Holographyforum.org / holowiki.org

For lack of a better term, I will call these knife-edge beamsplitters. They work fine as variable beamsplitters, with minimal losses. Attached is a one-page paper from an issue of the American Journal of Physics, 1976. The idea is simple, just intersect part of the beam with the edge of a mirror. (Just ignore the silly editor's note about the Edmund variable beamsplitter, we know about those.)