Applied Mechanics and Materials Vols. 764-765

Abstract: Acquiring three-dimensional data from a pair of stereo images is called stereovision that has been studied by researchers for decades. However, most of the previous studies on this topic focused on establishment of stereovision parameter matching and made conclusions on the premise of fixed focus. With the rapid development of multimedia technology, varifocal digital cameras have been widely used in many robotic applications recently. In general, error in the depth estimate becomes bigger when the focus and aperture is unknown or not fixed. For that reason, a three-stage framework is proposed in this paper to modify the conventional stereovision model for improving accuracy of depth estimation. The first stage is to modify the computational model of conventional stereovision for varifocal cameras. Then, the spacing of depth interval in non-uniform spacing of discrete depth levels can be altered, in particular, it is unaffected by changes in focal length. Finally, with considering the affine transformation, we add the deformation coefficient into the modified stereovision model for correcting three-dimensional affine deformations. Experimental results demonstrated that the depth estimation from stereo images using the proposed scheme was more accurate than conventional method.

Abstract: This paper propose an efficient VLSI architecture of camera distortion correction based on neural camera distortion model (NCDM). Different from conventional imaging method uses over two kind models to correct the camera and lenses distortions, the NCDM uses a single model to correct at once the geometry distortion and the unsymmetrical manufacture errors. The NCDM with four neurons perform the wide-angle distortion correction, results show that the maximal corrected error in a whole image is less than 1.1705 pixels, and that the MSE approaches 0.1743 between the corrected and ideal results. The distortion correction by NCDM is 429x more accurate than the conventional approach. The chip size of NCDM is 1.51 x 1.51 mm^2 that contains 126K gates by using TSMC 90 nm CMOS technology process. As working at 240Mhz, this architecture can correct 30 frames and Full-HD resolution video per second. Results show that the maximal corrected error in a whole image is less than 1.4 pixels, and that the mean square error approaches 0.0376 between the corrected and ideal results.

Abstract: To further robust confidentiality protecting against eavesdropping over optical code-division multiple-access (OCDMA) networks, this study improves the robustness of the network toward eavesdropping for encryption/decryption mechanism by using a specified storage register controller controlling optical switches approach in which Free-spectral-range group hopping code is used to generate a specific signature address. This paper presents an enhanced security mechanism to protect spectral-amplitude-coding optical code-division multiple-access (SAC-OCDMA) networks against eavesdropping. This study proposes an alternative to huge code-space size techniques such as wavelength hopping and exchange-encode for network protection against eavesdropping by exploiting the cyclic properties of arrayed-waveguide-grating routers and maximal-length sequence code (M-sequence code). In addition, the network is protected using a wavelength hopping based on optical switches and exchange the encode assignment scheme implemented using the exchange switches before import to arrayed-waveguide-grating routers (AWG).In this scheme, eavesdropper is difficult to solute correct user data bit , whatever there is using brute-force searching or simple energy detector..

Abstract: This paper proposes compensation method with liquid lens as field lens in 9x zoom lens intermediate optics. According to the droplet shape and location of liquid lens which can adjust reversibly to tune the focal length and position of the lens by changing the applied voltage on the set of electrodes and hence the liquid lens can replace more lens to reduce total length size of opto-mechanics system. In the proposed field lens scheme, we use CODE V built-in optimal method to find the best liquid lens parameter versus difference zoom of intermediate optics. There are several general optical aberrations taking into consideration. Comparing with original 9x intermediate optics without field lens technology, the maximum the spherical aberration (SA), the tangential coma (TCO), the tangential astigmatism (TAS), the transverse chromatic aberration (TCA) and the petzval surface curvature (PTZ), and modulation transfer function (MTF) improved by 42.8%, 87.5%, 92.5%, 77.8%, 9.06% and 2877%.

Abstract: The InGaN/AlGaN multiple-quantum-well heterostructures were fabricated by metal-organic chemical vapor deposition system with different indium and aluminum content during the growth of InGaN well layers and AlGaN barrier layers. Temperature-and incident-power-dependent photoluminescence were carried out to examine the recombination mechanisms in the heterostructures. Both of the localization effect and quantum-confined Stark effect are considered. From the experimental and theoretical analysis, the dependence of optical characteristics on the temperature and incident-power are consistent with the recombination mechanisms involving band-tail states and the screen of quantum-confined Stark effect.

Abstract: A combustion synthesis method has been developed for synthesis of Eu²⁺ doped CaAlSiN₃ phosphor and its photoluminescence properties were investigated. Ca, Al, Si, and Eu₂O₃ powders were used as the Ca, Al, Si and Eu sources. NaN₃ is added as the nitrogen source in the interior part of reactants and also as a reducing agent. While NH₄Cl is added for catalysis of the synthesis reaction. These powders were mixed and pressed into a compact which was then wrapped up with an igniting agent (i.e.,Mg+Fe₃O₄). The compact was ignited by electrical heating under a N₂ pressure of 0.2-1.0MPa. Effects of these experimental parameters on the photoluminescence properties and product yield were investigated. The synthesized CaAlSiN₃:Eu²⁺ phosphor absorbs light in the region of 200-600 nm and shows a broad band emission in the region of 500-800 nm due to the 4f⁶5d¹→4f⁷ transition of Eu²⁺. The peak emission intensity is ~106 % of a commercially available phosphor, YAG:Ce³⁺(P46-Y3), and the peak emission wavelength ranges from 610 to 680 nm depending on the Eu²⁺ concentration upon excitation at 460nm.The synthesized phosphor also shows excellent thermal and chemical stability and thus has a potential application as a red phosphor for white LED lighting.

Abstract: The objective of this paper is to integrate lenticular lens with switching images and embedding the infrared watermark to provide value-added and anti-counterfeiting features. Digital halftoning technique has been used to compose animated graphics and the infrared watermark. The infrared watermark consists of halftone dots in cyan, magenta, yellow, and black inks. The carbon material in black ink absorbs the infrared light and the watermark could be displayed under infrared detection. By using the lenticular lens, image-switching effect can be observed from different viewing angles. The results show that it is successful to implement a lenticular display with both image-switching feature and hidden watermark which can be decoded under infrared detection. The proposed method has many potential applications to anti-counterfeiting and brand protection.

Abstract: Learning of the rich historical and cultural backgrounds of scenic spots in a limited time is difficult for nonlocal and foreign tourists during their visit. However, tourists can enhance their visiting experience rapidly and familiarize themselves with and explore local histories and cultures by using digital technology. This study involved developing a smart tourism application system for historical and cultural scenic spots for tourists based on visual search technology. The results of the experiment indicated that the current accuracy of the image search identification is 86%.

Abstract: The FPGA platform is a developing area in the industry applications. With continuous advancement in science and technology, the image quality has entered an era of full-HD. Its resolution reaches 1920x1080 pixels, and its refresh rate comes to 60 fps (Frames Per Second). Taking the 1920x1080 P, 60 fps image sensor as an example, the eye diagram efficacy at both the image input end and the output end were measured. When the input signal was LVDS, the standard value of the eye width and height was 1.092 ns and 100mV respectively. The measured value was 1.297 ns and 149 mV respectively, which are 18% and 49% better than the standard value, respectively. When the output signal was HDMI, the standard [1] of the eye diagram was 424 ps and 400 mV respectively. The measured value was about 540 ps and 600 mV respectively, which are 27% and 50% better than the standard value, respectively. The results of measurement of the electrical characteristics of the system above show that our high-resolution image processing system platform has high reliability.

Abstract: Most anti-shake technologies can compensate the hand shake when taking a static picture. When people use the camera in the dim environment, the shutter opening time will be extended to increase exposure. However, the hand shake will cause the photos blurry if the shutter opening time was too long. The hand shake problem is even more serious when people doing the dynamic image recording. In the past years, the mobile phones with the digital camera and portable video camera were developed vigorously. Taking pictures and recording dynamic image have become the basic functions of mobile phones since the development of the 3G mobile phone. While the specifications of cameras become high resolution and high magnification optical zoom, the traditional electronic anti-shake technology will not be applied in the digital camera because of the large amount of computing power. It is also difficult to apply the optical anti-shake technology in thin 3C products because the volume of optical anti-shake module is too large. Thus, developing a new anti-shake technology which can be applied in the thin 3C products to enhance the photo and video quality is very important. In this paper, the image processing technologies will be applied to calculate the motion signal. Then, the voluntary and involuntary motion signals will be separated by the signal separation algorithm, and finally the dynamic image will be reconstruction by compensating the involuntary shake of each frame to enhance the quality of the dynamic image.