JPH10282417A - Compact zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compact standard zoom lens having a wide viewing angle by respectively providing a 1st lens group and a 2nd lens group with at least one aspherical surface and satisfying a specified condition. SOLUTION: The 1st lens group is constituted of two lenses being the 1st lens having negative power and the 2nd lens having positive power in turn from an object side. Then, the 1st lens group and the 2nd lens group are respectively provided with at least one aspherical surface so as to satisfy the condition of an expression. In the expression, f1 shows the focal distance of the 1st lens group, (fw) shows the focal distance of a whole system at the minimum focal distance end and (ft) shows the focal distance of the whole system at the maximum focal distance end. Besides, TDt shows a distance to the top of the surface of the 2nd lens group on the most image side from the top of the surface of the 1st lens on the object side at the maximum focal distance end, x2 shows the moving amount of the 2nd lens group in an optical axis direction (provided that the movement to the image side is defined as positive) a zooming time, BFw shows a back focus at the minimum focal distance end and Ymax shows the maximum image height.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact zoom lens, and more particularly to a small and wide-angle zoom lens suitable for use as a photographing lens for a single-lens reflex camera.

[0002]

2. Description of the Related Art In order to achieve compactness, various types of zoom lenses for single-lens reflex cameras composed of two groups, negative and positive, have been proposed in JP-A-4-46308, JP-A-5-88084 and the like. ing. On the other hand, JP-A-4-4630
8, JP-A-5-249374, JP-A-8-249.
No. 68938 proposes a standard zoom lens having a wide angle of view.

[0003]

Problems to be Solved by the Invention
JP, JP-A-5-249374, JP-A-8-6
Japanese Patent No. 8938 proposes a zoom lens having an angle of view of about 80 degrees at the wide end and effective for widening the angle of view. However, such a zoom lens has sufficient performance in terms of compactness. Has not been achieved.
Also, JP-A-4-46308, JP-A-5-880
No. 84 proposes a zoom lens that has been made compact, but such a zoom lens includes:
There is a problem that the angle of view is narrow. When trying to widen the angle of view, the front lens diameter must be increased due to lack of illuminance, or the number of aspherical surfaces must be increased by reducing the number of lenses. There is.

[0004] The present invention has been made in view of such circumstances, and has as its object to provide a small-sized standard zoom lens having a wide angle of view.

[0005]

In order to achieve the above object, a zoom lens according to a first aspect of the present invention comprises, in order from the object side, a first lens group having a negative power and a second lens group having a positive power. A first lens unit having positive power and a first lens having negative power in order from the object side, wherein the first lens unit and the second lens unit move together during zooming. The first lens group and the second lens
Each lens group has at least one aspheric surface, and satisfies the following conditions. -0.895 <f1 / √ (fw · ft) <-1.07 0.63 <TDt / √ (fw · ft) <0.9 0 <| x2 | / fw <1.0 0.63 <BFw / Ymax <1.62 where f1: first lens group Fw: focal length of the entire system at the minimum focal length end, ft: focal length of the entire system at the maximum focal length end, TDt: from the surface vertex of the object side surface of the first lens at the maximum focal length end X2: distance of the second lens unit in the optical axis direction during zooming
(However, it is positive when moving to the image side.), BFw: Back focus at minimum focal length end, Ymax: Maximum image height.

A zoom lens according to a second aspect of the present invention is the zoom lens according to the first aspect, wherein the lens closest to the image in the second lens group has a positive power and satisfies the following condition. It is characterized by. 2.0 <fe / f2 <100 where f2 is the focal length of the second lens group, and fe is the focal length of the lens closest to the image in the second lens group.

According to a third aspect of the present invention, in the zoom lens system according to the first aspect, at least one aspherical surface provided in the first lens group satisfies the following condition. . 0 <| {x (y) -x0 (y)} / fasp | <0.2 where x (y) is the light at height y in the direction perpendicular to the optical axis when the apex of the aspheric surface is the origin. The displacement in the axial direction, which is expressed by the following equation: x (y) = {c · y ² } / {1 + 1- (1-ε · c ² · y ² )} + ΣAiY ⁱ (where i
≧ 2. Where c: curvature, ε: quadratic surface parameter, Ai: i-th aspherical coefficient, x0 (y): the shape of the reference sphere with respect to the aspherical surface, and the apex of the aspherical surface the a displacement amount of the optical axis in the vertical height y from the optical axis when the origin, the following formula: x0 (y) = {c · y 2} / {1 + √ (1 -c ² · y ² )}, where fasp is the focal length of the aspheric surface.

According to a fourth aspect of the present invention, in the zoom lens system according to the first aspect, the second lens group includes, in order from the object side, a third lens having a positive power and a fourth lens having a positive power. It is characterized by comprising a lens, a fifth lens having a negative power, and a sixth lens having a positive power.

According to a fifth aspect of the present invention, in the zoom lens system according to the first or second aspect, the second lens group has a lens having negative power and satisfying the following condition. It is characterized by. 0.03 <D5 / TDt <0.13 where D5 is the core thickness of the lens having negative power.

According to a sixth aspect of the present invention, in the zoom lens system according to the first or second aspect, the second lens group includes a lens having a negative power and a positive power disposed on the image side thereof. And a lens that satisfies the following conditions. 0.70 <D5,6 / TDt <0.15, where D5,6 is the distance between the image side surface of the lens having negative power and the object side surface of the lens having positive power.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a zoom lens embodying the present invention will be described with reference to the drawings. 1 to 3 are lens configuration diagrams respectively corresponding to the zoom lenses according to the first to third embodiments, and show a wide end (minimum focal length end) [W].
2 shows the lens arrangement. Arrow m1 in FIGS.
And m2 are from the wide end (minimum focal length end) [W] to the tele end.
(Maximum focal length end) In zooming up to [T],
The movement of the first lens group Gr1 and the movement of the second lens group Gr2 are schematically shown. In the lens configuration diagram, ri (i = 1,
The surface marked with (2,3, ...) is the i-th surface counted from the object side, and the distance between the shaft top surfaces marked with di (i = 1,2,3, ...) is the object side Is the i-th axial top surface interval, and gi (i = 1, 2,
(3, ...) are the i-th lenses counted from the object side. Also, the surface marked with * for ri is an aspheric surface.

The first to third embodiments include, in order from the object side, a first lens unit Gr1 having a negative power and a second lens unit Gr2 having a positive power.
As shown by arrows m1 and m2 in FIG. 3, the zoom lens is of a type in which the first lens group Gr1 and the second lens group Gr2 move together during zooming.

In the first embodiment (FIG. 1), each lens group is configured as follows in order from the object side. The first lens group Gr1 includes a negative meniscus lens g1 convex on the object side and a positive meniscus lens g2 convex on the object side (both surfaces are aspherical). The second lens group Gr2 is
Aperture A, biconvex positive lens g3, and biconvex positive lens g4
And a biconcave negative lens g5 and a positive meniscus lens g6
(Both sides are aspheric).

In the second embodiment (FIG. 2), each lens group is configured as follows from the object side. The first lens group Gr1 includes a negative meniscus lens g1 (both surfaces are aspheric) convex to the object side, and a positive meniscus lens g2 convex to the object side. The second lens group Gr2 includes an aperture A, a positive meniscus lens g3 convex to the object side, a biconvex positive lens g4, a biconcave negative lens g5, and a positive meniscus lens g6 (both surfaces are aspherical). Consists of

In the third embodiment (FIG. 3), each lens unit is configured as follows in order from the object side. The first lens group Gr1 includes a negative meniscus lens g1 convex on the object side and a positive meniscus lens g2 (image side surface is aspheric) convex on the object side. Second lens group Gr2
Is the aperture A and the positive meniscus lens g3 convex on the object side.
And a biconvex positive lens g4, a biconcave negative lens g5, and a positive meniscus lens g6 (both surfaces are aspherical).

As described above, in the first to third embodiments, the first lens unit Gr1 includes, in order from the object side, the first lens g1 having a negative power and the second lens g2 having a positive power. The second lens group Gr includes two lenses.
Reference numeral 2 denotes an aperture A; a third lens g3 having positive power, and a fourth lens g having positive power, in order from the object side.
4, a fifth lens g5 having a negative power, and a sixth lens g6 having a positive power. Also, the first lens group Gr1 and the second lens group Gr
2 has at least one aspheric surface.

The first to third embodiments satisfy the following conditional expressions (1) to (4). In the zoom lens having a wide angle of view, by satisfying conditional expressions (1) to (4), it is possible to achieve compactness while securing sufficient performance. -0.895 <f1 / √ (fw · ft) <-1.07… (1) 0.63 <TDt / √ (fw · ft) <0.9… (2) 0 <| x2 | / fw <1.0… (3) 0.63 <BFw /Ymax<1.62 (4) where f1: focal length of the first lens group Gr1, fw: focal length of the entire system at the minimum focal length end [W], ft: total at the maximum focal length end [T]. Focal length of the system, TDt: from the vertex of the object side surface (surface of r1) of the first lens g1 of [T] at the end of the maximum focal length, to the image side of the second lens group Gr2
x2: the amount of movement of the second lens group Gr2 in the optical axis direction during zooming (however, the movement toward the image side is positive), BFw: minimum focal length Back focus at end [W], Ymax: maximum image height.

By satisfying conditional expression (1), the front lens diameter can be reduced. However, if the lower limit of conditional expression (1) is exceeded, it becomes difficult to correct aberrations (especially correction of distortion). When the value exceeds the upper limit of the expression (1), the front lens diameter becomes too large. When the value exceeds the upper limit of the conditional expression (2), it is not desirable in terms of compactness. Further, by satisfying conditional expressions (3) and (4), the lens barrel length can be reduced.

In the first to third embodiments, the lens g6 closest to the image side of the second lens group Gr2 has a positive power and satisfies the following conditional expression (5). . 2.0 <fe / f2 <100 (5) where f2 is the focal length of the second lens group Gr2, and fe is the focal length of the most image-side lens g6 of the second lens group Gr2.

Conditional expression (5) defines the power of the positive lens component provided closest to the image side of the second lens group Gr2. If the lower limit of conditional expression (5) is exceeded, the power of the positive lens component provided closest to the image side becomes too strong, especially at the wide-angle end.
As the distortion at [W] increases, the absolute value of the Petzval sum increases, and it becomes difficult to correct both. vice versa,
When the value exceeds the upper limit of conditional expression (5), the power of the positive lens component provided closest to the image side becomes too weak, and the field curvature at the wide end [W] tends to fall to the under side, which is desirable. Absent.

In the first to third embodiments, at least one aspherical surface provided in the first lens unit Gr1 satisfies the following conditional expression (6). 0 <| {x (y) -x0 (y)} / fasp | <0.2 (6) where x (y) is the height in the direction perpendicular to the optical axis when the apex of the aspheric surface is set as the origin. The displacement amount in the optical axis direction at y, which is represented by the following equation (AS1): x (y) = {c · y ² } / {1 + √ (1-ε · c ² · y ² )} + ΣAiY ⁱ (Where i
≧ 2. ) ... (AS1), where c: curvature, ε: quadratic surface parameter, Ai: i-th aspheric coefficient, x0 (y): the shape of the reference sphere with respect to the aspheric surface, Height in the direction perpendicular to the optical axis when the surface vertex of the sphere is the origin
A displacement amount of the optical axis direction in the y, the following equation (AS2): x0 (y) = {c · y 2} / {1 + √ (1-c 2 · y 2)} ... (AS2) Where fasp is the focal length of the aspheric surface.

By satisfying conditional expression (6), high performance can be ensured. If the lower limit of conditional expression (6) is exceeded, it will be difficult to correct distortion. If the upper limit of conditional expression (6) is exceeded, manufacturing will be difficult.

In the first to third embodiments, the second lens unit Gr2 has a negative power and the following conditional expression:
The lens g5 satisfying (7) is provided. By having such a lens g5, compactness can be achieved. 0.03 <D5 / TDt <0.13 (7) where D5 is the core thickness of the lens g5 having negative power.

In the first to third embodiments, the second lens unit Gr2 includes a lens g5 having a negative power and a lens g6 having a positive power disposed on the image side thereof.
The following conditional expression (8) is satisfied. By having the lenses g5 and g6 in this way, compactness can be achieved. 0.70 <D5,6 / TDt <0.15 (8) where D5,6 is the image side surface (r11 surface) of the lens g5 having negative power and the object side surface (r12 surface) of the lens g6 having positive power. (D11).

By satisfying conditional expressions (7) and (8), compactness can be achieved while ensuring sufficient performance. If the upper limits of conditional expressions (7) and (8) are exceeded, the overall length of the lens system becomes too large, which is not preferable in terms of compactness. If the lower limits of conditional expressions (7) and (8) are exceeded, it becomes difficult to correct aberrations (especially, correction of distortion and curvature of field) at each zoom position.

Also, as in the first to third embodiments,
The aspheric surface is the last lens (g) of each lens group Gr1 and Gr2.
2, g6). Each lens group G
By adding an aspherical surface to the last lens of r1 and Gr2, it becomes possible to effectively correct distortion and to facilitate adjustment during lens assembly.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a zoom lens embodying the present invention will be described more specifically with reference to construction data, aberration diagrams, and the like. Examples 1 to 1 given here as examples
Reference numeral 3 corresponds to the above-described first to third embodiments, respectively, and is a lens configuration diagram illustrating the first to third embodiments.
(FIGS. 1 to 3) show the corresponding lens configurations of Examples 1 to 3, respectively.

In the construction data of each embodiment, ri (i = 1, 2, 3,...) Is the radius of curvature of the i-th surface counted from the object side, and di (i = 1, 2, 3,. ..) indicates the i-th axial top surface distance counted from the object side, and Ni (i = 1, 2, 3, ...), νi (i = 1, 2,
3,...) Indicate the refractive index (Nd) and Abbe number (νd) of the i-th lens from the object side with respect to the d-line. A surface with a * mark on the radius of curvature ri indicates a surface constituted by an aspheric surface, and is defined by the above-described equation (AS1) representing the surface shape of the aspheric surface.

In the construction data, the distance between the upper surfaces of the axes (variable distance) that changes during zooming is from the wide end (minimum focal length end) [W] to the middle (intermediate focal length state).
This is the axial distance between the first lens unit Gr1 and the second lens unit Gr2 from [M] to the tele end (the maximum focal length end) [T].
Focal length f and F-number FNO of the whole system corresponding to each focal length state [W], [M], [T], and corresponding value of conditional expression (6) regarding aspheric surface {where, ymax: light of aspheric surface The maximum height (maximum effective diameter) perpendicular to the axis. } Are shown together with the construction data of each embodiment, and Table 1 shows corresponding values of the conditional expressions (1) to (5), (7), and (8) for each embodiment.

[0030]

[Aspherical surface coefficient of the third surface (r3)] ε = 1.0000 A4 = 0.14484652 × 10 ^-4 A6 = -0.65291776 × 10 ^-8 A8 = -0.67425630 × 10 ^-9 A10 = -0.13865674 × 10 ^-11 A12 = -0.93879171 × 10 ^-13

[Aspherical surface coefficient of fourth surface (r4)] ε = 1.0000 A4 = -0.20328051 × 10 ^-4 A6 = 0.20961320 × 10 ^-7 A8 = -0.62490139 × 10 ^-8 A10 = 0.50142956 × 10 ^-10 A12 = -0.32403584 × 10 ^-12

[Aspherical surface coefficient of the twelfth surface (r12)] ε = 1.0000 A4 = 0.72739758 × 10 ^-4 A6 = 0.10671272 × 10 ^-4 A8 = -0.35037130 × 10 ^-6 A10 = 0.90593566 × 10 ^-8 A12 =- 0.10805872 × 10 ^-9

[Aspherical surface coefficient of the thirteenth surface (r13)] ε = 1.0000 A4 = 0.22430848 × 10 ^-3 A6 = 0.79942847 × 10 ^-5 A8 = -0.12294852 × 10 ^-6 A10 = 0.31220146 × 10 ^-8 A12 =- 0.37244056 × 10 ^-10

[Corresponding value of conditional expression (6) on the third surface (r3)] y = 0.00ymax ... | {x (y) -x0 (y)} / fasp | = 0.00 y = 0.10ymax ... | {x (y) -x0 (y)} / fasp | = 1.29 × 10 ^-7 y = 0.20ymax… | {x (y) -x0 (y)} / fasp | = 2.12 × 10 ^-6 y = 0.30ymax… | {x (y) -x0 (y)} / fasp | = 1.07 × 10 ⁻⁵ y = 0.40ymax… | {x (y) −x0 (y)} / fasp | = 3.36 × 10 ⁻⁵ y = 0.50ymax ... | {x (y) -x0 (y)} / fasp | = 8.08 × 10 ^-5 y = 0.60ymax… | {x (y) -x0 (y)} / fasp | = 1.63 × 10 ^-4 y = 0.70ymax ... | {x (y) -x0 (y)} / fasp | = 2.88 × ^10-4 y = 0.80ymax ... | {x (y) -x0 (y)} / fasp | = 4.48 × ^10-4 y = 0.90ymax ... | {x (y) -x0 (y)} / fasp | = 5.98 × 10 ^-4 y = 1.00ymax ... | {x (y) -x0 (y)} / fasp | = 5.96 × 10 ^-Four

[Corresponding value of conditional expression (6) for fourth surface (r4)] y = 0.00ymax ... | {x (y) -x0 (y)} / fasp | = 0.00 y = 0.10ymax ... | {x (y) -x0 (y)} / fasp | = 1.14 × 10 ^-7 y = 0.20ymax… | {x (y) -x0 (y)} / fasp | = 1.76 × 10 ^-6 y = 0.30ymax… | {x (y) -x0 (y)} / fasp | = 8.96 × 10 ⁻⁶ y = 0.40ymax… | {x (y) −x0 (y)} / fasp | = 2.88 × 10 ⁻⁵ y = 0.50ymax … | {X (y) -x0 (y)} / fasp | = 7.31 × 10 ⁻⁵ y = 0.60ymax… | {x (y) −x0 (y)} / fasp | = 1.62 × 10 ⁻⁴ y = 0.70ymax ... | {x (y) -x0 (y)} / fasp | = 3.28 × ^10-4 y = 0.80ymax ... | {x (y) -x0 (y)} / fasp | = 6.32 × ^10-4 y = 0.90ymax ... | {x (y) -x0 (y)} / fasp | = 1.17 × ^10-3 y = 1.00ymax ... | {x (y) -x0 (y)} / fasp | = 2.14 × 10 ^-3

[0037]

[Aspherical surface coefficient of the first surface (r1)] ε = 1.0000 A4 = 0.41236826 × 10 ^-4 A6 = -0.63124702 × 10 ^-6 A8 = 0.48175257 × 10 ^-8 A10 = -0.21015355 × 10 ^-10 A12 = 0.40523287 × 10 ^-13

[Aspherical surface coefficient of the second surface (r2)] ε = 1.0000 A4 = 0.92361079 × 10 ^-5 A6 = -0.34522097 × 10 ^-6 A8 = -0.12050970 × 10 ^-7 A10 = 0.15457952 × 10 ^-9 A12 = -0.10054946 × 10 ^-11

[Aspherical surface coefficient of twelfth surface (r12)] ε = 1.0000 A4 = 0.33597140 × 10 ^-3 A6 = 0.17597856 × 10 ^-4 A8 = -0.52481319 × 10 ^-6 A10 = 0.12254211 × 10 ^-7 A12 =- 0.15885783 × 10 ^-9

[Aspherical surface coefficient of the thirteenth surface (r13)] ε = 1.0000 A4 = 0.43809173 × 10 ^-3 A6 = 0.14713782 × 10 ^-4 A8 = -0.27099882 × 10 ^-6 A10 = 0.61410112 × 10 ^-8 A12 =- 0.93541272 × 10 ^-10

[Corresponding value of conditional expression (6) for first surface (r1)] y = 0.00ymax ... | {x (y) -x0 (y)} / fasp | = 0.00 y = 0.10ymax ... | {x (y) -x0 (y)} / fasp | = 5.65 × 10 ^-7 y = 0.20ymax… | {x (y) -x0 (y)} / fasp | = 8.47 × 10 ^-6 y = 0.30ymax… | {x (y) -x0 (y)} / fasp | = 3.88 × 10 ⁻⁵ y = 0.40ymax… | {x (y) −x0 (y)} / fasp | = 1.06 × 10 ⁻⁴ y = 0.50ymax ... | {x (y) -x0 (y)} / fasp | = 2.17 × 10 ^-4 y = 0.60ymax… | {x (y) -x0 (y)} / fasp | = 3.62 × 10 ^-4 y = 0.70ymax ... | {x (y) -x0 (y)} / fasp | = 5.20 × ^10-4 y = 0.80ymax ... | {x (y) -x0 (y)} / fasp | = 6.65 × ^10-4 y = 0.90ymax ... | {x (y) -x0 (y)} / fasp | = 7.68 × 10 ^-4 y = 1.00ymax ... | {x (y) -x0 (y)} / fasp | = 8.08 × 10 ^-Four

[0043]

[Aspherical surface coefficient of fourth surface (r4)] ε = 1.0000 A4 = -0.39007489 × 10 ^-4 A6 = 0.10652789 × 10 ^-6 A8 = -0.66657690 × 10 ^-8 A10 = 0.73240637 × 10 ^-10 A12 = -0.39878293 × 10 ^-12

[Aspherical surface coefficient of the twelfth surface (r12)] ε = 1.0000 A4 = 0.91716676 × 10 ^-4 A6 = 0.11649911 × 10 ^-4 A8 = -0.31274493 × 10 ^-6 A10 = 0.96534532 × 10 ^-8 A12 =- 0.16071350 × 10 ^-9

[Aspherical surface coefficient of the thirteenth surface (r13)] ε = 1.0000 A4 = 0.25869274 × 10 ^-3 A6 = 0.94882593 × 10 ^-5 A8 = -0.95673341 × 10 ^-7 A10 = 0.30398427 × 10 ^-8 A12 =- 0.62483552 × 10 ^-10

[Corresponding value of conditional expression (6) for fourth surface (r4)] y = 0.00ymax ... | {x (y) -x0 (y)} / fasp | = 0.00 y = 0.10ymax ... | {x (y) -x0 (y)} / fasp | = 1.87 × 10 ^-7 y = 0.20ymax… | {x (y) -x0 (y)} / fasp | = 2.94 × 10 ^-6 y = 0.30ymax… | {x (y) -x0 (y)} / fasp | = 1.48 × 10 ⁻⁵ y = 0.40ymax… | {x (y) −x0 (y)} / fasp | = 4.68 × 10 ⁻⁵ y = 0.50ymax ... | {x (y) -x0 (y)} / fasp | = 1.15 × 10 ^-4 y = 0.60ymax… | {x (y) -x0 (y)} / fasp | = 2.43 × 10 ^-4 y = 0.70ymax ... | {x (y) -x0 (y)} / fasp | = 4.64 × ^10-4 y = 0.80ymax ... | {x (y) -x0 (y)} / fasp | = 8.26 × ^10-4 y = 0.90ymax ... | {x (y) -x0 (y)} / fasp | = 1.40 × 10 ^-3 y = 1.00ymax ... | {x (y) -x0 (y)} / fasp | = 2.30 × 10
^-3

[0048]

[Table 1]

FIGS. 4 to 6 are aberration diagrams respectively corresponding to the first to third embodiments. In each of FIGS.
(Minimum focal length end), [M] is middle (intermediate focal length state),
[T] is various aberrations at the telephoto end (maximum focal length end) (in order from the left, spherical aberration, astigmatism, distortion; Y ′: maximum image height)
Is shown. In each aberration diagram, a solid line (d) represents an aberration with respect to the d-line, a broken line (SC) represents a sine condition,
(DM) and solid line (DS) represent astigmatism with respect to d-line on the meridional surface and the sagittal surface, respectively.

The first to third embodiments can be understood from each aberration diagram while achieving an ultra-compact lens of approximately 25 mm in overall length (distance from the first surface to the last surface at the telephoto end [T]). In addition, it has high optical performance sufficiently corrected for aberration as a standard zoom lens with a wide angle of view.

[0051]

As described above, according to the present invention, it is possible to realize a small-sized and wide-angle standard zoom lens which is sufficiently corrected for aberration.

[Brief description of the drawings]

FIG. 1 is a lens configuration diagram of a first embodiment (Example 1).

FIG. 2 is a lens configuration diagram of a second embodiment (Example 2).

FIG. 3 is a lens configuration diagram of a third embodiment (Example 3).

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

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

FIG. 6 is an aberration diagram of the third embodiment.

[Explanation of symbols]

 Gr1 First lens group g1 First lens g2 Second lens Gr2 Second lens group A Aperture g3 Third lens g4 Fourth lens g5 Fifth lens g6 Sixth lens

Claims (6)

[Claims] 1. A first lens group having a negative power and a second lens group having a positive power are arranged in order from the object side.
In the zoom lens in which the lens groups move together, the first lens group includes, in order from the object side, a first lens having a negative power and a second lens having a positive power, and the first lens group And a zoom lens wherein each of the second lens group has at least one aspheric surface and satisfies the following condition: -0.895 <f1 / √ (fw · ft) <− 1.07 0.63 <TDt / √ (fw · ft) <0.9 0 <| x2 | / fw <1.0 0.63 <BFw / Ymax <1.62 where f1: focal length of the first lens group, fw: focal length of the entire system at the minimum focal length end, ft : Focal length of the entire system at the maximum focal length extremity; TDt: distance from the surface vertex of the first lens at the maximum focal length extremity on the object side surface to the surface vertex of the second lens group on the most image side surface; x2: zooming Of the second lens group in the optical axis direction
(However, it is positive when moving to the image side.), BFw: Back focus at minimum focal length end, Ymax: Maximum image height. 2. The zoom lens according to claim 1, wherein the lens closest to the image in the second lens group has a positive power and satisfies the following condition: 2.0 <fe / F2 <100 where f2 is the focal length of the second lens group, and fe is the focal length of the lens closest to the image in the second lens group. 3. The zoom lens according to claim 1, wherein at least one aspherical surface provided in the first lens group satisfies the following condition: 0 <| {x (y ) -x0 (y)} / fasp | <0.2, where x (y) is the displacement in the optical axis direction at a height y perpendicular to the optical axis when the apex of the aspheric surface is taken as the origin. Then, the following equation: x (y) = {c · y ² } / {1 + √ (1-ε · c ² · y ² )} + ΣAiY ⁱ (where i
≧ 2. Where c: curvature, ε: quadratic surface parameter, Ai: i-th order aspherical coefficient, x0 (y): represents the shape of the reference sphere with respect to the aspherical surface, and the surface vertex of the aspherical surface Height in the direction perpendicular to the optical axis when is the origin
A displacement amount of the optical axis direction in the y, the following formula: is represented by x0 (y) = {c · y 2} / {1 + √ (1-c 2 · y 2)}, fasp: Non The focal length of the sphere. 4. The method according to claim 1, wherein the second lens group includes:
2. A lens comprising a third lens having a positive power, a fourth lens having a positive power, a fifth lens having a negative power, and a sixth lens having a positive power. A zoom lens according to claim 1. 5. The zoom lens according to claim 1, wherein the second lens group includes a lens having negative power and satisfying the following condition: 0.03 < D5 / TDt <0.13 where D5 is the core thickness of the lens having negative power. 6. The second lens group includes a lens having a negative power and a lens having a positive power disposed on the image side thereof so as to satisfy the following condition. The zoom lens according to claim 1 or 2, wherein 0.70 <D5,6 / TDt <0.15, where D5,6: the distance between the image side surface of the lens having negative power and the object side surface of the lens having positive power. It is.