A telephoto lens

Abstract

The application discloses a telephoto lens, belonging to the technical field of lenses, comprising a first lens group with positive refractive power, a second lens group with positive refractive power, and an aperture between the first lens group and the second lens group, and the second lens group is moved on the optical axis to focus. The above-mentioned front group is essentially composed of three lens components, the first lens component is a positive lens arranged in sequence from the object side along the optical axis, with a convex surface facing the object side, the second lens component is composed of at least one lens, with positive refractive power, and the third lens component is a negative lens with a concave surface facing the image side; and the second lens and the third lens are glued together. The rear group comprises: a fourth lens component, which is a double-concave negative lens arranged in sequence from the object side along the optical axis; and a fifth lens component. The telephoto lens is designed by adopting eleven spherical glass lenses, so that the cost is greatly reduced and miniaturization is realized.

Description

Technical Field

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

[0002] With the continuous development of interchangeable cameras, still cameras and digital camcorders have been widely used and are increasingly moving towards higher pixel counts, which requires imaging lenses to develop higher performance. As a result, large-aperture zoom lenses with focused focal lengths are also constantly increasing. Telephoto lenses with a field of view between 20° and 30° are usually called standard portrait lenses. Telephoto portrait lenses with large apertures are better able to highlight people and objects.

[0003] Existing large-aperture telephoto standard portrait lenses generally employ a double Gaussian structure. However, due to its symmetry, it is difficult to miniaturize and lighten the size while maintaining optical performance. Current large-aperture standard portrait lenses generally use aspherical lenses, which are costly. The double Gaussian structure of standard portrait lenses results in a large spherical aberration due to its high angle of incidence, which is particularly noticeable at large apertures. When shooting video, a "breathing effect" is prone to occur, causing changes in the angle of view when focusing continuously at different distances. Summary of the Invention

[0004] The purpose of this invention is to address the problems in the existing technology where current large-aperture standard portrait lenses generally use aspherical lenses, which are costly. Standard portrait lenses generally adopt a double Gaussian structure, which results in large spherical aberration due to its high angle of incidence, especially noticeable at large apertures. When shooting video, this easily leads to a "breathing effect," causing changes in the field of view when focusing continuously at different distances. Therefore, this invention proposes a telephoto lens.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A telephoto lens includes a first lens group with positive refractive power and a second lens group with positive refractive power arranged sequentially from the object side to the image side, with the aperture located between the first lens group and the second lens group, so that the second lens group can be moved on the optical axis to perform focusing.

[0007] The aforementioned front group is essentially composed of three lens components. The first lens component is a positive lens arranged sequentially along the optical axis from the object side with its convex surface facing the object side. The second lens component is composed of at least one lens and has positive refractive power. The third lens component is a negative lens with its concave surface facing the image side. Furthermore, the second and third lenses are cemented together.

[0008] The rear group includes: a fourth lens component, which is a biconcave negative lens arranged in sequence from the object side along the optical axis; a fifth lens component, which is a biconvex positive lens; a sixth lens component, which is a biconcave negative lens; a seventh lens component, which is a biconvex positive lens component; an eighth lens, which is a biconvex lens; a ninth lens, which is a concave lens component with a convex surface facing the image side; a tenth lens, which is a biconcave negative lens component; an eleventh lens, which is a biconvex positive lens component.

[0009] As a further technical solution, the first lens group includes a cemented lens group, and the cemented lens group is a combination of a positive lens and a negative lens. The positive lens satisfies the following conditional formula:

[0010] 70≤Vd≤95.

[0011] As a further technical solution, the telephoto lens satisfies the following conditional formula:

[0012] 0.28<D / f<0.45;

[0013] Where, D: the air spacing between the front group and the rear group in the infinity focus state, f: the focal length of the telephoto lens in the infinity focus state.

[0014] As a further technical solution, the telephoto lens satisfies the following conditional formula:

[0015] 0.18<Ds / fR<0.33;

[0016] Where, Ds: the distance from the image-side lens surface of the seventh lens to the object-side lens surface of the eleventh lens, fR: the focal length of the rear group.

[0017] As a further technical solution, the lens satisfies the following conditional formula:

[0018] 0.35<dL8 / Ds<0.67;

[0019] Where, dL8: the central thickness of the eighth lens component, Ds: the distance from the image-side lens surface of the seventh lens element to the object-side lens surface of the eleventh lens element.

[0020] When focusing from an infinite object to a finite-distance object, the aperture is fixed.

[0021] As a further technical solution, it satisfies the following conditional formula: 0.70<fR / f<1.00, where, fR: the focal length of the rear group, f: the focal length of the telephoto lens in the infinity focus state.

[0022] In summary, the technical effects and advantages of this invention are as follows: This telephoto lens discloses an optical system composed of two lens groups, arranged from the object side to the image side. It consists of a first lens group with positive refractive power and a second lens group with positive refractive power. The first lens group has an L1 lens with positive refractive power and a convex surface towards the object side. The second lens group is composed of a rear group of lenses with positive refractive power. When focusing from an infinity object towards a close-range object, the second lens group moves to compensate. The moving group moves towards the object side, and when predetermined conditions are met, various aberrations and distortions are effectively corrected, resulting in excellent image quality for the entire image. This provides a compact optical system with high image quality.

[0023] The relative illumination of the optical lens of this invention is about 10-15% higher than that of a standard lens. A standard lens has a relative illumination of about 25%-30%, while this optical lens has a relative illumination as high as 40%, making it particularly suitable for applications where shading correction is not possible, such as recording dynamic footage. The optical lens of this invention is designed as a portrait lens, with a field of view of 14.03° to 14.46°. The change in viewing angle from infinity to the shortest shooting distance is very small. The optical distortion of this invention is extremely low, less than 1.0%.

[0024] In addition, the present invention uses eleven spherical glass lenses in its design, which greatly reduces costs and enables miniaturization. Attached Figure Description

[0025] Figure 1 A schematic diagram of the imaging lens of Embodiment 1 of the present invention is shown;

[0026] Figure 2 The diagram shows the spherical aberration, astigmatism, and distortion of the imaging lens provided in Embodiment 1 of the present invention at infinity (INF).

[0027] Figure 3 The diagram shows the spherical aberration, astigmatism, and distortion of the imaging lens provided in Embodiment 1 of the present invention at close range;

[0028] Figure 4 The diagram shows the aberration sector at infinity (INF) of the imaging lens provided in Embodiment 1 of the present invention.

[0029] In the diagram: 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. Ninth lens; 10. Tenth lens; 11. Eleventh lens. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0031] Reference Figure 1 A telephoto lens includes a first lens group with positive refractive power and a second lens group with positive refractive power arranged sequentially from the object side to the image side, with the aperture located between the first lens group and the second lens group, so that the second lens group can be moved on the optical axis to focus.

[0032] The aforementioned front group is essentially composed of three lens components. The first lens component 1 is a positive lens arranged sequentially along the optical axis from the object side with its convex surface facing the object side. The second lens component 2 is composed of at least one lens and has positive refractive power. The third lens component 3 is a negative lens with its concave surface facing the image side. Furthermore, the second lens 2 and the third lens 3 are cemented together.

[0033] The rear group includes: a fourth lens component 4, which is a biconcave negative lens arranged sequentially along the optical axis from the object side; a fifth lens component 5, which is a biconvex positive lens; a sixth lens component 6, which is a biconcave negative lens; a seventh lens component 7, which is a biconvex positive lens; an eighth lens 8, which is a biconvex lens; a ninth lens 9, which is a concave lens with its convex surface facing the image side; a tenth lens 10, which is a biconcave negative lens; and an eleventh lens 11, which is a biconvex positive lens.

[0034] The first lens group 1 includes a cemented lens group, which consists of a combination of positive and negative lenses. The positive lens satisfies the following condition:

[0035] 70≤Vd≤95.

[0036] Telephoto lenses meet the following conditions:

[0037] 0.28 <D / f<0.45;

[0038] Where D: the air gap between the front and rear elements when focusing at infinity, and f: the focal length of the telephoto lens when focusing at infinity.

[0039] Telephoto lenses meet the following conditions:

[0040] 0.18 <Ds / fR<0.33;

[0041] Where Ds is the distance from the image-side lens surface of the seventh lens 7 to the object-side lens surface of the eleventh lens 11, and fR is the focal length of the rear group.

[0042] It meets the following conditional lens requirements:

[0043] 0.35 < dL8 / Ds < 0.67;

[0044] Where, dL8: The central thickness of the eighth lens 8 component, Ds: The distance from the image-side lens surface of the seventh lens element to the object-side lens surface of the eleventh lens 11 element.

[0045] When focusing from an infinite-distance object to a finite-distance object, the aperture is fixed.

[0046] It satisfies the following conditional formula: 0.70 < fR / f < 1.00, where, fR: The focal length of the rear group, F: The focal length of the telephoto lens in the infinite-focus state.

[0047] Example 1

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[0050]

[0051] Variable interval data

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[0054] Example 2

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[0059] Variable interval data

[0060]

[0061] As described above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A telephoto lens, characterized in that, It includes a first lens group with positive refractive power and a second lens group with positive refractive power arranged successively from the object side to the image side, and the aperture is located between the first lens (1) group and the second lens (2) group, and the second lens (2) group is moved on the optical axis for focusing; The front group is substantially composed of three lens components. The first lens (1) component is a positive lens arranged successively from the object side along the optical axis with its convex surface facing the object side. The second lens (2) component is composed of at least one lens and has positive refractive power. The third lens (3) component is a negative lens with its concave surface facing the image side; and the second lens (2) and the third lens (3) are cemented together; The rear group includes: a fourth lens (4) component, which is a negative lens with double concave arranged successively from the object side along the optical axis; a fifth lens (5) component, which is a positive lens with double convex; a sixth lens (6) component, which is a negative lens with double concave; a seventh lens (7) component, which is a positive lens component with double convex; an eighth lens (8) is a double convex lens, a ninth lens (9) is a concave lens component with its convex surface facing the image side; a tenth lens (10) is a negative lens component with double concave; an eleventh lens (11) is a positive lens component with double convex; In the above telephoto lens, the optical elements with optical power are only the above eleven lenses.

2. A telephoto lens according to claim 1, characterized in that, The first lens (1) group includes a cemented lens group, which is a combination of a positive lens and a negative lens, and the positive lens satisfies the following conditional formula: 70 ≤ Vd ≤ 95.

3. A telephoto lens according to claim 1, characterized in that, The telephoto lens satisfies the following conditional formula: 0.28 <D / f <0.45; Where, D: the air spacing between the front group and the rear group in the infinite focus state, f: the focal length of the telephoto lens in the infinite focus state.

4. A telephoto lens according to claim 1 or 2, characterized in that, The telephoto lens satisfies the following conditional formula: 0.18 <Ds / fR <0.33; Where, Ds: the distance from the image-side lens surface of the seventh lens (7) to the object-side lens surface of the eleventh lens (11), fR: the focal length of the rear group.

5. A telephoto lens according to any one of claims 1-3, characterized in that, Its lens satisfies the following conditional formula: The telephoto lens satisfies the following conditional formula: 0.35 <dL8 / Ds <0.67; Where, dL8: the central thickness of the eighth lens (8) component, Ds: the distance from the image-side lens surface of the seventh lens element to the object-side lens surface of the eleventh lens (11) element; 6. A telephoto lens according to any one of claims 4, characterized in that, When focusing from an infinite object to a finite distance object, the aperture is fixed. Satisfies the following conditional formula: 0.70 <fR / f <1.00, where, fR: the focal length of the rear group, F: the focal length of the telephoto lens in the infinite focus state.

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