Wide-angle zoom lens

Abstract

The invention provides a wide-angle zoom lens, and solves the problem that the cost is increased while the performance of an existing external zoom lens is met. The wide-angle zoom lens comprises a first lens group with positive focal power, a second lens group with negative focal power, a diaphragm, a third lens group with positive focal power and a fourth lens group with positive focal power which are sequentially arranged from an object side to an image side along an optical axis, the third lens group is composed of a sixth lens with positive focal power, a seventh lens with positive focal power and an eighth lens with negative focal power which are sequentially arranged from the object side to the image side, and the seventh lens and the eighth lens are plastic aspheric lenses. According to the invention, the number of used lenses is reduced, and the plastic aspheric lens is reasonably adopted, so that the high-magnification zooming requirement of the lens is met, and the requirements of high resolution and low cost are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of lenses, and in particular to a wide-angle zoom lens. Background Art

[0002] Zoom lenses are increasingly popular in the market due to their continuously variable focal length and field of view within a certain range, adapting to a wide range of application scenarios. In recent years, with the increasing demand for compact cameras, the demand for wide-angle, high-magnification, and high-resolution external zoom lenses has gradually increased. Currently, the majority of zoom lenses on the market are internal zoom lenses, with external zoom lenses being relatively rare. Existing high-magnification external zoom lenses often suffer from high manufacturing costs and complex mechanical structures. There is a critical need to develop a low-cost product that meets the demand for high-magnification zoom and high-resolution performance.

[0003] Chinese patent document CN102540426B discloses a wide-angle zoom lens comprising, in order from the object side to the image side of its optical axis, a first lens group with positive optical power, a second lens group with negative optical power, a third lens group with positive optical power, and a fourth lens group with positive optical power. The third lens group comprises, in order from the object side to the image side, a sixth lens group with positive optical power, a seventh lens group with positive optical power, an eighth lens group with negative optical power, and a ninth lens group with positive optical power. The sixth lens group is aspherical, and the remaining lenses are spherical. This structure has a large number of lenses in the third lens group, and the lenses are primarily made of glass, which makes manufacturing difficult and costly. Summary of the Invention

[0004] The present invention proposes a wide-angle zoom lens, which reduces the number of lenses used and rationally adopts plastic aspherical lenses to meet the requirements of high-magnification zoom lenses and achieve high resolution and low cost, solving the problem that existing external zoom lenses meet performance requirements but increase costs.

[0005] The technical solution of the present invention is achieved as follows: a wide-angle zoom lens comprises a first lens group with positive refractive power, a second lens group with negative refractive power, an aperture stop, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, which are arranged in sequence from the object side to the image side along the optical axis;

[0006] The third lens group consists of a sixth lens with positive refractive power, a seventh lens with positive refractive power, and an eighth lens with negative refractive power, which are arranged in sequence from the object side to the image side. The seventh lens and the eighth lens are both plastic aspherical lenses.

[0007] Furthermore, the third lens group satisfies the conditional formula: 0.9<|f6 / f300|<1.2, 0.9<|f6 / f8|<1.2; wherein f6 is the focal length of the sixth lens, f8 is the focal length of the eighth lens, and f300 is the focal length of the third lens group.

[0008] Furthermore, the third lens group satisfies the conditional formula: |Vd6|>45, |Vd8|<24; wherein Vd6 is the dispersion coefficient of the sixth lens, and Vd8 is the dispersion coefficient of the eighth lens.

[0009] Furthermore, the focal length of the wide-angle zoom lens satisfies the following conditions: 0.5<|f200 / f300|<1, 1.1<|f200 / fw|<1.5, 1.5<|f300 / fw|<2; wherein f200 is the focal length of the second lens group, f300 is the focal length of the third lens group, and fw is the focal length of the close-range end lens (the focal length of the wide-angle zoom lens at wide angles).

[0010] Furthermore, both the object-side surface and the image-side surface of the eighth lens are concave surfaces.

[0011] Furthermore, the aperture is located at the front end of the sixth lens element.

[0012] Furthermore, the second lens group includes a third lens with negative optical power, a fourth lens with negative optical power, and a fifth lens with positive optical power, which are arranged in sequence from the object side to the image side. The fifth lens is a plastic aspherical lens.

[0013] Furthermore, the fifth lens element satisfies the conditional formula: |Vd5|<24, where Vd5 is the dispersion coefficient of the fifth lens element.

[0014] Furthermore, the plastic aspheric surface shape expression satisfies the following equation:

[0015]

[0016] Wherein, X is the depth of the aspheric lens in mm, Y is the distance from the optical axis to the lens surface in mm, C is the radius of curvature of the aspheric lens, C = 1 / R, k is the cone constant, and b, c, d, e, f, g, and h are the coefficients of the aspheric lens.

[0017] Furthermore, the first lens group includes a first lens with negative optical power and a second lens with positive optical power, which are arranged in sequence from the object side to the image side.

[0018] Furthermore, the first lens group satisfies the following conditions: |Vd1|<24, |Vd2|>60, |Nd1|>1.8; wherein Vd1 is the dispersion coefficient of the first lens, Vd2 is the dispersion coefficient of the second lens, and Nd1 is the refractive index of the first lens.

[0019] Furthermore, the fourth lens group includes a ninth lens having positive refractive power, wherein the object-side surface of the ninth lens is convex and the image-side surface is concave.

[0020] Furthermore, the first to fourth lens groups move to realize an external zoom function, and the fourth lens group moves to realize a focusing function.

[0021] Furthermore, the first lens group is formed by cementing a first lens and a second lens.

[0022] Beneficial effects of the present invention:

[0023] The wide-angle zoom lens of the present invention adopts a four-lens group mechanical structure, in which the third lens group uses only three lenses, one less lens than the prior art. In addition, the fifth lens, the seventh lens, and the eighth lens are all plastic aspherical lenses, which are easy to process and low in cost. By rationally distributing the aspherical surfaces in sensitive positions, the design difficulty and manufacturability of the lens are reduced. The other lenses are all glass spherical lenses. The optical architecture combining glass and plastic lenses effectively corrects chromatic aberration, meets the requirements of high-magnification zoom lenses, and achieves high resolution and low cost. The lens is suitable for external zoom photography equipment such as compact cameras.

[0024] The focal lengths of the second and third lens groups in wide-angle zoom lenses significantly influence the overall zoom ratio and group sensitivity of the lens. Excessively large or small focal lengths can result in an inability to achieve the desired zoom ratio or excessive group sensitivity, leading to poor manufacturability. The present invention limits the focal lengths of the lenses to ensure a wide field of view and well-balanced aberrations across focal lengths, achieving both zoom requirements and excellent manufacturability.

[0025] Compared with the previous method of using different aperture holes for different focal lengths, the aperture of the present invention is located at the front end of the sixth lens element, and the same aperture is used for zooming different focal lengths, eliminating the use of a shutter and greatly reducing the cost of the lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 1 is a schematic diagram of the close-up end structure of a zoom lens provided by an embodiment of the present invention;

[0028] Figure 2 Schematic diagram of spherical aberration at the close-range end of a zoom lens according to an embodiment of the present invention;

[0029] Figure 3 2. This is a schematic diagram of astigmatism at the close-range end of a zoom lens according to an embodiment of the present invention;

[0030] Figure 4 2 is a schematic diagram of distortion at the close-range end of a zoom lens according to an embodiment of the present invention;

[0031] Figure 5 Schematic diagram of Rayfan at the close-range end of a zoom lens according to an embodiment of the present invention;

[0032] Figure 6 1 is a schematic diagram of the structure of the telephoto end of a zoom lens provided by an embodiment of the present invention;

[0033] Figure 7 Schematic diagram of spherical aberration at the telephoto end of a zoom lens according to an embodiment of the present invention;

[0034] Figure 8 2 is a schematic diagram of astigmatism at the telephoto end of a zoom lens according to an embodiment of the present invention;

[0035] Figure 9 2 is a schematic diagram of the distortion at the telephoto end of a zoom lens according to an embodiment of the present invention;

[0036] Figure 10 FIG. 1 is a schematic diagram of a Rayfan at the telephoto end of a zoom lens according to an embodiment of the present invention.

[0037] First lens group 100 , second lens group 200 , third lens group 300 , fourth lens group 400 , first lens 1 , second lens 2 , third lens 3 , fourth lens 4 , fifth lens 5 , aperture 6 , sixth lens 7 , seventh lens 8 , eighth lens 9 , ninth lens 10 , filter 11 , image sensor 12 . DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0039] like Figure 1 As shown, a wide-angle zoom lens includes a first lens group with positive focal power, a second lens group with negative focal power, an aperture, a third lens group with positive focal power, and a fourth lens group with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis.

[0040] The first lens group includes a first lens having negative optical power and a second lens having positive optical power, arranged in sequence from the object side to the image side. The first lens group is formed by cementing the first lens and the second lens. The use of cemented lenses in the first lens group facilitates chromatic aberration correction at the wide-angle and telephoto ends of the zoom lens, achieving a reasonable balance of chromatic aberration throughout the zoom range, and improving the performance of the zoom lens of the present invention.

[0041] The second lens group includes a third lens with negative optical power, a fourth lens with negative optical power, and a fifth lens with positive optical power, which are arranged in sequence from the object side to the image side; the fifth lens is a plastic aspherical lens.

[0042] The third lens group consists of a sixth lens with positive refractive power, a seventh lens with positive refractive power, and an eighth lens with negative refractive power, arranged in sequence from the object side to the image side. The seventh and eighth lenses are both plastic aspherical lenses, and the object-side and image-side surfaces of the eighth lens are both concave.

[0043] The fourth lens group includes a ninth lens having positive optical power. The object-side surface of the ninth lens is convex, and the image-side surface is concave.

[0044] A filter and an image sensor are sequentially arranged on the image side of the fourth lens.

[0045] The fifth, seventh, and eighth lenses are all plastic aspherical lenses; by strategically placing aspherical surfaces in sensitive locations, the lens design and manufacturing complexity are reduced. The first, second, third, fourth, sixth, and ninth lenses are all glass spherical lenses. This strategic combination of glass spherical lenses and plastic aspherical surfaces fully utilizes the powerful aberration correction capabilities of aspherical lenses, improving the zoom lens's sharp imaging and resolution while maintaining a low cost.

[0046] The diaphragm is located at the front end of the sixth lens. The invention uses the same aperture for different focal lengths of the zoom lens, eliminating the use of a shutter. Compared with the early use of different aperture holes for different focal lengths, this greatly reduces the cost of the lens.

[0047] The first to fourth lens groups move to realize the external zoom function, and the fourth lens group moves to realize the focusing function.

[0048] The focal length of the wide-angle zoom lens satisfies the following conditions: 0.5<|f200 / f300|<1, 1.1<|f200 / fw|<1.5, 1.5<|f300 / fw|<2; wherein f200 is the focal length of the second lens group, f300 is the focal length of the third lens group, and fw is the focal length of the close-range lens (the focal length of the wide-angle zoom lens at wide angles).

[0049] The third lens group satisfies the following conditions: 0.9<|f6 / f300|<1.2, 0.9<|f6 / f8|<1.2; wherein f6 is the focal length of the sixth lens, f8 is the focal length of the eighth lens, and f300 is the focal length of the third lens group.

[0050] In this invention, the focal lengths of the second and third lens groups significantly influence the overall zoom ratio and group sensitivity of the lens. Excessively large or small focal lengths can result in an unattainable zoom ratio or excessive group sensitivity, leading to poor manufacturability. The above-described lens focal length configuration ensures a wide field of view for the zoom lens of this invention and effectively balances aberrations across focal lengths, achieving desired zoom ratios while ensuring excellent manufacturability.

[0051] In this embodiment, |f200 / f300|=0.78, |f200 / fw|=1.3, |f300 / fw|=1.66, |f6 / f300|=1.02, |f6 / f8|=1.02.

[0052] The first lens group satisfies the following conditions: |Vd1|<24, |Vd2|>60, |Nd1|>1.8; wherein Vd1 is the Abbe number of the first lens, Vd2 is the Abbe number of the second lens, and Nd1 is the refractive index of the first lens.

[0053] The fifth lens of the second lens group satisfies the conditional formula: |Vd5|<24, where Vd5 is the Abbe number of the fifth lens.

[0054] The third lens group satisfies the following conditions: |Vd6|>45, |Vd8|<24; wherein Vd6 is the Abbe number of the sixth lens element, and Vd8 is the Abbe number of the eighth lens element.

[0055] A lens that meets the above restrictions can effectively correct the chromatic aberration of the lens.

[0056] In this embodiment, Vd1 = 23.8, Vd2 = 60.4, Vd5 = 20.4, Vd6 = 49.6, Vd8 = 20.4, and Nd1 = 1.85.

[0057] Specifically, the basic lens data of this embodiment is shown in Table 1:

[0058] Table 1: Basic lens data

[0059]

[0060] In the above table, surface R1 is the surface of the lens close to the object side (abbreviated as "object side surface"), surface R2 is the surface of the lens close to the image side (abbreviated as "image side surface"), the radius of curvature R represents the curvature radius value of the corresponding surface, and the unit is mm. The surface spacing D represents the lens thickness of the corresponding surface or the spacing value between the lenses, and the unit is mm. The above table also gives the refractive index Nd and Abbe constant Vd (Vd is also called the dispersion coefficient) of the lens with respect to d light (wavelength of 587.6nm).

[0061] In this embodiment, the fifth lens, the seventh lens, and the eighth lens are all plastic aspheric lenses. The coefficients of the aspheric lenses are based on the center of the lens surface as the origin and the optical axis as the x-axis. The aspheric surface shape of the lens surface satisfies the following formula:

[0062]

[0063] Among them, X is the depth of the aspheric lens, in mm, Y is the distance from the optical axis to the lens surface, in mm, C is the radius of curvature of the aspheric lens, C = 1 / R, k is the cone constant, b, c, d, e, f, g, h are the coefficients of the aspheric lens, and the specific parameters of the coefficients are shown in Table 2:

[0064] Table 2:

[0065]

[0066] Specifically, the optical system parameters of this embodiment are shown in Table 3:

[0067] Table 3 Optical system parameters

[0068]

[0069] In the above table, the unit of paraxial focal length f is mm, the ω in the angle of view 2ω represents the half angle of view, and the unit of optical total length TTL is mm

[0070] like Figure 1 As shown, the near-focus section structure of the zoom lens of this embodiment was tested and the phase difference diagram was recorded. Figure 2-Figure 5 They are the spherical aberration diagram, astigmatism diagram, distortion diagram and Rayfan diagram at the near focus end.

[0071] like Figure 5 As shown, the telephoto structure of the zoom lens of this embodiment was tested and the aberration diagrams were recorded. Figure 6-Figure 9 They are the spherical aberration diagram, astigmatism diagram, distortion diagram and Rayfan diagram at the telephoto end.

[0072] From Table 3 and Appendix Figure 2-9 It can be seen that various aberrations of the zoom lens of this embodiment are well corrected, and the zoom lens can be applied to external zoom photography equipment such as compact cameras.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A wide-angle zoom lens comprising, arranged in order from the object side to the image side along the optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, an aperture stop, a third lens group having positive refractive power, and a fourth lens group having positive refractive power; characterized in that: The third lens group consists of a sixth lens with positive refractive power, a seventh lens with positive refractive power, and an eighth lens with negative refractive power, which are arranged in sequence from the object side to the image side. The seventh lens and the eighth lens are both plastic aspherical lenses.

2. The wide-angle zoom lens according to claim 1, wherein: The third lens group satisfies the following conditions: 0.9<|f6 / f300|<1.2, 0.9<|f6 / f8|<1.2; wherein f6 is the focal length of the sixth lens, f8 is the focal length of the eighth lens, and f300 is the focal length of the third lens group.

3. The wide-angle zoom lens according to claim 1 or 2, characterized in that: The third lens group satisfies the following conditions: |Vd6|>45, |Vd8|<24; wherein Vd6 is the Abbe number of the sixth lens element, and Vd8 is the Abbe number of the eighth lens element.

4. The wide-angle zoom lens according to claim 1 or 2, characterized in that: The focal length of the wide-angle zoom lens satisfies the following conditions: 0.5<|f200 / f300|<1, 1.1<|f200 / fw|<1.5, 1.5<|f300 / fw|<2; wherein f200 is the focal length of the second lens group, f300 is the focal length of the third lens group, and fw is the focal length of the wide-angle zoom lens at wide angles.

5. The wide-angle zoom lens according to claim 1 or 2, characterized in that: The object side and image side surfaces of the eighth lens are both concave, and the aperture is located at the front end of the sixth lens.

6. The wide-angle zoom lens according to claim 1, wherein: The second lens group includes a third lens with negative optical power, a fourth lens with negative optical power, and a fifth lens with positive optical power, which are arranged in sequence from the object side to the image side. The fifth lens is a plastic aspherical lens.

7. The wide-angle zoom lens according to claim 6, wherein: The fifth lens element satisfies the conditional formula: |Vd5|<24, where Vd5 is the dispersion coefficient of the fifth lens element.

8. The wide-angle zoom lens according to claim 1, wherein: The first lens group includes a first lens having negative optical power and a second lens having positive optical power, arranged in sequence from the object side to the image side; the first lens group satisfies the following conditions: |Vd1|<24, |Vd2|>60, |Nd1|>1.8; wherein Vd1 is the chromatic aberration coefficient of the first lens, Vd2 is the chromatic aberration coefficient of the second lens, and Nd1 is the refractive index of the first lens.

9. The wide-angle zoom lens according to claim 1, wherein: The fourth lens group includes a ninth lens having positive refractive power. The object-side surface of the ninth lens is convex, and the image-side surface is concave.

10. The wide-angle zoom lens according to claim 1 or 8, characterized in that: The first to fourth lens groups move to realize the external zoom function, and the fourth lens group moves to realize the focusing function; the first lens group is formed by gluing the first lens and the second lens.

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