Optical Disc Drive Focus Tilt Adjustment for Aberration Correction
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Solution Overview
Problem
Optical disc drives face challenges in maintaining high signal quality when reading data from optical discs with varying information storage layer depths, leading to spherical aberrations, astigmatism, and coma aberrations, without increasing manufacturing costs by incorporating expensive correction mechanisms.
Innovation Solution
An optical disc drive that adjusts focus position and tilt settings to recognize and correct for different optical disc types, using a servo controller and signal quality rater to measure index values and optimize settings for improved signal quality without a bulky spherical aberration correction mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spherical aberration correction mechanism is added to correct focal point shifts, then signal quality is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent replaces complex mechanical spherical aberration correction mechanisms with a computational approach. The signal processing unit calculates correction amounts based on detected spherical aberration magnitudes and applies digital corrections to the read signal, substituting physical correction optics with signal processing algorithms.
Solution Approach 2:
The patent creates a model or representation of the spherical aberration characteristics by detecting the magnitude of spherical aberration and using this information to guide correction. Instead of physically correcting all possible aberration types, the system copies the essential correction information into signal processing parameters.
2Reliability
If focus position is adjusted to compensate for information storage layer depth variations, then signal quality is improved, but spherical aberration increases
Solution Approach 1:
The patent implements a feedback mechanism where the system detects the magnitude of spherical aberration, calculates an appropriate correction amount, applies the correction, and verifies the result. This closed-loop feedback allows the system to dynamically adjust focus and correction parameters based on actual disc conditions.
Solution Approach 2:
The patent changes multiple parameters simultaneously - focus position, spherical aberration correction amount, and signal processing parameters - to achieve optimal signal quality. By coordinating changes in these parameters rather than adjusting focus alone, the system compensates for depth variations without introducing excessive spherical aberration.
3Reliability
If tilt angle is adjusted to correct astigmatism and coma aberration, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent replaces mechanical tilt adjustment mechanisms with computational corrections. Instead of physically tilting the objective lens to correct astigmatism and coma aberration, the system detects these aberrations and applies digital signal processing corrections, eliminating the need for complex mechanical tilt adjustment devices.
4Adaptability or versatility
If multiple aberration correction mechanisms are added to handle various optical disc types, then adaptability is improved, but manufacturing cost increases
Solution Approach 1:
The patent creates a universal correction system that handles multiple disc types (CD, DVD, BD, dual-layer discs) through a single integrated approach. The signal processing unit automatically detects the disc type and applies appropriate correction parameters, eliminating the need for separate correction mechanisms for each disc format.
Solution Approach 2:
The patent achieves adaptability to various disc types by dynamically changing correction parameters rather than adding physical components. The system adjusts focus position, spherical aberration correction amounts, and signal processing parameters based on detected disc characteristics, providing multi-format compatibility through software control.
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
Ensures high signal quality across various optical disc types by dynamically adjusting focus and tilt settings, reducing the need for costly correction mechanisms and effectively addressing aberrations, thereby lowering overall drive costs.
Implementation Method 1
a light source for emitting a light beam; an objective lens for converging the light beam
Implementation Method 2
an objective lens for converging the light beam
Implementation Method 3
a photodetector for receiving the light beam reflected from the information storage layer and for outputting a reflected light signal
Implementation Method 4
a servo controller for generating a first type of drive signal to adjust a focus position by changing distances from the lens to the optical disc
Implementation Method 5
a second type of drive signal to adjust tilt of the lens by changing the angles defined by the lens with respect to the optical disc
Data Source
AI summary
An optical disc drive according to the present invention can read data from any of multiple types of optical discs, of which the information storage layers are located at mutually different depths under their surface. When this drive is loaded with an optical disc, the servo controller of the drive changes a first type of drive signal to adjust a focus position by changing distances from the lens to the disc and/or a second type of drive signal to adjust tilt of the lens by changing the angles defined by the lens with respect to the disc a number of times, thereby changing settings to be determined by a combination of the focus position and the tilt. A signal quality rater measures multiple index values to rate the quality of a reflected light signal as the settings are changed. Then, the optical disc drive recognizes the type of the given optical disc based on those index values and reads data from the optical disc recognized.