Inclined Grating Structure for Invisible Light Reflection
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Solution Overview
Problem
Existing embedded grating structures in spectacle lenses are visible to casual observers and cause optical distortions, disrupting through-images, and existing coatings for light reflection are not unobtrusive.
Innovation Solution
An optical device with a grating structure embedded between media of the same refractive index, featuring inclined non-vertical grating walls with a reflective coating, designed to minimize visible optical effects and allow for non-disturbed through-images, incorporating a projector for image projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reflective coating is applied to the grating structure to promote light reflection, then light reflection efficiency is improved, but the grating becomes more visible to casual observers
Solution Approach 1:
The patent applies different surface orientations to different parts of the grating structure. The first surface part (facing the projector) has a specific inclination optimized for light reflection efficiency, while the second surface part (facing the external environment) has a different inclination that minimizes visibility. This local differentiation allows each surface to optimize for its specific function without compromising the other.
2Object-affected harmful factors
If the refractive indices either side of the grating are matched to avoid disturbing through-images, then through-image quality is improved, but light reflection from the grating to the eye is prevented
Solution Approach 1:
The patent changes the geometric parameters of the grating structure (surface inclinations, angles) rather than changing the refractive index parameter. By adjusting the inclination angles of the first and second surface parts, the patent achieves both objectives: minimizing visibility to casual observers and directing light to the user's eye, while maintaining refractive index matching between the lens material and surrounding medium.
3Ease of operation
If vertical grating walls are used for light redirection, then light redirecting function is achieved, but surface quality is lower and manufacturing precision is reduced
Solution Approach 1:
The patent replaces vertical grating walls with inclined surfaces that are curved to follow the curvature of the lens. This curvature allows for smoother surfaces that are easier to manufacture with high precision, while still achieving the required light redirection function through carefully designed inclination angles.
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 grating structure is substantially invisible to casual observers and reduces optical distortions, providing unobtrusive light redirection with enhanced optical functionality like image magnification and focus, while maintaining high coating quality and reduced visibility.
Implementation Method 1
the first surface part is inclined to reflect light, emitted from a projector and entering the lens through the surface closest to an eye of a user, in a first direction towards the eye of the user of the optical device, and wherein the second surface part is inclined relative to the first surface part to reflect said light in a second direction different to the first direction, away from the eye of the user
Data Source
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AI summary
An optical device comprising an optical grating structure embedded between media of substantially the same optical refractive index, the structure having an optical coating at the interface between the two media, wherein the structure comprises grating facets inclined relative to the interface plane such that, in use, anomalous optical effects due to coating are substantially reduced.