WO1992001958A1

WO1992001958A1 - Afocal optical observing system

Info

Publication number: WO1992001958A1
Application number: PCT/EP1991/001366
Authority: WO
Inventors: Udo Stenzel
Original assignee: Heckler & Koch Gmbh
Priority date: 1990-07-20
Filing date: 1991-07-19
Publication date: 1992-02-06
Also published as: CA2066654A1; EP0493562A1; DE4023192A1; JPH04506580A; DE4023192C2

Abstract

Disclosed is an afocal optical observing system, in particular a telescopic sight, with an objective lens (10') and an eyepiece (10''), and with angles magnification (V) which changes transversally to the optical axis and preferably decreases towards the edge of the field of vision. The target to be magnified can thus be detected comparatively easily with the low-magnification zone (34) and the observing system can subsequently be easily positioned so that the higher-magnification zone is aimed precisely at the target.

Description

Afocal optical imaging system

The invention is concerned with an afocal optical imaging system.

Such imaging systems are usually equipped with a lens and an eyepiece and are known, for example, as microscopes or telescopes, in particular riflescopes. They are used regularly for enlargement purposes. With these systems, in particular systems with a higher magnification, it is known that it is difficult to cover the object field sought with the field of view of the imaging system. The field of view of an imaging system regularly decreases with increasing magnification - with a constant field of view aperture. In particular, its field of vision is often considerably smaller than that of the naked eye. It is therefore often easy to aim at an object with the naked eye, but it is difficult to find it again with an enlarged imaging system.

An afocal imaging system is known, for example, from DE-AS 11 76 893 (LOY). This publication discloses an afocal attachment lens system for facial Field enlargement of a telescope. Both the telescope and the auxiliary lens system always have constant magnification everywhere.

An imaging system with a finite focal length, that is to say a focal imaging system, is known from US Pat. No. 3,953,111 (FISHER et al). This system consists of a group of several lenses arranged one after the other. It shows the areas close to the axis compared to areas away from the axis of an object, much larger. The resulting non-linear imaging or enlargement ratios are compensated for again by an optically downstream additional imaging system, namely non-linear imaging in the inverse direction. In the end result, the object is imaged with constant magnification over the entire field of view. The areas close to the axis, however, have a greater sharpness, more precisely a greater detail resolution.

For the rest, from DE-AS 12 67 966 (SCHIELE), US 4 185 897 (FRIEDER) and US 3 708 221 (SCHAEFER) individual lenses are known which have several coaxial zones of different focal lengths extending transversely to the optical axis and thus in general have different magnifications. A flat object, which is at a constant distance from these lenses, is thus imaged on a surface whose respective distance from the lens is correlated with the changing lens focal lengths, i. H. changes. The image of the object is therefore generally not on a plane, but on a curved surface.

The invention is concerned with the problem of eliminating, or at least reducing, the difficulties described at the beginning when aiming at an object by means of an afocal imaging system. 1 The above problem is solved according to the invention in that the angular magnification of the afocal system changes transversely to the optical axis (claim 1) and thereby preferably decreases towards the periphery (claim

5 2).

The advantage achieved thereby consists essentially in the fact that the object is first acquired comparatively easily with the zone (s) of lower magnification 10 and then the optical imaging system is positioned relative to the object in such a way that the zone of greatest magnification precisely targets the object.

According to the preferred embodiment of the invention _{j ^} g (claim 2), a zone of greatest magnification is thus arranged in the region of the optical axis and the enlargement of the remaining zone or zones decreases towards the periphery. As a rule, the quality of an optical image decreases from the optical axis in the direction of the periphery. The zone of the greatest magnification is therefore in an optically particularly favorable imaging area. A possible reduction in the imaging quality of the further zone (s) farther from the optical axis can be accepted. In any case, this area 5 essentially serves only for the rapid first detection of the object to be enlarged and its simple transfer into the central area near the axis.

According to a further preferred exemplary embodiment of the invention, the objective and the eyepiece are designed as follows to achieve zones of predetermined, changing angular magnification of the overall system: They each have the zones of the changing angular magnification. corresponding zones, which also extend transversely to the optical axis and are mutually adapted to one another in terms of focal length (claim 3).

The zone with the greatest magnification is advantageous formed as a central zone of constant magnification arranged centrally to the optical axis, while the enlargement of the other zones gradually and / or continuously decreases towards the periphery. This results in symmetrical conditions for the optically important central zone, as a result of which favorable imaging conditions are created (claim 4).

The imaging symmetry is further improved in that all zones are arranged axially symmetrically to the optical axis (claim 5).

A maximum of symmetry is achieved in that the central zone has a cross section in the form of a circular area and is surrounded concentrically or coaxially by the other zones (claim 6).

The initial fixing of the object to be magnified is especially true by a ^* in the peripheral area

- Arranged arranged free of enlargement or only slightly, but constantly enlarging or reducing zone (claim 7).

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the attached drawing. The drawing shows:

1 shows an embodiment for enlargement ratios achievable with the imaging system and

Fig. 2 shows a constructive embodiment.

In the drawings, parts with the same effect generally have the same reference number.

The exemplary embodiment shown in FIG. 1 has a circular central zone 30 of constant magnification arranged concentrically around the optical axis 20, l here 4: 1, on. The central zone 30 is concentrically surrounded by an annular transfer zone 32, which has an enlargement that decreases continuously radially outward from the optical axis 20. The transfer zone 5 is in turn surrounded concentrically by an annular peripheral zone 34 of constant magnification. However, their magnification is lower than in the adjacent transition zone 32. In the exemplary embodiment shown, the peripheral zone 34 has a magnification of 1: 1. _{Q The} object and image are therefore the same size. The magnification can also be slightly above or below (reduction).

The enlargement ratios are illustrated in FIG. 1 by ₅ differently sized black areas. These areas are of equal size within the peripheral zone 34; in the central zone 30 likewise, but four times larger than in the peripheral zone 34. In the transition zone 32, the areas grow continuously from the outer edge to the center, which is additionally illustrated by the star-like rays shown in FIG. 1.

The dashed lines in the area of the transition or transfer zone 32 in FIG. 1 illustrate the possibility of a gradual decrease in the magnification.

Such enlargement ratios not only offer the possibility of interesting and stimulating visual appearances. They also considerably facilitate the correct positioning of the afocal imaging system in relation to objects that are to be greatly enlarged. First of all, the object can be detected effortlessly via the peripheral zone 34, which is not or only slightly enlarging. The central zone 30 is then already in an approximately correct enlargement position to the object. Subsequently, there is no difficulty in aligning the central zone 30 with the object in such a way that the object to be imaged is fully grasped by it. The transfer zone 32 allows a comfortable optical transition from the peripheral zone 34 to the central zone 30.

Fig. 2 illustrates schematically an embodiment in the form of an afocal system, here an astronomical telescope.

Such a telescope is known to have an objective 10 '- possibly made up of several lenses and an eyepiece 10 "- possibly made up of several lenses. The magnification of a telescope, more precisely its angular magnification V, is known to be described by the following equation : V = f / f ". Here f is the focal length of the objective 10 'and f "the focal length of the eyepiece 10".

In the astronomical telescope, the distance d between 'the main planes H' and H "of the objective 10 'and the eyepiece 10" is the same everywhere, namely the sum of the focal lengths f, f ", ie d = f + f".

The central zones 30 'and 30 "of the objective 10' and the eyepiece 10" are arranged coaxially to one another on the optical axis 20 and together form the central magnification zone 30, which corresponds to the central zone 30 of the exemplary embodiment according to FIG. 1. The mutual distance d30 of the main planes H30 'and H30 "of the central zones 30', 30" is equal to the sum of the focal lengths f30 'and f30 "of the central zones 30'. 30" on the objective and eyepiece side. In this case, f30 'is larger than f30 ". The central zones 30' and 30" on the objective and eyepiece side accordingly limit a magnification zone V of approximately 4: 1, which is axially symmetrical to the optical axis 20. The central enlargement zone 30 has the shape of a cylinder in the illustrated embodiment. In principle, it can also have the shape of a cylindrical cone. The central enlargement zone 30 is concentrically surrounded by an annular jacket-shaped zone 32, which is delimited at its free ends by an objective-side and an eyepiece-side transfer zone 32 ', 32 ". Unlike the transfer zone 32 of FIG. 1, the annular jacket zone 32 has constant magnification, for example an angular magnification V = 2: 1. For the mutual distance d32 of the main planes H32 ', H32 "of the objective and eyepiece-side transfer zones 32', 32" again applies d32 = f32 '+ f32 ", where f32 'is the focal length of the lens-side transition zone 32' and f32" is the focal length of the eyepiece-side transition zone 32 ".

The ring jacket zone 32 is in turn surrounded by a peripheral ring jacket zone 34 concentrically. This ring jacket zone is delimited at its free ends by the annular peripheral zone 34 'of the objective 10' and the annular ^' peripheral zone 34 "of the eyepiece 10". Both peripheral zones 34 ', 34 "have the same focal length f34', f34". Therefore, f34 '= f34 "applies. Accordingly, the peripheral ring-clad zone 34 has the magnification factor 1, that is, it depicts the object in natural size. For the distance d34 between the main planes H34' and H34" of the objective and ocular-side peripheral zones 34 ', 34 "again applies d34 = f34 '+ f34", where f34' is the focal length of the objective-side peripheral zone 34 'and f34 "is the focal length of the eyepiece-side peripheral zone 34".

If, as in the exemplary embodiment in FIG. 2, it is assumed that the main planes H30 ', H32' and H34 'on the objective side lie in the main plane H' of the objective 10 'and the same applies accordingly to the eyepiece side, the following relations result:

d = d30 = d32 = d34 and d = f30 ^» + f30" = f32 '+ f32 "= f34' + f34". The following also applies:

f30 '> f 32'> f 34 'for the objective 10' and f30 "<f32" <f 34 "for the eyepiece 10".

The different focal lengths can be realized, for example, by different radii of curvature of the lens zones, alternatively or additionally, also by different optical densities. The optical density and / or the curvature increases on the lens side in steps from the optical axis to the periphery. The reverse is true on the eyepiece side.

In principle, a ring lens can be assigned to the two free ends of each ring jacket zone 32 and 34, and a total of optical axes 22 and 24 can be assigned to each ring jacket zone. The entirety of the optical axes 22 and 24 spans a cylinder jacket. The imaging device shown in FIG. 2 can thus be understood as a system which is constructed from a plurality of imaging units arranged coaxially to one another. In the exemplary embodiment shown, the ring lenses run symmetrically on both sides of the optical axes 22, 24. Alternatively, they can also be designed as “half lenses”, such that they lie only on one side of the optical axes 22, 24, approximately on the lens side the side facing away from the optical central axis 20 and reversed on the eyepiece side.

Furthermore, the focal lengths f32 ', f32 "of the objective and eyepiece-side transfer zones 32', 32" continuously from the focal lengths f34 'and f34 "of the peripheral zones 34', 34" into the focal lengths f30 'and f30 "of the central zones 30 ', 30 "pass over. If there is no enlargement in the peripheral ring jacket zone 34, ie f34 '= f34 "applies, these focal lengths can also go to infinity. In other words, the peripheral ring lenses can be replaced by plane-parallel glasses. Finally, the central zone 30, the annular cladding zone 32 and / or the peripheral zone 34 can be optically shielded from one another, for example by means of opaque surfaces, layers and / or foils.

Claims

10 Optical imaging device

1. Afocal optical imaging system, in particular a telescopic sight with a lens (10 ') and an eyepiece (10' '), characterized in that its angular magnification (V) changes transversely to the optical axis (20).

2. Imaging system according to claim 1 or 2, characterized in that the angular magnification (V) decreases gradually or continuously towards the periphery.

3. Imaging system according to claim 1, characterized gekenn¬ characterized in that the lens (10 ') and the eyepiece (10'') - to achieve zones (30, 32, 34) each predetermined angular magnification (V) - _l have zones (30 ', 30'',32', 32 '', 34 ', 34'') which are mutually matched to one another and essentially extend transversely to the optical axis (20).

4. Imaging system according to one of the preceding

Claims, characterized by a central zone (30) of constant magnification arranged centrally to the optical axis (20) and adjoining zones (32, 34) with a gradual or continuous decrease in the magnification (V).

5. Imaging system according to claim 4, characterized by a to the optical axis (20) axially symmetrical see arrangement of the zones (30, 32, 34) decreasing

Magnification (V).

6. Imaging system according to claims 4 and 5, characterized in that the central zone (30) has a cross section in the form of a circular area and is concentrically or coaxially surrounded by the other zones (32, 34).

7. Imaging system according to one of the preceding

Claims, characterized by an enlargement-free zone (34) arranged in the peripheral area or only slightly, but constantly enlarging or reducing.