Yirong Wu

Inverse synthetic aperture LADAR demonstration: system structure, imaging processing, and experiment result

A long-distance inverse synthetic aperture LADAR (ISAL) imaging experiment outdoors over 1xa0km for cooperative targets is demonstrated, which gets a two-dimensional high-resolution image with resolution exceeding 2.5xa0cm. The system utilizes an electro-optic in-phase and quadrature modulator to output a linear frequency-modulated continuous waveform (LFMCW) with a bandwidth of 6xa0GHz and pulse repetition frequency (PRF) of 16.7xa0KHz. For the problem of the coherence of the laser, the effects of the coherent processing interval (CPI) and time delay of the local oscillator (LO) on the coherence are discussed. The fiber delay line is set and the CPI is reduced to lower the requirement of the frequency stability of the laser source. The images are formed by two-dimensional Fourier transform and joint time-frequency transform methods, respectively. In this paper, we present the system structure, imaging processing, and the experiment result in detail. The experiment result validates the performance of our system for ISAL imaging.

Experiment of inverse synthetic aperture ladar at 1.1km

This manuscript describes an airborne SAL system for remote targets imaging. We have recently completed an experiment of ISAL at 1.1 km outdoor using the system. Relative motion was provided by a rotating platform with three cubes on while the SAL system kept stationary. System, signal collection, processing and the results are described in the paper. The result showed that the system had the ability to image for moving targets. Accurate rotating platform and complex target will be used to achieve further ISAL experiments on the next stage.

Three-dimensional inverse synthetic aperture lidar imaging for long-range spinning targets

We present a three-dimensional (3D) imaging method for long-range spinning targets. This method acquires multi-angle two-dimensional (2D) images of spinning targets by the inverse synthetic aperture lidar (ISAL) imaging technique. The 3D distribution of the scattering coefficients of a target has a mapping relationship with the series of 2D images. This mapping is analyzed, and a 3D Hough transform is used to implement inverse mapping. The parameter space of the Hough transform is the estimation of the 3D distribution of the scattering coefficients. The 3D point spread function obtained by the method has narrow main lobe widths and sufficiently low side lobes to achieve high image quality, which is verified by computer simulations. In the simulations, the main lobe widths in the three dimensions are 0.29xa0cm, 0.29xa0cm, and 3.48xa0cm, respectively. In outdoor experiments, 3D images of targets at 1xa0km away from the lidar were obtained. The images clearly show the 3D shape of targets.