Optical Unit Thermal Stress Management via Elastic Fastening
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Solution Overview
Problem
The existing optical units face issues with stress exerted on bonding portions due to thermal loads when a lens array and light emitting element array are bonded, especially when attached to a heat dissipation member with a large coefficient of thermal expansion, leading to potential cracking or peeling off, which affects the optical characteristics and reliability.
Innovation Solution
The optical unit includes a light emitting element array, a lens array, and a fixing part that allows for expansion and contraction in a plane parallel to the surface of a heat dissipation member with a larger coefficient of thermal expansion, using a combination of fixing screws and leaf springs or elastic members to manage thermal stress, ensuring accurate positioning and minimizing strain on the bonding areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the light emitting element array and lens array are firmly fixed together with solder to ensure accurate positioning, then positioning accuracy is improved, but residual stress causes bonding portions to crack or peel over time
Solution Approach 1:
The fixing structure is divided into multiple discrete fixing portions distributed across the bonding surface, rather than a single continuous bond. Each fixing portion independently secures the arrays while allowing localized stress relief, preventing crack propagation across the entire bonding interface.
Solution Approach 2:
The bonding structure implements different properties in different regions: areas with fixing portions have strong mechanical attachment, while areas between fixing portions allow controlled movement and stress relief. This local variation in bonding rigidity accommodates thermal expansion differences while maintaining overall positioning accuracy.
2Stability of the object's composition
If the optical module is rigidly attached to the heat dissipation member to ensure stable positioning, then positioning stability is improved, but thermal expansion mismatch causes stress and potential damage
Solution Approach 1:
The attachment structure transitions from a completely rigid connection to a semi-flexible connection that allows controlled movement. The fixing portions maintain positioning stability while the spaces between them and the elastic members enable the optical module to dynamically adjust to thermal expansion, reducing stress accumulation.
Solution Approach 2:
The structural rigidity parameter is varied across different regions of the attachment. Areas with fixing portions provide high rigidity for positioning, while regions with elastic members and spacing provide lower rigidity for stress absorption. This gradient in rigidity parameters allows simultaneous achievement of positioning stability and stress relief.
3Reliability
If elastic members are introduced to relieve thermal stress, then bonding durability is improved, but device complexity increases
Solution Approach 1:
The stress relief function is extracted as a separate, simple elastic member component rather than integrating complexity into the bonding structure itself. These elastic members are discrete elements that can be independently selected and positioned, simplifying the overall design while providing the necessary flexibility for thermal stress accommodation.
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 stress on the bonding portions, preventing cracking or peeling and maintaining the optical module's position, even under thermal expansion and contraction cycles, thus ensuring stable optical performance and reliability.
Implementation Method 1
a light emitting element array 102 in which a plurality of light emitting elements are arranged, and a lens array 101 disposed facing the light emitting element array 102 on an optical path of light emitted from the plurality of light emitting elements
Implementation Method 2
it is effective to collimate light emitted from the two-dimensional light emitting element array before condensing light
Implementation Method 3
The fastening part 110 is configured to fasten the optical module 161 so as to enable expanding and contracting in a plane parallel to the surface of the heat dissipation member 158
Data Source
AI summary
An optical unit includes an optical module that includes a light emitting element array in which a plurality of light emitting elements are arranged, a lens array disposed facing the light emitting element array on an optical path of light emitted from the plurality of light emitting elements, and a fixing part configured to fix the light emitting element array to the lens array. The optical unit also includes a member configured to have a larger coefficient of thermal expansion than a coefficient of thermal expansion of the light emitting element array and a fastening part configured to fasten the optical module on a surface of the member. The fastening part is configured to fasten the optical module so as to enable expanding and contracting in a plane parallel to the surface of the member.