High-Coverage 3D Scanning through Online Structured Light Calibration

Many 3D scanning techniques rely on two or more well calibrated imaging cameras and a structured light source. Within these setups the light source does not need any calibration. In fact the shape of the target surface can be inferred by the cameras geometry alone, while the structured light is only exploited to establish stereo correspondences. Unfortunately, this approach requires each reconstructed point to exhibit an unobstructed line of sight from three independent points of views. This requirement limits the amount of scene points that can be effectively captured with each shot. To overcome this restriction, several systems that combine a single camera with a calibrated projector have been proposed. However, this type of calibration is more complex to be performed and its accuracy is hindered by both the indirect measures involved and the lower precision of projector optics. In this paper we propose an online calibration method for structured light sources that computes the projector parameters concurrently with regular scanning shots. This results in an easier and seamless process that can be applied directly to most current scanning systems without modification. Moreover, we attain high accuracy by adopting an unconstrained imaging model that is able to handle well even less accurate optics. The improved surface coverage and the quality of the measurements are thoroughly assessed in the experimental section.