Notch filtering using a multiple passband AOTF in the SWIR region.

A notch filtering operation was accomplished using a TeO acousto-optic tunable filter (AOTF) with 16 simultaneous overlapping passbands in the shortwave infrared wavelength region. By switching off specific radio frequency signals applied to the AOTF, laser wavelengths corresponding to the inactive passbands are rejected, providing see-through capability with the remaining wavelengths. The rejection level was determined by leakage through the sidelobes of adjacent passbands, as was shown by theory and corresponding measurements.

Object detection with a field-portable spectropolarimetric imager.

A relatively compact, lightweight, and programmable spectropolarimetric imager was used to collect spectral and polarization data from various objects and backgrounds, both in the laboratory and in field tests. This imager uses a tellurium dioxide (TeO2) acousto-optic tunable filter and a liquid-crystal retardation plate with a CCD camera. The spectral images were collected 450-1000 nm at 10- or 20-nm intervals at two or four polarization settings for each spectral interval.

Imaging spectroradiometer for the 8-12-num region with a 3-cm(-1) passband acousto-optic tunable filter.

An imaging spectroradiometer was built covering the 8-12-mum region with an acousto-optic tunable filter with a 3-cm(-1) passband, along with a commercial infrared camera. The system field of view was 7.5 degrees x 10 degrees , and the resolution was nearly diffraction limited.

Acousto-optic tunable filter imaging spectrometer with full Stokes polarimetric capability.

Polarization is an important addition to spectral imaging in detecting and identifying objects of interest, and simple linear polarization measurements are often inadequate. Full polarization analysis can give additional information for discrimination where the polarization state is completely described by the Stokes parameters. An acousto-optic tunable filter (AOTF) imaging system was built incorporating two liquid-crystal variable retarders (LCVRs) that can provide complete spectral-polarimetric analysis, and it is believed to be the first demonstration of a full Stokes polarimetric AOTF spectral imaging system with no moving parts.

Acousto-optic tunable filter sidelobe analysis and reduction with telecentric confocal optics.

The acousto-optic tunable filter (AOTF) has optical sidelobes that are due to the acoustic field produced by the transducer. These sidelobes were analyzed by wave-vector phase matching between the optical and acoustic fields, which correlated with measurements made with a TeO2 AOTF. A white-light point source was filtered and imaged, showing reasonably large and slowly decreasing sidelobes covering a large spectral range.