PROBLEM TO BE SOLVED: To measure a constituent concentration such as a blood glucose concentration with a high degree of precision.SOLUTION: Laser diodes 1-1 and 1-2 modulate intensity of light of two waves with different wavelengths by the same frequency and by signals of different phases, and irradiate an object 11 to be measured with the light. An optical splitter 12 branches part of the light that is emitted from the laser diode 1-2 and propagates through an optical fiber 3-2. A light intensity measuring device 13 measures power of light emitted from the laser diode 1-2. An information processing device 10a changes the power of light emitted from the laser diode 1-2, and based on a result of measurement by the light intensity measuring device 13 at the time when the intensity of an electric signal output from a lock-in amplifier 9 reaches a minimum level, derives a constituent concentration of an object to be measured contained in the object 11 to be measured.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2016,JPO&INPIT
