RU2239214C2 - Ocular with external entrance pupil - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: device has three positive components. First component is a single meniscus directed to subject by convex portion, second component is glued together from biconvex lens and negative meniscus, directed to eye by convex portion, third component is made in form of biconvex lens. For focus distances and refraction coefficient of third component certain relation are true, which are shown in inventive formula.

EFFECT: higher quality, broad angle, large extension distance of pupil - over ten focus distances, high level of aberration correction including lowered value of astigmatism and low distortion.

3 dwg

Description

The present invention relates to optical systems, in particular to the eyepieces of observation devices, and can be used in optical circuits of microscopes, colposcopes, telescopes, binoculars.

When creating complex observational instruments containing a large number of optical components, it becomes necessary to use high-quality compact wide-angle eyepieces with a remote position of the entrance pupil, which can be up to ten focal lengths or more.

A compact eyepiece [1] is known, which contains a double-glued meniscus, the lenses of which are made in the form of positive and negative menisci facing concavity to the object, and two identical single plano-convex lenses, convex sides to each other. Such an eyepiece has good image quality, small dimensions, but insufficient entrance pupil, commensurate with the focal length.

The eyepiece [2] is also known, containing four single lenses, the first of which is the meniscus, facing the concavity to the object, the second is biconvex, the third is biconcave, and the fourth is biconvex. Such an eyepiece has large dimensions (its length is more than two focal lengths of the eyepiece) and a small extension of the entrance pupil.

Closest to the proposed one is a three-component eyepiece [3] with a magnification of 12 times, the first component of which is a single positive meniscus facing concavity to the object, the second is glued from a biconvex lens and a negative meniscus convex to the eye, and the third is a single positive meniscus facing concavity to the eye. This eyepiece has a significant (over ten focal lengths) projection of the entrance pupil, well-corrected aberrations of the axial beam and wide inclined beam of rays, slight image curvature and astigmatism, but the distortion is more than 4% for an angular field of 2ω ’= 43 °.

The objective of the invention is to provide a high-quality compact wide-angle eyepiece with a large projection of the entrance pupil. The technical result is the reduction of distortion while maintaining high image quality.

This is achieved by the fact that in the eyepiece, which consists of three positive components, the first of which is a single meniscus facing concavity to the object, the second is glued from a biconvex lens and a negative meniscus convex to the eye, the third is made in the form of a single lens, unlike known, the third component is a biconvex lens and the following conditions are true:

f ₁ ≥ 5.66 × f ₃

f ₃ ≤ 0.86 × n ₃ × f _OK ,

where f ₁ is the focal length of the first component;

f ₃ is the focal length of the third component;

f _OK is the focal length of the eyepiece;

n ₃ is the refractive index of the material of the third component.

Figure 1 presents a schematic optical diagram of the proposed eyepiece, figure 2 is a graph of transverse aberrations, figure 3 presents the curves of astigmatism and distortion.

The eyepiece (Fig. 1) consists of a positive meniscus 1 facing concavity to the object, a positive component glued from a biconvex lens 2, and a negative meniscus 3 facing a convexity to the eye, and a biconvex lens 4.

From the object plane, diverging beams of rays come into the eyepiece. Sequentially refracted on lenses 1, 2, 3, 4, diverging beams of rays are formed in parallel, necessary for viewing by the eye.

The design parameters of the proposed eyepiece are given in table 1.

The lens materials shown in Table 1 have the values of the refractive index n and the Abbe numbers ν indicated in Table 2.

The above design parameters allow you to get an eyepiece with the following characteristics:

- focal length f ’= 16.83 mm;

- a visible increase in G = 15 ^x ;

- angular field in the space of images 2ω = 43 °;

- removal of the entrance pupil S’p = 180 mm;

- removal of the exit pupil S’p ’= 17 mm;

- exit pupil diameter D ’= 1.7 mm.

Moreover, f ₁ = 135.56 mm f ₃ = 23.93 mm.

The previously imposed conditions are met:

135.56≥ 5.66 × 23.99 135.56≥ 135.44,

23.93≤ 0.86 × 1.6622 × 16.83 23.93≤ 24.06

Eyepiece aberrations are presented in Tables 3-5.

From the analysis of aberrations it follows that the eyepiece has improved image quality.

Thus, we obtained a compact eyepiece (its length is approximately equal to the focal length), which has a significant projection of the entrance pupil (more than ten focal lengths), a real front focal plane, which makes it possible to use it not only for observation, but also for measurement, a large projection exit pupil (slightly larger than the focal length), and having a high degree of aberration correction: a reduced value of astigmatism and distortion.

Sources of information

1. Patent of the Russian Federation No. 2010279, publ. 30.03.1994, IPC G 02 B 25/00.

2. USSR patent No. 1742773, publ. 06/23/1992, city, IPC G 02 B 25/00.

3. US Patent No. 3975088, publ. 08/01/1975, IPC G 02 B 25/00 (the closest analogue).

Claims (1)

An eyepiece with a remote entrance pupil, consisting of three positive components, the first of which is a single meniscus facing concavity to the object, the second is glued from a biconvex lens and a negative meniscus facing the bulge to the eye, the third is made in the form of a single lens, characterized in that the third the component is a biconvex lens and the following conditions are met in the eyepiece: f ₁ ≥ 5.66 × f ₃ ; f ₃ ≤ 0.86 × n ₃ × f _ok , where f ₁ is the focal length of the first component; f ₃ is the focal length of the third component; f _OK - the focal length of the eyepiece; n ₃ is the refractive index of the material of the third component.

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