2.2. Supported Devices

This section contains information on specific spectrometers supported by TII Spectrometry. For guidance on general use common to all supported devices, see Section 2.1.

Important

Not all spectrometers are supported on all platforms. For details, see Table 1.1.

2.2.1. Avenir Photonics

TII Spectrometry supports the Avenir Photonics Aris (visible) and Siena (near-IR) spectrometers. In addition to the standard spectrometer settings, the following settings are available in the Spectrometer menu:

LED

Toggles the spectrometer’s LED

Auto

Activates auto-exposure mode

External Trigger

Activates external triggering

Gain

(Avenir Siena only) sets the gain

NLIR

activates NLIR Spectrum upconverter support

In addition, the Burst Time-lapse Recording window contains the following settings:

Data Format

Changes the data format of the spectrometer for higher throughput.

• 32bit float

• 16bit Int

• 16bit Int (Half Spectral Resolution)

The default (32bit float) has the highest resolution and fidelity. To increase the spectral acquisition rate and to avoid filling up the spectrometer’s internal buffer, a more compact data format (16bit Int or 16bit Int (Half Spectral Resolution)) can be selected. The effect of this setting can be seen in Figure 2.15: When using the 32bit float format (blue), the spectrometer buffer fills up after approximately 180 spectra and the spectral acquisition rate slows down from 250 Hz to 125 Hz. For the 16bit Int (Half Spectral Resolution) setting (red & green), the spectrometer can continuously operate at full speed.

Fig. 2.15 Sustained spectral acquisition rate of an Avenir Aris spectrometer

2.2.2. ARCoptix

TII Spectrometry supports ARCoptix FTIR (FT-NIR and FT-MIR) spectrometers. Theses devices are based on a scanning Michelson interferometer and cover spectral ranges in the near and mid infra-red.

Note

ARCoptix spectrometers rely on a serverlet application that runs in the background. If the application is not already running, it will be started by TII Spectrometry. The initialization of this application as well as connection to and configuration of the spectrometer can take several 10s of seconds. In principle, connection to the serverlet application is also possible using over a network connection - see the section Remote Connections for details.

Important

Since the scan rate of the interferometer is fixed, no exposure time settings are available.

The Spectrometer menu contains the following options:

Apodization

Selects an apodization function to remove high-frequency noise at the expense of a reduced spectral resolution

Interferogram

Toggles the display of the raw interferogram data (bottom of Figure 2.16).

Fig. 2.16 The interferogram view

See also

See Section 5.1 (Fast Fourier Transform (FFT) Applied to FTIR Data) for guidance on how to analyze interferogram data.

Gain

Selects the gain of the spectrometer

Resolution

Selects the spectral resolution in 1/m. Higher numbers increase the scan speed but lower the spectral resolution by decreasing the scan range of the interferometer (Figure 2.17).

Fig. 2.17 Spectral acquisition rate vs resolution

Warning

Changing the spectrometer resolution will reconfigure and disconnect the spectrometer from TII Spectrometry. To continue using the spectrometer, simply connect again.

2.2.2.1. Remote Connections

Connections to the ARCoptix serverlet applications are possible over a network connection provided the computer running the serverlet application (‘host’) and the computer running TII Spectrometry (‘guest’) are part of the same subnet.

To establish a network connection:

1. on the host computer:

   • connect the spectrometer to a USB port

   • start the serverlet application:

     • on Windows, this is done by starting AoDAQWin.exe

     • on Linux, this is done by running AoDAQ_**, where ** indicates the suffix for the file version and operating system

   Tip

   Use AoDAQWin.exe -h (on Windows) for help. It may be helpful to:

   • run the application in verbose mode using AoDAQWin.exe -v for troubleshooting

   • manually set a port number for the TCP/IP connection using, e.g. AoDAQWin.exe -p 4711

2. on the guest computer:

   • start TII Spectrometry

   • open the Device Manager using File ‣ Connect ‣ Device Manager

   • enter the IP address and port number of the host computer and activate the ARCoptix (remote) device

     Tip

     The default port number is 1424.

   • click OK to establish the connection

Note

Remote and local spectrometers can be mixed - see Section 2.3 Using Multiple Spectrometers for details.

2.2.3. StellarNet

TII Spectrometry supports StellarNet spectrometers. In addition to standard spectrometer settings, the following settings are available in the Spectrometer menu:

X-Timing

Sets the X-timing

Temperature Compensation

Toggles temperature compensation using dark pixels to increase spectrometer stability during long recordings.

NLIR

activates NLIR Spectrum upconverter support

Fig. 2.18 StellarNet spectrometer timing

2.2.4. NLIR Spectrum

The NLIR Spectrum is a wavelength converter that uses sum-frequency generation (SFG) of a 1064 nm laser (\(\lambda_{\rm{pump}}\)) with mid-infrared light (\(\lambda_{\rm{MIR}}\)) in a non-linear crystal for spectral upconversion of the 1900-5300 nm mid-IR spectral range to the 682-886 nm visible range (\(\lambda_{\rm{NIR}}\)) (2.1).

(2.1)\[ \frac{1}{\lambda_{\rm{NIR}}} = \frac{1}{\lambda_{\rm{MIR}}} + \frac{1}{\lambda_{\rm{pump}}} \]

This device can be connected to supported spectrometers for recording MIR spectra using a VIS-NIR device. The NLIR Spectrum is supported if the spectral range of the connected spectrometer includes the output range of the upconverter (682-886 nm). In this case, the Spectrometer menu will include the Spectrometer ‣ NLIR submenu.

Use

Toggles spectral re-conversion using (2.1) solving for \(\lambda_{\rm{MIR}}\). The spectral axis will hence be in units of the original mid-IR light before upconversion.

Crop

Removes the spectral region outside of the upconversion output range.

The effect of these two settings is displayed in Figure 2.19: The bottom axis shows the wavelength of the upconverted spectrum, the top axis shows the wavelength of the original light before upconversion. The green region marks the spectral range of the wavelength converter - spectra will be cropped to this region if Crop is enabled.

Fig. 2.19 Spectral output of the NLIR Spectrum wavelength converter

2.2.5. NLIR Midwave

The NLIR Midwave is a combination of NLIR spectral upconverter and spectrometer. In addition to standard spectrometer settings, this device also allows external triggering, which can be activated using Spectrometer ‣ External Trigger ‣ Use External Trigger. The trigger edge (rising or falling) can be selected using Spectrometer ‣ External Trigger ‣ Trigger Edge. Spectra are automatically re-converted to the MIR range.