JPH11109232A - Zoom lens system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens system compact in structure although it satisfys a high variable power ratio and high image quality. SOLUTION: This system is composed, in order from the object side, of a first lens group Gr1 having a positive power, a second lens group Gr2 having a positive power, a third lens group Gr3 having a negative power and successive lens groups and at least the first lens group and the third lens group are moved to the object side at the time of zooming from the state of the shortest focal distance to the state of the longest focal distance so that an on-axis interval between the first lens group and the second lens group and an on-axis interval between the second lens group and the third lens group are increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens system used for a small photographing optical system.
The present invention relates to a compact and high-magnification zoom lens system suitable for a photographing optical system of a digital input / output device such as a digital still camera and a digital video camera.

[0002]

2. Description of the Related Art In recent years, with the spread of personal computers and the like, digital still cameras, digital video cameras, and the like (hereinafter, simply referred to as digital cameras) that can easily capture image information into digital devices have spread at the individual user level. It is getting. Such digital cameras are expected to be increasingly used as image information input devices in the future.

In general, the image quality of a digital camera is determined by the number of pixels of a solid-state imaging device such as a CCD (charge coupled device). At present, the mainstream of digital cameras for general use is a so-called VGA class solid-state imaging device having about 330,000 pixels. However, the image quality of this VGA class camera is inferior to the image quality of a camera using a conventional silver halide film. For this reason,
Recently, high quality digital cameras having more than one million pixels have been demanded in general digital cameras, and it is required that the photographic optical system of these digital cameras also satisfy high quality.

In these digital cameras for general use, it is also desired to perform image scaling, particularly optical zooming with little image degradation. A zoom lens system has been required.

[0005]

However, in a zoom lens system for a digital camera which has been conventionally proposed, a 10
Those satisfying high image quality exceeding 0,000 pixels were mostly those using an interchangeable lens for a single-lens reflex camera or very large digital cameras for business use. Therefore, such a zoom lens system is very large and expensive, and cannot be said to be suitable for a digital camera for general use.

On the other hand, a photographing optical system of a lens shutter camera for a silver halide film, which has been remarkably reduced in size and high in magnification in recent years, may be used for the photographing optical system of such a digital camera. Conceivable.

However, when the photographing optical system of the lens shutter camera is diverted to a digital camera as it is,
The light-gathering performance of the microlens provided on the front of the solid-state imaging device provided in the digital camera cannot be sufficiently satisfied, and the brightness of the image in the central part and peripheral part of the image changes extremely. This causes a problem. This is a problem that occurs because the exit pupil of the imaging optical system of the lens shutter camera is located near the image plane, and the off-axis light flux emitted from the imaging optical system is obliquely incident on the image plane. . In order to solve this problem, if the position of the exit pupil of the photographing optical system of the conventional lens shutter camera is to be moved away from the image plane, it is inevitable that the entire photographing optical system will become larger.

In view of the above problems, an object of the present invention is to provide a completely new and compact zoom lens system which satisfies high image quality at a high magnification.

[0009]

In order to achieve the above object, a zoom lens system according to claim 1 comprises, in order from the object side, a first lens group having a positive power and a second lens group having a positive power. A third lens group having negative power, and a subsequent group. When zooming from the shortest focal length state to the longest focal length state, the on-axis distance between the first lens group and the second lens group is determined. , So that both the on-axis spacing between the second lens group and the third lens group increases,
At least the first lens group and the second lens group move to the object side.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In this specification, “power” refers to an amount defined by the reciprocal of the focal length, and its deflecting action is caused not only by deflection on surfaces of media having different refractive indexes but also by deflection due to diffraction. It also includes deflection due to the refractive index distribution in the medium.

FIGS. 1 to 3 are sectional views showing the lens arrangement of the zoom lens systems according to the first to third embodiments of the present invention in the shortest focal length state. The zoom lens system according to each embodiment includes, in order from the object side, a first lens group Gr1 having a positive refractive power, a second lens group Gr2 having a positive refractive power, and a third lens group having a negative refractive power. Gr3, aperture S, succeeding lens group, low-pass filter L
F, during zooming from the shortest focal length end to the longest focal length end, the distance between the first lens group Gr1 and the second lens group Gr2 increases, and the second lens group Gr2 and the third lens group Gr2. The first lens group Gr1 and the third lens group G are arranged such that the distance between the first lens group Gr1 and the third lens group G3 is reduced.
r3 is a moving zoom lens system. The arrows in each drawing schematically represent the movement locus of each lens group, aperture, and low-pass filter during zooming from the shortest focal length state to the longest focal length state.

The zoom lens system according to the first embodiment includes, in order from the object side, a cemented lens DL1 of a negative meniscus lens L1 convex on the object side and a positive biconvex lens L2.
Lens group Gr1, negative meniscus lens L convex to the object side
2, a second lens group Gr2 including a positive meniscus lens L4 convex on the object side (image side aspherical), a negative meniscus lens L2 convex on the object side (both aspherical surfaces), and a biconcave negative lens A third lens unit Gr3 composed of L6 and a cemented lens DL2 of a biconvex positive lens L7, an aperture S, a positive meniscus lens (both aspherical surfaces) convex on the object side, and a negative meniscus lens convex on the object side A fourth lens unit Gr composed of a cemented lens DL3 of L9 and a biconvex positive lens L10, and a positive meniscus lens (both aspheric surfaces) L11 concave on the object side.
And a low-pass filter LF. During zooming from the shortest focal length state to the longest focal length state, the first lens group Gr1, the second lens group Gr2, and the fourth lens group Gr4 are moved to the object side, and the third lens group G is moved.
r3 is moved to the image side. Aperture S and low-pass filter L
F is fixed during zooming.

The zoom lens system according to the second embodiment includes, in order from the object side, a cemented lens DL1 of a negative meniscus lens L1 convex to the object side and a positive lens L2 biconvex.
Lens group Gr1, negative meniscus lens L convex to the object side
3, a second lens group Gr2 including a negative meniscus lens (both aspherical surfaces) L4 convex to the object side, and a cemented lens DL2 of a biconcave negative lens L5 and a biconvex positive lens L6. A fourth lens unit Gr4 including a group Gr3, an aperture S, and a biconvex positive lens (both aspheric surfaces) L7, a cemented lens DL3 of a negative meniscus lens L8 convex to the object side and a biconvex positive lens L9, and a biconcave Negative lens (both sides aspheric) L1
A fifth lens unit Gr5 including a low-pass filter L
F. When zooming from the shortest focal length state to the longest focal length state, the first lens group Gr
1, the second lens group Gr2, the fourth lens group Gr4, and the fifth lens group Gr5 are moved to the object side, and the third lens group Gr3 is moved.
To the image side. The diaphragm S moves integrally with the fourth lens unit Gr4 during zooming, and the low-pass filter LF is fixed during zooming.

The zoom lens system according to the third embodiment comprises, in order from the object side, a cemented lens D composed of a negative meniscus lens L1 convex on the object side (aspherical surface on the object side) and a biconvex positive lens L2.
A first lens group Gr1 composed of L1, a positive meniscus lens L3 convex to the object side, a negative meniscus lens L4 convex to the object side, and a positive meniscus lens L5 convex to the object side (image side is aspherical); A second lens group Gr2 comprising: a positive meniscus lens (image side aspheric) L6 convex to the object side;
A third lens group Gr3 including a positive meniscus lens L7 convex to the object side, a cemented lens DL2 of a biconcave negative lens L8 and a biconvex positive lens L9, an aperture S, and a biconvex positive lens (image side Spherical surface) L10, a negative meniscus lens L11 convex on the object side, and a negative meniscus lens L1 convex on the object side
2, a fourth lens unit Gr4 including a biconvex positive lens L13, and a biconcave negative lens (image side is aspheric) L14, and a low-pass filter LF. During zooming from the shortest focal length state to the longest focal length state, the first lens group Gr1 and the fourth lens group Gr4 are moved to the object side, and the second lens group Gr2 and the third lens group Gr3 are moved to the image side. The aperture S and the low-pass filter LF are fixed during zooming.

As described above, the zoom lens system according to each embodiment includes, in order from the object side, the first lens unit having positive power, the second lens unit having positive power, and the third lens unit having negative power. Group, and further have a subsequent group, when zooming from the shortest focal length state to the longest focal length state,
At least the first and second lens groups are arranged such that the distance between the first lens group and the second lens group and the distance between the second lens group and the third lens group are increased.
The lens group and the second lens group move to the object side.

By adopting this configuration, the zoom lens system of each embodiment can be made closer to the telephoto type in the longest focal length state, so that the entire lens length can be reduced. A sufficient back focus can be obtained to be close to the type. Further, the first lens group and the second lens group having a positive power correspond to the first lens group.
Since both move toward the object side so as to increase the distance between the lens group and the second lens group, the second lens group can mainly bear the zooming action. For this reason, it is possible to reduce the burden on the moving amount of the first lens group, and to reduce the overall length of the lens in the longest focal length state.

Hereinafter, conditions to be satisfied by the zoom lens system of each embodiment will be described. It is not necessary to satisfy all of the following conditions at the same time. It is preferable that the zoom lens system of each embodiment satisfies the condition defined by the following conditional expression range (1). 0.3 <(Dt−Dw) / fw <4.5 (1) where Dt is the axial distance between the first lens unit and the second lens unit in the longest focal length state, and Dw is the first lens unit in the shortest focal length state. And fw: focal length in the shortest focal length state.

The above condition indicates the amount of change in the axial distance between the first lens unit and the second lens unit. Exceeding the upper limit of conditional expression range (1) is not preferable because the axial distance between the first lens unit and the second lens unit becomes too large on the long focal length side, and the total lens length in the longest focal length state becomes large. vice versa,
If the lower limit value of the conditional expression range (1) is exceeded, the axial spacing between the first lens group and the second lens group does not change much, so that the zoom lens is close to what is called zoom floating. For this reason, the second lens group cannot sufficiently bear the zooming effect, and as a result, the amount of movement of the first lens group cannot be reduced, and the zoom lens system cannot be downsized.

It is preferable that the zoom lens system of each embodiment satisfies the condition defined by the following conditional expression range (2). 1.03 <βt2 / βw2 <1.5 (2) where βt2 is the lateral magnification of the second lens group in the longest focal length state, and βw2 is the lateral magnification of the second lens group in the shortest focal length state.

The above conditions indicate the load of the second lens group upon zooming. When the value exceeds the upper limit of conditional expression range (2),
Since the variable magnification load of the second lens group becomes large and the fluctuation of aberration of the second lens group becomes too large, it is not preferable because many lenses or aspherical surfaces are required for the second lens group to perform aberration correction. Conversely, if the lower limit value of the conditional expression range (2) is exceeded, the second lens group cannot be given a sufficient zooming action, so that the amount of movement of the first lens group cannot be reduced.

In the zoom lens system according to each of the embodiments, it is preferable that the succeeding lens group following the first to third lens groups includes at least one lens group having positive power. In order to provide sufficient back focus in the shortest focal length state, it is preferable that the configuration of the entire system approaches a retro type. However, when zooming from the shortest focal length state to the longest focal length state, the third lens having negative power is used. By performing zooming so that the distance between the lens group and the lens group having positive power in the succeeding group is reduced, the lens becomes closer to the retro type on the short focal length side, so that sufficient back focus can be obtained. Conversely, on the long focal length side, the lens becomes closer to the telephoto type, so that the overall length of the lens can be reduced.

The succeeding group has only one positive power.
It is preferable that the zoom lens be composed of two lens groups or two lens groups having positive power. If a negative lens group is arranged in the succeeding group, it becomes difficult to secure the back focus on the short focal length side, and the lens diameter of the subsequent group increases, which is not preferable. Also, if the succeeding group has three or more lens groups, it will have six or more lens groups as a whole, and the means for holding the lens groups, such as a lens barrel, becomes very complicated, resulting in high cost. Is not preferred.

It is desirable that the zoom lens system of each embodiment satisfies the condition defined by the following conditional expression range (3). 1.0 <img × R <15.0 (3) Where, img: Maximum image height (unit: mm), R: Effective of the lens surface located closest to the image side, excluding filters, etc., of the lens surfaces constituting the zoom lens system Diameter (unit: mm).

The above conditions are conditions for balancing the size of the zoom lens diameter and the correction of various aberrations with the conditions specific to the photographing optical system for a digital camera. In general, in a photographing optical system used for a digital camera using a solid-state imaging device, an incident light beam is converted into a light beam of the microlens in order to sufficiently satisfy the light-collecting performance of a microlens provided in front of the solid-state imaging device. Need to be made substantially perpendicular to the light. Therefore, a photographing optical system for a digital camera is required to be substantially telecentric on the image side in addition to correcting various aberrations in the same manner as a photographing optical system of a normal silver halide film camera. When the value exceeds the upper limit of the conditional expression range (3), it becomes unnecessary that the zoom lens system is substantially telecentric on the image side, and various aberrations, especially negative distortion on the short focal length side become too large. It becomes difficult to correct,
Undesirably, the inclination of the image surface toward the under side becomes remarkable.
Conversely, when the value exceeds the lower limit of the conditional expression range (3), it is difficult to satisfy the condition of being substantially telecentric, which is not desirable. In particular, if an attempt is made to improve the telecentricity in a state where the lower limit value is exceeded, the back focus of the zoom lens system becomes unnecessarily large, which leads to an increase in the size of the optical system, which is not desirable.

Regarding the above condition, it is more preferable to satisfy the following conditional expression range (3a) of the conditional expression range (3). 6.5 <img × R <9.5 (3a) Like the zoom lens system of each embodiment, in order from the object side, a first lens group having a positive power, a second lens group having a positive power, In a zoom lens system including a third lens group having power and a fourth lens group having positive power, a concave surface having a strong curvature is directed from the object side to the image side in order from the object side. A first sub-group of the third lens group including the first lens, and a second sub-group of the third lens group including at least one positive lens and one negative lens on the object side. desirable. By configuring the third lens unit in this manner, when the light beam is emitted from the concave surface having a strong curvature in the first sub-unit of the third lens unit, the emission angle of the off-axis light beam, particularly on the short focal length side, is reduced. Since the exit angle of the axial ray becomes small, it becomes possible to easily correct the aberration of the third lens unit and the second sub-unit.

It is preferable that the concave surface of the first sub-unit of the third lens unit satisfies the condition defined by the following conditional expression (4). -1.2 <f3 / rn <-0.8 (4) where, rn is the radius of curvature of the concave surface of the first lens unit in the third lens unit, and f3 is the focal length of the third lens unit.

The above condition stipulates the ratio between the radius of curvature of the concave surface of the third lens unit and the first sub unit having a strong curvature and the focal length of the third lens unit. It is. If the lower limit value of the conditional expression range (4) is exceeded, the curvature of the concave surface becomes too weak, and the above-mentioned effect, that is, the angle of emergence of the off-axis light beam and the axis when the light beam entering the concave surface exits from the concave surface The effect of reducing the exit angle of the upper ray cannot be sufficiently achieved. As a result, if the lower limit value of the conditional expression range (4) is exceeded, the light beam emitted from the first sub-group of the third lens group is emitted to the succeeding group while the angle between the off-axis ray and the on-axis ray is large. , Aberrations at the image plane,
In particular, the curvature of field and coma cannot be corrected by the succeeding lens group, which is not desirable. Conversely, when the value exceeds the upper limit of the conditional expression range (4), the curvature of the concave surface becomes too strong, and a very large aberration that occurs alone on the concave surface occurs. Therefore, this aberration is corrected on another surface. Becomes impossible,
Not desirable. When the value exceeds the upper limit value of the conditional expression range (4), the radius of curvature of the concave surface becomes too small, and it is difficult to manufacture, which is not desirable.

In the zoom lens system according to each embodiment, the first lens group includes, in order from the object side, a negative lens having a convex surface on the object side, a biconvex positive lens, and a positive lens having a convex surface on the object side. ing. In order to perform chromatic aberration correction in the first lens group, it is necessary to provide at least one positive lens and at least one negative lens in the first lens group. However, if the first lens group having a positive power as a whole is configured using only one positive lens and one negative lens, it is difficult to correct aberrations on the long focal length side, particularly spherical aberrations. become. Further, in order to correct higher-order spherical aberration on the long focal length side, the first lens group through which axial rays pass at a high ray height has a degree of design freedom (number of lenses) for further aberration correction. It is preferred to give. Further, when the first lens group is configured using only one positive lens and one negative lens, it becomes difficult to perform chromatic aberration correction within the range of the optical constants of existing glass or plastic.

It is desirable that the zoom lens system of each embodiment satisfies the condition defined by the following conditional expression range (5). 1.0 <m1 / Z <3.0 (5) where, m1: the amount of movement (mm) of the first lens group during zooming from the shortest focal length state to the longest focal length state, Z: zoom ratio (Z = ft / fw) : The focal length ratio between the shortest focal length state and the longest focal length state) The above condition represents the relationship between the amount of movement of the first lens unit during zooming from the shortest focal length state to the longest focal length state and the zoom ratio. I have. Generally, as the zoom ratio increases, the amount of movement increases. The condition defined by the conditional expression range (5) is a condition for providing a compact zoom lens having good optical performance by appropriately defining the amount of movement of the first lens group. Conditional expression range (5)
Exceeds the upper limit, the amount of movement of the first lens group is too large compared to the zoom ratio, and the total length in the longest focal length state is too large, so that a compact zoom lens cannot be obtained. Conversely, if the lower limit of the conditional expression range (5) is exceeded,
The moving amount of the first lens group is too small. If the amount of movement of the first lens group is small, the zoom ratio cannot be achieved unless the power of the first lens group is increased. As a result, the power of the first lens group becomes too large, and the amount of aberration generated in the first lens group becomes large, so that good optical performance cannot be obtained as a whole.

It is desirable that the zoom lens system of each embodiment satisfies the condition defined by the following conditional expression range (6). -1.2 <f3 / fw <-0.7 (6) where f3 is the focal length of the third lens group.

The above condition is a condition for defining the focal length of the third lens group. When the value exceeds the upper limit of conditional expression range (6), the overall length in the longest focal length state becomes too large, and it is difficult to obtain a compact zoom lens system. Conversely, when the value goes below the lower limit of the conditional expression range (6), it means that the power of the third lens group becomes excessively large, and the aberration generated in the third lens group, especially the Petzval sum becomes negatively large. A zoom lens system with good performance cannot be achieved in the system.

It is desirable that the zoom lens system of each embodiment satisfies the condition defined by the following conditional expression range (7). 1 <max (T1, T2, T3, T4) / fw <4 (7) where Ti is the thickness on the optical axis of the i-th lens group, and max (T1, T2, T3, T4) is the maximum value, It is.

The above conditions are for achieving a compact and high-magnification zoom lens system. If the lower limit of the conditional expression range (7) is exceeded, the thickness on the optical axis of each lens group becomes too small, and the processing requirements (core thickness, edge thickness, etc.) required for the lenses constituting each lens group are reduced. Not only is it difficult to ensure, but it is not possible to ensure the degree of design freedom required for aberration correction. On the other hand, when the value exceeds the upper limit of the conditional expression range (7), the thickness on the optical axis of each lens unit becomes too large, so that a compact zoom lens system cannot be achieved.

It is desirable that the zoom lens system of each embodiment satisfies the condition defined by the following conditional expression range (8). 6 <Lw / fw <10 (8) where Lw is the total length of the optical system (from the lens tip to the image plane) in the shortest focal length state.

The above condition represents the telephoto ratio in the shortest focal length state. If the lower limit value of the conditional expression range (8) is exceeded, the overall length of the optical system becomes too small, making it difficult to correct aberrations. In addition, it is difficult to satisfy a substantially telecentric condition required for a photographing optical system for a digital camera. Conversely, if the value exceeds the upper limit of conditional expression range (8), compactness cannot be achieved. Furthermore, as the total length increases, the illuminance on the image plane cannot be ensured, so that the diameter of the front lens needs to be increased, so that a compact zoom lens system cannot be achieved.

In each embodiment, it is desirable that the stop be fixed during zooming. When the diaphragm is moved, it is necessary to secure a space for a cam device for moving the diaphragm, a lens barrel, a cam driving device, and the like, and the size of an optical apparatus incorporating the zoom lens system is increasing.

In each embodiment, the aperture is set to the third
It is desirable to arrange between the lens group and the fourth lens group. By arranging the diaphragm between the third lens group and the fourth lens group, it is possible to prevent a decrease in the amount of peripheral light in a well-balanced manner when zooming from the shortest focal length state to the intermediate focal length state.

Further, it is desirable that the diameter of the open stop be constant during zooming. Normally, the aperture is open FNO
The aperture is narrowed down by opening and closing the aperture blades with respect to the circular aperture corresponding to. Further, in consideration of the influence on the image, it is desirable that the aperture shape of the open stop is a circle. Therefore, in consideration of the effect on the image, if the diameter of the open aperture is different at each focal length state during zooming, the aperture is controlled by either performing this circular aperture with aperture blades or arranging a plurality of circular apertures. You need to control. However, in the case of using the former diaphragm blade, a small number of diaphragm blades requires a large number of blades, such as five or six blades, in order to obtain a distorted opening shape and to approach a circle, which inevitably increases the cost. Further, when a plurality of circular openings are provided as in the latter case, not only the cost is increased but also a space for inserting the circular openings in the optical axis direction is required, so that the size of the optical system is increased.

[0039]

EXAMPLES Examples of the present invention will be described below with reference to construction data, aberration diagrams and the like.

The following Examples 1 to 3 respectively correspond to the above-described embodiments, and the lens arrangement diagrams representing the embodiments respectively show the lens configurations of the corresponding Examples 1 to 3.

In each embodiment, ri (i = 1, 2, 3,.
•) is the radius of curvature of the i-th surface counted from the object side, di (i =
) Indicates the i-th axial distance from the object side, and Ni (i = 1, 2, 3,...), Νi (i = 1, 2, 3, 3)
···) indicates the refractive index and Abbe number of the i-th lens counted from the object side with respect to the d-line. F represents the focal length of the entire system, and FNO represents the F number. In each embodiment, the focal length f of the entire system, the F-number FNO, and the air interval between the lens groups (axial upper surface interval) are, in order from the left, the shortest focal length end (wide angle end) (W), the middle The values correspond to the focal length (M) and the longest focal length end (telephoto end) (T).

Further, in each of the embodiments, the surface marked with * for the radius of curvature ri indicates a refractive optical surface having an aspherical shape, and is defined by the following expression representing the aspherical surface shape. .

X (H) = CH ² / ｛1+ (1-εC ² · H ² ) ^1/2 ｝ +｝ Ai · Hi (AS) where H: height in the direction perpendicular to the optical axis X (H): Displacement in the optical axis direction at the position of height H (based on surface vertex), C: Paraxial curvature, ε: Quadratic surface parameter, Ai: i-th order aspherical coefficient, Hi: H A symbol representing the i-th power of.

Example 1 f = 5.13 to 15.50 to 48.75 Fno = 2.66 to 3.56 to 4.10 [Radius of curvature] [Shaft upper surface interval] [Refractive index] [Abbe number] r1 = 23.669 d1 = 0.80 N1 = 1.849388 ν1 = 35.61 r2 = 15.029 d2 = 3.98 N2 = 1.588644 ν2 = 59.81 r3 = -147.036 d3 = 0.30 to 5.64 to 11.11 r4 = 42.197 d4 = 0.60 N3 = 1.847159 ν3 = 25.36 r5 = 23.400 d5 = 0.10 r6 = 10.023 d6 = 1.44 N4 = 1.503654 ν4 = 68.18 r7 * = 22.987 d7 = 0.30 ~ 5.10 ~ 9.44 r8 * = 14.424 d8 = 0.60 N5 = 1.782539 ν5 = 47.23 r9 * = 4.482 d9 = 3.24 r10 = -5.223 d10 = 0.60 N6 = 1.604389 ν6 = 58.70 r11 = 9.483 d11 = 0.96 N7 = 1.846660 ν7 = 23.82 r12 = -46.927 d12 = 6.09 ~ 2.29 ~ 0.10 r13 = ∞ d13 = 4.00 ~ 2.10 ~ 0.10 r14 * = 5.783 d14 = 2.33 N8 = 1.540252 ν8 = 63.98 r15 * = 15.691 d15 = 0.10 r16 = 5.798 d16 = 1.26 N9 = 1.807872 ν9 = 22.84 r17 = 3.458 d17 = 2.35 N10 = 1.487490 ν10 = 70.44 r18 = -18.251 d18 = 1.67 r19 * = 20.653 d19 = 0.64 N11 = 1.812273 ν11 = 43.62 r20 * = 16.906 d20 = 0.97〜 4.94〜 5.92 r21 = ∞ d21 = 3.70 N12 = 1.516800 ν12 = 64.20 r22 = ∞ [aspheric coefficient] r7 ε = 1.0000 A4 = 0.38500 × 10 ^-4 A6 = -0.10549 × 10 ^-5 A8 = 0.80390 × 10 ^-7 A10 = -0.31137 × 10 ^-8 A12 = 0.42844 × 10 ^-10 r8 ε = 1.0000 A4 = 0.30610 × 10 ^-3 A6 = -0.14630 × 10 ^-4 A8 = 0.10850 × 10 ^-5 A10 = 0.22479 × 10 ^-7 A12 = -0.99872 × 10 ^-9 r9 ε = 1.0000 A4 = -0.31241 × 10 ^-4 A6 = -0.76166 × 10 ^-5 A8 = 0.63520 × 10 ^-5 A10 = -0.11683 × 10 ^-5 A12 = 0.10450 × 10 ^-6 r14 ε = -1.2300 A4 = 0.34248 × 10 ^-3 A6 = -0.54773 × 10 ^-4 A8 = -0.20516 × 10 ^-5 A10 ^{= 0.77299 × 10 -7 A12 = -0.24094} × 10 -7 r15 ε = -23.9935 A4 = -0.39361 × 10 -3 A6 = -0.10203 × 10 -3 A8 = -0.13249 × 10 -6 A10 = -0.31746 × 10 - ⁶ A12 = -0.93381 × 10 ^-8 r19 ε = -262.8239 A4 = -0.97943 × 10 ^-2 A6 = -0.48211 × 10 ^-3 A8 = -0.39839 × 10 ^-4 A10 = 0.18777 × 10 ^-5 A12 = 0.43083 × 10 ^-6 r20 ε = -219.7065 A4 = -0.74424 × 10 ^-2 A6 = -0.59951 × 10 ^-3 A8 = 0.49871 × 10 ^-4 A10 = -0.44076 × 10 ^-7 A12 = -0.26050 × 10 ^-7 << Example 2 》 F = 5.13〜15.53〜48.75 Fno = 2.66〜 3.56〜 4.10 [Radius of curvature] [Spacing of shaft top surface] [Refractive index] [Abbe number] r1 = 42.497 d1 = 0.80 N1 = 1.847039 ν1 = 24.97 r2 = 22.419 d2 = 3.1 1 N2 = 1.711368 ν2 = 53.15 r3 = 174.766 d3 = 0.30 to 5.15 to 8.70 r4 = 17.562 d4 = 1.45 N3 = 1.710091 ν3 = 53.20 r5 = 28.856 d5 = 0.10 to 9.37 to 18.65 r6 * = 15.020 d6 = 0.60 N4 = 1.604151 ν4 = 58.72 r7 * = 5.591 d7 = 4.59 r8 = -6.044 d8 = 0.60 N5 = 1.707455 ν5 = 50.48 r9 = 7.823 d9 = 0.97 N6 = 1.846660 ν6 = 23.82 r10 = -528.494 d10 = 8.95〜 3.95〜 0.10 r11 = ∞ d11 = 0.10 r12 * = 11.489 d12 = 0.77 N7 = 1.743632 ν7 = 51.94 r13 * =-765.019 d13 = 0.52 ~ 0.10 ~ 0.05 r14 = 6.888 d14 = 0.95 N8 = 1.846660 ν8 = 23.82 r15 = 4.261 d15 = 5.30 N9 = 1.487490 ν9 = 70.44 r16 = -9.005 d16 = 3.03 r17 * =-181.264 d17 = 2.64 N10 = 1.846660 ν10 = 23.82 r18 * = 28.221 d18 = 0.50〜 4.68〜 7.30 r19 = ∞ d19 = 3.70 N11 = 1.516800 ν11 = 64.20 r20 = ∞ Coefficient] r6 ε = 1.0000 A4 = 0.79545 × 10 ^-3 A6 = 0.10681 × 10 ^-4 A8 = 0.14973 × 10 ^-6 A10 = -0.14948 × 10 ^-7 A12 = 0.37412 × 10 ^-9 r7 ε = 1.0000 A4 = 0.93137 × 10 ^-4 A6 = 0.32332 × 10 ^-4 A8 = -0.32740 × 10 ^-6 A10 = 0.23254 × 10 ^-7 A12 = 0.18805 × 10 ^-8 r12 ε = -2.0209 A4 = 0.79594 × 10 ^-4 A6 = -0.55679 × 10 ^-Four A8 = -0.36047 × 10 ^-5 A10 = -0.48183 × 10 ^-6 A12 = 0.68433 × 10 ^-8 r13 ε = 51835.4939 A4 = 0.12155 × 10 ^-3 A6 = -0.66671 × 10 ^-4 A8 = -0.19190 × 10 ^-5 A10 = -0.54460 × 10 ^-6 A12 = 0.65257 × 10 ^-8 r17 ε = -8963.6309 A4 = -0.24694 × 10 ^-2 A6 = -0.97831 × 10 ^-5 A8 = 0.76162 × 10 ^-6 A10 = 0.18169 × 10 ^-6 A12 = -0.28538 × 10 ^-8 r18 ε = -230.0027 A4 = -0.85 140 × 10 ^-3 A6 = -0.10417 × 10 ^-3 A8 = 0.99233 × 10 ^-5 A10 = -0.11358 × 10 ^-6 A12 = -0.50470 × 10 ^-8 << Example 3 >> f = 5.13 ~ 15.53 ~ 48.75 Fno = 2.66 ~ 3.56 ~ 4.10 [Radius of curvature] [Shaft upper surface interval] [Refractive index] [Abbe number] r1 * = 35.208 d1 = 0.80 N1 = 1.847058 ν1 = 25.03 r2 = 22.017 d2 = 2.83 N2 = 1.646732 ν2 = 56.15 r3 = 131.810 d3 = -0.09 r4 = 23.598 d4 = 1.69 N3 = 1.551261 ν3 = 62.91 r5 = 62.089 d5 = 0.30〜 9.61〜 19.63 r6 = 45.313 d6 = 0.60 N4 = 1.847851 ν4 = 27.85 r7 = 23.101 d7 = 0.10 r8 = 12.011 d8 = 1.99 N5 = 1.516706 ν5 = 66.55 r9 * = 142.466 d9 = 0.30〜 2.08〜 2.88 r10 = 22.155 d10 = 0.60 N6 = 1.755731 ν6 = 51.36 r11 * = 4.375 d11 = 1.37 r12 = 45.481 d12 = 0.60 N7 = 1.580806 ν7 = 60.27 r 13 = 44.894 d13 = 1.40 r14 = -5.149 d14 = 0.60 N8 = 1.581668 ν8 = 60.34 r15 = 9.295 d15 = 0.89 N9 = 1.846865 ν9 = 24.43 r16 = -48.451 d16 = 5.61 ~ 1.67 ~ 0.10 r17 = ∞ d17 = 4.19 ~ 2.78 ~ 0.10 r18 = 6.404 d18 = 2.41 N10 = 1.754785 ν10 = 51.52 r19 * =-56.050 d19 = 0.19 r20 = 508.618 d20 = 0.60 N11 = 1.831428 ν11 = 23.44 r21 = 9.812 d21 = 0.10 r22 = 6.068 d22 = 0.76 N12 = 1.798500 ν12 = 22.60 r23 = 5.681 d23 = 0.10 r24 = 4.615 d24 = 2.14 N13 = 1.487974 ν13 = 70.37 r25 = -9.907 d25 = 0.19 r26 = -10.899 d26 = 0.69 N14 = 1.785707 ν14 = 35.49 r27 * =-121.957 d27 = 2.22 to 5.47 ~ 4.90 r28 = ∞ d28 = 3.70 N15 = 1.516800 ν15 = 64.20 r29 = ∞ [Aspherical surface coefficient] r1 ε = 1.0000 A4 = -0.28052 × 10 ^-6 A6 = -0.51899 × 10 ^-8 A8 = 0.11505 × 10 ^-9 A10 = -0.12632 × 10 ^-11 A12 = 0.48961 × 10 ^-14 r9 ε = 1.0000 A4 = 0.13610 × 10 ^-4 A6 = -0.37279 × 10 ^-5 A8 = 0.37951 × 10 ^-7 A10 = 0.11805 × 10 ^-8 A12 =- 0.17702 × 10 ^-10 r11 ε = 1.0000 A4 = -0.41292 × 10 ^-3 A6 = 0.55282 × 10 ^-5 A8 = 0.12007 × 10 ^-4 A10 = -0.19595 × 10 ^-5 A12 = 0.10450 × 10 ^-6 r19 ε = 1 .0 ^{00 A4 = 0.43656 × 10 -3 A6} = -0.27060 × 10 -4 A8 = 0.25790 × 10 -5 A10 = -0.18154 × 10 -6 A12 = 0.62168 × 10 -8 r27 ε = -8963.6309 A4 = -0.24694 × ^{10 -2 A6 = -0.97831 × 10 -5} A8 = 0.76162 × 10 -6 A10 = 0.18169 × 10 -6 A12 = -0.28538 × 10 -8 r27 ε = 1.0000 A4 = 0.23012 × 10 -2 A6 = 0.16634 × 10 - ³ A8 = −0.93127 × 10 ⁻⁵ A10 = 0.13468 × 10 ⁻⁵ A12 = −0.26050 × 10 ⁻⁷ FIGS. 4 to 6 are aberration diagrams corresponding to Examples 1 to 3. Each aberration diagram represents a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram in order from the left side. Each aberration diagram shows, in order from the top, aberrations of the optical system corresponding to the shortest focal length state (wide-angle end), the intermediate focal length state, and the longest focal length state (telephoto end).

In each of the spherical aberration diagrams, the solid line d represents the amount of spherical aberration with respect to the d-line, and SC represents the amount of sine condition unsatisfaction. Also,
In each astigmatism diagram, a solid line DS is a sagittal surface, and a dotted line D
M represents a meridional surface, respectively. The vertical axis of the spherical aberration diagram represents the F-number of the light ray, and the vertical axes of the astigmatism diagram and the distortion diagram represent the maximum image height Y ′.

The values corresponding to the conditional expressions in each embodiment are shown below.

Embodiment 1 (1) (Dt-Dw) / fw: 1.78 (2) βt2 / βw2: 1.10 (3) img × R: 8.89 (4) f3 / rn: -1.07 (5) m1 / Z: 1.58 (6) f3 / fw <-0.7: -0.93 (7) max (T1, T2, T3, T4) / fw: 1.63 (4th lens group) (8) Lw / fw: 7.80 << Embodiment 2 (1) (Dt-Dw) / fw: 3.62 (2) βt2 / βw2: 1.06 (3) img × R: 8.00 (4) f3 / rn: -0.94 (5) m1 / Z: 2.57 (6) f3 /fw<-0.7: -1.02 (7) max (T1, T2, T3, T4) / fw: 2.32 (fifth lens group) (8) Lw / fw: 7.80 << Embodiment 3 >> (1) (Dt- Dw) / fw: 0.50 (2) βt2 / βw2: 1.30 (3) img × R: 8.15 (4) f3 / rn: -1.02 (5) m1 / Z: 1.58 (6) f3 / fw <-0.7:- 0.87 (7) max (T1, T2, T3, T4) / fw: 1.35 (4th lens group) (8) Lw / fw: 7.82

[0048]

As described in detail above, according to the zoom lens system of the present invention, it is possible to provide a compact zoom lens system despite satisfying high image quality at a high magnification. is there.

Therefore, when the zoom lens system according to the present invention is applied to a photographing optical system of a digital camera, it is possible to contribute to a higher function and a smaller size of the camera.

[Brief description of the drawings]

FIG. 1 is a lens configuration diagram of a zoom lens system according to a first embodiment.

FIG. 2 is a lens configuration diagram of a zoom lens system according to a second embodiment.

FIG. 3 is a lens configuration diagram of a zoom lens system according to a third embodiment.

FIG. 4 is an aberration diagram of the zoom lens system according to the first embodiment.

FIG. 5 is an aberration diagram of a zoom lens system according to a second embodiment.

FIG. 6 is an aberration diagram of a zoom lens system according to a third embodiment.

[Explanation of symbols]

 Gr1: first lens group Gr2: second lens group Gr3: third lens group Gr4: fourth lens group Gr5: fifth lens group

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoshi Okada 2-3-13 Azuchicho, Chuo-ku, Osaka-shi Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Tetsuo Kono 2-chome Azuchicho, Chuo-ku, Osaka-shi No. 13 Osaka International Building Minolta Co., Ltd. (72) Inventor Kazuhiko Ishimaru 2-3-13 Azuchicho, Chuo-ku, Osaka City Osaka International Building Minolta Co., Ltd.

Claims (3)

[Claims] A first lens group having a positive power, a second lens group having a positive power, a third lens group having a negative power, and a subsequent group. At the time of zooming from the shortest focal length state to the longest focal length state, the axial distance between the first lens group and the second lens group and the axial distance between the second lens group and the third lens group are both equal. A zoom lens system wherein at least the first lens group and the third lens group move to the object side so as to increase. 2. The zoom lens system includes, in order from an object side, a first lens group having a positive power, a second lens group having a positive power, a third lens group having a negative power, and a positive lens group. The zoom lens system according to claim 1, further comprising a fourth lens group having the following power: 3. The zoom lens system includes, in order from an object side, a first lens group having a positive power, a second lens group having a positive power, a third lens group having a negative power, and a positive lens group. 2. The zoom lens system according to claim 1, further comprising a fourth lens group having a positive power and a fifth lens group Gr5 having a positive power.