Directional Backlight Waveguide for Autostereoscopic Displays

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Solution Overview

Problem

Spatially multiplexed autostereoscopic display devices suffer from reduced spatial resolution, image flicker, and non-uniform viewing windows due to gaps between pixels, which limit viewing freedom and increase visual strain, and existing solutions either reduce brightness or increase image cross-talk.

Innovation Solution

A directional backlight system utilizing a waveguide with opposed guide surfaces, reflective ends, and light sources arranged to inject light at specific positions, allowing for efficient and uniform illumination across the display, with light extraction features and rear reflectors to direct light into optical windows, reducing bezel size and enhancing viewing freedom.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If light sources are positioned at the edges of the waveguide, then device complexity is reduced, but illumination uniformity across the display area deteriorates

Engineering Contradiction:

Improvelight source arrangementVSAvoidillumination uniformity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The waveguide is divided into multiple sections with light sources positioned at different locations (edge and intermediate positions). Each light source illuminates a specific region, and the combined effect achieves uniform illumination across the entire display area while maintaining relatively simple device structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the waveguide are provided with light sources at different positions tailored to their specific illumination requirements. Intermediate light sources are positioned to address regions that would otherwise be poorly illuminated, creating locally optimized illumination quality throughout the display

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If pixel aperture shape is adjusted to reduce flicker, then image stability improves, but display brightness decreases

Engineering Contradiction:

Improveimage stabilityVSAvoiddisplay brightness

Core Design Contradiction:

Stability of the object's compositionVSIllumination intensity

Solution Approach 1:

The flicker reduction function is extracted from the pixel aperture modification approach and implemented instead through the directional backlight system with controlled light extraction features. This allows the pixel aperture to maintain its original shape for brightness while the backlight system provides the stability function

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The directional backlight system acts as an intermediary between the light source and the display panel. It provides stabilized, directionally controlled illumination that reduces flicker without requiring changes to the pixel aperture, thereby preserving display brightness

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If parallax component is aligned with pixel array, then autostereoscopic function is achieved, but viewing window uniformity deteriorates due to electrode gaps

Engineering Contradiction:

Improveautostereoscopic functionVSAvoidviewing window uniformity

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The directional backlight provides locally optimized illumination that compensates for the non-uniformities introduced by electrode gaps. By controlling light extraction at specific locations through the second guide surface, uniform viewing windows are achieved while maintaining the parallax component alignment for autostereoscopic function

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The asymmetric positioning of light sources and the non-uniform light extraction features on the second guide surface are designed to compensate for the symmetric but problematic electrode gap pattern. This asymmetric illumination approach creates uniform viewing windows despite the underlying asymmetric electrode structure

Inventive Principle:

Principle #4Asymmetry

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 achieves high brightness, reduced image flicker, and low cross-talk, providing efficient and uniform illumination while minimizing bezel size and enhancing longitudinal viewing freedom in autostereoscopic displays.

Implementation Method 1

a waveguide comprising first and second, opposed guide surfaces for guiding input light along the waveguide

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

the waveguide further comprising a reflective end for reflecting the input light back through the waveguide

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 3

the second guide surface being arranged to deflect the input light after reflection from the reflective end as output light through the first guide surface

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS10488578B2Light input for directional backlight

Publication Date: 2019.11.26 REALD SPARK LLC

AI summary

A directional backlight may include a light guiding apparatus including at least one transparent optical waveguide for providing large area collimated illumination from localized light sources. The waveguide is arranged in a first part and a second part with a light injection aperture between the respective parts. Such controlled illumination may provide for efficient, multi-user autostereoscopic displays as well as improved 2D display functionality including high brightness displays and high display efficiency.