Optical Element with Liquid Crystal Alignment for AR Color Shift
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Solution Overview
Problem
Augmented reality glasses face the challenge of color shift due to wavelength-dependent light diffraction, requiring multiple light guide plates for each color, leading to a thick, heavy, and complex device configuration.
Innovation Solution
An optical element comprising optically-anisotropic members with liquid crystal compounds and a wavelength selective phase difference layer, where the liquid crystal alignment pattern's single period varies between members, allowing for reduced wavelength dependence of refraction angles and simultaneous emission of red, green, and blue light in the same direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple light guide plates are used for different colors to eliminate color shift, then color accuracy is improved, but device thickness and weight increase
Solution Approach 1:
The patent combines multiple light guide plates for different colors (red, green, blue) into a single integrated light guide plate. This is achieved by providing a single light guide plate with multiple diffraction elements, each having different diffraction characteristics for different wavelengths, thereby eliminating color shift without increasing device thickness through multiple separate plates.
Solution Approach 2:
The single light guide plate is designed to perform multiple functions by incorporating diffraction elements with different diffraction characteristics. Each diffraction element handles specific wavelength ranges (red, green, blue light), allowing one component to replace what would traditionally require multiple separate components, thus reducing overall device thickness and weight.
2Manufacturing precision
If multiple light guide plates are laminated for each color, then color shift is eliminated, but device complexity increases
Solution Approach 1:
The patent merges the functionality of multiple laminated light guide plates into a single light guide plate structure. By integrating multiple diffraction elements within one plate, the invention eliminates the need for complex lamination and alignment procedures while maintaining color accuracy, thereby reducing device configuration complexity.
Solution Approach 2:
Within the single light guide plate, the patent segments the optical path by providing multiple distinct diffraction elements, each optimized for specific wavelength ranges. This segmentation allows different color components to be handled separately within a unified structure, achieving color alignment without the complexity of multiple separate plates.
3Speed
If diffraction elements are used to introduce light at specific angles, then light propagation control is improved, but wavelength-dependent color shift occurs
Solution Approach 1:
The patent applies local quality by designing each diffraction element with specific diffraction characteristics tailored to particular wavelength ranges. Each diffraction element is optimized locally to handle red, green, or blue light differently, ensuring that light propagation control is achieved without wavelength-dependent color shift by matching diffraction properties to specific color components.
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 emission of light components with different wavelengths in the same direction, reducing the need for multiple light guide plates and simplifying the device configuration while maintaining high light transmission.
Implementation Method 1
an optical element that refracts transmitted light
Implementation Method 2
a wavelength selective phase difference layer that converts circularly polarized light in a specific wavelength range into circularly polarized light having an opposite turning direction
Implementation Method 3
light (projection light) projected from a display is diffracted (refracted) using a diffraction element to be incident into one end portion of a light guide plate
Data Source
AI summary
An object is to provide an optical element in which a wavelength dependence of refraction of transmitted light is small, and a light guide element including the optical element. The object can be achieved with an optical element including: a plurality of optically-anisotropic members including an optically-anisotropic layer that is formed using a liquid crystal compound and has a liquid crystal alignment pattern in which an optical axis rotates in an in-plane direction; and a wavelength selective phase difference layer that is disposed between two optically-anisotropic members and converts circularly polarized light in a specific wavelength range into circularly polarized light having an opposite turning direction, the optically-anisotropic layers of one optically-anisotropic member have the same liquid crystal alignment pattern, in a case where a length over which the direction of the optical axis rotates by 180° is set as a single period, the length of the single period in one or more optically-anisotropic members is different from that of another optically-anisotropic member, the liquid crystal compound of the optically-anisotropic layer is twisted and aligned, and the at least one optically-anisotropic member includes two optically-anisotropic layers having opposite twisted directions of twisted alignments of the liquid crystal compounds.