Optical Disc Mark Size Control for Crosstalk Reduction
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Solution Overview
Problem
Current multi-value recording techniques face issues with crosstalk and crosswrite due to recording marks exceeding the beam spot size on high-density optical discs, leading to decreased signal quality and linearity, especially at narrow track pitches.
Innovation Solution
The solution involves an information recording device and method that limits the size of recording marks to be equal to or smaller than the beam spot size, preventing crosstalk and crosswrite by generating recording pulses based on multi-value modulation data and ensuring all marks are recorded within the beam spot boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-value recording is performed by adjusting mark size according to modulation signal levels, then information recording density is improved, but crosstalk and crosswrite occur between adjacent tracks
Solution Approach 1:
The patent applies parameter changes by strictly controlling the mark size parameter to be within the beam spot diameter, regardless of the modulation signal level. This prevents the thermal diffusion that causes crosswrite to adjacent tracks while still enabling multi-value recording through controlled mark formation within the confined spatial boundary
Solution Approach 2:
The patent implements preliminary anti-action by pre-defining the mark size constraint (mark size ≤ beam spot diameter) before recording begins. This preventive measure ensures that even when recording high-density multi-value data, the marks will not exceed the boundary that would cause interference with adjacent tracks
2Quantity of substance
If track pitch is reduced to increase recording density, then information recording density is improved, but crosstalk between adjacent tracks increases
Solution Approach 1:
The patent changes the critical parameter from mark size to beam spot diameter, establishing that mark size must not exceed the beam spot diameter. This parameter relationship ensures that even with reduced track pitch, the marks remain confined within their respective beam spots, preventing crosstalk while maintaining high recording density
3Adaptability or versatility
If mark size exceeds beam spot size for deep gradation recording, then multi-value recording capability is improved, but linearity of level gradation deteriorates
Solution Approach 1:
The patent resolves this contradiction by changing the approach to multi-value recording: instead of varying mark size beyond beam spot boundaries, the patent maintains mark size within beam spot diameter and achieves multi-value recording through controlled mark formation processes. This preserves the linearity of level gradation while maintaining adaptability for recording multiple data levels
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
This configuration effectively reduces crosstalk and crosswrite, improving signal quality and playback accuracy by maintaining mark sizes within the beam spot limits, thereby enhancing the SNR and linearity of multi-value recordings.
Implementation Method 1
a recording mark of a size exceeding a beam spot is formed by a thermal action of recording laser beam irradiation
Data Source
AI summary
An information recording/playback device includes a recording pulse generation unit generates a recording pulse based on a multi-value modulation data, and a data recording unit records the mark on the recording medium based on the recording pulse. The data recording unit executes recording processing of setting sizes of all of marks to be recorded on the recording medium to a size equal to or smaller than a spot size at a half level of a maximum value of a two-dimensional light intensity distribution of a beam spot, and executes data recording processing of forming recording regions in modes having different densities of recording marks according to the levels of the multi-value modulation data.