Dual Waveguide Projection Display for Wide Field of View
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Solution Overview
Problem
Current head-mounted displays are limited in projecting color images over a wide field of view due to the inability of existing waveguide configurations to optimize diffraction gratings for a broad range of wavelengths, resulting in an unacceptably small exit pupil and restricted viewing angles, especially for color light sources.
Innovation Solution
The use of a dual-waveguide system with first and second waveguides, each equipped with input and output diffraction regions, to split and recombine image-bearing chromatic light across different ranges of field angles, allowing for a full-color image to be viewed over a larger range of angles, aligning with human peripheral and foveal vision capabilities without requiring additional optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single waveguide with fixed diffraction gratings is used, then the device complexity is low, but the field of view for color images is unacceptably small
Solution Approach 1:
The patent divides the waveguide system into multiple waveguides (first waveguide and second waveguide), each handling different ranges of field angles. The first waveguide handles a first range of field angles while the second waveguide handles a second range, allowing the system to achieve a broader overall field of view without requiring a single complex waveguide to handle all angles effectively
Solution Approach 2:
The patent extends the system from a single-waveguide one-dimensional configuration to a multi-waveguide configuration that operates across multiple dimensions of field angles. By stacking waveguides and assigning different angular ranges to each, the system achieves expanded field of view in the angular dimension without proportionally increasing complexity in other dimensions
2Adaptability or versatility
If diffraction gratings are optimized for a narrow band of wavelengths, then the manufacturing precision is easier to achieve, but the adaptability to broadband color light is poor
Solution Approach 1:
Each waveguide in the multi-waveguide system is equipped with diffraction gratings optimized for specific wavelength ranges and angular ranges. Rather than requiring a single grating to handle all wavelengths and angles perfectly, each waveguide segment has locally optimized gratings that work effectively for its designated portion of the overall field of view and spectral range
Solution Approach 2:
The multi-waveguide system achieves universal performance across broadband color light by combining multiple specialized waveguides. Each waveguide handles a specific portion of the spectral and angular range, and together they provide universal coverage for the full color spectrum and wide field of view, making the overall system adaptable to broadband light sources
3Adaptability or versatility
If a single waveguide handles all field angles, then the device complexity is low, but the exit pupil size becomes unacceptably small
Solution Approach 1:
The patent segments the angular handling function across multiple waveguides, with each waveguide responsible for a specific range of field angles. This segmentation allows each waveguide to maintain an adequate exit pupil for its designated angular range, while the combination of all waveguides provides a large effective exit pupil for the complete field of view
Solution Approach 2:
The multiple waveguides act as intermediaries that each handle specific portions of the light path for different angular ranges. By introducing these intermediate waveguide elements, the system achieves a larger effective exit pupil without requiring a single complex waveguide to handle all angles simultaneously
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 configuration enhances the field of view for color images, providing a wider horizontal field of view while maintaining a smaller vertical field, effectively addressing the limitations of previous technologies by ensuring color images can be seen over a broader range of angles, enhancing usability in applications like head-mounted displays for pilots.
Implementation Method 1
a waveguide assembly for expanding an input pupil of image-bearing light to an exit pupil and outputting the image-bearing light with the expanded exit pupil. In more detail, a waveguide 20 has an input diffraction region 22 for coupling image-bearing light with a small input pupil into the waveguide 20 for propagation by total internal reflection
Implementation Method 2
The second and third diffraction regions 26, 34 are arranged to expand the input pupil of the image-bearing light in first and second dimensions 25, 31 respectively
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The present invention provides a projection display (10) for projecting a color image to a viewer (12) overlaid on a real world scene viewed through the display. The display comprises an image generator (16) for generating image bearing chromatic light for injection into a waveguide assembly (28) at a first range of field angles (44) and a second range of field angles (46). The waveguide assembly comprises a first waveguide (30) having a first input diffraction region (32) arranged to couple image bearing chromatic light in the first range of field angles into the first waveguide to propagate by total internal reflection; and a second waveguide (40) having a second input diffraction region (42) arranged to couple image bearing chromatic light in the second range of field angles into the second waveguide to propagate by total internal reflection. The first and second waveguides have first and second output diffraction regions (48, 50) arranged to output image bearing chromatic light from the respective waveguides for projecting a color image in the first and second range of field angles to a viewer overlaid on a real world scene viewed through the waveguide assembly.