DD269694A1 - Weitwinkelokular - Google Patents

Abstract

The wide-angle eyepiece for telescopes with a large field of view comprises, successively from the side of the intermediate image to be imaged towards the eye, a negative, three-component cemented component of a biconcave, a biconvex and a biconcave lens, a positive cemented component of a biconvex lens and a convex-concave lens, a biconvex lens, whose interim image facing surface is aspheric, and a positive meniscus lens. figure

Description

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For this 1 page drawing

Field of application of the invention

The invention relates to a wide-angle eyepiece with a large field of view for telescopes, in particular for terrestrial telescopes.

Characteristic of the known state of the art

In the patent US 4525035 a six-lens eyepiece for a field of view of 80 ° is given. In this case, the distance of the exit pupil in relation to the focal length for a comfortable visual observation, especially for spectacle wearers, is too short.

in the patent US 4497546 another six-lens eyepiece for a field of view of 55 ° is given, in which a positive member is arranged in front of the intermediate image. Due to this arrangement, this type of eyepiece can not be used for larger fields of vision, e.g. up to 100 °, apply at a large intersection of the exit pupil.

In King, A .; Köhler, A .: "The telescopes and rangefinders", Berlin, Göttingen, Heidelberg 1959, pp 160-173 are given under No. 19 and 20 eyepieces for a field of view of 120 ° These eyepieces are complicated and have also a to For the eyepiece according to No. 20 the Petzval sum is not fixed. Under No. 18 an eyepiece with an aspherical surface for a field of view of 70 ° is given, which is not due to the Aufbhns of only four lenses can be used for larger visual fields, eg up to 100 °.

A wide-angle eyepiece has also been proposed for telescopes with a large field of view, in which a negative cemented element, a biconcave lens, a concave-convex lens and a weakly positive cemented element are arranged on the side of the intermediate image to be imaged. This eyepiece has the disadvantage that the mass and the diameter are large and it is expensive to manufacture.

The object of the invention is to eliminate the disadvantages of the prior art and to provide a Weitwinkeiokuiar for a large field of view with a simple structure.

Explanation of the essence of the invention

The invention has for its object to provide a Weitwinkeiokuiar for a field of view of 100 °, which has a small number of optical members, in which the intersection of the exit pupil is greater than 0.6 times the focal length of Okuiars, the maximum free diameter of the lenses not is greater than 1.5 times the diameter of the intermediate image to be imaged, the distortion correction corresponds to the angle condition and in which the Petzval sum is corrected. According to the invention, this object is achieved with a Weitwinkeiokuiar in that in a siebenlinsigen eyepiece from the side of the intermediate image to be imaged towards the eye, a negative dreilinsiges K ^; from a biconcave lens, a positive two-ling kite of a biconvex lens and a convex-concave lens, a biconvex lens whose surface facing the imaged intermediate image is aspheric, and a positive meniscus lens are arranged, the following conditional equations being satisfied:

0.8 Γ <Ii <1.2 f (1)

-5,5 f <f ', 4 <-4,0 Γ (2)

η, <1.60 (3)

V,> 60.0 (4)

n ₂ > 1.75 (5)

* ₂ < 29.0 (6)

n ₃ <1.56 (7)

V ₃ > 60.0 (8)

5.0 f <f ₆ <6.5 Γ (9)

n ₄ > 1.60 (10)

V ₄ <50,0 '(11)

n ₅ > 1.75 (12)

V ₆ <29.0 (13)

in which the symbols have meaning:

P - Garmamtbrennweite of the Okuiars

f'i, _m - focal length of the member from area i to m

f'i - focal length of the area i

l _k - air clearance k

nj -number n, of the lens j

V | In this case, it is advantageous that the aspheric surface of the lens L _{6 is} hyperbolic, for whose arrow height ζ the following relationship holds:

j I

where η is the vertex radius, a is a parameter and h is the distance of the points of the aspheric surface from the optical axis. The Weitwinkeiokuiar is characterized by the design data given in Table 1.

The image to be imaged by the eyepiece, z. Within the Okuiars arises between the three-pronged and zweilinsigen Kittgiied a real intermediate image, which has a minimum distance from the adjacent lens surfaces of this airspace according to condition (1), so uncleanliness on the Lens surfaces are not visible.

Due to its negative focal length according to condition (2), the trilobal cemented component close to the real intermediate image contributes substantially to reducing the amount of the Petzval sum, without adversely affecting other aberrations. The construction of this three-lens cemented element under the conditions (3) to (8) for the refractive indices and Abbe numbers results in a reduction of the color magnification error. The deflection of the principal ray away from the optical axis by the negative trilineal cemented element would result in a sharp increase in the diameters of the positive lenses and lens groups in known types of eyepieces. The increase in the lens diameters is limited by the strong positive refractive power of the real intermediate image-facing surface of the two-component cemented member according to the condition (9) and the conditions (1) and (2). The aberrations of the Okuiars and the distortion are adversely affected by this strong refractive power. The aberrations introduced by this positive surface are largely compensated by the following biconvex lens with the aspherical surface on the side facing the real intermediate image, which is advantageously designed as a hyperboloid.

Compliance with conditions (10) through (13) and the ocular eyeball positive meniscus lens support the full field correction of the eyepiece.

AusfQhrungsbelsplel

The invention will be explained in more detail with reference to the following drawing. It shows the

Fig. The lens sectional image of the wide-angle eyepiece.

In Fig. ₁ , along the optical axis 0-0 'from the side of the intermediate image to be imaged toward the eye, are a negative trilobal cemented K ₁ composed of a biconcave lens Li, a biconvex lens L ₂ and a biconcave lens L ₃ , a positive cemented member K]. from a biconvex lens U and a convex-concave lens Le, a biconvex lens U whose surface facing the imaged intermediate image is aspheric, and a positive meniscus lens L ₇ .

A good correction for an eye-side field angle of 25 '= 100 ° is achieved by the described arrangement of the lenses L ₁ to L ₇ with their radii r <, thicknesses d, refractive indices n, and Abbe's numbers v "the parameter a and the vertex radius η for the aspherical surface, whose arrow height ζ depends on the distance to the optical axis h according to the following relationship

2 α

and the aerial image distances Ik, the values of which are given in Table 1.

Table 1

f '= 1 1: 6.25 2σ = 100 °

radii = -2.6492 thick = 0.120 = 0.848 = 0.160 = 1.138 n. V. = 2.0448 = -2.3450 = 2.3450 distances = 1.040 - 0.240 = 2.Μ76 = -1.9S28 = 0.016 Γ2 r ₃ Γ4 = -5.3812 = 1.6962 aspheric di d ₂ d ₃ I ₁ = 0.816 1.55440 1.79192 1.51859 63,28 25,52 63,86 rs Γβ = -0.0015 d ₄ d ₆ = 0.016 = 0.532 1.68101 1.79192 54.74 "25.52 r? Γβ = -9.8512 = 1.3530 I ₂ = .642 a = 2.3740 d ₆ 1.68101 54,74 ra Γιο Petzval sum TP = 0.0024 * Γ I ₃ d ₇ 1.61521 58.36 Γΐΐ

Claims (3)

1. wide-angle eyepiece with asphere, consisting of seven arranged along an optical axis lenses, characterized in that successively from the side of the imaged Zwischenr lildes towards the eye, a negative dreilinsiges Kittglied K ₁ from a biconcave lens L ₁ , a biconvex lens L ₂ and a biconcave lens L ₃ , a positive cemented K ₂ composed of a biconvex lens L ₄ and a convexo concave lens L ₅ , a biconvex lens Le whose surface facing the image to be imaged is aspheric, and a positive meniscus lens L ₇ are arranged, the following Condition equations are eingahalten. 0.8 f <I ₁ <1.2 f -5.5 f <f ', 4 <-4.0 f n, < 1.60 V ₁ > 60.0 n ₂ > 1.75 V ₂ <29 , 0 n ₃ <1.56 V ₃ > 60.0 5.0 f < V ₅ < 6.5 fn ₄ > 1.60 V ₄ <50.0 n ₅ > 1.75 V ₅ <29.0, in which the symbols have the following meaning: f - total focal length of the eyepiece f'i.m - focal length of the limb from area i to m f'i - focal length of the area i Ik - air gap k ni - refractive index n _{e of} the lens j V] - Abbe number of the lens j 2. Wide-angle eyepiece with asphere according to claim 1, characterized in that the aspheric surface of the lens L _{6 is} hyperbolic, for whose arrow height ζ the following relationship applies: 'Ψ ^r i where T _{1 is} the vertex radius, a is a parameter and h is the distance of the points of the aspheric surface from the optical axis. 3. Wide-angle eyepiece with asphere according to Ap pruch 1 and 2, characterized in that the following constuction parameters are present: wherein the arrow height ζ the aspherical surface according to the following relationship depends on the distance to the optical axis h. Z α 2 α rr