Self-referencing interferometric microscope

A self-referencing interferometric microscope comprising:

• a first polarizing beamsplitter (PBS) to separate an illumination beam of the self-referencing interferometric microscope into a first optical beam in a first polarization state and a second optical beam in a second polarization state orthogonal to the first polarization state;
• a first pair of mirrors, in optical communication with the first PBS, to:
• direct the first optical beam from the first PBS around a first multi-leg optical path and back to the first PBS in a first direction, and
• direct the second optical beam from the first PBS around a second multi-leg optical path and back to the first PBS in a second direction opposite to the first direction;
• a first positioning stage to move one mirror of the first pair of mirrors so as to vary a lateral offset S1 between the first optical beam and the second optical beam;
• a first optical window arranged to be rotated about an axis perpendicular to the direction of the lateral offset and perpendicular to at least the first optical beam when the first optical beam passes through the first optical window such that the first optical beam and the second optical beam are shifted in a direction of the lateral offset with rotation of the first optical window when the first optical beam passes through the first optical window;
• an objective lens, in optical communication with the first PBS and the first optical window, to:
• focus the first optical beam and the second optical beam on a sample, the sample reflecting and/or scattering the first optical beam as a first return beam and reflecting and/or scattering the second optical beam as a second return beam, and
• collect the first return beam and the second return beam;
• a second PBS, in optical communication with the objective lens, to direct the first return beam in a first direction away from the second PBS and to direct the second return beam in a second direction away from the second PBS;
• a second pair of mirrors, in optical communication with the second PBS, to:
• direct the first return beam from second PBS around a third multi-leg optical path and back to the second PBS in a third direction, wherein the first return beam subsequently propagates away from the second PBS as a first output beam, and
• direct the second return beam from the second PBS around a fourth multi-leg optical path and back to the second PBS in a fourth direction opposite to the third direction, wherein the second return beam subsequently propagates away from the second PBS as a second output beam;
• at least one polarization control optic, in optical communication with the second PBS, to place the first output beam and the second output beam in a same polarization state;
• and
• an imaging device, in optical communication with the at least one polarization control optic, to detect an interferometric image formed at the imaging device by optical interference of the first output beam and the second output beam.