PROBLEM TO BE SOLVED: To provide an optical coherent tomographic apparatus which achieves an optimum lateral resolution when a light source emits measurement light with a long wavelength band of 1 μm or so.SOLUTION: An optical coherent tomographic apparatus comprise: a light source unit for generating light having a second wavelength band longer than a first wavelength band, while sweeping the wavelength； a division unit for dividing the generated light into measurement light and reference light； a scan unit for scanning the measurement light in a subject； an optical member having a second focal length longer than a first focal length, which first focal length has a lateral resolution of light of the first wavelength in the subject as a predetermined lateral resolution, the second focal length having a lateral resolution of light of the second wavelength in the subject higher than the predetermined lateral resolution, thus the optical member guiding the measurement light to the scan unit； a detection unit for detecting coherent light obtained by coherence between return light from the subject irradiated with the measurement light via the scan unit and the reference light； and image acquisition means for acquiring a tomographic image of the subject based on the detected coherent light.SELECTED DRAWING: Figure 5【課題】光源が発する測定光の波長帯域が１μｍ帯等の長波長帯である場合に最適な横分解能となる光干渉断層撮影装置を提供する。【解決手段】第１の波長帯域よりも長い第２の波長帯域の光を波長掃引しながら発生させる光源部と、発生された光を測定光と参照光とに分割する分割部と、被検査物において測定光を走査する走査部と、被検査物における第１の波長帯域の光の横分解能を所定の横分解能とする第１の焦点距離よりも長く且つ被検査物における第２の波長帯域の光の横分解能を所定の横分解能以上とするような第２の焦点距離を持ち、測定光を走査部に導く光学部材と、走査部を介して測定光を照射した被検査物からの戻り光と参照光とを干渉して得た干渉光を検出する検出部と、検出された干渉光に基づいて被検査物の断層画像を取得する画像取得手段と、を光干渉断層撮影装置に配する。【選択図】図５
