Method for manufacturing microlens array with high numerical aperture
By combining molding and optical coating and polishing technologies, high numerical aperture microlens arrays are manufactured, which solves the problem of difficult molding of high-refractive index materials in traditional methods, and achieves efficient and low-cost production.
Patent Information
- Application Number
- CN202311754555.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-19
- Publication Date
- 2025-06-20
AI Technical Summary
Traditional methods of manufacturing microlens arrays with high numerical apertures have problems such as difficult process and low yield, which are mainly due to the natural high melting point of high refractive index materials, which are difficult to directly mold.
By combining molding and optical coating and polishing, a base substrate of low melting point material is first created, then a high refractive index material is deposited on its surface, and finally a chemical solvent is used to separate the high refractive index material from the substrate to form a microlens array.
It reduces process difficulty, improves production efficiency, effectively reduces product costs, and realizes efficient manufacturing of high-numerical aperture microlens arrays.
Smart Images
Figure CN120178393A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of optical devices; and more particularly to a method for manufacturing a microlens array having a high numerical aperture. Background Art
[0002] A microlens is a small lens. The diameter of a microlens is typically between one millimeter (mm) and 10 micrometers (μm). A typical microlens includes a planar surface and a spherical convex or concave surface for refracting light. A microlens may include an aspherical lens or several optical material layers.
[0003] A microlens array can achieve functions such as focusing, imaging, beam collimation, beam transformation, wavefront sensing, and others within the field of micro-optics. Due to the small unit size and high integration degree of the microlens array, the microlens array can form many new optical systems and complete functions that traditional optical elements cannot. Microlens arrays are generally used in high-sensitivity imaging, fiber-coupled communication, laser beauty, laser processing, and detection.
[0004] Traditionally, dry etching has been used to manufacture microlens arrays having a high numerical aperture (the angular range within which a microlens can accept or emit light). High numerical aperture is relative to glass or optical plastic materials. For example, silicon has a refractive index of about 4, which is 2.5 times larger than the numerical aperture of a glass or optical plastic lens with a refractive index of 1.6. The main reason for the large relative aperture is the high refractive index of the lens material used in the microlens array. When other lens parameters are the same, the numerical aperture and the material will increase correspondingly.
[0005] Traditionally, the manufacturing of microlens arrays has been difficult and the yield has been low. This difficulty is due to the naturally high melting point of the high refractive index materials contained in the microlens array, resulting in the high refractive index materials being difficult to directly mold.
[0006] The method disclosed in the present invention enables the production of a microlens array having a high numerical aperture by combining molding, optical coating, and polishing, which reduces the process difficulty, improves the production efficiency, and effectively reduces the product cost.
[0007] The present disclosure first creates a base substrate (which is not part of the final microlens array), then creates a microlens array on top of this substrate, and then separates the two. Summary of the Invention
[0008] The present disclosure relates to a method for manufacturing a microlens array having a high numerical aperture. The present disclosure avoids the traditional schemes of etching silicon and other high refractive index materials.
[0009] The microlens array of the present disclosure can achieve functions such as beam collimation, homogenization, wavefront sensing, and high-sensitivity imaging. The microlens array of the present disclosure is generally used for high-sensitivity imaging, fiber-coupled communication, laser beauty, laser processing, and detection. The present disclosure relates to a manufacturing method of a microlens array with a high numerical aperture.
[0010] In one aspect, the process of the present disclosure first creates a base substrate (which is not part of the final microlens array). Since a low-melting-point material is selected for the base substrate, the substrate is easy to mold. Secondly, a microlens array is created on top of the substrate by depositing a high-refractive-index material on the base substrate. Finally, the microlens array is separated from the substrate.
[0011] The material for optical molding of the substrate is generally low-melting-point glass or optical plastic, and its refractive index is low (generally below 2). The high-refractive-index material has a high melting point and is difficult to directly mold. Therefore, for the substrate, a glass material with a low melting point and a low refractive index is used for molding. Then, a film with a high refractive index, such as a-Si, a-SiH, a-SiGeH, a-GeH, a-Ge, etc., is deposited on the surface of the glass or plastic material substrate. Finally, a chemical solvent is used to separate the high-refractive-index material constituting the microlens array from the substrate.
[0012] In one aspect, a method for manufacturing a microlens array is disclosed, wherein the method includes the following steps: obtaining or forming a substrate having a surface; depositing a high-refractive-index material on the surface of the substrate; and detaching the high-refractive-index material from the substrate, wherein the high-refractive-index material forms the microlens array. In this aspect, before detaching the high-refractive-index material from the substrate, the surface of the high-refractive-index material can be polished.
[0013] In this aspect, the completed microlens array can include a planar surface and a spherical convex surface or concave surface. The planar surface is the polished surface of the high-refractive-index material, and the spherical convex surface or concave surface of the high-refractive-index material is detached from the substrate.
[0014] Detaching the high-refractive-index material from the substrate can include using a chemical solvent. The chemical solvent can be selected to dissolve the substrate. In some aspects, if the substrate is plastic, the chemical solvent can be selected from the group consisting of cyclohexanone, chlorobenzene, N,N-dimethylformamide, and a toluene-acetone mixed solvent. Further, if the substrate is glass, the chemical solvent can be selected from the group consisting of benzene, toluene, xylene, acetone, chloroform, ethyl acetate, chloroform, dichloroethane, and hydrofluoric acid.
[0015] In a further aspect, the substrate may be formed by molding. The mold for forming the substrate may include a mold surface having a spherical convex or concave surface. In certain aspects, if the outer mold surface of the substrate (and the resulting substrate) has a spherical convex surface, the completed microlens array will have a spherical concave surface, and if the outer mold surface of the substrate (and the resulting substrate) has a spherical concave surface, the completed microlens array will have a spherical convex surface.
[0016] In yet a further aspect, forming the substrate by molding may include applying a certain amount of pressure and high temperature to a glass or plastic material, where the glass or plastic material then conforms to the desired shape of the microlens array present on the mold.
[0017] The high refractive index material may be deposited on the surface of the substrate by coating or plating, or more specifically by evaporation deposition, sputter coating, or ion beam sputtering. The high refractive index material may be selected from the group consisting of a-Si, a-SiH, a-SiGeH, a-GeH, and a-Ge.
[0018] In other aspects, the substrate may include a glass or optical plastic material. The refractive index of the high refractive index material may be higher than that of the substrate. Further, the melting point of the high refractive index material is higher than that of the substrate.
[0019] In another aspect, an anti-reflection (AR) coating is deposited on the surface of the substrate before depositing the high refractive index material on the surface of the substrate.
[0020] In a more specific aspect, a coating machine may be used to coat several micrometers to dozens of micrometers of amorphous silicon (a-Si), mixed amorphous silicon (a-Si:H), hydrogenated amorphous silicon germanium (a-SiGe:H), hybrid amorphous germanium (a-Ge:H), amorphous germanium (a-Ge), and other high refractive index films on the convex or concave side of the substrate. An anti-reflection (AR) coating may have been deposited on the convex or concave side of the substrate before depositing the high refractive index material on the convex or concave side of the substrate to reduce the reflectivity of the completed microlens array. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present disclosure will be better understood with reference to the following description taken in conjunction with the accompanying drawings. For purposes of illustration, certain embodiments of the present disclosure are shown in the drawings. In the drawings, the same reference numerals throughout indicate the same elements. However, it should be understood that the present invention is not limited to the exact arrangements, dimensions, and apparatus shown:
[0022] Figure 1 Illustrated is a substrate for manufacturing a microlens array having a convex curvature for manufacturing a microlens array with concave microlenses, all in accordance with one embodiment of the present disclosure;
[0023] Figure 2 illustrates a substrate having a coating thereon Figure 1 ;
[0024] Figure 3 illustrates a substrate and a coating in which the coating is polished Figure 2 ;
[0025] Figure 4 illustrates a microlens array having concave microlenses with a high numerical aperture
[0026] Figure 5 illustrates a substrate for manufacturing a microlens array, the substrate having a concave curvature for manufacturing a microlens array having convex microlenses, all in accordance with another embodiment of the present disclosure
[0027] Figure 6 illustrates a substrate having a coating thereon Figure 5 ;
[0028] Figure 7 illustrates a substrate and a coating in which the coating is polished; and Figure 6 ;
[0029] Figure 8 illustrates a microlens array having convex microlenses with a high numerical aperture DETAILED DESCRIPTION
[0030] The present disclosure relates to a method for manufacturing a microlens array having a high numerical aperture. The present disclosure avoids conventional schemes for etching silicon and other high refractive index materials
[0031] The microlens array of the present disclosure can achieve functions such as beam collimation, homogenization, wavefront sensing, and high-sensitivity imaging. The microlens array of the present disclosure is generally used for high-sensitivity imaging, fiber-coupled communication, laser beauty, laser processing, and detection. The present disclosure relates to a method for manufacturing a microlens array having a high numerical aperture
[0032] Compared with conventional machining techniques for manufacturing microlens arrays (such as micro-cutting and MEMS etching), the method of the present disclosure has the characteristics of high forming accuracy, high efficiency, good consistency, and low processing cost. The method of the present disclosure is suitable for mass production and manufacturing, and is one of the most effective methods for manufacturing optical microlens arrays
[0033] The present disclosure replaces the conventional scheme of etching silicon and other high refractive index materials by combining glass molding and optical coating polishing. The combination of glass molding and optical coating grinding and polishing can mass-produce microlens arrays with a high numerical aperture, reduce the process difficulty, improve the production efficiency, and effectively reduce the product cost
[0034] In one aspect, the process of the present disclosure first creates a base substrate (which is not part of the final microlens array); then creates a microlens array on top of the base substrate; and finally, separates the microlens array from the substrate.
[0035] In another aspect, the user starts with a mold, where the surface inside the mold has the shape of the desired microlens surface ingrained on it. At a certain amount of pressure and high temperature, a softened optical glass material (e.g., glass or plastic), which typically has a low melting point, is injected into the mold to create the substrate. After annealing, cooling, and solidifying, the substrate is removed from the mold.
[0036] Optionally, an anti-reflection (AR) film layer can be deposited (coated) on the molded microlens surface of the substrate such that the AR film layer is on the surface of the final microlens array.
[0037] Next, a high refractive index material, such as a coating of a-Si, a-SiH, a-SiGeH, a-GeH, a-Ge, is deposited on the AR film layer. If the AR film layer is not used, the coating of the high refractive index material is otherwise deposited (coated) on the molded microlens surface of the substrate. The coating of the high refractive index material can be deposited by evaporation deposition, magnetron sputtering, ion beam sputtering, or other methods. The coating processes for the AR film layer and the high refractive index material can be similar.
[0038] After drying, the optical plane of the high refractive index material is polished. Polishing generally requires rough grinding and / or fine grinding and polishing until the machined part reaches a satisfactory surface shape and dimensional accuracy.
[0039] Finally, the substrate is removed or separated from the microlens array by a chemical solvent, where a specific chemical solvent is used to dissolve the substrate (whether glass or plastic), leaving only the processed microlens array film with a high numerical aperture.
[0040] A high numerical aperture is related to glass or optical plastic materials. For example, silicon has a refractive index of about 4, which is 2.5 times larger than the numerical aperture of a glass or optical plastic lens with a refractive index of 1.6.
[0041] The main reason for the large relative aperture is the high refractive index of the lens material used in this way. When other lens parameters are the same, the numerical aperture and the material will increase accordingly.
[0042] As Figure 1 and Figure 5As shown, in the first step, a substrate 102 is provided or fabricated. The substrate 102 includes materials having a low melting point and a low refractive index, such as glass and plastics (e.g., optically transparent plastics). The substrate 102 may have a refractive index below two. Further, the substrate 102 preferably has a relatively low melting point. A low melting point material generally refers to a material with a softening temperature below 600 °C. Other materials for the substrate 102 are also possible. Preferably, the material will have a low melting point so that molding is easy to perform and will be compatible with the high refractive index material subsequently coated on top of it.
[0043] The substrate 102 can be fabricated by molding. Fabrication by glass or plastic lens molding means applying a certain amount of pressure to the substrate 102 material at a high temperature in order to copy the desired, intended shape of the microlenses present on the mold surface onto the surface of the softened substrate 102 material being molded.
[0044] After annealing, cooling, and solidification, a microlens array can be processed on the surface of the substrate 102 material (e.g., on the surface of an optical glass material).
[0045] In Figure 1 , the surface of the substrate 102 for fabricating the microlens array is shown to have a convex spherical structure. This will create a microlens array (microlenses) with concave spherical shapes. However, in addition to convex spherical and / or concave spherical shapes, other desired shapes can also be adapted, such as holes, pillars, etc.
[0046] In Figure 5 , the surface of the substrate 102 for fabricating the microlens array is shown to have a concave spherical structure. This will create a microlens array with convex microlenses.
[0047] Next, as shown in Figure 2 and Figure 6 , a high refractive index material 104 is coated on the surface of the substrate 102. Exemplary high refractive index materials 104 having a high refractive index include a-Si, a-SiH, a-SiGeH, a-GeH, or a-Ge (typically from a few microns to dozens of microns). These high refractive index materials 104 are deposited on the surface of the substrate 102, thereby creating Figure 2 the convex spherical shape shown in Figure 6 or the concave spherical shape shown in Figure 2 The convex spherical shape shown in Figure 4 will result in a concave spherical shape on the completed microlens array (see Figure 6 ), and the concave spherical shape shown in Figure 8 will result in a convex spherical shape on the completed microlens array (see
[0048] ). The deposition of the high refractive index material 104 can employ optical coating methods (e.g., evaporation deposition, magnetron sputtering, ion beam sputtering, and other methods).
[0048] The high refractive index material 104 can be selected based on the applied wavelength and / or the desired array transmittance. For example, tantalum pentoxide (TaO5) and silicon nitride (Si3N4) can be used in the visible light range (400 nm - 700 nm) and can be applied to visible light illumination and imaging. Si and a-Si, a-SiH, a-SiGeH, a-GeH, and a-Ge can be used at near-infrared and infrared wavelengths for applications such as focusing or collimation in optical communication systems and can be applied to near-infrared and infrared imaging.
[0049] Optionally, as Figure 3 and Figure 7 shown, before coating the surface of the substrate 102 with the high refractive index material 104, an anti-reflection (AR) coating 106 can be disposed on the surface of the substrate 102 and thus finally on the outer surface of the high refractive index material 104 of the microlens array to reduce the reflectivity of the microlens array.
[0050] The use and selection of the AR coating 106 can be related to the refractive index of the incident medium, the refractive index of the exit medium, the incident wavelength, and the incident angle. For example, when applied to the communication field, a wavelength of 1550 nm can be used. The high refractive index material 104 can be polysilicon with a refractive index of 3.48, and the substrate 102 can be low-melting glass with a refractive index of 1.45. The incident angle range can be 0° - 20°. In view of this, the designed AR coating 106 can be a single-layer Ta2O5 with a thickness of 182.6 nm.
[0051] Figure 3 and Figure 7 Also illustrated is the polishing process of the microlens array. The polishing process of an optical plane generally requires rough grinding, fine grinding, and polishing to continuously improve the surface accuracy of the machined part and reduce the surface roughness. Optical surface grinding uses micron-sized abrasive particles with a hardness higher than that of the material to be processed. Under the action of a hard grinding disk, micro-cutting and rolling effects are generated to remove a small amount of material from the surface to be processed, reduce the machining affected layer, reduce the surface roughness, and achieve the target values of the workpiece shape and size accuracy.
[0052] Next, as Figure 4 and Figure 8 shown, the high refractive index material 104 is detached from the substrate 102. Thereafter, the high refractive index material 104 forms a microlens array. Figure 4 and Figure 8 Illustrated is the microlens array detached from the substrate 102.
[0053] The substrate 102 can be removed, separated or dissolved from the high refractive index material 104 using a chemical solvent. If the substrate 102 is plastic, the entire product can be placed in a solvent configured to dissolve plastic (e.g., cyclohexanone, chlorobenzene, N,N-dimethylformamide or a toluene-acetone mixture). If the substrate 102 is glass, the entire product can be placed in a solvent configured to dissolve glass (e.g., benzene, toluene, xylene, acetone, chloroform, ethyl acetate, chloroform, dichloroethane and hydrofluoric acid or other solvents).
[0054] From the foregoing specification, these and other advantages of the present invention will be apparent to those skilled in the art. Accordingly, those skilled in the art will recognize that changes or modifications can be made to the above-described embodiments without departing from the broad inventive concept of the present invention. Therefore, it should be understood that the present invention is not limited to the specific embodiments described herein, but is intended to cover all changes and modifications within the scope and spirit of the present invention as set forth in the claims.
Claims
1. A method for manufacturing a microlens array, the method comprising the following steps: Obtain or form a substrate having a surface; Deposit a high refractive index material on the surface of the substrate; And Detach the high refractive index material from the substrate, wherein the high refractive index material forms the microlens array.
2. The method according to claim 1, wherein before detaching the high refractive index material from the substrate, further comprising the step of polishing the surface of the high refractive index material.
3. The method according to claim 2, wherein the completed microlens array includes a planar surface and a spherical convex surface or a spherical concave surface, the planar surface being the polished surface of the high refractive index material, and the spherical convex surface or the spherical concave surface of the high refractive index material being detached from the substrate.
4. The method according to claim 2, wherein detaching the high refractive index material from the substrate includes using a chemical solvent.
5. The method according to claim 4, wherein the chemical solvent is selected to dissolve the substrate.
6. The method according to claim 4, wherein if the substrate is plastic, the chemical solvent is selected from the group consisting of cyclohexanone, chlorobenzene, di-N-methylformamide, and a mixed solvent of toluene and acetone, and wherein if the substrate is glass, the chemical solvent is selected from the group consisting of benzene, toluene, xylene, acetone, chloroform, ethyl acetate, chloroform, dichloroethane, and hydrofluoric acid.
7. The method according to claim 1, wherein the substrate is formed by molding.
8. The method according to claim 7, wherein the mold for forming the substrate includes an external mold surface having a spherical convex surface or a spherical concave surface.
9. The method according to claim 8, wherein if the external mold surface of the substrate has a spherical convex surface, the completed microlens array will have a spherical concave surface, and if the external mold surface of the substrate has a spherical concave surface, the completed microlens array will have a spherical convex surface.
10. The method according to claim 7, wherein forming the substrate by molding includes applying a certain amount of pressure and high temperature to a glass or plastic material, wherein the glass or plastic is thereby conformed to the expected shape of the microlens array present on the mold.
11. The method according to claim 1, wherein before depositing the high refractive index material on the surface of the substrate, further comprising the step of depositing an anti-reflection (AR) coating on the surface of the substrate.
12. The method according to claim 1, wherein the high refractive index material is deposited on the surface of the substrate by evaporation deposition, sputter coating, or ion beam sputtering.
13. The method according to claim 1, wherein the high refractive index material is deposited on the surface of the substrate by coating or plating.
14. The method according to claim 1, wherein the high refractive index material is selected from the group consisting of a-Si, a-SiH, a-SiGeH, a-GeH, and a-Ge.
15. The method according to claim 1, wherein the substrate comprises glass or an optical plastic material.
16. The method according to claim 1, wherein the refractive index of the high refractive index material is higher than the refractive index of the substrate.
17. The method according to claim 1, wherein the melting point of the high refractive index material is higher than the melting point of the substrate.
18. A method for manufacturing a microlens array, the method comprising the following steps: Form a substrate having a desired microlens array surface by molding, wherein a certain amount of pressure and high temperature are applied to a glass or plastic material, and wherein the glass or plastic material is thereby conformed to the desired microlens array surface of the mold; Deposit a high refractive index material on the desired microlens array surface of the substrate, wherein the melting point of the high refractive index material is higher than the melting point of the substrate; Polish the surface of the high refractive index material; And Detach the high refractive index material from the substrate using a chemical solvent, wherein the high refractive index material forms the microlens array.
19. The method according to claim 18, wherein the completed microlens array comprises a planar surface and a spherical convex or concave surface, the planar surface being a polished surface of the high refractive index material, and the spherical convex or concave surface of the high refractive index material being detached from the substrate.
20. A method for manufacturing a microlens array, the method comprising the following steps: Provide a mold having a microlens array surface; Soften a glass or optical plastic substrate material and place the substrate material in the mold to form a substrate having the microlens array surface; Remove the substrate from the mold; Coat a high refractive index material on the microlens array surface of the substrate, Polish the surface of the high refractive index material, wherein the polished surface is opposite to the surface created by the microlens array surface of the substrate, and wherein the polished surface of the high refractive index material is flat; And Detach the high refractive index material from the substrate by dissolving the substrate in a chemical solvent, wherein the detached high refractive index material is the microlens array; Wherein if the microlens array surface of the mold has a spherical convex surface, the completed microlens array will have a spherical concave surface, and if the microlens array surface of the mold has a spherical concave surface, the completed microlens array will have a spherical convex surface.