Diffraction Optical Element Refractive Index Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing diffraction optical elements with two kinds of resins suffer from phase shifts in the transmitted wavefront due to refractive index differences, leading to blurred images and are prone to cracking from temperature changes due to uneven expansion and contraction.

Innovation Solution

A diffraction optical element design featuring a first resin layer with a diffraction grating shape and a second resin layer comprising a first portion and a second portion, where the refractive index difference between the center and circumference of the first annular section is minimized, and the layer thickness is optimized to prevent cracking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a second resin layer is provided on a first resin layer with a diffraction grating shape, then chromatic aberration can be suppressed, but a refractive index distribution occurs in the second resin layer causing phase shift and concentric striped patterns

Engineering Contradiction:

Improvechromatic aberration suppressionVSAvoidphase shift of transmitted wavefront

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by providing a first portion of the second resin layer on the first annular section with different optical properties than the rest of the second resin layer. This first portion has a refractive index that matches or closely approximates the refractive index of the first resin layer, thereby eliminating the refractive index difference that causes phase shifts and concentric striped patterns in the blurred image, while the rest of the second resin layer maintains the chromatic aberration suppression function.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If an intermediate layer is provided on the second resin layer to mitigate stepped shape influence, then concentric striped patterns are suppressed, but the total layer thickness increases causing internal distortion and cracks due to temperature changes

Engineering Contradiction:

Improveconcentric striped pattern suppressionVSAvoidcrack resistance of diffraction grating layer

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent applies parameter changes by precisely controlling the refractive index parameter of the first portion of the second resin layer to match or closely approximate the refractive index of the first resin layer. This parameter adjustment eliminates the need for an additional intermediate layer, thereby suppressing concentric striped patterns without increasing total layer thickness, and prevents internal distortion and cracks that would result from temperature-induced expansion and contraction in thicker structures.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If the second resin layer is held between base materials during curing, then the diffraction optical element can be formed, but cure shrinkage causes density differences and refractive index distribution

Engineering Contradiction:

Improvediffraction optical element formationVSAvoidrefractive index uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating a first portion of the second resin layer with specifically controlled optical properties that differ from the rest of the second resin layer. This first portion, located on the first annular section, has a refractive index matched to the first resin layer to compensate for shrinkage-induced refractive index changes, thereby maintaining manufacturing feasibility while ensuring refractive index uniformity in the critical optical region.

Inventive Principle:

Principle #3Local quality

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 reduces phase shifts in the transmitted wavefront and prevents cracking due to temperature changes, resulting in improved image clarity and durability of the optical element.

Implementation Method 1

a first resin layer having a diffraction grating shape is laminated on the base material

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

a difference between a refractive index of the second portion on a center of the first annular section and a refractive index of the second portion on a circumference of the first annular section is within 0.0005

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS10852460B2Diffraction optical element, manufacturing method thereof, and optical apparatus

Publication Date: 2020.12.01 CANON KK

AI summary

There is provided a diffraction optical element which comprises a base material, and in which a first resin layer having a diffraction grating shape and a second resin layer are laminated on the base material. The diffraction grating shape forms a plurality of concentric annular sections when planarly viewed from a lamination direction of the diffraction optical element. The second resin layer comprises a first portion and a second portion, and the first portion is provided on a first annular section of the first resin layer. The second portion is continuously provided from above the first portion to above a region including a periphery of the first resin layer. A difference between a refractive index of the second portion on a center of the first annular section and a refractive index of the second portion on a circumference of the first annular section is within 0.0005.