Advanced Digital Signal Processing for Hybrid Lidar
Quarterly rept. 1 Jan-30 Mar 2012
CLARKSON UNIV POTSDAM NY SCHOOL OF ENGINEERING
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Backscatter reduction is a critical stage in enhancing the usable range of any hybrid lidar-radar scheme that is deployed into a turbid underwater environment. In a highly scattering environment, many photons reaching the detector will have scattered off particulates in the water, while relatively few photons reaching the detector wifl have made the round-trip to and from the object of interest. This will cause the system to detect an object whose range is near the volumetric center of the scattering region, rather than the detecting the range to the object of interest. A similar problem is encountered in the radar areas of moving target indication MTI and through-the-wall radar imaging TWRI, in which radar clutter obscures the desired object return l,2j. Researchers in these areas have shown that the clutter has lower spatial frequencies than the object, meaning that the clutter return can theoretically be filtered out by a spatial filter without negatively impacting the target return. The backscatter in the turbid underwater environment is analogous to the clutter in these radar scenarios. An early solution to this problem was the use of delay line cancelers, with more recent work focusing on more sophisticated signal processing solutions such as FFT-based filters. The main idea behind the delay line canceler is that the clutter signal is a low frequency signal, which can be attenuated by the high-pass quality of a differentiator. Further modifications can be made to delay line cancelers to fine-tune the behavior, such as widening the clutter rejection region.
- Optical Detection and Detectors
- Radiofrequency Wave Propagation