Xu Duanyi

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.

Multilevel optical data recording methods on phase-change media

Multilevel data storage (ML) is a new method in the optical storage field, which is also a trend for improving the capability of future optical discs. This article introduces several ML methods based on phase-change media including pit depth modulation (PDM) and mark radial width modulation (MRWM). In addition, some disadvantages and advantages concerning the principle of these methods will be discussed. Finally, a new ML method will be advanced, through which the levels in one recording pit will be increased evidently.

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

When the techniques of integrating the variation of the pit depth and width simultaneously are adopted to conventional DVD, the high-density multilevel run-length limited read-only optical storage method is achieved. The dynamic range of readout signal is greatly enlarged in comparison with keeping one parameter varied, and the recording levels number can be obviously increased. The discs can be manufactured using standard photoresist mastering and replication techniques with great compatibility to conventional binary read-only discs. Experimental results show that eight-level read-only optical disc can be realized and the capacity can be increased to 20 GB.

Approximated Vector Diffraction Theory for Readout Signal of Multi-Level Run-Length-Limited Discs

Multi-level run-length-limited read-only optical storage is a kind of high density storage method. The width and height of recording marks are varied with different levels, which is the key technology for the optical storage. When the readout signal of these discs with complex recording marks is computed by vector analysis method, it is very hard and time-consuming. Approximated vector computation combines the convenience of scalar method and precision of vector method, which is effective for multi-level run-length-limited read-only optical storage.

Restriction of shot noise and material noise in a multilevel photochromic memory on signal-to-noise ratio

The recording density of multilevel photochromic memory is limited by the signal-to-noise ratio (SNR) of the readout signal. In this paper, shot noise and material noise are investigated through theoretical analysis of SNR. When the bandwidth of a system is less than 1MHz, the material noise takes a prominent position; when the bandwidth of the system is more than 10MHz, the shot noise becomes dominant. The thickness of recording layer can be optimized to maximize the SNR and reduce the influence of the bandwidth of the system on SNR.

Study Of Image Structure In The Focal Plane In Microphotolithography System.

Optical projection microlithography for fabricating fine line and optical data storage technique ave extended into submicron region. But many new technical problems will be appeared in transferring such exacting structure by optical method. One of the important subjects is the investigation of the light energy distribution on focal plane. this paper described the experimental results using an automatic focusing system which was produced by Tsinghua Univ. within +0.1u accurasy. Those have been colipared with the calculating results of perfect lens and residual aberration system,and the relation of them was also discussed.