A new high efficient DC-free 3-ary run-length limited (RLL) code for 3-level optical recording system is presented. Signal processing techniques, partial-response maximum-likelihood (PRML), which is used for recovery data from readout signal, is discussed.
Multi-level run-length-limited (ML-RLL) modulation on optical storage channels is a promising method to increase
the recording density effectively. In this paper, some experimental results of 4-level RLL modulation on
digital versatile disc (DVD) read-only discs are firstly presented. A new DC-free 4-ary RLL (2, 8) code with
code rate of 8/10 (bits/symbol) is designed, and partial-response maximum-likelihood (PRML) detection is used
to evaluate the bit error rate (BER) performance of multi-level readout signals. Experimental and simulation
results show the feasibility of 4-level RLL modulation on DVD channels.
This paper discussed the scheme of modeling compound aspheric components during the optimization process. First, the method to model the refractive index and thickness changes of the resin layer induced in the injection-mold process is described. It demonstrated the available constraints upon the refractive index difference between the resin and the glass during the optimization run. The tolerance aspects of such components are then investigated, including the refractive index and thickness of the resin layer, as well as the conventional surface roughness, element position and rotation errors, and surface slope errors; especially for the centering tolerance. It is shown that the approximate model might be useful for different combinations with UV-curable resins and glasses for aspheric lens design and fabrication. An objective for optical pickup system comprising one compound aspheric surface is designed with the scheme.
This paper discussed the scheme of modeling compound aspheric components during the optimization process. First, the method to model the refractive index and thickness changes of the resin layer induced in the injection-mold process is described. It demonstrated the available constraints upon the refractive index difference between the resin and the glass during the optimization run. The tolerance aspects of such components are then investigated, including the refractive index and thickness of the resin layer, as well as the conventional surface roughness, element position and rotation errors, and surface slope errors; especially for the centering tolerance. It is shown that the approximate model might be useful for different combinations with UV-curable resins and glasses for aspheric lens design and fabrication. An objective for optical
pickup system comprising one compound aspheric surface is designed with the scheme.
In this paper, theoretical work on the transmitted-aperture (TA) type super-RENS was introduced. Firstly, the forming of transmitted-aperture in the mask layer was studied based on laser-induced thermal model with Gauss assumption. A numerical simulation was carried out by FEMLAB. The simulation results showed that transmitted aperture would not be formed until the exposure power exceeded a threshold within a certain pulse time and vice versa. Secondly, a calculation model of electromagnetic field of TA type super-RENS disk was presented based on the three-dimensional finite-difference time-domain method (3D-FDTD) together with a vector method of Gaussian beam. Lorenz dispersive model was employed for mask layer and reflective layer. The distributions of electric field for TA type super-RENS were theoretically analyzed. Lastly, the static writing experiment for TA type Super-RENS was carried out with different power and pulse time, as well as for conventional CD-R/W. The experiment results well satisfied the simulation.
Multi-level optical storage is a promising approach to increase recording density and data transfer rate significantly without altering optical and mechanical parameters of current optical disc systems. Multi-level amplitude modulation and multi-level run-length limited modulation are two different important recording approaches. In this paper, we discuss and compare these two multi-level modulation principles and corresponding multi-level coding schemes. With advanced coding and signal detection, multi-level run-length limited modulation shows better performances in terms of higher recording density. We present a new 8-ary (1, 3) RLL code constructed by state splitting algorithm for photochromic storage channel. The proposed code has only two coding states and high coding density of 3.0 bits per minimum mark. The encoder/decoder is simple and easy for implementation, which can be applied in future high density multi-level optical storage systems.
Based on the focus pre-search a method is presented to measure the characters of the traverse focus error detection system. In the pre-search of traverse focus servo system, the traverse focus offset is measured by the focus error occurring time, and the traverse focus error sensitivity and linear range are measured by the focus error slope and peak-to-peak value. A traverse focus error detection system is measured. The results show that the traverse focus offset is too high to stable the focus servo.
Multi-wavelength and multi-level optical storage based on novel photochromic materials is a promising approach to increase recording density and transfer rates signicantly. In our research, three laser beams with dierent wavelength are simultaneously used to record information in one recording layer, which consists three kind of photochromic materials with spectrum sensitivity suitable for each used laser beam. On the other hand, the reectivity of photochromic materials varies nonlinearly with the exposure energy, which shows feasible for multilevel optical recording. The principle of the experimental system construction and a results are described in this paper. The proposed multi-wavelength and multi-level photochromic recording has the great potential to be applicable for future high density optical data storage.
4-Level Run-Length Limited (4L-RLL) optical storage based on photo-chromic materials is firstly investigated in this paper to our knowledge. Unlike binary recording, information in Multi-Level Run-Length Limited (ML-RLL) modulation system is carried in both the amplitude and length of the marks. ML-RLL optical storage can increase the recording density and data transfer rate with no changes to the optical/mechanical unit. For photo-chromic materials, different levels of input laser power amplitude give rise to different reflection levels. Using optimal write strategies, a 4 level linear playback signal was obtained and the sigma-to-dynamic range (SDR) of the 4-level signal was calculated. The results show that the SDR is low enough to provide low bits error rate (BER).
Two stage positioning method which is composed of coarse positioning and fine positioning is a way to increase the precision of linear feeding in high density disk mastering. The control method of two stage positioning is proposed in this paper. Different control models are compared and the suitable one is chosen. The PID controllers for coarse and fine tables are designed. The numerical simulating results show that the two stage positioning system with PID controllers has good performance in linear feeding with steady error less than 10nm. The coarse positioning table compensates the major component of displacement in linear feeding while the fine positioning table compensates the minor one. The two stage positioning system can well satisfied the requirement of high density disk mastering in theoretical.
In order to meet the requirement of focusing in the multi-wavelength mastering system, a pneumatic sensing system is designed. It detects the objective lens position signals and sends to the focus control system as the focus error signals instead of the feedback signals of light intensity used traditionally. So it can solve the auto-focus problem caused by introducing multi-wavelength lasers. The static and frequency response characteristics of the system are tested. It is proved by the experiment that the focus error is under ±0.1μm and can meet the needs of the three-wavelength system.
Multi-wavelength and multilevel (MWML) optical storage with photochromic media is a novel technology that can increase storage capacity and transfer rates significantly. Signal processing and coding methods for the MWML storage channel are introduced in this paper. Two-dimensional codes with parallel detection and equalization are studied to increase storage capacity and combat the crosstalk between different wavelength materials. Multilevel amplitude modulation and M-ary runlength-limited (RLL) codes are described and compared for achieving higher coding capacity. The novel MWML recording technology has the potential to be applicable for the next generation optical data storage.
The non-linearity of the super-RENS mask can be used in optical data storage, which can greatly increase the disk’s density. Experiment is carried on the traditional mastering system with modification. We adopt the SiN/Sb/SiN multiplayer as the mask to insert the optical mask. For 413nm semiconductor laser and lens with NA=0.9, the diffraction limit is 200nm theoretically. Mark-120nm much smaller than that size is generated in the experiment. The thickness of Sb in the mask layers has much effect on the mastering signal intensity. For different power, we should control the thickness of Sb film. The experiments results show that the super-RENS mask can actually reduce the size of the mark obviously and realize the high density optical storage.
Proc. SPIE. 5643, Advances in Optical Data Storage Technology
KEYWORDS: Mathematical modeling, Control systems, Signal processing, Optical tracking, Servomechanisms, Digital video discs, Optical discs, Filtering (signal processing), Process modeling, Device simulation
This paper considers the implementation of compensators for periodic disturbance cancellation, specifically applied to the removal of repeatable runout(RRO) from the position error signal(PES) in the high performance DVD player. The internal model principle is used for rejecting the sinusoidal disturbance caused by eccentric rotation of the disk, and the LQG methodology is used for the servo compensator design to improve the drive performance and meet the stability-robustness specifications in the frequency domain. A mathematical model of radial servo is constructed which forms the basis of a computer simulation. Simulation results are presented to show that LQG design is a viable approach.
A practical mastering technology was developed using a blue laser optical mastering system with a wavelength of 405 nm, a numeric aperture (NA) of 0.95 and a phase-shift apodizer. The laser is shaped and collimated by a space filter with its diameter 2μm, then is split into two beams by polarizing prism. One beam is used to detection of the optical power, and the other beam is used to write data on the disc. The phase-shift mask is lay between the collimating lens and the polarizing prism to optimizing the intensity distribution of Airy point on the disc. The lens with high NA 0.95 is designed to make the image point of the laser less then the diffraction point. The air-operated focus control device is used to focalize the light on the disc. Based on the technology, the recording spot with its diameter about 223nm is achieved.
Multi-wavelength photochromic storage is a new optical storage with high storage capacity based on photochromic principle. The storage mechanism, system structure and disc structure of multi-wavelength photochromic storage are presented. An experimental system with 3-wavelength lasers used to accomplish 3-wavelength photochromic storage is presented. Experiments on the 3-wavelength photochromic storage system have been carried out. The results show that two materials used in the experiment can be used in 3-wavelength photochromic storage and contrast of the readout signal is high. The results also show that little crosstalk between two materials generates, but a little crosstalk generates irradiated by 780 nm laser and the crosstalk do not affect the recognition of the information stored in the recording layer.
In order to increase storage capacity and data transfer rates, a sophisticated optical storage technology - Multi-layer and Multi-wavelength photochromic storage technology - has been developed. Based on the characteristics of Photochromic medium, Multi-laser can do parallel reading or writing. In this case, the error-correcting code of conventional Compact Disc could not adapt to the Multi-layer storage. This paper put forward an error-correcting code for the two-layer storage. And some simulations were carried out.
A novel storage system is introduced which bases on the "multilayer multilevel storage model." Three kinds of lasers that are different in wavelength are used to record data or test some storage material in this system. An example that is testing the photochromic material is also introduced to explain the usage of the system in testing storage material.
With the increasing demand of huge volume, high density and high transmission speed in optical storage, researches on multi-layer storage and multi-wavelength, multi-layer and multi-level storage in a single substrate have started both in China and abroad. This requests new feathers in optical system of optical disks. The objective lens in multi-layer storage needs compensations to varied spherical aberrations produced by varied thickness of storage layers; the objective lens in multi-wavelength and multi-layer storage needs apochromatism to broadband range. If the apochromatism is not ideal, it is needed that the spherical aberrations of multi-wavelength light are uniform and the multi-wavelength light beams are focused separately to obtain better result. A traditional micro-objective whose optical aberration is carefully corrected can be apochromatic to D, F and C in medium numerical aperture and can be used as objective lens of the optical disk of multi-wavelength, multi-layer and multi-level optical storage. This article gives an amended result based on C. G. Wyne's field flattener. The calculation result of optical aberration indicates that the spherical aberration is nearly zero and the secondary spectrum is less than 0.5 times of focal depth. It is also indicated that the MTF of a certain wavelength light matches the ideal MTF curve wherever on axis or off axis, wherever on meridian surface or on sagittal surface.
An experiment on the character of photochromic recording material is introduced. Numerical method is used to describe the material character. Based on it, the multi-level experiment demonstrates the availability using photochromic material as recoding medium of 4-level storage system. Finally, a further analysis on optimizing the exposal parameters of different levels of multi-level disc is presented.
A dual-laser DVR system, which utilizes chromatic aberration to obtain dual-layer storage, is reported in this paper. A non-achromatic objective lens is used, which is especially designed. It focuses 405 nm laser and 440 nm laser on two recording layers of the disc. Parallel accessing is avaialble to incrase data rate. Another key problem of the system is how to achieve space layer with high thickness stability. Some key problems of this system are discussed, such as: disc structure, writing and reading strategy, etc.
Two-photon single beam multi-layer writing and scanning confocal reading are performed in anthracene derivatives membrane by Ti:sapphire femtosecond laser and three-dimensional scanning confocal system. And a good result is achieved, Two-photon excitation can be produced inside the anthracene derivatives membrane, where is 100 μm from the surface of the recording material. The wavelength of the laser is 726 nm(363nm×2). The size of recording spot along longitidunal direction is less than 2 μm, and that along lateral direction is less than 1 μm. The signal keeps clear definition after many times of reading out, when the power of the reading laser is less than 5 mW.
In order to protect important content, such as the latest Hollywood movies, a new method of anti-piracy technology -- Embedded copy protection ASIC controlling scheme has been developed. The contents on the disk have been scrambled. Before the content playing, the VCD/DVD Player with embedded copy protection ASIC will detect the disk and need user inputs a license code. If the code matches the embedded ASIC key scheme, the disk will play, or the disk will be rejected.
Next generation of optical storage will use shorter wavelength lasers and higher NA lens to achieve large capacity and high density. But with increasing NA and decreasing wavelength, the depth of focus decreases rapidly. We describe a technique to get smaller width focus spot and longer depth of focus by shaping a focused Gaussian beam. The important feature of the filters is their simplicty. The apodization can be used for applications such as blue-ray optical data storage, super-REN storage and mastering.
An experiment for focusing in chromatic multilayer optical storage system is presented in this paper. There laser diodes with different wavelength as respectively light sources are used in this experiment system so that focusing and servo approach are different from that in traditional optical system. Astigmatic approach is applied for defocusing detection while servo controlling and signal processing circuits are redesigned. The model of the actuator suited this chromatic multilayer optical system is established and analyzed. The static and dynamic parameters of actuator are measured. This paper specifies the design and implementation technologies of focusing and servo controlling in the chromatic multilayer experiment optical system. The preliminary result gotten from this experiment system is also given in the paper.
Multi-wavelength photochromic storage is a new optical storage method based on the photochromic principle. In this paper, the storage method itself and the mathematic model developed to describe the change of the reflectance in the writing process are discussed. For the photochromic materials, which are sensitive to 650 nm and 532 nm laser respectively and mixed into one layer, the reflectance of the readout laser in the writing process was measured with a 3-wavelength photochromic storage system. The theoretical results of the model agree well with the experimental ones. It is also found that the photochromic optical storage has no threshold.
One way of achieving super-resolution is to convert the Guess distribution of the object space into square distribution of that. A special phase-shifting lens is designed for attaining the function. In developing designs for the special phase-shifting lens, algebraic approximate formulas are used to obtain a general understanding of the transition between the Guess distribution and the square distribution. Computer simulation was then used to obtain a detailed performance evaluation. The evaluation results indicated the following: the Guess distribution of the laser light is converted into the square distribution by the special phase-shifting lens.
Proc. SPIE. 4930, Advanced Optical Storage Technology
KEYWORDS: Laser sources, Super resolution, Data storage, Scanning electron microscopy, Near field scanning optical microscopy, Digital recording, Optical storage, Antimony, Germanium antimony tellurium, Near field optics
Recording experiments on Super-RENS mask were done for color (multi-wavelength digital data storage at various recording conditions.Through SEM, the recording marks were found reduced down notably. These micrograms were studied fully, and the results forcefully demonstrate the super-resolution recording effect in Super-RENS.
With the increasing demand of optical storage capacity, multi-level (ML) optical storage based on multi-level-amplitude modulation is receiving more and more attention, for it transmits more information ove a fixed bandwidth channel by using the available SNR more efficiently. We proposed an ML optical storage technology in azo LCP film based on polarization angle division. In this paper, the write strategy is developed by a ML write-compensation system that corrects for non-linearities of the data signal. The dynamic transmittance range is extended with the full monotonic range of angle and the varaition of each amplitude level relative to our dynamic range is improved. The experiments of imroved linear and nonlinear 16-level storage in azo LCP are demonstrated. The effects of thickness non-uniformity on linear and nonlinear 16-level storage are discussed.
The write strategy of the phase-change optical disk determines its read-out performance, and optimizing the write strategy is an important step of the recording process on the disk. The action on the phase-change material from the laser comes down to the thermal effect of the laser. In this paper, the temperature rise curves under different write strategies have been discussed at the aspect of thermal modal, and the optimum write strategy is brought forward, which could direct the actual write process design.
The principle of multi color storage using 3 lasers with different wavelength is introduced and the Method of Three-wavelength Confocal Adjustment (MTCA) is represented in detail. The three lasers are combined into a coaxial paralleled laser beam after passing through their own collimation system and one common light coupling system. Then they are focused in the same spot on the recording layer by an achromatic lens. The defocusing amounts' measurement bases on the knife-edge displacement method and displacement method of optoelectric detector. And then the 3 lasers can read and write confocally in recording media.
Multi-wavelength photochromic storage is a new optical storage method based on the photochromic principle. Experiments are carried out on 3 materials to test their sensitivity, crosstalk and operating time. One material of them is sensitive to lasers of 780 nm; the other, 650 nm and the last, 532 nm. The experimental results show: the three photochromic materials are all sensitive enough to record data. The crosstalk of 650 nm and 532 nm materials is neglectable, and they can be used in multi-wavelength optical storage as new photochromic materials. But the 780 nm material is also sensitive to 650 nm laser, and it results in obvious crosstalk. Therefore, the 780 nm material can't be of use only if it's improved greatly.
The optical non-linearity property of the Sb sandwiched structure was studied under the static condition via several experiments. The non-linearity effects of this sandwiched structure were clearly observed. And a primary explaining was given on the base of the experiment results. Conclusively, the optical non-linearity property of the Sb sandwiched structure is obvious. With this structure, the radius of the focused laser beam can be reduced effectively, almost 35% to approximately 50%. And the effect of this structure is not only the radius reducing of the focused laser beam, but also the increasing of power density. This phenomenon suits the analysis of energy localization in theory well.
Photon-mode recording of photochromic materials is regarded as a promising storage system, which has various advantages over the traditional heat-mode recording in terms of its data capacity and data-recording rate. Diarylethenes show good thermal stability and remarkable fatigue resistance, and these properties are indispensable for the applications to optical storage materials. In present work, several diarylethene compounds were synthesized, and a series of optical storage tests were carried out on the sample discs with diarylethenes as the recording materials. The recording based on these photochromic materials was photon-type,and the recorded regions appeared as faded dots. 780, 650 and 532 nm lasers were used for writing on the corresponding discs, and the recorded information were readout by the same lasers respectively. A two-wavelength optical storage was realized on a mixed diarylethene recording layer by two laser beams of 532 nm and 650 nm synchronously. A higher data capacity can thus be expected to reach by using a multi-wavelength optical storage like that. Although the diarylethenes satisfy the minimum demands of optical storage systems, these molecules have one unsolved drawback: the lack of a non-destructive capability. In this work, Electric-locked properties were investigated in a BT3FP-OH thin film; the electric trigger could prevent the photochromic reactions, which provided a practicable non-destructive readout method. Three kinds of diarylethene derivatives linked by solvatochromic dye units wer fabricated; the theoretical investigation showed that reading at the wavelength of about 650-750 nm would destroy the recorded information no longer. Thus a non-destructive method could be constructed on these diarylethene molecules.
Basing on the structure of multi-layer parallel-accessed disc, current modulation code is optimized to achieve higher density storage. Two problems, which may be serious after the optimization, are discussed: acceptable jitter and synchronization process of PLL. A novel method for procuring combined signal of channel bit clock for multi-layer disc is proposed, which satisfies the requirements of PLL. The novel method is at last proved by probabilistic theory. At the end of this paper, parameters of RLL for multi-layer disc are presented: d=4, k=10~15. These new parameters improve the track-density by 15% ~ 20%.
Diffractive optical element (DOE) can be used for beam transform to obtain a certain required focused spot. The phase design of the DOE can be considered as an optimization problem and can be optimized by many kinds of algorithms. In optimization, the intensities of the sampling points are optimized to be consistent with the required beam transform, but the other points are not consistent with such demand. In this paper, fine design of the DOE is completed with a new sampling interval on the focal plane. The simulated results show that the intensity of any point on the focal plane is fully filled with the required beam transform, besides the used sampling points in the optimization.
Diffractive optical element (DOE) can be used for beam smoothing, owing to its high light efficiency, design flexibility and so on. The phase design of the DOE can be considered as an optimization problem and optimized by many kinds of algorithms. In this paper, the hybrid algorithm, merging Hill-climbing with Simulated Annealing, is adopted to design the phase of the DOE. The designed phase is the sum of many kinds of sine function with different period, amplitude and initial phase, which the continuous phase DOE is ensured. The continuous phase DOE is fabricated by ion etching, with a rotating hollowed-out mask. Experiments of beam smoothing are carried out with a pulse working Nd:YAG laser, and spots with a rather good beam smoothing performance are obtained.
Diffractive optical element (DOE) can be used to realize beam smoothing. In order to realize true beam smoothing, a new design method with a more restrict way in the optimization has been proposed. In this paper, based on this new design method, polarization design is adopted to improve the performance of the DOE for true beam smoothing. The top non-uniformity can be held to be less than 2.7%, no matter which group of sampling points on the focal plane is chosen to be calculated.
The software industry loses billions of dollars each year due to software piracy. And CD-ROM technology is one of the most successful and fast growing methods for quickly and economically distributing information. So it is an urgency to find a good method to protect CD-ROM from being pirated. In this chapter, we will discuss some new technologies of anti- piracy. According to these discussions, we will put forward our new anti-piracy method.
The process of replication, such as molding, clamping, injection, metalizing, even extrusion and printing, put an important impact on the quality of the finished DVD discs. They are crucial to duplicator, but not so easy to detect by conventional analysis methods provided by current commercial off-line tester. We introduce a data-analysis method to enlarge the effects of replication process on the disc parameters, by means of eliminating the disturbance from pre- replication process. This method is named RES (Remainder Elimination of the effect Stamper) parameters. An example is given to show the status of disc's edges affected by molding, and the selection of different molding patterns is analyzed.
The mechanism of three dimensions digital data storage, including the construction of optical disk, seeking method, principle and method of reading/writing is described in this paper. With the technology of multi-layer, multi-color, longitudinal coding and masking, the new scheme can overcome the bottleneck of 3-D digital storage for tracking, focusing, data rate and do most of the advantages of 3-dimension optical storage for higher density and larger capacity.
In this paper, the objective of servo system in an optical disc player is discussed. The traditional servo method, zero- order indifferent PID adjustment, is analyzed. Based on the analysis, a new servo system, 1-order indifferent PI&PID adjustment, is provided. In the new adjustment method, the main error of low frequency from ECC and Imbalance will be reduced to minimum in theory. In the end of the paper, the stability of the new servo system is analyzed in detail.
The principle of modified repetitive control is analyzed. According to the model of tracking actuator, a simplified design method of modified repetitive control was introduced. The simulation result shows the modified system has good performance. Compared with classical control system, it increases servo accuracy and steady state robustness, decreasing error signal greatly.
The dependence of readout signal from embossed grooves on edge decline is studied by a simulation method. The disk is modeled as one-dimensional grating that consists of grooves with declining wall. The formula of readout signal is derived based on vector diffraction theory, then the effect of the wall decline is investigated. The simulation shows that the effect of wall decline depends on the polarization of incident light. When the electric vector of the incident light is perpendicular to the groove wall, the decline mainly influences the peak-valley value and the increasing rate of the readout signal. When the electric vector is parallel with the groove wall, the decline mainly influences the amplitude of readout signal.
This paper describes the structure of Personal Optical Disk Library (PODL), a kind of large capacity (40 GB) optical storage equipment for personal usage. With the knowledge engineering technology integrated in the PODL, it can be used on knowledge query, knowledge discovery, Computer-Aided Instruction (CAI) and Online Analysis Process (OLAP).
Jitter is defined by the variation of each pit length and timing variations between data and clock frequency on discs. As a comprehensive item, it relates with error rate directly. In this paper, the definition, determined and influence factors of jitter n are analyzed. According to the analysis, measurement methods of jitter are provided. The precision of a method. The method's precision and demand are calculated and explained in detail.
Optical recording has some inborn advantages over magnetic recording. Under some circumstances where magnetic recording can not meet the specific requirements, optical recording can play an important role. In this paper, an optical disk array was designed to record successive data with high speed and mass capacity under the circumstances where air-pressure is fairly low and with high electromagnetic interference.
In this 1D model of Magneto-Optical read channel, the isolated step response is modeled to be a Q function, and an equalizer parameter designing method based on the least square error criterion is given, which is suitable for both linear equalizers and feedback equalizers. The detection method can adopt the threshold detection and Viterbi detection. Although the model is linear, it is easy to simulate the non-linear characteristics like bloom or jitter in Magneto-Optical recording.
Magneto optical (MO) disks have shown great advantages in performance, reliability, price per bit, portability, rewrite cycles, high-density recording, and achieve life. For a 3.5' ISO standard MO media, the capacity of 1X-density disks is 128 MB, and 5X density disks have 540 MB/640 MB capacity, with track and bit density increased. Media testing is very important in research and manufacture of the disks. A media testing system for the characteristics of the recording layer of the 5X capacity MO disks is introduced in this paper. Many features and techniques are discussed such as to achieve high accuracy testing, flexibility to upgrade the system.
A multi-valued photochromic optical disk written by different flux irradiation based on the photon-mode recording property is presented to obtain high density and high speed. A four-valued (2-bit) photochromic storage is carried out by static testing on pyrrl fulgide derivative. A new nondestructive read out method--dual-beam compensation readout--is proposed and discussed.
In this paper, a high speed data recording system based on optical disk array is presented on the basis of careful analyses of the techniques to improve the data recording speed of the commercial optical drives. An ultra high speed and mass storage capacity are achieved in this system. Flexibility and portability are also gained by the design.
This paper provides a method to test some parameters of CDs. These parameters show the quality of the disks directly. The method is based on a commercial CD-ROM and a common computer. Some necessary circuits and software are added in. The analytic results can be provided.
An optical recording static tester with high performance but low cost based on a commercial optical disk drive is introduced. Its schematic diagram and optical system are described. A quasi-linear-region focusing search method is proposed and carried out. It is a simple reliable focusing search method based on the positive and negative feedback characteristics of the focusing error curve.
Slow access speed is still the problem to limit applications of rewritable optical disk drives. Dual stage actuators with a coarse and a fine actuator are used in optical disk drives. In this paper, the two-actuator cooperative seek control method, based on time optimal seek control, is presented, and the average seek time is analyzed theoretically.
In this paper, a writing and reading method of 3D optical digital storage is presented. The novel method is based on dual photon-absorption effective and multi-layer distribution of data. The potential problems of the method are discussed and analyzed.
This paper describes the probabilities of concurrent access to an optical jukebox in a hierarchical VOD system, it also explains some fundamental principles for the retrieval and storage of video data. Using a simplified general framework, both singled and multiple video streams playback are discussed. As a result, there are three ways to support more users to access an optical jukebox directly.
This paper introduces the design and implementation of a Multimedia Data Repository served as a multimedia information system, which provides users a Web accessible, platform independent interface to query, browse, and retrieve multimedia data such as images, graphics, audio, video from a large multimedia data repository. By integrating the multimedia DBMS, in which the textual information and samples of the multimedia data is organized and stored, and Web server together into the Microsoft ActiveX Server Framework, users can access the DBMS and query the information by simply using a Web browser at the client-side. The original multimedia data can then be located and transmitted through the Internet from the tertiary storage device, a 400 CDROM optical jukebox at the server-side, to the client-side for further use.
Based on nm fabrication technology, a developed player for dual and multilayer disk is proposed in this paper. A multifocus device with focus 8.5 mm is used. The distance between two neighbor focal plane is 0.45 mm. The numeral aperture of the developed player is 0.59, the focusing spot is 0.93 um. The developed player with the multifocus device is not only simple in structure, light in weight, but also can focus automatically at any layer of multilayer disk eve, no mechanical movement. Compared to the common CD player, the developed player is characteristic of only one multifocus device to focus and split beam, where the prism and the grating in common CD player are displaced, but the focusing and the tracing error signals can be obtained conveniently for servo detection.
Optical disk array improves performance of optical drive in many aspects. The mechanism of separate drive and disk reduce the MTTR (mean time to repaired) of single failure. So data security increases much better than other array system. Parallel structure and reasonable redundant data distribution multiply the I/O speed much more by reducing average distance between different data.
A holographic element for the common CD pick-up to play DVD is designed in this paper. The focus of holographic element is the same as that of the objective lens of CD player. The holographic element is fixed before the objective lens. The focus of DVD player with this holographic element is 8.5 mm, the number aperture is 0.75, and the focusing beam spot is 0.5 um. DVD player with the holographic element is characteristic of compensating the main optical error met in the common CD player well.
Optical array and special data arrangement affect data sharing feature of Video-on-Demand system significantly. Some aspects related to maximum user number have been analyzed in theory and verified in experiment.
The average distance between different data will decrease through reasonable data distribution. Redundant MacroBlock data strategy is such a way to reduce seeking distance, and improve seeking efficiency, which is presented in theory and experiment.
Video CD playback board is a built-in card for a conventional audio CD player that allows users to play back high quality full-motion video and stereo sound. The board is made up of the CL480 MPEG-1 audio/video decoder, the Bt851 NTSC/PAL video encoder and the CS4331 stereo D/A converter. By connecting the board to the DSP's serial data output of a audio CD player. Video CD discs can be played back by using the Subcode PQ search mode of the CD player. Audio CD players will simply evolve into Video CD player.
Several improvements to the optical disk drive and key parts have been carried out to enhance their function, storage density, capacity, data rate and reduce access time in recent years in the Optical Memory National Engineering Research Center (OMNERC). Approach for research on both of optical system and mechanic-electronic servo system are also reported in this paper. OMNERC of China started research and development on optical disk drive in the early 80's. In the past 15 years, many kinds of drives as phase-change erasable disk drive, CD-ROM drive, V-CD player etc. have been finished and some results of them have been playing important role in optical storage products manufacturing industry. In recent 5 years OMNERC has made the new optical drive model and some major technology research and development from the China national 8th five years science and technology development plan. The objective of this major subject is to make research and development on new generation multifunctional optical disk drive, especially on photo/thermo effect read, write and erase technology and drive as well as application systems. They are following projects: designing larger numerical aperture of objective lens used to enhance resolution and storage density, simplifying moving part of optical head to reduce its weight with holographic and other diffraction elements, increasing autofocusing and seeking precision, speed and proper frequency width of driving system, developing dual laser beams multifunctional optical head which is suitable for various inorganic and organic write once or erasable media, improving the data rate and reliability of storage data.
A real time non-contact dynamic testing method for an optical disk is proposed in this paper. The axial run-out and the tilt of the optical disk are measured by two quadrant detectors when the disk is turning at high speed in the drive. The analysis of the results is given with a brief discussion on the error in measurement.
In this paper, holographic optical elements (HOEs) used in optical disk systems are discussed. HOEs have been used to form several beams for detecting focusing and tracking error, as a beam splitter and a formatter of wavefront. It can also be used as an objective lens in the future.
A fully separated optical head means that the carrier and the actuator are separated completely. It causes the mass of the carrier to be less than 10 grams, or even less. It can increase the access rate greatly and avoid the cross interference between two stage seekings.
Progress of optical data storage technology and application systems, which have been obtained in recent years at Tsinghua University, are reviewed. In this paper, the new multifunction optical drive, miniaturizational optical head, high speed precise seeking system, automatic exchange disk system (jukebox), controller interface adapter, data compression technology, and various application systems are reported.