Hyperspectral imaging (HSI) is a technology that is rapidly transitioning from laboratory research and field demonstration to real-world deployment for a variety of applications. These applications include precision agriculture, manufacturing process monitoring, mineral and petroleum exploration, environmental management, disaster mitigation, defense intelligence/surveillance/reconnaissance for threat detection and identification, as well as a host of applications within the bio-medical field. Application-specific algorithms are continuously being developed to support the world-wide expanding use of HSI.
Hyperspectral imaging systems are finding broader applications in both the commercial and aerospace markets. It is becoming clear that to optimize the performance of these systems, their instrument transfer function needs to be tailored for each application. Vis-SWIR systems in the full 400nm to 2500nm waveband present particular design and manufacturing challenges. A single blazed grating is inadequate for a system operating in the full vis-SWIR wavelength range. In addition, optical materials and broad band coatings present a challenge for non-reflective systems. An understanding of the application and wavelengths of interest, combined with a judicious choice of a focal plane array, can then lead to an optimized system for the specific application. The ability to tailor the grating and manufacture a wide variety of grating profiles and substrate shapes becomes a significant performance enabler. This paper will discuss how the use of optical, coating, and grating design/analysis software, combined with grating manufacturing techniques assure meeting high performance requirements for different applications.
A range-gated underwater imaging system is described that utilizes a frequency doubled, Q- switched Nd:YAG 30 Hz laser source for illumination and a fast-gated microchannel plate intensified CCD array camera for detection. Laser pulse widths of 7 ns are timed relative to comparable camera gates with subnanosecond jitter. Results for a test bed system obtained in a 4 X 4 X 40 ft water tank with various targets are presented. Water quality was varied with the addition of progressive concentrations of Maalox as scattering agent, and monitored with a home-built laser transmissometer. The 1/4 in., high contrast target lines were able to be resolved at ranges exceeding four attenuation lengths. A simple analytical model for image signal-to-noise ratios is presented and a straightforward polarization discrimination scheme suggested for contrast enhancement. Polarization optics were incorporated into the range-gated test bed system and results obtained for targets of varying characteristic depolarization. In all but a few cases where target and background depolarizations were similar, the signal to noise is enhanced in spite of rejection of orthogonal polarization signal. Issues regarding the evolution of the test bed system to field operation are discussed and significant progress in the development of appropriate miniaturized and ruggedized components is presented
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