Cemented Optical Element With Fine Unevenness Structure
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Solution Overview
Problem
Cemented optical elements with large coefficients of thermal expansion experience lens distortion and separation due to radial stress from temperature changes, and suffer from light loss due to reflection at the adhesive interface caused by refractive index differences between lenses and adhesives, with existing cone-like protrusions being prone to fracture from adhesive curing shrinkage.
Innovation Solution
A cemented optical element featuring a first optical component with a resin lens and a second optical component, both with a fine unevenness structure on their joining surfaces, comprising a plurality of holes or columnar protrusions that increase joint strength and reduce reflectivity by forming a composite refractive index layer, preventing separation and fracture during curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If cone-like protrudes are formed on the lens surface to reduce reflection, then light reflection at the interface is reduced, but the protrudes are easily fractured by adhesive curing shrinkage causing separation
Solution Approach 1:
The fine unevenness structure is segmented into a periodic array of columnar protrudes with specific pitch and dimensions. This segmentation allows the structure to reduce reflection through diffraction while the distributed nature prevents stress concentration that would lead to fracture during adhesive curing.
Solution Approach 2:
The invention changes the geometric parameters of the unevenness structure from cone-like shapes to columnar protrudes with specific height (0.1-10 μm), width (0.01-1 μm), and pitch (0.1-10 μm) ratios. These parameter changes create a structure that is mechanically robust against curing shrinkage while maintaining optical performance through controlled light diffraction.
2Device complexity
If resin lenses are used to reduce weight and complexity, then device complexity is reduced, but lens separation occurs more prominently due to large coefficient of thermal expansion
Solution Approach 1:
The columnar protrude structure is applied locally at the joining interface of resin lenses, providing enhanced mechanical interlocking and stress distribution precisely where thermal expansion differences cause separation, while maintaining the overall simplicity of using resin lenses throughout the optical system.
3Ease of manufacture
If transparent adhesive is used to join optical elements, then optical elements can be joined in the optical axis direction, but light reflection occurs due to refractive index difference between lens and adhesive
Solution Approach 1:
The columnar protrude structure acts as an intermediary between the lens and adhesive, creating a transition zone with effective intermediate refractive index through its geometric structure. This intermediary structure reduces reflection by gradually transitioning the refractive index from the lens material through the protrude structure to the adhesive, rather than having a abrupt interface.
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 provides high joint strength and low reflectivity at the joining interface, preventing separation and maintaining optical performance across varying temperatures, while reducing light reflection and ensuring structural integrity.
Implementation Method 1
loss of the amount of transmitted light due to the light reflection at the adhesive interface depending on the difference in refractive indices between the lens and the transparent adhesive
Implementation Method 2
the fine unevenness structure is formed by a plurality of holes or columnar protrusions... forming a composite refractive index layer
Implementation Method 3
the radial stress applied to the joining surface increases due to an increase in the amount of expansion or shrinkage of the lens due to a temperature change... resin lenses... generally has the large coefficient of thermal expansion
Implementation Method 4
the cone-like protrude in the cemented optical element described in Japanese Patent Application Laid-Open No. 2005-157119 is easily fractured by the curing shrinkage of the adhesive
Data Source
AI summary
A cemented optical element having a first optical component, a second optical component, and a third optical component that contains a resin and is sandwiched between the first optical component and the second optical component. The first optical component contains a resin and has a line unevenness structure on at least a part of a surface in contact with the third optical component. The fine unevenness structure is formed by a plurality of holes or columnar protrusions.