Diffractive Optical Element Resin Layer Thickness Constraints
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Solution Overview
Problem
Diffractive optical elements manufactured using photocurable or thermosetting resin layers are prone to performance degradation due to moisture absorption, cracking, and peeling, especially in varying environmental temperatures, caused by differences in thermal expansion coefficients between substrates and resin layers.
Innovation Solution
A diffractive optical element is designed with specific thickness constraints for its resin layers, where the average film thickness of the first layer (t1) is between 1.1 times and 50 μm of the grating height, and the second layer (t2) is between 30 μm and (400 μm - t1 - d), with a total film thickness not exceeding 400 μm, to minimize stress and maintain optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resin layers are made thicker to improve manufacturing ease and reduce stress, then ease of manufacture improves, but moisture absorption increases causing optical performance degradation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of resin layers within specific ranges (first layer: 1.1d≤t1≤50 μm, second layer: 30 μm≤t2≤(400 μm−t1−d)) to optimize both manufacturing ease and optical performance. This quantitative parameter control resolves the contradiction by finding the optimal thickness window that balances stress reduction with moisture absorption prevention.
2Reliability
If resin layers are made thinner to reduce moisture absorption, then optical performance is preserved, but manufacturing precision requirements increase
Solution Approach 1:
The patent resolves this contradiction by establishing specific thickness parameter ranges that are thin enough to prevent moisture absorption issues (maintaining optical performance) but thick enough to be manufacturable. The constraints t1≤50 μm and t2≥30 μm create a manufacturable window that satisfies both precision requirements and practical manufacturing capabilities.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and specifying the optimal thickness ranges before manufacturing begins. The relationships 1.1d≤t1 and t2≤(400 μm−t1−d) are established in advance to guide the manufacturing process, ensuring that precision requirements are met without requiring complex real-time adjustments during production.
3Stability of the object's composition
If resin layer thickness is increased to reduce interface stress, then mechanical stability improves, but thermal expansion differences cause cracking and peeling
Solution Approach 1:
The patent resolves this contradiction by optimizing the thickness parameters of resin layers to balance stress distribution and thermal expansion effects. The specific ranges (t1: 1.1d≤t1≤50 μm, t2: 30 μm≤t2≤(400 μm−t1−d)) are designed to minimize both interface stress and thermal mismatch, preventing cracking and peeling while maintaining mechanical stability.
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 degradation of optical performance, prevents cracking, and reduces peeling at interfaces, ensuring stable operation across temperature and humidity variations.
Implementation Method 1
a step of curing the first material by applying heat or light energy to the first material
Implementation Method 2
a step of curing the first material by applying heat or light energy to the first material
Implementation Method 3
a diffraction grating being formed at the interface of the first layer and the second layer
Data Source
AI summary
A diffractive optical element prevents degradation of the optical performance of the element due to moisture absorption of the resin layers from taking place and also can prevent cracks of the resin layers and peeling of the resin layers along the interface thereof from taking place in a hot environment or in a cold environment. The diffractive optical element comprises a first layer and a second layer sequentially laid on a substrate, a diffraction grating being formed at the interface of the first layer and the second layer, the height d of the diffraction grating, the average film thickness t1 of the first layer and the average film thickness t2 of the second layer satisfying the relationship requirements expressed by the expressions of 1.1×d≤t1≤50 μm and 30 μm≤t2≤(400 μm−t1−d).