Seeing a double picture can be the case when using stereo microscopes or compound microscopes with a binocular head. This can be due to several reasons.
- Make sure that the two eyepieces are the correct distance to each other. Adjust the distance to suit your eyes.
- Make sure that the diopter compensation is properly set. One of the two eyepieces can be rotated to adjust for different eyesight of the two eyes. If you use glasses, then these will correct for the different vision. In this case make sure that the diopter adjustment is set the same.
- Stereo microscopes contain prisms which turn an inverted image right side up. If these prisms are shifted (because the microscope had to take a heavy bump), then there is the likely possibility that the two images do not overlap. In this case the microscope has to be taken apart and the prisms adjusted.