Segmented Imaging Directional Backlight for Autostereoscopic Displays
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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 gaps between pixels, which limit viewing freedom and increase visual strain, and existing solutions to reduce flicker either increase image cross-talk or compromise brightness and electronics.
Innovation Solution
A directional illumination apparatus with an imaging directional backlight system using waveguides and light extraction features that direct light into viewing windows, allowing for adjustable optical window profiles and independent control of light distribution to reduce image voids and enhance luminance, enabling privacy and wide-angle viewing modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If light extraction features are added to waveguide surfaces to direct light into viewing windows, then viewing freedom and luminance are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The waveguide surface is segmented into multiple light extraction features (prisms, gratings, or micro-lenses) distributed across the surface. Each feature independently directs light into specific viewing windows, enabling flexible control of light distribution and multiple viewing angles without requiring a completely new waveguide design
Solution Approach 2:
Light extraction features are added on the two-dimensional waveguide surface, transforming the otherwise planar light propagation into three-dimensional light redirection. This allows light to be extracted at various angles and positions, creating multiple viewing windows and improving viewing freedom without increasing waveguide thickness
2Illumination intensity
If curved light extraction features are used to reduce image voids at off-axis positions, then luminance uniformity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The light extraction features incorporate curvature and varying orientations along the waveguide surface, allowing the optical path to dynamically adapt to off-axis viewing positions. This dynamic light redirection compensates for the natural vignetting and image voids that occur at peripheral viewing angles, achieving uniform luminance distribution
Solution Approach 2:
The geometric parameters of light extraction features (curvature radius, orientation angle, spacing) are optimized to control light extraction efficiency at different positions. By varying these parameters across the waveguide surface, the system achieves uniform luminance output while maintaining manufacturability through standardized feature designs
3Adaptability or versatility
If multiple waveguides with different light extraction features are used to provide directional control, then viewing mode flexibility is improved, but system complexity and cost increase
Solution Approach 1:
Multiple waveguides are designed with different configurations of light extraction features, where each waveguide can serve multiple viewing modes (privacy mode, wide-angle mode, directional mode). This multi-functionality allows a single optical engine to support various display configurations, reducing the need for separate systems for each viewing mode
Solution Approach 2:
Different regions of the waveguide surface are equipped with locally optimized light extraction features tailored to specific viewing requirements. For example, certain areas may have features optimized for privacy mode while other areas support wide-angle viewing, allowing each region to perform its specialized function while contributing to the overall system flexibility
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 increased brightness, reduced image voids, and improved viewing freedom by directing light efficiently into viewing windows, allowing for both privacy and wide-angle viewing modes while maintaining uniform luminance and reducing system size and cost.
Implementation Method 1
The first light guiding surface may be arranged to guide light by total internal reflection
Implementation Method 2
The second light guiding surface comprises light extraction features and intermediate regions between the light extraction features, the light extraction features being arranged to deflect the reflected input light in directions allowing exit through the first guide surface
Data Source
AI summary
An imaging directional backlight apparatus includes a waveguide and a light source array, providing large area directed illumination from localized light sources. The waveguide may include a stepped structure, and the steps may further 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 define the relative positions of system elements and ray paths. The imaging directional backlight apparatus further includes multiple waveguides with light extraction features arranged to provide uniform output luminance at the seam between the waveguides.