Wide Angle Imaging Directional Backlights With Inclined Input Facets
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Solution Overview
Problem
Spatially multiplexed autostereoscopic displays suffer from reduced spatial resolution, image flicker, and non-uniform viewing windows due to the structure of pixel apertures and parallax components, limiting viewing freedom and causing visual strain.
Innovation Solution
A directional backlight system with a waveguide and array of light sources is used, where the waveguide has inclined input facets and a reflective end with positive optical power, directing light into optical windows distributed based on light source positions, and a control system adjusts light sources to compensate for illumination voids, enhancing uniformity and reducing stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional waveguide with planar input facets is used, then the structure is simple and easy to manufacture, but illumination uniformity is poor and dark outer portions appear for off-axis viewing positions
Solution Approach 1:
The patent applies asymmetry by introducing inclined input facets instead of planar facets. The inclined facets are angled relative to the waveguide axis, creating asymmetric light input geometry that directs light more effectively into the waveguide core and eliminates dark outer portions for off-axis viewing positions, thereby improving illumination uniformity across the display area.
Solution Approach 2:
The patent introduces a new geometric dimension by tilting the input facets at specific angles rather than keeping them parallel to the waveguide axis. This angular dimensionality change allows light to be directed into the waveguide at optimized angles, improving light distribution and eliminating the dark outer portions that appear with conventional planar facets.
2Illumination intensity
If light sources are positioned to illuminate the entire waveguide area, then brightness is increased, but viewing angle control deteriorates and cross-talk increases
Solution Approach 1:
The patent applies local quality by positioning individual light sources at specific lateral locations corresponding to their respective optical windows. Each light source illuminates a localized region of the waveguide that maps to a specific viewing angle range, ensuring that light is distributed uniformly across the display area while maintaining precise viewing angle control and minimizing cross-talk between adjacent viewing zones.
3Area of stationary object
If the waveguide uses a simple rectangular structure, then manufacturing is easier, but off-axis viewing positions create dark outer portions that reduce usable illumination area
Solution Approach 1:
The patent modifies the simple rectangular waveguide structure by introducing inclined input facets. These asymmetric facets are integrated into the waveguide fabrication process and enable the entire waveguide area to be utilized for illumination by directing light effectively to off-axis viewing positions, thereby increasing the usable illumination area without significantly complicating manufacturing.
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 lateral uniformity and reduced image flicker, increasing brightness and reducing stray light, allowing for wider angle viewing and efficient autostereoscopic displays with high uniformity and low cross-talk.
Implementation Method 1
a waveguide for guiding light, the waveguide comprising an input end and first and second, opposed light guiding surfaces for guiding the input light along the waveguide
Implementation Method 2
a reflective end facing the input end for reflecting the input light guided from the input end back through the waveguide
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An imaging directional backlight apparatus includes a waveguide and a light source array for providing large area directed illumination from localized light sources. The waveguide may include a stepped structure. The steps may include extraction features optically hidden to guided light, propagating in a first forward direction. Returning light propagating in a second backward direction may be refracted, diffracted, or reflected by the features, providing discrete illumination beams exiting from the top surface of the waveguide. Viewing windows are formed through imaging individual light sources and define the relative positions of system elements and ray paths. The uncorrected system creates non-illuminated void portions when viewed off-axis preventing uniform wide angle 2D illumination modes. The input end may have microstructures arranged to remove this non uniformity at wide angles. The microstructures may have reduced reflectivity for parts of the input end that contribute to stray light in privacy and autostereoscopic modes.