Holographic Waveguide Layout for 2D Eye Box Expansion
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Solution Overview
Problem
Existing head-up displays face challenges in reducing volume, maintaining a wide eye motion box, and achieving high luminance while being cost-effective due to the limitations of multiple mirrors and waveguides, which require precise alignment and increase manufacturing complexity.
Innovation Solution
A holographic waveguide with multiple holographic optical elements and a phase delay film to guide light efficiently, allowing for two-dimensional expansion and minimizing optical loss, thereby downsizing the display and maintaining high luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple mirrors are used to direct light in the head-up display system, then the optical path can be secured between the display and windshield, but the total volume of the system cannot be reduced below about 10L
Solution Approach 1:
The patent combines multiple optical functions (collimation, diffraction, total internal reflection, and image projection) into a single waveguide component. The waveguide integrates the functions previously performed by separate mirrors and optical elements, allowing the system volume to be reduced below 10L while maintaining the necessary optical path between the display and windshield.
Solution Approach 2:
The waveguide acts as an intermediary component that receives light from the display, processes it through multiple holographic optical elements, and directs the final image to the windshield. This intermediary structure eliminates the need for multiple separate mirrors and complex alignment mechanisms.
2Adaptability or versatility
If two waveguides are used to expand incident light in vertical and horizontal directions, then the eye motion box can be expanded, but the structural volume reduction is limited and manufacturing precision requirements increase
Solution Approach 1:
The patent expands the eye motion box by utilizing multiple dimensions within a single waveguide structure. The first and second holographic optical elements expand light in one dimension, while the third and fourth elements expand in another dimension, achieving two-dimensional eye motion box expansion within a single integrated component rather than requiring precise alignment of multiple waveguides.
Solution Approach 2:
The patent merges the functions of multiple waveguides into a single waveguide component. The multiple holographic optical elements are integrated within one waveguide, eliminating the need for precise alignment between separate waveguide components while achieving the same eye motion box expansion effect.
3Adaptability or versatility
If multiple holographic optical elements are used to achieve two-dimensional expansion, then the eye motion box is expanded, but the device complexity increases
Solution Approach 1:
The waveguide is designed as a multi-functional component that performs collimation, diffraction, total internal reflection, and two-dimensional light expansion simultaneously. The multiple holographic optical elements are integrated within this single universal structure, allowing the device to achieve eye motion box expansion without proportionally increasing overall device complexity.
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 holographic waveguide achieves downsizing and high luminance by optimizing light guidance through diffraction and reflection, expanding the eye motion box for improved visibility and reducing manufacturing complexity.
Implementation Method 1
HOE H1 collimates the incident light from a source if the light is not already collimated, and diffracts it such that the light is trapped inside the substrate thereof by total internal reflection
Implementation Method 2
HOE H1 collimates the incident light from a source if the light is not already collimated, and diffracts it such that the light is trapped inside the substrate
Implementation Method 3
The optical waves diffracted from H2 are trapped in the substrate and propagate toward a third HOE H3. The phase delay film changes the phase and polarization of light waves passing through it
Data Source
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AI summary
Disclosed is a holographic waveguide including a light guide unit configured to guide lights; a first holographic optical element disposed on one surface or the other surface of the light guide unit such that a light output from a light source is input and guided on the light guide unit and configured to diffract an input light; a second holographic optical element disposed on any one of the one surface and the other surface of the light guide unit, and configured to receive a light diffracted by the first holographic optical element and guided through the light guide unit and to direct a part of the received light to the other one of the one surface and the other surface of the light guide unit by diffraction; a third holographic optical element disposed on a surface opposite to the surface of the light guide unit on which the second holographic optical element is disposed, and configured to receive lights diffracted by the second holographic optical element and to guide the received lights to areas, which are different from areas where the first and second holographic optical elements are disposed, on the light guide unit by diffraction; and a fourth holographic optical element configured to receive a light diffracted by the third holographic optical element, and to allow the received light to be output from the light guide unit by diffraction.