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8 October 1998 Ultrathin film neutral density filter set for the infrared
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A set of neutral density filters covering the optical density range of OD 1 through OD 10 has been designed and constructed for use as calibration and reference filters in the infrared. The filters are optically flat, with a variation of at most one OD within the spectral range of 2 micrometer to 25 micrometer. Many filters exhibit better than 0.5 OD variation. They each are constructed of a metallic film supported by an ultrathin (100 nm) polyimide film substrate that minimizes the chance of etaloning within the filter. The polyimide substrate is sufficiently robust to withstand handling in a laboratory environment and provide long-lived performance. This paper details the theoretical model used to determine appropriate materials for these filters, as well as the vacuum deposition processes developed to construct them.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Glenn Lefever-Button, Joakim F. Lindblom, and Forbes R. Powell "Ultrathin film neutral density filter set for the infrared", Proc. SPIE 3425, Optical Diagnostic Methods for Inorganic Transmissive Materials, (8 October 1998);

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