In the present study, the advantages of multispectral imaging over hyperspectral imaging in real-time spectral imaging are briefly analyzed, and the advantages and disadvantages of snapshot spectral imaging and other spectral imaging technologies are briefly described. The technical characteristics of artificial compound eyes and multi-aperture imaging and the research significance of snapshot artificial compound eye multispectral imaging are also introduced. The classification and working principle of the snapshot artificial compound eye multispectral imaging system are briefly described. According to the realization method of the optical imaging system, the ACE snapshot multi-aperture multispectral imaging system is divided into plane and curved types. In the planar compound eye spectral imaging system, the technical progress of the multispectral imaging system based on the thin observation module by bound optics (TOMBO) architecture and the multispectral imaging system based on the linear variable spectral filter are introduced. At the same time, three curved multispectral imaging systems are introduced. Snapshot artificial compound eye multispectral imaging technology is also briefly analyzed and compared. The research results are helpful to comprehensively understand the research status of snapshot multispectral multi-aperture imaging technology based on artificial compound eyes and to lay the foundation for improving its comprehensive performance even further.

Optical imaging systems using varifocal lenses have been widely used in many applications over the past several decades, such as machine vision devices, consumer electronic products, and medical instruments. Traditional varifocal lenses often consist of multiple solid focal length refractive optical elements. The varifocal ability is obtained by dislocating these optical elements along the optical axis over specific distances using mechanical driving mechanisms. It makes the traditional optical varifocal imaging systems suffer from bulky dimensions, slow response speed, complicated configuration, and discrete magnifications. Adaptive varifocal lenses have been a better choice to address the aforementioned limitations of traditional varifocal lenses. Dielectric elastomer actuators (DEA), which can effectively respond to an electric field and result in shape deformation, have been used to develop various adaptive lenses. This paper aims to give a brief review of adaptive varifocal lenses based on DEA. First, this paper describes the basic physical mechanism of DEA. Second, this paper reviews adaptive varifocal liquid lenses based on DEA and introduces their material, structure, and fabrication process, focusing on their unique advantages, such as fast response speed and compactness. However, despite these merits, the adaptive varifocal liquid lens still has challenges in environment stability and liquid leakage. To address these challenges, adaptive varifocal soft solid lenses based on DEA have been proposed, which are also reviewed. In addition, other adaptive varifocal lenses, including metalens, Fresnel lens, microlens array, and Alvarez lens, are also presented. Finally, the prospects and challenges for the development of adaptive varifocal lenses based on DEA are discussed.

This paper presents a monocular biological microscope with colorful 3D reconstruction and an extended depth of field using an electrically tunable lens. It is based on a 4f optical system with an electrically tunable lens at the confocal plane. Rapid and extensive depth scanning while maintaining consistent magnification without mechanical movement is achieved. We propose an improved Laplacian operator that considers pixels in diagonal directions to provide enhanced fusion effects and obtain more details of the object. Accurate 3D reconstruction is achieved using the shape-from-focus method by tuning the focal power of the electrically tunable lens. We validate the proposed method by performing experiments on biological samples. The 3D reconstructed images obtained from the biological samples match the actual shrimp larvae and bee antenna samples. Two standard gauge blocks are used to evaluate the 3D reconstruction performance of the proposed method. The experimental results show that the extended depth of fields are 120 µm, 240 µm, and 1440 µm for shrimp larvae, bee tentacle samples, and gauge blocks, respectively. The maximum absolute errors are −39.9 μm and −30.6 μm for the first and second gauge blocks, which indicates 3D reconstruction deviations are 0.78% and 1.52%, respectively. Since the procedure does not require any custom hardware, it can be used to transform a biological microscope into one that effectively extends the depth of field and achieves highly accurate 3D reconstruction results, as long as the requirements are met. Such a microscope presents a broad range of applications, such as biological detection and microbiological diagnosis, where colorful 3D reconstruction and an extended depth of field are critical.