JPH04141615A - Compact zoom lens - Google Patents

Abstract

PURPOSE:To realize the zoom lens which consists of a small number of lens elements and has high performance while deterioration in various aberrations is suppressed by using a lens whose surfaces are both aspherical as at least one of lens elements which are relatively in front of an optical system in the zoom lens consisting of three positive, negative, and positive lens elements. CONSTITUTION:The zoom lens consists of the 1st lens group LI with positive refracting power, the 2nd lens group LII with negative refracting power, and the 3rd lens group LIII with positive refracting power and the air intervals of the groups LI - LIII are varied to vary the focal length of the whole system. Specially, the both-surface aspherical lenses is used in the lens group LI or LIII which are on the object side as compared with the lens group LIII. Consequently, when the both-surface aspherical lens is used in the 1st lens group, a comatic aberration which can not be compensated only by the front surface is compensated by the rear surface and a distortion aberration almost at the wide-angle end is compensated; when the both-surface aspherical lens is used in the 2nd group LII, effect to a spherical aberration is obtained and the spherical aberration which leans to the under side by the front surface is corrected toward the over side by the rear surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compact zoom lens, and more particularly to a zoom lens used in a single-lens reflex camera or the like.

[Disaster] Restructuring of the manufacturing industry - Currently - In order to make eye reflex cameras more compact and lower in cost, there is a demand for more compact and lower cost photographic lenses, while a lens system with a large zoom ratio is desired. ing. In order to make the lens system more compact while maintaining the zoom ratio, including the amount of lens movement during zooming,
It is necessary to increase the refractive power of each lens group, but increasing the refractive power while maintaining performance can be said to be the direction of increasing the number of lenses. On the other hand, in order to reduce costs, it is effective to reduce the number of lenses.

In this way, there are many conflicting elements involved in making the lens system more compact and lowering the cost while maintaining the zoom ratio.

In addition, as a method aiming at cost reduction by reducing the number of lenses, for example, JP-A-62-92909 and JP-A-1-2
01614, same], -223408, same 2-148
There are No. 010, etc. These zoom lenses have three components, positive and negative, and have a small number of lenses and two or more aspheric surfaces.

However, in recent years, technological advances in plastic molding, glass molding, etc. have been remarkable, and aspherical surfaces can be produced at low cost.In the present invention, the refractive power of each group is By effectively using aspherical surfaces to correct various aberrations caused by increasing the focal length in a well-balanced manner, the focal length can be increased from 35 to 105 mm while maintaining high optical performance.
To provide a compact, low-cost zoom lens with a small number of mm-class lenses.

In order to achieve the above object, the zoom lens of the present invention comprises, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a second lens group having a positive refractive power. In a zoom lens that changes the focal length of the entire system by changing the air distance between each group, the lens group that is closer to the object side than the third lens group has a double-sided aspherical lens. It is characterized by having

As mentioned above, in order to make a zoom lens compact by shortening its overall length and reducing the amount of movement, it is necessary to increase the refractive power of each group, but this significantly worsens various aberrations. Become. In the present invention, the positive and negative three
In a component zoom lens, by making at least one of the lenses relatively in the front of the optical system a double-sided aspherical lens, it is possible to suppress deterioration of various aberrations and realize a high-performance zoom lens with a small number of lenses. There is.

By using a double-sided aspherical lens, it becomes possible to correct various aberrations that cannot be suppressed by the object-side surface alone using the image-side surface. For example, when a double-sided aspherical lens is used in the lens group, especially when a double-sided aspherical lens is used as the lens closest to the image side in the lens group, the problem at the periphery of the screen that cannot be suppressed by the front surface alone. Comatic aberration can be corrected on the rear surface. It is also effective in correcting distortion near the wide-angle end. When a double-sided aspherical lens is used for the second lens group, it is effective for spherical aberration, and the spherical aberration that falls to the under side at the front surface can be corrected to the over side at the rear surface. It is also possible to prevent the occurrence of high-order comatic aberrations that could not be suppressed by the first lens group. Moreover, the same effect can be obtained not only by using a double-sided aspherical lens but also by using two or more single-sided aspherical lenses.

As described above, by using a double-sided aspherical lens or two or more aspherical surfaces relatively in the front, it is possible to reduce the number of lenses and make it more compact while maintaining optical performance. It consists of a lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, and the air distance between each group is changed. In a zoom lens that changes the focal length of the entire system by By adopting this configuration, it becomes possible to realize a zoom lens with even higher performance.

0.3〈φ, /φu＜1.0 ・・・・・・■0.
8〈φ3/φ−ku1.8 ・・・・・・■However, φ,: Refractive power of the 1st lens group φ3: Refractive power of the 3rd lens group φII: Refractive power of the entire system at the wide-angle end .

The above conditional expression (2) defines the ratio between the refractive power of the entire system and the refractive power of the first lens group at the wide-angle end. Conditional expression■
If the upper limit of is exceeded, the refractive power of the first lens group becomes excessive, and even if an aspherical surface is used in the first lens group, it becomes difficult to correct various aberrations that occur there, especially distortion and curvature of field. . When the lower limit of conditional expression (2) is exceeded, there is a marked tendency for coma aberration to occur at the periphery of the screen.

The above conditional expression (2) defines the ratio between the refractive power of the entire system and the refractive power of the third lens group at the wide-angle end. Conditional expression■
If the upper limit of is exceeded, the refractive power of the third lens group becomes excessive,
Even if an aspherical surface is used in the third lens group, it becomes difficult to correct various aberrations that occur there, especially spherical aberration. When the lower limit of conditional expression (2) is exceeded, there is a marked tendency for coma aberration to occur at the periphery of the screen.

Even when two or more aspherical surfaces are used in the first lens group or two or more aspherical surfaces are used in the second lens group, the same effect as when a double-sided aspherical lens is used as described above can be obtained. There is.

By the way, since the optical axis position of an aspherical surface is strictly one point, in the case of a double-sided aspherical lens, it is necessary to align the optical axes of both surfaces, which is extremely difficult to manufacture. On the other hand, when two single-sided aspherical lenses are used, the above-mentioned problem does not occur because the spherical side has a degree of freedom in positioning the optical axis, which is advantageous in manufacturing.

When the first lens group includes an aspherical surface, it is desirable that all the aspherical surfaces in the first lens group satisfy the following conditional expression (2).

Conditional formula (■) is as follows: When the maximum effective diameter of the aspherical surface is YllaX, O<y< o, 7Y, , for any height y in the direction perpendicular to the optical axis of x, where: ・(X(y) −L+(y)) < 0.01−■N
:Refractive index of the object-side medium of the aspherical surface N゛:Refractive index of the image-side medium of the aspherical surface X(y) :Surface shape of the aspherical surface ≧2 r: Reference radius of curvature of aspherical surface ε: Quadratic surface parameter A1: Aspherical coefficient'? ′: Paraxial radius of curvature of the aspheric surface.

When the upper limit of conditional expression (2) is exceeded, the tendency for positive distortion and positive deviation of the curvature of field increases in the intermediate field angle band in the intermediate focal length region from the wide-angle end. Moreover, when the lower limit is exceeded, negative distortion becomes large from the intermediate focal length region to the telephoto end, and in addition, the tendency for negative deviation of field curvature becomes significant over the entire zoom range.

When a double-sided aspherical lens is used in the first lens group, one surface satisfies the following conditional expression (■), and the other surface satisfies the following conditional expression (■).
It is desirable to satisfy the following.

Conditional formula (■) indicates that the maximum effective diameter of the aspherical surface is Y. 8, for any optical axis vertical height y of 0.7Y, (y<Y,...・
・It is ■.

Conditional formula (■) indicates that the maximum effective diameter of the aspherical surface is Y. 8, 0.7Y-s-<y<Y-. For any optical axis vertical height y of A, O〈φbi(N'-N)・□y・(X(y)−Xs(y))<0.03・・
...■.

In the Luns group, an aspherical surface that satisfies conditional formula (■) means that the negative refractive power is weak (the positive refractive power is strong) at the periphery, and this causes distortion near the wide-angle end. Corrects aberrations.

Furthermore, at this time, by using an aspheric surface that satisfies conditional expression (2), the curvature of field is favorably corrected.

When the second lens group includes an aspherical surface, it is desirable that all the aspherical surfaces in the second lens group satisfy the following conditional expression (2).

Conditional expression 〇 is O<y<o, 7Y, when the maximum effective diameter of the aspherical surface is YllaX. '(X(y)-XIl(y)) < 0.01...
-■ However, φ2: refractive power of the second lens group.

If the upper limit of conditional expression (2) is exceeded, the annular spherical aberration will have a large negative value, and a shift in focus position due to aperture will become a problem. Furthermore, if the lower limit is exceeded, the effect of correcting the spherical aberration on the annular beam becomes excessive, making it difficult to correct other aberrations and spherical aberration in a well-balanced manner. In this case, spherical aberration tends to take a wavy shape.

When a double-sided aspherical lens is used in the second lens group, one surface satisfies the following conditional expression (■), and the other surface satisfies the following conditional expression (■).
It is desirable to satisfy the following.

Conditional expression (2) is 0.7Y when the maximum effective diameter of the aspherical surface is Yes. For any height y in the optical axis vertical direction where <y<y, .

Conditional formula ■ is, when the maximum effective diameter of the aspherical surface is Y□8,
For any height y in the vertical direction of the optical axis where 0.7Y, , < y < Y, m, ・(X(y)-Xs(y)) < 0.04...
・−■.

In the second lens group, an aspherical surface that satisfies conditional expression (2) means that the positive refractive power is weak (the negative refractive power is strong) at the periphery. Furthermore, conditional expression (2) is a condition for correcting the inclination of spherical aberration to the under side to the over side within the range of the third-order aberration region. At this time, axial light that passes far from the optical axis of the lens may be overcorrected and go to the over side, so in order to return this light to the under side, it is necessary to satisfy conditional formula (■). What is necessary is to introduce an aspherical surface that has a weak negative refractive power (a strong positive refractive power) on the other surface around the periphery.

These aspheric surfaces also prevent the occurrence of higher-order comatic aberrations that could not be suppressed by the Luns group. For example, when the lower limit of conditional expression (■) is exceeded, off-axis peripheral coma and annular coma become large. As a result, the lateral aberration tends to appear wavy.

Further, an aspherical surface may be used in the third lens group, and in this case, it is desirable that all aspherical surfaces in the third lens group satisfy the following conditional expression (2).

Conditional expression (■) is expressed as (X(y)-Xs(y)) for any height y in the vertical direction of the optical axis where 0 < y < O-7Yaa-, where the maximum effective diameter of the aspherical surface is Yaay. <0.02・”−■.

When the upper limit of conditional expression (2) is exceeded, positive distortion and positive deviation of the curvature of field tend to increase in the intermediate field angle band from the wide-angle end to the intermediate focal length region. Moreover, when the lower limit is exceeded, negative distortion becomes large from the intermediate focal length region to the telephoto end, and in addition, the tendency for negative deviation of field curvature becomes significant over the entire zoom range.

When a double-sided aspherical lens is used in the third lens group, it is desirable that one surface satisfies the following conditional expression [phase] and the other surface satisfies the following conditional expression (2).

Here, the aspherical surface on the front surface has such a shape that the negative refractive power becomes weaker (the positive refractive power becomes stronger) at the periphery.

The conditional expression [phase] is 0.7Y, when the maximum effective diameter of the aspherical surface is Y3.8, . For any vertical height y of the optical axis, ・(X(y) Xs(y)) < O...[phase].

Conditional expression (■) is expressed as ' (X(y )-Xs(y)) < 0.04-...-
It is @.

In the third lens group, an aspherical surface that satisfies the conditional expression [phase] has weak negative refractive power at the periphery (positive refractive power is less than the chord
), which prevents an increase in distortion near the wide-angle end and also prevents the field curvature from tilting to the under side. Furthermore, at this time, by using an aspherical surface that satisfies conditional formula (■) on the rear surface,
This means that the curvature of field that could not be suppressed by the front lens alone has been successfully corrected.

The third lens group and the third lens group are defined by the following conditional expressions @ and [phase]
It is desirable that the system be configured to satisfy the following.

here, φ,: Refractive power of the entire system at the telephoto end β: Zoom ratio However, β=φ, /φ□ It is.

These are conditions for keeping the overall length of the lens system, the amount of movement for zooming, the back focus, and the state of correction of various aberrations in a good balance.

If the lower limit of the conditional expression @ is exceeded, the refractive power of the second lens group becomes too strong and it becomes difficult to maintain the back focus at an appropriate value (15% of the focal length at the wide-angle end) at the wide-angle end. This results in an increase in the lens diameter of the lens group and the third lens group.

Furthermore, if the upper limit is exceeded, the amount of movement of each group due to zooming becomes excessive, which is disadvantageous in terms of the R film configuration.

If the lower limit of the conditional expression [phase] is exceeded, the Petzval sum will take a large positive value, the image plane will tilt significantly in the negative direction, and the distortion at the wide-angle end will take a large negative value. become. Furthermore, if the upper limit is exceeded, it becomes necessary to increase the distance change between the second and third lens groups during zooming, and the distance between the second and third lens groups becomes large at the wide-angle end. Therefore, the total length of the lens increases.

Examples of the compact zoom lens according to the present invention will be shown below.

However, in each example, r: (i4, 2, 3., ,
) is the radius of curvature of the i-th surface counting from the object side, +L(i
・1.2゜3,,,,) indicates the i-th axial surface spacing counting from the object side, H: <i; 1+ 2+ 3. ---
)+ν, (i=1.2.3., , ) is the refractive index for the d-line of the i-th lens counting from the object side.

Indicates the Atsube number. Further, f indicates the focal length of the entire system, and FNo indicates the open F number.

In addition, in the examples, a surface with a radius of curvature marked with * indicates that it is an aspherical surface, and the surface shape of the aspherical surface (X
(y)).

<Example 1>f"'36.0~60.6~102.OFso=4.6
〜5.2〜5.651L is also 1 1 mJLl−
Nijirei 1r+ 1065.382 d+ 2,500 N+ 1.76200 ν
+ 40.36r3 36.078 d3 B, 300 N2 1.65830 ν2
58.52r13*219.147 Valve IJL J2r2: ε=0.100OOX 10A4”0.33
544X 1O-5 A6=0.78484X 10-'A8"0.53597X 1O-11 rs: E; O, 1OOOOOX 10A, = 0
．． 50819X 10-'A6"-0, 38338X 1O-6 As=0.25316x 10-@ A+e knee 0.l0100X 10-"A+2=0.2
5200X 10-” r7: ε=O, 100OOX 10A, =-0,8
3211X 10-' Aa=0.12892X 1O-6 As=-0,13908X 10-" A+ l!=-0,23400X 10-' llA+
2=0.49500X 10-” r8: ε=0.100OOX 10A,=-0,6
6437X 1 leaf 4 Aa: 0.54445X 1O-7 A, =-0,22886X 1 leaf 8 A+s;-0,40326X 1 leaf 12A+2"0.1
3579X 1O-13r,ll: ε;0.100
00×1OA, =-0,15813X 10=' Ae=0.32660X 10-” Ae=-0,16036X 1O-8 A+e:0.10807X 1O-11IA, 2=-0
, 29497X 1O-I3r, 2: ε=0.10
000X 10A, = 0.63377X 10-'A6"-0,53618X 1O-7 Ae=-0,10424x 1O-8 r, 3: ε=O, 100OOX 10A, = 0.1
1598X 1O-3 Aa=0.27162x 1O-6 Ae=0.12312X 10-9 <Example 2> f=36.0-60.6-102.0 NO 4,6-5.2-5.65 123.882 d.

1,90O N+ 1.76200 40.36 r3 rate 25.391 6.300 N2 1.65830 ν258.
52 rt* 97.697 d.

0.950~13.217~24.172 rle book 17.150 s6.50O 1,61800 63,39 rz -42,545 r+3 pieces 101.481 Length JJL grandchild JL rz: ε=0.10000×1O Aj=0 .64627X 1O-5 Ae-0,812νXl0-8 Ae=-0,30097X 10-"'r3:
t-=0.10000x 10A4=-0,12816
x 1O-5 A6: 0.36498 Knee 0.12292x 10-”'ε=O,100
OOX 10 A, = 0.17482
．． 25200X 1O-13r7: ε=O,100
OOX 10Aa=-0,70220x 10-' Aa=0.26665X 1O-6 Aa=-0,13127X 10-" A+5=-0,23400X 1O-111A+2"0
．． 49500x 1inch l3 r8: ε=O,100OOX 10A,=-0,8
4297X 1O-4 A6=0.18892X 1O-6 As=-0,21607X 1O-8 A+ 1l=-0,30123X 1 leaf 11A+2=-
0,35247X 10-”r,ll:ε:0.100
00 x 10 A, = -0,18252
ε=O, 100OOX 10Aa”0.26200X
10-' Aa=0.98210X 1 leaf 7 As-0,27905X 1 leaf 9 r13: ε'=o, 10000X i.

A4;'0.80376x 1 leaf 4 A6"0.26250X 110- 6A"0.14932X 10-8 <Example 3> f = 36.0~60.6~102.0F No =
4.6 ~ 5.2 ~ 5.657e 40.291 2.000 r + 3 pieces 105.345 Fum section lL rz: ε=o, 1oooox 10An=0.
69005x 1O-5 A8=0.40223x 1O-8 As"-0,83837X IQ-Isr3: ε=
0.10000x 10A, = -0,15797X 1
0” A6”-0,76416X 10-” Ae=-0,57177X 10-” r4: ε =0.100OOX 10A, =-0,
22,329 A@=0.21.757X 10-”Als”-0, l0100X 10-”Al 2 =0
．． 25200 x 1 leaf 13ε = O, 100OOX 1
0 A,=-0,57908x 10-' Aa=0.38554X 1O-6 As=0.10642x 10-” All!”-0,23400X 1O-IIIA+2
=0.49500X 10 bow 3r8: ε=O,1
00OOX 10A4=-0,73171x 10-' Aa:0.27232X 1O-6 As=-0,12718X 1O-8 A+e knee 0.60352X 1O-12A+2=-0
, 21775X 1O-13r+II: ε=0.
100OOX 10A, =-0,15354X 1 leaf 4 Aa=0.28167X 1O-7 Aa=-0,16810X 1 leaf 8 A+l! =0. Lens 33X 10-”Al2=-0,
36572X 10th edition 3rB: ε:0.100
00X10Aj=0.23886X 10-' Ae=0.64483X 10-'As"-0,13893X 1 leaf 9 r+3: ε=O, 100OOX 10AA=0.
78663X 10-' Ae: 0.20154X 1O-6 Ae=0.17815X 10-8 <Example 4> f=36.0-60.6-102. OF, 04.6-5
．． 2-5.65 z4. ! dL4~LZ, (114~1.3UUr+3*
156.985 [弗]■L section 1 r2: ε=0.10000×10 A,=0.60811X 1O-5 A6;0.53548X 10-” A8=0.46696X 1inch 11 rs: E=0.100OOX 10A, = 0
．． 55742x 1O-4 Ae=-0,39986x 1O-6 As"0.24204X 1O-8 Ats"-0,10100X 10-' llAl2=
0.25200X 1 leaf 13 r7: ε=O,100OOX 10A,=-0,8
1496X 10-4 /s: 0.12724X 1O-6 Aθ=-0,16510X 1 leaf 8 A+ll"-0,23400X 10-1@Al2=0
．． 49500X 1O-13re: ε=0.1
00OOX 10A, =-0,63147X 1 leaf 4 Aa=0.38948X 1O-7 Ae=-0,24566x 1O-8 A, e=-0,16357X 10 A12=0.71514X 10 r+ll: ε=0.10000X10A ,=-0
．． 13730
ε=O, 100OOX 10Aa=0.63464X
10-' Aa knee 0.62425X 1O-7 Ae=-0,94682X 1 leaf 9 r, 3: ε=0.100OOX 10A,=0.1
1940X 10'' As=0.31156x 1O-6 Aa=0.28779X 10-' Figures 1 to 4 are lens configuration diagrams corresponding to Examples 1 to 4, and the arrows in the figures indicate the 1st lens group and 3rd lens group
The movement of the lens group from the wide-angle end (W) to the telephoto end (T) is schematically shown.

Embodiment 1 includes, in order from the object side to the image side, a first lens group (LI) consisting of a concave negative meniscus lens, a biconvex positive second lens, a biconcave negative third lens, and A second lens group (Lm) consisting of a biconvex positive fourth lens, and a third lens group (LIII) consisting of an aperture (A) 9 biconvex positive fifth lens and a biconcave negative sixth lens. It is composed of. In the first embodiment, the image-side surface of the third lens, the object-side surface of the third lens, both surfaces of the fourth lens, the object-side surface of the fifth lens, and both surfaces of the sixth lens are aspherical.

In Examples 2 and 3, from the object side to the image side, the first lens group (LI) consists of a concave negative meniscus lens and a biconvex positive second lens.

A second lens group (LII
), and a third lens group (Lm) consisting of an aperture (A), a biconvex positive fifth lens, and a biconcave negative sixth lens. In addition, in Examples 2 and 3, the image side surface of the first lens, both surfaces of the second lens, the object side surface of the third lens,
Both surfaces of the fourth lens, the object side surface of the fifth lens, and both surfaces of the sixth lens are aspherical.

Embodiment 4 includes a first lens group (LI) consisting of a biconcave negative first lens and a biconvex positive second lens in order from the object side;
A second lens group (LIE) consisting of a biconcave negative third lens and a biconvex positive fourth lens, and an aperture (A) of 9 biconvex positive fifth lenses and a biconcave negative sixth lens. and a third lens group (LIII) consisting of. Furthermore, Example 4
, the image-side surface of the third lens, the object-side surface of the third lens, both surfaces of the fourth lens, the object-side surface of the fifth lens, and the sixth lens.
Both surfaces of the lens are aspheric.

5 to 8 are aberration diagrams corresponding to Examples 1 to 4, in which (W) is the aberration at the wide-angle end focal length, (M) is the intermediate focal length, and (T) is the aberration at the telephoto end focal length. It shows.

In addition, the solid line (d) represents the aberration for the d-line, and the broken line (
SC) represents the sine condition. Furthermore, the dashed line (DM) and the solid line (
DS) represents astigmatism on the meridional plane and the sagittal plane, respectively.

Table 1 shows φ1/φ− in conditional expression (■) in Examples 1 to 4.
The values of φ3/φ− in the two conditional expressions (2) are shown respectively.

Table 2 shows the values of in the conditional expression @ in Examples 1 to 4, respectively.

Tables 3 to 6 correspond to Examples 1 to 4, respectively, and show the conditional expressions for each aspherical surface for the value of y.
The middle part is expressed as (II), and the middle part of the conditional expression ■[phase]■ is expressed as (III).

In Tables 3 to 6, each aspherical surface means a lens surface counted in order from the object side, excluding the aperture.

Table 1 (Values for conditional expression ) (Example 1) Table 4 (Part 1) (Example 2) Table 4 (Part 2) (Example 2) Table 4 (Part 3) (Example 2) Table 5 (Part 1) ( Example 3) Table 5 (Part 2) (Example 3) Table 5 (Part 3) (Example 3) @Table 6 (Part 1) (Example 4) Table 6 (Part 2) (Example 4) Brother m As explained above, according to the present invention, it is possible to realize a low-cost and compact zoom lens with a small number of lenses while maintaining high optical performance.

In the present invention, by using a double-sided aspherical lens relatively in front of the optical system, or by using two or more aspherical surfaces relatively in front of the optical system while satisfying the above conditional expressions (1) and (2), each group Various aberrations caused by increasing the refractive power of the lens can be effectively corrected. As a result, it becomes possible to achieve a zoom lens with a focal length of 35 to 105 mm class using 6 to 7 lenses.

Furthermore, if the zoom lens according to the present invention is used in a -eye reflex camera, the camera can be made more compact and lower in cost.

[Brief explanation of drawings]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are lens configuration diagrams corresponding to Examples 1 to 4 of the present invention, respectively. Figure 5. Figure 6. 7 and 8 are aberration diagrams corresponding to Examples 1 to 4 of the present invention, respectively.

Claims (1)

[Claims] (1) Consisting of, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. , a zoom lens that changes the focal length of the entire system by changing the air distance between each group, characterized by having a double-sided aspherical lens in the lens group closer to the object than the third lens group. zoom lens. (2) The zoom lens according to claim 1, wherein the first lens group includes a double-sided aspherical lens. (3) The zoom lens according to claim 1, wherein the second lens group includes a double-sided aspherical lens. (4) Consisting of, in order from the object side, a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, with a gap between each group. A zoom lens that changes the focal length of the entire system by changing the air spacing, which includes two or more aspheric surfaces in at least one lens group closer to the object than the third lens group, and satisfies the following conditions: A zoom lens characterized by;0
．． 3<φ_1/φ_w<1.0 0.8<φ_3/φ_w<1.8 However, φ_1: Refractive power of the first lens group φ_3: Refractive power of the third lens group φ_w: Refraction of the entire system at the wide-angle end It is power. (5) The zoom lens according to claim 4, wherein the first lens group has two or more aspheric surfaces. (6) The zoom lens according to claim 4, wherein the second lens group has two or more aspheric surfaces.