Same as here: https://www.researchgate.net/post/Measuring_the_thickness_of_thin_films

Although hebal optics doesn't seem to be a known term either since Google Scholar gives me only two references.

It is a way to find the thickness of the membrane and I found it in a master's thesis of one of the professors in Algeria

All references containing "hebal optics" are theses, none is a journal publication. In that case the term cannot be considered known or even established. According to my dictionary, the word "hebal" doesn't even exist in the English language.

This is the source

[see previous answer, still valid]