Read-only Disc Research Articles

Blu-Ray Media Stability and Suitability for Long-Term Storage

Abstract The most recent generation of optical disc media available is the Blu-ray format. Blu-rays offer significantly more storage capacity than compact discs (CDs) and digital versatile discs (DVDs) and thus are an attractive option for the storage of large image or audio and video files. However, uncertainty exists on the stability and longevity of Blu-ray discs and the literature does not contain much information on these topics. In this study, the stabilities of Blu-ray formats such as read-only movie discs as well as many different brands of recordable and erasable media were evaluated. Testing involved the exposure of samples to conditions of 80 °C and 85 % relative humidity for intervals up to 84 days. Overall, the stability of the Blu-ray formats was poor with many discs significantly degraded after only 21 days of accelerated ageing. In addition to large increases in error rates, many discs showed easily identifiable visible degradation in several different forms. In a comparison with other optical disc formats examined previously, Blu-ray stability ranked very low. Other data from the study indicated that recording Blu-ray media with low initial error rates is challenging for some brands at this time, which is a factor that ultimately affects longevity.

Salvage the Post Life of Solid State Disk

The limited use lifetime is a significant drawback of the solid state disk (SSD). When the amount of bad blocks exceeds a threshold, the entire SSD is rendered non-functional as worn out. In this paper, we analysis the post life status of a SSD when its worn out and explain the endurance characteristic induced by Flash charge trap. The real achievable endurance is much more than the threshold endurance defined by the Flash chip manufacturers. Two methods are proposed to salvage the post life. The results show that the SSD could be used as a read-only disk or with the life time extended by 2X at most 6% user capacity penalty.

New Differential Phase Detection Method for Signal Waveform Modulation Multi-Level Discs

Signal waveform modulation multi-level (SWML) read-only discs employ sub-lands/sub-pits to achieve multi levels. However, the tracking error signal derived from the conventional differential phase detection (DPD) method deteriorates in the SWML read-only disc owing to sub-lands/sub-pits inserted in the conventional pits/lands. To solve this problem, a new DPD method, which employs a signal adjuster and a phase regenerator, is proposed. The experimental results show that the tracking error signal derived from the new DPD method has better characteristics of uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc.

Multilayer 500 Gbyte Optical Disk

To confirm the feasibility of realizing subterabyte or terabyte optical memories, we evaluated a multilayer read-only disk having 20 information layers. We propose a new disk structure, which is an alternative structure to reduce interlayer crosstalk, optimized by computer simulations. We fabricated multilayer read-only optical disks using a conventional manufacturing process for Blu-ray disk (BD) dual-layer media. Moreover, we improved the reproduction system to compensate for the large spherical aberration. From the experimental results, we obtained sufficiently low jitter values reproduced from a 20-layer disk. We confirmed the feasibility of the multilayer read-only disk with a capacity of 500 Gbytes.

新型多阶只读光盘的差分相位检测信号分析

To improve the tracking servo performance, a novel signal waveform multi-level (SWML) read-only disc realized on the digital versatile disc (DVD) platform is presented. The characteristic of the differential phase detection (DPD) signal of the SWML read-only disc is analyzed both in theory and experiment. The amplitude of the DPD signal of the SWML read-only disc in an open tracking servo loop is about 2/3 of that of the DVD read-only disc. The uniformity and symmetry of the DPD signal of the SWML read-only disc are similar to those of the DVD read-only disc and better than the former multi-level run-length limited (ML-RLL) read-only disc.

Read Channel for Multilevel Run-Length-Limited Read-Only Disc

A novel multilevel run-length-limited read channel which employs an interpolating timing recovery system and an adaptive partial-response maximum-likelihood (PRML) detector is developed. In proposed adaptive PRML detection system, we adopt a 112-levels adaptive Viterbi detector which uses every RF sample to adjust the reference levels for the calculation of branch metrics. The reference levels of adaptive Viterbi detector are also used to regenerate RF signals for phase error calculation. The usage of adaptive PRML detector makes the performance more robust, and the combination of Viterbi reference levels and RF generator makes the calculated phase errors more accurate.

Optical Head Using Single Objective Lens for Four Types of Optical Disks

An optical head using a single objective lens for Blu-ray disc (BD), high-density digital versatile disc (HD DVD), digital versatile disc (DVD), and compact disc (CD) has been developed, which is suitable for high-speed recording and reading. A relay lens unit, which consists of two convex lenses and one concave lens, corrects the spherical aberration and realizes high light power efficiency for each disk. A numerical aperture (NA) control element, which contains a liquid crystal aperture and a wavelength selective aperture, controls the NA of the objective lens for each disk. A coma aberration caused by the objective lens shift is detected based on differential phase detection signals for read-only disks and push–pull signals for recordable or rewritable disks, and is corrected by moving one of the lenses in the relay lens unit by an actuator. A diffraction-limited focused spot and good readout signal characteristics were obtained for each disk, and the validity of this optical design has been demonstrated.

Timing Recovery Method for Multilevel Run-Length-Limited Read-Only Disc

A novel timing recovery method for multilevel run-length-limited read-only disc is described. This timing recovery system employs interpolation method, which extracts multilevel run-length limited (ML-RLL) data directly from asynchronous oversampling RF data. The timing recovery system in the proposed read channel has a feedback architecture and consists entirely of digital circuits. It uses Viterbi detector output to calculate the phase error feedback to interpolator, and a special sync pattern is inserted to help frequency detection. The experimental results show that the acquisition time is much smaller than conventional timing recovery system.

Dynamic model of mastering for multilevel run-length limited read-only disc

A dynamic model of mastering for multilevel run-length limited read-only disc is built, and corresponding experiments on DVD are done to validate it. Results show that this model consists with real mastering process. Using the model, a preliminary write strategy for 4-level run-length limited read-only disc is calculated out. The readout signals of the disc optimizing by write strategy are very close to desired.

Low-Noise and Low-Environmental-Impact Reflective Material for High-Density Optical Data Storage

We designed a new reflective material for high-density optical data storage to manage both recording and reproducing properties and environmental impact. We achieved suitable characteristics using an Al based alloy including two additional elements. In the case that AlPdSnO2 was applied in a Blu-ray disc (BD) type write-once disk, recording and reproducing properties equivalent to those for the conventional Ag alloy of AgPdCu were achieved. Moreover, in the case that it was applied for a BD-type read-only disk, jitter was improved compared with the conventional Al alloy of AlTi.

Multilevel read-only optical recording methods

The advantages of read-only storage is the predominance of optical recording relative to magnetic and other rewritable methods. Multilevel (ML) read-only technology has been a trend to improve the data capacity and transfer rate. Based on the principle and coding method of ML, this paper demonstrates some ML read-only recording methods, of which a new ML read-only recording is developed. This recording method integrates amplitude modulation achieved by the reaction mechanism of physics and chemistry of photoresist with the run-length-limited technology. The discs can be achieved using standard photoresist mastering and replication techniques with great compatibility to conventional binary read-only discs.

Analysis of the Differential Phase Detection Signal in Multi-level Run-Length Limited Read-Only Disk Driver

Multilevel run-length-limited (ML-RLL) recording technology could be employed to increase the capacity of the read-only disc without changing optical and mechanical units. In this paper, the tracking error signal (TES) of differential phase detection (DPD) for ML-RLL digital versatile disk (DVD) read-only disk driver is analyzed in both theoretical and experimental way, the uniformity and symmetry of which are worse than that of the DVD read-only disk driver. The variation of peak to peak (PP) value distribution of the DPD signal in open loop of ML-RLL DVD read-only disk driver is about 2.6 times of that of the conventional DVD driver while the asymmetry is about 4 times. It is predicted that some improvements of the tracking servo system are needed in ML-RLL system.

Analysis of the effects of disk tilt on the differential-phase-detection signal in a high-density DVD read-only disk driver

A high-density DVD (HD-DVD) is one of the high-density optical storage technology newly designed to meet the demands of high-definition video broadcasting that is very sensitive to the radial tilt of a disk. An analytic model based on diffraction theory is presented in detail to calculate the tracking error signal of a HD-DVD read-only disk driver by using the differential-phase-detection (DPD) method when radial tilt of a disk occurs. The effects of the tilt on a DPD signal in a HD-DVD read-only disk driver are quantified and compared to those in a DVD read-only disk driver. Experimental measurements for the DPD signal under different radial tilt angles in a HD-DVD read-only disk driver are also reported.

Pit Depth and Width Modulation Multilevel Run-Length LimitedRead-Only Optical Storage

When the techniques of integrating the variation of the pit depth andwidth simultaneously are adopted to conventional DVD, the high-densitymultilevel run-length limited read-only optical storage method isachieved. The dynamic range of readout signal is greatly enlarged incomparison with keeping one parameter varied, and the recording levelsnumber can be obviously increased. The discs can be manufactured usingstandard photoresist mastering and replication techniques with greatcompatibility to conventional binary read-only discs. Experimentalresults show that eight-level read-only optical disc can be realizedand the capacity can be increased to 20 GB.

Multilevel Run-Length Limited Recording on Read-Only Disc

Multilevel run-length-limited (ML-RLL) recording technology is employed to increase the capacity of the read-only disc with no change on optical or mechanical units. 4L-RLL recording on read-only disc has been implemented with minimum recorded mark length same as that in conventional digital versatile disc (DVD). The capacity of a double layer DVD disc with 4L-RLL (2, 10) modulation reaches 15 GB. Experimental results show that the ratio of the standard deviation of noise to the dynamic range of readout signal amplitude is lower than 4.53%, which means that the requirement of signal detection for 4L-RLL can be satisfied.

Modeling and realization of a multilevel read-only disk

A model for exposing and developing photoresist using the reaction mechanism of physics and the chemistry of resist is built, and the micropatterns of recording marks on a stamper are calculated. Compared with our experimental results, the deviation of pit width in simulation is less than 8%. When the width of recording marks is varied by modulating laser power during exposure, a multilevel (ML) read-only disk can be achieved as a result of the corresponding readout signal. Experimental results show that an 8-level read-only optical disk can be realized. The model of mastering serves well for the development of novel ML disks in which the integration of conventional run-length deviations technologies can greatly increase recording density.

Design and experimental test of diffractive superresolution elements

By using previously established methods based on linear programming (MLP), we design and fabricate two types of diffractive superresolution element (DSE). The structure parameters and superresolution performances of the fabricated DSEs are tested. The test results agree well with the design results and are applicable to a writable or a read-only optical disk. Thus the application validity of the MLP is experimentally verified.

High-precision measurement of reflectance for films under substrates

A more accurate methodology to measure the reflectance of optical disks, taking into consideration the scattering losses at the surfaces of the disk, is proposed by the National Institute of Standards and Technology (NIST). The proposed method is a modification of the current standard, as described in Annex D of the Standard ECMA-267, second edition, for 120-mm DVD—Read-Only Disk (Dec. 1999, http:/www.ecma.ch/). The experiment shows that the optical losses could be, in some cases, as much as 2% of the incident light power. By accounting for the losses, as in the proposed method, the accuracy of the measured reflectance is significantly improved. Thus, the primary reference disks produced with this method have a higher accuracy in reflectance measurement for the use of optical disk industry.

Read-out of a read-only super-resolution optical disc with a Si mask

A novel read-only super-resolution optical disc structure (substrate/mask layer/dielectric layer) is proposed in this paper. By using a Si thin film as the mask layer, the recording pits with a diameter 380nm and a depth 50nm are read out on the dynamic measuring equipment; the laser wavelength λ is 632.8nm and the numerical aperture is 0.40. In the course of reproduction, the laser power is 5mW and the rotation velocity of the disc is 4ms-1. The optimum thickness of the Si thin film is 18nm and the signal-to-noise ration is 32dB.

Study on read-only optical disk with Sb mask super-resolution

In this note, by using Sb to replace the Al reflective layer in the conventional optical disk, the recording pits with a diameter 380 nm and a depth 50 nm are read out in the device, whose laser wavelength λ is 632.8 nm and numerical aperture (NA) is 0.40. In the course of reproduction, the readout laser power is 4 mW and the rotation velocity of the disk is 5 m/s. The optimum Sb film thickness is 28–30 nm and the CNR is 38–40 dB.