A photographing unit for a microscope has a photometric detector to measure brightness of light from a sample and includes a changing member which changes a brightness of light toward an observation system and a control unit which controls the light based on a detection output of the photometric detector. In addition, the changing member can be controlled based on the presence of an observer. A shielding member can be provided that automatically shields an optical path of the observation system. An illumination system for an index on a reticle can be provided so that the illumination of the reticle can be performed or extinguished at desired times. Additionally, the color of light with which the index is illuminated may be made distinguishable from the color of light from a sample, and the contrast of the index to the sample can be controlled.

A photographing unit for a microscope has a photometric detector to measure brightness of light from a sample and includes a changing member which changes a brightness of light toward an observation system and a control unit which controls the light based on a detection output of the photometric detector. In addition, the changing member can be controlled based on the presence of an observer. A shielding member can be provided that automatically shields an optical path of the observation system. An illumination system for an index on a reticle can be provided so that the illumination of the reticle can be performed or extinguished at desired times. Additionally, the color of light with which the index is illuminated may be made distinguishable from the color of light from a sample, and the contrast of the index to the sample can be controlled.

An apparatus for the exposure of additional information into the film plane of a camera, is located in a data back. The data back has a two-column liquid crystal display. Control of the data back takes place directly through the printer output of a computer. The data to be exposed can be entered for this purpose by means of the computer keyboard. The computer is simultaneously connected via the printer output to the code transducer and to the path measuring system of the zoom system of the photomicroscope. The overall magnification is calculated from the data which is read in, by means of a computer program, and is exposed in the photograph by means of the data back.

A reflection and refraction optical system includes a polarization beam splitter, a concave mirror, a lens group and a quarter waveplate, wherein an additional waveplate is provided to transform S-polarized light from the polarization beam splitter into circularly polarized light.

An imaging optical system includes a polarization beam splitter, a quarter waveplate, a reflection mirror and polarization state changing unit. The beam from an object plane is projected by way of the polarization beam splitter and the quarter waveplate to reflection mirror. The projected beam is reflected by the reflection mirror and is projected through the quarter waveplate and by way of the polarization beam splitter to an image plane, and the polarization state changing unit is disposed between the polarization beam splitter and the image plane to change the state of polarization of the beam projected by way of the polarization beam splitter. The polarization state changing unit includes a half waveplate effective to transform the beam projected by way of the polarization beam splitter into a rectilinearly polarized beam, being polarized in a desired direction.