JP2001042217A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photographing viewing angle at a wide-angle end being >=70 deg., a variable power ratio being about 2.5 and high optical performance all over the variable power range while miniaturizing an entire lens system by appropriately setting a moving condition or the like associated with refractive power or variable power. SOLUTION: This zoom lens is provided with a 1st lens group L1 having negative refractive power, a 2nd lens group L2 having the positive refractive power, a 3rd lens group L3 having the negative refractive power and a 4th lens group L4 having the positive refractive power in order from an object side, and the power is varied by changing a distance between the respective lens groups. The 1st group L1 is composed of four lenses; two meniscus negative lenses whose convex surfaces face to the object side, the negative lens and the positive lens. The 4th group L4 is provided with the negative lens and the positive lens and has an aspherical surface formed so that the positive refractive power gets weak from the center of the lens toward the periphery of the lens. When it is assumed that the distances between an (i)th group and the (i+1)th group at an wide-angle end and a telephoto end are DiW and DiT, D1W>D1T, D2W>D2T and D3W>D3T are satisfied.

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 more particularly, to a photographic camera or a video camera including a standard angle of view in which the entire lens system is compact, has high optical performance, and satisfactorily corrects distortion among various aberrations. Cameras and digital cameras,
The present invention also relates to a zoom lens suitable for an electronic still camera or the like.

[0002]

2. Description of the Related Art Recently, single-lens reflex cameras for film and C
2. Description of the Related Art As optical devices such as electronic still cameras that capture still images using CDs have been downsized, the size of the entire camera has been required, and a small-sized zoom lens having a wide angle of view has been required for the photographic lens used therein.

In general, a so-called negative lead type zoom lens, which is preceded by a lens group having a negative refractive power, is relatively easy to widen the angle of view. Is widely used.

For example, in JP-B-49-23912 and JP-A-57-163213, a first unit having a negative refractive power, a second unit having a positive refractive power, and a second unit having a negative refractive power are arranged in order from the object side. The zoom lens has four lens units, a third unit and a fourth unit having a positive refractive power. The first and second units are moved toward the image plane when zooming from the wide-angle end to the telephoto end. To the object side,
A zoom lens in which the third group is fixed or moved has been proposed.

In Japanese Patent Application Laid-Open Nos. 58-4113 and 5-241073, negative, positive,
A wide-angle zoom lens having a variable magnification ratio of about 2.5 to 3 having four lens groups of negative and positive refractive power and varying the air spacing of each group has been proposed. .

In Japanese Patent Application Laid-Open No. Hei 1-216310, a zoom lens having a relatively small number of lenses having a zoom ratio of about 2 and comprising four lens units having negative, positive, negative, and positive refractive powers sequentially from the object side is disclosed. is suggesting.

In Japanese Patent Application Laid-Open Nos. 5-313066 and 8-110470, negative, negative,
Consisting of five lens groups with positive, negative, and positive refractive power,
A zoom lens in which the magnification is changed by moving each lens group has been proposed.

In Japanese Patent Application Laid-Open Nos. Hei 3-80210 and Hei 4-264412, negative, positive,
A five-unit zoom lens having a zoom ratio of 2.5 to 4, which includes five lens units having negative, positive, and positive refractive powers, is disclosed.

[0009]

In recent years, as a zoom lens used for a single-lens reflex camera, a video camera or the like, a zoom lens having a wide angle of view and a high zoom ratio has been demanded with the miniaturization of the whole camera. I have.

As a zoom lens including a so-called standard angle of view having a focal length of 50 mm in terms of a single-lens reflex camera for 35 mm film, a negative lead type zoom lens in which a negative refractive power precedes is intended to achieve a high zoom ratio. In addition, the diameter of the stop increases, the entire lens system becomes larger, and the variation of various aberrations accompanying zooming increases, making it difficult to satisfactorily correct them.

For example, the shooting angle of view at the wide-angle end is about 70 degrees,
In a zoom lens having a zoom ratio of about 2.5, if the size of the entire lens system is to be reduced, fluctuations of various aberrations due to zooming become large, and it is necessary to correct these aberrations satisfactorily. It becomes very difficult.

According to the present invention, in a negative lead type zoom lens which is preceded by a lens unit having a negative refractive power, by appropriately setting the refractive power of each lens unit, the moving condition of each lens unit accompanying zooming, and the like. It is another object of the present invention to provide a zoom lens having high optical performance over the entire zoom range with a shooting angle of view of 70 degrees or more at the wide-angle end and a zoom ratio of about 2.5 while reducing the size of the entire lens system.

In addition, the present invention covers a wide-angle lens having a focal length of about 28 mm and a medium telephoto range of about 70 mm in terms of a 35 mm single-lens reflex camera, has an F-number of about 4, has a compact lens system, and has good optical performance. In particular, it is an object of the present invention to provide a zoom lens in which distortion at the wide-angle end is favorably corrected.

[0014]

According to a first aspect of the present invention, there is provided a zoom lens having a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a negative lens having a negative refractive power. A zoom lens having a third lens group and a fourth lens group having a positive refractive power, and changing a distance between the lens groups to perform zooming from a wide-angle end to a telephoto end; The group is composed of two meniscus negative lenses with the convex surface facing the object side, and four lenses, a negative lens and a positive lens. The fourth group has a negative lens and a positive lens, and has a lens center and a lens periphery. The distance between the i-th lens unit and the (i + 1) -th lens unit at the wide angle end is DiW, and the i-th lens unit and the (i +)-th lens unit at the telephoto end are as follows.
D1W> D1T (1) D2W <D2T (2) D3W> D3T (3) where DiT is the distance between one lens group.

According to a second aspect of the present invention, in the first aspect of the invention, the average value of the refractive power of the negative lens in the first lens group is p1Nave, and the focal length of the entire system at the wide-angle end and the telephoto end is fw, respectively. ft, the focal length of the ith lens group is fi, and the distance from the last lens surface of the fourth lens group to the rear principal point is OK4.
0.4 <p1Nave × fl <0.6

[0016]

(Equation 3)

It is characterized in that 0.95 <| f3 | / f2 <1.6 1.5 <f4 / f2 <3.5-0.05 <OK4 / fw <0.05.

In a third aspect of the present invention, in the first or second aspect of the invention, the first lens group has an aspherical surface having a shape in which negative refractive power becomes weaker from the center of the lens toward the periphery of the lens. I have.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, the second lens group and the fourth lens group move integrally during zooming.

A fifth aspect of the present invention is a zoom lens system according to any one of the first to fourth aspects, further comprising a meniscus positive lens having a convex surface facing the image side of the fourth lens group. It has a fixed fifth lens group, and the focal length of the fifth lens group is f5, and the focal length of the entire system at the wide-angle end and the telephoto end is f
w and ft,

[0021]

(Equation 4)

It is characterized by satisfying the following.

According to a sixth aspect of the present invention, in the first aspect of the present invention, at least one negative lens in the first lens group and at least one positive lens in the second lens group. The Abbe numbers of the lens materials are ν1N and ν2, respectively.
When P, 70 <ν1N 70 <ν2P is satisfied.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the second lens group includes a cemented lens of a meniscus-shaped negative lens and a positive lens, and a positive lens. The lens group is composed of a positive lens and two negative lenses. An aperture is arranged adjacent to the third group, and the aperture moves together with the third group during zooming.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, focusing is performed by three lenses on the image side of the first lens group.

According to a ninth aspect of the present invention, there is provided a photographing apparatus using the zoom lens according to any one of the first to eighth aspects.

[0027]

FIG. 1 is a lens sectional view of a numerical example 1 of the present invention described later. 2 and 3 are aberration diagrams at the wide-angle end and at the telephoto end in Numerical Example 1 described below of the present invention. FIG. 4 is a lens sectional view of Numerical Example 2 of the present invention, which will be described later. FIGS. 5 and 6 are aberration diagrams at the wide-angle end and at the telephoto end according to Numerical Example 2 of the present invention, which will be described later. FIG. 7 is a sectional view of a lens according to a third numerical example of the present invention, which will be described later. 8 and 9 are aberration diagrams at the wide-angle end and at the telephoto end according to Numerical Example 3 described later of the present invention. FIG. 10 is a sectional view of a lens according to a fourth numerical example of the present invention, which will be described later. FIGS. 11 and 12 are aberration diagrams at the wide-angle end and at the telephoto end in Numerical Example 4 of the present invention, which will be described later.

In FIGS. 1, 4 and 7, L1 denotes a first group (first lens group) having a negative refractive power, L2 denotes a second group (second lens group) having a positive refractive power, and L3 denotes a negative lens. L4 is a fourth group (fourth lens group) having a positive refractive power, and L5 is a fifth group (fifth lens group) having a positive refractive power. SP is an aperture. Arrows indicate the trajectories of the movements of the respective lens units when zooming from the wide-angle end to the telephoto end. The fifth
The lens group 5 is fixed.

In FIG. 10, L1 is the first negative refractive power.
L2 is a second group having a positive refractive power, L3 is a third group having a negative refractive power, and L4 is a fourth group having a positive refractive power. SP is an aperture. Arrows indicate the movement trajectories of the respective lens units when zooming from the wide-angle end to the telephoto end.

In the present embodiment, zooming is performed by changing the distance between the lens units so as to satisfy the conditional expressions (1) to (3). That is, when zooming from the wide-angle end to the telephoto end, the air gap between the first lens unit and the second lens unit decreases to an intermediate zoom position, and increases from the intermediate zoom position to the telephoto end. In zooming from the wide-angle end to the telephoto end, the air gap between the second and third lens units is increased, and the air gap between the third lens unit and the fourth lens unit is reduced.

In FIGS. 1, 4, and 7, each lens unit is moved so that the air gap between the fourth unit and the fifth unit increases. In each embodiment, the stop SP is provided between the second and third units, and is moved together with the third unit during zooming.

As described above, in the zoom lens according to the present invention, the first unit reciprocates convexly toward the image plane with a locus different from that of the other lens units, and the second and fourth units are integrated. The lens unit moves to the object side, the third lens unit moves to the object side, and the diaphragm is integrated with the third lens unit. The second group and the fourth group may be moved along different trajectories. However, the second group and the fourth group are particularly susceptible to manufacturing errors, that is, the lens group whose performance is greatly deteriorated due to the lens group falling down or decentering. Therefore, it is preferable that the relative positional relationship between the second and fourth units be fixed as an integral movement. As described above, the entire lens system is composed of five or four lens units, and the aperture diameter is reduced by changing the distance between the lens units during zooming, thereby achieving a compact zoom lens.

In this embodiment, the first unit is composed of two negative meniscus lenses having a convex surface on the object side, a negative lens, and a positive lens having a convex surface stronger on the object side than on the image side. . Then, the negative refractive power of the first lens group is set to 3
With the sharing of the negative lenses, barrel-shaped distortion generated on the wide-angle side is reduced. Further, in the numerical example 1 of FIG. 1, the first lens unit is formed by using an aspherical surface having a shape in which the negative refractive power becomes weaker from the center of the lens toward the periphery of the lens.
The barrel distortion generated on the wide angle side is further reduced.

The fourth lens unit includes a negative lens and a positive lens, and the lens surface on the image side of the positive lens is an aspheric surface in which the positive refractive power becomes weaker from the center of the lens toward the periphery of the lens. By using an aspherical surface having such a shape for the fourth lens unit, high-order sagittal curvature of field generated on the wide-angle side is favorably corrected.

The third unit is a cemented lens of a positive lens having a convex surface facing the image surface side and a negative lens having both concave lens surfaces, and a meniscus-shaped negative lens having a convex surface facing the image surface or both lens surfaces. Are composed of two groups of three negative lenses having concave surfaces, and good optical performance is obtained over the entire zoom range.

The zoom lens according to the present invention can be achieved by satisfying the above-mentioned conditions. However, it is possible to satisfactorily correct aberration fluctuations when widening the angle of view and increasing the zoom ratio. To obtain high optical performance over a range, it is preferable to satisfy at least one of the following conditions.

(A-1) The average value of the refractive power of the negative lens in the first lens unit is p1Nave, the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and ft, respectively, and the focal point of the i-th lens unit. When the distance is fi and the distance from the last lens surface of the fourth lens group to the rear principal point is OK4, 0.4 <p1Nave × fl <0.6 (4)

[0038]

(Equation 5)

0.95 <| f3 | / f2 <1.6 (6) 1.5 <f4 / f2 <3.5 (7) -0.05 <OK4 / fw <0.05 (8) ).

Conditional expression (4) is for reducing barrel-shaped distortion on the wide-angle side. When the average value of the refracting power of the negative lens in the first lens unit exceeds the lower limit and becomes larger, the condition at the wide-angle end is obtained. When the barrel-shaped distortion becomes large and the average value of the refractive power of the negative lens in the first group is weakened beyond the upper limit, the refractive power of the positive lens in the first group needs to be weakened accordingly. However, it is not preferable that aberration correction is not balanced in the entire lens system.

Conditional expression (5) defines the range of the focal length of the first lens unit. When the negative refractive power of the first lens unit is increased beyond the lower limit, various aberrations generated in the first lens unit become large. Become
It becomes difficult to correct this in a well-balanced manner with the other lens groups. If the negative refractive power of the first group is weakened beyond the upper limit, the lens system is unfavorably large in aberration correction but large.

Conditional expressions (6) and (7) define the focal length of the third lens unit and the focal length of the fourth lens unit with respect to the focal length of the second lens unit, respectively. It is. When the refractive powers of the third and fourth groups are both higher than the lower limit, spherical aberration, coma and astigmatism in the third and fourth groups are large, and these are corrected in a well-balanced manner. When the refractive powers of the third and fourth units are weakened beyond the upper limit, the overall length of the lens becomes longer.

The conditional expression (8) means that the fourth unit is a retro-type configuration. Even if the fourth unit is composed of two negative lenses and two positive lenses from the object side. This is to enable good aberration correction.
Exceeding the lower limit means that the retro type becomes weak. It is necessary to increase the number of lenses by changing the paraxial arrangement of the entire system.
The refracting power of the negative lens and the positive lens of the group increases, and various aberrations generated in this group increase, and it becomes difficult to correct these in a well-balanced manner by other lens groups.

(A-2) The first lens group has an aspherical surface in which negative refractive power becomes weaker from the center of the lens toward the periphery of the lens.

According to this, distortion at the wide-angle end can be satisfactorily corrected.

(A-3) The second lens unit and the fourth lens unit move integrally during zooming.

According to this, the mechanical structure can be simplified.

(A-4) On the image side of the fourth lens group, a fifth lens group fixed during zooming, comprising a meniscus-shaped positive lens having a convex surface facing the image side. Is the focal length of f5, and the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and
ft,

[0049]

(Equation 6)

Is satisfied.

By satisfying conditional expression (9), distortion fluctuation mainly due to zooming is reduced. If the positive refractive power of the fifth lens unit is increased beyond the lower limit value of conditional expression (9), the positive refractive power of the fourth lens unit needs to be weakened.
The amount of movement of the fourth to fourth groups during zooming becomes large, which is not preferable in terms of aberration correction and lens barrel structure. When the positive refractive power of the fifth unit becomes weaker than the upper limit, two positive lenses are used for the fourth unit as in the fourth embodiment of FIG. Also requires the use of an aspheric surface.

(A-5) At least one lens in the first lens group
Negative lenses and at least one negative lens in the second lens group
When the Abbe numbers of the materials of the positive lenses are ν1N and ν2P, respectively,

[0053]

(Equation 7)

Satisfying the following.

By using a low-dispersion glass satisfying conditional expression (10), lateral chromatic aberration at the wide-angle end and axial chromatic aberration at the telephoto end are reduced.

(A-6) The second lens group is composed of a cemented lens of a meniscus-shaped negative lens and a positive lens and a positive lens, and the third lens group is composed of a positive lens and two negative lenses. An aperture is arranged adjacent to the third lens group, and when zooming,
The diaphragm is to move integrally with the third lens unit.

As a result, the entire lens system is compact and a zoom lens having good optical performance is achieved.

(A-7) Focusing is performed by three lenses on the image side of the first lens group.

In the present embodiment, the first lens unit is divided into a meniscus-shaped negative lens unit 1a, a meniscus-shaped negative lens, a negative lens, and a positive lens unit 1b, and focusing is performed by the first lens unit. ing. Accordingly, when the lens is mounted on an autofocus camera which has recently become the mainstream among 35 mm single-lens reflex cameras, the weight of the focus lens can be reduced, and quick autofocus can be performed.

Next, numerical examples of the present invention will be described. In the numerical examples, ri is the radius of curvature of the i-th surface in order from the object side, di is the i-th optical member thickness or air gap in order from the object side, and ni and νi are the i-th optical elements in order from the object side. These are the refractive index and Abbe number of the material of the member.

The aspherical shape 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, and R as a paraxial radius of curvature.
When b, c, and d are aspherical coefficients

[0062]

(Equation 8)

This is represented by the following equation.

Table 1 shows the relationship between the above-described conditional expressions and various numerical values in the numerical examples. Numerical example 1 f = 28.8 to 68.1 FNo = 1: 4.1 to 4.1 2ω = 73.8 ° to 35.2 ° r 1 = 62.884 d 1 = 2.50 n 1 = 1.66672 ν 1 = 48.3 r 2 = 32.237 d 2 = variable r 3 = 48.729 d 3 = 1.75 n 2 = 1.71300 ν 2 = 53.9 r 4 = 26.300 d 4 = 0.05 n 3 = 1.51640 ν 3 = 52.2 r 5 = 24.514 (aspheric) d 5 = 7.05 r 6 = 664.303 d 6 = 1.60 n 4 = 1.49700 ν 4 = 81.5 r 7 = 52.418 d 7 = 2.58 r 8 = 36.999 d 8 = 2.90 n 5 = 1.84666 ν 5 = 23.9 r 9 = 60.102 d 9 = variable r10 = 33.840 d10 = 1.30 n 6 = 1.74077 ν 6 = 27.8 r11 = 22.976 d11 = 6.65 n 7 = 1.49700 ν 7 = 81.5 r12 = -97.063 d12 = 0.15 r13 = 28.623 d13 = 4.25 n 8 = 1.48749 ν 8 = 70.2 r14 = -477.622 d14 = variable r15 = (aperture) d15 = 2.40 r16 = -83.812 d16 = 2.50 n 9 = 1.83400 ν 9 = 37.2 r17 = -34.023 d17 = 1.10 n10 = 1.48749 ν10 = 70.2 r18 = 36.359 d18 = 2.85 r19 = -24.978 d19 = 1.10 n11 = 1.57099 ν11 = 50.8 r20 = -101.965 d20 = variable r21 = 79.651 d21 = 1.55 n12 = 1.84666 ν12 = 23.9 r22 = 32.501 d22 = 0.00 r23 = 32.501 d23 = 4.50 n13 = 1.58313 ν13 = 59.4 r24 = -37.667 (aspheric) d24 = variable r25 = -100.000 d25 = 2.40 n14 = 1.62299 ν14 = 58.2 r26 = -61.717 Focal length 28.80 50.84 68.14 Variable interval d 2 10.22 10.22 10.22 d 9 33.36 8.85 1.25 d14 4.90 7.53 8.76 d20 6.04 3.41 2.18 d24 1.60 21.12 37.08 skinf 38.44 38.44 38.44 Aspheric coefficient 5th surface bcd -2.727512e-06 -1.716067e-09 -1.513931e-11 24th surface bcd 1.270904e- 05 2.097545e-08 6.146049e-11 Numerical example 2 f = 28.8 ~ 68.0 FNo = 1: 4.1 ~ 4.1 2ω = 73.8 ° ~ 35.3 ° r 1 = 70.816 d 1 = 2.50 n 1 = 1.66672 ν 1 = 48.3 r 2 = 37.300 d 2 = variable r 3 = 67.088 d 3 = 1.80 n 2 = 1.71300 ν 2 = 53.9 r 4 = 29.330 d 4 = 5.73 r 5 = 348.894 d 5 = 1.60 n 3 = 1.49700 ν 3 = 81.5 r 6 = 44.804 d 6 = 3.85 r 7 = 37.314 d 7 = 2.90 n 4 = 1.84666 ν 4 = 23.9 r 8 = 58.787 d 8 = variable r 9 = 39.275 d 9 = 1.30 n 5 = 1.76182 ν 5 = 26.5 r10 = 25.531 d10 = 6.60 n 6 = 1.49700 ν 6 = 81.5 r11 = -72.797 d11 = 0.15 r12 = 29.012 d12 = 4.30 n 7 = 1.48749 ν 7 = 70.2 r13 = -425.716 d13 = variable r14 = (aperture) d14 = 2.40 r15 = -94.980 d15 = 2.50 n 8 = 1.83400 ν 8 = 37.2 r16 = -27.846 d16 = 1.10 n 9 = 1.48749 ν 9 = 70.2 r17 = 50.400 d17 = 2.53 r18 = -24.041 d18 = 1.10 n10 = 1.61772 ν10 = 49.8 r19 = -225.937 d19 = variable r20 = 99.732 d20 = 2.09 n11 = 1.84666 ν11 = 23.9 r21 = 34.152 d21 = 0.25 r22 = 39.994 d22 = 4.50 n12 = 1.58313 ν12 = 59.4 r23 = -32.508 (aspheric surface) d23 = variable r24 = -100.000 d24 = 2.40 n13 = 1.48749 ν13 = 70.2 r25 = -51.832 Focal length 28.80 50.98 68.02 Variable distance d 2 10.30 10.30 10.30 d 8 33.93 8.75 1.19 d13 4.90 8.15 9.60 d19 6.80 3.55 2.11 d23 1.60 20.60 36.15 skinf 38.07 38.07 38.07 Aspheric surface 23rd surface bcd 8.844111e-06 2.164434e-08 -2.624144e-12 Numerical example 3 f = 28.8 ~ 68.1 FNo = 1: 4.1 ~ 4.1 2ω = 73.8 ° ~ 35.3 ° r 1 = 54.386 d 1 = 2.50 n 1 = 1.77250 ν 1 = 49.6 r 2 = 31.766 d 2 = variable r 3 = 71.781 d 3 = 1.80 n 2 = 1.80610 ν 2 = 40.9 r 4 = 31.568 d 4 = 5.27 r 5 = -786.477 d 5 = 1.60 n 3 = 1.49700 ν 3 = 81.5 r 6 = 48.047 d 6 = 3.46 r 7 = 41.149 d 7 = 3.20 n 4 = 1.84666 ν 4 = 23.9 r 8 = 82.232 d 8 = variable r 9 = 34.531 d 9 = 1.30 n 5 = 1.76182 ν 5 = 26.5 r10 = 22.657 d10 = 6.90 n 6 = 1.49700 ν 6 = 81.5 r11 = -60.689 d11 = 0.15 r12 = 29.098 d12 = 3.70 n 7 = 1.51633 ν 7 = 64.1 r13 = 237.152 d13 = variable r14 = (aperture) d14 = 2.50 r15 = -75.084 d15 = 3.80 n 8 = 1.83400 ν 8 = 37.2 r16 = -24.069 d16 = 1.00 n 9 = 1.48749 ν 9 = 70.2 r17 = 52.970 d17 = 2.58 r18 = -24.824 d18 = 1.00 n10 = 1.5713 5 ν10 = 53.0 r19 = -75.298 d19 = variable r20 = 157.750 d20 = 1.00 n11 = 1.84666 ν11 = 23.8 r21 = 35.640 d21 = 0.15 r22 = 36.447 d22 = 4.40 n12 = 1.58313 ν12 = 59.4 r23 = -45.886 (aspherical surface) d23 = Variable r24 = -51.725 d24 = 2.00 n13 = 1.48749 ν13 = 70.2 r25 = -38.508 Focal length 28.81 50.81 68.10 Variable spacing d 2 10.14 10.14 10.14 d 8 34.28 9.00 1.09 d13 2.80 6.56 8.48 d19 9.63 5.88 3.95 d23 1.60 19.69 34.50 skinf 37.84 37.84 37.84 Aspheric surface 23rd surface bcd 1.294530e-05 2.664390e-08 4.748268e-11 Numerical example 4 f = 28.8-68.1 FNo = 1: 4.1-4.1 2ω = 73.8 ° -35.3 ° r 1 = 53.761 d 1 = 2.50 n 1 = 1.77250 ν 1 = 49.6 r 2 = 32.000 d 2 = variable r 3 = 67.719 d 3 = 1.80 n 2 = 1.80610 ν 2 = 40.9 r 4 = 29.656 d 4 = 6.25 r 5 = -388.452 d 5 = 1.60 n 3 = 1.49700 ν 3 = 81.5 r 6 = 55.962 d 6 = 1.33 r 7 = 39.377 d 7 = 3.50 n 4 = 1.84666 ν 4 = 23.9 r 8 = 83.663 d 8 = variable r 9 = 33.177 d 9 = 1.30 n 5 = 1.76182 ν 5 = 26.5 r10 = 22.220 d10 = 7.00 n 6 = 1.49700 ν 6 = 81.5 r11 = -65.652 d11 = 0.20 r12 = 26.718 d12 = 3.30 n 7 = 1.51633 ν 7 = 64.1 r13 = 82.391 d13 = variable r14 = (Aperture) d14 = 2.50 r15 = -124.431 d15 = 3. 80 n 8 = 1.74400 ν 8 = 44.8 r16 = -20.453 d16 = 1.00 n 9 = 1.51633 ν 9 = 64.1 r17 = -58.065 d17 = 1.70 r18 = -20.349 (aspherical surface) d18 = 1.00 n10 = 1.58313 ν10 = 59.4 r19 = 86.358 d19 = variable r20 = -102.433 d20 = 1.00 n11 = 1.84666 ν11 = 23.8 r21 = 113.670 d21 = 0.15 r22 = 82.103 d22 = 2.90 n12 = 1.58313 ν12 = 59.4 r23 = -40.591 (aspheric) d23 = 0.10 r24 = 165.251 d24 = 2.40 n13 = 1.51633 ν13 = 64.1 r25 = -95.599 d25 = variable r26 = Aperture Focal length 28.80 50.64 68.08 Variable interval d 2 10.79 10.79 10.79 d 8 37.07 9.76 1.08 d13 3.07 6.71 8.67 d19 9.50 5.86 3.90 d25 0.16 16.15 29.24 skinf 38.67 38.67 38.67 Aspheric coefficient 18th surface bcd 2.220671e-05 5.664624e-08 -2.092632e-10 23rd surface bcd 1.864594e-05 6.240546e-08 -4.798060e-11

[0065]

[Table 1]

Next, an embodiment of a photographing apparatus provided with the zoom lenses of Numerical Embodiments 1 to 4 will be described with reference to FIG.

FIG. 13A is a front view of the photographing apparatus, and FIG.
(B) is a side sectional view. In the drawing, reference numeral 10 denotes a photographing apparatus main body (housing), 11 denotes a photographing optical system using any one of the numerical examples 1 to 4, 12 denotes a finder optical system, and 13 denotes a film as a photosensitive surface.

By applying the zoom lenses of Numerical Examples 1 to 4 to the photographing optical system of the photographing apparatus, a compact and high-performance photographing apparatus can be realized.

[0069]

As described above, according to the present invention, in a negative lead type zoom lens which is preceded by a lens unit having a negative refractive power, the moving condition of each lens unit due to the refractive power of each lens unit and zooming. A zoom lens with high optical performance over the entire zoom range with a shooting angle of view of 70 degrees or more at the wide-angle end and a zoom ratio of about 2.5 while appropriately minimizing the lens system by appropriately setting Can be achieved.

In addition, according to the present invention, a wide-angle lens having a focal length of about 28 mm and 70 mm
It covers up to the middle telephoto range, has an F-number of about 4, and has a compact lens system with good optical performance.
In particular, it is possible to achieve a zoom lens in which distortion at the wide-angle end is favorably corrected.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 2 is an aberration diagram at a wide-angle end according to Numerical Embodiment 1 of the present invention.

FIG. 3 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention;

FIG. 4 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 5 is an aberration diagram at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 6 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention.

FIG. 7 is a sectional view of a lens according to a numerical example 3 of the present invention.

FIG. 8 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 9 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

FIG. 10 is a sectional view of a lens according to a numerical example 4 of the present invention.

FIG. 11 is an aberration diagram at a wide angle end according to Numerical Example 4 of the present invention.

FIG. 12 is an aberration diagram at a telephoto end in Numerical Example 4 of the present invention.

FIG. 13 is a schematic configuration diagram of an imaging device having a zoom lens according to Numerical Examples 1 to 4.

[Explanation of symbols]

 L1 First lens unit L2 Second lens unit L3 Third lens unit L4 Fourth lens unit L5 Fifth lens unit SP Aperture d d-line g g-line ΔM Meridional image plane ΔS Sagittal image plane

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H044 DA02 EF04 2H087 KA01 MA18 PA11 PA12 PA19 PB13 PB14 QA02 QA07 QA17 QA22 QA26 QA32 QA34 QA41 QA46 RA05 RA12 RA13 RA36 SA44 SA46 SA50 SA52 SA55 SA62 SB63 SA05 SA65 SB SB33 SB42

Claims (9)

[Claims] A first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power.
In a zoom lens having a lens group and a fourth lens group having a positive refractive power, and changing the distance between the lens groups to change the magnification from the wide-angle end to the telephoto end, the first lens group is The fourth lens is composed of two meniscus-shaped negative lenses with the convex surface facing the object side, and four lenses of a negative lens and a positive lens.
The group has a negative lens and a positive lens, and has an aspheric surface in which the positive refractive power becomes weaker from the center of the lens toward the periphery of the lens. The distance between the i-th lens group and the (i + 1) -th lens group at the wide angle end is DiW. , I-th lens unit and i-th lens at the telephoto end
A zoom lens characterized by satisfying D1W> D1T D2W <D2T D3W> D3T when the distance between the +1 lens group is DiT. 2. The average value of the refractive power of the negative lens in the first lens unit is p1Nave, the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and ft, and the focal length of the i-th lens unit is f.
i, when the distance from the final lens surface of the fourth lens unit to the rear principal point is OK4, 0.4 <p1Nave × fl <0.6 2. The zoom lens according to claim 1, wherein 0.95 <| f3 | / f2 <1.6 1.5 <f4 / f2 <3.5-0.05 <OK4 / fw <0.05. . 3. The zoom lens according to claim 1, wherein the first lens group has an aspheric surface having a negative refractive power that decreases from the center of the lens toward the periphery of the lens. 4. The zoom lens system according to claim 1, wherein said second lens group and said fourth lens group move integrally during zooming.
Or 3 zoom lenses. 5. A fifth lens group fixed during zooming, comprising a meniscus positive lens having a convex surface facing the image side, on the image side of the fourth lens group. To f
5. The focal lengths of the entire system at the wide-angle end and the telephoto end are respectively fw and f
Assuming that t, 5. The method according to claim 1, wherein the following condition is satisfied.
Term zoom lens. 6. When the Abbe numbers of materials of at least one negative lens in the first lens group and at least one positive lens in the second lens group are ν1N and ν2P, respectively, 70 < The zoom lens according to any one of claims 1 to 5, wherein ν1N 70 <ν2P is satisfied. 7. The second lens group includes a cemented lens of a meniscus-shaped negative lens and a positive lens, and a positive lens. The third lens group includes a positive lens and two negative lenses. The zoom lens according to any one of claims 1 to 6, wherein the zoom lens is disposed adjacent to the third lens group, and the zoom lens moves integrally with the third lens group during zooming. 8. The zoom lens according to claim 1, wherein focusing is performed by three lenses on the image side of the first lens group. 9. A photographing apparatus using the zoom lens according to claim 1. Description: