Objective Lens Actuator with Segmented Coils for Precision Alignment
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Solution Overview
Problem
Existing objective lens actuators for optical pickup heads lack efficient control over focusing, tracking, and tilt directions, particularly when writing data on writable optical recording media, leading to inaccuracies in laser beam alignment.
Innovation Solution
The objective lens actuator incorporates a ferromagnetic yoke, objective lens holder, tracking coils, focusing coils, magnetic element set, suspension wire set, and printed circuit board to generate magnetic fields and Lorentz forces, allowing precise movement of the objective lens for accurate alignment with the data storage medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional actuators with coils on objective lens bracket are used, then the structure is simple, but the control precision for focusing, tracking and tilt directions is insufficient
Solution Approach 1:
The actuator is divided into three independent functional modules: tracking coils for radial direction control, focusing coils for axial direction control, and tilt coils for angular control. Each module operates independently to control a specific degree of freedom, enabling precise multi-directional alignment while maintaining modular structural simplicity.
Solution Approach 2:
Different coil configurations are applied to different spatial locations: tracking coils are positioned on the objective lens bracket for radial control, focusing coils are integrated into the objective lens assembly for axial control, and tilt coils are located on the pickup head for angular control. This localized optimization ensures precise control for each specific alignment function.
2Manufacturing precision
If radial tilt control is not implemented, then the actuator structure is simpler, but writing accuracy on writable optical media cannot be maintained
Solution Approach 1:
The actuator system is designed to perform multiple functions: tracking (radial direction control), focusing (axial direction control), and tilt (angular control). This multi-functional design enables the same actuator to handle both reading and writing operations with high precision, particularly important for maintaining perpendicular light incidence during writing on writable optical media.
Solution Approach 2:
The tilt coil assembly is designed to be movable relative to the pickup head, allowing dynamic adjustment of the objective lens angle. This dynamic capability enables real-time compensation for tilt variations during writing operations, maintaining optimal writing accuracy without requiring complex fixed adjustment mechanisms.
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 design enhances signal quality by maintaining perpendicular light incidence on the data storage medium, improving focusing coil sensitivity by up to 75% compared to conventional techniques, ensuring accurate data writing and reading operations.
Implementation Method 1
The current is transferred through the printed circuit board, suspension wires, and another suspension wires to the tracking coils and the focusing coils to generate a strong magnetic field in air gaps formed between the inner yokes and the side flanges so that the tracking coils and the focusing coils can generate Lorentz forces
Implementation Method 2
The magnetic element set is located on the ferromagnetic yoke corresponding to the tracking coils and the focusing coils to generate a magnetic field perpendicular to the optical axis of the objective lens
Data Source
AI summary
An objective lens actuator is provided. An objective lens holder is movably located on a ferromagnetic yoke with corresponding to inner yokes thereof to hold an objective lens. Tracking coils and focusing coils are respectively located on different two opposite sides of the lens holder and the latter are surrounded with the inner yokes. A magnetic element set is located on the ferromagnetic yoke corresponding to the coils to generate a magnetic field perpendicular to the optical axis of the lens. A suspension wire set is connected to the lens holder and the coils to hang the lens holder and channel current to the coils. A damper holder is located on a ferromagnetic yoke to allow the wire set to pass through. A printed circuit board is located on the damper holder and coupled with the wire set to provide the current to the coils, to drive the lens holder.