Fiber Optic Imaging Element With Medium-Expansion And Fabrication Method Therefor

Abstract

A fiber optic imaging element includes medium-expansion and a fabrication method including: (1) matching a core glass rod with a cladding glass tube to perform mono fiber drawing; (2) arranging the mono fibers into a mono fiber bundle rod, and then drawing the mono fiber bundle rod into a multi fiber; (3) arranging the multi fiber into a multi fiber bundle rod, and then drawing the multi fiber bundle rod into a multi-multi fiber; (4) cutting the multi-multi fiber, and then arranging the multi-multi fiber into a fiber assembly buddle, then putting the fiber assembly buddle into a mold of heat press fusion process, and performing the heat press fusion process to prepare a block of the fiber optic imaging element with medium-expansion; and (5) edged rounding, cutting and slicing,

Claims

1. A fabrication method for a fiber optic imaging element with medium-expansion, comprising the following steps: (1) mono fiber drawing: finely grounding and polishing a surface of a middle-expansion core glass rod to a diameter of 28-29 mm, and then matching the middle-expansion core glass rod with a low refractive index cladding glass tube with a thickness of 4.25-4.75 mm and an inner diameter of 28.5-29.5 mm to perform mono fiber drawing so as to obtain a mono fiber with a diameter of 3.10-3.14 mm; (2) multi fiber drawing: arranging the mono fibers into a mono fiber bundle rod with an orthohexagonal cross section with 6 mono fibers on each side, and then uniformly inserting light absorbing glass fibers made by drawing a light absorbing glass rod and having a diameter of 0.43-0.47 mm in interstices of the mono fiber bundle rod, and drawing the mono fiber bundle rod inserted with the light absorbing glass fiber into a multi fiber with the orthohexagonal opposite side size of 1.175-1.225 mm, wherein the multi fiber comprises the mono fiber drawn by the combination of the rod and the tube and the light absorbing glass fiber which drawn by the light absorbing glass; (3) multi-multi fiber drawing: arranging the multi fiber into a multi fiber bundle rod with the orthohexagonal cross section with 14 mono fibers on each side, and drawing the multi fiber bundle rod into a multi-multi fiber with the orthohexagonal opposite side size of 1.085-1.135 mm; (4) fiber assembly arrangement and heat press fusion process: cutting the multi-multi fiber into a length of 113-133 mm, and then arranging the multi-multi fiber into a fiber assembly buddle with the orthohexagonal cross section with 17 multi-multi fibers on each side, then putting the fiber assembly buddle into a mold of heat press fusion process, designing the compression ratio of the heat press fusion process to be 0.78-0.84, and performing the heat press fusion process to prepare a block plate buddle of the fiber optic imaging element with medium-expansion; (5) finish machining: edged rounding, cutting and slicing, face grinding and polishing the prepared block plate buddle of the fiber optic imaging element with medium-expansion into a block of the fiber optic imaging element with medium-expansion, wherein the block is subjected to size processing, heating and twisting or stretching to be processed into a fiber optic faceplate with medium-expansion, a fiber optic image inverter with medium-expansion or a fiber optic taper with medium-expansion; wherein the core glass with medium-expansion rod is prepared from a core glass with medium-expansion; wherein the core glass with medium-expansion comprises the following components in percentage by weight: TABLE-US-00004 SiO.sub.2 5-9% Al.sub.2O.sub.3 0-1% B.sub.2O.sub.3 23-28%  CaO 0-3% BaO 6-12%  La.sub.2O.sub.3 30-34%  Nb.sub.2O.sub.5 4-8% Ta.sub.2O.sub.5 0-1% Y.sub.2O.sub.3 0-1% ZnO 4-9% TiO.sub.2 4-8% ZrO.sub.2 4-6% SnO.sub.2  0-1%.

2. (canceled)

3. The fabrication method for a fiber optic imaging element with medium-expansion according to claim 1, wherein the core glass with medium-expansion comprises the following components in percentage by weight: TABLE-US-00005 SiO.sub.2 9% Al.sub.2O.sub.3 1% B.sub.2O.sub.3 23%  BaO 12%  La.sub.2O.sub.3 34%  Nb.sub.2O.sub.5 4% Ta.sub.2O.sub.5 0.5%.sup.  ZnO 4% TiO.sub.2 8% ZrO.sub.2 4% SnO.sub.2 0.5%. 

4. The fabrication method according to claim 1, further comprising preparing a core glass with medium-expansion: (1) putting quartz sand, aluminum hydroxide, boric acid or boric anhydride, calcium carbonate, barium carbonate or barium nitrate, lanthanum oxide, niobium oxide, tantalum oxide, yttrium oxide, zinc oxide, titanium dioxide, zirconium oxide and stannic oxide into a platinum crucible according to the requirement of dosing; (2) melting for 4-8 hours at 1350-1450° C., stirring for 1-2 times in the melting process, then cooling to 1300-1340° C., and fining for 1-2 hours to obtain a fining glass melt; (3) allowing the fining glass melt to flow down through a material leaking port, and casting the fining glass melt in a mold to form a glass rod; (4) annealing the molded glass rod in an annealing furnace, preserving heat for 1 hour at 600-650° C., and cooling to 60° C. from 600-650° C. for 12 hours, and then cooling to room temperature along with the furnace to obtain the core glass with medium-expansion.

5. The fabrication method for a fiber optic imaging element with medium-expansion according to claim 1, wherein the core glass with medium-expansion has a refractive index of 1.80-1.82, a coefficient of mean linear thermal expansion of (68±5)×10.sup.−7/° C. in the range of 30-300° C., a strain point temperature of more than 600° C., and a devitrification temperature of more than 820° C.

6. A fiber optic imaging element with medium-expansion, wherein the fiber optic imaging element with medium-expansion is prepared by using the fabrication method according to claim 1.

7. The fiber optic imaging element with medium-expansion according to claim 6, wherein the fiber optic imaging element with medium-expansion has the coefficient of mean linear thermal expansion of (68±5)×10.sup.−7/° C. in the range of 30-300° C., and a heat-resistance temperature of more than 600° C.

8. The fiber optic imaging element with medium-expansion according to claim 6, wherein the fiber optic imaging element with medium-expansion has a spectral transmission of more than 65% in the wavelength range of 430 nm to 900 nm.

9. The fiber optic imaging element with medium-expansion according to claim 6, wherein the fiber optic imaging element with medium-expansion has a fiber diameter of less than or equal to 4.0 and a resolution of more than 120 1p/mm.

10. (canceled)

11. (canceled)

12. (canceled)

13. (canceled)

14. (canceled)

15. (canceled)

16. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The present invention will be further described with reference to drawings and embodiments.

[0050] FIG. 1 is a comparison diagram of tests of the coefficient of thermal expansion of embodiments in the present invention of the fiber optic imaging element with medium-expansion and a fiber optic imaging element with high-expansion;

[0051] FIG. 2 is a comparison diagram of tests of the coefficient of thermal expansion of embodiments of the core glass with medium-expansion of the present invention and a glass with high coefficient of thermal expansion;

[0052] FIG. 3 is a structural schematic diagram of the fiber optic imaging element with medium-expansion provided in the embodiment of the present invention;

[0053] FIG. 4 is a total reflection schematic diagram of the fiber optic being composed of the fiber optic imaging element with medium-expansion provided by the embodiment of the present invention.

[0054] Wherein 1 is a light absorbing glass fiber, 2 is a core glass, and 3 is a cladding glass.

DETAILED DESCRIPTION

[0055] In order to make the purposes, technical solutions and advantages of the present invention to be more clarity, the embodiments of the present invention are further described in detail below. The present invention will be further described in detail with reference to drawings and detailed embodiments, but not limited by the description.

[0056] The measured parameters, measuring methods and instruments of the core glass with medium-expansion used for the fiber optic imaging element with medium-expansion of the present invention are as follows:

[0057] (1) refractive index n.sub.D [the refractive index of glass at λ=589.3 nm];

[0058] (2) the average coefficient of thermal expansion α.sub.30/300[10.sup.−7/° C.] at 30-300° C.

[0059] In the specification, all “weight percent wt. %” are based on the total weight of the final glass composition, and chemical compositions (wt. %) of the glass of the embodiments are detailed listed in Table 1. Wherein the refractive index n.sub.D of glass is measured by a refractive index device; the coefficient of linear thermal expansion at 30-300° C. is measured by a horizontal dilatometer using the method specified in ISO 7991, and expressed by a coefficient of mean linear thermal expansion. Chemical compositions (wt. %) and glass performances of the embodiments are detailed listed in Table 1.

[0060] Referring to FIG. 1, in the range of 30-300° C., the fiber optic imaging element with high-expansion is 90.319×10.sup.−7/° C., and the coefficient of thermal expansion of the embodiments of the fiber optic imaging element with medium-expansion of the present invention respectively is 69.244×10.sup.−7/° C., 67.317×10.sup.−7/° C., 66.403×10.sup.−7/° C., 70.086×10.sup.−7/° C., 68.192×10.sup.−7/° C.

[0061] Referring to FIG. 2, in the range of 30-300° C., the coefficient of thermal expansion of the glass with high-expansion is 91.324×10.sup.−7/° C., and the coefficient of thermal expansion of the core glass with medium-expansion used in the present invention respectively is 70.234×10.sup.−7/° C., 67.918×10.sup.−7/° C., 66.830×10.sup.−7/° C., 71.094×10.sup.−7/° C., 68.607×10.sup.−7/° C.

[0062] CTE in figures is Coefficient of Thermal Expansion.

[0063] Referring to FIGS. 3 and 4, FIG. 3 is a structural schematic diagram of the fiber optic imaging element with medium-expansion. The outer layer of the core glass 2 is provided with the cladding glass 3, and the core glass 2 and the cladding glass 3 compose an fiber. The light absorbing glass fiber 1 are uniformly arranged between the cladding glasses to compose the fiber optic imaging element with medium-expansion.

TABLE-US-00003 TABLE 1 chemical compositions (wt. %) and physical values of the glass samples embodi- embodi- embodi- embodi- embodi- composition ment 1 ment 2 ment 3 ment 4 ment 5 SiO.sub.2 9 7 7 8 5 Al.sub.2O.sub.3 1 0 0 0 5 B.sub.2O.sub.3 23 25 25 24 28 CaO 0 0 0 0 3 BaO 12 8.4 10 7 6 La.sub.2O.sub.3 34 32.8 32 34 30 Nb.sub.2O.sub.5 4 7 6 7.5 8 Ta.sub.2O.sub.5 0.5 0.5 0.5 0 0.5 Y.sub.2O.sub.3 0 0 0 0.5 0 ZnO 4 8 8 7 9 TiO.sub.2 8 7 6 5 4 ZrO.sub.2 4 4 5 6 6 SnO.sub.2 0.5 0.26 0.5 1 0.5 α.sub.30/300[10.sup.−7/° C.] 70.234 67.918 66.830 71.094 68.607 n.sub.D 1.80 1.82 1.82 1.82 1.81

[0064] The raw materials used in the following embodiments and their requirements are as follows:

[0065] Quartz sand (high purity, 150 μm oversize is less than 1%, 45 μm undersize is less than 30%, the content of Fe.sub.2O.sub.3 is less than 0.01 wt. %), aluminum hydroxide (analytical purity, average particle size 50 μm), boric acid or boron anhydride (400 μm oversize is less than 10%, 63 μm undersize is less than 10%), calcium carbonate (analytical purity, average particle size 250 μm), barium carbonate (analytical purity, purity ≥99.0%), lanthanum trioxide (5N), niobium pentoxide (5N), tantalum pentoxide (5N), yttrium trioxide (5N), zinc oxide (analytical purity), titanium dioxide (chemical purity), zirconium oxide (analytical purity), stannic oxide (analytical purity).

Embodiment 1

[0066] Fabrication of core glass with medium-expansion:

[0067] Raw materials are selected according to the glass composition of embodiment 1 in Table 1, and oxides of elements with valence state change in the glass raw materials such as Fe.sub.2O.sub.3 are strictly controlled, and the content of Fe.sub.2O.sub.3 in a finished product of glass is less than 100 PPm. Ingredients of glass meet the chemical compositions of glass in Table 1, and then quartz sand, aluminum hydroxide, boric acid, calcium carbonate, barium carbonate, lanthanum oxide, niobium oxide, tantalum oxide, yttrium oxide, zinc oxide, titanium dioxide, zirconium oxide and stannic oxide are put into a platinum crucible and melted for 6 hours at 1400° C. In the glass melting process, the glass is stirred twice to melt evenly. After melting, the glass is cooled to 1320° C. and fining for 2 hours to obtain a molten glass. Thereafter, the molten glass is cast into a test specimen according to the specified requirements, then annealing is carried out and the annealing process is that preserving heat for 1 hour at 625° C., and cooling to 60° C. from 625° C. for 12 hours, and then cooling to room temperature along with the furnace. Its test performance is shown in Table 1, (1) a refractive index is 1.80; (2) a coefficient of mean linear thermal expansion at 30-300° C. is 70.234×10.sup.−7/° C.

[0068] Fabrication of the fiber optic imaging element with medium-expansion:

[0069] (1) mono fiber drawing: finely grounding and polishing a surface of an environment-friendly middle-expansion core glass rod with a high refractive index to a diameter of 28.5 mm, and then matching the middle-expansion core glass rod with a low refractive index cladding glass tube with a thickness of 4.5 mm and an inner diameter of 29.0 mm to drawing mono fiber so as to obtain a mono fiber with a diameter of 3.12 mm;

[0070] (2) multi fiber drawing: arranging the mono fibers into a mono fiber bundle rod with an orthohexagonal cross section with 6 mono fibers on each side, and then uniformly inserted light absorbing glass fibers made by drawing a light absorbing glass with a diameter of 0.44 mm in each interstices of the mono fiber array, and drawing the mono fiber bundle rod into a multi fiber with the orthohexagonal opposite side size of 1.200 mm;

[0071] (3) multi-multi fiber drawing: arranging the multi fiber into a multi fiber bundle rod with the orthohexagonal cross section with 14 mono fibers on each side, and drawing the multi fiber bundle rod into a multi-multi fiber with the orthohexagonal opposite side size of 1.110 mm;

[0072] (4) fiber assembly arrangement and heat press fusion process: cutting the multi-multi fiber into a length of 130 mm, and then arranging the multi-multi fiber into a fiber assembly buddle with the orthohexagonal cross section with 17 multi-multi fibers on each side, then putting the fiber assembly buddle into a mold of heat press fusion process, designing the compression ratio of the heat press fusion process to be 0.80, and the multi-multi fiber arranged into a fiber assembly buddle is performed the heat press fusion process to prepare a block plate buddle of the fiber optic imaging element with medium-expansion;

[0073] (5) finish machining: edged rounding, cutting and slicing, face grinding and polishing the prepared fused fiber optic block plate of the fiber optic imaging element with medium-expansion into a block of the fiber optic imaging element with medium-expansion, wherein the block is subjected to heating and twisting to be processed into a fiber optic image inverter with medium-expansion.

[0074] Its test performance is as follows, (1) an coefficient of mean linear thermal expansion at 30-300° C. is 69.244×10.sup.−7/° C.; (2) a heat-resistance temperature is 610.9° C.; (3) a fiber diameter is 3.98 μm, a resolution >120 1p/mm.

Embodiment 2

[0075] Fabrication of core glass with medium-expansion:

[0076] The actual composition of glass refers to embodiment 2 in Table 1, and uses the same requirements for raw material as embodiment 1. Quartz sand, aluminum hydroxide, boric anhydride, calcium carbonate, barium nitrate, lanthanum oxide, niobium oxide, tantalum oxide, yttrium oxide, zinc oxide, titanium dioxide, zirconium oxide and stannic oxide are put into a platinum crucible and melted for 8 hours at 1350° C. In the glass melting process, the glass is stirred once to melt evenly. After melting, the glass is cooled to 1300° C. and fining for 1 hour to obtain a molten glass. Thereafter, the molten glass is cast into a test sample according to the specified requirements, then annealing is carried out and the annealing process is that preserving heat for 1 hour at 600° C., and cooling to 60° C. from 600° C. for 12 hours, and then cooling to room temperature along with the furnace. The test conditions used are the same as embodiment 1, and the basic performances of samples are shown in Table 1. (1) a refractive index is 1.82; (2) an coefficient of mean linear thermal expansion at 30-300° C. is 67.918×10.sup.−7/° C.

[0077] Fabrication of fiber optic element with medium-expansion:

[0078] (1) mono fiber drawing: finely grounding and polishing a surface of an environment-friendly middle-expansion core glass rod with a high refractive index to a diameter of 29.0 mm, and then matching the middle-expansion core glass rod with a low refractive index cladding glass tube with a thickness of 4.75 mm and an inner diameter of 29.5 mm to perform mono fiber drawing so as to obtain a mono fiber with a diameter of 3.14 mm;

[0079] (2) multi fiber drawing: arranging the mono fibers into a mono fiber bundle rod with an orthohexagonal cross section with 6 mono fibers on each side, and then uniformly inserting light absorbing glass fibers made by drawing a light absorbing glass with a diameter of 0.43 mm in each interstices of the mono fiber array, and drawing the mono fiber bundle rod into a multi fiber with the orthohexagonal opposite side size of 1.205 mm, wherein the multi fiber comprises the mono fiber drawn by the combination of the rod and the tube and the light absorbing glass fiber drawn by the light absorbing glass rod;

[0080] (3) multi-multi fiber drawing: arranging the multi fiber into a multi fiber bundle rod with the orthohexagonal cross section with 14 mono fibers on each side, and drawing the multi fiber bundle rod into a multi-multi fiber with the orthohexagonal opposite side size of 1.105 mm;

[0081] (4) fiber assembly arrangement and heat press fusion process: cutting the multi-multi fiber into a length of 133 mm, and then arranging the multi-multi fiber into a fiber assembly buddle with the orthohexagonal cross section with 17 multi-multi fibers on each side, then putting the fiber assembly buddle into a mold of heat press fusion process, designing the compression ratio of the heat press fusion process to be 0.78, and the multi-multi fiber arranged into a fiber assembly buddle is performed the heat press fusion process to prepare a block plate buddle of the fiber optic imaging element with medium-expansion;

[0082] (5) finish machining: edged rounding, cutting and slicing, face grinding and polishing the prepared block plate buddle of the fiber optic imaging element with medium-expansion into a block of the fiber optic imaging element with medium-expansion, wherein the block is subjected to heating and stretching molding to be processed into a fiber optic taper with medium-expansion.

[0083] Its test performance is as follows, (1) a coefficient of mean linear thermal expansion at 30-300° C. is 67.317×10.sup.−7/° C.; (2) a heat-resistance temperature is 613.3° C.; (3) a fiber diameter is 4.0 μm, a resolution >120 1p/mm.

Embodiment 3

[0084] Fabrication of core glass with medium-expansion:

[0085] The actual composition of glass refers to embodiment 3 in Table 1, and uses the same raw material and requirements for raw material as embodiment 1. Raw materials are melted for 4 hours at 1450° C. In the glass melting process, the glass is stirred twice to melt evenly. After melting, the glass is cooled to 1340° C. and fining 2 hours to obtain a molten glass. Thereafter, the molten glass is cast into a test sample according to the specified requirements, then annealing is carried out and the annealing process is that preserving heat for 1 hour at 650° C., and cooling to 60° C. from 650° C. for 12 hours, and then cooling to room temperature along with the furnace. The test conditions used are the same as embodiment 1, and the basic performances of samples are shown in Table 1. (1) a refractive index is 1.82; (2) an coefficient of mean linear thermal expansion at 30-300° C. is 66.830×10.sup.−7/° C.

[0086] Fabrication of fiber optic element with medium-expansion:

[0087] (1) mono fiber drawing: finely grounding and polishing a surface of an environment-friendly middle-expansion core glass rod with a high refractive index to a diameter of 28.0 mm, and then matching the middle-expansion core glass rod with a low refractive index cladding glass tube with a thickness of 4.4 mm and an inner diameter of 28.5 mm to perform mono fiber drawing so as to obtain a mono fiber with a diameter of 3.11 mm;

[0088] (2) multi fiber drawing: arranging the mono fibers into a mono fiber bundle rod with an orthohexagonal cross section with 6 mono fibers on each side, and then uniformly inserting light absorbing glass fibers made by drawing a light absorbing glass with a diameter of 0.46 mm in each interstices of the mono fiber array, and drawing the mono fiber bundle rod into a multi fiber with the orthohexagonal opposite side size of 1.175 mm, wherein the multi fiber comprises the mono fiber drawn by the combination of the rod and the tube and the light absorbing glass fiber drawn by the light absorbing glass;

[0089] (3) multi-multi fiber drawing: arranging the multi fiber into a multi fiber bundle rod with the orthohexagonal cross section with 14 mono fibers on each side, and drawing the multi fiber bundle rod into a multi-multi fiber with the orthohexagonal opposite side size of 1.115 mm;

[0090] (4) fiber assembly arrangement and heat press fusion process: cutting the multi-multi fiber into a length of 128 mm, and then arranging the multi-multi fiber into a fiber assembly buddle with the orthohexagonal cross section with 17 multi-multi fibers on each side, then putting the fiber assembly buddle into a mold of heat press fusion process, designing the compression ratio of the heat press fusion process to be 0.84, and the multi-multi fiber arranged into a fiber assembly buddle is performed the heat press fusion process to prepare a block plate buddle of the fiber optic imaging element with medium-expansion;

[0091] (5) finish machining: edged rounding, cutting and slicing, face grinding and polishing the prepared block plate buddle of the fiber optic imaging element with medium-expansion into a block of the fiber optic imaging element with medium-expansion, wherein the block is subjected to size processing to be processed into a fiber optic faceplate with medium-expansion.

[0092] Its test performance is as follows, (1) a coefficient of mean linear thermal expansion at 30-300° C. is 66.403×10.sup.−7/° C.; (2) a heat-resistance temperature is 612.1° C.; (3) a fiber diameter is 3.99 μm, a resolution >120 1p/mm.

Embodiment 4

[0093] Fabrication of core glass with medium-expansion:

[0094] The actual composition of glass refers to embodiment 4 in Table 1, uses the same raw material and requirements for raw material as embodiment 1 and adopts the same melting process system and test conditions as embodiment 1. The basic performances of samples are shown in Table 1. (1) a refractive index is 1.82; (2) a coefficient of mean linear thermal expansion at 30-300° C. is 71.094×10.sup.−7/° C.

[0095] Fabrication of fiber optic imaging element with medium-expansion:

[0096] (1) mono fiber drawing: finely grounding and polishing a surface of an environment-friendly middle-expansion core glass rod with a high refractive index to a diameter of 28.5 mm, and then matching the middle-expansion core glass rod with a low refractive index cladding glass tube with a thickness of 4.5 mm and an inner diameter of 29.0 mm to perform mono fiber drawing so as to obtain a mono fiber with a diameter of 3.12 mm;

[0097] (2) multi fiber drawing: arranging the mono fibers into a mono fiber bundle rod with an orthohexagonal cross section with 6 mono fibers on each side, and then uniformly inserting light absorbing glass fibers made by drawing a light absorbing glass with a diameter of 0.45 mm in each interstices of the mono fiber array, and drawing the mono fiber bundle rod into a multi fiber with the orthohexagonal opposite side size of 1.200 mm, wherein the multi fiber comprises the mono fiber drawn by the combination of the rod and the tube and the light absorbing glass fiber which drawn by the light absorbing glass;

[0098] (3) multi-multi fiber drawing: arranging the multi fiber into a multi fiber bundle rod with the orthohexagonal cross section with 14 mono fibers on each side, and drawing the multi fiber bundle rod into a multi-multi fiber with the orthohexagonal opposite side size of 1.110 mm;

[0099] (4) fiber assembly arrangement and heat press fusion process: cutting the multi-multi fiber into a length of 133 mm, and then arranging the multi-multi fiber into a fiber assembly buddle with the orthohexagonal cross section with 17 multi-multi fibers on each side, then putting the fiber assembly buddle into a mold of heat press fusion process, designing the compression ratio of the heat press fusion process to be 0.82, and the multi-multi fiber arranged into a fiber assembly buddle is performed the heat press fusion process to prepare a block plate buddle of the fiber optic imaging element with medium-expansion;

[0100] (5) finish machining: rounding, cutting, end face grinding and polishing the prepared medium-expansion plate buddle into a block of the fiber optic imaging element with medium-expansion, wherein the block is subjected to heating and twisting molding or stretching molding to be processed into a fiber optic taper with medium-expansion.

[0101] Its test performance is as follows, (1) a coefficient of mean linear thermal expansion at 30-300° C. is 70.086×10.sup.−7/° C.; (2) a heat-resistance temperature is 612.7° C.; (3) a fiber diameter is 3.97 μm, a resolution >120 1p/mm.

Embodiment 5

[0102] Fabrication of core glass with medium-expansion:

[0103] The actual composition of glass refers to embodiment 5 in Table 1, uses the same raw material and requirements for raw material as embodiment 1 and adopts the same melting process system and test conditions as embodiment 1. The basic performances of samples are shown in Table 1. (1) a refractive index is 1.81; (2) a coefficient of mean linear thermal expansion at 30-300° C. is 68.607×10.sup.−7/° C.

[0104] Fabrication of fiber optic element with medium-expansion:

[0105] (1) mono fiber drawing: finely grounding and polishing a surface of an environment-friendly middle-expansion core glass rod with a high refractive index to a diameter of 28.5 mm, and then matching the middle-expansion core glass rod with a low refractive index cladding glass tube with a thickness of 4.25 mm and an inner diameter of 29.0 mm to perform mono fiber drawing so as to obtain a mono fiber with a diameter of 3.122 mm;

[0106] (2) multi fiber drawing: arranging the mono fibers into a mono fiber bundle rod with an orthohexagonal cross section with 6 mono fibers on each side, and then uniformly inserting light absorbing glass fibers made by drawing a light absorbing glass with a diameter of 0.44 mm in each interstices of the mono fiber array, and drawing the mono fiber bundle rod into a multi fiber with the orthohexagonal opposite side size of 1.192 mm;

[0107] (3) multi-multi fiber drawing: arranging the multi fiber into a multi fiber bundle rod with the orthohexagonal cross section with 14 mono fibers on each side, and drawing the multi fiber bundle rod into a multi-multi fiber with the orthohexagonal opposite side size of 1.085 mm;

[0108] (4) fiber assembly arrangement and heat press fusion process: cutting the multi-multi fiber into a length of 132 mm, and then arranging the multi-multi fiber into a fiber assembly buddle with the orthohexagonal cross section with 17 multi-multi fibers on each side, then putting the fiber assembly buddle into a mold of heat press fusion process, designing the compression ratio of the heat press fusion process to be 0.83, and the multi-multi fiber arranged into a fiber assembly buddle is performed the heat press fusion process to prepare a block plate buddle of the fiber optic imaging element with medium-expansion;

[0109] (5) finish machining: rounding, cutting, end face grinding and polishing the prepared medium-expansion plate buddle into a block of the fiber optic imaging element with medium-expansion, wherein the block is subjected to heating and twisting molding to be processed into a fiber optic image inverter with medium-expansion.

[0110] Its test performance is as follows, (1) a coefficient of mean linear thermal expansion at 30-300° C. is 68.192×10.sup.−′/° C.; (2) a heat-resistance temperature is 609.9° C.; (3) a fiber diameter is 3.98 μm, a resolution >120 1p/mm.

[0111] The present invention also provides an application for the fiber optic imaging element (including fiber optic faceplate, fiber optic image inverter, fiber optic taper, fiber optic bundle for image transmission, etc.), and the fiber optic imaging element with medium-expansion can be applied to low-level-light image intensifier and other field of photoelectron technology.

[0112] The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.