Remote Optical Imagery of Obscured Objects in Low-Visibility Environments Using Parametric Amplification
Abstract
The development of unconventional active optical sensors to remotely detect and spatially resolve suspected threats obscured by low-visibility observation conditions (adverse weather, clouds, dust, smoke, precipitation, etc.) is fundamental to maintaining tactical supremacy in the battlespace. In this report, the authors describe an innovative frequency-agile image intensifier technology based on time-gated optical parametric amplification (OPA) for enhanced light-based remote sensing through pervasive scattering and/or turbulent environments. Improved dynamic range characteristics derived from the amplified passband of the OPA receiver combined with temporal discrimination in the image capture process will offset radiant power extinction losses, while defeating the degradative effects of multipath dispersion and diffuse backscatter noise along the line-of-sight on resultant image contrast and range resolution. Our approach extends the operational utility of the detection channel in existing laser radar systems by increasing sensitivity to low-level target reflectivities, adding ballistic rejection of scatter and clutter in the range coordinate, and introducing multispectral and polarization discrimination capability in a wavelength-tunable, high gain nonlinear optical component with strong potential for source miniaturization. A key advantage of integrating amplification and frequency up-conversion functions within a phasematched three-wave mixing parametric device is the ability to perform background-free imaging with eye-safe or longer infrared illumination wavelengths (idler) less susceptible to scatter without sacrificing quantum efficiency in the detection process at the corresponding signal wavelength. We report benchmark laboratory experiments in which the OPA gating process has been successfully demonstrated in both transillumination and reflection test geomextended pathlengths representative of realistic coastal sea.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1997
- Accession Number
- ADA399123
Entities
People
- David E. Bliss
- Robert B. Asher
- Roya A. Hamil
- Stewart M. Cameron
Organizations
- Sandia National Laboratories