Optical Disk Drive PLL Locking Preceding Track
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Solution Overview
Problem
Optical disk drives face challenges in quickly locking the phase-lock loop (PLL) on target tracks due to low-quality wobble signals generated by land and groove tracks with unequal widths, leading to instability and prolonged data read/write operations.
Innovation Solution
The optical disk drive employs a strategy where it attempts to lock the PLL on a preceding track by one, shifting the beam spot to the target track while maintaining the PLL locked, and then begins reading or writing data from the target track, ensuring stable PLL synchronization even with low-quality wobble signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the optical disk drive attempts to lock the PLL directly on the target track, then the data read/write operation can start quickly, but the PLL locking fails or becomes unstable due to low-quality wobble signals from land and groove tracks with unequal widths
Solution Approach 1:
The optical disk drive performs preliminary PLL locking on a preceding groove track before the target land track. This preliminary action establishes stable synchronization early, allowing the system to then transition to the target track without losing PLL lock, thus resolving the contradiction between quick access and reliable locking
2Quantity of substance
If the optical disk drive uses land and groove tracks with unequal widths to store data, then the storage capacity is optimized, but the wobble signal quality deteriorates, causing PLL locking difficulties
Solution Approach 1:
The groove track serves as an intermediary medium with high-quality wobble signals. By performing preliminary PLL locking on the groove track before accessing the land track, the system uses the groove's superior wobble signal characteristics as a mediator to establish stable synchronization, which then enables reliable operation on the land track with its lower-quality wobble signal
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 reliable PLL locking and stable data read/write operations, reducing the likelihood of PLL failure and improving access performance by targeting a track with a higher-quality wobble signal before reaching the intended track.
Implementation Method 1
detecting the light that has been modulated by, and reflected from, the optical disk
Implementation Method 2
a photodetector for generating an electrical signal based on at least a part of the light beam that has been reflected from the optical disk
Data Source
AI summary
An optical disk drive is designed to read and/or write data from/on a spiral string of tracks where land and groove tracks are alternated. The drive includes: a light source for radiating a light beam; a lens for converging the light beam; a mechanism for moving the lens; a photodetector for generating an electrical signal based on at least a part of the light beam reflected from the optical disk; and a control section for controlling the light source and the mechanism responsive to the electrical signal. While performing a seek operation by having the lens moved by the mechanism such that a target track, from/on which the data should start being read or written, is irradiated with the light beam, the control section tries to get a PLL locked by irradiating another track, which precedes the target track by at least one, with the light beam.