Near Eye Display Waveguide Reflective Inclined Surface Ghost Image Reduction
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Solution Overview
Problem
Traditional near eye display devices suffer from ghost images due to secondary reflection stray light, affecting the visual quality and user experience.
Innovation Solution
The near eye display device incorporates a first waveguide element with a reflective inclined surface having distinct reflectivity distributions for different incident angle ranges and beam splitting elements with transflective coatings, ensuring that the image beam is not reflected twice, thereby preventing ghost images and maintaining good display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional near eye display uses a reflective inclined surface with uniform reflectivity, then the device structure is simple, but ghost images occur due to secondary reflection stray light
Solution Approach 1:
The reflective inclined surface is designed with spatially varying reflectivity: high reflectivity in the first incident angle range (for image beam) and low reflectivity in the second incident angle range (for stray light). This local quality differentiation eliminates ghost images while maintaining device simplicity.
Solution Approach 2:
The reflectivity parameter of the reflective inclined surface is changed as a function of incident angle. By adjusting the reflectivity parameter across different angle ranges, the system achieves both high image quality and effective stray light suppression without increasing structural complexity.
2Ease of manufacture
If beam splitting elements use conventional coatings, then manufacturing is easier, but display quality deteriorates due to wavelength-dependent reflectivity
Solution Approach 1:
The transflective coating is designed with specific optical parameters that achieve wavelength-insensitive reflectivity in the third incident angle range. This parameter optimization ensures consistent display quality across red, green, and blue wavelengths while remaining manufacturable.
Solution Approach 2:
The beam splitting element combines multiple layers including the transflective coating with specific optical properties. This composite structure achieves the desired wavelength-insensitive reflectivity characteristic while maintaining ease of manufacture through established coating techniques.
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 effectively reduces ghost images and enhances the visual quality by controlling secondary reflections, providing a better user experience with improved sight range and display quality.
Implementation Method 1
the image beam enters the first waveguide element via the first light incoming surface, and is reflected by the reflective inclined surface in the first waveguide element
Implementation Method 2
A surface of each of the plurality of first beam splitting elements is provided with a first transflective coating. The reflectivity of the transflective coating is insensitive to a wavelength change within a continuous incident angle range.
Data Source
AI summary
A near eye display device includes a display and a first waveguide element, the first waveguide element including a light incoming surface, a light exiting surface, a reflective inclined surface and beam splitting elements. An image beam provided by the display enters the first waveguide element via the light incoming surface and is reflected by the reflective inclined surface in the first waveguide element to the beam splitting elements, and is split by the beam splitting elements and leaves the first waveguide element via the light exiting surface. The reflective inclined surface has a first reflectivity distribution in a first incident angle range and a second reflectivity distribution in a second incident angle range. An angle in the second incident angle range is greater than an angle in the first incident angle range, and the first reflectivity distribution has a greater reflectivity average value than the second reflectivity distribution.