Cemented Substrate Optics for Compact Wide-FOV Head-Mounted Displays
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Solution Overview
Problem
Conventional compact optical display devices suffer from limitations such as large size, bulkiness, and sensitivity to eye movements, leading to poor image quality and impracticality, especially in head-mounted applications and mobile devices.
Innovation Solution
An optical device comprising first and second light-transmitting substrates optically cemented by an adhesive with a refractive index lower than the substrates, allowing light waves to impinge on the interface plane at specific angles for wide field-of-view and large eye-motion-box, using angular sensitive reflecting surfaces to enhance image quality and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional free-space optical module is used to increase field-of-view, then the field-of-view is improved, but the device becomes larger, heavier and bulkier
Solution Approach 1:
The patent merges the imaging lens and combiner functions into a single optical element. The light-transmitting substrate with embedded reflecting surfaces serves both to focus light from the display and to reflect the formed image to the viewer's eye, eliminating the need for separate conventional optical modules and reducing overall device size and weight.
Solution Approach 2:
The patent transitions from conventional free-space optics to planar integrated optics by embedding reflecting surfaces within a light-transmitting substrate. This dimensional integration allows optical functions to be performed within a compact planar structure rather than requiring extended three-dimensional optical paths, enabling wider field-of-view in a smaller form factor.
2Volume of moving object
If compact optical solutions are implemented to reduce device size, then device compactness is improved, but manufacturing complexity increases and eye-motion-box becomes very small
Solution Approach 1:
The patent segments the optical functionality into distinct embedded reflecting surfaces within the substrate, each with specific angular sensitivity characteristics. This segmentation allows complex optical functions to be achieved through simpler, modular optical elements that are easier to manufacture while maintaining compact dimensions and adequate eye-motion-box.
3Volume of moving object
If compact optical designs are used to reduce size, then device compactness is improved, but the system becomes sensitive to eye movements and image quality deteriorates
Solution Approach 1:
The patent implements local quality by creating angular-sensitive reflecting surfaces at specific locations and orientations within the substrate. Each reflecting surface is positioned and oriented to handle specific angular ranges of incoming and outgoing light, providing localized optical control that maintains image quality across different eye positions while keeping the overall device compact.
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 solution provides a compact display system with a wide field-of-view and large eye-motion-box, enabling high-quality images that accommodate eye movements, suitable for head-mounted and mobile applications.
Implementation Method 1
The substrates and the optical adhesive having a refractive index, the refractive index of the optical adhesive being lower than the refractive index of the first substrate defining a critical angle of the interface plane, part of the light waves entering the device through the input aperture and exiting the device through the output aperture, impinge on the interface plane of the first substrate having incidence angles smaller than the critical angle, another part of the light waves impinging on the interface plane, having incidence angles higher than the critical angle
Data Source
AI summary
An optical device, having at least first and second light-transmitting substrates, each having at least two external surfaces and an input aperture and an output aperture. The external surface of the first light-transmitting substrate is optically cemented to an external surface of the second light-transmitting substrate by an optical adhesive defining an interface plane. The refractive index of the optical adhesive is substantially lower than the refractive index of the first substrate. Part of the light waves entering the device through the input aperture and exiting the device through the output aperture impinge on the interface plane of the first substrate having incidence angles smaller than the critical angle. Another part of the light waves impinging on the interface plane have incidence angles higher than the critical angle. The interface plane is substantially transparent for the light waves impinging on interface plane having incidence angles smaller than the critical angle.