Fresnel lens and preparation method thereof

Abstract

The invention relates to the technical field of Fresnel lenses, and discloses a Fresnel lens and a preparation method thereof.The Fresnel lens comprises a first surface and a second surface which are oppositely arranged, the first surface is provided with a plurality of annular sawtooth structures, the annular sawtooth structures are concentrically arranged, each annular sawtooth structure comprises an effective face and an ineffective face, and the effective faces are arranged on the first surface. One end of the ineffective surface close to the second surface is provided with a support structure; the plurality of ineffective surfaces are coated with a light shielding material. According to the invention, under the condition that normal light emitting of the effective surface is not influenced, full shielding of the ineffective surface is realized, and the influence of stray light on imaging is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of Fresnel lenses, and in particular to a Fresnel lens and a preparation method thereof. Background Art

[0002] Fresnel lenses consist of a series of concentric grooves etched in plastic. They are thin and light, available in various sizes, and have excellent light-gathering capabilities. They are widely used in concentrated photovoltaic systems, imaging systems, passive infrared detectors, and lighting. However, Fresnel lenses have an effective surface and an ineffective surface. The position where the incident light focuses after passing through the ineffective surface is different from the position where the incident light focuses after passing through the effective surface, thus forming stray light, which affects the imaging effect of optical imaging devices (such as head-mounted display devices).

[0003] At present, a solution of shielding the ineffective surface is adopted to prevent stray light from interfering with imaging. However, when a shading material with good fluidity is used to shield the ineffective surface, it is easy to cause the shading material to flow to the effective surface, thereby affecting the light output effect of the Fresnel lens; when a shading material with poor fluidity is used to shield the ineffective surface, it may not be able to completely cover the ineffective surface, thereby failing to eliminate the influence of stray light. Summary of the invention

[0004] In view of this, the present invention provides a Fresnel lens and a preparation method thereof, so as to improve the problem that, in the process of achieving full shielding, the shading material flows onto the effective surface and affects the light emitting effect of the Fresnel lens.

[0005] In a first aspect, the present invention provides a Fresnel lens, comprising: a first surface and a second surface arranged opposite to each other, the first surface being provided with a plurality of annular sawtooth structures, the plurality of annular sawtooth structures being arranged concentrically, the annular sawtooth structures comprising an effective surface and an ineffective surface, a support structure being provided at one end of the ineffective surface close to the second surface; and a light-shielding material being coated on the plurality of ineffective surfaces.

[0006] In an optional implementation, the support structure is in an arc shape, and the angle between the support structure and the ineffective surface ranges from 20° to 80°.

[0007] In an optional embodiment, the maximum distance from the support structure to the ineffective surface ranges from 10 μm to 30 μm.

[0008] In an optional implementation, the thickness of the light-shielding material ranges from 10 μm to 30 μm, and the absorbance of the light-shielding material is greater than 3.

[0009] In an optional implementation, the shading material is thermosetting glue or UV curing glue.

[0010] In an optional implementation, the viscosity of the light-shielding material ranges from 5000 cp to 20000 cp.

[0011] In a second aspect, the present invention provides a method for preparing a Fresnel lens, the method comprising: forming an initial Fresnel lens, wherein the initial Fresnel lens comprises a first surface and a second surface arranged opposite to each other, the first surface is provided with a plurality of annular sawtooth structures, the plurality of annular sawtooth structures are arranged concentrically, the annular sawtooth structures comprise an effective surface and an ineffective surface, and a support structure is provided at one end of the ineffective surface close to the second surface; coating a shading material on the plurality of ineffective surfaces; and after the plurality of ineffective surfaces are covered with the shading material, curing the shading material to obtain the Fresnel lens provided by the first aspect or any one of its embodiments.

[0012] In an optional implementation, forming an initial Fresnel lens includes: forming an initial Fresnel lens based on an injection mold.

[0013] In an optional embodiment, before coating the shading material on multiple invalid surfaces, the method also includes: fixing the initial Fresnel lens on the printing platform; determining the printing path of the printing needle based on the positions of multiple annular serrated structures; coating the shading material on multiple invalid surfaces, including: printing the shading material onto the multiple invalid surfaces along the printing path based on preset printing parameters.

[0014] In an optional embodiment, before determining the printing path of the printing needle based on the positions of the plurality of annular sawtooth structures, the method further comprises: scanning the initial Fresnel lens by a spectral confocal sensor to determine the positions of the plurality of annular sawtooth structures.

[0015] In an optional embodiment, before curing the light-shielding material, the method further includes: acquiring the printing morphology of the light-shielding material by tilting the camera; and determining whether the invalid surface is covered by the light-shielding material based on the printing morphology.

[0016] In an optional implementation, the width of the printing needle ranges from 50 μm to 100 μm.

[0017] The Fresnel lens and the preparation method thereof provided by the present invention have the following beneficial effects:

[0018] (1) The Fresnel lens provided by the present invention can prevent the shading material from flowing to the effective surface when the shading material is coated on the ineffective surface by providing a support structure on the ineffective surface, thereby completing the full shielding of the ineffective surface without affecting the normal light emission of the effective surface, thereby reducing the influence of stray light on imaging. Moreover, by providing a support structure, a shading material with a lower viscosity can be selected to shield the effective surface, thereby reducing the thickness of the shading layer formed, thereby reducing light loss.

[0019] (2) Arranging the supporting structure into an arc shape can make the shading material fit more closely to the supporting structure, further preventing the shading material from contaminating the effective surface.

[0020] (3) The maximum distance from the support structure to the ineffective surface is limited to between 10 μm and 30 μm, which is close to the thickness of the shading material covering the ineffective surface. This can reduce the impact of the support structure on the light output of the effective surface and reduce light loss.

[0021] (4) By coating the shading material on multiple ineffective surfaces in a printing manner, the amount of shading material required to fully shield the ineffective surfaces can be clearly determined, and the material output of the printing needle can be accurately controlled so that the shading material evenly covers the ineffective surfaces.

[0022] (5) By determining whether the invalid surface is covered by the shading material through the printing morphology obtained by the tilted camera, the timing of full coverage can be accurately determined, the shading material can be cured in time, and the preparation efficiency of the Fresnel lens can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of a planar structure of a Fresnel lens according to an embodiment of the present invention;

[0024] Figure 2 yes Figure 1 AA cross-section diagram of ;

[0025] Figure 3 is a schematic diagram of a Fresnel lens and light positions according to an embodiment of the present invention;

[0026] Figure 4 is a schematic structural diagram of another Fresnel lens according to an embodiment of the present invention;

[0027] Figure 5 is a schematic diagram of a support structure according to an embodiment of the present invention;

[0028] Figure 6 yes Figure 5 A local enlarged schematic diagram of area B;

[0029] Figure 7 is a schematic diagram of the final state of the shading material on the ineffective surface according to an embodiment of the present invention;

[0030] Figure 8 is a schematic diagram of another Fresnel lens and light positions according to an embodiment of the present invention;

[0031] Fig. 9 is a schematic flow chart of a method for preparing a Fresnel lens according to an embodiment of the present invention;

[0032] Fig.10is a schematic flow chart of another method for preparing a Fresnel lens according to an embodiment of the present invention;

[0033] Fig.11 is a schematic diagram of a printing process according to an embodiment of the present invention.

[0034] Attached figures: 100, Fresnel lens; 110, first surface; 120, second surface; 130, annular sawtooth structure; 131, effective surface; 132, ineffective surface; 140, supporting structure; 150, shading material; 200, light source; 300, printing needle. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0036] For example, Figure 1 and Figure 2 As shown, the Fresnel lens 100 includes a first surface 110 and a second surface 120 that are arranged opposite to each other. The first surface 110 can be a light incident surface, and the second surface 120 can be a light emitting surface. That is, when in use, the first surface 110 is closer to the light source of the optical imaging device than the second surface 120.

[0037] A plurality of annular sawtooth structures 130 are convexly disposed on the first surface 110, and the plurality of annular sawtooth structures 130 are concentrically disposed and sequentially connected along the radial direction of the first surface 110. The center of the plurality of annular sawtooth structures 130 may be the central axis O of the first surface 110 and the second surface 120. The number of the annular sawtooth structures 130 may be determined by the designer according to actual needs.

[0038] like Figure 2 As shown, each annular sawtooth structure 130 includes an effective surface 131 and an ineffective surface 132. The top ends (the ends away from the first surface 110) of the effective surface 131 and the ineffective surface 132 of each annular sawtooth structure 130 intersect and are both side surfaces of the annular sawtooth structure 130. The ineffective surface 132 is close to the central axis O relative to the effective surface 131, and the effective surface 131 is far away from the central axis O relative to the ineffective surface 132, that is, the effective surface 131 is arranged away from the central axis O, and the ineffective surface 132 is arranged close to the central axis O.

[0039] In the process of using the Fresnel lens 100, if Figure 3As shown, the light emitted by the light source 200 is refracted through the effective surface 131 and finally focused to form an image. However, the light emitted by the light source 200 or the light emitted by the ambient light may also be refracted through the ineffective surface 132, and the propagation of this part of the light deviates from the normal path, which may form stray light and affect the imaging effect of the optical imaging device. For example, the stray light may reduce the contrast of the imaging picture.

[0040] In order to prevent stray light from interfering with the image, in some examples, a shading material is used to block the invalid surface to prevent light from passing through the invalid surface 132. However, when a shading material with good fluidity is used to block the invalid surface, it is easy to cause the shading material to flow to the effective surface, thereby affecting the light output effect of the Fresnel lens; when a shading material with poor fluidity is used to block the invalid surface, it may not be able to completely cover the invalid surface, thereby failing to eliminate the influence of stray light.

[0041] In view of this, the present invention provides a Fresnel lens, which can completely shield the ineffective surface without affecting the normal light emission of the effective surface by arranging a support structure on the ineffective surface, thereby reducing the influence of stray light on imaging.

[0042] The structure of the Fresnel lens provided by the present invention is described in detail below with reference to the accompanying drawings.

[0043] like Figures 4 to 7 As shown, the Fresnel lens provided by the present invention also includes a first surface 110 and a second surface 120 arranged opposite to each other, and the first surface 110 is provided with a plurality of annular sawtooth structures 130, the plurality of annular sawtooth structures 130 are arranged concentrically, and the annular sawtooth structures 130 include an effective surface 131 and an ineffective surface 132. However, the ineffective surface 132 of the Fresnel lens provided by the present invention is further provided with a support structure 140 at one end close to the second surface 120.

[0044] That is, relative to Figure 1 and Figure 2 The Fresnel lens 100 shown in the figure has a support structure 140 disposed at the bottom of the ineffective surface 132 of the Fresnel lens provided by the present invention, and the support structure 140 is located at the contact position between the ineffective surface 132 and the effective surface 131 of two adjacent annular sawtooth structures. By disposing the support structure 140 at the bottom of the ineffective surface 132, when a light-shielding material with good fluidity is selected to shield the ineffective surface, the light-shielding material can be prevented from flowing to the effective surface, thereby reducing light loss.

[0045] Furthermore, the ineffective surfaces 132 of the plurality of support structures 140 are coated with a light shielding material 150, that is, Figure 4 As shown, each ineffective surface 132 is coated with a light shielding material 150 .

[0046] When the Fresnel lens provided by the present invention is placed on a light source, Figure 8As shown, the light from the light source 200 reaching the ineffective surface 132 can be absorbed by the shading layer formed by the shading material 150, so that the light emitted by the Fresnel lens all comes from the light incident from the effective surface 131, reducing the influence of stray light on imaging.

[0047] The Fresnel lens provided by the present invention can prevent the shading material 150 from flowing to the effective surface 131 when the shading material 150 is coated on the ineffective surface 132 by arranging the support structure 140 on the ineffective surface 132, thereby completing the full shielding of the ineffective surface 132 without affecting the normal light emission of the effective surface 131, thereby reducing the influence of stray light on imaging. Moreover, by arranging the support structure 140, the shading material 150 with lower viscosity can be selected to shield the effective surface 131, thereby reducing the thickness of the formed shading layer, thereby reducing light loss.

[0048] The present invention does not limit the shape of the support structure. For example, the support structure 140 may be in an arc shape or a rectangular shape.

[0049] In one example, if Figure 5 and Figure 6 As shown, the support structure 140 is in an arc shape, and the angle θ between the support structure 140 and the invalid surface 132 ranges from 20° to 80°, that is, the angle θ between the support structure 140 and the invalid surface 132 can be any value between 20° and 80°, for example, the angle θ between the support structure 140 and the invalid surface 132 can be 20°, 30°, 45°, 60°, 70° or 80°, etc.

[0050] In this embodiment, the shading material is in an arc shape on the ineffective surface 132 , and the supporting structure 140 is also configured in an arc shape, so that the shading material and the supporting structure 140 can fit more closely, further preventing the shading material from contaminating the effective surface 131 .

[0051] In some embodiments, Figure 6 As shown, the maximum distance L1 from the support structure 140 to the invalid surface 132 ranges from 10 μm to 30 μm, that is, the maximum distance L1 from the support structure 140 to the invalid surface 132 can be any value from 10 μm to 30 μm, for example, the maximum distance L1 from the support structure 140 to the invalid surface 132 can be 10 μm, 12 μm, 20 μm, 25 μm, 28 μm or 30 μm, etc.

[0052] In this embodiment, the maximum distance L1 from the support structure 140 to the ineffective surface 132 is limited to between 10 μm and 30 μm, which is close to the thickness of the shading material covering the ineffective surface 132, thereby reducing the influence of the support structure 140 on the light output from the effective surface and reducing light loss.

[0053] Exemplarily, the thickness of the shading material ranges from 10 μm to 30 μm, that is, the thickness of the shading material can be any value between 10 μm and 30 μm, for example, the thickness of the shading material can be 10 μm, 12 μm, 20 μm, 25 μm or 30 μm, etc. The optical density (OD) of the shading material is greater than 3, the transmittance of light is 0%, and the reflectivity of light is less than 4%.

[0054] Specifically, absorbance, also known as optical density, is an important indicator to measure the degree to which a material transmits light. The OD value is used to describe the material's ability to absorb or block light. The larger the OD value, the stronger the material's ability to absorb or block light. An OD value of 3 means that the material can transmit 0.1% of the incident light, that is, 99.9% of the light is absorbed or reflected.

[0055] Exemplarily, the light-shielding material includes, but is not limited to, black materials such as thermosetting glue or ultraviolet (UV) curing glue.

[0056] Specifically, thermosetting glue is an adhesive that needs to be heated during the curing process. When heated to a certain temperature, the glue will undergo a chemical reaction to form an irreversible cross-linked structure, thereby hardening into a solid. Thermosetting glue has the advantages of high temperature resistance, chemical corrosion resistance, high strength and controllable curing; UV curing glue is an adhesive that cures under ultraviolet light. When UV glue is exposed to ultraviolet light of a specific wavelength, the photoinitiator therein will initiate a polymerization reaction, causing the glue to cure rapidly. UV curing glue has the advantages of high curing efficiency and environmental protection.

[0057] In some embodiments, the viscosity of the shading material ranges from 5000 centipoise (cp) to 20000 cp, that is, the viscosity of the shading material can be any value from 5000 cp to 20000 cp, for example, the viscosity of the shading material can be 5000 cp, 6000 cp, 8000 cp, 10000 cp, 18000 cp or 20000 cp, etc.

[0058] In this embodiment, the viscosity of the shading material is limited to 5000cp to 20000cp, which can make the fluidity more moderate, thereby avoiding excessive flow of the shading material, which makes it difficult to control the thickness and shape of the coating, and avoiding difficulty in spreading the shading material, thereby ensuring the uniformity of the coating and the consistency of the shading effect.

[0059] This embodiment also provides a method for preparing a Fresnel lens, such as Fig. 9 As shown, the method comprises the following steps:

[0060] Step S901, forming an initial Fresnel lens.

[0061] The initial Fresnel lens includes a first surface and a second surface that are arranged opposite to each other, the first surface is provided with a plurality of annular sawtooth structures, the plurality of annular sawtooth structures are arranged concentrically, the annular sawtooth structures include an effective surface and an ineffective surface, and a support structure is provided at one end of the ineffective surface close to the second surface. Figure 5 and Figure 6 As shown, relative to the Fresnel lens 100 , a support structure 140 is disposed at one end of the ineffective surface 132 close to the second surface 120 of the initial Fresnel lens.

[0062] The present invention does not limit the method of forming the initial Fresnel lens. For example, the initial Fresnel lens may be formed by an injection mold, or by 3D printing, laser etching, or photolithography.

[0063] Step S902: coating a light-shielding material on a plurality of ineffective surfaces.

[0064] For example, the shading material may be coated on each ineffective surface of the initial Fresnel lens by printing, coating, or chemical treatment (such as oxidation or nitridation). The shading material may be a black material such as thermosetting glue or ultraviolet curing glue.

[0065] Step S903, after the multiple ineffective surfaces are covered by the shading material, the shading material is cured to obtain a Fresnel lens.

[0066] The Fresnel lens may be any of the Fresnel lenses provided in the above embodiments. Figure 4 shown.

[0067] Specifically, the multiple invalid surfaces being covered by the shading material may mean that each invalid surface is completely blocked, that is, the shading material covers the entire area of ​​each invalid surface. Figure 7 As shown, an image containing position information of the shading material on the invalid surface can be collected by a camera or other equipment, and whether multiple invalid surfaces are covered by the shading material can be determined through the image.

[0068] The preparation method of the Fresnel lens provided in this embodiment first forms an initial Fresnel lens with a support structure at the bottom of the invalid surface, and then, based on the initial Fresnel lens, a shielding material is coated on multiple invalid surfaces, and after multiple invalid surfaces are covered by the shading material, the shading material is cured to obtain a Fresnel lens. In this embodiment, the initial Fresnel lens with a support structure is used in conjunction with the shading material to fully shield the invalid surface, which can prevent the shading material from flowing to the effective surface, and then complete the full shielding of the invalid surface without affecting the normal light emission of the effective surface, thereby reducing the influence of stray light on imaging. Moreover, by setting a support structure, a shading material with a lower viscosity can be selected to shield the effective surface, reducing the thickness of the formed shading layer, thereby reducing light loss.

[0069] In some optional embodiments, the preparation method of the Fresnel lens can be as follows: Fig.10 The steps shown include:

[0070] Step S1001: forming an initial Fresnel lens based on an injection mold.

[0071] Specifically, the injection mold is provided with a mold cavity, the structure of the mold cavity is the same as the structure of the initial Fresnel lens, and the injection mold can be used to form the initial Fresnel lens by liquid glue coating and curing or hot pressing molding.

[0072] In this embodiment, the initial Fresnel lens is formed by an injection mold, which can improve the manufacturing accuracy of the initial Fresnel lens. The injection mold can accurately control the amount of material used and can also produce a large number of initial Fresnel lenses in a short time, thereby improving the production efficiency of the initial Fresnel lens and reducing the production cost of the initial Fresnel lens.

[0073] Step S1002, fixing the initial Fresnel lens on the printing platform.

[0074] Specifically, after the initial Fresnel lens is formed, the initial Fresnel lens is placed on a printing platform of a 3D printing device, wherein the printing platform is provided with a vacuum adsorption device, and the initial Fresnel lens is fixed by the vacuum adsorption device to avoid position displacement of the initial Fresnel lens during subsequent printing, thereby preventing the shading material from flowing to the effective surface.

[0075] Step S1003, determining a printing path of the printing needle based on the positions of the plurality of annular sawtooth structures.

[0076] Specifically, after determining the positions of the plurality of annular sawtooth structures, the coordinate positions of the plurality of invalid surfaces can be determined, and then based on the coordinate positions of the plurality of invalid surfaces, a printing path of each invalid surface is generated to ensure that Fig.11The light shielding material ejected by the printing needle 300 can be accurately dropped on the ineffective surface. For example, the circle formed by the ineffective surface is the printing path of the ineffective surface.

[0077] The present invention does not limit the type of printing needles, and the printing needles can be selected according to the characteristics of the light-shielding material. The printing needles include but are not limited to ceramic needles or glass needles.

[0078] Exemplarily, the width of the printing needle ranges from 50 μm to 100 μm, that is, the width of the printing needle can be any value between 50 μm and 100 μm, for example, the width of the printing needle can be 50 μm, 60 μm, 80 μm, 90 μm or 100 μm.

[0079] In this embodiment, the width of the printing needle is limited to between 50 μm and 100 μm, which can accurately control the printing area and ensure that the shading material only covers the ineffective surface to avoid contamination of the effective surface. The printing plane line width is about 300 μm, for example, the range of the printing plane line width is 290 μm to 3100 μm.

[0080] In some optional embodiments, the initial Fresnel lens may be scanned by a spectral confocal sensor to determine the positions of the plurality of annular sawtooth structures.

[0081] Among them, the spectral confocal sensor is a high-precision optical measurement device that can accurately determine the position and shape of the surface of the object by measuring the reflection of light of different wavelengths on the surface of the object being measured. During the measurement process, the spectral confocal sensor emits a beam of polychromatic light, and light of different wavelengths is focused at different distances. By analyzing the wavelength of the reflected light, the distance between the surface of the object being measured and the spectral confocal sensor can be determined.

[0082] Specifically, by measuring the initial Fresnel lens from various angles and directions through the spectral confocal sensor, the height, width, angle and other information of each annular sawtooth structure can be determined, and then the specific position of each annular sawtooth structure, such as the center coordinates, radius and depth, can be accurately determined.

[0083] Step S1004: based on preset printing parameters, printing the shading material onto multiple invalid surfaces along the printing path.

[0084] Specifically, the preset printing parameters include but are not limited to printing pressure and printing speed, and the preset printing parameters are determined based on the amount of shading material required to cover the ineffective surface of the initial Fresnel lens, and the amount of shading material required to cover the ineffective surface of the initial Fresnel lens is determined based on experiments.

[0085] By controlling the printing air pressure and printing speed, the output of the printing needle can be precisely controlled to print the shading material circle by circle onto the ineffective surface of the initial Fresnel lens. During the printing process, precisely controlling the output of the printing needle can avoid the situation where the ineffective surface cannot be fully covered due to insufficient output, and avoid the situation where the shading material contaminates the effective surface due to excessive output.

[0086] For example, the printing method can be as follows: Fig.11 As shown, by controlling the printing needle 300 based on the printing path, the printing needle 300 can be located above the invalid surface, thereby accurately printing the shading material on the invalid surface.

[0087] Specifically, the light-shielding material (such as low-viscosity thermosetting glue) can be placed in a 3 mL cartridge, and the cartridge is connected to the printing needle to provide the light-shielding material for the printing needle.

[0088] Step S1005, obtaining the printing morphology of the shading material by tilting the camera.

[0089] Step S1006, based on the printing morphology, determine whether the invalid surface is covered by the shading material.

[0090] Specifically, the printed morphology captured by the tilted camera includes black and white lines. When white lines exist in the printed morphology, it can be determined that the invalid surface is not fully covered by the shading material; when white lines do not exist in the printed morphology, it can be determined that the invalid surface is fully covered by the shading material.

[0091] For example, the tilt camera includes multiple cameras, and the multiple cameras face different angles, and can simultaneously shoot the invalid surface from multiple viewing angles to obtain image information at different angles. By shooting at different angles, the morphological characteristics of the shading material on the invalid surface after printing can be more comprehensively understood.

[0092] Step S1007: after the multiple ineffective surfaces are covered by the shading material, the shading material is cured to obtain a Fresnel lens.

[0093] For details, please see Fig. 9 Step S903 of the illustrated embodiment will not be described in detail here.

[0094] The preparation method of the Fresnel lens provided in this embodiment, after forming the initial Fresnel lens, fix the initial Fresnel lens on the printing platform, then determine the printing path of the printing needle based on the position of multiple annular sawtooth structures, and print the shading material on multiple invalid surfaces along the printing path based on preset printing parameters, after printing, obtain the printing morphology of the shading material by tilting the camera, determine whether the invalid surface is covered by the shading material based on the printing morphology, and after the multiple invalid surfaces are covered by the shading material, solidify the shading material to obtain the Fresnel lens. In this embodiment, by coating the shading material on multiple invalid surfaces by printing, the amount of shading material required for full shading of the invalid surface can be determined, and the discharge amount of the printing needle can be accurately controlled so that the shading material uniformly covers the invalid surface. By determining whether the invalid surface is covered by the shading material by the printing morphology obtained by the tilted camera, the timing of full coverage can be accurately determined, and the shading material can be solidified in time, thereby improving the preparation efficiency of the Fresnel lens.

[0095] In this embodiment, a Fresnel lens is also provided. The Fresnel lens is prepared by the method for preparing a Fresnel lens provided by any of the above embodiments. For example, the structure of the Fresnel lens prepared by the method for preparing a Fresnel lens provided by any of the above embodiments can be as follows: Figure 8 shown.

[0096] In the description of the present invention, it is to be understood that the 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., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0097] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0098] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0099] In the description of this specification, the description with reference to the terms "this embodiment", "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0100] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0101] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the present invention.

Claims

1. A Fresnel lens, characterized in that: include: A first surface and a second surface are arranged opposite to each other, the first surface is provided with a plurality of annular sawtooth structures, the plurality of annular sawtooth structures are arranged concentrically, the annular sawtooth structure comprises an effective surface and an ineffective surface, and a support structure is provided at one end of the ineffective surface close to the second surface; A light shielding material is coated on the plurality of ineffective surfaces.

2. The Fresnel lens according to claim 1, characterized in that: The support structure is in an arc shape, and the angle between the support structure and the invalid surface ranges from 20° to 80°.

3. The Fresnel lens according to claim 1, characterized in that: The maximum distance from the support structure to the ineffective surface ranges from 10 μm to 30 μm.

4. The Fresnel lens according to claim 1, characterized in that: The thickness of the light-shielding material ranges from 10 μm to 30 μm, and the absorbance of the light-shielding material is greater than 3.

5. The Fresnel lens according to claim 1, characterized in that: The shading material is thermosetting glue or ultraviolet curing glue.

6. The Fresnel lens according to any one of claims 1 to 5, characterized in that: The viscosity of the light-shielding material ranges from 5000 cp to 20000 cp.

7. A method for preparing a Fresnel lens, characterized in that: The method comprises: Forming an initial Fresnel lens, wherein the initial Fresnel lens comprises a first surface and a second surface arranged opposite to each other, the first surface is provided with a plurality of annular sawtooth structures, the plurality of annular sawtooth structures are arranged concentrically, the annular sawtooth structure comprises an effective surface and an ineffective surface, and a support structure is provided at one end of the ineffective surface close to the second surface; coating a light-shielding material on a plurality of the ineffective surfaces; After the plurality of ineffective surfaces are covered by the shading material, the shading material is cured to obtain the Fresnel lens according to any one of claims 1 to 6.

8. The method according to claim 7, characterized in that The forming of the initial Fresnel lens comprises: Based on the injection mold, an initial Fresnel lens is formed.

9. The method according to claim 7, characterized in that: Before coating the shading material on the plurality of ineffective surfaces, the method further comprises: Fixing the initial Fresnel lens on a printing platform; Determining a printing path of the printing needle based on the positions of the plurality of annular sawtooth structures; The light-shielding material is applied to a plurality of the ineffective surfaces, comprising: Based on preset printing parameters, the light shielding material is printed onto the plurality of ineffective surfaces along the printing path.

10. The method according to claim 9, characterized in that Before determining the printing path of the printing needle based on the positions of the plurality of annular sawtooth structures, the method further includes: The initial Fresnel lens is scanned by a spectral confocal sensor to determine the positions of the plurality of annular sawtooth structures.

11. The method according to claim 9, characterized in that Before curing the shading material, the method further comprises: Obtaining the printed morphology of the shading material by tilting the camera; Based on the printing morphology, it is determined whether the invalid surface is covered by the light-shielding material.

12. The method according to claim 9, characterized in that The width of the printing needle ranges from 50 μm to 100 μm.

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