OBSERVATION TUBE FOR OPTICAL INSTRUMENT

PROBLEM TO BE SOLVED: To improve an observation tube for an optical instrument, especially, a microscope so that various functions can be realized time-continuously without unnecessarily attenuating light passing through the observation tube and without unnecessarily increasing structural height, thereby the reflection of the light to different units and (or) the reflection of the light into respective optical paths can be realized. SOLUTION: Only one beam splitter (1 or 2) is provided in the optical path of the observation tube. Each beam splitter (1 or 2) can rotate around the optical axis of the optical path and always resides at an acting position in the optical path. Each beam splitter (1 or 2) deflects the reflected part of the light to a simultaneous observation tube of the corresponding optical path of a photographing unit or a recording unit in accordance with its rotating position or makes the light couple with the optical path of the observation tube.