Diffraction Grating Layer Reduces Screen Door Effect in Head-Mounted Displays
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Solution Overview
Problem
Head-mounted display devices suffer from a screen door effect (SDE) due to non-light-emitting areas being recognizable, which affects the quality of the image displayed, especially when images are expanded by lenses for virtual or augmented reality experiences.
Innovation Solution
A display device configuration that includes a display substrate, a light-emitting device, an encapsulation layer, a filling layer, a first cover layer, and a diffraction grating layer with isolated diffraction patterns on an opposite substrate, which expands the light-emitting area by diffracting light, reducing the screen door effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a lens is used to expand the image in head-mounted display devices, then the field of view and immersion experience are improved, but a screen door effect occurs where non-light-emitting areas become recognizable, degrading image quality
Solution Approach 1:
The patent introduces a diffraction grating layer that utilizes the spatial dimension of light propagation to create multiple virtual light-emitting areas through diffraction. By arranging diffraction patterns in a periodic structure, the system expands the effective light-emitting area in the horizontal direction without increasing the physical display area, thereby reducing the screen door effect while maintaining compact form factor suitable for head-mounted displays
Solution Approach 2:
The diffraction grating layer creates multiple duplicate light emission patterns by diffracting light from the original light-emitting device. These duplicate patterns are positioned at intervals corresponding to the period of the diffraction grating, effectively copying the light-emitting area multiple times across the horizontal direction. This increases the perceived light-emitting area and reduces the visibility of non-light-emitting areas, thereby mitigating the screen door effect
2Device complexity
If the diffraction grating layer is positioned closer to the light-emitting device, then the structure is simplified, but blurring increases and image quality deteriorates
Solution Approach 1:
The patent optimizes the position parameter of the diffraction grating layer relative to the light-emitting device and cover layer. By adjusting this distance parameter, the system achieves a balance between structural simplicity and image quality. The optimal position ensures sufficient separation to minimize blurring while maintaining a compact overall structure, and the periodic pattern design allows the diffraction effect to be achieved without requiring complex multi-layer structures
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 increases the light-emitting area and reduces blurring, providing a high-quality image in head-mounted display devices by minimizing the recognition of non-light-emitting areas, thus enhancing the virtual or augmented reality experience.
Implementation Method 1
the plurality of diffraction patterns may diffract light generated from the light-emitting device to generate a reference light emission pattern and a plurality of duplicate light emission patterns
Data Source
AI summary
A display device includes a display substrate, a light-emitting device, an encapsulation layer over the display substrate and encapsulating the light-emitting device, a filling layer on the encapsulation layer, a first cover layer on the filling layer, an opposite substrate on the first cover layer, and a diffraction grating layer disposed between the first cover layer and the opposite substrate, wherein the diffraction grating layer includes a plurality of diffraction patterns spaced apart from each other by a certain distance, and the plurality of diffraction patterns protrude from the surface of the opposite substrate in a direction perpendicular to the opposite substrate, and the surface of the opposite substrate faces the display substrate.