Optical Disc Inspection Servo Stability via Velocity Variation
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Solution Overview
Problem
High-speed read/write operations on optical discs, such as Blu-ray discs, face challenges due to increased residual focus and tracking errors caused by mechanical vibrations and resonance, leading to instability in servo control and decreased symbol error rate, especially when rotational velocities exceed safe limits.
Innovation Solution
A method involving varying rotational velocities between two linear velocities (Lv1 and Lv2) to minimize mechanical interference, using frequency band-elimination filters to isolate and compare residual errors, ensuring servo stability and accurate measurement of optical disc quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rotational velocity is increased to achieve high-speed read/write operations, then productivity is improved, but residual focus and tracking errors increase due to mechanical vibrations and resonance
Solution Approach 1:
The patent applies dynamics by varying the rotational velocity between two different linear velocities (Lv1 and Lv2) during inspection instead of maintaining a constant high speed. This dynamic adjustment allows the system to operate at high speeds for productivity while periodically reducing speed to minimize mechanical vibrations and resonance that cause residual focus and tracking errors, thereby maintaining servo control stability.
Solution Approach 2:
The patent implements periodic action by alternating between two linear velocities (Lv1 and Lv2) in a periodic manner during the inspection process. This periodic velocity variation helps to disrupt and minimize continuous mechanical vibrations and resonance at high speeds, reducing residual errors while still maintaining overall high-speed operation for productivity.
2Productivity
If rotational velocity is increased beyond safe limits, then productivity is improved, but measurement precision deteriorates due to increased residual errors
Solution Approach 1:
The patent uses dynamics by switching between two linear velocities (Lv1 and Lv2) during inspection. When inspecting for residual errors, the system reduces rotational velocity to minimize vibrations and resonance, thereby improving measurement precision. During other phases, higher velocities are used to maintain productivity, achieving a balance between inspection speed and measurement accuracy.
Solution Approach 2:
The patent applies preliminary action by performing residual error measurements at reduced rotational velocities before or during the inspection process. This preliminary low-speed measurement phase ensures accurate detection of residual errors by minimizing mechanical interference, while the overall inspection maintains high-speed capability for productivity.
3Productivity
If constant high linear velocity is used during inspection, then productivity is improved, but manufacturing precision deteriorates due to mechanical vibrations affecting servo control
Solution Approach 1:
The patent implements dynamics by varying the rotational velocity between Lv1 and Lv2 instead of maintaining a constant high speed. This dynamic velocity adjustment allows the system to perform inspections that accurately reflect manufacturing quality by reducing speeds during critical measurement phases, while maintaining high overall throughput for productivity.
Solution Approach 2:
The patent uses periodic action by alternating between two velocity levels during inspection. This periodic variation in rotational velocity minimizes continuous mechanical vibrations that would otherwise degrade manufacturing precision measurements, while still maintaining high inspection throughput by spending the majority of time at higher velocities.
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 allows for precise inspection and high-quality signal writing on optical discs at elevated speeds, reducing residual errors and maintaining servo stability, thereby increasing production yield and reducing manufacturing costs.
Implementation Method 1
information can be read by irradiating the pits or marks with light and by detecting a variation in the intensity of the light reflected
Implementation Method 2
the portion of the storage layer irradiated with the laser beam will melt to precipitate Te or Te-M crystals with large particle sizes while being cooling
Implementation Method 3
the portion of the storage layer irradiated with the laser beam will melt to precipitate Te or Te-M crystals with large particle sizes while being cooling
Data Source
AI summary
A method for inspecting an optical information storage medium includes irradiating the medium with a laser beam and rotating the medium by a constant linear velocity control technique by reference to the radial location at which the laser beam forms a spot on the medium; changing the rotational velocities according to the radial location on the medium between at least two linear velocities; generating a focus error signal and/or a tracking error signal based on the light reflected from the medium; performing a focus control and/or a tracking control on the laser beam based on the focus and/or tracking error signal(s); and passing the branched outputs of control loops for the focus and/or tracking error signal(s) through predetermined types of frequency band-elimination filters to obtain residual errors of the focus and/or tracking error signal(s) and comparing the residual errors to predetermined reference values.