An apparatus is disclosed which may comprise a grating receiving light, a first prism moveable to coarsely select an angle of incidence of the light on the grating, and a second prism moveable to finely select an angle of incidence of the light on the grating. In one application, the apparatus may be...http://www.google.de/patents/US8126027?utm_source=gb-gplus-sharePatent US8126027 - Line narrowing module
