JPS6169015A - Bright wide angle zoom lens - Google Patents

Abstract

PURPOSE:To obtain a very bright wide angle zoom lens which has about 85 deg. covering power in the wide angle side, by forming surfaces of a lens nearest to the object side and a lens nearest to the image side in a rear group of the zoom lens to aspherical surfaces and changing radiuses of curvature monotonously from centers of lenses towards peripheral parts. CONSTITUTION:In the zoom lens which consists of a front lens group having a negative refracting power and the rear lens group having a positive refracting power and varies the magnification by movement of individual groups along the optical axis, surfaces of the lens nearest to the object side and the lens nearest to the image side in the rear lens group are formed to aspherical surfaces, and radiuses of curvature of these aspherical surfaces are changed monotonously from centers of lenses to peripheral parts including signs to satisfy conditions of formulas where Rc and Re are radiuses of curvature of the center and the outermost peripheral part of the aspherical lens nearest to the object side respectively and rc and re are those of the aspherical lens nearest to the image side.

Description

[Detailed description of the invention]

Technical field The present invention relates to a two-group type zoom lens mainly used in a 35mm 5LR camera.6 Prior art and its problems In recent years, the development of zoom lenses has been remarkable, especially in 35mm+
*There has been remarkable progress in wide-angle zoom lenses used in SLR cameras. Mainly 35mm5LR like this
Zoom lenses used in cameras require a sufficiently long back focus, so a retrofocus two-group movable type zoom lens consisting of a front group with negative refractive power and a rear group with positive refractive power is used. Are known. However, in this type of lens, it is extremely difficult to ensure that the FNO is sufficiently bright with an ultra-compact optical system including an ultra-wide angle as large as that of the present invention. That is. At the wide-angle end, the light diverging from the front group enters the rear group with sufficient distance between the front and rear groups, and at the telephoto end, the light with a high incident height corresponding to the long focal length is further diverged at the front group. Since the aberrations become high and incident on the rear group, various aberrations occurring in the rear group, especially spherical aberration and coma aberration, increase, making it difficult to obtain an optical system in which aberrations are well corrected as a whole. Purpose The present invention is mainly used for 35+u+SLR cameras [6
A, ,, , , , , , , , , , , , , , , , , , , , , , , , , , , , , . The object of the present invention is to provide a wide-angle zoom lens that has a diameter close to 85'' and is extremely bright with an F of 1:2.9. In a zoom lens, which consists of two lens groups: a front group with a strong power and a rear group with a positive refractive power, and which controls magnification by moving each group along the optical axis, the lens closest to the object side of the rear group The closest lens and the lens closest to the image side are made aspherical,
The aspherical surface satisfies the following conditions assuming that the radius of curvature, including the sign, changes monotonically from the center of the lens to the periphery. (1) Re −Rc > 0.31 RC1(2) r
c< Q < re where Rc: Radius of curvature of the center of the aspherical surface in the aspherical lens on the object side Re: Radius of curvature at the outermost periphery of the aspherical surface in the aspherical lens on the object side rc: Aspherical surface in the aspherical lens on the ll side Radius of curvature r at the center of the lens: Radius of curvature at the focal point of the aspherical surface of the aspherical lens on the image side Also, the front group in the above zoom lens is composed of four lenses: negative, positive, negative, and positive from the object side. has been done. 1. Condition (1) is mainly aimed at correcting 1 spherical aberration, especially spherical aberration on the telephoto side, and comatic aberration for off-axis light passing through the periphery of the lens closest to the object in the rear group. These are the intended conditions. In other words, for light that enters the rear group with a large aperture, the lens closest to the object in the rear group, which is most effective in correcting spherical aberration, is made aspheric, and the radius of curvature, including the sign, is monotonous from the center to the periphery. The relationship between the radius of curvature at the periphery and the radius of curvature at the center changes as Re-RC becomes larger than 0.31Rcl. FMol: This is to prevent the occurrence of spherical aberration and coma aberration at a brightness of 2.9. The condition (2) is a condition mainly aimed at correcting coma aberration of off-axis light on the wide-angle side that passes through the peripheral part of the lens closest to the image side of the rear group. That is, off-axis light incident on the wide-angle side generates comatic aberration with an abrupt over-component component relative to light passing through the rear group at a high incident height, corresponding to the brightness secured on the telephoto side. Therefore,
The most image-side lens in the rear group is made aspherical, and its radius of curvature changes monotonically from the center to the periphery while reversing its sign, thus preventing the occurrence of coma aberration. Furthermore, the zoom lens of the present invention is a 2x zoom lens including an ultra-wide angle lens, and by making the front group negative, negative, positive, it can be made ultra-compact and eliminates various aberrations, especially wide-angle zoom. Distortion aberration, which is a drawback of lenses, is well corrected.The aspheric shape formula is as follows, assuming that the optical axis is Z, and the plane passing through the apex of the aspheric surface and perpendicular to the optical axis is the χ, y plane. ρ = convex y
] It is expressed as Yuryo. Examples Examples of the present invention will be shown below. Here, f is the focal length,
r is the radius of curvature of each surface of the lens, d is the lens thickness or distance between lenses, n is the refractive index of each lens, and y is the Abbe number of each lens.

[Example 1] f = 24.7 to 48.5 FNO1: 2.9
surface r d n
vl 77.764 1.70
1.83400 37.22 31.076
8.61 3 -278.630 3.81 1.8051
8 25.44 -69.785 0.10 5 -157.564 1.60 1.8348
1 42.76 40.957 11.71 7 54.531 2.97 1.78470
26.28 156.136 41.41～
18.26～2.829 -85.354 2.9
2 1.48749 70.110 -52.2
31 0.10 11 26.465 2.97 1.6968
0 55.512 29.733 0.10 13 23.232 8.64 1.6204
1 60.314 -166.271 4.63
15 -75.555 3.57 1.8466
6 23.916 35.516 2.83 17 151.524 6.69 1.804
00 46.618 -63.550 Aspheric coefficient 9 surfaces a 1 = -0,43676X10- 'α2
= 0.74192X10-'' αcony 0.13809
o, 14707xlO″″13R (= 85.35
4 (p = 0.0) Re = -40,505Cp
= 14.44) 18 sides a 1 = 0.14325X
10-'α2 =0.10739X 10-'α:
l = -0,58310X 10-'αa =0.
36845X10-11 r, = -63,550 (ρ = 0.0) re = -2
1,467 (p = IO, 49)

[Example 2] f = 24.7 to 48.5 F, l: 2
．． 9th page rd n
ν1 111.790 1.70 1.834
00 37.22 36.200 7.82 3 -434.067 4.08 1.8051
8 25.44 -75.191 0.10 5 -325.977 1.60 1.8348
1 42.76 36.267 13.59 7 53.481 2.88 1.7g470
26.28 127.323 41.97～
18.49-2.829 251.385 2.
64 1.69680 55.510 -L184
．． 541 0.3411 23.148 8.
64 1.65160 58.512 -1114
．． 015 6.2913 -66.463 1.
89 1.84666 23.914 47.
470 0.75 15 51.955 2.85 1.6968
0 55.516 -487.401 5.41
17 -284.101 2.00 1.804
00 46.618 -93.738 Aspheric coefficient 9 surface a + = o, t3066xLO-”α2
= 0. :30tliao x 10-”α3=-
0,20988xtO-” α4= 0.55753X10-13RC= 25
1.385 Cp=O,O)R,2=384.
206 Cp = 13.49) 18 faces αg =
0.18268X10-'α2= 0.92073
X10-'α3=-〇, 45405X10-'
a a = 0.28708X10-1”r (==
93.738 (p = O0O) r e = 34
-035 (ρ=9.47) [Example 3] f ”24.7 to 48.5 FNo. 1: 2
．． 9th side r d
n ν1 96.304 1.7
0 1.83400 37.22 33.51
8 8.10 3 -458.939 4.05 1.8051
8 25.44 -73.960 0.10 5 -215.065 1.60 1.8348
1 42.76 39.238 13.12 7 54.595 2.89 1.78470
26.28 136.337 42.12~
18.53~2.829 -91.515 2.6
7 1.48749 70.110 -61.9
43 0.10 11 26.5?1 3.12 1.6968
0 55.512 30.513 0.11 13 24.029 g, 60 1.620
41 60.314 -181.941 4.7
215 -76.645 2.09 L, 84
666 23.916 42.226 1.2
6 17 67.728 2.23 1.6700
0 57.318 1594.165 4.35
19 -183.084 2.00 1.804
00 46.620 -69.868 Aspheric coefficient 9 surface α, = -0,35547X 10- 'α
2= 0.93944X10-9 α3 knee 0.10203X10- ” α4= 0.80836X10-” 'Rc' -9
1,515 (ρ=0.0)Re=52.005
(p = 13.19) 18 faces α, = 0.17
597X10- 'α2= 0.10082X10-
'α3=-0,48289X 10-'α4=
0.31020X10-”rc=-69,868(ρ==0.0)re=
-20,019' (p = 10.49) (p = 10.49) As explained above, according to the present invention, the lens closest to the object side and the lens closest to the image side of the rear group are subjected to the condition (
By using an aspherical lens that satisfies 1) and (2), various aberrations that were problems in the past can be well corrected,
It has a magnification ratio of 2 times diameter and a comprehensive angle of nearly 85° on the wide-angle side.
FNO1: 2.9 for a zoom lens in this class
This is an extremely bright and compact zoom lens. 90 Brief Description of Drawings Figure 1 is a lens configuration diagram of Example 1 of the present invention, and Figures 2, 3, and 4 are illustrations of Example 1 at long focus, intermediate focus, and short focus, respectively. FIG. FIG. 5 is a lens configuration diagram of Example 2 of the present invention, and FIGS. 6, 7, and 8 are aberration diagrams of Example 2 at long focus, intermediate focus, and short focus, respectively. FIG. 9 is a lens configuration diagram of Example 3 of the present invention, FIG.
FIG. 11 and FIG. 12 are aberration diagrams at a long focus, an intermediate focus, and a short focus, respectively, according to the third embodiment. Patent Applicant: Asahi Kogaku Kogyo Co., Ltd. -to-1 Fig. 1 Fig. 2 Sine condition Fig. 3 Fig. 14 Fig. Sine condition Fig. 5 Fig. 6 Positive 1 condition Fig. 7 Fig. 8 B condition Fig. 9 Figure 10 Sine condition Figure 11 Figure 12 Sine condition procedure hl Positive 1 Ken 1981 I
Patent Application No. 191993 No. 191993 dated October 2nd, 1987, Name of the invention: Bright wide-angle zoom lens 3, Relationship to the case of the person making the amendment Applicant's address: 2-36 Mano-cho, Karuhashi-ku, Tokyo, No. 9 Naya (0
52) Asahi Kogaku 1-Gyo Co., Ltd. Representative Toru Matsumoto 0 Agent residence 2rr136-9, Maeno-cho, Itabashi-ku, Tokyo, Otsu, Supplementary 1r: Contents of (1) Akira■, Tshi's "Details of the invention" Explanation during the week of J. It”re at the beginning of page 9, line 13 =21.467 (ρ=to, 49)
, n 31i're=21.467 (p=10.
4), 11 and Urao. (2) F re =34.035 (ρ=9.i?), fl on page 13 line 1
is corrected to Wre=34.035 (ρ=9.47)Jl. (3) Correct the month of Fre=-20, Olri (ρ=to, iq) on the 13th line of page 13 to 1i're=20.019 (p=10.49).

Claims (1)

[Claims] 1. From the object side, it consists of two lens groups: a front group with negative refractive power and a rear group with positive refractive power, and magnification can be changed by moving each group along the optical axis. In the zoom lens that controls the lens, the lens closest to the object side and the lens closest to the image side in the rear group are assumed to be aspherical surfaces, and the radius of curvature of the aspherical surface changes monotonically from the lens center to the periphery as follows. A bright wide-angle zoom lens with good performance that satisfies the following conditions. (1) R_e−R_c>0.3 | R_c | (2) r_c<0<r_e where R_c: radius of curvature of the center of the aspheric surface in the aspheric lens on the object side Re_: radius of curvature of the center of the aspheric surface in the aspheric lens on the object side Radius of curvature at the outermost periphery r_c: Radius of curvature at the center of the aspherical surface in the aspherical lens on the image side r_e: Radius of curvature at the outermost periphery of the aspherical surface in the aspherical lens on the image side, bright as described in claim 1 A bright wide-angle zoom lens characterized in that the front group is composed of four lenses: negative, positive, negative, and positive from the object side.