A typical task assigned for measuring a brain activity signal lasts from 10 to 30 seconds. This is the duration of time required for sufficiently inducing a brain activity such that it can be measured. The frequency bands of brain activity signals obtained by such a task lie between approximately 0.03 and 0.1 Hz. Therefore, the frequency band of the Mayer wave noise signal is very close to the frequency bands of brain activity signals. As a result, it is difficult to reduce the Mayer wave noise signal using a bandpass filter or a bandcut filter. Further, because a low-frequency fluctuation signal contains non-periodic and irregular changes, reducing it with a simple frequency filtering is difficult. To measure the blood dynamics inside the tissue of a test subject, the application provides a system comprising one or more light irradiating units (101) for irradiating the subject with light; one or more light detecting units for detecting (102) the emitted light that has been passed through or reflected within the tissue; a biological signal measuring unit (104) for measuring one or a combination of two or more factors selected from the pulsation, breathing, blood pressure, and temperature; means for analyzing (107) the relationship between an optical signal obtained by the light detecting unit and a biological signal using non-linear analysis; and means for performing a computation for separating a biological noise signal from the optical signal on the basis of the obtained relationship.
Biological optical measurement system