10 Hardware of Near-Infrared Spectroscopy
253
Fig. 10.23 Slit function of
the spectrometer
(b) Wavelength Interval for Measurement
Selecting the right wavelength interval for a measurement is important to obtain the
right spectral shape. Thus, the spectral shape is influenced by the wavelength interval
[13].
When the wavelength interval is larger than the wavelength resolution, some spectral components between the measurement points will not be measured. When the
interval is too narrow, some spectral components will be overlapped in the measurement. The following important aspects should be considered to enable an even/equal
measurement of all the spectral components.
(b-1) Wavelength Scanning Grating Spectrometer
The shape of the slit function of a wavelength scanning grating spectrometer is
usually triangular with a half bandwidth (HBW) of ω, as shown in Fig. 10.23.
When the wavelength interval λ is ω (Fig. 10.23b) or
ω
n
(Eq. 10.23), all the
spectral components will be measured evenly.
λ =
ω
n
(10.23)
λ Wavelength interval
ω HBW of the slit function
n
Integer 1, 2, …