Optical analysis method for inhomogeneous turbid media

An optical analysis method of determining a physical quantity of a medium from an intensity of light transmitted through or reflected by the medium, the medium being an absorbent and scattering medium containing a plurality of parts having different optical characteristics, characterized by comprising:

• the first step of making light having a known intensity incident on the medium;
• the second step of measuring the intensity of the light that emerges from the medium;
• the third step of storing light intensity numerical values;
• the fourth step of deriving a coefficient necessary for arithmetic operation by erasing or avoiding influence of inhomogeneous light scattering by arithmetic operation for a combination of the numerical values;
• the fifth step of storing the obtained coefficient;
• and the sixth step of performing linear algebraic operation for optimization in a wavelength range using the light intensity measurement values at a plurality of wavelengths,
• wherein the function used for the arithmetic operation is defined as simultaneous differential equations that describe light amount re-distribution by light scattering between the parts, i.e., a basic system that expresses light re-distribution given by
• dx/dt=−ax+by
• dy/dt=cx−dy
• where
• assuming that the medium contains two, first and second parts,
• x is a light intensity in the first part,
• y is a light intensity in the second part,
• a is a loss coefficient by absorption and scattering in the first part,
• b is a coefficient of a component of scattered light in the second part, which mixes into the first part,
• c is a coefficient of a component of scattered light in the first part, which mixes into the second part,
• d is a loss coefficient by absorption and scattering in the second part, and
• t is a penetration depth of the light into the inhomogeneous medium,
• and as a linear sum of exponential functions for t, which uses e as a base and is given by I = x + y = 1 2 ⁢ ( ⅇ - α ⁢ ⁢ t + ⅇ - β ⁢ ⁢ t )
• which represents a light intensity I standardized as a sum of general solutions x and y corresponding to the basic system, thereby derivatively calculating the physical quantity from the light amount measurement values on the basis of a relationship between the coefficients (a, b, c, d) and unknowns (α, β).