A half-frame circumferential fisheye lens with FOV 200°

Abstract

The utility model provides a kind of FOV200's half frame circle fish eye lens, comprising: first lens, second lens, third lens, aperture diaphragm, fourth lens, fifth lens and sixth lens are sequentially distributed from object side to image surface;The first lens has negative refractive power, the second lens has negative refractive power, the third lens, the fourth lens and the fifth lens all have positive refractive power, the sixth lens has negative refractive power, the fifth lens and the sixth lens cementing. The utility model realizes imaging by the optical structure of six glass lenses, while ensuring imaging definition and color restoration accuracy in realizing large field angle, improves creative expressiveness and picture quality, improves scene coverage range, better meets the wide area capture demand under the scene of shooting interesting sky, narrow indoor or making creative short film etc.

Description

Technical Field

[0001] This utility model relates to the field of optical lens technology, and more specifically to a half-frame circular fisheye lens with a field of view of 200°. Background Technology

[0002] With the development of the digital photography era, the popularity of APS-C cameras has increased significantly, and people's exploration of images has become more diversified and personalized, leading to the booming development of fields such as panoramic photography and creative art photography. Among them, the circular fisheye lens, which can capture a circular field of view, continues to attract the attention of creators with its unique, exaggerated, and impactful visual effects and ability to create an immersive experience. However, the FOV (field of view) of existing APS-C fisheye lenses is generally 180°, which limits the range of scenes that can be covered and makes it difficult to meet users' needs for wide-area capture in creative scenarios. Utility Model Content

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a half-frame circular fisheye lens with a field of view of 200°, so as to solve the technical problem of the limited field of view of existing half-frame fisheye lenses.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This invention provides a half-frame circular fisheye lens with a field of view (FOV) of 200°, comprising: a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens, and a sixth lens arranged sequentially from the object plane to the image plane; the first lens has negative refractive power and is a meniscus lens, with its object-side surface and image-side surface being convex and concave, respectively; the second lens has negative refractive power and both its object-side surface and image-side surface are concave; the third, fourth, and fifth lenses all have positive refractive power and both their object-side and image-side surfaces are convex; the sixth lens has negative refractive power and is a meniscus lens, with its object-side surface and image-side surface being concave and convex, respectively; the fifth lens is cemented to the sixth lens; the first, second, third, fourth, fifth, and sixth lenses are made of glass.

[0006] In one embodiment, the focal length of the lens is 6.5 ± 0.2 mm.

[0007] In one embodiment, the total optical length of the lens is 65±0.5mm.

[0008] In one embodiment, the aperture of the lens is F2.0.

[0009] In one embodiment, the first lens, the second lens, and the third lens form a front group, and the focal length of the front group satisfies -25≤f1≤-23, where f1 is the focal length of the front group.

[0010] In one embodiment, the fourth lens, the fifth lens, and the sixth lens form a rear group, and the focal length of the rear group satisfies 14.5≤f2≤15.5, where f2 is the focal length of the rear group.

[0011] In one embodiment, the fifth lens and the sixth lens form a cemented lens, wherein the focal length of the cemented lens satisfies 46.3≤f3≤46.6, where f3 is the focal length of the cemented lens.

[0012] In one embodiment, the lens satisfies 2.1≤BFL / EFL≤2.4, where BFL is the equivalent air distance from the image side of the last lens in the lens system to the image plane, and EFL is the focal length of the optical system in the infinity focusing state.

[0013] In one embodiment, the refractive index of the first lens is greater than or equal to 1.56 and less than or equal to 1.58, the refractive index of the second lens is greater than or equal to 1.44 and less than or equal to 1.46, the refractive index of the third lens is greater than or equal to 1.88 and less than or equal to 1.9, the refractive index of the fourth lens is greater than or equal to 1.83 and less than or equal to 1.85, the refractive index of the fifth lens is greater than or equal to 1.59 and less than or equal to 1.6, and the refractive index of the sixth lens is greater than or equal to 1.92 and less than or equal to 1.94.

[0014] In one embodiment, the Abbe number of the first lens is greater than or equal to 60.7 and less than or equal to 60.9, the Abbe number of the second lens is greater than or equal to 94.4 and less than or equal to 94.6, the Abbe number of the third lens is greater than or equal to 39.1 and less than or equal to 39.3, the Abbe number of the fourth lens is greater than or equal to 42.6 and less than or equal to 42.8, the Abbe number of the fifth lens is greater than or equal to 68.4 and less than or equal to 68.6, and the Abbe number of the sixth lens is greater than or equal to 18.88 and less than or equal to 18.91.

[0015] The advantages of this invention compared to existing technologies are as follows: This invention achieves imaging through an optical structure of six glass lenses, expands the incident light range through a negative diopter meniscus lens, adjusts the diopter by combining biconcave and biconvex lenses to reduce aberrations, and eliminates chromatic aberration by cemented lenses. While achieving a large field of view, it ensures image clarity and color reproduction accuracy, enhances creative expression and image quality, breaks through the current limitation of a 180° field of view, increases the scene coverage, and makes the field of view reach 200°, better meeting the wide-area capture needs in scenarios such as shooting interesting skies, narrow indoor spaces, or making creative short films.

[0016] The above description is only an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of this utility model more obvious and understandable, the following are preferred embodiments, which are described in detail below. Attached Figure Description

[0017] Figure 1 A schematic diagram of the structure of a half-frame circular fisheye lens with a field of view of 200° provided for this utility model;

[0018] Figure 2 MTF curves of a half-frame circular fisheye lens with a field of view of 200° at spatial frequencies of 10, 20 and 30 in the full field of view, provided for this utility model;

[0019] Figure 3 A relative illumination curve of a half-frame circular fisheye lens with a field of view of 200° is provided for this utility model.

[0020] Figure label:

[0021] 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Aperture stop. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. The technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0023] It should be understood that, when used in this specification and the appended claims, the terms “comprising” and “including” indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0024] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0025] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0026] See Figure 1 As shown, this embodiment discloses a half-frame circular fisheye lens with a FOV of 200°, comprising: a first lens 1, a second lens 2, a third lens 3, an aperture stop 7, a fourth lens 4, a fifth lens 5, and a sixth lens 6 arranged sequentially from the object plane to the image plane; the first lens 1 has negative refractive power and is a meniscus lens, with its object-side surface and image-side surface being convex and concave, respectively; the second lens 2 has negative refractive power and both its object-side surface and image-side surface are concave; the third lens 3, the fourth lens 4, and the fifth lens 5 all have positive refractive power and both their object-side surface and image-side surface are convex; the sixth lens 6 has negative refractive power and is a meniscus lens, with its object-side surface and image-side surface being concave and convex, respectively; the fifth lens 5 is cemented to the sixth lens 6; the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are made of glass.

[0027] Understandably, FOV (Field of View) refers to the angular range of objects that a lens can capture. Light rays originate from different angles of the subject and are refracted sequentially by the first lens 1 to the sixth lens 6 before being imaged on the image plane. The larger the FOV, the wider the range of angles of the subject that can be imaged by the lens. Diopter is a measure of a lens's ability to deflect light. Positive diopter converges light, while negative diopter diverges it. In this embodiment, the negative diopter of the first lens 1, the second lens 2, and the sixth lens 6, combined with the positive diopter of the third lens 3, the fourth lens 4, and the fifth lens 5, regulates the direction of light propagation to adapt to a large field of view imaging. Meniscus lenses, such as the first lens 1 and the sixth lens 6, are lenses with one convex and one concave side, which can balance aberrations. Biconcave lenses, such as the second lens 2, can enhance light divergence. Biconvex lenses, such as the third lens 3, the fourth lens 4, and the fifth lens 5, can enhance convergence, ensuring efficient light processing. The cemented design of the fifth lens 5 and the sixth lens 6 facilitates the adjustment of light refraction through material matching, reducing light deviation and achieving orderly guidance and imaging of light. Therefore, this embodiment, through the types and combinations of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6, can effectively receive light with a 200° field of view and ensure complete imaging and sharp edges under an ultra-large field of view.

[0028] This embodiment features a 200° FOV half-frame circular fisheye lens. It achieves imaging through an optical structure of six glass lenses, expands the incident light range through a negative diopter meniscus lens, adjusts the diopter by combining biconcave and biconvex lenses to reduce aberrations, and eliminates chromatic aberration through cemented lenses. While achieving a large field of view, it ensures image clarity and color reproduction accuracy, enhances creative expression and image quality, breaks through the current limitation of a 180° field of view, and increases the scene coverage, making the field of view reach 200°. This better meets the wide-area capture needs in scenarios such as shooting interesting skies, narrow indoor spaces, or producing creative short films.

[0029] In a further embodiment, the focal length of the lens is 6.5 ± 0.2 mm. The focal length is the distance from the center of the lens to the image plane, and it directly affects the field of view, determining the width of the lens's field of view. In this embodiment, the lens center refers to the equivalent center of the optical system from the first lens 1 to the sixth lens 6, that is, the theoretical center where light converges after refraction by each lens. The short focal length of 6.5 ± 0.2 mm allows the lens to receive light from a wider angle; when an object is imaged through the lens, the short focal length can compress a large area of ​​the scene onto a limited image plane.

[0030] In a further embodiment, the total optical length of the lens is 65±0.5mm. In this embodiment, the total optical length is the distance from the object side of the first lens 1 to the image plane, providing space for the first lens 1 to the sixth lens 6 to be arranged sequentially and to process light rays with a 200° field of view, thus balancing the imaging requirements of an ultra-large field of view with the portability of the lens.

[0031] In a further embodiment, the lens aperture is F2.0. F2.0 is a relatively large aperture, which adjusts the amount of light entering the lens by controlling the size of the aperture stop 7. In this embodiment, it ensures sufficient light entering the lens at a 200° field of view, which helps maintain image brightness and improve image quality.

[0032] In a further embodiment, the first lens 1, the second lens 2, and the third lens 3 form a front group, with the focal length of the front group satisfying -25 ≤ f1 ≤ -23, where f1 is the focal length of the front group. The focal length of the front group is the equivalent focal length of the combination of the front group lenses, i.e., the combination of the first lens 1, the second lens 2, and the third lens 3. In this embodiment, the distance from the equivalent center of the front group to the image plane is the focal length of the front group. The focal length of the front group is a negative focal length, which has the function of diverging light. The negative focal length of -25 ≤ f1 ≤ -23 can effectively expand the range of light reception and divergence, reasonably guiding ultra-wide-angle light to the rear group, ensuring that the rear group can focus enough light, thus laying the foundation for realizing ultra-wide field-of-view imaging.

[0033] In a further embodiment, the fourth lens 4, the fifth lens 5, and the sixth lens 6 form a rear group, with the focal length of the rear group satisfying 14.5 ≤ f2 ≤ 15.5, where f2 is the focal length of the rear group. The focal length of the rear group is the equivalent focal length of the rear lens combination, i.e., the combination of the fourth lens 4, the fifth lens 5, and the sixth lens 6. In this embodiment, the distance from the equivalent center of the rear group to the image plane is the focal length of the rear group. The focal length of the rear group is a positive focal length, which has the function of converging light rays. The positive focal length of 14.5 ≤ f2 ≤ 15.5 can cancel the diverging effect of the front group, ensuring that light rays over an ultra-wide range are accurately projected onto the image plane, guaranteeing clear and blur-free imaging under an ultra-large field of view.

[0034] In a further embodiment, the fifth lens 5 and the sixth lens 6 form a cemented lens, with a focal length satisfying 46.3 ≤ f3 ≤ 46.6, where f3 is the focal length of the cemented lens. A cemented lens is formed by bonding two lenses together with optical adhesive. In this embodiment, it is formed by cementing a biconvex, positively refractive fifth lens 5 with a meniscus, negatively refractive sixth lens 6. Specifically, when light passes through the cemented surface, refraction occurs due to the difference in refractive indices between the fifth lens 5 and the sixth lens 6, correcting chromatic aberration that a single lens cannot eliminate. Simultaneously, they work together to converge or diverge light. The focal length range of 46.3 to 46.6 ensures that while eliminating chromatic aberration, it also works with the rear lens group to converge light, guaranteeing the imaging effect.

[0035] In a further embodiment, the lens satisfies 2.1 ≤ BFL / EFL ≤ 2.4, where BFL is the equivalent air distance from the image side of the last lens in the lens system to the image plane, and EFL is the focal length of the optical system at infinity focus. The equivalent air distance refers to the distance traveled by light from the image side of the sixth lens 6 to the image plane within the lens medium, converted to its distance in air. The ratio of this equivalent air distance to the focal length of 6.5 ± 0.2 mm at infinity focus is the back focal ratio. In this embodiment, the back focal ratio provides a suitable propagation distance for the light, allowing it to be smoothly focused onto the image plane, reducing deviations when focusing large-angle light, and improving the stability and sharpness of imaging in a very large field of view.

[0036] In a further embodiment, the refractive index of the first lens 1 is greater than or equal to 1.56 and less than or equal to 1.58, the refractive index of the second lens 2 is greater than or equal to 1.44 and less than or equal to 1.46, the refractive index of the third lens 3 is greater than or equal to 1.88 and less than or equal to 1.9, the refractive index of the fourth lens 4 is greater than or equal to 1.83 and less than or equal to 1.85, the refractive index of the fifth lens 5 is greater than or equal to 1.59 and less than or equal to 1.6, and the refractive index of the sixth lens 6 is greater than or equal to 1.92 and less than or equal to 1.94. The refractive index is the ratio of the speed of light in a vacuum to the speed of light in a medium; it determines the angle of light refraction. In this embodiment, the first lens 1 to the sixth lens 6 are each made of glass material with a specific refractive index range. For example, the third lens 3 has a high refractive index of 1.88-1.9 to enhance deflection, while the second lens 2 has a low refractive index of 1.44-1.46 for appropriate adjustment. Together, they ensure accurate focusing of light over an ultra-wide range, reduce aberrations, and improve image quality. In addition, each lens is made of glass, which can maintain stable optical performance in complex environments, reduce imaging deviation caused by deformation, and extend the lens life to meet the needs of long-term high-quality shooting with ultra-wide field of view.

[0037] In a further embodiment, the Abbe number of the first lens 1 is greater than or equal to 60.7 and less than or equal to 60.9, the Abbe number of the second lens 2 is greater than or equal to 94.4 and less than or equal to 94.6, the Abbe number of the third lens 3 is greater than or equal to 39.1 and less than or equal to 39.3, the Abbe number of the fourth lens 4 is greater than or equal to 42.6 and less than or equal to 42.8, the Abbe number of the fifth lens 5 is greater than or equal to 68.4 and less than or equal to 68.6, and the Abbe number of the sixth lens 6 is greater than or equal to 18.88 and less than or equal to 18.91. The Abbe number reflects the degree of dispersion of the lens material for different wavelengths of light. Materials with high Abbe numbers have low dispersion, while materials with low Abbe numbers have high dispersion. By combining lenses with different Abbe numbers, the dispersion phenomenon in light propagation can be canceled, reducing chromatic aberration. In this embodiment, the fifth lens 5 and the sixth lens 6 are cemented together. The combination of high and low Abbe numbers cancels out dispersion, ensuring the color quality of the image at a 200° field of view.

[0038] See Figure 2 As shown, Figure 2 The MTF curves of the half-frame circular fisheye lens with a FOV of 200° in this embodiment are shown at spatial frequencies of 10, 20, and 30 within the full field of view. It can be seen that the MTF curves are ≥0.9 at 10cyc / mm@MTF from the center to the edge and ≥0.65 at the edge at 30cyc / mm@MTF, indicating high lens resolution and sharpness.

[0039] See Figure 3 As shown, Figure 3 This is a relative illumination curve of the half-frame circular fisheye lens with a FOV of 200° in this embodiment. As can be seen from the figure, the relative illumination at the edge is greater than 45%, which will not cause vignetting during photography and meets the imaging performance requirements.

[0040] This embodiment provides a half-frame circular fisheye lens with a field of view (FOV) of 200°. It achieves imaging through an optical structure of six glass lenses, expands the incident light range through a negative diopter meniscus lens, adjusts the diopter by combining biconcave and biconvex lenses to reduce aberrations, and eliminates chromatic aberration through cemented lenses. While achieving a large field of view, it ensures image clarity and color reproduction accuracy, improves creative expression and image quality, breaks through the current limitation of 180° field of view, and increases the scene coverage, making the field of view reach 200°. This better meets the wide-area capture needs in scenarios such as shooting interesting skies, narrow indoor spaces, or making creative short films.

[0041] The above examples are merely illustrative of the technical content of this utility model to facilitate reader understanding, but do not imply that the implementation of this utility model is limited to these embodiments. Any technical extensions or re-creations made based on this utility model are protected by this utility model. The scope of protection of this utility model is defined by the claims.

Claims

1. A half-frame circular fisheye lens with a FOV of 200°, characterized in that, include: The system comprises, in sequence from the object plane to the image plane, a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens, and a sixth lens; the first lens has negative refractive power and is a meniscus lens, with its object-side surface being convex and its image-side surface being concave, respectively; the second lens has negative refractive power and both its object-side surface and image-side surface are concave; the third, fourth, and fifth lenses all have positive refractive power and both their object-side and image-side surfaces are convex; the sixth lens has negative refractive power and is a meniscus lens, with its object-side surface and image-side surface being concave and its image-side surface being convex, respectively; the fifth lens is cemented to the sixth lens; and the first, second, third, fourth, fifth, and sixth lenses are made of glass.

2. The half-frame circular fisheye lens with a FOV of 200° according to claim 1, characterized in that, The focal length of the lens is 6.5±0.2mm.

3. The half-frame circular fisheye lens with a FOV of 200° according to claim 1, characterized in that, The total optical length of the lens is 65±0.5mm.

4. The half-frame circular fisheye lens with a FOV of 200° according to claim 1, characterized in that, The aperture of the lens is F2.

0.

5. The half-frame circular fisheye lens with a FOV of 200° according to claim 1, characterized in that, The first lens, the second lens, and the third lens form a front group, and the focal length of the front group satisfies -25≤f1≤-23, where f1 is the focal length of the front group.

6. The half-frame circular fisheye lens with a FOV of 200° according to claim 1, characterized in that, The fourth lens, the fifth lens, and the sixth lens form a rear group, and the focal length of the rear group satisfies 14.5≤f2≤15.5, where f2 is the focal length of the rear group.

7. The half-frame circular fisheye lens with a FOV of 200° according to claim 1, characterized in that, The fifth lens and the sixth lens form a cemented lens, and the focal length of the cemented lens satisfies 46.3≤f3≤46.6, where f3 is the focal length of the cemented lens.

8. The half-frame circular fisheye lens with a FOV of 200° according to claim 1, characterized in that, The lens satisfies 2.1≤BFL / EFL≤2.4, where BFL is the equivalent air distance from the image side of the last lens in the lens system to the image plane, and EFL is the focal length of the optical system in the infinity focusing state.

9. The half-frame circular fisheye lens with a FOV of 200° according to claim 1, characterized in that, The first lens has a refractive index greater than or equal to 1.56 and less than or equal to 1.58, the second lens has a refractive index greater than or equal to 1.44 and less than or equal to 1.46, the third lens has a refractive index greater than or equal to 1.88 and less than or equal to 1.9, the fourth lens has a refractive index greater than or equal to 1.83 and less than or equal to 1.85, the fifth lens has a refractive index greater than or equal to 1.59 and less than or equal to 1.6, and the sixth lens has a refractive index greater than or equal to 1.92 and less than or equal to 1.

94.

10. The half-frame circular fisheye lens with a FOV of 200° according to claim 1, characterized in that, The Abbe number of the first lens is greater than or equal to 60.7 and less than or equal to 60.9; the Abbe number of the second lens is greater than or equal to 94.4 and less than or equal to 94.6; the Abbe number of the third lens is greater than or equal to 39.1 and less than or equal to 39.3; the Abbe number of the fourth lens is greater than or equal to 42.6 and less than or equal to 42.8; the Abbe number of the fifth lens is greater than or equal to 68.4 and less than or equal to 68.6; and the Abbe number of the sixth lens is greater than or equal to 18.88 and less than or equal to 18.91.

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