In this paper, a two-dimensional, binary fringe pattern is designed as structured light for 3D measurement. A feature, i.e., a white cross, is placed in the center of the fringe grating. The cross serves as the axes of a reference frame. White square grids are alternated by black stripes vertically or horizontally elsewhere. The relative position of a given point on the fringe with respect to the center can be identified. When the fringe pattern is projected onto the surface of the object, its image is distorted. Therefore, image processing and pattern recognition algorithms are designed to calculate which row and column the particular point belongs to in the original fringe-frame. The pair of emitting and receiving angles for each point in the fringe and CCD frames, respectively, is acquired. Also the coordinate of each 3D point can be calculated. Compared with traditional digital moire methods, this method achieves an absolute measurement of 3D surfaces because the information contained in the pattern is globally structured. Therefore, discontinuity measurement can be solved more easily. Resolution of the proposed method is higher than that of current methods of coding patterns under the same line width limitation due to the principle of pattern design.
KEYWORDS: Digital signal processing, Image encryption, Computer security, Multimedia, Optical signal processing, Network security, Signal processing, Data modeling, Image processing, Telecommunications
In this paper, we present an approach of real-time implementation of multimedia data security based on virtual-optics with the aid of a parallel digital signal processor (DSP). In order to partially compensate the parallelism of optical processing lost by digital implementation, we make full use of parallel hardware architecture and parallel computation structure of the TMS320C6701 DSP, leading to a high-efficiency operation. This approach makes it possible for the virtual-optics imaging methodology (VOIM) to be realized in real-time applications in embedded systems for multimedia data security. Experiments with multimedia data are performed to validate the proposed method, and parameter-sensitivities are quantitatively analyzed and illustrated.
KEYWORDS: Receivers, Data modeling, Information security, Data communications, Computer security, Symmetric-key encryption, Telecommunications, Network security, Data hiding, Systems modeling
A virtual-optical based encryption model with the aid of public key infrastructure (PKI) is presented in this paper. The proposed model employs a hybrid architecture in which our previously published encryption method based on virtual-optics scheme (VOS) can be used to encipher and decipher data while an asymmetric algorithm, for example RSA, is applied for enciphering and deciphering the session key(s). The whole information security model is run under the framework of international standard ITU-T X.509 PKI, which is on basis of public-key cryptography and digital signatures. This PKI-based VOS security approach has additional features like confidentiality, authentication, and integrity for the purpose of data encryption under the environment of network. Numerical experiments prove the effectiveness of the method. The security of proposed model is briefly analyzed by examining some possible attacks from the viewpoint of a cryptanalysis.
KEYWORDS: Holograms, Reconstruction algorithms, 3D image reconstruction, Digital holography, Near field diffraction, Diffraction, Computer simulations, Optical simulations, Charge-coupled devices, 3D vision
This paper describes a method of numerical reconstruction for digital holography with changed viewing angles within the Fresnel domain. The proposed algorithm could not only reconstruct the real image of the original object with different focal lengths but also with changed viewing angles, which could be selected as any angle in space. Some representative simulations are presented to validate the proposed algorithm.
This paper proposes Variable Amplitude Fourier Series (VAFS). For a time-varying signal, the amplitude of VAFS vary as function of the time, which can be used as the tool of time-frequency localization. Based upon VAFS, Local Approximate Index(LAI) is proposed. LAI can be used to measure local maximal freuqency of signal. By using LAI, signal of time-varying can be segmented by frequently and time-invariant interval (TII) of signal can be obtained. Re-sampling of signal and speech segmentation can be effectively processed by using VAFS and LAI.
This paper describes a method of numerical reconstruction for digital holography with changed viewing angles within the Fresnel domain. The proposed algorithm could not only render the real image of the original object with different focal lengths but also with changed viewing angles selected in 3D space. The numerical reconstruction can be implemented by using the Fast Fourier Transform. Some representative simulations are presented to validate the proposed algorithm.
Velocity feedback based actin vibration control of axially moving continua, which include mechanical systems such as high-speed magnetic and paper tapes and band saws, is presented in this paper. Lyapunov direct method is used to prove the asymptotic stability of the closed- loop system under the proposed control law. The stability analysis is performed directly on the system's partial differential equation so that no approximation is involved. Thus the 'spillover' problem, which is caused by using finite dimensional (truncated) models to approximate the infinite dimensional models of distributed parameter systems, is eliminated. The proposed control law can be implemented in either distributed or discrete forms. The sufficient condition for stabilizing the system using non-collocated sensors and actuators is also given. A numerical example of an axially moving string is presented for illustration.
Control of a class of single-link flexible robot arms with bounded unknown pay-load is addressed in this paper. The Lyapunov's direct method is used to prove the asymptotical stability of the closed-loop system under the proposed linear controller. The stability analysis is performed directly on the system's partial differential governing equation, so that no approximation is involved. Thus the 'spillover' problem, which is caused by using finite dimensional (truncated) models to approximate the infinite dimensional models of distributed parameter systems, is eliminated. It is theoretically shown that a simple linear controller with feedback of only joint variables is sufficient to stabilize asymptotically the complex system of a flexible arm with bounded unknown payload. A numerical example of a single-link flexible arm with bounded unknown payload is presented for illustration.
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