8 New Trend in Instrumentation of NIR Spectroscopy …
203
Table 8.1 Operating parameters of the selected handheld NIR spectrometers available on the market
Spectrometer
Spectral region
Spectral resolution (at
wavelength) a [nm]
[nm]
[cm −1 ]
microPHAZIR (Thermo
Fisher Scientific)
1596–2396
6267–4173
11
MicroNIR Pro ES 1700
(VIAVI)
908–1676
11,013–5967
12.5 (at 1000) 25 (at
2000)
SCiO (Consumer Physics)
740–1070
13,514–9346
unknown b
NIRscan (Texas
Instruments)
900–1700
11,111–5882
10
NIRONE sensors (Spectral
Engines)
2000–2450
5000–4082
18–28 c
NeoSpectra (Si-Ware
Systems)
1350–2500
7407–4000
16 (at 1550)
nanoFTIR NIR (SouthNest
Technology)
800–2600
12,500–3846
2.5 (at 1000) 6 (at 1600)
13 (at 2400)
a ‘at wavelength’ parameter listed if available in the datasheet provided by the vendor
b SCiO presents to the operator interpolated spectra with 1 nm data spacing, but the real resolution
is considerably lower
c depending on the sensor implementation/factory configuration
Digital micromirror device (DMD) is a MEMS-based array of mirrors. DMD may
primarily be used to lower the cost of miniature dispersive scanning spectrometers,
and its key role is to enable replacing expensive micro-array detectors by a large
single-pixel detector, which is a much more cost-effective solution. DMD element is
used in DLP NIRscan module from Texas Instruments. The company’s proprietary
DLP technology is offered as two evaluation modules (EVMs): DLP NIRscan and
DLP NIRscan Nano (Fig. 8.6c).
There exist microscaled technology solutions other than MEMS, which are suitable for the construction of wavelength selectors in miniaturized NIR spectrometers. For example, a linear variable filter (LVF) is an optical bandpass filter, in
which through varying thickness of an optical coating, and thus, transparence against
different wavelengths varies linearly across a wedged geometry of the filter. LVF technology is cost-effective, and compared with MEMS relies less on large-scale manufacturing, although requires to be used with less affordable array detectors. On the
other hand, such configuration enables very rapid scanning capability. LVFs enable
constructing very compact spectrometers with no moving parts, which improves the
ruggedness of the spectrometer. A satisfying spectral resolution for real applications
and low power consumption should also be noted. DMDs coupled with InGaAs array
detectors are used in the line of NIR spectrometers, including specialized models
aimed for process control, that were introduced to the market by VIAVI (Fig. 8.6b).
It needs to be highlighted, that the design of a miniaturized NIR spectrometer
is a balance between the level of miniaturization, performance, and the economic
cost. Through accepting certain limitations, very affordable devices are feasible.
203
Table 8.1 Operating parameters of the selected handheld NIR spectrometers available on the market
Spectrometer
Spectral region
Spectral resolution (at
wavelength) a [nm]
[nm]
[cm −1 ]
microPHAZIR (Thermo
Fisher Scientific)
1596–2396
6267–4173
11
MicroNIR Pro ES 1700
(VIAVI)
908–1676
11,013–5967
12.5 (at 1000) 25 (at
2000)
SCiO (Consumer Physics)
740–1070
13,514–9346
unknown b
NIRscan (Texas
Instruments)
900–1700
11,111–5882
10
NIRONE sensors (Spectral
Engines)
2000–2450
5000–4082
18–28 c
NeoSpectra (Si-Ware
Systems)
1350–2500
7407–4000
16 (at 1550)
nanoFTIR NIR (SouthNest
Technology)
800–2600
12,500–3846
2.5 (at 1000) 6 (at 1600)
13 (at 2400)
a ‘at wavelength’ parameter listed if available in the datasheet provided by the vendor
b SCiO presents to the operator interpolated spectra with 1 nm data spacing, but the real resolution
is considerably lower
c depending on the sensor implementation/factory configuration
Digital micromirror device (DMD) is a MEMS-based array of mirrors. DMD may
primarily be used to lower the cost of miniature dispersive scanning spectrometers,
and its key role is to enable replacing expensive micro-array detectors by a large
single-pixel detector, which is a much more cost-effective solution. DMD element is
used in DLP NIRscan module from Texas Instruments. The company’s proprietary
DLP technology is offered as two evaluation modules (EVMs): DLP NIRscan and
DLP NIRscan Nano (Fig. 8.6c).
There exist microscaled technology solutions other than MEMS, which are suitable for the construction of wavelength selectors in miniaturized NIR spectrometers. For example, a linear variable filter (LVF) is an optical bandpass filter, in
which through varying thickness of an optical coating, and thus, transparence against
different wavelengths varies linearly across a wedged geometry of the filter. LVF technology is cost-effective, and compared with MEMS relies less on large-scale manufacturing, although requires to be used with less affordable array detectors. On the
other hand, such configuration enables very rapid scanning capability. LVFs enable
constructing very compact spectrometers with no moving parts, which improves the
ruggedness of the spectrometer. A satisfying spectral resolution for real applications
and low power consumption should also be noted. DMDs coupled with InGaAs array
detectors are used in the line of NIR spectrometers, including specialized models
aimed for process control, that were introduced to the market by VIAVI (Fig. 8.6b).
It needs to be highlighted, that the design of a miniaturized NIR spectrometer
is a balance between the level of miniaturization, performance, and the economic
cost. Through accepting certain limitations, very affordable devices are feasible.