Sub-pixel resolving modulation for non-line-of-sight imaging

Non-line-of-sight (NLOS) imaging is a rapidly developing technology with significant potential applications. Achieving fast and high-resolution imaging is crucial in practical scenarios. In existing NLOS imaging methods, most approaches rely on time-consuming scanning to detect scenes, which makes it challenging to achieve rapid acquisition. Some methods propose replacing the scanning process with array detectors; however, these approaches are limited by the number of pixels in the array detector and time jitter, making it difficult to achieve high-resolution object reconstruction. This paper introduces digital micromirror device (DMD) modulation into the scan-free NLOS system and proposes a high-resolution imaging method called pixel shift modulation non-line-of-sight (PSM-NLOS) imaging. By adopting a pixel shift modulation acquisition mechanism, we establish a fine scanning acquisition system based on DMD modulation, enabling rapid sub-pixel sampling. The light field evolution characteristic in non-confocal scenarios is investigated, and the effects of illumination and detection regions on time jitter are incorporated into the light field modeling. Considering issues such as ambient light and pixel crosstalk in the array detectors, we achieve high-resolution imaging of hidden objects through model inversion and frequency domain filtering. This method breaks the resolution limit of NLOS systems, enhancing the spatial resolution from 7 cm to 1 cm while significantly improving the reconstruction quality of hidden objects. Moreover, the modulation approach is compatible with various techniques such as the scan-free boundary migration method, the virtual waves method, and the light-cone transform method, and can also serve as an independent modulation strategy to enhance imaging resolution, demonstrating considerable reference value.