JPS6177818A - Zoom lens - Google Patents

Abstract

PURPOSE:To execute satisfactorily aberration correction and to provide a compact lens by adopting two different zoom systems for one zoom lens thereby expanding the variable power range thereof. CONSTITUTION:The 1st variable power is executed by moving respectively the 1st lens groups having positive refracting power and the 3rd lens group having positive refracting power to an object side and the 2nd lens group having negative refracting power to the image plane side respectively. As a result the higher rate of variable power is attained by assisting the variable power effect of the 2nd lens group and executing effectively the variable power in the zoom system in which the variable is executed by changing the spacing between the respective lens groups. The 2nd variable power is executed in the zoom position at the wide angle end by moving integrally the 1st lens group and the 2nd lens group to the object side and moving the 3rd lens group and 4th lens group respectively at different speeds to the respective image plane sides. The 1st lens group and 2nd lens group are so formed as to have the overall negative refracting power and the zoom lens is constituted overall of the three lens groups having negative, positive and positive refracting powers by which the 2nd variable power is executed. Such constitution is preferable to decrease the fluctuation in the aberration and to provide the prescribed variable power ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zoom lens, and more particularly to a high-power zoom lens that uses two zoom systems and is suitable for still cameras, cine cameras, video cameras, and the like.

Recently, zoom lenses with high zoom ratios have been required not only for TV cameras but also for general cameras. In order to achieve a high variable power zoom lens, for example, increase the amount of movement of the variable power lens group, or increase the refractive power of the variable power lens group by increasing the number of movable lens groups in the variable power lens group. There are ways to increase and reduce it.

However, these methods have drawbacks such as increasing the total length of the lens and making it difficult to perform good aberration correction.

In addition, K to further expand the magnification ratio by changing the magnification beyond the normal variable @ range is (a) replacing all or part of the imaging lens located behind the variable magnification lens with another lens ( b) Moving some of the lenses in the 4M+* lens (・→ inserting lenses inside the imaging lens or front and rear 1c lenses) 1/1 for focusing in front of the variable magnification lens
/ Noz group k (method of exchanging with BJ lens group) Zoom 1
/Method of attaching the converter lens to the front of the nozzle>7 is r). Is the method of [1] and et al. simply based on the focal length? For example, (a), (/
i.

Methods (ii) and (e) require ease of use during f-fold magnification, the need to prepare lenses for variable magnification, etc., and methods (b).
The disadvantage of this method is that the total length of the AJ image lens becomes longer, making the entire zoom lens larger.

Invention 1: Extra space in the lens system? Is it necessary to secure it and expand the magnification efficiently? [J] is the provision of a striped magnification zoom lens that can be used with [J].

Furthermore, it is an object of the present invention to provide a compact zoom lens whose zoom range is expanded from the wide-angle end to the wide-angle side.

The main features of the zoom lens for achieving the purpose of the present invention are: from the object side, from jlo, the first lens group has a positive refractive power, the second lens group has a negative refractive power, and the third lens group has a positive refractive power. The fourth lens group has a positive refractive power, and the interval between the four lens groups is changed to achieve the first magnification change. conduct,
The first lens cup and the second lens group are integrally moved on the optical axis from a zoom position at a wide-angle end, and the third lens group and the fourth lens group are each moved on the optical axis at different speeds. The first thing to do is to use V2 magnification to make the angle of view wider.

Next, a cross-sectional view of a lens according to an embodiment of the present invention is shown in FIG. In the same figure, 1, 11. ill, lV are the 11th, 2.8g3, and 4th lens groups, respectively, the arrows indicate the movement direction of each lens group during zooming, ■ indicates the first zooming state, and ■WW indicates the second zooming state. show.

In this example, the first lens group with positive refractive power and the third lens group with positive refractive power are moved toward the object side, and the second lens group with negative refractive power is moved toward the image plane side to achieve the first change. We're doing double that.

In this way, by moving the FG lens group toward the object side, moving a total of three lens groups, and changing the interval between each V lens group as a result of this zooming method, the second lens group can be moved.
It promotes the variable power effect of the lens group to efficiently change the power and achieve a high variable power ratio.

Then, at the wide-angle end zoom position, the first lens group and the second lens group
The j:v second magnification change is performed by moving the lens groups integrally toward the object side, with the third lens group and the fourth lens group 1 moving toward the image plane at different speeds. By adopting such a zoom system, we have achieved a zoom lens with minimal fluctuations in aberrations, a short overall lens length, and a concisely wide angle of view. In particular, in this example, the third and fourth lens groups are moved at different speeds, and the total lens groups of 3 degrees are moved independently, thereby increasing the diopter for aberration correction and increasing the magnification over the entire magnification range. 9. Good Maruji performance is 1 stop. Further, in this embodiment, since the second magnification change is performed by using the empty space above the zoom position at the wide-angle end, there is a feature that the basic overall length of the lens is not enlarged.

In this actual power mv11, the first lens group and the second lens group are set so that the total refractive power of both lens groups is negative, and the overall refractive power is composed of three lens groups with negative, positive, and positive refractive powers. It is preferable to perform the second magnification change in this manner in order to reduce aberration fluctuations and obtain a predetermined magnification ratio.

In this embodiment, the second magnification change may be performed by swJing each lens group so that the image plane coincides with the image plane at the 1f magnification only at the so-called super wide-angle end zoom position at the end of the magnification change. good. Eliminating the need for the intermediate region of the second magnification change in this way is preferable because it becomes possible to move all the valley lens groups in a straight line VC, and it also makes it easier to eliminate aberrations.

The object of the present invention is achieved by satisfying the above-mentioned conditions. More preferably, the amount of movement of the third lens group and the tA4 lens group in @22 variation is
, '4, then 0, 1 <t3/ t4<0.9...
(1) The condition is to move so that t-S is added.

Such a configuration is particularly effective, for example, when the aperture stop is located between the third V7 lens group and the fourth lens group. That is, if the third lens group and the fourth lens group are simply moved to the image IfiIil11, astigmatism becomes insufficiently corrected at the @l end as the magnification changes. Therefore, by moving the third lens group less than the fourth lens group, deterioration of astigmatism can be prevented. If the upper limit of the conditional expression fl+ is exceeded, the correction of astigmatism at this time will be insufficient, and if the lower limit is exceeded, the astigmatism will be overcorrected. The amount of movement of the 2 and 's4 lens groups must be increased, and as a result, the diameter of the front lens and the total length of the lens increase, which is not preferable.

In the present invention, in order to achieve good aberration correction over the entire first and second magnification changes, the third lens # is composed of three lenses with negative, positive, and positive refractive powers, and the second
Lens group tlL, three lenses with negative and positive refractive power,
It is preferable that the third lens # is composed of two lenses having positive and negative refractive powers.

Further, in the present invention, it is preferable to perform one focusing by moving the ml lens group, since the fluctuation of aberrations is small.

Next, numerical examples of the present invention will be shown. In numerical examples,
RI is the radius of curvature of the first lens from the object side, Di is the thickness and air gap of the first lens from the object side, and Ni and νi are the radius of curvature of the first lens from the object side, respectively.
These are the refractive index and Atsube number of the glass of the th lens.

This numerical value is implemented and smells (focal length of ml magnification is lOO
~290, and the focal length of the second variable magnification is 100~69.

As described above, according to the present invention, one zoom reflex camera (Il
? : Variable f by adopting two different zoom methods.
It is possible to achieve a compact zoom lens that enlarges the field of view and corrects all aberrations well.

Numerical Example f-69-100~300 FNO-1162ω-a
tg'-zt4°~&gi R1-111, 8801-Z86 N 1-1.
80518 v 1-25.4R2-70,93
D 2-7.06 N 2-1.51633
ν 2-641R3-6607, 27D 3-0
．． 20n 4- 123.63 D 4-4.
66 N 3-1.43749 v 3-
70. IR5--f979.4Q D 5-1 Engineering R6
--165.22 D 6-1.48 N
4-1.713QOy 4-53.8R7-60,
1907-5,61 R8--6&G2 D 8-1.50 N
5-1.69680 ν 5-55.5R9-4
1,2509-4,43N 6-1.80518
v 6-25.41 members 0-580.21 F)
10zu2R11= 104.40 Dll-7,
00N? =1.52301 v 7-50.
8nL2=-30,98012-207N 8-
1.80518y 8-25-. 4R13--
56, li6 D13-43 ■ Member 4- Diaphragm Li Di
4-1.97 1 circle 15- 24.23 1115-8.47
8 9-1.60311 ν 9-60.71t1
6--304.22 Di6-1.48 8IO
1,77250ylO”49.6R17-73,54L
)17-1.18ais-41,θl Di8-1
．． 97 Ni1-1゜83400 Shi11-3
7.2R19-15, 56019-6, 88N12-1
．． 60729 v12-49.21t21)-54
, 65D20-5.34R21-5519, 93021
-145N13-1.57501 Shi13-4L5
R22--47,97D22-5.32R23=-
20,93D23-0.99 N14-L8Q40
0 y14-4 & 6R24= 27.35 D
24-5.29 N15-1.61293 y1
5=37.0R25--3&38t3/t40.25

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a lens in a numerical example of the present invention, Figures 2-
FIG. 5 shows various aberration diagrams of numerical examples of the present invention. 1 in the figure. n, II[, Il/l/previous 1st, ag 2
, the third and fourth lens groups, IWT and lWW are the first and second variable magnification ranges, ΔS is the sagittal image plane, and 6M is the meridional image plane, respectively. Figure 2 shows

Claims (1)

[Claims] (1) In order from the object side, the first lens group has a positive refractive power, the second lens group has a negative refractive power, the third lens group has a positive refractive power, and the fourth lens group has a positive refractive power. It has four lens groups,
Performing a first magnification change by changing the intervals between the four lens groups, moving the first lens group and the second lens group together on the optical axis from the wide-angle end zoom position, and moving the first lens group and the second lens group together on the optical axis from the wide-angle end zoom position, A zoom lens characterized in that the second zooming is performed by moving the fourth lens group on the optical axis at different speeds. (2) In the second variable magnification, the first lens group and the second lens group are moved toward the object side, and the third lens group and the fourth lens group are moved toward the object side.
A patent characterized in that both lens groups are moved toward the image plane so that the following condition is satisfied: 0.1<t_3/t_4<0.9, where the amount of movement of the lens groups is t_3 and t_4, respectively. A zoom lens according to claim 1.