We experimentally study the behavior of one multimode fiber-hollow core fiber-multimode fiber structure when nanofilms are deposited on it with the aim of developing practical evanescent field-based devices, such as sensors, filters, etc. The electrostatic self-assembly (ESA) method is used as the deposition technique and the chosen polymers are PDDA and Poly R-478 because of their well-known optical properties and their potential application as humidity sensors. Three different types of hollow core, fibers are used for the fabrication of the devices and at two different wavelengths. An oscillatory-decreasing transmitted optical power is obtained as the thickness of the nanofilms is increased.
A novel binary level set method for boundary-based image segmentation is proposed, which is extended from region-based binary level set methods. The proposed binary level set method is based on the geometric active contour framework, which is a traditional level set method applied in boundary-based image segmentation. However, being different from the geometric active contour, the proposed binary level set method replaces the traditional level set function with a binary level set function to reduce the expensive computational cost of redistancing the traditional level set function. The experiments and complexity analysis show that the proposed binary level set method is more efficient than the geometric active contour for image segmentation while giving similar results to the geometric active contour.
An object tracking algorithm using an adaptive Kalman filter (KF) combined with mean shift (MS) is proposed. First, the system model of KF is constructed, then the center of the object predicted by KF is used as the initial value of the MS algorithm. The searching result of MS is fed back as the measurement of the adaptive KF, and the estimate parameters of KF are adjusted by the Bhattacharyya coefficient adaptively. The proposed method has the robust ability to track a moving object in consecutive frames under certain real-world complex situations, such as a moving object disappearing partially or totally due to occlusion, fast moving objects, and sudden changes in velocity of a moving object. The experimental results demonstrate that the proposed tracking algorithm is robust and practical.
We propose a new system of quantum key distribution via optical wireless communication links, where the required information, especially telephone conversation, can be secured by using a quantum code/decode (CODEC) technique incorporated in the networks. The entangled photons can be encoded into the classical information and then the decoded signal can also be retrieved. The proposed system consists of quantum key generation and uplink and downlink parts that can be implemented in the mobile telephone handset and networks. Such a system and technique show the feasibility of use for a perfectly security telephone networks.
A new unsymmetrical photochromic diarylethene
is synthesized, and the photochromic properties of it are also investigated. The compound exhibits good photochromism with UV/visible light irradiation. Compound
in polymethyl methacrylate (PMMA) film changes color upon
light irradiation from colorless to blue, in which the absorption maximum is observed at
. Photon-mode polarization multiplexing holographic optical recording is performed successfully using this compound as a recording medium. In the diarylethene
/PMMA film, polarization multiplexing hologram recording and retrieval, and a combination with the angular multiplexing scheme, are demonstrated systematically. The results indicate that recording capacity can be significantly improved with the combined method of polarization and angular multiplexing holographic recording.
We propose an all-optical wavelength conversion method that can preserve the polarization information of an original signal based on four-wave mixing in a semiconductor optical amplifier. Using this method, we experimentally demonstrate wavelength conversion for a 10-Gb/s polarization shift keying signal with 1.6-dB power penalty at a
bit error rate. To our knowledge, it is the first experiment reported on all-optical wavelength conversion for a polarization shift keying format. The converted polarization shift keying signal is successfully transmitted over a 75-km standard single mode fiber with 1.8-dB transmission penalty.
A new motion vector coding method with optimal predictive motion vector selection is proposed. To improve compression performance, the proposed encoder selects an optimal predictive motion vector that produces minimum bits for motion vector coding. The proposed decoder estimates the optimal predictive motion vector without additional information for indicating which predictor is to be used at the encoder side. Experimental results show that compared to the H.264/AVC standard, the proposed scheme improves coding efficiency for various video sequences.
In Itti's model, which was one of the representative saliency models proposed in 1998, a Gaussian pyramid is used to analyze color information in scene images, and to generate a color conspicuity map. In this conspicuity map, some important objects can be located by salient areas, but their contours cannot be described clearly and perfectly. In this work, a wavelet low-pass pyramid is used to generate a color conspicuity map, and the contours of important objects pop out perfectly from salient areas. Experimental results validate the superiority of the proposed method.
Experimental results about efficient band-edge light coupling into two-dimensional planar photonic crystals by the use of a gradual interface are reported. It is shown that a chirp of both the lattice period and the hole diameter on short lengths below
allows maintaining high optical transmission spectra close to the band-gap frequency where strongly dispersive phenomena can be exploited. If compared with nonoptimized structures, increased optical levels by
are obtained using gradual tapering stages.
We improve the beam uniformity passing through multimode fibers using piezoelectric-based spatial mode scrambling. Both fiber squeezing and stretching techniques are applied and compared. A more than sixfold difference in the power intensity crossing the output beam profile without mode scrambling can be reduced to a
variation. The efficiency of collecting useful optical power for detection is also significantly improved. Such modules can find various applications in medical imaging, disease diagnosis, and local area networks.
We propose a novel method of one-shot parallel complex Fourier-domain optical coherence tomography using a spatial carrier frequency for full range imaging. The spatial carrier frequency is introduced into the 2-D spectral interferogram in the lateral direction by using a tilted reference wavefront. This spatial-carrier-contained 2-D spectral interferogram is recorded with one shot of a 2-D CCD camera, and is Fourier-transformed in the lateral direction to obtain a 2-D complex spectral interferogram by a spatial-carrier technique. A full-range tomogram is reconstructed from the 2-D complex spectral interferogram. The principle of this method is confirmed by cross-sectional imaging of a glass slip object.
We optimize the layout of each light plane in a dual-view multistripe measurement system by employing spatial geometry analysis to avoid ambiguity. The imaging regions of every light plane can be labeled uniquely on two image planes within a certain measurement depth. Moreover, the flexible density of fringe patterns corresponding to the different measurement depths is immediately projected without the conventional coding procedure. Some experiments verify the effectiveness of the proposed method applied in high-resolution 3-D measurements.
The Fisherface method suffers from the problem of using all training face images to recognize a test face image. To tackle this problem, we propose combining a novel clustering method, affinity propagation (AP), recently reported in the journal
, with linear discriminant analysis (LDA) to form a new method, AP-LDA, for face recognition. By using AP, a representative face image for each subject can be obtained. Our AP-LDA method uses only these representative face images rather than all training images for recognition. Thus, it is more computationally efficient than Fisherface. Experimental results on several benchmark face databases also show that AP-LDA outperforms Fisherface in terms of recognition rate.
We present a theoretical analysis of the total collectible optical power of an arbitrarily shaped multimode optical fiber probe for contact sensing where the signal from the analyte is emitted or scattered on the outside surface of the fiber tip. Calculation results and optimization parameters are given for spherical, parabolic, and cone-shaped fiber probes. This analysis can be used to guide the design and optimization of various fiber sensors, including fluorescence, surface plasmon resonance, and surface enhanced Raman sensors.
In the existing frame-layer rate control for H.264, buffer status and content complexity are used improperly, causing quality fluctuations of high-motion video at low bit rates and high frame rates (under
). We propose an improved H.264 frame-layer rate control scheme to obtain steady video quality and stable buffer management. Experimental results showed that the proposed scheme performed better than existing schemes.
Ambient light in a scene can introduce errors into range data from most commercial three-dimensional range scanners, particularly scanners that are based on projected patterns and structured lighting. We study the effects of ambient light on a specific commercial scanner. We further present a method for characterizing the range accuracy as a function of ambient light distortions. After a brief review of related research, we first describe the capabilities of the scanner we used and define the experimental setup for our study. Then we present the results of the range characterization relative to ambient light. In these results, we note a systematic error source that appears to be an artifact due to a structured light pattern. We conclude with a discussion of this error and the physical meaning of the results overall.
We discuss a very simple method to encode binary data as circular polarization states with opposite helicity by means of a standard twisted nematic liquid crystal display (TN-LCD). This idea is applied to produce a steganographic imaging system, where binary data are hidden on a background with the same polarization but opposed helicity. A variant is also proposed that maintains some visible information. Experimental results obtained with a commercial TN-LCD are presented.
We propose a new scheme of computer-generated hologram (CGH) watermarking to resist rotation and scaling. To embed the inverse log-polar mapping of a mark pattern's CGH into a cover image, the twin image of the mark pattern can be directly reconstructed by fast Fourier transformation from the log-polar mapping of the watermarked image after rotation and scaling, not requiring a registration step in the extracting procedure. In an experiment, the information position of the twin image is located in the high-frequency domain and the redundant information of the low-frequency component is properly eliminated, so the contrast of the twin image is appropriately enhanced and the basic information of the mark pattern is effectively preserved to be recognized. The experimental results show that the mark-pattern's information can be effectively reconstructed when the watermarked image is scaled by 0.5 to 2 or rotated by any angle, so this watermarking scheme is effectively verified by experiment.
A simple and effective method is presented for fast decoding of H.264 scalable video coding (SVC). The up-sampling operation in H.264 SVC makes the decoder very complex, because convolution and complex memory transactions are inevitable. The proposed method exploits coded modes of neighboring macroblocks (MBs) for determining up-sampling operation on MB by MB. The experimental validation shows considerable improvement in decoding time, and the proposed method reduces the complexity by about 25 on average.
All-optical format conversion from inverse-return-to-zero (inverse-RZ) to non-return-to-zero (NRZ) is realized by using a half-bit-delay Mach-Zehnder delay interferometer. Experimental results demonstrate that the converted NRZ signal has better receiver sensitivity than the back-to-back inverse-RZ signal.