Directional Backlight Waveguide for Autostereoscopic Displays
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Solution Overview
Problem
Autostereoscopic displays with spatially multiplexed light modulation suffer from reduced spatial resolution, non-uniform viewing windows, and image flicker due to gaps between pixels and the structure of the parallax component.
Innovation Solution
A directional backlight system comprising a waveguide with an array of input light sources and curved reflecting mirrors to direct light into viewing windows, with additional light sources along the side surfaces to fill illumination voids and improve spatial uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If additional light sources are added along the side surfaces to fill illumination voids, then spatial uniformity is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies local quality by placing additional light sources specifically at locations where illumination voids occur (along side surfaces adjacent to the input end) rather than uniformly distributing light sources throughout the waveguide. This targeted approach improves spatial uniformity only where needed, avoiding unnecessary complexity in regions where the primary light sources already provide adequate illumination.
2Illumination intensity
If the waveguide area is increased to reduce dark outer portions for off-axis viewing, then viewing quality is improved, but system size increases
Solution Approach 1:
The patent addresses off-axis viewing quality by adding light sources locally at strategic positions along the side surfaces, specifically targeting regions that contribute to dark outer portions. This localized enhancement improves viewing quality without requiring a proportional increase in the overall waveguide area, thus avoiding a linear increase in system size.
Solution Approach 2:
Instead of increasing the waveguide area (two-dimensional expansion) to eliminate dark outer portions, the patent introduces a third dimension by placing light sources along the side surfaces. This vertical/dimensional approach to illumination fills in the dark regions without expanding the horizontal footprint of the waveguide, effectively solving the viewing quality issue while maintaining compact system dimensions.
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 enhances spatial uniformity of the output light, reduces power consumption, and maintains high spatial uniformity, thereby improving the viewing experience and reducing system size and cost.
Implementation Method 1
a waveguide (1) comprising an input end (2); an array (15) of input light sources arranged at different input positions in a lateral direction across the input end (2) of the waveguide (1) and arranged to input input light into the waveguide (1)
Implementation Method 2
a reflective end (4) having positive optical power facing the input end (2) for reflecting the input light back along the waveguide (1)
Implementation Method 3
the reflective end (4) having positive optical power
Implementation Method 4
additional light sources (17a-n) arranged to direct additional light into the waveguide (1) through one of the side surfaces (22, 24)
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An imaging directional backlight apparatus including a waveguide, a light source array, for providing large area directed illumination from localized light sources. The waveguide may include a stepped structure, in which the steps may further 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 to provide discrete illumination beams exiting from the top surface of the waveguide. Viewing windows are formed through imaging individual light sources and hence defines the relative positions of system elements and ray paths. Lateral nonuniformities of output image are improved by means of adjustment of input aperture shape and reflective aperture shape. Cross talk in autostereoscopic and privacy displays may further be improved by light blocking layers arranged on the input end of the waveguide.