JPH1172704A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact zoom lens having high magnification. SOLUTION: Relating to a zoom lens composed, in order from the object side, of a first group Gr1 having a negative power, a second group Gr2 having a positive power, a third group Gr3 having a positive power and a fourth group Gr4 having a positive power, at the time of performing power variation from the wide-angle end to the telescopic end, an interval between the first group Gr1 and the second group Gr2 is decreased, an interval between the second group Gr2 and the third group Gr3 is increased, an interval between the third group Gr3 and the fourth group Gr4 is decreased and the following conditional relation is satisfied: 0.1<|f2/ft|<0.2, where, f2: the focal distance of the second group Gr2, ft: the focal distance at the telescopic end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a zoom lens, and more particularly to a zoom lens suitable for a lens shutter camera and a still video camera having a high zoom ratio.

[0002]

2. Description of the Related Art Conventionally, as a zoom lens for a lens shutter having a high zoom ratio and starting with a negative lens group,
JP-A-3-240015, JP-A-4-23770
9 and JP-A-8-43737, the negative first lens unit and the positive second lens unit are arranged in order from the object side.
A four-component zoom type including a lens group, a positive third lens group, and a negative fourth lens group has been proposed.

[0003]

However, in each of the above arrangements, the power of each lens group is not sufficiently strong, so that the amount of movement of each lens group during zooming becomes too large, and the lens barrel configuration is reduced. It was a shackle when making it compact. An object of the present invention is to solve these problems and to provide a compact and high-magnification zoom lens.

[0004]

In order to achieve the above object, according to the present invention, a first lens unit having negative power, a second lens unit having positive power, and a positive lens are arranged in order from the object side. When performing zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group is reduced in a zoom lens composed of a third group having a zoom lens and a fourth group having a negative power. A zoom lens in which the distance between the second group and the third group increases and the distance between the third group and the fourth group decreases, wherein the following conditional expression is satisfied: . 0.1 <| f2 / ft | <0.2 where f2: focal length of the second lens unit ft: focal length at the telephoto end.

Further, a lens having a strong convex surface facing the object side is arranged on the object side in the second group. Further, the fourth group is composed of one lens.

[0006] As another configuration, in order from the object side,
A first group having negative power and a second group having positive power
When performing zooming from a wide-angle end to a telephoto end in a zoom lens including a lens unit, a third lens unit having a positive power, and a fourth lens unit having a negative power, the first lens unit and the second lens unit
A zoom lens in which a distance between groups decreases, a distance between the second group and the third group increases, and a distance between the third group and the fourth group decreases. Satisfy the configuration. 0.15 <| f1 / ft | <0.45 0.05 <| f4 / ft | <0.35 where f1: focal length of the first group f4: focal length of the fourth group ft: telephoto end Is the focal length of

Further, a lens having a strong convex surface facing the object side is arranged on the object side in the second group. Further, the fourth group is composed of one lens.

Further, as another configuration, in order from the object side,
A first group having negative power and a second group having positive power
When performing zooming from a wide-angle end to a telephoto end in a zoom lens including a lens unit, a third lens unit having a positive power, and a fourth lens unit having a negative power, the first lens unit and the second lens unit
A zoom lens in which a distance between groups decreases, a distance between the second group and the third group increases, and a distance between the third group and the fourth group decreases. Satisfy the configuration. 4 <| m1 / Z | <155 5 <| m4 / Z | <12 where: m1: the amount of movement of the first unit from the wide-angle end to the telephoto end m4: the amount of movement of the fourth unit from the wide-angle end to the telephoto end Movement amount Z: focal length at the telephoto end / focal length at the wide-angle end.

Further, a lens having a strong convex surface facing the object side is arranged on the object side in the second group. Further, the fourth group is composed of one lens.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show the lens configurations of the zoom lenses according to the first to third embodiments, respectively, and show the lens arrangement at the wide-angle end (W). As shown in these figures, the zoom lenses of the first to third embodiments each include, in order from the object side, a first group Gr1 having a negative power and a second group G1 having a positive power.
r2, a third lens unit Gr3 having a positive power, and a fourth lens unit Gr4 having a negative power.

The zoom lens is such that each lens group moves toward the object side during zooming from the wide-angle end (W) to the telephoto end (T). Arrows m1 to m4 in these figures are:
The movement from the wide-angle end (W) to the telephoto end (T) of each of the first to fourth groups Gr1 to Gr4 is schematically shown.

The present invention provides, in order from the object side, a first lens unit having negative power, a second lens unit having positive power, a third lens unit having positive power, and a fourth lens unit having negative power. When performing zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, the distance between the second group and the third group increases, A zoom lens in which the distance between the third group and the fourth group is reduced, and which satisfies the following conditional expression, has been proposed. 0.1 <| f2 / ft | <0.2 (1) where f2: focal length of the second lens unit ft: focal length at the telephoto end

[0013] By giving the first group negative power,
A focal length in a wide angle range is easily realized. Further, by configuring the following lens groups as a positive lens group, a positive lens group, and a negative lens group, an optical system having a high zoom ratio can be realized. Furthermore, in order to make the optical system compact, which has been particularly demanded in recent years, it is necessary to satisfy conditional expression (1). That is, if the power of the second lens unit is weak and exceeds the upper limit of the conditional expression (1), the moving amount of the second lens unit becomes too large, and it is impossible to achieve a compact optical system. Conversely, if the power of the second lens unit is too strong and falls below the lower limit of the conditional expression (1), it becomes difficult to correct spherical aberration particularly at the telephoto end, and it becomes impossible to satisfy desired optical performance.

Further, according to the present invention, by disposing a lens having a strong convex surface facing the object side on the object side in the second group, it is possible to obtain a zoom lens with better delineation performance. That is, in the present invention, since the negative lens group having a relatively high power is disposed in the first group, the light rays emitted from the first group have a high pop-up angle and a negative spherical aberration. In order to correct this in the second lens unit, a strong convex surface is provided on the surface closest to the object side in the second lens unit, so that the high pop-up angle generated in the first lens unit can be reduced. , And corrects negative spherical aberration, and plays a large role in total spherical aberration correction.

In order to achieve the compactness recently demanded, it is desirable that the fourth group, which is the last negative lens group, is composed of one lens. By configuring the final negative lens group with one thin lens, a compact lens barrel with a short optical axis direction can be realized.

Further, according to the present invention, in order from the object side, a first unit having a negative power, a second unit having a positive power,
A third group having positive power and a fourth group having negative power
When performing zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, the distance between the second group and the third group increases, A zoom lens in which the distance between the third group and the fourth group is reduced, and which satisfies the following conditional expression, has been proposed. 0.15 <| f1 / ft | <0.45 (2) 0.05 <| f4 / ft | <0.35 (3) where f1: focal length of the first group f4: focal length of the fourth group Focal length ft: focal length at the telephoto end.

By making the first group have a negative power,
A focal length in a wide angle range is easily realized. Further, by configuring the following lens groups as a positive lens group, a positive lens group, and a negative lens group, an optical system having a high zoom ratio can be realized. Furthermore, in order to make the optical system compact, which has been particularly demanded in recent years, it is necessary to satisfy conditional expression (2). That is, if the power of the first lens unit is weak and exceeds the upper limit of the conditional expression (2), the amount of movement of the first lens unit becomes too large, and it is impossible to achieve a compact optical system. On the other hand, if the power of the first lens unit is too strong and falls below the lower limit of the conditional expression (2), it becomes difficult to correct under-distortion at the wide-angle end and spherical aberration at the telephoto end, thereby satisfying desired optical performance. I can't do things.

In order to make the optical system compact,
It is necessary to satisfy conditional expression (3). That is, when the power of the fourth lens unit is weak and exceeds the upper limit of the conditional expression (3), the moving amount of the fourth lens unit becomes too large, and it is impossible to achieve a compact optical system. Conversely, if the power of the fourth lens unit is too strong and falls below the lower limit of the conditional expression (3), it becomes difficult to correct coma at the wide-angle end, and it becomes impossible to satisfy desired optical performance.

Further, according to the present invention, by disposing a lens with a strong convex surface facing the object side on the object side in the second group, it is possible to obtain a zoom lens with better delineation performance. That is, in the present invention, since the negative lens group having a relatively high power is disposed in the first group, the light rays emitted from the first group have a high pop-up angle and a negative spherical aberration. In order to correct this in the second lens unit, a strong convex surface is provided on the surface closest to the object side in the second lens unit, so that the high pop-up angle generated in the first lens unit can be reduced. , And corrects negative spherical aberration, and plays a large role in total spherical aberration correction.

In order to achieve the compactness recently demanded, it is desirable that the fourth group, which is the last negative lens group, is composed of one lens. By configuring the final negative lens group with one thin lens, a compact lens barrel with a short optical axis direction can be realized.

Also, according to the present invention, in order from the object side, a first unit having a negative power, a second unit having a positive power,
A third group having positive power and a fourth group having negative power
When performing zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, the distance between the second group and the third group increases, A zoom lens in which the distance between the third group and the fourth group is reduced, and which satisfies the following conditional expression, has been proposed. 4 <| m1 / Z | <15 (4) 5 <| m4 / Z | <12 (5) where, m1: the amount of movement of the first unit from the wide-angle end to the telephoto end m4: the wide-angle of the fourth unit The amount of movement from the end to the telephoto end Z: focal length at the telephoto end / focal length at the wide-angle end.

At this time, when the value goes below the lower limit of conditional expression (4), the amount of movement of the first lens unit becomes too small, and the intermediate focus which is originally removed due to a change in the distance between the first lens unit and the second lens unit. It becomes difficult to correct the field curvature from the distance to the telephoto end. On the other hand, when the value exceeds the upper limit of the conditional expression (4), the moving amount of the first lens unit becomes too large, which is against the compactness and cannot achieve a high zoom ratio.

If the amount of movement of the fourth lens unit becomes too small and falls below the lower limit of the conditional expression (5), a high magnification change required for the fourth lens unit and required for securing a desired zoom ratio is obtained. In order to secure the power, it is necessary to increase the power of the fourth lens unit. However, in this case, it becomes difficult to remove coma aberration particularly at the wide-angle end. On the other hand, when the value exceeds the upper limit of the conditional expression (5), the moving amount of the first lens unit becomes too large, which is against the compactness and cannot achieve a high zoom ratio.

Further, in the present invention, by disposing a lens having a strong convex surface facing the object side on the object side in the second group, it is possible to obtain a zoom lens with better delineation performance. That is, in the present invention, since the negative lens group having a relatively high power is disposed in the first group, the light rays emitted from the first group have a high pop-up angle and a negative spherical aberration. In order to correct this in the second lens unit, a strong convex surface is provided on the surface closest to the object side in the second lens unit, so that the high pop-up angle generated in the first lens unit can be reduced. , And corrects negative spherical aberration, and plays a large role in total spherical aberration correction.

In order to achieve the compactness recently demanded, it is desirable that the fourth group, which is the last negative lens group, is composed of one lens. By configuring the final negative lens group with one thin lens, a compact lens barrel with a short optical axis direction can be realized.

In the focusing system according to the present invention, good performance can be secured from infinity to proximity by configuring the first lens unit to extend toward the object side.

Hereinafter, the configuration of the zoom lens according to the present invention will be described more specifically with reference to construction data and aberration diagrams. Examples 1 to 3 below correspond to the first to third embodiments described above, respectively, and are lens configuration diagrams showing the first to third embodiments (FIGS. 1 to 3).
Shows lens configurations of Examples 1 to 3, respectively.

In each embodiment, ri (i = 1, 2, 3,...) Indicates the radius of curvature of the i-th surface counted from the object side, and di (i = 1, 2).
2,3 ...) indicates the i-th axial top surface distance counted from the object side, and Ni (i = 1,2,3 ...), νi (i = 1,2,3 ...) Is the refractive index for the d-line of the i-th lens counted from the object side,
Indicates Abbe number. In addition, the focal length f of the entire system, the F number FNO, and the interval that changes with zooming (the interval on the top of the shaft)
Are the wide-angle end (W), the intermediate focal length (M),
It corresponds to each value at the telephoto end (T). In each of the examples, the surface with asterisks (*) indicates that the surface is constituted by an aspheric surface.
Defined below.

Y = CX ² / {1+ (1-εC ² X ² ) ^1/2 } + {A _i X ⁱ where X: height in the direction perpendicular to the optical axis Y: displacement from the reference plane in the optical axis direction Amount C: paraxial curvature ε: quadratic surface parameter A _i : i-th order aspherical surface coefficient

[0030]

[Aspherical surface coefficient of first surface (r1)] ε = 2.8416 A4 = 0.23422721 × 10 ^-5 A6 = 0.22222019 × 10 ^-7 A8 = 0.16392 256 × 10 ^-8 A10 = -0.77087303 × 10 ^-11 A12 =- 0.52915194 × 10 ^-13 A14 = 0.41851353 × 10 ^-15 A16 = -0.16166790 × 10 ^-17

[Aspherical surface coefficient of the second surface (r2)] ε = 0.9887 A4 = -0.19720411 × 10 ^-5 A6 = 0.26861298 × 10 ^-6 A8 = -0.22845642 × 10 ^-8 A10 = 0.12886077 × 10 ^-10 A12 = 0.43797521 × 10 ^-12 A14 = -0.15349438 × 10 ^-14 A16 = -0.36417569 × 10 ^-16

[Aspherical surface coefficient of the eighth surface (r8)] ε = -0.3355 A4 = -0.40850445 × 10 ^-4 A6 = 0.24659493 × 10 ^-6 A8 = -0.10228846 × 10 ^-7 A10 = 0.71606264 × 10 ^-10 A12 = 0.39528711 × 10 ^-12 A14 = -0.19047572 × 10 ^-14 A16 = -0.57889647 × 10 ^-16

[Aspherical surface coefficient of the sixteenth surface (r16)] ε = 0.2365 A4 = -0.37778269 × 10 ^-4 A6 = -0.16216353 × 10 ^-5 A8 = 0.57150607 × 10 ^-7 A10 = -0.91603301 × 10 ^-9 A12 = 0.10271194 × 10 ^-10 A14 = -0.17911006 × 10 ^-12 A16 = 0.17037803 × 10 ^-14

[0035]

[Aspherical surface coefficient of the first surface (r1)] ε = -5.5840 A4 = 0.27982121 × 10 ^-4 A6 = -0.39757157 × 10 ^-6 A8 = -0.12679546 × 10 ^-7 A10 = -0.77738755 × 10 ^-11 A12 = 0.13747903 × 10 ^-11 A14 = 0.20341784 × 10 ^-13 A16 = -0.15869121 × 10 ^-15

[Aspherical surface coefficient of the second surface (r2)] ε = 1.1290 A4 = 0.14829423 × 10 ^-4 A6 = -0.16583137 × 10 ^-6 A8 = -0.68463895 × 10 ^-8 A10 = -0.33968930 × 10 ^-9 A12 = -0.58437138 × 10 ^-11 A14 = -0.12319780 × 10 ^-12 A16 = 0.67137534 × 10 ^-14

[0038] [aspherical coefficients of the eighth surface (r8)] ε = -1.9551 A4 = -0.98407854 × 10 -4 A6 = -0.95909548 × 10 -6 A8 = -0.30410832 × 10 -7 A10 = -0.93778248 × 10 - ¹⁰ A12 = -0.20269684 × 10 ^-11 A14 = 0.34645782 × 10 ^-12 A16 = -0.45196974 × 10 ^-14

[Aspherical surface coefficient of the 16th surface (r16)] ε = 0.0000 A4 = -0.64446070 × 10 ^-4 A6 = -0.88080303 × 10 ^-6 A8 = 0.11247651 × 10 ^-6 A10 = -0.15613719 × 10 ^-8 A12 = 0.13673463 × 10 ^-10 A14 = -0.11398501 × 10 ^-12 A16 = 0.56863013 × 10 ^-15

[Aspherical surface coefficient of the 17th surface (r17)] ε = 1.0000 A4 = −0.89399920 × 10 ⁻⁴ A6 = 0.16983126 × 10 ⁻⁵ A8 = −0.44363934 × 10 ⁻⁸ A10 = −0.49430088 × 10 ⁻¹⁰ A12 = 0.26874599 × 10 ^-12

[0041]

[Aspherical surface coefficient of first surface (r1)] ε = -13.2432 A4 = 0.35661812 × 10 ^-4 A6 = -0.36131641 × 10 ^-6 A8 = -0.71049480 × 10 ^-8 A10 = 0.22145 382 × 10 ^-10 A12 = 0.90126287 × 10 ^-12 A14 = 0.79604697 × 10 ^-14 A16 = -0.17916705 × 10 ^-15

[Aspherical surface coefficient of the second surface (r2)] ε = 1.2212 A4 = 0.23328434 × 10 ^-4 A6 = 0.54543924 × 10 ^-6 A8 = -0.31180976 × 10 ^-7 A10 = -0.15093511 × 10 ^-9 A12 = 0.11800131 × 10 ^-10 A14 = -0.56094624 × 10 ^-13 A16 = -0.12248 690 × 10 ^-14

[Aspherical surface coefficient of the eighth surface (r8)] ε = -1.4687 A4 = -0.63192669 × 10 ^-4 A6 = 0.54249754 × 10 ^-6 A8 = -0.40041865 × 10 ^-7 A10 = -0.53530 789 × 10 ^-9 A12 = -0.16312685 × 10 ^-10 A14 = 0.20817442 × 10 ^-11 A16 = -0.32076271 × 10 ^-13

[Aspherical surface coefficient of the sixteenth surface (r16)] ε = 0.0000 A4 = -0.12535303 × 10 ^-3 A6 = -0.12103538 × 10 ^-5 A8 = 0.11721425 × 10 ^-6 A10 = -0.15561916 × 10 ^-8 A12 = 0.14425895 × 10 ^-10 A14 = -0.97571851 × 10 ^-13 A16 = 0.39098959 × 10 ^-15

[Aspherical surface coefficient of the seventeenth surface (r17)] ε = 1.0000 A4 = -0.10588185 × 10 ^-3 A6 = 0.17678045 × 10 ^-5 A8 = -0.42477779 × 10 ^-8 A10 = -0.52173981 × 10 ^-10 A12 = 0.29671234 × 10 ^-12

FIGS. 4 to 6 are aberration diagrams respectively corresponding to the first to third embodiments. In each of FIGS. 4 to 6, the upper part shows the wide-angle end, the middle part shows the intermediate focal length, and the lower part shows the telephoto end. ing. In the spherical aberration diagram, the solid line (d) represents the d line, the dashed line (g) represents the g line, and the dashed line (sc) represents the sine condition. In the astigmatism diagram, a solid line (DS) and a broken line (DM) represent astigmatism of a sagittal light beam and a meridional light beam, respectively. Table 1 shows values corresponding to the conditional expressions (1) to (5) in Examples 1 to 3, respectively.

[0048]

[Table 1]

[0049]

As described above, according to the present invention,
A compact, high-power zoom lens can be provided.

[Brief description of the drawings]

FIG. 1 is a lens configuration diagram according to a first embodiment of the present invention.

FIG. 2 is a lens configuration diagram according to a second embodiment of the present invention.

FIG. 3 is a lens configuration diagram according to a third embodiment of the present invention.

FIG. 4 is an aberration diagram of the first embodiment of the present invention.

FIG. 5 is an aberration diagram of the second embodiment of the present invention.

FIG. 6 is an aberration diagram of a third embodiment of the present invention.

[Explanation of symbols]

 Gr1 First group Gr2 Second group Gr3 Third group Gr4 Fourth group

Claims (9)

[Claims] 1. A first lens unit having negative power, a second lens unit having positive power, a third lens unit having positive power, and a fourth lens unit having negative power in order from the object side. In the zoom lens configured, when zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, and the distance between the second group and the third group increases. A zoom lens having a reduced distance between the third group and the fourth group, wherein the following conditional expression is satisfied; 0.1 <| f2 / ft | <0.2 Here, f2: focal length of the second lens unit ft: focal length at the telephoto end. 2. The zoom lens according to claim 1, wherein a lens having a strong convex surface facing the object side is disposed on the object side in the second group. 3. The zoom lens according to claim 2, wherein the fourth group includes one lens. 4. A first lens unit having negative power, a second lens unit having positive power, a third lens unit having positive power, and a fourth lens unit having negative power are arranged in order from the object side. In the zoom lens configured, when zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, and the distance between the second group and the third group increases. 0.15 <| f1 / ft | <0.45, wherein the distance between the third group and the fourth group is reduced, wherein the following conditional expression is satisfied; 0.05 <| f4 / ft | <0.35, where f1: focal length of the first lens unit f4: focal length of the fourth lens unit ft: focal length at the telephoto end 5. The zoom lens according to claim 4, wherein a lens having a strong convex surface facing the object side is disposed on the object side in the second group. 6. The zoom lens according to claim 5, wherein the fourth group includes one lens. 7. A first lens unit having negative power, a second lens unit having positive power, a third lens unit having positive power, and a fourth lens unit having negative power are arranged in order from the object side. In the zoom lens configured, when zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, and the distance between the second group and the third group increases. A zoom lens having a reduced distance between the third group and the fourth group, wherein the following conditional expression is satisfied; 4 <| m1 / Z | <155 <| m4 / Z | <12, where m1: the amount of movement of the first unit from the wide-angle end to the telephoto end m4: the amount of movement of the fourth unit from the wide-angle end to the telephoto end Z: the focal length at the telephoto end / the wide-angle end The focal length. 8. The zoom lens according to claim 7, wherein a lens having a strong convex surface facing the object side is disposed on the object side in the second group. 9. The zoom lens according to claim 8, wherein the fourth group includes one lens.