Jinan University captures snapshots of fast-spinning objects

21 May 2025

Single-pixel sensor method improves monitoring of turbine blades and jet engines.

Objects rotating at high speed are a feature of modern engineering in various fields, and online inspection of them is a critical challenge.

A project at China's Jinan University has now developed a new imaging platform able to detect the rotation speed of a such objects and take images of the target in real time.

Published in Optics Letters, the findings could enable continuous monitoring of components like turbine and jet engine blades, to help detect early signs of wear or damage.

"Capturing clear images of fast-spinning objects is challenging because they tend to blur or look grainy," said team member Zibang Zhang from Jinan University.

"Although high-speed cameras can help, they are expensive and can't be used for long periods. Our method overcomes this challenge by virtually freezing time, exploiting the repetitiveness of the object's motion."

The imaging platform is based on the use of structured illumination and single-pixel detection. Patterned light is projected onto a scene, and the resulting intensity variations captured with a single-pixel sensor, allowing a computer to reconstruct a detailed image without needing a traditional camera detector.

Compared to traditional camera sensors, single-pixel detectors have higher sensitivity, a wider dynamic range and faster response, commented the project team. This makes them suitable for imaging fast-spinning objects.

"The key to the method is synchronization, which essentially freezes time by keeping the target object stationary compared to the pattern projection," explained Zhang. "By using synchronized illumination, we converted a dynamic imaging problem into a static imaging problem."

Integrated into smart manufacturing systems

The Jinan platform uses a digital micromirror device, capable of projection speeds up to 22,000 Hz, to illuminate the rotating object with a series of patterns. The single-pixel detector acquires a measurement for each pattern projection, and the projector switches to the next pattern when the object has spun around once.

To synchronize the projection, the researchers aimed a laser at one blade of the spinning object to create backscattered pulses, and used this as a timing mechanism. When the number of pulses matches the number of blades, it signals the projector to switch patterns, allowing clear imaging of the rotating object using just the single-pixel detector.

In trials, the researchers showed that their device could reconstruct real-time high-quality still images of a model jet engine 11 centimeters in diameter rotating at about 2,170 rpm, and a CPU cooling fan rotating at 14,700 rpm. The same approach, which requires no prior knowledge about an object, can also be used to image objects with unstable rotation speed.

"The system could detect wear or cracks that can develop in high-speed metal cutting and grinding tools over time, without stopping the machines," said Zhang. "In the future this technology could be integrated into smart manufacturing systems, aircraft maintenance platforms or even home appliances like car engines, blenders, fans, air conditioners and hard drives, making these devices smarter and safer."