Optical Information Device Crosstalk Reduction Method
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Solution Overview
Problem
Conventional optical disc information devices face challenges in reducing crosstalk when track pitch is reduced, leading to increased noise in reproduction signals, as existing methods like split photodetectors and waveform equalization are insufficient in minimizing crosstalk at high recording densities.
Innovation Solution
An optical information device with a split element that splits light flux into three regions, each with a specific gain equalizer to cancel adjacent track information, ensuring the ratio of information signals from different regions matches the gain ratios to effectively reduce crosstalk, and an adder combines these signals to produce a low-error reproduction signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the track pitch of the optical disc is reduced to improve recording density, then the recording density is improved, but crosstalk from adjacent tracks increases causing noise in reproduction signals
Solution Approach 1:
The photodetector is divided into multiple independent light receiving sections (first, second, third, and fourth sections) that detect light from different spatial regions. This segmentation allows separate processing of signals from the main track and adjacent tracks, enabling crosstalk cancellation through coordinated arithmetic operations on the individually detected signals.
Solution Approach 2:
The system uses feedback control where the detected crosstalk signals from adjacent tracks are processed and subtracted from the main track signal. The arithmetic operation unit performs real-time correction by feeding back the crosstalk cancellation result to the reproduction signal, continuously minimizing the harmful crosstalk effect.
2Object-affected harmful factors
If conventional split photodetector methods are used to reduce crosstalk, then some crosstalk reduction is achieved, but the crosstalk amount remains insufficiently minimized at high recording densities
Solution Approach 1:
The photodetector is divided into multiple independent light receiving sections (first, second, third, and fourth sections) that detect light from different spatial regions. This segmentation allows separate processing of signals from the main track and adjacent tracks, enabling crosstalk cancellation through coordinated arithmetic operations on the individually detected signals.
Solution Approach 2:
The system combines multiple detection signals (S1, S2, S3, S4) from different photodetector sections with different weighting coefficients (k1, k2, k3) to create a composite reproduction signal. This composite signal processing approach effectively cancels crosstalk while maintaining the main track signal, enabling higher recording densities.
3Device complexity
If only central light receiving section signal is subjected to waveform equalization, then waveform equalization is simplified, but crosstalk cancellation effectiveness is reduced
Solution Approach 1:
The photodetector is divided into multiple independent light receiving sections (first, second, third, and fourth sections) that detect light from different spatial regions. This segmentation allows separate processing of signals from the main track and adjacent tracks, enabling crosstalk cancellation through coordinated arithmetic operations on the individually detected signals.
Solution Approach 2:
The system uses feedback control where the detected crosstalk signals from adjacent tracks are processed and subtracted from the main track signal. The arithmetic operation unit performs real-time correction by feeding back the crosstalk cancellation result to the reproduction signal, continuously minimizing the harmful crosstalk effect.
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 effectively reduces crosstalk from adjacent tracks, allowing for accurate information reproduction at high recording densities with a low error rate, even when the track pitch is reduced below the optical cutoff distance.
Implementation Method 1
a laser light source that emits a light flux, an objective lens that converges the light flux emitted from the laser light source
Implementation Method 2
a split element that includes a center region including the center of an optical axis, a first end region disposed adjacent to one side of the center region in a direction perpendicular to a tangent to the information track, and a second end region disposed adjacent to the other side of the center region in the direction perpendicular to the tangent to the information track, and splits the light flux reflected and diffracted on the optical information medium
Data Source
AI summary
A ratio Xm of an information item recorded on an adjacent track relative to an information item recorded on a main track included in a first signal obtained from a first light flux having passed through a center region (6c) is different from ratios Xs1 and Xs2 of the information items recorded on the adjacent track relative to the information items recorded on the main track included in second and third signals obtained from second and third light fluxes having passed through first and second end regions (6r, 6l), and a ratio of respective gains of a first waveform equalizer (80c), a second waveform equalizer (80r), and a third waveform equalizer (80l) is determined so as to cancel the information item recorded on the adjacent track in each of frequency components of the first signal, the second signal, and the third signal.