Curved Optical Combiner Mapping for Undistorted AR Rendering

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Solution Overview

Problem

Existing augmented reality systems with curved optical combiners face challenges in accurately projecting undistorted images due to non-bijective mappings between display pixels and reflection locations, leading to warped and distorted perceptions.

Innovation Solution

An iterative search method is employed to determine the mapping between display pixels and reflection locations on a semi-reflective surface, adjusting the input image to compensate for the combiner's curvature, ensuring accurate projection aligned with the user's perspective.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If basic ray tracing and reflection principles are used to calculate reflection locations on a curved optical combiner, then the calculation is simple and straightforward, but the mapping between display pixels and reflection locations is not bijective, causing image distortion and warping

Engineering Contradiction:
Improvesimplicity of calculation methodVSAvoidimage accuracy
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The system performs preliminary calculations to determine the precise mapping between display pixels and reflection locations on the curved combiner surface before image rendering. By pre-computing the correct pixel-to-reflection-point correspondence that accounts for the curved geometry, the system establishes an accurate forward mapping that eliminates distortion. This preliminary action ensures that when pixels are mapped to their reflection locations, the resulting image appears undistorted to the user despite the curved surface.

Inventive Principle:
Principle #10Preliminary action

2Adaptability or versatility

If the optical combiner uses a curved semi-reflective surface to reflect images, then the system achieves glasses-free augmented reality functionality, but the reflection becomes degenerate at certain regions causing highly warped and distorted perceived images

Engineering Contradiction:
Improveglasses-free AR functionalityVSAvoidimage distortion
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The system applies local quality by treating different regions of the curved combiner surface with region-specific mapping calculations. Instead of using a uniform mapping approach, the system computes pixel-to-reflection-point correspondences that are tailored to each local region's geometry and curvature characteristics. This ensures that even in regions where degenerate reflections occur, the local mapping accurately compensates for the curvature effects, maintaining image quality across the entire curved surface.

Inventive Principle:
Principle #3Local quality

3Manufacturing precision

If iterative search is performed to find accurate mapping between display pixels and reflection locations, then image accuracy and undistorted perception are achieved, but computational complexity and processing time increase

Engineering Contradiction:
Improveimage accuracyVSAvoidcomputational complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The system performs preliminary computations to establish the pixel-to-reflection-point mapping before real-time image rendering. By pre-calculating and storing the correspondence between display pixels and their reflection locations on the curved combiner, the system creates a lookup table or pre-computed mapping structure. During actual operation, this pre-established mapping is applied directly without requiring iterative searches, significantly reducing computational complexity while maintaining high image accuracy.

Inventive Principle:
Principle #10Preliminary action

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 provides precise and adaptive image rendering, eliminating distortions and ensuring geometrically and photometrically accurate augmented reality content, particularly suitable for head-up displays and automotive applications.

Implementation Method 1

a semi-reflective surface of the optical combiner is curved; and at least one processor configured to: determine a relative location of eyes of at least one user with respect to the semi-reflective surface

Methodology Applied
Scientific EffectReflection: Reflection

Data Source

PatentEP4632466A1Compensating for optical combiner curvature
Publication Date: 2025.10.15 DISTANCE TECHNOLOGIES OY
  • EP4632466A1 patent drawingFigure 1A
  • EP4632466A1 patent drawingFigure 1B
  • EP4632466A1 patent drawingFigure 1C

AI summary

For a given region (114) of a light-emitting surface (116) of a display unit (104), an iterative search is performed to find a corresponding reflection portion (118) of a semi-reflective surface (110) of an optical combiner (106) where light rays emanating from the given region are incident and from which the light rays reflect towards a given eye, based on a curvature of the semi-reflective surface, a relative location of the semi-reflective surface with respect to the light-emitting surface, and the relative location of the given eye with respect to the semi-reflective surface. A viewing direction from the given eye towards the corresponding reflection portion is determined. A corresponding pixel location in the input image is determined based on the viewing direction. For the corresponding pixel location in the input image, colour values of a corresponding pixel in the input image are fetched and utilised to display colour at the given region of the light-emitting surface.