Multi-thread real-time data processing for an image-based partially coherent light interferometer

A parallel multi-channel partially coherent light interferometer has been built and optimized for 3D surface measurements of artworks at a depth resolution of one micrometer. The technique is based on the well known low coherence interferometry (LCI) principle and it is largely described in literature. Usually it uses a single point measure plus a bi-dimensional scanning system to acquire data from an area. Our instrument is equipped with a bi-dimensional image sensor (CMOS) instead of a one-dimensional photodetector and is able to directly acquire images, i.e. matrices of points, and make 3D measures with a single scanning along the depth direction, avoiding the use of any lateral scanning system. The data from the CMOS are read-out and the frames are sent to the PC via a USB2 connection. In order to perform the measure as fast as possible, data processing is performed in parallel with data acquisition, exploiting multi-thread capabilities of the C++ code. Despite the great data flow, the processing time is limited mainly by the USB2 transferring rate and data are acquired, in this framework, in real-time. We present results on a terracotta artwork under restoration revealing quantitatively the 3D structure of the surface, i.e. volumetric and topographic results. With this contact-less approach, and thanks to the IR radiation used as light source, it is moreover possible to achieve tomographic results, visualizing and actually measuring, the layered structure of a terracotta sculpture.