Researchers have created a quicker and more precise technique for obtaining and reconstructing high-quality 3D surface measurements. This method has the potential to significantly enhance the speed and accuracy of surface measurements utilized in industrial inspection, medical applications, robotic vision, and various other fields.
Researchers developed a faster and more accurate method for acquiring and reconstructing high-quality 3D surface measurements. The new fringe photometric stereo method requires fewer protected fringe patterns, which speeds up the scanning process. Image Credit: Ce Zhu, University of Electronic Science and Technology of China
Traditional 3D imaging works by comparing two viewpoints, similar to how our eyes work together to judge depth. In contrast, our new approach ‘feels’ the surface by projecting light patterns, almost like running a hand over it to detect changes. This can reduce the number of patterns used by more than two-thirds, which greatly speeds up the scanning process, and surprisingly, is even more accurate than the old technique.
Ce Zhu, Research Team Leader, University of Electronic Science and Technology of China
In this study, the researchers outlined their fringe photometric stereo method, demonstrating its ability to achieve high frame rates and micrometer-level accuracy while reducing noise variance by half.
Our approach is ideal for applications demanding real-time scanning, including industrial applications like detecting defects in printed circuit boards, batteries, or oil pipelines as well as medical procedures such as diagnostics and implant customization. It could also help advance robotics by improving human-robot interaction or offering vision guidance for tasks like folding clothes.
Ce Zhu, Research Team Leader, University of Electronic Science and Technology of China
Faster Acquisition Time
Precise 3D surface measurements and reconstructions are commonly obtained through a fringe projection profilometry technique called phase-shifting profilometry. In this method, a sequence of phase-shifted light patterns is projected onto the surface of an object. The reflected images are captured, and the phase differences are analyzed to generate a highly accurate 3D surface map.
However, this method is limited in many applications due to its lengthy scanning time, largely caused by the need for numerous multi-frequency fringe images to analyze phase differences. Traditionally, this step involves triangulation, which converts phase data—limited to a specific range—into continuous values, accurately representing the shape or surface. In their new approach, the researchers developed a technique that bypasses this process, using only a single frequency to significantly reduce the number of required fringe images.
To evaluate their new fringe photometric stereo technique, the researchers assembled an experimental setup with a 1280 × 960 camera equipped with an 8 mm lens and a projector with a resolution of 912 × 1140. Using this setup, they captured measurements of single objects and groups with continuous surfaces, including a human hand, a paper mask, a cloth toy, gypsum geometries, and clay handicrafts.
They further validated their approach with standard plane and sphere models, demonstrating that it effectively reduces noise compared to traditional fringe projection profilometry.
Creating Better Prosthetics
One application that this new method could be particularly useful for is customizing prosthetics. It can quickly acquire high-precision surface information from the residual limb, reducing errors associated with manual measurements and improving the fit of the prosthesis. This would also eliminate the need to apply plaster or other materials to the skin, making the experience much more comfortable for the patient.
Ce Zhu, Research Team Leader, University of Electronic Science and Technology of China
While the method currently provides enhanced scanning speed and accuracy for continuous surfaces, reconstructing the depth of objects with abrupt depth changes remains a challenge.
To overcome this, the researchers are integrating established surface reconstruction techniques from photometric stereo into their method. This enhancement is expected to expand the method’s applicability to more complex scenes and enable a broader range of promising applications.
Journal Reference:
Zhang, G., et al. (2024) Fringe Photometric Stereo. Optica. doi.org/10.1364/OPTICA.531601.