CN106950683B

CN106950683B - Long focus lens

Info

Publication number: CN106950683B
Application number: CN201710297598.9A
Authority: CN
Inventors: 叶波; 徐毅; 杨志全
Original assignee: Shenzhen Dongzheng Optical Technology Co Ltd
Current assignee: Shenzhen Dongzheng Optical Technology Co Ltd
Priority date: 2017-04-28
Filing date: 2017-04-28
Publication date: 2022-10-11
Anticipated expiration: 2037-04-28
Also published as: CN106950683A

Abstract

The invention discloses a telephoto lens, which has a first lens with positive focal power, and optical axes of the first lens are distributed in sequence from an object side to an image side; a second lens having a positive optical power; a third lens having a negative optical power; a fourth lens having a negative optical power; the telephoto lens satisfies: 0.55 and are woven into fabric EFL/TTL <1.65, wherein EFL is the effective focal length of the system, and TTL is the total optical length of the system. The telephoto lens of the invention realizes focusing by moving a single group of lenses, has good distortion and aberration control, short length, few lenses, small focusing load, easy guarantee of focusing speed, small lens volume and low cost, and is a good choice for consumers.

Description

Long focus lens

Technical Field

The invention relates to the field of optical devices, in particular to a telephoto lens.

Background

At present, a large number of lenses are introduced into a known telephoto lens with a drawing angle smaller than 20 degrees, so that the number of lenses is large, the focusing load is large, the focusing speed is not well guaranteed, and particularly, the lens is large in size and high in cost, so that a great burden is caused to consumers.

Disclosure of Invention

The invention aims to provide a telephoto lens which can correct various aberrations, has good imaging effect and high cost performance, realizes focusing by a single group of lenses, has small volume and easily ensures focusing speed.

The present invention provides a telephoto lens, whose optical axes are distributed in sequence from an object side to an image side,

a first lens having a positive optical power;

a second lens having a positive optical power;

a third lens having a negative optical power;

a fourth lens having a negative optical power;

the telephoto lens satisfies: 0.55 plus EFL/TTL <1.65, wherein EFL is the effective focal length of the system, and TTL is the optical total length of the system.

Further, the optical lens also comprises a fifth lens with positive focal power, and the fourth lens is fixedly glued with the fifth lens.

Further, the fourth lens and the fifth lens are fixedly glued to form a floating focusing lens group, and the floating focusing lens group meets the following requirements: 0.05 and < -L/H <0.15, wherein L is the total lens stroke, and H is the system image plane size.

Furthermore, at least one of the first lens, the second lens and the floating focusing lens group satisfies the following conditions: 1.42< -n < -1.62 and 65< lambda <95, wherein n is the refractive index of glass and lambda is the Abbe number of the glass.

Further, a diaphragm is arranged between the third lens and the fourth lens.

Further, the system of the telephoto lens satisfies: 0.6 and is composed of FE/EFL <0.8, wherein FE is the whole group focal length of all lenses in front of the diaphragm of the system, and EFL is the effective focal length of the system.

And a sixth lens having negative refractive power and disposed on a side of the fifth lens.

And a seventh lens having negative refractive power, which is provided on a side of the sixth lens.

And an eighth lens having positive refractive power, which is provided on a side of the seventh lens.

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

the telephoto lens of the invention realizes focusing by moving a single group of lenses, has good distortion and aberration control, short length, few lenses, small focusing load, easy guarantee of focusing speed, small lens volume and low cost, and is a good choice for consumers.

Drawings

Fig. 1 is a schematic structural diagram of a telephoto lens according to an embodiment of the present invention.

Fig. 2 is a graph of chromatic aberration on an axis of a telephoto lens according to an embodiment of the present invention.

Fig. 3 is a telephoto lens astigmatism graph according to an embodiment of the invention.

Fig. 4 is a distortion curve diagram of a telephoto lens according to an embodiment of the present invention.

Fig. 5 is a chromatic aberration of magnification curve of a telephoto lens according to an embodiment of the present invention.

Detailed Description

For further explanation of the principles and construction of the present invention, reference will now be made in detail to the preferred embodiments of the present invention, which are illustrated in the accompanying drawings.

Referring to fig. 1, the optical axes of the telephoto lens are sequentially distributed from the object side to the image side:

the object side surface of the first lens 1 with positive focal power is a convex surface, the first spherical surface of the first lens 1 is a convex surface, and the second spherical surface is a convex surface.

The object side surface of the second lens 2 with positive focal power is a convex surface, the third spherical surface of the second lens 2 is a convex surface, and the fourth spherical surface is a concave surface.

The object side surface of the third lens 3 with negative focal power is a concave surface, the third lens 3 is a concave surface, and the sixth spherical surface is a concave surface.

The object side surface of the fourth lens 4 with negative focal power is a convex surface, the seventh aspheric surface of the fourth lens 4 is a convex surface, and the eighth spherical surface is a concave surface.

The fifth lens 5 with positive focal power has a convex object-side surface, a convex ninth spherical surface and a concave tenth spherical surface of the fifth lens 5.

The sixth lens element 6 with negative refractive power has a convex object-side surface, the eleventh spherical surface of the sixth lens element 6 is a convex surface, and the twelfth spherical surface is a concave surface.

The seventh lens element 7 with negative refractive power has a concave object-side surface, a concave thirteenth spherical surface and a convex fourteenth spherical surface, respectively, of the seventh lens element 7.

The object side surface of the eighth lens 8 with positive focal power is a convex surface, the fifteenth spherical surface of the eighth lens 8 is a convex surface, and the sixteenth spherical surface is a convex surface.

Wherein, the eighth spherical surface of the fourth lens 4 and the ninth spherical surface of the fifth lens 5 are cemented. Namely, the fourth lens 4 is fixedly cemented with the fifth lens 5.

The fourth lens 4 and the fifth lens 5 are fixedly glued to form a floating focusing lens group, and the floating focusing lens group meets the following requirements: and 0.05 and < -L/H <0.15, wherein L is the total lens stroke, and H is the size of the system image surface 9.

The first lens 1, the second lens 2 and the floating focusing lens group have at least one lens satisfying the following conditions: 1.42< -n < -1.62 and 65< lambda <95, wherein n is the refractive index of glass and lambda is the Abbe number of the glass.

A diaphragm 10 is arranged between the third lens 3 and the fourth lens 4.

The system of the telephoto lens satisfies: 0.6 and is composed of FE/EFL <0.8, wherein FE is the whole group focal length of all lenses in front of the diaphragm of the system, and EFL is the effective focal length of the system.

For example, a specific telephoto lens has the following system parameters: TTL =60.5; EFL =72.5; h =21.6; f/# =2.4. The thickness column has a value of "/" before the interval at infinity, and "/" after the interval at the latest focus.

Fig. 2 is an on-axis chromatic aberration diagram of the telephoto lens according to the embodiment of the present invention, where the on-axis chromatic aberration diagram indicates the degree of deviation of different wavelength bands from ideal image plane positions in different pupil bands. The horizontal axis represents offset and the vertical axis represents normalized pupil band. Looking primarily at the smallest offset for all wavelengths near the 0.707 pupil band, the distance on the horizontal axis from the intersection of the wavelengths of the 0.84 pupil band 435.8nm and 656.3nm to the 486.1nm wavelength is about 0.04mm as in this figure.

Fig. 3 is an astigmatism graph of a telephoto lens according to an embodiment of the invention. Astigmatism represents the degree of deviation of the image field from the ideal image field in the design meridional and sagittal directions. The horizontal axis represents the offset amount, and the vertical axis represents the half-image height. If the image field deviation of the image system is within 0.06 in the whole field of view, the maximum deviation of the meridional and sagittal curves is about 0.04.

Fig. 4 is a distortion curve diagram of a telephoto lens according to an embodiment of the present invention. The distortion map represents the difference between the actual image height and the ideal image height. The horizontal axis represents the distortion percentage and the vertical axis represents the half-image height. It can be seen that the distortion of the system is within 0.5%, and the human eye generally cannot distinguish the distortion of the photographed object.

Fig. 5 is a graph illustrating a chromatic aberration of magnification of the telephoto lens according to the embodiment of the present invention. From this figure the total field of view of the system is at most around 14 microns.

The telephoto lens of the invention realizes focusing by moving a single group of lenses, has good distortion and aberration control, short length, few lenses, small focusing load, easy guarantee of focusing speed, small lens volume and low cost.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings are included in the present invention.

Claims

1. A telephoto lens having optical axes sequentially distributed from an object side to an image side,

a first lens having a positive optical power;

a second lens having a positive optical power;

a third lens having a negative optical power;

a fourth lens having a negative optical power;

the fourth lens is fixedly glued with the fifth lens;

a sixth lens having a negative refractive power provided on a side of the fifth lens image;

a seventh lens having a negative refractive power provided on a side of the sixth lens image;

an eighth lens with positive focal power arranged on the side of the seventh transmission mirror image;

the telephoto lens satisfies: 0.55 and straw EFL/TTL is less than 1.65, wherein EFL is the effective focal length of the system, and TTL is the total optical length of the system;

the fourth lens and the fifth lens are fixedly glued to form a floating focusing lens group, and the floating focusing lens group meets the following requirements: 0.05-plus L/H <0.15, wherein L is the total stroke of the lens, and H is the size of a system image surface;

the first lens with positive focal power has a convex object-side surface and a convex image-side surface;

the number of lenses having optical power was 8.

2. The telephoto lens system as claimed in claim 1, wherein at least one of the first lens element, the second lens element, and the floating focus lens group satisfies: 1.42-n-woven fabric (1.62) and 65-lambda <95, wherein n is the refractive index of glass and lambda is the Abbe number of glass.

3. The telephoto lens according to claim 1, wherein a stop is disposed between the third lens and the fourth lens.

4. A telephoto lens according to claim 3, wherein the system of the telephoto lens satisfies: 0.6 and is composed of FE/EFL <0.8, wherein FE is the whole group focal length of all lenses in front of the diaphragm of the system, and EFL is the effective focal length of the system.