SPECTRAFIRE, Far Infrared Reflectometer Attachment
|Shown attached to a personal computer for processing, the Spectrafire is an emissometer that uses an ellipsoidal collector, which allows this bench unit to be smaller than its predecessors.
Technology SPECTRAFIRE is a far infrared
reflectometer attachment designed for the
Thermo-Nicolet line of FTIR spectrometers. As a
system, the SPECTRAFIRE far IR reflectometer attached to the Thermo-Nicolet spectrometer
provides a Fourier transform infrared (FT-IR)
spectral reflectometer that measures spectral
total hemispherical reflectance using a
unique design for hemispherical energy collection
(patented). The instrument scans near-normal
hemispherical reflectance from 1.67 microns
to 40 microns. All compartments can be purged
to minimize signal losses due to absorption
by water and carbon dioxide. Normal emittance
is calculated by integrating the
measured spectral reflectance with respect
to the black body curve.
SPECTRAFIRE far IR reflectometer has two modes of operation:
absolute and relative/differential. In absolute
mode near-normal incident, hemispherical
reflectance is measured directly using an
internal calibration arm specifically matched
to the collector. Calibration is not required
in this mode. In relative (or differential)
mode, the internal calibration arm is not
used. Instead, the investigator supplies
a reference sample for the background run
and then measures the new sample.
In addition to cataloging and tracking
sample spectrums, total hemispherical emittance
can be determined for opaque samples by
using a specially calibrated puck. Emittance
calculated from the SPECTRAFIRE data does
not depend on knowing the source spectrum
and is not restricted to only 300K. SPECTRAFIRE
can be used to correctly determine emittance
at temperatures other than 300K and to correctly
determine emittance of non-gray bodies.
SPECTRAFIRE Far IR Reflectometer Optical Subsystem
Far IR Reflectometer
A collimated infrared beam passes from the
Nicolet through the port on the left side
of SPECTRAFIRE. An off-axis parabolic mirror
focuses the beam onto the sample. The sample
port is located on the top of SPECTRAFIRE.
The sample rests on top of the patented collector.
The incident beam is reflected off of the
sample and the reflected light over 2Pi
steradians is collected and refocused on the
detector. The signal from the detector is
relayed back to the FTIR electronics. There
is also a beam deflector arm built into the
collector that is used for the background
in absolute mode. This arm has been specifically
matched to the collector's reflectance. All
of the optics in SPECTRAFIRE have been coated
with unprotected gold for maximum reflectance
in the instruments spectral range.
Attachment of SPECTRAFIRE Far IR Reflectometer to the Thermo-Nicolet
The SPECTRAFIRE unit attaches to the right
side of the Nicolet spectrometer. A single
left-handed bolt secures it to the Nicolet.
The sample port for measuring spectral total
hemispherical reflectance is on the top
of the unit. On the back of the enclosure
there is a connector for the detector 9-pin
cable and there is a connector for the purge
The table below lists specifications for the SPECTRAFIRE Far IR Reflectometer.
*Note: terms reflectance, emittance and absorptance and terms reflectivity, emissivity and absorptivity are often used interchangeably. Spectroreflectometer, spectro-reflectometer and spectral reflectometer are also used interchangeably.