JPH05119258A - Wide-angle zoom lens - Google Patents

Abstract

PURPOSE:To obtain the wide-angle zoom lens for a small-sized, compact camera which has a positive-negative two-group constitution and has an about 73 deg. field angle at the wide-angle end, various aberrations excellently compensated, and an about X2 zoom ratio by satisfying conditions shown by specific expressions. CONSTITUTION:The wide-angle zoom lens consists of a 1st lens group with positive refracting power and a 2nd lens group with negative refracting power in order from the object side, and the power is varied by varying the interval between both the lens groups. The 1st lens group consists of a positive meniscus lens which has a convex surface on the object side, a cemented lens consisting of a positive meniscus lens and a biconcave lens, and a positive lens group following it in order from the object side and the 2nd lens group consists of a positive meniscus lens which has a convex surface on the image side and a following negative lens group; and the conditions shown by the inequalities I-IV are satisfied. Here, fF is the focal length of the 1st lens group, fw the focal length of the whole system at the wide-angle end, d34 the thickness of the cemented lens in the 1st lens group, r3 the radius of curvature of the object-side lens surface of the cemented lens, V2 the Abbe number of the positive meniscus lens in the cemented lens, and V3 the Abbe number of the biconcave lens in the cemented lens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide-angle zoom lens, and more particularly to a two-group zoom lens including a wide-angle range with an angle of view of 73 °, which is mainly used for a compact camera having a short back focus. Regarding the lens.

[0002]

2. Description of the Related Art Conventionally, a compact and low-cost two-group zoom lens has been used as a zoom lens for a compact camera, but in many cases, a wide-angle field angle is 60 °.
It was up to the point. In recent years, it has been desired to widen the angle of compact cameras, and the angle of view in the wide-angle range is widened to 70 ° or more. The following are known examples thereof.

First, there is JP-A-2-284109, which corrects chromatic aberration mainly by using a third lens in the first group as a cemented lens, but in this case, it occurs in the second group. However, the chromatic aberration of magnification cannot be corrected sufficiently.

In Japanese Patent Laid-Open No. 3-200913, since the first lens is a negative lens, it is disadvantageous when the aperture is set to be bright, and it is necessary to use an aspherical surface for aberration correction. Comes out.

Further, the one disclosed in Japanese Patent Laid-Open No. 3-204608 has a disadvantageous structure for brightening the aperture, as described above. In this prior example, it is as dark as F / 4.1 on the wide angle side.

Although there are many known examples in which the angle of view in the wide-angle range is about 60 °, there are known examples of the similar type of the present invention described later in JP-A-2-288823 and JP-A-2-2509.
There is a No. 17 one. In these prior art examples, the second lens is composed of a thick cemented lens of a biconcave lens and a biconvex lens in order from the object side. In these prior art examples, as described above, the angle of view in the wide-angle range is as narrow as about 60 °, and when trying to widen the wide-angle range, the back focus becomes very short, and the off-axis aberration, mainly distortion occurs. There is a drawback that the aberration cannot be corrected sufficiently.

[0007]

As mentioned above, in recent years,
A wider angle of the compact camera is desired, and the angle of view in the wide angle range is expanding to 70 ° or more. In a positive / negative two-group zoom lens having a simple group configuration, in many conventional examples of the related art, the angle of view in the wide-angle range is as narrow as about 60 °, and when trying to widen the wide-angle range, the back focus becomes very short, and However, there is a drawback that off-axis aberrations, mainly distortion aberrations, cannot be corrected sufficiently.

The field angle in the wide angle range of these conventional ones is 70 °
When expanding to the above, there are the following big problems. The back focus becomes very short. Large positive distortion at the wide-angle end. And the zoom ratio is about 2
If you try to secure about double, the following problems remain. The amount of change in chromatic aberration due to zooming is very large.

The present invention has been made in view of the above problems, and an object thereof is a two-group zoom lens having a simple positive and negative configuration, and various aberrations in which the field angle in a wide angle range is widened to about 73 °, Especially distortion and lateral chromatic aberration have been corrected well,
It is an object of the present invention to provide a wide-angle zoom lens for a compact camera having a zoom ratio of about 2 times.

[0010]

A wide-angle zoom lens of the present invention which achieves the above object comprises, in order from the object side, a first lens group having a positive refractive power and a second lens group having a negative refractive power. In the zoom lens configured to include a positive meniscus lens having a convex surface facing the object side and a positive meniscus lens, in order from the object side, the first lens group includes a positive meniscus lens and a positive meniscus lens. A cemented lens of a concave lens and a positive lens group following the cemented lens, and the second lens group includes a positive meniscus lens having a convex surface directed toward the image side and a negative lens group following the positive meniscus lens, and the following conditions are satisfied. It is a thing. 0.6 <f _F / f _W <1.0 (1) 0.18 <d ₃₄ / f _W <0.45 (2) -1.5 <r ₃ / f _W <- 0.8 (3) ν ₃ <ν ₂ (4) where f _F is the focal length of the first lens group, f _W is the focal length of the entire system at the wide-angle end, and d ₃₄ is the first The thickness of the cemented lens in the lens group, r ₃ is the radius of curvature of the object-side lens surface of the cemented lens, ν ₂ is the Abbe number of the positive meniscus lens in the cemented lens, and ν ₃ is the biconcave lens in the cemented lens. Abbe number.

[0011]

The function and operation of adopting the above configuration will be described below. The positive / negative two-group zoom lens has a simple group structure and is advantageous for downsizing and cost reduction, but maintains a zoom ratio of about 2 times and a wide-angle field angle of 70 ° or more. In the case of widening, there is the above-mentioned problem as a drawback.

Among these problems, the problem is mainly caused by an extremely large amount of aberration occurring in the second lens unit, that is, the negative lens unit. In the present invention, these aberrations are corrected to be positive. By devising the configuration of the second lens in the lens group, it is possible to perform good correction.

The above condition (1) is a condition related to the power arrangement in which the above-mentioned correction effect can be exhibited in the positive / negative two-group zoom lens, the angle of view in the wide-angle range can be widened to 70 ° or more, and aberration can be corrected well. , The focal length of the positive lens group that is the first group. When the value goes below the lower limit of the condition (1), it is advantageous to lengthen the back focus which becomes very short at the wide-angle end, but various aberrations in the positive lens become too large to correct. On the other hand, when the value exceeds the upper limit of the condition (1), the back focus that becomes short at the wide angle end cannot be sufficiently obtained.

Conditions (2), (3) and (4) are conditions concerning the second lens which is a cemented lens of a positive meniscus lens having a concave surface facing the object in the first group and a biconcave lens. Wide-angle field angle of 70 ° with positive / negative zoom lens
In the case of expanding to the above range, a large aberration will occur in the negative lens group which is the second group. This is because the angle of the exiting light beam at the wide-angle end becomes extremely large, and particularly the distortion aberration becomes large on the positive side. In the present invention, the cemented lens that is the second lens is formed into a thick biconcave lens shape, and is composed of a positive meniscus lens and a biconcave lens, and by providing the cemented surface with negative power, the negative lens group that is the second group. The negative distortion aberration that cancels the positive distortion aberration that occurs is effectively generated. Further, by increasing the thickness of the second lens, the position of the principal point in the first group can be moved rearward, and the back focus at the wide-angle end can be set longer.

Therefore, when the value goes below the lower limit of the condition (2), the positive distortion, which is a problem at the wide-angle end, cannot be completely corrected, and the back focus cannot be sufficiently obtained.
When the value exceeds the upper limit of the condition (2), the lens becomes large and the curvature of field due to the cemented lens becomes large on the positive side, so that the correction cannot be performed.

The condition (3) is a condition regarding the radius of curvature of the lens surface of the cemented lens closest to the object side. This lens surface produces negative distortion aberration to correct the problematic distortion aberration due to its negative action, but on the other hand, it has a large influence on various aberrations in the peripheral portion at the wide-angle end. is there.
When the value exceeds the upper limit of the condition (3), it is advantageous for correction of distortion, but the deterioration of aberration at the wide-angle end is remarkable, and it becomes impossible to correct particularly large positive field curvature and peripheral coma. When the value goes below the lower limit of the condition (3), the negative effect of this lens surface cannot be exhibited, and the astigmatic difference becomes large.

The condition (4) is a condition relating to each Abbe number of the lenses forming the cemented lens. In a positive / negative zoom lens, if it is attempted to widen the angle of view in the wide-angle range to 70 ° or more and to secure a zoom ratio of about 2 times, the magnification due to the magnification change due to the influence of the chromatic aberration generated in the negative second lens group. However, there is a drawback that the amount of change in chromatic aberration becomes large.

In the present invention, the second lens is composed of a cemented lens of a positive meniscus lens having a large Abbe number and a biconcave lens having a small Abbe number in order from the object side, whereby the chromatic aberration of magnification is effectively corrected, It suppresses changes in chromatic aberration of magnification due to zooming. In addition, chromatic coma aberration, which is particularly noticeable at the wide-angle end, is corrected in a well-balanced manner.

Further, the positive lens group following the cemented second lens is composed of a positive lens and a biconvex lens in order from the object, and the focal length f _{5 of the} biconvex lens is set under the following conditions. Aberrations in the positive first lens group can be corrected well. 0.94 <f ₅ / f _W <1.30 (5) If the upper limit of the above condition (5) is exceeded, the power of the positive first lens group becomes weak and the back focus at the wide angle end becomes short. I will pass. Further, if an attempt is made to supplement this positive component with the third lens component (positive lens), the field curvature will largely fall to the negative side, making correction difficult. When the value goes below the lower limit of the condition (5), the amount of field curvature aberration generated by the biconvex lens increases, which makes correction difficult. Further, the group interval at the telephoto end becomes small, and the lens groups interfere with each other.

Further, most of the image-side lens surface of the second lens is a cemented lens of a positive meniscus lens and a biconcave lens is a lens surface with a concave surface facing the image side, the curvature radius r ₅ below By setting the value within the range of the condition (6), it is possible to satisfactorily correct the field curvature aberration that occurs in the positive lens group that follows.

1.65 <r ₅ / f _W <4.60 (6) When the upper limit of the condition (6) is exceeded, the subsequent field curvature aberration generated in the positive lens group becomes large on the negative side. It falls down and it becomes difficult to correct. When the value goes below the lower limit of the condition (6), the spherical aberration at the telephoto end is overcorrected and becomes positive. Further, axial chromatic aberration is similarly overcorrected.

Further, in the present invention, the second lens group having a negative refractive power is arranged in order from the object side such that the positive meniscus lens having the convex surface facing the image surface side, the negative lens, and the convex surface facing the image surface side. By configuring with a negative meniscus lens, it is possible to suppress various aberrations occurring in the negative second group as much as possible, and to correct each aberration better.

Further, if the radius of curvature r _R of the lens surface closest to the image side of this negative lens group satisfies the following condition (7), the amount of aberration generated in this lens group can be further reduced. ..

−1.55 <r _R / f _W <−1.0 (7) When the upper limit of the condition (7) is exceeded, the radius of curvature of the lens surface in front of it in order to secure a negative power component. Becomes smaller, and it becomes difficult to correct off-axis aberrations such as coma. When the value goes below the lower limit of the condition (7), the astigmatic difference becomes large, and it becomes difficult to perform correction especially in the intermediate focal length state.

Further, in order to satisfactorily correct off-axis aberrations at the wide-angle end, it is desirable to set the condition (3) within the range of the following condition (8).

−1.30 <r ₃ / f _W <−0.88 (8) Here, when the upper limit of the condition (8) is exceeded, the field curvature increases to the positive side and the chromatic aberration of magnification increases. The amount of fluctuation in the lens increases, and the burden on the correction power of other lenses increases. On the other hand, when the value goes below the lower limit, the distortion correction power on this lens surface becomes insufficient, and it becomes necessary to further increase the thickness of the second lens, leading to an increase in size.

[0027]

EXAMPLES Examples 1 to 5 of the present invention will be described below. Embodiments 1 to 5 are zoom lenses for compact cameras, which are compact zoom lenses that secure an angle of view of about 73 ° at the wide-angle end and have a zoom ratio of about 2 times. 1A and 1B are lens cross-sectional views of Example 1, in which FIG. 1A shows the lens arrangement at the wide-angle end and FIG. 1B shows the lens arrangement at the telephoto end. As shown in FIG. First lens group G1 having a refractive power of
And a second lens group G2 having a negative refractive power, the zooming from the wide-angle end to the telephoto end is performed by reducing the distance between the groups, and each group moves toward the object side. There is.

The first lens group G1 is composed of, in order from the object side, a positive meniscus lens having a convex surface facing the object side, a cemented lens of a positive meniscus lens and a biconcave lens, a biconvex lens, and a biconvex lens. The lens group G2 includes, in order from the object side, a positive meniscus lens having a convex surface facing the image plane,
It consists of a biconcave lens and a negative meniscus lens with the convex surface facing the image side.

The group constructions of Examples 2 to 5 and the movement of zooming are the same as in the case of FIG. Although the lens arrangement is not shown, the third embodiment is similar to the first embodiment, and the second and fifth embodiments are different from the first embodiment, and the biconvex lens on the object side of the first lens group G1. A positive meniscus lens having a convex surface directed to the image surface is used instead of, and unlike Example 1, in the case of Example 4, a negative meniscus lens having a convex surface directed to the image surface is used instead of the biconcave lens of the second lens group G2. It uses a meniscus lens.

With respect to the aspherical surface, in the fifth embodiment, it is used as the first surface of the positive meniscus lens of the second lens group G2 on the image plane side, and the off-axis aberration is satisfactorily corrected. In addition,
Another example is a spherical system.

The lens data of each embodiment will be shown below.
In addition to the above, f is the focal length of the entire system, F _NO is the F number, 2ω is the angle of view, r ₁ , r ₂ ... Is the radius of curvature of each lens surface, and d ₁ , d ₂ ... Is each lens surface. The intervals between, n _d1 , n _d2 ...
Is the d-line refractive index of each lens, and ν _d1 , ν _d2 ... Is the Abbe number of each lens. Further, the aspherical shape has an optical axis direction of x,
When the direction orthogonal to the optical axis is y, it is expressed by the following equation. x = (y ² / r) / [1+ {1-P (y ² / r ² )} ^1/2 ] + A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰ + A ₁₂ y ¹² Where r is the paraxial radius of curvature, P is the conic coefficient, A ₄ , A ₆ ,
A ₈ , A ₁₀ , and A ₁₂ are aspherical coefficients.

[0032] Example 1 f = 29.07 ~ 40.01 ~ 53.85 F NO = 3.63 ~ 5.00 ~ 6.72 2ω = 73.2 ° ~ 56.8 ° ~ 43.7 ° r 1 = 23.0343 d 1 = 2.4337 n d1 =
1.69350 ν _d1 = 53.23 r ₂ = 63.9804 d ₂ = 1.8998 r ₃ = -29.2811 d ₃ = 2.9022 n _d2 =
1.58875 ν _d2 = 51.18 r ₄ = -13.8315 d ₄ = 6.3104 n _d3 =
1.83400 ν _d3 = 37.16 r ₅ = 56.9322 d ₅ = 0.9998 r ₆ = 121.1896 d ₆ = 4.2787 n _d4 =
_{1.62280 ν d4 = 57.06 r 7 =} -19.6402 d 7 = 0.1000 r 8 = 21.7688 d 8 = 1.7766 n d5 =
1.62299 ν _d5 = 58.14 r ₉ = -266.6185 d ₉ = 0.8000 r ₁₀ = ∞ (aperture) d ₁₀ = (variable) r ₁₁ = -27.1995 d ₁₁ = 2.5177 n _d6 =
1.49831 ν _d6 = 65.03 r ₁₂ = -16.8459 d ₁₂ = 0.1500 r ₁₃ = -77.8031 d ₁₃ = 1.1000 n _d7 =
_{1.69680 ν d7 = 55.52 r 14 =} 2378.3911 d 14 = 5.8724 r 15 = -11.3611 d 15 = 1.3997 n d8 =
1.72916 ν _d8 = 54.68 r ₁₆ = -38.4316 _{f F / f W = 0.813 d} 34 / f W = 0.317 r 3 / f W = -1.007 f 5 / f W = 1.114 r 5 / f W = 1.958 r R / f W = -1.322.

Example 2 f = 29.14 ~ 40.00 ~ 53.93 F _NO = 3.63 ~ 4.99 ~ 6.72 2ω = 73.1 ° ~ 56.8 ° ~ 43.7 ° r ₁ = 25.6318 d ₁ = 2.2098 n _d1 =
1.69700 ν _d1 = 48.51 r ₂ = 62.3196 d ₂ = 2.0193 r ₃ = -30.9326 d ₃ = 3.8482 nd ₂ =
1.51454 ν _d2 = 54.69 r ₄ = -12.9319 d ₄ = 6.1002 n _d3 =
1.83400 ν _d3 = 37.16 r ₅ = 84.8757 d ₅ = 0.9998 r ₆ = -214.4301 d ₆ = 3.6378 nd ₄ =
1.65160 ν _d4 = 58.52 r ₇ = -18.1189 d ₇ = 0.1200 r ₈ = 22.2647 d ₈ = 1.9995 n _d5 =
1.65160 ν _d5 = 58.52 r ₉ = -146.6088 d ₉ = 0.8000 r ₁₀ = ∞ (aperture) d ₁₀ = (variable) r ₁₁ = -25.8613 d ₁₁ = 2.6221 n _d6 =
1.51633 ν _d6 = 64.15 r ₁₂ = -17.5650 d ₁₂ = 0.1500 r ₁₃ = -96.6861 d ₁₃ = 1.4937 n _d7 =
1.78590 ν _d7 = 44.18 r ₁₄ = 808.6119 d ₁₄ = 6.5292 r ₁₅ = -11.9351 d ₁₅ = 1.7804 n _d8 =
1.73400 ν _d8 = 51.49 r ₁₆ = -34.9613 f _F / f _W = 0.814 d ₃₄ / f _W = 0.341 r ₃ / f _W = -1.062 f ₅ / f _W = 0.998 r ₅ / f _W = 2.913 r _R / f _W = -1.200.

[0034] Example 3 f = 29.23 ~ 40.01 ~ 53.64 F NO = 3.63 ~ 4.97 ~ 6.66 2ω = 72.9 ° ~ 56.8 ° ~ 43.9 ° r 1 = 24.0285 d 1 = 2.3417 n d1 =
1.69680 ν _d1 = 55.52 r ₂ = 59.4655 d ₂ = 2.1573 r ₃ = -27.8995 d ₃ = 3.9822 n _d2 =
1.58904 ν _d2 = 53.20 r ₄ = -14.2007 d ₄ = 6.1409 n _d3 =
1.83400 ν _d3 = 37.16 r ₅ = 76.0039 d ₅ = 0.9996 r ₆ = 437.2377 d ₆ = 3.5476 n _d4 =
1.67000 ν _d4 = 57.33 r ₇ = -20.8332 d ₇ = 0.1000 r ₈ = 22.9663 d ₈ = 1.7094 n _d5 =
1.64000 ν _d5 = 60.09 r ₉ = -174.3294 d ₉ = 0.8000 r ₁₀ = ∞ (aperture) d ₁₀ = (variable) r ₁₁ = -30.1600 d ₁₁ = 3.3670 n _d6 =
1.55232 ν _d6 = 63.75 r ₁₂ = -18.7066 d ₁₂ = 0.1500 r ₁₃ = -100.6374 d ₁₃ = 1.0999 n _d7 =
1.72916 ν _d7 = 54.68 r ₁₄ = 547.6828 d ₁₄ = 6.1976 r ₁₅ = -11.9327 d ₁₅ = 1.3991 n _d8 =
1.73400 ν _d8 = 51.49 r ₁₆ = -40.8158 f _F / f _W = 0.832 d ₃₄ / f _W = 0.35 r ₃ / f _W = -0.95 f ₅ / f _W = 1.089 r ₅ / f _W = 2.601 r _R / f _W = -1.400.

Example 4 f = 29.17 ~ 39.56 ~ 54.41 F _NO = 3.62 ~ 4.90 ~ 6.76 2ω = 73.0 ° ~ 57.2 ° ~ 43.3 ° r ₁ = 22.5135 d ₁ = 2.2664 n _d1 =
1.69700 ν _d1 = 48.51 r ₂ = 51.0694 d ₂ = 2.1268 r ₃ = -28.9074 d ₃ = 2.1252 n _d2 =
1.52307 ν _d2 = 58.49 r ₄ = -15.8952 d ₄ = 6.2301 n _d3 =
1.83400 ν _d3 = 37.16 r ₅ = 55.8012 d ₅ = 0.9986 r ₆ = 169.2437 d ₆ = 4.5857 n _d4 =
1.65160 ν _d4 = 58.52 r ₇ = -21.3333 d ₇ = 0.1200 r ₈ = 21.7572 d ₈ = 2.0282 n _d5 =
1.61700 ν _d5 = 62.79 r ₉ = -113.0489 d ₉ = 0.8000 r ₁₀ = ∞ (aperture) d ₁₀ = (variable) r ₁₁ = -25.1354 d ₁₁ = 3.0392 n _d6 =
1.51633 ν _d6 = 64.15 r ₁₂ = -15.6343 d ₁₂ = 0.1500 r ₁₃ = -31.3695 d ₁₃ = 1.4996 n _d7 =
1.69680 ν _d7 = 55.52 r ₁₄ = -52.6340 d ₁₄ = 5.6979 r ₁₅ = -11.4585 d ₁₅ = 1.7804 n _d8 =
1.73400 ν _d8 = 51.49 r ₁₆ = -36.9562 f _F / f _W = 0.816 d ₃₄ / f _W = 0.286 r ₃ / f _W = -0.991 f ₅ / f _W = 1.020 r ₅ / f _W = 1.913 r _R / f _W = -1.267.

[0036] Example 5 f = 29.05 ~ 40.01 ~ 54.02 F NO = 3.63 ~ 5.00 ~ 6.75 2ω = 73.3 ° ~ 56.8 ° ~ 43.6 ° r 1 = 21.7613 d 1 = 2.5513 n d1 =
1.69350 ν _d1 = 50.81 r ₂ = 63.2926 d ₂ = 1.9000 r ₃ = -28.0802 d ₃ = 2.9895 n _d2 =
1.58875 ν _d2 = 51.18 r ₄ = -12.7860 d ₄ = 3.1291 n _d3 =
1.83400 ν _d3 = 37.16 r ₅ = 117.4229 d ₅ = 1.6032 r ₆ = -90.9485 d ₆ = 4.1252 n _d4 =
_{1.61700 ν d4 = 62.79 r 7 =} -18.0250 d 7 = 0.1000 r 8 = 22.7271 d 8 = 1.7258 n d5 =
1.61700 ν _d5 = 62.79 r ₉ = -93.7331 d ₉ = 0.3000 r ₁₀ = ∞ (aperture) d ₁₀ = (variable) r ₁₁ = -30.1407 d ₁₁ = 2.0777 n _d6 =
1.49216 ν _d6 = 57.50 r ₁₂ = -17.9662 (aspherical surface) d ₁₂ = 0.1500 r ₁₃ = -66.1743 d ₁₃ = 1.0998 n _d7 =
1.69680 ν _d7 = 55.52 r ₁₄ = 1403.6084 d ₁₄ = 6.1683 r ₁₅ = -11.5419 d ₁₅ = 1.3998 n _d8 =
1.72916 ν _d8 = 54.68 r ₁₆ = -33.7759 Aspherical coefficients twelfth surface _{P = 1 A 4 = 0.17521 ×} 10 -5 A 6 = -0.73760 × 10 -7 A 8 = 0.35820 × 10 -8 A 10 = -0.89403 × 10 -10 A 12 = 0.66719 × 10 - ¹² f _F / f _W = 0.817 d ₃₄ / f _W = 0.211 r ₃ / f _W = -0.967 f ₅ / f _W = 1.026 r ₅ / f _W = 4.043 r _R / f _W = -1.160.

The wide-angle zoom lenses of Examples 1 to 3 described above have a wide-angle end (a) at a photographing magnification of 1/65 and a photographing magnification of 1/50.
2 (a), (b), and (a) in FIG. 2 to FIG. 6 in the standard state (b), the spherical aberration, astigmatism, distortion, and chromatic aberration of magnification at the telephoto end (c) at a photographing magnification of 1/50, respectively. It is shown in the aberration diagram of c).

[0038]

As is apparent from the above description, according to the present invention, the angle of view at the wide-angle end is as wide as about 73 °, and various aberrations are well corrected at the wide-angle end, resulting in a zoom of about 2 ×. A compact zoom lens for a compact camera having a simple structure, in which aberrations are well-balanced from the wide-angle end to the telephoto end while ensuring the ratio, is possible.

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view of a wide-angle zoom lens according to a first exemplary embodiment of the present invention at a wide-angle end (a) and a telephoto end (b).

FIG. 2 is an aberration diagram showing spherical aberration, astigmatism, distortion, and chromatic aberration of magnification at the wide-angle end (a), the standard state (b), and the telephoto end (c) of Example 1.

FIG. 3 is an aberration diagram similar to FIG. 2 of Example 2.

FIG. 4 is an aberration diagram similar to FIG. 2 of Example 3.

FIG. 5 is an aberration diagram similar to FIG. 2 of Example 4.

FIG. 6 is an aberration diagram similar to FIG. 2 of Example 5.

[Explanation of symbols]

 G1 ... First lens group G2 ... Second lens group

[Procedure amendment]

[Submission date] January 24, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

The wide-angle zoom lenses of Examples 1 to 5 described above have a wide-angle end (a) at a photographing magnification of 1/65 and a photographing magnification of 1/50.
2 (a), (b), and (a) in FIG. 2 to FIG. 6 in the standard state (b), the spherical aberration, astigmatism, distortion, and chromatic aberration of magnification at the telephoto end (c) at a photographing magnification of 1/50, respectively. It is shown in the aberration diagram of c).

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

Claims (1)

[Claims] 1. A zoom lens system comprising, in order from the object side, a first lens group having a positive refractive power and a second lens group having a negative refractive power, and changing the distance between the two lens groups to perform zooming. In the zoom lens to be performed, the first lens group includes, in order from the object side, a positive meniscus lens having a convex surface directed toward the object side, a cemented lens of a positive meniscus lens and a biconcave lens, and a positive lens group following the second lens group. The group consists of a positive meniscus lens having a convex surface directed toward the image side and a negative lens group following the lens, and a wide-angle zoom lens characterized by satisfying the following conditions: 0.6 <f _F / f _W <1.0 _{··· (1) 0.18 <d 34} / f W <0.45 ··· (2) -1.5 <r 3 / f W <-0.8 ··· (3) ν 3 <ν ₂ (4) where, f _F is the focal length of the first lens group, f _W is put on the wide-angle end Focal length of the entire system, d ₃₄ is the thickness of the cemented lens in the first lens group, r ₃ is the radius of curvature of the object side lens surface of the cemented lens, [nu ₂ is Abbe number of the positive meniscus lens in the cemented lens, ν ₃ is the Abbe number of the biconcave lens in the cemented lens.