone. During thermal bending, the light cone deforms only within this range, avoiding deformation in other directions and effectively ensuring dimensional accuracy, thereby ensuring sufficiently high optical performance of the U-shaped light cone.

[0076] 106 Place the light cone blank into the circular through hole formed by the semi-cylindrical groove 7 of the light cone blank fixing fixture 6 of the integrated hot bending forming mold and the semi-cylindrical groove 8 of the base 1, and fix it with bolts 9 to prevent it from moving. During this process, boron nitride solution needs to be coated on the surface of the light cone blank, and then mica sheets are used to isolate the mold and the light cone blank to prevent collapse and adhesion.

[0077] The boron nitride solution is prepared by combining nitrocellulose, boron nitride, and alcohol in a volume ratio of nitrocellulose: boron nitride: alcohol = 1: (2-3): (15-20). The main function of the nitrocellulose is to increase the adhesion of boron nitride to the optical fiber blank. If the volume ratio of the nitrocellulose, boron nitride, and alcohol is lower than the lower limit, the amount of nitrocellulose added is small, resulting in less boron nitride adhering to the optical cone blank, causing the blank to adhere to the mold and unable to be demolded. If the volume ratio of the nitrocellulose, boron nitride, and alcohol is higher than the upper limit, the nitrocellulose volume ratio is too large, resulting in uneven application of boron nitride. Therefore, it is necessary to ensure that the nitrocellulose, boron nitride, and alcohol maintain an appropriate ratio. Since the amount of nitrocellulose added is the smallest among the three components, the content of boron nitride and alcohol is adjusted with the volume of nitrocellulose as 1; when the volume of boron nitride is less than 2, the content is low and the isolation effect of boron nitride on the blank and the mold is poor. When the volume is greater than 3, the high concentration makes it difficult to apply and the application efficiency is reduced; the role of alcohol is to assist in application and achieve rapid volatilization. When the volume of alcohol is less than 15-20, a better concentration and a faster volatilization speed can be achieved. When the volume is less than 15 or greater than 20, the concentration will be too high or too low, which is not conducive to uniform application; the size of the mica sheet is 180×5×0.5mm (length×width×thickness).

[0078] After the light cone blank is secured, the gravity slider is gently placed in the position of the slide 4. The lower ends of the gravity sliders 2 and 3 are placed above the light cone blank. The circular through-hole formed by the semi-cylindrical groove 7 of the light cone blank fixing fixture 6 and the semi-cylindrical groove 8 of the base 1 on the lower sides of the sliders 2 and 3 is completely aligned with the light cone blank, ensuring the accuracy of the hot bending process. During this process, because the diameter of the U-shaped light cone is larger near the input end, the bending process requires greater force. On the other hand, the diameter of the stretched position of the bending point near the output end is smaller and easier to bend. Therefore, the basic weights of sliders 2 and 3 are 4-4.5kg and 3-3.5kg, respectively. Slider 2 is located at the large end face of the light cone blank, and the blank diameter remains consistent and unchanged. This fully considers the blank's shear resistance range and forming pressure requirements. When the weight of slider 2 is less than 4kg, the blank cannot be fully bent and formed during heating. When it is greater than 4.5kg, the blank's shape will be fractured during cooling. Slider 3 is located at the small end face of the light cone, and the diameter of the light cone blank is reduced, reducing the shear force it withstands to within the range of 3-3.5kg. In addition, the weight of the slider can be adjusted accordingly based on the diameter of the light cone blank, specifically by adding weights.

[0079] 108 Place the mold in a high-temperature annealing furnace and set the temperature system. When the temperature rises to 700-720℃, the pressure is applied continuously during hot bending. The forming temperature should be relatively lower than the drawing temperature. When it is lower than 700℃, the blank cannot be completely fitted with the forming groove. When it is higher than 720℃, the temperature is too high and the slider may easily cause unexpected deformation of the blank during forming. Keep it warm for 5-6 hours. If it is lower than 5 hours, it cannot be completely formed. If it is higher than 6 hours, the core and skin components in the blank will diffuse, resulting in reduced imaging quality. Ensure that the mold and the light cone blank are heated evenly, and the temperature of the center and outer side of the light cone blank is consistent, so that the light cone blank can be hot bent in one time under the temperature condition higher than the softening point of the core, skin and light absorbing glass.

[0080] After complete cooling, the U-shaped light cone blank, formed by hot bending, is removed. Due to its unique structure, a five-axis engraving machine is required to perform optical finishing on its outer shape and process the input and output end faces of the U-shaped light cone blank. A CNC machining center is then used to optically polish the input and output end faces. The optical surface roughness after polishing is controlled within 30-40nm. A roughness above 40nm will reduce the imaging quality of the light cone, while a roughness below 30nm will significantly increase the polishing time without significantly improving performance, resulting in increased costs.

[0081] 110 The optical properties of the obtained U-shaped light cone, such as magnification, shear distortion, serpentine distortion, dark spots, grid, transmittance, and resolution, are tested. The magnification, shear distortion, serpentine distortion, dark spots, grid, transmittance, and resolution of the U-shaped light cone are tested using conventional methods in the art.

[0082] The aforementioned U-shaped light cone is a type of rigid optical fiber image transmission element, and is widely used in optoelectronic coupling devices, such as charge coupled devices or image intensifiers, due to its high coupling efficiency.

[0083] The structure of the U-shaped light cone provided by the present invention is quite different from that of the conventional coaxial light cone, and a method for preparing a special-shaped U-shaped light cone is designed accordingly. In combination with the structural characteristics of the U-shaped light cone, it needs to have a relatively large length, which results in a great loss in the light transmission ability of the light cone. In the present invention, the wire insertion process and the preparation process are adjusted accordingly to ensure the optical performance of the U-shaped light cone. In addition, the core and skin glass of the U-shaped light cone are both glass materials with a relatively high expansion coefficient. Conventional quartz glass bending technology makes it difficult to achieve the bending process of the U-shaped light cone. The present invention designs a hot bending mold, and at the same time, in combination with the thermal physical characteristics of the U-shaped light cone, proposes a heat treatment process that matches it, which can achieve high-precision forming of the U-shaped light cone.

[0084] The present invention will be further described below with reference to more specific embodiments.

[0085] Example 1:

[0086] According to the core and sheath material ratios shown in Table 2, Example 1, core glass rods, sheath glass tubes, and sheath glass tubes were melted to produce the core and sheath glass rods. The glass material properties were tested, with the specific test results shown in Table 2. The light-absorbing glass composition and proportions (in wt%) were: SiO₂ 72%; Na₂O 5%; Fe₂O₃ 7%; CoO₃ 3%; MnO₂ 6%; and V₂O₅ 7%. The light-absorbing glass rods were melted to produce the core and sheath glass rods. A U-shaped light cone was then produced by combining the core and sheath glass rods and tubes according to the following method. The performance test results are detailed in Table 2.

[0087] The method for preparing the U-shaped light cone comprises the following steps:

[0088] 1. Preparation of Light Cone Blanks

[0089] The light cone blanks in this step are made from tens of millions, even hundreds of millions, of micron-sized glass fibers arranged in a tightly packed, regular pattern and then melt-pressed at high temperatures. The glass fibers consist of a high-refractive-index core and a low-refractive-index cladding glass. The core refractive index is 1.80, and the cladding refractive index is 1.505. The core diameter is 0.8d, and the cladding thickness is 0.2d.

[0090] The preparation of the light cone blank specifically includes the following steps:

[0091] 101 Drawing the first glass piece into a monofilament; drawing the light-absorbing glass rod into a light-absorbing glass monofilament.

[0092] The first glass component in this step consists of a screened core glass rod and a sheath glass tube. The core glass rod is cylindrical, and the sheath glass tube is a hollow circular tube. The core glass rod has a diameter of 30 mm, the glass tube has an inner diameter of 31.2 mm, and the sheath glass tube has a thickness of 3.7 mm. The selected sheath glass tube is nested on the surface of the core glass rod to form the first glass component. The component is then drawn in a high-temperature drawing furnace at a temperature of 785°C into a single filament with a diameter of 2.005 mm, which is then cut into short filaments of 1000 mm in length. The refractive index of the sheath glass tube is 1.505, and the refractive index of the core glass rod is 1.80. The light-absorbing glass rod is cylindrical and made of glass with excellent light absorption properties, exhibiting an absorption rate of over 95% per millimeter of length within the 500-600nm wavelength range. The diameter of the light-absorbing glass rod is 30mm, and the diameter of the drawn light-absorbing glass monofilament is 0.35mm. The sheath glass rod, like the light-absorbing glass rod, has a diameter of 30mm, and the diameter of the drawn interstitial monofilament is also controlled to 0.35mm, filling the same gap as the light-absorbing filament. The sheath glass tube, core glass rod, and light-absorbing glass are all multicomponent borosilicate glass. The composition ratios of the core and sheath are detailed in Table 2. The composition and ratios of the light-absorbing glass (in wt%) are: SiO2 72%; Na2O 5%; Fe2O3 7%; CoO 3%; MnO2 6%; and V2O5 7%. All three glass materials have high expansion coefficients. Specifically, at 30-300°C, the expansion coefficient of the core glass is 90×10 -7 1 / ℃, the expansion coefficient of the cladding glass is 88×10 -7 1 / ℃, the expansion coefficient of light-absorbing glass is 86×10 -7 1 / ℃. Softening temperature T of core glass f 700℃; cladding glass softening temperature T f 650℃; the softening temperature of light absorbing glass is T f It is 620℃.

[0093] 102 Arrange multiple monofilaments in a hexagonal close-packed manner, and insert light-absorbing glass fibers and white interstitial fibers into the gaps formed by the multiple monofilaments. In order to ensure the transmittance of the U-shaped light cone, it is designed that every two fiber cores share a light-absorbing glass fiber, and white interstitial fibers are inserted into the remaining gaps. For details, see Figure 4B The U-shaped light cone is inserted as shown in the figure, and then a primary composite rod is obtained; the primary composite rod is bundled and then drawn into a primary multifilament with a side size of 1.0mm on a high-temperature wire drawing machine, and then the primary multifilament is cut into a length of 650mm by a regular method. After hexagonal closest arrangement and bundling, a secondary composite rod is obtained. At this time, the number of light absorbing wires inserted needs to be reduced. The specific operation method is as follows Figure 4BAs shown in the wire insertion structure diagram, compared with the ordinary light cone multifilament structure, the number of light absorption wires is reduced from 27 to 19, a reduction of 17.6%.

[0094] To ensure the optical performance and resolution of the final fiber optic imaging element, the fiber undergoes two drawing processes to produce a single multifilament. In both steps, a high-precision glass fiber forming machine is used to heat and draw the glass. The heating rate during the heating process is 40°C / min. Once the temperature reaches 740°C, it is held at that temperature for 40 minutes. The temperature is then increased at 8°C / min until it reaches the drawing temperature. The drawing temperature for the single filament and the single multifilament reaches 780°C.

[0095] The primary composite rod and the secondary composite rod both have a regular hexagonal prism structure. In the steps of bundling multiple monofilaments in a hexagonal closest arrangement to obtain a primary composite rod, and in the steps of bundling multiple primary composite filaments in a hexagonal closest arrangement to obtain a secondary composite rod, the multiple monofilaments or primary composite filaments are regularly cut to a length of 1000 mm for the monofilaments and 650 mm for the primary composite filaments. After cutting, the monofilaments are arranged in a regular hexagonal mold, and then bundled to obtain the primary composite rod or the secondary composite rod.

[0096] 103 Place the secondary composite rod into a high-precision glass fiber forming machine and shape the U-shaped light cone according to its pixel size and overall size requirements (such as Figure 5 As shown), a hexagonal prism-shaped molten fiber bundle with a side size of 20 mm is drawn. The size is drawn according to the required product size requirements. According to the length parameter of the U-shaped light cone, it is cut into a molten fiber rod with a length of 360 mm, and then rolled on a lathe to obtain a cylindrical blank with a diameter of 15 mm.

[0097] 104 Place the cylindrical blank into a high temperature stretching furnace, and set the stretching temperature to 780°C. Figure 5 The U-shaped light cone shown has a cone ratio of 1 and an applied tensile force of 300 N. After the tensile process is completed, the light cone is cut from the center to obtain two symmetrical light cone blanks.

[0098] 106 Place the light cone blank into the circular through hole formed by the semi-cylindrical groove 7 of the light cone blank fixing fixture 6 of the above-mentioned integrated hot bending forming mold and the semi-cylindrical groove 8 of the base 1, and fix it with bolts 9 to prevent it from moving. During this process, boron nitride solution needs to be coated on the surface of the light cone blank, and then mica sheets are used to isolate the mold and the light cone blank.

[0099] The boron nitride solution is prepared by mixing nitrocellulose, boron nitride and alcohol in a volume ratio of nitrocellulose:boron nitride:alcohol=1:2:18; the size of the mica sheet is 180×5×0.5mm (length×width×thickness).

[0100] After the light cone blank is secured, the gravity sliders 2 and 3 are gently placed in the slots 4. The lower ends of the sliders 2 and 3 are positioned above the light cone blank, ensuring that the circular through-hole formed by the semi-cylindrical groove 7 of the light cone blank fixing fixture 6 and the semi-cylindrical groove 8 of the base 1 on the lower sides of the sliders 2 and 3 fits perfectly within the light cone blank. The basic weights of the sliders 2 and 3 are 4 kg and 3 kg, respectively. The slider 2 is positioned at the large end face of the light cone blank.

[0101] 108 Place the mold in a high-temperature annealing furnace, set the temperature system, and keep it warm for 5 hours when the temperature rises to 700°C.

[0102] After complete cooling, the U-shaped light cone blank, which had been heat-bent, was removed and its shape was optically finished using a five-axis engraving machine. The input and output end faces of the light cone were also machined. The input and output end faces were then optically polished using a CNC machining center. The optical surface roughness after polishing was controlled at 35nm.

[0103] 110 pairs of optical properties of the obtained U-shaped light cones, including magnification, shear distortion, serpentine distortion, dark spots, grids, transmittance, and resolution, were tested.

[0104] Example 2:

[0105] According to the core and sheath material ratios shown in Table 2, Example 2, a core glass rod, a sheath glass tube, and a sheath glass tube were melted to produce the core glass rod, sheath glass tube, and the glass material properties were tested. Specific test results are shown in Table 2. The composition and ratio of the light-absorbing glass were the same as in Example 1. The core and sheath glass rod and tube were then combined using the methods and parameters of Example 1 to produce a U-shaped light cone. The performance test results are detailed in Table 2.

[0106] Example 3:

[0107] According to the core and sheath material ratios shown in Table 2, Example 3, a core glass rod, a sheath glass tube, and a sheath glass tube were melted to produce the core glass rod, sheath glass tube, and the glass material properties were tested. Specific test results are shown in Table 2. The composition and ratio of the light-absorbing glass were the same as in Example 1. The core and sheath glass rod and tube were then combined using the methods and parameters of Example 1 to produce a U-shaped light cone. The performance test results are detailed in Table 2.

[0108] Example 4:

[0109] According to the core and sheath material ratios shown in Table 2, Example 4, a core glass rod, a sheath glass tube, and a sheath glass tube were melted to produce the core glass rod, sheath glass tube, and the glass material properties were tested. Specific test results are shown in Table 2. The composition and ratio of the light-absorbing glass were the same as in Example 1. The core and sheath glass rod and tube were then combined using the methods and parameters of Example 1 to produce a U-shaped light cone. The performance test results are detailed in Table 2.

[0110] Table 2. U-shaped light cone core and skin material composition and performance test table of the light cones prepared by combining them in Examples 1-4

[0111]

[0112]

[0113] From the data in Table 2, it can be seen that in Example 1, the refractive index of the core glass is 1.80, and the refractive index of the skin glass is 1.505. The refractive index difference is small, and the light collecting ability of the optical fiber is low, resulting in a low overall transmittance of the optical fiber cone; the expansion coefficient difference is 2×10 -7 (1 / ℃), which makes it difficult to eliminate the stress of the core and skin glass during the molding process, and the blank is prone to collapse. In Example 2, the refractive index of the core glass is 1.8, and the refractive index of the skin glass is 1.508. The difference is moderate, the optical fiber has good light collecting ability, and the transmittance is guaranteed to reach 68%. The expansion coefficient difference is 4×10 -7 (1 / ℃), which can effectively eliminate the stress of fiber drawing and avoid the collapse phenomenon. The shear distortion and image displacement can reach a low level, and the resolution reaches 114lp / mm. The refractive index of the core glass of Example 3 is 1.81, the refractive index of the skin glass is 1.51, and the expansion coefficient difference is 4×10 -7 (1 / ℃), which can effectively eliminate the stress of fiber drawing and avoid the collapse phenomenon. The shear distortion and image displacement can reach a low level. The resolution reaches 114lp / mm and the contrast performance is 1.6%, which is slightly lower than that of Example 2. The refractive index of the core glass of Example 4 is 1.805, and the refractive index of the skin glass is 1.51, with a small difference. The light cone transmittance is 64%, and the expansion coefficient difference is 8×10 -7 (1 / ℃), the core and skin materials are not well matched, resulting in the collapse of the blank, and the resolution of the blank is low, only reaching 101lp / mm; by coupling and comparing the U-shaped light cone with the same model of CMOS, it is found that the resolution of Example 1 after coupling with CMOS is 50lp / mm, the coupling resolution of Example 2 is the highest, reaching 52lp / mm, and the coupling resolution of Example 4 is the lowest, reaching 49lp / mm; the coupling efficiency has also reached a relatively high level, and there is no obvious loss compared to ordinary light cones of the same size. The coupling efficiency of Example 3 is the lowest, reaching 43%. Based on the performance indicators of the U-shaped light cones in the above embodiments, the U-shaped light cone obtained by the material composition ratio in Example 2 has the best performance. Based on this, the insertion method of the light absorption wire in the U-shaped light cone primary composite rod is adjusted to obtain U-shaped light cones with different wire insertion methods.

[0114] The components of the core glass in Example 2 were fixed, and U-shaped light cones with different taper ratios were prepared. Other preparation processes were fixed. The specific examples are as follows.

[0115] Example 5

[0116] Prepare core and skin glass rod tubes according to the core and skin glass component ratios shown in Example 2, and then Figure 4B The insertion method of the U-shaped light cone light absorbing wire of the design shown in the figure was used to prepare a U-shaped light cone with a cone ratio of 1.0:1 as Example 5, and its performance is shown in Table 3; the fixed processing steps were used to adjust the cone ratios to 1.6:1, 2.0:1; 3.0:1; 4.0:1; 5.0:1 in sequence to obtain Examples 6, 7, 8, 9, and 10. The specific test performance is shown in Table 3.

[0117] Comparative Example 1

[0118] Prepare the core and skin glass rod tube according to the core and skin glass component ratio shown in Example 2, and then adjust the insertion method of the light absorbing wire, such as Figure 8 As shown, a U-shaped light cone was prepared. The U-shaped light cone comprises a fiber structure composed of a core 30b, a cladding 40b, light-absorbing filaments 20b, and interstitial filaments 10b. The inserted light-absorbing filaments 20b and interstitial filaments 10b are inserted between the core 30b and the cladding 40b. The light-absorbing filaments 20b absorb stray light, while the interstitial filaments 10b reduce the porosity. The performance of the U-shaped light cone is shown in Table 3.

[0119] Comparative Example 2

[0120] According to the core and skin glass component ratio shown in Example 2, a core and skin glass rod tube is prepared, and then the ordinary light cone light absorption wire insertion method is used, such as Figure 9 As shown, a U-shaped light cone was prepared. The U-shaped light cone comprises a fiber structure composed of a core 30c, a cladding 40c, light-absorbing filaments 20c, and interstitial filaments 10c. The inserted light-absorbing filaments 20c and interstitial filaments 10c are inserted between the core 30c and the cladding 40c. The light-absorbing filaments 20c absorb stray light, while the interstitial filaments 10c reduce the porosity. The performance of the U-shaped light cone is shown in Table 3.

[0121] Table 3 Comparative table of U-shaped light cone performance prepared by different wire insertion methods in Examples 5-10 and Comparative Examples 1-2

[0122]

[0123]

[0124] The data in Table 3 shows that in Examples 5-10, with a fixed preparation process and light-absorbing filament insertion method, the transmittance of the U-shaped light cone decreases significantly with increasing taper ratio, which is normal. When the taper ratio is 5:1, the transmittance is 50%, the shear distortion is 50μm, the image displacement is 58μm, the dark spots meet the qualified standards, there are no internal grid defects, the contrast is 1.5%, and the resolution is 90lp / mm, which meets the application requirements. After coupling U-shaped light cones with different taper ratios to CMOS, the coupling resolution and coupling efficiency both decrease with increasing taper ratio. When the taper ratio is 5:1, the coupling resolution and coupling efficiency are the lowest, at 39lp / mm and 40%, respectively. Compared with a conventional light cone with the same taper ratio, the coupling resolution and coupling efficiency are not significantly reduced. After changing the insertion method and number of the light-absorbing filaments, the cone ratio was fixed at 1.6:1, and comparative examples 1 and 2 were prepared. Compared with Example 6, the transmittance of the U-shaped light cones of comparative examples 1 and 2 was increased by 1% and 3%. However, due to the reduction in the number of light-absorbing filaments, the stray light absorption ability was weakened, and the contrast value was increased, which did not meet the use requirements of the U-shaped light cone.

[0125] From the data in Tables 2 and 3, it can be concluded that the U-shaped light cones described in Examples 1-10 of the present invention have no external shape collapse; the magnification is (1.0-5.0):1; the shear distortion is less than or equal to 50 μm; the image displacement is less than or equal to 60 μm, and there are no dark spots with a diameter of more than 150 μm inside; the transmittance at a wavelength of 500 nm is greater than or equal to 50%; the contrast is less than or equal to 2.0%; the optical surface roughness is less than or equal to 30 nm; the coupling efficiency is 40-55%, and the coupling resolution is 39-51 lp / mm.

[0126] 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.

[0127] 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 U-shaped light cone, characterized in that: It includes a large end portion, a small end portion and a straight optical fiber portion arranged between the large end portion and the small end portion. The axis of the large end portion is parallel to the axis of the small end portion, and the angles between the axis of the large end portion and the axis of the small end portion and the axis of the straight optical fiber portion are both equal to 90°; the cone ratio of the U-shaped light cone is (1~5):

1.

2. The U-shaped light cone according to claim 1, wherein: The large end portion, small end portion and optical fiber portion all include tens of millions or even hundreds of millions of micron-sized glass fibers. Each of the glass fibers is composed of a high-refractive-index core and a low-refractive-index cylindrical cladding. The cladding is evenly coated on the cylindrical surface of the core. The refractive index of the core is 1.80-1.81, and the refractive index of the cladding is 1.50-1.

51.

3. The U-shaped light cone according to claim 2, wherein: The diameter of the glass fiber is 4 to 10 microns, the diameter of the core is 0.8 to 0.85 times the diameter of the glass fiber, and the thickness of the cladding is 0.15 to 0.2 times the diameter of the glass fiber.

4. The U-shaped light cone according to claim 1, wherein: The inner diameter of the large end portion is the same as the inner diameter of the optical fiber straight portion.

5. The U-shaped light cone according to claim 1, wherein: The U-shaped light cone has a shape without collapse; the magnification is (1.0-5.0):1; the shear distortion is less than or equal to 50 μm; the image displacement is less than or equal to 60 μm, and there are no dark spots with a diameter of more than 150 μm inside; the transmittance at a wavelength of 500 nm is greater than or equal to 50%; the contrast is less than or equal to 2.0%; the optical surface roughness is less than or equal to 30 nm; the coupling efficiency is 40-55%, and the coupling resolution is 39-51 lp / mm.

6. An integrated hot bending die for preparing the U-shaped light cone according to any one of claims 1 to 5, characterized in that: The integrated hot bending mold includes a base, the base has a slide groove adapted to the gravity slider, and a boss structure is provided below the slide groove; Before placing the light cone blank, the gravity slider and the light cone blank fixing fixture are completely separated from the base, and the gravity slider and the light cone blank fixing fixture are respectively arranged above the slide groove of the base, and the gravity slider moves freely in the slide groove along the z direction and is limited by the boss structure; After the light cone blank is placed, and the gravity slider is placed in the slide groove of the base, the lower end of the gravity slider contacts the light cone blank, and the weight of the gravity slider is supported by one end of the light cone blank; the light cone blank fixing fixture is connected to the base by bolts, and the center of the base has a semi-cylindrical groove, and the semi-cylindrical groove of the light cone blank fixing fixture is located directly above the semi-cylindrical groove at the center of the base. The two semi-cylindrical grooves are connected to form a circular through hole, and the light cone blank is placed in the circular through hole.

7. The integrated hot bending mold for preparing a U-shaped light cone according to claim 6, characterized in that: The slide groove and boss structure are respectively formed integrally with the base.

8. A method for preparing a U-shaped light cone according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. The first glass member is drawn into a monofilament; the light-absorbing glass rod is drawn into a light-absorbing glass monofilament; the skin glass rod is drawn into a gap wire; S2. Arranging multiple monofilaments in a hexagonal close-packed manner, and inserting light-absorbing glass monofilaments and interstitial wires into the gaps formed by the multiple monofilaments, using one light-absorbing glass monofilament for every two fiber cores, and inserting interstitial wires into the remaining gaps to obtain a composite rod; S3. The primary composite rods are bundled and drawn into a primary multifilament having a side dimension of 1.0 to 1.05 mm; the primary multifilament is then cut into 630 to 800 mm, and the hexagonal closest-packed arrangement and bundled to obtain a secondary composite rod; S4. The secondary composite rod is drawn to obtain a hexagonal prism-shaped melt fiber bundle having a side dimension of 20 to 50 mm, which is then cut to length into melt fiber rods having a length greater than 350 mm, and then rounded to obtain a cylindrical blank having a diameter of 10-45 mm; S5. The cylindrical blank is stretched at a temperature of 780 to 800°C and a tensile force of 300 to 400N. After stretching, it is cut from the center to obtain two symmetrical light cone blanks. S6. Fix the light cone blank, and then place the gravity slider on top of the light cone blank so that the circular through hole on the lower side of the slider completely matches the light cone; S7 step S6 of the light cone blank is subjected to high temperature bending, so that the light cone blank is bent at a temperature higher than the core, skin and light absorbing glass softening point conditions; S8. After cooling completely, take out the U-shaped light cone blank after hot bending and perform optical finishing on its shape. Then determine the optical axis, process the input and output end faces, and then use the machining center to perform optical polishing on the input and output end faces.

9. The preparation method according to claim 8, wherein In step S1, the first glass component includes a core glass rod and a skin glass tube of adapted sizes after screening, wherein the core glass rod is cylindrical and the skin glass tube is a hollow round tube; the skin glass tube is nested on the surface of the core glass rod to obtain the first glass component; the light-absorbing glass rod is cylindrical and has an absorption coefficient of more than 95% per millimeter of length in the 500-600nm band.

10. The preparation method according to claim 9, wherein In step S1, the diameter of the core glass rod is 30±1.0 mm, the inner diameter of the skin glass tube is 31.0-31.5 mm, and the thickness of the skin tube is 3.5-4.0 mm; the diameter of the light absorbing glass rod is 30±1.0 mm; and the diameter of the skin glass rod is 30±1.0 mm.

11. The preparation method according to claim 9, wherein In step S1, the diameter of the monofilament is 2.00-2.05 mm; the diameter of the light-absorbing glass monofilament is 0.3-0.5 mm; and the diameter of the interstitial filament is 0.3-0.5 mm.

12. The preparation method according to claim 9, wherein In step S1, the refractive index of the skin glass tube is 1.50-1.51; the refractive index of the glass rod is 1.80-1.

81.

13. The preparation method according to claim 8, wherein In step S6, during the fixing process, a boron nitride solution is coated on the surface of the light cone blank, and then a mica sheet is used to isolate the mold and the light cone blank.

14. The preparation method according to claim 13, wherein In step S6, the boron nitride solution is prepared by combining three components: nitrocellulose, boron nitride, and alcohol, with a volume ratio of nitrocellulose: boron nitride: alcohol = 1: (2-3): (15-20).

15. The preparation method according to claim 8, characterized in that In step S7, the high-temperature hot bending forming specifically includes: raising the temperature of the light cone blank in step S6 to 700-720°C and keeping the temperature for 5-6 hours.

16. A charge coupled device, characterized in that: The charge coupled device adopts the U-shaped light cone as described in any one of claims 1-5.

17. An image intensifier, characterized in that: The image intensifier adopts the U-shaped light cone as described in any one of claims 1-5.

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