CN110308545A - In away from long shot and picture pick-up device - Google Patents

Abstract

Away from long shot and picture pick-up device in one kind, it away from long shot include optical system in described, the optical system is configured in order by object side to image side: the first lens group of negative power, including at least two positive light coke eyeglasses, and the one side of the positive light coke eyeglass towards object side is convex surface；Diaphragm；Second lens group of positive light coke, including at least two positive light coke eyeglasses；The third lens group of negative power, including at least one minus power lens, the third lens group can be moved along optical axis direction to carry out focus operations；4th lens group of positive light coke；The minus power lens that the one side towards object side is concave surface are provided with by the diaphragm of first lens group.Wherein, the position between the first lens group, the second lens group and the 4th lens group is relatively fixed, and only the third lens group relatively moves in focussing process.It is applied to picture pick-up device away from long shot in provided by the present application, light-weight, structure is simple, good in optical property.

Description

Medium-distance telephoto lens and image pickup apparatus

Technical Field

The invention relates to the field of image pickup equipment, in particular to a medium-distance telephoto lens and the image pickup equipment.

Background

Medium and long focus lenses are developed to the present as interchangeable lenses, and the lenses have high performance, low chromatic aberration, miniaturization, better focusing mode and larger light flux amount as the key point of design. However, since a large-diameter lens has a smaller depth of field than a small-diameter lens, it is necessary to correct spherical aberration more favorably, and aberrations such as coma become a design problem. Usually, the characteristics of the medium-telephoto lens with the focal length below 135mm (fullsize) are similar to those of the standard lens, so the design usually adopts the design of triplets and gausss or the modified structure thereof.

The Gauss structure (gaussian structure) is generally composed of a first lens group and a second lens group, and the first lens group or the second lens group or the entire lens group is moved during focusing. Focusing in this manner causes a heavy weight of the focus group, and complicates the mechanism size of the lens and the structure of the lens focus drive, resulting in an increase in size and low end feeling of the lens.

Disclosure of Invention

An object of the present invention is to provide a medium telephoto lens and an image pickup apparatus capable of reducing the weight of a focus group and realizing miniaturization of the lens.

The invention is realized by the following steps:

a medium telephoto lens comprising an optical system configured with, in order from an object side to an image side:

the first lens group with negative focal power comprises at least two positive focal power lenses, and one surface of each positive focal power lens, facing to the object side, is a convex surface;

a diaphragm; in the first lens group, a negative power lens with a concave surface on one surface facing the object side is arranged beside the diaphragm;

a second lens group with positive focal power, which comprises at least two positive focal power lenses;

a third lens group of negative power including at least one negative power lens, the third lens group being movable in an optical axis direction to perform a focusing operation;

a fourth lens group of positive refractive power;

in the focusing process, the relative positions of the first lens group, the second lens group and the fourth lens group are fixed.

The invention also provides an image pickup apparatus, which comprises a body and the intermediate telephoto lens according to the technical scheme, wherein the intermediate telephoto lens is mounted on the body.

The invention has the beneficial effects that: the application provides an among the long-range telephoto lens, lens in with optical system divide into four groups, when focusing, only need to remove the third lens group can, that is to say, make the weight of focusing group lighter relatively, consequently, it is littleer to drive the required drive power of focusing drive structure that the third lens group removed, drive power demand to focusing drive structure reduces the back, the optional structural configuration of focusing drive structure increases, can choose the structure for use more simply, the lighter structure of weight, thereby make the whole weight reduction of long-range telephoto lens in the well, and can satisfy the miniaturized demand.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to these drawings without inventive effort.

Fig. 1a to fig. 1c are schematic structural diagrams of an optical system in a middle-range telephoto lens according to a second embodiment of the present invention when the optical system is in infinity focus, when the optical system is in middle-range focus (-0.025), and when the optical system is in near-end focus, respectively;

fig. 2 a-2 c are spherical phase difference graphs of the intermediate telephoto lens system according to the second embodiment of the present invention when the optical system is in infinity focus, in intermediate focus (-0.025), and in near focus, respectively;

fig. 3 a-3 c are astigmatism diagrams of an optical system in a telephoto lens system according to a second embodiment of the present invention when the optical system is in infinity focus, when the optical system is in middle-distance focus (-0.025), and when the optical system is in near-end focus;

fig. 4a to 4c are distortion diagrams of an optical system in a telephoto lens system according to a second embodiment of the present invention when the optical system is in infinity focus, when the optical system is in middle-distance focus (-0.025), and when the optical system is in near-end focus;

fig. 5a to 5c are schematic structural diagrams of an optical system in a telephoto lens system according to a third embodiment of the present invention when the optical system is in infinity focus, in middle-distance focus (-0.025), and in near-end focus, respectively;

fig. 6a to 6c are spherical phase difference graphs when the optical system in the intermediate telephoto lens system according to the third embodiment of the present invention is in infinity focus, in intermediate focus (-0.025), and in near focus, respectively;

fig. 7a to 7c are astigmatism diagrams of an optical system in a telephoto lens system according to a third embodiment of the present invention when the optical system is in infinity focus, when the optical system is in middle-distance focus (-0.025), and when the optical system is in near-end focus;

fig. 8a to 8c are distortion diagrams of an optical system in a telephoto lens system according to a third embodiment of the present invention when the optical system is in infinity focus, when the optical system is in middle-distance focus (-0.025), and when the optical system is in near-end focus;

fig. 9a to 9c are schematic structural diagrams of an optical system in a telephoto lens system according to a fourth embodiment of the present invention when the optical system is in infinity focus, in middle-distance focus (-0.025), and in near-end focus, respectively;

fig. 10a to 10c are spherical phase difference graphs of the intermediate telephoto lens system according to the fourth embodiment of the present invention when the optical system is in infinity focus, in middle-distance focus (-0.025), and in near-end focus, respectively;

fig. 11a to 11c are astigmatism diagrams of an optical system in a telephoto lens system according to a fourth embodiment of the present invention when the optical system is in infinity focus, when the optical system is in middle-distance focus (-0.025), and when the optical system is in near-end focus;

fig. 12a to 12c are distortion diagrams of an optical system in a telephoto lens system according to a fourth embodiment of the present invention when the optical system is in infinity focus, when the optical system is in middle-distance focus (-0.025), and when the optical system is in near-end focus;

fig. 13a to 13c are schematic structural diagrams of an optical system in a telephoto lens system according to a fifth embodiment of the present invention when the optical system is in infinity focus, in middle-distance focus (-0.025), and in near-end focus, respectively;

fig. 14a to 14c are spherical aberration diagrams of an optical system in a telephoto lens system according to a fifth embodiment of the present invention when the optical system is in infinity focus, in middle-distance focus (-0.025), and in near-end focus, respectively;

fig. 15a to 15c are astigmatism diagrams of an optical system in a telephoto lens system according to a fifth embodiment of the present invention when the optical system is in infinity focus, when the optical system is in middle-distance focus (-0.025), and when the optical system is in near-end focus;

fig. 16a to 16c are distortion diagrams of an optical system in a telephoto lens system according to a fifth embodiment of the present invention when the optical system is in infinity focus, when the optical system is in middle-distance focus (-0.025), and when the optical system is in near-end focus.

In the figure: g1-first lens group; g2-second lens group; g3-third lens group; g4-fourth lens group;

l11, L12, L13, L14, L15, L21, L22, L31, L32, L41, L42-lenses;

GG-image plane; ST-diaphragm.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance. The embodiments described below and the features of the embodiments can be combined with each other without conflict.

First embodiment

The present embodiment provides a medium telephoto lens, including an optical system, which is configured from an object side to an image side, and includes: the first lens group with negative focal power comprises at least two positive focal power lenses, and one surface of each positive focal power lens, which faces to the object side, is a convex surface; a diaphragm; a second lens group with positive focal power, which comprises at least two positive focal power lenses; a third lens group of negative power including at least one negative power lens, the third lens group being movable in an optical axis direction to perform a focusing operation; a fourth lens group of positive refractive power; the first lens group is provided with a negative power lens with a concave surface facing the object side beside the diaphragm. In the focusing process, the relative positions of the first lens group, the second lens group and the fourth lens group are unchanged, and only the third lens group moves.

In a preferred embodiment of the present invention, at least one positive power lens of the first lens group is configured to satisfy the following conditional expression:

Vd1a≥63.396； (1)

vd1a is the Abbe number of d ray of any positive power lens in the first lens group; at least one lens satisfying the following conditional expression is configured in the positive focal power lens of the second lens group:

Vd2a≥63.396 (2)；

and Vd2a is the Abbe number of d rays of any positive power lens in the second lens group.

Further, the first lens group includes a negative power lens satisfying the following conditional expression:

Vdv≤30.05 (3)；

wherein Vdv is an average value of abbe numbers of d rays of all negative power lenses in the first lens group.

The above conditional expressions (1) to (3) correct the axial chromatic aberration generated in the other lens by the abnormal partial dispersion characteristic of the positive power lens having a high abbe number. However, since low dispersion lenses are all of relatively low refractive index, they generally have a strong curvature, resulting in increased spherical aberration and astigmatism; therefore, the aberration is improved by disposing a negative lens having a high refractive index on the image side of the lens.

In a preferred embodiment of the present invention, the positive power lens closest to the object side in the first lens group satisfies the following conditional expression:

0.7≤f11/fefl≤1.3 (4)；

wherein f11 is the focal length of the positive power lens closest to the object side in the first lens group; the fefl is the focal length of the entire system when the object is shot at infinity.

The range in condition (4) is preferably: f11/fefl is more than or equal to 0.8 and less than or equal to 1.25; more preferably: f11/fefl is more than or equal to 0.9 and less than or equal to 1.20;

conditional expression (4) prescribes a positive power lens disposed on the most object side of the first lens group. If the positive focal power lens is above the upper limit of the formula, the total length of the lens can be increased, the correction of the axial chromatic aberration is difficult, and the second lens group can need stronger focal power to correct the spherical aberration generated by the negative lens in the first lens group; below the lower limit of the equation, the total lens length may be shortened due to the increase in the focal power, but the second order dispersion becomes large, and the correction of the on-axis chromatic aberration becomes difficult. Therefore, the range provided by the above conditional expression (4) is a preferable range.

For example, in one embodiment, the first lens group includes four lenses, which are a positive lens, a negative lens and a negative lens from the object side to the image side.

In a preferred embodiment of the present invention, the second lens group satisfies the following conditional expression:

0.3≤f2/fefl≤0.6 (5)；

wherein f2 is the focal length of the second lens group; the fefl is the focal length of the entire system when the object is shot at infinity.

The conditional formula (5) preferably ranges: f2/fefl is more than or equal to 0.35 and less than or equal to 0.55; more preferably: f2/fefl is more than or equal to 0.4 and less than or equal to 0.5.

Conditional expression (5) specifies the ratio of the focal length of the second lens group to the focal length of the entire system. Satisfying the formula is beneficial to the miniaturization of the lens and the good correction of the spherical aberration, coma aberration and other aberrations. If the optical system is above the upper limit of the formula, the first lens group has negative refractive power, and therefore, it may be difficult to correct spherical aberration and axial chromatic aberration, and the entire optical system may become large. If below the lower limit of this formula, the positive spherical aberration generated by the first lens group may be excessively corrected due to the enhancement of the power, resulting in excessive spherical aberration correction of the entire optical system, while coma is difficult to correct due to the increase of the power. Therefore, the range provided by the above conditional expression (5) is a preferable range.

In one embodiment, the second lens group includes two lenses of positive power.

In a preferred embodiment of the present invention, the first lens group, the second lens group, the third lens group and the fourth lens group simultaneously satisfy the following two conditional expressions:

－1.5≤f12/f3≤－1 (6)；

－1.5≤f4/f3≤－1 (7)；

wherein f12 is the combined focal length of the first lens group and the second lens group; f3 is the focal length of the third lens group; f4 is the focal length of the fourth lens group.

Conditional formula (6) is preferably: f12/f3 is not less than-1.45 and not more than-1.1; more preferably: f12/f3 is more than or equal to-1.40 and less than or equal to-1.2; conditional formula (7) is preferably: f4/f3 is not less than-1.45 and not more than-1.1; more preferably: f4/f3 is not less than-1.40 and not more than-1.2.

The optical system can be regarded as a TRIPLET type anamorphic lens after the first lens group and the second lens are combined into a focal point; as the special attribute of the lens, when the front and back positive and negative focal power lens groups are approximately symmetrical relative to the middle negative focal power lens group, various aberrations of the optical system can be well corrected. If the optical system is disposed in a range other than the conditional expression (6) and the conditional expression (7), the image heights of the light in the front lens group and the rear lens group are unbalanced, so that the correction unbalance of spherical aberration, coma aberration, and astigmatism is caused, thereby causing the optical performance to be degraded. Therefore, the ranges provided by the above conditional formula (6) and conditional formula (7) are preferable ranges.

It should be noted that the TRIPLET structure includes three independent lens groups, a long focal length can be obtained by the first two lens groups, and then the focal length can be shortened again by the third lens which is far away from the first two lens groups.

For example, in one embodiment, the third lens group comprises a negative power lens. The four lens groups comprise two positive power lenses which can be cemented to form a cemented lens.

In a preferred embodiment of the present invention, the optical system satisfies the following conditional expression:

0.9≤(OAL－BF)/fefl≤1.6 (8)；

wherein OAL is the total length of the optical system; BF is the distance from the R2 surface of the lens farthest from the object side in the optical system to the image plane GG.

Conditional formula (8) is preferably: (OAL-BF)/fefl is more than or equal to 0.95 and less than or equal to 1.5; more preferably: (OAL-BF)/fefl is more than or equal to 1.0 and less than or equal to 1.45.

The above (8) is for regulating the size of the lens, and ensuring the rear intercept and the reasonable exit pupil position of the lens. If the corresponding parameters of the optical system are below the lower limit of the conditional expression (8), the optical system is short, and the astigmatism, the coma aberration and the magnification chromatic aberration are difficult to correct; if the corresponding parameters of the optical system are above the upper limit of the conditional expression (8), the optical system may have insufficient back intercept and cannot meet the use of a specific camera. Therefore, the range provided by the above conditional expression (8) is a preferable range.

The present embodiment also provides an image pickup apparatus including a body and the intermediate telephoto lens provided as in the above embodiment, the intermediate telephoto lens being mounted on the body.

Second embodiment

As shown in fig. 1a to fig. 1c, the present embodiment provides an optical system in a specific intermediate telephoto lens, and the intermediate telephoto lens provided in the present embodiment satisfies the settings and conditions in the first embodiment, further, in the optical system, in the direction shown in the drawing, the left side is an object side, and the right side is an image side, the first lens group G1 includes four lenses, and from the object side to the image side, the lens L11, the lens L12, the lens L13, and the lens L14 are respectively, where the lens L11 is a positive power lens, the lens L12 is a positive power lens, the lens L13 is a negative power lens, the lens L14 is a negative power lens, and the lens L14 is located near the stop ST. The second lens group G2 includes, from object side to image side, a lens L21 and a lens L22, respectively, the lens L21 is a positive power lens, and the lens L22 is a positive power lens. The third lens group G3 includes a lens L31, and the lens L31 is a negative power lens. The fourth lens group G4 includes, from the object side to the image side, a lens L41 and a lens L42, respectively, the lens L41 is a positive power lens, the lens L42 is a negative power lens, and the lens L42 is the lens closest to the image plane GG.

Hereinafter, various numerical data of the optical system provided in the present embodiment are shown in a table form:

the symbols used in the following table are as follows: "R" is the radius of curvature; "D" is the on-axis surface distance between the currently numbered surface (ith surface) and the next surface (i +1 st surface); "Nd" is the refractive index; "Vd" is the Abbe number; "Fno" is the F number; "ω" is the half field angle. "∞" indicates that the surface is planar. Let f be 36.05, FNo 1.854, 2 ω be 34.05. The refractive index and Abbe number are those with respect to the d-line (wavelength 587.6 nm).

Table 1 shows basic data of the optical system:

No.	R	D	Nd	Vd
					0	0	inf
1	47.5004	3.85	2.00912	29.13
					2	-451.989	0.2
3	18.6536	4	1.51872	64.2
					4	19.5306	3.0015
5	-95.6761	1.3	1.66285	30.51
					6	13.988	4.776
7	-13.0306	1.3	2.00912	29.13
					8	-14.5607	1
STO	∞	4.0871
					10	80.9183	3.2	1.58568	53.4
11	-29.292	0.15
					12	17.3104	4.7	1.49845	81.61
13	-158.011	0.8
					14	-143.846	1	1.82858	24.38
15	17.4707	7.9309
					16	61.8848	5.3	1.90638	31.38
17	-24.9638	3.4436
					18	-23.2955	0.8	1.77615	25.78
19	-40.9804	18.4997
					20	∞	2.5	1.51872	64.2
21	∞	1

TABLE 1

Table 2 shows the focusing data:

D(0)	inf	1439	300
				D(13)	0.8	1.2552	2.9543
D(15)	7.9309	7.4762	5.7767

TABLE 2

Fig. 2 a-2 c are spherical aberration diagrams of the optical system provided in this embodiment, in which a solid line represents the spherical aberration of the optical system in this embodiment in d-line (wavelength 587.6nm), a dashed line represents the spherical aberration of the optical system in c-line (wavelength 656.3nm), and a dashed-dotted line represents the spherical aberration of the optical system in g-line (wavelength 435.8 nm). Fig. 3a to 3c are astigmatism diagrams of the optical system according to the present embodiment, in which a dotted line S represents a value at a sagittal image plane, and a dotted line T represents a value at a meridional image plane. Fig. 4 a-4 c are distortion diagrams of the optical system provided in the present embodiment. As can be seen from fig. 2a to 2c, the optical system in the intermediate telephoto lens provided according to the embodiment has excellent imaging performance.

Third embodiment

As shown in fig. 5a to 5c, the present embodiment provides an optical system in a specific intermediate telephoto lens, the intermediate telephoto lens provided in the present embodiment satisfies the settings and conditions in the first embodiment, and in addition, compared with the optical system in the second embodiment, in the four lenses of the first lens group G1, the lens L11 is a positive power lens, the lens L12 is a positive power lens, the lens L13 is a negative power lens, the lens L14 is a negative power lens, and the distance between adjacent lenses in the four lenses is greater than the distance between adjacent lenses in the four lenses in the second embodiment. The second lens group G2 comprises a lens L21 and a lens L22, wherein the lens L21 and the lens L22 are both positive power lenses. The third lens group G3 includes two lenses, i.e., a lens L31 and a lens L32 from the object side to the image side, the lens L31 is a positive power lens, the lens L32 is a negative power lens, and the lens L31 and the lens L32 are cemented together to form a negative power cemented lens. In the fourth lens group G4, the lens L41 is a positive power lens, the lens L42 is a positive power lens, and the lens L41 and the lens L42 are cemented together to form a cemented lens with positive power.

Hereinafter, various numerical data of the optical system provided in the present embodiment are shown in a table form: the symbols used in the following tables are the same as those in the second embodiment, and f is 43.77, FNo is 1.854, and 2 ω is 28.3.

Table 3 is the basic data for the optical system:

No.	R	D	Nd	Vd
					0	0	inf
1	42.9911	3.85	2.00912	29.13
					2	556.5372	1.1083
3	19.6866	4	1.62032	63.39
					4	21.4018	3.505
5	274.6606	1.3	1.74705	26.73
					6	15.3127	6.5401
7	-16.2421	1.3	1.85505	23.78
					8	-20.6481	1
STO	∞	2.3682
					10	339.0979	2.5	1.58041	54.38
11	-31.5985	0.15
					12	22.9312	4.7	1.49845	81.61
13	-72.2846	0.8
					14	-109.712	1.8354	2.00912	29.13
15	-36.6607	1	1.70057	28.58
					16	19.1514	8.4182
17	56.0338	5.3	2.00912	29.13
					18	-21.5301	0.8	1.77581	25.79
19	-200	23.3767
					20	∞	2.5	1.51872	64.2
21	∞	1

TABLE 3

Table 4 shows the focusing data:

D(0)	inf	1754	300
				D(13)	0.8	1.5714	5.3927
D(16)	8.4182	7.6467	3.8254

TABLE 4

Fig. 6a to 6c are spherical phase difference diagrams of the optical system provided in the present embodiment, in which the meanings represented by the solid line, the dashed line, and the dashed line are the same as those represented by the solid line, the dashed line, and the dashed line in fig. 2a to 2 c. Fig. 7a to 7c are astigmatism diagrams of the optical system provided in the present embodiment, in which a broken line S indicates a value at a sagittal image plane, and a broken line T indicates a value at a meridional image plane. Fig. 8a to 8c are distortion diagrams of the optical system provided in the present embodiment. As can be seen from fig. 6a to 8c, the optical system in the intermediate telephoto lens provided according to the embodiment has excellent imaging performance.

Fourth embodiment

As shown in fig. 9a to 9c, the present embodiment provides an optical system in a specific intermediate telephoto lens, and the intermediate telephoto lens provided in the present embodiment satisfies the settings and conditional expressions in the first embodiment, further, in the optical system, in the direction shown in the figure, the left side is an object side, and the right side is an image side, the first lens group G1 includes five lenses, which are a positive power lens L11, a positive power lens L12, a negative power lens L13, a positive power lens L14, and a negative power lens L15, respectively, and the lens L15 is located near the stop ST. The second lens group G2 is a lens L21 with positive power and a lens L22 with positive power from the object side to the image side, respectively. The third lens group G3 includes a negative power lens L31. The fourth lens group G4 includes a positive power lens L41 and a positive power lens L42, and the lens L42 is the lens closest to the image plane GG.

The symbols used in the following tables have the same meaning as those in the second embodiment, and f is 50.11, FNo is 1.867, and 2 ω is 24.65.

Table 5 shows basic data of the optical system:

No.	R	D	Nd	Vd
					0	∞	inf
1	39.1272	3.85	1.92811	30.81
					2	237.6518	1.5609
3	20.4615	4	1.51172	74.74
					4	21.9851	4.6691
5	114.2088	1.3	1.70335	28.45
					6	15.4428	5.7811
7	85.8214	2.1458	2.00912	29.13
					8	-60.5437	1.3284
9	-27.0514	1.3	1.73059	27.33
					10	45.436	3.4008
STO	0	3.2184
					12	54.4889	5	1.50813	76.45
13	-24.3009	0.15
					14	25.0543	4.7	1.49845	81.61
15	590.3517	0.8
					16	912.9539	1	1.65914	30.73
17	19.174	12.2728
					18	92.9823	5.3	2.00912	29.13
19	-22.4611	0.8	1.70116	28.55
					20	-200	23.9228
21	∞	2.5	1.51872	64.2
					22	∞	1

TABLE 5

Table 6 shows the focusing data:

D(0)	inf	1991	300
				D(15)	0.8	1.5992	6.0244
D(17)	12.2728	11.4735	7.0483

TABLE 6

Fig. 10a to 10c are spherical phase difference diagrams of the optical system provided in the present embodiment, in which the meanings represented by solid lines, broken lines, and chain lines are the same as those represented by solid lines, broken lines, and chain lines in fig. 1a to 1 c. Fig. 11a to 11c are astigmatism diagrams of the optical system according to the present embodiment, in which a broken line S indicates a value at a sagittal image plane, and a broken line T indicates a value at a meridional image plane. Fig. 12 a-12 c are distortion diagrams of the optical system provided in the present embodiment. As can be seen from fig. 10a to 12c, the optical system in the intermediate telephoto lens provided according to the embodiment has excellent imaging performance.

Fifth embodiment

As shown in fig. 13a to 13c, the present embodiment provides an optical system in a specific intermediate telephoto lens, and the intermediate telephoto lens provided in the present embodiment satisfies the settings and conditional expressions in the first embodiment, further, in the optical system, in the direction shown in the figure, the left side is an object side, and the right side is an image side, and the first lens group G1 includes a lens L11 with positive power, a lens L12 with positive power, a lens L13 with negative power, and a lens L14 with negative power; the second lens group G2 includes a lens L21 of positive power and a lens L22 of positive power; the third lens group G3 includes a negative power lens L31. The fourth lens group G4 includes a lens L41 of positive power and a lens L42 of positive power.

The symbols used in the following tables have the same meaning as those in the second embodiment, and f is 58.2, FNo is 1.877, and 2 ω is 21.05.

Table 7 shows basic data of the optical system:

No.	R	D	Nd	Vd
					0	∞	inf
1	80.5462	3.8994	2.00912	29.13
					2	-332.025	0.2
3	23.5508	8	1.59489	68.62
					4	32.0049	2.317
5	107.7737	4.4354	1.77022	25.96
					6	16.3806	6.0544
7	-19.1411	1.3	1.71667	27.88
					8	-26.3444	1
STO	0	2.7294
					10	-242.505	4	1.49845	81.61
11	-31.3769	0.15
					12	24.6918	5	1.49845	81.61
13	-82.2154	0.8
					14	6683.949	2.5326	1.60577	34.6
15	19.7488	10.7499
					16	100.5723	6.4824	2.00912	29.13
17	-20.2383	0.8	1.78015	26.91
					18	-200	24.1875
19	∞	4.2	1.51872	64.2
					20	∞	1

TABLE 7

Table 8 shows the focusing data:

D(0)	inf	2329	300
				D(13)	0.8	1.7427	8.3903
D(15)	10.7499	9.8072	3.1596

TABLE 8

Fig. 14a to 14c are spherical phase difference diagrams of the optical system provided in the present embodiment, in which the meanings represented by solid lines, broken lines, and chain lines are the same as those represented by solid lines, broken lines, and chain lines in fig. 1a to 1 c.

Fig. 15a to 15c are astigmatism diagrams of the optical system according to the present embodiment, in which a broken line S indicates a value at a sagittal image plane, and a broken line T indicates a value at a meridional image plane.

Fig. 16a to 16c are distortion diagrams of the optical system provided in the present embodiment.

As can be seen from fig. 14a to 16c, the optical system in the intermediate telephoto lens provided according to the embodiment has excellent imaging performance.

In the above second to fifth examples, the respective conditional formula is calculated as shown in the following table 9:

TABLE 9

It should be noted that, in the above embodiments, a lens group or a lens element is the same as a lens group or a lens element in other embodiments, and means that the object-side concave-convex state and the image-side concave-convex state of the lens or each lens element in the lens group are the same, and other parameters may be different, such as the thickness or the curvature of the surface.

In the intermediate telephoto lens provided by the application, aberrations such as spherical aberration and coma aberration are well corrected, the optical performance is high, and the size is small.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. An intermediate telephoto lens system comprising an optical system, the optical system being configured with, in order from an object side to an image side:

the first lens group with negative focal power comprises at least two positive focal power lenses, and one surface of each positive focal power lens, facing to the object side, is a convex surface;

a diaphragm; a negative power lens with a concave surface facing the object side is arranged beside the diaphragm of the first lens group;

a second lens group with positive focal power, which comprises at least two positive focal power lenses;

a third lens group of negative power including at least one negative power lens, the third lens group being movable in an optical axis direction to perform a focusing operation;

a fourth lens group of positive refractive power;

in the focusing process, the relative positions of the first lens group, the second lens group and the fourth lens group are fixed.

2. The intermediate telephoto lens according to claim 1, wherein at least one lens satisfying the following conditional expression is disposed in the positive power lens of the first lens group:

Vd1a≥63.396；

at least one lens satisfying the following conditional expression is configured in the positive focal power lens of the second lens group:

Vd2a≥63.396；

wherein,

vd1 a: the abbe number of the d ray of any positive focal power lens in the first lens group;

vd2 a: and the Abbe number of the d ray of any positive focal power lens in the second lens group.

3. The medium telephoto lens according to claim 2, wherein the first lens group includes a negative power lens satisfying the following conditional expression:

Vdv≤30.05；

wherein,

vdv: and the average value of the abbe numbers of the d rays of all the negative-power lenses in the first lens group.

4. The telephoto lens according to claim 3, wherein the positive power lens closest to the object side of the first lens group satisfies the following conditional expression:

0.7≤f11/fefl≤1.3；

wherein,

f 11: the focal length of the positive power lens closest to the object side in the first lens group;

fefl: the focal length of the entire system when the object is shot at infinity.

5. The medium telephoto lens according to claim 1, wherein the second lens group satisfies the following conditional expression:

0.3≤f2/fefl≤0.6；

wherein,

f 2: a focal length of the second lens group;

fefl: the focal length of the entire system when the object is shot at infinity.

6. The medium telephoto lens according to claim 1, wherein the first lens group, the second lens group, the third lens group, and the fourth lens group simultaneously satisfy the following two conditional expressions:

－1.5≤f12/f3≤－1；

－1.5≤f4/f3≤－1；

wherein,

f 12: a combined focal length of the first lens group and the second lens group;

f 3: a focal length of the third lens group;

f 4: a focal length of the fourth lens group.

7. The medium telephoto lens according to claim 1, wherein the optical system satisfies the following conditional expression:

0.9≤(OAL－BF)/fefl≤1.6；

wherein,

OAL: the full length of the optical system;

BF: the distance from the lens farthest from the object side to the image surface in the optical system;

fefl: the focal length of the entire system when the object is shot at infinity.

8. The telephoto lens system according to claim 1, wherein the third lens group includes a positive power lens and a negative power lens, and the positive power lens is located on a side of the negative power lens facing the object side.

9. The telephoto lens system according to claim 1, wherein the fourth lens group includes a positive power lens and a negative power lens.

10. An image pickup apparatus characterized by comprising a body and the intermediate telephoto lens according to any one of claims 1 to 9, the intermediate telephoto lens being mounted on the body.