Optical Pickup Beam Shaping Element Adhesive Positioning
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Solution Overview
Problem
Existing optical pickups face challenges in minimizing astigmatism caused by temperature changes, which affects the beam shaping element's position and leads to reduced light utilization efficiency and spot quality on optical discs, due to inadequate adjustment sensitivity and potential contact between the beam shaping element and the light source cover.
Innovation Solution
The optical pickup incorporates a positioning mechanism that adjusts the beam shaping element relative to the light source using a positioning portion with a specific adhesive, ensuring the beam shaping magnification is between 1.5 and 2.2, and utilizing an ultraviolet curable resin adhesive that does not react to the light source's emission, allowing for precise positioning and adhesion without astigmatism issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the beam shaping element is positioned close to the light source to improve light utilization efficiency, then the astigmatism correction capability is improved, but the beam shaping element may contact the light source cover due to thermal expansion, reducing reliability
Solution Approach 1:
The patent applies parameter changes by carefully selecting and controlling the distance L between the light source and beam shaping element, and by specifying the adhesive positioning parameters (distance from light source side surface, adhesive amount) to optimize the balance between light utilization efficiency and thermal expansion clearance, preventing contact while maintaining high efficiency
Solution Approach 2:
The patent employs beforehand cushioning by providing thermal expansion clearance space between the beam shaping element and light source cover, and by using adhesive with specific positioning characteristics to pre-compensate for thermal expansion effects, ensuring the beam shaping element does not contact the cover during temperature variations
2Manufacturing precision
If the distance between the light source and beam shaping element is adjusted to correct astigmatism, then the spot quality is improved, but the positioning precision is reduced due to low adjustable sensitivity
Solution Approach 1:
The patent resolves this contradiction by changing the positioning parameter from distance adjustment to adhesive-based positioning. By specifying the adhesive application position and amount, the beam shaping element can be precisely fixed at the optimal distance L, achieving both high spot quality and precise positioning without relying on sensitive distance adjustments
3Ease of manufacture
If a conventional adhesive is used to fix the beam shaping element, then the assembly is simplified, but astigmatism occurs due to adhesive positioning errors and thermal expansion
Solution Approach 1:
The patent applies parameter changes by specifying critical adhesive parameters: the distance from the light source side surface to the adhesive center position, and the adhesive amount. These parameter specifications ensure that the adhesive not only simplifies assembly but also maintains precise positioning to prevent astigmatism, resolving the contradiction between ease of manufacture and manufacturing precision
Solution Approach 2:
The adhesive serves as an intermediary element that combines the benefits of simple assembly with precise positioning. By carefully selecting and specifying the adhesive application parameters, it mediates between the beam shaping element and the holder, ensuring both ease of assembly and astigmatism control
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 solution effectively suppresses astigmatism caused by temperature changes, maintains high light utilization efficiency, and ensures a stable spot quality on optical discs, while allowing for easy adjustment and reliable adhesion of the beam shaping element.
Implementation Method 1
a center position of the adhesive is at a specified distance from a light source side surface of the beam shaping element
Implementation Method 2
a beam shaping element for shaping an elliptical light beam emitted from the light beam into a substantially circular light beam
Implementation Method 3
an objective lens for condensing a beam emitted from the light source on the optical disc
Implementation Method 4
an objective lens for condensing a beam emitted from the light source on the optical disc
Implementation Method 5
a detector for detecting the beam reflected by the optical disc
Data Source
AI summary
An adhesive positions a beam shaping element in such a manner as to satisfy the following relational expressions (1) and (2):0<L≦ΔWA/(α·Δ·SAS) (1)SAS=1000(0.5 m2+1.5m−2)[mλ/mm] (2),if it is assumed that m is the beam shaping magnification of a beam shaping element, L[mm] is the distance from a light source side surface of the beam shaping element to a center position of the adhesive, α[1/K] is the linear expansion coefficient of a light source retaining holder, ΔWA[mλ] is amount of astigmatic aberration caused by the beam shaping element, and ΔT[K] is an environmental temperature variation amount.