Optical Reproduction Signal Phase Offset Extraction
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Solution Overview
Problem
Existing methods for reproducing multilayered optical discs face challenges in accurately extracting phase offsets due to noise interference and limited amplification of AC components, leading to suboptimal signal-to-noise ratios and instability in reproduction signals.
Innovation Solution
A homodyne detection method is employed, utilizing a system that generates sets of signal and reference light beams with specific phase differences to calculate a reproduction signal through arithmetic operations involving difference signals and phase offsets, eliminating the need for low-pass filters and improving signal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low pass filter is used to extract phase offset components, then phase offset extraction is possible, but noise enters the reproduction signal band causing degraded signal quality
Solution Approach 1:
The patent segments the signal processing into distinct frequency domains by using band-pass filters to separate the reproduction signal band from the phase offset extraction band. The phase offset is extracted from a specific frequency band (e.g., 2-4 MHz) that is separated from the reproduction signal band, preventing noise contamination while maintaining extraction accuracy.
Solution Approach 2:
The patent introduces an intermediary frequency band as a mediator between the reproduction signal and phase offset extraction. By extracting phase offset information from an intermediate frequency range using band-pass filters before mixing with the reproduction signal, the system avoids direct noise contamination while maintaining accurate phase offset measurement.
2Power
If AC-coupling is used to amplify AC components, then amplification factor increases, but DC component cannot be effectively amplified
Solution Approach 1:
The patent segments the signal components by using band-pass filters to separate AC components (containing phase offset information) from DC components. This allows independent optimization of amplification for AC components while preserving DC component information through separate processing paths.
Solution Approach 2:
The patent changes the frequency domain parameters by using band-pass filtering to isolate specific frequency ranges. This enables selective amplification of AC components in the filtered band while maintaining the ability to process DC components separately, effectively resolving the amplification limitation of AC-coupling.
3Measurement precision
If homodyne detection is used to improve signal-to-noise ratio, then reproduction signal quality improves, but phase offset extraction becomes difficult due to noise
Solution Approach 1:
The patent segments the signal processing to extract phase offset information from a specific frequency band using band-pass filters before homodyne detection. By isolating the phase offset components in a separate frequency range, the system can accurately detect phase offset even in the presence of noise in the reproduction signal band.
Solution Approach 2:
The patent uses an intermediary frequency band as a mediator to extract phase offset information before it is mixed with the reproduction signal. This intermediary extraction step allows accurate phase offset measurement independent of the noise level in the final reproduction signal, enabling both high SNR and accurate phase offset detection.
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 approach enables accurate and stable reproduction of land/groove recording type optical media by effectively reducing noise interference and enhancing signal responsiveness, leading to improved signal-to-noise ratios and long-term stability.
Implementation Method 1
a homodyne detection method of amplifying a detection signal by using light interference
Implementation Method 2
as a homodyne system for detecting a light beam in which a signal light beam and a reference light beam are made to interfere with each other
Data Source
AI summary
Provided is a reproducing apparatus including: a reproduction signal generating circuit that calculates a first difference signal which is a difference between a first light receiving signal obtained by the first light receiving element and a second light receiving signal obtained by the second light receiving element, and a second difference signal which is a difference between a third light receiving signal obtained by the third light receiving element and a fourth light receiving signal obtained by the fourth light receiving element, and uses the first difference signal, the second difference signal, a phase difference between a crosstalk component and an average phase of the signal light beam, and an optical path length difference between the signal light beam and the reference light beam to obtain a reproduction signal; and a phase extraction circuit that obtains a successive change amount and updates with a successive variation.