Pancharatnam-Berry Phase Lens With Segmented Anisotropic Layers
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Solution Overview
Problem
Existing Pancharatnam-Berry phase optical elements (PB lenses) face challenges in achieving broadband diffraction efficiency and shorter focal lengths due to non-ideal wavelength dispersion in reactive mesogen (RM) layers and the need for precise alignment accuracy in multiple mask exposures.
Innovation Solution
The proposed optical element structure includes multiple optically anisotropic layers with specific alignment films and phase differences, allowing for improved alignment and phase control. This structure includes a first and second optically anisotropic layer with specific phase differences and alignment angles, and optionally a third layer, to enhance diffraction efficiency and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single optically anisotropic layer is used to achieve half-wave plate function, then the device complexity is reduced, but the diffraction efficiency cannot be maintained across broadband wavelengths due to non-ideal wavelength dispersion
Solution Approach 1:
The patent divides the single optically anisotropic layer into multiple layers (first, second, and optionally third layers), each with specific phase differences (120-150nm, 150-350nm, and 120-150nm respectively). This segmentation allows each layer to contribute differently to the overall optical function, enabling broadband diffraction efficiency while maintaining manageable device complexity through systematic design.
2Manufacturing precision
If multiple mask exposures are used to produce PB lens with specific molecular alignment, then the alignment precision can be improved, but the manufacturing time and process complexity increase
Solution Approach 1:
The patent introduces alignment films between optically anisotropic layers that pre-establish the required molecular alignment directions. This preliminary alignment setup allows subsequent layers to be formed with correct orientation without requiring complex multiple mask exposures, thereby reducing production time while maintaining high alignment precision.
3Length of moving object
If the focal length of PB lens is shortened, then the optical performance is improved, but the required alignment accuracy in multiple mask exposures becomes more stringent
Solution Approach 1:
The alignment films are used to pre-establish the molecular alignment directions before forming the optically anisotropic layers. This preliminary action ensures that even for short focal length PB lenses requiring high alignment accuracy, the correct orientation is achieved without needing extremely precise multiple mask exposures, thus enabling short focal lengths with practical manufacturing precision.
4Length of moving object
If the molecular rotation period is shortened to achieve shorter focal length, then the optical performance is improved, but the mask alignment accuracy requirement becomes more stringent
Solution Approach 1:
The alignment films are applied beforehand to define the molecular rotation directions. This preliminary action allows the molecules to align along predetermined paths with shorter rotation periods, eliminating the need for extremely precise mask alignment during the formation process. Thus, short molecular rotation periods can be achieved with practical mask alignment accuracy.
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 enables the achievement of high diffraction efficiency over a broad visible wavelength range and facilitates the production of PB lenses with shorter focal lengths, while simplifying the production process by reducing the required alignment accuracy.
Implementation Method 1
an optically anisotropic layer formed from a liquid crystal composition containing liquid crystal molecules
Implementation Method 2
an optical system including an optical element such as a Pancharatnam-Berry phase optical element (PBOE)
Implementation Method 3
a polarization sensitive photo-alignment layer (2) and a liquid crystal composition (3) arranged on said alignment layer (2), wherein an anisotropic alignment pattern corresponding to a polarization hologram is arranged in said photo-alignment layer and said liquid crystal composition (3) is aligned by said alignment pattern
Data Source
AI summary
Provided is an optical element that can achieve favorable optical characteristics. The optical element of the present invention includes, in the following order: a first alignment film; a first optically anisotropic layer containing a first anisotropic molecules; a second alignment film; and a second optically anisotropic layer containing a second anisotropic molecules.