Optical Disk Reproducing Device Nonlinear Crosstalk Suppression
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Solution Overview
Problem
Conventional optical disk reproducing devices face challenges in achieving high accuracy signal reproduction due to increased non-linear crosstalk when track pitch is reduced, and existing three-track detection systems are limited in suppressing crosstalk at narrower pitches.
Innovation Solution
An optical disk reproducing device with a groove-shaped track configuration, utilizing a laser light source, objective lens, division element, photodetector, non-linear processor, equalization processor, adder, reproduction signal processor, and gain controller to process light signals and suppress non-linear crosstalk by dividing and amplifying light fluxes from central and end regions, allowing for accurate signal reproduction at narrower track pitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If track pitch is reduced to increase disk capacity, then disk capacity increases, but crosstalk between adjacent tracks increases causing signal reproduction accuracy to deteriorate
Solution Approach 1:
The photodetector is divided into multiple independent light receivers (first light receiver for reproduction track, second and third light receivers for adjacent tracks). This segmentation allows separate detection and processing of signals from different tracks, enabling crosstalk cancellation through independent signal processing channels while maintaining high track density
Solution Approach 2:
The invention converts the harmful crosstalk effect into a useful signal by deliberately detecting adjacent track signals along with the reproduction track signal. The detected crosstalk components are then processed and subtracted from the reproduction signal, transforming the previously harmful interference into a cancelable artifact that improves overall signal accuracy
2Manufacturing precision
If track pitch is reduced below 0.24 μm, then track density increases, but non-linear crosstalk becomes significant making linear correction insufficient
Solution Approach 1:
The invention changes the processing approach from linear correction to non-linear processing. By applying non-linear arithmetic operations to the detected light amount signals, the system can compensate for non-linear crosstalk effects that occur at very narrow track pitches (below 0.24 μm), maintaining signal reliability while achieving high track density
Solution Approach 2:
The invention uses three light receivers instead of the conventional two, detecting not only the reproduction track but also both adjacent tracks. This excessive detection capability provides additional signal components that can be processed to cancel crosstalk, ensuring reliable reproduction even when track pitch is reduced to increase capacity
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 device effectively suppresses non-linear crosstalk and achieves highly accurate signal reproduction, enabling further capacity increase by improving track density, even at narrower track pitches than conventional systems.
Implementation Method 1
a laser light source that emits a light flux of a wavelength λ
Implementation Method 2
an objective lens with numerical aperture NA that allows the light flux emitted from the laser light source to be condensed and form a condensing spot on the optical disk
Implementation Method 3
a reflected light reflected and diffracted by the optical disk
Implementation Method 4
a reflected light reflected and diffracted by the optical disk
Implementation Method 5
a photodetector that has a central light receiver that receives the light flux in the central region and two end light receivers that receive the light fluxes in the end regions, and outputs a light amount signal corresponding to a light amount of each of the received light fluxes
Data Source
AI summary
An optical disk reproducing device includes a division element that divides a reflected light reflected and diffracted by an optical disk into a light flux in a central region and light fluxes in end regions; a photodetector that has a central light receiver that receives the light flux in the central region and at least two end light receivers that receive the light fluxes in the end regions, and outputs a light amount signal corresponding to a light amount of each of the received light fluxes; a non-linear processor that receives each of the light amount signals from the central light receiver and the end light receivers, and outputs linear signals and non-linear signals obtained by processing the light amount signals by linear and non-linear arithmetic operations; an equalization processor that receives the linear signals and the non-linear signals and outputs signals each amplified with a predetermined gain; an adder that adds the amplified signals and outputs an equalization signal; a reproduction signal processor that processes the equalization signal and outputs a reproduction signal and an equalization error signal; and a gain controller that receives the equalization error signal and controls an amplification gain of the non-linear signals.