High uniformity, high transmittance optical fiber image invertor and preparation method and application thereof

Abstract

The present invention relates to a high-uniformity, high-transmittance optical fiber image invertor and a preparation method and application thereof. The optical fiber image invertor comprises an input end, an output end and an optical fiber portion arranged between the input end and the output end; the surface of the input end and / or the output end has a thin film whose thickness gradually decreases from the center to the edge; the thickness and position of the thin film satisfy: x = -2×10 ‑7 y 6 +8×10 ‑9 y 5 ‑1×10 ‑4 y 4 ‑2×10 ‑6 y 3 ‑0.0315y 2 ‑1×10 ‑11 y+4.2165, where: x is the absolute thickness of the film, y is the distance from the center to the edge. The technical problem to be solved is to obtain a fiber optic image inverter with high uniformity and high transmittance by improving the drawing profile of the fiber optic image inverter and coating the homogenizing film at the same time.

Description

Technical Field

[0001] The invention relates to an optical fiber image transmission element, and in particular to an optical fiber image invertor with high uniformity and high transmittance, and a preparation method and application thereof. Background Art

[0002] Low-light-level night vision technology is a high-tech technology that studies the physical processes and implementation methods of mutual conversion, enhancement, processing, and display of light-electronic image information under night sky light or poor visibility conditions. It is an important part of modern optoelectronic imaging technology and one of the two major supporting technologies for military night vision equipment. The various low-light devices, instruments, and systems developed using this high-tech technology have very broad application prospects in many fields such as military, astronomy, aerospace, navigation, biology, medicine, nuclear physics, satellite monitoring, and high-speed photography, especially in the military field. Night combat, reconnaissance, command, fire control, artillery aiming, precision guidance, long-distance early warning, optoelectronic confrontation, etc. have played a huge role. Low-light-level night vision devices have the characteristics of small size, light weight, clear image, rich layers, easy operation, and high cost performance. The key to miniaturizing and lightweighting low-light-level night vision devices lies in the fiber optic image transmission element with image inversion function-the image invertor. The fiber optic image invertor can reverse the image by 180°, making the transmitted image an inverted image, such as Figure 1 As shown. It has the characteristics of high resolution, clear transmission, small size, light weight, etc. It is mainly used to replace the relay lens system in low-light night vision devices, and is also widely used in devices that require inverted images.

[0003] The problem of non-uniform transmittance of the image invertor in the prior art is quite serious, and the poor edge resolution leads to poor imaging clarity, which is closely related to the preparation process of the image invertor. The image invertor is made of tens of millions or even hundreds of millions of micron-sized pieces that are melt-pressed and twisted at high temperature (such as Figure 1 ), during the twisting process, only the optical fiber at the axis is not twisted and stretched, and the rest of the optical fibers are twisted and stretched to coil 180° at different helix angles. The farther from the axis, the smaller the helix angle; the greater the curvature, the longer the coiling distance; the greater the degree of stretching, the greater the taper formed, and the weaker the light transmission effect, resulting in a phenomenon of high transmittance in the center and low transmittance at the edge. This non-uniform transmittance will directly affect the imaging effect. Summary of the invention

[0004] In view of this, the main purpose of the present invention is to provide a fiber optic image inverter with high uniformity and high transmittance, and a preparation method and application thereof. The technical problem to be solved is to obtain a fiber optic image inverter with high uniformity and high transmittance by improving the drawing profile of the fiber optic image inverter and coating a homogenizing film at the same time.

[0005] The purpose of the present invention and the technical problem solved by the present invention are achieved by adopting the following technical solutions. The present invention proposes a high uniformity and high transmittance optical fiber image invertor, comprising an input end, an output end and an optical fiber portion arranged between the input end and the output end; the surface of the input end and / or the output end has a thin film whose thickness gradually decreases from the center to the edge; the thickness and position of the thin film satisfy: x = -2×10 -7 y 6 +8×10 -9 y 5 -1×10 -4 y 4 -2×10 -6 y 3 -0.0315y 2 -1×10 -11 y+4.2165, where: x is the absolute thickness of the film, y is the distance from the center to the edge.

[0006] Furthermore, in the aforementioned high-uniformity, high-transmittance optical fiber image inverter, the value of x is greater than 0, and the value of y is between 0-11.5.

[0007] Furthermore, in the aforementioned high-uniformity, high-transmittance optical fiber image inverter, the optical fiber image inverter is a biquadratic function type image inverter or a bicubic function type image inverter.

[0008] Furthermore, in the aforementioned high-uniformity, high-transmittance optical fiber image inverter, the thin film includes a homogenizing film layer and / or an anti-reflection film layer, and a film layer center is arranged at the center thereof.

[0009] The purpose of the present invention and the solution to the technical problem thereof can also be achieved by adopting the following technical solutions. A method for preparing a fiber optic image inverter with high uniformity and high transmittance proposed by the present invention comprises the following steps:

[0010] Preparation of torsion structure of image invertor;

[0011] Preparation of homogenizing film on the surface of image invertor.

[0012] Furthermore, in the aforementioned method for preparing a fiber optic image inverter with high uniformity and high transmittance, the preparation of the image inverter twisted structure comprises the following steps:

[0013] According to the optical fiber trajectory in the torsion zone of the image inverter, a double quadratic function type image inverter or a double cubic function type image inverter is prepared respectively.

[0014] Furthermore, in the aforementioned method for preparing a fiber optic image inverter with high uniformity and high transmittance, the preparation of the homogenizing film on the surface of the fiber optic image inverter comprises the following steps:

[0015] The surface of the optical fiber image invertor is coated with a thin film whose thickness gradually decreases from the center to the edge.

[0016] Furthermore, in the aforementioned method for preparing a fiber optic image inverter with high uniformity and high transmittance, the thin film includes a homogenizing film layer and / or an anti-reflection film layer, and a film layer center is arranged at the center thereof.

[0017] Furthermore, in the aforementioned method for preparing a fiber optic image inverter with high uniformity and high transmittance, the rotation speed of the film with a thickness gradually decreasing from the center to the edge is 10rpm-20rpm.

[0018] Furthermore, in the aforementioned method for preparing a fiber optic image inverter with high uniformity and high transmittance, the pressure of the film whose coating thickness gradually decreases from the center to the edge is 1.0-2.0Pa.

[0019] Furthermore, in the above-mentioned method for preparing a fiber image inverter with high uniformity and high transmittance, the vacuum degree of the film whose coating thickness gradually decreases from the center to the edge is less than or equal to 3×10 -4 .

[0020] Furthermore, in the aforementioned method for preparing a fiber optic image inverter with high uniformity and high transmittance, the gas flow rate of argon gas is 15-30 sccm when coating a thin film with a thickness gradually decreasing from the center to the edge.

[0021] Furthermore, in the aforementioned method for preparing a high-uniformity, high-transmittance optical fiber image inverter, the film whose coating thickness gradually decreases from the center to the edge is achieved by sputtering; pre-sputtering is started at 30-50W, and after sputtering for 3-5 minutes, the power is adjusted to 60-80W to start formal sputtering, and the sputtering time is 0.5-3 minutes.

[0022] The purpose of the present invention and the technical problem solved by the present invention can also be achieved by adopting the following technical solutions: The present invention provides a low-light-level night vision device, which includes the above-mentioned high-uniformity, high-transmittance optical fiber image invertor.

[0023] By means of the above technical solution, the optical fiber image invertor with high uniformity and high transmittance and its preparation method and application described in the present invention have at least the following advantages:

[0024] According to the non-uniform transmittance design of the image inverter, a homogenizing film is plated on the surface of the image inverter to effectively improve the non-uniform transmittance in the effective area. The homogenizing film has a thickness gradient trend that gradually decreases from the center to the edge. At the same time, according to the torsional structure curve and transmittance change of the image inverter, the torsional mode of the image inverter is optimized, and a bicubic function-type torsional structure curve is designed, which can greatly improve the vignetting defect. The prepared image inverter can effectively improve the resolution of the image inverter;

[0025] The present invention aims at the problem of uneven light transmittance at the output end face of the image inverter. The invention is designed based on the torsion structure curve of the image inverter and the surface microstructure of the image inverter, which can greatly improve the transmittance non-uniformity, make the output light of the image inverter uniform, and reduce the brightness difference between the periphery and the central area of ​​the image inverter.

[0026] The image invertor prepared by the invention can achieve a non-uniform transmittance of 0.98%-2.10% at a wavelength of 550nm, a transmittance uniformity of 97.9%-99.02%, and a central transmittance of 39.87%-41.08%.

[0027] 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

[0028] Figure 1 It is a schematic diagram of the twisting of the image invertor in the prior art;

[0029] Figure 2 It is a schematic diagram of the overall structure of the mechanical rotary coating device of the present invention;

[0030] Figure 3 It is a schematic diagram of the structure of the mechanical rotary coating device without a protective shell of the present invention;

[0031] Figure 4 It is a partial cross-sectional perspective view of the mechanical spin coating device of the present invention;

[0032] Figure 4A It is a schematic diagram of the structure of the rotating base of the mechanical rotating film coating device of the present invention;

[0033] Figure 5 A diagram of a snail-shaped mask of a mechanical rotary coating device of the present invention;

[0034] Figure 6 It is a biquadratic function torsion curve and expansion schematic diagram of the present invention;

[0035] Figure 7 The bicubic function torsion curve and expansion schematic diagram of the present invention;

[0036] Fig. 8A It is a structural schematic diagram of a dual quadratic function type image inverter with a homogenizing film deposited at the output end of the present invention;

[0037] Figure 8B It is a structural schematic diagram of a bicubic function type image invertor with a homogenizing film deposited on the output end of the present invention;

[0038] Fig. 9AIt is a structural schematic diagram of a double quadratic function type image inverter with a homogenizing film deposited on the output end and an anti-reflection film deposited on the input end of the present invention;

[0039] Fig. 9B It is a schematic structural diagram of a bicubic function type image inverter with a homogenizing film deposited on the output end and an anti-reflection film deposited on the input end of the present invention;

[0040] Fig. 10A It is a structural schematic diagram of a dual quadratic function type image inverter with a homogenizing film deposited at the input end of the present invention;

[0041] Fig. 10B It is a schematic structural diagram of a bicubic function type image invertor with a homogenizing film deposited at the input end of the present invention;

[0042] Fig.11A It is a schematic structural diagram of a double quadratic function type image inverter with an antireflection film deposited on the input end and a homogenizing film deposited on the output end of the present invention;

[0043] Fig. 11B It is a schematic structural diagram of a bicubic function type image inverter with an antireflection film deposited on the input end and a homogenizing film deposited on the output end of the present invention;

[0044] Fig. 12A It is a structural schematic diagram of a dual quadratic function type image inverter with a homogenizing film deposited on the output end and a homogenizing film deposited on the input end of the present invention;

[0045] Fig. 12B It is a structural schematic diagram of a bicubic function type image invertor with a homogenizing film deposited on the output end and a homogenizing film deposited on the input end of the present invention;

[0046] Fig.13A It is a structural schematic diagram of a double quadratic function type image inverter of the present invention in which a homogenizing film is deposited on the output end and a homogenizing film + an anti-reflection film is deposited on the input end;

[0047] Fig. 13B It is a structural schematic diagram of a bicubic function type image inverter of the present invention in which a homogenizing film is deposited on the output end and a homogenizing film + an anti-reflection film is deposited on the input end;

[0048] Fig.14A It is a schematic structural diagram of a double quadratic function type image inverter with a homogenizing film + an anti-reflection film deposited on the output end and a homogenizing film deposited on the input end of the present invention;

[0049] Fig. 14B It is a schematic structural diagram of a bicubic function type image inverter with a homogenizing film + an anti-reflection film deposited on the output end and a homogenizing film deposited on the input end of the present invention;

[0050] Fig.15A It is a structural schematic diagram of a double quadratic function type image inverter in which a homogenizing film + an anti-reflection film is deposited on the output end and a homogenizing film + an anti-reflection film is deposited on the input end of the present invention;

[0051] Fig. 15B It is a structural schematic diagram of a bicubic function type image inverter of the present invention in which a homogenizing film + an anti-reflection film is deposited on the output end and a homogenizing film + an anti-reflection film is deposited on the input end;

[0052] Fig.16 This is a graph showing the transmittance test results before and after coating of Example 1 of the present invention;

[0053] Fig.17 This is a graph showing the transmittance test results before and after coating of Example 2 of the present invention;

[0054] Fig.18 This is a graph showing the transmittance test results before and after coating of Example 3 of the present invention;

[0055] Fig.19 The transmittance test result diagram of Comparative Example 1 before and after coating;

[0056] Among them: 1-protective shell; 2-motor; 3-small gear; 4-large gear; 5-rotating base; 6-mask plate; 7-sample chamber; 8-platform; 91-output end, 92-output end, 10-input end, 20-input end, 11-homogenizing film, 21-homogenizing film, 12-anti-reflection film, 22-anti-reflection film, 13-film layer center, 23-film layer center, 33-film layer center, 43-film layer center, 14-double quadratic function type image inverter, 15-double cubic function type image inverter. DETAILED DESCRIPTION

[0057] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the high uniformity and high transmittance fiber image invertor and its preparation method and its specific implementation, features and effects proposed by the present invention in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features or characteristics in one or more embodiments may be combined in any suitable form.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the specification and claims of the present invention and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0059] In the description of the embodiments of the present invention, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0060] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0061] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0062] In the description of the embodiments of the present invention, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0063] In the description of the embodiments of the present invention, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention.

[0064] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0065] 1. Design of the torsion structure curve of the image invertor

[0066] During the torsion process of the image inverter, the deformation degree of the optical fiber in the edge area and the optical fiber in the center area is different, resulting in a difference in light transmission capacity. Changing the torsion mode of the image inverter will produce different light transmission effects. According to the thermodynamic and material mechanical properties of the image inverter during the torsion process (the change of the optical fiber trajectory during the heating and stretching process will affect the light transmission performance), the optical fiber trajectory and light transmission uniformity of the torsion zone of the image inverter are optimized, and the structural torsion curve with a double quadratic function and a double cubic function distribution in the cone change zone is designed. The image inverters corresponding to the two functions are called double quadratic function type image inverters and double cubic function type image inverters, such as Figure 6 , Figure 7 As shown. Figure 6 , Figure 7 It can be seen that the fiber curve of the bicubic function has a buffer zone compared to the curve of the quadratic function image inverter, which is beneficial to the transmission of optical signals. According to the theory and transmittance test results, the non-uniform transmittance of the bicubic function distribution is the lowest, which can reach 4.13%, effectively alleviating the vignetting defect and realizing a high-transmittance image inverter.

[0067] Among them, "center" refers to the exact center of the image inverter; "edge" refers to the edge of the effective area of ​​the image inverter, that is, the outermost optical fiber of the image inverter. `

[0068] Double quadratic function type image invertor:

[0069] The image invertor blank is fixed on the torsion rod by the stretching fixture, and then the torsion furnace is controlled by the mechanical operation panel to make the center of the image invertor blank coaxial with the center of the torsion inner furnace. The preparation work is now complete. First, heat the outer furnace to the preheating temperature (about 500-550℃. If it is lower than 500℃, the temperature difference between the inner and outer furnaces is too large, and the image invertor cannot be drawn. If it is higher than 550℃, there are too many internal defects of the image invertor). After stabilizing the temperature of the outer furnace for 15-20 minutes (the purpose is to fully preheat), use a heating ring with an inner diameter of 40mm and a width of 2mm (the function is to heat the middle part of the image invertor blank to the softening temperature) to start heating the inner furnace of the torsion furnace to the softening point temperature of the image invertor (about 780-830℃. If it is lower than 780℃, it cannot reach the softening temperature and cannot be twisted; if it is higher than 830℃, the viscosity of the image invertor blank is too small and it is impossible to twist out an image invertor with a regular shape). The servo motor and the torque sensor are used to apply two constant but opposite torques (10-15N) to both ends of the image invertor. The center of the image invertor blank in the inner furnace heating area gradually softens, and the torque is slowly applied to both ends until it rotates 180° relative to the inner furnace, then the inner furnace heating is stopped, and the outer furnace annealing program is started. Finally, the image invertor blank is taken out after it is cooled to room temperature. At this time, the temperature difference between the inner and outer furnaces is only 280°C, and the trend of the stretched image invertor cone surface change is nonlinear. The deformation area of ​​the image invertor presents a parabola shape of a double quadratic function, and the corresponding equation type is y=ax2 , where a is greater than or equal to 0.06. If it is less than 0.06, it cannot be twisted into an image invertor. Taking an image invertor blank with a height of 30 mm and a diameter of 26 mm as an example, when the twisting force is controlled at 14 N, a double quadratic function type image invertor can be realized. At this time, a is 0.084, and the corresponding equation is y = 0.084x 2 .

[0070] The starting external furnace annealing program includes: turning off the heating program on the mechanical control panel, and the cooling rate is 5-10°C / min. If the cooling program is not set and the temperature is naturally cooled, the cooling rate will be greater than 10°C / min, which will have an adverse effect on the life of the furnace.

[0071] Bicubic image invertor:

[0072] The twisting method is the same as that of the biquadratic function type image inverter, except that the heating coil of the bicubic function type image inverter is movable. The heating coil is initially located at one-fourth of the image inverter blank. After twisting 90°, the heating coil is moved to three-fourths of the image inverter blank and twisted 90° further. The image inverter prepared by this method will present an image inverter deformation zone in the shape of a cubic function double parabola. The corresponding equation type is y=ax 3 , a is greater than or equal to 0.0038; if a is less than 0.0038, it cannot be twisted into an image invertor. Taking an image invertor blank with a height of 30 mm and a diameter of 26 mm as an example, when the twisting force is controlled at 14N, a double quadratic function type image invertor can be realized. At this time, a is 0.0048, and the corresponding equation is y=0.0048x 3 .

[0073] 2. Design and preparation of homogenizing film on the surface of the image invertor

[0074] Using conventional methods (without using a rotary coating device and a mask plate) to coat a film of uniform thickness on the surface of the image invertor can only change the overall transmittance of the image invertor, but cannot improve the problem of different brightness between the edge and the center of the image invertor, and cannot achieve a high uniform transmittance effect. Therefore, a snail-shaped mask plate is designed to achieve a film with a thickness that gradually decreases from the center to the edge, combining the non-uniform transmittance characteristics of the image invertor (i.e., high transmittance in the center and low transmittance in the edge). Figure 5 As shown in FIG. 1 , the shaded part is the hollow part, and the shape is designed according to the non-uniform transmittance of the image inverter. First, a transmittance tester (i.e., a device for detecting the visible light transmittance and uniformity of an optical fiber image transmission element involved in the patent application with the publication number CN 111442908A) is used to obtain the transmittance distribution of the image inverter. Next, the functional relationship between the transmittance of the image inverter and the position of the effective area is obtained by fitting the obtained data. Then, the film thickness and position of the required coating film layer are calculated by the function. The function is: x = -2×10-7 y 6 +8×10 -9 y 5 -1×10 -4 y 4 -2×10 -6 y 3 -0.0315y 2 -1×10 -11 y+4.2165, where: x is the absolute thickness of the film layer, y is the distance from the center to the edge (x is greater than 0, y is between 0-11.5), and finally according to the formula The shape of the snail mask is obtained by and ρ = (1-d / H)r. Among them, θ(x) is the angle exposed to the steam flow, d0 is the thickness at the center of the film layer, θ0 is the opening angle at the center of the film layer, the distance between the evaporation source and the lower surface of the substrate to be plated is H, the distance between the shield and the lower surface of the substrate is d, the polar diameter from the center of the shield to the opening reference point is ρ, and the maximum radius of the glass substrate that the evaporation source can reach is r. Figure 5 As shown, the opening size of the snail-shaped mask plate tends to gradually decrease from the center to the edge. In conjunction with the rotary coating device, the middle area is exposed for a long time and the edge area is exposed for a short time during the coating process, so that the target film layer can be obtained.

[0075] Through the mechanical rotary coating device and the snail-shaped mask, it is finally possible to coat a thin film whose thickness gradually decreases from the center to the edge, and with an image inverter with non-uniform transmittance, a highly uniform transmittance image inverter is finally realized. In actual use, the homogenizing film can be coated on the input and output ends of the image inverter separately or at the same time. In addition, it can also be matched with an anti-reflection film to achieve high transmittance and ultra-high transmittance. The homogenizing film can reduce vignetting defects, and the anti-reflection film can increase the overall transmittance of the image inverter. The combination of the two can achieve low vignetting defects within the effective area and high transmittance.

[0076] The mechanical spin coating device is as follows: Figure 2-5 As shown, it includes a protective shell 1, a motor 2, a small gear 3, a large gear 4, a rotating base 5, a mask 6, a sample chamber 7, a platform 8 and a sample 9 fixed by screws. The protective shell 1 is fixedly connected to the platform 8, so that the whole device is in a regular shape (a rectangular parallelepiped with a length of 173mm, a width of 136mm and a height of 115mm), which is convenient for placement in the chamber. Among them, the platform 8 is a rectangular metal plate with a thickness of 3mm, so that the size can be reduced as much as possible while ensuring that the motor, sample chamber and other components can bear the load; as shown in FIG. Figure 4AAs shown, the rotating base 5 is a bearing structure composed of two concentric rings, which includes a non-rotating internal structure and a rotating external structure connected by steel balls, the internal structure is fixed to the sample chamber 7, the upper end face of the external structure is fixed to the large gear 4, and the lower end face of the external structure is fixed to the mask plate 6, so that the mask plate can be rotated and the sample chamber does not rotate. Specifically, the rotating base 5 is a high-precision bearing, the gap inside the bearing is very small, the distance between the two is filled with steel balls, the stability is very high, and there is no shaking, thereby ensuring high coaxiality. Since the rotating base 5 is a three-dimensional structure and is located between the sample chamber 7 and the mask plate 6, according to the direction of placing the high-stability, high-coaxiality mechanical rotary coating device on the coating equipment, the sample chamber 7 is fixed above the inside of the rotating base 5, and the mask plate 6 is fixed below the outside of the rotating base 5. The sample 9 is a fiber optic image invertor, and there are no requirements for its size and performance. Fiber optic image invertors of different sizes can be placed by changing the size of the sample chamber. The rotating base 5 is fixed with the mask plate 6, and the motor drives the rotating base 5 to rotate, while the sample chamber 7 remains stationary, so as to achieve the effect of the mask plate 6 rotating. Through the mechanical rotary coating device and the snail-shaped mask plate 6, a thin film with a thickness gradually decreasing from the center to the edge can be plated, and with the fiber optic image inverter with non-uniform transmittance, a fiber optic image inverter with high uniformity can be finally achieved.

[0077] The sample 9 is placed in the sample chamber 7. The sample chamber 7 is 4mm higher than the sample and has a built-in rubber pad to prevent the end face of the sample 9 from being damaged when the mechanical rotary coating device is inverted and disassembled. Specifically, the rubber pad is located between the large end face of the optical fiber inverter and the sample chamber 7. This arrangement can prevent the large end face of the optical fiber inverter from directly contacting the sample chamber 7; and the material of the sample chamber 7 is polytetrafluoroethylene. The reason for choosing polytetrafluoroethylene is first because it is light in weight and can reduce the overall weight of the device; secondly, it is because it can withstand higher temperatures than ordinary plastics. The upper end face of the sample chamber 7 is fixed to the platform 8 by screws, and its lower end face is fixed to the upper end face of the internal structure of the rotating base 5 by screws. The sample chamber 7 is a cylindrical groove with a diameter of 48mm and a depth of 45mm. One end of the platform 8 is fixed to the motor 2 by screws to ensure that the mask rotates without interference while ensuring the coating effect.

[0078] A small-diameter pinion 3 is installed at the tail end of the shaft of the motor 2. The rotation of the motor 2 drives the pinion 3 to rotate. This arrangement is to ensure that the rotation of the mask is not disturbed while ensuring the coating effect.

[0079] The pinion 3 is meshed and connected with the large diameter and hollow large gear 4, and the rotation of the pinion 3 drives the large gear 4 to rotate. In specific implementation, the diameter of the large gear 4 needs to be equal to the diameter of the outer side of the bearing. Considering that the sample chamber 7 needs to be placed in the middle of the large gear 4, the large gear 4 is set to be hollow. Among them, the diameter of the large gear 4 is consistent with the size of the rotating base, and the speed ratio of the pinion 3 and the large gear 4 is 5:1, at this time, the film formation uniformity is good; according to the speed ratio, the pinion 3 of the appropriate diameter is selected, and the speed is too fast or too slow, which is easy to cause poor film formation uniformity and stains on the surface of the film layer. The speed ratio design between the large and small gears is to control the speed of the bottom mask and improve the uniformity of the coating thickness. Combined with the position of the pinion and the speed ratio, the diameter of the pinion 3 is designed to be 3cm. At the same time, the mechanical rotary coating device can use large and small gears to drive in a limited space, so that the transmission efficiency is higher.

[0080] The motor 2 drives the small gear 3 to rotate, the small gear 3 drives the large gear 4 to rotate, the large gear 4 drives the outer part of the bearing to rotate, and the outer part of the bearing drives the mask to rotate, so that the sample does not rotate but the mask rotates by itself.

[0081] The large gear 4 is fixed to the upper end of the outer side of the rotating base 5 by screws. The rotation of the large gear 4 drives the rotating base 5 to rotate. There is a 1mm gap between the large gear 4 and the sample chamber 7 so that the large gear 4 will not be affected by the sample chamber 7 when rotating.

[0082] The outer lower end surface of the rotating base 5 is fixed to the mask 6 by screws, and the outer part of the rotating base 5 drives the mask 6 to rotate. The size of the mask 6 is equal to the outer size of the rotating base 5, and the gap between the two is 2mm, so that the mask 6 rotates without interference while ensuring the coating effect. Specifically, the mask 6 is a hollowed-out spiral copper plate with a thickness of 0.5mm and a diameter of 120mm. The hollowed-out middle part of the spiral copper plate has a larger opening, and the edge part has a smaller opening, that is, the middle exposure time is long and the edge exposure time is short during coating, which can achieve a gradient film with a thick middle film layer and a thin edge film layer. The thinner the copper plate is, the better it is on the premise of ensuring that the mask plate is not deformed, so that the sputtering material can be better attached to the sample; it has been found through testing that a mask plate with a thickness of less than 0.5mm is easy to deform. Considering that the mask 6 is fixed to the rotating base by screws, the diameter of the mask 6 is the same as the outer size of the rotating base to facilitate fixation.

[0083] The coating of the thin film optical fiber image invertor whose thickness gradually decreases from the center to the edge comprises the following steps:

[0084] 1) Place the assembled mechanical rotary coating device into the chamber of the magnetron sputtering coating machine; the chamber has good sealing performance and can be used to place samples or devices to be coated; if the mask plate is installed first, the sample cannot be installed, so if the device needs to be used, the sample must be installed first and then the mask plate;

[0085] 2) Turn on the power supply and adjust the speed of the mechanical rotary coating device; since the motor speed of the mechanical rotary coating device is adjustable, the motor speed can be adjusted to 10-20 rpm by turning the button;

[0086] 3) Closing the chamber and starting the coating. Closing the chamber and starting the coating specifically includes the following steps:

[0087] a. After closing the chamber of the coating equipment, turn on the mechanical pump to pre-vacuum. When the vacuum degree is less than or equal to 10Pa, turn off the mechanical pump, open the solenoid valve, and turn on the molecular pump.

[0088] b When the vacuum degree is less than or equal to 3×10 -4 Turn on the gas flowmeter and adjust the gas flow of argon and oxygen to 15-30 sccm. Then adjust the pressure in the chamber to 1.0-2.0 Pa through the G valve; the vacuum degree is less than or equal to 3×10 -4 It can meet the coating requirements. The lower the vacuum degree, the fewer impurities in the chamber; the lower the pressure in the chamber, that is, the working pressure, the higher the quality of the coated film, but the speed will be slower, so 1.0-2.0Pa is selected as the working pressure.

[0089] c. Turn on the sputtering power switch and adjust the power to 30-50W to start pre-sputtering. After sputtering for 3-5 minutes, open the baffle valve and adjust the power to 60-80W to start formal sputtering. The sputtering time is 0.5-3 minutes. The function of pre-sputtering is first to preheat the machine. It is not advisable to use high power when starting the machine. Secondly, it sputters away impurities on the surface of the target material.

[0090] d. After sputtering is completed, close the flapper valve, turn off the power switch, turn the gas flow meter knob to 0, close the solenoid valve, turn off the molecular pump, and open the valve connected to the air to balance the internal and external atmospheric pressure of the chamber;

[0091] e. Open the chamber of the coating equipment and take out the mechanical rotary coating device. After the coating is completed, a high uniformity and high transmittance optical fiber image invertor is obtained. Fig. 8A , Figure 8B , Fig. 9A , Fig. 9B , Fig. 10A , Fig. 10B , Fig.11A , Fig. 11B , Fig. 12A and Fig. 12BAs shown, the optical fiber image invertor can be used in an electric low-light night vision device. There are two types of optical fiber image invertors, namely, a double quadratic function type image invertor and a double cubic function type image invertor. Fig. 8A , Figure 8B , Fig. 9A , Fig. 9B , Fig. 10A , Fig. 10B , Fig.11A , Fig. 11B , Fig. 12A and Fig. 12B It can be seen that both the input and output end faces of the two different function types of image invertors can be coated with a homogenizing film layer, and even both ends can be coated with a homogenizing film layer at the same time. There are a total of 10 coating methods. Specifically, Fig. 8A , Fig. 9A , Fig. 10A , Fig.11A and Fig. 12A As shown, the dual quadratic function type image invertor 14 comprises an input end 10, an output end 91 and an optical fiber portion arranged between the input end 10 and the output end 91; the surface of the input end 10 and / or the output end 91 has a thin film whose thickness gradually decreases from the center to the edge; the thickness and position of the thin film satisfy: x = -2×10 -7 y 6 +8×10 -9 y 5 -1×10 - 4 y 4 -2×10 -6 y 3 -0.0315y 2 -1×10 -11 y+4.2165, where: x is the absolute thickness of the film, y is the distance from the center to the edge; the film includes homogenizing film layers 11, 21 and / or anti-reflection film layers 12, 22, the center of the homogenizing film layer 11 is provided with a film layer center 13, the center of the homogenizing film layer 21 is provided with a film layer center 43, the center of the anti-reflection film layer 12 is provided with a film layer center 23, and the center of the anti-reflection film layer 22 is provided with a film layer center 33. Figure 8B , Fig. 9B , Fig. 10B , Fig. 11B and Fig. 12B As shown, the bicubic function type image invertor 15 comprises an input end 20, an output end 92 and an optical fiber portion arranged between the input end 20 and the output end 92; the surface of the input end 20 and / or the output end 92 has a thin film whose thickness gradually decreases from the center to the edge; the thickness and position of the thin film satisfy: x = -2×10 -7 y 6 +8×10 -9 y5 -1×10 -4 y 4 -2×10 -6 y 3 -0.0315y 2 -1×10 -11 y+4.2165, wherein: x is the absolute thickness of the film, y is the distance from the center to the edge; the film comprises homogenizing film layers 11, 21 and / or anti-reflection film layers 12, 22, the homogenizing film layer 11 is provided with a film layer center 13 at its center, the homogenizing film layer 21 is provided with a film layer center 43 at its center, the anti-reflection film layer 12 is provided with a film layer center 23 at its center, and the anti-reflection film layer 22 is provided with a film layer center 33 at its center.

[0092] In summary, a thin film with a thickness gradually decreasing from the center to the edge can be plated by using a mechanical rotary coating device in conjunction with a snail-shaped mask, and a highly uniform transmittance image inverter can be realized by using a non-uniform transmittance image inverter. In addition, an anti-reflection film can be used to achieve high transmittance and ultra-high transmittance. The homogenization film can reduce vignetting defects, and the anti-reflection film can increase the overall transmittance of the image inverter. The combination of the two can achieve low vignetting defects within the effective area and high transmittance.

[0093] The above-mentioned “high uniformity and high transmittance” means that the transmittance uniformity of the image invertor at a wavelength of 550 nm is between 97.9% and 99.02%, and the central transmittance is between 39.87% and 41.08%.

[0094] The present invention is described in detail below with reference to specific embodiments.

[0095] The “center” mentioned below refers to the exact center of the image inverter, and the “edge” refers to the edge of the effective area of ​​the image inverter.

[0096] Embodiment 1:

[0097] This embodiment provides a dual quadratic function type image invertor, the manufacturing of which specifically includes the following steps:

[0098] S1, using the rod-tube combination method, a high-refractive-index glass rod and a low-refractive-index glass tube are combined together and then drawn (at a temperature of 1850°C) into a single filament (with a diameter of 3mm); the drawn single filament and a light-absorbing filament (with a diameter of 3mm) for absorbing stray light are arranged into a hexagonal shape and then drawn (at a temperature of 1845°C) into a primary multifilament (with a diameter of 1.3mm); the primary multifilament is arranged into a hexagonal shape again and drawn (at a temperature of 1450°C) into a secondary multifilament (with a diameter of 2mm); the secondary multifilament is placed in a melt-pressed mold and subjected to high temperature and high pressure (temperature of 650°C, pressure of 15 tons) to prepare a blank (with a height of 40mm and a diameter of 26mm). The refractive index of the glass rod at a wavelength of 550nm is 1.78, and its composition by weight percentage is: SiO2 54.12%; K2CO3 14.84%; Na2CO3

[0099] 11.10%; Al(OH) 35.99%; H2BO3 10.16%; CaCO3 2.88%; BaCO3 0.23%; CeO20.07%; MgCO3 0.46%; NiO 0.01%; Nb2O5 0.05%; Y2O3 0.01%; La2O3 0.08%. The refractive index of the glass tube at a wavelength of 550 nm is 1.49, and its composition by weight percentage is: SiO2 35.25%; KNO3 0.13%; Na2CO3 0.10%; Al(OH)3 0.84%; H2BO3 24.23%; CaCO3 10.26%; BaCO3 25.50%; MgCO3 0.21%; La2O3 1.68; Sb2O3 0.06%; TiO2 1.74%. The composition of the light absorbing wire by weight percentage is: SiO2 55.84%; K2CO3 11.27%; Na2CO3 6.11%; Al(OH)3 9.37%; H2BO3 8.56%; CaCO3

[0100] 2.67%; BaCO3 0.03%; CeO2 0.19%; MgCO3 0.40%; Fe2O3 0.02%; NiO0.87%; MnO2 2.87%; CoO 0.42%; La2O3 0.01%; V2O5 1.37%.

[0101] S2, fix the blank on the torsion rod through the torsion fixture, and then control the torsion furnace through the mechanical operation panel to make the center of the blank coaxial with the center of the torsion inner furnace, and the preparation work is completed. First, heat the outer furnace to the preheating temperature (about 550℃). After stabilizing the temperature of the outer furnace for 15 minutes (the purpose is to fully preheat, 20 minutes is OK), use a heating ring with an inner diameter of 40mm and a width of 2mm (the function is to heat the middle part of the blank to the softening temperature) to start heating the inner furnace of the torsion furnace at 10℃ / min to the softening point temperature of the blank (about 820℃). Apply two constant but opposite torsional forces (150N) to both ends of the blank through the servo motor and torsion force sensor. The center part of the blank in the heating area of ​​the inner furnace gradually softens, and torsional forces are applied to both ends until the relative rotation is 180°, then stop the inner furnace heating, start the outer furnace annealing program (cooling at a rate of 10℃ / min), and finally take out the image invertor blank after cooling to room temperature. At this time, the temperature difference between the inner and outer furnaces is only 280℃. The change trend of the twisted image invertor cone is nonlinear. The deformation zone of the image invertor presents a double quadratic function parabola shape. Taking the image invertor blank with a height of 26mm and a diameter of 22mm as an example, when the twisting force is controlled at 14N, the double quadratic function type image invertor can be realized. The corresponding equation type is y=0.087x 2 .

[0102] S3, polish the image inverter blank for 2 hours until the roughness reaches 20nm, and then perform performance testing to ensure that the transmittance, resolution and internal defects (such as defects, chicken wire, grid) of the image inverter meet the national standards (GJB9792-2020 Specification for Fiber Optic Image Transmission Coupling Elements).

[0103] S4, first use a transmittance tester (i.e., a device for detecting the visible light transmittance and uniformity of an optical fiber image transmission element as disclosed in the patent application with publication number CN 111442908A) to test the transmittance distribution at the output end of the dual quadratic function type image invertor, and then analyze the obtained data to obtain a non-uniform transmittance of 7.23% and a center transmittance of 45%. Then use a rotary coating device to coat a layer of gradient metal chromium film with a center thickness of 6nm and an edge thickness of 1nm, reducing the non-uniform transmittance to 2.1% and a center transmittance of 39.87%, as shown in Figure 13.

[0104] Specifically, the assembled rotary coating device was placed in the chamber of the magnetron sputtering coating machine; the power supply was turned on, and the rotation speed of the rotary coating device was adjusted to 10 rpm; the chamber was closed to start coating, and the distance between the mask plate and the optical fiber invertor was 1 mm.

[0105] The method of closing the chamber and starting the coating specifically comprises the following steps: a. after closing the chamber of the coating equipment, first open the mechanical pump to pre-vacuum, and when the vacuum degree reaches 10Pa, close the mechanical pump, open the solenoid valve, and turn on the molecular pump; b. when the vacuum degree reaches 2×10-4 1. Turn on the gas flowmeter and adjust the gas flow of argon to 25sccm. Then adjust the pressure in the chamber to 0.8Pa through the G valve. c. Turn on the sputtering power switch and adjust the power to 50W to start pre-sputtering. After 5 minutes of sputtering, open the baffle valve and adjust the power to 60W to start formal sputtering. The sputtering time is 50s. d. After the sputtering is completed, close the baffle valve, turn off the power switch, turn the gas flowmeter knob to 0, turn off the solenoid valve, turn off the molecular pump, and open the valve connected to the air to balance the internal and external atmospheric pressures of the chamber. e. Open the chamber of the coating equipment, take out the rotary coating device, and the coating is completed to obtain a high uniformity and high transmittance image inverter. The optical fiber image inverter can be used in an electric low-light night vision device.

[0106] As can be seen from FIG13 , the thickness of the chrome film gradually decreases from the center to the edge, the central transmittance of the image invertor decreases from 45% to 39.87%, and the vignetting defect decreases from 7.23% to 2.1%, which proves that the scheme can effectively reduce the vignetting defect.

[0107] Embodiment 2:

[0108] This embodiment provides a bicubic function type image invertor, and its production specifically includes the following steps:

[0109] S1, same as Example 1.

[0110] S2, the twisting method is the same as that of the biquadratic function type image inverter, the difference is that the heating coil of the bicubic function type image inverter is movable, and the position of the heating coil is initially located at one-fourth of the image inverter blank. After twisting 90°, the heating coil is moved to three-quarters of the image inverter blank and continues to twist 90°. During the stretching process, the center of the image inverter blank can maintain a straight area of ​​1mm, and then continue to apply a twisting force of 14N. The image inverter prepared by this method will show an image inverter deformation zone in the shape of a cubic function double parabola. Taking an image inverter blank with a height of 26mm and a diameter of 22mm as an example, when the twisting force is controlled at 14N, the bicubic function type image inverter can be realized using the above method, and the corresponding equation type is y=0.005x 3 .

[0111] S3, same as Example 1.

[0112] S4, using a transmittance tester (i.e., a device for detecting the visible light transmittance and uniformity of an optical fiber image transmission element as disclosed in the patent application with publication number CN 111442908A) to test the transmittance distribution at the output end of the bicubic function type image invertor, and then analyzing the obtained data to obtain a non-uniform transmittance of 4.13% and a central transmittance of 45%. Then, a layer of gradient metal chromium film with a center thickness of 6nm and an edge thickness of 1nm was plated using a rotary coating device, reducing the non-uniform transmittance to 0.98% and a central transmittance of 41.08%. The test results are shown in FIG14.

[0113] Specifically, the assembled mechanical rotary coating device is placed in the chamber of the magnetron sputtering coating machine; the power supply is turned on, and the rotation speed of the mechanical rotary coating device is adjusted to 10 rpm; the chamber is closed to start coating, and the distance between the mask plate and the optical fiber invertor is 1 mm.

[0114] The method of closing the chamber and starting the coating specifically comprises the following steps: a. after closing the chamber of the coating equipment, first open the mechanical pump to pre-vacuum, and when the vacuum degree reaches 10Pa, close the mechanical pump, open the solenoid valve, and turn on the molecular pump; b. when the vacuum degree reaches 2×10 -4 1. Turn on the gas flowmeter and adjust the gas flow of argon to 25sccm. Then adjust the pressure in the chamber to 0.8Pa through the G valve. c. Turn on the sputtering power switch and adjust the power to 50W to start pre-sputtering. After 5 minutes of sputtering, open the baffle valve and adjust the power to 60W to start formal sputtering. The sputtering time is 50s. d. After the sputtering is completed, close the baffle valve, turn off the power switch, turn the gas flowmeter knob to 0, turn off the solenoid valve, turn off the molecular pump, and open the valve connected to the air to balance the internal and external atmospheric pressures of the chamber. e. Open the chamber of the coating equipment, take out the rotary coating device, and the coating is completed to obtain a high uniformity and high transmittance image inverter. The optical fiber image inverter can be used in an electric low-light night vision device.

[0115] It can be seen from Figure 14 that before coating, the vignetting defect of the bicubic function type image inverter is lower than that of the biquadratic function type image inverter, indicating that the structure of the bicubic function type image inverter is optimal. After chrome film coating, the central transmittance of the image inverter is reduced from 45% to 41.08%, and the vignetting defect is reduced from 4.13% to 0.98%. The phenomenon of reducing vignetting defects is more obvious.

[0116] Embodiment 3:

[0117] This embodiment provides a bicubic function type image invertor, and its production specifically includes the following steps:

[0118] S1, same as Example 2.

[0119] S2, same as Example 2.

[0120] S3, same as Example 2.

[0121] S4, compared with Example 2, the difference of this example is that a layer of gradient titanium nitride film with a center thickness of 30nm and an edge thickness of 5nm is plated using a rotary coating device. The test results show that the non-uniform transmittance is reduced to 1.08%, and the center transmittance is 40.98%. The test results are shown in Figure 15.

[0122] Specifically, the assembled mechanical rotary coating device is placed in the chamber of the magnetron sputtering coating machine; the power supply is turned on, and the rotation speed of the mechanical rotary coating device is adjusted to 10 rpm; the chamber is closed to start coating, and the distance between the mask plate and the image invertor is 1 mm.

[0123] The method of closing the chamber and starting the coating specifically comprises the following steps: a. after closing the chamber of the coating equipment, first open the mechanical pump to pre-vacuum, and when the vacuum degree reaches 10Pa, close the mechanical pump, open the solenoid valve, and turn on the molecular pump; b. when the vacuum degree reaches 2×10 -4 1. Turn on the gas flowmeter and adjust the gas flow of argon to 25sccm. Then adjust the pressure in the chamber to 0.8Pa through the G valve. c. Turn on the sputtering power switch and adjust the power to 50W to start pre-sputtering. After 5 minutes of sputtering, open the baffle valve and adjust the power to 60W to start formal sputtering. The sputtering time is 230s. d. After sputtering, close the baffle valve, turn off the power switch, turn the gas flowmeter knob to 0, turn off the solenoid valve, turn off the molecular pump, and open the valve connected to the air to balance the internal and external atmospheric pressures of the chamber. e. Open the chamber of the coating equipment, take out the rotary coating device, and the coating is completed to obtain a high uniformity and high transmittance image inverter. The optical fiber image inverter can be used in an electric low-light night vision device.

[0124] As can be seen from FIG15 , by changing the coating material from chromium film to titanium nitride film, the central transmittance of the image invertor is reduced from 45% to 40.98%, and the vignetting defect is reduced from 4.13% to 1.08%, indicating that the purpose of homogenization can also be achieved by changing the coating material.

[0125] Comparative Example 1:

[0126] Compared with Example 2, the difference of this comparative example is that a metal chromium film with a thickness of 5 nm in the edge and center regions is plated on the output end of the bicubic function type image invertor using a conventional method (without using a rotary coating device, without a mask plate, and other operation steps and parameters are the same as those of Example 3). After testing, it is found that the non-uniform transmittance is reduced to 5.19% and the center transmittance is 36%. The test results are as follows Fig.16 As shown. Fig.16 It can be seen that the vignetting defect cannot be effectively reduced using this conventional method.

[0127] The non-uniform transmittance and center transmittance of the fiber optic image inverters of Examples 1-3 and Comparative Example 1 before and after coating were tested, and the test results are shown in Table 1. The test principle is: a beam of collimated incident light with a wavelength of 550nm is irradiated to the input end of the fiber optic image inverter, and the light from the output end of the fiber optic image inverter is received by a CCD camera to obtain a light intensity distribution diagram, and the relative transmittance is calculated by the luminous flux of the input and output light. Among them, the luminous flux is equal to the light intensity multiplied by the area, and the light intensity is measured by the transmittance tester. The center transmittance is the transmittance when the position is 0 (the exact center of the fiber optic image inverter). The non-uniform transmittance is the difference between the center transmittance and the transmittance at the edge of the effective area.

[0128] Table 1

[0129]

[0130] From the data in Table 1, it can be concluded that before coating, when the central transmittance of Examples 1-3 was maintained at 45%, the non-uniform transmittance of the bicubic function type image inverter was 4.13%, the transmittance uniformity was 95.87%, and the structure was optimal. The non-uniform transmittance of the biquadratic function type image inverter was 7.23%, the transmittance uniformity was 92.77%, and the structure was the worst. After coating, while ensuring that the non-uniform transmittance was around 1% on average, the central transmittance of the bicubic function type image inverter could reach 41.08%, while the central transmittance of the biquadratic function type image inverter was only 39.87%, which also shows that the bicubic function type image inverter structure is optimal.

[0131] In the specification of the present invention, a lot of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some embodiments, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this specification.

[0132] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0133] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0134] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A high uniformity and high transmittance optical fiber image invertor, characterized in that: The invention comprises an input end, an output end and an optical fiber part arranged between the input end and the output end; the surface of the input end and / or the output end has a thin film whose thickness gradually decreases from the center to the edge; the thickness and position of the thin film satisfy: x = -2×10 -7 y 6 +8×10 -9 y 5 -1×10 -4 y 4 -2×10 -6 y 3 -0.0315y 2 -1×10 -11 y+4.2165, where: x is the absolute thickness of the film, y is the distance from the center to the edge.

2. The high uniformity and high transmittance optical fiber image invertor according to claim 1, characterized in that: The value of x is greater than 0, and the value of y is between 0 and 11.

5.

3. The high uniformity and high transmittance optical fiber image invertor according to claim 1, characterized in that: The optical fiber image inverter is a biquadratic function type image inverter or a bicubic function type image inverter.

4. The high uniformity and high transmittance optical fiber image invertor according to claim 1, characterized in that: The film comprises a homogenizing film layer and / or an anti-reflection film layer, and a film layer center is arranged at the center thereof.

5. The high uniformity and high transmittance optical fiber image invertor according to claim 1, characterized in that: The optical fiber image invertor with high uniformity and high transmittance is prepared by the following steps: Preparation of torsion structure of image invertor; Preparation of homogenizing film on the surface of image invertor.

6. The high uniformity and high transmittance optical fiber image invertor according to claim 5, characterized in that: The preparation of the image invertor torsion structure comprises the following steps: According to the optical fiber trajectory in the torsion zone of the image inverter, a double quadratic function type image inverter or a double cubic function type image inverter is prepared respectively.

7. The high uniformity and high transmittance optical fiber image invertor according to claim 5, characterized in that: The preparation of the homogenizing film on the surface of the optical fiber image invertor comprises the following steps: The surface of the optical fiber image invertor is coated with a thin film whose thickness gradually decreases from the center to the edge.

8. The high uniformity and high transmittance optical fiber image invertor according to claim 7, characterized in that: The film comprises a homogenizing film layer and / or an anti-reflection film layer, and a film layer center is arranged at the center thereof.

9. The high uniformity and high transmittance optical fiber image invertor according to claim 7, characterized in that: The rotation speed of the film whose thickness decreases gradually from the center to the edge is 10rpm-20rpm.

10. The high uniformity and high transmittance optical fiber image invertor according to claim 7, characterized in that: The pressure of the film whose coating thickness gradually decreases from the center to the edge is 1.0-2.0Pa.

11. The high uniformity and high transmittance optical fiber image invertor according to claim 7, characterized in that: When coating a thin film whose thickness gradually decreases from the center to the edge, the gas flow rate of argon gas is 15-30 sccm.

12. The high uniformity and high transmittance optical fiber image invertor according to claim 7, characterized in that: The film with a thickness gradually decreasing from the center to the edge is plated by sputtering; the power is adjusted to 30-50W to start pre-sputtering, and after sputtering for 3-5 minutes, the power is adjusted to 60-80W to start formal sputtering, and the sputtering time is 0.5-3 minutes.

13. A low-light-level night vision device, characterized in that: The low-light-level night vision device comprises the optical fiber image invertor with high uniformity and high transmittance as described in any one of claims 1-12.

Images