Analysis of the measurement accuracy of a thermal 3D sensor for transparent objects

Abstract

Transparent, translucent, jet-black, or reflective surfaces are non-cooperative for 3D measurements using pattern projection in the visible or near-infrared spectrum. They either require additional object preparation like spraying or cannot be measured at all. Previous studies have demonstrated that “shape from heating” is an appropriate technique to capture such non-cooperative surfaces. Patterns are projected with long-wave infrared radiation which is absorbed on the surface and generates a heat pattern. The re-emitted thermal radiation can be recorded in the mid-wave infrared by a stereo camera setup. In this contribution, we present the experimental implementation of a thermal 3D sensor based on sequential fringe projection. We performed a sensor characterisation in terms of measurement accuracy and speed following the VDI/VDE guideline 2634 part 2. Furthermore, we developed a test specimen which allows for comparing our thermal 3D sensor with alternative 3D measurement techniques.