Optical Device Reflective Coating for Thin Glasses Broad FOV
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Solution Overview
Problem
Conventional wearable displays, particularly glasses-type, face challenges in achieving a thin glasses structure with a broad Field Of View (FOV) while avoiding visual patterns and maintaining performance across varying eye positions and pupil sizes.
Innovation Solution
The optical device incorporates a diffraction region on a substrate with a specific coating pattern, including lattice-type net meshes, which adjusts based on the distance between the substrate and the user's eyes and the wavelength band of the light source, to collect and radiate light beams, ensuring a broad FOV without visible visual patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar light guide structure with internal reflection is used, then the device can be manufactured using mold structure and formed of plastic, but the Field of View (FOV) is limited due to the thickness of the light guide and total internal reflection constraints
Solution Approach 1:
The patent changes the optical mechanism from total internal reflection to external reflection using a reflective coating layer. This parameter change allows the light guide thickness to be reduced significantly while expanding the FOV, as the reflective coating enables beam redirection without requiring thick light guide structures for total internal reflection
Solution Approach 2:
The patent introduces a reflective coating layer at a specific dimension within the light guide structure, adding a new functional layer that enables external reflection. This dimensional addition allows the system to achieve broad FOV without increasing overall device thickness, resolving the contradiction between manufacturability and FOV expansion
2Ease of operation
If segment partial PBS mirrors or prism mirrors are used for beam reflection, then the structure can guide beams to pupils, but visual patterns become visible and the FOV is restricted by the effective range of partial mirrors
Solution Approach 1:
The patent applies a reflective coating layer locally at a specific position within the light guide structure, creating a focused reflection zone. This localized reflection approach directs beams to pupils effectively while avoiding the periodic patterns that occur with segmented mirrors, as the reflection occurs at a continuous coating surface rather than discrete mirror segments
Solution Approach 2:
The patent uses a reflective coating that creates a uniform reflection surface, replacing the segmented mirror structure with a continuous reflective layer. This copying of the reflection function across a continuous surface eliminates the visual patterns associated with discrete mirror segments while maintaining effective beam guidance to pupils
3Area of stationary object
If the light guide thickness is increased to expand FOV through internal reflection, then more light can be transmitted, but the device thickness increases and performance degrades for varying eye positions
Solution Approach 1:
The patent changes the reflection mechanism from total internal reflection to external reflection using a reflective coating. This parameter change allows the light guide thickness to be minimized while achieving broad FOV, as external reflection does not require the thick structures needed for total internal reflection to maintain adequate light transmission
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 design enables the creation of a thin glasses structure with a broad FOV, eliminating visual unpleasantness and enhancing the usability of wearable displays by optimizing light beam distribution and visibility.
Implementation Method 1
a diffraction region (460) on a surface (451) of a substrate (450)... The diffraction region (460) diffracting light beams incident thereon and collecting the diffracted light beams in a space (901) above the surface (451) of the substrate (450)
Implementation Method 2
A coating pattern in the diffraction region may include lattice-type net meshes... A coating material of the diffraction region may be a material which may reflect light
Data Source
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AI summary
The present invention relates to an optical device that is capable of producing an image in the air, which includes a substrate having a reflective diffraction region formed into a net structure, and a light radiation unit which radiates a light beam onto one surface of the substrate. The diffraction region is capable of collecting light beams that are diffracted in the upper space of one surface of the substrate by diffracting the light beam which is incident on one surface of the substrate. Here, the light radiation unit may have a display source that generates the light beams which form the image, and a lens portion that radiates the generated light beams onto the substrate.