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.
With the principle of electrically controlled birefringence (ECB), we propose a new method to spatially separate the azimuthally and radially polarized beams. The method is premised on a regularized arrangement of liquid-crystal (LC) induced by sparse polymer ribbons.The ECB effect was achieved by a hole-patterned LC device with an initial radial alignment, which is induced by polymer ribbons pre-fabricated on the substrate. The polymer ribbons were formed on the substrate via the ultraviolet (UV) mask exposure method, which has the advantages of low cost, simple fabrication process and can be used for mass production. When the voltage signals are applied to the fabricated LC device, a gradient refractive index distribution will form inside the device. Restricted by the inherent polarization-sensitive properties of the nematic phase, it corresponds to the extraordinary optical component, which is exactly the radially polarized beam. According to the above principle, the extraordinary and ordinary polarized components can be separated. Experiments demonstrated that the spatial separation was effectively achieved by the proposed LC device. The proposed method has provided an approach for the light field manipulation based on patterned liquid crystal alignment.
Based on artificial compound eyes and human vision mechanisms, we propose a hybrid bionic imaging method to achieve field of view (FOV) extension and foveated imaging simultaneously. The imaging model of the proposed method is built, and the key parameters are deduced. Then, simulations are carried out to estimate the properties of the model, including FOV extension ratio (FER), foveal ratio, fovea moving range and so on. Finally, a prototype is developed, and imaging experiments are carried out. The experimental results accord with the simulations well, proving the potential of the proposed method for intelligent surveillance, automatic object detection and recognition with low cost.
KEYWORDS: Super resolution, Biomimetics, Retina, Image resolution, Visual process modeling, Imaging systems, Image processing, Image restoration, Statistical modeling, Signal to noise ratio
A novel super resolution reconstruction method is proposed to improve super resolution image performances. The proposed method uses bionic vision sampling model to obtain low resolution images and performs super resolution reconstruction in logarithmic polar coordinates. We carry out comparative experiments between the proposed method and the traditional method in terms of Peak Signal to Noise Ratio (PSNR), Structural Similarity Index Measure (SSIM) and Mean Squared Error (MSE). The results show that the performances of proposed method are better than that of the traditional method. Especially the SSIM of global image (butterfly), the proposed method is 34.45% higher than the traditional method.
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