Dichroic Combiner Backlight for HMD Edge Lighting
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Solution Overview
Problem
Edge-lit backlights for liquid crystal displays (LCDs) using single layers of white LEDs have limited color gamut and brightness, making them less suitable for head-mounted displays (HMDs) which require improved illumination.
Innovation Solution
Incorporating a dichroic combiner with multiple color LEDs (red, green, and blue) that are optically coupled to direct and combine light efficiently, allowing edge-lighting without direct LED placement along the edges, enhancing brightness and color gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single layer of white LEDs is used for backlight illumination, then the device structure is simple, but the color gamut and brightness are limited
Solution Approach 1:
The backlight is segmented into multiple independent LED assemblies, each containing multiple color LEDs (red, green, blue) that can be independently controlled. This segmentation allows each LED to contribute to specific color components, collectively achieving superior color gamut and brightness while maintaining manageable structural complexity through modular design
Solution Approach 2:
Multiple color LEDs (red, green, blue) are merged within each LED assembly and their light outputs are combined through optical coupling to the LCD panel. This merging of multiple light sources with different spectral characteristics achieves enhanced color gamut and brightness that exceeds what a single white LED can provide
2Illumination intensity
If multiple color LEDs are used to improve color gamut and brightness, then the illumination quality improves, but the device structure becomes more complex
Solution Approach 1:
The complex multi-color LED system is divided into multiple identical modular LED assemblies. Each assembly contains a standardized set of color LEDs (red, green, blue) with consistent optical coupling structures. This segmentation into repeating modules makes the complex structure manageable, manufacturable, and maintainable while achieving the desired illumination quality
Solution Approach 2:
Each LED assembly is designed with specific local optical properties - the optical coupling structure is optimized for each assembly to efficiently combine the light from its specific color LEDs. This local optimization ensures that each module contributes maximally to the overall illumination quality, with the collective effect providing superior brightness and color gamut across the entire display
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 provides improved brightness and color gamut for HMDs by spatially superimposing and homogenizing light from multiple color LEDs, enhancing the overall illumination quality for LCD panels.
Implementation Method 1
The dichroic combiner includes a substrate to propagate the first, second, and third light, and a first dielectric layer disposed within the substrate. The first dielectric layer is configured to: receive the first light propagating at a second direction from the first color LED; transmit the first light propagating at the second direction to a second dielectric layer; receive the second light propagating at a third direction from the second color LED; and reflect the second light to propagate at the second direction to the second dielectric layer.
Implementation Method 2
The first dielectric layer is configured to reflect the second light to propagate at the second direction to the second dielectric layer. The second dielectric layer is configured to reflect the first light to propagate at the first direction to the light output region; receive the second light reflected from the first dielectric layer propagating at the second direction; reflect the second light to propagate at the first direction to the light output region.
Implementation Method 3
The light guide is configured to combine the first light, second light, and third light received from the light output region of the dichroic combiner into combined light to illuminate the LCD panel; and direct the combined light to the pixels of the LCD panel.
Data Source
AI summary
A liquid crystal display (LCD) device including a backlight with an LED assembly. The LED assembly includes a dichroic combiner and two or more different color LEDs. A substrate of the dichroic combiner receives color light from multiple color LEDs at different input regions and propagating in different directions. Dielectric layers within the substrate selectively reflect or transmit the color light to spatially superimpose the color light, and output the color light in a particular direction at a light output region of the substrate. The light output regions of LED assemblies are arranged behind an LCD panel, along one or more edges, to illuminate the LCD panel. The LED assembly provides edge-lighting without requiring LED placement along the one or more edges.