This paper presents a new robust watermarking extract scheme for color image by using scale invariant features transform image correction. A binary watermark image is permuted with sequence numbers generated by a secret key in a spatiotemporal chaos system. Then, the binary image watermark was encoded by Gray code, and then adaptively embedded into low frequency components of discrete cosine transform domain in the original color image's blue channel. In watermarking extract scheme, the scale invariant features of images are extracted, and the match points between the watermarking image and the reference image are found. Then the watermarking image is corrected by affine transform of these match points. Although the watermark is only embedded into the blue channel, the other channel can provide the position information of the image processing operations. By comparing the intensities of the low frequency components of discrete cosine transform domain of the corrected and the original image, the extraction method of the watermark is calculating the probability of detecting '0' or '1'. At last, the watermark is extracted from the corrected image. Experimental results show that the proposed scheme is robust and secure against a wide range of image processing operations such as global affine transformation, filtering and lossy compression.
The network-attached optical disk storage system has the advantages of the network-attached storage system and the optical storage device. Due to the data reliability and the removability of the storage medium, this optical storage system is very effective on massive data providing and backup. Recently, achievements have been made in security models and policies in a distributed network system environment and the network-attached storage system environment. However, the relevant research is not enough in the network-attached optical disk storage system, especially in a network-attached optical disc device. So it is significant to analyze the security policy and setup a good security model for the network-attached optical disk storage system. This paper makes a theoretical analysis on the security policy in the network-attached optical disk storage system. Firstly, the difference of the network-attached optical disk storage system and the distributed network system environment is presented. The network-attached optical disk storage system is a special distributed network system, and to meet the requirements of the system security, we use the authentication and key exchange protocol method to decide who is authorized to have what access rights on which objects with respect to some security models and policies in compute system. Secondly, we compare the effect of several types of authentication and key distribution protocols in a distributed network system environment. Then we port these authentication and key exchange protocols on the network-attached optical disk storage system environment. Based on these analyses, this paper proposes a secure key management scheme for security services in the network-attached optical disk storage system over open networks. This scheme focuses on the framework for authentication and the centralized key management, and future work will focus on dynamic membership management.
Multilevel recording has been demonstrated to significantly increase the linear densities achieved with standard methods of binary encoding in optical data storage systems. In this paper we introduce the theoretical concepts and practical coding aspects behind multilevel optical recording system. We show that there are three-stage coding flow and explain how to design and implement the encoder. As an example we give a 5th-power finite state transition diagram of q=8 RLL (2, 10) encoder and compute its adjacent matrix. Especially we discuss the implement method to quickly search decoding table of slider decoder by way of computing the least Hamming distance.
This paper suggests a mode of the heat transfer between hybrid recording medium and the sliding air film. According to the differential theory and the symmetrical theory, the energy of the laser heating can be removed in subsection; the laser power from waveguide in track can be looked as the power in a moment. So we can get the simulation results of the average temperature of the medium. Since hybrid recording head gap is less than 20nm, the temperature gradient field of air film can be simulated by boundary layers theory. This paper simulated air film temperature heated by the near field optical in hybrid recording. The results show that air film heating-up has influence on the slider bearing system, such as fly height and pose. The simulation of the slider fly height and pose illuminate that in the extreme the effect of heating-up of the air film on fly height and pose must be emphasized enough.
A calorific equilibrium equation is used to derive the relativities of optimum recording power and pulse waveform parameters in various disc scanning velocities. Based on the model, a new recording parameters calibrating flow is given as a referenced process. A number of optical recording examples have been examined in detail, and the results have been compared with those calculated data by use of a general summation approach.
Vertical degree of pick-up and disc is an important factor that influences reading and writing date in DVD drive. Measuring and adjusting vertical degree of pick-up and disc is a key working procedure in DVD drive manufacture. Now, measuring method in actual production is an indirect measuring, which measure parallel between spindle motor and traverse. It’s not very accuracy as there are error in pick-up assembles. The paper suggests a new method to measure vertical degree of pick-up and disc, new method measure vertical degree of pick-up and disc directly. The key of new method is measure position of laser from pick-up. A specialty optical circuit and fine CCD camera is need. The CCD camera is responsibility for collection information of laser image of pick-up and sends information to a computer. The specialty software responsibility for calculating position of laser and calculating incline angle between pick-up and disc. Because of characteristic of DVD drive manufacture, the algorithm calculating position of laser image must be design for accuracy and quickness. The paper suggests a specialty algorithm to calculating position of laser image. The algorithm is very accuracy and quickly, it can measure 0.05-degree incline angle error. The new method is helpful to automatic adjusting technique vertical degree of pick-up and disc.
The paper suggests a new scheme of hybrid recording by high refractive index optical waveguide; analyzes the waveguide exit optical field and the near field optical spot energy distribute of the hybrid recording medium surface. We succeed to use the Maxwell electromagnetism theory to model and simulate the waveguide exit energy distribute, obtained the near field optical spot of the hybrid recording medium surface. According to energy balance way, a new model has been adopted and the hybrid recording medium temperature gradient has been studied. The Thermal modeling of two-dimensional transient temperature distributed by the finite element method is studied; with this tool, the hybrid recording medium temperature gradient has been obtained. The hybrid recording areal density may be decided by the dual-gradient (the thermal gradient and magnetic field gradient). According to the simulated results, the track density can reach 500KPTI, if the bit density is 1000kbPI, the area density will be 500Gb/in<sup>2</sup>.
The paper does simulating calculation for power loss problem of waveguide probe by using vector BPM method. The paper got following results: (1) The refractive index difference of core and clad of waveguide probe is one important factor of affecting output power of waveguide probe. (2) The shape of waveguide probe is another factor of effecting the output energy.
Evanescent energy can be used to get extremely small optical spots. For the data storage applications, optical near field is defined in terms of Evanescent coupling between the system used to read or write data and recording layer. Near-field techniques can be applied to optical data storage systems to greatly increase recording density. So near-field recording technique has great potential in optical disc recording system and hybrid recording system. The characteristic of near-field recording spot is of vital importance in the data storage system basing the near-field theory, so it is absolutely necessary to be analyzed and measured. This paper analyses characteristic of near-field spots. The heat response time of the near field to overcome super paramagnetic effect is calculated basing the heat transfer theory. A novel measuring method for the diameter of near-field recording spot is also presented. Since the grain of the recording media is tiny enough, with the aid of atomic force microscope (AFM), near-field optical lithography can be accomplished. The diameter of near-field recording spot can be obtained by specifically designed computer either. So the relationship between the near-field recording spot diameter and the probe size of near-field recording system, the near field recording distance coupling between head and disc can be got.
Higher recording density demands constant flying height over the entire recording area of the disk, however, in the recording procedure, the head doesn't always keep constant flying height, the flying height variation influences the recording density. This paper studies the head-disk coupling in waveguide probe near-field recording, and derives the relationship curve between half amplitude wide of static light distribution as well as static recording density and near-field coupling gap by computer simulation. After defining statistical recording density, we discuss the relationship between flying height variation of the flying optical head and statistical recording density in near-field optical recording.
The paper suggests a new scheme of hybrid recording by high refractive index optical waveguide. A recording bit will be determined by thermal gradient and magnetic field gradient, thermal field gradient be used to determine recording track width, and magnetic field gradient will determine recording bit width. In the scheme thermal gradient will be obtained by laser from an optical waveguide. The optical waveguide is flat structure and composed by three materials. The core is high refractive index material, and the clad is low refractive index material. The paper research relationship between track-width and structure of optical waveguide and analyses influence to track density by material refractive index and core thickness of optical waveguide. In theory the scheme can support 500kPTI track density.
Near-field Recording Optical Disc is a new optical disc recording technique. It has two characteristics: (1) ultra high recording density; (2) very high tracking speed. The paper introduces characteristic of near-field optical disc recording technique. The paper presents energy problem of read-writing system with dynamic state in near-field optical disc recording technique; and does simulating calculations for energy transporting problem between of flying head and optical disc.
The energy loss of fiber tapered is an important problem in research of Near-Field Optical disc technique. To calculate accurately energy loss, laser waveguide model in fiber tapered should be made. The paper discusses the problem of waveguide of fiber tapered with three layers medium (core, clad and air). The paper makes a model that transforms waveguide problem to problem of a series equation. If boundary condition is confirmed, numerical solution of waveguide in fiber tapered can be got by using the model. In the condition of column-symmetry field the paper provides an example.