CN111427139A

CN111427139A - Internal focusing type imaging lens

Info

Publication number: CN111427139A
Application number: CN202010380185.9A
Authority: CN
Inventors: 刘瑞军; 陈宝锋
Original assignee: Shenzhen Leiying Photoelectric Technology Co ltd
Current assignee: Shenzhen Leiying Photoelectric Technology Co ltd
Priority date: 2020-05-08
Filing date: 2020-05-08
Publication date: 2020-07-17

Abstract

The invention provides an inner focusing type imaging lens, which sequentially comprises the following components from an object side to an image side: a first lens group having positive power, a second lens group having positive power, a third lens group having negative power, a fourth lens group having positive power; in the focusing process, the third lens group moves towards the image side along the optical axis, and the positions of the first lens group, the second lens group and the fourth lens group relative to the image surface are kept unchanged; the first lens group comprises a first lens, a second lens, a third lens and a fourth lens; the second lens group comprises a fifth lens, a sixth lens and a seventh lens, and the fifth lens and the sixth lens are combined into a cemented lens group; the third lens group includes an eighth lens; the fourth lens group comprises a ninth lens and a tenth lens; the object side surfaces and the image side surfaces of the seventh lens element and the eighth lens element are aspheric. The invention reduces the weight of the focusing group and the total weight of the imaging lens, and is beneficial to the quick focusing of the imaging lens and the imaging equipment.

Description

Internal focusing type imaging lens

Technical Field

The invention relates to the technical field of optical imaging, in particular to an internal focusing type imaging lens.

Background

In recent years, in the photography market, a micro single camera is rapidly expanding, compared with a single lens reflex camera which is large in size and poor in portability, the micro single camera is small in size, light in weight and excellent in portability due to the fact that a light reflecting plate assembly is omitted, and meanwhile, due to the fact that the mature technology of a high-precision CCD is utilized, the micro single camera also has unsophisticated high-quality imaging quality. Furthermore, the camera can shoot sports or landscape images, has a shooting visual field angle from about 40 degrees to 90 degrees and an F number of 2 or less, can have brighter visual fields and visual fields, and can help shooting enthusiasts to shoot large-scene images more freely.

The lens of the micro single camera is the same as the lens of the single lens reflex, and users want the lens to have high performance and high imaging quality. On the one hand, because the micro single camera is small in size, the volume of the lens matched with the micro single camera is required to be as small as possible compared with that of a single lens reflex. Meanwhile, as the common users are common photography enthusiasts, the high cost performance is also required. Due to the above points, there are many constraints on the design of the micro-single lens.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides an internal focusing type imaging lens which is small in size and light in weight, an internal focusing component can be formed by only one lens, and the internal focusing type imaging lens has the characteristics of high focusing speed and excellent imaging performance.

In order to achieve the purpose, the invention adopts the following technical scheme:

An imaging lens comprising, in order from an object side to an image side: a first lens group having positive focal power, an aperture stop, a second lens group having positive focal power, a third lens group having negative focal power, a fourth lens group having positive focal power;

In the focusing process, the third lens group moves towards the image side along the optical axis, and the positions of the first lens group, the second lens group and the fourth lens group relative to the image surface are kept unchanged;

The first lens group comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power and a fourth lens with positive focal power; the second lens group comprises a fifth lens with negative focal power, a sixth lens with positive focal power and a seventh lens with positive focal power, and the fifth lens and the sixth lens are combined into a cemented lens group; the third lens group includes an eighth lens having negative optical power; the fourth lens group comprises a ninth lens with positive focal power and a tenth lens with negative focal power; surfaces of the object side and the image side of the seventh lens and the eighth lens are aspheric; the first lens group satisfies the following conditional expression:

0.3≤L1s/L≤0.5，(1)

where L1 s denotes an on-axis distance from the first lens group to the aperture stop, and L denotes an on-axis distance from a vertex of an object side surface of the first lens to a vertex of an image side surface of the tenth lens.

As a preferable mode, the second lens group satisfies the following conditional expression:

3≤(Cvob2-Cvim3)/φ≤4，(2)

Where Cvob2 denotes a curvature of a surface of the sixth lens element closer to the object side, Cvim3 denotes a curvature of a surface of the seventh lens element closer to the image side, and Φ denotes an optical power of the imaging lens.

As a preferable mode, the fourth lens group satisfies the following conditional expression:

6≤F4/F≤13，(3)

Where F denotes a focal length of the imaging lens, and F4 denotes a combined focal length of the fourth lens group.

0.6≤BFL/F≤0.7，(4)

wherein BF L represents a distance between a surface of the tenth lens of the fourth lens group close to the image side and an image plane, and F represents a focal length of the imaging lens.

As a preferable scheme, the imaging lens satisfies the following conditional expression:

30≤Vd4a-Vd4b≤50，(5)

Wherein, Vd4a is the abbe number of the ninth lens of the fourth lens group for light with the wavelength of 587.6nm, and Vd4b is the abbe number of the tenth lens of the fourth lens group for light with the wavelength of 587.6 nm.

Compared with the prior art, the invention has the following beneficial effects:

The imaging lens focusing assembly only consists of one lens, so that the weight of a focusing group and the load of a pushing motor are reduced, and the imaging lens and the imaging equipment can be rapidly focused; the sizes of focal powers of the front group and the rear group of the diaphragm are limited through the conditional expressions (1) and (2), so that the focal powers occupy the main part in the distribution, the subsequent lens group can better correct chromatic aberration, and the entrance pupil is closer to the first lens to reduce the incident aperture, thereby realizing the system miniaturization; the focusing lens adopts a glass aspheric surface to ensure the straight field curvature of an imaging surface, the off-axis large aberration generated by the front group and the rear group is balanced in the focusing process, and the lens has more uniform resolution from the edge to the center; the angle of light incident on the image plane is controlled through a reasonable optical structure, so that the brightness of the edge of the picture is effectively improved, and the dark corners are lightened; the ninth lens of the fourth lens group adopts an ultra-low dispersion weak positive focal power lens and a strong negative focal power tenth lens to further correct the negative chromatic aberration brought by the front group, thereby reducing the generation of purple edges of pictures.

To more clearly illustrate the structural features and technical means of the present invention and the specific objects and functions attained thereby, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments:

Drawings

FIG. 1 is a schematic structural view showing embodiment 1 of the present invention;

FIG. 2 is a diagram showing spherical aberration in infinity focusing according to embodiment 1 of the present invention;

FIG. 3 shows a schematic view of the curvature of field in infinity focusing according to example 1 of the present invention;

FIG. 4 shows a distortion diagram of embodiment 1 of the present invention in infinity focusing;

FIG. 5 is a schematic diagram showing spherical aberration at the closest in-focus distance in embodiment 1 of the present invention;

FIG. 6 is a schematic view showing curvature of field at the closest in-focus distance in example 1 of the present invention;

FIG. 7 is a diagram showing distortion at the closest in-focus distance in embodiment 1 of the present invention;

FIG. 8 is a schematic structural view showing embodiment 2 of the present invention;

FIG. 9 is a diagram showing spherical aberration in infinity focusing according to embodiment 2 of the present invention;

FIG. 10 shows a schematic view of the curvature of field in infinity focusing for example 2 of the present invention;

FIG. 11 shows a distortion diagram of embodiment 2 of the present invention in infinity focusing;

FIG. 12 is a diagram showing spherical aberration at the closest in-focus distance in embodiment 2 of the present invention;

FIG. 13 is a schematic view showing curvature of field at the closest in-focus distance in accordance with example 2 of the present invention;

FIG. 14 is a diagram showing distortion at the closest in-focus distance in embodiment 2 of the present invention;

FIG. 15 is a schematic structural view showing embodiment 3 of the present invention;

FIG. 16 is a diagram showing spherical aberration in infinity focusing according to embodiment 3 of the present invention;

FIG. 17 shows a schematic view of the curvature of field in infinity focusing for example 3 of the present invention;

FIG. 18 shows a distortion diagram in infinity focusing for example 3 of the present invention;

FIG. 19 is a diagram showing spherical aberration at the closest in-focus distance in embodiment 3 of the present invention;

FIG. 20 is a schematic view showing curvature of field at the closest in-focus distance in example 3 of the present invention;

FIG. 21 is a diagram showing distortion at the closest in-focus distance in embodiment 3 of the present invention;

FIG. 22 is a schematic structural view showing embodiment 4 of the present invention;

FIG. 23 is a diagram showing spherical aberration in infinity focusing according to embodiment 4 of the present invention;

FIG. 24 is a schematic view showing the curvature of field in infinity focusing according to example 4 of the present invention;

FIG. 25 shows a distortion diagram in infinity focusing for example 4 of the present invention;

FIG. 26 is a diagram showing spherical aberration at the closest in-focus distance in embodiment 4 of the present invention;

FIG. 27 is a diagram showing curvature of field at the closest in-focus distance in accordance with example 4 of the present invention;

Fig. 28 shows a distortion diagram at the closest in-focus distance in embodiment 4 of the present invention.

The attached drawings indicate the following:

Detailed Description

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the positions or elements referred to must have specific orientations, be constructed and operated in specific orientations, and thus, are not to be construed as limiting the present invention.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood as appropriate by those of ordinary skill in the art.

As shown in fig. 1 to 28, an imaging lens includes, in order from an object side to an image side, a first lens group G1 having positive power, an aperture stop STP, a second lens group G2 having positive power, a third lens group G3 having negative power, a fourth lens group G4 having positive power; the third lens group G3 moves in the optical axis toward the image side direction during focusing, and the first lens group G1, the second lens group G2, and the fourth lens group G4 remain unchanged with respect to the image plane IMG position;

the first lens group G1 includes a first lens L11 having negative power, a second lens L12 having negative power, a third lens L13 having positive power, and a fourth lens L14 having positive power, and the first lens group G1 satisfies the following conditional expression:

0.3≤L1s/L≤0.5，(1)

If the conditional expression (1) is met, the aperture diaphragm is positioned at a proper position in the optical system, so that the good imaging performance of the system is kept, and the aperture miniaturization of the optical system is facilitated; if the lower limit of the conditional expression (1) is lower, the aperture stop gradually approaches the object side, the aperture of the rear group lens near the image side increases, and the off-axis aberration, particularly the field curvature, generated in the rear group becomes more significant. If the upper limit of the conditional expression (1) is exceeded, the aperture stop comes closer to the image side, the aperture of the aperture stop front group is affected by the effect, and it becomes difficult to miniaturize the optical system.

the second lens group G2 includes a fifth lens L21 having negative power, a sixth lens L22 having positive power, and a seventh lens L23 having positive power, and the second lens group G2 satisfies the following conditional expressions:

3≤(Cvob2-Cvim3)/φ≤4，(2)

where Cvob2 represents the curvature of the surface of the sixth lens element near the object side, Cvim3 represents the curvature of the surface of the seventh lens element L23 near the image side, and phi represents the power of the imaging lens, the lens group satisfying the conditional expression (2) can correct chromatic spherical aberration well, and the off-axis chromatic aberration converges toward the optical axis, and if it is lower than the lower limit in the conditional expression (2), the angle of light exiting from the cemented lens group increases, and the corresponding coma aberration increases, and if it is higher than the upper limit in the conditional expression (2), the power shared by the power of the second lens group G2 decreases, so that the overall length of the imaging lens tends to increase.

the third lens group G3 includes an eighth lens L31 having negative power.

the fourth lens group G4 includes a ninth lens L41 having positive power, a tenth lens L42 having negative power, and the fourth lens group G4 satisfies the following conditional expression:

6≤F4/F≤13，(3)

0.6≤BFL/F≤0.7，(4)

30≤Vd4a-Vd4b≤50，(5)

if the conditional expressions (3), (4) and (5) are lower than the lower limit, the power of the fourth lens group is enhanced, the spherical aberration is increased, the distance from the photographic lens to the image plane is shortened, the lens close to the image plane is compressed in the outer diameter, the imaging brightness is affected, and if the conditional expressions (3), (4) and (5) are higher than the upper limit, the power of the fourth lens group is reduced, the total focal length of the fourth lens group is increased, the total focal length of the imaging lens is increased, and the total focal length of the imaging lens is increased.

in the present invention, a parallel glass plate G L configured by a filter is disposed between the negative lens L42 of the fourth lens group G4 and the image plane IMG the back focal length is the distance from the image side surface of L42 to the image surface IMG, where the parallel glass plate G L can be transformed into air.

Example 1

Fig. 1 is a schematic view showing the structure of an imaging lens according to embodiment 1, and numerical data of the imaging lens are shown in tables 1, 2, and 3:

TABLE 1

TABLE 2

TABLE 3

Number of noodles	k	A4	A6	A8	A10
						13	0	-7.55E-06	3.58E-09	-1.28E-11	1.11E-13
14	0	1.05E-05	-5.18E-09	-2.37E-11	3.64E-14
						15	0	9.27E-05	-5.08E-07	1.65E-09	-2.56E-12
16	0	1.03E-04	-4.96E-07	1.57E-09	-2.41E-12

Wherein, the surface number represents the surface number of each lens from the object side to the image side;

in the following table, the fourth, sixth, eighth, tenth order aspherical coefficients a4, a6, A8, a10 and the conic constant k of the aspherical surface are collectively shown.

The aspheric shape definition will be described, and the following embodiments will not be repeated to describe the aspheric shape definition:

And y is the radial coordinate from the optical axis.

z is the offset of the intersection point of the aspheric surface and the optical axis in the direction of the optical axis.

r is the curvature radius of the reference spherical surface of the aspheric surface.

Aspheric coefficients of K, 4 times, 6 times, 8 times, 10 times and 12 times

Fig. 2 to 4 show graphs of spherical aberration, curvature of field, and distortion in infinity focusing in example 1, and fig. 5 to 7 show graphs of spherical aberration, curvature of field, and distortion in closest focusing in example 1.

The spherical aberration curve diagram shows the spherical aberration curve when the F-number is 1.4, wherein, the F line, the D line and the C line respectively represent the spherical aberration at a wave length of 486nm, a wave length of 587nm and a wave length of 656nm, the abscissa represents the size of the spherical aberration value, and the ordinate represents the field of view. The field curvature curve diagram shows that the field curvature curve diagram is 31.6 at a half field angle omega ⁰A time field curve, wherein the solid line S represents the value of the chief ray d on the sagittal image surface, and the solid line T represents the chief ray d The value of the line on the meridian image surface, the abscissa represents the size of the curvature of field, and the ordinate represents the field of view. The distortion curve diagram shows that the half field angle omega is 31.6 ⁰Distortion curve of time, wherein the abscissa represents the distortion value and the ordinate represents the field of view. The above description of various spherical aberration, curvature of field, distortion graphs is the same as other embodiments, and will not be repeated herein. As can be seen from fig. 2 to 7, the imaging lens of embodiment 1 has a good imaging effect.

Example 2

As shown in fig. 8, the present embodiment is different from embodiment 1 in the lens parameters of the imaging lens. Hereinafter, table 4, table 5, and table 6 show various numerical data regarding the imaging lens of the present embodiment.

TABLE 4

TABLE 5

TABLE 6

Number of noodles	k	A4	A6	A8	A10
						13	0	-9.70E-06	-5.74E-11	-3.14E-12	7.01E-14
14	0	8.29E-06	-3.69E-09	-3.97E-11	5.52E-14
						15	0	8.61E-05	-4.12E-07	1.11E-09	-1.41E-12
16	0	9.59E-05	-4.02E-07	1.05E-09	-1.30E-12

FIGS. 9 to 11 show graphs of spherical aberration, curvature of field, and distortion in focusing at infinity in example 2, and FIGS. 12 to 14 show graphs of spherical aberration, curvature of field, and distortion in focusing at the closest distance in example 2. As can be seen from fig. 9 to 14, the imaging lens of the present embodiment has a good imaging effect.

Example 3

As shown in fig. 15, the present embodiment is different from embodiment 1 in the lens parameters of the imaging lens. Hereinafter, table 7, table 8, and table 9 show various numerical data regarding the imaging lens of the present embodiment.

TABLE 7

TABLE 8

TABLE 9

Number of noodles	k	A4	A6	A8	A10
						13	0	-1.14E-05	-2.00E-08	1.52E-10	-6.26E-13
14	0	9.43E-06	-2.65E-08	1.26E-10	-6.58E-13
						15	0	8.50E-05	-3.59E-07	7.89E-10	-8.25E-13
16	0	9.57E-05	-3.34E-07	6.44E-10	-5.51E-13

FIGS. 16 to 18 show graphs of spherical aberration, curvature of field, and distortion in focusing at infinity in example 3, and FIGS. 19 to 21 show graphs of spherical aberration, curvature of field, and distortion in focusing at the closest distance in example 3. As can be seen from fig. 16 to 21, the imaging lens of the present embodiment has a good imaging effect.

Example 4

As shown in fig. 22, the present embodiment is different from embodiment 1 in the lens parameters of the imaging lens. Hereinafter, table 10, table 11, and table 12 show various numerical data regarding the imaging lens of the present embodiment.

Watch 10

TABLE 11

TABLE 12

Fig. 23 to 25 show graphs of spherical aberration, curvature of field, and distortion in infinity focusing in example 4, and fig. 26 to 28 show graphs of spherical aberration, curvature of field, and distortion in closest focusing in example 4. As can be seen from fig. 23 to 28, the imaging lens of the present embodiment has a good imaging effect.

Table 9 shows a table of calculated values of conditional expressions 1 to 6 for each example:

TABLE 9

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. An internal focusing imaging lens, comprising, in order from an object side to an image side: a first lens group having positive focal power, an aperture stop, a second lens group having positive focal power, a third lens group having negative focal power, a fourth lens group having positive focal power;

The first lens group comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power and a fourth lens with positive focal power; the second lens group comprises a fifth lens with negative focal power, a sixth lens with positive focal power and a seventh lens with positive focal power, and the fifth lens and the sixth lens are combined into a cemented lens group; the third lens group includes an aspherical eighth lens having negative power; the fourth lens group comprises a ninth lens with positive focal power and a tenth lens with negative focal power; surfaces of the object side and the image side of the seventh lens and the eighth lens are aspheric; the first lens group satisfies the following conditional expression:

0.3≤L1s/L≤0.5，(1)

2. The inner focusing type imaging lens according to claim 1, wherein the second lens group satisfies the following conditional expression:

3≤(Cvob2-Cvim3)/φ≤4，(2)

3. The inner focusing type imaging lens according to claim 1, wherein the fourth lens group satisfies the following conditional expression:

6≤F4/F≤13，(3)

4. The inner focusing type imaging lens according to claim 1, wherein the fourth lens group satisfies the following conditional expression:

0.6≤BFL/F≤0.7，(4)

5. An internal focusing imaging lens according to any one of claims 1 to 5, wherein the fourth lens group satisfies the following conditional expression:

30≤Vd4a-Vd4b≤50，(5)