Compact interferometer

An interferometer comprising:

• a beamsplitter arranged to divide an input beam into first and second beams;
• path differencing optics arranged to direct the first and second beams in opposite directions around a cyclic path and back to the beamsplitter, wherein the beamsplitter is arranged to divide, on return to the beamsplitter, the first and second beams each into transmitted and reflected portions;
• a first detector array arranged to detect a first interference pattern generated from the transmitted portion of the first beam and the reflected portion of the second beam;
• wherein one or more components of the path differencing optics are arranged to keep the first and second beams in the optical plane and direct the first and second beams to be incident on the beamsplitter spatially offset, or spatially diverging, from an incidence position of the input beam on the beamsplitter;
• and
• a second detector array arranged to detect a second interference pattern generated from the reflected portion of the first beam and the transmitted portion of the second beam.

A spectrometer comprising an interferometer comprising:

• a beamsplitter arranged to divide an input beam into first and second beams;
• path differencing optics arranged to direct the first and second beams in opposite directions around a cyclic path and back to the beamsplitter, wherein the beamsplitter is arranged to divide, on return to the beamsplitter, the first and second beams each into transmitted and reflected portions;
• a first detector array arranged to detect a first interference pattern generated from the transmitted portion of the first beam and the reflected portion of the second beam, wherein one or more components of the path differencing optics are tilted to direct the first and second beams to be incident on the beamsplitter spatially offset, or spatially diverging, from an incidence position of the input beam on the beamsplitter;
• a second detector array arranged to detect a second interference pattern generated from the reflected portion of the first beam and the transmitted portion of the second beam;
• and
• an analyser configured to receive signals or data from the first and second detector arrays representing the first and second interference patterns, the analyser configured to generate a spectrum showing the relative spectral contents of the input beam.