Cholesteric Liquid Crystal Optical Element Sidelobe Suppression
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Solution Overview
Problem
Existing optical elements with cholesteric liquid crystal layers suffer from sidelobe issues, where light with wavelengths outside the intended reflection range is reflected, leading to reduced selectivity and increased reflectivity in unwanted regions.
Innovation Solution
The optical element incorporates a reflecting layer pair with overlapping reflection wavelengths and a retardation layer, featuring cholesteric liquid crystal layers with varying birefringence and alignment patterns to suppress sidelobe formation and enhance reflectivity by interfering reflected light components and converting incident polarized light effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cholesteric liquid crystal layer is used to achieve selective reflection, then reflection selectivity is improved, but sidelobe occurs causing unwanted wavelength reflection
Solution Approach 1:
The reflective layer is divided into multiple cholesteric liquid crystal layers with different helical pitch numbers. Each layer reflects light at different wavelengths, and by carefully selecting and combining layers, the patent achieves broad reflection wavelength coverage while suppressing sidelobe through the specific arrangement and selection of layers.
Solution Approach 2:
The patent changes the helical pitch number parameter across different cholesteric liquid crystal layers to create a gradient effect. By having layers with progressively different pitch numbers, the reflection characteristics are optimized to maintain high selectivity across a broad wavelength range while preventing unwanted sidelobe reflection.
2Adaptability or versatility
If multiple cholesteric liquid crystal layers with different helical pitch numbers are combined to broaden reflection wavelength range, then wavelength coverage is improved, but device complexity increases
Solution Approach 1:
The reflective layer is segmented into multiple cholesteric liquid crystal layers, each with specific helical pitch numbers. This segmentation allows the system to cover a broader wavelength range by combining the reflection characteristics of individual layers while maintaining a manageable structure through systematic organization.
Solution Approach 2:
Each cholesteric liquid crystal layer serves multiple functions: it contributes to broadening the overall reflection wavelength range while also providing specific wavelength selectivity. The layers work together to achieve both expanded coverage and maintained precision, making the complex structure functionally efficient.
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 configuration significantly reduces sidelobe occurrence and increases reflectivity by ensuring that only intended wavelengths are reflected, improving the optical element's selectivity and performance in applications like image display, head-mounted displays, and eye tracking.
Implementation Method 1
A layer (hereinafter, also referred to as 'cholesteric liquid crystal layer') obtained by immobilizing a cholesteric liquid crystalline phase is known as a layer that selectively reflects at least either right circularly polarized light or left circularly polarized light in a specific wavelength range
Implementation Method 2
the retardation layer being disposed between the reflective layers of the reflecting layer pair
Data Source
AI summary
Provided is an optical element in which the occurrence of sidelobe is suppressed and a reflectivity is high. The optical element includes: a reflecting layer pair and a retardation layer, the reflecting layer pair being a combination of two reflective layers where turning directions of circularly polarized light to be reflected are the same as each other and at least a part of reflection wavelength ranges is an overlapping part, and the retardation layer being disposed between the reflective layers of the reflecting layer pair, in which the reflective layer includes a cholesteric liquid crystal layer obtained by immobilizing a cholesteric liquid crystalline phase, the cholesteric liquid crystal layer has a liquid crystal alignment pattern in which a direction of an optical axis changes while continuously rotating in at least one in-plane direction, and in a case where a position corresponding to 10% of a total thickness of the reflective layer from one surface to another surface side of the reflective layer is set as X, a position corresponding to 90% of the total thickness of the reflective layer is set as Y, a region from the one surface to X is set as a first region, a region from X to Y is set as a second region, and a region from Y to the other surface is set as a third region, at least one of birefringences in the first region and the third region is less than a birefringence in the second region.