Optical Element with Rotating Axis Lambda-Half Plate for Directional Reflection
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Solution Overview
Problem
Existing optical elements fail to control the reflection direction of incident light effectively, particularly for polarized light, and struggle to suppress zero-order reflection while achieving desired directional reflection.
Innovation Solution
An optical element comprising a wavelength selective reflective polarizer and a λ/2 plate with an optically anisotropic layer, where the λ/2 plate has a liquid crystal alignment pattern with a continuously rotating optical axis, allowing circularly polarized light to be reflected in a direction different from the regular reflection direction by adjusting the 180° rotation pitch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reflection diffraction grating structure is used on a cholesteric liquid crystal layer, then high reflectivity and low zero-order diffraction efficiency are obtained, but the direction of reflected light is not controlled and zero-order reflection is suppressed
Solution Approach 1:
The optical element is divided into two functional layers: a wavelength selective reflective polarizer layer and a λ/2 plate layer with rotating optical axis. This segmentation allows each layer to perform its specific function - the polarizer provides wavelength-selective reflection while the λ/2 plate controls the reflection direction through its rotating optical axis pattern.
Solution Approach 2:
The λ/2 plate acts as an intermediary between the incident light and the reflective polarizer. It first converts the polarization state of incident light and then directs it to the polarizer, enabling control over the reflection direction without affecting the polarizer's wavelength-selective reflection function.
2Loss of energy
If an uneven diffraction grating structure is prepared on the cholesteric liquid crystal surface, then zero-order reflection is suppressed, but the direction of reflected light is not controlled
Solution Approach 1:
The optical element is divided into two functional layers: a wavelength selective reflective polarizer layer and a λ/2 plate layer with rotating optical axis. This segmentation allows each layer to perform its specific function - the polarizer provides wavelength-selective reflection while the λ/2 plate controls the reflection direction through its rotating optical axis pattern.
Solution Approach 2:
The optical axis orientation in the λ/2 plate is varied spatially according to a rotating pattern, changing the optical parameters across the layer. This parameter variation enables control over the reflection direction while maintaining suppression of zero-order reflection through the wavelength selective polarizer.
3Ease of operation
If a wavelength selective reflective polarizer and λ/2 plate with rotating optical axis are combined, then light can be reflected in a desired direction different from regular reflection, but the device complexity increases
Solution Approach 1:
The λ/2 plate and wavelength selective reflective polarizer are combined into a single integrated optical element with layered structure. This merging allows both functions - polarization-dependent wavelength selection and reflection direction control - to be achieved in one component rather than requiring separate elements.
Solution Approach 2:
The combined optical element performs multiple functions simultaneously: it acts as a wavelength selective filter, a polarizer, and a beam director. The λ/2 plate with rotating optical axis pattern provides both polarization conversion and direction control, while the reflective polarizer provides wavelength selection, creating a multi-functional component.
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 optical element successfully reflects light in a desired direction different from the regular reflection direction, enhancing control over light reflection and reducing zero-order reflection, with the ability to change the reflection direction by adjusting the 180° rotation pitch of the λ/2 plate.
Implementation Method 1
a wavelength selective reflective polarizer which selectively reflects specific circularly polarized light that is light in a specific wavelength range
Implementation Method 2
the λ/2 plate includes an optically anisotropic layer which has an optical axis in a direction parallel to a surface and is formed of a cured layer of a liquid crystal composition
Implementation Method 3
has a liquid crystal alignment pattern in which an orientation of the optical axis changes while continuously rotating in at least one direction in a plane of the optically anisotropic layer
Implementation Method 4
λ/2 plate which... has an optically anisotropic layer... formed of a cured layer of a liquid crystal composition
Implementation Method 5
light in the specific wavelength range which is circularly polarized light oriented in a direction opposite to that of the specific circularly polarized light among light incident on a surface of the optical element on the λ/2 plate side is reflected in a direction different from a regular reflection direction of the incident light
Data Source
AI summary
Provided is an optical element including a wavelength selective reflective polarizer and a λ/2 plate in which the λ/2 plate includes an optically anisotropic layer which has an optical axis in a direction parallel to a surface and is formed of a cured layer of a liquid crystal composition and has a liquid crystal alignment pattern in which an orientation of the optical axis changes while continuously rotating in at least one direction in a plane of the optically anisotropic layer, and light in the specific wavelength range which is circularly polarized light oriented in a direction opposite to that of the specific circularly polarized light among light incident on a surface of the optical element on the λ/2 plate side is reflected in a direction different from a regular reflection direction of the incident light.