Optical Arrangement Deflects External Light to Reduce Ghost Images
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Solution Overview
Problem
Optical devices for near-eye displays and head-up displays face challenges in minimizing ghost images caused by external light sources, which can lead to unwanted reflections and deflections of external scene light into the observer's eye, disrupting the intended image projection.
Innovation Solution
The implementation of a light-transmitting substrate with internal reflection and an optical coupling-out configuration, combined with an optical arrangement featuring high refractive index optical elements and a low refractive index interface region, deflects external scene light rays at specific angles, preventing them from entering the observer's eye and reducing ghost image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a light-transmitting substrate with internal reflection is used to guide light, then the device can achieve compact form factor and aperture multiplication, but external scene light can be reflected into the observer's eye causing ghost images
Solution Approach 1:
The patent introduces an optical arrangement with a first optical element and second optical element that acts as an intermediary between the light-transmitting substrate and the external scene. This intermediary structure selectively manages light paths: it allows guided image light to pass through while intercepting and deflecting external scene light that would otherwise reflect into the observer's eye and create ghost images.
Solution Approach 2:
The optical arrangement is positioned at a specific location (one of the two major surfaces) of the light-transmitting substrate, applying the ghost image mitigation function locally rather than requiring global modification of the entire substrate. The first and second optical elements are configured with specific orientations and refractive indices to create the deflecting interface region precisely where needed.
2Ease of manufacture
If partially reflective surfaces are used to couple out the image, then the desired partial reflectivity can be achieved, but unwanted reflections from external scene light can still occur
Solution Approach 1:
The optical arrangement with first and second optical elements serves as an intermediary layer between the partially reflective surfaces and the external scene. This intermediary structure deflects external scene light before it can interact with the partially reflective surfaces, preventing unwanted reflections while allowing the partially reflective surfaces to continue their function of coupling out the projected image.
3Object-generated harmful factors
If the optical arrangement deflects external scene light, then ghost images are reduced, but the optical path for useful light must be preserved
Solution Approach 1:
The optical arrangement is strategically positioned at one of the two major surfaces of the light-transmitting substrate, applying the deflecting function locally to external scene light paths while leaving the optical path for guided image light unaffected. The first optical element and second optical element are configured with specific orientations so that the deflecting interface region only intercepts external scene light at problematic angles.
Solution Approach 2:
The optical arrangement segments the light handling function: the first optical element receives and processes external scene light, the interface region deflects the unwanted light, and the second optical element transmits the deflected light away from the substrate. This segmentation allows useful guided light to pass through unaffected while isolating and deflecting only the harmful external scene light.
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 mitigates ghost images by deflecting unwanted external light away from the observer's eye, ensuring a clear and unobstructed view of both the projected image and the external scene, thereby enhancing the overall display performance and user experience.
Implementation Method 1
a light-transmitting substrate having at least two major surfaces for guiding light by internal reflection between the major surfaces
Implementation Method 2
an optical arrangement associated with at least one of the two major surfaces and including a first optical element and a second optical element optically coupled to the first optical element to define an interface region associated with at least a portion of the optical coupling-out configuration, the optical arrangement being deployed such that light rays emanating from an external scene and incident to the optical arrangement at a given range of incident angles are deflected at the interface region
Data Source
AI summary
An optical device has a light-transmitting substrate, an optical coupling-out configuration, and an optical arrangement. The light-transmitting substrate has at least two major surfaces and guides light by internal reflection between the major surfaces. The optical coupling-out configuration couples the light, guided by internal reflection, out of the light-transmitting substrate toward an eye of a viewer. The optical arrangement is associated with at least one of the two major surfaces, and has a first optical element and a second optical element. The optical elements are optically coupled to each other to define an interface region associated with at least a portion of the coupling-out configuration. The interface region deflects light rays that emanate from an external scene that are incident to the optical arrangement at a given range of incident angles.