Optical Element Bonding Member Elastic Modulus Thermal Stress
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Solution Overview
Problem
In optical devices, the use of resin lenses can lead to deterioration of optical performance due to deformation during heat caulking, and the difference in linear expansion coefficients between resin and glass lenses causes thermal stress, resulting in interface delamination and eccentricity issues when temperature changes.
Innovation Solution
An optical element comprising a first transparent member, a second transparent member with a different linear expansion coefficient, and a bonding member with an elastic modulus of 1700 MPa or less at -30°C, which is used to bond the members together, allowing for flexibility and reduced thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat caulking is used to attach the lens to the mounting member, then the lens can be strongly fixed with high positional precision, but the resin lens deforms during heat caulking causing deterioration of optical performance
Solution Approach 1:
The lens system is divided into two separate lenses: a glass lens that is heat-caulked to the mounting member, and a resin lens that is bonded to the glass lens. This segmentation allows the glass lens to bear the thermal stress of heat caulking while the resin lens maintains its optical precision through separate bonding.
Solution Approach 2:
The glass lens serves as an intermediary component between the mounting member and the resin lens. It absorbs the thermal stress from heat caulking and protects the resin lens from deformation, while still enabling strong fixing and high positional precision.
2Weight of moving object
If a resin lens is used to reduce weight, then the device becomes lighter, but the difference in linear expansion coefficient causes thermal stress and interface delamination
Solution Approach 1:
The glass lens acts as a mediator between the mounting member and the resin lens, absorbing thermal expansion differences due to its linear expansion coefficient being closer to the mounting member. This prevents thermal stress from transmitting to the resin lens interface, maintaining bonding reliability while preserving weight reduction benefits.
Solution Approach 2:
The optical system uses a composite structure combining glass and resin lenses. The glass lens provides thermal stability and structural support, while the resin lens provides weight reduction. Together they form a composite system that balances weight savings with interface bonding reliability.
3Reliability
If glass lens is used instead of resin lens, then thermal stress is reduced, but the device weight increases
Solution Approach 1:
The lens system is segmented into a glass lens for thermal stability and a resin lens for weight reduction. The glass lens handles thermal stress resistance while the resin lens contributes to overall weight reduction, achieving both goals simultaneously through functional segmentation.
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 relative displacement and maintains adhesive force between the lenses across temperature changes, preventing eccentricity and improving optical performance by accommodating thermal expansion differences.
Implementation Method 1
An elastic modulus of the bonding member is 1700 MPa or less at a temperature of −30° C.
Implementation Method 2
a second transparent member disposed in contact with the first transparent member and having a different linear expansion coefficient from the first transparent member
Data Source
AI summary
An optical element includes a first transparent member, a second transparent member disposed in contact with the first transparent member and having a different linear expansion coefficient from the first transparent member, and a bonding member configured to bond the first transparent member and the second transparent member to each other. An elastic modulus of the bonding member is 1700 MPa or less at a temperature of −30° C.