This is a microscope image of glass coated first with aluminum and then with photoresist, a light-sensitive material used to form a patterned coating on a surface. The darker patches are places where the photoresist has been exposed by a laser and will eventually lead to holes in the aluminum.
This picture represents part of a coronagraph mask manufacturing process. This optical mask helps a telescope directly image exoplanets (planets outside our solar system).
– Elizabeth Young
Elizabeth Young (graduate student), Department of Mechanical and Aerospace Engineering