SPECTRAL IMAGING LABORATORY
Laser Emission Spectrometers
The thermal infrared surface contamination sensor (TIRSCS) is shown at left with a CAD model explaining its internal components. The TIRSCS uses a 9.6 micron laser to vaporize surface contaminants. The contaminants are transparent in the visible but opaque at 9.6 microns. The vaporized contaminants generate a hot plume that can be detected using an infrared detector array. We used a 7 - 11 micron mercury cadmium telluride (MCT) detector with 7 x 576 pixels, developed by AIM. The MCT array was cooled to 60K using a stirling cycle cryo-cool to eliminate dark current.
Cryocooling and Calibration Components
Prism Assembly
A second cryo-cooler was used to cool the spectrometer optics to 200K to eliminate thermal background radition, and thereby increase the detection sensitivity of the system significantly. Cooling the optics required us to mount the optics in a dewar along with the detector array. This was very challenging because the optics needed to be isolated from the warm dewar walls, and it also need to stay in alignment after cool-down. The most challenging optics to maintain in alignment were the beam shearing prisms shown at left.
Flaming Teflon
First Spectrum Interferogram
The operation of the TIRSCS is shown on the far left where the laser is firing at themal paper mounted on teflon. The teflon spectrum is shown below the plume photo. The very first interferogram and spectrum captured by the TIRSCS are shown on the immediate left. This is a spectrum of a wavy long pass filter.