Waveguide Display Projector Alignment
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Solution Overview
Problem
Wide-screen augmented reality displays face challenges in achieving even illumination across the full width due to gaps between projectors, leading to undesirable optical effects like vertical striping when users change their perspective.
Innovation Solution
The use of a waveguide prism with input and output gratings allows light to be projected through different faces, enabling adjacent projectors to be positioned closely together, reducing gaps between fields of view and ensuring even illumination by aligning the edges of projectors on opposite sides of the waveguide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple input projectors are provided in parallel along the width of the display, then the desired augmentation image can be produced across the full width, but gaps between adjacent projectors produce undesirable optical effects like vertical striping
Solution Approach 1:
The patent applies dimensionality change by transitioning from a single-plane parallel projector arrangement to a multi-face three-dimensional arrangement. Projectors are positioned on opposite sides of the waveguide and project light through different faces (e.g., top and bottom faces) rather than adjacent faces. This spatial reconfiguration in three dimensions eliminates the gaps that cause vertical striping while maintaining full-width coverage, as the light paths through different faces do not create visible boundaries.
2Area of stationary object
If a single input projector with a pupil extending across the full width is provided, then the display can be illuminated across the full width, but the projector is expensive and complex to manufacture
Solution Approach 1:
The patent applies segmentation by dividing the single full-width projector into multiple smaller, standard projectors positioned on opposite sides of the waveguide. Each projector has a smaller, more manufacturable pupil size, yet collectively they illuminate the entire display width by projecting through different faces of the waveguide. This segmentation reduces individual projector complexity and cost while achieving the same overall coverage.
Solution Approach 2:
The patent merges the output of multiple separate projectors by having them project through different faces of the same waveguide. The waveguide acts as a common medium that combines the light paths from multiple projectors into a unified augmented reality display. This merging allows standard projectors to function together as a system equivalent to a single large projector, reducing cost and complexity.
3Volume of moving object
If expansion optics are provided to expand the field of view across the width of the display, then a smaller projector can be used, but the expansion optics take up significant space below the display
Solution Approach 1:
The patent uses dimensionality change to relocate the field-of-view expansion function from below the display to the waveguide structure itself. By utilizing the waveguide's three-dimensional geometry and having projectors on opposite sides project through different faces, the system achieves wide-field expansion without requiring additional expansion optics in the vertical space below the display. The waveguide's inherent optical path length and face geometry provide the expansion function.
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 improves the user experience by eliminating gaps between projector fields of view, providing continuous and even illumination across the display width, enhancing the viewing experience with reduced optical distortions.
Implementation Method 1
Light from the projector is coupled into the waveguide by a diffraction grating
Implementation Method 2
The projected light is totally internally reflected within the waveguide
Implementation Method 3
The light is then coupled out of the waveguide by another diffraction grating
Data Source
AI summary
A display system is disclosed for use in an augmented reality display (30), the system comprises a waveguide (32) having a front surface and a rear surface. A front input projector (34) projects polychromatic light through a front surface, and a back input projector (36) projects polychromatic light through the rear surface. Input light impinges on an input grating (38) on a rear surface of the waveguide (32), and light travels through the waveguide by total internal reflection. An output grating (40) is provided for coupling light out of the waveguide. A plurality of front and back input projectors (34, 36) are provided in a staggered configuration along the width of the waveguide (32) and respective edges of adjacent front and back input projectors are aligned along the width of the waveguide to permit a continuous projection of light.