3D Measurements in Cargo Inspection with a Gamma-Ray Linear Pushbroom Stereo System

In this paper we present a practical approach for 3D measurements in gamma-ray (or X-ray) cargo inspection. The linear pushbroom sensor model is used for such a gamma-ray scanning system. Thanks to the constraints of the real scanning system, we model the system by using a linear pushbroom model with only one rotation angle instead of three. This greatly simplifies the calibration procedure and increases the robustness of the parameter estimation. Using only the knowledge of the dimensions of a cargo container, we automatically calibrate the sensor and find all the sensor parameters, including the image center, the focal length, the 3D sensor starting location, the viewing direction, and the scanning speed. Then, a semi-automated stereo reconstruction approach is proposed to obtain 3D measurements of objects inside the cargo by using two such scanning systems with different scanning angles to construct a pushbroom stereo system. Experimental results of 3D measurements and visualization of a 3D cargo container and the objects inside are presented. With both the interactive matching procedure and the 3D visualization interface, the 3D measurements could add more value to today’s cargo inspection systems.