With the availability of small arc size high intensity discharge lamps a new polarization recovery system using polarization recycling in a light pipe is made possible. Combining light integration/homogenization with polarization recovery in an integrator rod leads to cost reduction and smaller light engines. The polarization recovery light pipe utilizes a reflective polarizer that works at normal incidence at its exit face and a high-reflective mirror with a transparent circular aperture at the entrance face. The reflected linearly polarized light is recycled by rotating its polarization by 90 degree(s) during one round-trip in the integrator rod. Different possibilities for achieving this polarization rotation, including retarders and phase control coatings are investigated. As much as 70% of the rejected polarized light can be recaptured with this system.
A wide-field ultraviolet lens was developed under a contract from the Massachusetts Institute of Technology Center For Space Research in support of the NASA High Energy Transient Experiment (HETE). This 35 mm f/2.5 seven element lens operates over a broad portion of the near-ultraviolet spectrum and over a 52 degree field of view. Operation at cryogenic temperatures required that the lens system exhibit minimal change in focus with temperature. Aluminum was selected as the lens barrel material based on athermalization issues and the desire to minimize weight. Elastomeric bonding of elements into subcells was used for assembly along with a single adjustable airspace to compensate for tolerances.