JP4723012B2 - Zoom lens system - Google Patents

Description

  The present invention relates to a compact zoom lens system having a zoom ratio suitable for a video camera, a digital camera, etc., and approximately 10 times.

  In a positive, negative, positive four-group zoom lens system in order from the object side, a rear focus using the final fourth lens group as a focus lens is often employed. However, in the rear focus type, if the shortest shooting distance is shortened, the amount of movement of the focus lens is large and takes time. There is also a problem that a large curvature of field occurs.

  An inner focus is also known in which the second lens group is a focus lens group. However, the negative second lens group, which is mainly responsible for the zooming action, changes its magnification greatly during zooming movement. Double is often included, and focusing becomes impossible at the same magnification. In order to avoid this, it is necessary to design with only a reduction magnification that does not pass through the same magnification or a variable magnification region with only an enlargement magnification, which is a design constraint condition.

Patent No. 2901144 Japanese Patent Laid-Open No. 11-38317 JP 2000-171712 A Patent No. 3097395 JP 2000-75204 A

In order to reduce the size of the lens, the lens types of the positive third lens group and the fourth lens group that form an image of divergent light from the negative second lens group are important.
SUMMARY OF THE INVENTION An object of the present invention is to obtain a zoom lens system that is a positive, negative, positive positive four-group zoom lens system in order from the object side and that can be miniaturized while having a zoom ratio of about 10 times. An object of the present invention is to propose a new configuration by paying particular attention to the configuration of the fourth lens group.

The present invention includes, in order from the object side, a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, from the short focal length end to the long focal length end. During zooming, in the zoom lens system in which the second lens unit moves from the object side to the image side and moves the fourth lens unit so as to correct the image plane movement accompanying zooming, the fourth lens unit is on the object side. In order, a 4a lens group consisting of a positive single lens and a 4b lens group consisting of a negative lens and a positive lens cemented lens, and the 4a lens group is a paraxial spherical surface at least on the object side surface. In comparison, the aspherical surface is such that the power decreases as the height from the optical axis increases, and the following conditional expressions (1) and (2) are satisfied.
(1) -0.55 <f _4a / f _4b <-0.07
(2) 0.15 <d _4ab / f ₄ <0.50
However,
f _4a ; focal length of the 4a lens group,
f _4b ; focal length of the 4b lens group
d _4ab ; the distance between the 4a lens group and the 4b lens group,
f ₄ ; focal length of the fourth lens group,
It is.

Specifically, for example, the first lens group includes, in order from the object side, a cemented lens of a negative lens and a positive lens, and a positive meniscus lens convex to the object side, and the second lens group in order from the object side. , A negative lens having a strong concave surface facing the image side, a cemented lens of a positive lens having a concave surface on the object side and a negative lens, and a positive lens. The third lens group includes a positive lens and a negative lens. It can comprise a bonded lens. It is preferable to satisfy the following conditional expression (3).
(3) 0.07 <f ₃ / f ₄ <2.50
However,
f ₃ ; focal length of the third lens group,
f ₄ ; focal length of the fourth lens group,
It is.

The zoom lens system of the present invention preferably satisfies the following conditional expression (4).
(4) -0.85 <fw / f 2 <-0.7
fw: focal length of the entire system at the short focal length end,
f ₂ : focal length of the second lens group
It is.

Moreover, it is preferable that the following conditional expressions (5) and (6) are satisfied.
(5) ν ₁₂ > 70
(6) 1.9 <ν ₁₁ / f ₁₁ + ((ν ₁₂ + ν ₁₃ ) / 2) / f _12-13 <2.9
However,
ν ₁₂ ; Abbe number of the second lens from the object side of the first lens group,
ν ₁₁ : Abbe number of the lens closest to the object side in the first lens group,
f ₁₁ [mm] ; focal length of the lens closest to the object side in the first lens group,
ν ₁₃ : Abbe number of the third lens from the object side of the first lens group,
f _12-13 [mm] ; the combined focal length of the second and third lenses from the object side of the first lens group,
It is.

In the case where the third lens group is composed of a cemented lens of a positive lens and a negative lens, the power of the non-joined surface of the positive lens becomes weaker as the height from the optical axis becomes higher than the paraxial spherical surface. It is preferable to satisfy the following conditional expressions (7) and (8).
(7) ν _3p > 80
(8) 3.8 <ν _3p / f _3p + ν _3n / f _3n <6.0
However,
ν _3p ; Abbe number of positive lens in the third lens group,
f _3p [mm] ; focal length of the positive lens in the third lens group,
ν _3n ; Abbe number of the negative lens in the third lens group,
f _3n [mm] ; focal length of the negative lens in the third lens group,
It is.

  According to another aspect, the present invention includes, in order from the object side, a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, from the short focal length end. In the zoom lens system in which the second lens unit moves from the object side to the image side at the time of zooming toward the long focal length end, and the fourth lens unit is moved so as to correct the image plane movement accompanying zooming, The lens group passes through the point where the magnification becomes equal during zooming, and the fourth lens group is the focus lens group in all zooming areas, and the second lens group is further focused in at least some zooming areas. A lens group;

In this aspect, a mode in which the ratio of the focusing movement amount of the fourth lens group to the focusing movement amount of the second lens group is constant in all zooming ranges and a mode in which the ratio is changed are possible. In the mode of making it constant, it is preferable to satisfy the following conditional expression (9).
(9) 0 <dX4 / dX2 <6
However,
dX4: Focusing movement amount of the fourth lens group,
dX2: Focusing movement of the second lens group,
It is.
If the value of dX4 / dX2 is an integer value, control is easy.

On the other hand, an aspect of changing, that is, an aspect of changing the ratio of the focusing movement amount of the fourth lens group to the focusing movement amount of the second lens group in accordance with the focal length change due to zooming from the short focal length end to the long focal length end. Then, it is preferable to change while satisfying the following conditional expression (10).
(10) 0 ≦ dX2 / dX4 ≦ 1
However,
dX4: Focusing movement amount of the fourth lens group,
dX2: Focusing movement of the second lens group,
It is.
The value of dX2 / dX4 can be changed stepwise in order from 0 to 1 from the short focal length end to the long focal length end and then to less than 1 (for example, 1/2, 1/3). it can.

  According to the present invention, it is possible to obtain a four-unit zoom lens system that is positive, negative, positive, and positive in order from the object side, and has a small zoom lens system with a zoom ratio of about 10 times.

It is a lens block diagram at the time of the infinity object point focus at the short focal distance end of 1st Example of the zoom lens system by this invention. FIG. 3 is a diagram illustrating various aberrations in the lens configuration in FIG. 1. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the 1st Example. FIG. 4 is a diagram illustrating various aberrations in the lens configuration in FIG. 3. It is a lens block diagram at the time of infinity object point focus at the long focal length end of the first embodiment. FIG. 6 is a diagram illustrating various aberrations in the lens configuration in FIG. 5. It is an aberration diagram at the time of finite distance object point focusing at the short focal length end of the first embodiment. It is an aberration diagram at the time of finite distance object point focusing at the intermediate focal length of the first embodiment. It is an aberration diagram at the time of finite distance object point focusing at the long focal length end of the first embodiment. It is a lens block diagram at the time of the infinity object point focus by the short focal distance end of 2nd Example of the zoom lens system by this invention. FIG. 11 is a diagram illustrating various aberrations in the lens configuration in FIG. 10. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the 2nd Example. FIG. 13 is a diagram illustrating various aberrations in the lens configuration in FIG. 12. It is a lens block diagram at the time of infinity object point focus at the long focal length end of the second embodiment. FIG. 15 is a diagram illustrating various aberrations in the lens configuration in FIG. 14. It is an aberration diagram at the time of finite distance object point focusing at the short focal length end of the second embodiment. It is an aberration diagram at the time of finite distance object point focusing at the intermediate focal length of the second embodiment. It is an aberration diagram at the time of finite distance object point focusing at the long focal length end of the second embodiment. It is a lens block diagram at the time of infinity object point focus at the short focal length end of the third embodiment of the zoom lens system according to the present invention. FIG. 20 is a diagram illustrating various aberrations in the lens configuration in FIG. 19. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the 3rd Example. FIG. 22 is a diagram illustrating various aberrations in the lens configuration in FIG. 21. It is a lens block diagram at the time of infinity object point focus at the long focal length end of the third embodiment. FIG. 24 is a diagram illustrating various aberrations in the lens configuration in FIG. 23. It is various aberrational figures at the time of the finite distance object point focus at the short focal length end of the third embodiment. It is an aberration diagram at the time of finite distance object point focusing at the intermediate focal length of the third embodiment. It is an aberration diagram at the time of finite distance object point focusing at the long focal length end of the third embodiment. It is a lens block diagram at the time of the infinity object point focus in the short focal distance end of 4th Example of the zoom lens system by this invention. FIG. 29 is a diagram illustrating various aberrations in the lens configuration in FIG. 28. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the 4th Example. FIG. 31 is a diagram illustrating various aberrations in the lens configuration in FIG. 30. It is a lens block diagram at the time of infinity object point focus at the long focal distance end of the fourth embodiment. FIG. 33 is a diagram of various aberrations in the lens configuration in FIG. 32. It is an aberration diagram at the time of finite distance object point focusing at the short focal length end of the fourth embodiment. It is an aberration diagram at the time of finite distance object point focusing at the intermediate focal length of the fourth embodiment. It is an aberration diagram at the time of finite distance object point focusing at the long focal length end of the fourth embodiment. It is a lens block diagram at the time of the infinity object point focus in the short focal distance end of 5th Example of the zoom lens system by this invention. FIG. 38 is a diagram of various aberrations in the lens configuration in FIG. 37. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the 5th Example. FIG. 40 is a diagram of various aberrations in the lens configuration in FIG. 39. It is a lens block diagram at the time of infinity object point focus at the long focal distance end of the fifth embodiment. FIG. 42 is a diagram of various aberrations in the lens configuration in FIG. 41. It is an aberration diagram at the time of finite distance object point focusing at the short focal length end of the fifth embodiment. It is an aberration diagram at the time of finite distance object point focusing at the intermediate focal length of the fifth embodiment. It is an aberration diagram at the time of finite distance object point focusing at the long focal length end of the fifth embodiment. It is a lens block diagram at the time of infinity object point focus in the short focal distance end of 6th Example of the zoom lens system by this invention. FIG. 47 is a diagram illustrating all aberrations with the lens configuration in FIG. 46. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the 6th Example. FIG. 49 is a diagram illustrating all aberrations with the lens configuration in FIG. 48. It is a lens block diagram at the time of infinity object point focus at the long focal distance end of the sixth embodiment. FIG. 52 is a diagram illustrating various aberrations in the lens configuration in FIG. 50. It is an aberration diagram at the time of finite distance object point focusing at the short focal length end of the sixth embodiment. It is an aberration diagram at the time of finite distance object point focusing at the intermediate focal length of the sixth embodiment. It is an aberration diagram at the time of finite distance object point focusing at the long focal length end of the sixth embodiment. It is a lens block diagram at the time of the infinity object point focus by the short focal distance end of 7th Example of the zoom lens system by this invention. FIG. 56 is a diagram illustrating all aberrations with the lens configuration in FIG. 55. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the said 7th Example. FIG. 58 is a diagram of various aberrations in the lens configuration in FIG. 57. It is a lens block diagram at the time of infinity object point focus in the long focal distance end of the said 7th Example. FIG. 60 is a diagram of various aberrations with the lens configuration in FIG. 59. It is various aberrational figures at the time of finite distance object point focusing at the short focal length end of the seventh embodiment. It is various aberrational figures at the time of the finite distance object point focus with the intermediate focal length of the same 7th example. It is an aberration diagram at the time of finite distance object point focusing at the long focal length end of the seventh embodiment. It is a lens block diagram at the time of the infinity object point focus in the short focal distance end of 8th Example of the zoom lens system by this invention. FIG. 65 is a diagram illustrating all aberrations with the lens configuration in FIG. 64. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the said 8th Example. FIG. 67 is a diagram showing aberrations with the lens configuration in FIG. 66. It is a lens block diagram at the time of infinity object point focus at the long focal distance end of the eighth embodiment. FIG. 69 is a diagram of various aberrations with the lens configuration of FIG. 68. It is an aberration diagram at the time of finite distance object point focusing at the short focal length end of the eighth embodiment. It is an aberration diagram at the time of finite distance object point focus at the intermediate focal length of the eighth embodiment. It is an aberration diagram at the time of finite distance object point focusing at the long focal length end of the eighth embodiment. It is a lens block diagram at the time of the infinity object point focus by the short focal distance end of 9th Example of the zoom lens system by this invention. FIG. 74 is a diagram of various aberrations with the lens configuration in FIG. 73. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the 9th Example. FIG. 76 is a diagram showing various aberrations with the lens configuration in FIG. 75. It is a lens block diagram at the time of infinity object point focus in the long focal distance end of the 9th Example. FIG. 78 is a diagram showing aberrations with the lens configuration in FIG. 77. It is various aberration figure at the time of the finite distance object point focus in the short focal distance end of the 9th Example. It is various aberration figure at the time of the finite distance object point focus with the intermediate focal length of the 9th example. It is various aberration figure at the time of the finite distance object point focus in the long focal distance end of the 9th example. It is a lens block diagram at the time of the infinity object point focus by the short focal distance end of 10th Example of the zoom lens system by this invention. FIG. 89 is an aberration diagram for the lens configuration of FIG. 82. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the 10th Example. FIG. 85 is a diagram of various aberrations in the lens configuration in FIG. 84. It is a lens block diagram at the time of the infinity object point focus in the long focal distance end of the 10th Example. FIG. 87 is a diagram showing various aberrations with the lens configuration in FIG. 86. It is various aberration figure at the time of finite distance object point focus in the short focal distance end of the 10th Example. It is various aberration figure at the time of finite distance object point focus in the intermediate focal length of the same 10th example. It is various aberrations at the time of finite distance object point focusing at the long focal length end of the tenth embodiment. It is a lens block diagram at the time of the infinity object point focus by the short focal distance end of 11th Example of the zoom lens system by this invention. FIG. 92 is a diagram of various aberrations with the lens configuration of FIG. 91. It is a lens block diagram at the time of infinity object point focus with the intermediate | middle focal distance of the 11th Example. FIG. 94 is an aberration diagram for the lens configuration in FIG. 93. It is a lens block diagram at the time of the infinity object point focus in the long focal distance end of the 11th Example. FIG. 96 is a diagram of various aberrations of the lens configuration in FIG. 95. It is various aberration figure at the time of finite distance object point focus in the short focal distance end of the 11th example. It is an aberration diagram at the time of finite distance object point focus at the intermediate focal length of the eleventh embodiment. It is various aberration figure at the time of the finite distance object point focus in the long focal length end of the eleventh example. It is a simple movement figure of the zoom lens system by this invention.

  The zoom lens system according to the present invention includes a positive first lens group 10, a negative second lens group 20, an aperture S, and a positive third lens group 30 in order from the object side, as shown in the simplified movement diagram of FIG. , And a positive fourth lens group 40. During zooming from the short focal length end to the long focal length end, the first lens group 10 and the third lens group 30 are not moved (fixed), and the second lens group 20 is moved to the image side. I is an image plane. The fourth lens group 40 moves in the optical axis direction in order to compensate for the focal movement that occurs during the above zooming. A diaphragm S is provided in the third lens group 30. Theoretically, focusing can be performed in any of the first lens group 10 to the second lens group. In the present embodiment, the second lens group 20 and the fourth lens group 40 are the focus lens group. Although there is a position where a lens system that does not cause focal movement at any object distance at zooming is classified as a zoom lens system and a lens system that produces focal movement is classified as a varifocal system, in this embodiment, the varifocal system is referred to as a varifocal system. This is called a zoom lens system.

  As shown in the lens configuration diagrams of the numerical examples, the fourth lens group 40 includes, in order from the object side, a 4a lens group 40a formed of a positive single lens, and a bonded lens composed of a negative lens and a positive lens. 4b lens group 40b, and 4a lens group 40a has an aspherical surface on which at least the object side surface has an aspheric surface whose power is weaker as the height from the optical axis is higher than that of the paraxial spherical surface. .

  Various positive / negative / positive four-group zoom lens systems are known, but the first lens group includes a negative cemented lens and a positive meniscus, and the second lens group includes three negative / positive lenses. The basic configuration is common, and variations are given by cemented lenses. The negative second lens group responsible for the main zooming function greatly affects the size of the lens system, and the amount of movement of the second lens group also increases as the zoom ratio increases.

  Therefore, the lens types of the positive third lens group and the fourth lens group that form an image of diverging light from the second lens group are important for downsizing the lens. In the present embodiment, the fourth lens group is composed of a 4a lens group composed of a positive single lens having an aspherical surface and a 4b lens group composed of a negative positive cemented lens, and satisfies the conditional expression (1). .

Conditional expression (1) defines the ratio of the focal lengths of the 4a lens group and the 4b lens group, and is a condition for miniaturization. If the lower limit of conditional expression (1) is exceeded, the focal length (f _4a ) of the 4a lens group becomes relatively large, leading to an increase in the size of the fourth lens group, which is disadvantageous for reducing the size of the entire lens. If the upper limit of conditional expression (1) is exceeded, f _4a becomes relatively small, which is advantageous for miniaturization, but the focal length (f _4b ) (negative of the 4b lens group is maintained in order to maintain the power of the entire four groups. (Power) becomes large, and spherical aberration and coma aberration cannot be maintained properly. Alternatively, when the absolute value of f _4b increases, the size of the fourth group also increases, and the effect of spherical aberration correction becomes weak, and spherical aberration becomes insufficiently corrected.

  Conditional expression (2) is a condition relating to the distance between the 4a lens group and the 4b lens group, and is a condition for keeping the fourth lens group compact and maintaining appropriate aberrations together with conditional expression (1). When the lower limit of conditional expression (2) is exceeded and the distance between the 4a lens group and the 4b lens group becomes small, the incident height to the 4b lens group becomes high and positive spherical aberration occurs greatly. Further, since the 4b lens group is a negative lens group, the effect of the telephoto type for reducing the overall length compared to the focal length is weakened, leading to an increase in the size of the entire lens group. If the distance exceeds the upper limit of conditional expression (2), the effect of reducing the total length increases, but the incident height to the 4b lens group also decreases and the effect of correcting aberrations decreases, making it impossible to maintain aberrations appropriately.

  Specifically, in the zoom lens system, for example, the first lens group includes, in order from the object side, a cemented lens of a negative lens and a positive lens, and a positive meniscus lens convex on the object side, and a second lens. The group includes, in order from the object side, a negative lens having a strong concave surface facing the image side, a cemented lens of a positive lens and a negative lens having a concave surface on the object side, and a positive lens. The third lens group is a positive lens. And a negative lens bonded lens. The order of the positive and negative lenses in the third lens group is flexible.

  Conditional expression (3) is a condition regarding the ratio of the focal lengths of the third lens group and the fourth lens group. If the power of the third lens group becomes stronger beyond the lower limit of conditional expression (3), aberrations will increase even if an aspherical surface is provided on the positive lens in the third lens group, and only the cemented lens of the positive and negative lenses will be used. The three lens groups cannot be configured. If the upper limit of conditional expression (3) is exceeded, when the focal length of the third lens group becomes relatively large, the chromatic aberration in the third lens group increases in proportion to the focal length, and the chromatic aberration of the entire lens system can be maintained. Disappear. In addition, when the focal length of the fourth lens group becomes relatively small, the power of the fourth lens group becomes too strong to properly maintain spherical aberration and coma aberration.

  Conditional expression (4) defines the power of the negative second lens group. If the power of the second lens unit becomes weaker than the upper limit of conditional expression (4), the amount of movement of the second lens unit at the time of zooming becomes large and the total lens length becomes small in order to obtain a zoom ratio of about 10 times. I can't keep it. When the negative power of the second lens group becomes stronger beyond the lower limit of conditional expression (4), the amount of movement during zooming can be reduced, but aberrations in the second lens group increase and aberrations are maintained throughout the entire zoom range. I can't do that.

  Conditional expression (5) is a condition relating to the Abbe number of the second positive lens from the object side of the first lens group, and is used to satisfactorily correct chromatic aberration in the first lens group together with conditional expression (6). It is a condition. In a zoom lens system having a high zoom ratio of about 10 times, the focal length at the end of the long focal length becomes very long, so that chromatic aberration tends to increase. In order to keep this small, the chromatic aberration of the first lens group must be kept appropriate. In order to reduce the size, the first lens group tends to have a relatively strong power and affects the spherical aberration on the long focal length side, so the aberration of the first lens group must be reduced.

  Conditional expression (6) is a condition regarding the power and glass material of each lens in the first lens group. When the glass material of the second lens of the first lens group is selected so as to satisfy the conditional expression (5) for correcting chromatic aberration, the third lens of the first lens group is used for correcting spherical aberration. It is preferable to select a glass having a relatively high refractive index. By satisfying conditional expression (6), it is possible to correct spherical aberration well while maintaining chromatic aberration.

  Conditional expressions (7) and (8) define conditions for favorably correcting the chromatic aberration of the third lens group. Although the chromatic aberration of the third lens group mainly affects the chromatic aberration of magnification of the entire lens system, the positive lens of the third lens group composed of a positive and negative cemented lens is a glass material with a particularly large Abbe number as in the conditional expression (7). Therefore, the chromatic aberration of magnification of the entire system can be appropriately maintained over the entire zoom range. If conditional expression (7) is exceeded, it will be difficult to maintain conditional expression (8). Conditional expression (8) is an achromatic condition for the third lens group. The positive lens and the negative lens are selected so as to satisfy the conditional expression (8), and the power is defined to eliminate the achromaticity in the third lens group. It becomes easy.

  In this zoom lens system, any lens group from the first lens group to the fourth lens group can be a focus lens group. However, in this embodiment, in particular, the two lens groups of the second lens group and the fourth lens group are used as the focus lens group. In a conventional 4-group zoom lens system for positive, negative, positive and positive for video, a large first lens group is not used as a focus lens group in order to save power in an electric drive system that moves a focus lens. Many. However, when the fourth lens group is a focus lens group, in a recent zoom lens system that is required to shorten the shortest shooting distance, the amount of movement of the fourth lens group becomes large and the focusing operation becomes slow. End up. Further, when the fourth lens group is moved greatly, the change in the distance from the third lens group increases, and this change in the distance increases the curvature of field. In order to solve this problem, a zoom lens system in which a second lens group having a large power is used as a focus lens group is also known. This inner focus type is advantageous in that the amount of movement of the focus lens group (second lens group) can be reduced and the change in aberration is small. However, when a high zoom ratio of about 10 times is achieved, the second lens group In many cases, the magnification is the same in the middle of the zoom range. At the same magnification zoom position, the vertical magnification is also the same magnification, so even if the second lens group is moved, the image point of the second lens group does not move and the second lens group cannot be focused.

  In this embodiment, in order to solve such problems, focusing is performed by moving both the second lens group and the fourth lens group. By moving the high power second lens group, the focus movement amount is reduced and the focus speed is increased as compared with the case of only the fourth lens group, and the change in field curvature is also reduced. Also, when the second lens unit is the same magnification, the fourth lens unit moves, so that there is focus sensitivity and focusing is possible.

  Conditional expression (9) is a condition regarding the movement amount ratio between the second lens group and the fourth lens group when both the second lens group and the fourth lens group are used as the focus lens group. Exceeding the lower limit of conditional expression (9) means that the fourth lens group does not move, and when the second lens group is moved to the same magnification position, a zoom area that cannot be focused is formed. When the upper limit of conditional expression (9) is exceeded, the movement amount of the second lens group becomes small, and the effect of reducing the movement amount of the fourth lens group becomes small. In other words, the amount of movement of the fourth lens group increases and it takes time to focus, and as a result, the distance from the third lens group also increases, resulting in field curvature.

  When the second lens group and the fourth lens group are moved and electrically controlled by a motor, it is easy to control the movement amount ratio (dX4 / dX2) in the conditional expression (9) as an integer. More specifically, the movement amount ratio is preferably about 1, 2, or 3.

  On the other hand, in recent zoom lens systems, the lens position is often digitally controlled, and in a step zoom lens in which the focal length area is divided into a plurality of stages, the amount of movement by focusing in one step in the control depends on the zoom area. It may become very small. In such a case, it is desirable to change the moving amount ratio (dX2 / dX4) between the second lens group and the fourth lens group depending on the zoom region. Specifically, on the short focal length side where the amount of focus movement per step is small, the amount of movement of the fourth lens group is small, so the relative amount of movement of the second lens group is small (or not moved dX2 = 0). It is preferable to increase the relative movement amount of the second lens group from the zoom intermediate region where the focus movement amount of the second lens group increases to the long focal length side.

  Conditional expression (10) indicates that when the movement amount ratio is changed according to the change in the focal length due to the zooming from the short focal length end to the long focal length end, the focus movement amount ratio between the second lens group and the fourth lens group is It represents a condition that should always be met. It is usually not possible to exceed the lower limit. Exceeding the upper limit means that the amount of movement of the second lens group becomes too large with respect to the amount of movement of the fourth lens group, and the disadvantage of the conventional method in which focusing is performed only with the second lens group appears. More specifically, the second lens group is not moved on the short focal length side, but is focused only by moving the fourth lens group (dX2 / dX4 = 0), and the second and fourth lens groups are integrated in the intermediate focal length range. (DX2 / dX4 = 1) and dX2 should be relatively small (dX2 / dX4 <1.0) on the telephoto side where the focus sensitivity of the second lens group is high. At this time, if dX2 / dX3 = 1/2 or 1/3, the control is easy when the second lens group and the fourth lens group are moved and electrically controlled by a motor.

Next, specific examples will be described. In the various aberration diagrams and tables, SA is spherical aberration, SC is a sine condition, chromatic aberration (axial chromatic aberration) diagram represented by spherical aberration, and d-line, g-line, and C-line are chromatic aberrations for each wavelength. , S is sagittal, M is meridional, Y is image height, W half angle of view (°), FNO. Is F number, Fe is effective F number, f is focal length of the entire system, fB is back focus, r is curvature Radius, d is the lens thickness or lens interval, N _d is the refractive index of the d-line, and ν is the Abbe number.

[Example 1]
1 to 9 show a first embodiment of the zoom lens system of the present invention. 1, 3, and 5 are lens configuration diagrams when focusing on an object point at infinity at the short focal length end, the intermediate focal length, and the long focal length end, respectively, and FIGS. 2, 4, and 6 are FIGS. FIGS. 7, 8, and 9 show various aberrations when focusing on a finite distance object point at the short focal length end, the intermediate focal length, and the long focal length end, respectively. Aberration diagrams, Tables 1A and 1B are numerical data. Table 1A shows the short focal length end, the intermediate focal length, and the long focal length end when focusing on an object point at infinity. Table 1B mainly shows a portion where the values of the short focal length end, the intermediate focal length, and the long focal length end when focusing on a finite distance object point are changed with respect to Table 1A. The finite distance is not constant and is indirectly expressed by the photographing magnification in each lens data.

  The first lens group 10 having a positive power includes, in order from the object side, a cemented lens of a negative lens and a positive lens, and a positive meniscus lens convex to the object side, and the second lens group 20 having a negative power includes In order from the object side, a negative lens having a strong concave surface facing the image side, a cemented lens of a positive lens and a negative lens having a concave surface on the object side, and a positive lens. The fourth lens group 40 includes, in order from the object side, a 4a lens group 40a composed of a positive single lens, and a fourth lens group composed of a negative lens and a positive lens. It consists of group 40b. On the image side of the fourth lens group, a cover glass (parallel flat plate) C (surface no. 21, 22) located in front of the image sensor is located. Focusing is performed by individually moving the second lens group 20 and the fourth lens group 40 with a constant movement amount ratio. The stop S is at a distance of 0.70 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 1A)
FNO. = 1: 2.9-3.2-3.6
f = 5.94-18.00-56.60
M = 0.000-0.000-0.000
fB = 5.67-5.67-5.67
Surface No. r d N _d ν
1 46.829 1.40 1.84666 23.8
2 27.662 5.57 1.49700 81.6
3 -174.104 0.10
4 25.347 3.72 1.72916 54.7
5 79.191 0.83-12.82-21.03
6 34.822 0.90 1.88300 40.8
7 7.429 2.81
8 -12.854 3.39 1.84666 23.8
9 -5.730 0.90 1.88300 40.8
10 45.452 0.34
11 23.938 1.87 1.64769 33.8
12 -41.572 22.10-10.10-1.90
13 * 13.500 2.31 1.49700 81.6
14 -14.030 0.90 1.61293 37.0
15 -106.309 13.68-9.87-12.78
16 * 15.792 2.22 1.58913 61.2
17 -38.529 5.88
18 15.674 0.90 1.84666 23.8
19 6.512 2.32 1.51742 52.4
20 27.209 0.80-4.61-1.70
21 ∞ 1.70 1.51633 64.1
22 ∞-
NO K A4 A6 A8
13 -0.10000 × 10 ¹ -0.10975 × 10 ^-4 0.74001 × 10 ^-6
16 -0.10000 × 10 ¹ -0.58875 × 10 ^-4 0.11028 × 10 ^-6 -0.57869 × 10 ^-8

(Table 1B)
Fe = 1: 2.9-3.3-3.9
M = -0.025--0.064--0.150
fB = 5.67-5.67-5.67
Surface No. d
5 0.80-12.61-19.20
12 22.13-10.32- 3.73
15 13.54- 8.82- 3.66
20 0.94- 5.66-10.82

[Example 2]
10 to 18 show a second embodiment of the zoom lens system of the present invention. 10, 12, and 14 are lens configuration diagrams at the time of infinite object point focusing at the short focal length end, the intermediate focal length, and the long focal length end, respectively, and FIGS. 11, 13, and 15 are FIGS. FIGS. 12, 14, and 18 are graphs showing various aberrations at the time of focusing on a finite distance object point at the short focal length end, the intermediate focal length, and the long focal length end, respectively. Table 2A and Table 2B are numerical data. The basic lens configuration and focusing method are the same as in the first embodiment. The stop S is at a distance of 0.70 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 2A)
FNO. = 1: 2.8-3.2-3.6
f = 5.90-18.00-56.00
M = 0.000-0.000-0.000
fB = 2.94-2.94-2.94
Surface No. r d N _d ν
1 49.280 1.40 1.84666 23.8
2 28.156 5.60 1.49700 81.6
3 -144.830 0.10
4 24.886 3.70 1.72916 54.7
5 74.471 0.81-12.75-20.86
6 * 31.213 1.00 1.85020 40.8
7 6.813 2.87
8 -14.908 2.37 1.80518 25.4
9 -6.290 0.90 1.88300 40.8
10 17.130 0.10
11 13.902 2.19 1.76182 26.5
12 -41.864 21.95-10.02-1.90
13 * 14.423 2.50 1.49700 81.6
14 -9.484 1.00 1.60342 38.0
15 -40.103 15.05-10.94-13.20
16 * 14.758 2.21 1.58913 61.2
17 -39.788 6.50
18 19.151 1.00 1.84666 23.8
19 6.530 3.00 1.51742 52.4
20 31.321 0.80-4.91-2.65
21 ∞ 2.00 1.51633 64.1
22 ∞-
NO K A4 A6 A8 A10
6 -0.10000 × 10 ¹ -0.35695 × 10 ^-4 0.22601 × 10 ^-5 -0.97278 × 10 ^-7 0.13092 × 10 ^-8
13 -0.10000 × 10 ¹ 0.13713 × 10 ^-4 0.24311 × 10 ^-6
16 -0.10000 × 10 ¹ -0.62768 × 10 ^-4 0.16857 × 10 ^-6 -0.69577 × 10 ^-8

(Table 2B)
Fe = 1: 2.8-3.3-3.7
M = -0.025--0.062--0.117
fB = 2.94-2.94-2.94
Surface No. d
5 0.75-12.30-17.32
12 22.02-10.46- 5.45
15 14.92-10.04- 6.10
20 0.93- 5.81- 9.75

[Example 3]
19 to 27 show a third embodiment of the zoom lens system of the present invention. 19, FIG. 21, and FIG. 23 are lens configuration diagrams at the time of focusing on an object point at infinity at the short focal length end, the intermediate focal length, and the long focal length end, respectively, and FIG. 20, FIG. 22, and FIG. FIG. 21 and FIG. 23 show various aberration diagrams, and FIG. 25, FIG. 26, and FIG. 27 show various aberration diagrams during finite distance object point focusing at the short focal length end, intermediate focal length, and long focal length end, respectively. Table 3A and Table 3B are numerical data. The basic lens configuration and focusing method are the same as in the first embodiment. The stop S is at a distance of 0.70 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 3A)
FNO. = 1: 2.8-3.2-3.6
f = 5.90-18.00-56.00
M = 0.000-0.000-0.000
fB = 3.91-3.91-3.9
Surface No. r d N _d ν
1 44.042 1.40 1.84666 23.8
2 27.472 5.82 1.43875 95.0
3 -120.611 0.10
4 25.064 3.78 1.72916 54.7
5 81.239 1.13-13.06-21.18
6 * 100.057 1.00 1.85020 40.8
7 7.220 2.59
8 -13.466 2.01 1.80518 25.4
9 -6.943 0.90 1.88300 40.8
10 17.219 0.12
11 14.736 2.32 1.76182 26.5
12 -23.771 21.95-10.02-1.90
13 * 11.881 2.46 1.43426 95.0
14 -11.599 1.00 1.60342 38.0
15 -50.091 13.19-9.50-12.62
16 * 15.761 3.08 1.58913 61.2
17 -32.685 6.44
18 21.123 1.00 1.84666 23.8
19 6.908 3.00 1.51742 52.4
20 51.360 0.80-4.48-1.36
21 ∞ 2.00 1.51633 64.1
22 ∞-
NO K A4 A6 A8 A10
6 -0.10000 × 10 ¹ -0.19860 × 10 ^-4 0.35050 × 10 ^-5 -0.14359 × 10 ^-6 0.18922 × 10 ^-8
13 -0.10000 × 10 ¹ 0.21211 × 10 ^-4 0.43985 × 10 ^-6
16 -0.10000 × 10 ¹ -0.82687 × 10 ^-4 0.43301 × 10 ^-6 -0.15 115 × 10 ^-7

(Table 3B)
Fe = 1: 2.8-3.3-4.5
M = -0.025--0.062--0.113
fB = 3.91-3.91-3.91
Surface No. d
5 1.06-12.60-17.47
12 22.02-10.48- 5.61
15 13.06- 8.58- 5.21
20 0.93- 5.40- 8.78

[Example 4]
28 to 36 show a fourth embodiment of the zoom lens system of the present invention. 28, 30, and 32 are lens configuration diagrams at the time of focusing on an object point at infinity at the short focal length end, the intermediate focal length, and the long focal length end, respectively, and FIGS. 29, 31, and 33 are FIGS. FIGS. 34, 35, and 36 are aberration diagrams at the time of finite distance object point focusing at the short focal length end, the intermediate focal length, and the long focal length end, respectively. Table 4A and Table 4B show the numerical data. The basic lens configuration and focusing method are the same as in the first embodiment. The stop S is at a distance of 0.70 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 4A)
FNO. = 1: 2.8-3.2-3.6
f = 5.90-18.00-56.00
M = 0.000-0.000-0.000
fB = 4.78-4.78-4.78
Surface No. r d N _d ν
1 47.995 1.40 1.84666 23.8
2 27.499 5.63 1.49700 81.6
3 -161.690 0.10
4 24.837 3.78 1.73400 51.5
5 77.075 0.80-12.76-20.85
6 * 31.831 1.00 1.85020 40.8
7 6.775 2.89
8 -11.859 2.20 1.80518 25.4
9 -6.102 0.90 1.88300 40.8
10 20.915 0.10
11 16.679 2.21 1.76182 26.5
12 -25.563 21.95-9.99-1.90
13 * 12.749 2.45 1.43426 95.0
14 -10.865 1.00 1.61293 37.0
15 -36.389 13.35-9.60-12.58
16 * 16.360 2.82 1.58913 61.2
17 -37.266 6.13
18 16.567 1.00 1.84666 23.8
19 6.888 3.00 1.51742 52.4
20 30.611 0.80-4.55-1.57
21 ∞ 1.70 1.51633 64.1
22 ∞-
NO K A4 A6 A8 A10
6 -0.10000 × 10 ¹ -0.21522 × 10 ^-4 0.27370 × 10 ^-5 -0.10386 × 10 ^-6 0.12934 × 10 ^-8
13 -0.10000 × 10 ¹ 0.16698 × 10 ^-4 0.18372 × 10 ^-5 -0.78848 × 10 ^-7
16 -0.10000 × 10 ¹ -0.67316 × 10 ^-4 0.22243 × 10 ^-6 -0.88 158 × 10 ^-8

(Table 4B)
Fe = 1: 2.8-3.3-4.4
M = -0.025--0.062--0.113
fB = 4.78-4.78-4.78
Surface No. d
5 0.73-12.30-17.19
12 22.02-10.45- 5.56
15 13.22- 8.69- 5.25
20 0.93- 5.46- 8.90

[Example 5]
37 to 45 show a fifth embodiment of the zoom lens system of the present invention. 37, 39, and 41 are lens configuration diagrams at the time of focusing on an object point at infinity at the short focal length end, the intermediate focal length, and the long focal length end, respectively, and FIGS. 38, 40, and 42 are FIGS. 39 and 41 are aberration diagrams. FIGS. 43, 44, and 45 are diagrams showing various aberrations at the time of finite distance object point focusing at the short focal length end, the intermediate focal length, and the long focal length end, respectively. Table 5A and Table 5B show the numerical data. The basic lens configuration and focusing method are the same as in the first embodiment. The stop S is at a distance of 0.70 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 5A)
FNO. = 1: 2.8-3.2-3.6
f = 5.94-18.00-56.60
M = 0.000-0.000-0.000
fB = 6.41-6.41-6.41
Surface No. r d N _d ν
1 45.832 1.40 1.84666 23.8
2 27.636 5.55 1.49700 81.6
3 -178.876 0.10
4 25.457 3.68 1.72916 54.7
5 78.187 0.92-12.92-21.12
6 42.092 0.90 1.88300 40.8
7 7.464 2.73
8 -12.922 3.29 1.84666 23.8
9 -5.841 0.90 1.88300 40.8
10 42.578 0.35
11 23.354 1.93 1.64769 33.8
12 -35.698 22.10-10.10-1.90
13 * 12.974 2.34 1.43426 95.0
14 -13.742 0.90 1.61293 37.0
15 -46.190 13.29-9.54-12.58
16 * 16.705 2.25 1.58913 61.2
17 -37.252 5.54
18 14.260 0.90 1.84666 23.8
19 6.495 2.31 1.51742 52.4
20 22.563 0.80-4.55-1.52
21 ∞ 1.70 1.51633 64.1
22 ∞-
NO K A4 A6 A8
13 -0.10000 × 10 ¹ -0.13404 × 10 ^-4 0.12644 × 10 ^-5 -0.28995 × 10 ^-7
16 -0.10000 × 10 ¹ -0.56029 × 10 ^-4 0.10702 × 10 ^-6 -0.51595 × 10 ^-8

(Table 5B)
Fe = 1: 2.8-3.3-4.4
M = -0.025--0.062--0.113
fB = 6.41-6.41-6.41
Surface No. d
5 0.86-12.46-17.42
12 22.16-10.56- 5.60
15 13.16- 8.63- 5.18
20 0.93- 5.47- 8.91

[Example 6]
46 to 54 show a sixth embodiment of the zoom lens system of the present invention. 46, 48, and 50 are lens configuration diagrams at the time of focusing on an object point at infinity at the short focal length end, the intermediate focal length, and the long focal length end, respectively, and FIGS. 47, 49, and 51 are FIGS. FIG. 48, FIG. 50 are aberration diagrams for the lens configuration, and FIG. 52, FIG. 53, and FIG. 54 are aberration diagrams for focusing at a finite distance object point at the short focal length end, intermediate focal length, and long focal length end, respectively. Table 6A and Table 6B show the numerical data. The basic lens configuration and focusing method are the same as in the first embodiment. The stop S is at a distance of 0.70 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 6A)
FNO. = 1: 2.8-3.2-3.6
f = 5.90-18.00-56.00
M = 0.000-0.000-0.000
fB = 4.38-4.38-4.38
Surface No. r d N _d ν
1 48.381 1.40 1.84666 23.8
2 26.352 5.74 1.48749 70.2
3 -180.593 0.10
4 25.617 3.99 1.73400 51.5
5 107.123 0.81-12.75-20.86
6 * 42.541 1.00 1.85020 40.8
7 7.356 2.79
8 -11.500 2.44 1.80518 25.4
9 -5.610 0.90 1.88300 40.8
10 36.083 0.10
11 24.415 1.99 1.76182 26.5
12 -26.626 21.95-10.01-1.90
13 * 12.371 2.65 1.49700 81.6
14 -8.487 1.00 1.56732 42.8
15 -364.165 13.15-9.49-12.72
16 * 14.782 2.45 1.58913 61.2
17 -51.567 6.66
18 14.841 1.00 1.84666 23.8
19 6.433 3.00 1.51742 52.4
20 30.641 0.80-4.46-1.23
21 ∞ 1.70 1.51633 64.1
22 ∞-
NO K A4 A6 A8 A10
6 -0.10000 × 10 ¹ -0.15179 × 10 ^-4 0.38697 × 10 ^-5 -0.13785 × 10 ^-6 0.18930 × 10 ^-8
13 -0.10000 × 10 ¹ 0.28326 × 10 ^-4 0.18229 × 10 ^-5 -0.64490 × 10 ^-7
16 -0.10000 × 10 ¹ -0.64 350 × 10 ^-4 0.34702 × 10 ^-6 -0.13361 × 10 ^-7

(Table 6B)
Fe = 1: 2.8-3.3-4.5
M = -0.025--0.062--0.113
fB = 4.38-4.38-4.38
Surface No. d
5 0.74-12.29-17.13
12 22.02-10.47- 5.64
15 13.02- 8.57- 5.25
20 0.93- 5.38- 8.70

[Example 7]
55 to 63 show a seventh embodiment of the zoom lens system of the present invention. 55, 57, and 59 are lens configuration diagrams at the time of focusing on an object point at infinity at a short focal length end, an intermediate focal length, and a long focal length end, respectively, and FIGS. 56, 58, and 60 are FIGS. FIG. 57, FIG. 59, and FIG. 63 show various aberrations during finite distance object point focusing at the short focal length end, intermediate focal length, and long focal length end, respectively. Table 7A and Table 7B show the numerical data. The basic lens configuration and focusing method are the same as in the first embodiment. The stop S is at a distance of 0.70 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 7A)
FNO. = 1: 2.8-3.2-3.6
f = 5.94-18.00-56.60
M = 0.000-0.000-0.000
fB = 6.63-6.63-6.63
Surface No. r d N _d ν
1 48.615 1.40 1.84666 23.8
2 27.260 5.68 1.48749 70.2
3 -157.966 0.10
4 24.989 3.87 1.72916 54.7
5 85.363 0.80-12.78-21.00
6 34.274 0.90 1.88300 40.8
7 7.331 2.83
8 -12.862 3.36 1.84666 23.8
9 -5.753 0.90 1.88300 40.8
10 62.110 0.30
11 24.942 1.82 1.64769 33.8
12 -48.037 22.10-10.12-1.90
13 * 12.987 2.32 1.43426 95.0
14 -14.055 0.90 1.61293 37.0
15 -46.035 13.25-9.51-12.63
16 * 16.899 2.17 1.58913 61.2
17 -36.362 5.23
18 13.818 0.90 1.84666 23.8
19 6.479 2.33 1.51742 52.4
20 21.067 0.80-4.54-1.43
21 ∞ 1.70 1.51633 64.1
22 ∞-
NO K A4 A6 A8
13 -0.10000 × 10 ¹ -0.21889 × 10 ^-4 0.15575 × 10 ^-5 -0.32228 × 10 ^-7
16 -0.10000 × 10 ¹ -0.55786 × 10 ^-4 0.11336 × 10 ^-6 -0.50252 × 10 ^-8

(Table 7B)
Fe = 1: 2.8-3.3-4.4
M = -0.025--0.062--0.113
fB = 6.63-6.63-6.63
Surface No. d
5 0.73-12.32-17.27
12 22.16-10.57- 5.63
15 13.12- 8.60- 5.17
20 0.93- 5.46- 8.89

[Example 8]
FIGS. 64 to 72 show an eighth embodiment of the zoom lens system of the present invention. 64, 66, and 68 are lens configuration diagrams at the time of focusing on an object point at infinity at the short focal length end, the intermediate focal length, and the long focal length end, respectively, and FIGS. 65, 67, and 69 are FIGS. FIG. 66, FIG. 68 are aberration diagrams for the lens configuration, and FIG. 70, FIG. 71, and FIG. 72 are diagrams for various aberrations during finite distance object point focusing at the short focal length end, intermediate focal length, and long focal length end, respectively. Table 8A and Table 8B show the numerical data. The basic lens configuration is the same as that of the first embodiment. In the focusing method, only the fourth lens unit moves at the short focal length end and f = 18, and the second and fourth lens units move at the same movement amount ratio (dX2 / dX4 = 1.0) at f = 32. It moves at dX2 / dX4 = 1/3 at the long focal length end. The stop S is at a distance of 1.25 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 8A)
FNO. = 1: 2.8-3.2-3.6
f = 5.94-18.00-56.60
M = 0.000-0.000-0.000
fB = 5.49-5.49-5.49
Surface No. r d N _d ν
1 56.804 1.40 1.84666 23.8
2 28.040 5.83 1.48749 70.2
3 -125.705 0.10
4 25.307 4.04 1.77250 49.6
5 90.627 1.04-12.97-21.24
6 72.399 0.90 1.88300 40.8
7 7.728 2.61
8 -16.628 3.45 1.84666 23.8
9 -6.057 0.90 1.88300 40.8
10 49.892 0.29
11 22.629 1.85 1.65446 33.6
12 -74.164 22.65-10.72-2.45
13 * 12.902 2.46 1.43426 95.0
14 -13.820 0.90 1.62588 35.7
15 -43.931 13.07-9.35-12.65
16 * 15.880 3.00 1.58913 61.2
17 -36.236 5.23
18 16.498 1.00 1.84666 23.8
19 6.824 3.00 1.51742 52.4
20 22.141 0.80-4.52-1.22
21 ∞ 1.70 1.51633 64.1
22 ∞-
NO K A4 A6
13 -0.10000 × 10 ¹ 0.11048 × 10 ^-4 0.18229 × 10 ^-5
16 -0.10000 × 10 ¹ -0.63958 × 10 ^-4 -0.10148 × 10 ^-6

(Table 8B)
Fe = 1: 2.8-3.3-4.6
M = -0.025--0.066--0.131
fB = 5.49-5.49-5.49
Surface No. d
5 1.04-12.97-18.42
12 22.65-10.72- 5.27
15 12.92- 8.16- 4.18
20 0.95- 5.71- 9.69

[Example 9]
73 to 81 show a ninth embodiment of the zoom lens system of the present invention. 73, 75, and 77 are lens configuration diagrams at the time of focusing on an object point at infinity at the short focal length end, the intermediate focal length, and the long focal length end, respectively, and FIGS. 74, 76, and 78 are FIGS. FIG. 75, FIG. 77, FIG. 79, and FIG. 81 show various aberrations when focusing on a finite distance object point at the short focal length end, intermediate focal length, and long focal length end, respectively. Table 9A and Table 9B show the numerical data. The basic lens configuration and focusing method are the same as in Example 8. The stop S is at a distance of 1.25 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 9A)
FNO. = 1: 2.9-3.4-3.4
f = 5.91-18.00-56.60
M = 0.000-0.000-0.000
fB = 6.28-6.28-6.28
Surface No. r d N _d ν
1 62.132 1.40 1.84666 23.8
2 28.852 6.03 1.48749 70.2
3 -100.000 0.10
4 25.250 4.09 1.77250 49.6
5 91.368 1.12-12.75-20.92
6 104.871 0.90 1.88300 40.8
7 8.619 2.46
8 -19.286 3.27 1.84666 23.8
9 -6.776 0.90 1.88300 40.8
10 17.947 0.39
11 15.516 1.96 1.72825 28.5
12 -104.266 22.56-10.93-2.76
13 * 11.248 2.62 1.43312 95.2
14 -18.768 0.90 1.62588 35.7
15 -106.721 12.10-8.26-11.38
16 * 11.746 3.00 1.58913 61.2
17 * -58.024 3.77
18 28.438 1.00 1.71736 29.5
19 5.672 3.00 1.51742 52.4
20 33.625 0.80-4.63-1.52
21 ∞ 1.70 1.51633 64.1
22 ∞-
NO K A4 A6
13 -0.10000 × 10 ¹ 0.33790 × 10 ^-5
16 -0.10000 × 10 ¹ 0.66354 × 10 ^-4 0.29304 × 10 ^-5
17 -0.10000 × 10 ¹ 0.15598 × 10 ^-3 0.28865 × 10 ^-5

(Table 9B)
Fe = 1: 2.9-3.4-3.9
M = -0.006--0.017--0.042
fB = 6.28-6.28-6.28
Surface No. d
5 1.12-12.75-19.45
12 22.56-10.93- 4.22
15 12.06- 7.96- 6.97
20 0.84- 4.94- 5.92

[Example 10]
82 to 90 show a tenth embodiment of the zoom lens system of the present invention. 82, 84, and 86 are lens configuration diagrams at the time of focusing on an object point at infinity at the short focal length end, the intermediate focal length, and the long focal length end, respectively, and FIGS. 83, 85, and 87 are FIG. FIG. 84, FIG. 86 are aberration diagrams for the lens configuration, and FIG. 88, FIG. 89, and FIG. 90 are aberration diagrams for focusing at a finite distance object point at the short focal length end, intermediate focal length, and long focal length end, respectively. Table 10A and Table 10B are the numerical data. The basic lens configuration and focusing method are the same as in Example 8. The stop S is at a distance of 1.25 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 10A)
FNO. = 1: 2.9-3.2-3.6
f = 5.94-18.00-56.60
M = 0.000-0.000-0.000
fB = 4.37-4.37-4.37
Surface No. r d N _d ν
1 58.509 1.40 1.84666 23.8
2 29.618 5.88 1.49700 81.6
3 -106.238 0.10
4 25.365 3.88 1.77250 49.6
5 80.491 1.15-12.86-21.01
6 108.017 0.90 1.88300 40.8
7 8.222 2.46
8 -17.114 3.27 1.84666 23.8
9 -6.917 0.90 1.88300 40.8
10 23.494 0.39
11 18.155 1.96 1.72825 28.5
12 -69.555 22.65-10.94-2.79
13 * 11.255 2.62 1.43312 95.2
14 -18.768 0.90 1.62588 35.7
15 -106.721 13.55-9.77-12.97
16 * 14.130 3.00 1.58636 60.9
17 -37.189 5.83
18 20.676 1.00 1.84666 23.8
19 6.477 3.00 1.51742 52.4
20 32.702 0.80-4.58-1.39
21 ∞ 1.70 1.51633 64.1
22 ∞-
NO K A4 A6
13 -0.10000 × 10 ¹ 0.66091 × 10 ^-5
16 -0.10000 × 10 ¹ -0.73349 × 10 ^-4 -0.92249 × 10 ^-7

(Table 10B)
Fe = 1: 2.9-3.3-4.7
M = -0.025--0.066--0.132
fB = 4.37-4.37-4.37
Surface No. d
5 1.15-12.86-18.18
12 22.65-10.94- 5.62
15 13.40- 8.58- 4.49
20 0.95- 5.77- 9.86

[Example 11]
91 to 99 show an eleventh embodiment of the zoom lens system of the present invention. 91, 93, and 95 are lens configuration diagrams at the time of focusing on an object point at infinity at the short focal length end, the intermediate focal length, and the long focal length end, respectively, and FIGS. 92, 94, and 96 are FIGS. 93, FIG. 98, and FIG. 99 are diagrams showing various aberrations at the time of focusing on a finite distance object point at the short focal length end, the intermediate focal length, and the long focal length end, respectively. Table 11A and Table 11B are numerical data. The basic lens configuration and focusing method are the same as in Example 8. The stop S is at a distance of 1.25 mm on the object side (front of the thirteenth surface) of the third lens group.

(Table 11A)
FNO. = 1: 2.9-3.2-3.6
f = 5.94-18.00-56.60
W = 31.2-10.6-3.4
fB = 4.19-4.19-4.19
Surface No. r d N _d ν
1 53.185 1.40 1.84666 23.8
2 28.947 6.09 1.43875 95.0
3 -91.990 0.10
4 24.938 3.98 1.77250 49.6
5 82.093 1.10-12.83-20.95
6 82.176 0.90 1.88300 40.8
7 8.086 2.51
8 -15.428 3.16 1.84666 23.8
9 -6.761 0.90 1.88300 40.8
10 23.456 0.41
11 18.509 1.96 1.72825 28.5
12 -53.039 22.65-10.91-2.79
13 * 11.255 2.62 1.43312 95.2
14 -18.768 0.90 1.62588 35.7
15 -106.749 13.81-9.93-12.96
16 * 14.130 3.00 1.58636 60.9
17 -37.189 6.14
18 25.209 1.00 1.84666 23.8
19 6.692 3.00 1.51742 52.4
20 54.789 0.80-4.69-1.65
21 ∞ 1.70 1.51633 64.1
22 ∞-
NO K A4 A6
13 -0.10000 × 10 ¹ 0.66091 × 10 ^-5
16 -0.10000 × 10 ¹ -0.73349 × 10 ^-4 -0.92249 × 10 ^-7

(Table 11B)
Fe = 1: 2.9-3.2-3.6
M = -0.025--0.064--0.150
fB = 4.19-4.19-4.19
Surface No. d
5 1.10-12.83-18.15
12 22.65-10.91- 5.59
15 13.66- 8.73- 4.56
20 0.95- 5.88-10.06

Table 12 shows values for each conditional expression in each example.

  As is apparent from Table 12, Examples 1 to 7 satisfy the conditional expressions (1) to (9), and Examples 8 to 11 satisfy the conditional expressions (1) to (8) and (10). In addition, various aberrations are corrected relatively well.

Claims (4)

In order from the object side, it consists of a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, and when zooming from the short focal length end to the long focal length end, In the zoom lens system in which the second lens group is moved from the object side to the image side, and the fourth lens group is moved so as to correct the image plane movement accompanying zooming,
The second lens group passes through a point where the magnification becomes equal during zooming ,
The fourth lens group is a focus lens group in all zooming areas, and the second lens group is a focus lens group in at least some zooming areas ;
The ratio of the focusing movement amount of the fourth lens group to the focusing movement amount of the second lens group is constant in all zooming areas; and
A zoom lens system characterized by satisfying the following conditional expression (9):
(9) 0 <dX4 / dX2 <6
However,
dX4: Focusing movement amount of the fourth lens group,
dX2: Focusing movement amount of the second lens group. 2. The zoom lens system according to claim 1 , wherein the value of dX4 / dX2 takes an integer value. In order from the object side, it consists of a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, and when zooming from the short focal length end to the long focal length end, In the zoom lens system in which the second lens group is moved from the object side to the image side, and the fourth lens group is moved so as to correct the image plane movement accompanying zooming,
The second lens group passes through a point where the magnification becomes equal during zooming ,
The fourth lens group is a focus lens group in all zooming areas, and the second lens group is a focus lens group in at least some zooming areas ;
The ratio of the focusing movement amount of the fourth lens group to the focusing movement amount of the second lens group changes according to the focal length change due to zooming from the short focal length end to the long focal length end, and
A zoom lens system characterized in that the moving amount ratio changes while satisfying the following conditional expression (10) .
(10) 0 ≦ dX2 / dX4 ≦ 1
However,
dX4: Focusing movement amount of the fourth lens group,
dX2: Focusing movement amount of the second lens group. 4. The zoom lens system according to claim 3 , wherein the value of dX2 / dX4 changes stepwise from 0 to 1 and then to less than 1 from the short focal length end to the long focal length end. .

Images