KR19980025176A - Variable-speed optical system - Google Patents

Abstract

The present invention provides a high-performance variable optical system that can be manufactured at low cost in a simple configuration.

The first lens group G1 of positive refractive power and the second lens group G2 of negative refractive power are sequentially turned on the object side, and the wide angle is reduced by reducing the air gap between the first lens group G1 and the second lens group G2. The shift from the end state to the telephoto end state is performed. The first lens group G1 includes a first lens component L1 of negative refractive power, a second lens component L2 of negative refractive power, and a third lens of positive refractive power, in which the surface of the object toward the object is concave toward the object in order from the object side. It is composed of component (L3) and satisfies condition 1.

Description

Variable-speed optical system

The present invention relates to a variable speed optical system, and more particularly to a variable speed optical system that is most suitable for a compact lens shutter camera.

BACKGROUND ART In recent years, in a photographing lens for a lens shutter type camera, a zoom lens has become mainstream, and various proposals have been made regarding a two-group zoom lens having a simple structure of a lens system.

The government two-group zoom lens is composed of a positive lens group and a negative lens group installed on its upper side, and changes (varies) the focal length of the entire lens system by changing the distance between the positive lens group and the negative lens group. Such a government group 2 zoom lens is disclosed in, for example, Japanese Patent Laid-Open No. 2-73322.

In a compact lens shutter camera, portability and lightness are important. From the viewpoint of portability, the camera body has been required to be smaller in size from the beginning. In addition, from a light point of view, it is required to be easy to purchase at low cost with the same performance, and therefore, low cost is required in manufacture of a camera and a lens.

BACKGROUND ART In recent years, as zoom lenses become more common, various proposals have been made regarding zoom lenses in order to achieve miniaturization and low cost. For example, Japanese Patent Laid-Open No. 3-127009 and Japanese Patent Laid-Open No. 5-257063 disclose a lens system in which a cost reduction is achieved while securing a predetermined variable ratio. In the lens system disclosed in these publications, the cost is reduced by reducing the number of lens components or by using a plastic material.

In general, since the plastic material 낮 has a lower melting point than the glass material, the manufacturing cost can be reduced in a compact lens shutter camera or the like which is easy to mold and mass-produced.

In the lens system disclosed in Japanese Patent Laid-Open No. 3-127009, the positive lens group is composed of two negative lenses and positive lenses. Therefore, the axial aberration, the axial aberration, and the aberration are corrected by converging the surface of the object side of the negative lens and the diverging effect of the upper surface, respectively, and forming both surfaces of the negative lens in an aspheric shape. In addition, the negative subgroup is composed of one lens to reduce the number of lens configurations and to achieve low cost.

On the other hand, in the lens system disclosed in Japanese Patent Laid-Open No. 5-257063, one plastic lens is used for each of the positive lens group and the negative lens group to achieve low cost.

However, in the lens system according to Japanese Patent Laid-Open No. 3-127009, at the time of manufacture, the object side of the negative lens in the positive lens group had strong positive refractive power, the upper side had negative refractive power, and both sides were aspheric surfaces. The performance deterioration due to the eccentricity that occurred was remarkable.

In the lens system according to Japanese Patent Laid-Open No. 5-257063, a low cost is achieved by introducing a plastic lens. However, since the positive lens group was composed of four lenses, it was not sufficient from the viewpoint of reducing the number of lens configurations. In addition, since the lens installed on the most object side faces the convex surface toward the object, the correction of the positive distortion aberration at the wide-angle end cannot be said to be sufficient.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object thereof is to provide a small sized optical system that can be manufactured at low cost with a variable ratio (zoom ratio) of more than twice and can be manufactured at low cost with a simple configuration.

In order to solve the above problems, in the first invention, the first lens group G1 having positive refractive power and the second lens group G2 having negative refractive power are sequentially formed on the object side. By reducing the air gap with the second lens group G2, the shift from the wide-angle end state to the telephoto end state is performed, and the first lens group G1 has a negative refractive power whose object side faces the concave surface in turn from the object side. A radius of curvature of the object-side surface of the first lens component L1, consisting of one lens component L1, a second lens component L2 of negative refractive power, and a third lens component L3 of positive refractive power, When the radius of curvature of the surface on the object side of the first lens component L1 is r12,

Conditional Expression 1

-1.43 (r11 + r12) / (r11-r12) -0.7

It provides a variable speed optical system, characterized in that to satisfy the conditions of.

According to the second invention, the first lens group G1 having the positive refractive power and the second lens group G2 having the negative refractive power are sequentially formed on the object side, and the first lens group G1 and the second lens group ( By reducing the space interval with G2), the shift from the wide-angle end state to the telephoto end state is performed, and the first lens group G1 has the first negative refractive power whose surface from the object side in turn faces the concave surface toward the object. The lens component L1, the second lens component L2 of negative refractive power and the third lens component L3 of positive refractive power, and the second lens component L2 comprises one or more plastic lenses LP1. The second lens group G2 provides a variable speed optical system, characterized in that it has one or more plastic lenses LP2.

According to a third aspect of the present invention, there is provided a positive lens group G1 having positive refractive power and a negative lens group G2 having negative refractive power arranged on the object side of the positive lens group G1. An aperture diaphragm S is disposed in the optical path between the lens group G1 and the negative lens group G2, and the lens group G1 has the first lens L1 of negative refractive power and the negative refractive power in order from the object side. It consists of two lenses (L2) and the third lens (L3) of positive refractive power, by changing the air gap between the positive lens group (G1) and the negative lens group (G2) to change the focal length of the whole optical system, When the radius of curvature of the object-side surface of the second lens L2 is r22 and the distance along the optical axis between the object-side surface of the second lens L2 and the aperture stop S is D,

Conditional Expression 2

1.5 r22 / D 4

It provides a modified optical system characterized by satisfying the conditions of.

Further, according to the fourth aspect of the present invention, the positive lens group G1 having positive refractive power and negative lens group G2 having negative refractive power are sequentially formed on the object side, and the positive lens group G1 and the negative lens group ( By changing the air gap with G2), the focal length of the whole optical system is changed, the focal length of the positive lens group G1 is f1, the focal length of the negative lens group G2 is f2, and the wide-angle end is made. When the focal length of the whole optical system in the state is fw and the focal length of the whole optical system in the telephoto end state is ft,

Conditional Expression 3

0.5 (f1 + | f2 | / (fwft) ^1/2 0.4

It provides a variable speed optical system characterized by satisfying the conditions of.

According to a fifth aspect of the present invention, the positive lens group G1 having positive refractive power and the negative lens group G2 having negative refractive power are sequentially formed on the object side, and the positive lens group G1 and the negative lens group are arranged. By varying the air gap at (G2), the focal length of the whole optical system is changed, the back focus at the wide-angle end state is Bfw, the lens length at the telephoto end state is TLt, and the overall optical system at the wide-angle end state. When the focal length is fw and the focal length of the whole optical system in the telephoto end state is ft,

Conditional Expression 4

(Bfw / TLt) ・ (ft / fw) 0.4

It provides a variable speed optical system characterized by satisfying the conditions of.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing the movement shape of each lens group at the time of shifting the refractive power of the shifting optical system and the shifting from the wide angle end state to the telephoto end state according to each embodiment of the present invention.

Fig. 2 is a diagram showing a lens configuration of a variable speed optical system according to the first embodiment of the present invention.

3 is an aberration diagram in the wide-angle end state of the first embodiment;

4 is an aberration diagram in the intermediate focal length state of the first embodiment;

5 is an aberration diagram in the telephoto end state of the first embodiment;

6 is a diagram showing a lens configuration of a variable speed optical system according to a second embodiment of the present invention.

7 is an aberration diagram in the wide-angle end state of the second embodiment.

8 is an aberration diagram in the intermediate focal length state of the second embodiment.

9 is a diagram of the aberration in the telephoto end state of the second embodiment;

Fig. 10 is a diagram showing a lens configuration of a variable speed optical system according to the third embodiment of the present invention.

Fig. 11 is the aberration diagram in the wide-angle end state of the third embodiment.

12 is the aberration diagram in the intermediate focal length state of the third embodiment.

Fig. 13 is an aberration diagram in the telephoto end state of the third embodiment.

Fig. 14 is a diagram showing a lens configuration of a variable speed optical system according to the fourth embodiment of the present invention.

Fig. 15 is the aberration diagram in the wide-angle end state of the fourth embodiment.

Fig. 16 is the aberration diagram in the intermediate focal length state of the fourth embodiment.

Fig. 17 is the aberration diagram in the telephoto end state of the fourth embodiment.

Fig. 18 is a diagram showing a lens configuration of a variable speed optical system according to the fifth embodiment of the present invention.

19 is an aberration diagram in the wide-angle end state of the fifth embodiment.

20 is the aberration diagram in the intermediate focal length state of the fifth embodiment.

Fig. 21 is an aberration diagram in the telephoto end state of the fifth embodiment.

Fig. 22 is a diagram showing the movement shape of each lens group at the time of shifting the refractive power of the variable speed optical system and the wide angle end state W to the telephoto end state T according to each embodiment of the present invention.

Fig. 23 is a diagram showing a lens configuration of a variable speed optical system according to the sixth embodiment of the present invention.

24 is the aberration diagram in the wide-angle end state of the sixth embodiment;

25 is the aberration diagram in the intermediate focal length state of the sixth embodiment;

Fig. 26 is the aberration diagram in the telephoto end state of the sixth embodiment;

FIG. 27 is a diagram showing a lens configuration of a variable speed optical system according to the seventh embodiment of the present invention. FIG.

Fig. 28 is the aberration diagram in the wide-angle end state of the seventh embodiment.

29 is the aberration diagram in the intermediate focal length state of the seventh embodiment.

30 is an aberration diagram in the telephoto end state of the seventh embodiment;

FIG. 31 is a diagram showing a lens configuration of a variable speed optical system according to an eighth embodiment of the present invention; FIG.

32 is an aberration diagram in the wide-angle end state of the eighth embodiment;

33 is the aberration diagram in the intermediate focal length state of the eighth embodiment.

Fig. 34 is the aberration diagram in the telephoto end state of the eighth embodiment.

Fig. 35 is a view showing the lens configuration of the variable magnification optical system according to the ninth embodiment of the present invention.

36 is the aberration diagram in the wide-angle end state of the ninth embodiment.

Fig. 37 is the aberration diagram in the intermediate focal length state of the ninth embodiment.

38 is an aberration diagram in the telephoto end state of the ninth embodiment;

Fig. 39 is a diagram showing a lens configuration of the variable magnification optical system according to the tenth embodiment of the present invention.

40 is an aberration diagram in the wide-angle end state of the tenth embodiment;

Fig. 41 is the aberration diagram in the intermediate focal length state of the tenth embodiment.

Fig. 42 is the aberration diagram in the telephoto end state of the tenth embodiment;

* Description of the symbols for the main parts of the drawings *

G1; First lens group G1 G2; Second lens group G2

Li; Each lens component S; Aperture aperture

In general, the government two-group zoom lens reduces the distance between the first lens group of positive refractive power and the second lens group of negative refractive power to perform the shift from the wide end state to the telephoto end state. The aperture stop is provided between the first lens group and the second lens group, and shifts integrally with the first lens group or independently of each lens group in shifting.

In miniaturizing the lens system, it is effective to strengthen the refractive power of the positive lens group and the refractive power of the negative lens group, respectively. However, in the case of wide-angle, the positive distortion aberration tends to increase due to the extreme asymmetry in the arrangement of the refractive power of the aperture diaphragm in the wide-angle end state. Therefore, it is necessary to suppress positive distortion aberration generated in the first lens group and the second lens group, respectively. In addition, to reduce the lens length in the telephoto end state, it is difficult to obtain sufficient back focus in the wide-angle end state, and the off-axis luminous flux passing through the lens component separated from the aperture stop is separated from the optical axis so that the lens diameter is reduced. It is easy to enlarge this size.

According to the present invention, a negative subgroup (first lens component L1 and a second lens component L2) disposed with the first lens group G1 having positive refractive power toward the object and the positive subgroup provided with the image (third lens component) L3), it is possible to generate negative distortion aberration in the first lens group G1 and to obtain sufficient back focus in the wide-angle end state.

For example, in the zoom lens disclosed in Japanese Patent Laid-Open No. 2-73322, since the negative subgroup is composed of the positive lens component and the negative bonded lens component, the number of lens configurations is large.

In the zoom lens disclosed in Japanese Patent Laid-Open No. 3-127009, the negative subgroup is composed of one negative lens. However, since both surfaces of the negative lens are formed in an aspherical shape, the deterioration in performance during eccentricity is very large. There was irrationality.

In the present invention, the negative subgroup is composed of two negative lens components L1 and L2, whereby deterioration in performance during eccentricity can be positively suppressed.

In addition, when the negative subgroup is composed of the positive lens and the negative lens, the main position of the negative subgroup is shifted upward, and when the predetermined refractive power is applied to the first lens group G1, the main interval between the negative subgroup and the positive subgroup is This shortens. As a result, the refractive power of the negative subgroup and the positive subgroup becomes stronger, and the performance deterioration due to the eccentricity increases.

In the present invention, the negative subgroup is composed of two negative lens components (L1 and L2) to shift the main point position of the negative subgroup to the object so as to deteriorate the refractive power of the negative subgroup and the positive subgroup, respectively, thereby performing performance by mutual eccentricity. Deterioration can be suppressed.

In the present invention, by configuring the object-side surface of the first lens component L1 toward the concave surface toward the object, negative distortion aberration can be efficiently generated to reduce the positive distortion value in the wide-angle end state.

In the second lens component L2, the off-axis light flux is separated from the optical axis in the wide-angle end state. Therefore, in order to correct coma aberration occurring in the first lens component L1 and to more efficiently correct distortion aberration in the wide-angle end state, at least one surface of the second lens component L2 is preferably formed aspheric. . It is particularly effective to form the object-side surface of the second lens component L2 in an aspherical shape.

As described above, in the present invention, by introducing a plastic lens, cost reduction or weight reduction can be achieved during mass production. Since plastic materials have a lower molding temperature than glass materials, they are suitable for cost reduction and aspheric surfaces can be introduced at low cost.

Next, the problem in the case of using a plastic material for a photographing lens is described.

The use of plastic lenses is very effective against low cost, but has the following problems.

① Since the change in refractive index due to temperature changes is larger than that of glass, the position of the upper surface tends to change with temperature.

② It is easy to change aberration according to temperature change because shape change is bigger than glass.

In the present invention, by using a plastic having a relatively weak refractive power, it is possible to suppress fluctuations in the position of the upper surface due to the temperature change of ①. That is, the variation of the image position can be prevented by providing a subplastic lens (second lens L2) in the first lens group G1 and a regular plastic lens (fourth lens L2) in the second lens group G2. It can cancel and the fluctuation | variation of the upper surface position according to a temperature change can be suppressed more favorable.

In addition, in the case where the plastic lens has a double-sided block lens shape or a double-sided concave lens shape, the change in refractive power of both lens surfaces due to temperature change is in the same direction, and thus the curvature of both surfaces becomes stronger because the volume expands when the temperature rises. On the contrary, the curvature of both sides weakens on falling. As a result, the fluctuation of refractive power and the aberration fluctuation by the temperature change become large. On the other hand, when the plastic lens has a meniscus shape, the change in refractive power of both lens surfaces due to the temperature change is in the opposite direction (when the curvature of one side becomes larger when the temperature changes, the curvature of the other surface becomes negative). The aberration fluctuations generated in the side face in the opposite directions on both lens surfaces, thereby suppressing the aberration fluctuations caused by temperature fluctuations.

In addition, it is known that the lens surface having a small height difference through which the on-axis luminous flux and the off-axis luminous flux pass is formed in an aspheric shape to be effective for correcting on-axis aberration. On the contrary, it is known that the lens surface through which the off-axis luminous flux passes away from the on-axis luminous flux has an aspherical surface shape and is effective for correcting off-axis aberration.

In the present invention, by introducing one plastic lens into the positive lens group G1 and the negative lens group G2, respectively, the number of lenses constituting the positive lens group G1 and the negative lens group G2 is reduced and the cost is reduced. Weight reduction and weight reduction can be achieved.

In the present invention, by making the plastic lens into a meniscus shape, it is possible to suppress fluctuations in refractive power and aberration in response to a temperature change of?.

In the zoom lens disclosed in Japanese Patent Laid-Open No. 5-257063, the problems 1 and 2 are solved in the same manner as in the present invention. However, the object-side surface of the first lens component faces the convex surface toward the object and did not contribute to the correction of the positive distortion aberration in the wide-angle end state.

In the present invention, the first lens component L1 faces the concave surface toward the object, and the first lens component L1 is actively contributed to aberration correction to achieve high performance and a reduction in the number of lens configurations.

In small lenses such as those used in compact lens shutter cameras, it is common to manufacture aspherical lenses (lenses formed with at least one surface in an aspherical shape) by a molding method. Plastic materials are the most suitable material for the mold molding method, but recent advances in technology have made it possible to manufacture glass molds at low cost. Therefore, the 1st lens group G1 can also be comprised only by a glass lens using a glass material for an aspherical lens.

However, when changing from the wide end state to the telephoto end state, the height from the optical axis of the luminous flux of the axis passing through the second lens group G2 approaches the optical axis. Therefore, when the plastic lens in the second lens group G2 has positive refractive power, at least one side of the positive plastic lens is aspherized to satisfactorily change the coma aberration occurring in the shift from the wide angle end state to the telephoto end state. It becomes possible to suppress it. As described above, when the plastic lens in the second lens group G2 has positive refractive power, it is preferable to form at least one surface of the positive plastic lens in an aspheric shape. In particular, it is more effective to aspherize at least the object-side surface of its regular plastic lens.

In the present invention, the interval between the negative subgroup G1a and the positive subgroup G1b is appropriately set to weaken the refractive power of the negative subgroup G1a and the positive subgroup G1b, respectively, thereby degrading performance due to mutual eccentricity. Suppress

Further, in the present invention, the distance between the positive lens group G1 and the negative lens group G2 is reduced in the shift from the telephoto end state to the wide end state. For this reason, as the telephoto end state approaches, the on-axis luminous flux passing through the negative lens group G2 falls from the optical axis, which tends to increase positive spherical aberration. In the present invention, the negative lens group G2 is composed of the positive lens L2P (fourth lens group L4) disposed toward the object and the negative lens L2N (5th lens group L5) disposed on the image side. The positive spherical aberration generated at (L2N) cancels the negative spherical aberration generated at the positive lens (L2P) to suppress the variation of the spherical aberration due to the shift to the telephoto end state in the wide-angle end state.

In addition, since the off-axis beam speed through which the negative lens group G2 passes due to the shift to the telephoto end state becomes closer to the optical axis, the object-side surface of the positive lens L2P is formed into an aspheric shape so as to be in the wide-angle end state. Suppresses fluctuations in coma aberration due to variations in telephoto end conditions.

The variable speed optical system of the present invention has been made based on the technical background as described above, and the wide angle is reduced by decreasing the air gap between the first lens group G1 having positive refractive power and the second lens group G2 having negative refractive power in turn on the object side. The shift from the end state to the telephoto end state is performed. Thus, the first lens group G1 has the first lens component L1 of negative refractive power, the second lens component L2 of negative refractive power, and the third of positive refractive power of which the surface of the object is sequentially directed from the object side toward the concave surface toward the object. It consists of the lens component L3.

Next, each conditional expression of this invention is demonstrated in detail.

In the first aspect of the invention, the first lens component L1 satisfies Conditional Expression 1 to achieve a high-performance variable optical system that can be miniaturized and reduced in cost. Further, in the second invention, a high-performance variable optical system aimed at miniaturization and low cost is achieved by introducing one or more plastic lenses into the second lens component L2 and the second lens group G2, respectively.

In the first invention, the following conditional expression 5 is satisfied. In the second invention, it is preferable that the following conditional expression 5 is satisfied.

Conditional Expression 5

-1.43 (r11 + r12) / (r11-r12) -0.7

Here, r11 is the radius of curvature of the surface of the first lens component L1 toward the object, and r12 is the radius of curvature of the upper surface of the first lens component L1.

Condition 5 is a conditional expression that defines the bending shape of the first lens component L1, and balances the correction of the positive distortion aberration in the wide-angle end state and the reduction of the variation of the coma aberration due to the angle of view. This is to prevent deterioration of the imaging performance due to.

If the upper limit of Conditional Equation 5 is exceeded, the divergence effect by the first lens component L1 becomes stronger, so that positive distortion aberration in the wide-angle end state can be corrected well, but fluctuations in coma aberration caused by the angle of view can be suppressed well. There will be no.

If the lower limit value of Conditional Expression 5 is less than, the drawing between the object side surface and the upper surface surface of the first lens component L1 is difficult in manufacturing, and the imaging property is deteriorated due to the eccentric error.

In the first and second inventions, it is preferable to satisfy the following Conditional Expressions 6 and 7.

Conditional Expression 6

2.0 | f11 | / f1 8.0

Conditional Expression 7

0.6 f13 / f1 0.95

Here, f1 is a focal length of the first lens group G1, f11 is a focal length of the first lens component L1, and f13 is a focal length of the third lens component L3.

Conditional Expression 6 defines an appropriate range for the focal length of the first lens component L1.

When the upper limit of Conditional Expression 6 is exceeded, the divergence of the first lens component L1 is weakened, so that it is not possible to sufficiently suppress positive distortion aberration occurring in the wide-angle end state. Further, in the wide-angle end state, the back focus is shortened and the off-axis luminous flux passing through the second lens group G2 is far from the optical axis, so the lens diameter of the second lens group G2 is enlarged. As a result, not only the miniaturization of the optical system but also the volume of the base material increases, which leads to weight and high cost, and the object of the present invention cannot be achieved. Moreover, it is more preferable to set the upper limit of conditional expression 6 to 4.5.

On the other hand, if the lower limit of Conditional Expression 6 is lower, the divergence of the second lens component L1 becomes stronger, so that the surface of the object side of the first lens component L1 faces the concave surface with a strong curvature toward the object, and the coma by the angle of view Fluctuations in aberration cannot be suppressed well.

Conditional Expression 7 defines an appropriate range for the focal length of the third lens component L3.

When the upper limit of Conditional Expression 7 is exceeded, the focal length of the third lens component L3 is turned on positively, and the composite focal length of the first lens component L1 and the second lens component L2 is turned on negatively. As a result, negative distortion aberration cannot be sufficiently generated in the entire first lens group G1, and positive false aberration cannot be corrected well in the wide-angle end state. Moreover, it is more preferable to set the upper limit of conditional formula to 0.90.

On the other hand, when the lower limit value of the conditional expression 7 is lower, the focal length of the third lens L3 becomes too small in the positive direction, so that the negative spherical aberration generated in the third lens component L3 increases, so that the entire first lens group G1 is full. The negative spherical aberration cannot be corrected sufficiently. Moreover, it is more preferable to set the lower limit of conditional formula 7 to 0.63.

In the second invention, it is preferable that the following conditional expression 8 is satisfied.

Conditional Expression 8

F12 / f1 3.0

Here, f12 is the paraxial focal length of the second lens component L2.

Condition 8 defines an appropriate range for the paraxial focal length of the second lens component L2 with one or more plastic lenses LP1.

When the lower limit of the conditional expression 8 is below, the refractive power of the second lens component L2 becomes strong. As a result, as described above, the influence of the refractive index change on the temperature change equation in the plastic lens LP1 becomes large, resulting in deterioration of the image due to the temperature change. Moreover, it is more preferable to set the lower limit of conditional expression 8 to 4.2.

Moreover, in 2nd invention, it is preferable to satisfy the following conditional formulas.

Conditional Expression 9

| F21 | / | f2 | 2.8

Here, f21 is the focal length of the plastic lens LP2 in the second lens group G2.

Conditional Expression 9 defines an appropriate range for the focal length of the plastic lens LP2 included in the second lens group G2.

When the lower limit of the conditional expression 9 is below, the refractive power of the plastic lens LP2 becomes strong. As a result, as described above, the influence of the refractive index change at the time of temperature change in the plastic lens LP2 becomes large, resulting in deterioration of the image due to the temperature change.

Further, the light beam side passing through the second lens component L2 is thicker than the light beam passing through the second lens group G2. For this reason, the change of the refractive index by the temperature change of the shift of the second lens component L2 is more affected than the second lens group G2. Therefore, the lower limit of conditional expression 8 is set larger than the lower limit of conditional expression 9.

In the third invention, the following conditional expression is satisfied.

Conditional Expression 10

1.5 r22 / D 4

Here, r22 is the radius of curvature of the image plane of the second lens (L2), D is the distance along the optical axis between the image plane of the second lens (L2) and the aperture stop (S).

Conditional Expression 10 defines an appropriate range for the radius of curvature of both lens surfaces of negative lens L2.

In the third invention, the lens group G1 comprises a negative subgroup G1a composed of two negative lenses L1 and L2 and a positive subgroup G1b composed of one positive lens L3 disposed above the negative subgroup G1a. It is composed. With such a configuration, a sufficient back focus can be secured at the wide end state, thereby miniaturizing the lens diameter and correcting the positive distortion aberration well. In addition, the upper lens surface of the negative lens L2 is the uppermost lens surface of the negative subgroup G1a, and the concave surface is turned toward the aperture stop by suppressing the occurrence of off-axis aberration.

When the upper limit of Conditional Expression 10 is exceeded, it is difficult to satisfactorily correct the negative spherical difference generated by the entire positive lens group G1 because the positive spherical aberration generated in the upper lens surface of the negative lens L2 is insufficient.

On the contrary, when the lower limit of Conditional Expression 10 is below, the coma aberration for the lower off-axis luminous flux becomes excessively corrected in the wide-angle end state, so that good imaging performance cannot be obtained in the entire screen.

In addition, in the third invention, it is preferable to satisfy the following conditional expression 11 in order to achieve a balance between miniaturization and high performance of the lens system.

Conditional Expression 11

0.02 D23 / ｜ f1a ｜ 0.08

Here, D23 is the axial air gap between the second lens L2 and the third lens L3, and f1a is the combined focal length of the first lens L1 and the second lens L2.

Conditional Expression 11 defines an appropriate range for the focal length fa of the negative subgroup G1a of the negative lenses L1 and L2 among the positive lens group G1. When the upper limit of Conditional Expression 11 is exceeded, the divergence effect by the negative subgroup G1a becomes stronger, and the lens length cannot be shortened in the telephoto end state. On the other hand, when the lower limit of Conditional Expression 11 is lower, the divergence action by the negative subgroup G1a becomes weaker, and it becomes difficult to satisfactorily correct the negative spherical aberration generated in the positive subgroup G1b.

In addition, it is preferable to introduce an aspherical surface into the negative lens group G2 in order to obtain higher imaging performance. In this case, it is particularly preferable to form the most object side surface of the negative lens group G2 in an aspheric shape. Since the height difference between the on-axis luminous flux passing through the negative lens group G2 and the off-axis luminous flux is large, by introducing an aspherical surface to the negative lens group G2, higher imaging performance can be obtained while widening and miniaturizing. As described above, in order to satisfactorily correct the positive spherical aberration generated in the negative lens group G2, the negative lens group G2 is disposed on the object side and the positive lens L2P (fourth lens L4). It is preferable to configure one negative lens (L2N: fifth lens L5).

In the third aspect of the invention, the negative lens group G2 has a positive refractive power on the object side in order to properly correct the axial aberration generated in each of the positive lens group G1 and the negative lens group G2 to achieve high performance and high variance. It is preferable to configure the four lenses L4 and the fifth lens L5 of negative refractive power to satisfy the following conditional expression (12).

Conditional Expression 12

0.08 D34 / | f2 | 0.40

Here, D45 is the axon air gap between the fourth lens L4 and the fifth lens L5, and f2 is the focal length of the negative lens group G2.

Conditional Expression 12 defines an appropriate range for the axial air gap D45 of the fourth lens L4 and the fifth lens L5 in the negative lens group G2. When the upper limit of the conditional expression 12 is exceeded, the fifth lens L5 opens the aperture diaphragm S in the wide-angle end state when the axial air gap between the positive lens group G1 and the negative lens group G2 is secured by a predetermined amount or more in the telephoto end state. Break away from). As a result, the fifth lens L5 is separated from the optical axis of the luminous flux of the shaft and the lens diameter cannot be miniaturized.

On the contrary, when the lower limit of Conditional Expression 12 is lower, the refractive power of the fourth lens L4 and the refractive power of the fifth lens L5 become stronger, and it becomes difficult to simultaneously correct the axial and off-axis aberrations.

In the third invention, it is preferable that the following conditional expression 13 is satisfied in order to satisfactorily correct positive distortion aberration occurring in the wide-angle end state and shorten the lens length in the telephoto end state.

Conditional Expression 13

0.1 f2 / f1a 0.5

If the lower limit of Conditional Expression 13 is below, it is difficult to satisfactorily correct the positive distortion aberration in the wide-angle end state. On the other hand, when the upper limit of Conditional Expression 13 is exceeded, the lens length in the telephoto end state becomes larger.

By the way, in the fourth invention according to another aspect of the present invention, the following conditional expression 14 is satisfied in order to realize miniaturization of the lens diameter and shortening of the lens length in the telephoto end state.

Conditional Expression 14

0.5 (f1 + | f2 |) / (fwft) ^1/2 1.2

Here, f1 is the focal length of the positive lens group G1, fw is the focal length of the whole optical system in the wide-angle end state, and ft is the focal length of the whole optical system in the telephoto end state.

Conditional Expression 14 defines an appropriate range for the sum of the focal length of the positive lens group G1 and the absolute value of the focal length of the negative lens group G2. When the upper limit of Conditional Expression 14 is exceeded, the lens length from the optical end state to the telephoto end state is enlarged. On the contrary, when the lower limit of the conditional expression 14 is lower, since the arrangement of the refractive power with the aperture stop S interposed in the wide-angle end state becomes extremely asymmetric, the positive distortion value cannot be corrected well.

Further, in the fifth aspect of the present invention, the following conditional expression 15 is satisfied in order to simultaneously achieve miniaturization and high variance of the lens system.

Conditional Expression 15

(Bfw / TLt) ・ (ft / fw) 0.4

Here, Bfw is the back focus at the wide end state, and TLt is the lens full length at the telephoto end state.

The back focus is an optical axis distance between an image plane and an image plane in the optical system, and the lens electric field is an optical axis distance between an object surface and an image plane in the optical system.

As described above, when the back focus in the wide-angle end state is shortened, the off-axis luminous flux passing through the negative lens group G2 falls from the optical axis, resulting in an enlargement of the lens diameter. Therefore, it is desirable to increase the ratio of the back focus to the focal length of the whole optical system in the wide-angle end state. In the telephoto end state, reducing the telephoto ratio (ratio of the lens total length to the focal length of the optical system focus) is directly linked to the miniaturization of the entire optical system.

The value of conditional expression 15 can be transformed into (Bfw / fw) / (TLt / ft). Therefore, the large value of Conditional Expression 15 means that the back focus in the wide-angle end state is large and the lens length in the telephoto end state is short. The upper limit of Conditional Expression 15 is a value set in order to balance with optical performance.

When the upper limit of Conditional Expression 15 is exceeded, the back focus in the wide-angle end state becomes too large, and it becomes difficult to independently correct the on-axis and off-axis aberrations. In addition, in order to downsize the optical system, it is preferable to set the lower limit of the conditional expression 15 to 0.15. Below this lower limit, the optical system becomes extremely large.

Further, from the third to the fifth invention, it is preferable to satisfy the following Conditional Expression 16 to satisfactorily correct the positive distortion aberration occurring in the wide-angle end state and to shorten the lens length in the telephoto end state.

Conditional Expression 16

1 | f1a | / (fwft) ^1/2 4

Conditional Expression 16 defines an appropriate range for the focal length of the negative subgroup G1a constituting the positive lens group G1. If the upper limit of Conditional Expression 16 is exceeded, the positive distortion aberration occurring in the wide-angle end state cannot be corrected well. On the other hand, when the lower limit of Conditional Expression 16 is lower, the lens length becomes extremely large in the telephoto end state.

In addition, although polycarbonate is used as a plastic material in each Example below, it is naturally possible to use other fat or oil resin materials.

In addition, by introducing more aspherical surfaces in the lens system, it is possible to satisfactorily correct spherical aberration generated in each lens group, thereby making it possible to make the lens system larger in diameter.

In any case, the image may be shifted by eccentrically all or part of the lens group with respect to the optical axis. In this case, for example, it is apparent that by combining the driving member for eccentrically driving the whole or a part of the lens group due to the shake of the lens system, an anti-vibration effect of correcting the fluctuation of the upper value due to the shake of the lens system or the like is obtained.

EXAMPLE

Next, each Example of this invention is described based on an accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the movement shape of each lens group at the time of the refractive power distribution of the variable speed optical system and the change from the wide angle end state W to the telephoto end state T concerning each Example of the beam invention. As shown in Fig. 1, the variable speed optical system according to each embodiment of the present invention is composed of a first lens group G1 having positive refractive power and a second lens group G2 having negative refractive power in order from the object side. Thus, in the change from the wide end state W to the telephoto end state T, the air gap between the first lens group G1 and the second lens group G2 is reduced.

In each embodiment, the aspherical surface has a height y in the direction perpendicular to the optical axis y, a displacement amount (sag amount) in the optical axis direction at height y, S (y), a reference paraxial curvature radius R, and the number of cones κ, n When the aspherical coefficient of difference is referred to as Cn, it is represented by Equation 1 below.

S (y) = (y ² / R) [1 + (1-κy ² / R ² ) ^1/2 ]

^{_{+ C 4 · y 4 + C}} 6 · y 6 + C 8 · y 8

+ C ₁₀ y ¹⁰ + ...

In each Example, an aspherical surface is marked with * on the right side of the surface number.

First embodiment

Fig. 2 is a diagram showing the lens configuration of the variable speed optical system according to the first embodiment of the present invention.

The shift optical system of FIG. 2 includes a first lens group G1 formed of a positive convex negative lens L1 in order from an object side, a bumeniscus lens L2 facing a convex surface toward an object, and a positive convex positive lens L3. And the second lens group G2 formed of the regular meniscus lens L4 facing the concave surface toward the object and the sub- meniscus lens L5 facing the concave surface toward the object. In addition, in the first embodiment, the regular meniscus lens L4 in the second lens group G2 is a plastic lens, and the surface of the object side thereof is formed in an aspherical shape.

In addition, the aperture stop S is provided between the first lens group G1 and the second lens group G2 and moves integrally with the first lens group G1 in shifting from the wide angle end state to the telephoto end state. .

FIG. 2 shows the positional relationship of each lens group in the wide-angle end state, and moves to the optical axis along the zoom trajectory indicated by the arrow in FIG. 1 when shifting to the telephoto end state.

Table 1 below lists the specifications of the first embodiment of the present invention. In Table 1, f represents a focal length, FNO represents a number, 2ω represents an angle of view, and Bf represents a back focus. Again, the surface number is shown in the order of the lens surface from the object side along the direction of the light ray, and the refractive index and the Abbe number indicate values for the d line (λ = 587.6 nm), respectively. In addition, in the lens specifications of Table 1, the plane whose radius of curvature is ∞ (infinity) represents a plane. In addition, although the radius of curvature of the surface representing the aperture diaphragm S is ∞, the lens surface is not present on the surface representing the aperture diaphragm S. FIG.

TABLE 1

3 to 5 are aberration diagrams of the first embodiment with respect to the d line (λ = 587.6 nm). 3 is a diagram of the aberration in the wide-angle end state, FIG. 4 is a diagram of the aberration in the intermediate focal length state, and FIG. 5 is a diagram of the aberration in the telephoto end state.

In each aberration diagram, FNO represents an F number and A (degrees) represents a change angle.

Moreover, in the aberration diagram which shows astigmatism, the solid line shows the surge top surface, and the broken line shows the meridional top surface. Again, in the aberration diagram showing spherical aberration, the broken line indicates the sine condition. Moreover, in the aberration diagram showing the coma aberration, the meridional coma aberration is displayed at the change angle A (degrees).

As is apparent from each aberration diagram, it can be seen that in this embodiment, the aberration is well corrected in each focal length state and has excellent imaging performance.

Second embodiment

FIG. 6 is a diagram showing a lens configuration of a variable speed optical system according to the second embodiment of the present invention.

The variable displacement optical system of FIG. 6 is formed of a bumeniscus lens L1 facing the concave surface toward the object side, a bumeniscus lens L2 facing the convex surface toward the object, and a positive convex positive lens L3. And a second lens group G2 formed of a lens group G1, a regular meniscus lens L4 facing the concave surface toward the object, and a bomeniscus lens L5 facing the concave surface toward the object. . Also in the second embodiment, as in the first embodiment, the regular meniscus lens L4 is a plastic lens and its surface on the object side is formed in an aspherical shape.

In addition, the aperture stop S is provided between the first lens group G1 and the second lens group G2 and integrally with the first lens group G1 when shifting from the wide angle end state to the telephoto end state. Move.

FIG. 6 shows the positional relationship of each lens group in the wide-angle end state and moves on the optical axis along the zoom trajectory shown by the arrow in FIG.

Table 2 below lists the specifications of the second embodiment of the present invention. In Table 2, f represents a focal length, FNO represents an F number, 2ω represents an angle of view, and Bf represents a back focus. Again, the surface number is followed by the order of the lens surface from the object side along the direction of propagation of the light rays. The refractive index and the Abbe number indicate the values for the d line (λ = 587.6 nm), respectively.

In addition, in the lens specifications of Table 2, the plane whose radius of curvature is ∞ (infinity) represents a plane. In addition, although the radius of curvature of the surface representing the aperture diaphragm S is ∞, the lens surface is not present on the surface representing the aperture diaphragm S. FIG.

TABLE 2

7 to 9 are aberration diagrams of the second embodiment with respect to the d line (λ = 587.6 nm). 7 is a diagram of aberrations in the wide-angle end state, FIG. 8 is a diagram of the aberrations in the intermediate focal length state, and FIG. 9 is a diagram of the aberrations in the telephoto end state.

In each aberration diagram, FNO represents F number and A (degree) shows a change angle.

In addition, in the aberration diagram showing the astigmatism aberration, the solid line indicates the upper surface of the sagittal and the broken line shows the upper surface of the meridional. In the aberration diagram showing the spherical aberration again, the broken line indicates the sine condition. In the aberration diagram showing the coma aberration, the meridional coma aberration is shown at the change angle A (degrees).

As is apparent from each aberration diagram, it can be seen that in this embodiment, the aberration is well corrected in each focal length state and has excellent imaging performance.

Third embodiment

Fig. 10 is a diagram showing a lens configuration of the variable magnification optical system according to the third embodiment of the present invention.

The shift optical system of FIG. 10 is formed of a bumeniscus lens L1 facing the concave surface toward the object in order from the object side, a bumeniscus lens L2 facing the convex surface toward the object, and a positive lens L3 of both convex faces. It consists of a first lens group G1, a regular meniscus lens L4 facing the concave surface toward the object, and a second lens group G2 formed from the bumeniscus lens L5 facing the concave surface toward the object. It is. Further, in the third embodiment, the sub-meniscus lens L2 and the regular meniscus lens L4 are plastic lenses, and both of them have an aspherical surface.

In addition, the aperture stop S is provided between the first lens group G1 and the second lens group G2, and integrally with the first lens group G1 in shifting from the wide angle end state to the telephoto end state. Move.

FIG. 10 shows the positional relationship of each lens group in the wide-angle end state, and moves to the optical axis along the zoom trajectory shown by the arrow in FIG. 1 when changing to the telephoto end state.

Table 3 below lists the specifications of the third embodiment of the present invention. In Table 3, f represents a focal length, FNO represents an F number, 2ω represents an angle of view, and Bf represents a back focus. Again, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number indicate values for the d line (λ = 587.6 nm), respectively. In addition, in the lens specifications of Table 3, the plane whose radius of curvature is ∞ (infinity) represents a plane. In addition, although the radius of curvature of the surface representing the aperture diaphragm S is ∞, the lens surface is not present on the surface representing the aperture diaphragm S. FIG.

TABLE 3

11 to 13 are aberration diagrams of the third embodiment with respect to the d line (λ = 587.6 nm). FIG. 11 is a diagram of the aberration in the wide-angle end state, FIG. 12 is a diagram of the aberration in the intermediate focal length state, and FIG. 13 is a diagram of the aberration in the telephoto end state.

In each aberration diagram, FNO represents F number and A (degree) shows a change angle.

In addition, in the aberration diagram showing the astigmatism aberration, the solid line shows the surge top surface, and the broken line shows the meridional top surface. In the aberration diagram showing the spherical aberration again, the broken line indicates the sine condition. In the aberration diagram showing the coma aberration, the meridional coma aberration is shown at the change angle A (degrees).

As is apparent from each aberration diagram, it can be seen that in this embodiment, the aberration is well corrected in each focal length state and has excellent imaging performance.

Fourth embodiment

Fig. 14 is a diagram showing a lens configuration of the variable magnification optical system according to the fourth embodiment of the present invention.

The variable optical system of FIG. 14 is a first lens group formed of a negative lens L1 having a double-sided concave toward the object in order from the object side, a bumeniscus lens L2 having a convex surface facing the object, and a positive lens L3 having a double-sided convex toward the object. And a second lens group G2 formed of a regular meniscus lens L4 facing the concave surface toward the object and a sub- meniscus lens L5 facing the concave surface toward the object. Also in the fourth embodiment, as in the third embodiment, the bumenis lens L2 and the static meniscus lens L4 are plastic lenses, and both of them have an aspherical surface.

In addition, the aperture stop S is provided between the first lens group G1 and the second lens group G2 and integrally moves with the first lens group G1 in the shift from the wide angle end state to the telephoto end state. do.

FIG. 14 shows the positional relationship of each lens group in the wide-angle end state, and moves to the optical axis along the zoom trajectory shown by the arrow in FIG.

Table 4 below lists the specifications of the fourth embodiment of the present invention. In Table 4, f represents a focal length, FNO represents an F number, 2ω represents an angle of view, and Bf represents a back focus. Again, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number indicate values for the d line (λ = 587.6 nm), respectively. In addition, in the lens specifications of Table 4, the plane whose radius of curvature is ∞ (infinity) represents a plane. In addition, although the radius of curvature of the surface representing the aperture diaphragm S is ∞, the lens surface is not present on the surface representing the aperture diaphragm S. FIG.

TABLE 4

15 to 17 are aberration diagrams of the fourth embodiment with respect to the d line (λ = 587.6 nm). FIG. 15 is a diagram of the aberration in the wide-angle end state, FIG. 16 is a diagram of the aberration in the intermediate focal length state, and FIG. 17 is a diagram of the aberration in the telephoto end state.

In each aberration diagram, FNO represents F number and A (degree) shows a change angle.

In addition, in the aberration diagram showing the astigmatism aberration, the solid line indicates the surge top surface and the broken line indicates the meridional top surface. In the aberration diagram showing the spherical aberration again, the broken line indicates the sine condition. In addition, in the aberration diagram showing the coma aberration, the meridional coma aberration is shown at the half angle of view A (degrees).

As is apparent from each aberration diagram, it can be seen that in this embodiment, the aberration is well corrected in each focal length state and has excellent imaging performance.

Fifth Embodiment

Fig. 18 is a diagram showing a lens configuration of the variable magnification optical system according to the fifth embodiment of the present invention.

The variable displacement optical system of FIG. 18 is formed of a bumeniscus lens L1 facing the concave surface toward the object in order from the object side, a bumeniscus lens L2 facing the convex surface toward the object, and a positive lens L3 of both convex faces. It consists of a first lens group G1, a regular meniscus lens L4 facing the concave surface toward the object, and a second lens group G2 formed from the bumeniscus lens L5 facing the concave surface toward the object. It is. Also in the fifth embodiment, as in the third embodiment, the bumenis lens L2 and the static meniscus lens L4 are plastic lenses, and both of them have an aspherical surface.

In addition, the aperture stop S is provided between the first lens group G1 and the second lens group G2 and integrally with the first lens group G1 in shifting from the wide angle end state to the telephoto end state. Move.

FIG. 18 shows the positional relationship of each lens group in the wide-angle end state, and moves to the optical axis along the zoom trajectory shown by the arrow in FIG.

Table 5 below shows the specification values of the fifth embodiment of the present invention. In Table 5, f represents a focal length, FNO represents an F number, 2ω represents an angle of view, and Bf represents a back focus. Again, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light ray, and the refractive index and the Abbe number indicate values for the d line (λ = 587.6 nm), respectively. In addition, in the lens specifications of Table 5, the plane whose radius of curvature is ∞ (infinity) represents a plane. In addition, although the radius of curvature of the surface representing the aperture diaphragm S is ∞, the lens surface is not present on the surface representing the aperture diaphragm S. FIG.

TABLE 5

19 to 21 are aberration diagrams of the fifth embodiment with respect to the d line (λ = 587.6 nm). FIG. 19 is a diagram of aberrations in a wide-angle end state, FIG. 20 is a diagram of aberrations in a medium focal length state, and FIG. 21 is a diagram of aberrations in a telephoto end state.

In each aberration diagram, FNO represents F number and A (degree) shows a change angle.

Also, in the aberration diagram showing the astigmatism aberration, the solid line shows the surge top surface and the broken line shows the meridional top surface. In the aberration diagram showing the spherical aberration again, the broken line indicates the sine condition. In the aberration diagram showing the coma aberration, the meridional coma aberration is shown at the change angle A (degrees).

As is apparent from each aberration diagram, it can be seen that in this embodiment, the aberration is well corrected in each focal length state and has excellent imaging performance.

Sixth embodiment

Fig. 23 shows a lens configuration of the variable speed optical system according to the sixth embodiment of the present invention. The variable optical system of FIG. 23 includes a positive lens group composed of a bumeniscus lens L1 facing a concave surface toward the object side, a bumeniscus lens L2 facing a convex surface toward the object side, and a double-sided convex lens L3. G1), and a negative lens group G2 composed of a regular meniscus lens L4 facing the concave surface toward the object and a sub- meniscus lens L5 facing the convex surface toward the object.

Further, the aperture stop S is disposed between the positive lens group G1 and the negative lens group G2 to move integrally with the positive lens group G1 at the time of shifting from the wide angle end state to the telephoto end state. FIG. 23 shows the positional relationship of each lens group in the wide-angle end state, and shifts the optical axis along the zoom trajectory indicated by the arrow in FIG. 22 when changing the telephoto end state.

Table 6 below lists the specifications of the sixth embodiment of the present invention. In Table 6, f represents a focal length, FNO represents an F number, 2ω represents an angle of view, and Bf represents a back focus. In addition, the surface number indicates the lens surface order from the object side along the traveling direction of the light beam, and the refractive index and the Abbe number indicate values for the d line (λ = 587.6 nm), respectively. In the lens specifications shown in Table 6, the plane with a radius of curvature ∞ (infinity) represents a plane. In addition, although the radius of curvature of the surface representing the aperture diaphragm S is ∞, the lens surface is not present on the surface representing the aperture diaphragm S. FIG.

TABLE 6

24 to 26 are aberration diagrams of the sixth embodiment with respect to the d line (λ = 587.5 nm). FIG. 24 is a diagram of aberrations in a wide-angle end state (shortest focal length state), FIG. 25 is a diagram of aberrations in an intermediate focal length state, and FIG. 26 is a diagram of aberrations in a telephoto end state (longest focal length state).

In each aberration diagram, FNO represents an F number, y represents an image height, and A represents an angle of view for each image height. In addition, in the aberration diagram showing astigmatism, the solid line represents the surge surface and the dashed line represents the meridional surface. In the aberration diagram showing spherical aberration, a broken line indicates a sine condition. As is apparent from each aberration, it can be seen that in this embodiment, the aberration is well corrected at each focal length state, and there is excellent imaging performance.

Seventh embodiment

Fig. 27 shows a lens configuration of the variable displacement optical system according to the seventh embodiment of the present invention. The variable optical system of FIG. 27 is a positive lens group G1 composed of a bumeniscus lens L1 facing a concave surface toward the object side, a bumeniscus lens L2 facing a convex surface toward the object side, and a double-sided convex lens L3. ) And a negative lens group G2 composed of a regular meniscus lens L4 facing a concave surface toward the object and a sub- meniscus lens L5 facing a convex surface toward the object.

Further, the aperture stop S is disposed between the positive lens group G1 and the negative lens group G2 to move integrally with the positive lens group G1 in the shift from the wide end state to the telephoto end state. FIG. 27 shows the positional relationship of each lens group in the wide-angle end state, and shifts the optical axis along the zoom trajectory indicated by the arrow in FIG. 22 when changing the telephoto end state.

Next, Table 7 lists the specifications of the seventh embodiment of the present invention. In Table 7, f denotes a focal length, FNO denotes an F number, 2ω denotes an angle of view, and Bf denotes a back focus. In addition, the surface number indicates the lens surface order on the object side along the traveling direction of the light beam, and the refractive index and the Abbe number indicate the value for the d line (λ = 587.6 nm), respectively. In the lens specifications shown in Table 7, the plane with a radius of curvature ∞ (infinity) represents a plane. Moreover, although the radius of curvature of the surface which shows the aperture diaphragm S is set to (∞), a lens surface does not exist in the surface which shows the aperture diaphragm S. FIG.

TABLE 7

28 to 30 are aberration diagrams of the seventh embodiment with respect to the d line (λ = 587.5 nm). FIG. 28 is a diagram of the aberration in the wide-angle end state, FIG. 29 is a diagram of the aberration in the intermediate focal length state, and FIG. 30 is a diagram of the aberration in the telephoto end state.

In each aberration diagram, FNO represents an F number, y represents an image height, and A represents an angle of view for each image height. In addition, in the aberration diagram showing astigmatism, the solid line represents the surge surface and the dashed line represents the meridional surface. In the aberration diagram showing spherical aberration, a broken line indicates a sine condition. As is apparent from the aberration diagrams, it can be seen that in the present embodiment, the aberrations are well corrected at each focal length state, thereby providing excellent imaging performance.

Eighth embodiment

FIG. 31 shows the lens configuration of the variable speed optical system according to the eighth embodiment of the present invention. 31 shows a positive lens group G1 composed of a bumenis lens L1 facing concave toward the object in order from the object side, a bumeniscus lens L2 facing toward the convex side toward the object, and a double-sided convex lens L3. ) And a negative lens group G2 made of a regular meniscus lens L4 facing a concave surface toward the object and a sub- meniscus lens L5 facing a convex surface toward the object.

Further, the aperture stop S is disposed between the positive lens group G1 and the negative lens group G2 to move integrally with the positive lens group G1 in the shift from the wide end state to the telephoto end state. FIG. 31 shows the positional relationship of each lens group in the wide-angle end state, and shifts the optical axis along the zoom trajectory indicated by the arrow in FIG. 22 when changing the telephoto end state.

Table 8 lists the specifications of the eighth embodiment of the present invention. In Table 8, f represents a focal length, FNO represents an F number, 2ω represents an angle of view, and Bf represents a back focus. In addition, the surface number indicates the lens surface order from the object side along the traveling direction of the light beam, and the refractive index and the Abbe number indicate the value for the d line (λ = 587.6 nm), respectively. In the lens specifications of Table 8, the plane of the radius of curvature ∞ (infinity) represents a plane. In addition, although the radius of curvature of the surface showing the aperture stop S is ∞, the lens surface does not exist on the surface representing the aperture stop S.

TABLE 8

32 to 34 are aberration diagrams of an eighth embodiment with respect to the d line (λ = 587.5 nm). 32 is a diagram of the aberration in the wide-angle end state, FIG. 33 is a diagram of the aberration in the intermediate focal length state, and FIG. 34 is a diagram of the aberration in the telephoto end state.

In each aberration diagram, FNO represents an F number, y represents an image height, and A represents an angle of view for each image height. In addition, in the aberration diagram showing astigmatism, the solid line represents the surge surface and the dashed line represents the meridional surface. In the aberration diagram showing spherical aberration, a broken line indicates a sine condition. As is apparent from each aberration, it can be seen that in this embodiment, the aberration is well corrected at each focal length state and there is excellent image forming performance.

9th embodiment

Fig. 35 shows the lens configuration of the variable speed optical system according to the ninth embodiment of the present invention. The variable-optical system of FIG. 35 is a positive lens group G1 composed of a bumeniscus lens L1 facing a concave surface toward the object side, a bumeniscus lens L2 facing a convex surface toward the object side, and a double-sided convex lens L3. ) And a negative lens group G2 made of a regular meniscus lens L4 facing a concave surface toward the object and a sub- meniscus lens L5 facing a convex surface toward the object.

Further, the aperture stop S is disposed between the positive lens group G1 and the negative lens group G2 to move integrally with the positive lens group G1 in the shift from the wide end state to the telephoto end state. FIG. 39 shows the positional relationship of each lens group in the wide-angle end state, and shifts the optical axis along the zoom trajectory indicated by the arrow in FIG. 22 when changing the telephoto end state.

Next, Table 9 lists the specifications of the ninth embodiment of the present invention. In Table 9, f represents a focal length, FNO represents an F number, 2ω represents an angle of view, and Bf represents a back focus. In addition, the surface number indicates the lens surface order from the object side along the traveling direction of the light beam, and the refractive index and the Abbe number indicate the value for the d line (λ = 587.6 nm), respectively. In the lens specifications of Table 9, the plane of the radius of curvature of ∞ (infinity) represents a plane. In addition, although the radius of curvature of the surface showing the aperture stop S is ∞, the lens surface does not exist on the surface representing the aperture stop S.

TABLE 9

36 to 38 are aberration diagrams of the ninth embodiment with respect to the d line (λ = 587.5 nm). 36 is a diagram of aberrations in a wide-angle end state (shortest focal length state), FIG. 37 is a diagram of aberrations in an intermediate focal length state, and FIG. 38 is a diagram of aberrations in a telephoto end state (longest focal length state).

In each aberration diagram, FNO represents an F number, y represents an image height, and A represents an angle of view for each image height. In addition, in the aberration diagram showing astigmatism, the solid line represents the surge surface and the dashed line represents the meridional surface. In the aberration diagram showing spherical aberration, a broken line indicates a sine condition. As is apparent from each aberration, it can be seen that in this embodiment, the aberration is well corrected at each focal length state and there is excellent image forming performance.

10th embodiment

Fig. 39 shows a lens configuration of the variable displacement optical system according to the tenth embodiment of the present invention. The variable magnification optical system of FIG. 39 is a positive lens group G1 composed of a bumeniscus lens L1 facing a concave surface toward the object side, a bumeniscus lens L2 facing a convex surface toward the object side, and a double-sided convex lens L3. ) And a negative lens group G2 made of a regular meniscus lens L4 facing a concave surface toward the object and a sub- meniscus lens L5 facing a convex surface toward the object.

Further, the aperture stop S is disposed between the positive lens group G1 and the negative lens group G2 to move integrally with the positive lens group G1 in the shift from the wide end state to the telephoto end state. FIG. 35 shows the positional relationship of the respective lens groups in the wide-angle end state, and shifts the optical axis along the zoom trajectory indicated by the arrow in FIG. 22 when changing the telephoto end state.

Next, Table 10 lists the specifications of the tenth embodiment of the present invention. In Table 10, f represents a focal length, FNO represents an F number, 2ω represents an angle of view, and Bf represents a back focus. In addition, the surface number indicates the lens surface order from the object side along the traveling direction of the light beam, and the refractive index and the Abbe number indicate the value for the d line (λ = 587.6 nm), respectively. In the lens specifications of Table 10, the plane of the radius of curvature of ∞ (infinity) represents a plane. In addition, although the radius of curvature of the surface showing the aperture stop S is ∞, the lens surface does not exist on the surface representing the aperture stop S.

TABLE 10

40 to 42 are aberration diagrams of the tenth embodiment with respect to the d line (λ = 587.5 nm). FIG. 40 is a diagram of aberrations in a wide-angle end state (shortest focal length state), FIG. 41 is a diagram of aberrations in an intermediate focal length state, and FIG. 42 is a diagram of aberrations in a telephoto end state (longest focal length state).

In each aberration diagram, FNO represents an F number, y represents an image height, and A represents an angle of view for each image height. In addition, in the aberration diagram showing astigmatism, the solid line represents the surge surface and the dashed line represents the meridional surface. In the aberration diagram showing spherical aberration, a broken line indicates a sine condition. As is apparent from each aberration, it can be seen that in this embodiment, the aberration is well corrected at each focal length state and there is excellent image forming performance.

And in each Example mentioned above, what used polycarbonate as a plastic material was illustrated. However, it is also possible to use plastic materials such as polyethylene and acrylic, and of course it is also possible to use glass materials instead of plastic materials.

As described in detail above, according to the present invention, it is possible to manufacture at low cost with a variable ratio (zoom ratio) of more than twice, and to realize a small-sized variable displacement optical system with high performance.

Claims (26)

A first lens group G1 having positive refractive power in turn toward the object, and a second lens group G2 having negative refractive power, By reducing the air gap between the first lens group G1 and the second lens group G2, a shift is made from the wide angle end state to the telephoto end state, The first lens group G1 includes a first lens component L1 of negative refractive power, a second lens component L2 of negative refractive power, and a third lens component of positive refractive power, in which the surface of the object faces the concave surface in order from the object side. Consisting of L3, When the radius of curvature of the object-side surface of the first lens component L1 is r11 and the radius of curvature of the image of the first lens component L1 is r12, -1.43 (r11 + r12) / (r11-r12) -0.7 Variable optical system, characterized in that to satisfy the conditions of. The method of claim 1, One or more surfaces of the second lens component (L2) are formed in an aspherical shape. The method of claim 2, When the focal length of the first lens group G1 is f1, the focal length of the first lens component L1 is f11, and the focal length of the third lens component L3 is f13, 2.0 | f11 | / f1 8.0, 0.6 f13 / f1 0.95 Variable optical system characterized by satisfying the conditions of. The method of claim 3, wherein The first optical lens group G1 is formed of three single lenses. It consists of a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power in turn on the object side, By reducing the air gap between the first lens group G1 and the second lens group G2, a shift is made from the wide angle end state to the telephoto end state, The first lens group G1 has a first lens component L1 of negative refractive power in which the object side faces the concave surface toward the object in order from the object side, a second lens component L2 of negative refractive power, and a third lens of positive refractive power. Composed of component (L3), The second lens component L2 is equipped with one or more plastic lenses LP1, The second optical lens group G2 includes at least one plastic lens LP2. The method of claim 5, When the radius of curvature of the surface on the object side of the first lens component L1 is r11 and the radius of curvature of the upper surface of the first lens component L1 is r12, -1.43 (r11 + r12) / (r11-r12) -0.7 Variable optical system, characterized in that to satisfy the conditions of. The method of claim 6, A variable optical system wherein the second lens component (L2) has at least one surface formed in an aspheric shape. The method of claim 7, wherein When the focal length of the first lens group G1 is f1 and the paraxial focal length of the second lens component L2 is f12, F12 / f1 3.0 Variable optical system characterized by satisfying the conditions of. The method of claim 5, When the focal length of the first lens group G1 is f1, the focal length of the first lens component L1 is f11, and the focal length of the third lens component L3 is f13, 2.0 | f11 | / f1 8.0, 0.6 f13 / f1 0.95 Variable optical system characterized by satisfying the conditions of. The method of claim 9, When the focal length of the first lens group G1 is f1 and the paraxial focal length of the second lens component L2 is f12, F12 / f1 3.0 Variable optical system, characterized in that the high water condition. The method of claim 10, The first optical lens group G1 is formed of three single lenses. The method of claim 5, When the focal length of the second lens group G2 is f and the focal length of the plastic lens LP2 in the second lens group G2 is f21, | F21 | / | f2 | 2.8 Variable optical system characterized by satisfying the conditions of. The method of claim 12, The plastic lens LP2 in the second lens group G2 has refractive power. The method of claim 13, At least one surface of the plastic lens LP2 in the second lens group G2 is formed in an aspheric shape. The method of claim 5, The first optical lens group G1 is formed of three single lenses. A positive lens group G1 having positive refractive power, and a negative lens group G2 having negative refractive power disposed above the positive lens group G1, An aperture stop S is disposed in the optical path between the positive lens group G1 and the negative lens group G2, The lens group G1 is composed of a first lens L1 of negative refractive power, a second lens L2 of negative refractive power, and a third lens L3 of positive refractive power in order from the object side, The focal length of the whole optical system is changed by changing the air gap between the positive lens group G1 and the negative lens group G2, When the radius of curvature of the upper surface of the second lens L2 is r22 and the distance along the optical axis between the upper surface of the second lens L2 and the aperture stop S is D, 1.5 r22 / D 0.4 Variable optical system, characterized in that to satisfy the conditions of. The method of claim 16, When the axial air gap between the second lens L2 and the third lens L3 is set to D23, and the composite focusing process of the first lens L1 and the second lens L2 is set to f1a, 0.02 D23 / | f1a | 0.4 Variable optical system characterized by satisfying the conditions of. The method of claim 17, The lens group G2 is composed of a fourth lens L4 of positive refractive power and a fifth lens L5 of negative refractive power in order from the object side. When the axial air gap between the fourth lens L4 and the fifth lens L5 is D45 and the focal length of the negative lens group G2 is f2, 0.08 D45 / ｜ f2 ｜ 0.40 Variable optical system characterized by satisfying the conditions of. The method of claim 18, When the combined focal length of the first lens L1 and the second lens L2 is f1a and the focal length of the negative lens group G2 is f2, 0.1 f2 / f1a 0.5 Variable optical system characterized by satisfying the conditions of. The method of claim 19, The positive lens group G1 includes one or more plastic lenses PL1, and the lens group G2 includes one or more plastic lenses PL2, and the refractive power of the plastic lens PL1 and the plastics. A variable optical system, characterized in that the refractive power of the lens PL2 is different from each other. It consists of a positive lens group (G1) having a positive refractive power and a negative lens group (G2) having a negative refractive power in turn on the object side, The focal length of the whole optical system is changed by changing the air gap between the positive lens group G1 and the negative lens group G2, The focal length of the positive lens group G1 is f1, the focal length of the negative lens group G2 is f2, the focal length of the whole optical system in the wide-angle end state is fw, and in the telephoto end state When the focal length of the whole optical system is ft, 0.5 (f1 + | f2 |) / (fwft) ^1/2 0.4 Variable optical system characterized by satisfying the conditions of. The method of claim 21, It consists of the negative partial group G1a which has negative refractive power of the said lens group G1, and the positive subgroup G1b which has positive refractive power arrange | positioned above the said negative subgroup G1a, When the focal length of the subgroup G1a is f1a, the focal length of the whole optical system in the wide-angle end state is fw, and the focal length of the whole optical system in the telephoto end state is ft, 1 | f1a | / (fwft) ^1/2 0.4 Variable optical system characterized by satisfying the conditions of. The method of claim 22, The positive lens group G1 includes one or more plastic lenses PL1, and the lens group G2 includes one or more plastic lenses PL2, and the refractive power of the plastic lens PL1 and the plastics. A variable optical system, characterized in that the refractive power of the lens PL2 is different from each other. It consists of a positive lens group (G1) having a positive refractive power and a negative lens group (G2) having a negative refractive power in turn on the object side, The focal length of the whole optical system is changed by changing the air gap between the positive lens group G1 and the negative lens group G2, The back focus in the wide-angle end state is Bfw, the lens length in the telephoto end state is TLt, the focal length of the whole optical system in the wide-angle end state is fw, and the focal length of the whole optical system in the telephoto end state is fw. in ft, (Bfw / TLt) · (ft / fw) 0.4 Variable optical system characterized by satisfying the conditions of. The method of claim 24, The lens group G1 includes a negative subgroup G1a having negative refractive power and a positive subgroup G1b having positive refractive power disposed above the negative subgroup G1a. When the focal length of the subgroup G1a is f1a, the focal length of the whole optical system in the wide-angle end state is fw, and the focal length of the whole optical system in the telephoto end state is ft, 1 | f1a | / (fwft) ^1/2 0.4 Variable optical system characterized by satisfying the conditions of. The method of claim 25, The positive lens group G1 includes one or more plastic lenses PL1, and the lens group G2 includes one or more plastic lenses PL2, and the refractive power of the plastic lens PL1 and the plastic A variable optical system, characterized in that the refractive power of the lens PL2 is different from each other.