Directional Backlight Waveguide Facets for Autostereoscopic Displays
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Solution Overview
Problem
Spatially multiplexed autostereoscopic displays face issues with reduced spatial resolution, non-uniform viewing windows, image flicker, and increased image cross talk, which limit viewing freedom and display brightness.
Innovation Solution
A directional backlight system comprising a waveguide with an input end, an array of light sources, first and second guide surfaces, and a reflective end, along with a rear reflector with a linear array of reflective facets, to guide and reflect light into optical windows, achieving high gain and efficient optical output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If spatially multiplexed autostereoscopic displays use conventional backlighting, then device complexity is reduced, but display brightness and optical efficiency deteriorate
Solution Approach 1:
The waveguide surface is segmented into multiple discrete light extraction features (facets) arranged in arrays, with each facet directing light to specific viewing windows. This segmentation enables precise control of light direction to multiple viewers simultaneously, improving display brightness and viewing freedom without requiring complex tracking systems.
Solution Approach 2:
The patent transitions from conventional omnidirectional backlighting to directional lighting by introducing angular dimension control through tilted facets. The facets are oriented at specific angles to redirect light into predetermined viewing windows, adding directional control in the angular dimension while maintaining a relatively simple planar waveguide structure.
2Reliability
If conventional backlighting is used, then manufacturing precision requirements are reduced, but image flicker and viewing freedom are worsened
Solution Approach 1:
Different regions of the waveguide surface are given different local properties through varying facet orientations and arrangements. Specific facet arrays are optimized for different viewing windows, with each local region tailored to direct light to particular angular zones. This local quality approach ensures reliable viewing freedom for multiple positions without requiring extreme precision across the entire surface.
Solution Approach 2:
The viewing windows and facet orientations are predetermined during design based on expected viewer positions. The optical paths are pre-configured to direct light to specific angular zones, eliminating the need for real-time tracking or adjustment. This preliminary configuration ensures reliable viewing freedom while reducing manufacturing precision requirements compared to dynamic systems.
3Loss of energy
If light extraction features are added to the waveguide, then optical efficiency is improved, but device complexity increases
Solution Approach 1:
The light extraction features (facets) are integrated directly into the waveguide structure itself, combining the light guiding function with the light extraction function in a single component. The facets are formed as part of the waveguide surface, eliminating the need for separate extraction elements and reducing overall device complexity while improving optical efficiency.
Solution Approach 2:
The waveguide surface serves multiple functions: it guides light from the backlight source, extracts light at specific angles to create viewing windows, and directs light to different spatial zones for multiple viewers. This multi-functionality reduces the need for additional components, improving optical efficiency without proportionally increasing device complexity.
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 enhances display brightness and efficiency, reduces image flicker and cross talk, and provides improved viewing freedom without the need for tracking technologies, thereby increasing device lifetime and reducing costs.
Implementation Method 1
the first guide surface being arranged to guide light by total internal reflection
Implementation Method 2
the second guide surface having a stepped shape comprising: a plurality of facets oriented to reflect light from each of the light sources, after reflection from the reflective end, through the first guide surface into a respective optical window
Implementation Method 3
a reflective end facing the input end for reflecting the input light back through the waveguide
Implementation Method 4
a rear reflector comprising a linear array of reflective facets arranged to reflect light from the light sources, that is transmitted through the plurality of facets of the waveguide, back through the waveguide to exit through the first guide surface
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A directional display may include a waveguide. The waveguide may include light extraction features arranged to direct light from an array of light sources by total internal reflection to an array of viewing windows and a reflector arranged to direct light from the waveguide by transmission through extraction features of the waveguide to the same array of viewing windows. The brightness of the directional display can be increased. An efficient and bright autostereoscopic display system can be achieved.