The invention features a method for determining a geometric property of a
test object, the method including: interferometrically profiling a first
surface of the test object in a first coordinate system;
interferometrically profiling a second surface of the test object in a
second coordinate system different from the first coordinate system;
providing a relationship between the first and second coordinate system;
and calculating the geometric property based on the interferometrically
profiled surfaces and the relationship between the first and second
coordinate system. In some embodiments, the relationship may be determined
by using calibrated gage blocks or by using a displacement measuring
interferometer. Corresponding system are also described.
