Objective  The pursuit of high-quality optical rapid imaging through scattering media is crucial for real-time and dynamic imaging applications. The primary focus is on achieving excellent imaging quality within a short camera exposure time, necessitating the identification and mitigation of factors that degrade optical rapid imaging. In this study, the single-shot speckle autocorrelation method, leveraging the optical memory effect, is employed to investigate optical rapid imaging through scattering media. To address the challenge of spatial coherence in laser beams, a rotating diffuser is introduced. This diffuser effectively eliminates spatial coherence, thus preventing the adverse impact of coherent noise on imaging quality. The speckle contrast serves as a metric to quantify the effectiveness of spatial coherence elimination. Parameters such as grain size, rotation rate of the diffuser, and camera exposure time are examined for their influence on speckle contrast. Furthermore, the study emphasizes the significance of optimizing imaging algorithms to enhance the quality of rapid imaging. A systematic exploration of experimental factors and imaging algorithms contributes to the overall understanding and improvement of high-quality optical rapid imaging through scattering medium.

  Methods  A rotating diffuser is introduced to eliminate the spatial coherence of the laser beam, so the impact of coherent noise on imaging quality is avoided. The speckle contrast can be used to measure the effect of eliminating the spatial coherence of the beam. For investigating the impact of rotating diffusers on the quality of optical rapid imaging, different cases involving 220-grit and 600-grit rotating diffusers, various rotational rates, and different camera exposure times are analyzed. The rotational rate of the diffuser ranges from 10 to 100 revolutions per second, increasing in increments of 10 revolutions per second. The camera exposure time is varied from 30 to 220 milliseconds, increasing in increments of 30 milliseconds. The study examines the speckle contrast and imaging correlation coefficient concerning the rotational rate of the diffuser and the camera exposure time (see Fig.5). To restore the point spread function of the system without relying on prior information of the target, an iterative optimization algorithm for the optical transfer function constraint is employed. The imaging algorithm, combining the point spread function with the speckle autocorrelation algorithm, enables the single-shot imaging of targets. The quality of this algorithm is analyzed and compared with the case where only the speckle autocorrelation algorithm is used (see Fig.10). This comprehensive analysis contributes to understanding and optimizing the factors affecting optical rapid imaging through scattering media.

  Results and Discussions  Some important results can be drawn from the experiments. Firstly, the speckle contrast decreases and the imaging correlation coefficient increases with the increase of the rotation rate of the rotating diffuser and the exposure time of the camera (Fig.5). Secondly, the change of the speckle contrast and imaging correlation coefficient with the rotation rate of the diffuser is relatively small after the camera exposure time exceeds 100 milliseconds. Thirdly, compared with the cases of 220 grits rotating diffusers, the speckle contrast decreases for 600 grits rotating diffusers. Fourthly, at the same rotating rate of the diffuser, the speckle contrast and imaging correlation coefficient change nonlinearly as the camera exposure time increases (Fig.6). Compared with using the single-shot speckle autocorrelation algorithm alone, the imaging quality of the point spread function combined with the speckle autocorrelation algorithm is significantly improved (Fig.10, Fig.11).

  Conclusions  The effects of the grain size, the rotation rate of rotating diffuser and the exposure time of camera on the speckle autocorrelation imaging is studied experimentally. For the high-quality and rapid imaging with a short camera exposure time, it is very important to choose the most appropriate rotational rate of the rotating diffuser, which can significantly improve the imaging quality. By directly extracting the point spread function from the optical speckle and combining it with the speckle autocorrelation algorithm, the high-quality and rapid imaging of the target through the scattering medium can be realized. The method can make the imaging quality under the camera exposure time of 40 milliseconds close to the imaging quality under the camera exposure time of 160 milliseconds.