A method for melt pressing and forming a blank plate of an optical fiber image inverter and an optical fiber image inverter

Abstract

The present invention discloses a melting and pressing forming method for a blank plate of an optical fiber image inverter and an optical fiber image inverter. The melting and pressing forming method includes: placing an optical fiber plate segment in a glass tube sleeve with a sealed bottom, and sealing a metal tube at the opening of the glass tube sleeve; placing the glass tube sleeve in a pressure-resistant sealed cylinder and fixing the glass tube sleeve; passing the metal tube through the sealing cover of the pressure-resistant sealed cylinder, tightening the sealing cover, and then placing the pressure-resistant sealed cylinder in a heating furnace; connecting the metal tube to a vacuum pumping device, heating the pressure-resistant sealed cylinder while raising the temperature, and then turning on the vacuum pumping device to evacuate the inside of the glass tube sleeve; after the vacuum degree reaches the design requirement, introducing an inert gas into the pressure-resistant sealed cylinder and applying pressure to the glass tube sleeve according to the set pressure of melting and pressing; after the melting and pressing is completed, releasing the gas in the pressure-resistant sealed cylinder to obtain a blank plate segment of the optical fiber image inverter. The optical fiber image inverter prepared by the melting and pressing forming method of the present invention will not have the problem of reduced edge resolution after torsion.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing optical fiber image transmission elements, and particularly to a method for hot pressing and forming a blank plate of an optical fiber image inverter and an optical fiber image inverter. Background Art

[0002] Optical fiber image transmission elements include optical fiber faceplates, optical fiber image inverters, optical fiber tapers, optical fiber image bundles, etc. They are excellent optoelectronic imaging devices. They are produced using a unique formula of skin material, core material, and absorption material and a drawing process that combines vacuum control and rod-tube combination, making the products have good airtightness, small distortion, and few spots. They have the characteristics of simple structure, small size, light weight, large numerical aperture, high light transmission efficiency, small inter-stage coupling loss, high coupling efficiency, high resolution, clear and real image transmission, zero thickness optically, and can effectively improve the edge image quality. Optical fiber image transmission elements are hard optical fiber image transmission elements formed by hot pressing tens of millions of parallel optical fibers. They are key materials for image intensifiers and high-definition displays and are widely used in various cathode ray tubes, camera tubes, CCD couplings, low-light level night vision, medical device displays, high-definition television imaging, and other instruments and equipment that require image transmission in the fields of national defense and military, public security and criminal investigation, aerospace, and medical science. They are high-tech cutting-edge products in the optoelectronics industry in this century.

[0003] The most typical application of an optical fiber image inverter is as the optical output window of a low-light level image intensifier, which plays an important role in improving the quality of imaging devices. Usually, the resolution is used to represent the quality of image transmission. Generally speaking, the resolution refers to the minimum distance that can distinguish between two targets, and it is commonly measured by the number of this distance contained in a unit length, that is, the logarithm of the line distance that can be distinguished per millimeter. The higher the resolution, the better the performance of image transmission, and the clearer the transmitted image.

[0004] In the prior art, the fusion pressing forming method of the fiber optic image inverter blank plate generally adopts mechanical fusion pressing forming. When the optical fibers are regularly arranged and have good optical insulation, the resolution of the fiber optic image transmission element mainly depends on the distance between the centers of adjacent optical fibers and the arrangement form. For fiber optic components with a fixed unit wire diameter, the resolution performance of the regular hexagonal fiber arrangement is 1.15 times that of the square arrangement. Therefore, when preparing high-resolution fiber optic components, the regular hexagonal arrangement is commonly used. The fiber bundle is arranged into a blank plate in the shape of a hexagonal prism, placed in a metal mold, and the mold is placed in a pit type hot press furnace. After heating, pressure is applied to the sleeve, the slider shrinks, and the blank plate fuses. However, this method of preparing the fiber optic panel section by mechanical hot pressing forming not only has low processing efficiency, but also uses a large number of complex auxiliary tooling and equipment. The consumption of raw materials and auxiliary materials such as mica sheets is serious, resulting in high production costs, low production efficiency, and long preparation cycles. The blank plates of the fiber optic image transmission elements prepared also have various problems such as unqualified performance indicators such as shear, magnification, dark spots, and reduced edge resolution. Moreover, the mechanical fusion pressing forming method is applicable to the blank plates of image inverters with a fiber wire diameter ≥ 4.5 microns.

[0005] Since the size of the unit fiber wire diameter directly determines the resolution performance of the fiber optic image transmission element. The fiber optic image inverter is formed by twisting the fiber optic plate blank at a high temperature by 180°. After twisting, the fiber optic structure will change to varying degrees. Theoretically, only the optical fibers at the axis are not twisted and stretched, and the rest of the optical fibers are twisted and stretched into double cone optical fibers coiled at different helix angles by 180°. This manufacturing process causes the resolution of the peripheral area of the ordinary image inverter to decrease, and in severe cases, it leads to a reduction in the viewing field of the image tube. During the twisting process, as the distance from the fiber to the center of the blank plate increases, the degree of twisting increases, and the degree of elongation and tapering of the fiber also gradually increases. Its numerical aperture gradually decreases, and the light flux and light grazing angle of the optical fiber also decrease accordingly, resulting in different degrees of loss of total internal reflection at the core-cladding interface, and the degree of crosstalk between optical fibers increases accordingly. Therefore, the numerical aperture, light flux, and contrast of the fiber optic image inverter also gradually decrease.

[0006] In the existing preparation process and material system of fiber optic image inverters, if a fiber optic image inverter with high resolution and an ultra-narrow twisted wire area needs to be prepared, it is necessary to continue to reduce the unit fiber wire diameter. However, in the current existing mechanical fusion pressing forming method, the fibers in six directions close to the slider will be severely deformed, resulting in the loss of the total internal reflection structure of the optical fibers, thus leading to the problem of reduced edge resolution in six directions, seriously affecting the resolution performance and structural uniformity of the fiber optic image inverter, and restricting the realization of the functions of lightweight and ultra-high definition image transmission of low-light night vision devices. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for melting and pressing a fiber optic image inverter blank to address the defects of the above-mentioned prior art, which can ensure that the optical fiber is evenly stressed and heated during the hot melting and pressing process, and avoid the reduction in edge resolution of the fiber optic image inverter after twisting.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for melting and pressing a blank plate of an optical fiber image invertor comprises the following steps:

[0010] (1) Place the screened optical fiber board segments in a glass tube sleeve with a sealed bottom, and seal the opening of the glass tube sleeve with a metal tube;

[0011] (2) placing the glass tube sleeve sealed with the metal tube in the pressure-resistant sealing cylinder and fixing the glass tube sleeve;

[0012] (3) Passing the metal tube at one end of the glass tube sleeve through the sealing cover of the pressure-resistant sealing cylinder, tightening the sealing cover, and then placing the pressure-resistant sealing cylinder in a heating furnace; the sealing cover is provided with an air inlet and a pressure relief port for pressurizing and relieving the glass tube sleeve and the optical fiber board section inside;

[0013] (4) The metal tube is connected to the vacuum pumping device, and the heating furnace is turned on to heat the pressure-resistant sealing tube. After a first preset time, the temperature rises to a first preset temperature, and the vacuum pumping device is turned on to start vacuuming and exhausting the inside of the glass tube sleeve;

[0014] (5) After the vacuum degree of the glass tube sleeve reaches the design requirement, an inert gas is introduced into the pressure-resistant sealing cylinder that has reached the second preset temperature through the gas inlet, and the glass tube sleeve is pressurized according to the set melt pressure;

[0015] (6) After the melting and pressurizing is completed, the heating furnace is turned off. When the temperature in the pressure-resistant sealing tube drops to the third preset temperature, the gas in the pressure-resistant sealing tube is released through the pressure relief port in the second preset time. When the temperature of the furnace body drops to room temperature and the gas pressure in the pressure-resistant sealing tube reaches the normal atmospheric pressure, the sealing cover of the pressure-resistant sealing tube is opened and the optical fiber board section after melting and pressing is taken out, thus obtaining the optical fiber invertor blank board section.

[0016] The opening of the glass tube sleeve is provided with a blank tube length of 10mm-20mm for sealing the metal tube. When the blank tube length is less than 10mm, the optical fiber board section filled inside may be contaminated during sealing, and when the blank tube length is greater than 20mm, there is a risk of cracking of the glass tube sleeve during sealing.

[0017] The fixing of the glass tube sleeve comprises filling positioning powder at the bottom of the pressure-resistant sealing tube and the gap between the inner wall of the pressure-resistant sealing tube and the glass tube sleeve.

[0018] The positioning powder is alumina powder or quartz sand particles, and the average particle size of the positioning powder is 50 to 100 microns.

[0019] The first preset time is 3 to 4 hours, and the first preset temperature is 630 - 650 °C.

[0020] The pressure of the melt pressing is 10 - 15 MPa; the time of the melt pressing is 2 - 4 hours; the second preset temperature is 660 - 700 °C; the third preset temperature is 580 - 620 °C; the second preset time is 2 - 4 hours; the inert gas is nitrogen or helium.

[0021] The glass tube sleeve is made of low - refractive - index glass, and the low - refractive - index glass is composed of the following components in mole percentage: SiO2 78.1 - 80.0%, Al2O3 3.1 - 7.0%, B2O3 2.0 - 8.0%, Li2O 0 - 1.0%, Na2O 0 - 2.9%, K2O 5.1 - 10.0%, CaO 1.1 - 3.0%, SrO 0 - 1.0%, ZnO 1.1 - 2.0%, TiO2 0 - 1.0%, CeO2 0.05 - 0.2%, MgF2 0 - 2.0%, CaF2 0.05 - 2.0%.

[0022] The preparation method of the glass tube sleeve includes the following steps:

[0023] (1) Glass melting: Weigh quartz sand, aluminum hydroxide, boric acid or boric anhydride, lithium carbonate, sodium carbonate, potassium carbonate or potassium nitrate, calcium carbonate, strontium carbonate, zinc oxide, titanium dioxide, cerium oxide, magnesium fluoride and calcium fluoride respectively according to the batching requirements, mix them evenly, and then put them into the glass melting pool in the kiln furnace to melt at 1500 - 1600 °C for 12 - 24 hours;

[0024] (2) Clarification and homogenization: After the raw materials are melted into the glass melt, the glass melt flows from the glass melting pool into the clarification pool at 1400 - 1470 °C for 4 - 6 hours. After the glass melt is clarified and homogenized to remove and absorb small bubbles, the glass liquid flows into the stirring pool to be fully stirred evenly, and then flows into the material basin to cool down;

[0025] (3) Tube drawing and forming: After the glass liquid cools down, the glass liquid flows from the material basin to the feeding channel, and then to the forming nozzle. After passing through the forming nozzle, the glass liquid is drawn by a tube drawing machine to produce a uniformly formed glass tube;

[0026] (4) Cutting and annealing: Cut the drawn - formed glass tube into a certain length as required, and then put the cut glass tube into an annealing furnace at 605 - 615 °C for annealing treatment.

[0027] The thickness of the glass tube sleeve is 1.0 - 15 mm.

[0028] The present invention also provides an optical fiber image inverter, comprising a plate segment of an optical fiber image inverter blank prepared by the hot pressing and forming method of the optical fiber image inverter blank; the unit fiber filament diameter of the plate segment of the optical fiber image inverter blank is ≤ 4 μm, the magnification distortion can reach 1 ± 0.5%, and the transmittance uniformity is < 2%; after cutting, rounding, and grinding the plate segment of the optical fiber image inverter blank, an optical fiber image inverter blank is prepared, and the optical fiber image inverter blank is torsionally formed at an angle of 180° in a torsion forming furnace in an ultra-narrow high-temperature zone, that is, an optical fiber image inverter with an ultra-narrow torsion wire zone is prepared; the optical fiber image inverter with the ultra-narrow torsion wire zone does not have the phenomenon of reduced resolution in six directions; the width of the heating furnace body in the ultra-narrow high-temperature zone is 3 - 4 mm, the distance between the heating furnace body and the surface of the optical fiber image inverter blank is 1.0 - 2.5 mm, and the torsion forming time for the optical fiber image inverter blank to be torsionally formed at an angle of 180° is 2 - 9 minutes.

[0029] Compared with the prior art, an optical fiber image inverter blank hot pressing and forming method of the present invention and an optical fiber image inverter torsionally formed therefrom have the following characteristics:

[0030] (1) The present invention can make the fiber bundle uniformly stressed during the hot pressing process, realize uniform heating and stress fusion of the blank in all directions, can solve the technical problem of reduced edge resolution in six directions of the torsionally formed optical fiber image inverter that is difficult to control in the prior art, and the transmittance uniformity of the obtained blank is < 2%.

[0031] (2) For the optical fiber image inverter blank hot pressing and forming method of the present invention, the qualified rate of the magnification distortion of the prepared optical image inverter blank is high, and the magnification distortion can reach 1 ± 0.5%.

[0032] (3) The optical fiber image inverter blank hot pressing and forming method of the present invention can save a large amount of raw materials and auxiliary materials required for mechanical hot pressing and forming, and greatly save the production cost.

[0033] (4) The optical fiber image inverter blank hot pressing and forming method of the present invention has good safety and high production efficiency.

[0034] The fiber optic image inverter blank and the fiber optic image inverter prepared by using the method for hot pressing and forming the fiber optic image inverter blank of the present invention have the advantages of high resolution, uniform transmittance, clear imaging, and no reduction in edge resolution. The fiber optic image inverter prepared by using the hot pressing and forming method of the present invention is applied to a low-light level image intensifier, which can effectively improve the imaging clarity of the low-light level image tube. Its products can meet the supporting requirements of the low-light night vision industry, and can also replace traditional fiber optic image transmission products, improve the comprehensive performance, and promote the development of optoelectronic devices in related fields such as spatial vision measurement and detection imaging towards high performance and wide field of view, having good application and promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 FIG. is a schematic structural diagram of a device for hot pressing and forming a fiber optic image inverter blank according to an embodiment of the present invention;

[0036] Figure 2 FIG. is a schematic structural diagram of a torsion forming heating furnace with an ultra-narrow high-temperature zone according to an embodiment of the present invention.

[0037] Among them, 101 is an optical fiber board section, 102 is a glass tube sleeve, 103 is a positioning powder, 104 is a sealing joint, 105 is an air inlet, 106 is a pressure relief port, 107 is a vacuum exhaust port, 108 is a pressure-resistant sealing cylinder, and 109 is a metal tube;

[0038] 801 is a torsion forming furnace with an ultra-narrow high-temperature zone, 802 is a heating element of the ultra-narrow high-temperature zone heating furnace, and 803 is a blank of a fiber optic image inverter. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] In order to make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] Refer to Figure 1 , for the device for hot pressing and forming a fiber optic image inverter blank, the arranged optical fiber board section 101 is placed in the glass tube sleeve 102. The pressure-resistant sealing cylinder 108 is provided with an air inlet 105 and a pressure relief port 106. The gap between the glass tube sleeve 102 and the pressure-resistant sealing cylinder 108 is filled with a positioning powder 103. The glass tube sleeve 102 is connected to the metal tube 109 through a sealing joint 104, and the optical fiber board section 101 in the glass tube sleeve 102 is evacuated through the vacuum exhaust port 107 formed by the metal tube 109.

[0041] Refer to Figure 2, is a schematic structural diagram of a narrow high-temperature zone torsion forming heating furnace. Inside the narrow high-temperature zone torsion forming furnace 801, there is a heating element 802 of the narrow high-temperature zone heating furnace. After the blank 803 of the fiber optic image inverter prepared by the melt pressing forming method of the present invention is heated by the heating element 802 of the narrow high-temperature zone heating furnace in the narrow high-temperature zone torsion forming furnace 801, a 180° angle torsion forming is achieved, and a narrow torsion wire zone fiber optic image inverter is prepared.

[0042] Table 1 Chemical composition (mol.%) and properties of low refractive index glass examples for glass sleeves

[0043] Composition (mol.%) Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[SiO2]]> 78.30 78.40 80.00 78.20 78.10 <![CDATA[Al2O3]]> 5.30 3.40 3.10 7.00 3.50 <![CDATA[B2O3]]> 3.00 8.00 2.00 2.10 2.20 <![CDATA[Li2O]]> 0.10 0.20 1.00 0.11 0.10 <![CDATA[Na2O]]> 2.90 0.20 0.30 0.10 0.20 <![CDATA[K2O]]> 6.70 5.10 8.25 7.90 10.00 CaO 1.30 1.20 2.10 1.10 3.00 SrO 0.20 0.10 1.00 0.10 0.20 ZnO 1.10 1.27 1.10 1.12 2.00 <![CDATA[TiO2]]> 0.50 0.01 1.00 0.01 0.30 <![CDATA[CeO2]]> 0.09 0.06 0.05 0.20 0.10 <![CDATA[MgF2]]> 0.11 2.00 0.05 0.06 0.20 <![CDATA[CaF2]]> 0.40 0.06 0.05 2.00 0.10 <![CDATA[α 30 / 300 [10 -7 / ℃]]]> 83 81 84 82 85 Strain point temperature 610 585 580 620 590 <![CDATA[Refractive index n D > 1.49 1.48 1.51 1.48 1.50

[0044] Example 1

[0045] Preparation method of glass tube sleeve:

[0046] Select raw materials according to the glass composition of Example 1 in Table 1 to make the batching meet the glass chemical composition in Table 1, and then prepare the glass tube sleeve according to the following steps:

[0047] (1) Glass melting: Weigh quartz sand, aluminum hydroxide, boric acid or boric anhydride, lithium carbonate, sodium carbonate, potassium carbonate or potassium nitrate, calcium carbonate, strontium carbonate, zinc oxide, titanium dioxide, cerium oxide, magnesium fluoride and calcium fluoride respectively according to the batching requirements, mix them evenly, and then put them into the glass melting pool in the kiln furnace to melt at 1600°C for 12 hours;

[0048] (2) Clarification and homogenization: After the raw materials are melted into the glass melt, the glass melt flows from the glass melting pool into the clarification pool at 1470°C for clarification and homogenization for 4 hours. After the glass melt removes and absorbs small bubbles through clarification and homogenization, the glass liquid flows into the stirring pool to be fully stirred evenly, and then flows into the material basin to cool down;

[0049] (3) Tube drawing and forming: After the glass liquid cools down, the glass liquid flows from the material basin to the feeding channel, and then to the forming nozzle. After passing through the forming nozzle, the glass liquid is drawn by a tube drawing machine to produce a uniformly formed glass tube;

[0050] (4) Cutting and annealing: Cut the drawn and formed glass tube into a certain length as required, and then put the cut glass tube into an annealing furnace at 615°C for annealing treatment.

[0051] A melt pressing forming method for a blank plate of a fiber optic image inverter includes the following steps:

[0052] (1) Place the arranged optical fiber board segments in the bottom-sealed glass tube sleeve, leaving a 15-mm long blank position at the opening of the glass tube sleeve for sealing the metal tube, and the metal tube is used for evacuating and exhausting the air inside the inner board segment of the glass tube sleeve;

[0053] (2) Place the glass tube sleeve with the sealed metal tube in a pressure-resistant sealed cylinder, and pre-fill quartz sand particles with a particle size of 75 microns at the bottom of the pressure-resistant sealed cylinder. The gap between the outer periphery of the glass tube sleeve and the inner wall of the pressure-resistant sealed cylinder is also filled with quartz sand particles to fix the glass tube sleeve without shaking;

[0054] (3) Pass the metal tube at one end of the glass tube sleeve through the sealing cover of the pressure-resistant sealed cylinder, tighten the sealing cover to fasten it, and then place the pressure-resistant sealed cylinder in a heating furnace; there are also an air inlet and a pressure relief port on the sealing cover for pressurizing and depressurizing the glass tube sleeve and the internal optical fiber board section;

[0055] (4) Connect the metal tube to a vacuum pumping device, turn on the heating furnace, and heat up for 3.5 hours. After the temperature rises to 640 °C, turn on the vacuum pumping device and start the vacuum exhaust operation for the inside of the glass tube sleeve;

[0056] (5) After the vacuum degree of the glass tube sleeve reaches the design requirement, introduce the inert gas nitrogen into the pressure-resistant sealed cylinder at a temperature of 680 °C through the air inlet, and pressurize the glass tube sleeve for 3 hours according to the set pressure of 13 MPa for fusion pressure;

[0057] (6) After the fusion pressure pressurization is completed, turn off the heating furnace. When the temperature inside the pressure-resistant sealed cylinder drops to 600 °C, slowly release the gas inside the pressure-resistant sealed cylinder in 3 hours. When the furnace body temperature drops to room temperature and the air pressure inside the pressure-resistant sealed cylinder reaches normal atmospheric pressure, open the sealing cover of the pressure-resistant sealed cylinder and take out the fused optical fiber board section to obtain the blank board section of the fiber optic image inverter.

[0058] The magnification distortion of the blank board section of the fiber optic image inverter is 1 ± 0.5%, and the transmittance uniformity of the blank board section of the fiber optic image inverter is 0.6%.

[0059] A preparation method of a fiber optic image inverter, including:

[0060] After processing the blank board section of the fiber optic image inverter by cutting, rounding, and grinding, a blank of the fiber optic image inverter is prepared. The blank of the fiber optic image inverter is twisted and formed at an angle of 180° in a twisting and forming furnace in an ultra-narrow high-temperature zone, and then a fiber optic image inverter with an ultra-narrow twisted wire zone is prepared; the width of the heating furnace body in the ultra-narrow high-temperature zone is 3 mm, the distance between the heating furnace body and the surface of the blank of the fiber optic image inverter is 1.5 mm, and the twisting and forming time for the blank of the fiber optic image inverter to twist 180° is 6 minutes. The prepared fiber optic image inverter does not have the problem of reduced edge resolution in six directions.

[0061] Example 2

[0062] A preparation method of a glass tube sleeve:

[0063] Select raw materials according to Example 2 of Table 1 for the glass composition to make the batching meet the glass chemical composition in Table 1, and then prepare the glass tube sleeve according to the following steps:

[0064] (1) Glass melting: Weigh quartz sand, aluminum hydroxide, boric acid or boric anhydride, lithium carbonate, sodium carbonate, potassium carbonate or potassium nitrate, calcium carbonate, strontium carbonate, zinc oxide, titanium dioxide, cerium oxide, magnesium fluoride and calcium fluoride respectively according to the batching requirements, mix them evenly, and then put them into the glass melting pool in the kiln furnace and melt at 1500 °C for 24 hours;

[0065] (2) Clarification and homogenization: After the raw materials are melted into the glass melt, the glass melt flows from the glass melting pool into the clarification pool at 1430 °C for clarification and homogenization for 6 hours. After the glass melt removes and absorbs small bubbles through clarification and homogenization, the glass liquid flows into the stirring pool and is stirred evenly, and then flows into the material basin to cool down;

[0066] (3) Tube drawing and forming: After the glass liquid cools down, the glass liquid flows from the material basin to the blanking channel and then to the forming nozzle. After passing through the forming nozzle, the glass liquid is drawn by a tube drawing machine to produce a uniformly formed glass tube;

[0067] (4) Cutting and annealing: Cut the drawn and formed glass tube into a certain length as required, and then put the cut glass tube into an annealing furnace at 610 °C for annealing treatment.

[0068] A method for hot pressing and forming a blank plate of an optical fiber image inverter includes the following steps:

[0069] (1) Place the arranged optical fiber board segments in the bottom-sealed glass tube sleeve, leaving a 10-mm long blank position at the opening of the glass tube sleeve for sealing the metal tube, and the metal tube is used for evacuating the air inside the inner board segment of the glass tube sleeve;

[0070] (2) Place the glass tube sleeve with the sealed metal tube in a pressure-resistant sealing cylinder, and pre-fill alumina powder with a particle size of 50 microns at the bottom of the pressure-resistant sealing cylinder. The space between the outer periphery of the glass tube sleeve and the inner wall of the pressure-resistant sealing cylinder is also filled with alumina powder to fix the glass tube sleeve without shaking;

[0071] (3) Pass the metal tube at one end of the glass tube sleeve through the sealing cover of the pressure-resistant sealing cylinder, tighten the sealing cover firmly, and then place the pressure-resistant sealing cylinder in the heating furnace; there are also an air inlet and a pressure relief port on the sealing cover for pressurizing and depressurizing the glass tube sleeve and the internal optical fiber board segments;

[0072] (4) Connect the metal tube to the vacuum pumping equipment, turn on the heating furnace, and heat up for 4 hours. After the temperature rises to 630 °C, turn on the vacuum pumping equipment and start the vacuum evacuation operation for the inside of the glass tube sleeve;

[0073] (5) After the vacuum degree of the glass tube sleeve reaches the design requirement, an inert gas nitrogen is introduced into the pressure-resistant sealed cylinder at 700 °C through the air inlet, and the glass tube sleeve is pressurized at a set pressure of 15 MPa for 2 hours according to the melt pressure;

[0074] (6) After the melt pressure is completed, turn off the heating furnace. When the temperature in the pressure-resistant sealed cylinder drops to 580 °C, slowly release the gas in the pressure-resistant sealed cylinder step by step over 4 hours. When the furnace body temperature drops to room temperature and the air pressure in the pressure-resistant sealed cylinder reaches normal atmospheric pressure, open the sealing cover of the pressure-resistant sealed cylinder, and take out the melt-pressed optical fiber board section, that is, the blank board section of the fiber optic image inverter is obtained.

[0075] The magnification distortion of the blank board section of the fiber optic image inverter is 1 ± 0.5%, and the transmittance uniformity of the blank board section of the fiber optic image inverter is 0.8%.

[0076] A preparation method of a fiber optic image inverter, comprising:

[0077] After cutting, rounding, and grinding the blank board section of the fiber optic image inverter, a blank of the fiber optic image inverter is prepared. The blank of the fiber optic image inverter is twisted and formed at an angle of 180° in a narrow high-temperature area twisting and forming furnace, that is, a fiber optic image inverter with a narrow twisted wire area is prepared; the width of the heating furnace body in the narrow high-temperature area is 4 mm, the distance between the heating furnace body and the surface of the blank of the fiber optic image inverter is 1.0 mm, and the twisting and forming time for the blank of the fiber optic image inverter to twist 180° is 9 minutes.

[0078] The fiber optic image inverter prepared after twisting the blank board section of the fiber optic image inverter does not have the problem of reduced edge resolution in six directions.

[0079] Example 3

[0080] Preparation method of glass tube sleeve:

[0081] Select raw materials according to the glass composition in Example 3 of Table 1, so that the batching meets the glass chemical composition in Table 1, and then prepare the glass tube sleeve according to the following steps:

[0082] (1) Glass melting: Weigh quartz sand, aluminum hydroxide, boric acid or boric anhydride, lithium carbonate, sodium carbonate, potassium carbonate or potassium nitrate, calcium carbonate, strontium carbonate, zinc oxide, titanium dioxide, cerium oxide, magnesium fluoride, and calcium fluoride respectively according to the batching requirements, mix them evenly, and then put them into the glass melting pool in the kiln furnace to melt at 1550 °C for 18 hours;

[0083] (2) Clarification and homogenization: After the raw materials are melted into the glass melt, the glass melt flows from the glass melting pool into the clarification pool at 1450 °C for clarification and homogenization for 5 hours. After the glass melt is clarified and homogenized to remove and absorb small bubbles, the glass liquid flows into the stirring pool to be fully stirred evenly, and then flows into the material basin to cool down;

[0084] (3) Tube drawing and forming: After the glass melt cools down, the glass melt flows from the material basin to the blanking channel and then to the forming nozzle. After passing through the forming nozzle, the glass melt is drawn by a tube drawing machine to produce a uniformly formed glass tube.

[0085] (4) Cutting and annealing: The drawn and formed glass tube is cut into a certain length as required, and then the cut glass tube is placed in an annealing furnace at 605 °C for annealing treatment.

[0086] A method for hot pressing and forming a blank plate of an optical fiber image inverter, comprising the following steps:

[0087] (1) Place the arranged optical fiber board segments in a bottom-sealed glass tube sleeve. A blank position of 20 mm in length is left at the opening of the glass tube sleeve for sealing a metal tube, and the metal tube is used for evacuating the air inside the board segments in the glass tube sleeve.

[0088] (2) Place the glass tube sleeve with the sealed metal tube in a pressure-resistant sealed cylinder, and pre-fill alumina powder with a particle size of 100 microns at the bottom of the pressure-resistant sealed cylinder. The gap between the outer periphery of the glass tube sleeve and the inner wall of the pressure-resistant sealed cylinder is also filled with alumina powder to fix the glass tube sleeve without shaking.

[0089] (3) Pass the metal tube at one end of the glass tube sleeve through the sealing cover of the pressure-resistant sealed cylinder, tighten the sealing cover, and then place the pressure-resistant sealed cylinder in a heating furnace; there are also an air inlet and a pressure relief port on the sealing cover for pressurizing and depressurizing the glass tube sleeve and the internal optical fiber board segments.

[0090] (4) Connect the metal tube to a vacuum pumping device, turn on the heating furnace, and heat up for 3 hours. After the temperature rises to 650 °C, turn on the vacuum pumping device and start the vacuum evacuation operation for the inside of the glass tube sleeve.

[0091] (5) After the vacuum degree of the glass tube sleeve reaches the design requirement, pass the inert gas helium into the pressure-resistant sealed cylinder at a temperature of 660 °C through the air inlet, and pressurize the glass tube sleeve at a set hot pressing pressure of 10 MPa for 4 hours.

[0092] (6) After the hot pressing and pressurizing are completed, turn off the heating furnace. When the temperature inside the pressure-resistant sealed cylinder drops to 620 °C, slowly release the gas inside the pressure-resistant sealed cylinder over 2 hours. When the furnace body temperature drops to room temperature and the air pressure inside the pressure-resistant sealed cylinder reaches normal atmospheric pressure, open the sealing cover of the pressure-resistant sealed cylinder and take out the hot-pressed optical fiber board segments, thus obtaining the blank plate segments of the optical fiber image inverter.

[0093] The magnification distortion of the blank plate segments of the optical fiber image inverter is 1 ± 0.5%, and the transmittance uniformity of the blank plate segments of the optical fiber image inverter is 1.0%.

[0094] A method for preparing an optical fiber image inverter, comprising:

[0095] After cutting, rounding, and grinding the plate segment of the optical fiber image inverter blank, an optical fiber image inverter blank is prepared. The optical fiber image inverter blank is torsionally formed at 180° in a torsion forming furnace with an ultra-narrow high-temperature zone, thereby obtaining an optical fiber image inverter with an ultra-narrow twisted wire zone. The width of the heating furnace body in the ultra-narrow high-temperature zone is 3 mm, the distance between the heating furnace body and the surface of the optical fiber image inverter blank is 2.5 mm, and the torsion forming time for the optical fiber image inverter blank to be torsionally formed by 180° is 2 minutes.

[0096] The optical fiber image inverter prepared by torsion of the plate segment of the optical fiber image inverter blank does not have the problem of reduced edge resolution in six directions.

[0097] Example 4

[0098] A method for preparing a glass tube sleeve:

[0099] Select raw materials according to the glass composition in Example 4 of Table 1 to make the batching meet the glass chemical composition in Table 1, and then prepare the glass tube sleeve according to the following steps:

[0100] (1) Glass melting: Weigh the raw materials such as quartz sand, aluminum hydroxide, boric acid or boric anhydride, lithium carbonate, sodium carbonate, potassium carbonate or potassium nitrate, calcium carbonate, strontium carbonate, zinc oxide, titanium dioxide, cerium oxide, magnesium fluoride, and calcium fluoride respectively according to the batching requirements, mix them evenly, and then put them into the glass melting pool in the kiln furnace to melt at 1560 °C for 16 hours;

[0101] (2) Clarification and homogenization: After the raw materials are melted into a glass melt, the glass melt flows from the glass melting pool into a clarification pool at 1450 °C for clarification and homogenization for 4 hours. After the glass melt removes and absorbs small bubbles through clarification and homogenization, the glass liquid flows into the stirring pool to be fully stirred evenly, and then flows into the material basin to cool down;

[0102] (3) Tube drawing and forming: After the glass liquid cools down, the glass liquid flows from the material basin to the blanking channel and then to the forming nozzle. After passing through the forming nozzle, the glass liquid is drawn by a tube drawing machine to produce a uniformly formed glass tube;

[0103] (4) Cutting and annealing: Cut the drawn and formed glass tube into a certain length as required, and then put the cut glass tube into an annealing furnace at 610 °C for annealing treatment.

[0104] A method for hot pressing and forming an optical fiber image inverter blank is the same as the preparation method in Example 1.

[0105] The magnification distortion of the obtained plate segment of the optical fiber image inverter blank is 1 ± 0.5%, and the transmittance uniformity of the plate segment of the optical fiber image inverter blank is 1.2%.

[0106] A method for preparing an optical fiber image inverter is the same as the preparation method in Example 1.

[0107] Example 5

[0108] Method for preparing a glass tube sleeve:

[0109] Select raw materials according to the glass composition in Example 5 of Table 1 to make the batching meet the glass chemical composition in Table 1, and then prepare the glass tube sleeve according to the following steps:

[0110] (1) Glass melting: Weigh quartz sand, aluminum hydroxide, boric acid or boric anhydride, lithium carbonate, sodium carbonate, potassium carbonate or potassium nitrate, calcium carbonate, strontium carbonate, zinc oxide, titanium dioxide, cerium oxide, magnesium fluoride and calcium fluoride respectively according to the batching requirements, mix them evenly, and then put them into the glass melting pool in the kiln furnace to melt at 1580 °C for 24 hours;

[0111] (2) Clarification and homogenization: After the raw materials are melted into the glass melt, the glass melt flows into the clarification pool at 1400 °C from the glass melting pool, and is clarified and homogenized for 6 hours. After the glass melt removes and absorbs small bubbles through clarification and homogenization, the glass liquid flows into the stirring pool to be fully stirred evenly, and then flows into the material basin to cool down;

[0112] (3) Tube drawing and forming: After the glass liquid cools down, the glass liquid flows from the material basin to the blanking channel and then to the forming nozzle. After passing through the forming nozzle, the glass liquid is drawn by a tube drawing machine to produce a uniformly formed glass tube;

[0113] (4) Cutting and annealing: Cut the drawn and formed glass tube into a certain length according to the requirements, and then put the cut glass tube into an annealing furnace at 605 °C for annealing treatment.

[0114] A method for hot pressing and forming a blank plate of an optical fiber image inverter is the same as the preparation method in Example 1.

[0115] The magnification distortion of the obtained blank plate segment of the optical fiber image inverter is 1 ± 0.5%, and the transmittance uniformity of the blank plate segment of the optical fiber image inverter is 1.1%.

[0116] A method for preparing an optical fiber image inverter is the same as the preparation method in Example 1.

[0117] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for hot-pressing and forming a blank plate of an optical fiber image inverter, characterized in that, It includes the following steps: (1) Place the arranged optical fiber board segments into a glass tube sleeve with a sealed bottom, and seal a metal tube at the opening of the glass tube sleeve; (2) Place the glass tube sleeve with the sealed metal tube into a pressure-resistant sealed cylinder and fix the glass tube sleeve; (3) Pass the metal tube at one end of the glass tube sleeve through the sealing cover of the pressure-resistant sealed cylinder, tighten the sealing cover, and then place the pressure-resistant sealed cylinder in a heating furnace; the sealing cover is provided with an air inlet and a pressure relief port for pressurizing and depressurizing the glass tube sleeve and the internal optical fiber board segments; (4) Connect the metal tube to a vacuum pumping device, turn on the heating furnace, heat up the pressure-resistant sealed cylinder, after a first preset time, the temperature rises to a first preset temperature, turn on the vacuum pumping device, and start the vacuum exhaust operation for the inside of the glass tube sleeve; (5) After the vacuum degree of the glass tube sleeve reaches the design requirement, introduce an inert gas into the pressure-resistant sealed cylinder at the second preset temperature through the air inlet, and pressurize the glass tube sleeve according to the set pressure of melting and pressing; (6) After the melting and pressing is completed, turn off the heating furnace. When the temperature in the pressure-resistant sealed cylinder drops to a third preset temperature, release the gas in the pressure-resistant sealed cylinder through the pressure relief port within a second preset time. When the furnace body temperature drops to room temperature and the air pressure in the pressure-resistant sealed cylinder reaches normal atmospheric pressure, open the sealing cover of the pressure-resistant sealed cylinder and take out the melted and pressed optical fiber board segments, thus obtaining the blank board segments of the fiber optic image inverter; The first preset time is 3 to 4 hours, and the first preset temperature is 630 - 650 °C; The pressure of melting and pressing is 10 - 15 MPa; the time of melting and pressing is 2 - 4 hours; the second preset temperature is 660 - 700 °C; the third preset temperature is 580 - 620 °C; the second preset time is 2 - 4 hours; the inert gas is nitrogen or helium; The glass tube sleeve is made of low refractive index glass, and the low refractive index glass is composed of the following components in mole percentage: SiO2 78.1 - 80.0%, Al2O3 3.1 - 7.0%, B2O3 2.0 - 8.0%, Li2O 0 - 1.0%, Na2O 0 - 2.9%, K2O 5.1 - 10.0%, CaO 1.1 - 3.0%, SrO 0 - 1.0%, ZnO 1.1 - 2.0%, TiO2 0 - 1.0%, CeO2 0.05 - 0.2%, MgF2 0 - 2.0%, CaF2 0.05 - 2.0%.

2. The hot pressing forming method of the optical fiber image inverter blank according to claim 1, characterized in that There is a blank tube length of 10 mm - 20 mm at the opening of the glass tube sleeve for sealing the metal tube.

3. The hot pressing forming method of the optical fiber image inverter blank according to claim 2, characterized in that Fixing the glass tube sleeve includes filling positioning powder in the gap between the bottom of the pressure-resistant sealed cylinder and the inner wall of the pressure-resistant sealed cylinder and the glass tube sleeve.

4. The hot pressing forming method of the optical fiber image inverter blank according to claim 3, characterized in that The positioning powder is alumina powder or quartz sand particles, and the average particle size of the positioning powder is 50 - 100 microns.

5. The melt pressing forming method of the optical fiber image inverter blank according to any one of claims 1-4, characterized in that The preparation method of the glass tube sleeve includes the following steps: (1)Glass melting: Weigh quartz sand, aluminum hydroxide, boric acid or boric anhydride, lithium carbonate, sodium carbonate, potassium carbonate or potassium nitrate, calcium carbonate, strontium carbonate, zinc oxide, titanium dioxide, cerium oxide, magnesium fluoride and calcium fluoride respectively according to the batching requirements, mix them evenly, and then put them into the glass melting pool in the kiln furnace to melt at 1500 - 1600 °C for 12 - 24 hours; (2)Clarification and homogenization: After the raw materials are melted into the glass melt, the glass melt flows from the glass melting pool into the clarification pool at 1400 - 1470 °C for clarification and homogenization for 4 - 6 hours. After the glass melt removes and absorbs small bubbles through clarification and homogenization, the glass liquid flows into the stirring pool to be fully stirred evenly, and then flows into the material basin to cool down; (3)Tube drawing and forming: After the glass liquid cools down, the glass liquid flows from the material basin to the feeding channel, and then to the forming nozzle. After passing through the forming nozzle, the glass liquid is drawn by a tube drawing machine to produce a uniformly formed glass tube; (4)Cutting and annealing: Cut the drawn and formed glass tube into a certain length as required, and then put the cut glass tube into an annealing furnace at 605 - 615 °C for annealing treatment.

6. The hot pressing forming method of the optical fiber image inverter blank according to claim 5, characterized in that, The thickness of the glass tube sleeve is 1.0 - 15 mm.

7. An optical fiber image inverter, characterized in that, It includes the fiber optic image inverter blank plate segment prepared by the hot pressing forming method of the fiber optic image inverter blank plate according to any one of claims 1 - 6; the unit fiber filament diameter of the fiber optic image inverter blank plate segment ≤ 4 μm, the magnification distortion can reach 1 ± 0.5%, and the transmittance uniformity < 2%; after cutting, rounding, and grinding processing of the fiber optic image inverter blank plate segment, a fiber optic image inverter blank is prepared. The fiber optic image inverter blank is torsionally formed at 180° in a narrow - width high - temperature area torsion forming furnace, that is, a fiber optic image inverter with a narrow torsion wire area is prepared; there is no phenomenon of reduced resolution in 6 directions in the fiber optic image inverter with a narrow torsion wire area; the width of the heating furnace body in the narrow - width high - temperature area is 3 - 4 mm, the distance between the heating furnace body and the surface of the fiber optic image inverter blank is 1.0 - 2.5 mm, and the torsion forming time for the fiber optic image inverter blank to be torsionally formed at 180° is 2 - 9 minutes.

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