DD221570A1 - PHOTOGRAPHIC WIDE-ANGLE LENS OF THE RETROFOK TYPE - Google Patents

Abstract

The invention relates to a wide-angle photographic lens of the retrofocus type. The aim of the invention is a retrofocus wide-angle lens with a field angle greater 90 and a relative opening greater than 1: 2.8. The object is to propose such a new constructive solution, in which an image error compensation, including coma compensation is guaranteed and at the same time a distortion deterioration is avoided up to the imaging scale b 16. The structural design of an objective that fulfills the abovementioned tasks is specified. The necessary construction data are contained in a table. figure

Description

Field of application of the invention

The invention relates to a wide-angle lens of the retrofocus type for photographic purposes. Characteristic of the known technical solutions

Wide-angle lenses of the retrofocus type in their constructive basic structure are known. The constructive solutions proposed for this purpose contain in the majority of cases at the same time different possibilities for compensating the astigmatic aberrations that occur in close-up shots.

Often, the image error compensation takes place by reducing a located in the front part of the lens airspace, as proposed in the invention descriptions DE-OS 2117367 and DE-OS 2413472. Another possibility for image aberration correction in close-up is according to the patents DE-OS 2224429 and DD-WP 149826 therein, an air space in the central lens part, z. B. to reduce the aperture space, proportional to the Objektivhub.

The solutions mentioned have the disadvantage that occurs in this type of astigmatic aberration compensation as unwanted by-coma. This is especially disturbing as a loss of contrast noticeable when at field angles over 90 °, the relative opening is greater than 1: 2.8.

Therefore, solutions have also been proposed in which the coma that occurs can in principle be kept small by changing several air spaces. In the patent DE-OS 2718521 a lens is described in which for an entire lens group is moved in the image-side lens part. Disadvantage of this solution is that in close-ups, the distortion extremely worsened and far exceeds the limit allowed for photographic purposes.

All solutions have another common disadvantage: the displacement element is very sensitive to centering, and in the object-side objective part heavy-duty glasses with refractive indices of over 1.7 are used in the scattering menisci, which are extremely expensive.

Object of the invention

The aim of the invention is a retrofocus wide-angle lens with a field angle greater than 90 ° and relative openings greater than 1: 2.8. The lens should be technologically easy to master in its production and only inexpensive glasses with refractive indices of crown glasses smaller than 1.7 included.

Essence of the invention

The invention is based on the object to propose such a new constructive solution, in which an image error compensation, including the Komakompensation is guaranteed and at the same time a distortion deterioration to the magnification ß = -1/6 is avoided. The object is achieved by a wide-angle photographic lens of the retrofocus type consisting of an object-side lens part with a collecting and two subsequent scattering menisci, all turn their cavity to the aperture and a final thick lens member, a central collecting lens part with at least one collecting lens member and the aperture space and a Image-side lens part having a lens element having a scattering cemented surface, a meniscus hollowing towards the aperture space and a further converging lens which turns its more curved surface toward the image by the weak lens member in the object-side objective part being weakly convergent and a cementing surface which collects hollow to the aperture space whose curvature is stronger than all other surfaces of the objective, the difference of the refractive indices of the adjacent glasses being less than 0.07, that in the central objective part a scattering meniscus us and below a biconvex lens are included, wherein the air space between the two lenses in the form of a collecting meniscus and that in the image-side lens part, the converging lens is a, his cavity facing the aperture space, collecting meniscus.

The necessary design data for such a constructed lens are given in Table 1. Due to the proposed constructive basic structure, there are several possibilities for image aberration in close-up photography:

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On the one hand, the air space existing between the object-side and the central objective part can be varied proportionally to the "objective stroke." On the other hand, it is possible to move the first air space of the object-side lens part as well as the air space between the object-side objective part and the central objective part, in proportion to the objective stroke

same amount but in the opposite direction to vary.

A lens constructed as described above allows close-up to the magnification ß = -1/6, wherein in all settings no coma occurs and the distortion remains significantly less than 5%. In all lenses, especially in the scattering menisci of the object-side lens portion, only glasses with refractive indices smaller than 1.7 are used on crown glasses. Since the displacement movements for image error compensation are relatively large, the sensitivity of the displacement element against decentring is low, d. H. the lens is easy to make.

embodiment

The invention will be explained in more detail with reference to an example. Table 1 gives the necessary design parameters for an objective according to the invention. The parameters ρ and q can vary in the bounds between zero and one and give equally well-corrected systems for each parameter value. For the special parameter pairs (0; 0), (0; 1,), (1; 0), variants with commercially available glass types of VEB JENAer Glaswerke result. Fig. Shows the sectional drawing of an objective according to the invention with a field angle of 26 ° = 93.5 ° and a relative opening 1: 2.4

According to FIG. 1, the object-side objective part consists of the collecting meniscus L ₁ , the two downstream scattering menisci L ₂ and L _3, and a weakly convergent thick lens element L ₄ , which contains a cemented surface ₈ which is extremely strongly bent through to the stop BL.

Due to the cemented surface caused by the two scattering menisci L ₂ , L ₃ spherical aberration is largely compensated. In order to achieve the desired effect and to influence as little as possible the entire scattering effect of the object-side objective part, this surface must be curved more than all other surfaces of the system. Furthermore, the refractive index jump must remain less than 0.07. The entire object-side objective part thus has only isoplanar error (coma) and no significant spherical aberration.

The air space L ₄ between the object-side and the central objective part is variable and serves to compensate for the astigmatic aberrations in close-up setting. It proportionally decreases with the objective stroke. Because of the vanishing spherical aberration of the object-side objective part, virtually no coma is created when compensating the astigmatic aberrations.

The central collecting objective part must cause a spherical overcorrection itself because of the lack of spherical overcorrection by the object-side objective part itself. This is achieved by the fact that it consists of a scattering meniscus L _s and a biconvex lens L _e .

The separating airspace I ₅ has the shape of a collecting meniscus and thus acts spherically overcorrecting. The following airspace I ₆ is the aperture space. The central objective part and the diaphragm space are followed by the image-side objective part. It consists of the divergent lens element L ₇ , which contains a scattering and iris-space-like cement surface r ₁₅ , which · its concave surface faces the image. The lens member L _{7 is} followed by two collecting menisci L ₈ and L ₉ , which turn their cavity of the diaphragm

Table 1

Focal length f = 1.00 relative aperture 1: 2.4

Cutting distance s' = 1.83 field angle 2 - "= 93.5 °

surface curvatures Thickness and air refractive indices 1.59142 Abbe distances n ₈ paid Vr ₁ = + 0.3088-0.0006p d, = 0.2376-0.0024p 61.0 + 0,019Oq 1.68101 1 / r ₂ = + 0.1439 + 0.0157q I ₁ = 0.0096-0.0048q 1 / r ₃ = + 0.6070-0.0204p d ₂ = 0.0912 54.7 -0.0321 q 1 / r ₄ = + 1.3025 + 0.0173p I ₂ = 0.3110 + 0.0322p 1.68101 + 0,01548q -0,0129q + 0,0274q 1 / r ₅ = + 0.5985-0.1242p d ₃ = 0.0864 54,7-1,4q -0,092Oq 1 / r ₆ = + 1.3857-0.0659p I ₃ = 0.2952-0.0168p 1,61685-0,00872p -0,1609q -0,0216q 1 / r ₇ = -0.0463 + 0.0548p d "= 0.1800 + 0.0408p 1,66885-0,01352p 36.7 + 1,2p -0,0539q + 0,0917q Vr ₈ = + 1.8626-0.1112q d ₅ = 0.3936 + 0.0096p 35.6 + 2.5p -0,0288q Vr ₉ = -0.3122-0.0499p | ₄ = 0.1944 + 0.0048p 1.64127 + 0,002513q -0,0213q + 0,0432q Vr ₁₀ = + 0.4148-0.0272p d ₆ = 0.0720 + 0.0048p 55.3 + 0,8q + 0,1263q 1 / r ₁₁ = + 1.3345-0.0147p I ₅ = 0.1066-0.0168p 1.57832 + 0,00711q + 0,0185q -0,0072q Vr ₁₂ = + 1.0113 + 0.0293p d ₇ = 0.3648-0.0096p 41.0 + 0,8q + 0,0477q -0,0240q Vr ₁₃ = -0.7124 + 0.0141p = ₆ = 0.1104 + 0.0096ρ + 0,1492q -0,0048q

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surface curvatures Thickness and air refractive indices Abbe distances Numbers Q _e 1 / r _l4 = + 0.2020 + 0.0072p dg = 0.4109 + 0.0427p 1.55440 + 0,01166p 63,3-2,8p -0,0162q +0.0331 q + 0,01166q -2,8q 1 / r ₁₅ = -1.1419 + 0.0768p d ₉ = 0.0960 1.74618 + 0,01549p 27,9-0,6p + 0.1013q ' + 0,01549q -0,6q Vr ₁₆ = + 0.5614 + 0.0135p I ₇ = 0.1488-0.0144p + 0,015Oq -0,0096q 1 / r _l7 = -0.3685 + 0.0575p d _l0 = 0.1584 + 0.0048p 1.68101 54.7 4-0,0688q + 0,0048q 1 / r ₁₈ = -0.9818 + 0.0569p I ₈ = 0.0058-0.001Op + 0,0438q -0,0010q 1 / r _lg = -0.0511 -0.0614p dn = 0.1776-0.0048p 1.59142 + 0.02379 61,0-2,6q -0,0393q -0,0048q 1 / r ₂₀ = -0.6662-0.0445p -0,0207q

0 <p <1; 0 <q <1; p + q <

Claims (4)

Invention claims: 1. Wide-angle photographic lens of retrofocus type consisting of an object-side lens part with a collecting and two subsequent scattering menisci, all of which turn their cavity to the aperture space and a final thick lens member; a central collecting lens part with at least one collecting lens member and the aperture space and an image-side lens part with a lens element having a scattering cemented surface, a meniscus hollow to the aperture space and a further converging lens, the more curved surface facing the image, characterized in that the thick Lens member in the object-side lens part is weakly convergent and has a diaphragm space to the hollow collecting putty whose curvature is stronger than all other surfaces of the lens, the difference in refractive indices of the adjacent glasses is less than 0.07, that in the central lens part a scattering meniscus and below a biconvex lens are included, wherein the air space between the two lenses in the form of a collecting meniscus and that in the image-side lens part, the converging lens is a, his cavity facing the aperture space, collecting meniscus. 2. Wide Angle Lens according to item 1, characterized in that the lenses of the lens have the design data listed in Table 1. 3. Wide-angle photographic lens according to item 1, characterized in that for the image error compensation in close-ups of existing between the object-side and the central lens part air space is proportional to the lens part existing air space proportional to the Objektivhub variable. 4. Wide Angle Lens according to item 1, characterized in that for the image error compensation in close-ups of the first air space of the object-side lens part by the same amount in the opposite direction as the air space located between the object-side and the central objective part is variable. For this 1 page drawing