External lens and imaging equipment

Abstract

The invention provides an external lens and imaging equipment, and the external lens comprises four 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 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 convex surface, and the image side surface of the third lens is a concave surface; the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a concave surface; the fourth lens can dynamically move on the optical axis to realize zoom switching of the external lens in different object distance states; 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 lt; tTL / flt; and 0.09%. According to the external lens and the imaging equipment provided by the invention, the imaging quality of the lens under different object distances can be 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 particularly to an external lens and an imaging device. Background Art

[0002] With the popularization of intelligent mobile devices such as smart phones, and in order to meet the pursuit of obtaining better shooting effects in different scenarios, the functions of the imaging module are constantly being improved and expanded. In order to obtain better shooting effects, an external lens is usually mounted at the lens of an electronic device. Since the configuration of the external lens is equivalent to increasing the original focal length of the lens of the electronic device, when taking pictures, the imaging quality and optical zoom ability of the electronic device equipped with the external lens can be comparable to those of a professional camera, far exceeding the shooting effect of the device itself. However, although most external lenses increase the original focal length of the lens of the electronic device, the field of view range is still small, and when shooting, the center of the captured image is clear, but the periphery of the image is blurred; moreover, the resolution of the existing external lenses is not high and cannot be matched with high-pixel imaging devices. Summary of the Invention

[0003] Aiming at the above problems, the purpose of the present invention is to provide an external lens and an imaging device, which can improve the imaging quality of the lens at different object distances and greatly improve the user experience.

[0004] The technical solution adopted by the present invention is as follows: An external lens, comprising a total of four lenses, which in sequence from the object side to the imaging surface along the optical axis include: a first lens with a negative optical power, whose object side is convex and whose image side is concave; a second lens with a positive optical power, whose object side is convex and whose image side is concave; a third lens with a negative optical power, whose object side is convex and whose image side is concave; a fourth lens with a positive optical power, whose object side is convex and whose image side is concave; The fourth lens can move dynamically on the optical axis to realize the zoom switching of the external lens in different object distance states; wherein, the total optical length TTL of the external lens and the effective focal length f of the external lens satisfy: 0 < TTL / f < 0.09.

[0005] Further preferably, the effective focal length f of the external lens satisfies: 140 mm < f < 990 mm; the maximum field of view FOV of the external lens satisfies: 149° < FOV < 150°.

[0006] More preferably, the maximum field of view FOV of the external lens and the aperture value Fno of the external lens satisfy: 59° < FOV / Fno < 60°; the half clear aperture d1 on the object side of the first lens and the half clear aperture d8 on the image side of the fourth lens satisfy: 2.01 < d1 / d8 < 2.18.

[0007] More preferably, the focal length f1 of the first lens and the effective focal length f of the external lens satisfy: -0.29 < f1 / f < -0.03; the curvature radius R1 of the object side of the first lens and the curvature radius R2 of the image side of the first lens satisfy: 2.98 < R1 / R2 < 5.33.

[0008] More preferably, the focal length f2 of the second lens and the effective focal length f of the external lens satisfy: 0.19 < f2 / f < 1.39; the curvature radius R3 of the object side of the second lens and the curvature radius R4 of the image side of the second lens satisfy: 0.95 < R3 / R4 < 0.97.

[0009] More preferably, the focal length f3 of the third lens and the effective focal length f of the external lens satisfy: -0.13 < f3 / f < -0.01; the curvature radius R5 of the object side of the third lens and the curvature radius R6 of the image side of the third lens satisfy: 2.43 < R5 / R6 < 2.86.

[0010] More preferably, the focal length f4 of the fourth lens and the effective focal length f of the external lens satisfy: 0 < f4 / f < 0.1; the curvature radius R7 of the object side of the fourth lens and the curvature radius R8 of the image side of the fourth lens satisfy: 0.18 < R7 / R8 < 0.21.

[0011] More preferably, the combined focal length f12 of the first lens and the second lens and the combined focal length f34 of the third lens and the fourth lens satisfy: -1.28 < f12 / f34 < -1.04; the combined focal length f34 of the third lens and the fourth lens and the distance CT34 between the third lens and the fourth lens on the optical axis satisfy: 25 < f34 / CT34 < 100.

[0012] More preferably, the half clear aperture d3 on the object side of the second lens and the sagittal height Sag3 of the half clear aperture on the object side of the second lens satisfy: 0.22 < Sag3 / d3 < 0.25; the half clear aperture d4 on the image side of the second lens and the sagittal height Sag4 of the half clear aperture on the image side of the second lens satisfy: 0.23 < Sag4 / d4 < 0.27.

[0013] The present invention also provides an imaging device, which has twelve lenses in total, and includes the above-mentioned external lens and the own lens in order from the object side to the imaging surface along the optical axis; the own lens is composed of eight lenses, and includes the following lenses in order from the object side to the imaging surface along the optical axis: a fifth lens having negative optical power, whose object side surface is convex and whose image side surface is concave; a sixth lens having negative optical power, whose object side surface is convex and whose image side surface is concave; a seventh lens element having negative optical power, whose object side surface is concave and whose image side surface is convex; an eighth lens having positive refractive power, whose object-side surface is convex and whose image-side surface is convex; A ninth lens having positive refractive power, whose object side surface is concave and whose image side surface is convex; A tenth lens having positive refractive power, whose object-side surface is convex and whose image-side surface is convex; The eleventh lens has a negative optical power, and its object side surface is concave and its image side surface is concave; The twelfth lens has positive refractive power, its object-side surface is convex, and its image-side surface is convex.

[0014] Compared with the prior art, the external lens and imaging device provided by the present invention can achieve zoom switching of the lens at different object distances by changing the air spacing distance between different lenses, thereby improving the imaging quality. It has one or more advantages such as miniaturization, ultra-wide angle, large target surface, large aperture, high-quality imaging, etc., which greatly improves the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 It is a schematic structural diagram of an external lens in Embodiment 1 of the present invention.

[0016] Figure 2 Schematic diagram of the structure of the external lens in Embodiment 2 of the present invention.

[0017] Figure 3 Schematic diagram of the structure of the external lens in Embodiment 3 of the present invention.

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

[0019] Figure 5 Schematic diagram of the structure of the imaging device in Embodiment 5 of the present invention.

[0020] Figure 6 This is an MTF curve diagram of the imaging device in Example 5 of the present invention when the object distance is 100 mm.

[0021] Figure 7 This is an MTF curve diagram of the imaging device in Example 5 of the present invention when the object distance is 200 mm.

[0022] Figure 8 This is an MTF curve diagram of the imaging device in Example 5 of the present invention when the object distance is 400 mm.

[0023] Fig. 9 This is an MTF curve diagram of the imaging device in Example 5 of the present invention when the object distance is 600 mm.

[0024] Fig.10 Schematic diagram of the structure of the imaging device in Embodiment 6 of the present invention.

[0025] Fig.11 This is an MTF curve diagram of the imaging device in Example 6 of the present invention when the object distance is 100 mm.

[0026] Fig.12 This is an MTF curve diagram of the imaging device in Example 6 of the present invention when the object distance is 200 mm.

[0027] Fig.13 This is an MTF curve diagram of the imaging device in Example 6 of the present invention when the object distance is 400 mm.

[0028] Fig.14 This is an MTF curve diagram of the imaging device in Example 6 of the present invention when the object distance is 600 mm.

[0029] Fig.15 Schematic diagram of the structure of the imaging device in Embodiment 7 of the present invention.

[0030] Fig.16 This is an MTF curve diagram of the imaging device in Example 7 of the present invention when the object distance is 100 mm.

[0031] Fig.17 This is an MTF curve diagram of the imaging device in Example 7 of the present invention when the object distance is 200 mm.

[0032] Fig.18 This is an MTF curve diagram of the imaging device in Example 7 of the present invention when the object distance is 400 mm.

[0033] Fig.19 This is an MTF curve diagram of the imaging device in Example 7 of the present invention when the object distance is 600 mm.

[0034] Fig. 20 Schematic diagram of the structure of the imaging device in Example 8 of the present invention.

[0035] Fig.21This is an MTF curve diagram of the imaging device in Example 8 of the present invention when the object distance is 100 mm.

[0036] Fig. 22 This is an MTF curve diagram of the imaging device in Example 8 of the present invention when the object distance is 200 mm.

[0037] Fig.23 This is an MTF curve diagram of the imaging device in Example 8 of the present invention when the object distance is 400 mm.

[0038] Fig.24 This is an MTF curve diagram of the imaging device in Example 8 of the present invention when the object distance is 600 mm.

[0039] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The external lens provided in the embodiment of the present invention is a zoom lens, with a total of four lenses, which include: a first lens, a second lens, a third lens and a fourth lens in sequence from the object side to the imaging surface along the optical axis. The first lens, the second lens and the third lens of the present invention do not move when the external lens is focused; the fourth lens can be moved along the optical axis in the external lens to complete the zoom switching of the external lens at different object distances. That is, the air spacing between the fourth lens and the third lens of the present invention on the optical axis is variable, and by changing the air spacing distance between different lenses, the zoom switching of the lens at different object distances can be achieved. The object distance range of the external lens of the present invention is 100mm~600mm. The external lens can be mounted in front of the object side of the lens of the imaging device to improve the image quality of the imaging device under the condition of an object distance of 100mm~600mm. The imaging device can be an electronic device such as a smart phone, a mobile terminal, a sports camera, etc.

[0048] In some embodiments, the first lens may have negative optical power, its object side surface is convex, and its image side surface is concave. The second lens may have positive optical power, its object side surface is convex, and its image side surface is concave. The third lens may have negative optical power, its object side surface is convex, and its image side surface is concave. The fourth lens may have positive optical power, its object side surface is convex, and its image side surface is concave.

[0049] In some embodiments, the total optical length TTL of the external lens and the effective focal length f of the external lens satisfy: 0 < TTL / f < 0.14. 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.

[0050] In some embodiments, the effective focal length f of the external lens satisfies: 140 mm < f < 990 mm; the maximum field of view FOV of the external lens satisfies: 149° < FOV < 150°. Meeting the above range endows the external lens with long focal length characteristics and ultra-wide angle. More specifically, 145.42 mm < f < 985.47 mm; 149.1° < FOV < 149.3°.

[0051] In some embodiments, the maximum field of view FOV of the external lens and the aperture value Fno of the external lens satisfy: 59° < FOV / Fno < 60°. Meeting the above range defines that the external lens has an appropriate field of view and aperture value, can collect light at a large angle and obtain good imaging quality. More specifically, 59.48° < FOV / Fno < 59.52°.

[0052] In some embodiments, the clear aperture semi-diameter d1 of the object side of the first lens and the clear aperture semi-diameter d8 of the image side of the fourth lens satisfy: 2.01 < d1 / d8 < 2.18. Meeting the above range can reasonably configure the clear aperture semi-diameters of the object side of the first lens and the image side of the fourth lens, which is beneficial to 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 transmission, and further improving the imaging quality of the external lens.

[0053] In some embodiments, the focal length f1 of the first lens and the effective focal length f of the external lens satisfy: -0.29 < f1 / f < -0.03; the curvature radius R1 of the object side of the first lens and the curvature radius R2 of the image side of the first lens satisfy: 2.98 < R1 / R2 < 5.33; 0.49 < (R1 - R2) / (R1 + R2) < 0.69. Meeting the above range, by setting the first lens to have negative refractive power and an appropriate surface shape, it is beneficial for the first lens to receive light at a larger angle and collect as much light as possible into the rear optical system, increasing the light flux while achieving a large field of view.

[0054] In some embodiments, the focal length f2 of the second lens and the effective focal length f of the external lens satisfy: 0.19 < f2 / f < 1.39; the curvature radius R3 of the object side surface of the second lens and the curvature radius R4 of the image side surface of the second lens satisfy: 0.95 < R3 / R4 < 0.97; -0.03 < (R3 - R4) / (R3 + R4) < -0.01. Meeting the above ranges defines that the second lens has an appropriate positive optical power and a suitable surface shape, has the effect of converging light, reduces the height of peripheral light, is beneficial to reducing the aperture of the rear lens, and at the same time is beneficial to balancing aberrations and improving resolution.

[0055] In some embodiments, the focal length f3 of the third lens and the effective focal length f of the external lens satisfy: -0.13 < f3 / f < -0.01; the curvature radius R5 of the object side surface of the third lens and the curvature radius R6 of the image side surface of the third lens satisfy: 2.43 < R5 / R6 < 2.86; 0.41 < (R5 - R6) / (R5 + R6) < 0.49. Meeting the above conditions, by reasonably setting the focal length and surface shape of the third lens, the light emitted by the second lens can be diverged, so that the light in the edge field of view shows an upward trend, which is beneficial to the image point on the imaging surface being away from the optical axis, which is beneficial to realizing a large target surface and obtaining a larger picture, can effectively eliminate aberrations, and improve the resolution ability of the external lens.

[0056] In some embodiments, the focal length f4 of the fourth lens and the effective focal length f of the external lens satisfy: 0 < f4 / f < 0.1; the curvature radius R7 of the object side surface of the fourth lens and the curvature radius R8 of the image side surface of the fourth lens satisfy: 0.18 < R7 / R8 < 0.21; -0.7 < (R7 - R8) / (R7 + R8) < -0.65. Meeting the above conditions, by reasonably setting the focal length and surface shape of the fourth lens, it is beneficial to light convergence, enables the light trend to transition smoothly to the rear, reduces the height of the light incident on the rear, slows down the upward trend of the light, avoids the light energy loss of the large field of view light reaching the rear system, is beneficial to improving the illuminance of the edge field of view, and is beneficial to realizing a short optical total length.

[0057] In some embodiments, the combined focal length f12 of the first lens and the second lens and the combined focal length f34 of the third lens and the fourth lens satisfy: -1.28 < f12 / f34 < -1.04; the combined focal length f34 of the third lens and the fourth lens and the spacing CT34 of the third lens and the fourth lens on the optical axis satisfy: 25 < f34 / CT34 < 100. Meeting the above ranges, by reasonably setting the focal length relationship of each lens, it is beneficial to 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, 25.3 < f34 / CT34 < 99.2.

[0058] In some embodiments, the clear aperture semi-diameter d3 of the object side surface of the second lens and the sagittal height Sag3 of the clear aperture of the object side surface of the second lens satisfy: 0.22 < Sag3 / d3 < 0.25; the clear aperture semi-diameter d4 of the image side surface of the second lens and the sagittal height Sag4 of the clear aperture of the image side surface of the second lens satisfy: 0.23 < Sag4 / d4 < 0.27. Meeting the above ranges helps to control the trend of light rays in the peripheral field of view and highlights the detailed information of the central field of view of the external lens.

[0059] In some embodiments, the total optical length TTL of the external lens and the clear aperture semi-diameter d1 of the object side surface of the first lens satisfy: 0.73 < TTL / d1 < 0.81. Meeting the above range is beneficial to the miniaturization of the external lens.

[0060] In some embodiments, the external lens satisfies the conditional formula: 11 mm < TTL < 12 mm, 2.5 < Fno < 2.52; where TTL represents the total optical length of the external lens, and Fno represents the aperture value of the external lens. The external lens provided by the embodiments of the present invention has at least the characteristics of miniaturization and large aperture. More specifically, 11.28 mm < TTL < 11.82 mm.

[0061] In some embodiments, the lens material of the external lens provided by the present invention can be glass or plastic. When the lens material is plastic, the production cost can be effectively reduced. When the lens material is glass, the geometric chromatic aberration of the optical system can be effectively corrected by the low dispersion characteristic of the glass itself. The external lens provided by the present invention can adopt an all-glass lens structure, which can reduce dispersion, effectively correct the chromatic aberration of the external lens, and improve the imaging quality.

[0062] In some embodiments, the first lens, the second lens, the third lens, and the fourth lens can adopt spherical lenses or aspherical lenses. Compared with the spherical lens structure, the aspherical structure can effectively reduce the aberration of the optical system, thereby reducing the number of lenses and the size of the lenses, and better realizing the miniaturization of the lens. More specifically, the first lens of the present invention adopts a spherical lens, and the second lens, the third lens, and the fourth lens can adopt aspherical lenses, which can effectively reduce the aberration of the external lens, reduce the number of lenses and the size of the lenses, and better realize the miniaturization of the lens.

[0063] In addition, the present invention also provides an imaging device, which sequentially includes, along the optical axis from the object side to the imaging surface: the above-mentioned external lens and its own lens. It can be understood that the external lens can be mounted in front of the object side of the lens of the imaging device. The own lens is composed of eight lenses, and along the optical axis from the object side to the imaging surface are: the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, and the twelfth lens.

[0064] Specifically, the fifth lens may have negative optical power, its object side surface is convex, and its image side surface is concave. 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 concave, and its image side surface is convex. The eighth lens may have positive optical power, its object side surface is convex, and its image side surface is convex. The ninth lens may have positive optical power, its object side surface is concave, and its image side surface is convex. The tenth lens may have positive optical power, its object side surface is convex, and its image side surface is convex. The eleventh lens may have negative optical power, its object side surface is concave, and its image side surface is concave. The twelfth lens may have positive optical power, its object side surface is convex, and its image side surface is convex.

[0065] In some embodiments, the imaging device may further include an aperture, and the aperture may be located between the eighth lens and the ninth lens. It is understood that the aperture is used to limit the amount of incoming light to change the brightness of the image.

[0066] In some embodiments, the imaging device may further include a filter, which is disposed between the twelfth 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.

[0067] In some embodiments, the tenth lens and the eleventh 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.

[0068] In some embodiments, the fifth lens, the seventh lens, the ninth lens, the tenth lens, and the eleventh lens are all glass spherical lenses; and the sixth lens, the eighth lens, and the twelfth lens are all glass aspherical lenses.

[0069] In some embodiments, the imaging device satisfies the conditional expressions: 2.6 mm < f’ < 2.75 mm, 1.05 < EPD’ < 1.15, 29 mm < TTL’ < 31 mm, 2.4 < Fno’ < 2.5, 15° < CRA’ < 17°, 149° < FOV’ < 150°, 6.5 mm < IH’ < 8 mm, 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, Fno’ represents the f-number of the imaging device, FOV’ represents the maximum field of view angle of the imaging device, and IH’ represents the true image height corresponding to the maximum field of view angle 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 be matched with a relatively large-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, 2.63 mm < f’ < 2.72 mm, 1.08 < EPD’ < 1.12, 29.28 mm < TTL’ < 30.15 mm, 2.41 < Fno’ < 2.44, 15.27° < CRA’ < 16.55°, 149.1° < FOV’ < 149.3°, 6.64 mm < IH’ < 7.44 mm.

[0070] In various embodiments of the present invention, when the lens is an aspherical lens, the aspherical surface shapes of each lens satisfy the following equation: ; where z is the distance between the curved surface and the vertex of the curved surface in the optical axis direction, h is the distance from the optical axis to the curved surface, c is the curvature of the vertex of the curved surface, K is the conic coefficient, and B, C, D, E, and F are the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order surface coefficients, respectively.

[0071] The present invention will be further described below with multiple embodiments. In each embodiment, the thickness, curvature radius, 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 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.

[0072] 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. The external lens 100 sequentially includes, along the optical axis from the object side to the virtual plane S9: a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4.

[0073] The first lens L1 has negative refractive power, its object side surface S1 is convex, and its image side surface S2 is concave; The second lens L2 has positive refractive power, its object-side surface S3 is convex, and its image-side surface S4 is concave; The third lens L3 has negative refractive power, its object-side surface S5 is convex, and its image-side surface S6 is concave; The fourth lens L4 has positive refractive power, its object-side surface S7 is convex, and its image-side surface S8 is concave; The first lens L1 is a glass spherical lens, and the second lens L2, the third lens L3, and the fourth lens L4 are all glass aspherical lenses.

[0074] The relevant parameters of each lens in the external lens 100 in Example 1 are shown in Table 1-1.

[0075] Table 1-1 The surface parameters of the aspherical lens of the external lens 100 in Example 1 are shown in Table 1-2.

[0076] Table 1-2 Among them, D0 in the above Table 1-1 is the object distance, that is, the distance between the first lens L1 and the object on the object side on the optical axis, CT34 is the distance between the third lens L3 and the fourth lens L4 on the optical axis, and CT4d is the distance between the fourth lens L4 and the virtual surface on the optical axis. The present application can achieve zooming of the external lens at different object distances by changing the distances CT34 and CT4d.

[0077] Specifically, the first lens L1, the second lens L2 and the third lens L3 of the present application do not move when the external lens is focused; the fourth lens L4 can move along the optical axis in the external lens to complete the zoom switching of the external lens at different object distances. The object distance range of the external lens 100 of this embodiment is 100mm~600mm.

[0078] Parameters of the external lens 100 of the first embodiment at different object distances are shown in Tables 1-3.

[0079] Table 1-3 Example 2 See also Figure 2 , 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 difference between this embodiment and Example 1 is that the optical parameters such as the curvature radius of each lens surface, the lens thickness, and the distance between lenses are different.

[0080] The relevant parameters of each lens in the external lens 200 in Example 2 are shown in Table 2-1.

[0081] Table 2-1 The surface parameters of the aspherical lens of the external lens 200 in Example 2 are shown in Table 2-2.

[0082] Table 2-2 Parameters of the external lens 200 of the second embodiment under different object distances are shown in Table 2-3.

[0083] Table 2-3 Example 3 See also Figure 3 , 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.

[0084] The relevant parameters of each lens in the external lens 300 in Example 3 are shown in Table 3-1.

[0085] Table 3-1 The surface parameters of the aspherical lens of the external lens 300 in Example 3 are shown in Table 3-2.

[0086] Table 3-2 Parameters of the external lens 300 of the third embodiment at different object distances are shown in Table 3-3.

[0087] Table 3-3 Example 4 See also Figure 4 , shown is a schematic structural diagram of an external lens 400 provided in Example 4 of the present invention. Compared with Example 1, the main difference between this embodiment is that the 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 400 in Example 4 are shown in Table 4-1.

[0089] Table 4-1 The surface parameters of the aspherical lens of the external lens 400 in Example 4 are shown in Table 4-2.

[0090] Table 4-2 Parameters of the external lens 400 of the fourth embodiment under different object distances are shown in Table 4-3.

[0091] Table 4-3 Please refer to Table 5-1 and Table 5-2, which show the optical characteristics of the above-mentioned embodiments 1 to 4 under different object distances, including the effective focal length f of the external lens, the total optical length TTL, the maximum field of view FOV, the aperture value Fno, and the numerical value corresponding to each conditional expression in each embodiment.

[0092] Table 5-1 Table 5-2 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.

[0093] See also Figure 5 , 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.

[0094] The own lens 510 includes, in sequence from the object side to the imaging surface S27 along the optical axis: a fifth lens L5, 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 and a filter G1.

[0095] Among them, the fifth lens L5 has negative focal power, its object side surface S10 is convex, and its image side surface S11 is concave. 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 concave, and its image side surface S15 is convex. The eighth lens L8 has positive focal power, its object side surface S16 is convex, and its image side surface S17 is convex. The ninth lens L9 has positive focal power, its object side surface S18 is concave, and its image side surface S19 is convex. The tenth lens L10 and the eleventh lens L11 form a cemented lens group with negative focal power, the tenth lens L10 has positive focal power, its object side surface S20 is convex, and its image side surface S21 is convex. The eleventh lens L11 has negative focal power, its object side surface S21 is concave, and its image side surface S22 is concave. The twelfth lens L12 has positive refractive power, and its object-side surface S23 is a convex surface and its image-side surface S24 is a convex surface.

[0096] The fifth lens L5, the seventh lens L7, the ninth lens L9, the tenth lens L10 and the eleventh lens L11 are all glass spherical lenses; the sixth lens L6, the eighth lens L8 and the twelfth lens L12 are all glass aspherical lenses.

[0097] The relevant parameters of each lens in the imaging device 500 in Example 5 are shown in Table 6-1.

[0098] Table 6-1 The surface parameters of the aspheric lens of the imaging device 500 in Example 5 are shown in Table 6-2.

[0099] Table 6-2 Please refer to Figure 6 , which is a graph of the MTF (modulation transfer function) of the imaging device 500 when the object distance is 100 mm, wherein the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. It can be seen from the graph that the MTF value of the present embodiment is above 0.25 in the entire field of view, and within 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 capability in both low-frequency and high-frequency conditions.

[0100] Figure 7 is a graph of the MTF (modulation transfer function) of the imaging device 500 when the object distance is 200 mm, Figure 8 is a graph of the MTF (modulation transfer function) of the imaging device 500 when the object distance is 400 mm, Fig. 9The MTF (Modulation Transfer Function) curve of the imaging device 500 when the object distance is 600 mm. As can be seen from the above figure, the MTF value is above 0.25 in the entire field of view, indicating that it has good imaging quality and good detail resolution ability in both low-frequency and high-frequency conditions.

[0101] This embodiment improves the imaging quality of the imaging device 500 at an object distance of 100 mm to 600 mm by attaching a zoom external lens 100 to the native lens 510 without changing the image plane position of the native lens 510 .

[0102] Example 6 See also Fig.10 , 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.

[0103] Fig.11 The MTF (Modulation Transfer Function) curve of the imaging device 600 when the object distance is 100 mm, the MTF value is above 0.15 in the entire field of view. Fig.12 is a graph of the MTF (modulation transfer function) of the imaging device 600 when the object distance is 200 mm, Fig.13 is a graph of the MTF (modulation transfer function) of the imaging device 600 when the object distance is 400 mm, Fig.14 is the MTF (Modulation Transfer Function) curve of the imaging device 600 when the object distance is 600mm. Figure 12 to Figure 14 It can be seen that the MTF value is above 0.2 in the whole field of view, which means that it has good imaging quality and good detail resolution ability in both low-frequency and high-frequency conditions.

[0104] In this embodiment, a zoom external lens 200 is attached to the original lens 510 to improve the imaging quality of the imaging device 600 at an object distance of 100 mm to 600 mm without changing the image plane position of the original lens 510 .

[0105] Example 7 See also Fig.15 , 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.

[0106] Fig.16 is a graph of the MTF (modulation transfer function) of the imaging device 700 when the object distance is 100 mm, Fig.17 is a graph of the MTF (modulation transfer function) of the imaging device 700 when the object distance is 200 mm, Fig.18 is a graph of the MTF (modulation transfer function) of the imaging device 700 when the object distance is 400 mm, Fig.19 is a graph of the MTF (modulation transfer function) of the imaging device 700 when the object distance is 600 mm. Figures 16 to 19 It can be seen that the MTF value is above 0.2 in the whole field of view, which means that it has good imaging quality and good detail resolution ability in both low-frequency and high-frequency conditions.

[0107] In this embodiment, a zoom external lens 300 is attached to the native lens 510 to improve the imaging quality of the imaging device 700 at an object distance of 100 mm to 600 mm without changing the image plane position of the native lens 510 .

[0108] Example 8 See also Fig. 20 , 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.

[0109] Fig.21 It is an MTF (Modulation Transfer Function) curve diagram of the imaging device 800 when the object distance is 100 mm, and the MTF value is above 0.15 in the entire field of view. Fig. 22 is a graph of the MTF (modulation transfer function) of the imaging device 800 when the object distance is 200 mm. Fig.23 is a graph of the MTF (modulation transfer function) of the imaging device 800 when the object distance is 400 mm. Fig.24 is the MTF (Modulation Transfer Function) curve of the imaging device 800 when the object distance is 600 mm. Figure 22 to Figure 24 It can be seen that the MTF value is above 0.2 in the whole field of view, which means that it has good imaging quality and good detail resolution ability in both low-frequency and high-frequency conditions.

[0110] In this embodiment, a zoom external lens 400 is attached to the native lens 510 to improve the imaging quality of the imaging device 800 at an object distance of 100 mm to 600 mm without changing the image plane position of the native lens 510 .

[0111] Please refer to Table 7, which shows the optical characteristics corresponding to the imaging devices provided in Examples 5 to 8, including the effective focal length f', the total optical length TTL', the aperture value Fno', the real image height IH' corresponding to the maximum field of view angle, the entrance pupil diameter EPD', and the chief ray incident angle CRA' at the maximum image height.

[0112] Table 7 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 can realize the zoom switching of the lens at different object distances by changing the air spacing distance between different lenses, thereby improving the imaging quality. It has one or more advantages such as miniaturization, ultra-wide angle, large target surface, large aperture, high-quality imaging, etc., which greatly improves the user experience.

[0113] 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.

[0114] 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 four lenses, characterized in that: It sequentially includes, from the object side to the imaging surface along the optical axis: A first lens with a negative optical power, whose object side is convex and whose image side is concave; A second lens with a positive optical power, whose object side is convex and whose image side is concave; A third lens with a negative optical power, whose object side is convex and whose image side is concave; A fourth lens with a positive optical power, whose object side is convex and whose image side is concave; The fourth lens can be dynamically moved on the optical axis to achieve zoom switching of the external lens at different object distances; Wherein, the total optical length TTL of the external lens and the effective focal length f of the external lens satisfy: 0 < TTL / f < 0.

09.

2. The external lens according to claim 1, characterized in that: The effective focal length f of the external lens satisfies: 140mm < f < 990mm; the maximum field of view FOV of the external lens satisfies: 149° < FOV < 150°.

3. The external lens according to claim 1, characterized in that: The maximum field of view FOV of the external lens and the aperture value Fno of the external lens satisfy: 59° < FOV / Fno < 60°; the clear aperture semi-diameter d1 of the object side of the first lens and the clear aperture semi-diameter d8 of the image side of the fourth lens satisfy: 2.01 < d1 / d8 < 2.

18.

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: -0.29 < f1 / f < -0.03; the curvature radius R1 of the object side of the first lens and the curvature radius R2 of the image side of the first lens satisfy: 2.98 < R1 / R2 < 5.

33.

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: 0.19 < f2 / f < 1.39; the curvature radius R3 of the object side of the second lens and the curvature radius R4 of the image side of the second lens satisfy: 0.95 < R3 / R4 < 0.

97.

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: -0.13 < f3 / f < -0.01; the curvature radius R5 of the object side of the third lens and the curvature radius R6 of the image side of the third lens satisfy: 2.43 < R5 / R6 < 2.

86.

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 < f4 / f < 0.1; the curvature radius R7 of the object side of the fourth lens and the curvature radius R8 of the image side of the fourth lens satisfy: 0.18 < R7 / R8 < 0.

21.

8. The external lens according to claim 1, characterized in that: The combined focal length f12 of the first lens and the second lens and the combined focal length f34 of the third lens and the fourth lens satisfy: -1.28 < f12 / f34 < -1.04; the combined focal length f34 of the third lens and the fourth lens and the distance CT34 between the third lens and the fourth lens on the optical axis satisfy: 25 < f34 / CT34 < 100.

9. The external lens according to claim 1, characterized in that: The clear aperture semi-diameter Sag3 of the object side of the second lens and the clear aperture semi-diameter Sag3 of the object side of the second lens satisfy: 0.22 < Sag3 / d3 < 0.25; the clear aperture semi-diameter Sag4 of the image side of the second lens and the clear aperture semi-diameter Sag4 of the image side of the second lens satisfy: 0.23 < Sag4 / d4 < 0.

27.

10. An imaging device, characterized in that: The system includes, from the object side to the imaging surface along the optical axis, the external lens as claimed in any one of claims 1 to 9 and the own lens; the own lens is composed of eight lenses, and from the object side to the imaging surface along the optical axis, the following are included: a fifth lens having negative optical power, whose object side surface is convex and whose image side surface is concave; a sixth lens having negative optical power, whose object side surface is convex and whose image side surface is concave; a seventh lens element having negative optical power, whose object side surface is concave and whose image side surface is convex; an eighth lens having positive refractive power, whose object-side surface is convex and whose image-side surface is convex; A ninth lens having positive refractive power, whose object side surface is concave and whose image side surface is convex; A tenth lens having positive refractive power, whose object-side surface is convex and whose image-side surface is convex; The eleventh lens has a negative optical power, and its object side surface is concave and its image side surface is concave; The twelfth lens has positive refractive power, its object-side surface is convex, and its image-side surface is convex.

Images