US Patent 11913776 Interference in-sensitive Littrow system for optical device structure measurement

Embodiments described herein provide for devices and methods of measuring a pitch P of optical device structures and an orientation angle ϕ of the optical device structures. One embodiment of the system includes an optical arm coupled to an arm actuator. The optical arm includes a light source. The light source emits a light path operable to be diffracted to the stage. The optical arm further includes a first beam splitter and a second beam splitter positioned in the light path. The first beam splitter directs the light path through a first lens and the second beam splitter directs the light path through a first dove prism and a second lens. The optical arm further includes a first detector operable to detect the light path from the first lens and second detector operable to detect the light path from the second lens.