GRIN optics for multispectral infrared imaging

Graded index (GRIN) optics offer potential for both weight savings and increased performance but have so far been limited to visible and NIR bands (wavelengths shorter than about 0.9 μm). NRL is developing a capability to extend GRIN optics to longer wavelengths in the infrared by exploiting diffused IR transmitting chalcogenide glasses. These IR-GRIN lenses are compatible with all IR wavebands (SWIR, MWIR and LWIR) and can be used alongside conventional wideband materials. Traditional multiband IR imagers require many elements for correction of chromatic aberrations, making them large and heavy and not well-suited for weight sensitive platforms. IR-GRIN optical elements designed with simultaneous optical power and chromatic correction can reduce the number of elements in wideband systems, making multi-band IR imaging practical for platforms including small UAVs and soldier handheld, helmet or weapon mounted cameras. The IR-GRIN lens technology, design space and anti-reflection considerations are presented in this paper.