Diffractive Optical Element Resin Layer Thickness Variation
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Solution Overview
Problem
Diffractive optical elements with circular and arc-shaped diffraction gratings suffer from reduced diffraction efficiency due to density differences in the resin layer caused by curing shrinkage, leading to deteriorated optical characteristics.
Innovation Solution
A diffractive optical element design where the resin layer has varying thicknesses in optical and non-optical effective regions, with a thicker resin layer in the non-optical regions to mitigate curing-induced shrinkage and density differences, ensuring consistent diffraction efficiency across the grating surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resin layer is formed with uniform thickness to prevent cracks from curing shrinkage, then crack prevention is achieved, but density differences occur in regions with different diffraction grating shapes (circular vs. arc), leading to reduced diffraction efficiency
Solution Approach 1:
The patent applies local quality by differentiating the resin layer thickness based on the underlying diffraction grating shape. Specifically, the resin layer is formed with a first thickness in regions corresponding to circular diffraction gratings and a second thickness in regions corresponding to arc-shaped diffraction gratings. This localized thickness adjustment compensates for the different curing shrinkage behaviors of resin over circular versus arc-shaped gratings, preventing both cracks and density differences that would otherwise occur with uniform thickness formation.
2Manufacturing precision
If the resin layer thickness is increased in non-optical effective regions, then the impact of curing shrinkage is reduced and density uniformity is improved, but the overall volume and mass of the resin layer increase
Solution Approach 1:
The patent implements local quality by selectively increasing the resin layer thickness only in non-optical effective regions where arc-shaped diffraction gratings are located. The resin layer maintains a first thickness in optical effective regions and increases to a second thickness in non-optical effective regions. This localized thickness enhancement addresses the curing shrinkage issue specifically where arc-shaped gratings cause density problems, while avoiding unnecessary volume increase in regions where circular gratings already provide sufficient structural support.
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 design effectively reduces the impact of curing shrinkage on diffraction efficiency, maintaining high optical performance by minimizing refractive index variations and preventing the deterioration of optical characteristics.
Implementation Method 1
cracks are prevented from being caused by stress acting on the optical adjustment layer due to curing shrinkage of the second optical material during manufacture
Implementation Method 2
a diffractive optical element having a diffractive action
Data Source
AI summary
A diffractive optical element includes: a substrate having a surface on which a diffraction grating is provided; and a resin layer provided on the surface of the substrate so as to cover the diffraction grating, wherein, in plan view as viewed along an optical axis direction, the diffraction grating includes: a first diffraction grating having a circular shape; and a second diffraction grating having an arc shape, the second diffraction grating being arranged on an outer side of the first diffraction grating, wherein the diffractive optical element includes an optical effective region and a non-optical effective region surrounding the optical effective region, wherein the second diffraction grating has an arc end positioned in the non-optical effective region, and wherein a thickness of the resin layer provided in the non-optical effective region is larger than a thickness of the resin layer provided in the optical effective region.