LADAR System and Algorithm Design for Spectropolarimetric Scene Characterization

We present a new active imaging architecture that enables rapid spectropolarimetric imaging in a compact system. The transmitter laser produces a synchronous cascade of closely spaced wavelengths, each of which is modulated with a unique amplitude pattern. Temporal multiplexing of the optical return signals is used to reduce system cost, size, weight, and power. This architecture enables a single laser and a single detector for all wavelengths and polarization states. This in turn enables pixel-by-pixel scene characterization, which could be used for target identification in future work. The basic hardware and software architecture will be presented in addition to technologies that are being investigated to develop this system architecture. We will introduce analytical expressions for the temporally multiplexed transmitted and detected signals based on the proposed hardware configuration. We then derive optimal and computationally efficient algorithms for the estimation of the overall range per pixel and the reflectivity per wavelength per pixel, as well as the Cramer-Rao lower bound on estimator variance. The bound and simulated performance yield guidelines for the system parameters required to achieve a desired level of fidelity of the spectral and polarimetric reflectivity. The proposed system is validated with laboratory data and explored via simulations.