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Multi-spectral Earth imaging sensors commonly use edge-bonded filter arrays (also known as “butcher blocks”) for spectral selection. These arrays are built from small filter “sticks” that are diced from coated wafers and then bonded together and placed in very close proximity to the detector array. Some filter designs are susceptible to excessive high angle scatter if the filters are constructed under less than ideal deposition conditions. This scatter can lead to optical crosstalk, which degrades system performance. Insufficient specifications and sub-optimum manufacturing practices lead to a phenomenon called angle resolved scatter (ARS), where light that should have been rejected by the filter is scattered into a very high-angle leak path, leading to optical crosstalk. The Landsat Data Continuity Mission’s (LDCM’s) operational land imager (OLI) instrument uses proximal filter arrays for spectral selection, so it is important to quantify the amount of transmitted, scattered light in wavelength ranges outside the pass band. This paper describes the scatter measurement techniques and Bi-Directional Transmission Distribution Function (BTDF) results for 3 OLI filters. |
