External lens and imaging device

Abstract

The present invention provides an external lens and an imaging device. The external lens has a total of four lenses, which sequentially include, along the optical axis from the object side to the imaging surface: 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 under 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. The external lens and the imaging device provided by the present invention can improve the imaging quality of the lens at different object distances and greatly improve the user experience effect.

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 imaging modules 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 configuring an external lens is equivalent to increasing the original focal length of the electronic device's lens, 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 electronic device's lens, the field of view 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 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:

[0005] An external lens, comprising a total of four lenses, which sequentially include from the object side to the imaging surface along the optical axis: a first lens with a negative optical power, the object side surface of which is convex and the image side surface of which is concave;

[0006] A second lens with a positive optical power, the object side surface of which is convex and the image side surface of which is concave;

[0007] A third lens with a negative optical power, the object side surface of which is convex and the image side surface of which is concave;

[0008] A fourth lens with a positive optical power, the object side surface of which is convex and the image side surface of which is concave;

[0009] The fourth lens can be dynamically moved on the optical axis to realize the zoom switching of the external lens under different object distance states;

[0010] 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.

[0011] 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°.

[0012] Further 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 semi-aperture d1 of the object side of the first lens and the semi-aperture d8 of the image side of the fourth lens satisfy: 2.01 < d1 / d8 < 2.18.

[0013] Further 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 radius of curvature R1 of the object side of the first lens and the radius of curvature R2 of the image side of the first lens satisfy: 2.98 < R1 / R2 < 5.33.

[0014] Further 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 radius of curvature R3 of the object side of the second lens and the radius of curvature R4 of the image side of the second lens satisfy: 0.95 < R3 / R4 < 0.97.

[0015] Further 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 radius of curvature R5 of the object side of the third lens and the radius of curvature R6 of the image side of the third lens satisfy: 2.43 < R5 / R6 < 2.86.

[0016] Further 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 radius of curvature R7 of the object side of the fourth lens and the radius of curvature R8 of the image side of the fourth lens satisfy: 0.18 < R7 / R8 < 0.21.

[0017] Further 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.

[0018] Further preferably, the semi-aperture d3 of the object side of the second lens and the sagittal height Sag3 of the semi-aperture of the object side of the second lens satisfy: 0.22 < Sag3 / d3 < 0.25; the semi-aperture d4 of the image side of the second lens and the sagittal height Sag4 of the semi-aperture of the image side of the second lens satisfy: 0.23 < Sag4 / d4 < 0.27.

[0019] The present invention also provides an imaging device, which has a total of twelve lenses and successively 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 successively along the optical axis from the object side to the imaging surface are:

[0020] The fifth lens with negative optical power, whose object side is convex and whose image side is concave;

[0021] The sixth lens with negative optical power, whose object side is convex and whose image side is concave;

[0022] The seventh lens with negative optical power, whose object side is concave and whose image side is convex;

[0023] The eighth lens with positive optical power, whose object side is convex and whose image side is convex;

[0024] The ninth lens with positive optical power, whose object side is concave and whose image side is convex;

[0025] The tenth lens with positive optical power, whose object side is convex and whose image side is convex;

[0026] The eleventh lens with negative optical power, whose object side is concave and whose image side is concave;

[0027] The twelfth lens with positive optical power, whose object side is convex and whose image side is convex.

[0028] Compared with the prior art, the external lens and the imaging device provided by the present invention can achieve zoom switching of the lens at different object distances by changing the air interval distance between different lenses, improve the imaging quality, and have one or more advantages such as miniaturization, ultra-wide angle, large target surface, large aperture, and high-quality imaging, greatly improving the user experience effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of the embodiments in conjunction with the accompanying drawings, where:

[0030] Figure 1 is a schematic structural diagram of the external lens in Embodiment 1 of the present invention.

[0031] Figure 2 is a schematic structural diagram of the external lens in Embodiment 2 of the present invention.

[0032] Figure 3 is a schematic structural diagram of the external lens in Embodiment 3 of the present invention.

[0033] Figure 4 is a schematic structural diagram of the external lens in Embodiment 4 of the present invention.

[0034] Figure 5 Schematic diagram of the imaging device in Embodiment 5 of the present invention.

[0035] Figure 6 MTF curve graph of the imaging device in Embodiment 5 of the present invention when the object distance is 100 mm.

[0036] Figure 7 MTF curve graph of the imaging device in Embodiment 5 of the present invention when the object distance is 200 mm.

[0037] Figure 8 MTF curve graph of the imaging device in Embodiment 5 of the present invention when the object distance is 400 mm.

[0038] Figure 9 MTF curve graph of the imaging device in Embodiment 5 of the present invention when the object distance is 600 mm.

[0039] Figure 10 Schematic diagram of the imaging device in Embodiment 6 of the present invention.

[0040] Figure 11 MTF curve graph of the imaging device in Embodiment 6 of the present invention when the object distance is 100 mm.

[0041] Figure 12 MTF curve graph of the imaging device in Embodiment 6 of the present invention when the object distance is 200 mm.

[0042] Figure 13 MTF curve graph of the imaging device in Embodiment 6 of the present invention when the object distance is 400 mm.

[0043] Figure 14 MTF curve graph of the imaging device in Embodiment 6 of the present invention when the object distance is 600 mm.

[0044] Figure 15 Schematic diagram of the imaging device in Embodiment 7 of the present invention.

[0045] Figure 16 MTF curve graph of the imaging device in Embodiment 7 of the present invention when the object distance is 100 mm.

[0046] Figure 17 MTF curve graph of the imaging device in Embodiment 7 of the present invention when the object distance is 200 mm.

[0047] Figure 18 MTF curve graph of the imaging device in Embodiment 7 of the present invention when the object distance is 400 mm.

[0048] Figure 19 MTF curve graph of the imaging device in Embodiment 7 of the present invention when the object distance is 600 mm.

[0049] Figure 20 It is a schematic structural diagram of the imaging device in Embodiment 8 of the present invention.

[0050] Figure 21 It is an MTF curve graph of the imaging device in Embodiment 8 of the present invention when the object distance is 100 mm.

[0051] Figure 22 It is an MTF curve graph of the imaging device in Embodiment 8 of the present invention when the object distance is 200 mm.

[0052] Figure 23 It is an MTF curve graph of the imaging device in Embodiment 8 of the present invention when the object distance is 400 mm.

[0053] Figure 24 It is an MTF curve graph of the imaging device in Embodiment 8 of the present invention when the object distance is 600 mm.

[0054] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. Specific Embodiments

[0055] To better understand the present application, more detailed descriptions of various aspects of the present application will be made 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 do not 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.

[0056] It should be noted that in this specification, the expressions such as first, second, and third are only used to distinguish one feature from another feature and do not represent any limitation on the feature. Therefore, without departing from the teachings of the present invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0057] In the drawings, for the sake of clarity, the thickness, size, and shape of the lenses have been slightly exaggerated. Specifically, the spherical or aspherical shapes shown in the drawings are shown by way of example. That is, the spherical or aspherical shapes are not limited to the spherical or aspherical shapes shown in the drawings. The drawings are only for illustration and are not drawn to an exact scale.

[0058] In this document, 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 to be photographed is called the object side surface of the lens, and the surface of each lens closest to the imaging surface is called the image side surface of the lens.

[0059] It should also be understood that the terms "comprise", "comprising", "have", "including" and / or "including" when used in this specification denote the presence of the stated features, elements and / or components, but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when an expression such as "at least one of..." appears after a list of listed features, it modifies the entire listed features, rather than an individual element in the list. In addition, when describing embodiments of the present application, the use of "may" means "one or more embodiments of the present application". And the term "exemplary" is intended to refer to an example or illustration.

[0060] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms (such as those defined in a common dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0061] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0062] The external lens provided by the embodiment of the present invention is a zoom lens, which has a total of four lenses. Along the optical axis from the object side to the imaging surface, it sequentially includes: a first lens, a second lens, a third lens and a fourth lens. 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 move 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 gap between the fourth lens and the third lens of the present invention on the optical axis is variable. By changing the air gap 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 100 mm to 600 mm. The external lens can be mounted in front of the object side of the lens of the imaging device to improve the image imaging quality of the imaging device when the object distance is between 100 mm and 600 mm. The imaging device can be an electronic device such as a smart phone, a mobile terminal, a sports camera, etc.

[0063] In some embodiments, the first lens may have a negative optical power, its object side is convex, and its image side is concave. The second lens may have a positive optical power, its object side is convex, and its image side is concave. The third lens may have a negative optical power, its object side is convex, and its image side is concave. The fourth lens may have a positive optical power, its object side is convex, and its image side is concave.

[0064] 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.

[0065] 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°.

[0066] 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 a suitable 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°.

[0067] In some embodiments, the clear aperture radius d1 of the object side of the first lens and the clear aperture radius 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 radii 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 thus improving the imaging quality of the external lens.

[0068] 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 a suitable surface shape, it is beneficial for the first lens to accommodate light at a larger angle and collect as much light as possible into the rear optical system, achieving a large field of view while increasing the light flux.

[0069] 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 radius of curvature R3 of the object side surface of the second lens and the radius of curvature 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, reducing 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.

[0070] 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 radius of curvature R5 of the object side surface of the third lens and the radius of curvature 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, making the light in the edge field of view show an upward trend, which is beneficial to the image point on the imaging surface being away from the optical axis, so as to be beneficial to achieving a large target surface and obtaining a larger picture, and can effectively eliminate aberrations and improve the resolution ability of the external lens.

[0071] 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 radius of curvature R7 of the object side surface of the fourth lens and the radius of curvature 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, making the light trend transition smoothly to the rear, reducing the height of the light incident on the rear, slowing down the upward trend of the light, avoiding the light energy loss of the large field of view light reaching the rear system, being beneficial to improving the illuminance of the edge field of view, and being beneficial to achieving a short optical total length.

[0072] 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 distance CT34 between 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.

[0073] 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 highlight the detailed information of the central field of view of the external lens.

[0074] In some embodiments, the overall 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.

[0075] In some embodiments, the external lens satisfies the conditional formula: 11 mm < TTL < 12 mm, 2.5 < Fno < 2.52; where TTL represents the overall 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.

[0076] In some embodiments, the lens material in 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.

[0077] 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 lens 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.

[0078] 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 the 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.

[0079] Specifically, the fifth lens may have a negative focal power, with its object side being convex and its image side being concave. The sixth lens may have a negative focal power, with its object side being convex and its image side being concave. The seventh lens may have a negative focal power, with its object side being concave and its image side being convex. The eighth lens may have a positive focal power, with its object side being convex and its image side being convex. The ninth lens may have a positive focal power, with its object side being concave and its image side being convex. The tenth lens may have a positive focal power, with its object side being convex and its image side being convex. The eleventh lens may have a negative focal power, with its object side being concave and its image side being concave. The twelfth lens may have a positive focal power, with its object side being convex and its image side being convex.

[0080] In some embodiments, the imaging device may further include a diaphragm, which may be located between the eighth lens and the ninth lens. It can be understood that the diaphragm is used to limit the amount of incident light to change the brightness of the imaging.

[0081] 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 interfering light to prevent the interfering light from reaching the imaging surface of the imaging lens and affecting normal imaging.

[0082] In some embodiments, the tenth lens and the eleventh lens may form a cemented lens group with a negative focal power, 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 processing difficulty of the imaging device and improving the assembly yield of the imaging device.

[0083] In some embodiments, the fifth lens, the seventh lens, the ninth lens, the tenth lens, and the eleventh lens all adopt glass spherical lenses; the sixth lens, the eighth lens, and the twelfth lens all adopt glass aspherical lenses.

[0084] 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 H’ 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.

[0085] In various embodiments of the present invention, when the lens is an aspherical lens, the aspherical surface shapes of the respective lenses satisfy the following equation:

[0086] ;

[0087] where z is the distance between the surface and the vertex of the surface in the optical axis direction, h is the distance from the optical axis to the surface, c is the curvature of the vertex of the surface, K is the conic coefficient, and B, C, D, E, and F are the surface coefficients of the fourth, sixth, eighth, tenth, and twelfth orders, respectively.

[0088] 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 the respective embodiments. The following embodiments are only the 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.

[0089] Embodiment 1

[0090] Please refer to Figure 1 , Figure 1FIG. 0 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.

[0091] The first lens L1 has a negative optical power. Its object side surface S1 is a convex surface, and its image side surface S2 is a concave surface.

[0092] The second lens L2 has a positive optical power. Its object side surface S3 is a convex surface, and its image side surface S4 is a concave surface.

[0093] The third lens L3 has a negative optical power. Its object side surface S5 is a convex surface, and its image side surface S6 is a concave surface.

[0094] The fourth lens L4 has a positive optical power. Its object side surface S7 is a convex surface, and its image side surface S8 is a concave surface.

[0095] 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.

[0096] The relevant parameters of each lens in the external lens 100 in Embodiment 1 are shown in Table 1-1.

[0097] Table 1-1

[0098]

[0099] The surface type parameters of the aspherical lenses of the external lens 100 in Embodiment 1 are shown in Table 1-2.

[0100] Table 1-2

[0101]

[0102] Among them, in Table 1-1 above, D0 is the object distance, that is, the distance between the first lens L1 and the object to be photographed 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 plane 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.

[0103] 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 in this embodiment is 100 mm to 600 mm.

[0104] The parameters of the external lens 100 in Embodiment 1 in different object distance states are shown in Table 1-3.

[0105] Table 1-3

[0106]

[0107] Example 2

[0108] Please refer to Figure 2 , which shows the structural schematic diagram of the external lens 200 provided in Example 2 of the present invention. Compared with Example 1, the main difference is that the optical parameters such as the curvature radius of each lens surface, the lens thickness, and the distance between lenses are different.

[0109] The relevant parameters of each lens in the external lens 200 in Example 2 are shown in Table 2-1.

[0110] Table 2-1

[0111]

[0112] The aspheric lens surface type parameters of the external lens 200 in Example 2 are shown in Table 2-2.

[0113] Table 2-2

[0114]

[0115] The parameters of the external lens 200 in this Example 2 under different object distance states are shown in Table 2-3.

[0116] Table 2-3

[0117]

[0118] Example 3

[0119] Please refer to Figure 3 , which shows the structural schematic diagram of the external lens 300 provided in Example 3 of the present invention. Compared with Example 1, the main difference is that the optical parameters such as the curvature radius of each lens surface, the lens thickness, and the distance between lenses are different.

[0120] The relevant parameters of each lens in the external lens 300 in Example 3 are shown in Table 3-1.

[0121] Table 3-1

[0122]

[0123] The aspheric lens surface type parameters of the external lens 300 in Example 3 are shown in Table 3-2.

[0124] Table 3-2

[0125]

[0126] The parameters of the external lens 300 in Embodiment 3 under different object distances are shown in Table 3-3.

[0127] Table 3-3

[0128]

[0129] Embodiment 4

[0130] Please refer to Figure 4 , which shows the structural schematic diagram of the external lens 400 provided in Embodiment 4 of the present invention. Compared with Embodiment 1, the main difference is that the optical parameters such as the radius of curvature of each lens surface, the lens thickness, and the distance between lenses are different.

[0131] The relevant parameters of each lens in the external lens 400 in Embodiment 4 are shown in Table 4-1.

[0132] Table 4-1

[0133]

[0134] The aspheric lens surface parameters of the external lens 400 in Embodiment 4 are shown in Table 4-2.

[0135] Table 4-2

[0136]

[0137] The parameters of the external lens 400 in Embodiment 4 under different object distances are shown in Table 4-3.

[0138] Table 4-3

[0139]

[0140] Please refer to Table 5-1 and Table 5-2, which show the corresponding optical characteristics of the above 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 values corresponding to each conditional formula in each embodiment.

[0141] Table 5-1

[0142]

[0143] Table 5-2

[0144]

[0145] Embodiment 5

[0146] The external lens of any of the above embodiments can be mounted in front of the object side of the lens of the imaging device, and the imaging device can be an electronic device such as a smart phone, a mobile terminal, or an action camera.

[0147] Please refer to Figure 5 , which shows a schematic structural diagram of an imaging device 500 equipped with an external lens provided in Embodiment 5 of the present invention, including the external lens 100 in Embodiment 1 above. The imaging device 500 further includes a built-in own lens 510 and an imaging element. The own lens 510 can be a multi-lens combination, and in this application, the own lens 510 is composed of eight lenses. The imaging element can be a CMOS image sensor or a CCD image sensor.

[0148] The own lens 510 sequentially includes, along the optical axis from the object side to the imaging plane S27: a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, a diaphragm ST, a ninth lens L9, a tenth lens L10, an eleventh lens L11, a twelfth lens L12, and a filter G1.

[0149] Among them, the fifth lens L5 has a negative optical power, its object side surface S10 is convex, and its image side surface S11 is concave. The sixth lens L6 has a negative optical power, its object side surface S12 is convex, and its image side surface S13 is concave. The seventh lens L7 has a negative optical power, its object side surface S14 is concave, and its image side surface S15 is convex. The eighth lens L8 has a positive optical power, its object side surface S16 is convex, and its image side surface S17 is convex. The ninth lens L9 has a positive optical 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 a negative optical power. The tenth lens L10 has a positive optical power, its object side surface S20 is convex, and its image side surface S21 is convex. The eleventh lens L11 has a negative optical power, its object side surface S21 is concave, and its image side surface S22 is concave. The twelfth lens L12 has a positive optical power, its object side surface S23 is convex, and its image side surface S24 is convex.

[0150] The fifth lens L5, the seventh lens L7, the ninth lens L9, the tenth lens L10, and the eleventh lens L11 all adopt glass spherical lenses; the sixth lens L6, the eighth lens L8, and the twelfth lens L12 all adopt glass aspherical lenses.

[0151] The relevant parameters of each lens in the imaging device 500 in Embodiment 5 are shown in Table 6-1.

[0152] Table 6-1

[0153]

[0154] The surface profile parameters of the aspherical lens of the imaging device 500 in Example 5 are shown in Table 6-2.

[0155] Table 6-2

[0156]

[0157] Please refer to Figure 6 , which shows the MTF (Modulation Transfer Function) curve of the imaging device 500 when the object distance is 100 mm. The abscissa in the figure represents the spatial frequency (unit: lp / mm), and the ordinate represents the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.25 in the entire field of view. In the range of 0 to 160 lp / mm, the MTF curve decreases uniformly 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 cases.

[0158] Figure 7 is the MTF (Modulation Transfer Function) curve of the imaging device 500 when the object distance is 200 mm, Figure 8 is the MTF (Modulation Transfer Function) curve of the imaging device 500 when the object distance is 400 mm, Figure 9 is the MTF (Modulation Transfer Function) curve of the imaging device 500 when the object distance is 600 mm. It can be seen from the above figures that 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 cases.

[0159] In this embodiment, by attaching a zoom external lens 100 to the own lens 510, without changing the position of the image plane of the own lens 510, the imaging quality of the imaging device 500 under the condition of object distances from 100 mm to 600 mm is improved.

[0160] Example 6

[0161] Please refer to Figure 10 , which shows the structural schematic diagram of the imaging device 600 equipped with an external lens provided in Embodiment 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 carried in this embodiment is the external lens 200 in the above-mentioned Example 2.

[0162] Figure 11 is the MTF (Modulation Transfer Function) curve of the imaging device 600 when the object distance is 100 mm, and the MTF value is above 0.15 in the entire field of view. Figure 12 is the MTF (Modulation Transfer Function) curve of the imaging device 600 when the object distance is 200 mm, Figure 13 is the MTF (Modulation Transfer Function) curve of the imaging device 600 when the object distance is 400 mm,Figure 14 The MTF (Modulation Transfer Function) curve graph of the imaging device 600 when the object distance is 600 mm. As can be seen from Figures 12 to 14 this, the MTF value is above 0.2 within the entire field of view, indicating that it has good imaging quality and good detail resolution ability in both low-frequency and high-frequency cases.

[0163] In this embodiment, by attaching a zoom external lens 200 to the own lens 510, without changing the position of the image plane of the own lens 510, the imaging quality of the imaging device 600 under the condition of object distances from 100 mm to 600 mm is improved.

[0164] Embodiment 7

[0165] Please refer to Figure 15 , which shows the structural schematic diagram of the imaging device 700 equipped with an external lens provided in Embodiment 7 of the present invention. The structure of the imaging device in this embodiment is basically the same as that in Embodiment 5, and the main difference is that: the external lens carried in this embodiment is the external lens 300 in the above-mentioned Embodiment 3.

[0166] Figure 16 The MTF (Modulation Transfer Function) curve graph of the imaging device 700 when the object distance is 100 mm, Figure 17 The MTF (Modulation Transfer Function) curve graph of the imaging device 700 when the object distance is 200 mm, Figure 18 The MTF (Modulation Transfer Function) curve graph of the imaging device 700 when the object distance is 400 mm, Figure 19 The MTF (Modulation Transfer Function) curve graph of the imaging device 700 when the object distance is 600 mm. As can be seen from Figures 16 to 19 this, the MTF value is above 0.2 within the entire field of view, indicating that it has good imaging quality and good detail resolution ability in both low-frequency and high-frequency cases.

[0167] In this embodiment, by attaching a zoom external lens 300 to the own lens 510, without changing the position of the image plane of the own lens 510, the imaging quality of the imaging device 700 under the condition of object distances from 100 mm to 600 mm is improved.

[0168] Embodiment 8

[0169] Please refer to Figure 20 , which shows the structural schematic diagram of the imaging device 800 equipped with an external lens provided in Embodiment 8 of the present invention. The structure of the imaging device in this embodiment is basically the same as that in Embodiment 5, and the main difference is that: the external lens carried in this embodiment is the external lens 400 in the above-mentioned Embodiment 4.

[0170] Figure 21It is a MTF (Modulation Transfer Function) curve graph of the imaging device 800 when the object distance is 100 mm, and the MTF value is above 0.15 within the entire field of view. Figure 22 It is a MTF (Modulation Transfer Function) curve graph of the imaging device 800 when the object distance is 200 mm. Figure 23 It is a MTF (Modulation Transfer Function) curve graph of the imaging device 800 when the object distance is 400 mm. Figure 24 It is a MTF (Modulation Transfer Function) curve graph of the imaging device 800 when the object distance is 600 mm. As can be seen Figures 22 to 24 from it, the MTF value is above 0.2 within the entire field of view, indicating that it has good imaging quality and good detail resolution ability in both low-frequency and high-frequency cases.

[0171] In this embodiment, by attaching a zoom external lens 400 to the own lens 510, without changing the position of the image plane of the own lens 510, the imaging quality of the imaging device 800 under the condition of object distance from 100 mm to 600 mm is improved.

[0172] Please refer to Table 7, which shows the optical characteristics corresponding to the imaging devices provided in Embodiments 5 to 8, including the effective focal length f’ of the imaging device, the total optical length TTL’, the aperture value Fno’, the true image height IH’ corresponding to the maximum field of view angle, the entrance pupil diameter EPD’, and the chief ray angle of incidence CRA’ at the maximum image height.

[0173] Table 7

[0174]

[0175] Combining the above embodiments, the external lens and imaging device provided by the present invention have the following advantages:

[0176] 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 interval distance between different lenses, improve the imaging quality, and have one or more advantages such as miniaturization, ultra-wide angle, large target surface, large aperture, and high-quality imaging, greatly improving the user experience effect.

[0177] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0178] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention shall be subject to the appended claims.

Claims

1. An external lens, comprising four lenses in total, characterized in that, It successively 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 under 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.

2. The external lens according to claim 1, characterized in that 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°.

3. The external lens according to claim 1, wherein 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, wherein, 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, wherein 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, wherein 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.

9. The external lens according to claim 1, wherein 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, comprising a total of twelve lenses, characterized in that, It successively includes, from the object side to the imaging surface along the optical axis: an external lens as described in any one of claims 1-9 and an in-house lens; the in-house lens is composed of eight lenses, and successively from the object side to the imaging surface along the optical axis are: A fifth lens with negative optical power, whose object side is convex and whose image side is concave; A sixth lens with negative optical power, whose object side is convex and whose image side is concave; A seventh lens with negative optical power, whose object side is concave and whose image side is convex; An eighth lens with positive optical power, whose object side is convex and whose image side is convex; A ninth lens with positive optical power, whose object side is concave and whose image side is convex; A tenth lens with positive optical power, whose object side is convex and whose image side is convex; An eleventh lens with negative optical power, whose object side is concave and whose image side is concave; A twelfth lens with positive optical power, whose object side is convex and whose image side is convex.

Images