Optical Lens Pre-Deviation for Track Locking Accuracy
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Solution Overview
Problem
Conventional optical disc devices face issues with track locking due to disc deviations causing radial and axial oscillations, leading to inaccurate focus and potential physical impacts, as the actuator's response to track error signals can result in inward or outward deviations of the optical lens, disrupting data reading.
Innovation Solution
A track locking method that pre-deviates the optical lens based on the flicker frequency of the track error signal by applying a braking force, ensuring accurate positioning over the destination track by adjusting the actuator's movement to compensate for disc deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If track locking is executed based on conventional methods without pre-deviation, then the optical lens may lock onto the destination track, but the lens deviates from the case center causing inward or outward deviation that can contact the case wall and disrupt data reading
Solution Approach 1:
The patent applies preliminary action by pre-deviating the optical lens in the opposite direction of the run-out effect before track locking occurs. The CPU calculates the run-out direction based on track error signals and proactively adjusts the lens position, so that when the lens locks onto the destination track, it remains centered in the case and avoids contacting the case wall, thereby preventing disruptions in data reading.
2Productivity
If the actuator responds faster than the sled mechanism during track seeking, then track locking can be executed quickly, but the optical lens completes locking before the sled mechanism reaches the proper position causing deviation from case center
Solution Approach 1:
The patent employs feedback by continuously monitoring the run-out effect through track error signals and using this information to adjust the optical lens position. The CPU calculates the run-out direction and magnitude based on detected track error signals and applies compensatory deviation to the lens, ensuring that even when the actuator responds faster than the sled mechanism, the lens remains properly positioned relative to the case center during and after track locking.
3Strength
If the optical lens is kept in the center of the case to avoid physical impact, then protection from damage is achieved, but the lens cannot accurately follow the destination track when disc deviations occur
Solution Approach 1:
The patent applies dynamics by making the optical lens position adaptive rather than static. Instead of keeping the lens fixed at the case center, the system dynamically adjusts the lens position based on real-time detection of run-out effects and track error signals. The CPU calculates the necessary deviation from center and applies it to the lens position, allowing the lens to follow the destination track accurately while minimizing contact with the case wall through continuous positional optimization.
Data Source
AI summary
A track locking method for use in an optical disc device comprising a pickup head. The pickup head comprises an actuator equipped with an optical lens controlling a laser focus on the optical disc. The pickup head is moved to a predetermined position. A track error signal in the optical disc device is detected. Whether a flicker frequency of the track error signal is less than a threshold is determined. Based on the determination, the actuator is provided with a braking force to pre-deviate the optical lens, and a track locking signal is delivered to the actuator and control parameters of the pickup head is stored to lock the laser focus on a destination track of the optical disc.