JPS6034734B2 - Zoom lens system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a wide-angle zoom lens, and more specifically, the present invention is composed of a first lens group having a negative focal length, a second lens group having a positive focal length, In a zoom lens in which the focal length of the entire system is made variable by making the air distance between both lens groups variable, the size can be reduced without worsening various aberrations despite extending the photographing area toward the wide-angle side. This is what I did.

As shown in Figure 1, from the object side, the negative first group 1 and the positive second group
A so-called reverse telephoto type zoom lens consisting of group B is an advantageous type for widening the angle of view, but since the distance between the first group 1 and the second group B is widest at the wide-angle end, which has the widest angle of view, There is a direction in which the ball lens diameter increases as the angle of view becomes wider.

These days, if you try to make the lens ultra-wide-angle, it becomes more noticeable, and if you try to make it smaller while trying to make it wider, the barrel distortion at the wide-angle end will increase rapidly, and it will be difficult to correct it. Become. The purpose of the present invention is to improve the above-mentioned drawbacks, but since this case relates to a zoom lens, this aberration correction does not only correct distortion at the wide-angle side, but also corrects other aberrations. It is an object of the present invention to provide a zoom lens system in which aberrations such as spherical aberration on the telephoto side and various aberrations at intermediate zoom positions are not worsened.

In order to achieve the above-mentioned object, the present invention makes any one surface in the diverging first lens group aspherical, and by satisfying the conditions described below, the angle of view at the wide-angle end reaches the square degree. , various aberrations including distortion can be corrected extremely well, and at the same time the entire lens system can be miniaturized.Furthermore, it is possible to keep the bride surface constant through mechanical correction. Therefore, it is particularly suitable as an ultra-wide-angle zoom for still cameras, movies, and televisions.

The present invention will be explained in detail below. It consists of a first lens group with a negative focal length and a second lens group that includes an aperture and has a positive focal length. In a zoom lens that changes the focal length, an aspherical surface is provided on an arbitrary surface in the first lens group, and the following conditions are satisfied in order to achieve a high degree of aberration correction. (1)
-3. Criticism-,. ,7 (o) 〇. 54 1 share,. 5 plates 〇. 35 striped horse <〇. 8 (W) o. 7<l curve l<2.0 (V) ○<center j<○-3 However, f,; Focal length W of the first lens group; Focal length of the entire system at the wide-angle end 8: At the telephoto end Focal length of the entire system lw; Distance (air distance) between the first and second lens groups at the wide-angle end hwi; i-plane (aspherical surface) at the wide-angle end when the object is at infinity Height h at which the paraxial ray passes
wi; Height at which the Kondo pupil ray passes through the i-plane (aspherical surface) at the wide-angle end when the object is at infinity hti; The height at which the Kondo pupil ray passes through the i-plane (aspherical surface) at the wide-angle end when the object is at infinity; The initial value is Qw, which is defined as the height at which the Kondo self-weight ray passes through the sphere (spherical surface).
,=0,hw,=1.0,Qw,=-1.0,hw,:
-tw, QT, = 0, hT = fT, QT1 = Ichiu, City 1 = Ichika This is what was paraxially tracked.

Here, Q is a parameter representing the angle of the light beam, and the suffix represents the wide-angle end and telephoto end. tw' represents the distance from the first surface of the entrance pupil at the wide-angle end, and tT represents the distance from the first surface of the entrance pupil at the telephoto end. Conditions (1) and (0) relate to the power arrangement of the lens system, and if the upper limit of condition (1) is exceeded, it becomes difficult to correct various aberrations including distortion.

Further, if the lower limit is exceeded, it is advantageous in terms of aggregation correction, but the entire lens system becomes larger, which is contrary to the purpose of obtaining a compact zoom lens. The upper limit value of condition (b) is also determined to make the entire lens system smaller, while the lower limit value of condition (b) is determined to prevent the disadvantage that the zooming movement amount becomes too small by 4 mm and the zoom ratio becomes small. This is what I did. Conditions (m) to (V) are conditions for the shape of the aspherical surface, and various quantities will be explained.

In general, the shape of an aspheric surface is as shown in Figure 2, where the near radius of curvature at the apex of the aspheric surface is R, the x-axis coincides with the direction of light travel on the optical axis, and the apex of the aspheric surface is perpendicular to the x-axis. When taking the y-axis that passes through , the deviation x in the day of the y-coordinate is expressed as.

The first term of this equation [1} is a quantity provided only by the paraxial radius of curvature R, and the second and subsequent terms give the quantity of the aspheric surface. The coefficient B of the second term has the following relationship with the third-order aspheric coefficient center.

J=8(N'-N)B ■ Also, the third term coefficient C has the following relationship with the fifth-order aspherical coefficient ○.

Q=48(N'-N)C (where N is the refractive index of the soot before the aspherical surface, and N' is the refractive index of the soot after the aspherical surface.

) Here, the aspherical coefficient center brings about the amount of change shown below with respect to the third-order aberration coefficient in aberration theory, that is, the amount of change in the third-order aberration caused by making the surface aspherical. (However, 1 is the spherical aberration coefficient, 0 is the coma aberration coefficient, m is the astigmatism coefficient, W
is the spherical field curvature aberration coefficient, and V is the distortion aberration coefficient.

) As shown in Figure 3, h and h are the paraxial tracking amounts, and h
'ma' indicates the height at which a ray of light that travels along the optical axis and forms an image on the optical axis cuts through each surface of the lens, and h'a shows the height at which a ray of light that enters obliquely and passes through the center of the aperture (paraxial pupil ray) cuts each surface of the lens. It shows the height passing through.

The quantities of h and h in equation '3' change depending on zooming when considering a particular surface. That is, when a certain aspherical mass center is introduced and zooming is performed, all third-order aberration coefficients change due to zooming. Therefore, conditional expression (m) mainly has the effect of correcting barrel distortion aberration at the wide-angle end, which is caused by downsizing the lens system, and corrects aberrations caused by zooming that do not have much effect on various aberrations at the telephoto end. It gives a suitable selection of surfaces that keep the variation well.

That is, when lhTi/hwi l exceeds its upper limit value of 0.8, the effect of correcting distortion aberration on the wide-angle side due to the aspherical surface has a strong negative effect on aberrations on the telephoto side. Therefore, aberration fluctuations due to zooming become too large, making it difficult to correct aberrations. On the other hand, if lhTi/hwi l is less than its lower limit value of 0.35, the diameter of the first lens group will increase significantly, making it impossible to design a compact lens. Therefore, by satisfying conditional expression (m), it is possible to be compact and to satisfactorily correct fluctuations in aberrations due to zooming. Next, the effects of the aspheric surface at the wide-angle end of conditional expressions (W) and (V) are made to be most effective.

That is, when an aspherical surface is introduced in order to correct the barrel-shaped distortion that is a problem at the wide-angle end, the third-order aberration coefficients change as shown in equation {3' above. In other words, the third-order aberration coefficients all change more or less with the introduction of the aspherical mass, and an attempt to correct the distortion ΔV causes the problem that other aberrations worsen. The conditional expression W is intended to eliminate this obstacle, and the variation of astigmatism (or curvature of field), which is relatively susceptible to the variation of distortion aberration ΔV, is 4. , things are desirable. From formula '31, the fluctuation of distortion △V is △V=hh3
Since the fluctuation Am of J and astigmatism is expressed as △m=h2h2↓, if h is made larger compared to the magnitude of h, that is, lh/
By setting the value of hl to a large value, the fluctuation of distortion △
It is possible to keep the variation △m of astigmatism small with respect to V. By doing this, the variation of coma aberration △0koh
It is clear that the spherical aberration variation △1=h4 can also be kept small. lhM/hwi
When the value of l is less than or equal to the lower limit of conditional expression W, the influence of the aspheric surface has a large influence on aberrations other than distortion.

In particular, a large amount of astigmatism occurs, making it difficult to correct the astigmatism using a spherical surface other than an aspherical surface. Furthermore, in this case, the amount of asphericalization for correcting distortion aberration, that is, the amount of deviation from the spherical surface, increases, so the amount of processing increases, which is difficult to manufacture. On the other hand, if the value of lhwi/hwil is greater than or equal to the upper limit of conditional expression N, the entire optical system becomes large and compactness is compromised. Therefore, as mentioned above, it is desirable that lh/hl take as large a value as possible within a range that does not compromise compactness. Conditional expression V gives an aspherical shape for eliminating barrel distortion.

In general, in a lens group that has negative power in the first group and positive power in the second group, and an aperture in the second group, under-distortion, that is, barrel-shaped distortion, is likely to occur, and the aberration coefficient of distortion is tends to take large positive values. Therefore, in order to correct this with an aspheric surface, the variation of the distortion aberration △V is △V=hh
Must be 3℃<0.

If h>0, h<0, then J>0 Must.

Moreover, when the center exceeds the upper limit value of conditional expression V, aberrations other than distortion deteriorate significantly, and it is no longer possible to correct these aberrations with surfaces other than the aspherical surface. In particular, astigmatism changes rapidly with respect to the angle of view and occurs in large quantities.
Therefore, various aberrations can be corrected satisfactorily only within the range of conditional expression V. Examples 1 to 5 will be described below.

Example 1 corresponds to the lens shapes shown in FIGS. 4a, b, c, Example 2 corresponds to the lens shapes shown in FIGS. 6a, b, c, and Example 3 corresponds to the lens shapes shown in FIGS. 8a, b. , c, Example 4 corresponds to the lens shapes shown in FIGS. 10a, b, and c, and Example 5 corresponds to the lens shapes shown in FIGS. 12a, b, and c. Example 1 f,=1.875 fw=l bw,=-1. Zw-0.88676 hw, '-1.17959hT
I=-0.630335 Zijl aberration coefficient f=1.0 f=1.1667 f=1.4774L
O. 006283 0.004537 -0
．． 000779T O. 000908 0.0
00472 -00004381 1.19712
1.36879 1.635831 above -○
-〇3259 -○-〇3803 10-〇87
49 dishes 0.02687 0.02728
0.02565P O. 09070 0
．． 09070 0.09070V O. 21
930 0.13874 0.052421
-227.00904 -274.14741 -2
87.56387 neck -25-49871 -27-5
2621 -11-226141F -1.5421
1 -1.91743 -00040011p
o. 53520 0.51273 0.45
421 gold -7-40910-8-64218 -9-
203730.27802 002480 -0
．． 36702 meals.

-07906 0-〇6639-. -01767-0
．． 54699 -0.44821 -0.408
12 total ---7295-o-65876-. -2
291811×O. 04636 0.052
36 0.079751×O. 81416
0.70772 0.3974811X -
0.03390 -0.03083 -0.054
461: Spherical aberration, B: Comatic aberration, m: Astigmatism, P:
Bevuar sum, v: distortion aberration, *: band spherical aberration,
5: Ring coma, IF: Feathered aberration, □: Arrow aberration, ↑:
Peripheral spherical aberration, every: Peripheral coma, Gold: Circumferential E-point aberration, Life:
Peripheral spherical defective field curvature, ◇: Peripheral distortion, 52: Force o aberration of annular coma, withdrawal aberration of IZ spherical aberration, 5: Coma o aberration However, fw = 1.0 at object infinity As mentioned above, the initial value is Qw, = 0, Qw・=-1, -
-lhw. =-tw, QT, :0, hT, =fT
, Misaki, = phrase, hT. =-Sheep.

This also applies to Examples 2 to 5 below.
RI surface aspherical aspherical coefficient; B=2.932×10-2 CI: 1.010XI.

-3D, = 6.3508 x 10-5 E, = 4.2858 x 10-4 Matashin: 0.1461 L fw = -1.875 Vessel = o-8868 False: Current Nada = 〇. 5344 End l=l Mountain ■l=Side 6 11 Example 2 f,=-1.8774 hwl=l fw21 hw,=-1.1777 and w 0
．． 84564 hT,: -0.62521 Seidel aberration coefficient, number f = 1.0 f = 1.157 f =
i. 4774L O. 002391 0.00
0981 -0.003217T O. 001
541 0.001234 0.0005911
1.28698 1.60834 2.
50436U O. 06718 0.077
79 0.09026m 0.01154
0.00746 0.00349P O
．． 09922 0.09922 0.09
922V O. 22617 0.14369
0.05496f -・98.22212 -2
35.53613-228. oo417 Hiroshi -19-
42143-20-〇9659-.

-709931F -2.34416 -2.7
2906 -070238 Window astringency poisoning Imperial family sickle Tsukiji Plexus poisoning blind love - 8: Umajishu - 82 characters Teiki = 8: Lunchtime declaration -
1.14556 -064693 -0224
561 studies×.

-10701 0-14767 0-247281
×O. 89580 0.87407 0
．． 778581ln
Hit 0.11751 0.1
0953 0.08368R, Surface Aspherical surface, Aspherical coefficient 8 = 2.9469 x 10-2 C, = 1.3667xlo-3 D, = -4.2675 x 10-5 E, = 8.3883xlo-4 Also centered・=○-1469 f,=-1.8774 fw Western=o-8456 ・Mother=Hanwani=0.5309 Song=1・1777 Example 3 f=1.0~1.5009=430~ At 31, F training technique 3.5 side repair. R D
N So1 3.105193 days) 0.08
333 1.6393044.902 0.993
43 0.495753 -2708355
0.22084 1.69895 30.104
-6.45838 0.016675 2
4.88625 0.08333 1.6260
6 39.106 1.23685 0.1
73407 1.45044 0.0880
5 1.67000 57.408 0.9460
0 0.027919 0.95138
0.29771 1.72342 38.001
0 3.0465611 1.05238
0.14826 1.60717 40.301
2-118.71302 0.1401413
Aperture surface 0.0364214 1.78
737 0-10159 1.60738 56
．． 8015 5.70494 0.0619
816 1.96287 0.07715
1.62299 58.2017 12.4239
2 0.08463f=1.0~1.5009
No =” 130-31 F/slang = 3.5 side repair R
D N Le18
-0.97642 0.13333 1.80
51825.4019 1-52402 0
．． 0541720 -2.65938 0.1
1667 1.72000 50.2021 -0.
91614 0.0291722 -7.67
927 0.10417 1.77250 49
．． 7023 -1.45012 0.0043
11-1 WI co1fw=1
hwl=-1.1493W:0.8838h
So, = -0.5980 Seidel aberration coefficient f = 1.0
f=1.1714 f=115009L
O. 004090 0.000920 -0
．． 006976T O. 001507 0.
000863 -0.0002441 1.53
799 1.93858 2.7745011
0.09306 0.10098 0
．． 09006m -0.00952 -0.01
050 -0.01188P O. 10789
0.10789 0.10789V
O. 22211 0.12321 0.044
77 Takashi -226-49796 -285-36145
-314-〇73711YO -2109019
-22-58253 -4-88570IF -2.
52705 -2.84819 -0.65751
Volume = Nada Gentaku = Nada Poison Damage - Isote Nutrient 0.18372
0.14398 0-03984 Western × -1-115
92 -0-55675 -0-195860.21
254 0.27025 0.38149
1×I. 11874 1.06776
0.9075711×O. 15352
0.13128 0.07997R, surface aspherical surface,
Aspheric coefficient B=2.5151×10-2 C,=2.6680xlo-3 0,=6.3508×10-5 E,! 4.2858×10-4 Matashin. =○-1286 f, fw=-1.875o Vessel=o-8838 False: Morikisha 203 Mizuki 1493 Example 4 f,=-1.8750 hw2=0.98546fw-
l hw2=-1.29193 and W:0.9
360 0T2=-0.6820 Seidel harvest coefficient f=1.0 f-1.1667 f=1.49
99L O. 005299 0.00086
8 0.004074T O. 002686
0.001527 0.0022621
1.25909 1.79741 1.49914
0 0.11936 0.07240 0
．． 12070! □ -0.01383 -0.0
1457 -0.01209P O. 105
20 0.10520 0.10520 yen.

-28010 0-〇7101 0-168285
22.5o484 -6.94862 -24.84
2611F -1.97978 -1.96571
-2.92514 steps. -07557 0 dishes 83
0-16175 Fri -7-06887-10.126
77 -8・92261 Life -0-22532-0-
65466 -0-342140.19255 0.
02899 0.14641 meals・0-49167-
. -39743-. -41004 neck X -1-435
30-0-24176 -0-710030.1957
9 0.25197 0.223091×
O. 96620 0.76719 09224
71lx o. 17894 0.06097
0.14427R2 surface Aspherical surface, aspherical coefficient &=3
．． 7518xlo-3 C2=-8.6396x10-4 D2=0 E2=.

or, Heart 2 =○-0187 Beauty=-1-8750 Vessel: o-9360 Kazuma = Masuwani =.

・52791 belt = Isshi foundation = skin.

Example 5 1=-1. hw5= 1.1189fw=
1 bw5 knee 0.8418 Otsu W = 0.
8937 hT5 engineering-0.4066 Seidel aberration coefficient f=l f=1.1667 f=1500
3L O. 005580 0003231
-0.002822T O. 001845
0.001303 0.0003771 1.
80427 1.94245 1.6114611
0115333 0.17978 0
．． 16626m -0.05479 -0.034
94 -0.01207P O. 08713
0.08713 0.08713V O
．． 31433 0.18991 0.0821
51 -154.02337 -190.01037
-160.81468 company -19-167o9 -20
-23031 -6-791761F -1.479
44 -1.58998 -0.21735 steps -
.

-20346 -0-24810-. -34493-5
．． 95885 -6.99596 -7.91
963 Bon -. -13551-. -47661-. -8
77930.44525 0.21573 -
0.02182 thoughts--. -02322-. -1493
8-. -29231-145349 -066207
-0.204421 sheep X. -40192 0
-36963 0-234571s 1.071
58 0.83300 0.1966111 length 0.20954 0.19678 0.
12514R5 surface aspherical surface, aspherical coefficient B=3.911
7×10-2 C5=3.2484xlo-2 D5=0 E5ni.

or Heart 5;○-1887 Beauty=-1-6667 Vessel o-8937 Continued = Sheep age =.

．． 4832 one end =. pain general = 〇. 7520

[Brief explanation of drawings]

FIG. 1 is a diagram showing zoom movement of a zoom lens system according to the present invention. Figure 2 is a diagram for explaining the definition of an aspherical surface. FIG. 3 is a diagram for explaining the definition of paraxial quantity. FIGS. 4a, b, and c are sectional views showing the lens shape corresponding to Example 1 of the present invention, in which a shows the state at the wide-angle end, b shows the middle state, and c shows the state at the telephoto end. Figure 5a
, b, and c are various aberration diagrams of Example 1, where a shows the state at the wide-angle end, b shows the middle state, and c shows the state at the telephoto end. FIGS. 6a, b, and c are cross-sectional views showing the lens shape corresponding to Example 2 of the present invention, and FIGS. 7a, b, and c are aberration diagrams thereof. FIGS. 8a, b, and c are cross-sectional views showing the lens shape corresponding to Example 3 of the present invention, and FIGS. 9a, b, and c are aberration diagrams thereof. 10a, b, and c are cross-sectional views showing lens shapes corresponding to Example 4 of the present invention,
Figures 11a, b, and c are aberration diagrams. Figure 12 a, b, c
13 is a sectional view showing a lens shape corresponding to Example 5 of the present invention, and FIGS. 13a, b, and c are aberration diagrams thereof. 1...First lens group, 0...Second lens group, R...Radius of curvature of the lens surface, D...Lens thickness. Grandchild's drawing No. 2 Box 3 Drawing Grandson 4 Drawing 4 Younger brother 5 Drawing Leopard 5 Drawing Tsutomu 6 ★Ah Drawing Y Son Ma Drawing Multi drawing 8 Murder drawing Rare drawing Leopard/O drawing ticket Illustration Thorn] --- Figure Son'2 figure Tsutomu'3 figure leopard/3 figure

Claims (1)

[Claims] 1 Consisting of a first lens group with a negative focal length and a second lens group that includes an aperture and has a positive focal length, the air gap between the first lens group and the second lens group In a zoom lens that changes the focal length of the entire system by changing the interval, an aspherical surface is provided on the i-th surface, which is an arbitrary surface of the first lens group, and the following conditions (
I)～(V)(I)−3.0<(f_1)/(fw)<−
1.17(II) 0.54<(lw)/(fw)<1.5
(III) 0.35<(■ti)/(■wi)<0.8(
IV) 0.7<|(■wi)/(hwi)|<2.0(V
)0<ψ_1<0.3 However, f_1; Focal length of the first lens group fw; Focal length of the entire system at the wide-angle end ft; Focal length of the entire system at the telephoto end lw; First lens at the wide-angle end Distance (air distance) between the group and the second lens group hwi; Height at which a paraxial ray passes through the i-th surface (aspherical surface) at the wide-angle end when the object is at infinity Wi; When the object is at infinity The height hti at which the paraxial pupil ray passes through the i-th surface (aspherical surface) at the wide-angle end when the object is far; the i-th surface (aspherical surface) at the telephoto end when the object is at infinity. A zoom lens system characterized in that a height ψ through which a paraxial pupil ray passes satisfies an aspheric coefficient with respect to a third-order aberration coefficient.