Optical scattering induced information scrambling is one of the biggest challenges that people have to face in optical imaging. Thus, how to overcome the scattering effect and suppress scattering-induced glares is critically important in many scenarios, including deep-tissue optical imaging in biomedical analysis and vehicle perception under the disturbance of rain and fog in daily life.

In recent years, people demonstrated that wavefront shaping can effectively suppress glares in the target region by modulating the incident wavefront. However, due to the inefficiency of the existing optimization framework and the inaccuracy in the determined scattering information, the experimentally achieved results are far from satisfactory. Moreover, there is also a lack of an appropriate physical model to instruct glare suppression, which restricts the range of the to-be-suppressed glares. Thus, how to efficiently suppress glares at a large scale with a finite number of optical controls remains a challenge.

To address this issue, a research group led by Dr. Zhaohui Li and Dr. Yuecheng Shen at Sun Yat-sen University developed a new wavefront shaping technique to suppress glares at a large scale. This method enables efficient glare suppression for 400 speckles with 400 independent controls and less than 1 second computational time. The relevant research results were published in Photonics Research, Volume 12, 2022 (Daixuan Wu, Jiawei Luo, Zhibing Lu, Hanpeng Liang, Yuecheng Shen, Zhaohui Li. Two-stage matrix-assisted glare suppression at a large scale[J]. Photonics Research, 2022, 10(12): 2693).

This method, named two-stage matrix-assisted glare suppression (TAGS), is originated from the famous Gerchberg-Saxton algorithm. Firstly, TAGS accurately analyzes and retrieves the transmission characteristics of speckles through only direct intensity measurements. Then, TAGS employs a randomly generated assisting matrix to suppress glares at a large scale. The introduction of the assisting matrix effectively improves the convergence speed and accuracy, leading to robustness in practical applications. Figure 1 (a) shows the schematic diagram of the TAGS. Two experimentally achieved glare suppression with TAGS are shown in Figs. 1(b) and (c).

Fig. 1 (a) Schematic diagram of TAGS. The inner loop in pink represents analyzing speckle information in the first stag, while the outer loop in blue indicates suppressing glares through wavefront modulation. (b) (c) The experimental results of suppressing glares at a large scale.

Dr. Shen says: "TAGS considerably reduces the difficulties in wavefront measurement and the complexity in the computational process. This superiority makes it suitable to suppress glares at a large scale with a limited number of controls. For future works, we will continue to explore more efficient methods to suppress glares, and also try multispectral glare suppression in various imaging scenarios."