Additive manufacturing method of an optical element and optical element

Abstract

The additive manufacturing method of the optical element provided in the application comprises the following steps: calculating the structure parameters of an axial gradient refractive index lens; establishing a UG three-dimensional model according to the structure parameters; adopting the forming slurry to perform light curing forming on the UG three-dimensional model; performing debinding treatment on the UG three-dimensional model after the light curing forming; performing sintering treatment on the green body after the debinding; and cleaning the sintered green body to obtain the lens with variable refractive index. The additive manufacturing method of the optical element provided in the application realizes the processing and manufacturing of the variable refractive index lens through DLP light curing 3D printing, improves the processing speed under the premise of ensuring the processing precision, and has the advantages of fast forming speed, small feature size and macro-micro cross-scale forming capability.

Description

Technical Field

[0001] This invention belongs to the field of optical technology, specifically relating to an additive manufacturing method for optical elements and optical elements. Background Technology

[0002] Variable refractive index optical devices, such as gradient refractive index lenses, are a class of optical devices that achieve various optical functions primarily through the non-uniform distribution of the refractive index of the medium. They are characterized by small size, light weight, flat end face, ease of processing, easy adjustment and alignment, easy coupling and assembly, and high coupling efficiency. They are widely used in medical, industrial diagnostics, fiber optic communication, microlens grids, optical instruments, missile-borne, spaceborne, intelligence gathering, and reconnaissance fields.

[0003] The design of general optical systems is primarily based on uniform refractive index lenses. To improve the imaging quality of the system, it is necessary to change the lens material, radius, or spacing to eliminate various aberrations. For a system to achieve sharp imaging, a combination of many lenses or lens groups is often required to ensure the imaging freedom of the optical system. If the system design is complex, multiple lens combinations will be used, and aberration correction must be considered for all these lenses, increasing the weight and size of the optical instrument and raising design costs. Gradient refractive index lenses can perfectly solve these problems. Utilizing the specific gradient refractive index distribution of the medium in the device, beam splitting, focusing, collimation, and coupling functions can be achieved. By controlling the coefficients of each order of the refractive index distribution, spherical aberration, field curvature, and chromatic aberration can also be effectively corrected. Therefore, using variable refractive index lenses in the objective lens design of telescopes and cameras can improve image quality while simplifying the structure, reducing size, and lightening weight. Gradient refractive index lenses can be divided into axial gradient refractive index lenses, radial gradient refractive index lenses, and spherically symmetric gradient refractive index lenses. A layered gradient refractive index lens is equivalent to a cylindrical mirror and can serve as a one-dimensional magnification optical element; an axially gradient refractive index spherical surface is equivalent to the aspherical effect of a regular lens in correcting aberrations; a weakly radially gradient refractive index spherical surface also has a similar effect to an aspherical surface; a simple axial plano-convex gradient refractive index lens can achieve sharp imaging; a two-lens gradient refractive index system can achieve the same image quality as a six-element double-Gaussian camera lens. From these characteristics of gradient refractive index, it can be seen that gradient refractive index lenses can be applied in the design of optical systems to reduce the number of optical system components and simplify the manufacturing process. Gradient refractive index lenses not only have broad application prospects in optical systems for micro-optical instruments and communications, but also point the way for optical design engineers to develop optical systems towards lightweight, miniaturized, high-quality, and easy-to-assemble designs. Currently, the most commonly used fabrication method is ion exchange. Ion exchange is usually carried out below the softening point of glass, and the exchange process typically takes tens to hundreds of hours, consuming a lot of energy and having limited depth, making it difficult to fabricate large-sized gradient refractive index optical elements. Summary of the Invention

[0004] Therefore, it is necessary to provide an additive manufacturing method for optical components that has fast forming speed, small feature size, and macro-micro scale forming capability.

[0005] To solve the above problems, the present invention adopts the following technical solution:

[0006] An additive manufacturing method for an optical element includes the following steps:

[0007] Calculate the structural parameters of an axially gradient refractive index lens, including the lens radius and thickness parameters.

[0008] A UG 3D model is established based on the structural parameters;

[0009] Preparation of molding slurry;

[0010] The UG 3D model is photopolymerized using the molding slurry.

[0011] Degreasing treatment is performed on the UG 3D model after photopolymerization molding;

[0012] The degreased green body is then sintered.

[0013] After cleaning the sintered blank, a lens with variable refractive index is obtained.

[0014] In some embodiments, the step of calculating the structural parameters of the axially gradient refractive index lens specifically includes the following steps:

[0015] The refractive index distribution of an axially gradient refractive index material can be expressed as:

[0016] n=n(Z=N 00 +N 01 Z+N 02 Z 2 +...

[0017] In the formula N 00 N 01 and N 02 These are the coefficients of the constant term, the linear term, and the quadratic term, respectively.

[0018] The formula for the optical power of a thin lens with an axially gradient refractive index in air is:

[0019] Φ=(n0-1)c1-(n T -1)c2

[0020] In the formula, n0 is the refractive index on the optical axis (equal to N). 00 ), n Tc1 and c2 are the maximum refractive index along the optical axis and the curvatures of the surfaces of the refractive index lens, respectively.

[0021] The radius and thickness parameters of the gradient refractive index lens are obtained based on the refractive index distribution of the axial gradient refractive index material and the optical power of the axial gradient refractive index thin lens in air.

[0022] In some embodiments, the step of preparing the molding slurry specifically includes the following steps:

[0023] Hydroxyethyl methacrylate, polyethylene glycol diacrylate, and diethylene glycol dibenzoate were mixed and ultrasonically stirred to obtain a homogeneous resin premix.

[0024] Sapphire is added to the resin premix, and light absorber and stabilizer are added at the same time for high-speed mixing to obtain the first slurry;

[0025] AlON was added to the resin premix, and a light absorber and a stabilizer were added simultaneously for high-speed mixing to obtain a second slurry.

[0026] Spinel is added to the resin premix, and light absorber and stabilizer are added at the same time for high-speed mixing to obtain a third slurry;

[0027] Polyimide was added to the resin premix, and light absorber and stabilizer were added simultaneously for high-speed mixing to obtain a fourth slurry;

[0028] A photoinitiator is added to the first slurry, the second slurry, the third slurry, and the fourth slurry, and the mixture is stirred evenly to obtain the molding slurry.

[0029] In some embodiments, the light absorber is Sudan Red G, the stabilizer is p-hydroxyanisole, and the photoinitiator is Irgacure 819.

[0030] In some embodiments, the step of curing the UG 3D model using the molding slurry specifically includes the following steps:

[0031] Based on the empirical formula of photopolymer additive manufacturing Calculate the exposure times of the first slurry, the second slurry, the third slurry, and the fourth slurry;

[0032] According to the exposure time, the first slurry is used to photocur the UG 3D model. After curing, the UG 3D model is cleaned and dried to remove the first slurry remaining on the UG 3D model.

[0033] Repeat the above steps, using the second slurry, the third slurry, and the fourth slurry to perform photocuring on the UG 3D model.

[0034] In some embodiments, the degreasing process of the UG 3D model after photopolymerization specifically includes the following steps:

[0035] The UG 3D model after photopolymerization is heated from room temperature to 100-110 degrees Celsius at a heating rate of 2-3℃ / mm, then heated to 160-170℃ at a heating rate of 0.5-0.8℃ / min, and held at 160-170℃ for 5 hours to allow some organic matter to vaporize and be discharged. Then, the temperature is increased to 1000℃ at a heating rate of 2℃ / mm and held at 1000℃ for 2 hours to complete the degreasing process.

[0036] In some embodiments, the step of sintering the degreased green body specifically includes the following steps:

[0037] The billet is placed in a sealed container filled with nitrogen gas, and heated to 1050-1100℃ at a heating rate of 3-4℃ / min, then heated to 1250-1300℃ at a heating rate of 1-1.5℃ / min, and held at 1250-1300℃ for 3 hours and cooled with the furnace.

[0038] In some embodiments, the entire sintering process is carried out at a pressure of <1 mbar.

[0039] In addition, the present invention also provides an optical element prepared by the additive manufacturing method of the optical element.

[0040] Compared to existing technologies, the additive manufacturing method for optical elements provided in this application calculates the structural parameters of an axial gradient refractive index lens, establishes a UG three-dimensional model based on the structural parameters, uses the molding slurry to perform photopolymerization molding on the UG three-dimensional model, degreases the photopolymerized UG three-dimensional model, sinters the degreased blank, and cleans the sintered blank to obtain a lens with variable refractive index. The additive manufacturing method for optical elements provided in this application realizes the processing and fabrication of variable refractive index lenses through DLP photopolymerization 3D printing, improves the processing speed while ensuring processing accuracy, and has the characteristics of fast forming speed, small feature size, and macro-micro cross-scale forming capability. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 A flowchart illustrating the steps of an additive manufacturing method for optical elements provided in an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of a variable refractive index lens provided in an embodiment of the present invention. Detailed Implementation

[0044] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0045] In the description of this invention, it should be understood that the terms "upper", "lower", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0048] Please see Figure 1 The additive manufacturing method for optical components provided in this application includes the following steps:

[0049] Step S110: Calculate the structural parameters of the axial gradient refractive index lens, including the radius and thickness parameters of the gradient refractive index lens.

[0050] Specifically, the steps for calculating the structural parameters of an axially gradient refractive index lens include the following:

[0051] The refractive index distribution of an axially gradient refractive index material can be expressed as:

[0052] n=n(Z=N 00 +N 01 Z+N 02 Z 2 +...

[0053] In the formula N 00 N 01 and N 02 These are the coefficients of the constant term, the linear term, and the quadratic term, respectively.

[0054] The formula for the optical power of a thin lens with an axially gradient refractive index in air is:

[0055] Φ=(n0-1)c1-(n T -1)c2

[0056] In the formula, n0 is the refractive index on the optical axis (equal to N). 00 ), n T c1 and c2 are the maximum refractive index along the optical axis and the curvatures of the surfaces of the refractive index lens, respectively.

[0057] The radius and thickness parameters of the gradient refractive index lens are obtained based on the refractive index distribution of the axial gradient refractive index material and the optical power of the axial gradient refractive index thin lens in air.

[0058] It is understandable that by calculating the structural parameters of the axially gradient refractive index lens and the coefficients of the refractive index distribution curve equation, the reflection structure and gradient elements are adjusted as a whole in the optical design software, and finally the structural parameters of the gradient refractive index lens (radius, thickness, etc.) are determined.

[0059] Step S120: Establish a UG 3D model based on the structural parameters.

[0060] Specifically, based on the structural parameters of the gradient refractive index lens, the part is exported as an STL file, and the coordinates of the STL are based on the values ​​of the part in the assembly coordinate system. In this way, after slicing the STL corresponding to each material, the arrangement of the sliced ​​materials in each layer is still the same as that in the assembly, which can meet the requirements of multi-material photopolymerization molding.

[0061] Step S130: Prepare molding slurry.

[0062] In some embodiments, the step of preparing the molding slurry specifically includes the following steps:

[0063] Hydroxyethyl methacrylate, polyethylene glycol diacrylate, and diethylene glycol dibenzoate were mixed and ultrasonically stirred to obtain a homogeneous resin premix.

[0064] Sapphire is added to the resin premix, and light absorber and stabilizer are added at the same time for high-speed mixing to obtain the first slurry;

[0065] AlON was added to the resin premix, and a light absorber and a stabilizer were added simultaneously for high-speed mixing to obtain a second slurry.

[0066] Spinel is added to the resin premix, and light absorber and stabilizer are added at the same time for high-speed mixing to obtain a third slurry;

[0067] Polyimide was added to the resin premix, and light absorber and stabilizer were added simultaneously for high-speed mixing to obtain a fourth slurry;

[0068] The first slurry, the second slurry, the third slurry, and the fourth slurry are mixed and a photoinitiator is added. After mixing evenly, the molding slurry is obtained.

[0069] Specifically, 29.5 wt% hydroxyethyl methacrylate (HEMA), 3.7 wt% polyethylene glycol diacrylate (PEGDA), and 13.1 wt% diethylene glycol dibenzoate (DEDB) were mixed and ultrasonically stirred to obtain a homogeneous resin premix. Subsequently, 53.7% sapphire, AlON, spinel, and polyimide (PI) were added to the resin premix, along with 0.0039 wt% of the light absorber Sudan Red G and 0.13 wt% of the stabilizer p-hydroxyanisole (MEHQ), and mixed at high speed to obtain homogeneous first, second, third, and fourth slurries, respectively. During the stirring process, vacuum treatment was continuously performed to prevent the formation of a large number of air bubbles in the slurries. Finally, 0.26 wt% of the photoinitiator Irgacure 819 was added to the above slurries, and after uniform mixing, a slurry for molding was obtained.

[0070] Step S140: Use the molding slurry to perform photopolymerization molding on the UG 3D model.

[0071] It is understandable that during photopolymerization, for each layer of the model corresponding to different raw materials, different slurry pools need to be transferred to the projection position of the light path to cure and form different materials within the layer. A 405nm wavelength light source was chosen, with a light intensity of approximately 0.317mW / cm². 2 The layer thickness parameter is 0.05mm.

[0072] Specifically, the exposure time can be calculated based on the empirical formula of photopolymer additive manufacturing. The exposure time for the first slurry is set to 12.5 seconds. After the first slurry is cured, the UG 3D model is cleaned and dried to remove any remaining first slurry from the UG 3D model and the substrate. The second slurry is then replaced with an exposure time of 13 seconds to cure. The UG 3D model is then cleaned and dried to remove any remaining second slurry from the UG 3D model and the substrate. The third slurry is then replaced with an exposure time of 15 seconds to cure. The workpiece is then cleaned and dried to remove any remaining third slurry from the UG 3D model and the substrate. Finally, the fourth slurry is replaced with an exposure time of 16.5 seconds to cure, removing any remaining slurry from the UG 3D model and the substrate.

[0073] Step S150: Degrease the UG 3D model after photopolymerization;

[0074] Degreasing can be understood as the process by which organic components acting as binders undergo a series of physical and chemical changes under external influences and are removed from the green body.

[0075] The green body is slowly heated in air to degrease, removing organic resin from the green body. In order to obtain a better degreasing effect, the heating curve is strictly controlled according to the thermogravimetric curve of the sample.

[0076] Specifically, the UG 3D model after photocuring is heated from room temperature to 100-110 degrees Celsius at a heating rate of 2-3℃ / mm, then heated to 160-170℃ at a heating rate of 0.5-0.8℃ / min, and held at 160-170℃ for 5 hours to allow some organic matter to vaporize and be discharged. Then, the temperature is increased to 1000℃ at a heating rate of 2℃ / mm and held at 1000℃ for 2 hours to complete the degreasing process.

[0077] Step S160: Sinter the degreased green body.

[0078] Specifically, the green body was placed in a sealed container filled with nitrogen and sintered at different heating rates in different temperature ranges. 1250℃ was selected as the final sintering temperature, and a temperature curve for the sintering process was developed.

[0079] The billet is placed in a sealed container filled with nitrogen gas, and heated to 1050-1100℃ at a heating rate of 3-4℃ / min, then heated to 1250-1300℃ at a heating rate of 1-1.5℃ / min, and held at 1250-1300℃ for 3 hours and cooled with the furnace.

[0080] Furthermore, the entire sintering process is carried out at a gas pressure of <1 mbar to prevent gas from filling the pores and hindering pore closure.

[0081] Step S170: After cleaning the sintered blank, a lens with variable refractive index is obtained.

[0082] Please see Figure 2 After processing, the lens is cleaned to obtain a lens with variable refractive index. In the figure, 1, 2, 3, and 4 represent regions with different refractive indices. Based on the size of different regions, the number of photopolymerization slice layers is planned to achieve rapid processing of high-precision variable refractive index lenses.

[0083] The additive manufacturing method for optical components provided in this application calculates the structural parameters of an axial gradient refractive index lens, establishes a UG three-dimensional model based on the structural parameters, uses the molding slurry to perform photopolymerization molding on the UG three-dimensional model, degreases the photopolymerized UG three-dimensional model, sinters the degreased blank, and cleans the sintered blank to obtain a lens with variable refractive index. The additive manufacturing method for optical components provided in this application realizes the processing and fabrication of variable refractive index lenses through DLP photopolymerization 3D printing, improves the processing speed while ensuring processing accuracy, and has the characteristics of fast forming speed, small feature size, and macro-micro cross-scale forming capability.

[0084] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. An additive manufacturing method for an optical element, characterized in that, Includes the following steps: Calculate the structural parameters of an axially gradient refractive index lens, including the lens radius and thickness parameters. A UG 3D model is established based on the structural parameters; Preparation of molding slurry; The UG 3D model is photopolymerized using the molding slurry. Degreasing treatment is performed on the UG 3D model after photopolymerization molding; The degreased green body is then sintered. After cleaning the sintered blank, a lens with variable refractive index is obtained; The steps for preparing the molding slurry specifically include the following: Hydroxyethyl methacrylate, polyethylene glycol diacrylate, and diethylene glycol dibenzoate were mixed and ultrasonically stirred to obtain a homogeneous resin premix. Sapphire is added to the resin premix, and light absorber and stabilizer are added at the same time for high-speed mixing to obtain the first slurry; AlON is added to the resin premix, and light absorber and stabilizer are added at the same time for high-speed mixing to obtain a second slurry; Spinel is added to the resin premix, and light absorber and stabilizer are added at the same time for high-speed mixing to obtain a third slurry; Polyimide was added to the resin premix, and light absorber and stabilizer were added simultaneously for high-speed mixing to obtain a fourth slurry; A photoinitiator is added to the first slurry, the second slurry, the third slurry, and the fourth slurry, and the mixture is stirred evenly to obtain the molding slurry; The photopolymerization process specifically includes the following steps: For each layer of the model corresponding to different raw materials, different slurry pools are transferred to the projection position of the optical path and solidified into different materials within the layer. The exposure time is set to 12.5s for the first slurry. First, the first slurry is cured. Then, the UG 3D model is cleaned and dried to remove the first slurry residue on the UG 3D model and the substrate. Replace the second slurry, set the exposure time of the second slurry to 13s, and complete the curing of the second slurry. Clean and dry the UG 3D model to remove the residual second slurry from the UG 3D model and the substrate. Replace the third slurry, set the exposure time of the third slurry to 15s, and complete the curing of the third slurry. Clean and dry the workpiece to remove the residual third slurry from the UG 3D model and the substrate. Replace the fourth slurry, set the exposure time of the fourth slurry to 16.5s, and complete the curing of the fourth slurry. Remove the residual slurry from the UG 3D model and the substrate. The molding process uses a 405nm wavelength light source with a light intensity of 0.317mW / cm2 and a layer thickness of 0.05mm.

2. The additive manufacturing method for optical elements according to claim 1, characterized in that, The light absorber is Sudan Red G, the stabilizer is p-hydroxyanisole, and the photoinitiator is Irgacure 819.

3. The additive manufacturing method for optical elements according to claim 1, characterized in that, The degreasing process for the UG 3D model after photopolymerization includes the following steps: The UG 3D model after photopolymerization is heated from room temperature to 100-110 degrees Celsius at a heating rate of 2-3℃ / mm, then heated to 160-170℃ at a heating rate of 0.5-0.8℃ / min, and held at 160-170℃ for 5 hours to allow some organic matter to vaporize and be discharged. Then, the temperature is increased to 1000℃ at a heating rate of 2℃ / mm and held at 1000℃ for 2 hours to complete the degreasing process.

4. The additive manufacturing method for optical elements according to claim 1, characterized in that, The sintering process for the degreased green body specifically includes the following steps: The billet is placed in a sealed container filled with nitrogen gas, and heated to 1050-1100℃ at a heating rate of 3-4℃ / min, then heated to 1250-1300℃ at a heating rate of 1-1.5℃ / min, and held at 1250-1300℃ for 3 hours and cooled with the furnace.

5. The additive manufacturing method for optical elements according to claim 4, characterized in that, The entire sintering process is carried out at a pressure of <1 mbar.

6. An optical element, characterized in that, It is prepared by the additive manufacturing method of the optical element according to any one of claims 1 to 5.

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