DE1497543C - Wide angle lens for camera purposes - Google Patents

Description

positive doublet lens, a negative single lens, ίο blett meniscus with concave front surface and L9 a cemented positive doublet meniscus with positive single lens.

The rest, in A b b. 1 have the usual meaning, i.e. dl, dl ... dl5 mean the axial lens thickness or

and nl, »2 ... η9 are the refractive indices of each Lens elements, all consecutively numbered starting from the object side.

The lenses according to claims 1 and 2 meet the following system requirements:

0.5 i / 9 < dll < 2 i / 9,

concave front surface and a positive single lens follows.

With a single-lens reflex camera, the
Focal length of the lens due to the swivel space required for the folding air gaps between the individual lenses, rl, r 2 ... mirrors, do not fall below a certain rl6, the radii of curvature of the individual lens surfaces. For example, it is necessary that the focal length of the lens is
a 35mm camera must be larger than about 35mm.
Due to this requirement, it has been difficult to date to 20
to get a super wide-angle lens because the distortion and coma in particular increase,
if the field of view is increased, although for
Obtaining a wide-angle lens, its focal length
has to be short, so far a lens of the introductory 25
described type has been used. on the other hand
In wide-angle lenses, the increase in spherical aberration is not particularly harmful
Influence on the image quality, but probably the increase
of astigmatism and distortion. Therefore 30
these last two lens defects must be sufficient
be corrected.

The well-known lenses of the type described in the introduction, but which instead of the cemented one positive doublet meniscus a positive single meniscus is provided as the penultimate lens segment, all have a focal length smaller than 1.5F, and have a significantly smaller aperture ratio than F / 2.8 when the field angle reaches 80 ° target.

Accordingly, the object of the invention is to provide objectives of the type described in the introduction in which the back focus is greater than 1.5F and in which the achievable field angle is above 80 °

7i5 - nA
78

| rlO |
7i8 - nl

> 0,

The design of the two lenses is based on the fact that the total focal length of the front action group Ll ... L3 is made negative in order to obtain a virtual image of the object, that this virtual image is generated at infinity with the aid of the lens group LA ... L8 and that with the help of the last lens L 9 for an aperture ratio of F / 2.8, the real image being generated in a predetermined position, at the same time various types of lens defects, in particular so that an image is obtained whose defects are the coma, the field curvature and if the directories mentioned above are well corrected, it is well that they are very well corrected. first necessary, various mistakes of the first

Two lenses of the type described in the introduction to correct the virtual image sufficiently. To which the in claims 1 and 2 according to the invention 50 for this purpose the chromatic aberration is characterized by design data, design of the front lens L1 as a negative lens solve this problem. The design data have been corrected here. But the other lens defects, e.g. B. those designated in the usual way; It means spherical aberration, the coma, the image field curvature r \, rl ... the radii of curvature of the individual lenses, the distortion and the like, become areas, i / l, i / 2 ... the axial Lens thickness or air 55 not corrected sufficiently. Their correction is carried out at intervals, «1, nl the refractive indices of the individual, therefore, through the rear group of effects, sufficient lens glides and v \, v2 the counting of the individual.

. Lens members, all away from the object scan- In other words, condition (1) provides for a

consecutively numbered. flat image, and it is the condition for L6

In the following, the two lenses on the basis of 60 are practically in the middle between LA-, L5 on the one hand and

Drawing explained in detail; it shows Ll, LS is located. With such an arrangement

A b b. 1 ύοη schematic lens structure and the main light rays practically run through the

A b b. 2 the correction state of the objective with the center of L6 (near the optical Ac'iso), and

the design data according to claim 1. It is possible to use the astigmatism

According to A b b. 1 is the lens, harmful influence called by the objectscite 65 to a minimum

starting out, formed by a front effect reduction, but at the same time keeping the spherical aberration group Li to L3 with a negative total focal length, gc- extremely small. If this condition were changed by a collecting group of effects LA to L9, the main rays of light would pass through the

Edge zone of L6 pass, which not only reduces the astigmatism, but also the spherical aberration would be greatly increased.

Condition (2) is used to correct the distortion and the internal coma for skewed light rays, d. H. for light rays that are outside the main light rays at a predetermined angle opposite de: 'optical axis arrive. This defect is very high in the lens system of this type. With in other words, r8 is chosen negative, therefore the difference in the height of incidence of oblique rays of light is greater, and thus the oblique rays of light become larger severely broken, so that those of the front impact group Ll ..-. L3 produced internal coma can be corrected sufficiently. If this condition were reversed, the one in the front would be The internal coma generated by the impact group increases, and its correction in the rear impact group would be difficult.

Condition (3) is used to correct the internal coma insofar as it is generated by oblique light rays, that is, light rays entering the system within the main light rays which are incident at a predetermined angle with respect to the optical axis. In other words, the angle of incidence of the oblique rays of light at r11 is greater than the angle of incidence of the oblique rays of light at r10, and the refraction by the surface r 11 becomes greater than that of the surfaces 10. However, if the direction of the sign of the inequality is reversed, namely while the refractive powers of r10 and r12 are kept constant, the Petzval sum changes little, therefore the corrective effect on astigmatism is reduced, and the difference in refraction caused by the different heights of incidence of the light rays passing through lens L6 continues to decrease . The converse condition (3) would therefore be useless for correction purposes.

The condition (4) serves to achieve the same object and effect as the condition (3). Namely, rll corrects the internal coma of those light rays which, within the main light rays, enter the system at a predetermined angle. But this internal coma is further corrected by the area r 13. The correction is carried out in such a way that the refractive index η 7 of the concave lens member Ll is increased and the refractive index w & of LS is decreased, whereby the positive curvature in the negative direction produced on the sagittal image surface is compensated for. If the direction of the sign of the inequality is reversed, the angle of incidence of the oblique rays of light becomes smaller, and the correction of the internal coma generated in the anterior group can therefore no longer be carried out.

The image of the object is produced by the lens elements Ll ... L8 practically in infinity if the above conditions are met. But it is not always necessary to create the image of the object in infinity. If, however, the absolute value of the total focal length of the lens elements Ll ... LS is smaller by more than twice the total focal length of the entire lens system L1 ... L9 and the latter focal length is positive, the total focal length of the lens elements L4 ... L8 becomes shorter, the load becomes excessive and the errors difficult to correct. On the other hand, if this focal length is negative, it is necessary that the lens L9 should have an extremely high refractive power. This in turn leads to a poor match and it becomes difficult to correct the error. Therefore, the total focal length of the lens elements L1 ... L 8 should preferably be greater than twice the focal length of the overall system Ll ... L9, and the virtual image or the image generated in infinity can be used as a real image behind the lens with the aid of the lens element L9 be generated.

Subject to the above conditions and using various other corrective measures as a result, the two wide-angle lenses according to claims 1 and 2 for camera purposes obtained with an aperture ratio of F / 2.8 at a field angle of 80 ° and above and whose focal length is more than 1.5 times the total system focal length, whereby at the same time the coma, the curvature of field and other lens errors are very well corrected.

The objective having the construction data according to claim 1 further has the following niches Aberration coefficient:

r I. π III-IV IV V 1 0.0151218 0.0243690 0.0785414 0.1924196 0.3100842 2 . -1.2116956 ; 0.1849224 -0.0564436 -0.4556300 0.0695358 3 0.1940116 0.1327508 0.1816670 0.1929328 0.1320126 4th 0.0020366 -0.0084990 0.0709364 0.1375674 -0.5740902 5 0.2697854 0.1225240 0.1112896 0.3619426 '0.1643776 6th . -14.7832946 1.9467302 -0.5127082 -0.0917724 0.1437694 7th 8.2949876 1.0188750 0.2502972 0.4889270 0.0600550 8th 1.1427144 -0.3703238 0.2400244 0.17344778 -0.0562194 9 2.4595612 -1.1583944 1.0911522 . 0.7803018 -0.3675034 10 -0.8247514 0.5723000 -0.7942446 -0.5212666 0.3617100 IL -1.9778536 -0.9953438 -1.0018022 -0.8265912 -0.4159774 12th 0.0175012 0.0588448 0.3957122 0.1099196 0.3695872 13th -1.6245810 -0.5333596 -0.3502104 -0.2235402 -0.0733896 14th 4,5683924 -0.6047468 0.1601082 0.5395192 -0.0714194 15th : -0.0005906 0.0066302 -0.1488556 -0.0211022 0.2368840 16 4,4003996 -0.7188146 0.2348398 0.3370592 -0.0550592

0.9417450

0.3215354 -0.0496962

0.1741644

0.2343562

Claims (2)

Patent claims: 1. Wide-angle lens with a back focus that is greater than the system focal length, the, of the Longer focal length counted, a dispersing lens group from a negative single meniscus with a convex front surface, a positive single lens and a negative meniscus with a convex Has front surface on which, after a larger air gap, a collecting the diaphragm Lirise group consisting of a cemented positive doublet lens, a negative single lens, a cemented positive doublet meniscus with a concave anterior surface and a positive single lens follows, characterized by the following design data: Focal length / = 1.0
Back focus B- f =
Field of view angle 2ß =
Relative opening F: 1.5597
84 °
2.8 nd vd nl = 1.62041 60.3 dl = 0.1125 dl = 0.2625 nl = 1.62041 60.3 d3 = 0.2292 i / 4 = 0.0042 «3 = 1.62041 60.3 d5 = 0.1125 d6 = 0.4083 «4 = 1.62004 36.3 dl = 0.1667 «5 = 1.51823, 59.0 t / 8 = 0.1250 i / 9 = 0.1042 «6 = 1.7847 i / 10 = 0.2208 i / 11 = 0.0979 «7 = 1.7847 26.1 i / 12 = 0.0417 «8 = 1.62041 60.3 i / 13 = 0.3250 t / 14 = 0.0042 "9 = 1.744 44.9 dl5 = 0.1458 rl = +2.5000 rl = +0.8958 r3 = +3.7500 τΑ = -3.7500 rS = +1.2500 _r 6 = +0.4583 rl = +1.0521 r8 = -0.7742 r9 = -1.4542 r10 = -3.5417 rll »= +1.3500 rl2 = -5.0000 rl3 = +1.1729 rU = -0.8333 rl5 = +8.0000 rU = -1.9423 2. Wide-angle lens according to the preamble of claim 1, characterized by the following Construction data: Focal length / = 1.0
Back focus Bf = 1.5032
Field of view 2/3 = 80 °
Relative opening F: 2.8 rl = +2.0873 rl = +0.7842 r3 = +4.6000 rA = -2.9420 rS = +1.1160 r6 = +0.4520 rl = +0.8400 rS = -0.8400 r9 = -1.4709 r10 = -40,000 rll = +0.9280 rl2 = -0.9200 rl3 = +1.1768 rl4 = -0.7440 rl5 = -8.8000 rl6 = -0.9616 nd Vi / dl = 0.180 nl = 1.62041 60.3 dl = 0.300 d3 = 0.552 «2 = 1.6228 56.9 dA = 0.004 dS = 0.092 n3 = 1.58913 61.2 i / 6 = 0.232 dl = 0.200 nA = 1.57501 41.3 i / 8 = 0.054 «5 = 1.56248 50.9 </ 9 = 0.088 t / 10 = 0.160 «6 = 1.51823 59.0 i / 11 = 0.112 dll = 0.028 nl = 1.7847 26.1 t / 13 = 0.180 π8 = 1.6679 55.5 dlA = 0.004 dXS = 0.104 π9 = 1.76684 46.2 1 sheet of drawings