Multi-Layer Optical Disk Format Compatibility
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Solution Overview
Problem
Conventional optical disks lack compatibility with both conventional and next-generation high-density optical disk formats, limiting the use of next-generation high-density disks in optical disk drives designed for earlier formats.
Innovation Solution
An information recording medium with multiple layers, each compatible with different formats, using a first objective lens with a high numerical aperture for near-field recording and a second objective lens with a lower numerical aperture for conventional formats, allowing recording and reproduction across various formats.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high numerical aperture objective lens is used for next-generation high-density optical recording, then the beam spot diameter is reduced and recording density is improved, but coma aberration increases proportionally to the cube of the numerical aperture
Solution Approach 1:
The patent changes the thickness parameter of the transparent substrate from conventional values (0.6mm for DVD, 1.2mm for BD) to a specific range of 0.05mm to 1.2mm. This parameter change optimizes the balance between achieving sufficient recording density and suppressing coma aberration. By carefully selecting substrate thickness within this range, the patent enables compatibility with both high-NA next-generation systems and conventional optical disk formats while controlling aberration effects.
Solution Approach 2:
The patent creates different local optical paths within the same substrate by forming information recording layers at different distances from the substrate surface. The first information recording layer is positioned at a distance suitable for high-NA near-field recording, while the second information recording layer is positioned at a distance suitable for conventional NA recording. This local differentiation allows each layer to be optimized for its specific recording system.
2Object-affected harmful factors
If the thickness of the transparent substrate is reduced to suppress coma aberration, then aberration is reduced, but compatibility with conventional optical disk formats that require specific substrate thicknesses is lost
Solution Approach 1:
The patent segments the information recording function into two separate information recording layers positioned at different distances from the substrate surface. This segmentation allows each layer to be independently optimized for different optical disk formats. The first layer serves next-generation high-density formats while the second layer serves conventional formats, enabling the single substrate to support multiple formats simultaneously.
Solution Approach 2:
The patent creates a universal optical disk that can be read by both conventional and next-generation optical disk drives. By incorporating multiple information recording layers at different positions, the single disk serves multiple functions: it is compatible with high-NA near-field recording systems and conventional NA recording systems simultaneously. This multi-functionality resolves the compatibility issue while maintaining reduced substrate thickness.
3Adaptability or versatility
If multiple information recording layers are formed at different distances from the substrate surface, then compatibility with both conventional and next-generation formats is achieved, but device complexity increases
Solution Approach 1:
The patent structures the optical disk with information recording layers nested at different depths within the substrate. The first information recording layer is positioned closer to the surface for near-field access, while the second layer is positioned deeper for conventional optical access. This nested arrangement allows both layers to coexist within a single disk structure without requiring separate physical disks, managing complexity through hierarchical organization.
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
Enables recording and reproduction of information on a single optical disk compatible with both conventional and next-generation high-density formats, ensuring compatibility and expanding the usability of next-generation disks with existing drives.
Implementation Method 1
an objective lens having a numerical aperture NA of 0.85, where laser beam is condensed onto the recording layer from the transparent cover layer side
Implementation Method 2
onto which information is to be recorded and/or from which information is to be reproduced using laser beam
Data Source
AI summary
An information recording medium includes a first information recording layer and a second information recording layer. The first information recording layer is formed at a laser beam entrance surface, and is configured so that information can be recorded thereupon and/or reproduced therefrom using a first objective lens having a numerical aperture NA1 and laser beam of a wavelength λ1. The second information recording layer is formed so as to have a distance to the laser beam entrance surface of 0.05 mm to 1.2 mm and is configured so that information can be recorded thereupon and/or reproduced therefrom using a second objective lens having a numerical aperture NA2 and laser beam of a wavelength λ2. When a diffraction limit δ2, determined by numerical aperture NA2 and wavelength λ2, is taken as δ2=0.61×λ2/NA2, a track pitch Tp1 of a track formed on the first information recording layer is Tp1<δ2.