Online visualization of small defects for a high-speed rotating object with single-pixel oblique detection

High-speed rotating objects are commonly observed in industrial applications and everyday life. The rotation speed is so high that even minor defects might lead to severe consequences. However, online inspection of such small defects is challenging for conventional imaging, as high-speed rotation of the object results in severe motion blur. In this Letter, we propose an online inspection method for detecting small defects in high-speed rotating objects. The method is based on “time-freezing” single-pixel imaging. The method can convert a dynamic imaging problem into a static imaging problem by exploiting the repetition of the object’s rotation. As such, the method can capture a series of images corresponding to different rotation angles of the target object, even when the object is in operation. To inspect small defects on the object’s surface, we propose the use of three equally spaced single-pixel detectors around the object to conduct oblique detection. The oblique detection can enhance the contrast of small features and allow for small defect inspection. We demonstrate the method in imaging an open hard disk that rotates at ~9,700 revolutions per minute. The artificial scratches and fingerprints can clearly be seen in the images reconstructed by the proposed method. We believe that this technique holds potential for online non-destructive testing and safety monitoring of various high-speed rotating machinery.