Dissertations / Theses on the topic 'Optical storage devices'

As the computer industry grows, so will the requirements for data storage. Magnetic memory has been the most stable method in terms of capacity and recording/reading speed. However, we have reached the point where a substantial increase in the capacity cannot be produced without increasing the size of the system. When compact discs (CDs) were introduced in the 1980�s they revolutionized the concept of data storage. While the initial force behind compact discs could easily be said to be the music industry, once recordable and rewritable discs became available they quickly found more use in the computer industry as backup devices. Since their inception, the capacity requirements have far exceeded what is available on a compact disc, and they are now following the same path as magnetic memories. Following this trend, it could be assumed that digital versatile discs or digital video discs (DVDs) have a limited lifetime as a storage medium. In fact it has been noted (Higuchi et al., 1999) that the maximum capacity of digital video discs will be reached in 3 � 5 years. The question then is, what comes next? The efficiency of conventional optical data storage is extremely poor. For an optically thick recording medium, both CDs and DVDs use less than 0.01% of the total volume to store the information. Three-dimensional bit optical data storage endeavors to increase the efficiency by recording information in a volume that is greater than 90% of the total volume. The concept of three-dimensional bit optical data storage was first proposed by Parthenopoulos and Rentzepis in 1989, where they demonstrated that capacities far exceeding that of compact discs could be achieved. Three-dimensional bit optical data storage relies on creating a highly localised chemical or physical change within a recording medium, such that further layers can be recorded without causing interference. Ideally the chemical/physical change in the material should be reversible to enable erasable/rewritable data storage. In order to create a highly localised effect nonlinear excitation can be used; whereby the excitation is limited to a small region around the focal spot. Depending on the material and recording method there are several techniques for reading the information such as transmission imaging or reflection confocal microscopy. However, all the recording and reading methods require focusing to a deep position within a recording medium, such focusing encounters spherical aberration as a result of the difference in the refractive indices between the immersion and recording media. This thesis has concentrated on several areas to understand and develop the concept of three-dimensional bit optical data storage. The photorefractive effect in crystals has been studied for many years and is now widely used in optoelectronic devices. The use of photorefractive polymers is a relatively new and exciting development in optical data storage. Until now they have been used solely in the area of holographic data storage. The research in this thesis was conducted using photorefractive materials that were fabricated in two polymer matrices, poly(N-vinylcarbazole) (PVK) and poly(Methyl Methacrylate) (PMMA). The recording samples also consisted of the following compounds in various proportions, 2,5-dimethyl-4-(p-nirtophenylazo)anisole (DMNPAA), 2,4,7-trinitro-9-fluorenone (TNF) and N-ethylcarbazole (ECZ). In this project two-photon excitation was used as the recording mechanism to achieve erasable/rewritable data storage in a photorefractive polymer. As a result of two-photon excitation, the quadratic dependence of excitation on the incident intensity produces an excitation volume that is confined to the focal region in both the transverse and axial directions. Therefore, focusing the laser beam above or below its previous position provides a method by which layers of information can be recorded in the depth direction of a material, without causing interference from neighbouring layers. The feasibility of two-photon excitation in photorefractive polymers is demonstrated in this thesis. The quadratic relationship between excitation and incident light in two-photon excitation requires high photon density to ensure efficient excitation. The use of ultra-short pulsed lasers, while effective, is not a practical solution for an optical data storage system. This thesis demonstrates the ability to produce three-dimensional erasable/rewritable data storage in a photorefractive polymer using continuous wave illumination. Using this technology it has been possible to achieve a density of 88 Gbits/cm3, which corresponds to a capacity of 670 Gbytes on a compact disc sized recording medium. This is an increase of 1000 times the capacity of a CD and 130 times the capacity of current DVDs. While erasable optical data storage is an exciting prospect there are problems associated with the deterioration of the information. For long term information storage a permanent recording process would be more practical. It is demonstrated that there is a point after which further increases in the recording power result in the formation of a micro-cavity. While two-photon excitation is the recording method for erasable data storage, the increase in power results in an increase in ultra-violet absorption such that multi-photon excitation may occur. This thesis demonstrates the ability to record multi-layered arrays of micro-cavities. The change in refractive index associated with an erasable bit is less than 1%. As a result only phase sensitive reading methods (transmission imaging or differential interference contrast (DIC) microscopy) can be used to image a recorded bit. Both transmission and DIC imaging systems have poor axial resolution and therefore limit the density of the recording system, as well as being large optical systems. The introduction of a split or quadrant detector reduces the size of the optical reading system and is demonstrated to be sensitive enough to detect the phase changes of a recorded bit. However, the change in refractive index across a micro-cavity is large enough that reflection confocal microscopy can be used to detect a bit. It is demonstrated in this thesis that multi-layered micro-cavity arrays can be read using reflection confocal microscopy. Focusing of light to deep positions within an optical thick recording medium has the effect of increasing spherical aberration resulting from the refractive index mismatching between the immersion and recording media. The work in this thesis illustrates the effect of spherical aberration on the performance of both the recording and reading systems. The work conducted in this thesis shows the ability to record multi-layered erasable/rewritable information in a photorefractive polymer using pulsed and continuous wave two-photon excitation. It has also been demonstrated that through multi-photon excitation multi-layered micro-cavity arrays can be fabricated. It has also been illustrated that while spherical aberration deteriorates the performance of the recording and reading systems it is possible to achieve a density of greater than 88 Gbits/cm3.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 1999.
Includes bibliographical references (leaves 106-116).
Three different types of optical fiber devices were investigated for this thesis: actively modelocked fiber lasers, optical fiber ring buffers, and passively mode-locked fiber lasers. Intra-cavity soliton compression was employed in an actively mode-locked fiber laser to reduce the pulse width by a factor of 4.4 below the pulse widths predicted by standard active mode-locking theory. Stability regions for these solitons were mapped out and compared to theoretical predictions. In the second device the dynamics of a 5 Gbit/sec packet of ONES and ZEROS loaded into a phase modulated optical fiber ring buffer were experimentally investigated. A new mode of operation was explored where the cavity length of the buffer was slightly detuned from the modulation frequency that was driving the phase modulator. An investigation into the conditions for successful loading and the storage behavior was performed. In addition, relaxation oscillations, which have affected the storage time of previous high-speed optical ring buffers, were nearly eliminated with a CW holding beam, and significantly enhanced storage times were obtained. Investigations of passively mode-locked fiber lasers included both soliton and stretched-pulse implementations. Two different versions using the soliton configuration were studied; in both cases a waveguide amplifier was used to provide gain, allowing short cavity lengths. A polarization additive-pulse mode- locked version generated 116-fs, 130 pJ solitons at a repetition rate of 130 MHz. Preliminary work was also completed on a second short cavity soliton laser with a semiconductor saturable absorber mirror as the mode-locking mechanism. Using the stretched-pulse cavity design, an environmentally-stable fiber laser was demonstrated to generate 1.8 nJ pulses that were compressible to sub-100 fs. 980-nm pumping requirements for this laser were only 200 mW. Lastly, the first observation and characterization of resonant sideband formation in stretched-pulse fiber lasers was completed. Experimental results were evaluated in conjunction with numerical simulations and a theoretical analysis.
by David John Jones.
Ph.D.

Theoretical and experimental techniques are developed to study three common approaches to focus error signal generation for optical data storage applications. Specifically, the astigmatic, obstruction knife edge (a.k.a. shaded aperture), and critical angle prism systems are studied. These techniques are then applied to a new focus detection system, based on a lateral shearing interferometer, developed by this author. The sensitivity of a given optical system to the primary design point, alignment errors, aberrations and optical recording medium topology are presented. A new approach to constructing the focus error signal for the astigmatic and interferometric techniques is presented which greatly reduces the alignment sensitivity.

A technique is presented that utilizes an on-axis intensity measurement to detect the reflected light from a multiple CD-ROM surface. The thesis includes a computer simulation of the detected signal for scans of various structures and discusses finite size detector effects. A suitably sized detector passes 77% of the total light flux at the detector plane without affecting the depth discrimination property of the technique. Experimentally, a breadboard Height Readout System (HRS) could detect height differences on test relief structures. A signal to noise ratio was obtained that corresponds to a noise equivalent height sensitivity of 30 Angstroms. Therefore, the HRS could discriminate between five levels on the test structure. An addition to the new technique uses a phase plate to determine if the focused beam is going into or out of a pit. Thus, the storage capability per unit area on the disk surface can be increased.

Light can be coupled out of a waveguide to a focused point by a focusing grating coupler and has possible applications in optical data storage. The grating can be fabricated with either e-beam techniques or holographic techniques. Two design methods are demonstrated that model the focusing grating coupler with holographic optical elements. Both methods take a geometrical optics approach to designing the holographic optical elements and both methods make use of commercially available ray trace programs. The first method uses complicated non-rotationally symmetric construction optics and requires either a modified ray trace program or special user defined surfaces. The second method involves a much simpler approach which did not require any changes to an existing ray trace program and requires only rotationally symmetric elements to correct the aberrations.

Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Adibi, Ali; Committee Member: Altunbasak, Yucel; Committee Member: Callen Jr, William R; Committee Member: Gaylord, Thomas K; Committee Member: McLaughlin, Steven W; Committee Member: Trebino, Rick.

Direct measurement of optical phase is used in a high-density optical disk reader. The increased density is achieved by introducing multiple pit depths to replace the single pit depths of a traditional compact disk. Having four independent pit depths can double the storage capacity of a disk. The multi-level pits are read by direct measurement of the phase difference between two laser spots focused onto the disk surface. Extraction of phase information utilizes the equations of phase shifting interferometry with four shifted fringe patterns created simultaneously by a compact optical head. The system speed is therefore limited by the readout electronics instead of by slow mechanical phase shifters. The resulting system can identify four independent levels as well as the direction of transition from one level to another. The system also has low sensitivity to vibrations and to changes in the fringe contrast and beam intensity.

This thesis concerns a study of the application, and performance optimization, of standard lead-lag compensation techniques to improve the closed loop performance of a focus servo system for an optical data storage device. Only with proper application of these compensation techniques will it be possible to meet the sub-micrometer focus error tolerances while maintaining the stability of the closed loop system. The performance indices used in this optimization study are the Integral of the Squared Error (ISE), the Integral of the Absolute Error (IAE), and the Integral of the Time multiplied by the Absolute Error (ITAE) as defined below, with the error function e(t) being the focus error of the closed loop servo system in response to a step input. ISE= ∫OT e²(t) dt IAE= ∫OT
e(t)
dt ITAE= ∫OT t
e(t)
dt

Three applications of Smith's model of magneto-optical effects in stratified magnetic media are presented. Each application involves the incident-angle dependence of magneto-optical effects which Smith's model treats explicitly. In addition. the three applications address current issues in magnetic and magneto-optical recording. The first problem considered is that of nonmagnetic surface layers which form on magnetic recording heads. The second is a theoretical treatment of effects which arise in magneto-optical recording when high numerical-aperture optical systems are combined with media exhibiting interference-enhanced optical properties. The final application is a novel technique for determining the entire dielectric tensor of materials used for magneto-optical recording. The incident-angle dependence of the longitudinal Kerr effect is employed to study nonmagnetic surface layers which form on ferrite recording heads. Calculations based on the Smith model show a correlation between the inert-layer thickness and the incident-angle dependence of the longitudinal Kerr effect. Experimental results confirm the shift in the angular position of the signal peak. in agreement with the theory for finite inert-layer thickness. An unambiguous determination of the inert-layer thickness for ferrite materials is prevented because of a periodic dependence of the peak angle on the inert-layer thickness. Jones-matrix algebra is used with the Smith model to quantitatively determine the effects of obliquely-incident rays on the reflectance and magneto-optical readout signals for various magneto-optical media structures. The most antireflective structure is found to be very sensitive to incident-angle effects. Structures with moderate reflectance (>10%). however. are not significantly affected by incident-angle effects. Finally. a technique for the determination of the optical and magneto-optical constants from multiple incident-angle measurements of reflectance and Kerr rotation is presented. The experimental system employs a Helium-Neon laser and a rotating differential detection system. The technique is used to investigate the optical properties of a series of Cu/Co multilayers and a comparison with a model based on the bulk optical. constants of Cu and Co is made. Anomalous behavior is observed for multilayers with very thin periods.

This study develops the foundation of a digitally implemented control system for the radial positioning of the read/write heads of an optical disk drive system. Topics addressed are: sample rate selection, state reconstruction, closed-loop system response, disk track-following filters, and measurement noise filters. Consideration is given to the unmodeled dynamic's influence on system performance, system sensitivity to parameter variations, and a one sample computational delay. What has been concluded from this work is that the system must be further desensitized to parameter variations, and, at this stage of the development of the control scheme, neither a computational delay nor the unmodeled dynamics degrade system performance significantly.

In this PhD Thesis I present some methods for characterizing PA-LCoS microdisplays. It is useful to fully characterize this type of devices for evaluating its performance required in different applications. We have tested its validity in different applications such as diffractive optics elements (DOEs). Finally we apply these microdisplays in a full holographic data storage scheme using a photopolymer as holographic recording medium. We evaluate the capability of PVA/AA photopolymer for this holographic data storage system that incorporates as a novelty a convergent correlator geometry.

Many applications in optical research require the use of diffraction limited point images with reduced spot sizes. The instrumentation that evaluates these small diameter images must have high resolution (sub-micron) capabilities. One method used to measure sub-micron optical point images is a scanning grating technique. However, many characteristics of this measurement technique have not been fully examined. In this paper, the sensitivity of this measurement technique to the scanning mechanism, beam characteristics, and grating tilt is evaluated.

ANP; FINEP; MCT; CAPES
Este trabalho objetiva otimizar a localização de um robô móvel para a inspeção dos tanques de armazenamento de GLP -- Gás Liquefeito de Petróleo -- e permitir a navegação autônoma deste robô por toda a superfície do tanque. A falta de marcos no interior dos tanques levou ao desenvolvimento de uma solução envolvendo detecção de pequenas estruturas com sensores LIDAR (Light Detection and Ranging - Detecção e Telemetria por Luz) aplicada aos cordões de solda, estes sim presentes no interior do tanque, que é apresentada na primeira parte do trabalho. Em seguida, aplicando uma técnica de fusão de dados, as diferentes fontes de odometria presentes no robô são combinadas, permitindo uma precisão mais elevada na inspeção de modo geral. Por fim, o mapeamento e navegação simultâneos do exterior da esfera é abordado, a fim de se adicionar uma camada suplementar ao mapa digital, indicando os locais onde existem falhas. Testes para validação de cada uma das técnicas foram efetuados e uma análise de desempenho é apresentada ao final do trabalho.
This work aims to optimize localization of a climbing inspection robot for spherical LPG -- Liquified Petroleum Gas -- tanks and allow autonomous navigation along the entire surface of these tanks. One solution envolving small structures detection using LIDAR sensors is applied to the weld beads that are present inside the tanks. This solution is developed on the first part of this work. Following, a data fusion technique is used to combine the diferent odometry sources on the robot, resulting in a better, higher precision on the inspection as a whole. Finnaly, simultaneous mapping and navigation on the exterior of the spherical tank was studied in order to add one extra layer to the digital map, pinpointing the places where failures and weld beams were found. Validation tests for each one of this techniques are carried out and a performance analysis is also documented herein.

Thesis (S.M.M.O.T.)--Massachusetts Institute of Technology, Sloan School of Management, Management of Technology Program, 2000.
Also available online at the DSpace at MIT website.
Includes bibliographical references (leaves 51-53).
Standards have been a very important issue in many industries as the innovators of the standard technology have tremendous power in the industry. The standard holders are supposed to have the dominant market position and technology leadership for further generation of the product as well as direct royalty income from the intellectual property. However, other various forces are also included in the evolution of the market and the technology. This thesis deals with the issues related to the evolution of standards in the optical storage device industry and other forces leading the market competition. Philips and Sony, the innovators of the CD technology, had taken the technology leadership of the industry for more than a decade. However, early followers such as Toshiba, Hitachi, and Panasonic took the leading position of the market, and competed with Philips and Sony for the standardization of DVD. The increased number of participants and the influence of complementors made the DVD standardization process much more complex. This trend will continue as current market leaders, who are late entrants, are added to the standard competition. This case shows that not only taking advantage from standardization but also proper market entry timing and continuous innovation is important for success in the optical storage market.
by Do-Joon Lee.
S.M.M.O.T.

An increased penetration of renewable energy into the electric power grid is desirable from an environmental standpoint as well as an economical one. However, renewable sources such as wind and solar energy are often variable and intermittent, and additionally, are non-dispatchable. Also, the locations with the highest amount of available wind or solar may be located in areas that are far from areas with high levels of demand, and these areas may be under the control of separate, individual entities. In this dissertation, a method that coordinates these areas, accounts for the variability and intermittency, reduces the impact of renewable energy forecast errors, and increases the overall social benefit in the system is developed. The approach for the purpose of integrating intermittent energy sources into the electric power grid is considered from both the planning and operations stages. In the planning stage, two-stage stochastic optimization is employed to find the optimal size and location for a storage device in a transmission system with the goal of reducing generation costs, increasing the penetration of wind energy, alleviating line congestions, and decreasing the impact of errors in wind forecasts. The size of this problem grows dramatically with respect to the number of variables and constraints considered. Thus, a scenario reduction approach is developed which makes this stochastic problem computationally feasible. This scenario reduction technique is derived from observations about the relationship between the variance of locational marginal prices corresponding to the power balance equations and the optimal storage size. Additionally, a probabilistic, or chance, constrained model predictive control (MPC) problem is formulated to take into account wind forecast errors in the optimal storage sizing problem. A probability distribution of wind forecast errors is formed and incorporated into the original storage sizing problem. An analytical form of this constraint is derived to directly solve the optimization problem without having to use Monte-Carlo simulations or other techniques that sample the probability distribution of forecast errors. In the operations stage, a MPC AC Optimal Power Flow problem is decomposed with respect to physical control areas. Each area performs an independent optimization and variable values on the border buses between areas are exchanged at each Newton-Raphson iteration. Two modifications to the Approximate Newton Directions (AND) method are presented and used to solve the distributed MPC optimization problem, both with the intention of improving the original AND method by improving upon the convergence rate. Methods are developed to account for numerical difficulties encountered by these formula- tions, specifically with regards to Jacobian singularities introduced due to the intertemporal constraints. Simulation results show convergence of the decomposed optimization problem to the centralized result, demonstrating the benefits of coordinating control areas in the IEEE 57- bus test system. The benefit of energy storage in MPC formulations is also demonstrated in the simulations, reducing the impact of the fluctuations in the power supply introduced by intermittent sources by coordinating resources across control areas. An overall reduction of generation costs and increase in renewable penetration in the system is observed, with promising results to effectively and efficiently integrate renewable resources into the electric power grid on a large scale.

Le premier volet de cette thèse est consacré à la modélisation des phénomènes de transport dans le LN. Partant d'une analyse critique des modèles de bande usuels, nous montrons leur inadéquation dans le cas du LN et nous proposons un modèle de saut basé sur la théorie des petits polarons. Nous étudions d'abord par simulation Monte-Carlo la décroissance d'une population de polarons liés NbLi4+ relaxant vers des pièges profonds FeLi3+. Nous montrons que les pièges FeLi3+ ont des rayons effectifs particulièrement grands, rayons qui augmentent encore à température décroissante, et limitent considérablement les longueurs de diffusion des polarons. Les résultats de simulations sont ensuite confrontés aux résultats expérimentaux obtenus par différentes techniques ; Absorption photo-induite, Raman, Enregistrement holographique et Pompe-sonde. Le deuxième volet de cette thèse est consacré aux applications électro-optiques dans le LN périodiquement polarisé (PPLN). Sous l’effet d’une tension électrique, l’indice de réfraction du PPLN est périodiquement diminué et augmenté, formant ainsi un réseau d’indice activable électriquement. Un premier composant utilisant l’effet électro-optique dans du PPLN a été développé et démontré expérimentalement. Dans ce composant, la lumière est défléchie sous l’effet de la tension électrique par le réseau d’indice. Ce déflecteur de Bragg atteint une efficacité de diffraction proche de 100% avec une faible tension de commande de l’ordre de 5 V. Un deuxième composant a également été proposé, où la lumière se propage perpendiculairement aux parois de domaines du PPLN. Dans cette configuration un réflecteur de Bragg électro-optique peut être réalisé
The first part of this thesis is devoted to the modeling of transport phenomena in the LN. From a critical analysis of the usual band models, we show their inadequacy in the case of LN and we propose a hopping model based on the theory of small polarons. We first study by Monte-Carlo simulation the population decay of bound polarons NbLi4+ in deep traps FeLi3+. We show that the traps (FeLi3+) have particularly large effective radii, which increase further at decreasing temperature, and considerably limit the diffusion lengths of the polarons. The results of simulations are then compared with experimental results obtained by different techniques; Light-induced absorption, Raman, Holographic storage and Pump-Probe. The second part of this thesis is devoted to electro-optical applications in the periodically poled LN (PPLN). Under the effect of an electrical voltage, the refractive index of the PPLN is periodically decreased and increased, thus forming an electrically activatable index grating. A first component using the electro-optical effect in PPLN has been developed and demonstrated experimentally. In this component, the light is deflected under the effect of the electrical voltage by the index grating. This Bragg deflector achieves a diffraction efficiency of close to 100% with a low drive voltage of the order of 5 V. A second component has also been proposed, where light propagates perpendicularly to the domain walls of the PPLN. In this configuration an electro-optic Bragg reflector can be realized

The existing power grids that form the basis of the respective electrical power infrastructures for various states and nations around the world, are expected to undergo a period of rapid change in the near future. The key element driving this change is the emergence of the Smartgrid. The Smartgrid paradigm represents a transition towards an intelligent, digitally enhanced, two-way power delivery grid. The aim of the Smartgrid is to promote and enhance the e_cient management and operation of the power generation and delivery facilities, by incorporating advanced communications, information technology, automation, and control methodologies into the power grid proper. Smartgrid's are currently an active topic for research, where the research is strongly focused on developing new technologies such as: demand response, power generation management, pricing modelling and energy markets participation, power quality, and self-healing scenarios. In recent times, in both the United States of America and Europe, many new projects have begun which are specifically directed towards developing “Smartgrid” technologies. In Australia, the Federal Government has recently initiated funding plans to promote the commercialisation of renewable energy. In order to exploit these developments, Edith Cowan University (ECU); which is a High Voltage (HV) customer for the major utility network of Western Australia, and which owns its own transformers and Low Voltage (LV) network; is planning to integrate renewable energy suppliers within its LV network. The aim of this research is to introduce a smart decision making system, which can manage the operation of disparate power generation sources installed on a LV network (microgrid); such as that owned by ECU on its campuses. The proposed energy management system is to gather data in real-time, and it must be capable of anticipating and optimising energy needs for each operational scenario that the microgrid might be expected to experience. The system must take into account risk levels, while systematically favouring low economic and environmental costs. A management system application, based on autonomous and distributed controllers, is investigated in a virtual environment. The virtual environment being a full-scale simulation of ECU's microgrid; with solar panels, wind turbines, storage devices, gas gen-sets, and utility supply. Hence the simulation studies were conducted on the basis of realistic demand trends and weather conditions data. The major factors for reducing the cost of generation in the case study, were identified as being: 1) demand forecasting; 2) generation scheduling; 3) markets participation; and 4) autonomous strategies configuration, which is required to cope with the unpredictable operation scenarios in LV networks. Due to the high uncertainty inherent within the operational scenarios; an Artificial Intelligence (AI) deployment for managing the distributed sub-systems was identified as being an ideal mechanism for achieving the above mentioned objectives. Consequently it is proposed that Multi-Agent System (MAS) technology be deployed, to enable the system to respond dynamically to the unpredictable operational conditions by updating the method of analysis. The proposed system is to behave in a strategic manner when dealing with the expected operational scenarios, by aiming to achieve the lowest possible cost of power generation for the microgrid. The simulated system is based on realistic operational scenarios, which have been scaled to suit the size and type of load in the case study. The distributed intelligent modules have proven to be successful in achieving the potential benefits of the dynamic operational conditions, by minimising the cost of power generation. The distributed intelligent modules, which form the basis of the proposed management systems, have been designed to perform the following functions: 1. Provide accurate demand forecasts through the utilisation of an AI-based adaptive demand forecasting model. The novel demand-forecast modelling technique, which was introduced to model demand in the case study, has been utilised to supply reasonably accurate demand forecasts to other stages of processing in the management system. The forecasts are generated from this model, by monitoring and controlling the forecasting error to ensure consistent and satisfactory forecasts. 2. Make optimum decisions concerning the operation of the power generators by considering the economic and the environmental costs. In order to deal with the complexity of the operational conditions, a smart and adaptive generation scheduling method was implemented for the case study. The method was primarily applied to control the charging/ discharging process of the Storage Devices (SDs) among the other generators. The proposed method aims at controlling the resources, and extracting the benefit of having an hourly based variable generation cost. 3. Integrate the microgrid into the electricity market, in order to enable the microgrid to offer its spinning and non-spinning power generation reserve as Ancillary Services (AS) to the grid. To this end, studying the operational mechanisms of the Australian market was essential prior to building the proposed market participation rules which form an integral part of the proposed management system. As a result we used the market data, by approaching the market operators to create a semi-realistic competitive market environment for our simulations. Consequently, a smart and adaptive pricing mechanism, that adapts the AS prices to the amount of electricity on offer, and the level of demand in the market has been presented. The motivation for introducing the proposed management system, is to achieve a transition plan for current microgrids, so that they can have a commercial connection to the future Smartgrid. The results obtained in this work show that there is a signi_cant economic and environmental advantage to be gained from utilising intelligence when managing electricity generation within a power grid. As a consequence, selecting the appropriate management strategy is fundamental to the success of the proposed management system. In conclusion, modelling of the proposed strategies using MAS technology has proven to be a successful approach, and one that is able to reflect the human attitude; in making critical decisions and in reducing the cost of generation.

碩士
立德管理學院
科技管理研究所
92
The purpose of this research is to develop a predicting S curve for same product of multi-tech, by investigating on the CD-ROM, DVD-ROM, and CD-RW in current market, so that a predicting model can be build and test. With the technology predicting S curve model and the characteristic price theorem of economics analysis combined together, this article not only describes what technology progress means to the change of market need, but develops a brand new idea of how to predict the technology in multi-dimensioned S curve as a mark-on tool between old and new technology when producers predict the progress of technology. The samples, 1522 in total, were taken by the PCDIY magazine from price checking on CD-ROM, DVD-ROM, and CD-RW from 1998 to 2003. The first published time of a product was either referenced on the ITIS yearly report or PCDIY magazine. Considering the theory of S curve and characteristic price theorem proposed by Forster(1986), Christensen(1992,1997), Lancaster(1966) and Rosen(1974), this research develop a better way to do the multi-dimensioned and single technology prediction respectively. What this research does is basically to provide two new ideas. First of all, it proposes that the technology S curse is actually containing both technology life cycle and physical property; as a result, the error of technology S curse can be reduced when in used. Second, developing a multi-dimensioned S curve predicting model would be more suitable and explainable than a single-dimensioned one. Meanwhile, with the technology S curse of a balanced market, it would make up the deficiency of applying the technology S curse on explaining the life cycle of a product or discussing the physical property of technology from the producer’s point of view in the past.

The non-interacting and high-speed nature of light makes it an ideal carrier of information that is essential for transmission of quantum information. Indeed, many proposals and demonstrations of quantum cryptography rely on the use of fibre-optic networks. Construction of a memory that can store light and preserve its quantum properties will be useful in a range of quantum information systems such as secure quantum communication and quantum computation. This is why a quantum memory for light is a remarkable objective. The key to quantum memory is to store the probability amplitude of the possible outcomes of measurement but without measurement. An important criterion for a quantum memory is that the efficiency of the recall must exceed 50%. This is the crucial no-cloning limit for security of information, since it guarantees that nobody can access the information by copying it. This benchmark is important because any kind of deterministic amplification of quantum information is fundamentally impossible. On-demand retrieval of information and ability to controllably manipulate the quantum information are also important for quantum applications. When light is absorbed by atoms, it is actually possible to reverse the absorption process. In our memory system: light is absorbed by an ensemble of atoms and, using careful conditioning and control, we can cause the stored light to be regenerated and released at a later time. This is done by applying a gradient of magnetic field along the atomic ensemble that is the basis for our optical memory. To recall the light we flip the sign of the gradient field. This kind of reversible absorption is called photon echo, hence the name of our scheme: The Gradient Echo Memory (GEM). This simple protocol is used in our experiment and can be applied to a range of different atomic systems. We have extended the GEM protocol and experimentally implemented a memory using three-level atoms. We used an off-the-shelf Rb vapour cell operating above room temperature as the memory medium. In this realisation, we broke the efficiency record with 87% recall of the input light pulse. Moreover, through complete state tomography of coherent states we have demonstrated the ability of our memory to noiselessly store quantum states of light. We have also demonstrated that the memory can store a string of pulses and then recall the pulses ondemand in arbitrary order allowing re-sequencing of the stored information. Furthermore, we have shown that pulses could be time-compressed, time-stretched or split into multiple smaller pulses and selectively recalled in several pieces. This technique enables the construction of an optical random-access memory for quantum information. Moreover, the scheme to manipulate the spectral properties of optical data, stored inside the memory, has been introduced. We have also investigated the possibility of obtaining large nonlinear phase shifts between single photons inside the memory. Such strong interactions can be used for the implementation of universal quantum gates.

碩士
國立臺灣大學
國際企業學研究所
89
Abstract Graduate Institute of International Business National Taiwan University Name: Steel Su June 2001 Advisor: Dr. M.J. Tang The Core Technology Platforms: A Building and Leveraging Strategy for Optical Storage Devices This study explores the competitive strategy of the optical storage devices (OSD) with a particular focus on the produce development strategy. In the past decade, computer peripheral industry in Taiwan exhibited phenomenal growth due to its technological infrastructure. The OSD industry in Taiwan quickly acquired a lion’s share in the world market and expanded its capacity as a rapid pace and thus has shown its important position in the Taiwanese information industry. One of the major goals of this study is to examine industry background and the dynamic trends in the industry and to study the dynamic competitive strategy in the industry, which may lead to a global leadership position for Taiwanese OSD producers. This study is based on relevant theories, consults historical reports and develops trend analysis. Finally, this thesis proposes an innovation and dynamic competitive strategy. According to the time-based competition, this study brings up a “core technology platform” construct and a building and stretching strategy. In fact, by the dynamic competition analysis, this technology-platform driven strategy has been adopted by a local company and proved to be successful in reducing the development time of OSD significantly. A number of suggestions are proposed at the end of the thesis. Keywords: Optical Storage Device, Products Platform, Industry Revolution, Dynamic Competence and Dynamic Strategic Strategy.

D.Ing. (Electrical and Electronic )
This thesis describes a neural network based system for the classification of handwritten digits as found on real-life mail pieces. The proposed neural network uses a modular architecture which lends itself to parallel implementation. This modular architecture is shown to produce adequate performance levels while significantly reducing the required training time. The aim of the system is not only to achieve a high recognition performance, but also to gain more insight into the functioning of the neural networks. This is achieved by using separate feature extraction and classification stages. The output of the feature extraction stage gives a good indication of the final performance level of the classifier, even before training. The need for an optimal feature set is expressed to elevate the performance levels even further.

by Lui Bong Chun, Richard.
Thesis (M.Phil.)--Chinese University of Hong Kong, 1995.
Includes bibliographical references.
Abstract
Acknowledgment
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Background for the Project --- p.1
Chapter 1.1.1 --- Interests in Blue-Green Laser --- p.1
Chapter 1.1.2 --- Progress of Blue-Green Laser --- p.2
Chapter 1.2 --- The Aim of the Project --- p.3
Chapter 1.3 --- Overview the Remaining Parts of this Thesis --- p.4
Chapter 1.4 --- References --- p.6
Chapter Chapter 2 --- Sum Frequency Generation --- p.8
Chapter 2.1 --- Introduction --- p.8
Chapter 2.2 --- Sum Frequency Generation --- p.8
Chapter 2.2.1 --- Theoretical Background for Sum Frequency Generation --- p.9
Chapter 2.2.2 --- The Coupled Wave Equations for SFG --- p.13
Chapter 2.2.3 --- Phase Matching Considerations --- p.16
Chapter 2.3 --- References --- p.18
Chapter Chapter 3 --- Cerenkov Radiation --- p.19
Chapter 3.1 --- Introduction --- p.19
Chapter 3.2 --- The Properties of Cerenkov Radiation by Using TM Mode --- p.21
Chapter 3.2.1 --- Refractive Index Notation --- p.23
Chapter 3.2.2 --- Fundamental Wave TM Guides Mode --- p.23
Chapter 3.2.3 --- Second Harmonic TM Radiation Mode --- p.24
Chapter 3.2.4 --- Efficiency of SHG --- p.25
Chapter 3.3 --- Simplified Model Analysis of Cerenkov Radiation in TE Mode --- p.29
Chapter 3.4 --- Simulation --- p.33
Chapter 3.4.1 --- Modeling the LiNb03 --- p.33
Chapter 3.4.2 --- Modeling an Asymmetric Slab Waveguide ´ؤPMMA doped with MNA on Fused Quartz --- p.37
Chapter 3.4.3 --- Modeling a Symmetric Slab Waveguide ´ؤPMMA doped with MNA on Fused Quartz --- p.42
Chapter 3.5 --- References --- p.47
Chapter Chapter 4 --- Ellipsometry --- p.49
Chapter 4.1 --- Introduction --- p.49
Chapter 4.2 --- General Principles --- p.49
Chapter 4.3 --- Basic Operation --- p.50
Chapter 4.4 --- The Optical Constants of the Bulk Materials --- p.51
Chapter 4.5 --- Calculation the Refractive Index of the Substrates --- p.53
Chapter 4.6 --- Ellipsometric Theory for the Thin Film --- p.57
Chapter 4.7 --- Measurement the Refractive Index and the Thickness of the Thin Film --- p.59
Chapter 4.7.1 --- Data --- p.62
Chapter 4.7.2 --- Discussions --- p.73
Chapter 4.8 --- Calculation the Refractive Index of the thin Film by Considering as a Bulk Material --- p.78
Chapter 4.9 --- References --- p.80
Chapter Chapter 5 --- Prism Coupling --- p.81
Chapter 5.1 --- Introduction --- p.81
Chapter 5.2 --- Coupling of a Plane Wave --- p.82
Chapter 5.3 --- Numerical Approach for the Calculation of the Coupling Efficiency --- p.85
Chapter 5.4 --- Experiment --- p.88
Chapter 5.4.1 --- Experimental Setup --- p.88
Chapter 5.4.2 --- Experimental Result and Discussions --- p.90
Chapter 5.5 --- References --- p.92
Chapter Chapter 6 --- Conclusion --- p.93
Chapter Chapter 7 --- Future Plans --- p.96
Chapter 7.1 --- Simplified Model of Corona Poling --- p.96
Chapter 7.2 --- Advanced Models of Poling --- p.98
Chapter 7.2.1 --- Slab Waveguide --- p.98
Chapter 7.2.2 --- Channel Waveguide --- p.99
Chapter 7.3 --- References --- p.100
Chapter Appendix 1 --- Materials' Descriptions --- p.A-l
Chapter A.1.1 --- 2-Methyl-4-Nitoaniline --- p.A-1
Chapter A.1.2 --- Poly ( Methyl Methacrylate ) --- p.A-3
Chapter A.1.3 --- References --- p.A-4
Chapter Appendix 2 --- Fabrication Procedures --- p.A-5
Chapter A.2.1 --- Cleaning the Apparatus --- p.A-5
Chapter A.2.2 --- Cleaning the Substrate --- p.A-5
Chapter A.2.3 --- Thin film Fabrication --- p.A-5
Chapter A.2.4 --- Thin Film Removal --- p.A-6
Chapter A.2.5 --- References --- p.A-6
Chapter Appendix 3 --- Alpha Step --- p.A-7
Chapter A.3.1 --- Introduction --- p.A-7
Chapter A.3.2 --- Experimental Setup --- p.A-8
Chapter A.3.3 --- Experimental Results --- p.A-9
Chapter A.3.3.1 --- Thin Film of PMMA without Dopant --- p.A-9
Chapter A.3.3.2 --- Thin Film of PMMA doped with MNA --- p.A-19
Chapter A.3.4 --- Discussions --- p.A-27
Chapter A.3.5 --- References --- p.A-28
Chapter Appendix 4 --- Scanning Electron Microscope --- p.A-29
Chapter A.4.1 --- Scanning Electron Microscope --- p.A-29
Chapter A.4.2 --- Reference --- p.A-30
Chapter Appendix 5 --- Gaussian Beam & Coordinate System Transformation --- p.A-31
Chapter A.5.1 --- Gaussian Beam in a Homogeneous Medium --- p.A-31
Chapter A.5.2 --- Transformation of the Coordinate Systems --- p.A-32
Chapter A.5.3 --- Reference --- p.A-32
Chapter Appendix 6 --- Waist Size Measurement of Gaussian Beam --- p.A-33
Chapter A.6.1 --- Waist Size Measurement of Gaussian Beam --- p.A-33
Chapter A.6.2 --- References --- p.A-34
Chapter Appendix 7 --- Quasi Phase Matching --- p.A-35
Chapter A. 7.1 --- Introduction --- p.A-35
Chapter A.7.2 --- Basic Concept of QPM --- p.A-36
Chapter A.7.3 --- References --- p.A-38
Chapter Appendix 8 --- Program Listing --- p.A-41
Chapter A.8.1 --- Program Listing ( Chapter 3 ) --- p.A-41
Chapter A.8.1.1 --- Program 3.1 (transcendental.m ) --- p.A-41
Chapter A.8.1.2 --- Program 3.2 (linbo3.m) --- p.A-42
Chapter A.8.2 --- Program Listing ( Chapter 4 ) --- p.A-45
Chapter A.8.2.1 --- Program 4.1 ( ellipsometry.m ) --- p.A-45
Chapter A.8.3 --- Program Listing ( Chapter 5 ) --- p.A-47
Chapter A.8.3.1 --- Program 5.1 ( parameter.m ) --- p.A-47
Chapter A.8.3.2 --- Program 5.2 ( coupling.m ) --- p.A-49
Chapter A.8.3.3 --- Program 5.3 ( v_3_amp.m ) --- p.A-50
Chapter A.8.3.4 --- Program 5.4 ( input_profile.m ) --- p.A-51

by Chung-Wing Ng.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.
Includes bibliographical references (leaves 100-107).
Abstracts in English and Chinese.
Abstract --- p.ii
Acknowledgment --- p.vi
Table of Contents --- p.vii
List of Tables --- p.x
List of Figures --- p.xi
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Image-based Video Description --- p.2
Chapter 1.2 --- Video Summary --- p.5
Chapter 1.3 --- Video Matching --- p.6
Chapter 1.4 --- Contributions --- p.7
Chapter 1.5 --- Outline of Thesis --- p.8
Chapter Chapter 2 --- Literature Review --- p.10
Chapter 2.1 --- Video Retrieval in Digital Video Libraries --- p.11
Chapter 2.1.1 --- The VISION Project --- p.11
Chapter 2.1.2 --- The INFORMEDIA Project --- p.12
Chapter 2.1.3 --- Discussion --- p.13
Chapter 2.2 --- Video Structuring --- p.14
Chapter 2.2.1 --- Video Segmentation --- p.16
Chapter 2.2.2 --- Color histogram Extraction --- p.17
Chapter 2.2.3 --- Further Structuring --- p.18
Chapter 2.3 --- XML Technologies --- p.19
Chapter 2.3.1 --- XML Syntax --- p.20
Chapter 2.3.2 --- "Document Type Definition, DTD" --- p.21
Chapter 2.3.3 --- "Extensible Stylesheet Language, XSL" --- p.21
Chapter 2.4 --- SMIL Technology --- p.22
Chapter 2.4.1 --- SMIL Syntax --- p.23
Chapter 2.4.2 --- Model of SMIL Applications --- p.23
Chapter Chapter 3 --- Overview of ADVISE --- p.25
Chapter 3.1 --- Objectives --- p.26
Chapter 3.2 --- System Architecture --- p.26
Chapter 3.2.1 --- Video Preprocessing Module --- p.26
Chapter 3.2.2 --- Web-based Video Retrieval Module --- p.30
Chapter 3.2.3 --- Video Streaming Server --- p.34
Chapter 3.3 --- Summary --- p.35
Chapter Chapter 4 --- Construction of Video Table-of-Contents (V-ToC) --- p.36
Chapter 4.1 --- Video Structuring --- p.37
Chapter 4.1.1 --- Terms and Definitions --- p.37
Chapter 4.1.2 --- Regional Color Histograms --- p.39
Chapter 4.1.3 --- Video Shot Boundaries Detection --- p.43
Chapter 4.1.4 --- Video Groups Formation --- p.47
Chapter 4.1.5 --- Video Scenes Formation --- p.50
Chapter 4.2 --- Storage and Presentation --- p.53
Chapter 4.2.1 --- Definition of XML Video Structure --- p.54
Chapter 4.2.2 --- V-ToC Presentation Using XSL --- p.55
Chapter 4.3 --- Evaluation of Video Structure --- p.58
Chapter Chapter 5 --- Video Summarization --- p.62
Chapter 5.1 --- Terms and Definitions --- p.64
Chapter 5.2 --- Video Features Used for Summarization --- p.65
Chapter 5.3 --- Video Summarization Algorithm --- p.67
Chapter 5.3.1 --- Combining Extracted Video Segments --- p.68
Chapter 5.3.2 --- Scoring the Extracted Video Segments --- p.69
Chapter 5.3.3 --- Selecting Extracted Video Segments --- p.70
Chapter 5.3.4 --- Refining the Selection Result --- p.71
Chapter 5.4 --- Video Summary in SMIL --- p.74
Chapter 5.5 --- Evaluations --- p.76
Chapter 5.5.1 --- Experiment 1: Percentages of Features Extracted --- p.76
Chapter 5.5.2 --- Experiment 2: Evaluation of the Refinement Process --- p.78
Chapter Chapter 6 --- Video Matching Using V-ToC --- p.80
Chapter 6.1 --- Terms and Definitions --- p.81
Chapter 6.2 --- Video Features Used for Matching --- p.82
Chapter 6.3 --- Non-ordered Tree Matching Algorithm --- p.83
Chapter 6.4 --- Ordered Tree Matching Algorithms --- p.87
Chapter 6.5 --- Evaluation of Video Matching --- p.91
Chapter 6.5.1 --- Applying Non-ordered Tree Matching --- p.92
Chapter 6.5.2 --- Applying Ordered Tree Matching --- p.94
Chapter Chapter 7 --- Conclusion --- p.96
Bibliography --- p.100

M.Ing.
Ice storage systems are used to store thermal energy in the form of ice build-up inside storage tanks. During off peak hours, the chiller is used to charge up the storage tank until it is full. During on peak hours, the storage is discharged to meet a certain fraction of the building cooling load. The control strategy employed determines the extent to which the storage compensates the chiller and visa versa. Given the way in which electricity rates are structured, ice storage systems become an effective energy management strategy. The objective of the study is to compare energy savings derived by using conventional control strategies versus optimal control. Conventional control strategies can be classified as chiller priority control, constant proportion control and storage priority control. In chiller priority control, the chiller meets the cooling load subject to a pre-set limit not being exceeded. Should the limit be exceeded, the remaining cooling load (at each time horizon) is compensated for by the storage. In constant proportion control, both the storage and chiller meets a constant proportion of the cooling load. Storage priority control attempts to discharge as much of the storage as possible, such that at the end of the planning horizon, the ice build up in the storage tank is just depleted. Optimal control employs dynamic programming to ensure that the integrated cost of energy, during the entire planning horizon, is minimal. A steady state ice storage plant model for analysing the performance of the control strategies is presented. The model computes the inlet and outlet temperatures into the various components of the air-conditioning plant, being the air-handling units, heat exchanger, ice storage tanks and chiller. The maximal possible discharge and charging rate at each time period (for the different control strategies) is determined using the model. Given the state of charge of the ice storage tank at each time period, it is then possible to calculate chiller power consumption. The power consumed by fans, fan coil units and pumps (in the air-conditioning plant) has not been calculated in the present analysis, however, the model can easily be extended to include such calculations. The ice storage plant model, enabled simulations of the different control strategies to be carried out over building cooling load profiles for summer and winter. Based on a 24-hour planning horizon, optimal control is found to be optimal and the only consistently performing strategy for all seasons. For the 5000 kWh ice storage plant investigated, optimal control yielded 25% energy savings in June and 12% in January, amounting to a potential of R 11 000 per month. Chiller priority control was near optimal in January but consumed 25% more energy than the base case (without storage) in June. Constant proportion control was optimal in January but poorer in June. Storage priority control is found to be optimal in June but the lowest performer in January. The drawback of optimal control and storage priority control, however, is that they require prediction of future cooling loads. The variance when using auto-regressive neural network to predict the load is expected to be in the region of 2% and thus considered acceptable. Chiller priority control and constant proportion control are instantaneous and simple to implement hence their popularity.

碩士
國立臺灣科技大學
電機工程系
102
As the technology is improved day by day, people’s requirement for electricity is growing afterwards. However, due to replacement of generator units, the power system is going to face a dilemma about lack of reverse margin. In addition, the nuclear disaster ,broke out on March 11th in Japen, leads to many discussions about nuclear safety. Thus, will the Long-Meng nuclear power plant be running or not? It is still a big issue in Taiwan. If the Long-Meng nuclear power plant don’t work on time, the rate of reserve margin will go down below 10%. It may impact on the reliability of power system. Although the government is planning to develop renewable energy source, it is not possible to compensate power shortage instantly. Therefore, a well demand-side management strategy, which is able to effectively reduce the peak load, should be a priority. Furthermore, in response to the intermittent characteristics of renewable energy, installation of energy storage device has become a necessary equipment. With techniques of load management and energy storage device, the demand-side management can be practical meaningfully. In this thesis, a household electricity, under time-of-use rate with renewable energy generators and energy storage device, is used.as an energy management model. “Peak-sheaving” and “Minimal Cost” are the objective function of proposed energy management system to optimize the schedule of energy storage device. Besides, to strengthen the demand-side management strategy in our country, this thesis recommends load factor as a reference index of power system reliability. As well, this thesis proposes an ideal of load factor incentive, with which it can lead people to rise load factor, to reduce the peak load of power system and to relieve system from the problem of reserve margin outage. In the end, this thesis will take the load factor incentive under consideration, and uses SQP function to solve “Minimal cost” and to determine optimal capacity of energy storage device.

碩士
國立中興大學
機械工程學系所
98
In this study, we present a collinear holographic storage system, which uses the digital micromirror device (DMD) and the holographic optical element (HOE), in order to realize an integrated collinear holographic storage system. We combine the system of the small-form-factor optical pickup head (SFFOPH) with the collinear holographic storage system which has been proposed by the Optware Corporation. The storage system consists of an HOE, a DMD, a green light laser with the wavelength of 532nm, and an objective lens. The functions of the HOE include diffraction, aberration-correcting, and servo-signal generation. The DMD is driven by the computer and outputs a 2-D page data in the system. There are three parts in the thesis. First, we designed the storage system by the optical simulation software, simplified the optical system, and reduced the number of optical components by adding the HOE. Secondly, we approximated the phase polynomial coefficients of the HOE by binary optics, and obtained its diffraction pattern by the etching processes after the photolithography. Subsequently, we measured the optical efficiencies of the HOE and then used the atomic force microscope (AFM) to verify if the requirements of the design were met. Finally, we set up the optical system to examine the effect of an integrated collinear holographic storage system. The experimental results show that the CCD receives the image pattern of the stored data from the HOE in the negative-one diffraction order and the photo detector receives the focusing error signal (FES) from the same HOE in the positive-one diffraction order.

碩士
國立清華大學
動力機械工程學系
89
In DVD-ROM, how to equalize the read-out radio frequency (RF) signal to reduce the jitter ratio has been an important issue so far. In this paper, we investigate the characteristic of the optical channel model in DVD-ROM and propose an Adaptive Neuro-Fuzzy Inference System (ANFIS) based equalizer together with a viterbi detector to form as a partial response maximum likelihood (PRML) system for DVD-ROM. Jitter performance using ANFIS based equalizer is compared with that of other linear filter based equalizers. By computer simulation, it shows that the proposed equalization method has better jitter performance than conventional linear filter based equalizers for the optical channel in DVD-ROM.

Wavelength division multiplexing (WDM) is essential for further enhancement of the transmission capacities of optical telecommunication systems. Key devices in WDM networks are multiplexing/demultiplexing components, which enable the combination/separation of several carrier waves with different wavelengths for the purpose of simultaneous transmission through one optical fibre. These components can be realized using Bragg diffraction from volume holographic gratings. Especially reflection holograms provide a pronounced wavelength selectivity which makes them attractive for free-space WDM applications. Holograms can be stored permanently in photorefractive lithium niobate crystals by the method of Thermal Fixing. Heating of the crystal during or after the recording process and subsequent development by homogeneous illumination at room temperature create nonvolatile holograms. The recording and development processes of Thermal Fixing in iron- and copper-doped lithium niobate crystals were investigated. Macroscopic Gaussian-shaped intensity patterns were used to analyse the origin of the fixing mechanism. Spatially resolved absorption measurements were performed to determine the concentration profiles of electron traps (Fe II/III) and protons. Results of computer simulations were compared with experimental results, which showed that protons can be found to work as compensators during hologram recording at temperatures around 180 degree C. Nevertheless thermal fixing without protons was possible, another compensation mechanism stood in. The obtained refractive-index changes were due to the electro-optic effect, other contributions could be neglected. With this detailed knowledge about thermal fixing, a two-channel demultiplexing unit was built by superposition of two thermally fixed reflection holograms in an iron-doped lithium niobate crystal. For this purpose a special two-beam interference setup with precisely adjustable writing angles was arranged in a vacuum chamber to eliminate thermally induced phase disturbances of the holographic recording procedure. Continuous development of the holograms by incoherent light was necessary. In the dark, the enhanced dark conductivity of the crystal used gave rise to a hologram degradation within about one day. Large diffraction efficiencies were attained (intensity losses between 2.3 and 5.2 dB only) uilizing crystals with high-quality polished surfaces. The crosstalk supression of the realized demultiplexer was > 25 dB, which is comparable with the performance of other multiplexing techniques like fibre Bragg gratings or arrayed-waveguide gratings. The low polarization dependence of the demultiplexer can be improved by superposition of two holograms for each channel.

碩士
國立中正大學
光機電整合工程所
95
The purpose of this work is to design a single objective lens which can be used for VCD, DVD and BD(blue-ray disk) specifications of optical data storage devices. The main challenge is to design such a lens can meet the requirements of various numerical apertures on different wavelengths. The current industrial solutions are based on two-lens or two-optical-pickup-head systems. The current design also requires expansive high refractive index glass material to fabricate the objective lens. The problems of them include the cost and size. The demand of high precision alignment of optical element also creates another problem. Our approach is to combine the diffractive optics and refractive optics on a so-called diffractive/refractive hybrid lens. The goal is to meet all the requirements of VCD, DVD and BD on a single polymer lens. One important improvement is that the lens can be fabricated by the low-cost plastic injection method. Based on the PMMA polymer material, we design an aspheric object lens. A multi-order diffractive grating is then designed on the aspheric surface. We optimize the aspheric surface and the multi-order diffractive grating using the ZEMAX software by considering the manufacturability. Finally, we came to a design, proved by computer simulation, which meets all requirements of VCD, DVD and BD specifications. We also made sensitivity analysis of the multi-order hybrid lens. The result shows that the designed lens has good sensitivity tolerance to the laser wavelength shift, machining tolerance and assembly errors. This article finally may suit 5 axes diamond turning take the low NA multi- steps compound lens as an example, simultaneously appraised the processing error creates the influence, measure its wavefront error 0.0295 λand Strehl ratio is the request which 0.875 tallies needs.

博士
國立交通大學
機械工程學系
100
An optical head composed of an optical module and a biaxial seesaw swivel actuator is designed for small form factor drives. This optical configuration has been fabricated and assembled for the proposed 635nm red-light small form factor (SFF) optical pickup head system. This system adopts a finite-conjugate objective lens with numerical aperture (NA) 0.65 for 635nm wavelength. A holographic optical element (HOE) is used for simplifying the optical configuration which provides a better approach for passive alignment. The assembly and alignment of various micro-optical components in optical pickup unit assembly were facilitated by using a flip chip bonder. Technological obstacles to the use of rotary-type swing arm actuators to actuate optical pickup modules in SFF disk drives stem from a hinge’s skewed actuation, subsequently inducing off-axis aberrations and deteriorating optical quality. Many SFF optical pickup heads based on the swing arm design utilize piezoelectricity or slim plate of metal to perform focusing action. The dual-stage seesaw type actuator is an enhanced driving mechanism used for swiveling the entire optical pickup heads devices. The configuration of the seesaw swivel actuator has unique features including a rotary actuator for coarse and fine tracking and a seesaw arm for swiveling along a pivot instead of a hinge to permit a tilt focus movement. A triple-layered bimorph bender made of piezoelectric materials (PZTs) is connected to the suspension of the pickup head, while the tunable vibration absorber unit is mounted on the seesaw swing arm to offer a balanced force to reduce vibrations in a focusing direction. The PZT micro-actuator is designed to satisfy stable focusing operation operational requirements and compensate for the tilt angle variation in focusing stroke. The performance of the biaxial dual-stage actuator is verified through simulation by finite-element methods, and the effectiveness is confirmed by experimental procedures and parametric design optimization. This integrated optical disk drive device, SFF optical module and dual-stage seesaw swivel actuator, is effectively self-aligned the optical axis for read/write performance in both experiment and simulation result. Dynamic measurements of motion trajectory based on laser sensing reveal significant optical axis correction with and without PZT micro-actuator compensation. The fabrication methodology for a dual-stage seesaw swivel actuator with SFF optical pickup module is investigated. Furthermore, the performances of dual-stage leverage mechanism based on optical sensing are experimentally evaluated to demonstrate the effectiveness of active tilt compensation. Simulation and experimental results are satisfactory and provide the feasibility of realizing the high-density portable optical storage system in compactness.

碩士
國立中正大學
光機電整合工程研究所
99
For solving the globe warming problem, the action of creating renewable energy by wildly building the solar and wind power plants has been undoubtly to become two major developments. Unfortunately, the above two major efforts accordingly rely on a huge budget as well as a suitable working place to fully display their function efficiency. On the other hand, a newly developed technique by piezoelectric power generator to create renewable energy has caused much attraction since its friendly adoption, nevertheless the surrounding environment is lack of sunlight and wind. Basing on the statement mentioned in the above, the piezoelectric element is the core of the piezoelectric energy conversion system in this study, which utilizes the external force on piezoelectric module to generate an available output power. At the beginning, the single-layer piezoelectric power generation device will be designed and fabricated, which is covered by rubber materials and posted on top and bottom sides of piezoelectric element. Then, to improve the efficiency of conversion power, an optimal geometric structure will be designed and conducted. In order to reduce the occupied space of piezoelectric power generation module and to further increase the efficiency of conversion power, multi-layer stackable piezoelectric power generation module will be constructed. In addition, a suitable energy storage system will be also developed to store the conversion power. Evidence indicated that the two set of optimal three-layer stackable piezoelectric power generation devices could obviously achieve an instantaneous output power (6.68mW). At the same time, a 15 mAh Ni-MH battery could be fully-charged within thirty hours by utilizing the two set of optimal three-layer stackable piezoelectric power generation devices constituting with energy storage system.

Οι ηλεκτροµηχανικές συσκευές αποθήκευσης δεδοµένων πολύ µικρής κλίµακας που βασίζονται στη χρήση ανιχνευτών (probes) αποτελούν ανερχόµενες εναλλακτικές επιλογές για τη βελτίωση της πυκνότητας αποθήκευσης, του χρόνου πρόσβασης των δεδοµένων και της απαιτούµενης ισχύος σε σχέση µε τις συµβατικές αποθηκευτικές συσκευές. Μία υλοποίηση µιας τέτοιας συσκευής χρησιµοποιεί θερµοµηχανικές µεθόδους για την αποθήκευση πληροφορίας σε λεπτές µεµβράνες πολυµερών υλικών. Σε αυτή την περίπτωση, η ψηφιακή πληροφορία αποθηκεύεται µε τη µορφή κοιλωµάτων πάνω στο πολυµερές υλικό, οι οποίες δηµιουργούνται από τις άκρες των ανιχνευτών διαµέτρου µερικών nm. Με στόχο την αύξηση του ρυθµού εγγραφής και ανάγνωσης χρησιµοποιούνται διατάξεις από ανιχνευτές που λειτουργούν παράλληλα, µε κάθε ανιχνευτή να εκτελεί λειτουργίες εγγραφής/ανάγνωσης/διαγραφής σε ξεχωριστό αποθηκευτικό πεδίο. Βασικές απαιτήσεις κατά τη λειτουργία τέτοιων συσκευών αποτελούν η εξαιρετικά µεγάλη ακρίβεια και η µικρή καθυστέρηση κατά τη µετακίνηση των ανιχνευτών πάνω από το πολυµερές υλικό. Η παρούσα διατριβή έχει ως αντικείµενο τη µελέτη των διατάξεων κίνησης και τη σχεδίαση πρωτότυπων αρχιτεκτονικών ελέγχου, που οδηγούν στη βελτίωση της απόδοσης των απαιτούµενων, σε συσκευές τέτοιου τύπου, λειτουργιών ελέγχου. Η µετατόπιση του αποθηκευτικού µέσου σε σχέση µε τη διάταξη των ανιχνευτών επιτυγχάνεται µε τη χρησιµοποίηση µικρής κλίµακας scanners, που έχουν δυνατότητες κίνησης σε δύο κατευθύνσεις (x/y). Πληροφορία για τη θέση του microscanner στις δύο κατευθύνσεις παρέχεται από θερµικούς αισθητήρες ανίχνευσης θέσης που κατασκευάζονται µαζί µε τη διάταξη µε τους ανιχνευτές και τοποθετούνται πάνω από το κινητό πλαίσιο. Η πλήρης κατανόηση της συµπεριφοράς των διατάξεων αυτών αποτελεί απαραίτητο στοιχείο για τον αποτελεσµατικό σχεδιασµό και την ανάλυση των συστηµάτων ελέγχου. Στα πλαίσια της διατριβής δηµιουργήθηκε ένα πλήρες µοντέλο της διάταξης του microscanner και των θερµικών αισθητήρων ανίχνευσης θέσης. Σύγκριση της απόκρισης του µοντέλου µε τις πειραµατικές µετρήσεις καταδεικνύει ότι το µοντέλο προσεγγίζει µε εξαιρετική ακρίβεια την απόκριση του συστήµατος. Το σύστηµα ελέγχου περιλαµβάνει, στην αρχή, τη λειτουργία αναζήτησης/ αποκατάστασης, κατά την οποία το σύστηµα εντοπίζει τη θέση όπου απαιτείται να πραγµατοποιηθεί εγγραφή ή ανάγνωση πληροφορίας µε εκκίνηση µία αυθαίρετη θέση του κινητού πλαισίου. Απαίτηση του συστήµατος κατά τη λειτουργία αυτή είναι η ελαχιστοποίηση του χρόνου πρόσβασης των δεδοµένων. Η γρήγορη πρόσβαση στα δεδοµένα αποτελεί µια σηµαντική πρόκληση στις συµβατικές αποθηκευτικές συσκευές. Με το πλεονέκτηµα των ελαφρύτερων µηχανικών µερών, οι υπό µελέτη συσκευές αποθήκευσης βασισµένες στην τεχνολογία MEMS θεωρούνται βασικές υποψήφιες για τη βελτίωση του χρόνου πρόσβασης των δεδοµένων. Οι σχετικές προοπτικές των συσκευών αυτών διερευνώνται αναλυτικά στα πλαίσια της διατριβής. Συγκεκριµένα, αρχικά µελετάται η απόδοση διαφόρων συστηµάτων µε βάση τη θεωρία ελέγχου βέλτιστου χρόνου. Τα αποτελέσµατα της µελέτης δίνουν το θεωρητικά βέλτιστο χρόνο πρόσβασης και την εξάρτησή του από τις παραµέτρους του κάθε συστήµατος. Στη συνέχεια, περιγράφεται η αρχιτεκτονική ελέγχου για τη λειτουργία αναζήτησης και παρουσιάζονται τα αποτελέσµατα που αντλήθηκαν από το περιβάλλον προσοµοίωσης και από την πειραµατική διάταξη. Τα αποτελέσµατα καταδεικνύουν ότι οι χρόνοι πρόσβασης των δεδοµένων που είναι δυνατό να επιτευχθούν µε τις συσκευές αυτές, είναι σηµαντικά µικρότεροι σε σχέση µε τις συµβατικές. Στη συνέχεια, ακολουθεί η λειτουργία παρακολούθησης, όπου η θέση των ανιχνευτών πρέπει να παραµένει στο κέντρο του επιθυµητού καναλιού, κατά τη διάρκεια εγγραφής/ανάγνωσης των δεδοµένων. Η απαίτηση για µεγάλη ακρίβεια στη µετακίνηση πάνω από τη νοητή γραµµή του κέντρου του καναλιού, της µίας ή περισσότερων κεφαλών που χρησιµοποιούνται κατά την εγγραφή/ανάγνωση, είναι σηµαντική για όλους τους τύπους αποθηκευτικών συσκευών. Οι απαιτήσεις για ακρίβεια γίνονται ακόµα πιο µεγάλες και κρίσιµες, στην περίπτωση των υπό µελέτη αποθηκευτικών συσκευών, όπου η ψηφιακή πληροφορία αποθηκεύεται σε µία περιοχή µε µέγεθος µερικών nm. Το σύστηµα ελέγχου, κατά τη λειτουργία αυτή, οφείλει να παρακολουθεί το επιθυµητό σήµα αναφοράς, και ταυτόχρονα να έχει ικανοποιητική απόρριψη των διαταραχών και να επιτυγχάνει την απαιτούµενη ακρίβεια ως προς τον προσδιορισµό της θέσης. Παράλληλα, σηµαντικό παράγοντα βελτιστοποίησης αυτής της λειτουργίας, αποτελεί ο ρυθµός εγγραφής/ανάγνωσης των δεδοµένων. Η πρώτη προσέγγιση για την αρχιτεκτονική ελέγχου, κατά τη λειτουργία αυτή, βασίζεται στην παρεχόµενη από τους θερµικούς αισθητήρες ανίχνευσης, πληροφορία της θέσης του microscanner. Η αρχιτεκτονική βασίζεται στον αλγόριθµο του γραµµικού τετραγωνικού ρυθµιστή (LQG) και η αξιολόγησή της γίνεται µε κριτήρια την ικανότητα παρακολούθησης της εισόδου, την απόρριψη των διαταραχών και την ακρίβεια ως προς τον προσδιορισµό της θέσης. Τα αποτελέσµατα που εξήχθησαν, κατά την υλοποίηση της αρχιτεκτονικής ελέγχου στην πειραµατική διάταξη, αναδεικνύουν ότι η αρχιτεκτονική πληρεί τις απαιτήσεις και η ακρίβεια µερικών nm που επιτυγχάνεται στον προσδιορισµό της θέσης επιτρέπει την αξιόπιστη εγγραφή και κατόπιν ανάγνωση δεδοµένων από την αποθηκευτική συσκευή. Μειονέκτηµα της παραπάνω προσέγγισης αποτελεί ο χαµηλής συχνότητας θόρυβος των θερµικών αισθητήρων, που επηρεάζει τη σωστή λειτουργία του κλειστού συστήµατος σε µεγάλες περιόδους λειτουργίας της συσκευής. Το πρόβληµα αυτό επιλύεται µε µία πρωτότυπη προσέγγιση που αναπτύχθηκε στα πλαίσια της διατριβής και βασίζεται στην πληροφορία, την προερχόµενη από τους θερµικούς αισθητήρες ανίχνευσης θέσης, σε συνδυασµό µε το προερχόµενο από το αποθηκευτικό µέσο σήµα σφάλµατος θέσης. Ο σχεδιασµός του συστήµατος ελέγχου, στην περίπτωση αυτή, εκµεταλλεύεται την εκ των προτέρων γνώση των χαρακτηριστικών θορύβου ως προς τη συχνότητα των δύο αισθητήρων ανίχνευσης θέσης, έτσι ώστε το σύστηµα ελέγχου που προκύπτει να χρησιµοποιεί την πιο αξιόπιστη µέτρηση σε κάθε περιοχή συχνοτήτων. Το πλαίσιο του σθεναρού ελέγχου, H∞, χρησιµοποιείται κατά το σχεδιασµό αυτής της αρχιτεκτονικής ελέγχου, µε διαχωρισµό ως προς τη συχνότητα. Με χρήση αυτής της µεθόδου, το σύστηµα ελέγχου δεν επηρεάζεται από τον χαµηλής συχνότητας θόρυβο των θερµικών αισθητήρων. Τα αποτελέσµατα που εξήχθησαν κατά την υλοποίηση της αρχιτεκτονικής ελέγχου στην πειραµατική διάταξη επιβεβαιώνουν τα παραπάνω. Η µέθοδος αυτή είναι πιο γενική και µπορεί να εφαρµοστεί σε κάθε πρόβληµα ελέγχου, που έχει δύο ή και περισσότερους αισθητήρες µε διαφορετικά χαρακτηριστικά απόδοσης σε διαφορετικές περιοχές συχνοτήτων.
Micro-electro-mechanical-system (MEMS)-based scanning-probe storage devices are emerging as potential ultra-high-density, low-access-time, and low-power alternatives to conventional data storage. One implementation of probe-based storage uses thermomechanical means to store and retrieve information in thin polymer films. Digital information is stored by making indentations on the thin polymer film with the tips of atomic force microscope (AFM) cantilevers, which are a few nanometers in diameter. To increase the data rate, an array of probes is used, in which each probe performs read/write/erase operations over an individual storage field. One of the primary challenges in building such devices is the extreme accuracy and the short latency required in the navigation of the probes over the polymer medium. This dissertation describes the design of novel control architectures and the characterization of their performance. The associated modelling effort, theoretical analysis, simulation work and experimental results are presented. Displacement of the storage medium relative to the array of cantilevers is achieved by using silicon-based micro-scanners with x/y-displacement capabilities. The x/y positional information can be provided by thermal position sensors that are fabricated on the cantilever-array chip and positioned directly above the scan table. A thorough understanding of the dynamics of these parts of the device is essential for effective design and analysis of the control architectures. In this dissertation a complete model of the micro-scanner and the thermal position sensors was developed. Comparison of the model response with the experimental data have shown that the model approximates the system response with an excellent accuracy. In general, the servo system in such a storage device has two functions. First, it locates the target track to which information is to be written or read back from, starting from an arbitrary initial position of the scan table carrying the storage medium. This is achieved by the so-called seek-and-settle procedure. The data access time depends on the duration of this operation, and therefore the minimization of its duration constitutes an important optimization factor. The speed of data access is a significant bottleneck in today’s computing systems. With the advantage of the lighter moving stage MEMS-based storage devices are widely touted to improve access times. In this dissertation these perspectives are examined in detail. Initially the time-optimal control theory has been studied for different system models and their performance has been examined regarding the optimal access time. The results of this study have provided the theoretically optimal access time for each model and its dependence on the system parameters. The control architecture for the seek operation has been designed. The simulation and experimental results show that the possible access times that can be achieved are significantly smaller than the conventional storage devices. The second function of the control system is to maintain the position of the read/write probes on the centre of the target track as they are being scanned along the length of this track during the normal read/write operation. This is achieved by the so-called track-follow procedure. Precise positioning and navigation of the read/write head(s) on the track centerlines is of paramount importance in all types of storage devices. The requirements become more crucial in the devices under study, where in order to achieve reliable storage and retrieval of data, accuracy in the order of a few nanometers in the scanner motion is needed. Therefore, the tracking of the reference signal, the disturbance rejection capabilities and the positioning resolution are considered as performance measures for the control system in this operation. Similarly, the read/write data rate constitutes an important optimization factor for this operation. The first approach of the control architecture for the track-follow procedure uses the position information from the thermal sensors. The control of the position in the x/y directions is realized using two independent feedback loops and each controller is based on the linear quadratic Gaussian regulator (LQG). For the evaluation of the proposed control architecture a detailed analysis has been performed in terms of the tracking performance, the disturbance rejection and the positioning resolution. The proposed architecture has been implemented in the experimental set-up and the analytical results are in agreement with those obtained experimentally. The experimental results show that the accuracy in the motion of the micro-scanner obtained with the proposed control architecture allows reliable storage and retrieval of data in the storage device. The disadvantage of the above control scheme originates from the low frequency noise of the thermal sensors that affects the closed loop performance for long term operation of the device. A novel control architecture was developed that addresses this problem by using medium-derived position information along with the thermal positioning sensor. The objective of this method is, using the a priori knowledge of the noise characteristics of the two sensors, to create a control structure that utilizes the best measurement in different frequency regions. The framework of the H∞ robust control was used for the design of this new frequency separated control architecture. Using this method the control system is not affected from the low frequency noise of the thermal sensors. The experimental results validate the performance of the proposed method. The developed methodology is more general and can be applied to any control problem that has two or more sensors with different performance characteristics in different frequency regions.