A hybrid Fresnel lens

Abstract

The present invention provides a hybrid Fresnel lens, which includes several full-wave regions. Each full-wave region is composed of sub-regions formed by arranging several concentric ring lens bodies and gaps between the rings. The several full-wave regions include a planar perforated portion disposed on the inner ring and a groove portion disposed on the outer ring, and the groove portion starts from the first sub-region that cannot be fabricated within the planar perforated portion. The hybrid Fresnel lens minimizes the shadow effect of the grooved Fresnel lens and the influence of the manufacturing limitations of the planar perforated Fresnel lens, making it have the characteristics of high gain and high bandwidth.

Description

Technical Field

[0001] The present invention relates to the field of optical technologies, and particularly to a hybrid Fresnel lens. Background Art

[0002] Fresnel lens antennas have the advantages of small volume, light weight, high gain, etc. Among them, the more subzones of the lens, the higher the gain. In the design of classical grooved Fresnel lenses, due to the height difference between adjacent subzones, a shadow effect will be generated, affecting the gain. The design of planar perforated Fresnel lenses circumvents the height difference of subzones in the classical grooved design by equivalently using the dielectric constants of materials and air in the original design in proportion, eliminating the shadow effect and increasing the gain. However, the fabrication of planar perforated Fresnel lenses is very difficult in practice because the perforation operation needs to be performed on the fabricated lens.

[0003] In recent years, with the development of 3D printing, the fabrication of planar perforated Fresnel lenses has become simple. By introducing hollow printing unit cells of different sizes to achieve different material ratios (infill percentages), the equivalent of different dielectric constants can be realized, and the larger the printing unit cell, the smaller the material ratio and the smaller the equivalent dielectric constant.

[0004] However, due to the nature of the Fresnel lens itself, the radius of the subzones decreases from the inner ring to the outer ring. In a full-wave zone, since the required dielectric constant becomes smaller, the size of the printing unit cells required for the subzones will become larger. During the actual fabrication process, when there are many subzones, it is very easy for the size of the printing unit cells to exceed the radius of the subzones. Further, during the 3D printing process, the molten material is deposited from the nozzle to the building area, and the diameter of the nozzle determines the size of the smallest printing feature. Usually, the nozzle is not replaced during one printing process, so the diameter of the nozzle is fixed. As a result, when designing a Fresnel lens antenna with many subzones, the planar perforated design cannot be fabricated, forcing the lens designer to abandon the intractable subzones in the planar perforated design, thereby reducing the gain to a level lower than that of the actually used grooved design; or only the classical grooved design can be used, which also affects the gain. Summary of the Invention

[0005] To solve the problem that when designing a Fresnel lens antenna with a large number of sub - regions, only the groove - type design, which is greatly affected by the shadow effect, can be used, resulting in low gain, the present invention provides a hybrid Fresnel lens. The Fresnel lens antenna is divided into a planar perforated part in the inner ring and a groove part in the outer ring. When designing, starting from the sub - region of the planar perforated part that cannot be fabricated, the classic groove - type design is adopted, so as to retain as many sub - regions of the planar perforated type that can be fabricated by 3D printing as possible, minimize the influence of the shadow effect, and maximize the gain.

[0006] To achieve the above - mentioned purpose, the specific technical solutions provided by the present invention are as follows:

[0007] A hybrid Fresnel lens includes several full - wave regions, and each full - wave region is composed of sub - regions arranged by several concentric - ring lens bodies and the gaps between the rings. Preferably, the several full - wave regions include a planar perforated part arranged in the inner ring and a groove part arranged in the outer ring, and the groove part starts from the first sub - region in the planar perforated part that cannot be fabricated.

[0008] Preferably, the fabrication includes 3D printing.

[0009] Preferably, the several full - wave regions are fixedly connected to each other through support arms.

[0010] Preferably, the ring widths of the concentric - ring lens bodies and the gaps between the rings gradually decrease along the direction extending outward from the center of the circle.

[0011] Preferably, in the planar perforated part, the heights of the concentric - ring lens bodies are the same; in the groove part, the heights of the concentric - ring lens bodies of each full - wave region gradually decrease along the direction extending outward from the center of the circle.

[0012] Preferably, the planar perforated part is provided with hollow printing units that penetrate the concentric - ring lens bodies, and the sizes of the hollow printing units of each full - wave region gradually increase along the direction extending outward from the center of the circle.

[0013] Preferably, the setting position of the groove part satisfies that in the planar perforated part, when the size of the hollow printing unit in the concentric - ring lens body is greater than the ring width of the concentric - ring lens body, the groove part starts to be set.

[0014] The beneficial effects of the present invention:

[0015] (1) The hybrid Fresnel lens antenna described in the present application combines the planar perforated Fresnel lens and the groove - type Fresnel lens, minimizing the influence of the shadow effect of the groove - type Fresnel lens and the manufacturing limitations of the planar perforated Fresnel lens, making it have the characteristics of high gain and high bandwidth.

[0016] (2) The present application can increase the gain and control the influence of the shadow effect while making the Fresnel lens antenna larger, so as to ensure the maximization of the gain.

[0017] (3) The hybrid Fresnel lens antenna described in the present application is based on a planar perforated Fresnel lens, and a grooved Fresnel lens body is arranged at the start of the first sub-region that cannot be fabricated in the planar perforated part, so that the whole can be directly fabricated by 3D printing. This avoids the situation where due to too many full-wave regions or sub-regions in the planar perforated Fresnel lens, the lens designer has to abandon the intractable sub-regions in the perforated design, thereby reducing the gain to a level lower than that of the actually used grooved design. Description of the Drawings

[0018] Figure 1 is a three-dimensional view of a grooved Fresnel lens;

[0019] Figure 2 is a schematic cross-sectional view of a grooved Fresnel lens;

[0020] Figure 3 is a three-dimensional view of a planar perforated Fresnel lens;

[0021] Figure 4 is a schematic cross-sectional view of a planar perforated Fresnel lens;

[0022] Figure 5 is a schematic structural view of a full-wave region in a planar perforated Fresnel lens;

[0023] Figure 6 is a three-dimensional view of a hybrid Fresnel lens in a preferred embodiment of the present application;

[0024] Figure 7 is a schematic cross-sectional view of a hybrid Fresnel lens in a preferred embodiment of the present application;

[0025] Figure 8 is the normalized radiation pattern of the waveguide at a target frequency of 30 GHz in a preferred embodiment of the present application;

[0026] Figure 9 is a schematic position view of the Fresnel lens and the waveguide in a preferred embodiment of the present application.

[0027] Among them, 1-full-wave region; 2-sub-region, 21-concentric ring lens body, 22-gap between rings; 3-planar perforated part; 4-grooved part; 5-hollow printing unit. Detailed Embodiment

[0028] As used in the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not use the difference in names as a way to distinguish components, but rather use the difference in the functions of the components as the criterion for distinction. As used throughout the specification and claims, the term "comprising" is an open-ended term and should be interpreted as "including but not limited to".

[0029] The orientation or positional relationships indicated by the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", and "vertical", etc. are based on the orientation or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention.

[0030] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "mounted", "connected", and "coupled" 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 direct connection, or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0031] In addition, in the description of the present invention, unless otherwise stated, the meanings of "several" and "multiple groups" are two or more.

[0032] The following description in the specification is the preferred embodiment for implementing the present application, but the description is for the purpose of explaining the general principles of the present application and is not used to limit the scope of the present application. The protection scope of the present application shall be subject to what is defined by the appended claims.

[0033] Referring to Figures 1 - 2 , which shows a perspective view and a cross-sectional schematic view of a grooved Fresnel lens. As can be seen from the figure, the grooved Fresnel lens includes several full-wave regions 1, and each full-wave region 1 further includes several sub-regions 2. By adjusting the height of each sub-region 2, the phase difference between adjacent regions is made equal to the required phase compensation. However, due to the height difference between adjacent sub-regions 2, the grooved Fresnel lens is affected by the shadow effect, thereby reducing its gain.

[0034] Referring to Figures 3 - 5, which shows a three-dimensional view, a cross-sectional schematic view of a planar perforated Fresnel lens, and a structural schematic view of a full-wave zone 1. As can be seen from the figure, the planar perforated Fresnel lens also includes several full-wave zones 1, each full-wave zone 1 includes several sub-zones 2, and the height of each sub-zone 2 is the same. The change in the relative permittivity in each sub-zone 2 is simulated by changing the percentage of the filling material. The planar perforated Fresnel lens can be realized by 3D printing. During the printing process, the molten material is deposited from the nozzle to the building area to form hollow printing units 5 of different sizes. The diameter of the nozzle determines the size of the smallest printing feature. Usually, the nozzle is not replaced during a 3D printing process, so the diameter of the nozzle is fixed. Therefore, only by increasing the air area can a lower percentage of the filling material be achieved, which leads to an increase in the size of the hollow printing unit 5.

[0035] However, for the planar perforated Fresnel lens, it cannot be manufactured in some cases: the decrease in the filling percentage from the inner sub-zone to the outer sub-zone of the full-wave zone 1 means an increase in the size of the hollow printing unit 5. At the same time, the ring width of the sub-zone 2 decreases step by step along the direction extending outward from the center of the circle, which is inversely proportional to the size trend of the hollow printing unit 5. Therefore, as the radius of the lens increases, the hollow printing unit 5 may be larger than the ring width of the sub-zone 2 that bears it, resulting in inability to print. In practical applications, it is very common for the planar perforated Fresnel lens to select a larger number of full-wave zones 1 or a larger number of sub-zones 2 in the design. This forces the lens designer to abandon the intractable sub-zone 2 in the planar perforated design, thus reducing the gain to a level lower than that of the actually used grooved design; or only the classic grooved design can be used, which also affects the gain.

[0036] Referring to Figures 6 - 7 , in a preferred embodiment of the present invention, a hybrid Fresnel lens is provided, which includes several full-wave zones 1 interconnected and fixed by support arms. Each full-wave zone 1 is composed of sub-zones 2 arranged by several concentric ring lens bodies 21 and inter-ring gaps 22, and the ring widths of the concentric ring lens bodies 21 and the inter-ring gaps 22 decrease step by step along the direction extending outward from the center of the circle.

[0037] Furthermore, the several full-wave zones 1 include a planar perforated part 3 arranged on the inner ring and a grooved part 4 arranged on the outer ring, and the grooved part 4 starts from the first sub-zone 2 that cannot be manufactured by 3D printing in the planar perforated part 3. Specifically, in the planar perforated part 3, the heights of the concentric ring lens bodies 21 are the same; in the grooved part 4, the heights of the concentric ring lens bodies 21 of each full-wave zone 1 decrease step by step along the direction extending outward from the center of the circle.

[0038] Furthermore, a hollow printing unit 5 that penetrates the concentric ring lens body 21 is provided in the planar punching portion 3, and the sizes of the hollow printing units 5 in each full-wave region 1 increase step by step along the direction extending outward from the center of the circle.

[0039] Furthermore, the setting position of the groove portion 4 satisfies: within the planar punching portion 3, when the size of the hollow printing unit 5 in the concentric ring lens body 21 is greater than the ring width of the concentric ring lens body 21, the groove portion 4 starts to be provided.

[0040] The design process of the hybrid Fresnel lens of the present invention is as follows:

[0041] Use a WR28 rectangular waveguide opening as the feed source of the lens antenna. The recommended frequency band of WR28 is 26.5 - 40 GHz, and the edge taper is selected to be -10 dB. Figure 8 Shows the normalized radiation pattern of the waveguide at a target frequency of 30 GHz. The -10 dB edge taper appears at 60°. The positions of the Fresnel lens and the waveguide are as Figure 9 shown. Considering a focal length of 30 mm, the radius R of the lens can be found through the following formula:

[0042] R = tan60°F1 - 1 where F is the focal length of the lens.

[0043] According to formula 1 - 1, the corresponding number W of full-wave regions 1 can be estimated:

[0044]

[0045] where λ is the design wavelength.

[0046] Generally, the number P of sub-regions 2 is selected to be 4, 8, or 16, which means that each sub-region 2 will correct the phase every 90°, 45°, or 22.5°. The larger the P value, the smaller the phase difference between adjacent sub-regions 2, the greater the gain of the Fresnel lens, and the narrower the ring width of the sub-region 2. Among them, due to the limitation of the 3D printer nozzle diameter (0.4 mm), taking P = 4 as an example, the number of sub-regions 2 is maximized to reduce the shadow effect. Table 1 below lists the design parameters:

[0047] Table 1 Parameter settings

[0048]

[0049]

[0050] According to the parameters determined in Table 1, the thickness d s and the outer radius b s of the s-th sub-region 2 in each full-wave region 1 of the grooved Fresnel lens can be obtained through formulas 1 - 3 and 1 - 4:

[0051]

[0052] where mod is the modulo operation for division to find the remainder, ε r is the relative permittivity of the material, ε r0 is the relative permittivity of air, P is the number of sub-regions 2 in full-wave region 1, and WP is the product of W and P.

[0053]

[0054] The ring width r of the s-th sub-region 2 s is:

[0055] r s = b s - b s-1 , s = 1, 2, …, WP, b0 = 0 1-5 In the design of a planar perforated Fresnel lens, the thickness d of all sub-regions 2 is the same:

[0056]

[0057] The radius of each sub-region 2 in the design of a planar perforated Fresnel lens can also be obtained using Equation 1-4, but the relative permittivity of each sub-region 2 is different from that in the design of a grooved Fresnel lens. In the grooved design, the relative permittivity of each sub-region 2 is the same as the material, while in the planar perforated Fresnel lens, the relative permittivity of each sub-region 2 in full-wave region 1 is different:

[0058]

[0059] Since different relative permittivities can be achieved by filling a certain proportion of air, another parameter, namely the filling percentage n s :

[0060]

[0061] During the 3D printing process of a planar perforated Fresnel lens, due to the fixed diameter of the nozzle, a lower filling percentage requires a larger hollow printing unit 5. By using the 3D printing simulation software ideaMaker, the size of the hollow printing unit 5 for different filling percentages can be found. The size of the hollow printing unit 5 can be determined by the number of hollow printing units 5 in an area of 10×10mm 2 .

[0062] The results show that within the limited 10×10mm 2In the effective medium region, as the filling percentage decreases, the number of hollow printing units 5 also decreases due to the increase in their size. Since the hollow printing units 5 become too large to fit within a 10×10 mm 2 area, this will result in an incorrect relative permittivity value.

[0063] Table 2 shows the parameters of sub-region 2 of the planar perforated Fresnel lens

[0064]

[0065] As can be seen from Table 2, the size of the hollow printing units 5 in the 8th sub-region 2 and the 12th sub-region 2 is larger than the ring width of sub-region 2, meaning that these two sub-regions 2 cannot be fabricated by 3D printing. Therefore, the part of the planar perforated Fresnel lens beyond the 8th sub-region 2 cannot be printed.

[0066] Also considering the derivative of the ring width of sub-region 2:

[0067]

[0068] As the number of sub-regions 2 increases, the ring width of the outer sub-regions 2 will decrease. Therefore, it is common for the size of the hollow printing units 5 in a sub-region 2 to be larger than the ring width of sub-region 2. In this case, the planar perforated Fresnel lens cannot be fully printed and can only be redesigned using the grooved type, resulting in a shadow effect and thus affecting the gain.

[0069] Therefore, in order to minimize the influence of the shadow effect of the grooved Fresnel lens and the manufacturing limitations of the planar perforated Fresnel lens, in the planar perforated Fresnel lens, when the size of the hollow printing units 5 is larger than the ring width of sub-region 2, the grooved Fresnel lens structure is started to be set. This hybrid structure can not only be directly fabricated by 3D printing but also has characteristics such as a small shadow effect and high gain.

[0070] Compared with the prior art, the beneficial effects of the hybrid Fresnel lens described in this application are as follows:

[0071] (1) The hybrid Fresnel lens antenna described in this application combines the planar perforated Fresnel lens and the grooved Fresnel lens, minimizing the influence of the shadow effect of the grooved Fresnel lens and the manufacturing limitations of the planar perforated Fresnel lens, making it have the characteristics of high gain and high bandwidth.

[0072] (2) This application can increase the size of the Fresnel lens antenna while increasing the gain and controlling the influence of the shadow effect to ensure the maximization of the gain.

[0073] (3) The hybrid Fresnel lens antenna described in this application is based on a planar perforated Fresnel lens, and a grooved Fresnel lens body is arranged at the start of the first sub-region that cannot be fabricated within the planar perforated portion, enabling its overall fabrication by direct 3D printing. This avoids the situation where, due to the excessive number of full-wave regions or sub-regions in the planar perforated Fresnel lens, lens designers are forced to abandon the intractable sub-regions in the perforated design, thereby reducing the gain to a level lower than that of the actually used grooved design.

[0074] The above description shows and describes several preferred embodiments of this application. However, as previously mentioned, it should be understood that this application is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the above teachings or the technology or knowledge in related fields. Any alterations and changes made by those skilled in the art that do not depart from the spirit and scope of this application shall fall within the protection scope of the appended claims of this application.

Claims

1. A hybrid Fresnel lens, comprising a plurality of full-wave zones, each full-wave zone being composed of sub-zones arranged by a plurality of concentric ring lens bodies and the gaps between the rings, characterized in that, The several full-wave regions include a planar perforated portion disposed on the inner ring and a groove portion disposed on the outer ring, and the groove portion starts from the first sub-region that cannot be fabricated within the planar perforated portion. In the planar perforated portion, the heights of the concentric ring lens bodies are the same; in the groove portion, the heights of the concentric ring lens bodies in each full-wave region gradually decrease along the direction extending outward from the center of the circle. A hollow printing unit penetrating the concentric ring lens bodies is provided in the planar perforated portion, and the sizes of the hollow printing units in each full-wave region gradually increase along the direction extending outward from the center of the circle. The fabrication includes 3D printing. During the printing process, the molten material is deposited from the nozzle onto the building area to form hollow printing units of different sizes.

2. The hybrid Fresnel lens according to claim 1, characterized in that, The several full-wave regions are fixedly connected to each other through support arms.

3. The hybrid Fresnel lens according to claim 2, characterized in that, The widths of the concentric ring lens bodies and the gaps between the rings gradually decrease along the direction extending outward from the center of the circle.

4. The hybrid Fresnel lens according to claim 3, characterized in that, The setting position of the groove portion satisfies that in the planar perforated portion, when the size of the hollow printing unit in the concentric ring lens body is greater than the width of the concentric ring lens body, the groove portion starts to be set.

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