I could use last week an optical microscope, didn't seem special in any way, 50x magnification, image viewable per a CCD camera on a computer screen besides through the ocular.
But the software of this microscope had a feature to show a 3D calculated topography view of the sample (silicon wafer with some laterally structured micron sized 40 nanometer high SiO2 squares). So in the software you could see the height of these squares (30-50 nm there, so some error) and also do virtual profilometer over these squares. There these height measurements were separated for green, red, blue, so 3 lines showing a 30-40 nm difference from silicon to a SiO2 square.
The manual didn't tell how the physics work, so can has someone here an idea how this might work. It looked like a cheap normal microscope, I suppose that it uses somehow the CCD data and reflected intensity of the squares, the height of the bigger squares was more accurately measured/extrapolated than smaller squares.
Also I can exclude it is a Normaski microscope
http://en.wikipedia.org/wiki/Differential_interference_contrast_microscopy
there were no polarisators or prisms inside the microscope.
https://snf.stanford.edu/SNF/equipment/characterization-testing/zygo/Zygo
This technique seems to come near, white light interferometry, but resolution is much better.
So can someone explain to me how this technique that is probably used in this microscope is called and what the accuracy is, what limits it?
Link to the specific model https://www.micro-shop.zeiss.com/?s=12128207d6c5cf&l=en&p=us&f=e&i=10247&o=&h=25&n=0&sd=490950-0002-000#490950-0002-000
