PROBLEM TO BE SOLVED: To surely obtain an interference signal.SOLUTION: Reflected light L21-L24 obtained by applying measuring light L1 to a measuring object Sb, and branching the reflected light, and reflected light L41-L44 obtained by branching reference light L3 and reflecting the light on reference mirrors 43, 53, 63 and 73 enter four interference signal generating devices 21-24. Although optical distances of four transmission routes of the reference light incident on the interference signal generation devices 21-24 are different from one another however, the distances are substantially the same as the optical distances of the reflected light L21-L24 of the measuring light incident on the interference signal generation devices 21-24. Therefore, an interference signal can be surely obtained from any of the interference signal generation devices 21-24.COPYRIGHT: (C)2013,JPO&INPIT【目的】干渉信号が必ず得られるようにする。【構成】4つの干渉信号生成装置21~24には測定光L1が測定対象Sbに照射され,反射した反射光が分岐された反射光L21~L24と,参照光L3が分岐され,参照ミラー43,53,63,73において反射された反射光L41~L44と,が入射する。干渉信号生成装置21~24に入射する参照光の4つの伝搬ルートの光学的距離は異なるが,干渉信号生成装置21~24に入射する測定光の反射光L21~L24の光学的距離とほぼ同じである。したがって,干渉信号生成装置21~24のうちのいずれかから必ず干渉信号が得られる。【選択図】図1
