Waveguide Pupil Replicator Using Dammann Grating for Larger Eye-Box
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Solution Overview
Problem
Conventional pupil replicators for head-up displays are bulky and heavy, compromising the design goals of reducing size and weight while maintaining image quality and eye-box expansion.
Innovation Solution
A pupil replicator system utilizing a waveguide with a Dammann grating to create and align duplicate image beams within the waveguide, employing beam aligning devices such as prisms or holographic optical elements to ensure parallel and equally spaced beams, allowing for a thinner waveguide design that maintains image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional pupil replicators are used to expand the eye-box, then image continuity is maintained, but the device size and weight increase significantly
Solution Approach 1:
The patent replaces conventional mechanical beam splitting optics with a Dammann grating-based diffraction system. The Dammann grating uses optical diffraction to create multiple equal-intensity beams from a single input beam, eliminating the need for bulky mechanical beam splitters and mirrors. This substitution of mechanical components with a diffraction-based optical element significantly reduces the device weight while maintaining the eye-box expansion function.
Solution Approach 2:
The patent changes the optical parameters of the beam propagation by using a thin waveguide with specific refractive index characteristics. By controlling the waveguide thickness and refractive index, the system achieves efficient beam duplication and alignment without requiring thick optical components. This parameter optimization allows for a compact, lightweight design that maintains image quality and eye-box area.
2Area of stationary object
If conventional pupil replicators are used to expand the eye-box, then image continuity is maintained, but the device volume increases
Solution Approach 1:
The patent replaces conventional mechanical beam splitting optics with a Dammann grating-based diffraction system. The Dammann grating uses optical diffraction to create multiple equal-intensity beams from a single input beam, eliminating the need for bulky mechanical beam splitters and mirrors. This substitution of mechanical components with a diffraction-based optical element significantly reduces the device weight while maintaining the eye-box expansion function.
Solution Approach 2:
The patent utilizes the waveguide dimension to propagate duplicate beams laterally across the field of view. By confining and guiding light within the waveguide structure, the system achieves eye-box expansion in the lateral dimension without increasing the overall device volume. The thin waveguide acts as an optical circuit that distributes beams efficiently in three-dimensional space.
3Length of stationary object
If waveguide thickness is reduced to decrease device size, then device compactness improves, but gaps between image replications increase
Solution Approach 1:
The patent optimizes the waveguide thickness parameter to achieve the desired balance between compactness and image quality. By carefully selecting the waveguide thickness and refractive index, the system maintains proper beam spacing and overlap even in thin waveguides. The Dammann grating design is also optimized to produce the correct beam angles for the specific waveguide thickness, ensuring continuous image perception.
Solution Approach 2:
The patent uses preliminary beam alignment through the Dammann grating to pre-establish the correct angular relationships between duplicate beams before they enter the waveguide. This preliminary action ensures that even in thin waveguides, the beams will emerge at the correct positions and angles to maintain image continuity, compensating for the reduced propagation distance.
4Illumination intensity
If Dammann grating is used to create duplicate beams, then beam intensity equality improves, but device complexity increases
Solution Approach 1:
The patent replaces conventional mechanical beam splitting optics with a Dammann grating-based diffraction system. The Dammann grating uses optical diffraction to create multiple equal-intensity beams from a single input beam, eliminating the need for bulky mechanical beam splitters and mirrors. This substitution of mechanical components with a diffraction-based optical element significantly reduces the device weight while maintaining the eye-box expansion function.
Solution Approach 2:
The patent combines multiple functions into the single Dammann grating element: beam splitting, intensity equalization, and angular distribution. Instead of using separate optical components for each function, the Dammann grating performs all these operations simultaneously through its diffraction pattern, reducing the overall device complexity despite the sophisticated optical physics involved.
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 system achieves a smaller and lighter pupil replicator that ensures continuous image perception across a larger eye-box by reducing gaps between image replications, thus enhancing user experience without compromising image continuity.
Implementation Method 1
a Dammann grating adapted to create a plurality of duplicate image beams having equal intensity, each duplicate image beam being identical to the incoming image beam
Implementation Method 2
reflect each of the plurality of duplicate image beams within the waveguide
Implementation Method 3
a beam aligning device adapted to receive each of the plurality of duplicate image beams and to reflect each of the plurality of duplicate image beams at a common angle relative to the waveguide
Data Source
AI summary
A pupil replicator for a head up display system includes a waveguide adapted to receive an incoming image beam, and including a transparent body having a partially transmissive top surface and a reflective bottom surface, a Dammann grating adapted to create a plurality of duplicate image beams having equal intensity, and reflect each of the plurality of duplicate image beams within the waveguide, and a beam aligning device adapted to receive each of the plurality of duplicate image beams and to reflect each of the plurality of duplicate image beams at a common angle relative to the waveguide, wherein, after being reflected by the beam aligning device, each of the plurality of duplicate image beams are parallel to one another.