JPH09159918A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the zoom lens which includes a wide-angle range and has a large power variation ratio and is made short in both lens diameter and overall lens length so that it is suitably mounted on a compact camera, etc., and superior in image forming performance. SOLUTION: This lens consists of a 1st lens group 1 with negative refracting power, a 2nd lens group 2 with positive refracting power, a 3rd lens group 3 with negative refracting power, a 4th lens group 4 with positive refracting power, and a 5th lens group 5 with negative refracting power in order from an object side. In this case, the intervals between the 1st lens group 1 and 2nd lens group 2, 2nd lens group 2 and 3rd lens group 3, and 4th lens group 4 and 5th lens group are made smaller at the telephoto end than at the wide-angle end while the interval between the 3rd lens group 3 and 4th lens group 4 is made larger; and a conditional expression of 3.6<=m5 T<=6.5 is met (m5T is the lateral power of the 5th lens group 5 at the telephoto end).

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 more particularly to a zoom lens suitable for a compact camera and including a wide angle range and a large zoom ratio.

[0002]

2. Description of the Related Art As a zoom lens for a lens shutter type compact camera, there have been many applications concerning a high zoom lens having a zoom ratio of 3 or more including a wide angle range, which is composed of 4 or more zoom groups.

Most of these zoom lenses have a zoom group having a negative refracting power on the most object side and the most image side, so that they have a structure suitable for widening the angle and compactness.

For example, the zoom lens described in each embodiment of Japanese Patent Laid-Open No. 3-240015 has a negative first lens group, a positive second lens group, and a positive third lens group in order from the object side. It consists of a negative fourth lens group, and the angle of view at the wide-angle end is 7
It has a zoom ratio of 4.7 times at 4 degrees.

The zoom lens described in Example 1 of Japanese Patent Laid-Open No. 7-151974 has a negative first lens group, a positive second lens group, a negative third lens group, and a positive third lens group in order from the object side. In the telephoto end, the distance between the first lens group and the second lens group and the distance between the fourth lens group and the fifth lens group are reduced at the telephoto end compared to the wide-angle end. It is a zoom lens in which the distance between the second lens group and the third lens group and the distance between the third lens group and the fourth lens group are widened, and a zoom ratio of 3.5 is achieved when the angle of view at the wide-angle end is 74 degrees. Have.

[0006]

However, Japanese Patent Laid-Open Publication No. Hei 3-2
The zoom lens described in each example of Japanese Patent No. 40015 has
According to the lens sectional view, the diameter of the front lens is larger than the diagonal length of the screen, and a more compact structure is desired for use in a compact camera. The zoom lens described in Example 1 of JP-A-7-151974 is desired to have a higher zoom ratio of, for example, 4 times or more. As described above, the conventional high zoom zoom lens for a compact camera including a wide angle range is required to be further improved in terms of both compactness and a zoom ratio.

The present invention includes a wide angle range, has a large zoom ratio, and has a compact lens diameter and overall lens length suitable for mounting on a compact camera or the like, and
The objective is to obtain a zoom lens with excellent imaging performance.

It is another object of the present invention to provide the zoom lens described above with a small number of lenses of 10 or less.

Further, the present invention satisfies the above-mentioned object, and an object thereof is to obtain a zoom lens suitable for a camera using a roll film of 24 mm width having a photographing image frame whose diagonal length is in the range of 33 mm to 36 mm. There is.

[0010]

A zoom lens according to the present invention comprises, in order from the object side, a first lens group having negative refracting power, a second lens group having positive refracting power, a third lens group having negative refracting power, and positive refracting power. It is composed of a fourth lens group having a power and a fifth lens group having a negative refractive power, and the movement of each lens group acts as follows.

First, in the zoom lens of the present invention, the first lens group and the second lens group, the second lens group and the third lens group, the fourth lens group and the fifth lens group at the telephoto end are compared with those at the wide-angle end. The distance between each of the third lens group and the fourth lens group increases, and the distance between the third lens group and the fourth lens group increases.

The change in the distance between the first lens group and the second lens group and the change in the distance between the fourth lens group and the fifth lens act on the magnification change.

The change in the distance between the second lens group and the third lens group and the change in the distance between the third lens group and the fourth lens group are
It is possible to suppress fluctuations due to zooming, such as astigmatism and coma.

Furthermore, the zoom lens of the present invention satisfies the following conditional expression.

3.6 ≦ m _5T ≦ 6.5, where m _5T : lateral magnification of the fifth lens group at the telephoto end The above conditional expression defines the lateral magnification of the fifth lens group at the telephoto end, If this lower limit is not reached, it will be difficult to shorten the total lens length including the high zoom ratio and the lens back at the telephoto end.
On the other hand, if the upper limit is exceeded, it will be difficult to correct various aberrations such as excessive spherical aberration that occurs at the telephoto end in the fifth lens group and astigmatism in the direction of overcorrection.

Further, it is desirable that the zoom lens of the present invention satisfies the following conditional expression.

−0.30 ≦ f ₅ / f _T ≦ −0.12 ... 0.30 ≦ Δt / f _W ≦ 0.60, where f ₅ : focal length of the fifth lens group f _W : Focal length of the entire system at the wide-angle end f _T : focal length of the entire system at the telephoto end Δt: difference between the wide-angle end and the telephoto end in the distance between the first lens group and the second lens group If the focal length of the lens group is specified and if the lower limit of this is not satisfied, a large number of lenses are required to correct the aberration. If the upper limit is exceeded, it is difficult to shorten the total lens length including the lens back at the telephoto end.

The above conditional expression is the first in zooming.
If the change in the distance between the lens group and the second lens group is specified and if the lower limit is not exceeded, the change in the lateral magnification of the second lens group during zooming becomes small, making it difficult to achieve a high zoom ratio. Moreover, if the upper limit is exceeded, the diameter of the front lens becomes excessively large.

Further, in the zoom lens of the present invention, the lens barrel structure can be simplified by moving the second lens group and the fourth lens group integrally during zooming.

In the zoom lens according to the present invention, the second lens group, the third lens group,
By moving the fourth lens group integrally or by moving the fifth lens group, focusing can be performed without increasing the front lens diameter.

Further, in the zoom lens of the present invention, it is desirable that the following conditional expression is satisfied.

85 mm ≦ L _T ≦ 125 mm, where L _T : total lens length including the lens back at the telephoto end The above conditional expression includes the lens back at the telephoto end suitable for the new film standard with a film width of 24 mm. It defines the total lens length. This film standard is described in, for example, December 11, 1994, page 11 of "Photo Industry", and has three screen size formats having a screen size smaller than that of a conventional 35 mm width roll film. . The diagonal length of the image frame of this film is in the range of 33 mm to 36 mm.

If the lower limit of the conditional expression is not satisfied, it becomes difficult to correct aberration when the zoom ratio is high, and it is difficult to obtain a zoom ratio of, for example, about 4 times. If the upper limit is exceeded, it will be difficult to obtain a compact camera that takes advantage of the characteristics of this film.

Further, the above conditional expressions (1) to (4) will have more preferable effects by limiting as follows.

4.0 ≦ m _5T ≦ 6.0 −0.22 ≦ f ₅ / f _T ≦ −0.15 0.35 ≦ Δt / f _W ≦ 0.46 Further, the aperture position of the zoom lens is the first position. 2 lens group, 3rd
It is preferable for the lens type to be located inside or in the vicinity of each of the lens group and the fourth lens group, and in the embodiments described later, the diaphragm is placed on the object side of the third lens group.

With the above operation, in the zoom lens according to the present invention, especially the second lens group and the fourth lens group can be configured with a small number of lenses, and as a result, the number of lenses of the entire system can be reduced.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a change in the distance between the second lens group and the third lens group and a change in the distance between the third lens group and the fourth lens group will be described in detail.

The distance between the second lens group and the third lens group is
By expanding, the astigmatism changes in the direction of overcorrection. Not limited to the present invention, in general, a zoom lens for a compact camera, which has a negative power with a strongest zoom component on the image side and performs zooming by this movement, in a zoom lens for a compact camera, the zoom lens moves relatively during zooming. As a result, astigmatism tends to change in the overcorrection direction on the telephoto side compared to the wide-angle side. Therefore, in the present invention, by widening the distance between the second lens unit and the third lens unit on the wide-angle side, the distance is relatively overcorrected compared to the telephoto side,
This compensates for the change in astigmatism due to the movement of the fifth lens group described above during zooming.

Further, the change in the distance between the third lens group and the fourth lens group acts on the correction of coma. When the distance between the second lens group and the third lens group and the distance between the third lens group and the fourth lens group are increased, the coma aberration changes in a relatively inward direction. Therefore, the change in the inward direction of the coma aberration caused by widening the distance between the second lens group and the third lens group on the wide-angle side expands the distance between the third lens group and the fourth lens group on the telephoto side. Caused by
It is possible to compensate for changes in coma aberration due to zooming.

[0030]

EXAMPLES Three types of examples relating to the zoom lens of the present invention are shown below.

In the second and third embodiments, the diagonal length is 33.
24m with shooting frame in the range of mm to 36mm
It is an example of a zoom lens suitable for a camera using an m-width roll film.

The meanings of the reference numerals in each embodiment are as follows.

F: focal length F: F number ω: half angle of view r: radius of curvature of refracting surface d: surface spacing _nd : refractive index of d-line of lens material ν _d : Abbe number of lens material Is indicated by "*", and the shape of the aspherical surface is expressed by the following equation.

[0034]

[Equation 1]

Where X is the apex of the aspherical surface as the origin, and the coordinates from the object side to the image side along the optical axis Y are the apices of the aspherical surface as the origin and the coordinates K, A _i , P _i : aspherical surface coefficient In the aspherical surface coefficient, “D + j” is “× 10 ^j ”,
“D-j” represents “× 10 ^−j ”.

Example 1 Table 1 shows lens data when f = 28.8 to 131.2, F = 3.9 to 10.0, 2ω = 76.0 ° to 18.6 °, and a lens sectional view. Is shown in FIG.

The lens groups composed of the first to fourth surfaces are the first lens group, the lens groups composed of the fifth to seventh surfaces are the second lens group, and the eighth surfaces to First
The lens group composed of one surface is the third lens group, the lens group composed of the twelfth to thirteenth surfaces is the fourth lens group,
The lens group including the 14th to 18th surfaces is referred to as a fifth lens group.

[0038]

[Table 1]

Table 2 shows the surface spacing of each lens group which varies according to the change in focal length.

[0040]

[Table 2]

Table 3 shows the aspherical surface coefficients.

[0042]

[Table 3]

Further, an aberration diagram is shown in FIG.

[Embodiment 2] Table 4 shows lens data when f = 23.1 to 89.4 F = 3.90 to 9.60 2ω = 75.8 ° to 21.8 °. Is shown in FIG.

The lens groups consisting of the first to fourth surfaces are the first lens group, the lens groups consisting of the fifth to sixth surfaces are the second lens group, and the seventh surface to the seventh surface. First
A lens group composed of 0 surface is a third lens group, a lens group composed of 11th to 12th surfaces is a 4th lens group,
A lens group including the 13th to 16th surfaces is referred to as a fifth lens group.

[0046]

[Table 4]

Table 5 shows the surface spacing of each lens group which varies according to the change in focal length.

[0048]

[Table 5]

Table 6 shows the aspherical surface coefficients.

[0050]

[Table 6]

Further, an aberration diagram is shown in FIG.

[Embodiment 3] Table 7 shows lens data when f = 23.1 to 116.3 F = 3.9 to 10.0 2ω = 75.2 ° to 16.8 °, and FIG. Is shown in FIG.

The lens groups composed of the first to fourth surfaces are the first lens group, the lens groups composed of the fifth to sixth surfaces are the second lens group, and the seventh surface to the seventh surface. First
A lens group composed of 0 surface is a third lens group, a lens group composed of 11th to 12th surfaces is a 4th lens group,
The lens group including the thirteenth to seventeenth surfaces is referred to as a fifth lens group.

[0054]

[Table 7]

Table 8 shows the surface spacing of each lens group which varies according to the change in focal length.

[0056]

[Table 8]

Table 9 shows the aspherical surface coefficients.

[0058]

[Table 9]

Further, an aberration diagram is shown in FIG.

Next, the conditional expressions in each of the above embodiments
The numerical values corresponding to are summarized in Table 10.

[0061]

[Table 10]

Regarding focusing from an infinitely distant subject to a short-distance subject, the fifth embodiment is used.
Good focusing can be achieved by moving the lens group to the image side, and in the second and third examples, moving the second lens group, the third lens group and the fourth lens group as a unit to the object side.

[0063]

According to claims 1 to 6, a wide-angle range is included,
It is possible to obtain a zoom lens having a large zoom ratio and a compactness suitable for being mounted on a compact camera and having excellent imaging performance.

[Brief description of the drawings]

FIG. 1 is a lens cross-sectional view at a wide-angle end in a zoom lens according to a first exemplary embodiment.

FIG. 2 is an aberration diagram of a zoom lens of Example 1. FIG.

FIG. 3 is a lens cross-sectional view at a wide-angle end in a zoom lens according to a second exemplary embodiment.

FIG. 4 is an aberration diagram of a zoom lens of Example 2.

FIG. 5 is a lens cross-sectional view at a wide-angle end in a zoom lens according to a third exemplary embodiment.

FIG. 6 is an aberration diagram of a zoom lens of Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st lens group 2 2nd lens group 3 3rd lens group 4 4th lens group 5 5th lens group

Claims (6)

[Claims] 1. A first lens unit having negative refracting power, a second lens unit having positive refracting power, a third lens unit having negative refracting power, a fourth lens unit having positive refracting power, and a fourth lens unit having negative refracting power in order from the object side. It includes a fifth lens group, and at the telephoto end, the first lens group and the second lens group, the second lens group and the third lens group, and the fourth lens group at the telephoto end, compared to the wide-angle end.
A zoom lens characterized in that the distance between the lens group and the fifth lens group decreases, the distance between the third lens group and the fourth lens group increases, and the following conditional expression is satisfied. 3.6 ≦ m _5T ≦ 6.5 However, m _5T : Lateral magnification of the fifth lens group at the telephoto end 2. The zoom lens according to claim 1, wherein the following conditional expression is satisfied. −0.30 ≦ f ₅ / f _T ≦ −0.12 0.30 ≦ Δt / f _W ≦ 0.60 However, f ₅ : focal length of the fifth lens group f _W : focal length of the entire system at the wide-angle end f _T : focal length of the entire system at the telephoto end Δt: difference between the wide-angle end and the telephoto end of the distance between the first lens group and the second lens group 3. The zoom lens according to claim 1, wherein the second lens unit and the fourth lens unit move integrally during zooming. 4. A second lens group and a third lens group during focusing.
The zoom lens according to claim 1, wherein the lens unit and the fourth lens unit are moved integrally. 5. The zoom lens according to claim 1, wherein the fifth lens group is moved during focusing. 6. The diagonal length of the image frame is 33 mm to 36 m.
The zoom lens according to claim 1, wherein when m, the following conditional expression is satisfied. 85 mm ≤ L _T ≤ 125 mm, where L _T : total lens length including the lens back at the telephoto end