Single-pixel imaging (SPI) is a novel imaging technique that has been widely studied in recent years. It retrieves spatial information of the target by using a single-pixel detector with no spatial resolution, minimizing the array size of imaging detector, that has unique advantage of making up for the shortcomings of the existing focal plane arrays (FPAs) imaging technology. It is believed that this SPI technology has great application value in special waveband imaging that array detector technology is underdeveloped or expensive.
After nearly 30 years of study, scientists have made great progress in the development of SPI. Achievements have been made in various applications, including special waveband imaging, e.g. terahertz and X-ray imaging, extremely low-light level imaging and 3D imaging.
However, due to its unique imaging mechanism, imaging speed of SPI is fundamentally limited by the refresh speed of a core device of the system, the spatial light modulator. This limitation constrains the speed of SPI at a slow level, which restricts its application to general imaging scenarios. The advantage of high detection bandwidth of single-pixel detectors cannot be utilized.
To address this problem, researchers at Shandong University propose and demonstrate a time-resolved single-pixel imaging (TRSPI) technology. This imaging technology is designed for high-speed but periodic scenes. It can realize ultrafast sampling of high-speed targets by fully exploring the spatial correlation information between a dynamic scenes and dynamic coded apertures. Based on ultrafast sampling, high-speed targets can be imaged by applying a typical SPI reconstruction. Imaging speed of TRSPI is ultimately determined by the acquisition speed of single-pixel detector. Therefore, an imaging speed of million frame-rate can be easily achieved by only using ordinary photodiodes.
The relevant research results are published in Photonics Research, Volume. 10, Issue 9, 2022 (Wenjie Jiang, Yongkai Yin, Junpeng Jiao, Xian Zhao, and Baoqing Sun. 2,000,000 fps 2D and 3D imaging of periodic or reproducible scenes with single-pixel detectors[J]. Photonics Research, 2022, 10 (9): 2157-2164).
TRSPI proposed in this work can achieve ultrafast imaging not only in 2D but also in 3D imaging by combining of Fourier transform profilometry (FTP). For the general imaging environment, they also propose a digital calibration scheme to ensure the reconstructed image quality (Fig.1).
Fig. 1 Experimental arrangement. (a) Complete diagram of the 2D imaging experimental setup. (b) Single-pixel detection module of the 3D imaging system.
The final experimental results show that the proposed scheme achieves 2D and 3D imaging with high spatial resolution and high image quality at an imaging speed of 2,000,000 fps (Fig.2).
Fig. 2 Imaging results. (a) 2D imaging results at different time instants in a resolution of 256×256 pixels. (b) 3D imaging results at different time instants with a measurement accuracy of over 95%.
Dr. Wenjie Jiang believes that the proposed imaging scheme excavates the application potential of SPI, which is of great significance for the development of SPI. On the other hand, this work also provides a powerful alternative for high-speed imaging. In the future, with a combination of high-speed single photon avalanche detector, imaging speed of the proposed scheme is expected to reach trillion frame rate or even higher.