Optical Disc Position Control Feedforward Integration
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Solution Overview
Problem
The existing position control methods for optical disc recording media, particularly those using adjacent track servo (ATS), face instability and oscillation issues due to tracking error components that increase over time, affecting the accuracy and reliability of information recording and reproduction.
Innovation Solution
A position control apparatus and method that incorporates a feedforward control system, integrating tracking error signals from both the reference surface and recording layer, and adjusts the transfer function of the reference surface loop to prevent oscillations, ensuring stable operation by providing a control signal based on the integration output and setting the control characteristic to maintain a gain of 0 dB or less in the entire control loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If adjacent track servo (ATS) is used for position control, then information recording by constant pitch is realized, but tracking error increases over time causing system instability and oscillation
Solution Approach 1:
The patent implements a feedback mechanism by integrating the recording layer tracking error signal over time and using this integrated value to adjust the reference surface tracking target position. This feedback loop compensates for cumulative tracking errors that would otherwise cause instability and oscillation, while maintaining the constant track pitch advantage of ATS.
Solution Approach 2:
The patent applies preliminary action by adjusting the reference surface tracking target position based on the integrated recording layer tracking error before the oscillation problem manifests. This proactive adjustment prevents tracking error accumulation from causing system instability, addressing the issue before it affects overall system reliability.
2Device complexity
If tracking error is not compensated, then system complexity is reduced, but tracking accuracy deteriorates over time
Solution Approach 1:
The patent introduces a feedback mechanism that integrates recording layer tracking error signals and uses them to adjust reference surface tracking targets. This maintains tracking accuracy over time without requiring complex real-time compensation systems, achieving a balance between simplicity and precision.
Solution Approach 2:
The patent uses the integrated tracking error signal as an intermediary element that bridges the recording layer and reference surface tracking systems. This intermediary allows error compensation to be applied smoothly without directly complicating the control system architecture, maintaining relative simplicity while improving accuracy.
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 stabilizes the control system, preventing oscillations and maintaining accurate track following, thereby enhancing the reliability and efficiency of information recording and reproduction on optical disc media.
Implementation Method 1
radiation of laser light for recording and laser light for adjacent track servo targeted at a recording layer and radiation of laser light for a reference surface targeted at the reference surface, onto an optical disc recording medium including the reference surface to which a position guider is provided and the recording layer where information recording is performed, through a common objective lens
Implementation Method 2
receives return light of the laser light for the adjacent track servo and the laser light for the reference surface
Data Source
AI summary
There is provided a position control apparatus including a light radiating/receiving unit that performs radiation of laser light for recording and laser light for adjacent track servo onto an optical disc recording medium through a common objective lens, and receives return light of the laser light for the adjacent track servo and the laser light for the reference surface, a tracking mechanism unit that displaces the objective lens, a reference surface tracking error signal generating unit that generates a reference surface tracking error signal, a reference surface tracking servo control unit that controls the tracking mechanism unit, a recording layer tracking error signal generating unit that generates a recording layer tracking error signal, an integrating unit that integrates the recording layer tracking error signal, an offset providing unit that provides an integration output by the integrating unit, and a feedforward control unit that generates a control signal.