270
T. Inagaki and S. Tsuchikawa
of Rayleigh and Mie scattering. Author explained that the equations are good for
use in predicting behavior of light propagation or diffusion within the 400–1300 nm
wavelength range. Author summarized also the mean values of coefficient a and
b (skin: a = 46.0 cm
−1 , b = 1.421, brain: a = 24.2 cm
−1 , b = 1.611, breast: a
= 16.8 cm
−1 , b = 1.055, bone: a = 22.9 cm
−1 , b = 0.716, other soft tissues: a
= 18.9 cm
−1 , b = 1.286, other fibrous tissues: a = 27.1 cm
−1 , b = 1.627, fatty
tissue: a = 18.4 cm
−1 , b = 0.672). Fujii et al. [6] investigated the effects of three
factors (trachea, refractive index mismatch at the boundary of trachea tissue, and
neck organs other than the trachea [spine, spinal cord, and blood vessels]) on light
propagation in the neck by 2D time-dependent radiative transfer equation. After they
constructed an anatomical model of human neck from MR image, they performed
segmentation of the MR image and recognized the pixel corresponding to organs of
the human neck: the trachea, spine, spinal cord, and blood vessels. They simulated the
light propagation in anatomical human neck models by numerical method and MC
simulation. They showed that reflection and refraction at the trachea tissue interface
significantly effect on the light intensities in the region between the trachea and the
front of the neck surface. So, it is necessary to take into account the refractive index
mismatch at the trachea tissue interface. Hoshi summarized the use of TR system for
clinical monitoring of tissue oxygenation [7].
11.6 Application of TOF-NIRS to Forest Products
As many reviews and manuscripts about application of TR spectroscopy for medical
and food product science are published, TR spectroscopic application for these
research area is briefly explained in previous chapter. In present chapter, the use
of TR spectroscopy for the determination of optical properties in wood is explained
in detail.
Wood is a natural material widely used in construction because of its versatility and
strength. As wood is a biomaterial, there are significant variations in wood properties
(e.g., density, moisture content, grain angle) between species and even among the
same species. From the point of view of quality assurance in industry, nondestructive
measuring and control of the mechanical, physical, and chemical properties of wood
are strongly desired. The light scattering in wood is especially complex because
of the complex cellular structure in wood. Softwood mainly possesses a tracheid
structure, arrayed along the longitudinal direction; whereas, hardwood structures
have wide variation of cell structure (e.g., tracheids, vessels, libriform wood fibers,
or ray cells). The optical properties of wood are significantly affected also by the
water retained in cell walls or cell lumens.
Some groups reported the use of TR diffuse reflectance spectroscopy to determine the optical properties of wood. D’Andrea et al. [10] decided μ a and
μ
s in the wavelength range of 700–1040 nm of two wood species treated in
different conditions (dry wood, wet wood, and degraded wood) by TR spectroscopy
with two orientations of the optical fiber (i.e., the emitted and detected fibers
T. Inagaki and S. Tsuchikawa
of Rayleigh and Mie scattering. Author explained that the equations are good for
use in predicting behavior of light propagation or diffusion within the 400–1300 nm
wavelength range. Author summarized also the mean values of coefficient a and
b (skin: a = 46.0 cm
−1 , b = 1.421, brain: a = 24.2 cm
−1 , b = 1.611, breast: a
= 16.8 cm
−1 , b = 1.055, bone: a = 22.9 cm
−1 , b = 0.716, other soft tissues: a
= 18.9 cm
−1 , b = 1.286, other fibrous tissues: a = 27.1 cm
−1 , b = 1.627, fatty
tissue: a = 18.4 cm
−1 , b = 0.672). Fujii et al. [6] investigated the effects of three
factors (trachea, refractive index mismatch at the boundary of trachea tissue, and
neck organs other than the trachea [spine, spinal cord, and blood vessels]) on light
propagation in the neck by 2D time-dependent radiative transfer equation. After they
constructed an anatomical model of human neck from MR image, they performed
segmentation of the MR image and recognized the pixel corresponding to organs of
the human neck: the trachea, spine, spinal cord, and blood vessels. They simulated the
light propagation in anatomical human neck models by numerical method and MC
simulation. They showed that reflection and refraction at the trachea tissue interface
significantly effect on the light intensities in the region between the trachea and the
front of the neck surface. So, it is necessary to take into account the refractive index
mismatch at the trachea tissue interface. Hoshi summarized the use of TR system for
clinical monitoring of tissue oxygenation [7].
11.6 Application of TOF-NIRS to Forest Products
As many reviews and manuscripts about application of TR spectroscopy for medical
and food product science are published, TR spectroscopic application for these
research area is briefly explained in previous chapter. In present chapter, the use
of TR spectroscopy for the determination of optical properties in wood is explained
in detail.
Wood is a natural material widely used in construction because of its versatility and
strength. As wood is a biomaterial, there are significant variations in wood properties
(e.g., density, moisture content, grain angle) between species and even among the
same species. From the point of view of quality assurance in industry, nondestructive
measuring and control of the mechanical, physical, and chemical properties of wood
are strongly desired. The light scattering in wood is especially complex because
of the complex cellular structure in wood. Softwood mainly possesses a tracheid
structure, arrayed along the longitudinal direction; whereas, hardwood structures
have wide variation of cell structure (e.g., tracheids, vessels, libriform wood fibers,
or ray cells). The optical properties of wood are significantly affected also by the
water retained in cell walls or cell lumens.
Some groups reported the use of TR diffuse reflectance spectroscopy to determine the optical properties of wood. D’Andrea et al. [10] decided μ a and
μ
s in the wavelength range of 700–1040 nm of two wood species treated in
different conditions (dry wood, wet wood, and degraded wood) by TR spectroscopy
with two orientations of the optical fiber (i.e., the emitted and detected fibers