JP2808915B2 - 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 telephoto zoom lens having a long focal length suitable for a 35 mm camera, a video camera, an electronic still camera, and the like. And a zoom lens having high optical performance over the entire zoom range at a high zoom ratio of about 4 by moving the lens group.

[0002]

2. Description of the Related Art Conventionally, a zoom lens comprising five lens groups as a whole and moving three or more lens groups at the time of zooming is disclosed in, for example, JP-A-60-175020 and JP-A-63-189819. And Japanese Patent Laid-Open No. 2-16
No. 8214, for example.

Japanese Patent Application Laid-Open No. Sho 60-175020 proposes a telephoto zoom lens having a relatively long focal length. In this publication, all of the five lens groups having a predetermined refractive power are moved or the four lens groups of the first, third, fourth, and fifth groups are moved.
The two lens groups are moved to, for example, the object side to perform zooming from the wide-angle end to the telephoto end, and have a zoom ratio of 3 and an F-number of 3.6 to 3.6.
A zoom lens of about 5.6 has been proposed.

Japanese Patent Laid-Open No. 63-189819 proposes a standard zoom lens having a relatively wide angle of view. In this publication, of the five lens units having a predetermined refractive power, zooming from the wide-angle end to the telephoto end is performed by changing the first unit toward the object side, integrating the third, fourth, and fifth units, or reciprocating each other. The whole is moved to the object side while changing the group interval.

In Japanese Patent Application Laid-Open No. 2-168214,
The first group of positive refractive power and the second group of negative refractive power in order from the object side.
The zoom lens has five lens units: a third 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. The group is fixed, and the first group is moved toward the object side so that the air gap between the first group and the second group monotonically increases, and the air gap between the second group and the third group monotonically decreases. A telephoto zoom lens in which the third and fifth units are integrated and moved toward the object side has been proposed.

As described above, the zoom type which comprises five lens groups as a whole, and performs zooming by moving three or more lens groups while maintaining a constant relationship, has a predetermined zooming ratio. Since it is easy to reduce the size of the entire lens system while securing it, it is used for zoom lenses such as 35 mm cameras and video cameras.

[0007]

Generally, in a zoom lens, it is desired to increase the magnification (higher magnification) at the same time as making the entire lens system compact. In order to increase the magnification of a zoom lens, it is necessary to increase the power of the lens group that contributes to zooming to increase the zooming effect, and to increase the amount of movement of the lens group that contributes to zooming. It becomes.

However, in the former case, it is necessary to increase the number of lens components in order to satisfactorily correct various aberrations, which causes a problem that it is difficult to make the entire lens system compact.

In the latter case, more space must be secured for the movement of the lens unit, and the overall length of the lens becomes longer. In particular, when the movement form of the lens unit is complicated,
There is a problem that it becomes difficult to support the movable lens group inside the lens barrel, and it becomes difficult to make the entire lens system compact.

According to the present invention, the zoom lens is composed of five lens groups having a predetermined refractive power as a whole, and the refractive power of each lens group, the moving condition of each lens group for performing zooming, and the like are appropriately set. This makes it possible to reduce the overall length of the lens while maintaining high optical performance over the entire zoom range.
And a telephoto zoom lens having a high magnification and a long focal length.

[0011]

A zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a positive lens unit. The zoom lens has five lens units, a fourth lens unit having a refractive power and a fifth lens unit having a negative refractive power. In zooming from the wide-angle end to the telephoto end, the first unit, the third unit, and the fifth unit are both objects. Side, the second and fourth units are fixed, the combined focal length of the first and second units at the wide-angle end is f12W, the focal length of the i-th unit is fi, and the entire system at the wide-angle end is Is the focal length of fW, the amounts of movement of the first and fifth units accompanying zooming are ST1 and ST5, respectively, and the distance from the lens surface closest to the object side to the lens surface closest to the image plane at the wide-angle end is TDW. 0.35 <ST1 / TDW <0.6 ‥‥‥ (1) 0.15 <ST5 / TDW <0.2 ‥‥‥ (2) 3.5 <is characterized by satisfying the f12W / fW <-1.3 ‥‥‥ (3) 0.35 <f3 / f4 <2.5 ‥‥‥ (4) following condition.

[0012]

1 to 3 are lens sectional views of Numerical Examples 1 to 3 of the present invention. In the figure, 1 is a first group of positive refractive power, 2
Denotes a second group of negative refractive power, 3 denotes a third group of positive refractive power, 4 denotes a fourth group of positive refractive power, 5 denotes a fifth group of negative refractive power, and SP denotes 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, the second and fourth units are fixed at the time of zooming from the wide-angle end to the telephoto end, and the first, third and fifth units are moved toward the object side to change the zooming effect of each lens. The groups are distributed in a well-balanced manner, thereby facilitating a high zoom ratio while reducing the overall length of the lens. The stop SP is moved integrally with the third lens unit.

In the above-described conventional zoom lens, at least one lens group moves non-linearly at the time of zooming, and uses a mechanical correction type which corrects image plane fluctuation (focus movement) accompanying zooming. . In order to move the lens group at this time while moving it in a non-linear manner, a cam barrel is disposed in the lens barrel, and the cam barrel is provided with a non-linear support groove (cam groove). As described above, in order to achieve a high-magnification zoom lens with high optical performance and a compact overall lens system,
It is necessary to effectively secure a space for movement of each lens group contributing to zooming in the lens system while making the refractive power of each lens group relatively weak.

In this embodiment, the compactness of the lens system is
In particular, it is designed to be most compact when stored, that is, when the overall length of the lens is the shortest.

In general, a lens group that moves during zooming moves according to a support groove provided in a cam barrel in a lens barrel. However, at this time, when the movement form of the lens group is complicated, it becomes difficult to provide a long support groove on a limited cam cylinder. For this reason, making the overall length of the lens to be the shortest when the lens is housed as in the present invention cannot be implemented with all conventional types of zoom lenses.

A desirable mode of movement of the lens units accompanying zooming is a case where the moving directions of the plurality of lens units are uniform as shown in FIG.

FIG. 13 is an exploded view of a cam barrel supporting each moving lens group according to the embodiment of the present invention. In the figure, reference numeral 70 denotes a cam barrel, groove 71 denotes a first group, groove 72 denotes a third group, Groove 73 is fifth
The movement form of a group is shown.

At this time, the support grooves on the cam cylinder are substantially parallel. When a plurality of lens groups move disturbingly toward the object side or the image side at the time of zooming, some of the plurality of support grooves on the cam cylinder also have a substantially vertical support groove. If the amount of movement of the lens group is increased during zooming,
It becomes difficult to reduce the size of the cam cylinder itself, and it becomes difficult to achieve a compact imaging system.

It is needless to say that reducing the number of moving lens groups associated with zooming also reduces the number of supporting grooves, which is desirable in terms of the configuration of the lens barrel.

The zoom lens of the present invention has high optical performance by configuring each element as described above based on the above considerations, and particularly, a zoom lens of a high magnification telephoto system in which the entire lens system becomes compact when the lens is housed. The lens has achieved.

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

Conditional expression (1) represents the distance from the most object side lens surface to the most image side lens surface of the lens system in the shortest focal length state at the wide-angle end, that is, the shortest lens length upon zooming with respect to the shortest overall lens length. This defines the range of the amount of movement of one group. Especially when the lens system is compact when storing the lens,
This is a conditional expression for easily realizing high zoom ratio.

If the upper limit of conditional expression (1) is exceeded and the amount of movement of the first lens unit during zooming becomes too large, the cam barrel and the lens barrel main body in the longest focal length state at the telephoto end. The length of the fitting portion becomes insufficient, and it becomes difficult to hold the lens system with high accuracy. If the amount of movement of the first lens unit due to zooming becomes smaller than the lower limit of conditional expression (1), the zooming effect based on the change in the distance between the first lens unit and the second lens unit will be sufficiently increased. For this reason, it is necessary to increase the refractive power of the first and second groups to a certain degree or more, and as a result, fluctuations of various aberrations, particularly spherical aberration and coma aberration, accompanying zooming increase. In addition, if the zoom lens is configured to have a variable power function and to be distributed to other lens groups, it is difficult to make the entire lens system compact.

Conditional expression (2) represents the distance from the lens surface closest to the object side to the lens surface closest to the image side of the lens system in the shortest focal length state at the wide-angle end, that is, the shortest lens length at the time of zooming. This defines the range of the amount of movement of the fifth group. In particular, this is a conditional expression for correcting the fluctuations of various aberrations accompanying zooming to be sufficiently small while achieving a high zooming ratio of about 4 times.

If the amount of movement of the fifth lens unit along with zooming exceeds the upper limit value of the conditional expression (2), the zooming action becomes large, which is advantageous for high zooming. Although the refractive power or the amount of movement of one group can be reduced, fluctuations of various off-axis aberrations increase, and it becomes difficult to maintain compactness during storage. If the amount of movement of the fifth lens unit along with the zooming becomes too small beyond the lower limit value of the conditional expression (2), the zooming action becomes small.
It is necessary to increase the zooming action of the group, and as a result, it becomes difficult to satisfactorily correct fluctuations in various aberrations caused by zooming, particularly fluctuations in spherical aberration.

Conditional expression (3) defines the ratio of the combined focal length of the first lens unit and the second lens unit at the wide-angle end to the focal length of the entire system at the wide-angle end. This is a conditional expression for achieving compactness of the entire lens system while favorably holding down, and particularly setting the back focus to an optimum length.

If the combined negative refractive power of the first and second units is too weak below the upper limit of conditional expression (3), the lens outer diameter of the third and subsequent lens units is reduced, and the aperture is reduced. SP second
This is advantageous for reducing the outer diameter of the lens barrel by reducing the diameter of the stop when it is disposed on the image plane side of the group. However, in order to secure the required back focus and keep the entire lens system compact, it is necessary to increase the negative refracting power of the fifth lens unit. As a result, the distortion of the threading type becomes large, which is not good. If the combined negative refractive power of the first and second units exceeds the lower limit of conditional expression (3), the back focus becomes too long, and not only the lens system is not compact, but also Variations in aberrations, particularly variations in spherical aberration and field curvature, increase. In addition, the diameter of the aperture must be increased in order to secure a required F number, which is not good because the outer diameter of the lens barrel increases.

Conditional expression (4) defines the ratio of the focal length of the third lens unit to the focal length of the fourth lens unit.

If the positive refractive power of the third lens unit becomes too weak beyond the upper limit of the conditional expression (4), the distance between the fourth lens unit and the fifth lens unit at the wide-angle end must be increased in order to obtain a predetermined zoom ratio. It is necessary to increase the size, and as a result, it becomes difficult to make the lens system compact. In order to maintain the compactness of the lens system, it is necessary to increase the refractive power of the second unit or the fifth unit, which causes an increase in aberration fluctuations and makes it difficult to perform good aberration correction. If the refractive power of the third lens unit becomes too strong beyond the lower limit value of the conditional expression (4), aberrations generated in the third lens unit, especially spherical aberrations, increase, and this is corrected well by other lens units. It becomes difficult.

In the present embodiment, in order to reduce aberration fluctuations particularly caused by zooming and to obtain good optical performance over the entire screen, the first lens unit is composed of a cemented lens of a negative lens and a positive lens and a positive lens. The second group is composed of a negative lens and a positive lens, both lens surfaces of which are concave.
The group consists of a cemented lens of a negative lens and a positive lens, and the fourth group consists of three lenses: a cemented lens of both lenses having a convex convex surface and a positive lens of both lenses having a convex convex surface. The fifth unit may be composed of three lenses, a negative lens and a cemented lens of a negative lens and a positive lens, or a single meniscus negative lens having a convex surface facing the object side.

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 numerical examples. Numerical Example 1 F = 77 to 292.5 FNO = 1: 4.14 to 5.75 2ω = 31.4 ° to 8.4 ° R 1 = 120.89 D 1 = 2.6 N 1 = 1.80518 ν 1 = 25.4 R 2 = 74.56 D 2 = 6.4 N 2 = 1.51633 ν 2 = 64.1 R 3 = -1146.43 D 3 = 0.2 R 4 = 83.96 D 4 = 4.5 N 3 = 1.48749 ν 3 = 70.2 R 5 = 464.02 D 5 = Variable R 6 = -167.64 D 6 = 1.5 N 4 = 1.83481 ν 4 = 42.7 R 7 = 29.60 D 7 = 6.4 R 8 = 44.16 D 8 = 3.0 N 5 = 1.84666 ν 5 = 23.9 R 9 = 257.97 D 9 = Variable R10 = (Aperture) D10 = 12.0 R11 = -335.07 D11 = 1.5 N 6 = 1.80518 ν 6 = 25.4 R12 = 83.68 D12 = 5.0 N 7 = 1.57099 ν 7 = 50.8 R13 = -38.19 D13 = Variable R14 = 89.14 D14 = 5.2 N 8 = 1.48749 ν 8 = 70.2 R15 = -32.66 D15 = 1.5 N 9 = 1.83400 ν 9 = 37.2 R16 = -165.67 D16 = 0.2 R17 = 50.71 D17 = 3.8 N10 = 1.51742 ν10 = 52.4 R18 = -97.22 D18 = Variable R19 = 660.33 D19 = 1.3 N11 = 1.77250 ν11 = 49.6 R20 = 34.42 D20 = 2.4 R21 = -95.53 D21 = 1.3 N12 = 1.77250 ν12 = 49.6 R22 = 39.82 D22 = 3.0 N13 = 1.76182 ν13 = 26.5 R23 = -372.61

[0034]

[Table 1] Numerical Example 2 F = 102.5 to 390.0 FNO = 1: 4.14 to 5.75 2ω = 23.8 ° to 6.4 ° R 1 = 124.04 D 1 = 3.4 N 1 = 1.80518 ν 1 = 25.4 R 2 = 79.88 D 2 = 9.0 N 2 = 1.51633 ν 2 = 64.1 R 3 = -17768.48 D 3 = 0.2 R 4 = 105.67 D 4 = 6.2 N 3 = 1.48749 ν 3 = 70.2 R 5 = 833.30 D 5 = Variable R 6 = -158.06 D 6 = 1.5 N 4 = 1.80400 ν 4 = 46.6 R 7 = 35.68 D 7 = 6.3 R 8 = 47.82 D 8 = 4.2 N 5 = 1.80518 ν 5 = 25.4 R 9 = 249.34 D 9 = Variable R10 = (Aperture) D10 = 13.7 R11 = -465.41 D11 = 1.5 N 6 = 1.84666 ν 6 = 23.8 R12 = 126.16 D12 = 5.8 N 7 = 1.51742 ν 7 = 52.4 R13 = -45.28 D13 = Variable R14 = 133.41 D14 = 6.5 N 8 = 1.51633 ν 8 = 64.1 R15 = -35.06 D15 = 1.5 N 9 = 1.83400 ν 9 = 37.2 R16 = -167.66 D16 = 0.2 R17 = 57.09 D17 = 5.0 N10 = 1.51742 ν10 = 52.4 R18 = -102.23 D18 = Variable R19 = 131.58 D19 = 1.3 N11 = 1.80400 ν11 = 46.6 R20 = 35.84 D20 = 3.0 R21 = -63.17 D21 = 1.3 N12 = 1.80400 ν12 = 46.6 R22 = 32.70 D22 = 4.0 N13 = 1.74077 ν13 = 27.8 R23 = -140.57

[0035]

[Table 2] Numerical Example 3 F = 51.5 to 195.0 FNO = 1: 4.14 to 5.14 2ω = 45.6 ° to 12.6 ° R 1 = 113.86 D 1 = 3.0 N 1 = 1.80518 ν 1 = 25.4 R 2 = 61.74 D 2 = 9.1 N 2 = 1.51633 ν 2 = 64.1 R 3 = -4499.50 D 3 = 0.2 R 4 = 71.72 D 4 = 6.7 N 3 = 1.48749 ν 3 = 70.2 R 5 = 47288.72 D 5 = Variable R 6 = -124.99 D 6 = 1.5 N 4 = 1.80400 ν 4 = 46.6 R 7 = 25.78 D 7 = 12.0 R 8 = 41.80 D 8 = 2.8 N 5 = 1.92286 ν 5 = 20.9 R 9 = 81.81 D 9 = Variable R10 = (Aperture) D10 = 1.6 R11 = -191.30 D11 = 1.5 N 6 = 1.80400 ν 6 = 46.6 R12 = -268.15 D12 = 3.2 N 7 = 1.59270 ν 7 = 35.3 R13 = -39.60 D13 = Variable R14 = 120.92 D14 = 5.2 N 8 = 1.48749 ν 8 = 70.2 R15 = -29.80 D15 = 1.5 N 9 = 1.84666 ν 9 = 23.9 R16 = -119.93 D16 = 0.2 R17 = 54.02 D17 = 4.4 N10 = 1.51742 ν10 = 52.4 R18 = -99.61 D18 = Variable R19 = 222.65 D19 = 1.5 N11 = 1.51633 ν11 = 64.1 R20 = 29.78

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

According to the present invention, the zoom lens is composed of five lens units having a predetermined refractive power as a whole, and the moving conditions of each lens unit and the lens configuration of each lens unit during zooming are described above. With such a setting, it is possible to achieve a compact zoom lens having a zoom ratio of about 4 and an F-number of about 4 having high optical performance with little aberration variation over the entire zoom range, while shortening the overall length of the lens. .

In particular, in the present invention, a zoom type capable of achieving compactness is applied, and a zoom configuration is provided in which the refracting power of each lens group is weakened so that the moving amount of the moving lens group can be supported even when the moving amount is large. This achieves a zoom lens that is effectively compact when stored, that is, when the overall length of the lens is the shortest.

[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 a sectional view of a lens according to a numerical example 2 of the present invention.

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

FIG. 4 is an aberration diagram at a wide angle end according to Numerical Embodiment 1 of the present invention.

FIG. 5 is an intermediate aberration diagram of the numerical example 1 of the present invention.

FIG. 6 is an aberration diagram at a telephoto end in Numerical Example 1 of the present invention.

FIG. 7 is an aberration diagram at a wide angle end according to Numerical Example 2 of the present invention.

FIG. 8 is an intermediate aberration diagram of the numerical example 2 of the present invention.

FIG. 9 is an aberration diagram at a telephoto end in Numerical Example 2 of the present invention;

FIG. 10 is an aberration diagram at a wide angle end according to Numerical Example 3 of the present invention.

FIG. 11 is an intermediate aberration diagram of the numerical example 3 of the present invention.

FIG. 12 is an aberration diagram at a telephoto end in Numerical Example 3 of the present invention.

FIG. 13 is an explanatory view of a cam groove of a cam cylinder according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 1st group 2 2nd group 3 3rd group 4 4th group 5 5th group SP stop d d-line g g-line ΔS sagittal image plane ΔM meridional image plane

Claims (3)

(57) [Claims] 1. A first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power, and a negative lens having a negative refractive power in order from the object side. The fifth lens group includes five lens groups. When zooming from the wide-angle end to the telephoto end, the first, third, and fifth groups are moved toward the object side, and the second and fourth groups are moved. With the group fixed, the combined focal length of the first and second groups at the wide-angle end is f12W, the focal length of the i-th group is fi,
The focal length of the entire system at the wide-angle end is fW, and the amounts of movement of the first and fifth units during zooming are ST1 and ST5, respectively, from the lens surface closest to the object side to the lens surface closest to the image plane at the wide-angle end. Is the distance of TDW A zoom lens that satisfies certain conditions. 2. The first group comprises a cemented lens of a negative lens, a positive lens, and a positive lens, the second group comprises a negative lens and a positive lens having both concave lens surfaces, and the third group comprises a negative lens. The fourth group is composed of a cemented lens of a positive lens and a negative lens having both convex lens surfaces, and the fourth group is composed of a positive lens having both convex surfaces of both lens surfaces. The fifth group is a negative lens. 2. The zoom lens according to claim 1, comprising a cemented lens of a negative lens and a positive lens. 3. The first group comprises a cemented lens of a negative lens and a positive lens and a positive lens, the second group comprises a negative lens and a positive lens having both concave lens surfaces, and the third group comprises a negative lens. The fourth group includes a cemented lens of a positive lens and a negative lens having both convex surfaces, and the fourth group includes a cemented lens of a positive lens and a negative lens having both convex surfaces, and the fifth group includes an object side. 2. The zoom lens according to claim 1, comprising a single meniscus lens having a convex surface facing the lens.