Liu Yongqi, Chi Cheng, Shan Yuefan, Cheng Dewen, Wang Yongtian
Opt Express. 2024 Nov 4;32(23):40666-40681. doi: 10.1364/OE.539454.
Optical image processing with high operational efficiency has been applied as a pre-processing imaging system for image recognition. Edge-enhanced imaging as a high-efficiency optical image processing method is of great significance for feature extraction and target recognition. However, the edge-enhanced imaging system based on the 4F system and the spatial filter transforms mainly work under coherent light illumination conditions, without continuously zooming to track the spatial position of the target. Here, we demonstrate a polarization-multiplexed zoom Moiré metalens for edge-enhanced imaging under incoherent light illumination. Metalens is designed to generate polarization-dependent optical transfer functions that produce edge-enhanced images with a resolution of 1.2 µm by digital subtraction. Furthermore, continuous zoom at the range of 1-2× is realized by constructing a Moiré metalens composed of cascaded metasurfaces. The cascaded metasurfaces consist of two center-aligned dielectric metasurfaces, each with a Moiré phase sensitive to the rotation angle. By rotating the metasurface, the phase profile of the cascaded metasurfaces changes, and the effect of continuous zoom is realized. The focal length can be actively changed from 38 µm to 77 µm with the focusing efficiency of 50.3%. This metalens can be applied to machine vision, microscopic imaging, and promotes the development of multi-functional integrated optical systems.
具有高运算效率的光学图像处理已被用作图像识别的预处理成像系统。边缘增强成像作为一种高效的光学图像处理方法，对于特征提取和目标识别具有重要意义。然而，基于4F系统和空间滤波器变换的边缘增强成像系统主要在相干光照明条件下工作，无法连续变焦以跟踪目标的空间位置。在此，我们展示了一种用于非相干光照明下边缘增强成像的偏振复用变焦莫尔超表面透镜。超表面透镜被设计成产生偏振依赖的光学传递函数，通过数字减法产生分辨率为1.2 µm的边缘增强图像。此外，通过构建由级联超表面组成的莫尔超表面透镜，实现了1-2倍范围内的连续变焦。级联超表面由两个中心对齐的介质超表面组成，每个超表面都有一个对旋转角度敏感的莫尔相位。通过旋转超表面，级联超表面的相位分布发生变化，从而实现连续变焦的效果。焦距可以从38 µm主动变化到77 µm，聚焦效率为50.3%。这种超表面透镜可应用于机器视觉、微观成像，并推动多功能集成光学系统的发展。
