Zoom lens

Abstract

The present invention relates to a zoom lens, comprising a first fixed lens group (G1) with positive focal power, a zoom lens group (G2) with negative focal power, an aperture (STO), a second fixed lens group (G3) with positive focal power, and a focusing lens group (G4) with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis, and also comprising a third fixed lens group (G5) with positive focal power located on the image side of the focusing lens group (G4). The zoom lens of the present invention can be changed by more than 3 times, and the maximum aperture can reach F1.1. A large aperture can be achieved in a small volume, and while infrared confocal imaging, 1X-3X focal length confocality is guaranteed, and the full focal length resolution meets 4K.

Description

Technical Field

[0001] The invention belongs to the technical field of optical imaging, and in particular relates to a zoom lens. Background Art

[0002] With the rapid development of security technology, the requirements for the clarity of surveillance video images are getting higher and higher, which has also led to the gradual occupation of the market by high-resolution cameras. In the existing technology, the resolution of large-aperture zoom lenses at the telephoto end is mostly at a low 2M level, and it cannot take into account infrared imaging, so it cannot meet the increasingly complex work requirements. In addition, the front lens diameter of the existing lens is large, making it difficult to achieve a large aperture while meeting the requirements of miniaturization. Summary of the invention

[0003] An object of the present invention is to provide a zoom lens.

[0004] To achieve the above-mentioned object, the present invention provides a zoom lens, comprising a first fixed lens group with positive focal power, a zoom lens group with negative focal power, an aperture stop, a second fixed lens group with positive focal power and a focusing lens group with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis, and also comprises a third fixed lens group with positive focal power located on the image side of the focusing lens group.

[0005] According to one aspect of the present invention, the zoom lens group is movable along the optical axis to achieve optical zooming of the zoom lens between a wide-angle end and a telephoto end;

[0006] The focusing lens group can move along the optical axis to compensate for changes in the image plane position during optical zooming.

[0007] According to one aspect of the present invention, the focal lengths FG1, FG2 and FG4 of the first fixed lens group, the zoom lens group and the focusing lens group respectively satisfy the following relationship with the wide-angle end focal length FW of the zoom lens: 4.09≤FG1 / FW≤4.33; -1.47≤FG2 / FW≤-1.24; 1.98≤FG4 / FW≤6.70.

[0008] According to one aspect of the present invention, the first fixed lens group includes a first lens having negative optical power, a second lens having positive optical power, and a third lens having positive optical power;

[0009] The first lens and the second lens are cemented together to form a cemented lens group.

[0010] According to one aspect of the present invention, the zoom lens group includes a fourth lens having negative power, a fifth lens having negative power, a sixth lens having negative power, and a seventh lens having positive power.

[0011] According to one aspect of the present invention, the second fixed lens group includes an eighth lens with positive focal power, a ninth lens with positive focal power, a tenth lens with negative focal power, an eleventh lens with positive focal power, a twelfth lens with positive focal power, a thirteenth lens with negative focal power and a fourteenth lens with positive focal power.

[0012] According to one aspect of the present invention, the focusing lens group includes a fifteenth lens having positive power, a sixteenth lens having positive power, and a seventeenth lens having negative power.

[0013] According to one aspect of the present invention, the third fixed lens group includes an eighteenth lens having positive refractive power.

[0014] According to one aspect of the present invention, the Abbe number Ab1 of the first lens and the Abbe number Ab5 of the fifth lens respectively satisfy the following conditions: Ab1≤30; Ab5≥85.

[0015] According to one aspect of the present invention, the Abbe number Ab7 of the seventh lens satisfies the following condition: Ab7≤23.

[0016] According to one aspect of the present invention, the stroke D2 of the zoom lens group and the stroke D4 of the focus lens group satisfy the following relationship: 10≤|D2 / D4|≤21.

[0017] According to one aspect of the present invention, the focal length FG2 of the zoom lens group and the focal length FG4 of the focus lens group satisfy the following relationship: -0.67≤FG2 / FG4≤-0.20.

[0018] According to one aspect of the present invention, the maximum lens diameter of the first fixed lens group The total length TTL of the zoom lens satisfies the following relationship:

[0019] According to the concept of the present invention, a zoom lens is proposed, which can be variable in magnification by more than 3 times and has a maximum aperture of F1.1. It can achieve a large aperture in a small volume and ensure confocality within the focal length of 1X-3X while achieving infrared confocal imaging, and the resolution of the entire focal length meets 4K.

[0020] According to one solution of the present invention, by reasonably setting the relationship between the focal lengths of the first fixed lens group, the zoom lens group and the focus lens group and the focal length of the wide-angle end of the zoom lens, the compatibility of large magnification and small volume can be achieved, ensuring that the resolution of the lens at the full focal length meets 4K.

[0021] According to one solution of the present invention, the first lens and the second lens in the first fixed lens group are cemented to form a cemented lens group, so that chromatic aberration can be corrected.

[0022] According to one solution of the present invention, by reasonably setting the relationship between the Abbe number of the first lens and the Abbe number of the fifth lens, the system chromatic aberration can be effectively corrected and infrared confocality can be achieved.

[0023] According to one solution of the present invention, by properly setting the Abbe number of the seventh lens, the aberration generated during the zooming process can be reduced to achieve a high resolution effect.

[0024] According to one solution of the present invention, by reasonably setting the relationship between the stroke of the zoom lens group and the stroke of the focus lens group, a large aperture can be achieved while meeting the miniaturization requirement.

[0025] According to one solution of the present invention, a large aperture can be maintained during zooming by properly setting the relationship between the focal length of the zoom lens group and the focal length of the focus lens group.

[0026] According to one solution of the present invention, miniaturization can be achieved by reasonably setting the relationship between the maximum lens diameter of the first fixed lens group and the total length of the zoom lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a diagram schematically showing the structure of a zoom lens according to a first embodiment of the present invention;

[0028] Figure 2 is a diagram schematically showing a defocus curve of a zoom lens at a wide-angle end according to a first embodiment of the present invention;

[0029] Figure 3 is a diagram schematically showing a defocus curve of a zoom lens at a telephoto end according to a first embodiment of the present invention;

[0030] Figure 4 is a diagram schematically showing a defocus curve of 850 nm at the wide-angle end of the zoom lens according to the first embodiment of the present invention;

[0031] Figure 5 is a diagram schematically showing the structure of a zoom lens according to a second embodiment of the present invention;

[0032] Figure 6 is a diagram schematically showing a defocus curve of a zoom lens at a wide-angle end according to a second embodiment of the present invention;

[0033] Figure 7 is a diagram schematically showing a defocus curve of a zoom lens at a telephoto end according to a second embodiment of the present invention;

[0034] Figure 8 is a diagram schematically showing a defocus curve of 850 nm at the wide-angle end of a zoom lens according to a second embodiment of the present invention;

[0035] Fig. 9 is a structural diagram schematically showing a zoom lens according to a third embodiment of the present invention;

[0036] Fig.10 is a diagram schematically showing a defocus curve of a zoom lens at a wide-angle end according to a third embodiment of the present invention;

[0037] Fig.11 is a diagram schematically showing a defocus curve of a zoom lens at a telephoto end according to a third embodiment of the present invention;

[0038] Fig.12 FIG. 8 is a diagram schematically showing a defocus curve of a zoom lens at the wide-angle end at 850 nm according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0041] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not therefore limited to the following embodiments.

[0042] See also Figure 1 The large aperture zoom lens of the present invention comprises a first fixed lens group G1 with positive focal power, a zoom lens group G2 with negative focal power, an aperture STO, a second fixed lens group G3 with positive focal power, a focus lens group G4 with positive focal power, and a third fixed lens group G5 with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis. The zoom lens group G2 can move along the optical axis to complete the optical zoom of the zoom lens between the wide-angle end and the telephoto end; the focus lens group G4 can move along the optical axis to compensate for the change of the image plane position during the optical zoom process.

[0043] In the present invention, the focal lengths FG1, FG2 and FG4 of the first fixed lens group G1, the zoom lens group G2 and the focus lens group G4 respectively satisfy the following relationship with the focal length FW of the zoom lens at the wide angle end: 4.09≤FG1 / FW≤4.33; -1.47≤FG2 / FW≤-1.24; 1.98≤FG4 / FW≤6.70. In this way, the compatibility of large magnification and small volume can be achieved, ensuring that the resolution of the lens at the full focal length meets 4K.

[0044] In the present invention, the first fixed lens group G1 includes a first lens L1 with negative power, a second lens L2 with positive power, and a third lens L3 with positive power. The first lens L1 and the second lens L2 are cemented to form a cemented lens group, so that chromatic aberration can be corrected. The zoom lens group G2 includes a fourth lens L4 with negative power, a fifth lens L5 with negative power, a sixth lens L6 with negative power, and a seventh lens L7 with positive power. The second fixed lens group G3 includes an eighth lens L8 with positive power, a ninth lens L9 with positive power, a tenth lens L10 with negative power, an eleventh lens L11 with positive power, a twelfth lens L12 with positive power, a thirteenth lens L13 with negative power, and a fourteenth lens L14 with positive power. The focusing lens group G4 includes a fifteenth lens L15 having positive power, a sixteenth lens L16 having positive power, and a seventeenth lens L17 having negative power. The third fixed lens group G5 includes an eighteenth lens L18 having positive power.

[0045] In the present invention, the Abbe number Ab1 of the first lens L1 and the Abbe number Ab5 of the fifth lens L5 respectively satisfy the following conditions: Ab1≤30; Ab5≥85. In this way, the system chromatic aberration can be effectively corrected and infrared confocality can be achieved. The Abbe number Ab7 of the seventh lens L7 satisfies the following condition: Ab7≤23. In this way, the aberrations generated during the zooming process can be reduced to achieve a high-resolution effect. The stroke D2 of the zoom lens group G2 and the stroke D4 of the focus lens group G4 satisfy the following relationship: 10≤|D2 / D4|≤21. In this way, a large aperture can be achieved while meeting the miniaturization requirements. The focal length FG2 of the zoom lens group G2 and the focal length FG4 of the focus lens group G4 satisfy the following relationship: -0.67≤FG2 / FG4≤-0.20. In this way, a large aperture can be maintained during zooming. The maximum lens diameter of the first fixed lens group G1 The total length TTL of the zoom lens satisfies the following relationship: In this way, miniaturization can be achieved.

[0046] In summary, the present invention adopts a five-group architecture of "positive-negative-positive-positive-positive" and a two-group linkage mode of "one magnification and one focus", and then through the reasonable allocation of group optical focal length, a zoom ratio of more than 3 times can be achieved, which meets the performance requirements of large aperture, small volume and large target surface, and achieves full-focal-length 4K imaging under large aperture conditions. In addition, through reasonable optical focal length distribution and the selection of specific glass materials, chromatic aberration and secondary spectral correction between 380 and 940nm at the telephoto end are achieved, and infrared confocality can be met during the 1X-3X zoom process, and excellent performance can be exerted in multiple scenarios and requirements. The present invention uses a variable aperture, and the maximum aperture can reach F1.1, which can meet the use requirements of various application scenarios. In addition, through reasonable optical focal length distribution, the processing and manufacturability of the components can be adjusted, thereby facilitating manufacturing and assembly.

[0047] The zoom lens of the present invention is described in detail in three embodiments. In the following embodiments, S1, S2, ..., SN are used to represent the surfaces of each optical element, the stop is denoted as STO, and the image plane is denoted as IMA. The plastic aspheric lens satisfies the following formula:

[0048]

[0049] Where z is the axial distance from the surface to the vertex at a height h perpendicular to the optical axis along the optical axis; c represents the curvature at the vertex of the aspheric surface; K is the quadratic constant of the surface, A4, A6, A8, A 10 , A 12 , A 14 and A 16 They are the aspheric coefficients of the fourth, sixth, eighth, tenth, twelfth, fourteenth and sixteenth orders respectively.

[0050] Parameters of various implementations that specifically meet the above conditional formula are shown in Table 1 below:

[0051]

[0052] Table 1

[0053] First Implementation Method

[0054] See also Figure 1 , the parameters of the zoom lens in this embodiment are shown in Table 2 below:

[0055]

[0056]

[0057] Table 2

[0058] The aspheric coefficients of the aspheric lenses in this embodiment are shown in Table 3 below:

[0059]

[0060]

[0061] Table 3

[0062] The zoom data of the zoom lens of this embodiment at the wide-angle end and the telephoto end are shown in Table 4 below:

[0063]

[0064] Table 4

[0065] Combination Figures 2 to 4 The zoom lens of this embodiment uses 18 lenses to achieve a maximum aperture of 1.1, a zoom ratio of more than 3 times, corrects the position chromatic aberration and magnification chromatic aberration between 380 and 940 nm, achieves day and night confocality at a focal length of 1X-3X, meets 4K resolution at full focal length, and achieves a large aperture in a small volume. It is easy to assemble and process, and can be produced efficiently.

[0066] Second implementation method

[0067] See also Figure 5 , the parameters of the zoom lens in this embodiment are shown in Table 5 below:

[0068]

[0069]

[0070] Table 5

[0071] The aspheric coefficients of the aspheric lenses in this embodiment are shown in Table 6 below:

[0072]

[0073]

[0074] Table 6

[0075] The zoom data of the zoom lens of this embodiment at the wide-angle end and the telephoto end are shown in Table 7 below:

[0076]

[0077] Table 7

[0078] Combination Figures 6 to 8 The zoom lens of this embodiment uses 18 lenses, the aperture at the wide-angle end can reach 1.1, the magnification ratio exceeds 3 times, and the position chromatic aberration and magnification chromatic aberration between 380 and 940nm are corrected to achieve 1X-3X focal length day and night parfocality, meet the full 4K resolution, and the lens size is small, which can achieve large aperture optical zoom.

[0079] The third implementation method

[0080] See also Fig. 9 , the parameters of the zoom lens in this embodiment are shown in Table 8 below:

[0081]

[0082]

[0083] Table 8

[0084] The aspheric coefficients of the aspheric lenses in this embodiment are shown in Table 9 below:

[0085]

[0086]

[0087] Table 9

[0088] The zoom data of the zoom lens of this embodiment at the wide-angle end and the telephoto end are shown in Table 10 below:

[0089]

[0090] Table 10

[0091] Combination Figures 10 to 12 The zoom lens of this embodiment uses 18 lenses, the aperture at the wide-angle end can reach 1.1, the magnification ratio exceeds 3 times, and the position chromatic aberration and magnification chromatic aberration between 380 and 940nm are corrected to achieve infrared confocality, meet 1X-3X day and night confocality, full focal length 4K resolution, small lens size, large aperture, and high image quality can still be achieved in low light.

[0092] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A zoom lens, comprising a first fixed lens group (G1) with positive power, a zoom lens group (G2) with negative power, an aperture stop (STO), a second fixed lens group (G3) with positive power, and a focusing lens group (G4) with positive power, which are arranged in sequence from the object side to the image side along the optical axis, wherein: The invention also comprises a third fixed lens group (G5) with positive refractive power located on the image side of the focusing lens group (G4), with a total of five lens groups, wherein the Abbe number Ab1 of the first lens (L1) in the first fixed lens group (G1) and the Abbe number Ab5 of the fifth lens (L5) in the zoom lens group (G2) respectively satisfy the following conditions: Ab1≤30; Ab5≥85; The zoom lens group (G2) includes a fourth lens (L4) with negative optical power, a fifth lens (L5) with negative optical power, a sixth lens (L6) with negative optical power and a seventh lens (L7) with positive optical power, a total of four lenses, and the focusing lens group (G4) includes a fifteenth lens (L15) with positive optical power, a sixteenth lens (L16) with positive optical power and a seventeenth lens (L17) with negative optical power, a total of three lenses.

2. The zoom lens according to claim 1, wherein: The focal lengths FG1, FG2 and FG4 of the first fixed lens group (G1), the zoom lens group (G2) and the focusing lens group (G4) respectively satisfy the following relationship with the wide-angle end focal length FW of the zoom lens: 4.09≤FG1 / FW≤4.33; -1.47≤FG2 / FW≤-1.24; 1.98≤FG4 / FW≤6.

70.

3. The zoom lens according to claim 1, wherein: The first fixed lens group (G1) includes the first lens (L1) with negative optical power, the second lens (L2) with positive optical power and the third lens (L3) with positive optical power, a total of three lenses; The first lens (L1) and the second lens (L2) are cemented together to form a cemented lens group.

4. The zoom lens according to claim 1, wherein: The second fixed lens group (G3) includes an eighth lens (L8) with positive focal power, a ninth lens (L9) with positive focal power, a tenth lens (L10) with negative focal power, an eleventh lens (L11) with positive focal power, a twelfth lens (L12) with positive focal power, a thirteenth lens (L13) with negative focal power and a fourteenth lens (L14) with positive focal power, totaling seven lenses.

5. The zoom lens according to claim 1, wherein: The third fixed lens group (G5) includes an eighteenth lens (L18) with positive refractive power, a total of one lens.

6. The zoom lens according to claim 1, wherein: The Abbe number Ab7 of the seventh lens (L7) satisfies the following condition: Ab7≤23.

7. The zoom lens according to claim 1, wherein: The stroke D2 of the zoom lens group (G2) and the stroke D4 of the focus lens group (G4) satisfy the following relationship: 10≤|D2 / D4|≤21.

8. The zoom lens according to claim 1, wherein: The focal length FG2 of the zoom lens group (G2) and the focal length FG4 of the focus lens group (G4) satisfy the following relationship: -0.67≤FG2 / FG4≤-0.

20.

9. The zoom lens according to claim 1, wherein: The maximum lens diameter of the first fixed lens group (G1) The total length TTL of the zoom lens satisfies the following relationship:

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