Apparatus for measuring absorption information in scattering medium and method therefor
First Claim
1. An apparatus for measuring absorption information in a scattering medium, comprisinglight-emitting means for emitting modulated light having a predetermined wavelength,light-incident means for forming the modulated light having the predetermined wavelength into a spot and causing the spot to be incident on the scattering medium,photodetecting means for photodetecting the modulated light, changed during propagation in the scattering medium, through an opening located near an outer surface of the scattering medium,signal extracting means for extracting a signal of one predetermined frequency component constituting the modulated light from signals photodetected by said photodetecting means,parameter detecting means for comparing the signal extracted by the signal extracting means with the signal of the predetermined frequency component of the modulated light to be incident on the scattering medium and detecting a predetermined parameter associated with propagation of a photon density wave having the predetermined frequency component in the scattering medium and absorption of the light of the predetermined wavelength constituting the photon density wave having the predetermined frequency component,first arithmetic processing means for calculating first absorption information associated with an absorptive constituent in the scattering medium, utilizing a relationship between the predetermined parameter and an absorption coefficient obtained when the photon density wave having the predetermined frequency component propagates in the scattering medium, andsecond arithmetic processing means for calculating second absorption information associated with the absorption coefficient in the scattering medium, on the basis of a plurality of first absorption information obtained by the first arithmetic processing means.
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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. A signal of a predetermined frequency component is extracted from this detection signal to detect a photon density wave propagating in the scattering medium. A signal extracted to correspond to this photon density wave is compared with the signal of the predetermined frequency component constituting the original incident modulated light to detect a predetermined quantitatively measurable parameter such as a phase difference at a detection point. This parameter has a specific relationship with the absorption coefficient by an absorptive constituent in the scattering medium as being derived from the photon diffusion theory, so that the predetermined parameter is appropriately arithmetically processed to obtain various kinds of absorption information (including the linear integration value of the absorption coefficient in the scattering medium and the concentration of a specific material) associated with absorption in the scattering medium.
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Citations
27 Claims
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1. An apparatus for measuring absorption information in a scattering medium, comprising
light-emitting means for emitting modulated light having a predetermined wavelength, light-incident means for forming the modulated light having the predetermined wavelength into a spot and causing the spot to be incident on the scattering medium, photodetecting means for photodetecting the modulated light, changed during propagation in the scattering medium, through an opening located near an outer surface of the scattering medium, signal extracting means for extracting a signal of one predetermined frequency component constituting the modulated light from signals photodetected by said photodetecting means, parameter detecting means for comparing the signal extracted by the signal extracting means with the signal of the predetermined frequency component of the modulated light to be incident on the scattering medium and detecting a predetermined parameter associated with propagation of a photon density wave having the predetermined frequency component in the scattering medium and absorption of the light of the predetermined wavelength constituting the photon density wave having the predetermined frequency component, first arithmetic processing means for calculating first absorption information associated with an absorptive constituent in the scattering medium, utilizing a relationship between the predetermined parameter and an absorption coefficient obtained when the photon density wave having the predetermined frequency component propagates in the scattering medium, and second arithmetic processing means for calculating second absorption information associated with the absorption coefficient in the scattering medium, on the basis of a plurality of first absorption information obtained by the first arithmetic processing means.
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23. A method of measuring absorption information in a scattering medium, comprising
the first step of emitting modulated light having a predetermined wavelength, the second step of forming the modulated light having the predetermined wavelength light into a spot and causing the spot to be incident on the scattering medium, the third step of photodetecting the modulated light, changed during propagation in the scattering medium, through an opening located near an outer surface of the scattering medium, the fourth step of extracting a signal of one predetermined frequency component constituting the modulated light from signals photodetected in the third step, the fifth step of comparing the signal extracted in the fourth step with the signal of the predetermined frequency component of the modulated light to be incident on the scattering medium and detecting a predetermined parameter associated with propagation of a photon density wave having the predetermined frequency component in the scattering medium and absorption of the light of the predetermined wavelength constituting the photon density wave having the predetermined frequency component, the sixth step of calculating first absorption information associated with an absorptive constituent in the scattering medium, utilizing a relationship between the predetermined parameter and an absorption coefficient obtained when the photon density wave having the predetermined frequency component propagates in the scattering medium, and the seventh step of calculating second absorption information associated with the absorption coefficient in the scattering medium, on the basis of a plurality of first absorption information obtained in the sixth step.
Specification