External lens and imaging equipment

Abstract

The invention provides an external lens and imaging equipment, and the external lens comprises five lenses which sequentially comprise 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 negative focal power, a fifth lens with negative focal power, a sixth lens with negative focal power, a fifth lens with negative focal power and a sixth lens with negative focal power from an object side to an imaging surface, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface; the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface; the image side surface of the fourth lens is a convex surface; the object side surface of the fifth lens is a concave surface, and the image side surface of the fifth lens is a convex surface; the first lens, the second lens, the third lens, the fourth lens and the fifth lens are cylindrical lenses; wherein the total optical length TTL of the external lens and the effective focal length f of the external lens meet the following conditions:-0.03 lt; tTL / flt; 0. According to the external lens and the imaging equipment provided by the invention, image information with a larger field angle can be obtained, the aspect ratio of wide-screen imaging is improved, and the experience effect of a user is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of imaging lenses, and in particular to an external lens and an imaging device. Background Art

[0002] With the popularity of smart mobile devices such as smartphones, and in order to meet the pursuit of better shooting effects in different scenarios, the functions of imaging modules are constantly being improved and expanded. In order to obtain better shooting effects, external lenses are usually installed at the lens of electronic devices. Due to the configuration of external lenses, the aspect ratio of widescreen imaging can be improved. However, the field of view is still small, and when shooting, the center of the image is clear, but the surroundings of the image are blurred; moreover, the resolution of existing external lenses is not high and cannot match high-pixel imaging devices. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to provide an external lens and imaging device, which have the characteristics of excellent imaging quality and can improve the aspect ratio of wide-screen imaging, thereby greatly improving the user experience.

[0004] The technical solution adopted by the present invention is: An external lens, comprising five lenses, which in order from the object side to the image plane along the optical axis include: a first lens with negative optical power, whose object side surface is convex and whose image side surface is concave; The second lens has a negative optical power, its object side surface is convex, and its image side surface is concave; The third lens has a negative optical power, its object side surface is concave, and its image side surface is convex; a fourth lens element having positive refractive power and a convex image-side surface; a fifth lens having negative optical power, whose object side surface is concave and whose image side surface is convex; The first lens, the second lens, the third lens, the fourth lens and the fifth lens are cylindrical lenses; The total optical length TTL of the external lens and the effective focal length f of the external lens satisfy: -0.03 <TTL / f<0。

[0005] Further preferably, the total optical length TTL of the external lens and the semi-aperture d1 of the object side of the first lens satisfy: 0.88 <TTL / d1<0.97。

[0006] More preferably, the total optical length TTL of the external lens and the sum ∑CT of the central thicknesses of the first to fifth lenses along the optical axis satisfy: 0.5 < ∑CT / TTL < 0.54; the sum ∑CT of the central thicknesses of the first to fifth lenses along the optical axis and the effective focal length f of the external lens satisfy: -0.02 < ΣCT / f < 0.

[0007] More preferably, the focal length f1 of the first lens and the effective focal length f of the external lens satisfy: 1.8 < f1 / f < 4.8; the curvature radius R1 of the object side surface of the first lens and the effective focal length f of the external lens satisfy: -0.05 < R1 / f < -0.02; the curvature radius R2 of the image side surface of the first lens and the effective focal length f of the external lens satisfy: -0.05 < R2 / f < -0.02.

[0008] More preferably, the focal length f2 of the second lens and the effective focal length f of the external lens satisfy: 0.04 < f2 / f < 0.1; the equivalent curvature radius R3’ of the object side surface of the second lens and the effective focal length f of the external lens satisfy: -0.53 < R3’ / f < -0.46; the equivalent curvature radius R4’ of the image side surface of the second lens and the effective focal length f of the external lens satisfy: -0.06 < R4’ / f < -0.02.

[0009] More preferably, the focal length f3 of the third lens and the effective focal length f of the external lens satisfy: 0.24 < f3 / f < 0.43; the equivalent curvature radius R5’ of the object side surface of the third lens and the effective focal length f of the external lens satisfy: 0.04 < R5’ / f < 0.11; the equivalent curvature radius R6’ of the image side surface of the third lens and the effective focal length f of the external lens satisfy: 0.08 < R6’ / f < 0.19.

[0010] More preferably, the focal length f4 of the fourth lens and the effective focal length f of the external lens satisfy: -0.04 < f4 / f < -0.01; the equivalent curvature radius R8’ of the image side surface of the fourth lens and the effective focal length f of the external lens satisfy: 0 < R8’ / f < 0.03.

[0011] More preferably, the focal length f5 of the fifth lens and the effective focal length f of the external lens satisfy: 0.01 < f5 / f < 0.05; the equivalent curvature radius R9’ of the object side surface of the fifth lens and the effective focal length f of the external lens satisfy: 0 < R9’ / f < 0.03; the equivalent curvature radius R10’ of the image side surface of the fifth lens and the effective focal length f of the external lens satisfy: 0.09 < R10’ / f < 0.19.

[0012] More preferably, the focal length f1 of the first lens and the combined focal length f2345 of the second lens, the third lens, the fourth lens, and the fifth lens satisfy: 1 < f1 / f2345 < 4; the clear aperture radius d1 of the object side surface of the first lens and the clear aperture radius d10 of the image side surface of the fifth lens satisfy: 2.8 < d1 / d10 < 3.

[0013] An imaging device, comprising a total of thirteen lenses, which sequentially include, along the optical axis from the object side to the imaging surface: the above-mentioned external lens and the built-in lens; the built-in lens is composed of eight lenses, and along the optical axis from the object side to the imaging surface, they are: A sixth lens with a negative optical power, the object side surface of which is convex and the image side surface of which is concave; A seventh lens with a negative optical power, the object side surface of which is convex and the image side surface of which is concave; An eighth lens with a negative optical power, the object side surface of which is concave and the image side surface of which is convex; A ninth lens with a positive optical power, the object side surface of which is convex and the image side surface of which is convex; A tenth lens with a positive optical power, the object side surface of which is concave and the image side surface of which is convex; An eleventh lens with a positive optical power, the object side surface of which is convex and the image side surface of which is convex; A twelfth lens with a negative optical power, the object side surface of which is concave and the image side surface of which is concave; A thirteenth lens with a positive optical power, the object side surface of which is convex and the image side surface of which is convex.

[0014] Compared with the prior art, the external lens and the imaging device provided by the present invention improve the imaging quality through specific surface shape combinations and reasonable optical power distributions, and have one or more advantages such as miniaturization, ultra-wide angle, large target surface, large aperture, and high-quality imaging. They can obtain picture information with a larger field of view angle, improve the aspect ratio of wide-screen imaging, and greatly improve the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where: Figure 1 is a schematic structural diagram of the external lens in Embodiment 1 of the present invention.

[0016] Figure 2 is a perspective view of the external lens in Embodiment 1 of the present invention.

[0017] Figure 3 is a schematic structural diagram of the external lens in Embodiment 2 of the present invention.

[0018] Figure 4Schematic diagram of the structure of the external lens in Embodiment 3 of the present invention.

[0019] Figure 5 Schematic diagram of the structure of the external lens in Embodiment 4 of the present invention.

[0020] Figure 6 Schematic diagram of the structure of the imaging device in Embodiment 5 of the present invention.

[0021] Figure 7 It is a field curvature curve diagram of the imaging device in embodiment 5 of the present invention.

[0022] Figure 8 This is a F-Tan (Theta) distortion curve diagram of the imaging device in Example 5 of the present invention.

[0023] Fig. 9 Graph showing the axial aberration of the imaging device in Embodiment 5 of the present invention.

[0024] Fig.10 This is an MTF curve diagram of the imaging device in Example 5 of the present invention.

[0025] Fig.11 This is a relative illumination curve diagram of the imaging device in Example 5 of the present invention.

[0026] Fig.12 Schematic diagram of the structure of the imaging device in Embodiment 6 of the present invention.

[0027] Fig.13 It is a field curvature curve diagram of the imaging device in Example 6 of the present invention.

[0028] Fig.14 This is a F-Tan (Theta) distortion curve diagram of the imaging device in Example 6 of the present invention.

[0029] Fig.15 Graph showing the axial aberration of the imaging device in Embodiment 6 of the present invention.

[0030] Fig.16 This is an MTF curve diagram of the imaging device in Example 6 of the present invention.

[0031] Fig.17 This is a relative illumination curve diagram of the imaging device in Example 6 of the present invention.

[0032] Fig.18 Schematic diagram of the structure of the imaging device in Embodiment 7 of the present invention.

[0033] Fig.19 It is a field curvature curve diagram of the imaging device in Example 7 of the present invention.

[0034] Fig. 20This is a F-Tan (Theta) distortion curve diagram of the imaging device in Example 7 of the present invention.

[0035] Fig.21 Graph showing the axial aberration of the imaging device in Embodiment 7 of the present invention.

[0036] Fig. 22 This is an MTF curve diagram of the imaging device in Example 7 of the present invention.

[0037] Fig.23 This is a relative illumination curve diagram of the imaging device in Example 7 of the present invention.

[0038] Fig.24 Schematic diagram of the structure of the imaging device in Example 8 of the present invention.

[0039] Fig.25 It is a field curvature curve diagram of the imaging device in Example 8 of the present invention.

[0040] Fig.26 This is a F-Tan (Theta) distortion curve diagram of the imaging device in Example 8 of the present invention.

[0041] Fig. 27 Graph showing the axial aberration of the imaging device in Embodiment 8 of the present invention.

[0042] Fig.28 This is an MTF curve diagram of the imaging device in Example 8 of the present invention.

[0043] Fig.29 This is a relative illumination curve diagram of the imaging device in Example 8 of the present invention.

[0044] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0045] In order to better understand the present application, a more detailed description will be made of various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of the embodiments of the present application, and are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0046] It should be noted that in this specification, the expressions of first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching of the present invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0047] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of explanation. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are only examples and are not drawn strictly to scale.

[0048] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object is called the object side of the lens, and the surface of each lens closest to the imaging plane is called the image side of the lens.

[0049] It should also be understood that the terms "comprises", "including", "having", "includes" and / or "comprising", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0050] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this article have the same meaning as commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that terms (such as terms defined in commonly used dictionaries) should be interpreted as having the same meaning as their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0051] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0052] The external lens provided in the embodiment of the present invention has a total of five lenses, which include: a first lens, a second lens, a third lens, a fourth lens and a fifth lens in sequence from the object side to the imaging surface along the optical axis. The first lens, the second lens, the third lens, the fourth lens and the fifth lens are all cylindrical lenses. The cylindrical lens of the present application has optical power in the Y-axis direction (vertical field of view) and has no optical power in the X-axis direction (horizontal field of view). The cylindrical lens can control the asymmetric optical path and is suitable for applications requiring one-dimensional focusing, beam shaping or astigmatism correction.

[0053] In some embodiments, the first lens may have a negative focal power, with its object side being convex and its image side being concave. The second lens may have a negative focal power, with its object side being convex and its image side being concave. The third lens may have a negative focal power, with its object side being concave and its image side being convex. The fourth lens may have a positive focal power, with its object side being either concave or convex and its image side being convex. The fifth lens may have a negative focal power, with its object side being concave and its image side being convex.

[0054] In some embodiments, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are cylindrical lenses. Among them, the first lens may be made of glass, and the second lens, the third lens, the fourth lens, and the fifth lens may be made of plastic.

[0055] In some embodiments, the optical total length TTL of the external lens and the effective focal length f of the external lens satisfy: -0.03 < TTL / f < 0. Meeting the above range can effectively limit the length of the lens while achieving a long focal length, which is beneficial to the miniaturization of the external lens.

[0056] In some embodiments, the optical total length TTL of the external lens and the clear aperture radius d1 of the object side of the first lens satisfy: 0.88 < TTL / d1 < 0.97. It can be understood that the clear aperture radius of the object side of the first lens is the clear aperture radius in the Y direction. Meeting the above range is beneficial to the miniaturization of the external lens.

[0057] In some embodiments, the optical total length TTL of the external lens and the sum ∑CT of the central thicknesses of the first lens to the fifth lens along the optical axis satisfy: 0.5 < ∑CT / TTL < 0.54. Meeting the above range can effectively compress the total length of the external lens, and is beneficial to the structural design and production process of the external lens.

[0058] In some embodiments, the sum ∑CT of the central thicknesses of the first lens to the fifth lens along the optical axis and the effective focal length f of the external lens satisfy: -0.02 < ΣCT / f < 0. Meeting the above range can effectively correct the field curvature and distortion of the external lens, and improve the imaging quality of the external lens.

[0059] In some embodiments, the focal length f1 of the first lens and the effective focal length f of the external lens satisfy: 1.8 < f1 / f < 4.8; the object-side curvature radius R1 of the first lens and the effective focal length f of the external lens satisfy: -0.05 < R1 / f < -0.02; the image-side curvature radius R2 of the first lens and the effective focal length f of the external lens satisfy: -0.05 < R2 / f < -0.02. It can be understood that the object-side curvature radius of the first lens is the same as the object-side equivalent curvature radius of the first lens, and the image-side curvature radius of the first lens is the same as the image-side equivalent curvature radius of the first lens. Satisfying the above ranges, by setting the first lens to have a negative refractive power and a suitable surface shape, it is beneficial for the first lens to collect a larger angle of light and collect as much light as possible into the subsequent optical system, increasing the light flux while achieving a large field of view. More specifically, 1.91 < f1 / f < 4.469.

[0060] In some embodiments, the focal length f2 of the second lens and the effective focal length f of the external lens satisfy: 0.04 < f2 / f < 0.1; the object-side equivalent curvature radius R3’ of the second lens and the effective focal length f of the external lens satisfy: -0.53 < R3’ / f < -0.46; the image-side equivalent curvature radius R4’ of the second lens and the effective focal length f of the external lens satisfy: -0.06 < R4’ / f < -0.02. Satisfying the above ranges can diverge a large range of light entering the system to a certain extent, which is beneficial for sharing the negative optical power of the first lens, avoiding excessive light deflection, and reducing the difficulty of aberration correction.

[0061] In some embodiments, the focal length f3 of the third lens and the effective focal length f of the external lens satisfy: 0.24 < f3 / f < 0.43; the object-side equivalent curvature radius R5’ of the third lens and the effective focal length f of the external lens satisfy: 0.04 < R5’ / f < 0.11; the image-side equivalent curvature radius R6’ of the third lens and the effective focal length f of the external lens satisfy: 0.08 < R6’ / f < 0.19. Satisfying the above ranges is beneficial for the smooth transition of light and improves the imaging quality of the external lens.

[0062] In some embodiments, the focal length f4 of the fourth lens and the effective focal length f of the external lens satisfy: -0.04 < f4 / f < -0.01; the image-side equivalent curvature radius R8’ of the fourth lens and the effective focal length f of the external lens satisfy: 0 < R8’ / f < 0.03. Satisfying the above conditions, by reasonably setting the focal length and surface shape of the fourth lens, it is beneficial for light convergence, enabling the light trend to smoothly transition to the rear, reducing the height of the light incident on the rear, slowing down the upward trend of the light, avoiding the loss of light energy of the large field of view light reaching the rear system, facilitating the improvement of the illuminance of the edge field of view, balancing aberrations, and being beneficial for achieving a short optical total length.

[0063] In some embodiments, the focal length f5 of the fifth lens and the effective focal length f of the external lens satisfy: 0.01 < f5 / f < 0.05; the equivalent curvature radius R9' of the object side surface of the fifth lens and the effective focal length f of the external lens satisfy: 0 < R9' / f < 0.03; the equivalent curvature radius R10' of the image side surface of the fifth lens and the effective focal length f of the external lens satisfy: 0.09 < R10' / f < 0.19. By satisfying the above conditions, the light can be diverged, making the light in the peripheral field of view show an upward trend, which is beneficial for the image points on the imaging surface to be away from the optical axis, so as to facilitate the realization of a large target surface and obtain a larger picture, effectively eliminate aberration, and improve the resolution ability of the external lens.

[0064] In some embodiments, the focal length f1 of the first lens and the combined focal length f2345 of the second, third, fourth, and fifth lenses satisfy: 1 < f1 / f2345 < 4. By satisfying the above range, through reasonable setting of the focal length relationships of each lens, it is beneficial for the smooth transition of light, and at the same time corrects various aberrations of the external lens, improving the imaging quality of the external lens. More specifically, 1.04 < f1 / f2345 < 3.84.

[0065] In some embodiments, the clear aperture radius d1 of the object side surface of the first lens and the clear aperture radius d10 of the image side surface of the fifth lens satisfy: 2.8 < d1 / d10 < 3. It can be understood that both the clear aperture radius of the object side surface of the first lens and the clear aperture radius of the image side surface of the fifth lens are the clear aperture radii in the Y direction. By satisfying the above range, the clear aperture radii of the object side surface of the first lens and the image side surface of the fifth lens can be reasonably configured, which is beneficial for restricting the size of the first lens, can provide a larger entrance pupil for the external lens to expand the aperture, enabling the external lens to have sufficient light passing amount, and further improving the imaging quality of the external lens. More specifically, 2.88 < d1 / d10 < 2.95.

[0066] In some embodiments, the curvature radius R1 of the object side surface of the first lens, the curvature radius R2 of the image side surface of the first lens, and the central thickness CT1 of the first lens satisfy: 0.99 < R1 / (R2 + CT1) < 1.04; 1 < R1 / R2 < 1.1. By satisfying the above range, the object side surface and the image side surface can be close to a concentric circle structure, which is beneficial for the light to enter the rear lens smoothly, can reduce the field curvature, correct off-axis point aberration, is beneficial for the correction of the aberration of the entire external lens, and improves the imaging quality of the external lens. More specifically, 1.01 < R1 / R2 < 1.06.

[0067] In some embodiments, the radius of curvature R1 of the object side surface of the first lens and the radius of curvature R2 of the image side surface of the first lens satisfy: 0 < (R1 - R2) / (R1 + R2) < 0.04. Satisfying the above range can effectively control the surface shape of the first lens, which is beneficial to increasing the field of view angle and at the same time controlling the front aperture of the external lens, achieving the balance between a large field of view and miniaturization.

[0068] In some embodiments, the external lens satisfies the conditional formula: -1350 mm < f < -800 mm, 15 mm < TTL < 17 mm, 2.4 < Fno < 2.5, 61° < CRA < 62°, where f represents the effective focal length of the external lens, TTL represents the total optical length of the external lens, Fno represents the aperture value of the external lens, and CRA represents the incident angle of the chief ray at the maximum image height of the external lens. Satisfying the above conditions indicates that the optical lens provided by the embodiments of the present invention at least has characteristics such as a large CRA, miniaturization, and a large aperture. More specifically, -1314.2 mm < f < -817.13 mm, 15.7 mm < TTL < 16.76 mm, 2.42 < Fno < 2.44, 61.4° < CRA < 61.9°.

[0069] The present invention also provides an imaging device, which has a total of thirteen lenses, and sequentially includes, along the optical axis from the object side to the imaging surface: the above-mentioned external lens and the own lens. The own lens is composed of eight lenses, and sequentially from the object side to the imaging surface along the optical axis are: the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, the twelfth lens, and the thirteenth lens. The external lens can be mounted in front of the object side of the lens of the imaging device. The imaging device can be an electronic device such as a smart phone, a mobile terminal, or an action camera. The external lens is detachably mounted on the imaging device, which can achieve convenient installation and disassembly, and at the same time improve the aspect ratio of the widescreen imaging, creating a visual experience comparable to that of a cinema. During the shooting process, it can also capture the unique glare effect under strong point light sources.

[0070] The external lens has optical power in the Y direction and no optical power in the X direction, and can obtain the picture information with a larger field of view angle in the Y direction. Then, the light rays entering the lens in the Y direction are compressed. On the premise that the image height remains unchanged, the imaging information becomes more dense. After being restored by the subsequent own lens, the compressed picture information is expanded, and the Y direction contains more picture information. Therefore, the imaging device equipped with the external lens can obtain the picture information with a larger field of view angle in the Y direction and improve the aspect ratio of the widescreen imaging.

[0071] Specifically, the sixth lens may have negative optical power, its object side surface is convex, and its image side surface is concave. The seventh lens may have negative optical power, its object side surface is convex, and its image side surface is concave. The eighth lens has negative optical power, its object side surface is concave, and its image side surface is convex. The ninth lens may have positive optical power, its object side surface is convex, and its image side surface is convex. The tenth lens may have positive optical power, its object side surface is concave, and its image side surface is convex. The eleventh lens may have positive optical power, its object side surface is convex, and its image side surface is convex. The twelfth lens may have negative optical power, its object side surface is concave, and its image side surface is concave. The thirteenth lens may have positive optical power, its object side surface is convex, and its image side surface is convex.

[0072] In some embodiments, the imaging device may further include an aperture, and the aperture may be located between the ninth lens and the tenth lens. It is understood that the aperture is used to limit the amount of incoming light to change the brightness of the image.

[0073] In some embodiments, the imaging device may further include a filter, which is disposed between the thirteenth lens and the imaging surface. The filter is used to filter out interference light to prevent the interference light from reaching the imaging surface of the imaging lens and affecting normal imaging.

[0074] In some embodiments, the eleventh lens and the twelfth lens can form a cemented lens group with negative optical focal length, which can effectively correct the chromatic aberration of the imaging device, reduce the eccentricity sensitivity of the imaging device, balance the aberration of the imaging device, and improve the imaging quality of the imaging device; it can also reduce the assembly sensitivity of the imaging device, thereby reducing the difficulty of the processing technology of the imaging device and improving the assembly yield of the imaging device.

[0075] In some embodiments, the sixth lens, the eighth lens, the tenth lens, the eleventh lens, and the twelfth lens are all glass spherical lenses; and the seventh lens, the ninth lens, and the thirteenth lens are all glass aspherical lenses.

[0076] In some embodiments, the imaging device satisfies the conditional expressions: 2.35 mm < f’ < 2.4 mm, 0.95 < EPD’ < 1, 38 mm < TTL’ < 40 mm, 2.4 < Fno’ < 2.45, 14° < CRA’ < 15°, where f’ represents the effective focal length of the imaging device, EPD’ represents the entrance pupil diameter of the imaging device, TTL’ represents the overall optical length of the imaging device, and Fno’ represents the f-number of the imaging device. Meeting the above conditions indicates that the imaging device provided by the embodiments of the present invention has at least: a relatively small overall optical length; a relatively large imaging surface, which can match a larger-sized chip to achieve high-definition imaging; and a relatively large f-number, enabling the lens to achieve high-definition imaging even in a relatively dark environment. More specifically, 2.36 mm < f’ < 2.39 mm, 0.97 < EPD’ < 0.99, 38.7 mm < TTL’ < 39.76 mm, 2.42 < Fno’ < 2.44, 14.41° < CRA’ < 14.54°.

[0077] The present invention will be further described below with multiple embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens are partially different. For specific differences, refer to the parameter tables of each embodiment. The following embodiments are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited only by the following embodiments. Any other changes, substitutions, combinations, or simplifications made without departing from the innovative points of the present invention should be regarded as equivalent replacement methods and are included in the protection scope of the present invention.

[0078] Embodiment 1 Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of the external lens 100 provided in Embodiment 1 of the present invention, Figure 2 and is a perspective view of the external lens 100. The external lens 100 sequentially includes, along the optical axis from the object side to the virtual plane S11: a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5.

[0079] The first lens L1 has a negative optical power. Its object side surface S1 is convex, and its image side surface S2 is concave; The second lens L2 has a negative optical power. Its object side surface S3 is convex, and its image side surface S4 is concave; The third lens L3 has a negative optical power. Its object side surface S5 is concave, and its image side surface S6 is convex; The fourth lens L4 has a positive optical power. Its object side surface S7 is convex, and its image side surface S8 is convex; The fifth lens L5 has a negative optical power. Its object side surface S9 is concave, and its image side surface S10 is convex; The first lens L1 is a glass cylindrical lens, and the second lens L2, the third lens L3, the fourth lens L4 and the fifth lens L5 are all plastic cylindrical lenses. It can be understood that in the present application, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4 and the fifth lens L5 are all cylindrical lenses. The cylindrical lenses of the present application have optical power in the Y-axis direction (vertical field of view) and have no optical power in the X-axis direction (horizontal field of view). The cylindrical lenses can control asymmetric optical paths and are suitable for applications requiring one-dimensional focusing, beam shaping or astigmatism correction.

[0080] The relevant parameters of each lens in the external lens 100 in Example 1 are shown in Table 1-1.

[0081] Table 1-1 The surface parameters of the cylindrical lens of the external lens 100 in Example 1 are shown in Table 1-2.

[0082] Table 1-2 The cylindrical surface shape of each lens satisfies the following equation: ; Among them, z is the distance between the surface and the vertex of the surface in the direction of the optical axis, y is the distance from the optical axis to the surface in the Y-axis direction, c is the curvature of the vertex of the surface, K is the quadratic surface coefficient, A2, A4, A6, A8, A 10 , A 12 They are the second-order, fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order surface coefficients respectively.

[0083] Specifically, the equivalent radius of curvature of each surface of the cylindrical mirror is R'=R / (1+2×A2×R), where A2 is the second-order surface coefficient corresponding to each surface in Table 1-2, and R is the radius of curvature corresponding to each surface in Table 1-1. It can be understood that the radius of curvature of the object side of the first lens is the equivalent radius of curvature of the object side of the first lens, and the radius of curvature of the image side of the first lens is the equivalent radius of curvature of the image side of the first lens. The convexity or concavity of the surface can be judged by the equivalent radius of curvature.

[0084] Example 2 See also Figure 3 , which is a schematic diagram of the structure of the external lens 200 provided in Example 2 of the present invention. Compared with Example 1, the main differences of this embodiment are: the object side surface S7 of the fourth lens L4 is a concave surface; the optical parameters such as the curvature radius of each lens surface, the lens thickness, and the distance between lenses are different.

[0085] The relevant parameters of each lens in the external lens 200 in Example 2 are shown in Table 2-1.

[0086] Table 2-1 The surface parameters of the cylindrical lens of the external lens 200 in Example 2 are shown in Table 2-2.

[0087] Table 2-2 Example 3 See also Figure 4 , shown is a schematic structural diagram of an external lens 300 provided in Example 3 of the present invention. Compared with Example 1, this embodiment mainly differs in that optical parameters such as the curvature radius of each lens surface, the lens thickness, and the distance between lenses are different.

[0088] The relevant parameters of each lens in the external lens 300 in Example 3 are shown in Table 3-1.

[0089] Table 3-1 The surface parameters of the cylindrical lens of the external lens 300 in Example 3 are shown in Table 3-2.

[0090] Table 3-2 Example 4 See also Figure 5 , which is a schematic diagram of the structure of an external lens 400 provided in Example 4 of the present invention. Compared with Example 1, this embodiment mainly differs in that: the object side surface S7 of the fourth lens L4 is a concave surface; and the optical parameters such as the curvature radius of each lens surface, the lens thickness, and the distance between lenses are different.

[0091] The relevant parameters of each lens in the external lens 400 in Example 4 are shown in Table 4-1.

[0092] Table 4-1 The surface parameters of the cylindrical lens of the external lens 400 in Example 4 are shown in Table 4-2.

[0093] Table 4-2 Please refer to Table 5, which shows the optical characteristics of the external lens in the above-mentioned embodiments 1 to 4, including the effective focal length f, the total optical length TTL, the aperture value Fno, the main ray incident angle CRA at the maximum image height, and the numerical value corresponding to each conditional expression in each embodiment.

[0094] Table 5 Example 5 The external lens of any of the above embodiments may be mounted in front of the object side of the lens of an imaging device, and the imaging device may be an electronic device such as a smart phone, a mobile terminal, or a sports camera.

[0095] See also Figure 6 , which is a schematic diagram of the structure of an imaging device 500 equipped with an external lens provided in Embodiment 5 of the present invention, includes the external lens 100 in Embodiment 1 above. The imaging device 500 also includes a built-in self-contained lens 510 and an imaging element. The self-contained lens 510 can be a multi-piece combined lens. In the present application, the self-contained lens 510 is composed of eight lenses. The imaging element can be a CMOS image sensor or a CCD image sensor.

[0096] The own lens 510 includes, in order from the object side to the imaging surface S29 along the optical axis: a sixth lens L6, a seventh lens L7, an eighth lens L8, an aperture ST, a ninth lens L9, a tenth lens L10, an eleventh lens L11, a twelfth lens L12, a thirteenth lens L13 and a filter G1.

[0097] Among them, the sixth lens L6 has negative focal power, its object side surface S12 is convex, and its image side surface S13 is concave. The seventh lens L7 has negative focal power, its object side surface S14 is convex, and its image side surface S15 is concave. The eighth lens L8 has negative focal power, its object side surface S16 is concave, and its image side surface S17 is convex. The ninth lens L9 has positive focal power, its object side surface S18 is convex, and its image side surface S19 is convex. The tenth lens L10 has positive focal power, its object side surface S20 is concave, and its image side surface S21 is convex. The eleventh lens L11 and the twelfth lens L12 form a cemented lens group with negative focal power, the eleventh lens L11 has positive focal power, its object side surface S22 is convex, and its image side surface S23 is convex. The twelfth lens L12 has negative focal power, its object side surface S23 is concave, and its image side surface S24 is concave. The thirteenth lens L13 has positive refractive power, and its object-side surface S25 is a convex surface and its image-side surface S26 is a convex surface.

[0098] The sixth lens L6, the eighth lens L8, the tenth lens L10, the eleventh lens L11 and the twelfth lens L12 are all glass spherical lenses; the seventh lens L7, the ninth lens L9 and the thirteenth lens L13 are all glass aspherical lenses.

[0099] The relevant parameters of each lens in the imaging device 500 in Example 5 are shown in Table 6-1.

[0100] Table 6-1 The surface parameters of the aspheric lens of the imaging device 500 in Example 5 are shown in Table 6-2.

[0101] Table 6-2 The shape of each aspherical surface of each lens satisfies the following equation: ; Among them, z is the distance between the surface and the vertex of the surface in the direction of the optical axis, h is the distance from the optical axis to the surface, c is the curvature of the surface vertex, K is the quadratic surface coefficient, B, C, D, E, and F are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order surface coefficients respectively.

[0102] Figure 7 The field curvature curve of Example 5 is shown, which indicates the degree of curvature of light of different wavelengths on the meridional image plane and the sagittal image plane, the horizontal axis indicates the offset (unit: mm), and the vertical axis indicates the half field angle (unit: °). It can be seen from the figure that the field curvature of the meridional image plane and the sagittal image plane is controlled within -0.03mm~0.04mm, indicating that the imaging device can well correct the field curvature.

[0103] Figure 8 The F-Tan (Theta) distortion curve of Example 5 is shown, which represents the F-Tan (Theta) distortion of light of different wavelengths at different image heights on the imaging surface, the horizontal axis represents the F-Tan (Theta) distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). It can be seen from the figure that the F-Tan (Theta) distortion of the imaging device is controlled within -85%~0, the image compression in the edge angle area is relatively gentle, and the clarity of the expanded image is effectively improved.

[0104] Fig. 9 The axial aberration curve of Example 5 is shown, which represents the aberration of each wavelength on the optical axis at the imaging surface, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial aberration is controlled within ±0.02mm, indicating that the imaging device can correct the axial aberration well.

[0105] Fig.10 The MTF (Modulation Transfer Function) curve of Example 5 is shown, which represents the imaging modulation degree of the lens at different spatial frequencies under each field of view, the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.2 in the entire field of view, and in the range of 0 to 160 lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution ability in both low-frequency and high-frequency conditions.

[0106] Fig.11 The relative illumination curve of Example 5 is shown, which represents the relative illumination values ​​at different viewing angles on the imaging surface, the horizontal axis represents the half viewing angle (unit: °), and the vertical axis represents the relative illumination (unit: %). It can be seen from the figure that the relative illumination value of the imaging device is still greater than 70% at the maximum half viewing angle, indicating that the imaging device has good relative illumination.

[0107] Example 6 See also Fig.12 , shown is a schematic structural diagram of an imaging device 600 equipped with an external lens provided in Example 6 of the present invention. The structure of the imaging device in this embodiment is basically the same as that in Example 5, and the main difference is that the external lens equipped in this embodiment is the external lens 200 in the above-mentioned Example 2.

[0108] Fig.13 The field curvature curve of Example 6 is shown. It can be seen from the figure that the field curvature of the meridian image plane and the sagittal image plane is controlled within -0.03mm~0.04mm, indicating that the imaging device can correct the field curvature well. Fig.14 The F-Tan (Theta) distortion curve of Example 6 is shown. It can be seen from the figure that the F-Tan (Theta) distortion of the imaging device is controlled within -85%~0, the image compression in the edge angle area is relatively smooth, and the clarity of the expanded image is effectively improved. Fig.15 The axial aberration curve of Example 5 is shown, which represents the aberration of each wavelength on the optical axis at the imaging surface, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial aberration is controlled within ±0.02mm, indicating that the imaging device can correct the axial aberration well. Fig.16 The MTF (Modulation Transfer Function) curve of Example 5 is shown. It can be seen from the figure that the MTF value of this embodiment is above 0.3 in the entire field of view. In the range of 0 to 160lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability in both low-frequency and high-frequency conditions. Fig.17 The relative illumination curve of Example 5 is shown. It can be seen from the figure that the relative illumination value of the imaging device is still greater than 70% at the maximum half field of view angle, indicating that the imaging device has good relative illumination.

[0109] Example 7 See also Fig.18 , shown is a schematic structural diagram of an imaging device 700 equipped with an external lens provided in Example 7 of the present invention. The structure of the imaging device in this embodiment is basically the same as that in Example 5, and the main difference is that the external lens equipped in this embodiment is the external lens 300 in the above-mentioned Example 3.

[0110] Fig.19 The field curvature curve of Example 7 is shown. It can be seen from the figure that the field curvature of the meridian image plane and the sagittal image plane is controlled within -0.03mm~0.04mm, indicating that the imaging device can correct the field curvature well. Fig. 20 The F-Tan (Theta) distortion curve of Example 7 is shown. It can be seen from the figure that the F-Tan (Theta) distortion of the imaging device is controlled within -85%~0, the image compression in the edge angle area is relatively smooth, and the clarity of the expanded image is effectively improved. Fig.21 The axial aberration curve of Example 7 is shown, which represents the aberration of each wavelength on the optical axis at the imaging surface, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial aberration is controlled within ±0.02mm, indicating that the imaging device can correct the axial aberration well. Fig. 22 The MTF (Modulation Transfer Function) curve of Example 7 is shown. It can be seen from the figure that the MTF value of this embodiment is above 0.3 in the entire field of view. In the range of 0 to 160lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability in both low-frequency and high-frequency conditions. Fig.23 The relative illumination curve of Example 7 is shown. It can be seen from the figure that the relative illumination value of the imaging device is still greater than 70% at the maximum half field of view angle, indicating that the imaging device has good relative illumination.

[0111] Example 8 See also Fig.24 , shown is a schematic diagram of the structure of an imaging device 800 equipped with an external lens provided in Example 8 of the present invention. The structure of the imaging device in this embodiment is basically the same as that in Example 5, and the main difference is that the external lens equipped in this embodiment is the external lens 400 in the above-mentioned Example 4.

[0112] Fig.25 The field curvature curve of Example 8 is shown. It can be seen from the figure that the field curvature of the meridian image plane and the sagittal image plane is controlled within -0.03mm~0.04mm, indicating that the imaging device can correct the field curvature well. Fig.26 The F-Tan (Theta) distortion curve of Example 8 is shown. It can be seen from the figure that the F-Tan (Theta) distortion of the imaging device is controlled within -85%~0, the image compression in the edge angle area is relatively smooth, and the clarity of the expanded image is effectively improved. Fig. 27The axial aberration curve of Example 8 is shown, which represents the aberration of each wavelength on the optical axis at the imaging surface, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial aberration is controlled within ±0.02mm, indicating that the imaging device can correct the axial aberration well. Fig.28 The MTF (Modulation Transfer Function) curve of Example 8 is shown. It can be seen from the figure that the MTF value of this embodiment is above 0.3 in the entire field of view. In the range of 0 to 160lp / mm, the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution capability in both low-frequency and high-frequency conditions. Fig.29 The relative illumination curve of Example 8 is shown. It can be seen from the figure that the relative illumination value of the imaging device is still greater than 70% at the maximum half field of view angle, indicating that the imaging device has good relative illumination.

[0113] Please refer to Table 7, which shows the optical parameters of the built-in lens 510 provided in Examples 5 to 8 and the imaging device equipped with an external lens, including the effective focal length f', aperture value Fno', maximum field of view FOVy in the Y direction, maximum field of view FOVx in the X direction, half image height ihy corresponding to the maximum field of view in the Y direction, and half image height ihx corresponding to the maximum field of view in the X direction.

[0114] Table 7 It can be seen from Table 7 that the imaging device equipped with an external lens can obtain image information with a larger field of view angle in the Y direction, thereby improving the aspect ratio of wide-screen imaging.

[0115] In summary of the above embodiments, the external lens and imaging device provided by the present invention have the following advantages: The external lens and imaging device provided by the present invention improve the imaging quality through specific surface shape matching and reasonable optical focal length distribution, have one or more advantages such as miniaturization, ultra-wide angle, large target surface, large aperture, high-quality imaging, etc., can obtain picture information with a larger field of view, improve the aspect ratio of wide-screen imaging, and greatly improve the user experience.

[0116] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0117] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An external lens, comprising five lenses, characterized in that: It successively includes from the object side to the imaging surface along the optical axis: A first lens with negative optical power, whose object side is convex and whose image side is concave; A second lens with negative optical power, whose object side is convex and whose image side is concave; A third lens with negative optical power, whose object side is concave and whose image side is convex; A fourth lens with positive optical power, whose image side is convex; A fifth lens with negative optical power, whose object side is concave and whose image side is convex; The first lens, the second lens, the third lens, the fourth lens and the fifth lens are cylindrical lenses; Wherein, the total optical length TTL of the external lens and the effective focal length f of the external lens satisfy: -0.03 < TTL / f < 0.

2. The external lens according to claim 1, characterized in that: The total optical length TTL of the external lens and the clear aperture radius d1 of the object side of the first lens satisfy: 0.88 < TTL / d1 < 0.

97.

3. The external lens according to claim 1, characterized in that: The total optical length TTL of the external lens and the sum ∑CT of the central thicknesses of the first lens to the fifth lens along the optical axis respectively satisfy: 0.5 < ∑CT / TTL < 0.54; The sum ∑CT of the central thicknesses of the first lens to the fifth lens along the optical axis respectively and the effective focal length f of the external lens satisfy: -0.02 < ΣCT / f < 0.

4. The external lens according to claim 1, characterized in that: The focal length f1 of the first lens and the effective focal length f of the external lens satisfy: 1.8 < f1 / f < 4.8; The curvature radius R1 of the object side of the first lens and the effective focal length f of the external lens satisfy: -0.05 < R1 / f < -0.02; The curvature radius R2 of the image side of the first lens and the effective focal length f of the external lens satisfy: -0.05 < R2 / f < -0.

02.

5. The external lens according to claim 1, characterized in that: The focal length f2 of the second lens and the effective focal length f of the external lens satisfy: 0.04 < f2 / f < 0.1; The equivalent curvature radius R3’ of the object side of the second lens and the effective focal length f of the external lens satisfy: -0.53 < R3’ / f < -0.46; The equivalent curvature radius R4’ of the image side of the second lens and the effective focal length f of the external lens satisfy: -0.06 < R4’ / f < -0.

02.

6. The external lens according to claim 1, characterized in that: The focal length f3 of the third lens and the effective focal length f of the external lens satisfy: 0.24 < f3 / f < 0.43; The equivalent curvature radius R5’ of the object side of the third lens and the effective focal length f of the external lens satisfy: 0.04 < R5’ / f < 0.11; The equivalent curvature radius R6’ of the image side of the third lens and the effective focal length f of the external lens satisfy: 0.08 < R6’ / f < 0.

19.

7. The external lens according to claim 1, characterized in that: The focal length f4 of the fourth lens and the effective focal length f of the external lens satisfy: -0.04 < f4 / f < -0.01; The equivalent curvature radius R8’ of the image side of the fourth lens and the effective focal length f of the external lens satisfy: 0 < R8’ / f < 0.

03.

8. The external lens according to claim 1, characterized in that: The focal length f5 of the fifth lens and the effective focal length f of the external lens satisfy: 0.01 < f5 / f < 0.05; the equivalent curvature radius R9' of the object side of the fifth lens and the effective focal length f of the external lens satisfy: 0 < R9' / f < 0.03; the equivalent curvature radius R10' of the image side of the fifth lens and the effective focal length f of the external lens satisfy: 0.09 < R10' / f < 0.

19.

9. The external lens according to claim 1, characterized in that: The focal length f1 of the first lens and the combined focal length f2345 of the second lens, the third lens, the fourth lens, and the fifth lens satisfy: 1 < f1 / f2345 < 4; the clear aperture radius d1 of the object side of the first lens and the clear aperture radius d10 of the image side of the fifth lens satisfy: 2.8 < d1 / d10 < 3.

10. An imaging device, characterized in that: It sequentially includes, along the optical axis from the object side to the imaging surface: the external lens as described in any one of claims 1-9 and the self-owned lens; the self-owned lens is composed of eight lenses, and sequentially along the optical axis from the object side to the imaging surface are: A sixth lens with a negative optical power, whose object side is convex and whose image side is concave; A seventh lens with a negative optical power, whose object side is convex and whose image side is concave; An eighth lens with a negative optical power, whose object side is concave and whose image side is convex; A ninth lens with a positive optical power, whose object side is convex and whose image side is convex; A tenth lens with a positive optical power, whose object side is concave and whose image side is convex; An eleventh lens with a positive optical power, whose object side is convex and whose image side is convex; A twelfth lens with a negative optical power, whose object side is concave and whose image side is concave; A thirteenth lens with a positive optical power, whose object side is convex and whose image side is convex.

Images