1. Field of the Invention
The present invention relates to a stereo microscope, more particularly for eye examination, with slewable, reflecting and/or refractive means for changing the relative position of the axes of the partial beams of rays and thus for changing the stereoscopic angle.
2. Related Art Today usual microscopes in this field comprise a fixed stereoscopic angle in the range of 8.degree. to 15.degree., for example 13.degree.. These instruments permit a stereoscopic viewing of the front section of the eye in an optical section, more particularly under a stereoscopic angle in the 8.degree.-15.degree. range. For observing the rear section of the eye, one normally uses additional lenses. These lenses cancel the refractive power of the cornea and the crystalline lens and permit a partial observation of lateral parts of the cornea and the vitreous body through integrated mirrors. Due to the unfavourable position of the iris, and the pupil, for observation, parts of both observation beams of rays are cut off. In the case of insufficient enlargement of the pupil, strong short-sightedness and in case of lateral observation of peripheral sections of the bottom and vitreous body, a binocular stereoscopic observation of the optical section may be difficult or even impossible because the binocular field of vision becomes very small. Then, only a monocular observation of the optical section or a binocular opthalmoscopy with focal illumination may be executed.
In order to improve the conditions of examination or operation, more particularly of the eye, stereo microscopes as described above, have already been proposed. A microscope of this kind is disclosed in CH-A-399 771 in which each partial beams of rays includes an optical, reflecting body rotating around an axis parallel to the optical axes of the partial beams of rays, this body displacing the partial beams of rays to the side. When the rotation of both optical bodies is coordinated, the stereoscopic angle angle varies as a function of the position of the bodies. This execution has important drawbacks. One must provide two separate, revolving supports for the optical bodies which must be driven from the outside by means of adequate gearings. The bearing of the supports for rotation inside of the tube around an axis parallel to the optical axes of the beams of rays is expensive. In relation to the luminous intensity, the execution is space consuming and the variability of the stereoscopic angle is limited.