Hang Chen

Optical hyperspectral data encryption in spectrum domain by using 3D Arnold and gyrator transforms

ABSTRACT In this letter, a hyperspectral image encryption algorithm based on 3D Arnold transform and gyrator transform in spectrum domain is proposed. First, the original hyperspectral cube will be scrambled by 3D Arnold transform in the spatial domain. Subsequently, the obtained intermediate data are converted into spectrum domain to create a new spectral image. This new spectral image is decomposed into numerous single pieces and encoded using gyrator transform. The corresponding decrypted hyperspectral cube can be recovered by performing along the reverse direction of the encryption process. Some numerical simulations have been performed to verify the validity and capability of the proposed hyperspectral encryption algorithm.

Effect of deposition power and pressure on rate deposition and resistivity of titanium thin films grown by DC magnetron sputtering

ABSTRACT Based on magnetron sputtering deposition technology, titanium (Ti) thin films are deposited on silicon (Si) substrate using different preparation conditions such as sputtering power and pressure. The influence of altering these conditions on deposition rate and microstructure is studied. The results show that sputtering power significantly affects the rate of deposition and the resistivity. The deposition rate of the Ti thin film increases when the resistivity decreases under sputtering powers of 150–225u2009W with a pressure of 0.8u2009Pa and Argon (Ar) flux of 80 sccm. As sputtering power was increased further (from 225 to 250u2009W), the deposition rate reduced and the resistivity augmented. Pressure also has influence on the deposition rate and resistivity – when pressure increases from 0.6 to 0.8u2009Pa, the deposition rate escalates while the resistivity reduces; when the pressure is raised from 0.8 to 1.0u2009Pa with Ar flux of 100 sccm, the deposition rate decreases and resistivity increases. The surface chemical compositions and the structures of the Ti film were studied by using X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD). Observing the cross-section of the thin-film samples produced by scanning electron microscope (SEM) reveals the influence of the preparation conditions used on the microstructure and confirms the influence of sputtering power and pressure on the resistivity.

Dense surface reconstruction based on the fusion of monocular vision and three-dimensional flash light detection and ranging

Abstract. A dense surface reconstruction approach based on the fusion of monocular vision and three-dimensional (3-D) flash light detection and ranging (LIDAR) is proposed. The texture and geometry information can be obtained simultaneously and quickly for stationary or moving targets with the proposed method. Primarily, our 2-D/3-D fusion imaging system including cameras calibration and an intensity-range image registration algorithm is designed. Subsequently, the adaptive block intensity-range Markov random field (MRF) with optimizing weights is presented to improve the sparse range data from 3-D flash LIDAR. Then the energy function is minimized quickly by conjugate gradient algorithm for each neighborhood system instead of the whole MRF. Finally, the experiments with standard depth datasets and real 2-D/3-D images demonstrate the validity and capability of the proposed scheme.

Hyperspectral and high-resolution image fusion based on second generation Bandelet transform

Abstract. A fusion algorithm of hyperspectral and high-resolution images based on principal component analysis (PCA) and second generation Bandelet transform is proposed. Primarily, the numerous components of the hyperspectral image are divided. Subsequently, the maximum rule is used to select the Bandelet coefficients and geometry flows of the hyperspectral image which are transformed by PCA in the following step. Finally, the fused image is reconstructed by taking inverse PCA and Bandelet transform. Some numerical simulations are made to test the validity and capability of the proposed fusion algorithm.

High resolution flash three-dimensional LIDAR systems based on polarization modulation

Two high resolution flash LIDAR systems based on polarization modulation are demonstrated in this paper. One utilizes a polarization beam splitter (PBS) and two charge coupled device (CCD) arrays; the other utilizes a micro-polarizer array and a CCD array. Compared with the traditional flash LIDAR systems, the main advantage of the presented flash LIDAR systems is replacing high bandwidth detectors with a polarization modulator and low bandwidth detectors. The polarization modulator is used to modulate the polarization state of the received laser pulse in time and the range information can be mapped into the intensity received by the low bandwidth detectors. The distance between the target and the system can be derived from intensity images that can be read out using low bandwidth detectors. Comparisons of the two systems indicate that they have the same range precision. Both demonstrated systems can achieve a high range precision of several millimeters. The system using a PBS and two CCD arrays can obtain higher resolution images, but it is crucial to align the two CCD arrays precisely.

Semi-active control of space manipulator soft contacting based on magnetorheological rotational damper:

A novel soft contacting technology is proposed to reduce the risks of contacts that space manipulator is on-orbit service. The magnetorheological (MR) rotational damper is considered and utilized for cushioning and vibration reduction in the space manipulator. Based on the extended manipulator model, a linear dynamic formulation of free-floating space manipulator is built. Subsequently, the mechanical property of magnetorheological rotational damper is analyzed by using Bingham model. Then, the optimal control force can be obtained by using the linear quadratic optimal control theory. Finally, the optimal control force is served as the parameters to achieve the semi-active control of soft contacting by employing the clipped optimal control theory. The hard contacting and passive control technology are introduced to make comparison with the results of soft contacting. Some numerical simulations are made to demonstrate the validity and capability of the proposed soft contacting technology.

Target Recognition Algorithm for Fused Hyperspectral Image by Using Combined Spectra

A spectrum recognition method of fused hyperspectral image is proposed based on the normalized spectral information divergence and normalized spectral angle mapper. First, the hyperspectral image and registered high-resolution image are fused. Subsequently, the spectrum of the targets in the original hyperspectral image is abstracted and regarded as the reference spectrum information. Finally, the spectral information from the fused hyperspectral image is used to recognize the targets by using the proposed algorithm. Some numerical simulations are made to test the validity and capability of the proposed combined spectrum recognition algorithm.

Dimension reduction for hyperspectral image based on the second generation bandelet transform

A dimensionality reduction method is proposed by using the second generation Bandelet transform. The redundant components of the hyperspectral cube are firstly partitioned into several subsets. Subsequently the Bandelet coefficients and the geometries flows of the hyperspectral image are generated by performing second generation Bandelet transform. In the follow step, Principal Components Analysis (PCA) is introduced to simplify the redundant data. Finally, the new reduced hyperspectral cube is reconstructed by taking inverse Bandelet transform. Some numerical simulations are made to test the validity and capability of the proposed dimensionality reduction algorithm.

Modeling and Simulation of the Optical Properties of Low-Speed Target in Near Space

A novel near space target optical properties modeling method based on the reverse Monte Carlo optical tracking is proposed. Both the environment characteristics in near space and the light transmission characteristics in different detection platform mode are considered and analysis in detail. The invalid light can be eliminated adaptively in this model. According to the phase relationship of target-observing systems-the sun, the optical properties of the target can be obtained. Some numerical simulations are made to test the accuracy and capability of the proposed modeling method.