JPS60260014A - Wide angle lens - Google Patents

Abstract

PURPOSE:To make a titled lens compact by constituting the front group of positive, negative, positive and positive lenses, constituting the rear group of a negative meniscus lens curved strongly to an image side, and making a refracting surface, a focal distance and a refractive index of a specified lens satisfy specified conditions. CONSTITUTION:A lens system is constituted of a front group consisting of a positive lens L1, a negative lens L2, a positive lens L3 and a positive lens L4 in order from an object side, and a rear group consisting of a negative meniscus lens whose convex surface is turned strongly to an image side. Also, at least one surface of refracting surfaces of the lens L3 and L4, and at least one surface of the fifth lens are formed to an aspherical surface, and also made to satisfy conditions of 0.45<f/¦f5¦<2.5, f5<0 and 1.7<N2 (provided that f5 and N2 denote a focal distance of the fifth lens L5, and a refractive index of a glass material of the second lens L2, respectively). As for this lens, the telephoto ratio is also small such as 0.96 or 0.92 while reaching a view angle 35 deg., and also various aberrations are corrected well.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Applications and Applications of the Lens) The present invention relates to a wide-angle lens having a telephoto ratio of less than 1 and a 5-group composition having a half angle of view of 35.

(Prior art) In order to widen the photographic lens and reduce the telephoto ratio for use in so-called compact cameras, attempts have been made to develop a lens that is an inverse version of the retrofocus type used as a wide-angle lens. .

Among these types of lenses, there are many lenses with a 5-group #I configuration, which have a strongly curved negative meniscus lens with the convex surface facing the opposite side as the rear group, and are
No. 56-95207, JP-A No. 58-1117, No. 58-62608, No. 59-44016
All of these have angles of view of 64 or less. Further, in JP-A No. 58-219509 υ, the angle of view of θ reaches 39, but the telephoto ratio is as large as 1.1, which cannot be said to be sufficient for compactness υ.

In JP-A-56-1, the strongly curved negative meniscus lens of the rear group is made of resin, although it has a four-group configuration.
No. 75612, same issue No. 56-94317, 4#58-5
No. 7106 can be seen. However, one disadvantage of resin lenses that are easy to process is that the refractive index changes significantly due to temperature rirv, which causes the pack focus to fluctuate. The flaws become noticeable. Also, this
In order to avoid this drawback, there is a system that utilizes a non-powerful Sonoside lens made into an aspherical surface, such as in Japanese Patent Application Laid-open No. 59-4401.6, but this inevitably places constraints on lens designers.

(Points to be solved by the invention) This invention achieves a half angle of view of 35 mm by adding aspherical surfaces to the front and rear groups in a so-called inverted trofocal lens. is 0
．． The objective is to obtain a compact wide-angle lens of 96 mm or less.

As a secondary feature, we are trying to create a lens with an aspherical surface that is easy to process, made of resin, while minimizing the effects of temperature degradation.

Structure of the Invention (Means for Solving Problems) In the present invention, the structure of the lens system includes, in order from the object side, a front group consisting of a positive lens L1, a negative lens L2, a positive lens L3, and a positive lens L4; At least one of the refractive surfaces of lenses L5 and L4, and at least one surface of the fifth lens are aspherical, and a rear group consisting of a negative meniscus L5 with a strongly convex surface facing 0.
45 <f/If51 <2.5 f5<O...
・(1) 1.7 (N2... (2) However
f5: 5th lens L5v) Focal length N2: 2nd lens L
The % mark indicates that the refractive index condition of the glass material of 2 is satisfied.

The number of aspherical surfaces is not limited to 1N for each of the front group and the f & group, but may be introduced for a total of three or more surfaces. In this case, the problem is the sum of the summer cover from the respective spherical surfaces of the front group and the rear group.

This displacement position is t, oxlo−, 1=Xs (0, 1f)+′Xr (
0°1f)□ (0,1j') t□ (0,1n<-
0,5X10-' (3) For the rear group, however, for the fifth surface, the following conditions are satisfied: C+2A2.

In a case where one of the positive lenses L3, L and the negative meniscus lens L5 are used as a four-lens set, the following conditions are satisfied.

0, 5 <'Lr/1f51< 5.0... Song (
5) However, one leg has four lens sets, L5 or L4 focal length (action), where the front group is positive, negative, positive, positive v) taJy2. In a wide-angle lens, in which the rear group is a negative meniscus lens with a strong curve toward the edge, in order to further reduce the telephoto ratio, it is necessary to increase the positive refractive power of the front group and the negative refractive power of the rear group. be. However, if the refractive power of the front group is strengthened, spherical aberration will be under-corrected, extroverted coma flare will occur, surface curvature will be under-corrected, and distortion will become strong and pincushion-like. Increasing the refractive power of the front and rear groups causes extroverted coma flare and increases pincushion distortion.

Condition (1) relates to the negative refractive power of the fifth lens L6 in the rear group, and when the lower limit is exceeded, the movement of the image-side principal point toward the front of the lens becomes small and the telephoto ratio becomes large. On the other hand, if the upper limit is exceeded, the curvature of field will be overcorrected, and the occurrence of extroverted coma and pincushion distortion will become significant.

Condition (2) is to keep the Benbar sum appropriate.
In general, compact lenses tend to have too small a Veravar sum. Therefore, by setting the refractive index of the second lens L2, which is a negative lens, to the range of condition V), the curvature of the iron (8) can be kept within an appropriate range.

Condition (3) is intended to correct the various aberrations mentioned above by making the positive lenses L5 and L, which are mapped to the front group, aspherical. By forming an aspherical surface whose paraxial curvature is displaced toward the object side as the lens moves toward the surface, it becomes possible to correct the various aberrations occurring in the front group. Also, y! In the JIIII surface, the paraxial curvature semi-cylindrical surface and the aspherical surface that is displaced toward the edge side serve as the aspherical surface that corrects each aberration.

Condition (4) relates to the aspherical shape of the negative meniscus lens L5 in the rear group, and the aspherical shape of the object 1ll1 surface is an extroverted coma, with the aspherical shape shifting from the paraxial curvature half-plane to the palmar side as it goes from the optical axis center to the periphery. This reduces pincushion distortion. Similarly, the above-mentioned aberrations are corrected by displacing the paraxial curvature half-plane on the cylindrical side toward the object side.

As is clear from condition (3J (4)), the above effect is not achieved independently for each V plane.

If the aspherical surface is a single surface, the above is the same, but when multiple surfaces are made aspherical, the surface that mainly provides the correction for the yield will be displaced as described above, but as an auxiliary It is often the case that the displacement is in the opposite direction a, which contributes to the positive aberration axis. However, it is sufficient that it falls within the range of conditions (3) and (4) as a whole.

The upper limit of condition (4) and the lower limit of condition (4) are the limits at which aberration correction due to aspherical deformation is effective υ, and condition (3)
The lower limit of ) and the upper limit of condition (4) are conditions to avoid overcorrection.Furthermore, in the V-lens system of this invention, the positive lenses L3 and L of the front group
, and one of the negative lenses in the rear group are till lenses. As mentioned in M, the focus of the resin lens changes due to the change in the refractive index due to the change in @, which has been a problem when used in cameras.

To deal with this, by configuring four sets of positive and negative lenses, it is possible to mutually cancel out the shadows of the vorticity changes. In this invention, the positive lens L3 or L4 and the negative lens L5 are made of resin. Although the power of the positive lens L5 or L4 is smaller than that of the negative lens L5, since it is located closer to MiJ than the negative lens L6, the negative lens The arrangement 17 is such that it is possible to suppress fluctuations in bank focus due to temperature key changes due to L.

Condition (5) is a range in which such back focus fluctuations can be offset.

(Example) Example 1 1 23.338 8.33 1.58913 61.
02 47.542 3.23 3 -63.764 1.67 1.84666 23
．． 9s 1212.959 0.33 7 74.0-73 6.17 1.6?895 :i
o, 18 -48.011 21.79 A1= 4.92612D-05P1= 2.0000
A2=-4,88022D-06P2=4.0000
A3=2.39993D-08P3=5.0000A4
=-7,78213D-10P4=6.0000A5
=-7,49195D-12P5=7.0000A6=
-6,60661D-14P6=8.0000A7=-
5,33,783D-16P7=9.0000A8=
-3,81073D-18ps=io,ooo.

A1=-2,76275D-04P1=2.00tlO
A2= 5.53218D-07P2= 4.0000
A3=-1,45347D-08P3=5.0000A
4=-1,98010D-10P4=6.0000A
5=-3,50886D-12P5=7.0000A
6=-4,52550D-14P6-8.0000A7
--5.55003D-18P7=10.0000AI
= 2.10215D-03P1= 2.000OA2
=1.53184D-06P2=4.000Of, 23
4=62.49F, =-85,84fB=46.5
8 1'D = 47.67 Telephoto ratio = 0.9425 L
12 R, D N AI = 3.39173D-03P1 = 2.000O
A2=-2,73359D-06P2=4. LI000
A3= 6.23249D-09P3= 5.0000
A4=-2,92059D 10 p4=tt, oθ
00A5--3.70598D-13pb=7. o'
oo.

A8= 1.076U3D-17Ps=10.0000
f, 234=64.58 f5=-95,16fB=
46.62 ΣD = 47.67 Telephoto ratio = 0.9429 Implementation IA3 RD N A7 = 9.19426D-21P7 = 10. OUO0A
l=2.57038D-03P1=2.0000A
2=5.02112D-07P2=4. UOOOA
3=2.69935D-08P3=5,ooo.

A4=-4,217030-10P4=6. Ooo.

A5=-7,62587D-12P5=7.0000
f12s<=64・52, f5=-93,50 fb=46.3 λD=47.72 W speed ratio=0.9402 Example 4 f=100 W=35.1° F4.0f, 2s+=6
2.81 Telephoto ratio=0.9385f5=-85,92 fit=46.14 ΣD=47.71 Example 5 f=100 W=35. OF4.0 f, 23* = 64.68 Shien ratio = 0.9372f,
=-94,27 fB =45.1 2D =48.62 Example 6 f=100 W=35. OF4.0 RD N 10 -19.4111 Ay=-i, o9yasp-17P7=10.0001
J aspherical 10 surfaces, to X (0,14J”) = 0.363
86X10-2A1= 2.88343D-03P1=
2.0000A2 9.90432D-07P2=
4.0000A3=-5,81352D-10P3=6
．． 0000A4=-8, 62134D-13P4=8.
0000A6=-3,56286D-16P5=10.
0000f12s4 = 65.51 js = -102,63 fB = 47.88 ΣD = 47.67 Telephoto ratio = 0.9555 Example 7 DN 1 23645 8.33 1.62041 60.3
2 46.865 3.23 3 -53.761 1.67 1.84666 23
．． 94, 45.425 0.81 5 50.615 6.17 1.72825 28.
5 Aspherical surface 8+m ΔX(0,1Of)=0.30774
xlO-3 = -1,06 (171D-01 AI = 4.95645D-04P1 = 2.0000
A2= 2.94707D-06P2= 4.0000
A3=1.98839D-08P3=5.0000A4
=-a, a3a6sl)-1o P4=6. o000A
5=-2,69120D-12P5=7.0000A6
--1.06186D-14P6=8.0OOOA7=
8.33083D-17P7= 9.0000A8±
2.91031D-18P8=10.0000 non-spherical 49iiiu alo, 13/)=0.10694XIO-
1K= -4,16566D-01 A1= 6.79564D-04P1= 2.0000
A2= 6.75223D-09F2- 4.0000
A3-4.41548D-(18P3=5.0000A
4--6.63263D-10P4=6.0000A5
=-9,01936D-12P5=7.0000A6
=-1,01266D-13P6=8.0000A7=
-9,57618D-18P7=10.0000A1=
2.76906D-03Pi-2,0000A2=
112684D-06P2=4.0000A3=-5
,81019D-10P3='6.0000A4=-8
,58020D-13P4=8.0OOOA5=-3,
54324D-16P5=10.0000f1u4=
65.72 f5 = -103,36 1B 247.79 ΣD = 47.67 Telephoto ratio = 0.9546 Example 8 f = 100 W = 35. OF4.0 RD N fi23a=61.50 Telephoto ratio=0.9388f5
ner 80.92 fB = 45.99 ΣD = 47:89 Example 9. f=100 W=34.9 F4.0Rp N f,2,4-=50.00 f5=-56,95fB=
54.11ΣD = 37.62 Telephoto ratio = 0.9173
Example 10 Rp N 1 24.380 8.12 1.60311 60.
710 −17.658 Aspheric surface 4ilkId(0,1f)/f=0.6X10−
3A4=7.28474D-10P4=6.0000
A5=-8,86419D-11P5=7.0000
A6=-1,42475D-12P6=8.0000
A7=-3,1]3952D-14P7=9.000
0A8=-3,36650D-16P8=10.00
00 non-spherical 1 with 9 surfaces u(0,13/)/f=0.38X
l 0-1rs= -a, o 3103D-02 A1= -8,48312D-03P1=2.0O00
A2=2.21494D-06P2=4.0000A
a= 1.25470D-07P3=5.0000A4
= −, 5, & 7302D-09 P4=6.0000
A5=-2,14538D-10P5=7.0000
A6=-4,07757D-12F6-8.0000
A7=-8,47523D-14F7-9.0000
A8=-1,38487D-15P8=10.000
0f12s4=63.58 fs =-85,39 h =43.2 ΣD =52.33 Telephoto ratio=0.9553 Example 11 Rl) N 10 -17.652 A1=-3,715$4D-o3 pl= z, ooo
.

A4=-1,10664D-12P4=8.0000
A5 knee 1.69979D-16P5=10.0000
9 aspheric surfaces ・6x(o, taf)/f-0,3818
0X10-IK=-3,03103D-02 AI=-8,48593D-03P1=2.0000A
2= 2.21714D-06P2= 4.0000A
3mi 1.25637D-07P3=5.0OOOA4
=-5,98291D-09P4=6.0000A5=
-2,14966D-10P5=7.0000A6 +
? -4.68841D-12P6=8.0(100A7
=-1497(i9D-14P7=9.0OOOA8=
-1,3E1900]) -15P8=10. ooooo.

A1= 3.81513jJ-03P1=2.000O
A2=-6,180521J-06P2=4.000
0A3=-1,06172υ-07pa=a,ooo
.

A4=-2,77537Ll, 09 P4=6.0O
00A5=-2,4581OL+-11P5=7.0
000f12s4 = 63.32 fr, = -85,37 h = 43.74 Σ11 = 51.15 Telephoto ratio = 0.9489 Among the above, in practical 10 and practical ffull, both surfaces of the fifth lens L are The paraxial curvature radius surface also has a gentle curvature (-) off-axis. This is to flatten coma aberration at an angle of view of 28 or more. If the side of the object is largely displaced, the occurrence of coma aberration can be suppressed. However, the curvature of the metaplane is insufficiently corrected. By displacing the □□□ side surface so that the curvature is also gentler off-axis, the coma aberration is flattened and the palmar curvature is also corrected. It is something.

The effects of the invention (the D8 light lens has an angle of view of 35, but the telephoto ratio is small at 0.96 to 0.92, and as shown in the Shikamo Valley compression map, the aberrations are well corrected). However, by appropriately selecting the refractive power and placement of the resin lens, the temperature-induced
This has the remarkable effect of eliminating the cliché.

[Brief explanation of the drawing]

1 to 1K11, each (a) is a structural cross-sectional view of Example 1 to Example 11C of the lens of the present invention;
(b) is the V aberration. Patent applicant: Roku Konishi Photography Industry Co., Ltd. Patent attorney: Fumi Sato (and one other person) Figure 1: F4. nw=35. n Spherical aberration Astigmatism Distortion aberration Fig. 2 Spherical aberration Astigmatism Distortion aberration Fig. 3 Spherical aberration Astigmatism Distortion aberration Fig. 4 F 4. (l W=35.1 Spherical aberration Astigmatism Distortion Fig. 5 F4.0 W=35.0 Spherical aberration Astigmatism Distortion Fig. 6 F4. (1, W=:'(5,0 Spherical aberration Astigmatism Distortion Fig. 7 F4. (l W = 34.9 Spherical aberration Astigmatism Distortion Fig. 8 F4. fl W-, '15. ('1 Spherical aberration Astigmatism Distortion Fig. 9 F4 .n W-34,9 Spherical aberration Astigmatism Distortion aberration Figure 1n F 4.+l W= 351 Spherical aberration Astigmatism Distortion aberration Figure 11 F4.n W=35.1 Spherical aberration Astigmatism Distortion aberration

Claims (1)

[Claims] A front group consisting of, in order from the object side, a positive lens L1, a negative lens L2, a positive lens L3, and a positive lens L, and a rear group consisting of a negative meniscus L5 with a strongly convex surface facing the image side. At least one of the refractive surfaces υ of lenses L3 and L4 and at least one surface of the fifth lens are aspherical, and 0.45 < fAf, + < 2.5 f5 < 0
1.7 (N2 However, f5: Focal length to the fifth lens N2: Second lens L2v Refractive index of glass material