Long focal length

Abstract

The application relates to the field of optical imaging technology, in particular to a long-focus lens. The long-focus lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged along the optical axis of the long-focus lens from the object side of the long-focus lens to the imaging surface; the first lens, the second lens, the third lens, the sixth lens and the eighth lens each have a negative focal power, and the fourth lens, the fifth lens and the seventh lens each have a positive focal power. Through reasonable collocation of the lenses, the imaging quality of the long-focus lens can be effectively improved, the cost is reduced, and the long-focus lens has a longer detection distance.

Description

Technical Field

[0001] This application relates to the field of optical imaging technology, and in particular to a telephoto lens. Background Technology

[0002] In recent years, with the rapid development of the high-definition camera vehicle module industry, forward-looking modules have been increasingly used in various vehicles, and the demand for forward-looking vehicle lenses has also increased. However, existing forward-looking vehicle lenses cannot meet the requirements for long-distance detection, and have poor imaging quality and high cost.

[0003] The information disclosed in this background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not form any part of the prior art and does not form prior art that may be taught to those skilled in the art. Summary of the Invention

[0004] This summary is provided to introduce, in a simplified form, the selected concepts that will be further described in the detailed embodiments below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0005] The purpose of this invention is to provide a telephoto lens with high imaging quality, high cost-effectiveness, and a longer detection range.

[0006] The present invention provides a telephoto lens, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis of the telephoto lens from the object side to the imaging plane.

[0007] The first lens, the third lens, the sixth lens, and the eighth lens each have negative optical power;

[0008] The second lens, the fourth lens, the fifth lens, and the seventh lens each have positive optical power.

[0009] Furthermore, the object-side surface of the first lens is convex along the optical axis, and the image-side surface of the first lens is concave along the optical axis;

[0010] The object surface of the second lens is convex along the optical axis, and the image surface of the second lens is concave along the optical axis.

[0011] The object-side and image-side surfaces of the third lens are both concave along the optical axis;

[0012] The object-side surface and image-side surface of the fourth lens are both convex along the optical axis;

[0013] The object surface and the image surface of the fifth lens are both convex along the optical axis;

[0014] The object surface and the image surface of the sixth lens are both concave along the optical axis;

[0015] The object surface and the image surface of the seventh lens are both convex along the optical axis;

[0016] The object surface of the eighth lens is concave along the optical axis, and the image surface of the eighth lens is convex along the optical axis.

[0017] Further, the telephoto lens further includes:

[0018] An aperture, the aperture is disposed between the fourth lens and the fifth lens;

[0019] A filter element, the filter element is a visible light filter, the visible light filter is disposed on one side of the eighth lens facing the imaging surface; or, the visible light filter element is a filter film layer, and the visible light filter film layer is plated on the object surface of the seventh lens.

[0020] Further, the telephoto lens satisfies: 12 < f < 30; where f is the effective focal length of the telephoto lens.

[0021] Further, the telephoto lens satisfies: 20° < 2θ < 50°; where 2θ is the full field angle of the telephoto lens.

[0022] Further, the telephoto lens satisfies: 1.4 < F# < 1.8; where F# is the aperture number of the telephoto lens.

[0023] Further, the telephoto lens satisfies: RI > 60%; where RI is the illuminance of the telephoto lens.

[0024] Further, the telephoto lens satisfies: 2 < T L / h < 5; where T L is the total optical length of the telephoto lens, and h is the image height of the telephoto lens.

[0025] Further, the telephoto lens satisfies: where is the combined optical power of the first lens, the second lens and the third lens, is the optical power of the telephoto lens.

[0026] Further, the telephoto lens satisfies: where is the combined focal power of the fourth lens, the fifth lens, the sixth lens, and the seventh lens, is the focal power of the telephoto lens.

[0027] Further, the telephoto lens satisfies: where, is the focal power of the eighth lens, is the focal power of the telephoto lens.

[0028] Further, the telephoto lens satisfies: 0.8 < SD1 / h < 1.2; where SD1 is the semi-aperture of the first lens, and h is the image plane height of the telephoto lens.

[0029] Further, the telephoto lens satisfies: R 16 < -20, 15 < CRA < 25; where R 16 is the radius of curvature of the image-side surface of the eighth lens, and CRA is the chief ray angle of the telephoto lens.

[0030] Further, the telephoto lens satisfies: V5 > 70, (V4 + V5) / V6 > 3, (R7 - R 11 ) / R 10 < 3;

[0031] where V4 is the Abbe number of the fourth lens, V5 is the Abbe number of the fifth lens, and V6 is the Abbe number of the sixth lens;

[0032] R7 is the radius of curvature of the object-side surface of the fourth lens, R 10 is the radius of curvature of the object-side surface of the fifth lens, R 11 is the radius of curvature of the object-side surface of the sixth lens.

[0033] Further, the telephoto lens satisfies: (R6 + R 13 ) / R 14 < 5;

[0034] where R6 is the radius of curvature of the image-side surface of the third lens, R 13 is the radius of curvature of the object-side surface of the seventh lens, R 14 is the radius of curvature of the image-side surface of the seventh lens.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] The telephoto lens provided by this invention includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis of the telephoto lens from the object side to the imaging plane. The first, second, third, sixth, and eighth lenses each have negative optical power, while the fourth, fifth, and seventh lenses each have positive optical power. Through the rational combination of these lenses, the imaging quality of the telephoto lens can be effectively improved, costs reduced, and the telephoto lens can achieve a longer detection distance. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the imaging of a telephoto lens provided in an embodiment of the present invention;

[0039] Figure 2 A defocus curve diagram of a telephoto lens provided in an embodiment of the present invention;

[0040] Figure 3 MTF curve of a telephoto lens provided in an embodiment of the present invention;

[0041] Figure 4 Illuminance curve diagram of a telephoto lens provided in an embodiment of the present invention;

[0042] Figure 5 A principal ray angle curve of a telephoto lens provided in an embodiment of the present invention;

[0043] Figure 6 The imaging point size of the telephoto lens provided in the embodiments of the present invention.

[0044] Figure label:

[0045] 1-First lens, 2-Second lens, 3-Third lens, 4-Fourth lens, 5-Fifth lens, 6-Sixth lens, 7-Seventh lens, 8-Eighth lens, 9-Aperture stop, 10-Visible light filter, 11-Cover glass. Detailed Implementation

[0046] The following detailed embodiments are provided to help the reader gain a full understanding of the methods, apparatus, and / or systems described herein. However, various modifications, alterations, and equivalents of the methods, apparatus, and / or systems described herein will be apparent after understanding the disclosure of this application. For example, the order of operations described herein is merely illustrative and is not limited to the order set forth herein; changes that will be apparent after understanding the disclosure of this application are possible, except for operations that must occur in a specific order. Furthermore, for clarity and brevity, descriptions of features known in the art may be omitted.

[0047] The features described herein may be implemented in different forms and are not to be construed as being limited to the examples described herein. Rather, the examples described herein have been provided merely to illustrate some of the many feasible ways in which the methods, devices, and / or systems described herein will be apparent upon understanding the disclosure of this application.

[0048] This application provides a telephoto lens with high imaging quality, high cost-effectiveness, and a longer detection range.

[0049] In the embodiments of this application, the first lens is the lens closest to the object (or subject), while the eighth lens is the lens closest to the imaging surface (or sensor chip). Furthermore, in this application, the radius of curvature, half-aperture, and thickness of the lens are all expressed in millimeters (mm), and the total optical length of the lens (T) is... L ), image plane height (h) and focal length (f).

[0050] In addition, the thickness of the lens, the distance between the lenses, and T L This distance is measured based on the optical axis of the lens. Furthermore, in the description of the lens shape, the statement that one surface of the lens is convex along the optical axis means that the paraxial region of the corresponding surface is convex, and the statement that one surface of the lens is concave along the optical axis means that the paraxial region of the corresponding surface is concave. Therefore, even when one surface of the lens is described as convex, the edge portion of said one surface may be concave. Similarly, even when one surface of the lens is described as concave, the edge portion of said one surface may be convex.

[0051] The telephoto lens provided in this application includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis of the telephoto lens from the object side to the imaging plane.

[0052] The first lens has negative optical power and is a meniscus lens with its concave surface facing the imaging plane. That is, the object surface of the first lens is convex along the optical axis, and the image surface of the first lens is concave along the optical axis.

[0053] The second lens has positive optical power and is a meniscus lens with its concave surface facing the imaging plane. That is, the object surface of the second lens is convex along the optical axis, and the image surface of the second lens is concave along the optical axis.

[0054] The third lens has negative optical power and is a biconcave lens, meaning that both the object-side and image-side surfaces of the third lens are concave along the optical axis.

[0055] The fourth lens has positive optical power and is a biconvex lens, meaning that both the object-side and image-side surfaces of the fourth lens are convex along the optical axis.

[0056] The fifth lens has positive optical power and is a biconvex lens, meaning that both the object-side and image-side surfaces of the fifth lens are convex along the optical axis.

[0057] The sixth lens has negative optical power and is a biconcave lens, meaning that both the object-side and image-side surfaces of the sixth lens are concave along the optical axis.

[0058] The seventh lens has positive optical power and is a biconvex lens, meaning that both the object-side and image-side surfaces of the seventh lens are convex along the optical axis.

[0059] The eighth lens has negative optical power and is a meniscus lens with its concave surface facing the object side. That is, the object surface of the eighth lens is concave along the optical axis, and the image surface of the eighth lens is convex along the optical axis.

[0060] In some embodiments, all lenses of the telephoto lens are glass spherical lenses, and each lens has a multilayer film with high transmittance on both sides.

[0061] In some embodiments, the telephoto lens may further include an aperture stop disposed between two adjacent lenses; for example, the aperture stop may be disposed between the fourth lens and the fifth lens. Distributing the aperture stop between the fourth and fifth lenses not only allows for precise adjustment of the amount of light transmitted, improving imaging performance and ensuring clear images can be captured even in low-light conditions, but also effectively controls the incident angle of the principal light rays reaching the imaging surface, better meeting the incident requirements of the sensor chip.

[0062] Preferably, the aperture is a light-blocking paper with a light-passing hole at its center. Using light-blocking paper as an aperture can reduce the requirements on the light-passing hole of the telephoto lens barrel to a certain extent, thereby maximizing the processing accuracy and reducing processing errors.

[0063] In some embodiments, the telephoto lens may also include a filter to suppress the transmission of light in non-operating wavelength bands, thereby effectively reducing chromatic aberration and stray light in the telephoto lens and improving imaging performance.

[0064] The filter is a visible light filter, which is disposed on the side of the eighth lens facing the imaging surface; or, the filter can be a visible light filter film layer coated on the object surface of the seventh lens.

[0065] In some embodiments, the telephoto lens further includes a cover glass. If a visible light filter is provided on the side of the seventh lens facing the imaging surface, the cover glass is provided on the side of the visible light filter facing the imaging surface; if there is no visible light filter, the cover glass is provided on the side of the eighth lens facing the imaging surface.

[0066] The telephoto lens involved in this application can satisfy the following conditional expression:

[0067] In some embodiments, 12 is satisfied <f<30;

[0068] In some embodiments, 20° < 2θ < 50° is satisfied;

[0069] In some embodiments, 1.4 is satisfied. <F#<1.8;

[0070] In some embodiments, RI > 60% is satisfied;

[0071] In some embodiments, satisfying 2 <T L / h<5;

[0072] In some embodiments, satisfying

[0073] In some embodiments, satisfying

[0074] In some embodiments, satisfying

[0075] In some embodiments, 0.8 is satisfied. <SD1 / h<1.2;

[0076] In some embodiments, R satisfies 16 <-20;

[0077] In some embodiments, 15 is satisfied. <CRA<25;

[0078] In some embodiments, V5 > 70 is satisfied;

[0079] In some embodiments, (V4+V5) / V6>3 is satisfied;

[0080] In some embodiments, (R7-R) is satisfied. 11 ) / R 10 <3;

[0081] In some embodiments, (R6+R) is satisfied.13 ) / R 14 <5.

[0082] In the above expressions, f is the effective focal length of the telephoto lens, 2θ is the full field angle of the telephoto lens, F# is the f-number of the telephoto lens, RI is the illuminance of the telephoto lens, T L is the total optical length of the telephoto lens, h is the image plane height of the telephoto lens, is the optical power of the telephoto lens, is the combined optical power of the first, second, and third lenses, is the combined optical power of the fourth, fifth, sixth, and seventh lenses, is the optical power of the eighth lens, SD1 is the semi-aperture of the first lens, R 16 is the radius of curvature of the image-side surface of the eighth lens, CRA is the chief ray angle of the telephoto lens, V4 is the Abbe number of the fourth lens, V5 is the Abbe number of the fifth lens, V6 is the Abbe number of the sixth lens, R7 is the radius of curvature of the object-side surface of the fourth lens, R 10 is the radius of curvature of the object-side surface of the fifth lens, R 11 is the radius of curvature of the object-side surface of the sixth lens, R6 is the radius of curvature of the image-side surface of the third lens, R 13 is the radius of curvature of the object-side surface of the seventh lens, R 14 is the radius of curvature of the image-side surface of the seventh lens.

[0083] Here, according to 12 < f < 30, it is at least possible to ensure that the telephoto lens has a relatively long detection distance and a relatively large detection angle; when f exceeds the upper limit, the detection angle of the telephoto lens is too small; when f is lower than the lower limit, the detection distance of the telephoto lens is short.

[0084] In addition, according to 20° < 2θ < 50° and 1.4 < F# < 1.8, it is at least possible to ensure that the telephoto lens has sufficiently good imaging quality; when the f-number F# exceeds the upper limit, the remaining aberration that can be corrected by the telephoto lens is excessive; when the f-number F# is lower than the lower limit, the aberration of the overall lens is too large and the imaging quality is poor.

[0085] In addition, according to RI > 60%, it is at least possible for the telephoto lens to have better imaging uniformity and improve the imaging quality.

[0086] In addition, according to 2 < T L / h < 5, it is at least possible to limit the total length of the telephoto lens and ensure that the telephoto lens has good imaging quality. When T L / h exceeds the upper limit, the total length of the telephoto lens is too long, or in other words, if the total length of the telephoto lens is shortened, the image height of the telephoto lens will be insufficient; when T LWhen the value of / h is lower than the lower limit, due to the excessive optical power of each lens, it will be difficult to correct the aberration of the telephoto lens and the resolution ability will be significantly reduced.

[0087] In addition, according to The first, second and third lenses form the front lens group of the telephoto lens, which is used to converge the object plane light with a wide viewing angle into the telephoto lens, while correcting lens distortion and not generating large aberrations; when the value exceeds the upper limit, the combined optical power of the front lens group is too strong. Although it can make the total length of the telephoto lens smaller, it will generate large spherical aberration and it is difficult to correct; when the value is lower than the lower limit, the optical power of the front lens group is weak. Although the spherical aberration is relatively reduced, its refractive power decreases, which will cause the total length of the telephoto lens to increase.

[0088] In addition, according to The fourth to seventh lenses form the middle lens group of the telephoto lens, which承接上述前透镜群并与前透镜群有效配合承接上述前透镜群并与前透镜群有效配合承接上述前透镜群并与前透镜群有效配合 (the description here seems a bit repetitive and might need to be refined in the original Chinese). The middle lens group mainly承担整体光焦度承担整体光焦度承担整体光焦度 (the description here seems a bit repetitive and might need to be refined in the original Chinese) the overall optical power in the telephoto lens and corrects the vertical aberration; when the value exceeds the upper limit, the optical power of the middle lens group is too strong. Although it can make the total length of the telephoto lens smaller, it will generate large spherical aberration, astigmatism, and excessive field curvature, and it is difficult to correct; when the value is lower than the lower limit, the optical power of the middle lens group weakens. Although the above-mentioned aberrations are relatively reduced, its refractive power decreases, which will cause the total length of the telephoto lens to increase.

[0089] In addition, according to The eighth lens承接上述透镜组承接上述透镜组承接上述透镜组 (the description here seems a bit repetitive and might need to be refined in the original Chinese). It is used to correct the aberration of the telephoto lens and improve the imaging quality; when the value exceeds the upper limit or is lower than the lower limit, the aberration correction ability of the eighth lens decreases.

[0090] In addition, according to 0.8 < SD1 / h < 1.2, the first lens plays a role in collecting light in the telephoto lens. The larger its outer diameter, the better the light collection effect; when this relational expression is satisfied, at least it can ensure that the telephoto lens has a good light collection effect, and at the same time ensure that the size of the telephoto lens is not too large.

[0091] In addition, according to R 16 <-20 and 15 < CRA < 25, at least it can effectively correct aberrations, and at the same time尽可能地改变长焦镜头的主光线角度尽可能地改变长焦镜头的主光线角度尽可能地改变长焦镜头的主光线角度 (the description here seems a bit repetitive and might need to be refined in the original Chinese) change the chief ray angle of the telephoto lens as much as possible, increase the chip compatibility of the telephoto lens, and increase the variety of optional sensor chips.

[0092] Therefore, according to V5 > 70, (V4 + V5) / V6 > 3, and (R7 - R 11 ) / R 10<3, at least it enables the middle lens group to provide the overall optical power of the telephoto lens while also effectively correcting optical aberrations.

[0093] Furthermore, according to (R6+R 13 ) / R 14 <5, at least can ensure that the distortion of the telephoto lens is well corrected, so that the imaging ratio of the telephoto lens is close to the actual ratio of the objective object.

[0094] Next, we will describe the in-vehicle surround view module based on a specific example.

[0095] like Figure 1 As shown, the telephoto lens includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, and an eighth lens 8.

[0096] The first lens 1 has negative optical power, and its object-side surface is convex along the optical axis, while its image-side surface is concave along the optical axis; the second lens 2 has positive optical power, and its object-side surface is convex along the optical axis, while its image-side surface is concave along the optical axis; the third lens 3 has negative optical power, and both its object-side and image-side surfaces are concave along the optical axis; the fourth lens 4 has positive optical power, and both its object-side and image-side surfaces are convex along the optical axis; the fifth lens... Lens 5 has positive optical power, and both the object-side and image-side surfaces of lens 5 are convex along the optical axis; lens 6 has negative optical power, and both the object-side and image-side surfaces of lens 6 are concave along the optical axis; lens 7 has positive optical power, and both the object-side and image-side surfaces of lens 7 are convex along the optical axis; lens 8 has negative optical power, and both the object-side and image-side surfaces of lens 8 are concave along the optical axis and convex along the optical axis; wherein, lens 5 and lens 6 form a cemented lens group.

[0097] The telephoto lens also includes an aperture stop 9, a visible light filter 10, and a cover glass 11. The aperture stop 9 is positioned between the fourth lens 4 and the fifth lens 5. The visible light filter 10 and the cover glass 11 are sequentially positioned on the side of the eighth lens 8 facing the imaging plane.

[0098] In this example telephoto lens,

[0099] In this example telephoto lens, the relevant parameters of each lens are shown in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] In Table 1, S1 and S2 represent the object-side and image-side surfaces of the first lens, respectively; S3 and S4 represent the object-side and image-side surfaces of the second lens, respectively; and so on. The fifth and sixth lenses form a cemented lens group, and S11 is both the image-side surface of the fifth lens and the object-side surface of the sixth lens.

[0104] In this example of the vehicle surround view module, the values ​​of the conditional expressions for the vehicle surround view module are shown in Table 2.

[0105] Table 2

[0106]

[0107]

[0108] Figure 2 The defocus curve of the telephoto lens in this example is presented. Figure 3 The MTF curve of the telephoto lens in this example is presented. Figure 4 The illuminance curve of the telephoto lens in this example is presented. Figure 5 The principal ray angle curve of the telephoto lens in this example is presented; Figure 6 The image point size of the telephoto lens in this example is shown.

[0109] Based on the above example, the telephoto lens of this application has the following advantages:

[0110] All eight lenses are all glass lenses, which gives the telephoto lens a long service life and stable operation, and reduces material and processing and assembly costs.

[0111] The aberrations of the telephoto lens in this application are effectively corrected, and it has the advantage of small focus drift caused by high and low temperatures, enabling the telephoto lens to adapt to different temperature conditions and with good temperature control.

[0112] The telephoto lens of this application, by reasonably matching the optical power of each lens, can reduce the total optical length of the telephoto lens to a certain extent, and ensure that high-quality images can be captured even in darker environments.

[0113] The eighth lens of the telephoto lens in this application uses a meniscus lens, which enables the telephoto lens to effectively control the angle of the principal ray, making it perfectly matched with the sensor chip and improving the chip compatibility of the telephoto lens.

[0114] The distortion of the telephoto lens in this application can be well corrected, so that the imaging ratio of the telephoto lens is close to the actual ratio of the objective object.

[0115] While this disclosure includes specific examples, it will be apparent upon understanding the disclosure of this application that various changes in form and detail may be made to these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered descriptive only and not for limiting purposes. The description of features or aspects in each example is to be considered applicable to similar features or aspects in other examples. Suitable results may be obtained if the described techniques are performed in a different order, and / or if components in the described system, architecture, apparatus, or circuit are combined in a different manner and / or if components in the described system, architecture, apparatus, or circuit are replaced or supplemented with other components or their equivalents. Therefore, the scope of this disclosure is not limited by the specific embodiments but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents shall be construed as included in this disclosure.

Claims

1. A telephoto lens, characterized in that, The telephoto lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis of the telephoto lens from the object side of the telephoto lens to the imaging plane, wherein the number of lenses is eight. The first lens, the third lens, the sixth lens, and the eighth lens each have negative optical power; The second lens, the fourth lens, the fifth lens, and the seventh lens each have positive optical power; The telephoto lens satisfies: 1.4 <F#<1.8; Where F# is the aperture number of the telephoto lens; The telephoto lens satisfies: -2 < φ 123 / φ<0; Where, φ 123 φ is the combined optical power of the first lens, the second lens and the third lens, and φ is the optical power of the telephoto lens; The telephoto lens satisfies: 0.6 < φ 4567 / φ<3; Where, φ 4567 The combined optical power of the fourth lens, the fifth lens, the sixth lens, and the seventh lens; The telephoto lens satisfies: V5>70, (V4+V5) / V6>3, (R7-R 11 ) / R 10 <3; Wherein, V4 is the Abbe number of the fourth lens, V5 is the Abbe number of the fifth lens, and V6 is the Abbe number of the sixth lens; R7 is the radius of curvature of the object-side surface of the fourth lens. 10 R is the radius of curvature of the object-side surface of the fifth lens. 11 The radius of curvature of the object-side surface of the sixth lens; The telephoto lens satisfies: (R6+R 13 ) / R 14 <5; Wherein, R6 is the radius of curvature of the image-side surface of the third lens, R 13 R is the radius of curvature of the object-side surface of the seventh lens. 14 The radius of curvature of the image-side surface of the seventh lens; The object-side surface of the first lens is convex along the optical axis, and the image-side surface of the first lens is concave along the optical axis. The object surface of the second lens is convex along the optical axis, and the image surface of the second lens is concave along the optical axis. The object-side and image-side surfaces of the third lens are both concave along the optical axis; The object-side surface and image-side surface of the fourth lens are both convex along the optical axis; The object-side and image-side surfaces of the fifth lens are both convex along the optical axis; The object-side and image-side surfaces of the sixth lens are both concave along the optical axis; The object-side and image-side surfaces of the seventh lens are both convex along the optical axis; The object surface of the eighth lens is concave along the optical axis, and the image surface of the eighth lens is convex along the optical axis.

2. The telephoto lens according to claim 1, characterized in that, Also includes: An aperture stop is disposed between the fourth lens and the fifth lens; The filter element is a visible light filter, which is disposed on the side of the eighth lens facing the imaging surface; or, the filter element is a visible light filter film layer, which is deposited on the object-side surface of the seventh lens.

3. The telephoto lens according to claim 1 or 2, characterized in that, The telephoto lens satisfies: 12 <f<30; Where f is the effective focal length of the telephoto lens.

4. The telephoto lens according to claim 1 or 2, characterized in that, The telephoto lens satisfies the following condition: 20° < 2θ < 50°; Wherein, 2θ is the full field of view of the telephoto lens.

5. The telephoto lens according to claim 1 or 2, characterized in that, The telephoto lens satisfies: RI > 60%; Where RI represents the illuminance of the telephoto lens.

6. The telephoto lens according to claim 1 or 2, characterized in that, The telephoto lens satisfies: 2 <T L / h<5; Among them, T L denoted as the total optical length of the telephoto lens, and h as the image plane height of the telephoto lens.

7. The telephoto lens according to claim 1 or 2, characterized in that, The telephoto lens satisfies: -2 < φ8 / φ < 0; Wherein, φ8 is the optical power of the eighth lens, and φ is the optical power of the telephoto lens.

8. The telephoto lens according to claim 1 or 2, characterized in that, The telephoto lens satisfies: 0.8 <SD1 / h<1.2; Wherein, SD1 is the half-aperture of the first lens, and h is the image plane height of the telephoto lens.

9. The telephoto lens according to claim 1 or 2, characterized in that, The telephoto lens satisfies: R 16 <-20,15 <CRA<25; Among them, R 16 Let CRA be the radius of curvature of the image surface of the eighth lens, and let CRA be the principal ray angle of the telephoto lens.

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