JPH01197718A - wide angle eyepiece - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a wide-angle eyepiece with a large field of view for telescopes, especially geodetic telescopes.

[Prior Art] U.S. Patent No. 4,525,0:15 includes 800
A six-member eyepiece for a field of view is described. In the case of this eyepiece, the back focal length of the exit pupil is too short for comfortable viewing with the naked eye, especially for spectacle users.

Another six-member eyepiece for a 55° field of view is described in U.S. Pat. No. 4,497,546, in which a converging lens system is provided in front of the intermediate image. . Due to this arrangement, this type of eyepiece cannot be used for large fields of view, for example up to 1000, in the case of a large exit pupil with a large rear focal length.

A. Oenig and ^ Oehler, “Telescopes and Rangefinders” Berlin, Göttingen, Heidelberg (1959), pp. 160-173, no.
No. 19 and No. 20, an eyepiece for a field of view of 120' is described. These eyepieces have a complex structure and similarly have a short focal length behind the exit pupil.

In the case of the No. 20 eyepiece, the Petzval sum is not corrected. No. 18 describes an eyepiece lens containing an aspherical surface with a field of view of 70', but this cannot be used for a large field of view of +00', for example, because of its structure consisting of only 4 lenses. .

A type of wide-angle eyepiece has also been proposed for telescopes with a large field of view, in which case a diverging cemented lens system,
A convergent cemented lens system, a biconcave lens, a concave-convex lens, and a weakly convergent cemented lens system are arranged. This eyepiece lens has the drawback that it is large in size and diameter, and its manufacturing technology is complicated.

(Problems to be Solved by the Invention) The object of the present invention is to eliminate the various drawbacks of the prior art as described above and to create a wide-angle eyepiece with a simple structure and a large field of view.

The object of the invention is to have a small number of optical elements and an exit lens larger than 0.6 times the focal length of the eyepiece.
! back focal length, the maximum free diameter of each lens is not larger than 1.5 times the diameter of its intermediate image to be imaged, the correction of its image distortion corresponds to the angular condition, and the Petzval sum The object of the present invention is to provide a wide-angle eyepiece for a 100° field of view in which the angle of view is corrected.

[Means to solve the problem]

According to the present invention, the above-mentioned problem can be solved by using an eyepiece lens consisting of seven lenses, in which order from the side of the intermediate image to be formed toward the eye, a biconcave lens L1 and a biconvex lens L2
and a diverging three-lens junction system consisting of a biconcave lens L3, and a convergent junction system consisting of a biconvex lens L4 and a biconcave lens L5, toward the intermediate image to be formed. Biconvex lens L6 with aspherical side surfaces
, and a convergent meniscus lens L7, and the following conditions are met: o, a f@<
li < 1.2 f' (t)-5,
5f'<f',,4<-4,Of' (2
) n, < 1.60 (3) υl >
60.0 (4) n2 > 1
．． 75 (5) υ2< 29.0
(6) 113 < 1.56
(7) υ, > 60.0
(8) 5, Of'<f',<6.
5 f' (9) n4 > 1.60
(10) v, < 50.0
(11) nIJ > 1.75
(12) υs < 29.0
This is solved by maintaining (13).

(Function) The aspherical surface of the lens L6 is a hyperboloid and its arch height is 2.
It is advantageous if it corresponds to the following formula (where γ is the radius of curvature of the top surface, ai is a parameter, and h is the distance from the optical axis to each point on the aspheric surface).

This wide-angle eyepiece is characterized by the structural data listed in Table 1 below.

The intermediate image to be imaged by this eyepiece, for example the rear intermediate image of a telescope objective, is the virtual object of this eyepiece. Inside this eyepiece, a real intermediate image is formed between the three-lens cemented system and the two-lens cemented system, which can be seen from both lens surfaces sandwiching this air gap under the above-mentioned conditions (
1) It has a minimum spacing according to the following, so that dirt, etc. on each lens surface cannot be visualized.

The three-lens combination directly in front of the real intermediate image contributes to reducing the value of the Petzval sum due to its negative focal length according to condition (2), without producing any other undesirable imaging errors. 3 above according to conditions (3) to 8) regarding the refractive index and Abbe number in 11iY
The structure of the cemented system consisting of lenses has a color magnification error (Far
bvergroesserungs-fehlcr). Deflection of the chief ray from the optical axis by the diverging three-lens combination may result in a significant increase in the diameter of each convergent lens and lens group. However, this increase in lens diameter is kept within limits by the strong convergent refractive power of the real intermediate image side '' surface of the two-lens cemented system in accordance with condition (9) above and by conditions (1) and (2). Various aberrations and image distortions of this eyepiece are adversely affected by its strong refractive power.

Even with this converging surface, the various aberrations introduced are compensated as fully as possible by the lens with an aspheric surface, preferably formed as a hyperboloid, on the real intermediate image side of the subsequent biconvex lens.

Maintaining the above conditions (IO) to 13) and the convergent meniscus lens on the ocular side of this eyepiece help the overall correction of this eyepiece for a large field of view.

(Example) The present invention will be described in more detail below with reference to the accompanying drawings.

A biconcave lens L1, a biconvex lens L, and a biconcave lens L3 are arranged along the front axis O-0° in order from the side of the intermediate image to be formed toward the eye in the eyepiece shown in the attached drawing. A diverging three-lens cemented system consisting of a biconvex lens I, and a convergent lens cemented system consisting of a biconvex lens I, 4 and a convex-concave lens [, 5] are directed toward the intermediate image to be imaged. A biconvex lens L6 having an aspherical surface and a convergent meniscus lens L° are arranged.

A good correction for an image plane angle of 2° and 100' on the naked eye side is radius γ4, thickness dj, and refractive index n, respectively.

and the Atsbe number υ6 and the parameter a and the radius of curvature of the top surface γ for its aspheric surface, and the arrangement of the air gap lk, where the arch height 2 of the aspheric surface is It depends on the distance ah to the optical axis according to the following formula, and the respective values above are listed in Table 1 below.

Table 1 f'-11: 6.25 2a"= 100'γ, -2
,6492 d+ 1-0.120 1.554406:1.28γ
2-2.0448 d2-0.848 1.74119225.52γ3-
2.3450 da -0,1601,5185963,86γ4婁2
．． :1450 11 Proverb 1.138 γrJ-3,9476 d4-1.040 1. I+810154.74γ,
-1,9928 d5- 02240 1.79192
25.52γ, -5,:j8+2 12-0.016γ. -1,6962 aspherical surface a = -0,0015 d,, ~0.8+6 1.68101 54.74
γ9- -9.8512 13 0. Old 6 γ1゜-1,415:10 dy -0,5:12 1.61521 5
8.36γ, -2,3740

[Brief explanation of the drawing]

The accompanying drawing is a schematic explanatory sectional view of a wide-angle eyepiece according to the invention. 0-0°...on the optical axis, K2...lens junction system 5, L2, L5, L4, L5, L6, L7...lens 1k...air gap Silence...exit pupil Fig .

Claims (1)

[Claims] (1) Consisting of seven lenses arranged along the optical axis;
In a wide-angle eyepiece including an aspherical lens, in order from the side of the intermediate image to be formed toward the eye, a biconcave lens L_1, a biconvex lens L_2, and a biconcave lens L.
A diverging three-lens cemented system K_1 consisting of a lens L_3, a convergent lens cemented system K_2 consisting of a biconvex lens L_4 and a biconcave lens L_5, and the surface facing the intermediate image to be formed is aspheric. A biconvex lens L_6 and a convergent meniscus lens L_7 are arranged, and the following conditions are met: 0.8f'<l_k<1.2f'-5.5f'<f'_1_ ．． _4<-4.0f'n_1
<1.60 υ_1>60.0 n_2>1.75 υ_2<29.0 n_3<1.56 υ_3>60.0 5.0f'<f'_5<6.5f'n_4>1.60υ_4<50 .0 n_5>1.75 υ_5<29.0 [However, f' is the total focal length of this eyepiece, f'_i
＿． _m is the focal length of the junction system from surfaces i to m, f'_i is the focal length of surface i, l_k is the distance of the air gap, n_j is the refractive index of lens j, and υ_j is the Abbe number of lens j. ] The above-mentioned wide-angle eyepiece is characterized in that the following is maintained. (2) The aspherical surface of the lens L_6 is a hyperboloid, and its arch height z corresponds to the following formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ where γ_j is the radius of curvature of the top surface, and a is a certain parameter. , and h is the distance from the optical axis to each point on the aspheric surface. (3) The eyepiece has the following characteristic values, namely ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ In this case, the arch height z of the above aspherical surface is the following formula ▲ The eyepiece according to claim 1 or 2, which depends on the distance h from the optical axis to each point of its aspheric surface according to a mathematical formula, a chemical formula, a table, etc.