Optical interferometer

An optical interferometer comprising:

• an optical fiber for outputting alight beam to be measured;
• a lens for converting the light beam from the optical fiber into a parallel light beam;
• a beam splitter for branching the light beam to two optical paths perpendicular to each other to make a reflected light beam and a transmitted light beam, the beam splitter for combining the reflected light beam and the transmitted light beam to output a wave-combined light beam;
• a first reflection unit for reflecting the reflected light beam to return the reflected light beam to the beam splitter, in which the reflected light beam returned to the beam splitter is in parallel to the reflected light beam emitted from the beam splitter;
• a second reflection unit for reflecting the transmitted light beam to return the transmitted light beam to the beam splitter, in which the transmitted light beam returned to the beam splitter is in parallel to the transmitted light beam emitted from the beam splitter;
• and
• a light receiver for receiving the wave-combined light beam from the beam splitter,
• wherein the incident beam is inclined with respect to a normal line of an incident surface of the beam splitter.