JPH0368909A - zoom lens - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a compact high-power zoom lens,
In particular, the present invention relates to a compact zoom lens with a short overall length suitable for use in video cameras and the like.

[Conventional technology]

Many compact zoom lenses have been proposed for use in video cameras and the like. For example, JP-A-59-28121, JP-A-61
By applying an aspherical surface to a zoom lens, as described in Japanese Patent Application Laid-open No. 140913, Japanese Patent Application Laid-Open No. 182011-1982, and Japanese Patent Application Laid-open No. 34505-1983.

Alternatively, by devising the focal length of the lenses that make up the zoom lens, the number of lenses in the zoom lens is small, the zoom lens is compact, and the performance is also good.

However, in the conventional example, a zoom lens with a zoom ratio of about 6x for a 172-inch image size has a ratio of the total length to the focal length at the wide-angle end of about 11 to 12, and in recent years, the overall size has become smaller and smaller. It is unsatisfactory for use with video cameras, etc.

[Problem to be solved by the invention]

Generally, if you try to shorten the overall length and obtain a compact zoom lens, you will need to lower the zoom ratio or use F/F.
It was necessary to increase the number. In addition, in order to shorten the overall length while maintaining high magnification, if the entire zoom lens system is similarly made smaller, the focal length of each lens group will become shorter, and the radius of curvature of each lens will become smaller. This has led to an increase in the lens aperture, difficulty in correcting various aberrations, an increase in the number of lenses, and a worsening of lens manufacturing tolerances.

The purpose of the present invention is to have a high magnification with a zoom ratio of about 6 times, a bright F number of around 1.4 to 1.8 at the wide-angle end, and a short ratio of the overall length to the focal length at the wide-angle end of around 7 to 9. It is an object of the present invention to provide a zoom lens which has a small number of lenses and whose aberrations are well corrected.

[Means to solve the problem]

In order to solve the above-mentioned problems and obtain the desired zoom lens, the zoom lens of the present invention has a configuration as described below. That is, in order from the object side, the first group (1) has a positive refractive power, and the second group (2) each has a negative refractive power and has the function of zooming by moving along the optical axis. 2) and the second group (3), and the second group (4) which has a positive refractive power, is always fixed, and is provided with a lens having at least one aspherical surface, and has a positive refractive power. From the object side, the V-group element lens (9) has a positive refractive power.
), a V-group second lens (10) having a negative refractive power, and a seventh-group third lens (11) having a positive refractive power. The structure is equipped with the following features.

In addition, in the above configuration, in order to shorten the overall length and obtain a lens with good performance, the following conditions (i) to (i
It is desirable to have a configuration that satisfies n).

2.7<If□/ffI<3.6 (i)1,
0< l fz / fI l <1.9 (
ii) 3.0<fI/fi<4.9 (City) However, f, is the focal length of the first group (1), fI is the focal length of the second group (2), and f□ is the focal length of the first group (2). Group ■ (3)
The focal length H, fw is the focal length of the entire zoom lens at the wide-angle end.

[For production]

Next, the operation of each part constituting the zoom lens of the present invention will be explained.

In the zoom lens according to the present invention, zooming is performed by simultaneously moving the second group (2) and the second group (3) along the optical axis while keeping the image plane at a constant position. Further, focusing is performed by moving the entire first group (5) or a portion thereof along the optical axis.

In addition, the diaphragm is placed close to the lens group (4) on the object side or the image plane side of the lens group (4), so that the rays reaching the center of the image plane are directed toward the lens in the lens group (4). Pass through a relatively high place. For this reason, the aspherical surface provided in the Ⅰ group (4) is
In particular, it has the effect of correcting aberrations of light rays that reach the center of the image plane.

Further, the V group (5) includes, in order from the object side, a V group first lens (9) having a positive refractive power, a V group second lens (10) having a negative refractive power, and a positive refractive power lens. Chapter V with power
It has a triplet configuration consisting of the third lens group (11), and in combination with the aspheric surface provided in the aforementioned group (4), it can effectively correct various aberrations with a small number of lenses in a zoom lens with a short overall length. It is effective in the action of This effect will be explained in detail below.

As mentioned above, shortening the total length of a zoom lens worsens various aberrations, making it impossible to achieve the desired performance.In addition, it is necessary to increase the number of lenses to correct the worsened various aberrations, and the number of lenses increases. In order to accommodate the increased lens space, the overall length also becomes longer. Therefore, when the overall length is shortened, a major challenge is how to properly correct various aberrations with a small number of lenses.

In order to solve the above problems, the configuration according to the present invention described above is most suitable.

First, as will be described later, in order to shorten the overall length, it is advantageous to shorten the distance between the lenses on the optical axis as much as possible, and to reduce the thickness of the lenses themselves along the optical axis. However, in general, the distance or thickness of lenses is an important degree of freedom in correcting aberrations, and reducing such distances or thicknesses is disadvantageous in correcting various aberrations. Therefore, in the past, the thickness of each lens in the lens groups corresponding to the above-mentioned lens group (4) and V group (5) was increased, or The distance between each corresponding lens group on the optical axis is relatively large, or the lens group corresponding to the V group (5) is composed of two lens groups with a relatively large distance on the optical axis. This corrects aberrations, resulting in a relatively long overall length. In contrast, the configuration according to the present invention allows aberrations to be well corrected even if the lens spacing on the optical axis or the lens thickness is reduced. As mentioned above, the aspherical surface provided in the above group (4) has the function of mainly correcting spherical aberration, and the aspherical surface provided in the group It mainly corrects peripheral aberrations such as points. but,
Since the length of the Vth group (5) on the optical axis is made as small as possible in order to shorten the overall length, residual aberrations such as spherical aberration cannot be fully corrected. For this reason, the V group (5) mainly corrects inherent aberrations corresponding to coma aberration, astigmatism, etc.
For this reason, the spherical aberration that cannot be corrected by the Vth group (5) alone is corrected by balancing it with the aspherical surface provided in the 2nd group (4), thereby achieving good overall aberration correction.

As mentioned above, in a zoom lens with a short overall length, it is necessary to properly correct aberrations with a small number of lenses.
) and the correction effect of the group V (5) triplet are combined to make this possible.

Next, in addition to the above-described configuration, effects of conditions (i) to (ni) desirable for shortening the overall length will be explained in detail.

One way to shorten the total length of a zoom lens is to uniformly reduce the focal lengths of the above-mentioned group (1), group (2), and group (3). By reducing the focal length of the groups, the radius of curvature of the lenses in each group also becomes smaller, which increases the amount of aberrations generated and makes the positioning accuracy of each group more difficult, which is unfavorable in terms of manufacturing. In addition, when the focal lengths of the above-mentioned group (1), (2), and (3) are made uniformly smaller than those of the conventional ones, the above-mentioned group (4) and V In group (5),
The height through which the light rays reaching the center of the image plane increases, the outer diameters of the lenses of the second group (4) and the V group (5) become larger, and the amount of aberrations generated increases. As the outer diameter of the lens increases, the thickness of the lens along the optical axis also increases to ensure margin for the lens edge, resulting in an increase in the size of the lens as a whole.

Further, as another method for shortening the total length, it is possible to reduce the distance between the lenses constituting the zoom lens on the optical axis, or to reduce the number of lenses. However, these factors reduce the degree of freedom in correcting aberrations and cause performance to deteriorate.

The zoom lens according to the present invention solves the problems when the overall length is shortened, including the above problems, by providing the above configuration and conditions (i) to (c).

Condition (i) relates to the ratio of the focal lengths of the first group (1) and the eleventh group (2). In the present invention, in the zoom lens, the first group (1) has particularly positive refractive power.
The overall length is shortened by reducing the focal length of the lens. If the focal length of the first group (1) is made smaller and the refractive power is made stronger, even if the zoom ratio is the same, the movement range of the n-th group (2) during zooming will be smaller, and the distance will be on the optical axis. The overall length can be shortened by reducing the spacing between the two. Also, if the focal length of the first group (1) is decreased,
The height of the light ray that passes through group (4) and reaches the center of the image plane becomes lower, and the height of the ray that passes through group (4) and reaches the center of the image plane becomes lower, and Can be made smaller. However, if the focal length of the first group (1) is made too small compared to the focal length of the n-th group (2), the moving range of the second group (3) that moves during zooming will become large and the overall length will decrease. As the length increases, the accuracy of positioning the n-th group (2) on the optical axis becomes more difficult. Furthermore, the height of the ray in the first group (1) of the ray that passes through the center of the aperture and reaches the most peripheral part of the image plane increases,
As the aperture of the first group (1) increases, the thickness on the optical axis increases, which is undesirable. If the upper limit of condition (i) is exceeded, the focal length of the first group (1) with respect to the n-th group (2) becomes larger as described above, and therefore the overall length becomes longer. (3) Positioning accuracy on the optical axis becomes difficult. In addition, the lower limit for Condition 1 (i) is set particularly small compared to the conventional 5, and the overall length is shortened.
If the focal length of the first group (1) with respect to the n-th group (2) is reduced beyond this, the positioning accuracy of the n-th group (2) on the optical axis becomes difficult, and furthermore, the In some cases, the height of the light ray that passes through and reaches the center of the image plane becomes higher.

Condition (ii) is related to the ratio of the focal distance yk of the first group (1) and the first TI group (3).6 In order to shorten the overall length, the focal length of the first group (3) must be It is preferable to reduce the movement range of the second lens group (3) during zooming by making the lens smaller and increasing the refractive power. However, the condition (ii
), the height of the light ray that leaves the group (3) and enters the group (4) increases, which is undesirable, and furthermore, the optical axis of the group (3) itself The above positioning accuracy becomes difficult. Furthermore, if the lower limit of condition (il) is exceeded, the range of movement of lens group (3) during zooming becomes too large. Furthermore, if the above conditions (i) and (ii) are exceeded, the first group (1) and the nth group (2
) and the third lens group (3) are no longer balanced, resulting in a problem in which variations in the aberrations due to zooming become large.

Condition (iii) defines the absolute amount of conditions (i) and (ii) above, and if the upper limit of condition (iii) is exceeded, the focal length of the first group (1) will be the same as the entire zoom lens. If it becomes too large relative to the focal length of the system, the total length becomes long and the entire lens becomes large, which is undesirable.If the lower limit is exceeded, the focal length of the first group (1) becomes too small, resulting in the problem described above. Problems arise such as variations in various aberrations due to zooming and deterioration of positioning accuracy of the lens on the optical axis.

Next, the effects of the above conditions will be explained using specific numerical examples.

FIG. 2 is a diagram showing the arrangement of each group constituting the zoom lens according to the present invention. In this figure, changes in various quantities when the focal length of each lens group is changed are shown in FIGS. 3 to 7. In addition, what is shown in each episode is the zoom ratio, the focal length of the entire system, and the optical axis where each of the above lens groups approaches each other during zooming. It is assumed to be constant.

FIG. 3 shows changes in the movement NL due to zooming of the n-th group (2) when the focal lengths of the first group (1) and the n-th group (2) are changed.

In FIG. 3, the horizontal axis shows the focal length of the n-th group (2), and the vertical axis shows the movement fit L of the n-th group (2). Also, in the figure a, the focal length fI of the first group (1) is 43.7 mm, b is f, 39.4 mm, and C is fI of 35.
The case of 0 mm is shown. From this figure, the first group (
By reducing the focal length of 1), the nth group (2)
It can be seen that the amount of movement has decreased significantly. Furthermore, it can be seen that it is particularly effective to make the focal length of the first group (1) smaller than the focal length of the n-th group (2) in order to reduce the amount of movement.

Figure 4 shows the height of the ray that passes through the second group (4) reaching the center of the image plane when the ratio of the focal lengths of the first group (1) and the n-th group (2) is changed. It is something that The horizontal axis of the figure is the absolute value of the ratio of the focal length of the first group (1) to the nth group (2), and the vertical axis is the ratio of the focal length of the first group (4) to the center of the image plane at the wide-angle end. It shows the height to pass. In addition, the height of the ray is the focal plane layer f of the first group (1), which is 43.7
mm, the focal length fI of the nth group (2) is -12.5 m
It is shown as a ratio when m is set to l. Also, a in the figure
is a case where the focal length fI of the first group (1>) is 43.7n+m.

b is f, is 39.4mm, and C is fx is 3
5.001111 cases are shown below. From this figure,
If the focal length of the first group (1) is the same, then the nth group (
It can be seen that if the focal length of 2) is made smaller, the ray height becomes higher, and if the focal length of the first group (1) is made smaller, the ray height becomes lower, but if the focal length is made too small, the ray height becomes higher. .

Similarly, FIG. 5 shows a ray (principal ray) that passes through the center of the diaphragm and reaches the outermost periphery of the image plane when the ratio of the focal lengths of the first group (1) and the n-th group (2) is changed. This figure shows the height at which the beam passes through the first group (1). The horizontal axis of the figure is the nth group (2
) to the focal length of the first group (1), the vertical axis is the ratio of the focal length of the first group (1) to
) indicates the height at which it passes. Note that the height of the ray is the first
The focal length mfx of group (1) is 43.7 mm, and the nth group (
It is shown as a ratio when the focal length fI of 2) is -12.5 mm, which is set to 1. Also, a in the figure is the first group (1)
When the focal length 11&fx of is 43.7n+n+,
b is f, is 39.4 mm.

Furthermore, C shows the case where fX is 35.0 mm.

From this figure, the focal length of the first group (1) and the nth group (2
) When the ratio of the focal lengths of the nth group (1) is kept constant and the focal length of the first group (1) is made small, the ray height becomes relatively low, but compared to the focal length of the nth group (2) If it is made too small, that is, the focal length of the first group (1) and the nth group (2)
It can be seen that when the ratio of the focal lengths of is decreased, the height of the ray increases.

On the other hand, FIG. 6 shows the positioning of the zoom lens of the n-th group (2) on the optical axis at the telephoto end when the ratio of the focal lengths of the first group (1) and the n-th group (2) is changed. Shows changes in accuracy. The horizontal axis of the figure is the ratio of the focal length of the first group (1) to the n-th group (2), and the vertical axis is the amount that equivalently represents the positioning accuracy on the optical axis. Unit amount (1m
m) indicates the amount of movement of the image plane on the optical axis when it moves (hereinafter referred to as sensitivity). Similarly, FIG.
FIG. 3 shows sensitivity changes at the telephoto end of the zoom lens of the (3) group when the ratio of the focal lengths of the group (1) and the n-th group (2) is changed. The horizontal axis in Fig. 7 is the first
The ratio of the focal lengths of the group (1), and the vertical axis is the sensitivity of the second group (3). From FIG. 6 and FIG. 7, it can be seen that the ratio of the focal length of the first group (1) to the n-th group (2) is constant and the first group (1) is
), the sensitivity of the n-th group (2) increases, and if the focal length of the first group (1) is constant, the n-th group ( It can be seen that when the ratio of 2) to the focal length is made small, the sensitivity of the n-th group (2) changes little, and the sensitivity of the 2-th group (3) becomes significantly smaller.

Therefore, while keeping these sensitivities at practically sufficient values,
In addition, the heights of the rays of the first group (1) and the second group (4) are lowered, and the amount of movement of the nth group (2) and the second group (3) is reduced. ! &It is important to set an appropriate focal length for each lens group.

If the conditions (i) to (iii) above are satisfied, the exit pupil distance and the positioning accuracy of the lens groups on the optical axis can be maintained at practically sufficient values, and the first group (1) and the second group (4) The height of the ray of light can be lowered to make the zoom lens compact, and the overall length of the zoom lens can be shortened, and variations in various aberrations due to zooming can be suppressed.

〔Example〕

Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a zoom lens according to an embodiment of the present invention. The zoom lens shown in the figure includes, from the object side, a first group (1) having positive refractive power;
The n-th group (2) and the ■-th group (3) each have negative refractive power and perform zooming while always keeping the image plane (8) at a constant position by moving relatively along the optical axis. , the second lens group (4), which has a positive refractive power and is always fixed during zooming and focusing, and at least one surface is an aspherical surface; ) and the image plane (8), and has the function of forming an image on the image plane (8) with a predetermined brightness and size, but has no effect as a lens.

A crystal plate (6) that serves as a low frequency optical filter.

Consists of.

The zoom lens in this example consists of the group (4) and the group V.
The distance between the group (5) on the optical axis and the exit pupil position is determined by the image plane (8).
The overall length is shortened by ensuring a sufficient distance from the distance and keeping it as small as possible.

Furthermore, by setting the focal lengths of the first group (1), the n-th group (2), and the ) and the displacement on the optical axis of the group (3)! It is made smaller and the first group (
By making the height of the light rays passing through the lens group 1) and the lens group 2 (4) as small as possible, the overall length is shortened, the lens is made more compact, and the amount of aberrations generated is reduced.

In addition, the first group (1) includes, in order from the object side, a cemented lens of a lens with a negative refractive index and a lens with a positive refractive index, and a cemented lens with a positive refractive power and a meniscus-like curvature. The n-th group (2) consists of a lens with a sharp surface facing toward the image plane, and in order from the object side, a lens with a negative refractive index, a lens with a negative refractive index, and a positive refractive index. The above conditions (i) to (ii
(i) Various aberrations are well corrected in each lens group having a focal length determined to shorten the overall length.

When the cemented lens in the first group (1) is eliminated, the focal length of the first group (1) is made shorter than that of the conventional lens. Furthermore, although separating the cementation increases the degree of freedom in correcting aberrations, for example, the occurrence of astigmatism becomes larger on the front and rear surfaces where the cementation is separated, or higher-order aberrations occur. This is not desirable because it can cause The curvature of the cemented surface of the cemented lens in the first group (1) is set so as to correct, in a well-balanced manner, variations in spherical aberration and chromatic aberration due to zooming, especially at the telephoto end of the zoom lens. Also, the first group (1)
The lens closest to the image plane in , in particular, suppresses the amount of spherical aberration and coma aberration, and reduces fluctuations due to zooming. Further, the cemented lens in the n-th group (2) is not preferable because if the cemented lens is eliminated, the tolerances of the lenses constituting the n-th group (2) will become stricter. Furthermore, the nth group (
2) The curvature of the cemented surface of the cemented lens in
The curvature is set so as to reduce fluctuations in chromatic aberration, particularly during zooming, in combination with the cemented surface of the cemented lens in group (1). As a result, aberrations in the entire zoom lens system are corrected in a well-balanced manner, especially when the focal length of the first group (1) is made small to make the entire zoom lens system compact. Furthermore, the shape of the lens 1 closest to the object side of the n-th group (2) is determined so as to particularly correct variations in distortion due to zooming.

Furthermore, it is desirable that the zoom lens according to the present invention satisfies the following conditions.

200 < lv, l
(iv) Here, y is expressed by the following formula.

1/ 1 = f1B (1/ (ft-+-ya, -1)
+i/(fi-z・ya,-,)+1/(fx-i・
Ya, -,)) However, b-+ + fI-, l ff-
3' is the first of the nth group (2) viewed from the object side.
represents the focal length of the lens, the second lens, and the third lens, and vl! -1! V, -yo, and V□-3 respectively indicate the Abbe numbers of the electron lens, the second lens, and the third lens of the n-th group (2) when viewed from the object side.

Condition (iv) is for properly correcting chromatic aberration in the entire zoom lens system by keeping the focal length of each lens group set in the zoom lens according to the present invention.

Further, in this embodiment, the Vth group (5) includes, in order from the object side, a first lens (9) having a positive refractive index.

Consisting of a second lens (10) with a negative refractive power and a third lens (11) with a positive refractive power, together with the aspherical surface provided in the above-mentioned No. 1 group (4), the entire zoom lens system This corrects various aberrations. The structure of the V group (5) is a so-called triplet structure, and with this structure, the height of the light ray at the second lens (10) in the V group (5) is changed to the first lens having a positive refractive index. By making it lower than the lens (9) and the third lens (11), the curvature of the field is reduced, and the degree of freedom for correcting various aberrations is increased.

Generally, in a triplet-configured lens, the distance between each lens in the triplet plays an important role in correcting aberrations, and when increasing the aperture, the overall thickness of the triplet lens system must be increased or the number of lenses must be increased. It is known that, if not, residual aberrations such as spherical aberration become large, and if the distance between the lenses is made small and the thickness of each lens is made thin, it becomes difficult to correct the aberrations. In the zoom lens of the present invention, as described above, the focal length of each lens group is determined so that the height of the light ray that enters the Vth group (5) and reaches the center of the image plane is as low as possible; By providing at least one aspherical surface in the second group (4), the V group (5), which has a triplet configuration with the thickness on the optical axis as thin as possible, corrects aberrations of the entire zoom lens system. are doing well.

The second lens (10) of the V group (5) has a shape in which the surface with a steep meniscus curvature faces the image plane side, and the spherical surface generated in the first lens (9) of the V group (5) Aberrations, coma aberration, and astigmatism are generated in opposite directions to achieve balance, reduce curvature of the field of view, and change the shape of the second lens (work 0) between the wide-angle end and the telephoto end of the zoom lens. Distortion is balanced. Group ■(4) and V above
The action of group (5) suppresses fluctuations in aberrations when focusing is performed by moving the entire zoom lens system and the second group (1).

Further, the focal length of the first lens (9) in the V group (5) is set to be small to some extent, so that the first lens (9) has a relatively small focal length.
Even if the distance between 9) and the second lens (1o) is made small, the difference in ray height between the first lens (9) and the second lens (10) can be made relatively large, which is effective in correcting aberrations. Group V (
In 5), the object side principal point position is brought closer to the aperture side to shorten the overall length.

As described above, with the zoom lens configuration of the present invention, the total length of the zoom lens can be shortened, and aberrations can be corrected well with a small number of lenses.

Next, specific numerical examples of the lens system shown in FIG. 1 will be shown. These are f=9.0 to 49.6. This is the case of a zoom lens with F=1.4.

r1=53.60. d, “0.90.n, =1.
8467,v, ”23.9r, = 28.92.d
, =6.50. n2=1.5891. v2:61.3
r, =-97,39,d, =0.20r4=
24.91. d4 =3.20. n, =1.5891
．． v, :61.3r, ``54-74pds'' variable r', = 23.40. dG=0.85. n4=1.
7432. v, =49.3r 7” 9.910-
d t ”3-41r, =-15,28,d, =0
．． 85. n, =1.7432. v, ”49.3r,
= 10.79. d,=2.72. n,=1.846
7, v, :23.9r 10:353-0. dxa”
Variable r 1□=-16,06,d, □:0.85.
n, :1.7234. v7=38. Or,
2=-7t, 54+d xz=variable r *1. =15
．． 43. d,, =3.7o, n, :1.5
891. v 8”61.3r 14 knees 78.11.
d i,=0.84r□, :Co(aperture L d 1
．． =3.20r,,=16.31. d 1G=
4.00. ng:1.7130. v, :5
3.9r,,=-71,84,d i,=0.30°r,,=35.60. d1. =0.85. n
1o=1.8052. v1o=25,4r 1s=9
．． 289. d,,=1.30r zll” 12
．． 53. dzg=:3.40. n1. =1.5
891. y, 1:61.3r*, □=-55,8
3,d21=11. Or2. = 00, dB:
5.78. nt□=1.5231. y, 2:5B, 5r
23=00 In the above, ri is the radius of curvature of the i-th lens surface from the object side, and when the center of curvature is on the image plane side when viewed from the lens surface, it is positive, and when it is on the object side, it is negative. . d,
represents the distance on the optical axis between the i-th lens surface and the (i+1)-th lens surface adjacent thereto. In addition, “j T vj is the refractive index of the j-th lens from the object side.

It shows the Atsube number.

Note that r1 to rs are the 0th group (1), rg to r111
1 is group ■ (2), r engineering, Jri2 is group ■ (3), r
□,.

r14 is group ■ (4), rzs to rzx are group 7 (5)
, r 22 T r =3 relates to the crystal plate (6).

In the above, d, d. , d□2 differ depending on the focal length fif. An example of this is shown in the table work.

Table 1. Also, the lens surface whose radius of curvature r is marked with a wooden mark is an aspherical surface, and its shape is expressed by the following equation using an aspherical coefficient.

Z=CY”/(1+fco5)+A, Y'+A, Y'+
Al1Y"+A, .Ylo, where Z is the distance from the tangent plane of the aspherical surface vertex of the point on the aspherical surface at the height Y from the optical axis, C is the curvature of the reference sphere (1, /r), and constant,
Y is the height from the optical axis, A4-A1° is the 4th to 1st order, respectively.
The zero-order aspheric coefficient is shown.

The aspheric coefficients in the above example are shown below.

13th side: K = -1,2439° A4 = -6,6990X10'', AG = 1.504
1X10-”A, = 1.9326xlO', A engineering.=
-1,8537X 10''''121 planes: K = -7
9,747°A4=2.9723XIO-! ',A, =-6,0
889X10 =A, =-1,7263X10-',
A. = 1.1177X10-1c' Figures 8 to 10
The figure shows the photographing distance of Example 1, so the focal length is 9.0[
Characteristic diagrams showing aberrations in the cases of mml, 32.6 [g+m], and 49.6 [:mm], Figs. 11 to 1
FIG. 3 is a characteristic diagram showing aberrations at each focal length at a shooting distance of 4 m, and FIGS. 14 to 16 are characteristic diagrams showing aberrations at each focal length at a shooting distance of 2 m.

In addition, (a) shown in the above characteristic diagram is the center of the imaging plane of the ray, (b) is the ray height at the imaging plane corresponding to 0.6 times the maximum angle of view at each focal length, ( C) is the ray height at the imaging plane corresponding to 0.9 times the maximum angle of view for each focal length,
It is a figure corresponding to each.

In Numerical Example 1 above, the condition (i).

Values corresponding to (ii) and (iii) are shown below.

fx / fx l =3.42 1 f, /f, l =1.34fa / fw
=4.28 Furthermore, the ratio of the total length to the focal length at the wide-angle end in Numerical Example 1 is 8.34.

Next, a specific numerical example of the lens system shown in FIG. 17, which is a second embodiment of the present invention, will be shown. These are f=9
．． 7-53.4. This is the case of a zoom lens with F=1.8.

r□=51.03. d, =0.90. n, =1.8
467,v, =23.9r, =27.47. d2
=4.78. n2=1.5891. v, =61.3r
, =-9], ,OO,d , =0.20r4=2
1.96. d4=2.77, n, =1.5891. v
, =61.3r, =49.92. ds=variable rG=20.98. d,,=0.85. n4=1.7
432. v4=49.3r7=9,007. d
, =2.78rs''-13-96, de=O
-85, n s ” 1-7432.!, = 49.3r
, = 10.34. d, =2.32. n, =1.
8467, v, =23.9r 10=305-L d
xa” variable r 11=-16,04,d, □=0.
85. n, =1.7215. v,=29.2r
xz”-75-46+d 1m=variable r *13:
13.79. d,,:3.03. n, =1.
5891. v, =61.3r i, =-79,06
, d 14=0.80r 1. :ω (aperture), d
ts=t, 80r 1. = 13.47. d1. =
3.68. n g=1.5891. V:61
．． 3r □7=-34.56. d 1□=0.20t
r 1s” 11.67, d 1.”0.85. n
,. =1.8467, v 1o:23.9? ,,
= 6.530. d,,=1. ．． 00r,,=
11.54. d2. "2.50.n,,"1.
5407. v 11=47.2r 21=28.4
6. d21=8. OOr, □=Co,
d2. =5.50. n, □=1.5163. v
1□=64.2r23= In the above equation, d 5 P dlON dtz differs depending on the focal length f. An example is shown in Table 2.

Table 2゜ In addition, the aspheric coefficient in the above is shown.

13th side: K = -1,1590° A4 = -1,2760X10-', A, = 6.31
20X10-'A, =-1,8170X10 =,A
,,=1.1470X10-10 In the above numerical example 2, the above condition (i).

Values corresponding to (h) and (iii) are shown below.

I fx / f, l = 3.36 I f,
/fI + =1.22f, /f, =3.
57 Furthermore, the ratio of the total length to the wide-angle end focal length in Numerical Example 2 is 6.75.

It goes without saying that the same performance can be obtained by forming an aspherical lens in the above example by coating a glass lens with a plastic material such as PMMA (polymethyl methacrylate). stomach.

For example, if the lens of the 2nd lens group in the second embodiment is
As shown in the figure, r books: l: 13.80. d1. =0.10. n
, =1.4920. v, =57.9r'2.
=13.87. d'13=3.15. n', =
1.5891. v, =61,3r□,=-79
．． 02. d i,==o,a.

Replace the aspheric coefficient on the 13th surface with: =-1,
1678°A, =-1,6212X10-', AG=7.82
53XIO-'A, =-2,2671X10"",
Similar performance can be obtained by setting A1°=1.2615×10−”.

〔Effect of the invention〕

As described above, according to the present invention, the zoom ratio is about 6 times, the F number is about 1.4 to 1.8, which is bright, the ratio of the total length to the wide-angle end focal length is about 7 to 9, and the lens has a small It is possible to realize a zoom lens in which aberrations are well corrected depending on the number of lenses.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the zoom lens configuration of the present invention and a first embodiment, FIG. 2 is a diagram showing the arrangement of lens groups in the zoom lens of the present invention, and FIGS. 3 to 7 are each A diagram showing changes in various quantities when changing the focal length of the lens group,
8 to 16 are characteristic diagrams showing aberrations in the first numerical embodiment of the present invention, FIG. 17 is a sectional view showing the zoom lens configuration in the second embodiment of the invention, and FIGS. 2
FIG. 6 is a characteristic diagram showing aberrations in a second numerical example of the present invention. Engraving of drawings (no changes in content) Collection l Surface 1...Group 1, 2...Group ■3...Group ■, 4...Group ■5...Group V, 6...Crystal plate 7...Aperture, ...Image plane 5! Engraving of the drawing (no change in content) 4 drawings engraving on Tamezu 1 Kei Kei Sota/h/,/Ren 3 Ki No. 7 (Q) (Q) (G) (b) (C) (b) (c) (b) (c) Engraving of drawings (no change in content) (α) Compilation of drawings (1)) (C) Engraving of drawings (no change in content) 3 Sui (α) CG ) Engraving of drawings (no change in content) Volume/4 Figure (b) (C) (b) (c) (Q) (b) (c) Engraving of drawings (no change in content) Volume/7 Figure K, ＝”＋ Toma ni To＞4qf To: R〉1 ε 63 ＼゛11−Ma1＼1)” くE To; i g;hssa1C:, ε (a) (b) (c) Engraving of drawings (no changes in content) Collection 2″7 Figure (α) Spherical lens. (b) Procedural amendment form for coat resin ( Method) Relationship with the person making the amendment (11 cases)

Claims (1)

[Claims] 1) In order from the object side, the I-th group (1
), Group II (2) and Group III (3) each have negative refractive power and perform zooming by moving along the optical axis, and have positive refractive power. , a zoom lens consisting of an IV group (4) that is always fixed and a V group (5) that has a positive refractive power and has an imaging function, in which at least one surface has a positive refractive power. A fourth group (4) including an aspherical lens, and a fourth group (1) which has a focusing function by moving in whole or in part along the optical axis. zoom lens. 2) The V group (5) includes, in order from the object side, a V group first lens (9) having a positive refractive power, a V group second lens having a negative refractive power (10), The zoom lens according to claim 1, comprising a third lens (11) of the V group having a positive refractive power. 3) Group I (1), Group II (2) and Group III (3) above
) The zoom lens according to claim 1 or 2, wherein the zoom lens has a configuration that satisfies the following conditions. 2.7<|f_ I /f_II|<3.6 1.0<|f_ I /f_III|<1.9 3.0<f_ I /f_w<4.9 However, f_ I is the above-mentioned group I ( 1) focal length, f_I
I is the focal length of the II group (2), f_III is the focal length of the III group
The focal length of group (3), f_w, is the focal length of the entire system at the wide-angle end of the zoom lens. 4) The zoom lens according to claim 1, 2 or 3, wherein the V group second lens (10) has a meniscus-shaped surface with a steep curvature facing the image plane side.