Curved Waveguide Combiner for HMDs
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Solution Overview
Problem
Current head-mounted and helmet-mounted displays (HMDs) face challenges in maintaining a lightweight and aesthetically appealing design with a curved combiner that minimizes wavefront errors and provides a collimated image, particularly in avionic and military applications where degraded visual environments require enhanced situational awareness and mission-critical information.
Innovation Solution
The implementation of a curved substrate waveguide combiner with an asymmetric optical system that pre-aberrates light to reduce wavefront errors, using a cylindrical or elliptical waveguide shape, and an input and output mechanism for total internal reflection, allowing for collimated light to be projected as a collimated virtual window or HUD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a curved combiner is used in HMDs, then the aesthetic appeal and field of view are improved, but wavefront errors increase and image quality deteriorates
Solution Approach 1:
The asymmetric projector pre-aberrates the light before it enters the curved waveguide combiner. This preliminary action of introducing controlled aberrations compensates for the wavefront errors that will be introduced by the curved combiner, ensuring that the final output image maintains acceptable wavefront quality and collimation
Solution Approach 2:
An asymmetric optical system is employed in the projector to counterbalance the symmetric curvature of the waveguide combiner. The asymmetric lens elements and optical path design create compensating aberrations that specifically address the wavefront errors induced by the curved combiner geometry
2Weight of moving object
If a curved substrate waveguide is used, then the device becomes lightweight and aesthetically attractive, but wavefront errors and collimation issues arise
Solution Approach 1:
The optical system pre-aberrates the light in advance to compensate for the wavefront errors that will be introduced by the curved waveguide. This preliminary correction ensures that despite the lightweight curved design, the final output maintains acceptable collimation and image quality
Solution Approach 2:
The asymmetric optical system modifies the light parameters (wavefront shape, ray angles) before entry into the waveguide. By changing the input light parameters to account for the curved geometry, the system maintains collimation quality while using a lightweight curved structure
3Device complexity
If traditional optical systems are used with curved combiners, then the design is simpler, but wavefront errors and image quality issues occur
Solution Approach 1:
Rather than using complex curved optics or multiple corrective elements, the system employs an asymmetric projector design that introduces controlled aberrations to counterbalance the curved combiner. This asymmetric approach achieves image quality correction with relatively simple optical components
Solution Approach 2:
The system converts the harmful wavefront errors introduced by the curved combiner into a beneficial solution by pre-introducing complementary aberrations. The asymmetric projector transforms the potential image quality problem into an opportunity for simplified optical design, avoiding the need for complex corrective optics
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 effectively reduces wavefront errors and maintains image quality, providing a lightweight and aesthetically attractive HMD or HUD with improved situational awareness and mission-critical information display, suitable for various environments including aviation and military use.
Implementation Method 1
Light from the projector enters the curved substrate waveguide and is ejected from the curved substrate waveguide via a suitable mechanism toward a user. After bouncing between surfaces of the curved substrate waveguide, the light is ejected as collimated light.
Implementation Method 2
The light is pre-aberrated to reduce wavefront errors due to the curved shape of the curved substrate waveguide. The asymmetric optical system is pre-aberrated to reduce wavefront errors associated with the curved waveguide combiner.
Implementation Method 3
After bouncing between surfaces of the curved substrate waveguide, the light is ejected as collimated light.
Data Source
AI summary
A head mounted or helmet mounted display (HMD), head up display (HUD, or collimated virtual window can be used in various applications including but not limited to avionic applications. The HMD, HUD, or collimated virtual window can include a cylindrical, elliptical, or curved substrate waveguide combiner. The cylindrical or curved substrate waveguide combiner can be used with a projector which provides pre-aberrated light. The cylindrical substrate waveguide combiner provides collimated light to a user with reduced wavefront errors.