The measurement of deviation of microscope stage from squareness to th
e optical axis is an important parameter in optical testing of microsc
opes. This test ensures that when the deviation is in the permitted li
mits, the optical axis of the microscope is normal to the stage and he
nce the movement of the microscope tube is in normal direction to the
stage. In the present article a simple method to measure the deviation
of the microscope stage from squareness to its optical axis has been
described using a parallel plate and autocollimators. Test results on
a few microscopes have been presented.