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4
Aligning the FlexIR Accessory
This accessory has been pre-aligned on the same make as your spectrometer. In most cases, little to no
further alignment is necessary. To assess the need for additional alignment, check the energy when in
the monitor mode of the spectrometer software. When using the specular or diffuse reflection probe,
slide the reference cap over the probe tip before monitoring the energy. No reference cap required for
ATR probes.
The alignment procedure requires that the IR beam pass through the hollow waveguide(s) and return
the beam through the hollow waveguide to reach the detector. Prior to adjusting the mirrors as
explained below a closed loop must be established. In other words, the alignment process for a diffuse
reflectance or a specular reflectance probe requires that the probe tip be positioned gently touch
ing the
diffuse reference disk or a specular mirror embedded in the reference cap included with the probe,
respectively. For an ATR probe, no reference or mirror is required. Simply be sure the ATR crystal surface
is clean.
Open the FTIR bench setup software display to monitor the interferogram signal strength. Please refer
to your FTIR software manual for details of this operation. Reduce the size of the FTIR aperture to
achieve acceptable interferogram signal strength. If your FTIR does not have an aperture, use an IR
beam-limiting screen placed at the right or left side of the FTIR sample compartment to reduce the
energy to an acceptable level.
Optimize the signal by adjusting the input mirror (Figure 3), which directs the IR beam into the hollow
waveguide(s), located below the installed probes. Rotate slowly the screws, positioned on the diagonal,
one at a time while maximizing the signal by monitoring the energy displayed through the FTIR software.
Figure 2: Assembled FlexIR Accessory
