Method and apparatus for measuring distance

An interferometry apparatus comprising:

• a laser source operable to emit a first light beam;
• a beam splitter arranged to split the first light beam into an object beam and a reference beam, the object beam passing along an object beam arm and the reference beam passing along a reference beam arm;
• an adaptive delay line located a distance along the object beam arm, the adaptive delay line being configured to provide, in use, one or more length-adjusted object beams;
• a beam splitter arranged to recombine the length-adjusted object beam(s) from the object beam arm and the reference beams from the reference beam arm;
• and
• a photodetector operable to detect interference between the length-adjusted object beam(s) and the reference beam;
• wherein the adaptive delay line comprises one or more etalons, wherein the object beam enters one of the etalons and is split into a plurality of length-adjusted object beams, whereby the adaptive delay line operates, in use, to provide a plurality of length-adjusted object beams.

A method of measuring distance using an interferometry apparatus comprising:

• operating a laser to provide a first light beam;
• splitting the first light beam into an object beam and a reference beam, the object beam passing along an object beam arm of the interferometry apparatus and the reference beam passing along a reference beam arm of the interferometry apparatus;
• providing an adaptive delay line located a distance along the reference beam arm, the adaptive delay line being configured to provide one or more length-adjusted reference beams, thereby adjusting an optical path difference in the interferometry apparatus;
• recombining the object beam from the object beam arm and the length-adjusted reference beam(s) from the reference beam arm;
• and
• detecting interference between the object beam and the length-adjusted reference beam(s),
• wherein the adaptive delay line comprises one or more etalons, wherein the reference beam enters one of the etalons and is split into a plurality of length-adjusted reference beams, whereby the adaptive delay line operates, in use, to provide a plurality of length-adjusted reference beams.

A method of measuring distance using an interferometry apparatus comprising:

• operating a laser to provide a first light beam;
• splitting the first light beam into an object beam and a reference beam, the object beam passing along an object beam arm of the interferometry apparatus and the reference beam passing along a reference beam arm of the interferometry apparatus;
• providing an adaptive delay line located a distance along the object beam arm, the adaptive delay line being configured to provide one or more length-adjusted object beams, thereby adjusting an optical path difference in the interferometry apparatus;
• recombining the length-adjusted object beam(s) from the object beam arm and the reference beam from the reference beam arm;
• and
• detecting interference between the length adjusted object beam(s) and the reference beam,
• wherein the adaptive delay line comprises one or more etalons, wherein the object beam enters one of the etalons and is split into a plurality of length-adjusted object beams, whereby the adaptive delay line operates, in use, to provide a plurality of length-adjusted object beams.