Real-time microscopic phase shifting profilometry

A real-time microscopic profilometry system based on digital fringe projection and parallel programming is presented. Structured light patterns are projected onto an object through one pathway of a stereoscopic operation microscope. The patterns are deformed by the shape of the object and are then recorded with a high-speed CCD camera placed in the other pathway of the microscope. As the optical pathways of both arms are separated and reach the same object point at a relative angle, the recorded patterns allow the full-field object height variations to be calculated and the three-dimensional shape to be reconstructed by employing standard triangulation techniques. The projected line patterns are pre-generated digitally and stored in the on-board flash memory of a compact pico-projector, composed of a light engine and a rapidly-switching digital micromirror device. Applying proper hardware triggering, the projector-camera system is synchronized to capture up to 120 unique deformed line patterns per second. Using standard 4-step phase shifting profilometry techniques and applying graphics processing unit programming for fast phase wrapping, scaling and visualization, we demonstrate the capability of the proposed system to generate 30 microscopic height maps per second. This allows the qualitative depth perception of the stereomicroscope operator to be enhanced by live quantitative height measurements with depth resolutions in the micrometer range.
A video of a real-time 3D measurement of a latex membrane is presented as it is deformed dynamically by the tip of a pen.