Stepped Waveguide for Autostereoscopic Display Illumination
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Solution Overview
Problem
Autostereoscopic displays face limitations in spatial resolution, image flicker, and cross-talk due to the alignment of parallax components and pixel apertures, leading to reduced viewing freedom and increased visual strain, while conventional backlights result in dark outer portions and inefficient use of light guide area due to vignetting at high angles.
Innovation Solution
A directional display device with a stepped waveguide and optical valve structure that directs light from multiple sources through a display panel to form viewing windows, using a reflective end and light extraction features to achieve wide-angle viewing and efficient illumination, allowing for time multiplexed autostereoscopic displays with high resolution and reduced flicker and cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional backlights are used with rectangular waveguides, then the structure is simple and easy to manufacture, but dark outer portions appear at off-axis positions reducing illumination uniformity
Solution Approach 1:
The waveguide structure is segmented into multiple regions with different functions: a first light input region for light sources, a light guiding region for light propagation, and a second light output region for light extraction. This segmentation allows optimization of light distribution to eliminate dark outer portions while maintaining manufacturing feasibility through standardized component assembly.
Solution Approach 2:
The patent transitions from a conventional 2D rectangular waveguide to a 3D stepped waveguide structure with multiple levels and regions. This dimensional change enables complex light path control and uniform illumination distribution across the output surface, solving the off-axis dark region problem while maintaining ease of manufacture through modular construction.
2Adaptability or versatility
If imaging directional backlights are used to direct light through display panels, then viewing windows are formed, but vignetting at high angles creates dark outer portions reducing usable backlight area
Solution Approach 1:
Different regions of the waveguide are assigned different optical properties and functions. The first light input region accepts light from sources, the light guiding region maintains total internal reflection, and the second light output region extracts light at optimized angles. This local quality differentiation eliminates vignetting effects and maximizes usable backlight area while maintaining viewing window functionality.
3Illumination intensity
If light extraction features are added to the waveguide, then light distribution is improved, but device complexity increases
Solution Approach 1:
The waveguide is divided into distinct functional regions (light input, light guiding, light output) with each region having optimized characteristics. This segmentation achieves uniform light distribution without requiring complex extraction features throughout the entire waveguide structure, thereby controlling device complexity while improving illumination uniformity.
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 wide-angle viewing with high uniformity and efficiency, reducing image flicker and cross-talk, and enabling the use of a thin optical structure for large area displays, while minimizing dark outer portions and enhancing display brightness.
Implementation Method 1
a waveguide comprising first and second, opposed guide surfaces for guiding light along the waveguide
Implementation Method 2
a reflective end for reflecting the 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
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. A rear reflector is arranged to receive light transmitted by the features and to provide polarization recirculation. Viewing windows are formed through imaging individual light sources and hence defines the relative positions of system elements and ray paths. Retarder stack arrangements are provided to increase the efficiency of polarization recirculation, reduce the visibility to damage and to reduce color changes with viewing angle.