This PDF file contains the front matter associated with SPIE Proceedings Volume 13084, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Spectral imaging is an imaging technique that introduces spectral filters in the imaging link to simultaneously obtain target spectral and spatial information. Among the spectral filters, liquid-crystal (LC) filters exhibit technical advantages of fast response speed, low power consumption, and large aperture. As a highly efficient electrically tunable microcavity interference filter structure, the miniaturized liquid-crystal Fabry-Pérot (LC-FP) is generally composed of a LC layer sandwiched by two highly reflective mirrors. By adjusting the applied voltage signals, the high spectral resolution spectrum selection and adjustment of transmitted beam is implemented. Generally, the birefringence difference of the LC material used determines the phase modulation capability, which in turn affects the device performance. In this paper, an electrically tunable LC-FP filter (ET LC-FP) with high-birefringence nematic LC mixture is proposed. The deviced ET LC-FP is constructed using a kind of high-birefringence nematic LC mixture (HB-45800) for achieving the typical electrically selecting and adjusting and jumping of spectral lightbeam outfrom the ET LC-FP filter. The electro-optical parameters of HB-45800 are: Δn = 0.385 at 589.3nm, the clear point is 95.1℃. The transmission spectral characteristics (1.5~15μm) of the ET LC-FP device were analyzed using a Fourier transform infrared spectrometer. Experiments demonstrate that an electrically tunable spectral resolution of better than 5nm is reached in the infrared domain of 1.5~3μm.

Depth from focus and defocus is an effective technique to extract depth information from a set of images, which is called focal stack. In prior studies, this technology was commonly operated on complex laboratory imaging equipment. In this paper, a new imaging system based on electrowetting liquid lens is proposed. Electrowetting liquid lens is one of the adaptive lens which has adjustable focal length controlled by voltage signal. The focal stack can be easily got by sweeping the applied voltage without mechanical moving part. To eliminate the field of view (FOV) variations during the process of capturing focal stack, which is called focal breathing, we proposed an algorithm based on conventional flow concatenation to align focal stack images. We test the proposed imaging system on both laboratory scene and mobile phones, and the experiments demonstrate this imaging system can capture high quality images and shows excellent performance in extracting depth information without complex mechanical structure.

This paper presents an electrically controlled liquid-crystal (LC) interference filter in the infrared multispectral imaging system. Based on the theory of multi-beam interference, the proposed structure utilizes a pair of parallel flat plates with a reflectivity of ~95% to form a Fabry-Perot (FP) cavity, realizing constructive interferences and destructive interferences in specific wavelengths for incident infrared broad-spectra. The filtering performance of the proposed structure can be controlled by incorporating electrode layers based on the electro-optical properties of LC. We simulate the filtering characteristics of the proposed structure according to the elastic continuum theory of LC. Then the zinc selenide (ZnSe)-based LC filter with a preset cavity depth of 50 μm was fabricated with light orientation instead of the conventional friction orientation method. An infrared spectra test system was built to measure the performance of the fabricated interference filter. The experimental results successfully demonstrate the filtering characteristics covering three important infrared window bands in accordance with the simulated results by applying different root mean square (RMS) voltages. Also, the fabricated filter brings a sharper transmission peak waveform in a higher frequency infrared band. The proposed filter has a low cost and weight and is easy to install, laying the foundation for developing full-wave infrared multispectral imaging systems.

Efficient absorption in the mid-long-wave infrared region is crucial for various applications, including thermal imaging and sensing, infrared spectroscopy, and camouflage. A multilayered metal-insulator-metal-based infrared plasmonic metamaterial absorber utilizing a stacked nanocavity meta-surface consisting of a double-layer cylindrical metal-insulator-metal structure (DCMIM) is proposed. This absorber demonstrates wideband absorption capabilities with an average absorption rate exceeding 75% in the 3–14μm range. To understand the spectral absorption mechanisms, a comprehensive analysis is conducted using the Finite Difference Time Domain and Fabry-Perot resonance model. The analysis reveals physical mechanisms such as strong coupling between plasmon resonances and phonon vibrations loss from the dielectric spacer, as well as localized surface plasmon resonance. It is worth noting that the quantities of plasma cavities significantly impacts the performance of the absorber. By adjusting the material type and thickness of the film layer, it becomes possible to effectively compensate for the performance limitations of a single dielectric layer material within specific wavelength bands. Experimental results, combined with theoretical analysis of the DCMIM structure, establish a new approach to the design of broadband infrared absorbers.

Polarization is the asymmetry of a light wave's electric field vibration direction with respect to its propagation direction, as a crucial clue for describing the light, which is one of the most apparent signs that distinguishes transverse waves from longitudinal waves. The current mainstream polarimetric cameras typically adopt a division of focal plane imaging architecture, in which a metal wire-grid structure is coupled with a detector to acquire the polarization state of the target. However, the structure of the division of focal plane reduces effective spatial resolution of the detector and requires complex registration algorithms to achieve pixel-level polarization acquisition, which leads to high equipment costs and impedes the development and application of polarimetric cameras in industrial production. In this paper, a single-layer twisted nematic liquid crystal (TNLC) is inserted to the imaging optical path of traditional camera to realize the polarization acquisition, allowing for a cost-effective transition from traditional devices to polarization imaging systems. The imaging detector coupled with the TNLC device can acquire polarization states ranging from 10 to 90-degree by adjusting the external voltage applied on the LC device. Moreover, a polarization angle calibration method based on a single-layer TNLC is proposed in this paper, providing a reliable reference for electrically controlled polarization angle acquisition. The experimental results acquired by presented imaging system demonstrate the feasibility and effectiveness of the proposed method. The TNLC based imaging scheme presented in this paper provides a solid foundation for developing simple, low-cost, and efficient polarimetric cameras.

Metasurfaces, enabling effective optical modulation of incident lightwave, can be employed as a promising candidate to implement different functions, thus significantly improving the lightwave controllability, validity and system integration. In this paper, the phase and intensity modulation, firstly, of the incident lightwave based on a single nanotip was researched. Then, the metasurface consist of nanotips with different structural parameters was designed according to the grayscale image obtained via diffractive network encoding, so as to realize the extending image depth of field. We demonstrate that the metasurface based on the nanotips antenna can achieve a large image depth range of field exceeding 50μm. Moreover, the maximum focal length can reach ~200μm after passing through the arrayed nanotips.

Light-field imaging is an effective and straightforward way to image with three-dimensional information. In this paper, a new type of the fully electrically controlled light-field camera based on electrowetting liquid lens and liquid crystal microlens array (EW-LCMLA) is proposed. In the proposed camera, a liquid-crystal microlens array (LCMLA) is placed on the CMOS sensor to get the raw light-field images. Unlike conventional light-field camera using LCMLA, the proposed camera can rapidly adjust the compound-eye degree of light-field image by inserting a liquid lens between main lens and LCMLA, and by switching the external voltage on the liquid lens, the camera can work on multiple imaging modes, such as light-field imaging, conventional two-dimensional imaging and focal-stack imaging. For further improve the . In this study, an algorithm based on focal stack theory is also proposed to extract the depth information from the raw light-field image and merge the image focus on different distances to get all-in-focus image. We test the different imaging mode of the camera in indoor environments, and the experiments demonstrate that the proposed camera can capture high quality image on different mode, and shows excellent focal length adjustment ability without complex mechanical structure.

The optical metasurface formed by the periodic arrangement of micro-nano structures with sub-wavelength size can efficiently sense and control the polarization, amplitude and phase of electromagnetic waves. When the light incident on the metasurface, the resonance response based on the plasmon will be generated at the position of wave vector matching in the periodic micro-nano structure, which will change the surface charge distribution characteristics. The properties of light reflection, light transmission, light absorption and local enhancement of the metasurface in infrared band can be effectively improved by setting the size, shape, material composition and period spacing of the surface micro -nano structure reasonably. Based on the characteristics of plasmon on solid surface, the metasurface composed of metal excitation layer of titanium array is designed. The local enhanced metasurface with low reflection characteristics is obtained by reasonable configuration of titanium structure parameters such as size and period. In order to further improve its optical transmittance in infrared band, a variety of substrate materials, such as silicon, silicon dioxide and zinc selenide, were simulated and verified. Finally, a zinc-selenide titanium array metasurface with an average transmittance of 68% in 1-14μm band was obtained.

A method of light wave modulation on a magnetic nano-tip hypersurface was investigated within the wavelength range of 3-14 μm, and a hypersurface was constructed on a silicon wafer using magnetic nano-film to perform light control using the magnetization of the magnetic nano-tip to achieve the desired light absorption. Through the magnetic nanotip hypersurface, the incident light waves hypersurface can be highly confined in the arrayed magnetic nanotip to achieve near-field light enhancement and light focusing, and significantly reduce the infrared reflectivity to achieve efficient absorption of infrared light waves. The infrared reflectivity of the structured surface shows a tunable variation by adjusting the structural parameters of the magnetic nano-tip super-surface. The experiments show that the silicon-based magnetic film nano-tip array achieves stronger nanofocusing and higher absorption rate than the conventional nano-tip array based on metal film.

Optical stealth technology is very significant in coping with high-sensitivity infrared image detectors and various guided detectors. In recent years, great efforts have been made developing absorbers in the infrared regime. Although these approaches promise distinct advantages in performance enhancement, there are still some problems, such as limitations on sample size and bandwidth. Thus, we proposed an ultra-broadband absorber with metal–insulator–metal three-layer construction by using periodic array of ultra-thin metallic ribbons on top of the silicon oxide layer placed on a metallic reflector. The simulation results demonstrate that the average absorption rate of near 90% is realized by the proposed absorbing structure in 5μm-14μm. Meanwhile, the proposed ultra-broadband absorber is low cost, compact, and large-area processing, which can be flexibly and easily scaled up for mass production via plasma enhanced chemical vapor deposition, magnetron-sputtering deposition, and electron-beam-evaporation deposition.

Aircraft icing is a severe threat to safe flight. The conditions and efficiency of current ice area and 3D ice shape measurement methods do not meet the research requirements for ice wind tunnel experiments. To address these issues, we propose a method for measuring ice area and 3D ice shape based on polarized light imaging for non-contact measurement. In this paper, we obtain p-polarized light image and s-polarized light image of the experimental area under the linearly polarized light environment. And we use the Otsu algorithm and the SAM (Segment Anything Model) algorithm to measure the ice area under different substrate conditions. On this basis, we extract the linearly polarized light reflected from the ice surface, and reconstruct the 3D ice surface shape by combining the linearly polarized laser scanning method based on polarized light imaging. The experimental results indicate that our method can detect the ice area in real time and the average measurement error of the ice area is less than 1.6%, which achieves superior measurement performance with different ice types at a low cost. For different ice shapes of highly transparent ice, the measurement results agree well with the design data, where the RMSE (Root Mean Square Error) of ice frustum measurement is 0.76 and the RMSE of three cross-sections of different ice shapes are 0.23, 0.27 and 0.45. The results verify the validity of ice area measurement based on polarized light imaging, and demonstrate the effect of complex ice shape measurement based on polarized light imaging, laying a foundation for the real-time measurement research in the ice wind tunnel.

When the wave-vector matching criteria is satisfied, the incident light can excite the surface plasmon on the surface of the metallic micro-nano arrays, as to form the resonant surface electromagnetic field. From the perspective of surface charge rearrangement, we propose interfinger-type metal grating and cover the grating with graphene to manipulate the polarization response of light waves. By using FDTD software, we simulate the transmittance of the structure to the infrared light with different polarization angles, and analyze the local electric field distribution at the edge of the grating. According to the simulation results, the metal grating with graphene can manipulate the light wave transmission well, absorbing the polarization component parallel to the grating's long axis and passing through the polarization component perpendicular to the grating's long axis.

A new type of liquid crystal microlens array (LCMLA) constructed by a single-layered LC materials is proposed. By controlling the applied signal voltage, a gradient electric field distribution is formed in the liquid crystal cavity, and the pointing vectors of the liquid crystal molecules are reoriented according to the formed electric field distribution, thus achieving the regulation of the light beam. The functional area of the basic annular integrated liquid crystal microlens is divided into three layers： The first layer is the main structural area, including four concentric ring electrode arrays with different radii, and the transparent ITO is selected as the electrode material; The middle layer is a silica insulation layer, and the main function is to insulate the first and third layers; The third layer is an aluminum metal electrode layer, which main function is to effectively isolate the electric field generated by the structural area of the first layer. Compared with traditional LC microlenses driven electrically，this structure mainly verifies the changes in the spatial electric field in the liquid crystal cavity under the action of the metal electrode baffle. The four concentric rings are modulated by independently driven-out signal voltages, and each ring produces a differentiated effect by applying different signal voltages. This research has laid a solid foundation for continuously developing LCMLA technology.

Polarimetric synthetic aperture radar (PolSAR) images are widely used in the fields of disaster detection and military reconnaissance. PolSAR image classification is one of the most important applications in PolSAR image interpretation. Existing image classification methods based on deep learning usually rely on a large number of labeled training data. Labeling large-scale data sets is expensive and time-consuming Therefore, semi-supervised learning is an important research direction in the field of image classification. Fixmath has achieved excellent semi-supervised classification performance for nature image, so it is introduced into the field of PolSAR image interpretation, and to improve the performance of semi-supervised PolSAR image classification. Fixmatch has the following advantages: (1) It extends the training data, using generated, labeled and unlabeled data to train the network. (2) By utilizing the information of unlabeled data, FixMatch can improve the generalization ability of the classification model, thus allowing the model to better predict on unseen data. Because of these two advantages, FixMatch has shown excellent results in semi-supervised PolSAR image classification. Experiments on two real PolSAR datasets show that the overall accuracy reaches 89.9 % when the number of labeled samples is set to 110, and reaches 98.6 % when the number of labeled samples is set to 1000.

With the widespread application and rapid development of remote sensing technology, the quality requirements for remote sensing images are gradually improving. Currently, relying solely on one sensor is difficult to ensure high signal-to- noise ratio while capturing images with high spatial and spectral resolution. Remote sensing image fusion technology obtains high-quality images by combining the spatial information and spectral (or spectral) information of different sensors. Meanwhile, in recent years, deep learning theory has developed rapidly and is widely applied in image processing such as remote sensing image fusion. Therefore, in order to gain a more systematic understanding of the current status of remote sensing image fusion based on deep learning and promote the development of remote sensing image fusion, this article first introduces commonly used remote sensing satellite images and traditional image fusion algorithms; Then, the remote sensing image fusion algorithm based on deep learning is emphasized, and the advantages and disadvantages of deep learning fusion methods (PanNet, LPPN, WSDFNet) are compared and analyzed; Finally, the future prospects of remote sensing image fusion methods based on deep learning are presented.

Images acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Terra and Aqua suffer from the common problem of the stripe noise, which heavily limits the application of the MODIS data. In this paper, we present an analysis of the shortcoming in recent variation-based destriping algorithm and also the characteristic of the stripe image, and then automatically detect the stripe lines, finally, we introduce several novel terms within this probabilistic model that are inspired by our analysis, therefore, a maximum a posteriori (MAP)-based destriping algorithm is proposed. A model of the high order spatial randomness of noise is incorporated into the data fidelity term, and a unidirectional adaptive total variation prior is incorporated into the prior term. What is more, the algorithm can automatically detect the stripe lines. An adaptive matrix obtained by the stripe detection is used to distinguish the stripe pixel and non-stripe pixel and then incorporated into the data fidelity term and the prior term to improve the destriping performance. To settle the nondifferentiability property of the TV and reduce the computational load in the process of destriping process, the split Bregman iteration algorithm is employed. As a result of these steps, we are able to produce high quality destriping results in low computation time. A number of comparative experiments including quantitative and qualitative analysis were performed to verify the superiority of the proposed algorithm.