Contrast enhancement type optical fiber image inverter and preparation method thereof

Abstract

The invention relates to a contrast enhancement type optical fiber image inverter and a preparation method thereof. The preparation method comprises the following steps: drawing contrast enhancement type filter glass into a light absorption wire; matching the skin material glass tube with the core material glass rod, and drawing into a monofilament and a round white filament; the drawn monofilaments are arranged into a primary composite rod with an orthohexagonal cross section, and triangular holes of the primary composite rod are evenly filled and inserted with light absorption filaments and round white filaments; drawing the combined primary composite rod into a primary multifilament; arranging the primary multifilaments into secondary composite rods with orthohexagonal cross sections, drawing the secondary composite rods into secondary multifilaments, cutting the secondary multifilaments in a fixed-length manner, and arranging the secondary multifilaments into rows of screen plate sections; and carrying out hot melt pressing forming and torsion forming to obtain the contrast enhancement type optical fiber image inverter. The contrast-enhanced optical fiber image inverter prepared by the method has the advantages of high resolution, high contrast, clear imaging, uniform transmittance, excellent internal quality and the like.

Description

Technical Field

[0001] The invention relates to the field of manufacturing optical fiber image transmission elements, and in particular to a contrast-enhanced optical fiber image invertor and a preparation method thereof. Background Art

[0002] The fiber optic image invertor is the core optical component in low-light-level night vision devices. It is an optoelectronic imaging component with excellent performance, large numerical aperture, high light transmission efficiency, high resolution, and true and clear image transmission. It has the characteristics of zero thickness in optics, simple structure, small size, light weight, good airtightness, small distortion, few spots, small interstage coupling loss, high coupling efficiency and improved edge image quality. It is the optical output window of the low-light-level image intensifier, 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.

[0003] The image transmission mechanism of the fiber optic image inverter is realized by utilizing the total reflection principle of the optical fiber. The optical fiber constituting the fiber optic image inverter is prepared by hot melting and pressing a low-refractive-index skin glass tube, a high-refractive-index core glass rod, and a light-absorbing glass yarn by utilizing a rod-tube combination and a vacuum drawing process. Since the optical fiber is completely tightly fused together by the skin glass, the adjacent optical fibers are close to each other, resulting in cross-talk between adjacent optical fibers. For example, due to the uneven temperature field or uneven drawing force during the preparation process, the uneven thickness of the skin glass tube may result, which may cause the input light to penetrate the skin glass during the total reflection process, resulting in light penetration and light leakage. Alternatively, the contact interface of the core glass or skin glass of the optical fiber destroys the total reflection condition of the light due to defects or contaminants, causing the light to be scattered here. These scattered lights enter the adjacent optical fibers and also cause cross-talk, which is an important factor directly affecting the contrast and clarity of the imaging quality of the fiber optic image transmission element.

[0004] In order to solve the problem of light crosstalk in optical fiber image inverters, it is usually adopted to fill the gaps between adjacent optical fibers with light-absorbing glass fibers to absorb stray light and reduce light crosstalk. The method of inserting light-absorbing glass fibers can effectively eliminate stray light. The light-absorbing glass is drawn into absorption fibers, and the light-absorbing glass fibers are inserted into the gaps between arranged optical fibers to absorb light crosstalk and light leakage. However, optical insulation cannot be completely achieved. The key lies in the problem of light-absorbing glass.

[0005] The function of light-absorbing glass is to absorb the stray light that penetrates the cortex of the optical fiber to achieve optical insulation and improve the contrast of the image. Light-absorbing glass is an important type of optical glass, which mainly achieves the absorption effect of interfering stray light and improves the clarity, contrast and other performance of optical components. However, with the expansion of application fields, the requirements for ultra-thin, high-definition and high-contrast have become increasingly higher in recent years. Therefore, light-absorbing glass is also required to have better light absorption effect, more thorough absorption of stray light, and cover the ultraviolet, visible to near-infrared bands.

[0006] Ordinary light-absorbing glass still has a high transmittance in the visible light range at a thickness of 0.5mm. As the thickness decreases, the transmittance will gradually increase. However, the light-absorbing materials of traditional optical fiber image transmission components generally have problems such as low stray light absorption efficiency and poor imaging contrast. In particular, the light-absorbing glass used in optical fiber image transmission components, after the existing light-absorbing glass is drawn to a fiber diameter of less than or equal to 4.0μm, the colored ions will easily diffuse into the cortex glass, resulting in ion penetration between the glasses, and even the edge of the optical fiber image inverter turns black after twisting or produces fixed pattern noise defects, such as white chicken wire and multifilament shadows, etc., resulting in the quality of the optical fiber image inverter and the qualified rate of finished products are very low, which cannot meet the batch application requirements of high-definition optical fiber image transmission components. The main reason for this is that the light absorption capacity of the light-absorbing glass material and the fixed pattern noise defect are a set of contradictions. The stronger the light absorption capacity of the light-absorbing glass is, the greater the probability of the fixed pattern noise defect is. The light absorption capacity of the light-absorbing glass is too weak, and the effect of improving the contrast of the optical fiber image inverter cannot be achieved. Summary of the invention

[0007] The main purpose of the present invention is to provide a method for preparing a contrast-enhanced optical fiber image invertor with high resolution, high contrast and clear imaging.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a contrast-enhanced optical fiber image invertor comprises the following steps:

[0010] (1) Drawing of light-absorbing wires, round white wires and monofilaments: Drawing contrast-enhanced filter glass into light-absorbing wires; matching low-refractive index skin glass tubes with high-refractive index core glass rods and then drawing them into round white wires; matching low-refractive index skin glass tubes with high-refractive index core glass rods and then drawing them into monofilaments;

[0011] (2) Drawing of primary multifilaments: Arranging the drawn single filaments into a primary composite rod with a regular hexagonal cross section, and filling and inserting the light absorbing filaments into the triangular pores of the primary composite rod evenly; filling and inserting the round white filaments into the triangular pores of the primary composite rod that are not inserted with the light absorbing filaments; and drawing the primary composite rod assembled as above into primary multifilaments;

[0012] (3) Drawing of secondary multifilaments: Arranging the drawn primary multifilaments into secondary composite rods with a regular hexagonal cross section, drawing the secondary composite rods into secondary multifilaments, cutting the secondary multifilaments to a fixed length and arranging them into screen plate segments;

[0013] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, hot melt pressing is performed according to the designed compression ratio of the plate segment before and after hot melt pressing, and hot melt pressing is performed under high temperature and pressure to obtain a fiber optic image invertor blank plate segment;

[0014] (5) Twisting molding: The fiber optic image inverter blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a fiber optic image inverter blank. The fiber optic image inverter blank is twisted at an angle of 180° in a twisting molding furnace to prepare a contrast-enhanced fiber optic image inverter.

[0015] The light absorbing wire has the same wire diameter as the round white wire, both of which are Φ0.3-0.45mm; the number of inserted light absorbing wires is 6N, where 6≤N≤9; the penetration of the contrast-enhanced filter glass and the leather glass used to prepare the leather glass tube does not exceed 20nm.

[0016] In the primary composite rod, the wire diameter of the monofilament is Φ2.0mm~3.0mm, and the number of monofilaments on each side is 8; the number of primary multifilaments on each side of the secondary composite rod is 10~15, and the hexagonal opposite side size of the primary multifilament is 1.0mm~2.0mm; the hexagonal opposite side size of the secondary multifilament is 1.0~1.6mm.

[0017] The contrast enhancement filter 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%, BaO0-1%, 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%, CuO 0.1-2%, and F2 0-1%.

[0018] Preferably, the contrast enhancement filter 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%, CaO1-2.5%, BaO 0-0.1%, SrO 0-0.2%, ZnO 0-0.1%, TiO20-0.3%, 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%, Cr2O3 0.1-1%, Nd2O3 0-0.5%, CuO 0.1-1%, F2 0.1-1%.

[0019] More preferably, the contrast enhanced filter 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%, MnO2 0.3%, Cr2O3 0.5%, CuO 0.8%, and F2 0.5%.

[0020] Furthermore, a method for preparing contrast-enhanced filter glass is also provided, comprising the following steps:

[0021] (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;

[0022] (2) Glass melting: adding the raw material mixture into a crucible, melting it at 1420-1520° C. for 5-8 hours, clarifying and stirring the raw material mixture 2-3 times after it is melted, discharging the melted and clarified glass liquid at 1360-1380° C., casting it into the required glass in a mold, and annealing the glass after it is cooled and solidified at a temperature of 550-600° C. for 24-36 hours to obtain a contrast-enhanced filter glass;

[0023] The contrast-enhanced filter glass has a spectral transmittance of ≤2.5% in the wavelength range of 380-760 nm at a thickness of 0.30±0.01 mm; a thermal expansion coefficient of (80±5)×10 －7 / ℃; no crystallization occurs when kept at 850℃ for 6 hours.

[0024] The present invention further provides a contrast-enhanced optical fiber image invertor, which is prepared according to the preparation method.

[0025] The unit fiber diameter of the contrast-enhanced optical fiber image invertor is less than 4.0 μm, and the central resolution is greater than 140 lp / mm; the crosstalk is less than <0.9% at a distance of 0.1 mm from the knife edge, and it has excellent fixed pattern noise performance, and there is no obvious multifilament boundary when observed under a 10x microscope; the collimated light transmittance is greater than 70% within the wavelength range of 380-760 nm, and the transmittance uniformity is less than 5%.

[0026] The present invention further provides an application of the contrast-enhanced optical fiber image invertor in a low-light-level image intensifier.

[0027] Compared with the prior art, the contrast-enhanced optical fiber image invertor of the present invention has the following advantages:

[0028] (1) The contrast-enhanced fiber image invertor of the present invention has a stably enhanced contrast ratio, uses less light-absorbing filaments, and can achieve an effect of less than 0.9% crosstalk at a distance of 0.1 mm from the blade.

[0029] (2) The contrast-enhanced fiber-optic image invertor of the present invention has high resolution, the unit fiber diameter is less than 4.0 μm, and the center resolution is greater than 140 lp / mm;

[0030] (3) The contrast-enhanced fiber-optic image invertor of the present invention has high transmittance and transmittance uniformity, with a collimated light transmittance greater than 70% and a transmittance uniformity less than 5% within a wavelength range of 380-760 nm;

[0031] (4) The contrast-enhanced optical fiber image invertor of the present invention has excellent fixed pattern noise performance. There is no obvious multifilament boundary when observed under a 10x microscope. The penetration of the contrast-enhanced optical filter glass and the leather glass does not exceed 20nm.

[0032] The contrast-enhanced fiber optic image invertor of the present invention has the advantages of high resolution, high contrast, clear imaging, uniform transmittance, excellent internal quality, etc. The contrast-enhanced fiber optic image invertor of the present invention is applied to the low-light-level image intensifier, which can effectively improve the observation clarity and resolution of the low-light-level image tube. The product can meet the supporting needs of the low-light-level night vision industry, and can also replace traditional fiber optic image invertor products, improve comprehensive use performance, and promote the development of optoelectronic devices in related fields such as space vision measurement and detection imaging towards high performance and wide field of view, and has a good prospect for application and promotion.

[0033] 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

[0034] Figure 1 A contrast test chart of a contrast-enhanced optical fiber image invertor provided by an embodiment of the present invention;

[0035] Figure 2 A transmittance curve of the contrast enhancement filter glass provided by an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the internal structure of an optical fiber constituting a contrast-enhanced optical fiber image invertor provided by an embodiment of the present invention;

[0037] Figure 4 for Figure 3 Enlarged view of point I. DETAILED DESCRIPTION

[0038] 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.

[0039] Table 1 Chemical composition (mol.%) and properties of contrast enhancement filter glass examples

[0040]

[0041] The glass sheets (thickness 0.30±0.01 mm) made from the raw materials of Examples 1 to 5 were tested to have a spectral transmittance of <2.5% in the wavelength range of 380-760 nm and no crystallization occurred after being kept at 850° C. for 6 hours.

[0042] See also Figure 1, which is a contrast test diagram of the contrast-enhanced optical fiber image inverter provided by an embodiment of the present invention, from which it can be seen that the crosstalk at a distance of 0.1 mm from the knife edge has an effect of less than 0.9%.

[0043] See also Figure 2 , which is the transmittance curve of the contrast-enhanced filter 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.

[0044] See also Figure 3 and Figure 4 , which is a schematic diagram of the internal structure of an optical fiber constituting a contrast-enhanced optical fiber image inverter provided by an embodiment of the present invention, a sheath glass tube and a core glass rod are matched and drawn into a monofilament, the monofilament comprising an outer sheath glass 2 and an inner core glass 3, the drawn monofilaments are arranged into a primary composite rod with a regular hexagonal cross-section according to the requirement of 8 monofilaments on each side, the light-absorbing filaments 1 drawn from the contrast-enhanced filter glass are uniformly filled and inserted into the triangular pores of the primary composite rod, the sheath glass tube and the core glass rod are matched and drawn into round white filaments 4, the round white filaments 4 are filled and inserted into the triangular pores of the primary composite rod where no light-absorbing filaments are inserted, and the opposite side size of the hexagon is L.

[0045] In this context, the contrast enhancement filter glass acts as a light absorbing material glass. All "mol. %" are based on the total molar amount of the final glass composition. The glass chemical composition (mol. %) of the examples is detailed in Table 1.

[0046] The parameters, measuring methods and instruments for the contrast enhancement filter glass of the present invention are as follows:

[0047] (1) The transmittance of contrast-enhanced filter glass is measured using a transmittance tester;

[0048] (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 "Determination of the average linear thermal expansion coefficient of glass".

[0049] Example 1

[0050] A method for preparing a contrast-enhanced optical fiber image invertor comprises the following steps:

[0051] (1) Drawing of light-absorbing yarn, round white yarn and monofilament:

[0052] a. Preparation of contrast-enhanced filter glass:

[0053] 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:

[0054] Raw material preparation: weigh raw materials 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, ferric oxide, nickel oxide, vanadium pentoxide, molybdenum trioxide, manganese dioxide, potassium chromate and copper oxide according to molar ratio, mix them evenly, and obtain a raw material mixture;

[0055] 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 homogenized 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 for 24 hours to obtain contrast-enhanced filter glass.

[0056] b. Drawing the contrast-enhanced filter glass with good light absorption performance into a light absorption wire with a wire diameter of Φ0.35 mm;

[0057] c. Matching the high strain point and low refractive index skin glass tube with the high refractive index core glass round rod, and drawing them into single wire with a wire diameter of Φ2.5mm and round white wire with a wire diameter of Φ0.35mm respectively;

[0058] (2) Drawing of primary multifilaments: Arrange the drawn monofilaments into a primary composite rod with a regular hexagonal cross section, wherein the number of monofilaments on each side of the primary composite rod is 8, and the total number of monofilaments in the arranged primary composite rod is 169, and the light absorbing wires are uniformly filled and inserted into the triangular pores of the primary composite rod; the number of inserted light absorbing wires is 42, and the round white wires are filled and inserted into the triangular pores of the primary composite rod that are not inserted with the light absorbing wires; draw the primary composite rod assembled as above into a primary multifilament, wherein the hexagonal opposite side size of the primary multifilament is 1.5 mm;

[0059] (3) Drawing of secondary multifilaments: Arrange the drawn primary multifilaments into secondary composite rods with a regular hexagonal cross section, where the number of strands on each side of the secondary composite rod is 13, and then draw the secondary composite rods into secondary multifilaments, where the hexagonal opposite side size of the secondary multifilaments is 1.3 mm. Cut the secondary multifilaments into fixed lengths and arrange them into screen plate segments;

[0060] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, hot melt pressing is performed according to the designed compression ratio of the plate segment before and after hot melt pressing, and hot melt pressing is performed under high temperature and pressure to obtain a fiber optic image invertor blank plate segment;

[0061] (5) Twisting molding: The fiber optic image inverter blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a fiber optic image inverter blank. The fiber optic image inverter blank is twisted at an angle of 180° in a twisting molding furnace to prepare a contrast-enhanced fiber optic image inverter.

[0062] The prepared contrast-enhanced optical fiber image inverter has a unit wire diameter of 3.97 μm, a crosstalk of 0.82% at a distance of 0.1 mm from the knife edge, high contrast and imaging clarity; a high central resolution of 144 lp / mm; excellent light transmission performance, a transmittance of more than 70% in the wavelength range of 380-760 nm, and a transmittance uniformity of less than 5%; excellent fixed pattern noise performance, and no obvious multifilament boundary when observed under a 10x microscope.

[0063] Example 2

[0064] A method for preparing a contrast-enhanced optical fiber image invertor comprises the following steps:

[0065] (1) Drawing of light-absorbing yarn, round white yarn and monofilament:

[0066] a. Preparation of contrast-enhanced filter glass:

[0067] 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:

[0068] 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;

[0069] 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 and cast it into the required glass in a mold. After the glass is cooled and solidified, annealing treatment is performed at 550°C and annealing time is 36 hours to obtain contrast enhanced filter glass.

[0070] b. Drawing the contrast-enhanced filter glass with good light absorption performance into a light absorption wire with a wire diameter of Φ0.3 mm;

[0071] c. Matching the high strain point low refractive index skin glass tube with the high refractive index core glass round rod, and then drawing them into single wire with a wire diameter of Φ2mm and round white wire with a wire diameter of Φ0.3mm respectively;

[0072] (2) Drawing of primary multifilaments: Arrange the drawn monofilaments into a primary composite rod with a regular hexagonal cross section, wherein the number of monofilaments on each side of the primary composite rod is 8, and the total number of monofilaments in the arranged primary composite rod is 169, and the light absorbing wires are uniformly filled and inserted into the triangular pores of the primary composite rod; the number of inserted light absorbing wires is 36, and the round white wires are filled and inserted into the triangular pores of the primary composite rod that are not inserted with the light absorbing wires; draw the primary composite rod assembled as above into a primary multifilament, wherein the hexagonal opposite side size of the primary multifilament is 2 mm;

[0073] (3) Drawing of secondary multifilaments: Arrange the drawn primary multifilaments into secondary composite rods with a regular hexagonal cross section, where the number of strands on each side of the secondary composite rod is 10, and then draw the secondary composite rods into secondary multifilaments, where the hexagonal opposite side size of the secondary multifilaments is 1.0 mm. Cut the secondary multifilaments into fixed lengths and arrange them into screen plate segments;

[0074] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, hot melt pressing is performed according to the designed compression ratio of the plate segment before and after hot melt pressing, and hot melt pressing is performed under high temperature and pressure to obtain a fiber optic image invertor blank plate segment;

[0075] (5) Twisting molding: The fiber optic image inverter blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a fiber optic image inverter blank. The fiber optic image inverter blank is twisted at an angle of 180° in a twisting molding furnace to prepare a contrast-enhanced fiber optic image inverter.

[0076] The prepared contrast-enhanced optical fiber image inverter has a unit wire diameter of 3.96 μm, a crosstalk of 0.87% at a distance of 0.1 mm from the knife edge, high contrast and imaging clarity; a central resolution of 144 lp / mm, and high resolution; excellent light transmission performance, with a transmittance of more than 70% in the wavelength range of 380-760 nm and a transmittance uniformity of less than 5%; and excellent fixed pattern noise performance, with no obvious multifilament boundaries observed under a 10x microscope.

[0077] Example 3

[0078] A method for preparing a contrast-enhanced optical fiber image invertor comprises the following steps:

[0079] (1) Drawing of light-absorbing yarn, round white yarn and monofilament:

[0080] a. Preparation of contrast-enhanced filter glass:

[0081] 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:

[0082] Raw material preparation: weigh raw materials 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 molar ratio, mix them evenly, and obtain a raw material mixture;

[0083] 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 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 is cooled and solidified, the annealing temperature is 580°C, and the annealing time is 30 hours, so as to obtain a contrast-enhanced filter glass.

[0084] b. Drawing the contrast-enhanced filter glass with good light absorption performance into a light absorption wire with a wire diameter of Φ0.45 mm;

[0085] c. Matching the high strain point low refractive index skin glass tube with the high refractive index core glass round rod, and then drawing them into single wire with a wire diameter of Φ3mm and round white wire with a wire diameter of Φ0.45mm respectively;

[0086] (2) Drawing of primary multifilaments: Arrange the drawn monofilaments into a primary composite rod with a regular hexagonal cross section, wherein the number of monofilaments on each side of the primary composite rod is 8, and the total number of monofilaments in the arranged primary composite rod is 169, and the light absorbing wires are uniformly filled and inserted into the triangular pores of the primary composite rod; the number of inserted light absorbing wires is 54, and the round white wires are filled and inserted into the triangular pores of the primary composite rod that are not inserted with the light absorbing wires; draw the primary composite rod assembled as above into a primary multifilament, wherein the hexagonal opposite side size of the primary multifilament is 1 mm;

[0087] (3) Drawing of secondary multifilaments: Arrange the drawn primary multifilaments into secondary composite rods with a regular hexagonal cross section, where each side of the secondary composite rod has 15 strands, and then draw the secondary composite rods into secondary multifilaments, where the hexagonal opposite side size of the secondary multifilaments is 1.6 mm. Cut the secondary multifilaments into fixed lengths and arrange them into screen plate segments;

[0088] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, hot melt pressing is performed according to the designed compression ratio of the plate segment before and after hot melt pressing, and hot melt pressing is performed under high temperature and pressure to obtain a fiber optic image invertor blank plate segment;

[0089] (5) Twisting molding: The fiber optic image inverter blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a fiber optic image inverter blank. The fiber optic image inverter blank is twisted at an angle of 180° in a twisting molding furnace to prepare a contrast-enhanced fiber optic image inverter.

[0090] The prepared contrast-enhanced optical fiber image inverter has a unit wire diameter of 3.98 μm, a crosstalk of 0.78% at a distance of 0.1 mm from the knife edge, high contrast and imaging clarity; a central resolution of 144 lp / mm, and high resolution; excellent light transmission performance, with a transmittance of more than 70% in the wavelength range of 380-760 nm and a transmittance uniformity of less than 5%; and excellent fixed pattern noise performance, with no obvious multifilament boundaries observed under a 10x microscope.

[0091] Example 4

[0092] A method for preparing a contrast-enhanced optical fiber image invertor comprises the following steps:

[0093] (1) Drawing of light-absorbing yarn, round white yarn and monofilament:

[0094] a. Preparation of contrast-enhanced filter glass:

[0095] 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:

[0096] 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;

[0097] Glass melting: Add the raw material mixture into a crucible and melt it at 1450°C for 7 hours. After the raw material mixture is melted, stir it for 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 the material at 1365°C and cast it into the required glass in a mold. After the glass is cooled and solidified, annealing is performed at 570°C for 26 hours to obtain a contrast-enhanced filter glass.

[0098] b. Drawing the contrast-enhanced filter glass with good light absorption performance into a light absorption wire with a wire diameter of Φ0.42 mm;

[0099] c. Matching the high strain point low refractive index skin glass tube with the high refractive index core glass round rod, and then drawing them into single wire with a wire diameter of Φ2.8mm and round white wire with a wire diameter of Φ0.42mm respectively;

[0100] (2) Drawing of primary multifilaments: Arrange the drawn monofilaments into a primary composite rod with a regular hexagonal cross section, wherein the number of monofilaments on each side of the primary composite rod is 8, and the total number of monofilaments in the arranged primary composite rod is 169, and the light absorbing wires are uniformly filled and inserted into the triangular pores of the primary composite rod; the number of inserted light absorbing wires is 48, and the round white wires are filled and inserted into the triangular pores of the primary composite rod that are not inserted with the light absorbing wires; draw the primary composite rod assembled as above into a primary multifilament, wherein the hexagonal opposite side size of the primary multifilament is 1.2 mm;

[0101] (3) Drawing of secondary multifilaments: Arrange the drawn primary multifilaments into secondary composite rods with a regular hexagonal cross section, where the number of strands on each side of the secondary composite rods is 14; draw the secondary composite rods into secondary multifilaments, where the hexagonal opposite side dimension of the secondary multifilaments is 1.5 mm; cut the secondary multifilaments into fixed lengths and arrange them into screen plate segments;

[0102] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, hot melt pressing is performed according to the designed compression ratio of the plate segment before and after hot melt pressing, and hot melt pressing is performed under high temperature and pressure to obtain a fiber optic image invertor blank plate segment;

[0103] (5) Twisting molding: The fiber optic image inverter blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a fiber optic image inverter blank. The fiber optic image inverter blank is twisted at an angle of 180° in a twisting molding furnace to prepare a contrast-enhanced fiber optic image inverter.

[0104] The prepared contrast-enhanced optical fiber image inverter has a unit wire diameter of 3.96 μm, a crosstalk of 0.84% ​​at a distance of 0.1 mm from the knife edge, high contrast and imaging clarity; a central resolution of 144 lp / mm, and high resolution; excellent light transmission performance, with a transmittance of more than 70% in the wavelength range of 380-760 nm and a transmittance uniformity of less than 5%; and excellent fixed pattern noise performance, with no obvious multifilament boundaries observed under a 10x microscope.

[0105] Example 5

[0106] A method for preparing a contrast-enhanced optical fiber image invertor comprises the following steps:

[0107] (1) Drawing of light-absorbing yarn, round white yarn and monofilament:

[0108] a. Preparation of contrast-enhanced filter glass:

[0109] 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:

[0110] 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;

[0111] Glass melting: Add the raw material mixture into a crucible and melt it at 1490°C for 8 hours. After the raw material mixture is melted, stir it 3 times, 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 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 590°C and annealing time is 28 hours to obtain contrast enhanced filter glass.

[0112] b. Drawing the contrast-enhanced filter glass with good light absorption performance into a light absorption wire with a wire diameter of Φ0.34 mm;

[0113] c. Matching the high strain point low refractive index skin glass tube with the high refractive index core glass round rod, and then drawing them into single wire with a wire diameter of Φ2.3mm and round white wire with a wire diameter of Φ0.34mm respectively;

[0114] (2) Drawing of primary multifilaments: Arrange the drawn monofilaments into a primary composite rod with a regular hexagonal cross section, wherein the number of monofilaments on each side of the primary composite rod is 8, and the total number of monofilaments in the arranged primary composite rod is 169, and the light absorbing wires are uniformly filled and inserted into the triangular pores of the primary composite rod; the number of inserted light absorbing wires is 36, and the round white wires are filled and inserted into the triangular pores of the primary composite rod that are not inserted with the light absorbing wires; draw the primary composite rod assembled as above into a primary multifilament, wherein the hexagonal opposite side size of the primary multifilament is 1.8 mm;

[0115] (3) Drawing of secondary multifilaments: Arrange the drawn primary multifilaments into secondary composite rods with a regular hexagonal cross section, where the number of strands on each side of the secondary composite rods is 11, and then draw the secondary composite rods into secondary multifilaments, where the hexagonal opposite side size of the secondary multifilaments is 1.1 mm. Cut the secondary multifilaments into fixed lengths and arrange them into screen plate segments;

[0116] (4) Hot melt pressing: placing the screen plate segment in a hot melt pressing furnace, hot melt pressing is performed according to the designed compression ratio of the plate segment before and after hot melt pressing, and hot melt pressing is performed under high temperature and pressure to obtain a fiber optic image invertor blank plate segment;

[0117] (5) Twisting molding: The fiber optic image inverter blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a fiber optic image inverter blank. The fiber optic image inverter blank is twisted at an angle of 180° in a twisting molding furnace to prepare a contrast-enhanced fiber optic image inverter.

[0118] The prepared contrast-enhanced optical fiber image inverter has a unit wire diameter of 3.95 μm, a crosstalk of 0.87% at a distance of 0.1 mm from the knife edge, high contrast and imaging clarity; a central resolution of 144 lp / mm, and high resolution; excellent light transmission performance, a transmittance of more than 70% in the wavelength range of 380-760 nm, and a transmittance uniformity of less than 5%; excellent fixed pattern noise performance, and no obvious multifilament boundary when observed under a 10x microscope.

[0119] 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 contrast-enhanced optical fiber image invertor, characterized in that: The following steps are involved: (1) Drawing of light-absorbing wires, round white wires and monofilaments: Drawing contrast-enhanced filter glass into light-absorbing wires; matching low-refractive index skin glass tubes with high-refractive index core glass rods and then drawing them into round white wires; matching low-refractive index skin glass tubes with high-refractive index core glass rods and then drawing them into monofilaments; (2) Drawing of primary multifilaments: Arranging the drawn single filaments into a primary composite rod with a regular hexagonal cross section, and filling and inserting the light absorbing filaments into the triangular pores of the primary composite rod evenly; filling and inserting the round white filaments into the triangular pores of the primary composite rod that are not inserted with the light absorbing filaments; and drawing the primary composite rod assembled as above into primary multifilaments; (3) Drawing of secondary multifilaments: Arranging the drawn primary multifilaments into secondary composite rods with a regular hexagonal cross section, drawing the secondary composite rods into secondary multifilaments, 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, hot melt pressing is performed according to the designed compression ratio of the plate segment before and after hot melt pressing, and hot melt pressing is performed under high temperature and pressure to obtain a fiber optic image invertor blank plate segment; (5) Twisting molding: The fiber optic image inverter blank plate segment formed by hot melt pressing is rounded, cut and ground to prepare a fiber optic image inverter blank. The fiber optic image inverter blank is twisted at an angle of 180° in a twisting molding furnace to prepare a contrast-enhanced fiber optic image inverter.

2. The preparation method according to claim 1, characterized in that: The light absorbing wire has the same wire diameter as the round white wire, both of which are Φ0.3-0.45mm; the number of inserted light absorbing wires is 6N, where 6≤N≤9; the penetration of the contrast-enhanced filter glass and the leather glass used to prepare the leather glass tube does not exceed 20nm.

3. The preparation method according to claim 2, characterized in that: In the primary composite rod, the wire diameter of the monofilament is Φ2.0mm~3.0mm, and the number of monofilaments on each side is 8; the number of primary multifilaments on each side of the secondary composite rod is 10~15, and the hexagonal opposite side size of the primary multifilament is 1.0mm~2.0mm; the hexagonal opposite side size of the secondary multifilament is 1.0~1.6mm.

4. The preparation method according to any one of claims 1 to 3, characterized in that The contrast enhancement filter glass comprises the following components in molar percentage: SiO2 64-78%, B2O3 3-16%, Al2O3 0-5%, Li2O 0-1%, Na2O0-6%, 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%, CuO 0.1-2%, F2 0-1%.

5. The preparation method according to claim 4, characterized in that: The contrast enhancement filter glass comprises the following components in molar percentage: SiO2 68-76%, B2O3 3-10%, Al2O3 3-5%, Li2O 0-1%, Na2O 2-6%, K2O3-9%, 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%, CeO20-0.1%, Fe2O3 0.1-6%, NiO 0.3-1%, V2O5 0-1%, Co2O3 0.1-1.5%, MoO30-0.2%, MnO2 0.1-2%, Cr2O3 0.1-1%, Nd2O3 0-0.5%, CuO 0.1-1%, F2 0.1-1%.

6. The preparation method according to claim 5, characterized in that: The contrast enhancement filter glass includes 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%, MnO2 0.3%, Cr2O3 0.5%, CuO0.8%, and F2 0.5%.

7. The preparation method according to claim 4, characterized in that: Also included is a method for preparing contrast-enhanced filter 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, clarifying and stirring the raw material mixture 2-3 times after it is melted, discharging the melted and clarified glass liquid at 1360-1380° C., casting it into the required glass in a mold, and annealing the glass after it is cooled and solidified at a temperature of 550-600° C. for 24-36 hours to obtain a contrast-enhanced filter glass; The contrast-enhanced filter glass has a spectral transmittance of ≤2.5% in the wavelength range of 380-760 nm at a thickness of 0.30±0.01 mm; a thermal expansion coefficient of (80±5)×10 －7 / ℃; no crystallization occurs when kept at 850℃ for 6 hours.

8. A contrast-enhanced optical fiber image invertor, characterized in that: It is prepared according to the preparation method according to any one of claims 1 to 7.

9. The contrast-enhanced fiber optic image invertor according to claim 8, characterized in that: The unit fiber diameter of the contrast-enhanced optical fiber invertor is less than 4.0 μm, the central resolution is greater than 140 lp / mm, the crosstalk is less than 0.9% at 0.1 mm from the knife edge, and there is no obvious multifilament boundary under a 10x microscope; the collimated light transmittance is greater than 70% within the wavelength range of 380-760 nm, and the transmittance uniformity is less than 5%.

10. Use of the contrast-enhanced optical fiber image invertor according to claim 8 or 9 in a low-light level image intensifier.

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