Waveguide Beam Shaping for Uniform Coherent Backlight
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Solution Overview
Problem
Existing optical devices are not suitable for compact, reliable, and efficient distribution of coherent light over a larger area, particularly for holographic displays, due to issues with temperature and humidity sensitivity, phase definition, and inefficient beam shaping.
Innovation Solution
An optical device comprising multiple waveguides and beam shaping structures that guide and manipulate light beams to achieve well-defined phases and uniform illumination, using techniques like total internal reflection and optical shaping elements to maintain coherence and reduce interference, with optional interferometer structures for temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single waveguide with beam shaping structure is used, then the device complexity is reduced, but the uniformity of illumination and phase definition deteriorate
Solution Approach 1:
The patent divides the single waveguide into multiple waveguides (first waveguide, second waveguide, etc.), each guiding light to separate beam shaping structures. This segmentation allows each waveguide-beam shaping structure combination to maintain well-defined phase relationships independently, while the overall device achieves uniform illumination across multiple light emitting areas through coordinated operation of multiple segments.
2Area of stationary object
If lenses are used to expand laser beam to large diameter, then the illumination area is increased, but the device dimensions and complexity increase
Solution Approach 1:
The patent transitions from using lenses in a conventional spatial arrangement to using waveguides that propagate light in confined dimensions with evanescent field coupling. Multiple beam shaping structures are arranged in a planar configuration within the waveguide layer, enabling large illumination area without proportionally increasing device thickness or overall complexity.
Solution Approach 2:
The waveguide acts as an intermediary structure that couples light from a compact laser source to multiple beam shaping structures. The evanescent field coupling mechanism allows efficient light distribution across multiple waveguides without requiring large optical components, thereby achieving large illumination area with compact device dimensions.
3Volume of stationary object
If holographic volume gratings are used, then the compactness is improved, but the stability to temperature and humidity changes deteriorates
Solution Approach 1:
The patent extracts the beam shaping and light distribution function from the holographic volume grating structure. Instead of relying on the grating's diffraction properties that are sensitive to environmental changes, the invention uses separate beam shaping structures coupled to waveguides, which provide stable phase definition and temperature compensation capabilities independent of humidity and temperature fluctuations.
4Device complexity
If a single light source is used, then the device complexity is reduced, but the uniformity of illumination over larger area deteriorates
Solution Approach 1:
The patent segments the single light source into multiple virtual sources by distributing light from one physical laser through multiple waveguides to separate beam shaping structures. Each waveguide-beam shaping structure combination creates a localized light emitting area with uniform illumination characteristics, and the overall device achieves large-area uniform illumination through the coordinated operation of multiple segmented units.
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 device provides stable, coherent, and uniform illumination over a larger area, maintaining phase definition despite temperature changes, and allows for a compact design, suitable for holographic displays and other applications like 3D sensing and LiDAR.
Implementation Method 1
using techniques like total internal reflection and optical shaping elements to maintain coherence
Implementation Method 2
at least a first beam shaping structure with a first light emitting area for emitting a light beam... configured such that the uniformity of the radiant density profile of a light beam emitted from the first light emitting area is higher than that of the light beam guided to the first beam shaping structure by the first waveguide
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Optical device (1) for controlling light from an external light source (2) comprising: at least a first and a second waveguide (3, 4) for guiding a light beam emitted from the external light source (2); and at least a first beam shaping structure (5) with a first light emitting area (6) for emitting a light beam and a second beam shaping structure (7) with a second light emitting area (6) for emitting a light beam, wherein the first waveguide (3) guides the light beam emitted from the external light source (2) to the first beam shaping structure (5) and the second waveguide (4) guides the light beam emitted from the external light source (2) to the second beam shaping structure (7); wherein the first and the second beam shaping structure (5, 7) are each configured such that the uniformity of the radiant density profile of a light beam emitted from the respective light emitting area (6, 8) of the respective beam shaping structure (5, 7) is higher than that of the light beam guided to the respective beam shaping structure (5, 7) by the respective waveguide (3, 4). Backlight unit (22) comprising such an optical device (1); and optical system, in particular holographic display, comprising such a backlight unit (22) and a spatial light modulator (17).