Optical Pickup Lens Holder Positioning to Prevent Disk Collisions
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Solution Overview
Problem
Optical pickup devices with a single actuator and multiple objective lenses of different working distances face challenges in preventing collisions and malfunctions due to focus servo failures and surface runout, particularly when recording or reproducing data on optical disks with varying standards like DVDs and BDs, leading to increased power consumption and potential collisions with protrusions or stack ribs.
Innovation Solution
An optical pickup device design featuring a lens holder that positions the objective lens with a shorter working distance closer to the optical disk, accompanied by a protective member protruding further than the lens, ensures that the objective lens with a shorter working distance does not collide with protrusions or stack ribs, even during inner peripheral recording, and maintains the actuator's power efficiency by optimizing the distance x between the lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single actuator is used to drive two objective lenses with different working distances, then the device complexity is reduced, but the reliability decreases due to potential collisions with protrusions and servo failures
Solution Approach 1:
A protective member is provided that extends closer to the optical disk than the second objective lens, creating a cushioning barrier before the lens can collide with protrusions or the disk surface. This prevents damage and servo failures while maintaining the single actuator configuration.
Solution Approach 2:
The protective member acts as an intermediary element between the second objective lens and the optical disk/protrusions. It mediates the potential collision by providing a physical barrier that prevents direct contact, thereby protecting the lens system while allowing the single actuator to maintain both lenses.
2Manufacturing precision
If the second objective lens is positioned closer to the optical disk to reduce working distance, then the recording density increases, but the harmful factors increase due to collision risk with protrusions
Solution Approach 1:
The protective member is positioned to extend closer to the optical disk than the second objective lens, creating a safety barrier that prevents the lens from colliding with protrusions or the disk surface during high-density recording operations.
Solution Approach 2:
The protective member is pre-positioned in the optical path before the second objective lens can potentially collide with protrusions. This preliminary protective arrangement is in place before any harmful collision can occur, enabling safe high-density recording.
3Ease of operation
If the objective lens for BDs is positioned at the same height as the DVD lens in the initial position, then the ease of operation improves for DVD focus servo, but the power consumption increases due to required offset for BD recording
Solution Approach 1:
The lens holder is designed with asymmetric positioning where the first objective lens is positioned at a first distance and the second objective lens is positioned at a second distance from the initial position. This local differentiation allows each lens to have optimal positioning characteristics while sharing the same actuator.
Solution Approach 2:
The lens holder can dynamically adjust its position along the optical axis to switch between lenses. By positioning lenses at different distances from the initial position, the system can switch between DVD and BD modes with minimal actuator movement, reducing power consumption while maintaining ease of operation.
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 prevents collisions and malfunctions by keeping the objective lens and protective member distant from stack ribs, ensuring reliable data recording and reproduction across various optical disk standards while minimizing power consumption and reducing the risk of servo failures.
Implementation Method 1
an objective lens for BDs having a working distance of W2 with respect to the BD
Implementation Method 2
a protective member which is more protruding toward the optical disk, by a distance d, than is the second proximal point of the second objective lens
Data Source
AI summary
A highly reliable optical pickup which is not likely to collide with an optical disk is provided. Relative positions of two objective lenses 100 and 101 (along a focus direction) on a lens holder 102 are determined so that, while the objective lens 101 having a longer working distance is focused on an optical disk 200, the objective lens 100 having a shorter working distance and a protective member 103 are at positions which are more distant from the optical disk 200 than a height h of a protrusion which is present in an inner peripheral region of the optical disk optical disk 200.