Squint-looking differential synthetic aperture ladar: signal processing and experimental demonstration

Area of Science:

• * Applied Physics
• * Optical Engineering
• * Signal Processing

Background:

• * Synthetic Aperture Ladar (SAL) systems offer high-resolution imaging capabilities.
• * Squint-looking configurations in SAL present unique challenges for image formation.
• * Common mode random phase errors (RPE) can degrade image quality in SAL systems.

Purpose of the Study:

• * To detail the signal processing mathematics for squint-looking differential synthetic aperture ladar (DSAL).
• * To experimentally demonstrate high-resolution image formation using DSAL.
• * To evaluate the robustness of the DSAL technique against common mode random phase errors.

Main Methods:

• * Developed data processing procedures based on DSAL principles and squint-looking synthetic aperture radar (SAR) theory.
• * Implemented a DSAL setup in "step-stop" strip map mode using a 1550 nm frequency chirped laser.
• * Introduced large common mode random phase error (RPE) using a random phase generator.

Main Results:

• * Achieved high-resolution DSAL images of a cooperative target at 1.85 m distance.
• * Demonstrated imaging at squint-looking angles of -10° to +10°.
• * Successfully focused DSAL images with and without significant RPE, validating the processing steps.

Conclusions:

• * The developed DSAL signal processing effectively forms high-resolution images.
• * The DSAL technique is robust in removing common mode phase errors in squint-looking configurations.
• * Experimental validation confirms the practical applicability of the DSAL approach for clear imaging.