JPH11167063A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zoom lens whose photographing view angle is wide and which has high optical performance all over the variable power range while miniaturizing an entire lens system by constituting the zoom lens of five lens groups as a whole and appropriately setting the moving conditions of the respective lens groups associated with the refractive power or the variable power of the respective lens groups. SOLUTION: This zoom lens is provided with a 1st group having negative refractive power, a 2nd group having the negative refractive power, a 3rd group having positive refractive power, a 4th group consisting of a single lens having the negative refractive power and a 5th group having the positive refractive power in order from an object side. In the case of varying power from a wide angle end to a telephoto end, the lens groups are moved so that an interval between the 1st and the 2nd groups may be changed, an interval between the 2nd group and the 3rd group may be decreased, an interval between the 3rd group and the 4th group may be increased and an interval between the 4th group and the 5th group may be decreased. In order to obtain the excellent optical performance, the lens is set to satisfy 2<(d2w-d2t)/(d4w-d4t)<6 assuming that an interval between an i-th group and an (i+1)th group at the wide angle end is (diw) and an interval between the i-th group and the (i+1)th group at the telephoto end is (dit).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens having a wide angle of view suitable for a photographic camera, a video camera, an SV camera (electronic still camera), and the like. It has five lens groups,
The present invention relates to a zoom lens excellent in portability, in which the size of the entire lens system is reduced by appropriately setting the lens configurations of these five lens groups.

[0002]

2. Description of the Related Art In recent years, an electronic still camera for photographing a still image using a CCD has been required to have a small-sized and wide-angle zoom lens for a photographing lens used with the miniaturization of the whole camera.

In general, a so-called negative lead type zoom lens, which is preceded by a lens group having a negative refractive power, is relatively easy to widen the angle of view. Many are used.

For example, in JP-B-49-23912 and JP-A-57-163213, a first unit having a negative refractive power, a second unit having a positive refractive power, and a second unit having a negative refractive power are arranged in order from the object side. The zoom lens has four lens units, a third unit and a fourth unit having a positive refractive power. When the magnification is changed from the wide-angle end to the telephoto end, the first unit is moved to the image plane side, and the second unit and the fourth unit are moved. A zoom lens in which the third lens unit is fixed or moved by moving the zoom lens toward the object side has been proposed.

In Japanese Patent Application Laid-Open No. 58-4113, there are four lens units of negative, positive, negative and positive refractive power in order from the object side, and the magnification is changed by changing the air spacing of each group. A wide-angle zoom lens having a zoom ratio of about 2.5 to 3 has been proposed.

Japanese Patent Application Laid-Open No. 1-216310 proposes a zoom lens having a relatively small number of lenses having a zoom ratio of about 2 and comprising four lens units having negative, positive, negative and positive refractive powers in order from the object side. doing.

In Japanese Patent Application Laid-Open Nos. 5-313066 and 8-110470, negative, negative,
There has been proposed a zoom lens composed of five lens units having positive, negative, and positive refractive power, and performing zooming by moving each lens unit.

[0008]

In recent years, as a zoom lens used for a single-lens reflex camera, a video camera or the like, a zoom lens having a wide angle of view and a high zoom ratio has been demanded with the miniaturization of the whole camera. I have.

Generally, the angle of view at the wide-angle end is about 70 degrees,
In order to obtain a wide-angle zoom lens having a zoom ratio of about 2.5 to 3 with 7 to 8 lenses while reducing the size of the entire lens system, various aberrations associated with zooming And it is very difficult to satisfactorily correct these aberrations.

According to the present invention, in a negative lead type zoom lens in which a lens unit having a negative refractive power precedes, the zoom lens is composed of five lens units as a whole, and each lens unit is associated with the refractive power of each lens unit and zooming. By appropriately setting the group moving conditions and the like, it is possible to reduce the size of the entire lens system while maintaining a high optics over the entire zoom range with a shooting angle of view of 70 ° or more at the wide angle end and a zoom ratio of about 2.5 to 3. It is intended to provide a high-performance zoom lens.

[0011]

The zoom lens according to the present invention comprises: (1-1) a first lens unit having a negative refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power in order from the object side. Group 5, a fourth group consisting of a single lens of negative refractive power, and a fifth group 5 of positive refractive power
When changing the magnification from the wide-angle end to the telephoto end, the distance between the first and second groups changes, and the distance between the second and third groups decreases. A feature is that the lens unit is moved so that the distance between the third unit and the fourth unit increases and the distance between the fourth unit and the fifth unit decreases.

[0012]

1 to 3 are lens sectional views of Numerical Examples 1 to 3 of the present invention. In the lens sectional views, (A) shows the zoom position at the wide angle end, (B) shows the middle position, and (C) shows the zoom position at the telephoto end.

In the figure, L1 is a first group having a negative refractive power, L2 is a second group having a negative refractive power, L3 is a third group having a positive refractive power, L4 is a fourth group having a negative refractive power, L5. Represents a fifth group having a positive refractive power. SP is an aperture, G is a glass block such as an infrared cut filter, and IP is an image plane. Arrows indicate the trajectories of the movements of the respective lens units when zooming from the wide-angle end to the telephoto end.

In this embodiment, zooming is performed by changing the distance between the lens groups. In particular, during zooming from the wide-angle end to the telephoto end, the air gap between the first and second groups is maximized at an intermediate zoom position, and the air gap between the second and third groups is reduced. The lens group is moved so that the air gap between the fourth group increases and the air gap between the fourth group and the fifth group decreases. A stop SP is provided between the third and fourth units, and is moved together with the third unit during zooming.

In the present embodiment, the first lens unit is fixed during zooming, but may be moved.

In this embodiment, the first lens unit is fixed at the time of zooming from the wide-angle end to the telephoto end, and the third, fourth and fifth units are monotonously moved toward the object side. Is moved so as to have a convex locus on the image surface side. The third and fifth units are moved together during zooming. This simplifies the moving mechanism while securing a predetermined zoom ratio.

[0017] At least one aspherical surface is provided in the first or second lens unit so that aberration fluctuation during zooming can be satisfactorily corrected. Further, an aspherical surface is provided on the lens surface on the image plane side of the positive lens of the fifth group to maintain good optical performance of the entire screen. The third group includes only one or a plurality of positive lenses.

Next, the features of each numerical example will be described. In Numerical Examples 1 to 3, the lens configuration of the first group is
It consists of a negative meniscus single lens with the convex surface facing the object side.

The second lens unit includes, in order from the object side, a negative lens having a sharp lens surface on the image side and a meniscus-shaped positive lens having a convex surface facing the object side. The third group is composed of two positive lenses. The fourth unit includes a negative single lens having both lens surfaces concave.

In the first and second numerical embodiments, the lens unit of the fifth group is constituted by a single positive lens having a convex surface on the object side. In Numerical Example 3, the lens unit of the fifth unit includes, in order from the object side, a positive lens with both lens surfaces convex and a negative meniscus lens with a concave surface on the object side. In Numerical Examples 1 to 3, the lens surface on the image plane side of the positive lens in the fifth unit is formed of an aspheric surface.

The zoom lens according to the present invention can be attained by adopting the above-mentioned constitution. However, the following conditions must be satisfied in order to further facilitate a wide angle of view and obtain good optical performance over the entire zoom range. Is good.

(A-1) When the distance between the i-th lens unit and the (i + 1) -th lens unit at the wide-angle end is diw, and the distance between the i-th lens unit and the (i + 1) -th lens unit at the telephoto end is dit, 2 <(d2w-d2t) / (D4w−d4t) <6 ‥‥‥ (1).

Conditional expression (1) relates to a change in the distance between the second and third lens groups and a change in the distance between the fourth and fifth lens groups due to zooming. If the upper limit of conditional expression (1) is exceeded and the change in the distance between the second and third lens groups becomes too large, the distance between the second and third lens groups becomes large at the wide angle end, and the diameter of the front lens becomes large. Not good.

If the change in the distance between the second lens unit and the third lens unit is too small below the lower limit of conditional expression (1), it becomes difficult to secure a predetermined zoom ratio.

It is more preferable that the numerical range of the conditional expression (1) is set to 2.3 <(d2w-d2t) / (d4w-d4t) <4.5４ (1a).

(A-2) When the distance between the i-th lens unit and the (i + 1) -th lens unit at the wide-angle end is diw, and the distance between the i-th lens unit and the (i + 1) -th lens unit at the telephoto end is dit, 1.5 <(d4w / d4t) ) <15 {(2) is satisfied.

Conditional expression (2) relates to the distance between the fourth lens unit and the fifth lens unit at the wide-angle end and the telephoto end. Conditional expression (2)
If the distance between the fourth lens group and the fifth lens group at the wide-angle end is too large beyond the upper limit of the above, it is not good because the rear lens diameter increases.

If the distance between the fourth lens unit and the fifth lens unit becomes too small below the lower limit of conditional expression (2), the position of the exit pupil greatly changes during zooming, which is not good. It is more preferable that the numerical range of the conditional expression (2) is set to 3 <(d4w / d4t) <12１２ (2a).

(A-3) When the distance between the i-th lens unit and the (i + 1) -th lens unit at the wide-angle end is diw, and the distance between the i-th lens unit and the (i + 1) -th lens unit at the telephoto end is dit, 0.3 <(d1w / d1t) ) <0.9 (3).

Conditional expression (3) relates to the ratio of the distance between the first lens unit and the second lens unit at the wide-angle end and the telephoto end. If the distance between the first lens unit and the second lens unit at the wide-angle end exceeds the upper limit of conditional expression (3), the front lens diameter increases, which is not good. If the distance between the first lens unit and the second lens unit at the telephoto end exceeds the lower limit value of the conditional expression (3), the total length increases, which is not good.

It is more preferable that the numerical range of the conditional expression (3) is set to 0.4 <(d1w / d1t) <0.6０．６ (3a).

Next, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air spacing from the object side, and Ni and νi are the i-th lens surfaces in order from the object side. The refractive index and Abbe number of glass. The aspheric surface shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the traveling direction of light is positive, R is the paraxial radius of curvature, and A, B, C, D, and E are aspherical coefficients, respectively. When

[0033]

(Equation 1) It is represented by the following equation.

Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples.

[0035]

[Outside 1]

[0036]

[Outside 2]

[0037]

[Outside 3]

[0038]

[Table 1]

[0039]

As described above, according to the present invention, a negative lead type zoom lens which is preceded by a lens group having a negative refractive power has a zoom lens composed of five lens groups as a whole. By appropriately setting the moving conditions of each lens group according to the power and zooming, it is possible to reduce the size of the entire lens system and to achieve a total zooming ratio of about 2.5 to 3 with a shooting angle of view of 70 ° or more. A zoom lens having high optical performance over the double range can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 2 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 3 is a sectional view of a lens according to a numerical example 3 of the present invention.

FIG. 4 is an aberration diagram at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 5 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 6 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention;

FIG. 7 is an aberration diagram at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 8 is an intermediate aberration diagram of the numerical example 2 of the present invention.

FIG. 9 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention;

FIG. 10 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 11 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 12 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

[Explanation of symbols]

 L1 First lens unit L2 Second lens unit L3 Third lens unit L4 Fourth lens unit L5 Fifth lens unit SP Aperture F Image plane d d line g g line ΔS Sagittal image plane ΔM Meridional image plane

Claims (13)

[Claims] A first lens unit having a negative refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit including a single lens having a negative refractive power. The zoom lens has five lens units, a fifth lens unit having a positive refractive power, and at the time of zooming from the wide-angle end to the telephoto end, the distance between the first unit and the second unit changes. The distance between the third group is reduced, the distance between the third group and the fourth group is increased, and the distance between the fourth group and the fifth group is moved so that the lens groups are moved. And zoom lens. 2. The apparatus according to claim 1, wherein an interval between the first and second groups is maximum at an intermediate zoom position.
Zoom lens. 3. The zoom lens according to claim 1, further comprising a stop between said third group and said fourth group. 4. The zoom lens according to claim 3, wherein the first group or the second group has at least one aspheric surface. 5. The zoom lens according to claim 4, wherein said third group includes only one or a plurality of positive lenses. 6. The zoom lens according to claim 5, wherein said stop moves integrally with said third lens unit in accordance with zooming. 7. The zoom lens according to claim 1, wherein the first lens unit is fixed during zooming. 8. The zoom lens according to claim 1, wherein the third unit and the fifth unit move integrally during zooming. 9. The zoom lens according to claim 1, wherein the fifth unit includes a single lens whose lens surface on the image plane side is an aspherical surface. 10. When the distance between the i-th lens unit and the (i + 1) -th lens unit at the wide-angle end is diw, and the distance between the i-th lens unit and the (i + 1) -th lens unit at the telephoto end is dit, 2 <(d2w−d2t) / (d4w−). The zoom lens according to any one of claims 1 to 9, wherein d4t) <6 is satisfied. 11. When the distance between the i-th lens unit and the (i + 1) -th lens unit at the wide angle end is diw, and the distance between the i-th lens unit and the (i + 1) -th lens unit at the telephoto end is dit, 1.5 <(d4w / d4t) <15 11. The zoom lens according to claim 1, wherein the following condition is satisfied. 12. When the distance between the i-th lens unit and the (i + 1) -th lens unit at the wide-angle end is diw, and the distance between the i-th lens unit and the (i + 1) -th lens unit at the telephoto end is dit, 0.3 <(d1w / d1t) <0 The zoom lens according to any one of claims 1 to 10, wherein the following formula is satisfied. 13. The zoom lens according to claim 1, wherein the zoom ratio is 2.2 or more.