Scene-based Algorithm for Range/Intensity Estimation Correction for the FLASH 3D LADAR System

In many laser radar systems the intensity value's strength is dependent on the reflectivity of the measured surface. High intensity values are necessary for accurate range measurements. When measuring a low-reflectivity surface the returning laser intensity will be low. This, in turn, results in high uncertainty in the range estimate. In this paper, an approach to correct the intensity values are presented which results in more accurate range estimates even on low-reflecting surfaces. Examples are shown using the ASC (Advanced Scientific Concepts) FLASH 3D LADAR sensor. During a data collection several series of measurements characterizing the shape of the return laser pulse from surfaces with known reflectivity were performed. Using principal components analysis (PCA), variation in pulse shape as a function of laser intensity was determined. These data were then used to identify a parametric model that described the variation in intensity values relative to the surface's reflectivity. Based on the model, an approach to systematically adjust intensity values has been developed. In this paper we will also examine laser timing jitter, intensity, and their effects on range estimation.