JPH03139607A - Power varying lens - Google Patents

Abstract

PURPOSE:To obtain a wide field angle at the wide-angle end and to increase the power variation ratio by providing a distributed index lens which has a refractive index distribution at right angles to the optical axis of at least one lens in a lens system. CONSTITUTION:The power varying lens consists of a 1st lens group which has negative refracting power, a 2nd lens group which has positive refracting power, a 3rd lens group, a 4th lens group, and a stop which is arranged closer to the image side than the 3rd lens group in order from the object side, and varies in power by varying the intervals of the respective lens groups, and the distributed index lens which has the refractive index distribution at right angles to the optical axis is provided in the lens system. The radial type distributed index lens has power in its medium and the radius of curvature can be made larger or smaller than that of a homogeneous lens with the same power, which is utilized to facilitate the compensation of various aberrations more. Consequently, the power varying lens for a camera which has the large power variation rate and the wide field angle at the wide-angle end is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable magnification lens for cameras, particularly video cameras.

[Prior art] Currently, lenses for consumer video cameras have a zoom ratio of 6.
-10 and an aperture ratio of F/1.2 to F72.0 are mainstream. This is because the above specifications are extremely efficient in terms of design and needs.

Many of the above-mentioned zoom lenses are called -M four-group zoom lenses, such as those shown in Japanese Patent Laid-Open Nos. 58102208 and 153913/1980.

These zoom lenses generally consist of, in order from the object side, a first lens group that has positive refractive power and is fixed during zooming and has a focusing function, and a second lens group that has negative refractive power and is movable and has a zooming function. Consisting of two lens groups, a third lens group that moves to compensate for movement of the image plane due to zooming, an aperture, and a fourth lens group that has positive refractive power and is always fixed and has an imaging function. has been done.

This type of four-group zoom lens is suitable for achieving high variable power and large aperture. However, since the first lens group has positive power, it is not suitable for widening the angle of view, and the angle of view at the wide end is limited to about 50".Currently available 4-group zooms When using a lens, the angle of view is small when photographing indoors, making it impossible to take a satisfactory image, and users desire a zoom lens with a wider angle of view.

On the other hand, there is a two-group zoom lens that has a wide angle of view.

It consists of a first lens group with negative refractive power and a second lens group with positive refractive power in order from the object side, and magnification is changed by changing the relative spacing between these lens groups. .

This two-group zoom lens has a negative lens group in front, so it is suitable for wide angles, but it is not suitable for high zoom ratios and large apertures, and the zoom ratio is generally around 2. It is.

In addition, in this two-group zoom lens, the aperture is generally located in the second lens group, and moves together with the second group during zooming. Moving the diaphragm in this manner is undesirable because it increases the cost of the lens frame structure.

As a zoom lens for a video camera aiming at a wide angle of view, Japanese Patent Laid-Open No. 63-292106 and Japanese Patent Laid-Open No. 1-191
A lens system described in '820 is known.

The former is a zoom lens consisting of three lens groups, negative, positive, and positive, but since the aperture moves together with the second lens group, the cost is high due to the construction of the lens frame. Furthermore, the F-number changes as the magnification changes, which is not preferable.

The latter zoom lens has a negative, positive, and positive three-group configuration, and each lens group is movable, and the aperture is divided between the second lens group and the third lens group.
Although it is fixed between the lens groups, the variable power ratio is small at 2 to 3, which is not fully satisfactory.

Furthermore, there is a zoom lens having a negative, positive, and positive three-group structure, which is described in Japanese Patent Laid-Open No. 40913/1983.

This lens system also has a zoom ratio of just under 3x, which is not fully satisfactory, and the maximum angle of view at the wide end is 45°.
It cannot be said that it has a wide angle of view.

[Problems to be solved by the invention] As described above, in conventional zoom lenses, if the zoom ratio is large, the angle of view at the wide end is narrow, and if the angle of view at the wide end is wide, the zoom ratio is small. It had the problem that.

The present invention provides a variable magnification lens for cameras that simultaneously satisfies the specifications of an aperture ratio of approximately F/2.8, an angle of view at the wide end of approximately 60° to 70°, and a variable power ratio of approximately 3 to 5. It is.

[Means for Solving the Problems] The variable power lens of the present invention includes, in order from the object side, a first lens group having a negative refractive power, a second lens group, a third lens group each having a positive refractive power, A lens system consisting of a fourth lens group and an aperture located closer to the image side than the third lens group, and which performs magnification by changing the distance between each lens group, and at least one light beam in the lens system. This lens has a refractive index distribution type lens that has a refractive index distribution in a direction perpendicular to the axis.

A refractive index distribution type lens having a refractive index distribution in a direction perpendicular to the optical axis using the variable magnification lens of the present invention described above is a so-called radial type lens, and the refractive index distribution is expressed by the following equation.

N(hl = NO+ N+h"+ N2h'+ N3
h'+...N here. is the refractive index on the optical axis, h is the distance in the radial direction from the optical axis, N (h) is the refractive index at a radial position from the optical axis, N, , N2. N3. ...are respectively secondary and 4
It is a constant of order, sixth order, etc.

A radial type gradient index lens has power in its medium, and it is possible to make the radius of curvature of the surface larger or smaller than a homogeneous lens with the same power, so this can be used. This makes it easier to correct various aberrations. Furthermore, by changing the refractive index distribution for each wavelength, chromatic aberration can be corrected with a single lens.

The variable power lens of the present invention uses at least one radial type gradient index lens described above in a lens system having the above-described lens configuration, thereby achieving the object of the present invention.

Since the variable power lens of the present invention has a configuration in which the negative lens group precedes the lens as described above, variable power is performed by moving the second lens group and the third lens group having positive refractive power. Therefore, in order to obtain a large zoom ratio, it is sufficient to increase the amount of movement of the second lens group and the third lens group, but in this case, the total length of the lens system increases. In addition, in order to obtain a large zoom ratio with a small amount of movement, it is possible to increase the power of the second and third lens groups, but this increases the amount of aberration generated in these lens groups, making it necessary to increase the number of lenses. As a result, it becomes difficult to obtain a large zoom ratio.

As mentioned above, the radial type gradient index lens is
The medium has power, and for example, if a positive lens has a refractive index distribution such that the medium has positive power, the overall power can be increased even with the same radius of curvature as a homogeneous lens.

In the present invention, with the lens configuration described above, a variable magnification lens is realized by using a gradient index lens in the lens system, and in particular, this lens is used in the second and third lens groups. It is desirable to use In order to obtain a large zoom ratio while keeping the overall length at a suitable level, at least one gradient index lens that satisfies the following condition (1) should be used in the second or third lens group. is desirable.

fil −1,0<NIPfw”<0 However, NIP is the second-order refractive index distribution coefficient for the d-line of the refractive index gradient lens used at least one in either the second lens group or the third lens group, f, is the focal length of the entire system at the wide end.

If the lower limit of the above condition (1) is exceeded, the influence of the medium of the gradient index lens becomes too large, which worsens off-axis aberrations, especially on the telephoto side, which is not preferable. In addition, if the upper limit is exceeded, the power of the surface becomes too strong to obtain the necessary positive refractive power, and the amount of aberration generated on that surface increases. It becomes impossible to correct it.

Further, since the variable power lens of the present invention has a large number of strong positive lens groups arranged on the image side, spherical aberration from the wide end to the telephoto end is insufficiently corrected. This is particularly affected by the fourth lens group, which has a large refraction of marginal rays. Therefore, if a gradient index lens is introduced into the fourth lens group and the correction term is generated by the medium or surface having a gradient index, positive spherical aberration will be generated and cancel each other out. Spherical aberration can be well corrected from to the telephoto end. Therefore, it is desirable to satisfy the following condition (2).

[21N1141 ・fw”<1.0 However, N +
i41 is the second-order refractive index distribution coefficient N for the d-line of at least one refractive index distribution type lens used in the fourth lens group.
, is the value of .

If the upper limit of condition (2) is exceeded, spherical aberration cannot be satisfactorily corrected from the wide end to the telephoto end.

Furthermore, since the lens system of the present invention has a wide angle of view of 60° or more at the wide end, negative distortion that occurs particularly at the wide end becomes a problem. This is mainly due to the influence of the first lens group, which has strong negative power. In order to correct this, it is sufficient to increase the positive power in the first lens group or to weaken the power of the negative lens. However, in this case, the power of the first lens group becomes weak, making it impossible to obtain the required angle of view at the wide end. Therefore, if a gradient index lens is used in the first lens group, it is effective to correct negative distortion on the wide side.

Next, for variable power lenses, the total length of the lens system.

Although it is desirable to fix the aperture and F number, it becomes extremely difficult to correct aberrations.

In order to achieve a wide angle of view, the present invention is based on a conventional two-group zoom lens consisting of a negative and a positive zoom lens, with the first lens group having negative power and the second to fourth lens groups. The whole was given positive power.

In general, when operating a zoom lens, it is easier to operate it if the overall length of the lens system does not change even during zooming, and users have high needs for a lens system whose F number does not change. In addition, in the case of a lens system for a video camera, the aperture is opened and closed electrically, so it is larger and heavier than the mechanical aperture of a silver halide camera. Therefore, it is undesirable for the diaphragm to move to change the magnification, both from a mechanical and cost perspective, and it is desirable that the diaphragm position is always fixed when changing the magnification. In order to satisfy each of the above requirements in a zoom lens having a four-group structure as described above, it is desirable that the first lens group, the diaphragm, and the fourth lens group remain fixed at all times during zooming.

In order to fix the lens group in a variable power lens,
As shown in Fig. 37, the entire structure from the second lens group to the fourth lens group is configured as a system that relays the virtual image formed by the lens group while keeping the distance between the object point and the image point constant. Bye. Furthermore, in order to obtain a large zoom ratio while keeping the aperture and fourth lens group fixed, the second and third lens groups must be moved during zooming, and both lens groups should be given strong positive power. It is necessary to.

In the lens system configured as described above, from the second lens group to the fourth lens group,
The absolute value of the overall imaging magnification up to the lens group is small on the wide side and large on the telephoto side. Therefore, the principal point of the entire system from the second lens group to the fourth lens group moves forward from the wide-angle side to the telephoto side. By the way, the second
Among the lens groups to the fourth lens group, the aperture is fixed near the fourth lens group. Therefore, on the tele side, the second
The aperture diaphragm is far away from the principal point of the entire system from the lens group to the fourth lens group. As a result of this 1, the entrance pupil on the telephoto side becomes distant, and the ray height of off-axis rays on the telephoto side increases, making it difficult to correct the aberration. Furthermore, if the F number is kept constant, the light beam on the wide-angle side becomes thicker than that on the telephoto side, making it difficult to correct not only off-axis aberrations but also axial aberrations.

In order to increase the variable power ratio of a variable power lens configured as in the present invention without moving the entrance pupil on the telephoto side away, or in other words, without worsening aberrations on the telephoto side, it is necessary to Either the power of the third lens group must be increased or the amount of movement during zooming must be increased. However, if the amount of movement during zooming is increased, the entrance pupil on the telephoto side will be farther away, and if the power is increased, the amount of aberration will increase, and this can only be corrected by increasing the number of lenses. As a result, the thicknesses of the second and third lens groups increase and the entrance pupil on the telephoto side becomes distant, making it difficult to correct aberrations.

So far, we have described a four-group zoom lens in which the overall length of the lens system, aperture position, and F-number do not change during zooming, which is the most difficult aberration correction process. However, depending on your needs, it may be desirable to make the overall length, aperture position, F2 number, etc. variable during zooming. This is because the degree of freedom is greater when the overall length, aperture position, and F-number are made variable than when they are fixed, which makes the design easier, and the object of the present invention can be achieved even if these are made variable. . In addition, in the case of a lens system like the present invention,
Since the diaphragm is opened and closed electrically, it is generally large and heavy due to electrical circuits, so moving it during zooming is a mechanical burden and increases the size of the lens system. Therefore, in the lens system of the present invention, it is preferable that the aperture position is fixed during zooming.

In order to better correct various aberrations when the aperture position is fixed, the following condition (3) is required, even when the overall length of the lens system and F-number are variable during zooming.

It is desirable to satisfy (4).

(3) -0,6<β<-0,2 +4) O<fw/f4<0.5, where β is the composite image formation of the second, third, and fourth lens groups at the wide end The magnification, f, is the focal length of the entire system at the wide end, and f4 is the focal length of the fourth lens group.

If the lower limit of condition (3) is exceeded, the second and third
．． The combined imaging magnification of the fourth lens group becomes a large negative value, and the principal point of the entire system of these lens groups moves toward the object side on the telephoto side.

This makes the entrance pupil too far away, which worsens off-axis aberrations on the telephoto side, which is undesirable. When the upper limit of condition (3) is exceeded, the negative power of the Luns group increases accordingly,
This is not preferable because aberrations occurring in the lens group, especially negative distortion on the wide side, cannot be corrected completely.

Condition (4) specifies the power of the fourth lens group; if the lower limit is exceeded, the ray height of the marginal rays of the second and third lens groups becomes too high on the telephoto side, making it difficult to correct aberrations on the telephoto side. This is not desirable because it makes it difficult. Condition (4)
If the upper limit of is exceeded, the power of the fourth lens group becomes too strong, and the aberration generated in that lens group increases, making it difficult to correct it.

Furthermore, if condition (3) is satisfied, the negative power of the first lens group becomes stronger, and the off-axis aberrations generated in the first lens group, especially the negative distortion on the wide side, become larger. . To prevent this, it is effective to make at least one surface of the first lens group an aspheric surface whose negative refractive power decreases as the distance from the optical axis increases. This aspheric surface is
When the origin is the intersection with the optical axis, the X axis is in the direction of the optical axis, and the y axis is in the direction perpendicular to the optical axis, it is expressed by the following equation.

However, r is the radius of curvature of the reference sphere, P is the conic constant, A2□
is the aspheric coefficient.

It is desirable that the aspherical surface used here satisfies the following condition (5).

(5) Σ1Δx l/h< 0.4 (y=
yic) However, 8X is the amount of displacement of the aspherical surface from the reference spherical surface,
h is the maximum image height, y is the height from the optical axis, and Y:c is the chief ray height at the maximum angle of view at the wide end on this plane. Further, Σ1Δx1 means the sum of the absolute values of ΔX for all five aspherical surfaces used in the first lens group.

If the range of condition (5) is exceeded, distortion will be overcorrected and coma will also increase, which is not preferable.

Further, in the variable power lens of the present invention, it is necessary to arrange an optical member such as an optical low-pass filter between the final lens surface and the image plane, and therefore, it is necessary to provide a sufficient back focus of the lens system. For this purpose, it is desirable that the position of the rear principal point of the entire lens system be as close to the image side as possible.

In the present invention, by using a meniscus lens with a concave surface facing the object side as the lens immediately on the image side of the aperture, off-axis aberrations can be reduced.
We succeeded in obtaining sufficient back focus for the lens system while minimizing the effect on the lens. The term "meniscus lens" as used herein refers to a single lens, or a cemented lens in which the entire cemented lens has a meniscus shape.

This meniscus lens satisfies the following condition (6) 6 It is desirable to do so.

f6) 0.1<r, /rb<2.0 but r a
+ r b is the radius of curvature of the most object-side surface and the most image-side surface of the lens immediately on the image side of the aperture, respectively.

If the lower limit of condition (6) is exceeded, paraxial rays will not be able to bounce up on the object side surface of the lens, and the rear principal point of the lens system will move toward the object side, making it impossible to obtain sufficient back focus. It disappears.

Moreover, if the upper limit is exceeded, the symmetry with respect to the aperture is broken and off-axis aberrations worsen, and spherical aberrations become insufficiently corrected, which is undesirable.

Furthermore, in the variable power lens of the present invention, focusing can be performed not only by extending the entire lens system or only the first lens group, but also by extending the entire or part of the fourth lens group. .

Generally, when focusing is performed by extending the first lens group, there is a feature that the amount of extension for focusing does not change even when the power is changed. However, it has the disadvantage that the lens that is fed out is heavy and that the light beam is easily cut off when it is fed out.

On the other hand, when focusing with the fourth lens group,
The lens is lightweight and the load during focusing is small. For this reason, focusing using the fourth lens group is very effective for increasing the focusing speed in odofocus.

[Example] Next, examples of the variable power lens of the present invention will be shown.

Example 1 f=7-28mm, F/2.8.

2 ω = 62.1' to 15.5', maximum image height 4.
0nvr, = 37.1060 d, = 1.1017 n+ = 1.69680
νI = 56.49rz = 11.4099 (aspherical surface) dz = 3.7939 r3 = -21,8892 d, -1,1034n, = 1.69680 v2
= 56.49r, = -820,0071 d4 = 0.7349 r5 = -3281,9987 d, = 1.8017 Gradient index lens r6 =
-50,2140 d6=DI (variable) rf=48.7137 dy" 2.1621 n4= '1.72916
v-=54.68r8: -75,4351 d,=02 (variable) rs+: 25.3157 d,=1.0000 n,=1.80518
νs = 25.43r,, = 12.8889 dlo = 5.2047 na = 1.69680
1) 6 = 56.49r11 = -57,1774 d++ = Ds (variable) r12 = (to) (aperture) dB = 1.6094 r+a = -5,4284 dl- = 1.3157 n7 = 1.72916
vt = 54-68r+4 = -6,3605 9 d, 4 = 3.4949 r+s = 13.6586 (Aspherical surface) dls =
0.8002 na= 1.78470V
8 = 26.22r+a = 5.9188 d, 6 = 0.9758 r+y = 10.3.754 dl7 = 3.5289 n, P = 1.7?250
v, q, -= 49.66r+s = -28,7
996 Aspheric coefficient (second surface) P = 1.0000, A, = -0,42810
X 10-'A6=-0.19924x llow'
, A, = -0,38654xlO-8 (15th surface) P = 1.0000, A4 = 0.3
9447xlO-”A, = 0.55540xlO-
' , A, = 0.24268x 10-'
f 7 14 28 D, 26.678 8.031 0.504
13, 0.804 9.775 0.502D
, 0.800 10.477 27.276 Gradient index lens O NONI N2d line 1.80
518 -0.91875x10-5 0.101
40X10-5C wire 1.79610-0.98228x
10-50.11050xlO-5F m 1.827
76 -0.77051x 10-' 0.8017
3x 10-6β=-0,392, fw/f,=0.2
191 Ax /h=0.0265, ra/rb
=0.854 Example 2 f = 7-28mm, F/2-8.

2 ω = 62.1” ~ 15.5°, maximum image height 4.0
mmr+ = 37.1206 d, = 1.1O17n, = 1.69680 v
, =56.49r2= 11.4530 (aspherical surface) d, = 3.7890 r, =-21,1381 d, = 1.1034 r4=-789,1964 d4=o, 7384 r5=-3134,7036 n2 = 1.69680 ν2 =56.49 ds= 1.8017 n3= 1.80518 ν3 =25.43 r6= -49,3024 d, =D, (variable) ry” 48.7609 d?= 2.2958 Refraction rate distribution type lens ra
= -76, 4592 da=D2 (variable) ro=25.6297 d, = 1.0000 jl, = 1.8051
8 v, ” 25.43 rl o = 12.7
260 d,,=5.2047 1. =1.69680 White=56.49r,, ”-53,9610 dz=Da (variable) rl□200 (aperture) d,□=1.6094 r+i =-5,4462 d,3 =1.3173 Mouth, = 1.72916
Schiff =54.68r+* =-6,337
5 d, 4=3.4934 r+s =14.0512 (aspherical surface) dl5 =0
．． 8002 n, = 1.78470 v,
=26.22r+s = 5.8979 d, 6 =0.9728 r,, = 10.2265 d,, =3.9445 r,, =-29,0317 Aspheric coefficient (second surface) P = 1. Rolo OO, A4= A, = -0,19965x 1O-6 (15th surface) P=1.0000. A4 = A, = 0.70555x 10-' 7 D, 26.54L D, 0.804 D, 0.800 Gradient index lens N.

d line 1.72916 C line 1.72510 F line 1.73844 I O, 88401 ? = 1.77250 ν, 9. =49.66 0.44582X 10-' A6= -0,36764x 10-"0.39811
X 10-” A, = 0.63900x 10 8 0.504 0.502 27.139 2 0.62785x 10-6 0.66914x 10-6 0.53149x 1O-6 N+p-fw!= -0,433x 10 -2β=-0
, 396, fw/f4=0.216z1Δxl/h=
0.0264, ra/rb=0.859 Example 3 f=7-21mm, F/2.8.

2ω=62.0°~20.8°, maximum image height 4.0m+n
r+=-346.3168 (Aspherical surface) d+=1.
1017 1. :1.69680 v+ = 5
6.49r2=12.5159 da=3.7467 rs=-25,4402 d3=1.1034 n2=1.69680
v2=56.49r4=105.9417 d4=0.7617 rs=138.5318 d,=1.8017 n,=1.80518
v-=25.43r, =-31,3951 d, =D, (variable) ry: 43.5604 d7=2.225I n, =1.72916
v4=54.684 r8” 186.1387 d8”D2 (variable) r9=24.6967 d9= 1.0 [100n5= 1.80518
1/6 = 25.43r1o = 13.7953 d+o = 5.2047 Gradient index lens r,
, = -38,8991 dll = D3 (variable) f, 2 = QQ (aperture) d, 2 = 1.6094 r + a = -5,4704 d,, = 1.3256 n, = 1.72916
vt = 54.68 rz = -6,2248 d, 4 = 3.5472 r, s = -982,0483 d, 5 = 0.8002 na = 1.78470
va ”26.22r, 6 = 10.8908 CIts = 1.317.3 r, 7 = 18.2530 d+t = 1.6961 n4. = 1.772
50 v,y,=49.66r,, =-13,
7688 Aspheric coefficient P = 1.000, A4 = 0.5
4180x 10-'A, = -0,12424x 1
0-6. A, = -0,14574x 1O-9f
7 12 21 D, 22.384 4.307 0.536
D, 1.873 10.599 1.376D
, 0.300 9.652 22.646 Gradient index lens N, N.

d@ 1.69680 -0.48643X10-
'C line 1.69303 -0.62004x 10-'
F line 1.70537 -0.17467xlO-'N+
p−fw” = −0,238X 10−2β=−0,
382, f, /f4=0.262Σ1Δxl/h=0
．． 0279, r, /rb=0.8792 0.82443x 10-6 0.68251x 10-' 0.11556X 10-5 Example 4 f = 6-18 mm, F/2.8.

2c, + = 70.5° to 23.9°, maximum image height 4. O
nv+r+=-89,8524 d,=1.1017 n=r2=IO,7
856 (aspherical surface) d, = 4.4483 r3 = -4994,8129 d3 = 1.1034 r4 = 101.8038 n2 = 1.69680 1,. 69680 ν, , =56.49 ν2 =56.49 d, =1.0000 r5=-57,3067 d, = 1.8017 ra"-28,5793 da"D+ (variable) ry=32.7861 d7= 2.2005 r8= 129.2445 d, ==D, (variable) r9= 23.3425 d, = 1.0000 rr o = 13.0179 d+o =5.2047 n,, = 1.6968Or
,, =-60,6437 1,72916 n, = 1.80518 4 n5 = 1.80518 7 C3 =25.43 ν4 =54.68 ν5 =25.43 ν, =56.49 d,, =D , (variable) r, 2: OO (aperture) d, 2 = 1.6094 r,, = -4,9043 (aspherical surface) dla = 1.0024 n7 = 1.72916
rz = -6,9744 d, 4 = 2.3912 = 54.68 rls = 102.9088 d+5 = 2.4417 Gradient index lens r+8
”-14,4377 Aspherical coefficient (second surface) P=1.0000.A,=-0,13802xlO
-"As" -〇, 17580x 10-6,
Aa = -0,53772x 10-' (13th surface) P = 1.0000, A, = 0.89510xl
O-”A,=-0,19456xlO-', A,
= 0.26833xlO-'f 6 1
0 18 D, 20.993 6.188 1.256
D, 5.204 1 (1,4360,5108 D, 0.7G3 10.337 25.
194 gradient index lens NoN, N2 dll 1.77250 ~0.86409x10-3
0.10410426xlO-3C, 76780-0,
95242xlO-” 0.10271xlO-3F
Line 178336 ~ 0.65799XIO-” O,
10788XIO-3N+ 1411fw2= 0.3
11 X 10-'β=-0,353, fW/f4=0
．． 258ΣΔx/h=0.0933, r
, /rb = 0.703 Example 5 f = 6 to 30 mm 2ω = 69.6° r + = 30.7107 d, = 1.1017 n, ” r, = 11.6112 (Aspherical surface) d, = 4. 59
99 rs = -27,9183 d, = 1.1034, F/2.8 n, = 1.69680 ~ 14.5° Maximum image height 4.0 mw + 1.69680 ν1 = 56.49 ν2 = 56.49 r4 == 856.7966 d4= 0.7986 r-=-209,3451 d, = 1.8017 n, = 1.80518
v, = 25.43r6=-61,381
7 d, = mouth, (variable) r7 = 40.0794 d, = 2.2005 Gradient index lens 1ra”
-688,2678 da=Dz (variable) r9=26.9091 d,=1.0000 n5=1.80518
v5 = 25.43r + o = 14.704
7 d, o ”5.2047 n, = 1.69680
v6=56.49r11 =-53,9850 d++=O3 (variable) r12 =QO (aperture) d1□=1.6094 rrz =-5,4990 d,, =1.3105 n, =1.72916
v7 = 54.68rz = -6,4900 ct, 4 = 2.7736 r, 5 = 12.9668 (aspherical surface) d, 5 = 0
．． 8002 08= 1.78470 ν,
=26.22r+a =6.0277 dla =1.1835 rIt =10.5920 d,, =2.4004 Gradient index lens 2r
, 8"-20,4772 Aspheric coefficient (second surface) P = 1.0000, A, = -0,50209
x 10-'A6=-0,10094x 10-6.
A, = -0,32970x 1O-8 (15th surface) P = 1.0000, A, = 0.44808xl
O-3A6=-0,13769X10-', A,
= 0.76060xlO-'f 7 1
4 30 D, 33.888 7.011 0.504
D2 0.804 14.514 0
．． 502030.800 13.967 34.486
Gradient index lens I 0NIN2 1 0.82721X 10-6 0.85521X 10-' 0.76187x 1O-6 d-line 1.72916 -0.41256x 1O-3C
Line 1.72510 = 0.41448x 1O-3F
Line 1.73844 -0.40809x 10-3 gradient index lens 2 NoN.

d line 1.77250 0.23466x 10-” C line 1.76780 0.22933x 1O-2F line 1.
78336 0.24710x 1O-2N+p-fw
” =-0,149x to-'N+ 1411・f,
” =0.845 xlO-'β=-0,322, fw
/f,=0.212Σ1Δxl/h=0.0846
, ra/rb = 0.8472 0.93255X 10-' 0.90057x to-' 0.10072X 10-3 Example 6 f = 7-21 mm, F/2.8.

2 ω=61.96~20.8°, maximum image height 4.0+
nw+rl = −207,8680 d,”1.0057 n,=1.89680
1/i = 56.49r2 = 12.1165 d2 = 3.7256 ra = -37,5005 (aspherical surface) 2 d3 = 1.2666 n2 = 1.6968
0r4 = 57.4633 d, = 0.8022 r5 = -128,8034 d, = 1.8318 r6 = -23,7042 da = n + (variable) r, = 38.0670 d, = 2.2482 r, = 153.3615 d8 = D2 (variable) r, = 26.4604 d9 = 5.1940 r,, = -37,5290 d,, =D, (variable) r11 = cx: + (aperture) dll = 1.6094 r1□ = -5,5369 1,80518 Gradient index lens 3 n4 = 1.72916 Si2 = 56.49 ν, = 25.43 ν4 = 54.68 d, 2 = 1.3210 16 = 1.72916
Sh. = 54.68 r, ==-6,2037 d, 3 = 3.5094 rl 4 = 306.4568 d+4 = 0.8002 n.

rls = 11.1446 d, 5 = 1.301O r, e = 21.1474 d,, =1.6961 r,, =-15,1468 Aspheric coefficient P=1.0000. A4= A, = 0.36792x 10-6 7 DI 22.746 D23.359 D, 0.500 Gradient index lens N.

D line 1.69680 C line 1.69303 Fil! 1.70537 2 2.270 15.780 9.328 na” 1.7725O 1 0,36146x 10-' 0.64370X 10-' 0.29711X 10-' 1.78470 Schiff =26.22 ν8 =49.66 0.70278X 10-' A, = -0,29020x to-81 0,589 1,453 19,608 2 0,17442X to-5 0,15450x 10-5 0.22089x 10-' N+p, fw" =- 0,177x IQ-2β=-
0,404, fw/f4=0.210Σ1Δx/h
=0.0204', ra/rb=0.893 Example 7 f=7-21mm, F/2.8.

2ω=62.2°~21.0°, maximum image height 4.0mmr
, = 139.2704 (aspherical surface) d, "4.400
[1n,”1.72825 v, =28.46r
2=-20,7046 d2= 1.2049 n2= 1.72916
v2= 54.68ra" 13.4437 d3=D+ (variable) r4= 37.5049 d4" 3.8033 n-= 1.72916
v3=54.68rs=-16,2306 d5=1.000On,=1.80518v,
=25.43r6= -124,0325 d6"D2 (variable) rt = 29.3692 d," 3.9000 ns = 1.69680
v5 = 56.495 r8 = -44,6011 d8 = D3 (variable) r9 = oo (aperture) d9 = 2.7053 rzo = -5,1791 d,, =0.8119 rz = -7,1518 d++ =1 .5738 "1□ Knee 6.0203 Aspheric coefficient P = 1.0000. A4 = A, = 0.91628x 10-" 7 D, 35.226 D20.800 D, 0.530 Gradient index lens N.

d line 1.77250 C line 1.76780 2 17.197 7.565 6.402 na= 1.80518 1 0.61681X 10-' 0.61479x 10-2 6 υ6 ='25.43 Gradient index lens 0.13273X 10-' A, = -0,13678x 10 1 7.844 0.811 15.928 2 -0.22401x 10-' 0.22829X 10-' F line 1.78337 -0.62152xlO-"
-[1,214[12xlO-'N+ 141'f
w”=0.302β=-0,337,f,/f,
=0.172Σ ^xl/h=0.0360, r
,/rb=0.860 Example 8 f=6-24mm, F/2.8.

2(,1=69.9°~18.2°, maximum image height 4.0m
mr+ = -150,2428 d1= 1.2000 11. = 1.72916
v1= 54.68r2= 12.9449 (
Aspheric surface) d2 = 2.5028 r3 = 38.8737 d3 = 5.4361 n2 = 1.80518
v2= 25.43r4= -20,1239 d4= 1.0416 na= 1.77250
V3 = 49.66r, = 70.3603 d5 = D, (variable) r, = 57.5209 da = 7.2517 n4 = 1.72916
v4"54.68rt"-14,2287 d, = 1.0000 n5 = 1.80518
v5 = 25.43i'8 = -64,6672 d8 = 0. (Variable) r9 = 42.2352 d, = 5.0191 na = 1.72916
V6 =54.68r+o =-29,1522 dlo”0.9025 n7=1.8051
8 1/7 = 25.43r++ = -46
,6193 d++=Da (variable) r, 2=(capital) (aperture) d, 2=04 (variable) rza =-4,3521 d+a =3.0076 Gradient index lens rz
=-5,7088 Aspheric coefficient P=1.0000. A, = -0,60947X
10-'Aa=-0.14192xlO-', A,
=-0,18155xlO-8f 6 1
2 24 D, 33.044 11.647
2.640D22.926 12.228 5.0
768 D3 0.800 12.865 29.05
5D4 1.400 3.095 6.6
10 refractive index gradient lens NoN.

d line 1.72916 -0.63215X 1[1-2
C line 1.72510 -0.63392x to-2F
Line 1.73844 -0.62803x 1O-2N,
+4+lfw” = 0.228β=-0,297,
fw/f4=0.215Σ1Δxl/h=o, 17
4, ra/rb=o, 7622 0.11343x 10-' 0.11916x to-' 0.10005x 10-' Example 9 f = 7-21mm, F/2.8. .

2ω=62.0°~21.2°, maximum image height 4.0mmr
+ = -112,6325 d+ = 1.0057 0. = 1.69680
ν+ = 56.49172 = 12.1148 d2 = 3.6530 r3 = -47, mouth 492 (aspherical surface) d3 = 1. , 1821 n2= 1.69680
V2 = 56.49r4 = 35.1681 9 d, = 0.9997 rs = -130,6409 d5 = 2.5481 n- = 184666
1/2 = 23.78 r6 = -20,4926 d, = D, (variable) r7 = 20.6117 d, = 2.7824 n4 = 1.72916
v4 =54.68ra: 35.2827 d, =D, (variable) r, = 23.5329 d, = 5.1967 gradient index lens rl
o = -54,6926 d,. =D3 (variable) r,, =11.2556 d,, =0.805On, =1.80518 v
, =25.43r+□=8.1751 d1□=0.9000 r+a =QQ (aperture) dla =1.6094 rz =-5,4331 0 d,4 =1.3044 n-=1.80548
v, =25.43r+5 =-6,4290 a,5 =3.2563 r+a =-264,'2006 d,6 =1.8071 n8"1..77250
v8=49.66r+y=-16,114
2 Aspheric coefficient P = 1.0000, A, = 0.7
2141xlO-'A, = 0.39739xlO=6
．． A, = -0,41865xlO-9f 7
12 21 D, 27.662 1.000 0.500
D, 7.058 24.162 0.500D
30.500. 8.936 16.441 Gradient index lens NoN+ N2 d-line 1.69680 -0.10464x 10-30
．． 81316x 10-'C line 1.69303-0.1
4252x10-30.59.519xlO-'F line 1
．． 70537 -0.16248xlO-' 0.1
3217xlO-'N+p-fw" =-0,513x
10-2β=-0,367, fw/f4=0.188
Σ1△xl/h=0.0462, ra/rb=
0.845 However, r r + r 2 +... is the radius of curvature of each lens surface, dl, d2. ... is the wall thickness and air spacing of each lens, n r .

n 2 + . . . is the refractive index of each lens; C2.
... is the Atsube number of each lens.

Example 1 has a configuration as shown in FIG. 1, in which the lens closest to the image side of the first lens group is a gradient index lens having positive refractive power. Further, by making the second surface an aspherical surface that satisfies condition (5), negative distortion on the wide side is favorably corrected. Moreover, the total length of the lens system, the aperture position,
The F number is Z.

- Does not change during minking.

The aberration situations in wide, standard, and telephoto in this example are as shown in FIGS. 10, 11, and 12, respectively.

Embodiment 2 has the configuration shown in FIG. 2, and uses a single gradient index lens that satisfies the condition (2) for the second lens group, and obtains a variable power ratio of 4x. In this embodiment as well, aberrations are more effectively corrected by using an aspherical surface like in the first embodiment. Also in this embodiment, the overall length of the lens system, the aperture position, and the F number are fixed.

The aberration situations in wide, standard, and telephoto in this example are as shown in FIGS. 13, 14, and 15, respectively.

Embodiment 3 has the configuration shown in FIG. 3, in which the positive lens of the third lens group is a gradient index lens that satisfies the condition +1.1. In this embodiment, the first surface is made an aspherical surface to correct negative distortion on the wide side. Also in this embodiment, the overall length of the lens system, the aperture position, and the F number are fixed.

The aberration situations in wide, standard, and telephoto in this example are as shown in FIGS. 16, 17, and 18, respectively.

Embodiment 4 has the configuration shown in FIG. 4, in which the lens closest to the image side is a gradient index layer lens with positive power, which corrects spherical aberration from the wide end to the telephoto end. In addition, the angle of view at the wide end is 70°, which is a very wide angle of view, and the second surface is made an aspherical surface to satisfactorily correct negative distortion that occurs at the wide end. This example also shows the total length of the lens system and the aperture position.

The F number is fixed.

The aberration situations in wide, standard, and telephoto in this example are as shown in FIGS. 19, 20, and 21, respectively.

Example 5 has the configuration shown in FIG. 5, and the second lens group meets the condition +
One gradient index lens satisfies condition (2), and the lens closest to the image side of the fourth lens group is a gradient index lens that satisfies condition (2), and the angle of view at the wide end is 70°.
It is a lens system with a variable power ratio of 5. In this fifth embodiment, as in the first embodiment, the second and fifth surfaces are made aspheric to satisfactorily correct aberrations. Also in this embodiment, the overall length of the lens system, the aperture position, and the F number are fixed.

The aberration situations in wide, standard, and telephoto in Example 5 are as shown in FIGS. 22, 23, and 24, respectively.

Example 6 has the configuration shown in FIG. 6, in which the third lens group is composed of one gradient index lens that satisfies condition (1). In this embodiment, the aperture position 4 and the F number are fixed, but the first lens group is moved during zooming to reduce the overall length.

The aberration situations in wide, standard, and telephoto in Example 6 are as shown in FIG. 25, FIG. 26, and FIG. 27, respectively.

Example 7 has the configuration shown in FIG. 7, in which the lens closest to the image side is a gradient index lens that satisfies condition (2), and is also a cemented lens to correct high-order spherical aberration. Furthermore, the first surface is made an aspherical surface to correct negative distortion on the wide side. Furthermore, by moving the first lens group during zooming, aberration correction becomes easier, and the number of lenses is reduced to seven. Note that the aperture position and F number are fixed.

The aberration situations in wide, standard, and telephoto in Example 7 are as shown in FIGS. 28, 29, and 30, respectively.

Example 8 has the configuration shown in FIG. 8, and the fourth lens group is set under the condition (
It is composed of one gradient index lens that satisfies 2). Also, by changing the diameter of the aperture during zooming, the overall length of the lens system, aperture position, and F number were fixed. Note that the F number will be variable unless the diameter of the aperture is changed during zooming.

The aberration situations in wide, standard, and telephoto in Example 8 are as shown in FIGS. 31, 32, and 33, respectively.

Example 9 has the configuration shown in FIG. 9, in which the third lens group is composed of one gradient index lens that satisfies condition (1). In this embodiment, the diaphragm is arranged in the fourth lens group, and the lenses sandwiching the diaphragm have a concentric shape with respect to the diaphragm, which is advantageous for correcting off-axis aberrations. In this embodiment, the aperture position and F number are fixed.

The aberration situations in wide, standard, and telephoto in Example 9 are as shown in FIGS. 34, 35, and 36, respectively.

[Effects of the Invention] The variable magnification lens of the present invention has the lens configuration as described above, and by appropriately using a gradient index lens, it has a wide angle of view of about 60° to 70° at the wide end. , a variable power ratio of about 3 to 5, and an aperture ratio of about F/2.8.

[Brief explanation of the drawing]

1 to 9 show Example 1 of the variable power lens of the present invention, respectively.
10 to 12 are aberration curve diagrams of Example 1, FIGS. 13 to 15 are aberration curve diagrams of Example 2, and FIGS. 16 to 18 are sectional views of Example 9. 3, FIGS. 19 to 21 are aberration curve diagrams of Example 4, FIGS. 22 to 24 are aberration curve diagrams of Example 5, and FIGS. 25 to 27 are aberration curve diagrams of Example 6. Aberration curve diagrams, FIGS. 28 to 30 are aberration curve diagrams of Example 7, FIGS. 31 to 33 are aberration curve diagrams of Example 8, and FIGS. 34 to 36 are aberration curve diagrams of Example 9. Figures 37 and 37 show the 2nd to 4th zoom groups using the 4-group zoom.
FIG. 3 is a diagram showing a configuration when a lens group is considered as one lens group.

Claims (1)

[Claims] In order from the object side, a first lens group having a negative refractive power, a second lens group, a third lens group, and a fourth lens group each having a positive refractive power.
A lens system consisting of a lens group and an aperture located closer to the image side than the third lens group, and which performs magnification by changing the distance between each lens group.At least one lens in the lens system is perpendicular to the optical axis. 1. A variable magnification lens comprising a gradient index lens having a gradient index in a direction.