Head-Mounted Display Diffractive Elements Screen-Door Effect
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Solution Overview
Problem
Pixelated displays often exhibit the screen-door effect due to gaps between adjacent pixels and subpixels, which can be objectionable in head-mounted displays where the optical system magnifies the image, leading to visible artifacts.
Innovation Solution
The use of different diffractive elements for each eye in a head-mounted display, where each element is optimized to reduce the screen-door effect for specific wavelengths, such as green and red, by configuring them to produce zero and first diffraction orders with intensities within 5% of each other for their respective wavelengths, thereby minimizing the perceived screen-door effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixelated displays are used in head-mounted displays, then the display can be compact and provide sufficient resolution, but gaps between pixels create the screen-door effect which is objectionable to viewers
Solution Approach 1:
A diffractive element is introduced as an intermediary component between the pixelated display and the viewer's eye. This diffractive element diffracts light from each pixel into multiple diffraction orders, creating virtual images of pixels that fill the gaps between actual pixels, thereby eliminating the screen-door effect while preserving the compact pixelated display structure
Solution Approach 2:
The invention transforms the problem from a two-dimensional pixel arrangement to a three-dimensional optical path manipulation. By using diffraction to create multiple virtual image planes at different depths, the solution adds a temporal/directional dimension to pixel presentation, allowing continuous perceived images without increasing physical pixel density
2Object-affected harmful factors
If different diffractive elements are used for each eye, then the screen-door effect is reduced for specific wavelengths, but the device complexity increases
Solution Approach 1:
Each diffractive element is customized with specific diffraction properties optimized for its corresponding eye and wavelength range. The left and right diffractive elements have different grating configurations tailored to reduce screen-door effect for their respective viewing paths, applying local optimization rather than a uniform solution
Solution Approach 2:
The invention varies key parameters of the diffractive elements including grating period, grating depth, and refractive index to optimize performance for different wavelengths and viewing angles. By adjusting these parameters, each diffractive element is tuned to minimize screen-door effect for its specific application while maintaining manufacturability
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 approach significantly reduces the perceived screen-door effect in head-mounted displays without compromising resolution, as the brain integrates the images from each eye to form a common perceived image, providing a more seamless viewing experience.
Implementation Method 1
The first diffractive element is configured to diffract a first wavelength λ1, but not a different second wavelength λ2, into zero and first diffraction orders having intensities within 5% of each other
Data Source
AI summary
Headsets and head-mounted displays including first and second diffractive elements are described. In some cases, the first and second diffractive elements include first and second grating surfaces, and for at least one wavelength, the first and second grating surfaces have at least one different corresponding diffractive property. The head-mounted display may include two-dimensionally pixelated adjacent first and second display surfaces for displaying images, and first and second diffractive elements disposed adjacent the respective first and second display surfaces. In some cases, the first diffractive element is configured to diffract a first wavelength λ1, but not a different second wavelength λ2, into zero and first diffraction orders having intensities within 5% of each other, and the second diffractive element is configured to diffract the second wavelength λ2, but not the first wavelength λ1, into zero and first diffraction orders having intensities within 5% of each other.