Adhesive-Free Stacked Light-Guide Substrate for Wide Field-of-View
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Solution Overview
Problem
Conventional compact optical modules for head-mounted displays become bulky and impractical as the desired field-of-view increases, with limited eye-motion-box and pupil motion, leading to sensitive performance and manufacturing challenges.
Innovation Solution
A compact light-guide optical element is fabricated using a substrate with parallel partially reflecting surfaces, formed by optically attaching transparent flat plates without adhesives and chemically strengthening the substrate, allowing for wide field-of-view and large eye-motion-box with improved optical quality and manufacturability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional free-space optical modules are used to increase field-of-view, then the optical performance is improved, but the device becomes larger, heavier and bulkier
Solution Approach 1:
The patent merges multiple optical functions (collimating, reflecting, and combiner functions) into a single integrated light-guide element. The light-guide substrate combines the collimating lens and reflecting surfaces in one component, eliminating the need for separate free-space optical modules and reducing overall device weight and size while maintaining wide field-of-view capability
Solution Approach 2:
The patent transitions from conventional two-dimensional optical paths to three-dimensional light guiding within the substrate. By utilizing total internal reflection and light trapping within the light-guide element's thickness dimension, the system achieves wide field-of-view without increasing the lateral footprint or weight of the device
2Adaptability or versatility
If conventional optical modules are used to increase field-of-view, then the optical performance is improved, but the device complexity increases
Solution Approach 1:
The patent merges multiple optical functions (collimating, reflecting, and combiner functions) into a single integrated light-guide element. The light-guide substrate combines the collimating lens and reflecting surfaces in one component, eliminating the need for separate free-space optical modules and reducing overall device weight and size while maintaining wide field-of-view capability
Solution Approach 2:
The light-guide element serves multiple functions simultaneously: it acts as a collimating lens, a reflecting surface, and a combiner for both non-see-through and see-through applications. This multi-functionality reduces the number of separate components needed and simplifies the overall optical system design
3Volume of moving object
If compact optical solutions are used to reduce device size, then the device compactness is improved, but the eye-motion-box becomes very small and performance becomes sensitive to eye movements
Solution Approach 1:
The patent transitions from conventional two-dimensional optical paths to three-dimensional light guiding within the substrate. By utilizing total internal reflection and light trapping within the light-guide element's thickness dimension, the system achieves wide field-of-view without increasing the lateral footprint or weight of the device
Solution Approach 2:
The patent changes the optical parameters by using specific refractive index materials and controlling the geometry of the light-guide element to optimize light trapping and guiding. By adjusting the substrate thickness, refractive index, and surface geometry, the system achieves a large eye-motion-box while maintaining compact form factor
4Ease of manufacture
If adhesive-based optical attachment is used to assemble light-guide elements, then the manufacturing process is simplified, but optical quality deteriorates due to adhesive interference
Solution Approach 1:
The patent removes the adhesive layer from the optical path by using adhesive-free attachment methods. The light-guide elements are bonded directly to each other through mechanical interlocking or friction fit, eliminating the adhesive interface that would otherwise interfere with optical quality and light transmission
Solution Approach 2:
The patent introduces a direct mechanical interface as an intermediary between optical elements, replacing the adhesive mediator. This direct contact interface maintains optical quality while providing sufficient mechanical bonding strength for assembly
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, high-quality optical system with wide field-of-view and large eye-motion-box, accommodating large eye movements while maintaining optical quality and simplifying the fabrication process, avoiding the limitations of conventional designs.
Implementation Method 1
the plates are optically attached to each other by an optically adhesive-free process
Implementation Method 2
light waves are trapped inside the substrate by total internal reflections from the external surfaces of the LOE
Implementation Method 3
light waves which are trapped inside the LOE are coupled out into the eyes of the viewer by an array of partially reflecting surfaces
Implementation Method 4
an array of selectively reflecting surfaces, which couple the light out of the substrate into the eye of a viewer
Implementation Method 5
the light waves-transmitting substrate is chemically strengthened by a surface finishing process
Data Source
Figure 1
Figure 2(a)~2(e)
Figure 3(a)~3(c)
AI summary
A method is described for fabricating an optical device that includes a light waves-transmitting substrate having at least two major surfaces and edges and a plurality of partially reflecting surfaces carried by the substrate, wherein the partially reflecting surfaces are parallel to each other and not parallel to any of the edges of the substrate. The method includes providing at least one transparent flat plate and plates having partially reflecting surfaces and optically attaching together the flat plates so as to create a stacked, staggered form. From the stacked, staggered form, at least one segment is sliced off by cutting across several plates and the segment is ground and polished to produce the light waves-transmitting substrate. The plates are optically attached to each other by an optically adhesive-free process.