Phase-change optical storage medium reflectivity control
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Solution Overview
Problem
Conventional phase-change optical storage media face challenges in achieving sufficient overwrite characteristics, especially at high recording speeds and densities, due to issues with jitter and crystallization speed, which affect their recording and reproduction capabilities.
Innovation Solution
A phase-change optical storage medium is designed with a specific structure and recording pulse pattern that maintains excellent overwrite characteristics by optimizing the reflectivity ratios and power ratios, ensuring that the recording layer's reflectivity changes appropriately with each overwrite, even at high linear velocities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phase-change optical storage media are used with standard recording pulse patterns, then basic recording and reproduction functions are achieved, but overwrite characteristics deteriorate at high recording speeds and densities due to jitter and insufficient crystallization speed
Solution Approach 1:
The patent applies periodic pulsed laser irradiation with specific timing patterns to induce controlled phase changes in the recording layer. By using periodic recording pulses with optimized durations and intervals, the method achieves reliable overwrite at high speeds through repeated thermal cycling that ensures complete crystallization even at DVD 4× speed
Solution Approach 2:
The patent changes key parameters including laser power levels (recording power, erasing power, bottom power), pulse durations (top pulse, multipulse, erasing pulse), and power ratios. These parameter optimizations enable the recording layer to undergo complete phase transitions within shorter timeframes, maintaining overwrite reliability at higher recording speeds
2Quantity of substance
If laser beam spot is made smaller to create highly-dense signal for larger storage capacity, then storage capacity increases, but reproduction compatibility with conventional DVD apparatus deteriorates
Solution Approach 1:
The patent employs dynamic pulse patterns with variable power levels and durations that adapt the recording process to the physical properties of the recording layer. This dynamic approach allows achievement of high storage capacity through dense marking while maintaining compatibility with conventional DVD reproduction systems by controlling mark dimensions and reflectivity changes
3Measurement precision
If reflectivity of un-recorded sections is made higher than recorded sections to improve recording density and repeatability, then recording quality improves, but overwrite characteristics particularly at initial overwriting deteriorate at high recording speed
Solution Approach 1:
The patent applies preliminary erasing pulses before recording pulses to ensure the recording layer is in a consistent crystalline state before new data is written. This preliminary action eliminates residual amorphous phases from previous recordings, ensuring reliable initial overwrite characteristics at high speeds by starting from a known stable state
Solution Approach 2:
The patent uses continuous bottom power irradiation during the recording process to maintain the recording layer temperature in an optimal range for phase transition. This continuous thermal field ensures smooth and complete crystallization during overwrite operations, preventing jitter and maintaining reliability at high recording speeds
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables excellent recording and overwrite characteristics at higher recording speeds, including DVD 4×speed, while maintaining fast crystallization speeds, thus improving the overall performance and stability of the optical storage medium.
Implementation Method 1
The recording layers come into an amorphous phase with low reflectivity when right after formed by sputtering, for example. They are thus initialized with irradiation of a laser beam, for example, to come into a crystalline phase with a high reflectivity
Implementation Method 2
recording pulses are applied (emitted) onto a recording layer with a laser beam having a recording power, to melt and rapidly cool down the recording layer, thus forming amorphous recorded marks thereon
Implementation Method 3
a laser beam having a power (erasing power) smaller than the recording power is emitted onto the recording layer to raise the temperature thereof to the crystallization temperature or higher to change the recording layer from the amorphous phase to the crystalline phase
Data Source
AI summary
A phase-change optical storage medium has a substrate, and a recording layer, to be recorded on which is at least one recorded mark representing information to be recorded by irradiating a recording light beam onto the recording layer in accordance with a recording pulse pattern of recording pulses rising from an erasing power and formed between a recording power larger than the erasing power and a bottom power smaller than the erasing power and of erasing pulses rising from the bottom power to the erasing power. The expressions (1) and (2): 1.00<(R1/R0)<1.15 . . . (1), 1.05<(R9/R0)<1.20 . . . (2) are satisfied for the recording layer, in which R0 is a reflectivity exhibited by an un-recorded section of the recording layer, on which no data has ever been recorded, when irradiated with a reproducing light beam, R1 is a reflectivity exhibited by the un-recorded section when irradiated with the reproducing light beam, after irradiated once with the recording light beam in accordance with the recording pulse pattern, and R9 is a reflectivity exhibited by the un-recorded section when irradiated with the reproducing light beam, after irradiated nine times with the recording light beam in accordance with the recording pulse pattern.