JPS6159409A - Wide-angle photographic lens - Google Patents

Abstract

PURPOSE:To obtain a wide-angle compact lens which consists of a front group of positive, negative, and positive constitution and a rear group having large curvature at an image side and has sufficient brightness and a wide view angle by setting the refracting power of the 2nd group lens of the front group and that of the lens of the rear group within the range of specific condition. CONSTITUTION:The wide-angle photographic lens consists of two groups, i.e. the front group composed of a positive, a negative, and a biconvex lens and the rear group of a negative meniscus lens having large curvature at the image side. Then, at least one surface of the front group and rear group is made aspherical, and an inequality holds, where f4 is the focal length of the rear group negative meniscus lens, N2 is the refractive index of the 2nd lens (negative lens in rear group), and (f) is the composite focal length of the whole system.

Description

[Detailed Description of the Invention] Purpose of the Invention (Usage on average! 17) This invention relates to a wide range of lenses, especially compact lenses with a telephoto ratio of 0°95 or less. A wide-angle lens with a small telephoto ratio, consisting of a concave and convex Thtj group and a rear group strongly curved toward the 1st side, has an angle of view of 329 mm and below, and is suitable for use in, for example, 35 mm lens shutter cameras. In addition, the telephoto ratio was about l, and even when an aspherical surface was introduced, the focal length was 0.95 or more, and when used in a 35 ml version camera, the film was 3 Q mm up to the surface
The following was 11 spicy.

On the other hand, the one in JP-A-55-73014 has a telephoto ratio of about 1 if! The i1 angle is 31.5 degrees, and the
I'i, iI of No. 4317! It is 11 angles and 30 degrees. JP-A-58-8541 as a compact structure
．． No. 0 can be seen, the F number is dark at 4 degrees 5 to 5.6, and the angle of view is 30.7. Japanese Patent Laid-Open No. 56-59217 has an aspherical surface added to the rear lens group, but the angle of view is 31.5 and the telephoto ratio is 0.95 or more.

(Problem to be solved by this invention) This invention is based on F.
Number Fi4. It has a brightness that can be widely used as a photographic lens, and an angle of view of 35mm, an unprecedented wide angle of view.In addition, the salt ratio is 0.94y,
When used in a 3511Im version camera, the lens is extremely short, with a length from the front of the lens to the film of less than 3 Q lTl1'11.

The #1I formation of the invention (1st step (1) + stage with M dog at one point) The lens of this application waits for the front quiet positive-negative-positive configuration, and the cunning is strongly curved negative to the 1st group side. It is 4N *
When the refractive index of the lens is 0.45<f/<2.5, t,<o...
...(1) f41 1.7 < N2 ....The condition of (2) is satisfied, and at least one of the refractive surfaces of the first group lens to the third group lens, and 1 of the 4th group lens
The surface or both surfaces are aspheric, and the degree of asphericity is determined by paraxial curvature.The amount of displacement of the refractive surface due to asphericity with respect to the generatrix surface is 0.5X10-2f<' for groups 1 to @3 without the first group. J! ((1,13 force + △Xs
(0,1f)+""s (0,1f) Also, for the 4th group, o, 1X 10-5f<, ΔX7 (013f) - ΔX8
((1, 14f) <03f ・・・・・・(4
) satisfies the conditions.

However, the aspherical shape If it is expressed as C*=C+2A2 (paraxial curvature) φ: Height from the original axis It is expressed as

More preferably 1.15〈f/f, 23〈2.0...
...(5) f4.2s: If the composite focal length of the front group is satisfied and an aspheric surface is introduced on each surface, -0.5X10 = <■1 (0゜l 3f) / f <
-0,1 mowing 0-4 ...... (6) When introducing to the side of the hoe of the th lun, 0, IXl 0-' (■2 (0,13f) /f
<0. I X 10r” - (7) Second
When on the object side of the lens -0,5X10-2<Ls (0,1f)/f<
-o, lX10-' (8) 0, lX10-' (ha, (0,1ha/f<o, 5xt) when on the side of the second lens
o-2... (9) When the third lens is on the object side -0.5X10-2! ,X5(0,1,f)/f<
-0,1 0-4 ...<IO) When on the side of the third lens, 0, I
0.5X10-2 (11) 0.5 when the fourth lens is concave on the object side 0-5<dt (0,13f) /f<0
．． 3...(12) When the edge side convex surface of the fourth lens is -0.5X10-" (Δx8(o, 14f)/f<
-Old
<0.3...(14) The iron side is 0.3X 10-'(cs(0,14f)/f<0.
3xtO-” It is desirable to satisfy the condition (15).

(Function) As mentioned above, in a wide-angle lens where the front group has a positive φ negative reference positive configuration and the rear group is a negative meniscus lens that is strongly curved toward one quadrant, attempts are made to make the telephoto ratio smaller than ever before. For example, there are eight options that strengthen the positive refractive power of the front group and the negative refractive power of the rear group.

Condition (1) Regarding the negative refractive power of the fourth lens, which is the rear group of 11-i, if the lower limit is exceeded, the movement of the fi 111 king point toward the front of the lens becomes small, making it impossible to make the lens compact. However, when the upper limit is exceeded, the edge surface curvature is overcorrected, and extroverted coma and pincushion distortion become more likely to occur.

Condition (2) is to keep the Veravar sum appropriate.
In general, compact lenses tend to have too small a perapard sum, and by increasing the refractive index of the second lens, which is a negative lens, in accordance with the range of this condition, the edge surface curvature can be kept within an appropriate range.

Condition (5) is intended to strengthen the refractive power of the front group and reduce the telephoto ratio; if the lower limit is exceeded, the effect cannot be obtained, and if the upper limit is exceeded, there will be insufficient correction of spherical aberration and pincushion distortion. Aberrations occur, an unpleasant extroverted coma occurs, and correction becomes difficult due to the aspherical surface.

As mentioned above, if the refractive power of the front group is strengthened to reduce the telephoto ratio, spherical aberration will be insufficiently corrected, extroverted coma flare will occur, edge curvature will be insufficiently corrected, and distortion will be strong. It tends to be pincushion shaped. Furthermore, increasing the refractive power of the VK lens causes extroverted coma flare and increases pincushion distortion.

Therefore, the reason why an aspherical shape is introduced to correct this is because the refractive power of the positive-negative-positive lens in the front group is too strong and cannot be sufficiently corrected by the concave lens in the rear group. Therefore, a surface with convex power should be deformed into an aspherical surface whose υ curvature becomes gentler as it goes outward from the optical axis due to paraxial curvature. It is better to deform an aspherical surface in a shape where the multi-curvature becomes stronger as you go to the parent sphere due to paraxial curvature.

Conditions (6) to (11) are related to such aspheric deformation, and Kume V+ (6) corrects the undercorrected spherical aberration and corrects the extroverted coma and pincushion distortion. However, in history, the curvature of the edge surface was also corrected and became more pronounced on the over side.

Condition (7) indicates that off the optical axis, the refractive surface deforms from the mother sphere to the (8) side, and compensates for insufficient correction of spherical aberration and edge curvature. Similarly to
21. , spherical aberration, and pincushion distortion are also reduced.

The line f(9) is a deformation similar to condition (7) and liJ, and is mainly effective for correcting spherical (lO) surface aberrations and curvature of the field of view.

Condition (10) (aspherical surface) The deformation direction and effect are based on condition (6)
).

Condition (1) is such that the lens is deformed to the r-region side with respect to the mesial sphere outside the optical axis, one extroverted coma is formed, and the spherical m1 aberration and pincushion distortion are also reduced.

Among the above valley P+■ limit fields, the positive lower limit and the negative upper limit are the limits at which the aspherical effect occurs, and the positive upper limit and negative lower limit are the limits at which the aspheric deformation becomes large. This is the limit at which the compensation is not excessive.

As is clear from the optical path diagram shown in FIG. 1, as the angle of view of the lens becomes wider, part A of the peripheral light beam enters the outside of the convex/concave/convex lens @1 at a large angle 17, and aberrations occur significantly in this part. This can be corrected by using an aspherical surface under conditions (6) to 11) described above. On the other hand, the B portion of the light beam passes through a point ti1 off the axis of the fourth lens, and this portion causes significant aberration. The condition for asphericalization for this is V+(
12) to 15).

By making the curvature of the refractive surface gentler with respect to the parent body outside the axis, the strip f+(12) can reduce the above-mentioned extroverted coma and pincushion distortion.

Strip 2F (13) makes the curvature of the aspherical displacement from the parent body in the off-axis direction become stronger, so that the introverted coma is generated more strongly than in the parent body, and as a result, the extroverted coma of the entire lens system is The number of frames is reduced. In addition, this causes a strong distortion aberration, and as a result, the pincushion distortion of the entire system is reduced.

In these articles f'F (12) (13), the condition (1
The lower limit of 2) and the upper limit of Kakizuna (13) are the limits at which the correction effect by the aspheric surface can be obtained, and Ei f! The upper limit of +1 odor and the lower limit of condition (13) are limits that do not cause over-correction.

The upper limit of the upper limit is when υ1 in the front group and one surface in the A table group are made aspherical, but of course it is not limited to this, and there are three surfaces in total of front and rear IF5. The above surfaces may be made aspheric. In such a case, the sum of the effects due to asphericity is good enough to produce the above result, and the direction of the spherical surface displacement of each individual surface is different from the above conditions (6) or ]3). will also occur.

Ei note (3) is a regulation regarding the total aspherical displacement of the front group in such a case, and condition (4) is a regulation regarding the displacement needle accounting of the rear group. The upper limit of condition (3) and the lower limit of condition (4) are the limits at which a correction effect can be expected, and conversely, the lower and upper limits are limits at which the displacement does not become excessive and an excessive aspherical effect does not occur.

When both surfaces of the fourth group lens are made aspheric under condition (4), it is desirable that the following conditions be satisfied: =, Sakae FF (14), (]5). Condition (15), along with condition (14), is a displacement in the direction in which both surfaces of the fourth group lens have a gentler curvature outside the matrix, and a displacement in the opposite direction to condition (13). Ru. This is to flatten coma aberration when the angle of view is 28 or more. Article Pl: (1 → makes the aspherical displacement of the object side large, which can flatten the coma aberration, but this results in insufficient correction of the 1-quadrant curvature and increases the pincushion total curvature aberration. However, by making the j-surface aspherical as in condition (15), it is also possible to correct the curved surface and pincushion distortion.

(Example) An example of implementing the lens system of the present invention will be shown below.

Examples 1 to 8 each use two aspheric surfaces, and Examples 9 and 10 each use three aspheric surfaces.

Among them, in Example 8, the third lens is a cemented lens for achromatization.

Examples 13.15 and 18 to 21 introduced aspherical surfaces on three surfaces, so the displacement direction of the surfaces met conditions (6) to 13.
) is not followed. Of these, 18 to 2 practical
1 is based on conditions (14) and (15).

In the table, R is half curvature, D is interval between refractive surfaces, N is refractive index, ν
is Atsube's number, W is the angle of view, fB is the back focus, K is the conic constant, and A is the aspheric coefficient.

Implementation 1" 1 1 (, DN ν 1 2a826 9.33 1
．． 62280 57.02 111
．． 880 3333 -95.275
2゜67 1.84666 23.94
45.833 3.005
54366 5.67 1.59270
35.36 -50.903 2
2.747 -14.991 333
1.69680 55.58
-18.930 fx2B, =65.67 ΣD250
07f4 = -98,79 Telephoto ratio = 0.92691n
=42.62 Example 2 f=100 W=35.6 F4.0RDN
ν 1 25.387 9.33 1.6228
0 57.02 44.798 333 3 -118.415 2fi7 1.846
66 23.94 45.426 3.00
5 55.596 5.67 1.5927
0 35.36 -53.948 22.75
7 -14.933 333 1.69680
55.58 -18.723 A8= 2soo37]J-16Pδ=IO,0000
f123. =66A8Σ1)=50.0
8f<=103.30 Telephoto ratio=0.
9270fb =42.62 Implementation N5 f=100 W=35.5 F4.0RD
N ν f1xs, =59.56 ΣD=45
．． 73f478.21 Telephoto ratio=0.9270
fB =46.97 Example 4 f=100 W=35.5 F4.0RDN
ν 1 233] 4 933
1.62280 57.02
66.942 3333 -11
5.005 2.67 1.84666 23
．． 94 36535 3.
005 56.237 5.
67 1.59270 35.36
-49.885 18.627
-15.016 333 1.69680
55.58 -19.209A
8ko243082L)-17)'8=1tJ,000
0A8=1.771271)-14)'8=10.0
0001123,=6438 ΣD=45
．． 95f4>101.08 Telephoto ratio=0.926
5fB = 46.70 Example 5. f=100 W=35.7 F4.0RDN
ν A8= 4.691281J-18P8=l(J, 0
00UA)l=1.73b781J-14)'8=
1(J, 0000f+, 23. = 64.63
ΣIJ=46.24j4= ]01. ], O
Telephoto ratio J, 9270f H=4646 Direction 6 f=100 W=35.6 F4.0RDN
ν 1 23.529 9.33
1.62280 57.03
-96.597 2.67 184666
23.94 49.246
1005 55.134 5
67 1.59270 35.36
-46.736 19487
-16149 333 1.69680
55.58 -20. )t38A6
= s, t41s51)-14p5= 8.000Of
]23. =64.08 Upper D=4613
1f4=-97,95 telephoto ratio=0.9272j-B
=45.91 Implementation 1"7 f=1 (10 shear 35 f F40RiJ
N 1 24.4+67 9.33
1.62280 57.02
73358 3.333 -817
(122,671,8466623,9452,896
3,00 fl:zs, =64.21 λD24
953f, Shi9138 Telephoto ratio = 0.9271
fb =43.18 Minoru μF 8 f-100W-35,7F4.0 RDNν 123.4229.331.6228057.0271
+6253.33 3-93. ti(+42671.8466623.94
46.4653.0(1 55633945(11,592703536-31,
9771,171,74,9503537-42,92
918,95 8-15,6853331,69fi8055.59-
20.130 f1234=63.77 AD
=46.28j5 =-96,52 telephoto ratio supplement, 9269
In =4641 (22 times performed 119 RD N ν ] 24.6:34 6.47
1.56883 56.31023F19
3.23 3 -76.31.1 1,62 1.
80518 25.4-4 8092
9 6.105 75, h46
387 1.60717 4(1,36-5(1
,,"(332L)52 A4= 4.72626Ll-+4 i'4= 8
．． 0t) 0(IA1= 2fi7076υ−t)a
pl=-2,0000A5=:C-6,06220
1ΣTo-17P5=10.0O(H+fL23.=
59.79 ΣLl =44.30f,
=-78,56 Telephoto ratio=U, 92691B =48.
39 Example 10 f=1(10W=36(IF4.0RJJ
N ν 1 24574 6.47 1.56883
56.32 97.945 3.23 3 -73.212 162 1.80518
25411 jlo, 620 6. ]057
6.39 (53R7], fi0717 40.3 (i
,)O:'r 4)l 2(1,Ll
27 -17.153 2. ,'IO16385
455,4)1 -23.722 fy3. =60.20 λD=44.3
(IJ4=-79,91 telephoto ratio=0.9260jB=4
8.30 (2 units carried out 1111 f=1 (10W=35.OF4.0 RD N F 1 25.317 833
1.60311 6U, 72
54.926 3.243 -
53.996 1.62 1.84666 2
394 93.997 3.6
45 72.903 6.33
1.62004 36.36
-48558 21.797 -1
7.232 259 1.51633 64.
18 -28.06 (IAδ21.
81 (to +86) - 18P8 = 1 (J, 00UOfl,
3. =62.98 +4 =-85,48 fB =45.88 ΣD =47.54 Telephoto ratio =0.9342 Example 12. f=100 W=35.1 F4.0RL
) N F 1 25.319 8.33
16 (1311607255,604324 3-54,1421,621,8466623,949
7,8283,64 573,4466,331,620043636-47
,65621,79 7-17,2342591,5163364,18-2
8,121 A8>1.3234OL)-18)'8=l(J, (+
000A8=126464D-15P8=10. (
10 (10:h2s, =62.82 f4 =-85,13 fB =46.03 ΣD =47.54 Telephoto ratio =0.9357 Example 13 RD N F 1 24.480 8.33
1.60311 60.72 54
．． 317 3.243 -5(1,
5641, 6218466623, 9474°154
3.64 5 70.278 6.33 1
．． 62004 36.36 -51.
826 21.777 -16.42
7 259 1.49200 55.08
-24.450 882 1.275041J-15)'8=10.0(
JIJOf□23. =64.2 f=-91,06 fB =45.67 ΣD =47.52 Telephoto ratio=0.9319 Example 14 f=100 W=35. IF”4.(IRD
N ν 8-27.375 tql) f, 23. =60.91 f4 =-87,12 fb =51.54 ΣI) =41.46 Telephoto ratio=093 13 false implementation 015 1 likelihood D N ν1
30.501 5.71 1.
51633 64.12 69.8
75 2.863 -72. h93
1,43 1.8051B 25.44
113.93/1 53B5
57.42B 3,43 1.6
2004 3636 -59.075
18. )307 -15.114
2.28 1.69680 555f123.
= 56.55 f, = -73,79 fB = 52.12 ΣD = 39.89 Telephoto ratio = 0.9201 Implementation E2 16 RI) N F 1 25.320 9.33
1.60311 60.72 55
．． 337 3.243 -54.1
30 1.62 1E4666 23.94
96987 3.645
73.386 633 1.6200
4 3636 -47. (16421
,797-17,2322,591,5163364,
18-27,933 A7 = 6.57642 14 1'7 = 9.0
000A8=1.264291J-15P8=IO
,00U.

A7=1.7510813-18)'7=1
0.00001su [＼ f123. = 63.06 f4 = -86,01 fB = 45.99 Σl) = 47.54 Telephoto ratio = 0.9353 %t) J) Example 17 f = 1 (40W = 35.0 F4.0RDN
ν 4 101.538 3.64f1
2. s, = 62.42 ΣI) = 47.5
4f4” 83.44 Telephoto ratio=0.9349fB
=45.95 (j 018 f=100 W=35.OF4.0RDN
ν 1 26.113 8.3]
1.60311 60.72 5
2.142 3.393 -841)
)56 2,03 1.84666 23.94
53858 3.055
46.093 7.46 1.6363
6 35.46 -54212 27
．． 3s7 -17.199 2.71
],,49200 55.08 -
18.298 A7=-2fi60451J-14P7=9.000
0AM=-359440i)16 PM=10.0
000 aspherical surface 8 to X8 (0,14f) /f=
0.5645X10-2f, 23=64.63 f4=-82,88 fb =39.82 ΣD =54.33 Telephoto ratio=0.9415 Actual color 019 f=100 W=35. OF4.08
-19.364 A8=-1,34896D-15k'8=01. (J(
H river (j9J aspherical 8th dg (Q, 14ha/f=0.3809
Mowing 0-2f12.5. = 63.97 f4 = -83,42 fH = 41.49 ΣLJ = 52.54 Telephoto ratio = 0.9403 Example 20 f = 100 W = 35. OF4. OB
-19318 8 aspherical surfaces ・MuXg (0,14c/f=0409
3X10-2f, 23. = 63.86 f4 = 82.40 fB = 41.42 ΣT) = 52.41 Telephoto ratio = (1,9383 Example 2) f = 100 W = 34.8 F4.08 -
18.4 (+7 8 aspherical surfaces ・x,, (0,14f”) /f=
0.5569 mowing 0-2ft23. = 63.48 f4 = 83.56 fB = 39.77 ΣD' = 54.55 Telephoto ratio = 0.9432 (4→ Effects of the Invention As seen in the above embodiments, the lens of this invention has a simple construction. Because of its configuration, it has F4, which is bright enough to be used as a photographic lens, and the angle of view is about 35, with a telephoto ratio of 0.95.
This makes it possible to obtain an extremely compact wide-angle lens with well-balanced aberration correction as shown in each aberration curve diagram.

[Brief explanation of drawings]

FIG. 1 is an optical path diagram of the lens of this invention, and FIGS.
In Figure 2, (a) is implemented, respectively, and vj of ul to 21 is
Figure Tiii, (b) is its aberration curve diagram. % Hariyama Ganto Konishi Roku Photography M Co., Ltd. Applicant's agent Patent attorney Fumi Sato (and 1 other person)

Claims (1)

[Claims] 1) A front group consisting of a positive lens, a negative lens, and a biconvex lens from the object side, and a rear group that is a negative meniscus lens strongly curved toward the image side. and at least one surface of each of the rear group is aspherical, and 0, 45<f/|f_4|<2.5, f_4<01.7
<N_2 However, f_4: Focal length of rear group negative meniscus lens N_2: A wide-angle photographic lens characterized by satisfying the refractive index condition of the second lens (negative lens in the front group) 2) Positive lens from the object side, It has a 4-group configuration: a front group consisting of a negative lens and a biconvex lens, and a rear group which is a negative meniscus lens strongly curved toward the image side. 0.45<f/|f_4|<2.5, f_4< 01.7
<N_2, and at least one surface of each of the front group and the rear group is made aspheric, and the amount of displacement of the refractive surface due to the asphericization with respect to the generatrix surface due to paraxial curvature is -0.5 with respect to the front group. ×10^-^2f<ΔX_1(0.13f)+
ΔX_3 (0.1f) + ΔX_5 (0.1f) - ΔX_
2 (0.13f) - ΔX_4 (0.1f) - ΔX_6(
0.1f)<-0.1×10^-^4f Regarding the rear group, 0, 1×10^-^3f<ΔX_7(0.13f)-Δ
X_8(0.14f)<0.3f However, ΔX(φ)=(Cφ^2)/{1+√[1-(1+k)
C^2φ^2]}+Σ_iA_iφPi−(C^*φ^
2)/[1+√(1-C^*^^2φ^2)]C^*=
Wide-angle photographic lens characterized by satisfying C+2A_2 3) Four groups: a front group consisting of a positive lens, a negative lens, and a biconvex lens from the object side, and a rear group which is a negative meniscus lens strongly curved toward the image side. The configuration is 0.45<f/|f_4|<2.5, f_4<01.7
<N_2, one or more surfaces of the front group and both surfaces of the rear group are made aspheric, and the amount of displacement of the refractive surface due to the asphericization with respect to the generatrix due to paraxial curvature is -0.5 with respect to the front group. ×10^-^2f<ΔX_1(0.13f)+
ΔX_3 (0.1f) + ΔX_5 (0.1f) - ΔX_
2 (0.13f) - ΔX_4 (0.1f) - ΔX_6(
0.1f) <-0.1×10^-^4f Regarding rear group 4 object side 0.1×10^-^1f<ΔX_7(0.13f)<0
．． Regarding the 3f image side, 0.3×10^-^3f<ΔX_8(0.14f)<0
．． A wide-angle photographic lens that satisfies 3×10^-^1f