Camera with pivotable prism

A camera (1), in particular in a space vehicle, having a housing (2) which contains at least one optically sensitive exposure surface (7), and a base lens (9), having a first fixed focal length, connected thereto in each case, and which projects on the at least one exposure surface (7) and which is situated on a first optical axis (10) for the exposure surface (7). To provide the camera with various fields of view, in particular for the approach of two satellites toward one another over large distances, at least two afocal supplementary lenses (11, 12) which are each parallel with respect to their optical axes (15, 16) and spaced at a distance from the first optical axis (10) are situated in the housing (2), whose optical paths are alternately coupleable with the aid of a pivotable prism (17), to form further fixed focal lengths in an optical path of the base lens (9).

This claims the benefit of German Patent Application DE 10 2010 017 057.7, filed May 21, 2010 and hereby incorporated by reference herein.

The present invention relates to a camera, in particular in a space vehicle, having a housing which contains at least one optically sensitive exposure surface, and a base lens, having a first fixed focal length, connected thereto in each case and which projects on the at least one exposure surface and which is situated on a first optical axis for the exposure surface.

BACKGROUND

Cameras having interchangeable lenses of different fixed focal lengths and zoom lenses having variable focal lengths are well known. In particular for space missions, not only are particularly stringent requirements imposed on such cameras with regard to the critical operating conditions, but in addition, such cameras having a low specific weight must also be automatically operable and low-maintenance. Furthermore, such cameras should have a wide field of view with a correspondingly large focal length range of the optical system used.

One option for adjusting variable focal lengths is zoom lenses, which allow different focal lengths by the displacement of individual optical lenses and/or lens groups. Appropriate provision of adjustment mechanisms is complicated and susceptible to malfunction, in particular under the conditions prevailing in space. A quasi-continuously tunable focal length range does not outweigh the aberrations of such zoom lenses which remain after reasonable effort has been expended.

Although multiple cameras having individual fixed focal lengths provide calibrated conditions for the individual focal lengths, with high measuring accuracy and reliability, they are rather costly and installation space-consuming due to the image capture and image processing electronics systems, together with corresponding optical sensors, which must be designed separately for each camera.

SUMMARY OF THE INVENTION

It is an object of the present invention to refine a camera, in particular for use in space, in such a way that it is possible to automatically change the focal lengths, using multiple fixed focal lengths.

The present invention provides a camera, in particular in a space vehicle, having a housing which contains at least one optically sensitive exposure surface, and a base lens, having a first fixed focal length, connected thereto in each case and which projects on the at least one exposure surface and which is situated on a first optical axis for the exposure surface, at least two afocal supplementary lenses which are each parallel with respect to their optical axes and spaced at a distance from the first optical axis being situated in the housing, and whose optical paths are alternately coupleable, with the aid of a pivotable prism, to form further fixed focal lengths in an optical path of the base lens.

The term “camera” is understood to mean a still camera or a camera which provides image sequences, preferably in real time, which has a light-sensitive chip, for example a CCD sensor, CMOS detector, or, depending on the optical radiation to be detected, another sensor suited for this purpose, as at least one exposure surface. An exposure surface may be associated with an associated base lens which is calibrated with the aid of the housing, for example. Alternatively, multiple exposure surfaces, preferably two exposure surfaces situated at a specified distance from one another, may be provided, with each of which a base lens is associated, so that stereo imaging of the optical targets on the exposure surfaces is possible when the camera is synchronously operated.

The camera is preferably used in space, for example in space vehicles such as satellites and the like. With the aid of the proposed camera as a so-called single-lens camera, having only one exposure surface and an associated optical system, distances may be observed and predicted over a wide range, from 2 km, for example, to a close range down to 60 cm, for example, for appropriate distance determination. When a binocular camera having two interspaced exposure surfaces, each having an optical system, is used, in addition to observation a rapid rotation of objects and the distance from other space vehicles such as non-cooperative satellites, landing areas, space debris, and the like may be ascertained with sufficient accuracy.

The base lens is preferably set to an infinite distance, and thus has a depth of field in a distance range of interest, such as the observation area, for the fixed focal length of 50 mm to 70 mm, for example. The base lens forms a first fixed focal length, a first prism face of the pivotable prism being permanently associated with the base lens, and a second prism face, situated parallel thereto and designed with an optical axis which is shifted parallel with respect to the optical axis of the base lens, being directed toward the field of view.

To change the fixed focal length, the output pupil of one of the afocal supplementary lenses is situated in front of this second prism face by appropriately swiveling the prism. One of the afocal supplementary lenses produces a larger fixed focal length when optically coupled to the base lens, and another afocal supplementary lens produces a smaller fixed focal length when coupled to the base lens. In this way the fixed focal length of the base lens is firmly established by the fixed focal lengths which are formed with the aid of the other supplementary lenses, thus allowing the fixed focal lengths to be changed from a wide-angle field of view to a close-range field of view, and vice versa, by rotating the prism in the same direction, and therefore, in a very rapid and efficient manner.

The afocal supplementary lenses may be designed according to the principle of a Kepler telescope, having a predefined angular magnification; for a predefined m-fold angular magnification this results in a fixed focal length of x*m for a supplementary lens of conventional design, and for an inverted supplementary lens, a fixed focal length of x/m. In each case x corresponds to the focal length of the supplementary lenses.

According to the concept of the present invention, the output pupils of the supplementary lenses are adjusted, for example with the aid of appropriate apertures or by a design of the angular magnification by the active lenses of a supplementary lens, in such a way that when they are swiveled into the second prism face, the output pupils coincide with the input pupil of the base lens. In this way, the same pupil may be adjusted at the base lens for all three fields of view.

For connecting the fixedly mounted supplementary lenses or aligning the optical path of the base lens to the desired field of view, the prism is swiveled in such a way that the second prism face is pivoted with respect to the first prism face about a common axis. As a result, the first prism face, which faces the input pupil of the base lens, rotates about the optical axis of the base lens, while the second prism face is aligned in each case with its optical axis coaxial to the optical axis of the supplementary lens which is swiveled by the prism into the optical path of the base lens. For swiveling the prism, a stepping motor may be provided which accommodates the appropriately mounted prism on a rotor situated coaxially to the first optical axis, i.e., the optical axis of the base lens. To be able to mask the stepping motor, which is thus situated in the optical axis of the base lens, from the optical path of the base lens during observation of the field of view, solely via the field of view, the second prism face of the prism is rotated into a position that is between the two supplementary lenses.

DETAILED DESCRIPTION

FIG. 1schematically shows camera1, which in the present case is a single-lens camera, having housing2which is formed from base plate3, frame4, and lens plate5. CCD chip6having sensitive exposure surface7, and which converts the optical signals striking exposure surface7and information into electrical signals, is fastened to base plate3. A subsequent signal processing unit having an image memory, computation programs, and the like is not illustrated.

Base lens9is mounted over sensitive exposure surface7on base plate3, calibrated with the aid of lens holder8, optical axis10of the base lens being perpendicularly centered on exposure surface7. Supplementary lenses11,12are accommodated in lens plate5, at a fixed distance from base lens9, in each case parallel to optical axis10via an optical axis15,16, respectively, and situated equidistantly about optical axis10via lens holders13,14at a calibrated distance from base lens9.

With reference to optical axes10,15,16, between the base lens on the one hand and supplementary lenses11,12on the other hand, prism17which is rotatable about optical axis10is axially provided with an optically transmissive prism face19which is aligned parallel to input pupil18of base lens9, and an optically transmissive prism face20which is aligned parallel to output pupils21,22of supplementary lenses11,12, respectively. The remaining prism faces of prism17are mirrored, so that prism17acts as a light distributor which, depending on the rotation of prism17, swivels one of supplementary lenses11,12into the optical path of base lens9, or with prism face20is directed onto the free space, in the present case, for example, outside the plane of the drawing. For this purpose, with the aid of mounting23, prism17is accommodated on rotor25of stepping motor24which rotates about optical axis10.

Base lens9is designed for a first fixed focal length of 63 mm, for example, and is focused to infinity. Supplementary lenses11,12, are designed as afocal Kepler telescopes with a predefined angular magnification, in the swiveled-in state supplementary lens11together with base lens9forming a near-field optical system having a fixed focal length of 200 mm, for example, while in the swiveled-in state supplementary lens12, having the inverse design, together with base lens9forms a far-field optical system having a fixed focal length of 20 mm, so that the overall result, for example, is a 10-fold multiplication of the focal length. Output pupils21,22of supplementary lenses11,12, respectively, are adjusted to input pupil18, so that when they are swiveled in toward base lens9after a beam passes through prism17, the output pupils coincide with the input pupil.

FIGS. 2athrough2cschematically show the three connection options of camera1inFIG. 1, with reference to central beam26a,26b,26c. With the aid of prism17, supplementary lenses11,12are connected to base lens9, or base lens9is operated without attachment.FIG. 2ashows the configuration of the near-field optical system having supplementary lens11connected in front of base lens9in order to form the fixed focal length of 200 mm, for example;FIG. 2bshows the configuration of the far-field optical system having supplementary lens12connected in front of base lens9in order to form the fixed focal length of 20 mm, for example; andFIG. 2cshows the optical path of base lens9, diverted around supplementary lenses11,12with the aid of prism17, having a fixed focal length of 63 mm, for example.

FIG. 3shows the optical path of base lens9through associated lens set27, with prism17situated downstream. Entrance aperture28is situated at prism face19in order to set a uniform input pupil of base lens9.

FIG. 4shows a combined illustration of the optical paths of overall optical system30of camera1inFIG. 1, formed by lens sets27of base lens9(FIG. 1), prism17, and lens sets29,31of supplementary lenses11,12(FIG. 1). Output pupils21,22are aligned with one another and with input pupil18of the base lens by the configuration of the active lenses of lens sets29,31, and of the diameter of input pupils32,33of supplementary lenses11,12.

FIG. 5shows schematically a camera with multiple exposure surfaces, preferably two exposure surfaces situated at a specified distance from one another, with each of which a base lens is associated, so that stereo imaging of the optical targets on the exposure surfaces is possible when the camera is synchronously operated. The second exposure surface106has an associated base lens109, prism117and supplementary lenses111and112. Together with the first exposure surface6, with base lens9, prism17, and supplementary lenses11and12, a processor100can use second exposure surface106to form a spatial image.

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