Directional Backlight Waveguide Segmentation for Vignetting
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Solution Overview
Problem
Spatially multiplexed autostereoscopic displays face issues with reduced spatial resolution, image flicker, and non-uniform viewing windows due to pixel gaps and the structure of parallax components, which limit viewing freedom and increase visual strain, while conventional backlights result in vignetting at high angles, reducing usable illumination area.
Innovation Solution
A directional backlight system with a waveguide and an array of light sources positioned laterally along its input surface, featuring reflective ends and light extraction features that image light into optical windows, and strips with refractive indices close to or differing from the waveguide to reduce light reflection and absorption, enhancing luminance control and privacy modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional backlights are used, then the display can be illuminated, but vignetting occurs at high angles reducing usable illumination area
Solution Approach 1:
The waveguide surface is segmented into multiple light extraction regions, each associated with a specific light source position. This segmentation allows different regions to extract light at different angles, eliminating vignetting and maximizing the usable illumination area across the entire waveguide surface.
Solution Approach 2:
Different regions of the waveguide are given different light extraction properties based on their position. Light extraction features are strategically placed and configured to optimize luminance distribution, ensuring that off-axis regions receive appropriate illumination without vignetting while maintaining overall luminance uniformity.
2Illumination intensity
If light extraction features are added to increase brightness, then illumination is improved, but system complexity increases
Solution Approach 1:
The waveguide structure is merged with integrated light extraction features that are formed as part of the waveguide manufacturing process. This integration eliminates the need for separate components, reducing system complexity while maintaining enhanced brightness through optimized light extraction at multiple positions.
3Object-affected harmful factors
If strips are added to reduce light reflection, then privacy and streak reduction are improved, but manufacturing complexity increases
Solution Approach 1:
The strips are designed with specific refractive index parameters that match or contrast with the waveguide material to optimize light reflection reduction. By carefully selecting strip material parameters and positioning, the patent achieves effective streak and reflection reduction while maintaining compatibility with standard manufacturing processes.
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 directional backlight system provides wide-angle viewing with reduced luminance for off-axis positions, increased brightness, and efficient light use, addressing the limitations of spatial resolution and flicker in autostereoscopic displays while minimizing image streaks and reflections.
Implementation Method 1
a waveguide comprising first and second, opposed guide surfaces for guiding light along the waveguide
Implementation Method 2
the waveguide further comprising a reflective end for reflecting input light from the light sources back along the waveguide
Implementation Method 3
the second guide surface being arranged to deflect the reflected input light through the first guide surface as output light
Implementation Method 4
the strips being arranged to reduce reflection of light incident thereon from inside the waveguide, the strip being adjacent to the input surface and extending along only parts of the at least one of the first guide surface and the second guide surface that are offset from the center of the input surface in the lateral direction
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An imaging directional backlight apparatus includes a waveguide and light source array for providing large area directed illumination from localized light sources. The waveguide may include a stepped structure in which steps may include extraction features optically hidden to guided light, propagating in a forward direction. Returning light propagating in a backward direction may be refracted, diffracted, or reflected by the features to provide discrete illumination beams exiting from the top surface of the waveguide. Viewing windows are formed through imaging individual light sources and defines the relative positions of system elements and ray paths. Alignment of the waveguide to mechanical and optical components may be provided by surface relief features of the waveguide arranged in regions adjacent the input surface and intermediate the light emitting regions of the light sources. Efficient, uniform operation may be achieved with low cross talk for application to autostereoscopic and privacy modes of operation.