Range compressed holographic aperture ladar

Date of Award

2016

Degree Name

Ph.D. in Electro-Optics

Department

Department of Electro-Optics and Photonics

Advisor/Chair

Advisor: Bradley D. Duncan

Abstract

3-D holographic ladar uses digital holography with frequency diversity to allow the ability to resolve targets in range. A key challenge is that since individual frequency samples are not recorded simultaneously, differential phase aberrations may exist between them making it difficult to achieve range compression. Specific steps for this modality are described so that phase gradient algorithms (PGA) can be applied to 3-D holographic ladar data for phase corrections across multiple temporal frequency samples. Substantial improvement of range compression is demonstrated in a laboratory experiment where our modified PGA technique is applied. Additionally, the PGA estimator is demonstrated to be efficient for this application and the maximum entropy saturation behavior of the estimator is analytically described. Simultaneous range-compression and aperture synthesis is experimentally demonstrated with a stepped linear frequency modulated waveform and holographic aperture ladar. The resultant 3D data has high resolution in the aperture synthesis dimension and is recorded using a conventional low bandwidth focal plane array. Individual cross-range field segments are coherently combined using data driven registration, while range-compression is performed without the benefit of a coherent waveform. Furthermore, a synergistically enhanced ability to discriminate image objects due to the coaction of range-compression and aperture synthesis is demonstrated. Two objects are then precisely located in 3D space, despite being unresolved in two directions, due to resolution gains in both the range and azimuth cross-range dimensions.

Keywords

Synthetic aperture radar, Holography, Three-dimensional imaging, Electrical Engineering, Optics, Physics, Remote Sensing, Synthetic aperture Ladar, aperture synthesis, digital holography, 3D, range compression, pulse compression, PGA

Rights Statement

Copyright © 2016, author

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