Abstract: A heterodyne optical interferometer incorporates error correction elements to correct a cyclic error that may be present in an interferometric measurement. The cyclic error can be caused by various factors such as an imperfect polarization relationship between two wavelength components, deficiencies in optical propagation paths (such as light leakage), imperfect optical coatings, and/or imperfect components. The cyclic error, which typically manifests itself as erroneous displacement information characterized by a low velocity sinusoidal frequency component, can be reduced or eliminated by using birefringent optical elements and other optical elements to alter certain characteristics of one or both wavelength components and reduce light leakage components in one or more light propagation paths in the heterodyne optical interferometer.

Abstract: An interferometer has a first input configured to provide a first measurement beam at a first frequency, and a second measurement signal at the first frequency. The interferometer has a second input configured to provide a reference beam at a second frequency that is different than the first frequency; an optical element comprising a first portion comprising a polarization beam splitter; and a diffraction grating disposed over the optical element configured to diffract the first measurement beam and the second measurement beam.

Abstract: A heterodyne optical interferometer incorporates error correction elements to correct a cyclic error that may be present in an interferometric measurement. The cyclic error can be caused by various factors such as an imperfect polarization relationship between two wavelength components, deficiencies in optical propagation paths (such as light leakage), imperfect optical coatings, and/or imperfect components. The cyclic error, which typically manifests itself as erroneous displacement information characterized by a low velocity sinusoidal frequency component, can be reduced or eliminated by using birefringent optical elements and other optical elements to alter certain characteristics of one or both wavelength components and reduce light leakage components in one or more light propagation paths in the heterodyne optical interferometer.

Abstract: Generally, in accordance with the various illustrative embodiments disclosed herein, a heterodyne optical interferometer incorporates error correction elements to correct a cyclic error that may be present in an interferometric measurement. The cyclic error can be caused by various factors such as an imperfect polarization relationship between two wavelength components, deficiencies in optical propagation paths (such as light leakage), imperfect optical coatings, and/or imperfect components. The cyclic error, which typically manifests itself as erroneous displacement information characterized by a low velocity sinusoidal frequency component, can be reduced or eliminated by using birefringent optical elements and other optical elements to alter certain characteristics of one or both wavelength components and reduce light leakage components in one or more light propagation paths in the heterodyne optical interferometer.

Abstract: An interferometer has a first input configured to provide a first measurement beam at a first frequency, and a second measurement signal at the first frequency.

Abstract: An interferometer has a first reflective surface having a nominal orientation; a second reflective surface having a nominal orientation orthogonal to the nominal orientation of the first reflective surface; a retroreflector facing the first reflective surface; a double polarizing beam splitter (DPBS) between the first reflective surface and the retroreflector; and a respective quarter-wave plate between the DPBS and each of the reflective surfaces. The DPBS has first and second beam-splitting surfaces each having a nominal orientation with respect to the first reflective surface. At least part of at least one of the first reflective surface, the second reflective surface and the beam-splitting surfaces is effectively tilted relative to the respective nominal orientation of such surface, and constitutes a respective tilted surface.

Abstract: An interferometer has a first reflective surface having a nominal orientation; a second reflective surface having a nominal orientation orthogonal to the nominal orientation of the first reflective surface; a retroreflector facing the first reflective surface; a double polarizing beam splitter (DPBS) between the first reflective surface and the retroreflector; and a respective quarter-wave plate between the DPBS and each of the reflective surfaces. The DPBS has first and second beam-splitting surfaces each having a nominal orientation with respect to the first reflective surface. At least part of at least one of the first reflective surface, the second reflective surface and the beam-splitting surfaces is effectively tilted relative to the respective nominal orientation of such surface, and constitutes a respective tilted surface.

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: An interferometer system includes a rhomboid assembly having a first optical stack and a second optical stack mounted on the first stack. The first stack includes a first prism having an angled face mounted to an angled face of a second prism. The interface between these angled faces includes a first polarizing beam-splitter. The second stack includes a third prism having an angled face mounted to an angled face of the fourth prism. The interface between these angled faces includes a second polarizing beam-splitter. First, second, third, and fourth wave plate elements are located in beam paths between the rhomboid assembly and at least one of a measurement optic and a reference optic. A redirecting optic is located at least adjacent to the vertical faces of the first and the third prisms.

Abstract: A multi-axis interferometer uses a combined beam for a first pass through the interferometer optics. Measurement and reference components of the combined beam that exit the interferometer optics are subject to walk-off that measurement or reference reflector misalignment can cause. A return reflector and non-polarizing beam splitter system split the combined beam into separated input beams for the various axes of the interferometer and return the separated beams for respective second passes through the interferometer optics. Walk-off for the separated beams in the interferometer optics cancels the walk-off for the combined beam to eliminate beam walk-off in separated output beams. Sharing a combined beam for a first pass through the interferometer optics reduces the sizes required for the interferometer optics and reference and measurement mirrors. The multi-axis interferometer may have a single return reflector.

Abstract: A multi-axis interferometer uses a combined beam for a first pass through the interferometer optics. Measurement and reference components of the combined beam that exit the interferometer optics are subject to walk-off that measurement or reference reflector misalignment can cause. A return reflector and non-polarizing beam splitter system split the combined beam into separated input beams for the various axes of the interferometer and return the separated beams for respective second passes through the interferometer optics. Walk-off for the separated beams in the interferometer optics cancels the walk-off for the combined beam to eliminate beam walk-off in separated output beams. Sharing a combined beam for a first pass through the interferometer optics reduces the sizes required for the interferometer optics and reference and measurement mirrors. The multi-axis interferometer may have a single return reflector.