Abstract: A refractive optical system may be a collimator, focusing optical system, reducer, or expander and includes an entrance optical element, an exit optical element, and a volume disposed between the entrance and exit optical elements. The volume is configured to have an index of refraction that is insensitive to changes in atmospheric conditions of the ambient environment. A surface of curvature of an input surface of the entrance optical element is parallel to a wavefront curvature of an input light beam and an output surface of the exit optical element is parallel to a wavefront curvature of an exit light beam. Accordingly, the wavefront curvature of the exit light beam is insensitive to the ambient environment permitting the production and operation environments to change without a change to the performance of the optical system.

Abstract: A beam distribution apparatus includes a stack of parallelogram prisms and beam-splitting coatings each located between opposing parallel faces of adjacent parallelogram prisms. The stack is mounted on an entrance face of a triangular prism. The triangular prism includes the entrance face, a reflective face, and an exit face. The reflective face has optical surfaces for shaping output beams from the stack and reflecting the output beams through the exit face.

Abstract: A system for measuring a displacement along a first axis includes an apparatus movable at least along a second axis perpendicular to the first axis, a measurement mirror mounted to the apparatus at an angle greater than 0° relative to the first axis, and an interferometer with a beam-splitter. The beam-splitter splits an input beam into a measurement beam and a reference beam, directs the measurement beam in at least two passes to the measurement mirror, and combining the measurement beam after said at least two passes and the reference beam into an output beam. At least exterior to the interferometer, the measurement beam travels in paths that are not parallel to the first axis.