JPH0830783B2 - High magnification zoom lens for compact cameras - Google Patents

Description

TECHNICAL FIELD The present invention relates to a compact high-zoom zoom lens suitable for a lens shutter camera or the like.

[Conventional technology]

Conventionally, as one of typical types of this type of zoom lens, there is a zoom lens described in JP-A-56-128911. This zoom lens is of a two-group type which is composed of a lens group having a positive refracting power and a lens group having a negative refracting power in order from the object side, and which moves during zooming as shown in FIG.

This type of zoom lens is a basic type because it is a telephoto type at the wide-angle end, the principal point is located on the object side, and the back focus is short.

On the other hand, if the zoom ratio is about 1.5, it is possible to obtain a compact zoom lens with a small number of components. However, if the zoom ratio is about 2, the amount of movement of the second lens unit, which is the zoom unit, during zooming becomes large. As a result, the light beam passing position in the lens system changes between the wide-angle side and the telephoto side. In particular, the off-axis ray that passes through the lens located closest to the image side of the second lens group becomes the peripheral portion and the lens outer diameter must be increased, which makes it difficult to balance chromatic aberration and various monochromatic aberrations. Not suitable for scaling.

There is also known a so-called three-group zoom composed of three lens groups such as an O-zoom lens disclosed in Japanese Patent Laid-Open No. 58-137813. However, these are basically a two-group zoom system, and although they are advantageous in correcting aberrations, they do not contribute to increasing the magnification.

On the other hand, the zoom lens disclosed in JP-A-60-57814 is
The lens system is composed of four lens units having positive, negative, positive and negative refractive powers in order from the object side, and each lens unit moves as shown in FIG. 7 during zooming. The zoom lens that is already commonly used is adopted for the zoom lens for the. Since this zoom lens does not need to make the back focus longer than necessary, it is configured as a telephoto type for compactness, and it is considered that the first lens group of the two-group zoom system is divided into two. You can However, the proposed zoom lens has a magnifying power of about 16 and a large number of lens components, and the magnifying power is such that it can be achieved even with the two-group zoom system.

As a lens system for a lens shutter, a single-focus lens that covers a field angle in a quasi-wide angle range for a long time has been used, and a developed version of the single-focus lens and a dual-focus switching system using a rear converter have been proposed. Further, a zoom lens of a two-group zoom system or a three-group zoom system which continuously varies the magnification is proposed, and a zoom lens of a four-group zoom system is also proposed with the intention of improving performance. In each of these zoom lenses, since the limiting condition of the back focus is not particularly set, the downsizing of the entire length is achieved. However, the conventional zoom lenses for these lens shutters are unsatisfactory in terms of the change of the angle of view due to the low zoom ratio as described above.

[Problems to be solved by the invention]

The present invention is intended for mounting on a lens shutter camera or the like which does not have a specific restriction condition on the back focus and has a zoom ratio of at least 2 times or more from the wide-angle end to the telephoto end (angle of view 63 ° to 51 °). It is an object of the present invention to provide a compact high-magnification zoom lens.

[Means for solving problems]

In order to achieve the above object, the zoom lens of the present invention comprises a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side. When,
It is composed of a fourth lens unit having a negative refracting power, and each of the first to fourth lens units is moved toward the object side along the optical axis when zooming to the telephoto end with the wide-angle end as a reference. It is a thing.

Zoom ratio for conventional lens shutter is 2
In contrast to the following, in order to secure a zoom ratio of at least 2 and shorten the overall length of the lens type, a 4-group zoom system is used, and the zoom ratio is shared by each lens group by moving each lens group. Achieved higher magnification.

Further, since there is no specific limitation on the total length of the lens system in the back focus, unlike the lens system for a single-lens reflex camera, it is a necessary condition to provide a telephoto type refractive power arrangement at the wide angle end. As a result, the fourth lens group has a negative refracting power as described above.

On the other hand, there is a point to be noted in the range in which the zoom ratio is shared by each lens group, and the movement of the second lens group is performed by moving toward the object side when zooming to the telephoto end with the wide-angle end as a reference. Miniaturization at the wide-angle end can be achieved.

The zoom lens of the present invention is based on the above-mentioned basic structure, and further satisfies the following conditions as a range in which the magnification of the lens group is shared.

(1) 0.03 (1 / mm) <(β _4T / β _4W ) ・ ψ _W <0.07 (1
/ mm) (2) 0.3 <β _2T · β _3T <0.7 (3) 5 (mm) <(1-β _4W ) / ψ ₄ <20 (mm) However, β _2T is the side of the second lens group at the telephoto end. magnification,
β _3T is the lateral magnification of the 3rd lens group at the telephoto end, β _4T is the lateral magnification of the 4th lens group at the telephoto end, β _4W is the lateral magnification of the 4th lens group at the wide angle end, and _W is the entire system at the wide angle end. Refractive power, ₄ is the refractive power of the fourth lens group.

The condition (1) defines the lateral magnification within the variable power range of the fourth lens group, which plays an important refractive power distribution particularly in constructing a lens system having a short back focus at the wide-angle end. If the upper limit of this condition (1) is exceeded, the zooming range of the fourth lens group will be wide, and the amount of zooming movement of the fourth lens group itself will be large, so the overall length of the lens system will be long and the flatness of the image plane will be high. In addition to the inability to compensate, difficulties in the mechanical structure around the lens system become noticeable. If the lower limit of this condition is exceeded, the magnification load of the second lens group and the third lens group will inevitably increase, and the amount of movement of the second lens group and the third lens group will increase, or the movement of the first lens group will increase. It is not preferable because the amount must be increased.

The condition (2) defines the sharing of the magnification change between the second lens unit and the third lens unit, and if the upper limit of this condition is exceeded, the amount of zooming movement of the second lens unit and the third lens unit becomes large, which is desirable. Absent. Further, if the lower limit of this condition (2) is exceeded, the burden magnification of the fourth lens group becomes large. If the refracting power of the fourth lens group is left as it is, the movement amount during zooming increases, and if the refracting power is increased, the movement amount increases. However, it is difficult to obtain good performance because various aberrations including field curvature are deteriorated.

The condition (3) defines the range of the back focus at the wide-angle end, which is determined by the refractive power of the fourth lens unit and the magnification of the fourth lens unit at the wide-angle end. This condition (3)
If the upper limit of the above is exceeded, the total length becomes longer, which is not desirable for the purpose of the present invention. Further, as a factor that exceeds the upper limit, the refracting powers of the first lens group and the third lens group are weakened, and as a result, the refracting power of the fourth lens group is weakened, and further, the refracting power of the second lens group is strengthened. The refracting power of the lens group may be weakened. Like this
If the refractive power of the lens group becomes weak, the back focus of the lens system becomes large, and as a result, the total length of the lens system becomes long, which is not preferable. When the value goes below the lower limit of the condition (3), the number of constituent lenses of the fourth lens group needs to be increased, and the number of manufacturing steps is required in terms of shape, which is not desirable.

Further, in the zoom lens of the present invention, it is desirable that each lens group has the following configuration. That is, the first lens group having a positive refractive power is composed of at least one negative lens and a positive lens, and the second lens group having a negative refractive power is a cemented lens of at least one positive lens and a negative lens. The third lens group having a positive refractive power is composed of at least two positive lenses and a negative lens, and the fourth lens group having a negative refractive power is
It is desirable to have at least one positive lens and at least one negative lens.

〔Example〕

Each of the embodiments of the zoom lens of the present invention has a lens configuration as shown in FIG. 2, that is, the first lens group
The lens configuration of G ₁ is composed of, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a positive lens, and a positive lens. The reason for adopting such a configuration is that it is necessary to appropriately distribute the refractive power to suppress the amount of aberration generated. It is possible to make the first lens group G ₁ into two lenses, but this is not preferable because the burden on each lens becomes large and the curvature of each surface becomes strong and the wall thickness must be made large. .

The second lens group G ₂ is composed of a cemented lens made up of a negative lens and a positive lens, and a negative meniscus lens in order from the object side, and aims to bring the front principal point to the object side, aiming to shorten the overall length. . The second lens group G ₂ largely contributes to the balance of the entire system of coma, distortion, and astigmatism, and the action of the surface closest to the object side is large and the action of overcorrecting these aberrations is strong. As a result, the aberrations produced by the other lenses are corrected in a well-balanced manner so that the aberrations of the entire system become good.

The third lens group G ₃ is composed of two positive lenses, a negative lens and a positive lens from the object side. This lens group
It is located where the incident height of the axial ray becomes high, and the front principal point is located on the object side due to the above configuration, which is effective in correcting spherical aberration.

The fourth lens group G ₄ is composed of a positive meniscus lens and a negative meniscus lens from the object side, and contributes to maintain the flatness of the image surface. The high-order aberration is generated by the action of the air lens sandwiched between both lenses of this lens group,
The aberrations generated in the first lens group to the third lens group are appropriately canceled.

 Next, the data of each Example are shown.

First Example f = 39.03 to 84.0, F4.5 to 5.6 r ₁ = 1000.000 d ₁ = 1.500 n ₁ = 1.84666 v ₁ = 23.88 r ₂ = 54.037 d ₂ = 3.500 n ₂ = 1.69680 v ₂ = 55.52 r ₃ = _{685.901 d 3 = 0.150 r 4 =} 30.109 d 4 = 3.600 n 3 = 1.51741 ν 3 = 49.21 r 5 = -735.755 d 5 = l 1 r 6 = -49.662 d 6 = 1.219 n 4 = 1.77250 ν 4 = 49.66 r 7 = 19.014 d ₇ ＝ 3.001 n ₅ = 1.80518 ν ₅ ＝ 25.43 r ₈ ＝ 94.078 d ₈ = 1.292 r ₉ ＝ －26.594 d ₉ ＝ 1.180 n ₆ ＝ 1.72916 ν ₆ ＝ 54.68 r ₁₀ ＝ －46.031 d ₁₀ ＝ l ₂ r ₁₁ = ∞ (aperture) d ₁₁ = 2.000 r ₁₂ = 39.181 d ₁₂ = 1.708 n ₇ = 1.60607 v ₇ = 48.71 r ₁₃ = -46.680 d ₁₃ = 0.150 r ₁₄ = 23.666 d ₁₄ = 2.521 n ₈ = 1.58144 v ₈ = 40.75 r ₁₅ = −30.712 d ₁₅ = 0.941 r ₁₆ = −21.719 d ₁₆ = 1.603 n ₉ = 1.80518 ν ₉ = 25.43 r ₁₇ = 24.143 d ₁₇ = 2.484 r ₁₈ = 45.176 d ₁₈ = 3.266 n ₁₀ = 1.56732 ν ₁₀ = 42.83 r ₁₉ = -21.874 d ₁₉ = l ₃ r ₂₀ = -26.797 d ₂₀ = 2.720 n ₁₁ = 1.68893 ν ₁₁ = 31.08 r ₂₁ = -16.928 d ₂₁ ＝ 3.000 r ₂₂ ＝ －15.303 d ₂₂ ＝ 1.295 n ₁₂ = 1.77250 ν ₁₂ ＝ 49.66 r ₂₃ ＝ －510.056 l ₁ l ₂ l ₃ Wide-angle end 1.55 6.568 13.44 Intermediate focal length 6.817 5.252 3.306 Telephoto end 15.018 8.553 3.116 β _2T / β _3T = 0.55 Second Example f = 41.8 to 115.2, F / 4.6 to F / 5.8 r ₁ = 576.703 d ₁ = 1.250 n ₁ = 1.84666 v ₁ = 23.88 r ₂ = 52.295 d ₂ = 3.334 n ₂ = 1.69680 v ₂ = 55.52 r _{3 = 315.082 d 3 = 0.044 r} 4 = 34.136 d 4 = 3.503 n 3 = 1.51733 ν 3 = 49.21 r 5 = -145.821 d 5 = l 1 r 6 = -46.750 d 6 = 1.180 n 4 = 1.77250 ν 4 = 49.66 r ₇ = 15.696 d ₇ 2.931 n ₅ = 1.80518 ν ₅ ＝ 25.43 r ₈ ＝ 57.301 d ₈ ＝ 2.000 r ₉ ＝ −38.594 d ₉ = 1.141 n ₆ = 1.72916 ν ₆ ＝ 54.68 r ₁₀ ＝ −54.320 d ₁₀ ＝ l ₂ r ₁₁ = ∞ (aperture) d ₁₁ = 1.950 r ₁₂ ＝ 133.176 d ₁₂ ＝ 2.650 n ₇ ＝ 1.67603 ν ₇ ＝ 38.63 r ₁₃ ＝ －41.274 d ₁₃ ＝ 0.165 r ₁₄ ＝ 16.466 d ₁₄ ＝ 3.500 n ₈ ＝ 1.57863 ν ₈ = 58.93 r ₁₅ = -123.275 d ₁₅ = 0.940 r ₁₆ = -46.483 d ₁₆ = 1.649 n ₉ = 1.80518 ν ₉ = 25.43 r ₁₇ = 18.973 d ₁₇ = 2.409 r ₁₈ = 42.751 d ₁₈ = 3.296 n ₁₀ = 1.56732 ν ₁₀ = 42.83 r ₁₉ = -28.426 d ₁₉ = l ₃ r ₂₀ = -32.306 d ₂₀ = 4.000 n ₁₁ = 1.78472 ν ₁₁ = 25.68 r ₂₁ = -19 .556 d ₂₁ = 2.998 r ₂₂ = -17.373 d ₂₂ = 1.288 n ₁₂ = 1.77250 ν ₁₂ = 49.66 r ₂₃ = -465.852 l ₁ l ₂ l ₃ wide-angle end 0.879 9.411 22.545 intermediate focal length 5.42 7.473 10.934 telephoto end 11.495 5.293 2.221 β _2T / β _3T = 0.648 Third embodiment f = 39.5~100.8, F / 4.5~F / 5.8 r 1 = 704.210 d 1 = 1.034 n 1 = 1.84666 ν 1 = 23.88 r 2 = 55.010 d 2 = 2.914 n 2 = 1.69100 ν 2 = 54.84 r ₃ = 483.967 d ₃ = 0.048 r ₄ = 39.471 d ₄ = 3.279 n ₃ = 1.53172 ν ₃ = 48.90 r ₅ = -144.953 d ₅ = l ₁ r ₆ = -38.351 d ₆ = 1.142 n ₄ = 1.78650 ν ₄ = 50.00 _{r 7 = 15.821 d 7 = 2.882} n 5 = 1.80518 ν 5 = 25.43 r 8 = 60.536 d 8 = 1.970 r 9 = -41.166 d 9 = 1.139 n 6 = 1.72600 ν 6 = 53.56 r 10 = -44.549 d 10 = l ₂ r ₁₁ = ∞ (aperture) d ₁₁ = 1.936 r ₁₂ ＝ 113.494 d ₁₂ ＝ 2.601 n ₇ = 1.66998 ν ₇ ＝ 39.27 r ₁₃ ＝ −40.273 d ₁₃ ＝ 0.080 r ₁₄ ＝ 15.651 d ₁₄ ＝ 3.500 n ₈ = 1.57250 ν _{8 = 57.76 r 15 = -84.039 d} 15 = 0.940 r 16 = -43.748 d 16 = 1.666 n 9 = 1.80518 ν 9 = 25.43 r 17 = 17.703 d 17 = 2.414 r 18 = 41.785 d 18 = 3.310 n 10 = 1.56732 ν ₁₀ = 42.83 r ₁₉ = -28.109 d ₁₉ = l ₃ r ₂₀ = -36.261 d ₂₀ = 3.907 n ₁₁ = 1.76182 ν ₁₁ = 26.52 r ₂₁ = -19. 227 d ₂₁ ＝ 3.003 r ₂₂ ＝ －16.570 d ₂₂ ＝ 1.196 n ₁₂ ＝ 1.78650 ν ₁₂ ＝ 50.00 r ₂₃ ＝ －7206.869 l ₁ l ₂ l ₃ Wide-angle end 0.649 6.461 13.086 Intermediate focal length 9.397 7.647 5.53 Telephoto end 19.718 10.224 2.222 β _2T / β _3T = 0.568 Where r ₁ , r ₂ , ..., r ₂₃ are the radii of curvature of the lens surfaces, d ₁ , d ₂ ,
…, D ₂₂ is the wall thickness and air space of each lens, n ₁ , n ₂ ,,, n ₁₂
Is the refractive index of each lens, and ν ₁ , ν ₂ , ..., ν ₁₂ are the Abbe numbers of each lens.

〔The invention's effect〕

The zoom lens of the present invention has a zoom ratio of about 2 to 3 which is not present in conventional zoom lenses for lens shutters, is a compact and lightweight lens system that is stable and high performance over the entire area.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a zoom lens of the present invention, FIG. 2 is a sectional view of the zoom lens of the present invention, FIG. 3 is an aberration curve diagram of Embodiment 1 of the present invention, and FIG. 5 is an aberration curve diagram of Example 2, FIG. 5 is an aberration curve diagram of Example 3 of the present invention,
FIG. 6 and FIG. 7 are diagrams showing the movement of each group during zooming of the conventional zoom lens.

Claims (3)

[Claims] 1. A first lens group having a positive refracting power, a second lens group having a negative refracting power, and a third lens group having a positive refracting power in order from the object side.
It is composed of a lens group and a fourth lens group having a negative refractive power, and each of the first lens group to the fourth lens group moves toward the object side along the optical axis when zooming to the telephoto end with the wide-angle end as a reference. A high-zoom zoom lens for compact cameras that moves and satisfies the following conditions. (1) 0.03 (1 / mm) <(β _4T / β _4W ) ・ ψ _W <0.07 (1
/ mm) (2) 0.3 <β _2T · β _3T <0.7 (3) 5 (mm) <(1-β _4W ) / ψ ₄ <20 (mm) However, β _2T is the second lens group at the telephoto end. Lateral magnification,
β _3T is the lateral magnification of the third lens group at the telephoto end, β _4T is the lateral magnification of the fourth lens group at the telephoto end, β _4W is the lateral magnification of the fourth lens group at the wide-angle end, and ψ _W is the entire system at the wide-angle end. , Ψ ₄ is the refractive power of the fourth lens group. 2. When zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group, and the third lens group and the fourth lens group. The high-zoom zoom lens for a compact camera according to claim (1), in which the distance between the two is reduced. 3. A first group is composed of at least one negative lens and a positive lens, a second group is composed of at least one cemented lens of a positive lens and a negative lens, and a third group is composed of at least two lenses. The high-zoom zoom lens for a compact camera according to claim (2), which includes a positive lens and a negative lens, and the fourth group includes at least one positive lens and a negative lens.