Polarization Diffraction Element for Zeroth-Order Stray Light Reduction

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Solution Overview

Problem

Existing liquid crystal diffraction elements fail to effectively convert zeroth-order rays into polarized light with opposite polarization states, leading to stray light issues, particularly in optical devices like AR glasses and VR displays.

Innovation Solution

The polarization diffraction element converts zeroth-order rays into levorotatory or dextrorotatory polarized light with specific ellipticity differences, ensuring they can be filtered by circularly polarizing plates, and achieves high diffraction efficiency for first-order rays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a liquid crystal diffraction element is used to diffract light, then diffraction efficiency is improved, but zeroth-order rays are not converted into polarized light with opposite polarization states, causing stray light issues

Engineering Contradiction:

Improvediffraction efficiencyVSAvoidstray light

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the polarization state parameter of zeroth-order rays by optimizing the liquid crystal alignment pattern and optical path design. This transforms the zeroth-order rays into polarized light with opposite polarization states (e.g., converting right-handed circularly polarized light to left-handed), enabling them to be effectively filtered by circularly polarizing plates and eliminating stray light while preserving high diffraction efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful zeroth-order rays that cause stray light into beneficial polarized light with opposite polarization states. By designing the liquid crystal diffraction element to specifically transform the polarization state of zeroth-order rays, these previously harmful components become useful for improving image quality when combined with circularly polarizing plates

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If circularly polarized light is used for diffraction, then polarization control is improved, but zeroth-order rays with the same polarization state cannot be filtered, leading to ghosting effects

Engineering Contradiction:

Improvepolarization controlVSAvoidghosting effects

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies inversion by converting zeroth-order rays with the same polarization state into polarized light with opposite polarization states. This inversion of polarization state allows the zeroth-order rays to be differentiated from the diffracted light and effectively filtered out by circularly polarizing plates, eliminating ghosting effects while maintaining reliable polarization control

Inventive Principle:

Principle #13The other way round (Inversion)

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

Reduces stray light by altering the polarization state of zeroth-order rays, minimizing ghosting effects in optical devices.

Implementation Method 1

The liquid crystal diffraction element having such a liquid crystal alignment pattern can diffract incident light at an angle depending on a wavelength

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

the liquid crystal diffraction element converts the diffracted circularly polarized light into circularly polarized light having an opposite turning direction

Methodology Applied

Scientific EffectPolarization conversion: Polarisation

Data Source

PatentUS20250251534A1Polarization diffraction element, optical element, and optical device

Publication Date: 2025.08.07 FUJIFILM CORP

AI summary

Provided are a polarization diffraction element, an optical element, and an optical device, which can reduce components capable of causing stray light. The polarization diffraction element is a polarization diffraction element in which, in a case where a dextrorotatory polarized light having an ellipticity εin of 0.95 or more is incident into the polarization diffraction element, a zeroth-order ray transmitted through the polarization diffraction element is to be a levorotatory polarized light, a linearly polarized light, or a dextrorotatory polarized light having an ellipticity ε0 satisfying a relationship of an expression (1): ellipticity εin−ellipticity ε0≥0.05, or in a case where a levorotatory polarized light having an ellipticity εin of 0.95 or more is incident into the polarization diffraction element, a zeroth-order ray transmitted through the polarization diffraction element is to be a dextrorotatory polarized light, a linearly polarized light, or a levorotatory polarized light having an ellipticity ε0 satisfying the relationship of the expression (1).