GB2573928A

GB2573928A - Two-group-type zoom lens and usage method therefor, and imaging apparatus comprising same

Info

Publication number: GB2573928A
Application number: GB1911608.6A
Authority: GB
Inventors: Yang Hersem; Lin Jiamin; Wang Eric; Lin Zheng
Original assignee: Azure Photonics Co Ltd
Current assignee: Azure Photonics Co Ltd
Priority date: 2017-07-31
Filing date: 2018-07-27
Publication date: 2019-11-20
Anticipated expiration: 2038-07-27
Also published as: GB201911608D0; CN107247323B; GB2573928B; DE112018000720B4; DE112018000720T5; WO2019024798A1; CN107247323A

Abstract

Disclosed is a two-group-type zoom lens, comprising: a first lens group (G1) having negative focal power, an aperture diaphragm (S) and a second lens group (G2) having positive focal power, these being sequentially and coaxially arranged from an object side to an image side. The first lens group (G1) comprises a first meniscus lens (L11) having negative focal power, a first biconcave lens (L12) having negative focal power and a first biconvex lens (L13) having positive focal power, these being sequentially and coaxially arranged from the object side to the image side. The second lens group (G2) comprises a second biconvex lens (L21) having positive focal power, a second meniscus lens (L22) having positive focal power, a second biconcave lens (L23) having negative focal power, a third biconvex lens (L24) having positive focal power, a third meniscus lens (L25) having negative focal power, a fourth meniscus lens (L26) having negative focal power and a fourth biconvex lens (L27) having positive focal power, these being sequentially and coaxially arranged from the object side to the image side.

Description

Specification

Zoom Lens Provided with Two Lens Groups, Method for Using Same, and Imaging Device Comprising Same

Technical Field [0001] The invention relates to the field of optical imaging, in particular to a zoom lens provided with two lens groups, a method for using the zoom lens, and an imaging device comprising the zoom lens.

Description of Related Art [0002] Machine vision lenses are developing towards fewer lenses, lower cost, compacter structure, smaller size, and higher imaging quality. Under the condition where no aspherical lens is used, camera lenses constituted by a few lenses are poor in imaging quality, while high-power lens groups generally cannot meet the requirement for a small size. At present, most zoom lenses in the art adopt two or three lens groups each including four lenses to realize zooming, thereby being complex in structure and high in cost.

Brief Summary of the Invention

Technical Issue [0003] The technical issue to be settled by the invention is to provide a zoom lens which is provided with two lens groups and is simple in structure and low in cost.

Solution to the Issue

Technical Solution [0004] The technical solution adopted by the invention to settle the above technical issue is as follows: [0005] A zoom lens provided with two lens groups comprises a first lens group having a negative power, an aperture stop, and a second lens group having a positive power, wherein the first lens group, the aperture stop, and the second lens group are coaxially arranged in sequence from an object side to an image side; the first lens group comprises a first crescent lens having a negative power, a first biconcave lens having a negative power, and a first biconvex lens having a positive power, and the first crescent lens, the first biconcave lens and the first biconvex lens are coaxially arranged in sequence from the object side to the image side; the second lens group comprises a second biconvex lens having a positive power, a second crescent lens having a positive power, a second biconcave lens having a negative power, a third biconvex lens having a positive power, a third crescent lens having a negative power, a fourth crescent lens having a negative power, and a fourth biconvex lens having a positive power, and the second biconvex lens, the second crescent lens, the second biconcave lens, the third biconvex lens, the third crescent lens, the fourth crescent lens and the fourth biconvex lens are coaxially arranged in sequence from the object side to the image side.

[0006] Optionally, the third biconvex lens and the third crescent lens are combined to form a first cemented lens having a positive power, and the fourth crescent lens and the fourth biconvex lens are combined to form a second cemented lens having a positive power.

[0007] Optionally, the zoom lens meets the following condition: 1,2<|fGI|/fG2<2.0, wherein “fGI” refers to the focal length of the first lens group, and “fG2” refers to the focal length of the second lens group.

[0008] Optionally, the zoom lens meets the following condition: 1,8<|fGI|/ft<2.6, 0.9<fG2/ft<1.8, wherein “ft” refers to the focal length of the zoom lens at a telephoto position.

[0009] Optionally, the zoom lens meets the following condition:

[0010] 2.4<fs/fG2<3.2, wherein “fs” refers to the effective focal length of the lenses L21-L23 of the second lens group G2.

[0011] Optionally, the aperture stop of the zoom lens is arranged between the first lens group and the second lens group and is kept stationary.

[0012] The invention further relates to a method for using the zoom lens provided with two lens groups. According to the method, the first lens group is moved towards the object side, and the second lens group is moved towards the image side to realize zooming.

[0013] The invention further relates to an imaging device which comprises the zoom lens mentioned above.

Beneficial Effects of the Invention

Beneficial Effects [0014] The invention has the following beneficial effects: two lens groups are used to realize zooming, so that the complex structure is greatly simplified while good imaging quality is ensured; all the lenses are made from spherical glass, so that the imaging quality is good; and the size is small, and the structure is compact.

Brief Description of the Drawings

Brief Description of the Several Views of the Drawings [0015] FIG. 1 is a structural diagram of a zoom lens provided with two lens groups in one embodiment of the invention;

[0016] FIG. 2 is a structural diagram of the zoom lens provided with two lens groups in a wide-angle state in the embodiment of the invention;

[0017] FIG. 3 is a structural diagram of the zoom lens provided with two lens groups in the middle in the embodiment of the invention;

[0018] FIG. 4 is a structural diagram of the zoom lens provided with two lens groups in a telephoto state in the embodiment of the invention;

[0019] FIG. 5 is a longitudinal spherical aberration curve chart of the zoom lens provided with two lens groups in the wide-angle state in one embodiment of the invention;

[0020] FIG. 6 is a longitudinal spherical aberration curve chart of the zoom lens provided with two lens groups in the middle in one embodiment of the invention;

[0021] FIG. 7 is a longitudinal spherical aberration curve chart of the zoom lens provided with two lens groups in the telephoto state in one embodiment of the invention;

[0022] FIG. 8 is an MTF diagram of the zoom lens provided with two lens groups in the wide-angle state in one embodiment of the invention;

[0023] FIG. 9 is an MTF diagram of the zoom lens provided with two lens groups in the middle in one embodiment of the invention;

[0024] FIG. 10 is an MTF diagram of the zoom lens provided with two lens groups in the telephoto state in one embodiment of the invention;

[0025] Reference Signs:

[0026] G1, first lens group; G2, second lens group; L11, first crescent lens; L12, first biconcave lens; L13, first biconvex lens; L21, second biconvex lens; L22, second crescent lens; L23, second biconcave lens; L24, third biconvex lens; L25, third crescent lens;

[0027] L26, fourth crescent lens; L27, fourth biconvex lens; S, aperture stop; H, sheet glass.

Embodiments

Detailed Description of the Invention [0028] The technical contents, objectives and effects of the invention are expounded below with reference to the embodiments and accompanying drawings.

[0029] As shown in FIG. 1, the zoom lens in this embodiment comprises a first lens group G1 having a negative power and a second lens group G2 having a positive power, wherein the first lens group G1 and the second lens group G2 are coaxially arranged in sequence from an object side to an image side along an axial incident light from left to right. When the zoom lens is used, the first lens group G1 is moved towards the object side, and the second lens group G2 is moved towards the image side to realize zooming of the zoom lens. FIG. 2 is a structural diagram of the zoom lens provided with two lens groups in a wide-angle state in this embodiment of the invention, FIG. 3 is a structural diagram of the zoom lens provided with two lens groups in the middle in this embodiment of the invention, and FIG. 4 is a structural diagram of the zoom lens provided with two lens groups in a telephoto state in this embodiment of the invention.

[0030] As shown in FIG. 1, the zoom lens provided with two lens groups in this embodiment adopts two dynamically-zooming transmission-type structures: the first lens group G1 having a negative power, an aperture stop S and the second lens group G2 having a positive power are coaxially arranged in sequence from the object side to the image side. The first lens group G1 having a negative power comprises a first crescent lens L11 having a negative power, a first biconcave lens L12 having a negative power, and a first biconvex lens L13 having a positive power, wherein the first crescent lens L11, the first biconcave lens L12, and the first biconvex lens L13 are coaxially arranged in sequence from the object side to the image side. The second lens group G2 having a positive power comprises a second biconvex lens L21 having a positive power, a second crescent lens L22 having a positive power, a second biconcave lens L23 having a negative power, a third biconvex lens L24 having a positive power, a third crescent lens L25 having a negative power, a fourth crescent lens L26 having a negative power, and a fourth biconvex lens L27 having a positive power, wherein the second biconvex lens L21, the second crescent lens L22, the second biconcave lens L23, the third biconvex lens L24, the third crescent lens L25, the fourth crescent lens L26, and the fourth biconvex lens L27 are coaxially arranged in sequence from the object side to the image side.

[0031] Furthermore, the third biconvex lens L24 and the third crescent lens L25 are combined to form a cemented lens having a positive power, and the fourth crescent lens L26 and the fourth biconvex lens L27 are combined to form a cemented lens having a positive power.

[0032] Furthermore, the zoom lens meets the following condition: 1,2<|fGI|/fG2<2.0, wherein “fGI” refers to the focal length of the first lens group, and “fG2” refers to the focal length of the second lens group.

[0033] Furthermore, the zoom lens meets the following condition: 1,8<|fG1 |/ft<2.6, 0.9<fG2/ft<1.8, wherein “ft” refers to the focal length of the zoom lens at a telephoto position.

[0034] Furthermore, the zoom lens meets the following condition: 2.4<fs/fG2<3.2, wherein “fs” refers to the effective focal length of the lenses L21-L23 of the second lens group G2.

[0035] Furthermore, the aperture stop of the zoom lens is arranged between the first lens group G1 and the second lens group G2 and is kept stationary.

[0036] In this solution, two lens groups are used to realize zooming, so that the complex structure is greatly simplified while a good imaging quality is ensured; all the lenses are made from spherical glass, so that the imaging quality is good; and the size is small, and the structure is compact.

[0037] Table 1 lists the detailed parameters of a specific example of the zoom lens of the invention, such as the radius of curvature, thickness, refractive index and dispersion coefficient of the lenses. Wherein, the surface numbers of the lenses are sequentially scheduled from the object side to the image side. For instance, “S1” refers to the surface, towards the object side, of the first lens L11; “S2” refers to the surface, towards the image side, of the first lens L11; “S” refers to the surface of the aperture stop, “S20” refers to the surface, towards the object side, of the sheet glass H, and “S21” refers to the surface, towards the image side, of the sheet glass H.

[0038] Table 1

[]

[] [Table 1]

Lens number	Surface number	Radius of curvature (mm)	Thickness or distance (mm)	Refractive index	Dispersion coefficient
L11	S1	26.675	1.51	1.95	18
	S2	10.678	1.87
L12	S3	-25.352	1.05	1.76	52.3
	S4	25.352	1.52
L13	S5	23.908	2.36	1.85	23.8
	S6	-36.478	D1
S	S7	oo	D2

L21	S8	45.699	1.67	1.88	40.1
	S9	-27.63	0.1
L22	S10	10.987	1.69	1.88	40.1
	S11	24.061	0.88
L23	S12	-35.542	1	1.73	28.3
	S13	8.882	5.69
L24	S14	39.754	3.47	1.9	37.4
	S15	-7.874	1.05	1.75	35
L25	S16	-28.533	0.1
	S17	17.917	1.05	1.85	23.8
L26	S18	7.162	3.15	1.5	81.6
L27	S19	-68.312	D3
H	S20	oo	1.6	1.52	64.1
	S21	co

[0039] Wherein, the thicknesses or distances “D1 ”, “D2” and “D3” respectively refer to the distance between the two surfaces at the wide end, in the middle, and at the tele end, and are shown in

Table 2.

[0040] Table 2

[] [Table 2]

Thickness	Wide end (mm)	Middle (mm)	Tele end (mm)
D1	17.26	8.41	2.83
D2	3.99	2.83	1.67
D3	9	10.16	11.32

[0041 ] The focal length f, aperture value FNO, half angle view ω, and image height Y of the zoom lens at the wide end, in the middle, and at the tele end in this embodiment of the invention are shown in Table 3.

[0042] Table 3

[] [Table 3]

Parameter	Wide end	Middle	Tele end
F (mm)	8.0	10	12.0
FNO	2.48	2.57	2.69
ω (°)	20.727	19.295	16.355
Y (mm)	7.01	7.02	7.02

[0043] Wavelength data of the zoom lens in this embodiment of the invention are shown in Table 4.

[0044] Table 4

[]

[] [Table 4]

Parameter	Wavelength (nm)
1	436
2	486
3	546
4	588
5	656

[0045] Clearly, the lenses of the zoom lens in this embodiment of the invention can also have other parameters other than those ones listed in the above tables.

[0046] FIGs. 5-7 are longitudinal spherical aberration curve charts of the zoom lens at the wide end, in the middle and at the tele end in one embodiment of the invention. In these figures, A, B, C, D, and E respectively represent test curves under the wavelengths of 436nm, 486nm, 546nm, 588nm, and 656nm.

[0047] As shown in the figures, the longitudinal spherical aberrations of the lens at the wide end, in the middle, and at the tele end under a light beam with a wavelength of 436nm and 656nm are all controlled within 0.004mm.

[0048] In addition, experiments shown that when the zoom lens in this embodiment is at the wide end, the tangent field curvature and the arc vector field curvature of the light beam with the wavelength of 546nm are controlled within (-0.027mm, 0.003mm), and the aberration rate is controlled within (-4.1%, 0%); when the zoom lens is in the middle, the tangent field curvature and the arc vector field curvature of the light beam with the wavelength of 546nm are controlled within (-0.025mm, 0.008mm), and the aberration rate is controlled within (-2.5%, 0%); and when the zoom lens in at the tele end, the tangent field curvature and the arc vector field curvature of the light beam with the wavelength of 546nm are controlled within (-0.020mm, 0.022mm), and the aberration rate is controlled within (-1.6%, 0%).

[0049] In addition, FIGs. 8-10 show MTF (modulation transfer function) test curves of the zoom lens at the wide end, in the middle, and at the tele end in this embodiment. As can be seen from the figures, when the zoom lens in this embodiment is at the wide end, in the middle, and at the tele end, the MTF in a 0.8 view field at 215 Ip/mm is greater than 0.3.

[0050] From the above description, the longitudinal spherical aberration, the field curvature and the aberration of the zoom lens at the wide angle, in the middle, and the tele end are corrected, and the straight sharpness of the transfer function is good. In addition, the complex structure of the zoom lens is greatly simplified while a good imaging quality is ensured; all the lenses are made from spherical glass, so that the imaging quality is good, the size is small; and the structure is compact, and the cost is low.

[0051] The embodiments described above are only preferred ones of the invention, and are not intended to limit the invention in any form. Any person skilled in this field can make certain alterations or modifications to achieve equivalent embodiments based on the technical contents disclosed above without deviating from the contents of the technical solutions of the invention. Any simple alterations, equivalent variations and modifications of the above embodiments obtained according to the technical essence of the invention should also fall within the scope of the technical solutions of the invention.

Claims

1. A zoom lens provided with two lens groups, comprising a first lens group having a negative power, an aperture stop, and a second lens group having a positive power, wherein the first lens group, the aperture stop and the second lens group are coaxially arranged in sequence from an object side to an image side; the first lens group comprises a first crescent lens having a negative power, a first biconcave lens having a negative power, and a first biconvex lens having a positive power, and the first crescent lens, the first biconcave lens and the first biconvex lens are coaxially arranged in sequence from the object side to the image side; and the second lens group comprises a second biconvex lens having a positive power, a second crescent lens having a positive power, a second biconcave lens having a negative power, a third biconvex lens having a positive power, a third crescent lens having a negative power, a fourth crescent lens having a negative power, and a fourth biconvex lens having a positive power, and the second biconvex lens, the second crescent lens, the second biconcave lens, the third biconvex lens, the third crescent lens, the fourth crescent lens and the fourth biconvex lens are coaxially arranged in sequence from the object side to the image side.

2. The zoom lens provided with two lens groups according to Claim 1, wherein the third biconvex lens and the third crescent lens are combined to form a first cemented lens having a positive power, and the fourth crescent lens and the fourth biconvex lens are combined to form a second cemented lens having a positive power.

3. The zoom lens provided with two lens groups according to Claim 1 or 2, wherein the zoom lens meets the following condition: 1,2<|fG1 |/fG2<2.0, wherein “fG1” refers to a focal length of the first lens group, and “fG2” refers to a focal length of the second lens group.

4. The zoom lens provided with two lens groups according to Claim 3, wherein the zoom lens meets the following conditions: 1,8<|fG 1 |/ft<2.6, 0,9<fG2/ft<1.8, wherein “ft” refers to a focal length of the zoom lens at a telephoto position.

5. The zoom lens provided with two lens groups according to Claim 3, wherein the zoom lens meets the following condition: 2.4<fs/fG2<3.2, wherein “fs” refers to an effective focal length of the second biconvex lens, the second crescent lens, and the second biconcave lens of the second lens group G2.

6. The zoom lens provided with two lens groups according to Claim 2, wherein the aperture stop of the zoom lens is arranged between the first lens group and the second lens group and is kept stationary.

7. A method for using the zoom lens provided with two lens groups according to any one of Claims 1-6, wherein the first lens group is moved towards the object side, and/or the second lens group is moved the image side to realize zooming.

8. An imaging device, comprising the zoom lens provided with two lens groups according to any one of Claims 1-6.