A method for connecting an optical fiber and a microlens

Abstract

The present invention discloses a method for connecting an optical fiber and a microlens, comprising the following steps: S100: preparing a conical microlens array female template; S200: performing the first mold turning to form a conical microlens array male template; S300: performing a smoothing and metallization treatment to form a combined male template with a spherical top and a conical bottom; S400: performing the second mold turning to form a combined female template with a spherical top and a conical bottom; S500: injecting a lens forming material to obtain a combined microlens with a spherical top and a conical bottom; S600: preparing an optical fiber beam combiner; S700: connecting the optical fiber with the combined microlens with a spherical top and a conical bottom; S800: demolding. The present invention can quickly and batch process microlenses on the end faces of optical fibers.

Description

Technical Field

[0001] The present invention belongs to the field of optical imaging, and particularly relates to a method for connecting an optical fiber and a microlens. Background Art

[0002] Using an array combination of multiple ordinary optical fibers or a single imaging optical fiber for imaging has always been a hot issue in the field of microscopic optical imaging. Since silica optical fibers have poor anti-bending ability and are easily broken, they are not suitable for optical imaging in complex environments. Correspondingly, although plastic optical fibers have good anti-bending ability, their numerical aperture is usually 0.5, and the corresponding field of view angle is a relatively large 60°. Therefore, when imaging with an optical fiber array, there will be too much repetition of the optical information conducted by adjacent optical fibers, resulting in a reduction in the effective information volume. Adding a microlens at the end face of the optical fiber is an effective method to reduce the field of view angle. For a single imaging optical fiber, if there is no microlens at its end face, the image conducted by it will be a discrete image, which is ultimately difficult to identify. Therefore, it is also extremely necessary to add a microlens at the end face of the imaging optical fiber for focusing.

[0003] Most of the existing literature still focuses on the processing methods of end-face microlenses for silica optical fibers (such as: Wang Tianhu. Research and Development of a Special Spherical Output Optical Fiber [D]. Henan University, 2006; Jiang Rongzhi, Chai Xiongliang, Zhang Xiaodong. A Method for Making a Spherical Lens Optical Fiber: CN101872037A [P]. 2010, etc.). Most of these processing methods use the hot melting method. However, since the melting point of silica optical fibers (about 1800 °C) is much higher than that of plastic optical fibers (about 120 °C), if the hot melting method corresponding to an optical fiber fusion splicer is used to process plastic optical fibers, it is extremely easy to directly melt the plastic optical fibers completely. Although Liu et al. explored a new method for thermally connecting plastic optical fibers and microlenses (Liu F, Yang Q, Bian H, et al. Artificial compound eye-tipped optical fiber for wide field illumination [J]. Optics Letters, 2019, 44(24): 5961-5964.), this method has high requirements for temperature and pressure control, and can only be processed one by one, with general processing efficiency. Summary of the Invention

[0004] Aiming at the defects of the prior art, the present invention provides a method for connecting an optical fiber and a microlens.

[0005] A method for connecting an optical fiber and a microlens, comprising the following steps: S100: preparing a conical microlens array negative template; S200: performing a first mold flipping using the conical microlens array negative template to form a conical microlens array positive template; S300: performing a smoothing and metallization treatment on the conical microlens array positive template to form a combined positive template with a spherical top and a conical bottom; S400: performing a second mold flipping using the combined positive template with a spherical top and a conical bottom to form a combined negative template with a spherical top and a conical bottom; S500: injecting a lens forming material into the combined negative template with a spherical top and a conical bottom to obtain a combined microlens with a spherical top and a conical bottom; S600: preparing an optical fiber bundle concentrator corresponding to the combined negative template with a spherical top and a conical bottom; S700: connecting the optical fiber and the combined microlens with a spherical top and a conical bottom through the optical fiber bundle concentrator; S800: demolding.

[0006] Optionally, in step S100, a protruding positioning frame is provided on the conical microlens array negative template; in step S200, a molding material is poured onto the surface of the microlens array positive template, cured, and the cured molding material is peeled off to complete the first mold flipping; the molding material is PDMS; in step S400, the combined negative template with a spherical top and a conical bottom is made of PDMS; in step S400, the combined negative template with a spherical top and a conical bottom has a plurality of concave holes with a spherical top and a conical bottom; in step S500, the microlens forming material is a UV-curing epoxy resin adhesive; in step S500, the obtained combined microlens with a spherical top and a conical bottom is in a liquid state; in step S600, the optical fiber bundle concentrator has a plurality of through holes, and the positions of the through holes correspond one-to-one to the positions of the concave holes with a spherical top and a conical bottom; in step S700, the optical fiber is passed through the through holes of the optical fiber bundle concentrator to contact the liquid microlens in the combined negative template, and a UV lamp is turned on for irradiation to cure the liquid microlens, so that the microlens is connected to the optical fiber.

[0007] The beneficial effects of the present invention: The present invention will get rid of the traditional hot melting method, and various-shaped microlenses can be processed on any optical fiber end face. This processing method has no special requirements for pressure and temperature, and can quickly and batch process microlenses on the optical fiber end face. It can process various microlens shapes, and this method can be applied in the fields of quartz, plastic, and special imaging optical fibers. The proposed method is of great significance for the improvement of optical fiber imaging and microscopic imaging technologies. Description of the Drawings

[0008] Figure 1 Schematic diagram of the connection between lenses of different shapes and optical fibers;

[0009] Figure 2 Conical microlens array negative template;

[0010] Figure 3 First mold flipping process;

[0011] Figure 4 is a conical microlens array male template;

[0012] Figure 5 is a conical microlens array male template after surface smoothing and metallization treatment;

[0013] Figure 6 is a partial side view of the conical microlens array male template after surface smoothing and metallization treatment;

[0014] Figure 7 is the second mold - turning process;

[0015] Figure 8 is a combined - shape female template with a spherical top and a conical bottom;

[0016] Figure 9 is a partial cross - sectional view of the combined - shape female template with a spherical top and a conical bottom;

[0017] Figure 10 is a schematic diagram of injecting lens - forming material using a micro - syringe;

[0018] Figure 11 is an optical - fiber beam combiner;

[0019] Figure 12 is a schematic diagram of the connection between an optical fiber and a microlens;

[0020] Explanation of the reference numerals in the figure: conical concave hole 1, positioning frame 2 of the lens array template, conical protrusion 3, positioning frame 4, combined - shape concave hole with a spherical top and a conical bottom 5, positioning frame 6, micro - syringe 7, microlens 8, through - hole 9, cross - positioning hole 10 of the optical - fiber beam combiner, optical fiber 11; Figure 12 The dashed arrow in represents UV light. Specific Embodiments

[0021] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings, so that the above - mentioned and other objects, features, and advantages of the present invention will be clearer. The same reference numerals indicate the same parts in all the drawings. The drawings are not deliberately drawn to scale, and the focus is on showing the gist of the present invention.

[0022] In the present invention, the microlens can have a variety of different shapes. For example, Figure 1 as shown, it can be a simple single - shape lens such as a hemispherical or conical shape, or it can be a combined - shape such as a spherical - top - and - conical - bottom shape. These lenses with different shapes can all be connected to the optical fiber with reference to the method introduced in the present invention.

[0023] Compared with a single-shaped lens, the combined-shaped lens has more excellent optical properties. It can reduce the acceptance angle of the optical fiber, increase the effective optical information amount per unit area, increase the effective optical information amount of a single optical fiber, and ultimately improve the imaging resolution when the fiber array is imaging, and ensure that the acceptance angles at different positions of the fiber microlens are the same. Since the combined-shaped lens with a cone bottom and a spherical top is more difficult to process and form than a single-shaped lens, the present invention focuses on a detailed introduction to the processing process of the combined-shaped lens.

[0024] This embodiment introduces the connection process between the combined-shaped lens and the optical fiber. Refer to Figures 2 to 12 , the present invention takes a plastic optical fiber (for example, a plastic optical fiber with a diameter of 0.25 mm) and a combined-shaped microlens as an example for elaboration.

[0025] S100: Prepare a negative template for a conical microlens array.

[0026] Specifically, a negative template for a microlens array as shown in Figure 2 can be designed by using 3D design software, where the conical part 1 is recessed into the template plane, and the size of a single conical part is in the micron order. The cross-shaped structure at the four corners is the positioning frame 2, and this part protrudes from the plane. The microlens array template is processed by using ultra-high-precision 3D printing technology.

[0027] S200: Use the negative template of the conical microlens array for the first mold flipping to form a positive template of the conical microlens array.

[0028] For example, the negative template obtained in step S100 can be placed in a box body, and a molding material, such as resin, etc., is injected into the box body. Preferably, polydimethylsiloxane (PDMS) is injected. The molding material fills the conical part 1 and covers the positioning frame 2, and the covering thickness is at least 1 mm higher than the top of the positioning frame 2. After curing treatment, the box body is removed to obtain an overall as shown in Figure 3 , and then the molded part is separated from the negative template (the first mold flipping), so as to obtain a positive template as shown in Figure 4 that matches the negative template of the conical microlens array. Wherein the conical part 3 protrudes from the template plane, and the positioning frames 4 at the four corners are recessed into the template plane.

[0029] Specifically, the PDMS curing agent and the prepolymer can be mixed in a ratio of 1:10, and after being fully stirred, the mixture is placed in a centrifuge and centrifuged at 1400 rpm for 2 minutes to remove air bubbles; then the mixture is poured onto the surface of the microlens array negative template, and the PDMS mixture and the microlens array negative template are placed in a vacuum pump to evacuate for 3 h; then, it is heated at 85 °C for 45 minutes to cure the mixture; the cured mixture is peeled off to complete the first mold flipping.

[0030] S300: Smooth and metallize the male template of the conical microlens array to form a male template with a combined shape of a cone bottom and a spherical top.

[0031] Smooth and metallize the surface of the male template obtained in step S200. The processed PDMS mold is as Figure 5 shown, where the partial side view is as Figure 6 shown. It should be noted that in Figure 6 , the middle horizontal line in the combined shape of the cone bottom and the spherical top only indicates the connection between the cone bottom and the spherical top. In the actual processing result, there is no such line and the curvature change from the cone bottom to the spherical top is continuous. At this time, the original conical part 3 has become a combined shape of a cone bottom and a spherical top.

[0032] S400: Use the male template with a combined shape of a cone bottom and a spherical top for the second replication to form a female template with a combined shape of a cone bottom and a spherical top.

[0033] In this step, contrary to the first replication, place the male template with a combined shape of a cone bottom and a spherical top obtained in step S300 into the box body, inject a molding material, such as resin, etc., preferably inject polydimethylsiloxane (PDMS). After curing treatment, remove the box body to obtain the whole as Figure 7 shown. Then separate the molded part from the male template with a combined shape of a cone bottom and a spherical top (the second replication) to obtain the PDMS mold as Figure 8 shown, where the cone bottom and spherical top part is recessed into the plane to form a cone bottom and spherical top concave hole 5, that is, a female template with a combined shape of a cone bottom and a spherical top. The positioning frame 6 protrudes from the plane, and the partial side view is as Figure 9 shown. Similar to Figure 6 , in Figure 9 , the middle horizontal line in the combined shape of the cone bottom and the spherical top only indicates the connection between the cone bottom and the spherical top. In the actual processing result, there is no such line and the curvature change from the cone bottom to the spherical top is continuous.

[0034] S500: Pour a lens molding material into the female template with a combined shape of a cone bottom and a spherical top to obtain a microlens with a combined shape of a cone bottom and a spherical top.

[0035] Specifically, the material used for the microlens can be a UV-curable epoxy resin glue of the NOA series. This series of glues is in a liquid state when not exposed to UV light, and will quickly cure and become transparent after being exposed to UV light. The refractive index range of this series of glues is relatively wide, and a specific glue model that matches the refractive index of the corresponding optical fiber can be selected.

[0036] As Figure 10As shown, a micro syringe 7 (for example, a syringe with a specification of 0.5 μl can be selected) is used to drop the same volume of NOA glue into each concave hole of the negative template. After standing for a period of time, each concave hole of the mold will have the same volume of NOA glue, and the shape is determined by the cone-bottom spherical-top concave hole 5, so as to obtain a cone-bottom spherical-top combined micro lens. It should be particularly noted that in order to ensure good connection between the subsequent micro lens and the optical fiber, the micro lens 8 composed of NOA glue is still in a liquid state at this time.

[0037] S600: Prepare an optical fiber bundle concentrator corresponding to the cone-bottom spherical-top combined negative template.

[0038] Using 3D design software to design an optical fiber bundle concentrator as shown in Figure 11 For example, the optical fiber bundle concentrator can be entirely made of resin, and it has a number of through holes 9, where the positions of the through holes 9 correspond one by one to the positions of the cone-bottom spherical-top concave holes 5. The designed size of the through hole 9 is 0.28 mm, and this size is slightly larger than the optical fiber diameter after considering the processing error of the ultra-high-precision 3D printing technology (±0.025 mm). Therefore, if no external force is applied, the optical fiber 11 will remain stationary after being inserted into the through hole 9, and it will move slowly with a little external force, which is suitable for controlling the optical fiber during the adhesion process between the optical fiber 11 and the NOA glue. At the same time, since the diameter of the through hole 9 is extremely close to the optical fiber diameter, after the optical fiber 11 passes through the through hole 9, due to the limitation of the through hole diameter, it will maintain a high degree of collimation, thereby ensuring the coaxiality of the connection between the optical fiber 11 and the micro lens 8. There are through cross positioning holes 10 at the four corners, and their positions and sizes are the same as those of the positioning frame 6.

[0039] S700: Connect the optical fiber to the cone-bottom spherical-top combined micro lens through the optical fiber bundle concentrator.

[0040] Specifically, place the optical fiber bundle concentrator on the combined negative template, align the through cross positioning holes 10 on the optical fiber bundle concentrator with the protruding positioning frame 6 on the cone-bottom spherical-top combined negative template, so as to align the optical fiber bundle concentrator with the PDMS combined negative template. After alignment, the alignment effect can be checked using a microscope and fine-tuned. At this time, the through holes 9 of the optical fiber bundle concentrator should correspond one by one to the cone-bottom spherical-top concave holes 5. During this process, contact between the surface of the optical fiber bundle concentrator and the surface of the PDMS mold should be avoided to prevent the NOA glue from blocking the through holes 9.

[0041] As shown in Figure 12 Then, insert the optical fibers 11 one by one through the through holes 9 of the optical fiber bundle concentrator into the concave holes 5 of the combined negative template to make them contact the liquid micro lens 8 (NOA glue). Turn on the UV lamp and irradiate the NOA glue from the side for 2 minutes to cure it. At this time, the NOA glue is already connected to the optical fiber, and the shape of the cured NOA glue is still cone-bottom spherical-top.

[0042] S800: Demold.

[0043] Remove the fiber optic beam combiner from the other end of the optical fiber. At this time, the optical fibers are still inserted into the concave holes 5 of the combined female template one by one. Since PDMS is permeable to gases and oxygen inhibits the free radical polymerization of the liquid NOA glue, when the center of the NOA glue has solidified, there is still an extremely thin layer of glue near the PDMS surface that has not solidified (Lei L, Wang N, Zhang X M, et al. Optofluidic planar reactors for photocatalytic water treatment using solar energy[J]. Biomicrofluidics, 2010, 4(4): 043004.). This uncured layer of glue ensures that the combination of the microlens and the optical fiber can be directly pulled off from the PDMS mold. At this time, the microlens with a specific shape and the optical fiber have been connected together.

[0044] Furthermore, if the shape and size of the required microlens are different from those in the embodiments of the present invention, only the shape and size of the concave holes of the microlens array template need to be changed, and other steps remain unchanged.

[0045] Using the present invention, microlenses can be processed on the surfaces of all optical fibers, such as quartz optical fibers, plastic optical fibers, special imaging optical fibers, etc.; there are no special requirements for the shape of the microlenses, and the processing of various microlenses can be satisfied, such as spherical, conical, etc.; batch processing can be carried out, greatly reducing the processing time; expensive processing equipment is not required, and the cost is low.

[0046] Many specific details have been set forth in the above description to facilitate a full understanding of the present invention. However, the above description is only the preferred embodiments of the present invention, and the present invention can be implemented in many other ways different from those described herein. Therefore, the present invention is not limited by the specific implementations disclosed above. At the same time, any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the protection of the technical solution of the present invention.

Claims

1. A method for connecting an optical fiber and a microlens, characterized in that, It includes the following steps: S100: Prepare a conical microlens array negative template; S200: Perform the first mold replication using the conical microlens array negative template to form a conical microlens array positive template; wherein, pour the molding material onto the surface of the microlens array negative template, cure it, and peel off the cured molding material to complete the first mold replication. The molding material is PDMS; S300: Smooth and metallize the conical microlens array positive template to form a combined positive template with a spherical top and a conical bottom; S400: Perform the second mold replication using the combined positive template with a spherical top and a conical bottom to form a combined negative template with a spherical top and a conical bottom; S500: Pour the lens molding material into the combined negative template with a spherical top and a conical bottom to obtain a combined microlens with a spherical top and a conical bottom. The microlens molding material is UV-curable epoxy resin glue; S600: Prepare an optical fiber bundle concentrator corresponding to the combined negative template with a spherical top and a conical bottom; S700: Connect the optical fiber to the combined microlens with a spherical top and a conical bottom through the optical fiber bundle concentrator; S800: Demold.

2. The connection method according to claim 1, characterized in that, In step S100, a protruding positioning frame is provided on the conical microlens array negative template.

3. The connection method according to claim 1, characterized in that In step S400, the combined negative template with a spherical top and a conical bottom is made of PDMS.

4. The connection method according to claim 1, characterized in that, In step S400, the combined negative template with a spherical top and a conical bottom has a plurality of concave holes with a spherical top and a conical bottom.

5. The connection method according to claim 1, wherein In step S500, the obtained combined microlens with a spherical top and a conical bottom is in a liquid state.

6. The connection method according to claim 1, characterized in that, In step S600, the optical fiber bundle concentrator has a plurality of through holes, and the positions of the through holes correspond one-to-one to the positions of the concave holes with a spherical top and a conical bottom.

7. The connection method according to claim 6, wherein In step S700, pass the optical fiber through the through holes of the optical fiber bundle concentrator to contact the liquid microlens in the combined negative template, turn on the UV lamp, and irradiate to cure the liquid microlens, so that the microlens is connected to the optical fiber.

Images