High-resolution sequential thermal fringe projection technique for fast and accurate 3D shape measurement of transparent objects

Three-dimensional (3D) shape measurement systems based on diffuse reflection of projected structured light do not deliver reliable data when measuring glossy, transparent, absorbent, or translucent objects. In recent years, we have developed a method based on stereo recording with infrared cameras and projection of areal aperiodic sinusoidal thermal patterns to detect such objects. However, the measurements took longer than 10 s, up to minutes; moreover, the measurement accuracy was improvable. Now, we have succeeded in both drastically reducing measurement time and significantly increasing measurement quality. This finally provides a technique for reliably measuring transparent objects, e.g., in series production. We demonstrate measurement examples achieved within 1 s and with 3D standard deviations less than 10 mu m. (C) 2021 Optical Society of America

Automated summary

A new method based on infrared cameras and thermal patterns has been developed to measure glossy, transparent, absorbent, or translucent objects, drastically reducing measurement time and improving measurement accuracy. This technique demonstrates reliable measurement of transparent objects in series production, achieving measurement within 1 second with 3D standard deviations less than 10 μm.