METHODS TO INCREASE THE NUMBER OF FILTERS PER OPTICAL PATH IN A DOWNHOLE SPECTROMETER.

摘要

Downhole spectrometer tools are provided with two ways to increase the number of filters on an optical path, A first approach employs multiple filter wheels that rotate alternately in a common plane to intersect, the optical path. Portions of the wheels are cut out to avoid mechanical interference between the wheels. A second approach drives the one or more filter wheels with a wobble that causes the filters to trace one or more hypocyeloidal curves that each intersect the optical path.