Obtain images of 3D objects quickly and efficiently

A team of experts from the University of Barcelona (UB) and the company Sensofar Tech has designed an innovative technology to obtain three-dimensional images of a study sample quickly, accurately and non-invasively. The new system is capable of characterizing the three-dimensional topography of an object with a speed and spatial resolution that exceed those of current systems for identifying and recognizing objects in three dimensions.

This system is a new advance in the field of optical profilometry, a technique that is commonly applied in quality control and inspection of parts in various business sectors, from components manufactured with 3D printers to coronary prostheses (stents) or the identification of defects or roughness on surfaces. This technological innovation is the work of a team that includes experts Martí Duocastella and Narcís Vilar, from the Faculty of Physics of the UB, and Roger Artigues and Guillem Carles, from the company Sensofar Tech.

More precision and speed to characterize 3D samples

Optical profilometry is a discipline that measures the three-dimensional profile of objects using light. «It is a decisive methodology in areas such as quality control in industrial processes or, on a scientific scale, in the measurement of micro and nanostructures. Typically, the measurement of the profile of a micrometric object is achieved using a microscope, with which a collection of hundreds of images is obtained at different heights and planes of the object,” details Martí Duocastella, professor at the Department of Applied Physics and member of the Institute. of Nanoscience and Nanotechnology of the UB (IN2UB).

«This is a process – continues the professor – that involves scanning the sample plane by plane, an inherently slow process. “In the new work, we present an innovation that is based on drastically reducing the acquisition time of this collection of images.”

The new system is capable of operating at the micrometer scale on relatively large samples and in real time (up to sixty topographies per second). “Current technological systems can only achieve these speeds in very fine samples, or in large samples, but with low spatial resolution,” says Duocastella. «It is likely that our system could have a more important impact due to its ability to characterize dynamic processes. Thus, thanks to our technology, we can characterize the rapid movement of a small device—with a gas sensor—in 3D, something that until now was impossible.

The technological innovation designed by the University of Barcelona and the company Sensofar Tech facilitates the characterization of the three-dimensional structure of objects much more quickly, accurately and economically than through other current systems. (Photo: University of Barcelona. CC BY)

Scan the sample thousands of times per second

In order to implement the new technology, «our idea is to intelligently interrogate the sample, similar to what is done in the game “Who's who?” Until now, profiles are acquired by asking in each plane if we had information: “Is the sample in plane 1?”, “Is it in plane 2?”, “In plane n?”. Each question involved making an image. On the other hand, in our work we show that it is possible to interrogate different planes together: “Is the sample between plane 1 and plane 7?” The result is that we achieved an enormous reduction in the number of images: if before we needed one hundred images, now we have enough with eight,” says the expert.

The new technique requires rapid scanning of the sample and synchronization of pulsed light of different durations. For fast scanning, an ultrafast liquid lens is used, developed by Professor Duocastella at Princeton University (United States), which allows scanning thousands of times per second. For synchronization, an in situ programmable gate array (FPGA) was used, which generated the signal to pulse the light and capture the camera image.

One of the most difficult phases was trying to achieve high data acquisition speeds. «In this case, the signal received from the sample is weaker, and greater signal precision is needed. However, thanks to the work of doctoral student Narcís Vilar, we were able to overcome these obstacles and successfully implement his new technology,” says Duocastella.

The team presents the technical details of the new technology in the academic journal Nature Communications, under the title “Fast topographic optical imaging using encoded search focal scan.” (Source: University of Barcelona)