Optical Disc Drive Tilt Control via Constant Rotation
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Solution Overview
Problem
Existing optical disc drives face challenges in accurately measuring and controlling the tilt quantity of optical discs due to variations in rotational frequency and disc resonance, leading to errors in tilt calculation and reduced performance, especially in high-density storage systems.
Innovation Solution
The optical disc drive maintains a constant rotational frequency and measures tilt quantities at multiple radial locations, using drive values to calculate and correct tilt, thereby minimizing the impact of disc resonance and variations in disc height, without relying on tilt sensors or complex gas flow regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the optical disc drive uses constant linear velocity (CLV) control to rotate the disc, then the storage density and read/write performance are improved, but the tilt measurement accuracy deteriorates due to rotational frequency variations causing disc height changes
Solution Approach 1:
The patent changes the rotational frequency parameter from variable (CLV control) to constant during tilt measurement. By rotating the disc at a constant frequency regardless of radial location, the disc height remains stable, eliminating the source of measurement error while allowing accurate tilt measurement across different storage density regions
Solution Approach 2:
The patent performs tilt measurement as a preliminary action before actual read/write operations. By measuring tilt at constant rotational frequency in advance and calculating compensation values, the system prepares correction data that can be applied during subsequent high-speed CLV operations without interfering with the productivity requirements
2Measurement precision
If the optical disc drive adds tilt sensors and gas flow regulation structures to improve tilt control accuracy, then the tilt measurement precision is improved, but the device complexity and thickness increase
Solution Approach 1:
The patent makes the optical disc itself serve as the measurement reference by utilizing its rotational characteristics. The disc's own rotation at constant frequency provides a stable reference frame for tilt measurement, eliminating the need for external tilt sensors or complex gas flow regulation structures that would add device complexity
Solution Approach 2:
The patent replaces complex mechanical tilt control structures (such as gas flow regulation mechanisms and physical tilt sensors) with an optical measurement method using the light beam and photodetector. This substitution reduces mechanical complexity while maintaining or improving measurement precision
3Productivity
If the optical disc drive increases the numerical aperture (NA) to improve storage density, then the storage capacity is improved, but the tilt tolerance range decreases due to the inverse cubic relationship
Solution Approach 1:
The patent implements a feedback mechanism by measuring the actual tilt angle and calculating compensation values that are applied to adjust the optical system. This closed-loop feedback allows the system to maintain accurate read/write performance even when operating with high NA where the tilt tolerance range is naturally narrower
Solution Approach 2:
The patent applies preliminary anti-action by calculating and applying tilt compensation values before actual read/write operations occur. By pre-correcting for the reduced tilt tolerance associated with high NA configurations, the system proactively counteracts the sensitivity issue rather than reacting to performance degradation
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 precise tilt control and accurate measurement across all radial locations, improving data read/write quality and reliability, and reducing the thickness and cost of optical disc drives by eliminating the need for tilt sensors and recesses.
Implementation Method 1
an optical system for irradiating the optical disc with a light beam
Implementation Method 2
a focus control section for controlling movement of the optical system perpendicularly to the optical disc based on drive values, thereby focusing the light beam onto a storage layer of the optical disc
Data Source
AI summary
An object of this invention is to measure the tilt quantity of, and perform a tilt control on, an optical disc accurately without depending on the rotation control method.An optical disc drive includes: a motor for rotating an optical disc; an optical system for irradiating the optical disc with a light beam; a moving mechanism for moving the optical system along the radius of the optical disc; a focus control section for controlling movement of the optical system perpendicularly to the optical disc based on drive values, thereby focusing the light beam onto a storage layer of the optical disc; and a tilt control section for measuring the tilt quantities of the storage layer at multiple different radial locations on the optical disc based on drive values for the respective radial locations when the focus control section focuses the light beam there. When the tilt control section measures the tilt quantities, the motor keeps the rotational frequency of the optical disc constant and the tilt control section uses the drive values obtained at the respective radial locations.