US 5,477,051 AGranted

Apparatus for measuring optical information in scattering medium and method therefor

AssigneeHamamatsu Photonics K.K.

InventorYutaka Tsuchiya

Life of this patent

Estimating the term…

Loading patent…

Abstract

Modulated light from a light source is incident on the surface of a scattering medium, and light passing through this scattering medium is externally detected. Components having a plurality of angular frequencies .omega..sub.1 and .omega..sub.2 corresponding to photon density waves propagating in the scattering medium are extracted from this detection signal. The extracted signals corresponding to these waves are compared with a signal of original modulated light to be incident on the scattering medium to detect a quantitatively measurable predetermined parameter such as a phase difference at a detection point for each angular frequency. The detected predetermined parameters have a predetermined relationship with absorptive and scattering constituents of the scattering medium. A pair of predetermined parameters are appropriately arithmetically calculated to eliminate the scattering coefficient, so that only the absorption coefficient can be independently calculated. Various pieces of information (including the linear integration value of the absorption coefficient in the scattering medium, the concentration of the specific material in the scattering medium, and the like) associated with absorption and the like in the scattering medium can be obtained in accordance with the calculated absorption coefficient.

Claims19

Dependent claims

An apparatus for measuring optical information in a scattering medium containing an absorptive constituent, comprising:

light-emitting means for emitting modulated light having a single predetermined light wavelength and at least two predetermined modulation frequency components;
light-incident means for causing said modulated light to be incident on the scattering medium;
photodetecting means for photodetecting the modulated light which has been changed during propagation in the scattering medium, through an aperture located near an outer surface of the scattering medium;
signal extracting means for extracting signals of said predetermined modulation frequency components constituting the modulated light from signals photodetected by said photodetecting means;
parameter detecting means for comparing said signals extracted by said signal extracting means with reference signals of said predetermined modulation frequency components of the modulated light to be incident on the scattering medium, respectively, and detecting predetermined parameters respectively corresponding to said signals having the predetermined modulation frequency components, said parameters being associated with propagation of said modulated light in the scattering medium and scattering and absorption of said modulated light in the scattering medium;
and
arithmetic processing means for calculating an absorption coefficient of the scattering medium by use of said parameters detected by the parameter detecting means, in accordance with a given relationship between the predetermined parameters and the scattering and absorption for said modulated light during propagation in the scattering medium.

4 more elements

A method of measuring optical information in a scattering medium containing an absorptive constituent, comprising:

emitting modulated light having a single predetermined light wavelength and at least two predetermined modulation frequency components;
causing said modulated light to be incident on the scattering medium;
photodetecting the modulated light which has been changed during the propagation in the scattering medium, through an aperture located near an outer surface of the scattering medium;
extracting signals of said predetermined modulation frequency components constituting the modulated light from signals photodetected in the photodetecting step;
comparing said signals extracted in the extracting step with reference signals of said predetermined modulation frequency components of the modulated light to be incident on the scattering medium, respectively, and detecting predetermined parameters respectively corresponding to said signals having the predetermined modulation frequency components, said parameters being associated with propagation of said modulated light in the scattering medium and scattering and absorption of said modulated light in the scattering medium;
and
calculating an absorption coefficient of the scattering medium by use of said parameters detected in the comparing step, in accordance with a given relationship between the predetermined parameters and the scattering and absorption for said modulated light during propagation in the scattering medium.

4 more elements

Dependencies are inferred from the claim text.