Subject: How do you measure laser interference with cameras?

I was at a lab recently in which they had an intricate microscope. It sent a 
laser into mirrors splitting it in two then used mirrors to send one half 
through an object and then looped the other around. Both lasers went the same 
distance and they were “linked” back together. At that point camera’s measured 
the interference. My two questions are how would they measure this with 
camera’s and also it was not in a closed environment, wouldn’t air born 
particles effect the study?

Re: How do you measure laser interference with cameras?