Pulse compression techniques to improve modulated pulsed laser line scan systems

Robert W. Lee; Justin K. Nash; Brandon Cochenour; Linda J. Mullen

doi:10.1117/12.2179824

19 May 2015 Pulse compression techniques to improve modulated pulsed laser line scan systems

Robert W. Lee, Justin K. Nash, Brandon Cochenour, Linda J. Mullen

Proceedings Volume 9459, Ocean Sensing and Monitoring VII; 94590C (2015) https://doi.org/10.1117/12.2179824
Event: SPIE Defense + Security, 2015, Baltimore, MD, United States

Abstract

A modulated pulse laser imaging system has been developed which utilizes coded/chirped RF modulation to mitigate the adverse effects of optical scattering in degraded visual underwater environments. Current laser imaging techniques employ either short pulses or single frequency modulated pulses to obtain both intensity and range images. Systems using short pulses have high range resolution but are susceptible to scattering due to the wide bandwidth nature of the pulse. Range gating can be used to limit the effects of backscatter, but this can lead to blind spots in the range image. Modulated pulse systems can help suppress the contribution from scattered light in generated imagery without gating the receiver. However, the use of narrowband, single tone modulation results in limited range resolution where small targets are camouflaged within the background. This drives the need for systems which have high range resolution while still suppressing the effects of scattering caused by the environment. Coded/chirped modulated pulses enable the use of radar pulse compression techniques to substantially increase range resolution while also providing a way to discriminate the object of interest from the light scattered from the environment. Linearly frequency chirped waveforms and phase shift keyed barker codes were experimentally investigated to determine the effects that pulse compression would have on intensity/range data. The effect of modulation frequency on the data produced with both wideband and narrowband modulation was also investigated. The results from laboratory experiments will be presented and compared to model predictions.

Citation Download Citation

Robert W. Lee, Justin K. Nash, Brandon Cochenour, and Linda J. Mullen "Pulse compression techniques to improve modulated pulsed laser line scan systems", Proc. SPIE 9459, Ocean Sensing and Monitoring VII, 94590C (19 May 2015); https://doi.org/10.1117/12.2179824

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