Light Guide Lens Layout for Compact AR Projection Assembly
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Solution Overview
Problem
Existing projection devices for augmented reality (AR) and electronic devices are bulky, have high Total Track Length (TTL), poor optical uniformity, low resolution, and lack durability and coupling strength, making them difficult to miniaturize and assemble efficiently.
Innovation Solution
A projection device design that places lenses closer to a light guide, using a specific arrangement of lenses with convex and concave surfaces, and adhesive contact with the light guide, along with a compact barrel and housing structure to enhance coupling and assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lenses are arranged farther from the light guide, then assembly and inspection are easier, but the device size and TTL increase
Solution Approach 1:
The first side lens is disposed to overlap with the light guide in the optical-axis direction, allowing the lens to be positioned within the spatial envelope of the light guide structure. This nesting arrangement reduces the overall TTL while maintaining assembly feasibility through precise alignment features.
Solution Approach 2:
The patent transitions from a linear arrangement where lenses are positioned sequentially along the optical axis to a multi-dimensional configuration where the first side lens overlaps with the light guide in the optical-axis direction. This dimensional reorganization reduces TTL while preserving manufacturing accessibility.
2Length of moving object
If lenses are arranged closer to the light guide, then the device is more compact, but coupling strength and assembly precision requirements increase
Solution Approach 1:
An adhesive layer is introduced as an intermediary between the first side lens and the light guide. This adhesive mediator compensates for minor alignment tolerances, reduces the need for ultra-precise assembly, and provides mechanical bonding that maintains the compact configuration while accommodating manufacturing variations.
Solution Approach 2:
The patent modifies the coupling parameters by introducing adhesive bonding with specific thickness and refractive index characteristics. This changes the interface properties between the lens and light guide, allowing for relaxed positional tolerances while maintaining optical performance and mechanical stability.
3Volume of moving object
If a compact barrel structure is used, then the device is miniaturized, but coupling strength between components may be reduced
Solution Approach 1:
The barrel structure employs composite construction combining rigid structural elements with adhesive bonding interfaces. The rigid portions maintain structural integrity and miniaturization, while the adhesive interfaces provide distributed coupling strength across multiple component junctions, achieving both compactness and mechanical robustness.
Solution Approach 2:
The adhesive bonding is applied in advance during the assembly process, creating pre-stressed joints that lock components in position before final assembly. This preliminary bonding action ensures strong coupling in the compact configuration without requiring oversized mechanical fasteners that would increase device volume.
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 design achieves a more compact, reliable, and durable projection device with improved optical uniformity and resolution, facilitating easier miniaturization and assembly.
Implementation Method 1
a first side lens disposed between the first side of the light guide and the first light source
Implementation Method 2
the first side lens is in contact with the light guide
Implementation Method 3
a lens group disposed at a fourth side of the light guide
Data Source
AI summary
An embodiment provides a projection device comprising: a light guide; a first light source disposed at a first side of the light guide; a lens group disposed at a fourth side of the light guide; and a first-side lens disposed between the first side of the light guide and the first light source, wherein the first side of the light guide overlaps the fourth side of the light guide in the optical-axis direction of the lens group, and the first-side lens comes into contact with the light guide.