JP3008700B2 - Zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens. .9
The present invention relates to a small zoom lens having a short overall lens length and suitable for a photographic camera, a video camera, an electronic still camera, and the like having excellent optical performance over the entire zoom range.

[0002]

2. Description of the Related Art A photographic camera, a video camera and the like have conventionally been required to have a zoom lens having high contrast and high optical performance over the entire zoom range.

A zoom lens whose focal length at the wide-angle end is shorter than the screen diagonal line and whose zoom ratio is 3 times or more is disclosed in, for example, JP-A-60-221717 and JP-A-63-708.
No. 19 has been proposed.

In this publication, four lenses of a first lens unit having a positive 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 having a positive refractive power are arranged in this order from the object side. We propose a zoom lens composed of groups.

In addition, Japanese Patent Application Laid-Open No. 62-247316 and Japanese Patent Application Laid-Open No. 62-24213 disclose a first lens unit having a positive refractive power and a negative lens unit in order from the object side. Second group of positive refractive power, third group of positive refractive power
Group, and a fourth lens group having a positive refractive power. The fourth lens group is moved, and the second group is moved to perform zooming. The fourth group is moved to perform image plane fluctuation and focusing caused by zooming. ing.

In Japanese Patent Application Laid-Open No. Sho 58-160913, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power are sequentially arranged from the object side.
It has four lens groups: a group, a third group having a positive refractive power, and a fourth group having a positive refractive power. The first group and the second group are moved to perform zooming, and an image accompanying the zooming is performed. The surface fluctuation is performed by moving the fourth lens unit. Then, focusing is performed by moving one or more of these lens groups.

[0007]

In general, in the above-described four-unit zoom lens system, it is necessary to maintain a high optical performance over the entire zooming range and obtain a predetermined aperture ratio and a zooming ratio while shortening the entire length of the lens system. It is important to appropriately set the optical constants of each lens group that constitutes.

For example, in the above-described four-unit zoom lens, if the lens arrangement of the fourth unit is not properly set, the overall length of the lens becomes long and the occurrence of various aberrations increases, and it is difficult to obtain an image of good image quality. It is becoming.

Conventionally, not only zoom lenses but also many photographing systems have variously used an aspherical surface in addition to a spherical surface to reduce the number of lenses and satisfactorily correct various aberrations. However, there are problems that the aspherical surface is difficult to manufacture and is not suitable for mass production.

According to the present invention, in a four-unit zoom lens, an aperture ratio F / 5 to 5 can be obtained while appropriately shortening the overall length of the lens by appropriately setting a moving condition of each lens unit and a lens configuration of the fourth unit mainly in response to zooming. A zoom lens having a high optical performance over the entire zoom range with a zoom ratio of about 8, a zoom ratio of about 4 to 5, or an aperture ratio of F / 4.3 to 5.8, and a zoom ratio of about 2.9, and over the entire screen. The purpose is to provide.

[0011]

According to a first aspect of the present invention, there is provided a zoom lens having a first unit having a positive refractive power, a second unit having a negative refractive power, a third unit having a positive refractive power, and The zoom lens has four lens units of a fourth group having a positive refractive power. Each of the first and second lens units is moved toward the object side during zooming from the wide-angle end to the telephoto end.
The distance between the groups is simply increased, the distance between the second group and the third group is moved so as to be simply reduced, and the fourth group is connected to a negative 41st lens having a concave surface facing the image plane side and a positive 41st lens. A cemented lens having a positive refractive power as a whole cemented with the 42nd lens, a positive 43rd lens having a convex surface facing the image surface side, and a negative 44th lens having a convex surface facing the image surface side, The focal lengths of the forty-first and forty-second lenses are f41 and f42, respectively,
The focal length of the lens surface on the image side of the third lens f43 _R, the focal distance f44 _F of the lens surface on the object side of said 44 lenses
When was _{0.20 <| f44 F | / f43} R <0.42 ( however _{f44 F <0) ······ (3} ) 0.35 <f42 / | f41 | <0.85 ··· (4) The following condition is satisfied.

[0012]

1 to 6 are sectional views of a numerical example 1 to 6 of the present invention at the wide-angle end.

In the drawing, L1 is a first lens unit having a positive refractive power, L2 is a second lens unit having a negative refractive power, L3 is a third lens unit having a positive refractive power, and L4 is a positive lens.
Denotes a fourth unit having a positive refractive power, SP denotes a stop, and is provided in front of the third unit.

In this embodiment, upon zooming from the wide-angle end to the telephoto end, each lens unit is moved toward the object side as indicated by an arrow, and the distance between the first and second units monotonically increases. The groups are moved so that the interval between them decreases monotonically. The aperture SP is the third
They are moved together with the group.

In this embodiment, as described above, the refracting power of the four lens units and the moving condition of each lens unit due to the magnification change are set, and the lens unit of the fourth unit is constituted by four lenses of a predetermined shape. I have.

As a result, a zoom lens having excellent optical performance over the entire zoom range of about 4 to 5 and F number of about 5 to 8 can be obtained while reducing the size of the entire lens system. In particular, the residual aberration caused by the first to third lens systems is favorably corrected by the fourth unit configured as described above.

Next, features of the fourth lens unit will be described.

The first lens unit is formed by using the shape and refractive index difference of the lens surface A on the image surface side of the positive 43rd lens and the lens surface B on the object side of the negative 44th lens in the fourth lens unit. From the third
Of the various aberrations caused by the lens system up to the group, mainly spherical aberration and coma are favorably corrected.

In particular, the lens surfaces A and B correct strong negative residual spherical aberration and negative residual coma (introverted coma) at the telephoto end. And the 41st lens and the 4th
As a whole, the two lenses are cemented to form a cemented lens having a positive refractive power, and the cemented lens surface C further corrects spherical aberration and coma in a well-balanced manner.

In the present invention, in order to satisfactorily correct the residual aberration caused by the first to third lens systems and obtain good optical performance over the entire screen, the focal points of the 41st lens and the 42nd lens are adjusted. The distances are f41 and f42, respectively, and the focal length of the lens surface A on the image plane side of the 43rd lens is f43.
_R, wherein 0.20 and a focal length of the object side lens surface B of the first 44 lens was _{f44 F <| f44 F | /} f43 R <0.42 ( where f44 _F <0) ······ (3) 0.35 <f42 / | f41 | <0.85 (4) The following condition is satisfied.

Conditional expression (3) is for appropriately setting the ratio of the refracting power of the lens surface A and the lens surface B, and mainly for correcting spherical aberration and coma in a well-balanced manner.

When the value exceeds the upper limit of conditional expression (3), the lens surface A
When the difference between the refractive powers of the lens surface and the lens surface B decreases, high-order spherical aberration becomes insufficiently corrected, and it becomes difficult to correct the spherical aberration and the coma aberration with another lens surface in a well-balanced manner. .

When the refractive power of the lens surface B exceeds the lower limit and becomes stronger than that of the lens surface A, the annular spherical aberration increases, and at the same time, the negative Petzval sum of the lens surface B increases. This is not good because the curvature of field increases in the positive direction.

Conditional expression (4) relates to the ratio between the refractive powers of the forty-first and forty-second lenses, and is mainly for correcting the on-axis and off-axis aberrations in a well-balanced manner based on conditional expression (3). is there.

If the negative refractive power of the 41st lens is too strong beyond the upper limit value of the conditional expression (4), it becomes difficult to correct high-order residual coma (introverted coma) together with spherical aberration in a well-balanced manner. Come.

On the other hand, if the negative refractive power of the 41st lens is too weak below the lower limit, high-order positive coma (extroverted coma) and high-order curvature of field are often generated, which is good. Absent.

In particular, when the refractive indices of the materials of the 41st lens and the 42nd lens are N41 and N42, respectively, the following condition is satisfied: N41> N42 (1)

Conditional expression (1) is used for bonding a negative 41-th lens having a relatively high refractive index and a positive 42-th lens having a low refractive index to form a positive lens as a whole. The refractive indices of both materials are set so that the lens surface C has a predetermined negative refractive power.

The correction ratio of the positive spherical aberration and the positive coma aberration on the cemented lens surface C is smaller than the total aberration correction ratio of the lens surface A of the 43rd lens and the lens surface B of the 44th lens. Thus, coma aberration is corrected more frequently, whereby various aberrations are corrected in a well-balanced manner.

Particularly, in the present invention, preferably, the fourth
The refractive indices of the materials of the first lens and the forty-second lens are N41,
When N42 is satisfied, the following condition is satisfied: 0.09 <| N41−N42 | (2)

Deviating from conditional expression (2), the forty-first lens and the fourth lens
When the refractive index difference between the materials of the two lenses becomes smaller, the correcting power of various aberrations on the cemented lens surface C becomes insufficient,
In order to obtain a predetermined correction power, the curvature of the cemented lens surface C must be increased. As a result, higher-order coma aberration and spherical aberration are generated more than the lens surface C, which is not good.

In the present invention, the third lens unit is composed of a positive 31st lens, a 32nd lens having both convex lens surfaces, and a 32nd lens having both concave lens surfaces. No. 32 with negative refractive power with convex surface facing
It is composed of lenses to correct aberration fluctuations due to zooming,
It is preferable to obtain high optical performance over the entire zoom range.

In the present invention, focusing is performed by moving the first and second lens units.

At this time, the first lens unit is composed of a negative meniscus eleventh lens having a concave surface facing the image surface side in order from the object side, a positive twelfth lens having both lens surfaces convex, and a convex surface facing the object side. It is composed of three meniscus positive thirteenth lenses.

A second meniscus negative second lens having a concave surface facing the image surface side, a negative second lens having both concave lens surfaces, a positive 23rd lens having both convex lens surfaces, It is composed of four negative 24th lenses with a strong concave surface facing the object side.

As a result, a change in the position of the entrance pupil during focusing is reduced, and the outer diameter of the first lens unit is reduced.

Also, aberration fluctuations during zooming and focusing are corrected well, and high optical performance is obtained over the entire zooming range and the entire object distance.

In the present invention, the focus is set to the third group,
Alternatively, a rear focus method in which the fourth lens unit is moved may be used. In order to simplify the mechanism, a general one-group focus is suitable.

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.

Table 1 shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples. Numerical Example 1 f = 28.8 to 143.5 fno = 1: 5.45 to 8.2 2ω = 73.8 ° to 17.1 ° R 1 = 145.16 D 1 = 2.40 N 1 = 1.884666 ν 1 = 23.8 R 2 = 54.78 D 2 = 1.50 R 3 = 56.20 D 3 = 6.90 N 2 = 1.60311 ν 2 = 60.7 R 4 = -243.27 D 4 = 0.15 R 5 = 38.22 D 5 = 4.20 N 3 = 1.69680 ν 3 = 55.5 R 6 = 110.11 D 6 = Variable R 7 = 73.28 D 7 = 1.20 N 4 = 1.80610 ν 4 = 41.0 R 8 = 13.84 D 8 = 4.66 R 9 = -52.03 D 9 = 1.10 N 5 = 1.80400 ν 5 = 46.6 R10 = 26.00 D10 = 0.80 R11 = 22.70 D11 = 3.80 N 6 = 1.84666 ν 6 = 23.9 R12 = -60.96 D12 = 0.87 R13 = -24.73 D13 = 1.10 N 7 = 1.65160 ν 7 = 58.5 R14 = -299.40 D14 = Variable R15 = ∞ (aperture) D15 = 1.00 R16 = 22.10 D16 = 2.60 N 8 = 1.74320 ν 8 = 49.3 R17 = -110.63 D17 = 0.15 R18 = 21.49 D18 = 3.20 N 9 = 1.48749 ν 9 = 70.2 R19 = -21.49 D19 = 0.90 N19 = 1.83400 ν10 = 37.2 R20 = 33.42 D20 = Variable R21 = 63.82 D21 = 1.00 N11 = 1.77250 ν11 = 49.6 R22 = 17.80 D22 = 3.80 N12 = 1.51823 ν12 = 59.0 R23 = -36.33 D23 = 4.35 R24 = -280.77 D24 = 3.80 N13 = 1.58913 ν13 = 61.2 R25 = -18.42 D25 = 2.97 R26 = -13.64 D26 = 1.30 N14 = 1.83481 ν14 = 42.7 R 27 = -29.71

[0041]

[Table 1] Numerical example 2 f = 28.8 to 132.0 fno = 1: 5.3 to 8.2 2ω = 73.8 ° to 18.6 ° R 1 = 143.57 D 1 = 2.40 N 1 = 1.84666 ν 1 = 23.8 R 2 = 53.73 D 2 = 1.50 R 3 = 54.90 D 3 = 6.90 N 2 = 1.60311 ν 2 = 60.7 R 4 = -250.94 D 4 = 0.15 R 5 = 37.74 D 5 = 4.20 N 3 = 1.69680 ν 3 = 55.5 R 6 = 110.18 D 6 = Variable R 7 = 73.35 D 7 = 1.20 N 4 = 1.80610 ν 4 = 41.0 R 8 = 13.86 D 8 = 4.65 R 9 = -53.01 D 9 = 1.10 N 5 = 1.80400 ν 5 = 46.6 R10 = 26.05 D10 = 0.80 R11 = 22.77 D11 = 3.80 N 6 = 1.84666 ν 6 = 23.9 R12 = -60.72 D12 = 0.86 R13 = -25.08 D13 = 1.10 N 7 = 1.65160 ν 7 = 58.5 R14 = -272.88 D14 = Variable R15 = ∞ (aperture) D15 = 1.00 R16 = 22.17 D16 = 2.60 N 8 = 1.74320 ν 8 = 49.3 R17 = -114.44 D17 = 0.15 R18 = 21.67 D18 = 3.20 N 9 = 1.48749 ν 9 = 70.2 R19 = -21.67 D19 = 0.90 N10 = 1.83400 ν10 = 37.2 R20 = 33.57 D20 = Variable R21 = 62.96 D21 = 1.00 N11 = 1.77250 ν11 = 49.6 R22 = 17.79 D22 = 3.80 N12 = 1.51823 ν12 = 59.0 R23 = -36.25 D23 = 4.33 R24 = -287.22 D24 = 3.80 N13 = 1.58913 ν13 = 61.2 R25 = -18.44 D25 = 2.96 R26 = -13.63 D26 = 1.30 N14 = 1.80610 ν14 = 41.0 R27 = -30.75

[0042]

[Table 2] Numerical Example 3 f = 30.9 to 130.7 fno = 1: 5.5 to 8.2 2ω = 70.0 ° to 18.8 ° R 1 = 145.37 D 1 = 2.10 N 1 = 1.884666 ν 1 = 23.8 R 2 = 55.21 D 2 = 1.50 R 3 = 56.31 D 3 = 5.10 N 2 = 1.60311 ν 2 = 60.7 R 4 = -295.19 D 4 = 0.15 R 5 = 37.27 D 5 = 3.80 N 3 = 1.69680 ν 3 = 55.5 R 6 = 105.49 D 6 = Variable R 7 = 68.74 D 7 = 1.20 N 4 = 1.80610 ν 4 = 41.0 R 8 = 13.53 D 8 = 4.48 R 9 = -57.43 D 9 = 1.10 N 5 = 1.80610 ν 5 = 41.0 R10 = 26.57 D10 = 0.80 R11 = 22.46 D11 = 3.80 N 6 = 1.84666 ν 6 = 23.9 R12 = -62.87 D12 = 0.93 R13 = -25.33 D13 = 1.10 N 7 = 1.60311 ν 7 = 60.7 R14 = -249.30 D14 = Variable R15 = ∞ (aperture) D15 = 1.00 R16 = 21.96 D16 = 2.60 N 8 = 1.72000 ν 8 = 50.3 R17 = -129.06 D17 = 0.15 R18 = 22.37 D18 = 3.20 N 9 = 1.48749 ν 9 = 70.2 R19 = -22.37 D19 = 0.90 N10 = 1.83400 ν10 = 37.2 R20 = 36.94 D20 = Variable R21 = 59.60 D21 = 1.00 N11 = 1.74320 ν11 = 49.3 R22 = 16.55 D22 = 4.00 N12 = 1.51823 ν12 = 59.0 R23 = -34.03 D23 = 4.36 R24 = -105.13 D24 = 3.50 N13 = 1.62299 ν13 = 58.2 R25 = -19.40 D25 = 2.96 R26 = -13.68 D26 = 1.30 N14 = 1 80610 ν14 = 41.0 R27 = -31.47

[0043]

[Table 3] Numerical example 4 f = 36.0 to 146.8 fno = 1: 5.8 to 8.2 2 ω = 62.0 ° to 16.9 ° R 1 = 74.03 D 1 = 2.00 N 1 = 1.805518 ν 1 = 25.4 R 2 = 41.21 D 2 = 8.40 N 2 = 1.48749 ν 2 = 70.2 R 3 = -130.85 D 3 = 0.12 R 4 = 27.39 D 4 = 4.90 N 3 = 1.48749 ν 3 = 70.2 R 5 = 65.45 D 5 = Variable R 6 = 206.52 D 6 = 1.20 N 4 = 1.77250 ν 4 = 49.6 R 7 = 12.32 D 7 = 3.40 R 8 = -37.65 D 8 = 1.10 N 5 = 1.78590 ν 5 = 44.2 R 9 = 66.58 D 9 = 0.40 R10 = 21.89 D10 = 3.00 N 6 = 1.84666 ν 6 = 23.9 R11 = -43.59 D11 = 0.45 R12 = -23.41 D12 = 1.00 N 7 = 1.74400 ν 7 = 44.8 R13 = 79.15 D13 = Variable R14 = ∞ (Aperture) D14 = 1.00 R15 = 28.27 D15 = 2.80 N 8 = 1.56384 ν 8 = 60.7 R16 = -28.27 D16 = 0.12 R17 = 15.92 D17 = 3.90 N 9 = 1.48749 ν 9 = 70.2 R18 = -19.67 D18 = 0.90 N10 = 1.83400 ν10 = 37.2 R19 = 34.22 D19 = Variable R20 = 221.30 D20 = 1.00 N11 = 1.77250 ν11 = 49.6 R21 = 30.00 D21 = 3.20 N12 = 1.51602 ν12 = 56.8 R22 = -25.08 D22 = 0.15 R23 = 48.71 D23 = 3.73 N13 = 1.51742 ν13 = 52.4 R24 = -18.54 D24 = 1.98 R25 = -14.18 D25 = 1.30 N14 = 1.77250 ν14 = 49.6 R26 = -345.28

[0044]

[Table 4] Numerical example 5 f = 39.14 to 145.76 fno = 1: 5.76 to 8.2 2 ω = 57.9 ° to 16.9 ° R 1 = 75.50 D 1 = 1.70 N 1 = 1.80518 ν 1 = 25.4 R 2 = 40.14 D 2 = 6.10 N 2 = 1.48749 ν 2 = 70.2 R 3 = -117.56 D 3 = 0.12 R 4 = 25.90 D 4 = 3.70 N 3 = 1.48749 ν 3 = 70.2 R 5 = 72.24 D 5 = Variable R 6 = 129.14 D 6 = 1.00 N 4 = 1.77250 ν 4 = 49.6 R 7 = 13.16 D 7 = 3.69 R 8 = -37.08 D 8 = 1.00 N 5 = 1.74400 ν 5 = 44.8 R 9 = 81.65 D 9 = 0.40 R10 = 22.97 D10 = 3.10 N 6 = 1.84666 ν 6 = 23.9 R11 = -49.85 D11 = 0.48 R12 = -25.94 D12 = 0.90 N 7 = 1.74400 ν 7 = 44.8 R13 = 69.80 D13 = Variable R14 = ∞ (Aperture) D14 = 1.00 R15 = 33.22 D15 = 2.50 N 8 = 1.65160 ν 8 = 58.5 R16 = -33.22 D16 = 0.12 R17 = 16.84 D17 = 3.60 N 9 = 1.48749 ν 9 = 70.2 R18 = -24.52 D18 = 0.80 N10 = 1.83400 ν10 = 37.2 R19 = 30.74 D19 = Variable R20 = 99.37 D20 = 1.00 N11 = 1.74320 ν11 = 49.3 R21 = 26.94 D21 = 2.50 N12 = 1.51823 ν12 = 59.0 R22 = -82.88 D22 = 1.66 R23 = 422.35 D23 = 3.50 N13 = 1.57135 ν13 = 53.0 R24 = -18.30 D24 = 3.12 R25 = -13.98 D25 = 1.00 N14 = 1.74320 ν14 = 49.3 R26 = -45.55

[0045]

[Table 5] Numerical example 6 f = 39.14 to 149.60 fno = 1: 5.7 to 8.2 2 ω = 57.9 ° to 16.5 ° R 1 = 71.45 D 1 = 1.90 N 1 = 1.805518 ν 1 = 25.4 R 2 = 40.97 D 2 = 7.20 N 2 = 1.48749 ν 2 = 70.2 R 3 = -128.11 D 3 = 0.12 R 4 = 26.43 D 4 = 4.60 N 3 = 1.48749 ν 3 = 70.2 R 5 = 55.32 D 5 = Variable R 6 = 133.60 D 6 = 1.20 N 4 = 1.77250 ν 4 = 49.6 R 7 = 12.35 D 7 = 3.49 R 8 = -35.98 D 8 = 1.10 N 5 = 1.78590 ν 5 = 44.2 R 9 = 67.47 D 9 = 0.40 R10 = 23.18 D10 = 3.00 N 6 = 1.84666 ν 6 = 23.9 R11 = -41.51 D11 = 0.31 R12 = -23.06 D12 = 1.10 N 7 = 1.74400 ν 7 = 44.8 R13 = 126.98 D13 = Variable R14 = ∞ (Aperture) D14 = 1.00 R15 = 31.69 D15 = 2.80 N 8 = 1.58913 ν 8 = 61.2 R16 = -29.37 D16 = 0.12 R17 = 15.92 D17 = 3.90 N 9 = 1.48749 ν 9 = 70.2 R18 = -21.12 D18 = 0.90 N10 = 1.83400 ν10 = 37.2 R19 = 30.42 D19 = Variable R20 = 936.21 D20 = 1.00 N11 = 1.65844 ν11 = 50.9 R21 = 33.43 D21 = 3.50 N12 = 1.53996 ν12 = 59.5 R22 = -30.19 D22 = 0.22 R23 = 52.85 D23 = 4.00 N13 = 1.51742 ν13 = 52.4 R24 = -18.23 D24 = 2.25 R25 = -14.31 D25 = 1.30 N14 = 1.77250 ν14 = 49.6 R26 = -261.62

[0046]

[Table 6]

[0048]

[Table 7]

[0049]

According to the present invention, as described above, the overall length of the four-unit zoom lens can be shortened by appropriately setting the moving conditions of each lens unit and the lens configuration of the fourth unit mainly in response to zooming. Aperture ratio F / 5 ~ 8, zoom ratio 4
A zoom lens having high optical performance over the entire zooming range with an aperture ratio of F4.3 to 5.8 and a zoom ratio of about 2.8 can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zoom lens at a wide-angle end according to a first numerical embodiment of the present invention.

FIG. 2 is a sectional view of a zoom lens at a wide-angle end according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a zoom lens at a wide-angle end according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a lens at a zoom position at a wide-angle end according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a lens at a zoom position at a wide-angle end according to Numerical Embodiment 5 of the present invention.

FIG. 6 is a lens cross-sectional view at a zoom position at a wide-angle end according to Numerical Embodiment 6 of the present invention.

FIG. 7 is an aberration diagram at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 8 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 9 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention;

FIG. 10 is an aberration diagram at a wide angle end according to Numerical Example 2 of the present invention.

FIG. 11 is an intermediate aberration diagram of the numerical example 2 of the present invention.

FIG. 12 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention;

FIG. 13 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 14 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 15 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

FIG. 16 is an aberration diagram at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 17 is an intermediate aberration diagram of the numerical example 4 of the present invention.

FIG. 18 is an aberration diagram at a telephoto end in Numerical Example 4 of the present invention.

FIG. 19 is an aberration diagram at a wide angle end according to Numerical Example 5 of the present invention.

FIG. 20 is an intermediate aberration diagram of the numerical example 5 of the present invention.

FIG. 21 is an aberration diagram at a telephoto end in Numerical Example 5 of the present invention.

FIG. 22 is an aberration diagram at a wide angle end according to Numerical Example 6 of the present invention.

FIG. 23 is an intermediate aberration diagram of the numerical example 6 of the present invention.

FIG. 24 is an aberration diagram at a telephoto end in Numerical Example 6 of the present invention.

[Explanation of symbols]

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

Continuation of the front page (56) References JP-A-4-293008 (JP, A) JP-A-3-75712 (JP, A) JP-A-3-6507 (JP, A) JP-A-63-70819 (JP) JP-A-56-133713 (JP, A) JP-A-60-14213 (JP, A) JP-A-2-287414 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (3)

(57) [Claims] 1. A first lens unit having a positive 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 having a positive refractive power. When zooming from the wide-angle end to the telephoto end, each lens unit is moved toward the object side, the distance between the first and second units is simply increased, and the distance between the second and third units is simply reduced. and moved to the positive refractive power of the cemented lens as a whole fourth group formed by bonding a negative 41st lens and a positive second lens having a concave surface on the image side, the image surface side positive 43 lens having a convex surface on and Ri formed of a negative 44th lens having a convex surface toward the image side, said 41 Ren,
And the focal lengths of the forty-second lens are f41 and f42, respectively.
Let the focal length of the lens surface on the image plane side of the 43rd lens be f4
3 _R, when the focal length of the lens surface on the object side of said 44 lens was _{f44 F 0.20 <| f44 F |} / f43 R <0.42 ( where f
_{44 F <0) 0.35 <f42} / | f41 | < zoom lens that satisfies the 0.85 condition:. 2. The zoom lens according to claim 1, wherein when the refractive indices of the materials of the 41st lens and the 42nd lens are N41 and N42, respectively, a condition of N41> N42 is satisfied. 3. The zoom according to claim 1, wherein the following condition is satisfied: 0.09 <| N41−N42 |, where the refractive indices of the materials of the 41st lens and the 42nd lens are N41 and N42, respectively. lens.