Small-size fisheye lens for large-target-surface imaging and optical system

Abstract

The invention discloses a small-size fisheye lens and a small-size fisheye lens device for large-target-surface imaging. The lens sequentially comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with negative focal power, a fourth lens with positive focal power, a diaphragm, a fifth lens with positive focal power, a sixth lens with positive focal power, a seventh lens with negative focal power and an eighth lens with positive focal power from an object side to an image side, the sixth lens and the seventh lens are mutually glued to form a first glued lens group, the eighth lens is an aspheric lens, the focal power of each lens is reasonably configured, and the image side lens is designed to be the glued lens and the aspheric lens, so that aberration such as spherical aberration, coma, astigmatism and image plane bending is effectively improved, and good imaging quality is realized. The method is suitable for the field of fisheye lens design.

Description

Technical Field

[0001] This invention relates to the technical field of fisheye lens design, specifically a small-volume fisheye lens and optical system for large target surface imaging. Background Technology

[0002] A fisheye lens is a lens with a focal length of 16mm or less and an angle of view close to or equal to 180°. It is an extreme wide-angle lens that maximizes the field of view. The front lens element of this type of lens has a very short diameter and protrudes forward in a parabolic shape. As a special type of ultra-wide-angle lens, the fisheye lens aims to achieve or exceed the range that the human eye can see. In recent years, the development of miniaturized, large-aperture, and high-resolution fisheye lenses has become increasingly important.

[0003] The mainstream fisheye lenses on the market today have the following drawbacks: large size and low resolution. They mainly use chips with 2 to 8 megapixels, which results in insufficient resolution in some scenes, making it impossible to distinguish clearly. The small imaging target area leads to poor performance in complex image processing and low-light environments, which is insufficient to meet the higher requirements of the application scenarios. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention provides a small-volume fisheye lens and optical system for imaging large target surfaces, solving the problems of large volume, low resolution, and small imaging target surface of existing fisheye lenses.

[0005] According to a first aspect of the present invention, a small-volume fisheye lens for large target surface imaging includes: From the object side to the image side, the lens consists of: a first lens with negative optical power, a second lens with negative optical power, a third lens with negative optical power, a fourth lens with positive optical power, an aperture stop, a fifth lens with positive optical power, a sixth lens with positive optical power, a seventh lens with negative optical power, and an eighth lens with positive optical power.

[0006] The small-volume fisheye lens according to embodiments of the present invention has at least the following beneficial effects: This invention designs the lens power from the object side to the image side to be negative, negative, negative, positive, positive, positive, negative, positive, and positive in sequence. After the three negative power lenses, three symmetrical positive power lenses are arranged behind them, which effectively improves aberrations such as spherical aberration, coma, astigmatism, and image plane curvature, thereby achieving good image quality. Compared with existing lenses on the market, it is smaller in size, has a larger imaging target area, and has excellent image quality, clear image, and various stray lights are effectively controlled.

[0007] According to some embodiments of the present invention, the sixth lens and the seventh lens are glued together to form a glued lens assembly.

[0008] According to some embodiments of the present invention, the eighth lens is an aspherical lens.

[0009] According to some embodiments of the present invention, the object side of the first lens is convex and the image side is concave; The object side of the second lens is convex, and the image side is concave. The object side of the third lens is concave, and the image side is convex. The fourth mirror, the fifth lens, and the sixth lens are all biconvex lenses; The seventh lens is a biconcave lens; The object side of the eighth lens is concave, and the image side is convex.

[0010] According to some embodiments of the present invention, the following conditional expressions are satisfied: 1.729≤Nd1≤2.1041; 1.487≤Nd2≤1.64; Wherein, Nd1 is the average refractive index of the d-line of the first lens and the second lens; Nd2 is the average refractive index of the d-line of the fifth lens and the sixth lens.

[0011] According to some embodiments of the present invention, the following conditional expressions are satisfied: 0.15≤t1 / T_1≤0.3; Where T_1 is the distance from the object side of the first lens to the aperture stop; t1 is the distance between the image side of the first lens and the object side of the second lens.

[0012] According to some embodiments of the present invention, the following conditional expressions are satisfied: 2.0 ≤ |fl1 / EFL| ≤ 4.5; Wherein, fl1 is the focal length of the first lens; EFL is the total focal length of the fisheye lens.

[0013] According to some embodiments of the present invention, the following condition is satisfied: 0.30≤|Y / sinω*TTL|≤1.088; Where Y is the image height of the lens; ω is the half field of view of the lens; and TTL is the distance from the eighth lens to the imaging plane.

[0014] According to some embodiments of the present invention, the following condition is satisfied: 8.1 ≤ TTL / EFL ≤ 10.5 Wherein, EFL is the focal length of the optical system; TTL is the distance from the eighth lens to the imaging plane.

[0015] An optical system according to a second aspect of an embodiment of the present invention includes the aforementioned small-volume fisheye lens.

[0016] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 A schematic diagram of an embodiment of a small-volume fisheye lens for large target surface imaging provided by the present invention; Figure 2 The present invention provides a small-volume fisheye lens for imaging large target surfaces, and an embodiment of its chromatic aberration diagram; Figure 3 The present invention provides a small-volume fisheye lens for imaging large target surfaces, and an optical fan pattern of one embodiment thereof; Figure 4 This invention provides a small-volume fisheye lens for imaging large target surfaces, and two structural schematic diagrams of its embodiments. Figure 5 The present invention provides a small-volume fisheye lens for imaging large target surfaces, and two embodiments thereof, including chromatic aberration diagrams. Figure 6 The present invention provides a small-volume fisheye lens for large target imaging, and two embodiments thereof, including the optical fan pattern.

[0018] Icon labels: First lens 101; Second lens 102; Third lens 103; Fourth lens 104; Fifth lens 105; Sixth lens 106; Seventh lens 107; Eighth lens 108; Aperture 109. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the drawings and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0021] In the description of this invention, "multiple" refers to two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features or their sequential relationship.

[0022] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are some embodiments of the present invention, not all embodiments.

[0024] A fisheye lens is a lens with a focal length of 16mm or less and an angle of view close to or equal to 180°. It is an extreme wide-angle lens that maximizes the field of view. The front lens element of this type of lens has a very short diameter and protrudes forward in a parabolic shape. As a special type of ultra-wide-angle lens, the fisheye lens aims to achieve or exceed the range that the human eye can see. In recent years, the development of miniaturized, large-aperture, and high-resolution fisheye lenses has become increasingly important.

[0025] The mainstream fisheye lenses on the market today have the following drawbacks: large size and low resolution. They mainly use chips with 2 to 8 megapixels, which results in insufficient resolution in some scenes, making it impossible to distinguish clearly. The small imaging target area leads to poor performance in complex image processing and low-light environments, which is insufficient to meet the higher requirements of the application scenarios.

[0026] To address the aforementioned problems, this invention proposes a small-volume fisheye lens and optical system for imaging large target surfaces, solving the issues of large volume, low resolution, and small imaging target surface of existing fisheye lenses.

[0027] refer to Figures 1 to 6 The present invention provides a small-volume fisheye lens and optical system for large target imaging, which are implemented in the following embodiments: Reference Figure 1 and Figure 4 The embodiment of the present invention includes, from the object side to the image side, the following components in sequence: a first lens 101 with negative optical power, a second lens 102 with negative optical power, a third lens 103 with negative optical power, a fourth lens 104 with positive optical power, an aperture stop 109, a fifth lens 105 with positive optical power, a sixth lens 106 with positive optical power, a seventh lens 107 with negative optical power, and an eighth lens 108 with positive optical power.

[0028] Among them, the sixth lens 106 and the seventh lens 107 are glued together to form a cemented lens group, and the eighth lens 108 is an aspherical lens.

[0029] Furthermore, in some embodiments of the present invention, the object-side surface of the first lens 101 is convex and the image-side surface is concave; the object-side surface of the second lens 102 is convex and the image-side surface is concave; the object-side surface of the third lens 103 is concave and the image-side surface is convex; the fourth lens, the fifth lens 105 and the sixth lens 106 are all biconvex lenses; the seventh lens 107 is a biconcave lens; and the object-side surface of the eighth lens 108 is concave and the image-side surface is convex.

[0030] This invention designs the lens power from the object side to the image side to be negative, negative, negative, positive, positive, positive, negative, positive, and positive in sequence. After the three negative power lenses, three symmetrical positive power lenses are arranged. The sixth lens 106 and the seventh lens 107 on the image side are cemented together to form a cemented lens group. The eighth lens 108 is designed as an aspherical lens, thereby effectively improving aberrations such as spherical aberration, coma, astigmatism, and image plane curvature. Various stray lights are effectively controlled. Compared with existing lenses on the market, it is smaller in size and has a larger imaging target area, which can realize a small-volume fisheye lens imaging solution with excellent image quality, clear image, and compact structure.

[0031] Furthermore, the small-volume fisheye lens of this embodiment satisfies the following conditional expression: 1.729≤Nd1≤2.1041;(1) 1.487≤Nd2≤1.64;(2) Wherein, Nd1 is the average refractive index of the first lens 101 and the second lens 102; Nd2 is the average refractive index of the fifth lens 105 and the sixth lens 106.

[0032] This invention limits the range of nitrile materials used in the first lens 101 and the second lens 102 by specifying the average refractive index values ​​of the two negative power lenses, the first lens 101 and the second lens 102. If the average refractive index of the first lens 101 and the second lens 102 is within the range of condition (1), the first lens 101 and the second lens 102 have strong refractive power, which is beneficial to increase the field of view and realize lens miniaturization, and is also beneficial to correct spherical aberration. If the average refractive index of the first lens 101 and the second lens 102 is lower than the lower limit of the range of condition (1), the refractive index of the nitrile material corresponding to the first lens 101 and the second lens 102 is too low, which leads to an increase in its dispersion coefficient, resulting in insufficient field of view and an increase in the half-aperture of the first lens 101, which leads to an excessively large lens opening angle, which is not conducive to processing and manufacturing.

[0033] This invention specifies the refractive index of the nitrile material used for the positive optical power lens after the aperture stop 109, namely the fifth lens 105 and the sixth lens 106, through conditional formula (2). The aim is to correct aberrations by using nitrile material with a higher Abbe number. If the average refractive index Nd2 of the fifth lens 105 and the sixth lens 106 is higher than the upper limit of conditional formula (2), the refractive index of the nitrile material used is too high, resulting in a decrease in the dispersion coefficient. This increases the optical power of the sixth lens 106 in the composite cemented lens, losing the ideal aberration correction effect of the cemented lens, making it difficult to correct spherical aberration, astigmatism, and coma in small-volume fisheye lenses. If the average refractive index Nd2 of the fifth lens 105 and the sixth lens 106 is lower than the lower limit of conditional formula (2), the refractive index of the nitrile material used is too low, and the dispersion coefficient of the fifth lens 105 and the sixth lens 106 increases, affecting the stability of small-volume fisheye lenses in high and low temperature environments.

[0034] In this embodiment of the invention, the small-volume fisheye lens satisfies the following condition: 0.15≤t1 / T_1≤0.3;(3) Where T_1 is the distance from the object side of the first lens 101 to the aperture stop 109; t1 is the distance between the image side of the first lens 101 and the object side of the second lens 102.

[0035] This invention limits the distance relationship between lenses in the optical system through conditional expression (3). Satisfying conditional expression (3) is beneficial for lens miniaturization, providing a compact small-volume fisheye lens solution, and effectively suppressing stray light generated between lens elements. If conditional expression (3) exceeds the lower limit, severe stray light will appear at the lens edge, seriously affecting the image quality. If conditional expression (3) exceeds the upper limit, the optical power will be weakened, which is more beneficial for lens miniaturization. At the same time, spherical aberration, astigmatism, and coma will also increase accordingly, making aberration correction difficult. Therefore, conditional expression (3) balances the needs of lens miniaturization, stray light suppression, and aberration correction.

[0036] According to some embodiments of the present invention, the small-volume fisheye lens of the present invention further satisfies the following conditional expression: 2.0≤|fl1 / EFL|≤4.5; (4) Where fl1 is the focal length of the first lens 101; EFL is the total focal length of the small-volume fisheye lens.

[0037] The present invention defines the relationship between the front group of the lens and the total focal length of the lens through condition (4). If condition (4) exceeds the lower limit, the overall structure of the lens will be too compact, the tolerance sensitivity between the lenses will increase, and it will be difficult to process and assemble. If condition (4) exceeds the upper limit, it will be difficult to increase the target surface, the lens resolution will decrease, and it will not meet the current market demand.

[0038] Furthermore, in some embodiments, the small-volume fisheye lens of the present invention satisfies the following condition: 0.30≤|Y / sinω*TTL|≤1.088; (5) Where Y is the image height of the lens; ω is the half field of view of the lens; and TTL is the total optical length of the lens.

[0039] The embodiments of the present invention limit the proportional relationship between image height, field of view and total optical length through conditional expression (5). If conditional expression (5) exceeds the lower limit, the total length of the optical system will be too large, which is not conducive to the miniaturization of the lens. If conditional expression (5) exceeds the upper limit, the optical power required for each lens in the small-volume fisheye lens will increase, making it difficult to correct spherical aberration, astigmatism and coma.

[0040] According to some embodiments of the present invention, the small-volume fisheye lens also satisfies the following condition: 8.1≤ TTL / EFL≤10.5; (6) Where EFL is the focal length of the small-volume fisheye lens; TTL is the total optical length of the small-volume fisheye lens.

[0041] The present invention defines the relationship between the total optical length and focal length of the fisheye lens through conditional formula (6) to limit the size of the fisheye lens. If conditional formula (6) exceeds the lower limit, various aberrations of the lens, especially chromatic aberration and field aberration, are difficult to suppress, resulting in a decrease in image quality. If conditional formula (6) exceeds the upper limit, miniaturization of the lens is difficult, and the edge illumination of the lens is difficult to improve, which cannot meet the current market demand.

[0042] The following are examples of small-volume fisheye lenses used for imaging large target surfaces.

[0043] Example 1 Reference Figure 1 The embodiment of the present invention includes, from the object side to the image side, the following components in sequence: a first lens 101 with negative optical power, a second lens 102 with negative optical power, a third lens 103 with negative optical power, a fourth lens 104 with positive optical power, an aperture stop 109, a fifth lens 105 with positive optical power, a sixth lens 106 with positive optical power, a seventh lens 107 with negative optical power, and an eighth lens 108 with positive optical power. The radius of curvature R (mm), spacing D (mm), refractive index Nd, and Abbe number ABV of each surface of the small-volume fisheye lens from the object side to the image side in this embodiment are shown in the table below.

[0044] Table 1

[0045] Among them, the sixth lens 106 and the seventh lens 107 are glued together to form a cemented lens, and the eighth lens 108 is an aspherical lens. The aspherical formula corresponding to the aspherical lens is as follows:

[0046] in, In Table 3, "*4" represents the value of item AH4, "*6" represents the value of item BH6, "*8" represents the value of item CH8, "*10" represents the value of item DH10, and "*12" represents the value of item EH12. The parameters of the incident and exit surfaces of the aspherical lens in this embodiment are shown in the following table.

[0047] Table 2

[0048] The small-volume fisheye lens structure provided in this embodiment is as follows: Figure 1 As shown, the parameters of each lens satisfy the requirements of conditions (1) to (6), referring to... Figure 2 and Figure 3 , Figure 2 This is a chromatic aberration diagram of the small-volume fisheye lens provided in this embodiment. Figure 3 The light field diagrams of the small-volume fisheye lens provided in this embodiment under different field of view show that, through simulation verification by optical design software, the small-volume fisheye lens provided in this embodiment effectively suppresses various aberrations such as chromatic aberration, spherical aberration, coma, and astigmatism, achieving relatively excellent imaging quality and a resolution of 20 megapixels.

[0049] Example 2 Reference Figure 4 The embodiment of the present invention includes, from the object side to the image side, the following components in sequence: a first lens 101 with negative optical power, a second lens 102 with negative optical power, a third lens 103 with negative optical power, a fourth lens 104 with positive optical power, an aperture stop 109, a fifth lens 105 with positive optical power, a sixth lens 106 with positive optical power, a seventh lens 107 with negative optical power, and an eighth lens 108 with positive optical power. The radius of curvature R (mm), spacing D (mm), refractive index Nd, and Abbe number ABV of each surface of the small-volume fisheye lens from the object side to the image side in this embodiment are shown in the table below.

[0050] Table 3

[0051] Among them, the sixth lens 106 and the seventh lens 107 are glued together to form a cemented lens, and the eighth lens 108 is an aspherical lens. The aspherical formula corresponding to the aspherical lens is as follows:

[0052] in, In Table 3, "*4" represents the value of item AH4, "*6" represents the value of item BH6, "*8" represents the value of item CH8, "*10" represents the value of item DH10, and "*12" represents the value of item EH12. The parameters of the incident and exit surfaces of the aspherical lens in this embodiment are shown in the following table.

[0053] Table 2

[0054] The small-volume fisheye lens structure provided in this embodiment is as follows: Figure 4 As shown, the parameters of each lens satisfy the requirements of conditions (1) to (6), referring to... Figure 5 and Figure 6 , Figure 5 This is a chromatic aberration diagram of the small-volume fisheye lens provided in this embodiment. Figure 6 The light field diagrams of the small-volume fisheye lens provided in this embodiment under different field of view show that, through simulation verification by optical design software, the small-volume fisheye lens provided in this embodiment effectively suppresses various aberrations such as chromatic aberration, spherical aberration, coma, and astigmatism, achieving relatively excellent imaging quality and a resolution of 20 megapixels.

[0055] In summary, this invention effectively corrects various aberrations of fisheye lenses, such as chromatic aberration, spherical aberration, coma, and astigmatism, by rationally configuring the optical power of the lenses in a small-volume fisheye lens and setting cemented and aspherical lenses. It achieves a balance between lens miniaturization and aberration correction. At the same time, it effectively controls various stray lights and limits the total length of the lens to the tens of millimeters. Compared with existing lenses on the market, it is smaller, with an imaging target surface of 1 inch, which is much larger than the current mainstream 1 / 2.7″ and 1 / 1.7″ target surface sizes, and a resolution of 20 megapixels.

[0056] This invention also proposes an optical system including the aforementioned small-volume fisheye lens, which has all the advantages of the aforementioned small-volume fisheye lens, and all aberrations are well corrected, forming a high-performance optical system.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0058] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A small-volume fisheye lens for imaging large target surfaces, characterized in that, include: From the object side to the image side, the lens consists of: a first lens with negative optical power, a second lens with negative optical power, a third lens with negative optical power, a fourth lens with positive optical power, an aperture stop, a fifth lens with positive optical power, a sixth lens with positive optical power, a seventh lens with negative optical power, and an eighth lens with positive optical power.

2. The small-volume fisheye lens according to claim 1, characterized in that: The sixth lens and the seventh lens are glued together to form a glued lens assembly.

3. The small-volume fisheye lens according to claim 2, characterized in that: The eighth lens is an aspherical lens.

4. The small-volume fisheye lens according to claim 3, characterized in that: The object side of the first lens is convex, and the image side is concave. The object side of the second lens is convex, and the image side is concave. The object side of the third lens is concave, and the image side is convex. The fourth mirror, the fifth lens, and the sixth lens are all biconvex lenses; The seventh lens is a biconcave lens; The object side of the eighth lens is concave, and the image side is convex.

5. The small-volume fisheye lens according to claim 4, characterized in that: The following conditions must be met: 1.729≤Nd1≤2.1041; 1.487≤Nd2≤1.64; Wherein, Nd1 is the average refractive index of the first lens and the second lens; Nd2 is the average refractive index of the fifth lens and the sixth lens.

6. The small-volume fisheye lens according to claim 4, characterized in that: The following conditions must be met: 0.15≤t1 / T_1≤0.3; Where t1 is the distance between the image side of the first lens and the object side of the second lens; T_1 is the distance from the object side of the first lens to the aperture stop.

7. The small-volume fisheye lens according to claim 4, characterized in that: The following conditions must be met: 2.0 ≤ |fl1 / EFL| ≤ 4.5; Wherein, fl1 is the focal length of the first lens; EFL is the total focal length of the small-volume fisheye lens.

8. The small-volume fisheye lens according to claim 4, characterized in that: The following condition must be met: 0.30 ≤ |Y / sinω*TTL| ≤ 1.088; Where Y is the image height of the small-volume fisheye lens; ω is the half field of view of the small-volume fisheye lens; and TTL is the total optical length of the small-volume fisheye lens.

9. The small-volume fisheye lens according to claim 4, characterized in that: The following conditions must be met: 8.1 ≤ TTL / EFL ≤ 10.5; Wherein, EFL is the focal length of the small-volume fisheye lens; TTL is the total optical length of the small-volume fisheye lens.

10. An optical system, characterized in that, Including small-volume fisheye lenses as described in any one of claims 1 to 9.

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