An interferometer includes a
light source, a
beam splitter, a measuring reflector, a reference
retroreflector, a
detector system, and two transparent plane plates. The
beam splitter splits a first beam of rays, emitted by the
light source, into at least one measuring beam and at least one
reference beam, via which a first splitting plane is defined. The measuring beam propagates in a measuring arm and the
reference beam propagates in a reference arm until being recombined at a recombining location in a first recombining plane. The first recombining plane is oriented parallel to the first splitting plane. The measuring reflector, on which the measuring beam falls perpendicularly at least twice, is disposed in the measuring arm and is joined to an object to be measured that is movable along a measuring direction. The reference
retroreflector, on which the
reference beam falls at least once, is disposed in the reference arm. At least one first distance
signal with regard to the position of the object to be measured is ascertainable via the
detector system from the interfering measuring and reference beams superposed at the recombining location. The first transparent plane plate and the second transparent plane plate are disposed parallel to each other in the beam path between the
light source and the
detector system. The reference
retroreflector is formed in the first plane plate and the
beam splitter is disposed on the second plane plate.