PROBLEM TO BE SOLVED: To provide an optical image formation method that can realize an enlargement of an imageable depth range at low costs.SOLUTION: An optical image formation method according to an embodiment includes: a scan step of scanning an object with signal light as alternately changing a phase difference between the signal light and reference light to preset two phase differences； a detection step of detecting interference light of the signal light via the object with the reference light； and an image formation step of forming a tomographic image on the basis of the detection result of a plurality of the interference light sequentially obtained in the detection step accompanied by the scanning； The image formation step is configured to include processing of generating, on the basis of the detection result of the interference light, an interference spectrum that has a region having two phase differences at both ends as a domain of definition and that consists of only a low frequency part with a background component as its center, and a high frequency part present in the vicinity of each of both ends. Scanning the object in the scanning step is executed at an over-sampling ratio at which the low frequency part and the high frequency part are separated.SELECTED DRAWING: Figure 6【課題】画像化可能な深度範囲の拡大を低コストで実現可能な光画像形成方法を提供する。【解決手段】実施形態の光画像形成方法は、信号光と参照光の間の位相差を既定の２つの位相差に交互に変更しながら対象物を信号光でスキャンするスキャンステップと、対象物を経由した信号光と参照光との干渉光を検出する検出ステップと、スキャンに伴い検出ステップで逐次に得られた複数の干渉光の検出結果に基づき断層像を形成する画像形成ステップとを含む。画像形成ステップは、干渉光の検出結果に基づいて、２つの位相差を両端とする範囲を定義域とし、かつ、背景成分を中心とする低周波数部と両端のそれぞれの近傍に存在する高周波数部のみからなる干渉スペクトルを生成する処理を含む。スキャンステップにおけるスキャンは、低周波数部と高周波数部とが分離されるオーバーサンプリングレシオで実行される。【選択図】図６
