It is possible to highly accurately measure the oxygen concentration of a substance to be measured without being influenced by the intensity of excitation light (L1), the concentration of fluorescent material, and the surrounding environment. Pulsed excitation light (L1) including a wavelength that can excite a fluorescent material contained in living matter is generated. The fluorescence lifetime (Tf) of the fluorescent material is longer than or equal to 4.8 nanoseconds. A predetermined position in the living matter is illuminated with the pulsed excitation light (L1). Further, light including fluorescence (Lf) emitted from the fluorescent material excited by illumination with the pulsed excitation light (L1) is received. The lifetime (Tf) of the fluorescence (Lf) included in the received light is calculated by time-resolving the intensity of the fluorescence (Lf) . Further, the oxygen concentration of the living matter is measured based on the lifetime (Tf)
Low-oxygen-region-analysis method and apparatus by time-resolved-measurement of light-induced-autofluorescence from biological-sample