Noncontact Terahertz Paintmeter for Real-Time Two-Dimensional Cross-Section Imaging of Paint Film Thickness

Non-contact, remote monitoring of thickness and drying progress of a paint film is required in fields of non-destructive testing and evaluation. For rapid image acquisition of 2D cross-section in paint film, we propose a terahertz (THz) paintmeter based on real-time 2D THz tomography, which is achieved by a combination of electro-optical time-to-space conversion and line focusing of a THz beam on a sample. To evaluate a potential of the proposed method, we demonstrate the real-time monitoring of the paint thickness distribution in a moving paint sample and the drying progress in a wet paint film. The THz paintmeter can be a powerful tool for quality control of the paint film on the inspection during painting process of car bodies or parts on a moving stage.