Compact Beam Expanding System Using Nested Substrates
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Solution Overview
Problem
Conventional compact optical display devices face challenges in achieving a wide field-of-view and large eye-motion-box while maintaining compactness, leading to poor image viewing quality, especially in head-mounted and mobile applications, due to the limitations of conventional free-space optical modules.
Innovation Solution
The design incorporates an optical device with multiple light-transmitting substrates that utilize total internal reflection and partially reflecting surfaces to expand the beam along both axes, allowing for a compact and high-quality image display with a wide field-of-view and large eye-motion-box, suitable for head-mounted and mobile applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional free-space optical modules are used, then the system can be implemented with standard components, but the system becomes larger, heavier and bulkier
Solution Approach 1:
The optical module is segmented into multiple thin light-transmissive substrates (first substrate, second substrate, third substrate) that can be manufactured separately and then assembled together. This segmentation allows each substrate to be manufactured using standard thin-film deposition techniques on flexible carriers, enabling compact final assembly while maintaining ease of manufacture through modular construction
Solution Approach 2:
Multiple functional layers are nested within thin substrates: beam splitting surfaces, beam expanding surfaces, and combiner surfaces are all integrated within the layered substrate structure. The first substrate contains beam splitting and first beam expanding surfaces, the second substrate contains the combiner surface, and the third substrate contains the second beam expanding surface, creating a nested configuration that achieves compactness without sacrificing manufacturability
2Adaptability or versatility
If the field-of-view is increased, then the image quality improves, but the system becomes larger and bulkier
Solution Approach 1:
Beam expansion is achieved in two perpendicular dimensions by utilizing surfaces inclined at different angles. The first beam expanding surface is inclined at a first angle to expand beam width in one dimension, while the second beam expanding surface is inclined at a second angle (perpendicular to the first) to expand beam width in the orthogonal dimension. This two-dimensional expansion approach enables wide field-of-view without increasing the physical size of the optical module
Solution Approach 2:
The patent employs angularly varying surface orientations rather than simple planar expansions. By using multiple surfaces with different inclination angles (first angle, second angle perpendicular to the first), the system creates an angular distribution of reflected light that effectively expands the field-of-view in multiple directions simultaneously, achieving a broader viewing cone from a compact structure
3Ease of operation
If the eye-motion-box is increased to accommodate eye movements, then the viewing comfort improves, but the system becomes larger
Solution Approach 1:
The eye-motion-box is expanded in two perpendicular dimensions through the use of beam expanding surfaces oriented at different angles. The first beam expanding surface expands the effective aperture in one dimension, while the second beam expanding surface (perpendicular to the first) expands it in the orthogonal dimension, creating a larger two-dimensional eye-motion-box that accommodates natural eye movements without increasing the physical footprint of the optical module
Solution Approach 2:
The multiple beam expanding surfaces serve dual functions: they simultaneously expand the field-of-view for different viewing angles and create a larger eye-motion-box to accommodate eye movements. This multi-functionality allows a single compact structure to address both field-of-view requirements and eye motion tolerance without requiring additional components or increasing overall size
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 enables a compact optical system with a large, high-quality image that accommodates eye movements, improving image viewing quality in head-mounted and mobile displays by expanding the field-of-view and eye-motion-box, making it suitable for practical implementation in devices like head-mounted displays and cellular phones.
Implementation Method 1
the input surface of the first substrate is a partially reflecting surface, such that part of the light waves passing through the input aperture is partially reflected by the partially reflecting input surface and coupled into the first substrate and another part passes through the partially reflecting input surface
Implementation Method 2
an input surface for coupling light waves into the substrate for effecting total internal reflection inside the substrate
Data Source
AI summary
There is provided an optical device, including an input aperture, an output aperture, at least first and second light-transmitting substrates each having two major surfaces and edges, an input surface for coupling light waves into the substrate for effecting total internal reflection inside the substrate, and an output surface for coupling light waves out of the substrate, a major surface of the first substrate is attached to a major surface of the second substrate and the input surface of the first substrate is a partially reflecting surface, such that part of the light waves passing through the input aperture is partially reflected by the partially reflecting input surface and coupled into the first substrate and another part passes through the partially reflecting input surface and is coupled by the input surface of the second substrate into the second substrate.