Compact Optical Pickup With Thin Movable Member And Dual-Axis Actuation
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Solution Overview
Problem
Optical disc devices face challenges in creating a compact and thin optical pickup that maintains electromagnetic and optical performance while accommodating multiple objective lenses for recording and reproduction from different types of optical discs, such as Blu-ray, DVDs, and CDs, due to the complexity and size requirements of magnetic circuits and standing mirrors.
Innovation Solution
The optical pickup design features a movable member with a center portion thinner than its sides, housing multiple objective lenses, and a configuration of coil blocks and magnets that allow for two-axis driving, along with strategically placed standing mirrors to reduce thickness and maintain performance, enabling compactness without compromising electromagnetic or optical functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple objective lenses are equipped in the optical pickup, then compatibility with multiple types of optical discs is improved, but the thickness of the optical pickup increases
Solution Approach 1:
The optical pickup is divided into separate functional modules: multiple objective lenses are mounted on a movable member that can be independently positioned, while magnetic circuits and standing mirrors are separately configured to serve specific lenses. This segmentation allows each component to be optimized for its specific function while maintaining overall compactness.
Solution Approach 2:
The patent transitions from a single-axis lens configuration to a multi-axis movable member that can position multiple lenses in both radial and focusing directions. This dimensional expansion allows multiple lenses to be arranged in a compact footprint without increasing overall thickness, as the movable member can be positioned at different heights and radial distances.
2Length of stationary object
If the thickness of the optical pickup is reduced, then compactness is improved, but the space available for magnetic circuits and standing mirrors is reduced
Solution Approach 1:
Different regions of the optical pickup are assigned different functional densities. The movable member with multiple lenses occupies a compact central volume, while magnetic circuits are strategically positioned in peripheral regions where they can exert magnetic fields without occupying significant space. Standing mirrors are placed at optimal positions to reflect light to specific lenses with minimal space consumption.
Solution Approach 2:
The patent employs a nested configuration where the movable member containing multiple objective lenses is positioned within the overall pickup structure, and magnetic circuits are arranged around and between the lenses. This nesting allows components to share spatial volume efficiently, with the movable member nested within the magnetic circuit arrangement, maximizing space utilization without increasing overall thickness.
3Length of stationary object
If magnetic circuits are made compact, then the thickness is reduced, but electromagnetic performance deteriorates
Solution Approach 1:
The patent employs dynamic positioning of the movable member with multiple lenses, allowing the system to adjust the position of each lens independently. This dynamic capability enables compact magnetic circuits to deliver sufficient electromagnetic force by positioning coils and magnets at optimal distances during operation, rather than requiring large static clearances.
Solution Approach 2:
The patent optimizes electromagnetic performance by carefully controlling parameters such as coil turns, current density, and magnetic flux density. By adjusting these parameters, compact magnetic circuits can generate sufficient force for lens positioning while maintaining a reduced thickness. The magnetic circuits are designed with optimized flux paths and pole piece geometries to maximize electromagnetic efficiency within limited space.
4Adaptability or versatility
If multiple objective lenses are mounted on a movable member, then adaptability is improved, but device complexity increases
Solution Approach 1:
The movable member is designed as a universal platform that can position multiple different types of objective lenses for different disc formats. The same actuator mechanism with magnetic circuits and standing mirrors can serve multiple lenses by adjusting the movable member position, eliminating the need for separate actuators for each lens type and reducing overall system complexity.
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 achieves a compact and thin optical pickup that maintains proper electromagnetic and optical performance, allowing for efficient recording and reproduction from various optical discs without increasing the thickness, thus addressing the challenges of size and performance in existing technologies.
Implementation Method 1
each of the coil blocks comprises a focusing coil and a tracking coil. The focusing coil has a coil axis extending in the focusing direction and is provided for driving the movable member in the focusing direction, while the tracking coil has a coil axis extending in the tangential direction and is provided for driving the movable member in the radial direction
Implementation Method 2
a standing mirror 135 to guide the laser light L to the objective lenses 112, 113; and a photodetector 143 to detect, for the laser light L reflected by and returning from the optical disc
Data Source
AI summary
An optical pickup is provided for driving objective lenses in focusing and radial directions. The pickup includes a movable member, and objective lenses at the center portion of the movable member. The pickup also includes coil blocks provided at two side portions of the movable member, and pairs of magnets flanking the coil blocks in a tangential direction perpendicular to the focusing and radial directions. Support members are attached to the side portions of the movable member, permitting the movable member to move in the focusing direction and the radial direction. Each coil block includes focusing and tracking coils for driving the movable member in the focusing direction and the radial direction. The center portion of the movable member, below which a reflector is arranged, is thinner than the side portions of the movable member.