A meta‐lens is an advanced flat optical device composed of artificial antennas. The amplitude, phase, and polarization of incident light can be engineered to satisfy the application requirements of meta‐lenses. Meta‐lenses can be designed to achieve a variety of functions, such as diffraction‐limited focusing, high focusing efficiency, and aberration correlation, which are useful in various application scenarios. This review focuses on the recent progress in meta‐lenses, from fundamentals to applications. The present challenges in this domain are summarized and future prospects are offered. The primary aim of this review is to provide the reader with a comprehensive understanding of meta‐lenses and potential inspiration for designing high‐performance meta‐lenses for feasible applications.

Optical metasurfaces, planar subwavelength nanoantenna arrays with the singular ability to sculpt wavefront in almost arbitrary manners, are poised to become a powerful tool enabling compact and high-performance optics with novel functionalities. A particularly intriguing research direction within this field is active metasurfaces, whose optical response can be dynamically tuned postfabrication, thus allowing a plurality of applications unattainable with traditional bulk optics. Designing reconfigurable optics based on active metasurfaces is, however, presented with a unique challenge, since the optical quality of the devices must be optimized at multiple optical states. In this article, we provide a critical review on the active meta-optics design principles and algorithms that are applied across structural hierarchies ranging from single meta-atoms to full meta-optical devices. The discussed approaches are illustrated by specific examples of reconfigurable metasurfaces based on optical phase-change materials.

A synergistic effect exists when BTAH and iodide ions are used together to prevent the corrosion of copper in sulfuric acid. The nature of this effect has been studied systematically by using electrochemical techniques and x‐ray photoelectron spectroscopy. The synergistic effect is due largely to the formation of a film of Cu(IBTA) complex and is probably polymeric in nature. This new complex film greatly depresses copper dissolution.

The optical illusion affects depth‐sensing due to the limited and specific light‐field information acquired by single‐lens imaging. The incomplete depth information or visual deception would cause cognitive errors. To resolve this problem, an intelligent and compact depth‐sensing meta‐device that is miniaturized, integrated, and applicable for diverse scenes in all light levels is demonstrated. The compact and multifunction stereo vision system adopts an array with 3600 achromatic meta‐lenses and a size of 1.2 × 1.2 mm2 to measure the depth over a 30 cm range with deep‐learning support. The meta‐lens array can act as multiple imaging lenses to collect light field information. It can also work with a light source as an active optical device to project a structured light. The meta‐lens array can serve as the core functional component of a light‐field imaging system under bright conditions or a structured‐light projection system in the dark. The depth information in both ways can be analyzed and extracted by the convolutional neural network. This work provides a new avenue for the applications such as autonomous driving, machine vision, human–computer interaction, augmented reality, biometric identification, etc.

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