Using a Single Imager and Structured Light for High Resolution and Accurate 3D Mapping of Microscopic Terrain on Mars

The navigational sensor onboard PIXL, the Micro Context Camera, is equipped with active LED multispectral floodlight and laser structured light capabilities. The first ensures a homogeneous lighted scene, to capture the optical context of the surface. The structured light consists of 2 illumination sources, each with their individual dot pattern projected onto the surface: One designed to keep optimal distance along the ∼ 120 μ m XRF pencil beam, during PIXL's XRF scan, and one designed for broad coverage enabling safe assessment of the terrain. By virtue of triangulation, including thermal calibration, the distance to the terrain is measured to accuracies of ∼ 50 microns. While the structured light offers very accurate absolute range measurements, the projected dot pattern is sparse, leaving much terrain area uncovered. The aim here is to resolve a high terrain resolution, making use of the accurate range measurements using the structured light. Often a terrain is resolved without the scaling dimension, and only produces a disparity map. To resolve the scale factor, one could rely on the actual motion between two observations, i.e. the baseline. However, due to significant positional drift due to the thermal environment on Mars, the usage of the structured light provides the scale factor. Instead, we merge the best of both worlds, applying a highly accurate range measurement to a high-resolution disparity map. This approach makes use of the motion capabilities of PIXL, using the hexapod actuator, or the robotic arm of the rover, but is not dependent on any motion metrology knowledge. Furthermore, this approach can be utilized on any single imager system with structured light and actuator capabilities.