Optical Device Bonding Member Stress Management
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Solution Overview
Problem
Optical devices with bonded optical elements of different materials face challenges in maintaining environmental resistance and optical performance due to differing linear expansion coefficients, leading to deformation and peeling issues under temperature changes.
Innovation Solution
The optical device incorporates a bonding member with specific thickness and mechanical properties, satisfying conditional expressions to reduce stress and deformation, eliminating the need for spacers and uniform adhesive thickness, thereby enhancing environmental resistance and optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is used to bond optical elements with different linear expansion coefficients, then the optical elements can be joined together, but the adhesive may deform due to environmental variations causing peeling and reduced optical performance
Solution Approach 1:
The patent changes the physical and chemical parameters of the bonding member by selecting materials with specific thermal expansion coefficients and elastic moduli that match the optical elements. The bonding member is designed to have a thermal expansion coefficient within 0.1×10^-6 to 1.0×10^-6 /°C and an elastic modulus within 70 to 150 GPa, creating a gradient that accommodates thermal stress while maintaining bonding strength.
Solution Approach 2:
The bonding member is designed as a composite structure with specific material composition, combining properties of different materials to achieve the desired thermal expansion coefficient and elastic modulus. This composite approach allows the bonding member to simultaneously provide mechanical strength and thermal stress resistance.
2Reliability
If spacer is provided to maintain uniform adhesive thickness, then deformation and peeling can be inhibited, but the device complexity increases and manufacturing becomes more difficult
Solution Approach 1:
The patent removes the spacer component from the bonding structure. Instead of using a separate spacer element to maintain uniform thickness, the bonding member itself is designed with optimized thickness and material properties that inherently prevent deformation and peeling, simplifying the overall device structure.
Solution Approach 2:
The functions of the spacer (maintaining uniform thickness) and the bonding member (providing mechanical strength and thermal stress resistance) are merged into a single component. The bonding member is designed to simultaneously serve as both the bonding agent and the thickness-maintaining element, eliminating the need for separate spacer components.
3Reliability
If adhesive thickness is increased to accommodate thermal expansion differences, then peeling can be prevented, but the adhesive itself deforms due to environmental variations reducing optical performance
Solution Approach 1:
The patent optimizes the thickness parameter of the bonding member to a specific range (0.1 to 1.0 mm) and changes the material parameters (thermal expansion coefficient and elastic modulus) to create a gradient structure. This allows the bonding member to accommodate thermal expansion differences without excessive thickness, preventing both peeling and self-deformation of the bonding material.
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
The solution effectively reduces stress and deformation in the bonding member, improving environmental resistance and optical performance by setting the bonding member's thickness and mechanical properties to match the ratio of the optical elements' expansion coefficients, preventing peeling and maintaining optical integrity across temperature variations.
Implementation Method 1
even if linear expansion coefficients of the two optical elements are mutually different, deformation of each optical element and peeling of the adhesive due to environmental variations such as temperature changes can be inhibited
Implementation Method 2
the following conditional expression is satisfied: 0.14≤te/tc×Log(E1×E2/Ec2)<0.40
Data Source
AI summary
An optical device including first and second optical elements formed of mutually different materials, and a bonding member bonding the first and second optical elements to each other, wherein the following conditional expression is satisfied:0.14<Log(te/tc)×Log(E1×E2/Ec2)<5.0where tc is a thickness in an optical axis direction of the bonding member on an optical axis, te is a thickness in the optical axis direction of the bonding member in a maximum diameter of interfaces between the first and second optical elements and the bonding member, and E1, E2, and Ec are respective Young's moduli of the first and second optical elements and the bonding member.