Light cone with high uniformity and high transmittance and preparation method and application thereof

Abstract

The present invention relates to a light cone with high uniformity and high transmittance, and a preparation method and application thereof. The light cone comprises a large end face portion, a small end face portion and an optical fiber portion arranged between the large end face portion and the small end face portion; the surface of the large end face portion and / or the small end face portion has a thin film whose thickness gradually decreases from the center to the edge. The technical problem to be solved is to obtain a light cone with high uniformity and high transmittance by improving the drawing profile of the light cone and coating a homogenizing film at the same time.

Description

Technical Field

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

[0002] Light cones are widely used in the coupling of charge-coupled devices (CCDs), image intensifiers, and photomultiplier tubes in the fields of national defense, scientific research, criminal investigation, aerospace, and medical treatment, and are also used in radiographic imaging, new fingerprint recognition, high-definition television imaging, and advanced office equipment imaging. In recent years, with the rapid development of digital image processing technology, the acquisition, storage, and transmission of high-fidelity images have become very convenient, and have become an important symbol of mankind's entry into the digital age. However, in the process of war, scientific research, production, and medical treatment, people often need to observe, analyze, and process weak images and events that are invisible to the naked eye. For example, they need to monitor and observe at night without light; they need to image and study objects that emit rays; they need to track and identify high-speed aircraft, and so on. In these cases, the brightness of the image is usually only 10 -3 ~10 -4 Candela, or even lower. Therefore, the image must be enhanced before observation, processing and analysis. Conventional image digital processing technology can no longer meet this requirement. Using fiber light cone coupling CCD, photomultiplier tube and image intensifier is the best choice to realize low-light imaging digitization and reduce the size of the device.

[0003] Among the many influencing factors, the main reason for the low coupling efficiency of the optical fiber light cone is the low transmittance at the edge of the light cone. The poor edge coupling resolution leads to poor imaging clarity, which has a lot to do with the preparation process of the optical fiber light cone. The light cone is obtained by high-temperature deformation after tens of millions or even hundreds of millions of micron-level melt-pressed fibers. The optical fiber in the center area of ​​the light cone produces axial stretching to form a straight tapered optical fiber; the optical fiber away from the axis not only produces axial elongation but also radial displacement to form a curved tapered optical fiber. It is precisely because of the inconsistent degree of deformation of the optical fiber in the center and edge areas that the transmittance distribution of the output end face of the light cone is different, and there is a trend of gradually decreasing transmittance from the center to the edge. This transmittance trend is called a vignetting defect. This vignetting defect of light transmission non-uniformity will deteriorate the coupling resolution of the light cone coupling optoelectronic device. Summary of the invention

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

[0005] The purpose of the present invention and the technical problem to be solved are achieved by adopting the following technical solutions. The present invention proposes a light cone with high uniformity and high transmittance, comprising a large end face, a small end face and an optical fiber part arranged between the large end face and the small end face; the surface of the large end face and / or the small end face has a thin film whose thickness gradually decreases from the center to the edge; the thickness and position of the thin film satisfy: x = -0.0002y 4 +2×10 -15 y 3 -0.0358y 2 -8×10 -13 y+8.8453, where: x is the absolute thickness of the film, y is the distance from the center to the edge.

[0006] Furthermore, in the aforementioned light cone with high uniformity and high transmittance, the value of x is greater than 0, and the value of y is between 0 and 11.5.

[0007] Furthermore, in the aforementioned light cone with high uniformity and high transmittance, the light cone is a linear function type light cone, a quadratic function type light cone or a cubic function type light cone.

[0008] Furthermore, in the aforementioned light cone with high uniformity and high transmittance, the thin film includes a homogenizing film layer, 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. The present invention proposes a method for preparing a light cone with high uniformity and high transmittance, comprising the following steps:

[0010] Preparation of the contour structure of the tapered region;

[0011] Preparation of light cone surface homogenization film.

[0012] Furthermore, in the above-mentioned method for preparing a light cone with high uniformity and high transmittance, the preparation of the contour structure of the cone-changing region comprises the following steps:

[0013] According to the structural contour curve of the linear function distribution, the quadratic function distribution or the cubic function distribution, a linear function type light cone, a quadratic function type light cone or a cubic function type light cone is prepared respectively.

[0014] Furthermore, in the aforementioned method for preparing a light cone with high uniformity and high transmittance, the preparation of the light cone surface homogenization film comprises the following steps:

[0015] The surface of the light cone 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 light cone with high uniformity and high transmittance, the thin film comprises a homogenizing film layer, a film layer center is arranged at the center thereof.

[0017] Furthermore, in the aforementioned method for preparing a light cone with high uniformity and high transmittance, the rotation speed of the coating is 10 rpm-15 rpm.

[0018] Furthermore, in the aforementioned method for preparing a light cone with high uniformity and high transmittance, the coating pressure is 0.8-1.0Pa.

[0019] Furthermore, in the above method for preparing a light cone with high uniformity and high transmittance, the vacuum degree of the coating is less than or equal to 2×10 -4 Pa.

[0020] Furthermore, in the aforementioned method for preparing a light cone with high uniformity and high transmittance, the gas flow rates of argon and oxygen during the coating are both 20-30 sccm, and the volume ratio of the two is 1:1.

[0021] Furthermore, in the aforementioned method for preparing a light cone with high uniformity and high transmittance, the coating 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 5-300 seconds.

[0022] The purpose of the present invention and the technical problem solved by the present invention can also be achieved by the following technical solutions: The present invention proposes a charge coupled device, which includes the above-mentioned light cone with high uniformity and high transmittance.

[0023] The purpose of the present invention and the technical problem solved by the present invention can also be achieved by the following technical solutions: In an image intensifier provided by the present invention, the charge coupled device comprises the above-mentioned light cone with high uniformity and high transmittance.

[0024] The purpose of the present invention and the technical problem to be solved can also be achieved by the following technical solutions: The present invention proposes a photomultiplier tube, wherein the charge coupled device comprises the above-mentioned light cone with high uniformity and high transmittance.

[0025] By means of the above technical solution, the light cone with high uniformity and high transmittance and its preparation method and application described in the present invention have at least the following advantages:

[0026] The present invention aims at the problem of uneven light transmittance at the light cone exit end face, and designs the contour structure of the light cone transition zone and the surface microstructure, which greatly alleviates the vignetting defect and effectively improves the transmittance non-uniformity, making the light cone exit light uniform and reducing the brightness difference between the periphery and the central area of ​​the light cone.

[0027] The present invention optimizes the stretched shape of the light cone according to the changes in the contour structure and transmittance of the light cone cone transition zone, designs a light cone cone transition zone contour curve in the shape of a cubic function, and greatly improves the vignetting defect; at the same time, coating a homogenizing film on the surface of the light cone is also an effective method for improving the vignetting defect. A mechanically rotating light cone coating device is used in conjunction with a snail-shaped mask designed according to the non-uniform transmittance of the light cone to prepare a thin film whose thickness gradually decreases from the center to the edge, and fully improves the non-uniformity of the transmittance of the light cone; the combination of the two can prepare a light cone with high uniformity and high transmittance, and effectively improve the coupling efficiency of the light cone and the optoelectronic coupling device;

[0028] The light cone prepared by the present invention can achieve a non-uniform transmittance of 1.78%-2.43% at a wavelength of 550nm, a transmittance uniformity of 97.57%-98.22%, and a central transmittance of 23%-40%.

[0029] 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

[0030] Figure 1A It is a linear function distribution profile curve diagram of the optical fiber in the light cone tapered region of the present invention;

[0031] Figure 1B It is a quadratic function distribution profile curve diagram of the optical fiber in the light cone tapered region of the present invention;

[0032] Figure 1C It is a cubic function distribution profile curve diagram of the optical fiber in the light cone tapered region of the present invention;

[0033] Figure 2A The first-order function type light cone peripheral optical fiber of the present invention;

[0034] Figure 2B It is the quadratic function type light cone peripheral optical fiber of the present invention;

[0035] Figure 2C It is the cubic function type light cone peripheral optical fiber of the present invention;

[0036] Figure 3 This is a snail-shaped mask diagram of the present invention;

[0037] Figure 4 It is a schematic diagram of the overall structure of the rotating light cone coating device of the present invention;

[0038] Figure 5 It is a schematic diagram of the structure of the rotating light cone coating device without a protective shell of the present invention;

[0039] Figure 6It is a partial cross-sectional perspective view of the rotating light cone coating device of the present invention;

[0040] Fig. 6A It is a schematic diagram of the structure of the rotating base of the rotating light cone coating device of the present invention;

[0041] Fig. 7A A light cone diagram of a linear function type light cone with a homogenized film deposited on the large end surface of the light cone according to the present invention;

[0042] Figure 7B The light cone diagram of the quadratic function type light cone of the present invention with a homogenized film deposited on the large end surface;

[0043] Figure 7C A light cone diagram of a cubic function type light cone with a homogenized film deposited on the large end surface of the light cone according to the present invention;

[0044] Fig. 8A A light cone diagram of a linear function type light cone with a homogenized film deposited on a small end face of the light cone according to the present invention;

[0045] Figure 8B The light cone diagram of the quadratic function type light cone of the present invention depositing a homogenizing film on the small end surface

[0046] Figure 8C The light cone diagram of the cubic function type light cone of the present invention depositing a homogenizing film on the small end surface

[0047] Fig.9A A light cone diagram of a linear function type light cone of the present invention in which both end surfaces are coated with a uniform film;

[0048] Fig. 9B A light cone diagram of a quadratic function type light cone of the present invention in which both end surfaces are coated with a uniform film;

[0049] Fig. 9C A light cone diagram of a cubic function type light cone of the present invention in which both end surfaces are coated with a uniform film;

[0050] Fig.10 This is a graph showing the transmittance test results before and after coating of Example 1 of the present invention;

[0051] Fig.11 This is a graph showing the transmittance test results before and after coating of Example 2 of the present invention;

[0052] Fig.12 This is a graph showing the transmittance test results before and after coating of Example 3 of the present invention;

[0053] Fig.13 This is a graph showing the transmittance test results before and after coating of Example 4 of the present invention;

[0054] Fig.14 This is a graph showing the transmittance test results before and after coating of Example 5 of the present invention;

[0055] Fig.15This is a graph showing the transmittance test results before and after coating of Comparative Example 1 of the present invention;

[0056] Fig.16 This is a graph showing the transmittance test results before and after coating of Comparative Example 2 of the present invention;

[0057] Among them: 1. Protective shell; 2. Motor; 3. Small gear; 4. Large gear; 5. Rotating base; 6. Mask; 7. Sample chamber; 8. Platform; 9. Sample; 10. Homogenized film layer; 11. Large end; 12. Small end; 13. Linear function type light cone; 14. Quadratic function type light cone; 15. Cubic function type light cone; 16. Center of film layer; 20. Homogenized film layer; 21. Large end face portion; 22. Small end face portion; 26. Center of film layer; 31. Large end face portion; 32. Small end face portion; 36. Center of film layer; 46. Center of film layer; 56. Center of film layer; 66. Center of film layer. DETAILED DESCRIPTION

[0058] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the light cone with high uniformity and high transmittance and its preparation method and its specific implementation methods, features and effects proposed by the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" do 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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).

[0064] 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.

[0065] 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.

[0066] 1. Design and preparation of the contour structure of the light cone transition area

[0067] During the drawing process of the light cone, the deformation degree of the optical fiber in the edge area and the optical fiber in the center area is different, resulting in differences in light transmission capacity. Changing the contour of the light cone will produce different light transmission effects. According to the thermodynamic and material mechanical properties during the drawing process of the tapered optical fiber array, the optical fiber trajectory and its light transmission uniformity in the light cone tapered area are optimized (the change of the optical fiber trajectory during the heating and stretching process will affect the light transmission performance), and the structural contour curves of the tapered area with linear function distribution, quadratic function distribution, and cubic function distribution are designed, such as Figure 1A , Figure 1B and Figure 1C As shown, the light cones corresponding to the three functions are called linear function light cone, quadratic function light cone and cubic function light cone, as shown in Figure 2A , Figure 2B and Figure 2C According to the theory and transmittance test, compared with the cone-change zone profile curve being a linear function or a quadratic function distribution, the vignetting defect value of the cubic function distribution is the lowest, which can reach 2.21%, effectively alleviating the vignetting defect and achieving a high-transmittance light cone.

[0068] The “center” refers to the exact center of the light cone; the “edge” refers to the edge of the effective area of ​​the light cone, that is, the outermost optical fiber of the light cone.

[0069] Take a light cone with a height of 45mm and a diameter of 24mm as an example.

[0070] Linear function light cone:

[0071] Fix the two ends of the light cone blank on the stretching rod through the stretching fixture, and then control the stretching furnace through the mechanical operation panel to make the center of the light cone blank coaxial with the center of the stretching inner furnace, and the preparation work is completed. First, heat the outer furnace to the preheating temperature. The preheating temperature of the outer furnace is set to 500-550℃. If the preheating temperature is lower than 500℃, the temperature difference between the outer furnace and the inner furnace is large, and it is not easy to draw the first-order function type light cone. If the preheating temperature is higher than 550℃, the temperature is too high, which will change the components inside the light cone. After stabilizing the temperature of the outer furnace for no less than 15 minutes (considering sufficient preheating), use a heating ring with an inner diameter of 60mm and a width of 11mm (its function is to heat the middle part of the light cone blank to the softening temperature) to start heating the inner furnace of the stretching furnace to the light cone softening point temperature. Through the servo motor and the tension sensor, two constant but opposite tensions are applied outward along the vertical light cone end face (the tension is adjusted according to the different function types of light cones). The center part of the light cone blank in the heating area of ​​the inner furnace gradually softens and slowly stretches to both sides under the action of the tension until it becomes a "dumbbell" shape with a thin middle and unchanged size at both ends. When the light cone blank is stretched to the target cone ratio, stop the inner furnace heating, start the outer furnace annealing program, and finally take out the light cone blank after cooling to room temperature. At this time, the temperature difference between the inner and outer furnaces is only 280-330℃ (below the lower limit or above the upper limit, a linear function curve-type light cone will not be stretched out). The trend of the stretched light cone surface change is linear, and the light cone deformation zone is infinitely close to the linear function straight line shape. The corresponding equation type is y=ax, where a>0.5, and it cannot be stretched into a fiber light cone if it is less than 0.5. The larger the value of a, the smaller the cone ratio, until it is 1:1. For example, when the cone ratio is fixed at 2:1, the tension is fixed at 500N, and the tension is applied for 150 minutes, the outer contour curve of the light cone is a linear function straight line shape, and the corresponding equation is y=3.75x.

[0072] 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.

[0073] Quadratic function type light cone:

[0074] The stretching method is the same as the stretching of the linear function type light cone, but the difference is that the outer furnace temperature of the quadratic function type light cone is 500-550℃, which is 40 to 60℃ lower than the outer furnace temperature of the linear function light cone. The inner diameter of the heating ring is 50mm and the width is 8mm. The difference between the outer furnace temperature and the inner furnace temperature is increased, making the gradient temperature zone of the entire furnace larger. The change trend of the stretched light cone surface is nonlinear. At this time, the deformation zone of the light cone presents a quadratic function parabola shape, and the corresponding equation type is y=ax 2 , where a>0.25, and if it is less than 0.25, it cannot be stretched into a light cone. The higher the value of a, the smaller the cone ratio, until it reaches 1:1. For example, when the cone ratio is fixed at 2:1, the tension is fixed at 500N, and the tension is applied for 130 minutes, the outer contour curve of the light cone is a quadratic function, and its corresponding equation is y=0.625x 2 .

[0075] Cubic function light cone:

[0076] The stretching method is the same as the stretching of the quadratic function type light cone. The difference is that the specifications of the heating ring in the furnace of the cubic function type light cone are replaced with a widened heating ring with an inner diameter of 50mm and a width of 16mm. The increase in the width of the heating ring increases the heating area in the center of the light cone blank, so that the center of the light cone blank can maintain a longer straight area during the stretching process, presenting a light cone deformation area in the shape of a cubic function double parabola. The corresponding equation type is y=ax 3 , where a>0.125, and less than 0.125 cannot be stretched into a light cone. There is no upper limit, the higher the value of a, the smaller the cone ratio, until 1:1. For example, when the cone ratio is fixed at 2:1, the tension is fixed at 500N, and the tension is applied for 110 minutes, the outer contour curve of the light cone is a cubic function shape, and its corresponding equation is y=0.104x 3 .

[0077] 2. Design and preparation of light cone surface homogenization film

[0078] 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 light cone can only change the overall transmittance of the light cone, but cannot improve the vignetting defect of the light cone to achieve the effect of high uniformity and high transmittance. Therefore, a film with a thickness gradually decreasing from the center to the edge is designed in combination with the non-uniform transmittance characteristics of the light cone (i.e., high transmittance in the center area and low transmittance in the edge area), as shown in Figure 7. Figure 3 As shown, the shaded part is the hollow part, and the shape is designed according to the non-uniform transmittance of the light cone. First, a transmittance tester (i.e., a device for detecting the visible light transmittance and uniformity of an optical fiber imaging element involved in a patent application with publication number CN111442908A) is used to obtain the transmittance distribution of the light cone. Next, the functional relationship between the transmittance of the light cone and the position of the small end face is obtained by fitting the obtained data, and then the film thickness and position of the required coating film are calculated by the function. The function is: x = -0.0002y 4 +2×10 -15 y 3 -0.0358y 2 -8×10 -13 y+8.8453. Among them: x is the 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 3 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 rotating light cone 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.

[0079] The rotating light cone coating device is as follows: Figure 4-6 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. Fig. 6AAs 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 rotating light cone 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 light cone, and there is no requirement for its size and performance. Light cones 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 2 drives the rotating base 5 to rotate, while the sample chamber 7 remains stationary, so that the mask plate 6 can rotate. The rotating light cone coating device is used in conjunction with the snail-shaped mask plate to finally coat a thin film whose thickness gradually decreases from the center to the edge, and with the light cone of non-uniform transmittance, a light cone with high uniformity and high transmittance is finally obtained.

[0080] 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 rotating light cone coating device is disassembled upside down. Specifically, the rubber pad is located between the large end face of the light cone and the sample chamber 7. This arrangement can prevent the large end face of the light cone from directly contacting the sample chamber 7. The sample chamber 7 is made of 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.

[0081] 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.

[0082] 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. The uniformity of film formation is good under this speed ratio; the pinion 3 with a suitable diameter is selected according to the speed ratio. Too fast or too slow speed is likely to cause poor uniformity of film formation and stains on the surface of the film layer. The speed ratio design between the large and small gears is intended 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 rotating light cone coating device with high stability and high coaxiality can use large and small gears for transmission in a limited space, so that the transmission efficiency is high.

[0083] 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.

[0084] 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 2mm 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.

[0085] 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 200mm. 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, so that a gradient film with a thick middle film layer and a thin edge film layer can be achieved. The thinner the copper plate is, the better it is on the premise of ensuring that the mask plate does not deform, 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.

[0086] The coating of the thin film light cone whose thickness gradually decreases from the center to the edge comprises the following steps:

[0087] 1) Place the assembled rotating light cone 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;

[0088] 2) Turn on the power supply and adjust the speed of the rotating light cone coating device; since the motor speed of the rotating light cone coating device is adjustable, turn the button to adjust the motor speed to 10-15rpm;

[0089] 3) Closing the chamber and starting the coating. Closing the chamber and starting the coating specifically includes the following steps:

[0090] 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.

[0091] b When the vacuum degree is less than or equal to 2×10 -4 Pa, turn on the gas flowmeter and adjust the gas flow of argon and oxygen to 20-30 sccm. Then adjust the pressure in the chamber to 0.8-1.0 Pa through the G valve; the vacuum degree is less than or equal to 2×10 -4 Pa 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. Therefore, 0.8-1.0Pa is selected as the working pressure.

[0092] 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 5-300 seconds. 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.

[0093] 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;

[0094] e. Open the chamber of the coating equipment and take out the rotating light cone coating device. After the coating is completed, a light cone with high uniformity and high transmittance is obtained. Fig. 7A , Figure 7B , Figure 7C , Fig. 8A , Figure 8B , Figure 8C , Fig.9A , Fig. 9B and Fig. 9CAs shown, the light cone can be used in a charge coupled device (CCD), an image intensifier or a photomultiplier tube. There are three types of light cones, namely, a linear function type light cone 13, a quadratic function type light cone 14, and a cubic function type light cone 15. Fig. 7A , Figure 7B , Figure 7C , Fig. 8A , Figure 8B , Figure 8C , Fig.9A , Fig. 9B and Fig. 9C It can be seen that the large and small end faces of the three different function types of light cones can be coated with a homogenizing film, and even both ends can be coated with a homogenizing film at the same time. There are a total of 9 coating methods. Specifically, Fig. 7A , Fig. 8A and Fig.9A As shown, the linear function type light cone 13 includes a large end portion 11, a small end portion 12 and an optical fiber portion arranged between the large end portion 11 and the small end portion 12; the surface of the large end portion 11 and / or the small end portion 12 has a thin film whose thickness gradually decreases from the center to the edge, and the thin film includes a homogenizing film layer 10 and / or a homogenizing film layer 20, and the center of the homogenizing film layer 10 is provided with a film layer center 16, and the center of the homogenizing film layer 20 is provided with a film layer center 46. The thickness and position of the thin film satisfy: x = -0.0002y 4 +2×10 -15 y 3 -0.0358y 2 -8×10 -13 y+8.8453, where x is the absolute thickness of the film and y is the distance from the center to the edge. Figure 7B , Figure 8B and Fig. 9B As shown, the quadratic function type light cone 14 includes a large end surface 21, a small end surface 22 and an optical fiber portion arranged between the large end surface 21 and the small end surface 22; the surface of the large end surface 21 and / or the small end surface 22 has a thin film whose thickness gradually decreases from the center to the edge, and the thin film includes a homogenizing film layer 10 and / or a homogenizing film layer 20, and the center of the homogenizing film layer 10 is provided with a film layer center 26, and the center of the homogenizing film layer 20 is provided with a film layer center 56. Figure 7C , Figure 8C and Fig. 9CAs shown, the cubic function type light cone 15 includes a large end portion 31, a small end portion 32 and an optical fiber portion arranged between the large end portion 31 and the small end portion 32; the surface of the large end portion 31 and / or the small end portion 32 has a thin film whose thickness gradually decreases from the center to the edge, and the thin film includes a homogenized film layer 10 and / or a homogenized film layer 20, and the center of the homogenized film layer 10 is provided with a film layer center 36, and the center of the homogenized film layer 20 is provided with a film layer center 66. The thickness and position of the thin film satisfy: x = -0.0002y 4 +2×10 -15 y 3 -0.0358y 2 -8×10 -13 y+8.8453, where: x is the absolute thickness of the film, y is the distance from the center to the edge.

[0095] The above-mentioned “high uniformity and high transmittance” means that the transmittance uniformity of the light cone at a wavelength of 550 nm is between 97.57% and 98.22%, and the central transmittance is between 23% and 40%.

[0096] The present invention is described in detail below with reference to specific embodiments.

[0097] The “center” mentioned below refers to the exact center of the light cone, and the “edge” refers to the edge of the effective area of ​​the light cone, that is, the outermost optical fiber of the light cone.

[0098] Embodiment 1:

[0099] This embodiment provides a linear function light cone, the preparation of which specifically includes the following steps:

[0100] S1, a high-refractive-index glass rod and a low-refractive-index glass tube are combined together using a rod-tube combination method and then drawn at 1850°C into a single filament with a wire diameter of 3 mm; the drawn single filament and a light-absorbing wire (wire diameter of 3 mm) for absorbing stray light are arranged into a hexagonal shape and then drawn at 1845°C into a primary multifilament with a wire diameter of 1.3 mm; the primary multifilament is arranged into a hexagonal shape again and drawn at 1845°C into a secondary multifilament with a wire diameter of 2 mm; 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 plate with a diameter of 26 mm and a height of 50 mm. The glass rod has a refractive index of 1.78 at a wavelength of 550 nm, and its composition by weight percentage is: SiO2 54.12%; K2CO3 14.84%; Na2CO3 11.10%; Al(OH)3 5.99%; H2BO3 10.16%; CaCO3 2.88%; BaCO3 0.23%; CeO2 0.07%; MgCO3 0.46%; NiO 0.01%; Nb2O5 0.05%; Y2O3 0.01%; La2O3 0.08%. The glass tube has a refractive index of 1.49 at a wavelength of 550 nm, 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 filament in weight percentage is: SiO2 55.84%; K2CO3 11.27%; Na2CO3 6.11%; Al(OH)3 9.37%; H2BO3 8.56%; CaCO3 2.67%; BaCO3 0.03%; CeO2 0.19%; MgCO3 0.40%; Fe2O3 0.02%; NiO 0.87%; MnO2 2.87%; CoO 0.42%; La2O3 0.01%; V2O5 1.37%.

[0101] S2, fix the two ends of the light cone blank with a diameter of 26mm and a height of 50mm on the stretching rod through the stretching fixture, and then control the stretching furnace through the mechanical operation panel to make the center of the light cone blank coaxial with the center of the stretching inner furnace, so far the preparation work is completed; first, heat the outer furnace to the preheating temperature of 550℃, stabilize the temperature of the outer furnace for 15 minutes, use the heating ring with an inner diameter of 60mm and a width of 11mm to start heating the inner furnace of the stretching furnace at 10℃ / min, until the light cone softening point temperature is 800℃, and apply two constant but opposite tensile forces of 500N along the vertical light cone end face through the servo motor and the tension sensor. The center part of the light cone blank in the heating area of ​​the inner furnace gradually softens, and is stretched to both sides under the action of the tension until it becomes a "dumbbell" shape with the middle thin and the two ends unchanged. When the light cone blank is stretched to the target cone ratio of 2:1, stop the inner furnace heating, start the outer furnace annealing program, cool down at a rate of 10℃ / min, and finally take out the light cone blank after it cools to room temperature. At this time, the temperature difference between the inner and outer furnaces is only 300°C, the change trend of the stretched light cone surface is linear, and the deformation zone of the light cone is infinitely close to the shape of a linear function. The corresponding equation type is y=4.55x, the cone ratio is fixed at 2:1, the tension is fixed at 500N, and the tension is applied for 150 minutes. The outer contour curve of the light cone is in the shape of a linear function.

[0102] S3, polish the large and small end faces of the stretched light cone blank for 2 hours, and perform performance testing after the roughness reaches 20nm level to ensure that the transmittance, resolution and internal defects (such as defects, chicken wire, grid) of the light cone meet the national standards (GJB9792-2020 Specification for Fiber Optic Image Transmission Coupling Elements).

[0103] S4, the difference between the transmittance at the axis 0 point and the transmittance at the boundary of the effective area (D = 25.00mm) represents the non-uniform transmittance (vignetting defect) in the tapered optical fiber array. The data obtained are analyzed using a transmittance tester (i.e., a device for detecting the visible light transmittance and uniformity of optical fiber imaging elements involved in the patent application with publication number CN 111442908A). The vignetting defect is 10.55% and the central transmittance is 45%. Then, a layer of gradient metal chromium film with a center thickness of 6nm and an edge thickness of 1nm is plated on the small end face of the light cone using a rotating light cone coating device, reducing the vignetting defect to 2.15% and the central transmittance to 36%. The test results are as follows: Fig.10 shown.

[0104] Specifically, the assembled rotating light cone 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 rotating light cone coating device is adjusted to 10 rpm; the chamber is closed to start coating, and the distance between the mask plate and the light cone is 1 mm.

[0105] The method of closing the chamber and starting the coating comprises the following steps: a. after closing the chamber of the coating equipment, first open the mechanical pump to pre-evacuate, and when the vacuum degree is 10Pa, close the mechanical pump, open the solenoid valve, and turn on the molecular pump; b. when the vacuum degree is 2×10 - 4 Pa, open the gas flowmeter, adjust the gas volume of argon and oxygen (the volume ratio of the two is 1:1) to 25sccm, and then adjust the pressure in the chamber to 0.8Pa through the G valve; c. Open the sputtering power switch, adjust the power to 50W to start pre-sputtering, open the baffle valve after 5 minutes of sputtering, adjust the power to 60W to start formal sputtering, and the sputtering time is 60 seconds; 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 rotating light cone coating device, and the coating is completed to obtain a light cone with high uniformity and high transmittance. The light cone can be used in a charge coupled device (CCD), an image intensifier or a photomultiplier tube.

[0106] from Fig.10 It can be seen that the thickness of the chrome film gradually decreases from the center to the edge. It can be seen that the transmittance at the center of the light cone decreases from 45% to 36%. Only the transmittance at the edge is lower than 36%. The transmittance at other positions of the light cone remains at about 36%, indicating that the design of the mask is basically reasonable. The transmittance at the edge is lower than 36% because the edge opening of the mask is small and the film layer is not easy to deposit.

[0107] Embodiment 2:

[0108] This embodiment provides a quadratic function type light cone, and its production specifically includes the following steps:

[0109] S1, same as Example 1.

[0110] S2, stretching method is the same as the stretching of the linear function light cone, the difference is that the outer furnace temperature of the quadratic function light cone is 550℃, the inner diameter of the heating ring is 50mm, and the width is 8mm. The corresponding equation type is y=0.826x 2 , the cone ratio is fixed at 2:1, the tension is fixed at 500N, and the tension is applied for 130 minutes. The outer contour curve of the light cone is a quadratic function shape.

[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 optical fiber image transmission elements involved in the patent application with publication number CN 111442908A) to analyze the obtained data, the vignetting defect is 14.23%, and the center transmittance is 45%. Then, a layer of gradient metal chromium film with a center thickness of 8nm and an edge thickness of 1nm is plated on the small end face using a rotating light cone coating device, reducing the vignetting defect to 2.43%, and the center transmittance is 23%. The test results are as follows Fig.11 shown.

[0113] Specifically, the assembled rotating light cone 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 rotating light cone coating device is adjusted to 10 rpm; the chamber is closed to start coating, and the distance between the mask plate and the light cone is 1 mm.

[0114] The method of closing the chamber and starting the coating comprises the following steps: a. after closing the chamber of the coating equipment, first open the mechanical pump to pre-evacuate, and when the vacuum degree is 10Pa, close the mechanical pump, open the solenoid valve, and turn on the molecular pump; b. when the vacuum degree is 2×10 - 4 Pa, open the gas flowmeter, adjust the gas flow of argon and oxygen (the volume ratio of the two is 1:1) to 25sccm, and then adjust the pressure in the chamber to 0.8Pa through the G valve; c. Open the sputtering power switch, adjust the power to 50W to start pre-sputtering, open the baffle valve after 5 minutes of sputtering, adjust the power to 60W to start formal sputtering, and the sputtering time is 80 seconds; 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 rotating light cone coating device, and the coating is completed to obtain a light cone with high uniformity and high transmittance. The light cone can be used in a charge coupled device (CCD), an image intensifier or a photomultiplier tube.

[0115] Depend on Fig.11 It can be seen that as the central transmittance of the quadratic function light cone decreases from 45% to 23%, its vignetting defect decreases from 14.23% to 2.43%.

[0116] Embodiment 3:

[0117] This embodiment provides a cubic function light cone, the preparation of which specifically includes the following steps:

[0118] S1, same as Example 1.

[0119] S2, the stretching method is the same as the quadratic function light cone stretching, the difference is that the heating ring in the furnace of the cubic function light cone is replaced with a widened heating ring with an inner diameter of 50mm and a width of 16mm. The corresponding equation type is y=0.15x 3 When the cone ratio is fixed at 2:1, the tension is fixed at 500N, and the tension is applied for 110 minutes, the outer contour curve of the light cone is a cubic function shape.

[0120] S3, same as Example 1.

[0121] S4, using a transmittance tester (i.e., a device for detecting the visible light transmittance and uniformity of optical fiber image transmission elements involved in the patent application with publication number CN 111442908A) to analyze the obtained data, the vignetting defect is 4.92%, and the center transmittance is 45%. Then, a layer of gradient metal chromium film with a center thickness of 3nm and an edge thickness of 1nm is plated on the small end face using a rotating light cone coating device, reducing the vignetting defect to 1.81% and the center transmittance to 40%. The test results are as follows Fig.12 shown.

[0122] Specifically, the assembled rotating light cone 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 rotating light cone coating device is adjusted to 10 rpm; the chamber is closed to start coating, and the distance between the mask plate and the light cone is 1 mm.

[0123] The method of closing the chamber and starting the coating comprises the following steps: a. after closing the chamber of the coating equipment, first open the mechanical pump to pre-evacuate, and when the vacuum degree is 10Pa, close the mechanical pump, open the solenoid valve, and turn on the molecular pump; b. when the vacuum degree is 2×10 - 4 Pa, open the gas flowmeter, adjust the gas flow of argon and oxygen (the volume ratio of the two is 1:1) to 25sccm, and then adjust the pressure in the chamber to 0.8Pa through the G valve; c. Open the sputtering power switch, adjust the power to 50W to start pre-sputtering, open the baffle valve after 5 minutes of sputtering, adjust the power to 60W to start formal sputtering, and the sputtering time is 40 seconds; 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 rotating light cone coating device, and the coating is completed to obtain a light cone with high uniformity and high transmittance. The light cone can be used in a charge coupled device (CCD), an image intensifier or a photomultiplier tube.

[0124] Depend on Fig.12 It can be seen that as the central transmittance of the cubic function light cone decreases from 45% to 40%, its vignetting defect decreases from 4.92% to 1.81%.

[0125] Embodiment 4:

[0126] This embodiment provides a cubic function light cone, the preparation of which specifically includes the following steps:

[0127] S1, same as Example 3.

[0128] S2, same as Example 3.

[0129] S3, same as Example 3.

[0130] S4, using a rotating light cone coating device, coated a layer of gradient metal chromium film with a center thickness of 3nm and an edge thickness of 1nm on the large end face of the cubic function light cone, reducing the vignetting defect to 1.82% and the center transmittance to 40%. The test results are as follows Fig.13 shown.

[0131] Specifically, the assembled rotating light cone 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 rotating light cone coating device is adjusted to 10 rpm; the chamber is closed to start coating, and the distance between the mask plate and the light cone is 1 mm.

[0132] The method of closing the chamber and starting the coating comprises the following steps: a. after closing the chamber of the coating equipment, first open the mechanical pump to pre-evacuate, and when the vacuum degree is 10Pa, close the mechanical pump, open the solenoid valve, and turn on the molecular pump; b. when the vacuum degree is 2×10 - 4 Pa, open the gas flowmeter, adjust the gas flow of argon and oxygen (the volume ratio of the two is 1:1) to 25sccm, and then adjust the pressure in the chamber to 0.8Pa through the G valve; c. Open the sputtering power switch, adjust the power to 50W to start pre-sputtering, open the baffle valve after 5 minutes of sputtering, adjust the power to 60W to start formal sputtering, and the sputtering time is 40 seconds; 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 rotating light cone coating device, and the coating is completed to obtain a light cone with high uniformity and high transmittance. The light cone can be used in a charge coupled device (CCD), an image intensifier or a photomultiplier tube.

[0133] Depend on Fig.13 It can be seen that no matter whether the equalizing film is plated on the large end or the small end of the cubic function light cone, the purpose of reducing the vignetting defect can be achieved.

[0134] Embodiment 5:

[0135] This embodiment provides a cubic function light cone, the preparation of which specifically includes the following steps:

[0136] S1, same as Example 3.

[0137] S2, same as Example 3.

[0138] S3, same as Example 3.

[0139] S4, using a rotating light cone coating device, a layer of gradient metal chromium film with a center thickness of 1.5nm and an edge thickness of 0.5nm was coated on the large and small end faces of the cubic function light cone, reducing the vignetting defect to 1.78% and the center transmittance to 40%. The test results are as follows Fig.14 shown.

[0140] Specifically, the assembled rotating light cone 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 rotating light cone coating device is adjusted to 10 rpm; the chamber is closed to start coating, and the distance between the mask plate and the light cone is 1 mm.

[0141] The method of closing the chamber and starting the coating comprises the following steps: a. after closing the chamber of the coating equipment, first open the mechanical pump to pre-evacuate, and when the vacuum degree is 10Pa, close the mechanical pump, open the solenoid valve, and turn on the molecular pump; b. when the vacuum degree is 2×10 - 4 Pa, open the gas flowmeter, adjust the gas flow of argon and oxygen (the volume ratio of the two is 1:1) to 25sccm, and then adjust the pressure in the chamber to 0.8Pa through the G valve; c. Open the sputtering power switch, adjust the power to 50W to start pre-sputtering, open the baffle valve after 5 minutes of sputtering, adjust the power to 60W to start formal sputtering, and the sputtering time is 15 seconds; 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 rotating light cone coating device, and the coating is completed to obtain a light cone with high uniformity and high transmittance. The light cone can be used in a charge coupled device (CCD), an image intensifier or a photomultiplier tube.

[0142] Depend on Fig.14 It can be seen that no matter whether the equalizing films are respectively coated on both ends of the cubic function light cone or the equalizing films are coated on both ends at the same time, the purpose of reducing the vignetting defect can be achieved.

[0143] Comparative Example 1:

[0144] The difference between this comparative example and Example 3 is that this comparative example uses a conventional coating method (without using a rotary coating device, without a mask plate, and other operating steps and parameters are the same as Example 3) to coat a uniform thin film with a thickness of 3nm on the small end face of the cubic function light cone. After the transmittance test, the vignetting defect is reduced to 4.90%, and the central transmittance is 40%. The test results are as follows Fig.15 As shown. Fig.15 It can be seen that the vignetting defect of the thin film with uniform coating thickness is reduced from 4.92% to 4.90%, and the central transmittance is reduced from 45% to 40%. Compared with Example 3, the central transmittance is the same, but the vignetting defect differs by 3.09%, indicating that the chromium film with uniform coating thickness cannot effectively improve the vignetting defect.

[0145] Comparative Example 2:

[0146] The difference between this comparative example and Example 3 is that this comparative example uses a conventional coating method (without using a rotary coating device, without a mask plate, and other operating steps and parameters are the same as Example 3) to coat a uniform thin film with a thickness of 5nm on the small end face of the cubic function light cone. After the transmittance test, the vignetting defect is reduced to 4.81%, and the central transmittance is 35%. The test results are as follows Fig.16 As shown. Fig.16 It can be seen that, by further increasing the film thickness, the vignetting defect increases by 3% and the central transmittance decreases by 5% compared with Example 3. This indicates that increasing the film thickness using conventional methods cannot improve the vignetting defect.

[0147] The non-uniform transmittance and center transmittance of the light cones of Examples 1-3 and Comparative Examples 1-2 before and after coating were tested by a transmittance tester (i.e., a device for detecting the visible light transmittance and uniformity of optical fiber imaging elements involved in the patent application with publication number CN 111442908A), 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 light cone, and the light from the output end of the light cone 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 light cone). The non-uniform transmittance is the difference between the center transmittance and the transmittance at the edge of the effective area.

[0148] Table 1

[0149]

[0150] It can be seen from the data in Table 1 that before coating, when the central transmittance of Examples 1-3 was maintained at 45%, the non-uniform transmittance of the cubic function type light cone was 4.92%, the transmittance uniformity was 95.08%, and the structure was optimal. The non-uniform transmittance of the quadratic function type light cone was 14.23%, the transmittance uniformity was 85.77%, and the structure was the worst. After coating, while ensuring that the non-uniform transmittance was around 2.1% on average, the central transmittance of the cubic function type light cone could reach 40%, while the central transmittance of the quadratic function type light cone was only 23%, which also shows that the cubic function type light cone structure is optimal. It can be seen from the data in Examples 3-5 that after the large end face or the small end face of the cubic function type light cone or both are coated with a homogenizing film, the non-uniform transmittance can be maintained at around 1.8% and the central transmittance can reach 40%. It can be seen from the data in Comparative Examples 1-2 that after the small end face of the cubic function type light cone is coated with a chrome film without using a rotary coating device, the non-uniform transmittance is almost not reduced, and the non-uniform transmittance cannot be improved.

[0151] In short, the unevenness of light transmission in the light cone can be improved by coating, and a homogenized film with thick middle, thin edge and radial thickness gradient can be plated. The high transmittance in the center of the light cone is matched with a thicker chrome film to greatly reduce the transmittance, and the low transmittance at the edge is matched with a thinner chrome film to reduce the transmittance slightly, so that the overall transmittance of the light cone is kept at a horizontal line, improving the unevenness of light transmission.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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 light cone with high uniformity and high transmittance, characterized in that: It comprises a large end face portion, a small end face portion and an optical fiber portion arranged between the large end face portion and the small end face portion; the surface of the large end face portion and / or the small end face portion has a thin film whose thickness gradually decreases from the center to the edge; the thickness and position of the thin film satisfy: x=-0.0002y 4 +2×10 -15 y 3 -0.0358y 2 -8×10 -13 y+8.8453, where: x is the absolute thickness of the film, y is the distance from the center to the edge.

2. The light cone with high uniformity and high transmittance as claimed in 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 light cone with high uniformity and high transmittance as claimed in claim 1, characterized in that: The light cone is a linear function type light cone, a quadratic function type light cone or a cubic function type light cone.

4. The light cone with high uniformity and high transmittance as claimed in claim 1, characterized in that: The film comprises a homogenizing film layer, the center of which is provided with a film layer center.

5. The light cone with high uniformity and high transmittance as claimed in claim 1, characterized in that: The light cone with high uniformity and high transmittance is prepared by the following steps: Preparation of the contour structure of the tapered region; Preparation of light cone surface homogenization film.

6. The light cone with high uniformity and high transmittance as claimed in claim 5, characterized in that: The preparation of the tapered zone profile structure comprises the following steps: According to the structural contour curve of the linear function distribution, the quadratic function distribution or the cubic function distribution, a linear function type light cone, a quadratic function type light cone or a cubic function type light cone is prepared respectively.

7. The light cone with high uniformity and high transmittance as claimed in claim 5, characterized in that: The preparation of the light cone surface homogenization film comprises the following steps: The surface of the light cone is coated with a thin film whose thickness gradually decreases from the center to the edge.

8. The light cone with high uniformity and high transmittance as claimed in claim 7, characterized in that: The film comprises a homogenizing film layer, the center of which is provided with a film layer center.

9. The light cone with high uniformity and high transmittance as claimed in claim 7, characterized in that: The rotation speed of the film whose thickness gradually decreases from the center to the edge is 10rpm-15rpm; the vacuum degree of the film whose thickness gradually decreases from the center to the edge is less than or equal to 2×10 -4 Pa, working pressure is 0.8-1.0Pa.

10. The light cone with high uniformity and high transmittance as claimed in claim 7, characterized in that: When coating the thin film whose thickness gradually decreases from the center to the edge, the gas flow rates of argon and oxygen are both 20-30sccm, and the volume ratio of the two is 1:1; the thin film whose thickness gradually decreases from the center to the edge is coated 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 5-300 seconds.

11. A charge coupled device, characterized in that: The charge coupled device comprises a light cone with high uniformity and high transmittance as described in any one of claims 1-10.

12. An image intensifier, characterized in that: The image intensifier comprises a light cone with high uniformity and high transmittance as described in any one of claims 1-10.

13. A photomultiplier tube, characterized in that: The photomultiplier tube comprises a light cone with high uniformity and high transmittance as described in any one of claims 1-10.

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