Optical Head Tracking Control via Segmented Detector
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Solution Overview
Problem
Conventional optical heads face challenges in achieving stable tracking control, especially when the rotational center of the information recording medium is not aligned with the transfer directions of the light-concentrating means, leading to offset tracking signals and unstable control.
Innovation Solution
The optical head design includes a light source, a light-concentrating element, a transfer mechanism, a splitting element, and a detector with division lines set parallel to the tangential directions of the track, allowing for precise splitting and detection of light beams between the outermost and innermost circumference of the recording area, reducing amplitude changes in tracking signals and enhancing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the rotational center of the information recording medium is not located on the extension line of the transfer directions of the light-concentrating means, then the optical head can be positioned at an arbitrary location on the disk, but the tracking signal exhibits offset and amplitude changes leading to unstable tracking control
Solution Approach 1:
The detector is divided into multiple detection regions (first detection region and second detection region) by a division line. This segmentation allows different regions to independently detect light beams from different objective lenses, enabling separate tracking signal generation for each lens position. The tracking signal for the first objective lens is generated without offset even when the rotational center is misaligned, resolving the contradiction between positioning flexibility and tracking stability.
Solution Approach 2:
Different detection regions are assigned to detect light beams from different objective lenses positioned at different radial locations. The first detection region detects light from the first objective lens (on the extension line), while the second detection region detects light from the second objective lens (off the extension line). This local quality assignment ensures each region optimizes detection for its specific lens position, maintaining tracking stability across different positioning scenarios.
2Adaptability or versatility
If conventional division line configurations are used with misaligned objective lenses, then the optical system can accommodate arbitrary rotational center positions, but tracking signals exhibit offset preventing stable tracking control
Solution Approach 1:
The detector surface is segmented into distinct detection regions corresponding to different objective lens positions. This segmentation enables the system to generate accurate tracking signals for each lens position independently, eliminating offset errors that would otherwise occur with misaligned rotational centers. The first detection region specifically handles light from the first objective lens positioned on the extension line, ensuring precise tracking signal generation.
Solution Approach 2:
The division line acts as an intermediary element that spatially separates detection regions for different objective lenses. This intermediary structure enables the detector to distinguish between light beams from different lens positions, allowing accurate tracking signal generation even when the rotational center is not aligned with the extension line of the light-concentrating means.
3Device complexity
If a single detector configuration is used for multiple objective lenses at different positions, then the device complexity is reduced, but tracking signal offset occurs when lenses are shifted
Solution Approach 1:
The detector is segmented into multiple detection regions on a single detector surface, with each region dedicated to detecting light from a specific objective lens position. This segmentation approach maintains the simplicity of a single detector device while eliminating tracking signal offset by ensuring each region processes light from its corresponding lens position independently, thus maintaining both low complexity and high reliability.
Solution Approach 2:
A single detector performs multiple functions by incorporating different detection regions that handle light from different objective lenses. This multi-functional design eliminates the need for separate detectors for each lens position, reducing device complexity while maintaining tracking stability through region-specific signal processing for each lens position.
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 configuration enables stable tracking control by minimizing amplitude changes in tracking signals, allowing for precise recording and reproduction of information, even when the rotational center is misaligned, thereby ensuring reliable data transfer.
Implementation Method 1
a light source which emits a beam of light; a light-concentrating element which concentrates the beam of light on an information recording medium
Implementation Method 2
a splitting element which splits a beam of light that returns from the information recording medium into a plurality of beams of light
Data Source
AI summary
An optical head which is capable of realizing a stable tracking control, even if the rotational center of an information recording medium is not located on the extension line of the transfer directions of a light-concentrating element, includes: a semiconductor laser which emits a beam of light; an objective lens which concentrates the beam of light on an optical disk; a transfer mechanism which transfers the objective lens between the outermost circumference and the innermost circumference of the recording area of the optical disk along the optical disk; and a photo-detector which detects a beam of light that returns from the optical disk. The photo-detector includes a plurality of areas which are divided by a division line. The division line is set parallel to the tangential directions of the track in a predetermined position on the transfer line of the objective lens between the outermost circumference and the innermost circumference of the recording area, and the plurality of areas are divided, by a lateral division line which intersects the division line, into a first area on which a beam of light that mainly includes a tracking component is incident and a second area on which a beam of light that does not include the tracking component is incident.