Filter Wedge Spectrometer for Field Use

Abstract

Two spectrometers, utilizing interference filter wedges, have been constructed for measurements under field conditions. One, operating from 1.6 micro. to 5.4 micro, has been flown unpressurized in an airplane to 12.2 km; the other, operating from 7.4 micro to 14.6 micro has been flown in a balloon to 33.3 km. Both instruments performed well, proving the interference filter wedge as avaluable tool for spectral measurements, especially in hostile environments.

Portable, Near-infrared Spectrophotometer for Rapid Soil Analysis

“…Worner (1989) constructed a visible spectrophotometer using a prism and a linear array detector in an attempt to overcome the environmental problems seen with gratings. Circular variable interference filters, which have spectral characteristics that can be varied by means of physical rotation, have been used in rugged field instruments for portable color measurement (Jauch, 1979) and for airborne infrared spectral measurements (Hovis et at, 1967).…”

Miniaturization of optical spectrometers

“…Another strategy to increase the ease of fabricating a wide range of transmission wavelengths is to use a linear variable filter, which is typically either a wedged (52) or composition-graded filter (53), where the transmission or reflection spectrum varies continuously along one axis of the filter. One approach here is to simply scan a spectrum by sliding the filter over a single detector (54). However, this is relatively slow and necessitates extra moving parts.…”