JP3144191B2 - 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 small zoom lens having a high zoom ratio and a wide angle of view suitable for a lens shutter camera, a video camera, and the like. The present invention relates to a zoom lens which is excellent in portability and has a reduced length (distance from one lens surface to an image surface).

[0002]

2. Description of the Related Art Recently, in a lens shutter camera, a video camera, and the like, a small zoom lens having a short overall lens length has been demanded with the downsizing of the camera. In particular, lens shutter cameras are becoming smaller and smaller due to the development of peripheral technology such as electric circuits for driving the zoom, and the photographic lenses provided with them are also required to have high zoom ratios and compact zoom lenses. I have.

Conventionally, as a zoom lens for a lens shutter, a so-called two-group zoom lens comprising two lens groups having positive and negative refractive powers has been mainly used. Since the two-unit zoom lens has a simple lens configuration and a moving mechanism at the time of zooming, it has advantages such as downsizing of the camera and relatively low cost. However, since the zooming operation must be performed by only one lens group, the zooming ratio is about 1.6 to 2 times. Forcibly increasing the zooming ratio requires an increase in the size of the lens system. At the same time, it becomes difficult to maintain high optical performance.

On the basis of a two-unit zoom lens, the first unit is divided into two lens units having a positive refractive power.
A three-unit zoom lens which aims at high zoom ratio as a three-unit configuration having positive and negative refractive powers is disclosed in, for example, JP-A-3-282409, JP-A-4-37810, and JP-A-4-7651.
No. 1 publication and the like.

However, if an attempt is made to achieve a wide-angle zoom lens system having a half-angle of view of 35 ° or more with this lens group configuration, the change in the position of the entrance pupil during zooming becomes large. For this reason, it is very difficult to suppress aberration fluctuations due to zooming when achieving high zooming.

In addition, a zoom lens having a wide angle of view and a high zoom ratio by increasing the half angle of view at the wide angle end to about 38 ° and the zoom ratio by about 3.5 times by grouping a plurality of lenses is known, for example. Kaihei 2-
No. 72316 and Japanese Patent Application Laid-Open No. 3-249614. However, these zoom lens systems both have a large front lens diameter and a large overall lens length, and are not always sufficient as a photographing lens of a compact camera.

In particular, when applied to a camera using an external finder, there is a problem that the lens barrel covers the field of view of the finder at the wide angle end. In addition, as a result, there arises a problem that the arrangement of the viewfinder and the form of the camera are restricted.

[0008]

Generally, in a zoom lens, if the refractive power of each lens unit is increased, the amount of movement of each lens unit for obtaining a predetermined zoom ratio is reduced, and the overall length of the lens is reduced. High magnification can be achieved. However, if the refractive power of each lens group is simply increased, the aberration variation accompanying zooming increases, and it is necessary to obtain good optical performance over the entire zoom range, especially when aiming for high zooming and a wide angle of view. There is a problem that it becomes difficult.

The present invention comprises five lens groups as a whole, and appropriately sets the moving conditions, refractive power, etc. of each lens group during zooming, the photographic field angle at the wide angle end is about 74 °, and the zoom ratio is 3 It is an object of the present invention to provide a zoom lens having high optical performance over the entire zoom range of about 0.5.

[0010]

A zoom lens according to the present invention has a first group of negative refractive power and a second group of negative refractive power in order from the object side.
At the wide-angle end, the combined lens unit includes a front lens unit having a positive refractive power, a fourth lens unit having a positive refractive power, and a fifth lens unit having a negative refractive power. And a rear group consisting of two lens groups. In zooming from the wide-angle end to the telephoto end, the first, second, and third groups have a combined refracting power of the front group that is longer than that of the wide-angle end. The fourth and fifth lens units move so as to be weaker at the end, and the distances between the fourth and fifth lens units are reduced. The focal length of the i-th lens unit is fi, the focal length of the entire system at the wide-angle end is fW, The lateral magnification at the wide-angle end of the i-th unit is βiW, and the combined refractive power of the front unit at the wide-angle end and the telephoto end is φ _123W , φ
_{Assuming 123T} and the zoom ratio as Z, 0.5 <| f5 / fW | <1.5 (1) 1.1 <β5W <1.8 (2) 1.0 <| f1 /FW|<6.0 (5) 1.0 <| f2 / fW | <6.0 (6) 0.25 <(φ123W / φ123T) / Z <0.8 (7) 0.25 <β4W <0.55 (8) 0.1 <f5 · (1−β5W) / fW <0.7 (9) I have.

[0011]

FIG. 1 is an explanatory diagram of a paraxial refractive power arrangement of a zoom lens according to the present invention. In FIG. 1, (A) is the wide-angle end,
(B) shows the telephoto end. 2 to 4 are lens cross-sectional views at the wide-angle end in Numerical Examples 1 to 3 of the present invention, respectively. FIGS. 5 to 13 are various aberration diagrams of Numerical Examples 1 to 3 of the present invention.

In the drawing, LF denotes a front group having a positive refractive power, LR denotes a rear group, SP denotes an aperture, and IP denotes an image plane. Li (i = 1 to
5) is the i-th group. Arrows indicate the moving direction of each lens group when zooming from the wide-angle side to the telephoto side.

The front unit LF includes a first unit L1 having a negative refractive power, a second unit L2 having a negative refractive power, and a third unit L3 having a positive refractive power.
It consists of two lens groups, and the combined refractive power at the wide-angle end is a positive refractive power. The rear unit LR is a fourth unit L4 having a positive refractive power.
And a fifth lens unit L5 having a negative refractive power.

At the time of zooming from the wide-angle end to the telephoto end, each of the first, second, and third units moves toward the object side with the second unit changing the relative positional relationship with the other lens units. The combined power of the front group moves so as to be weaker at the telephoto end than at the wide-angle end. In addition, the fourth and fifth units are moved toward the object side so that the distance between them is reduced. At this time, the lens is moved so that the distance between the third lens unit and the fourth lens unit is larger at the telephoto end than at the wide-angle end. Thereby, the combined system of the third group and the fourth group, when viewed as an independent system, is multiplied with magnification.

In the present invention, at the wide-angle end, the combined refractive power of the first and second units is negative, and the third unit having a positive refractive power and the entire front unit are of a retrofocus type. As a result, the front principal point of the front group is located on the image plane side, and widening the angle of view is facilitated while preventing interference between the lens surfaces of the front group and the rear group. Further, the first lens unit has a negative refractive power,
A strong negative refractive power as a retrofocus type in the front group at the wide-angle end as a negative refractive power of the first and second groups.
Allocated to the group to facilitate widening of the angle of view. Then, the fourth lens unit is moved toward the object side to focus from an object at infinity to an object at a short distance.

In the zoom lens of the present invention, the focal length f of the whole lens system is expressed by the following equation.

F = fA · β4 · β5 (β4> 0, β5> 0) (a) where fA represents the composite focal length of the front group, and βi represents the lateral magnification of the i-th group. .

In the present invention, as can be understood from the equation (a), at the time of zooming from the wide-angle end to the telephoto end, the values of the lateral magnifications β4 and β5 are increased and, at the same time, the combined focal length fA of the front group is increased. By reducing the combined refracting power of the front group, a more efficient zooming effect is achieved. Also, the distance between the fourth lens unit having a positive refractive power and the fifth lens unit having a negative refractive power is made narrower (decreased) at the telephoto end than at the wide-angle end, thereby giving a zooming effect to the fifth lens unit. It facilitates high magnification. Also, the rear lens unit has a more divergent (negative) refractive power at the telephoto end, and forms a telephoto type (telephoto type) together with the front lens unit having a positive refractive power to reduce the size of the entire lens system. I have.

In particular, in the present invention, by adopting a paraxial refractive power arrangement as shown in FIG. 1, the photographic field angle is widened so that the focal length at the wide angle end becomes smaller than the screen diagonal length.

Specifically, the front group is a first group having a negative refractive power,
The second lens unit includes a second lens unit having a negative refractive power and a third lens unit having a positive refractive power. The first lens unit and the second lens unit perform zooming from the wide-angle end to the telephoto end.
Each lens group moves toward the object side such that the distance between the groups increases and the distance between the second and third groups decreases. This enhances the zooming effect of the previous group.

In the present invention, the first mechanism is used to simplify the mechanism.
Although the group and the third group are moved integrally, they may be moved independently. According to this, the degree of freedom of design can be increased.

In the present invention, in the above lens configuration, the focal length of the i-th lens unit is fi, the focal length of the whole system at the wide-angle end is fW, the lateral magnification at the wide-angle end of the i-th unit is βiW, The combined refractive power of the front group at the telephoto end is φ
_{Assuming 123T} and the zoom ratio as Z, 0.5 <| f5 / fW | <1.5 (1) 1.1 <β5W <1.8 (2) 1.0 <| f1 /FW|<6.0 (5) 1.0 <| f2 / fW | <6.0 (6) 0.25 <(φ123W / φ123T) / Z <0.8 (7) 0.25 <β4W <0.55 (8) 0.1 <f5 · (1−β5W) / fW <0.7 (9) . This achieves high optical performance over the entire zoom range while further miniaturizing the entire lens system.

Next, the technical meaning of each of the above conditional expressions will be described.

The conditional expression (1) is mainly for effectively performing zooming with respect to the negative refractive power of the fifth lens unit. If the negative refractive power of the fifth lens unit becomes weaker beyond the upper limit of conditional expression (1), the zooming effect of the lens unit becomes weaker during zooming, so that a constant zoom ratio is obtained. For this purpose, the amount of movement of each lens group must be increased, and the overall length of the lens increases.

If the lower limit of conditional expression (1) is exceeded, it means that at the wide-angle end, the combined refractive power of the first to fourth units is positive and the refractive power of the fifth unit is negative at the wide-angle end. The effect as a telephoto type will be too strong.

As a result, the back focus of the lens system becomes too short, which leads to an increase in the outer diameter of the fifth lens group in order to secure a constant peripheral light amount, and at the same time, the refractive power of the lens group becomes strong. Too much distortion causes higher-order field curvature and astigmatism, which makes it difficult to correct them.

Conditional expression (2) relates to the lateral magnification of the fifth lens unit at the wide-angle end.

Assuming that the back focus of the lens system at the wide angle end is BfW, BfW = f5 · (1−β5W).

Therefore, in the present invention, the total length of the lens system and various aberrations are corrected in a well-balanced manner by appropriately setting the value of the conditional expression (2) together with the conditional expression (1).

When the imaging magnification is increased beyond the upper limit value of the conditional expression (2), the back focus becomes longer, but the first to fourth focal lengths are increased.
The refracting power of the group becomes too strong, and the aberration variation increases. On the other hand, if the imaging magnification becomes smaller than the lower limit, it becomes difficult to obtain a predetermined back focus, and the outer diameter of the lens of the fifth group increases, which is not good. The conditional expression (5) relates to the ratio of the refractive power of the first lens unit to the total system at the wide-angle end. If the upper limit of conditional expression (5) is exceeded, the refractive power of the first lens unit becomes too weak, and the total lens length is reduced. It gets bigger.
If the lower limit value is exceeded, the refractive power of the first lens unit becomes strong, so that it becomes difficult to secure a predetermined back focus at the wide-angle end. Conditional expression (6) relates to the ratio of the refractive power of the entire system at the wide-angle end to the refractive power of the second unit, and conditional expression (6)
When the value exceeds the upper limit, the refracting power of the second unit becomes weak, so that the amount of movement of the lens unit at the time of zooming becomes large, which leads to an increase in the lens system. If the lower limit value is exceeded, the refractive power of the second lens unit becomes too strong, and the refractive power of the third lens unit becomes too strong, making it difficult to correct spherical aberration. Conditional expression (7) relates to the zoom ratio of the front group. If the upper limit of conditional expression (7) is exceeded, the magnification change in the front group becomes too large, the refractive power of the lens group in the front group becomes strong, and the movement amount of each lens group during zooming increases. Come. In addition, if the lower limit is exceeded, the variable power share in the rear group becomes too large,
It is not good because the amount of movement of each lens unit in the rear group for securing a predetermined zoom ratio increases. Conditional expression (8) relates to the lateral magnification of the fourth lens unit at the wide-angle end. When the value exceeds the upper limit of conditional expression (8), it becomes difficult to obtain a back focus at the wide-angle end, which results in an increase in the outer diameter of the fifth lens unit. If the lower limit value is exceeded, the refractive power of the other lens units will increase in order to obtain a constant focal length, making it difficult to correct aberration fluctuations during zooming. Further, the focal length of the front group must be made longer, which is not good because the overall length of the lens becomes longer. Conditional expression (9) is for appropriately setting the refractive power and the lateral magnification of the fifth lens unit and mainly for obtaining a predetermined back focus. When the value exceeds the upper limit of conditional expression (9), the back focus becomes unnecessarily long at the wide-angle end, and the overall length of the lens increases. On the other hand, if the lower limit is exceeded, it becomes difficult to obtain a predetermined back focus at the wide-angle end, and the outer diameter of the lens of the fifth group increases, which is not good.

In the present invention, in order to widen the angle of view while minimizing aberration fluctuations due to zooming, and to ensure high optical performance over the entire screen, it is preferable to configure each lens unit as follows.

(1) When the combined refractive power of the front unit at the wide-angle end is _φ123W , 0.3 <fW · _φ123W <0.9 (3) 0.6 <f3 / fW <2.0 It is preferable that the following condition is satisfied.

Conditional expression (3) relates to the refractive power of the front lens group. If the upper limit of conditional expression (3) is exceeded, the refractive power of the front lens group becomes too strong at the wide-angle end, and the effect of the telephoto system becomes strong. It is difficult to obtain the back focus. or,
Exceeding the lower limit lowers the refractive power of the front group and increases the overall length of the lens.At the same time, the positive refractive power of the rear group must be increased to maintain the focal length at the wide-angle end. It becomes difficult to balance various aberrations.

Conditional expression (4) relates to the positive refractive power of the third lens unit.
Since the refracting power of the group is weak, the amount of movement of the lens group at the time of zooming is large, which leads to an increase in the lens system. If the lower limit is exceeded, high-order spherical aberration is strongly generated in the third lens unit, and it becomes difficult to correct this.

In the present invention, the upper and lower limits of the above-mentioned conditional expressions (3) and (4) must be satisfied in order to correct the optical performance satisfactorily while reducing the total length of the lens particularly at the wide-angle end. 0.35 <fW · φ _123W <0.80 (3a) 0.75 <f3 / fW <1.8 (4a) Good to set.

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

(2) The fourth group having a positive refractive power has at least 1
Each lens has a positive lens and a negative lens, of which the lens surface closest to the object side has a concave surface facing the object side, and the lens surface closest to the image surface has a convex surface facing the image surface side. Is good.

(3) When an aspherical surface is introduced into the zoom lens of the present invention, if an aspherical surface is introduced into the lens surface closest to the image plane, the curvature of field at the telephoto end, spherical aberration, and zooming will occur. It is possible to easily correct aberration fluctuation and aberration correction of the entire screen. In addition, if it is introduced into the fifth lens group, mainly off-axis aberration can be favorably corrected.

(4) The fifth group having a negative refractive power has at least 1
When there are a negative lens and a positive lens each having a concave surface facing the object side for each sheet, and the average values of Abbe numbers of the materials of the positive lens and the negative lens in the fifth group are ν5P and ν5N, respectively, 12 <ν5N −ν5P <35 (10) It is preferable to satisfy the following condition. If the upper limit or the lower limit of conditional expression (10) is not satisfied, chromatic aberration fluctuations during zooming often occur, and it becomes difficult to correct this with another lens group.

(5) The stop should be located at an appropriate distance from the lens surface closest to the image plane of the third lens unit to the lens surface closest to the image surface of the fourth lens unit so that the entrance pupil is located at an appropriate position. Are preferable because aberration fluctuation due to zooming can be suppressed. The stop may be moved independently of the other lens groups when zooming, or may be moved integrally with the other lens groups. This makes it possible to arrange the stop position near the entrance pupil position that moves during zooming, which is advantageous for preventing a change in field curvature aberration at the time of a small stop.

When focusing is performed by the fourth lens unit, and when the fourth lens unit includes an aperture, moving the focus unit with the aperture fixed on the optical axis is a driving operation for moving the aperture mechanism during focusing. This is preferable because torque can be reduced.

(6) If the fourth unit is divided into two or more lens units and the distance between the lens units is changed during zooming or during focusing, aberration variation during zooming and focusing is reduced. Is preferred.

(7) In the present invention, the focus is moved from the object at infinity to the object at a short distance by moving the fourth unit to the object side, but it may be moved by moving another lens unit. . For example, a method of moving the front group to the object side may be used.

When the back focus is sufficient at the wide-angle end, the fifth unit may be moved to the image plane side, and in this case, it is effective to reduce the outer diameter of the lens of the first unit. Becomes Alternatively, two or more lens groups in the first to fifth groups may be simultaneously moved.

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.

The aspheric surface has an X-axis in the optical axis direction, an H-axis in a direction perpendicular to the optical axis, a positive traveling direction of light, R is a paraxial radius of curvature,
When A, B, C, D, and E are aspheric coefficients, respectively,

[0053]

(Equation 1) It is represented by the following equation.

(Numerical Example 1) F = 28.84 to 89.41 fNO = 1: 3.8 to 8.2 2ω = 73.8 ° to 27.2 ° R 1 = -217.48 D 1 = 2.00 N 1 = 1.80518 ν 1 = 25.4 R 2 = -103.00 D 2 = 1.20 N 2 = 1.69680 ν 2 = 55.5 R 3 = 48.69 D 3 = Variable R 4 = 154.19 D 4 = 1.30 N 3 = 1.65844 ν 3 = 50.9 R 5 = 37.47 D 5 = Variable R 6 = 29.87 D 6 = 1.00 N 4 = 1.84666 ν 4 = 23.8 R 7 = 23.19 D 7 = 2.90 N 5 = 1.48749 ν 5 = 70.2 R 8 = -101.43 D 8 = 0.30 R 9 = 33.35 D 9 = 2.30 N 6 = 1.60311 ν 6 = 60.7 R10 = -173.29 D10 = variable R11 = -17.33 D11 = 0.87 N 7 = 1.64769 ν 7 = 33.8 R12 = -64.01 D12 = 1.00 R13 = ∞ (aperture) D13 = 1.00 R14 = -1012.52 D14 = 0.70 N 8 = 1.48749 ν 8 = 70.2 R15 = 39.15 D15 = 1.80 N 9 = 1.84666 ν 9 = 23.8 R16 = -37.96 D16 = 5.17 R17 = 40.91 D17 = 1.10 N10 = 1.84666 ν10 = 23.8 R18 = 11.63 D18 = 5.60 N11 = 1.58313 ν11 = 59.4 R19 = -23.69 D19 = variable R20 = -29.78 D20 = 3.60 N12 = 1.84666 ν12 = 23.8 R21 = -18.07 D21 = 0.20 R22 = -22.10 D22 = 1.30 N13 = 1.74320 ν13 = 49.3 R23 = 634.28 D23 = 4.38 R24 = -22.75 D24 = 1.50 N14 = 1.72916 ν14 = 54.7 R25 = -113.54 Aspheric coefficient R19 K = -1.96 × 10 ^-1 A = 0 B = 1.09 × 10 ^-5 C = 8.05 × 10 ^-8 D = -2.53 × 10 ^-9 E = 0

[0055]

[Table 1] (Numerical Example 2) F = 30.43 to 100.00 fNO = 1: 3.7 to 8.2 2ω = 70.8 ° to 24.4 ° R 1 = -677.46 D 1 = 2.00 N 1 = 1.80518 ν 1 = 25.4 R 2 = -69.17 D 2 = 1.20 N 2 = 1.69680 ν 2 = 55.5 R 3 = 63.43 D 3 = Variable R 4 = 3704.92 D 4 = 1.30 N 3 = 1.65844 ν 3 = 50.9 R 5 = 45.60 D 5 = Variable R 6 = 32.60 D 6 = 1.00 N 4 = 1.84666 ν 4 = 23.8 R 7 = 22.08 D 7 = 3.20 N 5 = 1.48749 ν 5 = 70.2 R 8 = -224.31 D 8 = 0.30 R 9 = 36.51 D 9 = 2.70 N 6 = 1.60311 ν 6 = 60.7 R10 = -122.67 D10 = variable R11 = ∞ (aperture) D11 = variable R12 = -17.93 D12 = 0.87 N 7 = 1.64769 ν 7 = 33.8 R13 = -71.56 D13 = 2.00 R14 = -228.00 D14 = 0.70 N 8 = 1.48749 ν 8 = 70.2 R15 = 44.17 D15 = 1.80 N 9 = 1.84666 ν 9 = 23.8 R16 = -46.21 D16 = 5.17 R17 = 39.16 D17 = 1.10 N10 = 1.84666 ν10 = 23.8 R18 = 13.54 D18 = 5.60 N11 = 1.58313 ν11 = 59.4 R19 = -22.09 D19 = variable R20 = -36.36 D20 = 3.60 N12 = 1.84666 ν12 = 23.8 R21 = -18.73 D21 = 0.20 R22 = -22.97 D22 = 1.30 N13 = 1.78590 ν13 = 44.2 R23 = -161.56 D23 = 4.50 R24 = -18.57 D24 = 1.50 N14 = 1.72916 ν14 = 54.7 R25 = -232.78 Aspherical coefficient R19 K = -3.97 × 10 ^-1 A = 0 B = 1.18 × 10 ^-5 C = 7.44 × 10 ^-8 D = -1.47 × 10 ^-9 E = 0

[0056]

[Table 2] (Numerical Example 3) F = 30.0 to 100.00 fNO = 1: 3.6 to 8.2 2ω = 71.6 ° to 24.4 ° R 1 = -228.47 D 1 = 2.00 N 1 = 1.80518 ν 1 = 25.4 R 2 = -61.62 D 2 = 1.20 N 2 = 1.69680 ν 2 = 55.5 R 3 = 60.27 D 3 = Variable R 4 = 300.46 D 4 = 1.30 N 3 = 1.65844 ν 3 = 50.9 R 5 = 47.91 D 5 = Variable R 6 = 32.90 D 6 = 1.00 N 4 = 1.84666 ν 4 = 23.8 R 7 = 22.76 D 7 = 3.20 N 5 = 1.48749 ν 5 = 70.2 R 8 = -264.26 D 8 = 0.30 R 9 = 34.66 D 9 = 2.50 N 6 = 1.60311 ν 6 = 60.7 R10 = -148.49 D10 = variable R11 = ∞ (aperture) D11 = 1.70 R12 = -18.05 D12 = 0.87 N 7 = 1.64769 ν 7 = 33.8 R13 = -63.03 D13 = 2.00 R14 = -167.30 D14 = 0.70 N 8 = 1.48749 ν 8 = 70.2 R15 = 46.92 D15 = 1.80 N 9 = 1.84666 ν 9 = 23.8 R16 = -49.81 D16 = 5.17 R17 = 36.08 D17 = 1.10 N10 = 1.84666 ν10 = 23.8 R18 = 14.30 D18 = 5.60 N11 = 1.58313 ν11 = 59.4 R19 = -24.31 D19 = variable R20 = -19.49 D20 = 3.60 N12 = 1.84666 ν12 = 23.8 R21 = -16.47 D21 = 4.50 R22 = -16.05 D22 = 1.50 N13 = 1.77250 ν13 = 49.6 R23 = 185.92 aspheric coefficients R19 K = -6.76 × 10 ^{- 1} A = 0 B = 1.7138 × 10 ^-8 C = 7.38 × 10 ^-8 D = -1.15 × 10 ^-9 E = 0 Aspheric coefficient R22 K = 0 A = 0 B = 1.69 × 10 ^-5 C = 3.53 × 10 ^-8 D = -1.80 × 10 ^-8 E = 0

[0057]

[Table 3]

[0058]

As described above, according to the present invention, the wide-angle end photographing is performed by appropriately configuring the moving conditions and the refracting power of each lens unit during zooming by forming the lens system from five lens units as a whole. A zoom lens having high optical performance over the entire zoom range with an angle of view of about 74 degrees and a zoom ratio of about 3.5 can be achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a paraxial refractive power arrangement of a zoom lens according to the present invention.

FIG. 2 is a sectional view of a lens at a wide-angle end according to Numerical Embodiment 1 of the present invention.

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

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

FIG. 5 is an aberration diagram at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 6 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 7 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention.

FIG. 8 is an aberration diagram at a wide angle end according to Numerical Example 2 of the present invention.

FIG. 9 is an intermediate aberration diagram of the numerical example 2 of the present invention.

FIG. 10 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention.

FIG. 11 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 12 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 13 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

[Explanation of symbols]

 L1 First group L2 Second group L3 Third group L4 Fourth group L5 Fifth group SP Aperture IP Image plane dd line gg line S. C Sine condition ΔS Sagittal image plane ΔM Meridional image plane

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (4)

(57) [Claims] 1. A first lens unit having a negative refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power. Has a front lens unit having a positive refractive power, a rear lens unit including a fourth lens unit having a positive refractive power, and a fifth lens unit having a negative refractive power, and when zooming from the wide-angle end to the telephoto end. The first, second, and third units move so that the combined refractive power of the front unit becomes weaker at the telephoto end than at the wide-angle end, and the fourth and fifth units move so that the distance between them decreases. do it
And the focal length of the i-th lens unit is fi
The focal length of the system is fW, and the lateral magnification at the wide-angle end of the i-th lens unit is
βiW, combined refractive power of the front group at wide-angle end and telephoto end
When φ is _{123 W} , φ _123T and the zoom ratio is Z, 0.5 <| f5 / fW | <1.5 1.1 <β5W <1.8 1.0 <| f1 / fW | <6.0 1.0 <| f2 / fW | <6.0 0.25 <(φ123W / φ123T) / Z <0.8 0.25 <β4W <0.55 0.1 <f5 · (1-β5W) / fW A zoom lens that satisfies the condition of <0.7 . 2. In zooming from the wide-angle end to the telephoto end, each lens unit moves toward the object side so that the distance between the first and second units increases and the distance between the second and third units decreases. The zoom lens according to claim 1, wherein 3. When the combined refractive power of the front unit at the wide-angle end is φ _{123 W} , the following condition is satisfied: 0.3 <fW · φ _123W <0.9 0.6 <f3 / fW <2.0 The zoom lens according to claim 2, wherein: 4. The fifth group includes at least one negative lens and a positive lens each having a concave surface facing the object side, and the average value of Abbe numbers of the materials of the positive lens and the negative lens in the fifth group. each Nyu5P, when the ν5N, 12 <zoom lens according to claim 1, characterized by satisfying the ν5N-ν5P <35 following condition.