Diffractive Optical Element Ring Zone Design for Shrinkage Stress
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Solution Overview
Problem
Manufacturing diffractive optical elements by cementing two materials faces challenges in achieving desired optical characteristics due to shrinkage stress during curing, and existing methods are complex.
Innovation Solution
A diffractive optical element comprising a first material layer with a diffractive grating shape and a second material layer laminated on top, forming concentric annular ring zones, where the radius of the innermost ring zone is less than the distances between ring zones, and the phase difference function is designed to optimize refractive index differences and curing stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If two materials are cemented to form a diffractive optical element, then the manufacturing process can be simplified, but shrinkage stress during curing deteriorates the optical characteristics
Solution Approach 1:
The patent applies preliminary action by designing the diffractive grating structure with specific geometric parameters (ring zone radius relationships) before the cementing process. The innermost ring zone radius is designed to be less than the distance to adjacent ring zones, which pre-compensates for the shrinkage stress that will occur during curing. This preliminary structural design ensures that even after shrinkage, the optical characteristics remain within desired tolerances.
Solution Approach 2:
The patent employs parameter changes by optimizing the geometric parameters of the diffractive grating, specifically the radius of the innermost ring zone and its relationship to adjacent ring zones. By setting the innermost ring zone radius to be less than the distance to adjacent ring zones, the structure compensates for shrinkage stress effects. Additionally, the phase difference function parameters are optimized to maintain diffraction efficiency despite the curing process.
2Manufacturing precision
If the diffractive grating structure is optimized for diffraction efficiency, then optical performance improves, but the manufacturing complexity increases
Solution Approach 1:
The patent uses parameter changes to optimize the phase difference function parameters and ring zone dimensions to achieve high diffraction efficiency. The specific parameter relationship (innermost ring zone radius less than distance to adjacent zones) simplifies the design space while maintaining optimal optical performance.
Solution Approach 2:
The patent employs composite materials by combining the diffractive grating structure with a cementing material having specific refractive index properties. This composite approach allows the structure to achieve both mechanical integrity and optimal diffraction performance without increasing design complexity.
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 approach allows for the easy attainment of desired optical characteristics by reducing shrinkage stress and improving diffraction efficiency, simplifying the manufacturing process while maintaining high optical performance.
Implementation Method 1
a diffractive optical element comprising: a first material layer that has a diffractive grating shape; and a second material layer that is laminated on the first material layer, the diffractive grating shape forming a plurality of concentric annular ring zones
Implementation Method 2
an even-order phase difference function at the radius as a variable is φ(r), a start phase of the phase difference function is C, and a remainder obtained by dividing the added value of φ(r) and C by 2π is MOD(r)
Implementation Method 3
a difference in refractive index between the first material layer and the second material layer is Δn
Data Source
AI summary
A diffractive optical element includes: a first material layer that has a diffractive grating shape; and a second material layer that is laminated on the first material layer, the diffractive grating shape forming a plurality of concentric annular ring zones in a plan view from a lamination direction of the first material layer and the second material layer, and a radius of an innermost first ring zone among the plurality of ring zones is less than any one of distances between the ring zones.