Optical fiber image transmitting element with square structure and preparation method of optical fiber image transmitting element

Abstract

The invention relates to an optical fiber image transmitting element with a square structure and a preparation method thereof, and the preparation method comprises the following steps: drawing a square wire: matching a square skin glass tube with a square core glass rod with a high refractive index, and then carrying out monofilament drawing to obtain a drawn square monofilament; drawing the square core material glass rod with high refractive index into a square gap wire; the method comprises the following steps: preparing a square light absorption material glass rod from light absorption material glass, and drawing the square light absorption material glass rod into a square light absorption wire; drawing a square primary multifilament, and drawing a square secondary multifilament; and finally, carrying out hot melt pressing molding and processing molding to obtain the optical fiber image transmitting element with a square structure. The optical fiber image transmitting element with the square structure can be applied to an enhanced charge-coupled device, and has the advantages of high coupling efficiency, high resolution, high contrast ratio, high light transmittance and clear imaging.

Description

Technical Field

[0001] The invention relates to the field of manufacturing optical fiber image transmission components, and in particular to an optical fiber image transmission component with a square structure and a preparation method thereof. Background Art

[0002] An enhanced charge coupled device (ICCD) is a digital low-light imaging device formed by cascade coupling of a fiber optic image inverter, a fiber optic light cone or a fiber optic panel and a CCD image sensor. It has been widely used in digital all-weather display systems such as low-light night vision systems, space remote sensing detection, and tracking systems.

[0003] The fiber optic image transmission element is the core optical component in the enhanced charge coupled device detection system. It is an excellent photoelectric imaging component with large numerical aperture, high light transmission efficiency, high resolution, true and clear image transmission, zero thickness in optics, simple structure, small size, light weight, good air tightness, small distortion, few spots, small inter-stage coupling loss, high coupling efficiency and improved edge image quality. As the optical output window of the enhanced charge coupled device, it plays an important role in improving the quality of imaging devices and is a high-tech cutting-edge product in the world's optoelectronics industry today. The coupling efficiency, light transmittance, coupling resolution, fiber leakage rate and other properties of the fiber optic image transmission element determine the detection and identification field of view, imaging quality and service life of the detection system.

[0004] In order to meet the development requirements of high contrast, high resolution and high transmittance imaging of digital display detection system, it has been hoped to improve the clarity of optical fiber image transmission components by improving the absorption effect of light absorbing glass. Traditional optical fiber image transmission components are all round wire structures, and their preparation usually adopts the combination of round rods and round tubes. Specifically, the optical fiber is drawn and formed by combining a high refractive index core glass rod with a round end face and a low refractive index skin glass tube, and a single wire with a round end face is prepared. The single wire is arranged into a primary composite rod, and every three circular single wires form a triangular cavity. Then, light absorbing glass wires are inserted into the triangular cavity and drawn into a hexagonal primary composite wire as a whole. The primary composite wire is arranged into a secondary composite rod and drawn into a secondary composite wire. The secondary composite wire is cut and arranged, and the optical fiber image transmission component blank is prepared after hot melt pressing. The blank is subjected to subsequent optical finishing, taper processing or 180° twisting molding, etc., to prepare different types of optical fiber image transmission components.

[0005] However, the structural design of the circular unit wire currently used in China has very limited effects on improving coupling efficiency and light transmittance, and is prone to produce moiré fringes, which deteriorates the molding quality. The main reason is that the tightly stacked structure of the circular unit wire will have a large number of triangular gaps, and these triangular gaps will produce a lot of invalid light flux. This part of the invalid light flux is difficult to absorb through the light-absorbing glass, resulting in difficulty in improving the light transmittance of the optical fiber imaging element. Summary of the invention

[0006] The main purpose of the present invention is to provide a square-structured optical fiber imaging element with high coupling efficiency, high resolution, high contrast, high light transmittance and clear imaging, and a preparation method thereof.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a square-structured optical fiber image transmission element comprises the following steps:

[0009] (1) Drawing of square wire: A square skin glass tube with a low refractive index is matched with a square core glass rod with a high refractive index, and then single wire drawing is performed to obtain a drawn square single wire;

[0010] A square core glass rod with a high refractive index is drawn into a square gap wire;

[0011] A square light absorbing glass rod is prepared from the light absorbing glass, and the square light absorbing glass rod is drawn into a square light absorbing wire;

[0012] (2) Drawing of square primary multifilaments: Arranging the drawn square monofilaments into a primary composite rod with square end faces, and uniformly inserting the square light absorbing wires and the square interstitial wires into the gaps between the square monofilaments, and drawing the primary composite rods assembled as above into square primary multifilaments;

[0013] (3) Drawing of square secondary multifilaments: Arranging the drawn square primary multifilaments into secondary composite rods with square end faces, bundling the secondary composite rods and drawing them into secondary multifilaments, and then cutting the secondary multifilaments to a fixed length and arranging them into screen plate segments;

[0014] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, and hot melt pressing at a certain compression ratio to obtain a blank plate segment of a square optical fiber imaging element;

[0015] (5) Processing and molding: The blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a square-structured optical fiber imaging element blank. The square-structured optical fiber imaging element blank is subjected to subsequent optical finishing, and then heated and tapered or twisted 180° to obtain a square-structured optical fiber imaging element.

[0016] The end face size of the square core glass rod is (20-30) mm×(20-30) mm, and the four edges of the square core glass rod are chamfered at 45°, of which three edges are 45° protective chamfers, and the protective chamfer size is 2% of the side size of the end face of the square core rod, and the chamfer size of the fourth edge is 20% of the side size of the end face of the square core rod; the inner four-side size of the skin glass tube is 22 mm-32 mm, and the wall thickness of the skin glass tube is 3.8-4.2 mm.

[0017] The core glass rod is a square rod with chamfered corners, and the four opposite sides of the square single wire are 2.54mm to 7mm; the end faces of the square light absorption wire and the square gap wire are both squares, the end faces of the square light absorption wire and the square gap wire have the same area, and the side length of the square is 0.7mm to 1.95mm.

[0018] In the primary composite rod, the number of square monofilaments on each side is 4-16, and the opposite side size of the square primary multifilament is 1.02mm-1.60mm;

[0019] The number of square primary multifilaments on each side of the secondary composite rod is 18 to 32; the opposite side dimensions of the square secondary multifilaments are 0.5 to 1.6 mm, and the diagonal dimensions of the primary composite rod and the secondary composite rod are both no more than 46 mm.

[0020] The light absorbing glass comprises the following components in molar percentage: SiO2 64-78%, B2O3 3-16%, Al2O3 0-5%, Li2O 0-1%, Na2O 0-6%, K2O 0-12%, MgO 0-1.5%, CaO 0-2.5%, BaO 0-1%, SrO 0-1%, ZnO 0-1%, TiO2 0-1%, ZrO2 0-1%, CeO2 0-1%, Fe2O3 0-6%, NiO 0.1-1%, V2O5 0-1%, Co2O3 0-2%, MoO3 0-0.2%, MnO2 0.1-2.5%, Cr2O3 0.1-2%, Nd2O3 0-1%, CuO0.1-2%, F2 0-1%.

[0021] Preferably, the light absorbing glass comprises the following components in molar percentage: SiO2 68-76%, B2O3 3-10%, Al2O3 3-5%, Li2O 0-1%, Na2O 2-6%, K2O 3-9%, MgO 0.2-1.0%, CaO 1-2.5%, BaO0-0.1%, SrO 0-0.2%, ZnO 0-0.1%, TiO2 0-0.3%, ZrO2 0-0.3%, CeO2 0-0.1%, Fe2O3 0.1-6%, NiO 0.3-1%, V2O5 0-1%, Co2O3 0.1-1.5%, MoO3 0-0.2%, MnO2 0.1-2.0%, Cr2O3 0.1-1%, Nd2O3 0-0.5%, CuO 0.1-1%, F2 0.1-1%.

[0022] More preferably, the light absorbing glass comprises the following components in molar percentage: SiO2 73%, B2O3 4%, Al2O3 4.8%, Na2O 5.2%, K2O 7%, MgO 0.5%, CaO 1.5%, SrO 0.1%, Fe2O3 0.4%, NiO0.4%, Co2O3 1.0%, MnO2 0.3%, Cr2O3 0.5%, CuO 0.8%, and F2 0.5%.

[0023] Furthermore, a method for preparing the light absorbing glass is also provided, comprising the following steps:

[0024] (1) Raw material preparation: quartz sand, boric acid, aluminum oxide, lithium carbonate, sodium carbonate, potassium carbonate, basic magnesium carbonate, calcium carbonate, barium nitrate, strontium carbonate, zinc oxide, titanium dioxide, zirconium oxide, cerium oxide, iron trioxide, nickel oxide, vanadium pentoxide, cobalt trioxide, molybdenum trioxide, manganese dioxide, potassium chromate, neodymium oxide, copper oxide and calcium fluoride are weighed according to a molar ratio, and mixed evenly to obtain a raw material mixture;

[0025] (2) Glass melting: Add the raw material mixture into a crucible and melt it at 1420-1520°C for 5-8 hours. After the raw material mixture is melted, stir it 2-3 times until a clear and homogenized glass liquid is formed. Discharge the glass liquid at 1360-1380°C and cast it into the required glass in a mold. After the glass is cooled and solidified, anneal it at a temperature of 550-600°C for 24-36 hours to obtain a light absorbing material glass. The light absorbing material glass is drawn into a light absorbing material glass rod.

[0026] The light absorbing glass of the present invention has a spectral transmittance of ≤2.5% in the wavelength range of 380-760nm at a thickness of 0.30±0.01mm and a thermal expansion coefficient of (80±5)×10 －7 / ℃; no crystallization occurs when kept at 850℃ for 6 hours.

[0027] The present invention further provides a square-structured optical fiber image transmission element, which is prepared according to the preparation method.

[0028] The present invention further provides an application of the square-structured optical fiber imaging element in an enhanced charge coupled device. The square-structured optical fiber imaging element of the present invention can be applied to a detection system.

[0029] Compared with the prior art, the square-structured optical fiber image transmission element of the present invention has at least the following advantages:

[0030] (1) The square-structured optical fiber image transmission element of the present invention has a unit wire diameter of less than 4.0×4.0 μm and a center resolution of greater than 140 lp / mm, eliminating the moiré fringe effect caused by the coupling of round wires and square pixels, thereby improving coupling efficiency and imaging clarity;

[0031] (2) The shear distortion of the square-structured optical fiber imaging element of the present invention is less than 10 μm, and the optical fiber leakage ratio is less than 5%, thereby improving the detection sensitivity;

[0032] (3) The square-structured optical fiber image transmission element of the present invention has a transmittance of >70% in the wavelength range of 380-760nm;

[0033] (4) The square-structured optical fiber imaging element of the present invention has a crosstalk of less than 1.0% at a distance of 0.1 mm from the blade, has excellent fixed pattern noise performance, and has no obvious multifilament boundary when observed under a 10x microscope.

[0034] The structural design of the square-structured optical fiber image transmission element of the present invention can well avoid the gap of the triangular hole, and the four-sided close stacking method can well improve the compactness and light transmittance of the optical fiber image transmission element, which is of great help to improve the clarity of the optical fiber image transmission element. The square-structured optical fiber image transmission element of the present invention has the advantages of high coupling efficiency, high resolution, high contrast, high light transmittance, and clear imaging. The square-structured optical fiber image transmission element of the present invention is applied to an enhanced charge coupled device to achieve efficient coupling with an ICCD, which can effectively improve the imaging clarity and light transmittance of a micro-light image tube.

[0035] 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 preferred embodiments of the present invention are described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of the internal structure of an optical fiber of a square-structured optical fiber imaging element provided by an embodiment of the present invention;

[0037] Figure 2 for Figure 1 Enlarged view of point I.

[0038] Figure 3 A schematic diagram of the end face of a core glass rod for drawing a single filament of a square structure optical fiber imaging element provided in an embodiment of the present invention;

[0039] Figure 4 This is a transmittance curve of the light absorbing glass provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0041] Table 1 Chemical composition (mol.%) and properties of light absorbing glass examples

[0042]

[0043] The glass sheets (thickness 0.30±0.01 mm) made of the raw materials of Examples 1 to 5 were tested. The spectral transmittance of the glass sheets of each Example in the wavelength range of 380-760 nm was <2.5%, and there was no phase separation or crystallization when kept at 850° C. for 6 hours.

[0044] See also Figure 1 and Figure 2 , which is a schematic diagram of the internal structure of an optical fiber constituting a square structure optical fiber imaging element provided in an embodiment of the present invention, wherein a skin glass tube and a core glass rod are matched and drawn into a square monofilament, wherein the square monofilament comprises an outer skin glass 1 and an inner core glass 2, and the drawn square monofilaments are arranged into a primary composite rod with a square end face according to the requirement of 20 square monofilaments on each side, and square light absorbing filaments 3 drawn from square light absorbing glass and square gap filaments 4 drawn from a square core glass rod are uniformly filled and inserted into the pores of the primary composite rod, and the opposite side dimension of the square primary composite rod is K, and the opposite side dimension of the monofilament is D.

[0045] See also Figure 3, which is a schematic diagram of the end face of the core glass rod for drawing the single filament of the square structure optical fiber imaging element provided in an embodiment of the present invention, the side edge dimension of the end face of the core glass rod is A, and the four edges of the square core glass rod are chamfered at 45°, of which three edges are 45° protective chamfers, and the protective chamfer dimension b is 2% of the side edge dimension of the end face of the core glass rod, that is, b=0.02A, and the chamfer dimension a of the fourth edge is 20% of the side edge dimension of the end face of the core glass rod, that is, a=0.2A.

[0046] See also Figure 4 , is the transmittance curve of the light absorbing glass. It can be seen that it has strong light absorption ability and filtering effect in the wavelength range of 380-760nm, and the spectral transmittance is less than 2.5%. It can be seen that the light absorption effect on visible light is very obvious.

[0047] Herein, all "mol. %" are based on the total molar amount of the final glass composition. The glass chemical compositions (mol. %) of the examples are listed in detail in Table 1.

[0048] The parameters, measuring methods and instruments for the light absorbing glass of the present invention are as follows:

[0049] (1) The transmittance of the light absorbing glass is measured using a transmittance tester;

[0050] (2) Average linear thermal expansion coefficient α at 30-300℃ 30 / 300 [×10 -7 / ℃] is measured using a horizontal dilatometer and the method specified in GB / T 16920-2015.

[0051] The square in the present invention refers to a square. For example, a square monofilament refers to a monofilament with a square end face, and a square light-absorbing yarn refers to a light-absorbing yarn with a square end face.

[0052] Example 1

[0053] (1) Drawing of square single wire, square gap wire and square light absorbing wire:

[0054] a. Matching a square skin glass tube with a low refractive index with a square core glass rod with a high refractive index, and then drawing a single wire to obtain a drawn square single wire; the opposite side dimension of the square single wire is 5 mm; the end face dimension of the square core glass rod is 25 mm×25 mm, and the four edges of the square core glass rod are chamfered, of which three edges are protective chamfers with a protective chamfer dimension of 0.5 mm×45°, and the chamfer dimension of the fourth edge is 5 mm×45°; drawing a square core glass rod with a high refractive index into a square gap wire with an end face side length dimension of 1.4 mm; the inner four opposite sides of the skin glass tube are 26 mm, and the wall thickness is 4.0 mm;

[0055] b. Preparation of light absorbing glass:

[0056] Select raw materials according to the glass composition of Example 1 in Table 1, so that the ingredients meet the glass chemical composition of Table 1, and then prepare the contrast enhancement filter glass according to the following steps:

[0057] (1) Raw material preparation: weigh raw materials of quartz sand, boric acid, aluminum oxide, sodium carbonate, potassium carbonate, basic magnesium carbonate, calcium carbonate, barium nitrate, strontium carbonate, zinc oxide, titanium dioxide, zirconium oxide, cerium oxide, iron trioxide, nickel oxide, vanadium pentoxide, molybdenum trioxide, manganese dioxide, potassium chromate and copper oxide according to a molar ratio, mix them evenly, and obtain a raw material mixture;

[0058] (2) Glass melting: Add the raw material mixture into a crucible and melt it at 1420° C. for 8 hours. After the raw material mixture is melted, stir it twice, each stirring speed is 50 rpm, each stirring time is 1 hour, and the interval time between the two stirrings is 30 minutes, until a clear and homogenous glass liquid is formed. Then, discharge the material at 1380° C. and cast it into the required glass in a mold. After the glass is cooled and solidified, annealing treatment is performed at 600° C. and annealing time is 24 hours to obtain a light absorbing material glass.

[0059] c. preparing a square light absorbing glass rod with good light absorbing performance from the light absorbing glass, and drawing the square light absorbing glass rod into a square light absorbing wire with a side size of 1.4 mm;

[0060] (2) Drawing of square primary multifilaments: Arranging the drawn square monofilaments into a primary composite rod with square end faces, wherein the number of square monofilaments on each side of the primary composite rod is 6, and inserting the square light absorbing wire into the pores between the square monofilaments, and drawing the primary composite rod assembled as above into a square primary multifilament with a side size of 1.6 mm;

[0061] (3) Drawing of square secondary multifilaments: Arrange the drawn square primary multifilaments into secondary composite rods with square end faces, and the number of square primary multifilaments on each side of the secondary composite rods is 18; bundle the secondary composite rods and draw them into secondary multifilaments with opposite side dimensions of 0.5 mm, and then cut the secondary multifilaments to a fixed length and arrange them into screen plate segments;

[0062] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, and hot melt pressing under high temperature and pressure, controlling the compression ratio before and after the hot melt pressing to be 0.86, to obtain a blank plate segment of a square structure optical fiber imaging element with a unit wire diameter of 3.98 μm;

[0063] (5) Processing and molding: The blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a square-structured optical fiber imaging element blank. The square-structured optical fiber imaging element blank is subjected to subsequent optical processing and then twisted 180° to obtain a square-structured optical fiber image inverter.

[0064] Example 2

[0065] (1) Drawing of square monofilaments and square light-absorbing filaments:

[0066] a. Matching a square skin glass tube with a low refractive index with a square core glass rod with a high refractive index, and then drawing a single wire to obtain a drawn square single wire; the square single wire has a side size of 2.54 mm; the end face size of the square core glass rod is 20 mm×20 mm, and the four edges of the square core glass rod are chamfered, of which three edges are protective chamfers with a protective chamfer size of 0.4 mm×45°, and the chamfer size of the fourth edge is 4 mm×45°; the square core glass rod with a high refractive index is drawn into a square gap wire with an end face side size of 0.7 mm; the inner four-side side size of the skin glass tube is 22 mm, and the wall thickness is 3.8 mm;

[0067] b. Preparation of light absorbing glass:

[0068] Select raw materials according to the glass composition of Example 2 in Table 1, so that the ingredients meet the glass chemical composition of Table 1, and then prepare the contrast enhancement filter glass according to the following steps:

[0069] Raw material preparation: weigh raw materials quartz sand, boric acid, aluminum oxide, lithium carbonate, sodium carbonate, potassium carbonate, basic magnesium carbonate, calcium carbonate, zirconium oxide, nickel oxide, cobalt trioxide, molybdenum trioxide, manganese dioxide, potassium chromate, copper oxide and calcium fluoride in a molar ratio, mix them evenly, and obtain a raw material mixture;

[0070] Glass melting: Add the raw material mixture into a crucible and melt it at 1520°C for 5 hours. After the raw material mixture is melted, stir it 3 times, each stirring speed is 80rpm, each stirring time is 1 hour, and the interval time between each stirring is 1 hour, until a clear and homogenized glass liquid is formed, then discharge the material at 1360°C, cast it into the required glass in a mold, and anneal it after the glass is cooled and solidified. The annealing temperature is 550°C and the annealing time is 36 hours to obtain a light absorbing material glass.

[0071] c. preparing a square light absorbing glass rod with good light absorbing performance from the light absorbing glass, and drawing the square light absorbing glass rod into a square light absorbing wire with a side size of 0.7 mm;

[0072] (2) Drawing of square primary multifilaments: Arranging the drawn square monofilaments into a primary composite rod with square end faces, wherein the number of square monofilaments on each side of the primary composite rod is 12, and inserting the square light absorbing wire into the pores between the square monofilaments, and drawing the primary composite rod assembled as above into a square primary multifilament with a side size of 1.1 mm;

[0073] (3) Drawing of square secondary multifilaments: Arrange the drawn square primary multifilaments into secondary composite rods with square end faces, and the number of square primary multifilaments on each side of the secondary composite rods is 28; bundle the secondary composite rods and draw them into secondary multifilaments with opposite side dimensions of 1.6 mm, and then cut the secondary multifilaments to a fixed length and arrange them into screen plate segments;

[0074] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, and hot melt pressing under high temperature and pressure, controlling the compression ratio before and after the hot melt pressing to be 0.83, to obtain a blank plate segment of a square structure optical fiber imaging element;

[0075] (5) Processing and forming: The blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a square-structured optical fiber imaging element blank. The square-structured optical fiber imaging element blank is subjected to subsequent optical processing and then heated to form a cone to obtain a square-structured light cone with a unit wire diameter of 3.95 μm.

[0076] Example 3

[0077] (1) Drawing of square monofilaments and square light-absorbing filaments:

[0078] a. Matching a square skin glass tube with a low refractive index with a square core glass rod with a high refractive index, and then drawing a single wire to obtain a drawn square single wire; the square single wire has a side size of 7 mm; the end face size of the square core glass rod is 30 mm × 30 mm, and the four edges of the square core glass rod are chamfered, of which three edges are protective chamfers with a chamfer size of 0.6 mm × 45°, and the chamfer size of the fourth edge is 6 mm × 45°; the square core glass rod with a high refractive index is drawn into a square gap wire with an end face side size of 1.95 mm; the inner four-side side size of the skin glass tube is 32 mm, and the wall thickness is 4.2 mm;

[0079] b. Preparation of light absorbing glass:

[0080] Select raw materials according to the glass composition of Example 3 in Table 1, so that the ingredients meet the glass chemical composition of Table 1, and then prepare the contrast enhancement filter glass according to the following steps:

[0081] (1) Raw material preparation: weigh raw materials of quartz sand, boric acid, aluminum oxide, sodium carbonate, potassium carbonate, basic magnesium carbonate, calcium carbonate, strontium carbonate, ferric oxide, nickel oxide, cobalt oxide, manganese dioxide, potassium chromate, copper oxide and calcium fluoride according to a molar ratio, mix them evenly, and obtain a raw material mixture;

[0082] (2) Glass melting: Add the raw material mixture into a crucible and melt it at 1470°C for 7 hours. After the raw material mixture is melted, stir it twice, each stirring speed is 70 rpm, each stirring time is 2 hours, and the interval time between each stirring is 30 minutes, until a clear and homogenous glass liquid is formed. Then, discharge the material at 1370°C and cast it into the required glass in a mold. After the glass is cooled and solidified, annealing treatment is performed at 580°C for 30 hours to obtain a light absorbing material glass.

[0083] c. preparing a square light absorbing glass rod with good light absorbing performance from the light absorbing glass, and drawing the square light absorbing glass rod into a square light absorbing wire with a side size of 1.95 mm;

[0084] (2) Drawing of square primary multifilaments: Arranging the drawn square monofilaments into a primary composite rod with square end faces, wherein the number of square monofilaments on each side of the primary composite rod is 4, and inserting the square light absorbing wire into the pores between the square monofilaments, and drawing the primary composite rod assembled as above into a square primary multifilament with a side size of 1.02 mm;

[0085] (3) Drawing of square secondary multifilaments: Arrange the drawn square primary multifilaments into secondary composite rods with square end faces, and the number of square primary multifilaments on each side of the secondary composite rods is 28; bundle the secondary composite rods and draw them into secondary multifilaments with opposite side dimensions of 0.52 mm, and then cut the secondary multifilaments to a fixed length and arrange them into screen plate segments;

[0086] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, and hot melt pressing under high temperature and pressure, controlling the compression ratio before and after the hot melt pressing at 0.85, to obtain a blank plate segment of a square structure optical fiber imaging element;

[0087] (5) Processing and molding: The blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a square-structured optical fiber imaging element blank. The square-structured optical fiber imaging element blank is subjected to subsequent optical processing and then twisted 180° to obtain a square-structured optical fiber inverter with a unit wire diameter of 3.95 μm.

[0088] Example 4

[0089] (1) Drawing of square monofilaments and square light-absorbing filaments:

[0090] a. Matching a square skin glass tube with a low refractive index with a square core glass rod with a high refractive index, and then drawing a single wire to obtain a drawn square single wire; the square single wire has a side size of 3 mm; the end face size of the square core glass rod is 25 mm×25 mm, and the four edges of the square core glass rod are chamfered, of which three edges are protective chamfers with a protective chamfer size of 0.5 mm×45°, and the chamfer size of the fourth edge is 5 mm×45°; the square core glass rod with a high refractive index is drawn into a square gap wire with an end face side size of 0.8 mm; the inner four-side side size of the skin glass tube is 26 mm, and the wall thickness is 3.9 mm;

[0091] b. Preparation of light absorbing glass:

[0092] Select raw materials according to the glass composition of Example 4 in Table 1, so that the ingredients meet the glass chemical composition of Table 1, and then prepare the contrast enhancement filter glass according to the following steps:

[0093] Raw material preparation: weigh raw materials quartz sand, boric acid, aluminum oxide, sodium carbonate, potassium carbonate, basic magnesium carbonate, calcium carbonate, barium nitrate, titanium dioxide, ferric oxide, nickel oxide, cobalt oxide, manganese dioxide, potassium chromate, neodymium oxide, copper oxide and calcium fluoride in a molar ratio, mix them evenly, and obtain a raw material mixture;

[0094] Glass melting: Add the raw material mixture into a crucible, melt it at 1450°C for 7 hours, stir it after it melts, stir it 3 times, the speed of each stirring is 60rpm, the stirring time is 1.5 hours, the interval time between each stirring is 40 minutes, until a clear and homogenized glass liquid is formed, then discharge it at 1365°C, cast it into the required glass in a mold, and anneal it after the glass cools and solidifies, the annealing temperature is 570°C, and the annealing time is 26 hours, to obtain a light absorbing material glass;

[0095] c. preparing a square light absorbing glass rod with good light absorbing performance from the light absorbing glass, and drawing the square light absorbing glass rod into a square light absorbing wire with a side size of 0.8 mm;

[0096] (2) Drawing of square primary multifilaments: Arranging the drawn square monofilaments into a primary composite rod with square end faces, wherein the number of square monofilaments on each side of the primary composite rod is 10, and inserting the square light absorbing wire into the pores between the square monofilaments, and drawing the primary composite rod assembled as above into a square primary multifilament with a side size of 1.0 mm;

[0097] (3) Drawing of square secondary multifilaments: Arrange the drawn square primary multifilaments into secondary composite rods with square end faces, and the number of square primary multifilaments on each side of the secondary composite rods is 30; bundle the secondary composite rods and draw them into secondary multifilaments with opposite side dimensions of 1.4 mm, and then cut the secondary multifilaments to a fixed length and arrange them into screen plate segments;

[0098] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, and hot melt pressing under high temperature and pressure, controlling the compression ratio before and after the hot melt pressing at 0.85, to obtain a blank plate segment of a square structure optical fiber imaging element;

[0099] (5) Processing and molding: The blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a square-structured optical fiber imaging element blank. The square-structured optical fiber imaging element blank is subjected to subsequent optical processing and then twisted 180° to obtain a square-structured optical fiber inverter with a unit wire diameter of 3.97 μm.

[0100] Example 5

[0101] (1) Drawing of square monofilaments and square light-absorbing filaments:

[0102] a. Matching a square skin glass tube with a low refractive index with a square core glass rod with a high refractive index, and then drawing a single wire to obtain a drawn square single wire; the square single wire has a side size of 6 mm; the end face size of the square core glass rod is 25 mm×25 mm, and the four edges of the square core glass rod are chamfered, of which three edges are protective chamfers with a protective chamfer size of 0.5 mm×45°, and the chamfer size of the fourth edge is 5 mm×45°; the square core glass rod with a high refractive index is drawn into a square gap wire with an end face side size of 1.6 mm; the inner diameter of the skin glass tube is 26 mm, and the wall thickness is 4.1 mm;

[0103] b. Preparation of light absorbing glass:

[0104] Select raw materials according to the glass composition of Example 5 in Table 1, so that the ingredients meet the glass chemical composition of Table 1, and then prepare the contrast enhancement filter glass according to the following steps:

[0105] Raw material preparation: weigh raw materials quartz sand, boric acid, lithium carbonate, barium nitrate, strontium carbonate, zinc oxide, titanium dioxide, zirconium oxide, cerium oxide, ferric oxide, nickel oxide, vanadium pentoxide, cobalt oxide, molybdenum trioxide, manganese dioxide, potassium chromate, neodymium oxide and copper oxide according to molar ratio, mix them evenly, and obtain a raw material mixture;

[0106] Glass melting: Add the raw material mixture into a crucible, melt it at 1490°C for 8 hours, stir it 3 times after it melts, each stirring speed is 70rpm, each stirring time is 2 hours, and the interval time between each stirring is 30 minutes, until a clear and homogenized glass liquid is formed, then discharge it at 1370°C, cast it into the required glass in a mold, and anneal it after the glass cools and solidifies, the annealing temperature is 590°C, and the annealing time is 28 hours, to obtain a light absorbing material glass;

[0107] c. preparing a square light absorbing glass rod with good light absorbing performance from the light absorbing glass, and drawing the square light absorbing glass rod into a square light absorbing wire with a side size of 1.6 mm;

[0108] (2) Drawing of square primary multifilaments: Arranging the drawn square monofilaments into a primary composite rod with square end faces, wherein the number of square monofilaments on each side of the primary composite rod is 5, and inserting the square light absorbing wire into the pores between the square monofilaments, and drawing the primary composite rod assembled as above into a square primary multifilament with a side size of 1.1 mm;

[0109] (3) Drawing of square secondary multifilaments: Arrange the drawn square primary multifilaments into secondary composite rods with square end faces, and the number of square primary multifilaments on each side of the secondary composite rods is 28; bundle the secondary composite rods and draw them into secondary multifilaments with opposite side dimensions of 0.66 mm, and then cut the secondary multifilaments to a fixed length and arrange them into screen plate segments;

[0110] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, and hot melt pressing under high temperature and pressure, controlling the compression ratio before and after the hot melt pressing to be 0.84, to obtain a blank plate segment of a square structure optical fiber imaging element;

[0111] (5) Processing and molding: The blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a square-structured optical fiber imaging element blank. The square-structured optical fiber imaging element blank is subjected to subsequent optical processing and then heated to perform a taper process to obtain a square-structured light cone with a unit wire diameter of 3.96 μm.

[0112] The square-structured optical fiber image inverter or square-structured optical fiber light cone prepared in each embodiment of the present invention has a shear distortion of less than 10μm, an optical fiber leakage ratio of less than 5%, a center resolution of more than 140lp / mm, and eliminates the moiré fringe effect caused by the coupling of round filaments and square pixels. The transmittance is greater than 70% in the wavelength range of 380-760nm, and the crosstalk is less than <1.0% at a distance of 0.1mm from the blade. It has excellent fixed pattern noise performance and has no obvious multifilament boundary when observed under a 10x microscope.

[0113] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a square-structured optical fiber imaging element, characterized in that: The steps include: (1) Drawing of square wires: matching a square skin glass tube with a low refractive index with a square core glass rod with a high refractive index to draw a single wire to obtain a drawn square single wire; drawing a square core glass rod with a high refractive index into a square gap wire; preparing a square light absorbing glass rod from light absorbing glass, and drawing the square light absorbing glass rod into a square light absorbing wire; (2) Drawing of square primary multifilaments: Arranging the drawn square monofilaments into a primary composite rod with square end faces, and uniformly inserting the square light absorbing wires and the square interstitial wires into the gaps between the square monofilaments, and drawing the primary composite rods assembled as above into square primary multifilaments; (3) Drawing of square secondary multifilaments: Arranging the drawn square primary multifilaments into secondary composite rods with square end faces, bundling the secondary composite rods and drawing them into secondary multifilaments, and then cutting the secondary multifilaments to a fixed length and arranging them into screen plate segments; (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, and hot melt pressing at a certain compression ratio to obtain a blank plate segment of a square optical fiber imaging element; (5) Processing and molding: The blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a square-structured optical fiber imaging element blank. The square-structured optical fiber imaging element blank is subjected to subsequent optical finishing, and then heated and tapered or twisted 180° to obtain a square-structured optical fiber imaging element.

2. The preparation method according to claim 1, characterized in that: The square core glass rod is a square rod with chamfered corners, and the square monofilament has four opposite sides with dimensions of 2.54 mm to 7 mm. The end faces of the square light absorbing wires and the square gap wires are both squares, the end faces of the square light absorbing wires and the square gap wires have the same area, and the side length of the square is 0.7 mm to 1.95 mm.

3. The preparation method according to claim 2, characterized in that: The end face size of the square core glass rod is (20-30) mm×(20-30) mm, and the four edges of the square core glass rod are chamfered at 45°, of which three edges are 45° protective chamfers, and the protective chamfer size is 2% of the end face side size of the square core glass rod, and the chamfer size of the fourth edge is 20% of the end face side size of the square core glass rod; the inner four-side opposite side size of the skin glass tube is 22 mm-32 mm, and the wall thickness of the skin glass tube is 3.8-4.2 mm.

4. The preparation method according to claim 3, characterized in that: In the primary composite rod, the number of square monofilaments on each side is 4-16, and the opposite side size of the square primary multifilament is 1.02mm-1.60mm; The number of square primary multifilaments on each side of the secondary composite rod is 18 to 32; the opposite side dimensions of the square secondary multifilaments are 0.5 to 1.6 mm; The diagonal dimensions of the primary composite rod and the secondary composite rod are both no more than 46 mm.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The light absorbing glass comprises the following components in molar percentage: SiO2 64-78%, B2O3 3-16%, Al2O3 0-5%, Li2O 0-1%, Na2O 0-6%, K2O0-12%, MgO 0-1.5%, CaO 0-2.5%, BaO 0-1%, SrO 0-1%, ZnO 0-1%, TiO2 0-1%, ZrO20-1%, CeO2 0-1%, Fe2O30-6%, NiO 0.1-1%, V2O5 0-1%, Co2O3 0-2%, MoO3 0-0.2%, MnO2 0.1-2.5%, Cr2O3 0.1-2%, Nd2O3 0-1%, CuO 0.1-2%, and F2 0-1%.

6. The preparation method according to claim 5, characterized in that: The light absorbing glass comprises the following components in molar percentage: SiO2 68-76%, B2O3 3-10%, Al2O3 3-5%, Li2O 0-1%, Na2O 2-6%, K2O 3-9%, MgO 0.2-1.0%, CaO 1-2.5%, BaO 0-0.1%, SrO 0-0.2%, ZnO 0-0.1%, TiO2 0-0.3%, ZrO2 0-0.3%, CeO2 0-0.1%, Fe2O3 0.1-6%, NiO 0.3-1%, V2O5 0-1%, Co2O3 0.1-1.5%, MoO3 0-0.2%, MnO2 0.1-2.0%, Cr2O3 0.1-1%, Nd2O3 0-0.5%, CuO 0.1-1%, F2 0.1-1%.

7. The preparation method according to claim 6, characterized in that: The light absorbing glass comprises the following components in molar percentage: SiO2 73%, B2O3 4%, Al2O3 4.8%, Na2O 5.2%, K2O 7%, MgO 0.5%, CaO 1.5%, SrO 0.1%, Fe2O3 0.4%, NiO 0.4%, Co2O3 1.0%, MnO2 0.3%, Cr2O3 0.5%, CuO 0.8%, and F2 0.5%.

8. The preparation method according to claim 5, characterized in that: Also included is a method for preparing light absorbing glass, comprising the following steps: (1) Raw material preparation: quartz sand, boric acid, aluminum oxide, lithium carbonate, sodium carbonate, potassium carbonate, basic magnesium carbonate, calcium carbonate, barium nitrate, strontium carbonate, zinc oxide, titanium dioxide, zirconium oxide, cerium oxide, iron trioxide, nickel oxide, vanadium pentoxide, cobalt trioxide, molybdenum trioxide, manganese dioxide, potassium chromate, neodymium oxide, copper oxide and calcium fluoride are weighed according to a molar ratio, and mixed evenly to obtain a raw material mixture; (2) Glass melting: adding the raw material mixture into a crucible, melting it at 1420-1520° C. for 5-8 hours, stirring it 2-3 times after the raw material mixture is melted until a clear and homogenized glass liquid is formed, discharging the glass liquid at 1360-1380° C., casting it into the required glass in a mold, and annealing it after the glass is cooled and solidified, at a temperature of 550-600° C. for 24-36 hours, to obtain a light absorbing material glass, and drawing the light absorbing material glass into a light absorbing material glass rod; The light absorbing glass has a spectral transmittance of ≤2.5% in the wavelength range of 380-760nm at a thickness of 0.30±0.01mm and a thermal expansion coefficient of (80±5)×10 －7 / ℃; no crystallization occurs when kept at 850℃ for 6 hours.

9. A square optical fiber image transmission element, characterized in that: It is prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the square-structured optical fiber imaging element according to claim 9 in an enhanced charge coupled device.

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