Co-Planar Waveguide Projection Display for Compact Cockpit HUDs
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Solution Overview
Problem
Conventional head-up displays are excessively large and bulky due to their spherical lens systems, making them unsuitable for restricted spaces such as aircraft cockpits, helmet-mounted, or head-mounted applications.
Innovation Solution
A compact projection display system utilizing plate-like waveguides with input and coupling gratings that match their dispersion characteristics to minimize chromatic aberration, allowing for a small image-providing light source and enabling a large field of view while maintaining image quality through waveguiding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional spherical lens systems are used to generate collimated display, then the display can provide a collimated image to the viewer, but the optical system becomes excessively large and bulky
Solution Approach 1:
The patent replaces conventional spherical lens systems with a waveguide-based optical system using diffraction gratings and total internal reflection. This substitution eliminates the need for large collimating lenses while maintaining the ability to generate collimated displays, thereby reducing the overall optical system size and volume.
Solution Approach 2:
The patent transitions from volumetric spherical lens systems to planar waveguide structures. By confining and guiding light within a thin plate-like waveguide using total internal reflection and diffraction gratings, the system achieves collimated display functionality in a two-dimensional plane rather than requiring three-dimensional lens assemblies, dramatically reducing system volume.
2Ease of manufacture
If diffractive gratings are used in waveguides, then chromatic dispersion occurs causing chromatic aberration in the displayed image
Solution Approach 1:
The patent acknowledges that diffractive gratings inherently produce chromatic dispersion, but converts this harmful effect into a beneficial one by deliberately designing the grating parameters to disperse different wavelengths in specific directions. The waveguide geometry and grating configurations are optimized so that chromatically dispersed light rays are guided and redirected to converge at the correct output locations, transforming the dispersion from a defect into a functional feature that enables wavelength-specific routing.
Solution Approach 2:
The patent employs precise control of grating parameters (period, orientation, depth) and waveguide geometric parameters (thickness, refractive index, shape) to manage chromatic dispersion. By adjusting these parameters, the system compensates for the inherent chromatic aberration of diffractive elements, ensuring that different wavelengths are properly directed and focused to maintain image quality without requiring additional corrective optical elements.
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 a compact, efficient, and aberration-free display that can provide a large field of view with a small optical system, suitable for restricted environments by using waveguiding techniques and matching grating dispersions to eliminate chromatic aberration, allowing for the use of small, cost-effective light sources.
Implementation Method 1
an input grating within the first plate-like waveguide for receiving the image bearing light and directing the light to propagate internally by total internal reflection
Implementation Method 2
a transmission grating on or within the first plate-like waveguide arranged to direct said image bearing light internally along the first plate-like waveguide
Implementation Method 3
a second plate-like waveguide which second plate-like waveguide includes a coupling grating arranged to receive the image bearing light from the first plate-like waveguide
Implementation Method 4
an exit grating arranged to diffract received image bearing light out of the second plate-like waveguide
Data Source
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AI summary
A projection display is provided including a first plate-like waveguide (7), an image providing light source device (10 and 11) located to inject image bearing light into the first plate-like waveguide 7. An input means (12) is provided on the waveguide (7) to reflect the image bearing light internally along the waveguide (7). A transmission grating (13) within the first plate-like waveguide (7) is provided to output image bearing light from the waveguide (7). A second plate-like waveguide (8) is located co-planar with the first plate-like waveguide (7) and has a coupling grating (17) therein to receive the image bearing light from the first plate-like waveguide (7). The second plate-like waveguide (8) also includes an exit grating (18) therein for diffracting the received image bearing light, diffracted by the coupling grating (17) out of the second plate-like waveguide (8) towards a viewer (6).