Light-absorbing glass for high-contrast fiber optic image inverter and fabrication method thereof

Abstract

Disclosed in the present invention are a light absorption material glass for a high-contrast optical fiber inverter and a preparation method therefor, belonging to the field of optical fiber image transmission element manufacturing. The light absorbing material glass is composed of the following components in percentage by mole: 60-69.9 of SiO 2, 1.0-10.0 of Al 2O 3, 10.1-15.0 of B 2O 3, 1.0-8.0 of Na 2O , 3.0-10.0 of K 2O, 0.1-1.0 of MgO, 0.5-5.0 of CaO, 0-0.1 of ZnO, 0-0.1 of TiO 2, 0.1-1.0 of ZrO 2, 3.0-6.5 of Fe 2O 3, 0.1-0.5 of Co 2O 3, 0.51-1.5 of V 2O 5 and 0.1-1.0 of MoO 3. The light absorption material glass disclosed by the present invention has good light absorption capability, and when applied to an optical fiber inverter, can improve the contrast ratio of the optical fiber inverter.

Description

TECHNICAL FIELD The present invention relates to the field of manufacturing of fiber optic imaging elements, and in particular to a light-absorbing glass for a high-contrast fiber optic image inverter and a fabrication method thereof. BACKGROUND ART As is well known, low-level-light vision technology plays a very important role in observation at night. The low-level-light vision device, which is widely used in the field of night vision, has the abilities to observe and aim under low-level-light conditions at night with the characteristics of high resolution and good stereoscopic vision, and is a main equipment for soldiers to fight at night, ensuring the soldiers to complete the tasks of detecting, aiming and hitting combat objectives at night. In the early stage of the development of low-level-light vision technology, due to cost constraints, the requirements for imaging resolution and image quality were relatively low. However, with the development of fiber optic imaging elements and the performance improvement and price reduction of various electronic products, the demand for low-level-light vision devices with high contrast is gradually realized and technically feasible. From the ordinary contrast to the low-standard contrast and further to the high contrast in nowadays, the high contrast has become a mainstream development trend. The high contrast of the low-level-light vision device refers to the degree of difference between light and dark in a picture, and the contrast has a critical influence over the visual effect. When the contrast is increased, the bright parts in a picture become brighter and the dark parts become darker, with the difference between light and dark being enhanced. The higher the contrast is, the clearer and more conspicuous the image transmitted becomes, while the low contrast will make the entire image transmitted dim. The high contrast helps greatly in the clarity and detail presentation of the image transmitted. There are two ways to increase the contrast. The first way is to enhance the brightness so as to increase the contrast. Such means is relatively simple. Nevertheless, the brightness cannot be enhanced indefinitely due to the problems of such as the service life of image tubes and the light leakage of elements, and the falsely high brightness will cause the transmitted images distorted due to the high brightness, resulting in undesirable effects. The second way is to make the dark parts even darker and to reduce the minimum brightness, so that the difference between light and dark becomes more obvious. Fiber optic imaging elements include fiber optic faceplates, fiber optic image inverters, fiber optic tapers, fiber optic bundles for image transmission, etc., and are photoelectric imaging components with excellent performances. Most typically, the fiber optic imaging elements are applied as the optical input and output windows for the low-level-light image intensifiers, playing an important role in improving the quality of imaging devices. The image transmission mechanism of the fiber optic imaging elements is realized under the principle of the total reflection of optical fibers. The optical fibers in the fiber optic imaging elements are fabricated by cladding glass tubes with a low refractive index, core glass rods with a high refractive index and light-absorbing glass fibers, and are fabricated by a drawing process of vacuum control and rod-tube combination via heat press fusion. Since the optical fibers are totally fused together with the cladding glass, the adjacent optical fibers are arranged close to one another, resulting in optical crosstalk among the adjacent fibers. Alternatively, the problems such as uneven wall thickness of the cladding glass tubes may be caused by uneven temperature field or drawing force during fabrication, and these may eventually result in the phenomenon of light permeation where the input light penetrates the cladding glass during total reflection, leading to light leakage. Alternatively, due to the presence of defects or pollutants in the core glass or the cladding glass contact interfaces of the optical fibers, the condition for total reflection of light is destroyed, so that the light scatters at these places, and the scattered light enters into the adjacent fibers to result in optical crosstalk. The presence of stray light is an important factor that directly affects the imaging quality of the fiber optic imaging elements such as contrast. In order to solve the problems above, the gaps among the adjacent optical fibers are usually filled with the light-absorbing glass fibers, which are used to absorb the stray light so as to improve the imaging quality of the fiber optic imaging elements. The light-absorbing glass fibers are inserted into the gaps of the arranged optical fibers for the absorption of such as optical crosstalk and light leakage. However, a complete optical insulation cannot be achieved, a key reason for which is the material of the light-absorbing glass. The ordinary light-absorbing glass still has a relatively high transmittance within the visible light range at a thickness of 0.5 mm, and with the reduction of thickness, the transmittance increases gradually. For the conventional light-absorbing glass in the fiber optic imaging elements, the problems such as low absorption efficiency of stray light and poor imaging contrast appear commonly. Especially for the optical fibers with a fiber diameter of no more than 4 pm used in the fiber optic imaging elements, the coloring ions in the light-absorbing glass may diffused into the cladding glass, failing to meet the application requirements for the fiber optic imaging elements with high contrast. Therefore, the capability of the low-level-light vision devices to capture sufficiently clear detail information has a lot to do with the contrast of the fiber optic imaging elements. The contrast is an important performance index in the fiber optic imaging transmission products. With the development of fiber optic imaging transmission technology, the requirements for various performances of products increase continuously, and the fiber optic image inverters are the key material to ensure the imaging quality of the low-level-light vision devices. However, the current light-absorbing glass in the fiber optic image inverter products commonly have the problems such as low absorption efficiency of stray light and low imaging contrast. SUMMARY In order to solve the technical problems in the prior art, the present invention provides a light-absorbing glass with good light absorption performance used for high-contrast fiber optic image inverters. To achieve the object above, the technical solution of the present invention is as follows: The present invention provides a composition of a light-absorbing glass for a high-contrast fiber optic image inverter, consisting of the following components in molar percentage: SiO2 60.0-69.9% AI2O3 1.0-10.0% B2O3 10.1-15.0% Na2O 1.0-8.0% K2O 3.0-10.0% MgO 0.1-1.0% CaO 0.5-5.0% TiO2 0-0.1% ZrO2 0.1-1.0% Fe2O3 3.0-6.5% Co2030.1-0.5% V2O5 0.51-1.5% MoO3 0.1-1.0%. Preferably, the composition of a light-absorbing glass consists of the following components in molar percentage: SiO2 60.0-65.0% AI2O3 3.0-6.0% B2O3 11.0-15.0% Na2O 5.0-8.0% K2O 3.0-8.0% MgO 0.1-1.0% CaO 1.0-2.5% ZnO 0-0.1% TiO2 0-0.1% ZrO2 0.1-1% Fe2O3 5.0-6.5% Co2030.1-0.5% V2O5 0.51-1.0% MoO3 0.1-1.0%. Preferably, the composition of a light-absorbing glass consists of the following components in molar percentage: SiO2 60.7% B2O3 11.3% Na2O 8.0% K2O 3.0% MgO 0.1% CaO 2.5% ZnO 0.01% TiO2 0.02% ZrO2 1.0% Fe20s 6.5% CO2O3 0.2% V2O5 0.6% MoO3 1.0%. The present invention further provides a method for preparing a light-absorbing glass for a high-contrast fiber optic image inverter by using the composition described above, comprising the following steps: (1) raw material formulating: weighing quartz sand, aluminum oxide, boric acid or boric anhydride, sodium carbonate, potassium carbonate, basic magnesium carbonate, calcium carbonate, zinc oxide, titanium dioxide, zirconium oxide, ferric oxide, cobalt trioxide, vanadium pentoxide and molybdenum oxide in proportion and mixing evenly to obtain a raw material mixture; (2) glass melting: putting the raw material mixture in a crucible for high-temperature melting, fining after the raw material mixture is molten, casting the obtained molten glass after melting and fining into a specified specification in a mold, and annealing after the glass is cooled and solidified to obtain the light-absorbing glass. The high-temperature melting includes melting at a temperature within a range of 1450-1550°C for 3-5 hours, and stirring the raw material mixture for 1-2 times during the melting process. The fining is conducted at a temperature within a range of 1300-1400°C for 1-2 hours. The annealing is conducted by preserving at a temperature within a range of 500-549°C for 2-3 hours, and then cooling to room temperature within 20-24 hours. The method further includes: after the molten glass is cast and before totally solidified, using a vibrator to vibrate the molten glass evenly to remove internal holes and bubbles in the molten glass. After melting, the light-absorbing glass has the advantages of such as no stones or bubbles or holes inside, no crystallization after retaining at 820°C for 6 hours, good anti-crystallization performance and excellent chemical stability. The present invention further provides a light-absorbing glass for a high-contrast fiber optic image inverter, prepared by the method described above. The light-absorbing glass has a strong and uniform light absorption ability and light spectrum absorption effect within a wavelength range of 400-700 nm at a thickness of 0.3±0.01 mm, with a light spectrum transmittance of no more than 0.1%. The present invention further provides a method for preparing a high-contrast fiber optic image inverter by using the light-absorbing glass described above, including: (1) matching a core glass rod with a high refractive index and a cladding glass tube with a low refractive index, and combining the rod and the tube to draw into a mono fiber; (2) arranging the drawn mono fibers into a multi fiber assembly as required, and inserting light-absorbing glass fibers drawn from the light-absorbing glass into the multi fiber assembly evenly, followed by drawing into a multi fiber, the multi fiber including the mono fibers drawn by combining the rods and the tubes and the light-absorbing glass fibers drawn from the light-absorbing glass; (3) arranging the multi fibers into a multi-multi assembly as required, drawing the multimulti assembly into a multi-multi fiber with a diameter of no more than 4 pm, then arranging the multi-multi fibers into a fiber assembly bundle, and subjecting the fiber assembly bundle to heat press fusion to form a fiber optic faceplate block, obtaining the high-contrast fiber optic image inverter. In the present invention, by means of the insertion and adjustment of the light-absorbing glass fibers, the diameter of the optical fibers is reduced, and the contrast of the fiber optic image inverters is increased. Further, the high-contrast fiber optic image inverter prepared by the method has an optical crosstalk of less than 1.0% at 0.1 mm from a cutting edge. Further, the high-contrast fiber optic image inverter prepared by the method has an excellent performance index of fixed-pattern noise, and shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. Further, the high-contrast fiber optic image inverter prepared by the method has a transmittance of more than 70% within a wavelength range of 400-700 nm. The present invention further provides a use of the high-contrast fiber optic image inverter prepared by the method described above in a low-level-light image intensifier. The light-absorbing glass in the present invention can be applied to a high-contrast fiber optic image inverter, and the high-contrast fiber optic image inverter can be applied to a low-level-light image intensifier. The light-absorbing glass in the present invention is suitable for glass fibers being used as a glass material for extra-mural absorption in the fabrication of fiber optic imaging elements, and is especially suitable for preparing high-contrast fiber optic image inverters. The fiber optic imaging elements include fiber optic faceplates, fiber optic image inverters, fiber optic tapers, fiber optic bundles for image transmission, etc. In the present invention, SiO2 is a main body to form the structure network of glass and is a component that plays a major role in the glass structure network. The molar percentage (mol.%) of SiO2 is 60-69.9. When the content of SiO2 is lower than 60 mol.%, it is difficult to obtain a thermal expansion coefficient similar to the cladding glass, and meanwhile the chemical resistance of the glass will be reduced; when the content of SiO2 is higher than 69.9 mol.%, the high temperature viscosity of the glass will be increased, resulting in an excessively high temperature for glass melting. AI2O3 belongs to the intermediate oxides of the glass. Al3+ has two coordination states, that is, in tetrahedron or octahedron. When oxygen is sufficient in the glass, aluminumoxygen tetrahedron [AIO4] is formed, which forms a continuous network with siliconoxygen tetrahedron. When oxygen is insufficient in the glass, aluminum-oxygen octahedron [AlOe] is formed, which acts as a network modifier and is in the holes of the silicon-oxygen structural network. Thus, within a certain content range, AI2O3 may serve as the main body to form the glass network together with SiO2. When the content of AI2O3 is higher than 10.0 mol.%, the viscosity of the glass at high temperatures will be significantly increased, leading to an increase in the temperature for glass melting. Therefore, the molar percentage (mol.%) of AI2O3 is 1.0-10.0. B2O3 is a glass-forming oxide and a component of the glass structure network, and meanwhile is a fluxing agent to reduce the viscosity of glass melting. Boron-oxygen triangle [BO3] and boron-oxygen tetrahedron [BO4] are the structural elements. Boron may exist as triangle [BO3] or boron-oxygen tetrahedron [BO4] under different conditions. At the condition of high-temperature melting, it is usually difficult for boron to form boron-oxygen tetrahedron but can only exist in the form of trihedral, while at low temperatures, B3+ has the tendency to capture free oxygen to form tetrahedron under certain conditions, which makes the structure compact and thus improves the low-temperature viscosity of glass. Nevertheless, B2O3 has the characteristics of reducing glass viscosity at high temperatures and increasing glass viscosity at low temperatures, and it is also a main component to reduce the refractive index of the glass, both of which determine that the content range of B2O3 is relatively small. The molar percentage (mol.%) of B2O3 is 10.1-15.0. When the content of B2O3 is higher than 15.0 mol.%, the refractive index of the glass will be reduced and the phase separation tendency of the glass will be increased. Na2O is a network modifier oxide of the glass structure. When the content of Na2O is higher than 8.0 mol.%, the thermal expansion coefficient of the glass will be increased and meanwhile the refractive index of the glass will be increased. Therefore, the molar percentage (mol.%) of Na2O is 1.0-8.0. K2O is a network modifier oxide of the glass structure. When the content of K2O is higher than 10.0 mol.%, the thermal expansion coefficient of the glass will be increased and meanwhile the refractive index of the glass will be increased. Therefore, the molar percentage (mol.%) of K2O is 3.0-10.0. MgO is a network modifier oxide of the glass structure. When the content of MgO is higher than 1.0 mol.%, the crystallization tendency of the glass will be increased, and meanwhile the density of the glass will be reduced and the refractive index of the glass will be increased. Therefore, the molar percentage (mol.%) of MgO is 0.1-1.0. CaO is a network modifier oxide of the glass structure. When the content of CaO is higher than 5.0 mol.%, the chemical resistance of the glass will be reduced, the refractive index of the glass will be increased, and the crystallization tendency of the glass will be increased. Therefore, the molar percentage (mol.%) of CaO is 0.5-5.0. ZnO is used to adjust the crystallization temperature and chemical resistance of the glass. The molar percentage of ZnO is 0-0.1 mol.%. When the content of ZnO is higher than 0.1 mol.%, the chemical resistance of the glass will be reduced and the tendency of crystallization will be increased. TiO2 is used to adjust the chemical resistance and crystallization of the glass. The molar percentage (mol. %) of TiO2 is 0-0.1. When the content of TiO2 is higher than 0.1 mol.%, the chemical resistance of the glass will be reduced and the tendency of crystallization will be increased. ZrO2 is used to adjust the chemical resistance and crystallization of the glass. The molar percentage (mol.%) of ZrO2 is 0.1-1.0. When the content of ZrO2 is higher than 1.0 mol.%, the chemical resistance of the glass will be reduced and the tendency of crystallization will be increased. Fe2Os is a light-absorbing coloring agent for the light-absorbing glass. The molar percentage (mol.%) of Fe2Os is 3.0-6.5. In the present invention, Fe2Os is a light-absorbing agent that plays a major role. Fe3+ ions have a good light absorption performance, and the light absorption range is mainly concentrated within a region from visible light to infrared ray. When the content of Fe20s is higher than 6.5 mol.%, the chemical resistance of the glass will be reduced and the crystallization tendency of the glass will be increased. When the content of Fe2Os is less than 3.0 mol.%, the coloring of Fe2Os will become unstable or even fade during drawing fibers at high temperatures, which directly affects the light absorption effect, thereby making a serious impact on improving the image transmission quality of the fiber optic image inverters and failing to meet the application requirements for improving the contrast of the fiber optic image inverters. CO2O3 is a coloring agent for the light-absorbing glass. The molar percentage (mol.%) of CO2O3 is 0.1-0.5. CO2O3 can bind to the iron ions to form a stable form in the glass, thereby making the coloring of the light-absorbing material more stable. When the content of CO2O3 is higher than 0.5 mol.%, the chemical resistance of the glass will be reduced, and the crystallization tendency of the glass will be increased. V2O5 is a coloring agent for the light-absorbing glass. The molar percentage (mol.%) of V2O5 is 0.51-1.5. V2O5 can fix the coloring of the iron ions, thereby making the coloring of the light-absorbing material more stable. When the content of V2O5 is higher than 1.5 mol.%, the chemical resistance of the glass will be reduced, and the crystallization tendency of the glass will be increased. MoOs is a transition metal oxide and also a coloring agent for the light-absorbing glass. The molar percentage (mol.%) of MoOs is 0.1-1.0. MoOs can bind to the iron ions and cobalt ions to form stable coloring in the glass. With the composite absorption, it can be ensured that the stray light within a wavelength range of 400-700 nm will be absorbed, achieving a desirable light absorption effect and avoiding the appearance of obvious transmittance peaks within the visible light region in a light absorption curve. Nevertheless, when the content of MoOs is higher than 1.0 mol.%, the chemical resistance of the glass will be reduced, and the crystallization tendency of the glass will be increased. Compared with the prior art, the light-absorbing glass for a high-contrast fiber optic image inverter in the present invention has the following characteristics: (1) The light-absorbing glass has good light absorption performance. The light-absorbing glass has a strong and uniform light absorption ability and light spectrum absorption effect within a wavelength range of 400-700 nm at a thickness of 0.3±0.01 mm, with a light spectrum transmittance of no more than 0.1%. (2) The light-absorbing glass has a thermal expansion coefficient and viscosity properties similar to the cladding glass, and the thermal expansion coefficient of the glass is (82±2)x10-7 / °C. (3) The light-absorbing glass has a good performance on chemical stability and anti-crystallization. The light-absorbing glass has no stones or bubbles or holes inside after melting, and has no phase separation or crystallization after retaining at 820°C for 6 hours, which has a good anti-crystallization performance and excellent chemical stability. The high-contrast fiber optic image inverter prepared by the light-absorbing glass described above has the following advantages: (1) The high-contrast fiber optic image inverter has an optical crosstalk of less than 1.0% at 0.1 mm from a cutting edge. (2) The high-contrast fiber optic image inverter has an excellent performance of fixed-pattern noise, and shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. (3) The high-contrast fiber optic image inverter has a transmittance of more than 70% within a wavelength range of 400-700 nm. (4) The light-absorbing glass in the present invention is applied to the fiber optic image inverter, by which the absorption of the stray light among optical fibers can be effectively improved to reduce the optical crosstalk among the fibers, thereby achieving the effects of improving the contrast and clarity of imaging in the fiber optic image inverters. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram of the internal structure of the optical fiber forming fiber optic imaging elements provided in an embodiment of the present invention. Figure 2 is a schematic diagram of the structure of the optical fiber provided in an embodiment of the present invention. Figure 3 is a diagram of contrast test on the high-contrast fiber optic image inverter prepared in Example 1 of the present invention. In these figures, 1 represents light-absorbing glass, 2 represents core glass and 3 represents cladding glass. DETAILED DESCRIPTION OF THE EMBODIMENTS In order to make the purposes, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with accompanying drawings and specific embodiments, which are however not intended to limit the present invention. Referring to Fig. 1 and Fig. 2, a cladding glass tube and a core glass rod are matched and then drawn into a mono fiber. The mono fiber includes an outer cladding glass 3 and an inner core glass 2. The mono fibers are closely arranged into a hexahedron with a cross section of a regular hexagonal. Light-absorbing glass fibers drawn from light-absorbing glass 1 are disposed among the adjacent mono fibers. After the light-absorbing glass fibers are inserted into the hexahedron, a multi fiber assembly is assembled, which is subsequently drawn into a multi fiber as shown in Fig. 1. The method of extra-mural absorption fibers by using the light-absorbing glass in the present invention can effectively absorb the optical crosstalk inside optical fibers. In the present invention, all the "molar percentage mol.%" is based on the total molar quantity of the final glass composition. The chemical composition (mol.%) of the glasses in the Examples are listed in detail in Table 1. Among them, the transmittance of the glasses at 400-700 nm is measured on a transmittance device, and the thickness 5 of the glass sheets is 0.3±0.01 mm; the crystallization temperature is measured on a gradient crystallization furnace; the linear expansion coefficient 030 / 300 [10-7 / °C] at 30-300°C is measured on a horizontal dilatometer and expressed as an average linear expansion coefficient, and is measured in accordance with the method specified in ISO 7991. 10 Table 1 Chemical composition (mol.%) and glass properties of Examples Composition Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 SiO2 60.7 65.0 60.0 69.9 64.14 64.7 AI2O3 5.07 1.0 10.0 3.0 3.1 3.67 B2O3 11.3 15.0 12.0 10.1 13.53 10.2 Na2O 8.0 5.5 3.73 3.0 5.87 1.0 K2O 3.0 3.31 4.63 7.9 3.33 10.0 MgO 0.1 0.5 1.0 0.19 0.53 0.2 CaO 2.5 1.73 2.0 0.5 1.91 5.0 ZnO 0.01 0.1 0.02 0 0 0.02 TiO2 0.02 0.01 0.02 0.1 0 0.01 ZrO2 1.0 0.5 0.3 0.1 0.26 0.2 Fe2Os 6.5 5.72 5.0 4.1 6.03 3.0 CO2O3 0.2 0.33 0.1 0.5 0.3 0.2 V2O5 0.6 0.8 1.0 0.51 0.78 1.5 MoOs 1.0 0.5 0.2 0.1 0.22 0.3 Transmittance 0 0 0 0 0 0 Thermal          80       81       84       84       83       82 expansion coefficient The raw materials used in the Examples and the requirements for the raw materials are as follows: Quartz sand or crystal powder (high pure, oversize at 150 pm sieve is no more than 1 %, undersize at 45 pm sieve is no more than 30%, Fe2Os content is less than 1 ppm), aluminum oxide powder (analytical pure, average particle size of 50 pm), boric acid or boric anhydride (oversize at 400 pm sieve is no more than 10%, undersize at 63 pm sieve is no more than 10%), sodium carbonate (industrial soda ash), potassium carbonate (analytical pure, purity>99.0%), basic magnesium carbonate (chemical pure, average particle size of 50 pm), calcium carbonate (analytical pure, average particle size of 250 pm), zinc oxide (analytical pure), titanium dioxide (analytical pure), zirconium oxide (analytical pure), ferric oxide (analytical pure), cobalt trioxide (analytical pure), vanadium pentoxide (analytical pure), molybdenum oxide (analytical pure). Example 1 Fabrication of light-absorbing glass: Firstly, raw materials were selected according to the glass composition of Example 1 in Table 1 and formulated to meet the chemical composition of the glass in Table 1. Then a quartz crucible was used to melt the raw materials at 1500°C for 4 hours. In the glass melting process, stirring was carried out for 1 to 2 times to make the glass molten evenly. After melting, the molten glass was subjected to fining at 1350°C for 2 hours. Subsequently, the molten glass was cast into specified specifications. After the molten glass was cast and before totally solidified, a vibrator was used to vibrate the molten glass evenly to remove internal holes and bubbles in the molten glass. After cooling and solidifying, the annealing process was conducted by preserving heat for 2 hours at 530°C and cooling to room temperature within 24 hours. The light-absorbing glass in the present invention was obtained. The basic properties of the sample are shown in Table 1, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 80x10'7 / °C. The process of preparing a high-contrast fiber optic image inverter by using the light-absorbing glass described above included the following steps: (1) a core glass rod with a high refractive index and a cladding glass tube with a low refractive index was matched, and the rod and the tube were combined to be drawn into a mono fiber; (2) the drawn mono fibers were arranged into a multi fiber assembly as required, and light-absorbing glass fibers drawn from the light-absorbing glass were inserted into the assembly evenly, followed by being drawn into a multi fiber, the multi fiber including the mono fibers drawn by combining the rods and the tubes and the light-absorbing glass fibers drawn from the light-absorbing glass; (3) the multi fibers were arranged into a multi-multi assembly as required, the multimulti assembly was drawn into a multi-multi fiber with a diameter of no more than 4 pm, then the multi-multi fibers were arranged into a fiber assembly bundle, and the fiber assembly bundle was subjected to heat press fusion to form a fiber optic faceplate block. The high-contrast fiber optic image inverter was obtained. Referring to Fig. 3, the contrast test on the fiber optic image inverter prepared by using the light-absorbing glass in the present invention shows that the high-contrast fiber optic image inverter prepared has an optical crosstalk of 0.90% at 0.1 mm from the cutting edge, that is, to have a contrast of less than 1.0% at 0.1 mm from the cutting edge. Moreover, the high-contrast fiber optic image inverter shows no obvious multimulti fiber boundary under the observation of 10-fold microscope. The high-contrast fiberoptic image inverter has a transmittance of 71% within a wavelength range of 400-700 nm. Example 2 Fabrication of light-absorbing glass: The actual composition of the glass referred to Example 2 in Table 1. The same raw materials and raw material requirements as those in Example 1 were used. Then a quartz crucible was used to melt the raw materials at 1450°C for 5 hours. In the glass melting process, stirring was carried out for 1 to 2 times to make the glass molten evenly. After melting, the molten glass was subjected to fining at 1400°C for 1 hour. Subsequently, the molten glass was cast into specified specifications, vibrated evenly and then annealed. The annealing process was conducted by preserving heat for 2.5 hours at 525°C and cooling to room temperature within 20 hours. The light-absorbing glass in the present invention was obtained. The basic properties of the sample are shown in Table 1, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 81 xW7 / °C. The process of preparing the high-contrast fiber optic image inverter was as same as Example 1. The high-contrast fiber optic image inverter prepared has an optical crosstalk of 0.96% at 0.1 mm from the cutting edge. Moreover, the high-contrast fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The high-contrast fiber optic image inverter has a transmittance of 72% within a wavelength range of 400-700 nm. Example 3 Fabrication of light-absorbing glass: The actual composition of the glass referred to Example 3 in Table 1. The same raw materials and raw material requirements as those in Example 1 were used. Then a quartz crucible was used to melt the raw materials at 1550°C for 3 hours. In the glass melting process, stirring was carried out for 1 to 2 times to make the glass molten evenly. After melting, the molten glass was subjected to fining at 1300°C for 2 hours. Subsequently, the molten glass was cast into specified specifications and then annealed. The annealing process was conducted by preserving heat for 3 hours at 540°C and cooling to room temperature within 21 hours. The light-absorbing glass in the present invention was obtained. The basic properties of the sample are shown in Table 1, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 84xW7 / °C. The process of preparing the high-contrast fiber optic image inverter was as same as Example 1. The high-contrast fiber optic image inverter prepared has an optical crosstalk of 0.89% at 0.1 mm from the cutting edge. Moreover, the high-contrast fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The high-contrast fiber optic image inverter has a transmittance of 71 % within a wavelength range of 400-700 nm. Example 4 Fabrication of light-absorbing glass: The actual composition of the glass referred to Example 4 in Table 1. The same raw materials and raw material requirements as those in Example 1 were used. Then a quartz crucible was used to melt the raw materials at 1480°C for 5 hours. In the glass melting process, stirring was carried out for 1 to 2 times to make the glass molten evenly. After melting, the molten glass was subjected to fining at 1380°C for 1.5 hours. Subsequently, the molten glass was cast into specified specifications and then annealed. The annealing process was conducted by preserving heat for 2 hours at 500°C and cooling to room temperature within 22 hours. The light-absorbing glass in the present invention was obtained. The basic properties of the sample are shown in Table 1, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 84x10'7 / °C. The process of preparing the high-contrast fiber optic image inverter was as same as Example 1. The high-contrast fiber optic image inverter prepared has an optical crosstalk of 0.82% at 0.1 mm from the cutting edge. Moreover, the high-contrast fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The high-contrast fiber optic image inverter has a transmittance of 71 % within a wavelength range of 400-700 nm. Example 5 Fabrication of light-absorbing glass: The actual composition of the glass referred to Example 5 in Table 1. The same raw materials and raw material requirements as those in Example 1 were used. Then a quartz crucible was used to melt the raw materials at 1460°C for 4 hours. In the glass melting process, stirring was carried out for 1 to 2 times to make the glass molten evenly. After melting, the molten glass was subjected to fining at 1350°C for 2 hours. Subsequently, the molten glass was cast into specified specifications and then annealed. The annealing process was conducted by preserving heat for 3 hours at 549°C and cooling to room temperature within 20 hours. The light-absorbing glass in the present invention was obtained. The basic properties of the sample are shown in Table 1, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 83xlO'7 / °C. The process of preparing the high-contrast fiber optic image inverter was as same as Example 1. The high-contrast fiber optic image inverter prepared has an optical crosstalk of 0.86% at 0.1 mm from the cutting edge. Moreover, the high-contrast fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The high-contrast fiber optic image inverter has a transmittance of 71 % within a wavelength range of 400-700 nm. Example 6 Fabrication of light-absorbing glass: The actual composition of the glass referred to Example 5 in Table 1. The same raw materials and raw material requirements as those in Example 1 were used. Then a quartz crucible was used to melt the raw materials at 1470°C for 5 hours. In the glass melting process, stirring was carried out for 1 to 2 times to make the glass molten evenly. After melting, the molten glass was subjected to fining at 1370°C for 2 hours. Subsequently, the molten glass was cast into specified specifications and then annealed. The annealing process was conducted by preserving heat for 3 hours at 540°C and cooling to room temperature within 24 hours. The light-absorbing glass in the present invention was obtained. The basic properties of the sample are shown in Table 1, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 82x10'7 / °C. The process of preparing the high-contrast fiber optic image inverter was as same as Example 1. The high-contrast fiber optic image inverter prepared has an optical crosstalk of 0.92% at 0.1 mm from the cutting edge. Moreover, the high-contrast fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The high-contrast fiber optic image inverter has a transmittance of 72% within a wavelength range of 400-700 nm. The descriptions above are only preferred embodiments of the present invention, and are not intended to be used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A composition of a light-absorbing glass for a high-contrast fiber optic image inverter, consisting of the following components in molar percentage:SiO2 60.0-69.9%AI2O3 1.0-10.0%B2O3 10.1-15.0%Na2O 1.0-8.0%K2O 3.0-10.0%MgO 0.1-1.0%CaO 0.5-5.0%ZnO 0-0.1%TiO2 0-0.1%ZrO2 0.1-1.0%Fe2O3 3.0-6.5%Co2030.1-0.5%V2O5 0.51-1.5%MoO3 0.1-1.0%.

2. The composition according to claim 1, wherein the composition consists of the following components in molar percentage:SiO2 60.0-65.0%AI2O3 3.0-6.0%B2O3 11.0-15.0%Na2O 5.0-8.0%K2O 3.0-8.0%MgO 0.1-1.0%CaO 1.0-2.5%ZnO 0-0.1%TiO2 0-0.1%ZrO2 0.1-1%Fe2Os 5.0-6.5%Co2030.1-0.5%V2Os 0.51-1.0%MoO3 0.1-1.0%.

3. The composition according to claim 1, wherein the composition consists of the following components in molar percentage:SiO2 60.7%AI2O3 5.07%B2O3 11.3%Na2O 8.0%K2O 3.0%MgO 0.1%CaO 2.5%ZnO 0.01%TiO2 0.02%ZrO2 1.0%Fe2Os 6.5%Co2O3 0.2%V2O5 0.6%MoO3 1.0%.

4. A method for preparing a light-absorbing glass for a high-contrast fiber optic image inverter by using the composition according to claim 1,2 or 3, comprising the following steps:(1) raw material formulating: weighing quartz sand, aluminum oxide, boric acid or boric anhydride, sodium carbonate, potassium carbonate, basic magnesium carbonate, calcium carbonate, zinc oxide, titanium dioxide, zirconium oxide, ferric oxide, cobalt trioxide, vanadium pentoxide and molybdenum oxide in proportion and mixing evenly to obtain a raw material mixture;(2) glass melting: putting the raw material mixture in a crucible for high-temperature melting, fining after the raw material mixture is molten, casting the obtained molten glass after melting and fining into a specified specification in a mold, and annealing after the glass is cooled and solidified to obtain the light-absorbing glass.

5. The method according to claim 4, wherein the high-temperature melting comprises melting at a temperature within a range of 1450-1550°C for 3-5 hours, and stirring the raw material mixture for 1-2 times during the melting process;the fining is conducted at a temperature within a range of 1300-1400°C for 1-2 hours;the annealing is conducted by preserving at a temperature within a range of 500-549°C for 2-3 hours, and then cooling to room temperature within 20-24 hours;the method further includes: after the molten glass is cast and before totally solidified, using a vibrator to vibrate the molten glass evenly to remove internal holes and bubbles in the molten glass.

6. A light-absorbing glass for a high-contrast fiber optic image inverter, prepared by the method according to claim 4 or 5.

7. The light-absorbing glass according to claim 6, wherein the light-absorbing glass has a strong and uniform light absorption ability and light spectrum absorption effect within a wavelength range of 400-700 nm at a thickness of 0.3±0.01 mm, with a light spectrum transmittance of no more than 0.1%.

8. A method for preparing a high-contrast fiber optic image inverter by using the light-absorbing glass according to claim 6 or 7, comprising:(1) matching a core glass rod with a high refractive index and a cladding glass tube with a low refractive index, and combining the rod and the tube to draw into a mono fiber;(2) arranging the drawn mono fibers into a multi fiber assembly as required, and inserting light-absorbing glass fibers drawn from the light-absorbing glass into the multifiber assembly evenly, followed by drawing into a multi fiber, the multi fiber comprising the mono fibers drawn by combining the rods and the tubes and the light-absorbing glass fibers drawn from the light-absorbing glass;(3) arranging the multi fibers into a multi-multi assembly as required, drawing the multi-5 multi assembly into a multi-multi fiber with a diameter of no more than 4 pm, then arranging the multi-multi fibers into a fiber assembly bundle, and subjecting the fiber assembly bundle to heat press fusion to form a fiber optic faceplate block, obtaining the high-contrast fiber optic image inverter.

9. The method according to claim 8, wherein the high-contrast fiber optic image inverter io has an optical crosstalk of less than 1.0% at 0.1 mm from a cutting edge, shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope, and has a transmittance of more than 70% within a wavelength range of 400-700 nm.

10. Use of the high-contrast fiber optic image inverter prepared by the method according to claim 8 or 9 in a low-level-light image intensifier.