Fabrication method and use of F40 mm large-size and high-contrast

Abstract

The present invention discloses a fabrication method and use of a 40 mm sized fiber optic image inverter, belonging to the field of manufacturing of fiber optic imaging elements. The light-absorbing glass for preparing the 40 mm sized fiber optic image inverter consists of the following components in molar percentage: SiO.sub.2 60-69.9, Al.sub.2O.sub.3 1.0-10.0, B.sub.2O.sub.3 10.1-15.0, Na.sub.2O 1.0-8.0, K.sub.2O 3.0-10.0, MgO 0.1-1.0, CaO 0.5-5.0, ZnO 0-0.1, TiO.sub.2 0-0.1, ZrO.sub.2 0.1-1.0, Fe.sub.2O.sub.3 3.0-6.5, Co.sub.2O.sub.3 0.1-0.5, V.sub.2O.sub.5 0.51-1.5 and MoO.sub.3 0.1-1.0. The 40 mm sized fiber optic image inverter has the advantages of low crosstalk of stray light, high resolution and high contrast.

Claims

1. A method for preparing a 40 mm sized fiber optic image inverter, comprising the following steps: (1) mono fibers and light-absorbing glass fibers preparing: matching core glass rods with a high refractive index and cladding glass tubes with a low refractive index, followed by drawing to obtain mono fibers, wherein each of the mono fibers has a diameter of 3.20-4.20 mm; drawing light-absorbing glass into light-absorbing glass fibers, wherein each of the light-absorbing glass fibers has a diameter of 0.49-0.64 mm; (2) multi fiber assemblies drawing: arranging the mono fibers to form a mono fiber hexagonal prism with a hexagonal cross section, and inserting the light-absorbing glass fibers into gaps among the mono fibers drawn to obtain multi fiber assemblies, wherein in the mono fiber hexagonal prism, there are 4 mono fibers at each side of the hexagonal cross section of the mono fiber hexagonal prism with the total number of the mono fibers to be 37, and the number of the light-absorbing glass fibers inserted is 24-60; then drawing the multi fiber assemblies into multi fibers, wherein each of the multi fibers has a hexagonal cross section corresponding to that of the multi fiber assembly, and a distance between opposite sides of the hexagonal cross section of the multi fiber is 0.78-0.98 mm; (3) multi-multi assemblies drawing: arranging the multi fibers to form a multi fiber hexagonal prism with a hexagonal cross section to obtain multi-multi assemblies, wherein in the multi-multi assemblies arranged by the multi fibers, there are 17 multi fibers at each side of the hexagonal cross section of the multi fiber hexagonal prism with the total number of the multi fibers to be 817; then drawing the multi-multi assemblies into multi-multi fibers, wherein each of the multi-multi fibers has a hexagonal cross section corresponding to that of the multi-multi assembly, and a distance between opposite sides of the hexagonal cross section of the multi-multi fiber is 0.87-0.89 mm; and (4) heat press fusing and twisting: cutting the multi-multi fibers into a fixed length and arranging into a fiber assembly bundle, followed by subjecting to heat press fusion according to a designed compression ratio before and after heat press fusion of the fiber assembly bundle to obtain a fiber optic faceplate block of the 40 mm sized fiber optic image inverter with a fiber pitch of no more than 4.0 m; then subjecting both ends of the fiber optic faceplate block to a twisting operation at an angle of 180 to obtain the 40 mm sized fiber optic image inverter with an effective area of more than 40 mm, wherein the light-absorbing glass consists of the following components in molar percentage: TABLE-US-00006 SiO.sub.2 60.0-69.9% Al.sub.2O.sub.3 1.0-10.0% B.sub.2O.sub.3 10.1-15.0% Na.sub.2O 1.0-8.0% K.sub.2O 3.0-10.0% MgO 0.1-1.0% CaO 0.5-5.0% ZnO 0-0.1% TiO.sub.2 0-0.1% ZrO.sub.2 0.1-1.0% Fe.sub.2O.sub.3 3.0-6.5% Co.sub.2O.sub.3 0.1-0.5% V.sub.2O.sub.5 0.51-1.5% MoO.sub.3 0.1-1.0%. the fiber optic image inverter has an optical crosstalk of less than 1.0% at 0.1 mm from a cutting edge; the fiber optic image inverter has a resolution of more than 140 lp/mm; the fiber optic image inverter has a light spectrum transmittance of more than 70% within a wavelength range of 400-700 nm.

2. The method according to claim 1, wherein a method for preparing the light-absorbing glass comprises 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; and (2) glass melting: putting the raw material mixture in a crucible for 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.

3. The method according to claim 2, wherein the 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; and 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.

4. The method according to claim 1, wherein a method for preparing the core glass rod comprises the following steps: (1) putting raw materials of quartz sand, boric acid or boric anhydride, calcium carbonate, strontium carbonate, barium nitrate, titanium dioxide, lanthanum oxide, gadolinium oxide and niobium oxide in a platinum crucible according to formulating requirements; (2) melting at a first temperature, stirring for 2-3 times during the melting process, and then cooling to a second temperature for fining; (3) casting the obtained molten glass after fining into a specified glass product; and (4) annealing the glass product molded in an annealing furnace, followed by furnace cooling to room temperature.

5. The method according to claim 4, wherein the first temperature is within a range of 1450-1550 C., the second temperature is within a range of 1380-1420 C., and the melting is conducted for 5-10 hours; the fining is conducted for 1.5-2.5 hours; the annealing is conducted by preserving at a temperature within a range of 590-610 C. for 1.5-2.5 hours, and then cooling to 100 C. within 20-24 hours.

6. The method according to claim 5, wherein the light-absorbing glass has a light absorption ability and light spectrum absorption effect within a wavelength range of 400-700 nm at a thickness of 0.30.01 mm, with a light spectrum transmittance of no more than 0.1%.

7. The method according to claim 5, wherein a core glass used for the core glass rod has the high refractive index of 1.79-1.82, and consists of the following components in molar percentage: SiO.sub.2 20-25%, B.sub.2O.sub.3 19-27%, CaO 0.5-5%, SrO 1-5%, BaO 15-25%, TiO.sub.2 10-15%, La.sub.2O.sub.3 5-15%, Gd.sub.2O.sub.3 7.1-10% and Nb.sub.2O.sub.5 1-5%.

8. The method according to claim 7, wherein the core glass consists of the following components in molar percentage: TABLE-US-00007 SiO.sub.2 20.0-24.0% B.sub.2O.sub.3 20.0-27.0% CaO 0.5-2.5% SrO 2.5-4.0% BaO 16.0-21.0% TiO.sub.2 10.0-13.0% La.sub.2O.sub.3 5.0-8.0% Gd.sub.2O.sub.3 7.1-8.5% Nb.sub.2O.sub.5 1.0-3.5%.

9. The method according to claim 8, wherein the core glass has a mean linear thermal expansion coefficient of (894)10.sup.7/ C. within a range of 30-300 C.

10. The method according to claim 1, wherein the light-absorbing glass consists of the following components in molar percentage: TABLE-US-00008 SiO.sub.2 60.0-65.0% Al.sub.2O.sub.3 3.0-6.0% B.sub.2O.sub.3 11.0-15.0% Na.sub.2O 5.0-8.0% K.sub.2O 3.0-8.0% MgO 0.1-1.0% CaO 1.0-2.5% ZnO 0-0.1% TiO.sub.2 0-0.1% ZrO.sub.2 0.1-1% Fe.sub.2O.sub.3 5.0-6.5% Co.sub.2O.sub.3 0.1-0.5% V.sub.2O.sub.5 0.51-1.0% MoO.sub.3 0.1-1.0%.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram of the internal structure of the optical fiber forming the (40 mm sized fiber optic image inverter provided in an embodiment of the present invention.

(2) FIG. 2 is a schematic diagram of the structure of the optical fiber provided in an embodiment of the present invention.

(3) FIG. 3 is a diagram of contrast test on the 40 mm sized optic image inverter prepared in Example 1 of the present invention.

(4) In these figures, 1 represents light-absorbing glass, 2 represents core glass and 3 represents cladding glass.

DETAILED DESCRIPTION OF THE INVENTION

(5) 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.

(6) 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 an orthohexagonal. 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 FIG. 1, in the multi fiber that has a cross section of an orthohexagonal, a distance L between opposite sides of the hexagonal is 0.78-0.98 mm.

(7) The parameters of the glasses in the present invention to be measured and the measurement methods and instruments are as follows: (1) refractive index n.sub.D [refractive index of glass at =589.3 nm]; (2) mean thermal expansion coefficient .sub.30/300[10.sup.7/ C.] at 30-300 C.; (3) crystallization temperature of glass Tc ( C.).

(8) Among them, the refractive index n.sub.D of glass is measured on a refractive index device; the transmittance of glass at 400-700 nm is measured on a transmittance device, and the thickness of glass sheet is 0.30.01 mm; the linear expansion coefficient .sub.30/300[10.sup.7/ C.] at 30-300 C. is measured on a horizontal dilatometer and expressed as a mean linear expansion coefficient, and is measured in accordance with the method specified in ISO7991; the anti-crystallization temperature of glass is measured in accordance with Standard practices for measurement of liquidus temperature of glass by the gradient furnace method specified in ASTM C829-1981.

(9) 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 core glasses and the light-absorbing glasses in the Examples are listed in detail in Table 1 and Table 2, respectively.

(10) TABLE-US-00004 TABLE 1 Chemical composition (mol. %) and glass properties of core glasses in Examples Example Example Example Example Example Composition 1 2 3 4 5 SiO.sub.2 23.66 20.00 25.00 20.10 21.00 B.sub.2O.sub.3 26.84 23.75 19.00 19.60 27.00 CaO 1.17 0.50 2.50 5.00 0.80 SrO 3.43 2.53 1.00 1.20 5.00 BaO 16.22 19.63 25.00 15.00 20.10 TiO.sub.2 10.06 12.69 10.00 15.00 11.00 La.sub.2O.sub.3 7.67 8.16 5.00 15.00 7.00 Gd.sub.2O.sub.3 7.73 7.74 10.00 8.10 7.10 Nb.sub.2O.sub.5 3.22 5.00 2.50 1.00 1.00 .sub.30/300 [10.sup.7/ C.] 85 91 93 89 87 n.sub.D 1.81 1.81 1.80 1.82 1.79

(11) TABLE-US-00005 TABLE 2 Chemical composition (mol. %) and glass properties of light-absorbing glasses in Examples Example Example Example Example Example Example Composition 1 2 3 4 5 6 SiO.sub.2 60.7 65.0 60.0 69.9 64.14 64.7 Al.sub.2O.sub.3 5.07 1.0 10.0 3.0 3.1 3.67 B.sub.2O.sub.3 11.3 15.0 12.0 10.1 13.53 10.2 Na.sub.2O 8.0 5.5 3.73 3.0 5.87 1.0 K.sub.2O 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 TiO.sub.2 0.02 0.01 0.02 0.1 0 0.01 ZrO.sub.2 1.0 0.5 0.3 0.1 0.26 0.2 Fe.sub.2O.sub.3 6.5 5.72 5.0 4.1 6.03 3.0 Co.sub.2O.sub.3 0.2 0.33 0.1 0.5 0.3 0.2 V.sub.2O.sub.5 0.6 0.8 1.0 0.51 0.78 1.5 MoO.sub.3 1.0 0.5 0.2 0.1 0.22 0.3 Transmittance 0 0 0 0 0 0 Thermal expansion 80 81 84 84 83 82 coefficient

(12) The raw materials used in the Examples and the requirements for the raw materials are as follows:

(13) Quartz sand or crystal powder (high pure, oversize at 150 m sieve is no more than 1%, undersize at 45 m sieve is no more than 30%, Fe.sub.2O.sub.3 content is less than 1 ppm), aluminum oxide powder (analytical pure, average particle size of 50 m), boric acid or boric anhydride (oversize at 400 m sieve is no more than 10%, undersize at 63 m sieve is no more than 10%), sodium carbonate (industrial soda ash), potassium carbonate (analytical pure, purity99.0%), basic magnesium carbonate (chemical pure, average particle size of 50 m), calcium carbonate (analytical pure, average particle size of 250 m), 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), strontium carbonate (analytical pure, purity99.0%), barium nitrate (analytical pure, purity99.0%), lanthanum oxide (5N), gadolinium oxide (5N), niobium oxide (5N).

Example 1

(14) Fabrication of Core Glass Rod:

(15) Firstly, raw materials were selected according to the glass composition of Example 1 in Table 1. The oxides of the elements with variable valences (for example, Fe.sub.2O.sub.3) in the raw materials of glass is required to be strictly controlled, so that the Fe.sub.2O.sub.3 content in the finished glass is lower than 150 ppm. The raw materials were formulated to meet the chemical composition of the glass in Table 1. Then a platinum crucible was used to melt the raw materials at 1550 C. for 6 hours. In the glass melting process, stirring was carried out for 2 to 3 times to make the glass molten evenly. After melting, the molten glass was cooled to 1420 C. for fining for 2 hours. Subsequently, the molten glass was cast into a specified test product. Thereafter, annealing was carried out by preserving heat for 2 hours at 605 C. and then cooling to 100 C. within 24 hours, followed by furnace cooling to room temperature. The tested properties are shown in Table 1: (1) the refractive index is 1.81; (2) the mean linear expansion coefficient at 30-300 C. is 8510.sup.7/ C.

(16) Fabrication of Light-Absorbing Glass:

(17) Firstly, raw materials were selected according to the glass composition of Example 1 in Table 2 and formulated to meet the chemical composition of the glass in Table 2. 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 2, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 8010.sup.7/ C.

(18) The process of preparing the 40 mm sized fiber optic image inverter by using the light-absorbing glass described above included the following steps: (1) mono fiber and light-absorbing glass fiber preparing: the core glass rod with a high refractive index and a cladding glass tube with a low refractive index were matched, followed by drawing to obtain a mono fibers, wherein each of the mono fibers had a diameter of 3.70 mm; the light-absorbing glass was drawn into a light-absorbing glass fibers, wherein each of the light-absorbing glass fibers had a diameter of 0.56 mm; (2) multi fiber assemblies drawing: the mono fibers were arranged to form a mono fiber hexagonal prism with a hexagonal cross section and the light-absorbing glass fibers were inserted into gaps among the mono fibers drawn to obtain a multi fiber assemblies, wherein in the mono fiber hexagonal prism, there were 4 mono fibers at each side of the hexagonal cross section of the mono fiber hexagonal prism with the total number of the mono fibers to be 37, and the number of the light-absorbing glass fibers inserted was 42; then the multi fiber assemblies were drawn into a multi fibers, wherein each of the multi fibers had a hexagonal cross section corresponding to that of the multi fiber assembly, and a distance between opposite sides of the hexagonal cross section of the multi fiber was 0.88 mm;

(19) (3) multi-multi assemblies drawing: the multi fibers were arranged to form a multi fiber hexagonal prism with a hexagonal cross section to obtain a multi-multi assemblies, wherein in the multi-multi assemblies arranged by the multi fibers, there were 17 multi fibers at each side of the hexagonal cross section of the multi fiber hexagonal prism with the total number of the multi fibers to be 817; then the multi-multi assemblies were was drawn into a multi-multi fibers, wherein each of the multi-multi fibers had a hexagonal cross section corresponding to that of the multi-multi assembly, and a distance between opposite sides of the hexagonal cross section of the multi-multi fiber was 0.87 mm;

(20) (4) heat press fusing and twisting: the multi-multi fibers were cut into a fixed length and arranged into a fiber assembly bundle; subsequently, the fiber assembly bundle was subjected to heat press fusion according to a compression ratio designed for heat press fusion of the fiber assembly bundle to obtain a 40 mm sized fiber optic faceplate block with a fiber pitch of 3.99 m; then both ends of the fiber optic faceplate block were subjected to a twisting operation at an angle of 180 to obtain the $40 mm sized fiber optic image inverter with an useful area of more than 40 mm.

(21) Referring to FIG. 3, the contrast performance test on the 40 mm sized fiber optic image inverter prepared by using the light-absorbing glass described above shows that the 40 mm sized 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 40 mm sized fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The 40 mm sized fiber optic image inverter has a transmittance of 72% within a wavelength range of 400-700 nm.

Example 2

(22) Fabrication of Core Glass Rod:

(23) 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 in Table 1 were used. Then the raw materials were molten at 1500 C. for 8 hours. In the glass melting process, stirring was carried out for 2 times to make the glass molten evenly. After melting, the molten glass was cooled to 1400 C. for fining for 1.5 hours. Subsequently, the molten glass was cast into a specified test product. Thereafter, annealing was carried out by preserving heat for 1.5 hours at 600 C. and then cooling to 100 C. within 23 hours, followed by furnace cooling to room temperature.

(24) The same test conditions as Example 1 were used. The basic properties of the sample are shown in Table 1: (1) the refractive index is 1.81; (2) the mean linear expansion coefficient at 30-300 C. is 9110.sup.7/ C.

(25) Fabrication of Light-Absorbing Glass:

(26) The actual composition of the glass referred to Example 2 in Table 2. 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 2, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 8110.sup.7/ C.

(27) The process of preparing the 40 mm sized fiber optic image inverter was substantially the same as Example 1, except that: (1) mono fiber and light-absorbing glass fiber preparing: each of the mono fibers had a diameter of 3.20 mm; each of the light-absorbing glass fibers had a diameter of 0.49 mm; (2) multi fiber assemblies drawing: the number of the light-absorbing glass fibers inserted was 60; then drawing the multi fiber assemblies into a multi fiber, and a distance between opposite sides of the hexagonal cross section of multi fiber was 0.78 mm; (3) multi-multi assemblies drawing: a distance between opposite sides of the hexagonal cross section of in the multi-multi fiber was 0.87 mm; (4) heat press fusing and twisting: the multi-multi fibers were cut into a fixed length and arranged into a fiber assembly bundle; subsequently, the fiber assembly bundle was subjected to heat press fusion according to a compression ratio designed for heat press fusion of the fiber assembly bundle to obtain a 40 mm sized fiber optic faceplate block with a fiber pitch of 3.94 m; then both ends of the fiber optic faceplate block were subjected to twisting operation at an angle of 180 to obtain the $40 mm sized fiber optic image inverter with an useful area of more than 40 mm.

(28) The 40 mm sized fiber optic image inverter prepared has an optical crosstalk of 0.86% at 0.1 mm from the cutting edge. Moreover, the 40 mm sized fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The 40 mm sized fiber optic image inverter has a transmittance of 71% within a wavelength range of 400-700 nm.

Example 3

(29) Fabrication of Core Glass Rod:

(30) 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 in Table 1 were used. Then the raw materials were molten at 1480 C. for 10 hours. In the glass melting process, stirring was carried out for 3 times to make the glass molten evenly. After melting, the molten glass was cooled to 1380 C. for fining for 2.5 hours. Subsequently, the molten glass was cast into a specified test product. Thereafter, annealing was carried out by preserving heat for 2.5 hours at 595 C. and then cooling to 100 C. within 20 hours, followed by furnace cooling to room temperature.

(31) The same test conditions as Example 1 were used. The basic properties of the sample are shown in Table 1: (1) the refractive index is 1.80; (2) the mean linear expansion coefficient at 30-300 cis 9310.sup.7/ C.

(32) Fabrication of Light-Absorbing Glass:

(33) The actual composition of the glass referred to Example 3 in Table 2. 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 2, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 8410.sup.7/ C.

(34) The process of preparing the 40 mm sized fiber optic image inverter was substantially the same as Example 1, except that: (1) mono fiber drawing: each of the mono fibers had a diameter of 4.20 mm; each of the light-absorbing glass fibers had a diameter of 0.64 mm; (2) multi fiber assemblies drawing: the number of the light-absorbing glass fibers inserted was 24; then the multi fiber assemblies were drawn into a multi fibers, and a distance between opposite sides of the hexagonal cross section of the multi fiber was 0.98 mm; (3) multi-multi assemblies drawing: a distance between opposite sides of the hexagonal cross section of the multi-multi fiber was 0.89 mm; (4) heat press fusing and twisting: the multi-multi fibers were cut into a fixed length and arranged into a fiber assembly bundle; subsequently, the fiber assembly bundle was subjected to heat press fusion according to a compression ratio designed for heat press fusion of the fiber assembly bundle to obtain a 40 mm sized fiber optic faceplate block with a fiber pitch of 3.98 m; then both ends of the fiber optic faceplate block were subjected to twisting operation at an angle of 180 to obtain the 40 mm sized fiber optic image inverter with an useful area of more than 40 mm.

(35) The 40 mm sized fiber optic image inverter prepared has an optical crosstalk of 0.96% at 0.1 mm from the cutting edge. Moreover, the 40 mm sized fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The d40 mm sized fiber optic image inverter has a transmittance of 71% within a wavelength range of 400-700 nm.

Example 4

(36) Fabrication of Core Glass Rod:

(37) 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 in Table 1 were used. Then the raw materials were molten at 1450 C. for 5 hours. In the glass melting process, stirring was carried out for 2 to 3 times to make the glass molten evenly. After melting, the molten glass was cooled to 1390 C. for fining for 2 hours. Subsequently, the molten glass was cast into a specified test product. Thereafter, annealing was carried out by preserving heat for 2 hours at 610 C. and then cooling to 100 C. within 24 hours, followed by furnace cooling to room temperature.

(38) The same test conditions as Example 1 were used. The basic properties of the sample are shown in Table 1: (1) the refractive index is 1.82; (2) the mean linear expansion coefficient at 30-300 C. is 8910.sup.7/ C.

(39) Fabrication of Light-Absorbing Glass:

(40) The actual composition of the glass referred to Example 4 in Table 2. 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 2.5 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 2, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 8410.sup.7/ C.

(41) The process of preparing the 40 mm sized fiber optic image inverter was as same as Example 1. The 40 mm sized fiber optic image inverter prepared has an optical crosstalk of 0.89% at 0.1 mm from the cutting edge. Moreover, the 40 mm sized fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The 40 mm sized fiber optic image inverter has a transmittance of 71% within a wavelength range of 400-700 nm.

Example 5

(42) Fabrication of Core Glass Rod:

(43) 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 in Table 1 were used, and the same melting process system and test conditions were adopted. The basic properties of the sample are shown in Table 1: (1) the refractive index is 1.79; (2) the mean linear expansion coefficient at 30-300 C. is 8710.sup.7/ C.

(44) Fabrication of Light-Absorbing Glass:

(45) The actual composition of the glass referred to Example 5 in Table 2. 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 2, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 8310.sup.7/ C.

(46) The process of preparing the 40 mm sized fiber optic image inverter was as same as Example 1. The 40 mm sized fiber optic image inverter prepared has an optical crosstalk of 0.91% at 0.1 mm from the cutting edge. Moreover, the 40 mm sized fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The 40 mm sized fiber optic image inverter has a transmittance of 71% within a wavelength range of 400-700 nm.

Example 6

(47) The fabrication process and the properties of the core glass rod were as same as Example 1.

(48) Fabrication of Light-Absorbing Glass:

(49) The actual composition of the glass referred to Example 5 in Table 2. 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 2, wherein the visible light transmittance of the sample with a thickness of 0.3 mm is 0%, and the thermal expansion coefficient is 8210.sup.7/ C.

(50) The process of preparing the 40 mm sized fiber optic image inverter was as same as Example 1. The 40 mm sized fiber optic image inverter prepared has an optical crosstalk of 0.90% at 0.1 mm from the cutting edge. Moreover, the 40 mm sized fiber optic image inverter shows no obvious multi-multi fiber boundary under the observation of 10-fold microscope. The 40 mm sized fiber optic image inverter has a transmittance of 71% within a wavelength range of 400-700 nm.

(51) 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.