Planar Light Waveguide Illumination for Direct-View Displays
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Solution Overview
Problem
Current illumination units for direct-view displays, particularly for autostereoscopic and holographic applications, face challenges in achieving high refresh rates, homogeneous illumination, and precise collimation of light, which are essential for clear 3D presentations. Existing technologies struggle with the manufacturing complexity and cost-effectiveness of volume gratings, as well as the angular selectivity and diffraction efficiency required for these displays.
Innovation Solution
A flat illumination unit with a planar light waveguide featuring a deflection layer with a polarisation-sensitive function and a tapering cladding, combined with an electrowetting prism cell array, allows for controlled output coupling and deflection of light, enabling a narrower angular spectrum of plane waves and improved collimation. This design includes a volume grating with reduced thickness and increased angular selectivity, achieved through the use of the second Bragg's diffraction order, which simplifies production and enhances diffraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If volume gratings with high angular selectivity are used to achieve precise collimation, then the angular spectrum of plane waves is narrowed, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the physical parameters of the volume grating by reducing its thickness and utilizing the second Bragg diffraction order instead of the first. This parameter change achieves the desired angular selectivity and collimation while significantly reducing manufacturing complexity and cost compared to traditional thick volume gratings
Solution Approach 2:
Instead of using the conventional first Bragg diffraction order with thick gratings, the patent inverts the approach by using the second Bragg diffraction order with a reduced thickness grating. This inverted approach achieves the same or better angular selectivity while simplifying manufacturing
2Measurement precision
If the cladding thickness is reduced to improve light coupling, then the angular spectrum is narrowed, but the structural stability may be compromised
Solution Approach 1:
The patent applies local quality by creating a non-uniform cladding structure where the thickness varies along the direction of light propagation. The cladding is thicker at the input end and progressively thinner toward the output end, optimizing light coupling at each location while maintaining overall structural integrity through the gradual transition
3Productivity
If the refresh rate of the SLM is increased to achieve high-quality 3D presentation, then the image quality improves, but the required voltage and current increase
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing multiple frames of holographic data in advance. This allows the system to switch between pre-computed frames at high refresh rates without requiring real-time computation power, thereby achieving high productivity without proportionally increasing power consumption
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 enables high refresh rates, homogeneous illumination, and precise collimation of light, effectively addressing the limitations of existing technologies by reducing the thickness and production complexity of volume gratings, while maintaining high diffraction efficiency and allowing for full-color presentations with reduced tracking accuracy requirements.
Implementation Method 1
The injected light propagates through the planar LWG in the form of pencils of rays or wave fields under the conditions of total internal reflection (TIR)
Implementation Method 2
the planar light waveguide comprises on top of the cladding a deflection layer with a polarisation-sensitive function or with a specifiable output coupling characteristic for areally output coupling and deflecting the evanescent wave field of the light which propagates in the light waveguide
Implementation Method 3
achieved through the use of the second Bragg's diffraction order, which simplifies production and enhances diffraction efficiency
Data Source
AI summary
The present invention relates to a lighting device having a planer optical fiber and at least one light source device for illuminating a controllable spatial light modulator, wherein the optical fiber comprises a light-conducting core and a cover coating, and the light modulator comprises a pixel matrix, the light source device is disposed on the side of the optical fiber, and the light emitted by at least one light source of the light source device propagates laminarly in the optical fiber. The lighting unit according to the invention is characterized in that the planar optical fiber comprises a deflecting coating having a selective polarization function for laminarly decoupling and deflecting the evanescent wave field of the light propagating in the optical fiber, wherein the thickness of the cover coating reduces in the direction of light propagation.