PROBLEM TO BE SOLVED: To accurately specify a blood injection time by a simple method.SOLUTION: A light emitting part 21 emits first light with a first wavelength &lambda；1 and second light with a second wavelength &lambda；2. A light receiving part 22 outputs a first signal and a second signal according to the intensity of the first light and the second light that pass through or are reflected by a biological tissue 30 of a subject to be examined respectively. A first operation part 41 acquires a degree of dimming A1 of the first light based on the first signal, and a degree of dimming A2 of the second light based on the second signal. A second operation part 42 acquires a degree of dimming Ab derived from blood based on the degree of dimming A1 of the first light and the degree of dimming A2 of the second light. A third operation part 43 specifies a blood injection time T to the biological tissue 30 based on a change with time of the degree of dimming Ab derived from blood following the oppression of the biological tissue 30. An output part 14 outputs the specified blood injection time T.【課題】簡便な手法によって血液充填時間を正確に特定する。【解決手段】発光部２１は、第１波長λ１を有する第１の光、および第２波長λ２を有する第２の光を出射する。受光部２２は、被検者の生体組織３０を通過または反射した第１の光および第２の光の強度に応じて、それぞれ第１信号および第２信号を出力する。第１演算部４１は、第１信号に基づいて第１の光の減光度Ａ１を取得し、第２信号に基づいて第２の光の減光度Ａ２を取得する。第２演算部４２は、第１の光の減光度Ａ１および第２の光の減光度Ａ２に基づいて、血液由来の減光度Ａｂを取得する。第３演算部４３は、生体組織３０の圧迫に伴う血液由来の減光度Ａｂの経時変化に基づいて、生体組織３０への血液充填時間Ｔを特定する。出力部１４は、特定された血液充填時間Ｔを出力する。【選択図】図１
