The present invention relates to an optical system for merging a first and a second partial image beam, each proceeding from a specimen, into a resultant image beam. Such systems are used in particular in optical instruments for the examination of multiple prepared specimens such as, for example, comparison microscopes or comparison macroscopes.
When comparative examinations are carried out, the image of a first sample is usually compared with the image of a second sample. Comparison microscopes and comparison macroscopes in which partial image beams deriving from two objectives can be combined, by means of an optical system such as, for example, a comparison bridge, into one resultant image beam that can be viewed by the user, are known for carrying out such examinations. A variety of possibilities for depiction usually exist in this context, the resultant image being generated from the partial images by corresponding setting of stops; a mixing or superimposition of the respective partial images, or partial side-by-side placement or juxtaposition of portions of the partial images, is possible in this context.
An optical system of the generic kind is described in DE 1 623 228 A. The comparison bridge that is described comprises two movable stop arrangements in order to generate the image configurations described above. For this purpose, the user must operate with both hands, during the examination, rotary knobs located approximately at shoulder height; this proves to be uncomfortable and difficult to handle. In particular, the use of both hands during operation is necessary, so that no other activities can be performed simultaneously.
Other embodiments of comparison bridges that can be operated with one hand are known, for example from DE 938271 A. These comparison bridges have the disadvantage, however, that the various image configurations described above cannot be displayed. In particular, variable juxtaposition of subregions of an image, and displacement of the separating line, are not possible.
In order to improve the mechanical comparison bridges just described, motorized configurations have been developed that offer convenient usability for a plurality of different image configurations. These motorized embodiments have, however, the disadvantage of considerable additional design complexity and therefore also of increased acquisition and maintenance costs.