Fresnel lens, straight-through type Fresnel lens group and optical equipment

Abstract

The invention provides a Fresnel lens, a straight-through type Fresnel lens group and optical equipment, and belongs to the technical field of optical lenses. The Fresnel lens comprises a lens body and a light shielding layer. At least one surface of the mirror body is a Fresnel surface, the Fresnel surface is provided with an ineffective surface, at least partial area of at least one ineffective surface is provided with a concave shading area, the shading area is filled with the shading layer, and the shading layer and the mirror body are in smooth transition. Accurate shielding of the invalid surface of the Fresnel lens is realized, and the imaging quality is improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optical lenses, and more particularly, to Fresnel lenses, through-type Fresnel lens groups, and optical devices. Background Art

[0002] In current optical solutions for virtual reality (VR) technology, the through-type aspherical lens group has the advantages of low design and processing difficulty, high luminous efficiency (luminous efficiency > 50%), and no stray light. At the same time, it has the disadvantages of a relatively large overall length and thickness of the system (overall system length > 35 mm), which is not conducive to the thin and light design of the product. The catadioptric (Pancake) aspherical lens group has the advantages of better imaging quality and a relatively thin overall length of the system (overall system length ≤ 30 mm), but at the same time, it has a relatively low luminous efficiency (luminous efficiency < 25%) and phenomena such as ghost images.

[0003] Based on this, a multi-piece Fresnel lens optical solution (through-type Fresnel lens group) is reviewed and investigated to meet the strong market demand for high luminous efficiency and thinness of products.

[0004] The through-type Fresnel lens group is expected to combine the advantages of high luminous efficiency of the through-type aspherical lens group and relatively thinness of the catadioptric (Pancake) aspherical lens group. However, since the through-type Fresnel lens group has a Fresnel lens, and the Fresnel lens has an ineffective surface, stray light will exist on the ineffective surface, which will affect the imaging quality. Therefore, it is necessary to block or adjust the parameters of the ineffective surface during use.

[0005] Therefore, it is necessary to design a Fresnel lens that can improve the imaging quality without increasing the thickness, weight, and cost.

[0006] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present disclosure, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0007] The purpose of the present disclosure is to overcome the above-mentioned deficiencies of the prior art, and provide a Fresnel lens, a through-type Fresnel lens group, and an optical device, which can improve the imaging quality without increasing the thickness, weight, and cost of the Fresnel lens.

[0008] According to one aspect of the present disclosure, a Fresnel lens is provided, which includes a lens body and a light-shielding layer;

[0009] At least one surface of the lens body is a Fresnel surface, the Fresnel surface has an ineffective surface, at least a part of at least one of the ineffective surfaces has a recessed light-shielding area, the light-shielding layer fills the light-shielding area, and the light-shielding layer is smoothly transitioned with the lens body.

[0010] In an embodiment of the present disclosure, the Fresnel surface has a plurality of said ineffective surfaces; the number of the light-shielding layers is plural; the plural light-shielding layers correspond to the plural ineffective surfaces one by one.

[0011] In an embodiment of the present disclosure, the ineffective surface includes a first apex surface, a draft surface, and a second apex surface that are connected in sequence;

[0012] At least one of the first apex surface, the draft surface, and the second apex surface has a light-shielding region.

[0013] In an embodiment of the present disclosure, the material of the light-shielding layer is a black organic material.

[0014] In an embodiment of the present disclosure, the thickness of the light-shielding layer is not greater than 5 μm; the light transmittance of the light-shielding layer to visible light is 0 to 0.1%.

[0015] According to another aspect of the present disclosure, there is provided a method for manufacturing a Fresnel lens, which is manufactured by the following method:

[0016] Provide a mold for manufacturing a Fresnel lens;

[0017] At least a partial region of the mold corresponding to the ineffective surface of the Fresnel lens is formed with a light-shielding layer; the ineffective surface includes a first apex surface, a draft surface, and a second apex surface;

[0018] Fill the mold with a lens body material to form a lens body;

[0019] Demold to obtain a Fresnel lens with a light-shielding layer on the ineffective surface.

[0020] In an embodiment of the present disclosure, forming a light-shielding layer at least in a partial region of the mold corresponding to the ineffective surface of the Fresnel lens includes:

[0021] Print black ink at least in a partial region of the mold corresponding to the ineffective surface of the Fresnel lens. After curing, add a mask plate process. After exposure and development, a light-shielding region is formed at least at one of the first apex surface, the draft surface, and the second apex surface of the mold; the viscosity of the black ink at room temperature is 10,000 to 30,000 mPa·s.

[0022] In an embodiment of the present disclosure, the bonding strength between the light-shielding layer and the lens body is not less than 100 times the bonding strength between the light-shielding layer and the mold.

[0023] According to another aspect of the present disclosure, there is provided a through-type Fresnel lens group, and the through-type Fresnel lens group has the above-mentioned Fresnel lens.

[0024] According to another aspect of the present disclosure, there is provided an optical device including the above Fresnel lens; or including the above through-type Fresnel lens group.

[0025] The Fresnel lens, the through-type Fresnel lens group and the optical device provided by the present disclosure solve the problem of stray light (glare) caused by the introduction of the Fresnel lens, improve the imaging effect of the near-eye display system as a whole, and do not increase the thickness, weight and cost of the Fresnel lens, which has important practicality and commercial value.

[0026] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings here are incorporated into the specification and constitute a part of this specification, showing the embodiments in line with the present disclosure, and are used together with the specification to explain the principles of the present disclosure. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic diagram of the light path principle of the Fresnel lens.

[0029] Figure 2 It is a schematic diagram of the light output of the Fresnel lens.

[0030] Figure 3 It is a schematic diagram of the comparative experiment results in the embodiment of the present disclosure.

[0031] Figure 4 It is a schematic diagram of the preparation process of the Fresnel lens in an embodiment of the present disclosure.

[0032] Figure 5 It is a schematic diagram of the preparation process of the Fresnel lens in an embodiment of the present disclosure.

[0033] Figure 6 It is a schematic diagram of the preparation process of the Fresnel lens in an embodiment of the present disclosure.

[0034] Figure 7 It is a schematic diagram of the preparation process of the Fresnel lens in an embodiment of the present disclosure.

[0035] Figure 8 It is a schematic diagram of the preparation process of the Fresnel lens in an embodiment of the present disclosure.

[0036] Figure 9 It is a schematic diagram of the preparation process of the Fresnel lens in an embodiment of the present disclosure.

[0037] Figure 10 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0038] Figure 11 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0039] Figure 12 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0040] Figure 13 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0041] Figure 14 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0042] Figure 15 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0043] Figure 16 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0044] Figure 17 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0045] Figure 18 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0046] Figure 19 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0047] Figure 20 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0048] Figure 21 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0049] Figure 22 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0050] Figure 23 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0051] Figure 24 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0052] Figure 25 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0053] Figure 26 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0054] Figure 27 In one embodiment of the present disclosure, it is a schematic diagram of the preparation process of a Fresnel lens.

[0055] Figure 28 In the related art, it is a schematic diagram of the structure of a Fresnel lens with a light-shielding layer.

[0056] Figure 29 It is a schematic diagram of the imaging results before and after the improvement of the Fresnel lens of the present disclosure.

[0057] Description of reference numerals:

[0058] 1. Light-shielding layer; 3. Invalid surface; 4. First vertex surface; 5. Draft surface; 6. Second vertex surface; 7. Effective surface; 8. Lens body. Detailed implementation manners

[0059] Now, example embodiments will be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed descriptions will be omitted. In addition, the drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale.

[0060] The terms "a", "an", "the", "said" and "at least one" are used to indicate the presence of one or more elements / components / etc.; the terms "comprising" and "having" are used to mean an open inclusion and mean that there may be additional elements / components / etc. in addition to the listed elements / components / etc.; the terms "first", "second", etc. are only used as labels and are not a limitation on the quantity of their objects.

[0061] The relevant noun definitions involved in the present disclosure are as follows:

[0062] Aspherical lens: A lens with a refractive surface that is an aspherical curved surface, which has a better radius of curvature and can maintain good aberration correction to obtain the required performance.

[0063] This Fresnel lens, also called a thread lens, has a multi-layer concentric annular serrated structure extending from the center of the lens on the lens surface. The cross-section of the concentric annular serrated structure is serrated. The annular serrated structure can be regarded as formed by the curved surface of a convex lens collapsing in multiple levels towards the lens body to reduce the central thickness. See Figure 1, each layer has an annular curved surface effective area that maintains the original convex lens surface's effective refraction of light. The corresponding surface is called the effective surface 7. The annular curved surface as the effective area becomes the outer side of the concentric annular serrated structure, while the collapsed fault surface becomes the inner side of the concentric annular serrated structure, which is generally a cylindrical surface. The inner inclined surface of the concentric annular serrated structure of the Fresnel mirror is an ineffective area for lens imaging, and the corresponding surface is called the ineffective surface 3, which reflects the object light to form stray light that is unfavorable for lens imaging. The Fresnel lens does not change important optical parameters such as the original convex lens's focal length, but reduces the thickness of the lens body, saves materials, makes the lens lighter, and is also cheaper. Usually, the Fresnel lens is divided into two types: the Fresnel lens with an equal tooth height structure and the Fresnel lens with an equal tooth pitch structure.

[0064] From the perspective of imaging, compared with ordinary spherical or aspherical lenses, the Fresnel lens has a relatively arranged first surface and second surface. At least one of the first surface and the second surface is set as a Fresnel surface, and the remaining surface can be a plane. It can be understood that the first surface can be a Fresnel surface, or the second surface can be a Fresnel surface, or both the first surface and the second surface are Fresnel surfaces. The Fresnel surface has a plurality of concentric annular serrated structures. The serrated structure includes an effective surface 7 and an ineffective surface 3. The effective surface 7 and the ineffective surface 3 are usually connected in a way of fillet transition. The effective surface 7 is farther from the center of the Fresnel lens than the ineffective surface 3. Among them, see Figure 1 , the effective surface 7 can deflect the incident light, and the light emerging from the effective surface 7 is used for light output and imaging. Based on the serrated structure, the ineffective surface 3 includes a first apex surface 4, a second apex surface 6, and a draft surface 5. The first apex surface 4 is connected to the adjacent effective surface 7, the second apex surface 6 is connected to the adjacent effective surface 7, and the draft surface 5 is located between the first apex surface 4 and the second apex surface 6, connecting the first apex surface 4 and the second apex surface 6. In the actual manufacturing process, the apex surface is a fillet surface, and the draft surface 5 is a cylindrical surface. Among them, the cylindrical surface is perpendicular to the plane. In the actual manufacturing process, the cylindrical surface will have an error inclination of 2-5 degrees, forming an inclined surface towards the outside.

[0065] From the difference point of structure, the special feature of the Fresnel lens compared with ordinary lenses lies in the existence of the ineffective surface 3 (the first apex surface 4, the second apex surface 6, and the draft surface 5). In terms of imaging quality, ordinary spherical or aspherical lenses do not have stray light, and the imaging quality is good. See Figure 1 And Figure 2 , the Fresnel lens has stray light, and the stray light will affect the imaging quality. Therefore, it can be judged from the difference in the structure between the Fresnel lens and ordinary lenses that the ineffective surface 3 (the first apex surface 4, the second apex surface 6, and the draft surface 5) is the cause of the generation of stray light.

[0066] Under the same conditions, ray simulations were carried out on the Fresnel lens and the aspherical lens. Based on the simulation results, it was further verified that there is no stray light in the aspherical lens, while there is stray light in the Fresnel lens.

[0067] To further confirm the source of the stray light, an experimental verification was carried out on a common Fresnel lens. Refer to Figure 3 , and some light-shielding materials were used to shield the first apex surface 4, the draft surface 5, the first apex surface 4 and the draft surface 5 respectively. Then, a laser light source was used to test the Fresnel lens before and after shielding. It can be seen that after shielding the ineffective surface 3, the stray light of the laser light source has been improved. Based on this, it is considered that the reason for the existence of stray light in the Fresnel lens is due to the special structure of it, that is, the ineffective surface 3 (the first apex surface 4, the second apex surface 6 and the draft surface 5) it has is the cause of the stray light.

[0068] The ineffective surface 3 of the Fresnel lens is in the μm level in terms of size. At present, it is impossible to directly and precisely shield the ineffective surface 3 of the Fresnel lens. However, if the ineffective surface 3 is not shielded, stray light will be generated, seriously affecting the imaging quality.

[0069] For this reason, the present disclosure provides a Fresnel lens, including a lens body 8. One surface of the lens body 8 is a Fresnel surface, and the Fresnel surface has a plurality of ineffective surfaces 3 and a plurality of effective surfaces 7 corresponding to the plurality of ineffective surfaces 3 one by one.

[0070] In the related art, the following several methods are usually adopted to reduce the influence of stray light on the imaging quality:

[0071] First, a light-shielding material is chemically deposited on the entire Fresnel surface, and then the non-light-shielding area (effective surface) is removed by laser ablation. The light-shielding area (ineffective surface) needs to be retained without ablation, so as to retain the light-shielding material on the ineffective surface, and then it can play a role in improving the stray light.

[0072] Second, a light-shielding pattern is made on a transparent substrate, and then it is aligned and bonded with the Fresnel lens, so that the light-shielding pattern is aligned with the ineffective surface of the Fresnel lens, and the ineffective surface is shielded to reduce the influence of stray light on the ineffective surface.

[0073] Third, change the inclination angle of the ineffective surface. By changing the draft angle of the Fresnel lens (small inside and large outside), the reflection and refraction directions of light are changed, so as to improve the stray light.

[0074] However, none of the above three schemes can achieve precise shielding of the ineffective surface, and they also increase the weight, thickness and cost of the Fresnel lens.

[0075] In an exemplary embodiment of the present disclosure, to solve the above problems, the Fresnel lens has a first surface and a second surface arranged opposite to each other. One of the first surface and the second surface is set as the Fresnel surface, and the other surface of the first surface and the second surface can be set as an aspherical surface, for example, a plane. Among them, the Fresnel surface is an equal tooth height structure. The Fresnel surface has a plurality of concentric annular serrated structures, and the concentric annular serrated structures include an effective surface 7 and an ineffective surface 3 arranged opposite to each other. The ineffective surface 3 is closer to the center of the Fresnel lens than the effective surface 7. At least a part of at least one of the ineffective surfaces 3 has a recessed light-shielding area, and the light-shielding layer 1 fills the light-shielding area. Among them, the light-shielding layer 1 is used to block the Fresnel surface of the Fresnel lens. By blocking the ineffective surface 3 on the Fresnel surface, the phenomenon of stray light can be reduced, and the imaging quality of the Fresnel lens can be improved. In this example, the light-shielding layer 1 and the lens body 8 have a smooth transition. It can be understood that among the multiple ineffective surfaces 3 of the Fresnel surface, some of the ineffective surfaces 3 may have recessed light-shielding areas, or all of the ineffective surfaces 3 may have recessed light-shielding areas. In this way, on the basis of not affecting the imaging quality, the light-shielding layer 1 replaces a part of the thickness of the lens body 8, which neither increases the weight, thickness, and cost of the Fresnel lens nor realizes light shielding, reduces stray light, and improves the imaging quality. It can be understood that the light-shielding layer 1 and the lens body 8 are integrally provided. The light-shielding layer 1 only fills the light-shielding area (that is, the surface of the light-shielding layer 1 is smoothly connected to the surface of the lens body 8, there is no step structure or protruding structure, and there is no situation of blocking the adjacent effective surface 7, and no loss of effective light will be caused).

[0076] In an exemplary embodiment of the present disclosure, the material of the light-shielding layer 1 is a black organic material, and black has a better light-shielding effect.

[0077] In an exemplary embodiment of the present disclosure, the thickness of the light-shielding layer 1 is 0 to 5 μm.

[0078] In an exemplary embodiment of the present disclosure, the transmittance of the light-shielding layer 1 to visible light is 0 to 0.1%.

[0079] In an exemplary embodiment of the present disclosure, the material of the light-shielding layer 1 is black ink, and the viscosity of the black ink at room temperature (room temperature, about 25 - 26 degrees) is 10,000 to 30,000 mPa·s.

[0080] In an exemplary embodiment of the present disclosure, according to the specific structure of the ineffective surface 3, the ineffective surface 3 is divided into a first apex surface 4, a draft surface 5, and a second apex surface 6 connected in sequence. The first apex surface 4 and the second apex surface 6 are connected to the effective surfaces 7 on both sides.

[0081] In an exemplary embodiment of the present disclosure, the light-shielding area is an independent area. The light-shielding area may be located on the first vertex surface 4 of the ineffective surface 3. It can be understood that the range of the light-shielding area may cover the entire first vertex surface 4 or may cover a part of the first vertex surface 4.

[0082] Based on the above structure, this example also proposes a method for preparing a Fresnel lens. Before the Fresnel lens is formed, refer to Figure 4 , through a high-precision printing technique, first print a light-shielding material on the mold to form a light-shielding layer 1. The position of the light-shielding layer 1 on the mold corresponds one-to-one with the corresponding area of the ineffective surface 3 of the Fresnel lens. Refer to Figure 5 , and then immediately perform injection molding of the lens body 8. Refer to Figure 6 . After the lens body 8 is formed, demolding is carried out. In this way, when the lens body 8 is demolded, the light-shielding layer 1 is demolded together with the lens body 8, and the light-shielding layer 1 only exists in the designated area of the ineffective surface 3 of the lens body 8 and is integrated with the lens body 8, forming a Fresnel lens with a glare-shielding function. When applied in a virtual reality device, it can shorten the system thickness and improve the reality image quality.

[0083] Based on the concept of the present disclosure, the mold of the Fresnel lens is used as the tool for printing the light-shielding layer 1 at the same time. Before the lens body 8 is formed, the light-shielding material can be accurately printed at the same position as the ineffective surface 3 on the metal mold to form the light-shielding layer 1, and then steps such as the preparation of the lens body 8 are carried out, so as to accurately perform the shielding.

[0084] During the printing process, the wetting performance between the light-shielding material and the mold has an important impact on the printing quality and the adhesion of the light-shielding material. If the light-shielding material cannot be fully wetted on the mold surface, it will cause the light-shielding material not to spread evenly, resulting in printing defects such as uneven color and uneven thickness. Therefore, evaluating the wetting performance of different light-shielding materials on the mold is of great significance for the control of printing quality and the selection of light-shielding materials.

[0085] Therefore, before the preparation, it is necessary to first select a suitable light-shielding material. The contact angle is one of the important parameters for measuring the wetting performance of a liquid on a solid surface. By measuring the contact angle, the wetting performance of different light-shielding materials on the mold can be evaluated. The contact angle measuring instrument can quickly and accurately evaluate the wetting performance of different light-shielding materials on the mold by measuring the contact angle of the liquid droplet on the solid surface. During the measurement process, the light-shielding material is dropped on the mold surface, and the contact angle measuring instrument is used to record the shape and angle of the liquid droplet. By analyzing the size and change of the contact angle, the wetting performance of the light-shielding material on the mold surface can be judged, and according to the wetting performance of each light-shielding material, a suitable light-shielding material is selected. In this example, the selected light-shielding material is a black ink with a viscosity of 10000 - 30000 mPa·s at room temperature (about 25 - 26 degrees Celsius).

[0086] The preparation method specifically includes the following steps:

[0087] S01. Design a mold adapted to the structure of the Fresnel lens based on its structure; in the Fresnel lens, the first apex surface 4 on the invalid surface 3 is of the same size as the first apex surface 4 at the same position on the mold, the second apex surface 6 on the invalid surface 3 is of the same size as the second apex surface 6 at the same position on the mold, and the draft surface 5 on the invalid surface 3 is of the same size as the draft surface 5 at the same position on the mold. Therefore, the light-shielding layer 1 can be designed according to the parameters of the mold.

[0088] S02. Obtain the position parameters of the serrated structure on the Fresnel surface, match the range and related parameters of the first apex surface 4 on the serrated structure, input the related parameters into the 3D printer table device, and at the same time fix the mold on the printer table through a clamping fixture to prevent relative movement between the mold and the 3D printer table device during printing, which may cause printing errors. Refer to Figure 4 , the printing needle of the 3D printer table device is aligned with the area of the first apex surface 4 on the mold. Under the drive of the 3D printer table device, after the black ink in the printing needle is ejected, it is accurately sprayed on the area of the first apex surface 4 of the invalid surface 3. After printing, the black ink is photocured by a UV lamp to form the light-shielding layer 1, and the light-shielding layer 1 is preliminarily adhered to the mold. Among them, the diameter of the printing needle is 2 - 30 μm. The line width required to be printed and blocked by a single serration in the Fresnel surface ≤ 30 μm, the wavelength of the UV lamp is 350 - 400 nm, the curing time is 5 - 40 s, the position and area of the light-shielding layer 1 are the same as the width of the first apex surface 4 it fills. In this embodiment, the width of the light-shielding layer 1 is 1 - 30 μm.

[0089] S03. Refer to Figure 5 , inject the material of the lens body 8 into the mold, and after curing, form the lens body 8;

[0090] S04. Refer to Figure 6 , demold to obtain a Fresnel lens with a light-shielding layer 1 on the invalid surface 3.

[0091] For the Fresnel lens prepared by the above preparation method, refer to Figure 29, which can improve the glare phenomenon of the Fresnel lens. The mirror body 8 and the shading layer 1 are integrally arranged, and the mirror body 8 of the formed Fresnel lens naturally has a concave shading area, and the shading layer 1 is embedded in the shading area, and the surface of the shading layer 1 and the effective surface 7 and the draft surface 5 of the mirror body 8 are smoothly transitioned, and there is no step structure or convex structure. In terms of overall thickness, the shading layer 1 replaces a part of the thickness of the mirror body 8 material, and the total size of the Fresnel lens remains unchanged. The Fresnel lens prepared by the above method has a concave shading area on its mirror body 8 naturally. In this way, the total thickness of the serrated structure of the Fresnel lens remains unchanged, and the weight is reduced. At the same time, since the material of the mirror body 8 used becomes smaller, the preparation cost is reduced. At the same time, the shading layer 1 is used to precisely shield the designated area of the invalid surface 3. Based on its special structural form (the shading layer 1 and the mirror body 8 are integrally arranged, and the surface of the shading layer 1 is smoothly connected to the surface of the mirror body 8, and there is no step structure or raised structure), there will be no shielding of the adjacent effective surface 7, and no loss of effective light will be caused.

[0092] In an embodiment of the present disclosure, the areas of the first vertex surface 4 and the second vertex surface 6 of the invalid surface 3 may be the same. It is understandable that the areas of the first vertex surface 4 and the second vertex surface 6 of the invalid surface 3 may also be different.

[0093] In an embodiment of the present disclosure, the shading area may be an independent area, and the shading area is located on the second vertex surface 6 of the invalid surface 3. It can be understood that the range of the shading area may cover the entire second vertex surface 6 or a part of the second vertex surface 6. In this example, see Figure 7 , Figure 8 and Figure 9 The light-shielding layer 1 can be prepared on the second top-angle surface 6 by the same method as that of preparing the light-shielding layer 1 on the first top-angle surface 4.

[0094] In an embodiment of the present disclosure, the shading area may be an independent area, and the shading area is located on the draft surface 5 of the invalid surface 3. It can be understood that the range of the shading area may cover the entire draft surface 5 or a part of the draft surface 5. In this example, see Figure 10 , Figure 11 and Figure 12 The shading layer 1 can be prepared on the draft surface 5 by the same method as that of preparing the shading layer 1 on the first vertex surface 4, wherein in step 2, the area of the shading layer 1 printed on the mold is the same as the area of the draft surface 5.

[0095] In an exemplary embodiment of the present disclosure, the light-shielding region may be an independent region located on the first apex surface 4 and the draft surface 5 of the invalid surface 3. It can be understood that the range of the light-shielding region may cover the entire first apex surface 4 and the draft surface 5, or may cover a part of the first apex surface 4 and the draft surface 5. In this example, refer to Figure 13 、 Figure 14 and Figure 15 , the light-shielding layer 1 may be prepared on the first apex surface 4 and the draft surface 5 by the same method as that for preparing the light-shielding layer 1 on the first apex surface 4. Wherein, in step 2, the area of the light-shielding layer 1 printed on the mold is the same as the total area of the first apex surface 4 and the draft surface 5.

[0096] In an exemplary embodiment of the present disclosure, the light-shielding region may be an independent region located on the second apex surface 6 and the draft surface 5 of the invalid surface 3. It can be understood that the range of the light-shielding region may cover the entire second apex surface 6 and the draft surface 5, or may cover a part of the second apex surface 6 and the draft surface 5. In this example, refer to Figure 16 、 Figure 17 and Figure 18 , the light-shielding layer 1 may be prepared on the second apex surface 6 and the draft surface 5 by the same method as that for preparing the light-shielding layer 1 on the first apex surface 4. Wherein, in step 2, the area of the light-shielding layer 1 printed on the mold is the same as the total area of the second apex surface 6 and the draft surface 5.

[0097] In an exemplary embodiment of the present disclosure, the light-shielding region may be an independent region located on the first apex surface 4, the second apex surface 6 and the draft surface 5 of the invalid surface 3. It can be understood that the range of the light-shielding region may cover the entire first apex surface 4, the second apex surface 6 and the draft surface 5, that is, the light-shielding layer 1 covers the entire invalid surface 3, or may cover a part of the first apex surface 4, the second apex surface 6 and the draft surface 5. In this example, refer to Figure 19 、 Figure 20 and Figure 21 , the light-shielding layer 1 may be prepared on the first apex surface 4, the second apex surface 6 and the draft surface 5 by the same method as that for preparing the light-shielding layer 1 on the first apex surface 4. Wherein, in step 2, the area of the light-shielding layer 1 printed on the mold is the same as the total area of the first apex surface 4, the second apex surface 6 and the draft surface 5.

[0098] In an exemplary embodiment of the present disclosure, the light-shielding region may include two independent sub-light-shielding regions respectively located on the first apex surface 4 and the second apex surface 6 of the invalid surface 3. It can be understood that the range of one of the sub-light-shielding regions may cover the entire first apex surface 4, or may cover a part of the first apex surface 4, and the other sub-light-shielding region may cover the entire second apex surface 6, or may cover a part of the second apex surface 6. In this example, refer to Figure 22 、Figure 23 And Figure 24 For Figure 24 , the light-shielding layer 1 can be prepared on the first apex surface 4 and the second apex surface 6 by the same method as that for preparing the light-shielding layer 1 on the first apex surface 4. Among them, in step 2, the areas of the two light-shielding layers 1 printed on the mold are the same as the areas of the first apex surface 4 and the second apex surface 6, respectively.

[0099] In an embodiment of the present disclosure, when performing ink printing, there will be a phenomenon that the ink exceeds the printing area. In this regard, the ink exceeding the printing area can be removed to ensure that the light-shielding layer 1 is accurately obtained. In this example, after the ink is printed on the mold and cured, a mask is used, and after the exposure and development processes, the ink exceeding the specified area is removed, so as to accurately form the light-shielding layer 1 on the first apex surface 4, the draft surface 5, and / or the second apex surface 6.

[0100] In an embodiment of the present disclosure, the bonding strength between the light-shielding layer 1 and the lens body 8 is not less than 100 times the bonding strength between the light-shielding layer 1 and the mold. In this way, it can be ensured that the light-shielding layer 1 can be smoothly demolded.

[0101] In another embodiment of the present disclosure, refer to Figure 25 and Figure 26 And Figure 27 , the lens body 8 can be formed inside the mold by printing.

[0102] In another embodiment of the present disclosure, both the first surface and the second surface of the Fresnel lens are provided as Fresnel surfaces, and the light-shielding layer 1 is provided on the ineffective surface 3.

[0103] In another embodiment of the present disclosure, the Fresnel surface can be an equal pitch structure.

[0104] The Fresnel lens proposed in the present disclosure can effectively improve the glare caused by the ineffective surface 3 of the Fresnel lens and improve the imaging quality of the Fresnel lens. Applying the Fresnel lens of the present disclosure to a virtual reality device to form a multi-piece Fresnel direct-through optical VR solution has the advantages of high luminous efficiency and high image quality, can compete with the current mainstream Pancake VR optical solution in the market, and has great application value.

[0105] Specifically, the Fresnel lens proposed in the present disclosure can be perfectly integrated with the light-shielding material, which is different from existing other solutions, and the light-shielding design can be selectively carried out.

[0106] Based on the above structure of the Fresnel lens, the present disclosure also provides a direct-through Fresnel lens group, wherein the direct-through Fresnel lens group has the above Fresnel lens.

[0107] Based on the structures of the above Fresnel lens and the through-type Fresnel lens group, the present disclosure also provides an optical device, where the optical imaging device has the above Fresnel lens; or, has the above through-type Fresnel lens group. The optical device can be an imaging device, a camera device, etc.

[0108] The Fresnel lens in the embodiments of the present disclosure is of an integral structure. Compared with other related technologies, for example, referring to Figure 28 , in the way of forming a light-shielding layer on the ineffective surface 3 of the Fresnel lens, the present disclosure realizes the precise printing and shielding of the ineffective surface 3 of the Fresnel lens, improves the glare phenomenon of the Fresnel lens, and thus is beneficial to using the Fresnel lens in a virtual reality device, solves the difficulty of directly and precisely shielding the ineffective surface 3 of the Fresnel lens before, and at the same time does not increase the weight, thickness and cost of the Fresnel lens, and has high practicability and economy.

[0109] Those skilled in the art will readily conceive of other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure, which follow the general principles of the present disclosure and include known common knowledge or conventional technical means in the technical field not disclosed by the present disclosure. The specification and examples are only to be considered as exemplary, and the true scope and spirit of the present disclosure are pointed out by the appended claims.

Claims

1. A Fresnel lens, characterized in that, The Fresnel lens includes a lens body and a light-shielding layer; At least one surface of the lens body is a Fresnel surface, and the Fresnel surface has an ineffective surface. At least part of at least one of the ineffective surfaces has a recessed light-shielding area, and the light-shielding layer fills the light-shielding area, and the light-shielding layer is smoothly transitioned with the lens body.

2. The Fresnel lens according to claim 1, wherein The Fresnel surface has a plurality of the ineffective surfaces; the number of the light-shielding layers is a plurality; and the plurality of light-shielding layers correspond to the plurality of ineffective surfaces one by one.

3. The Fresnel lens according to claim 1, wherein, The ineffective surface includes a first apex surface, a draft surface, and a second apex surface that are connected in sequence; At least one of the first apex surface, the draft surface, and the second apex surface has a light-shielding area.

4. The Fresnel lens according to claim 1, characterized in that, The material of the light-shielding layer is a black organic material.

5. The Fresnel lens according to claim 1, wherein The thickness of the light-shielding layer is not greater than 5 μm; the light transmittance of the light-shielding layer to visible light is 0 to 0.1%.

6. A preparation method of a Fresnel lens, characterized in that, It is prepared by the following method: Provide a mold for preparing a Fresnel lens; At least part of the area of the mold corresponding to the ineffective surface of the Fresnel lens, form a light-shielding layer; the ineffective surface includes a first apex surface, a draft surface, and a second apex surface; Fill the mold with lens body material to form a lens body; Demold to obtain a Fresnel lens with a light-shielding layer on the ineffective surface.

7. The manufacturing method of the Fresnel lens according to claim 6, characterized in that, Forming a light-shielding layer at least part of the area of the mold corresponding to the ineffective surface of the Fresnel lens includes: Print black ink at least part of the area of the mold corresponding to the ineffective surface of the Fresnel lens. After curing, add a mask plate process. After exposure and development, form a light-shielding area at least one of the first apex surface, the draft surface, and the second apex surface corresponding to the mold; the viscosity of the black ink at room temperature is 10,000 to 30,000 mPa·s.

8. The preparation method of the Fresnel lens according to claim 7, wherein The bonding strength between the light-shielding layer and the lens body is not less than 100 times the bonding strength between the light-shielding layer and the mold.

9. A direct-through Fresnel lens group, characterized in that, The through-type Fresnel lens group has the Fresnel lens according to any one of claims 1-8.

10. An optical device, characterized in that, It includes the Fresnel lens according to any one of claims 1-8; or, includes the through-type Fresnel lens group according to claim 9.

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