JP2002244045A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact zoom lens having a variable power ratio of about 10 and suitable to be used in a digital still camera, a video camera or the like using a CCD of a high picture element type. SOLUTION: This zoom lens has four lens groups of a first lens group having positive refracting power, a second lens group having negative refracting power and moved for variable power, a third lens group having positive refracting power and a fourth lens group having positive refracting power and moved so as to correct the positional change of an image surface at the time of the variable power in this order from an object side, and has a variable power area in which the third lens group is not moved in an optical axis direction at the time of zooming and a variable power area in which the third lens group is moved in the optical axis direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, and is used for a digital still camera or a video camera. This relates to a high-magnification zoom lens.

[0002]

2. Description of the Related Art In recent years, personal computers have become widespread, and image data has been frequently handled using personal computers, and the demand for digital still cameras and the like for capturing image data has increased. These cameras require compact, high-performance, high-power zoom lenses. In order to increase the zoom ratio of the zoom lens, for example, there are methods of increasing the amount of movement of the zooming lens unit, increasing the refractive power of the zooming lens unit, and increasing the number of zooming lens units. . However, these methods have drawbacks such as an increase in the overall length of the lens and difficulty in excellent aberration correction.

A large number of zoom lenses suitable for a camera using a solid-state image pickup device such as a CCD have been disclosed in the art. For example, Japanese Patent Application Laid-Open Nos. Hei 9-236748 and Hei 9
JP-A-311272 and the like.

[0004]

However, in the embodiment of Japanese Patent Application Laid-Open No. 9-236748, although high imaging performance corresponding to a high-pixel type CCD is obtained, the zoom ratio is slightly about 3 times. It is unsatisfactory. Also, the embodiment disclosed in Japanese Patent Application Laid-Open No. 9-31272 is
Although the zoom ratio is as high as 2 ×, the imaging performance is somewhat unsatisfactory when using a high pixel type CCD.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a zoom ratio of about 10 which is suitable for use in digital still cameras, video cameras, etc. using a high-pixel type CCD. And to provide a compact zoom lens.

[0006]

The above object is achieved by the following means. That is, (1) a first lens group having a positive refractive power, a second lens group having a negative refractive power and moving for zooming, and a third lens group having a positive refractive power in order from the object side. And a fourth lens group having a positive refractive power and moving to correct a change in the position of the image plane during zooming, wherein the third lens group is positioned in the optical axis direction during zooming. A zoom lens, comprising: a variable power region that does not move in the direction of the arrow; and a variable power region in which the third lens group moves in the optical axis direction.

(2) When zooming from the wide-angle end to the telephoto end,
(1) wherein the first lens unit has two regions, a first variable power region in which the third lens group does not move in the optical axis direction, and a second variable power region in which the third lens unit moves in the optical axis direction. The zoom lens according to (1).

(3) The zoom lens according to (2), wherein the third lens group moves to the image side in the second variable magnification area.

(4) The zoom lens according to (2) or (3), wherein the second lens group and the third lens group move integrally in the second variable power range. .

(5) The zoom lens according to any one of (2) to (4), wherein the following conditional expression is satisfied in the second variable power region.

0 <| D _g3 / f ₃ | <0.5 [1] where f _{3 is} the focal length of the third lens group D _{g3 is} the third lens group (6) The zoom lens according to any one of (2) to (4), wherein the following conditional expression is satisfied in the second variable power region.

0 <| D _g3 / f ₃ | <0.1 [2] where f _{3 is} the focal length of the third lens group D _{g3 is} the third lens group (7) The zoom lens according to any one of (1) to (6), wherein upon zooming from the wide-angle end to the telephoto end, the first lens group is fixed.

Next, the zoom lens of the present invention will be described. In the zoom lens of the present invention, the first lens group having a positive refractive power, the second lens group having a negative refractive power, the third lens group having a positive refractive power, and the fourth lens having a positive refractive power The second lens group is moved in the direction of the optical axis to change the magnification from the wide-angle end to the telephoto end.
By moving the lens group, a change in the position of the image plane during zooming is corrected. Further, the third lens group has an area that is fixed during zooming and an area that is movable. As a result, it is not necessary to secure an extra space in the lens system in advance, so that the size can be reduced, and the magnification can be efficiently increased.

Also, when zooming from the wide-angle end to the telephoto end, the third
In the first variable magnification area where the lens group is fixed and in the second variable magnification area where the third lens group moves in the optical axis direction, it is preferable that the third lens group moves to the image side at the time of the second magnification change. By doing so, it is possible to secure a long moving distance of the second lens group, which is the lens group for zooming, to reduce the refractive power of the second lens group, and to reduce various aberrations generated in the second lens group. Can be smaller.

In the second zooming, it is preferable that the second lens unit and the third lens unit are integrally moved. In this way, it can be mechanically simplified.

Further, it is preferable that the first lens unit is fixed at the time of zooming from the wide-angle end to the telephoto end. By doing so, it is not necessary to move the first lens group having a relatively large lens diameter, so that power can be saved and the mechanism can be simplified.

Hereinafter, conditional expressions [1] and [2] will be described. Conditional expressions [1] and [2] are for defining the moving distance of the third lens unit at the time of the second magnification change, and are for obtaining good imaging performance while being sufficiently compact. It is. When the value exceeds the upper limit of the conditional expression, a large moving distance of the second lens unit can be secured. However, a change in various aberrations generated in the third lens unit becomes large. It will be difficult. Conditional expression [2] is more preferable than conditional expression [1].

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A zoom lens according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a lens group and a movement locus of a zoom lens according to the present invention.

As shown in FIG. 1, the zoom lens includes, in order from the object side, a first lens unit 1GL having a positive refractive power,
Second lens group 2 having negative refractive power and moving for zooming
GL, a third lens group 3GL having a positive refractive power, and
The fourth lens unit 4GL includes a fourth lens unit 4GL that has a positive refractive power and moves to correct a change in the position of the image plane during zooming.

For zooming from the wide-angle end to the telephoto end, there are two areas, a first zooming area and a second zooming area. At first,
In the movement from the wide angle end to the first variable power range, the first lens group 1G
L is fixed, and the second lens group 2GL moves. The third lens group 3GL is fixed, and the fourth lens group 4GL has a positive refractive power and moves to correct a change in the position of the image plane during zooming. Next, in the movement from the first variable power area to the second variable power area, the first lens group 1GL is fixed, and the second lens group 2GL and the third lens group 3GL move integrally to the image side. The fourth lens unit 4GL has a positive refractive power and moves to correct a change in the position of the image plane during zooming.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments relating to the zoom lens of the present invention will be described. The symbols used are as follows.

F: focal length F: F number ω: half angle of view r: radius of curvature of each lens surface d: lens thickness or lens interval n _d : refractive index ν _d : Abbe number f ₃ : third lens group _Dg3 : moving distance of the third lens group Next, the aspherical surface has an X-axis in the optical axis direction and a height in a direction perpendicular to the optical axis of h, and κ, A ₄ , A ₆ , A ₈ , A ₁₀ , and A ₁₂ are represented by the following equations when aspherical coefficients are used.

[0023]

(Equation 1)

FIGS. 2, 4 and 6 show the state of an object at infinity in the middle range, respectively. In the figure, 1G
L indicates the first lens group, 2GL indicates the second lens group, 3GL indicates the third lens group, and 4GL indicates the fourth lens group. B indicates a parallel optical block such as a filter and a CCD dust-proof glass.

(Example 1) FIG. 2 is a sectional view of a lens of Example 1, and FIG. 3 is a lens aberration diagram of Example 1 at the wide-angle end, the intermediate range, and the telephoto end. Tables 1 and 2 show lens data.

[0026]

[Table 1]

[0027]

[Table 2]

Example 2 FIG. 4 is a sectional view of a lens of Example 2, and FIG. 5 is a lens aberration diagram of Example 2 at the wide-angle end, in the middle range, and at the telephoto end. Tables 3 and 4 show lens data.

[0029]

[Table 3]

[0030]

[Table 4]

(Embodiment 3) FIG. 6 is a sectional view of a lens according to Embodiment 3, and FIG. 7 is a lens aberration diagram of Embodiment 3 at the wide-angle end, the intermediate range, and the telephoto end. Tables 5 and 6 show lens data.

[0032]

[Table 5]

[0033]

[Table 6]

[0034]

According to the above configuration, the following effects can be obtained. 10 suitable for use in digital still cameras, video cameras, etc. using a high pixel type CCD
It has a zoom ratio of about 2 times and can provide a compact zoom lens.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration and a movement locus of a lens group of a zoom lens according to the present invention.

FIG. 2 is a lens cross-sectional view of Example 1.

FIG. 3 is a lens aberration diagram at a wide angle end, an intermediate range, and a telephoto end according to the first exemplary embodiment.

FIG. 4 is a sectional view of a lens according to a second embodiment.

FIG. 5 is a lens aberration diagram at a wide angle end, an intermediate range, and a telephoto end according to a second embodiment.

FIG. 6 is a sectional view of a lens according to a third embodiment.

FIG. 7 is a lens aberration diagram at a wide angle end, an intermediate range, and a telephoto end according to a third embodiment.

[Explanation of symbols]

 1GL 1st lens group 2GL 2nd lens group 3GL 3rd lens group 4GL 4th lens group

Claims (7)

[Claims] 1. A first lens group having a positive refractive power, a second lens group having a negative refractive power and moving for zooming, and a third lens group having a positive refractive power in order from the object side. ,as well as,
A fourth lens group having a positive refractive power and moving to correct a change in the position of the image plane during zooming, wherein the third lens group does not move in the optical axis direction during zooming A zoom lens, comprising: a variable power region; and a variable power region in which the third lens group moves in an optical axis direction. 2. A first variable magnification area in which the third lens group does not move in the optical axis direction when changing magnification from a wide angle end to a telephoto end.
2. The zoom lens according to claim 1, wherein the third lens group has two regions of a second variable magnification region that moves in an optical axis direction. 3. 3. The zoom lens according to claim 2, wherein the third lens group moves to the image side in the second variable power region. 4. The zoom lens according to claim 2, wherein the second lens group and the third lens group move integrally in the second variable power region. 5. The zoom lens according to claim 2, wherein the following conditional expression is satisfied in the second variable power region. 0 <| D _g3 / f ₃ | <0.5 where f ₃ : focal length of the third lens group D _g3 : moving distance of the third lens group 6. The zoom lens according to claim 2, wherein the following conditional expression is satisfied in the second variable power region. 0 <| D _g3 / f ₃ | <0.1 where f ₃ : focal length of the third lens group D _g3 : moving distance of the third lens group 7. The zoom lens according to claim 1, wherein at the time of zooming from a wide-angle end to a telephoto end, the first lens group is fixed.