Linear Fresnel Spectrometer Chip with Gradient Line Grating

NASA's Langley Research Center has built a very small spectrometer by integrating a differential linear Fresnel lens onto an imaging chip. NASA is using the lens/chip in a very small spectrometer that will be mounted on the tires of a rover to analyze soil on the Moon or Mars. The spectrometer is useful for space-constrained applications. It combines good resolution with small size and potentially reduced manufacturing costs. The ultra-compact integration of the spectrometer is enabled by the use of an optimized Fresnel grating. Since Fresnel imaging works as valid focal points of spectrum within the short optical distance, the shorter optical path length required (compared to a traditional Fraunhofer lens) enables the small size. Further, the evolution to a differentially linear Fresnel lens (instead of circular Fresnel) avoids the need for aperture slit driver electronics and moving parts, and simplifies manufacturing. The linear Fresnel gratings lend themselves to mass production via plastic injection molding or nano-imprint lithography. NASA is seeking partners to develop the spectrometer for commercial applications.