Optical Disk TPP Signal Frequency-Shifting for High-Density Data Reproduction
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Solution Overview
Problem
Current optical disk technologies face limitations in recording and reproducing high-density data due to resolution constraints imposed by light diffraction, particularly when attempting to read marks with periods below the λ/2NA resolution limit, which restricts the ability to store and retrieve high-definition and ultra-high definition image data effectively.
Innovation Solution
An information processing apparatus and method that employs a photo-detecting section with split detectors A and B to generate a Tangential Push-pull (TPP) signal, which is then processed to extract high-frequency components from the record signal on an optical disk. This involves frequency-shifting the TPP signal to the high-frequency range using a carrier signal, allowing for the reproduction of data beyond the conventional cut-off frequency limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the interval between marks on the optical disk is reduced to increase recording density, then data storage capacity is improved, but reproduction becomes infeasible when the interval falls below the resolution limit of λ/2NA
Solution Approach 1:
The patent changes the frequency parameter of the carrier signal to enable frequency-shifting of the TPP signal. By modulating the carrier frequency and performing frequency-shifting operations, the system can extract high-frequency components that were previously inaccessible, thus resolving the contradiction between increased recording density and reproduction feasibility
Solution Approach 2:
The patent introduces a carrier signal as an intermediary to facilitate the extraction of high-frequency components. The carrier signal acts as a mediator that, when frequency-shifted and combined with the TPP signal, enables the recovery of mark information at intervals below the conventional resolution limit
2Measurement precision
If the numerical aperture of the optical pickup is increased to improve resolution, then reproduction capability is improved, but the system complexity and cost increase
Solution Approach 1:
Instead of changing the physical parameter of numerical aperture, the patent changes the signal processing parameters by introducing frequency-shifting operations. This allows the system to achieve enhanced resolution capability through signal processing rather than hardware modification, thereby avoiding increased device complexity
Solution Approach 2:
The patent replaces the mechanical/optical approach of increasing numerical aperture with an electrical signal processing approach. By using frequency-shifting and carrier modulation, the system achieves improved resolution without modifying the physical optical pickup components
3Measurement precision
If the wavelength of the laser beam is reduced to improve resolution, then reproduction capability is improved, but the energy consumption and system complexity increase
Solution Approach 1:
The patent substitutes the physical approach of reducing laser wavelength with an electrical signal processing approach. By using frequency-shifting operations on the TPP signal, the system achieves improved resolution without changing the laser characteristics, thereby maintaining energy consumption at acceptable levels
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 the successful reproduction of high-density data on optical disks, including ultra-high definition images, by overcoming the resolution limitations of traditional optical pickup systems, thereby increasing data storage capacity and quality.
Implementation Method 1
a photo-detecting section (22) configured to receive reflected light from the disk
Implementation Method 2
this method of reproduction using an optical pickup is subject to resolution-level constraints stemming from diffraction of light
Data Source
Figure 1(A)~1(B)
Figure 2
Figure 3(A)~3(B)
AI summary
There are provided an optical disk from which high-density data is reproduced and a reproduction apparatus that reproduces data from such an optical disk having high-density data recorded thereon. A photo-detecting section has two split detectors A and B in the direction of tracks on the disk. A signal processing section generates a TPP (Tangential Push-pull) signal made of a differential signal derived from detection signals from the detectors A and B, and further generates a reproduced signal by extracting from the TPP signal a high-frequency component signal in a record signal recorded on the disk. The disk is structured to have the record signal recorded on a carrier signal over the disk formed with a protruding and recessed pattern having a high frequency higher than or equal to a cut-off frequency. The signal processing section reconstitutes the high-frequency component signal in the record signal recorded on the disk by frequency-shifting the TPP signal obtained as a readout signal from a superimposed signal having the carrier signal and the record signal superimposed with each other.