Longfa Pan

Multi-level read-only recording using signal waveform modulation

A novel multi-level read-only recording using signal waveform modulation (SWM) is presented. The SWM is realized by inserting a sub-pit/sub-land to the original land/pit. Numerical simulation provides a helpful tool for the write strategy optimization. This method is experimentally validated on the DVD platform. Comparing with 2-level recording, an increase of 50% in capacity can be expected. It shows superiority over signal amplitude modulation (SAM) multi-level in replication processing, capacity increase and servo performance.

Comb-drive tracking and focusing lens actuators integrated on a silicon-on-insulator wafer.

This paper reports integrated tracking (horizontal) and focusing (vertical) actuators using microelectromechanical (MEMS) technology for optical storage. The design, fabrication and characterization of the integrated tracking and focusing actuators are demonstrated. The integrated tracking and focusing lens actuators that consist of springs, a lens holder and comb-drive actuators are implemented to obtain the two-dimensional tuning effect of an objective lens. A two-mask process is used to define the actuators on a silicon-on-insulator (SOI) wafer. The DC displacements and the frequency responses are characterized by applying voltage to the micro lens actuators. Displacements are experimentally characterized with ± 24.6μm in tracking direction and 5.7μm in focusing direction. Moreover, the influences of the cross-axis coupling are measured and evaluated. This MEMS device which has a small form factor provides an excellent response time and size reduction. The minimization and integration of the lens actuators can offer low costs in assembly and expand the application area of the optical head.

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.

Constrained Code and Partial-Response Maximum-Likelihood Detection for High Density Multi-Level Optical Recording Channels

A new efficient four-ary (1,4) run-length limited (RLL) code is presented, which is intended for high density multi-level optical recording channels. By using proposed hybrid DC control scheme, the new code can achieve acceptable DC suppressing characteristics while maintaining high code rate. The bit error rate (BER) performances of this new code on blue laser recording systems are evaluated by using partial-response maximum-likelihood (PRML) detection. The feasibility of using four-ary RLL modulation and PRML detection is studied in this paper, and these techniques show great potential to be applicable in high-density multi-level optical recording channels.

DC-free four-ary (2, 8) run-length limited code for multi-level recording channels

A new high efficient DC-free (2,8) run-length limited (RLL) code for four-level optical recording channels is proposed. The proposed code can be represented by a finite state diagram (FSM) with three states and implemented easily. The code rate and density ratio of the code are 5/6 bits/symbols and 2.50 bits/minimum-recorded-mark, respectively. On the basis of the experimental results, the performances of the code are evaluated by using partial-response maximum-likelihood (PRML) technology, which is suitable for detecting multi-level RLL signals. By using four-ary (2,8)RLL modulation and PRML technology, one can increase the recording density 66.7% relative to conventional binary RLL modulation currently used in digital versatile disc (DVD), meanwhile the bit error rate (BER) still be acceptable.

New Efficient Run-Length Limited Code for Multilevel Read-Only Optical Disc

Multilevel recording with run-length limited (RLL) modulation is a novel way to significantly increase the recording density without changing the optical or mechanical units of current optical disc systems. In this paper, a new efficient 4-ary RLL(2,13) code with special constraint is designed for four-level RLL modulation on read-only digital versatile disc (DVD-ROM). This code can result in alternate multilevel pits and lands on the disc, and reduce the difficulty of multilevel disc replication. Further more, simulation results show the symbol error rate (SER) performance can be improved about 3 dB when the proposed code is used for optical recording channel with partial-response maximum-likelihood (PRML) detection.

A new four-ary run-length-limited (2,12) code for multilevel optical recording channels

In this paper, we introduce a new four-ary run-length-limited (d,k)=(2,12) code for multilevel optical recording channels. This code has a simple one-codeword look-ahead encoder and a sliding block decoder. The code rate is 4/5 (bits/symbol), and the density ratio is 2.4 bits/Tmin, which is larger than that of binary codes used for typical optical recording systems. The encoding and decoding rules of the proposed code are simple and easy for implementation. With the bit error rate (BER) performance evaluation, this code shows feasible to be applied in high-density multilevel optical storage systems.

Improved mastering material for multilevel blue laser disc

In order to get a small-sized pit, the reaction threshold of a photoresist is enhanced by increasing the prebake temperature and time. With the improved photoresist, a pit size corresponding to or even smaller than the minimum pit on a blue laser disc can be obtained on an industrial DVD product line. The improved photoresist may serve as the master material of future multilevel blue laser discs, which might provide a potential solution for the fabrication of multilevel blue laser discs.

4-level run-length limited optical storage on photo-chromic materials

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).

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.