Waveguide Pupil Banding Mitigation via Angle Dispersion
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Solution Overview
Problem
Prior art projection displays using waveguide techniques suffer from pupil banding, a phenomenon where the intensity of the image modulates as the observer's line of sight changes, due to non-overlapping pupils of image bearing light at certain viewing angles.
Innovation Solution
The solution involves a projection display with a first and second waveguide element, each with a grating that directs image bearing light under total internal reflection, and an optical element that disperses incident light to occupy a continuum of angles, mitigating pupil banding and reducing chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If waveguide techniques are used to generate a collimated display with large exit pupil and field of view, then the display area and viewing characteristics are improved, but pupil banding occurs causing image intensity modulation
Solution Approach 1:
The waveguide is divided into multiple waveguide elements (first waveguide element, second waveguide element, etc.), each handling different portions of the light path. This segmentation allows independent optimization of each element and prevents pupil banding by distributing the light guidance across multiple elements rather than a single waveguide.
Solution Approach 2:
Different waveguide elements are positioned at different locations and orientations to create overlapping pupils. The first waveguide element creates a first pupil, the second waveguide element creates a second pupil, and their overlap ensures uniform image intensity across the field of view, eliminating pupil banding while maintaining large display area.
2Ease of operation
If gratings are used to direct light under total internal reflection, then light propagation control is improved, but chromatic aberration increases
Solution Approach 1:
The invention introduces an optical element that disperses light in a dimension perpendicular to the grating planes. This additional dimensional control allows the system to compensate for chromatic aberration introduced by the gratings, while maintaining effective light propagation control through the waveguide elements.
Solution Approach 2:
An optical element acts as an intermediary between the gratings and the final image output. This intermediary component corrects the chromatic aberration introduced by the gratings through dispersion, allowing the gratings to maintain their light propagation control function while eliminating their harmful chromatic effects.
3Reliability
If multiple waveguide elements are used to create overlapping pupils, then pupil banding is mitigated, but device complexity increases
Solution Approach 1:
Multiple waveguide elements are merged into a single integrated waveguide structure. The first waveguide element, second waveguide element, and any additional elements are combined into one cohesive component, reducing device complexity while maintaining the overlapping pupil configuration that mitigates pupil banding.
Solution Approach 2:
The waveguide elements serve multiple functions simultaneously: they guide light through total internal reflection, create overlapping pupils to eliminate banding, and can be integrated into a single structure. This multi-functionality reduces the need for separate components, thereby reducing overall device complexity.
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 ensures that each discrete point in the field of view occupies a continuum of angles, preventing pupil banding and minimizing chromatic aberration, resulting in a stable and clear image display across varying viewing angles.
Implementation Method 1
a first grating associated with the first waveguide element arranged to direct the image bearing light internally along the first waveguide element under total internal reflection
Implementation Method 2
via which the image bearing light is outputted from the first waveguide element
Implementation Method 3
an optical element associated with each waveguide element arranged to disperse incident image bearing light such that each discrete point in the field of view of the image to be viewed by the observer occupies a continuum of angles within the first and second waveguide elements
Data Source
AI summary
An image-providing light source device 58 is arranged to inject a non-coherent and collimated image into waveguide element 60. Light forming the image is dispersed by an optical element 76 so as to occupy a continuum of angles within the waveguide 60. The optical element 76 and a grating 70 are arranged such that the light exiting the waveguide occupies a single angle. Thereby, pupil banding of light exiting the waveguide 60 is mitigated.