JPH06130299A - Zoom lens - Google Patents

Abstract

PURPOSE:To obtain a zoom lens provided with four lens groups as a whole and setting a moving condition accompanied with a refracting power, a variable power, etc., of the respective lens groups appropriately and provided with high optical performance extending over the whole variable power range. CONSTITUTION:This lens is provided with a first group L1 of positive refracting power, a second group L2 of negative refracting power, a third group L3 of positive refracting power, and a fourth group L4 of positive refracting power arranged sequentially from a material side, and each lens group is moved to the material side so as to increase a gap between the first group L1 and the second group L2 simply and to decrease the gap between the second group L2 and the third group L3 simply, and the fourth group L4 is comprised of an adhesive 41th lens in which a negative 41th lens whose concave surface is faced with an image surface side and a positive 42th lens are joined and provided with the positive refracting power, a positive 43th lens whose convex surface is faced with the image surface side, and a negative 44th lens of meniscus shape whose convex surface is faced with the image surface side.

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 particularly to an F number of about 5 to 8 and a zoom ratio of about 4 to 5, or an F number of about 4.3 to 5.8 and a zoom ratio of 2. .9
The present invention relates to a small-sized zoom lens having a short total lens length, which is suitable for a photographic camera, a video camera, an electronic still camera, and the like having good optical performance over the entire zoom range.

[0002]

2. Description of the Related Art Conventionally, a zoom lens having high contrast and high optical performance over the entire zoom range has been required for photographic cameras, video cameras and the like.

Zoom lenses having a focal length at the wide-angle end shorter than the diagonal line of the screen and a zoom ratio of 3 times or more are disclosed, for example, in Japanese Patent Laid-Open Nos. 60-221717 and 63-708.
It is proposed in Japanese Patent Publication No. 19 and the like.

In the publication, four lenses are provided in order from the object side: a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power. We propose a zoom lens composed of a group.

In addition, as a four-group zoom lens composed of four lens groups, in JP-A-62-247316 and JP-A-62-24213, the first group having a positive refractive power and the negative group are arranged in order from the object side. Second group of positive power, third positive power
Group, and four lens groups of the fourth group having a positive refractive power, the second group is moved to perform zooming, and the fourth group is moved to perform image plane variation and focus due to zooming. ing.

Further, in JP-A-58-160913, the first group having a positive refractive power and the second group having a negative refractive power are sequentially arranged from the object side.
An image having four lens groups, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, by moving the first lens group and the second lens group to perform zooming, The surface movement is performed by moving the fourth group. Then, focusing is performed by moving one or more lens groups among these lens groups.

[0007]

Generally, in the above-described four-group zoom lens, it is necessary to shorten the total lens length, maintain high optical performance over the entire zoom range, and obtain a predetermined aperture ratio and zoom ratio. It is important to properly set the optical constants of each lens unit that constitutes the lens.

For example, in the above-mentioned four-group zoom lens, unless the lens configuration of the fourth group is properly set, the total lens length becomes long and various aberrations increase, so that it is difficult to obtain an image with good image quality. Is coming.

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

In the four-group zoom lens according to the present invention, by appropriately setting the moving condition of each lens group and the lens configuration of the fourth group mainly with zooming, the overall lens length can be shortened and the aperture ratio F / 5 to 5 can be obtained. A zoom lens having high optical performance over the entire zoom range with a zoom ratio of about 8 and 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. For the purpose of providing.

[0011]

A zoom lens according to the present invention comprises, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens group. The fourth of refractive power
The zoom lens has four lens groups, and when zooming from the wide-angle end to the telephoto end, each lens group is moved toward the object side, and the distance between the first group and the second group is simply increased. The fourth group is moved so that the interval between the groups is simply reduced, and the fourth group is constructed by cementing a negative forty-first lens and a positive forty-second lens with a concave surface facing the image side, and having a positive refractive power as a whole. It is characterized by including a forty-first lens combination, a positive forty-third lens having a convex surface directed toward the image side, and a negative forty-fourth lens having a strong convex surface directed toward the image side.

[0012]

1 to 7 are lens cross-sectional views at the wide-angle end in Numerical Embodiments 1 to 7 of the present invention.

In the figure, L1 is a first group having a positive refractive power, L2 is a second group having a negative refractive power, L3 is a third group having a positive refractive power, and L4.
Is a fourth lens unit having a positive refractive power, and SP is an aperture stop, which is provided in front of the third lens unit.

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

In this embodiment, as described above, the refracting powers of the four lens groups and the moving conditions of each lens group due to zooming are set, and the lens structure of the fourth lens group is composed of four lenses having a predetermined shape. There is.

As a result, a zoom lens having a good optical performance over the entire zooming range of a zooming ratio of about 4 to 5 and an F number of about 5 to 8 is obtained while the overall size of the lens system is reduced. In particular, residual aberrations due to the lens systems from the first group to the third group are satisfactorily corrected by the fourth group constructed as described above.

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

An image side lens surface A of the positive forty-third lens element in the fourth lens group and an object side lens surface B of the negative forty-fourth lens element make use of their shapes and refractive index differences to make the first lens group. From the third
Among the residual aberrations due to the lens system up to the group, mainly spherical aberration and coma are well corrected.

In particular, the lens surfaces A and B correct strong negative residual spherical aberration and negative residual coma (inward coma) at the telephoto end. And the 41st lens and the 4th
A cemented 41st lens having a positive refractive power as a whole in which two lenses are cemented is used, and spherical aberration and coma are further corrected in good balance by the cemented lens surface C.

Particularly, when the refractive indexes of the materials of the 41st lens and the 42nd lens are N41 and N42, respectively, the condition N41> N42 (1) is satisfied.

Conditional expression (1) is a bonding method for forming a positive lens as a whole by cementing a negative 41st lens having a relatively high material refractive index and a positive 42nd lens having a low material refractive index. The refractive indexes of both materials are set so that the lens surface C has a negative refractive power of a predetermined strength.

The correction ratio of the positive spherical aberration and the positive coma aberration on the cemented lens surface C is higher than the total correction ratio of the aberrations on the lens surface A of the 43rd lens and the lens surface B of the 44th lens. As a result, the coma aberration is corrected more often, so that various aberrations are corrected in a well-balanced manner.

Particularly preferably in the present invention, the fourth
The refractive indexes of the materials of the 1st lens and the 42nd lens are N41,
When N42, the condition 0.09 <| N41−N42 | ... (2) is satisfied.

Conditional expression (2) is not satisfied and the 41st lens and the 4th lens
As the difference in refractive index between the two lens materials becomes smaller, the correction power for various aberrations on the cemented lens surface C becomes insufficient,
In order to obtain a predetermined correction force, the curvature of the cemented lens surface C must be increased, and as a result, a lot of higher-order coma aberration and spherical aberration are generated than the lens surface C, which is not good.

In addition, in the present invention, in order to satisfactorily correct the residual aberration due to the lens systems from the first group to the third group and obtain good optical performance over the entire screen, the 41st lens and the 42nd lens should be used. The focal lengths are f41, f42,
The focal length of the lens surface A on the image side of the 43rd lens is f
43 _R , when the focal length of the object-side lens surface B of the forty-fourth lens is f44 _F 0.20 <| f44 _F | / f43 _R <0.42 (however, f44 _F <0) -(3) 0.35 <f42 / | f41 | <0.85 ... (4) It is good to satisfy the condition.

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

If the upper limit of conditional expression (3) is exceeded, the lens surface A
When the difference between the refracting powers of the lens surface B and the lens surface B becomes smaller, the higher-order spherical aberration becomes insufficiently corrected, and it becomes difficult to correct the spherical aberration and the coma aberration in good balance with other lens surfaces. .

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

Conditional expression (4) relates to the ratio of the refracting powers of the forty-first lens and the forty-second lens, and is mainly for correcting well-balanced axial and off-axis aberrations based on the conditional expression (3). is there.

When the upper limit of conditional expression (4) is exceeded and the negative refracting power of the forty-first lens becomes too strong, it becomes difficult to correct high-order residual coma aberration (inward coma) together with spherical aberration in good balance. Come on.

If the negative refracting power of the forty-first lens becomes too weak below the lower limit, high-order positive coma aberration (extroverted coma) and high-order field curvature will occur frequently. Absent.

In the present invention, the third lens group is cemented with, in order from the object side, a positive 31st lens, a 32nd lens having both convex lens surfaces and a 32nd lens having both lens surfaces concave, and as a whole, the object side. Laminating the negative refractive power with the convex surface facing the 32nd
It is composed of a lens that corrects 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 group and the second group.

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

A negative 21st meniscus lens having a concave surface facing the image side in the second lens group, a negative 22nd lens having concave surfaces on both lens surfaces, and a positive 23rd lens having convex surfaces on both lens surfaces, It is composed of four negative 24th lenses with a strong concave surface facing the object side.

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

Further, the aberration variation during zooming and focusing is satisfactorily corrected, 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 that is performed by moving the fourth group may be used. Further, if the mechanism is to be simplified, a general first group focus is suitable.

Next, numerical examples of the present invention will be shown. 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 gap from the object side, and Ni and νi are respectively from the object side of the i-th lens. The refractive index of glass and the Abbe number.

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 2 ω = 73.8
° ~ 17.1 ° R 1 = 145.16 D 1 = 2.40 N 1 = 1.84666 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 N10 = 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 R27 = -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 1
8.6 ° 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 2 ω = 70.0 ° to
18.8 ° R 1 = 145.37 D 1 = 2.10 N 1 = 1.84666 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 °
~ 16.9 ° R 1 = 74.03 D 1 = 2.00 N 1 = 1.80518 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
° ~ 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
° ~ 16.5 ° R 1 = 71.45 D 1 = 1.90 N 1 = 1.80518 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] Numerical Example 7 f = 36.0 to 103.48 fno = 1: 4.3 to 5.75 2 ω = 62.0
° ~ 23.62 ° R 1 = 80.36 D 1 = 2.00 N 1 = 1.80518 ν 1 = 25.4 R 2 = 42.75 D 2 = 8.40 N 2 = 1.48749 ν 2 = 70.2 R 3 = -119.19 D 3 = 0.12 R 4 = 27.82 D 4 = 4.90 N 3 = 1.48749 ν 3 = 70.2 R 5 = 67.58 D 5 = Variable R 6 = 158.57 D 6 = 1.20 N 4 = 1.77250 ν 4 = 49.6 R 7 = 12.52 D 7 = 3.48 R 8 = -38.97 D 8 = 1.10 N 5 = 1.78590 ν 5 = 44.2 R 9 = 71.10 D 9 = 0.40 R10 = 21.98 D10 = 3.00 N 6 = 1.84666 ν 6 = 23.9 R11 = -51.16 D11 = 0.81 R12 = -22.67 D12 = 1.00 N 7 = 1.74400 ν 7 = 44.8 R13 = 107.39 D13 = Variable R14 = ∞ (Aperture) D14 = 1.00 R15 = 34.18 D15 = 3.70 N 8 = 1.60311 ν 8 = 60.7 R16 = -29.04 D16 = 0.12 R17 = 16.19 D17 = 5.80 N 9 = 1.48749 ν 9 = 70.2 R18 = -17.82 D18 = 0.90 N10 = 1.83400 ν10 = 37.2 R19 = 31.21 D19 = variable R20 = 149.88 D20 = 0.80 N11 = 1.77250 ν11 = 49.6 R21 = 33.81 D21 = 3.06 N12 = 1.51602 ν12 = 56.8 R22 =- 22.49 D22 = 0.12 R23 = 45.54 D23 = 3.73 N13 = 1.51742 ν13 = 52.4 R24 = -17.51 D24 = 1.59 R25 = -14.60 D25 = 1.30 N14 = 1.77250 ν14 = 49.6 R26 = 982.32

[0047]

[Table 7]

[0048]

[Table 8]

[0049]

As described above, according to the present invention, in the four-group zoom lens, the total lens length is shortened by appropriately setting the moving condition of each lens group and the lens configuration of the fourth group mainly with the zooming. While the aperture ratio is F / 5 to 8 and the zoom ratio is 4
It is possible to achieve a zoom lens having a high optical performance over the entire zoom range with an aperture ratio of about F4 to about 5.8, a aperture ratio of F4.3 to about 5.8, and a zoom ratio of about 2.8.

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view at a zoom position at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 2 is a lens cross-sectional view at a zoom position at a wide-angle end according to Numerical Embodiment 2 of the present invention.

FIG. 3 is a lens cross-sectional view at a zoom position at a wide-angle end according to Numerical Embodiment 3 of the present invention.

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

FIG. 5 is a lens cross-sectional view 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 a lens cross-sectional view at a wide-angle end zoom position according to Numerical Embodiment 7 of the present invention.

FIG. 8 is an aberration diagram at the wide-angle end according to Numerical Example 1 of the present invention.

FIG. 9 is an intermediate aberration diagram of Numerical example 1 of the present invention.

FIG. 10 is an aberration diagram at a telephoto end according to Numerical Example 1 of the present invention.

FIG. 11 is an aberration diagram at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 12 is an intermediate aberration diagram of Numerical example 2 of the present invention.

FIG. 13 is an aberration diagram at a telephoto end according to Numerical Example 2 of the present invention.

FIG. 14 is an aberration diagram at the wide-angle end according to Numerical Example 3 of the present invention.

FIG. 15 is an intermediate aberration diagram of Numerical example 3 of the present invention.

FIG. 16 is an aberration diagram at a telephoto end according to Numerical Example 3 of the present invention.

FIG. 17 is an aberration diagram at a wide-angle end according to Numerical Example 4 of the present invention.

FIG. 18 is an intermediate aberration diagram of Numerical example 4 of the present invention.

FIG. 19 is an aberration diagram at a telephoto end according to Numerical Example 4 of the present invention.

FIG. 20 is an aberration diagram at a wide-angle end according to Numerical Example 5 of the present invention.

FIG. 21 is an intermediate aberration diagram of Numerical Example 5 of the present invention.

FIG. 22 is an aberration diagram at a telephoto end according to Numerical Example 5 of the present invention.

FIG. 23 is an aberration diagram at a wide-angle end according to Numerical Example 6 of the present invention.

FIG. 24 is an intermediate aberration diagram of Numerical Example 6 of the present invention.

FIG. 25 is an aberration diagram at a telephoto end according to Numerical Example 6 of the present invention.

FIG. 26 is an aberration diagram at a wide-angle end according to Numerical Example 7 of the present invention.

FIG. 27 is an intermediate aberration diagram of Numerical Example 7 of the present invention.

FIG. 28 is an aberration diagram at a telephoto end according to Numerical Example 7 of the present invention.

[Explanation of symbols]

 L1 1st group L2 2nd group L3 3rd group L4 4th group SP Aperture d d line g g line ΔM Meridional image surface ΔS Sagittal image surface

Claims (4)

[Claims] 1. Four lens groups, in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, and a fourth group having a positive refractive power. When the magnification is changed from the wide-angle end to the telephoto end, each lens group is moved toward the object side, the distance between the first and second groups is simply increased, and the distance between the second and third groups is simply decreased. The fourth lens unit is configured by cementing a negative forty-first lens having a concave surface facing the image surface side and a positive forty-second lens together, so that the fourth lens unit has a positive refracting power as a whole. A zoom lens comprising a positive forty-third lens having a convex surface directed toward the surface side and a negative forty-fourth lens having a strong convex surface directed toward the image surface side. 2. The zoom lens according to claim 1, wherein the conditions of N41> N42 are satisfied when the refractive indexes of the materials of the 41st lens and the 42nd lens are N41 and N42, respectively. 3. The zoom lens system according to claim 1, wherein when the refractive indices of the materials of the 41st lens and the 42nd lens are N41 and N42, 0.09 <| N41-N42 | is satisfied. lens. 4. The focal lengths of the 41st lens and the 42nd lens are f41 and f42, respectively, the focal length of the image surface side lens surface of the 43rd lens is f43 _R , and the object side lens surface of the 44th lens. When the focal length of is f44 _F , then 0.20 <| f44 _F | / f43 _R <0.42 (where f
The zoom lens according to claim 2, wherein the condition of 44 _F <0) 0.35 <f42 / | f41 | <0.85 is satisfied.