To provide an interferometer that can inhibit, in the interferometer at least a part of which is constituted of an optical fiber, back-scattered light generated in the optical fiber on a measurement optical path or a branch optical path that has branched from a reference optical path from influencing light interference.SOLUTION: An interferometer having a first branch part that causes emitted light from a light source to be branched into measurement light and reference light and a multiplexing part that irradiates an inspected object with the measurement light and multiplexes the measurement light reflected from the inspected object and the reference light to generate interference light, includes: a second branch part that causes the measurement light or reference light to be branched； a branch light path at least a part of which is constituted of an optical fiber and through which branched light different from the measurement light or reference light that is branched by the second branch part passes； a scattered light path extending up to a portion where back-scattered light generated by the branched light being back-scattered in the branch light path reaches the multiplexing part； and a back-scattered light removing part that is provided in the branch light path and removes the back-scattered light.SELECTED DRAWING: Figure 1【課題】少なくとも一部が光ファイバで構成される干渉計において、測定光路又は参照光路から分岐した分岐光路上の光ファイバ内で生じた後方散乱光が光干渉に影響することを抑止できる干渉計を提供すること。【解決手段】光源からの出射光を測定光と参照光とに分岐する第１の分岐部と、前記測定光を被検査物に照射し、該被検査物から反射した前記測定光と前記参照光とを合波して干渉光を生成する合波部を備える干渉計であって、前記測定光或いは前記参照光を分岐する第２の分岐部と、該第２の分岐部によって分岐された測定光或いは参照光とは異なる分岐光が通る少なくとも一部が光ファイバで構成された分岐光路と、該分岐光路において前記分岐光が後方散乱することにより発生する後方散乱光が前記合波部に至るまでの散乱光路と、前記分岐光路に設けられた前記後方散乱光を除去する後方散乱光除去部を備えた。【選択図】図１
