JPS584112A - Standard lens with wide picture angle - Google Patents

Abstract

PURPOSE:To make back focus to >=0.9 time a focal distance and make the configuration compact to efficiently compensate various aberrations in a lens system having F2 and a 56 deg. picture angle to be used for a 35mm. single-lens reflex camera by composing the lens system of 6 Gaussian lenses and satisfying specific conditions. CONSTITUTION:A lens system is composed of a front group consisting of a positive meniscus lens L1 with a projected surface opposed to the object side, a negative meniscus lens L2 with a projected surface opposed to the object side and a positive meniscus lens L3 with a projected surface opposed to the object side and a back group consisting of a negative meniscus lens L4 with a projected surface opposed to the image side, a positive meniscus lens L5 with a projected surface opposed to the image side and a convex lens L6 with projected surfaces on both the sides and conditions (1)-(8) are satisfied. Where, n1-n6 are the refractive indexes of lenses L1-L6 to a line (d), fF is the composite focal distance of the front group, r5 is the radius of curvature of the lens L3, r9 is the radius of curvature of the lens L5 on the object side, r12 is the radius of curvature of the lens L6 on the image side, and (f) is the composite focal distance of the whole system. Consequently, a lens system having an aperture ratio of F/2 and a about 56 deg. picture angle is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a standard lens for cameras having an aperture ratio of /2 and a large aperture of approximately -560 mm and a wide angle.

Conventionally, most lens threads called standard lenses for -eye reflex cameras have a key of about 46' angle III. However, in recent years, in the field of pre-press photography, a wider lens is required as a standard lens.
I'm getting older. -The idea is to obtain a lens with an angle of 56°, an aperture ratio of about k''/2, a long enough back focus to be conveniently used as a lens for a single-lens reflex camera, and a compact overall system.711) Conventionally, a Gaussian type lens is often used as a standard lens, but with this type, one corner is widened to 56° (in this case, it becomes difficult to maintain a large back focus). On the other hand, the retrofocus type used as a wide-angle lens is advantageous in lengthening the back focus, but it is difficult to compact the raw silk.Therefore, the positive, positive, and negative By arranging the lenses to be positive, negative, and positive, the divergence action of the negative lens is performed quickly, thereby widening one corner (even though it is long), ensuring good focus, and consolidating all the threads compactly. There are two known lenses for these tights, disclosed in Publication No. 30821/1982, with an angle of 56° and diameter ratio F/'1.8.
~2, a back focus of approximately 0.85 times the composite focal length of all threads is achieved. However, aberration correction is necessary
L/L is also smaller than the amount of light, which causes a decrease in contrast at the periphery of the screen.The main causes of this are astigmatism, which occurs at wide-angle angles, and curvature. This is due to the inconsistency of the mounting surface due to the height of the image and the inconsistency in correction of coma flare.

Invention 1 Basically, the same lens configuration as above is adopted, and the back focus is set to 0 of the composite focal length of all threads.
．． It has been increased to more than 9 points, and also has an angle of 56°, which has well corrected various aberrations from the center of -l to the periphery.
Q provides a standard lens with a wide angle of view of 24!4ML
) ◎ Hereinafter, the present invention will be referred to as ll? -Explain in detail.

As shown in Figure 1, the standard lenses for Misfire 1 are a positive meniscus lens L1 with a convex surface facing the object side, and a negative meniscus lens L1 with a convex surface facing the object side. Lens L2 and object 114
11 convex surface') loJ offset positive meniscus lens L3
A negative meniscus lens L4 with the same concave and convex surfaces arranged in one frame, a positive meniscus lens L5 with a convex surface facing 1 [11411], and a biconvex lens L6 are arranged. The sum of the historical conditions 111 to IB) is the f value.

ill nl, nI, ns
> 1.75121 ns
> 1.81+31 1.71 >
n2 > 1.6141 1.82
> ni > 1.77+51
4f > fF > 3.35f
(6) 0.34f > r5 >
0.29f(7) 2.42f>
1r91 > 1.45ff8)
1.69f > 1r121 >
0.9f However, nI to ns are respectively lens L]
Or the refractive index of lens L6 for the d-line, fF? is the composite focal length of the front group, and r5 is the cutoff m[
The curvature semipole of kl, ys is the radius of curvature of the truncated side surface of lens L5, r12 is the tm radius of the 1st violet side surface of lens L6, and f is the composite focal length of all threads.

The lens thread according to the present invention has an angle of 56° and an aperture ratio of F/'2
Various aberrations must be well corrected under the strict condition of obtaining a back focus fB>0.9ff. For this reason, it is necessary to use a steel material with a ratio of refractive index of # - for each lens, so that a spherical rout that generates the absolute value of the 111I ratio of the valley lens surface, which is necessary for fulfilling the required A11l prayer, is required. ,
It is necessary to keep coma aberration as small as possible. On the other hand, regarding the shell lens among the valley lenses, by keeping the no-gauge ratio below a certain level,
Coupled with the positive lens's 1/N refraction M index, even if the Betsuvialo II is made smaller and one corner is made wider, the one-sided curvature II is
Jl must not be able to correct B well.

Conditions... to +41 are the refractive indexes of each lens based on the request from Kami ml.

Among these conditions, (mouth is a positive lens, eye lens L+).

This is a condition for adding the refractive indices of I, s, and L5. Under these conditions, if the refractive index of the upper ml valley lens is lower than the lower limit, the pedestal /
The kj value of the radius of curvature of the 6-distance circle becomes too small, and the violets caused by various aberrations in the 6-distance circle become noticeable, making correction difficult.

Furthermore, when the bending angle is large, the image plane IN# music also becomes large γS.

Condition (2) is a condition that allows the refracted lamp 4 to have a correct angle L6, and when the refractive index becomes lower than the lower limit, it becomes difficult to correct astigmatism and distortion.

Condition (3) is a condition that determines the mars of the negative lens L2, and if it exceeds the lower limit, it must be 411! It becomes difficult to correct spherical aberration and astigmatism while maintaining a good back focus.

That is, the lens L2 is a lens that has one function in order to reduce the back focus, but when its refractive index decreases, it obtains the refractive power necessary to maintain a predetermined back focus. Therefore, 'I!' of L2! The curvature of the r-plane becomes extremely strong, and the aberrations that occur there cannot be corrected. −10,000, as the refractive index increases beyond the upper limit, the Betsuvial sum becomes large,
It is not possible to correct the curvature of the face.

Condition (4) defines the refractive index of the negative lens L4. If the refractive index becomes lower than the lower limit, astigmatism, distortion, and coma that occur on the side surface of L4 will become excessive, and other surfaces will be affected. It becomes impossible to correct it. On the other hand, if the upper limit of 8 is exceeded, the Betsuvial sum becomes large, and the curvature of the 1#1 plane cannot be corrected.

Kuni 1 condition (5) can be achieved by adding the 8-component focal length m of IIIJ#. In Kumushiru TBL, the sweet and sour focal length of the front group exceeds the lower limit. The effect of the divergence effect becomes weaker and quieter, making it difficult to obtain a long back focus. - If the upper limit is exceeded, the back focus may be advantageous for rice < f 6 ta/), or the rear group jIthl shinai will be tilted too much, resulting in correction of various aberrations or Komachi 611:.

As mentioned above, the refractive index ε of the pot, the valley, and the front group and dt,
By adding up the refractive power distribution of t# and giving an appropriate IIB ratio for the first and third points of the four-legged foot, it becomes possible to appropriately correct the various returns. Condition (6) or +8
) ii It's a lot of things that were established for this purpose.

Since the uninvented type of lens thread uses the firing action of the second lens L2 to obtain a back 7 orcus, the curvature of the first surface of this lens is strengthened by increasing the negative refractive power with an oil comb. ) must be n, must not be. Moreover, in the present invention, it is necessary to generate a slightly longer spherical aberration and to balance the Je shape of the spherical aberration on the Gaussian one-cycle surface in a well-balanced manner.
Because of this (3), the army has no choice but to become even stronger. Therefore, the angle of incidence of the axial dead line on this surface becomes large, and the wave generated by spherical aberration becomes extremely large. In order to cancel this spherical aberration, it is necessary to increase the refractive power of the side surface of the third lens L3, and the ratio of this circle becomes quite small. -Man, @L3 object 1 for Sotomoto Iwao
Ill[i! Since the amount of coma aberration generated in ii is particularly large, unless this is minimized as much as possible, it will not be possible to correct it in other aspects. Therefore, the radius of curvature of the object @ surface of L3 must be determined in consideration of the balance between spherical yield and coma aberration.

Condition (6) is the object 11ill[ of the third lens L3 above.
The radius of curvature of iI is determined, and if r5 becomes smaller than the lower limit of condition (6), it becomes difficult to correct spherical aberration and coma aberration. On the other hand, if r5 increases beyond the upper limit, the object 11N[@
The radius of curvature of the surface r4 must also be increased, and the negative refractive power (2) becomes weak (which makes it even more difficult to maintain a long back focus).

According to Condition 5 (b), when the refractive power of the front group is #L plus n, in order to make the distance between the i points of all threads f, the force is applied to the rear group)
Therefore, strong positive refractive power is required. This positive refractive power is shared by the fifth lens L5, A6/Z1, and 5(7)26 in the folding lens, and the positive refractive power of the 7X is also reflected. .Therefore, the /I!r11o of this lens is
The aberrations generated are also large, and in particular, the occurrence of off-axis aberrations such as astigmatism, coma aberration, and distortion part aberration is sometimes large in the case of #11111(2) of the fifth lens L5. Most of these aberrations are included in the opposing 5I! The effect of the negative A11l folding sword on the platform of the 4-lens L4 'fT
However, if the generated wave is too large, it will not be possible to correct it in other ways. In short, it is necessary to minimize the amount of aberration generated on the object side of L5. For this purpose, the condition (1st δ) is to use a material with a corrosion rate of IwJ for CL5, to make the radius of curvature r9 of the object side of L5 as large as possible, and to satisfy the condition (7) In the 10 conditions (7) that bring about good results,
If the absolute value of f9 becomes smaller than the lower limit, the aberration force j during this period becomes too large and cannot be corrected. - If the upper limit is set and the size increases, the positive refractive power of the fifth lens L5 will become weaker, and even if the m-refractive power of the sixth lens L6 is tilted. The rear q as a whole will not be able to maintain the necessary positive Hi analysis.

A sixth lens that, together with the fifth lens L5, provides the positive refractive power of the rear group.
Regarding the lens L6, it is also necessary to keep the aberration generated at the valley surface as small as possible. For this the condition (
2], the refractive index of L6 is increased to make the radius of curvature of each surface as large as possible, and further conditions (8
) is desirable.

Condition (8) determines the value of the radius of curvature H2 of one side surface of L6, or if the absolute value of j12 becomes smaller than the lower limit, the spherical aberration generated on this surface becomes excessive and correction becomes difficult.

On the other hand, if the value exceeds the upper limit, the positive refractive power of the sixth lens L6 becomes too weak, and even if the refractive power of the fifth lens L5 is made stronger, it becomes impossible to maintain a positive refractive power as a rear group. Furthermore, the positive refractive power of the typeface V@blood of L6 is also strong (and in this aspect, the distorted sailing that is taught is corrected by n, f, i
(1, iru.

If the above-mentioned equation 4 is satisfied, the astigmatism is 1
It is possible to properly correct various effects such as surface curvature, and the mouth ratio is F/2, and the large diameter of -5b0.
It has a wide angle and has a back focus of around 0.9f.
With this method, it is possible to obtain a clear single mound that still maintains the contrast.

Examples of the present invention will be shown below.

Example 1] "l 1.135 dl O,085nl 1.80610
ν1 40J5r2 4.249 (1z O,002 rH0,501 dg O,039n2 1.62004 ν2
36,25r4 0.290 No. 6 0.034 rs o3os da 0.06・nl 1.80610
v3 40.95r6 0.365 ds O,280 17-0,356 d7 0. t17On4 1.78472 1
/4 25.68rll -3,018 ds O,01 rl+ -1,531 dl 0. L) 86 nl 1.772
50 ν5 49.66rlG -0,41
7 (1+o 0.002 rH3,730 dll 0.086 n6 1.81554
v6 44.45r12 -1.037 f-I F/2 2ω-56° fB-0,9
13fP-3,432cJ-1,668 [Example 2] rl 1.102 dl 0.085 nl 1.7725
0 νl 49.66r2 4.205 dg 0.002 rH0,499 ds O,034n2 1.651U(I
ν2 56.15r4 0.285 da 0゜04 rs 0.31j da 0.085 nl 1.7725
0 y3 49.66r6 o. 382 dl 0.24tl r7 -0.339 d? 0.024 ni 1.8051
8 us 25.43r8 -3.514 da O, LllO r9 -2.117 dl 0.109 nl 1.7550
(ly5 52.33rlo -0,37
Reference dlo O,002 r114.410 dll 0.1J97 n6 1.8630
tl y6 41.53rl2 -1.203 f-I F/2 2ω-56° tm-0
, 912fF-3, 911cJ-1, ti4Ll [Example 3] rl 1.068 dl O, 085nl 1.77250
1 49.66r2 3.841 dz O,002 1s 0.500 dl 0.030 B2 1.6970
U ν2 48.51r4 0.289 d4 0.040 r5 0.323 ds o, oss nl 1.7859
0 ys 44.18r6 0.403 ds O,240 1t -tl, 344 dt O,023n4 1. 'it051g 74
25.43ya -4,751 dl 0.0LL+ r9 -2.352 d9 0.116 ns 1.816LJU
ys 46.62rlO-0,382 dlo 0.002 rll 3.293 dls O,HJ2 ns 1.84100
y643.23r12 -1.538 f=l F/2 2ω 56° f B=0.
'j l UfF-3,836cJ residence 1.646 In the above example, fl, ..., rl2 are the radius of curvature of each surface, and dl, ..., dll are the mutual curvature of the valley surfaces. Between -1i1,..., ns is 6/
Zu no Ku? r rate, ν1. ..., Shiro is the Atsube description of each lens, f is the composite sunspot distance of all threads, F/ is the 111 number, ω is the half-angle, (B is the back focus, fF is the composite focal length of the front group) , eJ represents the telephoto ratio. In the examples, all have a telephoto ratio of 1.661, indicating that the lens threads according to the present invention are organized into 7) parts.

The aberration profiles of each example are as shown in Figures 2 to 4. Here, FIG. 2 shows Example 11, and FIG. 3 shows the actual model.
Example 2 and FIG. 4 correspond to Example 3, respectively. In each figure, person 1 has spherical aberration IBI, astigmatism, 1
01 represents image output aberration, and IDI represents coma aberration. From these aberration diagrams, it can be seen that the lens system according to the invention maintains a good aberration correction shape m.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a lens system according to the present invention, and FIGS. 2 to 4 are aberration curve diagrams of examples of the present invention. Figure 1 Figure 2 (A) (B) (Li ('9) (C)
r”B) (C)
αυFigure 4

Claims (1)

[Scope of Claims] Sequentially from the font side, there is a tE meniscus V lens with a convex surface facing the font side, and a second lens of a negative meniscus lens with a convex surface facing the object. A front group consisting of a third lens of a positive meniscus lens with a convex surface facing the object, a fourth lens of a negative meniscus lens with a convex surface facing the image side, and a fourth lens of a positive meniscus lens with a convex surface facing the podium. A standard lens with a wide corner, which is characterized by comprising raw silk of 5 lenses and a rear group in which biconvex lenses are arranged, and satisfying each of the following conditions. +11 nl, nl, n6
＞1.75+21 nll
> 1.81F31 1.71 >
n2 > 1.614) 1.82
> n4 > 1.77+51 4
f > fF > 3.35f (6
J O, 34f > r5
> 0.29f(7) 2.42f
> 1r91 > 1.45f
+8) 1.69f > 1
r121 > 0.9f However, n
l to n6 are the refractive indices of the l-th lens to the 6-th lens, respectively, fIF is the sweet-acid focal length of the front group, y5 is the radius of curvature of the object 11111 surface of the third lens, and 9 is the a of the object-plane of the fifth lens. Single radius, r12 is 1m of the 6th lens
The radius of curvature of the surface, f, is the sweet-acid focal length of all threads.