3D shape measurement of objects with uncooperative surface by projection of aperiodic thermal patterns in simulation and experiment

Abstract. 3D shape measurement systems based on diffuse reflection of projected structured light are widely used. Unfortunately, this measurement principle does not work for uncooperative materials, i.e., materials with optical properties such as being glossy, transparent, absorbent, or translucent. Recently, it was shown that 3D reconstruction of an uncooperative object can be performed by a two-step process. In the first step, the object absorbs a projected thermal pattern. In the second step, after energy conversion, the object surface reemits a diffused thermal pattern according to Planck’s law. To achieve high 3D result qualities in short measurement times, projection parameters such as irradiance pattern and irradiation period must be optimized depending on optical and thermal material properties, e.g., complex spectral refractive index, thermal conductivity, specific heat capacity, or emissivity. Therefore, we have developed a simulation tool to describe the entire measurement process beginning with the projection unit, followed by the interaction of the irradiation with the measurement object, reemission of thermal radiation and recording unit, and finally the 3D reconstruction. In this contribution, we present our simulation tool, verify it with measurement results, and apply it to investigations of the influence of projection and material parameters on the 3D result quality.