Corrective optics for head mounted displays reducing screen door effect
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Solution Overview
Problem
Existing electronic display technologies face challenges in reducing fixed pattern noise, particularly the 'screen door effect,' due to the visibility of sub-pixel boundaries, which is exacerbated by magnification and difficult to control with multi-step fabrication processes like micro-lens arrays and dual gratings.
Innovation Solution
An electronic display assembly with a display element and a corrective element that diffuses light to reduce the apparent distance between sub-pixels, using features such as sinusoidal gratings, holographic diffusers, or square gratings to blur sub-pixels and mask dark spaces, thereby minimizing the visibility of sub-pixel boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnification of pixel is increased to improve display resolution, then image quality is improved, but boundaries between sub-pixels become visible resulting in increased fixed pattern noise
Solution Approach 1:
A corrective optical element is introduced as an intermediary between the display element and the user's eye. This element contains a plurality of features (such as microlens array or diffraction grating) that modify the light paths from sub-pixels, causing the dark spaces between adjacent sub-pixels to appear filled with light from neighboring sub-pixels, thereby masking the screen door effect while preserving the magnified image quality
2Object-generated harmful factors
If micro-lens array or dual gratings are used to reduce screen door pattern, then fixed pattern noise is reduced, but fabrication complexity increases due to multi-step processes and alignment requirements
Solution Approach 1:
The patent combines multiple optical functions (magnification and screen door effect reduction) into a single corrective optical element. This element integrates both a magnification portion and a corrective portion, eliminating the need for separate components and reducing fabrication steps. The unified structure allows for simpler manufacturing processes such as injection molding or stamping, while maintaining the dual functionality of magnifying the display image and reducing the visibility of sub-pixel boundaries
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 solution effectively reduces fixed pattern noise by blurring sub-pixels to mask dark spaces, improving image quality and reducing the 'screen door effect' while simplifying the manufacturing process and avoiding alignment errors.
Implementation Method 1
The corrective element has a plurality of features configured to diffract light emitted by the first plurality of sub-pixels such that an apparent distance between the two adjacent sub-pixels of the first type, viewed at a viewing distance away from the electronic display assembly, is less than the sub-pixel distance
Implementation Method 2
The corrective element has a plurality of features configured to diffuse light emitted by the first plurality of sub-pixels such that an apparent distance between the two adjacent sub-pixels of the first type, viewed at a viewing distance away from the electronic display assembly, is less than the sub-pixel distance
Data Source
AI summary
An electronic display assembly includes a display element and a corrective element coupled to the display element. The display element has a first plurality of sub-pixels of a first type and a second plurality of sub-pixels of a second type. Two adjacent sub-pixels of the first plurality of sub-pixel are separated by a sub-pixel distance. The corrective element has a plurality of features configured to diffuse light emitted by the first plurality of sub-pixels such that an apparent distance between the two adjacent sub-pixels of the first type, viewed at a viewing distance away from the electronic display assembly, is less than the sub-pixel distance.