256
T. Okura
j
Measurement number (a smaller number corresponds to a shorter wavelength)
f
Minimum measurement number that satisfies the condition
λ n − λ f
< <
g
Maximum measurement number that satisfies the condition
λ g − λ n
< <.
Based on the above calculations, the reflectance or transmittance at any wavelength λ n with the wavelength resolution can be acquired. The actual wavelength
resolution following these calculations will be a convolution of the slit function with
the wavelength resolution ω, and the triangular shape with the wavelength resolution
. If ω is very small compared to , the actual wavelength resolution will be close
to . If ω and are almost identical, then the total wavelength resolution will be
approximately 1.43 × .
(c-3) Preprocessing of the Spectral Data
The absorbance A(λ n ) of the spectrum S(λ n ) can be calculated using Eq. 10.27 if
required.
A(λ n ) = − log(S(λ n ))
(10.27)
Using the spectral data A(λ n ) or S(λ n ), the calibration can be established using
statistics. Various data preprocessing steps, such as smoothing, can be applied prior
to the statistical analysis to obtain good calibrations.
10.3 Designing a NIR Spectrometer for Special Materials
The main application of NIR spectroscopy is to measure the ingredients of a certain
material, which is an easy and non-destructive method used onsite. An appropriate
method of designing such a spectrometer is explained in the following sections. The
performance of the desired instrument should be examined before commencing the
design. It is particularly critical to assess the permissible noise levels with respect to
the desired instrument.
When an instrument is designed without knowledge of the allowable noise levels
for a particular application, the instrument should be repeatedly improved until satisfactory calibration is achieved. Generating calibrations repeatedly to evaluate the
instrument is a waste of time and money.
The efficient design process of NIR spectroscopy with minimum waste is
explained in Fig. 10.26. The process involves three steps, namely the first test
measurement, the second step to determine the specification, and the third step
involving the final manufacture of the instrument.
T. Okura
j
Measurement number (a smaller number corresponds to a shorter wavelength)
f
Minimum measurement number that satisfies the condition
λ n − λ f
< <
g
Maximum measurement number that satisfies the condition
λ g − λ n
< <.
Based on the above calculations, the reflectance or transmittance at any wavelength λ n with the wavelength resolution can be acquired. The actual wavelength
resolution following these calculations will be a convolution of the slit function with
the wavelength resolution ω, and the triangular shape with the wavelength resolution
. If ω is very small compared to , the actual wavelength resolution will be close
to . If ω and are almost identical, then the total wavelength resolution will be
approximately 1.43 × .
(c-3) Preprocessing of the Spectral Data
The absorbance A(λ n ) of the spectrum S(λ n ) can be calculated using Eq. 10.27 if
required.
A(λ n ) = − log(S(λ n ))
(10.27)
Using the spectral data A(λ n ) or S(λ n ), the calibration can be established using
statistics. Various data preprocessing steps, such as smoothing, can be applied prior
to the statistical analysis to obtain good calibrations.
10.3 Designing a NIR Spectrometer for Special Materials
The main application of NIR spectroscopy is to measure the ingredients of a certain
material, which is an easy and non-destructive method used onsite. An appropriate
method of designing such a spectrometer is explained in the following sections. The
performance of the desired instrument should be examined before commencing the
design. It is particularly critical to assess the permissible noise levels with respect to
the desired instrument.
When an instrument is designed without knowledge of the allowable noise levels
for a particular application, the instrument should be repeatedly improved until satisfactory calibration is achieved. Generating calibrations repeatedly to evaluate the
instrument is a waste of time and money.
The efficient design process of NIR spectroscopy with minimum waste is
explained in Fig. 10.26. The process involves three steps, namely the first test
measurement, the second step to determine the specification, and the third step
involving the final manufacture of the instrument.