Optical filters utilizing more of the spectral band maximize performance and spur innovations in weather satellites and lidar.
From weather satellites to lidar for self-driving cars, precision optical filters play a vital role in making sensors work. Today, the ability to interrogate more and more sections of spectrum promises enhanced capabilities for these and other applications. On the horizon are materials and techniques that could make precision optical filters tunable. However, performance, cost, and other issues must be addressed.
An illustration of today’s state-of-the-art capabilities can be found in the next-generation weather satellite GOES-16, which began operating in late 2017. The satellite collects three times the data at four times the resolution of its predecessors, thanks to precision optical filters that span the spectrum, from blue at 470 nm to LWIR at 13.3 µm.
“It does cover a broad spectral range with a number of high-performance bands, especially in the longwave and midwave [IR] that allows some additional details,” said Dave Harrison, business development manager for image and sensing at Materion Corp.’s Precision Optics, based in Westford, Mass. The company supplied the filters used in the satellite.
The satellite’s Advanced Baseline Imager has 16 spectral bands, compared to five for previous GOES imagers. The increase is part of an overall trend of more spectral bands in instruments.
For every band, the goal is to maximize transmission of a spectral region and block everything else, with a sharp slope in the transition region. This is accomplished by putting down multiple layers of coatings on a substrate, with perhaps 100 or more of the right thickness and composition needed to create the desired spectral response.
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