Image processing plays a vital role in artificial visual systems, which have diverse applications in areas such as biomedical imaging and machine vision. In particular, optical analog image processing is of great interest because of its parallel processing capability and low power consumption. Here, we present ultra-compact metasurfaces performing all-optical geometric image transformations, which are essential for image processing to correct image distortions, create special image effects, and morph one image into another. We show that our metasurfaces can realize binary image transformations by modifying the spatial relationship between pixels and converting binary images from Cartesian to log-polar coordinates with unparalleled advantages for scale- and rotation-invariant image preprocessing. Furthermore, we extend our approach to grayscale image transformations and convert an image with Gaussian intensity profile into another image with flat-top intensity profile. Our technique will potentially unlock new opportunities for various applications such as target tracking and laser manufacturing.

图像处理在人工视觉系统中起着至关重要的作用，在生物医学成像和机器视觉等领域有着广泛的应用。特别是，光学模拟图像处理因其并行处理能力和低功耗而备受关注。在这里，我们提出了执行全光学几何图像变换的超紧凑超表面，这对于图像处理纠正图像失真、创建特殊图像效果以及将一幅图像变成另一幅图像至关重要。我们表明，我们的超表面可以通过修改像素之间的空间关系并将二值图像从笛卡尔坐标转换为对数极坐标来实现二值图像转换，对于尺度和旋转不变的图像预处理具有无与伦比的优势。此外，我们将我们的方法扩展到灰度图像转换，并将具有高斯强度分布的图像转换为另一个具有平顶强度分布的图像。我们的技术将有可能为目标跟踪和激光制造等各种应用带来新的机遇。