Optical Recording Medium Asymmetric Interlayer Spacing
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Solution Overview
Problem
Multilayer optical discs face interference issues due to reflected light from other layers returning along the same optical path as the readout layer, leading to signal degradation and reduced quality of servo and reproduction signals.
Innovation Solution
The optical recording medium is designed with non-equal interlayer spacings between all combinations of recording layers, ensuring that reflected lights from other layers do not return along the same optical path as the readout layer by setting specific thickness relationships between intermediate layers, thereby avoiding interference fringes on the light receiving element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If equal thickness intermediate layers are used between recording layers, then manufacturing is simplified, but reflected light from other layers returns along the same optical path causing interference and signal degradation
Solution Approach 1:
The patent applies asymmetry by making the intermediate layers have different thicknesses from each other. Specifically, the first intermediate layer has a different thickness than the second intermediate layer, which breaks the symmetry that causes reflected light to return along the same optical path. This asymmetric design prevents interference fringes while maintaining manufacturing feasibility through precise thickness control during production.
2Reliability
If non-equal interlayer spacings are used to prevent interference, then signal quality is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by specifically controlling the thickness parameters of the intermediate layers. The first intermediate layer is set to 3-10 μm and the second intermediate layer is set to 10-20 μm, creating a defined parameter range that prevents interference while being achievable with current manufacturing capabilities. This quantitative approach balances signal quality improvement with manufacturing precision requirements.
3Object-affected harmful factors
If larger interlayer spacings are used to prevent light interference, then interference is reduced, but disc thickness increases and compatibility with existing discs is reduced
Solution Approach 1:
The patent applies local quality by creating different spacing conditions at different locations between recording layers. The first intermediate layer (3-10 μm) and second intermediate layer (10-20 μm) have different local thickness qualities, which prevents interference while keeping the overall disc thickness within acceptable ranges for compatibility with existing optical disc drives and standards.
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 design effectively reduces light quantity variation caused by interference, resulting in improved servo and reproduction signal quality and ensures compatibility with existing optical discs by maintaining relatively short spacings between layers.
Implementation Method 1
the light 108 irradiated from the optical head is focused on the recording layer 101
Implementation Method 2
reflected light from a desired recording layer (hereinafter, 'readout layer') having information reproduced therefrom
Implementation Method 3
a problem of mixing a signal of the recording layer 103 with a reproduction signal occurs... forms a light-dark distribution on a light receiving element due to interference
Data Source
AI summary
An optical recording medium is provided having a plurality of laminated recording layers, wherein the recording layers are formed such that a spacing between each pair of recording layers of all recording layer combinations selected from the plurality of recording layers is different from that of each other pair. Accordingly, a return of lights reflected by other layers to an optical head along the same optical path as reflected light from a readout layer during the reproduction can be avoided. Therefore, use of the optical recording medium, from which a good reproduction signal can be obtained, can suppress a deterioration of a servo signal and a reproduction signal of a reproducing device due to a variation of interference fringes on a light receiving element.