Optical Recording Medium Layer Reflectance Control
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Solution Overview
Problem
Conventional optical recording media with multiple layers face challenges in maintaining stable signal readout due to interference from reflection light from non-target layers, leading to increased spherical aberration and jitter, which affects recording and reproduction quality.
Innovation Solution
The optical recording medium is designed with specific reflectance and transmittance settings between layers, along with controlled interlayer distances and refractive indices, to minimize interference from non-target layers' reflection light and effectively correct spherical aberration using spherical aberration correcting units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple recording layers are added to increase recording capacity, then recording capacity is improved, but interference from reflection light of non-target layers increases
Solution Approach 1:
The patent applies local quality by assigning different reflectance values to different recording layers. Specifically, the first recording layer has a first reflectance value while the second recording layer has a second reflectance value, creating localized optical property differences that enable selective reflection control for each layer
Solution Approach 2:
The patent changes the optical parameters (reflectance and transmittance) of the recording layers to solve the interference problem. By controlling the reflectance of each layer to specific values and the transmittance between layers, the patent minimizes harmful reflection light interference while maintaining multiple recording capabilities
2Quantity of substance
If interlayer distance is reduced to increase recording density, then recording density is improved, but spherical aberration increases
Solution Approach 1:
The patent changes the optical parameters of the layers, specifically setting the refractive index of the first recording layer to a first value and the second recording layer to a second value, which helps control spherical aberration while maintaining small interlayer distances for high recording density
3Strength
If protection layer thickness is increased to protect information recording face, then protection is improved, but spherical aberration increases
Solution Approach 1:
The patent changes the refractive index parameter of the protection layer to a specific value that balances protection functionality with minimal spherical aberration introduction, allowing adequate protection while maintaining optical performance
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 reduces the influence of reflection light from non-target layers, stabilizes signal readout, and suppresses spherical aberration, resulting in improved recording and reproduction accuracy and reduced jitter.
Implementation Method 1
reflectance of the first information recording face is set as α1, and reflectance of the h-th information recording face is set as αh
Implementation Method 2
refractive index of a protection layer from the surface to the first information recording face is set as n1, and refractive index of a protection layer from the (h−1)th information recording face to the h-th information recording face is set as nh
Implementation Method 3
The diverging beam 70 emitted from the light source 1 passes through a collimate lens 53 having spherical aberration correcting units 93 and whose focal length f1 is 15 mm
Data Source
AI summary
The present invention provides an optical information medium capable of suppressing the influence of reflection light from an unnecessary information recording face and effectively eliminating spherical aberration at the time of recording/reproducing information to/from a recording medium having a plurality of information recording faces. When reflectance of an information recording face is αh and transmittance between information recording faces is th, αh and th of the optical information medium are set so as to satisfy ((α(h−1)2×α(h−2))/(th2×αh))<0.01.