Waveguide Display Assembly for 3D Head-Up Displays
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Solution Overview
Problem
Autostereoscopic 3D head-up displays using waveguides face challenges in maintaining image quality due to brightness gradients caused by diffraction efficiency gradients in holographic materials, which are not applicable in systems with switchable Bragg grating elements, and conventional waveguides are not designed for 3D imaging as they emit light for both eyes simultaneously.
Innovation Solution
A waveguide display assembly with a passband filter layer divided into independently switchable area segments, synchronized with an image-generating unit to ensure that only one eye receives the 2D image, using a conventional waveguide that emits light over its entire surface, eliminating the need for additional homogenization measures and maintaining uniform image illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switchable Bragg grating elements are used to enable autostereoscopic 3D imaging, then the ability to display separate images for each eye is improved, but brightness uniformity deteriorates due to diffraction efficiency gradients in holographic materials
Solution Approach 1:
The waveguide display assembly divides the light-emission surface into multiple independently controllable segments. Each segment can be selectively activated to emit light for either the left eye or right eye, enabling separate image delivery to each eye while allowing compensation for brightness variations through independent segment control
Solution Approach 2:
Different segments of the light-emission surface are assigned different functional properties - some segments are optimized for left-eye image delivery while others are optimized for right-eye image delivery. This local differentiation enables simultaneous optimization for 3D imaging capability and brightness uniformity across different viewing zones
2Ease of manufacture
If a conventional waveguide is used that emits light over its entire surface, then image homogenization is simplified, but the ability to deliver separate images to each eye for 3D imaging is lost
Solution Approach 1:
The waveguide's light-emission surface is segmented into multiple independently controllable regions. This segmentation enables selective activation of specific segments to deliver images to specific eyes, providing autostereoscopic 3D capability while maintaining the advantage of using a conventional waveguide structure that naturally provides uniform illumination across its surface
3Illumination intensity
If the entire light-emission surface is activated simultaneously, then image brightness is maximized, but cross-talk between left and right eye images occurs
Solution Approach 1:
The waveguide display assembly dynamically controls the activation state of different segments of the light-emission surface. Segments are activated or deactivated in real-time based on which eye should receive light, enabling maximum brightness when the correct segment is active while preventing cross-talk by ensuring only the appropriate segment emits light at any given moment
Solution Approach 2:
The system employs periodic or sequential activation of different segments corresponding to left-eye and right-eye images. By alternating or synchronizing the activation of segments with the display refresh rate, the system delivers separate images to each eye over time while maintaining the perception of simultaneous 3D imagery, thus preventing cross-talk while preserving brightness
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
This solution achieves high-quality autostereoscopic 3D imaging without brightness gradients, enhancing the suitability of the display for vehicles by ensuring that image content for one eye does not reach the other eye's spatial region, thus improving image quality and efficiency.
Implementation Method 1
a passband filter layer (6) which completely covers the light-emission surface (4) and which, in this covered area, is divided into a plurality of area segments (61, 62, 63) that can be switched to light transmission independently of one another
Implementation Method 2
a planar waveguide (optical waveguide), the installation space required for the HUD in relation to the size of the virtual image can be considerably reduced
Data Source
AI summary
A waveguide display assembly includes a flat waveguide; a passage filter layer, which is divided into a plurality of area segments, which can be switched to light passage independently of each other; an image-generating unit, which is configured to generate different 2D images, each of which is intended only for one eye of a user for autostereoscopic 3D presentation, and to couple the 2D images into the waveguide in the form of collimated light beams, the propagation directions of which correspond to individual pixels; and a control unit, which is configured to control the image-generating unit and the passage filter layer such that only one or a subset of the area segments is switched to light passage at a time and, synchronously therewith, the image-generating unit generates only one image area segment of the 2D image intended for one eye of the user.