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. We analyzed a portion of these data to assess the effectiveness of this system for object detection. We present our measurements and discuss the analysis results.

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. Real-time images were digitally recorded, and software was used to enhance the data and increase the camera temperature sensitivity to less than a millidegree Kelvin. The minimum discernible intensity was 10(-3) that of a globar source at 900 K, and emission from SF(6)could be imaged at ambient temperatures.

Improved crystal quality and harmonic generation in GaSe doped with indium.

GaSe crystals were doped with indium, and improvements in the mechanical properties and second-harmonic efficiency over pure crystals were obtained. Both effects are due to an improvement in the crystal quality of the material, and it was shown that doping with low levels of indium did not alter the intrinsic value of the nonlinear d coefficient.

White-light imaging by use of a multiple passband acousto-optic tunable filter.

White-light imaging was accomplished by operation of a TeO(2) acousto-optic tunable filter (AOTF) with 40 simultaneous overlapping passbands from 400 to 700 nm. The AOTF was chromatically compensated by a wedge applied to the output surface of the AOTF, and the measured spatial resolution correlated well with predictions. Switching off specific rf's applied to the AOTF produced optical rejection corresponding to the inactive passbands. A rejection ratio of 30 dB was demonstrated, and the rejection level was found to be controlled by leakage through the sidelobes of adjacent passbands.

Randomly phased geometrical laser array.

A novel geometrical laser array is presented in which high far-field intensities can be generated without phase control of the laser elements. The array was analyzed by randomly varying the phasing of the elements and calculating the maximum far-field intensity. In the worst possible phasing conditions, the maximum far-field intensity remained high and was nearly constant with regard to the number of array elements. By increasing the geometrical spacing factor, the maximum intensity will approach that of a perfectly phased array.