To provide an interferometer capable of inhibiting backscattering light scattering backward of scattering light generated in an optical fiber in a reference optical path, at least part of which is configured using the optical fiber, from entering a measurement optical path.SOLUTION: An interferometer 100 for leading light output from a light source 101 to a beam splitter 102 to divide the light into measurement light and reference light； irradiating a subject with the measurement light obtained by the division； leading the measurement light reflected from the subject to a beam splitter 103 through the beam splitter 102； leading the reference light obtained by the division by the beam splitter 102 to the beam splitter 103 through an optical fiber； and multiplexing the measurement light and the reference light that are led by the beam splitter 103 to generate interference light includes a 0-point adjustment mechanism 30 configured using a free space, the 0-point adjustment mechanism being arranged on a path on which the reference light from the beam splitter 102 reaches the beam splitter 103 through the optical fiber.SELECTED DRAWING: Figure 1【課題】少なくとも一部を光ファイバで構成する参照光路において、光ファイバ内で生じた散乱光の内、後方へ散乱する後方散乱光が測定光路に入り込むこと抑止することができる干渉計を提供すること。【解決手段】光源１０１から出力された光を、ビームスプリッタ１０２に導いて測定光と参照光とに分割し、分割した測定光を被検物に照射し、該被検物から反射した測定光を、ビームスプリッタ１０２を経由してビームスプリッタ１０３に導き、ビームスプリッタ１０２で分割した参照光を、光ファイバを経由してビームスプリッタ１０３に導き、ビームスプリッタ１０３に導かれた測定光と参照光とが合波して干渉光を生成する干渉計１００において、参照光が、ビームスプリッタ１０２から光ファイバを経由してビームスプリッタ１０３に至る経路にフリースペースで構成した０点調整機構３０を配置した。【選択図】図１
