Metasurface, composed of designed two-dimensional array of meta-atoms, provides an alternative approach to achieve efficient electromagnetic wave manipulation. Metasurface holography is an emerging and promising imaging technology with improved image quality and spatial resolution compared to traditional holography. Many devices are fabricated only by coding specific phase responses of the designed metasurfaces. However, the modulation of both the amplitude and phase responses of electromagnetic waves can significantly improve the quality of the holographic image. In this paper, we employ bi-layered split rings as meta-atoms, which can fully control the transmission amplitude and phase independently. Furthermore, we present an algorithm based on the inverse angular spectrum diffraction theory to obtain the amplitude and phase information for the shape and arrangement of the meta-atoms. The proof-of-concept experiments in the microwave regime demonstrate that the inverse angular spectrum diffraction theory shows better image quality than the conventional Gerchberg-Saxton (GS) algorithm, especially when the number of meta-atoms is the same or even slightly fewer. The proposed approach provides an innovative and effective method for holograms design and expands the route to versatile applications related to holographic technologies.

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Dark-field confocal microscopy is effectively used for 3D surface and subsurface measurement due to its ability to suppress strong reflected signals from measured surfaces. However, in 3D characterization of microstructure morphology, edge imaging degrades due to the influence of microstructure edge occlusion, so the microstructure edge position cannot be accurately determined. This limitation is serious when dark-field confocal microscopy is used for width determination of deep grooves/step samples. In this paper, a method for determining the width for deep grooves in dark-field confocal microscopy is proposed to determine the edge position with the groove's lower surface in focus. Experimental results show the width determination method has higher precision compared to conventional 1/4 edge determination, reducing the standard deviation by 57.58 %.

Quality control is essential to ensure the performance and yield of microdevices in industrial processing and manufacturing. In particular, 3D microscopy can be considered as a separate branch of microscopic instruments and plays a pivotal role in monitoring processing quality. For industrial measurements, 3D microscopy is mainly used for both the inspection of critical dimensions to ensure the design performance and detection of defects for improving the yield of microdevices. However, with the progress of advanced manufacturing technology and the increasing demand for high‐performance microdevices, 3D microscopy has ushered in new challenges and development opportunities, such as breakthroughs in diffraction limit, 3D characterisation and calibrations of critical dimensions, high‐precision detection and physical property determination of defects, and application of artificial intelligence. In this review, we provide a comprehensive survey about the state of the art and challenges in 3D microscopy for industrial measurements, and provide development ideas for future research. By describing techniques and methods with their advantages and limitations, we provide guidance to researchers and developers about the most suitable technique available for their intended industrial measurements.