Optical Pickup Adhesive Fixation for Focus Offset Control

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Solution Overview

Problem

Conventional optical pickups for high-density optical disks like BDs experience significant focus offset and positional deviation due to inadequate fixation methods, leading to unstable servo systems and deteriorated reproduction signals, especially under varying temperature and humidity conditions.

Innovation Solution

The optical pickup design incorporates a support holder with concave portions and an optical base with corresponding convex portions, where the convex portions are arranged to minimize UV light radiation unevenness, ensuring symmetrical adhesive application and reduced curing shrinkage, thereby maintaining the optical detector's precise position.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional fixation methods with photo-curable adhesives are used to adjust and fix the optical detector, then the optical detector can be positioned with high accuracy initially, but significant focus offset and positional deviation occur under varying temperature and humidity conditions

Engineering Contradiction:

Improveinitial positioning accuracy of optical detectorVSAvoidstability of optical detector position under varying temperature and humidity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the physical state of the adhesive from liquid to solid through photo-curing, and selects adhesives with specific viscosity ranges (20000-50000 mPa·s) to control curing shrinkage. This parameter optimization ensures the adhesive maintains strong bonding while minimizing dimensional changes that cause focus offset under varying environmental conditions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite fixation system combining mechanical structures (convex portions and concave portions with specific dimensional relationships where 2a ≤ b) with photo-curable adhesive materials. This composite approach provides both mechanical positioning accuracy and chemical bonding strength, preventing positional deviation while maintaining focus stability across temperature and humidity variations

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If the convex portions of the optical base extend beyond the support holder to facilitate adhesive application, then adhesive application is simplified, but UV light radiation becomes uneven causing curing shrinkage and focus offset

Engineering Contradiction:

Improveease of adhesive applicationVSAvoiduniformity of UV light radiation and adhesive curing

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent deliberately designs the convex portions with asymmetric dimensional relationships where the distance between convex portions (2a) is less than or equal to half the width of the support holder (b/2). This asymmetric configuration ensures that even when convex portions extend beyond the holder, UV light can uniformly irradiate all adhesive application points without being blocked, eliminating uneven curing and focus offset while maintaining ease of adhesive application

Inventive Principle:

Principle #4Asymmetry

3Quantity of substance

If high-density recording is implemented on optical disks, then storage capacity increases, but the optical spot size must be reduced requiring shorter wavelength lasers and higher numerical aperture lenses

Engineering Contradiction:

Improvestorage capacity of optical diskVSAvoidoptical spot size control

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent changes the wavelength parameter of the laser from conventional 660nm (DVD) to 405nm (blue laser), and increases the numerical aperture from 0.6 to 0.85. These parameter changes reduce the optical spot size by approximately 5 times, enabling high-density recording on BDs while maintaining precise focus control through the optimized adhesive fixation system that prevents focus offset

Inventive Principle:

Principle #35Parameter changes

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 effectively suppresses focus offset and signal asymmetry, ensuring excellent signal characteristics for high-density optical disks by minimizing positional deviation and maintaining signal integrity during long-term storage and use.

Implementation Method 1

said optical base and said support holder are fixed by photo-curable adhesives for adhering said convex portions and said support holder to each other

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Data Source

PatentUS8238218B2Optical pickup, optical information device, computer, optical disk player, car navigation system, optical disk recorder, and optical disk server

Publication Date: 2012.08.07 PANASONIC HOLDINGS CORP

AI summary

To provide an optical pickup and an optical information device, capable of obtaining excellent signal characteristics for an optical disk on and/or from which recording and/or reproducing are performed using a laser. The optical pickup includes an optical detector, a support holder for holding the optical detector, and an optical base for fixing the support holder. The support holder has at least two notches at its both ends, the optical base has convex portions corresponding to the notches of the support holder, the optical base and the support holder are fixed by photo-curable adhesives for bonding the convex portions and the support holder to each other, and the shortest distance between the side faces of the convex portions, which do not face each other, is equal to or less than the width of the support holder in the direction of right and left ends.