Light cone with high uniformity and high transmittance, preparation method therefor and use thereof

Abstract

A light cone (15) with high uniformity and high transmittance, a preparation method therefor and the use thereof. The light cone (15) comprises a larger end face portion (31), a smaller end face portion (32), and an optical fiber portion arranged between the larger end face portion (31) and the smaller end face portion (32), wherein a thin film (10, 20), the thickness of which gradually decreases from the center to the edge, is provided on the surface of the larger end face portion (31) and / or the smaller end face portion (32). By means of plating the light cone (15) with the thin film (10, 20) while improving the drawn contour of same, the light cone with high uniformity and high transmittance is obtained.

Description

Highly uniform and highly transmittance light cone and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on November 30, 2023, with application number 202311624365.7 and invention name “Light cone with high uniformity and high transmittance, and its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application 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

[0004] 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 entering 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 under no lighting conditions; they need to conduct imaging research on objects that emit rays; they need to track and identify high-speed moving aircraft, and so on. In these cases, the brightness of the image is usually only 10 -3 ~10 -4 Candela, or even lower. Therefore, image enhancement is necessary before observation, processing, and analysis. Conventional image digitization techniques are no longer sufficient. Utilizing fiber-optic taper coupling with CCDs, photomultiplier tubes, and image intensifiers is the optimal choice for digitizing low-light-level imaging and reducing device size.

[0005] Among the many influencing factors, the main reason for the low fiber cone coupling efficiency is the low transmittance at the edge of the cone. The poor edge coupling resolution leads to poor imaging clarity, which is closely related to the preparation process of the fiber cone. The cone is obtained by melting and pressing tens of millions or even hundreds of millions of micron-sized fibers and then deforming them at high temperature. The optical fiber in the center of the cone undergoes axial stretching, forming a straight tapered fiber; the optical fiber away from the axis not only produces axial elongation but also radial displacement, forming a curved tapered 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 at the output end face of the cone differs, and the transmittance tends to gradually decrease 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 cone coupling optoelectronic device.

[0006] Summary of the Invention

[0007] In view of this, the main purpose of this application is to provide a light cone with high uniformity and high transmittance, and its preparation method and application. 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.

[0008] The purpose of this application and the technical problems it solves are achieved by adopting the following technical solutions. This application proposes a light cone with high uniformity and high transmittance, comprising a large end portion, a small end portion, and an optical fiber portion disposed between the large end portion and the small end portion; the surface of the large end portion and / or the small end portion has a thin film with a thickness gradually decreasing from the center to the edge; the thickness and position of the thin film satisfy the following conditions: dx = -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.

[0009] 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.

[0010] 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.

[0011] Furthermore, in the aforementioned light cone with high uniformity and high transmittance, the thin film includes a homogenizing film layer, the center of which is provided with a film layer center.

[0012] The purpose of this application and the solution to its technical problems can also be achieved by adopting the following technical solutions. This application proposes a method for preparing a light cone with high uniformity and high transmittance, comprising the following steps:

[0013] Preparation of the contour structure of the tapered region;

[0014] Preparation of light cone surface homogenization film.

[0015] Furthermore, in the aforementioned method for preparing a light cone with high uniformity and high transmittance, the preparation of the contour structure of the cone-transformation region includes the following steps:

[0016] According to the structural contour curves 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.

[0017] 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:

[0018] The surface of the light cone is coated with a thin film whose thickness gradually decreases from the center to the edge.

[0019] Furthermore, in the aforementioned method for preparing a light cone with high uniformity and high transmittance, the thin film includes a homogenizing film layer, the center of which is provided with a film layer center.

[0020] 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.

[0021] Furthermore, in the aforementioned method for preparing a light cone with high uniformity and high transmittance, the coating pressure is 0.8-1.0 Pa.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The purpose of the present application and the solution to its technical problems can also be achieved by adopting the following technical solutions: The present application proposes a charge coupled device, which includes the above-mentioned light cone with high uniformity and high transmittance.

[0026] The purpose of this application and the solution to its technical problems can also be achieved by adopting the following technical solutions: This application proposes an image intensifier, wherein the charge coupled device includes the above-mentioned light cone with high uniformity and high transmittance.

[0027] The purpose of this application and the solution to its technical problems can also be achieved by adopting the following technical solutions: This application proposes a photomultiplier tube, wherein the charge coupled device includes the above-mentioned light cone with high uniformity and high transmittance.

[0028] By means of the above technical solution, the highly uniform and highly transmittance light cone described in this application and its preparation method and application have at least the following advantages:

[0029] This application addresses the problem of uneven light transmittance at the light cone's exit end face. By designing the contour structure and surface microstructure of the light cone's transition zone, this approach significantly alleviates vignetting defects and effectively improves transmittance non-uniformity, making the light cone's exit light uniform and reducing the brightness difference between the cone's periphery and center.

[0030] This application optimizes the stretched shape of the light cone based on the changes in the profile structure and transmittance of the light cone's cone transition zone, designs a light cone's cone transition zone profile 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 to improve 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 with a thickness gradually decreasing from the center to the edge, fully improving the non-uniformity of the light cone's transmittance. The combination of the two can produce a light cone with high uniformity and high transmittance, effectively improving the coupling efficiency of the light cone and the optoelectronic coupling device.

[0031] The light cone prepared in the present application has a non-uniform transmittance of 1.78%-2.43% at a wavelength of 550 nm, a transmittance uniformity of 97.57%-98.22%, and a central transmittance of 23%-40%.

[0032] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application and to implement it in accordance with the contents of the specification, the following is a detailed description of the preferred embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1A is a linear function distribution profile curve of the optical fiber in the tapered region of the present application;

[0034] FIG1B is a graph showing the quadratic function distribution profile of the optical fiber in the light cone tapered region of the present application;

[0035] FIG1C is a cubic function distribution profile curve of the optical fiber in the tapered region of the present application;

[0036] FIG2A is a peripheral optical fiber of a linear function light cone of the present application;

[0037] FIG2B is a quadratic function type light cone peripheral optical fiber of the present application;

[0038] FIG2C is a cubic function type light cone peripheral optical fiber of the present application;

[0039] FIG3 is a diagram of a snail-shaped mask of the present application;

[0040] FIG4 is a schematic diagram of the overall structure of the rotating light cone coating device of the present application;

[0041] FIG5 is a schematic diagram of the structure of the rotating light cone coating device without a protective shell of the present application;

[0042] FIG6 is a partial cross-sectional perspective view of the rotating light cone coating device of the present application;

[0043] FIG6A is a schematic diagram of the structure of a rotating base of the rotating light cone coating device of the present application;

[0044] FIG7A is a light cone diagram of a linear function type light cone with a large end surface deposited equalizing film according to the present application;

[0045] FIG7B is a light cone diagram of a quadratic function type light cone with a large end surface deposited equalizing film according to the present invention;

[0046] FIG7C is a light cone diagram of a cubic function type light cone with a large end surface deposited equalizing film according to the present application;

[0047] FIG8A is a light cone diagram of a linear function type light cone with a small end face deposited on a uniform film according to the present invention;

[0048] FIG8B is a light cone diagram of a quadratic function type light cone with a small end face deposited with a homogenizing film according to the present invention.

[0049] FIG8C is a light cone diagram of a cubic function light cone with a small end face deposited with a uniform film according to the present invention.

[0050] FIG9A is a light cone diagram of a linear function light cone of the present application with both end surfaces coated with a uniform film;

[0051] FIG9B is a light cone diagram of a quadratic function light cone of the present invention, in which both end surfaces are coated with a uniform film;

[0052] FIG9C is a light cone diagram of a cubic function light cone of the present application with both end surfaces coated with a uniform film;

[0053] FIG10 is a graph showing the transmittance test results before and after coating of Example 1 of the present application;

[0054] FIG11 is a graph showing the transmittance test results before and after coating of Example 2 of the present application;

[0055] FIG12 is a graph showing the transmittance test results before and after coating of Example 3 of the present application;

[0056] FIG13 is a graph showing the transmittance test results before and after coating of Example 4 of the present application;

[0057] FIG14 is a graph showing the transmittance test results before and after coating of Example 5 of the present application;

[0058] FIG15 is a graph showing the transmittance test results before and after coating of Comparative Example 1 of the present application;

[0059] FIG16 is a graph showing the transmittance test results before and after coating of Comparative Example 2 of the present application;

[0060] 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 surface; 22. Small end surface; 26. Center of film layer; 31. Large end surface; 32. Small end surface; 36. Center of film layer; 46. Center of film layer; 56. Center of film layer; 66. Center of film layer. DETAILED DESCRIPTION

[0061] To further illustrate the technical means and effectiveness of this application to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the highly uniform and highly transmittance light cone, its preparation method, and its specific implementation, features, and effectiveness. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features or characteristics of one or more embodiments may be combined in any suitable manner.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0063] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0064] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0065] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0066] In the description of the embodiments of the present application, 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).

[0067] In the description of the embodiments of the present application, 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. They are only for the convenience of describing the embodiments of the present application 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. Therefore, they should not be understood as limiting the embodiments of the present application.

[0068] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0069] 1. Design and preparation of the light cone tapered area profile structure

[0070] 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's tapered zone 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's tapered zone are optimized (the change of the optical fiber trajectory during the heating and stretching process will affect the light transmission performance). The structural contour curves of the tapered zone are designed to have a linear function distribution, a quadratic function distribution, and a cubic function distribution, as shown in Figures 1A, 1B, and 1C. The light cones corresponding to the three functions are called linear function light cones, quadratic function light cones, and cubic function light cones, as shown in Figures 2A, 2B, and 2C. According to theory and transmittance tests, compared with the case where the contour curve of the tapered zone is 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 light cone with high transmittance.

[0071] 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.

[0072] Take a light cone with a height of 45mm and a diameter of 24mm as an example.

[0073] Linear function light cone:

[0074] Using the stretching fixture, secure the ends of the light cone blank to the stretching rods. Then, control the stretching furnace via the mechanical operation panel to align the center of the light cone blank with the center of the inner stretching furnace. This completes the preparations. First, heat the outer furnace to the preheating temperature, set at 500-550°C. If the preheating temperature is lower than 500°C, the temperature difference between the outer and inner furnaces will be large, making it difficult to draw the initial linear function light cone. If the preheating temperature is higher than 550°C, the excessive temperature will alter the composition of the light cone. After stabilizing the outer furnace temperature for at least 15 minutes (allowing for sufficient preheating), 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) is used to heat the inner furnace of the stretching furnace to the light cone softening point. A servo motor and a tension sensor are used to apply two constant but opposite tensile forces outward along the perpendicular light cone end face (the magnitude of the tensile force is adjusted according to the different function types of light cones). The center part of the light cone blank in the inner furnace heating area gradually softens and is slowly stretched to both sides under the action of the tension until it becomes a "dumbbell" shape with a thin center and unchanged dimensions at both ends. When the light cone blank is stretched to the target cone ratio, the inner furnace heating is stopped and the outer furnace annealing program is started. Finally, the light cone blank is removed after cooling to room temperature. At this time, the temperature difference between the inner and outer furnaces is only 280-330°C (below the lower limit or above the upper limit, a linear function curve-shaped light cone will not be stretched). 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. If it is less than 0.5, it cannot be stretched into a fiber light cone. The larger 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 150 minutes, the outer contour curve of the light cone is a linear function straight line shape, and its corresponding equation is y=3.75x.

[0075] The external furnace annealing program includes: turning off the heating program on the mechanical control panel, and cooling the temperature at a rate of 5-10 ° C / min. If the cooling program is not set and the temperature is cooled naturally, the cooling rate will be greater than 10 ° C / min, which will have a negative impact on the life of the furnace.

[0076] Quadratic function type light cone:

[0077] The stretching method is the same as the stretching of the linear function type light cone. 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. The corresponding equation type is y=ax 2, where a>0.25. 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 .

[0078] Cubic function light cone:

[0079] The stretching method is the same as that for the quadratic function light cone, except that the heating ring in the furnace for the cubic function light cone is replaced with a wider heating ring with an inner diameter of 50mm and a width of 16mm. The increased width of the heating ring increases the heated area at the center of the light cone blank, allowing the center of the light cone blank to maintain a longer straight area during the stretching process, resulting in a light cone deformation zone with a cubic function double parabola shape. The corresponding equation type is y = ax 3 , where a>0.125. If it is less than 0.125, it cannot be stretched into a light cone. There is no upper limit. 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 110 minutes, the outer contour curve of the light cone is a cubic function, and its corresponding equation is y=0.104x 3 .

[0080] 2. Design and preparation of light cone surface homogenization membrane

[0081] Using conventional methods (without a rotary coating device or a mask) to deposit a uniformly thick film on the surface of a light cone only changes the overall transmittance of the light cone, but does not improve the vignetting defects of the light cone to achieve high uniformity and high transmittance. Therefore, taking into account the non-uniform transmittance characteristics of the light cone (i.e., high transmittance in the center and low transmittance in the edge), a film with a thickness that gradually decreases from the center to the edge is designed, as shown in Figure 7. A snail-shaped mask is shown in Figure 3. The shaded area is the hollowed-out portion, and its shape is designed based on the non-uniform transmittance of the light cone. First, a transmittance tester (i.e., a device for measuring the visible light transmittance and uniformity of optical fiber imaging elements, as described in patent application CN 111442908A) is used to obtain the transmittance distribution of the light cone. Next, a functional relationship between the transmittance of the light cone and the position of the small end face is fitted based on the obtained data. The thickness and position of the required film are then calculated from this function: dx = -0.0002y 4 +2×10 -15 y 3 -0.0358y 2 -8×10 -13y+8.8453. Where: x is the thickness of the film layer, y is the distance from the center to the edge (x is greater than 0, and y is between 0-11.5). The shape of the snail mask is finally obtained according to the formulas θ(x)=θ0d(x) / d0 and ρ=(1-d / H)r. Where θ(x) is the angle exposed to the vapor 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 coated 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. As shown in Figure 3, the opening size of the snail mask gradually decreases from the center to the edge. In conjunction with the rotating light cone coating device, the exposure time of the middle area is long and the exposure time of the edge area is short during the coating process, and the target film layer can be obtained.

[0082] The rotating light cone coating device is shown in Figures 4-6, and 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 entire device has a regular shape (it is 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 Figure 6A, 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 6, so that the mask can rotate without rotating the sample chamber. Specifically, the rotating base 5 is a high-precision bearing with a very small gap inside the bearing. The distance between the two is filled with steel balls, which has high stability and will not shake, 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 in 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 are no requirements 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 and the mask plate 6 are fixed together, and the motor 2 drives the rotating base 5 to rotate, while the sample chamber 7 remains stationary, so that the effect of the mask plate 6 rotating can be achieved. By using the rotating light cone coating device in combination with the snail-shaped mask, it is finally possible to coat a thin film whose thickness gradually decreases from the center to the edge, and to match a light cone with non-uniform transmittance, ultimately obtaining a light cone with high uniformity and high transmittance.

[0083] 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 inverted and disassembled. 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 material of the sample chamber 7 is polytetrafluoroethylene. The reason for choosing polytetrafluoroethylene is firstly because it is light in weight and can reduce the overall weight of the device; secondly, 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.

[0084] 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.

[0085] The pinion 3 meshes with the large, hollow gear 4, which has a larger diameter. Rotation of the pinion 3 drives the large gear 4. In practice, the diameter of the large gear 4 needs to be equal to the outer diameter of the bearing. Considering that the sample chamber 7 needs to be placed in the center of the large gear 4, the large gear 4 is hollow. The diameter of the large gear 4 matches the dimensions of the rotating base. The speed ratio between the pinion 3 and the large gear 4 is 5:1, which ensures good film uniformity. The appropriate diameter of the pinion 3 is selected based on the speed ratio. Excessively fast or slow speeds can easily lead to poor film uniformity and surface stains. The speed ratio between the large and small gears is designed to control the rotation speed of the bottom mask and improve the uniformity of the coating thickness. Considering the position of the pinion and the speed ratio, the diameter of the pinion 3 is designed to be 3 cm. Furthermore, this highly stable and coaxial mechanical rotating light cone coating device allows for the use of large and small gears within a limited space, resulting in high transmission efficiency.

[0086] 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.

[0087] The large gear 4 is fixed to the upper end of the outer portion of the rotating base 5 by screws. The rotation of the large gear 4 drives the rotating base 5 to rotate. There is a 2 mm 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.

[0088] The outer lower end surface of the rotating base 5 is fixed to the mask 6 by screws. 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 rotation of the mask 6 is not disturbed while ensuring the coating effect. Specifically, the mask 6 is a spiral copper plate with a hollow middle, which has a thickness of 0.5mm and a diameter of 200mm. The hollow 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, while ensuring that the mask is not deformed, so that the sputtering material can better adhere to the sample; tests have found that mask plates with a thickness of less than 0.5mm are prone to deformation. 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.

[0089] The deposition of the thin film light cone with thickness gradually decreasing from the center to the edge comprises the following steps:

[0090] 1) Place the assembled rotating light cone coating device into the chamber of the magnetron sputtering coating machine; the chamber has good sealing properties 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;

[0091] 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 10-15 rpm;

[0092] 3) Closing the chamber and starting film coating. Closing the chamber and starting film coating specifically includes the following steps:

[0093] 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.

[0094] b When the vacuum degree is less than or equal to 2×10 -4 Pa, open the gas flow meter 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 film layer, but the speed will be slower. Therefore, 0.8-1.0Pa is selected as the working pressure.

[0095] 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.

[0096] 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 connecting the air to balance the internal and external atmospheric pressures of the chamber;

[0097] e. Open the chamber of the coating equipment and remove the rotating light cone coating device. Coating is complete, resulting in a highly uniform and highly transmittance light cone, as shown in Figures 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B, and 9C. These light cones can be used in charge-coupled devices (CCDs), image intensifiers, or photomultiplier tubes. There are three types of light cones: a linear function type 13, a quadratic function type 14, and a cubic function type 15. As can be seen from Figures 7A, 7B, 7C, 8A, 8B, 8C, 9A, 9B, and 9C, both large and small end faces of the three different function types of light cones can be coated with a homogenized film, and even both ends can be coated simultaneously, resulting in nine coating methods. Specifically, as shown in Figures 7A, 8A, and 9A, the linear function light cone 13 includes a large end portion 11, a small end portion 12, and an optical fiber portion disposed 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 with a thickness gradually decreasing from the center to the edge. The thin film includes a homogenizing film layer 10 and / or a homogenizing film layer 20. 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: dx = -0.0002y 4 +2×10 -15 y 3 -0.0358y 2 -8×10 -13y+8.8453, where x is the absolute thickness of the film and y is the distance from the center to the edge. As shown in Figures 7B, 8B, and 9B, the quadratic function-shaped light cone 14 includes a large end portion 21, a small end portion 22, and an optical fiber portion disposed between the large end portion 21 and the small end portion 22. The surface of the large end portion 21 and / or the small end portion 22 comprises a thin film whose thickness gradually decreases from the center to the edge. The thin film comprises a homogenizing film layer 10 and / or a homogenizing film layer 20. 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. As shown in Figures 7C, 8C, and 9C, the cubic function light cone 15 includes a large end portion 31, a small end portion 32, and an optical fiber portion disposed 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 comprises a thin film whose thickness gradually decreases from the center to the edge. The thin film comprises a homogenizing film layer 10 and / or a homogenizing film layer 20. The center of the homogenizing film layer 10 is provided with a film layer center 36, and the center of the homogenizing film layer 20 is provided with a film layer center 66. The thickness and position of the thin film satisfy the following conditions: dx = -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.

[0098] 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%.

[0099] The present application is described in detail below with reference to specific embodiments.

[0100] 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.

[0101] Example 1:

[0102] This embodiment provides a linear function light cone, the production of which specifically includes the following steps:

[0103] S1, use the rod-tube combination method to combine a high-refractive-index glass rod and a low-refractive-index glass tube together, and then draw them into a single filament at 1850°C with a wire diameter of 3 mm; the drawn single filament and the light-absorbing filament (wire diameter of 3 mm) used to absorb stray light are arranged into a hexagonal shape and then drawn into a primary multifilament at 1845°C with a wire diameter of 1.3 mm; the primary multifilament is arranged into a hexagonal shape again and drawn into a secondary multifilament at 1845°C 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 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%; and La2O3 0.08%. The glass tube has a refractive index of 1.49 at a wavelength of 550 nm, and its composition by weight 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%; and 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%.

[0104] In step S2, a 26mm diameter, 50mm height taper blank is secured to the stretching rod at both ends using a stretching fixture. The stretching furnace is then controlled via the mechanical control panel to align the center of the taper blank with the center of the inner stretching furnace. This completes the preparation process. The outer furnace is preheated to 550°C. After stabilizing the temperature for 15 minutes, the inner furnace is heated at a rate of 10°C / min using a heating ring with an inner diameter of 60mm and a width of 11mm. The temperature is then raised to the taper's softening point of 800°C using a servo motor and a tension sensor. Two constant but opposite tensile forces of 500N are applied outward perpendicular to the taper's end face. The center of the taper blank gradually softens in the heated area of ​​the inner furnace and is stretched to its sides by the tension until it forms a "dumbbell" shape with a tapered center and constant dimensions at both ends. When the taper blank reaches the target taper ratio of 2:1, heating in the inner furnace is stopped and the outer furnace annealing process is initiated. The temperature is then cooled at a rate of 10°C / min until it reaches room temperature and the taper blank is removed. 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.

[0105] S3, polish the large and small end faces of the stretched light cone blank for 2 hours. After the roughness reaches 20nm, perform performance testing to ensure that the transmittance, resolution and internal defects of the light cone meet national standards.

[0106] S4: The difference between the transmittance at the axis zero and the transmittance at the boundary of the active area (D = 25.00 mm) represents the non-uniform transmittance (vignetting defect) within the tapered fiber array. Data analysis using a transmittance tester (i.e., a device for measuring the visible light transmittance and uniformity of fiber optic imaging elements, as described in patent application publication number CN111442908A), revealed a vignetting defect of 10.55% and a central transmittance of 45%. A layer of graded chromium film with a center thickness of 6 nm and an edge thickness of 1 nm was then applied to the small end face of the light cone using a rotating light cone coating device. This reduced the vignetting defect to 2.15%, and the central transmittance to 36%. The test results are shown in Figure 10.

[0107] Specifically, the assembled rotating light cone 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 rotating light cone coating device was adjusted to 10 rpm; the chamber was closed and coating was started, and the distance between the mask plate and the light cone was 1 mm.

[0108] The process of closing the chamber and starting the film deposition specifically includes the following steps: a. After closing the chamber of the film deposition 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 open the molecular pump; b. When the vacuum degree reaches 2×10-4 Pa, open the gas flowmeter and adjust the gas volume of argon and oxygen (the volume ratio of the two is 1:1) to 25sccm. Next, adjust the pressure in the chamber to 0.8Pa through the G valve. c. Open the sputtering power switch and adjust the power to 50W to start pre-sputtering. After sputtering for 5 minutes, open the baffle valve and adjust the power to 60W to start the main sputtering. The sputtering time is 60 seconds. d. After sputtering is completed, close the baffle valve, turn off the power switch, turn the gas flowmeter knob to 0, close the solenoid valve, turn off the molecular pump, and open the valve connecting to the air to balance the internal and external atmospheric pressures of the chamber. e. Open the chamber of the coating equipment and remove the rotating light cone coating device. The coating is completed, and a light cone with high uniformity and high transmittance is obtained. The light cone can be used in a charge-coupled device (CCD), image intensifier, or photomultiplier tube.

[0109] As can be seen from Figure 10, 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 mask design is basically reasonable. The transmittance at the edge is lower than 36% because the edge opening of the mask is small, making it difficult for the film layer to be deposited.

[0110] Example 2:

[0111] This embodiment provides a quadratic function light cone, the production of which specifically includes the following steps:

[0112] S1, same as Example 1.

[0113] S2, the 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 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 shape.

[0114] S3, same as Example 1.

[0115] In step S4, data was analyzed using a transmittance meter (the device for measuring the visible light transmittance and uniformity of optical fiber imaging components, as described in patent application publication number CN111442908A). The result was a vignetting defect of 14.23% and a central transmittance of 45%. A gradient chromium film with a center thickness of 8 nm and an edge thickness of 1 nm was then applied to the small end facet using a rotating light cone coating device. This reduced the vignetting defect to 2.43% and the central transmittance to 23%. The test results are shown in Figure 11.

[0116] Specifically, the assembled rotating light cone 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 rotating light cone coating device was adjusted to 10 rpm; the chamber was closed and coating was started, and the distance between the mask plate and the light cone was 1 mm.

[0117] The process of closing the chamber and starting the film deposition specifically includes the following steps: a. After closing the chamber of the film deposition 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 open the molecular pump; b. When the vacuum degree reaches 2×10 -4 Pa, open the gas flowmeter and adjust the gas flow of argon and oxygen (the volume ratio of the two is 1:1) to 25sccm. Next, adjust the pressure in the chamber to 0.8Pa through the G valve. c. Open the sputtering power switch and adjust the power to 50W to start pre-sputtering. After sputtering for 5 minutes, open the baffle valve and adjust the power to 60W to start the main sputtering. The sputtering time is 80 seconds. d. After sputtering is completed, close the baffle valve, turn off the power switch, turn the gas flowmeter knob to 0, close the solenoid valve, turn off the molecular pump, and open the valve connecting to the air to balance the internal and external atmospheric pressures of the chamber. e. Open the chamber of the coating equipment and remove the rotating light cone coating device. The coating is completed, and a light cone with high uniformity and high transmittance is obtained. The light cone can be used in a charge-coupled device (CCD), image intensifier, or photomultiplier tube.

[0118] As can be seen from FIG11 , 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%.

[0119] Example 3:

[0120] This embodiment provides a cubic function light cone, the production of which specifically includes the following steps:

[0121] S1, same as Example 1.

[0122] S2, the stretching method is the same as the quadratic function light cone stretching, the difference is that the specifications of the heating ring in the furnace of the cubic function light cone are 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.

[0123] S3, same as Example 1.

[0124] In step S4, data was analyzed using a transmittance meter (the device for measuring the visible light transmittance and uniformity of optical fiber imaging components, as described in patent application publication number CN111442908A), revealing a vignetting defect of 4.92% and a central transmittance of 45%. A gradient chromium film with a center thickness of 3 nm and an edge thickness of 1 nm was then applied to the small end face using a rotating light cone coating device. This reduced the vignetting defect to 1.81% and the central transmittance to 40%. The test results are shown in Figure 12.

[0125] Specifically, the assembled rotating light cone 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 rotating light cone coating device was adjusted to 10 rpm; the chamber was closed and coating was started, and the distance between the mask plate and the light cone was 1 mm.

[0126] The process of closing the chamber and starting the film deposition specifically includes the following steps: a. After closing the chamber of the film deposition 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 open the molecular pump; b. When the vacuum degree reaches 2×10 -4 Pa, open the gas flowmeter and adjust the gas flow of argon and oxygen (the volume ratio of the two is 1:1) to 25sccm. Next, adjust the pressure in the chamber to 0.8Pa through the G valve. c. Open the sputtering power switch and adjust the power to 50W to start pre-sputtering. After sputtering for 5 minutes, open the baffle valve and adjust the power to 60W to start the main sputtering. The sputtering time is 40 seconds. d. After sputtering is completed, close the baffle valve, turn off the power switch, turn the gas flowmeter knob to 0, close the solenoid valve, turn off the molecular pump, and open the valve connecting to the air to balance the internal and external atmospheric pressures of the chamber. e. Open the chamber of the coating equipment and remove the rotating light cone coating device. The coating is completed, and a light cone with high uniformity and high transmittance is obtained. The light cone can be used in a charge-coupled device (CCD), image intensifier, or photomultiplier tube.

[0127] As can be seen from FIG12 , 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%.

[0128] Example 4:

[0129] This embodiment provides a cubic function light cone, the production of which specifically includes the following steps:

[0130] S1, same as Example 3.

[0131] S2, same as Example 3.

[0132] S3, same as Example 3.

[0133] In S4, a rotating light cone coating device was used to deposit a gradient chromium film with a center thickness of 3 nm and an edge thickness of 1 nm on the large end face of the cubic function light cone. This reduced the vignetting defect to 1.82% and the center transmittance to 40%. The test results are shown in Figure 13.

[0134] Specifically, the assembled rotating light cone 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 rotating light cone coating device was adjusted to 10 rpm; the chamber was closed and coating was started, and the distance between the mask plate and the light cone was 1 mm.

[0135] The process of closing the chamber and starting the film deposition specifically includes the following steps: a. After closing the chamber of the film deposition 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 open the molecular pump; b. When the vacuum degree reaches 2×10 -4 Pa, open the gas flowmeter and adjust the gas flow of argon and oxygen (the volume ratio of the two is 1:1) to 25sccm. Next, adjust the pressure in the chamber to 0.8Pa through the G valve. c. Open the sputtering power switch and adjust the power to 50W to start pre-sputtering. After sputtering for 5 minutes, open the baffle valve and adjust the power to 60W to start the main sputtering. The sputtering time is 40 seconds. d. After sputtering is completed, close the baffle valve, turn off the power switch, turn the gas flowmeter knob to 0, close the solenoid valve, turn off the molecular pump, and open the valve connecting to the air to balance the internal and external atmospheric pressures of the chamber. e. Open the chamber of the coating equipment and remove the rotating light cone coating device. The coating is completed, and a light cone with high uniformity and high transmittance is obtained. The light cone can be used in a charge-coupled device (CCD), image intensifier, or photomultiplier tube.

[0136] As can be seen from FIG13 , whether the equalizing film is deposited on the large end or the small end of the cubic function light cone, the purpose of reducing the vignetting defect can be achieved.

[0137] Example 5:

[0138] This embodiment provides a cubic function light cone, the production of which specifically includes the following steps:

[0139] S1, same as Example 3.

[0140] S2, same as Example 3.

[0141] S3, same as Example 3.

[0142] In S4, a rotating light cone coating device was used to deposit a gradient chromium film with a center thickness of 1.5 nm and an edge thickness of 0.5 nm on both the large and small end faces of the cubic function light cone. This reduced vignetting to 1.78% and achieved a center transmittance of 40%. The test results are shown in Figure 14.

[0143] Specifically, the assembled rotating light cone 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 rotating light cone coating device was adjusted to 10 rpm; the chamber was closed and coating was started, and the distance between the mask plate and the light cone was 1 mm.

[0144] The process of closing the chamber and starting the film deposition specifically includes the following steps: a. After closing the chamber of the film deposition 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 open the molecular pump; b. When the vacuum degree reaches 2×10 -4 Pa, open the gas flowmeter and adjust the gas flow of argon and oxygen (the volume ratio of the two is 1:1) to 25sccm. Next, adjust the pressure in the chamber to 0.8Pa through the G valve. c. Open the sputtering power switch and adjust the power to 50W to start pre-sputtering. After sputtering for 5 minutes, open the baffle valve and adjust the power to 60W to start the main sputtering. The sputtering time is 15 seconds. d. After sputtering is completed, close the baffle valve, turn off the power switch, turn the gas flowmeter knob to 0, close the solenoid valve, turn off the molecular pump, and open the valve connecting to the air to balance the internal and external atmospheric pressures of the chamber. e. Open the chamber of the coating equipment and remove the rotating light cone coating device. The coating is completed, and a light cone with high uniformity and high transmittance is obtained. The light cone can be used in a charge-coupled device (CCD), image intensifier, or photomultiplier tube.

[0145] As can be seen from FIG14 , whether the equalizing films are deposited on both ends of the cubic function light cone respectively or are deposited on both ends simultaneously, the purpose of reducing the vignetting defect can be achieved.

[0146] Comparative Example 1:

[0147] 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 the 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 shown in Figure 15. As can be seen from Figure 15, the vignetting defect of the 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.

[0148] Comparative Example 2:

[0149] The difference between this comparative example and Example 3 is that this comparative example uses a conventional coating method (no rotary coating device, no 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 transmittance testing, the vignetting defect is reduced to 4.81%, and the central transmittance is 35%. The test results are shown in Figure 16. As can be seen from Figure 16, as the film thickness is further increased, the vignetting defect increases by 3% and the central transmittance decreases by 5% compared with Example 3. This shows that increasing the film thickness using conventional methods does not improve the vignetting defect.

[0150] 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 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 CN111442908A). 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 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.

[0151] Table 1

[0152] 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 light cone was 4.92%, the transmittance uniformity was 95.08%, and the structure was optimal. The non-uniform transmittance of the quadratic function light cone was 14.23%, the transmittance uniformity was 85.77%, and the structure was the worst. After coating, while ensuring that the average non-uniform transmittance was around 2.1%, the central transmittance of the cubic function light cone could reach 40%, while the central transmittance of the quadratic function light cone was only 23%, which also shows that the cubic function light cone structure is optimal. It can be seen from the data of Examples 3-5 that after the large end face or small end face or both of them were coated with a homogenizing film, the non-uniform transmittance could be maintained at around 1.8% and the central transmittance could reach 40%. It can be seen from the data of Comparative Examples 1-2 that after the small end face of the cubic function light cone was coated with a chromium film without using a rotary coating device, the non-uniform transmittance was almost not reduced, and the non-uniform transmittance could not be improved.

[0153] In short, coating can improve the unevenness of light transmission in the light cone by creating a uniform coating that is thick in the center, thin at the edges, and with a gradual radial thickness change. The high transmittance in the center of the light cone is combined with a thicker chrome coating to significantly reduce transmittance, while the low transmittance at the edges is combined with a thinner chrome coating to slightly reduce transmittance. This maintains a consistent transmittance across the entire light cone, thus improving unevenness.

[0154] In the specification of the present application, a large number of specific details are described. However, it is understood that the embodiments of the present application 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.

[0155] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner unless there is any contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0156] In addition, the various implementation methods of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

[0157] The above is merely a preferred embodiment of the present application and does not constitute any form of limitation to the present application. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present application still fall within the scope of the technical solution of the present application.

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: dx = -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. A method for preparing a light cone with high uniformity and high transmittance, characterized in that: The following steps are involved: Preparation of the contour structure of the tapered region; Preparation of light cone surface homogenization film.

6. The method for preparing a 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 method for preparing a 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 method for preparing a 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 method for preparing a light cone with high uniformity and high transmittance as claimed in claim 5, 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 method for preparing a light cone with high uniformity and high transmittance as claimed in claim 5, 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 1-4.

12. An image intensifier, characterized in that: The charge coupled device comprises a light cone with high uniformity and high transmittance as described in any one of claims 1-4.

13. A photomultiplier tube, characterized in that: The charge coupled device comprises a light cone with high uniformity and high transmittance as described in any one of claims 1-4.

Images